Condensed Gas Pad Conditioner

Abstract

The polishing system includes a platen for supporting a polishing pad, a carrier head for holding a substrate against the polishing pad, a source of dry ice particles, and a pad conditioner. The pad conditioner includes a compressor for generating a compressed gas stream, a mixer coupled to the source and the compressor for mixing the dry ice particles with the compressed gas stream to form a stream of compressed gas with entrained dry ice particles, and a nozzle coupled to the mixer for directing the stream of compressed gas with entrained dry ice particles onto the polishing surface of the polishing pad at a sufficient velocity to condition the polishing pad.

Description

Technical Field

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

Background Art

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

[0003] Chemical mechanical polishing (CMP) is an accepted method of planarization. This planarization method generally requires that the substrate be mounted on a carrier head 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 press the substrate against the polishing pad. A polishing fluid is generally supplied to the surface of the polishing pad.

[0004] A polishing system generally includes a conditioner system for conditioning the polishing pad. Conditioning of the polishing pad maintains the polishing surface at a consistent roughness 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, for example, a conditioner disk having diamond particles, and the conditioner disk is placed in contact with the polishing pad.

Summary of the Invention

[0005] In one aspect, a polishing system includes a platen that supports a polishing pad, a carrier head that holds a substrate against the polishing pad, a dry ice particle source, and a pad conditioner. The pad conditioner includes a compressor for generating a compressed gas stream, a mixer coupled to the source and the compressor for mixing dry ice particles with the compressed gas stream to form a compressed gas stream entraining the dry ice particles, and a nozzle coupled to the mixer for directing the compressed gas stream entraining the dry ice particles toward a polishing surface of the polishing pad at a speed sufficient to condition the polishing pad.

[0006] In another aspect, a method of conditioning a polishing pad includes mixing dry ice particles with a stream of compressed air to form a stream of compressed gas entraining the dry ice particles and directing the stream of compressed gas entraining the dry ice particles through a nozzle adapted to condition a surface of the polishing pad at a sufficient speed.

[0007] Embodiments can optionally include one or more of the following advantages, without limitation.

[0008] Cryogenic condensed gas can be more effective than diamond abrasive disks in conditioning and / or cleaning. For example, due to the sublimation of the condensed gas, debris can be lifted from the polishing pad, enhancing the increased cleanliness. As another example, due to the impact of the particles of the condensed gas on the pad, the desired roughness can be reached more quickly. Since the entire radial length of the polishing pad is conditioned at once, the need for sweeping the conditioning area is reduced, and the conditioning uniformity can be improved. The pad conditioning and / or cleaning time is reduced, and thus the system duty cycle can be improved. There is no need for a replaceable conditioning disk that wears out, reducing the polishing system downtime for maintenance for conditioning disk replacement. The accumulation of dry abrasive particles on the conditioning disk can be prevented, which can improve the polishing quality by reducing scratches and defects. Since less time is spent on the pad conditioner cleaning process, the productivity of the polishing system can be improved.

[0009] 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, as well as from the claims.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0011] Like reference numerals and symbols in the various drawings indicate like elements.

[0012] During chemical mechanical polishing, the surface of the polishing pad may become smoother due to friction and compression, and polishing debris may be pushed into the polishing pad. A polishing system generally includes a conditioner system having a conditioner head and a conditioner disk with an abrasive lower surface to condition the polishing pad, maintain a consistent roughness for each substrate, and remove polishing debris. However, the conditioner disk itself wears out and needs to be replaced periodically. This required stopping the polishing system for maintenance. Moreover, the abrasive slurry may splash and stick to the conditioning disk. The accumulation of dried or solidified polishing fluid on the polishing pad over time has multiple adverse effects. For example, larger particles may be removed and return to the polishing surface, thus posing a risk of scratching and defects. A significant amount of non-productive time is required to clean the conditioner head and conditioner disk to prevent the accumulation of dried polishing fluid.

[0013] An alternative technique for conditioning is to direct the injection of cryogenic compressed gas, such as dry ice particles (i.e., solid CO2), onto the polishing pad. When injected at a sufficiently high speed, the impact of the particles can abrade the polishing surface and release debris. Moreover, the sublimation of the particles generates a gas that can carry away the debris.

[0014] The use of dry ice has been proposed for temperature control of the surface of the polishing pad, but the operating regime for performing the conditioning process is quite different, for example, it should be at a higher speed and with a larger particle size. In short, the use of dry ice for temperature control does not essentially lead to the conditioning process.

[0015] FIG. 1 shows a polishing system 20 operable to polish a substrate 10. The polishing system 20 includes a rotatable platen 24 with a polishing pad 30 thereon. The platen 24 is operable to rotate about an axis 25 (see arrow A in FIG. 2). For example, a motor 22 can rotate a drive shaft 28 to rotate the platen 24. The polishing pad 30 can be a two-layer polishing pad having an outer polishing layer 34 with a polishing surface 36 and a softer backing layer 32.

[0016] The polishing system 20 includes a supply port 64, for example, at an end of a slurry supply arm 62, for supplying a polishing liquid 60, such as a polishing abrasive slurry, onto the polishing pad 30.

[0017] The polishing system 20 includes a carrier head 70 operable 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 for contacting the back side of the substrate 10 and a plurality of pressurizable chambers 82 for applying different pressures to different zones on the substrate 10, such as different radial zones. The carrier head 70 is suspended from a support structure 72, such as a carousel or a 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. Further, the carrier head 70 can vibrate laterally across the polishing pad 30 by moving, for example, in a radial slot in the carousel 72 driven by an actuator, or by moving back and forth along a track driven by an actuator, such that the rotation of the carousel driven by a motor or the movement along the track driven by an actuator. During operation, the platen 24 is rotated about its central axis 25, the carrier head 70 is rotated about its central axis 71, and is translated laterally across the upper surface of the polishing pad 30.

[0018] Referring to FIG. 2, in some embodiments, the polishing system 20 includes a temperature control system 40 for controlling 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 operate by supplying a temperature-controlled medium, such as a liquid, vapor, or spray, from a source 48 onto the polishing surface 36 of the polishing pad 30 (or onto the polishing liquid already present on the polishing pad).

[0019] An exemplary temperature control system 40 includes an arm 42 that extends over the platen 24 and the polishing pad 30, from the edge of the polishing pad to the center of the polishing pad 30, or 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 platen 24. The base 44 can include one or more actuators for raising or lowering the arm 42, such as a linear actuator, and / or a rotary actuator for swinging the arm 42 laterally on the platen 24. The arm 42 is arranged to avoid colliding with other hardware components, such as the polishing head 70 and the slurry distribution arm 62.

[0020] The arm 42 can include or support one or more apertures 46, such as nozzles, through which the temperature-controlled medium is sprayed onto the polishing pad. Although FIG. 2 shows a single arm, there can be multiple arms, such as one arm dedicated to heating and one arm dedicated to cooling.

[0021] In the case of cooling, the cooling medium can be a gas, such as air, or a liquid, such as water. The medium can be at room temperature or cooled below room temperature, for example, at 5 - 15°C. In some embodiments, the cooling system uses sprays of air and liquid, for example, aerosolized sprays of a liquid, such as water. In particular, the cooling system can have nozzles that generate aerosolized sprays of water cooled below room temperature. In some embodiments, a solid material can be mixed with the gas and / or liquid. The solid material can be a cooled material, such as ice, or a material that absorbs heat by a chemical reaction when dissolved in, for example, water.

[0022] In the case of heating, the heating medium can be a gas, such as steam or heated air, or a liquid, such as heated water, or a combination of gas and liquid. The medium is above room temperature, for example, at 40 - 120°C, for example, at 90 - 110°C. The medium can be water, such as substantially pure deionized water, or water containing additives or chemicals. In some embodiments, the temperature control system uses sprays of steam. The steam can contain additives or chemicals.

[0023] The polishing system 20 can also include a high-pressure rinse system 50. The high-pressure rinse system 50 includes a plurality of nozzles 54, for example, 3 - 20 nozzles, that direct a cleaning fluid, such as water, at high intensity onto the polishing pad 30 to wash the pad 30 and remove used slurry, polishing debris, etc.

[0024] As shown in FIG. 2, an exemplary rinse system 50 includes an arm 52 that extends over the platen 24 and the polishing pad 30, from the edge of the polishing pad to the center of the polishing pad 30, or at least near the center of the polishing pad 30 (for example, within 5% of the total radius of the polishing pad).

[0025] The arm 52 can be supported by a base 54, and the base 54 can be supported on the same frame 40 as the platen 24. The base 54 can include one or more actuators for raising or lowering the arm 52, such as a linear actuator, and / or a rotary actuator for swinging the arm 52 laterally on the platen 24.

[0026] The arm 52 is arranged to avoid colliding 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 platen 24, the arm of the high-pressure rinse system 50 can be between the slurry delivery arm 62 and the arm of the conditioner system.

[0027] In some embodiments, the polishing system 20 includes a wiper blade or body 66 for uniformly distributing the polishing liquid 60 across the polishing pad 30. Along the rotation direction of the platen 24, the wiper blade 66 can be between the slurry supply arm 62 and the carrier head 70.

[0028] The polishing system 20 can also include a high-pressure rinse system 50. The high-pressure rinse system 50 includes a plurality of nozzles 56, for example, 3 to 20 nozzles, that direct a cleaning fluid, such as water, onto the polishing pad 30 at a high intensity to wash the pad 30 and remove used slurry, polishing debris, etc.

[0029] Referring to FIGS. 1 and 2, the polishing system 20 includes a conditioning system 100 that uses the injection of cryogenic condensed gas to condition the polishing surface 36 of the polishing pad 30. An exemplary conditioning system 100 includes an arm 102 that extends over the platen 24 and the polishing pad 30, from the edge of the polishing pad to the center of the polishing pad 30, or at least near the center of the polishing pad 30 (e.g., within 5% of the total radius of the polishing pad).

[0030] The arm 102 can be supported by a base 104, and the base 104 can be supported on the same frame 40 as the platen 24. The base 104 can include one or more actuators for raising or lowering the arm 102, such as a linear actuator, and / or a rotary actuator for swinging the arm 102 laterally on the platen 24.

[0031] The arm 104 is arranged to avoid colliding with other hardware components such as the rinse system 50, the temperature control system 40, the slurry supply arm 62, and the polishing head 70. Along the rotation direction of the platen 24, the arm 102 of the conditioning system 100 can be between the carrier head 70 and the arm 42 of the temperature control system (if present) or the slurry supply arm 62. Along the rotation direction of the platen 24, the components can be arranged in the following order, namely, 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 supply arm 62, the wiper blade 66 (optional), and the polishing head 70.

[0032] The conditioning system 100 is configured to direct cryogenic condensed gas through one or more openings 106 at, for example, one or more nozzles 108 formed in or suspended from the arm 102. In particular, the conditioning system can have a plurality of openings 106. The nozzle 108 can be a convergent-divergent nozzle, such as a Venturi nozzle. Each nozzle 108 can provide exactly one opening 106. During operation, the arm 102 can be supported by the base 104 such that the nozzle 108 is separated from the polishing pad 30 by a gap 128. The gap 128 can be 1 to 10 cm.

[0033] The various apertures 106 can direct the injection 122 of cryogenic condensed gas onto different radially - oriented zones 124 on the polishing pad 30. Adjacent radially - oriented zones may overlap. Optionally, some of the apertures 106 can be oriented such that the central axis (D) of the spray from that aperture is at an angle oblique to the polishing surface 36. The injection can be directed from one or more of the apertures 106 to have a horizontal component (D) in a direction opposite to the direction of movement (E) of the polishing pad 30 in the area affected by the rotation of the platen 24.

[0034] Figures 1 and 2 show apertures 106 and nozzles 108 spaced at uniform intervals, but this is not required. The apertures, for example, the nozzles, can be distributed non - uniformly either radially or angularly or both. For example, the apertures 106 can be made more dense towards the outer edge of the polishing pad 30 (to compensate for the larger area covered at the outer radius). Further, Figures 1 and 2 show nine apertures, but more or fewer apertures may be used.

[0035] The injection 122 of cryogenic condensed gas can contain cryogenic solid particles of the condensed gas carried by a carrier gas. In particular, the cryogenic solid particles can be dry ice particles, i.e., solid carbon dioxide. The carrier gas can be air or a purified gas such as nitrogen.

[0036] Referring to FIG. 3, an exemplary 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 and dried air is then mixed with dry ice in a mixer 134, for example, dry ice particles are entrained in the compressed air stream. The mixer 134 can include a feeder 136 for receiving dry ice pellets or slabs and a grinder 138, such as a pair of bladed rollers, for grinding large dry ice pieces into smaller particles suitable for entrainment in the compressed air stream.

[0037] The particles can have an average diameter of from 0.05 to 5 mm, for example, from 0.1 to 1 mm. In some embodiments, they 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, they 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.

[0038] Optionally, the compressed air stream containing dry ice particles is directed through a filter 140 to block dry ice particles larger than a threshold size.

[0039] The compressed air stream containing dry ice particles passes through the opening 106 of the nozzle 108 to form a jet 122 of dry ice particles 126 directed onto the surface 36 of the polishing pad 30. For example, the compressed air stream containing dry ice particles can pass through, for example, insulated conduits supplied by pipes, tubes, etc., and the conduit 140 in the arm 102 to reach the nozzle 108. FIG. 3 shows a single nozzle, but as shown in FIGS. 1 and 2, there can be multiple openings and multiple nozzles.

[0040] When the compressed gas passes through nozzle 108 or exits opening 106, the compressed gas can expand so that dry ice particles are conveyed at high speed. The impact of the dry ice particles on the polishing surface and the sublimation of the dry ice can abrade polishing pad 30 and / or remove and carry away debris adhering to the polishing pad, thereby functioning to condition polishing pad 30.

[0041] In some embodiments, the dry ice particles impact the polishing surface at speeds 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, such as at least 100 m / s, such as at least 150 m / s, such as at least 200 m / s, such as at least 250 m / s, such as at least 300 m / s, such as 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, such as at most 150 m / s, such as at most 200 m / s, such as at most 250 m / s, such as at most 300 m / s, such as at most 343 m / s (Mach 1), such as at most Mach 1.25. In some embodiments, the dry ice particles reach supersonic speeds, i.e., above 343 m / s, within or at the outlet of the nozzle.

[0042] Some embodiments have been described. It will be understood, however, that various modifications can be made. Accordingly, other embodiments fall within the scope of the following claims.

Claims

1. A platen for supporting a polishing pad, a carrier head for holding a substrate against the polishing pad, a source of dry ice particles, a compressor for generating a compressed gas stream, and a mixer coupled to the source and the compressor for mixing the dry ice particles with the compressed gas stream to form a stream of compressed gas containing dry ice particles, and a conditioner nozzle coupled to the mixer for directing the stream of compressed gas containing dry ice particles onto the polishing surface of the polishing pad at a sufficient velocity to condition the polishing pad A polishing system comprising.

2. The polishing system of claim 1, further comprising a grinder for drying ice flakes and crushing the ice flakes to form the dry ice particles.

3. The polishing system of claim 1, wherein the grinder is configured to form dry ice particles having an average diameter of 0.1 to 5 mm.

4. The polishing system of claim 1, further comprising a controller for operating the compressor such that the stream of compressed gas containing 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 over the platen, and the pad conditioner comprises a plurality of nozzles coupled to the mixer for directing the stream of compressed gas containing 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 uniformly 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 arranged more closely spaced towards the edge than the center of the platen.

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

10. The polishing system according to claim 9, further comprising an arm supporting a nozzle for directing a temperature control medium onto the polishing pad.

11. The polishing system according to 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 above-mentioned order along the rotation direction of the platen.

12. The polishing system according to claim 10, further comprising a pad rinse system including an arm supporting a nozzle for directing a cleaning medium onto the polishing pad.

13. The polishing system according to claim 12, wherein the carrier head, the arm of the conditioner system, the arm of the pad rinse system, the arm of the temperature control system, and the slurry supply arm are arranged in the above-mentioned order along the rotation direction of the platen.

14. A method of conditioning a polishing pad, comprising: mixing dry ice particles with a stream of compressed air to form a stream of compressed gas containing dry ice particles; directing the stream of compressed gas containing dry ice particles onto the polishing surface of the polishing pad through a nozzle at a sufficient speed for conditioning the polishing pad. The method includes.

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

16. The method according to claim 14, wherein the stream of compressed gas containing dry ice particles flows through the nozzle at supersonic speed.

17. The method according to claim 14, wherein the stream of compressed gas containing dry ice particles impacts the polishing surface at a speed between 100 m / s and Mach 1.

5.

18. The method according to claim 14, further comprising distributing a temperature control medium onto the polishing surface through a second nozzle.

19. The method according to claim 14, further comprising distributing a rinse liquid onto the polishing surface through a third nozzle.

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