SEMICONDUCTOR DEVICE PRODUCTION METHOD AND SEMICONDUCTOR PRODUCTION APPARATUS
A semiconductor device production method of the present invention first collects data including an initial volume of plating solution, volume of replenished solution, number of wafers processed, value of current applied and volume of waste solution in a step of filling a metal plating film in a via hole or a trench formed in an insulating film on a semiconductor substrate. Then, a cumulative charge during the plating is calculated based on the obtained current value. Also, a total volume of plating solution is calculated. Furthermore, an amount of decomposition products of suppressors contained in the plating solution based on the calculated total volume of plating solution, the volume of waste solution and the calculated cumulative charge. The semiconductor substrate is plated only when the amount of decomposition products is equal to or smaller than a predetermined threshold.
The present application claims the benefit of Japanese Patent Application No. 2008-060835 filed Mar. 11, 2008, the subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a semiconductor device production method and a semiconductor production apparatus and particularly to a plating method and a plating apparatus used in a metal wiring process for semiconductor devices.
2. Description of the Related Art
In prior art electroplating, metal-plating is performed while additives are supplied (reference is made, for example, to Japanese Laid-Open Patent Application No. 2001-152398). The concentration of additives are measured based on the current-potential curve in some cases (for example, Kimiko OYAMADA et al., “Plating Time Dependence of Filling Ability with Additives by Copper Electroplating”, Journal of Japan Institute of Electronics Packaging, Vol. 7, No. 3, pp. 261-265 (2004)).
In prior art plating, the concentration of constituents of additives, such as brightener, leveler and suppressor, contained in the plating solution are measured during electroplating. Each constituent is added as needed so to maintain the concentration in a specific range during electroplating.
Specifically, the concentrations of constituents of additives are measured based on the current-potential curve of the plating solution containing the additive obtained at the CV (cyclic voltammetry) electrode placed in the plating solution within the plating apparatus.
SUMMARY OF THE INVENTIONIt is difficult in the prior art electroplating method and electroplating apparatus to measure and assess the concentration of all constituents present in the plating solution including by-products produced in the course of plating. Therefore, it is difficult to fill a metal in the wiring regions consisting of nanoscale microstructures in semiconductor devices without creating any voids.
The purpose of the present invention is to fill a metal in wiring regions consisting of nanoscale microstructures in a semiconductor device without creating any voids and seams so as to reduce electric defects, thereby improving the production yield of semiconductor devices.
In order to achieve the above purpose, a semiconductor device production method of the present invention first collects data including an initial volume of plating solution, volume of replenished solution, number of wafers processed, value of current applied and volume of waste solution in a step of filling a metal plating film in a via hole or a trench formed in an insulating film on a semiconductor substrate. Then, a cumulative charge during the plating is calculated based on the obtained current value. Also, a total volume of plating solution is calculated. Furthermore, an amount of decomposition products of suppressors contained in the plating solution based on the calculated total volume of plating solution, the volume of waste solution and the calculated cumulative charge.
It is preferable in the above semiconductor device production method that a predetermined volume of waste solution when the amount of decomposition products exceeds a predetermined value and fresh plating solution be replenished.
A semiconductor production apparatus of the present invention is used to fill a metal plating film in a via hole or a trench formed in an insulating film on the semiconductor substrate. The semiconductor production apparatus of the present invention comprises a unit circulating plating solution, a unit replenishing plating solution and a unit discharging the plating solution. The apparatus further comprises a unit collecting data including an initial volume of plating solution, volume of replenished solution, number of wafers processed, value of current applied and volume of waste solution, a unit calculating a cumulative charge during plating based on the obtained current value, a unit a total volume of plating solution and a unit calculating an amount of decomposition products of suppressors contained in the plating solution based on the calculated total volume of plating solution, the volume of waste solution and the calculated cumulative charge.
It is preferable for the above semiconductor production apparatus that the unit discharging the plating solution discharges a predetermined volume of plating solution when the amount of decomposition products exceeds a predetermined value.
The present invention prevents defective filling due to fluctuations in the plating solution composition by calculating and controlling the amount of by-products (the amount of decomposition products) produced during electroplating, thereby improving the production yield of semiconductor devices.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
A first embodiment of the present invention is described hereafter with reference to
In
Here, three additives are used, including a suppressor, accelerator (brightener), and leveler. The additives play an important role in filling copper in microstructures. Their role is briefly described hereafter.
The suppressor consists of PEG (poly(ethylene glycol))-PPG (poly(propylene glycol)) polymers (high molecules) and suppresses the growth of copper film. The accelerator (brightener) consists of sulfur-containing organic substances and accelerates the growth of copper film. The leveler consists of amine-based organic compounds and s the growth of copper film in an area of the wafer surface where the electric field concentrates and does not suppress the growth of copper film in an area of the wafer surface where the electric field does not concentrate. Therefore, the leveler serves to improve the smoothness of the copper film.
It is very important to control the composition of the plating solution for filling a copper film in nanoscale microstructures such as vias, contact holes, and trenches without creating gaps and defects such as voids and seams. However, it has been found that the composition of the plating solution changes as a result of electrolysis in the course of electroplating. Furthermore, it is not sufficient to simply control the concentrations of the above additives for predetermined value ranges in order to fill a metal in nanoscale microstructures. This is because the three additives are electrolyzed into different substances (by-products) including those having different molecular structures.
Speaking of the additive concentration control, the supply valve 9 on the circulation line 3 is opened to add fresh plating solution to the plating solution for controlling the additive concentration. Such concentration control has conventionally been used because of the belief that the by-products have no or little influence on filling properties. However, investigation by the inventor of the present application revealed that defective filling occurs in vias of nanoscale microstructures, as mentioned above. Moreover, it is difficult to measure an amount of the by-products during a plating processing. In the electroplating apparatus, shown in
The monitoring unit 6 and control unit 1 can be realized for example by dedicated arithmetic circuits, or hardware including a processor and memory such as RAM (random access memory) and ROM (read only memory) and software stored in the memory and running on the processor. In this embodiment, the monitoring unit 6 and control unit 1 are realized by a computer and programs running on the computer. The monitoring unit 6 can acquire the data described above from various sensors that acquire such data directly or based on the operation states of the electroplating apparatus indirectly.
The model used by the control unit 1 for calculating the amount of decomposition products (the amount of by-products) is described hereafter. In this embodiment, as shown in
The above model equation particularly obtains the amount of decomposition products produced (Gn) in each wafer processing using a cumulative charge (integrated current value) calculated from the value of current applied to the wafer processed (for example, calculated using the number of wafers processed and the value of current applied) and calculates the amount of decomposition products remaining after each discharging waste solution based on the volume of waste solution in relation to the total volume of plating solution. Then, each amount of decomposition products remaining between discharges is cumulated to obtain the amount of decomposition products contained in the plating solution after the n-th wafer processing (Nbn). The amount of decomposition products produced during the subsequent plating operation is added to the amount of decomposition products Nbn to obtain the amount of decomposition products at the time of the subsequent plating operation. The data (particularly the current value) used for calculating the amount of decomposition products Nbn should be obtained at least at a sampling rate higher than 2 Hz. This is because there is some influence on the accuracy of calculation of the amount of by-products. For example, sampling rates higher than 2 Hz increase the calculation accuracy more than 3%. In the above equation (1), the total volume of plating solution (V2) and the volume of waste solution (V1) are constant. However, when volume of waste solution and the volume of replenished solution in each operation are different, the amount of decomposition products can be calculated using their respective values.
In
The mechanism of occurrence of defective filling in vias is described hereafter.
Therefore, even if fresh plating solution is added to control the amounts of three additives, it is impossible to control the by-products produced in the above mechanism or reduce defective filling. A fundamental solution removes the by-products from the plating solution and bring them to the outside, namely discharging waste solution. Hence, it is most important to control the volume of waste solution. In the electroplating apparatus of this embodiment, the waste valve 5 on the SAC line 4 is opened to release the plating solution when the amount of by-products calculated by the above equation (1) exceeds a predetermined value. In this structure, the by-products are discharged by releasing the plating solution and the amount of by-products present in the plating solution and responsible for voids and seams can be reduced.
In liquid chromatography, an intensity of refractive-index for a column retention time is observed. Molecules having such different molecular weights emerge in retention times different from those in which the suppressor is observed; therefore, they can be detected separately. In actual observation, peaks supposedly for by-products other than the suppressor were observed in times longer than the retention time (observation time) in which the suppressor was observed. This liquid chromatography was of the size exclusion mode. In this mode, molecules having smaller molecular weights enter the column deep inside and have difficulty coming out of the column, lengthening their column retention time. In measurement, peaks were observed in the longer retention times. Therefore, the detected by-products presumably had molecular weights smaller than the suppressor and the above inventor's model was verified.
Second EmbodimentA second embodiment provides a filling method creating no defects such as voids and seams based on the first embodiment of the present invention.
What is important here is that the steps of measuring the concentrations of additives, which is conventionally performed outside the recipe, and determining whether the concentrations are appropriate are newly provided and, furthermore, the mechanism and step of replenishing plating solution when the concentrations of additives are outside predetermined value ranges (S1NG) is provided. What is more important is that the step of collecting apparatus data, calculating the amount of by-products, and determining whether the mount is appropriate is newly provided and, furthermore, the mechanism and step of discharging the solution when the amount of by-products is outside a predetermined value range (S4NG) is provided. Because these are performed within the recipe, it is possible to feedback the calculated result using the apparatus data collected in situ. Then, the volume of replenished solution and the volume of waste solution are controlled according to the amount of by-products. Therefore, the accuracy of calculation of the amount of by-products is significantly improved.
In the above explanation, the recipe start (operation start) is the initial point. However, needless to say, the calculation accuracy will not be so different even if the initial point is when a lot is engaged in the apparatus (track-in).
Third EmbodimentA third embodiment of the present invention will be described hereafter. The third embodiment of the present invention relates to an electroplating method in which the optimum volume of waste solution is determined. The plating solution is expensive and it is preferable that the volume of waste solution is minimized. Then, in this embodiment, a technique of determining the optimum volume of waste solution based on the quantity of wafers to be processed, namely the amount of by-products to be produced, total volume of plating solution, and volume of waste solution, will be described.
As predicted above,
In this embodiment, the volume of waste solution can previously be determined as described above. Defective filling due to abnormal apparatus states can be prevented by storing the obtained value in the monitoring unit 6 in
In the above embodiments, copper is filled. However, needless to say, the same is true for other metal films such as silver and aluminum.
As described above, the present invention prevents defective filling due to change in the composition of plating solution and improves the production yield of semiconductor devices.
The present invention is not restricted to the above embodiments. Various modifications and applications are available without departing from the technical idea of the present invention. For example, in the above embodiments, the present invention is applied to a semiconductor production apparatus having a circulation line and a sub-circulation line. The invention of the present application is applicable to a semiconductor production apparatus having only one circulation line as shown in
The semiconductor device production method and semiconductor production apparatus of the present invention is capable of obtaining the amount of by-products to be produced by calculation and can use this capability for controlling the amount of by-products for a constant value, therefore providing a useful production technique for the semiconductor device wiring process in which metals are filled in nanoscale microstructures. The present invention also has applications in plating process for MEMSs.
Claims
1. A semiconductor device production method having a step of filling a metal plating film in a via hole or a trench formed in an insulating film on a semiconductor substrate, the step of filling the metal plating film comprising the steps of:
- collecting data including an initial volume of plating solution, volume of replenished solution, number of wafers processed, value of current applied and volume of waste solution;
- calculating a cumulative charge during the plating based on the value of current applied;
- calculating a total volume of plating solution; and
- calculating an amount of decomposition products of suppressors contained in the plating solution based on the calculated total volume of plating solution, the volume of waste solution and the calculated cumulative charge.
2. The semiconductor device production method according to claim 1, further comprising the steps of:
- discharging a predetermined volume of plating solution when the amount of decomposition products exceeds a predetermined value; and
- replenishing plating solution.
3. A semiconductor production apparatus for filling a metal plating film in a via hole or a trench formed in an insulating film on a semiconductor substrate, comprising:
- a unit circulating plating solution;
- a unit replenishing plating solution;
- a unit discharging the plating solution;
- a unit collecting data including an initial volume of plating solution, volume of replenished solution, number of wafers processed, value of current applied and volume of waste solution;
- a unit calculating a cumulative charge during the plating based on the value of current applied;
- a unit calculating a total volume of plating solution; and
- a unit calculating an amount of decomposition products of suppressors contained in the plating solution based on the calculated total volume of plating solution, the volume of waste solution and the calculated cumulative charge.
4. The semiconductor production apparatus according to claim 3, wherein the unit discharging the plating solution discharges a predetermined volume of plating solution when the amount of decomposition products exceeds a predetermined value.
Type: Application
Filed: Mar 9, 2009
Publication Date: Sep 17, 2009
Inventors: Shin-ichi IMAI (Osaka), Tomoya Tanaka (Toyama), Masakai Kitabata (Toyama)
Application Number: 12/400,363
International Classification: C25D 21/12 (20060101); C25D 17/00 (20060101);