JPS61284926A - Method for cutting and removing masking sheet for processing silicon wafer - Google Patents

Abstract

PURPOSE:To automate the process for improving the productivity as well as for increasing the yield rate of wafers by successively paying out and contacting an energized heating wire with the outer periphery of a rotating wafer so as to cut away the out sheet portion, and thereafter successively paying out and contacting a non-energized wire with the outer periphery of the rotating wafer. CONSTITUTION:Since a rocking plate 6 approaches in the direction of an arrow 6 to the outer periphery of a rotating silicon wafer 1, a heated energized heating wire 13 (heater wire) contacts therewith, so that the out sheet portion 3' of a masking sheet 3 is cut away along the outer periphery of the silicon wafer 1. Further, since a non-energized wire 13' (dummy wire) which is not heated comes into contact with the portion under the energized heating wire 13, the out sheet 3' which has been cut off, and lumps or refuses of the sheet produced by the heating are surely separated from the silicon wafer 1, and the dust sheet 3'' which has been cut off falls below. The angles between the silicon wafer 1 and the energized heating wire 13 and the non-energized wire 13' are somewhat wider than right angle at the outer periphery of the silicon wafer 1 with regard to the direction in which the wire is running.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a method for applying the following steps before lapping or cutting the back surface of a silicon wafer for IC, LSI, super LSI, etc.
This relates to a method for automatically cutting and removing a masking sheet stuck to one side of a silicon wafer along the outer periphery of the silicon wafer, and in the so-called IC manufacturing process, it includes slicing, lapping, polishing, and so on in the crystal process. Or it is used in the process leading to the back grinder.

(Prior art) The so-called IC manufacturing process includes a crystal process, a wafer pre-process, a post-wafer process, an assembly process,
The crystal process can be divided into stages such as an inspection process, from Si crystal growth to slicing, and then to lapping and polishing or back grinding. The purpose of this lapping is to remove most of the strained layer formed on the slice surface during slicing, and to thin the thick slices after slicing to a specified thickness by lapping to give the surface a mirror finish for forming circuit surfaces. It is in. Needless to say, considerable precision is required for surface roughness and flatness.

In addition, in the post-wafer process process, due to the recent demand for lighter, thinner, shorter, and smaller IC packages, the wafer itself has to be replaced after the wafer process is completed in order to shorten the chip size, as well as to solve issues such as mounting problems and heat generation. Increasingly, a process is being used to reduce the thickness of the material. Of course, it can be said that there is no need to make the wafer thinner if it is a CMO5 or the like which inherently generates less heat, but if the package is to be made very small, it will naturally be necessary to make the wafer thinner. In this step as well, in order to make it thinner, the back surface must be ground, and it goes without saying that one step of lapping or back grinding is required.

By the way, conventionally, in the pre-wrapping stage,
Apply wax to the circuit surface of the silicon wafer, fix it to the internal gear table, and erage the back side.
Alternatively, a masking sheet (for example, laminate) was adhered to the circuit surface, the circuit surface was fixed by suction, and the back surface was wrapped. This was for the purpose of protecting the circuit surface of the silicon wafer during the lapping and etching or back grinding steps. However, the application of wax and the adhesion of masking sheets were all done manually.

In particular, the work of cutting and removing the out-sheet portion of the masking sheet protruding from the silicon wafer along the outer periphery of the silicon wafer has currently relied on manual work by skilled workers.

(Problems to be Solved by the Present Invention) In the conventional technique as described in L, the method of applying wax to a silicon wafer requires an enormous amount of time and labor;
Needless to say, there was a significant drawback in terms of inefficiency, and the problem was the same in the method of adhering the masking sheet, which was done manually.

In particular, the work of cutting and removing the out-sheet portion of the masking sheet along the outer periphery of the silicon wafer is not only inherently inefficient as it must be done by skilled workers.
It also included significant drawbacks in terms of yield rate. In other words, since the out-sheet portion of the masking sheet is manually cut along the outer periphery of the silicon wafer with a cutter, no matter how skilled the worker is, he or she ends up applying irregular external pressure to the outer periphery of the silicon wafer. It was unavoidable that the yield rate would be reduced due to chipping and edge chips occurring on the outer periphery, and mistakes such as accidentally cutting off circuits. moreover,
When cutting and removing the out-sheet part, which is the peripheral part of the masking sheet, it is fine as long as the cut surface is uniform.
In some cases, scraps (so-called sink marks) are left behind, and in such cases, the blades catch on the edges during lapping, resulting in damage to extremely expensive silicon wafers and, in some cases, even the diamond blades of the lapping equipment. It also had the disadvantage that it could lead to damage.

Of course, there is a high demand for automation, but there are difficult problems for the following reasons.

(1) The outer diameter accuracy of silicon wafers inevitably varies by ±0.5 mm from the standard value for each lot.

(2) The number of positioning flats is not constant, either one or two, depending on the film or wafer size.

(3) A large number of wafers that have already been cracked or chipped will be pasted with the masking sheet.

(4) In order to improve the yield rate, it is desirable to cut along the outer periphery of the wafer.
Problems 2) and (3) must be resolved.

(Means for solving the problem) In the present invention, as a method of cutting and removing the out-sheet portion of the masking sheet stuck to the silicon wafer along the outer periphery of the silicon wafer, unnecessary external pressure is applied to the silicon wafer. In order to avoid damage to the outer periphery of the masking sheet, to avoid creating irregular cross-sections such as whiskers on the cut surface of the masking sheet, and to be able to deal with even small chips, we use a heated electrical heating wire for cutting. This heater wire is sent out one after another with an appropriate angle and tension to the silicon wafer, and is brought into contact with the outer periphery of the silicon wafer, and the out sheet part of the masking sheet is cut by heat, and the cut masking sheet In order to reliably separate sheet clumps that may occur due to heat or heat from the silicon wafer, another unheated, non-energized wire is also brought into contact with the outer periphery of the silicon wafer at an appropriate angle and tension relative to the silicon wafer. This method automates the cutting of the out-sheet portion of a silicon wafer to the outside shape using a wire.

(Example) A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the preliminary stage of carrying out the method of the present invention, but if viewed over time, first a masking sheet 3 is attached to the circuit surface of a silicon wafer 1. At this stage, the masking sheet 3 has a slightly larger diameter than the outer diameter of the silicon wafer 1, and an out-sheet of 3° occurs. In this state, when the silicon wafer 1 moves as shown by arrow 1, the silicon wafer is positioned by simultaneously catching the silicon wafer from both sides as shown by catcher 4, 4'' or arrow 2.3, and moves as shown by arrow 4. The wafer 1 is placed on a carriage and a turntable 5 and fixed under vacuum.

Next, FIG. 2 is a diagram showing the main parts of the apparatus for carrying out the method of the present invention. Following arrow 4 in FIG. 1, the catch and turntable 5 are rotated approximately 90 degrees as indicated by arrow 5, and the The wafer 1 is in a standing state. On the other hand, on the single moving plate 6, a energizing pulley 7 and an insulated non-energizing pulley 9, which are integrally formed, and an energizing pulley 8 and an insulated non-energizing pulley 10 are pivotally mounted.
The wire 13° fed out from the wire contacts the outer periphery of the silicon wafer 1 between the non-energized pulley toBt and the non-energized pulley 9 according to the arrow shown in FIG. 2, and cleans and separates the cut surface of the outsheet 3°. Thereafter, the outsheet 3' is heated and heated between the energizing pulley 8 and the energizing pulley 7 to heat and cut the outsheet 3'', and then proceeds in the direction of the arrow 7 and is wound up by the wire winding pobbin 12.

Incidentally, when the silicon wafer 1 is in a standing state, the movable plate 6 rotates slightly in the direction of the arrow 6 and moves until the wire 13.13' comes into contact with the outer periphery of the silicon wafer 1.

FIG. 3 is an enlarged view of the main parts of the apparatus implementing the method of the present invention, in which the silicon wafer 1 rotates in the direction of arrow 8 as the catch and turntable 5 rotate. As the movable plate 6 approaches the outer periphery of the rotating silicon wafer 1 in the direction of the arrow 6, the heated energized heating wire 13 (heater wire) comes into contact with the outer periphery of the silicon wafer 1 and causes the masking sheet 3 to come out. Seat part 3°
Furthermore, a non-energized wire 13° (tammy wire) that is not heated is placed below the energized heating wire 13.
further contacts the silicon wafer 1, so that the cut out sheet 3'' and sheet lumps and scraps generated by heating are reliably separated from the silicon wafer 1, and the cut dust sheet 3'' falls downward. Note that the heating of the energized heating wire 13 may be the minimum amount of heating suitable for cutting. Further, FIG. 4 is a schematic cross-sectional plan view taken along line A-A of the main parts of the apparatus in which method tb of the present invention is implemented.
3. The angle at which the non-energized wire 13° intersects is not 90 degrees, but the outer periphery of the silicon wafer 1 is at a slightly wider angle than a right angle with respect to the direction of movement of the wire. In other words, in FIG. 4, the silicon wafer 1, which is slightly inclined toward the front, rotates to the right, and the energized heating wire 13 and the non-energized heating wire 13''
The cut surface is formed more smoothly because the cut surface moves slightly downward as shown in FIG. 3 from the bottom to the top. In addition, energized heating wire 13, non-energized wire 13°
is under some tension, and the advancing plate 6 is elastically pressing in the direction of arrow 6 in Fig. 3, so
The same tension is applied to the contact between the positioning flat 2 of the silicon wafer 1, the energized heating wire 13, and the non-energized wire 13°.

FIGS. 5 and 6 are front views showing the state of contact between the chipped hole on the outer periphery of the silicon wafer 1 and the energized heating wire 13,
FIG. 7 is a side view of FIG. 6, but the energized heating wire 13
Since the position detection point sp is set by the sensor S, when a chip d exists on the silicon wafer 1, if the dead point dp is an obtuse angle, it can be cleared as is, but if it is an acute angle, If there is a crack, the energized heating wire 13 gets caught at the dead point dp and as it moves in the direction of the arrow 9, the position detection point Sp also shifts to Sp', so the sensor S detects this and automatically stops the silicon wafer. Expansion of damage caused by No. 1 and cutting of the wire can be avoided.

Incidentally, the presence of the Teflon-coated safety block 14'' of the guide block 14 in FIG. 4 allows the cut dust sheet 3'' to fall downward more reliably.

In this way, the masking sheet 3 of the silicon wafer 1 is automatically and precisely cut and removed immediately before lapping.

(Effects of the present invention) The present invention has the above-mentioned configuration and automates this process, which has traditionally been carried out manually by skilled workers.
) Not only does this dramatically improve productivity by increasing processing speed and being applicable to silicon wafers of all outer diameters and shapes, but also (2) significantly lowering conventional labor costs;
3) The yield rate of silicon wafers (chips) has been increased to almost 100%, and -) Although lapping is done in a thoroughly clean room, the cutting method using heated wire as in the present invention does not generate dust. In this sense, it does not damage the chip, and
Since the heating of the wire is kept to a minimum, processing can be done with almost no smoke generation, and the practical effects are truly great, such as improving the durability of the expensive blades used in lapping equipment. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing a pre-stage of implementing the method of the present invention, FIG. 2 is a diagram showing the main parts of an apparatus for implementing the method of the present invention,
Fig. 3 is an enlarged view of the main part, Fig. 4 is a schematic cross-sectional plan view of the main part A-A, and Figs. 5 and 6 show the state of contact between the chip and the wire around the outside of the silicon wafer. Front view,
FIG. 7 is a side view of FIG. 6. [Explanation of symbols] 1...Silicon wafer, 2...Positioning flat, 3...Masking sheet, 3'--Out sheet, 3"...Dust sheet, 4.4'-...Catcher -15...Catch and turntable, 6...Commuting plate, 7.8...Electrifying pulley, 9.10-...
- De-energized pulley, 11... wire bobbin, 12...
Wire winding bobbin, 13...Electric heating wire, 13
゛...Non-current wire, 13"...13. after dislocation.
14...Guide block, 14°...Safety block, d...Chip flaw, dp...Put point,
S...sensor, s p-...position detection point, 5p
'++・Sp after rearrangement.

Claims (1)

[Claims] The energized heating wires are sequentially brought out and brought into contact with the outer periphery of the rotating silicon wafer, and the out-sheet portion of the masking sheet that is stuck to the silicon wafer is cut and removed along the outer periphery of the silicon wafer, and then the non-energized wires that are not heated are sequentially removed. A method for cutting and removing a masking sheet for silicon wafer processing, characterized in that the outer periphery of the silicon wafer is at a slightly wider angle than perpendicular to the direction in which the wires are fed out and brought into contact with each other.