JPH0211011B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a thin film, and in particular, in forming a transparent conductive film on an amorphous hydrogenated silicon layer using a magnetron sputtering method. The present invention relates to a method for performing magnetron sputtering without damaging the surface of an amorphous hydrogenated silicon layer.

[Prior art]

Recently, vacuum evaporation, sputtering, CVD, and the like have been widely used as thin film forming methods. Among these methods, the sputtering method has low deposition temperature, high film adhesion strength, and the composition of the formed film that relatively faithfully reproduces the composition of the target, so it is possible to change the target material. It has the advantage of being able to easily form various thin films, and is used in the field of semiconductor device manufacturing.
This is a relatively commonly used method.

When forming a semiconductor thin film using this sputtering method, a magnet was attached to the back surface of the target to increase the deposition rate, and a magnetic field of about 250 gauss was created on the target surface. The so-called magnetron sputtering method is widely used.

However, when a transparent conductive film is formed on an amorphous hydrogenated silicon layer using this magnetron sputtering method, there is a problem that the amorphous hydrogenated silicon layer is damaged and the device characteristics deteriorate. It was happening.

For example, as shown in the cross-sectional schematic diagram in Figure 1,
A metal electrode 2 made of a thin chromium film formed on an insulating glass substrate 1 and indium tin oxide (ITO)
In forming a photoelectric conversion element with a sandwich structure in which a photoconductor layer 4 made of an amorphous hydrogenated silicon (a:SiH) layer is sandwiched between a transparent electrode 3 made of a thin film, amorphous hydrogenated When the magnetron sputtering method described above is used in the process of forming an ITO thin film on a silicon layer, there are disadvantages in that dark current increases and device characteristics deteriorate (brightness ratio decreases).

This is because the surface of the amorphous hydrogenated silicon layer is damaged by particles during the sputtering process for forming the ITO thin film.
Si and H, Si and Si in amorphous hydrogenated silicon layer
The bond between them is broken and the amorphous silicon hydride is activated. As a result, the carriers generated are likely to be captured by activated Si and H, resulting in a shortened carrier life. It is also considered that the potential barrier at the interface between the ITO thin film and the amorphous hydrogenated silicon layer becomes lower, making it easier for electron injection from the ITO thin film side.

In order to eliminate such inconveniences, a method has been considered in which the electric power at the initial stage of film deposition is lowered to near the lower limit that can be discharged in the sputtering process. Although this method can reduce damage to the surface of the amorphous hydrogenated silicon layer and improve device characteristics, this method dramatically slows down the deposition rate, lengthens the deposition time, and increases productivity. There was a problem with poor sex.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
The purpose of this invention is to reduce damage to the surface of the amorphous silicon hydride layer and increase the deposition rate when forming a transparent conductive film on the amorphous silicon hydride layer by magnetron sputtering.

[Structure of the invention]

In order to achieve the above object, the present invention provides a thin film forming method for depositing a transparent conductive film on an amorphous hydrogenated silicon layer, which comprises increasing the magnetic field on the surface of the target on which the transparent conductive film is to be formed to 500 Gauss. (Gauss) or higher, and deposits a transparent conductive film by magnetron sputtering, which further increases the magnetic field (2 to 3 times that of conventional methods). 500 Gauss or more), it is possible to lower the applied voltage between the target and the substrate, and the bonds between Si and H and Si and Si in the amorphous hydrogenated silicon layer are less likely to be broken by sputter particles. This invention was developed with the focus on the ability to prevent activation of amorphous silicon hydride, and the present invention involves forming a magnetic field of 500 Gauss or more on the surface of a target in a sputtering method.

As a result, the same current can be obtained with a lower applied voltage, so the energy given to the particles, that is, the deposition rate, which is proportional to the applied voltage, can be deposited without decreasing, and the surface of the amorphous hydrogenated silicon layer can be damaged. can be given very little.

〔Example〕

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

First, an example of a sputtering apparatus for carrying out the sputtering method of the embodiment of the present invention is shown in FIGS. 2 and 3.

As shown in FIG. 2, this apparatus consists of a substrate holder 12 formed in a vacuum chamber 11 and a substrate 1 for forming a thin film placed on the substrate holder 12.
3, the target section 14 is arranged to face the target section 3.
It further includes a DC power supply 15 for applying voltage, a vacuum evacuation system 16 for evacuating the inside of the chamber, and a gas supply system 17 for introducing a predetermined gas into the chamber. Equipped with:

Further, as shown in an enlarged view in FIG. 3, the target section 14 includes a target 18, a back plate 19, and samarium cobalt (SmCo ₅ ).

Next, a method for forming a photoelectric conversion element using this apparatus and a magnetron sputtering method according to an embodiment of the present invention will be described.

First, a thin chromium film with a thickness of approximately 3000 Å is deposited on a glass substrate using electron beam evaporation. At this time, the substrate temperature is 250°C. Next, it is divided into desired shapes using photolithography to form a plurality of chromium electrodes.

Furthermore, plasma chemical vapor deposition method (plasma CVD method)
An amorphous silicon layer serving as a photoconductor is deposited to a thickness of about 1 μm. The production conditions were to use monosilane (SiH ₄ ) gas and to maintain a substrate temperature of 200°C to 200°C.
300℃, pressure 0.2~0.5 Torr, power density 20~
It is 70mw/ ^cm2 .

Subsequently, using the above-mentioned apparatus, an indium tin oxide film of about 0.1 μm is deposited as a transparent electrode. The film deposition conditions were as follows: indium tin oxide (90 mol% indium oxide In ₂ O ₃ + 10 mol% tin oxide) as the target.
SnO ₂ ), oxygen partial pressure 6×10 ^-5 Torr, total pressure (argon Ar + oxygen O ₂ ) = 4×10 ^-3 Torr substrate temperature
10~40℃, power is 145W (290V x 0.5V) 0.1μ
The film is deposited until it reaches m.

And finally, oxygen + argon (Ar) at 200℃
Heat treatment is carried out for about 30 minutes in an atmosphere or air.

The photoelectric conversion element thus formed has a current value of 6×
It shows good characteristics, being blocked around 10 ^-9 A/cm ² .

For comparison, a ferrite magnet was used as in the conventional magnetron sputtering method, and a magnetic field of about 270 Gauss was formed while generating almost the same amount of power as the embodiment of the present invention (144 W = 380 V x 0.38 A). in
Curve B shows the current-voltage characteristic curve in the dark of the photoelectric conversion element when an ITO thin film is deposited. It can be seen from the curve that the current increases with the applied voltage.

Further, curve C shows the current-voltage characteristic curve of a photoelectric conversion element in which an ITO thin film was formed using a conventional magnetron sputtering method and using a power of 17 W at the initial stage of film deposition.

The characteristic curve A of the photoelectric conversion element formed by the method of the embodiment of the present invention shows almost the same characteristics as the curve C, and the film deposition rate is much higher than that of the curve C.

In this way, by increasing the magnetic field, damage to the surface of the amorphous hydrogenated silicon layer caused by spatter particles of the transparent conductive film material can be suppressed, and the film deposition rate can be reduced without impairing the properties of the device. It has now become possible to fabricate a transparent conductive film with high productivity.

In addition, in the example, the magnet disposed in the magnet part in the sputtering device was replaced with a rare earth magnet instead of the conventional ferrite magnet, but the method is not necessarily limited to this method, and other methods may be used. It is also possible to strengthen the magnetic field by

In addition to SmCo ₅ , magnets include yttrium cobalt (YCO ₅ ), cesium cobalt (CeCo ₅ ), and plutonium cobalt (PrCo ₅ ).
Other magnets may also be used.

Furthermore, the magnetic field at the target surface is 500
It is desirable to maintain it at a level of 700 Gauss or above Gauss.

〔Effect of the invention〕

As explained above, in the present invention, when a transparent conductive film is formed on an amorphous hydrogenated silicon layer by magnetron sputtering, the magnetic field on the target surface of the transparent conductive film material is set to 500 Gauss or more. This prevents the amorphous silicon hydride layer from being damaged by spatter particles of the transparent conductive film material.
The bond between Si and Si is broken by sputter particles, suppressing the activation of amorphous silicon hydride, and making it transparent and conductive without impairing device properties or slowing down the film deposition rate. It becomes possible to create a film.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional schematic diagram of a normal photoelectric conversion element, Fig. 2 is a diagram showing a sputtering device used in the sputtering method of the embodiment of the present invention, Fig. 3 is an enlarged view of the main parts of the sputtering device, and Fig. 4 is the current of the photoelectric conversion element formed by the method of the embodiment of the present invention and the photoelectric conversion element formed by the conventional method.
FIG. 3 is a diagram showing a voltage characteristic curve. DESCRIPTION OF SYMBOLS 1...Glass substrate, 2...Metal electrode, 3...Transparent electrode, 4...Photoconductor layer, 11...Vacuum chamber, 12...Substrate holder, 13...Substrate, 14
...Target section, 15...DC power supply, 16...
Vacuum exhaust system, 17... Gas supply system, 18... Target, 19... Back plate, 20... Magnet, A... Current-voltage characteristics of photoelectric conversion element formed using the sputtering method of the embodiment of the present invention Curves B, C...Current-voltage characteristic curves of photoelectric conversion elements formed by conventional methods.

Claims (1)

[Claims] 1. A thin film forming method for depositing a transparent conductive film on an amorphous hydrogenated silicon layer, the method comprising: applying a magnetic field of 500 gauss on the surface of a target on which the transparent conductive film is to be formed; A method for forming a thin film, characterized in that a transparent conductive film is deposited by magnetron sputtering while maintaining the above conditions.