JPH0443244A - Clean room - Google Patents

Abstract

PURPOSE:To reduce diffusion of chemical substances in the air and to alleviate an increase in chemical contamination of a wafer by providing a bent part at the inlet of a return passage, and feeding the flow along the bent part. CONSTITUTION:The air raised under pressure in a ceiling 2 by a ceiling fan 4 is purified by a ceiling filter and fed into a clean room 1. The clean air flows in the clean room, flows to under a floor 3 through a grating floor 8, and again returned in the ceiling 2 through a return passage 5 partitioned by a partition plate 6 from the clean room. Here, a bent 7 made of a straight line for connecting a circular arc having a radius of 1/3 of the width (1) of the return passage at the inlet of the return passage at the return passage side of the partition plate to the ceiling side end of the return passage in contact with the arc is provided. Thus, since the air stream is not peeled but fed smoothly along the bent 7, the air stream is not disordered like prior art to reduce diffusion of chemical substances in the return passage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a clean room for performing semiconductor construction and the like.

[Conventional technology]

In conventional clean rooms, in order to control the airflow inside the clean room and achieve good laminar flow, Japanese Patent Application Laid-Open No. 1-281349
Various efforts have been made as seen in Japanese Patent Application Laid-Open No. 1-58947.

However, in the conventionally known examples, there is nothing that rectifies the flow in the return flow path.

In addition, conventionally, in order to purify the air sent into a clean room,
In general, high-performance filters called HEPA or ULPA or chemical filters that remove chemicals from the air are used.

Both tJLPA and chemical filters are used. However, there is no control such as allowing air to flow through the chemical filter as necessary.

[Problem to be solved by the invention]

Conventionally, in clean rooms where semiconductors are manufactured, studies have been conducted on how to reduce the amount of microscopic dust floating in the air, and how to remove dust generated inside the clean room using airflow without adhering to wafers. However, as the degree of integration of semiconductors increases, not only such dust but also chemical contamination caused by chemical substances in the air adhering to the wafer surface has become a serious problem to be solved.

Filters called chemical filters are generally used to remove chemical substances from the air, but chemical filters do not have as high a dust collection efficiency as HEPA or ULPA filters.

Therefore, chemical filters are not sufficient to clean the air, and to solve this problem, if chemical filters are used in combination with HEPA or ULPA, the pressure loss of the flow becomes large, and clean room running Cost increases.

Chemical contamination of wafers generally occurs when hazardous chemicals leak from equipment for some reason and their vapors enter the air. To reduce and prevent such chemical contamination, the following passive and active methods can be considered.

A passive method is to prevent the spread of chemical contamination, which requires solving the technical problem of how to minimize the spread of chemical substances mixed into the air.

Aggressive methods, on the other hand, remove chemicals from the air. At this time, there is a technical problem of how to take such measures only when necessary without reducing the cleanliness regarding dust.

An object of the present invention is to solve the above two technical problems.

[Means to solve the problem]

Think about technical issues by dividing them into two methods: passive methods and active methods.

(1) Passive method: The technical issue in this case is how to minimize the diffusion of chemical substances mixed into the air. There are two types of diffusion mechanisms. One is molecular diffusion and the other is turbulent diffusion. Of these two diffusion mechanisms, turbulent diffusion has a much larger scale than molecular diffusion. Therefore, it is effective to take measures to reduce turbulent diffusion. Turbulent diffusion results from turbulence in the flow. Generally, in a laminar flow clean room,
Most of the flow disturbances occur on the wall surface.

Furthermore, the turbulence increases when the flow velocity is high.

A portion where the flow velocity is high and a wall surface exists is a return flow path. In particular, at the entrance of the return flow path, the flow changes direction significantly, so a vortex area where the flow separates occurs there, and the flow is greatly disturbed. Therefore, in order to reduce the diffusion of chemical substances, it is effective to rectify the return flow path, especially the flow at the entrance thereof, to eliminate the eddy region.

In other words, as a negative method, measures are taken to eliminate the vortex region of the flow at the entrance of the return flow path. in particular,
The following two measures apply:

1) A curved portion is provided at the entrance of the return flow path so that the flow flows along the curved portion.

2) At the entrance of the return flow path, the vortex area is sucked into the partition plate that divides the return flow path and the clean room.

To achieve this, the partition plate is made of double walls and a flow path is formed between them, so that the flow near the partition plate at the entrance of the return flow path flows through the flow path between the double walls.

(2) Active method: The technical challenge of the active method is to remove chemicals from the air by having the flow pass through a chemical filter only when necessary, without deteriorating the cleanliness regarding dust. That's true. Such issues are
The problem is solved by the following means.

The return flow path is formed by two flow paths. It is possible to freely control which flow path the air flows through. A chemical filter is installed in one of the two flow paths. Normally, air is allowed to flow through the channel without a chemical filter. Furthermore, the chemical substances in the air are monitored, and when the concentration of the problematic substance exceeds a certain value, the flow path is switched to the chemical filter side to remove the chemical substance. Switching between the flow path without a chemical filter and the flow path with a chemical filter is performed using a damper or the like.

[Effect]

1. Passive method 1) Providing a curved part on the partition plate between the return channel and the clean room: Figure 9(a), which will be explained using Figure 1, shows a clean room. Air pressurized by a ceiling fan 4 is sent from the ceiling 2 into the clean room 1 after being purified by a ceiling filter (HEPA filter). Clean air flows through the clean room,
It passes through the grating floor 8, flows into the underfloor 3, is separated from the clean room by a partition plate 6, passes through a return channel 5, and returns to the ceiling 2 again. As shown in the figure, since the direction of the airflow changes significantly at the entrance of the return flow path, in the case of a normal partition plate, the flow separates as shown in (d), and the vortex area f
′ is formed, the turbulence of the flow increases, and the diffusion of chemicals in the air increases. Therefore, in the present invention, on the return flow path side of the partition plate, the width of the return flow path (
A curved line 7 was provided (b) consisting of a circular arc with a radius of 1/3 of that in 1) and a straight line connecting the end of the return flow path behind the ceiling in contact with the circular arc. As shown in Figure (c), by doing this, the airflow flows smoothly along the curve 7 without separation, so there is no turbulence in the airflow as in the conventional case, and therefore, the return flow Diffusion of chemicals in roads is reduced.

2) Making the partition plate a double wall: This will be explained using Figure 2. The partition plate separating the return flow path 5 and the clean room 1 is composed of a partition plate 6 and a partition plate 6', and an inter-partition flow path 10 is formed between them. The airflow f changes its direction significantly at the entrance of the return flow path, so it begins to separate there, but the fluid at a low velocity in the part where it begins to separate is sucked into the inter-partition flow path 10 and flows there. Since the flow returns to the ceiling, turbulence in the flow of the return channel 5 is prevented from developing. Therefore, the diffusion of chemical substances in the return flow path is reduced.

2. Proactive method This will be explained using Figure 3. The inlet of the return flow 15 is divided into two parts: an inlet 1.4 and an inlet 14'. When the damper 11 at the entrance 14 is open, air flows through the entrance 1
4, enters the return channel 5, returns to the attic 2, and connects the fan 4.
The pressure is increased by the ceiling filter 9 and cleaned by the ceiling filter 9. When the damper at the inlet 14 is closed and the fan 13 is started, air enters from the inlet 14', passes through the chemical filter 12, removes the mixed chemicals, and then returns to the return flow path 5. It flows.

On the other hand, the concentration of chemical substances in the air is
Air is sucked in from the gas chromatograph 16 and constantly monitored by the gas chromatograph 16, and the results are sent to the computer 1.
Sent to 7.

Normally, the damper at the entrance 14 is open and the fan 1
3 is stopped, the air flows without passing through the chemical filter 12. However, when the concentration of the chemical substance monitored by the gas chromatograph 16 exceeds a specified value, the computer issues a signal to start the motor that drives the damper 11 to close the damper 11, and at the same time, the fan 13 Issue a command to start. By doing so, air passes through the chemical filter 12 and flows into the return flow path. Furthermore, since it is an abnormal situation for air to pass through the chemical filter in this way, the alarm system W20 is activated to notify the operator 18 of this fact. The worker 18 searches for the cause of the high concentration of chemical substances in the air, takes measures, and after completing the measures, sends a release signal from the computer 17, the fan 13 stops, and at the same time, the damper 11 opens to return to the normal state. Return to

By the above means, chemical substances in the air can be removed only when necessary, without deteriorating the dust collection efficiency.

〔Example〕

Two embodiments of the passive method are shown in FIGS. 1 and 2, respectively. What is shown in Fig. 1 is that by providing a curved part on the partition plate, generation of eddy acid at the entrance of the return flow path is prevented.
This is an example of eliminating the development of turbulence in the flow and minimizing the diffusion of chemical substances in the air.

The curved shape is as described above.

What is shown in Figure 2 is that the partition plate is made of double walls.
This is an example of preventing flow separation and reducing the diffusion of chemical substances. The width of the inter-partition plate flow path 10 made of double walls is about 10 to 20% of the return flow path width. In this embodiment, the width is 10% of the return flow path. In addition, in this embodiment, the partition plate 6' is made shorter at the entrance side of the return flow path by about 1/3 of the width of the return flow path than the partition plate 6, so that the fluid that is about to be separated can pass through the flow path between the partition plates. It makes it easy to get sucked into 1o.

〔Effect of the invention〕

According to the present invention, the spread of chemical contamination of wafers is reduced in a simple manner by passively reducing the diffusion of chemical substances in the air. Proactive methods also remove chemicals from the air only when necessary.
It is possible to prevent chemical contamination while keeping running costs almost unchanged and maintaining cleanliness with respect to dust.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram of a second embodiment of the present invention, and FIG. 3 is an explanatory diagram of a third embodiment of the present invention. .

Claims (1)

[Scope of Claims] 1. A clean room into which clean air is introduced from the ceiling, a return passage through which the clean air returns from the clean room to above the ceiling, and a partition wall that partitions the clean room and the return passage. A clean room comprising: a curved portion of the partition plate protruding toward the return flow path near a boundary between the return flow path and the clean room.