JPS5813006B2 - Sankabutsuhandoutaihakumakuno Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide a manufacturing method for producing a semiconductor thin film with good reproducibility and having any resistance value in a wide range from low resistance to high resistance.

Conventionally, oxide semiconductors such as ZnO, TiO2, and SnO2 are materials that have a wide range of uses, mainly in the electronics industry, such as transparent electrodes, fluorescent materials, and thermistors, and various thin film technologies have been provided to date. , with a few exceptions, has become well known.

The present invention relates to this exceptional matter, and specifically relates to valence control of semiconductors.

Indeed, this problem is a practical problem, especially regarding obtaining a desired semiconductor thin film with good reproducibility.

For example, ZnO, Ti02, In203, etc. are known as n-type semiconductors, and are generally known to be produced when metal or metal ions are in excess in an ionic crystal that deviates from the stoichiometric composition.

Therefore, although it is theoretically possible to obtain a semiconductor thin film by thinning the film by vacuum evaporation, the reproducibility is poor.

This is mainly because when known evaporation methods such as electron beam heating and resistance heating are used for oxide powders such as ZnO and Ti02, a metal-excess state can be created due to the thermal dissociation phenomenon of the oxides that inevitably occur. However, it is difficult to obtain reproducibility sufficient for practical use, and methods of valence control are usually used.

Nesa Glass, which is well known as a transparent electrode, is made by doping a glass substrate with Sb203 based on Sn02, and has a sheet resistance of about 10Ω/cr' and a visible light transmittance of 80% or more. are obtained.

The manufacturing method for this thin film is called the spray method, and Sn
, a method of spraying a solution of Sb chloride, which has the disadvantage that low melting point materials such as plastics cannot be used as the substrate material, and in terms of reproducibility, although it is more practical than the vacuum evaporation method, it is not sufficient. Moreover, it has the disadvantage that substrate temperature control is very strict and it is difficult to obtain a uniform film on a large area substrate.

The present invention is intended to eliminate the above-mentioned drawbacks, and provides a manufacturing method for obtaining an oxide semiconductor thin film with good reproducibility and having any resistance value in a wide range from low resistance to high resistance. be.

Specifically, the present invention is a method of controlling electrical conductivity by using C atoms for valence control.

The present invention will be explained in detail below.

The present invention includes Al203, In203, Sb203, Bi2
It has the effect of lowering the resistance value in 03, As203, Cr203, etc., and has the effect of lowering the resistance value in v205, Ta205, etc.
l) For the compound of the form 205, it has the effect of giving a higher resistance value than that of the pure one, and in any case relates to a method by which the resistance value can be controlled.

Furthermore, the above-mentioned thin film can be formed on any substrate depending on the purpose, such as glass, plastic, and semiconductors such as Si.

This will now be explained with reference to FIG. 1, taking an example of Al203.

This FIG. 1 is an example of an apparatus for carrying out the present invention.

In the vacuum container 4, the substrate 2 and the evaporation source are arranged facing each other.

The evaporation source is a known electron beam evaporation source, resistance heating evaporation source,
Any configuration such as an induction heating evaporation source may be used.

For convenience of explanation, a resistance heating method was adopted.

Evaporated substance 1 (In case of Al20: Al, In2
When making Qa, high purity metals such as In are commonly used.

] is vaporized by the heating power source 1 via the insulated introduction terminal 15.
1, the boat, basket, etc. 5 is electrically heated.

Although one end of the evaporation source is DC grounded, this is not necessarily the case, and it may be grounded via a capacitor.

Although the substrate 2 is shown held by a substrate holder 6, for example, when it is desired to form a coating on a plastic film, a film feeding and winding mechanism may be used instead. Generally, when forming a film on an insulating substrate, measures such as arranging an electrode with openings such as a mesh on the front side of the substrate, on the evaporation source side, will naturally be taken depending on the type and shape of the substrate. The explanation has been simplified.

An electrode 3 for plasma formation is provided in a space between the evaporation source and the substrate 2.

Due to the plasma generation method, it is difficult to confine the glow in a limited space.If the vacuum container 4 is made of metal and the glow is generated using the high-frequency electrode 3, the electrode shape may be shaped like a coil with one end open, for example. When this occurs, a dense region is created inside the coil, and the plasma is generated over almost the entire area, but the purpose of the present invention is to form plasma in at least the above-mentioned space.

The method of generating plasma using the Gujiichi discharge is not limited to the high frequency method, and may be any method such as normal DC glow or hot cathode glow, but a typical high frequency method will be described.

This is composed of a high frequency power source 14 (not shown, which usually includes a matching box for efficiently transmitting power) for generating high frequency glow and a high frequency electrode 3.

The high frequency electrode 3 often has a spiral structure made of aluminum or copper pipe, but the shape may be cylindrical or other appropriately designed shape.

The vacuum container 4 is made of glass, stainless steel, or the like, and is connected to a vacuum evacuation line 12 made of, for example, an oil diffusion pump, a water-cooled trap, and an oil rotary pump.

Further, variable leak valves 7 and 8 are connected to the vacuum container 4 and connected to a gas source (not shown).

Note that the substrate 2 is biased to a ground potential or a negative potential by a DC power supply 13.

When an insulating material is used as a substrate, it is common to apply a substrate potential to the electrodes such as the mesh mentioned above.

The basic operation will be explained by taking as an example the case where Al203 is created on a glass substrate using this apparatus.

The inside of the vacuum container 4 is in advance IX10-
5 to IX10-6 mmHg.

Since this degree of vacuum affects the coating, it should be evacuated within the above-mentioned range for practical purposes.

After that, by adjusting the variable leak valves 7 and 8, the
2 for example 8X10-'mmHg-C02 to 3X10-
``Stabilize the partial pressure to 1 mnHg.

You are free to control the pressure in the system by converting it into nitrogen, or to set the conditions and use the uncorrected value.
The reproducibility is the same in either case.

The purity of the introduced gases 029 and CO210 is sufficient when they are introduced directly from a commercially available pressure cylinder through a pressure reducing valve and a tank reservoir (not shown), but depending on the purpose, gases for the purpose of removing water vapor may be used. You are free to add purification equipment, etc.

In this state, the high frequency power supply 14 is operated to generate a high frequency discharge.

A dark area called an ion sheath is formed near the high-frequency electrode 3.

Although it depends on the conditions, the area where whiteish light emission is already observed is the plasma area, and the key is to expose the metal vapor described later in this area, so it is natural that the geometry, slits, etc. should be devised for this purpose. It is.

A placed on top of the tungsten basket 5! The particles are vaporized by adjusting the external heating power source 11.

As a result of interaction with the plasma, this vapor flow forms an Al203 film on the substrate, and by adjusting the ratio of 02/CO2, an appropriate amount of C atoms are included, which become donors and improve the conductivity. Thus, the desired oxide semiconductor thin film can be obtained.

It was also confirmed that CO can be used as a gas for electron valence control, but due to its toxicity, it would be better to use CO2 in practice.

Note that the oxide film whose valence could be controlled with CO2/CO is Al2
Besides 03, sb2o35In2032B1203,A
(M
metal) 203 (Metal) 205.

Furthermore, the higher the voltage applied to the substrate 2, the better it is not necessarily; as a general tendency, in order to increase the adhesion between the substrate and the film, it is better to have it as high as about IKv or higher (although it varies depending on the material, If the voltage exceeds ~4KV, the adhesion strength will actually decrease), but the number of defects in the film will increase, which will have a negative effect on the semiconductor properties, so it is appropriate to apply a voltage of 200 to 500V (a negative value with respect to the evaporation source). It is.

The range in which the resistance value can be minimized within the range of the partial pressure ratio of 02 and CO2, and 02 and CO2, cannot be uniquely determined by the values of the configuration parameters of the present invention, and the purpose is limited to obtaining the minimum value. Therefore, we did not define the scope.

The relationship between the surface resistance of Al203 and CO2 partial pressure obtained by the present invention is shown in FIG. 2, and the results obtained by the conventional method are shown in FIG. 3, and the reproducibility and controllability of the two were compared.

Figure 2 shows a high frequency voltage of 2KVp, a high frequency power of 300W, and a constant substrate bias voltage of 300cm from AAl to Al203.
The obtained results show that the surface resistance changes depending on the partial pressure of CO2, and the obtained values are distributed in the hatched range from the solid line to the broken line.

Note that the introduction pressure was constant at 5×10 −′ mmHg.

The film thickness was controlled to approximately 1500 people.

FIG. 3 is a diagram showing the results of valence control using Sn by a conventionally used binary vapor deposition method, unlike the present invention in which C is used for atomic control.

That is, these results were obtained by separately depositing Al and Sn from two evaporation sources.

The same experiment as shown in FIG. 2 was repeated under the same conditions, and Sn was heated in a W (tungsten) boat at a constant value of 025 x 10 mmHg.

The variation in resistance value is about 1/5 smaller in the present invention around the minimum value.

It is presumed that this variation is due to the fact that it is difficult to control the vaporization process in the conventional process of obtaining a coating by vaporizing a solid. is used as a valence control agent, it is thought to exhibit excellent controllability.

In any case, the resistance value can be controlled with similar accuracy not only for Al203 but also for any of the other oxide semiconductors mentioned above, and the practical value is extremely high.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of an example of a device for carrying out the present invention, Fig. 2 is a relationship between the surface resistance of Al203 and CO2 partial pressure obtained by the present invention, and Fig. 3 is a conventional method. FIG. 2 is a relationship diagram between surface resistance and Sn vapor pressure obtained by a binary vapor deposition method. 1... Evaporated substance, 2... Substrate, 3...
... Electrode, 4 ... Vacuum container, 5 ...
・Boat or basket, 7...variable leak valve, 9...02 gas inlet, 10...
...CO2 gas inlet, 11...Heating power supply, 13...DC power supply, 14...High frequency power supply.

Claims (1)

[Claims] 1 A substrate and an evaporation source are arranged facing each other in a vacuum container, a mixed gas plasma of oxygen and carbon monoxide or oxygen and carbon dioxide is formed in the space between them, and a vapor flow generated from the evaporation source is exposed to the plasma. An oxide semiconductor characterized by forming an oxide semiconductor thin film whose valence is controlled by C atoms on a substrate placed at the same potential as the evaporation source or at a negative potential (relative to the evaporation source). Method for manufacturing thin films.