JP2010030007A - Grinder and scratch detection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scratch detection apparatus for a wafer and a grinder equipped with the scratch detection device. <P>SOLUTION: The grinder includes a chuck table for holding a wafer and a grinding means having a grinding wheel for grinding the wafer held on the chuck table. The grinder further includes a scratch detection means for detecting a scratch produced on a ground surface of the wafer. The scratch detection means includes an oblique light beam irradiation means for obliquely irradiating the wafer onto a region corresponding to a radius of the wafer with a light beam, a line scan lens for forming an image of the region corresponding to the radius of the wafer, a line scan camera for photographing the image formed by the line scan lens, and a scratch determination means for determining presence/absence of the scratch based on the image photographed by the line scan camera, and detects the scratch during at least one revolution of the chuck table. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a scratch detection device capable of detecting a scratch on a wafer grinding surface and a grinding device provided with the scratch detection device.

  A semiconductor wafer in which a number of devices such as IC and LSI are formed on the surface, and each device is partitioned by a line to be divided (street), the back surface is ground by a grinding machine and processed to a predetermined thickness. The division line is cut by a dicing machine and divided into individual devices, which are used for electric devices such as mobile phones and personal computers.

  A grinding apparatus for grinding a back surface of a wafer includes a chuck table for holding a wafer, a grinding means for rotatably supporting a grinding wheel provided with a grinding wheel for grinding the wafer held by the chuck table, and a grinding region And a grinding water supply means for supplying the grinding water to the wafer, and the wafer can be processed to a predetermined thickness.

  By the way, when the thickness of the wafer is reduced to 100 μm or less, and further to 50 μm or less, grinding distortion generated on the back surface of the wafer may cause a decrease in the bending strength of the device, and etching or the like may be performed to improve the bending strength. When the distortion is removed, the gettering effect for holding the heavy metal floating inside the wafer on the back surface side is lost, and the quality of the device is remarkably deteriorated.

In view of this, the present applicant has proposed a vitrified bond grindstone in Japanese Patent Application Laid-Open No. 2006-1007, which mainly suppresses grinding distortion and maintains the bending strength while maintaining the gettering effect as a grindstone for finish grinding.
JP 2006-1007 A

  However, when the ground surface of the wafer ground using the vitrified bond grindstone disclosed in Patent Document 1 is observed, there may be a wafer containing scratches at a ratio of 1 to 40-50 wafers. However, there is a problem that the bending strength at the scratched portion is lowered.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a scratch detection device capable of detecting a scratch generated on a grinding surface of a wafer, and a grinding device equipped with the scratch detection device. That is.

  According to the first aspect of the present invention, there is provided a grinding apparatus comprising a chuck table for holding a wafer and a grinding means having a grinding wheel for grinding the wafer held by the chuck table, which is generated on a grinding surface of the wafer. The apparatus further comprises scratch detecting means for detecting scratches, and the scratch detecting means includes oblique light irradiating means for irradiating light to an area corresponding to the wafer radius with respect to the wafer, and an area corresponding to the wafer radius. A line scan lens that forms an image, a line scan camera that captures an image formed by the line scan lens, and a scratch determination unit that determines whether or not there is a scratch from an image captured by the line scan camera, A scratch is detected during at least one rotation of the chuck table. Grinding device is provided that.

  Preferably, the scratch detection means of the grinding apparatus further includes a frame body that surrounds the line scan lens and is open to the wafer side, and a water supply means that supplies water to the frame body, and the frame body and the wafer are partitioned. Space is filled with water.

  Preferably, the scratch detection means of the grinding apparatus increases the transmission intensity of the reflected light reflected on the surface of the wafer in proportion to going from the center of the wafer disposed in the region corresponding to the radius of the wafer to the outer periphery. And a gradient filter.

  According to a fifth aspect of the present invention, there is provided a scratch detection device for detecting a scratch generated on a grinding surface of a wafer held on a chuck table, wherein the light is inclined at least in a region corresponding to the wafer radius with respect to the wafer. Oblique light irradiating means for irradiating, a line scan lens for imaging an area corresponding to at least the radius of the wafer, a line scan camera for imaging an image formed by the line scan lens, and an image captured by the line scan camera There is provided a scratch detection device comprising a scratch determination means for determining presence / absence of a scratch from an image, and detecting the scratch during at least one rotation of the chuck table.

  According to the grinding device of the present invention, since the scratch detection device having the line scan camera arranged so as to follow the direction of the scratch is provided, the scratch can be immediately detected from the grinding surface of the wafer. Or the scratch removal grinding is performed to transport the scratch-free wafer to the next process, so that the scratch-free wafer can be produced efficiently.

  Further, according to the scratch detection device of the present invention, it is possible to reliably detect a scratch formed on the grinding surface.

  Hereinafter, a wafer grinding method and a grinding apparatus according to embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a semiconductor wafer before being processed to a predetermined thickness. A semiconductor wafer 11 shown in FIG. 1 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and a plurality of streets partitioned by the plurality of streets 13 are formed. A device 15 such as an IC or LSI is formed in the region.

  The semiconductor wafer 11 configured as described above includes a device region 17 in which the device 15 is formed, and an outer peripheral surplus region 19 that surrounds the device region 17. A notch 21 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  A protective tape 23 is attached to the surface 11a of the semiconductor wafer 11 by a protective tape attaching process. Therefore, the front surface 11a of the semiconductor wafer 11 is protected by the protective tape 23, and the back surface 11b is exposed as shown in FIG.

  Hereinafter, a grinding apparatus 2 for grinding the back surface 11b of the semiconductor wafer 11 thus configured to a predetermined thickness will be described with reference to FIG. The housing 4 of the grinding device 2 is composed of a horizontal housing part 6 and a vertical housing part 8.

  A pair of guide rails 12 and 14 extending in the vertical direction are fixed to the vertical housing portion 8. A grinding means (grinding unit) 16 is mounted along the pair of guide rails 12 and 14 so as to be movable in the vertical direction. The grinding unit 16 is attached to a moving base 18 that moves up and down along a pair of guide rails 12 and 14 via a support portion 20.

  The grinding unit 16 includes a spindle housing 22 attached to the support portion 20, a spindle 24 rotatably accommodated in the spindle housing 22, and a servo motor 26 that rotationally drives the spindle 24.

  As best shown in FIG. 6, a mounter 28 is fixed to the tip of the spindle 24, and a grinding wheel 30 is screwed to the mounter 28. For example, the grinding wheel 30 is configured by affixing a plurality of grinding wheels 34 in which diamond abrasive grains having a grain size of 0.3 to 1.0 μm are hardened by vitrified bonds to a free end portion of a wheel base 32. Therefore, the grinding surface is a mirror surface.

  Grinding water is supplied to the grinding means (grinding unit) 16 via a hose 36. Preferably, pure water is used as the grinding water. As shown in FIG. 6, the grinding water supplied from the hose 36 is formed in the grinding water supply hole 38 formed in the spindle 24, the space 40 formed in the mounter 28, and the wheel base 32 of the grinding wheel 30. It is supplied to the wafer 11 held on the grinding wheel 34 and the chuck table 54 via a plurality of grinding water supply nozzles 42.

  Referring back to FIG. 3, the grinding apparatus 2 includes a grinding unit feed mechanism 44 that moves the grinding unit 16 in the vertical direction along the pair of guide rails 12 and 14. The grinding unit feed mechanism 44 includes a ball screw 46 and a pulse motor 48 fixed to one end of the ball screw 46. When the pulse motor 48 is pulse-driven, the ball screw 46 rotates and the moving base 18 is moved in the vertical direction via the nut of the ball screw 46 fixed inside the moving base 18.

  A chuck table unit 50 is disposed in the recess 10 of the horizontal housing portion 6. As shown in FIG. 4, the chuck table unit 50 includes a support base 52 and a chuck table 54 that is rotatably disposed on the support base 52. The chuck table unit 50 further includes a cover 56 having a hole through which the chuck table 54 is inserted.

  The chuck table unit 50 is moved in the front-rear direction of the grinding apparatus 2 by the chuck table moving mechanism 58. The chuck table moving mechanism 58 includes a ball screw 60 and a pulse motor 64 connected to one end of a screw shaft 62 of the ball screw 60.

  When the pulse motor 64 is pulse-driven, the screw shaft 62 of the ball screw 60 rotates, and the support base 52 having a nut screwed to the screw shaft 62 moves in the front-rear direction of the grinding device 2. Therefore, the chuck table 54 also moves in the front-rear direction according to the rotation direction of the pulse motor 64.

  As shown in FIG. 3, the pair of guide rails 66 and 68 and the chuck table moving mechanism 58 shown in FIG. 4 are covered with bellows 70 and 72. That is, the front end portion of the bellows 70 is fixed to the front wall that defines the recess 10, and the rear end portion is fixed to the front end surface of the cover 56. The rear end of the bellows 72 is fixed to the vertical housing portion 8, and the front end thereof is fixed to the rear end surface of the cover 56.

  In the horizontal housing portion 6 of the housing 4, a first wafer cassette 74, a second wafer cassette 76, a wafer transfer means 78, a wafer temporary mounting means 80, a wafer carry-in means 82, and a wafer carry-out means 84 are provided. A cleaning means 86 is provided. Further, an operation means 88 and a monitor 89 are provided in front of the housing 4 for an operator to input grinding conditions and the like.

  Further, a cleaning water spray nozzle 90 for cleaning the chuck table 54 is provided at the approximate center of the horizontal housing portion 6. The cleaning water jet nozzle 90 ejects cleaning water toward the wafer after grinding held by the chuck table 54 in a state where the chuck table unit 54 is positioned in the wafer carry-in / carry-out region.

  The chuck table unit 50 pulse-drives the pulse motor 64 of the chuck table moving mechanism 58 to receive the wafer from the grinding area on the back side of the apparatus and the wafer carry-in means 82 shown in FIG. It is moved to and from the wafer loading / unloading area on the near side.

  A scratch detection device 94 is disposed above the wafer carry-in / out region (wafer attach / detach region). As an alternative, as shown in FIG. 4, a scratch detection device 94 may be disposed above the grinding region.

  As best shown in FIG. 4, the scratch detection device 94 includes a frame body 96 containing an optical system, a support member 98 that supports the frame body 96, and a rotating cylinder 100 to which the base end portion of the support member 98 is fixed. And a fixed cylinder 102 fixed to the upper surface of the horizontal partial housing 6. The frame body 96 of the scratch detection device 94 is approximately 90 degrees in the clockwise direction with respect to the detection position shown in FIGS. It is attached to the horizontal portion 6 of the housing 4 so as to be rotatable between the rotated retracted position.

  As shown in FIG. 8, the frame body 96 of the scratch detection device 94 includes a vertical frame body portion 96 a extending in a substantially vertical direction with respect to the chuck table 54 and an inclined frame body portion 96 b inclined with respect to the chuck table 54. Contains.

  A glass plate 104 is disposed between the vertical frame portion 96a and the inclined frame portion 96b, and a glass plate 106 is disposed in the vicinity of the lower end portion of the vertical frame portion 96a. A water filling chamber 108 is defined by the glass plates 104 and 106 and the tip of the vertical housing portion 96a and the tip of the inclined housing portion 96b.

  Reference numeral 110 denotes a water supply port, and the water supply port 110 is connected to a water source (not shown) via a pipeline. The distance between the tip of the housing 96 and the wafer 11 is preferably maintained at about 0.5-1 mm.

  As shown in FIG. 7, the vertical frame portion 96 a of the frame 96 extends in the radial direction of the wafer 11 held on the chuck table 54, and covers at least a region corresponding to the radius of the wafer 11. Have a size. The inclined frame body portion 96b has a similar size in the radial direction of the wafer 11. 11 c is the center of the wafer 11.

  Referring to FIG. 8 again, the inclined frame body portion 96b is attached with an oblique light irradiation unit 112 that uniformly irradiates light to a region corresponding to the wafer radius with respect to the wafer 11. The oblique light irradiation unit 112 includes a point light source such as a halogen lamp and an optical element that converts light from the point light source into a line beam. Alternatively, the oblique light irradiation unit 112 may be composed of a large number of LEDs.

  An inclined filter 114 is disposed on the glass plate 106. The inclined filter 114 is disposed so as to cover the region from the center of the wafer 11 to the outer periphery, and the transmission intensity of the reflected light reflected by the wafer 11 increases in proportion as it goes from the center of the wafer 11 to the outer periphery. It has the following characteristics. This is because the amount of reflected light is smaller than the center because the peripheral speed of the wafer 11 is faster, and the inclined filter 114 corrects this to a uniform amount of light.

  A conventionally known line scan lens 116 capable of forming an image corresponding to the radius of the wafer 11 is provided above the inclined filter 114. The line scan lens 116 is attached to the vertical frame portion 96a so as to be disposed at an intermediate portion between the center and the outer periphery of the wafer 11.

  Reference numeral 118 denotes a line scan CCD camera in which a large number of pixels (for example, 1024 pixels) are arranged in a line in the radial direction of the wafer 11 and picks up an image formed by the line scan lens 116. The pixel scanning direction of the line scan CCD camera 118 follows the direction in which scratches are formed, and is arranged in a line in the radial direction of the wafer 11.

  The grinding operation of the grinding device 2 configured as described above will be described below. The wafer housed in the first wafer cassette 74 is a semiconductor wafer having a protective tape mounted on the front surface side (surface on which the circuit is formed), and therefore the wafer is positioned with the back surface positioned on the upper side. Housed in the first cassette 74. As described above, the first wafer cassette 74 that accommodates a plurality of semiconductor wafers is mounted with a predetermined cassette of the housing 4 in the carry-in area.

  When all of the unprocessed semiconductor wafers contained in the first wafer cassette 74 placed in the cassette carry-in area are carried out, a plurality of semiconductor wafers are accommodated in place of the empty wafer cassette 74. A new first wafer cassette 74 is manually placed in the cassette loading area.

  On the other hand, when a predetermined number of ground semiconductor wafers are loaded into the second wafer cassette 76 placed in the predetermined cassette unloading area of the housing 4, the second wafer cassette 76 is manually unloaded. A new empty second wafer cassette 76 is placed in the cassette unloading area.

  The semiconductor wafer accommodated in the first wafer cassette 74 is conveyed by the vertical movement and forward / backward movement of the wafer conveyance means 78 and is placed on the wafer temporary placement means 80. The wafer placed on the temporary wafer placement means 80 is centered here, and then the chuck table of the chuck table unit 50 positioned in the wafer carry-in / out area by the turning operation of the wafer carry-in means 82. 54 and is sucked and held by the chuck table 54.

  When the chuck table 54 sucks and holds the wafer in this way, the chuck table moving mechanism 58 is operated to move the chuck table unit 54 and position it in the grinding area behind the apparatus.

  When the chuck table unit 50 is positioned in the grinding area, the center of the wafer held by the chuck table 54 is positioned slightly beyond the outer circumference circle of the grinding wheel 30.

  Next, the chuck table 54 is rotated at, for example, about 100 to 300 rpm, the servo motor 26 is driven to rotate the grinding wheel 30 at 4000 to 7000 rpm, and the pulse motor 48 of the grinding unit feed mechanism 44 is driven to rotate forward. The grinding unit 16 is lowered.

  Then, as shown in FIG. 6, the back surface of the wafer 11 is ground by pressing the grinding wheel 34 of the grinding wheel 30 against the back surface (surface to be ground) of the wafer 11 on the chuck table 54 with a predetermined load. By grinding in this way for a predetermined time, the wafer 11 is ground to a predetermined thickness.

  When grinding is completed, the chuck table moving mechanism 58 is driven to position the chuck table 54 in the wafer loading / unloading area on the front side of the apparatus. If the chuck table 54 is positioned in the wafer loading / unloading area, the cleaning water is sprayed from the cleaning water spray nozzle 90 and the ground surface (back surface) of the ground wafer 11 held by the chuck table 54 is held. Wash.

  After the surface to be ground (back surface) of the wafer 11 is cleaned in this way, the oblique light irradiation unit 112 is driven while the chuck table 54 is rotated, and the scratch detection device 94 detects the scratch on the surface to be ground.

  In order to detect the scratch formed on the wafer 11 by the scratch detection device 94 of the present embodiment, first, water is supplied from the water source to the water filling chamber 108 through the water supply port 110, and the water filling chamber 108 is made into water. To fill. Since there is a slight gap between the wafer 11 and the front end of the frame body 96, a constant amount of water is always supplied from the water source to the water filling chamber 108 in order to constantly replenish the water flowing out from the gap.

  Since the grinding of the wafer 11 is performed while supplying the grinding water, the grinding surface of the wafer 11 is contaminated when the grinding is performed. In this embodiment, however, the water filling chamber 108 is always filled with water to detect the scratch. For this purpose, the water filled in the water filling chamber 108 is clean water that is not so contaminated.

  When light is evenly irradiated from the oblique light irradiation unit 112 to the wafer 11 in a region corresponding to the radius of the wafer, the ground surface of the wafer 11 becomes a mirror surface, so that most of the reflected light is mirror-finished. Although the light is regularly reflected by the wafer 11 and does not enter the line scan lens 116, the scattered light scattered by the scratch enters the line scan lens 116 through the glass plate 106 and the inclined filter 114, and the radius of the wafer 11 is made by the line scan lens 116. A region corresponding to is imaged.

  The image formed by the line scan lens 116 is picked up by the line scan CCD camera 118. The output of the line scan CCD camera 118 is input to the scratch determination unit 120 and the monitor 89. The signal input to the scratch determination unit 120 is a signal obtained by appropriately image-processing the output of the line scan CCD camera 118.

  In the scratch determination unit 120, the scattered light reflected by the wafer 11 is detected as the background voltage 122. When the scratch is detected, the light emitted from the oblique light irradiation unit 112 is more scattered and input to the line scan lens 116.

  Therefore, the scratch determination unit 120 detects the spike voltage 126. Reference numeral 124 denotes a predetermined threshold value for determining whether or not there is a scratch. If the voltage value is larger than the threshold value, it is determined that there is a scratch, and if it is smaller, it is determined that there is no scratch.

  The scratch determination unit 120 determines whether or not the threshold value is exceeded in block 128. If the determination is negative, that is, if it is determined that there is no scratch, the wafer cleaning process shown in block 130 is performed. That is, after the wafer held by the chuck table 54 is released, the wafer is transferred to the cleaning means 86 by the wafer unloading means 84.

  The wafer conveyed to the cleaning means 86 is cleaned and spin-dried here. Next, the wafer is stored in a predetermined position of the second wafer cassette 76 by the wafer transport means 78.

  If it is determined in block 128 that the threshold value has been exceeded, the process proceeds to block 132 where it is determined whether or not 30 or more pixels of the line scan CCD camera 118 are continuous. That is, in this determination block 132, a length of a predetermined length or more is determined as a scratch. If the block 132 is negative, it is determined that there is no scratch, and the wafer cleaning process of the block 130 is performed.

  On the other hand, if the determination block 132 is affirmative, it is determined that there is a scratch, and the scratch removal grinding process of block 134 is performed. That is, the chuck table moving mechanism 58 is driven to position the chuck table 54 again in the grinding region, and grinding by about 1 μm is performed by the grinding wheel 30.

  On the other hand, the scratch 136 imaged by the line scan CCD camera 118 is displayed on the monitor 89, and the operator of the grinding apparatus 2 observes the scratch 36 on the monitor 89 and sets the threshold value 122 of the scratch determination unit 120 to a preferable value. .

  In the scratch detection device 94 of this embodiment, scratch detection is performed while the chuck table 54 is rotated at 30 to 100 rpm. Preferably, the scratch detection is completed while the chuck table 54 is rotated at least once.

  According to the above-described embodiment, since the scratch detection device 94 provided with the line scan CCD camera 118 is provided so as to follow the direction of the scratch, the scratch can be immediately detected from the grinding surface of the wafer, and if there is a scratch, the grinding is performed. Continuing or performing scratch removal grinding to transport the scratch-free wafer to the next process, so that a wafer without scratch can be produced efficiently.

It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of the semiconductor wafer where the protective tape was stuck. 1 is an external perspective view of a grinding apparatus according to an embodiment of the present invention. It is a perspective view of a chuck table unit and a chuck table feed mechanism. It is a perspective view of the grinding wheel seen from the lower side. It is a longitudinal cross-sectional view of a grinding wheel. It is a figure explaining the arrangement | positioning relationship of the frame of the scratch detection apparatus with respect to a wafer. It is the longitudinal cross-sectional view of the frame of the scratch detection apparatus which concerns on this invention embodiment, and the block diagram of a scratch determination part.

Explanation of symbols

2 Grinding machine 11 Semiconductor wafer 16 Grinding means (grinding unit)
24 Spindle 26 Servo voter 30 Grinding wheel 34 Grinding wheel 54 Chuck table 94 Scratch detection device 96 Frame body 112 Oblique light irradiation unit 114 Inclination filter 116 Line scan lens 118 Line scan CCD camera 120 Scratch determination unit 136 Scratch

Claims (6)

A grinding apparatus comprising a chuck table for holding a wafer and a grinding means having a grinding wheel for grinding a wafer held on the chuck table,
It further comprises a scratch detection means for detecting a scratch generated on the ground surface of the wafer,
The scratch detection means includes oblique light irradiating means for inclining and irradiating light onto an area corresponding to the wafer radius, a line scan lens for forming an image corresponding to the wafer radius, and the line scan lens. A line scan camera that picks up an image formed in step Scratch determination means for determining the presence or absence of scratches from the image picked up by the line scan camera,
A grinding apparatus for detecting a scratch during at least one rotation of the chuck table. The scratch detection means further includes a frame body that surrounds the line scan lens and is open to the wafer side, and a water supply means that supplies water to the frame body,
2. The grinding apparatus according to claim 1, wherein a space partitioned by the frame body and the wafer is filled with water.   The scratch detection means further includes a tilt filter in which the transmission intensity of the reflected light reflected by the wafer increases proportionally from the center to the outer periphery of the wafer disposed in a region corresponding to the radius of the wafer. The grinding apparatus according to claim 1 or 2. A monitor connected to the line scan camera;
The grinding apparatus according to any one of claims 1 to 3, wherein a scratch threshold value in the scratch determination means can be set by observing scratches on the monitor. A scratch detection device for detecting a scratch generated on a grinding surface of a wafer held on a chuck table,
Oblique light irradiating means for irradiating light to the wafer at an angle corresponding to at least the area corresponding to the radius of the wafer;
A line scan lens that images at least a region corresponding to the radius of the wafer;
A line scan camera that captures an image formed by the line scan lens;
Scratch determining means for determining the presence or absence of scratches from the image captured by the line scan camera,
A scratch detection device that detects a scratch during at least one rotation of the chuck table.   A tilt filter is further provided in which the transmission intensity of the reflected light reflected from the wafer surface increases proportionally from the center of the wafer disposed in a region corresponding to the radius of the wafer toward the outer periphery. Item 6. The scratch detection device according to Item 5.

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