SYSTEM AND METHOD FOR IN-SITU HEAD RINSE
A carrier head and a method of cleaning the carrier head are disclosed. The carrier head may have one or more openings through a sidewall that extend into a cavity within the carrier head using a fluid passage. The openings may each have a lip. The lip may have a chamfered edge. Additionally, a fluid passage may slope generally downward from the openings to the cavity. The chamfered lips and the sloped fluid passage reduce back splashing and help ensure that sufficient rinsing fluid reaches the cavity to rinse polishing fluid and particles from the carrier head. The present invention relates to carrier heads for polishing or planarizing semiconductor substrates by chemical mechanical polishing (CMP) or electrochemical mechanical polishing (ECMP). The cavities in the carrier head are cleaned by rinsing fluid (i.e., liquid or gas) from inside the cavity towards a substrate receiving side of the carrier head.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/738,775, filed Nov. 22, 2005, and U.S. Provisional Patent Application Ser. No. 60/759,142, filed Jan. 13, 2006, which are both herein incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
Embodiments of the present invention generally relate to a carrier head for a chemical mechanical polishing system and a method of cleaning a carrier head.
2. Description of the Related Art
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize substrates. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with the polishing article in a CMP apparatus. The polishing article and the substrate are moved relative to each other resulting in polishing or rubbing movement between the surface of the substrate and the polishing article.
As part of the manufacturing process of semiconductor devices, semiconductor substrates are increasingly being polished by CMP. Generally, the substrate to be polished is mounted on a substrate carrier which holds the substrate using a combination of vacuum suction or other means and, most often, the substrate backing pad to contact the rear side of the substrate. The retaining lip or ring is generally provided around the edge of the substrate to keep the substrate contained under the substrate carrier.
In a typical operation, the substrates may be sequentially polished at two, three or more polishing stations. Thereby, a multi-step polishing process in which, for example, a rough polish is followed by two successively finer polishes is applied. One method of achieving increasingly fine polishing is to use slurries having different characteristics or particle sizes at the different polishing stations. Cross-contamination of slurries between different platens is a concern. Therefore, it would be beneficial to ensure that intermixing of polishing slurries of different chemistries is kept to a minimum.
For ease of description and understanding, the following description will refer to substrates, which include but are not limited to semiconductor wafers, semiconductor workpieces, optical planks, memory disks and the like. The present invention may be applied to any generally disc shaped workpiece.
SUMMARY OF THE INVENTIONA carrier head and a method of cleaning the carrier head are disclosed. The carrier head may have one or more openings through a sidewall that extend into a cavity within the carrier head using a fluid passage. The openings may each have a lip. The lip may have a chamfered edge. Additionally, a fluid passage may slope generally downward from the openings to the cavity. The chamfered lips and the sloped fluid passage reduce back splashing and help ensure that sufficient rinsing fluid reaches the cavity to rinse polishing fluid and particles from the carrier head. The present invention relates to carrier heads for polishing or planarizing semiconductor substrates by CMP or electrochemical mechanical polishing (ECMP). The cavities in the carrier head are cleaned by rinsing fluid (i.e., liquid or gas) from inside the cavity towards a substrate receiving side of the carrier head.
In one embodiment, a carrier head is described comprising a backing assembly, a retaining ring, wherein a cavity is present between the retaining ring and the backing assembly, and a fluid rinsing system for rinsing the cavity.
In another embodiment, a carrier head is described comprising a top surface, a side surface substantially perpendicular to the top surface, and a fluid passage extending into the carrier head through the side surface to a cavity.
In yet another embodiment, a carrier head cleaning method is described comprising flowing a cleaning fluid through at least one opening in the carrier head, wherein the cleaning fluid flows to a cavity within the carrier head, the opening and the cavity are coupled together by a fluid passageway having sidewalls, and at least one sidewall of the fluid passageway is sloped from the opening toward the cavity.
BRIEF DESCRIPTION OF THE DRAWINGSSo that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
DETAILED DESCRIPTIONA carrier head and a method of cleaning the carrier head are disclosed. The carrier head may have one or more openings through a sidewall that extend into a cavity within the carrier head using a fluid passage. The openings may each have a lip. The lip may have a chamfered edge. Additionally, a fluid passage may slope generally downward from the openings to the cavity. The chamfered lips and the sloped fluid passage reduce back splashing and help ensure that sufficient rinsing fluid reaches the cavity to rinse polishing fluid and particles from the carrier head. The present invention relates to carrier heads for polishing or planarizing semiconductor substrates by CMP or ECMP. The cavities in the carrier head are cleaned by rinsing fluid (i.e., liquid or gas) from inside the cavity towards a substrate receiving side of the carrier head.
A controller 108 may be provided to facilitate control and integration of the modules of the system 100. The controller 108 may include a central processing unit (CPU) 110, a memory 112, and support circuits 114. The controller 108 may be coupled to the various components of the system 100 to facilitate control of, for example, the planarizing, cleaning, and transfer processes.
The factory interface 102 may include a metrology module 190, a cleaning module 116 and one or more wafer cassettes 118. An interface robot 120 may be employed to transfer substrates 122 between the wafer cassettes 118, the cleaning module 116 and an input module 124. The input module 124 may be positioned to facilitate transfer of substrates 122 between the planarizing module 106 and the factory interface 102 by grippers. In one embodiment, the grippers may be vacuum grippers. In another embodiment, the grippers may be mechanical clamps.
The metrology module 190 may be a non-destructive measuring device suitable for providing a metric indicative of the thickness profile of a substrate. The metrology module 190 may include eddy sensors, an interferometer, a capacitance sensor and other suitable devices. Examples of suitable metrology modules include iScan™ and iMap™ substrate metrology modules, available from Applied Materials, Inc. The metrology module 190 provides the metric to the controller 108 wherein a target removal profile is determined for the specific thickness profile measured from the substrate.
The planarizing module 106 may include at least a first ECMP station 128, disposed in an environmentally controlled enclosure 188. Examples of planarizing modules 106 that can be adapted to benefit from the invention include MIRRA®, MIRRA MESA™, REFLEXION®, REFLEXION® LK, and REFLEXION LK Ecmp™ CMP Systems, all available from Applied Materials, Inc. of Santa Clara, Calif. Other planarizing modules, including those that use processing pads, planarizing webs, or a combination thereof, and those that move a substrate relative to a planarizing surface in a rotational, linear or other planar motion may also be adapted to benefit from the invention.
In the embodiment depicted in
The exemplary planarizing module 106 may also include a transfer station 136 and a carousel 134 that are disposed on an upper or first side 138 of a machine base 140. In one embodiment, the transfer station 136 includes an input buffer station 142, an output buffer station 144, a transfer robot 146, and a load cup assembly 148. The input buffer station 142 receives substrates from the factory interface 102 by means of the loading robot 104. The loading robot 104 may also be utilized to return polished substrates from the output buffer station 144 to the factory interface 102. The transfer robot 146 is utilized to move substrates 122 between the buffer stations 142, 144 and the load cup assembly 148.
In one embodiment, the transfer robot 146 includes two gripper assemblies, each having pneumatic gripper fingers that hold the substrate 122 by the substrate's edge. The transfer robot 146 may simultaneously transfer a substrate to be processed from the input buffer station 142 to the load cup assembly 148 while transferring a processed substrate from the load cup assembly 148 to the output buffer station 144. An example of a transfer station that may be used to advantage is described in U.S. Pat. No. 6,156,124, which is herein incorporated by reference in its entirety.
The carousel 134 may be centrally disposed on the base 140. The carousel 134 may include a plurality of arms 150, each supporting a carrier head assembly 152. Two of the arms 150 depicted in
In one embodiment, the planarizing head may be a TITAN HEAD™ or TITAN PROFILER™ wafer carrier manufactured by Applied Materials, Inc. The planarizing head 204 may comprise a housing 214 and retaining ring 224 that defines a center recess in which the substrate 122 is retained. The retaining ring 224 circumscribes the substrate 122 disposed within the planarizing head 204 to prevent the substrate from slipping out from under the planarizing head 204 while processing. The retaining ring 224 may be made of plastic materials such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), and the like, or conductive materials such as stainless steel, Cu, Au, Pd, and the like, or some combination thereof. It is further contemplated that a conductive retaining ring 224 may be electrically biased to control the electric field during ECMP. Conductive or biased retaining rings tend to slow the polishing rate proximate the edge of the substrate. It is contemplated that other planarizing heads may be utilized.
The first ECMP station 128 may include a platen assembly 230 that is rotationally disposed on the base 140. The platen assembly 230 may be supported above the base 140 by a bearing 238 so that the platen assembly 230 may be rotated relative to the base 140. An area of the base 140 circumscribed by the bearing 238 is open and provides a conduit for the electrical, mechanical, pneumatic, control signals and connections communicating with the platen assembly 230.
Conventional bearings, rotary unions and slip rings, collectively referred to as rotary coupler 276, are provided such that electrical, mechanical, fluid, pneumatic, control signals and connections may be coupled between the base 140 and the rotating platen assembly 230. The platen assembly 230 may be coupled to a motor 232 that provides the rotational motion to the platen assembly 230. The motor 232 is coupled to the controller 108 that provides a signal for controlling for the rotational speed and direction of the platen assembly 230.
A top surface 260 of the platen assembly 230 supports a processing pad assembly 222 thereon. The processing pad assembly may be retained to the platen assembly 230 by magnetic attraction, vacuum, clamps, adhesives and the like.
A plenum 206 is defined in the platen assembly 230 to facilitate uniform distribution of electrolyte to the planarizing surface 126. A plurality of passages, described in greater detail below, may be formed in the platen assembly 230 to allow electrolyte, provided to the plenum 206 from an electrolyte source 248, to flow uniformly though the platen assembly 230 and into contact with the substrate 122 during processing. It is contemplated that different electrolyte compositions may be provided during different stages of processing.
The processing pad assembly 222 may include an electrode 292 and at least a planarizing portion 290. The electrode 292 may be comprised of a conductive material, such as stainless steel, copper, aluminum, gold, silver and tungsten, among others. The electrode 292 may be solid, impermeable to electrolyte, permeable to electrolyte or perforated. At least one contact assembly 250 extends above the processing pad assembly 222 and is adapted to electrically couple the substrate being processed on the processing pad assembly 222 to the power source 242. The electrode 292 may also be coupled to the power source 242 so that an electrical potential may be established between the substrate and electrode 292.
A meter 240 may be provided to detect a metric indicative of the electrochemical process. The meter may be coupled or positioned between the power source 242 and at least one of the electrode 292 or contact assembly 250. The meter may also be integral to the power source 242. In one embodiment, the meter is configured to provide the controller 108 with a metric indicative of processing, such as charge, current and/or voltage. This metric may be utilized by the controller 108 to adjust the processing parameters in-situ or to facilitate endpoint or other process stage detection.
A window 246 may be provided through the pad assembly 222 and/or platen assembly 230, and is configured to allow a sensor 254, positioned below the pad assembly 222, to sense a metric indicative of polishing performance. In one embodiment, the sensor 254 may be an eddy current sensor. The metric, provided by the sensor 254 to the controller 108, provides information that may be utilized for processing profile adjustment in-situ, endpoint detection or detection of another point in the electrochemical process. In one embodiment, the sensor 254 may be an interferometer capable of generating a collimated light beam, which during processing, is directed at and impinges on a side of the substrate 122 that is being polished. The interference between reflected signals is indicative of the thickness of the conductive layer of material being processed. One sensor that may be utilized to advantage is described in U.S. Pat. No. 5,893,796, which is hereby incorporated by reference in its entirety.
Embodiments of the processing pad assembly 222 suitable for removal of conductive material from the substrate 122 may generally include a planarizing surface 126 that is substantially dielectric. Other embodiments of the processing pad assembly 222 suitable for removal of conductive material from the substrate 122 may include a planarizing surface 126 that is substantially conductive. At least one contact assembly 250 may be provided to couple the substrate to the power source 242 so that the substrate may be biased relative to the electrode 292 during processing. Apertures 210, formed through the planarizing layer 290 and the electrode 292 and any elements disposed below the electrode, allow the electrolyte to establish a conductive path between the substrate 112 and electrode 292.
In one embodiment, the planarizing portion 290 of the processing pad assembly 222 is a dielectric, such as polyurethane. Examples of processing pad assemblies that may be adapted to benefit from the invention are described in United States Patent Publication No. 2004/0023610 A1 and United States Patent Publication No. 2004/0020789 A1, both of which are hereby incorporated by reference in their entireties.
During polishing of the substrate on one polishing pad using slurry, the chemistries of the slurry may contaminate the carrier head. In the event that chemistries of the slurry are not compatible to a second slurry provided on a second platen, cross-contamination may occur when a substrate is sequentially polished on the first platen and then on a second platen. Cross-contamination should particularly be avoided if the chemistries of the first slurry are incompatible with the chemistries of the second slurry. Incompatibility can be characterized as a large difference in polarization voltage, or by precipitation when mixed. Independent of the specific example given above, any cross-contamination of a second slurry with chemistry of the first slurry should, in general, be avoided. Therefore, a rinsing system according to the present invention is provided.
The cleaning of the carrier head to avoid cross-contamination due to transfer of a substrate from a first to a second platen may be conducted while the carrier head with the substrate is still positioned above the first polishing station. Alternatively, rinsing may be conducted while the carrier head with the substrate positioned therein is transferred from the first polishing station to the second polishing station. Even though cross-contamination may occur if the rinsing is conducted while the carrier head and the substrate are positioned over the second polishing station, an appropriate method can be conducted over the second polishing station. For example, rinsing may be conducted with appropriate chemistry or with a sufficient amount of fluid such that detrimental effects on the slurry of the further polishing station can be prevented. According to a further alternative, as described below, the head rinse of any of the embodiments described herein may be conducted in parallel to the pad cleaning during which the pad is rinsed. Thereby, any cross contamination by rinsing over the platen of the second polishing station is removed from the platen of the second polishing station.
According to another embodiment, the head rinse of any of the embodiments described herein may be conducted in parallel with the wafer rinse, during which the head presses down on the wafer, while water or cleaning chemical is delivered on the pad.
Before a substrate is received by any of the carrier heads, the head may be rinsed. The rinsing may be performed before the substrate enters the load cup and the system. The cavities in the carrier head may be cleaned by rinsing fluid from inside the cavity towards a substrate receiving side of the carrier head. It may be possible that the head is additionally washed with a gap wash from below when the carrier head is located in the load cup.
After the substrate enters the system and is carried by the carrier head, the substrate is moved to the first platen. In one embodiment, the first polishing step may be an ECMP process. Thereby, an electrolyte, such as EP3.1 commercially available from Applied Materials Inc., may be used for the ECMP process. However, ECMP processes with other electrolytes or CMP processes may also be used. The carrier head may then be rinsed.
After the first polishing, the substrate may be moved by the carousel 134 to the second platen. A rinsing of the carrier head may take place over the second platen in addition to or in place of the rinsing at the first platen. The cavities inside the carrier head, especially the gap between the membrane and the retaining ring, may be rinsed from the side or from above. The cavities in the carrier head may be cleaned by rinsing fluid from inside the cavity towards a substrate receiving side of the carrier head.
The head rinse over the second platen may be conducted together with the pad wash of the second platen before polishing. The pad rinse or pad clean may be conducted by provided rinsing fluid on the platen and rotating the platen at high speed. In one embodiment, the platen may be rotated from about 60 to about 150 rpm. In another embodiment, the rinsing fluid for the pad rinse may be provided from about 8 to about 12 l/min. In another embodiment, the rinsing fluid may be provided at about 10 l/min.
After the pad clean and the head rinse have been conducted, the substrate may be polished on the second platen. The head rinse reduces the cross-contamination of, for example, electrolyte from the first platen to the slurry on the second platen.
After the polishing step on the second platen, the pad and the substrate may be rinsed over the second platen. In one embodiment, a head rinse may be conducted over the second platen before the substrate is moved to the next platen. Thereby, a cross-contamination of the slurry of the second platen to the slurry of the third platen may be reduced.
According to a further alternative, the substrate may first be moved to the third platen and a pad clean, a substrate rinse, and/or a head rinse may be conducted over the third platen. After the polishing step on the third platen, a post rinse in form of a head rinse according to any of the above described embodiments on the third platen may be conducted. In one embodiment, slurry 66XX from Cabot may be used on the third platen. Additionally or alternatively to the post rinse, a rinsing in the load cup before transfer of the substrate to the factory interface may be conducted.
The rinsing steps described above may be conducted through a fluid passage in the side or a top of the carrier head body and/or the cover of the carrier head. Since the slurry is intended to be removed from the cavity and the fluid passage, an opening from the substrate receiving side of the carrier head is less effective. The fluid passage may be adapted to deliver the rinsing fluid, such as DI water, in the cavity at a top side of the membrane unit which is opposite to the wafer receiving side or a side surface. The rinsing fluid should typically not be provided from the substrate receiving side of the membrane unit as the only rinse because undesirable contaminants may remain.
It is to be understood that while only one opening has been shown in
As may be seen from
A further embodiment of the fluid passage is shown in
For constructional purposes, generally, there is a small space 510 between the membrane unit 530 and the retaining ring 535. Further, space 512 may be present at least behind a part of the membrane unit 530. These cavity-forming spaces or gaps may be required to vertically move the substrate 502 with respect to the retaining ring 535. A vertical movement of the membrane unit 530 and, thereby the substrate 510 with respect to the retaining ring 535 is desired, for example, to adjust the polishing pressure.
The rinsing system in
A detailed side view of an embodiment of a fluid passage 522 is shown in
Alternatively, a sparger or any other means appropriate to improve the removal of chemistry on the interior walls of the cavity can be applied. For example, the fluid passage 522 can be shaped to provide a helix type flow of the liquid rinsing into cavity 510, 512.
A further embodiment of a carrier head 600 will now be described with respect to
In the event the fluid is provided through the spindle 650, no external spray arm is required. The fluid providing system is part of the carrier head itself. Thus, generally four variations may be employed. An external fluid providing system (spray arm) may provide the fluid in the cavity from top, an external fluid providing system (spray arm) may provide the fluid in the cavity from the side, an internal fluid providing system (through spindle) may provide the fluid in the cavity from top, and an internal fluid providing system (though spindle) may provide the fluid in the cavity from the side of the cavity.
As already discussed with respect to the previous embodiments, gap 610 and space 612 extend mainly around the entire perimeter of the carrier head. Thus, a plurality of fluid passages 622 may be provided. The fluid passages 622 may be equally spaced around the perimeter.
The system shown in
Generally, the rinsing of the gap and the space by inserting the rinsing fluid through a fluid passage with an opening at the top or the side of the carrier head can be conducted over a platen, in-between a platen or in the load cup. Thereby, repeating rinsing at the various locations between the polishing steps may be conducted. Nevertheless, throughput has to be considered. The head rinse through the fluid passages from the side downward or from the top downward, can be used to keep the carrier head clean in general. This may, for example, be done as an alternative to or in addition to the gap wash from the bottom in the load cup. Whenever, a cleaning of the carried head is required with or without a substrate being attached to the carrier head, this additional rinsing of the carrier head may be conducted in the load cup, over a platen or in-between two platens. If the head rinse according to any of the embodiments should be combined with the gap wash from below, the carrier head would be required to be in the load cup where the gap wash from below is located.
Some of the detailed embodiments above refer to systems with ECMP and CMP platens. However, the carrier heads for rinsing the cavities from top down and the methods described above can also be used similarly for systems having only CMP processes. Any cross-contamination between slurries or between electrolytes and slurries or vice versa may be efficiently reduced by the carrier heads according to the invention and the methods according to the invention described herein.
While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof in the scope thereof is determined by the claims that follow.
Claims
1. A carrier head, comprising:
- a backing assembly;
- a retaining ring, wherein a cavity is present between the retaining ring and the backing assembly; and
- a fluid rinsing system for rinsing the cavity.
2. The carrier head of claim 1, wherein the fluid rinsing system supplies fluid to at least one opening in the head extending to the cavity.
3. The carrier head of claim 2, wherein the at least one opening is positioned substantially perpendicular to a substrate receiving surface of the carrier head.
4. The carrier head of claim 2, wherein the at least one opening has a top wall that has a higher elevation on the carrier head than a top wall of the cavity.
5. The carrier head of claim 2, wherein the at least one opening comprises a lip portion having at least one chamfered edge.
6. The carrier head of claim 1, wherein the cavity is coupled with a plurality of openings.
7. A carrier head, comprising:
- a top surface; and
- a side surface substantially perpendicular to the top surface, wherein a fluid passage extends through the carrier head from the side surface to a cavity.
8. The carrier head of claim 7, wherein the fluid passage has a lip portion coupled with the side surface, the lip portion having at least one surface positioned at an angle relative to the side surface such that the lip portion slopes into the fluid passage.
9. The carrier head of claim 8, wherein the fluid passage comprises an upper surface and a lower surface, wherein the upper surface and the lower surface each slope downward from the lip portion to a cavity positioned opposite the lip portion.
10. The carrier head of claim 8, wherein the fluid passage comprises side surfaces, wherein the side surfaces converge toward the cavity positioned opposite the lip portion.
11. The carrier head of claim 10, wherein the cavity is coupled with a plurality of fluid passages.
12. The carrier head of claim 10, wherein an upper edge of the lip portion is at a higher elevation than a top wall of the cavity.
13. The carrier head of claim 7, further comprising:
- a retaining ring; and
- a backing assembly, wherein the cavity is present between the retaining ring and the backing assembly.
14. A carrier head cleaning method, comprising:
- flowing a cleaning fluid through at least one opening in a carrier head, the cleaning fluid flowing to a cavity within the carrier head, wherein the opening and the cavity are coupled together by a fluid passageway having sidewalls, and at least one sidewall of the fluid passageway is sloped from the opening toward the cavity.
15. The method of claim 14, wherein the flowing is performed in a load cup.
16. The method of claim 14, wherein the flowing is performed over a platen.
17. The method of claim 14, further comprising:
- rotating the carrier head during the flowing.
18. The method of claim 17, further comprising:
- polishing a substrate at a first platen, wherein said flowing is performed over the first platen.
19. The method of claim 17, further comprising:
- polishing a substrate at a first platen, wherein said flowing is performed over a platen different from said first platen.
20. The method of claim 14, wherein the at least one opening is substantially perpendicular to a substrate receiving surface of the carrier head.
Type: Application
Filed: Nov 22, 2006
Publication Date: Jan 3, 2008
Inventors: Antoine Manens (Sunnyvale, CA), Alain Duboust (Sunnyvale, CA), Paul Butterfield (San Jose, CA), Yan Wang (Sunnyvale, CA), Shi-Ping Wang (Fremont, CA), Zhihong Wang (Santa Clara, CA), Andrew Nagengast (Sunnyvale, CA), Wei-Yung Hsu (Santa Clara, CA), Liang-Yuh Chen (Foster City, CA)
Application Number: 11/562,811
International Classification: B24B 53/007 (20060101);