Low-Temperature Metal CMP to Minimize Dishing and Erosion and Improve Pad Asperities

Abstract

The chemical mechanical polishing system includes a platen supporting a polishing pad having a polishing surface, a coolant source, a dispenser having one or more apertures suspended above the platen that directs coolant from the coolant source onto the polishing surface of the polishing pad, and a controller coupled to the coolant source and configured to cause the coolant source to deliver coolant through a nozzle onto the polishing surface during selected steps of the polishing operation.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to chemical mechanical polishing (CMP), and more particularly to temperature control during CMP. [Background technology]

[0002] Integrated circuits are typically formed on a substrate by sequentially 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 then planarizing the filler layer. For certain applications, the filler layer is planarized until the top surface of a patterned layer is exposed. For example, a metal layer can be deposited on a patterned insulating layer to fill the trenches and holes in the insulating layer. After planarization, the remaining metal within the trenches and holes in the patterned layer forms vias, plugs, and lines that provide conductive paths between thin-film circuits on the substrate. As another example, a dielectric layer can be deposited on a patterned conductive layer and then planarized to allow for subsequent photolithography steps.

[0003] Chemical mechanical polishing (CMP) is one accepted planarization method. This planarization method typically requires the substrate to be mounted on a carrier head. The exposed surface of the substrate is typically placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate, pressing it against the polishing pad. A polishing slurry containing abrasive particles is typically supplied to the surface of the polishing pad. Summary of the Invention

[0004] In one aspect, a chemical mechanical polishing system includes a platen supporting a polishing pad having a polishing surface, a coolant source, a dispenser having one or more apertures suspended above the platen that directs coolant from the coolant source onto the polishing surface of the polishing pad, and a controller coupled to the coolant source and configured to cause the coolant source to deliver coolant through a nozzle onto the polishing surface during selected steps of the polishing operation.

[0005] Implementations of any of the above aspects may include one or more of the following features.

[0006] The coolant source may include a liquid coolant source. The liquid coolant source may include one or more of liquid nitrogen or liquid carbon dioxide.

[0007] The coolant source can include a gaseous coolant source. The gaseous coolant source can include one or more of a gas formed from liquid nitrogen or a gas formed from liquid carbon dioxide. The gaseous coolant source can include a compressed gas. The gaseous coolant source can be connected to a vortex tube configured to direct a flow of cold gas onto the polishing pad.

[0008] The nozzle may be configured to start and stop fluid flow through the nozzle.

[0009] The selected step is Conditioning The selected step can be a metal removal step. The selected step can be an overcoat removal step. Polishing (over-polishing) It can be a step.

[0010] In another aspect, a method of a chemical mechanical polishing system includes bulk polishing a substrate with a polishing pad at a first temperature range, and performing metal removal, over polishing, of the substrate with the polishing pad. Polishing ,or conditioningor performing one or more of the steps of: heating the polishing pad at a temperature of the polishing surface of the polishing pad that is reduced to a second temperature range that is lower than the first temperature range. conditioning This includes:

[0011] Implementations of any of the above aspects may include one or more of the following features.

[0012] The temperature can be reduced using a coolant connected to an arm having one or more nozzles suspended above the polishing surface of the polishing pad, and the nozzles on the arm can be configured to direct coolant from a coolant source onto the polishing surface of the polishing pad to reduce the temperature of the polishing surface. The coolant source can include a liquid coolant source. The liquid coolant source can include one or more of liquid nitrogen or liquid carbon dioxide. The coolant source can include a gaseous coolant source. The gaseous coolant source can include one or more of a gas formed from liquid nitrogen or a gas formed from liquid carbon dioxide. The gaseous coolant source can include a compressed gas. The gaseous coolant source can be connected to a vortex tube configured to direct a flow of cold gas onto the polishing pad.

[0013] The nozzle may be configured to start and stop fluid flow through the nozzle.

[0014] Potential advantages may include, but are not limited to, one or more of the following:

[0015] Controlling the temperature of various components can reduce the effects of temperature-dependent processes such as dishing, erosion, and corrosion. Temperature control can also create more uniform pad asperities, thus improving polishing uniformity and extending pad life, for example, for removing metal residues.

[0016] In one example, the temperature of the polishing process is increased. In particular, steam, i.e., gaseous HO generated by boiling, can be injected into the slurry to transfer energy with a low liquid content (i.e., low dilution) and quickly and efficiently increase the temperature of the slurry. This can increase the polishing rate, for example, during bulk polishing.

[0017] In another example, the metal removal step of the polishing operation, Polishing Step, or conditioning The temperature of the polishing pad surface during one or more of the steps can be reduced, which can reduce dishing and erosion and / or improve the uniformity of the pad asperities, thus improving polishing uniformity and extending pad life.

[0018] In addition, the temperature of various components of the CMP apparatus can be reduced, thereby reducing the galvanic reaction rate and reducing corrosion of various components, which can reduce defects in the polished wafers.

[0019] This can improve polishing predictability during the CMP process, reducing polishing variability from polishing run to polishing run and improving wafer-to-wafer uniformity.

[0020] 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 explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic plan view showing an example of a polishing apparatus. [Figure 2A] 1 is a schematic cross-sectional view illustrating an example carrier head vapor processing assembly. [Figure 2B] FIG. 1 is a schematic cross-sectional view of an example conditioning head steam processing assembly. [Figure 3A]1 is a schematic cross-sectional view showing an example of a polishing station of a polishing apparatus. [Figure 3B] 1 is a schematic top view illustrating a polishing station of an example chemical mechanical polishing apparatus. [Figure 4A] 1 is a schematic cross-sectional view of an example steam generator. [Figure 4B] FIG. 1 is a schematic cross-sectional top view of an example steam generator. DETAILED DESCRIPTION OF THE INVENTION

[0022] Chemical mechanical polishing operates by a combination of mechanical abrasion and chemical etching at the interface between the substrate, the polishing fluid, and the polishing pad. During the polishing process, a significant amount of heat is generated by friction between the surface of the substrate and the polishing pad. In addition, some processes also conditioning A disk, for example a disk coated with abrasive diamond particles, is pressed against a rotating polishing pad until the polishing pad surface Conditioning Textured and in-situ pad conditioning Includes steps. conditioning Polishing processes can also generate heat. For example, in a typical one-minute copper CMP process with a nominal downforce pressure of 2 psi and a removal rate of 8000 Angstroms / minute, the surface temperature of a polyurethane polishing pad can increase by approximately 30°C.

[0023] On the other hand, the slurry dispensed on the polishing pad can act as a heat sink. Collectively, these effects result in variations in the temperature of the polishing pad, both spatially and over time.

[0024] Both chemically related variables in the CMP process, such as the onset and rate of the reactions involved, and mechanically related variables, such as the surface friction coefficient, storage modulus, and viscoelasticity of the polishing pad, are highly temperature dependent. Consequently, variations in the surface temperature of the polishing pad can result in changes in removal rate, polishing uniformity, erosion, dishing, and residue. Polishing (over-polishing) Step, or conditioning By more tightly controlling the temperature of the surface of the polishing pad during one or more of the steps, temperature variations can be reduced, which can improve polishing performance, for example, as measured by within-wafer or between-wafer non-uniformity.

[0025] Generally, as the temperature of the polishing liquid 38 increases, the polishing rate of the polishing liquid 38 increases. Conversely, as the temperature of the polishing liquid 38 decreases, the polishing rate of the polishing liquid 38 decreases. An increase in the polishing rate may be desirable in some stages of the polishing operation (e.g., during bulk polishing), while a decrease in the polishing rate may be desirable in other stages of the polishing operation (e.g., during the metal removal step, over polishing step, etc.). Polishing Steps, and conditioning It may be desirable to

[0026] Additionally, debris and slurry may accumulate on various components of the CMP apparatus during CMP. Mechanical and chemical etching by the debris and slurry may cause dishing and erosion of the polishing pad and may corrode various components of the CMP apparatus.

[0027] A technique that may address one or more of these challenges is to preheat the polishing pad and / or slurry during portions of the polishing process, e.g., during bulk polishing. For example, various components of the CMP apparatus (e.g., polishing fluid 38 from polishing fluid reservoir 37) can be heated using steam, i.e., gaseous H2O, to increase the polishing rate during the polishing process. Additionally, the temperature of the polishing pad and various components can be reduced to allow for a metal removal step, over a period of time, e.g., using vortex tube cooling and / or by dispensing a coolant. Polishing Step, or conditioning The polishing rate of the slurry chemistry during one or more of the steps can be reduced.

[0028] FIG. 1 is a plan view of a chemical mechanical polishing apparatus 2 for processing one or more substrates. The polishing apparatus 2 includes a polishing platform 4 that at least partially supports and houses multiple polishing stations 20. For example, the polishing apparatus may include four polishing stations 20a, 20b, 20c, and 20d. Each polishing station 20 is adapted to polish a substrate retained by a carrier head 70. Not all components of each station are shown in FIG. 1.

[0029] The polishing apparatus 2 also includes a plurality of carrier heads 70, each configured to hold a substrate. The polishing apparatus 2 also includes a transfer station 6 for loading and unloading substrates onto and from the carrier heads. The transfer station 6 may include a plurality of load cups 8, e.g., two load cups 8a, 8b, adapted to facilitate transfer of substrates between the carrier heads 70 and a factory interface (not shown) or other device (not shown) by a transfer robot 9. The load cups 8 generally facilitate transfer between the robot 9 and each of the carrier heads 70 by loading and unloading the carrier heads 70.

[0030] The stations of the polishing apparatus 2, including the transfer station 6 and the polishing station 20, may be positioned at substantially equal angular intervals around the center of the platform 4. This is not a requirement, but may provide a good footprint for the polishing apparatus.

[0031] For polishing operations, one carrier head 70 is positioned at each polishing station. During loading and unloading of station 6, two additional carrier heads can be positioned to exchange polished substrates for unpolished substrates while other substrates are polished at polishing station 20.

[0032] The carrier heads 70 are carried by a support structure that allows each carrier head to be moved along a path that sequentially passes through the first polishing station 20 a, the second polishing station 20 b, the third polishing station 20 c, and the fourth polishing station 20 d, thereby allowing each carrier head to be selectively positioned over the polishing stations 20 and the load cup 8.

[0033] In some implementations, each carrier head 70 is coupled to a carriage 78 that is mounted to the support structure 72. The carriage 78 can be moved along the support structure 72, for example, along a track, to position the carrier head 70 over a selected polishing station 20 or load cup 8. Alternatively, the carrier heads 70 can be suspended from a carousel, the rotation of which causes all of the carrier heads to move simultaneously along a circular path.

[0034] Each polishing station 20 of the polishing apparatus 2 may include, for example, a port at the end of a slurry dispenser 39 (e.g., a dispenser arm) that dispenses a polishing liquid 38 (see FIG. 3A), such as a polishing slurry, onto the polishing pad 30. Each polishing station 20 of the polishing apparatus 2 may also include a pad conditioner 93 that polishes the polishing pad 30 to maintain the polishing pad 30 in a consistent polishing condition.

[0035] 3A and 3B 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 rests. The platen 24 is operable to rotate about an axis 25 (see arrow A in FIG. 3B). 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 and a softer backing layer 32.

[0036] 1, 3A, and 3B, the polishing station 20 can include a supply port, for example at the end of a slurry delivery arm 39, for dispensing a polishing liquid 38, such as a polishing slurry, onto the polishing pad 30.

[0037] The polishing station 20 can include a pad conditioner 90 having a conditioner disk 92 (see FIG. 2B) to maintain the surface roughness of the polishing pad 30. The conditioner disk 92 can be positioned on a conditioner head 93 at the end of an arm 94. The arm 94 and conditioner head 93 are supported by a base 96. The arm 94 can pivot to sweep the conditioner head 93 and conditioner disk 92 laterally across the polishing pad 30. A cleaning cup 250 can be positioned adjacent to the platen 24 in a position that allows the arm 94 to move the conditioner head 93.

[0038] 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 is connected by drive shaft 74 to a carrier head rotation motor 76 so that the carrier head can rotate about axis 71. Optionally, carrier head 70 can be oscillated laterally, e.g., on a carousel slider, by movement along the track or by rotational oscillation of the carousel itself.

[0039] Carrier head 70 may include a flexible membrane 80 having a substrate mounting surface that contacts the backside of substrate 10 and a plurality of pressurizable chambers 82 that apply different pressures to different areas on substrate 10, e.g., different radial areas. Carrier head 70 may include a retaining ring 84 that holds the substrate. In some implementations, 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.

[0040] In operation, the platen is rotated about its central axis 25, and the carrier head is rotated about its central axis 71 (see arrow B in FIG. 3B) and translated laterally across the top surface of the polishing pad 30 (see arrow C in FIG. 3B).

[0041] 3A and 3B, as the carrier head 70 sweeps across the polishing pad 30, any exposed surfaces of the carrier head 70 tend to become coated with slurry. For example, the slurry may stick to the outer or inner diameter surfaces of the retaining ring 84. Generally, if any surface is not kept wet, the slurry tends to solidify and / or dry. As a result, particulates may form on the carrier head 70. If these particulates are dislodged, they may scratch the substrate, resulting in polishing defects.

[0042] Additionally, the slurry may cake on the carrier head 70, or the sodium hydroxide in the slurry may crystallize on one of the surfaces of the carrier head 70 and / or substrate 10, corroding the surface of the carrier head 70. The caked slurry is difficult to remove, and the crystallized sodium hydroxide is difficult to put back into solution.

[0043] Similar problems occur with conditioner head 92; for example, particulates may form on conditioner head 92, the slurry may stick to conditioner head 92, or the sodium hydroxide in the slurry may crystallize on one of the surfaces of conditioner head 92.

[0044] One solution is to clean the components, such as the carrier head 70 and the conditioner head 92, with a stream of liquid water. However, the components can be difficult to clean with a stream of water alone, and a significant amount of water may be required. In addition, the components that contact the polishing pad 30, such as the carrier head 70, the substrate 10, and the conditioner disk 92, can act as a heat sink, which interferes with the uniformity of the polishing pad temperature.

[0045] 2A, polishing apparatus 2 includes one or more carrier head vapor-processing assemblies 200. Each vapor-processing assembly 200 can be used to clean and / or preheat carrier head 70 and substrate 10.

[0046] The vapor-processing assembly 200 can be part of the load cup 8, such as part of load cup 8a or 8b. Alternatively or additionally, the vapor-processing assembly 200 can be provided in one or more inter-platen stations 9 located between adjacent polishing stations 20.

[0047] The load cup 8 includes a pedestal 204 that holds the substrate 10 during the loading / unloading process. The load cup 8 also includes a housing 206 that surrounds or substantially surrounds the pedestal 204. A plurality of nozzles 225 are supported by the housing 206 or a separate support to deliver vapor 245 to the carrier head and / or substrate positioned within a cavity 208 defined by the housing 206. For example, the nozzles 225 can be positioned on one or more interior surfaces of the housing 206, such as on the floor 206a and / or sidewalls 206b and / or ceiling of the cavity. The nozzles 225 can be configured to start and stop fluid flow through the nozzles 225, for example, using the controller 12. The nozzles 225 can be oriented to direct the vapor inward into the cavity 206. The vapor 245 can be generated using a vapor generator 410, such as a vapor generator described further below. The drain 235 allows excess water, cleaning solution, and cleaning by-products to pass through and prevent accumulation in the load cup 8 .

[0048] The actuator provides relative vertical motion between the housing 206 and the carrier head 70. For example, the shaft 210 can support the housing 206 and can be vertically actuable to raise or lower the housing 206. Alternatively, the carrier head 70 can move vertically. The platform 205 can be coaxial with the shaft 210. The platform 204 can be vertically movable relative to the housing 206.

[0049] In operation, carrier head 70 can be positioned over load cup 8, and housing 206 can be raised (or carrier head 70 can be lowered) so that carrier head 70 is partially within cavity 208. Substrate 10 can be chucked onto carrier head 70 starting on pedestal 204, and / or dechucked onto pedestal 204 starting on carrier head 70.

[0050] The vapor is directed through the nozzles 225 to clean and / or preheat one or more surfaces of the substrate 10 and / or carrier head 70. For example, one or more of the nozzles can be positioned to direct the vapor onto the outer surface of the carrier head 70, the outer surface 84a of the retaining ring 84, and / or the lower surface 84b of the retaining ring 84. One or more of the nozzles can be positioned to direct the vapor onto the front surface, i.e., the surface to be polished, of the substrate 10 held by the carrier head 70, or onto the lower surface of the membrane 80 if the substrate 10 is not supported on the carrier head 70. One or more nozzles can be positioned below the pedestal 204 to direct the vapor upward onto the front surface of the substrate 10 positioned on the pedestal 204. One or more nozzles can be positioned above the pedestal 204 to direct the vapor downward onto the back surface of the substrate 10 positioned on the pedestal 204. Carrier head 70 can rotate within load cup 8 and / or move vertically relative to load cup 8 to allow nozzles 225 to treat different areas of carrier head 70 and / or substrate 10. Substrate 10 can be placed on pedestal 205 to allow for vapor treatment of an inner surface of carrier head 70, for example, the underside of membrane 82 or the inner surface of retaining ring 84.

[0051] Vapor is circulated from a vapor source through a supply line 230 through the housing 206 to a nozzle 225. The nozzle 225 can spray vapor 245 to remove organic residue, by-products, debris, and slurry particles remaining on the carrier head 70 and substrate 10 after each polishing operation. The nozzle 225 can spray vapor 245 to heat the substrate 10 and / or carrier head 70.

[0052] The inter-platen station 9 may be similarly constructed and operated, but does not necessarily have a substrate support pedestal.

[0053] The vapor 245 delivered by the nozzles 225 can have an adjustable temperature, pressure, and flow rate that varies to clean and preheat the carrier head 70 and the substrate 10. In some implementations, the temperature, pressure, and / or flow rate can be independently adjustable for each nozzle or between groups of nozzles.

[0054] For example, when steam 245 is generated (e.g., in steam generator 410 of FIG. 4A), the temperature of steam 245 can be between 90 and 200° C. When steam 245 is dispensed by nozzle 225, e.g., due to heat losses during transfer, the temperature of steam 245 can be between 90 and 150° C. In some implementations, steam is delivered by nozzle 225 at a temperature between 70 and 100° C., e.g., between 80 and 90° C. In some implementations, the steam delivered by the nozzle is superheated, i.e., above its boiling point.

[0055] The flow rate of the steam 245 can be 1 to 1000 cc / min, depending on the heater power and pressure when the steam 245 is delivered by the nozzle 225. In some implementations, the steam is mixed with other gases, such as air or N2. Alternatively, the fluid delivered by the nozzle 225 is substantially pure water. In some implementations, the steam 245 delivered by the nozzle 225 is mixed with liquid water, such as aerosolized water. For example, the liquid water and steam can be combined in a relative flow ratio (e.g., flow rates in sccm) of 1:1 to 1:10. However, if the amount of liquid water is small, e.g., less than 5 wt%, e.g., less than 3 wt%, e.g., less than 1 wt%, the steam will have excellent heat transfer properties. Thus, in some implementations, the steam is dry steam, i.e., substantially free of water droplets.

[0056] To avoid thermal degradation of the membrane, water can be mixed with the steam 245 to reduce the temperature, for example, to around 40-50° C. The temperature of the steam 245 can be reduced by mixing cooled water with the steam 245 or by mixing water of the same or substantially the same temperature with the steam 245 (because liquid water transfers less energy than gaseous water).

[0057] In some implementations, a temperature sensor 214 can be installed at or near the vapor-processing assembly 200 to detect the temperature of the carrier head 70 and / or the substrate 10. A signal from the sensor 214 can be received by the controller 12 to monitor the temperature of the carrier head 70 and / or the substrate 10. The controller 12 can control the delivery of vapor by the assembly 100 based on the temperature measurements from the temperature sensor 214. For example, the controller can receive a target temperature value. If the controller 12 detects that the temperature measurement exceeds the target value, the controller 12 stops the flow of vapor. As another example, the controller 12 can reduce the vapor delivery rate and / or reduce the vapor temperature, e.g., to prevent overheating of components during cleaning and / or preheating.

[0058] In some implementations, the controller 12 includes a timer. In this case, the controller 12 can initiate when vapor delivery begins and can stop vapor delivery when the timer expires. The timer can be set based on empirical testing to obtain a desired temperature of the carrier head 70 and substrate 10 during cleaning and / or preheating.

[0059] 2B shows a conditioner steam processing assembly 250 that includes a housing 255. The housing 255 may form a "cup" that receives the conditioner disk 92 and the conditioner head 93. Steam is circulated through a supply line 280 within the housing 255 to one or more nozzles 275. The nozzles 275 spray steam 295 to each conditioningPolishing by-products, such as debris or slurry particles, remaining on the conditioner disk 92 and / or conditioner head 93 after operation can be removed. Nozzles 275 can be located within the housing 255, for example, on the floor, sidewalls, or ceiling of the interior of the housing 255. The nozzles 275 can be configured, for example, using the controller 12, to start and stop fluid flow through the nozzles 275. One or more nozzles can be positioned to clean the bottom surface of the pad conditioner disk and / or the bottom, sidewalls, and / or top surface of the conditioner head 93. Steam 295 can be generated using a steam generator 410. A drain 285 can allow excess water, cleaning solution, and cleaning by-products to pass through to prevent them from accumulating in the housing 255.

[0060] Conditioner head 93 and conditioner disk 92 can be lowered at least partially into housing 255 for steaming. When conditioner disk 92 is returned to operation, conditioner head 93 and conditioner disk 92 are lifted out of housing 255 and positioned over polishing pad 30 to remove the polishing pad 30. conditioning do. conditioning Upon completion of the operation, the conditioner head 93 and conditioner disc 92 are lifted off the polishing pad and rotated back into the housing cup 255 to remove any polishing by-products on the conditioner head 93 and conditioner disc 92. In some implementations, the housing 255 is vertically operable, for example, mounted on a vertical drive shaft 260.

[0061] Housing 255 is positioned to receive pad conditioner disk 92 and conditioner head 93. Conditioner disk 92 and conditioner head 93 may rotate within housing 255 and / or move vertically within housing 255 to allow nozzle 275 to steam various surfaces of conditioner disk 92 and conditioner head 93.

[0062] The steam 295 delivered by the nozzles 275 can have an adjustable temperature, pressure, and / or flow rate. In some implementations, the temperature, pressure, and / or flow rate can be independently adjustable for each nozzle or between groups of nozzles. This allows for variation and therefore more effective cleaning of the conditioner disk 92 or conditioner head 93.

[0063] For example, when steam 295 is generated (e.g., in steam generator 410 of FIG. 4A), the temperature of steam 295 can be between 90 and 200° C. When steam 295 is dispensed by nozzle 275, e.g., due to heat losses during transfer, the temperature of steam 295 can be between 90 and 150° C. In some implementations, steam can be delivered by nozzle 275 at a temperature between 70 and 100° C., e.g., between 80 and 90° C. In some implementations, the steam delivered by the nozzle is superheated, i.e., above its boiling point.

[0064] The flow rate of the steam 2945 can be 1 to 1000 cc / min when the steam 295 is delivered by the nozzle 275. In some implementations, the steam is mixed with other gases, such as air or N2. Alternatively, the fluid delivered by the nozzle 275 is substantially pure water. In some implementations, the steam 295 delivered by the nozzle 275 is mixed with liquid water, such as aerosolized water. For example, the liquid water and steam can be combined at a relative flow ratio (e.g., flow rates in sccm) of 1:1 to 1:10. However, if the amount of liquid water is small, such as less than 5 wt. %, such as less than 3 wt. %, such as less than 1 wt. %, the steam will have excellent heat transfer properties. Therefore, in some implementations, the steam is dry steam, i.e., does not contain water droplets.

[0065] In some implementations, a temperature sensor 264 can be installed in or near the housing 255 to detect the temperature of the conditioner head 93 and / or the conditioner disk 92. The controller 12 can receive a signal from the temperature sensor 264 to monitor the temperature of the conditioner head 93 or the conditioner disk 92, for example, to detect the temperature of the pad conditioner disk 92. The controller 12 can control the delivery of steam by the assembly 250 based on the temperature measurements from the temperature sensor 264. For example, the controller can receive a target temperature value. If the controller 12 detects that the temperature measurement exceeds the target value, the controller 12 stops the flow of steam. As another example, the controller 12 can reduce the steam delivery rate and / or reduce the steam temperature, for example, to prevent overheating of components during cleaning and / or preheating.

[0066] In some implementations, the controller 12 uses a timer. In this case, the controller 12 can start a time when steam delivery begins and stop steam delivery when the timer expires. The timer can be set based on empirical testing to obtain a desired temperature of the conditioner disc 92 during cleaning and / or preheating, for example, to prevent overheating.

[0067] 3A , in some implementations, the polishing station 20 includes a temperature sensor 64 that monitors the temperature of the polishing station or components of the polishing station / within the polishing station, such as the temperature of the polishing pad 30 and / or the polishing liquid 38 on the polishing pad. For example, the temperature sensor 64 may be an infrared (IR) sensor, such as an IR camera, positioned above the polishing pad 30 and configured to measure the temperature of the polishing pad 30 and / or the polishing liquid 38 on the polishing pad. In particular, the temperature sensor 64 is 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 spanning the radius of the polishing pad 30.

[0068] In some implementations, the temperature sensor is a contact sensor rather than a non-contact sensor. For example, the temperature sensor 64 can be a thermocouple or an IR thermometer positioned on or in the platen 24. Additionally, the temperature sensor 64 can be in direct contact with the polishing pad.

[0069] In some implementations, multiple temperature sensors can be spaced at different 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 instead of or in addition to an IR camera.

[0070] 3A, the temperature sensor 64 is positioned to monitor the temperature of the polishing pad 30 and / or the polishing liquid 38 on the pad 30, but can also be positioned inside the carrier head 70 to measure the temperature of the substrate 10. The temperature sensor 64 can be in direct contact with the semiconductor wafer of the substrate 10 (i.e., a contact sensor). In some implementations, multiple temperature sensors are included in the polishing station 22, for example, to measure the temperature of different components of / within the polishing station.

[0071] The polishing system 20 also includes a temperature control system 100 that controls the temperature of the polishing pad 30 and / or the polishing liquid 38 on the polishing pad. The temperature control system 100 may include a cooling system 102 and / or a heating system 104. At least one of the cooling system 102 and the heating system 104, and in some implementations both, operate by delivering a temperature-controlled medium, such as a liquid, water vapor, or mist, onto the polishing surface 36 of the polishing pad 30 (or onto the polishing liquid already on the polishing pad).

[0072] For the cooling system 102, the cooling medium can be a gas, such as air, or a liquid, such as water. The medium can be at room temperature or chilled below room temperature, for example, between 5 and 15°C. In some implementations, the cooling system 102 uses a mist of air and liquid, such as an aerosolized mist of liquid (e.g., water). In particular, the cooling system can have a nozzle that generates an aerosolized mist of water chilled below room temperature. In some implementations, a solid material can be mixed with the gas and / or liquid. The solid material can be a chilled material, such as ice, or a material that absorbs heat when dissolved in water, for example, by a chemical reaction.

[0073] The coolant can be delivered in the coolant delivery arm by flowing through one or more apertures, such as holes or slots, optionally formed in the nozzle, which can be provided by a manifold connected to a coolant source.

[0074] 3A and 3B, an example cooling system 102 includes an arm 110 that extends over the platen 24 and polishing pad 30 from the edge of the polishing pad to the center of the polishing pad 30, or at least near the center (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 that raises and lowers the arm 110 and / or a rotary actuator that rotates 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 conditioner disk 92, and the slurry dispenser 39.

[0075] The exemplary cooling system 102 includes a plurality of nozzles 120 suspended from an arm 110. Each nozzle 120 is configured to spray a liquid cooling medium, such as water, onto the polishing pad 30. The arm 110 can be supported by a base 112 such that the nozzles 120 are separated from the polishing pad 30 by a gap 126. Each nozzle 120 can be configured to start and stop fluid flow through each nozzle 120, for example, using the controller 12. Each nozzle 120 can be configured to direct aerosolized water in a mist 122 toward the polishing pad 30.

[0076] Cooling system 102 can include a liquid coolant source 130 and a gas coolant source 132 (see FIG. 3B). The liquid from source 130 and the gas from source 132 can be mixed in a mixing chamber 134 (see FIG. 3A), for example, in or on arm 110, before being directed through nozzle 120 to form mist 122. When dispensed, this coolant can be below room temperature, for example, between -100 and 20°C, for example, below 0°C.

[0077] The coolant used in the cooling system 102 can include, for example, liquid nitrogen or a gas formed from liquid nitrogen and / or dry ice. In some implementations, water droplets can be added to the gas stream. The water can be cooled to form ice droplets that efficiently cool the polishing pad via the latent heat of fusion of the ice droplets. Additionally, the ice or water droplets can prevent the polishing pad 30 from drying out as it is cooled by the cooled gas. Ethanol or isopropyl alcohol, rather than water, can be injected into the gas stream to form frozen particles.

[0078] Gas from a gas source 132, for example, compressed gas, can be connected to a vortex tube 50, which can separate the compressed gas into a cold stream and a hot stream and direct the cold stream to a nozzle 120 onto the polishing pad 30. In some implementations, the nozzle 120 is the lower end of the vortex tube, which directs the cold stream of compressed gas onto the polishing pad 30.

[0079] In some implementations, process parameters such as flow rate, pressure, temperature, and / or liquid-to-gas mixture ratio can be independently controlled for each nozzle (e.g., by controller 12). For example, the coolant for each nozzle 120 can be routed through an independently controllable chiller to independently control the temperature of the mist. As another example, a separate pair of pumps, one for gas and one for liquid, can be connected to each nozzle to independently control the flow rate, pressure, and gas-to-liquid mixture ratio for each nozzle.

[0080] The various nozzles can spray onto different radial regions 124 on the polishing pad 30. Adjacent radial regions 124 may overlap. In some implementations, the nozzles 120 generate mist that impinges on the polishing pad 30 along an elongated region 128. For example, the nozzles can be configured to generate mist in a generally flat, triangular-shaped volume.

[0081] One or more of the elongated regions 128, for example all of the elongated regions 128, can have a longitudinal axis that is parallel to a radius extending through the region 128 (see region 128a). Alternatively, the nozzle 120 generates a cone-shaped mist.

[0082] 1 shows the mist itself overlapping, the nozzles 120 can be oriented so 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 so that the elongated region 128 is at an oblique angle to a radius through the elongated region (see region 128b).

[0083] At least some of the nozzles 120 can be oriented so that the central axis of the mist (see arrow A) from that nozzle is at an oblique angle to the polishing surface 36. In particular, the mist 122 can be directed from the nozzles 120 so 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.

[0084] 3A and 3B show the nozzles 120 spaced at uniform intervals, this is not a requirement. The nozzles 120 can be distributed unevenly radially, angularly, or both. For example, the nozzles 120 can be packed more closely together radially toward the edge of the polishing pad 30. Additionally, while FIGS. 3A and 3B show nine nozzles, there can be more or fewer nozzles, e.g., between 3 and 20 nozzles.

[0085] 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 mist 122, gas from the gas coolant 132 via the mist 122, cold stream 52 from the vortex tube 50, or a combination thereof. In some embodiments, the temperature of the polishing surface 36 can be reduced to 20° C. or less. Polishing Step, or conditioning By reducing the temperature during one or more of the steps, the selectivity of the polishing fluid 38 can be reduced, thereby reducing dishing and erosion of soft metals during CMP.

[0086] In some implementations, a temperature sensor measures the temperature of the polishing pad or polishing liquid on the polishing pad, and the controller executes a closed-loop control algorithm to control the flow rate of the coolant relative to the flow rate of the polishing liquid so as to maintain the polishing pad or polishing liquid on the polishing pad at a desired temperature.

[0087] Lowering the temperature during CMP can be used to reduce corrosion, e.g., during the metal removal step, over Polishing Step, or conditioning By reducing the temperature during one or more of the steps, galvanic corrosion of various components can be reduced because galvanic reactions can be temperature dependent. Additionally, during CMP, the vortex tube 50 can use gases that are inert in the polishing process. In particular, gases that are oxygen-free (or have less oxygen than atmospheric air) can be used to create a localized inert environment, reducing oxygen within the localized inert environment and thereby reducing corrosion. Examples of such gases include nitrogen and carbon dioxide, e.g., evaporated from liquid nitrogen or dry ice.

[0088] By lowering the temperature of the polishing surface 36, e.g. conditioning In this step, the storage modulus of polishing pad 30 can be increased and the viscoelasticity of polishing pad 30 can be reduced. The increased storage modulus and reduced viscoelasticity can be combined with a reduced downforce on pad conditioner disk 92 and / or a reduced downforce by pad conditioner disk 92. conditioningThis, combined with the reduced aggressiveness of the pad 30, can result in a more uniform pad asperity. The benefits of uniform pad asperity include reduced scratching of the substrate 10 during subsequent polishing operations, as well as increased life of the polishing pad 30.

[0089] In some implementations, instead of or in addition to using a coolant to reduce the temperature of the polishing liquid, a heated fluid, e.g., steam, can be injected into the polishing liquid 38 (e.g., slurry) to increase the temperature of the polishing liquid 38 before the polishing liquid 38 is dispensed. Alternatively, a heated fluid, e.g., steam, can be directed onto the polishing pad, i.e., to adjust the temperature of the polishing liquid after the polishing liquid is dispensed.

[0090] For the heating system 104, the heating fluid can be a gas, such as steam (e.g., from a steam generator 410, see FIG. 4A) or heated air, or a liquid, such as heated water, or a combination of gas and liquid. The heating fluid is at a temperature higher than room temperature, e.g., 40-120°C, e.g., 90-110°C. The fluid can be water, such as substantially pure deionized water, or water containing additives or chemicals. In some implementations, the heating system 104 uses a mist of steam. The steam can contain additives or chemicals.

[0091] The heated fluid can be delivered by flowing through apertures, such as holes or slots, provided by, for example, one or more nozzles on the heated delivery arm, which apertures can be provided by a manifold connected to a source of heated liquid.

[0092] An example heating system 104 includes an arm 140 that extends over the platen 24 and polishing pad 30 from the edge of the polishing pad to the center of the polishing pad 30, or at least near the center (e.g., within 5% of the total radius of the polishing pad). The arm 140 can be supported by a base 142, which can be supported on the same frame 40 as the platen 24. The base 142 can include one or more actuators, such as a linear actuator that raises and lowers the arm 140 and / or a rotary actuator that rotates the arm 140 laterally over the platen 24. The arm 140 is positioned to avoid collisions with other hardware components, such as the polishing head 70, the pad conditioner disk 92, and the slurry dispenser 39.

[0093] Along the rotation direction of the platen 24, the arm 140 of the heating system 104 can be positioned between the arm 110 of the cooling system 110 and the carrier head 70. Along the rotation direction of the platen 24, the arm 140 of the heating system 104 can be positioned between the arm 110 of the cooling system 110 and the slurry dispenser 39. For example, the arm 110 of the cooling system 110, the arm 140 of the heating system 104, the slurry dispenser 39, and the carrier head 70 can be positioned in that order along the rotation direction of the platen 24.

[0094] A plurality of openings 144 are formed in the bottom surface of the arm 140. Each opening 144 is configured to direct gas or water vapor, e.g., steam, onto the polishing pad 30. The arm 140 can be supported by a base 142 such that the openings 144 are separated from the polishing pad 30 by a gap. The gap can be 0.5 to 5 mm. In particular, the gap can be selected so that heat from the heated fluid does not significantly dissipate before it reaches the polishing pad. For example, the gap can be selected so that steam emitted from the openings does not condense before it reaches the polishing pad.

[0095] The heating system 104 can include a steam source 148, such as a steam generator 410 (see FIG. 4A), which can be connected to the arm 140 by piping. Each opening 144 can be configured to direct steam toward the polishing pad 30.

[0096] In some implementations, process parameters, such as flow rate, pressure, temperature, and / or liquid-to-gas mixture ratio, can be independently controlled for each nozzle. For example, the fluid for each opening 144 can be routed through an independently controllable heater to independently control the temperature of the heated fluid, e.g., the temperature of the vapor.

[0097] The various openings 144 can direct the vapor onto different radial zones on the polishing pad 30. Adjacent radial zones may overlap. Optionally, some of the openings 144 can be oriented so that the central axis of the mist from that opening is at an oblique angle to the polishing surface 36. The vapor can be directed from one or more of the openings 144 to have a horizontal component in a direction opposite to the direction of motion of the polishing pad 30 in the region of impingement, such as caused by rotation of the platen 24.

[0098] While Figure 3B shows the openings 144 spaced evenly apart, this is not a requirement. The nozzles 120 can be distributed non-uniformly, radially, angularly, or both. For example, the openings 144 can be more closely packed toward the center of the polishing pad 30. As another example, the openings 144 can be more closely packed at a radius corresponding to the radius at which the polishing liquid 38 is delivered to the polishing pad 30 by the slurry dispenser 39. Additionally, while Figure 3B shows nine openings, there can be more or fewer openings.

[0099] Referring to FIGS. 3A and 3B, steam 245 from a steam generator 410 (see FIG. 4A) can be injected into the polishing liquid 38 (e.g., slurry) to raise the temperature of the polishing liquid 38 before it is dispensed. The advantage of using steam 245 to heat the polishing liquid 38 instead of using liquid water is that less steam 245 needs to be injected into the polishing liquid 38 because the latent heat of vaporization allows for more energy to be transferred from the steam compared to liquid water. Also, because less steam 245 is required to raise the temperature of the polishing liquid 38 than liquid water, the polishing liquid 38 is not overly diluted. Steam can be injected into the polishing liquid at a flow rate ratio of 1:100 to 1:5. For example, a small amount of steam 245, e.g., 1 cc of steam 245 (at 1 atmosphere) per 50 cc of polishing liquid 38, can be used to heat the polishing liquid 38.

[0100] The steam 245 and polishing liquid 38 can be mixed in a mixing chamber 35 located in the arm of the slurry dispenser 39. A heated fluid, such as steam 245, can also be used to heat the slurry dispenser 39 and / or the polishing liquid reservoir 37, which can then heat the polishing liquid 38 before dispensing it onto the polishing pad 30.

[0101] Steam 245 can also be used to heat other liquids used in CMP, such as deionized water and other chemicals (e.g., cleaning chemicals). In some embodiments, these liquids can be mixed with polishing liquid 38 before being dispensed by slurry dispenser 39. The increased temperature can increase the chemical etch rate of polishing liquid 38, improving its efficiency and requiring less polishing liquid 38 during the polishing operation.

[0102] In some implementations, a temperature sensor measures the temperature of the mixture, and a controller executes a closed-loop control algorithm to control the flow rate of the steam relative to the flow rate of the polishing liquid to maintain the mixture at a desired temperature.

[0103] In some implementations, a temperature sensor measures the temperature of the polishing pad or the slurry on the polishing pad, and the controller executes a closed-loop control algorithm to control the flow rate of the steam relative to the flow rate of the polishing liquid to maintain the polishing pad or the slurry on the polishing pad at a desired temperature.

[0104] The controller 12 can control the flow of steam 245 through a nozzle or valve (e.g., a steam valve) (not shown) located between the steam generator 410 and the slurry dispenser 39, and the controller 12 can control the flow of polishing liquid 38 through a nozzle or valve (e.g., a polishing liquid valve) (not shown) located between the polishing liquid reservoir 37 and the slurry dispenser 39.

[0105] The steam 245 and polishing liquid 38 can be mixed in a mixing chamber 35 located in the arm of the slurry dispenser 39. A heated fluid, such as steam 245, can also be used to heat the slurry dispenser 39 and / or the polishing liquid reservoir 37, which can then heat the polishing liquid 38 before dispensing it onto the polishing pad 30.

[0106] Steam 245 can also be used to heat other liquids used in CMP, such as deionized water and other chemicals (e.g., cleaning chemicals). In some embodiments, these liquids can be mixed with polishing liquid 38 before being dispensed by slurry dispenser 39. The increased temperature can increase the chemical etch rate of polishing liquid 38, improving its efficiency and requiring less polishing liquid 38 during the polishing operation.

[0107] The polishing system 20 may also include a high-pressure rinse system 106. The high-pressure rinse system 106 includes a plurality of nozzles 154, e.g., 3-20 nozzles, that direct a cleaning fluid, e.g., water, onto the polishing pad 30 at high intensity to clean the pad 30 and remove used slurry, polishing debris, etc.

[0108] 3B , an example rinsing system 106 includes an arm 150 that extends over the platen 24 and polishing pad 30 from the edge of the polishing pad to the center of the polishing pad 30, or at least near the center (e.g., within 5% of the total radius of the polishing pad). The arm 150 can be supported by a base 152, which can be supported on the same frame 40 as the platen 24. The base 152 can include one or more actuators, such as a linear actuator that raises and lowers the arm 150 and / or a rotary actuator that rotates the arm 150 laterally over the platen 24. The arm 150 is positioned to avoid collisions with other hardware components, such as the polishing head 70, the pad conditioner disk 92, and the slurry dispenser 39.

[0109] The arm 150 of the rinsing system 106 can be positioned between the arm 110 of the cooling system 110 and the arm 140 of the heating system 140 along the rotational direction of the platen 24. For example, the arm 110 of the cooling system 110, the arm 150 of the rinsing system 106, the arm 140 of the heating system 104, the slurry dispenser 39, and the carrier head 70 can be positioned in that order along the rotational direction of the platen 24. Alternatively, the arm 140 of the cooling system 104 can be positioned between the arm 150 of the rinsing system 106 and the arm 140 of the heating system 140 along the rotational direction of the platen 24. For example, the arm 150 of the rinsing system 106, the arm 110 of the cooling system 110, the arm 140 of the heating system 104, the slurry dispenser 39, and the carrier head 70 can be positioned in that order along the rotational direction of the platen 24.

[0110] While Figure 3B shows the nozzles 154 spaced evenly apart, this is not a requirement. Additionally, while Figures 3A and 3B show nine nozzles, there can be more or fewer nozzles, for example, between 3 and 20 nozzles.

[0111] The polishing system 2 may also include a controller 12 that controls the operation of various components, such as the temperature control system 100. The controller 12 is configured to receive temperature measurements for each radial zone of the polishing pad from the temperature sensors 64. The controller 12 may compare the measured temperature profile with a desired temperature profile and generate a feedback signal to a control mechanism (e.g., actuator, power supply, pump, valve, etc.) for each nozzle or opening. The feedback signal is calculated by the controller 12, for example, based on an internal feedback algorithm, to cause 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.

[0112] In some implementations, the polishing system 20 includes a wiper blade or body 170 that distributes the polishing liquid 38 evenly across the polishing pad 30. Along the direction of rotation of the platen 24, the wiper blade 170 can be between the slurry dispenser 39 and the carrier head 70.

[0113] FIG. 3B shows separate arms for each subsystem, e.g., heating system 102, cooling system 104, and rinsing system 106, and the various subsystems can be included in a single assembly supported by a common arm. For example, the assembly can include a cooling module, a rinsing module, a heating module, a slurry delivery module, and optionally a wiper module. Each module can include a body, e.g., an arc-shaped body, that can be secured to a common mounting plate, which can be secured at the end of the arm such that the assembly is positioned above the polishing pad 30. Various fluid delivery components, e.g., piping, passages, etc., can extend within each body. In some implementations, the modules can be separately separable from the mounting plate. Each module can have similar components that perform the functions of the arms of the associated system described above.

[0114] Referring to FIG. 4A, steam for the processes described herein or for other applications in a chemical mechanical polishing system can be generated using a steam generator 410. The exemplary steam generator 410 can include a canister 420 that encloses an interior volume 425. The walls of the canister 420 can be made of a thermally insulating material, such as quartz, that has a very low amount of mineral contaminants. Alternatively, the walls of the canister can be formed of another material; for example, the interior surface of the canister can be coated with polytetrafluoroethylene (PTFE) or another plastic. In some implementations, the canister 420 can be 10 to 20 inches long and 1 to 5 inches wide.

[0115] 4A and 4B, in some embodiments, the interior volume 425 of the canister 420 is divided into a lower chamber 422 and an upper chamber 424 by a barrier 426. The barrier 426 can be made of the same material as the canister walls, e.g., quartz, stainless steel, aluminum, or a ceramic such as alumina. Quartz may be advantageous because it has a low risk of contamination. The barrier 426 can include one or more apertures 428. The apertures 428 can be located at, e.g., only at, the edge of the barrier 426 where the barrier 426 meets the interior wall of the canister 420. The apertures 428 can be located near the edge of the barrier 426, e.g., between the edge and the center of the barrier 426. In some implementations, the apertures are also positioned away from the edge, e.g., uniformly spaced across the width of the barrier 426, e.g., across the area of ​​the barrier 426. The barrier 426 can substantially prevent liquid water 440 from entering the upper chamber 424 by blocking droplets splashing from the boiling water, thereby allowing dry steam to accumulate in the upper chamber 424. The apertures 428 allow steam to pass from the lower chamber 422 and enter the upper chamber 424. The apertures 428, particularly those near the edges of the barrier 426, can allow steam to condense on the walls of the upper chamber 424 and drip into the lower chamber 422, reducing the liquid content in the upper chamber 426 and allowing the liquid to be reheated by the water 440.

[0116] 4A, a water inlet 432 can connect a water reservoir 434 to a lower chamber 422 of a canister 420. The water inlet 432 can be located at or near the bottom of the canister 420 to provide water 440 to the lower chamber 422.

[0117] One or more heating elements 430 can surround a portion of the lower chamber 422 of the canister 420. The heating element 430 can be, for example, a heating coil, e.g., a resistive heater, wrapped around the outside of the canister 420. The heating element can also be provided by a thin film coating on the material of the sidewall of the canister, which can act as a heating element when an electric current is applied.

[0118] A heating element 430 may also be disposed within the lower chamber 422 of the canister 420. For example, the heating element may be coated with a material that prevents contaminants, such as metal contaminants, from the heating element from being introduced into the vapor.

[0119] Heating element 430 can apply heat to the bottom portion of canister 420 up to minimum water level 443a, i.e., heating element 430 can cover the portion of canister 420 below minimum water level 443a to prevent overheating and reduce unnecessary energy consumption.

[0120] A vapor outlet 436 can connect the upper chamber 424 to a vapor delivery passage 438. The vapor delivery passage 438 can be located at or near the top of the canister 420, for example, in the ceiling of the canister 420, to allow vapor to pass from the canister 420 into the vapor delivery passage 438 and into various components of the CMP apparatus. The vapor delivery passage 438 can be used to direct vapor toward various areas of the chemical mechanical polishing apparatus, for example, to vapor clean and preheat the carrier head 70, the substrate 10, and the pad conditioner disk 92.

[0121] 4A, in some embodiments, a filter 470 is coupled to the vapor outlet 438 configured to reduce contaminants in the vapor 446. The filter 470 can be an ion exchange filter.

[0122] Water 440 can flow from water reservoir 434 through water inlet 432 and into lower chamber 422. Water 440 can fill canister 420 to at least a water level 442 above heating element 430 and below barrier 426. As water 440 heats, gaseous medium 446 is generated and rises through apertures 428 in barrier 426. Apertures 428 allow the vapor to rise while simultaneously allowing condensates to fall, resulting in a water vapor gaseous medium 446 that is substantially free of liquid (e.g., has no liquid water droplets suspended in the vapor).

[0123] In some embodiments, the water level is determined using a water level sensor 460 that measures the water level 442 in a bypass tube 444. The bypass tube connects the water reservoir 434 to the steam delivery passage 438 in parallel with the canister 420. The water level sensor 460 can indicate where the water level 442 is in the bypass tube 444, and therefore in the canister 420. For example, because the water level sensor 444 and the canister 420 are equally pressurized (e.g., both receive water from the same water reservoir 434, both have the same pressure at the top, e.g., both connect to the steam delivery passage 438), the water level 442 is the same in the water level sensor and the canister 420. In some embodiments, the water level 442 in the water level sensor 444 can otherwise indicate the water level 442 in the canister 420, e.g., the water level 442 in the water level sensor 444 is scaled to indicate the water level 442 in the canister 420.

[0124] During operation, water level 442 within canister 420 is above minimum water level 443a and below maximum water level 443b, with minimum water level 443a being at least above heating element 430 and maximum water level 443b being sufficiently below steam outlet 436 and barrier 426 to provide sufficient space to allow gaseous medium 446, e.g., steam, to accumulate near the top of canister 420 while still being substantially free of liquid water.

[0125] In some embodiments, controller 12 is coupled to a valve 480 that controls fluid flow through water inlet 432, a valve 482 that controls fluid flow through steam outlet 436, and / or a water level sensor 460. Using water level sensor 460, controller 90 is configured to restrict the flow of water 440 into canister 420 and restrict the flow of gas 446 out of canister 420 to maintain water level 442 above minimum water level 443a (and above heating element 430) and below maximum water level 443b (and below barrier 426, if present). Controller 12 can also be coupled to a power source 484 for heating element 430 to control the amount of heat delivered to water 440 in canister 420.

[0126] 1, 2A, 2B, 3A, 3B, and 4A, the controller 12 can monitor temperature measurements received by sensors 64, 214, and 264 and control the temperature control system 100, the water inlet 432, and the steam outlet 436. The controller 12 can continuously monitor the temperature measurements and control the temperature in a feedback loop to regulate the temperatures of the polishing pad 30, the carrier head 70, and the conditioner disk 92. For example, the controller 12 can receive the temperature of the polishing pad 30 from the sensor 64 and control the water inlet 432 and the steam outlet 436 to control the delivery of steam onto the carrier head 70 and / or the conditioner head 92 to increase the temperature of the carrier head 70 and / or the conditioner head 92 to match the temperature of the polishing pad 30. Reducing the temperature difference can help prevent the carrier head 70 and / or conditioner head 92 from acting as a heat sink on the relatively hot polishing pad 30, which can improve within-wafer uniformity.

[0127] In some embodiments, controller 12 stores desired temperatures for polishing pad 30, carrier head 70, and conditioner disk 92. Controller 12 can monitor temperature measurements from sensors 64, 214, and 264 and control temperature control system 100, water inlet 432, and steam outlet 436 to achieve the desired temperatures for polishing pad 30, carrier head 70, and / or conditioner disk 92. By ensuring that the temperatures achieve the desired temperatures, controller 12 can improve within-wafer and between-wafer uniformity.

[0128] Alternatively, the controller 12 can raise the temperature of the carrier head 70 and / or the conditioner head 92 to slightly above the temperature of the polishing pad 30, allowing the carrier head 70 and / or the conditioner head 92 to cool to the same or substantially the same temperature as the polishing pad 30 as they move from their respective cleaning and preheating stations to the polishing pad 30.

[0129] In another process, the temperature of the polishing fluid 38 is increased for the bulk polishing operation. After the bulk polishing operation, the temperature of the various components of the carrier head 70 (e.g., polishing surface 36, conditioner disk 92) is increased for the metal removal operation, over Polishing behavior, and / or conditioning It can be cooled for operation.

[0130] A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. a platen supporting a polishing pad having a polishing surface; a coolant source configured to supply a coolant comprising liquid nitrogen; a dispenser having one or more apertures suspended above the platen to direct the coolant from the coolant source onto the polishing surface of the polishing pad; a controller coupled to the coolant source and configured to cause the coolant source to deliver the coolant through a nozzle onto the polishing surface during a conditioning step in which a conditioning disk is pressed against the rotating polishing pad to condition the polishing surface of the polishing pad.

2. The system of claim 1 , wherein the nozzle is configured to start and stop fluid flow through the nozzle.

3. Bulk polishing the substrate with the polishing pad at a first temperature range; and performing a conditioning step of pressing a conditioning disk against the rotating polishing pad to condition the polishing surface of the polishing pad at a temperature of the polishing surface of the polishing pad that has been reduced to a second temperature range that is lower than the first temperature range by supplying a coolant including liquid nitrogen to the polishing pad.

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