JPH01137652A - Plate bonding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of a flat plate bonding method that can withstand high temperature thermal cycles, the present invention relates to a flat plate bonding method that is highly heat resistant and provides a strong bonding force between both hand plates without the risk of contamination. a step of forming an extremely thin layer of a reagent having the ability to oxidize at least one of a pair of flat plates between the plates; The method includes a step of removing by drying, and a step of pressurizing and heating the pair of flat plates.

[Industrial application field]

The present invention relates to a flat plate adhesion method, and particularly to an improvement in a flat plate bonding method that can withstand high temperature thermal cycles.

One method for manufacturing silicon-on-insulators (hereinafter abbreviated as Sol) used in the manufacturing process of semiconductor devices is to bond a silicon substrate to another substrate, and then thin the silicon substrate by polishing or etching. There is a way to do it.

The silicon substrate forming the above-described SOI substrate is thinned to a thickness of about 1 μm, and devices are formed thereon.

In the device forming process, heating and cooling steps at around 1,000° C. are repeatedly performed.

Therefore, during this device formation process, a large stress is applied to the thin film, and there is a possibility that distortion or cranking may occur.

When used in such applications, there is a need for a flat plate adhesion method that applies less stress to the thin film and does not cause distortion or cracks.

Note that when applied to semiconductor processes, the possibility of impurity contamination should also be eliminated.

Under the above circumstances, there is a need for a flat plate adhesion method that does not cause distortion or cracks and is free from the possibility of impurity contamination.

[Conventional technology]

The most common conventional flat plate adhesion method is a method using a polymer adhesive. However, this method cannot be applied to semiconductor processes because the adhesive solvent is difficult to remove and the heat resistance is poor.

As an adhesion method applicable to semiconductor processes, there is a melt adhesion method using phosphorus silicate glass (hereinafter abbreviated as PSG).

In this method, PSG is deposited on the bonding surfaces of a pair of flat plates, and the bonding surfaces are pressed together and melted and bonded by applying pressure and heat.

As the concentration of R(P) increases, this PSG has a lower softening point (which makes it easier to melt), but at the same time there is a risk of contamination with phosphorus.

Also, due to the difference in thermal expansion coefficient between PSG and silicon,
After melting at a high temperature (750-1,100°C), when the temperature is returned to room temperature, a large stress is applied between the two.

For this reason, when the silicon substrate is thinned, distortion and cranking occur, making it difficult to form devices.

Another method is to form a very thin layer of water on the bonding surfaces of a pair of silicon substrates, but in this case, it is difficult to form silanol groups densely over the entire surface of the silicon substrates, so it is difficult to form silanol groups uniformly over the entire surface. Cannot form siloxane bonds and has weak bonding strength.

[Problem to be Solved by the Invention 3] The problem with the conventional flat bonding method described above is that the method using a polymer adhesive is difficult to manufacture Sol substrates for semiconductor devices due to heat resistance and the risk of contamination. This is difficult to apply.

In addition, the melt bonding method using PSG has the risk of contamination with impurities and the occurrence of distortions and cranks due to stress, making it difficult to form devices on thin film silicon of Sol, or even if devices can be formed, the characteristics may be inferior. There is a strong possibility that such problems will occur.

In addition, the method of forming siloxane bonds using water has the disadvantage of weak bonding strength because it is difficult to form siloxane bonds densely over the entire surface.

It is an object of the present invention to provide a flat plate adhesion method that can be easily carried out under the above circumstances, has high heat resistance, and can provide a strong bonding force between both flat plates without the risk of contamination.

[Means for solving problems]

The above problem is solved by the process of forming an extremely thin layer of reagent between the plates that has the ability to oxidize at least one of the plates, and by air drying the excess reagent that is not bonded to the plate. This problem is solved by the flat plate bonding method according to the present invention, which includes a step of removing the pair of flat plates, and a step of pressurizing and heating the pair of flat plates.

[Effect]

That is, in the present invention, as shown in FIG.
and 82, and the flat plates A1 and B of this reagent 3
After removing the excess reagent 3 that is not bound to 2 by dissipating it as X z O by air drying, the pair of flat plates A
Since 1 and B2 are heated while being pressurized, XZO
As shown in FIG. 1(b), it becomes possible to firmly bond and integrate both flat plates A1 and B2 by siloxane bonds (Si-0).

2 (Si -0 - There is.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 2 in the case of a silicon substrate.

First, as shown in FIG. 2(a), the silicon substrate A4 and the silicon substrate B5 are 2-inch silicon wafers, and the silicon oxide film 6 is a wet thermal oxide film with a thickness of 3,000 mm on the surface of the silicon substrate B5. is forming.

A small drop of hydrogen peroxide 7 is dropped onto the surface of the silicon oxide film 6 formed on the surface of the silicon substrate B5 (.

One silicon substrate A4 is immersed in a hydrogen fluoride (HF) solution to remove the natural oxide film, quickly taken out from the hydrogen fluoride solution, washed with pure water, and removed with pure water to form a silicon oxide film. Place it on top of 6.

50g r between silicon substrate A4 and silicon substrate B5
A pressure of /Cm2 is applied so that the hydrogen peroxide 7 is spread evenly between the side substrates.

Leave it in this state for about 48 hours to air dry.

In this step, excess hydrogen peroxide 7 and moisture are dried and removed. After this process, as shown in Figure 2 fat,
Silanol groups (Si-0-H) on the surfaces of both silicon substrates
is thought to be formed.

Next, in this state, put it in an electric furnace and gradually raise the temperature, and when it reaches 800 degrees Celsius, hold it for 10 minutes, then turn off the power and let the furnace cool naturally, and when it reaches room temperature, take out the silicon substrate, and both silicon substrates will be They are firmly bonded via a silicon oxide film 6.

The mechanism is that the silanol groups (Si-OH) on the surfaces of both silicon substrates dissipate H and O through thermal decomposition during the heating process, and a strong siloxane bond (Si-0) is created between the two silicon substrates. Conceivable.

Note that the present invention is not limited to the above embodiments,
For example, a pair of P-type silicon substrates without an oxide film and an N
By using a type silicon substrate, it is also possible to form a large-area PN junction surface.

Further, the same effect can be obtained by using nitric acid (HNO, ) instead of hydrogen peroxide 7 as a reagent capable of oxidizing silicon.

Furthermore, as a means of forming silanol groups, uniform adhesion can be achieved by leaving both silicon substrates in a container filled with hydrogen peroxide vapor, and then putting both silicon substrates together and performing the heating process described above. .

In order to investigate this bonding state, both bonded silicon substrates were crushed and examined in detail, but the unbonded portion was about 10% in the case of hydrogen peroxide and about 20% in the case of nitric acid.
It was strongly glued all over.

In an example of the conventional method using water instead of hydrogen peroxide, approximately 40%
The degree of no adhesion was observed, demonstrating the superiority of the present invention.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a silanol group is formed by a process that can be carried out very easily,
By pressurizing and heating, it is possible to obtain a strong siloxane bond, and it is possible to bond silicon substrates that are not contaminated with impurities, so it is possible to create a SOR substrate with silicon substrates that is highly heat resistant and free of distortion and stress. It has advantages such as making it possible to produce , and can be expected to have a significant quality improvement effect, making it extremely useful industrially.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the present invention. FIG. 2 is a diagram showing an embodiment according to the present invention. In the figure, 1 is a flat plate A, 2 is a flat plate B, 3 is a reagent, 4 is a silicon group (anti-A, 5 is a silicon substrate B; 6 is a silicon oxide film, 7 is hydrogen peroxide, shows.

Claims (1)

[Claims] A step of forming an extremely thin layer of a reagent having the ability to oxidize at least one of a pair of flat plates between the plates, and removing any excess of the reagent that is not bonded to the flat plate. A flat plate adhesion method comprising: a step of removing by natural drying; and a step of pressurizing and heating the pair of flat plates.