JPH03214724A - Thin-film manufacturing method - Google Patents

Abstract

PURPOSE:To enable each of a plurality of types of raw material gases to be dissociated under optimum conditions by passing the raw material gases to be introduced into a reaction bath through an independently temperature- controlled conduit. CONSTITUTION:When producing a thin film by dissolving a reaction gas obtained by mixing a plurality of raw material gases 41 and 42 within a reaction bath 1 for depositing a degradation generated object, at least one raw material gas is introduced into the reaction bath 1 through independently temperature- controlled conduits 51 and 52, thus giving a dissociation energy which is optimum to the raw material gas and generating a radical which is best suited for film formation. Thus, even if raw material gases, where a plurality types of raw material gases are mixed, are cracked, generation of an undesirable radical, etc., can be prevented, dissociation can be made under optimum conditions, and the film quality of the thin film can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing thin films such as amorphous silicon-based thin films that are used as materials for non-quality silicon solar cells, amorphous silicon thin film transistors, and the like.

[Conventional technology]

Recently, the field of application of thin films has been expanding, especially in the field of semiconductor industry. Such thin films include thin films of non-quality silicon, polycrystalline silicon, silicon oxide or silicon nitride. CVD technology is generally used as a method for manufacturing thin films, in which dissociation energy is applied to a raw material compound gas to deposit a thin film of a desired composition made of decomposition products. For example, a method for producing a non-quality silicon-based thin film is to excite gas molecules of a silane-based raw material gas using plasma discharge, thermal energy, laser, ultraviolet light, or other light, decompose them, and deposit them on a substrate to form a thin film. Methods of forming are known.

[Problem to be solved by the invention]

A-SiG is a non-quality material that has a desired optical band gap by adding elements other than silicon to the thin film material.
In the case of forming a compound semiconductor such as e:H or a-SiC:H, germane (GeH*), methane (CH*), etc. are used in addition to silane (SiH*) as a raw material gas. In addition, when doping non-quality materials with boron, phosphorus, etc., diborane (BJa) and phosphine (PHs)
is added to the reaction gas. When using a reaction gas that is a mixture of such different types of raw material gases, energy for decomposing the raw material gases is given to the gas that is the most difficult to decompose among the raw material gases so that it can be decomposed. For this reason, gases with low decomposition energy cannot be dissociated under optimal conditions, resulting in the generation of undesirable radicals and the like.

An object of the present invention is to provide a thin film manufacturing method that dissociates each of a plurality of types of raw material gases under optimal conditions.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a thin film manufacturing method in which a reaction gas obtained by mixing a plurality of raw material gases is decomposed in a reaction tank and decomposition products are deposited, in which at least one raw material gas is It shall be introduced into the reaction tank through a temperature-controlled conduit.

[Effect]

By passing raw material gases with different dissociation energies through conduits whose temperatures are independently controlled, the optimal dissociation energy can be given to the raw material gases, and radicals most suitable for film formation can be generated. Therefore, even when decomposing a raw material gas made by mixing a plurality of types of raw material gases, generation of undesirable radicals etc. is prevented and a healthy thin film is formed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an apparatus for an embodiment of the present invention, in which a substrate temperature control heater 2 is provided inside a vacuum chamber (reaction chamber) 1 having a carrier gas inlet 11 and a gas exhaust port 12. A substrate 3 is placed on top of it. Two types of raw material gases are blown onto this substrate from a plurality of gas introduction ports 41.42 through connected raw material gas reaction tubes 51.52. Raw material gas reaction tube 51. 52 is covered with a protective cover 6 and can be controlled to an arbitrary temperature by a reaction tube temperature control heater 7, so that it is possible to freely control the dissociation of the raw material gas passing through the inside. By using this apparatus, for example, when forming an alloy semiconductor such as non-quality silicon germane from two types of gases such as silane and germane having different dissociation energies, the two types of gases can be separated into separate source gas reaction tubes 51 and 52. The gases can be introduced into the vacuum chamber 1 and dissociated at different optimum temperatures.

This makes it possible to generate radicals most suitable for film formation from each gas, so for example, the dissociation temperature of silane can be set to 90°C.
0-1200℃, germane dissociation temperature 600-80℃
When the temperature is controlled at 0°C, by controlling the flow rate ratio of the raw material gas, the optical bandgap Eg is 1.3 to 1.3°C, as shown in FIG. 104-10 in the 7eV range
-' It is possible to form a silicon germane film having a photoconductivity σph of S/cI1 and a photodark conductivity ratio σph/σd of 5 digits or more. At this time, hydrogen is flowed as a carrier gas from the carrier gas inlet 11 to form a laminar flow in the vacuum chamber. By changing the raw material gases to silane and methane, it is possible to create silicon carbide, and by changing the raw material gases to silane and ammonia, it is also possible to form silicon nitride. As the type of carrier gas, it is also possible to use gases such as He and N8. Further, when forming a film from three source gases, that is, when doping silicon germane, silicon carbide, etc., three source gas reaction tubes may be used.

FIG. 3 is a sectional view showing an apparatus according to another embodiment of the present invention, which differs from the apparatus shown in FIG. 1 in that the source gas reaction tube 51.
The protective cover 6 surrounding the reaction tube temperature control heater section 7 that heats the reaction tubes 52 is exhausted from the preliminary exhaust boat 61, and the two raw material gas reaction tubes 51. 52 is that a heat reflecting plate 62 is provided between them. Since the heater section was separately vented, it was possible to prevent contamination of impurities from the heater, and by providing the heat reflecting plate 62, the independence of temperature control of the heater 7 for controlling the temperature of the reaction tube was greatly improved.

FIG. 4 shows an apparatus for yet another embodiment of the present invention, in which the interior of a vacuum chamber 1 having a first raw material gas inlet 41, a second raw material gas inlet 42, and an exhaust port 12 is shown. A heater 7 for controlling the temperature of the reaction tube is connected to the first raw material gas inlet 41.
A raw material gas reaction tube 51 having a diameter is connected thereto, and an RF or DC electrode 8 is installed beyond that. A susceptor 21 having a heater 71 is installed to face this electrode, and a source gas reaction tube 51 is placed on the substrate 3 above the susceptor 21.
A thin film is formed by plasma CVD using gas dissociated by passing through and gas supplied through the second raw material gas inlet 42 as raw materials. For example, P-type a-SiC using silane, methane, diporane, and hydrogen as raw material gases:
When producing an H film, by supplying diborane diluted with hydrogen through the raw material gas reaction tube 51, it is possible to significantly improve the boron decomposition ratio. Reaction tube 51
For example, when heating the temperature to 500-1000℃, the fifth
As shown by ● in the figure, the activation degree of boron can be improved by more than one order of magnitude compared to the conventional plasma CVDO example ○. In addition, if two or more types of gases are desired to react, a second source gas reaction tube may be provided. Although this embodiment combines plasma CVD and thermal CVD, optical CVD and thermal CVD may also be combined.

The raw material gas reaction tubes of each device must be made of materials that can withstand high temperatures and do not release impurities, such as quartz or silicon carbide. A material such as alumina is used.

〔Effect of the invention〕

According to the present invention, by passing the raw material gases introduced into the reaction tank through independently temperature-controlled conduits, it is possible to give each gas the necessary dissociation energy and perform decomposition under optimal conditions. Ta. For this reason, it is possible to independently control the decomposition of raw material gases with different dissociation energies, and to produce composite materials such as alloy semiconductors made of component elements deposited from each raw material gas.
The film quality of s could be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an apparatus for one embodiment of the present invention;
The figure shows the relationship between the optical dark conductivity and the optical bandgap of the silicon germane film produced using the apparatus shown in Figure 1, and Figure 3.
4 is a cross-sectional view of an apparatus for different embodiments of the present invention, and FIG. 5 is a-SiC manufactured with the apparatus of FIG. 4.
: It is a relationship diagram between the characteristics of the H film and the amount of diborane gas added. 1: Vacuum chamber, 3: Substrate, 41, 42: Raw material gas inlet,
51.52F raw material gas reaction tube, 7: Heater.

Claims (1)

[Claims] 1) In a thin film manufacturing method in which a reaction gas formed by mixing multiple raw material gases is decomposed in a reaction tank and decomposition products are deposited, at least one raw material gas is introduced into the reaction tank through an independently temperature-controlled conduit. A thin film manufacturing method characterized by introducing.