In-situ conditioner disk cleaning in CMP

Abstract

The polishing system includes a platen for holding a polishing pad, a carrier head for holding a substrate against the polishing pad, a conditioner including a conditioner head for holding a conditioner disk against the polishing pad, a motor for moving the conditioner head laterally with respect to the platen, a conditioner disk cleaning station disposed adjacent to the platen for cleaning the conditioning disk, and a controller configured to move the conditioner head back and forth between a first position where the conditioner head is over the polishing pad and a second position where the conditioner head is at the conditioner disk cleaning station during polishing of the substrate to the motor.

Description

Technical Field

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

Background Art

[0002] Integrated circuits are generally formed on a substrate by successive deposition of conductive, semiconductive, or insulating layers on a silicon wafer. One manufacturing step involves depositing a fill layer over a non-planar surface of a lower layer and planarizing the fill layer. In some applications, such as metal polishing, the fill layer is planarized until the upper surface of the underlying patterned layer is exposed. In other applications, such as oxide polishing, the fill layer is planarized until a predetermined thickness remains over the non-planar surface. Additionally, planarization of the substrate surface is typically required for photolithography.

[0003] Chemical mechanical polishing is an accepted method of planarization. This planarization method generally requires that the substrate be placed on a carrier or polishing head and the surface of the substrate to be polished be exposed. The substrate is then placed against a rotating polishing pad. The carrier head may also rotate and / or vibrate to provide additional movement between the substrate and the polishing surface. Further, a polishing fluid, generally including an abrasive and at least one chemically reactive agent, may be spread over the polishing pad.

[0004] When the polisher is in operation, the pad is pressurized and shear and friction generate heat and wear. Slurry and abraded material from the wafer and pad are pushed into the pores of the pad material, and the material itself is matted and 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 the captured slurry and remating, re-expanding, or re-roughening the pad material.

[0005] A polishing system generally includes a conditioner system for conditioning the state of a polishing pad. Conditioning the polishing pad maintains the polishing surface at a consistent roughness to ensure a uniform polishing state between wafers. Conventional conditioner systems have a conditioner head that holds a conditioner disk with abrasive particles on the bottom surface, for example, diamond particles, which 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 can be conditioned after each substrate is polished, or after several substrates are polished. The pad can also be conditioned simultaneously as the substrate is being polished.

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

[0007] In one aspect, a polishing system includes a platen for holding a polishing pad, a carrier head for holding a substrate against the polishing pad, a conditioner including a conditioner head for holding a conditioner disk against the polishing pad, a motor for moving the conditioner head laterally relative to the platen, a conditioner disk cleaning station disposed adjacent to the platen for cleaning the conditioner disk, and a controller configured to move the conditioner head back and forth between a first position where the conditioner head is over the polishing pad and a second position where the conditioner head is at the conditioner 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 sweeping a conditioner disk between a first position in contact with the polishing pad and a second position at a conditioner disk cleaning station during polishing of the substrate.

[0009] One or more of the following possible advantages may be realized. For example, corrosion of the conditioner disk during polishing of a tungsten layer can be reduced. Thereby, the risk of substrate defects or scratch marks can be reduced. Accumulation of slurry on the bottom surface of the conditioner disk is avoided, which can reduce the risk of coagulation and defects. The conditioner disk can also have a longer life.

[0010] Details of one or more implementations 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

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] Like reference numerals and symbols in various drawings indicate like elements.

[0013] As described above, the chemical mechanical polishing process can include a pad conditioning step in which a conditioner disk, for example, a disk coated with abrasive diamond particles, is pressed against a rotating polishing pad to condition and texture the surface of the polishing pad. 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 simultaneously with polishing, thereby being more time-efficient 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 generally contacts the polishing pad after the substrate has been polished and generally after the pad has been washed to remove the slurry. This reduces the exposure of the conditioning disk to the slurry but has a lower throughput.

[0014] When the conditioner disk is not being used for conditioning, the conditioner disk can be placed at the cleaning station. In the case of conventional "in situ" and "ex situ" conditioning, this is done once per substrate. In the case of "ex situ" conditioning, the disk is placed at the cleaning station while the substrate is being polished and returned to the polishing pad after each polishing operation. In the case of "in situ" conditioning, the disk is placed at the cleaning station after the polishing operation and returned to the polishing pad when a new substrate has been loaded and is ready for polishing.

[0015] Some polishing processes, such as the polishing of tungsten (W), pose a risk of corrosion to the stainless steel backing layer of the conditioning disk. As a result, in situ conditioning can result in a significantly shorter conditioner disk life, as the disk must be replaced before the corrosion poses a risk of contamination to the polishing process. On the other hand, ex situ conditioning has a lower throughput.

[0016] A technique that can mitigate these problems is to position the cleaning station at a location where the conditioning disk can be periodically cleaned during the polishing operation. In particular, the conditioner disk cleaning station can be positioned at the edge of the platen in a location that can be reached by sweeping the disk with the conditioner arm. This allows the conditioning disk to be cleaned, for example, with each sweep of the arm.

[0017] As shown in FIGS. 1-3, chemical mechanical polishing system 20 includes a rotatable platen 24 on which polishing pad 30 is positioned. Platen 24 is operable to rotate about axis 25 (see arrow A in FIG. 2). For example, motor 22 can rotate driver shaft 28 to rotate platen 24. Polishing pad 30 can be a two-layer polishing pad having an outer polishing layer 32 with a polishing surface 36 and a softer backing layer 34.

[0018] Polishing system 20 includes, for example, a supply port 64 at the end of slurry supply arm 62 to dispense a polishing liquid 60, such as a polishing agent slurry, onto polishing pad 30. In some implementations, polishing system 20 includes a wiper blade or body 66 to evenly disperse polishing liquid 60 across polishing pad 30 (see FIG. 2).

[0019] Carrier head 70 is suspended from a support structure 72, such as a carousel or track, and is connected by driver shaft 74 to a carrier head rotation motor 76 so that carrier head can rotate about axis 71 (see arrow B in FIG. 2). Optionally, carrier head 70 can vibrate laterally, for example, on a slider on carousel or track 72 or by the rotational vibration of the carousel itself (see arrow C in FIG. 2). During operation, the platen is rotated about its central axis 25, the carrier head is rotated about its central axis 71, and is translated laterally across the upper surface of polishing pad 30. Carrier head 70 can include a flexible membrane 80 having a substrate mounting surface for contacting the back side of substrate 10, and a plurality of pressurizable chambers 82 for applying different pressures to different zones on substrate 10, such as different radially oriented zones. The carrier head can also include a retaining ring for holding the substrate. Carrier head 70 can include a retaining ring 84 for holding the substrate under membrane 80.

[0020] The polishing station 20 also includes a pad conditioner 40 having a conditioner disk 50 for maintaining 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 adhered to the lower surface of a backing plate 54. The backing plate 54 can be of other materials such as ceramics, but is generally a metal such as stainless steel. In some implementations, other compositions, such as abrasive particles made of silicon carbide, can be used instead of or in addition to the diamond particles.

[0021] During conditioning, the abrasive regions move relative to the surface of the polishing pad 30, thereby abrading and re-texturing the polishing surface 36. For example, both the polishing pad 30 and the conditioning disk 50 can rotate (see arrows A and E in FIG. 2).

[0022] The conditioner disk 50 can be held by a conditioner head 46 at the end of an arm 42. The arm 42 and the conditioner head 46 are supported by a base 48. The arm 42 can oscillate to sweep the conditioner head 46 and the conditioner disk 50 laterally across the polishing pad 30. For example, the base 48 is driven by a motor 49 to pivot about a vertical axis, thereby sweeping the arm 42 and the conditioner head 46 laterally over the platen 24 and the polishing pad 30.

[0023] The conditioner head 46 includes a mechanism for attaching the conditioner disk 50 to the conditioner head 46 (such as a mechanical mounting system, for example, bolts or screws, or a magnetic mounting system), and a mechanism for rotating the conditioner disk 50 about the axis 41 (such as a driver belt passing through an arm or rotor within the conditioner head). In addition, the pad conditioner 40 can also include a mechanism for adjusting the pressure between the conditioner disk 50 and the polishing pad 30 (such as a pneumatic or mechanical actuator within the conditioning head or base), and / or a mechanism for varying the vertical position of the conditioner disk 50 relative to the polishing pad 30. For example, the conditioner head 46 can include an upper portion 46a, a lower portion 46b that holds the conditioner disk 50, and an actuator for adjusting the vertical position of the lower portion 46b relative to the upper portion 46a or for adjusting the pressure of the conditioner disk 50 on the polishing pad 30. However, these mechanisms can have many possible implementations (and are not limited to those shown in FIG. 1). As another example, a vertical actuator can be positioned on the base 48 to raise and lower the arm 42, or the arm can be pivotally attached to the base 48 in a manner that allows the arm to swing vertically to lower the conditioner head 46 and raise it from the polishing pad 30.

[0024] The polishing station 20 also includes a conditioner cleaning station 100 disposed adjacent to the platen 24. The conditioner cleaning station 100 can include a brush 110 having a brush surface 112 for contacting the bottom surface of the conditioner disk 50. The brush surface 112 can be sponge-like, for example, a porous surface, or can have bristles. The brush surface, whether sponge-like or with bristles, can be provided by a polymer material that does not interact with the chemical action used in the CMP process, such as nylon, polyvinyl chloride (PVC), polyvinyl acetal (PVA), polypropylene, or polyurethane.

[0025] As shown in FIG. 1, the brush 110 can be a disk-shaped brush having a generally flat circular surface 112. The brush 110 can be supported on a support 114 that can be rotated by a motor 116 about a vertical axis, for example, an axis perpendicular to the surface of the conditioner disk 50.

[0026] Alternatively, as shown in FIG. 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, for example, an axis parallel to the surface of the conditioner disk 50. The axis of rotation can be substantially perpendicular to the direction of movement of the conditioner head 46 when the arm 42 sweeps the conditioner head 46 across the brush 110.

[0027] The conditioner cleaning station 100 can also include one or more nozzles 120 for spraying one or more fluids onto the bottom surface of the conditioner disk 50 from a source 122 when the conditioner disk 50 is disposed in the cleaning station 100, for example, when the conditioner disk 50 is over the brush 110. The fluid can be a liquid, such as deionized water (DI water), or a cleaning agent, for example, one or more of water with a pH adjuster. The fluid can be a gas, such as air, nitrogen gas, or vapor.

[0028] In some implementations, the fluid source 122 includes a reservoir 122a of cleaning liquid, such as DI water, and a pump 124 can be used to direct the cleaning liquid through one or more nozzles onto the conditioner disk 50. This can wash the polishing liquid off the conditioner disk and the conditioner head to reduce the potential for corrosion.

[0029] In some implementations, the fluid source 122 includes a compressor 122b for directing a jet of gas, such as air, through one or more nozzles onto the conditioner disk 50. This can dry the conditioner disk and the conditioner head.

[0030] In some implementations, the conditioner disk cleaning system 100 uses multiple fluids and there is one or more dedicated nozzles for each fluid, in other words, each nozzle accepts only one fluid. In some implementations, valves and piping can be used such that the fluid directed through the nozzles can be selected from multiple fluids.

[0031] The temperature of the fluid can be controlled using a heater and / or a cooling device 122c. The temperature can be in the range of 0 to 100 °C. The heater and / or cooling device can be provided by a heat exchanger thermally coupled to the reservoir 122a to control the temperature of the fluid in the reservoir or to a fluid line that conveys the fluid from the source, such as the reservoir, to the nozzle 120.

[0032] In either the case of a disk-shaped brush or a cylindrical brush, the upper surface 112 of the brush 110 that contacts the conditioning disk 50 can be coplanar with the polishing surface 36 of the polishing pad 30. This enables the arm 42 to sweep into the conditioner cleaning station 100 and contact the conditioner disk 50 against the brush 110 without the need to change the vertical position of the conditioner disk 50, for example, without the need to retract the conditioner disk 50. However, in some implementations, the upper surface 112 of the brush 110 is above or below the polishing surface 36, in which case the conditioner disk can be raised and lowered as the conditioner disk moves from the polishing pad 30 to the cleaning station 100.

[0033] In some implementations, the polishing system 20 includes a platen shield 150, in other words, a wall surrounding the platen 24, to prevent slurry discharged by the centrifugal motion of the platen 24 from splashing onto other nearby components. The arm 42 can project beyond the wall 150, and the conditioner head 46 extends below the top of the wall to hold the conditioner disk against the polishing pad 30. However, the platen shield 150 can be provided with an aperture 152 through which the conditioner head 46 can move laterally to reach the conditioning disk cleaning station 100. Again, this enables the arm 42 to sweep into the conditioner cleaning station 100 and contact the conditioner disk 50 against the brush 110 without the need to change the vertical position of the conditioner disk 50, for example, without the need to retract the conditioner disk 50. In some implementations, a portion 154 of the wall extends to surround the conditioning disk cleaning station 100.

[0034] The movement of the conditioner head 46, e.g., the lateral sweep and vertical actuation (shown by arrow D in FIG. 2) of the conditioner disk 50 and / or the conditioner head 46, is controlled by the controller 90. For example, the controller 90 can be coupled to the motor 49 to control the lateral position of the arm 42 and the conditioner head 46. The controller 90 can also be coupled to appropriate components, e.g., the pump 124 or the compressor 122b, to control the flow of fluid from the nozzle, and to the motor 116 to control the rotation of the brush 110.

[0035] During operation, while the substrate 10 is being polished on the polishing pad 30, the controller 90 can cause the conditioner head 46 and the conditioner disk 50 to sweep laterally back and forth along a path 130 that covers both the polishing pad 30 and the pad conditioner cleaning station 100. One end point 132 of the path 130 can be located above the pad conditioner cleaning station 100. The other end point 134 of the path is on the polishing pad, e.g., in a location close to the center and the axis of rotation 25 of the platen 24, as far as the conditioner head 46 can reach on the arm. Thereby, with each sweep of the conditioner head 46, the conditioner disk 50 can enter the pad conditioner cleaning station 100 and be cleaned to remove polishing fluid and debris. This can prevent corrosion of the conditioner disk 50 with a limited impact on the throughput of the substrate, or without impact.

[0036] In some implementations, the sweep pattern is set such that the conditioner head 50 remains stationary at the end point 132, e.g., at the conditioner disk cleaning station 100, for a certain period of time (referred to as the dwell time). The dwell time of the conditioner head 50 at the conditioner disk cleaning station 100 can be set by the user, e.g., from 1 second to 10 seconds. In some implementations, the sweep pattern is set such that the conditioner head 50 moves more slowly through the conditioner disk cleaning station 100 than when it moves over the polishing pad.

[0037] In some implementations, the sweep pattern is set such that when the carrier head reaches the end point 132, the conditioner disk 50 is completely removed from the polishing pad 30. However, the sweep pattern can also be set such that when the carrier head reaches the end point 132, a portion of the conditioner disk 50 is on the polishing pad 30 and a portion of the conditioner disk 50 is on the brush 110.

[0038] In some implementations, the sweep pattern is set such that the conditioner head 50 does not enter the pad conditioner cleaning station 100 during each sweep, but still enters the pad conditioner cleaning station 100 periodically, e.g., every 2 - 10 sweeps. In this case, the controller 90 causes the conditioner head 46 and the conditioner disk 50 to perform one or more sweeps where both end points are on the polishing pad 30, followed by a sweep where the end point is on the pad conditioner cleaning station 100.

[0039] In one implementation, the polishing system 20 includes a second conditioner cleaning station 160. This second conditioner cleaning station 160 can be disposed further along the sweep path from the platen 24 to the conditioner head 46 than the conditioner cleaning station 100. The second conditioner cleaning station 160 can include a cleaning cup containing a cleaning liquid for rinsing or cleaning the conditioner head 46 and the conditioner disk 50. The arm 42 can move the conditioner head 46 out of the cleaning cup and place the conditioner head 46 on the polishing pad 30. During operation, the conditioner head 46 can be moved to the second cleaning station 160 after the polishing operation (shown by path 136 in FIG. 3). The conditioner head 46 is then returned to the polishing pad 30 when a new substrate is loaded and ready for polishing.

[0040] The controller 90, and other control of the other functional operations described herein, can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, or in combinations thereof. The controller 90 and other functions can be implemented using one or more non-transitory computer program products, that is, 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 apparatus, such as a programmable processor, a computer, or multiple processors or computers. The controller 90 and other functions can be implemented using, for example, one or more programmable processors executing one or more computer programs 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).

[0041] Some embodiments of the present invention have been described. It will be understood, however, that various changes can be made. For example, Rather than sweeping along an arcuate path, the conditioner head may be moved linearly, for example, conveyed along a linear rail. ● The polishing pad may be a belt driven by a roller rather than a circular pad on a platen. ● The polishing pad may be a fixed abrasive pad or other material.

[0042] Accordingly, other embodiments fall within the scope of the appended claims.

Claims

1. A platen for holding a polishing pad, a carrier head for holding a substrate with respect to the polishing pad, a conditioner including a conditioner head for holding a conditioner disk with respect to the polishing pad, a motor for moving the conditioner head laterally with respect to the platen, a conditioner disk cleaning station disposed adjacent to the platen for cleaning the conditioning disk, a controller configured to move the conditioner head back and forth between a first position where the conditioner head is on the polishing pad and a second position where the conditioner head is at the conditioner disk cleaning station during polishing of the substrate to move the conditioner head with respect to the motor A polishing system comprising.

2. The polishing system according to claim 1, wherein the conditioner disk cleaning station includes a brush arranged such that the conditioner head contacts the conditioner disk when the conditioner head is at the conditioner disk cleaning station.

3. The polishing system according to claim 2, wherein the brush is a disk having a flat surface for contacting the conditioner disk.

4. The polishing system according to claim 2, wherein the brush is a cylinder having a cylindrical outer surface for contacting the conditioner disk.

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

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

7. The polishing system according to claim 1, wherein an upper surface of the brush is coplanar with a polishing surface.

8. The polishing system according to claim 1, wherein the conditioner disk cleaning station includes one or more nozzles for directing fluid onto the conditioner disk when the conditioner head is at the conditioner disk cleaning station.

9. The polishing system according to claim 8, wherein the fluid includes water.

10. The polishing system according to claim 8, wherein the fluid includes air or nitrogen.

11. The polishing system according to claim 1, wherein the conditioner comprises an actuator configured to move the conditioning disk in a vertical direction.

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

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

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

16. Contacting a substrate with a polishing pad; Sweeping a conditioning disk between a first position in contact with the polishing pad and a second position at a conditioning disk cleaning station during polishing of the substrate A method of chemical mechanical polishing.

17. The method according to claim 16, including maintaining the conditioning disk at a consistent height when the conditioning disk moves from the first position to the second position.

18. The method according to claim 16, including moving the conditioner head to the second position with each sweep of the conditioner head during polishing of the substrate.

19. The method according to claim 16, including moving the conditioner head to the second position less than all sweeps of the conditioner head during polishing of the substrate.

20. The method according to claim 16, including scrubbing the conditioning disk with a brush at the conditioning disk cleaning station.

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