JPH0331479A - Heat treatment - Google Patents

Abstract

PURPOSE:To prevent the generation of dust in a reaction tube by introducing an etching gas contg. halogen compds. into the reaction tube after heat treatment to remove the reaction product depositing on the legion except the soaking region. CONSTITUTION:The reaction tube 1 after heat treatment is evacuated, and an etching gas contg. a halogen compd. such as ClF3, oxygen, etc., is introduced from its source 9b to fill the tube. The deposit 14 on the inner wall surface 13 of the tube 1 except the soaking region 7 formed in the film forming stage is etched by the ClF3 in the etching gas, and the generation of particles in the tube 1 is prevented. The etching product is discharged to the outside of the tube 1 along with the exhaust. Consequently, the generation of dust due to the deposit on the inner wall of the tube 1 after heat treatment is prevented with easy operation without disturbing the temp. profile.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a heat treatment method.

(Prior art) Conventionally, in step 5 of a semiconductor wafer manufacturing process, there is a step of forming a film on the surface of a semiconductor wafer (hereinafter abbreviated as wafer) by dry processing. In this step, the reactant that forms a film on the wafer surface also adheres to the inner wall surface of the reaction tube. This adhered substance tends to separate from the inner wall surface of the reaction tube and become particles, and is likely to adhere to the wafer. Examples of methods for cleaning the adhered substance attached to the inner wall of the reaction tube include, for example, JP-A-64-17857 and JP-A-1-1. It is described in many publications such as No. 92385. That is, dry etching is used to remove and clean the reactants adhering to the inner wall surface of the reaction tube.

(Problem to be solved by the invention) However, with conventional reaction tube cleaning methods.

It had the following drawbacks.

Plasma coils and plasma generation electrodes are installed around the reaction tube to generate plasma, which poses a major hindrance to forming a soaking area during film formation. There was a drawback that it had to be.

This reaction tube had a heavy load and had to be removed after the temperature had cooled down to room temperature after the reaction, resulting in a long cleaning operation time.

Further, there are IJF, means for cleaning using gas, and the like. However, in the case of heat treatment, there was a drawback that all the reaction deposits deposited during the heat treatment could not be cleaned even by using ClF2 gas.

As a result of detailed investigation by the present inventors, the object to be processed, for example, 2
It was found that the reaction deposits adhering to the inner wall of the reaction tube in the soaking area where rows of 00 semiconductor wafers were formed were hard to peel off and were strong.

The object of the present invention was made in view of the above problems, and it is an object of the present invention to provide a heat treatment method that prevents the generation of dust due to deposits on the inner wall of a reaction tube after heat treatment.

C Structure of the Invention] (Means for Solving the Problems) The present invention forms a soaking area in a reaction tube, and heat-treats the object to be treated by providing the object to be treated in the soaking area. When removing the kimono, the inside of the reaction tube is evacuated to a predetermined degree of vacuum, and then an etching gas containing at least a halogen element compound such as CjlF3 is introduced into one reaction tube, and the reaction tube is filled with the reaction tube to remove the reaction adhered outside the soaking area. It is characterized by removing deposits.

(Function and Effect) Since an etching gas containing at least a halogen element compound such as The present invention provides a heat treatment method that removes adhering substances and prevents the generation of dust.

Therefore, since it is possible to remove reaction deposits without applying plasma action, the cleaning step can be performed at an appropriate timing after the heat treatment of the object to be processed without removing one reaction tube.

(Example) Hereinafter, an example in which the method of the present invention is applied to a batch heat treatment process for semiconductor wafers will be described with reference to the drawings.

First, the heat treatment apparatus will be explained with reference to No. 21i1. A processing section ■ consisting of a horizontal reaction tube ■ and a storage table (for example, a wafer boat) containing a large number of processed objects 1 such as wafers inserted into this processing section ■ are loaded and unloaded at predetermined positions. It consists of a loading mechanism■.

The processing section (2) has a reaction tube (2) made of a material that is heat resistant and does not easily react with the processing gas, such as quartz, and a cylindrical heating mechanism, such as a coil wound around the reaction tube, coaxially surrounding the reaction tube. It consists of a heater 0.

This heater 0 uniformly heats the arrayed portion of a plurality of wafers, for example 200 wafers, housed in the reaction tube ω.
A coil is wound outside the reaction tube so that the wafers are heated to 00° C. Usually, the area where the wafers are arranged is set as a soaking area. This soaking area is generally formed wider than the wafer arrangement position.

Furthermore, a gas supply port (2) is provided at the end of the reaction tube (ω) on the opening (2) side for supplying a reaction gas, such as SiH gas, N, O gas, etc., into the reaction tube (ω). In addition, the reaction tube ω
An exhaust port (10) is provided on the opposite side of the opening (2). Further, the exhaust system is provided with a mechanism for appropriately adjusting the exhaust amount so that the amount of introduced reaction gas is exhausted.

Furthermore, a switching valve (11) is provided in the piping system connected to the gas supply port (1), so that two systems of gas can be selectively introduced. That is, from one piping system, reactive gases such as monosilane (SiH4) and nitrous oxide (S
The reaction gas supply source (9a
).

The other system uses a gas such as chlorine trifluoride (CIF3) to etch the reactants attached during the film forming process.
) and oxygen (01) into the reaction tube ω
The etching gas supply source (9b) is connected to the etching gas supply source (9b) so as to be introduced into the etching gas.

In addition, a lid (12) that makes the inside of the reaction tube ω airtight is provided in conjunction with the loading mechanism ■, and a wafer boat (12) containing a plurality of wafers ■ is installed at the tip of the loading mechanism ■. The lid body (12) is configured to airtightly cover the inside of the reaction tube ω at the same time as this wafer boat is loaded into a predetermined position inside the reaction tube ω.

Next, a film forming process and a cleaning process using the above-mentioned heat treatment apparatus will be explained.

First, when a current is applied to heater 0 to generate heat, a temperature profile shown in FIG. 2 is formed in the reaction tube after a predetermined period of time.

On the other hand, a large number of wafers (2) are automatically transferred to a wafer boat (2) by a wafer transfer mechanism (not shown), and the wafer (2) is placed on the tip of the loading mechanism (4).

Then, by driving the loading mechanism ■ that places the wafer ( ) on the wafer boat, the wafer ■ is placed at a predetermined position in the reaction tube ω.
That is, the wafer is loaded into the wafer placement area.

Thereafter, select the switching valve (11) to supply 1, for example, monosilane (SiH4) at 300% from the 1 reaction gas supply source (9a).
It is introduced at a rate of ccZ minutes, and nitrogen oxide (Neo) is introduced at a rate of 20 a/min as a carrier gas. By supplying this reaction gas for a predetermined period of time, an amorphous (Sin) layer grows on the surface of the sea urchin 4 due to a thermal reaction.

This process is called the HTO process.

At this time, a film of reaction deposits also adheres to the inner wall surface (13) of one reaction tube (1). That is, in the area around the wafer ■ of the reaction tube ■,
An amorphous (Sin, ) layer is deposited. In addition, the inner wall surface (1
3) A relatively large amount of polysilicon (poj!y-8L) or amorphous silicon (Si) is attached.

Here, the linear expansion coefficient of poly-silicon (pony-Si) and amorphous silicon (Si) is significantly different from that of the reaction tube ■, and the film quality is poor because it is attached outside the soaking area. Therefore, the attached substance (14) is the reaction tube ω
It has been found that the particles are easily separated from the inner wall surface (13) of the inner wall surface (13) and easily formed into particles. A feature of this embodiment is to prevent the generation of particles.

After the above heat treatment is completed, the inside of the reaction tube ω is filled with nitrogen (N
The atmosphere is replaced with the atmosphere gas of 2) to return it to atmospheric pressure, and unloaded from the reaction tube (2) to the wafer boat.

Next, after - times of heat treatment or after a predetermined number of heat treatments, the easily peeled polysilicon (pony-SL) attached to the inner wall surface (13) of the reaction tube ω is removed.

The process of removing the attached substance (14) such as amorphous silicon (Si) will be described. First, as shown in Figure 1, since there is no need to heat the inside of the reaction tube, turn off the power to heater 0. The loading mechanism (2) is driven to carry the loading mechanism (2) into the reactor tube (2), and the opening of the reaction tube (ω) is hermetically sealed with the lid (12).

The inside of this hermetically sealed reaction tube ω is 0. Evacuate to about ITorr. The etching gas supply source (9) is connected to the switching valve (11) of the piping system connected to the gas supply port 0 in the reaction tube.
b) Select side. From this source (9b) an etching gas such as chlorine trifluoride (CaF3) gas is supplied.

An etching gas containing about 5% oxygen is introduced into the reaction tube ω at a flow rate of, for example, 500 cc for 7 minutes at room temperature to fill the reaction tube. At this time, the exhaust process is continued at an appropriate exhaust amount. This exhaust flow can be selected in relation to the etching rate. The chlorine trifluoride (CAPS) of this etching gas contacts and etches the amorphous silicon (SL) adhered to the inner wall surface of the reaction tube (1) and the loading mechanism. This etched product is discharged to the outside of the reaction tube ω along with the exhaust gas. In other words, in the film formation process described above, in the wafer peripheral region ■, the inner wall surface of the reaction tube ω (
13), but polysilicon (poffiy-8i) and amorphous silicon (
A large amount of Si) is attached. Substances (14) adhering to the inner wall surface (13) other than the soaking area (2) are etched with an etching gas (16) containing chlorine trifluoride (CaF) to prevent particle generation in the reaction tube ω. To prevent. At this time, since amorphous (Sin, ) is hardly etched, only poffiy-5i, which easily peels off, and amorphous silicon (Si) are etched when selected, preventing only the generation of particles and changing the temperature characteristics of the soaking part. Compared to the conventional cleaning method, the effect of the above embodiment is that the etching gas is turned into plasma, carbon is decomposed, and the decomposed compound is used to remove the deposited substance (14) inside the reaction tube ω. The temperature profile is not disturbed by the arrangement of a plasma generating power source, and the operation is easy. Further, in the apparatus using this method, there is no need to provide a plasma device.

Although the above embodiments have been explained at room temperature (25°C), cleaning can be performed even at a high temperature, for example, 25°C to 800°C. or,
The same cleaning performance can be obtained with a vertical furnace.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a reactor for explaining one embodiment in which the method of the present invention is applied to a heat treatment process, and FIG. 2 is an explanatory diagram of the configuration of the heat treatment apparatus of FIG. 1. 1... Reaction tube 7... Wafer peripheral area 9... Gas supply port 9a... Reaction gas supply source 9b... Etching gas supply source

Claims (1)

[Claims] A soaking area is formed in the reaction tube, and when the object to be treated is placed in the soaking area and the reaction deposits attached to the inner wall of the reaction tube are removed by heat treatment, the inside of the reaction tube is kept at a predetermined degree of vacuum. After evacuation, at least ClF_
A heat treatment method characterized by introducing and filling an etching gas containing a secondary halogen element compound to remove reaction deposits that have adhered to areas other than the soaking area.