JPS63232416A - Formation of thin-film through photochemical vapor growth - Google Patents

Abstract

PURPOSE:To form the vapor growth of a thin-film positively as an excellent film by each conducting the supply of a raw material gas to a reaction chamber, to which a base body to be formed by vapor growth is arranged, optical irradiation and the exhaust of the reaction chamber intermittently and performing the stoppage of optical irradiation and exhaust during the stoppage interval of the supply of the raw gas. CONSTITUTION:The supply of a raw gas to a reaction chamber, to which a base body to be formed by vapor growth is disposed, optical irradiation and the exhaust of the reaction chamber are each conducted intermittently, and the stoppage of optical irradiation and exhaust are performed during the stoppage interval of the supply of the raw gas. Accordingly, deposit species or active species formed by a photo- reaction on the base body to be formed by vapor growth or near it can reach to the base body to be formed by vapor growth, but the generation of deposits or extraneous matters to an optical introduction section is avoided because the species are removed before they diffuse and reach to the optical introduction, thus excellently shaping a thin-film through a photochemical reaction by efficient optical irradiation onto the base body to be formed by vapor growth.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming an i-film by photochemical vapor deposition.

[Summary of the invention]

In the present invention, the supply of raw material gas to the reaction chamber in which the substrate to be vaporized is placed, the irradiation with light, and the evacuation from the reaction chamber are performed intermittently, and the light is supplied during the period when the supply of the raw material gas is stopped. The irradiation is stopped and the air is evacuated to avoid the formation of deposits in the reaction chamber, especially on the light introduction part, and the deposits obstruct the light irradiation onto the vapor phase growth substrate. The purpose is to improve the film quality of the vapor phase grown 'a' film by avoiding deterioration in photochemical reactions.

[Conventional technology]

For example, a semiconductor manufacturing process often involves forming a silicon thin film, a silicon oxide thin film, a nitride film, and the like. These thin films are produced using chemical vapor deposition method (hereinafter referred to as CVD method).
Formation is widely practiced.

This CVD method includes a thermal CVD method in which a target thin film is deposited on a vapor phase growth substrate, such as a wafer, by thermally decomposing a source gas on the surface of a vapor phase growth substrate under normal pressure or reduced pressure; The plasma CVD method, which converts raw material gas into plasma, is widely used. On the other hand, as semiconductor wafers become larger in diameter, forming thin films on them may lead to changes in characteristics due to thermal strain and deformation of the semiconductor wafer, the generation of defective products, and a decrease in reliability. In order to avoid this, it is desirable that the heating temperature of the wafer, that is, the substrate to be vapor-phase grown, be as low as possible when forming the thin film. However, ``double thermal decomposition C
In the case of the VD method, a high substrate temperature of 400°C to 700°C is required, and in particular, in the manufacturing process of semiconductor devices, for example, thin film formation, such as the formation of silicon polycrystals, by the CVD method is performed after depositing a low-melting-point deposited bottom layer. If this is attempted, the electric-wound metal layer may melt or soften, resulting in the inconvenience. In contrast, in the plasma CVD method,
Although the substrate temperature can be lowered to about 200 DEG C. to 300 DEG C., in this case there is a disadvantage that the substrate subjected to vapor phase growth, that is, the semiconductor wafer, is damaged by irradiation due to the impact caused by the plasma.

On the other hand, the photochemical CVD method (Semiconductor World) 1 performs vapor phase growth by applying light energy to the raw material gas.
98 Chiku 9' P105-110) has been attracting attention because it can be grown in a vapor phase at low temperatures and does not cause damage due to irradiation.

[Problem that the invention seeks to solve]

As mentioned above, when photochemical CVD is used, thin films can be grown in vapor phase at low temperatures, such as 300 degrees Celsius or lower, for example, 200 degrees Celsius, and thermal deformation can be achieved even when the substrate to be vapor phase grown is a large diameter semiconductor wafer. Alternatively, although it has the advantage of effectively avoiding the occurrence of distortion, in this case, the reaction occurs on the wall surface of the reaction chamber, for example, the light source placement area, or the light introduction part such as the light introduction window from the light source part to the reaction chamber. When product deposition or adhesion occurs, it obstructs light transmission and reduces the efficiency of photochemical reactions, which in turn leads to deterioration of the quality of the thin film produced on the vapor growth substrate.

For example, when ultraviolet rays or laser light irradiation that causes a photochemical reaction is focused on or near the surface of the substrate to be vapor-phase grown, products can be efficiently generated on the surface of the substrate to be vapor-phase-grown, Plaque or adhesion of the product on other parts is to a large extent avoided. This has been demonstrated in Japanese Patent Application Laid-Open No. 56-117 by using a laser beam in a thin film formation method by thermal decomposition.
This is also disclosed in Publication No. 45759. However, in the photochemical reaction described above, even if the ultraviolet rays or laser light is focused on the substrate surface, in reality, the deposited species or active species generated here will spread within the reaction chamber over time. A phenomenon occurs in which the light reaches the wall surface of the reaction chamber and the light introduction part, and deposits or attachments are generated there.

The work to eliminate the accumulation of products or deposits on such unnecessary parts requires considerable effort, and in particular the light introduction part requires high cleaning. Methods such as replacing the window glass made of glass have been used, but the complexity and cost of replacing the glass windows have become problems.

In the present invention, such problems are solved and light irradiation is performed well to ensure that a thin film can be formed as a high-quality film by vapor phase growth.

[Means for solving problems]

In the present invention, as described above, the generation of deposits or adhesion to the light introducing portion is caused by the presence of Wi species or active species that have reacted by photoreaction, for example, photodissociation, on or near the surface of the semiconductor substrate to be grown in vapor phase. These deposited species or particles reach the walls of the reaction chamber over time and adhere to the light introduction section, such as a window that introduces light from outside the reaction chamber, or the wall surface of a light source placed inside the reaction chamber. Before the active species reach the light introduction part, the reactor is evacuated in order to make it difficult for the dissociated deposited species or active species to reach the light introduction part.

That is, the present invention provides a method for forming a thin film by photochemical vapor deposition, in which supply of raw material gas to a reaction chamber in which a substrate to be vapor-deposited is disposed, light irradiation, and evacuation of the reaction chamber are performed intermittently, respectively. Light irradiation is stopped and exhaust is performed during the period in which the supply of raw material gas is stopped.

[Effect]

According to the method of the present invention, the supply of raw material gas is stopped intermittently, and the light irradiation is stopped and the reaction chamber is evacuated during the period when the supply is stopped. Although deposited species or activated species generated by photoreaction in the vicinity of the substrate may reach the vapor phase growth substrate, they are diffused and removed before reaching the light introduction section. The generation of deposits or attachments is thereby avoided, and as a result, light irradiation onto the substrate to be vapor-phase grown can be performed efficiently, and thin film formation can be achieved through the photochemical reaction. It can be formed to a film thickness of .

〔Example〕

An embodiment of the present invention will be described in detail with reference to FIG.

In the figure, (1) is a reaction chamber, in which a substrate (2) to be subjected to vapor phase growth, such as a semiconductor wafer, is placed, and a heater or the like is used to heat it to a required temperature, for example, 200°C below 300°C. It is placed on a placement stand (4) comprising means (3). Reference numeral (5) denotes a raw material gas supply port, which is connected to the raw material gas supply source (6) via an opening/closing means (7) for supplying and stopping the supply of raw material gas.

Further, (8) is an exhaust port connected by an exhaust pump to exhaust the inside of the reaction chamber. (9) is a light source such as an ultraviolet lamp or excimer laser, and (10) is a window provided in the reaction chamber (1), which is made of a transparent plate such as quartz glass that transmits the light from the light source (9) and is airtight. It is sealed and sealed. This: g(1
0) is itself considered to be a lens system, but the light source (
A lens system is placed on the optical path from the light source (9).
The light from the vapor phase growth substrate (2) is focused at or near the surface of the substrate (2).

Further, a cooling means (11) such as a cooling pipe to which cooling water is supplied is arranged in the window (10) to cool the window (lO).

In such a configuration, for example, when a polycrystalline silicon film is vapor-phase grown on the substrate (2) to be vapor-phase grown, a source gas such as monosilane S is used together with a carrier gas Hz.
iH+ is supplied from the raw material gas supply port (5), and the substrate (2) to be subjected to vapor phase growth is heated to, for example, 200° C. by the heating means (3). On the other hand, light is irradiated from the light source (9). In this way, the silicon thin film can be grown on the substrate (2) by photodissociation, that is, a photochemical reaction, of the source gas efficiently by the light focused on or near the surface of the substrate (2). However, especially in the present invention, the pressure programming diagram in the reaction chamber (1) is shown in FIG.
1 is maintained at the pressure p1 for performing the required photochemical CVD for a predetermined period τ1, and at this time, light is irradiated from the light source (9) to form a thin film on the substrate (2). At τ2, first, the light irradiation from the light source (9) is cut off, and then the exhaust pump is operated from the exhaust port (8) to exhaust the inside of the reaction chamber (1) to the required pressure p2.
Reduce the pressure to After that, in the next section τ3, the exhaust is stopped and the raw material gas is supplied, and the raw material gas is supplied with light irradiation from the light source (9), and the inside of the reaction chamber (1) is brought to the required pressure p1, and the substrate ( 2) Perform vapor phase growth of a thin film on top. Repeat these operations.

In addition, during this vapor phase growth, the substrate (2) is rotated so that a uniform thin film can be formed on the substrate (2), or two layers perpendicular to each other in the direction along the surface of the substrate (2) are rotated.
This is done by moving in the direction.

In the CVD method described above, the window (1) in the reaction chamber (1) is
0), no deposits are attached, several thousand or several μm
It was possible to form a thin film without causing any inconvenience to light irradiation.

In the above example, the light source (9) is connected to the reaction chamber (1).
When the light source is installed outside, but when it is installed inside the reaction chamber +1), it is possible to avoid the occurrence of deposits or adhesion on the wall surface of the light source or the window or introduction part of the light source.

In the above example, the method of the present invention is applied to the formation of a silicon thin film, but the method of the present invention can be applied to the formation of various other thin films.

Further, as an optical lens system for focusing the light from the light source (9) on the base (2) J:, for example, a compound lens system consisting of a combination of a concave lens system and a convex lens system is used, and the distance between the two is changed. ) It is also possible to provide a function to move the irradiation position on the substrate (2) and further rotate the placement table (4) of the substrate (2) so that the thin film can be vapor-phase grown uniformly on the substrate (2). .

In addition, in the illustrated example, the vapor phase growth substrate (2) is arranged at the lower part of the reaction chamber (1), and the raw material gas is supplied from above, but the arrangement may be changed in various ways. For example, the substrate (2) can be placed upward, with its thin film forming surface facing downward, and the raw material gas supply section can be placed below other parts, for example.

〔Effect of the invention〕

As described above, according to the present invention, a thin film is vapor-phase grown on the substrate (2) by irradiating light to cause a photoreaction on or in the vicinity E of the substrate (2) to be vapor-phase-grown. However, over time, the deposited species or active species diffuse and before they spread to the light source introduction window (10) of the reaction chamber (1), the reaction chamber (1) is evacuated and the active species are once removed. As a result, the generation of deposits M1 or deposits on the window (10) and the walls of the reaction chamber (1) is avoided, and therefore the required 15% deposits on the substrate (2) are avoided. In addition to being able to reliably produce a thin film of good quality, the cleaning work for cleaning the window after this vapor phase growth is extremely simplified, and the frequency of window replacement can be reduced.
Work efficiency is improved.・′

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an example of Yi'R that implements the method of the present invention, and FIG. 2 is an explanatory diagram of its operation. +11 is a reaction chamber, (2) is a substrate to be subjected to vapor phase growth, (3) is a heating means, (4) is a placement table, (10) is a window, (9) is a light source, and (8) is an exhaust port.

Claims (1)

[Claims] In a method for forming a thin film by photochemical vapor deposition, supply of a raw material gas to a reaction chamber in which a substrate to be vapor-deposited is placed, irradiation with light, and exhaust of the reaction chamber are performed intermittently, respectively, and supply of the raw material gas. A method for forming a thin film by photochemical vapor deposition, characterized in that light irradiation is stopped and exhaust is performed during a stop period.