Condensed gas pad regulator

Abstract

The polishing system includes a platform supporting a polishing pad; a carrier head that maintains a substrate against the polishing pad; a source of dry ice particles; and a cushion adjuster. The pad conditioner includes a compressor that generates a flow of compressed gas, a mixer coupled to the source and the compressor to mix the dry ice particles with the flow of compressed gas to form a flow of compressed gas having entrained dry ice particles, and a nozzle coupled to the mixer. The nozzle is coupled to the mixer to direct the flow of compressed gas with entrained dry ice particles onto a polishing surface of the polishing pad at a speed sufficient to adjust the polishing pad.

Description

Technical Field

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

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

[0003] Chemical mechanical polishing (CMP) is a well-known planarization method. This planarization method generally requires mounting the substrate on a carrier or polishing head. The exposed surface of the substrate is generally placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it against the polishing pad. A polishing liquid is generally supplied to the surface of the polishing pad.

[0004] Polishing systems typically include a conditioner system to condition 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 (e.g., with diamond particles) that is placed in contact with the polishing pad. Summary of the invention

[0005] In one aspect, a polishing system includes: a platform supporting a polishing pad; a carrier head maintaining a substrate against the polishing pad; a source of dry ice particles; and a pad conditioner. The pad conditioner includes: a compressor generating a compressed gas flow, a mixer coupled to the source and the compressor to mix the dry ice particles with the compressed gas flow to form a compressed gas flow with entrained dry ice particles, and a nozzle coupled to the mixer to direct the compressed gas flow with entrained dry ice particles onto a polishing surface of the polishing pad at a sufficient velocity to condition the polishing pad.

[0006] In another aspect, a method of conditioning a polishing pad includes the steps of mixing dry ice particles with a compressed air flow to form a compressed gas flow with entrained dry ice particles; and directing the compressed gas flow with entrained dry ice particles through a nozzle onto a polishing surface of the polishing pad at a sufficient velocity to condition the polishing pad.

[0007] Optionally, embodiments may include, but are not limited to, one or more of the following advantages.

[0008] Cold condensed gases may be more effective than diamond grinding discs in conditioning and / or cleaning. For example, sublimation of condensed gases may lift debris from the polishing pad and may provide increased cleanliness. As another example, the impact of condensed gas particles on the pad may achieve a desired roughness more quickly. The entire radial length of the polishing pad may be adjusted at one time, thereby reducing or avoiding the need to clean the conditioning area and improving conditioning uniformity. Pad conditioning and / or cleaning time may be reduced, thereby improving system duty cycle. The need for worn replaceable conditioning discs is avoided, thereby reducing downtime of the polishing system for maintenance to replace conditioning discs. Accumulation of dry abrasive particles on the conditioning disc may be avoided, which may improve polishing quality by reducing scratches and defects. The productivity of the polishing system may be improved because less time is spent on pad conditioner cleaning processes.

[0009] The 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

[0010] Figure 1 is a schematic cross-sectional view of a polishing system including a pad conditioner system.

[0011] Figure 2 is a schematic top view of the polishing system.

[0012] Figure 3 It is a schematic diagram of the regulation system.

[0013] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0014] During the chemical mechanical polishing process, the polishing pad surface can become smoother due to friction and compression, and polishing debris can be forced into the polishing pad. The polishing system typically includes a conditioner system having a conditioner head and a conditioner disk with an abrasive lower surface to condition the polishing pad and keep the polishing pad at a consistent roughness between substrates and remove polishing debris. However, the conditioning disk itself wears and needs to be replaced regularly. This requires shutting down the polishing system for maintenance. In addition, the abrasive slurry can splash and stick to the conditioning disk. Over time, the accumulation of dried or solidified polishing liquid on the polishing pad has a variety of detrimental effects. For example, larger particles may be dislodged and returned to the polishing surface, creating a risk of scratches and defects. Cleaning the conditioning head and conditioning disk to prevent the accumulation of dried polishing liquid requires a lot of non-productive time.

[0015] An alternative conditioning technique is to direct a jet of cold condensed gas (e.g., dry ice particles, i.e., solid CO2) onto the polishing pad. If sprayed at a high enough velocity, the impact of the particles can abrade the polishing surface and loosen debris. In addition, the sublimation of the particles generates gas that can carry away debris.

[0016] Although dry ice has been proposed for temperature control of the polishing pad surface, the mode of operation for performing the conditioning process would be completely different, for example, higher speeds and larger particle sizes. In short, the use of dry ice for temperature control does not inherently result in a conditioning operation.

[0017] Figure 1 A polishing system 20 is shown that is operable to polish a substrate 10. The polishing system 20 includes a rotatable platform 24 on which a polishing pad 30 is located. The platform 24 is operable 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 two-layer polishing pad having an outer polishing layer 34 having a polishing surface 36 and a softer backing layer 32.

[0018] The polishing system 20 includes a supply port 64 (eg, at a distal end of a slurry supply arm 62 ) to dispense a polishing liquid 60 (eg, abrasive slurry) onto the polishing pad 30 .

[0019] The polishing system 20 includes a carrier head 70 that can be operated to hold the substrate 10 against the polishing pad 30. The carrier head 70 can 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 that apply different pressures to different areas (e.g., different radial areas) on the substrate 10. The carrier head 70 is suspended from a support structure 72 (e.g., a turntable or track) and is connected to a carrier head rotation motor 76 by a carrier drive shaft 74 so that the carrier head can rotate about an axis 71. In addition, the carrier head 70 can swing laterally across the polishing pad 30, for example, by moving in radial slots in the turntable 72 driven by an actuator, by rotation of the turntable driven by a motor, or by moving back and forth along the track driven by an actuator. In operation, the platform 24 rotates about its central axis 25, and the carrier head 70 rotates about its central axis 71 and translates laterally across the top surface of the polishing pad 30.

[0020] refer to Figure 2 In some embodiments, the polishing system 20 includes a temperature control system 40 to control the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad. The temperature control system 40 can provide a cooling system and / or a heating system. The temperature control system 40 can be controlled by delivering a temperature-controlled medium (e.g., liquid, vapor, or spray) from a source 48 to the polishing surface 36 of the polishing pad 30 (or to the polishing liquid already present on the polishing pad).

[0021] The example temperature control system 40 includes an arm 42 that extends over the platform 24 and polishing pad 30 from the edge of the polishing pad to at least near the center of the polishing pad 30 (e.g., within 5% of the total radius of the polishing pad). The arm 42 can be supported by a base 44, and the base 44 can be supported on the same frame 40 as the platform 24. The base 44 can include one or more actuators (e.g., linear actuators) to raise or lower the arm 42, and / or a rotary actuator to swing the arm 42 laterally over the platform 24. The arm 42 is positioned to avoid collision with other hardware components (e.g., the polishing head 70 and the slurry dispensing arm 62).

[0022] The arm 42 may include or support one or more apertures 46 (eg, nozzles) through which the temperature control medium is sprayed onto the polishing pad. Figure 2 A single arm is shown, multiple arms (eg, one arm dedicated to heating and one arm dedicated to cooling) are possible.

[0023] For cooling, the cooling medium may be a gas, such as air, or a liquid (e.g., water). The medium may be at room temperature or cooled to below room temperature, for example, at 5 degrees Celsius to 15 degrees Celsius. In some embodiments, the cooling system uses a spray of air and liquid, for example, an atomized spray of a liquid (e.g., water). In particular, the cooling system may have a nozzle that generates an atomized spray of water that is cooled to below room temperature. In some embodiments, a solid material may be mixed with the gas and / or liquid. The solid material may be a frozen material, such as ice, or a material that absorbs heat when dissolved in water, such as by a chemical reaction.

[0024] For heating, the heating medium can be a gas (e.g., steam or heated air), or a liquid (e.g., heated water), or a combination of a gas and a liquid. The medium is above room temperature, e.g., at 40 to 120 degrees Celsius, e.g., at 90 to 110 degrees Celsius. The medium can be water, e.g., substantially pure deionized water, or water containing additives or chemicals. In some embodiments, the temperature control system uses a steam spray. The steam can include additives or chemicals.

[0025] The polishing system 20 may also include a high pressure rinse system 50. The high pressure rinse system 50 includes a plurality of nozzles 54, for example (three to twenty nozzles) to direct a cleaning fluid (eg, water) at high intensity onto the polishing pad 30 to clean the pad 30 and remove spent slurry, polishing debris, etc.

[0026] like Figure 2 , the example rinsing system 50 includes an arm 52 that extends over the platform 24 and polishing pad 30 from an edge of the polishing pad to at least near the center of the polishing pad 30 (eg, within 5% of the total radius of the polishing pad).

[0027] The arm 52 may be supported by a base 54, and the base 54 may be supported on the same frame 40 as the platform 24. The base 52 may include one or more actuators (e.g., linear actuators) to raise or lower the arm 52, and / or a rotary actuator to swing the arm 52 laterally on the platform 24.

[0028] The arm 52 is positioned to avoid collision with other hardware components, such as the polishing head 70, the slurry distribution arm 62, and the temperature control system 40. Along the rotation direction of the platform 24, the arm of the high pressure wash system 50 may be located between the slurry delivery arm 62 and the arm of the conditioner system.

[0029] In some embodiments, the polishing system 20 includes a wiper blade or body 66 to evenly distribute the polishing liquid 38 across the polishing pad 30. The wiper blade 66 can be located between the slurry delivery arm 62 and the carrier head 70 along the direction of rotation of the platform 24.

[0030] The polishing system 20 may also include a high pressure rinse system 50. The high pressure rinse system 50 includes a plurality of nozzles 54 (eg, three to twenty nozzles) to direct a cleaning fluid (eg, water) at high intensity onto the polishing pad 30 to clean the pad 30 and remove spent slurry, polishing debris, and the like.

[0031] refer to Figure 1 and Figure 2 , the polishing system 20 includes a conditioning system 100 that uses a cold condensing gas jet to condition a polishing surface 36 of a polishing pad 30. The exemplary conditioning system 100 includes an arm 102 that extends over the platform 24 and the polishing pad 30 from an edge of the polishing pad to, or at least near, the center of the polishing pad 30 (e.g., within 5% of the total radius of the polishing pad).

[0032] The arm 102 may be supported by a base 104, and the base 104 may be supported on the same frame 40 as the platform 24. The base 104 may include one or more actuators (e.g., linear actuators) to raise or lower the arm 102, and / or a rotary actuator to swing the arm 104 laterally on the platform 24.

[0033] The arm 104 is positioned to avoid collision with other hardware components, such as the rinse system 52, the temperature control system 40, the slurry dispensing arm 62, and the polishing head 70. Along the rotation direction of the platform 24, the arm 102 of the conditioning system 100 may be located between the carrier head 70 and the arm 42 of the temperature control system (if present) or the slurry dispensing arm 62. Along the rotation direction of the platform 24, the components may be arranged in the following order: the arm 102 of the conditioning system 100, the arm 52 of the rinse system 50 (optional), the arm 42 of the temperature control system 40 (optional), the slurry dispensing arm 62, the wiper blade 66 (optional), and the polishing head 70.

[0034] The conditioning system 100 is configured to direct the cold condensing gas through one or more openings 106 (e.g., in one or more nozzles 108) formed in the arm 102 or suspended from the arm 102. In particular, the conditioning system can have a plurality of openings 106. The nozzles 108 can be convergent-divergent nozzles, such as Venturi nozzles. Each nozzle 108 can provide exactly one opening 106. In operation, the arm 110 can be supported by the base 104 so that the nozzles 108 are separated from the polishing pad 30 by a gap 126. The gap 126 can be 1 cm to 10 cm.

[0035] The various openings 106 can direct the jet 122 of cold condensing gas onto different radial zones 124 on the polishing pad 30. Adjacent radial zones can overlap. Optionally, some of the openings 106 can be oriented so that the central axis (D) of the spray from the opening is at an oblique angle relative to the polishing surface 36. The jet can be directed from one or more openings 106 to have a horizontal component (D) in the impact region in a direction opposite to the direction of motion (E) of the polishing pad 30 due to the rotation of the platform 24.

[0036] Although Figure 1 and Figure 2 The openings 106 and nozzles 108 are illustrated as being spaced at uniform intervals, but this is not required. The openings (e.g., nozzles) may be distributed non-uniformly radially or angularly, or both. For example, the openings 106 may be more densely clustered toward the outer edge of the polishing pad 30 (to compensate for the larger area being covered at the outer radius). In addition, although Figure 1 and Figure 2 Nine openings are shown, but the number of openings may be greater or lesser.

[0037] The jet 122 of cold condensed gas may include cold solid particles of condensed gas carried by a carrier gas. In particular, the cold solid particles may be dry ice particles, i.e. solid carbon dioxide. The carrier gas may be air or a purge gas, such as nitrogen.

[0038] refer to Figure 3 , the example conditioning system 100 draws air into a compressor 130. The compressed air is directed through a dryer 132 to remove excess water from the air stream. The compressed dry air is then mixed with dry ice in a mixer 134, for example, so that dry ice particles are entrained in the compressed air stream. The mixer 134 may include a feeder 136 that receives dry ice pellets or chunks of dry ice, and a chopper 138 (e.g., a pair of rollers with blades) that shreds large chunks of dry ice into smaller particles suitable for entrainment into the compressed air stream.

[0039] The particles may have an average diameter of 0.05 mm to 5 mm, for example 0.1 mm to 1 mm. In some embodiments, the particles have an average diameter of at least 0.05 mm, for example at least 0.1 mm, for example at least 0.2 mm, for example at least 0.3 mm, for example at least 0.5 mm, for example at least 1 mm. In some embodiments, the particles have an average diameter of at most 0.1 mm, for example at most 0.2 mm, for example at most 0.3 mm, for example at most 0.5 mm, for example at most 2 mm, for example at most 3 mm, for example at most 5 mm.

[0040] Optionally, the compressed air flow with entrained dry ice particles is directed through a filter 140 to block dry ice particles that exceed a threshold size.

[0041] The compressed air flow with entrained dry ice particles passes through the opening 106 of the nozzle 108 to form a jet 122 of dry ice particles 126 that is directed onto the surface 36 of the polishing pad 30. For example, the compressed air flow with entrained dry ice particles can be passed through an insulated conduit (e.g., provided by a pipe, tube, etc.) and conduit 140 in the arm 102 to the nozzle 108. Figure 3 A single nozzle is shown, but there may be multiple openings and multiple nozzles, such as Figure 1 and Figure 2 As shown in .

[0042] When the compressed gas passes through the nozzle 108 or exits the opening 106, it may expand so that the dry ice particles are carried at high speed. The impact of the dry ice particles on the polishing surface and the sublimation of the dry ice may serve to abrade the polishing pad 30 and / or dislodge and carry away debris stuck to the polishing pad, thereby conditioning the polishing pad 30.

[0043] In some embodiments, the dry ice particles impact the polishing surface at a speed of up to Mach 1.5. In some embodiments, the dry ice particles impact the polishing surface at a speed of at least 50 m / s, for example, at least 100 m / s, for example, at least 150 m / s, for example, at least 200 m / s, for example, at least 250 m / s, for example, at least 300 m / s, for example, at least 343 m / s. In some embodiments, the dry ice particles impact the polishing surface at a speed of at most 100 m / s, for example, at most 150 m / s, for example, at most 200 m / s, for example, at most 250 m / s, for example, at most 300 m / s, for example, at most 343 m / s (1 Mach), for example, at most 1.25 Mach. In some embodiments, the dry ice particles reach supersonic speeds in the nozzle or at the outlet, i.e., above 343 m / s.

[0044] A number of embodiments have been described. However, it should be understood that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A polishing system comprising: a platform supporting a polishing pad; a carrier head that maintains a substrate against the polishing pad; Source of dry ice pellets; as well as a pad conditioner comprising: a compressor generating a compressed gas stream, a mixer coupled to the source and the compressor to mix the dry ice particles with the compressed gas stream to form a compressed gas stream with entrained dry ice particles, and a conditioner nozzle coupled to the mixer to direct the compressed gas stream with entrained dry ice particles onto a polishing surface of the polishing pad at a sufficient velocity to condition the polishing pad.

2. The polishing system of claim 1, comprising a shredder for a block of dry ice and shredding the block to form the dry ice particles. 3 . The polishing system of claim 1 , wherein the shredder is configured to form dry ice particles having an average diameter of 0.1 mm to 5 mm.

4. The polishing system of claim 1, comprising a controller that operates the compressor such that the compressed gas stream with entrained dry ice particles impinges on the polishing surface at a velocity between 100 m / s and Mach 1.

5.

5. The polishing system of claim 1 , wherein the pad conditioner comprises an arm extending above the platform, wherein the pad conditioner comprises a plurality of nozzles coupled to the mixer to direct the flow of compressed gas with entrained dry ice particles onto the polishing surface at a sufficient velocity to condition the polishing pad.

6. The polishing system of claim 5, wherein the plurality of nozzles are evenly spaced along the arm.

7. The polishing system of claim 5, wherein the plurality of nozzles are non-uniformly spaced along the arm.

8. The polishing system of claim 7, wherein the nozzles are more densely spaced closer to an edge of the platform than to the center of the platform.

9. The polishing system of claim 5, further comprising a slurry supply arm having a port to dispense polishing liquid to the polishing pad.

10. The polishing system of claim 9, further comprising a temperature control system including an arm supporting a nozzle to direct a temperature control medium onto the polishing pad.

11. The polishing system of claim 10, wherein the carrier head, the arm of the conditioner system, the arm of the temperature control system, and the slurry supply arm are arranged in the stated order along a rotational direction of the platform.

12. The polishing system of claim 10, further comprising a pad rinsing system including an arm supporting a nozzle to direct a cleaning medium onto the polishing pad.

13. The polishing system of claim 12, wherein the carrier head, the arm of the conditioner system, the arm of the pad washing system, the arm of the temperature control system, and the slurry supply arm are arranged in the stated order along a rotational direction of the platform.

14. A method for conditioning a polishing pad, comprising the steps of: mixing the dry ice particles with a compressed air stream to form a compressed gas stream having entrained dry ice particles; as well as The stream of compressed gas with entrained dry ice particles is directed through a nozzle onto a polishing surface of the polishing pad at a sufficient velocity to condition the polishing pad.

15. The method of claim 14, wherein the dry ice particles have an average diameter of 0.1 mm to 5 mm.

16. The method of claim 14, wherein the compressed gas stream with entrained dry ice particles flows through the nozzle at a supersonic velocity.

17. The method of claim 14, wherein the compressed gas stream with entrained dry ice particles impinges on the polishing surface at a velocity between 100 m / s and Mach 1.

5.

18. The method of claim 14, further comprising the steps of: A temperature control medium is dispensed onto the polishing surface through a second nozzle.

19. The method of claim 14, further comprising the steps of: A rinsing fluid is dispensed onto the polishing surface through a third nozzle.

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