Low Temperature Metal CMP that Minimizes Dishing and Corrosion while Improving Pad Asperity

Abstract

To provide a chemical mechanical polishing system that can improve predictability of polishing during the CMP process, reduce polishing variations from one polishing operation to another polishing operation, and improve wafer-to-wafer uniformity.SOLUTION: A chemical mechanical polishing system includes a platen 24 to support a polishing pad 30 having a polishing surface, a source of coolant, a dispenser 39 having one or more apertures suspended over the platen 24 to direct coolant from the source of coolant onto the polishing surface of the polishing pad 30, and a controller 12 coupled to the source of coolant and configured to cause the source of coolant to deliver the coolant through nozzles 120 onto the polishing surface during a selected step of a polishing operation.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present disclosure relates to chemical mechanical polishing (CMP), and more particularly to temperature control during CMP.

Background Art

[0002] Integrated circuits are generally formed on a substrate by sequentially depositing conductive, semiconductive, or insulating layers on a semiconductor wafer. In various manufacturing processes, it is necessary to planarize the layers on the substrate. For example, one manufacturing step involves depositing a filler layer on an uneven surface and planarizing the filler layer. In certain applications, the filler layer is planarized until the upper surface of the patterned layer is exposed. For example, a metal layer can be deposited on a patterned insulating layer to fill the grooves and holes in the insulating layer. After planarization, the remaining portions of the metal within the grooves and holes of the patterned layer form vias, plugs, and lines that provide conductive paths between the thin film circuits on the substrate. As another example, a dielectric layer can be deposited on a patterned conductive layer and then planarized to enable subsequent photolithography steps.

[0003] Chemical mechanical polishing (CMP) is an acceptable planarization method. This planarization method generally requires placing the substrate on a carrier head. The exposed surface of the substrate is generally placed in contact with a rotating polishing pad. The carrier head applies a controllable load to the substrate to press the substrate against the polishing pad. A polishing slurry containing abrasive particles is generally supplied to the surface of the polishing pad.

Summary of the Invention

[0004] In one aspect, a chemical mechanical polishing system includes a platen that supports a polishing pad having a polishing surface, a coolant source, a dispenser suspended above the platen having one or more apertures that direct 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 can include a liquid coolant media source. The liquid coolant media source can include one or more of liquid nitrogen or liquid carbon dioxide.

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

[0008] The nozzle can be configured to initiate and stop a fluid flow through the nozzle.

[0009] The selected step can be a conditioning step. The selected step can be a metal removal step. The selected step can be an over-polishing step.

[0010] In another aspect, a method of a chemical mechanical polishing system includes bulk polishing a substrate at a first temperature range using a polishing pad and performing one or more of metal removal, over-polishing, or conditioning steps of the substrate using the polishing pad, or conditioning the polishing pad at a temperature of the polishing surface of the polishing pad reduced to be a second temperature range lower than the first temperature range.

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

[0012] The temperature reduction can be performed using a coolant connected to an arm having one or more nozzles suspended over the polishing surface of the polishing pad, and the nozzles on the arm can be configured to direct the 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 cooling medium source. The liquid cooling medium source can include one or more of liquid nitrogen or liquid carbon dioxide. The coolant source can include a gas cooling medium source. The gas cooling medium source can include one or more of a gas formed from liquid nitrogen or a gas formed from liquid carbon dioxide. The gas cooling medium source can include a compressed gas. The gas cooling medium source can be connected to a vortex tube configured to direct a low-temperature gas stream onto the polishing pad.

[0013] The nozzles can be configured to start and stop a fluid flow through the nozzles.

[0014] Possible advantages can include, but are not limited to, one or more of the following.

[0015] By controlling the temperatures of various components, the effects of temperature-dependent processes such as dishing, erosion, and corrosion can be reduced. The temperature control can also create a more uniform pad asperity and thus improve the uniformity of polishing and extend the life of the pad, for example, to remove metal residues.

[0016] In one example, the temperature of the polishing process is increased. In particular, steam, i.e., gaseous H2O generated by boiling, is injected into the slurry to transfer energy with a low liquid content (i.e., low dilution) to rapidly and efficiently increase the temperature of the slurry. This can increase the polishing rate, for example, during bulk polishing.

[0017] In another example, the temperature of the polishing pad surface can be reduced during one or more of the metal removal step, over-polishing step, or conditioning step of the polishing operation. This can reduce dishing and corrosion and / or improve the uniformity of pad asperity, thus improving the uniformity of polishing and extending the life of the pad.

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

[0019] This can improve the predictability of polishing during the CMP process, reduce the variation in polishing for each polishing operation, and improve the uniformity for each wafer.

[0020] Details of one or more implementations are set forth in the accompanying drawings and the following description. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0021]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Mode for Carrying Out the Invention

[0022] Chemical mechanical polishing operates by a combination of mechanical polishing and chemical etching at the interface between a substrate, a polishing liquid, and a polishing pad. During the polishing process, a significant amount of heat is generated by the friction between the surface of the substrate and the polishing pad. In addition, some processes also include an in-situ pad conditioning step of pressing a conditioning disk, for example, a disk coated with polishing diamond particles, against the rotating polishing pad so that the surface of the polishing pad is conditioned (conditioning) and textured. The polishing of the conditioning process may 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 the polyurethane polishing pad may rise by about 30°C.

[0023] On the other hand, the slurry distributed on the polishing pad can act as a heat sink. Overall, these effects result in spatial and time-dependent variations in the temperature of the polishing pad.

[0024] Variables related to chemistry in the CMP process, such as variables as the start and rate of the reactions involved, and variables related to machinery, such as the surface friction coefficient, storage elastic modulus, and viscoelasticity of the polishing pad, both depend strongly on temperature. As a conclusion, variations in the surface temperature of the polishing pad may result in variations in the removal rate, polishing uniformity, erosion, dishing, and residues. By more tightly controlling the temperature of the surface of the polishing pad during one or more of the metal removal step, over-polishing step, or conditioning step, the temperature variations can be reduced, and for example, the polishing performance, as measured by non-uniformity within a wafer or non-uniformity between wafers, can be improved.

[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), and 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, and conditioning step).

[0026] Furthermore, 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] Techniques that can address one or more of these issues include preheating the polishing pad and / or slurry during portions of the polishing process, such as during bulk polishing. For example, various components of a 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, for example, using vortex tube cooling and / or by distributing a coolant, the temperature of the polishing pad and various components can be reduced to reduce the polishing rate of the slurry chemical during one or more of the metal removal step, overpolishing step, or conditioning step.

[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 a plurality of polishing stations 20. For example, the polishing apparatus can include four polishing stations 20a, 20b, 20c, and 20d. Each polishing station 20 is adapted to polish a substrate held 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 that loads substrates onto and unloads substrates from the carrier heads. The transfer station 6 includes 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 stations 20, can be positioned at substantially equal angular intervals around the center of the platform 4. This is not a requirement, but it can provide a good footprint for the polishing apparatus.

[0031] For the polishing operation, one carrier head 70 is positioned at each polishing station. When loading and unloading at station 6, two additional carrier heads can be positioned so that the polished substrate can be exchanged with an unpolished substrate while other substrates are being polished at the polishing stations 20.

[0032] The carrier head 70 is held by a support structure that can move each carrier head along a path that sequentially passes through the first polishing station 20a, the second polishing station 20b, the third polishing station 20c, and the fourth polishing station 20d. Thereby, each carrier head can be selectively positioned over the polishing station 20 and the load cup 8.

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

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

[0035] Figures 3A and 3B show an example of the 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 Figure 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] Referring to FIGS. 1, 3A, and 3B, the polishing station 20 can include a supply port, such as 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 the conditioner head 93 are supported by a base 96. The arm 94 can pivot to sweep the conditioner head 93 and the conditioner disk 92 laterally across the polishing pad 30. A cleaning cup 250 can be disposed adjacent to the platen 24 at a position where the arm 94 can move the conditioner head 93.

[0038] The carrier head 70 is operable to hold the substrate 10 in contact with the polishing pad 30. The carrier head 70 is suspended from a support structure 72, such as a carousel or a track, and is connected by a drive shaft 74 to a carrier head rotation motor 76 such that the carrier head can rotate about an axis 71. Optionally, the carrier head 70 can vibrate laterally, for example, on a slider of the carousel, by movement along a track or by rotational vibration of the carousel itself.

[0039] The carrier head 70 can include a flexible membrane 80 having a substrate mounting surface that contacts the back surface of the substrate 10, and a plurality of pressurizable chambers 82 that apply different pressures to different regions on the substrate 10, for example, different radial regions. The carrier head 70 can include a retaining ring 84 for holding the substrate. In some embodiments, 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, such as metal.

[0040] During 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 is translated laterally across the upper surface of the polishing pad 30 (see arrow C in FIG. 3B).

[0041] Referring to FIGS. 3A and 3B, as the carrier head 70 sweeps across the polishing pad 30, any exposed surface of the carrier head 70 tends to be coated with slurry. For example, the slurry may adhere to the outer diameter or inner diameter surface of the retaining ring 84. Generally, for any surface that is not maintained in a wet state, the slurry tends to solidify and / or dry. As a result, fine particles can occur on the carrier head 70. If these fine particles are removed, the fine particles may scratch the substrate and cause polishing defects.

[0042] Furthermore, the slurry may stick to the carrier head 70, or sodium hydroxide in the slurry may crystallize on one of the surfaces of the carrier head 70 and / or the substrate 10, which may corrode the surface of the carrier head 70. The stuck slurry is difficult to remove, and the crystallized sodium hydroxide is difficult to return to solution.

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

[0044] One solution is to wash the components, such as the carrier head 70 and the conditioner head 92, with a liquid water stream. However, the components may be difficult to wash with only a water stream and may require a significant amount of water. In addition, components that contact the polishing pad 30, such as the carrier head 70, the substrate 10, and the conditioner disk 92, may act as heat sinks that interfere with the uniformity of the polishing pad temperature.

[0045] To address these problems, as shown in FIG. 2A, the polishing apparatus 2 includes one or more carrier head vapor treatment assemblies 200. Each vapor treatment assembly 200 can be used to clean and / or preheat the carrier head 70 and the substrate 10.

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

[0047] The load cup 8 includes a mount 204 that holds the substrate 10 during the load / unload process. The load cup 8 also includes a housing 206 that surrounds or substantially surrounds the mount 204. A plurality of nozzles 225 are supported by the housing 206 or a separate support to deliver vapor 245 to a 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 inner 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 initiate and stop fluid flow through the nozzles 225, for example using a controller 12. The nozzles 225 can be oriented to direct vapor inwardly into the cavity 206. The vapor 245 can be generated using a vapor generator 410, such as a vapor generator described further below. A drain 235 can prevent accumulation in the load cup 8 by allowing excess water, cleaning solution, and cleaning by-products to pass through.

[0048] The actuator provides relative vertical movement between the housing 206 and the carrier head 70. For example, a shaft 210 can support the housing 206 and be vertically actuatable to move the housing 206 up and down. Alternatively, the carrier head 70 can move vertically. The mount 205 can be coaxial with the shaft 210. The mount 204 can be vertically movable relative to the housing 206.

[0049] During operation, the carrier head 70 can be positioned over the load cup 8, and the housing 206 can be raised (or the carrier head 70 can be lowered) such that the carrier head 70 is partially within the cavity 208. The substrate 10 can be chucked on the mount 204 and started on the carrier head 70 and / or de-chucked on the carrier head 70 and started on the mount 204.

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

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

[0052] The platen - to - platen station 9 can be constructed and operated similarly, but does not necessarily have a substrate support gantry.

[0053] The vapor 245 delivered by the nozzle 225 can have adjustable temperature, pressure, and flow rate that vary the cleaning and preheating of the carrier head 70 and the substrate 10. In some implementations, the temperature, pressure, and / or flow rate can be adjusted independently for each nozzle or among groups of nozzles.

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

[0055] The flow rate of the vapor 245 can be between 1 and 1000 cc / min depending on the output and pressure of the heater when the vapor 245 is delivered by the nozzle 225. In some implementations, the vapor is mixed with other gases, e.g., mixed with air or N2. Alternatively, the fluid delivered by the nozzle 225 is substantially pure water. In some implementations, the vapor 245 delivered by the nozzle 225 is mixed with liquid water, e.g., aerosolized water. For example, the liquid water and the vapor can be combined at a relative flow rate ratio of 1:1 to 1:10 (e.g., in terms of flow rate in sccm). However, when 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 vapor will have excellent heat transfer properties. Thus, in some implementations, the vapor is dry vapor, i.e., substantially free of water droplets.

[0056] To avoid deterioration of the membrane due to heat, water can be mixed with the vapor 245 to reduce the temperature to, for example, about 40 to 50 °C. The temperature of the vapor 245 can be reduced by mixing cooled water into the vapor 245, or by mixing water at the same or substantially the same temperature into the vapor 245 (since liquid water transfers less energy than gaseous water).

[0057] In some embodiments, a temperature sensor 214 can be installed in or near the vapor treatment 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 measurement 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 can stop the flow of vapor. As another example, the controller 12 can reduce the vapor delivery flow rate and / or reduce the vapor temperature to prevent overheating of components, for example, during cleaning and / or preheating.

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

[0059] Figure 2B shows a conditioner steam treatment assembly 250 including a housing 255. The housing 255 can form a "cup" that receives a conditioner disk 92 and a conditioner head 93. Steam is circulated through a supply line 280 in the housing 255 to one or more nozzles 275. The nozzles 275 can spray steam 295 to remove abrasive by-products, such as debris or slurry particles, remaining on the conditioner disk 92 and / or the conditioner head 93 after each conditioning operation. The nozzles 275 can be disposed within the housing 255, for example, on the floor, side walls, and ceiling inside the housing 255. The nozzles 275 can be configured to start and stop the fluid flow through the nozzles 275, for example, using a controller 12. One or more nozzles can be positioned to clean the bottom surface of the pad conditioner disk, and / or the bottom surface, side walls, and / or top surface of the conditioner head 93. The steam 295 can be generated using a steam generator 410. A drain 285 can prevent accumulation in the housing 255 by allowing excess water, cleaning solution, and cleaning by-products to pass through.

[0060] The conditioner head 93 and the conditioner disk 92 can be lowered at least partially into the housing 255 for steam treatment. When the conditioner disk 92 is returned to operate, the conditioner head 93 and the conditioner disk 92 are lifted out of the housing 255 and positioned on a polishing pad 30 to condition the polishing pad 30. When the conditioning operation is complete, the conditioner head 93 and the conditioner disk 92 are lifted from the polishing pad and rotated back to the housing cup 255 to remove abrasive by-products on the conditioner head 93 and the conditioner disk 92. In some implementations, the housing 255 is vertically operable and is attached, for example, to a vertical drive shaft 260.

[0061] The housing 255 is positioned to receive the pad conditioner disk 92 and the conditioner head 93. The conditioner disk 92 and the conditioner head 93 rotate within the housing 255 and / or move vertically within the housing 255 to enable the nozzle 275 to steam-treat various surfaces of the conditioner disk 92 and the conditioner head 93.

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

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

[0064] The flow rate of the vapor 2945 can be from 1 to 1000 cc / min when the vapor 295 is delivered by the nozzle 275. In some implementations, the vapor is mixed with other gases, for example, mixed with air or N2. Alternatively, the fluid delivered by the nozzle 275 is substantially pure water. In some implementations, the vapor 295 delivered by the nozzle 275 is mixed with liquid water, for example, aerosolized water. For example, the liquid water and the vapor can be combined at a relative flow rate ratio of 1:1 to 1:10 (e.g., in terms of flow rate in sccm units). However, when the amount of liquid water is small, for example, less than 5 wt%, for example, less than 3 wt%, for example, less than 1 wt%, the vapor will have excellent heat transfer properties. Thus, in some implementations, the vapor is dry vapor, 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, and for example, can detect the temperature of the pad conditioner disk 92. The controller 12 can control the delivery of the vapor by the assembly 250 based on the temperature measurement value from the temperature sensor 264. For example, the controller can receive a target temperature value. If the controller 12 detects that the temperature measurement value exceeds the target value, the controller 12 stops the vapor flow. As another example, the controller 12 can reduce the vapor delivery flow rate and / or reduce the vapor temperature to prevent overheating of components during, for example, cleaning and / or preheating.

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

[0067] Referring to FIG. 3A, in some implementation examples, the polishing station 20 includes a temperature sensor 64 that monitors the temperature of the polishing station or components within the polishing station, such as the temperature of the polishing pad 30 and / or the polishing fluid 38 on the polishing pad. For example, the temperature sensor 64 can 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 fluid 38 on the polishing pad. In particular, the temperature sensor 64 is configured to measure the temperature at a plurality of points along the radius of the polishing pad 30 to generate a radial temperature profile. For example, the IR camera can have a field of view across the radius of the polishing pad 30.

[0068] In some implementation examples, 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 within the platen 24. In addition, the temperature sensor 64 can be in direct contact with the polishing pad.

[0069] In some implementation examples, a plurality of temperature sensors can be spaced apart at different radial positions across the polishing pad 30 to provide the temperature at a plurality of points along the radius of the polishing pad 30. This technique can be used instead of or in addition to an IR camera.

[0070] In FIG. 3A, although 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, it can 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 embodiments, for example, a plurality of temperature sensors are included in the polishing station 22 to measure the temperature of different components in the polishing station / 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 can include a cooling system 102 and / or a heating system 104. In some embodiments, at least one, and in some embodiments both, of the cooling system 102 and the heating system 104 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] In the case of 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 cooled below room temperature, for example, it can be 5 - 15°C. In some embodiments, the cooling system 102 uses a mist of air and liquid, such as an aerosolized mist of a liquid (e.g., water). In particular, the cooling system can have a nozzle that generates an aerosolized mist of water cooled below room temperature. In some embodiments, a solid material can be mixed with the gas and / or liquid. The solid material can be a cooled material, such as ice, or a material that absorbs heat, for example, by a chemical reaction when dissolved in water.

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

[0074] As shown in FIGS. 3A and 3B, in one example, a cooling system 102 includes an arm 110 that extends over the platen 24 and the polishing pad 30, from the edge of the polishing pad to the center of the polishing pad 30, or at least near the center (e.g., within 5% of the total radius of the polishing pad). The arm 110 can be supported by a base 112, and the base 112 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 moves the arm 110 up and down, 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 the 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 the 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 the fluid flow through each nozzle 120, for example, using a controller 12. Each nozzle 120 can be configured to direct the aerosolized water in the mist 122 toward the polishing pad 30.

[0076] The cooling system 102 can include a liquid cooling medium source 130 and a gas cooling medium source 132 (see FIG. 3B). The liquid from the medium source 130 and the gas from the medium source 132 can be mixed in a mixing chamber 134 (see FIG. 3A), which is, for example, in or on the arm 110, before being directed through the nozzles 120 to form the mist 122. When dispensed, this coolant can be below room temperature, such as -100 to 20°C, such as 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. Ice droplets can be formed by cooling water and efficiently cooling the polishing pad by the latent heat of fusion of the ice droplets. Additionally, the ice droplets or water droplets can prevent drying when the polishing pad 30 is cooled by the cooled gas. Ethanol or isopropyl alcohol can be injected into the gas stream instead of water to form frozen particles.

[0078] The gas from the gas source 132, such as compressed gas, can be connected to a vortex tube 50 that can separate the compressed gas into a low-temperature stream and a high-temperature stream and direct the low-temperature stream to the nozzle 120 onto the polishing pad 30. In some implementations, the nozzle 120 is the lower end of the vortex tube that directs the low-temperature 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 mixing ratio can be controlled independently for each nozzle (e.g., by the controller 12). For example, the coolant for each nozzle 120 can be flowed through an independently controllable chiller to independently control the temperature of the mist. As another example, separate pairs 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 mixing ratio for each nozzle.

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

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

[0082] Although FIG. 1 shows the mists themselves overlapping, the nozzle 120 can be oriented so that the elongated regions do not overlap. For example, at least some of the nozzles 120, for example all of the nozzles 120, can be oriented such that the elongated region 128 is at an oblique angle to the radius through the elongated region (see region 128b).

[0083] At least some of the nozzles 120 can be oriented such that the central axis of the mist from the nozzle (see arrow A) is at an oblique angle to the polishing surface 36. In particular, the mist 122 can be directed from the nozzle 120 so as to have a horizontal component in a direction opposite to the direction of movement of the polishing pad 30 (see arrow A) in the region of collision caused by the rotation of the platen 24.

[0084] FIGS. 3A and 3B show the nozzles 120 spaced at uniform intervals, but this is not a requirement. The nozzles 120 can be distributed non-uniformly radially, angularly, or both. For example, the nozzles 120 can be more closely packed along the radius towards the edge of the polishing pad 30. Additionally, although FIGS. 3A and 3B show nine nozzles, there can be more or fewer nozzles, for example 3 to 20 nozzles.

[0085] The cooling system 102 can be used to lower the temperature of the polishing surface 36. For example, the temperature of the polishing surface 36 can be lowered using liquid from the liquid coolant 130 via the mist 122, gas from the gas coolant 132 via the mist 122, the cold stream 52 from the vortex tube 50, or combinations thereof. In some embodiments, the temperature of the polishing surface 36 can be lowered to 20 °C or less. By lowering the temperature during one or more of the metal removal step, the overpolishing step, or the conditioning step, and by reducing the selectivity of the polishing fluid 38, dishing and erosion of the soft metal during CMP can be reduced.

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

[0087] The reduction of temperature during CMP can be used to reduce corrosion. For example, by lowering the temperature during one or more of the metal removal step, the overpolishing step, or the conditioning step, galvanic corrosion of various components can be reduced because galvanic reactions can be temperature-dependent. In addition, during CMP, the vortex tube 50 can use a gas that is inert in the polishing process. In particular, a gas that does not contain oxygen (or has less oxygen than the atmosphere) can be used to create a localized inert environment and reduce the oxygen within the localized inert environment, thereby resulting in a reduction of corrosion. Examples of such gases include, for example, nitrogen and carbon dioxide evaporated from liquid nitrogen or dry ice.

[0088] By reducing the temperature of the polishing surface 36, for example, in the case of the conditioning step, the storage modulus of the polishing pad 30 can be increased and the viscoelasticity of the polishing pad 30 can be reduced. The increased storage modulus and reduced viscoelasticity can be combined with a reduction in the downforce on the pad conditioner disk 92 and / or a reduction in the aggressiveness of conditioning by the pad conditioner disk 92 to result in a more uniform pad asperity. The advantages of a uniform pad asperity are that scratching of the substrate 10 during subsequent polishing operations is reduced and the life of the polishing pad 30 is increased.

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

[0090] In the case of 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 a gas and a liquid. The heating fluid is at a temperature higher than room temperature, for example, 40 - 120°C, for example, 90 - 110°C. The fluid can be water, such as substantially pure deionized water, or water containing additives or chemicals. In some embodiments, the heating system 104 uses a mist of steam. The steam can contain additives or chemicals.

[0091] The heating fluid can be delivered by flowing it through an aperture, such as a hole or slot, provided by, for example, one or more nozzles on a heating delivery arm. The aperture can be provided by a manifold connected to a source of heated liquid.

[0092] One example of a heating system 104 includes an arm 140 that extends over the platen 24 and the polishing pad 30, from the edge of the polishing pad to the center of the polishing pad 30, or at least near the center (e.g., within 5% of the total radius of the polishing pad). The arm 140 can be supported by a base 142, and the base 142 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 for moving the arm 140 up and down, and / or a rotational actuator for rotating the arm 140 laterally on 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 direction of rotation 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 direction of rotation 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 direction of rotation 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 a gas or water vapor, such as steam, onto the polishing pad 30. The arm 140 can be supported by the base 142 such that the openings 144 are separated from the polishing pad 30 by a gap. The gap can be between 0.5 and 5 mm. In particular, the gap can be selected such that the heat of the fluid does not dissipate significantly before the heating fluid reaches the polishing pad. For example, the gap can be selected such that the steam radiated from the openings does not condense before reaching 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 mixing ratio, can be controlled independently for each nozzle. For example, the fluid for each opening 144 can be passed through an independently controllable heater to independently control the temperature of the heated fluid, such as the temperature of the steam.

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

[0098] FIG. 3B shows openings 144 spaced at equal intervals, but 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 spaced toward the center of the polishing pad 30. As another example, the openings 144 can be more closely spaced 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, although FIG. 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 a polishing liquid 38 (e.g., slurry), and the temperature of the polishing liquid 38 can be increased before the polishing liquid 38 is dispensed. The advantage of using steam 245 to heat the polishing liquid 38 instead of using liquid water is that, due to the latent heat of vaporization, more energy can be transferred from the steam compared to liquid water, so that a smaller amount of steam 245 needs to be injected into the polishing liquid 38. Also, since less steam 245 is required to increase the temperature of the polishing liquid 38 than liquid water, the polishing liquid 38 is not overly diluted. The 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 atm) can be used for 50 cc of the polishing liquid 38 to heat the polishing liquid 38.

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

[0101] The steam 245 can similarly 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 the polishing liquid 38 before being dispensed by the slurry dispenser 39. The increase in temperature can increase the chemical etching rate of the polishing liquid 38, improve its efficiency, and reduce the amount of polishing liquid 38 required 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 so as to maintain the mixture at a desired temperature.

[0103] In some implementation examples, the 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 vapor relative to the flow rate of the polishing liquid so as 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 the vapor 245 through a nozzle or valve (e.g., a vapor valve) (not shown) located between the vapor generator 410 and the slurry dispenser 39, and the controller 12 can control the flow of the 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 vapor 245 and the polishing liquid 38 can be mixed within a mixing chamber 35 located within the arm of the slurry dispenser 39. The heating fluid, such as the vapor 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 it is dispensed onto the polishing pad 30.

[0106] The vapor 245 can similarly 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 the polishing liquid 38 before being dispensed by the slurry dispenser 39. The increase in temperature can increase the chemical etching rate of the polishing liquid 38, improve its efficiency, and reduce the amount of polishing liquid 38 required during the polishing operation.

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

[0108] As shown in FIG. 3B, in one example, the rinse system 106 includes an arm 150 that extends over the platen 24 and the polishing pad 30 from the edge of the polishing pad to the center of the polishing pad 30, or at least near the center (e.g., within 5% of the total radius of the polishing pad). The arm 150 can be supported by a base 152, and the base 152 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 moves the arm 150 up and down and / or a rotary actuator that rotates the arm 150 laterally on 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] Along the rotation direction of the platen 24, the arm 150 of the rinse system 106 can be positioned between the arm 110 of the cooling system 110 and the arm 140 of the heating system 140. For example, the arm 110 of the cooling system 110, the arm 150 of the rinse 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 rotation direction of the platen 24. Alternatively, along the rotation direction of the platen 24, the arm 140 of the cooling system 104 can be positioned between the arm 150 of the rinse system 106 and the arm 140 of the heating system 140. For example, the arm 150 of the rinse 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 rotation direction of the platen 24.

[0110] FIG. 3B shows nozzles 154 spaced at equal intervals, but this is not a requirement. In addition, FIGS. 3A and 3B show nine nozzles, but there can be more or fewer nozzles, such as 3 to 20 nozzles.

[0111] The polishing system 2 can 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 from the temperature sensor 64 for each radial region of the polishing pad. The controller 12 can compare the measured temperature profile to a desired temperature profile and generate a feedback signal to a control mechanism (e.g., an 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 the 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 evenly distributes the polishing fluid 38 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, such as 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, such as an arcuate body, that can be fixed to a common mounting plate, and the common mounting plate can be fixed at the end of the arm such that the assembly is positioned over the polishing pad 30. Various fluid delivery components, such as pipes, passages, etc., can extend inside each body. In some implementations, the modules are separable from the mounting plate individually. Each module can have similar components that perform the functions of the arms of the associated systems described above.

[0114] Referring to FIG. 4A, steam for the processes described herein or for other uses 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 internal volume 425. The walls of the canister 420 can be made of a thermally insulating material with a very low amount of mineral contaminants, such as quartz. Alternatively, the walls of the canister can be formed of another material, for example, the inner surface of the canister can be coated with polytetrafluoroethylene (PTFE) or another plastic. In some implementations, the canister 420 can be 25.4 - 50.8 cm (10 - 20 inches) in length and 2.54 - 12.7 cm (1 - 5 inches) in width.

[0115] Referring to FIGS. 4A and 4B, in some embodiments, the internal volume 425 of the canister 420 is divided by a barrier 426 into a lower chamber 422 and an upper chamber 424. The barrier 426 can be made of the same material as the canister wall, such as a ceramic like quartz, stainless steel, aluminum, or alumina. Quartz may be excellent in terms of low contamination risk. The barrier 426 can include one or more apertures 428. The apertures 428 can be disposed, for example, only at the edges of the barrier 426 where the barrier 426 meets the inner wall of the canister 420. The apertures 428 can be disposed near the edges of the barrier 426, for example, between the edge of the barrier 426 and the center of the barrier 426. In some implementations, the apertures are also positioned uniformly spaced apart from the edges, for example, across the width of the barrier 426, for example, across the area of the barrier 425. The barrier 426 can substantially prevent liquid water 440 from entering the upper chamber 424 by blocking water droplets bouncing from boiling water. This allows dry steam to accumulate in the upper chamber 424. The apertures 428 allow steam to pass from the lower chamber 422 into the upper chamber 424. The apertures 428, particularly those near the edges of the barrier 426, can cause condensation 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 enabling the liquid to be reheated by the water 440.

[0116] Referring to FIG. 4A, the water inlet 432 can connect a water reservoir 434 to the lower chamber 422 of the canister 420. The water inlet 432 can be disposed 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 wound around the outside of the canister 420, such as a resistive heater. The heating element can also be provided by a thin film coating on the material of the side wall of the canister, and when a current is applied, the thin film coating can act as a heating element.

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

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

[0120] The vapor outlet 436 can connect the upper chamber 424 to the vapor delivery passage 438. The vapor delivery passage 438 can be disposed at or near the top of the canister 420, for example, on the ceiling of the canister 420, to allow vapor to enter 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, for example, to collect vapor and direct it towards various areas of the chemical mechanical polishing apparatus to steam clean and preheat the carrier head 70, the substrate 10, and the pad conditioner disk 92.

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

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

[0123] In some embodiments, the water level is determined using a water level sensor 460 that measures the water level 442 in the bypass tube 444. The bypass tube connects the water reservoir 434 in parallel with the canister 420 to the vapor delivery passage 438. The water level sensor 460 can indicate where the water level 442 is within the bypass tube 444 and thus within the canister 420. For example, since 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 are connected to the vapor 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 within the water level sensor 444 can otherwise indicate the water level 442 within the canister 420, e.g., the water level 442 within the water level sensor 444 is scaled to indicate the water level 442 within the canister 420.

[0124] During operation, the water level 442 within the canister is above the minimum water level 443a and below the maximum water level 443b. The minimum water level 443a is at least above the heating element 430, and the maximum water level 443b is well below the vapor outlet 436 and the barrier 426, allowing a gas medium 446, e.g., vapor, to accumulate near the top of the canister 420 while still providing sufficient space that is substantially free of liquid water.

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

[0126] Referring to FIGS. 1, 2A, 2B, 3A, 3B, and 4A, the controller 12 can monitor the temperature measurements received by the sensors 64, 214, and 264 and control the temperature control system 100, the water inlet 432, and the vapor outlet 436. The controller 12 continuously monitors the temperature measurements and controls the temperature within a feedback loop to adjust the temperatures of the polishing pad 30, the carrier head 70, and the conditioner disk 92. For example, the controller 12 receives the temperature of the polishing pad 30 from the sensor 64 and controls the water inlet 432 and the vapor outlet 436 to control the delivery of vapor onto the carrier head 70 and / or the conditioner head 92 to raise 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 the conditioner head 92 from acting as a heat sink on the relatively hot polishing pad 30 and can improve the uniformity within the wafer.

[0127] In some embodiments, the controller 12 stores desired temperatures for the polishing pad 30, the carrier head 70, and the conditioner disk 92. The controller 12 monitors temperature measurements from sensors 64, 214, and 264 and controls the temperature control system 100, the water inlet 432, and the steam outlet 436 to bring the temperatures of the polishing pad 30, the carrier head 70, and / or the conditioner disk 92 to the desired temperatures. By bringing the temperature to the desired temperature, the controller 12 can improve the uniformity within the wafer and the uniformity between wafers.

[0128] Alternatively, the controller 12 can raise the temperature of the carrier head 70 and / or the conditioner head 92 until it slightly exceeds 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 raised for the bulk polishing operation. After the bulk polishing operation, the temperatures of various components of the carrier head 70 (e.g., the polishing surface 36, the conditioner disk 92) can be cooled for the metal removal operation, the over-polishing operation, and / or the conditioning operation.

[0130] Numerous 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 present invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A platen that supports a polishing pad having a polishing surface, A coolant source, A dispenser suspended above the platen, having one or more apertures for directing coolant from the coolant source onto the polishing surface of the polishing pad, A controller coupled to the coolant source, Bulk-polishing a metal layer of a substrate using the polishing pad having a surface of the polishing pad having a first temperature, After the bulk polishing, removing metal from the substrate such that the upper surface of the underlying patterned layer is exposed, After removing the metal from the substrate, over-polishing the substrate using the polishing pad in which the temperature of the surface of the polishing pad is reduced by the coolant to a second temperature lower than the first temperature of the surface of the polishing pad during bulk polishing A controller configured as such, A chemical mechanical polishing system comprising the above.

2. The system according to claim 1, wherein the coolant source includes a liquid cooling medium source.

3. The system according to claim 2, wherein the liquid cooling medium includes one or more of liquid nitrogen or water.

4. The system according to claim 1, wherein the coolant source includes a gas cooling medium source.

5. The system according to claim 4, wherein the gas cooling medium includes one or more of nitrogen or carbon dioxide.

6. The system according to claim 4, wherein the gas cooling medium source includes compressed gas.

7. The system according to claim 4, wherein the gas cooling medium source is connected to a vortex tube configured to direct a low-temperature gas stream onto the polishing pad.

8. The system according to claim 1, wherein the one or more apertures are configured to initiate and stop fluid flow through the one or more apertures.

9. Bulk-polishing a metal layer of a substrate using a polishing pad having a surface of the polishing pad having a first temperature, After the bulk polishing, removing metal from the substrate such that the upper surface of the underlying patterned layer is exposed, After removing the metal from the substrate, the polishing pad is lowered for over-polishing with a coolant so that the temperature of the surface of the polishing pad has a second temperature lower than the first temperature of the surface of the polishing pad during bulk polishing, and the substrate is over-polished using the polishing pad. A chemical mechanical polishing method comprising the above.

10. The method according to claim 9, wherein lowering the temperature includes flowing the coolant onto the polishing surface through one or more nozzles suspended on an arm above the polishing surface of the polishing pad.

11. The method according to claim 10, wherein the coolant includes a liquid cooling medium.

12. The method according to claim 11, wherein the liquid cooling medium includes one or more of liquid nitrogen or water.

13. The method according to claim 10, wherein the coolant includes a gas cooling medium.

14. The method according to claim 13, wherein the gas cooling medium includes one or more of nitrogen or carbon dioxide.

15. The method according to claim 13, including flowing the gas cooling medium from a compressed gas source.

16. The method according to claim 13, including directing the gas cooling medium through a vortex tube so as to direct a low-temperature gas stream onto the polishing pad.

17. The method according to claim 10, including starting and stopping a fluid flow through the one or more nozzles.

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