Measuring equipment

Abstract

To provide a measuring device that can measure a thickness or a height of a plate-like material in a short time.SOLUTION: A measuring device includes holding means 3 that holds a plate-like material 10, and measuring means 6 that measures a thickness or a height of the plate-like material 10 held on the holding means 3. The measuring means 6 includes a light source 62 in a predetermined wavelength region, a condenser lens 61a that irradiates the plate-like material 10 held on the holding means 3 with light L1 emitted by the light source 62, a collimator lens 66 that generates parallel light from return light L2 reflected on the plate-like material 10, a transmission filter 67 that transmits interference light W of the return light L2 from which the parallel light is generated, a sensor 68 that has coordinates to receive the interference light W transmitting through the transmission filter 67 and detect light intensity Q, and control means that determines coordinate positions S1-S4 with the high light intensity Q detected by the sensor 68 as the thickness or the height of the plate-like material 10.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a measuring device for measuring the thickness or height 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 of the wafer is ground and thinned using a grinding machine, 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] If a contact type measuring means is used for the above-mentioned grinding device, in which the blower is brought into contact with the grinding surface of the wafer to measure the thickness of the wafer, this may cause scratches on the grinding surface. Therefore, in recent years, non-contact type measuring means have been adopted that measure the thickness using the spectral interference waveform of light reflected from the grinding surface (top surface) of the wafer and light that passes through the wafer and is reflected from the reflecting surface (bottom surface) (see, for example, Patent Document 1).

[0005] Furthermore, even 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 focal point is positioned at a certain depth from the top surface, and in order to accurately measure the thickness or height of the wafer, a non-contact type measuring means is used that measures the thickness using the spectral interference waveform of light reflected from the top surface of the wafer and light that has passed through the wafer and reflected from the bottom surface, as described above (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-021916 [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 non-contact type measuring means employed in the technologies described in the above Patent Documents 1 and 2 is configured to irradiate light onto the wafer, disperse the returning light reflected by the upper and lower surfaces of the wafer using a diffraction grating to obtain a spectral interference waveform, and then calculate (Fourier transform) the light intensity for each wavelength to detect the thickness or height of the wafer, which has the problem that the thickness of a desired region of the wafer cannot be measured in a short time.

[0008] The present invention has been made in view of the above-mentioned circumstances, and its main technical object is to provide a measuring device that can measure the thickness or height of a plate-like object in a short 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 measuring device for measuring the thickness or height of a plate-like object, comprising: Applicable A holding means for holding a plate-like object, and a plate-like object held by the holding means. Applicable and a measuring means for measuring the thickness or height of the plate-like object, the measuring means including a light source of a predetermined wavelength range and a measuring means for measuring the thickness or height of the plate-like object held by the holding means. Applicable a condenser lens for irradiating the plate-like object; Applicable A collimating lens converts the return light reflected by the plate-like object into parallel light, and a lens that transmits the interference light of the return light converted into parallel light. The optical element is configured by a transmission film designed and manufactured so that the position of transmission changes according to the interference light that changes in accordance with the thickness of the plate-like object. A transmission filter is used, and the light intensity is detected by receiving the interference light transmitted through the transmission filter. At the same time, the peak of the light intensity is detected. coordinate Locatable a sensor and a light intensity detected by the sensor A peak appearsand a control means for setting the coordinate position to the thickness or height of the plate-like object.

[0010] It is preferable that the light emitted from the light source is guided to the condenser lens by a first optical fiber, and the returned light is guided to the collimator lens by a second optical fiber, with the first optical fiber and the second optical fiber being connected by an optical circulator. It is also preferable that the thickness of the plate-like object is measured using interference light between the returned light reflected on the upper surface of the plate-like object and the returned light reflected on the lower surface of the plate-like object. Furthermore, it is also possible to measure the height of the upper surface of the plate-like object using interference light between a reference light having a specified optical path length and the returned light reflected on the upper surface of the plate-like object, measure the height of the lower surface of the plate-like object using interference light between the reference light and the returned light reflected on the lower surface of the plate-like object, and measure the thickness of the plate-like object based on the difference between the height of the upper surface and the height of the lower surface of the plate-like object. [Effects of the Invention]

[0011] The measuring device of the present invention includes a holding means for holding a plate-like object, and a measuring device for measuring a plate-like object held by the holding means. Applicable and a measuring means for measuring the thickness or height of the plate-like object, the measuring means including a light source of a predetermined wavelength range and a measuring means for measuring the thickness or height of the plate-like object held by the holding means. Applicable a condenser lens for irradiating the plate-like object; Applicable A collimating lens converts the return light reflected by the plate-like object into parallel light, and a lens that transmits the interference light of the return light converted into parallel light. The optical element is configured by a transmission film designed and manufactured so that the position of transmission changes according to the interference light that changes in accordance with the thickness of the plate-like object. A transmission filter is used, and the light intensity is detected by receiving the interference light transmitted through the transmission filter. At the same time, the peak of the light intensity is detected. coordinate Locatable a sensor and a light intensity detected by the sensor A peak appears Since the device is configured to include a control means for converting the coordinate position into the thickness or height of the plate-like object, there is no need to separate the returned light using a diffraction grating and calculate the light intensity for each wavelength (Fourier transform, etc.) in order to measure the thickness of the plate-like object, and the thickness of the plate-like object can be measured in a short time. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 2 is an overall perspective view of the measuring device. [Figure 2] FIG. 2 is a perspective view of a wafer that is an object to be measured. [Figure 3] 2 is a block diagram showing an optical system of a measuring means attached to the measuring device of FIG. 1. FIG. [Figure 4] FIG. 4 is a conceptual diagram showing the functions of the transmission filter and sensor of the measuring means in FIG. 3. [Figure 5] FIG. 4 is a block diagram showing another embodiment of the measuring means shown in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a measuring device configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0014] 1 shows an overall perspective view of a measurement device 2 of this embodiment. The measurement device 2 includes at least a holding means 3 that holds a plate-like object (wafer 10) to be measured, which is disposed on a base 2a, and a measurement means 6 that measures the thickness of the wafer 10 held by the holding means 3. The measurement device 2 of this embodiment also includes a moving means 4 that moves the holding means 3 in the X-axis and Y-axis directions, and a frame 5 that includes a vertical wall 5a erected on the side of the moving means 4 and a horizontal wall 5b that extends horizontally from the upper end of the vertical wall 5a. An optical system (described in detail later) of the measurement device 6 is housed inside the horizontal wall 5b.

[0015] 1, the holding means 3 includes a rectangular X-axis direction movable plate 31 mounted on the base 2a so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 32 mounted on the X-axis direction movable plate 31 so as to be movable in the Y-axis direction, a cylindrical support column 33 fixed to the upper surface of the Y-axis direction movable plate 32, and a rectangular cover plate 34 fixed to the upper end of the support column 33. A chuck table 35 extending upward through an elongated hole formed in the cover plate 34 is disposed on the cover plate 34. The chuck table 35 is a means for holding the wafer 10 using an XY plane specified by the X and Y coordinates as a holding surface, and is configured to be rotatable by a rotation drive means (not shown) housed in the support column 33. The holding surface of the chuck table 35 is configured as an adsorption chuck 36 made of a porous material having air permeability. The suction chuck 36 is connected to a suction means (not shown) by a flow path passing through the support 33, and four clamps 37 are arranged at equal intervals around the suction chuck 36 to grip an annular frame F when holding the wafer 10 (described later) on the chuck table 35.

[0016] The moving means 4 includes an X-axis moving means 4a that moves the chuck table 35 in the X-axis direction and a Y-axis moving means 4b that moves the chuck table 35 in the Y-axis direction. The X-axis moving means 4a converts the rotational motion of the motor 42a into linear motion via a ball screw 42b and transmits the linear motion to the X-axis movable plate 31, moving the X-axis movable plate 31 in the X-axis direction along a pair of guide rails 2b, 2b arranged on the base 2a along the X-axis direction. The Y-axis moving means 4b converts the rotational motion of the motor 44a into linear motion via a ball screw 44b and transmits the linear motion to the Y-axis movable plate 32, moving the Y-axis movable plate 32 in the Y-axis direction along a pair of guide rails 31a, 31a arranged on the X-axis movable plate 31 along the Y-axis direction.

[0017] 2 shows a wafer 10, which is a plate-like object whose thickness is measured by the measuring means 6 of this embodiment. The wafer 10 is, for example, a sapphire (Al2O3) substrate having a plurality of devices 12 formed on a surface 10a and partitioned by planned division lines 14. The devices 12 are, for example, optical devices such as LEDs.

[0018] 3 is a block diagram showing an outline of the optical system of the measuring means 6 of this embodiment. The measuring means 6 includes a light source 62 that irradiates light L1 in a predetermined wide wavelength range, a condenser 61 equipped with a condenser lens 61a that irradiates the light L1 emitted by the light source 62 onto the wafer 10 held on the chuck table 35 of the holding means 3, a collimating lens 66 that converts return light L2 reflected by the wafer 10 and traveling backward into parallel light, a transmission filter 67 that transmits interference light W that constitutes the return light L2 converted into parallel light, and a sensor 68 equipped with a coordinate that receives the interference light W that has transmitted through the transmission filter 67 and detects light intensity Q. The control means 100 measures the coordinate position where the light intensity Q detected by the sensor 68 is high as the thickness (or height) of the wafer 10 and displays the measurement result on the display means 7.

[0019] The light source 62 can be, for example, a light source capable of emitting light L1 having a wavelength in the 1280 to 1360 nm range, and can be selected from, for example, an LED, an SLD (Superluminescent diode), an SC (SuperContinuum) light source, and the like.

[0020] The transmission filter 67 is a so-called gray-scale conversion filter, known as a frequency filter utilizing Fourier transform. The transmission filter 67 transmits the interference light W constituting the return light L2. As shown in FIG. 4, the transmission filter 67 is configured with a transmission film designed and manufactured so that the transmission position changes depending on the interference light W1 to W4, which changes depending on the thickness of the wafer 10. More specifically, for example, as can be seen from the figure, when the thickness of the wafer 10 is 100 μm, the return light L2 reflected on the upper and lower surfaces of the wafer 10 is composed of interference light W1, which is transmitted effectively only through position 67a of the transmission filter 67 and is hardly transmitted at other positions. Furthermore, when the thickness of the wafer 10 is 300 μm, the interference light W2 constituting the return light L2 is transmitted effectively only through position 67b of the transmission filter 67 and is hardly transmitted at other positions. Similarly, when the thickness of the wafer 10 is 500 μm, the interference light W3 constituting the return light L2 is transmitted only through position 67c of the transmission filter 67 with good transmission, and is hardly transmitted through other positions. Furthermore, when the thickness of the wafer 10 is 700 μm, the interference light W4 constituting the return light L2 is transmitted only through position 67d of the transmission filter 67 with good transmission, and is hardly transmitted through other positions. Note that in the embodiment shown in FIGS. 3 and 4, the return light L2 is composed of the interference light W3 (shown by a solid line), and the interference lights W1, W2, and W4 are shown by dashed lines. Furthermore, for convenience of explanation, the embodiment of FIG. 4 shows only an example in which four types of interference light W1 to W4 are transmitted through corresponding positions 67a to 67d of the transmission filter 67. However, an actual transmission filter 67 is designed and manufactured so that the transmission positions change corresponding to the respective interference lights W formed when the thickness of the wafer 10 varies between 100 μm and 800 μm, for example.

[0021] Here, the sensor 68 detects any one of the interference lights W1 to W4 that has passed through the transmission filter 67, and peaks S1 to S4 with high light intensity Q appear at coordinate positions corresponding to the detected interference lights W1 to W4. As described above, the coordinate positions of the peaks S1 to S4 detected by the sensor 68 are stored in the control means 100 so as to correspond to the thickness (or height) of the wafer 10, and therefore, as shown on the display means 7, the thickness of the wafer 10 can be measured based on the coordinate positions 68a to 68d at which the peaks S1 to S4 appear.

[0022] When measuring the thickness of the wafer 10 using the measuring means 6 of the above-described embodiment, the wafer 10 shown in FIG. 2 is placed on the chuck table 35 and held by suction. Next, the moving means 4 is operated to position the wafer 10 directly below the condenser 61. Note that before positioning the wafer 10 directly below the condenser 61, an image of the position to be measured on the wafer 10 (e.g., measurement position P on the planned dividing line 14) may be captured by an imaging means (not shown), and measurement position information may be stored in the control means 100. Based on the measurement position information, the wafer 10 may be positioned directly below the condenser 61. In this embodiment, light L1 emitted by the light source 62 is guided to the condensing lens 61a of the condenser 61 by the first optical fiber 63 and irradiated onto the measurement position P on the wafer 10. Light L1 irradiated onto the wafer 10 is reflected by the upper surface (front surface 10a) and the lower surface (back surface 10b) of the wafer 10. The reflected return light L2 passes through a first optical fiber 63, is guided by an optical circulator 65 to a second optical fiber 64, reaches a collimating lens 66, and is irradiated onto a transmission filter 67. As described with reference to FIGS. 3 and 4, if the return light L2 is composed of interference light W3, the interference light W3 will be transmitted well through position 67c of the transmission filter 67 and will be barely transmitted at other positions. This will cause a peak S3 with a high light intensity Q to appear at coordinate position 68c of the sensor 68 corresponding to position 67c. The thickness (500 μm) corresponding to coordinate position 68c where peak S3 was detected is measured. The thickness (500 μm) measured in this manner is stored in the control means 100 in association with the XY coordinates that identify the measurement position P. After measuring the thickness at the measurement position P, the moving means 4 is operated as necessary to move the measurement position P on the wafer 10, and thicknesses at other positions are also measured as appropriate and stored in the control means 100.

[0023] According to the above-described embodiment, it is not necessary to measure the thickness of a plate-like object by separating the return light L2 using a diffraction grating and performing a Fourier transform on the light intensity for each wavelength, as in the prior art, and the thickness of the plate-like object can be measured in a short time. Furthermore, since the thickness of a plate-like object can be easily and efficiently measured as described above, the efficiency of laser processing and grinding processing can also be improved.

[0024] The present invention is not limited to the above-described embodiment of the measuring device 1. Fig. 5 shows a measuring device 6', which is another embodiment of the measuring device 6 disposed in the above-described measuring device 1. Note that the measuring device 6 and the measuring device 6' have roughly the same configuration, and the same members are assigned the same numbers, and newly added members are assigned new numbers.

[0025] The measuring means 6' in the illustrated embodiment includes a light source 62 similar to that of the measuring means 6, and light L1 emitted by the light source 62 is guided to a condenser lens 61a through a first optical fiber 63, and returned light L2 is guided to a collimator lens 66 through a second optical fiber 64. The first optical fiber 63 and the second optical fiber 64 are connected to an optical circulator 65'. The optical circulator 65' in this embodiment branches the light L1 into an optical path 81 that is different from the first optical fiber 63 and the second optical fiber 64. The light L1 guided to the optical path 81 has its optical path changed by a reflecting mirror 69 and is guided to a reflecting mirror 61b fixed to the condenser 61. The returned light L3 reflected by the reflecting mirror 61b is guided to the second optical fiber 64 by the optical circulator 65' and is irradiated onto a transmission filter 67 via a collimator lens 66 together with the returned light L2. As can be seen from the figure, the optical path length from the optical circulator 65' to the reflecting mirror 61b is a specific value that is not affected by the thickness of the wafer 10 and does not change regardless of the position of the collector 61, and the return light L3 reflected by the reflecting mirror 61b and traveling backward will be referred to as reference light L3 hereinafter. The optical path length from the optical circulator 65' to the reflecting mirror 61b is set shorter than the optical path length from the optical circulator 65' to the surface of the suction chuck 36 of the chuck table 35, and in this embodiment, it is set to be shorter by, for example, 1000 μm than the optical path length from the optical circulator 65' to the surface of the suction chuck 36 of the chuck table 35.

[0026] In the measurement means 6′, light L1 emitted by a light source 62 is guided to a condenser lens 61a by a first optical fiber 63, and is also branched in an optical circulator 65′ and guided to a reflecting mirror 61b via a reflecting mirror 69. The light L1 is irradiated onto the wafer 10 via the condenser lens 61a, and return light L2 including light reflected from the front surface 10a and the back surface 10b and reference light L3 reflected by the reflecting mirror 61b form return light L2+L3, which passes through the optical circulator 65′, a second optical fiber 64, and a collimating lens 66 and is then irradiated onto a transmission filter 67.

[0027] As described above, the transmission filter 67 is a filter that transmits the interference light constituting the return light L2+L3 and is set so that the position through which it transmits changes in accordance with the interference light that changes in accordance with the thickness and height of the wafer 10. The sensor 68 can identify the coordinate position at which a high peak of the light intensity Q that is transmitted through the transmission filter 67 and irradiated appears. The control means 100 measures the heights of the upper surface (front surface 10a) and lower surface (back surface 10b) of the wafer 10 and the thickness of the wafer 10 based on the coordinate positions. More specifically, as shown in FIG. 5 , interference light W5 between the reference light L3 contained in the return light L2+L3 and the return light reflected by the front surface 10a of the wafer 10 passes through a predetermined position 67e of the transmission filter 67 and causes a peak S5 with a high light intensity Q to appear at a coordinate position 68e of the sensor 68. Based on the coordinate position 68e at which the peak S5 is detected, the height of the front surface 10a of the wafer 10 is measured to be 450 μm. At the same time, interference light W6 between the reference light L3 and return light reflected by the back surface 10b of the wafer 10 passes through a predetermined position 67f of the transmission filter 67, causing a peak S6 with high light intensity Q to appear at a coordinate position 68f of the sensor 68, and based on the coordinate position 68f where the peak S6 is detected, the height of the back surface 10b of the wafer 10 is measured to be 800 μm. Note that the above height is based on the optical path length of the reference light L3 and is the difference between the optical path length of the reference light L3 and the optical path length from the optical circulator 65′ to the front surface 10a, and the difference between the optical path length of the reference light L3 and the optical path length from the optical circulator 65′ to the back surface 10b. Since the optical path length from the optical circulator 65' to the reflecting mirror 61b is set to be 1000 μm shorter than the optical path length from the optical circulator 65' to the surface of the suction chuck 36 of the chuck table 35, the height value of the front surface 10a of the wafer 10 (450 μm) is smaller than the height value of the back surface 10b (800 μm).

[0028] In the above embodiment, the height value (450 μm) of the front surface 10a of the wafer 10 and the height value (800 μm) of the back surface 10b are measured, and the thickness of the wafer 10 at the measurement position P is calculated by calculating the difference between these values ​​(350 μm). As described above, the returned light L2 includes light reflected from the front surface 10a and the back surface 10b of the wafer 10, and the interference light W7 constituting the reflected light passes through a predetermined position 67g of the transmission filter 67, so that a peak S7 with a high light intensity Q is detected at a coordinate position 68g of the sensor 68. Then, by referring to the table stored in the control means 100 described above, the thickness corresponding to the coordinate position 68g where the peak S7 was detected is measured to be 350 μm. In the above embodiment, the light L1 is described as passing through the wafer 10. However, by using a configuration such as the measuring means 6', which measures the difference in the optical path length between the reference light L3, whose optical path length is specified, and the reflected light reflected by the wafer 10, it is possible to accurately measure the height of the surface 10a of the wafer 10 even if the wafer 10 does not pass through the light L1.

[0029] According to the above-described measuring means 6', the height can be easily measured based on the difference in the optical path length between the reference light L3 and the return light L2 reflected by the wafer 10 using the reference light L3 with a specified optical path length, and therefore the height and thickness of the wafer 10 can be measured in a short time without dispersing the light with a diffraction grating and calculating the light intensity for each wavelength (Fourier transform).

[0030] In the above embodiment, the measuring device 2 has been described as a device that solely measures the thickness or height of a wafer, but the present invention is not limited to this and may be disposed in a processing device that processes a plate-like object, for example, in a laser processing device that positions the focal point of a laser beam having a wavelength that is transparent to the plate-like object inside and irradiates it, forming a modified layer inside and using it as the starting point for division. [Explanation of symbols]

[0031] 2: Measuring equipment 2a: Base 3: Holding means 31:X-axis movable plate 32: Y-axis direction movable plate 33: Prop 34: Cover material 35: Chuck table 36: Vacuum chuck 4. Transportation 4a:X-axis movement means 4b: Y-axis movement means 5:Frame body 6, 6': Measurement means 62: Light source 61: Concentrator 61a: Condenser lens 61b: Reflective mirror 62: Light source 63: First Optical Fiber 64: Second optical fiber 65, 65': Optical circulator 66: Collimating lens 67:Transmission filter 67a~67d:Position 68: Sensor 68a~68d: Coordinate position 69: Reflective mirror 7:Display means 10: Wafer 12: Device 14: Planned division line 81: Light path L1: light L2: Return light Q: Light intensity W, W1 to W7: Interference light S1 to S7: Light intensity peaks

Claims

1. A measuring device for measuring the thickness or height of a plate-like object, holding means for holding the plate-like object; and measuring means for measuring the thickness or height of the plate-like object held by the holding means, the measuring means comprises a light source of a predetermined wavelength range, a condenser lens that irradiates the light emitted by the light source onto the plate-like object held by the holding means, a collimator lens that converts the return light reflected by the plate-like object into parallel light, a transmission filter that transmits the interference light of the return light that has been converted into parallel light and is composed of a transmission film designed and manufactured so that the transmission position changes in accordance with the interference light that changes in accordance with the thickness of the plate-like object, a sensor that receives the interference light that has transmitted through the transmission filter, detects the light intensity, and is capable of identifying the coordinate position where the peak of the light intensity is detected, and control means that determines the coordinate position where the peak of the light intensity detected by the sensor appears as the thickness or height of the plate-like object; A measuring device comprising:

2. 2. The measurement device according to claim 1, wherein the light emitted by the light source is guided to the focusing lens by a first optical fiber, and the returning light is guided to the collimating lens by a second optical fiber, and the first optical fiber and the second optical fiber are connected by an optical circulator.

3. 3. The measuring device according to claim 1, wherein the thickness of the plate-like object is measured by interference light between return light reflected from the upper surface of the plate-like object and return light reflected from the lower surface of the plate-like object.

4. 3. The measuring device according to claim 1 or 2, wherein the height of the upper surface of the plate-like object is measured using interference light between a reference light having a specified optical path length and return light reflected from the upper surface of the plate-like object, the height of the lower surface of the plate-like object is measured using interference light between the reference light and return light reflected from the lower surface of the plate-like object, and the thickness of the plate-like object is measured from the difference between the height of the upper surface and the height of the lower surface of the plate-like object.

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