Gas entrainment during jetting of fluid for temperature control in chemical mechanical polishing

Abstract

To provide a chemical mechanical polishing system including a pad cooling assembly which can decrease a temperature of a polishing pad efficiently and reduce wafer-to-wafer non-uniformity.SOLUTION: A chemical mechanical polishing system includes a platen to support a polishing pad 30 having a polishing surface 36, and a pad cooling assembly. The pad cooling assembly has a nozzle 120 suspended by an arm 110 and positioned to spray a coolant fluid 142 from a supply source onto the polishing surface 36 of the polishing pad 30; and an opening in the arm adjacent the nozzle 120 and a passage extending in the arm 110 from the opening, the opening positioned sufficiently close to the nozzle 120 that flow of the coolant fluid 142 from the nozzle 120 entrains air from the opening.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] TECHNICAL FIELD This disclosure relates to temperature control during chemical mechanical polishing (CMP), and more particularly, to cooling of a polishing pad during CMP. [Background technology]

[0002] Integrated circuits are typically formed on a substrate by successively depositing conductive, semiconductive, or insulating layers on a semiconductor wafer. Various manufacturing processes require planarization of layers on the substrate. For example, one manufacturing step involves depositing a filler layer over a non-planar surface and polishing the filler layer until the top surface of a patterned layer is exposed. As another example, a layer may be deposited over a patterned conductive layer and planarized to allow for subsequent photolithography steps.

[0003] Chemical mechanical polishing (CMP) is one of the accepted methods of planarization. This planarization method typically involves mounting a substrate on a carrier head. The exposed surface of the substrate is typically positioned against a rotating polishing pad. The carrier head applies a controllable load to the substrate, pressing it against the polishing pad. An abrasive slurry, typically containing abrasive particles, is supplied to the surface of the polishing pad.

[0004] The removal rate in a polishing process can be sensitive to temperature, and various techniques have been proposed to control the temperature during polishing. Summary of the Invention

[0005] In one aspect, a chemical mechanical polishing system includes a platen for supporting a polishing pad having a polishing surface, and a pad cooling assembly having an arm extending across the platen, a nozzle suspended by the arm and connected to a source of coolant fluid positioned to spray coolant fluid from the source onto the polishing surface of the polishing pad, an opening in the arm adjacent the nozzle, and a passageway extending from the opening into the arm, the opening positioned sufficiently proximate to the nozzle such that a flow of coolant fluid from the nozzle entrains air from the opening.

[0006] In another aspect, a method of temperature control for a chemical mechanical polishing system includes supporting a nozzle on a support arm, supplying a coolant fluid from a coolant source through the nozzle onto the polishing pad, and entraining air from an opening in the support arm in the flow of coolant fluid from the nozzle.

[0007] Potential advantages may include, but are not limited to, one or more of the following:

[0008] The temperature of the polishing pad can be reduced more efficiently than simply directing coolant to the polishing pad, without requiring more energy. The temperature of the polishing pad, and therefore the polishing process temperature, can be controlled and made more uniform across the wafer, resulting in less wafer-to-wafer non-uniformity (WIWNU). The temperature of the polishing pad surface can be reduced during one or more of the metal cleaning, overpolishing, or conditioning steps of the polishing operation. This reduces dishing and erosion, and / or improves the uniformity of the pad topography. Thus, polishing uniformity is improved and pad life is extended.

[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 become apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0010] [Figure 1A] 1 is a schematic cross-sectional view of an example of a polishing station of a polishing apparatus. [Figure 1B] 1 is a schematic top view of an exemplary polishing station of a chemical mechanical polishing apparatus. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a coolant supply arm. [Figure 3A] 13 is a schematic cross-sectional view of another implementation of a coolant supply arm. [Figure 3B] 13 is a schematic top view of another implementation of a coolant supply arm. FIG. [Figure 4A] 13A-13C are schematic cross-sectional views of further implementations of the coolant supply arm; [Figure 4B] 13A and 13B are schematic top views of further implementations of the coolant supply arm; [Diagram 5] FIG. 2 is a schematic diagram of a coolant supply system. [Figure 6] 3 is a flow diagram of an example method for controlling the temperature of the chemical mechanical polishing system of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Chemical mechanical polishing works by a combination of mechanical polishing and chemical etching at the interface between the substrate, the polishing fluid, and the polishing pad. During the polishing process, friction between the surface of the substrate and the polishing pad generates a significant amount of heat. In addition, some processes include an in-situ pad conditioning step, in which a conditioning disk (e.g., a disk coated with abrasive diamond particles) is pressed against the rotating polishing pad to condition and smooth the polishing pad surface. The polishing of the conditioning process may also generate heat. For example, a typical 1-minute copper CMP process at a nominal downforce pressure of 2 psi and a removal rate of 8000 Å / min may cause the surface temperature of a polyurethane polishing pad to increase by about 30°C.

[0012] For example, both chemical reaction-related variables (e.g., variables such as the onset and rate of the reactions involved) and mechanical-related variables (e.g., the surface friction coefficient and viscoelasticity of the polishing pad) in the CMP process are highly temperature-dependent. As a result, the fluctuation of the surface temperature of the polishing pad can cause changes in removal rate, polishing uniformity, erosion, dishing, and residue. By more closely controlling the temperature of the surface of the polishing pad during polishing, the temperature fluctuation can be reduced, and the polishing performance, for example, measured based on the intra-wafer non-uniformity or inter-wafer non-uniformity, can be improved.

[0013] One technique proposed to control the temperature of the chemical mechanical polishing process is to spray a coolant, e.g., cold water, onto the polishing pad. Electric power is required to reduce the temperature of the coolant, and heat may be transferred to the coolant as it moves from the heat source to the supply port. However, by positioning the nozzle that sprays the coolant onto the polishing pad near the opening, some air can be entrained into the coolant flow to achieve a gas cooling effect, thus expanding the cooling capacity of the cooling system. This can improve the cooling efficiency of the polishing pad. In particular, when the nozzle that sprays the coolant is supported by the support plate of the arm, the entrained air may flow from above the support plate, e.g., above the arm. This air should be cooler than the air adjacent to the polishing pad and that may have absorbed heat radiated from the polishing pad.

[0014] 1A and 1B show an example of a polishing station 20 of a chemical mechanical polishing system. The polishing station 20 includes a rotatable, disk-shaped platen 24 on which a polishing pad 30 is placed. The platen 24 is operable to rotate about an axis 25 (see arrow A in FIG. 1B). For example, a motor 22 can turn a drive shaft 28 to rotate the platen 24. The polishing pad 30 can be a two-layer polishing pad with an outer polishing layer 34 and a softer backing layer 32.

[0015] The polishing station 20 may include a supply port, for example, at the end of a slurry supply arm 39, for supplying a polishing fluid 38, such as a polishing slurry, onto the polishing pad 30. The polishing station 20 may further include a pad conditioner with a conditioning disk to maintain the surface roughness of the polishing pad 30.

[0016] Carrier head 70 is operable to hold substrate 10 against polishing pad 30. Carrier head 70 is suspended from a support structure 72 (e.g., a carousel or track) and connected by a drive shaft 74 to a carrier head rotation motor 76, which enables carrier head 70 to rotate about axis 71. Alternatively, carrier head 70 can be oscillated laterally by movement along a track, or by rotational oscillation of the carousel itself, for example, on a slider on the carousel.

[0017] The carrier head 70 may include a flexible membrane 80 having a substrate mounting surface that contacts the backside of the substrate 10, and a number of pressurizable chambers 82 that apply different pressures to different zones (e.g., different radial zones) of the substrate 10. The carrier head 70 may include a retaining ring 84 that holds the substrate. In some implementations, the retaining ring 84 may include a lower plastic portion 86 that contacts the polishing pad and an upper portion 88 of a harder material (e.g., metal).

[0018] During operation, the platen rotates about its central axis 25 and the carrier head rotates about its central axis 71 (see arrow B in FIG. 1B) and moves laterally across the upper surface of polishing pad 30 (see arrow C in FIG. 1B).

[0019] In some implementations, the polishing station 20 includes a temperature sensor 64 for monitoring the temperature within the polishing station or the temperature of a component of or within the polishing station (e.g., the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad). For example, the temperature sensor 64 may be an infrared (IR) sensor (e.g., an IR camera) positioned above the polishing pad 30 and configured to measure the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad. In particular, the temperature sensor 64 may be configured to measure the temperature at multiple points along the radius of the polishing pad 30 to generate a radial temperature profile. For example, the IR camera may have a field of view that spans the radius of the polishing pad 30.

[0020] In some implementations, the temperature sensor is a contact sensor rather than a non-contact sensor. For example, the temperature sensor 64 may be a thermocouple or an IR thermometer positioned on or in the platen 24. Additionally, the temperature sensor 64 may be in direct contact with the polishing pad.

[0021] In some implementations, multiple temperature sensors may be spaced at various radial locations across the polishing pad 30 to provide the temperature at multiple points along the radius of the polishing pad 30. This technique can be used in place of or in addition to an IR camera.

[0022] 1A, the temperature sensor 64 is shown positioned to monitor the temperature of the polishing pad 30 and / or the slurry 38 on the pad 30, but may also be positioned inside the carrier head 70 to measure the temperature of the substrate 10. The temperature sensor 64 may be in direct contact with the semiconductor wafer of the substrate 10 (i.e., may be a contact type sensor). In some implementations, multiple temperature sensors are included within the polishing station 22, for example, to measure the temperatures of various components of or within the polishing station.

[0023] The polishing system 20 further includes a temperature control system 100 for controlling the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad. The temperature control system 100 may include a cooling system 102. The cooling system 102 operates by supplying a coolant to the polishing surface 36 of the polishing pad 30 (or to the polishing fluid already present on the polishing pad).

[0024] The coolant may be a gas (e.g., air) and / or a liquid (e.g., water). The gaseous component of the coolant, if present, may be air or another gas inert to the polishing process (such as nitrogen, carbon dioxide, argon, or another noble gas), or a mixture thereof. The liquid component of the coolant, if present, may be water or another liquid (such as ethanol or isopropyl alcohol), or a mixture thereof. The liquid component may be inert to the polishing process. The coolant may be at room temperature or may be chilled to below room temperature, i.e., below 20° C. For example, the coolant may be between 5 and 15° C. In some embodiments, the coolant is at or below 0° C.

[0025] In some implementations, the coolant is a substantially pure gas. In some implementations, the coolant is a spray of gas and liquid, for example, an aerosolized spray of liquid, such as water, in a gas carrier, such as air. In some implementations, the cooling system can have a nozzle that generates an aerosolized spray of water that is cooled to below room temperature.

[0026] In some implementations, the coolant includes particles of a solid material mixed with a gas and / or liquid. The solid material may be a chilled substance, such as ice, dry ice, or frozen ethanol or isopropyl alcohol. In some implementations, the coolant is a spray of gas (e.g., air) and solid particles (e.g., ice particles), but is substantially free of a liquid phase. The solid material may be a substance that absorbs heat by a chemical reaction when dissolved in water.

[0027] The coolant may be supplied through one or more apertures (e.g., holes or slots) in the coolant supply arm, optionally formed in the nozzle. The apertures may be provided by a manifold connected to a coolant source.

[0028] 1A and 1B, the exemplary heating system 102 includes an arm 110 that extends across the platen 24 and polishing pad 30 from the edge of the polishing pad 30 to or at least near the center of the polishing pad (e.g., within 5% of the total radius of the polishing pad). The arm 110 can be supported by a base 112, which can be supported on the same frame 40 as the platen 24. The base 112 can include one or more actuators, such as a linear actuator for raising or lowering the arm 110 and / or a rotary actuator for swinging the arm 110 laterally over the platen 24. The arm 110 is positioned to avoid collisions with other hardware components, such as the polishing head 70, the pad conditioning disk 92, and the slurry dispenser 39.

[0029] The exemplary cooling system 102 includes a number of nozzles 120 suspended on an arm 110. Each nozzle 120 is configured to spray a liquid coolant (e.g., water) onto the polishing pad 30. Fluid connections between a coolant source and the nozzles may be provided on the outside of the arm (e.g., on top of the arm) and / or on the inside of the arm by tubing, piping, or the like. The arm 110 may be supported by a base 112 such that the nozzles 120 are separated from the polishing pad 30 by a gap 126.

[0030] Each nozzle 120 can be configured, for example, using the controller 12, to start and stop the flow of fluid through each nozzle 120. Each nozzle 120 can be configured to direct aerosolized water in a spray 122 toward the polishing pad 30.

[0031] The cooling system 102 may include a source of coolant, which may be liquid, gas, or a combination of liquid and gas. The source may include a source 130 for liquid coolant and / or a source 132 for gas coolant (see FIG. 1B). The liquid from source 130 and the gas from source 132 may be mixed in a mixing chamber in or on the arm 110 before being directed through the nozzle 120 to form the spray 122. The coolant may be below room temperature when delivered (e.g., −100 to 20° C., e.g., below 0° C.).

[0032] The coolant used in the cooling system 102 may include, for example, cold water, liquid nitrogen, liquid ethanol or isopropyl alcohol, a gas formed by evaporation of one or more of liquid nitrogen, ethanol or isopropyl alcohol, or dry ice. In some implementations, water droplets may be added to the gas flow. The water may be cooled to form ice droplets, which efficiently cool the polishing pad due to their latent heat of melting. Furthermore, the ice or water droplets may prevent the polishing pad 30 from drying out when it is being cooled by the chilled gas. Instead of water, ethanol or isopropyl alcohol may be injected into the gas flow to form frozen particles.

[0033] Gas (e.g., compressed gas) from a gas source 132 can be connected to the vortex tube 50. The vortex tube 50 can separate the compressed gas into a cold stream and a hot stream and direct the cold stream to the nozzle 120 and toward the polishing pad 30. In some implementations, the nozzle 120 is the lower end of the vortex tube that directs the cold stream of compressed gas onto the polishing pad 30.

[0034] In some implementations, process parameters (e.g., flow rate, pressure, temperature, and / or mixture ratio of liquid and gas) can be controlled (e.g., by the controller 12) independently for each nozzle. For example, the coolant for each nozzle 120 can flow through an individually controllable chiller to individually control the temperature of the spray. As another example, a separate pair of pumps (one for the gas and one for the liquid) can be connected to each nozzle to individually control the flow rate, pressure, and mixture ratio of gas and liquid for each nozzle.

[0035] The various nozzles can spray different radial zones 124 on the polishing pad 30. Adjacent radial zones 124 may overlap. In some implementations, the nozzles 120 generate sprays that impinge on the polishing pad 30 along an elongated region 128. For example, the nozzles can be configured to generate a spray in a generally planar triangular volume.

[0036] One or more of the elongated regions 128, for example all of the elongated regions 128, may have a longitudinal axis parallel to a radius extending through the region 128 (see region 128a). Alternatively, the nozzle 120 generates a cone-shaped spray.

[0037] 1A shows the sprays overlapping themselves, the nozzles 120 can be oriented such that the elongated regions do not overlap. For example, at least some of the nozzles 120 (e.g., all of the nozzles 120) can be oriented such that the elongated region 128 is at an oblique angle to a radius passing through the elongated region (see region 128b).

[0038] At least some of the nozzles 120 can be oriented such that the central axis of the spray from that nozzle (see arrow A) is at an oblique angle to the polishing surface 36. In particular, the spray 122 can be directed from the nozzles 120 such that it has a horizontal component in a direction opposite to the direction of motion of the polishing pad 30 (see arrow A) in the region of impingement caused by the rotation of the platen 24.

[0039] 1A and 1B show the nozzles 120 as being uniformly spaced apart, this is not required. The nozzles 120 may be non-uniformly distributed radially, angularly, or both. For example, the nozzles 120 may be more tightly clustered along the radial direction toward the end of the polishing pad 30. Additionally, while FIGS. 1A and 1B show nine nozzles, there may be more or fewer nozzles, e.g., between 3 and 20 nozzles.

[0040] The cooling system 102 can be used to reduce the temperature of the polishing surface 36. For example, the temperature of the polishing surface 36 can be reduced using liquid from the liquid coolant 130 via the spray 122, gas from the gas coolant 132 via the spray 122, cold flow 52 from the vortex tube 50 (see FIG. 5), or a combination thereof. In some embodiments, the temperature of the polishing surface 36 can be reduced to 20° C. or lower. Lower temperatures during one or more of the metal cleaning, overpolishing, or conditioning steps can reduce dishing and erosion of soft metals during CMP by reducing the selectivity of the polishing fluid 38.

[0041] In some implementations, a temperature sensor measures the temperature of the polishing pad 30 or the polishing liquid 38 on the polishing pad 30, and the controller 12 executes a closed-loop control algorithm to control the flow rate of the coolant relative to the flow rate of the polishing liquid 38 to maintain the polishing pad 30 or the polishing liquid 38 on the polishing pad 30 at a desired temperature.

[0042] Lower temperatures during CMP can be used to reduce corrosion. For example, lower temperatures during one or more of the metal cleaning, overpolishing, or conditioning steps can reduce galvanic corrosion in various components, since galvanic reactions are temperature dependent. Additionally, inert gases can be used in the polishing process during CMP. In particular, gases lacking oxygen (or having less oxygen than normal atmosphere) can be used to create a local inert environment that reduces oxygen within the local inert environment, resulting in reduced corrosion. Examples of such gases include nitrogen and carbon dioxide, for example evaporated from liquid nitrogen or dry ice.

[0043] For example, lowering the temperature of the polishing surface 36 for the conditioning step can increase the storage modulus of the polishing pad 30 and decrease the viscoelasticity of the polishing pad 30. The increased storage modulus and decreased viscoelasticity, combined with a lower down force on the pad conditioning disk 92 and / or less aggressive conditioning by the pad conditioning disk 92, can result in a more uniform pad roughness. The benefit of the uniform pad roughness is reduced scratches on the substrate 10 during subsequent polishing operations as well as increased life of the polishing pad 30.

[0044] As shown in FIG. 5, each nozzle 120 may be a converging-diverging (CD) nozzle. A converging-diverging (CD) nozzle may also be described as a de Laval nozzle or a supersonic nozzle. Each nozzle 120 has a converging section 202 (e.g., an input port) where gas (e.g., gas from a gas source 132) enters the nozzle 120 at subsonic speed. A pump 222 may induce the gas from the gas source 132, through a dispenser 210, and into the CD nozzle 120. For example, the gas entering the converging section 202 may be at room temperature (e.g., 20 to 30° C.) or below room temperature and may enter at a rate of 0 to 1000 liters / minute per nozzle (e.g., 500 liters / minute per nozzle). From the converging section 202, the gas enters a choke point, or throat 204, where the cross-sectional area of ​​the nozzle 120 is smallest. The velocity of the gas increases as the gas flows from the converging section 202 through the throat 204 to the diverging section 206 (e.g., output port). The throat 204 increases the velocity of the gas flowing through it, so that the velocity of the gas increases up to supersonic speeds as the gas enters and exits the diverging section 206. For example, the gas exiting the diverging section 206 may be at a temperature below room temperature, for example, −100 to 20° C., −90 to 0° C., −80 to −25° C., or −70 to −50° C.

[0045] The gases used in the cooling system 102 may include, for example, air, nitrogen, carbon dioxide, argon, or evaporated gases such as vaporized ethanol or isopropyl alcohol. The gases may be cooled even before being delivered to the CD nozzles 120. For example, the cooled gas may be cold air (e.g., air cooled by passing through a heat exchanger), cold nitrogen gas (e.g., evaporated from liquid nitrogen), or cold carbon dioxide gas (e.g., from the sublimation of dry ice).

[0046] The CD nozzle 120 can be used to cool the polishing pad 30. For example, the diffusion section 206 can deliver cooled gas directly onto the polishing pad 30. For example, the outlet from the diffusion section 206 can be located about 1 to 10 cm from the polishing surface 36, and the nozzle 120 can be oriented such that the gas flow impinges on the polishing surface.

[0047] In some implementations, the liquid coolant source 130 can supply liquid (e.g., water) through a dispenser 210. The dispenser 210 can be an injector positioned to inject water into the gas flow through the nozzle 120. For example, the injector 210 can be positioned to inject water droplets into the contraction section 202, into the throat 204 (as shown in FIG. 5), into the divergence section 206, or directly behind the divergence section 206.

[0048] The flow rate of liquid coolant into the gas stream (e.g., in the nozzle 120) can be controlled by a valve 212. The dispenser 210 can deliver the water droplets 208 at a rate of, for example, 0 to 300 milliliters per minute (e.g., 3 to 50 milliliters per minute). The liquid flow rate can be about 0.001% to 1% (e.g., 0.01 to 0.1%) of the gas flow rate. As the gas flows through the CD nozzle 120, the water droplets 208 can be cooled by the gas as the gas flowing through the CD nozzle 120 cools. In some implementations, the water droplets 208 cool to form ice droplets. The ice droplets can be uniform in size (e.g., approximately 10 μm in diameter).

[0049] In some implementations, the water droplets 208 are further provided directly on the polishing pad 30. The water droplets 208 can further cool the polishing pad 30 together with the cooled gas. Furthermore, the ice or water droplets can prevent the polishing pad 30 from drying out when the polishing pad 30 is being cooled by the cooled gas. In some implementations, the cooled gas freezes the water droplets 208 to form ice droplets. The ice droplets can cool the polishing pad 30 together with the cooled gas. As the ice droplets absorb heat and melt into water, the latent heat of fusion can cool the polishing pad 30, so the ice droplets can efficiently cool the polishing pad 30. Furthermore, the ice droplets can be used to polish and clean the polishing pad 30.

[0050] In some implementations, the coolant may be substantially liquid only (eg, not mixed with gas).

[0051] 2, the arm 110 includes a support plate 138 above which the nozzles 120 are suspended. Each nozzle 120 may be positioned above a corresponding passage 114 through the support plate 138. In some implementations, rather than individual passages, there is a slot extending along the support plate 138, and the nozzles 120 are positioned above the slot.

[0052] In some implementations, the nozzles 120 are suspended within the arm 110. For example, the support plate 138 can be covered by a cover 134 to form a chamber 135, and the nozzles 120 can be suspended within the chamber 135 from a ceiling 135 of the cover 134. All of the nozzles 120 can be housed within the common chamber 135 (see FIG. 1A). However, the cover is optional, and the top surface of the support plate 138 can be generally open to the environment, with the nozzles 120 similarly uncovered. In this case, the nozzles 120 can be suspended by struts or a framework extending from the support plate 138.

[0053] 1A and 2 show the nozzles 120 positioned entirely above the top surface of the support plate 138, this is not required. For example, each nozzle 120 may extend partially into a corresponding passage 114 in the support plate 138. However, the bottom of the nozzles 120 does not protrude below the bottom surface of the support plate 138.

[0054] The nozzles 120 are separated from the polishing pad 30 by a gap 126. The nozzles 120 spray liquid coolant with entrained gas onto the polishing pad 30 through passages 114 in the support plate 138. Each nozzle 120 may have a separate passage 114. Although the passages 114 are shown as circular (in a top view of the arm), the passages may have other cross-sectional shapes (e.g., rectangular, oval, etc.).

[0055] The space between the inner surface 118 of the passage 114 and the outer surface of the nozzle 120 provides a gap 116. The gap may be approximately 5 to 10 mm wide. The gap 116 functions as an opening that allows additional air, indicated by arrows 140, to be entrained in the coolant fluid flow 142. The air entrained in the coolant fluid flow 142 can increase the total mixture of gas and coolant flow directed at the slurry 38 on the upper surface 36 of the polishing pad 30, thus increasing the heat transfer from the slurry 38 and the polishing pad 30. As shown, the entrained air flows from above the support plate 138. Simply increasing the gas flow rate can further improve the heat transfer. However, without being limited to any particular theory, the air from above the support plate 138 may be cooler than the air directly above the polishing pad. The air directly above the polishing pad may have absorbed heat from the polishing pad to further improve heat transfer.

[0056] 3A and 3B, in some implementations, the nozzles 120 are suspended on an arm 110 within a housing 136. The arm 110 may be configured as described above, except as noted below. All of the nozzles 120 may be positioned within a common chamber of a single housing 136. Alternatively, as shown in FIG. 3B, at least one of the nozzles 120 (e.g., all of the nozzles 120) may have a dedicated housing 136 such that there is a single nozzle 120 within a chamber provided by the housing 136. Each nozzle is suspended above a support plate 138, for example, from a ceiling 154 of the housing 136.

[0057] The top surface 146 of the support plate 138 may have an aperture 144. The aperture 144 connects to an air plenum 148 formed in the body of the support plate 138. In particular, the plenum 148 may surround and connect to three sides of the passageway 114. Thus, the passageway 114 has openings on three sides 150 to the plenum 148 to allow air flow 140, and one side 152 is closed.

[0058] The nozzles 120 spray the liquid coolant through the passages 114 in the support plate 138. Air flow through the housing 136 is generally blocked, but air can enter the plenum through the apertures 144. Thus, the plenum 148 provides an opening that allows air to enter the passages 114 and be entrained in the spray from the nozzles 120. Thus, this configuration can also increase the total mixture of gas and coolant flow directed at the slurry 38 on the polishing pad 30, which in turn increases the heat transfer from the slurry 38 and the polishing pad 30. Because the apertures 144 are on the top surface of the support plate 138, the entrained air flows from above the support plate 138. However, this configuration may not be as efficient as the configuration of FIG. 2.

[0059] Figures 4A and 4B show a configuration similar to that shown in Figures 3A and 3B, but with the passages 114 open on only one side 150 to the plenum 148. Again, the plenum 148 provides an opening that allows air to enter the passages 114 and be entrained in the spray from the nozzles 120, thereby increasing the total amount of gas and coolant flow to the slurry 38 on the polishing pad 30. However, this configuration may not be as efficient as the configuration of Figures 3A and 3B.

[0060] The polishing system 20 may include a heating system (e.g., an arm having an aperture for supplying a heated fluid (e.g., steam) onto the polishing pad), a high-pressure rinsing system (e.g., an arm having a nozzle for spraying rinsing fluid onto the polishing pad), and a wiper blade or wiper body for evenly distributing polishing fluid 38 across the polishing pad 30.

[0061] The above-described polishing apparatus and method can be applied in a variety of polishing systems. Either or both of the polishing pad and the carrier head can move to generate relative motion between the polishing surface and the substrate. For example, the platen can orbit rather than rotate. The polishing pad can be a circular (or some other shape) pad fixed to the platen. The polishing layer can be a standard (e.g., polyurethane with or without fillers) abrasive material, a soft material, or a fixed abrasive material.

[0062] It should be understood that the term relative positioning is used to refer to the relative positioning within a system or of a substrate, and that the polishing surface and substrate may be held in a vertical orientation or some other orientation during the polishing operation.

[0063] The polishing system 20 may further include a controller 12 that controls the operation of various components (e.g., the temperature control system 100). The controller 12 is configured to receive temperature measurements from the temperature sensors 64 for each radial zone of the polishing pad. The controller 12 may compare the measured temperature profile to a desired temperature profile and generate a feedback signal to a control mechanism (e.g., an actuator, a power supply, a pump, a valve, etc.) for each nozzle or opening. The feedback signal causes the control mechanism to adjust the amount of cooling or heating so that the polishing pad and / or slurry reaches (or at least approaches) the desired temperature profile, calculated by the controller 12, for example, based on an internal feedback algorithm.

[0064] The functional operations of the controller 12 may be implemented using one or more computer program products (i.e., one or more computer programs tangibly embodied in a non-transitory machine-readable storage medium for execution by or to control the operation of a data processing device (e.g., a programmable processor, a computer, or multiple processors or computers).

[0065] FIG. 6 is a flow diagram of an example of a method 600 for controlling the temperature of the chemical mechanical polishing system of FIG. 2. A nozzle is supported on a support arm (602). A coolant fluid is supplied to the nozzle from a coolant source (604). The coolant fluid can be a liquid (e.g., liquid water), liquid ethanol, and / or liquid isopropyl alcohol. The coolant fluid can be a gas formed, for example, by chilling air, by evaporating liquid nitrogen, by evaporating liquid ethanol, by evaporating liquid isopropyl alcohol, and / or by sublimating dry ice. The coolant fluid is cooled by flowing the coolant fluid through the nozzle (606). The coolant fluid is flowed through the nozzle to reduce the temperature of the coolant fluid. Air from an opening in the support arm is entrained in the flow of cooled coolant fluid from the nozzle, forming a mixture of cooled coolant fluid and entrained gas (608). The mixture of cooled coolant fluid and entrained gas is directed onto the polishing pad (610). The mixture of coolant fluid and entrained gas is delivered onto the polishing pad at a temperature below 0° C. The mixture of coolant fluid and entrained gas may be delivered onto the polishing pad at a temperature of −70 to −50° C.

[0066] Several embodiments of the present invention have been described. However, it will be understood that various modifications can be made without departing from the spirit and scope of the invention.

[0067] For example, while the above description focuses on supplying coolant to the polishing pad, it is possible to supply coolant to other components to control their temperature. For example, coolant can be sprayed onto the substrate while it is positioned in the transfer station (e.g., the load cup). As another example, the load cup itself can be sprayed with coolant. As yet another example, the conditioning disk can be sprayed with coolant.

[0068] 1B shows the arm 110 as linear, the arm may be arcuate. Additionally, various subsystems may be included within a single assembly supported by a common arm. For example, the assembly may include a cooling module, as well as one or more of a rinsing module, a heating module, a slurry supply module, and optionally a wiper module.

[0069] Accordingly, other embodiments are within the scope of the following claims.

Claims

1. 1. A chemical mechanical polishing system comprising: a platen for supporting a polishing pad having a polishing surface; 1. A pad cooling assembly comprising: an arm extending across the platen; a nozzle suspended by the arm and connected to a source of coolant fluid positioned to spray coolant fluid from the source onto the polishing surface of the polishing pad; an opening in the arm adjacent the nozzle and a passageway extending from the opening into the arm, the opening being positioned sufficiently close to the nozzle such that a flow of coolant fluid from the nozzle entrains air from the opening; Includes pad cooling assembly A chemical mechanical polishing system comprising:

2. The system of claim 1 , wherein the arm comprises a support plate having an aperture therethrough, the nozzle being oriented to spray coolant fluid through the aperture.

3. The system of claim 2 , wherein the opening is provided by a gap between an inner surface of the aperture and the nozzle.

4. The system of claim 3 , wherein a bottom of the nozzle is positioned above the support plate.

5. The system of claim 3 , wherein a portion of the nozzle extends into the aperture.

6. The system of claim 2 , wherein a top portion of the support plate is uncovered.

7. The system of claim 2 , wherein the arm comprises a housing that covers the support plate.

8. 8. The system of claim 7, further comprising a passageway through the housing for connecting an interior of the housing to an external atmosphere.

9. The system of claim 7 , wherein a plurality of nozzles are suspended by said arms, said plurality of nozzles being within a common chamber of said housing.

10. The system of claim 7 comprising a passageway extending laterally through said support plate from at least one sidewall of said aperture, said opening being defined by said passageway.

11. The system of claim 7 comprising a plurality of passages extending laterally through the support plate from different side walls of the aperture, the opening being defined by the plurality of passages.

12. The system of claim 1 , wherein the nozzle comprises a converging-diverging nozzle.

13. 10. The system of claim 1, comprising a controller coupled to a coolant source and configured to cause the coolant source to supply the coolant fluid to the nozzle at a rate of between 50 and 100 standard liters per minute.

14. 1. A method of temperature control for a chemical mechanical polishing system, comprising: supporting the nozzle on a support arm; supplying a coolant fluid from a coolant source through the nozzle; entraining air through an opening in the support arm in a flow of coolant fluid from the nozzle and directing a mixture of the coolant fluid and the entrained air onto a polishing pad; The method includes:

15. The method of claim 14 , wherein flowing the coolant fluid through the nozzle reduces a temperature of the coolant fluid.

16. The method of claim 14 , wherein the coolant fluid is a gas.

17. 17. The method of claim 16, comprising forming the coolant fluid by chilling air, by evaporating liquid nitrogen, by evaporating liquid ethanol, by evaporating liquid isopropyl alcohol, and / or by sublimating dry ice.

18. The method of claim 14 , wherein the fluid is a liquid.

19. 20. The method of claim 18, wherein the fluid comprises liquid nitrogen, liquid water, liquid ethanol, and / or liquid isopropyl alcohol.

20. 15. The method of claim 14, comprising delivering the mixture of coolant fluid and entrained air onto the polishing pad at a temperature below 0°C.

21. 21. The method of claim 20, comprising delivering the mixture of coolant fluid and entrained air onto the polishing pad at a temperature between -70 and -50 degrees Celsius.

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