JP3156452B2 - Clean air supply device and supply method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

Since it is necessary to rapidly process a large amount of information, the capacity of a semiconductor integrated circuit constituting the main body of an information processing device has been increased, and LSIs and VLSIs have been put into practical use. ULSI is under development. Here, since the increase in capacity is mainly performed by downsizing unit elements, the pattern width of conductor lines, electrodes, and the like has been greatly reduced. For example, a 64 Mbit D-RAM
The minimum line width has been reduced to 0.3 μm, and will tend to shrink in the future.

A semiconductor integrated circuit is formed on a substrate (wafer) made of a single semiconductor such as silicon (Si) or a compound semiconductor such as gallium arsenide (GaAs) by thin film forming technology, photolithography technology (photolithography), impurity element implantation. Although it is manufactured using technology, the main work is to supply clean air and maintain a constant temperature and humidity because the pattern is fine and the characteristics of circuit elements are sensitive to the external environment. It takes place in a clean room that is kept.

[0004]

2. Description of the Related Art In many cases, cleanliness of a clean room in which semiconductor devices are manufactured is controlled to a class of 10 or less (with dust having a particle diameter of 0.3 μm within 10 cubic feet). After removing the dust through the filter, it is supplied to the clean room at a constant temperature and humidity.

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

[0006] When a work involving generation of harmful gas is performed in a clean room, it is general that all air is exhausted to the outside of the clean room. From a practical point of view, after a part of exhaust gas from the clean room is filtered through a filter, fresh air is often added from the outside and reused.

Here, of the various operations performed in the clean room, various chemicals are used in the photolithography technology and the thin film forming technology (abbreviation: CVD) by vapor phase growth. In some cases, the vapor of the chemical or the vapor of the reaction product is not completely exhausted from the exhaust duct, and a part of the vapor passes through the filter and then recirculates to the clean room. In order to cope with this, an adsorption treatment using an adsorbent such as activated carbon is performed, but the effect is not sufficiently improved.

[0008]

As the pattern becomes finer, the diameter of the collecting aperture (eye) of the filter becomes finer, and the load on the air-conditioning fan increases. In addition, harmful gases and vapors of reaction products may be contained in the circulating clean air, and the problem is that they are not completely removed even by adsorbents such as activated carbon. It is an issue.

[0009]

An object of the present invention is to provide a device for supplying clean air into a clean room by spraying pure water from a plurality of nozzles onto an air flow supplied from the outside to form a mist (mist). Means, a means for spraying liquid air from a plurality of nozzles to the mist to freeze moisture present in the mist, a means for removing the fine-grain ice frozen from the mist through an eliminator, and a cooling means for flowing liquid nitrogen. A plurality of pipes and regeneration pipes through which the heated nitrogen gas flows are arranged alternately at a fine interval. An air flow is supplied to a pipe row which can switch a medium flowing in the pipes at any time, and residual moisture is removed. The problem can be solved by using a clean air supply device including a means for removing 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, conventionally, dust is removed by a physical method of making a mesh of a filter fine, and chemicals with a high vapor pressure and harmful substances that are mixed in are removed. While the method of removing gas with an adsorbent is used, the present invention adds a mist composed of pure water to adsorb fine dust contained in the air, After dissolving the above gas, this mist is frozen and a method of removing fine ice is taken to obtain clean dry air.

That is, particles (Pa) conventionally produced by fine dust contained in the air or friction during work.
rticle) has only become a problem, but recently there has also been a problem with the removal of gases contained in the factory environment and gases entering from the manufacturing process.

That is, in the CVD process, monosilane (SiH ₄ ) is generally used to form a silicon dioxide (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ) thin film, and a semiconductor layer is formed. Arsine (AsH ₃ ), diborane (B ₂ H ₆ ), etc. are used for formation. In the MOCVD process, hexamethyldisilazane (abbreviated as HMDS), tertiary butyl arsine (abbreviated as TBA), tertiary butyl phosphine
(Abbreviation TBP) is generally used.

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

As a solution to this problem, the inventor has noted that dust is easily trapped by moisture, and that any harmful gas in the integrated circuit manufacturing process or any gas used in the CVD reaction is easily dissolved in water.

The clean air supply device according to the present invention comprises the following processing steps. In the first stage, pure air is sprayed on the air sent to the clean room by a blower (Fan) to form a mist, which adsorbs particles such as dust and simultaneously dissolves a water-soluble gas. In the second stage, the mist is frozen by spraying liquid air,
Eliminate most of the ice with the Eliminator. In the third step, mist that has not been removed in the second step is passed through a plurality of pipes through which liquid nitrogen (N ₂ ) flows, and is condensed and removed on the pipes to form dry air.

Here, when the liquid air is sprayed in the second stage, the mist formed in the first stage is easily frozen and adheres to the eliminator to prevent clogging since the boiling point of the liquid air is -194.2 ° C. Occurs. To prevent this, use an eliminator with a built-in heater so that the attached ice is liquefied, and a drain-pan with a built-in heater is provided under the eliminator.
It is necessary to drain the dropped water.

Further, since the mist that cannot be removed in the second stage freezes on the pipe through which the liquid N ₂ flows in the third stage, it is necessary to remove the mist. prepare the pipe column, the air flow path by the to keep the ice growth alter the pipe of the flow of the liquid N ₂ can be prevented from clogging, if necessary. Next, the high-purity dry air thus formed is supplied with the required temperature and humidity through a temperature and humidity controller, and then supplied to a clean room.

[0018]

FIG. 1 is a block diagram of a clean air supply device. The air taken in by a first blower 1 is fed to a clean air supply device 3 after dust is removed by a filter 2. Here, the clean air supply device 3 is composed of three regions of a pure water spraying unit 4, a first stage cooling unit 5, and a second stage cooling unit 9, and the air is configured to sequentially pass through each region. ing.

Here, the pure water spraying section 4 is configured to spray pure water from the pipe to the inflowing air, dust is adsorbed by mist generated in this area, and water-soluble gas is dissolved. I do. Next, the first-stage cooling unit includes a liquid-air spraying unit 6, an eliminator 7, and a drain-pan 8 for storing and draining liquefied water. The mist is immediately frozen by the generated liquid air, becomes fine rime ice, floats, and then deposits on the eliminator 7.

Here, the eliminator 7 is formed of a copper (Cu) net in which a heater is embedded, and the water liquefied by the heating is received by the drainage tray 8 and then discharged outside the apparatus.
Next, the second-stage cooling unit 9 is configured such that a plurality of cooling pipes 11 and regeneration pipes 12 are alternately arranged and can be switched at any time, and a drainage tray 13 is placed below this, and Liquid N ₂ is supplied to the cooling pipe 11, and N ₂ gas heated to 40 ° C. is supplied to the regenerating pipe 12 to cool the rime ice that could not be captured by the eliminator 7 of the first cooling unit 5. The water is captured by the pipe 11, but when ice accumulates on the surface of the pipe 11 and the air flow path narrows, the pipe is switched, and the liquid N ₂ is supplied to the regeneration pipe 12.
And liquefied by flowing N ₂ gas through the cooling pipe 11, and received by the drainage tray 13 to remove it outside the apparatus.

Although pure dry air could be obtained by such a method, this air was then sent to a temperature / humidity controller 15, which in this example was at 24 ° C. and 40% RH, The clean room 16 is supplied 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]

According to the present invention, dust and harmful gas can be removed at the same time. In addition, the quality of the semiconductor integrated circuit can be improved, the pressure loss of the blower can be reduced as compared with the case of using a filter with a small collecting aperture, so that power can be saved, and the number of filter replacements can be reduced. Was.

[Brief description of the 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 unit 4 Pure water spray unit 5 First stage cooling unit 6 Liquid air spray unit 7 Eliminator 8, 13 Drain tray 9 Second stage cooling unit 11 Cooling pipe 12 Regeneration pipe 16 Clean room

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F24F 3/16 B01D 50/00 502 B01D 51/02 F24F 7/06

Claims (2)

(57) [Claims] An apparatus for supplying clean air into a clean room comprises: means for spraying pure water from a plurality of nozzles into an air flow supplied from the outside to form a mist; and supplying liquid air to the mist from the plurality of nozzles. Means for spraying to freeze the water present in the mist, means for removing the fine-grain ice frozen from the mist through an eliminator, a cooling pipe through which liquid nitrogen flows, and a regeneration pipe through which heated nitrogen gas flows. A plurality of pipes are alternately arranged at a fine interval; a means for supplying the air flow to a pipe row capable of switching a medium flowing in the pipe at any time to remove residual moisture; And a means for adjusting the temperature and humidity of the air to be supplied to a clean room. 2. A mist is formed by spraying pure water onto an air flow introduced into the clean room from the outside, and then the liquid mist is sprayed onto the mist to freeze the mist. A method of supplying clean air, comprising removing ice by passing through a gap between pipes to form dry air, and then adjusting the temperature and humidity of the dry air to supply the dry air to a clean room.