Control of carrier head sweep and platen shape

Abstract

The controller of the chemical mechanical polishing system is configured to cause the carrier head to sweep across the polishing pad according to a sweep profile. The controller is also configured to select values ​​for several control parameters in order to minimize the difference between a target removal profile and an expected removal profile. The several control parameters include several residence time parameters. The relationship between the several control parameters and the removal rate is stored in a data structure representing a first matrix, which includes several columns, each containing a column for each residence time parameter, and rows for each position on the substrate, and the controller is configured to calculate the expected removal profile by multiplying the first matrix by a second matrix representing the control parameter values ​​as part of the value selection.

Description

[Technical Field]

[0001] This disclosure relates to chemical mechanical polishing, and more specifically, to the control of the platen shape in conjunction with carrier head sweeping in chemical mechanical polishing. [Background technology]

[0002] Integrated circuits are typically formed on a substrate by continuously depositing conductive, semiconductive, or insulating layers onto a silicon wafer. One manufacturing step involves depositing a filler layer on a non-planar surface and planarizing that filler layer. For specific applications, the filler layer is planarized until the top surface of the patterned layer is exposed. For example, a conductive filler layer may be deposited on a patterned insulating layer to fill trenches or holes within the insulating layer. After planarization, the portions of the metal layer remaining between the raised insulating layer patterns form vias, plugs, and lines that provide conductive paths between thin-film circuits on the substrate. For other applications, such as oxide polishing, the filler layer is planarized, for example, by polishing for a predetermined time, leaving a portion of the filler layer on the non-planar surface. Furthermore, planarization of the substrate surface is usually required for photolithography.

[0003] One problem in CMP (chemical mechanical polishing) is the variation in the material removal rate of the substrate and the subsequent thickness profile. Variations in the material removal rate can occur due to variations in slurry distribution, the condition of the polishing pad, the relative speed between the polishing pad and the substrate, and inconsistent loads on the substrate from the pressurized chamber of the carrier head. These variations, along with variations in the initial thickness of the substrate layer, result in variations in the final thickness of the substrate layer, particularly near the edges of the substrate. [Overview of the project]

[0004] In one embodiment, a chemical mechanical polishing apparatus has a platen for supporting a polishing pad. The platen has a central section including a top surface, and an annular flexure surrounding or enclosed by the central section, the annular flexure having a top surface including a first edge coplanar with the top surface near the top surface, and a second edge further away from the central section. An actuator is positioned to bend the annular flexure to correct the vertical position of the second edge of the annular flexure relative to the central section. A carrier head holds the surface of the substrate in contact with the polishing pad. A motor generates relative motion between the platen and the carrier head to polish the upper layer on the substrate. A controller is configured to select values ​​for a plurality of control parameters to minimize the difference between a target removal profile and an expected removal profile. The plurality of control parameters include a first parameter representing the degree of flexure of the flexure. The relationship between multiple control parameters and the removal rate is stored in a data structure representing a first matrix, which includes multiple columns, each containing a column for the degree of deflection of the deflected portion and a row for each position on the substrate, representing the expected removal profile. The controller is configured to calculate the expected removal profile by multiplying the first matrix by a second matrix representing the control parameter values ​​as part of the selection of the above values.

[0005] In another embodiment, a chemical mechanical polishing apparatus comprises a platen for supporting a polishing pad, a carrier head for contacting the polishing pad and holding the surface of a substrate, a motor for controlling the lateral position of the carrier head on the polishing pad, and a controller. The controller is configured to cause the motor to sweep the carrier head across the polishing pad according to a sweep profile. The controller is also configured to select values ​​for a plurality of control parameters in order to minimize the difference between a target removal profile and an expected removal profile, the plurality of control parameters including a plurality of dwell time parameters, each of which dwell time parameters represents the amount of time the carrier head spends over each different zone on the polishing pad. The relationship between the plurality of control parameters and the removal rate is stored in a data structure representing a first matrix, the first matrix including a plurality of columns, each containing a column for each dwell time parameter, and a row for each position on the substrate, and the controller is configured to calculate the expected removal profile by multiplying the first matrix by a second matrix representing the control parameter values ​​as part of the selection of the above values.

[0006] Certain embodiments of the subject matter of the invention described herein may be implemented to achieve one or more of the following technical advantages:

[0007] It is possible to correct the radially specific thickness profile, thereby reducing in-wafer and inter-wafer non-uniformity. Material removal can correct thickness profile non-uniformity in edge regions induced after the main polishing step, or it is possible to compensate for the input substrate film thickness profile before subjecting it to major polishing. The amount of deflection by the annular deflection section (e.g., displacement from the planar configuration) corrects the pressure applied to the substrate surface rather than through the back surface of the substrate, improving the specificity of the polishing position during position-specific polishing.

[0008] The substrate residence time as a function of radial position can be made an additional adjustable parameter, allowing for greater flexibility in selecting values ​​for other parameters, such as carrier head pressure and platen edge displacement. The "Preston matrix" used for calculating carrier head pressure can be modified to include the relationship between deflection (e.g., displacement from the planar configuration) and the polishing profile. Similarly, the Preston matrix can include the relationship between residence time and polishing profile at various radial positions. This allows for the execution of an optimization algorithm to select deflection and / or residence time to provide the desired polishing profile.

[0009] Details of one or more embodiments are described in the accompanying drawings and the following specification. Other embodiments, features, and advantages will become apparent from the specification and drawings, as well as from the claims. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic cross-sectional view of an example of an optical monitoring system and a polishing apparatus having two annular flexible sections is shown. [Figure 2A-B] A schematic top view of a polishing pad, including the inner and outer regions where polishing speed is high, is shown. [Figure 3A-B] A schematic cross-sectional view of an exemplary polishing apparatus is shown, in which the lower and upper platens are divided into regions to achieve the desired polishing. [Figure 4A] A schematic top view is shown of multiple annular zones on the polishing pad for setting the residence time. [Figure 4B] A schematic graph of the carrier head sweep profile is shown. [Figure 5] A schematic diagram of an exemplary computing device is shown. [Modes for carrying out the invention]

[0011] In the figures, like reference numerals indicate like elements.

[0012] In some chemical mechanical polishing operations, part of the substrate may be under-polished or over-polished. In particular, the substrate tends to be over-polished or under-polished at or near the edge of the substrate. One technique for dealing with such polishing non-uniformities is to have a plurality of controllable pressurizable chambers within the carrier head. However, the pressure applied from the back side of the substrate tends to "spread", which can make it difficult to correct for radial local polishing non-uniformities. Another technique is to transfer the substrate to another "touch up" tool, for example to perform edge correction. However, additional tools take up valuable space in the clean room and can negatively impact throughput.

[0013] An alternative approach is to have a platen that includes one or more individually controllable annular deflectable portions that can deflect, for example, upward or downward. In this case, a portion of the substrate is moved over the deflected deflectable portion, which consequently causes the pressure between the polishing pad and the substrate to increase or decrease at the said portion, and thus enables radially focused polishing of the edge portion of the substrate.

[0014] Assuming that a portion of the platen can deflect, the effect on polishing will depend on the radial position of the substrate and the degree of deflection. Therefore, some technique for selecting the radial position and degree of deflection of the substrate is needed. To address this, a "Preston matrix" can be used to calculate a predicted polishing profile as a function of control parameter values. The dwell time of the substrate at each of a plurality of positions, and the degree of deflection, can be treated as control parameters that are part of the Preston matrix. This enables an optimization algorithm to be executed to select the amount of deflection and / or dwell time to provide the desired polishing profile.

[0015] FIG. 1 shows a polishing system 20 operable to polish a substrate 10. The polishing system 20 includes a rotatable platen 24, and a main polishing pad 30 is positioned on the rotatable platen 24. The platen is operable to rotate about a rotation axis 25. To rotate the platen 24, for example, a motor 21 can rotate a drive shaft 22 (represented by an arrow B in FIGS. 2A and 2B). In some embodiments, the platen 24 includes a central section 26 configured to provide an annular upper surface 28 that supports the main polishing pad 30.

[0016] The main polishing pad 30 can be fixed to the upper surface 28 of the central section 26 of the platen 24, for example, by an adhesive layer. When worn, the main polishing pad 30 can be removed and replaced. The main polishing pad 30 can be a two-layer polishing pad including an outer polishing layer 32 having a polishing surface and a softer backing layer 34.

[0017] The polishing system может include a pad cleaning system such as a polishing liquid delivery arm 82 and / or a rinse liquid delivery arm. During polishing, the arm 82 is operable to discharge a polishing liquid 89, for example, a slurry containing polishing particles. In some embodiments, the polishing system 20 includes a combined slurry / rinse arm. Alternatively, the polishing system can include a port in the platen operable to discharge the polishing liquid 80 onto the main polishing pad 30. The polishing system 20 can also include a conditioning system 40 including a rotatable conditioning head 42, and the conditioning head 42 can include, for example, a polishing lower surface on a removable conditioning disk to condition the polishing surface 36 of the main polishing pad 30.

[0018] The polishing system 20 includes a carrier head 70 that is operable to hold the substrate 10 in contact with the main polishing pad 30. The carrier head 70 is suspended from a support structure 72, such as a carousel or track, and is connected by a drive shaft 74 to a carrier head rotary motor 76, which allows the carrier head to rotate around an axis 71. Furthermore, an actuator 78 is capable of oscillating the carrier head 70 laterally across the polishing pad. This can be done, for example, by moving it within the radial slot of the carousel so that an actuator, such as a linear actuator, is driven; by rotating the carousel so that an actuator, such as a motor, is driven; or by moving it back and forth along a track so that an actuator is driven. During operation, the platen 24 is rotated around its central axis 25, and the carrier head is rotated around its central axis 71 and translated laterally across the uppermost surface of the polishing pad.

[0019] The carrier head 70 may include a retaining ring 73 for holding the substrate 10 under the flexible film 144. The carrier head 70 also includes one or more individually controllable pressurizable chambers (e.g., three chambers 77a-77c) defined by the film, which can apply individually controllable pressure to the relevant zones on the flexible film 144 and therefore on the substrate 10. For simplicity of explanation, only three chambers are illustrated in Figure 1, but there may be one or two chambers, or four or more chambers, for example, five chambers.

[0020] A controller 90, such as a programmable computer, is connected to motors 21 and 76 to control the rotational speeds of the platen 24 and carrier head 70, and to actuator 78 to control the radial position of the carrier head on the platen 24. For example, each motor may include an encoder that measures the rotational speed of its associated drive shaft. A feedback control circuit, which may be located in the motor itself or be part of the controller or another circuit, receives the rotational speed measured from the encoder and adjusts the current supplied to the motor to ensure that the rotational speed of the drive shaft matches the rotational speed received from the controller.

[0021] The controller can also control other components of the polishing system, such as a pressure regulator that controls the pressure in chambers 77a-77c, or a pump that controls the flow rate of the polishing fluid.

[0022] The polishing system 20 also includes at least one annular flexure 50 fixed to a platen 24 and rotating with the platen 24. A portion of the polishing pad 30 supported on the platen 24 extends above the flexure 50. The flexure 50 is deformable by at least one actuator 52. In particular, the flexure 50 and the actuator 52 are operable to flex the flexure 50 along an arc 15 (see Figure 2A) that covers at least the entire portion of the substrate above the flexure. In some embodiments, the flexure 50 is configured and the actuator is positioned so that the flexure 50 flexes along its entire circumference. Such a configuration may be mechanically simpler and more reliable to position than deforming an angularly limited portion of the flexure 50.

[0023] The polishing system 20 may include an annular flexible portion 50a projecting outward from the outer edge of the platen 24. Alternatively, if the platen 24 includes an annular support surface 28, the polishing system may include an annular flexible portion 50b projecting inward from the inner edge of the annular platen 24. Alternatively, there may be two flexible portions, for example, one for the outer edge of the platen 24 and the other for the inner edge of the platen 24, and the other for the inner edge of the platen 24.

[0024] The polishing pad 30 extends over the flexible portion 50a and / or flexible portion 50b. When the polishing system includes an annular flexible portion 50b projecting inward, the polishing pad 30 can be annular, in which case the opening 38 is aligned with the recess 27 of the platen to allow the flexible portion 50b to be movable in the vertical direction. When the polishing system includes only an annular flexible portion 50a projecting outward, the polishing pad 30 can be circular (not annular in this context).

[0025] When the annular flexible portion 50 is bent upward, a limited radial portion of the polishing pad 30 is biased upward. If a portion of the substrate 10 is located above the flexible portion, the pressure on that portion will increase. Conversely, when the annular flexible portion 50 is bent downward, a limited radial portion of the polishing pad 30 is biased downward. If a portion of the substrate 10 is located above the flexible portion, the pressure on that portion will decrease. In this specification, the terms “upward” and “downward” refer to the orientations shown in Figure 1. “Upward” refers to the direction from the platen 24 through the polishing pad 30 toward the substrate 10, and “downward” refers to the opposite direction. During operation, the polishing surface may be oriented perpendicular to gravity or in any other direction.

[0026] The annular flexible portion 50 extends from the outer edge of the platen 24 to a distance within 5% to 20% of the radius of the polishing pad 30 (for example, 5% to 15%, 5% to 10%, 10% to 15%, or 15% to 20%). The outer edge of the polishing pad 30 can be aligned with the outer edge of the outer flexible portion 50a, or set to be set back by up to approximately 1 inch from that edge, or can extend beyond that edge. In the case of an annular polishing pad 30, the inner edge of the polishing pad 30 can be aligned with the inner edge of the inner flexible portion 50b, or set to be set back by up to approximately 1 inch from that inner edge, or can extend beyond that inner edge.

[0027] As shown in the example in Figure 1, the polishing system 20 includes an annular flexible portion 50 that projects radially outward from the central section 26 of the platen 24. When not flexible or deformed, the uppermost surface of the annular flexible portion 50 is substantially coplanar with the upper surface 28 of the platen 24. The inner edge of the annular flexible portion 50 is fixed to the platen 24 and is rotatable with the platen 24. Therefore, the annular flexible portion 50 rotates with the platen 24 when the drive shaft 22 rotates the platen 24 (therefore, the annular flexible portion 50 does not require a separate motor for rotation).

[0028] The annular flexure 50 is connected to at least one actuator 52, which is positioned to be supported by the central section 26 of the platen 24. In some embodiments, such as the example in Figure 1, the actuator 52 is positioned to apply a substantially lateral force to the flange 54, which protrudes downward from the outer edge of the annular flexure 50. In such embodiments, the actuator 52 applies either an inward force (e.g., a force toward the axis of rotation 25) or an outward force (e.g., a force away from the axis of rotation 25). The system 20 includes a sufficient number of actuators 52 to control the outer edge of the annular flexure 50 around the circumferential surface of the platen 24. The system 20 may include two or more, four or more, or eight or more actuators 52. If multiple actuators are present, they may be spaced at uniform angles around the axis of rotation 25 of the platen 24.

[0029] While the actuator 52 is applying an inward force, the outer edge of the upper surface of the annular flexible portion 50 bends downward. Conversely, while the actuator 52 is applying an outward force, the outer edge of the upper surface of the annular flexible portion 50 bends upward. The controller 90 controls the actuator 52 to adjust the force on the flange 54, thereby controlling the outer edge of the upper surface of the annular flexible portion 50 to bend upward or downward.

[0030] The above system may be configured such that the annular flexible portion 50 flexes along its entire circumference. In some embodiments, a single actuator is present, and the flexible portion 50 has sufficient rigidity in the angular direction so that the flexible portion 50 flexes along its entire circumference due to pressure from the actuator within a limited area. In some embodiments, multiple actuators are present, and the actuators are electrically coupled to a single control signal so that all actuators are driven together. In some embodiments, each of the actuators 52 is individually controllable by the controller 90, but the controller 90 controls all the actuators 52 to flex the annular flexible portion 50 along its entire circumference.

[0031] In many polishing processes, pressure control is reduced in the radially outermost region of the three chambers 77a to 77c, resulting in insufficient polishing at the outer edge of the substrate 10, and consequently, an increase in the thickness of the layer at the outer edge of the substrate 10. Therefore, in order to increase the pressure between the substrate 10 and the polishing pad 30, the annular flexible portion 50 is bent upward and biased against the lower surface of the substrate 10.

[0032] The controller 90 operates the actuator 52 to change the position of the outer edge of the annular flex portion 50 upward or downward by a specific distance. In some embodiments, the above distance is within the range of 1 micron to 300 microns (e.g., 1 micron to 250 microns, 10 microns to 250 microns, 50 microns to 250 microns, 10 microns to 50 microns, or 1 micron to 50 microns).

[0033] In some embodiments, an annular platen 24 includes a recess 27 at its center, which extends partially through the thickness of the platen 24 and is aligned with the rotation axis 25. For example, the recess 27 can be circular, and its center may be coaxial with the rotation axis 25. In some embodiments, the recess 27 extends through the entire thickness of the platen 24.

[0034] The recess accommodates a central annular flexure 50b, which includes a flange 54 and one or more actuators 52 for applying force to the flange 54. The inner edge of the central annular flexure 50b (for example, the one closest to the rotation axis 25) flexes upward or downward based on the force applied to the flange 54 by the actuators 52, while the outer edge of the central annular flexure 50b remains substantially coplanar with the upper surface 28.

[0035] The central annular flexure 50b extends from the inner edge of the platen 24 to a distance within 5% to 25% of the innermost radius of the polishing pad 30 (for example, 5% to 15%, 5% to 10%, 10% to 25%, or 15% to 25%).

[0036] The arrangement of the actuator 52, the outer annular flex portion 50a, and the central annular flex portion 50b defines the area of ​​the pad 30, within which the pressure between the pad 30 and the substrate 10 is at least partially controlled by the amount of deflection provided by the actuator 52. Referring to Figures 2A and 2B, top views of the polishing pad 30 and the substrate 10 are shown, schematically illustrating a specific polishing area. Figure 2A shows one embodiment in which the device 100 includes only the outer annular flex portion 50a, and Figure 2B shows an embodiment in which the device 100 includes both the outer annular flex portion 50a and the central annular flex portion 50b. During the polishing operation, a retaining ring 73 surrounds the substrate 10 within the device 100, but this component is visually omitted in Figures 2A and 2B for simplification.

[0037] Referring to Figures 1 and 2A, a top view of the pad 30 and substrate 10 supported by the platen 24 is shown, where the system 20 includes only the outer annular flexure 50a. The central section 26 of the platen 24 supports the central region 31 of the pad 30. The annular flexure 50a is circumferentially arranged around the platen 24 and supports the outer region 33. The outer edge of the outer region 33 flexes upward or downward, while the inner edge of the outer region 33 remains substantially coplanar with the central region 31.

[0038] The substrate 10 is moved by the carrier head 70 such that a portion 12 of the substrate 10 is above the outer region 33. Depending on whether the flex portion 50a is biased upward or downward, the pressure on the portion 12 of the substrate 10 increases or decreases in the outer region 33. Due to the rotation of the carrier head 70 and the substrate 10 (indicated by arrow A), the polishing speed increases or decreases in the annular portion 12a of the substrate 10 (compared to the flex portion remaining in a planar state).

[0039] Referring to Figures 1 and 2B, a top view of the pad 30 and substrate 10 supported by the platen 24 is shown, where the system 20 includes an annular flexure 50 and a central annular flexure 50b. The central annular flexure 50b defines the inner region 35 of the polishing pad 30, and the outer annular flexure 50a defines the outer region 33. The polishing pad 30, supported by the central section 26 which remains substantially planar during polishing, is defined as the central region 31. Thus, the outer region 33 and the inner region 35 define two regions from which the pressure between the substrate 10 and the polishing pad 30 can be modified.

[0040] As the substrate 10 passes over the inner region 35 by the carrier head 70 (not shown), a portion 13 of the substrate 10 overlaps the inner region 35. While the inner region 35 is bent upward or downward by the central annular flex portion 51, the portion 13 is subjected to increased or decreased pressure. Here again, due to the rotation of the carrier head 70 and the substrate 10 (indicated by arrow A), the polishing speed increases or decreases in the annular portion 13a of the substrate 10. In the embodiments of Figures 2A and 2B, assuming that the edges of the substrate are under-polished, it is possible to increase the polishing speed of the portion 13 of the substrate 10 overlapping the inner region 35 and the portion 12 of the substrate 10 overlapping the outer region 33 to correct and thus improve uniformity within and between wafers.

[0041] In some embodiments, the polishing apparatus includes an in-situ monitoring system 160, which includes an optical monitoring system, such as a spectroscopic monitoring system that can be used to measure the spectrum of light reflected from the substrate being polished. The monitoring system 160 may include a sensor supported on the platen, for example, the end of an optical fiber connected to a light source 162 and a photodetector 164. As the platen rotates, the monitoring system 160 receives measurements at a sampling frequency, at which point the measurements are obtained at a position in an arc traversing the substrate 10. From the measurements, the in-situ monitoring system 160 generates a signal dependent on the thickness of the material layer being polished, such as a thickness profile. In addition or alternatively, the in-situ monitoring system 160 generates a signal dependent on the polishing rate of the material layer being polished, such as a polishing rate profile.

[0042] The controller 90 receives the above signal, converts the signal into a process profile, such as a thickness profile or a polishing rate profile, and compares the process profile with a target profile. For example, the target profile may be a predetermined target thickness profile for the radially dependent thickness of the layer at the end of polishing, or a target polishing rate profile storing a radially dependent target polishing rate during polishing. The process profile may be based on the radial width of the substrate 10, or a measurement over a portion of the radial width of the substrate 10. In some embodiments, the controller 90 calculates a process profile for the portion of the substrate 10 corresponding to the outermost annular region of the substrate 10, for example, calculating a process file for the outermost 5%, outermost 10%, or outermost 20% of the substrate.

[0043] The controller 90 compares the process profile with the target profile. If the process profile differs from the target profile by more than a threshold amount, the controller 90 decides to change the polishing parameters. If the above difference occurs within a region of the substrate that can be controlled by the flex portion, for example, within the outermost annular region near the edge of the substrate 10, the flex portion can be used to compensate for the deviation of the process profile from the target profile.

[0044] If the polishing speed of the above-mentioned area of ​​the substrate exceeds the target polishing speed, the controller 90 can decide to position that area over the flexible portion and bend the flexible portion downward. By bending it downward, the polishing speed within that area decreases, and the target polishing speed profile is achieved. If the polishing speed within that area of ​​the substrate falls below the target polishing speed for that area, the controller 90 can decide to position that area over the flexible portion and bend the flexible portion upward in order to increase the polishing speed of that area.

[0045] The carrier head 70 passes the substrate 10 over the central region 31, and the optical monitoring system 160 receives a signal indicating the updated thickness of the upper layer of the material, for example, an updated thickness profile, and calculates a new uniformity for the updated thickness profile.

[0046] The controller 90 compares the updated uniformity with the uniformity threshold. If the uniformity falls below the uniformity threshold, the controller 90 decides to stop intensifying the polishing in the area of ​​the substrate 10 that corresponds to the area where the uniformity threshold was exceeded.

[0047] Figure 1 shows only one technique for adjusting the height of the platen's end, and other techniques are possible. The flexible portion may be detachable from the platen or may be integral with the platen. The flexible portion may have a substantially uniform thickness as shown in Figure 1, or it may be tapered, for example, the end of the flexible portion may be thinner than the portion near the central region of the platen. The actuator 52 may be a pneumatic linear actuator or rotary actuator that moves an adjustment screw. The actuator 52 may be capable of pushing or pulling laterally the portion of the flange that extends downward, or applying a force directly perpendicular to the flange.

[0048] In some embodiments, the platen includes an upper platen 312 supported on a lower platen 310. The upper platen 312 is composed of several parts that act independently to achieve a desired configuration of the polishing pad 30. Figures 3A and 3B show an exemplary configuration of a rotatable platen 24, in which the upper platen 312 is divided into several parts by a flexure 314, for example, at a point that is more flexible than the surrounding material. The flexure 314 can be realized by an annular region of the upper platen 312 in which the thickness of the material is reduced, or it can be separately composed of a material that is more flexible than the rest of the upper platen 312, for example, the outer region 316 or the inner section 318. The reduced-thickness region can be formed by a recess built into the lower surface of the platen 24, i.e., the uppermost surface of the platen can be substantially planar when not actively biased.

[0049] The lower platen 310 includes a recess 328 in which an actuator is located. The actuator applies a vertical force to the inner section 318. In such embodiments, the vertical position of the inner section 318 is controlled to adjust the polishing speed within the outer region 316. In the example of Figure 3A, the recess 328 houses two actuators 330 and 332 supported by a support 327. The actuators 330 and 332 apply a vertical force (for example, parallel to the central axis 125) to the inner section 318, displacing the inner section 418 upward or downward relative to the edge of the outer region 316 to achieve differential polishing in the area of ​​the substrate 10 that is in contact with the outer region 316.

[0050] In some embodiments, the upper platen 312 is divided into two or more regions having different polishing speeds. In the embodiment shown in Figure 3B, three actuators 330, 332, and 334 are supported by a support 327 within a recess 328. The actuators 330, 332, and 334 control the positions of the inner section 318 and the central section 320. In such embodiments, the vertical positions of the inner section 318 and the central section 320 are controlled independently, so that one or more sections create a position differential that generates a pressure bias against the substrate 10.

[0051] Returning to Figure 1, the polishing speed (i.e., the speed at which material is removed from the substrate 10) can vary according to several polishing system control parameters, such as the degree of deflection of the flexible section 50, the residence time of the carrier head 70 and the substrate 10 at each of several radial distances from the rotation axis 25 of the platen 24, and the pressure in the chambers 77a to 77c, the pressure on the holding ring 73, the rotation speed of the carrier head 70, the rotation speed of the platen 24, etc. Therefore, the combination of such parameters can determine the surface profile of the substrate 10 after polishing.

[0052] Generally, the polishing system 20 is controlled so that the polished substrate has a target surface profile, for example, a target thickness across the substrate surface. The target surface profile may be uniform (e.g., planar) or non-uniform across the substrate surface. The target surface profile can be set as a function of the distance from the center of the substrate 10, for example, assuming that the polishing is angularly symmetric, although this assumption is not mandatory. The target surface profile can be set manually by the polishing system manufacturer, by the polishing system operator, for example, by an employee of a semiconductor factory, or it may be automatically generated by computer software based on measurements of the performance of other tools in the semiconductor factory, for example, to compensate for non-uniform deposition or removal by those other tools.

[0053] The controller 90 may be configured to store a target removal profile. The controller 90 uses the target removal profile to set values ​​for polishing control parameters for the polishing system 20, such as the pressure in the chambers 77a-146c of the carrier head 140, the degree of deflection of the deflection section 50, and the residence time of the carrier head 70 and the substrate 10 at each of several radial distances from the rotation axis 25 of the platen 24. The target removal profile represents a desired amount of material to be removed across the front surface of the substrate. In some embodiments, the target removal profile may be determined based on an initial surface profile of the substrate 10 (such as measured at a measurement station before polishing or measured by an in-site monitoring system), for example, by the controller 90 or by another computer system that transfers the target removal profile to the controller 90. For example, the target removal profile may be calculated as follows: TRP = ISP - TSP (1) However, TRP is the target removal profile, ISP is the initial surface profile, and TSP is the target surface profile. Alternatively, if the initial surface profile is unknown, it may be set to a default value. Furthermore, in some situations, the polishing system operator may want to remove a target amount from the substrate rather than achieving a target profile. In addition, in some situations, the polishing system operator may simply set the target removal profile based on, for example, a priori principle or prior experience. In this last case, the user can generate the target removal profile by user input, for example, to the controller 90 or to another computer system that transfers the target removal profile to the controller 90.

[0054] The controller 90 can generate and store an expected removal profile (i.e., the amount of material expected to be removed across the front surface of the substrate 10) for a given set of values ​​for the polishing control parameters.

[0055] In general, it is advantageous to select values ​​for polishing control parameters, such as the pressure in the chambers 77a-77c of the carrier head 70, the degree of deflection of the deflection section 50, and the residence time of the carrier head 70 at each of several radial distances from the rotation axis 25 of the platen 24, so that the expected removal profile closely approximates (including exactly matches) the target removal profile. For example, if the expected removal profile closely approximates the target removal profile, then the actual removal profile, i.e., the amount actually removed from the substrate during polishing, should also closely approximate the target removal profile.

[0056] It should be noted that the removal profiles described herein can be expressed as the amount of material removed from the substrate surface, i.e., as the material removal rate (for example, by dividing the removal profile by the actual or expected time spent polishing). Furthermore, it should be understood that the data used for calculations may be stored in various different units, as long as the data is converted to a consistent unit for calculation purposes.

[0057] As a simplified model, the expected removal rate for any given position can depend linearly on each polishing control parameter. That is, assuming only one polishing control parameter changes while the others remain constant, the removal rate at each radial position on the substrate can be a linear function of the changed polishing control parameter.

[0058] The relationship between polishing control parameters and the removal profile can be determined based on measurement data. For example, the removal profile can be measured for a test substrate, and each test substrate is polished using a different set of calibration values ​​for the polishing control parameters. In particular, one substrate can be polished according to a set of baseline calibration values ​​for the polishing control parameters, and a baseline removal profile is measured from this one substrate. Then, additional substrates are polished for each control parameter set by the process, where the control parameter is set to a modified calibration value different from the baseline calibration value (although other control parameters are set to their own baseline calibration values), and the adjusted removal profile is measured from these additional substrates.

[0059] In some embodiments, various profiles generated from experimental measurements, such as a base removal profile and a tuned removal profile, include measured removal values ​​for multiple locations below each chamber. Similarly, a calculated expected removal includes calculated values ​​for expected removal at multiple locations below each chamber. In some embodiments, the profiles, such as the base removal profile, the tuned removal profile, and the expected removal profile, include values ​​for 20 to 300 locations on the substrate. For example, these profiles may include values ​​for locations on the substrate spaced at constant intervals of 1 mm.

[0060] In some embodiments, the expected removal profile can be calculated as follows: TIFF2026510522000002.tif8170 However, ERP is the expected removal profile, BRP is the baseline removal profile, [K] is a constant matrix (called the "Preston matrix") having several columns equal to the total number N of polishing control parameters and several rows equal to the total number M of radial positions on the substrate surface where the above profile is measured, and [P'] is a vector of adjusted polishing control parameter values. Here, the "*" operation indicates multiplication of each entry in the vector rather than dot product or cross product. That is, the i-th component of ERP is equal to the sum of the i-th component of BRP and the i-th component of the column vector obtained from the multiplication of [K][P'] and the i-th component of BRP and the i-th component of VAP. The total number of positions M can be greater than the number of chambers in the carrier head and greater than the total number N of polishing control parameters.

[0061] The total number of positions M can be greater than the number of chambers in the carrier head and greater than the total number of polishing control parameters N.

[0062] The baseline removal profile uses default polishing control parameter values ​​P01, P02, ... P0 NIt can be determined by polishing the test wafer with a set of them and comparing the measured surface profile after polishing (e.g., at a measurement station) with the initial surface profile. For example, the baseline removal profile can be calculated as follows. BRP = ISP - BSP (3) Where BRP is the baseline removal profile, ISP is the initial surface profile, and BSP is the default polishing control parameter values P01, P02, … P0 N It is the baseline surface profile realized as a result of polishing the test substrate with.

[0063] The constants of the matrix [K] can be determined from the baseline removal profile and the modified removal profile. As described above, the modified removal profile can be generated by polishing additional substrates for each parameter and modifying that parameter for one substrate at a time. For example, the modified removal profile can be calculated according to the following formula for each modified parameter. ARP i = ISP - ASP i (4) Where ARP i is the adjusted removal profile obtained from the adjustment of the i-th polishing parameter, ISP is the initial surface profile, and ASP i is the adjusted surface profile measured as a result of adjusting the i-th parameter.

[0064] In particular, the constant values of the matrix [K] can be calculated as follows. TIFF2026510522000003.tif16170Where K x,i is the value of the matrix [K] corresponding to the substrate profile position x for the i-th parameter, ARP x,i is the amount of material removed at the radial position x for the i-th adjusted parameter, BRP xThis is the amount of material removed at radial position x according to the previously calculated baseline removal profile, PA i This is the i-th parameter value used to generate the i-th adjusted removal profile, P0 i This is the i-th parameter value for the baseline removal profile.

[0065] Therefore, the matrix [K] can be expressed as follows: TIFF2026510522000004.tif17170 where M is the total number of radial positions x on the substrate where profile measurement is performed, and N is the total number of parameters.

[0066] Variable expressions for vector [P']: P1', P2'...P N ' is defined as follows: TIFF2026510522000005.tif10170 However, P i ' is the value of the vector [P'] corresponding to the i-th parameter, and P0 i This is the i-th parameter value of the baseline removal profile, P i This is a variable proposed parameter value.

[0067] Therefore, the expected removal profile can be expressed as follows: TIFF2026510522000006.tif22170 However, ERP is the expected removal profile and BRP is the baseline removal profile, and the values ​​of matrix [K] and vector [P'] are calculated as described above with reference to equations (5) and (7).

[0068] The polishing control parameters may include parameters representing the pressure in each chamber 77a-77c within the carrier head 70. Therefore, at least two of the polishing control parameters are the pressures in the carrier head chambers. The chamber pressure values ​​can be expressed in units of psi, but other units, such as pascals, are also possible.

[0069] The polishing control parameters may include parameters representing the rotational speed of the platen 24 and / or the rotational speed of the carrier head 70. The rotational speed value can be in rpm, but other units are also possible, such as the drive current of each motor.

[0070] The polishing control parameters may include a parameter representing the degree of deflection of the deflection section 50. If the system 20 includes both an outer deflection section 50a and an inner deflection section 50b, there will be two parameters, one for the inner deflection section and one for the outer deflection section. The value for the degree of deflection can be in units of distance, such as microns or mills (1 / 1000 of an inch), but other units are possible, for example, current or voltage in the case of an electromechanical actuator, or pressure in the case of a pneumatic actuator.

[0071] To set the sweep profile for the carrier head 70, the polishing control parameters may include multiple parameters representing residence time. In particular, each of these parameters may represent the residence time of the carrier head in each different radial annular zone on the platen.

[0072] For example, referring to Figure 4A, the platen 24 can be divided into several concentric annular zones 200, for example, zones 200a to 200e. Optionally, a circular central zone, for example, zone 202f, may be present. Figure 4 shows seven zones, but this is not mandatory; i.e., there could be 2 to 20 zones. In at least one of the zones, the substrate will overlap the flange 54, for example, the substrate will overlap the outer region 33. Each zone can be represented by a radial distance (e.g., the average of the inner and outer diameters of the zone) or by a range of radial distances (e.g., the inner and outer diameters of the zone).

[0073] During operation, the carrier head 70 sweeps laterally over the platen 24 and polishing pad, for example, along the radius of the platen 24 (illustrated by arrow C). For each zone, there may be a corresponding dwell time control parameter that represents the dwell time of the carrier head 70 within or within that zone. The substrate may span multiple zones, where each dwell time control parameter may represent the dwell time of the center point (on the axis 71) of the carrier head within or within that respective zone. The value of the dwell time parameter can be expressed in units of a fraction of total time (i.e., the sum of the total dwell times will be equal to 1), but other units, such as expected time, e.g., seconds, are possible.

[0074] Once the dwell time parameter value is calculated (the calculation of the parameter value will be described later), the dwell time parameter value can be converted into a sweep profile. Generally, in a sweep profile, the dwell time for each zone is allocated according to the dwell time parameter value.

[0075] In some embodiments, the carrier head sweeps within each zone at a constant speed, although this speed may differ from zone to zone. Referring, for example, to Figure 4B, one possible technique is to set the carrier head sweep speed (i.e., the slope of line 202) for each zone 200a to 200f according to the reciprocal of a fraction indicated by the residence time parameter of that zone. For example, given an oscillation period T, the residence time for a half sweep (inward or outward) for a given zone i is T*DT i It can be calculated as / 2, however, DT iis the fractional dwell time value for the i-th zone. For example, the amount of time T1 that the center of the substrate 10 spends in the outermost zone 200a during an inward sweep would be T*DT1 / 2. In this case, the speed at which the carrier head sweeps across a particular zone i is (R 1i / R 2i ) / (T i ) can be made, however R1 i and R2 i is the inner and outer diameters of the i-th zone. As a result, the velocity of the carrier head during time T1 and the slope of line 202 are given by 2*(R 11 / R 21 ) / (T*DT1) will be the result.

[0076] In some embodiments, the appropriate combination of parameters can be determined by solving for each parameter that minimizes the difference between the expected removal profile and the target removal profile; that is, the value of ERP-TRP is minimized. In many cases, one or more different sets of parameters can be mathematically determined to provide an expected removal profile equal to the target removal profile such that ERP-TRP = 0. In other cases, the difference between the expected removal profile and the target removal profile can be minimized to an acceptable non-zero value using the following formula. TIFF2026510522000007.tif9170 However, Δ is the difference value, ERP x This is the variable value of the expected removal profile at the radial position x on the substrate, and TRP x P is a constant value of the target removal profile at radial position x. i The value of can be calculated to find a removal profile that closely approximates the target removal profile.

[0077] In some cases, an iterative process (e.g., Newton's optimization method) can be used in conjunction with equation (9) to determine the appropriate combination of parameter values ​​to find the minimum difference between the predicted pressure profile and the target pressure profile, for example, to find the minimum value of Δ. For example, commercially available solver functions (e.g., Microsoft Excel solver functions, MATLAB solver functions, and / or Wolfram Mathematica solver functions) can be used to determine the appropriate combination of parameter values. In some cases, several appropriate combinations of parameter values ​​may exist.

[0078] As described above, once an appropriate set of parameter values ​​is determined, the controller 190 may be configured to store the parameter values ​​and accordingly perform polishing techniques to provide one or more substrates having a target surface profile.

[0079] In most cases, when all other parameter values ​​are kept constant, the polishing speed at a particular location on the substrate 10 can change linearly at that location on the substrate due to the pressure applied to the substrate on the polishing pad.

[0080] In some cases, an iterative process (e.g., Newton's optimization method) can be used in conjunction with equation (16) or (17) to determine a suitable combination of chamber pressures to find the minimum difference between the expected pressure profile and the target pressure profile, for example, to find the minimum value of Δ. For example, a commercially available solver function can be used to determine a suitable combination of chamber pressures. In some cases, several suitable combinations of chamber pressures may exist.

[0081] Once an acceptable predicted pressure profile is determined, interpolation and / or extrapolation techniques (other known mathematical approximation techniques can also be used) can be applied to the measured baseline pressure distribution to determine the corresponding chamber pressure for each chamber. When using a pressure distribution from a single baseline pressure, it may be necessary to assume a zero-scale pressure distribution (i.e., little to no polishing pressure is applied when the chamber is not pressurized).

[0082] Figure 5 is a block diagram of an exemplary computer system 500. For example, the controller 190 is an example of the system 500 described herein and may be a computer system used by any user accessing the resources of system 500. System 500 includes a processor 510, memory 520, storage device 530, and one or more input / output interface devices 540. Each of the components 510, 520, 530, and 540 can be interconnected, for example, using a system bus 550.

[0083] The processor 510 can process instructions for execution within the system 500. In this specification, the term “execution” refers to the technique by which program code causes the processor to execute one or more processor instructions. In some implementations, the processor 510 is a single-threaded processor. In some implementations, the processor 510 is a multi-threaded processor. The processor 510 can process instructions stored in memory 520 or storage device 530. The processor 510 can perform operations such as controlling polishing operations as described herein.

[0084] Memory 520 stores information within the system 500. In some implementations, memory 520 is a computer-readable medium. In some implementations, memory 520 is a volatile memory unit. In some implementations, memory 520 is a non-volatile memory unit.

[0085] The storage device 530 can provide a large-capacity storage device for the system 500. In some implementations, the storage device 530 is a non-transient computer-readable medium. In various different implementations, the storage device 530 may include, for example, a hard disk device, an optical disk device, a solid-state drive, or a flash drive. In some implementations, the storage device 530 may be a cloud storage device, for example, a logical storage device, which includes one or more physical storage devices distributed over a network and accessed using the network.

[0086] The input / output interface device 540 provides input / output operation for the system 500. In some implementations, the input / output interface device 540 may include one or more network interface devices, such as an Ethernet interface, and / or wireless interface devices. The network interface device enables the system 500 to communicate, for example, by sending and receiving data over a network. In some implementations, a mobile computer, a mobile communication device, and other devices may be used.

[0087] Software can be implemented by instructions that, when executed, cause one or more processing units to perform the processes and functions described above. Such instructions may include, for example, interpreted instructions such as script instructions, or executable code, or other instructions stored on computer-readable media.

[0088] An exemplary processing system is illustrated in Figure 5, but the subject matter and functional operation of the invention described herein can be implemented in other types of digital electronic circuits, including the structures disclosed herein and their structural equivalents, or in computer software, firmware, or hardware, or in a combination of one or more thereof. Implementation of the subject matter of the invention described herein, such as storing, maintaining, and displaying artifacts, can be implemented as one or more computer programs, i.e., as one or more modules of computer program instructions recorded on a tangible program carrier, such as a computer-readable medium, for execution by or control of the processing system. The computer storage medium can be a machine-readable storage device, a memory device, or a combination of one or more thereof.

[0089] Computer programs (also known as programs, software, software applications, scripts, executable logic, or code) can be written in any form of programming language, including compiled or interpreted programming languages, or declarative or procedural languages, and can be deployed as standalone programs or as modules, components, subroutines, or other units suitable for use in a computing environment. Computer-readable media suitable for storing computer program instructions and data include any form of non-volatile or volatile memory, media, and memory devices.

[0090] Throughout this specification, references to measurable values, such as quantities and temporal durations, should be considered as disclosures of the exact value, approximate values, and approximate values, for example, within a range of ±10% of the value. For example, a reference to 100 microns in this specification may be considered to mean exactly 100 microns, approximately 100 microns, or within a range of ±10% of 100 microns.

[0091] This specification includes several details, which should be interpreted not as limitations on the scope of claims, but as descriptions of features specific to particular embodiments. Certain features described herein in relation to separate embodiments may be combined. Conversely, various features described in relation to one embodiment may be realized separately or in any suitable subcombination in multiple embodiments.

Claims

1. A chemical mechanical polishing apparatus, A platen for supporting a polishing pad, comprising: a central section including an upper surface; and an annular flexible section surrounding or enclosed by the central section, having an uppermost surface including a first edge in the vicinity of the upper surface that is on the same plane as the upper surface and a second edge further away from the central section; An actuator is positioned to bend the annular bending portion so as to correct the vertical position of the second edge of the annular bending portion with respect to the central section, A carrier head for holding the surface of the substrate by contacting the polishing pad, A motor for generating relative motion between the platen and the carrier head so as to polish the upper layer on the substrate, A controller configured to select values ​​for a plurality of control parameters in order to minimize the difference between a target removal profile and a predicted removal profile, wherein the plurality of control parameters include a first parameter representing the degree of deflection of the deflection portion, and the relationship between the plurality of control parameters and the removal rate is stored in a data structure representing a first matrix, the first matrix including a plurality of columns including a column for the degree of deflection of the deflection portion represented in the predicted removal profile and a row for each position on the substrate, and the controller is configured to calculate the predicted removal profile by multiplying the first matrix by a second matrix representing the control parameter values ​​as part of the selection of the values, A chemical mechanical polishing apparatus equipped with the necessary components.

2. The polishing apparatus according to claim 1, wherein the carrier head includes a plurality of individually pressurizable chambers, the plurality of polishing control parameters include a plurality of chamber pressure parameters, and each chamber pressure parameter is associated with each of the plurality of pressurizable chambers.

3. The polishing apparatus according to claim 2, wherein the plurality of columns of the first matrix include columns for each chamber pressure parameter.

4. The polishing apparatus according to claim 2, wherein the value of the chamber pressure parameter is expressed in units of pressure.

5. The polishing apparatus according to claim 1, wherein the platen includes the annular flex portion surrounding the central division, and the first matrix includes a column for the degree of flex of the flex portion surrounding the central division.

6. The polishing apparatus according to claim 1, wherein the platen includes the annular flex portion enclosed by the central division, and the first matrix includes a column for the degree of flex of the flex portion enclosed by the central division.

7. The polishing apparatus according to claim 1, wherein the platen includes a first annular flex portion surrounding the central division and a second annular flex portion surrounded by the central division, and the first matrix includes a first column for the degree of flex of the first annular flex portion and a second column for the degree of flex of the second annular flex portion.

8. The polishing apparatus according to claim 1, wherein the degree of deflection of the deflected portion is measured in units of distance.

9. The polishing apparatus according to claim 1, wherein the controller is configured to apply a minimization algorithm to reduce the difference between a predicted thickness profile and a target thickness profile, and the application of the minimization algorithm includes iteratively calculating the predicted removal profile using various values ​​for the degree of deflection of the deflected portion.

10. A chemical mechanical polishing apparatus, A platen for supporting the polishing pad, A carrier head for holding the surface of the substrate by contacting the polishing pad, A motor for controlling the lateral position of the carrier head on the polishing pad, A controller configured to cause the motor to sweep the carrier head across the polishing pad according to a sweep profile, wherein the controller is configured to select values ​​for a plurality of control parameters in order to minimize the difference between a target removal profile and an expected removal profile, the plurality of control parameters including a plurality of dwell time parameters, each of which dwell time parameters represents the amount of time the carrier head spends over each different zone on the polishing pad, the relationship between the plurality of control parameters and the removal speed is stored in a data structure representing a first matrix, the first matrix including a plurality of columns including a column for each dwell time parameter represented by the expected removal profile and a row for each position on the substrate, and the controller is configured to calculate the expected removal profile by multiplying the first matrix by a second matrix representing the control parameter values ​​as part of the selection of values, A chemical mechanical polishing apparatus equipped with the necessary components.

11. The polishing apparatus according to claim 10, wherein the carrier head includes a plurality of individually pressurizable chambers, the plurality of polishing control parameters include a plurality of chamber pressure parameters, and each chamber pressure parameter is associated with each of the plurality of pressurizable chambers.

12. The polishing apparatus according to claim 11, wherein the plurality of columns of the first matrix include columns for each chamber pressure parameter.

13. The polishing apparatus according to claim 11, wherein the value of the chamber pressure parameter is expressed in units of pressure.

14. The polishing apparatus according to claim 11, wherein the controller is configured to apply a minimization algorithm to reduce the difference between a predicted thickness profile and a target thickness profile, and the application of the minimization algorithm includes iteratively calculating the predicted removal profile using various values ​​for each residence time parameter.

15. The polishing apparatus according to claim 11, wherein the controller is configured to calculate a sweep profile from the values ​​of the plurality of residence time parameters.

16. The polishing apparatus according to claim 15, wherein the controller is configured to set the sweep profile, which includes the respective speeds for each of the plurality of annular zones on the platen.

17. The polishing apparatus according to claim 16, wherein the controller is configured to set the speed of each of the plurality of annular zones to a constant value within each of the zones.

18. The polishing apparatus according to claim 17, wherein the value of the residence time parameter is expressed as a percentage of the total time.

19. The polishing apparatus according to claim 17, wherein the controller is configured to calculate the sweep speed for each of the plurality of annular zones in inverse proportion to the value of the residence time parameter for that zone.

20. The polishing apparatus according to claim 10, wherein the value of the dwell time for the i-th zone is a fractional value.

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