JPH0520657B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a method for heating the workpiece and/or its vicinity in a clean room such as a clean tunnel, clean tube, clean bench, or clean booth. The present invention relates to a method and an apparatus for preventing contamination of a workpiece by particulates generated by an operator of the workpiece by forming an upward air current from the workpiece and/or its vicinity.

[Conventional technology and its problems]

Conventional indoor air purification methods and devices can be roughly divided into (1) mechanical filtration methods (for example, HEPA filters), and (2) electrostatic filter methods that electrostatically collect particulates. Each of these methods had the following drawbacks.

The main components of the mechanical filtration device (1) are a fan and a filter, but it is necessary to use a fine-mesh filter to increase the cleanliness of the air. This method generally has high dust collection efficiency, but also high pressure loss. Therefore, if a coarse filter is used in an attempt to reduce pressure loss, the dust collection efficiency will decrease. In addition, the pressure loss due to clogging increases significantly, and the life of the filter is shortened. For example, when replacing filters in a clean room in a semiconductor manufacturing factory, the factory is stopped during that time and it takes a considerable amount of time to recover.

Additionally, in order to improve the cleanliness of the air, the number of ventilations can be increased, but in this case the power cost will be high.

The main components of the electrostatic filter method (2), which collects fine particles electrostatically, are a fan, a pre-charging section, and an electrostatic filter.The pre-charging section requires a high-voltage power supply, so the device is Due to its large size, there are safety issues, as well as the accumulation and scattering of particles on the electrode plates, and the high cost of operating with a considerable safety margin in order to maintain a high degree of cleanliness, making maintenance management complicated. There is a problem of size.

In the future, as industrial technology becomes more sophisticated, clean rooms with ultra-high cleanliness will be required.
It is thought that a high level of cleanliness up to the 10th class level can be achieved using the method and applied technology described above, but in this case there is a problem with economic efficiency.
Furthermore, it is considered difficult to achieve an ultra-high clean room such as Class 1 with current technology.

For example, in the semiconductor industry, products with ultra-high integration (e.g. 16 Mbits) will be required in the near future.
This is considered difficult to achieve with current clean room technology. The higher the cleanliness level, the greater the influence of dust from workers.For example, in the current highest-level downflow clean room, in order to eliminate the influence of dust from workers on workpieces, it is necessary to at least remove dust from workers. It is necessary to isolate 70cm to 1m from the wafer.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an air cleaning method and apparatus that can easily maintain a workpiece or its vicinity at an air cleanliness class of 100 or lower.

[Structure of the invention]

The present invention provides a workpiece on a workbench in a clean room and/or
A method for preventing contamination of a workpiece, the method comprising forming an upward air current from the workpiece and/or its vicinity by heating the workpiece or its vicinity.

and Workpieces on the workbench in the clean room and/or
An apparatus for preventing contamination of a workpiece, which is provided with a heating section that heats the workpiece and/or its vicinity in order to generate an upward air current in the vicinity thereof.

It is.

Hereinafter, the present invention will be explained in detail based on the drawings.

As an example, FIG. 1 shows a schematic diagram of a clean tunnel combination method (a method of keeping only the work area at a high level of cleanliness) in a clean room for manufacturing semiconductors. In FIG. 1, the interior of a clean room 1 is maintained at a medium level of cleanliness using a conventional mechanical filter, and only the work area is maintained at a high degree of cleanliness using the method of the present invention. The air in clean room 1 is
The air from which coarse particles in the outside air 2 have been removed by the prefilter 3 and the air in the clean room 1 are sent to the air intake port 4.
After the air taken out from the air is conditioned (temperature and humidity controlled) by an air conditioner 6 via a fan 5,
It is supplied after removing particulates using a HEPA filter 7, and is maintained at a cleanliness level (class) of approximately 100,000.

On the other hand, the work area has a clean tunnel 1 consisting of a fan section 8, a ULPA filter section 9, an infrared irradiation and surface temperature measurement section 10 for work objects, and a work table 12.
1, and the surface of the workpiece and its vicinity are maintained at about cleanliness class 1. clean tunnel 11
So, the cleanliness (class) in clean room 1
100000 air is sucked by fan 8 and ULPA
A filter further removes fine particles, increasing the cleanliness level to class 10.

When processing a workpiece on a workbench, the workpiece 13 and/or its vicinity are monitored by the temperature sensor 10 and heated to an appropriate temperature. An updraft is mainly generated in the workpiece and/or its vicinity due to the thermophoretic action, and direct contamination of the workpiece by fine particles generated by the worker is prevented by an action similar to that of an air curtain. Therefore, the area near the surface of the workpiece is maintained at the cleanliness level of a clean room.

The surface temperature of the workpiece and/or its vicinity is 0.1 to 20°C, preferably 1 to 5°C, compared to the surrounding temperature.
kept high (e.g. 2.0±0.1℃), 0.03cm~0.3
An updraft of approximately cm/sec is generated.

Note that when working on a workbench, the air is pressurized to the extent that the dirty air in the cleanroom 1 does not flow back through the exhaust port from the clean tunnel 11 where the workbench is located into the cleanroom 1. There is almost no air flow descending onto the workbench within the tunnel. Temperature control is performed by detecting the surface temperature of the workpiece with a temperature sensor and transmitting it to the infrared irradiation output control circuit.If the temperature is lower than the set value, the irradiation output will be increased, and if the opposite is the case, the output will be increased. By lowering the temperature, the temperature is maintained within a certain range (usually ±0.1℃).

Any temperature sensor may be used as long as it can measure the surface of the workpiece and/or its vicinity, but from the viewpoint of workability of the workpiece, non-contact thermometers,
For example, infrared thermometers, optical fiber thermometers, and echo quartz thermometers are practically preferred.

The workpiece may be heated by any method as long as it can heat the workpiece, but heating with infrared rays and laser beams are preferred from the viewpoint of temperature accuracy, ease of control, operability, workability, etc. Used singly or in combination. Moreover, heating can be performed efficiently by using a reflecting plate or a condensing lens.

The temperature of the surface of the workpiece and its vicinity varies depending on the type of equipment (for example, clean tunnel or clean tube), type of work, work content, work form, work scale, particle size and density of fine particles, etc. or,
The cleanliness of the surface of the workpiece and its vicinity also differs depending on the type of work (eg, work content in semiconductor manufacturing).

〔Effect of the invention〕

1. By heating the workpiece and/or its vicinity to a higher temperature than the ambient temperature, the surface of the workpiece and its vicinity can be kept at an ultra-high level of cleanliness (super clean).

2 By combining the conventional method using mechanical filters and this method, an ultra-high cleanliness environment could be achieved relatively easily and economically.

3. It is more effective when the particle size is extremely fine (e.g. <0.1 μm), and it is extremely effective in fields such as the semiconductor industry, where control of ultra-fine particles will be necessary as technology develops in the future (e.g., semiconductor industry). In,
In the production environment of 4M bits, it is necessary to control ultrafine particles of 0.05 μm).

4. Conventional technology For example, in the mechanical filter method, it was theoretically difficult to remove particles when they became extremely fine (eg, <0.1 μm), but according to the present invention, on the contrary, the more fine the particles, the more effective they are.

5 At ultra-high cleanliness levels (e.g. class 10), the influence of dust from workers and work equipment is significant (e.g. around 50% of the dust that adheres to wafers in semiconductor manufacturing is generated by workers. However, in the present invention, the surface of the workpiece and the vicinity thereof are cleaned from the inside (fine particles move away from the surface of the workpiece upwards), so even if sudden dust generation occurs in the surrounding area, the surface of the workpiece is cleaned from the inside. Its impact is small.

6 Filters used in conventional methods often have pinholes, so maintenance of the process is troublesome when obtaining high cleanliness using conventional methods, but by combining with the method of the present invention, maintenance is easy. As a result, ultra-high cleanliness can be stably obtained for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining the method and apparatus of the present invention. 1...Clean room, 2...Outside air introduction pipe, 3
...Prefilter, 4...Air intake port, 5...
Fan, 6... Air conditioner, 7... HEPA filter, 8... Fan, 9... ULPA filter, 10... Infrared irradiation device and temperature sensor,
11...Clean tunnel, 12...Workbench, 1
3... Work object.

Claims (1)

[Claims] 1. A workpiece characterized by heating the workpiece on a workbench in a clean room and/or the vicinity thereof to form an upward air current from the workpiece and/or the vicinity thereof. How to prevent contamination. 2. The method according to claim 1, wherein the heating source is an infrared ray and/or a laser beam. 3 Claim 2 that focuses infrared rays and/or laser beams on the workpiece and/or its vicinity
The method described in section. 4. The method according to claim 3, wherein a reflecting plate and/or a condensing lens are used when condensing the infrared rays and/or laser beam. 5. The method according to any one of claims 1 to 4, wherein the heating temperature increase is 0.1°C to 20°C. 6. The method according to any one of claims 1 to 5, in which highly clean air is obtained by combining an air cleaning method using a mechanical filter and a method of heating the workpiece and/or its vicinity. 7. Preventing contamination of the workpiece by providing a heating section that heats the workpiece and/or the vicinity thereof in order to generate an upward air current on the workpiece and/or the vicinity thereof on the workbench in the clean room. device to do. 8.In order to generate an upward air current on the workpiece on the workbench in the clean room and/or in the vicinity thereof, a heating section is provided to heat the workpiece and/or its vicinity, and the workpiece is discharged from the cleanroom and circulated. 8. An apparatus for preventing contamination of a workpiece according to claim 7, further comprising a mechanical filter for removing particulates from the air.