JPH0735368A - Device and method for supplying clean air - Google Patents

Abstract

PURPOSE:To eliminate dust and harmful gas simultaneously by adding mist consisting of pure water to make it absorb dust in the air and make water-soluble gas dissolve therein. CONSTITUTION:Three regions are formed, namely, a pure water spray part 4, first-stage cooling part 5, and second-stage cooling part 9, through which a flow of air is passed in sequence. In the pure water spray part 4 pure water is sprayed against air flowing in and mist produced thereby adsorbs dust; water- soluble gas is also dissolved. In the first-stage cooling part 5 liquid air sprayed from a liquid-air sprayer 6 makes the mist instantly freeze into fine particulates of ice, which are deposited on an eliminator 7. Water resulting from their melting by heat from a heater in the eliminator 7 is received in a drain pan 8 and discharged out of the apparatus. In the second-stage cooling part 9, in the beginning, liquid N2 is passed through a cooling pipe 11 and N2 gas, through a regenerative pipe 12 in a setup to capture particulates of ice which have not been caught by the eliminator 7 in the first-stage cooling part 5, take the resulting water in a drain pan 13, and discharge it out of the apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus structure and a clean air supply method for supplying clean air to a clean room.

Since it is necessary to process a large amount of information quickly, the semiconductor integrated circuit which constitutes the main body of an information processing apparatus has a large capacity and LSI and VLSI have been put into practical use, but the capacity has further increased. ULSI development is underway. Here, since the large capacity is mainly achieved by downsizing the unit element, the pattern width of the conductor lines and electrodes has been greatly reduced. For example, a 64 Mbit D-RAM
The minimum line width is 0.3 μm, which is becoming finer, and it tends to be further reduced in the future.

A semiconductor integrated circuit is a thin film forming technique, a photolithography technique (photolithography), and an impurity element implantation on a substrate (wafer) made of a single semiconductor such as silicon (Si) or a compound semiconductor such as gallium arsenide (GaAs). Although manufactured using technology, the pattern is fine and the characteristics of circuit elements sensitively affect the external environment, so the main work is to supply clean air and maintain a constant temperature and humidity. It is carried out in a clean room where it is held.

[0004]

2. Description of the Related Art The cleanliness of a clean room where semiconductor devices are manufactured is often controlled at a cleanliness of class 10 or less (with less than 10 dust particles of 0.3 μm in 1 cubic foot). After removing dust through a filter, it is supplied to a clean room while maintaining a constant temperature and humidity.

However, the minimum line width is sub-half micron (Su
In the process of forming fine patterns such as (b-halfmicron), the presence of dust more than 1/10 of the pattern rule is not allowed in order to secure a high manufacturing yield. In other words, the size of the particles allowed to form a wiring pattern with a width of 0.3 μm is 0.03 μm (300 Å) or less. Therefore, fine particles are removed using various filters. However, since the pressure loss increases in proportion to the decrease in the collection port diameter of the filter, the load on the air conditioning fan increases, and the frequency of replacement of the filter also increases.

When working in a clean room with generation of harmful gas, it is common to exhaust all the air to the outside of the clean room, but in many cases it is economical. From the standpoint of cleanliness, it is often the case that a part of the exhaust gas from the clean room is filtered through a filter and then fresh air is added from the outside for reuse.

Among the various operations performed in the clean room, various chemicals are used for the photo-etching technique and the thin film forming technique (abbreviated as CVD) by vapor phase growth. A chemical vapor or a vapor of a reaction product may not be completely exhausted from the exhaust duct, and a part of the vapor may be circulated to the clean room again after passing through the filter, which causes a problem. On the other hand, a treatment of adsorbing with an adsorbent such as activated carbon is performed, but the effect is not sufficiently improved.

[0008]

As the pattern becomes finer, the collection port diameter (eyes) of the filter becomes finer, and the load on the air conditioning fan increases. In addition, the circulating clean air may contain harmful gases and vapors of reaction products, and the problem is that they are not completely removed by adsorbents such as activated carbon. It is an issue.

[0009]

[Means for Solving the Problems] The above problem is that an apparatus for supplying clean air into a clean room creates mist (mist) by spraying pure water from a plurality of nozzles on an air stream supplied from the outside. Means, means for spraying liquid air from this nozzle with multiple nozzles to freeze the water present in the mist, means for removing fine-grained ice that has frozen the mist through an eliminator, and cooling for flowing liquid nitrogen. Plural pipes and regeneration pipes through which heated nitrogen gas flows are arranged alternately at fine intervals, and an air flow is supplied to the pipe line that can switch the medium flowing through the pipes at any time to remove residual moisture. The problem can be solved by using a clean air supply device including a means for removing the air flow and a means for adjusting the air flow to a predetermined temperature and humidity and then supplying the air to the clean room.

[0010]

[Function] As a method of producing clean air to be supplied to a clean room, dust is removed by a physical method that is conventionally used to make the mesh of the filter fine, and chemicals with high vapor pressure and harmful harmful substances are mixed. While a method of removing gas with an adsorbent is used, in the present invention, a mist of pure water is added to adsorb fine dust contained in the air, and at the same time, water-soluble with a high vapor pressure is used. After the gas of No. 3 is dissolved, the mist is frozen and fine ice is removed to obtain clean dry air.

That is, conventionally, fine particles contained in the air or particles (Pa
However, recently, the removal of gas contained in the factory environment and gas mixed in from the manufacturing process has become a problem.

That is, in the CVD process, monosilane (SiH ₄ ) is generally used to form a thin film of silicon dioxide (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ), and the semiconductor layer Arsine (AsH ₃ ) and diborane (B ₂ H ₆ ) are used for formation. In the MOCVD process, hexamethyldisilazane (abbreviation HMDS), tert-butylarsine (abbreviation TBA), tert-butylphosphine
(Abbreviation TBP) and the like are commonly used.

Further, hydrofluoric acid (HF) is frequently used as an etching agent for SiO _2, but when this HF vapor is mixed with air and hits a glass filter constituting the filter, the boric acid (B ₂ O ₃ ) Component to generate boron fluoride (BF ₃ ) and release it into the clean room.It is also noted that ammonia (NH ₃ ) and hydrogen sulfide (H ₂ S ) And other harmful gases are included. For these reasons, in order to obtain a semiconductor integrated circuit with a high yield, it is necessary to remove harmful gas together with particles such as dust.

As a solution to this problem, the inventor has noticed that dust is easily trapped by moisture, and that harmful gas in the manufacturing process of integrated circuits and gas used in the CVD reaction are easily dissolved in water.

The clean air supply apparatus according to the present invention comprises the following processing steps. In the first step, pure air is sprayed on the air sent to the clean room by a fan (fan) to create a mist, which adsorbs particles such as dust and at the same time dissolves a water-soluble gas. In the second stage, spray liquid air to freeze the mist,
Remove most of the ice with an Eliminator. In the third step, the liquid nitrogen (N ₂ ) is passed between a plurality of pipes, and the mist that could not be removed in the second step is condensed and removed on the pipes to obtain dry air.

When liquid air is sprayed in the second step, since the boiling point of the liquid air is -194.2 ° C, the mist formed in the first step easily freezes and adheres to the eliminator to cause clogging. Occurs. To prevent this, an eliminator with a built-in heater is used to liquefy the ice that has adhered, and a drainage pan (Drain-pan) with a built-in heater is provided under the eliminator.
It is necessary to drain the dripping water.

In addition, the mist that could not be completely removed in the second step is frozen on the pipe in which the liquid N ₂ is flowing in the third step, and it is necessary to remove it. If a pipe row is prepared and the pipe through which the liquid N ₂ flows is changed as necessary, it is possible to prevent the passage of air from being blocked by the growth of ice. Next, the high-purity dry air thus formed is supplied to a clean room after being provided with necessary temperature and humidity through a temperature / humidity controller.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a clean air supply apparatus, in which the air taken in by a first blower 1 is filtered by a filter 2 to remove dust and sent into a clean air supply apparatus 3. Here, the clean air supply device 3 is composed of three regions of the pure water spraying unit 4, the first-stage cooling unit 5, and the second-stage cooling unit 9, and the air is configured to sequentially pass through each region. ing.

Here, the deionized water spraying section 4 is constructed so that deionized water is sprayed into the inflowing air from the pipe, and the mist generated in this area adsorbs the dust and dissolves the water-soluble gas. To do. Next, the first-stage cooling unit is composed of a liquid air spraying unit 6, an eliminator 7, and a drain pan (Drain-pan) 8 for collecting and discharging liquefied water, and spraying from the liquid air spraying unit 6 The liquid air immediately freezes the mist to form fine fog ice, which floats and then deposits on the eliminator 7.

Here, the eliminator 7 is formed of a net made of copper (Cu) in which a heater is embedded, and the water liquefied by heating is received by the drainage tray 8 and discharged to the outside of the apparatus.
Next, the second-stage cooling unit 9 is configured so that a plurality of cooling pipes 11 and regeneration pipes 12 are alternately arranged and can be switched at any time, and a drain tray 13 is placed under this, and initially, Liquid N ₂ was passed through the cooling pipe 11, and N ₂ gas heated to 40 ° C. was passed through the regeneration pipe 12 to cool the misty ice that could not be captured by the eliminator 7 of the first stage cooling unit 5. Although it is captured by the pipe 11, when ice accumulates on the surface of the pipe 11 and the air flow path becomes narrow, the pipe is switched, and the liquid N ₂ is fed to the regeneration pipe 12.
And liquefy by flowing N ₂ gas through the cooling pipe 11, and receive it by the drain tray 13 to remove it outside the device.

By using this method, pure dry air could be obtained. This air was then sent to the temperature / humidity controller 15, and in this case, it was set at 24 ° C. and 40% RH, It is supplied to the clean room 16 through a performance filter (HEPA filter) 18. A part of the air discharged from the clean room 16 is pressurized by the second blower 17 and recirculated to the clean air supply device 3.

[0022]

The present invention makes it possible to remove dust and harmful gas at the same time. In addition, the quality of the semiconductor integrated circuit can be improved, and the pressure loss of the blower is reduced compared to the case of using a filter with a small collection port diameter, so power consumption can be saved and the number of filter replacements can be reduced. It was

[Brief description of drawings]

FIG. 1 is a configuration diagram of a clean air supply device according to the present invention.

[Explanation of symbols]

 3 Clean Air Supply Device 4 Pure Water Spraying Section 5 First Stage Cooling Section 6 Liquid Air Spraying Section 7 Eliminator 8, 13 Drain Dish 9 Second Stage Cooling Section 11 Cooling Pipe 12 Regeneration Pipe 16 Clean Room

Claims (2)

[Claims] 1. A device for supplying clean air into a clean room, a means for spraying pure water from a plurality of nozzles onto an air stream supplied from the outside to form a mist, and liquid mist for the mist through the plurality of nozzles. Means for spraying to freeze the water present in the mist, means for removing fine-grained ice that has frozen the mist through an eliminator, cooling pipes through which liquid nitrogen flows, and heated nitrogen gas for regeneration A plurality of pipes are alternately arranged at fine intervals, and a means for removing the residual moisture by supplying the air flow to a pipe array capable of switching the medium flowing in the pipe at any time, and a predetermined air flow. A means for adjusting the temperature and humidity of the above and supplying the same to a clean room, and a clean air supply device. 2. A mist is prepared by spraying pure water onto an air flow introduced into a clean room from the outside, then spraying liquid air on the mist to freeze it, and then cooling the air flow containing fine ice with an eliminator. A clean air supply method characterized in that ice is removed by passing through a gap between pipes to obtain dry air, and then the dry air is temperature-humidity adjusted and supplied to a clean room.