JPS6195544A - Pelletizing method - Google Patents

Abstract

PURPOSE:To prevent the waste of silicon etc. from sticking on the surface of a pellet, by applying a laser beam into a cut groove formed in a wafer by half-cutting, so as to pelletize the wafer. CONSTITUTION:A wafer 1 is half-cut along a cutting line of each pellet unit by a dicing saw 5, so as to form cut grooves 6. Next, a laser beam 8 is applied from a laser light source 7 into each of the cut grooves 6 in a substrate 2. An uncut portion 2a and a back electrode 4 are melted by the laser beam 8, and thus the wafer 1 is separated into individual pellets 9. By this method, pelletizing can be conducted without using mechanical cracking, occurrence of an extraneous substance due to breakage of silicon etc. can be eliminated, and the sticking of this substance on the surfaces of the pellets can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to pelletizing technology, and in particular to a technology that is effective when applied to separate wafers for diodes into individual pellets.

[Background technology]

Due to its structure, a diode wafer has a thick metal electrode formed on its back surface. Therefore, if you use a dicing saw to pelletize using the full-cut method that cuts all the way to the back metal electrode, the blade will become clogged with chips from the pan, etc. that make up the back metal electrode, and the blade will soon become unusable. There is a problem with becoming. On the other hand, if you attempt to pelletize using the half-cut method, which involves mechanical cracking after dicing the wafer halfway through, the uncut portion of the wafer that will be cracked and the metal electrode on the back will be chipped, resulting in the generation of silicon, silver, and other debris. The inventor has discovered that there are problems such as adhesion to the surface of the pellet. In particular, in the case of glass-sealed diodes, it is true that when the above-mentioned silicon debris is mixed with pellets inside the glass tube, it may become a source of short circuit (short bar) between opposing electrodes within the glass tube. elucidated by the inventor.

It is also possible to scribe using a laser beam, but the inventor has discovered that the laser melts the wafer surface and scatters silicon and metal, which adheres to the pellet surface and becomes foreign matter. It was.

Regarding wafer pelletizing technology, please refer to Kogyo Kenkyukai, published November 15, 1983, "Electronic Materials J 19.
It is explained in the November 1982 special edition, pages 67 and 68.

[Purpose of the invention]

An object of the present invention is to provide a technique that allows venotization without adhesion of silicon or other debris to the pellet surface.

Another object of the present invention is to provide a pelletizing technique that prevents clogging of blades.

Still another object of the present invention is to provide a technique that allows pelletizing without mechanical racking.

The foregoing and other objects and novel features of the present invention will be apparent from the written description and accompanying drawings.

[Summary of the Invention] A brief overview of typical inventions disclosed in this application is as follows.

That is, by half canting the wafer and pelletizing it by irradiating the inside of the cut with a laser beam, it is possible to prevent debris such as silicon from adhering to the pellet surface.
The above objective can be achieved.

〔Example〕

FIGS. 1(a), (bl, and cl) are partial cross-sectional views showing a pelletizing method according to an embodiment of the present invention in the order of steps.

First, in FIG. 1 (al is a partial cross-sectional view showing a part of a wafer before pelletizing), the wafer 1 is made of a substrate 2 made of a material such as silicon.

Since the wafer 1 of this embodiment is for diode,
A surface electrode 3 on the front side (upper surface in the figure) is formed for each pellet unit, and a back electrode 4 made of silver or the like is formed on the back side.
is provided, and the thickness of this back electrode 4 is formed as a film thicker than K for a diode.

For such a wafer 1, first, as shown in FIG. 1(b), a half-cut is performed to cut halfway near the bottom of the substrate 2 with a dicing saw 5 along the cutting line of each pellet unit to form a kerf. form 6.

Next, as shown in FIG. 1(c) K, the groove 6 of the substrate 2 of the half-cut wafer 1 is irradiated with laser light 8 from the laser light source 7 above.

In this case, since the laser beam 8 has excellent straightness and sufficient power, the uncut portion 2a of the substrate 2 and the back electrode 4 are melted by the laser beam 8, and simply irradiating the laser beam 8 melts the uncut portion 2a of the substrate 2 and the back electrode 4. In this pelletizing operation, the laser beam 8 is irradiated deep into the kerf 6, so that the wafer surface is irradiated with the laser beam. Unlike in the case where molten silicon or molten metal is cut into the kerf 6.
This prevents the pellets from scattering to the outside from above and attaching to the pellet surface, making it possible to pelletize with a high yield.

〔effect〕

(1) After the wafer is partially cut in advance, the kerf is irradiated with a laser tt to separate it into individual pellets, thereby making it possible to pelletize the wafer without using mechanical racking.

(2) Because of (1) K, there is no generation of foreign matter due to chipping of silicon, etc., it is possible to prevent foreign matter from adhering to the pellet surface, and it is possible to pelletize with a high yield.

(3) Since the wafer is cut in half, it is possible to prevent the blade of the dicing saw from clogging.

(4) Since the laser beam is irradiated across the kerf, the molten material of the silicon and back electrode does not jump out of the kerf, preventing the molten material from scattering around the outside and adhering to the pellet surface. can.

(5) If the wafer is a diode wafer,
Since the back electrode is thick, sufficient cutting performance can be exhibited by applying laser beam cutting, which is extremely advantageous.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, various types of laser light sources such as carbon dioxide lasers and solid-state lasers can be used, and materials other than silicon may also be used as the wafer substrate material.

Furthermore, the half-cut of the wafer only needs to be deep enough so that it does not reach the back electrode trap and cause clogging of the blade, but it only needs to be deep enough to prevent molten silicon etc. from scattering under external pressure.

[Application field]

The above explanation has mainly been about the application of the invention made by the present inventor to diodes, which is the background field of application, but the invention is not limited thereto. Widely applicable to wafer pelletization.

[Brief explanation of the drawing]

FIGS. 1(a), 1(c), and 1(c) are partial cross-sectional views of a part of a wafer sequentially showing a pelletizing method according to an embodiment of the present invention. 1... Wafer, 2... Substrate , 3... surface electrode, 4
... Back electrode, 5... Dicing saw, 6... Cut groove, 7... Laser light source, 8... Laser light, 9...
·pellet. N, -ノ

Claims (1)

[Claims] 1. A pelletizing method for separating a wafer into individual pellets, the method comprising partially cutting the wafer in advance and then irradiating laser light into the grooves to separate the wafer into individual pellets. . 2. The pelletizing method according to claim 1, wherein the wafer is a diode wafer and has a thick metal electrode as a back electrode.