Polishing carrier head with electromagnetic pressure control

Abstract

A carrier head for positioning a substrate on a polishing surface includes a housing, a support comprising multiple channels therethrough, and a plurality of pressure control elements secured within the multiple channels of the support. Each pressure control element includes an electromagnetic actuator, a first flexible membrane secured to the support such that portions of the first flexible membrane extending from each channel to define a balloon at each channel with each balloon defining a chamber such that actuation of the electromagnetic actuator adjusts a gas pressure in the respective chamber, and a pressure sensor arranged within the chamber.

Description

[0001] Attorney Docket No.023832WO01; 05542-1605WO1 POLISHING CARRIER HEAD WITH ELECTROMAGNETIC PRESSURE CONTROL TECHNICAL FIELD [1] The present disclosure relates generally to profile control of a polishing process, and more particularly to a carrier head having electromagnetic actuators. BACKGROUND [2] An integrated circuit is typically formed on a substrate (e.g., a semiconductor wafer) by the sequential deposition of conductive, semiconductive or insulative layers on a silicon wafer, and by the subsequent processing of the layers. [3] One fabrication step involves depositing a filler layer over a non-planar surface and planarizing the filler layer. For certain applications, the filler layer is planarized until the top surface of a patterned layer is exposed. In addition, planarization may be used to planarize the substrate surface, e.g., of a dielectric layer, for lithography. [4] Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier head. The exposed surface of the substrate is placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it against the polishing pad. In some situations, the carrier head includes an inner membrane that forms multiple independently pressurizable chambers, with the pressure in each chamber controlling the polishing rate in each corresponding region on the substrate. A polishing liquid, such as slurry with abrasive particles, is supplied to the surface of the polishing pad. SUMMARY [5] In general, an aspect disclosed herein is a carrier head for positioning a substrate on a polishing surface including a housing; a support including multiple channels therethrough; and a plurality of pressure control elements secured within the multiple channels of the support, each pressure control element including an electromagnetic actuator, a first flexible membrane secured to the support such that portions of the first flexible membrane extending from each channel to define a balloon at each channel, each balloon defining a chamber such that actuation Attorney Docket No.023832WO01; 05542-1605WO1 of the electromagnetic actuator adjusts a gas pressure in the respective chamber, and a pressure sensor arranged within the chamber. [6] Examples may include one or more of the following features. Each electromagnetic actuator of the plurality of pressure control elements may include an electromagnet. Each electromagnetic actuator may include a casing, a permanent magnet slidingly disposed in the casing, and the electromagnet is fixedly disposed within the casing. Each casing may include an annular flange defining an opening, the opening fluidically coupling a cavity of the casing to the respective chamber of the pressure control element. The permanent magnet can be arranged between the opening and the electromagnet. The carrier head may include a spring between the electromagnet and the permanent magnet, a spring between the permanent magnet and the opening, or both. Each electromagnetic actuator of the plurality of pressure control elements may include a seal arranged within a sidewall of the respective channel, the seal encompassing a magnetically susceptible plunger within the channel, and each electromagnet is arranged in a sidewall of the respective channel. The support may include multiple channels and each pressure control element of the plurality of pressure control elements is arranged within a respective channel of the multiple channels. A cross section of the chamber can be circular in shape and the plurality of pressure control elements may be arranged in a plurality of arcuate zones. The support may include an upper support and a lower support, and the first flexible membrane is clamped between the upper support and the lower support. The multiple channels may be arranged in a radial array in the support. The multiple channels may be arranged in concentric rings around a centerpoint of the support. The carrier head may include a second flexible membrane supported by the support and arranged such that an inner surface of the second flexible membrane contacts a lower surface of all of the balloons. The carrier head may include a second flexible membrane having an upper surface, a lower surface, and secured to the housing such that the chamber of the first flexible membrane applies pressure through the second flexible membrane. The second flexible membrane defines a pressurizable chamber between the housing and the first flexible membrane. The carrier head may include a controller configured to control a pressure in the chamber of one of the plurality of pressure control elements based on data received from the respective pressure sensor. The support can be removably secured to the housing, and the plurality of pressure control elements may be removably secured to the support. The first flexible membrane can be removably secured to the support by an annular clamp Attorney Docket No.023832WO01; 05542-1605WO1 around an edge of the support. The first flexible membrane can be adhesively secured to a lower surface of the support. [7] In general, an aspect disclosed herein is a chemical mechanical polishing system. The chemical mechanical polishing system includes a platen having a top surface to hold a polishing pad. The chemical mechanical polishing system includes a carrier head for positioning a substrate on a polishing surface, may include. The chemical mechanical polishing system includes a housing including a support. The chemical mechanical polishing system includes a plurality of pressure control elements secured to the support, each pressure control element including an electromagnetic actuator, and a first flexible membrane secured to the support and defining a sealed chamber below the electromagnetic actuators such that actuation of the electromagnetic actuator provides independently adjustable pressure in the sealed chamber. [8] Certain implementations can include one or more of the following advantages. Pressure can be applied to a substrate in a manner that varies both radially and angularly about the center of the substrate. This permits profile control, i.e., control of the polishing rate or total amount removed as a function of position on a two-dimensional map of the substrate, in a manner that can compensate for angular variation in thickness of an incoming substrate and / or angular variations in the polishing rate of the polishing process. The pressure applied over a region can be controlled via an electromagnetic actuator to deform a portion of an inner membrane. The inner membrane contacts and presses against an inner surface of the lower membrane on top of the region. Thus, the polishing process of each region of the layer on the substrate can be controlled independently, and possibly with higher resolution than conventional techniques. [9] Moreover, in comparison to using pneumatic control, using electromagnetic actuators permits scaling to a much larger number of control regions in a more feasible manner. A carrier head using electromagnetic actuators uses fewer pneumatic control lines through the rotary union than a carrier head using a pneumatic line for each pressure control element. In particular, electromagnetic control of individual actuators is a cost-effective and technologically simpler means of controlling individual actuators. Further, control software separating arrays of actuators into groups increases the polishing control of regions on substrates including polishing or production defects. Attorney Docket No.023832WO01; 05542-1605WO1

[0010] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages are apparent from the description and drawings, and from the claims. DESCRIPTION OF DRAWINGS

[0011] FIG.1 illustrates a schematic cross-sectional view of an example of a polishing apparatus.

[0012] FIG.2 illustrates a schematic cross-sectional view of a carrier head that has electromagnetic actuators.

[0013] FIGS.3A-3C illustrate a schematic cross-sectional view of an implementation of one of the electromagnetic actuators in three states.

[0014] FIGS.4A-4C illustrate an example cross-sectional view of another implementation of one of the electromagnetic actuators in a positive, negative, and neutral pressure state, respectively.

[0015] FIG.5 illustrates a schematic bottom view of a portion of a support having channels in a rectangular array.

[0016] FIG.6 illustrates a schematic bottom view of the support of FIG.5 overlain with example control groups.

[0017] FIG.7. illustrates a schematic bottom view of a portion of a carrier head having a support with channels in a polar array.

[0018] In the figures, like numbering indicates like elements. DETAILED DESCRIPTION

[0019] Polishing rate variations between different regions of a substrate can lead to the different regions of the substrate reaching their target thickness at different times. On the one hand, the different regions of the substrate may not reach the desired thickness or may be over- polished if polishing of the regions is halted simultaneously. On the other hand, halting polishing for different zones at different times can result in defects or lowered throughput of the polishing apparatus. Thus, there is a need to be able to independently control the pressures on different regions in order to independently control the polishing rates of those regions. Attorney Docket No.023832WO01; 05542-1605WO1

[0020] In an idealized process, due to the rotation of the carrier head and the platen, the polishing rate on a substrate would be angularly symmetric about the axis of rotation of the substrate. In practice however, the polishing process can result in angular variation in the polishing rate. In addition, a substrate to be polished can have a top layer with an initial thickness that varies angularly, i.e., that has angular non-uniformity. Finally, in some manufacturing processes it may be desirable to induce angular non-uniformity in the thickness of the layer being polished in order to compensate for non-uniformity in other processing steps, e.g., deposition steps. Eliminating angular non-uniformity induced by the polishing process or when polishing a layer with an angularly non-uniform initial thickness, or purposely providing angular variation in the thickness when polishing a layer, remains a challenge.

[0021] Some carrier heads use chambers in which pressure is controlled by an external pneumatic source, e.g., through pressure lines that pass through a rotary union. Hypothetically a carrier head could have multiple chambers that are angularly distributed in order to address angular variations. However, this results in a very large number of chambers and a corresponding large number of pressure lines through the rotary union. This may not be feasible due to the small area available in the carrier head and the limitations on rotary unions.

[0022] A carrier head that uses multiple electromagnetic actuators can address this problem. Electromagnetic actuators can have a small form factor and be individually addressed by electronic signal, thus enabling use of a significant number of actuators and thereby providing increased resolution of polishing control compared to a single pressurized chamber beneath the carrier head. In addition, the electromagnetic actuators can be distributed angularly around the carrier head, and each electromagnetic actuator can be independently controlled, permitting reduction or deliberate introduction of angular non-uniformity.

[0023] FIG.1 illustrates an example of a polishing station 120 of a chemical mechanical polishing system 100. The polishing station 120 includes a rotatable disk-shaped platen 124 supporting a polishing pad 130. The platen 124 is operable to rotate about an axis 125. For example, a motor 122 can turn a drive shaft 128 to rotate the platen 124. The polishing pad 130 is a two-layer polishing pad with an outer polishing layer 134 and a softer backing layer 132.

[0024] The polishing station 120 can include a supply port, e.g., at the end of a slurry supply arm 139, to dispense a polishing liquid 138, such as an abrasive slurry, onto the polishing pad 130. The polishing station 120 can also include a conditioner system to periodically abrade the Attorney Docket No.023832WO01; 05542-1605WO1 polishing pad 130 to maintain a polishing surface 136 of the polishing pad 130 in a consistent roughness.

[0025] A carrier head 150 is operable to hold a substrate 10 against the polishing pad 130. The carrier head 150 can include a housing 154 that can be secured to a drive shaft 170. The carrier head 150 includes a flexible lower membrane 152 having a substrate mounting surface to contact the substrate 10, e.g., a back side of substrate 10. The carrier head 150 can include a retaining ring 160 to hold the substrate 10 below the lower membrane 152. In some implementations, the retaining ring 160 may include a lower plastic portion 162 that contacts the polishing pad 130 and an upper portion 164 of a harder material.

[0026] Here and throughout the specification, references to relative directions are made including ‘upper’ and ‘lower.’ As used herein, ‘upper’ will refer to elements toward the top of the figure, e.g., closest to the drive shaft 170 or carrier head 150, while ‘lower’ will refer to elements toward the bottom of the figure, e.g., closest the platen 124 or motor 122. However, the polishing station could be implemented to have the substrate 10 held upside-down or vertical relative to gravity.

[0027] The carrier head 150 is suspended from a support structure 140, e.g., a carousel or a track, and is connected by the drive shaft 170 to a carrier head rotation motor 142 so that the carrier head 150 can rotate about a central axis 156. Optionally, the carrier head 150 can oscillate laterally, e.g., on sliders on the carousel, by movement along the track, or by rotational oscillation of the support structure 140. In operation, the platen 124 is rotated about the platen central axis 125. The carrier head 150 is rotated about the carrier head central axis 156 and translated laterally across the top surface 136 of the polishing pad 13.

[0028] Circuitry 180, e.g., a circuit board having one or more elements such as a microcontroller, is secured to the carrier head 150. For example, the circuitry can be mounted on the top of the carrier head 150. For another example, the circuitry can be mounted inside the carrier head 150.

[0029] The circuitry 180 sends and receives data and / or power on an electric line 187. The electric line 187 transfers data and / or power to an input-output (IO) block 182. The data can include pressure data that represents a pressure signal, e.g., a voltage value, for one or more of the pressure control elements 184. The electric line 187 is routed through the drive shaft 170 and a rotary electrical union 174, e.g., a slip ring, to the stationary components of a voltage source Attorney Docket No.023832WO01; 05542-1605WO1 and / or the controller 190. Alternatively, the circuitry 180 could communicate with the controller 190 and / or the IO block 182 by a wireless signal. As another example, the electric line 187 is provided by separate wires, such as a voltage wire and a data wire.

[0030] In such examples, the voltage wire and data wire can replace or supplement the electrical line 187. The voltage line, data line, or both, can be routed through the rotary electrical union 174. In addition, the number of elements 184 can be scaled up by appropriate modification of the data provided by the controller 190 and / or the IO block 182. Larger numbers of elements 184 are independently controlled with more control values and identification values in the data. The circuitry 180 is configured to interpret the larger data quantity without having to increase the number of rotary electrical unions.

[0031] In another example, the IO block 182 is arranged on the carrier head 150 and the rotary electrical union 174 provides electrical connection between the controller 190 and IO block 182 through the drive assembly 172.

[0032] In some examples, a frame of data transmitted by the controller 190 includes a control value for each of the elements 184, and the circuitry 180 is configured to determine which control value is associated with each electromagnetic actuator 198 by the order of the control values within the frame. Thus, the frames of data transmitted by the controller 190 include information which provides independent control for each actuator 198. In another example, each electromagnetic actuator 198 can be assigned a unique identification value. Therefore, the frames of data can include a control value and an identification value for one or more actuator 198. The circuitry 180 receives the data and determines the control value to apply to the appropriate actuator 198 based on the identification value. Thus, the circuitry 180 controls each actuator 198 independently.

[0033] Optionally, one or more pneumatic connections extend through the drive shaft 170 to connect pressurizable components in the carrier head 150 to a rotary pneumatic union 144. The rotary pneumatic union 144 is a multi-channel pneumatic interface through which individually pressurizable connections extend. Individual pressure control valves control pressure delivered by a gas pressure source connected to the rotary pneumatic union 144.

[0034] The carrier head 150 includes multiple independently operable pressure control elements 184 positioned above the lower membrane 152 and secured to a support 188. The support 188 is removably mounted to the housing 154 of the carrier head 150. The support 188 Attorney Docket No.023832WO01; 05542-1605WO1 being removably mounted allows a technician to efficiently change the support 188, such as to a different support having a different number or arrangement of elements 184. Different supports can have different functions, such as one support for polishing process defect correction and another for polishing profile control.

[0035] The support 188 being efficiently changeable allows for increased flexibility in system 100 process control and reduced downtime for maintenance or changing of the different supports. In the example carrier head 150 illustrated in FIG.1, the support 188 supports four elements 184, though the support 188 could support a different number of elements 184.

[0036] A plurality of channels 194 are formed through the support 188, e.g., one for each pressure control element 184. The channel 194 extends vertically in the support 188. In some examples, the channel 194 extends entirely through the support 188 from a top surface to a bottom surface of the support 188.

[0037] The pressure control elements 184 are mounted in the channels 194. The pressure control elements 184 being mounted into the support 188 facilitate changing the elements 184 concurrently. In some examples, each of the pressure control elements 184 is removably mounted to the support 188 such that an individual pressure control element 184 can be replaced. In FIG.1, four pressure control elements 184 are depicted, but this number may be much larger, e.g., 20 to 400 pressure control elements 184. The number of pressure control elements 184 is regulated by the size of the hardware involved in the individual pressure control elements 184.

[0038] FIG.2 illustrates an example cross-sectional view of another configuration of pressure control elements 184 within a larger support 188 supported by the carrier head 150. One pressure control element 184 is indicated with a dashed box at an end of the support 188. The housing 154 includes an upper carrier 154a and a lower carrier 154b connected by a flexure 158. The flexure 158 flexible such that the lower carrier 154b is vertically movable relative to the upper carrier 154a. The flexure 158 seals a space between the upper carrier 154a and the lower carrier 154b and defines a carrier head chamber 195.

[0039] The carrier head chamber 195 is pressurizable by the gas pressure source connected to the rotary pneumatic union 144. Gas pressure in the carrier head chamber 195 can be controlled to adjust the vertical position between the lower carrier 154b and the upper carrier 154a. The support 188 is loaded in the lower carrier 154b. Therefore, the vertical position of the support Attorney Docket No.023832WO01; 05542-1605WO1 188 and pressure control elements 184 mounted therein is controllable by adjusting gas pressure in the head chamber 195.

[0040] An inner membrane 192 is attached to the support 188 and is composed of a flexible material which, in some examples, can be the same material from which the lower membrane 152 is made. The inner membrane 192 is attached to the support 188 such that an associated chamber 196 is defined for each pressure control element 184. For example, the inner membrane 192 can include a planar portion 192a and multiple cylindrical cells 192b descending from the planar portion 192a, with the interior of each cell 192b providing a chamber 196.

[0041] The support 188 can includes a top portion and a removable lower portion, the lower portion having channels aligned with the channels in the top portion. The planar portion 192a of the inner membrane 192 can be clamped between the top portion of the support 188 and the lower portion of the support 188 with the cylindrical cells 192b extending into or through the channels 194 in the lower potion. This affixes the membrane 192 in place and secures the chambers 196 for the respective pressure control elements 184.

[0042] In some examples, the chambers 196 are filled with an inert gas, e.g., nitrogen, argon, carbon dioxide, helium, or combinations thereof. The chambers 196 being filled with an inert gas may improve the engineering of the chamber 196 construction. The chamber 196 being filled with the inert gas can reduce variation of the individual pressures within the chambers thus reducing temperature or time dependence on the pressures within the chambers 196.

[0043] Each pressure control element 184 is positioned in the support 188 and are collectively arranged in a two-dimensional array. The support 188 is arranged in the carrier head 150 such that the array is substantially parallel to the top surface of the platen 124. Each pressure control element 184 includes an electromagnetic actuator 198 and a portion of the membrane 192 extending below each respective actuator 198. The portion of the membrane 192 which defines each chamber 196 provides an independently pressurizable balloon 220 for the respective pressure control element 184. The volume enclosed by each balloon 220 defines the chamber 196 for each pressure control element 184.

[0044] An expanded view of a pressure control element 184 is shown in FIG.3A. The electromagnetic actuator 198 includes an electromagnet 310 and a magnetically susceptible plunger 312 arranged within a channel 194 in the support 188. An example of the plunger 312 is a permanent magnet. Each electromagnetic actuator 198 is independently actuatable to vary the Attorney Docket No.023832WO01; 05542-1605WO1 vertical position of a plunger 312 within the channel 194. The plunger 312 has a similar diameter to the channel 194 such that motion of the plunger 312 is constrained to be substantially parallel with the carrier head axis 156. Thus, assuming the chamber 196 is sealed, varying the vertical position of the plunger 312 within the channel 194 causes the gas pressure within the chamber 196 to change.

[0045] A pressure sensor 318 is arranged in the chamber 196 and transmit data representative of the gas pressure within the chamber 196. The pressure sensor 318 is positioned on the plunger 312 though this is exemplary; other positions within the chamber 196 can be imagined. In general, the pressure sensor 318 is positioned to receive information indicative of a pressure in the chamber 196 and generate a signal thereof.

[0046] Each balloon 220 includes a cylindrical portion 204 along sidewalls 206 of the channel 194, an annular section 210 extending laterally outward from the lower edge of the cylindrical portion 204 along the bottom of the support 188, a horizontal section 212 that will contact the lower membrane 152, and a vertical or accordion section 214 extending from the outer edge of the horizontal section 212 to the outer edge of the annular section 210.

[0047] The bottom surface of the horizontal section 212 of each balloon 220 contacts an upper surface of the lower membrane 152. The movement of the plunger 312 in the channel 194 changes the gas pressure in the chamber 196 which causes balloon 220 to deform, e.g., expand or contract. Thus, adjusting gas pressures in the chamber 196 causes the pressure of the associated balloon 220 on the lower membrane 152 to change. Each pressure control element 184 thereby provides independently adjustable pressure on the substrate 10 through the flexible lower membrane 152.

[0048] The balloon 220 sealed to the support 188 defines the chamber 196 for each pressure control element 184. It is to be understood that the inner membrane 192 includes a balloon 220 for each pressure control element 184 supported in the support 188. In some examples, the inner membrane 192 is provided as a single unitary membrane, though in other examples, the inner membrane 192 is composed of individual sub-membranes that each provide one balloon 220 for each pressure control element 184.

[0049] The balloon 220 forms a gas-tight seal with the support 188, e.g., the balloon 220 is hermetically sealed. The balloon 220 forming a gas tight seal with the support 118 prevents gas from transferring between the chamber 196 and the surrounding environment when pressure is Attorney Docket No.023832WO01; 05542-1605WO1 applied to the substrate 10. Preventing gas transfer from the chamber 196 increases the gas pressure consistency in the chambers 196. Preventing gas transfer from the chamber 196 increases the accuracy by which the pressure applied by the balloon 22 against the substrate 10 is controlled.

[0050] In some implementations, the pressure in an inner volume 193 (see FIG.2A) between the upper surface of the lower membrane 152 and the support 188 (i.e., above the lower membrane 152 but below or outside the inner membranes 192) can be controlled to adjust pressure between the lower membrane 152 and the substrate 10. The pressure between the lower membrane 152 and the substrate 10 can be in a range from 0 pounds per square inch (psi) to 6 psi. In some examples, the load between the lower membrane 152 and the substrate 10 is maximized when all of the pressure control elements 184 are operating at maximum pressure. The load can be considered the product of the total pressure applied by the lower membrane 184 to the substrate 10 and the total surface area of the contacting area between the lower membrane 184 and the substrate 10. The pressure applied by the balloons 220 contacting the substrate 10 can thus be in a range from 0 psi to 6 psi. Thus, when the respective balloon 220 of each of the pressure control elements 184 is applying 6 psi to the individual contact area between the balloon 220 and substrate 10, the load of the lower membrane 152 on the substrate 10 is about 6 psi.

[0051] Referring to FIGS.3A-3C, a close-up view of the pressure control element 184 and balloon 220 is shown in three pressure states. The electromagnet 310 is powered by the circuitry 180 to generate a magnetic field which causes the plunger 312 to move within the channel 194. The electromagnet 310 can cause the plunger 312 to move up or down within the channel 194 based on the polarity or strength of the generated magnetic field. The balloon 220 encloses the chamber 196 at the end of the channel 194 further from the housing 154, e.g., nearer the lower membrane 152. As the plunger 312 moves within the channel 194, the pressure of the gas within the chamber 196 is changed.

[0052] The gas pressure within the chamber 196 is correlated with the strength and polarity of the magnetic field generated by the electromagnet 310. A magnetic field having a relatively high field strength can cause a large displacement of the plunger 312 which generates a large pressure change in the chamber 196. Conversely, a magnetic field having a relatively low field strength can cause a smaller displacement of the plunger 312 which generates a smaller pressure change in the chamber 196. Displacement of the plunger 312 upward, e.g., toward the housing 154, Attorney Docket No.023832WO01; 05542-1605WO1 reduces the pressure in the chamber 196 while displacement downward, e.g., toward the lower membrane 152, increases the gas pressure in the chamber 196.

[0053] In an example shown in FIG.3B, as the plunger 312 is moved downward by the magnetic field applied by the electromagnet 310, pressure within the sealed chamber 196 increases and the balloon 220 is biased outward by the increased gas pressure. As shown in FIG. 3C, by the magnetic field applied by the electromagnet 310 moves the plunger 312 moved upward. Thus, gas pressure within the sealed chamber 196 decreases and the balloon 220 is pulled inward, e.g., toward the support 188.

[0054] A seal 314 encircles the plunger 312 within the actuator 184a to prevent fluid passing into or out of the chamber 196 from around the plunger 312 under increased or reduced gas pressures. The seal 314 is soft to allow motion of the plunger 312 upward and downward, e.g., toward or away from the chamber 196, within the support 188. In some examples, a lubricant is provided between the seal 314 and the plunger 312 to reduce friction.

[0055] FIGS.4A-4C show a second exemplary electromagnetic pressure control element 184b. The pressure control element 184b is a self-contained example which can be individually and removably installed to the support 188 thereby reducing downtime on carrier head 150 maintenance or if a single pressure control element 184b fails to function as desired.

[0056] The actuator 184b has a casing 402 having a cavity 406 in which the plunger 412 and electromagnet 110 are constrained. The electromagnet 110 is disposed at a fixed position within the cavity 406. The plunger 412 is slidingly disposed to move upward and downward within the cavity 406. Between the electromagnet 410 and the plunger 412 is a restorative element, e.g., upper spring 404, which provides a restoring force to the plunger 412 when displaced from a neutral position. Examples of the restorative element includes coil springs, leaf springs, or accordion membranes.

[0057] The casing 402 has an annular flange 416 extending inward from the outer edge of the casing 402 toward the center. The annular flange 416 defines an opening 414 which connects the cavity 406 to a chamber 420 defined by a balloon 413. The balloon 413 is sealed, e.g., bonded, to the casing 402 through an adhesive or other temporary or permanent fixture means. Therefore replacing a pressure control element 184 and associated balloon 413 reduces replacement complexity and system downtime by allowing removal and reinstallation as a complete unit. Examples of the balloon 413 can be provided by a continuous membrane, such as inner Attorney Docket No.023832WO01; 05542-1605WO1 membrane 192. In other examples, each balloon 413 is independently adhered to the support 188.

[0058] The associated balloon 413 for each pressure control element 184b contacts the membrane beneath the support 188. The membrane is not shown in FIGS.4A-4C.

[0059] A second restorative element, e.g., lower spring 405, is between the plunger 412 and the end of the casing 402 having the opening 414. The lower spring 405 is shown on one side of the pressure control element 184b though this is exemplary. In general, the restorative element can surround the lower side of the plunger 412 to provide the restorative force.

[0060] A pressure sensor 318 is arranged in the cavity 406 and positioned on the casing 402. The pressure sensor 318 is positioned to receive information indicative of a pressure in the chamber 420 and generate a signal thereof. The pressure sensor 318 is shown near the opening 414 in FIGS.4A-4C, though this is exemplary and non-limiting. In other examples, the pressure sensor 318 is attached to the plunger (e.g., as shown in FIGS.3A-3C), or to a sidewall of the casing 402.

[0061] A bridge circuit 408 is in electrical connection with the electromagnet 410 and the pressure sensor 318. The signals generated by the pressure sensor 318 are received by the bridge circuit 408 and communicated to the electromagnet 410 which establishes a feedback control loop between the electromagnet 410 and the pressure sensor 318. In this manner, the circuitry 180 controls the pressure in the chamber 420 according to signals received from the pressure sensor 318.

[0062] The perimeter shape of the inner membrane 192 controls the area of the lower membrane 152 to which pressure is applied, and thus defines a controllable area on the substrate 10 for the pressure control elements 184. An example of the perimeter shape can be defined by the outer edge of the outer-most balloons 220 of the inner membrane 192. If the perimeter shape of the inner membrane 192 is smaller than the perimeter of the inner surface of the lower membrane 152, contact pressure on the substrate 10 is based on gas pressure in a region between the perimeter shape of the inner membrane 192 and the perimeter of the inner membrane 192, e.g., the gas pressure within the inner volume 193.

[0063] In some implementations, the controllable areas for the pressure control elements 184 are hexagonal in cross-section. This can include examples in which the elements 184 are hexagonal in cross-section, the balloons 220 are hexagonal in cross-section, the elements 184 are Attorney Docket No.023832WO01; 05542-1605WO1 arrayed in hexagonal groups, or a combination thereof. In these examples, the cross-sections are parallel to the plane of the platen 124. Hexagonal control areas can beneficially increase the quantity of controllable pressure control elements 184 for a carrier head 150.

[0064] The specific shape of the controllable area for the electromagnetically controlled elements 184 can depend on the array. For example, the controllable area for the electromagnetically controlled pressure control elements 184 can be larger in size with a pie or trapezoidal shape at the center of a substrate 10, while gradually become smaller in size with an arcuate shape toward the substrate 10 edge.

[0065] The total number of the electromagnetic elements 184 can be driven by the cost of electromagnetic materials, or by size restrictions of the carrier head 150. For example, a polishing head using electromagnetic pressure control can have 100 electromagnetic elements 184.

[0066] In some implementations, the angular and radial arrangement of the controllable areas for the electromagnetic elements 184 around a center axis can be non-uniform. For example, if one or more regions in the substrate 10 needs higher definition control than the rest, therein more refined (smaller) electromagnetic actuators can be arranged.

[0067] In some implementations, the pressure control elements 184 span the substrate 10, e.g., the pressure applied to the entire substrate 10 is controlled by the pressure control elements 184. However, in some implementations, a hybrid approach can be used in which the pressure in one region of the substrate is controlled by pressure control elements 184 and pressure in another region of the substrate 10 is controlled by a pressurizable chamber that is pneumatically controlled such as inner volume 193, e.g., by a pressure line that extends through the drive shaft and rotary union.

[0068] The pressure control elements 184 can be arranged in any array that provides sufficient gaps between the individually controlled elements 184 to avoid collision between the balloons 220 and provides a desired polishing resolution of the substrate 10. In some implementations, the pressure control elements 184 are disposed in a regular array, e.g., a rectangular, hexagonal, or polar array.

[0069] FIG.5 shows a quadrant 500 of an exemplary support 502 having an array 506 of channels 504 in which pressure control elements may be installed. The array 506 is rectilinear, e.g., the channels 504 are arranged in a sequence of rows and columns. In other examples, all or Attorney Docket No.023832WO01; 05542-1605WO1 a portion of the channels of the array 506 can be arranged in a circular pattern such as in concentric rings centered around axis 156, or in a hexagonal array.

[0070] The pressure control elements 184 of any array described herein can be controlled in groups which can be defined in control software stored on the controller 190. Some examples of the chemical mechanical polishing system 100 include pressure control element management software which can store groups of pressure control elements 184. Such software can control the pressure applied to the substrate 10 according to individual pressure control elements 184, or one or more groups of pressure control elements.

[0071] FIG.6 shows the view of FIG.5 having the groups 508 overlay the array 506. Control software loaded on the controller 190 subdivides the pressure control elements 184 into multiple groups 508, e.g., rectangular groups in the example of FIG.6. The groups 508 can include one or more pressure control elements 184. The shape of the groups 508 in this example correspond to the rectilinear arrangement of the array 506 though this is nonlimiting.

[0072] In another example, the pressure control elements 184 can be disposed at different angular positions around the carrier head axis 156, such as in concentric rings. Thus, the controllable area for each pressure control element 184 of a ring spans a certain arc length of the ring. FIG.7 shows a bottom view of the carrier head 150 and an exemplary support 602 having a radial array 606 of channels 604. The channels 604 are arranged in concentric rings centered around carrier head axis 156. In other examples, a portion of the array 606 can be arranged in a circular pattern, while another portion can be arranged in a rectilinear pattern.

[0073] The channels 604 within a ring can have a uniform size and / or be spaced uniformly around the ring. A ring that is further from the carrier head axis 156 has a larger number of channels 604 compared to a ring that is closer to the axis 156. In some implementations, the controllable areas for the pressure control elements 184 have a uniform size and are spaced uniformly across multiple rings.

[0074] In some implementations, the controllable areas for the pressure control elements 184 in different rings span the same central angle (in degrees / radians). Thus, the controllable area for the elements 184 in rings further from the center of the carrier head 150 are circumferentially longer compared to a ring that is closer to the center.

[0075] In some implementations, the controllable areas for the pressure control elements 184 are progressively narrower, e.g., smaller radial width, the further the ring is from the center of Attorney Docket No.023832WO01; 05542-1605WO1 the carrier head 150. In some implementations, the controllable areas for the pressure control elements 184 in a first ring can span a smaller angle (in degrees / radians) than in a second ring that is closer to the center of the carrier head 150 than the first ring.

[0076] Other examples of groups are wedge, hexagonal, arcuate, or circular. The shape of the group can correspond to the general shape of the defect in the substrate 10 being corrected during polishing. One example is an arcuate group along an edge of the substrate 10 for correcting asymmetric edge deviations from a polishing profile.

[0077] As used in the instant specification, the term substrate can include, for example, a product substrate (e.g., which includes multiple memory or processor dies), a test substrate, a bare substrate, and a gating substrate. The substrate can be at various stages of integrated circuit fabrication, e.g., the substrate can be a bare wafer, or it can include one or more deposited and / or patterned layers.

[0078] The above-described polishing apparatus and methods can be applied in a variety of polishing systems. Either the polishing pad, or the carrier heads, or both can move to provide relative motion between the polishing surface and the substrate. For example, the platen may orbit rather than rotate. The polishing pad can be a circular (or some other shape) pad secured to the platen.

[0079] The term “controller” refers to data processing hardware and encompasses all kinds of apparatus, devices, and machines for processing data, including by way of example a programmable digital processor, a digital computer, or multiple digital processors or computers.

[0080] A computer program, which may also be referred to or described as a program, software, a software application, a module, a software module, a script, or code, can be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a data communication network.

[0081] The processes and logic flows described in this specification can be performed by one or more programmable computers executing one or more computer programs to perform functions by operating on input data and generating output. For a system of one or more Attorney Docket No.023832WO01; 05542-1605WO1 computers to be “configured to” perform particular operations or actions means that the system has installed on its software, firmware, hardware, or a combination of them that in operation cause the system to perform the operations or actions. For one or more computer programs to be configured to perform particular operations or actions means that the one or more programs include instructions that, when executed by data processing apparatus, cause the apparatus to perform the operations or actions.

[0082] Computers suitable for the execution of a computer program include, by way of example, can be based on general or special purpose microprocessors or both, or any other kind of central processing unit. The essential elements of a computer are a central processing unit for performing or executing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data.

[0083] Control of the various systems and processes described in this specification, or portions of them, can be implemented in a computer program product that includes instructions that are stored on one or more non-transitory computer-readable storage media, and that are executable on one or more processing devices. The systems described in this specification, or portions of them, can be implemented as an apparatus, method, or electronic system that may include one or more processing devices and memory to store executable instructions to perform the operations described in this specification.

[0084] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. Attorney Docket No.023832WO01; 05542-1605WO1

[0085] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0086] Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.

[0087] Other embodiments are within the scope of the following claims.

Claims

Attorney Docket No.023832WO01; 05542-1605WO1 WHAT IS CLAIMED IS:

1. A carrier head for positioning a substrate on a polishing surface, comprising: a housing; a support comprising multiple channels therethrough; and a plurality of pressure control elements secured within the multiple channels of the support, each pressure control element including: an electromagnetic actuator, a first flexible membrane secured to the support such that portions of the first flexible membrane extending from each channel to define a balloon at each channel, each balloon defining a chamber such that actuation of the electromagnetic actuator adjusts a gas pressure in the respective chamber, and a pressure sensor arranged within the chamber.

2. The carrier head of claim 1, wherein each electromagnetic actuator of the plurality of pressure control elements comprises an electromagnet.

3. The carrier head of claim 2, wherein each electromagnetic actuator comprises a casing, a permanent magnet slidingly disposed in the casing, and the electromagnet is fixedly disposed within the casing.

4. The carrier head of claim 3, wherein each casing comprises an annular flange defining an opening, the opening fluidically coupling a cavity of the casing to the respective chamber of the pressure control element.

5. The carrier head of claim 4, wherein the permanent magnet is arranged between the opening and the electromagnet. 19 998287.docAttorney Docket No.023832WO01; 05542-1605WO1 6. The carrier head of claim 5, comprising a spring between the electromagnet and the permanent magnet, a spring between the permanent magnet and the opening, or both.

7. The carrier head of claim 1, wherein the support comprises multiple channels and each pressure control element of the plurality of pressure control elements is arranged within a respective channel of the multiple channels.

8. The carrier head of claim 2, wherein each electromagnetic actuator of the plurality of pressure control elements comprises a seal arranged within a sidewall of the respective channel, the seal encompassing a magnetically susceptible plunger within the channel, and each electromagnet is arranged in a sidewall of the respective channel.

9. The carrier head of claim 1, wherein a cross section of the chamber is circular in shape and the plurality of pressure control elements are arranged in a plurality of arcuate zones.

10. The carrier head of claim 1, wherein the support comprises an upper support and a lower support, and the first flexible membrane is clamped between the upper support and the lower support.

11. The carrier head of claim 1, wherein the multiple channels are arranged in a radial array in the support.

12. The carrier head of claim 1, wherein the multiple channels are arranged in concentric rings around a centerpoint of the support.

13. The carrier head of claim 1, comprising a second flexible membrane supported by the support and arranged such that an inner surface of the second flexible membrane contacts a lower surface of all of the balloons. 20 998287.docAttorney Docket No.023832WO01; 05542-1605WO1 14. The carrier head of claim 1, further comprising a second flexible membrane having an upper surface, a lower surface, and secured to the housing such that the chamber of the first flexible membrane applies pressure through the second flexible membrane.

15. The carrier head of claim 14, wherein the second flexible membrane defines a pressurizable chamber between the housing and the first flexible membrane.

16. The carrier head of claim 1, comprising a controller configured to: control a pressure in the chamber of one of the plurality of pressure control elements based on data received from the respective pressure sensor.

17. The carrier head of claim 1, wherein the support is removably secured to the housing, and the plurality of pressure control elements are removably secured to the support.

18. The carrier head of claim 1, wherein the first flexible membrane is removably secured to the support by an annular clamp around an edge of the support.

19. The carrier head of claim 1, wherein the first flexible membrane is adhesively secured to a lower surface of the support.

20. A chemical mechanical polishing system, comprising: a platen having a top surface to hold a polishing pad; and a carrier head for positioning a substrate on a polishing surface, comprising: a housing including a support; a plurality of pressure control elements secured to the support, each pressure control element including: an electromagnetic actuator, and 21 998287.docAttorney Docket No.023832WO01; 05542-1605WO1 a first flexible membrane secured to the support and defining a sealed chamber below the electromagnetic actuators such that actuation of the electromagnetic actuator provides independently adjustable pressure in the sealed chamber. 998287.doc

Images