Steam generation for chemical mechanical polishing

Abstract

A chemical mechanical polishing system includes a platen supporting a polishing pad, a carrier head holding a substrate in contact with the polishing pad, a motor generating relative motion, a steam generator, and an arm extending over the platen having at least one opening for delivering steam from the steam generator onto the polishing pad. The steam generator includes a canister, a barrier within the canister dividing the canister into a lower chamber having a water intake and an upper chamber having a steam outlet, a heating element configured to heat a portion of the lower chamber, and a nucleating surface positioned in the lower chamber. The barrier has openings that allow steam to pass from the lower chamber to the upper chamber and condensate to pass from the upper chamber to the lower chamber.

Description

【Technical Field】 【0001】 The present disclosure relates to the generation of steam for cleaning or preheating during chemical mechanical polishing (CMP). 【Background Art】 【0002】 Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconductive, or insulating layers on a semiconductor wafer. In various manufacturing processes, planarization of the layers on the substrate is required. For example, one manufacturing step involves depositing a fill layer on a non-planar surface and planarizing the fill layer. For a particular application, the fill layer is planarized until the top surface of the patterned layer is exposed. For example, a metal layer can be deposited on a patterned insulating layer to fill trenches and holes within the insulating layer. After planarization, vias, plugs, and lines that provide conductive paths between thin film circuits on the substrate are formed by the portions of metal remaining within the trenches and holes of the patterned layer. 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 one recognized planarization method. In this planarization method, typically, it is necessary to attach the substrate to a carrier head. The exposed surface of the substrate is typically 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. Usually, a polishing slurry containing abrasive particles is supplied to the surface of the polishing pad. 【0004】 It has been proposed that steam be used for various purposes in a CMP system, such as heating or cleaning various components such as a polishing pad, a substrate, a carrier head, or a conditioning disk. 【Summary of the Invention】 【0005】 In one embodiment, a chemical mechanical polishing system includes a platen supporting a polishing pad, a carrier head holding a substrate in contact with the polishing pad, a motor generating relative motion between the platen and the carrier head, a steam generator, and an arm extending over the platen having at least one opening for delivering steam from the steam generator onto the polishing pad. The steam generator includes a canister, a barrier within the canister dividing the canister into a lower chamber having a water intake and an upper chamber having a steam outlet, a heating element configured to heat a portion of the lower chamber, and a nucleating surface positioned in the lower chamber. The barrier has openings that allow steam to pass from the lower chamber to the upper chamber and condensate to pass from the upper chamber to the lower chamber. 【0006】 In another embodiment, the steam generator includes a canister and a barrier within the canister that divides the canister into a lower chamber having a water intake and an upper chamber having a steam outlet, the barrier having openings that allow steam to pass from the lower chamber to the upper chamber and condensate to pass from the upper chamber to the lower chamber, a heating element configured to heat a portion of the lower chamber, and a wire that provides a nucleating surface and extends from the lower chamber into the upper chamber through one of the openings of the barrier. 【0007】 Possible benefits may include, but are not limited to, one or more of the following: 【0008】 Steam, or gaseous H2O produced by boiling, can be generated in sufficient quantities with low levels of contaminants. Furthermore, steam generators can produce virtually pure gas, such as steam with little or no suspension. Such steam, also known as dry steam, can provide gaseous H2O with higher energy transfer and less liquid content than other steam alternatives such as flash steam. Because the steam can be generated with reduced "collisions," the likelihood of water droplets entering the gas stream is low, and the pressure becomes more uniform over time. Water droplets that flow out of the reservoir can be returned to the reservoir, for example, via a bypass channel, thereby improving the "drying" of the steam. 【0009】 The substrate and / or one or more components of the CMP apparatus can be cleaned or preheated quickly and efficiently. Therefore, defects on the substrate can be reduced and uniformity between wafers can be improved. 【0010】 Details of one or more embodiments are specified in the accompanying drawings and the following description. Other embodiments, features, and advantages will become apparent from the description and drawings, as well as from the claims. [Brief explanation of the drawing] 【0011】 [Figure 1] This is a schematic plan view of an example of a polishing apparatus. [Figure 2A] This is a schematic cross-sectional view of an example of a polishing station in a polishing apparatus. [Figure 2B] This is a schematic top view of an exemplary polishing station in a chemical mechanical polishing apparatus. [Figure 3A] This is a schematic cross-sectional view of an exemplary carrier head steam processing assembly. [Figure 3B] This is a schematic cross-sectional view of an exemplary conditioning head steam treatment assembly. [Figure 4A] This is a schematic cross-sectional view of an exemplary steam generator. [Figure 4B] This is a schematic cross-sectional view of the barrier inside the canister of an exemplary steam generator. [Figure 5] This is a schematic cross-sectional view of a portion of the lower chamber having nucleating particles of an exemplary steam generator. [Figure 6] This is a schematic cross-sectional view of a portion of the lower chamber having a roughened inner surface of an exemplary steam generator nucleation canister. [Figure 7] This is a schematic cross-sectional view of an exemplary steam generator having a canister and a wire extending in a loop through the passage. [Modes for carrying out the invention] 【0012】 Steam, i.e., H2O gas produced by boiling, can be used to clean and / or preheat substrates and / or one or more components used in CMP equipment. In the case of preheating, temperature fluctuations can be reduced by more precisely controlling the temperature of the substrate or system components (e.g., polishing pads), which can improve polishing performance, for example, by measuring inhomogeneity within or between wafers. A potential advantage of steam is that, compared to hot water, less steam may be required to impart the same amount of energy as hot water, for example, due to the latent heat of steam. In the case of cleaning, steam may be more effective than liquid water in dissolving or otherwise removing polishing byproducts. 【0013】 A potential problem during steam generation is "collision," where water in the boiler canister forms bubbles, causing water to be ejected upwards and mixing liquid water droplets into the gas flow directed towards the CMP system. This results in "wetter" steam, which may have a lower heat capacity. Bubbles can also cause large fluctuations in steam pressure at the boiler outlet line. Collision is particularly problematic in smaller capacity boilers or boilers with high power density, for example, around 35 W / in. 3 This seems to be a particular problem with boilers exceeding a certain size. 【0014】 A technique to address this is to introduce a surface that increases nucleation. In particular, a metal wire can penetrate the boiling canister and extend through the outlet to a bypass channel. In addition to providing a nucleating surface, water droplets flowing out of the canister can be trapped by the wire and returned to the reservoir. 【0015】 Figure 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 one or more polishing stations 20 for polishing substrates held on a carrier head 70. For example, the polishing apparatus may include four polishing stations 20a, 20b, 20c, and 20d. 【0016】 The polishing apparatus 2 also includes a number of carrier heads 70, each configured to carry a substrate. The polishing apparatus 2 also includes a transfer station 6 for loading substrates onto and unloading them from the carrier heads. The transfer station 6 may include one or more load cups 8 (e.g., two load cups 8a, 8b) and is adapted to facilitate the transfer of substrates between the carrier heads 70 and a factory interface (not shown) or other device (not shown) by a transfer robot 9. 【0017】 For polishing operations, one carrier head 70 may be positioned at each polishing station. Two additional carrier heads can be positioned within the load and unload station 6 so that polished substrates can be exchanged for unpolished substrates while other substrates are being polished at the polishing station 20. 【0018】 Each carrier head 70 is held by a support structure that allows it to move 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. This makes it possible to selectively position each carrier head on the polishing station 20 and the load cup 8. 【0019】 In some embodiments, each carrier head 70 is coupled to a carriage 78 attached to a support structure 72. By moving the carriage 78 along the support structure 72 (e.g., a track), the carrier head 70 can be positioned over a selected polishing station 20 or load cup 8. Alternatively, the carrier head 70 can be suspended from a carousel, and rotation of the carousel moves all of the carrier heads simultaneously along a circular path. 【0020】 Each polishing station 20 of the polishing apparatus 2 can include, for example, a port at an end of a slurry supply arm 39 for supplying a polishing liquid 38, such as a polishing slurry (see FIG. 3A), onto the polishing pad 30. Each polishing station 20 of the polishing apparatus 2 can also include a pad conditioner 93 for lapping the polishing pad 30 to maintain the polishing pad 30 in a constant polishing condition. 【0021】 In addition, each polishing station 20 can include a heating system 104 having an arm 140 extending over the platen 24 to provide vapor onto the polishing pad. 【0022】 FIGS. 2A and 2B 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 the polishing pad 30 is placed. The platen 24 is operable to rotate about an axis 25 (see arrow A in FIG. 2B). 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. 【0023】 Referring to FIGS. 1, 2A, and 2B, the polishing station 20 can include a supply port, for example, at an end of a slurry supply arm 39 for supplying a polishing liquid 38, such as a polishing slurry, onto the polishing pad 30. 【0024】 The polishing station 20 may include a pad conditioner 90 equipped with a conditioner disc 92 (see Figure 3B) to maintain the surface roughness of the polishing pad 30. The conditioner disc 92 may 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 swing to sweep the conditioner head 93 and the conditioner disc 92 laterally across the polishing pad 30. A cleaning cup 250 may be positioned adjacent to the platen 24 in a position from which the arm 94 can move the conditioner head 93. 【0025】 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 (e.g., a carousel or track) and connected by a drive shaft 74 to a carrier head rotary motor 76, thereby allowing the carrier head to rotate around an axis 71. Optionally, the carrier head 70 may vibrate laterally by movement along the track or by rotational vibration of the carousel itself, for example, on a slider on the carousel. 【0026】 The carrier head 70 may include a flexible film 80 having a substrate mounting surface that contacts the back side of the substrate 10, and a plurality of pressurizable chambers 82 for applying different pressures to different zones (e.g., different radial zones) on the substrate 10. The carrier head 70 may 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 made of a harder material (e.g., metal). 【0027】 During operation, the platen rotates around its central axis 25, and the carrier head rotates around its central axis 71 (see arrow B in Figure 2B), translating laterally across the upper surface of the polishing pad 30 (see arrow C in Figure 3B). 【0028】 Referring to Figures 2A and 2B, as the carrier head 70 sweeps across the polishing pad 30, the exposed surface of the carrier head 70 tends to become covered with slurry. For example, slurry may adhere to the outer or inner diameter surface of the retaining ring 84. In general, on surfaces that are not kept moist, the slurry tends to solidify and / or dry out. As a result, fine particles may form on the carrier head 70. If these fine particles detach, they can scratch the substrate and result in polishing defects. 【0029】 Furthermore, the slurry may adhere to 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 the substrate 10, corroding the surface of the carrier head 70. Removing the adhered slurry is difficult, and returning the crystallized sodium hydroxide to the solution is also difficult. 【0030】 Similar problems can occur with the conditioner head 92, for example, fine particles may form on the conditioner head 92, the slurry may adhere to the conditioner head 92, and sodium hydroxide in the slurry may crystallize on one of the surfaces of the conditioner head 92. 【0031】 One solution is to clean the components (e.g., the carrier head 70 and the conditioner head 92) with a liquid water jet. However, cleaning the components with a water jet alone is difficult and may require a considerable amount of water. Furthermore, the components that come into contact with the polishing pad 30 (e.g., the carrier head 70, the substrate 10, and the conditioner disc 92) may act as heat sinks, hindering the uniformity of the polishing pad temperature. 【0032】 To address these issues, the polishing apparatus 2 includes one or more carrier head steam treatment assemblies 200, as shown in Figure 3A. Each steam treatment assembly 200 may be used for cleaning and / or preheating the carrier head 70 and the substrate 10. 【0033】 The steam treatment assembly 200 may be part of the load cup 8, for example, part of load cup 8a or 8b. Alternatively or additionally, the steam treatment assembly 200 may be provided in one or more inter-platen stations 9 located between adjacent polishing stations 20. 【0034】 The load cup 8 includes a pedestal 204 for holding the substrate 10 during the load / unload process. The load cup 8 also includes a housing 206 that surrounds, or substantially surrounds, the pedestal 204. A plurality of nozzles 225, supported by the housing 206 or a separate support, deliver steam 245 to a carrier head and / or substrate positioned within a void 208 defined by the housing 206. For example, the nozzles 225 may be positioned on one or more inner surfaces of the housing 206 (e.g., the floor 206a and / or side walls 206b and / or ceiling of the void). The nozzles 225 may be directed to direct the steam inward into the void 206. The steam 245 can be generated by using a steam generator 410, for example, a steam generator further described later. A drain 235 may allow excess water, cleaning fluid, and cleaning by-products to pass through to prevent accumulation in the load cup 8. 【0035】 The actuator provides relative vertical motion between the housing 206 and the carrier head 70. For example, the shaft 210 may be able to actuate vertically to support the housing 206 and move the housing 206 up and down. Alternatively, the carrier head 70 may be able to move vertically. The pedestal 205 may be on the axis of the shaft 210. The pedestal 204 may be able to move perpendicularly to the housing 206. 【0036】 During operation, the carrier head 70 may be positioned on the load cup 8, and the housing 206 may be raised (or the carrier head 70 may be lowered) so that the carrier head 70 partially enters the gap 208. The substrate 10 may start on the pedestal 204 and chuck onto the carrier head 70, and / or start on the carrier head 70 and dechuck onto the pedestal 204. 【0037】 Steam is directed through the nozzles 225 to clean and / or preheat one or more surfaces of the substrate 10 and / or the carrier head 70. For example, one or more of the nozzles may be positioned to direct the steam to 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 may be positioned to direct the steam to the front surface of the substrate 10 held by the carrier head 70, i.e., the surface to be polished, or to direct the steam to the lower surface of the film 80 if the substrate 10 is not supported by the carrier head 70. One or more nozzles can be positioned below the pedestal 204 to direct the steam upward to 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 steam downward to the back surface of the substrate 10 positioned on the pedestal 204. The carrier head 70 can rotate within the load cup 8 and / or move perpendicular to the load cup 8 so that the nozzle 225 can process different areas of the carrier head 70 and / or the substrate 10. The substrate 10 can be placed on the pedestal 205 so that the inner surface of the carrier head 70, for example the underside of the film 82, or the inner surface of the retaining ring 84 can be steam-treated. 【0038】 Steam is circulated from the steam source through the supply line 230, through the housing 206, and to the nozzle 225. The nozzle 225 may spray steam 245 to remove organic residues, by-products, debris, and slurry particles left on the carrier head 70 and substrate 10 after each polishing operation. The nozzle 225 may also spray steam 245 to heat the substrate 10 and / or the carrier head 70. 【0039】 The platen-to-platen station 9 can be constructed and operated similarly, but it does not require a board support pedestal. 【0040】 The steam 245 delivered by the nozzle 225 can be adjusted in temperature, pressure, and flow rate to vary the cleaning and preheating of the carrier head 70 and the substrate 10. In some embodiments, the temperature, pressure, and / or flow rate may be independently adjustable for each nozzle or between groups of nozzles. 【0041】 For example, when steam 245 is generated (for example, in the steam generator 410 in Figure 4A), the temperature of steam 245 may be 90-200°C. For example, if steam 245 is supplied by nozzle 225 due to heat loss during passage, the temperature of steam 245 may be 90-150°C. In some embodiments, the steam is delivered by nozzle 225 at a temperature of 70-100°C (e.g., 80-90°C). In some embodiments, the steam delivered by nozzle is superheated (i.e., to a temperature above its boiling point). 【0042】 When steam 245 is delivered by the nozzle 225, the flow rate of steam 245 can be 1 to 1000 cc / min depending on the heater output and pressure. In some embodiments, the steam is mixed with other gases, for example, a normal atmosphere or N2. Alternatively, the fluid delivered by the nozzle 225 is substantially pure water. In some embodiments, the steam 245 delivered by the nozzle 225 is mixed with liquid water, for example, aerosolized water. For example, liquid water and steam can be combined in a relative flow rate ratio of 1:1 to 1:10 (e.g., a flow rate of sccm). However, if the amount of liquid water is low (e.g., less than 5% by weight, e.g. less than 3% by weight, e.g. less than 1% by weight), the steam will have excellent heat transfer properties. Therefore, in some embodiments, the steam is dry steam, i.e., substantially free of water droplets. 【0043】 To avoid thermal degradation of the film, the temperature of the steam 245 can be reduced (for example, to around 40-50°C) by mixing it with water. The temperature of the steam 245 can be reduced by mixing it with cooled water or water at the same temperature or substantially the same temperature (because liquid water transfers less energy than gaseous water). 【0044】 In some embodiments, a temperature sensor 214 can be installed in or adjacent to the steam processing assembly 200 to detect the temperature of the carrier head 70 and / or the substrate 10. The signal from the sensor 214 can be received by a controller 12 to monitor the temperature of the carrier head 70 and / or the substrate 10. Based on the temperature measurement from the temperature sensor 214, the controller 12 can control the steam delivery by the assembly 100. For example, the controller may receive a target temperature value. If the controller 12 detects that the temperature measurement has exceeded the target value, the controller 12 stops the steam flow. As another example, the controller 12 may reduce the steam delivery flow rate and / or steam temperature to prevent overheating of components, for example, during cleaning and / or preheating. 【0045】 In some embodiments, the controller 12 includes a timer. In this case, the controller 12 may start when steam delivery begins and stop steam delivery when the timer expires. The timer may be set based on empirical testing to achieve desired temperatures for the carrier head 70 and the substrate 10 during washing and / or preheating. 【0046】 Figure 3B shows a conditioner steam treatment assembly 250 including a housing 255. The housing 255 may be in the shape of a “cup” that receives a conditioner disc 92 and a conditioner head 93. Steam is circulated through a supply line 280 within the housing 255 to one or more nozzles 275. The nozzles 275 may spray steam 295 to remove abrasive by-products (e.g., debris or slurry particles) left on the conditioner disc 92 and / or conditioner head 93 after each conditioning operation. The nozzles 275 may be located within the housing 255, for example, on the floor, side walls, or ceiling of the housing 255. One or more nozzles may be positioned to clean the underside of the pad conditioner disc and / or the underside, side walls, and / or top surface of the conditioner head 93. Steam 295 can be generated using a steam generator 410. Drain 285 can allow excess water, cleaning fluid, and cleaning by-products to pass through, preventing their accumulation in housing 255. 【0047】 The conditioner head 93 and conditioner disc 92 can be lowered at least partially into the steam-treated housing 255. When the conditioner disc 92 returns to operation, the conditioner head 93 and conditioning disc 92 are lifted from the housing 255 and positioned on the polishing pad 30 to condition the polishing pad 30. Once the conditioning operation is complete, the conditioner head 93 and conditioning disc 92 are lifted from the polishing pad and swung back into the housing cup 255 to remove polishing by-products on the conditioner head 93 and conditioner disc 92. In some embodiments, the housing 255 is vertically operable and is mounted, for example, on a vertical drive shaft 260. 【0048】 The housing 255 is positioned to receive the pad conditioner disc 92 and the conditioner head 93. The conditioner disc 92 and the conditioner head 93 can rotate within the housing 255 and / or move vertically within the housing 255 so that the nozzle 275 can steam treat various surfaces of the conditioning disc 92 and the conditioner head 93. 【0049】 The steam 295 delivered by the nozzle 275 can be adjusted in temperature, pressure, and / or flow rate. In some embodiments, the temperature, pressure, and / or flow rate may be independently adjustable for each nozzle or between groups of nozzles. This allows for variations in the cleaning of the conditioner disc 92 or conditioner head 93, and consequently, more effective cleaning. 【0050】 For example, when steam 295 is generated (for example, in the steam generator 410 in Figure 4A), the temperature of steam 295 may be 90-200°C. For example, if steam 295 is supplied by nozzle 275 due to heat loss during passage, the temperature of steam 295 may be 90-150°C. In some embodiments, steam may be delivered by nozzle 275 at a temperature of 70-100°C (e.g., 80-90°C). In some embodiments, the steam delivered by nozzle is superheated (i.e., to a temperature above its boiling point). 【0051】 When steam 295 is delivered by the nozzle 275, the flow rate of steam 295 can be 1 to 1000 cc / min. In some embodiments, the steam is mixed with other gases, for example, a normal atmosphere or N2. Alternatively, the fluid delivered by the nozzle 275 is substantially pure water. In some embodiments, the steam 295 delivered by the nozzle 275 is mixed with liquid water, for example, aerosolized water. For example, liquid water and steam can be combined in a relative flow rate ratio of 1:1 to 1:10 (e.g., a flow rate of sccm). However, if the amount of liquid water is low (e.g., less than 5% by weight, e.g. less than 3% by weight, e.g. less than 1% by weight), the steam will have excellent heat transfer properties. Therefore, in some embodiments, the steam is dry steam, i.e., does not contain water droplets. 【0052】 In some embodiments, a temperature sensor 264 can be installed inside or adjacent to the housing 255 to detect the temperature of the conditioner head 93 and / or the conditioner disc 92. The controller 12 can receive signals from the temperature sensor 264 to monitor the temperature of the conditioner head 93 or the conditioner disc 92 and, for example, detect the temperature of the pad conditioner disc 92. Based on the temperature readings from the temperature sensor 264, the controller 12 can control the steam delivery by the assembly 250. For example, the controller may receive a target temperature value. If the controller 12 detects that the temperature reading exceeds the target value, the controller 12 stops the steam flow. As another example, the controller 12 may reduce the steam delivery flow rate and / or steam temperature to prevent overheating of components, for example, during cleaning and / or preheating. 【0053】 In some embodiments, the controller 12 uses a timer. In this case, the controller 12 may start the timer when steam delivery begins and stop steam delivery when the timer expires. The timer may be set based on empirical testing to achieve a desired temperature of the conditioner disc 92 during washing and / or preheating, for example, to prevent overheating. 【0054】 Returning to Figure 2A, in some embodiments, the polishing station 20 includes a temperature sensor 64 for monitoring the temperature within the polishing station, or the temperature of the components of the polishing station or components within the polishing station (e.g., the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad). For example, the temperature sensor 64 may be an infrared (IR) sensor (e.g., an IR camera) positioned above the polishing pad 30 and configured to measure the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad. In particular, the temperature sensor 64 may be configured to measure the temperature at multiple points along the radius of the polishing pad 30 in order to generate a radial temperature profile. For example, the IR camera may have a field of view that spans the radius of the polishing pad 30. 【0055】 In some embodiments, the temperature sensor is a contact sensor rather than a non-contact sensor. For example, the temperature sensor 64 may be a thermocouple or IR thermometer positioned on or inside the platen 24. In addition, the temperature sensor 64 may be in direct contact with the polishing pad. 【0056】 In some embodiments, multiple temperature sensors may be spaced apart at various radial positions across the polishing pad 30 to provide 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. 【0057】 In Figure 2A, the temperature sensor 64 is shown positioned to monitor the temperature of the polishing pad 30 and / or the slurry 38 on the pad 30, but it may be positioned inside the carrier head 70 to measure the temperature of the substrate 10. The temperature sensor 64 may be in direct contact with the semiconductor wafer of the substrate 10 (i.e., it may be a contact sensor). In some embodiments, for example, multiple temperature sensors are included in the polishing station 22 to measure the temperature of various components of the polishing station or various components within the polishing station. 【0058】 The polishing system 20 also includes a temperature control system 100 for controlling the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad. The temperature control system 100 may include a cooling system 102 and / or a heating system 104. At least one of the cooling system 102 and the heating system 104, and in some embodiments both, operate by delivering a temperature-controlled medium, such as a liquid, vapor, or spray, onto the polishing surface 36 of the polishing pad 30 (or onto the polishing liquid already present on the polishing pad). 【0059】 Regarding the cooling system 102, the cooling medium may be a gas (e.g., air) or a liquid (e.g., water). The medium may be at room temperature or cooled to below room temperature, for example, 5-15°C. In some embodiments, the cooling system 102 uses a spray of air and liquid (e.g., an aerosolized spray of a liquid such as water). In particular, the cooling system may have a nozzle that generates an aerosolized spray of water cooled to below room temperature. In some embodiments, a solid material may be mixed with the gas and / or liquid. This solid material may be a cooled material such as ice, or a material that absorbs heat through a chemical reaction when dissolved in water, for example. 【0060】 The cooling medium can be delivered by flowing it through one or more openings (e.g., holes or slots) optionally formed in a nozzle in a coolant delivery arm. The openings may be provided by a manifold connected to a coolant source. 【0061】 Referring to Figures 3A and 3B, the exemplary cooling system 102 includes an arm 110 extending across 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 thereto (e.g., within 5% of the total radius of the polishing pad). The arm 110 may be supported by a base 112, which may be supported on the same frame 40 as the platen 24. The base 112 may include one or more actuators, e.g., a linear actuator for raising or lowering the arm 110, and / or a rotary actuator for swinging the arm 110 laterally over the platen 24. The arm 110 is positioned to avoid collision with other hardware components such as the polishing head 70, the pad conditioning disc 92, and the slurry supply arm 39. 【0062】 An 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 (e.g., 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 gaps. 【0063】 Each nozzle 120 may be configured to direct aerosolized water in a spray 122 toward the polishing pad 30. The cooling system 102 may include a liquid cooling medium source 130 and a gas source 132 (see Figure 3B). The liquid from source 130 and the gas from source 132 may be mixed, for example, in or on the arm 110 in a mixing chamber before being directed through the nozzle 120 to form the spray 122. Alternatively, the liquid from the source may be injected into the gas flow in the nozzle 120. 【0064】 In some embodiments, process parameters (e.g., flow rate, pressure, temperature, and / or liquid-gas mixing ratio) can be controlled independently for each nozzle. For example, the coolant for each nozzle 120 may flow through an independently controllable cooler to independently control the spray temperature. 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 gas and liquid flow rates, pressures, and mixing ratios for each nozzle. 【0065】 Various nozzles can spray onto various radial zones on the polishing pad 30. Adjacent radial zones may overlap. In some embodiments, the nozzle 120 generates a spray that strikes the polishing pad 30 along an elongated region 128. For example, the nozzle may be configured to generate a spray onto a generally planar triangular volume. 【0066】 One or more of the elongated regions 128, for example, all of the elongated regions 128, may have a longitudinal axis parallel to the radius extending through the region 128 (see region 128a). Alternatively, the nozzle 120 generates a conical spray. Sprays 122 from adjacent nozzles 120 may overlap, or the nozzles 120 may be oriented so that the elongated regions do not overlap. For example, at least some nozzles 120 (e.g., all nozzles 120) may be oriented so that the elongated regions 128 are oblique to the radius passing through the elongated regions (see region 128b). 【0067】 At least some of the nozzles 120 can be oriented such that the central axis of the spray from the nozzle (see arrow D) is oblique to the polishing surface 36. In particular, the spray 122 can be directed from the nozzles 120 such that it has a horizontal component in the opposite direction to the direction of motion of the polishing pad 30 (see arrow E) in the impact area caused by the rotation of the platen 24. 【0068】 Figure 2B shows the nozzles 120 spaced uniformly apart, but this is not mandatory. The nozzles 120 may be unevenly distributed radially, angularly, or both. For example, the nozzles 120 may be more densely clustered along the radial direction toward the edge of the polishing pad 30. In addition, while Figure 2B shows nine nozzles, there may be more or fewer nozzles, for example, 3 to 20 nozzles. 【0069】 Referring to Figures 2A and 2B, for the heating system 104, the heating medium may include steam (e.g., steam from steam generator 410, see Figure 4A). The heating medium may optionally include other gases, such as nitrogen or air, or liquid droplets, such as heated water. However, in some embodiments, the heating medium consists of water, which may be advantageous due to water's high heat capacity. The medium is above room temperature (e.g., 40-120°C, e.g., 90-110°C). 【0070】 In some embodiments, the heating medium is substantially pure deionized water. However, in some embodiments, the steam may contain additives or chemicals. The steam can be delivered by flowing onto the polishing pad 30 through openings (e.g., holes or slots) in the delivery arm. 【0071】 The flow rate of the heating medium onto the polishing pad 30 can be set so that the condensation on the polishing pad is 0.07 to 0.4 L / min of water. In some embodiments, the steam is mixed with other gases, for example, a normal atmosphere or N2. Alternatively, the medium delivered by the opening 144 is substantially pure water. In some embodiments, the steam delivered by the opening 144 is mixed with liquid water, for example, aerosolized water. If the amount of liquid water is low (e.g., less than 5% by weight, e.g. less than 3% by weight, e.g. less than 1% by weight), the steam will have excellent heat transfer properties. Therefore, in some embodiments, the steam is dry steam, i.e., substantially free of water droplets. Generally, liquid water is not intentionally introduced into the steam flow, but some amount of water droplets may be present, for example, due to condensation by cooling as it passes from the steam generator 410, or due to boiling of water in the steam generator that generates water droplets. 【0072】 An exemplary heating system 104 includes an arm 140 extending across 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 there (e.g., within 5% of the total radius of the polishing pad). The arm 140 may be supported by a base 142, which may be supported on the same frame 40 as the platen 24. The base 142 may include one or more actuators, e.g., a linear actuator for raising or lowering the arm 140, and / or a rotary actuator for swinging the arm 140 laterally over the platen 24. The arm 140 is positioned to avoid collision with other hardware components such as the polishing head 70, the pad conditioning disc 92, and the slurry supply arm 39. 【0073】 Along the rotational direction of the platen 24, the arm 140 of the heating system 104 may be positioned between the arm 110 of the cooling system 110 and the carrier head 70. Along the rotational direction of the platen 24, the arm 140 of the heating system 104 may be positioned between the arm 110 of the cooling system 110 and the slurry delivery arm 39. For example, the arm 110 of the cooling system 110, the arm 140 of the heating system 104, the slurry delivery arm 39, and the carrier head 70 may be positioned in this order along the rotational direction of the platen 24. 【0074】 Multiple openings 144 are formed on the underside of the arm 140. Each opening 144 is configured to direct a gas or steam (e.g., steam) onto the polishing pad 30. The openings 144 can pass through a plate 145 forming the floor of the arm 140 from a common manifold 146 inside the arm 140, which is connected to a heating medium source, such as a steam generator 410. The arm 140 can be supported by a base 142 such that the openings 144 face the polishing pad 30 and are separated from the polishing pad 30 by a gap G. The gap G may be 0.5 to 5 mm. In particular, the gap may be selected so that the heat of the heating fluid does not dissipate significantly before the fluid reaches the polishing pad 30. For example, the gap may be selected so that the steam released from the openings 144 does not condense before reaching the polishing pad. 【0075】 The heating system 104 may include a steam source 148, for example, a steam generator 410 (see Figure 4A), which may be connected to the arm 140 by a tube 150. 【0076】 As shown in Figure 1, in some embodiments, each polishing station 20 has a separate steam generator 410. This allows the individual steam generators 410 to be constructed with a lower volumetric capacity compared to having a common steam generator that supplies steam to all polishing stations 20. In addition, this allows each steam generator to be operated with its own control algorithm, enabling optimization of power consumption and steam generation at a particular station. This makes it possible to generate steam at lower power or to more reliably reach the desired pressure. However, in some embodiments, the polishing system uses a common steam generator that supplies steam to all polishing stations 20. 【0077】 Returning to Figures 2A and 2B, in some embodiments, the opening 144 from the manifold 146 to the environment is a "dam," a machined opening of a predetermined size (set by machining), and does not have a valve to independently control the flow rate through the opening. However, in some embodiments, the arm may include a valve so that process parameters (e.g., flow rate, pressure, and / or liquid-gas mixing ratio) can be controlled independently for each nozzle. 【0078】 Various openings 144 can direct the vapor of the spray 152 to various radial zones 154 on the polishing pad 30. Adjacent radial zones 154 may overlap. The central axis of the spray 152 from the openings 144 may be perpendicular to the polishing surface 36. Optionally, one or more of the openings 144 may be oriented such that the central axis of the spray from that opening is oblique to the polishing surface 36. The vapor may be directed from one or more of the openings 144 such that it has horizontal components in the direction opposite to the direction of motion of the polishing pad 30 in the impact area caused by the rotation of the platen 24. 【0079】 Figures 2A and 2B show the openings 144 spaced uniformly apart, but this is not mandatory. The openings 144 may be unevenly distributed radially, angularly, or both. For example, the openings 144 may be more densely clustered toward the edges of the polishing pad 30, for example, to compensate for a larger surface area at a larger radius. As another example, the openings 144 may be more densely clustered at radii corresponding to the radius through which the polishing fluid 39 is delivered to the polishing pad 30 by the slurry delivery arm 39. In addition, Figure 3B shows nine openings, but there may be more or fewer openings. 【0080】 The polishing system 20 may also include a high-pressure rinsing system 106. The high-pressure rinsing system 106 includes a number of nozzles 154, for example 3 to 20 nozzles, which direct a cleaning solution, such as water, onto the polishing pad 30 with high force to clean the pad 30 and remove used slurry, polishing debris, etc. 【0081】 As shown in Figure 2B, an exemplary rinsing system 106 includes an arm 160 that extends across 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 thereto (e.g., within 5% of the total radius of the polishing pad). The arm 160 may be supported by a base 162, which may be supported on the same frame 40 as the platen 24. The base 162 may include one or more actuators, e.g., a linear actuator for raising or lowering the arm 160, and / or a rotary actuator for swinging the arm 160 laterally over the platen 24. The arm 160 is positioned to avoid collisions with other hardware components such as the polishing head 70, the pad conditioning disc 92, and the slurry supply arm 39. 【0082】 Along the rotational direction of the platen 24, the arm 160 of the rinsing system 106 may be located 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 160 of the rinsing system 106, the arm 140 of the heating system 104, the slurry delivery arm 39, and the carrier head 70 may be positioned in this order along the rotational direction of the platen 24. Alternatively, along the rotational direction of the platen 24, the arm 140 of the cooling system 104 may be located between the arm 160 of the rinsing system 106 and the arm 140 of the heating system 140. For example, the arm 160 of the rinsing system 106, the arm 110 of the cooling system 110, the arm 140 of the heating system 104, the slurry delivery arm 39, and the carrier head 70 may be positioned in this order along the rotational direction of the platen 24. 【0083】 Figure 2B shows the nozzles 164 spaced at uniform intervals, but this is not mandatory. In addition, while Figures 2A and 2B show nine nozzles, there may be more or fewer nozzles, for example, 3 to 20 nozzles. 【0084】 The polishing system 2 may also include a controller 12 that controls the operation of various components (e.g., a temperature control system 100). The controller 12 is configured to receive temperature measurements from a temperature sensor 64 for each radial zone of the polishing pad. The controller 12 can compare the measured temperature profile with a desired temperature profile and generate a feedback signal for each nozzle or opening to a control mechanism (e.g., an actuator, power supply, pump, valve, etc.). 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 reach (or at least approach) the desired temperature profile. 【0085】 In some embodiments, the polishing system 20 includes a wiper blade or body 170 for uniformly distributing the polishing fluid 38 across the polishing pad 30. Along the rotational direction of the platen 24, the wiper blade 170 may be located between the slurry delivery arm 39 and the carrier head 70. 【0086】 Figure 3B shows separate arms for each subsystem (e.g., heating system 102, cooling system 104, and rinsing system 106), but various subsystems may be included in a single assembly supported by a common arm. For example, the assembly may include a cooling module, a rinsing module, a heating module, a slurry delivery module, and optionally a wiper module. Each module may include a body (e.g., a curved body) that can be fixed to a common mounting plate, which can be fixed to the end of the arm so that the assembly is positioned on the polishing pad 30. Various fluid delivery components (e.g., tubes, passages, etc.) may extend inside each body. In some embodiments, the modules are separately detachable from the mounting plate. Each module may have similar components to perform the function of the arm of the associated system described above. 【0087】 Referring to Figure 4A, steam for the processes described herein, or for other uses in chemical mechanical polishing systems, can be generated using a steam generator 410. An exemplary steam generator 410 may include a canister 420 enclosing an internal space 425. The walls of the canister 420 may be made of an insulating material (e.g., quartz) with very low levels of mineral contaminants. Alternatively, the walls of the canister may be formed of another material, for example, the inner surface of the canister may be coated with polytetrafluoroethylene (PTFE) or another plastic. In some embodiments, the canister 420 may be 10 to 20 inches long and 1 to 5 inches wide. The volume of the canister may be 1 to 3 liters, for example, 1 to 1.5 liters if each station has a separate steam generator, or 2 to 3 liters if there is a steam generator common to all stations. 【0088】 Referring to Figures 4A and 4B, in some embodiments, the internal space 425 of the canister 420 is divided into a lower chamber 422 and an upper chamber 424 by a barrier 426. The barrier 426 may be made of the same material as the canister wall, for example, quartz, stainless steel, aluminum, or ceramic such as alumina. Quartz may be advantageous in that it has a low risk of contamination. The barrier 426 can substantially prevent liquid water 440 from entering the upper chamber 424 by blocking water droplets scattered by boiling water. This allows dry steam to accumulate in the upper chamber 424. 【0089】 The barrier 426 includes one or more openings 428. The openings 428 allow steam to pass from the lower chamber 422 into the upper chamber 424. The openings 428, and in particular the openings 428 near the edges of the barrier 426, allow condensation on the walls of the upper chamber 424 to drip into the lower chamber 422, reducing the liquid content in the upper chamber 426 and making it possible to reheat the liquid with water 440. 【0090】 The opening 428 may be located at the edge of the barrier 426 (e.g., only the edge) where the barrier 426 contacts the inner wall of the canister 420. The opening 428 may be located near the edge of the barrier 426 (e.g., between the edge of the barrier 426 and the center of the barrier 426). This configuration may be advantageous in that the barrier 426 does not have an opening in the center, thus reducing the risk of liquid droplets entering the upper chamber, while also allowing condensation on the side walls of the upper chamber 424 to flow out of the upper chamber. 【0091】 However, in some embodiments, the openings are further positioned away from the edges so that they are uniformly spaced, for example, across the width of the barrier 426, or across the area of ​​the barrier 425. 【0092】 Referring to Figure 4A, the water intake 432 can connect the water reservoir 434 to the lower chamber 422 of the canister 420. The water intake 432 may be located at or near the bottom of the canister 420 to supply water 440 to the lower chamber 422. 【0093】 One or more heating elements 430 may surround a portion of the lower chamber 422 of the canister 420. The heating element 430 may be, for example, a heating coil (e.g., a resistance heater) wound around the outside of the canister 420. The heating element may also be provided by a thin film coating on the material of the canister's side wall. When an electric current is applied, this thin film coating may function as a heating element. 【0094】 The heating element 430 may also be located within the lower chamber 422 of the canister 420. For example, the heating element may be coated with a material that prevents contaminants (e.g., metallic contaminants) from moving from the heating element into the vapor. 【0095】 The heating element 430 can apply heat to the bottom of the canister 420 up to the minimum water level 443a. In other words, the heating element 430 can cover the portion of the canister 420 below the minimum water level 443a, thereby preventing overheating and reducing unnecessary energy consumption. 【0096】 The steam outlet 436 may connect the upper chamber 424 to a steam delivery passage 438. The steam delivery passage 438 may be located above or near the top of the canister 420 (e.g., on the ceiling of the canister 420). This allows steam to travel from the canister 420 through the steam delivery passage 438 to various components of the CMP apparatus. The steam delivery passage 438 can be used to deliver steam to various areas of the chemical mechanical polishing apparatus, for example, for steam cleaning and preheating of the carrier head 70, substrate 10, and pad conditioner disc 92. 【0097】 Referring to Figure 4A, in some embodiments, a filter 470 is connected to a steam outlet 438 configured to reduce contaminants in the steam 446. The filter 470 may be an ion exchange filter. 【0098】 Water 440 can flow from the water reservoir 434 through the intake port 432 into the lower chamber 422. Water 440 can fill the canister 420 to a water level 442 that is at least above the heating element 430 and below the barrier 426. When the water 440 is heated, a gaseous medium 446 is generated and rises through the openings 428 in the barrier 426. The openings 428 allow the vapor to rise and condensates to dissipate simultaneously, resulting in a gaseous medium 446 in which the water is substantially free of liquid (e.g., no liquid water droplets are suspended in the vapor). 【0099】 In some embodiments, the water level is determined using a water level sensor 460 that measures the water level 442 in a bypass pipe 444. The bypass pipe runs parallel to a canister 420 and connects a water reservoir 434 to a steam delivery passage 438. The water level sensor 460 can indicate where the water level 442 is in the bypass pipe 444 and, consequently, in the canister 420. For example, since the water level sensor 444 and the canister 420 are equally pressurized (for example, both receive water from the same water reservoir 434, both have the same pressure above, and for example, both are connected to a steam delivery passage 438), the water level 442 is the same between the water level sensor and the canister 420. In some embodiments, the water level 442 of the water level sensor 444 may otherwise indicate the water level 442 of the canister 420, for example, the water level 442 of the water level sensor 444 is scaled to indicate the water level 442 of the canister 420. 【0100】 During operation, the water level 442 in 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 steam outlet 436 and barrier 426, so that there is enough space for the gaseous medium 446 (e.g., steam) to accumulate near the top of the canister 420 without substantially containing liquid water. 【0101】 In some embodiments, the controller 12 is connected to one, two, or all of the following: i) a valve 480 that controls the fluid flow to the assembly, for example, the canister 420 and the bypass pipe 444; ii) a valve 482 that controls the gas flow from the assembly, for example, to the steam delivery passage 438; and / or iii) a water level sensor 460. Using the water level sensor 460, the controller 12 is configured to regulate the flow of water 440 flowing into the canister 420 and the flow of gas 446 leaving the canister 420 to maintain a 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 may be further connected to a power supply 484 for the heating element 430 to control the amount of heat delivered to the water 440 in the canister 420. 【0102】 As mentioned above, a potential problem during steam generation is "collision," meaning that the water 440 in the canister 420 may form bubbles and the water may be scattered upwards, increasing the likelihood of liquid droplets passing through the outlet 436, or increasing the likelihood of large fluctuations in the steam pressure within the steam delivery passage 438. For example, pressure fluctuations of ±10% of the total steam pressure (when the total variance is 20%) and some abrupt pressure drops of 15-25% of the total steam pressure have been observed. 【0103】 A technique to address this is to introduce a surface within the canister 430 that increases nucleation. Increased nucleation can increase the rate of bubble formation (in terms of the number of bubbles), reduce the average size of bubbles, and consequently reduce collisions. An acceptable pressure fluctuation level is ±5% of the total vapor pressure (when the total variance is 10%). 【0104】 As an example, as shown in Figure 5, particles 500 can be scattered on the floor 430a of the canister. The particles may be made of a material that does not react with water (e.g., ceramic, glass, or precious metal). The particles 500 may be flakes, beads, etc. The particles may have a width of 0.2 to 3 mm along their maximum dimensions. However, a potential hazard is that the particles 432 may clog the inlet valve 480 or (especially in the case of small particles) be agitated by boiling water and carried by the steam flow through the outlet 436 to reach and damage the substrate. 【0105】 As another example, as shown in Figure 6, at least a portion 512 of the inner surface 510 of the canister can be treated or manufactured to have a higher surface roughness. The portion 512 may have a surface roughness Ra value of at least 1 μm, for example, at least 4 μm, for example, at least 8 μm. As shown in Figure 6, this portion can cover all of the floor 430a of the canister and part (but not all) of the side wall 430b. Alternatively, the portion 512 can cover part or all of the inner surface of the floor 430a of the canister 430, but not the side wall 430b of the canister 430a. Alternatively, the entire inner surface of the canister 430 can be roughened. Surface roughness can be introduced to the inner surface of the canister 430 by etching the quartz of the canister, for example, with a hydrofluoric acid (HF) cleaning solution. 【0106】 As another example, as shown in Figure 7, a wire 530 made of a metal that does not react with water (e.g., a precious metal such as platinum or gold) can be placed inside the canister 430. The gauge of the wire may be 20 to 40. The wire 530 can provide a bubble nucleating surface for the water 440 inside the canister 430. Even a single wire 530 may be sufficient to reduce impact and pressure fluctuations to an acceptable level. 【0107】 The wire 530 can be passed through either the opening 428 or the outlet 436. In particular, the wire 430 can be extended downward from the outlet 436 to the bypass pipe 444. In this configuration, the wire 430 can provide a surface from which liquid water droplets can accumulate and flow back into the main water volume 440 in the steam generator 410 through the bypass pipe 444. This can reduce the liquid water droplet content in the steam output by the steam generator 410, and thus make the steam "drier". 【0108】 In fact, in some embodiments, the wire 530 can be extended to form a loop through the bypass pipe 444. This can be achieved during the assembly of the steam generator, for example, by passing the wire 530 through each component before fixing the piece to the assembly. One end of the wire 530 can be wrapped around the other end to form a loop. A potential advantage of the looped wire is that the wire 530 is fixed in place and does not move due to the fluid flow. 【0109】 In some embodiments, the wires are not electrically connected to the external components of the canister 430 and passages 434, 438, and 444. Since the wires are not used to transmit signals from the sensors, electrical passthroughs are not required. 【0110】 Referring to Figures 1, 2A, 2B, 3A, 3B, and 4A, the controller 12 can monitor temperature readings 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 readings and control the temperature in a feedback loop to adjust the temperatures of the polishing pad 30, the carrier head 70, and the conditioning disc 92. For example, the controller 12 can receive the temperature of the polishing pad 30 from sensor 64 and control the water inlet 432 and the steam outlet 436 to control the delivery of steam to the carrier head 70 and / or the conditioner head 92, thereby raising 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 helps prevent the carrier head 70 and / or the conditioner head 92 from acting as a heat sink on the relatively hot polishing pad 30, thereby improving uniformity within the wafer. 【0111】 In some embodiments, the controller 12 stores desired temperatures for the polishing pad 30, carrier head 70, and conditioner disc 92. The controller 12 monitors temperature readings from sensors 64, 214, and 264 and controls the temperature control system 100, water inlet 432, and steam outlet 436 to bring the temperatures of the polishing pad 30, carrier head 70, and / or conditioner disc 92 to the desired temperatures. By bringing the temperatures to the desired temperatures, the controller 12 can improve uniformity within the wafer and uniformity between wafers. 【0112】 Alternatively, the controller 12 can raise the temperature of the carrier head 70 and / or the conditioner head 92 slightly above the temperature of the polishing pad 30 so that the carrier head 70 and / or the conditioner head 92 cool to the same or substantially the same temperature as the polishing pad 30 when they move from their respective washing and preheating stations to the polishing pad 30. 【0113】 Several embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications can be made without departing from the essence and scope of the present invention. Accordingly, other embodiments are also within the scope of the following claims.

Claims

[Claim 1] A chemical mechanical polishing system, A platen that supports the polishing pad, A carrier head that holds a substrate in contact with the polishing pad, A motor that generates relative motion between the platen and the carrier head, A steam generator, Canister, A barrier within the canister that divides the canister into a lower chamber having a water intake and an upper chamber having a steam outlet, wherein the barrier has openings that allow steam to pass from the lower chamber to the upper chamber and condensate to pass from the upper chamber to the lower chamber. A heating element configured to apply heat to a portion of the lower chamber, and Nucleation surface positioned in the lower chamber A steam generator equipped with, An arm extending over the platen having at least one opening for delivering steam from the steam generator onto the polishing pad, A chemical mechanical polishing system equipped with the following features. [Claim 2] The system according to claim 1, wherein the nucleating surface includes fine particles on the floor of the canister. [Claim 3] The system according to claim 1, wherein the nucleating surface includes at least a portion of the inner surface of the lower chamber of the canister, having a roughness selected to facilitate the nucleation of vapor bubbles. [Claim 4] The system according to claim 3, wherein the nucleating surface has an average roughness Ra value of at least 1 μm. [Claim 5] The system according to claim 3, wherein the nucleating surface is rougher than the second portion of the inner surface of the canister. [Claim 6] The system according to claim 1, wherein the nucleating surface includes a wire. [Claim 7] The system according to claim 6, wherein the wire is made of a precious metal. [Claim 8] The system according to claim 7, wherein the wire is made of platinum. [Claim 9] The system according to claim 6, wherein the wire penetrates one of the openings in the barrier. [Claim 10] The system according to claim 9, wherein the wire extends into the steam delivery passage through the steam outlet of the canister. [Claim 11] The system according to claim 10, wherein the steam generator includes a bypass pipe parallel to the canister that connects the water intake and the steam outlet, and the wire extends from the steam delivery passage into the bypass pipe. [Claim 12] The system according to claim 11, wherein the wire passes through the bypass pipe, through the water intake of the canister, and into the lower chamber of the canister. [Claim 13] The system according to claim 12, wherein the wire forms a closed loop. [Claim 14] The system according to claim 6, wherein the wire is not electrically connected to the passage of the steam generator for transporting water and steam and to the external components of the canister. [Claim 15] The system according to claim 1, wherein the water intake is located on the floor of the lower chamber of the canister, and the steam outlet is located on the ceiling of the upper chamber of the canister. [Claim 16] A steam generator, Canister and, A barrier within the canister divides the canister into a lower chamber having a water intake and an upper chamber having a steam outlet, wherein the barrier has openings that allow steam to pass from the lower chamber to the upper chamber and condensate to pass from the upper chamber to the lower chamber. A heating element configured to apply heat to a portion of the lower chamber, A wire provides a nucleating surface and extends from the lower chamber through one of the openings of the barrier into the upper chamber. A steam generator equipped with the following features. [Claim 17] The apparatus according to claim 16, wherein the wire extends through the steam outlet of the canister into the steam delivery passage. [Claim 18] The apparatus according to claim 17, further comprising a bypass pipe connecting the water intake port and the steam outlet parallel to the canister, wherein the wire extends from the steam delivery passage into the bypass pipe. [Claim 19] The apparatus according to claim 18, wherein the wire passes through the bypass pipe, through the water intake port of the canister, and into the lower chamber of the canister. [Claim 20] The system according to claim 19, wherein the wire forms a closed loop.

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