JPS61294826A - Low pressure cvd apparatus - Google Patents

Abstract

PURPOSE:To eliminate the peeling of the CVD film which has adhered to the inner wall of a reaction vessel by covering the cooled portions to be contacted with the reaction gas such as the vacuum sealing portions of the reaction vessel, particularly the inner walls of the metal doors, with a protective covers which produce no impurities at elevated temperatures. CONSTITUTION:A quartz reaction tube 2 comprises a stainless steel door 3 provided with a gas introducing pipe 4 and for taking in and out a sample, a back door 3' which also serves as a flange for connecting a stainless steel piping 8, and protective quartz covers 7, 7' which cover the surfaces of the doors 3, 3' without contacting with these surfaces. The protective cover 7 is formed into the shape of a bottomed cylinder having a diameter which is slightly smaller than the inner diameter of the reaction tube 2, and disposed with its opening side being directed toward the central portion of the reaction tube 2. On the other hand, the protective cover 7' is formed into the shape of a bottomed cylinder having a diameter which is slightly smaller than the inner diameter of the reaction tube 2, and disposed with its opening side being directed toward the central portion of the reaction tube 2. Further, the base of the protective cover 7' is provided with an opening of a small diameter, and a cylindrical body of a small diameter is connected with this opening.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to low pressure CVD used for manufacturing semiconductor devices, etc.
Concerning improvements to equipment.

[Technical background of the invention and its problems]

In recent years, with the increase in density and integration of semiconductor devices, the diameter of 3i wafers, which are substrates, is rapidly increasing. for example,
With the improvement of single crystal 3i manufacturing technology, the diameter of 3i wafers has increased from 1 inch in the early 1970s to 2 inches, 3 inches, and 4 inches, and has now reached 256 bits in bit D RAM. Si substrates with a diameter of 5 inches are becoming mainstream.

The increase in the diameter of such Sil plates has also led to the increase in the size of semiconductor device manufacturing equipment.

A CVD (Chemical Vapor Deposition) apparatus used for thin film formation is used to form a 3i oxide film, an S1 nitride film, etc. on a 3i substrate by reacting raw materials SiH4 with a gas such as 02 or 5iH2Cλ2 with a gas such as N83.

This type of apparatus is classified into normal pressure CVD apparatus and reduced pressure CVD apparatus depending on the pressure inside the reaction vessel. Among them, reduced pressure C
The VD device evacuates the cylindrical quartz reaction tube, keeps the 3i substrate at a uniform temperature of 500 to 900 ['C] in a heating furnace, and forms a thin film by CVD reaction. In comparison, it has excellent productivity and uniformity.

The large diameter of the 3i substrate mentioned above is naturally achieved by low pressure CVD.
It is necessary to increase the diameter of the quartz reaction tube that is the reaction vessel of the device. In addition, increasing the diameter of the quartz reaction vessel requires improving its mechanical strength because the inside is evacuated. For this reason, it is difficult to integrally form the reaction container with quartz or the like. Furthermore, the demand for automation of manufacturing equipment in general requires automatic door type reaction vessels.

On the other hand, in a conventional low pressure CVD apparatus as shown in FIG. n23.23' is made of a metal material such as stainless steel. Therefore, at the contact portion between the quartz tube 22 and the rn23, 23', a resin-based O-ring 28 is arranged, which serves both as a buffering effect and as a vacuum seal. For this purpose, the metal door portions 23, 23' are equipped with coolers 4427, 27' for suppressing the temperature rise of the ring 28 due to radiation and conduction from the furnace body heating the reaction area. In FIG. 3, 21 is a heating furnace, 24 is a gas inlet, 25 is a Si wafer, 26 is a sample stage, 29 is a door support, and 30 is a support.

Using such a low pressure CVD apparatus, Si is deposited on a 3i substrate.
When a M oxide film or a nitride film is formed on 3, these CV
The film formed by the D reaction is also formed on the inner wall of the quartz reaction tube or the metal door other than the 3i substrate. As a result, CVs formed on the inner wall of the reaction vessel where the deposition temperature is low, that is, on the metal door part.
DIm peels off as the film thickness increases and floats inside the reaction vessel. The CVD film that has peeled off from the door portion and is floating adheres to the Si substrate as a foreign substance. The peeled film deposited on the Si substrate is covered with a normal 5ifl film, Si nitride film, etc., and is incorporated as a defect. This has caused a problem in that defects occur in the CVD film formed on the Si substrate.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to prevent the occurrence of defects due to re-adhesion of CVOS peeled off from the cooled portion of the inner wall of the reaction vessel to the sample substrate. The object of the present invention is to provide a low-pressure CVD apparatus capable of forming high-quality CVOI.

[Summary of the invention]

The gist of the present invention is to cover the cooled parts of the reaction vessel that are in contact with the reaction gas, such as the vacuum-sealed part, especially the inner wall of metal 1 vinegar, with a protective cover that does not generate impurities at high temperatures. The objective is to eliminate peeling of the CVD film.

That is, the present invention includes a vacuum reaction container that accommodates a sample substrate, a means for introducing a reaction gas into the container, a means for exhausting the gas in the container, and a means for heating the sample substrate, In the low pressure CVD apparatus that deposits and forms a thin film on the sample substrate by chemical reaction, a quartz plate or the like is installed between the cooling section and the sample substrate so that the cooling section on the inner wall of the container is not exposed to the sample substrate. A protective cover is provided.

〔Effect of the invention〕

According to the present invention, by providing the protective cover, the cooling portion of the inner wall of the reaction vessel is not exposed to the sample substrate. As a result, CVD1 adhered to the inner wall of the reaction vessel, especially to parts such as the cooled metal 1 door! peeling can be prevented.

Therefore, defects in the CVD film formed on the sample substrate can be reduced, and the quality of the CVDII film can be improved.

[Embodiments of the invention].

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing a reduced pressure CVD apparatus according to an embodiment of the present invention. A Si wafer (sample substrate) 5 placed on a sample stage 6 is placed inside the quartz reaction tube 2 . The quartz reaction tube 2 is made of stainless steel (SUS) equipped with a gas introduction tube 4.
316) sample entry/exit door 3. It is composed of a back door 3' which also serves as a flange for connecting the stainless steel piping 8, and a quartz protective cover 7,7' which covers the surfaces of these doors 3.3' without contacting the surfaces. Here, the doors 3° 3' are cooled by a cooling mechanism (not shown).

Further, the protective cover 7 is formed into a bottomed cylindrical shape with a diameter slightly smaller than the inner diameter of the reaction tube 2, and is disposed with its opening side facing the center of the reaction tube 2. On the other hand, the protective cover 7' is formed into a bottomed cylindrical shape having a diameter slightly smaller than the inner diameter of the reaction tube 2, and is disposed with its open side facing the center of the reaction tube 2.

Further, a small diameter opening is provided in the bottom plate portion of the protective cover 7', and a small diameter cylindrical body is connected to this opening.

The reaction tube 2 is placed in a heating furnace 1 for heating the 5i wafer 5. In such a reaction tube 2, a reaction gas supplied from a gas introduction tube 4 is reacted on a 3i wafer 5 to form a film, and then an exhaust trap 10. The structure is such that exhaust is performed by a vacuum exhaust pump 13 via a gate valve 11 and a conductance adjustment valve 12. Further, this device is equipped with a computer 14 and the like that collectively control the gas flow rate control system 4', the temperature side system 1', and the pressure side system 9'.

In such a configuration, dichlorosilane (S i 82 CJ22 ) and ammonia (NH
3), 80 [cc] and 800 [cc], respectively.
cc] was introduced into the reaction vessel, and the internal pressure of the vessel was 0.6 [tO
rr], sample temperature 800['C condition niyori, 3i
2000 [people] thick CVDII on wafer 5! i!
(silicon nitride film) was formed. This CVD reaction is repeated to reduce the amount of foreign matter of 0.5 [μm] or more in the reaction tube 2.
When the quantity was measured on an inch Si wafer, the results shown in FIG. 2 were obtained.

Here, the curve l1la in the figure shows the amount generated by the device of this embodiment shown in FIG. 1, and the curved line 11a shows the amount generated by the conventional device. As can be seen from Fig. 2, the amount of foreign matter generated increases rapidly with the conventional device depending on the number of times the silicon nitride film is formed, but with the device of this embodiment, it remains almost constant regardless of the number of times the silicon nitride film is formed. The value is at a low level of 20 [pieces/wafer] or less. The cause of this is the effect of covering the inner wall of the stainless steel 13.3' constituting the reaction vessel with quartz, and this proves the effectiveness of the quartz protective cover 7.7' of the present invention.

According to this embodiment, the quartz protective cover 7.7
' By providing a cooled stainless steel 11
3.3' can be prevented from being exposed to the Si wafer 5. Therefore, it is possible to reduce the amount of CVDI deposited on the cooled 113.3'.
It is possible to prevent the CVD film attached to the film from peeling off.

Therefore, C of the Si nitride film formed on the 3i wafer 5 is
It is possible to reduce the occurrence of defects in the VD film, and CVDII
can improve film quality. Another advantage is that it can be realized with a simple structure by simply adding a quartz protective cover 7,7' to the conventional device.

Note that the present invention is not limited to the embodiments described above. For example, the protective cover is arranged so as to cover the door, but if there is a cooling section in a part other than the door, it may also cover the cooling section. In other words, the effect of the present invention can be obtained by covering the cooled portion of the reaction vessel that is exposed to the sample with a protective cover. Furthermore, the protective cover is not necessarily limited to quartz, but may also be made of silicon carbide (S i C), alumina (Aλ203
) or sintered silicon nitride (Si3N+), etc.
Any material that does not generate impurities at temperatures above 00 ['C] can be used. Further, in the embodiment, a part of the inside of the reaction vessel was covered with quartz, but the reaction tube itself may have a double structure made of quartz. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a low pressure CVD apparatus according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the relationship between the number of film formations and the number of foreign particles generated, and Fig. 3 is a diagram showing a conventional low pressure CVD apparatus. FIG. 1...Heating furnace, 1'...Heating furnace control system, 2.
...Reaction tube, 3,3'...Vacuum sealed front door, 4...Gas inlet, 4'...Gas control system, 5...Si
Wafer (sample substrate), 6...sample stand, 7.7'...
Quartz protective cover, 8... Vacuum piping, 9... Vacuum gauge, 9'... Pressure control system, 10... Exhaust trap, 11... Gate valve, 12... Butterfly valve, 13. ...Vacuum pump, 14...Calculator.

Claims (3)

[Claims] (1) comprising a vacuum reaction container for accommodating a sample substrate, a means for introducing a reaction gas into the container, a means for exhausting the gas in the container, and a means for heating the sample substrate;
In the low pressure CVD apparatus for depositing and forming a thin film on the sample substrate by chemical reaction, a protective cover is arranged between the cooling section and the sample substrate so that the cooling section on the inner wall of the container is not exposed to the sample substrate. Decompression C characterized by
VD device. (2) The reduced pressure CVD according to claim 1, wherein the protective cover is made of a quartz plate.
Device. (3) The container is formed of a quartz reaction tube and a metal door that closes the opening of the reaction tube, and the door is cooled. low pressure CVD equipment.