JP5274919B2 - Grinding device and scratch detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scratch detection device of a wafer, and also to provide a grinding device equipped with the same. <P>SOLUTION: The grinding device is provided with a chuck table for holding the wafer and a grinding means having a grinding wheel for grinding the wafer held at the chuck table. The grinding device is further provided with a scratch detection means for detecting a scratch caused on the grinding face of the wafer. The scratch detection means includes a light beam irradiating means for irradiating light beam to the wafer, a converging means for converging a reflective light from an area where the light beam is irradiated, a light receiving means for receiving the reflective light which is converged by the converging means, and a determining means for determining the existence of the scratch when a light amount detected by the light receiving means exceeds a predetermined threshold value. The light receiving means is configured to be a shape to follow a direction where the scratch is formed. <P>COPYRIGHT: (C)2010,JPO&amp;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. 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 can maintain grinding strength by suppressing grinding distortion, and can also maintain a gettering effect, mainly as a grinding wheel for finish grinding.
JP 2006-1007 A

  However, when the grinding 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 to 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 detection means for detecting scratches, the scratch detection means for condensing the reflected light from the light beam irradiation means for irradiating the wafer with the light beam and the region irradiated with the light beam. Means, a light receiving means for receiving the reflected light collected by the light collecting means, and a determination means for determining that there is a scratch when the amount of light detected by the light receiving means exceeds a predetermined threshold. A grinding device is provided in which the means is formed in a shape following a scratch extending in the radial direction of the wafer .

  Preferably, the grinding apparatus includes a beam splitter disposed between the light collecting unit and the light receiving unit, an imaging unit on which reflected light branched to one side by the beam splitter is incident, and is connected to the imaging unit The other reflected light branched by the beam splitter is guided to the light receiving means, and the threshold value of the scratch determination means is set by observing the scratch on the monitor.

Preferably, the light receiving means is constituted by a line sensor, and the line sensor is positioned in a shape following a scratch extending in the radial direction of the wafer . As an alternative, the light receiving means comprises a slit mask having a slit and a light receiving element, and the slit of the slit mask is positioned in a shape following a scratch extending in the radial direction of the wafer .

  Preferably, the chuck table is movable between an attachment / detachment position where the wafer is attached / detached and a grinding position where the wafer is ground by the grinding means, and the scratch detection means is disposed at either the attachment / detachment position or the grinding position. .

  Preferably, the grinding device further includes a frame body surrounding the light collecting means and opened to the wafer side, and a water supply means for supplying water into the frame body, and a space partitioned by the frame body and the wafer is made of water. be satisfied.

According to the eighth 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, the light beam irradiation means for irradiating the wafer with a light beam, and the light beam. The light collecting means for collecting the reflected light from the region irradiated with the light, the light receiving means for receiving the reflected light collected by the light collecting means, and the amount of light detected by the light receiving means exceeds a predetermined threshold value. There is provided a scratch detection device including a scratch determination unit that determines that there is a scratch, and the light receiving unit is configured to follow a scratch extending in the radial direction of the wafer .

According to the grinding device of the present invention, since the light receiving means includes the scratch detection device configured to follow the scratch extending in the radial direction of the wafer, the scratch can be immediately detected from the grinding surface of the wafer, and the scratch is detected. If there is, the grinding is continued or the scratch removal grinding is performed so that the wafer without the scratch is conveyed to the next process, so that the wafer without the scratch can be produced efficiently.

  Further, according to the scratch detection device of the present invention, it is possible to reliably detect the 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, the scratch detection device 94 may be disposed above the grinding region.

  As shown in FIG. 7, the scratch detection device 94 includes a housing 96, a laser diode (LD) 98 attached to the tip of the housing 96, and an objective lens 100 that converts reflected light scattered by the wafer 11 into a collimated beam. And a beam splitter 102 for branching the collimated beam.

  The scratch detector 94 further includes a condenser lens 104 that condenses the collimated beam reflected by the beam splitter 102, a slit mask 106 in which a slit 105 is positioned at the focal position of the condenser lens 104, a light receiving element 108, A scratch determination unit 110 connected to the light receiving element 108 is included.

  The scratch detection device 94 further includes a condenser lens 132 that condenses the collimated beam that has passed through the beam splitter 102, and an imaging means 134 such as a CCD camera. An image picked up by the image pickup means 134 is displayed on the monitor 89.

  A partition wall 136 is provided near the lower end of the housing 96 of the scratch detection device 94, and a water filling chamber 138 is defined between the front end portion of the housing 96 and the wafer 11 held by the partition wall 96 and the chuck table 54. ing.

  One end 140 a of the pipeline 140 is connected to the water source 142, and the other end 140 b opens to the water filling chamber 138. 144 is a switching valve, and 146 is a water pressure gauge. The distance between the tip of the housing 96 and the wafer 11 is preferably maintained at about 0.5-1 mm.

  The LD 98 is attached to the housing 96 so that the laser beam emitted from the LD 98 with an inclination with respect to the wafer 11 is irradiated onto the wafer 11 immediately below the objective lens 100. In the illustrated embodiment, two LDs 98 are provided, but one LD 98 or three or more LDs 98 may be provided.

  As shown in FIG. 8, the scratch 148 formed during the back surface grinding of the wafer 11 is often formed to extend long in the radial direction. Reference numeral 150 denotes a measurement position where the light beam is irradiated by the LD 98.

  Therefore, the slit 105 of the slit mask 106 in the scratch detection device 94 of the present embodiment extends in a direction following the direction in which the scratch is formed, that is, in a direction perpendicular to the paper surface. As shown in FIG. 9, the slit 105 of the slit mask 106 preferably has a width of 0.1 to 0.3 mm and a length of about 2 mm.

  The light receiving element 108 is also preferably configured in a shape that follows the direction in which the scratch is formed. As the light receiving element 108, for example, a photomultiplier tube is preferably used. As another embodiment constituting the light receiving means, a line sensor may be arranged at a position where the slit mask 106 is provided. In this case, the light receiving element 108 is omitted, the line sensor extends in a direction following the direction in which the scratch is formed, and an output signal from the line sensor is input to the scratch determination unit 110.

  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 manner, the LD 98 is driven while the chuck table 54 is rotated, and the scratch detection device 94 detects scratches on the surface to be ground.

  In order to detect a scratch formed on the wafer 11 by the scratch detection device 94 of the present embodiment, first, water is supplied from the water source 142 to the water filling chamber 138 and the water filling chamber 138 is filled with water.

  Since there is a slight gap between the wafer 11 and the front end of the housing 96, a constant amount of water is always supplied from the water source 142 to the water filling chamber 138 in order to constantly replenish the water flowing out from this gap.

  Since the grinding of the wafer 11 is performed while supplying grinding water, the grinding surface of the wafer 11 is contaminated when the grinding is performed. In this embodiment, however, the water filling chamber 138 is always filled with water to detect scratches. For this purpose, the water filled in the water filling chamber 138 is clean water that is not very contaminated.

  When the wafer 11 is irradiated with a laser beam inclined, most of the reflected light is specularly reflected by the mirror-finished wafer 11 and enters the objective lens 100 because the ground surface of the wafer 11 is a mirror surface. Although not scattered, the scattered light scattered by the scratch enters the objective lens 100 as indicated by reference numeral 112 and is converted into a collimated beam by the objective lens 100.

  This collimated beam is split into two beams by the beam splitter 102. The collimated beam reflected by the beam splitter 102 is condensed by the condenser lens 104, and is input to the light receiving element 108 through the slit 105 of the slit mask 106, and is converted into a current value according to the input light quantity, and a scratch determination unit. 110 is output.

  In the scratch determination unit 110, the scattered light is detected as a background current 114 as shown in FIG. When the laser beam emitted from the LD 98 detects a scratch, the laser beam is greatly scattered by the scratch and input to the objective lens 100.

  Therefore, the scratch determination unit 110 detects the spike currents 118 and 120. Reference numeral 116 denotes a predetermined threshold for determining whether or not there is a scratch. If the current value is larger than this, it is determined that there is a scratch, and if it is smaller, it is determined that there is no scratch.

  When the scratch determination unit 110 determines that there is no scratch as shown in block 122, the wafer cleaning process shown in block 124 is performed. In other words, 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.

  When the scratch determination unit 110 determines that there is a scratch as indicated by block 126, the scratch removal grinding process of block 128 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 with about 1 μm by the grinding wheel 30 is performed.

  After the grinding, the wafer is positioned again in the wafer loading / unloading area by the chuck table moving mechanism 58, and the scratch detection process of the block 130 is performed. That is, the wafer 11 is irradiated with a laser beam from the LD 98 while rotating the wafer 11 by the chuck table 54, and the scratch determination unit 110 determines again whether or not there is a scratch. When it is finally determined that there is no scratch, a wafer cleaning process of block 124 is performed.

  Referring to FIG. 7 again, the collimated beam transmitted through the beam splitter 102 is condensed by the condenser lens 132 and input to the imaging means 134 such as a CCD camera. The scratch 152 imaged by the imaging means 134 is displayed on the monitor 89, and the operator of the grinding apparatus 2 observes the scratch 152 on the monitor 89 and sets the threshold value 116 of the scratch determination unit 110 to a preferable value.

  According to the above-described embodiment, since the scratch detection device 94 having the light receiving portion including the slit mask 106 and the light receiving element 108 is provided so as to follow the scratch direction, the scratch can be immediately detected from the ground surface of the wafer. If there is, the grinding is continued or the scratch removal grinding is performed so that the wafer without scratch is conveyed to the next process, so that the 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 longitudinal cross-sectional view of the scratch detection apparatus which concerns on this invention embodiment. It is explanatory drawing explaining the scratch formed in the wafer. It is dimension explanatory drawing of a slit mask. It is a block diagram which shows the process after the scratch determination part and scratch determination of embodiment of this invention.

Explanation of symbols

2 Grinding machine 11 Semiconductor wafer 16 Grinding means (grinding unit)
24 Spindle 26 Servo motor 30 Grinding wheel 34 Grinding wheel 54 Chuck table 94 Scratch detector 98 Laser diode (LD)
DESCRIPTION OF SYMBOLS 100 Objective lens 102 Beam splitter 104,132 Condensing lens 106 Slit mask 108 Light receiving element 110 Scratch determination part 134 Imaging means 138 Water filling chamber 152 Scratch

Claims (8)

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 detecting means includes a light beam irradiating means for irradiating the wafer with a light beam, a condensing means for condensing reflected light from a region irradiated with the light beam, and the light collected by the condensing means. A light receiving means for receiving the reflected light, and a determination means for determining that there is a scratch when the amount of light detected by the light receiving means exceeds a predetermined threshold,
2. A grinding apparatus according to claim 1, wherein the light receiving means is configured to follow a scratch extending in a radial direction of the wafer . A beam splitter disposed between the light collecting means and the light receiving means;
Imaging means on which the reflected light branched to one side by the beam splitter is incident;
A monitor connected to the imaging means,
2. The grinding according to claim 1, wherein the other reflected light branched by the beam splitter is guided to the light receiving means, and the threshold value of the scratch determination means can be set by observing a scratch on the monitor. apparatus. 3. The grinding apparatus according to claim 1, wherein the light receiving means is composed of a line sensor, and the line sensor is positioned in a shape following a scratch extending in a radial direction of the wafer . The light receiving means is composed of a slit mask having a slit and a light receiving element,
3. The grinding apparatus according to claim 1, wherein the slit of the slit mask is positioned in a shape following a scratch extending in the radial direction of the wafer .   5. The grinding apparatus according to claim 4, wherein the light receiving element is a photomultiplier tube. The chuck table has a detaching position for detaching the wafer is a wafer movable between a grinding position for grinding by the grinding means,
The grinding apparatus according to any one of claims 1 to 5, wherein the scratch detection means is disposed at either the attaching / detaching position or the grinding position. A frame body that surrounds the light collecting means and is open to the wafer side; and a water supply means for supplying water into the frame body,
The grinding apparatus according to claim 1, wherein a space partitioned by the frame body and the wafer is filled with water. A scratch detection device for detecting a scratch generated on a grinding surface of a wafer held on a chuck table,
A light beam irradiation means for irradiating the wafer with a light beam;
Condensing means for condensing the reflected light from the region irradiated with the light beam;
A light receiving means for receiving the reflected light collected by the light collecting means;
Comprising a scratch determination means for determining that there is a scratch when the amount of light detected by the light receiving means exceeds a predetermined threshold,
The scratch detection apparatus, wherein the light receiving means is configured to follow a scratch extending in the radial direction of the wafer .

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