JPH1123374A - Thermometer for heat treatment furnace - Google Patents

Abstract

[PROBLEMS] To provide a thermometer for a heat treatment furnace which can be used for a long time even at a high temperature. SOLUTION: In a heat treatment furnace thermometer 16A in which an insulating tube 18 provided with a thermocouple 19 made of platinum and platinum rhodium at a tip portion in a protective tube 20 made of silicon carbide, a tip of the insulating tube 18 is provided. A cap body 25 made of platinum or platinum rhodium covering the thermocouple 19;
A protective cap 21 having a coating layer 26 made of iridium or an iridium alloy that covers the outer surface of the cap body 25 is attached.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a thermometer for a heat treatment furnace.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, various heat treatment furnaces are used to perform heat treatment such as oxidation, diffusion and annealing on a semiconductor wafer to be processed. In order to measure the temperature inside the heat treatment furnace, FIG.
A thermometer 16 as shown in FIG.

The thermometer 16 comprises an insulating tube 18, a thermocouple 19 disposed at the tip of the insulating tube 18, and a thermocouple 1.
And a protection tube 20 for accommodating the insulating tube 18 including the insulating tube 9. As the thermocouple 19, a thermocouple capable of measuring a temperature in a high temperature region, for example, 1050 to 1250 ° C.,
For example, a thermocouple made of platinum and platinum rhodium is preferable.
The material of the protective tube 20 is preferably silicon carbide which is used in a semiconductor manufacturing apparatus or the like as a material which can be used with a stable performance in a high temperature region higher than a normal temperature of a quartz material.

[0004]

However, in the above-mentioned thermometer for a heat treatment furnace, in a high temperature range of 1050 to 1250 ° C., platinum or platinum rhodium of the thermocouple 19 reacts with silicon which is a component of the protection tube 20 to lower the temperature. Alloy to melting point. For this reason, the thermocouple 19 tends to cause a decrease in electromotive force or disconnection in a short period of time, and may not be able to perform temperature measurement.

Accordingly, the present invention has been made to solve the above problems. An object of the present invention is to provide a thermometer for a heat treatment furnace that can be used for a long time even at a high temperature.

[0006]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the present invention is a method for protecting an insulating tube made of silicon carbide having a thermocouple made of platinum and platinum rhodium at the tip. In a thermometer for a heat treatment furnace housed in a tube, a tip body of the insulating tube is made of platinum or platinum rhodium covering the thermocouple, and iridium or an iridium alloy covering the outer surface of the cap body. A protective cap having a coating layer is attached. According to the thermometer, the protective cap attached to the distal end of the insulating tube has an outer surface of a cap body made of platinum or platinum rhodium, which is the same material as the thermocouple,
Since a coating layer made of iridium or an iridium alloy that is chemically stable with respect to silicon as a component of the protective tube is provided, even if the operating temperature of the heat treatment furnace is as high as 1250 ° C., silicon and platinum or platinum rhodium are used. Does not react, it can prevent the low melting point alloying of the thermocouple,
Long-term use at high temperatures becomes possible.

According to a second aspect of the present invention, there is provided a thermometer for a heat treatment furnace in which an insulating tube having a thermocouple made of platinum and platinum-rhodium at its tip is housed in a protective tube made of silicon carbide. A double protective cap having an inner cap made of platinum or platinum-rhodium covering the thermocouple and an outer cap made of iridium or an iridium alloy covering the outside of the inner cap is attached to the tip. . According to the thermometer, an inner cap made of platinum or platinum rhodium, which is the same material as the thermocouple, has a protective cap attached to the distal end of the insulating tube,
Since the protective cap has a dual structure with an outer cap made of iridium or an iridium alloy that is chemically stable to silicon as a component of the protective tube, the operating temperature of the heat treatment furnace is 1250.
Even at temperatures as high as ° C., silicon and platinum or platinum rhodium do not react, preventing the low melting point alloying of thermocouples and allowing long-term use at high temperatures.

According to a third aspect of the present invention, there is provided a thermometer for a heat treatment furnace in which an insulating tube having a thermocouple made of platinum and platinum rhodium disposed at a tip portion is housed in a protective tube made of silicon carbide. A protective cap having a cap body made of platinum or platinum rhodium covering the thermocouple and a coating layer made of alumina covering the outer surface of the cap body is attached to the tip. According to the thermometer, the protective cap attached to the tip of the insulating tube is formed on the outer surface of the cap body made of platinum or platinum rhodium, which is the same material as the thermocouple, chemically with respect to silicon, which is a component of the protective tube. Since a coating layer made of stable alumina is provided, even if the operating temperature of the heat treatment furnace is as high as 1250 ° C., silicon and platinum or platinum rhodium do not react, preventing the low-melting alloy of the thermocouple. And can be used for a long time at a high temperature.

[0009]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a partial cross-sectional side view showing a thermometer for a heat treatment furnace according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view showing an example of a heat treatment furnace using the thermometer for a heat treatment furnace of FIG. FIG. 3 is an enlarged sectional view of a main part of the thermometer for a heat treatment furnace in FIG.

First, an example of a heat treatment furnace using the heat treatment furnace thermometer according to the embodiment of the present invention will be described. In FIG. 2, reference numeral 1 denotes a semiconductor wafer W as an object to be processed.
Is a vertical heat treatment furnace for treating
Has a vertically long cylindrical reaction tube 2 whose lower end is open.
The reaction tube 2 is formed of, for example, quartz, and has an introduction tube portion 3 for introducing a processing gas at a lower side surface thereof,
A not-shown discharge pipe for discharging the waste gas after the treatment is provided. The reaction tube 2 is attached via a fixture 5 to a base plate 4 having an opening at the center. The reaction tube 2 may have a double tube structure of an inner tube and an outer tube.

A heater 6 for heating the inside of the reaction tube 2 is provided around the reaction tube 2. The heater 6 mainly includes a heat insulating material 7 surrounding the periphery of the reaction tube 2 and a resistance heating wire 8 spirally arranged on the inner periphery of the heat insulating material 7. The heater 6 is provided with a temperature sensor 9. It is preferable that the heater 6 is divided into a plurality of zones in the height direction, and that the temperature is controlled independently for each zone. The heater 6 is provided on the base plate 4. It is preferable that a soaking tube 10 is provided between the reaction tube 2 and the heater 6.

A lid 11 for opening and closing the open end of the reaction tube 2 is disposed below the reaction tube 2. On the lid 11, a large number of semiconductor wafers W are horizontally arranged at predetermined intervals in multiple stages. A supporting wafer boat 12 is placed via a heat retaining tube 13. The lid 11 is mounted on a lift 15 of a lift 14. With this elevating mechanism 14,
The loading and unloading of the wafer boat 12 into and from the reaction tube 2 and the opening and closing of the lid 11 are performed.

In order to detect the temperature in the furnace of the heat treatment furnace 1 configured as described above, a thermometer for the heat treatment furnace (also a temperature sensor for the heat treatment furnace) is used in the reaction tube 2 or between the reaction tube 2 and the soaking tube 10. Hereinafter, simply referred to as a thermometer.) 16A is inserted and arranged. FIG. 2 shows a thermometer 16 </ b> A inserted between the reaction tube 2 and the soaking tube 10 and a thermometer 16 </ b> A inserted into the reaction tube 2 from below through the lid 11. The latter type of thermometer 16 </ b> A is mounted on a lift 15 via a bracket 17. The thermometer 16
A can be used not only for measuring the temperature inside the furnace, but also for inspecting and calibrating the temperature sensor 9 provided in the heater 6.

The thermometer 16A is, as shown in FIG.
It has a long insulating tube 18, a thermocouple 19 disposed at the tip of the insulating tube 18, and a protective tube 20 for housing the insulating tube 18 including the thermocouple 19. A protection cap 21 for covering and protecting the thermocouple 19 is attached to the portion as described later. The insulating tube 18 is preferably formed of a material having excellent insulation and heat resistance, for example, alumina (Al ₂ O ₃ ) ceramic. The insulating tube 18 has a wire 1 of a thermocouple 19 attached thereto.
Insertion holes 22 for individually inserting 9a and 19b are provided in the axial direction. It is preferable that a concave portion 23 or a cutout for accommodating the thermocouple 19 is formed at the distal end of the insulating tube 18 so that the thermocouple 19 does not directly touch the protective cap 21.

As the thermocouple 19, a thermocouple made of platinum and platinum rhodium capable of stably and accurately measuring a high-temperature region, specifically, a pure platinum wire and platinum (Pt)
An R thermocouple composed of a combination of alloy wires of 87% and rhodium (Rh) 13% is used. The protective tube 20 is made of silicon carbide (Si) as a material that withstands use in a temperature range higher than quartz and does not become a contamination source for a semiconductor wafer.
C). One end of the protective tube 20 is open, and the insulating tube 18 is connected to the protective tube 20 from the open end.
Is inserted in a non-contact state. In the case of the type in which the thermometer 16A is inserted and arranged between the reaction tube 2 and the soaking tube 10, the opening end of the protection tube 20 is made of a sealing material 24 made of, for example, an alumina adhesive (trade name: Aron Ceramic, Sumiceram, etc.). It is preferable to seal with.

As shown in FIG. 3, the protective cap 21 attached to the distal end of the insulating tube 18 includes a cap main body 25 made of the same material as the thermocouple 19, such as platinum or platinum rhodium. And an outer layer 25 made of iridium or an iridium alloy. The above protective cap 2
The cap body 25, which is the first base material, is formed in a cap shape fitted and covered with the tip of the insulating tube 18.

As a method of forming the coating layer 26 of iridium or an iridium alloy on the outer surface of the cap body 25, a method of applying a film by, for example, sputtering or vapor deposition, or a method of applying an iridium compound is preferable. The protective cap 21 configured as described above is attached to the insulating tube 18.
Of the protective cap 21 on the insulating tube 18 to prevent the protective cap 21 from falling off, protect the exposed end face of the cap body 25 and prevent silicon from entering. It is preferable to seal and bond with.

According to the heat treatment furnace thermometer 16A according to the first embodiment thus configured, the protection cap 21 attached to the tip of the insulating tube 18 is made of platinum or the same material as the thermocouple 19. Since a coating layer 26 made of iridium or an iridium alloy having a property chemically stable with respect to silicon as a component of the protective tube 20 is provided on an outer surface of a cap body 25 made of platinum rhodium, the heat treatment furnace 1 is used. Even when the temperature is as high as 1250 ° C., silicon and platinum or platinum rhodium do not react with each other, so that the low-melting alloy of the thermocouple 19 can be prevented, and long-term use at high temperature is possible. The covering layer 26 can prevent not only the thermocouple 19 but also the cap body 25 of the protective cap 21 itself from being alloyed with a low melting point, thereby improving durability.

FIGS. 4 and 5 are enlarged cross-sectional views showing the main parts of a thermometer for a heat treatment furnace according to the second and third embodiments of the present invention. Have the same reference numerals. First, in the thermometer 16B for the heat treatment furnace shown in FIG.
And a coating layer 26 made of alumina for coating the outer surface of the cap body 25. As a method of forming the coating layer 26 made of alumina (Al ₂ O ₃ ) on the outer surface of the cap main body 25, a method of applying an alumina paste, which is a paste-like alumina, is preferable.

In the thermometer 16B for the heat treatment furnace according to the second embodiment, the protective cap 21 attached to the distal end of the insulating tube 18 is also made of the same material as the thermocouple 19, such as platinum or platinum rhodium. Since the outer surface of the main body 25 is provided with the coating layer 26 made of alumina chemically stable to silicon as a component of the protective tube 20, the operating temperature of the heat treatment furnace 1 becomes as high as 1250 ° C. However, silicon and platinum or platinum rhodium do not react with each other, so that the low-melting alloy of the thermocouple 19 can be prevented, and long-term use at a high temperature becomes possible. In order to prevent the outer diameter of the protective cap 21 from increasing, a small-diameter portion 28 smaller than the outer diameter of the insulating tube 18 is formed at the distal end of the insulating tube 18, and a size corresponding to the small-diameter portion 28 is formed. The protective cap 21 may be formed and attached.

In the thermometer 16C for the heat treatment furnace shown in FIG.
1 is an inner cap 21a made of platinum or platinum rhodium of the same material as the thermocouple 19;
a is formed as a double protective cap having an outer cap 21b made of iridium or an iridium alloy that covers the outside of a. The inner cap 21a and the outer cap 21b are preferably formed as thin caps each having a thickness of 0.1 to 0.3 mm, and the inner cap 21a is preferably inserted into the outer cap 21b and joined by welding.

According to the thermometer 16C for the heat treatment furnace according to the third embodiment, the protective cap 21 attached to the tip of the insulating tube 18 is made of the same material as the thermocouple 19, such as platinum or platinum rhodium. Since it has a double structure of the cap 21a and the outer cap 21b made of iridium or an iridium alloy having a property chemically stable to silicon as a component of the protective tube 20, the operating temperature of the heat treatment furnace 1 is 1250 ° C. And platinum or platinum rhodium do not react even when the temperature becomes high, and the thermocouple 19
Can be prevented from being alloyed at a low melting point, and can be used for a long time at a high temperature.

A thermometer 16T for a heat treatment furnace as shown in FIGS. 6 and 7 was prepared for a thermocouple deterioration comparison test, and a thermoelectromotive force deterioration test was performed at 1250 ° C. in the atmosphere using the thermometer 16T for the heat treatment furnace. And compared them. The thermometer 16T for the heat treatment furnace is provided with the first
The third embodiment is configured by inserting three insulating tubes 18 having the protective caps 21 of the thermometers 16A to 16C according to the third embodiment and the insulating tube 18 of the conventional thermometer 16 without the protective cap. . As a result of the thermocouple deterioration test, as shown in FIG.
3.5 hours after reaching, the electromotive force degradation was observed,
After an hour, it was disconnected. In contrast, the above first to first
Heat treatment furnace thermometers 16A to 16A according to third embodiment
In the case of C, the value of the electromotive force was almost constant even after use at 1250 ° C. for 1000 hours, and there was no disconnection. In addition, about the state of the thermometer for the heat treatment furnace after the test,
Some discoloration was observed on the surface of the coating layer 26 of the protective cap 21 and the surface of the outer cap 21b of the double cap, but there was almost no effect on the thermocouple.

The embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to the above embodiments, and various design changes and the like can be made without departing from the gist of the present invention. Is possible. For example, it is desirable that a concave portion 23 or a notch portion for accommodating the thermocouple 19 is provided at the distal end portion of the insulating tube 18, but it is not necessary to provide the concave portion 23.

In the above embodiment, the reaction tube 2 and the soaking tube 1
A thermometer in which the opening end of the protective tube 20 is sealed with a sealing material 24 is shown as a type inserted between the reaction tubes 2 and 0.
In the case of a type inserted into the first heat-shrinkable tube 3 as shown in FIG.
0, the insulating tube 18 is covered so as to seal the open end of the protection tube 20, and the bracket 17, the protection tube 20, and the first heat shrink tube 30 are similarly covered with the second heat shrink tube 31, It is preferable to seal and fix the opening end of the protection tube 20 with the insulating tube 18 and the bracket 17.

[0026]

In summary, according to the present invention, the following effects can be obtained.

(1) According to the thermometer for a heat treatment furnace of the first aspect, the protective cap attached to the tip of the insulating tube is protected on the outer surface of the cap body made of platinum or platinum rhodium, which is the same material as the thermocouple. Since a coating layer made of iridium or an iridium alloy that is chemically stable to silicon as a component of the tube is provided, the operating temperature of the heat treatment furnace is 125.
Even at a high temperature of 0 ° C., silicon and platinum or platinum rhodium do not react, preventing the thermocouple from being alloyed at a low melting point, and allowing long-term use at a high temperature.

(2) According to the thermometer for a heat treatment furnace of the present invention, the protective cap attached to the tip of the insulating tube is made of platinum or platinum rhodium, which is the same material as the thermocouple, Since it has a double structure with an outer cap made of iridium or an iridium alloy that is chemically stable to silicon as a component, even when the operating temperature of the heat treatment furnace is as high as 1250 ° C., silicon and platinum or platinum rhodium are used. Does not react, it is possible to prevent the thermocouple from being alloyed at a low melting point, and it is possible to use the thermocouple for a long time at a high temperature.

(3) According to the thermometer for a heat treatment furnace of the third aspect, the protective cap attached to the tip of the insulating tube is protected on the outer surface of the cap body made of platinum or platinum rhodium, which is the same material as the thermocouple. Because a coating layer made of alumina that is chemically stable to silicon, which is a component of the tube, is provided, silicon and platinum or platinum rhodium react even when the operating temperature of the heat treatment furnace is as high as 1250 ° C. Therefore, alloying of the thermocouple with a low melting point can be prevented, and long-term use at a high temperature becomes possible.

[Brief description of the drawings]

FIG. 1 is a partially sectional side view showing a thermometer for a heat treatment furnace according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing an example of a heat treatment furnace in which the heat treatment furnace thermometer of FIG. 1 is used.

FIG. 3 is an enlarged cross-sectional view of a main part of the thermometer for a heat treatment furnace in FIG.

FIG. 4 is an enlarged sectional view of a main part showing a thermometer for a heat treatment furnace according to a second embodiment of the present invention.

FIG. 5 is an enlarged sectional view of a main part showing a thermometer for a heat treatment furnace according to a third embodiment of the present invention.

FIG. 6 is a partial cross-sectional side view showing a thermometer for a heat treatment furnace manufactured for a thermocouple deterioration comparison test.

FIG. 7 is a plan view of the thermometer for the heat treatment furnace of FIG. 6 as viewed from the tip end side.

FIG. 8 is a graph showing test results of a thermoelectromotive force deterioration test.

FIG. 9 is a partial cross-sectional side view showing another example of the sealing structure of the base end portion in the heat treatment thermometer.

FIG. 10 is a partial cross-sectional side view showing an example of a conventional thermometer for a heat treatment furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat treatment furnace 16A-16C Thermometer for heat treatment furnace 18 Insulation tube 19 Thermocouple 20 Protective tube 21 Protective cap 25 Cap body 26 Coating layer 21a Inner cap 21b Outer cap

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Keiichiro Matsushita 1915, Morizoe-jima, Shimodate-shi, Ibaraki Pref.

Claims (3)

[Claims] 1. A thermometer for a heat treatment furnace comprising an insulating tube having a thermocouple made of platinum and platinum-rhodium disposed at a tip end thereof in a protective tube made of silicon carbide. A thermometer for a heat treatment furnace, comprising a protective cap having a cap body made of platinum or platinum rhodium covering a pair and a coating layer made of iridium or an iridium alloy covering an outer surface of the cap body. 2. A thermometer for a heat treatment furnace in which an insulating tube having a thermocouple made of platinum and platinum-rhodium disposed at a tip thereof is housed in a protective tube made of silicon carbide. A thermometer for a heat treatment furnace, comprising: a double protective cap having an inner cap made of platinum or platinum rhodium covering a pair and an outer cap made of iridium or an iridium alloy covering the outside of the inner cap. 3. A thermometer for a heat treatment furnace in which an insulating tube having a thermocouple made of platinum and platinum rhodium disposed in a tip thereof is housed in a protective tube made of silicon carbide. A thermometer for a heat treatment furnace, comprising a protective cap having a cap body made of platinum or platinum rhodium covering a pair and a coating layer made of alumina covering the outer surface of the cap body.