JPS62203330A - Semiconductor heat treatment apparatus with reaction tube washing means - Google Patents

Abstract

PURPOSE:To facilitate washing the inside of a reaction tube easily at any time by the action of plasma by a method wherein etching gas is made to flow in the reaction tube and a radio frequency voltage is applied to plasma generating electrodes provided on the outer wall of the reaction tube facing each other. CONSTITUTION:A reaction tube 5 is depressurized and etching gas (g) is made to flow in it. A radio frequency voltage is applied 10 to electrodes 9a and 9b to create a plasma inside the reaction tube 5. Reaction products deposited on the inner wall of the reaction tube 5 are removed by the action of the plasma and the inside of the reaction tube 5 is washed cleanly. As the etching gas, NF3, SF6, CF4 or the like is used in accordance with the composition of the deposited product. 30kHz-40kHz is employed as a frequency of the voltage. The electrodes 9a and 9b surround the reaction tube 5 and are composed of divided mesh-type metal elements, cylindrical conductors or the like and always attached to the apparatus. With this constitution, washing can be performed easily at any time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a semiconductor heat treatment apparatus equipped with a means for cleaning a reaction tube used in heat treatment of semiconductors.

[Conventional technology 1 Heat treatment of semiconductors such as low pressure CVD (vapor phase growth)
A semiconductor to be processed is housed in a reaction tube made of an insulating ceramic material such as quartz, alumina, or Vilex,
Generally, heat treatment is carried out by supplying a predetermined reaction gas into the reaction tube while heating the reaction tube from the outside. In this heat treatment step, polycrystalline Si and S are formed on the inner wall of the reaction tube.
i02 etc. gradually adhere. When this deposit accumulates, it peels off from the inner wall of the reaction tube and adheres to the surface of the semiconductor to be processed, impeding good film formation on the surface.

[Problems to be Solved by the Invention] Conventionally, in order to clean a reaction tube to remove such deposits, the reaction tube was generally removed from the apparatus and carried out manually using an acid agent. It was time consuming and extremely troublesome. On the other hand, recently, without removing the reaction tube, an electrode is inserted into the reaction tube during cleaning, an etching gas is supplied, and a high frequency voltage is applied to the electrode to generate plasma inside the tube. A means was developed to remove the deposits by the action of However, with this method, each time the reaction tube is cleaned, it is necessary to accurately insert a long electrode in the length direction inside the tube, which is still troublesome.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor heat treatment apparatus equipped with a reaction tube cleaning means that can easily clean reaction tubes at any time.

[Means for Solving the Problems] The configuration of the present invention for solving the above problems will be described below with reference to FIGS. 1 to 3 corresponding to embodiments.

The present invention comprises a heating furnace F equipped with a heater 4 on the inner wall of a cylindrical furnace body, and an insulating ceramic material disposed inside the heating furnace to accommodate a semiconductor to be processed and heated by the heater 4. A semiconductor heat treatment apparatus comprising a reaction tube 5, in which a predetermined etching gas q is supplied into the reaction tube during cleaning of the reaction tube, and a high frequency electric field is applied to generate plasma. It is equipped with plasma generating electrodes 9a and 9b facing the outer wall of the reaction tube 5.

[Operation of the invention] In the semiconductor heat treatment apparatus having the above structure, when cleaning the reaction tube 5, a predetermined etching gas q is injected into the reaction tube.
At the same time, a high frequency voltage is applied to the plasma generation electrodes ga and gb to generate plasma in the reaction tube 5. Due to the action of this plasma, reaction products deposited on the inner wall of the reaction tube 5 are removed, and the inside of the reaction tube is well cleaned. Since the electrodes 9a and 9b mentioned above are permanently installed in the device, the cleaning action can be easily performed at any time.

[Embodiment 1] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a vertical furnace. In the figure, 1 is an outer cylinder, 2 is an inner cylinder disposed inside this outer cylinder, and 3 is an inner wall of this inner cylinder. These are the heat insulating materials fixed to the cylindrical furnace body. 4 is an electric heater arranged on the inner wall of this furnace body. The heating furnace F is configured by the above components. Reference numeral 5 denotes a reaction tube made of quartz that is placed inside the heating furnace F at a distance from the heater 4. The upper end of this reaction tube is closed leaving a gas inlet, and the lower end is open. . 6 is a gas inlet provided at the upper end of the reaction tube 5. A flange 7 holds a semiconductor device boat (not shown) inserted into the reaction tube 5 and closes the lower open end of the reaction tube 5. Reference numeral 8 denotes a gas exhaust port provided on the flange 7 and communicating with the inside of the reaction tube 5. Reference numerals 9a and 9b are plasma generation electrodes disposed between the reaction tube 5 and the heater 4 so as to face the outer wall of the reaction tube 5, respectively. These electrodes 9a.

The tubes 9b are each formed into a substantially semi-cylindrical shape from a mesh-like or plate-like high-temperature resistant metal material, and are opposed to each other with the reaction tube 5 in between. 10 is a high frequency generator connected to supply high frequency voltage to the electrodes 9a and 9b.

The semiconductor heat treatment apparatus configured as described above houses a semiconductor to be processed in a reaction tube 5, supplies a predetermined reaction gas into the tube through a gas inlet 6, and heats the semiconductor by heating it with a heater 4. However, during this heat treatment process, reaction products adhere and accumulate on the inner wall of the reaction tube 5 as described above.

In this apparatus, in order to clean the reaction tube 5 to remove this deposit, the pressure inside the reaction tube 5 is reduced and a predetermined etching gas q is supplied in place of the above reaction gas, and a high frequency generator 10 is used to clean both electrodes. Applying a high frequency voltage to 9a and 9b,
A high frequency electric field is generated within the reaction tube 5. As a result, plasma is generated inside the reaction tube 5, and the reaction products deposited on the inner wall of the reaction tube 5 are removed by the action of this plasma.
The inside of the reaction tube 5 is well cleaned. The etching gas q may be NF3.8F6. CF4
etc., and the frequency of the high frequency voltage is 30 K
Those in the range of Hz to 40 MHz are appropriately used. In this device, the plasma generation type FFAs 9a and 9b are fixedly installed in the device, so each time the reaction tube is cleaned, it is necessary to remove the reaction tube from the device and insert the electrode material into the reaction tube properly. The reaction tube can be easily cleaned at any time without requiring any troublesome operations.

Next, two different modifications of the present invention will be explained with reference to FIGS. 2 and 3. These modified examples differ from the above embodiments mainly in the structure of the reaction tube portion. In FIGS. 2 and 3, the same parts as those in the apparatus shown in FIG. 1 are given the same reference numerals, and their explanations will be omitted. First, in Figure 2,
5 is a reaction tube whose upper end is closed and whose lower end is open; 1
Reference numeral 1 designates a gas supply port provided on the flange 7, and 12 designates a gas supply pipe that communicates with the gas supply port and stands upright within the reaction tube 5, and allows gas to flow down into the reaction tube 5 from its open end.

13 is a high frequency matching device attached to the outer surface of the outer cylinder 1;
This high frequency matching box includes a high frequency generator 10 and electric Ni9a, 9.
b, and performs a matching function to apply an appropriate high frequency voltage to both electrodes.

In this embodiment as well, the inside of the reaction tube 5 is depressurized, the etching gas q as described above is supplied from the gas supply port 11, and a high frequency voltage is applied to the electrodes 9a and 9b. Plasma is generated, and due to the action of this plasma, not only the reaction tube 5 but also the reaction products attached to the gas supply tube 12 are removed and cleaned.

Next, in the modified example shown in FIG. 3, the reaction tube 5 has a double tube configuration, where 5A is an external reaction tube, and 5B is a tube having a smaller diameter than the external reaction tube and is inserted concentrically into the external reaction tube. 5Ba is a plurality of gas exhaust holes arranged in parallel on the upper side of the internal reaction tube.

The lower end of the internal reaction tube 5B communicates with the gas supply port 11 via a gas supply path provided in the flange 7. 14
is a gas passage formed between the tube walls of both reaction tubes 5A and 5B, through which the exhaust gas from the gas exhaust hole 5Ba flows down.

This gas passage communicates with the gas discharge port 8 at the lower end side.

In this modification as well, the inside of the reaction tube 58.5A is reduced by reducing the pressure inside the reaction tube 5[3, 5A, supplying the etching gas q from the gas supply port 11, and applying a high frequency voltage to the electrodes 9a, 9b. Plasma is generated, and the reaction tubes 5B and 5A are cleaned by the action of the plasma. That is, the present invention is also effective for cleaning such double reaction tubes.

It should be noted that although the present invention is applied to a vertical furnace in both the embodiment and each of the modifications described above, the present invention can be similarly applied to a horizontal furnace.

Next, a specific example of forming the snow shovel for plasma generation used in the present invention will be explained. In FIG. 4(A), the same parts as 'IAa' in FIG. 1 are given the same reference numerals. Figure 4 (
Reference numeral 16 in A) is a large number of insulators having heater wire holding grooves on both sides as shown in FIG. 3 of Japanese Utility Model Publication No. 59-6632. These insulators are attached to the inside of the inner cylinder 2 via the heat insulating material 3 by the mounting rods 17 or 17a, so that the insulators are alternated in adjacent rows as shown in FIG. 4(B). There is. The heater wire 4 is held in the heater wire holding groove of each insulator 16, forming a so-called bad heater. A predetermined mounting rod 17a among the many mounting rods has a long length and is made to protrude inwardly than the insulator 16, and is made of a high temperature resistant material with an insulating ring 20 interposed on the protruding end side. The net-like electrode 9a is held and attached.

In FIG. 5(A), a plurality of insulators 18a are mounted inside with a mounting rod 19 so that insulators 18a similar to the insulators 16 are located inside the above-mentioned bad heater consisting of a row of heater wires 4 and insulators 16. An electrode 9 made of a wire material that can withstand high temperatures similar to the heater wire 4 is inserted into the cylinder 2 and placed in the holding groove of the insulator 18a.
A is retained. That is, this electrode is connected to the reaction tube 5.
It is formed of a large number of wire rods laid along the length of the wire and spaced apart from each other in the circumferential direction.

In FIG. 5(B), an insulator 18b having a wide holding groove is used in place of the above-mentioned insulator 18a, and an electrode 9b made of a high temperature resistant strip material is held in the insulator.

Each electrode 9a, 9b in FIGS. 5(A) and 5(B) was formed of a wire rod or a strip-shaped material parallel to the heater wire 4, respectively.
The electrodes may be provided such that the linear or band-shaped material forming the electrodes is oriented perpendicular to the heater wire 4. In this way, the stray capacitance between the electrode and the heater is reduced, so
Preferred for supplying high frequency energy.

Note that the plasma generating electrode may be provided in the form of a net or a plate in contact with the outer wall of the reaction tube, but this is not practical because the electrode material expands or creeps due to high temperature heating.

[Effects of the Invention] As described above, the semiconductor heat treatment apparatus according to the present invention is provided with a plasma generation electrode facing the outer wall of the reaction tube,
When cleaning the reaction tube, an etching gas is supplied into the reaction tube, and a high frequency voltage is applied to the electrode to generate plasma inside the reaction tube using a high frequency electric field, and the inside of the reaction tube is cleaned by the action of the plasma. This eliminates the need for troublesome work such as removing the reaction tube from the apparatus every time it is cleaned or inserting a long electrode into the reaction tube, as in the past. can be washed very easily at any time.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an outline of an embodiment of the present invention, FIGS. 2 and 3 are longitudinal sectional views showing an outline of different modifications of the invention, and FIGS. 4(A) and 5. (A) and (B) are main part cross-sectional explanatory views showing specific examples of different configurations of electrodes and heaters in the present invention, respectively, and FIG. 4(B) is a specific configuration of the heater in FIG. 4(A). FIG. 1...Outer cylinder, 2...Inner cylinder, 3...Insulating material, 4...
・Heater, F...Heating furnace, 5...Reaction tube, 5A...
・External reaction tube, 5B...Inner reaction tube, 9a, 9b...
- Plasma generation electrode, q... etching gas, 10
...High frequency generator. Figure 4 (A) CB) Figure 5 and A) (B)

Claims (5)

[Claims] (1) A heating furnace equipped with a heater on the inner wall of a cylindrical furnace body, and a reaction tube made of an insulating ceramic material that is disposed inside the heating furnace, houses a semiconductor to be processed, and is heated by the heater. In a semiconductor heat treatment apparatus which supplies a predetermined etching gas into the reaction tube during cleaning of the reaction tube and generates plasma by applying a high frequency electric field, the heating furnace is located inside the heating furnace and faces the outer wall of the reaction tube. A semiconductor heat treatment apparatus equipped with a reaction tube cleaning means, characterized in that it is equipped with a plasma generation electrode. (2) The semiconductor heat treatment apparatus according to claim 1, wherein the plasma generation electrode is comprised of a divided mesh metal body that substantially surrounds the outer wall of the reaction tube. (3) The semiconductor heat treatment apparatus according to claim 1, wherein the plasma generation electrode is comprised of a divided cylindrical conductor substantially surrounding the outer wall of the reaction tube. (4) The plasma generation electrode is composed of a large number of linear metal bodies or band-shaped metal bodies installed at intervals in the circumferential direction along the length direction of the reaction tube. The semiconductor heat treatment apparatus according to item 1. (5) The plasma generation electrode comprises a large number of linear metal bodies or band-shaped metal bodies installed at intervals in the length direction along the circumferential direction of the reaction tube. The semiconductor heat treatment apparatus according to item 1.