Semiconductor wafer grinding device and grinding method

Abstract

The present invention provides a grinding method of a semiconductor wafer, comprising the steps of: measuring the crystal orientation at the outer peripheral portion of at least one of a plurality of semiconductor wafers cut from the same ingot, and storing the measured crystal orientation as crystal orientation data corresponding to the circumferential displacement of the semiconductor wafer from a reference position; grinding conditions including the direction and frequency of the applied ultrasonic waves are changed according to the crystal orientation, grinding is carried out, and the effective grinding conditions are stored as learning data; detecting a reference position for another semiconductor wafer, and estimating the crystal orientation of the grinding position of the semiconductor wafer by referring to the crystal orientation data according to the detected reference position; and setting a grinding condition at the grinding position of the semiconductor wafer by referring to the learning data, and grinding the outer peripheral part of the semiconductor wafer by applying the grinding condition set for the grinding spindle. By adopting the grinding method, the processing of the peripheral part of the semiconductor wafer can be realized with high efficiency and high yield.

Description

Technical Field

[0001] This invention relates to a grinding apparatus and grinding method for grinding semiconductor wafers, and more particularly to a grinding apparatus and grinding method suitable for grinding the outer peripheral portion of semiconductor wafers. Background Technology

[0002] It is known to apply ultrasonic waves to a grinding wheel used to flatten the surface and back of a wafer cut from a spindle to prevent wheel clogging during the grinding process. For example, the grinding apparatus described in Patent Document 1 includes a chuck table for holding the workpiece and a grinding unit for grinding the workpiece held in the chuck table, in order to effectively apply ultrasonic vibrations to the grinding wheel. Furthermore, the grinding unit has a rotating spindle and a wheel provided at one end of the rotating spindle. The grinding wheel is mounted on a wheel seat, and the unit has a wheel base and a grinding wheel mounted on the wheel base. An ultrasonic transducer is provided in either the wheel seat or the grinding wheel, and a power supply unit for applying power to the ultrasonic transducer is provided in the rotating spindle.

[0003] Furthermore, Patent Document 2 describes a grinding wheel for grinding a wafer held on a holding table, which has the following structure in order to properly transmit ultrasonic vibrations to the grinding wheel and grind the wafer well. These include a first annular plate mounted on a support of a grinding apparatus, a cylinder hanging from the outer periphery of the first annular plate, a second annular plate connected to the lower end of the cylinder, a grinding wheel arranged in a ring on the lower surface of the second annular plate, an annular ultrasonic oscillation section arranged around an opening on the upper surface of the second annular plate, and an ultrasonic receiving section that receives the ultrasonic vibrations transmitted from the ultrasonic oscillation section to the grinding wheel.

[0004] Patent Document 3 describes another example of grinding a wafer by applying ultrasonic vibration to a grinding wheel. In this publication, in the plateau processing of a substrate, in order to eliminate cracks and other defects on the surface of the substrate and perform processing with low damage, a chamfering device for grinding the end face of the workpiece has the following structure: It includes a vibrating flange that is fitted and fixed to the spindle of a grinding unit; a grinding wheel with a grinding wheel on its lower outer surface that is fitted to the vibrating flange; and a piezoelectric element disposed on the bottom surface of the grinding wheel, which is lower than the upper surface of the grinding wheel, on the outer periphery of the vibrating flange, and subjected to ultrasonic vibration in the radial direction. Thus, while applying ultrasonic vibration to the grinding wheel from the piezoelectric element, plateau processing is performed on the end face of the workpiece by cutting in the radial direction. Existing technical documents Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-23693 Patent Document 2: Japanese Patent Application Publication No. 2018-47508 Patent Document 3: Japanese Patent Application Publication No. 2017-177251 Patent Document 4: Japanese Patent Application Publication No. 2021-14107 Patent Document 5: Japanese Patent Application Publication No. 2017-183503 Non-patent literature

[0006] Non-patent literature 1: Yamada et al., "Second Report on Precision Laser Cutting of SIC: Relationship between Operating Direction and Crack Extension / Connection", Journal of the Abrasive Processing Society, Vol. 65, No. 10, pp. 549-555, October 2021. Summary of the Invention The technical problem that the invention aims to solve

[0007] In grinding relatively hard materials such as silicon single-crystal wafers freshly cut from ingots, from the viewpoint of improving grinding efficiency and yield, the grinding of the wafer's surface and back side is combined with high-speed feed grinding (rough grinding) with high grinding load and fine grinding (fine grinding) with reduced feed rate to reduce grinding load. Since grinding the wafer's surface and back side is planar grinding, in the case of single-crystal wafers, by keeping the feed direction of the grinding wheel constant on the wafer surface, grinding can always be performed towards the same crystal orientation. As a result, differences in bonding states, such as cracking, caused by differences in crystal orientation, can be avoided. That is, the stress generated on the wafer due to the movement of the grinding wheel on the wafer surface theoretically has no difference in position on the wafer surface, enabling uniform processing on the wafer surface and suppressing the frequency of defects such as cracks.

[0008] In contrast, edge processing, which is the side processing of a wafer, involves rolling a grinding wheel around the wafer in the circumferential direction. Because the cross-sectional shape of the edge is conical, including arcs or similar shapes, the crystal orientation of the grinding section constantly changes. In materials with crystalline structures, different crystal orientations result in varying grinding loads or resistances even when the same grinding conditions are applied to the grinding wheel. Therefore, in grinding silicon wafers, it is practical to empirically determine grinding conditions that prevent undesirable defects such as cracking, which are most likely to occur due to poor grinding, and to perform grinding under constant conditions at all circumferential positions of the wafer. However, in this case, to cope with subtle strength changes caused by the wafer's condition, the feed rate needs to be reduced until the grinding conditions become the safest, relaxed ones, thus not fully utilizing the machine's capabilities. Furthermore, if the grinding resistance of the wafer deviates from expectations, the grinding conditions need to be re-determined empirically.

[0009] The grinding apparatus described in Patent Document 1 above removes grinding chips that are trapped between the abrasive grains of the grinding wheel due to ultrasonic vibrations. This allows for efficient grinding even of brittle and hard materials. While this grinding apparatus is indeed useful in surface grinding, in single-crystal wafers, the crystal orientation constantly changes along the circumferential sides. Even under the same grinding conditions, the grinding stress and resistance generated on the wafer will vary. Therefore, to improve grinding efficiency, variable grinding conditions are needed to achieve the same processing effect without causing excessive grinding resistance.

[0010] In the planar grinding of a wafer based on a combination of rough and fine grinding as described in Patent Document 2, the output of ultrasonic waves is increased during rough grinding to increase the amplitude of the grinding wheel, while the output of ultrasonic waves is reduced during fine grinding to cause the grinding wheel to fall within a reduced target amplitude, thereby improving processing efficiency. In the grinding apparatus of Patent Document 2, since it is planar grinding, only one target amplitude needs to be set for the grinding wheel during both rough and fine grinding. However, in the grinding of the outer peripheral edge of a wafer, since the wafer exhibits different grinding resistance depending on its circumferential position, setting only a single target amplitude for the grinding wheel may not result in optimal grinding conditions. To improve grinding efficiency, it is preferable to set the target amplitude of ultrasonic excitation according to the circumferential position of the wafer.

[0011] In Patent Document 3, ultrasonic vibration is applied to the grinding wheel during chamfering of wafers, etc., to promote the inflow and outflow of coolant, thereby promoting the cleaning of the grinding surface and the removal of grinding chips. The chamfering device described in Patent Document 3 is not limited to the processing of single-crystal wafers, but is a general chamfering process. Therefore, in order to process regardless of changes in the circumferential grinding resistance or internal stress of the material being processed, safer (more relaxed) processing conditions are provided to prevent defects such as cracks and chips.

[0012] This invention addresses the problems of the prior art described above, and its objective is to efficiently and with high yield process the peripheral portion of semiconductor wafers. Specifically, in chamfering, a peripheral beveling process, an ultrasonic vibration method and apparatus are employed to address changes in bonding states, such as cracking, caused by variations in crystal orientation. Furthermore, other objectives include improving the processing efficiency and accuracy of chamfering based on the aforementioned objectives, or readily applying existing chamfering apparatuses to achieve at least one of the multiple objectives encompassing the above-mentioned features. Technical means to solve the problem

[0013] The present invention, which achieves the above-mentioned objective, is a semiconductor wafer grinding apparatus (wafer grinding apparatus) capable of grinding the outer periphery of a semiconductor wafer, comprising: a worktable for holding a semiconductor wafer and capable of rotation; a grinding spindle capable of grinding the outer periphery of the semiconductor wafer; and a shape measuring device disposed non-contactly with the semiconductor wafer to measure the external shape of the semiconductor wafer, wherein the grinding spindle comprises: a grinding wheel for grinding the outer periphery of the semiconductor wafer; an ultrasonic application unit for applying ultrasonic waves to the grinding wheel; and an ultrasonic control unit for controlling at least one of the direction and frequency of the ultrasonic waves applied by the ultrasonic application unit, wherein the ultrasonic control unit controls at least one of the direction and frequency of the ultrasonic waves applied to the grinding wheel located at the grinding position based on the change in circumferential position of the semiconductor wafer from the feature portion to the grinding position measured and detected by the shape measuring device.

[0014] Furthermore, based on this feature, preferably, the ultrasonic control unit controls at least one of the direction, frequency, and intensity of the ultrasonic wave applied to the grinding wheel located at the grinding position according to the different crystal orientations at the feature portion and the grinding position; preferably, the ultrasonic control unit has a storage unit for storing crystal orientation data, the crystal orientation data describing the relationship between the circumferential position of the semiconductor wafer relative to the feature portion of the semiconductor wafer and the crystal orientation, and the ultrasonic control unit refers to the crystal orientation data stored in the storage unit to control at least one of the direction and frequency of the ultrasonic wave applied to the grinding wheel located at the grinding position.

[0015] In addition, it is preferable to store cutting condition data describing the relationship between crystal orientation and grinding conditions in the storage unit, wherein the grinding conditions include the grinding speed and feed rate of the grinding wheel, and at least one of the direction and frequency of the ultrasonic waves applied to the grinding wheel.

[0016] Another feature of the present invention for achieving the above-mentioned objective is a grinding method for grinding the outer periphery of a semiconductor wafer mounted on a rotary table, comprising the following steps: measuring the crystal orientation at the outer periphery of at least one of a plurality of semiconductor wafers cut from the same ingot, and storing it as crystal orientation data corresponding to the circumferential displacement of the semiconductor wafer from a reference position; grinding the semiconductor wafer for which the crystal orientation has been measured, changing the grinding conditions including the direction and frequency of the applied ultrasonic waves according to the crystal orientation, and storing the effective grinding conditions as learning data; detecting a reference position for other semiconductor wafers cut from the same ingot, estimating the crystal orientation of the grinding position of the semiconductor wafer based on the detected reference position and referring to the crystal orientation data; and setting the grinding conditions at the grinding position of the semiconductor wafer with reference to the learning data, and grinding the outer periphery of the semiconductor wafer by applying the grinding conditions set for the grinding wheel (grinding spindle).

[0017] Another aspect of the present invention for achieving the above-mentioned objective is a grinding method for grinding the outer periphery of a semiconductor wafer mounted on a rotary table, comprising the following steps: for one of a plurality of semiconductor wafers, measuring the crystal orientation at the outer periphery of the semiconductor wafer and storing it as crystal orientation data corresponding to the circumferential displacement of the semiconductor wafer from a reference position; for the other semiconductor wafers, detecting the reference position and estimating the crystal orientation at the grinding position of the semiconductor wafer based on the detected reference position and the crystal orientation data; setting grinding conditions at the grinding position of the semiconductor wafer with reference to the relationship between crystal orientation and grinding conditions pre-stored as learning data; and applying the set grinding conditions to a grinding wheel to grind the outer periphery of the semiconductor wafer, wherein the grinding conditions include at least one of the direction and frequency of the ultrasonic wave applied to the grinding wheel, and also include the grinding speed and feed rate of the grinding wheel. Preferably, the semiconductor wafer is composed of multiple single-crystal silicon wafers cut from the same ingot, and the reference position is formed at substantially the same crystal orientation position in each semiconductor wafer.

[0018] Another aspect of the present invention is a semiconductor wafer grinding apparatus capable of grinding the outer periphery of a wafer, characterized in that it comprises: a grinding wheel for grinding the outer periphery of the wafer; and an ultrasonic wave application unit for applying ultrasonic waves to the grinding wheel, the grinding wheel having a first grinding wheel disposed in a first direction in the thickness direction of the wafer and a second grinding wheel disposed in a second direction in the thickness direction opposite to the first direction.

[0019] In the above-mentioned wafer grinding apparatus, the first grinding wheel and the second grinding wheel preferably overlap each other in the thickness direction.

[0020] Furthermore, in the above-mentioned wafer grinding apparatus, it is preferable that the grinding wheel has a third grinding wheel located between the first grinding wheel and the second grinding wheel in the thickness direction. Invention Effects

[0021] By employing this invention, in a wafer peripheral grinding apparatus, the direction and frequency of ultrasonic vibration applied to the grinding wheel are varied according to the circumferential position of the wafer mounted in the grinding apparatus. Therefore, grinding conditions can be altered based on changes in the crystal orientation of the wafer along its circumferential direction, easily addressing changes in bonding states such as cracking caused by variations in crystal orientation. Furthermore, since optimal grinding conditions can be applied to chamfering processes where the grinding wheel axis is tilted according to the wafer's circumferential position, processing efficiency is improved, and the application of inappropriate processing conditions is avoided, leading to increased processing accuracy and yield. Moreover, since only the direction and frequency of ultrasonic vibration are varied according to the wafer's circumferential position, processing apparatuses utilizing existing ultrasonic excitation devices can be used. Even when a new ultrasonic excitation device is added to a peripheral chamfering processing apparatus as a peripheral grinding apparatus, the process is the same as adding an ultrasonic excitation device to a surface grinding apparatus, making it easy to add an ultrasonic excitation device. Attached Figure Description

[0022] Figure 1A This is a block diagram of one embodiment of the grinding apparatus of the present invention. Figure 1B yes Figure 1A A schematic top view of the grinding device shown. Figure 2 yes Figure 1B A schematic front view of the grinding device shown. Figure 3A This is a partial front view illustrating the chamfering grinding of a wafer using the grinding spindle of a grinding machine. Figure 3B This is a partial front view showing other examples of grinding spindles. Figure 4 This is a partial front view illustrating an example of grinding the end face of a wafer to make it flat. Figure 5 This is a schematic top view illustrating the end face grinding of the wafer and the verification (learning) of the grinding results. Figure 6 This is a flowchart illustrating one embodiment of the grinding method of the present invention. Figure 7 This is a front view of an embodiment of a grinding apparatus equipped with the grinding wheel apparatus of the present invention. Figure 8 This is a schematic side view of an embodiment of the grinding wheel apparatus of the present invention. Figure 8(a) is an example of a hat-shaped grinding wheel with two parallel axes. Figure 8 (b) is an example of a hat-shaped grinding wheel whose two axes are separated in the circumferential direction of the wafer. Figure 9 This is a schematic side view of another embodiment of the grinding wheel apparatus of the present invention. Figure 10 This is a schematic side view of another embodiment of the grinding wheel device of the present invention. Figure 11 This is a schematic side view of another embodiment of the grinding wheel device of the present invention. Detailed Implementation

[0023] Hereinafter, an embodiment of the semiconductor wafer grinding apparatus of the present invention (wafer grinding apparatus 10) will be described with reference to the accompanying drawings. Figure 1A This is a block diagram of one embodiment of the wafer grinding apparatus 10. Figure 1B This is a rough top view. Figure 2 Is as Figure 1A , 1B The front view of the processing section 16, the main part of the wafer grinding apparatus 10 shown.

[0024] The wafer grinding apparatus 10 comprises a supply and recovery unit 12 for supplying and recovering wafers W relative to the apparatus 10, a measurement unit 14 for detecting features such as notches and orientation planes formed on the wafer W during peripheral grinding and performing pre-alignment and pre-processing measurements, a processing unit 16 for grinding the wafer W, a cleaning / drying unit 80 for cleaning and drying the wafer W after grinding, a crystal state measurement unit 22 for primarily measuring the crystal orientation of the wafer W before and / or after grinding, and a transport unit 24 for unmanned transport of the wafer W within the apparatus 10. These components are controlled via an operation panel 17 and a control device 15.

[0025] The control device 15 also includes an ultrasonic oscillation device control unit 100 and a grinding wheel control unit 90, which will be described in detail later. The grinding wheel control unit 90 (learning model storage unit) stores a learning model, and various programs and data used for processing using the learning model are stored in a storage unit (memory) 92. The control device 15, for example, inputs ultrasonic application conditions and grinding conditions, determines whether the edge shape of the wafer obtained after grinding under these ultrasonic application conditions and grinding conditions becomes the target edge shape, and generates a learning model. It should be noted that the ultrasonic oscillation device control unit 100 and the grinding wheel control unit 90 may also be provided in the processing unit 16.

[0026] In the supply and recovery section 12, multiple wafers W cut from the same ingot are collected in the wafer cassette 30 for preparation. Additionally, wafers W that have undergone chamfering are returned to the wafer cassette 30 after various measurements are completed and transported to the next process. To enable the wafers W to move from the wafer cassette 30 of the supply and recovery section 12 to the measurement section 14, and from the crystal state measurement section 22 to the wafer cassette 30 of the supply and recovery section 12, a supply and recovery robot 34 equipped with a cassette platform and a transport arm 36 is provided. The transport arm 36 is configured to move along a guide rail 38.

[0027] The measurement unit 14 performs thickness measurement, orientation plane detection, and pre-alignment of the wafer W undergoing chamfering. The measurement unit 14 includes a measurement stage 50, a thickness sensor 51, and an orientation plane detection sensor 54. The orientation plane detection sensor 54 is a laser sensor that detects the position of the orientation plane (feature portion) of the wafer W. It should be noted that the measurement unit 14 is provided independently from the processing unit 16, which will be described later. This is because grinding fluid or the like is sometimes used in the processing unit 16 during grinding. When grinding fluid or the like is used, it is possible for the grinding fluid or the like to adhere to the wafer W and its surroundings. When using an image (laser) sensor or the like, providing the measurement unit 14 independently from the processing unit 16 allows for more accurate measurements. On the other hand, the measurement can also be performed in the processing section 16 (measurement during processing). In this case, the measurement section 14 only needs to be configured to detect the position of the feature portion of the wafer W by means of a contact type and / or an eddy current type sensor.

[0028] The processing unit 16 is the main part of the wafer grinding apparatus 10, performing roughing and finishing processes from the outer peripheral grinding of the wafer W. The processing unit 16 includes a wafer positioning unit 60 and an outer peripheral grinding device 62. The wafer positioning unit 60 holds the wafer W and has a wafer stage 134 that is movable in the front-back direction (Y-axis direction), the left-right direction (X-axis direction), the up-down direction (Z-axis direction), and the rotational direction about the central axis (θ-axis). Figure 2 An AE sensor 58 is provided on the back of the wafer stage 134, and a shape measuring device 52 and an orientation plane detection sensor 54 for measuring the shape of the wafer are provided near the outer periphery of the wafer W. It should be noted that the processing unit 16 is equipped with the orientation plane detection sensor 54, but if the measuring unit 14 has already detected the orientation plane and referred to its position coordinates, the processing unit 16 may not be equipped with the orientation plane detection sensor 54. Specifically, the shape measuring device 52 is a laser displacement meter, etc. Alternatively, sensors or measuring devices for measuring the crystal state, as described later, may also be optionally provided.

[0029] The cleaning / drying unit 80 cleans and dries the wafer W after grinding. While the wafer W, held on the cleaning table 82, is rotated, cleaning fluid is sprayed onto the surface of the wafer W to remove dirt adhering to its surface. It should be noted that the wafer grinding apparatus 10 may not have a separate cleaning / drying unit 80. The cleaning / drying function may be performed by other parts. Alternatively, the cleaning / drying function itself may not be present.

[0030] The crystal state measuring unit 22 measures the crystal state of the wafer W before and / or after chamfering. The crystal state measuring unit 22 includes a measuring stage 86 and a crystal state measuring instrument 84. The measuring stage 86 holds the wafer W and rotates and moves it up and down. The crystal state measuring instrument 84 is a precision optical measuring instrument such as a Raman microscope. It should be noted that an AE sensor or similar device can also be used in the crystal state measurement.

[0031] The transport unit 24 transports wafers W to various parts of the wafer grinding apparatus 10. A horizontal guide 110 is provided, along with a slider 112 that can slide along 110, and a transport arm 114 is mounted on 112. An adsorption pad is installed at the top of the transport arm 114, allowing it to move horizontally and vertically while holding the wafer W in its adsorption.

[0032] Next, use Figure 2 The structure of the processing unit 16, a characteristic part of the present invention, will be described below. As described above, the processing unit 16 includes a wafer positioning unit 60 and a peripheral grinding device 62. The wafer positioning unit 60 includes an X-axis base 121 mounted on a main body base 141, an X-axis guide rail 122, an X-axis linear guide 123, and an X-axis drive unit 125 equipped with a ball screw and a servo motor. Figure 2 An X-axis worktable 124 that moves in the X direction. A Y-axis guide rail 126 and a Y-axis linear guide 127 are assembled on the X-axis worktable 124. A Y-axis drive unit with a ball screw (not shown) and a servo motor is used. Figure 2 The Y-stage 128 moves in the Y direction.

[0033] A Z-stage 131 is assembled on the upper part of the Y-stage 128. The Z-stage 131 is guided by a Z-axis guide rail 129 and a Z-axis linear guide (not shown), and moves in the Z-direction as shown in the figure using a Z-axis drive mechanism 130 equipped with a ball screw and a stepper motor. An θ-axis motor 132 and an θ-axis spindle are assembled on the Z-stage 131. A wafer stage 134, serving as a wafer holding unit for holding and holding wafers W, is mounted on the θ-axis. The wafer positioning unit 60 rotates the wafer W in the θ-direction and moves it in the X, Y, and Z directions.

[0034] In the machining section 16, such as Figure 1BAs shown, two peripheral grinding units 62 are arranged at intervals in the circumferential direction. In each peripheral grinding unit 62, a grinding wheel 155 is mounted at the end of the shaft of a spindle motor 156. On the opposite side of the grinding wheel of the spindle motor 156, a piezoelectric actuator 172 is mounted to excite the shaft of the spindle motor 156 horizontally by ultrasonic waves, and a piezoelectric actuator 174 is mounted to excite the shaft of the spindle motor 156 vertically. The piezoelectric actuators 172 and 174 are connected to an ultrasonic oscillation device 170. The grinding wheel 155, the spindle motor 156, and the piezoelectric actuators 172 and 174 form a grinding spindle 180.

[0035] In this embodiment, the wafer W to be ground is a silicon wafer sliced ​​from a monocrystalline silicon ingot, with a diameter of approximately φ50 to 300 mm and a thickness of less than 900 μm. It should be noted that the material of the wafer W that can be retrieved by the wafer grinding apparatus 10 is not limited to the above. It is particularly suitable for SiC wafers desired for applications such as power devices. While SiC is known to be a difficult-to-machine material, this embodiment allows for efficient grinding.

[0036] Typically, in a single-crystal wafer, since the crystal orientation changes regularly in the circumferential direction at the edge (outer peripheral surface) of the wafer W, X-ray diffraction and optical imaging methods are used to pre-detect the crack surfaces formed by the crystal's crack development. At a predetermined angle relative to the detected crack surfaces, an orientation plane or notch is formed in the preceding process to serve as a positioning reference for the wafer W. This data is stored in the grinding wheel control unit 90 of the control device 15.

[0037] Next, use Figure 3A and Figure 5 The peripheral grinding (chamfering) of a wafer W according to one embodiment of the present invention will be described. In the peripheral grinding apparatus 62, grinding wheels 155 are mounted vertically spaced apart. U Or grinding wheel 155 L The grinding spindle 180. The spindle motor 156 of the grinding spindle 180 has two independent shafts, each with a flared, cap-shaped grinding wheel 155 mounted at its top. U 155 L The shafts of the spindle motor 156 are all horizontal shafts.

[0038] The outer peripheral surface shape of wafer W is in most cases an arc-shaped increase in thickness from the center of the thickness direction (vertical direction) upwards or downwards or towards the inner diameter side. To form this shape, a grinding wheel 155 rotating about a horizontal axis is specified. U 155 LThe cross-sectional shape. In this embodiment, the grinding wheel 155 U 155 L The cross-sectional shape is a cone (cap-shaped) with a smaller diameter at the top and widening towards the base. That is, it is bell-shaped (the shape of the "bell" part of a brass instrument). In other words, the grinding wheel 155... U 155 L The cross-sectional shape is formed into a mountain shape that tapers from the root (foot) towards the top. It should be noted that the grinding position of the wafer W changes sequentially in the circumferential direction by driving the θ-axis motor 132 of the wafer positioning unit 60.

[0039] An orientation plane detection sensor 54 capable of detecting the position of the orientation plane formed on the wafer W is arranged around the peripheral grinding apparatus 62. Based on the orientation plane position detected by the orientation plane detection sensor 54, the circumferential position (coordinates) of the wafer W at the grinding position is determined. Based on the determined circumferential position (coordinates) of the grinding position, and referring to the crystal orientation data stored in the grinding wheel control unit 90, the crystal orientation at the grinding position is determined. It should be noted that an AE sensor 58 is installed on the wafer stage 134 on which the wafer W is placed. Figure 1B , Figure 3A This device detects the acoustic energy generated at the grinding location of the wafer W during grinding, continuously monitoring the plastic deformation, cracking, and wear of the wafer W. Alternatively, it can replace the AE sensor with sensors such as acceleration sensors that monitor vibrations generated during grinding.

[0040] However, in the outer periphery of the wafer W, which is a single-crystal wafer, the crystal orientation is not constant but varies, unlike the upper and lower planar portions. Therefore, it is impossible to grind along a single crystal orientation. As described in Patent Document 5 and Non-Patent Document 1, if the crystal orientation is different, the bonding state within the wafer W is different, and the progression of cracking caused by grinding is different. That is, if the wafer W is ground under constant grinding conditions (e.g., constant rotational speed of the grinding wheel 155, constant depth of cut of the grinding wheel 155, etc.), cracking progression points and cracking progression delay points will occur, and the amount of grinding chips generated will also differ. In order to maintain machining accuracy, it is necessary to reduce the grinding depth, but in this case, the grinding efficiency is reduced.

[0041] To eliminate this defect, the inventors implemented a grinding method corresponding to the crystal orientation, thereby setting grinding conditions in a way that makes the cracking progression uniform in the circumferential position of the wafer W, thus improving processing accuracy and grinding efficiency. It should be noted that although a method was considered to use the rotational speed and depth of cut of the grinding wheel 155 controlled according to the grinding position of the wafer W to achieve uniformity of the grinding results, the grinding time required may increase.

[0042] Therefore, the basic grinding conditions of the grinding wheel 155 remain unchanged; in other words, the operating state of the spindle motor 156 itself remains unchanged. However, by ultrasonically vibrating the grinding spindle 180, which includes the spindle motor 156, the grinding conditions are substantially altered. Thus, a piezoelectric actuator 172 for horizontal (or axial) vibration and a piezoelectric actuator 174 for vertical vibration are installed on the opposite side of the axial grinding wheel from the spindle motor 156. When the magnitude of the ultrasonic vibration force generated by each piezoelectric actuator 172, 174 is changed, a vibration force with altered magnitude and direction is obtained as a result of combining the ultrasonic vibration forces. This vibration force is applied from the grinding wheel 155 to the wafer W, substantially changing the grinding conditions.

[0043] In the above embodiment, two grinding wheels 155 of the same shape are arranged at intervals, one above the other. U 155 L Therefore, a tiny gap is formed between them to allow the two grinding wheels 155 U 155 L Without contact, the unprocessed portion is produced in a strip-like pattern. This is achieved by changing the two grinding wheels to 155... U 155 L The circumferential position is used to eliminate this problem. Figure 3B An example is shown where the unprocessed portion has been eliminated.

[0044] Figure 3B (a) shows grinding wheel 155 U 155 L The main view of the configuration status. Figure 3B (b) shows from Figure 3B (a) Grinding wheel 155 as observed in section AA U 155 L A schematic diagram of the configuration status. As shown in Figure (a), the grinding wheel 155 U 155 L The grinding wheels are arranged vertically along the thickness direction of the wafer W. In other words, the grinding wheel 155... U In the thickness direction of wafer W, a grinding wheel 155 is positioned slightly above the center of the thickness of wafer W. L The grinding wheel is positioned below the center of the thickness of wafer W along its thickness direction. (Grinding wheel 155) U 155 L For roughly the same shape, each grinding wheel is 155. U 155 L It is capable of grinding beyond the center portion of the wafer W in the thickness direction. That is, grinding can be performed from the front side of the machining section 16 (two grinding wheels 155). U155 L When viewed from the side, the two grinding wheels are 155. U 155 L The grinding areas overlap each other in the thickness direction of the wafer W. In other words, it should be noted that the two grinding wheels 155 overlap from the front side of the machining section 16. U 155 L When viewed from the side, the two grinding wheels are 155. U 155 L The grinding zones can also be non-overlapping in the thickness direction of the wafer W. Grinding wheel 155 U The lower end and the grinding wheel 155 U 155 L The upper end can be separated at intervals in the thickness direction of the wafer W. Additionally, the grinding wheel 155... U 155 L They can be roughly the same shape, but can also be different shapes. Furthermore, as shown in Figure (b), the two grinding wheels are 155... U 155 L The center position changes δ2 in the circumferential direction and separates δ in the vertical direction. 1. In other words, as shown in Figure (b), when viewed from the AA section direction, the two grinding wheels 155 U 155 L It is configured in a serrated shape. This prevents grinding omissions during the peripheral grinding of wafer W. It should be noted that... Figure 3B In the illustrated embodiment, the grinding spindle 180 is also subjected to ultrasonic excitation, causing the grinding wheel 155 to vibrate. U 155 L The grinding conditions are substantially changed. Therefore, a piezoelectric actuator 172 for horizontal (or axial) excitation and a piezoelectric actuator 174 for vertical excitation are mounted on opposite sides of the grinding wheel on the grinding spindle 180. Therefore, it is possible to change the grinding conditions according to the crystal orientation to perform peripheral grinding of the wafer.

[0045] Figure 4 Other examples of grinding wheels 155 are shown in the front view. Figure 4 The grinding wheel 155 shown P Unlike the embodiments described above, only one grinding wheel 155 is used. PThe outer periphery shape of wafer W changes from the arc shape described in the above embodiment to a vertical surface shape (i.e., the side surface shape of a cylinder). At the top and bottom edges of wafer W, when the edges formed by the upper and lower surfaces of wafer W and the outer periphery surface form a 90° angle, cracking and other defects are easily generated during operation. Therefore, only the very near edges of the upper and lower edges are machined with a rounded shape, and most of the outer periphery surface is machined into a cylindrical surface. Grinding wheel 155 P Its cross-sectional shape is an arc shape formed only in the parts near the upper and lower edges, and it is a disc shape connected by vertical lines.

[0046] With grinding wheel 155 P The curvature of the arc-shaped portion corresponding to the upper and lower edges is smaller than the outer diameter curvature of the wafer W (1 / R, R: wafer radius). This setting of the grinding wheel 155... P The shape, therefore even when grinding with a 155 grinding wheel P Rotation also eliminates the risk of accidentally machining other parts of the wafer W. Grinding wheel 155 P The tip of wafer W is ground. Grinding wheel 155. P Two grinding wheels 155 are configured in the thickness direction of wafer W. U 155 L The position between. For example, grinding wheel 155. P In the thickness direction of wafer W, it is positioned opposite to the center of the thickness of wafer W. Figure 4 In the illustrated embodiment, the piezoelectric actuator 172 for horizontal (or axial) excitation and the piezoelectric actuator 174 for vertical excitation are also mounted on the opposite side of the grinding wheel of the grinding spindle 180, applying ultrasonic waves to the grinding spindle 180, causing the grinding wheel 155 to... P The grinding conditions are substantially changed. As a result, it is possible to change the grinding conditions according to the crystal orientation to perform peripheral grinding of wafer W.

[0047] Figure 5 A grinding spindle 180 for cylindrical surface grinding is shown. P Two grinding spindles 180 for surface grinding U 180 L An example of the peripheral grinding apparatus 62. Based on the position (coordinates) of the wafer measured by the shape measuring device 52 and the orientation plane detection sensor 54, the crystal orientation at the processing position is determined by referring to the crystal orientation data stored in the learning model storage unit (grinding wheel control unit 90). It should be noted that, as mentioned above, the learning model storage unit stores the learning model and (training) data used for machine learning. The data used for machine learning includes the ultrasonic application conditions, grinding conditions, and the edge shape of the final wafer. The crystal orientation in the wafer varies depending on its material, (product) type, etc., but the relationship is obvious, and the crystal orientation of the wafer at any location is pre-included in the aforementioned data and stored.

[0048] Based on the determined crystal orientation, the direction and frequency of the ultrasonic excitation force generated by each piezoelectric actuator are determined, and the grinding spindles at 180° are then used for further analysis. U 180 L 180 P Peripheral grinding is performed by applying the determined excitation force. Each grinding spindle is 180°. U 180 L 180 P The application is differentiated based on the processing requirements of wafer W. This allows for peripheral grinding corresponding to the crystal orientation to be performed throughout the entire circumference of wafer W.

[0049] Next, use Figure 6 This paper describes a method for applying ultrasonic waves corresponding to crystal orientation. In a single-crystal wafer W, as described in Patent Document 5, the crystal orientation changes at the outer periphery. Therefore, the direction and frequency of the ultrasonic excitation force are changed according to the outer periphery of the wafer W. The crystal orientation and the rate of crack propagation of the wafer are theoretically determined based on the material mechanical properties of the crystal. However, deviations from the theory cannot be eliminated in actual wafer W; therefore, a learning effect is utilized in this embodiment.

[0050] In multiple wafers W cut from the same ingot, since orientation planes should be formed at locations with substantially the same crystal orientation, the shape to be processed (edge ​​target shape) determined by the shape measuring device 52 is read in step S610, using the orientation plane detected by the orientation plane detection sensor 54 as a reference for the first wafer W. Then, the grinding conditions are initially set for the wafer W (step S612). The initial grinding conditions are set based on the material mechanical properties of the crystal or based on the grinding results of previously ground wafers W of the same type.

[0051] Based on the set grinding conditions, the actual ultrasonic application conditions are set (step S614). The effect of driving the piezoelectric actuators 172 and 174 to apply ultrasonic waves is determined in advance during preliminary tests, or set based on previous grinding results of the same type of wafer W.

[0052] Since the grinding conditions for wafer W and the application conditions for piezoelectric actuators 172 and 174 have been determined, grinding (edge ​​grinding) is actually performed on the outer periphery of wafer W (step S620). During the grinding process, the position coordinates of the grinding area and the corresponding crystal orientation are confirmed and recorded using AE sensor 58 and shape measuring device 52 (step S630). After the overall grinding of the outer periphery of wafer W is completed, the shape and crystal state after grinding are measured (step S632). The measurement in step S632 can be performed in the processing unit 16 (see reference 16). Figure 1B This can be performed separately in the crystal state measuring unit 22 (see reference). Figure 1B )conduct.

[0053] Next, using the measurement results from the shape measuring device 52 and the crystal state measurement results, it is determined whether the peripheral grinding result of the wafer W conforms to the target shape proposed in step S610 (step S640). If it conforms to the target shape, the grinding conditions and ultrasonic application conditions at this time are stored as grinding condition data in the storage unit 92 of the grinding wheel control unit 90 (learning model storage unit) of the control device 15. Afterwards, peripheral grinding of other wafers W is performed using the grinding condition data. At this time, the state of the grinding position, i.e., the crystal orientation, is determined based on the orientation plane position, etc. If the target shape is not met in step S640, the ultrasonic application conditions are changed (step S650). Specifically, referring to the grinding condition database (step S652), the learning model is changed and a new one is created (step S654). Then, return to step S614 and repeat steps S614 to S654 until the target edge shape (target outer perimeter shape) is achieved.

[0054] Once the learning model is created, the data used in the model is used to perform peripheral grinding on other wafers. If the crystal orientation at the orientation plane position differs from the orientation stored in the learning model, this difference is compensated for, and the model is applied. It should be noted that during the processing of wafers W other than the reference wafer W, if they exhibit cracking behavior different from the data stored in the learning model, the data in the learning model can be updated at any time.

[0055] As described above, according to various embodiments of the present invention, in the peripheral processing of wafer W, by changing the conditions for applying ultrasonic waves according to the processing position, the rate of cracking progression caused by different crystal orientations can be controlled, enabling homogeneous processing. This improves processing efficiency and increases the yield in the peripheral processing of wafers. Furthermore, the grinding wheels used have a structure that makes it difficult for cavities to form. If ultrasonic waves are applied, the vibration effect makes it easier to eliminate clogging of the grinding wheels. As a result, grinding can be performed while maintaining sharpness, and thus, a grinding surface with fewer bumps and unevenness can be produced.

[0056] Hereinafter, an embodiment of the grinding wheel apparatus 1801 of the present invention will be described with reference to the accompanying drawings. Figure 7 This is a schematic front view of a wafer grinding apparatus 101 equipped with the grinding wheel apparatus 1801 shown in this embodiment. The wafer grinding apparatus 101 includes a wafer holding section 201, a grinding wheel section 501, a wafer supply / receiving section (not shown), a wafer cleaning / drying section, a wafer transport unit, and a control section that controls the operation of each part of the wafer grinding apparatus 10.

[0057] The aforementioned grinding wheel apparatus includes a structure that reduces the retention of grinding chips at the grinding location for chamfering the outer periphery of semiconductor wafers. Furthermore, according to the grinding wheel disclosed below, even when ultrasonic vibration is applied to the grinding wheel, peripheral chamfering can be performed with high throughput.

[0058] The wafer holding unit 201 has an X stage 241, which moves in the X direction as shown in the figure via an X-axis base 211 mounted on the main body base 111, two X-axis guide rails 221, four X-axis linear guides 231, and an X-axis drive mechanism 251 equipped with a ball screw and a stepper motor.

[0059] A Y-stage 281 is assembled on the X-stage 241. The Y-stage 281 moves in the Y direction of the figure via two Y-axis guide rails (not shown), four Y-axis linear guides 271, and a Y-axis drive mechanism 321 with a ball screw and a stepper motor (not shown). A Z-stage 311 is assembled on the Y-stage 281. The Z-stage 311 is guided by two Z-axis guide rails 291 and four Z-axis linear guides (not shown), and moves in the Z direction as shown in the figure by a Z-axis drive mechanism 301 equipped with a ball screw and a stepper motor.

[0060] A rotary spindle 331 is assembled on the Z-stage 311, and a wafer stage 341 for holding and holding a wafer W is mounted on the rotary spindle 331. The wafer stage 341 rotates around the rotation axis. In the wafer holding part 201, the wafer W is translated in the rotation θ direction and the X, Y, and Z directions, thereby positioning the wafer W at the processing position set later in the grinding wheel part 501.

[0061] In the grinding wheel section 501, a rotary table 531 is arranged at the top, and a grinding wheel base 1581 is arranged at the bottom. A pair of grinding wheel devices 1801 are mounted on the rotary table 531. These devices include grinding wheels 1551a (1551aU) and 1551a (1551aL) for grinding the outer periphery of a (semiconductor) wafer W, and a grinding spindle (spindle motor 1561). Grinding wheel 1551aU grinds the upper outer periphery of the wafer W, and grinding wheel 1551aL grinds the lower outer periphery of the wafer W. In Figure 1, the rotary table 531 rotates along a horizontal plane. When grinding the upper outer periphery of the wafer W, grinding wheel 1551aU is brought close to the wafer W (as shown in Figure 1). When grinding the lower outer periphery of the wafer W, the rotary table 531 is rotated half a turn to bring grinding wheel 1551aL close to the wafer W.

[0062] It should be noted that the grinding wheel device 1801 has two grinding spindles on the rotary table 531, and grinding wheels 1551a (1551aU) and 1551a (1551aL) are respectively arranged on the two grinding spindles, but the arrangement of grinding wheels 1551a is not limited to the above situation. In addition, the grinding wheel device 1801 may also not have a rotary table 531. For example, the grinding wheel device may also have grinding wheels 1551a (1551aU) and 1551a (1551aL) arranged vertically with a specified gap, and a grinding spindle equipped with each spindle motor 1561.

[0063] The grinding wheel 1551a of the grinding wheel device 1801 configured on the turntable 531 is formed into a flared hat-shaped grinding wheel 1551a (1551aU, 1551aL) capable of grinding the periphery of the wafer into an ellipsoidal surface.

[0064] The grinding wheel assembly 1801 is mounted opposite the wafer W on the upper part of the grinding wheel base 1581 located below the grinding wheel section 501. A disc-shaped grinding wheel 1551b is mounted on the grinding wheel assembly 1801 mounted on the grinding wheel base 1581. This disc-shaped grinding wheel 1551b is used to grind the periphery of the wafer W into a flat portion with a substantially vertical surface (cylindrical surface). Of course, considering the processing purpose and processing time, a cap-shaped grinding wheel 1551a and a disc-shaped grinding wheel 1551b can be selectively used as the grinding wheels mounted on the grinding wheel base 1581 and the rotary table 531.

[0065] Figure 2 Details of the cap-shaped grinding wheel 1551a are shown. Figure 8(a) is an example of a hat-shaped grinding wheel 1551a disposed at the top of each of two parallel horizontal axes, and is a side view of the hat-shaped grinding wheel 1551a. Each grinding wheel 1551a is a hat-shaped shape conforming to the cross-sectional shape of the wafer W being processed, and in the cross-sectional shape of the wafer W, it is a curved surface shape in which the thickness of the wafer W changes smoothly in an arc shape from the center in the thickness direction. That is, the grinding wheel 1551a is formed into a flared shape with a smaller diameter at the end on the wafer W side and a larger diameter at the bottom as it approaches the spindle motor 1561 side. In other words, it is a shape with a curved slope of a cone or frustum, and a gradually widening "flared" portion at the top of a brass instrument.

[0066] The size of the grinding wheel 1551a is not particularly limited, but in order to improve the flexibility of the layout of the device, especially the ability to set it up even in a limited and narrow space, the diameter of the grinding wheel 1551a (maximum diameter in the rotation direction) is preferably 0.1 or more, more preferably 0.2 or more, more preferably 1.0 or less, more preferably 0.5 or less, and even more preferably 0.3 or less, relative to the diameter of the wafer W to be ground.

[0067] The two grinding wheels 1551aU and 1551aL, positioned vertically, are substantially identical in shape. Therefore, by placing their respective axes of rotation at equal distances from the center of the wafer W in the thickness direction, the outer peripheral surface of the wafer W is ground symmetrically. However, in Figure 2 In (a), to avoid interference between the movements of the upper and lower grinding wheels 1551aU and 1551aL, a small gap needs to be formed between the two grinding wheels 1551aU and 1551aL. As a result, an unprocessed area is formed at the center of the wafer W in the thickness direction.

[0068] The simplest way to eliminate this problem is as follows: Figure 8 As shown in (b), the grinding positions of the two grinding wheels 1551aU and 1551aL overlap. More specifically, the two grinding wheels 1551aU and 1551aL are positioned at different circumferential locations on the wafer W to avoid interference between the grinding wheels 1551aU and 1551aL (staggered arrangement). Figure 8 In (b), regarding the upper and lower grinding wheels 1551aU and 1551aL, let the interaxial distance between them be δ in the circumferential direction of the wafer W. 11 In the wafer thickness direction, let the interaxial distance be δ. 21 This ensures that each part is thicker than the wafer W, and that the grinding areas overlap. This prevents the occurrence of areas missed during grinding.

[0069] Figure 9Another example of a grinding wheel 1551b for grinding the outer peripheral surface of a wafer is shown in a side cross-sectional view. This is used when it is necessary to make the outer peripheral surface of the wafer W flat. In the case of flat grinding of the outer peripheral surface of the wafer W, when corners are formed at the upper edge (the junction with the upper surface) and the lower edge (the junction with the lower surface), the probability of cracks or the like arising from the upper and lower edges increases due to operations such as transport between wafer processing steps and during the processing stroke.

[0070] Taking these factors into consideration, the cross-sectional shape of the grinding wheel 1551b for surface grinding was determined. Specifically, a large portion of the wafer W in the thickness direction (the central portion of the grinding wheel 1551b) is assumed to be flat, i.e., as a straight line or curvature R. G The curve is designed such that the portion machining the upper and lower edges (the outer diameter end of the grinding wheel 1551b) is a smooth arc or other curved shape. Furthermore, the curvature of this curved portion is smaller than the outer diameter curvature (1 / Rw1) of the wafer W. This prevents the grinding wheel 1551b from accidentally interfering with the wafer W and deviating from the desired shape during surface grinding. It should be noted that the grinding wheel 1551b can also be used for subsequent machining of the aforementioned... Figure 2 In (a), the unprocessed area at the center of the wafer W in the thickness direction, caused by the tiny gap between the upper and lower grinding wheels 1551aU and 1551aL, is processed.

[0071] Figure 10 and Figure 11 The combination is shown Figure 8 , Figure 9 Examples of grinding wheel devices 1801b and 1801c consisting of grinding wheels 1551a and 1551b and ultrasonic application unit 1701 are shown. Figure 10 This is an example of a hat-shaped grinding wheel. Figure 11 This is an example of a disc-type grinding wheel. This is particularly noticeable if the wafer W is a single-crystal wafer, but the crystal orientation of the wafer W changes in the circumferential direction. As described in Non-Patent Document 1, when the crystal orientation at the processing location of the wafer W is different, even under the same grinding conditions, the progression of cracking will differ, becoming either too large or too small compared to the expected grinding amount. Therefore, in order to substantially change the grinding conditions without altering the rotational speed of the spindle motor 1561 connected to the grinding wheel, a piezoelectric actuator 1721 for axial excitation and a piezoelectric actuator 1741 for vertical excitation are attached to the spindle motor 1561, forming grinding wheel devices 1801b and 1801c. By controlling the piezoelectric actuators 1721 and 1741, the direction and frequency of the applied ultrasonic waves are changed, altering the grinding conditions of the grinding wheels 1551a and 1551b. Thus, the rate of cracking can be controlled, and a uniform grinding result in the circumferential direction of the wafer can be obtained.

[0072] from Figure 9 , Figure 10 The configuration of the grinding wheels 1551a and 1551b and the workpiece W is understandable, as the rotation direction of the workpiece W is different from that of the grinding wheels 1551a and 1551b. In the past, during the grinding of a workpiece W using a grinding wheel, the grinding wheel and the workpiece W rotated in the same direction (rotated in the same plane). In this conventional structure, sometimes strip-shaped unevenness, known as "streaks," would be produced on the surface of the workpiece W after grinding. To address this, a method sometimes called "spiral grinding" is used, which involves slightly tilting the rotation direction of the grinding wheel to suppress the formation of streaks.

[0073] The semiconductor wafer grinding wheel apparatus of the present invention is a technique that suppresses the formation of streaks using a method different from "helical grinding". By using grinding wheels 1551a and 1551b with different shapes than conventional grinding wheels, a state is created in which the rotation direction of the workpiece W is different from the rotation direction of the grinding wheels 1551a and 1551b. Thus, the formation of streaks is suppressed, similar to "helical grinding". By using ultrasonic excitation, the formation of strip-like unevenness on the surface can be further suppressed. The resulting surface becomes more uniform (e.g., pear-skin-like).

[0074] Furthermore, there are various requirements regarding the edge shape and surface condition of the wafer W, depending on the type of product and the type of subsequent processes. Not only flat surfaces, but surfaces with specified surface roughness are sometimes also targeted after grinding. Using ultrasonic excitation not only further suppresses streaks but also makes it easier to control the surface condition along the ground target, which is preferable.

[0075] In the above description, it is assumed that a single-crystal silicon wafer W is used as the wafer W to be ground, but the wafer is not limited to a single-crystal silicon wafer. It can also be a wafer made of other materials such as lithium tantalate or lithium niobate, or of course, a polycrystalline wafer.

[0076] Postscript (1) A semiconductor wafer grinding wheel apparatus, disposed in a semiconductor wafer grinding device, having a grinding wheel for grinding the peripheral portion of the semiconductor wafer, characterized in that it comprises: A rotary drive unit, which has the grinding wheel disposed at one end and drives the grinding wheel to rotate; and a processing unit, which controls the rotation and feed rate of the grinding wheel, the rotary drive unit being configured to enable the grinding wheel to rotate about an axis opposite to the thickness direction of the semiconductor wafer. (2) According to the semiconductor wafer grinding wheel apparatus of (1), the rotating drive unit is provided in a pair, each of the rotating drive units has the grinding wheel at one end, and the grinding wheel can rotate about an axis orthogonal to the thickness direction of the semiconductor wafer, and the shape of each grinding wheel is formed as a trumpet shape for grinding the upper half or lower half of the peripheral portion of the semiconductor wafer. (3) According to the semiconductor wafer grinding wheel apparatus of (2), the pair of grinding wheels are configured to change their circumferential positions relative to the semiconductor wafer. (4) According to the semiconductor wafer grinding wheel apparatus of (3), the pair of grinding wheels are configured to grind the semiconductor wafer by overlapping each other in the vertical direction. (5) According to the semiconductor wafer grinding wheel apparatus of (1), the rotary drive unit is configured to enable the grinding wheel to rotate about an axis orthogonal to the thickness direction of the semiconductor wafer, and the axial end face of the grinding wheel is a flat surface or a concave surface with a curvature smaller than the outer diameter curvature of the semiconductor wafer being ground. (6) The semiconductor wafer grinding wheel apparatus according to (1) is characterized in that it is provided with an ultrasonic application unit for applying ultrasonic waves to the grinding wheel, a machining unit for controlling the rotation and feed amount of the grinding wheel, and an ultrasonic control unit for controlling at least one of the direction and frequency of the ultrasonic waves applied by the ultrasonic application unit. (7) The semiconductor wafer grinding wheel apparatus according to (2) is characterized in that it is provided with an ultrasonic application unit for applying ultrasonic waves to each of the grinding wheels, a processing unit for controlling the rotation and feed amount of the grinding wheels, and an ultrasonic control unit for controlling at least one of the direction and frequency of the ultrasonic waves applied by the ultrasonic application unit. (8) The semiconductor wafer grinding wheel apparatus according to (5) is characterized in that it is provided with an ultrasonic application unit for applying ultrasonic waves to the grinding wheel, a processing unit for controlling the rotation and feed amount of the grinding wheel, and an ultrasonic control unit for controlling at least one of the direction and frequency of the ultrasonic waves applied by the ultrasonic application unit. Explanation of reference numerals in the attached figures

[0085] 10, 101: Wafer grinding device; 12: Supply and recovery unit; 14: Measurement unit; 15: Control device; 16: Processing unit; 17: Operation panel; 22: Crystal state measurement unit; 30: Wafer box; 34: Supply and recovery robot; 36: Conveyor arm; 38: Guide rail; 50: Measurement stage; 51: Thickness sensor; 52: Shape measuring device; 54: Orientation plane detection sensor; 58: AE sensor; 60: Wafer positioning unit; 62: Peripheral grinding device; 80: Cleaning / drying unit; 82: Cleaning station; 84: Crystal state measuring device; 86: Measurement stage; 90: Grinding wheel control unit; 92: Storage unit (memory); 100: Ultrasonic oscillation device control unit; 1 10: Horizontal guide; 111: Main body base; 112: Slider; 114: Conveyor arm; 121, 211: X-axis base; 122, 221: X-axis guide rail; 123, 231: X-axis linear guide; 124, 241: X-axis stage; 125, 251: X-axis drive unit; 126: Y-axis guide rail; 127, 271: Y-axis linear guide; 128, 281: Y-axis stage; 321: Y-axis drive mechanism; 129, 291: Z-axis guide rail; 130: Z-axis drive unit; 301: Z-axis drive mechanism; 131, 311: Z-axis stage; 132: Theta-axis motor; 134, 341: Wafer stage; 141: Main body base; 155, 155 U 155 L Grinding wheels; 156, 156 U 156 L : Spindle motor; 170: Ultrasonic oscillation device; 172, 172 U 172 L : Piezoelectric actuator (horizontal excitation); 174, 174 U 174 L : Piezoelectric actuator (vertical excitation); 180, 180 U 180 L : Grinding spindle; W: wafer; δ1, δ 21 Vertical deviation; δ2, δ 11 : Circumferential deviation; 201: Wafer holding part; 311: Rotary spindle; 501: Grinding wheel part; 531: Rotary table; 1551a, 1551aU, 1551aL: (hat-shaped, trumpet-shaped) grinding wheel; 1551b: (disc-shaped) grinding wheel; 1561: Spindle motor; 1581: Grinding wheel base; 1701: Ultrasonic application unit; 1721: Piezoelectric actuator (for horizontal or axial excitation); 1741: Piezoelectric actuator (for vertical excitation); 1801, 1801b, 1801c: Grinding wheel device.

Claims

1. A semiconductor wafer grinding apparatus, capable of grinding the outer periphery of a semiconductor wafer, characterized in that, It includes: a worktable for holding semiconductor wafers and capable of rotation; a grinding spindle capable of grinding the outer periphery of the semiconductor wafer; and a shape measuring device configured non-contactly with the semiconductor wafer to measure its shape. The grinding spindle comprises: a grinding wheel for grinding the outer periphery of a semiconductor wafer; an ultrasonic application unit for applying ultrasonic waves to the grinding wheel; and an ultrasonic control unit for controlling at least one of the direction and frequency of the ultrasonic waves applied by the ultrasonic application unit. The ultrasonic control unit controls at least one of the direction and frequency of the ultrasonic waves applied to the grinding wheel located at the grinding position, based on the change in the circumferential position of the semiconductor wafer from the feature portion to the grinding position as measured and detected by the shape measuring device.

2. The semiconductor wafer grinding apparatus according to claim 1, characterized in that, The ultrasonic control unit controls at least one of the direction, frequency, and intensity of the ultrasonic waves applied to the grinding wheel located at the grinding position, based on the different crystal orientations of the feature portion and the grinding position.

3. The semiconductor wafer grinding apparatus according to claim 2, characterized in that, The ultrasonic control unit has a storage unit for storing crystal orientation data, which describes the relationship between the circumferential position of the semiconductor wafer relative to the feature portion of the semiconductor wafer and the crystal orientation. The ultrasonic control unit refers to the crystal orientation data stored in the storage unit to control at least one of the direction and frequency of the ultrasonic waves applied to the grinding wheel located at the grinding position.

4. The semiconductor wafer grinding apparatus according to claim 3, characterized in that, The storage unit stores cutting condition data describing the relationship between crystal orientation and grinding conditions, the grinding conditions including the grinding speed and feed rate of the grinding wheel, and at least one of the direction and frequency of the ultrasonic waves applied to the grinding wheel.

5. A method for grinding a semiconductor wafer, used to grind the outer periphery of a semiconductor wafer mounted on a rotary table, characterized in that, Includes the following steps: For at least one of a plurality of semiconductor wafers cut from the same ingot, the crystal orientation at the outer periphery of the semiconductor wafer is measured and stored as crystal orientation data corresponding to the circumferential displacement of the semiconductor wafer from a reference position. For a semiconductor wafer whose crystal orientation has been measured, grinding is performed by changing the grinding conditions, including the direction and frequency of the applied ultrasonic waves, according to the crystal orientation, and the effective grinding conditions are stored as learning data. For other semiconductor wafers cut from the same ingot, a reference position is detected, and the crystal orientation of the grinding position of the semiconductor wafer is estimated based on the detected reference position and the crystal orientation data. as well as Referring to the learning data, grinding conditions are set at the grinding position of the semiconductor wafer, and the outer periphery of the semiconductor wafer is ground by applying the grinding conditions set for the grinding spindle.

6. A method for grinding a semiconductor wafer, used to grind the outer periphery of a semiconductor wafer mounted on a rotary table, characterized in that, Includes the following steps: For one semiconductor wafer among multiple semiconductor wafers, the crystal orientation at the outer periphery of the semiconductor wafer is measured and stored as crystal orientation data corresponding to the circumferential displacement of the semiconductor wafer from the reference position; For other semiconductor wafers, a reference position is detected, and the crystal orientation of the grinding position of the semiconductor wafer is estimated based on the detected reference position and the crystal orientation data. The grinding conditions at the grinding location of the semiconductor wafer are set by referring to the relationship between crystal orientation and grinding conditions that are pre-stored as learning data. as well as The set grinding conditions are applied to the grinding wheel to grind the outer periphery of the semiconductor wafer. The grinding conditions include at least one of the direction and frequency of the ultrasonic waves applied to the grinding wheel, as well as the grinding speed and feed rate of the grinding wheel.

7. The method for grinding semiconductor wafers according to claim 6, characterized in that, The semiconductor wafer is composed of multiple single-crystal silicon wafers cut from the same ingot, and the reference position is where each semiconductor wafer is formed at a substantially identical crystal orientation position.

8. A semiconductor wafer grinding apparatus capable of grinding the outer periphery of a wafer, characterized in that, have: A grinding wheel that grinds the outer periphery of the wafer; and An ultrasonic wave application unit applies ultrasonic waves to the grinding wheel. The grinding wheel has a first grinding wheel disposed in a first direction in the thickness direction of the wafer and a second grinding wheel disposed in a second direction in the thickness direction opposite to the first direction.

9. The semiconductor wafer grinding apparatus according to claim 8, characterized in that, The first grinding wheel and the second grinding wheel overlap each other in the thickness direction.

10. The semiconductor wafer grinding apparatus according to claim 9, characterized in that, The grinding wheel has a third grinding wheel located between the first grinding wheel and the second grinding wheel in the thickness direction.

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