CN102814874B - Processing unit (plant) - Google Patents

Abstract

The processing device of the present invention has a chuck table, a processing unit, an imaging unit, and a processing feed unit, and the imaging unit includes: a camera that photographs the workpiece; a focus moving unit that moves the focus point of the camera closer to and away from the workpiece; a control unit that operates the focus moving unit to move the focus point of the camera closer to and away from the workpiece while irradiating the radio frequency at predetermined intervals; flashing, making the camera continuously capture a plurality of images in synchronization with the irradiation of the stroboscopic light; A map in which the height position of the camera is associated with the sum of the differential values is stored; and a focus point determination unit selects a maximum value of the differential value from the map stored in the map generation storage unit, and determines the maximum value for the differential value. The location of the focus.

Description

Processing device

technical field

The present invention relates to processing devices such as cutting devices and laser processing devices that process workpieces such as semiconductor wafers.

Background technique

The wafer formed on the surface of multiple devices such as IC and LSI is divided by the planned dividing line by a cutting device (cutting device) or laser processing device and divided into individual devices along the planned dividing line. The divided devices are widely used for mobile Electrical equipment such as telephones and personal computers.

A processing device such as a dicing device or a laser processing device includes at least: a chuck table that holds a workpiece such as a semiconductor wafer; a processing unit that processes the workpiece held on the chuck table; and photographs the workpiece held by the chuck table. a camera unit; and a processing feed unit that performs processing feed on the chuck table and the processing unit.

The imaging unit generally includes a camera that captures the object to be processed and a microscope that magnifies the image captured by the camera. It can detect the planned division line of the area to be processed and position the cutting blade or laser processing head to the division to be processed with high precision. reservation line.

In addition, the imaging unit has the following autofocus function: position the wafer directly below the imaging unit to take pictures, make the imaging unit capture multiple images while performing step-by-step processing, perform differential processing on the captured images, and differentiate The position where the sum of the values is the largest is used as the focusing point to position the imaging unit (see Japanese Patent Application Laid-Open No. 61-198204).

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

However, in the autofocus mechanism disclosed in Patent Document 1, when performing autofocus, the imaging unit is lowered and stopped in stages at intervals of, for example, 1 μm, and the imaging unit repeatedly captures and captures images at this position. There is a problem that the productivity is poor due to relatively long time.

Contents of the invention

The present invention has been made in view of such a problem, and an object of the present invention is to provide a processing device capable of shortening the time for autofocusing.

According to the present invention, there is provided a processing device including: a chuck table holding a workpiece; a processing unit for processing the workpiece held on the chuck table; and photographing the workpiece held by the chuck table. and a processing feed unit for performing relative processing feed on the chuck table and the processing unit, the processing device is characterized in that the imaging unit has: a camera, which photographs the workpiece; The radio frequency flash is irradiated to the imaging area of the camera; the focusing point moving part makes the focusing point of the camera approach and move away from the workpiece; the control part makes the focusing point of the camera stop stepwise; Continuous movement, while operating the focus point moving part to make the focus point of the camera approach and move away from the workpiece, irradiate a radio frequency flash at predetermined intervals, and make the camera continuously capture a plurality of images in synchronization with the irradiation of the strobe light a map generation storage unit, which calculates the sum of differential values of a plurality of pixels constituting the image based on a plurality of images captured by the camera, generates a map, and stores the map, which is the height position of the camera and the differential value and a focus point determination unit that selects the maximum value of the differential value from the map stored in the map generation storage unit, and determines the position of the focus point.

According to the automatic focusing mechanism of the processing device of the present invention, the camera can be continuously moved without stepwise stopping the focus point of the camera, and at the same time, images can be taken in at necessary intervals to determine the focus point position, so it has the advantage of improving work efficiency. Effect.

Description of drawings

FIG. 1 is a schematic configuration diagram of a cutting device according to an embodiment of the present invention.

2 is a perspective view of a semiconductor wafer supported on a ring frame via a dicing tape.

FIG. 3 is a schematic diagram illustrating the structure and function of the imaging unit according to the embodiment of the present invention.

4 is a diagram showing an example of a map showing the relationship between the height position of the camera and the sum of the differential values of the pixels of the captured image.

Label description

2: Cutting device

14: X-axis feed mechanism

20: chuck table

36: Y-axis feed mechanism

42: Pulse motor

44: Z-axis feed mechanism

46: cutting unit

50: Cutter

54: camera unit

68: objective lens

70: Xenon flash

74: CCD camera

76: monitor

82: Focus point moving part

84: Control Department

86: Map generation storage unit

88: Focus point determination unit

detailed description

Next, the cutting device 2 according to the embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a cutting device 2 . The cutting device 2 includes a pair of guide rails 6 extending in the X-axis direction mounted on a stationary base 4 .

The X-axis moving block 8 moves in the machining feed direction, that is, the X-axis direction, by an X-axis feed mechanism (X-axis feed unit) 14 composed of a ball screw 10 and a pulse motor 12 . A chuck table 20 is mounted on the X-axis moving block 8 via a cylindrical support member 22 .

The chuck table 20 has a suction portion (suction chuck) 24 formed of porous ceramics or the like. A plurality of (four in this embodiment) clampers 26 for clamping the annular frame F shown in FIG. 2 are arranged on the chuck table 20 .

As shown in FIG. 2, on the surface of the semiconductor wafer W as the processing object of the cutting device 2, a first street S1 and a second street S2 are vertically formed. A plurality of devices D are formed in the divided regions.

The wafer W is attached to a dicing tape T serving as an adhesive tape, and the outer peripheral portion of the dicing tape T is attached to an annular frame F. As shown in FIG. Thus, the wafer W is supported by the ring frame F via the dicing tape T, and the wafer W is supported and fixed on the chuck table 20 by clamping the ring frame F with the clamper 26 shown in FIG. 1 .

The X-axis feed mechanism 14 includes a scale 16 disposed on the stationary base 4 along the guide rail 6 , and a reading head 18 disposed on the lower surface of the X-axis moving block 8 for reading the X coordinate value of the scale 16 . The read head 18 is connected to the controller of the cutting device 2 .

A pair of guide rails 28 extending along the Y-axis direction are also fixed on the stationary base 4 . The Y-axis moving block 30 moves in the Y-axis direction by a Y-axis feed mechanism (index feed mechanism) 36 composed of a ball screw 32 and a pulse motor 34 .

A pair (only one is shown) of guide rails 38 extending in the Z-axis direction is formed on the Y-axis moving block 30 . The Z-axis moving block 40 moves in the Z-axis direction by a Z-axis feed mechanism 44 composed of a ball screw and a pulse motor 42 (not shown).

46 is a cutting unit, and the spindle housing 48 of the cutting unit 46 is inserted into and supported by the Z-axis moving block 40 . A main shaft is housed in the main shaft case 48, and the main shaft is rotatably supported by an air bearing. The main shaft is rotationally driven by a motor (not shown) housed in a main shaft case 48 , and a cutting blade 50 is detachably attached to the front end of the main shaft.

An alignment unit 52 is mounted on the spindle housing 48 . The alignment unit 52 has an imaging unit 54 for imaging the wafer W held by the chuck table 20 . The cutting blade 50 and the imaging unit 54 are arranged side by side in the X-axis direction.

Next, the configuration of the imaging unit 54 according to the embodiment of the present invention will be described in detail with reference to FIG. 3 . The imaging unit 54 has a housing 56 accommodating the objective lens 68 facing the imaging area, and a partition plate 58 having a light transmission window 59 is attached near the front end of the housing 56 .

A water-filled chamber 60 is defined in a space partitioned by the front end portion of the frame body 56 , the partition plate 58 , and the wafer W held by the chuck table 20 . The distance between the front end 56a of the frame body 56 and the wafer W held by the chuck table 20 is preferably about 0.5 to 1 mm. During the knife mark inspection of the wafer W, water from the water source 64 is supplied to the water filling chamber 60 through the on-off valve 66 and the water supply port 62 to fill the water filling chamber 60 .

The imaging unit 54 of the present embodiment includes a xenon strobe lamp 70 as a type of strobe light source. A part of the strobe light emitted from the xenon flash lamp 70 is reflected by the dichroic mirror 72 and irradiates the wafer W held by the chuck table 20 through the objective lens 68 and the light transmission window 59 .

On the optical axis of the objective lens 68, a CCD camera 74 for imaging the wafer W irradiated with stroboscopic light is arranged. Images captured by the CCD camera 74 are displayed on a monitor 76 .

The CCD camera 74 photographs the imaging area of the wafer W held by the chuck table 20 in synchronization with the emission of the xenon flash lamp 70 , and the photographed image is displayed on the monitor 76 . The xenon flash lamp 70 and the CCD camera 74 are connected to the control unit 80 and controlled by the control unit 80 .

The control unit 80 includes: a focusing point moving unit 82 that moves the focusing point of the CCD camera 74 closer to and away from the wafer W; and a control unit 84 that operates the focusing point moving unit 82 to move the focusing point of the CCD camera 74 closer to and away from the wafer W. At the same time, the xenon flash lamp 70 is turned on at predetermined intervals (for example, every time the CCD camera 74 moves 1 μm in the Z-axis direction), and the CCD camera 74 is synchronized with the light emission of the xenon flash lamp 70 to continuously capture images of the imaging area of the wafer W.

The control unit 80 also has: a map generation storage unit 86, which divides a plurality of images captured by the CCD camera 74 into a plurality of pixels, generates and stores the sum of the differential values for each pixel and the Z-axis direction position of the CCD camera 74 (Height position) A map 85 such as that shown in FIG. The position of the focus point.

The generation of the map 85 shown in FIG. 4 utilizes, for example, the autofocus method disclosed in Japanese Patent Application Laid-Open No. 61-198204. In this autofocus method, an image captured by the CCD camera 74 is divided into, for example, 256×256 pixels, 3×3 pixels are taken out from these pixels as one block and differential processing is performed, whereby the sum of the differential values is compared with the CCD camera 74 The height position (Z position) is associated.

This process is performed every time the CCD camera 74 descends by 1 μm, and the map 85 shown in FIG. 4 that correlates the height position (Z position) of the CCD camera 74 with the sum of the differential values of the pixels of the captured image is generated.

When the CCD camera 74 captures an image at the focus point, the image can be clearly imaged, so the sum of the differential values of the pixels is the largest. In addition, regarding the details of the autofocus method, the contents disclosed in Japanese Patent Application Laid-Open No. 61-198204 are incorporated into this specification.

Autofocus of the imaging unit 54 configured as described above will be described below. First, the wafer W to be cut is sucked and held by the chuck table 20 , and the X-axis feed mechanism 14 is driven to position the wafer W directly under the imaging unit 54 .

A drive pulse signal DR is output from the focus point moving unit 82 of the control unit 80 to the pulse motor 42 of the Z-axis feed mechanism 44 to drive the pulse motor 42 . While continuously lowering the imaging unit 54 by the pulse motor 42 , a drive signal is output from the control unit 84 to the xenon flash lamp 70 every time the height position drops by, for example, 1 μm, so that the xenon flash lamp 70 emits light.

In synchronization with this light emission, a control signal is output from the control unit 84 to the CCD camera 74 , and the CCD camera 74 captures an imaging area of the wafer W illuminated by the stroboscopic light from the xenon strobe lamp 70 .

The captured image is displayed on the monitor 76 and taken into the control unit 80. The map generation and storage unit 86 of the control unit 80 is divided into 256×256 pixels, and 3×3 pixels are regarded as a block. The differential processing is performed, and the sum of all the pixels subjected to the differential processing is calculated. By repeating this operation every time the imaging unit 54 descends by 1 μm without stopping the imaging unit 54 , the map 85 shown in FIG. 4 is generated and stored.

In the focus point determination part 88, the Z position (height position) of the CCD camera 74 whose differential value of the pixel is the largest is selected from the map 85 stored by the map generation storage part 86, and this position is determined as the position of the CCD camera 74. focus point position. In FIG. 4, the Z3 position is determined as the focus point position.

When the continuously descending CCD camera 74 overshoots the focus point position, the pulse motor 42 is rotated in the reverse direction to raise the CCD camera 74 while searching for the focus point position.

In the autofocus method of this embodiment, the xenon flash lamp 70 is made to emit light at predetermined intervals while the CCD camera 74 is continuously lowered, and the imaging area is captured by the CCD camera 74 in synchronization with the light emission to perform autofocus. By stopping the CCD camera step by step in this way, images can be captured continuously at necessary intervals, so that automatic focusing can be effectively performed.

In the above-mentioned embodiment, the example in which the autofocus mechanism of the imaging unit 54 of the present invention is applied to the cutting device 2 has been described, but the present invention is not limited thereto, and can also be similarly applied to other devices such as laser processing devices. Automatic focusing of the camera unit of the processing device.

Claims (1)

1. A processing device comprising: a chuck table holding a workpiece; a processing unit for processing the workpiece held on the chuck table; and an imaging unit for photographing the workpiece held by the chuck table ; and a processing feed unit that performs relative processing feed to the chuck table and the processing unit, The processing device is characterized in that, The camera unit has: A camera that photographs the workpiece; a stroboscopic light source that irradiates a radio frequency flash to the imaging area of the camera; a focus point moving unit that moves the focus point of the camera closer to and away from the workpiece; The control unit moves the camera continuously without stopping the focusing point of the camera in stages, and moves the focusing point of the camera close to and away from the workpiece while operating the focusing point moving unit at a predetermined rate. irradiating a radio frequency flash at intervals, causing the camera to continuously capture a plurality of images synchronously with the irradiation of the stroboscopic light; A map generation storage unit that calculates the sum of differential values of a plurality of pixels constituting the image based on a plurality of images captured by the camera to generate and store a map that is the height position of the camera and the differential value. obtained by correlating the sum of ; and A focus point determination unit selects the maximum value of the differential value from the map stored in the map generation storage unit, and determines the position of the focus point.