US 20060070872 A1
A method and apparatus for processing a substrate by electrochemical mechanical planarization and electrochemical mechanical plating is disclosed. Included are various embodiments of a processing pad article comprising an open cell foam subpad that is adapted to retain an electrolyte while encountering centrifugal motion, and simultaneously provide electrical and/or abrasive contact to a feature side of a substrate. Also disclosed is a platen capable of holding an electrolyte during processing at a desired RPM, then releasing the electrolyte centrifugally at a higher RPM. The release is actuated by an operator or by centrifugal force.
1. A substrate processing article adapted to polish a substrate, comprising:
a conductive layer having a first contact surface and a fastener adapted to couple to a power supply; and
a second contact surface, wherein the first and second contact surfaces are adapted to polish the substrate.
2. The substrate processing article of
3. The substrate processing article of
4. The substrate processing article of
5. The substrate processing article of
6. The substrate processing article of
7. The substrate processing article of
8. The substrate processing article of
9. The substrate processing article of
an electrode adapted to couple to a power supply, wherein the second contact surface includes a plurality of electrochemical cells when in contact with an electrolyte and the substrate.
10. An apparatus for polishing a substrate, comprising:
a first contact surface adapted to couple to a power source; and
a second contact surface disposed below the first contact surface, the second contact surface adapted to receive and retain an electrolyte and couple to an electrode in communication with the power source, wherein at least one electrochemical cell is created when the power source is activated and the substrate is in contact with the first and second contact surfaces.
11. The apparatus of
12. The apparatus of
13. The apparatus of
14. The apparatus of
15. The apparatus of
16. The apparatus of
17. An apparatus for performing an electrochemical process on a substrate, comprising:
a pad having a processing layer adapted to couple to an electrode, the processing layer comprising:
a plurality of elevated portions; and
a plurality of interstitial areas comprising open cell foam, supporting and surrounding the plurality of elevated portions, wherein a portion of the plurality of elevated portions and the open cell foam is adapted to contact the substrate.
18. The apparatus of
19. The apparatus of
20. The apparatus of
21. The apparatus of
a plurality of electrochemical cells when the processing layer and the electrode is coupled to a power source and the processing layer is in contact with the substrate.
22. The apparatus of
This application claims benefit of U.S. provisional patent application Ser. No. 60/615,198, filed Oct. 1, 2004, which is herein incorporated by reference.
1. Field of the Invention
Embodiments of the present invention generally relate to a processing apparatus for planarizing or polishing a substrate. More particularly, the invention relates to polishing pad design for planarizing or polishing a semiconductor wafer by electrochemical mechanical planarization.
2. Description of the Related Art
In the fabrication of integrated circuits and other electronic devices on substrates, multiple layers of conductive, semiconductive, and dielectric materials are deposited on or removed from a feature side, i.e., a deposit receiving surface, of a substrate. As layers of materials are sequentially deposited and removed, the feature side of the substrate may become non-planar and require planarization. Planarization is a procedure where previously deposited material is removed from the feature side of a substrate to form a generally even, planar or level surface. The process is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage and scratches. The planarization process is also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even or level surface for subsequent deposition and processing.
Electrochemical Mechanical Planarization (ECMP) is one exemplary process which is used to remove materials from the feature side of a substrate. ECMP typically uses a pad having conductive properties adapted to combine physical abrasion with electrochemical activity that enhances the removal of materials. The pad is attached to an apparatus having a rotating platen assembly that is adapted to couple the pad to a power source. The apparatus also has a substrate carrier, such as a polishing head, that is mounted on a carrier assembly above the pad that holds a substrate. The polishing head places the substrate in contact with the pad and is adapted to provide downward pressure, controllably urging the substrate against the pad. The pad is moved relative to the substrate by an external driving force and the polishing head typically moves relative to the moving pad. A chemical composition, such as an electrolyte, is typically provided to the surface of the pad which enhances electrochemical activity between the pad and the substrate. The ECMP apparatus effects abrasive or polishing activity from frictional movement while the electrolyte combined with the conductive properties of the pad selectively removes material from the feature side of the substrate.
Although ECMP has produced good results in recent years, there is an ongoing effort to develop pads with improved polishing qualities combined with optimal electrical properties that will not degrade over time and require less conditioning, thus providing extended periods of use with less downtime for replacement. Inherent in this challenge is the difficulty in producing a pad that will not react with process chemistry, which may cause degradation, or require excessive conditioning.
Platen rotation is another parameter that affects the planarizing process. Electrolyte retention in the current conductive pad design becomes difficult when the platen is rotated at higher revolutions per minute (RPM). When the pad is rotated to the desired RPM, the electrolyte tends to be removed axially from the substrate due to centrifugal force, and a break in the conductive current is sustained. This may result in uneven processing or possibly a total cessation of material removal.
Therefore, there exists a need in the art for a processing article or pad that is adapted for the removal of conductive materials and other materials on a feature side of a substrate designed to facilitate electrolyte retention during rotation.
The present invention generally provides an article of manufacture and an apparatus for planarizing a layer on a substrate using electrochemical dissolution processes, polishing processes, and/or combinations thereof.
In one embodiment, a substrate processing article is described having a conductive layer having a first contact surface and a fastener adapted to couple to a power supply, and a second contact surface, wherein the first and second contact surfaces are adapted to polish the substrate.
In another embodiment, an apparatus for polishing a substrate is described having a first contact surface adapted to couple to a power source and a second contact surface disposed below the first contact surface. The second contact surface is adapted to receive and retain an electrolyte and couple to an electrode in communication with the power source, wherein at least one electrochemical cell is created when the power source is activated and the substrate is in contact with the first and second contact surfaces.
In another embodiment, an apparatus for performing an electrochemical process on a substrate is described. The apparatus includes a pad having a processing layer adapted to couple to an electrode. The processing layer includes a plurality of elevated portions and a plurality of interstitial areas. The plurality of interstitial areas comprise open cell foam supporting and surrounding the plurality of elevated portions and a portion of the plurality of elevated portions and the open cell foam is adapted to contact the substrate.
A rotatable platen assembly is also described having a controlled valve assembly. In one embodiment, the valve assembly is RPM controlled. The valves are configured to open at a desired RPM whereby spent or used electrolyte is centrifugally forced out of the platen. In another embodiment, the valves are operator or mechanically actuated, at parameters defined by the user.
So 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.
The words and phrases used in the present invention should be given their ordinary and customary meaning in the art by one skilled in the art unless otherwise further defined. The embodiments described herein may relate to removing material from a substrate, but may be equally effective for electroplating a substrate by adjusting the polarity of an electrical source. Common reference numerals may be used in the Figures, where possible, to denote similar elements depicted in the Figures.
The planarizing module 105 shown in
The exemplary system 100 generally includes a base 108 that supports one or more ECMP stations 102, 103, one or more polishing stations 106, a transfer station 110, conditioning devices 182, and a carousel 112. The transfer station 110 generally facilitates transfer of substrates 114 to and from the system 100 via a loading robot 116. The loading robot 116 typically transfers substrates 114 between the transfer station 110 and an interface 120 that may include a cleaning module 122, a metrology device 104 and one or more substrate storage cassettes 118.
The transfer station 110 comprises at least an input buffer station 124, an output buffer station 126, a transfer robot 132, and a load cup assembly 128. The loading robot 116 places the substrate 114 onto the input buffer station 124. The transfer robot 132 has two gripper assemblies, each having pneumatic gripper fingers that hold the substrate 114 by the substrate's edge. The transfer robot 132 lifts the substrate 114 from the input buffer station 124 and rotates the gripper and substrate 114 to position the substrate 114 over the load cup assembly 128, then places the substrate 114 down onto the load cup assembly 128. An example of a transfer station that may be used is described in U.S. Pat. No. 6,156,124, issued Dec. 5, 2000, entitled “Wafer Transfer Station for a Chemical Mechanical Polisher,” incorporated herein by reference to the extent it is not inconsistent with this application.
The carousel 112 generally supports a plurality of carrier heads 204, each of which retains one substrate 114 during processing. The carousel 112 articulates the carrier heads 204 between the transfer station 110 and stations 102, 103 and 106. One carousel that may used is generally described in U.S. Pat. No. 5,804,507, issued Sep. 8, 1998, entitled “Radially Oscillating Carousel Processing System for Chemical Mechanical Polishing,” which is hereby incorporated by reference to the extent it is not inconsistent with this application.
The carousel 112 is centrally disposed on the base 108. The carousel 112 typically includes a plurality of arms 138 and each arm 138 generally supports one of the carrier heads 204. Two of the arms 138 depicted in
Generally the carrier head 204 retains the substrate 114 while the substrate 114 is disposed in the ECMP stations 102, 103 or polishing station 106. The arrangement of the ECMP stations 102, 103 and polishing stations 106 on the system 100 allow for the substrate 114 to be sequentially processed by moving the substrate between stations while being retained in the same carrier head 204.
To facilitate control of the polishing system 100 and processes performed thereon, a controller 140 comprising a central processing unit (CPU) 142, memory 144 and support circuits 146 is connected to the polishing system 100. The CPU 142 may be one of any form of computer processor that can be used in an industrial setting for controlling various drives and pressures. The memory 144 is connected to the CPU 142. The memory 144, or computer-readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits 146 are connected to the CPU 142 for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like.
Power to operate the polishing system 100 and/or the controller 140 is provided by a power supply 150. Illustratively, the power supply 150 is shown connected to multiple components of the polishing system 100, including the transfer station 110, the factory interface 120, the loading robot 116 and the controller 140.
The processing pad assembly 222 may be adapted to releasably couple to an upper surface of the platen assembly 230. The pad assembly 222 generally includes an electrode 292, an article support layer or sub-pad 350 and an elevated portion 330. A processing surface 125 is generally defined at least by the elevated portion 330 and, in another embodiment, may include the upper surfaces of a plurality of interstitial pads 320 disposed in a plurality of pad perforations 305. The elevated portion 330 may be a conventional polishing material, such as polymer based pad materials. Alternatively, the elevated portion 330 may be made of, or coated with, a conductive material, such as a conductive or dielectric filler material disposed in a conductive polymer matrix. In one embodiment, the elevated portions 330 are abrasive-free and may be include tin and/or nickel particles that may enhance conductivity in at least the elevated portions 330 of the processing pad assembly 222.
The electrode 292 is disposed on the top surface of the platen assembly 230 and is coupled to the power source 242 by connections that may be routed through a hollow drive shaft 260 coupled to the platen assembly 230. The electrode 292 is typically comprised of a conductive material, such as stainless steel, aluminum, gold, silver, among others. The electrode 292 may be solid, impermeable to electrolyte, permeable to electrolyte or perforated, or combinations thereof. In the embodiment depicted in
The platen assembly 230 is rotationally disposed on a base 108 and is typically supported above the base 108 by a bearing 238 so that the platen assembly 230 may be rotated relative to the base 108. The platen assembly 230 may be fabricated from a rigid material, such as a metal or rigid plastic, and in one embodiment the platen assembly 230 has an upper surface that is fabricated from or coated with a dielectric material, such as CPVC. The platen assembly 230 may have a circular, rectangular or other plane form.
Electrolyte may be provided from the source 248, through appropriate plumbing and controls, such as conduit 241, to nozzle 255 above the processing pad assembly 222 of the ECMP station 102. Optionally, a plenum 206 may be defined in the platen assembly 230 for containing an electrolyte and facilitating ingress and egress of the electrolyte to the pad assembly 222. A detailed description of an exemplary planarizing assembly suitable for incorporation with the present invention can be found in the description of the Figures in United States Patent Publication No. 2004/0163946 (Attorney Docket No. 004100.P10), entitled “Pad Assembly for Electrochemical Mechanical Processing,” filed Dec. 23, 2003, which is incorporated herein by reference to the extent it is not inconsistent with this application.
In the embodiment shown in
In a typical ECMP process, a potential difference or bias is applied between the electrode 292, performing as a cathode, and the feature side 115 of the substrate 114, performing as the anode. The application of the bias allows removal of conductive material, such as copper-containing and tungsten-containing materials, on the feature side 115 of the substrate 114. Examples of suitable parameters for ECMP that may be used are disclosed in U.S. Patent Publication No. 2004/0020789 (Attorney Docket No. 004100.P5), entitled “Conductive Polishing Article for Electrochemical Mechanical Polishing,” filed Jun. 6, 2003, which is incorporated herein by reference to the extent the application is not inconsistent with this application.
It can be appreciated by those skilled in the art that polarity could be altered and material could be deposited on the feature side 115. For example, the feature side 115 could be biased by the processing surface 125 to perform as a cathode, and the electrode 292 could perform as an anode and a plating solution could be delivered to the processing surface 125.
As the feature side 115 of the substrate 114 may contain conductive material to be removed from the substrate 114, fewer biasing contacts for biasing the substrate 114 are required. As the conductive material to be removed from the substrate 114 comprises isolated islands of conductive material disposed on the substrate 114, more biasing contacts for biasing the substrate 114 are required. Embodiments of the processing pad assembly 222 suitable-for residual removal of material from the substrate 114 may generally include a processing surface 125 that is substantially conductive. In one embodiment, excess conductive material is removed from the feature side 115 of the substrate 114 wherein a conductive, abrasive-free processing surface 125 provides a suitable array and distribution of biasing contacts, and the residual material is removed by an electrochemical mechanical removal process provided by the conductive processing surface 125. In another embodiment, the processing surface 125 may further include abrasive particles as described herein to enhance mechanical removal.
The processing surface 125 may further include a patterned surface 251 formed on the upper surface of the elevated portions 330 to facilitate polishing of the substrate 114. Patterns of the pattered surface 251 may include a plurality of small protrusions adjacent shallow depressions in the processing surface 125. The protrusions may take any geometrical form, such as ovals, circles, rectangles, hexagons, octagons, triangles, or combinations thereof and may be formed by compression molding and/or embossment of the processing surface 125. Alternatively, the processing surface may be substantially flat or planar having negligible raised or lowered portions on the processing surface 125.
Processing Pad Articles
In this embodiment, the processing layer 290 has a plurality of elevated portions 330 having a first contact surface 332 and a support surface or second side 334 is coupled to the second surface 322 of perforated sub-pad 350. The second side 322 of perforated sub-pad 350 is disposed on the second side 334 of the elevated portion 330 by a layer of binder 340. The elevated portion 330 may be made of a material that is conductive and abrasive, or the elevated portion 330 may be a dielectric abrasive material that functions solely as an abrading element.
In one embodiment, the elevated portions 330 are abrasive-free and may include conductive fillers, such as tin or nickel. In another embodiment, the elevated portions 330 include a plurality of abrasive particles 335 that are adapted to provide increased mechanical abrasion to the feature side 115 of the substrate 114. The abrasive particles may be conductive, dielectric, or combinations thereof. Examples of abrasive particles 335 include ceramic particles, inorganic particles, organic particles, polymer particles, metals, or combinations thereof. Other abrasive particles 335 include particles comprising metals, such as aluminum, ceria, silica, combinations thereof or oxides thereof. In another embodiment, the elevated portions 330 are made a conductive composite material having any of the abrasive particles 335 mentioned above bound in a conductive polymer. In another embodiment, the abrasive particles 335 mentioned above are bound in a polymer that is substantially dielectric.
The elevated portions 330 and the sub-pad 350 are made of materials that exhibit a differing modulus of elasticity or hardness. The sub-pad 350 is softer and capable of deformation under compressive forces while the elevated portion 330 is harder as it must resist the compressive forces to function as an abrading mechanism.
In this embodiment, the interstitial pad 320 is disposed in the pad perforations 305 by the binder 340 or the stainless steel Velcro® connection 328. Electrolyte 311 is provided to the process pad assembly 222 via the nozzle 255. The interstitial pad 320 is open cell foam that is capable of retaining water at about 10 to about 20 times its own weight, for example, from about 14 to about 18 times its own weight. The interstitial pad 320 is configured to retain the electrolyte when the platen assembly 230 is rotated and is configured to provide enhanced electrolyte retention at higher RPM's. The interstitial pad 320 may be made of a polymer material such as a microcellular polyurethane material having a modulus range from about 2 psi to about 90 psi at 25% deflection. In one embodiment, the interstitial pad 320 is a high performance foam available from Rogers Corporation, such as a urethane foam sold under the trade name PORON®. The open cell foam also facilitates conductivity in a plurality of electrochemical cells 310 formed when the feature side 115 of the substrate 114 is in communication with the processing pad assembly 222 and a potential bias is applied between the electrode 292 and the elevated portions 330.
In an operation in reference to
In this embodiment, the operational process is substantially similar to the previous embodiment and certain parameters are omitted for the sake of brevity. Electrolyte 311 is provided to the process pad assembly 222 by the nozzle 255. The platen assembly 230 is rotated and the electrolyte 311 is retained in the open cell foam that comprises the interstitial pad 320. In one embodiment, the feature side 115 of the substrate 114 is urged against the process pad assembly 222 and the feature side 115 contacts the first contact surface 332 of the elevated portion 330. In another embodiment, continued urging or compression causes the interstitial pad 320 to compress under the elevated portions 330 as shown in
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.