JPS59102570A - Polishing method for wafer - Google Patents

Abstract

PURPOSE:To improve polishing efficiency and to produce high quality wafer, by thermally adhering two sheets of wafers while maintaining flatness to form a complex wafer having high flatness then polishing with both face polisher and separating. CONSTITUTION:At first a wafer 15 is heated on a heating board 12 while maintaining high flatness then small amount of wax 10 is dripped to overlap the wafers 16. Thereafter it is pressure contacted by a weight 13 to form a wax layer 10 having uniform thickness and cooled simultaneously by a cooling board to form a complex wafer having high flatness. Said complex wafer is mounted in a plurality of hole sections of carrier 2 to polish while increasing holding force of upper and lower surface plates 3, 4 but polishing agent containing separated grinding particles fed from said hole section 9 will not intrude into contacting face thus to prevent polishing on contacting face. After polishing, solution such as trichlane is heated to separate two sheets of wafers 15, 16. Consequently polishing performance is improved to produce a high quality wafer where only single face is polished.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a wafer polishing method, and the present invention relates to a method for polishing a wafer, and the present invention is a polishing method that obtains a high-precision single-sided mirror surface without damaging the wafer and improves polishing efficiency. Regarding the method.

[Prior art]

Wafers are required to have high dimensional accuracy and large diameter in order to respond to higher integration and lower prices of semiconductor devices.

Conventional wafer polishing equipment attaches the wafer to an adhesive, and then attaches the wafer to a rotating disk while supplying abrasive material.
In the past, only one side of the wafer was polished while pressing the attached adhesive tool. However, in the current state of high dimensional accuracy and large diameter, precision is required when attaching wafer to the adhesive tool. However, as an alternative to this method, a double-sided polishing device that does not require the pasting process has been developed.

Since both sides of the wafer polished by this double-sided polishing apparatus are polished, a new technical problem has arisen in the semiconductor manufacturing process, which has conventionally polished only one side.

One way to solve this problem is to stack two wafers and polish only one side of the wafers.

First, in giving a detailed explanation, an outline of the double-sided polishing apparatus will be explained using FIG. 1. In the figure, a wafer 1, which is a workpiece, is mounted in a hole in a carrier 2. As shown in FIG. The wafer 1 mounted on the carrier 2 in this manner is sandwiched between elastic nonwoven fabrics 5 attached to each of the upper surface plate 3 and the lower surface plate 4. Further, the carrier 2 is held between the gears of the sender gear 6 on the inner periphery and the innoternal gear 7 on the outer periphery, and the upper and lower surface plates 3.4 and the carrier 2 are rotated by the drive shaft 8 and fed into the borehole 9. Wafer 1
Both sides of the plate are polished.

In this double-sided polishing apparatus, when two wafers 1 are simply stacked and polished as shown in FIG. The two wafers are rotated and the mating surfaces of the wafers are polished. Furthermore, there is the problem that foreign matter may get mixed into the mating surface of the wafer, causing scratches or other damage on the mating surface.Furthermore, as shown in FIG. It is possible to polish it, but in this case,
There is a problem in that the rotation of the carrier 2 causes the wafer to fly out from the recessed hole, resulting in damage to the wafer.

In addition, as shown in FIG. 3, when polishing is performed by holding wafers one by one in the cavity of the carrier 2 (in this case, both sides of the wafer are polished), the thickness of the carrier 2 is adjusted to the thickness of the wafer. Since it is necessary to reduce both the thickness and the thickness, the tooth tips of the carrier 2 are also thin, and the remaining portion of the tooth tips is reduced.

As a result, when trying to increase polishing efficiency by increasing the polishing height, the strength of the tooth tips is limited, making it impossible to raise the polishing height. There was a problem in that the number of sheets was also limited and the polishing efficiency was reduced.

[Purpose of the invention]

The present invention solves all of the above technical problems.
The purpose is to provide a method for polishing wafers.

[Summary of the invention]

That is, in the present invention, two wafers are bonded together while maintaining highly accurate flatness, and after this is mounted on a carrier of a double-sided polishing device and polished, the two wafers are separated so that only one side is polished. The wafer is heated while maintaining its flatness, then an adhesive is added to this wafer, and another wafer is placed on top of this wafer and pressed. The two wafers pressed together in this way are cooled while maintaining their flatness to form a two-piece wafer, which is then polished using a double-sided polishing machine and then placed in an adhesive melt. , the two wafers are separated by heating and melting the adhesive.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below. The two wafers are bonded together using wax or cross-adhesive liquid. That is, in FIG. 1, (1) shows the wafer 1''5.
(2) The figure shows the bonded surface of the wafer 15t16 with the wax 10 interposed between them, (3) The figure shows the cross 1
The wafers 15 and 16 are bonded using the adsorption force of 1.

The above bonding process will be explained using FIG. 6. In this bonding process, heating plates 12 each having a high flatness are used.
Then, the heavy steel 13 and the cooling plate 14 are used.

First, the wafer 15 is heated on the heating plate 12 while maintaining high flatness. A small amount of wax 10 is dropped onto the wafer 15 heated in this manner. Next, another wafer 16 is placed on top of this and pressed against the wafer 13. By pressing in this manner, the wax 10 has a uniform thickness and forms a 1° layer of wax between the wafers 15 and 16. Next, this is sandwiched between cooling plates 14 and wafers 15 and 16 are simultaneously cooled to form two wafers with high flatness, with wax 10 in the middle.

After polishing these two integrated wafers using a double-sided polishing device, they are heated in a solution such as trichloride to separate the wafers to obtain single-sided polished wafers.

The operation of this embodiment configured as above will be explained next.

First, a wafer 15 is heated on a heating plate 12 having a high degree of flatness, a small amount of wax 10 is dropped onto the wafer 15, another wafer 16 is stacked on top of the wafer 15, and the wafer 16 is pressed by a heavy cloth 13 having a high degree of flatness. By the way, wax 10 is wafer 1.
While melting due to the heat of 5, two wafers 15.160
It is spread out in an even layer in between. In this state, next step 1.
By simultaneously cooling the wafers 15, 16 with the cooling plate 14 having a high degree of flatness, the wafers 15, 16 and the wax 10 are cooled and solidified without causing any thermal distortion. When solidified in this way, it becomes a highly flat surface with wax 10 as an intermediate layer. The total thickness of the two wafers 15 and 16 and the wax layer 10 becomes one wafer.

The wafers 15 and 16 are mounted in the cavity of the carrier 2, as shown in FIG.

In this case, since the mounted sea urchin 1 is thick, the carrier 2 can have a sufficiently thick structure, and the tooth tip strength of the carrier 2 can also be made sufficiently strong.

Therefore, a large number of holes are provided in the carrier 2, a large number of uninos are attached to the holes, and the upper and lower surface plates 3. .

Polish by increasing the clamping force (polishing pressure) in step 4.

In addition, the abrasive containing free abrasive grains supplied from the cavity 9 is
The two sheets of Unino 115 and 16 are integrated through the wax layer 10 and do not penetrate. Also, even if it does get in, it will be protected by the wax layer 10 and no polishing will occur on the mating surfaces of the wafers 15, 16.

After polishing in this manner, the two wafers 15 and 16 are separated by heating in a solution such as Unino Tori-Triclean.

Although the above explanation has been made using wax as an example of the adhesive, the same effect can be obtained by using a cross adhesive liquid.

〔Effect of the invention〕

According to the sea urchin polishing method of the present invention described in detail above, the sea urchin 1 is heated while maintaining its flatness, and the sea urchin I
・By adding adhesive on top and placing another wafer on top of it and pressing it together while maintaining its flatness, the adhesive is melted by the heat of the wafer and stretched evenly.
A uniform intermediate layer can be formed between the sheets of sea urchin.

By simultaneously cooling the two integrated wafers with the intermediate layer while maintaining their flatness, thermal distortion between them can be prevented, resulting in an integrated composite with high flatness. You can get Unino.

When polishing the composite Unino made in this way using a double-sided polishing machine, the thickness of the carrier can be increased to sufficiently increase its strength, making it possible to attach a large number of Unino at the same time. , polishing can be performed with increased polishing pressure, and polishing efficiency can be greatly improved.

Furthermore, since we have formed an intermediate layer of glue on the mating surfaces of the two Uni-Nos, this intermediate layer protects the mating surfaces and prevents them from being polished or scratched even if foreign matter intervenes. , it has excellent effects such as being able to obtain high quality Unino 1 that is polished on only one side.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing a conventional polishing method using a double-sided polishing device, FIG. 4 is a diagram showing the polishing method of this embodiment using a double-sided polishing device, and FIG. The figure is a diagram showing a state in which two wafers are stacked in this example.
The figure shows the process of overlapping and fixing two sheets of Unino® using wax as an adhesive. 2...Carrier 3...Upper surface plate 4...Lower surface plate 5...Nonwoven fabric 6...Center gear 7...Internal gear 10...Wax
11...Cross 12...Heating plate
15... Weight 14... Cooling plate 15.
16...Unino\. Agent Patent Attorney Susuki 1) Interest and Retaliation Research 1 Kokuhiro 21 yen 1 Mo 3 Figure 84 Sen 5 Sen 7/1 Figure 6 Convex

Claims (1)

[Claims] The wafer is heated while maintaining its flatness, then a bonding material is added onto this wafer, and another wafer is placed on top of this wafer and crimped, and the two wafers crimped in this way are The two wafers are simultaneously cooled while maintaining their flatness to form two integrated wafers, and this wafer is polished using a double-sided polishing machine, and then heated and melted in an adhesive melt to form the two wafers. A method for polishing a wafer, characterized by separating the wafer.