JPH05144802A - Cleaning method for semiconductor manufacturing device - Google Patents

Abstract

PURPOSE:To provide the cleaning method for a semiconductor manufacturing device with which a semiconductor substrate can be left on the inner wall of a furnace core tube for heat treatment, and the impurity particles, which contaminate the substrate being heattreated, can be removed. CONSTITUTION:The title cleaning method is the method to clean the semiconductor manufacturing device having a heat treatment tube 1, and the heat treatment tube 1 is baked using cleaning gas of the same type as the processing gas used for treatment to be conducted before heat treatment.

Description

Detailed Description of the Invention

(Table of Contents) -Industrial application field-Prior art-Problems to be solved by the invention-Means for solving the problems-Action (Fig. 1) -Examples (1) First example ( (FIG. 2) (2) Second embodiment (FIG. 3) (3) Third embodiment (FIG. 4)

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a semiconductor manufacturing apparatus, and more particularly to a method for cleaning a semiconductor manufacturing apparatus having a heat treatment tube such as a furnace core tube.

In recent years, as the performance of semiconductor devices has improved, heavy metal particles causing adhesion of oxygen to the surface of a semiconductor substrate, introduction of stacking faults, reduction of lifetime or leakage current, which causes formation of a natural oxide film. It is necessary to prevent contamination of the semiconductor substrate with impurities during the heat treatment such as contamination of the semiconductor substrate or contamination of alkali particles that causes surface inversion.

[0004]

2. Description of the Related Art Conventionally, a method for cleaning a heat treatment pipe, for example, a furnace core pipe of an oxidation furnace is performed as follows. That is, HF
After the surface of the furnace core tube is lightly etched using a chemical solution of a system or a chemical solution composed of a mixed solution of H ₂ O ₂ / NH ₄ OH to remove the surface layer of the inner wall of the furnace core tube, usually an inert gas such as N
_{2 The} furnace core tube is baked at a temperature near the heat treatment temperature while flowing gas.

As a result, contaminant impurity particles such as oxygen particles and heavy metal particles attached to the inner wall of the furnace core tube are removed. After cleaning the furnace core tube in this manner, the semiconductor substrate is set in the furnace core tube, and oxygen gas is flowed to thermally oxidize the semiconductor substrate to form, for example, a field oxide film.

[0006]

By the way, there are cases where the leakage current of the transistor formed by using the field oxide film thus formed becomes large. For example, in the case of a MOS transistor, the leakage current between the source / drain (S / D) region layer and the substrate may be large, and in the case of a bipolar transistor, between the emitter / base or the base / collector. There is a case that the leakage current of becomes large, which is a problem. this is,
In the above cleaning method, the inside of the furnace core tube is not cleaned to the required extent, and the remaining Na, Fe, Cu particles, etc. are out-diffused from the inner wall of the furnace core tube during the oxidation treatment, and an oxide film is being formed. It is considered that this is because of being mixed into the semiconductor substrate.

The present invention has been made in view of such conventional problems, and removes impurity particles remaining on the inner wall of a furnace core tube for heat-treating a semiconductor substrate and contaminating the semiconductor substrate being heat-treated. An object of the present invention is to provide a cleaning method of a semiconductor manufacturing apparatus capable of performing the cleaning.

[0008]

[Means for Solving the Problems]
As shown in (a) and (b), firstly, there is provided a method of cleaning a semiconductor manufacturing apparatus having a heat treatment tube 1, wherein a cleaning gas 2 of the same type as the process gas 3a used for the treatment is used before the treatment. This is achieved by a method for cleaning a semiconductor manufacturing apparatus, characterized in that the heat treatment tube 1 is air-baked. Secondly, a semiconductor manufacturing apparatus having the heat treatment tube 1 is an oxidation furnace, an annealing furnace or a CVD furnace. This is achieved by the method for cleaning a semiconductor manufacturing apparatus according to the first invention, and thirdly, the cleaning gas 2 and the process gas 3a are nitrogen (N ₂ )
Gas, oxygen (O ₂ ) gas, mixed gas of argon (Ar) gas + oxygen (O ₂ ) gas, or silane (SiH ₄ ) gas, the semiconductor production according to the first or second invention. This is accomplished by a method of cleaning the device.

[0009]

According to the experiment conducted by the inventor of the present application, as shown in FIG. 1 (a), a specific type of cleaning gas (A) 2 flowing when air-baking the heat treatment tube 1 is selected. It was found that only the contaminant particles 4a were removed. In Table 1,
The results of such experiments will be shown.

[0010]

[Table 1]

[0011] Table 1 sets the wafer baking the furnace core tube at a temperature 1200 ° C. in a cleaning gas (A) consisting of N ₂ gas, the cleaning gas (A) and the same type of N ₂ gas (A ) Or cleaning gas (A) and a different kind of O ₂ gas (B) in a process gas at a temperature of 1200
After the heat treatment at ° C, the contaminant particles remaining on the wafer were investigated by atomic absorption spectrometry.

According to Table 1, when the process gas is the same kind of N ₂ gas (A) as the cleaning gas (A),
The residual amount of alkali particles and metal particles is small, but when the process gas is an O ₂ gas (B) of a type different from the cleaning gas (A), Na particles, Fe particles and Cu particles are particularly large.

This result shows that only the contaminant particles (X) 4a of a specific type are removed according to the type of the cleaning gas (A) 2 that is flown when the heat treatment tube 1 is air-baked. (FIG. 1 (a)). Therefore, it is necessary to use the same type of process gas (A) as the cleaning gas (FIG. 1B). Otherwise, contaminant particles (Y) 4b will come out during the heat treatment (Fig. 1).
(C)).

According to the cleaning method of the semiconductor manufacturing apparatus of the present invention, the heat treatment tube 1 is air-baked using the same type of gas as the gas used for the treatment before the treatment, so that the heat treatment is performed during the heat treatment. Contamination particles 4, which should come out of the inner wall of the tube 1.
For example, alkali particles, heavy metal particles, etc. are all exhausted when the heat treatment tube 1 is baked. Therefore, since the contaminant particles 4 do not remain on the inner wall of the heat treatment tube 1 when the semiconductor substrate is heat-treated, the semiconductor substrate can be heat-treated in a clean state.

For example, for an oxidation furnace, oxygen (O ₂ )
Gas, argon (Ar) gas + oxygen (O ₂ ) gas mixed gas, nitrogen (N ₂ ) gas for the annealing furnace, or silane (SiH ₄ ) gas for the CVD furnace. As a result, a clean oxide film, a silicon film, or the like can be formed on the semiconductor substrate, or contamination particles can be prevented from entering the semiconductor substrate.

As a result, the device characteristics can be improved.

[0017]

Embodiments (1) First Embodiment FIGS. 1A to 1C are sectional views for explaining a method of manufacturing a MOS transistor including a method for cleaning an oxidation furnace according to a first embodiment of the present invention. is there.

First, a method of cleaning the furnace core tube (heat treatment tube) of the oxidation furnace will be described. That is, the surface of the furnace core tube is lightly etched using an HF-based chemical solution or a chemical solution composed of a mixed solution of H ₂ O ₂ / NH ₄ OH to remove the surface layer of the inner wall of the furnace core tube. Then, pure water cleaning is performed to wash away the chemical liquid. As a result, contaminant particles contained in the surface layer of the inner wall of the furnace core tube are removed.

Next, after setting the furnace core tube in the oxidation furnace body, while flowing an O ₂ gas which is a cleaning gas of the same kind as the process gas used for the oxidation treatment, is it the same as the oxidation (heat treatment) temperature, for example, 1000 ° C. Alternatively, the furnace core tube is baked at a higher temperature.

As a result, Na attached to the inner wall of the furnace core tube
Contaminant particles that can be removed by O ₂ gas are removed from the contaminated particles such as alkali particles such as or heavy metal particles such as Fe or Cu. It should be noted that the cleaning of the furnace core tube is usually not performed frequently, but is performed regularly after a certain period of time.

After cleaning the furnace core tube in this manner, as shown in FIG. 2A, after setting the semiconductor substrate 6 on which the nitride film 7 is selectively formed on the furnace core tube, oxygen gas is flown. Then, the semiconductor substrate 6 is selectively thermally oxidized to form a field oxide film 8 (FIG. 2B). Then, the nitride film 7
Is removed, an element isolation region 9 in which the field oxide film 8 is formed and an element formation region 10 surrounded by the element isolation region 9 are formed (FIG. 2C). An SiO ₂ film may be formed under the nitride film 7 to relieve stress on the semiconductor substrate 6.

As described above, according to the first embodiment of the present invention, before the oxidation treatment, the furnace core tube is burned by using O ₂ gas as the same kind of cleaning gas as the process gas used for the oxidation treatment. Therefore, all the pollutant particles that should come out from the inner wall of the furnace core tube during the heat treatment are exhausted by the air baking of the furnace core tube. For this reason, when the semiconductor substrate 6 is oxidized, the contaminant particles to be emitted by the heat treatment using O ₂ gas do not remain on the inner wall of the furnace core tube. Therefore, the semiconductor substrate 6 is oxidized in a clean state. Therefore, a clean field oxide film 8 can be formed, and contamination particles can be prevented from entering the semiconductor substrate 6.

As a result, the electrical characteristics and reliability of the finally formed MOS transistor can be improved. Although the O ₂ gas is used as the cleaning gas and the process gas in the first embodiment, a mixed gas of Ar gas + O ₂ gas may be used.

(2) Second Embodiment FIGS. 3A to 3C show the CVD of the second embodiment of the present invention.
FIG. 6 is a cross-sectional view illustrating a method of manufacturing a MOS transistor including a method of cleaning a furnace.

First, a method of cleaning the furnace core tube of the CVD furnace will be described. That is, the chemical solution treatment is performed in the same manner as in the first embodiment to remove the contaminant particles contained in the surface layer of the inner wall of the furnace core tube.

Then, after setting the furnace core tube in the CVD furnace body, silane (S
iH ₄ ) Flowing gas while forming film (heat treatment) at temperature 65
Bake the furnace core tube at a temperature equal to or higher than 0 ° C.

As a result, Na adhering to the inner wall of the furnace core tube
Among the contaminated particles such as alkali particles such as and heavy metal particles such as Fe and Cu, those which can be removed by SiH ₄ gas are removed. After cleaning the furnace core tube in this way, the semiconductor substrate 6 on which the gate insulating film 11 has been formed is set in the furnace core tube (FIG. 3A), and SiH ₄ gas is flown to heat the semiconductor substrate 6. Then, the gate insulating film 11 on the semiconductor substrate 6
A polysilicon film 12 is formed on the upper surface (FIG. 3B).
After that, when the polysilicon film 12 is patterned, the gate electrode 12a is formed (FIG. 3C).

As described above, according to the second embodiment of the present invention, SiH ₄ is used as the cleaning gas of the same kind as the process gas used for forming the polysilicon film 12 before the formation of the polysilicon film 12 by the CVD method. Since the furnace core tube is air-baked by using gas, all the pollutant particles to be discharged from the inner wall of the furnace core tube during the formation of the polysilicon film 12 are exhausted by the furnace core tube being air-baked. For this reason, when the polysilicon film 12 is formed on the gate insulating film 11 on the semiconductor substrate 6, the contaminant particles to be emitted by the heat treatment using SiH ₄ gas do not remain on the inner wall of the furnace core tube. The polysilicon film 12 can be formed on the gate insulating film 11 in a clean state, and contamination particles can be prevented from entering the semiconductor substrate 6.

As a result, it is possible to improve the element characteristics and reliability of the finally formed MOS transistor or the like. (3) Third Embodiment FIGS. 4A to 4C are cross-sectional views illustrating a method for manufacturing a MOS transistor including a method for cleaning an annealing furnace according to a third embodiment of the present invention.

First, the field oxide film 8 of the semiconductor substrate 6
Forming a gate insulating film 11 on the semiconductor substrate 6 in the element formation region 10 surrounded by the element isolation region 9 in which
Further, the gate electrode 12a is selectively formed on the gate insulating film 11 (FIG. 4A).

Next, using the gate electrode 12a as a mask, conductive type impurities are selectively ion-implanted into the semiconductor substrate 6 in the element forming region 10 to form an S / D region layer.
13a and 13b are formed (FIG. 4B).

Next, the conductivity of the ion implantation region layers 13a and 13b
To activate and re-distribute the type impurities.
Do the rules. Therefore, the cleaner for the furnace core tube of the annealing furnace is
Perform That is, in the same manner as in the first embodiment, the chemical solution
Treatment to remove contaminant particles contained in the surface layer of the inner wall of the furnace core tube.
Leave. Next, the furnace core tube was set in the annealing furnace body.
After that, the same type of process gas used for the annealing treatment
N as a leaning gas ₂Annealing while flowing gas
(Heat treatment) Temperature, for example 900 ° C or higher
Bake the furnace core tube at a low temperature. This allows the furnace core tube
Alkali particles such as Na adhering to the inner wall, Fe, Cu, etc.
N out of pollutant particles such as heavy metal particles₂Can be removed by gas
Contaminating particles are removed.

After cleaning the furnace core tube in this manner, the ion-implanted semiconductor substrate 6 is set in the furnace core tube and, as shown in FIG. 4C, N ₂ gas (process gas) is flown. The semiconductor substrate 6 is heated to activate the ion-implanted conductivity type impurities and redistribute them to obtain S / D.
The region layers 14a and 14b are formed.

As described above, according to the third embodiment of the present invention, the furnace core tube is pre-baked before the annealing treatment by using N ₂ gas as the same kind of cleaning gas as the process gas used for the annealing treatment. Therefore, the pollutant particles that should come out from the inner wall of the furnace core tube during the annealing treatment are all exhausted by the air baking of the furnace core tube. Therefore, the semiconductor substrate 6
Since the contaminated particles to be emitted by the heat treatment using N ₂ gas do not remain on the inner wall of the furnace core tube when annealing the semiconductor substrate 6, the semiconductor substrate 6 can be annealed in a clean state, and the semiconductor substrate 6 can be annealed. It is possible to prevent contamination particles from entering the substrate 6.

As a result, the electrical characteristics and reliability of the finally formed MOS transistor can be improved.

[0036]

As described above, according to the cleaning method of the semiconductor manufacturing apparatus of the present invention, the heat treatment pipe is pre-baked using the same type of gas as the gas used for the treatment before the treatment. Depending on the type of gas that flows when the heat treatment tube is air-baked, even if only certain types of contaminant impurity particles are removed, the contaminant impurity particles that should come out from the inner wall of the heat treatment tube during the heat treatment are The processing tube is completely burned out.

Therefore, when the semiconductor substrate is heat-treated, contaminant impurity particles do not remain on the inner wall of the furnace core tube.
The semiconductor substrate can be heat-treated in a clean state. Therefore, a clean oxide film, a silicon film, or the like can be formed on the semiconductor substrate, or contamination impurity particles can be prevented from entering the semiconductor substrate.

As a result, the device characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a principle diagram illustrating a cleaning method for a semiconductor manufacturing apparatus according to the present invention.

FIG. 2 is a cross-sectional view illustrating the first embodiment of the present invention.

FIG. 3 is a cross-sectional view explaining a second embodiment of the present invention.

FIG. 4 is a sectional view for explaining a third embodiment of the present invention.

[Explanation of symbols]

 1 heat treatment tube, 2 cleaning gas, 3a, 3b process gas, 4a, 3b pollutant particles, 6 semiconductor substrate, 7 nitride film, 8 field oxide film, 9 element isolation region, 10 element formation region, 11 gate insulating film, 12 Polysilicon film, 12a gate electrode, 13a, 13b ion implantation region layer, 14a, 14b S / D region layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 29/784

Claims (3)

[Claims] 1. A method for cleaning a semiconductor manufacturing apparatus having a heat treatment pipe (1), wherein the heat treatment is performed using a cleaning gas (2) of the same type as a process gas (3a) used for the treatment before the treatment. A method for cleaning a semiconductor manufacturing apparatus, characterized in that the tube (1) is baked. 2. The method for cleaning a semiconductor manufacturing apparatus according to claim 1, wherein the semiconductor manufacturing apparatus having the heat treatment pipe (1) is an oxidation furnace, an annealing furnace or a CVD furnace. 3. The cleaning gas (2) and the process gas (3a) are nitrogen (N ₂ ) gas, oxygen (O ₂ ) gas, a mixed gas of argon (Ar) gas + oxygen (O ₂ ) gas or silane ( The cleaning method for a semiconductor manufacturing apparatus according to claim 1 or 2, wherein SiH ₄ ) gas is used.