Polishing carrier head with multiple angularly pressurizable zones - Patent Application 20070122997

Abstract

To provide a carrier head for a polishing system which can compensate for angular variations in the thickness of a substrate and / or angular variations in the polishing rate of a polishing process.SOLUTION: A carrier head for a polishing system includes a housing, a flexible membrane, a first plurality of pressure supply lines, a second plurality of pressure supply lines, and a valve assembly. The flexible membrane defines multiple independently pressurizable chambers. The valve assembly has multiple valves coupled to respective pressure chambers from the multiple independently pressurizable chambers. Each valve is configured to selectively couple the respective pressure chamber to one pressure supply line from a pair of pressure supply lines that include a pressure supply line from the first plurality of pressure supply lines and a pressure supply line from the second plurality of pressure supply lines.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to profile control of a polishing process, and more particularly to a carrier head having a membrane with pressurizable areas arranged in multiple angular directions. [Background technology]

[0002] Integrated circuits are typically formed on a substrate (eg, a semiconductor wafer) by successive deposition of conductive, semiconductive, or insulating layers onto a silicon wafer and by sequential processing of the layers.

[0003] One manufacturing step involves depositing a filler layer over a non-planar surface and planarizing the filler layer. In certain applications, the filler layer is planarized until the top surface of the patterning layer is exposed or a desired thickness remains above the underlying layer. Furthermore, planarization can be used to planarize the substrate surface, for example, for dielectric layers, for lithography purposes.

[0004] Chemical-mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that a substrate be mounted on a carrier head. The exposed surface of the substrate is placed in contact with a rotating polishing pad. The carrier head exerts a controllable load on the substrate, pressing it against the polishing pad. In some situations, the carrier head includes a membrane that forms multiple independently pressurizable radial concentric chambers, and the pressure in each chamber controls the polishing rate in each corresponding region on the substrate. A polishing liquid (such as a slurry containing 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, a flexible membrane extending below the housing, a first plurality of pressure supply lines, a second plurality of pressure supply lines, and a valve assembly. The flexible membrane divides a space above the flexible membrane into a plurality of independently pressurizable chambers. The valve assembly is coupled to the first plurality of pressure supply lines, the second plurality of pressure supply lines, and the plurality of independently pressurizable chambers. The valve assembly includes a plurality of valves. Each respective valve of the plurality of valves is coupled to a respective pressure chamber from the plurality of independently pressurizable chambers. Each respective valve is configured to selectively couple the respective pressure chamber to one pressure supply line from a pair of pressure supply lines, including a pressure supply line from the first plurality of pressure supply lines and a pressure supply line from the second plurality of pressure supply lines.

[0006] In another aspect, a carrier head for holding a substrate in a polishing system includes a housing and a flexible membrane extending below the housing, the flexible membrane dividing a space above the flexible membrane into a plurality of independently pressurizable chambers arranged in a pole array.

[0007] Implementations may include one or more of the following features.

[0008] The plurality of independently pressurizable chambers may include a first plurality of independently pressurizable chambers, and the plurality of valves may include a first plurality of valves. Each different valve of the first plurality of valves may be configured to selectively couple a different pressure chamber of the first plurality of pressure chambers to a different pair of pressure supply lines. The plurality of independently pressurizable chambers may include a second plurality of independently pressurizable chambers, and the plurality of valves may include a second plurality of valves. Each different valve of the second plurality of valves may be configured to selectively couple a different pressure chamber of the second plurality of pressure chambers to a different pair of pressure supply lines.

[0009] At least one valve from the first plurality of valves and at least one valve from the second plurality of valves may couple each chamber to the same pair of pressure supply lines, e.g., for every valve from the first plurality of valves, there may be a corresponding valve from the second plurality of valves that couples each chamber to the same pair of pressure supply lines.

[0010] The plurality of independently pressurizable chambers may include chambers positioned at different angular positions about a central axis of the carrier head. The plurality of independently pressurizable chambers may include chambers positioned at different radial positions from the central axis of the carrier head.

[0011] The plurality of angularly separated chambers may be equally spaced about the central axis. The plurality of independently pressurizable chambers may be arranged in a pole array. The pole array includes a central chamber and a plurality of radial rings. Each radial ring may include a plurality of angularly separated chambers. Different pressure supply lines from a first plurality of pressure supply lines may be coupled to chambers in different rings. Different pressure supply lines from a second plurality of pressure supply lines may be coupled to chambers in different angular segments.

[0012] The support plate may be flexibly connected to the housing such that it is vertically movable relative to the housing. A flexible membrane may be fixed to the support plate, and a plurality of chambers may be formed between the flexible membrane and the support plate. The space between the support plate and the housing may be controllably pressurizable.

[0013] Particular implementations may include, but are not limited to, one or more of the following possible advantages.

[0014] Each independent chamber can be pressurized to apply a respective pressure to the substrate such that the applied pressure varies both radially and angularly around the center of the substrate being polished. This allows for profile control to compensate for angular variations in the thickness of the incoming substrate and / or angular variations in the polishing rate of the polishing process. The pressure applied across an area can be controlled by a valve switching between two pressure magnitudes applied to the chamber, which then applies a corresponding pressure to the area. Thus, the polishing process of each area of ​​a layer on the substrate can be independently controlled with greater precision. Furthermore, compared to using pressure chambers without valves, the method allows for scalability to a greater number of control areas in a more feasible manner. In particular, fewer rotary connections are required, and the number of rotary connections is orders of magnitude less than the number of independent pressurizable chambers.

[0015] 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 explanation of the drawings]

[0016] [Figure 1A] 1 shows a schematic cross-sectional view of an embodiment of a polishing apparatus. [Figure 1B] 1 shows a schematic cross-sectional view of a carrier head. [Figure 2A] 1 shows a schematic diagram illustrating a pressure control assembly for controlling pressure on a substrate. [Figure 2B] FIG. 1 shows a schematic bottom view of a carrier head having independently pressurizable chambers within a pole array. [Figure 2C] FIG. 2C shows an enlarged view of a section of the polar array from FIG. 2B. [Figure 3A] 1 shows a schematic top view of an exemplary annular valve assembly having a valve bank mounted on top of a support plate. [Figure 3B]1 shows a schematic top view of an exemplary valve bank. [Figure 4A] 1 shows a top view of a polishing pad, showing where in-situ measurements are made on a substrate. [Figure 4B] 10 shows a schematic top view of the distribution of multiple locations where in situ measurements are made on separate pressurizable chambers of a membrane. [Figure 5] FIG. 1 is a flow diagram illustrating an exemplary profile control process using an independent pressurizable chamber during polishing. DETAILED DESCRIPTION OF THE INVENTION

[0017] Variations in the polishing rate between different regions of a substrate can result in different regions of the substrate reaching their target thickness at different times. On the other hand, different regions of the substrate may not reach the desired thickness if polishing of multiple regions is stopped simultaneously. On the other hand, stopping polishing of different areas at different times can cause defects in the polishing apparatus or reduce throughput. Therefore, it is necessary to enable independent control of pressure for different regions.

[0018] In an ideal process, rotation of the carrier head and platen would cause the polishing rate on the substrate to be angularly symmetric about the substrate's axis of rotation. However, in practice, the polishing process can result in angular variations in the polishing rate. Furthermore, the substrate being polished may have a top layer with an initial thickness that varies angularly, i.e., has angular non-uniformity. Finally, in some manufacturing processes, it may be desirable to induce angular non-uniformity in the thickness of the polished layer to compensate for non-uniformity in a subsequent processing step, such as a deposition step. Eliminating angular non-uniformity induced by the polishing process when polishing a layer with an initial thickness that is angularly non-uniform, or intentionally providing angular variations in thickness when polishing a layer, remains a challenge.

[0019] However, a carrier head using multiple independently pressurizable, angularly positioned chambers can address this issue. The pressurizable chambers can be angularly and radially positioned about a central axis of the carrier head, with each pressurizable chamber connected to a respective valve. Each valve can switch between a respective pair of pressure inputs. The pressure in each chamber can thereby be independently controlled, allowing for the reduction or intentional introduction of angular non-uniformity.

[0020] 1A shows one embodiment of a polishing apparatus 100. The polishing apparatus 100 includes a rotatable, disk-shaped platen 120 on which a polishing pad 110 rests. The platen 120 is operable to rotate about an axis 125. For example, a motor 121 can turn a drive shaft 124 to rotate the platen 120. The polishing pad 110 can be removably secured to the platen 120 by, for example, an adhesive layer. The polishing pad 110 can be a two-layer polishing pad having an outer polishing layer 112 and a softer backing layer 114.

[0021] The polishing apparatus 100 may include a mixed slurry / rinse arm 130. During polishing, the arm 130 is operable to dispense a polishing liquid 132, such as a polishing slurry, onto the polishing pad 110. The polishing apparatus may also include a polishing pad conditioner that polishes the polishing pad 110 to maintain the polishing pad 110 in a constant polishing condition.

[0022] The polishing apparatus 100 includes a carrier head 140 operable to hold the substrate 10 against the polishing pad 110. The carrier head 140 can be configured to independently control polishing parameters (e.g., pressure) for each of multiple areas on the substrate 10.

[0023] Referring to FIG. 1B, the carrier head 140 may include a housing 144 that may be connected to the drive shaft 152, a support plate 184 that extends above the flexible membrane 182, and a retaining ring 142 for holding the substrate 10 below the membrane 182.

[0024] The underside 200 of the membrane 182 provides a mounting surface for the substrate 10. The membrane 182 may include a horizontally extending main portion 202 and multiple flaps 204. The main portion 202 may be circular and provide the mounting surface. The multiple flaps 204 extend upward from the underside of the main portion 202. The flaps 204 are secured to the support plate 184, for example, by clamps. The flaps 204 thereby divide the space above the membrane into multiple independently controllable pressurizable chambers 185. In particular, as described further below, the pressurizable chambers 185 are angularly disposed about the central axis 159 of the carrier head. The membrane 182 may be made of a flexible and somewhat elastic material, for example, a rubber such as silicone rubber or neoprene. The membrane may be formed from a thermosetting material using a mold, whereby the molded membrane forms the main portion 202 and the flaps 204 as a single body.

[0025] In some embodiments, the support plate 184 is flexibly connected to the housing 144, thereby allowing the support plate to move vertically relative to the housing. For example, the support plate 184 may be coupled to the housing by a flexure 210 (e.g., an annular membrane) formed of plastic or rubber (e.g., silicone rubber or neoprene). The inner edge of the flexure 210 may be clamped between the top of the support plate 184 and a clamp ring 212. The outer edge of the flexure may be clamped between the retaining ring 142 and the housing 144.

[0026] Support plate 184 is more rigid than membrane 182. For example, support plate 184 can be metal (e.g., aluminum or stainless steel) or hard plastic (e.g., polyetheretherketone (PEEK) or polyphenylene sulfide (PPS)). Each independently controllable pressurizable chamber 185 formed above membrane 182 is sealed by support plate 184.

[0027] The area between the support plate 184 and the housing 144 may be sealed by an inflatable seal 220, for example, by a flexible membrane or bellows, thereby forming a pressurizable upper chamber 222 between the housing 144 and the support plate 184. Alternatively, flexures 210 may provide the seal. Thus, the pressure in the upper chamber 222 may control the vertical position of the support plate 184 or the downward force of the support plate 184 on the membrane 182. In some embodiments, the pressure in the upper chamber 222 may control the pressure of the retaining ring 142 on the polishing pad.

[0028] In some embodiments, the support plate 184 is not movable relative to the housing 144. For example, the support plate 184 may be fixed to the housing 144 or may be provided by a portion of the housing 144. In this case, the seal 210 or the chamber 222 is present.

[0029] Returning to the independently pressurizable chambers 185 formed by membrane 182, the pressure applied over an area of ​​substrate 10 depends on the pressure within the associated chamber 185. Because the chambers are positioned at different angular and radial orientations around the center of the carrier head, the pressure on substrate 10 can also be independently controlled at each annular and angular position. Although only 10 chambers are shown in FIG. 1 for ease of illustration, there may be between 20 and 100 chambers, e.g., 66 chambers.

[0030] A valve assembly 189, e.g., a type of device that connects two or more valves such that various stand-alone valves can be combined into a single body configuration, is secured to carrier head 140. For example, the valve assembly can be mounted on top of housing 144 of carrier head 140, as shown in Figures 1A and 1B. In another embodiment, the valve assembly can be mounted on top of support plate 184 inside carrier head 140, as shown in Figure 3A.

[0031] 1B, each chamber 185 is connected to a dedicated valve in valve assembly 189, for example, by pressure output line 187. Each pressure output line 187 may be provided by a passageway and / or flexible tubing through support plate 184 and / or housing 144. Although only one pressure output line 187 is shown in FIG. 1B for ease of illustration, there may be a separate pressure output line 187 for each chamber 185.

[0032] Valve assembly 189 can receive multiple pressure inputs from multiple pressure sources 181 via multiple pressure supply lines 183. Again, for ease of illustration, only one pressure supply line 183 and one pressure source 181 are shown in FIGS. 1A and 1B, but there can be more pressure supply lines, e.g., 8 to 16 pressure supply lines, and there can be more pressure sources, e.g., 8 to 16 pressure sources. Pressure supply lines 183 can be provided by passages and / or flexible tubing through drive shaft 152 and / or housing 144, and rotary union 214 extending through upper chamber 222. Pressure can be routed from a stationary component, such as pressure source 181, to carrier head 140 via rotary gas pressure union 156.

[0033] Valve assembly 189 can also receive data from controller 190 via data lines 186. Voltage supply lines 183 and data lines 186 may be routed through drive shaft 152 and rotary electrical union 158 (e.g., slip rings) to stationary components such as controller 190.

[0034] The valve assembly 189 can independently control each valve based on the data to switch each corresponding chamber 185 between a pair of corresponding pressure supply lines, i.e., each pressure output line 187 can be selectively coupled to one of two pressure supply lines 183 by an associated valve.

[0035] Data line 186 can transfer multiple frames of data, each frame of the multiple frames can include data representing a pressure switching signal, or equivalent pressure signal, for one or more of the independent chambers. In some embodiments, the frame of data transmitted by controller 190 includes a control value and an identification value associated with each valve (or equivalently, each chamber) to which the control value applies, and valve assembly 189 is configured to determine pressure switching to the chambers based on the control value and the identification value.

[0036] By including the valve assembly 189, the number of pressure sources and pressure input lines can be reduced by at least half compared to a carrier head having a comparable number of chambers but without the valve assembly. Thus, the number of independently controllable pressurizable chambers can be scaled up with a smaller increase in the number of rotary connections, while still maintaining the adjustability of the pressure in each chamber. With that in mind, the polishing assembly can be simpler in design and more reliable under operation.

[0037] FIG. 2A is a schematic diagram showing a portion of the carrier head 140, the substrate 10, and the polishing pad 110. As shown in FIG. 2A, the pressure control assembly includes a valve assembly 189, two pressure source banks 181a and 181b, and a controller 190. The valve assembly 189 is connected to each pressurizable chamber 185 via a respective pressure output line 187. While FIG. 2A shows ten independent pressurizable chambers 185a-185j, as discussed above, the total number of chambers can be greater than ten. For example, in a configuration such as that shown in FIG. 2B, there can be 66 chambers.

[0038] Returning to Figure 2A, each chamber 185a-185j is connected via a respective pressure output line (e.g., 187a-187j) to a respective valve within valve assembly 189. Each valve can control / switch the pressure output line between a pair of pressure supply lines to apply a selected pressure to the associated pressure chamber.

[0039] Pressure source banks 181a and 181b may each include multiple pressure sources. As shown in FIG. 2A , pressure source bank 181a may have three primary pressure sources 181a-1 through 181a-3, and bank 181b may have two secondary pressure sources 181b-1 and 181b-2. Each pressure source may provide pressure at an independently controllable magnitude. Each pressure source from each bank is connected to valve assembly 189 by a separate pressure supply line 183. For example, pressure source 181a-1 inside pressure bank 181a is connected to valve assembly 189 by pressure supply line 183a-1. Inside the valve assembly, each pressure supply line may be split to connect to multiple different valves.

[0040] Each valve inside the valve assembly 189 is connected to two pressure sources, a pair of pressure sources: a primary pressure and a secondary pressure. The primary pressure may be derived from a pressure source inside the primary pressure bank 181a, and the secondary pressure may be derived from a pressure source inside the secondary pressure bank 181b. For example, the valves inside the valve assembly are connected to a pair of pressure sources (e.g., 181a-2 and 181b-1) using a pair of separate pressure supply lines (e.g., 183a-2 and 183b-1). The pressure source banks and the total number of pressure sources inside the pressure banks in FIG. 2A are merely exemplary; thus, more pressure sources may be incorporated inside the pressure banks, and more pressure banks may be included. For example, there may be at least four primary pressure sources within the primary pressure bank 181a, and at least four secondary pressure sources inside the secondary pressure bank 181b. There may be eight primary pressure sources inside the primary pressure bank 181a. There may be four secondary pressure sources inside secondary pressure bank 181b. Data line 186 connecting controller 190 and valve assembly 189 may be split into multiple threads (e.g., 186a-186c) outside the valve assembly, such that each valve is connected to a separate data line. With this in mind, each valve may be independently controlled based on frames of data transmitted from controller 190. In some embodiments, data line 186 may also be split inside the valve assembly.

[0041] FIG. 2B shows a schematic bottom view of an exemplary carrier head having a pressurizable chamber 185 disposed within a pole array. The chamber is divided into multiple (e.g., nine) concentric rings surrounding a circular central chamber (e.g., 185-66) by angularly extending membrane walls (provided by flaps 204 of membrane 182). At least two of the rings may have the same radial width. For example, the outer two rings may have the same width, which may be different from the width of the other rings. Alternatively, each ring may have a different width, or all rings may have the same width. In some embodiments, at least one chamber is narrower than another chamber radially closer to the center of the carrier head. For example, the concentric rings may have progressively narrower widths as the rings move away from the center of the carrier head.

[0042] Chambers in different rings may be connected to different primary pressure sources, while multiple chambers in a particular ring may be connected to a common primary pressure source, as will be explained further below.

[0043] At least two of the rings, e.g., the outer eight rings, are further divided into multiple arcuate sections by multiple radially extending membrane walls (provided by flaps 204 of membrane 182). For example, a ring may be divided into eight sections by seven radially extending membrane walls. In some embodiments, each section spans the same central angle, e.g., 45 degrees or a quarter of π in radians. In this case, the arcuate chambers in rings farther from the center of the carrier head are longer. In some embodiments, the multiple sections are equally spaced around the central axis. Alternatively, depending on the polishing requirements, at least two sections (e.g., 60 degrees) may have a larger central angle than the other sections (e.g., 30 degrees).

[0044] Multiple chambers within a particular section may be connected to a common secondary pressure source. However, in some pairs of sections, chambers in different sections of the pair may be connected to different secondary pressure sources. In some embodiments, each section is connected to a different secondary pressure source. Alternatively, some sections are connected to the same secondary pressure source, but some sections are connected to different pressure sources. For example, adjacent sections may be connected to different pressure sources.

[0045] 2C shows eight arcuate chambers 185-1 through 185-8 within section 185-S2. Each arcuate chamber within the same section occupies the same central angle relative to each ring in which it resides. Assuming eight rings and eight sections formed by flaps 204 of membrane 182, there are 64 arcuate chambers 185-1 through 185-64.

[0046] Optionally, one or more inner ring-shaped chambers 185-65 may surround the central circular chamber 185-66. For example, there may be a ring-shaped chamber 185-65 disposed between the central circular chamber 185-66 and the ring divided into sections. Thus, in this embodiment, there are 66 chambers formed by the membranes. Each of the 64 chambers is connected to a respective primary pressure source and a respective secondary pressure source. Meanwhile, the inner ring-shaped chamber 185-65 and the central circular chamber 185-66 are connected only to their respective primary pressure sources. The primary pressure sources for the chambers 185-65 and 185-66 may be obtained from different pressure banks (e.g., 181c).

[0047] 1B, in some embodiments, as shown in FIG. 3A, valve assembly 189 may be secured to the top of support plate 184 inside housing 144. Annular valve assembly 310 may include multiple valve banks 320 angularly arranged around and secured to the top surface of support plate 184. Each valve within valve bank 320 controls the pressure supplied to each arcuate chamber of the corresponding section to which the valve bank is assigned. For example, as shown in FIG. 3B, valve bank 320 is assigned to section 185-S8, and each valve within the valve bank (e.g., 330a-330h) is connected to each respective arcuate chamber (e.g., 185a-185h) via a respective pressure output line (e.g., 187a-187h). Each valve is also connected to a respective primary pressure source (e.g., 181a-1 to 181a-8) via a respective pressure supply line (e.g., 183a-1 to 183a-8). Meanwhile, all valves in each valve bank are connected to a common secondary pressure source (e.g., 181b-1) via pressure supply line 183b-1. Thus, each valve in valve bank 320 can switch between a respective pair of primary pressures and a common secondary pressure to be applied to each arcuate chamber in its associated section. With respect to central chambers 185-65 and 185-66, each independent pressure source 181c-1 and 181c-2 is applied directly to the two chambers without valves via pressure supply lines 183c-1 and 183c-2, although this is not explicitly shown in FIG. 3A for ease of illustration.

[0048] In some embodiments, the total number of combinations of primary and secondary pressure sources. Among all the chambers, there are at least two separate chambers, each connected to a separate valve that can switch the pressure output line between a respective pair of primary and secondary pressure sources. In this case, each of the two chambers is connected to a separate valve, but each valve couples the associated chamber to the same pair of pressure sources. The two chambers may be located in the following manner: for example, they may be on the same ring but on different pairs of sections; in another embodiment, they may be on different pairs of rings and different pairs of sections.

[0049] In some embodiments, each arcuate chamber on the same concentric ring shares the same primary pressure source. For example, 185-1 and 185-9 are two angular sections of the outermost ring, and although they do not belong to the same section, they share the same primary pressure source 181a-1 via their respective pressure output lines and respective pressure supply lines. Each arcuate chamber within the same section shares a common secondary pressure source, as previously described. For example, arcuate chambers 185-1 through 185-8 in section 185-S8 share the same secondary pressure source 181b-1. In some embodiments, one secondary pressure source is shared by chambers in more than one section. For example, four independent secondary pressure sources (e.g., 181b-1 through 181b-4) are shared by eight sections (e.g., 185-S1 through 185-S8). That is, one secondary pressure source is shared by chambers in a pair of sections. For example, the pair of sections 185-S2 and 185-S6 share the same secondary pressure source 181b-2. In another embodiment, the chambers in the pair of sections 185-S8 and 185-S7 share the same secondary pressure source 181b-4. Without loss of generality, the most separated sections may share the same secondary pressure source to achieve the best control performance.

[0050] In this embodiment, there are at least eight primary pressure sources (e.g., 181a-1 to 181a-8), each shared by the chambers on a respective outer concentric ring, two independent primary pressure sources (e.g., 181c-1 and 181c-2), one for each of the inner chambers 185-65 and 185-66, and four secondary pressure sources, each shared by the chambers in a respective pair of the four pairs of sections.

[0051] 1A , carrier head 140 is suspended from support structure 150 (e.g., a carousel) and connected by drive shaft 152 to carrier head rotation motor 154, thereby allowing carrier head 140 to rotate about axis 155. Optionally, carrier head 140 can oscillate laterally, for example, on a slider on carousel 150 or by rotational oscillation of the carousel itself. In operation, the platen rotates about its central axis 125, and each carrier head rotates about its central axis 155 and moves laterally across the top surface of the polishing pad.

[0052] The polishing apparatus may include an in-situ monitoring system 160, which can determine whether to adjust the polishing rate or whether adjustments to the polishing rate should be made, as described below. In some embodiments, the in-situ monitoring system 160 may include an optical monitoring system, such as a spectroscopic monitoring system. In other embodiments, the in-situ monitoring system 160 may include an eddy current monitoring system.

[0053] The in-situ monitoring system 160 includes a sensor 164 and a circuit 166 coupled to the sensor for sending and receiving signals to and from a controller 190 (e.g., a computer). The sensor 164 may 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 the circuit 166 may be a digital electronic signal that passes through a rotary coupler 129 (e.g., a slip ring) in the drive shaft 124 to the controller 190. Alternatively, the circuit 166 may communicate with the controller 190 via wireless signals.

[0054] 4A, if the detector is located within the platen, in situ measurements of the thickness of the layer on the substrate are taken at a sampling frequency as the sensor 164 of the in-situ monitoring system 160 moves beneath the carrier head due to the rotation of the platen (indicated by arrow 404). Measurements are thereby taken at locations 401 within an arc across the substrate 10. For example, points 401a-401k represent locations of measurements by the monitoring system on the substrate 10 (the number of points is exemplary; more or fewer measurements than shown may be taken depending on the sampling frequency). Due to the rotation of the carrier head 140 as the sensor 164 is swept by the motor 121, measurements are taken from different radial and angular positions on the substrate 10.

[0055] Thus, for any scan of the in-situ monitoring system across a substrate, based on timing, motor encoder information, rotational position sensor data (e.g., from an optical isolator sensor attached to the edge of the platen positioned to detect a flange), and optical or eddy current detection of the edge of the substrate and / or retaining ring, the controller 190 can calculate both the radial position (relative to the center of the particular substrate 10 being scanned) and the angular position (relative to a reference angle of the particular substrate 10 being scanned) for each measurement from the scan.

[0056] 4B, during one rotation of the platen, in situ measured data corresponding to different positions 403a-403o are collected by sensor 164. Based on the radial and angular positions of positions 403a-403o, each measured data collected at positions 403a-403o is associated with a separate chamber section 185-1 through 185-66. Specifically, data collected at positions 403f-403j is associated with central circular chamber section 185-66, and data collected at positions 403e and 403k is associated with innermost ring-shaped chamber section 185-65. Data collected at positions 403a and 403b is associated with arcuate chamber area 185-56 in section 185-S4, that collected at positions 403c and 403d is associated with arcuate chamber area 185-64 in section 185-S4, that collected at positions 403l and 403m is associated with arcuate chamber area 185-8 in section 185-S3, and that collected at positions 403n and 403o is associated with arcuate chamber area 185-1 in section 185-S3. Note that for ease of illustration, there are two arcuate chambers in each section depicted in FIG. 4B, but the number of arcuate chambers in each section can be eight or more. The number of spectra associated with each chamber area may vary from one rotation of the platen to another. Of course, the number of positions given above is merely exemplary, as the actual number of measurements associated with each chamber area will depend at least on the sampling rate, the rotational speed of the platen, and the radial width of each chamber area.

[0057] For each measurement, the controller 190 can calculate a characteristic value. The characteristic value is typically the thickness of the layer under polishing, but can also be a related characteristic such as thickness removed. Furthermore, the characteristic value can be a physical property other than thickness, such as metal line resistance. In addition, the characteristic value can be a more general representation of the progress of the substrate through the polishing process (e.g., an index value representing the time or number of platen rotations at which a spectrum can be expected to be observed in the polishing process according to a given progress).

[0058] Generally, a desired thickness profile will be achieved for the substrate at the end of the polishing process (or at an endpoint when the polishing process is stopped). The desired thickness profile may include the same predetermined thickness for all areas of the substrate 10, or different predetermined thicknesses for different areas of the substrate 10. When multiple substrates having non-uniform initial thicknesses are polished simultaneously, the multiple substrates may have the same desired thickness profile or different desired thickness profiles.

[0059] In some embodiments, the controller and / or computer can schedule adjustments to the polishing rate of the control zone at a predetermined rate (e.g., 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) to maintain the measured thickness relationship between the control zone and the reference zone the same as the thickness relationship indicated by the desired thickness profile(s) at the endpoint time throughout the polishing process. In some ideal situations, the adjustments can be zero at the pre-scheduled adjustment times. In other embodiments, the adjustments can be made at a rate determined in situ. For example, if the measured thicknesses of different zones differ significantly from the desired thickness relationship, the controller and / or computer can determine to make frequent adjustments to the polishing rate.

[0060] During polishing, the pressure applied to each region of the layer on the substrate is equal to the pressure applied in each chamber in membrane 182 as the pressure is transmitted from the chamber to the corresponding region of the substrate. Thus, controlling the pressure applied over a controlled region of the substrate includes switching the pressure between a pair of primary and secondary pressures associated with the corresponding chamber. In some embodiments, preset magnitudes of the primary and secondary pressures can be learned from open-loop polishing experiments. In that case, the thickness profile at the end of polishing is measured and analyzed to determine what magnitude difference should exist between the primary and secondary pressures.

[0061] FIG. 5 shows a flow diagram of a profile control process (500) using independent pressurizable chambers during polishing. The process includes identifying an expected thickness for each control zone at a predicted time (502), identifying a measured thickness for the control zone (504), identifying a pressure between a pair of pressure sources to apply to the control zone (506), and switching the pressure applied to the control zone via a valve in a valve assembly (508). Steps 502-506 can be implemented using an in-situ monitor system and controller, and step 508 can be performed in the valve assembly 189. A signal representing the desired pressure for each control zone (or switching between a pair of primary and secondary pressures) is transferred from the monitor system 160 to the valve assembly 189. In some embodiments, an identification signal for each chamber is processed in the controller 190. However, in some embodiments, the identification signal can be processed in the valve assembly 189. It should be noted here that the switching between the primary and secondary pressures applied within each arcuate chamber is sufficiently accurate for the purpose of controlling the polishing rate on the corresponding control zone, and that delicate presetting of the pressure source can further improve the control results.

[0062] The term substrate as used herein can include, for example, a product substrate (e.g., containing multiple memory or processor dies), a test substrate, a bare substrate, and a gating substrate. The substrate can be at various stages of integrated circuit manufacturing; for example, the substrate can be a bare wafer, or the substrate can include one or more deposited and / or patterned layers. The term substrate can include a circular plate and a rectangular thin plate.

[0063] The above-described polishing apparatus and method can be applied to various polishing systems. Either or both of the polishing pad and the carrier head can move to create relative motion between the polishing surface and the substrate. For example, the platen can orbit rather than rotate. The polishing pad can be a circular (or some other shape) pad fixed to the platen. Some aspects of the endpoint detection system can be applicable to linear polishing systems, for example, where the polishing pad is a linearly moving continuous belt or reel-to-reel belt. The polishing layer can be a standard abrasive (e.g., polyurethane with or without fillers), a soft material, or a fixed abrasive. Although terms relating to relative orientation are used, it should be understood that the polishing surface and substrate can be held in a vertical orientation or in some other orientation.

[0064] The control of the various systems and processes described herein, or portions thereof, may be implemented in a computer program product that includes instructions stored on one or more non-transitory computer-readable storage media and executable on one or more processing devices. The systems described herein, or portions thereof, may be implemented as an apparatus, method, or electrical system that may include one or more processing devices and memory that store executable instructions that perform the operations described herein.

[0065] While this specification contains numerous details of specific implementations, these should not be construed as limiting on any scope of the invention or the scope of the claims, but rather as descriptions of features that may be specific to particular embodiments of a particular invention. Certain features described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as working in a particular combination, or even initially claimed as such, in some cases one or more features in a claimed combination may be excluded from that combination, and a claimed combination may be directed to subcombinations or variations of subcombinations.

[0066] Similarly, while the figures show operations in a particular order, it should not be understood that the operations need to be performed in the particular order shown, or in the order that they occur, or that all of the operations described need to be performed, to achieve desirable results. Moreover, the separation of various system modules and components in the embodiments described above should not be understood as requiring such separation in all embodiments. It should also be understood that the program components and systems described may generally be integrated into a single software product or packaged into multiple software products.

[0067] Specific embodiments of the present invention have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. By way of example, the processes depicted in the accompanying figures do not necessarily require the particular order shown or order of occurrence to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous.

[0068] Other embodiments are within the scope of the following claims.

Claims

1. 1. A carrier head for holding a substrate in a polishing system, comprising: housing, a flexible membrane extending below the housing, the flexible membrane dividing a space above the flexible membrane into a plurality of independently pressurizable chambers; a plurality of independently pressurizable pressure supply lines, the number of chambers being greater than the number of pressure supply lines; and a valve assembly supported by the housing and coupled to the pressure supply line and the plurality of independently pressurizable chambers, the valve assembly having a plurality of valves, each valve of the plurality of valves coupled to a respective chamber from the plurality of independently pressurizable chambers, each valve configured to selectively couple the respective chamber to one of two different pressure supply lines from the plurality of pressure supply lines, the plurality of valves including solenoid valves; The carrier head, wherein the valve assembly is configured to receive data on a data line and to selectively actuate valves of the plurality of valves based on the data.

2. 2. The carrier head of claim 1, wherein the plurality of independently pressurizable pressure supply lines includes a first plurality of pressure supply lines and a second plurality of pressure supply lines, each valve configured to selectively couple a respective one of the chambers to one pressure supply line from the first plurality of pressure supply lines and one pressure supply line from the second plurality of pressure supply lines.

3. 10. The carrier head of claim 1, wherein the valve assembly is configured to receive multiple frames of data on the data line, each frame including data representing a pressure switching signal or equivalent pressure signal for one or more of the independent chambers.

4. 4. The carrier head of claim 3, wherein the frame of data includes a control value and an identification value associated with each valve or chamber, and the valve assembly is configured to determine pressure switching to a chamber based on the control value and the identification value.

5. The carrier head of claim 3 , wherein the data lines are split into multiple threads outside the valve assembly.

6. 1. A carrier head for holding a substrate in a polishing system, comprising: housing, a flexible membrane extending below the housing, the flexible membrane dividing a space above the flexible membrane into a plurality of independently pressurizable chambers; a plurality of independently pressurizable pressure supply lines, the number of chambers being greater than the number of pressure supply lines; and a valve assembly coupled to the pressure supply line and to the plurality of independently pressurizable chambers, the valve assembly including a plurality of valve banks angularly distributed about a central axis of the carrier head, each valve bank having a plurality of valves, each valve of the plurality of valves coupled to a respective chamber from the plurality of independently pressurizable chambers, each valve configured to selectively couple the respective chamber to one of two different pressure supply lines from the plurality of pressure supply lines.

7. 7. The carrier head of claim 6, wherein the plurality of independently pressurizable pressure supply lines includes a first plurality of pressure supply lines and a second plurality of pressure supply lines, each valve configured to selectively couple a respective one of the chambers to one pressure supply line from the first plurality of pressure supply lines and one pressure supply line from the second plurality of pressure supply lines.

8. The carrier head of claim 6 , wherein the carrier head includes a support plate that is vertically movable relative to the housing, the flexible membrane and the valve assembly being fixed to the support plate.

9. The carrier head of claim 6 , wherein the valve assembly is fixed to the housing.

10. The carrier head of claim 6 , wherein the plurality of valve banks are distributed at different angular positions about the central axis of the carrier head.

11. 11. The carrier head of claim 10, wherein the plurality of independently pressurizable chambers comprises chambers arranged in a plurality of sections at different angular positions about the central axis of the carrier head, each of the plurality of sections having a valve bank.

12. 12. The carrier head of claim 11 , wherein the independently pressurizable chambers are arranged in a polar array including a plurality of sections positioned at different angular positions about the central axis of the carrier head, each section including a plurality of arcuate chambers positioned at different radial distances from the central axis.

13. The carrier head of claim 12 , wherein each valve in each valve bank is coupled to the same first pressure supply line.

14. The carrier head of claim 13 , wherein each valve in each valve bank is coupled to a different second pressure supply line.

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