阅读说明：本技术 边缘位置检测装置和边缘位置检测方法 (Edge position detection device and edge position detection method ) 是由 小松淳 于 2021-06-02 设计创作，主要内容包括：本发明提供边缘位置检测装置和边缘位置检测方法,提高被加工物的边缘的位置的检测精度。对圆盘状的被加工物的边缘的位置进行检测的边缘位置检测装置具有：卡盘工作台,其具有对被加工物进行保持的保持面；激光位移计,其具有照射单元和受光单元,该照射单元包含配置在卡盘工作台上方的光源,以横贯被加工物的边缘的方式照射线状激光束,该受光单元包含沿着线状激光束的照射区域的长度方向以规定的间隔排列并分别接受线状激光束的反射光的多个光电转换元件；移动机构,其使激光位移计和卡盘工作台沿着照射区域的长度方向相对地移动；和计算单元,其具有处理器,根据由受光单元取得的受光量的变化的信息计算被加工物的边缘的位置。(The invention provides an edge position detection device and an edge position detection method, which can improve the detection precision of the edge position of a processed object. An edge position detection device for detecting the position of the edge of a disc-shaped workpiece includes: a chuck table having a holding surface for holding a workpiece; a laser displacement meter having an irradiation unit including a light source disposed above the chuck table and irradiating a linear laser beam so as to traverse an edge of the workpiece, and a light receiving unit including a plurality of photoelectric conversion elements arranged at predetermined intervals along a longitudinal direction of an irradiation region of the linear laser beam and receiving reflected light of the linear laser beam; a moving mechanism for relatively moving the laser displacement meter and the chuck table along the length direction of the irradiation region; and a calculation unit having a processor for calculating the position of the edge of the workpiece based on the information on the change in the amount of light received acquired by the light receiving unit.)

1. An edge position detection device for detecting the position of the edge of a disc-shaped workpiece,

the edge position detection device includes:

a chuck table having a holding surface for holding the workpiece;

a laser displacement meter including an irradiation unit including a light source disposed above the chuck table, for irradiating a linear laser beam that is shaped into a line perpendicular to a traveling direction of the linear laser beam from the light source toward the holding surface so as to traverse an edge of the workpiece, and a light receiving unit including a plurality of photoelectric conversion elements that are arranged at predetermined intervals along a longitudinal direction of an irradiation region of the linear laser beam and receive reflected light of the linear laser beam;

a moving mechanism that relatively moves the laser displacement meter and the chuck table along the longitudinal direction of the irradiation region; and

and a calculation unit having a processor for calculating the position of the edge of the workpiece based on the information on the change in the amount of light received acquired by the light receiving unit.

2. The edge position detecting apparatus according to claim 1,

the chuck table is rotatable about a prescribed axis of rotation,

the longitudinal direction of the irradiation region is arranged along a predetermined direction perpendicular to the predetermined rotation axis, the laser displacement meter and the chuck table are moved by the moving mechanism at a relative moving speed V along the longitudinal direction in a state where the linear laser beam is irradiated onto the workpiece held by the holding surface, before and after the movement time T of the laser displacement meter at the relative movement speed V, when the light receiving amount of the 1 st photoelectric conversion element and the light receiving amount of the 2 nd photoelectric conversion element of the adjacent 1 st photoelectric conversion element and the adjacent 2 nd photoelectric conversion element are not changed and the light receiving amount of the 2 nd photoelectric conversion element is changed, the calculation means calculates the position of the edge of the workpiece by calculating the position that is separated by V · T from the original position of the 2 nd photoelectric conversion element before the movement time T to the position of the 1 st photoelectric conversion element adjacent thereto.

3. An edge position detection method for detecting the position of the edge of a disc-shaped workpiece,

the edge position detection method comprises the following steps:

a holding step of holding one surface side of the workpiece by a holding surface of a chuck table;

a 1 st detection step of irradiating a linear laser beam shaped in a line perpendicular to a traveling direction onto the other surface side of the object located on the opposite side of the one surface so as to traverse an edge of the object, and detecting reflected light by a 1 st photoelectric conversion element and a 2 nd photoelectric conversion element adjacent to the 1 st photoelectric conversion element among a plurality of photoelectric conversion elements arranged at a predetermined interval along a longitudinal direction of an irradiation region of the linear laser beam and receiving reflected light of the linear laser beam;

a 2 nd detection step of detecting that the amount of light received by the 2 nd photoelectric conversion element has changed by relatively moving the linear laser beam and the chuck table in the longitudinal direction of the irradiation region irradiated onto the other surface side in a state where the linear laser beam is irradiated onto the other surface side so as to traverse the edge of the workpiece; and

an edge position calculating step of calculating an edge position based on a 1 st time T from the detection timing in the 1 st detection step to the detection timing in the 2 nd detection step₁A distance V.T calculated by the product of the linear laser beam and the relative movement velocity V of the chuck table in the longitudinal direction₁From which is calculatedThe position of the 2 nd photoelectric conversion element in the 1 st detection step is separated from the position of the 1 st photoelectric conversion element by V.T₁And calculating the position of the edge of the workpiece.

4. The edge position detection method according to claim 3,

the chuck table is rotatable about a prescribed axis of rotation,

the longitudinal direction of the irradiation region is arranged along a predetermined direction perpendicular to the predetermined rotation axis,

the edge position calculating step further has the steps of:

a rotation starting step of starting the chuck table to rotate around the predetermined rotation axis at a predetermined rotation speed V after the holding step_RRotating;

a 3 rd detection step of detecting that the amount of light received by the 3 rd photoelectric conversion element of the 1 st photoelectric conversion element, the 2 nd photoelectric conversion element, the 3 rd photoelectric conversion element, and the 4 th photoelectric conversion element arranged on a straight line at the predetermined interval has changed; and

a 4 th detection step of detecting that the light receiving amount of the reflected light has changed in the 4 th photoelectric conversion element,

the edge position calculating step includes the steps of:

a 1 st calculation step of calculating a deviation of V.T. from the position of the 2 nd photoelectric conversion element to the position of the 1 st photoelectric conversion element in the 1 st detection step₁Is calculated as the chuck table has rotated by V_R·T₁The 1 st position of the edge of the workpiece;

a 2 nd calculation step of calculating a 2 nd time T from the detection timing in the 2 nd detection step to the detection timing in the 3 rd detection step₂Calculating the deviation of the position of the 3 rd photoelectric conversion element from the position of the 2 nd photoelectric conversion element in the 2 nd detection step to the position of the 2 nd photoelectric conversion element by V.T₂From the position of the chuck table, thereby calculating the chuck table rotation V_R·(T₁+T₂) The 2 nd position of the edge of the workpiece; and

a 3 rd calculation step of calculating a time T from the detection timing in the 3 rd detection step to the detection timing in the 4 th detection step₃Calculating the deviation of the 4 th photoelectric conversion element from the 3 rd photoelectric conversion element in the 3 rd detection step to the 3 rd photoelectric conversion element₃From the position of the chuck table, thereby calculating the chuck table rotation V_R·(T₁+T₂+T₃) The 3 rd position of the edge of the workpiece.

Technical Field

The present invention relates to an edge position detection device and an edge position detection method for detecting a position of an edge of an outer peripheral portion of a disc-shaped workpiece.

Background

A plate-shaped workpiece such as a semiconductor wafer has chamfered outer peripheral portions on the front and back sides. When the back surface side of the workpiece whose outer peripheral portion is chamfered is ground, for example, to a thickness of about half the original thickness, a so-called blade (also referred to as a sharp edge) is formed on the outer peripheral portion of the workpiece.

When the blade is formed on the outer peripheral portion, cracks, chipping, breakage, and the like are likely to occur in the workpiece. Therefore, in order to prevent cracks and the like, there is known a technique of removing an outer peripheral portion of a workpiece on a front surface side by cutting or the like (that is, after trimming), and then grinding and thinning a rear surface side (for example, see patent document 1).

When the front-side outer peripheral portion is trimmed, first, the position of the edge of the front-side outer peripheral portion is detected while the back side of the workpiece is held by the chuck table. Then, the range of the front surface side on which cutting is performed is determined with the position of the edge as a reference.

For detecting the position of the edge, for example, a laser displacement meter is used. The laser displacement meter comprises: a laser irradiation unit that irradiates a linear laser beam; and a light receiving unit that receives reflected light of the linear laser beam from the front surface side.

The light receiving unit includes a line sensor in which a plurality of photoelectric conversion elements are arranged at predetermined intervals along the longitudinal direction of the linear laser beam, and receives reflected light of the linear laser beam irradiated so as to traverse the edge of the workpiece. However, since the reflected light cannot be received at a position between two adjacent photoelectric conversion elements, the accuracy of detecting the position of the edge depends on the interval at which the photoelectric conversion elements are arranged.

Patent document 1: japanese patent laid-open No. 2000-173961

Disclosure of Invention

The present invention has been made in view of the above problems, and an object of the present invention is to improve the accuracy of detecting the position of an edge when a light receiving unit has a plurality of photoelectric conversion elements arranged at predetermined intervals.

According to one aspect of the present invention, there is provided an edge position detecting device for detecting a position of an edge of a disc-shaped workpiece, the edge position detecting device including: a chuck table having a holding surface for holding the workpiece; a laser displacement meter including an irradiation unit including a light source disposed above the chuck table, for irradiating a linear laser beam that is shaped into a line perpendicular to a traveling direction of the linear laser beam from the light source toward the holding surface so as to traverse an edge of the workpiece, and a light receiving unit including a plurality of photoelectric conversion elements that are arranged at predetermined intervals along a longitudinal direction of an irradiation region of the linear laser beam and receive reflected light of the linear laser beam; a moving mechanism that relatively moves the laser displacement meter and the chuck table along the longitudinal direction of the irradiation region; and a calculation unit having a processor for calculating the position of the edge of the workpiece based on the information on the change in the amount of light received acquired by the light receiving unit.

Preferably, the chuck table is rotatable about a predetermined rotation axis, the longitudinal direction of the irradiation region is arranged along a predetermined direction perpendicular to the predetermined rotation axis, the laser displacement meter and the chuck table are moved by the moving mechanism at a relative moving speed V along the longitudinal direction in a state where the linear laser beam is irradiated to the workpiece held by the holding surface, and the calculating unit calculates a position that is away from an original position before the moving time T of the 2 nd photoelectric conversion element to a position of the 1 st photoelectric conversion element adjacent thereto by V · T before the moving time T of the 2 nd photoelectric conversion element before and after the moving time T of the laser displacement meter at the relative moving speed V when the light receiving amount of the 1 st photoelectric conversion element is changed, thereby calculating the position of the edge of the workpiece.

According to another aspect of the present invention, there is provided an edge position detecting method for detecting a position of an edge of a disc-shaped workpiece, the edge position detecting method including the steps of: a holding step of holding one surface side of the workpiece by a holding surface of a chuck table; a 1 st detection step of irradiating a linear laser beam shaped in a line perpendicular to a traveling direction onto the other surface side of the object located on the opposite side of the one surface so as to traverse an edge of the object, and detecting reflected light by a 1 st photoelectric conversion element and a 2 nd photoelectric conversion element adjacent to the 1 st photoelectric conversion element among a plurality of photoelectric conversion elements arranged at a predetermined interval along a longitudinal direction of an irradiation region of the linear laser beam and receiving reflected light of the linear laser beam; a 2 nd detection step of detecting that the amount of light reflected by the 2 nd photoelectric conversion element has changed by relatively moving the linear laser beam and the chuck table in the longitudinal direction of the irradiation region irradiated to the other surface side in a state where the linear laser beam is irradiated to the other surface side so as to traverse the edge of the workpiece; and an edge position calculation step of calculating an edge position based on a 1 st time T from the detection timing in the 1 st detection step to the detection timing in the 2 nd detection step₁A distance V.T calculated by the product of the linear laser beam and the relative movement velocity V of the chuck table in the longitudinal direction₁Calculating the deviation of the position of the 2 nd photoelectric conversion element from the position of the 1 st photoelectric conversion element in the 1 st detection step to the position of the 1 st photoelectric conversion element by V.T₁And calculating the position of the edge of the workpiece.

Preferably, the chuck table is rotatable about a predetermined rotation axis, the longitudinal direction of the irradiation region is arranged in a predetermined direction perpendicular to the predetermined rotation axis, and the edge position calculating step further includes: a rotation starting step of starting the chuck table after the holding stepAt a predetermined rotational speed V around the predetermined axis of rotation_RRotating; a 3 rd detection step of detecting that the amount of light received by the 3 rd photoelectric conversion element of the 1 st photoelectric conversion element, the 2 nd photoelectric conversion element, the 3 rd photoelectric conversion element, and the 4 th photoelectric conversion element arranged on a straight line at the predetermined interval has changed; and a 4 th detection step of detecting that the amount of light received by the 4 th photoelectric conversion element has changed, the edge position calculation step including the steps of: a 1 st calculation step of calculating a deviation of V.T. from the position of the 2 nd photoelectric conversion element to the position of the 1 st photoelectric conversion element in the 1 st detection step₁Is calculated as the chuck table has rotated by V_R·T₁The 1 st position of the edge of the workpiece; a 2 nd calculation step of calculating a 2 nd time T from the detection timing in the 2 nd detection step to the detection timing in the 3 rd detection step₂Calculating the deviation of the position of the 3 rd photoelectric conversion element from the position of the 2 nd photoelectric conversion element in the 2 nd detection step to the position of the 2 nd photoelectric conversion element by V.T₂From the position of the chuck table, thereby calculating the chuck table rotation V_R·(T₁+T₂) The 2 nd position of the edge of the workpiece; and a 3 rd calculation step of calculating a time T from the detection timing in the 3 rd detection step to the detection timing in the 4 th detection step₃Calculating the deviation of the 4 th photoelectric conversion element from the 3 rd photoelectric conversion element in the 3 rd detection step to the 3 rd photoelectric conversion element₃From the position of the chuck table, thereby calculating the chuck table rotation V_R·(T₁+T₂+T₃) The 3 rd position of the edge of the workpiece.

An edge position detection device according to an embodiment of the present invention includes a chuck table and a laser displacement meter. The laser displacement meter comprises: an irradiation unit that irradiates a linear laser beam shaped into a line perpendicular to a traveling direction so as to traverse an edge of a workpiece; and a light receiving unit including a plurality of photoelectric conversion elements arranged at predetermined intervals along a longitudinal direction of an irradiation region of the linear laser beam and receiving reflected light of the linear laser beam.

The edge position detection device further includes: a moving mechanism for relatively moving the laser displacement meter and the chuck table along the length direction of the irradiation area of the linear laser beam; and a calculation unit that calculates a position of an edge of the workpiece based on information on a change in the amount of light received acquired by the light receiving unit.

By determining the position of the edge using the light receiving unit while moving the laser beam by the moving mechanism, the position of the edge of the workpiece can be detected even at a position corresponding to a position between adjacent photoelectric conversion elements. That is, the accuracy of detecting the edge of the workpiece can be improved as compared with the case where the edge position is detected by stopping the line sensor.

Drawings

Fig. 1 (a) is a partially sectional side view of the edge position detection device, and fig. 1 (B) is a perspective view of the edge position detection device.

Fig. 2 (a) is a diagram schematically illustrating the structure of the laser displacement meter, and fig. 2 (B) is a bottom view of the laser displacement meter.

FIG. 3 (A) shows the time t₁A graph of the laser beam at time, and (B) of FIG. 3 shows a time t₁A graph of the output voltage of each photoelectric conversion element at the time.

FIG. 4 (A) shows the time t₂A graph of the laser beam at time, and (B) of FIG. 4 shows a time t₂A graph of the output voltage of each photoelectric conversion element at the time.

Fig. 5 is a graph showing temporal changes in output voltages of the 1 st and 2 nd photoelectric conversion elements.

Fig. 6 is a flowchart of the edge position detection method according to embodiment 1.

Fig. 7 (a) is a view showing a 1 st modification, fig. 7 (B) is a view showing a 2 nd modification, and fig. 7 (C) is a view showing a 3 rd modification.

Fig. 8 (a) is a view showing a 1 st position of an edge between the 1 st and 2 nd photoelectric conversion elements, fig. 8 (B) is a view showing a 2 nd position of an edge between the 2 nd and 3 rd photoelectric conversion elements, and fig. 8 (C) is a view showing a 3 rd position of an edge between the 3 rd and 4 th photoelectric conversion elements.

Fig. 9 is a diagram illustrating a method of determining the coordinates of the center.

Fig. 10 is a flowchart of the edge position detection method according to embodiment 3.

Description of the reference symbols

2: an edge position detecting device; 4: a chuck table; 6: a frame body; 6 a: a recess; 8: a perforated plate; 8 a: a holding surface; 10: an output shaft; 10 a: a rotation axis; 11: a workpiece; 11 a: a front side; 11 b: a back side; 11 c: a peripheral portion; 11 d: an edge; 11 e: a center; 12: a laser displacement meter; 12 a: irradiating the area; 14: a laser irradiation unit; 14 a: a light source; 14 b: a lens; 14 c: a housing; 14 d: an opening; 16: the 1 st direction; 18: a light receiving unit; 18 a: a housing; 18 b: a condenser lens; 18 c: a line sensor; 18 d: a photoelectric conversion element; 18 e: a prescribed interval; 20: a moving mechanism; 22: a base part; 24: a guide rail; 26: a ball screw; 28: a pulse motor; 30: a control unit; 32: a calculation unit; a: a specified direction; B. c: a vertical bisector; LA: a laser beam; t: a movement time; v: the relative moving speed; v_R: the speed of rotation.

Detailed Description

An embodiment of one embodiment of the present invention will be described with reference to the drawings. Fig. 1 (a) is a partially sectional side view of the edge position detection device 2, and fig. 1 (B) is a perspective view of the edge position detection device 2.

In fig. 1 (a), a part of the edge position detection device 2 is shown by functional blocks, and in fig. 1 (B), a part of the elements of the edge position detection device 2 is omitted. First, the workpiece 11 to be detected will be described.

The workpiece 11 of the present embodiment is a disk-shaped wafer made of a semiconductor material such as silicon, but the material, structure, size, and the like of the workpiece 11 are not particularly limited. A plurality of lines to be divided (not shown) are set in a grid shape on the front surface (the other surface) 11a side of the workpiece 11, and devices (not shown) such as an IC (Integrated Circuit) are formed in each region divided by the plurality of lines to be divided.

The outer peripheral portions of the front surface 11a and the rear surface (one surface) 11b located on the opposite side of the front surface 11a are chamfered to form so-called inclined surfaces. An edge 11d defining the diameter of the workpiece 11 is provided on an outer peripheral portion 11c located between the front surface 11a and the rear surface 11 b.

The edge 11d is circular in plan view. In fig. 1 (a) and 1 (B), the center 11e of the circle is shown on the front surface 11 a. The rear surface 11b side of the workpiece 11 is held by a disk-shaped chuck table 4. The chuck table 4 has a disk-shaped frame 6 made of metal.

A disc-shaped recess 6a is formed in the upper portion of the frame 6. A suction passage (not shown) is formed in the bottom of the recess 6 a. One end of the suction path is exposed to the bottom surface of the recess 6a, and the other end of the suction path is connected to a suction source (not shown) such as an ejector.

A disk-shaped porous plate 8 having substantially flat upper and lower surfaces is fixed to the concave portion 6 a. When the suction source is operated, a negative pressure is generated on the upper surface of the porous plate 8. The upper surface of the porous plate 8 and the upper surface of the frame 6 positioned on the outer periphery of the porous plate 8 function as a holding surface 8a for sucking and holding the workpiece 11.

A rotation drive source (not shown) such as a motor is connected to the bottom of the chuck table 4. An output shaft 10 of the rotation drive source is fixed to a central portion of the bottom surface of the housing 6. When the output shaft 10 is rotated, the chuck table 4 is rotated about a rotation axis (predetermined rotation axis) 10a substantially parallel to the Z-axis direction (vertical direction, height direction) of the edge position detection device 2.

A laser displacement meter 12 is disposed above the chuck table 4. The laser displacement meter 12 can irradiate the holding surface 8a with the linear laser beam LA so that the longitudinal direction of the irradiation region 12a (see fig. 1B) when irradiated onto the holding surface 8a is along a predetermined direction a perpendicular to the rotation axis 10 a.

Fig. 2 (a) is a diagram schematically illustrating the structure of the laser displacement meter 12, and fig. 2 (B) is a bottom view of the laser displacement meter 12. The laser displacement meter 12 has a light source 14a including a semiconductor laser (laser diode).

The laser beam emitted from the light source 14a is incident on a laser beam marker such as a Powell lens, a Lineman lens, a cylindrical lens, or the like (hereinafter, simply referred to as a lens 14 b).

The lens 14b shapes the laser beam incident on the lens 14b into a linear laser beam LA having a predetermined length in the 1 st direction 16 perpendicular to the traveling direction of the laser beam (the direction in which the laser beam travels from the light source 14a toward the holding surface 8a) and having a substantially uniform output in the 1 st direction 16.

That is, the 1 st direction 16 corresponds to the longitudinal direction of the irradiation region 12a when the linear laser beam LA is irradiated onto the holding surface 8 a. The light source 14a and the lens 14b are housed in a case 14c, and the light source 14a, the lens 14b, the case 14c, and the like constitute a laser irradiation unit 14.

A rectangular opening 14d having a length along the 1 st direction 16 is formed in the bottom of the housing 14 c. The laser beam LA emitted from the opening 14d is reflected (regular reflection) from the measurement object and enters the light receiving unit 18 adjacent to the laser irradiation unit 14.

The light receiving unit 18 has a housing 18a fixed adjacent to the housing 14 c. A condenser lens 18b is fixed to the housing 18 a. The condenser lens 18b may be a single lens or may be composed of a plurality of lenses like an ernostatr-type lens. The light condensed by the condenser lens 18b is incident on the line sensor 18 c.

The line sensor 18c includes a plurality of photoelectric conversion elements 18d arranged at predetermined intervals 18e (see fig. 3B and the like) along the longitudinal direction of the irradiation region 12a of the laser beam LA. In the present embodiment, the predetermined interval 18e is 10 μm.

Each photoelectric conversion element 18d is a photosensor such as a phototransistor. Each photoelectric conversion element 18d photoelectrically converts reflected light received from a measurement object at every predetermined sampling period (for example, 0.1s) and outputs a voltage signal corresponding to the amount of received light (in this specification, seconds may be referred to as "s").

The voltage signal (i.e., an Analog signal) is converted into a Digital signal by a predetermined processing circuit (not shown) having an Analog-to-Digital Converter (ADC) or the like, and is processed by a control unit 30 (described later).

Here, the arrangement, operation, and the like of the laser displacement meter 12 in the edge position detection device 2 will be described with reference to fig. 1 (a) and 1 (B). The laser displacement meter 12 is disposed such that the longitudinal direction of an irradiation region 12a of the linear laser beam LA irradiated on the front surface 11a side is parallel to a predetermined direction a.

The laser displacement meter 12 is connected to a moving mechanism 20 that moves the laser displacement meter 12 relative to the chuck table 4 in a predetermined direction a. The moving mechanism 20 includes a plate-like base portion 22 fixed to a base (not shown) of the edge position detection device 2.

A pair of guide rails 24 parallel to the predetermined direction a are provided on one surface of the base portion 22. In fig. 1 (a), 1 guide rail 24 is shown. An upper portion of the housing (i.e., the housing 14c or 18a) of the laser displacement meter 12 is slidably mounted on the pair of guide rails 24.

A nut portion (not shown) is provided on a side surface of the housing of the laser displacement meter 12, and a ball screw 26 substantially parallel to the guide rail 24 is rotatably connected to the nut portion. A bearing is connected to one end of the ball screw 26, and a pulse motor 28 is connected to the other end of the ball screw 26.

When the ball screw 26 is rotated by the pulse motor 28, the laser displacement meter 12 moves along the guide rail 24. For example, the laser displacement meter 12 is moved at a relative movement speed of 10 μm/s with respect to the chuck table 4.

The laser displacement meter 12 and the pulse motor 28 are connected to a control unit 30. The control unit 30 controls operations of the suction source and the rotation drive source of the chuck table 4, the laser displacement meter 12, the pulse motor 28, and the like.

The control Unit 30 is constituted by a computer including a processor (Processing device) represented by a CPU (Central Processing Unit), a main Memory such as a DRAM (Dynamic Random Access Memory), an SRAM (Static Random Access Memory), a ROM (Read Only Memory), and an auxiliary Memory such as a flash Memory, a hard disk drive, and a solid state drive.

The auxiliary storage device stores software including a predetermined program. The function of the control unit 30 is realized by operating a processing device or the like in accordance with the software. The auxiliary storage device stores a predetermined program.

When the processing device executes the program, a part of the control unit 30 functions as the calculation unit 32. The calculation unit 32 calculates the position (XY coordinates) of the edge 11d of the workpiece 11 using the initial position of each photoelectric conversion element 18d, the moving speed and moving time of the laser displacement meter 12, the digital signals, and the like.

The initial position of each photoelectric conversion element 18d is, for example, the origin (X) from the rotation axis 10a₀，Y₀) This is grasped in advance by the calculation unit 32. In the present embodiment, the moving direction of the laser displacement meter 12 coincides with the predetermined direction a.

Here, an outline of calculating the position of the edge 11d using the edge position detection device 2 will be described. FIG. 3 (A) shows the time t₁A pattern of laser beams LA. The laser beam LA is irradiated along a predetermined direction a onto the outer peripheral portion 11c of the workpiece 11 held on the holding surface 8a so as to traverse the edge 11 d.

The light quantity of the reflected light from the front surface 11a is larger than the light quantity of the reflected light from the holding surface 8 a. Therefore, as shown in fig. 3B, the output voltage of the photoelectric conversion element 18d receiving the reflected light from the front surface 11a is at a high level (H), and the output voltage of the photoelectric conversion element 18d receiving the reflected light from the holding surface 8a is at a low level (L).

FIG. 3 (B) shows the time t₁A graph of the output voltage of each photoelectric conversion element 18d at that time. In FIG. 3B, the 1 st photoelectric conversion element 18d₁On the front surface 11a, and a 1 st photoelectric conversion element 18d₁Adjacent 2 nd photoelectric conversion element 18d₂Is located on the upper surface of the outer peripheral portion of the frame body 6.

In the figure3 (B), the edge 11d can be said to be located on 2 photoelectric conversion elements 18d (1 st photoelectric conversion element 18 d)₁And the 2 nd photoelectric conversion element 18d₂) However, the position of the edge 11d cannot be determined with higher accuracy than the predetermined interval 18 e. That is, in the situation of fig. 3 (B), it is not possible to specify where the edge 11d is located at the predetermined interval 18 e.

Therefore, in the present embodiment, the laser displacement meter 12 is moved by the moving mechanism 20 relative to the chuck table 4 at the relative moving speed V along the longitudinal direction of the laser beam LA in a state where the laser beam LA is irradiated.

FIG. 4 (A) shows the time t₁At time T after the lapse of time (i.e., after the shift time T)₂A pattern of laser beams LA. In fig. 4 (a), the time t is shown by a solid line for the laser beam LA and the laser displacement meter 12₂In the case of (1), the time t is indicated by a two-dot chain line₁The case (1). In addition, it is assumed that the moving time T is larger than the sampling period.

The light receiving unit 18 also moves in the predetermined direction a along with the movement of the laser displacement meter 12. At time t₂In the 1 st photoelectric conversion element 18d₁Without changing the output voltage of the 2 nd photoelectric conversion element 18d₂When the output voltage of (2) is changed, the 2 nd photoelectric conversion element 18d₂Corresponds to the position of the edge 11 d.

FIG. 4 (B) shows the time t₂A graph of the output voltage of each photoelectric conversion element 18d at that time. In fig. 4 (B), time t is indicated by a solid line₂The photoelectric conversion elements 18d are each indicated by a two-dot chain line at time t₁The photoelectric conversion elements 18d in the above case.

The calculating unit 32 calculates the slave time t₁Second photoelectric conversion element 18d₂Position of (i.e., at time t)₂The original position advanced by the time T) to the 1 st photoelectric conversion element 18d₁Is apart from the coordinates of the position P of V · T. Thereby, the time t is calculated₂The coordinates (i.e., position) of the edge 11 d.

FIG. 5 is a more simplified view showing the 1 st photoelectric conversion element 18d shown in FIG. 4 (B), respectively₁And the 2 nd photoelectric conversion element 18d₂A graph of the time variation of the output voltage of (1). The numeral 1 enclosed by a circle denotes a 1 st photoelectric conversion element 18d₁The numeral 2 enclosed by a circle indicates the 2 nd photoelectric conversion element 18d₂。

In fig. 5, L indicated on the right side of the figure indicates that the output voltage is at a low level, and similarly, H indicates that the output voltage is at a high level. The dotted arrow indicates time t₁Time of reflection, the solid arrow being the time t₂The reflected light of time. The hollow arrow indicates the moving direction of the laser displacement meter 12.

In the present embodiment, by moving the laser displacement meter 12, the position of the edge 11d of the workpiece 11 can be detected even at a position corresponding to a position between the adjacent 2 photoelectric conversion elements 18 d. That is, the detection accuracy of the edge 11d can be improved as compared with the case where the position of the edge 11d is detected by stopping the line sensor 18 c.

Next, an edge position detection method for detecting the position of the edge 11d of the workpiece 11 using the edge position detection device 2 will be described. Fig. 6 is a flowchart of the edge position detection method according to embodiment 1.

First, as shown in fig. 1a, the back surface 11b side of the workpiece 11 is held by the holding surface 8a so that the front surface 11a of the workpiece 11 is exposed upward (holding step S10). At this time, the center 11e of the front face 11a is located on the rotation axis 10a or in the vicinity of the rotation axis 10 a.

After the holding step S10, the laser displacement meter 12 and the chuck table 4 are moved in the predetermined direction a at the relative movement speed V by the movement mechanism 20 in a state where the linear laser beam LA is irradiated onto the front surface 11a so as to traverse the edge 11 d. At this time, as shown in fig. 5, the 1 st photoelectric conversion element 18d₁Is located at the 2 nd photoelectric conversion element 18d₂The forward position.

At time t₁(detection timing), the 1 st photoelectric conversion element 18d₁A 2 nd photoelectric conversion element 18d on the front surface 11a₂Not on the front face 11a but outside the edge 11 d. Calculation sheetThe cell 32 detects an output voltage corresponding to the light receiving amount of each photoelectric conversion element 18d (the 1 st detection step S20).

At S20 (time t)₁) Then, in the 2 nd photoelectric conversion element 18d₂At a time t first on the front side 11a₂(detection timing), No. 2 photoelectric conversion element 18d₂Changes from L to H. The calculation unit 32 detects at time t₂2 nd photoelectric conversion element 18d₂Is changed (the 2 nd detection step S30).

At S30 (time t)₂) After that, the calculation unit 32 calculates the movement distance V · T according to 1 photoelectric conversion element 18d (i.e., from the time T)₁To time t₂Moving time T (1 st time T)₁) And the product of the relative moving speed V) to calculate the position of the edge 11d (edge position calculating step S40).

For example, the calculation unit 32 calculates the slave time t₁Second photoelectric conversion element 18d₂To time t₁1 st photoelectric conversion element 18d₁Is separated from V.T (i.e., V.T)₁) Coordinates (position) of (a). Thereby, the position of the edge 11d is calculated.

As a specific example, when V is 10 μm/s and T is 0.4s, the calculation unit 32 calculates the time T from the time T₁Second photoelectric conversion element 18d₂To time t₁1 st photoelectric conversion element 18d₁Is separated from the coordinates (position) of 4 μm.

In the present embodiment, the position of the edge 11d is determined based on the information on the change in the amount of light received acquired by the light receiving unit 18 by moving the laser displacement meter 12 in this manner. Therefore, even at positions corresponding to between 2 photoelectric conversion elements 18d, the position of the edge 11d can be detected.

Note that, when the predetermined interval 18e is D, the calculating unit 32 may calculate the time t₁1 st photoelectric conversion element 18d₁To time t₁Second photoelectric conversion element 18d₂Is away from the coordinates of (D-V · T), thereby calculating the position of the edge 11D.

Next, a modification of embodiment 1 will be described. Fig. 7 (a) is a view showing a 1 st modification. In modification 1, the laser displacement meter 12 is moved in the direction opposite to that of embodiment 1. In the 1 st modification, time t₁1 st photoelectric conversion element 18d₁And the 2 nd photoelectric conversion element 18d₂The output voltages of (a) and (b) are all H.

Time t₂1 st photoelectric conversion element 18d₁Is not changed but is H, but at time t₂Second photoelectric conversion element 18d₂Changes from H to L. In modification 1, the coordinates of the edge 11d are also calculated through S10 to S40.

Fig. 7 (B) is a view showing a modification example 2. In modification 2, the coordinates of the edge 11d on the opposite side of the center 11e of the front surface 11a from the coordinates of the edge 11d calculated in embodiment 1 are calculated.

In the 2 nd modification, time t₁1 st photoelectric conversion element 18d₁Is L, at time t₁Second photoelectric conversion element 18d₂The output voltage of (d) is H. In addition, time t₂1 st photoelectric conversion element 18d₁Is not changed but is L, but at time t₂Second photoelectric conversion element 18d₂Changes from H to L.

Fig. 7 (C) is a view showing a modification example 3. In modification 3, the laser displacement meter 12 is moved in the opposite direction to that in modification 2. In modification 3, time t₁1 st photoelectric conversion element 18d₁And the 2 nd photoelectric conversion element 18d₂The output voltages of (a) and (b) are all L.

Time t₂1 st photoelectric conversion element 18d₁Is not changed but is L, but at time t₂Second photoelectric conversion element 18d₂Changes from L to H. In the 2 nd and 3 rd modifications, the coordinates of the edge 11d are also calculated through S10 to S40.

Next, embodiment 2 will be explained. In embodiment 2, the predetermined interval 18e is 10 μm, but the relative movement speed V is 1000 μm/s, and the sampling period is 1 ms.

In this case, the laser displacement meter 12 moves 1000 μm in the predetermined direction a within 1 second, and 1000 data (H/L of output voltage) are obtained for each photoelectric conversion element 18 d. Therefore, 1000 data can be obtained in the range of 1000 μm using 1 photoelectric conversion element 18 d.

That is, the resolution of 1 photoelectric conversion element 18d is 1 μm (1000 μm/1000). In embodiment 1, since the relative movement speed V is 10 μm/s and the sampling period is 0.1s, the resolution of 1 photoelectric conversion element 18d is 1 μm (10 μm/10).

However, in embodiment 2, the relative movement speed V can be increased by shortening the sampling period as compared with embodiment 1. That is, the time required for the movement of the laser displacement meter 12 can be shortened as compared with embodiment 1.

Next, embodiment 3 will be explained. In embodiment 3, the laser displacement meter 12 is moved relative to the chuck table 4 in a predetermined direction a, and the chuck table 4 is rotated at a predetermined rotational speed V around the rotation axis 10a_R(for example, 10rpm is 60 degrees/1 second).

Thereby, a plurality of coordinates of the edge 11d are detected. If the coordinates of the edge 11d at three or more points are detected, the coordinates (X) of the center 11e of the workpiece 11 can be determined_C，Y_C) (refer to fig. 9). Further, due to the coordinates (X) of the rotation axis 10a₀，Y₀) Is known and can therefore be based on the coordinates (X)₀，Y₀) To determine the coordinates (X)_C，Y_C) The offset (see fig. 9).

An edge position detection method according to embodiment 3 will be described with reference to fig. 8 (a) to 10. Fig. 10 is a flowchart of the edge position detection method according to embodiment 3. In embodiment 3, after the holding step S10, the chuck table 4 is started to rotate at a predetermined rotation speed V around the rotation axis 10a_RThe rotation is performed (rotation start step S12).

Then, the 1 st detection is performed in sequenceStep S20 (time t)₁) And a 2 nd detection step S30 (time t)₂). Thus, at time t₂The 1 st photoelectric conversion element 18d can be obtained₁And the 2 nd photoelectric conversion element 18d₂The coordinates of the edge 11d therebetween.

After the 2 nd detection step S30, except for the 2 nd photoelectric conversion element 18d₂In addition, the 3 rd photoelectric conversion element 18d arranged linearly at a predetermined interval 18e along the longitudinal direction of the laser beam LA is used₃And the 4 th photoelectric conversion element 18d₄Further, other portions of the edge 11d are detected.

While rotating the chuck table 4 at a rotational speed V_RThe laser displacement meter 12 is moved at a relative movement speed V with respect to the chuck table 4 while being rotated. Then, the 3 rd photoelectric conversion element 18d is detected₃Is changed from L to H (detection step S32 No. 3). In the present embodiment, S30 (time t)₂) The detection timing in S32 is set as time t₃。

Further, while the chuck table 4 is rotated at the rotation speed V_RThe laser displacement meter 12 is moved at a relative movement speed V with respect to the chuck table 4 while being rotated. Then, the 4 th photoelectric conversion element 18d is detected₄Is changed from L to H (the 4 th detection step S34). In the present embodiment, S32 (time t)₃) The detection timing in S34 is set as time t₄。

After the 4 th detection step S34, the calculation unit 32 calculates the 1 st to 3 rd positions of the edge 11d (edge position calculation step S40). The edge position calculating step S40 includes calculating the 1 st position (X) of the edge 11d₁，Y₁) Step S42.

In the 1 st calculation step S42, the calculation unit 32 calculates the 1 st detection step S20 (time t)₁) The 2 nd photoelectric conversion element 18d in (1)₂To time t₁1 st photoelectric conversion element 18d₁Is located at a distance of V.T₁Coordinates (position) of (a). In addition, the 1 st time T₁Is at time t₂And time t₁Difference between (T)₁＝t₂-t₁)。

FIG. 8A shows the photoelectric conversion element 18d located at the 1 st position₁And the 2 nd photoelectric conversion element 18d₂Figure 1 of the edge 11d in between. Time 1T₁For example 0.4 s. In this case, the calculation chuck table 4 is rotated by V_R·T₁Position 1 (X) of edge 11d when the angle is 24 degrees (60 degrees/1 second) or 0.4s₁，Y₁) (i.e., time t)₂The coordinates of the edge 11d at that time).

The edge position calculating step S40 further includes calculating the 2 nd position (X) of the edge 11d₂，Y₂) Step S44. In the 2 nd calculation step S44, the calculation unit 32 calculates the result from the 2 nd detection step S30 (time t)₂) The 3 rd photoelectric conversion element 18d in (1)₃To time t₂Second photoelectric conversion element 18d₂Is located at a distance of V.T₂Coordinates (position) of (a). In addition, the 2 nd time T₂Is at time t₃And time t₂Difference between (T)₂＝t₃-t₂)。

FIG. 8 (B) shows the photoelectric conversion element 18d located at the 2 nd position₂And the 3 rd photoelectric conversion element 18d₃(number 3 enclosed by a circle) of the 2 nd position of the edge 11 d. Time 2T₂For example 0.8 s.

In this case, it is calculated that the chuck table 4 has rotated V from the initial position_R·(T₁+T₂) Position 2 (X) of edge 11d at 72 degrees (60 degrees/1 second) · 1.2s ═ 72 degrees₂，Y₂) (i.e., time t)₃The coordinates of the edge 11d at that time).

The edge position calculating step S40 further includes calculating the 3 rd position (X) of the edge 11d₃，Y₃) Step S46. In the 3 rd calculating step S46, the calculating unit 32 calculates the result from the 3 rd detecting step S32 (time t)₃) The 4 th photoelectric conversion element 18d in (1)₄To time t₃Time 3 rd photoelectric conversion element 18d₃Is located at a distance of V.T₃Coordinates (position) of (a). In addition, the 3 rd time T₃Is at time t₄And time t₃Difference between (T)₃＝t₄-t₃)。

FIG. 8 (C) shows the photoelectric conversion element 18d located at the 3 rd position₃And the 4 th photoelectric conversion element 18d₄(number 4 enclosed by a circle) of the 3 rd position of the edge 11 d. Time 3T₃For example, 1.0 s.

In this case, it is calculated that the chuck table 4 has rotated V from the initial position_R·(T₁+T₂+T₃) Position 3 (X) of edge 11d when (60 degrees/1 second) · 2.2s ═ 132 degrees₃，Y₃) (i.e., time t)₄The coordinates of the edge 11d at that time).

Thus, as shown in fig. 9, the coordinates of different three points of the edge 11d can be obtained. If the coordinates of three or more points of the edge 11d are used, the coordinates (X) of the center 11e can be determined_C，Y_C). FIG. 9 is a diagram showing coordinates (X) of the determination center 11e_C，Y_C) The method of (1).

After the edge position calculating step S40, a center position shift calculating step S50 is performed. In S50, for example, by calculating the connection (X)₁，Y₁) And (X)₂，Y₂) Perpendicular bisector B and connect (X) of line segment of (A)₂，Y₂) And (X)₃，Y₃) The coordinates (X) of the center 11e are calculated from the intersection of the vertical bisectors C of the line segments_C，Y_C)。

Due to the coordinates (X) of the rotation axis 10a₀，Y₀) Is known and therefore the center 11e can be determined relative to the coordinates (X)₀，Y₀) Coordinate (X) of_C，Y_C) Of (3) is detected. This displacement is used to correct the position of the cut-in cutting tool (not shown) in, for example, a removal (trimming) step of the outer peripheral portion 11c on the front surface 11a side performed after the edge position detection.

The structure, method, and the like of the above embodiments can be modified as appropriate without departing from the object of the present invention. The 1 st calculation step S42, the 2 nd calculation step S44, and the 3 rd calculation step S46 may not necessarily be calculated in this order. In additionIn the edge position detection method according to embodiment 3, the coordinates (X) of the center 11e may be calculated from different coordinates of 4 or more points_C，Y_C)。