JPS6037116A - Optical irradiating furnace - Google Patents

Abstract

PURPOSE:To improve responding properties and the accuracy of control by using a heat-sensitive element in which each tip section of a pair of metallic wires such as a pair of wires constituting a thermocouple is connected to a metallic thin-film and formed integrally. CONSTITUTION:When a lamp 2 is conducted and light-emitted, the temperature of a semiconductor wafer 7 is elevated while a metallic plate 12 in a heat-sensitive element 1 is also heated, and the temperature can be measured with excellent reproducibility. An electric signal corresponding to a deviation between the result of the measurement of the temperature and a set temperature is outputted from a control section 9, the power of the lamp is controlled, and the semiconductor wafer 7 is heated according to a predetermined temperature curve. Since the tip sections of metallic wires 11 are connected integrally to a thin wide metallic plate 12, the temperature of the heat-sensitive element 1 rapidly changes, thus accurately measuring the temperature with superior responding properties. Since the metallic plate 12 and the wires 11 are sealed in a light- transmitting vessel 14, these plate and wires do not contaminate a material to be treated at all, and the metallic plate 12 is not oxidized and performance does not deteriorate, and thermal responding properties can be controlled by selecting the kind of a gas to be filled.

Description

[Detailed description of the invention] The present invention relates to a light irradiation furnace.

Among the devices generally used for heat treatment, the light irradiation furnace, which irradiates the workpiece with synchrotron radiation from an incandescent light bulb, has various features, so it can be used for heat treatment and drying of steel materials, plastic molding, thermal property testing equipment, etc. It is widely used. Particularly recently, processes that require heating in semiconductor manufacturing, such as impurity diffusion processes, chemical vapor deposition processes, recovery processes for crystal defects in ion implantation layers, heat treatment processes for electrical activation, and even The use of a light irradiation furnace as a heating furnace for carrying out a heat treatment process for nitriding or oxidizing the surface layer of a silicon wafer, in place of the conventionally used electric furnace, high frequency furnace, etc., is being considered. This is because the light irradiation furnace does not contaminate the object to be treated or give an electrically negative effect, and has low power consumption. This is because uniform heating cannot be achieved and it is not possible to cope with the recent increase in the area of semiconductors.

By the way, in order to perform feedback control on the heating temperature of the object to be processed or to activate a safety function in the event of an abnormal heating operation, it is necessary to measure the temperature inside the light irradiation furnace or the temperature of the object to be processed itself. There is. Conventionally, when the object to be processed is a semiconductor wafer, the temperature has been measured by placing a thermocouple in direct contact with the semiconductor wafer, or by exposing the thermocouple to a radiation space near the wafer. However, with this method, the semiconductor wafer is contaminated by the thermocouple, and the heating conditions for the thermocouple and the semiconductor wafer by light irradiation are different, so it is difficult to obtain sufficient temperature measurement accuracy, especially fast response, and the temperature of both. There were problems such as not being able to obtain a correlation. Furthermore, when heating a semiconductor wafer by setting it in a susceptor of an appropriate size, there is a method of embedding a thermocouple in the susceptor to measure the temperature, but this method requires sensitive temperature and pressure control because the susceptor has a large heat capacity. Furthermore, as mentioned above, there was a drawback that the response was not fast, and the correlation between the temperatures of the semiconductor wafer and the susceptor was lost in high-speed heating. For this reason, in any case, it is quite difficult to accurately measure the temperature and to feedback control the intensity of the irradiated light based on the temperature measurement result.

Therefore, the present invention does not contaminate the workpiece, has a fast response, and has a good correlation between temperature changes between the workpiece and the sensor, and feeds back the intensity of the irradiated light based on the temperature measurement result. The purpose is to provide a light irradiation furnace that can be controlled, and its configuration is such that each end of a pair of metal wires, such as a pair of metal wires constituting a thermocouple, is connected to a metal plate or thin metal film. to form an integrated heat-sensitive element, place it in a light-transmitting container, and place it in a semiconductor wafer.
The intensity of the irradiated light is controlled by the electric signal of the heat-sensitive element that changes in response to the irradiated light or a portion thereof.

The present invention will be explained below with reference to the embodiments shown in the drawings.As shown in FIGS. 1 and 2, the upper and lower surfaces of the furnace are
Twelve 850 W halogen lamps 2 are arranged closely in a planar manner, and a reflective member 5 is provided on the back of the lamps so that the light emitted from the lamps 2 is directed toward the heating space 5. A sub-reflecting member 4 is also provided on the side, and cooling channels are provided inside the reflecting member 5 and the sub-reflecting member 4 to cool them with water. A reaction vessel 6 made of quartz glass is disposed in the heating space 5, and a semiconductor wafer 7, which is an object to be processed, is supported in the center of the reaction vessel 6 by a support 8 made of quartz. A heat-sensitive element 1 is disposed in the lower part of the reaction vessel 6, and its lead wire 15 is connected to a control unit 9. An electric signal from the heat-sensitive element 1 is input to the control unit 9, and based on the electric signal, a lamp 2 is The power supplied to is controlled.

FIG. 6 shows the structure of the heat-sensitive element 1, in which a pair of wires 1
1, 114'i: Diameter Q,! It consists of a platinum-platinum-rhodium thermocouple of 1 day f, and each end is connected to a nickel metal plate 12 of 6III square and 0.1 fi thick, making it integral. The wire 11 is a ceramic insulation tube 16
These are transparent containers 14 made of quartz tubes.
It is hermetically sealed with argon gas at a pressure of 500 wHf, and a lead wire 15 is drawn out from the sealing part 14a.

When the lamp 2 is energized to emit light, the temperature of the semiconductor wafer 7 rises, but at the same time, the Kinjo plate 12 in the heat-sensitive element 1 is also heated, and if the wire 11 constitutes a thermocouple, the heating temperature increases. A corresponding electromotive force is generated and the temperature is measured. and,
Even if the metal plate connecting the ends of a pair of metal wires is a so-called metal thin film on a quartz substrate, the temperature can be measured with similar reproducibility by detecting the change in resistance of the metal thin film as the temperature rises. can. Then, an electric signal corresponding to the deviation between this side temperature result and the set temperature is outputted from the control section 9 to control the lamp power, and the semiconductor wafer 7 is heated according to a predetermined temperature curve.

This means that if you determine the correlation between the heating temperature or light output and the electrical signal of the heat-sensitive element after designing and manufacturing the light irradiation furnace, you can control the light output or wafer temperature using the electrical signal of the heat-sensitive element. It is from.

In this way, in the sensor of the present invention, the end of the metal wire 11 is integrally connected to the thin and wide metal plate 12 by welding or the like to form a heat-sensitive element.
While taking care to reduce the heat capacity, the area receiving light is large, and the influence of the amount of heat conducted through the wire 11 and escaping is small, resulting in a quick temperature change, allowing for good responsiveness and accurate temperature measurement. In addition, since the metal plate 12 and the wire 11 are stuck inside the transparent container 14, there is no possibility that they will contaminate the object to be processed. If the metal plate 12 is filled with gas, the metal plate 12 will not be oxidized and its performance will not deteriorate.Furthermore, the thermal response can be controlled by selecting a vacuum or a non-oxidizing gas 81 to be filled. . This is because, while a vacuum improves the temperature rise characteristics, the cooling characteristics slow down.
This is because filling with gas conversely improves the cooling characteristics, and the characteristics change depending on the type of gas.

Next, to show the results of a thorough investigation of the temperature measurement accuracy, in the above example filled with argon gas, the object to be processed was a silicon wafer with a thickness of 0.5 + a + and a diameter of 4 inches, and the rise was approximately When the temperature is raised at a rate of 00°C/100°C, the rising temperature detected by the thermal element 1 is approximately 160°C24
It was confirmed that the response was sufficiently fast and the correlation was high.
It showed fast response even when the temperature dropped. When the power load was kept constant, the temperature of the object to be treated and the temperature detected by the heat-sensitive element 1 showed a linear correlation, and the results were also good for the 41i male. Therefore, the electric signal from the heat-sensitive element 1 faithfully responds to the temperature of the semiconductor wafer 7, and if the correlation is determined in advance, the lamp power can be controlled based on this, so that the semiconductor wafer 7 is always kept at a predetermined level. Heating can be done according to the temperature curve.

As explained above, the light irradiation furnace of the present invention connects each end of a pair of metal wires, for example, a pair of wires constituting a thermocouple, to a metal plate or thin metal film to form an integrated heat-sensitive element, Place this in a transparent container and use semiconductor ueno.
- The intensity of the irradiated light is controlled by the electric signal of the heat-sensitive element that changes in response to the irradiated light or a part of it, so it does not contaminate the object to be treated and has good responsiveness and control accuracy. Therefore, it is possible to provide a light irradiation furnace that can accurately control the temperature of the wafer or the light output of the lamp by feeding back the intensity of the irradiation light based on the measurement results.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of an embodiment of the present invention, FIG. 2 is a side sectional view of the same, and FIG. 6 is a plan view of a heat-sensitive element. DESCRIPTION OF SYMBOLS 1...Thermal element 2...Lamp 6...Reflection member 5...Heating space 6...Reaction container 7...Hanmenbushi wafer 9...Control unit 11...Wire 12. ...Metal plate 14...Transparent container Applicant USHIO INC. Agent Patent attorney Toranosuke Tahara

Claims (1)

[Claims] A heat-sensitive element is formed by connecting each end of a pair of metal wires to a metal plate or thin metal film, and this is placed in a light-transmitting container to receive light or a portion thereof that irradiates a semiconductor wafer. A light irradiation furnace characterized in that the intensity of irradiation light is controlled by a changing electric signal of the heat-sensitive element.