JPH0555373A - Wafer cracking method and device - Google Patents

Abstract

PURPOSE:To enable a wafer to be uniformly cracked by a method wherein the surface of the wafer is very slightly diced so as to obliquely cut the wafer, and a cutter blade is pushed up against the rear of the wafer so as to give a shock to enable the wafer to be cracked. CONSTITUTION:When a wafer is cut into rectangular chips, the side of the chip which can be cut vertical to the surface of the wafer is cut nearly as deep as the thickness of the wafer with a diamond cutter or the like, and the other sides of the chip which are obliquely cut are slightly cut. The cutter blade 31 is pushed up against the rear of the wafer along a dicing line provided to the surface of the wafer with a push machine 35. Therefore, an impact force is uniformly applied to the wafer from end to end along a fine line with a cutter blade 31, the wafer is cracked along its crystal axis responding to the dicing line provided to its front side, where a crack starts from the dicing line provided to the surface reaching to the rear, and the wafer is obliquely cracked. By this setup, a wafer is uniformly cracked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer cracking method and apparatus for cutting and separating chips from a wafer such as a semiconductor substrate. More specifically, the present invention relates to a wafer cracking method and apparatus for cutting and separating a wafer having a crystallographic direction oblique to the substrate surface along the crystallographic direction.

[0002]

2. Description of the Related Art Conventionally, for example, semiconductor chips are formed by forming the same circuit in a grid pattern on a wafer, which is a single semiconductor substrate, and cutting and separating the same circuit into the grid pattern to form each chip. There is. Normally, this cutting can be done perpendicularly to the substrate.Therefore, the wafer is attached to an elastic film such as vinyl chloride film, and the entire thickness of the wafer is cut with a diamond cutter. A method is adopted in which 3/4 of the thickness is cut and the rest is cracked for separation.

However, depending on the type of semiconductor, the crystal forming the wafer grows in an oblique direction with respect to the surface of the wafer, and it may be necessary to cut and separate along the crystal direction. For example, in the case of a laser emitting device,
A wafer with aluminum wiring on a silicon semiconductor substrate with a crystal orientation of <111> is made into a chip and used as a silicon submount.
A semiconductor laser is mounted on the surface of the silicon submount. The structure of this silicon submount has an angle of 19.5 ° with respect to the vertical direction as shown in the side view of FIG.

Such diagonal cutting with respect to the vertical direction cannot be performed by a conventional dicing machine for processing a silicon submount which requires a fine precision of 1 μm or less.

A conventional method of cutting and separating a wafer of this type will be described with reference to FIGS. That is, FIG. 6 is a plan view of a wafer, and the grid-like lines of the cross-section in the same drawing are dicing lines, FIG. 7 is a partially enlarged view of a part thereof, and FIG. 8 is an explanatory view showing a method for cracking the wafer. In these figures, 1 is a wafer, 2 is a dicing line for half dicing, and 3 is a full dicing line cut to the back of the wafer. That is, since the crystal direction of the dicing line 3 is not oblique, the dicing line 3 can be cut perpendicularly to the front surface of the wafer 1, and the dicing line 2 cuts to the back surface of the wafer 1. Since it is necessary to cut diagonally and obliquely, only the surface of the wafer 1 is cut with a diamond cutter. The place where only this surface is diced is shown by a notch 2a in FIG. 5 is expanded tape, 6 is tantalum plate, 7 is silicone rubber sheet, 8
Is the cracking rod, and C is the cracking direction.

For cracking, first, the wafer 1 is attached to the expanding tape 5, and the dicing line 3 is fully diced and the dicing line 2 is half-diced with a diamond cutter. Then, the silicon rubber sheet 7, the tantalum plate 6 and the expanding tape 5 are integrated and attached with the front side of the silicon submount wafer 1 facing downward, and the silicon submount wafer 1 is bonded in a direction perpendicular to the dicing line 3 (half dicing). The silicon sub-mount wafer 1 was cracked by tracing it in the direction C while pressing the cracking rod 8 having a sharp tip in the direction (parallel to the line 2) by hand.

[0007]

SUMMARY OF THE INVENTION The conventional manual cracking method is not efficient, and the cracking force applied to the cracking rod 8 is not uniform. There is a problem that the cracked state becomes uneven, and as shown in P of FIG. 9, an abec defect and a cracking defect Q, which are not cut and both are defective, and a crack residue is easily generated.

In view of such a situation, the present invention provides a method and an apparatus for reliably cracking a wafer having a crystal growth direction oblique to the surface of the wafer with good work efficiency and preventing occurrence of defects. With the goal.

[0009]

A wafer cracking method for obliquely cutting and separating a wafer surface according to the present invention is to perform a shallow dicing on the wafer surface perpendicularly to the wafer surface, and then from the back surface of the wafer to the dicing. This is done by abutting the cutter blade along the line with a pushing mechanism to crack.

The wafer cracking apparatus according to the present invention comprises a moving table which moves laterally along a guide,
A moving mechanism for moving the moving table at a predetermined pitch,
A wafer holder fixed on the moving table, a wafer fixed on the wafer holder, a cutter blade arranged on the lower side of the wafer, and a push-up for pushing the cutter blade to hit the wafer. The moving mechanism and the pushing-up mechanism are synchronized with each other to automatically operate the moving and pushing-up.

[0011]

According to the present invention, when cutting a wafer into rectangular chips, a side that can be cut perpendicularly to the wafer surface cuts almost the entire thickness of the wafer with a diamond cutter, etc. As for the side to be cut diagonally, the front surface is cut shallowly and the cutter blade is abutted from the back side of the wafer along the dicing line on the front surface, so that a uniform impact force is applied from the edge of the wafer to the thin line by the cutter blade. Then, a crack along the crystal axis corresponding to the dicing line formed on the front surface enters from the dicing line on the front surface to the back surface and cracks obliquely.

Since all the chips have the same size, by shifting the wafer by chip intervals and repeating the impact caused by the push-up, cracks in a grid pattern can be formed on the wafer for separation.

[0013]

The present invention will be described below with reference to the drawings. 1 is a schematic perspective view of a wafer cracking apparatus according to the present invention, FIG. 2 is a schematic perspective view of a moving table portion, FIG. 3 is a cross-sectional explanatory view of a wafer holding portion, and FIG. 4 is a schematic perspective view of a push-up portion. In these figures, 10 is a moving table, 20 is a wafer holding part, 30 is a push-up part, 40 is a frame, and a microscope 41 is attached to the end part.

As shown in FIG. 2, the moving table 10 has a table 11 fixed to an LM guide 13 via a ball screw 12 and a moving mechanism 14 connected to the ball screw 12 through the ball screw 12 as shown by an arrow A. It can be moved in either the left or right direction at a fixed pitch. The moving mechanism 14 can be composed of a pulse motor, a coupling, or the like.

The wafer holding unit 20 is fixed to the table 11 by a holder guide 26 so that the wafer 1 can be moved at a constant pitch by moving the moving table 10 at a constant pitch. A state in which the wafer 1 is held by the wafer holder 20 is shown in a sectional view in FIG.

In FIG. 3, 1 is a wafer, 21 is an expanded tape having the back surface of the wafer 1 attached thereto, and 22 is a transparent resin plate, such as an acrylic plate or a vinyl chloride plate. This is a reinforcing plate for holding the wafer 1 when it is pushed up by the push-up mechanism 30 from the back surface of the wafer 1. Reference numeral 23 is a transparent elastic sheet, for example, a silicone rubber sheet or a urethane rubber sheet is used. These are for absorbing the impact when the wafer 1 is pushed up from the back surface and preventing unnecessary cracks from entering the wafer 1. Reference numeral 24 denotes an expand sheet for fixing the transparent resin plate 22 and the elastic sheet 23 so that they can be placed on the surface of the wafer 1 and for protecting the surface of the wafer 1. In this example, the wafer 1 Although the same material as that of the expanding sheet 21 attached to the back surface of the wafer 1 is used, it can also be used as the elastic sheet 23 because it protects the surface of the wafer 1 and has elasticity. The transparent resin plate 22 and the elastic sheet 23 are made of a transparent material so that the dicing line of the wafer can be seen from the upper side and the position of the cutter blade 31 can be easily aligned.

The wafer holding section 20 can be constructed by fixing these to the hold plate 25 so that the expand sheet 21 attached to the back surface of the wafer 1 is on the lower side.

After the wafer 1 is adhered to the expanding sheet 21 in advance, the dicing line 3 which can be cut perpendicularly to the front surface of the wafer 1 is cut almost to the back surface of the wafer 1 with a diamond cutter or the like, and the dicing line 2 which cannot be cut vertically is formed. Is diced to a slight depth only on the surface of the wafer 1. If the dicing depth of this dicing line 2 is too deep, it cannot be cut along the crystal direction, and if it is too shallow, it will not crack even if an impact is applied from the backside by a cutter blade, so it is 1/10 to 1 of the wafer thickness. It is preferable that the depth is / 4th.

Next, the push-up portion 30 will be described. The push-up portion 30 has a cutter blade 31 as shown in a schematic perspective view in FIG.
Is held by a cutter holder 32, the cutter holder 32 is fixed to a slide block 33, and the push-up mechanism 35 moves the cutter holder 32 up and down.

The cutter blade 31 has a length corresponding to the diameter of the wafer 1 so as to hit the back surface of the half-diced dicing line 2 of the wafer 1, and the tip has a thin structure with a thickness of about 10 μm and is abrasion resistant. Therefore, the surface is hardened and formed of carbon steel, super steel, etc.

The push-up mechanism 35 includes a bracket 36 for holding the slide block 33, an air cylinder 37, and an air cylinder.
37 The push-up button 38 at the center and an air cylinder drive mechanism such as a solenoid valve (direction control valve) not shown. The push-up button 38 is arranged so as to be located right below the center of the slide block 33, and is arranged at a slight distance from the slide block 33. These are for applying the impact force to hit the cutter blade against the back surface of the wafer 1.

With the wafer breaking apparatus having this structure, the silicon submount wafer 1 with aluminum wiring is attached to the expanding sheet 21, and the dicing line 3 in a direction that can be cut perpendicularly to the plane of the wafer 1 has a thickness of 230. μm
Was diced to almost the back surface, and the dicing line 2 in a direction that could not be cut vertically was diced to a depth of about 40 μm. In this state, the transparent resin plate 22 and the elastic sheet 23 were fixed to the hold plate 25 and fixed to the table 11. Microscope 41
Then, the dicing line 2 of the wafer 1 and the line of the cutter blade 31 are aligned with each other by rotating the hold plate 25 and finely adjusting the table 11. Here, the cutter blade 31 is aligned with the dicing line 2 on the surface, not at the position where the wafer is cracked, because cracks easily form along the crystal growth direction from the dicing portion. Dicing line 2 which is the width of the chip
The moving mechanism 14 was adjusted so as to move by 1 mm each, and this moving pitch was synchronized with the pushing pitch of the pushing mechanism 35. The push-up force of the air cylinder 37 of the push-up mechanism 35 was 7 kg, and the push-up button 38 was pushed up by the pulse motor. The distance between the push-up button 38 and the slide block 35 is about 4 mm, and the distance between the cutter blade 31 and the expanding sheet 21 is also about 4 mm. An impact force larger than the push-up force of the push-up button is applied to the wafer 1, and the wafer 1 is oriented in the crystal direction. A crack was generated along the line.

Expanded sheet with this crack
When the expanded sheet 21 is expanded by heating the wafer 1 attached to the substrate 21 to 70 ° C. and stretching it, the intervals between the cut portions are expanded, and the chips are separated and picked up and used in the next step.

As a result of cracking a wafer by this method, the number of man-hours (actual time required for human beings) per wafer is reduced from the conventional 20 minutes to 2 minutes, which can be greatly reduced.
Moreover, the yield due to cracks has improved significantly from the conventional 60% to 100%.

In the example described above, the example of the silicon submount wafer was described, but the present invention can be applied to the case where other thin substrates are obliquely cut.

[0026]

As described above, according to the present invention, in order to cut a wafer obliquely, the wafer surface is diced to a slight depth, and the back surface thereof is pushed up by a cutter blade and cracked by an impact. It can be cracked uniformly and can be automated. As a result, the man-hours for cracking work can be greatly reduced, and the yield can be greatly improved, which can greatly contribute to cost reduction.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a wafer cracking apparatus that is an embodiment of the present invention.

FIG. 2 is a schematic perspective view of a moving table portion.

FIG. 3 is a cross-sectional explanatory view of a wafer holder.

FIG. 4 is a schematic perspective view of a push-up portion.

FIG. 5 is a side view of a silicon submount cut obliquely.

FIG. 6 is a plan view in which a wafer has a dicing line.

7 is a partially enlarged view of FIG.

FIG. 8 is a diagram illustrating a conventional wafer cracking method.

FIG. 9 is an explanatory plan view showing an example of a defect due to conventional wafer cracking.

[Explanation of symbols]

 1 Wafer 10 Moving Table 13 LM Guide 14 Moving Mechanism 20 Wafer Holding Unit 31 Cutter Blade 35 Push-up Mechanism

Claims (3)

[Claims] 1. A wafer cracking method for cutting and separating a wafer having a crystallographic direction oblique to the surface obliquely along the crystallographic direction, wherein the wafer surface is subjected to shallow dicing in a direction perpendicular to the wafer surface. Then, a wafer cracking method in which a cutter blade is abutted from the back surface of the wafer along a line of the dicing by a push-up mechanism to crack. 2. A back surface of the wafer is attached to an expanding sheet, a transparent resin plate is arranged on the front surface side of the wafer via a transparent elastic sheet to fix the wafer, and from the front surface side of the wafer. 2. The wafer cracking method according to claim 1, wherein the dicing line is aligned with the cutter blade, and the cutter blade is abutted against the expanded sheet on the back surface of the wafer. 3. A moving table that moves laterally along a guide, a moving mechanism that moves the moving table at a predetermined pitch, a wafer holding part fixed on the moving table, and a wafer holding part. The fixed wafer, a cutter blade disposed below the wafer, and a push-up mechanism that pushes up the cutter blade and hits the wafer, and the moving mechanism and the push-up mechanism are synchronized. Wafer cracking device that automatically activates push-up.