JP2000124460A - Characteristic improvement method in manufacture process of non-single crystalline semiconductor thin film element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate for combination defect of a non-single crystalline semiconductor thin film and restrain characteristic deterioration of the element, by a method which is easy and excellent in cost performance in a manufacturing process of an element (such as a thin film field effect transistor, an optical conduction element and a photoelectromotive element) based on a structure wherein a non-single crystalline semiconductor thin film is deposited on a substrate. SOLUTION: After a gate electrode 28 is formed by vacuum deposition or sputtering on a supporting substrate 26, an i-type amorphous silicon film 30 is deposited by thermal CVD of 650 deg.C of silane and in this stage, the structure body is immersed in high pressure water of 110 deg.C for 15 hours. Then, an insulation film 32, a source metallic film 34 and a drain metallic film 36 are deposited by vacuum deposition or sputtering and a source and a drain are formed by sputtering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for manufacturing a semiconductor thin film device such as a thin film field effect transistor, a photoconductive device, and a photovoltaic device, and more particularly, to a non-single-crystal semiconductor thin film deposited on a substrate. A method for improving the characteristic deterioration caused by the bonding defect of the above.

[0002]

2. Description of the Related Art A thin film field effect transistor (hereinafter referred to as TF)
Abbreviated as T. 2.) Semiconductor thin-film devices such as photoconductive devices and photovoltaic devices typically have a structure in which a non-single-crystal semiconductor thin film is deposited on a substrate such as glass, metal, or single-crystal semiconductor. This non-single-crystal semiconductor thin film has a plasma CV
D, thermal CVD, sputtering, etc. As a material of the thin film, a silicon film is typical, but a germanium film, a silicon nitride film, a silicon oxide film, a silicon oxynitride film, a silicon carbide film, a silicon germanium alloy film, etc. may be used according to the purpose. TFT ・
Elements such as a photoconductive element and a photovoltaic element have been described in detail in many documents, and therefore, only the portions related to the present invention will be described below.

[0003]

SUMMARY OF THE INVENTION Plasma CVD / Heat C
Many non-single-crystal semiconductor thin films deposited on a substrate by a VD / sputtering method or the like have a large number of silicon atom bond defects inside and at the interface. (There are many defects in the order of plasma CVD / thermal CVD / sputtering.) Bonding defects of silicon atoms cause unintended levels in the gap. The in-gap level is closely related to charge generation and carrier recombination, and is the largest factor that greatly affects device characteristics such as a TFT, a photoconductive device, and a photovoltaic device. Further, if there are many bonding defects, a problem of causing structural distortion is caused. In addition, since the defective portion is very active, impurities are easily adsorbed, which causes a defect level. These problems cause, for example, a decrease in the on / off ratio due to a leak current when the TFT is off, and a decrease in the power generation efficiency in the photovoltaic element.

[0004] In order to improve the deterioration of the device characteristics due to the above-mentioned coupling defect in the non-single-crystal semiconductor thin film, it is necessary to compensate for the coupling defect in the film. For this purpose, conventionally, a hydrogen plasma method and a hydrogen ion implantation method described in detail below have been proposed.

The former hydrogen plasma method is a method in which a non-single-crystal semiconductor thin film is exposed to DC plasma of hydrogen or deuterium in a champer. (For details, see “POST-HYDROGE
NATION OF CVD DEPOSITED a-Si FILMS ”N. Sol et al.
See J. Non-Crystal. Solids Vol. 35 & 36 p291, 1980. However, in this method, the contaminants and the material of the vessel wall adhering to the chamber wall of the chamber are sputtered and adhere to the non-single-crystal semiconductor thin film, and the adhered substance becomes a defect level inside or at the interface of the non-single-crystal semiconductor thin film. Is formed. Also, it is not easy to properly compensate for defects by this method because there are too many parameters defining the plasma.

The latter hydrogen ion implantation method is a method in which hydrogen ions are accelerated at a high voltage to strike a non-single-crystal semiconductor thin film. (See “HYDOROGEN IMPLANTATION INTO
CVDAMORPHOUS SILICON ”T. Suzuki et al. JJ App
l See Phys. Vol. 19 Supplement p91, 1980. In this method, new bonding defects are generated at the time of hydrogen ion implantation, and it is necessary to recover the bonding defects by heat treatment. However, such heat treatment after hydrogen ion implantation
Since it is necessary to perform the bonding at a temperature at which hydrogen ions that compensated for the bonding defect do not separate or deviate, it is very difficult to completely recover the bonding defect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and does not take impurities into the inside or the interface of the non-single-crystal semiconductor thin film and does not cause a defect in bonding. It is an object of the present invention to compensate for a bonding defect generated inside or at an interface of a non-single-crystal semiconductor thin film by a method excellent in performance.

[0008]

According to a first aspect of the present invention, there is provided a method of manufacturing a device having a structure in which a non-single-crystal semiconductor thin film is deposited on a substrate. Wherein the substrate on which the non-single-crystal semiconductor thin film is deposited is kept in water at 110 ° C. or higher for 1 hour or more. Although the water is slight, it is ionized, and the ion concentration increases rapidly with increasing temperature. The hydrogen ions permeate and diffuse into the non-single-crystal semiconductor thin film, and act on defect bonds of silicon atoms to compensate for the defects. Further, since both the hydrogen ion concentration and the diffusion rate of hydrogen ions in the thin film increase at a high temperature, this effect is more effective as the treatment is performed at a higher temperature.

A characteristic improving method according to a second aspect of the present invention is characterized in that the water according to the first aspect is heavy water. Heavy water is also slightly ionized, similar to light water, and compensates for defect bonding, similar to light water hydrogen ions. The higher the processing temperature, the more effective.

According to a third aspect of the present invention, there is provided a method for improving characteristics, wherein the water according to the first aspect is a mixture of light water and heavy water. Depending on the material and thickness of the non-single-crystal semiconductor thin film to be treated, it is effective to use mixed water of light water and heavy water.

According to a first aspect of the present invention, there is provided a method for improving characteristics of any one of a silicon film, a germanium film, a silicon nitride film, a silicon oxide film, a silicon oxynitride film, a silicon carbide film, and a silicon germanium alloy film. It can be effectively applied to a non-single-crystal semiconductor thin film.

In the method of the present invention, the treatment temperature and treatment time in light water or heavy water, or a mixed water thereof,
110 ° C. and 1 hour are set. This condition is 1
In water treatment at 10 ° C. or less, or at 110 ° C. for 1 hour or less, the temperature was set based on the fact that the desired effect was not seen at all. It is considered that at such a temperature of about 110 ° C., the degree of ionization of water is extremely small, and the amount of hydrogen for compensating for bond defects is small.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method of the present invention, a non-single-crystal semiconductor deposited on a substrate at an appropriate stage of a manufacturing process of a semiconductor thin film device such as a thin film field effect transistor, a photoconductive device, and a photovoltaic device. In order to improve the characteristic deterioration due to the bonding defect of the thin film, the substrate on which the non-single-crystal semiconductor thin film is deposited is subjected to a boiling treatment to compensate for the bonding defect.

The boiling process is performed using a boiling device 10 having a structure as schematically shown in FIG. 4, for example. In this apparatus 10, a pressure gauge 14, a thermometer 16, a propeller 18 for stirring high-temperature and high-pressure water, and a metal fitting 20 for mounting and holding a sample are mounted on a stainless steel container 12 capable of withstanding high temperature and high pressure. Have been. The external heater 22 and the temperature control device 24 surrounding the side of the container 12
The temperature of the high-pressure water in 2 is controlled.

Embodiment 1 FIG. 1 shows a structural example of a bottom gate type TET as a non-single-crystal semiconductor thin film element. After forming the gate electrode 28 on the support substrate 26 by vacuum evaporation or sputtering, 650 ° C.
An i-type amorphous silicon film 30 is deposited by thermal CVD. At this stage, the structure is put into the water boiling apparatus 10 shown in FIG. 4, and the temperature is kept at 110 ° C., and the water is boiled for 15 hours. Then, the insulating film 32 and the source metal film 3
4 and a drain metal film 36 are deposited by vacuum evaporation or sputtering, and a source and a drain are formed by patterning. In FIG. 1, an n + type amorphous silicon film for ohmic contact and an insulating film necessary for various etchings are omitted.

In order to evaluate the performance of the TFT prepared as described above, the TFT prepared by the above-described process including the water boiling treatment at 110 ° C. for 15 hours was combined with the TFT prepared at 181 ° C. (corresponding to 10 atm) for 2 hours. T created in the process including processing
FT and T created by a process that does not include boiled water
The gate voltage / drain current characteristics of each of the FTs were compared and tested with low-voltage driving (10 V) (in each case, the channel size ratio was W / L = 15). The result is shown in FIG. The dashed line in the figure indicates the characteristics of the TFT, and the solid line indicates the TFT.
And the dotted line show the characteristics of the TFT, respectively.
It can be seen that the leakage current of the TFT subjected to the water boiling treatment and the TFT is reduced as compared with the TFT not subjected to the treatment. In particular, it can be seen that the TFT subjected to the high-temperature boiled treatment has a more remarkable decrease in leak current than the TFT.

FIG. 2 is a schematic side sectional view of a top gate type TFT in which a gate electrode is deposited on the top of the device. If the present invention is applied to the manufacturing process of this type of TFT, the same effects as described above can be obtained.

Embodiment 2 FIG. 3 shows a structural example of a photovoltaic element as a non-single-crystal semiconductor thin film element. Supporting transparent glass substrate 4 having a transparent conductive film ITO layer 38 on the upper surface
On p. 0, ap + type amorphous silicon film 42, an i type amorphous silicon film 44, and an n type amorphous silicon film 46 are sequentially deposited from the bottom by thermal CVD. At this stage, the structure is put into the water boiling apparatus 10 shown in FIG.
The mixture is kept at 50 ° C. and boiled for 5 hours. Thereafter, an aluminum electrode 48 (n side) is formed on the top of the structure.

To evaluate the performance of the photovoltaic element prepared as described above, the power generation efficiency was examined. As a result, AM1.5,
Maximum output 7m in artificial sunlight irradiation of a 100 mW / cm ²
Power of W / cm ² was obtained. In addition, 18
An element produced at 1 ° C. (10 atm) for 2 hours also obtains an output of 7 mW / cm ² . Since the maximum output is 5 mW / cm ² in the element not subjected to the water boiling treatment, the power generation efficiency is improved by 40% under any of the above-mentioned conditions.

[Embodiment 3] The water boiling process in the process of manufacturing the TFT described in Embodiment 1 is performed using heavy water or a mixed water of 50% each of light water and heavy water. Both of these treatments are performed at 120 ° C. (2 atm) for 20 hours.

In order to evaluate the performance of the TFT prepared as described above, a TFT prepared by a process including a boiling process using heavy water and a TFT prepared by a process including a boiling process using a mixed water of heavy water. The gate voltage / drain current characteristics of the TFT thus fabricated and a TFT fabricated by a process not including the water-boiling treatment were compared by low-voltage driving (10 V). FIG. 6 shows the result. The dashed line in the figure is the TFT
, The solid line indicates the TFT characteristics, and the dotted line indicates the TFT characteristics. The TFT subjected to the water-boiled treatment and the TFT are compared with the TFT not subjected to the treatment.
It can be seen that the leakage current is reduced. In addition, it can be seen that the leakage current is significantly reduced in the TFT subjected to the water boiling treatment using the mixed water of the light water and the heavy water as compared with the TFT subjected to the water boiling treatment using the heavy water. From these results,
Depending on the purpose, it is also effective to use heavy water or a mixture of light water and heavy water.

Embodiment 4 The i-type amorphous silicon film 44 of the photovoltaic element described in Embodiment 2 is deposited by sputtering. In addition, the water boiling treatment of Example 2 was performed at 150 ° C.
5 hours using heavy water.

In order to evaluate the performance of the photovoltaic element prepared as described above, the power generation efficiency was examined in the same manner as in Example 2. Photoelectric output under the same solar simulator as in Example 2, respectively in the case of organic-free processing 5 mW / cm ² and 3 mW / cm ²
It is. Therefore, the power generation efficiency is improved by less than 70%.

[Supplementary Explanation] In the treatment in the water boiling apparatus 10 shown in FIG. 4, it is necessary to stir the high-temperature water with the stirring propeller 18 to keep the sample temperature high. If a leak port is provided in the container 12 of the water boiler 10 and steam is ejected from the leak port, bubbles are generated inside the high-pressure water and contribute to stirring.

When the method of the present invention is applied to the manufacturing process of the TFT illustrated in FIG. 1 and the photovoltaic device illustrated in FIG. 3, before the electrodes are formed on the surface of the non-single-crystal semiconductor thin film. It is desirable to perform boiling treatment. If the boil treatment is performed after the formation of the electrode, the supply of hydrogen or deuterium is prevented by the electrode, and the electrode is further damaged. When an electrode is formed in a step after the water boiling treatment of the present invention, the characteristic improving effect of the present invention is not impaired unless a high temperature as high as 400 ° C. is involved in this step.

Thermal CVD at 650.degree.
In a plasma CVD or sputtering method kept at 50 ° C. or higher, a non-single-crystal semiconductor thin film may not be amorphous but may have many fine crystals. In such a case, many surface levels and interface levels corresponding to the levels in the gap of the amorphous non-single-crystal semiconductor thin film are generated on the surface and the interface of the fine crystal. The method of the present invention can be applied to such a case. It goes without saying that the concentration of these levels is determined by the particle size and concentration of the fine crystals, and therefore the effect when the present invention is applied is different.

[0027]

As described above, the method for improving characteristics according to the present invention is a very simple method of immersing a substrate on which a non-single-crystal semiconductor thin film is deposited in high-temperature water for a certain period of time or more. Bonding defects can be effectively compensated by penetrating and diffusing ionized ions into the inside and the interface of the non-single-crystal semiconductor thin film. As a result, the leakage current when the TFT is off can be reduced, and the power generation efficiency of the solar cell can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view showing a bottom gate type thin film field effect transistor according to an embodiment of the present invention.

FIG. 2 is a schematic side sectional view showing a top gate thin film field effect transistor according to an embodiment of the present invention.

FIG. 3 is a schematic side sectional view of a photovoltaic device according to an embodiment of the present invention.

FIG. 4 is a schematic side sectional view showing a water boiling apparatus according to an embodiment of the present invention.

FIG. 5 is a graph showing a gate voltage / drain current characteristic of a thin film field effect transistor formed by a process including a boiling process using light water according to an embodiment of the present invention.

FIG. 6 is a graph showing gate voltage / drain current characteristics of a thin-film field-effect transistor formed by a process including a boiling process using heavy water and a mixture of heavy water and heavy water according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Water boiler 12 Stainless steel container 14 Pressure gauge 16 Thermometer 18 High pressure water stirring propeller 20 Sample holding fixture 24 Temperature controller 22 External heater 26 Support substrate 28 Gate electrode 30 i-type amorphous silicon film 32 Insulating film 34 Source metal film 36 Drain metal film 40 Supporting transparent glass substrate 38 Transparent electrode ITO 42 p + type amorphous silicon film 44 i-type amorphous silicon film 46 n-type amorphous silicon film 48 aluminum electrode

Claims (4)

[Claims] In a device manufacturing process mainly comprising a structure in which a non-single-crystal semiconductor thin film is deposited on a substrate, the substrate on which the non-single-crystal semiconductor thin film is deposited is placed in water at 110 ° C. or higher.
A characteristic improvement method characterized by holding for a time or longer. 2. The method for improving characteristics according to claim 1, wherein the water according to claim 1 is heavy water. 3. The method for improving characteristics according to claim 1, wherein the water according to claim 1 is a mixed water of light water and heavy water. 4. The method for improving characteristics according to claim 1, wherein the non-single-crystal semiconductor thin film is a silicon film, a germanium film, a silicon nitride film, a silicon oxide film, a silicon oxynitride film, or silicon carbide. Film or a silicon germanium alloy film.