JPH04186614A - Chemical vapor growing apparatus - Google Patents

Abstract

PURPOSE:To obtain a chemical vapor growing apparatus which can easily and effectively detect an etching end time at the time of self-cleaning by obtaining a light emitting unit for emitting light to a reaction tube out of reaction chamber, and a photodetector for photodetecting a reflected light from the tube and detecting the amount of a chemical vapor growing film of the wall of the chamber by the amount of reflected light. CONSTITUTION:Laser light is projected onto a reaction tube 1 by an etching end time detector 11 during self-cleaning process, and the intensity of the reflected light is monitored by a photodetector in the detector. That is, if a polycrystalline silicon film is almost etched, the intensity (amount) of the reflected light is largely reduced. Accordingly, reduction of the intensity (amount) of the reflected light is detected thereby to detect the etching end time at the time of self-cleaning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reduced pressure CVD apparatus equipped with a self-cleaning mechanism.

[Conventional technology]

Conventionally, some low pressure CVD apparatuses insert a semiconductor substrate into a reaction tube, heat the reaction tube, and supply a reaction gas into the tube to form a chemical vapor deposition film on the semiconductor substrate. In this type of low-pressure CVD apparatus, a chemical vapor deposition film is also formed on the wall surface of the reaction chamber, so this film is periodically cleaned using an etching gas. This will be explained with reference to FIG.

FIG. 2 is a schematic configuration diagram showing a conventional vertical reduced pressure CVD apparatus equipped with a self-cleaning mechanism.

In the figure, reference numeral 1 denotes a reaction tube made of quartz. This reaction tube 1 has a double tube structure including an inner tube 1a and an outer tube 1b, and is supported and fixed to a manifold 2. Further, the outer tube 1b can be removed upward from the manifold 2, and is configured so that the inside of the outer tube 1b (inside the reaction tube 1) is sealed when attached to the manifold 2. 3 is a boat for supporting a semiconductor substrate, and this port 3 is inserted into the reaction tube 1 and connected to the manifold 2.
is supported by 4 is a heater for heating the reaction tube 1; 5 is a process gas supply tube to which process gas A used for producing a chemical vapor deposition film is supplied; the tube is connected to the manifold 2; The inner peripheral side of 1a is communicated with a process gas supply bag '11 (not shown). Reference numeral 6 denotes an exhaust pipe connected to the manifold 2, and the exhaust pipe 6 communicates between the inner pipe 1a and the outer pipe 1b and an evacuation means such as a vacuum pump (not shown).

Reference numeral 7 denotes an etching gas supply pipe for introducing etching gas B (described later) into the reaction tube 1, which is connected to the manifold 2 in the same way as the process gas supply pipe 5, and is connected to the inside of the inner pipe 1a and to the etching gas supply device (not shown). ).

Next, the operation of the conventional vertical reduced pressure CVD apparatus configured as described above will be explained. The inside of the reaction tube 1 is heated to about 500 to 800° C. by the heater 4, and the semiconductor substrate is inserted into the reaction tube 1 while being supported on the boat 3. Note that after the semiconductor substrate is inserted, the inside of the reaction tube 1 is sealed. Then, the inside of the reaction tube 1 is reduced to a predetermined pressure (approximately 0.1 to 1 Torr) using a vacuum pump, etc., and the process gas A (for example, silane gas when depositing polycrystalline silicon) is supplied from the process gas supply tube 5 to the reaction tube 1. Introduced into tube 1. Thereby, a thin film is formed on the semiconductor substrate by chemical vapor phase reaction. After the film formation is completed, the pressure inside the reaction tube 1 is increased to atmospheric pressure, and the semiconductor substrate is taken out from the reaction tube 1, thereby completing the work. In this device, when a film is deposited on a semiconductor substrate, a film is also deposited on the wall of the reaction chamber of the reaction tube 1 at the same time, so it is necessary to clean the reaction tube 1 at a certain point (hereinafter referred to as self-cleaning). ). Self-cleaning is carried out by supplying an etching gas B such as chlorine trifluoride into the reaction tube 1 from the etching gas supply pipe 7, and etching the deposited film on the reaction chamber wall of the reaction tube 1 in a plasma state. Ta.

[Problem to be solved by the invention]

However, when performing self-cleaning as described above, if over-etching is performed, the reaction tube 1 made of quartz will also be etched, so it is necessary to detect when the etching of the deposited film on the wall of the reaction chamber is completed. . Therefore, there is a problem in that the etching time must be set in accordance with the total thickness of the deposited film.

[Means to solve the problem]

The chemical vapor deposition apparatus according to the present invention includes a light irradiation device that irradiates light to the reaction tube from outside the reaction chamber while etching gas is supplied to the reaction tube, and a light irradiation device that receives and reflects the reflected light from the reaction tube. The device is equipped with a light receiving device that detects the amount of chemical vapor grown film on the wall surface of the reaction chamber based on the amount of light.

[For production]

When the chemical vapor deposition film on the wall surface of the reaction chamber is etched, the amount of reflected light from the reaction tube decreases, and the end time of etching can be detected from the change in the amount of light.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG.

FIG. 1 is a schematic configuration diagram showing a vertical reduced pressure CVD apparatus according to the present invention. In this figure, the same or equivalent members as those explained in FIG. 2 are given the same reference numerals, and detailed explanation will be omitted. In addition, in FIG. 1, a heater for heating the reaction tube 1 is omitted. In FIG. 1, 11 is an etching end time detection device. This etching end time detection device 11 is equipped with a laser beam irradiation function and a light receiving function, and it reacts with a laser beam to the reaction tube 1, irradiates it from outside, and detects part of the laser beam reflected by the reaction tube 1. It is configured to receive light from a portion of the camera. In this embodiment, the position where the laser beam is irradiated is set in the vicinity of the exhaust pipe in the reaction tube 1. The light receiving device provided in the etching end time detection device 11 is configured to be able to continuously observe (monitor) the intensity (light amount) of the reflected light from the reaction tube 1.

Next, a procedure for detecting the etching end time using the etching end time detection device 11 configured as described above will be explained. During self-cleaning, the pressure inside the reaction tube 1 is reduced to a predetermined pressure by a vacuum pump or the like, and an etching gas (for example, chlorine trifluoride, etc.) is introduced into the reaction tube 1. The deposited film on the wall surface of the reaction chamber is etched and removed by the etching gas. During this self-cleaning process, the etching end time detection device 11 irradiates the reaction tube 1 with laser light, and the intensity of the reflected light is monitored by a light receiving device within the etching end time detection device 11.

At the initial stage of etching the deposited film, since a polycrystalline silicon film exists on the wall surface of the reaction chamber, most of the laser light is reflected by the reaction tube 1, and the reflected light is received by the light receiving device. Then, as the polycrystalline silicon film on the wall surface of the reaction chamber is etched, the laser light begins to pass through the reaction tube 1, and the intensity (light amount) of the reflected light gradually decreases.

That is, when most of the polycrystalline silicon film is etched, the intensity (amount of light) of the above-mentioned reflected light is significantly reduced.

Therefore, in the etching end time detection device 11 according to the present invention, the light receiving device monitors the intensity (light amount) of the reflected light from the reaction tube 1 and detects a decrease in the intensity (light amount) of the reflected light. Accordingly, the end time of etching during self-cleaning can be detected.

Furthermore, as shown in this embodiment, if a laser beam is irradiated to a position near the exhaust pipe 6 in the reaction tube 1 to detect the presence or absence of a deposited film in that part, this type of vertical CVD
In the apparatus, since the deposited film near the exhaust pipe 6 is etched last, it is possible to accurately detect the etching status of the deposited film in substantially the entire reaction tube.

Furthermore, by using a device that integrates a light irradiation mechanism and a light receiving mechanism like the etching end time detection device 11 used in this embodiment, it is possible to downsize and easily install the device, and the optical system adjustment becomes easier.

〔Effect of the invention〕

As explained above, the chemical vapor deposition apparatus according to the present invention includes a light irradiation device that irradiates light from outside the reaction chamber to the reaction tube while etching gas is supplied to the reaction tube, and a light irradiation device that irradiates light from outside the reaction tube. As the chemical vapor deposition film on the reaction chamber wall is etched, the reflected light from the reaction tube will be reflected from the reaction tube. Since the amount of light decreases, the end time of etching can be detected from this change in the amount of light. Therefore, according to the chemical vapor deposition apparatus according to the present invention, it is possible to easily and reliably detect the end time of etching during self-cleaning.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a vertical reduced pressure CVD apparatus according to the present invention. FIG. 2 is a schematic configuration diagram showing a conventional vertical reduced pressure CVD apparatus equipped with a self-cleaning mechanism. DESCRIPTION OF SYMBOLS 1... Reaction tube, 1a... Inner tube, 1b... Outer tube, 7... Etching gas supply pipe, 11... Etching end time detection device.

Claims (1)

[Claims] In a chemical vapor deposition apparatus in which a chemical vapor deposition film formed on the reaction chamber wall of a reaction tube made of quartz is removed by an etching gas, a reaction is applied to the reaction tube while the etching gas is supplied to the reaction tube. A light irradiation device that irradiates light from the outside, and a light receiving device that receives reflected light from a reaction tube and detects the amount of chemical vapor deposition film on the wall surface of the reaction chamber based on the amount of reflected light. Chemical vapor deposition equipment.