JPS6314420A - Manufacture of thin film - Google Patents

Abstract

PURPOSE:To manufacture the defectless non-single crystal film of good quality by a method wherein the formation of a thin film and a plasma treatment using hydrogen or halogen compound are performed repeatedly. CONSTITUTION:The formation of a thin film and the plasma treatment using hydrogen or halogen compound are performed repeatedly. For example, a glass substrate is heated up to 250oC in a glow discharge device, SiH4 of reaction gas and GeH4 of 5 SCCM respectively and H2 of 100 SCCM are allowed to flow, and the pressure of the glow discharge device is maintained at 0.5 Torr. Then, SiH4 and GeH4 are allowed to flow intermittently, H2 is permitted to flow continuously, and high frequency power of 10W is applied continuously. In addition to the above-mentioned process A, a flush annealing operation is performed intermittently while a plasma treatment is being performed as the process B, and an a-SiGe : H film is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a thin film of a non-single crystal material, and particularly to a manufacturing method suitable for forming a silicon compound thin film.

[Conventional technology]

asi manufactured by glow discharge method using SiH4:
H (amorphous silicon) solar cells have a photoelectric conversion efficiency of over 10%. In order to further improve the efficiency, it is effective to stack solar cells made of materials with different optical band gaps, and from this point of view, the above a-8i:H
A combination of a-8ioe and other substances is considered, for example, in the description of JP-A-55-8092, a-8ioe
:H.

In the description of JP-A-55-151329, a-8i
F:H and a mixture of these a-8iGeF:
The manufacturing method of H is described in Japanese Patent Application Laid-Open No. 57-78183. However, since it is not possible to form a high-quality film with these substances using only the conventional glow emission method, a film formation method combining sputtering has been proposed, for example, as in JP-A-58-10817. Currently, sufficient film quality is not obtained.

Hydrogen plasma treatment is a common method for improving film quality. JP-A-59-72776 discloses that after forming the pj curve (or 0 layer), it is exposed to hydrogen plasma, and then the i layer is formed.
JP-A-59-35016 discloses that a microcrystalline film is formed at high temperature and then subjected to hydrogen plasma treatment. In addition, as a method for more effective plasma processing, JP-A-57-
There are methods described in Japanese Patent Application Laid-open No. 181117 and Japanese Patent Application Laid-open No. 160124/1983.

[Problem that the invention seeks to solve]

a-8iGe, a-8i F, a-8i C, a
Amorphous Si such as -8iN, a -8iSn
Since the compound has a different covalent bond radius and air negativity with s Si, it has the property of being more likely to cause defects than a-8i.

In film formation using conventional glow radiation, sputtering method, etc.
As the composition ratio of substances other than Si increases, the number of defects increases dramatically, and it is currently difficult to produce a high-quality film using this method alone. Defects in the film are H, F, C1
However, since the bonding energy between these and Si is different from the bonding energy with other halogen substances, forming a film using the glow discharge method tends to result in termination on only one side. There is.

Therefore, if the glow discharge method or sputtering method is used in conjunction with the Dame no Ike method of terminating a halogen substance such as H or F, it is possible to produce a high-quality material without any defects.

For example, H'! A hydrogen plasma treatment method is available as a means for i-termination, but its drawbacks are that the amount of hydrogen introduced is small and the concentration of introduced hydrogen is depth dependent, and the amount introduced becomes smaller as the distance from the surface increases.

Therefore, all but one surface layer is not terminated with H, and the defects remain as they are. In order to increase the amount of hydrogen introduced, it is possible to increase the hydrogen plasma treatment temperature (JP-A-57-181117, etc.), but if a transparent conductive film is formed, these substances will diffuse and damage the cell. This will have a negative impact on the characteristics.

The object of the present invention is to eliminate the above-mentioned drawbacks. The objective is to produce a high quality non-single crystal film without defects.

[Means for solving problems]

The above purpose is to form an extremely thin non-single crystal film and then perform plasma treatment using a halogen substance such as hydrogen or fluorine. If this process is repeated, a good quality film with no defects will be formed. The thickness of the layer formed at one time depends on the depth to which sufficient hydrogenation can be achieved in the subsequent plasma treatment, but it is possible to hydrogenate or halogenate to a deeper depth if the treatment is performed at high temperature and with a large amount of energy. is clear. However, in reality, although there is a difference in the bonding energy strength between the constituent substances and the hydrogen or halogen substance, it is necessary to carry out the process at a temperature below the temperature at which the hydrogen or halogen substance once bonded is thermally re-released.
For example, in the case of a-8i:H, the thickness is preferably 300C8 degrees or less, and the J thickness at this time is preferably 100 angstroms or less. In the case of plastic treatment with a halogen substance, although the temperature varies depending on the bond energy, the film thickness is preferably less than the above, and this method is applicable to all non-single crystal films.

If it is necessary to increase the amount introduced, flash annealing, laser annealing, etc. may be performed during plasma processing to increase the temperature only on the surface. This also shortens the processing time.

[Operation] Hydrogenation or halogenation can be performed at low temperatures in order to plasma-treat extremely thin films. Furthermore, since defects caused by the glow discharge method can be completely compensated for, a film of good quality can be formed. Furthermore, this is a problem with the glow discharge method. Non-uniformity in film quality in the film thickness direction is also eliminated, and even when the film is thin, the same film quality as when it is thick can be obtained.

If only the surface layer is heated by flash annealing, laser annealing, etc. during plasma processing, a densified amorphous film will be formed.

Therefore, films with different optical gaps are formed.

Furthermore, the film thus formed is not only thermally stable and durable, but also exhibits significantly less photodegradation.

〔Example〕

The present invention will be explained in detail below.

Example 1 This will be explained using FIG. 1. A glass substrate is heated to 250C in a glow discharge device, and 3iH, which is a 1-reactive gas, is heated to 250C.
4 and G e H4 are each 58CCM%H1 is 1
The flow is 1005 CC and the pressure is maintained at 0.5 Torr.

SiH4 and G e H, were flowed intermittently by an ultra-high-speed mass flow meter, while % H, was flowed continuously;
A high frequency power of 10 W is continuously applied.

FIG. 1 shows the process for each hour, and in this example, only the process personnel were operated.

When SiH4 and GeH4 were flowed for 20 seconds and paused for 40 seconds, film formation was performed for 25 minutes, and a-8iGe:HJ of 1000 angstroms was formed. It can be seen from this that about 40 angstroms are formed in one film formation. When comparing the film thus formed with the same film formed in 1°J by continuously flowing SiH4 and GeH,i under the same conditions, it was found that although the optical gap remained the same, the flow was intermittently for 1° of light guide. The difference was about one order of magnitude more clearly.

Example 2 Film formation was carried out in the same manner as in Example 1, but step B in FIG.
As shown in Figure 2, when flash annealing was performed intermittently during plasma treatment, the optical gap became smaller and a film was obtained in which the conductivity hardly changed even with continuous light irradiation.

The optical gap depends on the flash annealing irradiation time, and the longer the irradiation time, the smaller the value. For example, if flash annealing is not performed, 1.50e
When the optical gap was V, it became 1.45 eV when irradiation was performed for 20 mIJ seconds at 1 second intervals, and 1.40 eV when it was 50 msec.

〔Effect of the invention〕

According to the present invention, in order to plasma-process a thin film after heating, plasma processing in the same temperature range as the film-forming temperature, such as 200 to 300 C, is effective.

Further, processing can be performed with low energy without causing damage due to plasma, and defects can be completely compensated for regardless of the film thickness.

By heating only the surface layer during plasma treatment, it is possible to control the film properties such as the optical gap, which not only provides thermal stability but also significantly reduces photodeterioration.

[Brief explanation of drawings]

FIG. 1 is a process diagram for forming a non-single crystal film according to the present invention.

Claims (1)

[Claims] 1. A method for producing a thin film, which comprises repeating the formation of a thin film and the plasma treatment using hydrogen or a halogen substance. 2. Claim 1, characterized in that the thickness of the thin film formed each time is 100 angstroms or less
2. Method for producing a thin film described in Section 1. 3. The method for manufacturing a thin film according to claims 1 and 2, characterized in that in the steps of forming the thin film and the plasma treatment, plasma is continuously discharged. 4. The thin film manufacturing method according to claim 1, wherein in the plasma treatment step, only the surface layer of the formed thin film is heated. 5. Claim 4, wherein the heating method is flash annealing or laser annealing.
2. Method for producing a thin film described in Section 1. 6. The thin film manufacturing method according to claim 5, wherein the heating is performed intermittently.