JP5496710B2 - Wafer positioning method and apparatus - Google Patents

Description

  The present invention relates to a wafer positioning method and apparatus, and more specifically, a wafer positioning technique suitably employed when various wafers such as silicon, crystal, and sapphire are put into various apparatuses such as a grinding machine and an inspection machine. About.

  Silicon, quartz, sapphire, and other wafers are made by slicing a single crystal to about 0.5 mm to 1 mm, and the outer diameter of the wafer is 50 mm to 50 mm by industry organizations such as SEMI (Semiconductor Equipment and Materials International). Standardized in the range of about 300 mm, there are currently wafers with outer diameters such as 2, 3, 4, 6, 8, 12 inches.

  In addition, since the wafer is a single crystal, its crystal structure affects the operation of the semiconductor device that is the final product, so that the outer peripheral edge of the wafer has an optimum crystal orientation for the operation of the semiconductor device, As a mark for making the crystal orientation known in a later step, a notch called orientation flat (orientation flat (OF)) or notch is provided at a predetermined position. In addition, the surface of the wafer is usually mirror-polished, so it is easy to distinguish the front and back surfaces. However, if the front and back surfaces are the same, the front and back surfaces are the same. Since the distinction cannot be made, a sub-orientation flat for discriminating the front and back surfaces is provided at a predetermined angle from the orientation flat.

  Therefore, when a wafer having such a configuration is put into a processing apparatus such as a grinding machine that performs further processing or various apparatuses such as an inspection machine that performs inspection, it is necessary to position the wafer based on the orientation flat. is there.

  As a technique for positioning the wafer, for example, various positioning techniques have been developed and proposed as disclosed in Patent Documents 1 to 3.

  All of these conventional positioning technologies detect the orientation flat, which is a notch in the wafer, by using an optical sensor while rotating the wafer, but the orientation flat detection accuracy is low and the equipment configuration is complicated. There was room for further improvement, such as being lacking or general versatility.

JP-A-5-251546 JP-A-9-213771 JP 2003-289097 A

  The present invention has been made in view of such conventional problems. The object of the present invention is to put various wafers such as silicon, quartz, and sapphire into various apparatuses such as a grinding machine and an inspection machine. In addition, a highly versatile wafer positioning method that uses a single line sensor to detect positioning reference parts such as orientation flats and notches provided on the outer peripheral edge of the wafer, and enables positioning with high detection accuracy. Is to provide.

  Another object of the present invention is to provide a wafer positioning apparatus with a simple structure that can suitably carry out the above positioning method.

  In order to achieve the above object, the wafer positioning method of the present invention optically detects a positioning reference portion such as an orientation flat or a notch provided on the outer peripheral edge of a disk-shaped wafer, and uses this positioning reference portion. A method of positioning a wafer as a reference. After the wafer is centered, the outer peripheral edge of the wafer is optically measured by a single line sensor while rotating the wafer once at a high speed. After storing the rotation angle position coordinate of the wafer from which the minimum value of the light-shielding width is obtained as a temporary position of the positioning reference portion, the wafer is measured while rotating the wafer at a low speed with reference to the stored temporary position, and the positioning is performed. An accurate position of the reference part is detected.

  Here, “high speed” and “low speed” are terms used to indicate the relative rotational speeds at two rotational speeds having different speeds. For the two rotational speeds to be compared, The higher rotation speed is referred to as high speed, and the lower rotation speed is referred to as low speed (hereinafter the same shall apply in the specification and claims).

The following configuration is adopted as a preferred embodiment.
(1) The wafer positioning method includes the following steps.
(I) Centering step for centering the wafer (ii) While the wafer is rotated once at high speed, the outer peripheral edge of the wafer is optically measured by the line sensor, and the light shielding width of the line sensor is minimized. A temporary position detecting step for storing the rotation angle position coordinates of the wafer from which the value has been obtained as a temporary position of the positioning reference portion; and (iii) the wafer at a low speed based on the temporary position stored in the temporary position detecting step. Position determining step of optically measuring the outer peripheral edge of the wafer by the line sensor while detecting the accurate position of the positioning reference portion

(2) In the temporary position detection step, the maximum value of the light shielding width of the line sensor is stored as the value of the outermost periphery of the wafer.

(3) In the position determination step, after rotating the wafer at a high speed to a detection preparation position before the temporary position, the outer peripheral edge of the wafer is optically moved by the line sensor while rotating at a low speed. Measure and detect the rotation angle position coordinates of the two wafers whose light-shielding width change amount of the line sensor exceeds a threshold value as both end positions of the positioning reference portion, and determine the positioning reference from the center rotation angle position coordinates of these end positions. The exact position of the part was calculated and detected.

(4) The second detection preparation position that passes through the other end position of the positioning reference portion after the wafer is rotated at a low speed from the detection preparation position and the one end position of the positioning reference portion is detected by the line sensor. And the other end position of the positioning reference portion is detected by the line sensor.

(5) After determining the accurate position of the positioning reference portion of the wafer, the outer peripheral edge of the wafer was optically measured by the line sensor while rotating the wafer once, and the positioning reference portion was removed. The light shielding widths of the line sensors at a plurality of positions are compared and calculated, the maximum difference is calculated, and the presence or absence of centering abnormality is determined by comparing the maximum difference with a centering determination threshold value.

(6) After determining the exact position of the positioning reference portion of the wafer, the outer peripheral edge of the wafer is optically measured by the line sensor while rotating the wafer once, and the light shielding width of the line sensor is determined. The presence / absence of an outer periphery defect is determined by comparison with an outer periphery determination threshold value.

(7) For a wafer provided with an auxiliary positioning reference portion such as a sub-orientation flat on the outer peripheral edge, the wafer is rotated from an accurate position of the positioning reference portion of the wafer to a position before the auxiliary positioning reference portion. The light shielding width of the line sensor at the front position is stored, and the wafer is further rotated to the passing position of the auxiliary positioning reference portion, and the light shielding width of the line sensor at the passing position is stored. Is rotated in the reverse direction to the center position of the auxiliary positioning reference portion, the light shielding width of the line sensor at the center position is stored, and the light shielding width at the center position, and the light shielding width at the near position and the passing position are stored. The front and back surfaces of the wafer are determined by comparing and calculating the light shielding width of the larger one and comparing the difference with the front and back determination threshold value.

  Further, the wafer positioning apparatus of the present invention is an apparatus that suitably implements the positioning method, and includes a wafer holding section that holds the wafer in a horizontal state and horizontally rotates the wafer. And a single line sensor for optically measuring an outer peripheral edge portion of the wafer placed and held on the wafer rotating means, and a centering means for centering the wafer placed and held on the wafer rotating means. And a control means for controlling the wafer rotation means, the centering means and the line sensor means in conjunction with each other. The control means is configured to execute the positioning method described above. Characterized in that it is configured to control the means and the line sensor means.

The following configuration is adopted as a preferred embodiment.
(1) The wafer rotating means includes rotating spindle means that is driven to rotate about a vertical axis, and vacuum chuck means that is provided at the upper end of the rotating spindle means and sucks and holds the wafer in a horizontal state. The vacuum chuck of the vacuum chuck means also has a function as the wafer holding unit for mounting and holding the wafer in a horizontal state.

(2) The centering means includes a pair of centering members disposed opposite to each other with the wafer holding portion of the wafer rotating means interposed therebetween, and one of the pair of centering members defines a reference position for centering. The other is a movable side centering member that moves and positions the wafer relative to the reference centering member.

(3) The line sensor means is provided such that the line sensor is movable between a measurement position and a standby position with respect to the wafer holding portion of the wafer rotation means, and the line sensor is in the measurement position. The linear sensor portion is configured to coincide with the radial direction of the wafer.

(4) A centering state determination unit that determines the presence / absence of centering abnormality of the wafer based on a preset centering determination threshold value from the measurement result of the line sensor unit.

(5) Outer peripheral part determination means for determining the presence or absence of a chip on the outer periphery of the wafer based on a preset peripheral part determination threshold value from the measurement result of the line sensor means.

(6) Front / back determination means for determining the front / back of the wafer based on a preset front / back determination threshold value from the measurement result of the line sensor means is provided.

  The wafer positioning method of the present invention optically detects a positioning reference portion such as an orientation flat or a notch provided on the outer peripheral edge of a disc-shaped wafer, and performs wafer positioning based on the positioning reference portion. After centering the wafer, the outer peripheral edge of the wafer is optically measured by a single line sensor while rotating the wafer once at a high speed, and the minimum value of the light shielding width of the line sensor is obtained. After storing the rotation angle position coordinates of the wafer as a temporary position of the positioning reference portion, the wafer is measured while rotating the wafer at a low speed on the basis of the stored temporary position, and the accurate position of the positioning reference portion is determined. Since it is configured to detect, when various wafers such as silicon, quartz, sapphire, etc. are put into various devices such as grinding machines and inspection machines, To provide a highly versatile wafer positioning method that can detect positioning reference portions such as orientation flats and notches provided on the outer peripheral edge of the wafer using the line sensor, and perform positioning with high detection accuracy. Can do.

1 shows a wafer positioning apparatus according to an embodiment of the present invention, FIG. 1A is a perspective view showing a schematic configuration of a main part of the wafer positioning apparatus, and FIG. 1B is a point in FIG. It is the enlarged view which looked at the part in a chain line circle in the B direction. It is a block diagram which shows schematic structure of the positioning device. 3A to 3D are plan views for explaining the centering process by the centering portion of the positioning device. 4A to 4D are schematic views for explaining a wafer positioning process by the positioning apparatus. It is a front view for demonstrating the shape dimension of the wafer used as the positioning target of the positioning device. FIG. 6A shows the measurement result of the outer peripheral edge of the wafer to be positioned by the positioning device, FIG. 6A is a measurement diagram showing the relationship between the orientation flat and the sub orientation flat at the outer peripheral edge of the wafer, and FIG. It is a measurement diagram which expands and shows the part in the dashed-dotted line circle | round | yen in Fig.6 (a). 7A shows a wafer to be positioned by the positioning apparatus, FIG. 7A is a front view showing a wafer in which an orientation flat is provided on the outer peripheral edge of the wafer as a positioning portion, and FIG. 7B is an enlarged view of the orientation flat of the wafer. FIG. 7C is an enlarged front view corresponding to FIG. 7B showing a wafer in which a notch is provided as a positioning reference portion instead of the orientation flat. It is a top view which shows the modification of centering of the positioning device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Throughout the drawings, the same reference numeral indicates the same component or element.

  A wafer positioning apparatus according to the present invention is shown in FIGS. 1 to 7. Specifically, this positioning apparatus is provided in the vicinity of an input portion of a grinding machine, an inspection machine or the like, and FIG. And an apparatus for positioning a disk-shaped wafer W as shown in (b), wherein the target wafer W has an orientation flat O (large D-cut) as a positioning reference portion at the outer peripheral edge thereof. A sub-orientation flat SO (small D-cut) for discriminating the front and back surfaces Wa and Wb is provided at a position at a predetermined angle (90 ° in the illustrated case) from the orientation flat O.

  Specifically, as shown in FIGS. 1 and 2, the positioning apparatus includes a wafer rotating unit (wafer rotating unit) 1, a centering unit (centering unit) 2, a line sensor unit (line sensor unit) 3, and positioning confirmation. Part (positioning determination means) 4, centering state determination part (centering state determination means) 5, outer peripheral part determination part (outer peripheral part determination means) 6, front / back determination part (front / back determination means) 7, and apparatus control part (control means) 8 As a main part.

  The wafer rotating unit 1 is configured to place and hold the wafer W in a horizontal state and rotate the wafer W horizontally. The wafer rotating unit 1 includes a rotating main shaft portion (rotating main shaft means) 10 and a vacuum chuck portion (vacuum chuck means) 11 as main portions. .

  The rotation main shaft portion 10 is configured such that the rotation main shaft 15 is rotatably supported around a vertical axis, and is rotated forward and backward by a rotation drive source 16 at a predetermined rotation speed. Specifically, the rotation main shaft 15 is drivingly connected to a drive motor 16 which is a rotation drive source via power transmission means such as a power transmission belt and a gear mechanism (not shown) or directly without these power transmission means. Has been. In the illustrated embodiment, the rotary main shaft 15 is in the form of a direct drive mechanism in which the drive motor 16 is directly connected to the drive motor 16. A servo motor is used as the drive motor 16 and is electrically connected to the wafer rotation control unit 100 of the apparatus control unit 8 (see FIG. 2).

  The vacuum chuck unit 11 sucks and holds the wafer W on the rotating main shaft unit 10 in a horizontal state, and the chuck body 20 in the form of a rotating disk is integrated with the upper end portion 15a of the rotating main shaft 15 in a horizontal state. The wafer W is provided on the chuck body 20 by suction. Specifically, the upper surface 20a of the chuck body 20 is a horizontal flat surface, and is a suction surface that also functions as a wafer holding unit for mounting and holding the wafer W in a horizontal state. A plurality of suction ports (not shown) for suction (not shown) are opened on the upper surface 20a, and the suction ports can communicate with a negative pressure source 21 such as a vacuum pump through an air pipe (not shown). ing.

  Further, the chuck body 20 is formed of a material that does not damage the wafer W by sliding during centering of the wafer W, which will be described later, and suction during suction holding, and is attached to the upper end portion 15a of the rotating spindle 15 so as to be removable and replaceable. According to the structure, the chuck body 20 can be replaced in accordance with the outer diameter of the wafer W. The chuck body 20 of the illustrated embodiment is available in two types for wafers of 2 to 3 inches and for wafers of 4 to 8 inches, and can be applied to most currently manufactured wafers. In addition, even larger wafers can be handled according to the purpose. Drive units such as a vacuum pump and a switching valve constituting the negative pressure source 21 are electrically connected to the wafer rotation control unit 100 of the apparatus control unit 8 in the same manner as the drive motor 16 (see FIG. 2).

  The wafer W is sucked and held in a horizontal state on the upper surface 20 a of the chuck main body 20 by the suction action of the chuck main body 20 driven by the negative pressure of the negative pressure source 21, and the rotating spindle 15 is driven by the rotation of the drive motor 16. Thus, the rotation is controlled in the forward rotation direction X or the reverse rotation direction Y at a predetermined rotation speed (high speed or low speed) described later. In the illustrated embodiment, for the convenience of explanation of the positioning step described later, the counterclockwise direction is the forward rotation direction X and the clockwise direction is the reverse rotation direction Y as viewed from above the apparatus. However, the present invention is not limited to this.

  The centering unit 2 performs centering of the wafer W placed and held on the wafer rotating unit 1, and includes a pair of centering members 30, 31 and an advance / retreat drive source 32 as main parts.

  The pair of centering members 30 and 31 are disposed to face each other with the chuck main body 20 serving as a wafer holding portion of the wafer rotating unit 1 interposed therebetween, and can be moved forward and backward in the chuck main body 20 direction (arrow direction), respectively. Has been.

  One centering member 30 constitutes a reference side centering member that defines a reference position for centering, and a plurality of (four in the illustrated case) support members 36, 36,... . Specifically, each support member 36 is in the form of a cylindrical support roller, and is supported on the mounting member 37 so as to be upright and freely rotatable, and the mounting member 37 is fixed to the base 35. It is attached to and supported by. Further, the support roller 36 is formed of a material having elasticity that does not damage the wafer W by abutment locking with the outer peripheral edge portion We of the wafer W during centering of the wafer W described later.

  And all the supporting rollers 36, 36,... On the base 35 are arranged to simultaneously contact and support the outer peripheral edge We of the target wafer W. In the reference-side centering member 30 of the illustrated embodiment, a plurality of types of bases including support rollers 36, 36,... Arranged in correspondence with various sizes (outer diameter dimensions) of the target wafer W are provided. 35, 35,... Are prepared.

  With such a configuration, in the centering member 30 of the illustrated embodiment, when the model number of the target wafer W is changed or changed, the plurality of types of bases 35, 35,... By selecting and exchanging a dedicated one corresponding to the size of the target wafer W, it is possible to deal with most of the currently manufactured wafers of model numbers (outer diameter dimensions).

  The reference side centering member 30 is movable between a forward position shown in FIGS. 3B and 3C and a backward position shown in FIGS. 3A and 3D (arrows in FIG. 1). The reference position of the centering is defined at the forward position (the position in FIGS. 3B and 3C).

  The other centering member 31 constitutes a movable centering member that moves the wafer W with respect to the reference centering member 30, and one support member 39 is provided on the base 38. Specifically, the support member 39 has the same elasticity as the support member 36 of the reference centering member 32 and is in the form of a cylindrical support roller, and can stand up on the base 38 and freely rotate. Is pivotally supported.

  The movable-side centering member 31 is movable between a forward position shown in FIG. 3C and a retracted position shown in FIGS. 3A, 3B, and 3D (arrows in FIG. 1). The centering is completed at the forward position (the position of FIG. 3C).

  The reference side and movable side centering members 30 and 31 are drivingly connected to an advancing / retreating drive source 32, respectively. The advancing / retreating drive source 32 moves the reference side and movable side centering members 30, 31 between the advancing position and the retreating position, respectively. Although not specifically shown, the advancing / retreating cylinder device or the feed screw mechanism An advancing / retreating drive device including a drive motor is preferably employed, and an advancing / retreating cylinder device is used in the illustrated embodiment. The advancing / retreating cylinder devices that are drivingly coupled to the reference side and movable side centering members 30 and 31 are electrically connected to the centering control unit 101 of the device control unit 8 (see FIG. 2).

  Next, the centering process of the wafer W by the centering unit 2 will be described with reference to FIG.

Wafer W centering process:
(1) The wafer W is placed on the chuck main body 20 of the vacuum chuck unit 11 in the wafer rotating unit 1 (see FIG. 3A) manually or by an automatic supply device.

(2) The reference side centering member 30 of the centering portion 2 moves forward to the reference position and stops (see FIG. 3B).

(3) While the movable side centering member 31 of the centering portion 2 moves forward, the wafer W is pushed toward the reference side centering member 30 at the reference position by the support roller 39 (see FIG. 3C). When the outer peripheral edge We of the wafer W is sandwiched from both sides by the support rollers 36, 36,..., 39 of the centering members 30, 31, the movable side centering member 31 is stopped. It coincides with the center of the wafer rotating unit 1, that is, the center of the rotation spindle 15 (= center of the chuck body 20) P, and the centering (centering) of the wafer W is completed.

  The advance position of the reference side centering member 30 (the position shown in FIGS. 3B and 3C) defines a reference position for centering, and is therefore set to a fixed fixed position determined in advance. Yes.

  On the other hand, the stop position of the movable side centering member 31 is a preset advance position of the movable side centering member 31 or a pressure when the centering member 31 abuts and locks the outer peripheral edge We of the wafer W of the support roller 39. Is detected by a sensor, and the wafer W is prevented from being damaged. In addition to this, as a means for preventing damage and the like, a shock-absorbing means (elastic spring) is provided at the tip of the piston rod of the advance / retreat cylinder device so that the movable side centering member 31 pushes the wafer W elastically. (Not shown) is also preferably employed. In the illustrated embodiment, this buffering configuration is adopted to simplify the device configuration.

(4) When the centering of the wafer W is completed, the negative pressure source 21 of the vacuum chuck unit (vacuum chuck means) 11 is driven by a negative pressure, and the wafer W is attracted by the chuck body 20 so that the upper surface 20a of the chuck body 20 is It is adsorbed and fixed on top and held in a horizontal state.

(5) Both centering members 30 and 31 of the centering portion 2 are retracted to the standby position at the beginning of movement and stopped (see FIG. 3D).

  The line sensor unit 3 optically measures the outer peripheral edge of the wafer W placed and held on the wafer rotating unit 1, and includes a single line sensor 40 and an advancing / retreating drive source 41 as main parts. ing.

  The line sensor 40 optically measures the outer peripheral edge portion We of the wafer W as an object. In the illustrated embodiment, the light projecting unit 40a and the light receiving unit 40b are arranged to face each other with the wafer W interposed therebetween. A transmission type sensor is used.

  The line sensor 40 has an arrow between a measurement position (position shown in FIG. 1) and a standby position (position in the front direction of the position shown in FIG. 1) with respect to the wafer holding unit 20 of the wafer rotating unit 1. It is provided to be movable in the direction.

  Further, in the state where the line sensor 40 is at the measurement position, the linear sensor portion, that is, the light receiving portion 45b of the light receiving portion 40b is aligned with the radial direction of the wafer W as shown in FIG. It is configured. Thereby, the light projection from the light projecting part 45a of the light projecting part 40a is blocked by the outer peripheral edge We of the wafer W and received by the light receiving part 45b of the light receiving part 40b. The position of the outer peripheral edge (edge) of the wafer W is measured and detected from the width BW (see FIG. 1B), and the measurement result is sent to the processing unit 103 of the apparatus control unit 8 (see FIG. 2).

  In the present embodiment, the light blocking width BW in the light receiving portion 45b of the line sensor unit 3 is configured to detect the length corresponding to the light blocking width by reading the diffraction of light at the outer peripheral edge (edge) position of the wafer W. Therefore, the positioning described later is possible regardless of whether the wafer W is transparent or opaque.

  Note that, as in the present embodiment, the light receiving unit 40b of the line sensor 40 is arranged on the upper and lower side of the wafer W to be measured, thereby illuminating light from outside the apparatus (factory light) and illuminating light from inside the apparatus. The influence of other light such as (in-flight fluorescent lamp) is minimized.

  The line sensor 40 (40a, 40b) is attached to and supported by the support body 46, and the support body 46 is drivingly connected to the advance / retreat drive source 41. The advancing / retreating drive source 41 causes the line sensor 40 to move back and forth between the measurement position and the standby position. Although not specifically shown, the advancing / retreating cylinder device or the advancing / retreating drive device including a feed screw mechanism and a drive motor, Is preferably employed, and in the illustrated embodiment, an advancing and retracting cylinder device is used. This forward / backward cylinder device is electrically connected to the line sensor control unit 102 of the device control unit 8 (see FIG. 2).

  The positioning determination unit 4 determines the position of the orientation flat O that is the positioning reference portion of the wafer W from the measurement result of the line sensor unit 3. The wafer rotation unit 1, the line sensor unit 3, and the apparatus control unit 8 described above. The positioning calculation unit 110 of the processing unit 103 constituting a part of the processing unit 103 is configured as a main part.

  In the positioning calculation unit 110, the calculation circuit 110 a compares and calculates the measurement result of the line sensor unit 3 with the positioning determination threshold value α stored in the storage circuit 110 b, and the position (rotational angle position) of the orientation flat O of the wafer W is calculated. (Coordinates) are determined, and specifically, are determined according to the following orientation flat position determination process (see FIGS. 4A and 4B).

  In this case, the positioning determination threshold α is set as an added value of the D-cut width Hs (see FIG. 5) of the sub orientation flat SO and the centering error (however, a value not exceeding the D cut width Ho (see FIG. 5) of the orientation flat O). In the illustrated embodiment, α is set to 0.2 mm (the maximum value of the D-cut width Hs of the sub orientation flat SO) +0.6 mm (centering error) = 0.8 mm.

Orientation flat position determination process:
A. Preparation (temporary position detection step): (See FIG. 4A)
The wafer W centered on the wafer rotating unit 1 and held in a horizontal state is rotated 360 degrees (one rotation) at a high speed in the normal rotation direction X by the wafer rotating unit 1, and the outer peripheral edge of the wafer W is detected by the line sensor 40. We (edge position) is measured (the arrow direction (without reference sign) in FIG. 4A indicates the measurement direction, which is the reverse direction to the normal rotation direction X of the wafer W). The rotation angle position coordinates from which the width BWmax is output and the rotation angle position coordinates from which the minimum light shielding width BWmin is output are stored in the storage circuit 110b of the positioning calculation unit 110.

  In this case, the maximum light shielding width BWmax is a value of the outermost periphery of the wafer W and is used as a reference for the positioning determination threshold value α. This is for avoiding the influence of the outer diameter error of the wafer W or the like when the position of the orientation flat O is measured and detected. That is, when trying to determine with the absolute value of the light-shielding width BW, the measured value must be within a certain range, so the positional relationship between the line sensor 40 and the wafer W is adjusted strictly or is a set value. Although it is necessary to change the positioning determination threshold value α, it is not determined by the absolute value as in the present embodiment, and only the difference from this reference value is determined based on the maximum measured value of the outer peripheral edge portion We of the wafer W. By determining in step (2), even if the positional relationship between the line sensor 40 and the wafer W is not so strict, it can be determined without any problem.

  Further, the rotation angle position coordinate of the wafer W when the minimum light shielding width BWmin is obtained is stored as an approximate position (temporary position) of the orientation flat O. This is to shorten the measurement time later.

B. Determination of orientation flat position (position determination process) : (See FIG. 4B)
A. The outer peripheral edge portion We of the wafer W is rotated by the line sensor 40 while rotating the wafer W at a low speed in the normal rotation direction X with reference to the temporary position (rotational angle position coordinate) of the orientation flat O stored in the preparation (temporary position detection step). Is measured optically to detect the exact position of the orientation flat O.

  Specifically, the wafer W is rotated at a high speed in the normal rotation direction X to the first detection preparation position at an angle θ1 before the temporary position of the orientation flat O, and then rotated at a low speed by the line sensor 40. The outer peripheral edge We of the wafer W is optically measured, and two rotational position coordinates of the wafer W where the amount of change in the light-shielding width of the line sensor 40 exceeds the positioning determination threshold value α are detected as both end positions of the orientation flat O. The correct position of the orientation flat O is calculated and detected from the center rotational position coordinates of both end positions.

In the illustrated embodiment, the correct orientation flat O position is detected by the following procedure.
(1) Rapid feed of wafer W (preparation for detecting one end of orientation flat O):
The wafer W is rotated (fast-forwarded) in the normal rotation direction X at a high speed to a first detection preparation position that is θ1 ° (about 30 ° in the illustrated embodiment) before the temporary position of the orientation flat O.

(2) Detection of one end of orientation flat O:
When the wafer W is rotated at a low speed in the normal rotation direction X from the first detection preparation position until the amount of change in the light-shielding width BW of the line sensor 40 exceeds the positioning determination threshold value α, and when the positioning determination threshold value α is exceeded. The rotation position coordinate of the wafer W is detected and stored as one end position of the orientation flat O (operation (i) → (ii) in FIG. 4B).

(3) Rapid feed of wafer W (preparation for detection of opposite end (other end) of orientation flat O):
The wafer W is rotated (fast-forwarded) in the forward rotation direction X at a high speed from the one end position of the orientation flat O detected in (2) to a second detection preparation position of θ2 ° (about 45 ° in the illustrated embodiment). (Operation from (ii) to (iii) in FIG. 4B).

(4) Detection of the other end of the orientation flat O:
The wafer W is rotated at a low speed in the reverse direction Y from the second detection preparation position until the amount of change in the light-shielding width BW of the line sensor 40 exceeds the positioning determination threshold value α, and the wafer W at the time when this threshold value is exceeded. The rotational position coordinate is detected and stored as the other end position of the orientation flat O (operation (iii) → (iv) in FIG. 4B).

(5) Determination of orientation flat O:
The center rotation angle position coordinate of the both end positions of the orientation flat O is calculated and determined as the correct position of the orientation flat O (operation (v) in FIG. 4B).

  The centering state determination unit 5 determines the presence or absence of a centering abnormality of the wafer W based on a preset centering determination threshold β from the measurement result of the line sensor unit 3. The centering state calculation unit 111 of the processing unit 103 that constitutes a part of the unit 3 and the apparatus control unit is configured as a main part.

  In the centering state calculation unit 111, the calculation circuit 111a compares the measurement result of the line sensor unit 3 with the centering determination threshold value β stored in the storage circuit 111b to determine whether there is a centering abnormality in the wafer W. Specifically, the determination is made according to the following centering state confirmation process (see FIG. 4C).

Centering status confirmation process:
After the exact position of the orientation flat O of the wafer W is determined, the outer peripheral edge We of the wafer W is optically measured by the line sensor 40 while rotating the wafer W at 360 ° in the normal rotation direction X at a high speed. (The arrow direction in FIG. 4C (no reference sign) indicates the measurement direction, which is the reverse direction to the normal rotation direction X of the wafer W.) A plurality of positions off the orientation flat O (in the illustrated embodiment) (4) (i) to (iv)), the light shielding width BW of the line sensor 40 is compared and calculated, the maximum difference is calculated, the maximum difference is compared with the centering determination threshold value β, and the maximum difference is calculated. Is greater than the centering determination threshold β, it is determined that the centering is abnormal.

  The outer peripheral part determination part 6 determines the presence or absence of a chip | tip of the outer periphery of the wafer W based on the preset positioning determination threshold value (peripheral part determination threshold value) (alpha) from the measurement result of the line sensor part 3, and the wafer mentioned above The rotation part 1, the line sensor part 3, and the outer peripheral part calculation part 112 of the processing part 103 that constitutes a part of the apparatus control part are configured as main parts.

  In the outer periphery calculation unit 112, the calculation circuit 112a compares the measurement result of the line sensor unit 3 with the positioning determination threshold value α stored in the storage circuit 112b to determine whether the outer periphery of the wafer W is missing. It is comprised so that it may determine, and specifically, it determines according to the following wafer peripheral state confirmation processes (refer FIG.4 (c)). This wafer outer peripheral state confirmation step is performed simultaneously with the centering state confirmation step.

Wafer peripheral condition confirmation process:
After the exact position of the orientation flat O of the wafer W is determined, the outer peripheral edge We of the wafer W is optically measured by the line sensor 40 while rotating the wafer W at 360 ° in the normal rotation direction X at a high speed. If there are one or more locations where the light shielding width BW of the line sensor 40 exceeds the positioning determination threshold value α, it is determined that there is peripheral chipping.

  The front / back determination unit 7 determines the front / back of the wafer W from the measurement result of the line sensor unit 3 based on a preset front / back determination threshold value γ. The wafer rotation unit 1, the line sensor unit 3, and the apparatus described above The front / back operation unit 113 of the processing unit 103 constituting a part of the control unit is configured as a main part.

  The front / back operation unit 113 is configured such that the arithmetic circuit 113a compares the measurement result of the line sensor unit 3 with the front / back determination threshold value γ stored in the storage circuit 113b to determine the front / back of the wafer W. Specifically, the determination is made according to the following wafer front / back confirmation process (see FIG. 4D).

  In this case, the front / back determination threshold value γ is related to the rotational direction angular position of the sub orientation flat SO with respect to the orientation flat O, and there are a plurality of types of positional relation between the orientation flats O and SO (the center G of the wafers W of both of them). And 45 °, 90 °, etc.). Therefore, the storage circuit 113b stores the front / back determination threshold value γ corresponding to each of the plurality of types in advance, and is selected and set according to the target wafer W or appropriately input corresponding to the target wafer W. Is set.

Wafer front and back confirmation process:
(1) The wafer W is slowed by θ3 ° (about 80 ° in the illustrated embodiment) in the reverse direction Y from the correct position (determined position) of the orientation flat O determined in (5) of the above-described orientation flat position determination step. And the sensor light-shielding width BW (A) of the line sensor 40 at this position (i) (a position near the outside of the passage side end of the sub orientation flat SO that is the auxiliary positioning reference portion) is stored.

(2) Further, the wafer W is rotated at a low speed from the accurate position (determined position) of the orientation flat O in the reverse rotation direction Y to a position of θ4 ° (about 100 ° in the illustrated embodiment). ii) The sensor light-shielding width BW (B) of the line sensor 40 at (the outer proximity position of the front side end of the sub orientation flat SO) is stored.

(3) Thereafter, the wafer W is moved at a low speed from the correct position (determined position) of the orientation flat O to the position of (θ3 ° + θ4 °) / 2 (about 90 ° in the illustrated embodiment) in the forward rotation direction X. The sensor light-shielding width BW of the line sensor 40 at this position (the center position of the sub-orientation flat SO) is compared with the larger light-shielding width BW of (A) and (B), and the difference between the two When it is larger than the determination threshold γ, it is determined that the sub-orientation flat SO is present, and the front and back of the wafer W is determined from the calculation result.

  Incidentally, the light shielding width BW of the line sensor 40 at the position of the sub-orientation flat SO is much narrower than the light shielding width BW of the line sensor 40 at the position of the orientation flat O as shown in FIG. ), Hard to distinguish. Further, the light shielding widths BW (A) and (B) of the line sensor 40 at the both end positions of the sub-orientation flat SO are easy to understand as shown in FIG. ) Is small and difficult to understand. Even in the case of such a sub-orientation flat SO that is difficult to discriminate, according to the wafer front / back confirmation step, it can be discriminated stably.

  The apparatus control unit (control means) 8 controls the wafer rotating unit 1, centering unit 2, and line sensor unit 3 in conjunction with each other. Specifically, the CPU, ROM, RAM, and I / O port are controlled. It is a CNC device composed of a microcomputer composed of the above.

  The apparatus control unit 8 incorporates a control program for executing the above-described wafer W positioning process and the like. As shown in FIG. The wafer rotation control unit 100 to be controlled, the centering control unit 101 for controlling the drive source of the centering unit 2, the line sensor control unit 102 for controlling the drive source of the line sensor unit 3, and the positioning calculation unit 110 described above, The processing unit 103 includes a centering state calculation unit 111, an outer periphery calculation unit 112, and a front / back calculation unit 113.

  The main control unit 120 includes various information necessary for driving the drive sources of the above-described units 1, 2, and 3, such as the normal / reverse rotation speed of the rotation main shaft unit 10 in the wafer rotation unit 1, the rotation stop timing, and the vacuum chuck. The operation timing of the unit 11, the operation timing of the advance / retreat drive source 32 in the centering unit 2, the operation timing of the line sensor 40 and the operation timing of the advance / retreat drive source 41 in the line sensor unit 3, and the calculation units 110 to 113 in the processing unit 103. Information such as threshold values α, β, γ, etc. necessary for the above are input and set appropriately as NC (numerical control) data in advance or with a keyboard of an operation panel, etc., and according to these data, each control unit 100 described above is set. , 101, 102 and the processing unit 103 are controlled.

  Each of the control units 100, 101, 102 and the processing unit 103 includes a drive motor 16, a negative pressure source 21, an advance / retreat drive source 32, an advance / retreat drive source 41, a line sensor 40, and other drive units. Various electrical information obtained from these is compared with the various set values set in advance by the main control unit 120, and based on the calculation results, the driving units 3 to 6 are compared. The operation is driven and controlled.

  In the positioning apparatus configured as described above, the apparatus control unit 8 controls the wafer rotating unit 1, the centering unit 2, and the line sensor unit 3 to perform the above-described series of positioning steps ((1) The wafer W centering process, (2) orientation flat position determination process, (3) centering state confirmation process, (4) wafer outer periphery state confirmation process, and (5) wafer front / back confirmation process) are performed sequentially in succession or concurrently. Is done.

  In addition, the shape dimension of the wafer W used as the object of the positioning apparatus of this embodiment is demonstrated with reference to FIG.

  The target wafer W is provided with an orientation flat O (large D cut) as a positioning reference portion and a sub orientation flat SO (small D cut) for discriminating the front and back surfaces Wa and Wb at the outer peripheral edge thereof. However, most of the wafers W in the current standard are also targeted.

  That is, in FIG. 5, the outer diameter D of the wafer W is 50 mm to 200 mm (2, 3, 4, 6, 8 inches), the D cut width dimension Ho of the orientation flat O is 1 mm to 3 mm, and the D cut width dimension of the sub orientation flat SO. The target is Hs of 0.1 mm to 0.2 mm.

  As described above in detail, according to the present embodiment, when the wafer W is put into a grinding machine, an inspection machine or the like, after the wafer W is centered, the wafer W is rotated once at a high speed, and a single line sensor is used. After optically measuring the outer peripheral edge We of the wafer W by 40 and storing the rotation angle position coordinate of the wafer W at which the minimum value of the light-shielding width BW of the line sensor 40 is stored as the temporary position of the orientation flat O Since the wafer W is measured while rotating at a low speed with the stored temporary position as a reference, the accurate position of the orientation flat O is detected, and the wafer W is positioned based on the orientation flat O. Various effects as listed below can be obtained, and various wafers such as silicon, quartz and sapphire can be positioned with high detection accuracy. The method of positioning a high use of wafer can be provided.

(1) It is possible to respond to positioning of a plurality of model numbers (2, 3, 4, 6, 8 inches) of wafers W with high accuracy by simple changeover. Incidentally, it has been experimentally found that the positioning error of the orientation flat O falls within the range of 0.2 ° according to the positioning method of the illustrated embodiment.

(2) The centering portion 2 is composed of a pair of centering members 30 and 31 (a reference side centering member 30 and a movable side centering member 31), and the position of the base 38 of the movable side centering member 31 is adjustable. Since it is possible to deal with most of the outer diameter wafers currently manufactured, when changing the model number of the target wafer W, the support rollers 36, 36, Is replaced with a dedicated one corresponding to the outer diameter of the target wafer W, and the position of the base 38 provided with the support roller 39 of the movable side centering member 31 is changed to the above reference. It is possible to cope with this by simply changing and adjusting according to the base 35 of the side centering member 30. Part 2 there is no need to replace the whole.

(3) The chuck main body 20 of the vacuum chuck portion 11 has a mounting structure that can be removed and replaced with the rotary main shaft 15 of the rotary main shaft portion 10, and corresponds to the outer diameter size of the wafer W (in the illustrated embodiment). Can be easily replaced as described above, so that it is not necessary to adjust the position each time the model number of the wafer W is changed.

(4) As described above, in the present embodiment, the various determinations based on the measurement results by the line sensor 40 are determined based on the difference between the measured value and the reference value, not the absolute value. It suffices that the peripheral edge We is within the measurement range of the line sensor 40.

  Therefore, the position of the line sensor 40 is not easily influenced by the roundness of the outer diameter of the wafer W or the dimensional error, and fine adjustment and resetting of the threshold value are not required as in the case of absolute value measurement.

(5) Further, as described above, it is difficult to be influenced by the roundness and dimensional error of the outer diameter of the wafer W, so that it is possible to stably determine the sub-orientation flat SO with few steps, and therefore, the front / back determination of the wafer W using the sub-oriented flat SO. Is possible.

(6) Multiple types of measurements such as “Wafer W centering”, “Detection of orientation flat”, “Centering error confirmation”, “Outer edge check”, “Front / back discrimination (by sub orientation flat position detection)” Discrimination can be made.

  That is, in the present embodiment, the various determinations based on the measurement results by the line sensor 40 are performed by detecting and measuring the outer peripheral edge portion We of the wafer W, and determining the measured value for each threshold value. Various determinations can be made only by entering the predetermined range even at the position of the outer peripheral edge We.

  The above-described embodiment is merely a preferred embodiment of the present invention, and the present invention is not limited thereto, and various design changes can be made within the scope. The modification examples are listed below.

(1) In the illustrated embodiment, as the line sensor 40, a transmissive sensor is used in which the light projecting unit 40a and the light receiving unit 40b are arranged to face each other with the wafer W interposed therebetween. A reflection type sensor in which the light receiving unit 40b is arranged in parallel with the wafer W on the same surface (front surface Wa or back surface Wb) may be used.

(2) In the illustrated embodiment, the target wafer W is provided with the orientation flat O and the sub orientation flat SO on the outer peripheral edge portion thereof, but the wafer without the sub orientation flat SO is also a target. In this case, the front / back determination unit 7 for determining the front / back side of the wafer W does not function, but in the first place, since this type of wafer is mirror-polished only on the front side, it is easy to distinguish the front and back sides. The front / back determination by the front / back determination unit 7 is not necessary.

(3) In the illustrated embodiment, the target wafer W is provided with the orientation flat O at the outer peripheral edge portion thereof, but even the wafer W with the notch N as shown in FIG. It is possible to respond without doing. That is, since the width of the notch N is narrower than the width of the orientation flat O, it is possible to measure without any problem with the same detection operation as in the above-described embodiment.

(4) The centering portion 2 of the illustrated embodiment is configured such that support rollers 36 and 39 are provided as support members on the reference side and movable side centering members 30 and 31, for example, having a structure as shown in FIG. Can also be adopted.

  That is, as shown in the figure, the reference side centering member 130 includes a cylindrical support surface 130a having an arc-shaped cross section along the outer peripheral edge portion We of the target wafer W, and the movable side centering member 131 is a flat support surface. 131a. In the centering unit 2 having such a configuration, the reference-side centering member 130 is dedicated to the target wafer W of each model number. Therefore, when changing the model number of the wafer W, the reference-side centering member 130 is also replaced and changed. Will be.

(5) The target wafer W may be transparent or opaque. That is, in the positioning technique (method and apparatus) of the present invention, the line sensor unit 3 does not simply measure the light shielding width of the outer peripheral edge We of the wafer W, but reads the diffraction of light at the edge position. Since the length corresponding to the light-shielding width is detected, positioning is possible regardless of whether the wafer W is transparent or opaque.

W Wafer Wa Wafer surface Wb Wafer back surface Wa Wafer outer peripheral edge G Wafer center O Orientation flat (positioning reference part)
BW Shading width 1 Wafer rotating part (Wafer rotating means)
2 Centering section (centering means)
3 Line sensor (line sensor means)
4 Positioning confirmation part (positioning confirmation means)
5 Centering state determination unit (centering state determination means)
6 Outer peripheral part determination part (outer peripheral part determination means)
7 Front / back determination section (front / back determination means)
8 Device control unit (control means)
10 Rotating spindle (Rotating spindle means)
11 Vacuum chuck (vacuum chuck means)
15 Rotating spindle 16 Drive motor (Rotation drive source)
20 Chuck body (wafer holding part)
21 negative pressure source 30 reference side centering member 31 movable side centering member 32 advance / retreat drive source 40 line sensor 41 advance / retreat drive source 100 wafer rotation control unit 101 centering control unit 102 line sensor control unit 103 processing unit 110 positioning calculation unit 111 centering state calculation Part 112 outer peripheral part calculating part 113 front and back calculating part 120 main control part 130 reference side centering member 131 movable side centering member

Claims (12)

A method of optically detecting a positioning reference portion such as an orientation flat or a notch provided on the outer peripheral edge of a disk-shaped wafer, and positioning the wafer with reference to the positioning reference portion,
After the wafer is centered, the outer peripheral edge of the wafer is optically measured by a single line sensor while rotating the wafer once at a high speed, and the rotation of the wafer at which the minimum value of the light shielding width of the line sensor is obtained. After storing the position coordinates as a temporary position of the positioning reference portion, the measurement is performed while rotating the wafer at a low speed with the stored temporary position as a reference, and an accurate position of the positioning reference portion is detected. Wafer positioning method. (1) Centering step for centering the wafer (2) While the wafer is rotated once at high speed, the outer peripheral edge of the wafer is optically measured by the line sensor, and the light shielding width of the line sensor is minimized. A temporary position detecting step for storing the rotational position coordinates of the wafer from which the value has been obtained as a temporary position of the positioning reference unit; and (3) the wafer at a low speed on the basis of the temporary position stored in the temporary position detecting step. 2. The position determination step of detecting an accurate position of the positioning reference portion by optically measuring an outer peripheral edge portion of the wafer by the line sensor while rotating. Wafer positioning method. The position determination step optically measures the outer peripheral edge of the wafer by the line sensor while rotating at a low speed after rotating the wafer to a detection preparation position before the temporary position, Two wafer rotation position coordinates whose light-shielding width change amount of the line sensor exceeds a threshold value are detected as both end positions of the positioning reference section, and an accurate position of the positioning reference section is determined from the center rotation position coordinates of these both end positions. The wafer positioning method according to claim 2, wherein the wafer is calculated and detected. The wafer is rotated at a low speed from the detection preparation position, the one end position of the positioning reference portion is detected by the line sensor, and then the second detection preparation position that has passed the other end position of the positioning reference portion is high speed. 4. The wafer according to claim 3, wherein the wafer is rotated and rotated in the reverse direction at a low speed from the second detection preparation position, and the other end position of the positioning reference portion is detected by the line sensor. Positioning method. After determining the exact position of the positioning reference portion of the wafer, the outer peripheral edge portion of the wafer is optically measured by the line sensor while rotating the wafer once, and a plurality of positions deviating from the positioning reference portion. 5. The light shielding width of the line sensor is compared and calculated, a maximum difference is calculated, and the presence or absence of centering abnormality is determined by comparing the maximum difference with a centering determination threshold value. The wafer positioning method according to any one of the above. After determining the exact position of the positioning reference part of the wafer, the outer peripheral edge of the wafer is optically measured by the line sensor while the wafer is rotated once, and the light shielding width of the line sensor is determined as the outer peripheral part. 6. The wafer positioning method according to claim 1, wherein the presence / absence of an outer peripheral chip is determined by comparison with a threshold value. For a wafer provided with an auxiliary positioning reference portion such as a sub-orientation flat on the outer peripheral edge, the wafer is rotated from an accurate position of the positioning reference portion of the wafer to a position before the auxiliary positioning reference portion. The shading width of the line sensor is stored, and the wafer is further rotated to the passing position of the auxiliary positioning reference portion, and the shading width of the line sensor at the passing position is stored. Rotate in the reverse direction to the center position of the positioning reference portion, store the light shielding width of the line sensor at the center position, and the larger of the light shielding width at the center position and the light shielding width at the near position and the passing position 2. The front and back sides of the wafer are determined by comparing and calculating the light-shielding width of the wafer and comparing the difference with a front and back determination threshold value. Wafer positioning method of any one of al 6. A positioning device that optically detects a positioning reference portion such as an orientation flat or a notch provided on the outer peripheral edge of a disk-shaped wafer, and positions the wafer with reference to the positioning reference portion,
A wafer rotating means for horizontally rotating the wafer, having a wafer holding section for placing and holding the wafer in a horizontal state;
Centering means for centering the wafer placed and held on the wafer rotating means;
A single line sensor means for optically measuring the outer peripheral edge of the wafer placed and held on the wafer rotating means;
Control means for controlling the wafer rotation means, centering means and line sensor means in conjunction with each other,
The control means is configured to control the wafer rotating means, the centering means, and the line sensor means so as to execute the positioning method according to any one of claims 1 to 4. Wafer positioning device. The centering means includes a pair of centering members disposed opposite to each other with a wafer holding portion of the wafer rotating means interposed therebetween,
One of the pair of centering members constitutes a reference side centering member that defines a reference position of centering, and the other constitutes a movable side centering member that moves and positions the wafer relative to the reference centering member. The wafer positioning apparatus according to claim 8. 10. The wafer according to claim 8, further comprising centering state determination means for determining presence / absence of a centering abnormality of the wafer based on a measurement result of the line sensor means based on a preset centering determination threshold value. Positioning device. The outer peripheral part determination means which determines the presence or absence of the chip | tip of the outer periphery of the said wafer based on the preset outer peripheral part determination threshold value from the measurement result of the said line sensor means is provided. Wafer positioning device. 10. The wafer positioning apparatus according to claim 8, further comprising front / back determination means for determining the front / back of the wafer based on a preset front / back determination threshold value from a measurement result of the line sensor means.

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