JPH0653366B2 - Pellet manufacturing method - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to pellets for thyristors made of silicon (S
i) A pellet manufacturing method used when trepanning the wafer.

[Technical background of the invention and its problems]

Generally, thyristors (thyristors) used for high power control.
The material for (er) is obtained by trepanning with a cylindrical diamond grindstone. That is, as shown in FIG. 3, first, the Si wafer (A) is fixed to the base (B) with an adhesive and the trepanning diamond grindstone (C) is indicated by an arrow.
The disc-shaped pellets (E) were cut out by rotating while feeding in the (D) direction.

Then, in the cutting of the pellet (E) by the above-mentioned conventional method, the feed in the direction of the arrow (D) of the diamond grindstone (C) is left in the vicinity of the other end side main surface of the Si wafer (A) by about 10 μm. After stopping, Si with pellet (E) still attached
The wafer (A) was melted with an adhesive and separated from the base (B), and then the pellet (E) was separated by a breaking treatment. As a result, as shown in FIG. 4, a burr-shaped edge portion (F) remains at the edge portion of the braked pellet (E). The edge portion (F) causes damage such as chipping or cracking when the pellet (E) and the substrate are bonded with an alloy in the next alloying step, which is one of the causes of the yield reduction. If you try not to force the edge part (F), it can be achieved by cutting to the adhesive part and completely cutting the Si wafer (A). Is poor, and the adhesive adheres to the blade portion of the diamond grindstone (C). Therefore, the diamond grindstone (C) is apt to cause clogging, and the grinding resistance remarkably increases with the increase in the number of times of machining to reach the end of its service life. Therefore, the diamond grindstone (C) must be frequently replaced.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pellet manufacturing method capable of performing pellet manufacturing with high efficiency and high accuracy.

[Outline of Invention]

For example, a trepanning grinding wheel is detachably attached to a base such as a vacuum chuck, and an insertion plate made of a flexible elastic member that is unlikely to cause clogging of the trepanning grinding wheel is detachably attached, and the wafer is fixed to the base via the insertion plate After that, when the pellets are cut out from the wafer by the trepanning grindstone, the trepanning grindstone is fed until a part of the insertion plate is cut so that the pellets are completely cut and separated from the wafer.

Example of Invention

 An embodiment of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, the pellet manufacturing method of this embodiment includes a holding step in which a disk-shaped Si wafer (1) is vacuum-sucked to a vacuum chuck (2) via an insertion plate (3). , A trepanning step of obtaining a pellet (5) (see FIG. 2) forming a cut disk from the wafer (1) held and fixed to the true suction chuck (2) by the trepanning grinding wheel (4) in this holding step, The pellet (5) obtained in the trepanning step is washed with water or the like. Then, the vacuum chuck (2) has a cylindrical base (6).
And the one end of which is arranged inside the base (6) has a suction port (7) ...
As a suction path (9) opening on the upper surface (8) of the base (6),
The vacuum source (10) connected to the other end of the suction path (9) and the interposition of a flexible elastic member detachably mounted on the upper surface (8) of the base (6). It consists of a board (3). The suction passage (9) is a main passage (11) coaxially arranged inside the base (6).
And branch from this main road (11) and as the suction port (7) ... the upper surface (8)
It consists of a branch road (12) ... The insert plate (3) is made of a synthetic resin that does not easily cause clogging of the grinding wheel (4), such as hard rubber, and has a disk shape with a thickness of 0.1 mm and a diameter of 125 mm. ing.
When the insertion plate (3) is placed at a predetermined position on the upper surface of the base (6), the through holes (13) communicating with the suction ports (7) are bored. There is. The upper surface of this insertion plate (3) is the wafer (1)
Is the adsorption surface (14) on which is adsorbed. Then, by operating the vacuum source (10), the branch path (12) ...
A vacuum can be drawn via (11), and the wafer (1) can be vacuum-sucked on the suction surface (14) via the insertion plate (3). Then, the grinding wheel (4) used in the trepanning process is a hollow cylindrical grinding part.
(15) and a cylindrical mounting portion (16) coaxially protruding from the rear end of the grinding portion. The grinding part (15) comprises a core body (17) made of metal and having a bottomed cylindrical shape, and a grinding body (17) with a thickness of about 50 μm formed on inner and outer wall surfaces with a thickness of about 0.2 mm. It consists of a grain layer (18). The abrasive grain layer (18) is composed of, for example, a binder (19) such as copper, and abrasive grains (20) such as diamond dispersed and held in the binder (19). Further, the attachment portion (16) is attached to a drive mechanism (not shown), and the drive mechanism causes the grinding wheel (4) to move in the direction of the arrow.
While being rotationally driven in the (21) direction, it is fed and driven in the direction of the arrow (22) to perform the trepanning process of the wafer (1). Then, as shown in Fig. 2, the grinding wheel (4) cuts into a part of the insertion plate (3) without stopping the feeding even after the cutting of the wafer (1) is completed. . After that, the grinding wheel (4) is retracted in the direction of the arrow (23) to finish the grinding. Thus, from the wafer (1), pellets
(5) is completely separated from other parts. Then vacuum source (10)
Then, the vacuum suction of the wafer (1) is released, and then only the pellet (5) is picked up by a suction arm (not shown) to perform the cleaning process.

Thus, according to the pellet manufacturing method of this embodiment, the base
The fixing of the wafer (1) to the (6) is made of a flexible elastic member that is less likely to cause clogging than the wafer (1) and is a base.
(6) and wafer (1) with an insertion plate that can be detachably attached
The pellet (5) is completely separated from the wafer (1) because it is done through (3) and the trepanning grinding wheel (4) is also cut into a part of the insertion plate (3). can do. Therefore, as in the prior art, the pellet (5) is attached by leaving the wafer (1) uncut, and the complexity of separating the pellet (5) from the wafer (1) in the next braking step is eliminated. At the same time, the process is shortened and the processing efficiency is improved. In addition, the wafer (1)
Since the burr-like edge portion generated at the end edge portion is eliminated, there is no possibility of occurrence of defects such as chipping in the alloy step of adhering the pellet (5) and the substrate in the next step with an alloy. In addition, since the insert plate (3) is made of a material that does not easily cause clogging of the grinding wheel, the life of the grinding wheel (4) is extended.
By the way, when only Si wafer (1) is ground by conventional incomplete cutting, if 30 pellets (5) are trepanning processed, the grinding resistance in the normal direction will be about doubled due to clogging. According to the method of performing a complete cutting using the insertion plate (3) of this example, almost no clogging occurs even when processing 30 pellets (5), the increase in the grinding resistance in the normal direction, It was about 20% at most.

Generally, this is done within the range of the optimum feed rate of the wafer (1) of the grinding wheel (4) that does not cause clogging, but in the case of incomplete cutting, the grinding wheel (4)
This is because the feed rate of the grinding wheel (4) is deviated outside the range of the optimum feed rate as the tip of the grinding wheel stops in the middle of the wafer (1), and the grinding wheel (4) easily becomes clogged. . On the other hand, in the case of complete cutting, the tip of the grinding wheel (4) stops after entering the insertion plate (3), so at least when the wafer (1) is cut out. The feed speed of the grinding wheel (4) can be set to an optimum state, and the clogging of the grinding wheel (4) can be improved as compared with the case of incomplete cutting. Even if the tip of the grinding wheel (4) enters the interposing plate (3), the interposing plate (3) is made of a material that is less likely to be clogged than the wafer (1). The clogging of the grinding wheel (4) due to 3) can be avoided. In addition, even if the tip of the grinding wheel (4) reaches the inside of the insertion plate (3) and the feeding is stopped and the feeding speed is deviated from the range of the optimum feeding speed, the wafer (1) at this time is the grinding wheel. Since it has been completely cut by (4), the grinding wheel (4) is hardly clogged. Furthermore, the interposition plate (3)
Since it is removably attached to the base (6) and the wafer (1), it can be used for a large number of trepanning processes, and the insert plate (3) is a grinding wheel ( Even if it is worn out due to multiple cuts due to 4), it can be easily replaced, and in terms of production efficiency and economy,
Has a significant improvement effect.

Although hard rubber is used as the interposition plate (3) in the above-mentioned embodiment, any material such as a plastic sheet may be used as long as the grinding wheel is less likely to cause clogging. Also, the through holes formed in the insertion plate (3).
The (13) ... may be randomly distributed without being associated with the suction ports (7).

Furthermore, in the above example, the wafer (1) was sucked by the vacuum chuck through the interposing plate (3), but similarly,
The wafer (1) may be adsorbed and fixed by an electrostatic chuck via the insertion plate (3). In this case, it is not necessary to provide a through hole in the insertion plate (3).

〔The invention's effect〕

According to the pellet manufacturing method of the present invention, the wafer is fixed through an interposing plate made of a flexible elastic member that is unlikely to cause clogging of the trepanning grinding wheel, and the cutting wheel is cut by the trepanning process. Since the pellets are completely cut from the wafer by performing cutting up to a part of the interposing plate, it is not necessary to separate the pellets from the wafer by breaking in a subsequent process. As a result, various problems associated with braking are eliminated. Further, since the insertion plate is detachably attached to the holding portion and the wafer, it can be used for a large number of trepanning processes, and it has been worn down due to a large number of cuts made by the trepanning grinding wheel. However, it can be easily replaced. According to the present invention combined with the above effects, it is possible to greatly improve the production efficiency and the processing accuracy.

[Brief description of drawings]

FIG. 1 is an explanatory view of an apparatus used in a pellet manufacturing method according to an embodiment of the present invention, FIG. 2 is an explanatory view of the same trepanning process, FIG. 3 is an explanatory view of a conventional pellet manufacturing method, and FIG. It is a figure which shows the pellet by the conventional method. (1): Wafer, (2): Vacuum chuck (holding member),
(3): Insert plate, (4): Grinding wheel, (5): Pellet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsutoshi Higuchi 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Inside the Toshiba Industrial Research Institute (56) Reference JP-A-60-31918 (JP, A) JPB 57-43408 (JP, B2)

Claims (2)

[Claims] 1. A holder for holding a wafer by a flexible elastic member which is less likely to cause clogging of the holding member than the wafer, and which holds the wafer via the holding member and an insertion plate detachably attached to the wafer. And a trepanning step of cutting out a pellet forming a disk from the wafer while cutting a hollow cylindrical trepanning grindstone with respect to the wafer held by the holding member while rotating a hollow cylindrical trepanning grindstone. A method for producing a pellet, comprising: 2. The pellet manufacturing method according to claim 1, wherein the holding member is held by vacuum suction through an insertion plate having a hole.