JP2012190930A - Wafer and transfer method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer in which the bottom face of a circular recess is not contaminated with foreign matter during transportation, and to provide a transfer method of wafer.SOLUTION: In a wafer having a circular recess and an annular protrusion surrounding the circular recess on the reverse face, inner peripheral wall of the annular protrusion is inclined so that the diameter of the circular recess increases from the top face of the annular protrusion toward the bottom face of the circular recess. In the transfer method, a plurality of support fingers are inserted into the circular recess, and the wafer is transported while supporting the upper inner peripheral wall of the annular protrusion by means of the support fingers.

Description

  The present invention relates to a wafer having a circular concave portion and an annular convex portion surrounding the circular concave portion, and a wafer transport method for transporting the wafer.

  In a semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and ICs, LSIs, and the like are divided into the partitioned regions. Form the device. Then, the semiconductor wafer is divided into individual semiconductor chips (devices) by cutting the semiconductor wafer along a street with a cutting device.

  A wafer to be divided into individual chips is ground to a predetermined thickness by grinding the back surface before cutting along the street. In recent years, in order to achieve a reduction in weight and size of electrical equipment, it has been required to make the wafer thinner, for example, about 50 μm.

  Such thin wafers are difficult to handle and may be damaged during transportation. Therefore, Japanese Patent Application Laid-Open No. 2007-19461 discloses a grinding method in which only the back surface corresponding to the device region of the wafer is ground and an annular convex portion (annular reinforcing portion) is formed on the back surface of the wafer corresponding to the outer peripheral surplus region surrounding the device region. Proposed in the gazette.

  A wafer ground by such a grinding method has a circular concave portion on the back surface of the wafer corresponding to the device region, and the circular concave portion is surrounded by an annular convex portion acting as a reinforcing portion. Conventionally, the bottom surface of the circular recess is directly sucked by a suction pad and transported.

JP 2007-19461 A

  By the way, when the wafer device is an individual semiconductor device, a metal film serving as an electrode is formed on the bottom surface of the circular recess. In such a wafer, when the circular recess is directly sucked and transported by the suction pad, foreign matter (contamination) adheres to the circular recess due to contact with the suction pad, which causes a problem when the metal film is formed.

  On the other hand, in non-contact conveyance using a Bernoulli pad, the negative concave portion of the wafer may bend due to the negative pressure generated and be damaged from the boundary between the circular convex portion and the circular concave portion. There is also difficulty in transporting.

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer and a wafer transport method that solve the above-described conventional problems.

  According to the first aspect of the present invention, a wafer having a circular concave portion and an annular convex portion surrounding the circular concave portion on the back surface, the diameter of the circular concave portion being changed from the upper surface of the annular convex portion to the bottom surface of the circular concave portion. There is provided a wafer characterized in that the inner peripheral wall of the annular convex portion is inclined so as to become larger.

  According to a second aspect of the present invention, there is provided a wafer transport method for transporting a wafer according to the first aspect, wherein a plurality of support fingers are inserted into the circular recesses, and the support fingers are moved radially outward. There is provided a method for transporting a wafer, wherein the wafer is transported in a state where an upper portion of the inner peripheral wall of the annular convex portion is supported by the supporting finger.

  According to the first aspect of the present invention, foreign matter (contamination) does not adhere to the bottom surface of the circular concave portion during wafer conveyance, and the possibility of breakage from the boundary between the annular convex portion and the circular concave portion during conveyance is reduced. There is provided a wafer having a circular concave portion and an annular convex portion surrounding the circular concave portion on the back surface.

  According to the second aspect of the present invention, there is no risk of foreign matter (contamination) adhering to the bottom surface of the circular concave portion, and the wafer transport method in which the risk of breakage from the boundary between the annular convex portion and the circular concave portion during transport is reduced. Is provided.

It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of the semiconductor wafer by which the protective tape was stuck on the surface. 1 is a perspective view of a grinding apparatus suitable for carrying out the wafer transport method of the present invention. It is a principal part perspective view of a wafer carrying-out mechanism (unloading arm). It is a perspective view of the formation method of the wafer of a 1st embodiment of the present invention. It is a partial cross section side view of the formation method of the wafer of a 1st embodiment. It is explanatory drawing of the formation method of the wafer of 1st Embodiment. It is a longitudinal cross-sectional view of the wafer formed with the formation method of the wafer of 1st Embodiment. It is a partial cross section side view which shows the formation method of the wafer of 2nd Embodiment of this invention. It is a partial cross section side view explaining the conveyance method of this invention. It is a partial cross section side view explaining the conveyance method of this invention.

  Hereinafter, 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. The 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.

  Referring to FIG. 3, there is shown a perspective view of a grinding apparatus 2 suitable for carrying out the wafer forming method and wafer transport method of the present invention. Reference numeral 4 denotes a base of the grinding apparatus 2, and a column 6 is erected on the rear side of the base 4. A pair of guide rails 8 extending in the vertical direction are fixed to the column 6.

  A grinding unit (grinding means) 10 is mounted along the pair of guide rails 8 so as to be movable in the vertical direction. In the grinding unit 10, a support bracket 34 that supports the housing 20 of the grinding unit 10 is attached to the moving base 12 that moves in the vertical direction along the pair of guide rails 8.

  The grinding unit 10 includes a housing 20, a spindle 22 rotatably accommodated in the housing 20, a motor 24 that rotationally drives the spindle 22, a wheel mount 26 fixed to the tip of the spindle 22, and a detachable attachment to the wheel mount 26. It includes a grinding wheel 28 which is mounted as possible.

  The grinding unit 10 includes a grinding unit feed mechanism 18 including a ball screw 14 and a pulse motor 16 that move the grinding unit 10 up and down along a pair of guide rails 8. When the pulse motor 16 is driven, the ball screw 14 rotates and the moving base 12 is moved in the vertical direction.

  A chuck table mechanism 36 having a chuck table 38 is disposed at an intermediate portion of the base 4. The chuck table 38 is moved in the Y-axis direction between a wafer carry-in / carry-out region and a cutting region facing the grinding unit 10 by a chuck table moving mechanism (not shown). A bellows 40 covers the chuck table mechanism 36.

  Two cassette mounting tables 42 and 44 are integrally formed on the front portion of the base 4, and a cassette 46 for storing a wafer before grinding is mounted on the cassette mounting table 42. A cassette 48 for accommodating the wafer after grinding is placed on the top.

  In addition to the two cassette mounting tables 42 and 44, a wafer transfer robot 50, a positioning mechanism 52 having a plurality of positioning pins 54, a wafer loading mechanism (loading arm) 56, and a wafer carry-out are provided on the front side portion of the base 4. A mechanism (unloading arm) 58 and a spinner cleaning unit 60 having a spinner table 61 are provided.

  Referring to FIG. 4, a perspective view of a main part of a wafer unloading mechanism (unloading arm) 58 is shown. The wafer carry-out mechanism 58 includes a swivel arm 62, a head part 64 attached to the tip of the swivel arm 62, a pair of extendable support members 66 and 68 attached to the head part 64, and support members 66 and 68. It is comprised from the support finger 70 with which the front-end | tip was mounted | worn.

  The support finger 70 is preferably formed from an elastic member such as rubber. The pair of support members 66 and 68 are expanded and contracted with respect to the head portion 64 by, for example, an air cylinder accommodated in the head portion 64.

  Next, with reference to FIGS. 5 to 7, a method for forming a wafer according to the first embodiment of the present invention will be described. As best shown in FIG. 6, the forming method of the present embodiment is ground using a grinding wheel 28 in which a plurality of grinding wheels 32 having inclined outer peripheral surfaces 32 a are arranged annularly at the lower end of the base 30. To implement. The outer peripheral surface 32 a of the grinding wheel 32 is inclined outward in the radial direction as the distance from the base 30 increases.

  The wafer 11 is suction-held on the protective tape 23 side by the chuck table 38, and the back surface 11 b of the wafer 11 is set to face the grinding wheel 32. Here, the relationship between the wafer 11 held on the chuck table 38 and the grinding wheel 32 mounted on the grinding wheel 28 will be described with reference to FIG.

  The rotation center P1 of the chuck table 38 and the rotation center P2 of the grinding wheel 32 arranged in an annular shape are eccentric, and the outer diameter of the grinding wheel 32 is the boundary line 25 between the device region 17 of the wafer 11 and the outer peripheral surplus region 19. The relationship is such that the grinding wheel 32 which is smaller than the diameter and larger than the radius of the boundary line 25 and which is annularly arranged passes through the rotation center P 1 of the chuck table 38.

  As shown in FIGS. 5 and 6, while rotating the chuck table 38 in the direction indicated by arrow a at 300 rpm, for example, the grinding wheel 28 is rotated in the direction indicated by arrow b at 6000 rpm, for example, and the grinding unit feed mechanism 18 is It operates to bring the grinding wheel 32 of the grinding wheel 28 into contact with the back surface of the wafer 11. Then, the cutting wheel 28 is moved at a low speed in the direction indicated by the arrow c while being ground and fed by a predetermined amount at a predetermined grinding feed speed.

  As a result, on the back surface of the semiconductor wafer 11, as shown in FIG. 8, a region corresponding to the device region 17 is ground and removed to form a circular recess 72 having a predetermined thickness (for example, 50 μm), and an outer peripheral surplus region. The region corresponding to 19 is left, and an annular convex portion 74 including the outer peripheral surplus region 19 is formed.

  The inner peripheral wall 74 b of the annular convex portion 74 is inclined so that the diameter of the circular concave portion 72 increases from the upper surface 74 a of the annular convex portion 74 toward the bottom surface 72 a of the circular concave portion 72. In other words, the inner peripheral wall 74b of the annular protrusion 74 is inclined radially outward from the back surface 11b of the wafer 11 toward the front surface 11a.

  Referring to FIG. 9, there is shown a partial cross-sectional side view of a wafer forming method according to a second embodiment of the present invention. In the present embodiment, the circular recess 72 is formed by first grinding the back surface of the wafer corresponding to the device region 17 of the wafer 11 using a grinding wheel that is not inclined. By this grinding, the inner peripheral wall 74 c of the annular convex portion 74 becomes perpendicular to the bottom surface 72 a of the circular concave portion 72.

  Next, the inner peripheral wall 74 c of the annular convex portion 74 is trimmed by the cutting blade 80 attached to the inclined spindle 78 to form the inner peripheral wall 74 b inclined to the annular convex portion 74. Trimming with the cutting blade 80 attached to the inclined spindle 78 in this way can also form the inclined inner peripheral wall 74b in the annular convex portion 74, as in the first embodiment.

  As a modification of the second embodiment, first, the cutting blade 80 attached to the inclined spindle 78 is inclined to the back surface 11b of the wafer 11 corresponding to the boundary line 25 between the device region 17 and the outer peripheral surplus region 19 of the wafer 11. An annular groove may be formed, and then a circular recess may be formed by grinding on the inner peripheral side of the annular groove. That is, in this modification, the circular recess forming step and the trimming step of the wafer forming method of the second embodiment are reversed.

  After the grinding of the back surface 11b of the wafer 11 by the formation method of the first embodiment, the wafer 11 is moved to the wafer carry-in / out region by driving the chuck table moving mechanism, and is moved from the chuck table 38 by the wafer carry-out mechanism 58. It is carried out. This unloading method (conveying method) will be described in detail with reference to FIGS.

  As shown in FIG. 10, the turning arm 62 is lowered with the support members 66 and 68 of the wafer carry-out mechanism 58 contracted, and the support fingers 70 at the tips of the support members 66 and 68 are inserted into the circular recesses 72 of the wafer 11. To do.

  Then, the air cylinder built in the head portion 64 is driven to extend the support members 66 and 68 as indicated by an arrow A in FIG. 11, and the support finger 70 supports the upper part of the inner peripheral wall 74 b of the annular convex portion 74. To do.

  The expansion and contraction of the support members 66 and 68 is performed by an air cylinder accommodated in the head portion 64, but by inserting a spring in the middle of the support members 66 and 68, the inner peripheral wall 74 b of the annular convex portion 74 by the support fingers 70 is formed. The upper support can be made more reliable.

  After releasing the suction and holding of the chuck table 38, the swivel arm 62 is lifted in a state where the upper part of the inner peripheral wall 74b of the annular convex portion 74 is supported by the support finger 70, and then swiveled counterclockwise in FIG. The wafer 11 is placed on the spinner table 61 by transporting to the spinner table 61 of the spinner cleaning unit 60 and drawing the support members 66 and 68 into the head portion 64 by the air cylinder.

  After the wafer 11 is cleaned and spin-dried by the spinner cleaning unit 60, the cleaned wafer 11 is sucked and held by the wafer transfer robot 50 and inserted into a predetermined position of the cassette 48.

  In the above-described embodiment, the example in which the present invention is applied to the semiconductor wafer 11 has been described. However, the wafer is not limited to the semiconductor wafer, and includes other wafers such as a sapphire wafer and a SiC wafer.

  Further, the semiconductor wafer 11 shown in FIG. 1 has a plurality of devices 15 formed on its surface 11a, but the wafer of the present invention includes a wafer cut from an ingot having no device on the surface.

  Further, the wafer 11 shown in FIG. 8 and FIG. 9 has an inner peripheral wall 74b in which the annular convex portion 74 is inclined, but the inclined inner peripheral wall 74b may be formed in a step shape. The formation method of the inclined inner peripheral wall 74b is not limited to the formation method of the first and second embodiments described above.

2 Grinding apparatus 10 Grinding unit 11 Semiconductor wafer 17 Device area 19 Peripheral surplus area 28 Grinding wheel 32 Grinding wheel 38 Chuck table 58 Wafer unloading mechanism (unloading arm)
62 Rotating arm 64 Head portion 66, 68 Support member 70 Support finger 72 Circular concave portion 74 Annular convex portion 74b Inclined inner peripheral wall

Claims (2)

A wafer provided on the back surface with a circular concave portion and an annular convex portion surrounding the circular concave portion,
A wafer characterized in that the inner peripheral wall of the annular convex portion is inclined so that the diameter of the circular concave portion increases from the upper surface of the annular convex portion toward the bottom surface of the circular concave portion. A wafer transport method for transporting a wafer according to claim 1,
A plurality of support fingers are inserted into the circular recess, and the wafer is transported in a state where the support fingers are moved radially outward and supported above the inner peripheral wall of the annular projection by the support fingers. Wafer transport method.

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