JP3164046B2 - Furnace tube cleaning mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning mechanism for a furnace core tube used in a heat treatment furnace for performing heat treatment such as oxidation, diffusion, or annealing.

[0002]

2. Description of the Related Art Generally, in heat treatment processes such as oxidation, diffusion, and annealing processes, contaminants such as metal are scattered from a semiconductor substrate wafer or the like and adhere to a furnace core tube. If heat treatment of the next wafer is performed in such a state, contaminants move to the wafer, causing defects such as a defect in the semiconductor wafer and a decrease in withstand voltage of the insulating film.

Therefore, conventionally, the work is periodically stopped to clean the furnace material such as the furnace core tube. The conventional cleaning method removes the furnace core tube from the heat treatment furnace and removes it by slightly etching it with a chemical such as HF + HNO ₃ or removing it by cleaning it with a chemical such as HC1. are doing.

[0004] However, in this method, the furnace core tube and the like must be removed each time cleaning is performed, so that the wafer heat treatment is interrupted during that time, and the production capacity is reduced. It may be damaged during operation.

As a cleaning method without removing the furnace core tube, there is a method of removing heavy metals by flowing hydrochloric acid or trichloroethane in a high temperature state. In this method, when hydrochloric acid is used, the furnace core tube is removed. Corrosion of metal pipes before and after,
Alternatively, when trichloroethane is used, there is a problem that carbon remains in the furnace core tube.

[0006] As a cleaning method for solving these problems,
It is disclosed in JP-A-4-282828. In this cleaning method, ultraviolet rays are radiated while supplying a halogen-based gas into a contaminated furnace core tube of a heat treatment furnace to turn halogens into radicals, and heavy metals and the like adhering to inner walls are radicalized and gasified and removed. .

[0007]

In the above-described conventional cleaning method, ultraviolet rays must be irradiated, and there is no means for recognizing how long the ultraviolet rays should be irradiated and the degree of removal of the contaminated metal. There is a problem that the power consumed by the ultraviolet lamp wastefully is large and the operation cost is high.
In addition, the equipment requires an ultraviolet lamp and a power supply for turning on the ultraviolet lamp in the current equipment, so that the equipment cost increases and the stop time cannot be predicted.

[0008] The inner wall portion where the metal adheres to the furnace core tube does not differ for each processing, and the wafer loading tool used is a board.
As long as the distances are the same, the portion where the metal adheres is almost the same. Therefore, when fluorine gas is used as a halogen-based gas, fluorine radicals etch the metal-free portion of the furnace core tube made of quartz, and the thickness is locally reduced by several times of excessive ultraviolet irradiation. . In particular, when the neck portion of the gas introduction port or the gas exhaust port becomes thin, it may be damaged by a slight mechanical impact.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a furnace core tube cleaning mechanism which can easily and effectively clean contaminant metals adhering to the inner wall of the furnace core tube by heat treatment and which is inexpensive.

[0010]

Means for Solving the Problems] Features of the present invention, the heat treatment
Contaminated metal adhering to the inner wall of the furnace core tube is converted to halide
Means for supplying a halogen-based gas to be changed to the furnace core tube;
Outside the furnace core tube exposed from the heater of the heat treatment furnace
Irradiates a laser beam toward the inner wall at the substantially central part of the furnace core tube
And the reflected light from the inner wall and the contamination
Ru cleaning mechanism der furnace core tube and a ellipsometer for measuring the thickness of the metal.

[0011]

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a flow chart for explaining a cleaning mechanism of a furnace core tube according to an embodiment of the present invention.
First, in step A of FIG. 1, when the processing of the wafer that has been heated in the temperature range of 700 to 950 degrees Celsius is completed, the supply of the reaction gas is stopped and the remaining reaction gas is exhausted. And, we introduced the furnace core tube such as nitrogen to the atmosphere.
Next, in step B of FIG. 1, the hatch 10 of the furnace core tube is opened, and a boat on which a plurality of wafers are mounted is pulled out from the furnace core tube. At this time, the temperature in the furnace core tube is 7 degrees Celsius, which is the processing temperature.
It is kept between 00 and 950 degrees. Next, step C
Then, the opening of the furnace core tube is closed with a hatch 10.

In step D, a halogen-based gas such as a fluorine-based gas such as F ₂ , CH ₃ F, or COF ₂ or N ₂ is placed in the furnace core tube contaminated with the metal in consideration of safety.
OC1, C1 _2, by introducing a chlorine-based gas such as CC1 _4, to a halide by reaction of contaminant metals by gas while the supply and exhaust of the gas. Since the halogen compound is volatile, it is discharged outside the furnace core tube with the exhaust of the exhaust device.

At this time, in step E, the inner wall of the furnace core tube is irradiated with laser light from the outside exposed from the heater of the furnace core tube made of quartz, the reflected light is subjected to deflection analysis, and the film thickness of the contaminated metal is determined. Is measured. A commercially available ellipsometer is used for this measurement.

Next, in step F, the reflectance of the ellipsometer beam light changes due to the presence of metal contaminants attached to the quartz surface in the furnace, and it is determined whether or not the contamination has been removed. Further, since the temperature at the time of removing the contaminated metal is not different from the temperature at the time of the treatment, the hatch of the furnace core tube and the joint structure of the gas supply tube do not cause any trouble due to thermal expansion.

FIG. 2 is a sectional view showing a heat treatment apparatus for explaining a cleaning mechanism for cleaning the inside of the furnace core tube. The heat treatment furnace generally includes a vertical furnace and a horizontal furnace, but FIG. 2 shows a case where a cleaning mechanism is applied to a horizontal furnace. As shown in FIG. 2, the cleaning mechanism is connected to a gas inlet 3 of a furnace core tube 1 whose interior is empty and closed by a hatch 10, and supplies a processing gas through an opening / closing valve 7 through a pipe 9 a. A gas supply pipe 9 connected to the gas supply tube 6 for supplying a halogen-based gas; and a floodlighting mirror for transmitting laser light through the window 8a to the halogenated metal film adhered to the furnace core tube 1 by the halogen-based gas. Tube 5a
An ellipsometer having a light entrance barrel 5b for entering laser light reflected from a metal film through a window 8b, and a gas outlet 4 for discharging a halide volatilized by heating the heater 2.
An ellipsometer provided with an exhaust device (not shown) for exhausting air from the furnace is a well-known measuring device, and therefore its description is omitted, but the window 8a in the portion of the furnace core tube 1 exposed from the heater 2 is omitted.
The laser beam is projected obliquely from the light projecting lens barrel 5a toward the substantially central inner wall of the furnace core tube 1, and the reflected light is transmitted through a window 8b located at a position deviated from the heater 2 so as to enter the light entrance mirror. The light enters the cylinder 5b. Then, the thickness of the metal film is measured by analyzing the polarization of the reflected light by a polarization analyzer (not shown).

FIG. 3 is a graph showing the removal effect of the cleaning method of the present invention. Here, in order to confirm the cleaning effect, Ge contamination on the furnace core tube when the wafer on which SiGe was grown was heat-treated was examined. So G
e. A wafer that has been subjected to a heat treatment in a state of being contaminated (before cleaning) and a wafer that has been subjected to a heat treatment after performing the cleaning method of the present invention (after cleaning) are taken out and adhered to the respective wafer surfaces. The amount of Ge was measured.

As a result, as shown in FIG. 3, the amount of Ge contaminated in the furnace which had been contaminated to a level of 10 ¹¹ atoms / cm ² before cleaning was reduced to 10 ⁸ atoms / cm ² by performing cleaning.
ms / cm ² level. The washing temperature was 900 degrees Celsius and the washing time was 40 minutes. Such a cleaning method is particularly suitable for removing a metal having a property of being volatile when converted into a halide, and has a knowledge that it can sufficiently cope with contamination of TaO5 film by Ta or B after ion implantation. Obtained.

When heating is performed simultaneously with the flow of the halogen-based gas, the heating temperature is a temperature at which the heat treatment furnace is used on a daily basis, or a temperature slightly higher than that (up to 9 degrees Celsius).
Cleaning (up to 50 degrees) allows faster removal without causing furnace failure. Replacement with a semiconductor wafer to be processed next can be performed quickly.

[0021]

As described above, the cleaning method and the mechanism of the present invention introduce the halogen-based gas, maintain the furnace temperature at the processing temperature, and remove the contaminant metal adhering to the furnace inner wall into the state of the halide. It can be volatilized and exhausted and removed. Therefore, there is no need to take out the furnace core tube or irradiate with ultraviolet light as in the conventional case, and there is an effect that the time interrupted by cleaning can be greatly reduced and the production capacity can be improved.

Further, if necessary, the temperature is raised to 900 degrees Celsius where no trouble occurs, so that the contaminated metal can be removed more quickly. Furthermore, it consumes halogen gas and electric power without waste,
There is also an effect that an appropriate stop time of the device is sufficient, and the operation cost can be reduced and the operation rate can be improved.

[Brief description of the drawings]

[1] washer furnace tube in an embodiment of the present invention
It is a flowchart for demonstrating a structure .

FIG. 2 is a sectional view showing a heat treatment apparatus for explaining a cleaning mechanism for cleaning the inside of a furnace core tube.

FIG. 3 is a graph showing the removal effect of the cleaning method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace core tube 2 Heater 3 Gas inlet 4 Gas outlet 5a Projection lens barrel 5b Light entrance lens barrel 6,7 Opening / closing valve 8a, 8b Window 9 Gas supply pipe 9a Pipe 10 Hatch

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/205 H01L 21/22-21/24 H01L 21/31 H01L 21/365 H01L 21/38-21 / 40 H01L 21/469 H01L 21/86

Claims (1)

(57) [Claims] 1. Contamination adhering to an inner wall of a furnace core tube of a heat treatment furnace.
Halogen-based gas that converts metal to halide
Means for supplying to the tube and exposed from the heater of the heat treatment furnace.
From the outside of the furnace core tube to an inner wall at a substantially central portion of the furnace core tube.
A projection lens barrel that irradiates the laser beam toward the
Ellipsometry for measuring the thickness of the contaminated metal by receiving light
And a cleaning mechanism for the furnace core tube.