Method and apparatus for monitoring, dosing and distribution of chemical solutions

Abstract

It is an object of the present invention to provide a system and method for monitoring, dosing and distribution of a chemical composition in a material treatment process, the chemical composition containing at least one additive for maintaining quality of the chemical treatment process. The system and method include: at least one chemical containing unit configured to contain the chemical composition for the chemical treatment process; a dosing unit fluidly communicating with the at least one chemical containing unit configured to receive the chemical composition therefrom and to add a selected dose of the at least one additive to the chemical composition therein; an online monitor configured to monitor a property of the chemical composition at the dosing unit and to transmit a signal corresponding to the monitored property; and a controller programmed and configured to receive the signal from the online monitor and send a signal to the dosing system to add the selected dose to the chemical composition therein in response to the monitored property.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority under 35 U.S.C. §119(e) of U.S. provisional application Ser. No. 60/465,184 filed on Apr. 23, 2003, 60/542,741, filed on Feb. 5, 2004, 60/476,931 filed on Jun. 9, 2003, and 60/556,864 filed on Mar. 26, 2004, the entire contents of which are incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO SEQUENTIAL LISTING

Not applicable.

BACKGROUND OF THE INVENTION

1) Field of the Invention

This invention is directed to the field of management of chemical compositions used in material treatment processes. This invention is particularly directed to the field of management of electroplating bath solutions.

2) Description of the Related Art

Many material treatment processes utilize a chemical composition. In order to smoothly operate such a process, upsets or deviations in the quality of the chemical composition should be avoided. Otherwise, quality of the treated material will vary over time. Also, the process might need to be shut down in order to bring the quality of the chemical composition back into the specification of the process. Such a shutdown is often prohibitively expensive.

Some examples of material treatment processes include chemical mechanical polishing/planarization (CMP), electrochemical polishing/planarization (ECP), or copper electroplating (ECD) of semiconductor wafers or coated semiconductor wafers.

Regarding ECD, achieving defect-free copper interconnects on integrated circuits by electroplating has involved the development of a new process called “superfilling” or “bottom-up plating”. Key parts in this process are the organic additives used in the plating bath. These critical components, called brighteners, suppressors, and levelers, have specifically been tailored to promote the critical bottom-up plating or superconformal deposition that allows high-aspect ratio trenches and vias to be filled correctly. Furthermore, since these additives become depleted during the deposition process, bath monitoring, dosing and solution delivery are critical to process stability, uniform deposition rate, and obtaining the correct physical properties of the copper layer (such as morphology, microstructure, conductivity and grain size).

Presently, copper bath monitoring is performed by measuring the composition of the inorganic and organic components in the bath solution contained in the reservoir tank of the process tool. This is done commercially by offline or online methods:

Methods of offline measurements used to analyze bath composition include: titration, high performance liquid chromatography (HPLC), cyclic voltammetric stripping (CVS), and modified CVS. Titration is used to measure the inorganic components such as copper, acidity and chloride. CVS and HPLC are used to measure the concentration of the organic additives, the brightener, suppressor and leveler. With respect to CVS, ECI Technology has commercial equipment based on this technique [Bratin P., Chalyt G., Pavlov M., “Control of Damascene Copper Processes by Cyclic Voltammetric Stripping, Plating & Surface Finishing, March 2000, pp. 14-16]. With respect to HPLC, Dionex discloses this technique [Dionex Industry Brief; “Analysis of Copper Plating Baths”, pp. 1-8]. U.S. Pat. Nos. 6,365,033 and 6,551,479 disclose pulsed voltammetric stripping.

One of the main limitations of CVS is its sensitivity to matrix effects of the electrolyte, since the copper stripping is dependent not only on the individual additives but also their interaction and degradation in the bath solution [Sun, Zhi-Wen and Dixit, Girsih, “Optimized bath control for void-free copper deposition”, Solid State Technology, November, 2001, pp. 97-102; and Taylor, T., Ritzdorf, T., Lindberg F., Carpenter B., LeFebvre M., “Electroplating bath controls for copper interconnects”, Solid State Technology, November, 1998]. Also, measurement time tends to be long (several hours) and large volumes of electrolytes are used, increasing the consumption and waste stream of these expensive chemicals. High performance liquid chromatography (HPLC) also generates large amounts of waste and also has a relatively long response time.

Methods of online measurements include periodic sampling of the bath and analysis at or near the plating tool to monitor bath component concentrations. One limitation to many of these methods is that plating bath breakdown products are not measured, although they are critical to determining bath quality. Some examples of online monitoring include the following. Bratin P., Chalyt G., Pavlov M., “Control of Damascene Copper Processes by Cyclic Voltammetric Stripping, Plating & Surface Finishing, March 2000, pp. 14-16 disclose several types of online monitor methods that measure component concentration by titration and cyclic voltammetric stripping. A company named Technic, Inc. provides online AC/DC voltammetric monitoring. Also, a company named ATMI offers titration/pulsed cyclic galvanostatic analysis. As another example, U.S. Pat. No. 6,635,157 discloses online titration and CVS. As further examples, U.S. Pat. Nos. 6,365,157 and 6,551,749 disclose online CVS monitoring.

One of the key objectives electroplating bath management is to maintain concentrations in the baths at desired levels by consistently dosing additives and fresh solution (inorganic solution) to counterbalance depletion of the additives in the bath due to byproduct formation during plating, degradation, and/or solution bleeding.

Current state-of-the-art dosing and bleeding of the bath is performed at the reservoir tank of the process tool. For instance, the makeup electrolyte (inorganic components) is delivered from a sub-fab chemical delivery system to the process tool and dosed into the reservoir tank. The additives are stored in small containers in the process tool and are dosed directly into the reservoir tank. Bleeding of the bath is also performed at the reservoir tank. Dosing control is performed by two methods: open-loop and closed-loop controls.

With regard to open-loop control, U.S. Pat. No. 6,471,845 B1 discloses empirical equations used for dosage based on previously defined consumption rates of the various components, and which accounts for the number of wafers processed, the plating current density, and other factors. As another example, U.S. Pat. No. 6,458,262 B1 discloses a chemical consumption process model based on off-line or online measurements to achieve bath control. As an example, U.S. Pat. No. 5,352,350 discloses empirical equations used for online, open loop control of the bath concentrations. These models are tool, chemistry and production regime specific. By design, they can, at best, only control conditioned plating solution around well-known operating conditions.

Others recognize that open-loop control fails to correct for local variations in consumption associated with plating fluctuations or changing bath equilibrium as degradation products are formed [Bratin P., Chalyt G., Pavlov M., “Control of Damascene Copper Processes by Cyclic Voltammetric Stripping, Plating & Surface Finishing, March 2000, pp. 14-16]. Also, these types of models are likely only valid in the vicinity of a known operating regime and have limited ability to accommodate process upsets or disturbances. Since open loop control does not detect process changes as it assumes steady-state operation, it could eventually lead to serious copper interconnects defects.

With regard to closed-loop control, bath sampling with either offline or online analysis is performed as described above. The results are sent back to the process engineer who doses the plating bath accordingly to maintain it in optimal condition. Offline or online analysis is used to “correct” for concentrations that drift due to incorrect open-loop control. However, current online bath component analysis is performed in 20-40 minutes depending on the type of equipment, which is not quite “real-time”. In addition, communication of the online monitor to the dosing system of commercial plating tools is not yet automatic and requires development of communication protocols to effectively use the process signal to control the bath concentrations. U.S. Pat. No. 6,592,736 provides one example of a closed-loop control.

As mentioned above, most commercial copper interconnect plating tools are stand-alone systems where the additives and makeup electrolyte are added individually to a reservoir tank located inside the plating tool and recirculated to and from the wafer plating cells. A portion of the bath solution in the reservoir tank can be bled out periodically to reduce contamination buildup. However, depending on wafer plating production levels, additive bottles may need to be changed quite frequently at the tool, which increases the risk of operator error and contamination (for example, from an incorrect bottle exchange).

Online monitoring for concentration control may be integrated into the tool or not. For those tools that do not integrate online monitoring with the tool, they are disadvantageous because they require process engineer intervention to correct the bath concentrations. Furthermore, most semiconductor fabs or foundries utilize more than one wafer-plating tool in production. Since each tool is controlled separately, inconsistencies in the bath solution between tools can develop which can ultimately result in different properties of the copper interconnect deposit for different tools.

In light of the problems associated with electroplating bath solutions having undesirable qualities, a need exists for improvement in the management of electroplating bath solutions.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system for monitoring, dosing and distribution of a chemical composition in a material treatment process, the chemical composition containing at least one additive for maintaining quality of the chemical treatment process. The system comprises: at least one chemical containing unit configured to contain the chemical composition for the chemical treatment process; a dosing unit fluidly communicating with at least one chemical containing unit configured to receive the chemical composition therefrom and to add a selected dose of at least one additive to the chemical composition therein; an online monitor configured to monitor a property of the chemical composition at the dosing unit and to transmit a signal corresponding to the monitored property; and a controller programmed and configured to receive the signal from the online monitor and send a signal to the dosing system to add the selected dose to the chemical composition therein in response to the monitored property.

It is another object to provide a method for monitoring, dosing and distribution of a chemical composition in a chemical treatment process, the chemical composition containing at least one additive for maintaining quality of the chemical treatment process. The method comprises the following steps. A flow of the chemical composition is allowed from at least one chemical containing unit to a dosing unit. A property of the chemical composition is monitored with an online monitor at a location intermediate to the chemical containing unit and the dosing unit or at the dosing unit. A signal associated with the monitored property is sent by the online monitor to a controller. The controller determines whether at least one additive should be added to the chemical composition at the dosing unit based upon the monitored property, thereby resulting in a decision to add or not a selected amount of at least one additive to the chemical composition at the dosing unit based upon the signal from the online monitor. A signal associated with the decision is sent from the controller to the dosing unit. The selected amount of at least one additive is allowed to be added or not be added to the chemical composition at the dosing unit in response to the signal associated with the decision. The chemical composition is allowed to flow from the dosing unit to the chemical containing unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the inventive system including an optional chemical dispensing unit.

FIG. 2 is a schematic of an embodiment of the invention also including a dosing unit reservoir; a dosage element; a fresh chemical composition supply tank; a fluid bleed tank; a conduit allowing the chemical composition to bypass the chemical containing unit; and a conduit/valve arrangement allowing the chemical composition to bypass the dosing unit reservoir, dosage element, fresh chemical composition supply tank, bleed tank, and optional chemical dispensing unit.

FIG. 3 is a schematic of another embodiment of the invention also including multiple chemical containing units; a dosing unit reservoir; a dosage element; a fresh chemical composition supply tank; a bleed tank; a conduit allowing the chemical composition to bypass the chemical containing units; a conduit/valve arrangement allowing the chemical composition to bypass the dosing unit reservoir, dosage element, fresh chemical composition supply tank, bleed tank, and optional chemical dispensing unit; a manifold and reservoir downstream of the chemical containing units; and a second online monitor.

FIG. 4 is a schematic another embodiment of the invention also including multiple chemical containing units; a dosing unit reservoir; a dosage element; a fresh chemical composition supply tank; a bleed tank; a conduit allowing the chemical composition to bypass the chemical containing units; and a conduit/valve arrangement allowing the chemical composition to bypass the dosing unit reservoir, dosage element, fresh chemical composition supply tank, bleed tank, and optional chemical dispensing unit.

FIG. 5 is a schematic of a preferred configuration of the dosage element.

FIG. 6 is a schematic of a preferred configuration of the optional chemical dispensing unit.

DESCRIPTION OF PREFERRED EMBODIMENTS

The inventive system allows a chemical composition associated with a material treatment process to be monitored, dosed, and distributed to a chemical containing unit in which the dosing occurs at a location other than at the chemical containing unit. This lessens the risk of operator error and contamination because the frequency of changing the additive bottles at the chemical containing unit is decreased. For example, an incorrect bottle exchange will result in contamination.

When there is a plurality of chemical containing units, the risk of operator error and contamination is multiplied. Many chemical treatment facilities, such as semiconductor fabs or foundries utilize more than one wafer-plating tool in production. Since each tool is controlled separately, inconsistencies in the bath solution between tools can develop which can ultimately result in different properties of the copper interconnect deposit for different tools. Thus, the invention is especially advantageous with use with several chemical containing units.

Also, when a controller is integrated with online monitoring, the risk of operator error is lessened because of the relative lack of transliteration errors made by an operator in between analysis of offline data and decisions to add the additives. Thus, in the invention, process engineer intervention is not needed to correct the bath concentrations.

The controller is analyzer-independent and will not need any modifications if the bath management system were to be used in conjunction with different instrumentation systems. It only involves sequential discrete control thereby facilitating the control scheme and reducing the implementation cost.

In many prior art system, chemical consumption process model based on offline or online measurements is utilized to achieve bath control. However, the equation in these types of models are presumably only valid in the vicinity of a known operating regime and have limited ability to accommodate process upsets or disturbances. In contrast, the inventive controller does not rely upon a model, but instead makes additive decisions based upon real time analysis data.

This invention is especially advantageous when implemented in management of electroplating bath solutions wafer-plating tools in semiconductor fabs or foundries.

With reference to the Figures and Tables I-III, the inventive system and method and preferred embodiments thereof are illustrated.

TABLE I
First legend to reference characters in the figures
10   inventive system
5    chemical containing unit
11   optional chemical delivery unit
20   piping from dosing unit to chemical delivery unit
25   conduit
40   conduit
41   communication link from controller to online monitor
42   communication link from controller to dosing unit
45   dosing unit
55   online monitor
65   controller
100  preferred embodiment of the inventive system
110  chemical delivery unit
112  chemical delivery element
120a pressure-feed vessel 1
120b pressure-feed vessel 2
130  blanket gas system
140  conduit
150  bypass
151  valve
152  valve
160  day tank
200  controller
210  communication link from controller to blending tank unit
220  communication link from controller to dosing unit
230  communication link from controller to optional chemical delivery
     unit
240  communication link from controller to monitor 1
245  communication link from controller to monitor 2
250  communication link from controller to chemical containing unit
250a communication link from controller to chemical containing unit
250b communication link from controller to chemical containing unit
250c communication link from controller to chemical containing unit
250d communication link from controller to chemical containing unit
251  communication link from controller to valve
252  communication link from controller to valve
260  communication link from controller solvent supply tank
270  communication link from controller to bleed tank

TABLE II
Second legend to reference characters in the figures
300  chemical containing element
300a chemical containing element 1
300b chemical containing element 2
300c chemical containing element 3
300d chemical containing element 4
320  inlet to chemical containing element
320a inlet to chemical containing element 1
320b inlet to chemical containing element 2
320c inlet to chemical containing element 3
320d inlet to chemical containing element 4
330  outlet from chemical containing element
330a outlet from chemical containing element 1
330b outlet from chemical containing element 2
330c outlet from chemical containing element 3
330d outlet from chemical containing element 4
340  chemical containing element outlet manifold
350  chemical containing element outlet reservoir
360  pump
400  dosing unit reservoir
415  dosing unit circulation pump
420  piping from dosing unit to optional chemical delivery unit
425  piping from reservoir to dosage element
426  conduit
427a conduit
427b conduit
427c conduit
427d conduit
427e conduit
428a three way valve
428b three way valve
428c three way valve
428d three way valve
429a conduit
429b conduit
429c conduit
429d conduit
430  piping from dosage element to reservoir
431  conduit
435  piping from conduit to fluid bleed tank
437  valve
440  pump

TABLE III
Third legend to reference characters in the figures
450  dosage element
460  piping from optional chemical delivery unit to chemical containing
     unit
461  piping for parallel loop
471  valve
472  dosing pump
473  valve
474  flowmeter
480a chemical additive container
480b chemical additive container
480c chemical additive container
480d chemical additive container
600  fluid bleed tank
610  fluid bleed tank outlet
700  fresh chemical composition supply tank
701  piping from fresh chemical composition supply tank to dosing unit
800  monitor
810  piping from dosing unit 400 to monitor 800
820  piping from monitor
850  monitor
860  piping to monitor
870  piping from monitor

As illustrated in FIG. 1, the inventive system includes a chemical containing unit 5 through which the chemical composition flows. The chemical composition contains certain chemical constituents, such as additives of the chemical composition which are consumed and/or degraded in a material treatment process. The chemical containing unit 5 is operatively associated with the material treatment process which occurs either adjacently to chemical containing unit 5 or remotely therefrom. For example, when the chemical containing unit 5 may be located remotely from the material treatment process, it can be part of a larger chemical distribution system that incorporates bulk chemical distribution equipment. Preferably, the chemical containing unit is an electroplating bath reservoir associated with one or more electroplating (ECD) tools in the clean room of a fab and the dosing unit is located in a chemical room located in the sub-fab. More preferably, the electroplating tools are used to electroplate semiconductor wafers with copper. Also preferably, the chemical containing unit is an electrolyte reservoir for supplying an electrochemical planarization (ECP) electrode system in the clean room of a fab and the dosing unit is located in a chemical room located in the sub-fab. Also preferably, the chemical containing unit is a chemical reservoir for supplying a chemical mechanical planarization (CMP) system in the clean room of a fab and the dosing unit is located in a chemical room located in the sub-fab.

The chemical composition flows via conduit 40 to dosing unit 45. At dosing unit 45, the online monitor 55 monitors a property of the chemical composition. Preferably, the monitored property is a concentration of one or more chemical constituents of the chemical composition. More preferably, it is the concentration of one or more additives or of degradation products resultant from a chemical treatment process associated with the chemical composition operatively associated with the chemical containing unit 5.

The online monitor 55 may be any online monitor known to those ordinary skilled in the art suitable for use in the invention. A preferred online monitor is a “real-time analyzer”, RTA, available from Technic, Inc, Cranston, in R.I., U.S.A.

Another monitor suitable for use in the invention is the ECI system available from ATMI, Danbury, Conn., U.S.A.

The online monitor 55 sends a signal associated with the monitored property to the controller 65 via communication link 41. Based upon this signal, the controller 65 determines whether or not to add one or more additives to the chemical composition at the dosing unit 45, thereby resulting in a decision. The controller 65 sends a signal associated with the decision to dosing unit 45 via communication link 42. Based upon this signal, one or more additives are added or not to the chemical composition at the dosing unit 45. Preferably, the dosing unit 45 includes a mixing element so that the chemical composition and any additives are well mixed. Preferred examples of additives include brighteners, suppressors, and levelers.

The chemical composition flows from the dosing unit 45 via conduit 20 to the optional chemical delivery unit 11. Optional chemical delivery unit 11 delivers the chemical composition to the chemical containing unit 5 via optional conduit 25. As the chemical delivery unit 11 and conduit 25 are optional, the inventive system 10 may be configured such that the chemical composition flows directly from the dosing unit 45 to the chemical containing unit via conduit 20.

As best shown in FIG. 2, a preferred embodiment 100 of the inventive system includes a chemical containing unit 300 through which the chemical composition may flow either batch-wise or continuously. The chemical composition contains certain chemical constituents, such as additives of the chemical composition which are consumed and/or degraded in a material treatment process. The chemical containing unit 300 is operatively associated with the material treatment process which occurs either adjacently to chemical containing unit 300 or remotely therefrom. For example, when the chemical containing unit 300 may be located remotely from the material treatment process, it can be part of a larger chemical distribution system that incorporates bulk chemical distribution equipment.

Preferably, the chemical containing unit 300 includes inlet and outlet valves and a level sensor. When the level sensor senses a selected high level, the inlet and outlet valves close thereby preventing the flow of the chemical composition thereinto. When desired, an optional conduit 461 may be provided through which the chemical composition bypasses the chemical containing unit 300. Thus, the chemical composition may continue to flow through the system 100 when the inlet and outlet valves of chemical containing unit 300 are closed. This bypass flow may be implemented via signals sent between chemical containing unit 300 and controller 200 via communication link 250. This helps continue mixing of the chemical composition as well as maintaining a steady flow of it through the system, especially if the tool is disconnected.

The chemical composition flows from the chemical containing unit 300 via conduit 330 to conduit 140, and thenceforth past valve 151 and bypass conduit 150 to dosing unit reservoir 400. Dosing unit reservoir 400 and dosage element 450 together comprise a dosing unit analogous to dosing unit 45. At least a portion of the chemical composition is routed via piping 810 from the dosing unit reservoir 400 to online monitor 800, at which a property of the chemical composition is monitored. Preferably, the monitored property is a concentration of one or more chemical constituents of the chemical composition. More preferably, it is the concentration of one or more additives or of degradation products resultant from a material treatment process associated with the chemical composition operatively associated with the chemical containing unit 300.

The online monitor 800 sends a signal associated with the monitored property to controller 200. Based upon the signal, the controller 200 determines whether or not to add one or more additives at dosing unit reservoir 400 to the chemical composition, thereby resulting in a decision. A signal associated with this decision is sent from controller 800 via communication link 220 to the dosage element 450. In response to this signal, the dosage element 450 will or will not add one or more additives to the flow of chemical composition through piping 425 to dosage element 450. When additives are added to the chemical composition, the chemical composition with the added additives flows back to dosing unit reservoir 400 via piping 430. Preferably, the dosing unit 450 includes a mixing element so that the chemical composition and any additives are well mixed.

Also based upon the signal from online monitor 800, the controller 200 determines whether or not to supply fresh chemical composition via piping 701 from fresh chemical composition supply tank 700 to dosing unit reservoir 400. Based upon a signal from controller 200 via communication link 260, an outlet valve of the fresh chemical composition supply tank 700 opens and a suitable delivery means allows the fresh chemical composition to flow therefrom to dosing unit 400.

The fresh chemical composition is understood to be those portions of the chemical composition, excluding any additives added to the chemical composition by dosing unit reservoir 400 and any degradation products formed as a result of the material treatment process. When the invention is preferably applied to management of electroplating baths for wafer plating tools at a semiconductor fab or foundry, the fresh chemical composition is also referred to as fresh inorganic solution. In this instance, the fresh inorganic solution primarily contains CuSO₄, H₂SO₄, and a source of Cl⁻.

Also based upon the signal from online monitor 800, the controller 200 determines whether or not to bleed chemical composition at fluid bleed tank 600 via outlet 610. Based upon a signal from controller 200 via communication link 270, chemical composition is bled from conduit 420 via a valve associated with piping 435. Preferably, the fluid bleed tank 600 includes a level sensor. When the level sensor senses a selected high level, an outlet valve of the fluid bleed tank 600 opens and chemical solution exits therefrom via outlet 610. In such a scenario, the valve and level sensor may optionally be associated with controller 200 and decisions to allow the chemical composition to exit from outlet 610 are made by the controller 200.

The fresh chemical composition at fresh chemical composition tank 700 may alternatively include one or more of the additives added to the chemical composition at dosing unit 400 or degradation products from the material treatment process. In that case, it contains only minimal concentrations of them. For example, spent chemical composition bled from fluid bleed tank 600 may be regenerated and then stored in fresh chemical composition supply tank 700.

With the aid of pump 440, the chemical composition flows from dosing unit reservoir 400 via conduit 420 to optional chemical delivery unit 110. Chemical delivery unit 110 includes a means suitable to deliver the chemical composition therefrom to chemical containing unit via optional conduit 460. The chemical composition then flows into the chemical containing unit 300 via inlet 320. It is understood that the system 100 may be configured such that the chemical composition flows directly from the dosing unit reservoir 400 to inlet 320 of chemical containing unit via conduit 420.

As best shown in FIG. 4, this embodiment 100 of the inventive system includes all the components illustrated in FIG. 2, except that four chemical containing units 300a-d and associated inlets 320a-d and outlets 330a-d along with associated communication links 250a-d are present. The benefits of implementing the invention with a plurality of chemical containing units is that such a centralized system helps to consistently maintain a chemical compositions having substantially the same properties at each of the chemical containing units even if they are running at different production capacities. In addition, one online monitor may be used for monitoring the bath composition for many tools, thereby reducing cost of ownership. Also, since the monitor and dosing unit is advantageously located in a separate location from the chemical containing units, chemical exchange and chemical handling are not performed in the location in which the material treatment process occurs. If the invention is implemented in management of electroplating bath solutions of wafer-plating tools in semiconductor fabs or foundries, the dosing unit and monitor may be located in the sub-fab room or chemical room, rather than the cleanroom area of the fab. Thus, less handling is done in the cleanroom thereby lessening the risk of contamination. In addition, there is a potentially smaller footprint in the cleanroom.

As best shown in FIG. 3, another preferred embodiment 100 of the system includes the same components illustrated in FIG. 2, except that four chemical containing units 300a-d, associated with inlets 320a-d, outlets 330a-d, and communication links 250a-d are used, and it further includes a second monitor 850 associated with a communication link 245 between the monitor 850 and controller 200, a chemical containing unit outlet reservoir 350, and a pump 360. Operation of this embodiment allows control over the quality of multiple chemical containing units, such as four chemical containing units 300a-d, in a centralized scheme.

In this embodiment, monitor 850 monitors a property of the chemical composition at reservoir 350 via piping 860 and returns it to reservoir 350 via piping 870. This embodiment is especially advantageous when the monitor 800, dosing unit reservoir 400 and dosage element 450 are located far from the chemical containing units 300a-d. For example, when the invention is implemented for management of electroplating baths of wafer-plating tools, the chemical containing units 300a-d (in this case wafer-plating tools) are located in the fab and the dosing unit reservoir 400, dosage element 450, and monitor 800 are located in the sub-fab room. Whether or not the invention is applied to management of these baths, the following situation occurs. For a given plug of chemical composition flow, monitoring of a property by monitor 850 and monitor 800 may result in different measurements due to the lag time of the plug's flow between reservoir 350 and dosing unit reservoir 400. In order to help compensate for this difference, monitor 850 and monitor 800 together provide signals to controller 200 regarding the monitored property via communication links 245 and 240. Based upon these signals, the controller 200 will implement the best decision regarding the addition of one or more additives to the chemical composition. Also, if monitor 800 detects potential contamination of the chemical composition, selected valves isolating the chemical composition in the chemical treatment units and associated piping and the dosing unit may be shut down so as to not contaminate the whole system.

A preferred embodiment of the dosage element 450 is best illustrated in FIG. 5. During a period in which the additives are not being added to the chemical composition, flow of the composition to dosage element 450 via piping 425 does not ordinarily occur (by action of closed valves not shown). When the controller 200 sends a signal to the dosage element to begin dosing the additives to the composition, pump 415 is activated and the composition flows to dosage element 450 via piping 425 into conduit 426. Addition to the chemical composition of additive from additive container 480a is described below.

At the moment that dosage element 450 receives a signal from the controller 200 to begin dosing the additive from container 480a, a flushing cycle is initiated. In the flushing cycle, valve 471 is opened. This operation lasts for a specified time in order to flush the contents of the line from valve 471 to valve 473. After the flush has been completed, the pump is deactivated, and valves 473, 471 are closed. The dosing element 450 receives another signal from the controller 200 to begin dosing the additive from container 480a, the three way valve 428a is opened, the pump 472 is activated, and valve 473 is opened. At this point, the upstream portion of three-way valve 428a is closed while the other two portions are open. Also the in-line portions of valves 428b, 428c and 428d are opened while the remaining portions of these valves adjacent conduits 429b, 429c and 429d remain closed. By action of pump 472, the additive from container 480a flows through conduit 429a and past conduit 427b, open three-way valve 428b, conduit 427c, open three-way valve 428c, conduit 427d, open three-way valve 428d, and into conduit 427e past pump 472. The amount of the additive is preferably controlled by one of two methods. The flow rate at flow meter 474 is monitored during the flushing cycle and then integrated over time, thereby yielding a relationship between the volume of flow past the pump 472 and the time during which the pump 472 is activated. Based upon this time/flow relationship, the amount of time which pump 472 is activated during the dosing determines the volume of additive added.

When the selected amount of additive from container 480a is determined to be introduced into conduit 427b or downstream thereof, the upstream and downstream portions of three-way valve 428a adjacent conduits 427a and 427b are opened and the remaining portion adjacent conduit 429a is closed. Substantially simultaneously, valve 471 is opened and by action of pumps 472 and 415, the chemical composition flows into conduit 427a via conduit 426 and piping 425. The in-line portions of three-way valves 428b, 428c and 428d are open, thereby allowing the chemical composition to flow through conduits 427b, 427c, 427d, 427e, and valve 473. The chemical composition then enters conduit 431 where it is directed to piping 430 via pump 415 and into the dosing unit reservoir 400. If the controller 200 indicates that no other additive should be dosed, once a selected amount of chemical composition has flowed through this loop of conduits parallel conduit 426, valves 471 and 473 are closed and pumps 472 and 415 shut down. At this point, flow of the chemical composition between dosing unit reservoir 400 and dosage element 450 is interrupted.

Those skilled in the art will understand that addition of any other of the additives from containers 480b, 480c or 480d may be achieved in the same manner with the addition and flushing sequences as described above.

A preferred embodiment of chemical delivery unit 110 is best illustrated in FIG. 6. Chemical composition flows into day tank 160 via either conduits 150 or 420. The chemical composition flows out of day tank 160 through conduit 161 and into pressure-feed vessel 120a, while at the same time chemical composition flows out of pressure-feed vessels 120b and into conduit 460 by action of blanket gas system 130. Flow of chemical composition through conduit 161 and into or out of pressure feed vessels 120a and b is achieved by known arrangements of valving in order to avoid mixing the two flows. When a sensor in pressure-feed vessel 120a senses a high liquid level and a sensor in pressure-feed vessel 120b senses a low liquid level, flow of the chemical composition thereinto is interrupted, while at the same time, flow out of pressure-feed vessel 120b is also interrupted. At this point, the filling and emptying of the two pressure-feed vessels 120a, b is switched, i.e., pressure-feed vessel 120a is emptied by flow of chemical composition out of it and into conduit 460 by blanket gas system 130, while pressure-feed vessel 120b is being filled.

Pressure sensors may be used to determine the beginning and end of a fill or empty cycle as described above instead of liquid level sensors.

The online monitor 800 may be any online monitor known to those ordinarily skilled in the art suitable for use in the invention. A preferred online monitor is a “real-time analyzer”, RTA, available from Technic, Inc, Cranston, in R.I., U.S.A. Another monitor suitable for use in the invention is the ECI system available from ATMI, Danbury, Conn., U.S.A.

Optionally and in some situations, based upon a signal from online monitor 800, the controller 200 determines that the flow of chemical composition should bypass the dosing unit reservoir 400. This situation is especially desirable when the controller 200 determines that the one or more additives should be added to the chemical composition at dosing unit reservoir 400 by dosage element 450.

The above bypass is implemented in the following manner. Controller 200 determines whether or not to allow the flow of chemical composition to bypass the dosing unit reservoir 400. A signal based upon this determination is sent from controller 200 to valves 151 and 152 via communication links 251 and 252 to allow the valves to remain open, remain closed, open from a closed position, or close from an open position. When chemical composition is flowing from chemical containing unit 300 to dosing unit reservoir 400 via outlet 330 and conduit 140, a decision by the controller 200 to allow the chemical composition to bypass these components results in a signal from controller 200 to close valve 151 and open valve 152. The chemical composition then leaves conduit 140, enters conduit 150 and flows to chemical delivery unit 110. In this instance, pump 440 is actuated such that the flow of chemical composition from dosing unit reservoir 400 to the optional chemical delivery unit is interrupted. Actuation of the pump 440 is preferably controlled by the controller 200 at the same time the bypass is implemented. Otherwise, the pump 440 could be damaged.

As described above, the flow of chemical composition may optionally be allowed to bypass the dosing unit reservoir 400 because the controller 200 determines that one or more additives should be added to the chemical composition. In this instance and contemporaneously with the bypass of the flow of chemical composition via conduit 150 as described above, a flow of chemical composition to and from the dosing unit reservoir 400 and dosage element 450 via piping 425 and 430 occurs. The one or more additives are then added to the chemical composition by dosage element 450 as described above. When addition to the chemical composition of the one or more additives is completed and the combined chemical composition and additives enter the dosing unit reservoir 400, controller 200 sends signals to valve 151 to open and valve 152 to close, thereby allowing the chemical composition to flow from chemical containing unit 300 to dosing unit reservoir 400.

Preferably, when one or more additives are being added to the chemical composition by dosage element 450, an otherwise interrupted flow of chemical composition from/to the dosing unit reservoir 400/dosage element 450 via piping 425 and 430 is allowed to commence. This may occur by actuation of one or more valves to close and operation of one or more pumps to be interrupted. At the same time, the chemical composition from chemical containing unit 300 bypasses dosing unit reservoir 400 as described above.

Also preferably, when addition to the chemical composition of the one or more additives is completed, the flow of chemical composition from/to the dosing unit reservoir 400/dosage element 450 via piping 425 and 430 ceases. At the same time, controller 200 sends signals to valve 151 to open and valve 152 to close, thereby allowing the chemical composition to flow from chemical containing unit 300 to dosing unit reservoir 400.

It should be understood that valves 151, 152 could be electric solenoid or pneumatic valves. In the case of electric solenoid valves actuation of valves 151, 152 is performed as described above, i.e., by the sending of a signal from controller 200. However, it should be also be understood that in the case of pneumatic valves, they need not be actuated directly by controller 200 via signals along communication links 251, 252. For example, the controller may send a signal to a source of compressed air which then pressurizes a pneumatic line which ultimately opens or closes a pneumatic valve. The source of compressed may be located adjacent the controller 200, at the valve 151, 152, or any point therebetween. For that matter, any pneumatic valve or pump may be controlled by controller 200 in this manner.

In these above preferred situations, two modes of chemical composition flow are described. When no addition of one or more additives to the chemical composition occurs, a main recirculation mode is present and the chemical composition is allowed to flow from the chemical containing unit 300 to the dosing unit reservoir 400 and thenceforth to optional chemical delivery unit 110 via conduit 420 and optional conduit 46 to chemical containing unit 300. This flow is referred to as loop C.

When addition of one or more additives to the chemical composition does occur, a dosing mode is present and the chemical composition flows from the chemical containing unit 300 through outlet 330, conduit 150 to chemical delivery unit 110 and thence forth to the chemical containing unit 300 via conduit 460 and inlet 320. This flow is referred to as loop A. In the same mode and at the same time, the chemical composition flows from/to the dosing unit reservoir 400/dosage element 450 via piping 425 and 430. This flow is referred to as loop B. The benefits of such a two-mode system are that solution recirculation feeding the chemical containing unit (or wafer-coating tool if the invention is implemented in management of electroplating bath solutions) can still be done while dosing inside the dosing unit is occurring. Thus continuous chemical delivery is achieved.

Predictive Corrective Controller

While any one of the closed-loop control schemes known in the art may be used with controllers 65, 200, the inventors have invented a particularly advantageous control solution that overcomes the disadvantages presented by the prior art. The solution is a control system (programmable logic controller (PLC), Industrial PC or alike) suitably programmed with a closed loop feedback dosing algorithm that utilizes actual process concentration data to correct for consumption of critical components in the chemical composition. It may also provide a predicted dosing volume in-between actual concentration data times, if the later are too large. It may also correct the dose when an actual value becomes available. It maintains the levels of one or more additives within a desired range by specifying amounts of additives and/or fresh chemical composition to be added to the chemical composition, as well as specifying when preset volumes of chemical composition should be bled from the system.

The algorithm has several advantages. It is substantially independent of any changes in the kinetics of the chemical composition constituents, such as consumption rates, production mode, as well as independent of process tool specificities. It is also substantially independent of changes in the chemical composition's chemistry, such as variance of bulk chemical supplies, acidity, etc. Also, it is not dependent upon any one type of online monitor. Additionally, it is also scalable and thus able to support multiple chemical composition management configurations. Furthermore, the dosing frequency is tunable and dosing could take place even if actual process concentration data are not continuously available. In other words, addition of one or more additives may be made in between actual measurements of one or more properties by a monitor. Finally, the controller is robust enough to tolerate variable bath bleeding rates and typical process disturbances, such as addition of deionized water.

Due to the long sampling time of current online analyzers, the algorithm will predict concentrations at a desired frequency, also known as the dosing frequency. Each set of data either monitored or predicted is inspected by a diagnostic function to determine whether the operating mode of the system should be switched from the main recirculation mode to the dosing mode. If addition of one or more additives is determined by the algorithm as necessary, the controller will put the system in the dosing mode. As a result, the flow through loop C will be interrupted and flows through loops A and B commenced.

The algorithm will compute additive and fresh chemical composition volumes to bring all chemical composition concentrations of interest back to setpoint values. The calculated volumes are introduced into the system as described above. When the chemical composition and additives are deemed to be suitably mixed, the system is switched back from the dosing mode to the main recirculation mode and flow through loop C resumed.

In the absence of any control, the additive concentrations in the chemical composition will naturally deplete as a result of the ongoing material treatment process. If no action is taken, such concentrations will eventually cross below a threshold resulting in improper material treatment. In the case of electroplating bath solutions for wafer-coating, such phenomena as unacceptable metal deposition and formation of voids may occur.

For each additive, the dosing aims to re-establish target concentration in the solution. At time t, flows of the chemical composition through loops A and B commence. The concentration in the chemical containing unit will continue to decrease at rate r(t) due to the on-going material treatment process. The dosing is performed in the dosing unit by adding a volume V_dosed(t) of nominal additive at time t. Such a volume will make the system's additive concentration within a predetermined concentration range around the setpoint when the recirculation mode commences again at time t+Δt.

Various aspects of the predictive corrective algorithm are now described as follows.

TABLE IV
Nomenclature
Component Symbol
Continuous	Discrete
Time	Time	Description
VPT		Chemical containing
		unit volume
VBT		Dosing unit reservoir
		volume
Vdosed(t)	Vi	Volume Dosed at time
		t or ti
Vbleed(t) = α(t) · VBT	αi · VBT	Volume Bled at time
		t or ti
C0		Target concentration in
		chemical containing unit
{overscore (C)}		Nominal concentration of
		chemical additive
t	ti	Time the dosing is
		started or ith
		dosing time
	θRTA	Monitor time delay
	$f_s=\frac{1}{{\theta }_{\mathrm{RTA}}}$	Monitor sampling frequency
$\mathrm{\Delta t}=N·{\theta }_{\mathrm{RTA}},N\in \{1,2,\dots \}$	Δt = ti+1 − ti	Dosing period
$f_d=\frac{1}{\mathrm{\Delta t}}$		Dosing frequency
CPT(t)	Ci,PT	Concentration in
		chemical containing
		unit at time t or ti
CPT(t + Δt)	Ci+1,PT	Concentration in
		chemical containing
		unit at time t +
		Δt or ti+1
CBT(t)	Ci,BT	Concentration in
		dosing unit
		reservoir at time
		t or ti
C(t)	Ci	Concentration in
		chemical containing
		unit or dosing unit
		reservoir at time t or ti
$r\left(t\right)=\stackrel{.}{C}\left(t\right)=\frac{dC}{dt}$	$r_i={\stackrel{.}{C}}_i$	Chemical Consumption Rate at time t or ti
$\delta \left(t\right)=\ddot{C}\left(t\right)=\frac{d^{2}C}{{\mathrm{dt}}^2}$	${\delta }_i={\ddot{C}}_i$	Consumption Rate variation at time t or ti
{circumflex over (X)}(t)	{circumflex over (X)}i	Estimated value of
		physical quantity X
		(C, r, . . . etc) at time
		t or ti

TABLE VI
Assumptions
Assumption	Continuous Time	Discrete Time
1	Perfect mixing	CPT(t) = CBT(t) = C(t)	Ci,PT = Ci,BT = Ci
	during recirculation
2	Dosing reservoir is	CBT(t) = CBT(t + Δt)	Ci,BT = Ci+1,BT
	reaction free:
3	Constant Consumption Rate over θRTA:	$\begin{array}{c}r\left(t-\mathrm{\Delta t}\right)=r\left(t-{\theta }_{\mathrm{RTA}}\right)\forall \mathrm{\Delta t}\in \left[0,{\theta }_{\mathrm{RTA}}\right]\\ C_{\mathrm{PT}}\left(t\right)={\int }_{t-\mathrm{\Delta t}}^{t}r\left(t-\mathrm{\Delta t}\right)dx+C_{\mathrm{PT}}\left(t-\mathrm{\Delta t}\right)\\ =r\left(t-{\theta }_{\mathrm{RTA}}\right)\mathrm{\Delta t}+C_{\mathrm{PT}}\left(t-\mathrm{\Delta t}\right)\end{array}\hspace{1em}$	Ci,PT = ri−1Δt + Ci−1,PT
4	Constant Consumption Rate variation over 2θRTA:	$\begin{array}{c}\delta \left(t-\mathrm{\Delta t}\right)=\delta \left(t-2{\theta }_{\mathrm{RTA}}\right)\forall \mathrm{\Delta t}\in \left[0,{\theta }_{\mathrm{RTA}}\right]\\ r\left(t\right)={\int }_{t-\mathrm{\Delta t}}^t\delta \left(t-\mathrm{\Delta t}\right)dx+r\left(t-\mathrm{\Delta t}\right)\\ =2\delta \left(t-2{\theta }_{\mathrm{RTA}}\right)\mathrm{\Delta t}+r\left(t-\mathrm{\Delta t}\right)\end{array}\hspace{1em}\hspace{1em}$	ri = δi−1Δt + ri−1

1. Dosing Algorithm for Single Component Case:
a) Continuous-Time Single Component Dosing (CTSC)

In one preferred embodiment, dosing is performed in the dosing unit reservoir 400 by adding a volume V_dosed(t) of nominal solution at time t. Such volume will make the system's concentration reach its target value at time t+Δt. This statement translates into the following equation:
(Mass in System at t+Δt)=(Mass in dosing unit reservoir at t)+(Mass added into dosing unit reservoir at t)+(Mass in chemical containing unit at t+Δt)−(Mass bled off the System at t)  Eq. 1 $\begin{array}{cc}\begin{array}{c}{C}_0·\left(V_{\mathrm{BT}}+V_{\mathrm{PT}}+V_{\mathrm{dosed}}\left(t\right)\right)=C_{\mathrm{BT}}\left(t\right)·V_{\mathrm{BT}}+\stackrel{\_}{C}·V_{\mathrm{dosed}}\left(t\right)+\\ C_{\mathrm{PT}}\left(t+\Delta t\right)·V_{\mathrm{PT}}-V_{\mathrm{bleed}}\left(t\right)·C\left(t\right)\\ =\left(1-\alpha \left(t\right)\right)·C\left(t\right)·V_{\mathrm{BT}}+\stackrel{\_}{C}·\\ V_{\mathrm{dosed}}\left(t\right)+C\left(t+\Delta t\right)·V_{\mathrm{PT}}\end{array}& \mathrm{Eq}.2\end{array}$
V_dosed(t) may be solved: $\begin{array}{cc}{V}_{\mathrm{dosed}}\left(t\right)=\frac{\left[C_0-\left(1-\alpha \left(t\right)\right)·C\left(t\right)\right]·V_{\mathrm{BT}}+\left[C_0-C\left(t+\Delta t\right)\right]·V_{\mathrm{PT}}}{\stackrel{\_}{C}-C_0}& \mathrm{Eq}.3\end{array}$

In the previous expression the concentrations at time t and at time t+Δt are unknown. It takes θ_RtA for the monitor to generate one set of results. Only C (t−θ_RTA) and the previous rate are available through the monitor 800 and/or direct computation respectively. Using assumption 3, one can estimate the concentration at time t:
Ĉ(t)=r(t−Δt)Δt+C(t−Δt)  Eq. 4

Furthermore, the concentration at the end of the dosing period i.e. at t+Δt is not known. The consumption rate is not necessarily constant from one sampling period to the next. However, using assumption 4, one can estimate the consumption rate:
{circumflex over (r)}(t)=δ(t−Δt)Δt+r(t−Δt)  Eq. 5

Thus, the estimated concentration at t+Δt using Eq. 4 and Eq. 5 is: $\begin{array}{cc}\begin{array}{c}\hat{C}\left(t+\Delta t\right)=\hat{r}\left(t\right)\Delta t+\hat{C}\left(t\right)=\left[\delta \left(t-\Delta t\right)\Delta t+r\left(t-\Delta t\right)\right]·\\ \Delta t+r\left(t-\Delta t\right)\Delta t+C\left(t-\Delta t\right)\\ =\delta \left(t-\Delta t\right){\left(\Delta t\right)}^2+2r\left(t-\Delta t\right)\Delta t+\\ C\left(t-\Delta t\right)\end{array}& \mathrm{Eq}.6\end{array}$

Eq. 3 may be rewritten by replacing the concentration at time t [C(t)] and consumption rate [{circumflex over (r)}(t)] by their estimated values in Eq. 4 and in Eq. 6 respectively to determine the volume to be dosed into the system: $\begin{array}{cc}{\hat{V}}_{\mathrm{dosed}}\left(t\right)=\frac{\begin{array}{c}\left\{C_0-\left(1-\alpha \left(t\right)\right)·\left[r\left(t-\Delta t\right)\Delta t+C\left(t-\Delta t\right)\right]\right\}·V_{\mathrm{BT}}+\\ \left\{C_0-\lfloor \delta \left(t-\Delta t\right){\left(\Delta t\right)}^2+2r\left(t-\Delta t\right)\Delta t+C\left(t-\Delta t\right)\rfloor \right\}·V_{\mathrm{PT}}\end{array}}{\stackrel{\_}{C}-C_0}& \mathrm{Eq}.7\end{array}$
b) Discrete Time Single Component (DTSC) Dosing Algorithm:

In another preferred embodiment, the CTSC dosing algorithm utilizes a discrete time controller to control the chemical composition concentration. Like in the continuous case, the volume V_i of nominal solution at time t_i will make the system's concentration reach its target value when the blending tank unit 400 is interfaced at time t_i+1. This statement translates into the following equation:
(Mass in System at t_i+1)=(Mass in dosing unit reservoir at t_i)+(Mass added to dosing unit reservoir at t_i)+(Mass in chemical containing unit at t_i+1)−(Mass bled off the System at t_i)  Eq. 1′
C₀·(V_BT+V_PT+V_i)=C_i·V_BT+{overscore (C)}·V_i+C_i+1·V_PT−α_i·V_BT·C_i  Eq. 2′

V_i may be solved: $\begin{array}{cc}{V}_i=\frac{\left[C_0-\left(1-{\alpha }_i\right)·C_i\right]·V_{\mathrm{BT}}+\left[C_0-C_{i+1}\right]·V_{\mathrm{PT}}}{\stackrel{\_}{C}-C_0}& \mathrm{Eq}.3^{\prime }\end{array}$

The concentrations C_i and C_i+1 are unknown. Using assumption 3, one can estimate the concentration at time t_i: $\begin{array}{cc}{\hat{C}}_i=r_{i-1}\Delta t+C_{i-1}=\sum _{k=0}^{i-1}{r}_k\Delta t+C_0& \mathrm{Eq}.4^{\prime }\end{array}$

Using assumption 4, one can estimate the consumption rate: $\begin{array}{cc}{\hat{r}}_i={\delta }_{i-1}\Delta t+r_{i-1}=\sum _{k=0}^{i-1}{\delta }_k\Delta t+r_0& \mathrm{Eq}.5^{\prime }\end{array}$

The estimated concentration at t_i+1 using Eq. 4′ and Eq. 5′ is: $\begin{array}{cc}{\hat{C}}_{i+1}=\left(\sum _{k=0}^{i-1}{\delta }_k\Delta t+r_0\right)\Delta t+\sum _{k=0}^{i-1}{r}_k\Delta t+C_0& \mathrm{Eq}.6^{\prime }\end{array}$

Eq. 3′ may be rewritten using Eq. 4′ and Eq. 6′ to determine the volume to be dosed into the system: $\begin{array}{cc}{\hat{V}}_i=\frac{\begin{array}{c}\left({\alpha }_i·C_0-\left(1-{\alpha }_i\right)·\sum _{k=0}^{i-1}{r}_k\Delta t\right)V_{\mathrm{BT}}+\\ \left(\sum _{k=0}^{i-1}{\delta }_k\Delta t+r_0+\sum _{k=0}^{i-1}{r}_k\right)\Delta t·V_{\mathrm{PT}}\end{array}}{C_0-\stackrel{\_}{C}}& \mathrm{Eq}.7^{\prime }\end{array}$
2. Dosing Algorithm for Multi-Component Case:
a) Discrete Time Multi-Component (DTMC) Dosing Algorithm:

In another preferred embodiment, multiple components are controlled using a discrete time algorithm in the controller 200. Like in the single component case, the volume V_i,j of Component j nominal solution at time t_i will make the system's j^th concentration reach its target value when the dosing unit reservoir 400 is circulated back to the chemical containing unit 300 at time t_i+1. This statement translates into the following equation:
(Mass of j^th Component in System at t_i+1)=(Mass of j^th Component in dosing unit reservoir at t_i)+(Mass of j^th Component added to dosing unit reservoir at t_i)+
(Mass of j^th Component in chemical containing unit at t_i+1)−(Mass of j^th Component bled off the System at t_i)  Eq. 1″ $\begin{array}{cc}{C}_{0,j}·\left(V_{\mathrm{BT}}+V_{\mathrm{PT}}+\sum _{k=1}^n{V}_{i,k}\right)=C_{i,j}·V_{\mathrm{BT}}+\stackrel{\_}{C_j}·V_{i,j}+C_{i+1,j}·V_{\mathrm{PT}}-{\alpha }_i·V_{\mathrm{BT}}·C_{i,j}j\in \left[1,n\right]& \mathrm{Eq}.2^{″}\end{array}$ $\mathrm{Let}{C}_i=\left[\begin{array}{c}{C}_{i,1}\\ \dots \\ C_{i,j}\\ \dots \\ C_{i,n}\end{array}\right],V_i=\left[\begin{array}{c}{V}_{i,1}\\ \dots \\ V_{i,j}\\ \dots \\ V_{i,n}\end{array}\right]\mathrm{and}$ $A=\left[\begin{array}{ccccc}\left(C_{0,1}-{\stackrel{\_}{C}}_1\right)& C_{0,1}& \dots & \dots & C_{0,1}\\ \dots & \dots & \dots & \dots & \dots \\ C_{0,j}& \dots & \left(C_{0,j}-{\stackrel{\_}{C}}_j\right)& \dots & C_{0,j}\\ \dots & \dots & \dots & \dots & \dots \\ C_{0,n}& \dots & \dots & C_{0,n}& \left(C_{0,n}-{\stackrel{\_}{C}}_n\right)\end{array}\right]$

Using the above notations, Eq. 2″ becomes:
V_i=A⁻¹·[((1−α_i)·C_i−C₀)·V_BT+(C_i+1−C₀)·V_PT]  Eq. 3″

In the previous expression the concentration vectors C_i and C_i+1 are unknown but can be estimated. If $r_i=\left[\begin{array}{c}{r}_{i,1}\\ \dots \\ r_{i,j}\\ \dots \\ r_{i,n}\end{array}\right]$
is the rate vector, then the current (i.e. at time t_i) concentration vector: $\begin{array}{cc}{\hat{C}}_i=r_{i-1}\Delta t+C_{i-1}=\sum _{k=0}^{i-1}{r}_k\Delta t+C_0& \mathrm{Eq}.4^{″}\end{array}$

Like in the single component case, one can estimate the current consumption rate vector: $\begin{array}{cc}{\hat{r}}_i={\delta }_{i-1}\Delta t+r_{i-1}=\sum _{k=0}^{i-1}{\delta }_k\Delta t+r_0& \mathrm{Eq}.5^{″}\end{array}$

The concentration vector may be estimated at t_i+1 using Eq. 4″ and Eq. 5″: $\begin{array}{cc}{\hat{C}}_{i+1}=\left(\sum _{k=0}^{i-1}{\delta }_k\Delta t+r_0\right)\Delta t+\sum _{k=0}^{i-1}{r}_k\Delta t+C_0& \mathrm{Eq}.6^{″}\end{array}$

Eq. 3″ may be rewritten using Eq. 4″ and Eq. 6″ to determine the volume to be dosed into the system: $\begin{array}{cc}\begin{array}{c}{\hat{V}}_i=A^{-1}·[\left(\left(1-{\alpha }_i\right)·\sum _{k=0}^{i-1}{r}_k\Delta t-{\alpha }_i·C_0\right)V_{\mathrm{BT}}+\\ \left(\sum _{k=0}^{i-1}{\delta }_k\Delta t+r_0+\sum _{k=0}^{i-1}{r}_k\right)\Delta t·V_{\mathrm{PT}}]\end{array}& \mathrm{Eq}.7^{″}\end{array}$
b) Corrected Discrete Time Multi-Component (CDTMC) Dosing Algorithm:

In another preferred embodiment, a monitor is used to correct the DTMC dosing volume. The monitor utilized for concentration measurements can have a significant dead time θ_RTA. In other words: $\hspace{1em}\{\begin{array}{c}{C}_{\mathrm{measured}}\left(t\right)=C_{\mathrm{actual}}\left(t-{\theta }_{\mathrm{RTA}}\right),0\le t<\infty \\ C_{\mathrm{measured}}\left(t\right)=0,t<0\end{array}$

The monitor transfer function in the s-domain (frequency domain) is C_measured(s)=e^−sθRTA·C_actual(s). However, this formulation is impractical as the actual concentration is being sampled. Therefore, a discrete time representation in the z-domain may be utilized:
C_i,measured=Z^−θRTA·C_i,actual where z=e^sθRTA meaning that
C_i,j^measured=z^−θRTA·C_i,j^actual=C_i−1,j^measured.

Due to the monitor dead time, C_i is available at t_i+1 and C_i+1 at t_i+2. Therefore at t_i+2, one must correct the dosed volume calculated based on the reading at time t_i. The error of the dosed volume of the j^th at t_i−2 is defined and corrected at t_i as follows: $\begin{array}{cc}\{\begin{array}{c}{\varepsilon }_{i,j}={\lambda }_j·\left(V_{i-2,j}-{\hat{V}}_{i-2,j}\right)+\left(1-{\lambda }_j\right)·{\varepsilon }_{i-1,j},i\ge 2\\ {\varepsilon }_{1,j}={\varepsilon }_{0,j}=0\end{array}& \mathrm{Eq}.8^{″}\end{array}$

This exponentially weighted moving average error is either positive or negative. To demonstrate that the error ε_i,j is a weighted average of all the previous deviations of the estimated volume from the real dosed volume, recursively for ε_i−k,j is substituted recursively: $\hspace{1em}\begin{array}{cc}\{\begin{array}{c}{\varepsilon }_{i,j}={\lambda }_j·\sum _{k=2}^i{\left(1-{\lambda }_j\right)}^{i-k}·\left(V_{k-2,j}-{\hat{V}}_{k-2,j}\right)+{\left(1-{\lambda }_j\right)}^{i-1}·{\varepsilon }_{1,j},i\ge 2\\ {\varepsilon }_{1,j}={\varepsilon }_{0,j}=0\end{array}& \mathrm{Eq}.9^{″}\end{array}$

The weights ${\lambda }_j·\sum _{k=2}^i{\left(1-{\lambda }_j\right)}^{i-k}$
decrease geometrically with the age of the error.

Furthermore, the weights sum to unity, since: $\begin{array}{cc}{\lambda }_j·\sum _{k=2}^i{\left(1-{\lambda }_j\right)}^{i-k}={\lambda }_j·\sum _{k=0}^{i-2}{\left(1-{\lambda }_j\right)}^k={\lambda }_j·\frac{1-{\left(1-{\lambda }_j\right)}^{i-3}}{1-\left(1-{\lambda }_j\right)}=1-{\left(1-{\lambda }_j\right)}^{i-3}& \mathrm{Eq}.{10}^{″}\end{array}$

Let $\lambda =\left[\begin{array}{ccccc}{\lambda }_1& 0& \cdots & \cdots & 0\\ 0& \cdots & \cdots & \cdots & \cdots \\ \cdots & \cdots & {\lambda }_j& \cdots & \cdots \\ \cdots & \cdots & \cdots & \cdots & 0\\ 0& \cdots & \cdots & 0& {\lambda }_n\end{array}\right]$
the diagonal matrix of the weights of each component
and ${\varepsilon }_i=\left[\begin{array}{c}{\varepsilon }_{i,1}\\ \cdots \\ {\varepsilon }_{i,j}\\ \cdots \\ {\varepsilon }_{i,n}\end{array}\right].$

Using the above notations, Eq. 8″ becomes: $\begin{array}{cc}\{\begin{array}{c}{\varepsilon }_i=\lambda ·\left(V_{i-2}-{\hat{V}}_{i-2}\right)+\left(I-\lambda \right)·{\varepsilon }_{i-1},i\ge 2\\ {\varepsilon }_0={\varepsilon }_1=0\end{array}& \mathrm{Eq}.{11}^{″}\end{array}$

ε_i−k is recursively substituted: $\hspace{1em}\begin{array}{cc}\{\begin{array}{c}{\varepsilon }_i=\sum _{k=2}^i{\left(I-\lambda \right)}^{i-k}·\lambda ·\left(V_{k-2}-{\hat{V}}_{k-2}\right)+{\left(I-\lambda \right)}^{i-1}·{\varepsilon }_1,i\ge 2\\ {\varepsilon }_0={\varepsilon }_1=0\end{array}& \mathrm{Eq}.{12}^{″}\end{array}$

Thus, the corrected volume at time t_i can be calculated as follows: $\begin{array}{cc}{\hat{V}}_i=A^{-1}·\left[\left(\left(1-{\alpha }_i\right)·\sum _{k=0}^{i-1}{r}_k\Delta t-{\alpha }_i·{ℂ}_0\right)V_{\mathrm{BT}}+\left(\sum _{k=0}^{i-1}{\delta }_k\Delta t+r_0+\sum _{k=0}^{i-1}{r}_k\right)\Delta t·V_{\mathrm{PT}}\right]\pm {\varepsilon }_i& \mathrm{Eq}.{13}^{″}\end{array}$

In equation 13″, absolute value of error is added when under dosing occurred at previous time step, otherwise value of error is subtracted when over dosing occurred at previous time step.

As seen above, the algorithm determines a rate of depletion over a depletion time period of at least one of the additives in the chemical composition based upon a concentration of the additive measured by the monitor in comparison to a concentration of the additive previously measured by the monitor. The algorithm also predicts an amount of at least one additive that when added to the chemical composition will maintain a concentration of the additive within a predetermined concentration range around a predetermined setpoint concentration. The algorithm also corrects the predicted amount by adding to, or subtracting from, the predicted amount, an amount of the additive based upon previous concentrations of the additive measured by the monitor. The corrected amount is the dose added to the chemical composition by the dosage element.

In contrast to prior art controllers, the algorithm has the following additional novel features. The amount added to or subtracted from the predicted amount is based upon at least two previous measurements by the monitor of the concentration of the at least one additive. Also, the time interval between additions of the at least one additive is less than a time interval between measurements by said monitor. Furthermore, the time interval in between additions is also tunable, i.e., it may be varied to any interval no less than the time it takes the dosage element to add the at least one additive. Moreover, the predicted amount is also based upon a derivative of the depletion rate. Finally, the predicted amount does not depend upon a variable condition at said chemical containing unit.

Having described novel systems and methods for monitoring, dosing and distribution of chemical compositions in material treatment processes, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the claims.

Claims

1. A system for monitoring, dosing and distribution of a chemical composition in a material treatment process, the chemical composition containing at least one additive for maintaining quality of the chemical treatment process, said system comprising:

at least one chemical containing unit configured to contain the chemical composition for the chemical treatment process;

a dosing unit fluidly communicating with said at least one chemical containing unit configured to receive the chemical composition therefrom and to add a selected dose of the at least one additive to the chemical composition therein;

a online monitor configured to monitor a property of the chemical composition at said dosing unit and to transmit a signal corresponding to the monitored property; and

a controller programmed and configured to receive the signal from said online monitor and send a signal to said dosing unit to add the selected dose to the chemical composition therein in response to the monitored property.

2. The system of claim 1, wherein the controller comprises a processor programmed with an algorithm such that the processor:

determines a rate of depletion over a depletion time period of at least one of the at least one additive in the chemical composition based upon a concentration of the at least one of the at least one additive measured by said monitor in comparison to a concentration of the at least one of the at least one additive which was last measured by said monitor;

predicts an amount of the at least one of the at least one additive that when added to the chemical composition will maintain a concentration of the additive within a predetermined concentration range around a predetermined setpoint concentration; and

corrects the predicted amount by adding to, or subtracting from, the predicted amount, an amount of the at least one additive based upon a previous measurement by said monitor of the concentration of the at least one additive, wherein the corrected amount is the selected dose.

3. The system of claim 1, wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

4. The system of claim 2, wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

5. The system of claim 1, further comprising:

a chemical delivery unit in fluid communication with said at least one chemical containing unit and said dosing unit and configured to deliver the chemical composition to said at least one chemical containing unit

6. The system of claim 5, further comprising:

a first valve arrangement in fluid communication with said chemical containing unit and said dosing unit, said first valve arrangement configured to allow or prevent a flow of the chemical composition from said chemical containing unit to said dosing unit; and

a second valve arrangement in fluid communication with said chemical containing unit and said chemical delivery unit, said second valve arrangement configured to allow or prevent a flow of the chemical composition from said chemical containing unit to said chemical delivery unit.

7. The system of claim 6, wherein said controller comprises a processor programmed with an algorithm such that it:

determines whether said system should operate in a main recirculation mode in which said first valve arrangement allows a flow of the chemical composition from said at least one chemical containing unit to said dosing unit and said second valve arrangement prevents a flow of the chemical composition from said at least one chemical containing unit to said dosing unit, or in a dosing mode in which said first valve arrangement prevents a flow of the chemical composition from said chemical containing unit to said dosing unit and allows a flow of the chemical composition from said at least one chemical containing unit to said chemical delivery unit.

8. The system of claim 7, wherein in response to said algorithm determining that the system should operate in the main recirculation mode, said controller i) sends a signal to either open said first valve arrangement or to allow said first valve arrangement to remain open so that a flow of the chemical composition is allowed from said at least one chemical containing unit to said dosing unit, and ii) sends a signal either to close said second valve arrangement or to allow said second valve arrangement to remain open so that a flow of the chemical composition is prevented from said at least one chemical containing unit to said dosing unit.

9. The system of claim 8, wherein said dosing unit comprises:

a dosing unit reservoir configured to receive a flow of the chemical composition from said at least one chemical containing unit and direct a flow of the chemical composition from said dosing unit to said chemical delivery unit; and

a dosage element configured to receive a flow of the chemical composition from said dosing unit reservoir and direct a flow of the chemical composition to said dosing unit reservoir, said dosage element also configured to add the selected dose to the chemical composition, wherein in response to said algorithm determining that the system should operate in the dosing mode, said controller i) sends a signal to and actuates said first valve arrangement to prevent a flow of the chemical composition from said at least one chemical containing unit to said dosing unit, and sends a signal to and actuates said second valve arrangement to allow a flow of the chemical composition from said at least one chemical containing unit to said chemical delivery unit.

10. The system of claim 9, wherein:

said first valve arrangement comprises a first valve, a first conduit in fluid communication with and extending from said chemical containing unit to said first valve, and a second conduit in fluid communication with and extending from said first valve to said dosing unit, said first valve disposed intermediate said first and second conduits, wherein an open position of said first valve allows a flow of the chemical composition from said first conduit to said second conduit and a closed position of said first valve prevents a flow of the chemical composition from said first conduit to said second conduit;

said second valve arrangement comprises a second valve, a third conduit in fluid communication with and extending from said first conduit to said second valve, and a fourth conduit in fluid communication with and extending from said second valve to said chemical delivery unit, said second valve disposed intermediate said third and fourth conduits, wherein an open position of said second valve allows a flow of the chemical composition from said first conduit to said fourth conduit via said third conduit and a closed position of said second valve prevents a flow of the chemical composition from said third conduit to said fourth conduit.

11. The system of claim 10, wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

12. The system of claim 5, wherein wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

13. The system of claim 1, wherein said at least one chemical containing unit comprises at least two chemical containing units.

14. The system of claim 13, further comprising:

a plurality of chemical containing unit outlets, said plurality equal to the number of said at least two chemical containing units, wherein each of said chemical containing unit outlets is associated with a respective one of said at least two chemical containing units;

a chemical containing unit outlet manifold in fluid communication with said plurality of chemical containing unit outlets;

a chemical containing element outlet reservoir in fluid communication with said chemical containing unit outlet manifold and said dosing unit.

15. The system of claim 14, wherein wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

16. A method for monitoring, dosing and distribution of a chemical composition in a chemical treatment process, the chemical composition containing at least one additive for maintaining quality of the chemical treatment process, comprising the steps of:

a) allowing the chemical composition to flow from at least one chemical containing unit to a dosing unit;

b) monitoring a property of the chemical composition with an online monitor at a location intermediate the chemical containing unit and the dosing unit or at the dosing unit;

c) sending from the online monitor to a controller a signal associated with the monitored property;

d) determining at the controller whether the at least one additive should be added to the chemical composition at the reservoir based upon the monitored property, thereby resulting in a decision to add or not a selected amount of the at least one additive to the chemical composition at the reservoir based upon the signal from the online monitor;

e) sending from the controller to the dosing unit a signal associated with the decision;

f) allowing the selected amount of the at least one additive to be added or not be added to the chemical composition at the dosing unit in response to the signal associated with the decision;

g) allowing the chemical composition to flow from the dosing unit to the chemical containing unit.

17. The method of claim 1, further comprising the steps of:

determining by the controller a rate of depletion over a depletion time period of at least one of the at least one additive in the chemical composition based upon a concentration of the at least one of the at least one additive measured by said monitor in comparison to a concentration of the at least one of the at least one additive previously measured by said monitor;

predicting by the controller an amount of at least one of the at least one additive that when added to the chemical composition will maintain a concentration of the additive within a predetermined concentration range around a predetermined setpoint concentration; and

correcting by the controller the predicted amount by adding to, or subtracting from, the predicted amount, an amount of the at least one additive based upon a previous concentration of the at least one additive measured by said monitor, wherein the corrected amount is the selected dose.

18. The system of claim 17, wherein the at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

19. The system of claim 16, wherein the at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

20. The system of claim 16, wherein said step of allowing the chemical composition to flow from the dosing unit to the at least one chemical containing unit comprises:

allowing the chemical composition to flow from the dosing unit to a chemical delivery unit; and

delivering the chemical composition from the at least one chemical delivery unit to the chemical containing unit.

21. The system of claim 20, further comprising the steps of:

providing a first valve arrangement in fluid communication with the chemical containing unit and the dosing unit, the first valve arrangement configured to allow or prevent a flow of the chemical composition from the chemical containing unit to the dosing unit; and

providing a second valve arrangement in fluid communication with the chemical containing unit and the chemical delivery unit, the second valve arrangement configured to allow or prevent a flow of the chemical composition from the chemical containing unit to the chemical delivery unit.

22. The system of claim 21, further comprising the step of:

determining by the controller whether to perform said method in a main recirculation mode in which the first valve arrangement allows a flow of the chemical composition from the at least one chemical containing unit to the dosing unit and the second valve arrangement prevents a flow of the chemical composition from the at least one chemical containing unit to the dosing unit, or in a dosing mode in which the first valve arrangement prevents a flow of the chemical composition from the chemical containing unit to the dosing unit and allows a flow of the chemical composition from the at least one chemical containing unit to the chemical delivery unit, thereby resulting in a mode decision.

23. The system of claim 22, further comprising the step of:

in response to the processor determining that said method should be performed in the main recirculation mode, sending a signal to either open said first valve arrangement or to allow said first valve arrangement to remain open so that a flow of the chemical composition is allowed from said at least one chemical containing unit to said dosing unit.

24. The system of claim 22, further comprising the step of:

in response to the processor determining that said method should be performed in the dosing mode, i) sending a signal either to close the first valve arrangement or to allow the first valve arrangement to remain closed so that a flow of the chemical composition is prevented from the at least one chemical containing unit to the dosing unit, and ii) sending a signal either to open the second valve arrangement or to allow the second valve arrangement to remain open so that a flow of the chemical composition is allowed from the at least one chemical containing unit to the chemical delivery unit.

25. The method of claim 24, further comprising the steps of:

providing the dosing unit with a reservoir and a dosage element;

sending by the controller a signal to the dosage element to add the selected amount to a flow of the chemical composition from the dosing unit reservoir;

adding by the dosage element the selected amount to the flow of chemical composition from the dosing unit reservoir; and

allowing the combined flow of the selected amount of the at least one additive and the chemical composition to flow from the dosage element to the dosing unit reservoir.

26. The method of claim 17, wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

27. The method of claim 23, wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

28. The method of claim 24, wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

29. The method of claim 16, wherein said at least one chemical containing unit comprises at least two chemical containing units.

30. The method of claim 29, comprising the further steps of:

providing a plurality of chemical containing unit outlets, the plurality being equal to the number of the at least two chemical containing units, wherein each of the chemical containing unit outlets is associated with a respective one of the at least two chemical containing units;

providing a chemical containing unit outlet manifold in fluid communication with the plurality of chemical containing unit outlets;

providing a chemical containing unit outlet reservoir in fluid communication with the chemical containing unit outlet manifold and the dosing unit;

allowing a flow of the chemical composition from the plurality of chemical containing unit outlets to the chemical containing unit outlet reservoir; and

allowing a flow of the chemical composition from the chemical containing unit outlet reservoir to the dosing unit.

31. The method of claim 30, wherein said at least one chemical containing unit is an electroplating bath of a wafer electroplating tool.

32. The system of claim 2, wherein the processor is programmed with the algorithm such that the amount added to or subtracted from the predicted amount is based upon at least two previous measurements by said monitor of the concentration of the at least one additive.

33. The system of claim 2, wherein the processor is programmed with the algorithm such that a time in between additions of the at least one additive is less than the time in between measurements by said monitor.

34. The system of claim 34, wherein the processor is programmed with the algorithm such that a frequency of additions of the at least one additive by said dosing unit may be varied.

35. The system of claim 2, wherein the processor is programmed with the algorithm such that the predicted amount is also based upon a derivative of the depletion rate.

36. The system of claim 2, wherein the processor is programmed with the algorithm such that the predicted amount does not depend upon a variable condition at said chemical containing unit.

37. The system of claim 2, wherein the processor is programmed with the algorithm such that the predicted amount does not depend upon a time interval between successive measurements by said monitor.

38. The method of claim 17, wherein the amount added to or substracted from the predicted amount is based upon at least two previous measurements by the monitor of the concentration of the at least one additive.

39. The method of claim 17, further comprising the step of:

varying a time interval between additions of the at least one additive such that the time in between additions is less than a time interval between measurements by said monitor.

40. The method of claim 39, further comprising the step of:

varying a frequency of additions of the at least one additive by said dosing unit.

41. The method of claim 17, wherein the predicted amount is also based upon a derivative of the depletion rate.

42. The method of claim 17, wherein the predicted amount does not depend upon a variable condition at said chemical containing unit.