Polished carrier head with floating edge control

Abstract

The present application discloses a polishing carrier head utilizing floating edge control. A carrier head for holding a substrate in a polishing system includes: a housing; an annular body vertically movable relative to the housing by an actuator; a first annular diaphragm fixed for movement beneath the annular body, thereby forming at least one lower pressurizable chamber between the first annular diaphragm and the annular body; and at least one pressure supply line connected to the at least one lower pressurizable chamber. The annular body includes an upper portion and at least one lower rod extending downwardly from the upper portion, wherein the at least one lower rod is positioned within the at least one lower pressurizable chamber.

Description

Technical Field

[0001] The present disclosure relates generally to chemical mechanical polishing, and more particularly to controlling the polishing rate near the edge of a substrate. Background Art

[0002] Integrated circuits are typically formed on a substrate (eg, a semiconductor wafer) by sequentially depositing conductive, semiconductive, or insulating layers on a silicon wafer and by subsequent processing of these layers.

[0003] 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 a fixed surface of the patterned layer remains or the desired thickness remains above the underlying layer. Additionally, planarization can be used to planarize substrate surfaces, such as dielectric layers, for photolithography.

[0004] Chemical mechanical polishing (CMP) is an accepted planarization method. 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, pushing it against the polishing pad. In some polishing machines, the carrier head includes a diaphragm that forms a plurality of independently pressurizable radially concentric chambers, wherein the pressure in each chamber controls the polishing rate in each corresponding area on the substrate. A polishing liquid, such as a slurry with abrasive particles, is supplied to the surface of the polishing pad. Summary of the Invention

[0005] In one aspect, a carrier head for holding a substrate in a polishing system includes: a housing; an annular body vertically movable relative to the housing by an actuator; a first annular diaphragm fixed for movement below the annular body to form at least one lower pressurizable chamber between the first annular diaphragm and the annular body; and at least one pressure supply line connected to the at least one lower pressurizable chamber. The annular body includes an upper portion and at least one lower rod extending downwardly from the upper portion, wherein the at least one lower rod is located within the at least one lower pressurizable chamber.

[0006] Certain implementations may include, but are not limited to, one or more of the following possible advantages.

[0007] The described techniques can improve overall uniformity across a substrate undergoing polishing. The system can adjust the load distribution at the edge of the substrate by applying different distributed pressures over different areas of the substrate and applying one or more concentrated forces at different locations on the edge region of the substrate. The system can adjust one or more pressures within one or more pressurizable chambers formed by the first annular diaphragm to vary the loading area and the amount of distributed pressure on the substrate.

[0008] The system may also include an annular body having one or more downwardly projecting lower rods. The system can deform the second annular diaphragm using different pressure supplies to cause the one or more lower rods to displace substantially downward, thereby contacting one or more corresponding focusing areas of the substrate and applying one or more corresponding focusing forces to the one or more corresponding focusing areas of the substrate. The location of the focusing areas where the corresponding focusing forces are applied can also be adjusted by varying the shape, position, and number of the lower rods attached to the annular body.

[0009] Thus, the system readily adapts to various edge polishing profiles and can adjust the combination of forces applied to an annular edge region of a substrate to tailor the polishing rate within that region. In some implementations, the system can increase the effective pressure across at least a portion of the region and decrease the effective pressure across other portions of the region to adjust the polishing rate for a specific region of the substrate. Consequently, the polishing process of an annular edge region of a layer on a substrate can be dynamically controlled with greater resolution.

[0010] More specifically, the magnitude of the effective pressure and the effective area of ​​the edge region are determined based on the combination of loading from each chamber (ie, distributed and concentrated forces), providing more flexibility to apply a specific pressure distribution to the exterior of the wafer.

[0011] 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 will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic cross-sectional view of an example of a polishing apparatus is illustrated.

[0013] Figure 2 A schematic cross-sectional view of a carrier head is shown.

[0014] Figure 3 is a schematic cross-sectional view of a pressure control assembly for controlling pressure on an edge region of a substrate.

[0015] Figures 4A-4C Each diagram illustrates another example of a pressure control assembly.

[0016] Figures 5A-5C Schematic illustration of how a pressure control assembly applies an effective force to an area of ​​a substrate.

[0017] Figures 6A-6C Graphic Figure 3 Schematic cross-sectional views of a pressure controller assembly in different states.

[0018] Figures 7A-7FGraphic Figure 4A Schematic cross-sectional views of a pressure controller assembly in different states.

[0019] Figures 8A-8F Graphic Figure 4B Schematic cross-sectional views of a pressure controller assembly in different states.

[0020] Figures 9A-9C Graphic Figure 4C Schematic cross-sectional views of a pressure controller assembly in different states.

[0021] Figure 10 is a flow chart illustrating an example edge profile control process using a pressure controller assembly during polishing.

[0022] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0023] In an idealized process, the polishing rate across the substrate would be radially uniform from the substrate's axis of rotation due to the rotation of the carrier head and table. However, in practice, the polishing process can result in radial variations in the polishing rate. Furthermore, the substrate being polished may have initial radial non-uniformity, i.e., the top layer may have an initial thickness that varies radially from the substrate's axis of rotation.

[0024] Variations in polishing rates between different regions of the substrate, or a non-uniform initial profile of the substrate, or both, can cause different regions of the substrate to reach their target thicknesses at different times.

[0025] More specifically, if polishing of regions is stopped simultaneously, different regions of the substrate may not reach the desired thickness, resulting in a non-uniform thickness profile on the substrate. Specifically, an annular region approximately 10 mm wide and beginning approximately 4-6 mm from the edge of the substrate (also referred to as a "check mark region") may be substantially free of non-uniformity. Specifically, after the polishing process, the check mark region may have a slower polishing rate or be under-polished compared to the central region of the substrate.

[0026] A technique for correcting the polishing rate in the calibration mark region is to modify the pressure in the outermost chamber of the carrier head. This changes the pressure at the edge region of the substrate (e.g., the outermost 15-20 mm of the substrate). However, increasing the pressure in the outermost chamber can result in significant over-polishing of the outermost 1-2 mm of the substrate.

[0027] However, a carrier head employing the techniques described herein can provide superior control over pressure distribution and reduce non-uniformity near the substrate edge. The carrier head can include a pressure control assembly comprising a first annular diaphragm forming one or more pressurizable chambers and an annular body having one or more downwardly protruding lower rods. Optionally, the annular body can include a second annular diaphragm forming another pressurizable annular chamber. In practice, the system can adjust the pressure within each chamber formed by the annular diaphragms, using a controller to control both the size of the contact area between the assembly and the substrate and the pressure across the contact area. These chambers can also deform due to different pressures within the other annular chamber. Specifically, the other chamber can deform to displace one or more lower rods downward to contact and apply force to the substrate's concentration area. The assembly can apply a distributed force within the substrate's controllable contact area, a concentrated force at the substrate's controllable concentration area, or both a distributed force within the substrate's controllable contact area and a concentrated force at the substrate's controllable concentration area.

[0028] Therefore, the system can apply various combinations of distributed and focused forces to the edge region of the substrate in a controllable manner with high resolution. In view of this, the system can achieve effective control of polishing the edge region of the substrate, thereby allowing the reduction of non-uniformity in the edge region of the substrate.

[0029] Figure 1 An example of a polishing apparatus 100 is shown. The polishing apparatus 100 includes a rotatable, disc-shaped table 120 on which a polishing pad 110 is positioned. The table 120 is operable to rotate about an axis 125. For example, a motor 121 can rotate a drive shaft 124 to rotate the table 120. The polishing pad 110 can be removably secured to the table 120, for example, via an adhesive layer. The polishing pad 110 can be a dual-layer polishing pad having an outer polishing layer 112 and a softer backing layer 114.

[0030] The polishing apparatus 100 may include a dispensing port 130 for delivering a polishing liquid, such as a polishing slurry, onto the polishing pad 110. The polishing apparatus may also include a polishing pad conditioner for grinding the polishing pad 110 to maintain the polishing pad 110 in a consistent polishing state.

[0031] The polishing apparatus 110 may include a carrier head 140 operable to hold the substrate 10 against the polishing pad 110. The carrier head 140 may be configured to independently control polishing parameters, such as pressure, for each of a plurality of zones on the substrate 10.

[0032] The carrier head 140 is suspended from a support structure 150 (e.g., a turntable) and is connected to a carrier head rotation motor 154 via a drive shaft 152, enabling the carrier head to rotate about an axis 155. Optionally, the carrier head 140 can be caused to oscillate laterally, for example, on a slider on the turntable 150, or by the turntable's own rotational oscillation. In operation, the table is caused to rotate about its central axis 125, and each carrier head is caused to rotate about its central axis 155 and translate laterally across the top surface of the polishing pad.

[0033] The carrier head 140 may include: a housing 144 that can be connected to the drive shaft 152; a support plate 184 that can extend above the flexible central diaphragm 182; an annular pressure control assembly 195 that surrounds the flexible central diaphragm 182; and a retaining ring 142 that surrounds the annular pressure control assembly 195 to hold the substrate 10 below the flexible central diaphragm 182.

[0034] The lower surface of the flexible central diaphragm 182 provides a mounting surface for the substrate 10. The flexible central diaphragm 182 may include one or more flaps fixed to a support plate 184 to form one or more pressurizable chambers. These chambers are connected to one or more pressure supplies 181 via corresponding pressure supply lines 183 to apply different pressures to the inner region of the substrate (e.g., an area at least 6 mm away from the edge of the substrate) during polishing, allowing the system to adjust the corresponding polishing area on the corresponding area in the substrate.

[0035] The pressure control assembly 195 may also form one or more pressurizable chambers. Each of the pressurizable chambers is connected to a different pressure supply 181 via a corresponding pressure supply line 183. A detailed structural description of the pressure control assembly 195 will be discussed below.

[0036] The polishing apparatus may further include a valve assembly 189, for example, a device for controllably connecting the various chambers to various pressure supplies. For example, the valve assembly may be mounted on top of the housing 144 of the carrier head 140, such as Figure 1 For another example, the valve assembly can be mounted on top of a support plate 184 inside the carrier head 140. Alternatively, each chamber can also be directly connected to the pressure supply 181 via a pressure supply line 183, as discussed above.

[0037] The polishing apparatus may include a controller 190 for controlling the pressure of each chamber formed within the pressure control assembly 195. For example, in the case where the pressure valve assembly 189 is in use, each chamber of the pressure control assembly may be connected to a dedicated valve in the valve assembly 189 via a corresponding pressure output line 187. Each pressure output line 187 may be provided by a passage through the housing 144, or by a flexible tube, or both. Although for ease of illustration, Figure 1 Only one pressure output line 187 is shown in FIG, but there will be a separate pressure output line 187 for each chamber within the pressure control assembly 195.

[0038] The valve assembly 189 can receive multiple pressure inputs from multiple pressure sources 181 via multiple pressure supply lines 183. Figure 1 1 and 156. The pressure supply line 183 and pressure source 181 are shown in FIG. 1 , but there may be more pressure supply lines, for example, eight to sixteen pressure supply lines, and there may be more pressure sources, for example, eight to sixteen pressure sources. The pressure supply line 183 may be provided by a passage through the drive shaft 185 and / or the housing 144, and / or by a flexible tube, and by a rotary joint 214 extending through the housing 144. Pressure may be directed from a stationary component (e.g., the pressure source 183) to the carrier head 140 through the rotary pneumatic joint 156.

[0039] Figure 2 A schematic cross-sectional view of carrier head 140 is shown. Carrier head 140 includes a support plate 184 and a central diaphragm 182 having a plurality of annular flaps 204. These flaps may be secured to support plate 184 via reinforcement. Central diaphragm 182 may be made of a flexible and slightly elastic material, such as a rubber such as silicone rubber or neoprene. The diaphragm may be formed from a thermoset material by using a mold to form the molded diaphragm into a single body.

[0040] In some implementations, the support plate 184 is coupled to the housing 144 via a flexure 210 (e.g., an annular diaphragm) formed of plastic or rubber (e.g., silicone rubber or neoprene). The inner edge of the flexure 210 can be clamped between the top of the support plate 184 and a clamping ring 212, and the outer edge of the flexure can be clamped between the retaining ring 142 and the housing 144.

[0041] The area between the support plate 184 and the housing 144 may be sealed by an inflatable seal 220 , such as by a flexible diaphragm or bellows, to form a pressurizable upper chamber 222 between the housing 144 and the support plate 184 .

[0042] Alternatively, the flexure 210 can provide a seal. The pressure in the upper chamber 222 can thus control the vertical position of the support plate 184, or the downward pressure of the support plate 184 on the central diaphragm 182. In some implementations, the pressure in the upper chamber 222 can control the pressure of the retaining ring 142 on the polishing pad. In some implementations, the central diaphragm 180 is clamped directly to the housing 144; the separate support plate 184 is omitted, and its function is provided by the housing 144.

[0043] The carrier head 140 further includes an annular pressure control assembly 195 positioned between the retaining ring 142 and the central diaphragm 182. The assembly 195 includes an actuator 256 that is positioned below the housing 144, for example, below the flexure 210. In some implementations, the top of the actuator 256 can be constrained by the bottom surface of the flexure 210 such that the top of the actuator 256 cannot move vertically.

[0044] Actuator 256 may include a pressurizable bladder 285 connected to a corresponding pressure output line 187 or directly to pressure supply line 183 (not shown). Valve assembly 189 or pressure supply 181 may provide or vary the pressure applied to pressurizable bladder 285. Bladder 285 may be made of a deformable material (such as plastic or rubber, for example, silicone rubber or neoprene) so that bladder 285 can deform due to changes in pressure within the bladder. Alternatively, actuator 256 may be provided by a motor (e.g., a linear actuator or a piezoelectric device).

[0045] The pressure control assembly 195 also includes an annular body 254 that is vertically movable relative to the housing 144 via an actuator 256. The annular body 254 includes an upper portion 254a and at least one lower rod 290 projecting downwardly from the upper portion 254a. The annular body is made of a hard plastic or metal, such as polyetherketone (PEEK) or polyphenylene sulfide (PPS) having a Young's modulus of approximately 400-500 ksi, or a metal such as aluminum or stainless steel. The upper portion 254 of the annular body is connected to the actuator 256. For example, the upper annular rod 261 of the annular body 254 can extend into a groove formed by the bottom surface of the pressurizable bladder 285.

[0046] To move annular body 254 , controller 190 may increase pressure within bladder 256 to expand the bladder, thereby applying substantially downward pressure to upper annular stem 261 to displace annular body 254 downward relative to housing 144 .

[0047] The pressure control assembly 195 further includes a first annular diaphragm 252 secured to an upper portion of the annular body 254 to form at least one lower pressurizable chamber (e.g., 281 and / or 283) between the first annular diaphragm 252 and the annular body 254, wherein at least one lower rod 290 is located within the at least one lower pressurizable chamber. The first annular diaphragm 252 can be secured to the upper portion 254a of the annular body 254 by a clamp or adhesive material, or by elastomeric overmolding of the diaphragm. The first annular diaphragm 252 can be made of any suitable elastic or plastic material having a Young's modulus of approximately 100 psi, such as a rubber, e.g., silicone rubber or neoprene.

[0048] In operation, the various chambers 222, 285, etc. can be pressurized so that the bottom surface of the first annular diaphragm 252 is at substantially the same height as the central diaphragm 182. Combined, the central diaphragm 182 and the annular diaphragm 252 cover substantially the entire top surface of the substrate 10 during polishing. The diaphragms 182, 252 can also adjust the pressure applied to corresponding areas of the substrate to correct local polishing rates. In some implementations, when the substrate is not being polished, a gap may exist between the central diaphragm 182 and the annular diaphragm 252, and when the substrate is being polished, the gap is closed under the appropriate pressure formed by the diaphragms 182 and 252 within each chamber.

[0049] Each of the one or more hypothetical chambers 281 , 283 formed by the first annular diaphragm 252 may be connected to the valve assembly 189 via a respective pressure output line 187 or may be connected directly to a respective pressure supply (not shown) via a respective pressure supply line 183 .

[0050] Because bladder 285 and each of chambers 281 and 283 are connected to respective pressure supplies, the area of ​​the base plate to which pressure is applied by assembly 195 can be controlled based on the overall combination of the chamber pressures. For example, the contact area between first annular diaphragm 252 and the base plate, or whether at least one lower rod 290 in a respective chamber can contact or exert a force on the top surface of the diaphragm, or both, depends on the pressure conditions within the bladder and each chamber. The pressure conditions can be, for example, the ratio of the pressure between the bladder and the chamber formed by the first annular diaphragm, or the ratio of the pressure within each chamber formed by the first annular diaphragm. Details of the different configurations resulting from different pressure conditions are further described below.

[0051] The pressurizable chamber formed by the first annular diaphragm may comprise two, three or more chambers. Details of alternative arrangements are further described below.

[0052] Furthermore, the number of lower rods may be three, five, or more, and the shape of the lower rods may be rectangular, cylindrical, or any other suitable shape that permits the force to be applied to a substantially concentrated area. One or more of the lower rods may further include a flange portion oriented in a substantially horizontal direction, for example, with the axial direction of the flange portion being in the horizontal direction. Details of alternative lower rod configurations are further described below.

[0053] Figure 3 is a schematic cross-sectional view of a pressure control assembly 195 for controlling pressure on an edge region of a substrate.

[0054] The pressure control assembly 195 includes an annular body 254 configured to be positioned over an edge region of the substrate 10. The annular body 254 may include one or more lower rods 290a, 290b, and 290c, and an upper post 261.

[0055] Pressure control assembly 195 also includes an actuator 256 secured above annular assembly 254. Actuator 256 includes a diaphragm or shell 310 that forms a pressurizable bladder 285. A passageway or conduit 325 through a portion of diaphragm 310 is configured to connect to an external pressure supply / output line 187b. Through pressure supply line 187b and passageway 325, pressurizable bladder 285 can be supplied with a specific amount of pressure. To connect with annular body 254, actuator 256 may include a groove 361 in a bottom surface of diaphragm 310. Groove 361 is configured to engage and be secured to upper stem 261 of the annular body, e.g., by a press fit or adhesive attachment, to name a few examples.

[0056] The pressure control assembly 195 further includes a first annular diaphragm 252 secured to the upper portion 254a of the annular body 254 to form one or more pressurizable chambers 281, 283 with the lower portion of the annular body. The first annular diaphragm 252 can be secured to the annular body 254 by any suitable connection (e.g., by a clamp ring 305 or an adhesive). Each of the diaphragms 281, 283 formed by the first annular diaphragm 252 can enclose one or more lower rods 290a, 290b extending downwardly from the annular body 254.

[0057] During an initial state, e.g., prior to a polishing operation, the lower rods are not in contact with the inner surface of the diaphragm 252. However, at least one of the lower rods is configured to displace to contact a focused region of a corresponding portion of the inner surface of the diaphragm 252 and exert a force in that focused region. During polishing, this results in a focused force being transmitted in a narrow annular region on the back surface of the substrate. At least one of the lower rods 290 can be displaced, for example, by one or more pressure changes in one or more chambers 281, 283, or a pressure change in the bladder 285, or both.

[0058] Each chamber 281 and 283 includes a channel, a tube, or both for connecting to a corresponding pressure supply / output line 187 to apply a corresponding pressure in each chamber. Each channel can be positioned through any suitable portion of the diaphragm 252 or the annular body 254. For example, channel 315 is formed from the top surface of the annular body 254 and extends substantially downward to the lower surface of the lower rod 290a. As another example, channel 320 is formed from the side surface of the annular body 254 and extends horizontally for a first portion, and then extends substantially downward for a second portion to the bottom surface of the annular body 254. Optionally, each channel can include a pipe or tube for connecting to a corresponding pressure supply line.

[0059] In the case where the polishing apparatus 100 includes the valve assembly 189, each pressure supply line 187a, 187b, and 187c is connected to a corresponding valve in the valve assembly 189 to apply a specific pressure to the corresponding chamber 281, 283, and 285. The controller 190 can control the pressure change in each chamber through the valve assembly 190 so that the final configuration of the assembly 195 changes accordingly.

[0060] The above-described materials, shapes, and configurations for each component of assembly 195 are purely exemplary for ease of illustration, and any other suitable materials, designs, and configurations may also be employed.

[0061] Figures 4A-4C Each illustrates another example of a pressure control assembly 195. In some implementations, reference Figure 4A , the annular body 254 of the pressure control assembly 195 may include a second annular diaphragm 254b fixed to the annular body 254 to define the upper annular chamber 450. At least one lower rod 290 is fixed to the bottom surface of the second annular diaphragm. The second annular diaphragm 254b is configured to deform downward in response to an increase in pressure in the upper annular chamber 450, thereby displacing the at least one lower rod (e.g., 290b) downward, thereby contacting and exerting a force on the top surface of the first annular diaphragm 252.

[0062] In some embodiments, the first annular diaphragm 252 is fixed to the annular body 254 to define a single lower chamber 481. Each of the chambers 285, 450, and 481 is independently pressurizable and each is connected to a pressure supply line via a corresponding channel or tube. For example, the upper annular chamber 450 can be connected to the pressure supply line using a tube 413 in a channel passing through one side of the annular body 254. As another example, the chamber can be connected to the pressure supply line via a channel 415 located on the other side of the wake body 254.

[0063] In addition, one of the lower rods (e.g., the radially outermost rod 290a) includes a flange 291a extending radially outward (radially outward from the center of the carrier head) into the chamber 481. The flange 291a can have any suitable annular profile. For example, the surface of the flange 291a can be planar and horizontal, planar and tilted relative to the horizontal, or non-planar. When the rod 290a with the flange 291a contacts the substrate and applies a focused force to the substrate, the applied force should be less than that of a rod without the flange.

[0064] In some implementations, reference Figure 4B In the configuration presented in FIG. 1 , the first annular diaphragm 252 may form two chambers 483 and 485, as for Figure 3 The first chamber 483 includes a lower rod 290a having an inwardly extending flange 291a, and the second chamber 485 includes two lower rods 290b, 290c without flanges. Each of the chambers 285, 450, 483 and 485 is connected to a different pressure supply line through a corresponding channel or pipe.

[0065] Each lower rod may have a corresponding length, width and depth. Alternatively, each lower rod may be substantially the same in shape. The bottom surface of one or more lower rods may be configured to be coplanar in the initial state. Alternatively, the bottom surface of the lower rod may be positioned in different horizontal positions. Specifically, in an implementation that does not include the upper annular chamber 450, the two rods in the rod may have a coplanar bottom surface so that pressure is applied to two separated annular regions by the two rods. On the other hand, in an implementation that includes the upper annular chamber 450, when the upper annular chamber 250 is not pressurized, the rod (e.g., middle rod 290b) attached to the second annular diaphragm may be shorter or have a slightly concave bottom surface.

[0066] In some implementations, reference Figure 4CIn the configuration presented in FIG, the first annular diaphragm 252 can form three chambers 487, 488 and 489, each of which has a corresponding lower rod. Similarly, each of the chambers 285, 487, 488 and 489 is connected to a different pressure supply line.

[0067] Figures 5A-5C A schematic diagram illustrates how pressure control assembly 195 applies effective forces to regions of a substrate. Initially, assembly 195 adjusts the magnitude of the applied forces in a manner similar to system 500 to apply forces of varying magnitude and type to different regions of substrate 515. Based on Newton's laws, the forces presented in the figures described below are reaction forces, each having the same magnitude but opposite direction to the corresponding force applied to the substrate. For simplicity, these reaction forces are also referred to as forces applied to the substrate.

[0068] refer to Figure 5A Schematic system 500 includes a spherical or annular bladder 520 formed from a spherical or annular diaphragm 520, along with a pressure P contained within, a fixture-shaped part 510 placed on top of the bladder, and a substrate 515 on which the bladder 520 is initially placed. The fixture-shaped part 510 includes a horizontal portion 510a and a vertical portion 510b. The horizontal portion of the part 510 contacts the upper portion of the bladder in such a way that the initial contact area between the part 510 and the bladder 520 can be a substantially point or circular area (depending on whether the fixture is circular). The vertical portion 510b of the part 510 is not initially in contact with the substrate 515 or the bladder 520, but is configured to displace downwardly under the influence of a force applied to the horizontal portion of the part 510. The bladder is also deformable under both the internal pressure P and an external force.

[0069] Initially, a downward force F, or a force substantially associated with gravity, is applied to horizontal portion 510a of part 510. Within the area of ​​contact region 510 between bladder 520 and substrate 515, a certain pressure 525 is exerted on the substrate due to force F. The magnitude of pressure 525 depends on the magnitude of the downward force and the area of ​​contact region 501 between bladder 520 and substrate 515. Pressure 525 and the like are referred to as distributed forces or loads in the following description.

[0070] refer to Figure 5BAs the magnitude of the downward force F increases, the bladder 520 deforms into an elliptical cross-sectional profile, and the part 510 and its vertical portion 510b are displaced downwardly closer to the substrate 515. The pressure 545, or distributed force, applied by the bladder to the substrate increases as the downward force F increases. Alternatively or additionally, the contact area 501 between the bladder 520 and the substrate 515 may increase. The amount of change in the contact area between the bladder and the substrate depends, at least in part, on the mechanical properties of the material from which the bladder is made, the magnitude of the internal pressure P, and the magnitude of the downward force F.

[0071] refer to Figure 5C , the magnitude of the downward force F increases further, causing the bladder 520 to further deform, and the vertical portion 510b of the component to displace further downward, ultimately contacting the substrate 515 within the second contact area 502 and applying a force directly to the substrate 515 within the second contact area 502. If the bottom surface 511 of the vertical portion 510b has a narrow profile, e.g., no wider than 5 mm, no wider than 3 mm, or no wider than 2 mm, the applied force can be considered a concentrated force, or a concentrated force, or more generally, a concentrated pressure 570.

[0072] In some implementations, the different internal pressures P of the chamber can be varied to change the contact area between the bladder and the substrate while maintaining the same external load F. Thus, the system 500 can have more different magnitudes and types of forces applied to different areas of the substrate using different combinations of downward force F and internal pressure P, a concept similarly employed in the techniques described below.

[0073] In the following instructions, we will combine Figures 6A-6C 、 Figure 7A-7B 、 Figures 8A-8F as well as Figure 9A - Figure 9C To describe Figure 3 and Figures 4A-4C The different states of each example configuration of the assembly 195 are presented in FIG. The details of each state in conjunction with the polishing area of ​​the different edge areas will be discussed below.

[0074] Figures 6A-6C Graphic Figure 3 Schematic cross-sectional views of the pressure controller assembly 195 in different states.

[0075] Back reference Figure 3The first example pressure controller assembly 195 includes three chambers: a bladder formed by the actuator 256 and two chambers 281 and 283 formed by the first annular diaphragm 252. Each chamber is connected to a corresponding pressure supply P1, P2, and P3. The pressures P1, P2, and P3 are variable by either: a variable pressure supply tank; or by switching between different pressure supplies via the valve assembly 189 under the control of the controller 190. In the equilibrium state, the pressure P1 should be balanced with the other two pressures P2 and P3.

[0076] refer to Figure 6A , assembly 195 is in a first state, in which the lower rod is not displaced and in contact with the first diaphragm. Therefore, in this first state, assembly 195 applies only distributed forces 610 and 620 to substrate 10, where the magnitudes of pressures 610 and 620 are equal to pressures P3 and P2 in the corresponding chambers. This first state is also referred to as a wide contact patch.

[0077] refer to Figure 6B , assembly 195 is now in the second state. In order to change from the first state to the second state, assembly 195 increases the pressure of P2 and P3 so that in the equilibrium state, the contact area between the first annular diaphragm and the substrate is reduced. In equilibrium, the increased P2 and P3 multiplied by the reduced contact area is equal to P1 multiplied by the contact surface of the upper rod. In some implementations, as long as the ratio of (P2+P3) to P1 increases, assembly 195 can increase P1, P2 and P3 together to reach the second state. In the second state, assembly 195 can apply an increased amount of pressure 630 and 640 to a smaller area in the substrate, thereby increasing the polishing rate in the smaller area. The magnitude of pressure 630 and 640 is based on the pressure P3 and P2 in each chamber, respectively. The second state is also referred to as a narrow contact patch.

[0078] refer to Figure 6C, assembly 195 is now in the third state. To transition from the first state to the third state, assembly 195 increases pressure P1, displacing one or more lower rods downward, thereby contacting and applying force to the first diaphragm. Because the contact area between the lower rods and the first diaphragm is small, assembly 195 ultimately applies a relatively concentrated force to the substrate. For example, the central rod of the annular body contacts the first diaphragm and subsequently applies a concentrated force 660 to the substrate. As long as the ratio of (P2 + P3) to P1 decreases, the assembly can alternatively increase P1, P2, and P3 together, and P1 is sufficiently greater than P2 and P3 to displace one of the rods into contact with the first diaphragm. Other forces exerted on the substrate are distributed forces 650 and 670, which depend on the internal pressures P3 and P2 within each chamber, respectively. In the third state, assembly 195 can apply both distributed loads and distributed forces to the edge region. More specifically, assembly 195 can control (e.g., increase) the polishing rate in the central region of the substrate edge in a concentrated manner by using the concentrated force 660. The third state is also called a center-grouped wide contact patch.

[0079] Figures 7A-7F Graphic Figure 4A Schematic cross-sectional views of the pressure controller assembly 195 in different states.

[0080] Back reference Figure 4A , the second example pressure controller assembly 195 includes three chambers, namely, a bladder formed by the actuator 256, a single chamber 481 formed by the first diaphragm, and a chamber 450 formed by the second annular diaphragm (e.g., annular body 254). Each chamber is connected to a corresponding pressure supply P1, P2, and P5, and the pressures P1, P2, and P5 are interchangeable to allow the assembly 195 to achieve different states.

[0081] refer to Figure 7A , assembly 195 is in a first state, in which the lower rod is not displaced and in contact with the first diaphragm. Therefore, in this first state, assembly 195 applies only a uniformly distributed force 710 on substrate 10, where the magnitude of pressure 710 is equal to pressure P2 within chamber 481. This first state is also referred to as a wide contact patch.

[0082] refer to Figure 7B, assembly 195 is in a second state. In the second state, no lower rod contacts the first diaphragm, and the assembly applies a uniform distributed load 715 to a smaller area of ​​substrate 10 (compared to the first state). To change from the first state to the second state, assembly 195 can reduce the ratio of P1 to P2 and maintain P5 less than P2. The second state is also known as a narrow contact patch and is used to control the polishing rate of a smaller edge area during polishing.

[0083] refer to Figure 7C , assembly 195 is in the third state. In the third state, the outermost lower rod 290a displaces downward, ultimately contacting the first diaphragm and applying a concentrated force 720 thereto. Consequently, assembly 195 applies both a uniformly distributed load 725 and a concentrated force 720 to substrate 10. To transition from the first state to the third state, assembly 195 increases the ratio of P1 to P2 while maintaining pressure P5 less than pressure P2. The third state, also known as an outer, concentrated, widened contact patch, is used to apply higher pressure to the outer edge regions while still applying pressure across a wide area.

[0084] refer to Figure 7D , assembly 195 is in the fourth state. In the fourth state, central lower rod 290b displaces downward, ultimately contacting the first diaphragm and applying concentrated force 730 thereto. Thus, assembly 195 applies both a uniformly distributed load 735 and concentrated force 730 to substrate 10. To transition from the first state to the fourth state, assembly 195 increases the ratio of pressure P5 to pressure P2. This fourth state, also known as a center-focused widened contact patch, is used to apply higher pressure to the center region while still applying pressure across a wide area.

[0085] refer to Figure 7E , assembly 195 is in the fifth state. In the fifth state, both outermost lower rod 290a and central lower rod 290b are displaced downward, ultimately contacting the first diaphragm and applying concentrated forces 740 and 745 to the first diaphragm. Consequently, assembly 195 applies a uniformly distributed load 750 to the edge regions, a concentrated force 740 to the outer edge regions, and another concentrated force 745 to the central edge region of substrate 10. To transition from the first state to this state, assembly 195 increases the ratio of pressure P1 to pressure P2, or to pressure P5, or to pressure P2 + P5, and increases the ratio of pressure P5 to pressure P2. The fifth state, also referred to as a wide contact patch with outer and central concentrations, is used to apply more concentrated pressure to both the outer and central edge regions.

[0086] refer to Figure 7F, assembly 195 is in the sixth state. Only central lower rod 290b is displaced downward, contacting the first diaphragm and applying concentrated force 755 to the first diaphragm. Consequently, assembly 195 applies a uniformly distributed load 760 to the edge region and a concentrated force 755 to the central edge region of substrate 10. To transition to this state, the assembly decreases the ratio of pressure P1 to both pressures P2 and P5, and increases the ratio of pressure P5 to P2. The sixth state, also known as a centrally concentrated narrow contact patch, applies higher pressure to the central edge region, but with a narrower overall control area (compare to FIG. 7D ).

[0087] Figures 8A-8F Graphic Figure 4B Schematic cross-sectional views of the pressure controller assembly 195 in different states.

[0088] Back reference Figure 4B The third example pressure controller assembly 195 includes four chambers, namely, a bladder formed by the actuator 256, chambers 483 and 485 formed by the first diaphragm, and chamber 450 formed by the second annular diaphragm 254b (or annular body 254). Each chamber is connected to a corresponding pressure supply P1, P2, P3, and P5, and the pressures P1, P2, P3, and P5 are interchangeable to allow the assembly 195 to reach different states.

[0089] refer to Figure 8A , assembly 195 is in a first state, in which no lower rod is displaced and in contact with the first diaphragm. Therefore, in the first state, assembly 195 applies distributed pressures 805 and 810 only to the outer and inner edge regions of substrate 10. The magnitude of each pressure 805 and 810 is equal to the corresponding pressures P3 and P2. This first state is also referred to as a wide contact patch.

[0090] refer to Figure 8B , assembly 195 is in the second state. In the second state, no lower rod contacts the first diaphragm. Therefore, the assembly applies distributed loads 815 and 820 to smaller inner and outer regions of substrate 10. To change from the first state to the second state, assembly 195 can increase the ratio of P2 + P3 to P1 and maintain P5 less than P2 + P3. The second state, also known as a narrow contact patch, is used to control the polishing rate of smaller edge regions during polishing.

[0091] refer to Figure 8C, assembly 195 is in the third state. In the third state, the outermost lower rod 290a displaces downward, ultimately contacting the first diaphragm and applying a concentrated force 825 to the first diaphragm. Consequently, assembly 195 applies uniformly distributed loads 830 and 835 to the outer and inner edge regions, exerting a concentrated force 825 on substrate 10. To transition from the first state to this state, assembly 195 increases the ratio of P1 to P2, or to P3, or to P2 + P3, while maintaining pressure P5 less than pressure P2. The third state, also known as an outer focused widened contact patch, is used to apply higher pressure to the outer edge regions while still applying pressure across a wide area.

[0092] refer to Figure 8D , assembly 195 is in the fourth state. In the fourth state, central lower rod 290b displaces downward, ultimately contacting the first diaphragm and applying concentrated force 845 to the first diaphragm. Assembly 195 thus applies uniformly distributed loads 840, 850 to the outer and inner edge regions, and applies concentrated force 845 to substrate 10. To transition from the first state to this state, assembly 195 increases pressure P5 relative to P2, or relative to P3, or relative to the ratio of P2 + P3. This fourth state, also known as a center-focused widened contact patch, is used to apply higher pressure to the center region while still applying pressure across a wide area.

[0093] refer to Figure 8E , assembly 195 is in the fifth state. In the fifth state, both outermost lower rod 290a and central lower rod 290b are displaced downward, contacting the first diaphragm and applying concentrated forces 855 and 865 to the first diaphragm. Consequently, assembly 195 applies uniformly distributed loads 860 and 870 to the outer and inner edge regions, applies concentrated force 855 to the outer edge region, and applies another concentrated force 865 to the central edge region of substrate 10. To transition from the first state to this state, assembly 195 increases the ratio of pressure P1 to both pressures P2 and P3, and increases pressure P5 to P2, or to P3, or to the ratio of P2 + P3. The fifth state, also referred to as a wide contact patch with outer and central concentrations, is used to apply more concentrated pressure to both the outer and central edge regions.

[0094] refer to Figure 8F, assembly 195 is in the sixth state. In the sixth state, only the central lower rod 290b is displaced downward, thereby contacting the first diaphragm and applying a concentrated force 880 to the first diaphragm. Therefore, assembly 195 applies uniform distributed loads 875 and 885 to the outer edge region and the inner edge region, and applies a concentrated force 880 to the central edge region of substrate 10. To change from the first state to this state, assembly 195 increases the ratio of pressure P1 to both pressures P2 and P3, and increases pressure P5 to P2, or to P3, or to the ratio of P2+P3. The sixth state is also referred to as a center-focused plus narrow contact patch, which is used to apply higher pressure to the central edge region, but with a narrower total control area (compared to FIG. 8D ).

[0095] Figures 9A-9C Graphic Figure 4C Schematic cross-sectional views of the pressure controller assembly 195 in different states.

[0096] See back Figure 4C The fourth example pressure controller assembly 195 includes four chambers, namely, a bladder formed by the actuator 256, and chambers 487, 488, and 489 formed by the first diaphragm. Optionally, the assembly 195 may include another chamber (not shown) formed by the second diaphragm 254b of the annular body 254. Each chamber is connected to a corresponding pressure supply P1, P2, P3, and P4, and the pressures P1, P2, P3, and P4 are interchangeable to permit the assembly 195 to achieve different states.

[0097] refer to Figure 9A , assembly 195 is in a first state, in which no lower rod is displaced and in contact with the first diaphragm. Therefore, in the first state, assembly 195 applies distributed pressures 905, 910, and 915 only to the three edge regions of substrate 10. The magnitude of each pressure 905, 910, and 915 is equal to the corresponding pressures P4, P3, and P2. This first state is also referred to as a wide contact patch.

[0098] refer to Figure 9B, assembly 195 is in a second state. In the second state, none of the lower rods are in contact with the first diaphragm, and central chamber 488 is not in contact with substrate 10. Therefore, assembly 195 applies distributed loads 940 and 945 to two regions of substrate 10 with smaller areas (i.e., the inner and outer regions). To change from the first state to the second state, assembly 195 can reduce the ratio of pressure P1 to pressure P2, or to pressure P4, or to pressure P2 + P4. Optionally, assembly 195 can also reduce the ratio of pressure P3 to pressure P1, or to pressure P2, or to pressure P4, or to any combination of pressures P1, P2, and P4. The second state, also known as a narrow contact patch, is used to control the polishing rate of smaller edge regions during polishing.

[0099] refer to Figure 9C , assembly 195 is in a third state. In the third state, the outermost lower rod is displaced downward, contacting the first diaphragm and applying concentrated force 925 to the first diaphragm. Assembly 195 thus applies uniformly distributed loads 920, 930, and 935 to the outer edge region, the central marginal region, and the inner edge region, and applies concentrated force 825 to the outer region of substrate 10. To move from the first state to this state, assembly 195 increases the ratio of pressure P1 to P2, and optionally increases the ratio of pressure P1 to P3, or to P4. The third state, also referred to as an outer, concentrated wide contact patch, is used to apply more concentrated pressure to the outer edge region.

[0100] Figure 10 is a flow chart illustrating an example edge profile control process 1000 using a pressure controller assembly during polishing. The process may be performed by one or more computers located in one or more locations. Alternatively, the process 1000 may be stored as instructions in one or more computers. Once executed, these instructions may cause one or more components of a polishing apparatus to perform the process. For example, Figure 1 The controller 190 shown in FIG. 1 or the in-situ monitoring system 160 including the controller 190 may perform process 1000. In some implementations, the in-situ monitoring system 160 may include an optical monitoring system, such as a spectrophotometric monitoring system. In other implementations, the in-situ monitoring system 160 may include an eddy current monitoring system.

[0101] like Figure 1As shown in FIG, in-situ monitoring system 160 includes a sensor 164 and circuitry 166 coupled to the sensor for sending and receiving signals to and from a controller 190 (e.g., a computer). Sensor 164 can be, for example, the end of an optical fiber for collecting light for an optical monitoring system, or the core and coil of an eddy current monitoring system. The output of circuitry 166 can be a digital electronic signal that is transmitted to controller 190 via a rotary coupler 129 (e.g., a slip ring) in drive shaft 124. Alternatively, circuitry 166 can communicate with controller 190 via wireless signals.

[0102] The system first receives data representing a desired thickness profile for a polished substrate. The desired thickness profile may be specified via a user input interface, by a user request, or may be encoded in a computer program executed by controller 190. Controller 190 may then determine a desired thickness for an edge region of the substrate based on the received data (1002).

[0103] The system determines the measured thickness of the edge region of the substrate (1004). More specifically, for each measurement, the controller 190 can calculate a characterizing value. The characterizing value is typically the thickness of the layer under polishing, but can also be a related property, such as the thickness removed. In addition, the characterizing value can be a physical property other than thickness, such as metal line resistance. In addition, the characterizing value can be a more general representation of the substrate's progress through the polishing process, such as an index value that indicates the time or number of stage rotations at which the spectrum will be observed during the polishing process after a predetermined progress. The system can then determine the difference between the current polishing rate and the desired polishing rate to achieve the desired thickness profile in the edge region of the substrate after polishing.

[0104] In response, the system can periodically adjust the polishing rate. In some implementations, the system adjusts the polishing rate at a predetermined rate, such as every given number of revolutions, e.g., every 5 to 50 revolutions, or every given number of seconds, e.g., every 2 to 20 seconds, as scheduled. In some ideal cases, the adjustment can be zero at the pre-scheduled adjustment time. In other implementations, adjustments can be made at a rate determined in situ. For example, if the measured thickness of the edge region differs significantly from the expected thickness profile, the controller 190 and / or computer can determine the frequency of the polishing rate adjustments.

[0105] In order to adjust the polishing rate at the edge region of the substrate under polishing at a given adjustment rate, the controller 190 may apply different combinations of loads having different types and sizes after determining the combinations.

[0106] Therefore, in response to determining the difference, the system determines a combination of loads to be applied to the loading area of ​​the edge region of the substrate (1006). More specifically, the system can determine the load type (concentrated force and distributed force) or component pattern (e.g., wide contact patches, narrow contact patches, centrally clustered wide contact patches, externally clustered wide contact patches, or external-centrally clustered wide contact patches as described above) to adjust the polishing rate on the corresponding edge region of the substrate to achieve substantially within-wafer uniformity after polishing.

[0107] After determining the load magnitude, load type, or assembly mode, the controller 190 controls the valve assembly 189 or the pressure supply tank 181 to change one or more pressures in one or more chambers to achieve the determined load or assembly mode (1008). As a result, when polishing the substrate, the system can accurately control the polishing rate at the corresponding portion of the edge region.

[0108] As used in this specification, the term substrate may include, for example, a production substrate (e.g., including multiple memory or processor dies), a test substrate, a bare substrate, and a gated substrate. A substrate may be at various stages of integrated circuit fabrication, for example, a bare wafer, or it may include one or more deposited and / or patterned layers. The term substrate may include both circular disks and rectangular sheets.

[0109] The polishing apparatus and method described above can be applied in a variety of polishing systems. The polishing pad, the carrier head, or both can be movable to provide relative motion between the polishing surface and the substrate. For example, the table can orbit rather than rotate. The polishing pad can be a round (or some other shaped) pad fixed to the table. Some aspects of the endpoint detection system can be applied to linear polishing systems, for example, where the polishing pad is a continuous or roll-to-roll belt that moves linearly. The polishing layer can be a standard (e.g., polyurethane with or without fillers) polishing material, a soft material, or a fixed abrasive material. The term relative positioning is used; it should be understood that the polishing surface and substrate can be held in a vertical orientation or some other orientation.

[0110] Control of the various systems and processes described in this specification, or portions thereof, can be implemented as a computer program product comprising instructions stored in one or more non-transitory computer-readable media, and these instructions are executable on one or more processing devices. The systems described in this specification, or portions thereof, can be implemented as apparatuses, methods, or electronic systems that may include one or more processing devices and memory storing executable instructions for performing the operations described in this specification.

[0111] Although this specification contains many specific implementation details, these implementation details should not be interpreted as limiting the scope of any invention or the scope of what may be claimed, but rather as descriptions of features that may be specific to a particular embodiment of a particular invention. Certain features described in this specification in the context of separate embodiments may also be implemented in a single embodiment in combination. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable subcombination. Furthermore, although features may be described above as functioning in certain combinations and even initially claimed as such, in some cases, one or more features from a claimed combination may be deleted from the combination, and a claimed combination may be directed to a subcombination or a variation of a subcombination.

[0112] Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims.

[0113] Other embodiments are within the scope of the following claims.

Claims

1. A carrier head for holding a substrate in a polishing system, comprising: case; a flexible central diaphragm having one or more flaps for forming one or more pressurizable chambers; retaining ring; an annular pressure control assembly located between the retaining ring and the flexible central diaphragm, the annular pressure control assembly comprising: an annular body that is vertically movable relative to the housing by an actuator, the annular body comprising an upper portion and at least one lower rod extending downwardly from the upper portion; and a first annular diaphragm fixed to the annular body and extending below the annular body to form at least one lower pressurizable chamber between the first annular diaphragm and the annular body, wherein the at least one lower rod is located inside the at least one lower pressurizable chamber; and at least one pressure supply line connected to the at least one lower pressurizable chamber.

2. The carrier head of claim 1, wherein the actuator comprises a pressurizable bladder between the housing and the annular body.

3. The carrier head of claim 2, wherein the bottom surface of the pressurizable bladder includes an annular groove, and the annular body includes an annular upper stem extending into the annular groove.

4. The carrier head of claim 3, wherein the bottom surface of the pressurizable bladder is configured to exert downward pressure on the annular upper stem of the annular body.

5. The carrier head of claim 2 , wherein the bottom surface of the first annular diaphragm is configured to apply pressure to the substrate in a loading area, the loading area comprising dimensions controlled by the pressure in the bladder and the pressure in the at least one lower pressurizable chamber.

6. A carrier head for holding a substrate in a polishing system, comprising: case; a flexible central diaphragm having one or more flaps for forming one or more pressurizable chambers; retaining ring; an annular pressure control assembly located between the retaining ring and the flexible central diaphragm, the annular pressure control assembly comprising: an annular body that is vertically movable relative to the housing by an actuator, the annular body comprising an upper portion and at least one lower rod extending downwardly from the upper portion; and a first annular diaphragm secured to the annular body and extending below the annular body to form at least one lower pressurizable chamber between the first annular diaphragm and the annular body, wherein the at least one lower rod is located within the at least one lower pressurizable chamber, wherein the annular body includes an upper portion for engaging the actuator and a second annular diaphragm secured to the upper portion to define the first chamber, wherein the at least one lower rod includes a first lower rod secured to a bottom portion of the second annular diaphragm, and wherein the second annular diaphragm is configured to deform downwardly in response to an increase in pressure in the first chamber to displace the first lower rod downwardly to contact a top surface of the first annular diaphragm and exert a force from the first lower rod on the top surface of the first annular diaphragm; and At least one pressure supply line is connected to the at least one lower pressurizable chamber.

7. The carrier head of claim 6, wherein the actuator comprises a pressurizable bladder, and wherein: An upper rod extends vertically upward from the top surface of the second annular diaphragm into the bladder bag.

8. The carrier head of claim 6, wherein the first downrod is out of contact with the top surface of the first annular diaphragm when pressure in the first chamber increases.

9. The carrier head of claim 6, wherein the at least one downrod comprises a second downrod secured to an edge of the annular body.

10. The carrier head of claim 9, wherein the second lower rod includes a downwardly extending flange.

11. The carrier head of claim 1 , wherein the at least one lower pressurizable chamber comprises two chambers, wherein: Each of the two chambers is connected to a respective pressure supply via one of the plurality of pressure supply lines.

12. The carrier head of claim 1, wherein the at least one downbar includes an inwardly extending flange.

13. The carrier head of claim 1, wherein the at least one downbar is secured to an edge of the annular body.

14. The carrier head of claim 13, wherein the at least one downbar includes an inwardly extending flange.

15. The carrier head of claim 1 , wherein the at least one lower pressurizable chamber comprises three chambers, wherein: Each of the three chambers encloses one of the at least one downrod, wherein each of the three chambers is connected to a respective pressure supply via one of the plurality of pressure supply lines.

16. The carrier head of claim 1 , comprising a plurality of pressure supplies, each pressure supply of the plurality of pressure supplies coupled to a corresponding pressure supply line of the plurality of pressure supply lines, and wherein: Each pressure supply is capable of independently adjusting the pressure in the at least one lower pressurizable chamber.

17. The carrier head of claim 1, wherein the first annular diaphragm is made of an elastomer.

18. The carrier head of claim 1, wherein the annular body is made of plastic.

19. The carrier head of claim 1, wherein the first annular diaphragm is configured to contact an area on the top surface of the substrate, the area expanding radially inward as a ring shape having a width of 4-6 mm from an edge of the substrate.

20. A carrier head for holding a substrate in a polishing system, comprising: case; a flexible central diaphragm having one or more flaps for forming one or more pressurizable chambers; retaining ring; an annular pressure control assembly positioned between the retaining ring and the flexible central diaphragm, the annular pressure control assembly comprising: a first annular diaphragm extending below the housing; means for controlling the size of a loading area in which a combination of loads is applied to the substrate; wherein the combination of loads comprises at least one of pressure and a focused force; means for controlling the pressure applied to the substrate in the loading area; and Means for controlling the focusing force applied to the substrate in a focusing region in the loading area.

21. The carrier head of claim 20, further comprising: a first annular diaphragm secured to the annular body and extending below the annular body to form at least one lower pressurizable chamber between the first annular diaphragm and the annular body, wherein at least one lower rod is located within the at least one lower pressurizable chamber; wherein the size of the loading area is controlled by a shape of the at least one lower pressurizable chamber, the shape being changeable based on a pressure in the at least one lower pressurizable chamber; wherein the focusing force applied to the substrate is controlled based at least in part on a pressure in the at least one lower pressurizable chamber.

22. The carrier head of claim 21, wherein the at least one lower rod is configured to contact the top surface of the first annular diaphragm and exert the focused force on the top surface of the first annular diaphragm based at least in part on the pressure in the at least one lower pressurizable chamber.

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