Lighting equipment

Abstract

The present invention provides an illumination device, which is a lighting device with clear contrast and can achieve optimal focus. The illumination device is installed in a shooting device for shooting a workpiece held on a chuck worktable, and comprises: a light source; an objective lens having a fine hole in the center of the objective lens, the objective lens being arranged to face the workpiece held on the chuck worktable; and an optical fiber, one end of the optical fiber being inserted into the fine hole of the objective lens, and the other end being optically coupled with the light source.

Description

Technical Field

[0001] The present invention relates to a lighting device installed in a photographing device, wherein the photographing device comprises: a chuck table for holding a workpiece; and a photographing unit for photographing the workpiece held on the chuck table. Background Art

[0002] A wafer having multiple devices such as ICs and LSIs formed on the front side is divided by a plurality of intersecting predetermined dividing lines and is divided into individual device chips by a dicing device or a laser processing device. The divided device chips are used in electronic devices such as mobile phones and personal computers.

[0003] A dicing device or a laser processing device is equipped with an imaging device having an autofocus function for imaging a wafer and detecting a region to be processed (see, for example, Patent Document 1).

[0004] According to the technology described in Patent Document 1, an imaging unit of an imaging device is moved at a predetermined pitch relative to an object to be processed (wafer), and an image of the object to be processed is captured corresponding to each pitch. Each image thus obtained is stored in a control unit as image information, and a differential value of sampling points constituting a photographing area of ​​each image corresponding to each pitch is calculated. The position of the imaging unit at which the image with the differential value being the maximum is determined as a focus position, i.e., a position of best focus (just focus).

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 61-198204

[0006] In the past, multiple light sources were arranged around the lens that faces the wafer and constitutes the imaging unit, and light was irradiated from the outside to the inside to make the entire imaging area uniformly bright. However, when irradiating light in this way, the light irradiated on the wafer is scattered and light overlap occurs, resulting in a problem that even if the focus position is reached, the contrast is not clear and it is difficult to achieve the best focus. Summary of the invention

[0007] Therefore, an object of the present invention is to provide a lighting device installed in a photographing device, which has clear contrast and can achieve optimal focusing.

[0008] According to the present invention, there is provided a lighting device installed in a photographing device for photographing a workpiece held on a chuck worktable, wherein the lighting device comprises: a light source; an objective lens having a fine hole in the central portion of the objective lens, the objective lens being arranged to be opposite to the workpiece held on the chuck worktable; and an optical fiber, one end of the optical fiber being inserted into the fine hole of the objective lens, and the other end being optically coupled to the light source.

[0009] Preferably, the light source is selected from the group consisting of a superluminescent diode light source, an amplified spontaneous emission light source, a supercontinuum light source, a light emitting diode light source, a halogen light source, a xenon light source, a mercury light source, a metal halide light source and a laser light source.

[0010] According to the present invention, the end of the optical fiber inserted into the fine hole formed in the center of the lens opposite to the workpiece becomes a point light source, and the conical light is irradiated onto the workpiece. There is no light overlap in the shooting area, the contrast of the captured image is clear, and optimal focusing can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is an overall stereoscopic view of a laser processing device having a camera device in which a lighting device according to an embodiment of the present invention is installed.

[0012] Figure 2 It is enlarged to show Figure 1 A perspective view of the photographing device shown.

[0013] Figure 3 It is used to illustrate Figure 2 A partially sectional side view of the structure of the shooting device shown.

[0014] Description of symbols

[0015] 1: laser processing device; 2: base; 4: frame; 4b: horizontal wall; 10: wafer; 12: device; 14: predetermined dividing line; 20: holding unit; 25: chuck table; 30: moving mechanism; 40: laser light irradiation unit; 42: condenser; 50: shooting device; 60: shooting unit; 62: objective lens housing; 62a: connecting part; 621: objective lens; 621a: lens; 621b: fine hole; 64: camera; 66: autofocus mechanism; 66a: pulse motor; 70: lighting device; 72: optical fiber; 74: light source; 100: control unit; 102: differential processing unit; 104: autofocus control unit. DETAILED DESCRIPTION

[0016] Hereinafter, a lighting device according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0017] Figure 1 The entire perspective view of the laser processing device 1 having the lighting device 70 of the present embodiment is shown. The laser processing device 1 has: an imaging device 50 including a holding unit 20 for holding a workpiece and an imaging unit 60 for imaging the workpiece held on the holding unit 20; a moving mechanism 30 for moving the holding unit 20; and a laser beam irradiation unit 40 for irradiating a laser beam to the workpiece held on the holding unit 20.

[0018] The holding unit 20 includes: a rectangular X-axis movable plate 21 mounted on the base 2 so as to be movable in the X-axis direction indicated by the arrow X in the figure; a rectangular Y-axis movable plate 22 mounted on the X-axis movable plate 21 so as to be movable in the Y-axis direction indicated by the arrow Y in the figure; a cylindrical support 23 fixed on the upper surface of the Y-axis movable plate 22; and a rectangular cover plate 26 fixed on the upper end of the support 23. A circular chuck table 25 is arranged on the cover plate 26, and the chuck table 25 extends upward through a long hole formed in the cover plate 26. The chuck table 25 is configured to be rotatable by a rotation drive mechanism not shown in the figure. The holding surface constituting the upper surface of the chuck table 25 is formed of a porous material and has air permeability, and is connected to a suction unit not shown in the figure by a flow path passing through the inside of the support 23. The chuck table 25 is further provided with a clamp 27 for fixing an annular frame unit F, which supports the workpiece via a protective tape T (see also FIG. Figure 2 ). In addition, for example Figure 2 As shown, the workpiece in this embodiment is a wafer 10 divided by a plurality of planned dividing lines 14 on the front surface 10 a to form a plurality of devices 12 .

[0019] return Figure 1 Continuing the description, the moving mechanism 30 includes: an X-axis direction feed mechanism 31, which is arranged on the base 2 and feeds the holding unit 20 in the X-axis direction; and a Y-axis direction feed mechanism 32, which feeds the Y-axis movable plate 22 in the Y-axis direction. The X-axis direction feed mechanism 31 converts the rotational motion of the pulse motor 33 into linear motion by means of a ball screw 34 and transmits it to the X-axis direction movable plate 21, so that the X-axis direction movable plate 21 moves forward and backward along the guide rails 2a, 2a on the base 2 in the X-axis direction. The Y-axis direction feed mechanism 32 converts the rotational motion of the pulse motor 35 into linear motion by means of a ball screw 36 and transmits it to the Y-axis direction movable plate 22, so that the Y-axis direction movable plate 22 moves forward and backward along the guide rails 21a, 21a on the X-axis direction movable plate 21 in the Y-axis direction. Although not shown in the figure, the X-axis direction feed mechanism 31, the Y-axis direction feed mechanism 32 and the chuck table 25 are provided with a position detection unit, which can accurately detect the X-axis direction position, the Y-axis direction position and the circumferential rotation position of the chuck table 25 and transmit them to the control unit 100 described later (see Figure 2 , Figure 3 ), according to the indication signal indicated from the control unit 100, the X-axis direction feeding mechanism 31, the Y-axis direction feeding mechanism 32 and the rotation driving mechanism of the chuck worktable 25 (not shown) are driven to position the chuck worktable 25 at an arbitrary coordinate position and rotation angle.

[0020] A frame 4 is erected on the side of the moving mechanism 30. The frame 4 has a vertical wall portion 4a disposed on the base 2 and a horizontal wall portion 4b extending in the horizontal direction from the upper end portion of the vertical wall portion 4a. An optical system (not shown) of a laser beam irradiation unit 40 is accommodated inside the horizontal wall portion 4b of the frame 4. A condenser 42 constituting a part of the laser beam irradiation unit 40 is disposed on the lower surface of the front end portion of the horizontal wall portion 4b, and a condenser lens (not shown) and the like are built into the condenser 42. The laser beam irradiation unit 40 is provided with a laser oscillator (not shown), and the laser beam emitted from the laser oscillator is condensed by the condenser lens of the condenser 42 and irradiated to a predetermined position of the workpiece held by the holding unit 20.

[0021] Below, refer to Figure 2 , Figure 3 , the imaging unit 60 constituting the imaging device 50 of this embodiment together with the above-mentioned holding unit 20 and the lighting device 70 installed in the imaging device 50 are described. In addition, Figure 2 FIG. 1 is a perspective view showing an enlarged image of an image pickup device 50 composed of a holding unit 20 and an image pickup unit 60 for picking up an image of the wafer 10 held on the holding unit 20. Figure 3 To explain more specifically Figure 2 The imaging device 50 shown is a side view showing a part of the imaging device 50 in cross section.

[0022] The photographing unit 60 has an objective lens housing 62 and an imaging optical system 64a, the imaging optical system 64a is used to photograph the wafer 10 held on the holding unit 20 from above the objective lens housing 62 through the objective lens housing 62, and the photographing unit 60 has: a camera 64 for photographing the front surface 10a of the wafer 10 by visible light; and an autofocus mechanism 66, which adjusts the focus by raising and lowering the objective lens housing 62 in the Z-axis direction (up and down direction) indicated by the arrow Z in the figure. In addition, the camera 64 and the autofocus mechanism 66 are fixed to the inside of the horizontal wall portion 4b of the frame 4 and near the lower surface of the front end portion of the horizontal wall portion 4b by a fixing unit omitted from the figure.

[0023] like Figure 3 As shown, the objective lens housing 62 has an objective lens 621 inside. In addition, in the illustrated embodiment, an example in which the objective lens 621 is composed of a collection of multiple convex lenses is shown as an example, but the present invention is not limited to this, and the objective lens 621 can also be composed of a single convex lens or a combination of a convex lens and a concave lens.

[0024] The autofocus mechanism 66 comprises a pulse motor 66a and an externally threaded component 66b connected to the output shaft of the pulse motor 66a. The externally threaded component 66b is screwed with an internally threaded portion (not shown) of a connecting portion 62a formed on the objective lens housing 62, and the pulse motor 66a is rotated forward and reversed according to an instruction signal from the control unit 100, so that the objective lens housing 62 supported on the lower surface of the horizontal wall portion 4b that can be lifted and lowered freely in the Z-axis direction shown by the arrow Z is lifted and lowered to a desired position.

[0025] The control unit 100 is composed of a computer, and has: a central processing unit (CPU) that performs calculations according to a control program; a read-only memory (ROM) that stores the control program, etc.; a readable and writable random access memory (RAM) that temporarily stores image information captured by the camera 64 and other calculation results, etc., as well as an input interface and an output interface (detailed illustration omitted). In addition, the control unit 100 functions as a control unit for controlling each operating unit of the above-mentioned laser processing device 1, and also has: a differential processing unit 102 that records the image captured by the camera 64 and performs differential processing on the image; and an autofocus control unit 104 that issues an instruction signal for controlling the above-mentioned autofocus mechanism 66.

[0026] The imaging device 50 of the present embodiment is provided with an illumination device 70. The illumination device 70 includes an optical fiber 72 and a light source 74. One end 72a of the optical fiber 72 is inserted into the interior of the objective lens housing 62 and into a fine hole 621b formed at the center of the lowest lens 621a, which is opposite to the wafer 10 held by suction on the chuck table 25, among the multiple lenses constituting the objective lens 621. In addition, a light source 74 is provided at the other end 72b of the optical fiber 72 in an optically coupled manner, and light from the light source 74 is input from the end 72b. In addition, it is preferred that the diameter of the optical fiber 72 and the inner diameter of the fine hole 621b of the lens 621a are as small as possible, and the diameter of the optical fiber 72 is set to about 50 μm, for example, and the inner diameter of the fine hole 621b is slightly larger than the diameter of the optical fiber 72, for example, set to a diameter of about 51 μm to 53 μm. In addition, the light source 74 can be selected from a variety of light sources, for example, any one of an SLD light source, an ASE light source, a supercontinuum light source, an LED light source, a halogen light source, a xenon light source, a mercury light source, a metal halide light source, and a laser light source can be selected.

[0027] The laser processing device 1 includes the imaging device 50 to which the lighting device 70 of the present embodiment is mounted. The laser processing device 1 roughly has the above-described structure, and its operation will be described below.

[0028] When the wafer 10 is laser processed, the moving mechanism 30 is operated, such as Figure 2As shown, the wafer 10 held by the holding unit 20 is positioned directly below the imaging unit 60. After the wafer 10 is positioned directly below the objective lens housing 62 of the imaging unit 60, the front surface 10a of the wafer 10 is photographed to detect alignment of the processing area (scheduled dividing line 14).

[0029] When performing alignment, the light source 74 is first operated. By operating the light source 74, light L is input from the other end 72b of the optical fiber 72. As described above, one end 72a of the optical fiber 72 is inserted into the fine hole 621b, which is provided at the center of the lens 621a, which is arranged at the lowest position opposite to the wafer 10 among the multiple lenses constituting the objective lens 621. Therefore, the one end 72a of the optical fiber 72 becomes a point light source, and the light L diffused in a cone shape from the center of the lens 621a is irradiated toward the front surface 10a of the wafer 10.

[0030] As described above, in a state where the light L is irradiated to the front side 10a of the wafer 10, the image information captured by the camera 64 of the imaging unit 60 is sent to the control unit 100, and the pulse motor 66a of the autofocus mechanism 66 is operated by the autofocus control unit 104 of the control unit 100, so that the objective lens housing 62 is raised and lowered at a predetermined interval. The image information captured by the camera 64 at predetermined intervals is stored in the memory of the control unit 100. The differential processing unit 102 of the control unit 100 performs differential processing on the image information stored at the predetermined intervals, and calculates the differential values ​​of each sampling point in the imaging area. By finding each differential value of each image captured at a predetermined interval, the position corresponding to the image where the differential value becomes the maximum value is determined as the best focus position, and the autofocus mechanism 66 is operated to position the objective lens 621 at the best focus position.

[0031] By positioning the objective lens 621 at the position determined as the best focus, the front side 10a of the wafer 10 is clearly photographed by the camera 64, so that the area to be processed (the predetermined dividing line 14) can be well detected and the position can be stored in the control unit 100 to complete the alignment. In particular, according to the present embodiment, since the end 72a of the optical fiber 72 positioned in the fine hole 621b formed in the center of the lens 621a opposite to the wafer 10 becomes a point light source and irradiates the front side 10a of the wafer 10 with a conical light L, there is no overlap of light in the photographing area, and the contrast of the photographed image is clear, thereby solving the problem of difficulty in performing the best focus.

[0032] As described above, after the alignment is performed and the position of the planned dividing line 14 to be processed is detected and stored in the control unit 100, the moving mechanism 30 is operated to position the holding unit 20 directly below the condenser 42 of the laser beam irradiation unit 40. Then, the predetermined laser processing is performed along the planned dividing line 14 of the wafer 10 based on the position information of the planned dividing line 14 stored in the control unit 100.

[0033] In the above embodiment, an example is shown in which the lighting device 70 of the embodiment of the present invention is installed in the shooting device 50 of the laser processing device 1, but the present invention is not limited to this. For example, it can also be installed in the shooting device of a cutting device that cuts the workpiece using a cutting tool.

Claims

1. A lighting device installed in a photographing device for photographing a workpiece held on a chuck table, wherein: The lighting device has: light source; an objective lens having a fine hole at a central portion thereof, the objective lens being arranged to face the workpiece held on the chuck table; as well as An optical fiber, one end of which is inserted into the fine hole of the objective lens, and the other end of which is optically coupled with the light source, The one end of the optical fiber inserted into the fine hole becomes a single point light source of the lighting device and irradiates conically diffused light from the point light source toward the workpiece, and the conically diffused light is directly irradiated onto the workpiece.

2. The lighting device according to claim 1, wherein: The light source is selected from the group consisting of a superluminescent diode light source, an amplified spontaneous emission light source, a supercontinuum light source, a light emitting diode light source, a halogen light source, a xenon light source, a mercury light source, a metal halide light source, and a laser light source.

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