Grinding device

Abstract

A polishing apparatus is provided that can determine wafer state changes with greater precision and faster response. [Solution] The polishing apparatus comprises a detection device and a control device. The detection device periodically detects the reference position which rotates together with the polishing head. The control device determines the state change of the substrate based on the reference position periodically detected by the detection device.

Description

Technical Field

[0001] The present invention relates to a polishing apparatus.

Background Art

[0002] As a technique in the manufacturing process of semiconductor devices, chemical mechanical polishing (CMP) is known. A polishing apparatus for performing CMP includes a polishing table that supports a polishing pad and a polishing head for holding a wafer.

[0003] When polishing a wafer using such a polishing apparatus, the wafer is slidably contacted with the polishing surface by relatively moving the polishing table and the polishing head, and the polished surface of the wafer is polished.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, based on the film thickness distribution of a wafer, the state change of the wafer (e.g., the end point of polishing) is determined or the polishing state of the wafer is monitored. However, the methods for monitoring (determining) the state of the wafer held by the polishing head in real time are limited.

[0006] For example, a method is known for determining the state change of a wafer based on the motor torque of the polishing table, which changes along with the frictional force between the wafer and the polishing pad. However, such a method indirectly monitors the state change of the wafer based on the motor current supplied to the polishing table. A more accurate and responsive method for determining the state change of a wafer is desired.

[0007] Therefore, the present invention aims to provide a polishing apparatus that can determine wafer state changes with greater accuracy and faster response. [Means for solving the problem]

[0008] In one embodiment, a polishing apparatus is provided. The polishing apparatus comprises a polishing table that supports a polishing pad, a polishing head that holds the substrate with the exposed surface of the substrate facing the polishing surface of the polishing pad, a detection device that detects a reference position of the substrate, and a control device electrically connected to the detection device, wherein the detection device periodically detects the reference position which rotates together with the polishing head, and the control device determines the state change of the substrate based on the reference position periodically detected by the detection device.

[0009] In one embodiment, the reference position corresponds to the position of a notch formed on the periphery of the substrate, the detection device projects light from the outside of the substrate toward the periphery of the substrate, detects the reflected light reflected from the periphery of the substrate, and the control device determines the notch position based on the intensity of the reflected light detected by the detection device. In one embodiment, the substrate has a structure that includes multiple materials with different coefficients of friction, and the control device determines the polishing endpoint as a state change based on the change in the coefficient of friction between the substrate and the polishing pad, which is caused by the change in the surface structure of the substrate as the polishing progresses. In one embodiment, the control device measures the phase of the reference position and determines the polishing abnormality of the substrate based on the magnitude of the phase change when the state change is determined.

[0010] In one embodiment, when the components of the polishing apparatus, including at least the polishing pad, the polishing table, and the polishing head, are defined as polishing components, the control device determines that at least one of the following occurs as a polishing abnormality: an abnormality of the substrate itself and an abnormality of the polishing components. In one embodiment, the control device determines a change in the polishing conditions of the substrate as a change in state based on a change in the coefficient of friction between the substrate and the polishing pad. In one embodiment, the polishing apparatus is equipped with a film thickness sensor embedded in the polishing table, the film thickness sensor periodically detects a signal reflecting the film thickness of the substrate as the polishing table rotates, the control device measures the film thickness of the substrate based on the signal detected by the film thickness sensor, determines the substrate angle as the circumferential angle of the substrate specified by the reference position based on the phase of the reference position detected by the detection device and the phase of the signal detected by the film thickness sensor, and creates film thickness distribution information of the substrate based on the determined substrate angle and the measured film thickness of the substrate. In one embodiment, the control device calculates the rotation time of the substrate per unit angle from the time interval of the reference position detected by the detection device, and determines the substrate angle based on the rotation time of the substrate and the time interval from the time the detection device detected the reference position to the time the film thickness sensor detected a signal. [Effects of the Invention]

[0011] According to the above-described method, the polishing apparatus can determine the state change of the substrate with greater precision and faster response. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram showing one embodiment of a polishing apparatus. [Figure 2] This is a cross-sectional view of the polishing head. [Figure 3] This is a schematic diagram showing the elastic membrane connected to the underside of the head body. [Figure 4] FIG. 4(a), FIG. 4(b), and FIG. 4(c) are diagrams showing examples of the film thickness distribution along the circumferential direction of the wafer at the peripheral portion of the wafer. [Figure 5] It is a diagram showing the positional relationship between the wafer and the polishing pad. [Figure 6] It is a diagram showing the polishing head disassembled by each component. [Figure 7A] It is a diagram showing a detection device. [Figure 7B] It is a diagram showing a detection device. [Figure 7C] It is a diagram showing a detection device. [Figure 7D] It is a diagram showing a detection device. [Figure 7E] It is a diagram showing a detection device. [Figure 8] It is a diagram showing a light guide structure constituting a detection device. [Figure 9] It is a diagram showing a detection unit constituting a detection device. [Figure 10] During the polishing of the wafer, it is a diagram showing the movement of the wafer surrounded by the retainer ring. [Figure 11A] It is a diagram showing the presence or absence of detection of reflected light at the peripheral portion of the wafer by a photodetector. [Figure 11B] It is a diagram showing the presence or absence of detection of reflected light at the peripheral portion of the wafer by a photodetector. [Figure 11C] It is a diagram visualizing the notch position detected by a photodetector. [Figure 12] It is a timing chart showing the notch positions periodically detected by a photodetector. [Figure 13] It is a diagram showing the processing flow of a control device for determining the state change of the wafer. [Figure 14] It is a cross-sectional view showing another embodiment of the light guide structure. [Figure 15] It is a diagram showing light passing through a cell structure. [Figure 16A] It is a diagram showing a plurality of cell structures arranged annularly side by side. [Figure 16B]This figure shows multiple cell structures arranged in multiple rows in the height direction of the polishing head. [Figure 17] This figure shows another embodiment of the light guide structure. [Figure 18] This is a top-down view of a glass body. [Figure 19] This diagram shows the change in contact point position. [Figure 20A] This figure shows another embodiment of the detection unit. [Figure 20B] This figure shows another embodiment of the detection unit. [Figure 21A] This figure shows another embodiment of the detection unit. [Figure 21B] This figure shows another embodiment of the detection unit. [Figure 22] This figure shows one embodiment of a film thickness sensor. [Figure 23] This is a timing chart showing the phase of the notch position detected by the detection device and the phase of the signal detected by the film thickness sensor. [Figure 24] This diagram shows the processing flow of the control device that determines the notch angle. [Figure 25] This diagram shows the mounting angle of the detection unit. [Figure 26] This diagram shows the processing flow of the control device when polishing a wafer. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted. In the multiple embodiments described below, the configuration of one embodiment that is not specifically described is the same as that of the other embodiments, so redundant descriptions are omitted.

[0014] Figure 1 is a schematic diagram showing one embodiment of a polishing apparatus. As shown in Figure 1, the polishing apparatus comprises a polishing head (substrate holder) 1 that holds and rotates a wafer W, which is an example of a substrate; a polishing table 3 that supports a polishing pad 2; a polishing liquid supply nozzle 5 that supplies polishing liquid (slurry) to the polishing pad 2; and a control device 9 that controls the operation of these components of the polishing apparatus.

[0015] The polishing head 1 positions the exposed surface (i.e., the surface to be polished) of the wafer W opposite the polishing surface 2a of the polishing pad 2. The polishing head 1 and the polishing table 3 rotate in the same direction, and in this state, the polishing head 1 presses the wafer W against the polishing surface 2a.

[0016] The polishing table 3 is connected to the table motor 13 and is configured to be rotatable. The polishing pad 2 is attached to the upper surface of the polishing table 3. The polishing head 1 is connected to the polishing head shaft 11. The polishing head shaft 11 is configured to move up and down relative to the head arm 16 by a vertical movement mechanism 27.

[0017] The control unit 9 consists of at least one computer. The control unit 9 includes a storage device 9a in which a program is stored, and a processing unit 9b that performs calculations according to the instructions contained in the program. The processing unit 9b includes a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), etc., that performs calculations according to the instructions contained in the program stored in the storage device 9a.

[0018] The polishing apparatus is equipped with a polishing head height sensor 39 facing the bridge 28. The polishing head height sensor 39 is electrically connected to the control device 9. The control device 9 measures the height of the polishing head 1 based on the signal sent from the polishing head height sensor 39.

[0019] The polishing head 1, which holds the wafer W, is moved from the wafer W transfer position to a position above the polishing table 3 by the rotation of the head arm 16. The polishing head 1 and the polishing table 3 are rotated respectively, and polishing fluid is supplied onto the polishing pad 2 from the polishing fluid supply nozzle 5 located above the polishing table 3.

[0020] The polishing head 1 presses the wafer W against the polishing surface 2a of the polishing pad 2, causing the wafer W to slide against the polishing surface 2a of the polishing pad 2 in the presence of the polishing liquid. The surface of the wafer W is polished by the chemical action of the chemical components of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid.

[0021] In the embodiment shown in Figure 1, the polishing apparatus is a face-down type polishing apparatus. In one embodiment, the polishing apparatus may be a face-up type polishing apparatus. In this case, although not shown, the polishing head 1 holds the wafer W so that the surface to be polished of the wafer W is facing upward, and the polishing tool holding the polishing pad 2 presses against the surface to be polished of the wafer W.

[0022] As shown in Figure 1, the polishing apparatus includes a dressing unit 50 for dressing the polishing surface 2a of the polishing pad 2. The dressing unit 50 includes a dresser 51 that slides against the polishing surface 2a, a dresser shaft 52 to which the dresser 51 is connected, and a swing arm 55 that rotatably supports the dresser shaft 52.

[0023] Figure 2 is a cross-sectional view of the polishing head. As shown in Figure 2, the polishing head 1 comprises a head body 102 connected to a polishing head shaft 11 and a retainer ring 103 arranged to surround the wafer W. The retainer ring 103 is configured to move up and down independently of the head body 102.

[0024] The polishing head 1 has a plurality of pressing elements for pressing the wafer W against the polishing surface 2a of the polishing pad 2. Examples of pressing elements include a pressurizing mechanism provided on the polishing head 1, or a piezoelectric element provided on the polishing head 1. In this embodiment, the pressing element is a pressurizing mechanism provided on the polishing head 1.

[0025] Figure 3 is a schematic diagram showing an elastic membrane connected to the lower surface of the head body. As shown in Figures 2 and 3, the polishing head 1 is equipped with an elastic membrane 110 connected to the lower surface 102a of the head body 102.

[0026] The elastic film 110 that contacts the back surface of the wafer W has a plurality of walls 114. In the embodiment shown in Figure 3, the plurality of walls 114 are arranged along the radial and circumferential directions of the polishing head 1. The retainer ring 103 is positioned to surround the elastic film 110.

[0027] Multiple walls 114 form multiple pressure chambers 116 arranged along the radial and circumferential directions of the polishing head 1. The pressurizing mechanism, acting as a pressing element, has pressure chambers 116 formed in the elastic membrane 110. A fluid supply source (see Figure 1) supplies fluid to the pressure chambers 116, pressurizing them.

[0028] The polishing apparatus includes a pressure regulating device (i.e., a pressure regulator) 165 capable of individually controlling the pressing force of multiple pressing elements. The pressure regulating device 165 is configured to individually adjust the pressure within the pressure chamber 116.

[0029] Each pressure chamber 116 is connected to a pressure regulator 165 via a rotary joint 182, and fluid from a fluid supply source is supplied to each pressure chamber 116 through a fluid line 173. The pressure regulator 165 is electrically connected to a control device 9, which is configured to independently regulate the pressure in each pressure chamber 116.

[0030] The pressure regulating device 165 can also create negative pressure within the pressure chamber 116. Each pressure chamber 116 is also connected to an atmospheric release mechanism (not shown), allowing the pressure chamber 116 to be released into the atmosphere.

[0031] Figures 4(a), 4(b), and 4(c) show examples of film thickness distribution along the circumferential direction of the wafer at the periphery of the wafer. Figure 4(a) shows the initial film thickness distribution before wafer polishing. Figure 4(b) shows the film thickness distribution of the wafer when polished with a conventional polishing apparatus. Figure 4(c) shows an illustrative example of the film thickness distribution of the wafer when polished with the polishing apparatus of this embodiment.

[0032] In Figures 4(a) to 4(c), the position of wafer angle (i.e., substrate angle) 0 degrees is set to a characteristic location where the circumferential angle (or orientation) of the wafer can be identified. In the examples shown in Figures 4(a) to 4(c), the position of wafer angle 0 degrees is the position of a notch formed on the periphery of the wafer (i.e., the reference position).

[0033] In Figure 4(a), the initial film thickness distribution before polishing shows a peak at a wafer angle of 180 degrees, indicating film thickness variation with a certain peak width and height. Possible causes of this initial film thickness distribution include the characteristics of the film deposition equipment and the influence of various processes used to form the multilayer wiring.

[0034] When a wafer with the initial film thickness distribution shown in Figure 4(a) is polished using a conventional polishing apparatus, the polishing proceeds almost uniformly in the circumferential direction, resulting in a film thickness distribution on the polished wafer that is almost the same as before polishing (see Figure 4(b)). Such variations in film thickness distribution can cause problems such as misfocusing in the next exposure process, leading to a decrease in semiconductor manufacturing yield.

[0035] In Figure 4(c), when the polishing apparatus of this embodiment polishes a wafer having the initial film thickness distribution shown in Figure 4(a), the polishing apparatus can reduce the circumferential film thickness variation compared to the initial film thickness distribution by relatively increasing (or decreasing) the polishing rate at the peak position.

[0036] Figure 5 shows the positional relationship between the wafer and the polishing pad. The imaginary line VL is defined as a line segment extending parallel to the polishing pad 2 and passing through the center CT of the polishing surface 2a. When the center CP of the wafer W is placed on the imaginary line VL, the polishing surface 2a can be divided into an upstream side of the imaginary line VL and a downstream side of the imaginary line VL with respect to its rotational direction. The upstream side of the imaginary line VL and the downstream side of the imaginary line VL are, in other words, the upstream side and the downstream side of the wafer W with respect to the direction of movement of the polishing surface 2a.

[0037] The virtual circle S shown in Figure 5 is the rotational trajectory of the polishing surface 2a passing through the center CP of the wafer W. Of the two intersection points of the tangent line T of the virtual circle S at the wafer center CP and the wafer circle, the upstream intersection is defined as the polishing head angle of 0 degrees, and the downstream intersection is defined as the polishing head angle of 180 degrees. Of the two intersection points of the imaginary line VL and the wafer circle, the intersection closer to the center of the polishing surface is defined as the polishing head angle of 270 degrees, and the intersection closer to the outer circumference of the polishing surface is defined as the polishing head angle of 90 degrees. Here, the wafer circle is a circle representing the outline of the wafer W.

[0038] The polishing head angle is the initial rotation angle of the polishing head 1 at the start of polishing the wafer W. The rotation angle of the polishing head 1 is detected by a rotary encoder 41 (see Figure 1) attached to the polishing head motor 18. The rotary encoder 41 is a rotation angle detector that detects the rotation angle of the polishing head 1.

[0039] To improve the uniformity of the film thickness distribution, it is important to acquire (create) accurate film thickness distribution information (wafer map) during the polishing of the wafer W. Furthermore, in order to acquire accurate film thickness distribution information, it is important to accurately identify the reference position of the wafer angle (i.e., the notch position). Film thickness distribution information is information that associates the coordinate position of the wafer W, centered on the reference position of the wafer W, with the film thickness of the wafer W in the radial and circumferential directions.

[0040] Monitoring the polishing state of wafer W is important in order to determine changes in the wafer's state (e.g., polishing endpoint, polishing abnormalities, changes in polishing conditions). To accurately monitor the polishing state of wafer W, it is crucial to accurately identify the reference position of the wafer angle.

[0041] Therefore, in order to achieve the objectives of obtaining accurate film thickness distribution information and determining the state changes of the wafer W, the polishing apparatus has a configuration that accurately identifies the reference position. This configuration will be described below.

[0042] Figure 6 shows the polishing head disassembled into its components. As shown in Figure 6, when the polishing head 1 is disassembled, a detection device 500 for detecting the notch position as a reference position is positioned between the head body 102 and the retainer ring 103.

[0043] Figures 7A to 7E show the detection device. Figure 8 shows the light guide structure that constitutes the detection device. Figure 9 shows the detection unit that constitutes the detection device. The detection device 500 is configured to project light from the outside of the wafer W toward the peripheral edge PP of the wafer W and to detect the reflected light reflected by the peripheral edge PP of the wafer W.

[0044] The detection device 500 includes a light guide structure 501 positioned adjacent to the peripheral edge PP of the wafer W, and a detection unit 550 that guides light to the peripheral edge PP of the wafer W through the light guide structure 501 and detects the notch position NT from the reflected light reflected from the peripheral edge PP of the wafer W.

[0045] In the embodiment shown in Figure 6, the light guide structure 501 has an annular shape along the circumferential direction of the wafer W, but in one embodiment, the light guide structure 501 may have an arc shape along the circumferential direction of the wafer W. The light guide structure 501 does not necessarily have to be positioned adjacent to all of the peripheral edge PP of the wafer W, but may be positioned adjacent to only a part of the peripheral edge PP.

[0046] The light guide structure 501 comprises a plurality of optical fibers 502 arranged along the circumferential direction of the wafer W, and a fiber holder 503 that holds the plurality of optical fibers 502. It is desirable that the optical fibers 502 be arranged at equal intervals. The fiber holder 503 shown in Figure 8 has an L-shape.

[0047] Specifically, the fiber holder 503 has a main body portion 503a sandwiched between the head body 102 and the retainer ring 103, and a bent portion 503b that is bent from the main body portion 503a. When the polishing head 1 holds the wafer W, the bent portion 503b extends downward from the main body portion 503a toward the peripheral edge PP of the wafer W (see Figures 7A and 8).

[0048] Figure 7C shows the positional relationship between the detection unit and the polishing head when viewed from above. Figure 7D shows the polishing device as viewed from the direction of line A in Figure 7C. Figure 7E shows the polishing device as viewed from the direction of line B in Figure 7C.

[0049] As shown in Figures 7C to 7E, the detection unit 550 is supported by a unit supporter 16-1 extending from the head arm 16. The detection unit 550 is positioned radially outward of the light guide structure 501 and outside the polishing head 1. The detection unit 550 is positioned downstream of the polishing head 1 in the rotational direction of the polishing table 3. Note that the detection unit 550 does not necessarily have to be positioned as shown in Figures 7C to 7E.

[0050] As shown in Figure 9, the detection unit 550 includes a light source 551 that emits light, a half mirror 552 for guiding the light emitted from the light source 551 to the light guide structure 501, and a photodetector 553 for detecting the reflected light reflected from the peripheral edge PP of the wafer W.

[0051] Light emitted from the light source 551 is reflected by the half mirror 552 and incident on the optical fiber 502 from its fiber end 502a. Fiber end 502a is the end of the optical fiber 502 adjacent to the detection unit 550. Light incident on from fiber end 502a irradiates the peripheral edge PP of the wafer W from fiber end 502b. Fiber end 502b is the end of the optical fiber 502 adjacent to the peripheral edge PP of the wafer W.

[0052] Figure 10 shows the movement of a wafer surrounded by a retainer ring during wafer polishing. As shown in Figure 10, when the polishing table 3 and polishing head 1 are rotated in the same direction, the wafer W comes into contact with the inner surface of the retainer ring 103 (see contact point A). Contact point A is located on the rotational trajectory (i.e., virtual circle S) of the polishing surface 2a passing through the center CP of the wafer W.

[0053] During the polishing of the wafer W, the wafer W within the retainer ring 103 rotates around the contact point A. Therefore, a detection unit 550 is placed in a region of a certain width adjacent to the retainer ring 103 (including the contact point A), and light is continuously shone from the light source 551 toward the peripheral edge PP of the rotating wafer W.

[0054] Figures 11A and 11B show whether or not reflected light from the wafer periphery is detected by the photodetector. As shown in Figure 11A, when light is shone on the periphery PP of the wafer W other than the notch position NT, the light is reflected from the periphery PP of the wafer W, and the reflected light is incident on the fiber end 502b. The incident reflected light is detected by the photodetector 553 through the fiber end 502a and the half mirror 552.

[0055] By continuously irradiating with light, the light is directed to a notch position NT formed on the peripheral edge PP of the rotating wafer W. In this case, as shown in Figure 11B, the irradiated light passes through the wafer W through the notch position NT and is not reflected at the peripheral edge PP of the wafer W. Alternatively, the irradiated light may be reflected with a different intensity than the reflected light at the peripheral edge PP other than the notch position NT, depending on the irradiation conditions and the shape of the notch position NT (for example, diffuse reflection from the corners of the notch).

[0056] Figure 11C is a diagram visualizing the notch position detected by the photodetector. The photodetector 553 is configured to detect different light intensities at the notch position NT and at the peripheral area PP other than the notch position NT. When the wafer W rotates at a constant speed around contact A, the photodetector 553 detects reflected light with a constant intensity (i.e., first reflected light) for a certain long time, and detects reflected light with a different intensity from the first reflected light (i.e., second reflected light) for a certain short time, or blocks the detection of the first reflected light.

[0057] The intensity of the first reflected light is greatest at the position where the peripheral edge PP of the wafer W is closest to the retainer ring 103, and gradually decreases as the wafer W moves away from the retainer ring 103. Furthermore, the photodetector 553 detects the second reflected light or blocks the detection of the first reflected light at the notch position NT. Therefore, as shown in Figure 11C, the photodetector 553 detects the reflected light corresponding to the contour of the wafer W.

[0058] The timing at which the photodetector 553 detects the second reflected light or blocks the detection of the first reflected light corresponds to the timing at which the notch position NT passes through the photodetector 553. Hereinafter, the timing at which the notch position NT passes through the photodetector 553 may be referred to as the notch timing.

[0059] Figure 12 is a timing chart showing the notch position periodically detected by the photodetector. The relationship between the rotation speed of the polishing head 1 and the rotation speed of the wafer W is usually constant if there is no change in the polishing conditions of the wafer W. Therefore, under conditions where the rotation speed of the wafer W is constant, the notch timing occurs at a constant period, and at this time, the photodetector 553 periodically detects the notch position NT at a constant time interval.

[0060] Figure 12 shows the first reflected light detected by the photodetector 553 as a non-peaked value, and the second reflected light (or the blockage of detection of the first reflected light) detected by the photodetector 553 as a peaked value.

[0061] Figure 13 shows the processing flow of the control device that determines the state change of the wafer. The photodetector 553 is electrically connected to the control device 9. The control device 9 is configured to determine the notch position NT based on the intensity of the reflected light detected by the photodetector 553.

[0062] First, the control device 9 acquires the notch position NT periodically detected by the photodetector 553 (see step S101), and measures the phase of the reference position based on the acquired notch position NT (see step S102). In Figure 12, the control device 9 measures the notch position NT at regular time intervals (see t1).

[0063] Subsequently, the control device 9 determines whether or not a phase shift (change) has occurred in the measured phase (see step S103). If it determines that no phase shift has occurred (see "No" in step S103), it repeats steps S101 and S102.

[0064] If the control device 9 determines that a phase shift has occurred (see "Yes" in step S103), it determines the state change of the wafer W (see step S104). In Figure 12, the control device 9 measures the notch position NT at a second time interval (t2) that is different from the first time interval (t1) (t1 ≠ t2).

[0065] The control device 9 determines the state change of the wafer W based on the change in the rotational speed of the wafer W. The wafer W may have a structure that includes multiple materials with different coefficients of friction. For example, the wafer W may have upper and lower layers with different coefficients of friction, or it may have materials with different coefficients of friction (e.g., a wiring layer) within the same plane.

[0066] As the polishing of the wafer W progresses, the surface structure of the wafer W changes, which in turn changes the coefficient of friction between the surface of the wafer W being polished and the polishing surface 2a of the polishing pad 2. When the coefficient of friction changes, the rotational speed of the wafer W also changes, and as a result, the phase of the notch position NT also changes. The control device 9 determines the state change of the wafer W, for example, the polishing endpoint, by measuring this phase shift of the notch position NT.

[0067] If the magnitude of the phase shift depends on the structure of the wafer W, the control device 9 can determine the polishing endpoint of the wafer W based on the magnitude of the phase shift determined by the structure of the wafer W. In that case, the control device 9 can determine a polishing abnormality of the wafer W based on the magnitude of the phase shift when the state change of the wafer W is determined. Specifically, when the control device 9 measures a phase shift of a magnitude different from the magnitude of the phase shift corresponding to the polishing endpoint of the wafer W, the control device 9 may determine a polishing abnormality of the wafer W.

[0068] Polishing components are defined as the elements necessary to polish the wafer W, including at least the polishing pad 2, the polishing table 3, and the polishing head 1. Wafer polishing abnormalities include abnormalities in the wafer W itself, such as damage to the wafer W, or abnormalities in the polishing components. The control device 9 determines that a wafer polishing abnormality is either an abnormality in the wafer W or an abnormality in the polishing components, or at least one of these.

[0069] Examples of abnormalities in the polishing components include damage to the polishing pad 2, the elastic membrane 110, and the retainer ring 103. Other examples of abnormalities in the polishing components include failure of the table motor 13 and the polishing head motor 18, and damage to structures such as bearings.

[0070] Changes in the polishing conditions of the wafer W may cause changes in the state of the wafer W. For example, changes in the material of the polishing fluid, the flow rate of the polishing fluid, the pressure of the fluid supplied to the elastic film 110, and changes in the surface state of the polishing pad 2 may cause changes in the state of the wafer W. Therefore, the control device 9 may determine that changes in the polishing conditions of the wafer W are the cause of such changes in the state of the wafer W.

[0071] According to this embodiment, the detection device 500 can accurately and quickly detect the notch position NT of the wafer W surrounded by the retainer ring 103 from outside the polishing head 1 during the polishing of the wafer W. Furthermore, the control device 9 can determine the state change of the wafer W with greater accuracy based on the phase of the notch position NT detected by the detection device 500. In this way, the control device 9 can directly monitor the state change of the wafer W without employing indirect methods such as those based on changes in the motor current of the polishing table 3.

[0072] Although not shown in the figures, the polishing apparatus may have the configuration shown in Patent Document 1 (i.e., a reference position detection device that detects a reference position (notch position) located inside the retainer ring 103 during polishing of the wafer W) or the configuration shown in Patent Document 2 (a configuration that identifies a reference position of the substrate angle based on signals obtained from multiple film thickness sensors). It is possible to identify the notch position NT with such a configuration, and the control device 9 may determine the state change of the wafer W based on the phase of the notch position NT measured based on the above configuration.

[0073] Figure 14 is a cross-sectional view showing another embodiment of the light guide structure. In the embodiment shown in Figure 14, the light guide structure 501 does not include an optical fiber 502, but instead includes a cell structure 510 of a reflective optical system that allows light to pass through and reflect back. The cell structure 510 has an L-shape and includes a main body portion 510a, a bent portion 510b, and a reflective member 511 positioned at the connection between the main body portion 510a and the bent portion 510b. Examples of reflective members 511 include mirrors and prisms.

[0074] Figure 15 shows light passing through a cell structure. As shown in Figure 15, light emitted from the light source 551 enters the cell structure 510, is bent at a right angle by the reflecting member 511, and irradiates the peripheral edge PP of the wafer W. The light reflected from the peripheral edge PP of the wafer W enters the cell structure 510, is bent at a right angle by the reflecting member 511, and is detected by the photodetector 553.

[0075] Figure 16A shows a plurality of cell structures arranged in a ring. As shown in Figure 16A, the light guide structure 501 comprises a plurality of cell structures 510 arranged in a ring. Cell structures 510 adjacent to each other are shielded from light. Therefore, light that passes through a cell structure 510 does not enter an adjacent cell structure 510.

[0076] In the embodiment shown in Figure 16A, the multiple cell structures 510 are arranged in a single row in the height direction of the polishing head 1 (i.e., in the extension direction of the polishing head shaft 11). Therefore, the width of the light irradiated onto the peripheral edge PP of the wafer W corresponds to the thickness of the bent portion 510b of the light guide structure 501. The thickness of the bent portion 510b corresponds to the distance DA in the radial direction of the wafer W. The photodetector 553 detects the reflected light corresponding to the distance DA.

[0077] Figure 16B shows a plurality of cell structures arranged in multiple rows in the height direction of the polishing head. In the embodiment shown in Figure 16B, the plurality of cell structures 510 are arranged in multiple rows (for example, 3 rows) in the height direction of the polishing head 1. Therefore, the width of the light incident on the peripheral portion PP of the wafer W corresponds to the total thickness of the plurality of bent portions 510b. In Figure 16B, since 3 rows of cell structures 510 are arranged, the photodetector 553 detects reflected light corresponding to distance DB. Distance DB corresponds to 3 times distance DA.

[0078] In the embodiment shown in Figure 16B, the photodetector 553 can detect reflected light over a wider range in the radial direction of the wafer W. In the embodiments shown in Figures 11A to 11C, the light guide structure 501 may also include a plurality of optical fibers 502 and fiber holders 503 arranged in multiple rows in the height direction of the polishing head 1.

[0079] Figure 17 shows another embodiment of the light guide structure. As shown in Figure 17, the light guide structure 501 may include a glass body 520. Figure 18 is a top view of the glass body. As shown in Figure 18, the annular glass body 520 has an L-shaped cross-section and includes a main body portion 520a, a bent portion 520b, and a reflective surface 520c formed at the connection portion between the main body portion 520a and the bent portion 520b.

[0080] The glass body 520 has essentially the same configuration as the cell structure 510. Specifically, the glass body 520 corresponds to an integrally molded member of a plurality of cell structures 510 arranged in a ring shape.

[0081] Figure 19 shows a change in the contact position. As described above, during the polishing of the wafer W, the wafer W inside the retainer ring 103 rotates around the contact A. However, if the coefficient of friction between the polishing surface of the wafer W and the polishing surface 2a of the polishing pad 2 changes, the position of contact A may change (see Figure 19). Therefore, the control device 9 may determine the state change of the wafer W based on such a change in the contact position between the wafer W and the retainer ring 103.

[0082] Figures 20A and 20B show other embodiments of the detection unit. The detection unit 550 is configured to detect a peripheral region R of the wafer W, including the contact point with the retainer ring 103. Specifically, the detection unit 550 includes a light-receiving cell 560 extending parallel to the light-guiding structure 501.

[0083] The peripheral region R corresponds to a wide, arc-shaped space including the contact point. The width of the light-receiving cell 560 is greater than or equal to the peripheral region R. The light-receiving cell 560 is configured to output an electrical signal corresponding to the intensity of reflected light incident from the peripheral region PP of the wafer W. In one embodiment, the detection unit 550 may have the light-receiving cell 560 instead of the photodetector 553. However, the detection unit 550 may have the light-receiving cell 560 in addition to the photodetector 553.

[0084] In the embodiment shown in Figure 20B, the light-receiving cell 560 has a plurality of cell bodies 560a arranged parallel to the light-guiding structure 501, but it may also have a single cell body having a size of or greater than the peripheral region R.

[0085] The light-receiving cell 560 is configured to detect reflected light from the light-guiding structure 501 in the peripheral region R. The control device 9 is electrically connected to the light-receiving cell 560 and acquires the signal detected by the light-receiving cell 560. Subsequently, the control device 9 determines the state change of the wafer W based on the change in the peripheral region R over time.

[0086] Figures 21A and 21B show other embodiments of the detection unit. The detection unit 550 may include an imaging camera 570 for imaging the peripheral region R. The detection unit 550 may have the imaging camera 570 instead of the photodetector 553, or it may have the imaging camera 570 in addition to the photodetector 553.

[0087] The imaging camera 570 is configured to capture reflected light from the light guide structure 501 in the peripheral region R. Based on the image data acquired from the imaging camera 570, the control device 9 measures the change in the contact position in the peripheral region R and determines the change in the state of the wafer W.

[0088] The imaging camera 570 does not necessarily have to be attached to the unit supporter 16-1, as long as it is in a position where it can image the light guide structure 501; it may also be placed on the wall (not shown) housing the polishing device.

[0089] As described above, if the notch position NT of the wafer W can be identified, accurate film thickness distribution information (wafer map) can be obtained (created), thereby improving the uniformity of the film thickness distribution of the wafer W. Therefore, the configuration for obtaining film thickness distribution information will be described below.

[0090] Figure 22 shows one embodiment of a film thickness sensor. As shown in Figure 22, the polishing apparatus includes a film thickness sensor 60 embedded in the polishing table 3. As the polishing table 3 rotates, the film thickness sensor 60 traces the same trajectory as the virtual circle S (i.e., the rotational trajectory of the polishing surface 2a passing through the center CP of the wafer W) and passes over the surface of the wafer W to be polished.

[0091] The film thickness sensor 60 is configured to detect a physical quantity corresponding to the film thickness that changes according to the film thickness of the wafer W (specifically, a signal that reflects the film thickness of the wafer W). Examples of the film thickness sensor 60 include an optical sensor or an eddy current sensor.

[0092] If the film thickness sensor 60 corresponds to an eddy current sensor, the eddy current sensor is configured to detect eddy currents corresponding to the film thickness of the wafer W by passing a magnetic flux through the conductive film of the wafer W using its sensor coil, thereby generating eddy currents, and outputting an eddy current signal. The control device 9 determines the film thickness of the wafer W based on the eddy current signal.

[0093] If the film thickness sensor 60 corresponds to an optical sensor, the film thickness sensor 60 is configured to shine light on the polished surface of the wafer W, receive the reflected light from the wafer W, and decompose the reflected light according to its wavelength. The control device 9 measures the intensity of the reflected light at each wavelength over a predetermined wavelength range, generates a spectrum representing the intensity of light at each wavelength from the obtained light intensity data (optical signal reflecting the film thickness of the wafer W), and determines the film thickness of the wafer W from the spectrum.

[0094] The control device 9 measures the film thickness of the wafer W based on a signal detected by a film thickness sensor 60 that rotates with the rotation of the polishing table 3. Furthermore, the control device 9 determines the wafer angle specified by the notch position NT based on the phase of the notch position NT detected by the detection unit 550 and the phase of the signal detected by the film thickness sensor 60. Hereinafter, the wafer angle specified by the notch position NT may be referred to as the notch angle.

[0095] Figure 23 is a timing chart showing the phase of the notch position detected by the detection device and the phase of the signal detected by the film thickness sensor. Figure 24 is a diagram showing the processing flow of the control device that determines the notch angle. In Figure 23, the upper time chart shows the timing of notch position detection by the detection unit 550, and the lower time chart shows the timing of wafer measurement by the film thickness sensor.

[0096] First, the control device 9 starts polishing the wafer W (see step S201) and acquires the signal detected by the film thickness sensor 60 and the notch position detected by the detection unit 550 (see steps S202A and S202B).

[0097] The detection unit 550 periodically detects the notch position NT as it passes through the peripheral region R as the polishing head 1 rotates. As shown in Figure 23, the time interval of the notch position NT detected by the detection unit 550 when the wafer W rotates once is defined as time Tc.

[0098] In this case, the control device 9 calculates time Tc (see step S203) and calculates the time it takes for the wafer W to rotate by 1 degree, that is, the rotation time of the wafer W per unit angle (see step S204). The time it takes for the wafer W to rotate by 1 degree is calculated by dividing time Tc by 360 degrees (Tc / 360) under conditions in which the wafer W rotates stably.

[0099] Furthermore, as shown in step S205, the control device 9 calculates the time interval (i.e., time Ta) from the time the detection unit 550 detects the notch position NT to the time the film thickness sensor 60 detects the signal (see Figure 23).

[0100] Subsequently, as shown in step S206, the control device 9 calculates the notch angle from the time the detection unit 550 detects the notch position NT until the film thickness sensor 60 detects a signal by dividing the time Ta by the time it takes for the wafer W to rotate once (Tc / 360) (Ta / (Tc / 360)).

[0101] Figure 25 shows the mounting angle of the detection unit. As shown in Figure 25, the point on the imaginary line VL is defined as the device angle origin CO. In the embodiment shown in Figure 25, the detection unit 550 is positioned offset by a mounting angle θR from the device angle origin CO on the imaginary line VL.

[0102] Therefore, the control device 9 determines the notch angle taking into account the mounting angle θR. Specifically, the control device 9 subtracts the mounting angle θR from the notch angle calculated in step S206 (Ta / (Tc / 360)-θR) (see step S207).

[0103] In this way, the control device 9 can determine the notch angle from the device angle origin CO. Note that if the mounting angle θR is zero, that is, if the detection unit 550 is positioned at the device angle origin CO, the control device 9 determines (specifies) the notch angle without subtracting the mounting angle θR.

[0104] In this way, the control device 9 can derive the notch angle from the device angle origin CO by calculating time Ta and time Tc based on signals obtained from the detection unit 550 and the film thickness sensor 60.

[0105] Subsequently, the control device 9 creates a notch angle-referenced film thickness distribution information (wafer map) by associating the identified notch angle with the film thickness measured based on the signal detected by the film thickness sensor 60 (see step S208).

[0106] Figure 26 shows the processing flow of the control device when polishing a wafer. First, the film thickness of the wafer W is measured by a film thickness measuring instrument (not shown) provided on the polishing device or separate from the polishing device. The control device 9 acquires the initial film thickness distribution of the wafer W measured by the film thickness measuring instrument (see step S301).

[0107] Subsequently, the control device 9 starts polishing the wafer W (see step S302). After starting the polishing of the wafer W, the control device 9 executes steps S202 to S208 in Figure 24 to create film thickness distribution information based on the notch angle (see step S303). It is desirable that the film thickness distribution information be measured and updated multiple times periodically during the polishing of the wafer W.

[0108] The measurement methods using a film thickness measuring instrument installed in a polishing apparatus can be broadly classified into two types: a method for measuring the absolute film thickness of the wafer W (first measurement method) and a method for measuring the amount of polishing (second measurement method). In the first measurement method, the film thickness measuring instrument outputs the film thickness value of the wafer W (for example, thickness = 100 nm). In the second measurement method, the film thickness measuring instrument outputs the amount of polishing (for example, amount of polishing from a certain reference value = 50 nm).

[0109] When the first measurement method is performed, the control device 9 starts polishing the wafer W and creates film thickness distribution information. Step S301 may be omitted, or step S301 may be performed and the acquired initial film thickness may be compared with the film thickness distribution information created at the beginning of polishing to detect measurement anomalies. When the second measurement method is performed, after performing step S301, the control device 9 starts polishing the wafer W. In this case, the control device 9 subtracts the amount of polishing measured by the film thickness measuring instrument from the initial film thickness of the wafer W measured in step S301 or the film thickness distribution information created in advance in step S303 to create film thickness distribution information.

[0110] The control device 9 identifies a specific location on the wafer W (a location with a particularly thick or particularly thin film thickness) based on the film thickness distribution information, and operates the pressure adjustment device 165 based on the rotation angle of the polishing head 1 obtained from the rotary encoder 41 (see Figure 1) which detects the rotation angle of the polishing head 1. Alternatively, the control device 9 may identify the specific location on the wafer W from the initial film thickness distribution measured by a film thickness measuring instrument (see step S301) without using the film thickness distribution information obtained during polishing.

[0111] The control device 9 operates the pressure regulating device 165 to individually control the pressure of the fluid supplied to the pressure chamber 116, thereby actively polishing areas of the wafer W where the film is thick, or actively polishing areas of the wafer W other than those where the film is thin (see step S304).

[0112] Subsequently, the control device 9 determines whether the film thickness of the wafer W has reached the polishing endpoint by measuring the phase shift (change) of the notch position NT. If no phase shift occurs, the control device 9 continues polishing the wafer W (see "No" in step S305). If a phase shift occurs, the control device 9 terminates the polishing of the wafer W (see "Yes" in step S305).

[0113] To further improve the uniformity of the film thickness, after polishing the wafer W in the polishing apparatus is completed, the wafer W may be transported to a film thickness measuring instrument (not shown) to create film thickness distribution information for the wafer W, and then the wafer W may be transported to a different finishing polishing apparatus (for example, a face-up type polishing apparatus) to polish the wafer W additionally. However, this method increases the number of times the wafer W is transported.

[0114] According to this embodiment, the control device 9 creates film thickness distribution information during the polishing of the wafer W. Therefore, after the polishing of the wafer W is completed, the wafer W can be transported to the finishing polishing apparatus without transporting the wafer W to the film thickness measuring instrument. Consequently, the number of times the wafer W is transported can be reduced, and as a result, the throughput of the wafer W can be improved.

[0115] 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]

[0116] 1 Polishing head 2 polishing pads 2a Polished surface 3 Polishing Table 5. Polishing fluid supply nozzle 9 Control device 9a Storage device 9b Processing unit 11 Polished Head Shaft 13 Table motor 16 Head Arm 16-1 Unit Supporter 18 Polishing head motor 27 Vertical movement mechanism 28 Bridge 39. Polishing head height sensor 41 Rotary Encoder 50 Dressing Units 51 Dresser 52 Dresser Shaft 55 Swivel Arm 60 Film Thickness Sensor 102 Head Body 102a Bottom side 103 Retainer Ring 110 Elastic membrane 114 Wall 116 Pressure Chamber 165 Pressure Regulator 173 Fluid lines 182 Rotary Joint 500 detection devices 501 Light guide structure 502 Fiber Optic 502a Fiber end 502b Fiber end 503 Fiber holder 503a Main body 503b Bent section 510 Cell Structure 510a Main Unit 510b Bent section 511 Reflective material 520 glass body 520a Main Unit 520b Bent section 520c reflective surface 550 detection units 551 Light source 552 Half Mirror 553 Photodetector 560 photodetector cells 560a Cell 570 Imaging Camera Center of the CT polished surface CP wafer core VL imaginary line S Virtual Yen T tangent W wafer PP peripheral area NT notch position A Contact DA distance DB distance R peripheral region CO device angle origin θR mounting angle

Claims

1. A polishing device, A polishing table that supports the polishing pad, The polishing head holds the substrate with the exposed surface of the substrate facing the polishing surface of the polishing pad, A detection device for detecting the reference position of the substrate, The detection device comprises a control device electrically connected to the detection device, The detection device periodically detects the reference position which rotates together with the polishing head. The control device is a polishing apparatus that determines the state change of the substrate based on the reference position periodically detected by the detection device.

2. The aforementioned reference position corresponds to the position of a notch formed on the peripheral edge of the substrate. The detection device is Light is projected from the outside of the substrate toward the peripheral edge of the substrate. The reflected light reflected from the peripheral edge of the substrate is detected, The polishing apparatus according to claim 1, wherein the control device determines the notch position based on the intensity of the reflected light detected by the detection device.

3. The substrate has a structure that includes multiple materials with different coefficients of friction. The polishing apparatus according to claim 1, wherein the control device determines the polishing endpoint as a state change based on a change in the coefficient of friction between the substrate and the polishing pad, which is caused by a change in the surface structure of the substrate that changes as the polishing progresses.

4. The polishing apparatus according to claim 1, wherein the control device measures the phase of the reference position and determines a polishing abnormality of the substrate based on the magnitude of the phase change when the state change is determined.

5. When the components of the polishing apparatus, including at least the polishing pad, the polishing table, and the polishing head, are defined as polishing components, The polishing apparatus according to claim 4, wherein the control device determines the occurrence of at least one of the following as the polishing abnormality: an abnormality of the substrate itself and an abnormality of the polishing component.

6. The polishing apparatus according to claim 1, wherein the control device determines a change in the polishing conditions of the substrate as a change in state based on a change in the coefficient of friction between the substrate and the polishing pad.

7. The polishing apparatus is equipped with a film thickness sensor embedded in the polishing table, The film thickness sensor periodically detects a signal reflecting the film thickness of the substrate as the polishing table rotates. The control device is Based on the signal detected by the film thickness sensor, the film thickness of the substrate is measured. Based on the phase of the reference position detected by the detection device and the phase of the signal detected by the film thickness sensor, the substrate angle is determined as the circumferential angle of the substrate specified by the reference position. The polishing apparatus according to claim 1, which creates a substrate thickness distribution information based on the specified substrate angle and the measured substrate thickness.

8. The control device is From the time interval of the reference position detected by the detection device, the rotation time of the substrate per unit angle is calculated. The polishing apparatus according to claim 7, wherein the angle of the substrate is determined based on the rotation time of the substrate and the time interval from the time the detection device detects a reference position to the time the film thickness sensor detects a signal.

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