JPH0221142A - Super clean chamber of constant temperature - Google Patents

Abstract

PURPOSE:To provide a chamber in which there is no fluctuation of temperature spacially and temporally by providing means to mix the air flow in channel in a channel between a blower and HEPA filter. CONSTITUTION:In order to bring the temperature distribution in a chamber within + or -0.01 deg.C it is necessary to mix sufficiently the air flow between a blower 9 and HEPA filter 2. In order to mix sufficiently the air flow in a channel in front of the HEPA filter it is recommendable to arrange a minute mixing device 21 which disturbs minutely the air flow flowing through the channel on the downstream side of a rough mixing device 20 which mixes mutually the air flows which flow through the channel at a remote position. For the rough mixing device 20 a laminate consisting of small channels which bundles respectively independent small channels a, b, c, and laminating at least part of the small channels which are inclined so as to displace mutually the positions of air intake ports and the positions of air outlet ports is preferable, and for the minute mixing device 21 a filling material 26 with a large cavity ratio is preferable.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is an ultra-constant temperature cleaning system that maintains an ultra-constant temperature state in which the temporal and spatial temperature distribution width is within ±0.01°C within a clean space. Concerning the chamber.

[Background of the invention and prior art]

Ultra-LSI microfabrication is performed using the II small projection exposure method, electron beam/X
Step-and-repeat methods, such as line exposure methods, have become mainstream. This is a method in which the wafer is exposed while being moved many times, and the XY child table that performs the movement is equipped with a precision positioning device. Currently, the most accurate detector for positioning is a laser interferometer that uses a He-Ne laser as a light source.

The laser wavelength remains constant only in vacuum, and changes in air as the refractive index changes. Therefore, in order to maintain the accuracy of the laser length measuring device, the refractive index of the air must not change, that is, the temperature and humidity must be controlled.

The measurement environment must be controlled to keep the pressure constant. For example, 16Mbit DRM has a minimum line width of 0.
．． 5μm, and the alignment accuracy is accordingly 0.1
μm is required. Regarding temperature control, what is the relationship between temperature and refractive index?

(n+ s/n-1) X 10' -(0,931+
0.006(σ”-3)-0,003(t-zO))
x (t-20) where r n1m'Refractive index of air in industrial standard state G: Reciprocal of vacuum wavelength (μm) Also, if the refractive index changes by Δn before and after the measurement, the error Δd is.

Δd−(Δn/n)d.

However, do is the optical path length after the change.9For example, in order to measure a 10clI length with an accuracy of 0.1μm or less, temperature control is ±0.01℃.
Must be less than or equal to

Conventionally, in a clean area space, it has been difficult to maintain an ultra-constant temperature state within a set temperature range of ±0.01° C. both spatially and temporally. For example, from May 27, 1988
At the 6th Air Purification and Contamination Control Research Conference held on the 29th, Mr. Tadashi Kashima and others presented ``Development of Super Constant Clean Booth'' on pages 81 to 84 of the same report. Temperature distribution at ±0.0
The temperature was set at 5°C.

[Problem that the invention seeks to solve]

As for the constant temperature clean chamber, the applicant and others have been working to improve its performance along with the development results under the trade name "Thermal Chamber." However, it is difficult to control the temperature distribution both spatially and temporally.
It has been found that even if the amount of heat exchange in the air cooler and heater is accurately controlled, it is not possible to achieve the temperature of 0.01°C. In other words, although the technology to maintain constant cooling temperature, heating temperature, air volume, etc., the technology to supply rectified air into the chamber using a laminar flow method, and the insulation technology have been achieved to a certain extent, it is difficult to maintain temperature distribution by ±0. ,Of
``That alone is not enough to get a C.

It turns out that there are other factors as well.

Therefore, it is an object of the present invention to investigate other factors and to obtain an ultra-constant temperature clean chamber that achieves a temperature distribution of ±0.01°C both spatially and temporally.

[Structure of the invention]

The gist of the present invention, which aims to achieve the above object, is to install a conditioned air supply duct equipped with an air cooler, an air heater, and a blower outside a chamber, IIEP temperature-controlled air
In a constant temperature clean chamber in which air is blown into the chamber through an A filter and part or all of the air in the chamber is returned to the conditioned air supply duct,
Means for mixing the air flows in the two passages is provided in the passage between the blower and the II E P^ filter.1 Furthermore, on the upstream side of the air cooler and/or the air heater, roughness within the passage cross section is provided. It is characterized by installing a heat exchange tk adjustment unit consisting of different meshes.

In other words, as a result of numerous tests and studies conducted by the present inventors, it was found that even if the temperature distribution in the chamber is controlled to be ±0.01°C even if a tffll system is used to maintain a constant heat supply with a constant air flow rate. It has been found that there is a limitation, which is due to the airflow through the heat exchanger having an airflow distribution greater than ±0.01°C. The airflow flowing into the supply air plenum behind the II EP A filter itself has a temperature distribution both in cross section and in time. This is because the air passing through the heat exchanger has a different velocity distribution on the heat exchange surface, microscopically the amount of heat exchange differs at each position on the heat exchange surface, and the velocity distribution of the air flow changes on the blower discharge side. It turns out that it depends on what you do. Therefore, the blower and H[! It is important to sufficiently mix the airflow with the P^ filter and to adjust the heat exchange amount in the heat exchanger so that it does not differ on the heat exchange surface.

The means for mixing the airflow in the passage in front of the It E P A filter includes a coarse mixing means that mixes the airflows at distant positions flowing through one passage with each other, and a cotton mixing means that finely disturbs the airflow flowing through nine passages. It is preferable to arrange the cotton mixing means downstream of the mixing means. In this case, as the coarse mixing means,
A laminate of small passages each consisting of a bundle of independent small passages,
It is preferable that at least a part of the small passages be stacked in an inclined manner so that the positions of the air intake and outlet are displaced from each other, and the cotton mixing means is preferably packed with a large void ratio. The heat exchange amount adjustment unit installed on the upstream side of the heat exchanger has a frame stretched across the cross section of the two passages to form numerous openings, and mesh bodies with different roughness can be removably installed in these openings. It is preferable that

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically explained below according to the embodiments shown in the drawings.

Fig. 1 shows an embodiment of an ultra-constant temperature clean chamber according to the present invention, in which a chamber 1 is installed in a planar manner on one side in a chamber 1 in which a chamber space is formed by six parallel faces. H [! Temperature-adjusted clean air is blown out through the PA filter 2, and the air inside the chamber 1 is
By introducing the rethane into the rethane chamber 4 through the suction port 3 provided on the side facing the PA filter 2, a constant temperature clean room having a horizontal laminar airflow pattern is constructed. Although the present invention can be similarly applied to a vertical laminar airflow pattern, the present invention will be described in detail with reference to one example.

A duct 6 leading from the rethane chamber (exhaust plenum) 4 to the air supply plenum 5 behind the HEPA filter 2 is provided outside the chamber 1, and an air cooler 7.
An air heater 8 and a blower 9 are arranged. Into the duct 6, air from the rethane chamber 4 as well as outside air is taken in from the outside air intake port IO as needed.

The duct 6 is constructed using a heat insulating material, and is designed to substantially prevent heat from entering or exiting between the duct 6 and the air outside the system.

The air cooler 7 is a fin-tube heat exchanger, and a closed type water-cooled condensing unit 11 circulates and supplies the empty refrigerant thereto. At that time, low pressure gauge 12 and high pressure gauge 1
3, the refrigerant pressure before and after the air cooler 7 is controlled to be constant, and thereby the refrigerant temperature of the air cooler 7 is maintained constant. 14 indicates a pressure switch for this control. An air heater 8 installed on the downstream side of the air cooler 7 is an electric heater, and by controlling its energization (2), the temperature of the air passing therethrough is controlled. This is chamber 1's H [! The temperature controller 16 receives the detected value of the temperature sensor 15 placed near the blowing surface of the PA filter and controls the thyristor 17 to heat the air that has been cooled by the air cooler 7 in this way. The set temperature is adjusted by reheating in the air heater 8, and constant temperature can be obtained by precisely adjusting the temperature in the air heater 8. This is conventional technology. However, with this alone, even if the air cooler 7 and air heater 8 are precisely controlled, the temperature distribution within the chamber 1 will be within ±0.
It is impossible to keep the temperature within 0.01°C.

One of these is that the flow of air discharged from the blower 9 has a temperature distribution, and the other is that the amount of heat exchanged in the air cooler 7 and air heater 8 differs microscopically depending on the position of the fins. be. The former factor is reduced to a certain degree by the natural air mixing during the flow of air in the duct 6 and through the supply air plenum 5, and the latter factor is reduced to a certain extent by reheating in the air heater 8. . Therefore, the temperature distribution of the space within the chamber 1 can be kept within ±0.1°C. However, it is difficult to consistently achieve a temperature within ±O1 old °C.
The former factor is eliminated by the air flow mixing means 20.21 installed in the air flow passage between the air cooler 7 and the latter factor is eliminated by the heat exchange amount adjustment unit 23 installed upstream of the air cooler 7.

The temperature distribution within the chamber 1 was successfully kept within ±0.01''C.

FIG. 2 is a perspective view showing an example of the air flow mixing means 20. As shown in FIG. ,
By slanting and stacking the air inlets and outlets so that they are displaced from each other, the air currents flowing through the nine passages at separate locations are mixed with each other.

In other words, with respect to the main air flow in the direction of the arrow shown in the figure, by installing a stack of small passages in the passage-cup and slanting a part of the small passages, the airflow that has passed through the inclined small passages can be reduced. The air flows out from an outlet at a position different from the inlet position, so that the flow position within the passage is forcibly changed, and at the same time, mixing of air flows occurs on the outlet side. In the example of FIG. 2, the laminate of the small passage is (a),
It consists of a combination of three units: [Yes]) and (C). (a) is a straight-travel unit in which only small passages parallel to the main airflow direction are arranged in a row (in Fig. 2, the rows of small passages are arranged vertically.The following (c) and (C) But the same)
(b) is an elevated unit in which inclined small passages are arranged vertically in a row so that the entrance position of the small passage is downward and the position of the exit is upward; (b) is a rising unit with the entrance position of the small passageway upward. This is a descending unit in which inclined small passages are vertically arranged in a row so that the dovetail exit is located downward, and these are shown in side view in FIGS. 3 to 5. (a), (b), and (C) are all made up of rows of small passages with approximately the same cross-sectional area, but (b) and (C) have a number of inclined small passages because the small roads are inclined. is about half of (a). In Figure 2, by appropriately arranging the units (B) and (C), a part of the main airflow in the two passages is forcibly guided partially from the bottom to the top and from the top to the bottom. However, instead of this vertical deflection, it is also possible to perform horizontal deflection, or deflection in both vertical and horizontal directions. According to the airflow mixing means 20 configured in this way, the temperature distribution of the airflow inside the duct discharged from the blower 9 can be reduced without pressure loss. In this case, it is possible to reduce the temperature distribution by making the cross section of the small passage smaller and arranging a large number of inclined units in an intersecting manner, but this alone cannot completely eliminate the temperature distribution in the micro cross section. has its limits.

For this reason, it is preferable to arrange the fine mixing means 21 on the downstream side of the air flow mixing means 20. Figure 6 shows this fine mixing means 21.
This is an example in which a container-shaped body is made by stretching a large-grained body over a frame 25 that is large enough to close the cross section of 9 passages, and a filling material 26 with a large void ratio is placed inside the container-shaped body.
It is packed with. This packing 26 may be of any type as long as it disturbs the air flow with a small cross-section; however, according to experiments conducted by the present inventors, a synthetic resin cage-shaped packing proposed in Japanese Utility Model Publication No. 53-17312 (manufactured by Sumitomo Chemical Co., Ltd. :Product name: Summit Ring) was found to be suitable. This filling body is made up of three-dimensional polypropylene resin linear bodies several meters in diameter, and has an overall external shape similar to a diamond (7 to 8 car in external dimensions).
), and was originally developed to improve air-water contact in cooling towers and the like. In the present invention, such a filling 2
It has been found that by arranging the airflow mixing means 2 in the duct, it is possible to mix the airflow in the narrow cross section.
This eliminates the temperature distribution of the airflow on a narrow cross section, which could not be completely removed even with zero.

On the other hand, in order to eliminate the cause of the temperature distribution of airflow caused by microscopic differences in the amount of heat exchange in the air cooler 7 and the air heater 8 depending on the position of the fins, the heat exchanger as shown in FIG. An exchange amount adjustment unit is installed upstream of the air cooler 7. This is a device in which a large number of mesh units 28 having different roughnesses are prepared, and these can be fitted into arbitrary positions of a frame 29. In the illustrated example, nine mesh units 28 having different roughness can be fitted into a frame 29. In this way.

If a heat exchange amount adjustment unit that appropriately adjusts the mesh roughness distribution is placed in the air passage before entering the air cooler 7,
The spatial temperature distribution of the outlet air before the air cooler can be reduced. In this case, it is actually convenient to adjust the roughness distribution on-site according to the measured value of the temperature distribution within the chamber 1.

[Function and effect of the invention]

The effects of the present invention will be explained based on typical test results conducted by the present inventor.

The chamber used for the test has a planar dimension of 1480 x 17
20cm, ceiling height 1500mm, HEPA filter outlet size 1620 x 10104O, heat source is a sealed water-cooled condensing unit AC200V x 3
φX 1 , IKW (50Ilz) and an electric heater (Bare Ni-Cr), and the chamber was covered with a vinyl curtain.

(Comparative Example) In Fig. 8(a) and 0)), the air flow mixing means 20 and 21 according to the present invention are not installed, and the heat exchange amount adjusting unit 2
This figure shows the air temperature distribution and wind speed distribution in the conditioned air supply duct at each position in the conditioned air supply duct when 3 is not used.
m/s). The frame in each diagram indicates the duct cross section, the measurement position is the O mark position in the diagram, ~ is during temperature fluctuation, the value in parentheses is the average temperature at that point, and the value in brackets is the average wind speed at that point. It shows.

From the results in Figure 8, it can be seen that the average value variation ΔTNAX is already 0.12°C, which is the measured value at the inlet of the air cooler after passing through the rethane chamber. . Also, when heat is exchanged with the air cooler and electric heater, ΔT HAM is 2.5 to 3. ,O'
However, due to the mixing effect of the fan, the temperature decreases to about 0.5°C at the fan outlet. Also,
Due to the rapid expansion from the fan outlet into the duct and the mixing effect due to distance, the midstream of the duct is 0.08°C, and the downstream is 0.04°.
C and ΔT MAX are decreasing. Also, the average is changing (T
f, v,) is also 0.10 → 0 from the fan outlet to downstream
．． The temperature decreased from 0.8℃ to 0.07℃. However, the temperature distribution of ±0.01°C intended by the present invention cannot be achieved even behind the HEPA filter.

(Example of the present invention) Air flow mixing means 20 as shown in FIG. 2 and air flow mixing means 21 as shown in FIG. Heat exchange 1 as shown in the diagram! The same test as in the comparative example was conducted except that the iPI adjustment unit 23 was arranged. The mesh units of the heat exchange ffi adjustment unit 23 were 50 mesh and 150 mesh. Further, as the filling material for the air flow mixing means 21, Summit Ring (trade name, diamond type, porosity: 94.5χ), which was explained in the text, was used. Figure 9(a)
and (b) show the results of measurements similar to those of the comparative example.

From the results shown in FIGS. 9(a) and 9(b), it can be seen that ΔT 11AX is 0.07°C in front of the air cooler. The air temperature distribution increases due to heat exchange when passing through the air cooler and electric heater, but due to the effect of the heat exchange amount adjustment unit, the temperature distribution is reduced by ΔTM.

is suppressed to a range of 1.5 to 2.0°C. After that, at the fan exit, the temperature decreases to 0.4°C due to the mixing effect of the fan, and due to the mixing effect due to the rapid expansion and distance from the fan to the duct, the temperature decreases to 0.06°C in the midstream of the duct.
ΔTIIAX downstream of the duct after passing through 0 and 21
It can be seen that the temperature decreased to 0.01°C.

In addition, the average fluctuation temperature (Tf, v,) decreased from 0.04 to 0.03 to 0.01°C from the fan outlet to downstream.
The effects of the present invention are clear when compared with those of comparative examples.

FIG. 1θ and FIG. 11 are graphs showing ΔT MAX and Tf, v, values at each measurement position of the comparative example and the example of the present invention. The position of the horizontal axis of each plot is 0, which corresponds to the duct position (measurement position) shown at the top of the figure.
The mixing cell in the figure is the air current mixing means 20, and the mixing filling is the air current mixing means 21.

In addition, as a result of measuring the temporal and spatial temperature distribution inside the chamber in the case of the comparative example and the inventive example, it was found that ΔTI in the comparative example at a set value of 23°C without disturbance.
The maximum value of IIAX is 0.041°C.

The value of Tf was 0.032°C, but in the example of the present invention, a temperature distribution of ±0.01°C was achieved, and Tf...
The value was confirmed to be 0.007°C.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of the ultra-constant temperature cleaning chamber according to the present invention, FIG. 2 is an overall perspective view showing an example of the rough air flow mixing means according to the present invention, and FIG. 3 is the straight-advance unit of FIG. 2. FIG. 4 is a side sectional view of the ascending section unit of FIG. 2, FIG. 5 is a side sectional view of the lower section unit of FIG. 2, and FIG.
The figure is a perspective view showing an example of a fine air flow mixing means according to the present invention, FIG. 7 is an exploded perspective view showing a heat exchange ti11 conditioning unit according to the present invention, and FIGS. 8(a) and 8(b) are comparative examples. Figure 9 (
Figures a) and 9(b) are diagrams showing the measured values of the temperature distribution and wind speed distribution at each position cross section of the duct in the ultra-constant temperature clean chamber of the present invention, and Figure 10 is a diagram showing the measured values of the temperature distribution and wind speed distribution at each position cross section of the duct of the comparative example. FIG. 11 is a diagram showing the variation in the temperature average value at each cross section of the duct according to the present invention and the state in which the average temperature is fluctuating. 1...chamber, 2...■EP^fil. 3. Suction port, 4. Rethane chamber 5. Air supply chamber, 6. Conditioned air supply duct, 7.
・Air cooler, 8...Air heater. 9...Blower, 10...Outside air intake, 11...Water cooling condensing unit, 15...Temperature sensor,
20... Coarse air flow mixing means, 21... Fine air flow mixing means, 2
3. Heat exchange amount adjustment unit. 26... Filling with large porosity. Figure 6 Figure 7 Hawk Figure 8 (b) Figure 8 (al Figure 9 (al) Procedure amendment group (voluntary) July 28, 1988

Claims (7)

[Claims] (1) A conditioned air supply duct equipped with an air cooler, an air heater, and a blower is installed outside the chamber, and air adjusted to a predetermined temperature is supplied from the conditioned air supply duct to the HEP.
In a constant temperature clean chamber in which air is blown into the chamber through an A filter and part or all of the air in the chamber is returned to the conditioned air supply duct,
An ultra-constant temperature cleaning chamber characterized in that the passage between the blower and the HEPA filter is provided with means for mixing airflow in the passage. (2) The means for mixing the airflow in the passage consists of a coarse mixing means that mixes the airflows flowing through the passage at separate positions, and a fine mixing means that finely disturbs the airflow flowing through the passage, and is downstream of the coarse mixing means. 2. The ultra-constant temperature cleaning chamber according to claim 1, further comprising a fine mixing means disposed in the chamber. (3) The rough mixing means is a stacked body of small passages each having a bundle of independent small passages, and at least a part of the small passages is tilted so that the positions of the air intake and outlet are mutually displaced. 3. The ultra-constant temperature cleaning chamber according to claim 2, wherein the ultra-constant temperature cleaning chamber is formed by laminating layers. (4) The ultra-constant temperature cleaning chamber according to claim 2, wherein the fine mixing means comprises a packing having a large void ratio. (5) A conditioned air supply duct equipped with an air cooler, an air heater, and a blower is installed outside the chamber, and air adjusted to a predetermined temperature is supplied from the conditioned air supply duct to the HEP.
In a constant temperature clean chamber in which air is blown into the chamber through an A filter and part or all of the air in the chamber is returned to the conditioned air supply duct,
An ultra-constant temperature cleaning chamber characterized in that a heat exchange amount adjustment unit made of a mesh whose roughness differs in the cross section of the passage is installed upstream of the air cooler and/or the air heater. (6) The heat exchange amount adjustment unit forms a large number of openings with a frame stretched across the cross section of the passage,
6. The ultra-constant temperature cleaning chamber according to claim 5, wherein a mesh body having different roughness is removably installed in the opening. (7) A conditioned air supply duct equipped with an air cooler, an air heater, and a blower is installed outside the chamber, and air adjusted to a predetermined temperature is supplied from the conditioned air supply duct to the HEP.
In a constant temperature clean chamber in which air is blown into the chamber through an A filter and part or all of the air in the chamber is returned to the conditioned air supply duct,
In the passage between the blower and the HEPA filter, means for mixing the airflow in the passage are provided, upstream of the air cooler and/or the air heater, comprising a mesh whose roughness differs within the passage cross-section. An ultra-constant temperature clean chamber featuring a heat exchange amount adjustment unit.