JP2005085946A - Wafer conveyance method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly take a reinforcing substrate, having a thickness capable of enduring with respect to a polishing work into or out of a wafer cassette. <P>SOLUTION: There are provided a wafer 1, the reinforcement substrate 21 of a ceramic plate or a glass plate attached to the wafer 1, and the wafer cassette 14 having grooves 17, 17 provided therein for accommodating the wafer 1, to which the reinforcing substrate 21 is attached. A slope 26 is formed at the end of the reinforcing substrate 21 with an inclination angle 2° to 10°, corresponding to an inclined side wall 19 of the groove of the wafer cassette 14 and with the length of the slope being set to 0.5 mm to 3 mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wafer transfer method, and more particularly to a wafer transfer method that reduces defects when a reinforcing substrate is attached to a thinned wafer for transfer.

  In a semiconductor device, in order to form a semiconductor element with high efficiency and low loss, it is desired to reduce the thickness of the wafer. For example, since the package thickness of a transistor is 500 μm or less, it is essential to reduce the thickness of the wafer in consideration of the thickness of the element portion to be formed, the height of the bonding wire, and the like. In order to reduce the thickness of the wafer, the back surface of the wafer is ground.

  A conventional wafer transfer method will be described with reference to FIG.

4A is a cross-sectional view (hereinafter referred to as a side cross-sectional view) in which the side surface of the wafer cassette 14 is cut. The wafer 1 has a thickness of about 460 μm (in the case of 4 inches), and an epitaxial layer is formed on the surface thereof. That is, the wafer 1 is exposed to a high temperature atmosphere of about 900 ° C., and silicon and SiH ₂ CL ₂ (dichlorosilane) are reacted to grow an epitaxial layer by silicon growth on the surface of the wafer 1 to, for example, 30 μm or less. Thereafter, a predetermined element diffusion region 2 is formed on the surface of the wafer 1 through processes such as impurity diffusion and heat treatment, and pattern formation using a photoresist.

  After that, in order to store the wafer 1 in a wafer carrier 14 for grinding to a predetermined finished thickness, the wafer 1 is transferred to the surface of the wafer 1 on which the element diffusion region 2 is formed. The reinforcing substrate 11 is a ceramic plate or a glass plate that is attached to prevent cracking due to damage to the wafer 1 during grinding. The end portion of the reinforcing substrate 11 is chamfered in order to smoothly put in and out the wafer cassette used when the wafer 1 is transferred to the B / G grinding apparatus.

  The chamfer 18 of the reinforcing substrate 11 is usually in the shape of R0.1 to R0.5 mm in the semicircular type (FIG. 4B), and is in the shape of C0.1 to C0.5 mm in the corner type ( FIG. 4 (C)).

  The wafer cassette 14 has a plurality of grooves 17 for storing the wafer 1. In order to smoothly put in and out the wafer, the groove 17 is also provided with an inclined side wall 19 (see, for example, Patent Document 1).

The wafers 1 are stored one by one in the groove of the wafer cassette with the reinforcing substrate attached, and the cassette is set in a B / G grinding apparatus. In the grinding apparatus, the wafers are taken out one by one from the wafer cassette, and the exposed back surface of the wafer 1 is subjected to B / G grinding. The wafer 1 having a desired thickness is finished by the B / G grinding amount at this time (FIG. 4D).
JP-A-9-162276

  The finished thickness of the wafer 1 that is currently generally employed is about 150 μm to 300 μm. When the wafer 1 is ground until this finished thickness is reached, a surface tape is applied to protect the wafer from damage during grinding and scratches on the pattern surface.

  However, when the demand for thinning the wafer increases and the amount of B / G grinding needs to be increased, the thickness of the conventional protective tape is not sufficient to prevent damage to the wafer during grinding. For this reason, it has become necessary to increase the thickness of the protective tape to reduce the damage to the wafer, or to use a tape substrate with increased hardness. However, with this method, it is difficult to stably cut the tape completely, and there is a problem that the tape is ground at the same time during B / G grinding, causing a baking state. Further, when a substrate having a high hardness is used, the life of the cutter being cut off is 1/3 or less of that of a normal one, so that the replacement frequency is high and the productivity is remarkably lowered. Therefore, when the thickness is 150 μm or less, a reinforcing material is inevitably required.

  Therefore, the above-described reinforcing substrate 11 that is generally employed is attached to the wafer 1 and is ground. However, when the reinforcing substrate 11 as shown in FIG. 4 is used, the reinforcing substrate 11 is frequently cracked, resulting in a deterioration in the arrival rate, which is the ratio of the completed wafer without being broken.

  In FIG. 5, the enlarged view of the groove | channel 17 part at the time of using the reinforcement board | substrate 11 is shown. The wafer 1 is accommodated in the groove 17 of the wafer cassette 14 together with the reinforcing substrate 11. Here, as described above, the groove 17 of the wafer cassette 14 has the inclined side wall 19 in order to smoothly take in and out the wafer 1. However, when the above-described reinforcing substrate 11 is used in the existing wafer cassette 14, although the end portion of the reinforcing substrate 11 is chamfered, the chamfer length is shorter and the inclination angle is larger than the inclined side wall 19 of the wafer cassette. The chamfered portion hits the inner wall of the groove 17.

  In that case, when the wafer is taken out, it is bitten into the groove and cannot be taken out by the vacuum chuck. Moreover, when it stores, it pushes into the part of a groove | channel, and also bites into a groove | channel. Therefore, there is a problem that the wafer cannot be taken out even in the next process.

  Further, since the wafer cassette adapted to the shape of the reinforcing substrate 11 is a custom-made product, there is a problem that the cost is very high for mass production of thinned wafers.

  Further, in order to fit the reinforcing substrate 11 to the groove of the wafer cassette 14, the reinforcing substrate 11 is thinned to reduce the total thickness. Consequently, a thickness sufficient to protect the wafer 1 cannot be secured. .

  The present invention makes it possible to store in a wafer cassette a wafer to which a reinforcing substrate having a thickness capable of withstanding grinding is attached. First, the end portion is formed in accordance with the shape of the groove of the wafer cassette. The problem is solved by providing a step of preparing a reinforcing substrate, a step of attaching the reinforcing substrate to a wafer, and a step of storing and transporting the wafer in the groove of the wafer cassette.

  Second, a step of forming an end of at least one main surface side of the reinforcing substrate having two parallel main surfaces in accordance with the shape of the groove of the wafer cassette, a step of attaching the reinforcing substrate to the wafer, And the step of storing the wafer in the groove of the wafer cassette and transporting the wafer.

  The groove has an inclined side wall, and an inclined surface chamfered at an angle corresponding to the inclined side wall is formed at an end of the reinforcing substrate.

  Further, the length of the inclined surface is equal to or longer than the length of the inclined side wall.

  Further, the angle of the inclined surface is equal to or larger than the angle of the inclined side wall.

  The wafer has a finished thickness of 100 μm or less.

  In the semiconductor device of the present invention, an inclined surface having an angle corresponding to the inclined side wall of the groove of the wafer cassette is formed at the end of the reinforcing substrate attached to the wafer. Therefore, the reinforcing substrate can be smoothly put in and out of the groove of the wafer cassette even if the reinforcing substrate is held to a thickness that can withstand the grinding operation. Thereby, the defect which a reinforcement board | substrate and a wafer break at the time of conveyance can be reduced. That is, the arrival rate is greatly improved, the number of wafers corresponding to market requirements can be secured, and the cost of wafers per sheet can be reduced.

  Further, the inclined surface corresponding to the inclined side wall may be formed only on the main surface side facing the main surface to which the wafer is fixed. That is, since the area on the main surface side to which the wafer is bonded can be sufficiently secured, the support strength at the time of B / G grinding is not deteriorated.

  The wafer transfer method of the present invention will be described with reference to FIGS.

  The wafer transfer method of the present invention includes a step of forming an end portion of at least one main surface side of a reinforcing substrate having first and second main surfaces in accordance with the shape of a groove of a wafer cassette, and the reinforcing substrate It comprises a step of attaching to a wafer and a step of storing the wafer in the groove of the wafer cassette and transporting it.

  1st process (FIG. 1): The process of forming the edge part of the at least one main surface side of the reinforcement board | substrate which has two main surfaces parallel to a wafer according to the shape of the groove | channel of a wafer cassette.

  The reinforcing substrate 21 is a ceramic plate or a glass plate that is attached to prevent cracking due to damage to the wafer 1 during grinding. The end portion of the reinforcing substrate 21 is chamfered in order to smoothly put in and out the wafer cassette used when the wafer 1 is transferred to the B / G grinding apparatus.

  The reinforcing substrate 21 has a first main surface 24 and a second main surface 25 that are parallel to a main surface on which an element diffusion region of the wafer 1 to be attached in a later step is formed, and the second main surface 25. The side is bonded to the wafer 1 by an adhesive 12. The end portion of the reinforcing substrate 21 is chamfered at a predetermined angle, and the area and shape of the second main surface 25 fixed to the wafer 1 are approximately the same as or slightly larger than the wafer 1. In the present embodiment, as an example, a description will be given of a reinforcing substrate 21 for grinding to about 100 μm when the thickness of the wafer 1 before grinding is 460 μm (4 inches) or 625 μm (5 inches). In this case, the thickness of the reinforcing substrate is about 400 μm.

  The end portion of the reinforcing substrate 21 has a first inclined surface 26 and a second inclined surface 27 which are inclined with respect to the first and second main surfaces 24 and 25 by chamfering. The first inclined surface 26 is chamfered in accordance with the shape of the groove of the wafer cassette (FIG. 1A).

  FIG. 1B shows an enlarged view of the groove 17 portion of the wafer cassette 14 in order to explain the first inclined surface 26 and the second inclined surface 27. The wafer cassette 14 will be described later, and the wafer 1 to be attached in a later process is also shown here. The wafer cassette 14 is formed with a plurality of grooves 17 for accommodating the end portions of the wafer 1.

  The groove 17 has an inclined side wall 19 having an inclination angle α1 and an inclined surface length β1 so that the wafer 1 can be taken in and out smoothly. Here, the angle α1 of the inclined side wall 19 is an angle inclined inward with respect to the side wall in the vicinity of the groove bottom, and the length β1 of the inclined surface is the horizontal length from the groove bottom to the end of the inclined side wall 19. Say.

  The first inclined surface 26 is formed corresponding to the inclination of the inclined side wall 19 so as not to contact the inclined side wall 19 of the groove 17. Specifically, the length β2 of the inclined surface of the first inclined surface 26 is longer than the length β1 of the inclined surface of the inclined side wall 19, and the inclination angle α2 is equal to or more than the angle α1 of the inclined side wall. Also chamfer so that it tilts inward at a large angle.

  Here, the length of the inclined surface of the first inclined surface 26 refers to the length in the horizontal direction from the end of the reinforcing substrate 21 to the end of the first inclined surface 26, and the inclination angle is the angle of the reinforcing substrate 21. An angle inclined inward with respect to the first main surface 24 is said.

  At this time, the second inclined surface 27 does not need to be shaped to match the inclined side wall 19 of the groove 17. If the chamfered shape is adjusted to the inclined side wall 19 like the first inclined surface 26, the area of the second main surface 25 to which the wafer 1 is fixed is reduced, and reinforcement during grinding becomes insufficient. That is, the second inclined surface 27 is formed with an angle and a length that can secure the second main surface 25 in as large an area as possible in consideration of the thickness of the wafer 1 and the reinforcing substrate 21.

  On the other hand, even if the area of the first main surface 24 is smaller than that of the wafer 1, it does not affect the grinding so much. Therefore, the first inclined surface 26 is matched to the shape of the groove 17 of the wafer cassette and corresponds to the inclination of the inclined side wall 19. Chamfer. Thereby, even if it is the thickness of the conventional reinforcement board | substrate 21, accommodation in the existing wafer cassette 14 is attained.

  For example, in the present embodiment, the length β2 of the first inclined surface 26 is 0.5 mm to 3.0 mm from the tip, and the angle α2 of the inclined surface is 2 ° to 10 ° inside the first main surface 24. Chamfer to slope.

  Second step (see FIG. 2): A step of attaching the reinforcing substrate to the wafer.

The wafer 1 has a thickness of about 460 μm, for example, and an epitaxial layer is formed on the surface. That is, the wafer 1 is exposed to a high temperature atmosphere of about 900 ° C., and silicon and SiH ₂ CL ₂ (dichlorosilane) are reacted to grow an epitaxial layer by silicon growth on the surface of the wafer 1 to, for example, 30 μm or less. Thereafter, the wafer 1 is subjected to processes such as impurity diffusion and heat treatment, and pattern formation with a photoresist, thereby forming a predetermined element diffusion region 2 on the surface of the wafer 1 (FIG. 2A).

  After the element diffusion region 2 is formed, the second main surface 25 of the reinforcing substrate 21 for surface protection and reinforcement is attached to the surface of the wafer 1 on which the element diffusion region is formed with the adhesive 12, and the back surface of the wafer 1 is attached. Exposed.

  During B / G grinding, wafer cracks often occur due to poor adhesion at the edge of the wafer 1, so that the area and shape of the second main surface 25 and the wafer 1 are substantially the same or the second main surface as described above. 25 is slightly larger than the wafer 1. The area of the second main surface 25 is ensured by adjusting the amount of chamfering of the second inclined surface 27 in the first step (FIG. 2B).

  3rd process (refer FIG. 3): The process of accommodating a wafer in the groove | channel of a wafer cassette, and conveying.

  FIG. 3A shows a perspective view of the entire wafer cassette 14, and FIG. 3B shows a side sectional view of a groove that accommodates the wafer 1. FIG.

  As shown in FIG. 3A, the wafer carrier 14 has a plurality of grooves 17 for accommodating the wafer 1 on the side surfaces 16 arranged opposite to each other. Further, as described above, the groove 17 is provided with the inclined side wall 19 that makes it possible to smoothly take in and out the wafer 1.

  As shown in FIG. 3B, the wafers 1 are stored one by one in the groove 17 of the wafer cassette 14 with the reinforcing substrate 21 attached, and are transferred to the B / G grinding apparatus. As shown in FIG. 1, a first inclined surface 26 is formed at the end portion of the reinforcing substrate 21 corresponding to the inclined side wall 19 provided in the groove 17 of the wafer cassette 14.

  As shown in FIG. 1B, the first inclined surface 26 has a length β2 equal to or longer than the length β1 of the inclined side wall 19 and an inclination angle α2 is equal to or larger than the angle α1 of the inclined side wall 19.

  That is, the end portion of the reinforcing substrate 21 does not bite into the inclined side wall 19 of the groove 17, and the reinforcing substrate 21 to which the wafer 1 is attached has a thickness that can withstand grinding. It can be inserted and stored and taken out.

The wafers 1 stored in the wafer cassette 14 with the reinforcing substrate attached are stored one by one in the groove of the wafer cassette, and the cassette is set in the B / G grinding apparatus. In the grinding apparatus, the wafers are taken out one by one from the wafer cassette, and the exposed back surface of the wafer 1 is subjected to B / G grinding (see FIG. 4D). At this time, since the conventional reinforcing substrate 21 is attached to the wafer, even if a load is applied to the wafer surface by B / G grinding, the wafer 1 is not cracked during grinding, and the finished thickness is 100 μm or less. Therefore, wafer thinning can be realized.

It is a sectional side view which shows the reinforcement board | substrate and wafer conveyance method of this invention. It is a side view explaining the wafer and reinforcement board | substrate of this invention. It is (A) perspective view and (B) side sectional drawing explaining the wafer conveyance method of this invention. It is a sectional side view explaining the conventional wafer conveyance method. It is a sectional side view explaining the conventional wafer and a reinforcement board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer 2 Element diffusion area 11 Reinforcement substrate 12 Adhesive 14 Wafer cassette 17 Groove 19 Inclined side wall 21 Reinforcement substrate 24 1st main surface 25 2nd main surface 26 1st inclined surface 27 2nd inclined surface

Claims (6)

A step of preparing a reinforcing substrate whose end is formed in accordance with the shape of the groove of the wafer cassette;
Attaching the reinforcing substrate to the wafer;
And a step of storing the wafer in the groove of the wafer cassette and transferring the wafer. Forming at least one main surface end of the reinforcing substrate having two parallel main surfaces in accordance with the shape of the groove of the wafer cassette;
Attaching the reinforcing substrate to the wafer;
And a step of storing the wafer in the groove of the wafer cassette and transferring the wafer. 3. The groove according to claim 1, wherein the groove has an inclined side wall, and an inclined surface chamfered at an angle corresponding to the inclined side wall is formed at an end of the reinforcing substrate. Wafer transfer method. 4. The wafer transfer method according to claim 3, wherein a length of the inclined surface is equal to or longer than a length of the inclined side wall. The wafer conveyance method according to claim 4, wherein an angle of the inclined surface is equal to or larger than an angle of the inclined side wall. The wafer transfer method according to claim 1, wherein the wafer has a finished thickness of 100 μm or less.

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