CMP temperature control system cleaning

Abstract

A chemical mechanical polishing apparatus has a heating system, a source of purge gas, a source of purge liquid, and a controller. The heating system includes a source of heating gas, an arm extending over the platform, and a manifold having a plurality of openings in the arm, the manifold positioned over the platform and separated from the polishing pad for delivery of the heating gas onto the polishing pad. The controller is configured to cause the heating gas to flow from the heating gas source through the manifold and the plurality of openings to heat the polishing pad during a polishing operation, and to cause the apparatus to perform a purge operation, the purge operation alternates between flowing purge gas from a purge gas source and flowing purge liquid from a purge liquid source through a manifold and a plurality of openings.

Description

Technical Field

[0001] The present disclosure relates to chemical mechanical polishing (CMP), and more particularly to a temperature control device for CMP, and cleaning of the temperature control device. Background Art

[0002] Integrated circuits are typically formed on a substrate by sequentially depositing a conductive layer, a semiconductive layer, or an insulating layer on a semiconductor wafer. Various manufacturing processes require a planarized layer on the substrate. For example, one manufacturing step involves depositing a filler layer on a non-planar surface and planarizing the filler layer. For some applications, the filler layer is planarized until the top surface of the patterned layer is exposed. For example, a metal layer may be deposited on the patterned insulating layer to fill the grooves and holes in the insulating layer. After planarization, the remaining portions of the metal in the grooves and holes of the patterned layer form vias, plugs, and lines to provide conductive paths between thin film circuits on the substrate. As another example, a dielectric layer may be deposited on the patterned conductive layer and then planarized to enable subsequent photolithography steps.

[0003] Chemical mechanical polishing (CMP) is an accepted planarization method. The planarization method generally requires that the substrate be mounted on a carrier head. The exposed surface of the substrate is generally placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push the substrate against the polishing pad. A polishing slurry having abrasive particles is generally supplied to the surface of the polishing pad. In addition, the temperature of the polishing pad can be controlled, for example, by directing a heating or cooling fluid onto the surface of the polishing pad. Summary of the invention

[0004] In one aspect, a chemical mechanical polishing apparatus has a platform holding a polishing pad, a carrier for holding a substrate against a polishing surface of the polishing pad during a polishing process, a heating system, a purge gas source, a purge liquid source, and a controller. The heating system includes a heated gas source, an arm extending above the platform, and a manifold having a plurality of openings, the manifold being positioned above the platform and separate from the polishing pad for delivering heated gas to the polishing pad. The controller is configured to cause heated gas to flow from the heated gas source through the manifold and the plurality of openings to heat the polishing pad during a polishing operation, and to cause the apparatus to perform a purge operation that alternates between flowing a purge gas from the purge gas source and flowing a purge liquid from the purge liquid source through the manifold and the plurality of openings.

[0005] In another aspect, a chemical mechanical polishing apparatus has a platform holding a polishing pad, a carrier for holding a substrate against a polishing surface of the polishing pad during a polishing process, a heating system, and a controller. The heating system includes an arm extending above the platform and having a manifold with a plurality of openings, the manifold being positioned above the platform and separate from the polishing pad for delivering a heated gas to the polishing pad; a source of heated liquid; and a boiler having an inlet for the heated liquid and a steam outlet, the steam outlet being coupled to the manifold in the arm by a fluid delivery line. The controller is configured to cause the heated gas to flow from the boiler through the manifold and the plurality of openings to heat the polishing pad during a polishing operation, and to cause the apparatus to perform a purge operation that alternates between filling and draining the boiler with the heated liquid.

[0006] In another aspect, a chemical mechanical polishing apparatus has a platform holding a polishing pad, a carrier for holding a substrate against a polishing surface of the polishing pad during a polishing process, a heated gas source, and an arm extending on the platform. The arm includes a diffuser plate and a distribution plate, the diffuser plate partitioning a volume inside the arm into an upper gas chamber coupled to the heated gas source, and a lower gas chamber, and the distribution plate provides a lower surface of the arm and has a plurality of openings uniformly disposed on the distribution plate, and wherein the diffuser plate includes a plurality of apertures non-uniformly distributed on the diffuser plate so as to induce a non-uniform mass flow of the heated gas through the plurality of openings.

[0007] Embodiments may include, but are not limited to, one or more of the following possible advantages. The cleaning procedure may reduce the accumulation of contaminants (e.g., scale accumulation) in the polishing pad heating system. This may reduce the likelihood that the contaminants reach the substrate and cause defects (e.g., scratches). The cleaning procedure may be performed during idle time of the polishing machine and thereby avoid significantly affecting production. The use of an internal diffuser plate in the heating manifold allows for the establishment of different flow rates of heating fluid to different areas of the polishing pad, which may help to establish a desired temperature distribution on the polishing pad, such as a more uniform temperature distribution, which may improve polishing uniformity. The internal diffuser allows the heating fluid distribution plate to have a small pore size, which may reduce the likelihood of splashes entering the heating manifold. The temperature variation of the polishing operation may be reduced. This may improve the predictability of the polishing process. The temperature variation from one polishing operation to another polishing operation may be reduced. This may improve wafer-to-wafer uniformity and may improve the repeatability of the polishing operation.

[0008] Plates with different aperture patterns can be swapped into the fluid distributor to provide different temperature profiles. This allows for rapid testing of different temperature profiles or modifications to the polisher for processes that require new temperature profiles.

[0009] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the detailed description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic cross-sectional view showing an example of a polishing apparatus.

[0011] Figure 2 A schematic top view of an exemplary chemical mechanical polishing apparatus is shown.

[0012] Figure 3 A flow chart illustrating a process for cleaning a heated transfer arm.

[0013] Like reference numbers in the various drawings indicate like elements. DETAILED DESCRIPTION

[0014] Chemical mechanical polishing operates by a combination of mechanical grinding and chemical etching at the interface between the substrate, the polishing liquid and the polishing pad. Both chemical-related variables in the CMP process (e.g., such as the initiation and rate of the participating reactions) and mechanical-related variables (e.g., the surface friction coefficient and viscoelasticity of the polishing pad) are closely related to temperature. Therefore, changes in the surface temperature of the polishing pad can lead to changes in removal rate, polishing uniformity, corrosion, dishing, and residue. By more tightly controlling the temperature of the polishing pad surface during polishing, temperature changes can be reduced and polishing performance (e.g., measured by intra-wafer non-uniformity or inter-wafer non-uniformity) can be improved.

[0015] Some techniques have been proposed for temperature control. As an example, a temperature control medium (e.g., liquid, vapor, or spray) can be dispensed onto the polishing surface of the polishing pad (or the polishing liquid on the polishing pad). Specifically, a dispensing arm can extend over the polishing pad, and the temperature control medium (e.g., vapor) can be dispensed from the bottom of the arm onto the polishing surface to heat the polishing pad. In addition, it may be desirable to provide a non-uniform mass flow of the temperature control medium along the radius of the polishing pad. For example, an annular region of the pad away from the axis of rotation has a larger surface area and therefore will require a larger mass flow.

[0016] However, problems can arise from contamination of the manifold that delivers the temperature control fluid to the polishing pad, for example, mineral buildup on the inner or outer surfaces of the manifold. For example, scale buildup is the result of hardened calcium and mineral deposits drying and attaching to the surface.

[0017] One possible source of contamination is splashing of polishing chemicals on the polishing pad. For example, the impact of a temperature-controlled medium (e.g., steam) on the polishing liquid can cause some droplets of the polishing liquid to be thrown back into the distribution arm. If the droplets pass through the distribution nozzle at the bottom of the arm, the chemical may accumulate in the distribution manifold inside the arm.

[0018] One technique to at least partially address this problem is to have the bottom of the arm provided by a heated diffuser plate having small holes through which a temperature controlled medium (e.g., steam) will pass to contact the polishing pad. The small holes reduce the likelihood of splashed back liquid entering the interior of the distribution manifold. The holes can be arranged at a uniform density along the length of the distribution arm. In order to establish a non-uniform mass flow, the manifold may include an internal diffuser plate having apertures arranged at non-uniform intervals along the length of the distribution arm. Therefore, the pressure and mass flow through the small holes in the distribution plate will be higher below the area of ​​the diffuser plate with a higher aperture density.

[0019] Another possible source of contamination is contaminants from the temperature control medium itself. Ultrapure water, such as semiconductor-grade water with 1 to 2 contaminant molecules per million water molecules, can be used in boilers to generate steam. However, even with ultrapure water, over time contaminant molecules can accumulate on the inner surfaces of the boiler or distribution manifold, forming scale.

[0020] Two techniques that at least partially address the problem are: 1) performing a purge operation in which gas and clean fluid are alternately directed through the distribution manifold to flush contaminants from the distribution manifold, and 2) periodically draining all water from the boiler and refilling it with fresh ultrapure water.

[0021] The two technologies can be used alone or in combination, and also alone or in combination with a distribution arm having an internal diffuser plate.

[0022] Figure 1 and Figure 2 An example of a polishing station of a chemical mechanical polishing system 20 is shown. The polishing system 20 includes a rotatable disc-shaped platform 24 on which a polishing pad 30 is disposed. The platform 24 is operable to rotate about an axis 25 (see FIG. Figure 2 2. For example, the motor 22 can rotate the drive shaft 28 to rotate the platform 24. The polishing pad 30 can be a two-layer polishing pad having an outer polishing layer and a softer backing layer 32.

[0023] The polishing station 20 may include a supply port 39 for dispensing a polishing liquid 38, such as an abrasive slurry, onto the polishing pad 30. The exact location of the supply port 39 may vary between different embodiments, but typically, the supply port 39 is located at the end of the arm near the center of the polishing pad 30. For example, the supply port 39 may be located at the end of the slurry supply arm 170 (see FIG. Figure 2 Alternatively, the supply port 39 may be located at the end of the heated delivery arm 110 .

[0024] The polishing station 20 may include a conditioning plate 92 (see Figure 2) to maintain the surface roughness of the polishing pad 30. The conditioning disk 90 can be located at the end of an arm 94, which can swing to sweep the disk 90 radially across the polishing pad 30.

[0025] The carrier head 70 is operable to hold the substrate 10 against the polishing pad 30. The carrier head 70 is suspended from a support structure 72, such as a turntable or track, and is connected to a carrier head rotation motor 76 via a drive shaft 74 so that the carrier head can rotate about an axis 71. Alternatively, the carrier head 70 can oscillate laterally, such as on a slider on a turntable, by movement along a track, or by rotational oscillation of the turntable itself.

[0026] The carrier head 70 may include a flexible membrane 80 having a substrate mounting surface that contacts the back side of the substrate 10 and a plurality of pressurizable chambers 82 that apply different pressures to different areas, such as different radial areas, on the substrate 10. The carrier head may also include a retaining ring 84 to retain the substrate.

[0027] In some embodiments, the polishing station 20 includes a temperature sensor 64 for monitoring the temperature of the polishing station or a component of the polishing station / components in the polishing station, such as the temperature of the polishing pad and / or the slurry on the polishing pad. For example, the temperature sensor 64 can be an infrared (IR) sensor, such as an IR camera, which is located above the polishing pad 30 and is configured to measure the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad. Specifically, the temperature sensor 64 can be configured to measure the temperature at multiple points along the radius of the polishing pad 30 so as to generate a radial temperature profile. For example, the IR camera can have a field of view that spans the radius of the polishing pad 30.

[0028] In some embodiments, 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 infrared thermometer positioned on or in the platform 24. In addition, the temperature sensor 64 can be in direct contact with the polishing pad.

[0029] In some embodiments, multiple temperature sensors may be spaced apart at different radial locations of the polishing pad 30 to provide temperatures at multiple points along the radius of the polishing pad 30. This technique may be used in place of or in addition to infrared cameras.

[0030] Although in Figure 1, the temperature sensor is shown as being positioned to monitor the temperature of the polishing pad 30 and / or the slurry 38 on the polishing pad 30, but the temperature sensor 64 may also be positioned inside the carrier head 70 to measure the temperature of the substrate 10. The temperature sensor 64 may be in direct contact with the semiconductor wafer of the substrate 10 (i.e., a contact sensor). In some embodiments, multiple temperature sensors are included in the polishing station 22, for example, to measure the temperature of components of the polishing station / different components in the polishing station.

[0031] The polishing system 20 also includes a temperature control system 100 (see Figure 2 ) 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 heating system 102 and / or a cooling system 104 (see Figure 2 At least one of the cooling system 104 and the heating system 102, and in some implementations both the cooling system 104 and the heating system 102, operates by delivering a temperature control fluid 130 (e.g., a liquid, vapor, or spray) to the polishing surface 36 of the polishing pad 30 (the temperature control fluid may be delivered directly to the polishing surface or to a thin layer of liquid already present on the polishing surface).

[0032] For the heating system 102, a distribution arm 120 extends above the platen 24 and the polishing pad 30. The interior of the distribution arm 120 includes a heating manifold for distributing a heating fluid 140 from an inlet 122 to a plurality of apertures 124 in a bottom surface of the distribution arm 120 and onto the polishing surface 36.

[0033] The heating fluid 140 can be a gas, such as steam or heated air. The gas can, but need not, carry an atomized liquid. When the heating fluid reaches the polishing surface 36, the heating fluid 140 is above room temperature, such as at a temperature of 40°C to 120°C, such as at a temperature of 90°C to 110°C. The heating fluid 140 can be water, such as substantially pure deionized water, or water including additives or chemicals. In some embodiments, for the heating operation, the heating system 102 directs dry steam onto the polishing pad, for example, the heating fluid 140 consists of dry steam without additives or chemicals or an atomized liquid.

[0034] In the case where the heating fluid 140 is steam, the steam may be generated at the boiler 110. The steam from the boiler 110 may flow through a fluid delivery line 118, which may be provided to the distribution arm 120 by a pipe, a flexible pipe, a channel, or some combination thereof passing through a solid body. The boiler may include an insulated tank 160 having a lower portion surrounded by a heating element 162 (e.g., a resistive heating coil). A steam outlet 164 leading to the valve 110a is located at the upper portion of the tank 160.

[0035] The inlet / outlet 166 at the bottom of the tank 160 allows liquid (e.g., ultrapure water) to be pumped into the tank 160 from the DI water source 170 (e.g., when valve 170a is open); or allows the liquid in the tank 160 to be discharged through the discharge outlet 172 (e.g., when valve 172a is open).

[0036] The heating system 102 may also include a purge gas supply 112 that provides a purge gas (e.g., N2), and optionally includes a purge liquid supply 114 that provides a purge liquid (e.g., deionized (DI) water). The DI water source 114 may also provide a DI water source 170. Water and N2 gas are typically available from supply pipes in a semiconductor manufacturing facility. The purge gas and purge liquid may also flow to the distribution arm 120 via a fluid delivery line 118.

[0037] Each of boiler 110, purge gas supply 112, and purge liquid supply 114 may be coupled to fluid delivery line 118 via associated valves 110a, 112a, 114a, and controller 90 may control the opening and closing of the valves to control which fluids flow to dispensing arm 120, as discussed further below.

[0038] The dispensing arm 120 extends over the platform 24 and the polishing pad 30 from the edge of the polishing pad to or at least close to (e.g., within 5% of the total radius of the polishing pad) the center of the polishing pad 30. The arm 120 may be supported by a base 121, and the base 121 may be supported on the same frame 40 as the platform 24. The base 121 may include one or more actuators, such as a linear actuator for raising or lowering the arm 120, and / or a rotary actuator for swinging the arm 120 laterally on the platform 24. The arm 120 is positioned to avoid collision with other hardware components, such as the polishing head 70 and the pad conditioning disk 92.

[0039] The distribution arm 120 can be generally linear and can have a substantially uniform width along its length, although other shapes such as a fan (also referred to as a "pie slice"), an arc, or a triangular wedge (all bottom views of the arm) can be used to achieve the desired effect of temperature control of the polishing pad 30. For example, the distribution arm 120 can be curved, such as forming a portion of an arc or spiral.

[0040] A plurality of openings 124 are formed through a distribution plate 126 that provides a bottom surface of the distribution arm 120. Each opening 124 is oriented to direct the heating fluid 140 onto the polishing pad 30, for example, for a cylindrical hole, the central axis may be perpendicular to the polishing surface. The openings 124 may be relatively small, for example, 0.25 mm to 1 mm in diameter. Such relatively small openings may reduce the likelihood of splashing back liquid into the interior of the distribution manifold.

[0041] The size of the openings 124 is uniform and distributed in the distribution plate 126 at a uniform density. In some embodiments, there are three rows of openings 124 extending longitudinally along the distribution arm 120, wherein the rows are staggered. Since the distribution plate 126 is prefabricated, the size and position of the openings 124 are set, for example, and cannot be adjusted during the polishing operation.

[0042] The arm 120 can be supported by the base 121 so that the opening 124 is separated from the polishing pad 30 by a gap 128. The gap 128 can be 0.5 mm to 5 mm. Specifically, the gap can be selected so that the heat of the heating fluid is not significantly dissipated before the fluid reaches the polishing pad. For example, the gap 128 can be selected so that the steam from the opening does not condense before reaching the polishing pad.

[0043] To provide a non-uniform mass flow, a diffuser plate 130 is positioned inside the arm 120 to divide the manifold into an upper plenum 132 and a lower plenum 134. The fluid delivery line 118 is coupled to the upper plenum 132 and delivers a fluid (e.g., a heating fluid 140) to the upper plenum 132. The distributor arm 120 may have a single inlet 122 through which various fluids (e.g., a heating medium, a purge gas, and a liquid) enter the upper plenum 132. The inlet 122 may be located at a distal end of the arm 120 relative to the axis of rotation of the platform 24.

[0044] A plurality of apertures 136 are formed through the diffuser plate 130 to fluidically couple the upper plenum 132 to the lower plenum 134. The apertures 136 may be uniform in size. The apertures 136 may be wider than the openings 124, although this is not required. For example, the apertures 136 may span 0.5 to 3 cm.

[0045] Unlike the openings 124, the apertures 136 are disposed at a non-uniform density along the length of the polishing arm 120. Specifically, the apertures 136 are disposed at a greater density as the distance from the rotational axis 25 of the platform 24 increases. Thus, the apertures 136 are more closely spaced at the end of the arm near the center of the polishing pad 30 than at the end of the arm where the base 121 is connected. This creates a pressure gradient within the lower chamber 134 such that the pressure in the lower chamber 134 increases with distance from the rotational axis 25. As a result, the mass flow of the heating fluid 140 through the openings 124 increases with distance from the rotational axis 25.

[0046] The pattern of apertures 136 in the diffuser plate 130 can be designed to meet the specific needs of various temperature control profiles. In some cases, the temperature control profile can define the mass flow rate of the heated fluid onto the polishing pad as a function of the radial distance from the axis of rotation of the platen. For example, the mass flow rate can increase parabolically with distance from the axis of rotation.

[0047] Rather than having a uniform size and a non-uniform distribution, the apertures 136 may be uniformly distributed but have a non-uniform size to achieve a similar mass flow profile for the heating fluid 140 .

[0048] Because the distribution plate 126 and the diffuser plate 130 are prefabricated with set positions and sizes for the openings 124 and apertures 136, the sizes of the openings 124 and apertures 136 do not change during the polishing operation. However, to change the distribution of the heating fluid 140, the distribution arm 120 can be removed and replaced with a new diffuser plate 130 with a different aperture pattern. Thus, different plates with different opening patterns can be used to provide different temperature profiles for different polishing operations. This allows for rapid testing of different temperature profiles or modifications to the polisher for processes that require a new temperature profile.

[0049] For example, the radial temperature distribution during polishing of a substrate without temperature control by the arm can be measured. An opening pattern is calculated that will provide a mass flow profile to compensate for non-uniformities in the radial temperature distribution, for example, as the inverse of the radial temperature distribution. A base plate having openings arranged in a pattern can be manufactured or selected from a set of prefabricated base plates. The base plate is then installed in the arm and used during polishing of the substrate.

[0050] Figure 1 and Figure 2 The number of openings or apertures is schematic and not necessarily illustrative. In particular, there may be a greater number of openings, for example, fifty to two hundred openings. In addition, although Figure 2 Circular openings are shown, but the openings may be rectangular, such as square, hexagonal, or other shapes. Optionally, some of the openings 124 may be oriented so that the central axis of the spray from the openings is at an oblique angle relative to the polishing surface 36. The heating fluid (e.g., steam) may be directed from one or more openings 124 to have a horizontal component in a direction opposite to the direction of motion of the polishing pad 30 in the impact region caused by the rotation of the platform 24.

[0051] For the cooling system 104, the coolant may be a gas, such as air, or a liquid, such as water. The coolant may be at room temperature or cooled to below room temperature, such as 0 to 15°C. In some embodiments, the cooling system 104 uses a spray of air and liquid, such as an atomized spray of a liquid (e.g., water). Specifically, the cooling system may have a nozzle that produces an atomized spray of water cooled to below room temperature. In some embodiments, the spray may include solid materials, such as ice particles formed by passing water droplets through a Laval nozzle, etc. The coolant may be delivered by flowing through one or more apertures 152 in the coolant delivery arm 150, the aperture 152 being, for example, a hole or slot optionally formed in the nozzle. The aperture may be provided by a manifold connected to a coolant source 154. The arm 150 may be constructed similarly to the arm 120 of the heating system.

[0052] Along the rotation direction of the platform 24, the arm 150 of the cooling system 104 may be positioned between the arm 120 of the heating system 102 and the carrier head 70. Along the rotation direction of the platform 24, the arm 150 of the cooling system 104 may be positioned between the arm 120 of the heating system 102 and the slurry delivery arm 170. For example, the arm 150 of the cooling system 104, the arm 120 of the heating system 102, the slurry delivery arm 170, and the carrier head 70 may be positioned in sequence along the rotation direction of the platform 24.

[0053] although Figure 2 Separate arms are shown for each subsystem (e.g., heating system 102, cooling system 104, and rinsing system 106), but the various subsystems may be included in a single assembly supported by a shared arm. For example, an assembly may include a cooling module, a rinsing module, a heating module, a slurry delivery module, and an optional wiper module. Each module may include a body, such as an arched body, which may be secured to a shared mounting plate, and the shared mounting plate may be secured to the end of the arm so that the assembly is positioned on the polishing pad 30. Various fluid delivery components, such as air chambers, pipes, channels, etc., may extend within each body. In some embodiments, the modules may be individually removable from the mounting plate. Each module may have similar components to perform the functions of the arms of the associated systems described above.

[0054] return Figure 1 The polishing system 20 also includes a controller 90 to control the operation of various components, such as the temperature control system 100. The controller 90 can be coupled to the boiler 110 to control the temperature and generation rate of the steam. Similarly, the controller 90 can be coupled to the valve 156 (see Figure 2) to control the flow rate of coolant from coolant source 154, is coupled to coolant source 154 to control the temperature of the coolant, and is coupled to valves 110a, 112a, 114a to control the flow of heating fluid 150, purge gas, and purge liquid. One or more valves may be provided by one or more liquid flow controllers (LFCs).

[0055] The controller 90 can be configured to receive temperature measurements from the temperature sensor 64. The controller 90 can compare the measured temperature to a desired temperature and generate feedback signals to a control mechanism (e.g., an actuator, power supply, pump, valve, etc.) for the flow rates of the corresponding heating fluid and cooling fluid. The controller 90 uses the feedback signals, for example based on an internal feedback algorithm, to cause the control mechanism to adjust the amount of cooling or heating so that the polishing pad and / or slurry reaches (or at least moves closer to) the desired temperature.

[0056] As described above, contaminants may accumulate inside the manifolds (eg, the upper plenum 132 and the lower plenum 134 ) in the fluid distribution arm 120 of the heating system 102 . Figure 3 is a flow chart illustrating a process 300 of performing a purge operation to flush contaminants out of a distribution manifold.

[0057] In short, the polishing system 20 alternates between directing a purge gas through the manifold (306) and directing a purge liquid through the manifold (304).

[0058] When the manifold begins to fill with steam or atmospheric air, first, the purge liquid flows until all gas initially in the transfer line 118 and the manifold is completely purged through the opening 124 (302).

[0059] The polishing system then alternates between flowing the purge gas (304) and flowing the purge liquid (306). The two steps may be repeated five to twenty times. The purge gas may flow for 5 to 20 seconds, and the purge liquid may flow for 5 to 20 seconds. In some implementations, there is a 50% duty cycle, i.e., the purge gas and purge liquid are flowed for equal durations. A potential advantage of the short duration of 5 to 20 seconds between the gas and liquid is improved cleanliness compared to simply flowing the purge liquid or gas continuously. Without being limited to theory, the gas pulses may propel the purge liquid at high speeds, and the leading edge of the purge liquid may more effectively remove contaminants from the walls of the manifold.

[0060] Once steps 304 and 306 have been repeated the necessary number of times, a final purge gas step (308) may be performed in which the purge gas flows until all of the purge liquid in the delivery line 118 and manifold is purged through opening 124.

[0061] The purge gas may be purified N2 gas, although other purified gases, such as a particle-free atmosphere, may also be used. For example, for steps 304 and 308, the purge gas may be delivered by closing valves 110a and 114a and opening valve 112a. Alternatively, valve 110a may remain open (or the system may be implemented without valve 110a), but valve 172a remains closed.

[0062] In some implementations, the purge liquid for steps 304 and 308 can be delivered by opening valve 114a and closing valves 112a and 110a; the purge liquid, such as DI water, will flow into the manifold through delivery line 118. In this case, process 300 can be performed intermittently between polishing operations, for example, once every fifty to three hundred substrates, and can be performed without placing the polishing system in an idle mode.

[0063] However, in some implementations, for steps 302 and 306, the purge liquid is delivered from the heating medium source 170 and through the boiler 110. For such operations, valves 114a, 112a are closed and valve 110a is opened. The heating element 162 is disabled, for example, the resistive heater is closed, and valve 170a is opened and liquid (e.g., DI water) is pumped into the boiler 110 so that the tank 160 is filled and the heated liquid is pushed through the delivery line 118 to the manifold of the distribution arm 120. In this case, because the boiler is disabled, the process 300 can be performed intermittently, for example, when the polishing system is placed in an idle mode, for example, about once a day. For example, the polishing system can enter the idle mode to perform other maintenance, or when switching to polishing a different batch of substrates.

[0064] Once the purge operation is complete, valve 170a is closed and valve 172a is opened to allow the liquid in fluid delivery line 118 and tank 160 to drain. Valve 112a may be opened to provide back pressure to the fluid in delivery line 118. In some implementations, the liquid level is reduced until tank 160 is partially filled (310).

[0065] However, in some implementations, valve 172a remains open until the liquid is completely drained from the boiler (312), i.e., the tank 160 is empty. In this case, the boiler is then refilled (314), for example, by opening valve 170a and closing valves 172a and 112a. Optionally, in order to additionally purge the tank 160, the draining of the boiler 312 and the refilling of the boiler 314 may be repeated, for example, two to ten times, for example three or four times. This may help prevent scale accumulation inside the tank 160. In the case of performing multiple refilling steps, all steps except the last refilling step may completely fill the tank 160. For the last refilling step, the tank should be partially refilled. Subsequently, the heating element 162 may be reopened to resume the production of steam.

[0066] Relative positioning terminology is used to represent relative positioning in the system; it will be understood that the polishing surface and substrate may be maintained in a perpendicular orientation or some other orientation during the polishing operation.

[0067] The functional operation of the controller 90 can be implemented using one or more computer program products, that is, one or more computer programs tangibly implemented in a non-transitory computer-readable storage medium, for execution by a data processing device or for controlling the operation of a data processing device, which can, for example, become a processor, a computer, or multiple processors or computers.

[0068] A number of embodiments of the present invention have been described. However, it will be appreciated that various modifications may be made without departing from the spirit and scope of the present invention. For example, although a heating fluid is described above, the arms of the cooling system may be similarly configured but with a coolant flowing through the arms rather than a heating fluid. Similar advantages apply if the cooling system has arms 140 of similar physical structure. For example, the radial profile of the mass flow rate of the coolant may compensate for non-uniformity of temperature, in this case by lowering the temperature rather than raising it.

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

Claims

1. A chemical mechanical polishing device, comprising: a platform for holding a polishing pad; a carrier for holding a substrate against a polishing surface of the polishing pad during a polishing process; as well as a heating system comprising a heating gas source, an arm extending above the platform, and a manifold having a plurality of openings, the manifold being positioned above the platform and separate from the polishing pad for delivering the heating gas onto the polishing pad; Purify gas source; Purify liquid sources; as well as a controller configured to cause the heated gas to flow from the heated gas source through the manifold and the plurality of openings to heat the polishing pad during a polishing operation, and to cause the apparatus to perform a first purge operation alternating between flowing a purge gas from the purge gas source and flowing a purge liquid from the purge liquid source through the manifold and the plurality of openings.

2. The apparatus of claim 1, wherein the controller is configured to iterate flowing the purge gas and flowing the purge liquid for two to ten iterations.

3. The apparatus of claim 2, wherein the controller is configured to flow the purge gas for five to twenty seconds for each iteration.

4. The apparatus of claim 2, wherein the controller is configured to cause the purified liquid to flow for five to twenty seconds for each iteration.

5. The apparatus of claim 1, comprising a shared fluid delivery line coupling the heating gas source and the purge gas source to the manifold.

6. The apparatus of claim 5, wherein the source of heated gas comprises a boiler having an inlet for a source of heated liquid, a discharge, and a steam outlet coupled to the shared fluid transport line.

7. The apparatus of claim 6, wherein the purified liquid source is used as a heated liquid source coupled to the boiler.

8. The apparatus of claim 7, wherein the controller is configured to cause the purified liquid to flow from the purified liquid source by filling the boiler with the purified liquid until the purified liquid flows through the steam outlet.

9. The apparatus of claim 8, wherein the controller is configured to cause the purified liquid to be discharged from the boiler.

10. The apparatus of claim 5, wherein the controller is configured to cause the apparatus to perform a second purge operation that alternates between alternately filling and draining the boiler.

11. The apparatus of claim 10, wherein the controller is configured such that filling and draining of the boiler are performed iteratively while a heating element of the boiler is disabled.

12. The apparatus of claim 10, wherein the controller is configured to iteratively drain and fill the boiler two to ten times.

13. The apparatus of claim 11, comprising the source of heated liquid, and wherein the source of heated liquid is a water source, such that the heated gas comprises steam.

14. A chemical mechanical polishing device, comprising: a platform for holding a polishing pad; a carrier for holding a substrate against a polishing surface of the polishing pad during a polishing process; Heating system, including: an arm extending above the platform, the arm having a manifold with a plurality of openings, the manifold being positioned above the platform and separate from the polishing pad for delivering the heated gas to the polishing pad; Heating the liquid source, a boiler having an inlet for the heating liquid and a steam outlet, the steam outlet being coupled to the manifold in the arm by a fluid delivery line; and A controller is configured to cause the heated gas to flow from the boiler through the manifold and the plurality of openings to heat the polishing pad during a polishing operation and to cause the apparatus to perform a purge operation that alternates between filling and draining the boiler with the heated liquid.

15. The apparatus of claim 14, wherein the controller is configured such that filling and draining of the boiler are performed iteratively while a heating element of the boiler is disabled.

16. The apparatus of claim 15, wherein the controller is configured to iteratively drain and fill the boiler between two and ten times.

17. A chemical mechanical polishing device, comprising: a platform for holding a polishing pad; a carrier head for holding a substrate against a polishing surface of the polishing pad during a polishing process; a heating gas source; as well as An arm extends above the platform, the arm including a diffuser plate and a distributor plate, the diffuser plate dividing the volume inside the arm into an upper gas chamber coupled to the heated gas source, and a lower gas chamber, and the distributor plate providing a lower surface of the arm and having a plurality of openings uniformly arranged on the distributor plate, and wherein the diffuser plate includes a plurality of apertures non-uniformly distributed on the diffuser plate so as to cause a non-uniform mass flow of the heated gas through the plurality of openings.

18. The apparatus of claim 17, wherein the platform is rotatable about an axis of rotation.

19. The apparatus of claim 18, wherein the plurality of apertures are distributed such that the mass flow rate is a monotonically increasing function of radial distance from the axis of rotation of the platform.

20. The apparatus of claim 19, wherein the plurality of holes are distributed such that the mass flow rate is a parabolically increasing function of radial distance from the axis of rotation of the platform.

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