Polishing head with flexure extending through pressure chamber

Abstract

A carrier head for chemical mechanical polishing includes: a housing for attachment to a drive shaft; a membrane module disposed below the lower carrier body; and a flexure. The membrane assembly includes a membrane support and a flexible membrane secured to the membrane support to define a plurality of pressurizable lower chambers, where the flexible membrane has a lower surface providing a substrate mounting surface. The flexible seal forms a pressurizable upper chamber between the housing and the membrane support. A flexure connects the membrane support to the housing, and the flexure extends through the pressurizable upper chamber.

Description

Technical Field

[0001] This disclosure relates to a carrier head for use in chemical mechanical polishing (CMP). Background Technology

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

[0003] Chemical mechanical polishing (CMP) is a recognized planarization method. This planarization method typically requires mounting a substrate on a carrier head. A rotating polishing pad is usually placed against the exposed surface of the substrate. The carrier head provides a controlled load on the substrate to push it against the polishing pad. A polishing slurry containing abrasive particles is typically supplied to the surface of the polishing pad. Summary of the Invention

[0004] In one aspect, a carrier head for chemical mechanical polishing includes: a housing for attachment to a drive shaft; a membrane assembly disposed below a carrier body; and a flexure. The membrane assembly includes a membrane support and a flexible membrane fixed to the membrane support to define a plurality of pressurizable lower chambers, wherein the flexible membrane has a lower surface providing a substrate mounting surface. A flexible seal forms a pressurizable upper chamber between the housing and the membrane support. The flexure connects the membrane support to the housing and extends through the pressurizable upper chamber.

[0005] In another aspect, a chemical mechanical polishing system includes a pressure plate, a carrier head, and a controller. The carrier head includes a housing for attachment to a drive shaft, and the housing includes an upper carrier body and a lower carrier body vertically movable relative to the upper carrier body. A first flexible seal forms a first pressurizable chamber between the upper carrier body and the lower carrier body. A membrane assembly is disposed below the lower carrier body, and the membrane assembly includes a membrane support and a flexible membrane fixed to the membrane support to define a plurality of pressurizable lower chambers. The flexible membrane has a lower surface that provides a substrate mounting surface. A second flexible seal forms a second pressurizable chamber between the upper carrier body and the lower carrier body. The controller is configured to receive signals from sensors arranged to generate data indicating the pressure in the second pressurizable chamber and is configured to control a pressure source to pressurize the second pressurizable chamber based on the signals.

[0006] In another aspect, a method for chemical mechanical polishing includes the following steps: loading a substrate into a carrier head having a housing and a membrane assembly, the housing having an upper carrier body and a lower carrier body, the membrane assembly being located below the lower carrier body, wherein a space between the lower carrier body and the membrane assembly defines a pressurizable chamber; measuring the distance from a sensor in the lower carrier body to the membrane assembly; and controlling the pressure in the pressurizable chamber based on the measured distance. Controlling the pressure in the pressurizable chamber includes the following step: maintaining a consistent total downward pressure on the membrane assembly when the distance between the sensor and the membrane assembly changes.

[0007] Advantages may include (but are not limited to) the following: The sensor can detect changes in the distance between the carrier body and the membrane module. Such changes in distance can occur even if the chamber pressure remains constant, such as due to wear of the retaining ring. The controller can reduce the pressure in the chamber above the membrane module to maintain a consistent load on the substrate during multiple polishing operations, thereby improving wafer-to-wafer uniformity. The vertical position of the membrane module can be changed without distorting the pressure distribution across the entire membrane.

[0008] Details of one or more implementations are set forth in the accompanying drawings and the embodiments described below. Other aspects, features, and advantages will become apparent from the embodiments, the drawings, and the claims. Attached Figure Description

[0009] Figure 1 This is a schematic cross-sectional view of an example of a polishing device.

[0010] Figure 2A This is a schematic cross-sectional view of the carrier head.

[0011] Figure 2B This is a schematic cross-sectional view of another implementation of the carrier head.

[0012] Figure 3This is a schematic top view of the flexural element from the carrier head.

[0013] Figure 4 This is a schematic top view of another implementation of a flexural component.

[0014] Figure 5 It is a flowchart depicting a chemical mechanical polishing method for controlling the pressure in one or more pressurized chambers. Detailed Implementation

[0015] In some polishing systems, a membrane in a carrier head is used to apply pressure to a substrate during polishing. For example, a chamber above the membrane assembly can be pressurized to force the membrane against the substrate. However, as the retaining ring of the carrier head wears, the height of the body supporting the membrane may decrease, and therefore the load on the substrate may increase even if the chamber pressure remains constant, leading to wafer-to-wafer inhomogeneities. For example, as the retaining ring wears, the deflection of the flexure connecting the membrane assembly to the carrier head increases, resulting in a greater downward force on the membrane assembly, which may in turn increase the load on the flexible membrane and the substrate. A potential solution is to adjust the chamber pressure applied to the membrane assembly to compensate for any changes in the downward force from the flexure, so that the total load on the substrate remains relatively constant. The carrier head has a diaphragm that separates the membrane assembly from the body that provides the chamber pressure, allowing the membrane assembly to be loaded independently of the vertical movement of the body to which the membrane assembly is attached.

[0016] However, an additional problem is that the actual downward force from the flexure on the membrane assembly is not suitable for direct measurement. However, the distance from the substrate to the membrane assembly can be measured, for example, by a sensor attached to the substrate. As the measurement distance decreases, the pressure in the chamber between the diaphragm and the membrane assembly can be reduced, thereby reducing changes in the load on the substrate and membrane, and reducing membrane sidewall bending when the retaining ring wears. This reduces wafer-to-wafer inhomogeneity due to retaining ring wear or membrane aging. The retaining ring and membrane can thus have a longer service life before replacement is required.

[0017] Figure 1 An example of a chemical mechanical polishing apparatus 100 is shown. The polishing apparatus 100 includes a rotatable disc-shaped pressure plate 120 on which a polishing pad 110 is located. The pressure plate can be rotated about an axis 125. For example, a motor 121 (such as a DC induction motor) can rotate a drive shaft 124 to rotate the pressure plate 120.

[0018] The polishing pad 110 may be a two-layer polishing pad having an outer polishing layer 112 and a softer backing layer 114. In some implementations, a plurality of slurry delivery channels 116 are formed in the top surface of the polishing layer 112 of the polishing pad 110.

[0019] The polishing apparatus 100 may include a port 130 for dispensing polishing liquid 132 (such as abrasive slurry) onto the polishing pad 110. The polishing apparatus may also include a polishing pad adjuster to abrade the polishing pad 110 to maintain the polishing pad 110 in a consistent abrasive state.

[0020] The polishing apparatus 100 includes at least one carrier head 140. The carrier head 140 is operable to press a substrate 10 against a polishing pad 110, such as during a polishing process. The carrier head 140 can at least control the pressure applied to the substrate 10, such as downward pressure on the back side of the substrate, which results in upward pressure on the front side of the polishing pad on the substrate 10.

[0021] The carrier head 140 may include a retaining ring 142 to secure the substrate 10 beneath the flexible membrane 144. The carrier head 140 also includes one or more independently controllable pressurized lower chambers 146 defined by the flexible membrane 144, such as three chambers 146a-146c, which can apply independently controllable pressure to relevant areas on the flexible membrane 144, and thus apply independently controllable pressure to the substrate 10. Although for ease of illustration, Figure 1 Only three chambers 146a-146c are shown, but there may be one or two chambers, or four or more chambers, such as five chambers.

[0022] The carrier head 140 is suspended from the self-supporting structure 150 (e.g., a turntable or track) and connected to a carrier head rotation motor 154 (e.g., a DC induction motor) by a drive shaft 152, allowing the carrier head to rotate about axis 155. Each carrier head 140 may optionally oscillate laterally, e.g., on a slider on the support structure 150, or by the rotation of the turntable itself, or by sliding along the track. In typical operation, the pressure plate rotates about its central axis 125, and each carrier head rotates about its central axis 155 and translates laterally across the top surface of the polishing pad.

[0023] A controller 190 (such as a programmable computer) is connected to motors 121 and 154 to control the rotational speed of the pressure plate 120 and the carrier head 140.

[0024] Reference Figure 2AThe carrier head 140 includes a housing 102 having an upper carrier body 104 and a download body 106, a universal joint 108 (which can be considered part of the download body 106), a retaining ring 142 connected to the housing 102 (e.g., connected to the upper carrier body 104 or the download body 106), and a membrane assembly 400. The volume between the download body 106 and the upper carrier body 104 can be sealed by an upper flexible seal 164 to provide a load chamber 111. This upper flexible seal 164 is flexible to accommodate changes in the vertical position between the upper carrier body 104 and the download body 106. In some implementations, the upper carrier body 104 and the download body 106 are replaced by a unitary body.

[0025] The upper carrier body 104 is fixed to the drive shaft 152 to rotate the entire carrier head 140. The upper carrier body 104 may generally be circular. A passage may extend through the upper carrier body 104 for pneumatic control of the carrier head 140. The download body 106 is located below the upper carrier body 104 and is vertically movable relative to the upper carrier body 104. A load chamber 111 is located between the upper carrier body 104 and the download body 106 to apply a load (e.g., downward pressure or weight) to the download body 106. The vertical position of the download body 106 relative to the polishing pad is also controlled by the load chamber 111. In some embodiments, the vertical position of the download body 106 relative to the upper carrier body 104 is controlled by an actuator.

[0026] The universal joint 108 allows the download body 106 to move omnidirectionally and vertically relative to the upper carrier body 104, while preventing the download body 106 from moving laterally relative to the upper carrier body 104. However, in some implementations, there is no universal joint.

[0027] The substrate 10 is held below the carrier head 140 by a retaining ring 142, which secures the substrate 10 to prevent lateral movement. The retaining ring 142 may also provide active edge processing control; controlling the pressure on the polishing pad in a region outside the substrate but adjacent to the substrate edge can affect the polishing rate at the substrate edge. Some implementations may include an outer ring that provides positioning or reference for the carrier head to the surface of the polishing pad.

[0028] The volume between the download body 106 and the membrane assembly 500 can be sealed by a lower flexible seal 162 to form a pressurized upper chamber 134. This lower flexible seal 162 is flexible to accommodate changes in the vertical position between the download body 106 and the membrane assembly 500. The pressure in the pressurized upper chamber can control the downward load on the membrane assembly 500 and / or the vertical position of the membrane assembly 500 relative to the housing.

[0029] Each chamber in the carrier head 140 can be fluidly coupled to an associated pressure source (e.g., pressure source 922), such as a pump or pressure or vacuum line, via a passage through the upper carrier body 104 and the lower carrier body 106. The load chamber 111, the pressurizable upper chamber 134, and each independently pressurizable lower chamber 146 may have one or more passages. One or more passages from the lower carrier body 106 can be linked to passages in the upper carrier body 104 via flexible conduits extending to the inside of the load chamber 111 or the outside of the carrier head 140. Pressurization of each chamber can be controlled independently relative to the other chambers; for example, chamber pressurization can be individually controlled. In particular, pressurization of each lower chamber 146 can be independently controlled. This allows different pressures to be applied to different radial regions of the substrate 10 during polishing, thereby compensating for uneven polishing rates.

[0030] The membrane assembly 400 may include a membrane support 138 and a flexible membrane 144. The flexible membrane 144 has a circular lower portion 170 with a lower outer surface 174 that provides a mounting surface for the substrate 10. The flexible membrane 144 also has a plurality of folds 172, such as annular folds, extending from an inner surface 176 of the lower portion 170 to define individually controllable pressurizable lower chambers 146. For example, the ends of the folds 172 (e.g., the ends adjacent to the lower portion 138a) may be clamped to the membrane support 138.

[0031] The membrane support 138 may include a disc-shaped lower portion 138a and an annular upper portion 138b extending upward from the disc-shaped lower portion 138a at its outer edge. A fold 172 of the flexible membrane 144 may be clamped to the disc-shaped lower portion 138a. The membrane support 138 may be formed of a material more robust than the membrane 144, such as metal, ceramic, or hard plastic. The membrane support 138 may be considered non-flexible under the pressure conditions typically occurring in polishing processes.

[0032] The pressurizable upper chamber 134 is configured to extend across the top of the membrane support 138 and is included by the lower flexible seal 162. Specifically, the bottom of the pressurizable upper chamber 134 may be defined by the top surface 139 of the disc-shaped lower portion 138a, the sides may be defined by the inner surface 141 of the annular upper portion 138b, the top may be defined by the bottom surface 161 of the lower flexible seal 162 and the bottom surface 107 of the lower body body 106.

[0033] Still refer to Figure 2AThe carrier body 106 is connected to the membrane assembly 400 via a flexure 160. The flexure 160 is more robust than the lower flexible seal 162, but less robust than the membrane support 138. The membrane assembly 400 is suspended from the upper carrier body 106 via the flexure 160. Furthermore, the flexure 160 acts as a spring, pushing the membrane assembly 400 to a “neutral” position while still allowing the membrane assembly 400 to move vertically relative to the housing 102 based on the pressure in the pressurizable upper chamber 134. The flexure 160 can be connected to the carrier body 106 and the membrane assembly 400 using fasteners (e.g., adhesives, screws, bolts, clamps, or interlocking, to name a few).

[0034] The flexure 160 extends through a pressurized upper chamber 134 between the inner surface 141 of the upper portion 138b of the membrane assembly 400 and the sidewall 163 of the downwardly projecting 189 of the body 106. The projecting 189 extends downward toward the top surface 139 of the lower portion 138a of the membrane support 138.

[0035] Therefore, the pressurizable upper chamber 134 may include a lower portion 134a below the flexure 160 and an upper portion 134b above the flexure 160. The lower portion 134a and the upper portion 134b are fluidly coupled to maintain the same pressure. In some implementations, the flexure 160 has a gap or orifice to allow gas flow. For example, see reference... Figure 3 The flexural element 160 may be an annular body including a plurality of orifices 180. As another example, see [reference needed]. Figure 4 The flexural element 160 may be provided by a plurality of arcuate elements 182, which are spaced apart by gaps 184. In some implementations, the lower portion 134a and the upper portion 134b are connected by a passage 186 through the housing 102, such as through the lower body body 106. In this case, the flexural element 160 may be a fluid-impermeable annular body, such as a solid unit body without orifices 180 or gaps 184.

[0036] The upper flexible seal 164 and the lower flexible seal 162 may be made of flexible materials, such as rubber, like silicone rubber, ethylene propylene diene terpolymer (EPDM) or fluoroelestomer, or plastic film, such as polyethylene terephthalate (PET) or polyoxymethylene.

[0037] The flexure 160 has sufficient rigidity to resist lateral movement so that the membrane assembly 400 is maintained in a central position below the substrate body 106. However, the flexure 160 may have sufficient vertical flexibility to allow vertical movement of the membrane assembly 400 relative to the housing 102. The flexure 160 allows the assembly 400 to move vertically relative to the substrate body 106 by flexure (e.g., bendable deflection). The advantage of having a flexure 160 extending through the upper chamber 134 is that the pressure in the pressurizable upper chamber 134 can be adjusted without causing a pressure difference across the flexure 160, thus avoiding pressure reflection across the flexure that could skew the pressure distribution across the membrane 144, e.g., the pressure distribution against the substrate 10. The advantage of pressure on both sides of the flexure 160 is reduced stress caused by bending the flexure 160 due to pressure applied only on one side.

[0038] Controller 190 regulates the pressure in various chambers of carrier head 140. Controller 190 is coupled to multiple pressure sources, such as pressure sources 922, 924, and 926. Pressure sources 922, 924, and 926 can be, for example, pumps, facility gas lines, and controllable valves. Each of pressure sources 922, 924, and 926 can be individually connected to a pressurized chamber. Figure 2A In the example, pressure source 922 is connected to load chamber 111, pressure source 924 is connected to pressurizable lower chamber 146, and pressure source 926 is connected to pressurizable upper chamber 134. Although only one pressure source 924 is shown for ease of illustration, each lower chamber 146 may have one, so that each lower chamber 146a-146c can be controlled individually.

[0039] One or more sensors 930 measure the pressure(s) applied by pressure sources 922, 924, 926, such as the pressure in the individual pressurizable lower chamber 146, pressurizable upper chamber 134, and load chamber 111. The sensors 930 transmit the measured pressure(s) to a controller 190. The controller 190 causes the pressure sources 922, 924, 926 to increase and / or decrease the pressure in the pressurizable lower chamber 146, pressurizable upper chamber 134, and / or load chamber 111.

[0040] When the carrier head 140 performs a polishing operation, the retaining ring 142 wears. As the retaining ring 142 wears, the flexor 160 flexes to apply increased downward pressure to the film support 138, and thus to the substrate 10, resulting in an increased polishing rate of the substrate 10. To compensate for the increased load (e.g., applied pressure) on the substrate 10 caused by the wear of the retaining ring 142, the pressure in the pressurizable upper chamber 134 can be adjusted (e.g., reduced pressure) to maintain a consistent total load on the substrate 10.

[0041] The increased downward pressure from wear on the retaining ring 142, due to the bending of the lower seal 162 and the increased pressure on the membrane assembly 400, can also lead to wear on the membrane 144. The increased pressure can cause one or more walls of the lower chamber 146 to bend or flex, which further increases wear on the membrane 144.

[0042] Reference Figure 2B To determine the necessary change in pressure, sensor 950 can measure the distance or change in distance from sensor 950 to membrane assembly 400, and controller 190 can detect the change in distance based on the signal from sensor 950. Sensor 950 can be a magnetic (e.g., eddy current), radar, laser, optical, ultrasonic, or other similar proximity sensor.

[0043] Sensor 950 may be fixed in carrier head 140, e.g., fixed to download body 106. Sensor 950 is positioned to measure the distance between sensor 950 and a target. For example, the target may be a portion of the top surface of membrane assembly 400 (e.g., the top surface of membrane support 138, such as the top surface of the annular upper portion 138b of membrane support 138), below sensor 950. Therefore, sensor 950 can measure the distance between download body 106 and membrane support 138 of membrane assembly 400.

[0044] Before using sensor 950 to perform distance measurements, the upper pressurized chamber 136 can be pressurized or vented to the atmosphere to allow the membrane assembly 400 to remain on the polishing pad. This ensures that the bottom of the membrane assembly 400 is aligned with the bottom surface 142 of the retaining ring 140.

[0045] In addition, sensor 950 is connected to controller 190 and reports the measured distance or changes in the measured distance to controller 190 (e.g., a reduction in distance due to wear of retaining ring 142). Controller 190 may then cause pressure source 926 to reduce the pressure in pressurizable upper chamber 134 to maintain the load on substrate 10.

[0046] The controller 190 can be configured to adjust the pressure of the pressurizable upper chamber 134 based on the measured distance between the sensor 950 and the target. That is, the controller 190 can be configured such that when the flexure 160 flexes and reduces the distance between the sensor 950 and the target, thereby increasing the pressure applied to the substrate 10 by the flexure 160, the controller 190 reduces the pressure of the pressurizable upper chamber 134 to compensate for the increased pressure applied by the flexure 160.

[0047] The pressure in the pressurizable upper chamber 134 can be a function of the measured distance between the sensor 950 and the target (e.g., surface 402). For example, the pressure in the pressurizable upper chamber 134 can decrease when the measured distance between the sensor 950 and the target decreases. The controller 190 can receive the expected pressure, such as polishing formula represented by data stored in a non-transitory computer-readable medium, and the distance measurement from the sensor 950. The controller 190 calculates a corrected pressure for the pressurizable upper chamber 134 based on the expected pressure and the distance measurement. The amount of pressure reduction in the pressurizable upper chamber 134 can be stored in a lookup table that correlates the pressure change with the distance. The pressure change can be a non-linear function of the distance and depends on the design of the flexure 160. Furthermore, the pressure change can be stored in the lookup table as an absolute pressure change or a percentage change relative to the expected pressure. This change is applied to the expected pressure by necessary subtraction or multiplication based on the type of change (e.g.), to calculate the corrected pressure.

[0048] To determine the functional relationship between distance and pressure difference, a series of paired measurements can be performed using retaining rings 142 with different degrees of wear (e.g., new retaining rings and used retaining rings) for i) distance and ii) total downpressure from membrane module 400. Specifically, retaining rings 142 can be mounted on carrier head 140, which is positioned above a pressure sensor (e.g., a pressure sensor pad), and the pressurizable upper chamber 134 can be pressurized to a consistent pressure for each pair of measurements.

[0049] Distance is measured by sensor 950, while the total applied pressure from membrane assembly 400 is measured by another sensor (e.g., a pressure sensor pad). Multiple paired measurements provide the increase in applied pressure as a function of distance measurement. The pressure offset of the pressurizable upper chamber 134 that brings the total applied pressure back to a consistent pressure value can be calculated as a function of the measured distances of the paired measurements.

[0050] Figure 5 This is a flowchart depicting a method 500 for controlling pressure in one or more pressurizable chambers. Method 500 can be used to control any of the devices and systems disclosed herein, such as device 100. Method 500 includes loading a substrate into a carrier head (step 502). The carrier head may have a housing and a membrane assembly, the housing having an upper carrier body and a lower carrier body, the membrane assembly being located below the lower carrier body. The lower carrier body and the membrane assembly may be connected by a flexure, and the space between the lower carrier body and the membrane assembly defines a pressurizable chamber. The pressurizable chamber is connected to a pressure source and one or more pressure sensors that can measure the pressure within the chamber, and a controller can adjust the pressure source based on the sensor readings to increase, decrease, or maintain the pressure within the chamber.

[0051] The housing includes a sensor for measuring the distance between the housing (e.g., the download body) and the membrane assembly. Method 500 includes measuring the distance from the sensor in the download body to the membrane assembly (step 504). The distance between the download body and the membrane assembly is at least partially related to the pressure within the pressurizable chamber.

[0052] Method 500 includes controlling the pressure in the pressurizable chamber based on the measured distance (step 506). Controlling the pressure in the pressurizable chamber includes maintaining a consistent total downward pressure on the membrane assembly when the distance between the sensor and the membrane assembly changes (such as when the retaining ring wears or when the membrane bends). Step 506 may include reducing the pressure in the pressurizable chamber as the measured distance decreases. In one example, step 506 may include controlling the pressure in the pressurizable chamber by compensating for changes in the load on the membrane assembly based on wear of the retaining ring.

[0053] The controllers and other computing devices of the systems described herein can be implemented as digital electronic circuits or computer software, firmware, or hardware. For example, the controller may include a processor to execute a computer program stored in a computer program product, such as a computer program stored on a non-transitory machine-readable storage medium. Such computer programs (also referred to as programs, software, software applications, or code) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as standalone programs or as modules, components, subroutines, or other units suitable for use in a computing environment.

[0054] In the context of a controller, “configuration” means that the controller has the necessary hardware, firmware, or software or combination thereof to perform the desired function at runtime (as opposed to simply being programmable to perform the desired function).

[0055] While this document contains numerous details of specific implementations, these details should not be construed as limiting any invention or the scope of any possible claims, but rather as descriptions of specific features of specific embodiments of a particular invention. Certain features described in the context of individual embodiments in this document may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination. Furthermore, although features may be described above as operating in certain combinations, and even initially claimed in this way, in some cases, one or more features from a claimed combination may be removed from that combination, and the claimed combination may involve sub-combinations or variations thereof.

[0056] Several embodiments of the invention have been described. However, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Therefore, other implementations are within the scope of the appended claims.

Claims

1. A carrier head for chemical mechanical polishing, comprising: A housing for attachment to a drive shaft, wherein the housing includes an upper carrier body and a lower body body that is vertically movable relative to the upper carrier body. A first flexible seal forms a first pressurizable chamber between the upper carrier body and the lower body body; A membrane assembly is disposed below the main body of the download body. The membrane assembly includes a membrane support and a flexible membrane fixed to the membrane support to define a plurality of pressurizable lower chambers. The flexible membrane has a lower surface that provides a substrate mounting surface. as well as The second flexible seal forms a second pressurizable chamber between the download body body and the membrane support; as well as A flexure connects the membrane support to the body of the downloader, the flexure extending through the second pressurizable chamber.

2. The carrier head of claim 1, wherein a first portion of the second pressurizable chamber above the flexure is fluidly connected to a second portion of the second pressurizable chamber below the flexure.

3. The carrier head of claim 2, wherein the flexure includes a plurality of orifices that fluidly connect the first portion of the second pressurizable chamber to the second portion of the second pressurizable chamber.

4. The carrier head as claimed in claim 2, wherein the flexure comprises a plurality of arcuate members separated by a plurality of gaps.

5. The carrier head of claim 2, wherein the first portion of the second pressurizable chamber and the second portion of the second pressurizable chamber are fluidly connected through a passage through the body of the downloader.

6. The carrier head of claim 1, wherein the first portion of the second pressurizable chamber is a downwardly projecting annular chamber surrounding the body of the downloader.

7. The carrier head of claim 6, wherein the second portion of the second pressurizable chamber is a disc-shaped chamber extending across substantially all of the support plate.

8. The carrier head as claimed in claim 1, wherein the flexure is horizontally arranged between the download body body and the membrane support.

9. The carrier head of claim 8, wherein the flexure is disposed between the annular upper portion of the membrane support and the downward projection of the download body body.

10. The carrier head of claim 1, wherein the membrane support comprises a plate horizontally spanning over the plurality of pressurizable chambers.

11. The carrier head of claim 10, wherein the plate is more robust than the flexible membrane.

12. The carrier head of claim 1, further comprising a retaining ring connected to the download body body, wherein wear on the retaining ring causes a reduction in the distance between the membrane support and the download body body.

13. The carrier head of claim 1, wherein the flexure has sufficient rigidity to horizontally center the membrane assembly within the housing.

14. The carrier head of claim 1, wherein the flexure has sufficient rigidity to vertically center the membrane assembly within the housing.

15. A carrier head for chemical mechanical polishing, comprising: Housing for attachment to the drive shaft; A membrane assembly is disposed below the main body of the download body. The membrane assembly includes a membrane support and a flexible membrane fixed to the membrane support to define a plurality of pressurizable lower chambers. The flexible membrane has a lower surface that provides a substrate mounting surface. as well as A flexible seal forms a pressurizable upper chamber between the housing and the membrane support; as well as A flexure is used to connect the membrane support to the housing, the flexure extending through the pressurizable upper chamber.

16. The carrier head of claim 15, wherein a first portion of the pressurized upper chamber above the flexure is in fluid connection with a second portion of the pressurized upper chamber below the flexure.

17. The carrier head of claim 16, wherein the flexure includes a plurality of orifices fluidly connecting the first portion of the pressurizable upper chamber to the second portion of the pressurizable upper chamber.

18. The carrier head of claim 16, wherein the flexure comprises a plurality of arcuate members spaced apart by a plurality of gaps.

19. The carrier head of claim 16, wherein the first portion of the pressurizable upper chamber and the second portion of the pressurizable upper chamber are fluidly connected through a passage through the body of the downloader.

20. The carrier head of claim 15, wherein the first portion of the pressurizable upper chamber is a downwardly projecting annular chamber surrounding the body of the downloader.

21. The carrier head of claim 20, wherein the second portion of the pressurizable upper chamber is a disc-shaped chamber extending across substantially all of the support plate.

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