A workpiece single-sided polishing apparatus, a workpiece single-sided polishing method, and a silicon wafer manufacturing method.

Abstract

To provide a single-sided polishing device of a work-piece, a single-sided polishing method of the work-piece, and a manufacturing method of a silicon wafer, capable of measuring a dynamic displacement magnitude of an abrasive pad in single-sided polishing.SOLUTION: A single-sided polishing device of a work-piece further comprises a font surface displacement measurement part which can measure a deviation of an exposure upper surface that is an upper surface of a polishing pad and is a part which is not covered with a polishing head. A single-sided polishing method of the work-piece polishes one surface of the work-piece while measuring the displacement of the exposure upper surface by the font surface displacement measurement part that can measure the displacement of the exposure upper surface in a polishing step. A manufacturing method of a silicon wafer uses the single-sided polishing method of the work-piece.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a single-sided polishing apparatus for a workpiece, a single-sided polishing method for a workpiece, and a method for manufacturing a silicon wafer using the single-sided polishing method for a workpiece.

Background Art

[0002] In the single-sided polishing of a workpiece (for example, a silicon wafer), while rotating a polishing platen and a polishing pad having a diameter larger than that of the wafer, the polishing pad is pressed against the wafer to polish the wafer. At that time, since the polishing platen and the polishing pad are rotating, pressure loading and pressure release repeatedly occur on the polishing pad with respect to the pressing pressure from the wafer. In such polishing, it is known that the viscoelasticity of the polishing pad affects particularly the polishing amount distribution in the outer peripheral portion of the wafer, and polishing pads having various physical property values (including viscoelasticity) have been proposed (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, it has been difficult to represent the displacement amount of the polishing pad during actual polishing only by the method of grasping the physical property values of the conventional polishing pad. In contrast, although Patent Document 2 proposes measuring the deformation of the polishing pad when the wafer is pressed, it has not been possible to measure the behavior in which the deformation of the polishing pad recovers after pressing. For this reason, a method capable of measuring the dynamic displacement amount of the polishing pad during single-sided polishing has been desired.

[0005] Therefore, the present invention aims to provide a workpiece single-sided polishing apparatus, a workpiece single-sided polishing method, and a silicon wafer manufacturing method that are capable of measuring the amount of dynamic displacement of the polishing pad during single-sided polishing. [Means for solving the problem]

[0006] The gist of the present invention is as follows: (1) A workpiece single-sided polishing apparatus, A polishing plate having a larger diameter than the aforementioned workpiece, A polishing pad attached to the polishing platen, A polishing head capable of holding the workpiece and pressing it against a polishing pad, The system includes a polishing liquid supply nozzle for supplying polishing liquid to the polishing pad, A workpiece single-sided polishing apparatus, further comprising a surface displacement measuring unit capable of measuring the displacement of the exposed upper surface, which is the upper surface of the polishing pad and not covered by the polishing head.

[0007] (2) The workpiece single-sided polishing apparatus according to (1) above, further comprising a polishing liquid removal unit for removing the polishing liquid from the exposed upper surface.

[0008] (3) The polishing liquid removal unit is configured to allow air to be blown onto the exposed upper surface, the workpiece single-sided polishing apparatus as described in (2) above.

[0009] (4) A workpiece single-sided polishing apparatus according to any one of (1) to (3) above, wherein the surface displacement measuring units are arranged in multiple locations.

[0010] (5) A workpiece polishing apparatus for a workpiece as described in any one of (1) to (4) above, wherein the workpiece is a wafer.

[0011] (6) A method for polishing one side of a workpiece, Using a polishing plate having a diameter larger than the workpiece, a polishing pad attached to the polishing plate, a polishing head capable of holding the workpiece and pressing it against the polishing pad, and a polishing fluid supply nozzle for supplying polishing fluid to the polishing pad, The polishing process includes supplying the polishing fluid from the polishing fluid supply nozzle to the polishing pad, rotating the polishing platen and the polishing pad, and pressing the workpiece against the polishing pad to polish one side of the workpiece, A method for polishing one side of a workpiece, characterized in that, in the polishing step, one side of the workpiece is polished while measuring the displacement of the exposed upper surface, which is the upper surface of the polishing pad and the portion not covered by the polishing head, using a surface displacement measuring unit capable of measuring the displacement of the exposed upper surface.

[0012] (7) The method for polishing one side of a workpiece as described in (6) above, wherein one side of the workpiece is polished while removing the polishing liquid from the exposed upper surface.

[0013] (8) The method for polishing one side of a workpiece as described in (7) above, wherein one side of the workpiece is polished while removing the polishing liquid by blowing air onto the exposed upper surface.

[0014] (9) Further includes a preliminary step of measuring the displacement of the exposed upper surface without pressing the workpiece against the polishing pad, A method for polishing one side of a workpiece according to (6) or (7) above, wherein the dynamic change in the displacement of the exposed upper surface during one-sided polishing of the workpiece is calculated by comparing the measurement results from the preliminary step with the results of measuring the displacement of the exposed upper surface while the workpiece is pressed against the polishing pad.

[0015] (10) A method for polishing one side of a workpiece as described in any one of (6) to (9) above, wherein the workpiece is a silicon wafer.

[0016] (11) A method for manufacturing a silicon wafer using the single-sided polishing method of the workpiece described in (10) above. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a single-sided polishing apparatus for a workpiece, a single-sided polishing method for a workpiece, and a method for manufacturing a silicon wafer, which are capable of measuring the dynamic displacement amount of a polishing pad during single-sided polishing.

Brief Description of the Drawings

[0018] [Figure 1] It is a schematic top view of a single-sided polishing apparatus for a workpiece according to an embodiment of the present invention. [Figure 2] It is a schematic side view of a single-sided polishing apparatus for a workpiece according to an embodiment of the present invention. [Figure 3] It is a diagram showing the relationship between the measurement time and the displacement of the exposed upper surface. [Figure 4] It is a diagram showing data with outliers removed in FIG. 3. [Figure 5] It is a diagram showing time moving average data with the time width (how many times the rotation period) of the centered moving average of the data in FIG. 4 changed. [Figure 6] It is a diagram showing data obtained by averaging the data in FIG. 4 by N. [Figure 7] It is a diagram showing data obtained when a preliminary step of similarly measuring the displacement of the exposed upper surface is performed without pressing the wafer against the polishing pad. [Figure 8] It is a diagram showing the relationship between the measurement time and the absolute amount of displacement of the exposed upper surface. [Figure 9] It is a diagram when air blowing is not performed.

Mode for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be exemplified and described in detail with reference to the drawings.

[0020] <Single-sided Polishing Apparatus for Workpiece> FIG. 1 is a schematic top view of a single-sided polishing apparatus for a workpiece according to an embodiment of the present invention. FIG. 2 is a schematic side view of a single-sided polishing apparatus for a workpiece according to an embodiment of the present invention.

[0021] As shown in Figures 1 and 2, this single-sided polishing apparatus 1 comprises a polishing platen 2 having a diameter larger than the workpiece (e.g., a silicon wafer) W, a polishing pad 3 attached to the upper surface of the polishing platen 2, a polishing head 4 capable of holding the workpiece W and pressing it against the polishing pad 3, and a polishing fluid supply nozzle 6 that supplies polishing fluid (polishing slurry) 5 to the polishing pad 3.

[0022] In the illustrated example, the upper surface of the polishing pad 3 slides against one side (bottom surface) of the workpiece W, polishing one side of the workpiece W. Although not shown in Figure 2, the polishing head 4 may also have a backing pad that holds the upper surface of the workpiece W and a retainer ring (whose inner diameter is equal to or greater than the diameter of the workpiece W) that holds the side. The polishing liquid 5 contains at least a water-soluble polymer and may further contain abrasive particles and an alkaline solution, and the water-soluble polymer can function as a protective agent for the workpiece W.

[0023] Although not shown in the diagram, the polishing head 4 may also comprise a shaft portion for raising, lowering, and rotating the polishing head 4, and a rotating frame portion provided at the lower end of the shaft portion, with a backing pad attached to its lower surface. The single-sided polishing device 1 is connected to the polishing platen 2 and includes a rotating mechanism (shaft, motor, etc.) for rotating the polishing platen 2.

[0024] Here, as shown in Figures 1 and 2, the upper surface of the polishing pad 3 consists of a portion covered by the polishing head 4 and a portion not covered by the polishing head 4 (hereinafter referred to as the exposed upper surface 7). The exposed upper surface 7 of the polishing pad (the portion not covered by the polishing head 4) is present with polishing fluid 5 during polishing, but is not pressed by the polishing head 4 or any other mechanism. Furthermore, this single-sided polishing device 1 is equipped with a surface displacement measuring unit 8 capable of measuring the displacement of the exposed upper surface 7. The surface displacement measuring unit 8 is not particularly limited, but can be a non-contact displacement meter such as a laser displacement meter.

[0025] As shown in Figure 2, the surface displacement measuring section 8 is enclosed in a waterproof container 9, thereby protecting it from splashing of the polishing liquid 5. In this example, the waterproof container 9 is made of transparent acrylic. In addition, in this example, the waterproof container 9 has a liquid drainage slope 10, which prevents the adhering polishing liquid 5 from remaining attached to the waterproof container 9.

[0026] Furthermore, as shown in Figure 2, this single-sided polishing apparatus 1 is further equipped with a polishing fluid removal unit 11 for removing the polishing fluid 5 from the exposed upper surface 7. The polishing fluid removal unit 11 only needs to be a mechanism that can remove the polishing fluid from the surface without applying enough pressure to affect the measurement of the displacement of the polishing pad 3. In this example, the polishing fluid removal unit 11 is an air blowing unit configured to blow air 12 onto the exposed upper surface 7. This air blowing unit is positioned above the measurement point, and by blowing air onto the polishing pad 3 from above, the polishing fluid 5 can be removed from the measurement point.

[0027] As shown in Figure 1, it is preferable that the single-sided polishing apparatus 1 has multiple surface displacement measuring units 8. Three surface displacement measuring units 8 are arranged corresponding to the three measurement points A, B, and C in Figure 1, but the number of surface displacement measuring units 8 is not limited to this example. In the illustrated example, measurement point A is the measurement point at the position immediately after the polishing pad 3 is released from the pressure generated between it and the workpiece W, and measurement points B and C are points where a predetermined time has elapsed after the release from the pressure. In this example, measurement points A to C are arranged at equal intervals. On the other hand, the measurement points can be arranged in various ways that are suitable for observing the dynamic change in the displacement of the exposed upper surface 7 of the polishing pad 3, and for example, they do not necessarily have to be arranged at equal intervals. For example, they may be placed at the position immediately after the polishing pad 3 is released from the pressure generated between it and the workpiece W, and at the measurement point corresponding to the position where the shape of the polishing pad 3 has almost recovered. The following describes the operation and effects of the workpiece single-sided polishing apparatus of this embodiment.

[0028] The single-sided polishing apparatus 1 for workpiece W in this embodiment is equipped with a surface displacement measuring unit 8 capable of measuring the displacement of the exposed upper surface 7. By continuously measuring the displacement of the exposed upper surface 7 during single-sided polishing of the workpiece W using the surface displacement measuring unit 8, the dynamic displacement behavior of the polishing pad, including the loading and depressurization of the pressing pressure from the workpiece W, can be grasped. By appropriately selecting the resolution of the surface displacement measuring unit 8, for example, it is possible to grasp the temporal change in the displacement of the polishing pad 3 on the order of a few microns. Therefore, it becomes possible to evaluate variations in the physical properties of the polishing pad that could not be determined by measuring the amount of displacement of the polishing pad (on the order of several hundred microns) when the wafer is pressed against it. Thus, according to the single-sided polishing apparatus 1 of this embodiment, it is possible to measure the dynamic displacement of the polishing pad during single-sided polishing.

[0029] Here, it is preferable that the single-sided polishing apparatus 1 further includes a polishing liquid removal unit 11 for removing the polishing liquid 5 from the exposed upper surface 7. This is because it is possible to accurately measure the dynamic displacement of the polishing pad 3 during single-sided polishing without being affected by the polishing liquid 5. It is preferable that the polishing liquid removal unit 11 is configured to be able to blow air 12 onto the exposed upper surface 7. This is because it is possible to avoid being affected by the polishing liquid 5 with a simple configuration.

[0030] Furthermore, it is preferable that the surface displacement measuring units 8 be arranged in multiple locations. This is because it is possible to grasp the temporal change in the displacement of the polishing pad 3 within one cycle, which includes the loading and depressurization of the pressing pressure from the workpiece W. By arranging multiple locations in the circumferential direction of the polishing pad 3, it is possible to grasp the temporal change at the same location within the polishing pad 3, thereby enabling more accurate measurement of the dynamic changes of the polishing pad 3.

[0031] <Method for polishing one side of a workpiece> One example of a method for polishing one side of a workpiece according to one embodiment of the present invention can be performed using the workpiece polishing apparatus of the above embodiment. The method for polishing one side of a workpiece according to this embodiment includes a polishing step in which, using a polishing platen 2 having a larger diameter than the workpiece W, a polishing pad 3 attached to the polishing platen 2, a polishing head 4 capable of holding the workpiece W and pressing it against the polishing pad 3, and a polishing liquid supply nozzle 6 for supplying polishing liquid 5 to the polishing pad 3, one side of the workpiece W is polished by pressing the workpiece W against the polishing pad 3 while rotating the polishing platen 2 and the polishing pad 3, and supplying polishing liquid 5 from the polishing liquid supply nozzle 6 to the polishing pad 3.

[0032] In the polishing process, one side of the workpiece W is polished while measuring the displacement of the exposed upper surface 7 using a surface displacement measuring unit 8 capable of measuring the displacement of the exposed upper surface 7.

[0033] According to the polishing method for the workpiece W of this embodiment, in the polishing process, the displacement of the exposed upper surface 7 is continuously measured by the surface displacement measuring unit 8 during single-sided polishing, thereby enabling the dynamic displacement behavior of the polishing pad 3, including the loading and depressurization of the pressing pressure from the workpiece W, to be grasped. By appropriately selecting the resolution of the surface displacement measuring unit 8, for example, it is possible to grasp the temporal change in the displacement of the polishing pad 3 by several microns. Thus, according to the single-sided polishing method of the workpiece W of this embodiment, the amount of dynamic displacement of the polishing pad during single-sided polishing can be measured.

[0034] In the single-sided polishing method, it is preferable to polish one side of the workpiece W while removing the polishing fluid 5 from the exposed upper surface 7. This is because the dynamic displacement of the polishing pad 3 during single-sided polishing can be accurately measured without being affected by the polishing fluid 5. In the polishing process, it is preferable to polish one side of the workpiece W while removing the polishing fluid by blowing air 12 onto the exposed upper surface 7. This is because it is possible to avoid being affected by the polishing fluid 5 using a simple method.

[0035] In the single-sided polishing method, it is preferable to further include a preliminary step of measuring the displacement of the exposed upper surface 7 without pressing the workpiece W against the polishing pad 3, and to calculate the dynamic change in the displacement of the exposed upper surface 7 during single-sided polishing of the workpiece W by comparing the measurement results from the preliminary step with the results of measuring the displacement of the exposed upper surface 7 with the workpiece W pressed against the polishing pad 3. This is because the dynamic change in the displacement of the exposed upper surface 7 during single-sided polishing of the workpiece W can be calculated as an absolute value (absolute amount). In this preliminary step, the polishing head 4 is not in contact with the polishing pad 3 and is waiting above the polishing pad 3, so that pressure from the polishing head 4 is not transmitted to the polishing pad 3. However, polishing fluid 5 is supplied, and at the displacement measurement point, the polishing fluid 5 is removed by the polishing fluid removal unit 11 while the measurement is performed.

[0036] <Manufacturing method for silicon wafers> A method for manufacturing a polished workpiece according to one embodiment of the present invention involves manufacturing a polished workpiece by polishing one side of the workpiece W using the single-sided polishing method of the workpiece W described in the above embodiment. Here, the workpiece W is a silicon wafer. According to the method for manufacturing a polished workpiece of this embodiment, the amount of dynamic displacement of the polishing pad during single-sided polishing can be measured.

[0037] While not particularly limited, in a workpiece single-sided polishing apparatus and a workpiece single-sided polishing method, a silicon wafer can be suitably used as the workpiece. When applied to a silicon wafer manufacturing method, the process can include all normal manufacturing steps except for single-sided polishing. For example, single-sided polishing according to this disclosure can be applied to wafers that have been obtained by pulling single crystals using the Czochralski method, slicing them, and then undergoing processing steps such as lapping, etching, and double-sided polishing.

[0038] The following describes embodiments of the present invention, but the present invention is not limited in any way to the following embodiments. [Examples]

[0039] To verify the effects of the present invention, five p-type silicon wafers with a diameter of 300 mm were polished on one side using a single-sided polishing apparatus as shown in Figures 1 and 2. During the polishing process, the dynamic change in the displacement of the exposed upper surface was measured using a laser displacement meter while air was blown onto the exposed upper surface. A Keyence IL-100 laser displacement meter was used (measurement range: -2 mm to 2 mm, resolution: 2 μm, sampling time: 10 ms). The wafer pressure applied by the polishing head was set to 20 kPa, and the rotation speed of the polishing pad was set to 40 rpm.

[0040] Figure 3 shows the relationship between measurement time and displacement of the exposed surface. Displacement gauges 1 to 3 in Figure 3 correspond to measurement points A to C, respectively. As shown in Figure 3, there may be gaps in the data. Therefore, the time average was calculated for each measurement data x(t,n) from all 5 measurements (sample size N=5).<x(t,n)> Tp-Ave Therefore, a value that is discontinuous in time and significantly different from other values ​​(an extremely large leap) (|x(t,n)-<x(t,n)> Tp-Ave We removed values ​​where the displacement was >200 μm (which we considered to be an extreme leap). The data after removing the leap values ​​is shown in Figure 4. In Figure 4, only the data from displacement gauge 3 is shown.

[0041] The data in Figure 4 is centrally moved using a rotation period Tr of the polishing head and rotary platen.<x(t,n)> Tr-Ave ) was done. Any magnification is acceptable as long as vibrations and jump values ​​can be removed, but if a large magnification is used, the data for the start and end times of polishing will be largely lost in the centered moving average. From this perspective, in the following, moving average data of 4 times the rotation period Tr was used. Figure 5 shows the time moving average data of the data in Figure 4 with the time width (how many times the rotation period it is) changed. Also, Figure 6 shows the N average every time t for N measurements in the data in Figure 4.<x(t,n)> Tr,N-Ave This is the diagram.

[0042] Figure 7 shows the data obtained when a preliminary step was performed in which the displacement of the exposed upper surface was similarly measured without pressing the wafer against the polishing pad. Note that even in this state, there is significant vibration (unevenness) because there is variation in the thickness of the polishing pad surface (occurring during manufacturing, bonding, and dressing). Here, Figure 6<x(t,n)> N,Tr-Ave From Figure 7 x bg Subtract the mean value (take the difference) from the data.

[0043] Figure 8 shows the relationship between the measurement time and the absolute amount of displacement of the exposed upper surface, obtained by taking the difference in this way. Since the inclination of the laser displacement meter was set to 30°,<x(t,n)> N,Tr-Ave -x bg The absolute amount of displacement of the polishing pad was obtained by multiplying by cos30°. As shown in Figure 8, with the polishing pad used in this embodiment, the amount of displacement between the polishing heads (displacement gauges 1-3) due to the rotation of the surface plate did not instantly recover completely, and it became clear that some displacement remained, allowing us to measure the dynamic amount of displacement of the polishing pad during single-sided polishing. As shown in Figure 8, it can be seen that the displacement is negative, but its absolute value increases with the progression of polishing time. From this, it is clear that the displacement does not instantly and completely recover even after the load from the wafer is removed, but remains, and that the displacement accumulates due to repeated loading. In this way, we were able to measure the dynamic displacement of the polishing pad during single-sided polishing.

[0044] Figure 9 shows the case where air blowing was not performed (otherwise the same procedure was followed). Without air blowing, the displacement of the polishing pad could not be captured due to the effects of polishing head contact at the beginning of polishing, slurry inflow, and slurry film during polishing. (In this example, the data shows a positive value (tensile state relative to the polishing pad), indicating that the viscoelastic properties of the polishing pad could not be evaluated.) [Explanation of Symbols]

[0045] 1: Workpiece single-sided polishing device, 2: Polishing surface plate, 3: Polishing pad, 4: Polishing head, 5: Polishing liquid, 6: Polishing fluid supply nozzle, 7:Exposed top surface, 8: Surface displacement measurement section, 9: Waterproof container, 10: Liquid drainage slope, 11: Polishing liquid removal section, 12: Air

Claims

1. A workpiece single-sided polishing device, A polishing plate having a larger diameter than the aforementioned workpiece, A polishing pad attached to the polishing platen, A polishing head capable of holding the workpiece and pressing it against a polishing pad, The system includes a polishing liquid supply nozzle for supplying polishing liquid to the polishing pad, The polishing pad is further provided with a plurality of surface displacement measuring units capable of measuring the displacement of the exposed upper surface, which is the upper surface of the polishing pad that is not covered by the polishing head. A workpiece single-sided polishing apparatus characterized in that the plurality of surface displacement measuring units are arranged in the circumferential direction of the polishing pad.

2. The workpiece single-sided polishing apparatus according to claim 1, further comprising a polishing liquid removal unit for removing the polishing liquid from the exposed upper surface.

3. The polishing fluid removal unit is configured to allow air to be blown onto the exposed upper surface, as described in claim 2, for single-sided polishing of a workpiece.

4. The workpiece is a wafer, as described in any one of claims 1 to 3, and is a one-sided polishing apparatus for a workpiece.

5. A method for polishing one side of a workpiece, Using a polishing plate having a diameter larger than the workpiece, a polishing pad attached to the polishing plate, a polishing head capable of holding the workpiece and pressing it against the polishing pad, and a polishing fluid supply nozzle for supplying polishing fluid to the polishing pad, The polishing process includes supplying the polishing fluid from the polishing fluid supply nozzle to the polishing pad, rotating the polishing platen and the polishing pad, and pressing the workpiece against the polishing pad to polish one side of the workpiece, A method for polishing one side of a workpiece, characterized in that, in the polishing step, one side of the workpiece is polished while measuring the displacement of the exposed upper surface, which is the upper surface of the polishing pad that is not covered by the polishing head, using a plurality of surface displacement measuring units capable of measuring the displacement of the exposed upper surface in the circumferential direction of the polishing pad.

6. The method for polishing one side of a workpiece according to claim 5, wherein one side of the workpiece is polished while removing the polishing liquid from the exposed upper surface.

7. The method for polishing one side of a workpiece according to claim 6, wherein in the polishing step, one side of the workpiece is polished while removing the polishing liquid by blowing air onto the exposed upper surface.

8. The process further includes a preliminary step of measuring the displacement of the exposed upper surface without pressing the workpiece against the polishing pad, A method for polishing one side of a workpiece according to any one of claims 5 to 7, wherein the dynamic change in the displacement of the exposed upper surface during one-sided polishing of the workpiece is calculated by comparing the measurement results in the preliminary step with the results of measuring the displacement of the exposed upper surface while the workpiece is pressed against the polishing pad.

9. The method for polishing one side of a workpiece according to any one of claims 5 to 7, wherein the workpiece is a silicon wafer.

10. A method for manufacturing a silicon wafer using the single-sided polishing method of a workpiece described in claim 9.

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