Inspection device

Abstract

To provide an inspection device capable of detecting presence or absence of a modified layer formed in a wafer by an inexpensive device configuration by avoiding enlargement of a diameter of a condensing lens to be used.SOLUTION: An inspection device includes: a table 35 for supporting an object W to be inspected; light irradiation means 6 for irradiating the object W to be inspected supported by the table 35 with light; and light receiving means 7 for receiving reflected light reflected from the object W to be inspected. The receiving means 7 includes: a camera 71; and a diffusion plate 72 arranged between the object W to be inspected and the camera 71.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inspection apparatus for inspecting a test object.

Background Art

[0002] A wafer on which a plurality of devices such as ICs and LSIs are formed on a surface partitioned by a planned division line is irradiated by positioning a condensing point of a laser beam having a wavelength that is transmissive to the wafer inside from the back surface of the wafer corresponding to the planned division line, and a modified layer is formed along the planned division line. Then, for example, the back surface of the wafer is ground and thinned, and an external force is applied to divide the wafer into individual device chips, which are used in electrical devices such as mobile phones and personal computers (see, for example, Patent Documents 1 and 2).

[0003] By the way, if the above-mentioned modified layer is not properly formed inside the planned division line, the wafer cannot be divided into individual device chips, and there is a problem of damaging the wafer. Therefore, by utilizing the phenomenon that unevenness occurs on the back surface side of the wafer due to the modified layer, light is irradiated onto the back surface of the wafer, reflected, and projected, and a method for detecting the presence or absence of the modified layer based on the principle of a so-called magic mirror and an inspection apparatus suitable therefor have been proposed by the present applicant (see Patent Document 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method of detecting the presence or absence of a modified layer by the technique described in Patent Document 3 above, as the diameter of the wafer increases, it is necessary to increase the diameter of the condenser lens that condenses the light reflected from the wafer onto the imaging lens, which results in a problem of increased cost. Furthermore, since the contrast of the projected modified layer is not clear, as the devices formed on the wafer become smaller and the modified layer formed on the dicing planned line becomes finer, it becomes difficult to accurately determine the presence or absence of the modified layer.

[0006] The present invention has been made in view of the above facts, and its main technical problem is to provide an inspection apparatus that can detect the presence or absence of a modified layer formed on a wafer with an inexpensive device configuration by avoiding an increase in the diameter of the condenser lens to be used.

Means for Solving the Problems

[0007] In order to solve the above main technical problem, according to the present invention, there is provided an inspection apparatus for inspecting an object to be inspected, including a table for supporting the object to be inspected, a light irradiation means for irradiating light onto the object to be inspected supported by the table, and a light receiving means for receiving the reflected light reflected from the object to be inspected. The light receiving means includes a camera and a diffusion plate disposed between the object to be inspected and the camera. The object to be inspected is a wafer on which minute irregularities are formed on the surface due to a modified layer formed inside. The light irradiated by the light irradiation means is light having a wavelength corresponding to the shape and dimensions of the irregularities formed on the surface due to the modified layer formed on the wafer. Based on the irregularity shape due to the modified layer formed on the surface of the object to be inspected imaged by the camera via the diffuser plate, the presence or absence of the modified layer formed inside the wafer is inspected. An inspection apparatus is provided.

[0008] The light irradiation means includes a white light source, a diffraction grating for splitting the white light emitted by the white light source, and a light selection means for selecting light of a specific wavelength from the light of a plurality of wavelengths split by the diffraction grating, and it is preferable to irradiate the object to be inspected with the light of the selected specific wavelength. Also, the light selection means can select the light of a plurality of wavelengths split by the diffraction grating by means of a pinhole mask.

[0009] The optical sorting means preferably includes a first condenser mirror that reflects light of a plurality of wavelengths spectrally dispersed by the diffraction grating, a second condenser mirror that has the same focal length as the first condenser mirror and is disposed at a point-symmetric position with the center of symmetry being the focus, an optical path conversion mirror that is positioned at the focus of the second condenser mirror and converts the optical path, and the pinhole mask that sorts light of a plurality of wavelengths whose optical path has been converted by the optical path conversion mirror. Further, it is preferable to provide a third condenser mirror between the optical path conversion mirror and the pinhole mask so that the focus of the third condenser mirror is positioned on the pinhole mask. Also, the white light source can be selected from any of an SLD light source, an ASE light source, an LED light source, a supercontinuum light source, a halogen light source, a xenon light source, a mercury light source, and a metal halide light source.

Effects of the Invention

[0010] The inspection apparatus of the present invention is an inspection apparatus for inspecting an object to be inspected, including a table that supports the object to be inspected, a light irradiation means that irradiates light onto the object to be inspected supported by the table, and a light receiving means that receives reflected light reflected from the object to be inspected. The light receiving means includes a camera and a diffuser disposed between the object to be inspected and the camera. The object to be inspected is a wafer on which minute irregularities are formed on the surface due to a modified layer formed inside. The light irradiated by the light irradiation means is light having a wavelength corresponding to the shape and dimensions of the irregularities formed on the surface due to the modified layer formed on the wafer. Based on the irregularity shape due to the modified layer formed on the surface of the object to be inspected imaged by the camera via the diffuser plate, the presence or absence of the modified layer formed inside the wafer is inspected. Therefore, by appropriately diffusing the reflected light on the diffuser, minute unevenness formed on the surface due to a modified layer formed inside the workpiece can be captured by the camera, avoiding an increase in the diameter of the condenser lens and configuring the inspection apparatus at low cost. Also, by splitting white light with a diffraction grating and irradiating the object to be inspected with light of a specific wavelength, the contrast can be clarified with light of a wavelength suitable for the object to be inspected, and a modified layer or the like can be surely detected.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of an inspection apparatus configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0013] FIG. 1 shows an overall perspective view of an inspection apparatus 1 of the present embodiment. The inspection apparatus 1 includes at least a table 35 that supports an object to be inspected, a light irradiation means 6 that irradiates light onto the object to be inspected supported by the table 35, and a light receiving means 7 that receives reflected light reflected from the object to be inspected.

[0014] The table 35 of the inspection apparatus 1 of this embodiment forms part of the holding means 3. The inspection apparatus 1 includes a base 2, and the holding means 3 includes a pair of guide rails 2a, 2a arranged in parallel along the X-axis direction on the base 2, and a rectangular X-axis direction movable plate 31 movably mounted thereon, and a rectangular Y-axis direction movable plate 32 movably mounted on the X-axis direction movable plate 31 along the guide rails 36, 36 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. The table 35 in the holding means 3 is a circular member extending upward through a long hole formed in the cover plate 34 and is configured to be rotatable by a rotation driving means (not shown). The table 35 is formed of a porous material having air permeability and has a holding surface 35a defined in the X-axis direction and the Y-axis direction. The holding surface 35a is connected to a suction means (not shown) by a flow path passing through the support column 33. The X-axis direction is the direction indicated by the arrow X in FIG. 1, and the Y-axis direction is the direction indicated by the arrow Y and is a direction orthogonal to the X-axis direction. The plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

[0015] On the back side of the holding means 3 on the base 2, a frame body 5 is erected which includes a vertical wall portion 5a extending upward from the upper surface of the base 2 and a horizontal wall portion 5b extending substantially horizontally. The optical systems of the light irradiation means 6 and the light receiving means 7 are accommodated in the horizontal wall portion 5b of the frame body 5. On the lower surface of the tip of the horizontal wall portion 5b of the frame body 5, a light irradiation portion 6a of the light irradiation means 6 and a light receiving portion 7a of the light receiving means 7 are arranged side by side in the X-axis direction. As shown in FIG. 2, the light irradiation portion 6a and the light receiving portion 7a are arranged so as to face each other while being inclined in the X-axis direction. In FIG. 2, for the sake of explanation, the inside of the light receiving means 7 is shown through. The light L irradiated from the light irradiation portion 6a is irradiated so that the incident angle with respect to the vertical axis P on the back surface of the object to be inspected, for example, a wafer W in which a modified layer is formed in advance along the planned division line, at a predetermined height is θ1, and the light receiving portion 7a is arranged to receive the reflected light at a reflection angle θ2 (=θ1) at which the light L is irradiated on the wafer W and reflected. As shown in the figure, the light receiving means 7 includes a camera 71 that receives the reflected light reflected on the wafer W of the object to be inspected, and a diffusion plate 72 disposed between the workpiece (wafer W) on the table 35 and the camera 71. As the diffusion plate 72, for example, frosted glass or a frosted sheet or the like is adopted. As the frosted glass, for example, ground glass that forms fine irregularities on the surface of the glass by sandblasting or the like to diffuse light is preferable, and as the frosted sheet, a resin sheet having a surface processed according to the ground glass is preferable.

[0016] The above-described table 35 is moved by the moving means 4. The moving means 4 includes an X-axis moving means 42 that relatively moves the table 35 of the holding means 3, the light irradiation means 6, and the light receiving means 7 in the X-axis direction, and a Y-axis moving means 44 that relatively moves the table 35 of the holding means 3, the light irradiation means 6, and the light receiving means 7 in the Y-axis direction.

[0017] The X-axis moving means 42 includes a motor 42a disposed on the base 2 and a ball screw 42b connected to the motor 42a and extending in the X-axis direction. The nut portion (not shown) of the ball screw 42b is fixed to the lower surface of the X-axis movable plate 31. Then, the X-axis moving means 42 converts the rotational motion of the motor 42a into a linear motion by the ball screw 42b and transmits it to the X-axis movable plate 31, and advances and retreats the X-axis movable plate 31 in the X-axis direction along the guide rails 2a, 2a on the base 2.

[0018] The Y-axis moving means 44 includes a ball screw 44b extending in the Y-axis direction on the X-axis movable plate 31 and a motor 44a connected to one end of the ball screw 44b. The nut portion of the ball screw 44b is formed on the lower surface of the Y-axis movable plate 32 (not shown). Then, the Y-axis moving means 44 converts the rotational motion of the motor 44a into a linear motion by the ball screw 44b and transmits it to the Y-axis movable plate 32, and advances and retreats the Y-axis movable plate 32 in the Y-axis direction along the guide rails 36, 36 on the X-axis movable plate 31.

[0019] Each operating part including the X-axis moving means 42, the Y-axis moving means 44, etc. of the inspection device 1, and the above camera 71 are connected to the control means 10 of the inspection device 1. Further, a display means 8 is connected to the control means 10. The image captured by the camera 71 is sent to the display means 8 via the control means 10 and displayed.

[0020] By the way, the light irradiation means 6 suitable for the present invention can adopt various forms. With reference to FIG. 3, the light irradiation means 6A adopted as the first embodiment will be described.

[0021] The light irradiation means 6A includes a white light source 61, a step motor 62, a diffraction grating 63 driven by the step motor, a pinhole mask 64 having a pinhole H, and a reflection mirror 65 that reflects the light passing through the pinhole H of the pinhole mask 64 to change the optical path. The light reflected by the reflection mirror 65 is irradiated from the light irradiation unit 6a. The white light source 61 is a light source that irradiates light L0 in which light having a wavelength (for example, 400 nm to 800 nm) called visible light is substantially evenly mixed. For example, it is preferably any one of an SLD light source, an ASE light source, an LED light source, a supercontinuum light source, a halogen light source, a xenon light source, a mercury light source, and a metal halide light source. The white light L0 irradiated from the white light source 61 is adjusted to parallel light and irradiated.

[0022] The diffraction grating 63 diffracts the irradiated white light L0 and disperses it with an angle for each wavelength. More specifically, as shown in FIG. 3, the white light L0 irradiated from the white light source 61 is dispersed by the diffraction grating 63 into blue light Lb with a short wavelength, green light Lg with a wavelength longer than that of the blue light Lb, and red light Lr with a wavelength even longer than that of the green light Lg and irradiated. In FIG. 3, for convenience of explanation, the white light L0 is shown to be dispersed into three lights, i.e., blue light Lb, green light Lg, and red light Lr. However, as described above, the white light L0 contains light of all wavelengths included in visible light evenly mixed, and actually, it is dispersed into a plurality of finer colors (such as purple, light blue, yellow, orange, etc.).

[0023] The above-described step motor 62 functions as a rotating means for rotating the diffraction grating 63. By operating the step motor 62, the angle of the diffraction grating 63 can be adjusted in the direction indicated by R1 in the figure, and the optical paths of the blue light Lb, green light Lg, and red light Lr diffracted by the diffraction grating 63 are changed in the direction indicated by the arrow R2, so that only the light of a specific wavelength (blue light Lb in FIG. 3) can selectively pass through the pinhole H of the pinhole mask 64. That is, in this first embodiment, the step motor 62 and the pinhole mask 64 function as light selection means for selecting light of a specific wavelength from the light of a plurality of wavelengths (blue light Lb, green light Lg, red light Lr) diffracted by the diffraction grating 63. In FIG. 3, the blue light Lb is selectively passed through the pinhole H of the pinhole mask 64 and is irradiated from the light irradiation unit 6a. However, based on the instruction signal from the above-described control means 10, by operating the step motor 62, the diffraction grating 63 can be rotated to select and irradiate light of various wavelengths from the light irradiation unit 6a.

[0024] The operation and effects when the light irradiation means 6A realized by the above-described first embodiment is adopted as the light irradiation means 6 of the inspection apparatus 1 shown in FIG. 1 will be described. The wafer W, which is the object to be inspected, is sucked and held on the table 35, and the moving means 4 is operated to move it directly below the light irradiation means 6 and the light receiving means 7. Next, the light irradiation means 6A shown in FIG. 3 is operated to irradiate white light L0 from the white light source 61. The white light L0 is diffracted and dispersed by the diffraction grating 63, and light of a specific wavelength is selected by the step motor 62 and the pinhole mask 64 that function as light selection means, and is irradiated onto the back surface of the wafer W. The light irradiated from the light irradiation means 6A is reflected from the back surface of the wafer W, and the reflected light is imaged by the camera 71 of the light receiving means 7. Here, as described above, a diffusion plate 72 is disposed between the wafer W and the camera 71. The light reflected from the surface of the wafer W is appropriately diffused by the diffusion plate 72, so that the minute unevenness formed on the surface due to the modified layer formed inside the wafer W can be captured by the camera 71. Further, by operating the above-described step motor 62 to change the wavelength of the light selected by the pinhole mask 64 and adjusting the wavelength of the light irradiated from the light irradiation unit 6a of the light irradiation means 6A, the state of the wafer W, which is the object to be inspected, for example, the material of the wafer W, the shape of the unevenness due to the modified layer, and It is possible to select light of an appropriate wavelength according to the dimensions of the unevenness, clarify the contrast of the image captured by the camera 71, and more reliably inspect the presence or absence of the modified layer formed inside the wafer W.

[0025] The light irradiation means 6 of the present invention is not limited to the above-described first embodiment. Based on FIG. 4, the light irradiation means 6B, which can be adopted as a second embodiment of the light irradiation means 6, will be described.

[0026] The light irradiation means 6B includes a white light source 61, a diffraction grating 63, and a pinhole mask 64 that selects light of a plurality of wavelengths (such as blue light Lb, green light Lg, and red light Lr), similar to the light irradiation means 6A described with reference to FIG. 3. In addition, it further includes a first condenser mirror 66 that reflects light of a plurality of wavelengths dispersed by the diffraction grating 63, a second condenser mirror 67 that has the same focal length as the first condenser mirror 66 and is disposed at a point-symmetric position centered on the focal point indicated by point C in the figure, an optical path conversion mirror 65 that is positioned at the focal point of the second condenser mirror 67 and converts the optical path, and a step motor 62 that adjusts the reflection angle of the optical path conversion mirror 65. Note that the diffraction grating 63 of this light irradiation means 6B is fixed. According to the light irradiation means 6B shown as this second embodiment, light of a plurality of wavelengths (blue light Lb, green light Lg, and red light Lr) diffracted and dispersed by the diffraction grating 63 is condensed by the condensing surface 66a of the first condenser mirror 66, guided to the second condenser mirror 67, and further, the light condensed by the condensing surface 67a of the second condenser mirror is guided to the above-mentioned pinhole mask 64. The light selection means in this second embodiment includes the first condenser mirror 66, the second condenser mirror 67, the optical path conversion mirror 65, the step motor 62, and the pinhole mask 64.

[0027] As the light irradiation means 6 of the inspection apparatus 1 shown in FIG. 1, the above-mentioned light irradiation means 6B shown in FIG. 4 is used. By operating the step motor 62 to adjust the angle of the optical path conversion mirror 65 in the direction indicated by arrow R3, the angle of the light reflected by the optical path conversion mirror 65 is adjusted in the direction indicated by arrow R4. Similar to the above-mentioned first embodiment, the wavelength of the light selected by the pinhole mask 64 can be changed to adjust the wavelength of the light irradiated from the light irradiation unit 6a of the light irradiation means 6B. It is possible to select and irradiate light of an appropriate wavelength according to the state of the wafer W to be inspected, for example, the material of the wafer W, the shape of the unevenness caused by the modified layer, and the dimensions of the unevenness. Due to the action of the diffusion plate 72, the contrast of the image captured by the camera 71 can be made clearer, and the presence or absence of the modified layer formed inside the wafer W can be inspected more reliably.

[0028] Furthermore, the light irradiation means 6 of the present invention is not limited to the above-described first and second embodiments. Based on FIG. 5, a light irradiation means 6C that can be adopted as a third embodiment of the light irradiation means 6 will be described.

[0029] As understood from FIG. 5, in addition to having a configuration disposed in the light irradiation means 6B described with reference to FIG. 4, the light irradiation means 6C includes a third condenser mirror 68 between the optical path conversion mirror 65 and the pinhole mask 64. The focus of the light condensed by the condensing surface 68a of the third condenser mirror 68 is set to be positioned at the pinhole H of the pinhole mask 64. Furthermore, a reflection mirror 69 that reflects light passing through the pinhole H of the pinhole mask 64 is provided. Note that the reflection mirror 69 is not an essential component, and the light that has passed through the pinhole H of the pinhole mask 64 may be irradiated directly from the light irradiation unit 6a.

[0030] Also in the light irradiation means 6C shown as this third embodiment, a step motor 62 is disposed with respect to the optical path conversion mirror 65. Based on the instruction signal from the control means 10, the step motor 62 is operated to adjust the angle of the optical path conversion mirror 65 in the direction indicated by the arrow R5, whereby the angle of the light reflected by the optical path conversion mirror 65 is adjusted in the direction indicated by the arrow R6. The light selection means in this third embodiment includes the above-described first condenser mirror 66, second condenser mirror 67, optical path conversion mirror 65, step motor 62, pinhole mask 64, and also includes a third condenser mirror 68.

[0031] In the above-described light irradiation means 6C, since the light (blue light Lb, green light Lg, red light Lr, etc.) guided to the pinhole H of the pinhole mask 64 is condensed by the third condenser mirror 68, compared with the light irradiation means 6A and light irradiation means 6B constituting the above-described first and second embodiments, it becomes possible to more limit and select the wavelength of the light passing through the pinhole H of the pinhole mask 64, further clarify the contrast of the image captured by the camera 71, and more reliably inspect the presence or absence of a modified layer formed inside the wafer W.

Description of Symbols

[0032] 1: Inspection device 2: Base 2a: Guide rail 3: Holding means 35: Table 31: X-axis movable plate 32: Y-axis movable plate 34: Cover plate 35: Table 35a: Holding surface 4: Moving means 42: X-axis moving means 44: Y-axis moving means 5: Frame 5a: Vertical wall portion 5b: Horizontal wall portion 6, 6A, 6B, 6C: Light irradiation means 6a: Light irradiation portion 61: White light source 62: Stepper motor 63: Diffraction grating 64: Pinhole mask 65: Reflecting mirror 66: First condenser mirror 66a: Condensing surface 67: Second condenser mirror 67a: Condensing surface 68: Third condenser mirror 68a: Condensing surface 69: Reflecting mirror 7: Light receiving means 71: Camera 72: Diffusion plate 8: Display means 10: Control means

Claims

1. An inspection apparatus for inspecting an object to be inspected, comprising: a table for supporting the object to be inspected; light irradiation means for irradiating light onto the object to be inspected supported by the table; and light receiving means for receiving the reflected light reflected from the object to be inspected. The light receiving means includes a camera and a diffusion plate disposed between the object to be inspected and the camera. The object to be inspected is a wafer in which minute unevenness is formed on the surface due to a modified layer formed inside. The light irradiated by the light irradiation means is selected according to the shape and dimensions of the unevenness formed on the surface due to the modified layer formed on the wafer, and the wavelength of the light corresponding thereto. An inspection apparatus for inspecting the presence or absence of a modified layer formed inside the wafer based on the uneven shape caused by the modified layer formed on the surface of the object to be inspected imaged by the camera via the diffusion plate.

2. The light irradiation means includes a white light source, a diffraction grating for dispersing the white light emitted by the white light source, and light selection means for selecting light of a specific wavelength from the light of a plurality of wavelengths dispersed by the diffraction grating, and is configured to irradiate the object to be inspected with the selected specific wavelength of light. The inspection apparatus according to claim 1.

3. The inspection apparatus according to claim 2, wherein the light selection means selects the light of a plurality of wavelengths dispersed by the diffraction grating by means of a pinhole mask.

4. The light selection means includes a first condenser mirror for reflecting the light of a plurality of wavelengths dispersed by the diffraction grating, a second condenser mirror having the same focal length as the first condenser mirror and disposed at a point-symmetric position with the center of symmetry being the focus, an optical path conversion mirror for converting the optical path positioned at the focus of the second condenser mirror, and the pinhole mask for selecting the light of a plurality of wavelengths whose optical path has been converted by the optical path conversion mirror. The inspection apparatus according to claim 3.

5. The inspection apparatus according to claim 4, further comprising a third condenser mirror between the optical path conversion mirror and the pinhole mask, wherein the focus of the third condenser mirror is positioned at the pinhole mask.

6. The white light source is any one of an SLD light source, an ASE light source, an LED light source, a supercontinuum light source, a halogen light source, a xenon light source, a mercury light source, and a metal halide light source. The inspection apparatus according to any one of claims 2 to 5.

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