JPS62159419A - Apparatus for forming amorphous semiconductor thin film - Google Patents

Abstract

PURPOSE:To enhance the doping efficiency by independently supplying a doping gas for forming an amorphous silicon film separately from a silane gas of a main material gas. CONSTITUTION:A DC discharge is generated by power supplied from a power source 12 between enamelled cathodes 9 made of a hollow cylindrical metal and a mesh anode 11 to generate a plasma 10. Gas to the cathodes 9 is supplied from independent material gas inlet tubes 7 through insulator connecting tubes 17 into the cathodes 9. The supplied gas is efficiently ionized in the high density negative glow plasma 10 generated in the cathodes, and deposited on a substrate 3.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to an amorphous semiconductor thin film production device in which a compound gas is decomposed by a plasma reaction using glow discharge and deposited on a substrate.

[Prior art and its problems]

Figure 2 shows a typical generation device that is conventionally used to deposit semiconductor films by decomposing semiconductor raw material gas through a plasma reaction using glow discharge. The explanation will be given by taking the case of creating a semiconductor thin film as an example. Monosilane or a mixed gas of monosilane and hydrogen as a raw material gas is introduced from an introduction pipe 7 into a reaction chamber 6 connected to a vacuum evacuation system via an exhaust pipe 8. , a glow discharge is generated between the electrodes 1° and 2 under a reduced pressure of around 1 Torr. As a result, active species such as monosilane and hydrogen are generated in the discharge plasma due to the collision of high-speed electrons, and these are deposited on the substrate 3 placed on the lower bridge 2 heated by the heater 4, forming a semiconductor thin film. is generated. The properties of the semiconductor thin film thus produced depend largely on the properties of the discharge plasma. There are two methods of plasma generation: the direct voltage application method (hereinafter referred to as DC) and the high frequency (hereinafter referred to as RF) voltage application method, but currently the insulator substrate is
The RF application method is mainly used because of its advantages such as the ability to obtain uniform plasma. However, R.F.
In the discharge, artificial control of the plasma other than the input power is
l! There are problems in that the research method for evaluating the physical properties of plasma has not been sufficiently established both theoretically and experimentally. Therefore, it is difficult to apply the optimum discharge conditions for growing a semiconductor thin film of a certain quality in one generation apparatus to another generation apparatus. Furthermore, in the production apparatus having the structure shown in FIG. 2, for example, in the case of p-type, B! +1 &, PH for n type. Doping gas such as or a-3iC: H1
l! A compound raw material gas such as CJx+GeH4 for producing an a-3t alloy thin film such as or a-3iGe:HII is mixed with 5IH4 as the main raw material gas and introduced into the reaction chamber 6 via the introduction pipe 7. Therefore, various gases with different decomposition energies are introduced into the reaction chamber through the same introduction tube and decomposed under the same plasma glow discharge conditions. Since each raw material gas is not necessarily decomposed under the optimum conditions, it is difficult to obtain optimum p-type and n-type amorphous silicon films or amorphous alloy films.

[Purpose of the invention]

The present invention has been made in order to eliminate the drawbacks seen in the above-mentioned conventional devices, and it is easy to control discharge adapted to each of different types of raw material gases, and provides high-quality p-type and n-type amorphous semiconductor thin films. Or amorphous alloy ml
An object of the present invention is to provide an apparatus for producing an amorphous semiconductor thin film.

[Key points of the invention]

In the amorphous semiconductor thin film production apparatus according to the present invention, one common Ml electrode and a plurality of cylindrical individual electrodes each having an opening facing the common Ml electrode are arranged in a reaction chamber that can be evacuated.
Independently controllable power sources are connected between the poles and the individual electrodes, and the internal spaces of the individual electrodes are communicated with independent raw material compound gas introduction pipes. As a result, the hollow electrode method generates high-density, high-energy plasma in the cylindrical electrode that cannot be obtained with DC discharge or RF discharge between parallel plate electrodes, and more actively excite and dissociate the raw material gas. The above object can be achieved because each individual electrode is used for each raw material compound gas and the discharge is carried out under independent glow discharge conditions adapted to that gas.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the invention, and parts common to those in FIG. 2 are given the same reference numerals. In the drawing, reference numeral 9 indicates a hollow cathode made of metal that is hollow and cylindrical, and generates plasma 10 by performing DC discharge between it and the mesh electrode 11 using power supplied from a power source 12. In this case, 5i, which is necessary for the production of p-type and n-type amorphous silicon films or amorphous alloy films, is
A plurality of hollow cathodes 9 are arranged vertically and horizontally at appropriate intervals depending on the type of raw material compound gas such as Ha+BtHt+PIIt+CJt+GeHa. In addition, gas is introduced into each hollow cathode 9 independently from the raw material gas introduction pipe 7 through the insulating connecting pipe 17 into the hollow cathode Fi, where the high-density gas generated in the cathode is They are efficiently ionized or dissociated in the negative glow plasma 10, and these products pass through the mesh anode 11 and are deposited on the substrate 3 on the mount 1 installed on the opposite side of the discharge area and the mesh electrode. At this time, the RF electric field generated by RF'giil [14] connected between the mesh electrode 11 and the substrate mount 1 helps to make the deposition uniform. The substrate 3 can be heated to an arbitrary temperature by a heater 4 provided on the mounting base 1. The power supplied from the DC power supply 15 to each hollow cathode 9 can be adjusted by a variable resistor 13 connected between each hollow cathode. For example, when the voltage of the power supply 15 is 400 to
In the case of 500 W, the current flowing between the hollow cathode 9 and the mesh anode 11 is adjusted between 0 and 100 WA by controlling the variable resistor 13, and therefore the discharge power between the hollow cathode 9 and the mesh anode 11 is adjusted between 0 and 50 W. As a result, the discharge power between the hollow cathode 9, which supplies a material gas that is easier to decompose compared to SIH, such as CJt, and the mesh gas, is 172 to 1/2 that in the case of the hollow cathode 9, which supplies SiH. 3, allowing discharge to occur under optimal conditions. The device shown in Figure 1 uses a debo-up method in which the substrate 3 is installed at the top in order to prevent particles (attached to the electrodes, etc.) from falling onto the substrate, but the substrate is installed at the bottom. Of course, the present invention can also be effectively implemented in a debo-down method in which the substrate is placed in a vertical plane or in a method in which the substrate is arranged in a vertical plane.

【Effect of the invention】

The present invention includes a hollow electrode that can independently supply doping gas for producing p-type and n-type amorphous silicon films or compound gas for producing an amorphous alloy thin film separately from silane gas, which is the main raw material gas, Plasma can be generated between each hollow electrode and the common 7S pole under decomposition conditions according to the decomposition energy of each source gas. As a result, an amorphous silicon film of each conductivity type with excellent doping efficiency or an amorphous alloy film with good film quality can be obtained. In particular, when creating an amorphous large MW pond using the generation 'A'If according to the present invention, the p layer, 1
It is possible to obtain a great effect in the formation of each layer and N5 film, contributing to higher efficiency of solar cells.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional device. l: Substrate mounting stand, 3: Substrate, 6: Reaction chamber, 7: Gas introduction tube, 9z hollow cathode, 11: Mesh anode, 12: DC
Power supply, 13: Variable resistance, 14: RFii source, 17: Insulated connection tube, 〆・-゛)
C-P's

Claims (1)

[Claims] 1) In a device in which an amorphous semiconductor is deposited on a substrate by decomposing a compound gas by a plasma reaction using a glow discharge generated between electrodes, one common electrode and an opening are located in a reaction chamber that can be evacuated. A plurality of cylindrical individual electrodes were arranged facing each other, independently controllable power sources were connected between the common electrode and the individual electrodes, and the internal spaces of the individual electrodes were connected to independent compound gas introduction pipes. An amorphous semiconductor thin film production device characterized by the following.