In-situ regulator disk cleaning during CMP

Abstract

In one embodiment, a polishing system includes: a platform holding a polishing pad; a carrier head that maintains a substrate against the polishing pad; an adjuster including an adjuster head to maintain an adjuster disk against the polishing pad; a motor that moves the regulator head that is laterally movable relative to the platform; the adjusting disc cleaning station is positioned to be adjacent to the platform so as to clean the adjusting disc; and a controller configured to move the regulator head back and forth between a first position, at which the regulator head is above the polishing pad, and a second position, at which the regulator head is in the regulator disk cleaning station, during polishing of the substrate.

Description

Technical Field

[0001] The present disclosure relates to chemical mechanical polishing (CMP), and more particularly to polishing pad conditioners. Background Art

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconducting, or insulating layers on a silicon wafer. One manufacturing step involves depositing a fill layer over the non-planar surface of the underlying layer and planarizing the fill layer. For some applications, such as metal polishing, the fill layer is planarized until the top surface of the underlying patterned layer is exposed. For other applications, such as oxide polishing, the fill layer is planarized until a predetermined thickness is left over the non-planar surface. In addition, photolithography typically requires planarization of the substrate surface.

[0003] Chemical mechanical polishing is a recognized planarization method. This planarization method generally requires mounting the substrate on a carrier or polishing head, exposing the surface of the substrate to be polished. Next, the substrate is placed against a rotating polishing pad. The carrier head may also rotate and / or oscillate to provide additional movement between the substrate and the polishing surface. In addition, a polishing liquid, which generally includes an abrasive and at least one chemical reactant, may be spread on the polishing pad.

[0004] As the polisher operates, the pad is subjected to compression, shear, and friction, which generates heat and wear. Slurry and abrasive material from the wafer and pad are forced into the pores of the pad material, and the material itself becomes matte or even partially melted. These effects, sometimes referred to as "glazing," reduce the roughness of the pad and the ability to apply fresh slurry to the substrate. Therefore, it is desirable to condition the pad by removing trapped slurry and unmatting, re-expanding, or re-roughening the pad material.

[0005] Polishing systems typically include a conditioning system that conditions the polishing pad. Conditioning of the polishing pad maintains a consistent roughness on the polishing surface to ensure uniform polishing conditions from wafer to wafer. Conventional conditioner systems have a conditioner head that holds a conditioner disk having an abrasive lower surface, such as with diamond particles, that is placed in contact with the polishing pad. The contact and movement of the abrasive surface against the polishing pad roughens the polishing surface. The pad may be conditioned after polishing each substrate or after polishing multiple substrates. The pad may also be conditioned while polishing the substrate.

[0006] Slurry and polishing debris can adhere to the conditioning disk. Therefore, the polishing system can also include a conditioning disk cleaning station. The conditioning operation is performed, for example, by sweeping the conditioning disk back and forth across the polishing pad multiple times. After the pad has been conditioned for the desired time, the conditioning disk is lifted from the polishing pad and moved to a separate cleaning station for cleaning. The conditioning disk can be returned to the polishing pad for use with a new substrate. Summary of the invention

[0007] In one aspect, a polishing system includes: a platform that holds a polishing pad; a carrier head that holds a substrate against the polishing pad; a conditioner that includes a conditioner head to hold a conditioner disk against the polishing pad; a motor that moves the conditioner head that is laterally movable relative to the platform; a conditioning disk cleaning station that is positioned adjacent to the platform to clean the conditioning disk; and a controller that is configured to cause the motor to move the conditioner head back and forth between a first position where the conditioner head is above the polishing pad and a second position where the conditioner head is in the conditioning disk cleaning station during polishing of the substrate. .

[0008] In another aspect, a method of chemical mechanical polishing includes contacting a substrate with a polishing pad; and scanning a conditioning pad between a first position contacting the polishing pad and a second position in a conditioning pad cleaning station during polishing of the substrate.

[0009] One or more of the following possible advantages may be achieved. For example, during polishing of the tungsten layer, corrosion of the adjuster disk may be reduced. Thus, the risk of defects or scratches on the substrate may be reduced. Slurry buildup on the bottom surface of the adjuster disk may be avoided, thereby reducing the risk of solidification and defects. The adjuster disk may also have a longer life.

[0010] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic cross-sectional side view of a polishing system including a conditioner disk cleaning system.

[0012] Figure 2 is a schematic top view of the polishing system.

[0013] Figure 3 is a schematic perspective view of a conditioner head placed on a polishing pad.

[0014] Figure 4 is a schematic cross-sectional side view of a polishing system including another embodiment of a conditioner disk cleaning system.

[0015] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0016] As described above, a chemical mechanical polishing process may include a pad conditioning step in which a conditioner disk (e.g., a disk coated with abrasive diamond particles) is pressed against a rotating polishing pad to condition and texture the polishing pad surface. In an "in-situ" conditioning process, the conditioner disk contacts the polishing pad while the substrate is being polished. This allows conditioning to be performed while polishing, thus saving time and having a higher substrate throughput. However, the conditioning disk is exposed to the polishing slurry. In an "ex-situ" conditioning process, the conditioner disk contacts the polishing pad after the substrate has been polished, typically after the pad has been cleaned to remove the slurry. This reduces the exposure of the conditioning disk to the slurry, but has a lower throughput.

[0017] When the conditioner disk is not being used for conditioning, it can be placed in the cleaning station. This occurs once per substrate for both traditional "in-situ" and "ex-situ" conditioning. For "ex-situ" conditioning, the disk is placed in the cleaning station while the substrate is being polished and is returned to the polishing pad after each polishing operation. For "in-situ" conditioning, the disk is placed in the cleaning station after the polishing operation and is returned to the polishing pad when a new substrate is loaded and ready for polishing.

[0018] Some polishing processes, such as tungsten (W) polishing, pose a risk of corrosion to the stainless steel backing of the adjustment disk. As a result, in-situ adjustment can lead to a significantly shorter adjuster disk life, as the disk must be replaced before corrosion poses a risk of contamination of the polishing process. Ex-situ adjustment, on the other hand, has a lower yield.

[0019] A technique that can alleviate these problems is to place a cleaning station in a position where the conditioning disc can be periodically cleaned during the polishing operation. Specifically, the conditioning disc cleaning station can be located at the edge of the platform, in a position that the conditioner arm can reach as it sweeps the disc. This permits cleaning of the conditioning disc, for example, with each sweep of the arm.

[0020] like Figures 1 to 3 , the chemical mechanical polishing system 20 includes a rotatable platform 24 on which a polishing pad 30 is located. The platform 24 can be operated to rotate about an axis 25 (see Figure 2 2. For example, the motor 22 can rotate the drive shaft 28 to rotate the platform 24. The polishing pad 30 can be a dual-layer polishing pad having an outer polishing layer 32 and a softer backing layer 34, wherein the outer polishing layer 32 has a polishing surface 36.

[0021] The polishing system 20 includes a supply port 64, for example, at the end of a slurry supply arm 62, to dispense a polishing liquid 60 (eg, abrasive slurry) onto the polishing pad 30. In some embodiments, the polishing system 20 includes a wiper blade or body 66 (see Figure 2 ) to evenly distribute the polishing liquid 60 across the polishing pad 30.

[0022] The carrier head 70 is suspended from a support structure 72 (eg, a turntable or track) and is connected to a carrier head rotation motor 76 via a drive shaft 74 so that the carrier head can rotate about an axis 71 (see FIG. Figure 2 Optionally, the carrier head 70 may be swung laterally (see arrow B in FIG. Figure 2 The polishing pad 30 is moved by the carrier head 70, e.g., on a slider on a turntable or track 72; or by rotational swing of the turntable itself. In operation, the platform rotates about its central axis 25, and the carrier head rotates about its central axis 71 and translates laterally across the top surface of the polishing pad 30. The carrier head 70 may include a flexible membrane 80 having a substrate mounting surface to contact the back side of the substrate 10, and a plurality of pressurizable chambers 82 to apply different pressures to different zones on the substrate 10, such as different radial zones. The carrier head may also include a retaining ring to retain the substrate. The carrier head 70 may include a retaining ring 84 to retain the substrate under the membrane 80.

[0023] The polishing system 20 also includes a pad conditioner 40 having a conditioner disk 50 to maintain the surface roughness of the polishing pad 30. The bottom surface of the conditioner disk 50 includes one or more abrasive regions 52 that contact the polishing surface 36 during the conditioning process. The abrasive regions can be provided by abrasive diamond particles fixed to the lower surface of a backing plate 54. The backing plate 54 is typically metal (e.g., stainless steel), although other materials (e.g., ceramics) are possible. In some embodiments, abrasive particles of other compositions (e.g., silicon carbide) are used instead of or in addition to diamond particles.

[0024] During conditioning, the abrasive region moves relative to the surface of the polishing pad 30, thereby abrading and retexturing the polishing surface 36. For example, both the polishing pad 30 and the conditioning disk 50 may rotate (see Figure 2 Arrows A and E).

[0025] Conditioning disk 50 may be maintained by conditioner head 46 at the end of arm 42. Arm 42 and conditioner head 46 are supported by base 48. Arm 42 may swing so that conditioner head 46 and conditioner disk 50 may be swept laterally across polishing pad 30. For example, base 48 may be driven by motor 49 to pivot about a vertical axis so that arm 42 and conditioner head 46 may be swept laterally over platform 24 and polishing pad 30.

[0026] Conditioner head 46 includes a mechanism for attaching conditioner disk 50 to conditioner head 46 (e.g., a mechanical attachment system, such as bolts or screws, or a magnetic attachment system) and a mechanism for rotating conditioner disk 50 about axis 41 (e.g., a drive belt via an arm or rotor inside conditioner head). In addition, pad conditioner 40 may also include a mechanism for adjusting the pressure between conditioner disk 50 and polishing pad 30 (e.g., a pneumatic or mechanical actuator inside the conditioner head or base) and / or a mechanism for changing the vertical position of conditioner disk 50 relative to polishing pad 30. For example, conditioner head 46 may include an upper portion 46a, a lower portion 46b that maintains conditioner disk 50, and an actuator that adjusts the vertical position of lower portion 46b relative to upper portion 46a, or adjusts the pressure of conditioner disk 50 on polishing pad 30. However, these mechanisms may have many possible embodiments (and are not limited to Figure 1 As other examples, a vertical actuator may be located in base 48 to raise and lower arm 42, or the arm may be pivotally attached to base 48 in a manner that permits it to swing vertically to lower and raise conditioner head 46 from polishing pad 30.

[0027] The polishing system 20 also includes a conditioning disk cleaning station 100 positioned adjacent to the platform 24. The conditioning disk cleaning station 100 may include a brush 110 having a brush surface 112 to contact the bottom surface of the conditioner disk 50. The brush surface 112 may be sponge-like (e.g., a porous surface), or may have bristles. The brush surface (whether sponge-like or bristle-like) may be provided by a polymer material that does not interact with the chemicals used in the CMP process, such as nylon, polyvinyl chloride (PVC), polyvinyl acetal (PVA), polypropylene, or polyurethane.

[0028] like Figure 1 , the brush 110 may be a disc-shaped brush having a generally planar circular surface 112. The brush 110 may be supported on a support 114, which may be rotated by a motor 116 about a vertical axis (eg, an axis orthogonal to the surface of the adjuster disk 50).

[0029] Alternatively, if Figure 4 , the brush 110 can be a cylindrical brush having a cylindrical surface 112. The brush 110 can be supported on a support that can be rotated by a motor about a horizontal axis (e.g., an axis parallel to the surface of the conditioner disk 50). When the arm 42 sweeps the conditioner head 46 across the brush 110, the axis of rotation can be substantially orthogonal to the direction of motion of the conditioner head 46.

[0030] Conditioning disc cleaning station 100 may also include one or more nozzles 120 to spray one or more fluids from source 122 onto the bottom surface of conditioner disc 50 when conditioner disc 50 is placed in conditioning disc cleaning station 100 (e.g., when conditioner disc 50 is above brush 110). The fluid may be a liquid, such as one or more of: deionized water (DI water), or water with a cleaning chemistry (e.g., a pH adjuster). The fluid may be a gas, such as air, nitrogen, or steam.

[0031] In some embodiments, fluid source 122 includes a reservoir 122a of a cleaning liquid (e.g., DI water), and pump 124 may be used to direct the cleaning fluid through one or more nozzles onto conditioner disk 50. This may purge the polishing liquid from the conditioner disk and conditioner head to reduce the potential for corrosion.

[0032] In some embodiments, the fluid source 122 includes a compressor 122b to direct a jet of gas (eg, air) via one or more nozzles onto the regulator disk 50. This may dry the regulator disk and the regulator head.

[0033] In some embodiments, the conditioning disc cleaning station 100 uses multiple fluids and there are one or more dedicated nozzles for each fluid, ie, each nozzle receives only a specific fluid. In some embodiments, valves and conduits may be used so that the fluid directed through the nozzle may be selected from a plurality of fluids.

[0034] A heater and / or cooler 122c may be used to control the temperature of the fluid. The temperature may be in the range of 0 degrees Celsius to 100 degrees Celsius. The heater and / or cooler may be provided by a heat exchanger thermally coupled to the reservoir 122a to control the temperature of the fluid in the reservoir or thermally coupled to a fluid line that carries the fluid from a source (e.g., a reservoir) to the nozzle 120.

[0035] For a disc-shaped brush or a cylindrical brush, the top surface 112 of the brush 110 that will contact the conditioning disk 50 can be coplanar with the polishing surface 36 of the polishing pad 30. This permits the arm 42 to sweep the conditioner disk 50 into the conditioning disk cleaning station 100 and into contact with the brush 110 without having to change the vertical position of the conditioner disk 50, e.g., without having to retract the conditioner disk 50. However, in some embodiments, the top surface 112 of the brush 110 is above or below the polishing surface 36; in this case, the conditioner disk can be raised or lowered as it is transferred from the polishing pad 30 to the conditioning disk cleaning station 100.

[0036] In some embodiments, the polishing system 20 includes a platform shield 150, i.e., a wall surrounding the platform 24 to prevent slurry expelled by the centrifugal movement of the platform 24 from splashing onto other nearby components. The arm 42 may protrude above the wall 150, with the conditioner head 46 extending below the top of the wall to maintain the conditioner disk against the polishing pad 30. However, the platform shield 150 may be provided with an aperture 152 through which the conditioner head 46 may be moved laterally to reach the conditioning disk cleaning station 100. This again permits the arm 42 to sweep the conditioner disk 50 into the conditioning disk cleaning station 100 and into contact with the brush 110 without having to change the vertical position of the conditioner disk 50, e.g., without having to retract the conditioner disk 50. In some embodiments, a portion 154 of the wall extends to surround the conditioning disk cleaning station 100.

[0037] The movement (e.g., lateral sweep) of the regulator head 46 is controlled by the controller 90. Figure 2 4 and 5. The controller 90 may be coupled to the motor 49 to control the lateral position of the arm 42 and the regulator head 46. The controller 90 may also be coupled to appropriate components (e.g., a pump 124 or a compressor 122b) to control the flow of fluid from the nozzle, and to the motor 116 to control the rotation of the brush 110.

[0038] In operation, as the substrate 10 is polished on the polishing pad 30, the controller 90 can sweep the conditioner head 46 and the conditioner disk 50 back and forth laterally along a path 130 that covers both the polishing pad 30 and the conditioning disk cleaning station 100. One end 132 of the path 130 can be located above the conditioning disk cleaning station 100. The other end 134 of the path is above the polishing pad, for example, near the center of the platform 24 and the rotation axis 25 so that the conditioner head 46 can reach the point of the arm. Therefore, with each sweep of the conditioner head 46, the conditioner disk 50 enters the conditioning disk cleaning station 100 and can be cleaned to remove polishing fluid and debris. This can prevent corrosion of the conditioner disk 50 with only limited or no impact on the yield of the substrate.

[0039] In some embodiments, the sweep mode is configured so that the conditioner head 46 remains stationary at the end point 132 (e.g., in the conditioning disc cleaning station 100) for a period of time (referred to as the dwell time). The dwell time of the conditioner head 46 in the conditioning disc cleaning station 100 can be set by the user, for example, from one to ten seconds. In some embodiments, the sweep mode is configured so that the conditioner head 46 travels slower when moving through the conditioning disc cleaning station 100 than when moving over the polishing pad.

[0040] In some embodiments, the sweeping pattern is configured such that when the carrier head reaches endpoint 132, the conditioner disk 50 is completely removed from the polishing pad 30. However, the sweeping pattern can also be configured such that when the carrier head reaches endpoint 132, a portion of the conditioner disk 50 is above the polishing pad 30 and a portion of the conditioner disk 50 is above the brush 110.

[0041] In some embodiments, the sweep pattern is configured so that the conditioner head 46 does not enter the conditioning disk cleaning station 100 with each sweep, but still periodically (e.g., every two to ten sweeps) enters the conditioning disk cleaning station 100. In this case, the controller 90 will cause the conditioner head 46 and conditioner disk 50 to perform one or more sweeps with both endpoints above the polishing pad 30, followed by a sweep with an endpoint above the conditioning disk cleaning station 100.

[0042] In some embodiments, polishing system 20 includes a second conditioner cleaning station 160. Second conditioner cleaning station 160 can be positioned farther from platform 24 along the sweep path of conditioner head 46 than conditioning disk cleaning station 100. Second conditioner cleaning station 160 can include a cleaning cup containing a cleaning fluid for rinsing or cleaning conditioner head 46 and conditioner disk 50. Arm 42 can move conditioner head 46 away from the cleaning cup and place conditioner head 46 atop polishing pad 30. In operation, conditioner head 46 can be moved to second cleaning station 160 ( Figure 3 When a new substrate has been loaded and is ready for polishing, the conditioner head 46 then returns to the polishing pad 30.

[0043] Other control of the operation of the controller 90 and other functions described in this specification may be implemented in digital electronic circuitry or in computer software, firmware, or hardware, or a combination thereof. The controller 90 and other functions may be implemented using one or more non-transitory computer program products, i.e., one or more computer programs tangibly embodied in a machine-readable storage device, for execution by or to control the operation of a data processing device, such as a programmable processor, a computer, or multiple processors or computers. The controller 90 and other functions may be implemented using one or more programmable processors executing one or more computer programs, for example, in a general purpose computer, or using dedicated logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0044] A number of embodiments of the present invention have been described. However, it should be understood that various modifications may be made. For example: • The adjuster head may move linearly, for example carried along a linear track, rather than swept along an arcuate path. The polishing pad can be a belt driven by rollers rather than a round pad on a platform. The polishing pad can be a fixed abrasive pad or other materials.

[0045] Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A polishing system comprising: a platform that holds a polishing pad; a carrier head that maintains a substrate against the polishing pad; a conditioner including a conditioner head to maintain a conditioner disk against the polishing pad; a motor that moves the regulator head laterally movable relative to the platform; an adjustment disk cleaning station positioned adjacent to the platform for cleaning the adjustment disk; as well as A controller is configured to cause the motor to move the conditioner head back and forth between a first position where the conditioner head is above the polishing pad and a second position where the conditioner head is in the conditioning disk cleaning station during polishing of the substrate.

2. The polishing system of claim 1, wherein the conditioning disk cleaning station includes a brush positioned to contact the conditioner disk when the conditioner head is in the conditioning disk cleaning station.

3. The polishing system of claim 2, wherein the brush is a disk having a flat surface to contact the conditioner disk.

4. The polishing system of claim 2, wherein the brush is cylindrical having a cylindrical outer surface to contact the conditioner disk.

5. The polishing system of claim 2, wherein the brush has a sponge-like surface.

6. The polishing system of claim 2, wherein the brush has bristles.

7. The polishing system of claim 1, wherein a top surface of the brush is coplanar with a polishing surface of the polishing pad.

8. The polishing system of claim 1, wherein the conditioning disk cleaning station includes one or more nozzles to direct fluid onto the conditioner disk while the conditioner head is in the conditioning disk cleaning station.

9. The polishing system of claim 5, wherein the fluid comprises water.

10. The polishing system of claim 5, wherein the fluid comprises air or nitrogen.

11. The polishing system of claim 1, wherein the conditioner comprises an actuator configured to vertically move the conditioning disk.

12. The polishing system of claim 11, wherein the controller is configured to cause the actuator to maintain the conditioning disk at a consistent height as the conditioner head moves from the first position to the second position.

13. The polishing system of claim 1, wherein the controller is configured to cause the motor to move the conditioner head to the second position with each sweep of the conditioner head during polishing of the substrate.

14. The polishing system of claim 1, wherein the controller is configured to cause the motor to move the conditioner head to the second position at less than all sweeps of the conditioner head during polishing of the substrate.

15. The polishing system of claim 14, wherein the controller is configured to cause the motor to periodically move the conditioner head to the second position during polishing of the substrate.

16. A method for chemical mechanical polishing, comprising the following steps: contacting the substrate with a polishing pad; as well as During polishing of the substrate, a conditioning disk is swept between a first position contacting the polishing pad and a second position in a conditioning disk cleaning station.

17. The method of claim 16, comprising the steps of: The adjustment disk is maintained at a consistent height as the adjustment disk moves from the first position to the second position.

18. The method of claim 16, comprising the steps of: The conditioning disk is moved to the second position with each sweep of the conditioning disk during polishing of the substrate.

19. The method of claim 16, comprising the steps of: The conditioning disk is moved to the second position with less than all sweeps of the conditioning disk during polishing of the substrate.

20. The method of claim 16, comprising the steps of: A brush is used in the conditioning disc cleaning station to scrub the conditioning disc.

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