Thickness Measuring Device

Abstract

To provide a measuring device capable of measuring a thickness of a plate-like object in a short time.SOLUTION: A thickness measuring device for measuring a thickness of a plate-like object W includes at least holding means 20 for setting an X-axis and Y-axis plane for holding the plate-like object W as a holding surface, and measuring means 10 for measuring the thickness of the plate-like object W held by the holding means 20, wherein the measuring means 10 includes a light source 1 having a predetermined wavelength region, a scanning mirror 3 for positioning the light emitted from a light source 2 with a coordinate specified by an X-coordinate and Y-coordinate on the plate-like object W held by the holding means 20, a diffusion film 4 for projecting reflected light L3 which is reflected from a surface Wa and a rear face Wb of the plate-like object W held by the holding means 20, and forms a spectral interference waveform, light detection means 5 for detecting intensity of the light corresponding to the wavelength of the spectral interference waveform projected onto the diffusion film 4, storage means 110 for storing the intensity of the light corresponding to the wavelength detected by the light detection means 5 for each of the coordinates, and calculation means 120 for calculating the thickness of each of the coordinates through Fourier transformation of the intensity of the light corresponding to the wavelength stored in the storage means 110.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thickness measurement device for measuring the thickness of a plate-like object. [Background technology]

[0002] Wafers have multiple devices such as ICs and LSIs formed on their surface, separated by planned dividing lines. The back side is ground using a grinding machine to thin the wafer, and then the wafer is divided into individual device chips using a dicing machine and laser processing machine. These chips are then used in electrical devices such as mobile phones and personal computers.

[0003] A grinding device that grinds the back surface of a wafer is generally composed of a chuck table that holds the wafer, a grinding means that has a rotatable grinding wheel that grinds the wafer held on the chuck table, and a measuring means that measures the thickness of the wafer held on the chuck table, and can process the wafer to the desired thickness.

[0004] As the above-mentioned measuring means, if a contact type measuring means is used in which a prober is brought into contact with the ground surface of the wafer to measure the thickness of the wafer, the ground surface will be damaged, so a non-contact type measuring means is used in which light is irradiated from the ground surface of the wafer and the thickness is measured by Fourier transforming the spectral interference waveform between the light reflected from the ground surface of the wafer and the light that has passed through the wafer and reflected from the opposite surface (see, for example, Patent Document 1).

[0005] Furthermore, when a laser beam having a wavelength that is transparent to the wafer is irradiated by positioning the focal point inside the wafer to form a modified layer inside, the thickness of the wafer is measured by the spectral interference waveform of the light reflected from the front surface and the light reflected from the back surface of the wafer (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-21916 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-122894 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, the technologies described in Patent Documents 1 and 2 above are configured to detect the thickness of the wafer by separating the return light reflected from the top and bottom surfaces of the wafer using a diffraction grating and calculating (Fourier transform) the light intensity for each wavelength. In order to detect the thickness over the entire wafer, it is necessary to change the irradiation position by moving the position of the wafer held on the chuck table, which is time-consuming.

[0008] The present invention has been made in view of the above circumstances, and its main technical object is to provide a measuring device that can measure the thickness of a plate-like object in a short period of time. [Means for solving the problem]

[0009] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a thickness measurement device for measuring the thickness of a plate-like object, which comprises at least a holding means for holding the plate-like object with an X-axis / Y-axis plane as a holding surface, and a measuring means for measuring the thickness of the plate-like object held by the holding means, and the measuring means includes a light source having a predetermined wavelength range and a measuring means for measuring the thickness of the plate-like object held by the holding means by irradiating the light emitted from the light source onto the plate-like object. above to Leave Coordinates specified by X and Y coordinates While changing a scanning mirror for positioning the plate-like object, and reflected light that is reflected from the front and back surfaces of the plate-like object held by the holding means to form a spectral interference waveform; The scanning mirror moves from different angles to different positions. projection And a light detection means for detecting the intensity of light corresponding to the wavelength of the spectral interference waveform projected onto the diffusion film; a storage means for storing the intensity of light corresponding to the wavelength detected by the light detection means for each coordinate; and a calculation means for calculating the thickness for each coordinate by performing a Fourier transform on the intensity of light corresponding to the wavelength stored in the storage means. Furthermore, according to the present invention, there is provided a thickness measurement device for measuring the thickness of a plate-like object, comprising at least a holding means for holding the plate-like object with an X-axis and Y-axis plane as a holding surface, and a measurement means for measuring the thickness of the plate-like object held by the holding means, the measurement means including a light source having a predetermined wavelength range, a scanning mirror for positioning the light emitted from the light source at coordinates specified by X- and Y-coordinates on the plate-like object held by the holding means, a diffusion film for projecting reflected light that is reflected from the front and back surfaces of the plate-like object held by the holding means and forms a spectral interference waveform, a light detection means for detecting the intensity of light corresponding to the wavelength of the spectral interference waveform projected onto the diffusion film, and a storage means for storing the intensity of light corresponding to the wavelength detected by the light detection means for each coordinate. and a calculation means for calculating a thickness for each coordinate by performing a Fourier transform on the intensity of light corresponding to the wavelength stored in the storage means, wherein the device is equipped with a branching means for branching the light emitted by the light source for each wavelength, the light detection means detects the intensity of light for each wavelength projected onto the diffusion film, the storage means stores the light intensity for each wavelength corresponding to the coordinate, and when the device is equipped with a branching means for branching the light emitted by the light source for each wavelength, the holding means is equipped with a Z-axis moving means for moving in a Z-axis direction perpendicular to the X-axis and Y-axis, and the holding means is positioned in the Z-axis direction in accordance with the X-coordinate and Y-coordinate of the light positioned on the plate-like object by the scanning mirror so that the intervals for each wavelength projected onto the diffusion film are constant.

[0010] The device may include wavelength switching means for switching the light emitted by the light source according to wavelength with a time difference, the light detection means for detecting the intensity of the light for each wavelength projected onto the diffusion film, and the storage means for storing the light intensity for each wavelength corresponding to coordinates.Alternatively, the device may include branching means for branching the light emitted by the light source according to wavelength, the light detection means for detecting the intensity of the light for each wavelength projected onto the diffusion film, and the storage means for storing the light intensity for each wavelength corresponding to coordinates.

[0011] The light source may be a broadband light source or a multi-wavelength light source. When the light source is provided with a wavelength switching means for switching the light emitted by the light source according to wavelength with a time difference, the light detection means is preferably one of a camera, a line sensor, a PD, and a PMT. When the light source is provided with a branching means for branching the light emitted by the light source according to wavelength, the light detection means is preferably one of a camera and a line sensor.

[0012] When the light source is provided with a branching means for branching the light emitted by the light source into wavelengths, the holding means preferably includes a Z-axis moving means for moving in a Z-axis direction perpendicular to the X-axis and Y-axis, and the holding means is preferably positioned in the Z-axis direction in accordance with the X- and Y-coordinates of the light positioned on the plate-like object by the scanning mirror so that the intervals for each wavelength projected onto the diffusion film are constant. When the diffusion film is a transmissive type, the light detecting means is preferably disposed on the back side of the diffusion film, and when the diffusion film is a reflective type, the light detecting means is preferably disposed on the front side of the diffusion film. [Effects of the Invention]

[0013] The thickness measurement device of the present invention is a thickness measurement device for measuring the thickness of a plate-like object, and includes at least a holding means for holding the plate-like object with an X-axis / Y-axis plane as a holding surface, and a measuring means for measuring the thickness of the plate-like object held by the holding means, and the measuring means includes a light source having a predetermined wavelength range and a measuring means for measuring the thickness of the plate-like object held by the holding means by irradiating the light emitted by the light source onto the plate-like object. above to Leave Coordinates specified by X and Y coordinates While changing a scanning mirror for positioning the plate-like object, and reflected light that is reflected from the front and back surfaces of the plate-like object held by the holding means to form a spectral interference waveform; The scanning mirror moves from different angles to different positions. projection And The scanning mirror is configured to include a diffusion film that detects the intensity of light corresponding to the wavelength of the spectral interference waveform projected onto the diffusion film, a light detection means that detects the intensity of light corresponding to the wavelength detected by the light detection means for each coordinate, and a calculation means that performs a Fourier transform on the intensity of light corresponding to the wavelength stored in the storage means to calculate the thickness for each coordinate.This makes it possible to measure the thickness of a plate-like object at multiple desired coordinate positions depending on the speed of the scanning mirror, thereby solving the problem of not being able to measure the thickness of a plate-like object at multiple positions in a short period of time. The thickness measurement device of the present invention includes at least a holding means for holding a plate-like object with an X-axis and Y-axis plane as a holding surface, and a measuring means for measuring the thickness of the plate-like object held by the holding means, the measuring means including a light source having a predetermined wavelength range, a scanning mirror for positioning light emitted from the light source at coordinates specified by X and Y coordinates on the plate-like object held by the holding means, a diffusion film for projecting reflected light that is reflected from the front and back surfaces of the plate-like object held by the holding means and forms a spectral interference waveform, a light detection means for detecting the intensity of light corresponding to the wavelength of the spectral interference waveform projected onto the diffusion film, a memory means for storing the light intensity corresponding to the wavelength detected by the light detection means for each coordinate, and a calculation means for calculating the thickness for each coordinate by Fourier transforming the light intensity corresponding to the wavelength stored in the memory means. and a stage, and is equipped with a branching means for branching the light emitted by the light source into wavelengths, the light detection means detects the intensity of the light for each wavelength projected onto the diffusion film, and the memory means stores the light intensity for each wavelength corresponding to the coordinates, and when the branching means for branching the light emitted by the light source into wavelengths is provided, the holding means has Z-axis movement means for moving in the Z-axis direction perpendicular to the X-axis and Y-axis, and the holding means positions itself in the Z-axis direction in accordance with the X-coordinate and Y-coordinate of the light positioned on the plate-like object by the scanning mirror so that the intervals for each wavelength projected onto the diffusion film are constant.Since this makes it possible to measure the thickness of a plate-like object at multiple desired coordinate positions depending on the speed of the scanning mirror, and this solves the problem of not being able to measure the thickness of a plate-like object at multiple positions in a short time. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a simplified diagram of a thickness measurement device according to an embodiment of the present invention. [Figure 2] 2 is a perspective view showing a mode in which a wafer is held by a holding means of the thickness measuring device shown in FIG. 1. FIG. [Figure 3] 2 is a plan view of a wafer whose thickness is measured by the thickness measurement device shown in FIG. 1. [Figure 4] 2 is a conceptual diagram showing information on the light intensity and calculated thickness stored in the control means of the thickness measurement device shown in FIG. 1. FIG. [Figure 5] FIG. 10 is a simplified diagram showing another embodiment of the thickness measurement device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a thickness measurement device configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0016] 1 shows a simplified diagram illustrating the configuration of a thickness measurement device 1 of this embodiment. The thickness measurement device 1 is a device that measures the thickness of a plate-like object (wafer W). The thickness measurement device 1 includes at least a holding means 20 that holds the wafer W using a plane defined by X and Y coordinates as a holding surface 21, and a measurement means 10 that measures the thickness of the wafer W held by the holding means 20.

[0017] The measurement means 10 includes a light source 2 having a predetermined wavelength range, a scanning mirror 3 that positions light L1 emitted by the light source 2 at a desired coordinate position on the wafer W held by the holding means 20, which is specified by the X and Y coordinates on the wafer W, a diffusion film 4 that projects reflected light L3 having a light intensity corresponding to a wavelength based on a spectral interference waveform generated by reflection from the front surface Wa and back surface Wb of the wafer W held by the holding means 20, a light detection means 5 that detects the light intensity corresponding to the wavelength projected onto the diffusion film 4, a memory means 110 that stores the light intensity corresponding to the wavelength detected by the light detection means 5 for each coordinate, and a calculation means 120 that performs a Fourier transform on the light intensity corresponding to the wavelength stored in the memory means 110 to calculate the thickness for each coordinate. In this embodiment, the memory means 110 and the calculation means 120 are provided in a control means 100 provided in the thickness measurement device 1. In the embodiment shown in Fig. 1, light L1 emitted from the light source 2 is collimated by a collimating lens 7 and guided to a wavelength switching means 6 disposed between the collimating lens 7 and the scanning mirror 3. The wavelength switching means 6 is a means for switching the incident light L1 between wavelengths with a time difference.

[0018] The light source 2 can be appropriately selected from a broadband light source or a multi-wavelength light source. In the case of a broadband light source, a light source that irradiates light containing wavelengths of, for example, 450 to 900 nm approximately uniformly is used, and in the case of a multi-wavelength light source, a light source that irradiates light of multiple wavelengths that are discretely and uniformly spaced between, for example, 450 to 900 nm is used. The light source 2 in this embodiment is selected from, for example, an SC (Super Continuum) light source or an SLD (Super Luminescent Diode) light source.

[0019] The scanning mirror 3 is, for example, a galvanometer scanner, and is a mirror that can quickly control the reflecting mirror 32 to a desired orientation by controlling the driver 31 with the control means 100. In the scanning mirror 3 of this embodiment, the driver 31 rotates the reflecting mirror 32 in the X-axis and Y-axis directions to reflect the light L2 irradiated from the wavelength switching means 6 and position it at a desired measurement position defined by the X- and Y-coordinates on the wafer W held by the holding means 20. Note that the scanning mirror 3 of the present invention is not limited to the galvanometer scanner shown in the figure, and any well-known mirror used in so-called laser scanning can be used. For example, the scanning mirror 3 may be configured with an X-axis mirror that changes the light irradiation position on the wafer W solely in the X-axis direction and a Y-axis mirror that changes the light irradiation position on the wafer W solely in the Y-axis direction.

[0020] The wavelength switching means 6 shown in Fig. 1 is configured, for example, by a so-called sweep device that switches the light L1 emitted from the light source 2 to light L2 with a time difference for each wavelength and irradiates the light. More specifically, this can be achieved by using an optical fiber that generates wavelength dispersion. This can be achieved by disposing a diffraction grating in a long optical fiber so that the reflection position varies for each wavelength, and by setting the reflection distance for light with a short wavelength to be short and the reflection distance for light with a long wavelength to be long. As a result, the light L2 irradiated from the wavelength switching means 6 is configured, as conceptually shown in Fig. 1, with blue light L2a, which has a short wavelength, irradiated first, followed by green light L2b, yellow light L2c, and red light L2d, which are irradiated in order of decreasing wavelength. In the embodiment shown in FIG. 1, for convenience of explanation, the wavelength switching means 6 is described as being composed of four types of wavelengths of light (blue light L2a, green light L2b, yellow light L2c, and red light L2d), but in reality, the wavelength switching means 6 generates and irradiates light in which the gradation at the boundary between each color changes even more finely with a time difference for each wavelength, and the light is dispersed into a large number of wavelengths at even finer intervals.

[0021] As can be seen from the figure, when the light L2 is irradiated onto the measurement position (P0) of the wafer W held by the holding means 20, reflected light L3 is generated, having a light intensity corresponding to the wavelength based on the spectral interference waveform generated by reflection from the front and back surfaces Wa and Wb of the wafer W. The reflected light L3 is projected onto the front surface 4a of the diffusion film 4 in the order of wavelengths time-shifted by the wavelength switching means 6, i.e., in the order of the shortest wavelength blue light L3a irradiated first, followed by green light L3b, yellow light L3c, and red light L3d. The light intensity corresponding to the wavelength based on the spectral interference waveform is detected on the back surface 4b of the diffusion film 4. The diffusion film 4 is a so-called light diffusion film of a transmissive type that diffuses incident light brightly and evenly. As shown in FIG. 1, a light detection means 5 is disposed on the back surface 4b. The light detection means 5 can be selected from, for example, a camera configured with a CMOS sensor, a photodiode (PD), a photomultiplier tube (PMT), a line sensor, etc. The light detection means 5 in this embodiment is, for example, a camera formed of a CMOS sensor, and is composed of a plurality of pixels defined corresponding to a two-dimensional area specified by the X and Y coordinates of the area on the wafer W where the light L2 is irradiated. The light detection means 5 detects the intensities of light corresponding to the wavelengths of the reflected light L3 sequentially received with a time difference by the action of the wavelength switching means 6, detects a spectral interference waveform, and stores the light intensities for each coordinate position on the wafer W in the storage means 110 of the control means 100. The light intensities of the reflected light L3 stored in the storage means 110 are calculated (Fourier transformed) by the calculation means 120 of the control means 100, and the thickness for each coordinate position on the wafer W is calculated. Information regarding the thickness calculated by the calculation means 120 is stored in an appropriate memory of the control means 100.

[0022] The thickness measurement device 1 of this embodiment has roughly the configuration as described above, and the manner in which the thickness of a plate-like object is measured using this embodiment will be described in more detail.

[0023] 2 shows a silicon (Si) wafer W whose thickness is measured by the thickness measurement device 1 of this embodiment. The wafer W is placed on a holding surface 21 supported by a cylindrical member 22 of a holding means 20 of the thickness measurement device 1, with the front surface Wa facing upward and the back surface Wb facing downward. The holding surface 21 is a plane defined by the X-axis and Y-axis and is formed of an air-permeable material. A suction means (not shown) is connected to the holding surface 21, and by operating the suction means, a negative pressure is generated on the holding surface 21, thereby suction-holding the wafer W.

[0024] 3 shows a plan view of the wafer W held by the holding means 20. By operating the light source 2 and the scanning mirror 3 of the thickness measurement device 1, predetermined measurement positions specified by the X and Y coordinates on the wafer W shown in the figure, i.e., (x1, y1), (x2, y1), (x3, y1), (x4, y1), (x n-1 ,y m ), (x n ,y m ) is irradiated with light L2 (coordinates are partially omitted in FIG. 3). In this embodiment, light L2 passes through wavelength switching means 6 and includes blue light L2a, green light L2b, yellow light L2c, and red light L2d, each with a time difference for each wavelength. For example, as shown in FIG. 1, light L2 is irradiated at measurement position P0 on the wafer W, and is reflected from the front surface Wa and back surface Wb of the wafer W to form reflected light L3 having a light intensity corresponding to the wavelength based on a spectral interference waveform generated according to the thickness. This reflected light L3 is composed of blue light L3a, green light L3b, yellow light L3c, and red light L3d, which are dispersed with a time difference, and is projected onto the front surface 4a of the diffusion film 4. The light intensity with a time difference for each wavelength is detected by light detection means 5 from the back surface 4b side of the diffusion film 4. In this way, once the light intensities with time differences for each wavelength have been detected at all measurement positions specified by the X and Y coordinates on the wafer W, the light intensities for each wavelength for each coordinate position specified by the X and Y coordinates are stored in the storage means 110, as shown on the right side of FIG. 4.

[0025] The calculation means 120 provided in the control means 100 calculates the thickness for each coordinate, as shown in the lower part of Fig. 4, by Fourier transforming the light intensity corresponding to the wavelength stored in the storage means 110. The calculated thickness information for each coordinate is stored in an appropriate memory (not shown) of the control means 100.

[0026] According to the above embodiment, it becomes possible to measure the thickness of a plate-like object (wafer W) at multiple desired coordinate positions depending on the speed of the scanning mirror 3, thereby resolving the problem of not being able to measure the thickness of multiple positions on the wafer W in a short period of time.

[0027] When the thickness measurement device 1 is applied to a grinding device or polishing device (not shown), the thickness of the wafer W can be measured in a short time when the wafer W is ground or polished to a desired thickness, thereby improving the productivity of the grinding and polishing processes. Also, when the device is applied to a laser processing device that irradiates the wafer W with a laser beam having a wavelength that is transparent to the wafer, positioning the focal point inside the wafer to form a modified layer inside the wafer W, the thickness of the wafer at multiple positions along a desired planned dividing line can be measured in a short time, improving productivity.

[0028] In the above-described embodiment, a configuration has been disclosed in which light L1 emitted by a light source 2 is guided to a wavelength switching means 6 that switches between wavelengths with a time difference, light L2 switched by the wavelength switching means 6 with a time difference between wavelengths is irradiated onto a wafer W via a scanning mirror 3 to form reflected light L3, and the intensity of the light for each wavelength projected onto a diffusion film 4 is detected for each wavelength by a detection means 5. However, the present invention is not limited to this, and a thickness measurement device 1' shown in FIG. 5 as another embodiment may also be used. The thickness measurement device 1' will be described with reference to FIG. 5. Note that the same components as those in the thickness measurement device 1 shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0029] The thickness measurement device 1′ shown in FIG. 5 replaces the wavelength switching means 6 of the above-described embodiment with a branching means 8 that branches the light L1 emitted by the light source 2 into light L4 for each wavelength. The branching means 8 is, for example, a transmission diffraction grating. The thickness measurement device 1′ also includes a holding means 20′. The holding means 20′ includes a holding surface 21′ made of a breathable material and connected to a suction means (not shown), and a cylindrical member 22′ including an elevation means (not shown) connected to a control means 100. The control means 100 and the elevation means can adjust the height of the holding surface 21′ to a desired position in the Z-axis direction indicated by the arrow Z in the figure. The light L4 irradiated onto the plate-like object (wafer W) held on the holding surface 21′ becomes reflected light L5 having a light intensity corresponding to the wavelength based on the spectral interference waveform generated by reflection from the front surface Wa and back surface Wb of the wafer W, and is projected onto the surface 4a of the diffusion film 4. The reflected light L5 projected onto the diffusion film 4 is detected for each wavelength by a light detection means 5' disposed on the rear surface 4b side. The light detection means 5' of the thickness measurement device 1' shown in FIG. 5 may be, for example, a line sensor, and the reflected light L5 guided to the line sensor is detected for its light intensity by a plurality of light receiving elements disposed in series in the line sensor. The light intensity signal detected by the light detection means 5' is sent to the control means 100, where the thickness for each coordinate can be calculated by a calculation such as a Fourier transform. The procedure for measuring the thickness of a wafer W using this thickness measurement device 1' will now be described in more detail.

[0030] In the holding means 20' of the thickness measurement device 1' shown in FIG. 5, a wafer W is placed with its front surface Wa facing upward and held by suction on a holding surface 21' positioned at height H0, for example, by the lifting means housed in a cylindrical member 22'. Next, light L1 emitted by the light source 2 is converted into parallel light by a collimating lens 7 and directed to the branching means 8. The light L1 directed to the branching means 8 is branched into light L4 having a dispersed divergence according to wavelength. The light L4 emitted from the branching means 8 is reflected by the reflecting mirror 32 of the scanning mirror 3 and, by operating the driving unit 31 of the scanning mirror 3, is irradiated onto a predetermined measurement position P1, specified by the X and Y coordinates, on the wafer W held by suction on the holding surface 21' of the holding means 20'.

[0031] In the thickness measurement device 1' shown in Figure 5, light L4 is split and dispersed by splitting means 8 into light beams of each wavelength. When light L4 is irradiated onto measurement position P1 on the wafer W and reflected, a spectral interference waveform generated by reflection from the front and back surfaces Wa and Wb of the wafer W becomes reflected light L5, which varies depending on the thickness of the wafer at the irradiated position. When this reflected light L5 is projected onto the front surface 4a of the diffusion film 4, light L4 is projected onto position 41 on the diffusion film 4 with a predetermined width corresponding to the wavelength range of 450 to 900 nm split and dispersed by the splitting means 8. The light intensity corresponding to this width can be detected from the back surface 4b of the diffusion film 4 by light detection means 5'. As a result, the light intensity for each wavelength based on the spectral interference waveform is stored in memory means 110 in correspondence with the X and Y coordinates of measurement position P1, as shown on the right side of Figure 4.

[0032] 5, when the scanning mirror 3 is operated to move the light L4 irradiated from the branching means 8 from the measurement position P1 on the wafer W to another position specified by the X and Y coordinates (for example, measurement position P2 or P3) to measure the thickness, the reflected light L5 reflected at measurement position P2 or P3 when the surface Wa of the wafer W is at height H0 travels a different distance from the scanning mirror 3 to the diffusion film 4 compared to when the light is irradiated at measurement position P1, and the intervals between each wavelength of the reflected light L5 projected onto the surface 4a of the diffusion film 4 change. As a result, the light detecting means 5' cannot accurately detect the spectral interference waveform that forms the light intensity corresponding to the wavelength, and the thickness of the wafer W cannot be accurately calculated. Therefore, in this embodiment, the height of the holding surface 21' of the holding means 20' is moved in the direction indicated by the arrow Z1 or Z2 by operating the above-mentioned lifting means in accordance with the X and Y coordinates of the light L4 positioned on the wafer W by the scanning mirror 3 so that the reference wavelength interval, for example, matches the wavelength interval of the reflected light L5 projected onto the surface 4a of the diffusion film 4 when the height of the surface Wa of the wafer W is positioned at H0 and light L4 is irradiated at the measurement position P1.

[0033] In the thickness measurement device 1' of the above-described embodiment, the height of the holding surface 21' of the holding means 20' is moved in the direction indicated by the arrow Z1 or Z2 in accordance with the X and Y coordinates of the light L4 positioned on the wafer W by the scanning mirror 3, and positioned at the desired position in the Z-axis direction. This prevents the distance from the scanning mirror 3 to the diffusion film 4 from changing, and the intervals for each wavelength of the reflected light L5 projected onto the surface 4a of the diffusion film 4 are constant, making it possible to accurately measure the thickness of the wafer W at any measurement position.

[0034] Like the thickness measurement device 1, the thickness measurement device 1' described above also makes it possible to measure the thickness of a plate-like object (wafer W) at a plurality of desired coordinate positions according to the speed of the scanning mirror 3, thereby solving the problem of not being able to measure the thickness of the wafer W in a short time. Note that, in the thickness measurement device 1' described above, an example has been shown in which the light detection means 5' is configured with a line sensor, but the present invention is not limited to this, and for example, the camera used in the thickness measurement device 1 described above can also be used.

[0035] Even when the thickness measurement device 1' is applied to a grinding device or polishing device (not shown), the thickness of the wafer W can be measured in a short time when the wafer W is ground or polished to a desired thickness, thereby improving the productivity of the grinding and polishing processes. Also, when the device is applied to a laser processing device that irradiates the wafer W with a laser beam having a wavelength that is transparent to the wafer, positioning the focal point inside the wafer W to form a modified layer inside the wafer W, the thickness of the wafer W at multiple positions along a desired planned dividing line can be measured in a short time, improving productivity.

[0036] In the above embodiment, the diffusion film 4 is a transmissive type, and an example is shown in which the light detection means 5 is arranged on the back surface 42 side of the diffusion film 4. However, if the diffusion film 4 is a reflective type, the light detection means 5, 5' can be arranged on the front surface 41 side of the diffusion film 4 to achieve the same function. [Explanation of symbols]

[0037] 1, 1': Thickness measuring device 2:Light source 3: Scanning mirror 31: Drive unit 32: Reflective mirror 4: Diffusion film 5, 5': Light detection means 6: Wavelength switching means 7: Collimating lens 8: Branching means (diffraction grating) 10:Measuring methods 20, 20': Holding means 21, 21': Holding surface 22, 22': cylindrical member 100: Control means 110: Storage means 120: Calculation method L1, L2, L4: light L3, L5: Reflected light W: Wafer

Claims

1. A thickness measurement device for measuring the thickness of a plate-like object, The apparatus includes at least a holding means for holding a plate-like object with a holding surface in the X-axis and Y-axis plane, and a measuring means for measuring the thickness of the plate-like object held by the holding means, The measuring means is a thickness measuring device comprising: a light source having a predetermined wavelength range; a scanning mirror that positions the light emitted from the light source on the plate-like object held by the holding means while changing the coordinates specified by X and Y coordinates; a diffusion film on which reflected light that is reflected from the front and back surfaces of the plate-like object held by the holding means to form a spectral interference waveform is projected at different angles and positions in accordance with the operation of the scanning mirror; a light detection means that detects the intensity of light corresponding to the wavelength of the spectral interference waveform projected onto the diffusion film; a memory means that stores the light intensity corresponding to the wavelength detected by the light detection means for each coordinate; and a calculation means that performs a Fourier transform on the light intensity corresponding to the wavelength stored in the memory means to calculate the thickness for each coordinate.

2. 2. The thickness measurement device according to claim 1, further comprising a wavelength switching means for switching the light emitted by the light source for each wavelength with a time difference, the light detection means for detecting the intensity of the light for each wavelength projected onto the diffusion film, and the storage means for storing the light intensity for each wavelength corresponding to the coordinates.

3. 2. The thickness measurement device according to claim 1, further comprising a branching means for branching the light emitted by the light source into light beams of different wavelengths, the light detection means detecting the intensity of the light beams of different wavelengths projected onto the diffusion film, and the storage means storing the intensity of the light beams of different wavelengths in correspondence with the coordinates.

4. 4. The thickness measuring device according to claim 1, wherein the light source is a broadband light source or a multi-wavelength light source.

5. 3. The thickness measurement device according to claim 2, wherein when a wavelength switching means for switching the light emitted by the light source for each wavelength with a time difference is provided, the light detection means is one of a camera, a line sensor, a PD, and a PMT.

6. 4. The thickness measuring device according to claim 3, wherein when a branching means for branching the light emitted by the light source into light beams of different wavelengths is provided, either a camera or a line sensor is used as the light detecting means.

7. 4. The thickness measurement device according to claim 3, wherein when the device is provided with a branching means for branching the light emitted by the light source into wavelengths, the holding means is provided with a Z-axis moving means for moving in a Z-axis direction perpendicular to the X-axis and Y-axis, and the holding means is positioned in the Z-axis direction in accordance with the X-coordinate and Y-coordinate of the light positioned on the plate-like object by the scanning mirror so that the intervals for each wavelength projected onto the diffusion film are constant.

8. 2. The thickness measuring device according to claim 1, wherein when the diffusion film is a transmissive type, the light detecting means is disposed on the back side of the diffusion film, and when the diffusion film is a reflective type, the light detecting means is disposed on the front side of the diffusion film.

9. A thickness measuring device for measuring the thickness of a plate-like object, The apparatus includes at least a holding means for holding a plate-like object with a holding surface in the X-axis and Y-axis plane, and a measuring means for measuring the thickness of the plate-like object held by the holding means, the measuring means includes a light source having a predetermined wavelength range, a scanning mirror that positions the light emitted from the light source at coordinates specified by X and Y coordinates on the plate-like object held by the holding means, a diffusion film that projects reflected light that is reflected from the front and back surfaces of the plate-like object held by the holding means and forms a spectral interference waveform, a light detecting means that detects the intensity of light corresponding to the wavelength of the spectral interference waveform projected onto the diffusion film, a memory means that stores the light intensity corresponding to the wavelength detected by the light detecting means for each coordinate, and a calculation means that calculates the thickness for each coordinate by performing a Fourier transform on the light intensity corresponding to the wavelength stored in the memory means, a branching means for branching the light emitted by the light source into light beams of different wavelengths, the light detecting means detecting the intensity of the light beams of different wavelengths projected onto the diffusion film, and the storage means storing the intensity of the light beams of different wavelengths in correspondence with coordinates; When the light source is provided with a branching means for branching the light emitted by the light source into wavelengths, the holding means is provided with a Z-axis moving means for moving in the Z-axis direction perpendicular to the X-axis and Y-axis, and the holding means is positioned in the Z-axis direction in accordance with the X-coordinate and Y-coordinate of the light positioned on the plate-like object by the scanning mirror so that the intervals for each wavelength projected onto the diffusion film are constant.

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