JPS6211231A - Bonding method for wafer and mask - Google Patents

Abstract

PURPOSE:To prevent the insertion of air between a wafer and a mask by a method wherein pressure in a space on the lower surface side of the mask is lowered, the mask is directed downward, and deflected to a projecting shape and the central section of the mask and the central section of the wafer are brought into contact first. CONSTITUTION:A space 11 closed between a stage 3' and a top surface plate 8 is formed. The space is evacuated while nitrogen gas is fed into the space 11 as shown in the arrow N2, and displacement is made larger than the quantity of nitrogen gas fed and the inside of the space 11 is decompressed. The quantity of decompression is brought to 50-400mmHg. A mask 2' is deflected downward to a projecting shape by the decompression of the space 11. Nitrogen gas is ejected as shown in the arrow n2 from a section in the vicinity of the center of a suction pad under the state, and the central section of a wafer 1 is blown up. Consequently, the wafer 1 is deflected upward to the projecting shape and blown up, and the central section of the wafer 1 and the central section of the mask 2' are brought into contact first. The whole surface of the wafer 1 is introduced to the state in which it is fast stuck uniformly to the whole surface of the mask 2'. Accordingly, the whole surface can be bonded completely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of bringing a wafer into close contact with the lower surface of a horizontally supported mask in a semiconductor wafer manufacturing process.

[Background of the invention]

FIG. 2 is an explanatory diagram of an example of a method for bringing the wafer 1 into close contact with the mask 2.

The stage 3 has a structure in which it is precisely driven in two horizontal orthogonal axes, the X and Y directions (the Y axis is perpendicular to the plane of the paper), and the Z axis direction.

There are many small holes 4 on the top surface of the stage 3 that can move up and down.
A vacuum suction/4' tube is formed by providing The wafer 1 is suctioned and held by this suction/nine, and the stage 3
After precisely driving the wafer 1 in the X and Y planes to align it with the mask 2, the stage 3 is raised in the direction of the arrow 2 to bring the wafer 1 into close contact with the mask 2.

However, without applying excessive pressure to the mask 2,
It is not easy to bring the wafer 1 and mask 2 into close contact with each other with uniform pressure.

In order to press the wafer 1 against the mask 2 with uniform force without applying an excessive pressing force to the mask 2, the present inventors have created a method shown in FIG. 3 and are currently filing a separate application. In this method (hereinafter referred to as the method of the prior application), the small hole 4 forming the adsorption/radish is connected to the exhaust cylinder 706 and the nitrogen cylinder 7 via the switching valve 5.

The switching valve 5 is operated to the A position to communicate the exhaust pump 6 to the small hole 4, and after adsorbing and positioning the wafer 1' as shown by the imaginary line, the stage 3 is raised and the wafer l' and the mask 2 are made to face each other with a small distance, and then the switching valve 5 is operated to the B position to blow out nitrogen gas from the small hole 4, blowing up the wafer as shown by the solid line 1 and bringing it into close contact with the mask 2.

According to the method of the prior application, since the wafer 1 is pushed up by the nitrogen gas flow, the wafer 1 is uniformly pressed against the mask 4 over its entire surface, and there is no risk of receiving excessive pressing force or impact force.

Furthermore, when nitrogen is used as the ejecting gas, it does not react with the photosensitizer applied to the wafer.

When carrying out this method, inert gas can be used instead of nitrogen gas, but nitrogen is cheaper than inert gas and therefore has higher practical value.

As a result of repeated practical tests on the device of the above-mentioned prior application, the inventor of the present invention discovered the following problems.

As shown in FIG. 3, when the wafer 1' is pushed up to the 1st position and brought into close contact with the mask 2, there is a risk that gas will be trapped between the two members, and the trapped gas will be tightly attached. prevent.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is an improvement on the method of the previous application (that is, the method of blowing up the wafer with nitrogen gas and bringing it into close contact with the mask) to sandwich gas between the wafer and the mask. The object is to provide a method for bringing a wafer and a mask into close contact with each other without the risk of being trapped.

[Summary of the invention]

The method of the present invention created to achieve the above object is to lower the pressure in the space below the mask by 50 to 400 m Hg than the space above the mask, and to direct the mask downward. It is characterized in that it is bent into a convex shape, the center of the mask and the center of the wafer are brought into contact first, and the gas between both members is pushed out toward the periphery.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram schematically depicting an apparatus configured to carry out the method of the present invention, and is not an accurate projection diagram in terms of dimensions and shape.

8 is a top plate on which the mask 2' is placed, and is provided with an opening 8a. Mask 2' is attached to cover this opening 8a.

A bellows 9 and a gas bearing 10 are provided between the stage 3' and the top plate 8 to form a sealed space 11.

While nitrogen gas is supplied into the sealed space 11 as shown by arrow N, the sealed space 11 is evacuated as shown by arrow V to replace the air in this space 11 with nitrogen. This is to create an atmosphere that does not react with the photosensitive agent applied to the mask 1.

In addition to the amount of nitrogen gas supplied, the amount of exhaust gas is increased to reduce the pressure in the sealed space 11. The above pressure reduction amount is 50~400■H
Let it be g. By reducing the pressure in the space, the mask 2' is bent downward into a convex shape as shown in the figure.

However, this Figure 1 is drawn with the amount of distortion enlarged and exaggerated.
Actual distortion is microscopic.

In this way, a downwardly convex pendant is provided to the mask 2', and nitrogen gas is ejected from near the center of the suction/gradient as indicated by arrow n, blowing up the center of the wafer 1. When the button is pressed, the wafer 1 is slightly bent and blown upward in a convex manner, and the center of the wafer 1 and the center of the mask 2' first come into contact with each other. In this case, if the amount of pressure reduction is less than 5 (1 mHg), sufficient deflection to achieve the desired purpose cannot be obtained, so it is necessary to reduce the pressure to 50 + mHg or more.

After that, while controlling the air pressure inside the closed space,
By controlling the vertical movement of the stage 3', as shown in FIG. 3, the entire surface of the wafer 1 is pressed upward by the jet stream of nitrogen while the mask 2 and the wafer 1 both remain flat. The entire surface of the mask 2 is brought into a state of uniform close contact.

According to this embodiment, as explained with reference to FIG. 1, the center of the wafer 2' and the center of the mask 1 first come into contact and come into close contact, and the contact area gradually expands toward the periphery. Therefore, there is a gas (in this case nitrogen gas) between both parts.
There is no risk of it getting caught and trapped. Therefore, the entire surface is completely adhered without being hindered by the trapped gas. However, the amount of pressure reduction mentioned above is 400 mHg.
If it exceeds this amount, the amount of deflection will be excessive, and there is a risk that a gap in adhesion will occur when the reduced pressure is released and the flat surface is restored.

Therefore, the amount of pressure reduction must be within 400 llmHg.

〔Effect of the invention〕

As described in detail above, when the adhesion method of the present invention is applied and the wafer is blown up with nitrogen gas and brought into contact with the mask, there is no risk of gas being trapped between the wafer and the mask, and the entire surface is covered. It has an excellent practical effect of being able to achieve uniform and complete adhesion.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram for explaining the adhesion method of the present invention, Figure 2 is a schematic diagram for explaining the adhesion method of the present invention.
The figure is an explanatory diagram of a general method for bringing a wafer into close contact with a mask, and FIG. 3 is an explanatory diagram of a technique related to a prior application to which the method of the present invention is applied. 1.1'...Wafer, 2...Mask, 2'...Wafer bent in a downwardly convex shape, 3...Stage that can move up and down, 4...Vacuum suction/f-rad 8... Top plate, 8a... Opening, 9... Bellows, 10... Gas bearing, 11... Sealed space.

Claims (1)

[Claims] The wafer is suctioned and held by a vacuum suction pad provided on the top surface of the vertically movable stage, and the vertically movable stage is raised so that the suctioned and held wafer faces the mask through a small gap, and nitrogen is removed from the suction pad. In the method of blowing out gas to blow the wafer up and bring it into close contact with the mask, the space under the mask is set to 50 mmHg.
A method of connecting a wafer and a mask, characterized in that the pressure is reduced within a range of ~400 mmHg and the mask is bent downward in a convex manner, so that the center of the mask and the center of the wafer first come into contact with each other. Close contact method.