Measuring device

Abstract

The present application provides a measuring device which can detect the positional relationship between a machining tool such as a grinding tool or a cutting tool and a holding unit holding a workpiece without requiring work proficiency. The measuring device measures the positional relationship between a chuck table holding a workpiece and a machining tool machining the workpiece held by the chuck table, wherein the measuring device includes: a broadband light source; a mirror which reflects light emitted from the broadband light source and introduces the light into the machining tool; a chromatic condenser lens which is disposed between the broadband light source and the mirror or between the mirror and the machining tool; a light branching portion which branches reflected light reflected by the workpiece through the mirror and the chromatic condenser lens; and a position detection unit which detects the position of the machining tool based on the intensity of light corresponding to the wavelength of the reflected light branched by the light branching portion.

Description

Technical Field

[0001] The present invention relates to a measuring device that measures the positional relationship between a chuck table and a machining tool that performs machining on a workpiece held by the chuck table. Background Technology

[0002] The wafer is divided by multiple intersecting predetermined dividing lines to form multiple devices such as ICs and LSIs on the front side. After the back side of the wafer is ground to the desired thickness by a grinding device, it is divided into individual device chips by a dicing device. The divided device chips are used in electronic devices such as mobile phones and personal computers.

[0003] The grinding apparatus includes: a chuck stage for holding a wafer; and a grinding unit having grinding tools rotatably mounted on the wafer held by the chuck stage, the grinding apparatus being capable of grinding the wafer with high precision (see, for example, Patent Document 1).

[0004] In addition, the cutting apparatus includes: a chuck stage for holding the wafer; and a cutting unit having cutting tools rotatably capable of cutting the wafer held by the chuck stage. The cutting apparatus is capable of dividing the wafer into individual device chips with high precision (see, for example, Patent Document 2).

[0005] Patent Document 1: Japanese Patent Application Publication No. 07-130692

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-091781

[0007] In any of the aforementioned grinding or cutting devices, to ensure high-precision machining, it is necessary to accurately control the positional relationship between the holding surface (upper surface) of the chuck table and the machining tool relative to that holding surface. In conventional grinding devices, the following problem exists: to control the grinding feed of the grinding unit and bring the lower surface of the grinding wheel close to and slightly in contact with the upper surface of the chuck table, determining the origin for accurately positioning the lower surface of the grinding wheel is a tedious and skillful task.

[0008] Furthermore, in the cutting apparatus, a detection unit, consisting of a light-emitting element and a light-receiving element facing each other with a gap, is positioned near the location where the cutting tool is located. The tip of the cutting tool is inserted into the gap of the detection unit, and the origin position of the cutting tool is determined based on the change in the amount of light received by the light-receiving element that receives the light emitted by the light-emitting element. However, there are the following problems: the detection unit is separately arranged from the chuck table of the workpiece, and deviations may occur between the position of the detection unit and the upper surface of the chuck table, or wear and damage to the cutting tool may occur, making it impossible to detect the accurate origin. Summary of the Invention

[0009] Therefore, the object of the present invention is to provide a measuring device that can detect the positional relationship between a machining tool, such as a grinding wheel or a cutting tool, and a chuck table that holds the workpiece, without requiring skilled operation.

[0010] According to the present invention, a measuring device is provided that measures the positional relationship between a chuck table holding a workpiece and a machining tool performing machining on the workpiece held by the chuck table. The measuring device comprises: a broadband light source; a reflector that reflects light emitted from the broadband light source and directs it to the machining tool; a chromatic aberration focusing lens disposed between the broadband light source and the reflector or between the reflector and the machining tool; a light branch that branches the reflected light returned along the reflector and the chromatic aberration focusing lens and reflected by the machining tool; and a position detection unit that detects the position of the machining tool based on the intensity of light corresponding to the wavelength of the reflected light branched by the light branch.

[0011] Preferably, the measuring device also includes a beam splitter disposed between the broadband light source and the reflector, which splits the light emitted by the broadband light source into a first optical path toward the reflector and a second optical path perpendicular to the first optical path. The chromatic aberration focusing lens is disposed between the broadband light source and the beam splitter, and the light emitted by the broadband light source is guided to the reflector and the chuck stage.

[0012] According to the present invention, the machining tool is positioned in an area having multiple focusing points corresponding to the wavelengths of multiple lights formed by the chromatic aberration focusing lens, thereby enabling accurate detection of the distance between the upper surface of the chuck table and the lower surface of the machining tool, allowing the determination of the origin for controlling the machining tool without requiring skilled operators. Furthermore, it solves the problem of inaccurate detection of the distance between the upper surface of the chuck table and the lower surface of the machining tool due to a deviation between the position of the detection unit that detects the position of the machining tool and the position of the upper surface of the chuck table. Attached Figure Description

[0013] Figure 1This is a perspective view of the cutting device using the measuring apparatus of this embodiment.

[0014] Figure 2 It constitutes Figure 1 The diagram shows a cross-sectional view of the optical system housing of the measuring device and a block diagram illustrating the structure of the measuring device.

[0015] Figure 3 It is the Z-coordinate table stored in the control unit.

[0016] Figure 4 This is a cross-sectional view of the optical system housing container in other embodiments of the measuring device and a block diagram showing the structure of the measuring device.

[0017] Label Explanation

[0018] 1: Cutting device; 1A: Housing; 4: Box holding area; 4A: Box; 5: Temporary worktable; 6: Conveying mechanism; 7: Holding unit; 12: Cutting unit (machining tool); 12a: Cutting tool; 14: Operation panel; 20: Chuck worktable; 30: Measuring device; 31: Broadband light source; 32: Light branch; 33: Light guide; 34: Optical system storage container; 34a: Opening; 35: Collimating lens; 36: Chromatic aberration focusing lens; 37: Reflector; 38: Position Detection unit; 382: Beam splitter; 384: Line sensor; 40: Support substrate; 50: Measuring device; 53: Light guide; 54: Optical system storage container; 54a: First opening; 54b: Second opening; 54c: First shutter; 54d: Second shutter; 55: Collimating lens; 56: Chromatic focusing lens; 57: Reflector; 60: Grinding unit (machining tool); 62: Grinding wheel; 64: Grinding tool; 100: Control unit; 120: Z coordinate table. Detailed Implementation

[0019] Hereinafter, the measuring device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0020] exist Figure 1 The diagram shows a perspective view of the cutting device 1 using the measuring device 30 of this embodiment. Figure 1As shown, the cutting device 1 has a generally rectangular parallelepiped-shaped housing 1A. The cutting device 1 includes: a housing 4A, which is placed in the housing 1A housing holding area 4; a loading and unloading mechanism 3, which loads the wafer, which is the workpiece, from the housing 4A to a temporary worktable 5; a conveying mechanism 6, which has a rotating arm that conveys the wafer loaded onto the temporary worktable 5 to a holding unit 7; an imaging unit 11, which images the wafer held on the holding unit 7; a cutting unit 12, which has an annular cutting tool 12a provided as a processing tool for cutting the wafer; a conveying mechanism 13, which is used to convey the wafer that has undergone cutting from the holding unit 7 to a cleaning position; and an operation panel 14, which is used by the operator to set processing conditions, etc.

[0021] Inside the housing 1A of the cutting device 1 is a drive mechanism (not shown) for moving the chuck table 20, which constitutes the holding unit 7, relative to the cutting unit 12 in the X-axis direction indicated by arrow X in the figure. Additionally, a drive mechanism (not shown) is provided on the cutting unit 12 for moving the cutting tool 12a, which constitutes the cutting unit 12, in the Y-axis direction (indicating the indexing feed direction) and the Z-axis direction (indicating the cutting direction). Furthermore, inside the cylindrical component 25 that supports the chuck table 20 is a rotary drive mechanism (not shown), configured to allow the chuck table 20 to rotate arbitrarily in the circumferential direction.

[0022] In this embodiment, the measuring device 30 detects the positional relationship between the holding unit and the cutting tool 12a of the cutting unit 12, which serves as a machining tool, based on the intensity of light. Figure 1 As shown, the optical system storage container 34 constituting the measuring device 30 is positioned on the chuck stage 20 for use. Figure 1 In the illustrated embodiment, a support base plate 40 is provided for attracting and holding the optical system housing 34 on the chuck stage 20, and the chuck stage 20 is attracted and held by means of the support base plate 40. Hereinafter, reference will be made to... Figure 1 and Figure 2 The measuring device 30 will be described in detail.

[0023] like Figure 2As shown, the measuring device 30 of this embodiment includes: a broadband light source 31 that emits broadband light L0; an optical fiber FB that transmits the light L0 emitted by the broadband light source 31; a light branching section 32 that directs the light L0 emitted by the broadband light source 31 and branches the reflected light L1 reflected back by the cutting tool 12a; a light guiding section 33 that guides the light L0 into the optical system housing 34 shown in cross-section in the figure; a collimating lens 35 disposed within the optical system housing 34 to make the light L0 guided from the light guiding section 33 parallel light; and a chromatic aberration focusing lens 3. 6. The light L0, which is collimated by the collimating lens 35 and becomes parallel light, is introduced; the reflector 37 reflects the light L0 introduced from the chromatic aberration condenser lens 36 and guides it through the opening 34a of the optical system receiving container 34 to the cutting tool 12a located above; and the position detection unit 38 detects the position of the cutting tool 12a based on the intensity (light intensity) of the light corresponding to the wavelength of the reflected light L1 reflected by the cutting tool 12a that returns along the reflector 37, the chromatic aberration condenser lens 36, the optical fiber FB and is branched by the light branching section 32. Furthermore, the present invention is not limited to the above embodiment; for example, the chromatic aberration condenser lens 36 may be disposed between the reflector 37 and the cutting tool 12a.

[0024] The broadband light L0 generated by the broadband light source 31 can be, for example, white light with a well-balanced wavelength range of 150 nm to 850 nm. The lamp constituting the broadband light source 31 can be, for example, a halogen lamp, a xenon lamp, or a plasma lamp. The wavelength range of the light constituting the broadband light L0 emitted from the broadband light source 31 is not limited to the aforementioned range (150 nm to 850 nm), and can be a narrower or wider range; there is no particular limitation on the wavelength range.

[0025] The light L0 generated by the broadband light source 31 travels directly through the optical branch 32 on the optical fiber FB and is guided into the optical system receiving container 34 via the light guide 33. The light L0 guided into the optical system receiving container 34 shines from the light guide 33 onto the collimating lens 35 and becomes parallel light, and is then guided into the chromatic aberration condenser lens 36. The chromatic aberration condenser lens 36 is a lens that converges the guided broadband light L0, and is a lens that forms a focusing point along a predetermined width on the optical axis according to the length of each wavelength of the light L0 that passes through the chromatic aberration condenser lens 36.

[0026] In this embodiment, the light L0 passing through the chromatic aberration focusing lens 36 is reflected by the reflector 37, changing the light path upward by 90 degrees. The light L0 irradiated upward from the opening 34a forms a focusing point at different positions of each wavelength within a specified range of 30 mm above the front of the chuck stage 20 by the action of the chromatic aberration focusing lens 36.

[0027] More specifically, the focusing point P0 of the 500nm wavelength light contained in the light L0 is formed exactly 30mm from the front surface of the chuck stage 20. A focusing point of shorter wavelength light, such as 200nm, is formed 15μm below the focusing point P0. Conversely, a focusing point of longer wavelength light, such as 800nm, is formed 15μm above the focusing point P0. In other words, the focusing point of the light L0 generated by the broadband light source 31 is formed by the chromatic aberration focusing lens 36 at a height of approximately -15μm to +15μm from the upper surface of the chuck stage 20. In addition, the height positions of the focusing points (P0, P1, P2) formed by the measuring device 30 can be determined in advance through experiments, etc.

[0028] like Figure 2 As shown, when the front end of the cutting tool 12a of the cutting unit 12 is positioned in the region where the focusing points P1, P0, and P2 of light L0 are formed, light of a predetermined wavelength at the position where the focusing points are formed at the front end of the cutting tool 12a is positioned is reflected on the cutting tool 12a to generate reflected light L1. The reflected light L1 is not broadband light, but mainly contains light of a predetermined wavelength at the position where the focusing points are formed at the front end of the cutting tool 12a, as described above.

[0029] The reflected light L1, which is reflected at the tip of the cutting tool 12a, returns along the optical path followed by the light L0 irradiated from the broadband light source 31, and reaches the light branching section 32 via the reflecting mirror 37, the chromatic aberration focusing lens 36, the collimating lens 35, the light guide section 33, and the optical fiber FB, etc. Figure 2 As shown, the optical path is branched by the optical branch 32 into a different optical path from the optical path connected to the broadband light source 31, and then introduced to the position detection unit 38. The optical branch 32 is a structure that branches the light passing through the optical fiber FB, and a well-known optical circulator can be used for example.

[0030] The position detection unit 38 includes, for example, a diffraction grating 382 that separates and disperses the introduced reflected light L1 according to each wavelength; and a line sensor 384 that receives the light L2 dispersed by the diffraction grating 382 and detects the light intensity of each wavelength corresponding to the receiving position. The line sensor 384 is a sensor composed of multiple light-receiving elements such as a CCD arranged in a row in a predetermined direction, and detects the light intensity using each light-receiving element. The signal detected by the line sensor 384 is sent to the control unit 100, and the wavelength and light intensity of the reflected light L1 are detected based on the signal detected by the position detection unit 38.

[0031] The measuring device 30 and the cutting device 1 using the measuring device 30 in this embodiment have a structure that is roughly as described above. The method for measuring the positional relationship between the upper surface of the chuck table 20 of the holding unit 7 of the cutting device 1 and the front end 12b of the cutting tool 12a of the cutting unit 12 used as a machining tool using the measuring device 30 is as follows.

[0032] First, as according to Figure 1 As explained, the optical system housing 34 constituting the measuring device 30 is fixed to the disc-shaped support base plate 40, and is attracted and held on the chuck stage 20 constituting the holding unit 7 of the cutting device 1 by means of the support base plate 40. At this time, it is fixed in such a way that the center of the opening 34a of the optical system housing 34 is located at the center of the chuck stage 20.

[0033] If the optical system storage container 34 is attracted and held on the chuck stage 20, the drive mechanism (not shown) is activated, thereby moving the chuck stage 20 in the X-axis direction, positioning the center position of the opening 34a of the optical system storage container 34 directly below the imaging unit 11, and detecting (aligning) the center position coordinates of the light L0 illuminating upward from the opening 34a.

[0034] If alignment is performed as described above, the chuck stage 20 is further moved in the X-axis direction, and the cutting unit 12 is moved in the Y-axis direction, thereby positioning the cutting tool 12a directly above the center position coordinate of the opening 34a of the optical system housing 34. Next, as... Figure 2 As shown, the cutting tool 12a is lowered in the direction indicated by arrow R1, and controlled to be at a height of 30mm from the upper surface of the chuck table 20. At this time, the position of the tip of the cutting tool 12a may not be exactly 30mm from the upper surface of the chuck table 20 due to the control error of the cutting unit 12 and the shape deviation of the cutting tool 12a, but has a specified error.

[0035] When the position of the tip of the cutting tool 12a is controlled at a distance of 30 mm from the upper surface of the chuck table 20, as described above, in the cutting apparatus 1 of this embodiment, it is assumed that the error converges to within the range of ±15 μm, i.e., 30 μm. Here, the broadband light source 31 of the measuring device 30 is activated to illuminate light L0, which is white light. As described above, the light L0 illuminating from the broadband light source 31 forms a focused point in the area where the tip 12b of the cutting tool 12a exists through the optical path formed by the optical fiber FB, the optical branch 32, the optical guide 33, the collimating lens 35, the chromatic aberration focusing lens 36, and the reflecting mirror 37. This light L0, via the chromatic aberration focusing lens 36, forms a focused point at different positions along a predetermined width on the optical axis within a predetermined range, including a position 30 mm from the upper surface of the chuck table 20, according to the length of each wavelength constituting the light L0. Assuming that in the case of... Figure 2 When the cutting tool 12a is positioned at P2, as shown, light with a wavelength of 800 nm that forms a focal point at position P2 is reflected most strongly, while light of other wavelengths is reflected less strongly.

[0036] The reflected light L1, reflected at position P2 as described above, is guided back along the reflector 37, chromatic aberration focusing lens 36, collimating lens 35, light guide section 33, and optical fiber FB to the light branch section 32. In the light branch section 32, the reflected light L1 is branched towards the position detection unit 38 side but not towards the broadband light source 31 side. The reflected light L1 branched towards the position detection unit 38 side is guided to the diffraction grating 382 of the position detection unit 38. As described above, the diffraction grating 382 has the function of separating and dispersing the incident light according to each wavelength. The reflected light L1 reflected at the tip of the cutting tool 12a passes through the diffraction grating 382, ​​thus becoming dispersed light L2 dispersed according to the wavelength length, and irradiates the line sensor 384. Here, when the aforementioned diffuse light L2 is introduced into the position detection unit 38, the diffuse light L2 is not broadband light but light that strongly reflects the wavelength (800nm) of light that forms a focal point at the position shown in P2. Therefore, the light intensity signal of the diffuse light L2 illuminating the line sensor 384 is sent to the control unit 100, and the intensity signal can be obtained. Figure 2 The waveform shown in example (a) is shown in the lower right corner (shown by solid lines).

[0037] If a peak is detected at the position corresponding to the wavelength 800 nm by the dispersed light L2 as described above, then refer to the data pre-stored in the control unit 100. Figure 3The Z-coordinate table 120 is shown. The Z-coordinate table 120 records the wavelength of the peak of the waveform detected by the line sensor 384 and the corresponding Z-coordinate value. That is, when the wavelength of the peak is 800 nm, according to the Z-coordinate table 120, the Z-coordinate value is "+15.0 μm". Therefore, when the upper surface of the chuck table 20 is used as a reference, the height position (Z-coordinate) of the cutting tool 12a is detected as Z = 30 mm + 15.0 μm.

[0038] Assuming in such Figure 2 When the cutting tool tip is at position 12a (shown by the double-dotted line), as shown, light L0 is reflected at position P1. At position P1, light with a wavelength of 200nm forms a focused point, and therefore, the diffused light L2 of the reflected light L1 reflected at position P1 is detected by the line sensor 382. Figure 2 A peak (shown by the dashed line) appears at a wavelength of 200 nm, as shown in (c). Based on the waveform shown in (c), refer to... Figure 3 The Z-coordinate table 120 shows the Z-coordinate value as "-15.0 μm". Therefore, when the upper surface of the chuck table 20 is used as a reference, the height position (Z-coordinate) of the cutting tool 12a is detected as Z = 30 mm - 15.0 μm.

[0039] In addition, in such Figure 2 When positioned as shown by the cutting tool 12a' (indicated by the double-dotted line), light L0 is reflected at position P0. At position P0, the 500nm wavelength light forms a focused point, and therefore, the diffused light L2 of the reflected light L1 reflected at position P0 is detected by the line sensor 382. Figure 2 A peak (shown by the dashed line) appears at a wavelength of 500 nm, as shown in (b). Based on the waveform shown in (b), refer to... Figure 3 The Z-coordinate table 120 shown indicates that the Z-coordinate value is "0.0 μm". Therefore, when the upper surface of the chuck table 20 is used as a reference, the height position (Z-coordinate) of the cutting tool 12a is detected as Z = 30 mm (+0.0 μm).

[0040] As described above, the position of the cutting unit 12 can be accurately detected based on the intensity (peak) of the light corresponding to the wavelength of the reflected light L1 branched from the light branch 32. Furthermore, Figure 3The Z-coordinate table 120 of this embodiment stores Z-coordinates in units of 2.5 μm, with each 50 nm wavelength stored. However, the present invention is not limited to this. By appropriately selecting the diffraction grating 382 and the line sensor 384, the resolution for detecting Z-coordinate values ​​can be further refined, resulting in higher precision in Z-coordinate detection. Furthermore, in the above embodiment, the Z-coordinate value is detected using the Z-coordinate table 120, and the Z-coordinate position of the cutting tool 12a, which is positioned by the control, is determined by adding the height position (30 mm) of the cutting tool 12a. However, the Z-coordinate position, i.e., the height position, can also be directly stored by adding 30 mm to the Z-coordinate table 120 beforehand.

[0041] As described above, by accurately detecting the position of the cutting tool 12a of the cutting unit 12 relative to the upper surface of the chuck table 20, the origin position of the cutting tool 12a can be accurately grasped when controlling it, and the cutting tool 12a can be accurately positioned relative to the workpiece during cutting.

[0042] According to the present invention, various modifications are provided, not limited to the embodiments described above. (See also...) Figure 4 Other implementation methods will be described. Additionally, Figure 4 Other embodiments shown illustrate an example of applying the measuring device 50 of the present invention to a grinding unit 60 (only a portion is shown). The following description is based on an example of detecting the position of the lower surface of the grinding wheel 62 of the grinding tool 64, using the upper surface of the circular chuck table 20 (shown only in cross-section in the figure) as a reference. For structures identical to those described previously, the same reference numerals are used, and detailed descriptions are omitted where appropriate.

[0043] Figure 4 The measuring device 50 shown, like the previously described embodiment, includes: a broadband light source 31 that emits broadband light L0; an optical fiber FB that transmits the light L0 emitted by the broadband light source 31; and a light branching section 32 that allows the light L0 emitted by the broadband light source 31 to proceed straight and branches the reflected light L1. The measuring device 50 also includes: a light guide section 53 that guides the light L0 into an optical system receiving container 54; a collimating lens 55 that makes the light L0 guided from the light guide section 53 in the optical system receiving container 54 parallel; a chromatic aberration focusing lens 56 that guides the light L0 that has become parallel light through the collimating lens 55; and a reflecting mirror 57 that reflects the light L0 guided from the chromatic aberration focusing lens 56 and guides it to the grinding tool 64 side. The measuring device 50 also has a beam splitter 58 between the broadband light source 31 and the reflecting mirror 57, which branches into a first optical path L3 toward the reflecting mirror 57 and a second optical path L4 perpendicular to the first optical path L3.

[0044] Beam splitter 58 consists of two right-angle prisms, whose inclined surfaces are joined together using a suitable optical thin film to form an inclined surface 58a that functions as a beam splitter. Thus, light L0 emanating from the broadband light source 31 is split in two by the inclined surface 58a of beam splitter 58, branching into light traveling along a first, direct optical path L3 and light reflected by the inclined surface 58a and traveling along a second optical path L4 perpendicular to the first optical path L3. Figure 4 Understandably, the chromatic aberration focusing lens 56 is positioned between the broadband light source 31 and the beam splitter 58.

[0045] A first shutter 54c and a second shutter 54d are provided in the optical system housing 54. The first shutter 54c moves forward and backward in the direction indicated by arrow R2, thereby opening or closing the first opening 54a through which the first optical path L3 passes. The second shutter 54d moves forward and backward in the direction indicated by arrow R3, thereby opening or closing the second opening 54b through which the second optical path L4 passes. In this embodiment, when the first opening 54a is open, the second opening 54b is closed. Conversely, when the second opening 54b is open, the first opening 54a is closed. The optical system housing 54 is positioned directly above the center of the chuck stage 20 by a fixing fixture (not shown). Hereinafter, reference will be made to... Figure 4 The steps for using the measuring device 50 to detect the position of the lower surface of the grinding wheel (machining tool) 64 are explained.

[0046] If the optical system storage container 54 is positioned on the chuck table 20 using the aforementioned fixing fixture, the chuck table 20 is moved to position the area of ​​the optical system storage container 54, including the center position of the first opening 54a, directly below the grinding tool 64 of the grinding unit 60.

[0047] Next, the grinding wheel 62 is lowered in the direction indicated by arrow R4, as shown in the figure, to a height of 50 mm from the upper surface of the chuck table 20. At this time, the position of the lower surface of the grinding wheel 64 may not be exactly 50 mm from the upper surface of the chuck table 20 due to control errors of the grinding unit 60, shape deviations of the grinding wheel 64, etc., and has a specified error.

[0048] Here, with the first opening 54a of the optical system housing 54 of the measuring device 50 closed by the first shutter 54c and the second opening 54b opened by the second shutter 54d, the broadband light source 31 of the measuring device 50 is activated to illuminate broadband light L0. As described above, the light L0 illuminating from the broadband light source 31 passes through the optical fiber FB, the optical branch 32, the light guide 53, the collimating lens 55, and the chromatic aberration focusing lens 56 and illuminates the inclined surface 58a of the beam splitter 58. The second light path L4, formed by reflection on the inclined surface 58a, illuminates the upper surface of the chuck stage 20. In this state, when the optical system housing 54 is slightly lowered in the direction indicated by arrow R5 to reach a predetermined position, the focusing point P1' of the light passing through the second light path L4 is positioned on the front surface of the chuck stage 20 and reflected to form reflected light L5. The reflected light L5 returns along the optical path followed by light L0, is branched by the optical branch 32, and is dispersed by the diffraction grating 382 of the position detection unit 38 to form dispersed light L6. The dispersed light L6 is detected by the line sensor 384, thus... Figure 4 As shown in the lower right (d), a peak waveform of light with a wavelength of, for example, 700 nm appears (shown by dashed lines). In this embodiment, the beam is set to form a focal point P0' of light with a wavelength of 500 nm at a distance of 35 mm from the center of the optical axis traveling to the right within the optical system housing 54, thus further directly lowering the optical system housing 54 slightly. As a result, the waveform detected by the position detection unit 38 can be moved to the position of 500 nm wavelength shown in (e) (shown by solid lines), and when viewed from the center of the optical axis traveling within the optical system housing 54, the distance to the upper surface of the chuck stage 20 can be accurately 35 mm.

[0049] If, as described above, the distance from the optical axis traveling within the optical system housing 54 to the upper surface of the chuck stage 20 is exactly 35 mm, then the second shutter 54d is closed and the first shutter 54c is opened. The light traveling along the first optical path L3 within the optical system housing 54 is then reflected by the mirror 57 and passes through the first opening 54a toward the grinding tool 64 positioned above. The light L0, guided by the collimating lens 55 to the chromatic aberration focusing lens 56 as described above, is positioned 35 mm in front of the inclined surface 58a of the beam splitter 58. In this embodiment, the distance from the inclined plane 58a to the reflector 57 is set to 20 mm. Therefore, the focusing point of the light passing through the first optical path L3, branched from the inclined plane 58a and guided to the grinding wheel 64 side via the reflector 57, is formed at a position 15 mm above the center of the reflector 57. That is, it is formed at different positions corresponding to the wavelength along a predetermined range on the optical axis approximately 50 mm from the upper surface of the chuck table 20. Figure 4 As shown, when the lower end of the grinding wheel 64 is located at position P2, light of the wavelength with a focusing point at position P2 is reflected most strongly, while light of other wavelengths is reflected less strongly.

[0050] The reflected light L5, reflected at position P2 as described above, passes through mirror 57, beam splitter 58, and returns along chromatic aberration focusing lens 56, collimating lens 55, light guide section 53, and optical fiber FB to be guided to light branch section 32. In light branch section 32, the reflected light L5 is branched towards position detection unit 38, but not towards broadband light source 31. The reflected light L5 branched to position detection unit 38 is guided to diffraction grating 382 of position detection unit 38. As described above, diffraction grating 382 has the function of separating and dispersing according to each wavelength. The reflected light L5 reflected at the tip of cutting tool 12a becomes dispersed light L6, dispersed according to wavelength, via diffraction grating 382, ​​and illuminates line sensor 384. The light intensity signal of the dispersed light L6 illuminating line sensor 384 is sent to control unit 100, thereby enabling, for example, the previously described embodiment. Figure 2 The result, as shown in the lower right corner, represents the peak of each wavelength. Here, when the reflected light L5 reflected at position P2 is introduced into position detection unit 38, the waveform shown in (a) (shown by solid line) can be obtained. That is, based on the dispersed light L6 obtained by dispersing the reflected light L5 reflected at position P2, it can be understood that a peak is formed at the position corresponding to wavelength 800nm.

[0051] If, as described above, a peak is detected at a position corresponding to wavelength 800 nm based on the dispersed light L6, then refer to, for example, data pre-stored in the control unit 100. Figure 3The Z-coordinate table 120, as shown, indicates that the Z-coordinate value is "+15.0μm". Therefore, when the upper surface of the chuck table 20 is used as a reference, the height position of the cutting tool 12a is detected as Z = 50mm + 15.0μm.

[0052] Assuming the lower end of the grinding wheel 64 is at position 64 (shown by the double-dotted line), the light passing through the first optical path L3 is reflected at position P1. At position P1, the 200nm wavelength light forms a focal point. Therefore, when the reflected light L5 formed at position P1 is guided to the position detection unit 38 and the dispersed light L6 is detected by the line sensor 382, ​​in Figure 2 A peak appears at the position shown in (c). Based on the waveform shown in (c), refer to... Figure 3 The Z-coordinate table 120 shows that the Z-coordinate value is "-15.0μm". Therefore, when the upper surface of the chuck table 20 is used as the reference, the height position of the grinding wheel 64” is Z = 50mm - 15.0μm.

[0053] Furthermore, when the lower end of the grinding wheel 64 is in the position shown by the double-dotted line (64'), the light passing through the first optical path L3 is reflected at position P0. At position P0, the light with a wavelength of 500nm forms a focused point, therefore... Figure 2 A peak appears at the position shown in (b), referencing Figure 3 The Z coordinate table 120 shows that the Z coordinate value is "0.0μm". With the upper surface of the chuck table 20 as the reference, the height position Z of the grinding tool 64' is detected as 50mm (+0.0μm).

[0054] As described above, even in other embodiments, the positional relationship between the holding unit that holds the workpiece and the machining tool that performs machining on the workpiece held by the holding unit can be accurately measured. Furthermore, even when the present invention is applied to the grinding unit 60 of a grinding apparatus, the positional relationship between the chuck table constituting the holding unit and the machining tool can be detected.

Claims

1. A measuring device for measuring the distance between the upper surface of a chuck table holding a workpiece and the lower surface of a machining tool used to machine the workpiece held by the chuck table, wherein, The measuring device has the following features: Broadband light source; A reflector that reflects the light emitted by the broadband light source and directs it to the processing tool; A chromatic aberration focusing lens is disposed between the broadband light source and the reflector or between the reflector and the processing tool; A light branch that branches the reflected light that is reflected by the processing tool and returns along the mirror and the chromatic aberration condenser lens; The position detection unit detects the intensity of light corresponding to the wavelength of the reflected light branched by the optical branch and outputs a signal of the detected light intensity. as well as The control unit detects the position of the machining tool based on the signal detected by the position detection unit.

2. The measuring device according to claim 1, wherein, The measuring device also includes a beam splitter disposed between the broadband light source and the reflector, which splits the light emitted by the broadband light source into a first optical path toward the reflector and a second optical path perpendicular to the first optical path. The optical system housing housing, which houses the optical system including the reflector, the chromatic aberration condenser lens, and the beam splitter, has a first opening for a first optical path to pass through and guide the light to a machining tool above, and a second opening for a second optical path to pass through and guide the light to a holding unit below. The chromatic aberration focusing lens is positioned between the broadband light source and the beam splitter. The position detection unit detects and outputs a signal of the detected light intensity, which corresponds to the wavelength of the reflected light from the processing tool after the light branched into a first optical path is guided through the first opening to the processing tool and reflected thereon, and the intensity of the reflected light from the holding unit after the light branched into a second optical path is guided through the second opening to the holding unit and reflected thereon. The control unit detects the position of the machining tool and the position of the holding unit based on the signal detected by the position detection unit.

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