JP2595838B2 - Gas suction device in aqueous solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
The present invention relates to a gas suction device in an aqueous solution for suctioning and removing adhering gas.

Various functional components have been put into practical use in response to the progress of information processing technology, and many of them use crystals. For example, semiconductor integrated circuits are made using a silicon (Si) single crystal substrate (wafer) as a substrate, and semiconductor lasers are made using a compound semiconductor wafer such as gallium arsenide (GaAs) or indium phosphide (InP) as a substrate. .

Also, crystal is used for the vibrator, and a ferroelectric wafer such as lithium niobate (LiNbO ₃ ) or niobium tantalate (LiTaO ₃ ) is used for the surface acoustic wave filter. The formation is taking place.

Here, the thickness of each of these wafers is a few.
It is 100 μm in size.Single-crystal ingots obtained by the pulling method (Bridgeman method) or the like are sliced to the required thickness using a slicer, and the surface is polished to smooth the wafer surface. Imperfect surface treatment is performed to remove impurities and crystal defects existing on the surface.

[0005] Devices are formed using such a clean and smooth wafer. The present invention relates to an apparatus for sucking and removing a gas generated when performing such a chemical surface treatment.

[0006]

2. Description of the Related Art In a device forming process, a chemical surface treatment is frequently used. Hereinafter, the description will be made by limiting the target to a semiconductor wafer, particularly a Si wafer.

As a chemical surface treatment of a Si wafer, there are cases where a plurality of wafers are vertically mounted on a basket and collectively performed. On the other hand, the back side is suctioned using a wafer holder having a vacuum chuck function. However, there is also a single wafer processing in which only the surface of the wafer is immersed in the processing liquid in this state.

In such single-wafer processing, when a chemical reaction involves the generation of gas, the gas adheres to the wafer and is not easily separated, and therefore, the gas generation position often becomes a defect.

For example, when the surface treatment of a Si wafer is performed by using a mixed solution of hydrofluoric acid (HF) and nitric acid (HNO ₃ ), oxygen (O ₂ ), nitrogen oxide (N0), nitrogen peroxide ( NO ₂ )
And the like, and these gases adhere to the wafer and do not easily come off, so that a non-etched portion is formed, resulting in a defect.

As a method for removing this, nitrogen (N ₂ )
For example, a method of bubbling by sending fine bubbles such as a method, a method of providing an ultrasonic vibrator in a processing tank to vibrate the processing liquid, and a method of spraying the processing liquid from a nozzle are adopted.

However, it is difficult to perform surface treatment under uniform conditions over the entire area of the wafer by any of these methods.
The production yield is adversely affected. For these reasons, it has been necessary to commercialize a method for uniformly performing a chemical surface treatment without causing a flow pattern or the like on a wafer processing surface.

[0012]

In the case where one surface of a substrate to be processed is subjected to a chemical surface treatment by a single-wafer processing method, a gas is generated by a chemical reaction, and the non-surface-treated portion is formed by the adhesion to the wafer. Or a flow pattern of gas is generated, which causes a defect.

[0013] Therefore, it is an object to quickly remove the gas causing such a defect.

[0014]

An object of the present invention is to provide a wiping mechanism, which is attached to a substrate to be processed while reciprocating in contact with or approaching the lower surface of the substrate in contact with an aqueous solution. A jig for sucking gas is provided with a stretched porous polytetrafluoroethylene film on a hollow cylindrical mesh holding cylinder having one end sealed, and this mesh holding cylinder is connected to an exhaust system, The problem can be solved by configuring a gas suction device in an aqueous solution, which is characterized by suction.

[0015]

The present invention utilizes a fluororesin, especially polytetrafluoroethylene (hereinafter, abbreviated as PTFE), which has excellent chemical resistance and a small critical surface tension. Wiper to be passed through [Wip for short
er)] and connect it to the exhaust system to exhaust only gas.

That is, as shown in FIG. 1, an expanded porous PTFE membrane 2 is adhered to a mesh holding cylinder 1 having a large number of holes formed in a mesh shape to constitute a wiping portion 3,
The mesh holding cylinder 1 is used by being connected to an exhaust system.

That is, the wiping unit 3 is reciprocated over the entire area of the wafer 6 while being in contact with the lower surface of the wafer 6 which is held by the wafer holding unit 4 and is in contact with the jetting aqueous solution 5, thereby adhering to the lower surface. This is to suck and remove the bubbles that are generated.

The inventors have the general formula of (CF ₂ CF ₂ ) _n
After compressing the PTFE powder, the material uniaxially or biaxially stretched under special conditions is made up of fine fibrils called fibrils and island-like or granular nodules called nodes that connect them. And a continuous porous structure in which extremely fine gaps between these fibrils and nodes are connected to each other, and are marketed under the trade name of GORE-TEX (Japan GORE-TEX Co., Ltd.). I noticed that

In addition, these porous structures are used as filters that take advantage of chemical stability, thermal stability, water repellency, and flame retardancy to capture dust in gas, insulating materials such as coaxial cables, and the like. Sportswear is introduced.

The inventor makes use of the water repellency of this material to make a filter that does not allow water to pass through but only gas, and attaches it to the tip of a wiper used in automobiles and the like, and reciprocates in the liquid. And only the gas is sucked by vacuum suction.

Hereinafter, the reason why a porous structure made of a fluororesin such as PTFE does not allow water to pass but gas will pass will be described. As a method for quantitatively indicating the wettability of a solid surface by a liquid, there is a "critical surface tension of wetting γ _c ".

[0022] When the definition of the gamma _c placing the liquid on the solid surface, when the contact angle of the liquid becomes 0 °, refers to the surface tension value of the liquid, the gamma _c of PTFE with 18.5 dyn / cm is there. In addition, polyfluoroethylene (CF ₂ CHF) _n, which is a similar fluororesin, is 22 dyn / cm, and polychlorotrifluoroethylene (CF ₂ CFCl) _n is 31 dyn / cm, which is proportional to the decrease in F atoms. Therefore, the value of γ _c increases.

As compared with the value of γ _c of this material, the wettability is good when the surface tension of the contacting liquid is small.
On the other hand, if it is large, the liquid is repelled. Here, the surface tension of water is as large as 72.28 dyn / cm (23 ° C.), so it is repelled, but H of H ₂ is 1.98 dyn / cm (-253.1 ° C.), and 〃 of N ₂ is 6.16 dyn / cm ( -183.1 ℃), ₂ of O ₂ is as small as 13.55 dyn / cm (-183.6 ℃),
Therefore, it can be seen that light is transmitted.

From the above, the present invention provides a porous structure.
Among the fluorine resins, _cPTFE with small value
Using a membrane as a filter and a wiper equipped with a vacuum suction mechanism
Adsorbs only gas adhering to the lower surface of wafer
This eliminates the occurrence of defects in chemical surface treatment
Is what you do.

[0025]

FIG. 2A is a sectional structural view of the wiping unit 3 shown in FIG. 1, and FIG. 2B is a sectional view taken along line XX 'of FIG. Alternatively, the state where the wiping unit 3 is rotated along the wafer surface to suck the gas 13 is shown.

Here, the mesh holding tube 1 is made of a non-rusting tube-shaped material, the through holes 8 are opened in a mesh shape, and this holding tube is inserted into the adapter 9. Further, a portion of the joint 10 following this is connected to a wiper mechanism so as to be able to perform a wiping motion, and is connected by a tube 11 to an exhaust system composed of a rotary pump via a vacuum trap.

A 1 mm thick PTFE membrane 2 made of a porous structure is fitted and covered on the mesh holding cylinder 1, and is fixed to the adapter 9 by a mesh retainer 12. Using such a wiping unit 3, a mixed solution of HF and HNO ₃ is used as the aqueous solution 5 shown in FIG. 1, while the Si wafer is vacuum-suctioned by the wafer holding unit 4 and lowered to the liquid level.
The wiping unit 3 operated the exhaust system to reciprocate in contact with the lower surface of the wafer 6.

As a result, the mixed solution of HF and HNO ₃ did not enter the trap, and only the gas could be removed, thereby preventing the occurrence of defects due to the remaining etching gas.

[0029]

According to the present invention, when performing a single wafer type chemical surface treatment, it is possible to remove only gas generated on the lower surface of the substrate to be processed, thereby eliminating the occurrence of defects. Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a gas suction device according to the present invention.

FIG. 2 is a sectional structural view of a wiping unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mesh holding cylinder 2 PTFE film 3 Wiping part 4 Aqueous solution 6 Wafer 8 Through hole 13 Gas

Claims (1)

(57) [Claims] A jig provided with a wiping mechanism, for sucking a gas adhering to a substrate to be processed while reciprocating in contact with a lower surface of the substrate to be in contact with an aqueous solution or close to a point of contact, An aqueous solution comprising a stretched porous polytetrafluoroethylene membrane provided on a hollow cylindrical mesh holding cylinder whose one end is sealed, wherein the mesh holding cylinder is connected to an exhaust system and sucked. Inside gas suction device.