Grinding method

Abstract

This invention provides a polishing method that can accurately detect the polishing endpoint, which is the point where a structure with a small surface area is exposed. [Solution] This polishing method polishes the layer to be polished 101 on multiple endpoint target structures 102 distributed across the entire surface of the workpiece W by supplying polishing liquid onto the polishing pad 2 and pressing the workpiece W against the polishing pad 2 with the polishing head 1. During the polishing of the layer to be polished 101, the thickness T1 of the layer to be polished 101 on the multiple endpoint target structures 102 is measured by the film thickness sensor 21, and the polishing endpoint of the layer to be polished 101 is detected when multiple measured values ​​of the thickness T1 of the layer to be polished 101 reach a target value.

Description

Technical Field

[0001] The present invention relates to a technique for polishing a workpiece having a pattern formed therein, such as a wafer, a substrate, a wiring board, or a corner board, and particularly relates to a technique for detecting an end point of polishing of the workpiece.

Background Art

[0002] A semiconductor device is manufactured through a front process (i.e., a device wafer manufacturing process) including element formation, wiring formation, and wafer characteristic inspection, and a back process (i.e., a packaging process) including an assembly process and an inspection process. Recently, three-dimensional packaging that stacks in the height direction as an intermediate process has been introduced between the front process and the back process.

[0003] In the above-described front process and intermediate process, there is a process of polishing the surface of a wafer with a CMP (chemical mechanical polishing) apparatus. The CMP apparatus executes wafer polishing as follows. While rotating a polishing table holding a polishing pad, a polishing liquid (typically, a slurry containing abrasive grains) is supplied onto the polishing pad. The wafer is pressed against the polishing pad by a polishing head and is brought into sliding contact with the polishing pad. The surface of the wafer is flattened by a combination of the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and the polishing pad.

[0004] The polishing of the wafer is stopped when the upper layer is polished and the polishing stopper layer is exposed. There is a torque monitoring method for such a technique for detecting the end point of wafer polishing. This torque monitoring method monitors a current (hereinafter referred to as a torque current) supplied to a motor that rotates the polishing table during the polishing of the wafer, and detects the polishing end point at the time when the torque current changes across a threshold value.

[0005] Figure 11 is a schematic diagram showing an example of a wafer cross-section. As the wafer is polished, the upper layer 501 forming the surface of the wafer is polished little by little, and eventually the polishing stopper layer 502 is exposed. Since the upper layer 501 and the polishing stopper layer are made of different materials, the frictional resistance between the upper layer 501 and the polishing pad is different from the frictional resistance between the polishing stopper layer 502 and the polishing pad. Therefore, when the polishing stopper layer 502 is exposed, the torque current changes significantly. In other words, the point where the torque current changes significantly is the point where the polishing stopper layer 502 is exposed, i.e., the polishing endpoint. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2004-249458 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, recently, due to the structure of semiconductor devices, there are wafers with a small surface area for the polishing stopper layer. When polishing such wafers, even if the polishing stopper layer is exposed, the torque current does not change significantly, and as a result, it may not be possible to detect the end point of the wafer polishing.

[0008] Therefore, the present invention provides a polishing method that can accurately detect the polishing endpoint, which is the point where a structure with a small surface area is exposed. [Means for solving the problem]

[0009] In one embodiment, a polishing method is provided, in which a polishing fluid is supplied onto a polishing pad, and a workpiece is pressed against the polishing pad by a polishing head, thereby polishing a layer to be polished on a plurality of endpoint target structures distributed across the entire surface of the workpiece; during the polishing of the layer to be polished, the thickness of the layer to be polished on the plurality of endpoint target structures is measured by a film thickness sensor; and the polishing endpoint of the layer to be polished is detected when the plurality of measured values ​​of the thickness of the layer to be polished on the plurality of endpoint target structures reach a target value.

[0010] In one embodiment, the surface coverage ratio, which is the ratio of the area of ​​the end faces of the plurality of endpoint target structures to the area of ​​the surface of the workpiece, is 0.2 to 20%. In one embodiment, the plurality of endpoint target structures are located at the same location within a plurality of chips distributed on the surface of the workpiece. In one embodiment, the polishing endpoint of the layer to be polished is the point at which all of the plurality of endpoint target structures are exposed.

[0011] In one embodiment, the polishing method further includes, during the polishing of the layer to be polished, creating a current film thickness profile of the layer to be polished from the plurality of measured values, and performing profile control to bring the current film thickness profile closer to a target film thickness profile by adjusting the plurality of pressing forces of the polishing head against a plurality of regions of the workpiece based on the plurality of measured values. In one embodiment, the target film thickness profile is a flat film thickness profile. In one embodiment, the film thickness sensor is an optical film thickness sensor or an eddy current film thickness sensor. In one embodiment, the polished layer and the plurality of endpoint target structures are composed of different materials. In one embodiment, the plurality of endpoint target structures are formed from an insulating material or a metal. In one embodiment, the layer to be polished is formed from an insulating material, silicon, or a metal. [Effects of the Invention]

[0012] The thickness of the film being polished on multiple endpoint target structures corresponds to the amount of polishing required to expose those structures. Therefore, based on multiple measurements of the film thickness on the multiple endpoint target structures, the polishing endpoint of the film can be accurately detected. Furthermore, since the multiple endpoint target structures are distributed across the entire surface of the workpiece, the polishing head can control the film thickness profile of the film being polished based on multiple measurements of its thickness. In particular, if the film being polished has a flat film thickness profile, multiple endpoint target structures can be exposed simultaneously. As a result, dishing caused by localized over-polishing can be prevented. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing one embodiment of a polishing apparatus. [Figure 2] This is a cross-sectional view showing one embodiment of a polishing head system including a polishing head and a plurality of pressure regulators. [Figure 3] This is a cross-sectional view showing an example of the surface structure of a workpiece before polishing. [Figure 4] This is a schematic diagram showing an example of multiple endpoint target structures distributed on the surface of a workpiece. [Figure 5] Figures 5(a) to 5(c) show examples of changes in the thickness of the layer to be polished when the layer to be polished on a workpiece is being polished. [Figure 6] Figures 6(a) to 6(c) are plan views showing examples of arrangements of multiple film thickness sensors. [Figure 7] This figure shows an example of how the film thickness profile of the layer to be polished changes when the layer to be polished on a workpiece is being polished. [Figure 8] This is a cross-sectional view showing another example of the surface structure of a workpiece before polishing. [Figure 9] Figures 9(a) and 9(b) are plan views showing examples of the arrangement of an optical film thickness sensor and an eddy current film thickness sensor. [Figure 10] It is a cross-sectional view showing still another example of the surface structure of the workpiece before being polished. [Figure 11] It is a schematic view showing an example of a cross-section of a wafer.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of a polishing apparatus. As shown in FIG. 1, the polishing apparatus includes a polishing table 3 that supports a polishing pad 2, a polishing head 1 that presses a workpiece W against the polishing pad 2, a table motor 6 that rotates the polishing table 3, a polishing liquid supply nozzle 5 for supplying a polishing liquid such as slurry onto the polishing pad 2, and a polishing control unit 9 for controlling the operation of the polishing apparatus. The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the workpiece W.

[0015] The polishing head 1 is connected to a head shaft 10, and the head shaft 10 is connected to a polishing head rotation device 15. The polishing head rotation device 15 is configured to rotate the polishing head 1 together with the head shaft 10 in the direction indicated by the arrow. The configuration of the polishing head rotation device 15 is not particularly limited. In one example, the polishing head rotation device 15 includes an electric motor, a belt, a pulley, and the like. The polishing table 3 is connected to the table motor 6, and the table motor 6 is configured to rotate the polishing table 3 and the polishing pad 2 in the direction indicated by the arrow. The polishing head 1, the polishing head rotation device 15, and the table motor 6 are connected to the polishing control unit 9, and the operations of the polishing head 1, the polishing head rotation device 15, and the table motor 6 are controlled by the polishing control unit 9.

[0016] The workpiece W is polished as follows: The table motor 6 and the polishing head rotating device 15 rotate the polishing table 3 and the polishing head 1 in the direction indicated by the arrows in Figure 1, while polishing fluid is supplied from the polishing fluid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. As the workpiece W is rotated by the polishing head 1, the workpiece W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1 while polishing fluid is present on the polishing pad 2. The surface of the workpiece W is polished by the chemical action of the polishing fluid and the mechanical action of the abrasive grains contained in the polishing fluid and / or the polishing pad 2.

[0017] The polishing control unit 9 comprises a storage device 9a in which a program is stored, and an arithmetic unit 9b that performs calculations according to the instructions contained in the program. The polishing control unit 9 is composed of at least one computer. The storage device 9a comprises a main memory such as random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or solid-state drive (SSD). Examples of arithmetic units 9b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the polishing control unit 9 is not limited to these examples.

[0018] The polishing apparatus further includes a film thickness sensor 21 for measuring the film thickness of the workpiece W on the polishing pad 2. The film thickness sensor 21 is fixed to the polishing table 3 and rotates with the polishing table 3. The position of the film thickness sensor 21 is such that it crosses the surface of the workpiece W on the polishing pad 2 each time the polishing table 3 and the polishing pad 2 complete one rotation. The film thickness sensor 21 is configured to measure the film thickness at multiple measurement points on the surface of the workpiece W each time it crosses the surface of the workpiece W.

[0019] Specific examples of the film thickness sensor 21 include an optical film thickness sensor and an eddy current film thickness sensor. The optical film thickness sensor is configured to detect the thickness of the polished layer 101 from the optical information contained in the reflected light from the workpiece W by irradiating light onto the surface of the workpiece W. In one example, the optical film thickness sensor detects the thickness of the polished layer 101 from the shape or characteristic quantity of the spectrum of the reflected light from the workpiece W. The eddy current sensor is configured to induce eddy currents in the metal formed on the workpiece W and detect the thickness of the metal from the impedance caused by the magnetic field of these eddy currents. However, the type of film thickness sensor 21 is not particularly limited as long as it can measure the film thickness of the workpiece W.

[0020] The measured thickness of the layer to be polished 101 output from the film thickness sensor 21 may be a numerical value that directly indicates the thickness of the layer to be polished 101, or it may be an index that indirectly indicates the thickness. The film thickness sensor 21 is electrically connected to the polishing control unit 9, and the measured film thickness is transmitted from the film thickness sensor 21 to the polishing control unit 9.

[0021] Figure 2 is a cross-sectional view showing one embodiment of a polishing head system including a polishing head 1 and a plurality of pressure regulators. The polishing head 1 comprises a carrier 31 fixed to the end of a head shaft 10, an elastic membrane 34 attached to the lower part of the carrier 31, and a retainer ring 32 positioned below the carrier 31. The retainer ring 32 is positioned around the elastic membrane 34.

[0022] The elastic membrane 34 comprises a contact portion 35 having a contact surface 35a that can contact the upper surface of the workpiece W, and inner wall portions 36a, 36b, 36c and an outer wall portion 36d connected to the contact portion 35. The contact portion 35 has substantially the same size and shape as the upper surface of the workpiece W. The inner wall portions 36a, 36b, 36c and the outer wall portion 36d are endless walls arranged concentrically. The outer wall portion 36d is located outside the inner wall portions 36a, 36b, 36c and is arranged to surround the inner wall portions 36a, 36b, 36c.

[0023] Multiple (four in this embodiment) pressure chambers C1, C2, C3, and C4 are provided between the elastic membrane 34 and the carrier 31. The pressure chambers C1, C2, C3, and C4 are formed by the contact portion 35, inner wall portions 36a, 36b, and 36c, and outer wall portion 36d of the elastic membrane 34. In this embodiment, the elastic membrane 34 forms four pressure chambers C1 to C4, but in one embodiment, the elastic membrane 34 may form three pressure chambers, or it may form five or more pressure chambers.

[0024] An annular membrane (rolling diaphragm) 37 is positioned between the carrier 31 and the retainer ring 32, and a pressure chamber C5 is formed inside this membrane 37. Gas transfer lines F1, F2, F3, F4, and F5 are connected to the pressure chambers C1, C2, C3, C4, and C5, respectively. The gas transfer lines F1, F2, F3, F4, and F5 extend via a rotary joint 40 attached to the head shaft 10.

[0025] Gas transfer lines F1, F2, F3, F4, and F5 are connected to a compressed gas supply source (not shown) which serves as a utility supply source in the factory where the polishing equipment is installed. Compressed gas, such as compressed air, is supplied to pressure chambers C1, C2, C3, C4, and C5, respectively, through gas transfer lines F1, F2, F3, F4, and F5.

[0026] Pressure regulators Ra1, Ra2, Ra3, Ra4, and Ra5, which are pressure regulating devices, are installed on the gas transfer lines F1, F2, F3, F4, and F5, respectively. Compressed gas from the compressed gas supply source is supplied independently to the pressure chambers C1 to C5 through the pressure regulators Ra1 to Ra5 ​​and the gas transfer lines F1 to F5. The pressure regulators Ra1 to Ra5 ​​are configured to regulate the pressure of the compressed gas in the pressure chambers C1 to C5.

[0027] The pressure regulators Ra1 to Ra5, which are pressure regulating devices, are connected to the polishing control unit 9. The operation of the pressure regulators Ra1 to Ra5 ​​is controlled by the polishing control unit 9. The polishing control unit 9 sends pressure command values ​​for pressure chambers C1 to C5 to the pressure regulators Ra1 to Ra5, and the pressure regulators Ra1 to Ra5 ​​operate so that the pressure in pressure chambers C1 to C5 is maintained at the corresponding pressure command value.

[0028] The pressure regulators Ra1 to Ra5 ​​can independently change the pressure within the pressure chambers C1 to C5. Therefore, the polishing head 1 can independently adjust the polishing pressure on four corresponding areas of the workpiece W, namely the central part, the inner middle part, the outer middle part, and the edge part, and the pressing force of the polishing pad 2 of the retainer ring 32 against the polishing surface 2a. For example, the polishing head 1 can press different areas of the surface of the workpiece W against the polishing surface 2a of the polishing pad 2 with different polishing pressures. Thus, the polishing head system, including the polishing head 1 and the pressure adjusting devices (pressure regulators Ra1, Ra2, Ra3, Ra4, Ra5), can control the film thickness profile of the workpiece W to achieve a target film thickness profile.

[0029] Figure 3 is a cross-sectional view showing an example of the surface structure of a workpiece W before polishing. As shown in Figure 3, the workpiece W before polishing has a surface structure that includes a polishing layer 101 and a plurality of endpoint target structures 102 covered by the polishing layer 101. Examples of workpiece W include wafers, substrates, wiring boards, and corner substrates used in the manufacture of semiconductor devices. In one embodiment, the surface structure of the workpiece W shown in Figure 3 is applied to the manufacture of shallow trench isolation (STI).

[0030] Each endpoint target structure 102 has a convex shape. Multiple endpoint target structures 102 are arranged in parallel at the same height, and the polished layer 101 is formed to cover the end faces 102a of the multiple endpoint target structures 102. The polished layer 101 and the endpoint target structures 102 are made of different materials. In this embodiment, the polished layer 101 is made of an insulating material such as silicon dioxide (SiO2), and the endpoint target structure 102 is made of silicon nitride (SiN), which is an insulating material different from the insulating material that makes up the polished layer 101. The insulating material that makes up the polished layer 101 has the property of transmitting light. Therefore, in this embodiment, an optical film thickness sensor is used as the film thickness sensor 21.

[0031] Figure 4 is a schematic diagram showing an example of multiple endpoint target structures 102 distributed on the surface of a workpiece W. The endpoint target structures 102 shown in Figure 4 are schematic representations, and the relative size of the endpoint target structures 102 with respect to the workpiece W does not necessarily represent the actual relative size.

[0032] As shown in Figure 4, the multiple endpoint target structures 102 are distributed across the entire surface of the workpiece W. In the example shown in Figure 4, the workpiece W has multiple chips 108 formed on its surface, which are distributed across the entire surface of the workpiece W and arranged at equal intervals. The chips 108 are aligned along the orientation of the silicon crystal, indicated by the notches 110. Each chip 108 contains at least one endpoint target structure 102 (two endpoint target structures 102 in the example shown in Figure 4). The multiple endpoint target structures 102 are located in the same place within the multiple chips 108. Therefore, in the example shown in Figure 4, the endpoint target structures 102 are uniformly distributed across the entire surface of the workpiece W.

[0033] The polishing method of this embodiment is applicable to polishing a workpiece W with a surface coverage ratio of 0.2 to 20% for multiple endpoint target structures 102. In particular, the polishing method of this embodiment is applicable to polishing a workpiece W with a very low surface coverage ratio for multiple endpoint target structures 102, for example, for polishing a workpiece W with a surface coverage ratio of 0.2 to 5%, or 1 to 5%. Surface coverage ratio is the ratio of the area of ​​the end faces 102a (see Figure 3) of the multiple endpoint target structures 102 to the surface area of ​​the workpiece W.

[0034] Figures 5(a) to 5(c) show examples of changes in the thickness of the polished layer 101 of a workpiece W as it is being polished. More specifically, Figure 5(a) shows the initial stage of polishing the polished layer 101 of the workpiece W, Figure 5(b) shows the middle stage of polishing the polished layer 101 of the workpiece W, and Figure 5(c) shows the final stage of polishing the polished layer 101 of the workpiece W.

[0035] During the polishing of the layer to be polished 101, the film thickness sensor 21 shown in Figure 1 measures the thickness T1 of the layer to be polished 101 on multiple endpoint target structures 102. The thickness T1 of the layer to be polished 101 corresponds to the distance from the exposed surface (polished surface) 101a of the layer to be polished 101 to each endpoint target structure 102. The polishing control unit 9 acquires multiple measurements of the thickness T1 of the layer to be polished 101 on the multiple endpoint target structures 102 from the film thickness sensor 21. The multiple measurements of thickness T1 correspond to each of the multiple endpoint target structures 102. That is, each measurement of thickness T1 indicates the thickness T1 of the layer to be polished 101 on each endpoint target structure 102.

[0036] As shown in Figures 5(a) to 5(c), as the layer to be polished 101 is polished, the thickness T1 of the layer to be polished on the multiple endpoint target structures 102 decreases. During the polishing of the layer to be polished 101, the polishing control unit 9 monitors multiple measurements of the thickness T1 corresponding to each of the multiple endpoint target structures 102 and detects the polishing endpoint based on the multiple measurements of the thickness T1 of the layer to be polished 101.

[0037] As shown in Figure 5(c), the polishing endpoint of the layer to be polished 101 is the point at which the thickness T1 of the layer to be polished 101 on the multiple endpoint target structures 102 reaches the target value of 0, that is, the point at which the multiple endpoint target structures 102 are exposed. As explained with reference to Figure 4, the multiple endpoint target structures 102 are distributed over the entire surface of the workpiece W, and the point at which all of these endpoint target structures 102 are exposed is the polishing endpoint of the layer to be polished 101.

[0038] The endpoint target structure 102 is relatively small relative to the surface of the workpiece W. In order for the film thickness sensor 21 to accurately measure the thickness of the polished layer 101 on each endpoint target structure 102, it is desirable that the effective measurement range of the film thickness sensor 21 be as small as possible.

[0039] The film thickness sensor 21 measures the thickness of the polished layer 101 at multiple measurement points on the surface of the workpiece W as it moves across the surface of the workpiece W each time the polishing table 3 rotates. Therefore, as shown in Figure 5(a), the multiple measurements of the thickness of the polished layer 101 obtained each time the polishing table 3 rotates include measurements of the thickness T1 of the polished layer 101 on multiple endpoint target structures 102, and measurements of the thickness T2 of the polished layer 101 at locations other than the multiple endpoint target structures 102.

[0040] Conventional polishing endpoint technology calculates the average of all measurements of different film thicknesses acquired each time the polishing table rotates, and detects the polishing endpoint based on that average. In contrast, in this embodiment, the polishing endpoint of the layer to be polished 101 is detected based solely on the measured thickness T1 of the layer to be polished 101 on the multiple endpoint target structures 102. More specifically, the polishing control unit 9 detects the polishing endpoint when the measured thickness T1 of the layer to be polished 101 on the multiple endpoint target structures 102 reaches a target value. In this embodiment, the target value for the thickness T1 of the layer to be polished 101 is 0. Therefore, the polishing control unit 9 can accurately detect the polishing endpoint of the layer to be polished 101, which is the point when all of the multiple endpoint target structures 102 are exposed.

[0041] The polishing control unit 9 extracts a measured value of the thickness T1 of the polished layer 101 on a plurality of endpoint target structures 102 (hereinafter sometimes referred to as a target measurement value) from a plurality of measurement values, including measured values ​​of the thickness T1 and T2 of the polished layer 101, acquired each time the polishing table 3 rotates. In one embodiment, the polishing control unit 9 calculates the average of a plurality of measurement values, including measured values ​​of the thickness T1 and T2 of the polished layer 101, acquired each time the polishing table 3 rotates, and extracts a target measurement value that is smaller than that average. In another embodiment, the polishing control unit 9 creates a normal distribution of a plurality of measurement values, including measured values ​​of the thickness T1 and T2 of the polished layer 101, acquired each time the polishing table 3 rotates, and extracts the target measurement value from the normal distribution. However, the method for extracting the target measurement value from a plurality of measurement values, including measured values ​​of the thickness T1 and T2 of the polished layer 101, is not limited to these embodiments, and known data processing methods can be used.

[0042] The effective measurement range of the film thickness sensor 21 may be larger than the area of ​​the end face 102a of each endpoint target structure 102. In such cases, the necessary film thickness information can be obtained by known data processing techniques as described below. • Noise reduction using filtering • Synchronization detection using a phase-locked loop (PLL) • Signal amplification using a lock-in amplifier • Time gating method • Optimization of sampling frequency • Use of multiplex sensor arrays • Waveform analysis using digital signal processing (DSP) • Local signal detection using wavelet transform • Dynamic noise suppression using adaptive filters • Signal enhancement through envelope detection • Identifying periodic signals using Fourier transforms • Signal enhancement using phase detection • Correlation analysis Machine learning

[0043] The film thickness sensor 21 rotates with the polishing table 3 and measures the film thickness at multiple measurement points on the workpiece W. The movement path of the film thickness sensor 21 is uniquely determined by the distance between the film thickness sensor 21 and the rotation center of the polishing table 3. Therefore, the installation position of the film thickness sensor 21 may be determined based on the positions of multiple endpoint target structures 102 so that the film thickness sensor 21 measures the thickness T1 of the polished layer 101 on as many endpoint target structures 102 as possible each time the polishing table 3 rotates. In one embodiment, multiple film thickness sensors 21 may be placed on the polishing table 3.

[0044] Figures 6(a) to 6(c) are plan views showing examples of arrangements of multiple film thickness sensors 21. In the example shown in Figure 6(a), the two film thickness sensors 21 are positioned at different radial distances from the center CP of the polishing table 3, and are located at the same position in the circumferential direction of the polishing table 3. In this example, the two film thickness sensors 21 measure the film thickness at multiple measurement points on the workpiece W while traveling along different paths. One of the two film thickness sensors 21 travels along a path that passes through the center of the workpiece W.

[0045] In the example shown in Figure 6(b), the two film thickness sensors 21 are positioned at the same radial distance from the center CP of the polishing table 3, but at different positions in the circumferential direction of the polishing table 3. In this example, the two film thickness sensors 21 measure the film thickness at multiple measurement points on the workpiece W while traveling along the same path through the center of the workpiece W.

[0046] In the example shown in Figure 6(c), the two film thickness sensors 21 are positioned at different radial distances from the center CP of the polishing table 3 and at different positions in the circumferential direction of the polishing table 3. In this example, the two film thickness sensors 21 measure the film thickness at multiple measurement points on the workpiece W while traveling along different paths. One of the two film thickness sensors 21 travels along a path that passes through the center of the workpiece W.

[0047] As explained with reference to Figure 4, the multiple endpoint target structures 102 are distributed across the entire surface of the workpiece W. Therefore, the polishing control unit 9 can measure the film thickness profile of the polished layer 101 from multiple target measurements, which are multiple measurements of the thickness T1 of the polished layer 101 on the multiple endpoint target structures 102.

[0048] Figure 7 shows an example of the change in the film thickness profile of the layer to be polished 101 of the workpiece W while it is being polished. The polishing control unit 9 is configured to create the current film thickness profile of the layer to be polished 101 from multiple target measurements while the layer to be polished 101 is being polished. The film thickness profile is the distribution of the thickness of the layer to be polished 101 in the radial direction of the workpiece W.

[0049] The polishing control unit 9 performs profile control to bring the current film thickness profile closer to the target film thickness profile by adjusting multiple pressing forces of the polishing head 1 against multiple regions of the workpiece W based on multiple target measurement values. The multiple pressing forces of the polishing head 1 are adjusted by the pressure of compressed gas in multiple pressure chambers C1 to C4 shown in Figure 2, and the pressure of compressed gas in pressure chambers C1 to C4 can be adjusted by multiple pressure regulators Ra1, Ra2, Ra3, and Ra4 shown in Figure 2.

[0050] The film thickness profile created immediately after the start of polishing of the layer to be polished 101 is the initial film thickness profile. As shown in Figure 7, as the layer to be polished 101 is polished, the film thickness profile of the layer to be polished 101 gradually changes from the initial film thickness profile to the target film thickness profile. Then, as described above, when all of the multiple target measurement values ​​reach the target value (0 in this embodiment), that is, when all the endpoint target structures 102 are exposed, the polishing of the layer to be polished 101 is completed.

[0051] As shown in Figure 7, the target film thickness profile is a flat film thickness profile. Towards the end of polishing the layer to be polished 101, the layer to be polished 101 is polished while maintaining a flat film thickness profile. Therefore, multiple endpoint target structures 102 distributed across the entire surface of the workpiece W can be exposed simultaneously. As a result, dishing caused by localized overpolishing can be prevented.

[0052] The above-described embodiment of the polishing method can be applied not only to polishing workpieces W having the surface structure shown in Figure 3, but also to polishing workpieces with other surface structures, as long as the multiple endpoint target structures are distributed across the entire surface of the workpiece. For example, the polishing method of the above embodiment can also be applied to polishing workpieces having a TSV (Through Silicon Via) surface structure, which will be described below.

[0053] Figure 8 is a cross-sectional view showing another example of the surface structure of a workpiece W before polishing. The surface structure of the workpiece W shown in Figure 8 is applied to the manufacture of TSVs (Through Silicon Vias). As shown in Figure 8, the workpiece W before polishing has a surface structure that includes a polishing layer 201 and a plurality of endpoint target structures 202 covered by the polishing layer 201. The polishing layer 201 is formed from silicon, and the plurality of endpoint target structures 202 are formed from metal (e.g., copper). In the example shown in Figure 8, the exposed surface (polished surface) 201a of the polishing layer 201 is the back surface of the workpiece W.

[0054] The multiple endpoint target structures 202 are distributed across the entire surface of the workpiece W, similar to the embodiment described with reference to Figure 4. More specifically, the workpiece W has multiple chips formed on its surface, which are distributed across the entire surface of the workpiece W and arranged at equal intervals. Each chip contains at least one endpoint target structure 202. The multiple endpoint target structures 202 are located at the same location within the multiple chips. Thus, the endpoint target structures 202 are uniformly distributed across the entire surface of the workpiece W.

[0055] The range of surface coverage, which is the ratio of the area of ​​the end faces 202a of the multiple endpoint target structures 202 to the surface area of ​​the workpiece W, is the same as in the embodiments described with reference to Figures 3 and 4.

[0056] The embodiments of the polishing apparatus and polishing method described with reference to Figures 1 to 7 can be applied to polishing a workpiece W having the surface structure shown in Figure 8. That is, during the polishing of the layer to be polished 201, the film thickness sensor 21 shown in Figure 1 measures the thickness of the layer to be polished 201 on a plurality of endpoint target structures 202. The polishing control unit 9 acquires multiple measurement values ​​(i.e., target measurement values) of the thickness of the layer to be polished 201 on the plurality of endpoint target structures 202 from the film thickness sensor 21 and detects the polishing endpoint when the target measurement value reaches the target value. In this embodiment, the target value is 0. Therefore, the polishing control unit 9 can accurately detect the polishing endpoint of the layer to be polished 201, which is the point at which all of the plurality of endpoint target structures 202 are exposed.

[0057] If the multiple endpoint target structures 202 are made of metal, as in the embodiment shown in Figure 8, the polishing apparatus shown in Figure 1 may be equipped with both an optical film thickness sensor and an eddy current film thickness sensor as the film thickness sensor 21. The polishing control unit 9 detects the polishing endpoint of the layer to be polished 201 based on multiple measurements of the thickness of the layer to be polished 201 measured by the optical film thickness sensor. Polishing of the workpiece W continues even after the polishing endpoint of the layer to be polished 201 is detected, i.e., after the multiple endpoint target structures 202 are exposed. The polishing control unit 9 then detects the polishing endpoint of the multiple endpoint target structures 202 based on multiple measurements of the thickness (height) of the multiple endpoint target structures 202 measured by the eddy current film thickness sensor. The polishing endpoint of the multiple endpoint target structures 202 is the point at which the thickness (height) of the multiple endpoint target structures 202 reaches the target value. According to the polishing method of this embodiment, the multiple endpoint target structures 202 can be aligned to a desired thickness (height).

[0058] Figures 9(a) and 9(b) are plan views showing examples of the arrangement of an optical film thickness sensor and an eddy current film thickness sensor. In the example shown in Figure 9(a), the optical film thickness sensor 21A and the eddy current film thickness sensor 21B are positioned at the same radial distance from the center CP of the polishing table 3, but at different positions in the circumferential direction of the polishing table 3. In this example, the optical film thickness sensor 21A and the eddy current film thickness sensor 21B measure the film thickness at multiple measurement points on the workpiece W while traveling along the same path through the center of the workpiece W.

[0059] In the example shown in Figure 9(b), the first pair of optical film thickness sensors 21A and eddy current film thickness sensors 21B are positioned at different radial distances from the center CP of the polishing table 3 compared to the second pair of optical film thickness sensors 21C and eddy current film thickness sensors 21D. In this example, the first pair of optical film thickness sensors 21A and eddy current film thickness sensors 21B measure the film thickness at multiple measurement points on the workpiece W while traveling along a path that passes through the center of the workpiece W. The second pair of optical film thickness sensors 21C and eddy current film thickness sensors 21D measure the film thickness at multiple measurement points on the workpiece W while traveling along a different path than the first pair of optical film thickness sensors 21A and eddy current film thickness sensors 21B.

[0060] Figure 10 is a cross-sectional view showing yet another example of the surface structure of a workpiece W before polishing. As shown in Figure 10, the workpiece W before polishing has a surface structure including a polishing layer 301 and a plurality of endpoint target structures 302 covered by the polishing layer 301. The polishing layer 301 is made of a metal (e.g., copper), and the plurality of endpoint target structures 302 are made of an insulating material (e.g., silicon nitride (SiN) or silicon dioxide (SiO2)). Therefore, the film thickness sensor 21 for measuring the thickness of the polishing layer 301 is an eddy current film thickness sensor.

[0061] The multiple endpoint target structures 302 are distributed across the entire surface of the workpiece W, similar to the embodiment described with reference to Figure 4. More specifically, the workpiece W has multiple chips formed on its surface, which are distributed across the entire surface of the workpiece W and arranged at equal intervals. Each chip contains at least one endpoint target structure 302. The multiple endpoint target structures 302 are located at the same location within the multiple chips. Thus, the endpoint target structures 302 are uniformly distributed across the entire surface of the workpiece W.

[0062] The range of surface coverage, which is the ratio of the area of ​​the end faces 302a of the multiple endpoint target structures 302 to the surface area of ​​the workpiece W, is the same as in the embodiments described with reference to Figures 3 and 4.

[0063] The embodiments of the polishing apparatus and polishing method described with reference to Figures 1 to 9 can be applied to polishing a workpiece W having the surface structure shown in Figure 10. Specifically, during the polishing of the layer to be polished 301, the film thickness sensor 21, which is an eddy current type film thickness sensor, measures the thickness of the layer to be polished 301 on a plurality of endpoint target structures 302. The polishing control unit 9 obtains multiple measurement values ​​(i.e., target measurement values) of the thickness of the layer to be polished 301 on the plurality of endpoint target structures 302 from the film thickness sensor 21 and detects the polishing endpoint when the target measurement value reaches the target value. In this embodiment, the target value is 0. Therefore, the polishing control unit 9 can accurately detect the polishing endpoint of the layer to be polished 301, which is the point at which all of the plurality of endpoint target structures 302 are exposed.

[0064] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims. [Explanation of Symbols]

[0065] 1 Polishing head 2 polishing pads 2a Polished surface 3 Polishing Table 5. Polishing fluid supply nozzle 6 Table motors 9 Polishing Control Unit 10 Head Shaft 15. Polishing head rotation device 21 Film Thickness Sensor 31 Careers 32 Retainer Rings 34 Elastic membrane 35 Contact area 35a Contact surface 36a,36b,36c Inner wall 36d Exterior wall 37 Membrane (Rolling Diaphragm) 40 Rotary Joint 101,201,301 Layer to be polished 102,202,302 End-point target structure C1,C2,C3,C4,C5 Pressure chamber F1, F2, F3, F4, F5 Gas Transfer Line Ra1, Ra2, Ra3, Ra4, Ra5 Pressure Regulator (Pressure Regulating Device) W Workpiece

Claims

1. By supplying polishing fluid onto the polishing pad and pressing the workpiece against the polishing pad with the polishing head, the layers to be polished on multiple endpoint target structures distributed across the entire surface of the workpiece are polished. During the polishing of the layer to be polished, the thickness of the layer to be polished on the plurality of endpoint target structures is measured by a film thickness sensor. A polishing method that detects the polishing endpoint of the layer to be polished when multiple measurements of the thickness of the layer to be polished on the multiple endpoint target structures reach a target value.

2. The polishing method according to claim 1, wherein the surface coverage ratio, which is the ratio of the area of ​​the end faces of the plurality of endpoint target structures to the area of ​​the surface of the workpiece, is 0.2 to 20%.

3. The polishing method according to claim 1, wherein the plurality of endpoint target structures are located at the same location among a plurality of chips distributed on the surface of the workpiece.

4. The polishing method according to claim 1, wherein the polishing endpoint of the layer to be polished is the point at which all of the plurality of endpoint target structures are exposed.

5. During the polishing of the layer to be polished, a current film thickness profile of the layer to be polished is created from the multiple measurement values. The polishing method according to claim 1, further comprising performing profile control to bring the current film thickness profile closer to a target film thickness profile by adjusting a plurality of pressing forces of the polishing head against a plurality of regions of the workpiece based on the plurality of measured values.

6. The polishing method according to claim 5, wherein the target film thickness profile is a flat film thickness profile.

7. The polishing method according to claim 1, wherein the film thickness sensor is an optical film thickness sensor or an eddy current film thickness sensor.

8. The polishing method according to claim 1, wherein the layer to be polished and the plurality of endpoint target structures are composed of different materials.

9. The polishing method according to claim 8, wherein the plurality of endpoint target structures are formed from an insulating material or a metal.

10. The polishing method according to claim 8, wherein the layer to be polished is formed from an insulating material, silicon, or a metal.

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