JPH0620959A - Photo chemical vapor growth apparatus - Google Patents

Abstract

PURPOSE:To obtain a photo chemical vapor growth apparatus which has realized sharp reaction within a reaction vessel and can control film thickness and interface. CONSTITUTION:A photo chemical vapor growth apparatus comprises a shutter mechanism 17 for optical separation between a light source 8 and a reaction vessel 1 in oder to form a film on a substrate 3 by irradiation with ultravioret beam or vaccuum ultravioret beam to the reaction vessel 1 through a light transmitting window 7 and then decomposing the introduced reaction gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photochemical gas for irradiating a reaction tank with ultraviolet light or vacuum ultraviolet light to excite a reaction gas introduced into the reaction tank to accelerate a chemical reaction to form a film. The present invention relates to a phase growth apparatus (hereinafter simply referred to as a photo CVD apparatus).

[0002]

2. Description of the Related Art As an optical CVD apparatus of this type, in Japanese Patent Application No. 3-84043 filed on the same day, as shown in FIG. 4 of the accompanying drawings, a susceptor B having a variable temperature is arranged in a reaction tank A. A substrate C to be formed into a film is attached to B, a nozzle E having a thin slit-shaped opening D for introducing a reaction gas is provided on the side wall of the reaction tank A, and the bottom wall of the reaction tank A is provided. An exhaust port F for discharging a reaction gas is provided at an end portion of the reaction vessel, and a light source G for emitting ultraviolet light or vacuum ultraviolet light and a reflection plate for preventing loss of light emitted from the light source G are provided above the reaction tank A. A light source chamber I accommodating H is provided, and the light source chamber I and the reaction tank A are partitioned by a light transmission window J made of synthetic quartz. Further, in the reaction tank A, a large number of small chambers are provided above the susceptor B. Synthetic quartz inert gas ejection plate K with holes
In addition, there is proposed a flow guard frame in which a large number of synthetic quartz flow guard plates M are arranged at regular intervals in a flow guard frame L and fixed to the upper wall of the reaction tank A. In this apparatus, the purge gas introduced from the conduit N provided through the upper wall of the reaction tank A is filled with a gap between the light transmission window J and the inert gas ejection plate K, and the inert gas ejection plate K is small. Each hole and flow guard plate M of the flow guard member
By ejecting the gas through the space, the reaction gas introduced from the nozzle E is concentrated near the substrate and the light source chamber I
The film is attached to the light transmission window J that separates the reaction chamber A and the reaction tank A so that the light intensity is not reduced.

When forming a film using such an optical CVD apparatus, first, an inert gas whose flow rate is adjusted is passed through an inert gas jet plate K, and a reaction gas whose flow rate is adjusted is supplied to a nozzle E.
Is introduced into the reaction tank A. On the other hand, the substrate C to be deposited on the susceptor B is heated to a desired temperature in advance, and when the flow of the reaction gas and the inert gas reaches a steady state, the light source G is used to decompose the introduced reaction gas. When turned on, the reaction tank A is irradiated with ultraviolet light or vacuum ultraviolet light through the light transmitting window J and the light transmitting inert gas jetting plate K. When several kinds of films are formed on the same substrate, after forming the first film, the light source G is once turned off, the reaction gas is replaced, and the gas flow is again in a steady state. A desired film structure is formed by performing light irradiation and repeating this operation.

[0004]

By the way, the above-mentioned optical CV is used.
In the conventional photo-CVD apparatus including the D apparatus, it takes time until the intensity of the light emitted from the light source becomes constant, which makes it difficult to precisely control the film thickness. That is,
As shown in FIG. 5 of the accompanying drawings, generally, in a photo CVD apparatus, the intensity of light after the light source is turned on does not become constant immediately,
It can be seen that about 10 minutes have passed before it becomes constant. It is completely unknown how much film is deposited within 10 minutes from such lighting until the light intensity becomes constant. Generally, for long-time film formation, such instability of light intensity in the initial stage of lighting does not have a great influence, but a solar cell or a thin film transistor (TF) is used.
T), or when forming a thin film in a device such as a superlattice, the initial instability of light intensity causes a large error in the estimation of the film thickness. The largest cause of this instability is that it takes a certain amount of time for the discharge to stabilize, but as long as the light source device has such light intensity characteristics, controlling the thickness of the thin film is extremely difficult. It is difficult and causes a problem that a device as designed cannot be manufactured.

Therefore, the present invention solves the problems associated with such light source characteristics, improves the sharpness of the reaction in the reaction tank, and provides a photo-CVD apparatus capable of controlling the film thickness and the interface. Is intended.

[0006]

In order to achieve the above object, a photo-CVD apparatus according to the present invention is provided with a reaction tank having a reaction gas introduction port for introducing a reaction gas and a light transmission window, and a light transmission window. It has a light source that irradiates ultraviolet light or vacuum ultraviolet light into the reaction tank to decompose the introduced reaction gas to deposit a film on the substrate, and a shutter mechanism that optically isolates the light source from the reaction tank. It has a feature.

[0007]

In the photo-CVD apparatus of the present invention thus constructed, the shutter mechanism controls the irradiation of light from the light source into the reaction tank, and in the closed state the light is emitted from the light source even when the light source is on. Light is prevented from entering the reaction tank through the light transmission window, and the reaction can be started by opening the shutter mechanism. That is, the light source is turned on sufficiently before the start of film formation, and the irradiation of light into the reaction tank is blocked by the shutter mechanism until the light intensity from the light source stabilizes. Therefore, the start and end of the reaction can be controlled only by the opening / closing operation of the shutter mechanism, and the light can be always radiated into the reaction tank with a constant light intensity. As a result, if the other conditions are kept constant, the desired film thickness of the desired material can be controlled only by the film formation time, and it becomes possible to manufacture a device such as a multilayer film or a superlattice. .

[0008]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3 of the accompanying drawings. FIG. 1 illustrates the present invention as a light C
An embodiment applied to a VD device is shown. Illustrated light CV
In the apparatus D, 1 is a vacuum tank, that is, a reaction tank, in which a susceptor 2 having a variable temperature is provided, and a substrate 3 on which a film is grown is mounted on the susceptor 2. A nozzle 5 having a thin slit-shaped opening 4 for introducing a reactive gas is provided on the side wall of the vacuum chamber 1.
Is connected via an external conduit 6 to a reaction gas supply source (not shown). The nozzle 5 is made of Al alloy and is positioned so that the reaction gas can be introduced almost parallel to the surface of the substrate 3 on the susceptor 2. In the case of the mercury sensitization method which is often used in the photo CVD method, the Al alloy forming the nozzle 5 may react with mercury to generate dust, so that such a reaction is prevented. Therefore, the nozzle 5 may be anodized. A light transmission window 7 made of synthetic quartz is provided on the upper wall of the vacuum chamber 1 at a position facing the substrate 3, and a light source 8 for emitting ultraviolet light or vacuum ultraviolet light and an ultraviolet light from the light source 8 are provided outside the light transmission window 7. A light source chamber containing a reflection plate 9 that reflects light or vacuum ultraviolet light and directs it onto the substrate 3 through the light transmission window 7 to prevent light loss.
10 is installed. On the inner surface of the light transmitting window 7,
Leave a slight gap between the inner surface of the light transmitting window 7 and
A spout 11 for introducing an inert gas, which is made of synthetic quartz and has a large number of small gas spout holes, is provided. The gap between the spout 11 and the inner surface of the light transmission window 7 is above the vacuum chamber 1. It is connected to an inert gas source (not shown) via a conduit 12 mounted on the outside of the wall. Inert gas spouting part
A flow guard member 13 is attached to the lower side of 11.
The flow guard member 13 is configured by mounting a flow guard plate 15 made of a thin synthetic quartz plate in a flow guard frame body 14 at regular intervals, and each flow guard plate 15 is provided with a reaction gas from the nozzle 5. It is oriented so as to extend in a direction transverse to the flow direction and further direct the inert gas ejected from the inert gas ejection portion 11 downward toward the substrate 3 on the susceptor 2. Therefore, the height of each flow guard plate 15 in the flow guard member 13 can be arbitrarily set according to the inner size of the vacuum chamber 1 and the like. The flow guard member 13 together with the inert gas ejection part 11 is the vacuum chamber 1.
It is fixed inside the upper wall. An exhaust port 16 is provided near one end of the bottom wall of the vacuum chamber 1 as shown in the figure. Further, a shutter mechanism 17 is provided between the light transmission window 7 and the light source chamber 10, and this shutter mechanism 17 is provided with a shutter 19 which is supported by a shutter guide 18 so as to be openable and closable, and this shutter 19 is shown in FIG. As described above, it can be opened and closed by the air cylinder 20. Further, the shutter mechanism 17 is
In order to prevent light from the light source 8 from leaking into the vacuum chamber 1 when the shutter 19 is closed to prevent the formation of a multilayer film without sagging at the interface, the gap between the shutter guide 18 and the shutter 19 is as narrow as possible, for example, 1.0 Further, the surfaces of the shutter guide 18 and the shutter 19 are coated with a low reflectance of ultraviolet light or vacuum ultraviolet light. Since the light source 8 is provided on the atmosphere side as in the case of a normal photo-CVD apparatus, in the illustrated apparatus, the light source chamber 10 is provided for the purpose of preventing absorption of ultraviolet light or vacuum ultraviolet light emitted from the light source 8 by oxygen. The air inside is configured to be constantly purged with nitrogen gas, and when the shutter 19 is closed, the air in the space surrounded by the shutter guide 18, the shutter 19 and the light transmission window 7 is not sufficiently purged with nitrogen gas. Therefore,
A nitrogen gas introduction part 21 and a discharge part 22 are provided below the shutter guide 18 to prevent air from remaining in the space through which light passes.

The operation of the illustrated apparatus thus configured will be described below. When the apparatus is operated to form a film on the substrate, the light source 8 is turned on in advance, for example, 20 minutes or more before the start of film formation, and the shutter 19 is kept closed. The flow rate of the reaction gas is adjusted and introduced from the external conduit 6 through the thin slit-shaped opening 4 of the nozzle 5 into a sheet shape substantially parallel to the surface of the substrate 3. The inert gas whose flow rate is adjusted is introduced downward from the inert gas jetting portion 11 with respect to the flow of the sheet-like reaction gas. In addition, the heater incorporated in the susceptor 2 is operated in advance to heat the substrate 3 to a desired temperature,
When the flow of the reaction gas and the inert gas reaches a steady state, the air cylinder 20 of the shutter mechanism 17 is operated to open the shutter 18, and the ultraviolet light or vacuum ultraviolet light from the light source 8 is introduced into the reaction tank 1. Irradiate to start the reaction. As a result, the reaction gas is decomposed and the reaction product is deposited on the substrate, thus forming a film.

FIG. 3 shows basic characteristics of how the light intensity on the substrate 3 corresponds to the opening / closing of the shutter 19. When the shutter 19 is opened and closed at one-minute intervals as shown in FIG. 3A, the light intensity on the substrate 3 is 0 when the shutter is closed and 1.0 (relative intensity) when the shutter is open, and FIG. The intensity of the light is
It can be seen that it changes only during the opening and closing time of the shutter (about 0.5 seconds). Moreover, since the light source 8 is turned on in advance and is in a stable state, when the shutter 19 is opened, extremely stable light intensity can be given. Therefore, it becomes possible to control the start and end of the reaction in the reaction tank 1 only by opening and closing the shutter 19, and in that case, the uncertain factor of the reaction is the time required for opening and closing the shutter 19 (about 0.5
Seconds) only. For example, let's say 50 angstroms / mi
When depositing a thin film of 50 Å at a film forming rate of n 2, the time required to open and close the shutter 19 is only 1.7% of the entire film forming time. Therefore, it is possible to start and end the reaction very sharply. As a result, gas switching and shutters 19 are substantially unaffected by changes in light intensity.
It is possible to manufacture a device such as a multilayer film or a superlattice in which the interface is not sagging and the film thickness is controlled only by opening and closing.

In the illustrated embodiment, the shutter guide 18, the shutter 19 and the light source chamber 10 receive light and heat radiation from the light source 8 directly when the power of the light source 8 is strong.
It is heated to a temperature above 0 ° C. Therefore, if necessary, the shutter guide 18 and the shutter 19 may be provided with water channels inside so that they can be cooled. Further, in the illustrated apparatus, the light source is installed in the atmosphere, but the present invention can be implemented with a structure in which the light source is installed in the vacuum chamber.

[0012]

As described above, in the photo-CVD apparatus according to the present invention, since the shutter mechanism is provided between the light source and the reaction tank to optically isolate it, it is possible to start film formation in the reaction tank. At the same time, it is possible to irradiate ultraviolet light or vacuum ultraviolet light with stable light intensity, which enables stable and reproducible film thickness control, and manufactures a debye such as a multilayer film or superlattice without sagging at the interface. be able to. Further, since the photochemical reaction in the reaction tank can be controlled only by opening and closing the shutter, the reaction switching time can be shortened and the operating rate of the apparatus can be significantly improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a shutter mechanism in the apparatus of FIG.

FIG. 3 is a graph showing characteristics of changes in light intensity on a substrate due to opening and closing of a shutter mechanism.

FIG. 4 Separately filed photo-CVD as an example of the prior art
FIG. 3 is a schematic cross-sectional view showing the device.

FIG. 5 is a graph showing basic characteristics of a light source in a conventional photo CVD apparatus.

[Explanation of symbols]

 1: Reaction tank 3: Substrate 5: Reactive gas introduction nozzle 7: Light transmission window 8: Light source 17: Shutter mechanism

Front page continuation (72) Inventor Akitoshi Suzuki, Hagien 2500, Chigasaki, Kanagawa Prefecture, Japan Vacuum Technology Co., Ltd. (72) Izumi Nakayama 2500, Hagien, Chigasaki City, Kanagawa Prefecture, Japan Vacuum Technology Co., Ltd.

Claims (1)

[Claims] 1. A reaction tank equipped with a reaction gas inlet for introducing a reaction gas and a light transmitting window, and irradiating the reaction tank with ultraviolet light or vacuum ultraviolet light through the light transmitting window to decompose the introduced reaction gas. A photochemical vapor deposition apparatus comprising: a light source for depositing a film on a substrate by means of a substrate; and a shutter mechanism for optically separating the light source and the reaction tank.