JPS5837247B2 - Manufacturing method of amorphous silicon - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing amorphous silicon used in thick batteries, electrophotographic photoreceptors, and the like.

In recent years, amorphous silicon obtained by vapor phase growth has attracted attention because it is extremely useful in solar cells and other applications.

As a conventional method for manufacturing amorphous silicon, for example, Japanese Patent Application No. 54-89440 (
An example is a vapor deposition method based on a direct current ion plating method as disclosed in Japanese Patent Application Laid-Open No. 56-13776.

This method involves placing a silicon evaporation source and a substrate in a vacuum chamber, evaporating silicon from the evaporation source, and irradiating the vapor with thermionic electrons emitted from a tungsten heater to activate the silicon vapor. By ionizing the vapor and causing the generated silicon ions to collide with the substrate to which a negative DC voltage has been applied, amorphous silicon is formed on the surface of the substrate.

Note that at this time, hydrogen gas or the like can be added to make the silicon film contain hydrogen gas or the like.

However, in such a DC ion plating method, tungsten evaporates from the tungsten heater for emitting thermoelectrons, and becomes mixed into the formed amorphous silicon as an undesirable impurity, and also prevents the generation of silicon ions. In order to carry out the process regularly, the evaporation rate from the silicon evaporation source cannot be kept below a certain level, and therefore it may not be possible to form amorphous silicon with the desired performance.

Amorphous silicon formed by the method described above has many so-called dangling bonds due to its irregular atomic arrangement structure, which is of poor quality.

This dangling bond is a state in which electrons that should form a bond do not form a bond and remain as they are, or a state in which a covalent bond remains broken, and for this reason, the effects of silicon as a semiconductor material, such as the Kyuden phenomenon, are insufficient. There is a drawback that it is not fully utilized.

On the other hand, a method is also known in which silane (SIH4) gas is decomposed by glow discharge to form amorphous silicon with silicon ions, and at the same time, active hydrogen atoms generated are introduced into the amorphous silicon to seal the dangling bonds. However, in this method, it is impossible to arbitrarily change the ratio of hydrogen atoms to silicon, and it is therefore difficult to obtain amorphous silicon with desired characteristics.

Also known is a super-sota method for silicon in a hydrogen gas atmosphere, but this method has the disadvantage of slow film formation speed.

In view of the above-mentioned circumstances, the present invention provides a method for easily manufacturing amorphous silicon in which the dangling bonds are sealed, and therefore has excellent performance as a semiconductor material, and also has desired properties and functions. The purpose is to

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

In the present invention, as shown in FIG. 1, a vacuum pump (not shown) is connected to a bell jar 1 forming a vacuum chamber via an exhaust path 3 having a butterfly valve 2, and thereby the inside of the bell jar 1 is For example 10-6~10''
Torro high vacuum state and the bell jar 1
Ionized hydrogen obtained by discharging hydrogen gas in a hydrogen discharge tube 4 connected in communication with the ionized hydrogen is introduced into the bell jar 1, and the silicon evaporation source 5 is heated in the bell jar 1 where the ionized hydrogen is present. The silicon is evaporated from this, and the substrate 7 placed opposite the silicon evaporation source 5 is heated in advance by the heater 8, and the evaporated metasilicon is deposited on the surface of the substrate γ, thereby forming an amorphous Manufacture silicon.

6 is a shutter. In the above, any heating means such as resistance heating, electron gun heating, induction heating, etc. can be used to heat the silicon evaporation source 5, and the heating temperature of the substrate 7 is about 500° C. from room temperature. It can be set to any value up to 200-300°C, but generally
Set within the range.

FIG. 2 shows the hydrogen discharge tube 4 in detail, including a glass hydrogen supply tube 11 through which hydrogen gas flows, and this hydrogen supply tube 11.
Discharge electrodes 12 and 13 provided inside the discharge electrodes 12 and 12
．． 13, and a cooling mantle tube 14 provided on the outer periphery of the hydrogen supply tube 11 in a discharge region between 13 and 13, and discharge by a voltage from a power source 15 while the hydrogen gas pressure in the discharge region is maintained at 10' Torr or less. Electrode 12.1
3, a discharge is caused to occur, whereby a portion of the hydrogen gas is ionized to produce ionized hydrogen, which is introduced into the bell jar 1 from the hydrogen supply pipe outlet 16 together with the non-ionized hydrogen gas.

Cooling water is then allowed to flow through the cooling jacket pipe 14,
Overheating is prevented.

In addition, the distance between the discharge electrodes 12 and 13 is usually "O~15cwL"
1 Applied voltage C is 500 to 800V.

Further, even if a voltage is applied with the polarity opposite to that shown in FIG. 2, the purpose can be sufficiently achieved.

Furthermore, in order to discharge hydrogen gas, a high frequency power source can be used instead of a DC power source. In this case, an improvement in the discharge efficiency is expected, and the discharge electrodes 12 and 13 are exposed inside the hydrogen supply pipe 11. Since it is sufficient to provide a high-frequency coil around the outer periphery of the discharge electrode 12i3, it is possible to avoid introduction of the electrode material of the discharge electrode 12i3 as an impurity.

The hydrogen gas supplied to the hydrogen discharge tube 4 may be obtained from a hydrogen gas cylinder as is, but it is necessary to avoid undesirable impurities from being mixed into the amorphous silicon formed on the substrate 7. Therefore, it is preferable to supply high-purity hydrogen gas to the hydrogen discharge tube 4.

Although various methods are known for obtaining high-purity hydrogen gas, it is convenient to use a hydrogen purifier as shown in FIG. 3, for example.

This hydrogen purifier consists of an inner tube 21 made of palladium, an outer tube 22 surrounding the inner tube 21, and a heater 23 that heats the inner tube 21. Heater 2 while letting gas flow through
When the inner tube 21 is heated by 3, the hydrogen gas flows through the inner tube 2.
As a result, high-purity hydrogen gas is obtained from a discharge tube 24 made of a glass tube connected to the inner tube 21.

Since the present invention is as described above, the silicon vapor evaporated from the silicon evaporation source 5 in the bell jar 1 passes through the space where ionized hydrogen exists and is deposited on the substrate 1. When bonding, ionized hydrogen is introduced, and the dangling bonds are eventually blocked by hydrogen atoms.The amorphous silicon becomes the substrate γ.
Formed on the surface.

In the present invention, the active hydrogen atoms to be introduced into the amorphous silicon are obtained from the ionized hydrogen generated by the hydrogen discharge tube 4, so the amount of ionized hydrogen introduced into the bell jar 1 is reduced. , for example, by changing the amount of hydrogen gas supplied to the hydrogen discharge tube 4, the discharge voltage in the hydrogen discharge tube 4, etc.
Therefore, it is possible to control the hydrogen introduction rate in the amorphous silicon formed on the substrate 7, and it is possible to obtain amorphous silicon having the desired performance.

Furthermore, by appropriately selecting the position of the hydrogen supply tube outlet 16 of the hydrogen discharge tube 4, it is expected that ionized hydrogen can be used efficiently and the rate of introduction into amorphous silicon will be improved.

Since ionized hydrogen loses its ionized state when it collides with metal, it is particularly preferable to do so when the bell jar 1 is made of metal.

If the hydrogen supply tube 11 in the hydrogen discharge tube 4 is made of glass, the initial ionized hydrogen will adhere to the inner surface of the hydrogen supply tube 11 and will not be transported over a long distance, but the subsequent ionized hydrogen will be transferred to the ionized hydrogen that has already adhered. Since this prevents the hydrogen from adhering to the hydrogen supply pipe 11, it can be transported over a sufficiently long distance.

In addition, in the present invention, as shown in FIG. 1, a doping agent evaporation source 9 is provided, and phosphorus, arsenic, boron, antimony, etc. are evaporated simultaneously with the evaporation of silicon from the silicon evaporation source 5, thereby converting these into impurities. Therefore, amorphous silicon can be produced as an n-type or p-type semiconductor.

As the doping agent, it is also possible to use compounds such as phosphine, arsine, diborane, etc. In this case, it is sufficient to simply allow these gases to exist in the bell jar 1.

Furthermore, in the present invention, a member that generates undesirable impurity vapor such as a tungsten heater is not required in the bell jar 1, compared to a DC ion plating method that uses a tungsten heater for generating thermionic electrons. Therefore, amorphous silicon with the desired components can be obtained, and since there is no limit to the evaporation rate in the silicon evaporation source 5, amorphous silicon with desired performance can be obtained by controlling this as desired. .

Furthermore, as shown in FIG. 1, by providing a butterfly valve 2 and other pressure control mechanisms in the exhaust passage 3 for exhausting the inside of the bell jar 1, the hydrogen pressure containing ionized hydrogen inside the bell jar 1 can be kept at 10 Torr or less. It can be controlled to any size, and from this point of view as well, the hydrogen introduction rate can be controlled to obtain amorphous silicon with desired performance.

It is preferable to use the butterfly valve 2 as the air pressure control mechanism because the air pressure can be easily controlled over a wide range of 10''-10-2 Torr.

In addition, by applying a DC negative voltage of IKV or less to the substrate 7, it is possible to adsorb ionized hydrogen to the surface of the substrate 7, and in this way, the hydrogen content in the amorphous silicon to be formed can be reduced to the above-mentioned level. This can be further improved.

Next, to briefly explain a specific example of the present invention, a silicon evaporation source 5 is heated by an electron gun, a certain substrate 7 is heated to a temperature of 200° C. by a quartz plate, and the discharge voltage 5 in the hydrogen discharge tube 4 is
A hydrogenated amorphous silicon film was formed on the substrate 7 by vapor deposition for 10 minutes while introducing ionized hydrogen obtained by discharging hydrogen gas at 50 V and a discharge current of 0.8 A.

The deposition rate at this time was IOOOA/min.

The resulting hydrogenated amorphous silicon film has an optical gap of approximately 1.9 eV and a photoresponsiveness of 1015 photons/CrIl. The resistance value change due to ICr7
(8・CrrL)-1teata.

As described above, according to the method of the present invention, the dangling bonds are blocked by hydrogen atoms by an extremely simple method, and therefore, it has excellent performance as a semiconductor material, and also includes conditions that can be arbitrarily and accurately controlled. Amorphous silicon having desired performance can be easily produced.

In addition, the method of the present invention has a faster deposition rate than the sputtering method, and has a faster deposition rate than the DC ion plating method.
The obtained hydrogenated amorphous silicon film has good optical gap and photoresponsiveness.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of the structure of an apparatus used in the method for producing amorphous silicon of the present invention, Fig. 2 is a cross-sectional view of a hydrogen discharge tube, and Fig. 3 is a schematic diagram showing an example of a hydrogen purifier. It is a sectional view for brightness. 1...Bell jar, 2...Butterfly valve, 3...
- Exhaust path, 4... Hydrogen discharge tube, 5... Silicon evaporation source, 6... Shutter, 7... Substrate, 8... Heater, 9... Doping agent evaporation source, 11... Hydrogen Supply pipe, 12, 13...Discharge electrode, 14...Cooling mantle tube, 15...Power supply, 16...Hydrogen supply pipe outlet, 21.
...Inner pipe, 22...Outer pipe, 23...Heater 24
...Discharge pipe.

Claims (1)

[Scope of Claims] 1. Ionized hydrogen generated by electric discharge is introduced into a vacuum chamber in which a silicon evaporation source and a substrate are arranged, and silicon is evaporated from the silicon evaporation source in an atmosphere where this ionized hydrogen exists. 1. A method for producing amorphous silicon, which comprises first depositing the amorphous silicon on the surface of the substrate, thereby making the amorphous silicon into which hydrogen atoms have been introduced form a shape on the surface of the substrate. 2. Claims characterized in that the doping agent is evaporated from a doping agent evaporation source disposed in the vacuum chamber at the same time as the silicon is evaporated, thereby forming amorphous silicon containing the doping agent. 1st
A method for producing amorphous silicon as described in . 3. The amorphous silicon manufacturing method according to claim 1 or 2, wherein the inside of the vacuum chamber is maintained at a controlled degree of vacuum of 10 -2 Torr or less. 4. The method for producing amorphous silicon according to claim 1, 2, or 3, characterized in that the ionized hydrogen is introduced into the vicinity of the silicon evaporation source or the substrate. 5. The amorphous silicon manufacturing method according to claim 1, 2, 3, or 4, characterized in that a negative direct current voltage of O to IKV is applied to the substrate.