JPS6355857B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Recently, light irradiation equipment has been attracting attention as a heating furnace for heat treatment of semiconductor wafers. In other words, it uses light as a heat source, and can be roughly divided into two types: light emitted from a discharge tube and light emitted from an incandescent filament. Synchrotron radiation, a light illumination device using an incandescent light bulb, is currently recommended.

By the way, a halogen light bulb is a type of incandescent light bulb that has a small amount of halogen element sealed together with an inert gas inside the bulb.The halogen light bulb has a small bulb, long life, and high efficiency, so it is suitable for semiconductor wafers. It is also often used as a light source for processing light irradiation equipment. The reason why halogen bulbs have such excellent properties is that the equilibrium state of the reaction between halogen gas and tungsten inside the bulb is different between the high temperature area near the tungsten filament and the low temperature area near the bulb wall. This is because a cyclic reaction called a halogen cycle takes place.
That is, in the high temperature section, halogen and tungsten dissociate, and the partial pressure of tungsten increases, suppressing the evaporation of the filament.In the low temperature section, tungsten halide with a sufficiently high boiling point is formed, preventing tungsten vapor deposition on the valve wall. This prevents the absorption and attenuation of optical output. However, in order for this cyclic reaction to take place, the valve wall temperature must be within a so-called halogen cycle range.
The possible range differs depending on the type of halogen element, but for example, for those containing chlorine and bromine, the possible range is about 100 to 650°C, and if the valve wall is outside this range, tungsten will evaporate on the valve wall. This will cause the bulb to turn black and significantly shorten the life of the bulb.
When a halogen bulb is used as a heat source for various purposes including heat treatment of semiconductor wafers, it is very often used at temperatures higher than the above-mentioned temperature range. For this reason, the valve wall temperature is adjusted by cooling with cold air. However, in order to be able to handle large objects, long tubular halogen bulbs are installed closely together and used as a surface light source, but cooling with cold air often does not allow sufficient adjustment. . This is because when the temperature of the bulb wall is high, for example 800 to 1000 degrees Celsius, the flow rate of cold air is increased and the heat transfer coefficient is increased to lower the temperature to the appropriate temperature, but the downstream side of the surface light source is lowered to the appropriate temperature. Therefore, if the flow rate was increased too much, the temperature of the bulb on the upstream side would become overcooled, and conversely, if the upstream side was brought to the proper temperature, the downstream side would overheat, resulting in a problem that shortened the bulb's lifespan.

Therefore, the present invention provides a light irradiation device that can extend the life of a halogen bulb by maintaining the temperature of both the upstream and downstream bulb walls within an appropriate range that allows the halogen cycle when cooling with cooling air. The purpose is to provide And this purpose is
A transparent container that surrounds the object to be processed, a long tubular halogen incandescent light bulb that is placed outside the transparent container and irradiates the object to be processed, a mirror that is placed close to the halogen incandescent light bulb, and a mirror between the outer surface of the transparent container and the mirror. and a means for circulating cooling air for cooling the bulb wall of the halogen incandescent bulb along the longitudinal direction of the halogen incandescent bulb, and the circulating air makes the inlet temperature of the cooling air higher than the outside air temperature. This is achieved by a light irradiation device.

Embodiments of the present invention will be specifically described below with reference to the drawings.

A container 1 into which objects to be processed are loaded is a transparent box-shaped container made of quartz glass, and cooperates with a lid 11 to form a closed space. A pair of air supply and exhaust ports 1a are provided on the side surface of the container 1, so that the inside of the container 1 can be depressurized and the atmosphere can be adjusted. A reflecting member 2 is arranged in a box shape close to the outer wall of the container 1 so as to substantially seal the container 1. This reflecting member 2 has a mirror inner surface, has a water conduit 21 formed therein, and is connected to a cooling water supply mechanism. Of these reflective members 2, the side reflective member 2a can be opened and closed, and the container 1 can be taken out. A plurality of semicircular grooves are provided on the inner surface of the upper reflecting member 2b to form a cavity 4 for receiving a long tubular halogen light bulb 3. Air passage members 5, 5 are arranged in series before and after the holding portion of the light bulb 3, and one air passage member 5 is connected to a cooling fan 6 so that the air inside is sucked. Furthermore, a circulation duct 7 is connected to this cooling fan 6, and one end of this circulation duct 7 is connected to the other air passage member 5, so that the cooling air sucked by the cooling fan 6 flows into the upstream side of the light bulb 3 again. I'm starting to do that. A heat exchanger 8 is interposed in the circulation duct 7, and when the temperature of the discharged cooling air is high, the heat exchanger 8 cools it to an appropriate temperature. Note that instead of circulating all of the cooling air as in this embodiment, only a portion of the high-temperature cooling air drawn from the downstream side of the light bulb 3 is circulated, so that it is mixed with low-temperature outside air and has a temperature higher than the outside air temperature. It may be made to flow in from the upstream side at an appropriate temperature.

The reason why the inlet temperature of the cooling air is made higher than the outside air temperature by circulating the cooling air is that even if the air volume is increased, the temperature of the valve wall on the upstream side does not decrease much, and only the temperature on the downstream side is affected. When the air volume is lowered, the temperature rise on the downstream side due to the reduction is smaller than the temperature rise on the upstream side, and in any case, the temperature difference between the upstream and downstream sides becomes smaller, This is because the imbalance between superheating and supercooling can be eliminated, and the temperature can be easily adjusted to within the halogen cycle range.

Next, to give a specific numerical example, a tubular halogen bulb 3 with an outer diameter of 8 mm and a rating of 2 KW is placed with a center distance of 2.
When the lights were arranged in parallel at 0mm and the cooling air was circulated at an air volume of ^0.15m3 per minute while removing heat by the heat exchanger 8, the inlet temperature was 45℃, and the temperature after cooling the bulbs 3 was The outlet temperature was 110°C. and
After being lit for 5,500 hours, the bulb wall on the downstream side turned black, indicating that under these conditions, the lifespan of Bulb 3 was 5,500 hours. In contrast, when outside air at 15°C was blown without circulating cooling air as before, the outlet temperature was 80°C, and the upstream bulb wall turned black after being lit for 1,500 hours. This example shows that the present invention significantly extends the life of the light bulb.

As explained above, the present invention circulates the cooling air and makes the inlet temperature higher than the outside air temperature, which makes it possible to reduce the temperature difference between the upstream and downstream valve walls. It is possible to provide a light irradiation device in which both the downstream side and the downstream side can be easily adjusted within the halogen cycleable range, and the life of the halogen bulb is therefore extremely long.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view taken along the line--FIG. 1, and FIG. 3 is a vertical cross-sectional view taken along the line--FIG. 1. 1... Container, 2... Reflective member (mirror), 3...
...Halogen light bulb, 5...Air path member, 6...Cooling fan, 7...Circulation duct, 8...Heat exchanger.

Claims (1)

[Claims] 1. A transparent container surrounding the object to be treated, a long tubular halogen incandescent bulb located outside the transparent container and irradiating the object to be treated, a mirror disposed close to the halogen incandescent bulb, and an outer surface of the transparent container. means for circulating cooling air for cooling the bulb wall of the halogen incandescent bulb along the length of the halogen incandescent bulb between the mirrors, and making the inlet temperature of the cooling air higher than the outside air temperature by circulating air. Characteristic light irradiation device.