JPH0963913A - Clean room for wet process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet process clean room whose flame-retardant properties are ensured and in which wafers are prevented from being contaminated by boron. SOLUTION: The filter paper of a filter 10 which serves as a ceiling is formed of glass fibers, and a clean bench 2 where an air filter formed of filter paper impregnated with L-tartaric acid is used is installed in a clean room. The filter paper of the filter 10 serving as a ceiling is formed of glass fibers impregnated with L-tartaric acid, and an electret filter, a membrane filter, or a filter formed of filter paper impregnated with L-tartaric acid is used as a filter of the clean bench 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet process clean room used in an LSI electronic device manufacturing process.

[0002]

2. Description of the Related Art An aqueous solution of hydrofluoric acid is used in a wet process for cleaning wafers, and therefore, hydrofluoric acid vapor circulates in a clean room. Therefore, when a filter made of conventional borosilicate glass fiber is used, boron oxide in the composition reacts with hydrofluoric acid to produce boron trifluoride, and gaseous boron trifluoride contaminates the wafer. Was.

In a clean room of a conventional cleaning process, a filter made of borosilicate glass fiber is used as a filter for a ceiling and a filter for a clean bench, but the filter for a clean bench is exposed to a high concentration of hydrofluoric acid vapor. Therefore, in recent years, as a hydrofluoric acid resistant filter,
Electret filters (polypropylene) and membrane filters (polytelorafluoroethylene) are recommended.

When the above-mentioned electret filter is used for a clean bench, boron trifluoride is not generated from the clean bench, so that the contamination of the wafer is alleviated. However, although the concentration is low, the ceiling filter also circulates air. Since it is exposed to hydrofluoric acid vapor, boron trifluoride is generated from the ceiling filter and cannot be adsorbed and collected by an electret filter or the like. As a result, the wafer is contaminated.

Therefore, it is conceivable to use an electret filter or a membrane filter for the clean bench filter and the ceiling filter. However, since these filters are made of resin, they are inferior in flame retardance and are perforated by a flame. There is a risk of Therefore, it is not preferable to use the above-mentioned type of filter for the ceiling in order to ensure the flame retardancy of the room.

[0006]

Therefore, it is an object of the present invention to provide a clean room for a wet process, which can secure flame retardancy as a clean room and can suppress the contamination of a wafer with boron to a low level.

[0007]

In the clean room for wet process of the present invention, the filter paper constituting the ceiling is made of glass fiber, and a clean bench using an air filter made of filter paper impregnated with L-tartaric acid is used. It is installed indoors.

Since L-tartaric acid is impregnated on the filter paper of the air filter used in the clean bench, this L-tartaric acid and boron trifluoride are chemically bonded, and boron trifluoride in the atmosphere is present. Is adsorbed and collected. Further, in a hydrofluoric acid vapor atmosphere, L-tartaric acid has a coating effect on the surface of the filter paper, and since boron trifluoride and L-tartaric acid are stably bound, the generation of boron is low.

On the other hand, since the filter filter paper constituting the ceiling is made of glass fiber, the flame resistance of the room as a whole is secured.

Therefore, in the wet room clean room of the present invention, it is possible to ensure flame retardancy as a whole room and to suppress the contamination of the wafer with boron to a low level.

Hereinafter, a specific description will be given. [Experiment 1 / Test for Boron Concentration Measurement in Clean Bench by Loading Hydrofluoric Acid Vapor] The apparatus shown in FIG. 2 was used to load the hydrofluoric acid vapor to measure the boron concentration downstream of the filter. In FIG. 2, reference numeral 40 is a hydrofluoric acid vapor generator, reference numeral 41 is a fan, reference numeral 42 is a filter, reference numeral 43 is pure water bubbling, and 44 is a pump.

FIG. 3 shows the result of this experiment 1. When hydrofluoric acid vapor is loaded, the conventional ULPA is used.
In the filter (using borosilicate fiber filter paper), the higher the hydrofluoric acid vapor concentration, the higher the boron concentration, but the boron concentration downstream of the filter using the filter paper impregnated with L-tartaric acid is the hydrofluoric acid vapor concentration. It turns out that it does not increase even if it is raised. That is, in this experiment, the boron concentration was 18 ng / m ³
And is constant. [Experiment 2 / Boron trifluoride loading test] The boron concentration was measured at the downstream A of the conventional ULPA filter and the downstream B of the filter using the filter paper impregnated with L-tartaric acid by the apparatus shown in FIG. In FIG. 4, reference numeral 50 is a hydrofluoric acid vapor generator, reference numeral 51 is a conventional ULPA filter, reference numeral 52 is a fan, reference numeral 53 is a filter using a filter medium impregnated with L-tartaric acid, and reference numerals 54 and 55 are pure water. Bubbling, reference numerals 56 and 57, denote pumps.

FIG. 5 shows the results of this experiment 2. From this, the boron concentration in the downstream B of the filter 53 is completely different even if the amount of boron generated in the downstream A of the conventional ULPA filter 51 increases. It can be seen that it does not change and is constant.

As described above from Experiments 1 and 2, it is clear that when the structure of the present invention is adopted, the contamination of the wafer with boron can be suppressed to a low level.

Similarly to the above, when the filter constituting the ceiling is made of filter paper in which glass fiber is impregnated with L-tartaric acid,
Since the amount of boron generated from the filter can be suppressed to a low level, the contamination of the wafer can be suppressed to a low level by adopting any of an electret filter, a membrane filter or a filter made of a filter paper impregnated with L-tartaric acid as a filter for a clean bench. It is clear that you can.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In this wet process clean room, as shown in FIG. 1, ULPA is installed in the ceiling filter 10.
A filter is used, a perforated plate is used for the floor plate 11, and air is circulated by the blower 13 in the route of the space K1 above the filter 10 for the ceiling → the room R → the space K2 below the floor plate 11 → the air passage AR for circulation. It is something that is done. In this clean room, as shown in FIG. 1, a clean bench 2 having a filter 20 made of filter paper impregnated with L-tartaric acid is installed on a wafer cleaning device 3 in the room.

In FIG. 1, reference numeral 12 is a blank panel, reference numeral 13 is a blower, reference numeral 21 is a blower, and a large number of arrows indicate the flow of air.

The filter 10 for the ceiling has a filter paper made of borosilicate glass fiber, and the ceiling of the room is formed by using a large number of the filters. In this embodiment, borosilicate glass fibers that are generally used are used, but other types of glass fibers may be used.

The filter 20 is formed by attaching a filter paper bent in a zigzag cross section to an airtight outer periphery in a frame of an aluminum mold, and the filter paper is a thin fiber (fiber diameter) made of borosilicate glass fiber as a basic material. Distribution 0.2
˜2.65 μm, average diameter 0.85 μm), and a small amount of large-diameter fibers (E glass fiber: fiber diameter distribution 8 to 24 μm) for reinforcing the small-diameter fibers with each other, and 7 of the attached paper weight. % L-tartaric acid. This filter 20 can be manufactured by the following operations. First, as a basic material, fine fibers made of borosilicate glass fibers (fiber diameter distribution 0.2 to 2.65 μm, average diameter 0.
85 μm) and a small amount of large diameter glass fibers (E glass fiber: fiber diameter distribution 8 to 24) for reinforcing the small diameter fibers.
(.mu.m) is dispersed in water adjusted to pH 3.2 with a sulfuric acid solution for papermaking. After the above-mentioned papermaking, the sheet-like material was dipped in an emulsion containing 2% acrylic resin as a binder, 0.3% fluororesin as a water repellent, and 1% L-tartaric acid as a water repellent. To 130 ° C
The filter paper is manufactured by drying with a steam dryer. The air filter can be manufactured by folding the filter paper in a zigzag cross section and sealingly attaching it to a frame of an aluminum mold member with urethane resin.

When the boron concentration in the wet room clean room was measured, it was found that the boron concentration in the clean room was 300 ng / m ³ .
The concentration in the clean bench 2 was 10 ng / m ³ .

In the same manner as in the above embodiment, when the filter constituting the ceiling is made of filter paper in which glass fiber is impregnated with L-tartaric acid, the amount of boron generated from the filter can be suppressed to a low level. Whether a filter, a membrane filter, or a filter made of filter paper impregnated with L-tartaric acid is adopted, the contamination of the wafer can be suppressed to a low level.

[0023]

The present invention having the above-mentioned structure has the following effects.

Due to the operation described in the latter part of the column for means for solving the problems, it was possible to provide a clean room for a wet process in which flame retardancy as a clean room can be secured and wafer contamination by boron can be suppressed to a low level.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a wet process clean room according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of an apparatus used in Experiment 1.

FIG. 3 is a graph showing the relationship between the concentration of hydrofluoric acid vapor in air and the concentration of boron measured by the apparatus shown in FIG.

FIG. 4 is a conceptual diagram of an apparatus used in Experiment 2.

5 is a graph showing the relationship between the concentration of hydrofluoric acid vapor and the concentration of boron in the air measured by the apparatus shown in FIG.

[Explanation of symbols]

 2 Clean bench 10 Filter for ceiling 11 Floor board 12 Blank panel 13 Blower 20 Filter

Claims (3)

[Claims] 1. A wet process characterized in that the filter paper constituting the ceiling is made of glass fiber, and a clean bench using an air filter made of filter paper impregnated with L-tartaric acid is installed indoors. For clean room. 2. A wet process characterized in that the filter constituting the ceiling is made of a filter paper obtained by impregnating glass fiber with L-tartaric acid, and a clean bench using an electret filter or a membrane filter is installed indoors. For clean room. 3. A clean bench using a filter composed of a filter paper in which L-tartaric acid is impregnated on glass fiber as the filter constituting the ceiling, and a filter made of filter paper impregnated with L-tartaric acid is installed in the room. A characteristic clean room for wet processes.