JPH0430196B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solar cell having a deposited layer of amorphous silicon (hereinafter referred to as "a-silicon") on a substrate.

In recent years, a-silicon has attracted attention as a material for solar cells due to its manufacturing advantages, such as its ability to be manufactured over a large area at high speed compared to crystalline silicon, and its excellent performance.

For example, they are used in semiconductor devices such as silicon diodes, silicon transistors, silicon controlled rectifiers, field effect transistors (FETs), solar cells, and electrophotographic photoreceptors. In these semiconductor devices, there are generally two types of contact between the semiconductor layer and the electrode: rectifying contact and non-rectifying contact. In general, solar cells that utilize output current require non-rectifying contact, that is, ohmic contact, between the electrode and the semiconductor layer, and if this is insufficient, the solar cell will fail. Function is lost.

Conventionally, as a method for obtaining such ohmic contact, a so-called a-silicon P ⁺ layer in which boron, aluminum, gallium, indium, etc. from the periodic table group are doped into the a-silicon layer or a layer from the periodic table group is used. The a-silicon layer is formed by heavily doping phosphorus, arsenic, antimony, bismuth, etc. into the a- ^silicon layer.
A silicon layer is provided.

However, in the above method, in addition to complicating the process due to the formation of the heavily doped layer, a relatively large amount of the dopant in the heavily doped layer in contact with the a-silicon layer is diffused into the a-silicon layer, and the a-silicon There were drawbacks such as the inability to control the valence electrons of the layer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a solar cell in which, when an a-silicon layer is provided on a substrate, good ohmic contact can be obtained between the a-silicon layer and the substrate with an extremely simple layer structure.

The object comprises the steps of forming an antimony layer on a substrate, and forming a deposited layer of a-silicon on the antimony layer by magnetron sputtering in the presence of hydrogen gas ionized by glow discharge. and when providing the deposited layer of a-silicon, ensuring that ohmic contact is obtained between the antimony layer and the deposited layer of a-silicon, and further forming the antimony layer;
This is achieved by a method of manufacturing a solar cell in which the step of providing the a-silicon deposit layer can be performed continuously through the same or adjacent vacuum chambers.

That is, in the present invention, antimony, which has a particularly low melting point and has the property of easily diffusing into the a-silicon layer, is deposited on an insulating substrate such as glass or plastic or a metal substrate such as stainless steel or aluminum. A layer is provided (or directly if the substrate is made of antimony), and a deposited layer of an a-silicon layer is provided thereon, for example, by the method described below. By doing so, an ohmic contact is formed between the antimony layer and the a-silicon layer, and a capable function as a solar cell can be provided. The reason why such ohmic contact can be obtained is that a.
- When silicon, which flies with high kinetic energy when the silicon layer is deposited, collides with the antimony layer, it loses the kinetic energy and at the same time generates high thermal energy (reaching a high temperature of around 1000 degrees Celsius). As a result, silicon and antimony are mixed in an atomic state by vibration, and a layer in which antimony is diffused into the a-silicon layer is formed near the interface between the antimony layer and the a-silicon layer. be done.

It is presumed that such a diffusion layer is a layer in which antimony is diffused in an a-silicon layer at an amount of about 10 atomic % to 0.1 atomic %.

By the way, a-silicon is amorphous, which means that it has an irregular atomic arrangement structure, so there are many tangling bonds in which covalent bonds remain broken. Doping cannot be obtained and a desirable solar cell cannot be obtained. Therefore, as described in, for example, US Pat. No. 4,217,374, hydrogen, fluorine, etc. are introduced to seal the dangling bonds inherent in the structure of a-silicon and improve the semiconductor properties.

In addition, in the sputtering method, in a vacuum chamber of 10 ^-1 to 10 ^-3 Torr in which hydrogen gas, argon gas, and optionally doping gases such as diborane, fesufin, arsine, etc. are present,
A target made of silicon is bombarded with argon ions to knock out silicon, which is deposited on the antimony layer of the substrate, and an a-silicon layer with dangling bonds sealed by hydrogen gas is deposited.

Thus, good ohmic contact between both layers is achieved simply by providing on the antimony layer a deposited layer of a-silicon obtained by the method described above.

If necessary, the deposited layer may be annealed by heat treatment at around 100 to 300° C. in order to achieve more perfect ohmic contact.

In addition, in the glow discharge method, sputtering method, vapor deposition method, etc., the step of forming an antimony layer on the substrate and the step of forming an a-silicon layer thereon are performed, for example, in the same vacuum chamber or in adjacent vacuum chambers. A manufacturing method that can be carried out continuously throughout is preferred.

The reason for this is that after the antimony layer is formed, when it is transferred to another device and the a-silicon layer is formed, the surface layer of the antimony layer is oxidized and altered, and the a-silicon layer is deposited on top of it. This is because good ohmic contact may not be achieved when this is done.

Unavoidably, antimony layer and a-
When forming a silicon layer, it is desirable to perform a treatment such as sputter etching with argon gas, ion etching, or surface reduction with active hydrogen before depositing the a-silicon layer.

Embodiments of the present invention will be described below with reference to the drawings.
In the apparatus shown in FIG. 1, a vacuum pump (not shown) is connected inside the bell gear 1 through an exhaust passage 3 having a butterfly valve 2, thereby maintaining the inside of the bell gear 1 in a vacuum state of, for example, 10 ^-6 Torr. year,
A substrate 4 made of stainless steel is placed inside the bell gear 1, and heated to a temperature by a heater 5.
After heating the antimony evaporation source 8 provided opposite to the substrate 4 to 300°C using a resistance heating method and performing evaporation for 2 seconds to form an antimony layer 30 with a thickness of 1000 Å on the substrate, the antimony evaporation source 8 is heated to 300°C. Heating was stopped and shutter S was closed.

Next, at the temperature of the substrate 4 of 300℃, -
A DC voltage of 0.3KV is applied, and a DC voltage of 600V is applied between the electrode portions 22 and 26 of the hydrogen discharge tube 7, and the hydrogen gas flow is ionized and activated by glow discharge, and is introduced into the bell gear 1. At the same time, argon gas was introduced through the introduction pipe 9 to adjust the pressure inside the bell jar 1 to 10 ^-2 Torr. On the other hand, the cathode target 12 made of silicon
The magnetron sputtering device 10 equipped with the above is operated by applying a high frequency voltage between the cathode target 12 and the anode 13.
An a-silicon layer was formed.

As shown in FIG. 3, the magnetron sputtering device 10 has a cathode target 12 having a circumferential surface expanding outward, and a cathode target 12.
It consists of an anode plate 13 disposed at the center bottom of the cathode target 12 and a permanent magnet 14 disposed on the outer periphery of the cathode target 12 or further behind it. The glow discharge plasma generated between the cathode target 1 and the cathode target 1 is
As a result of being restrained near the surface of the cathode target 12, the material particles of the cathode target 12 are ejected with high efficiency by the argon ions present at high density in the plasma. It is configured to perform sputtering with high efficiency in the space surrounded by the extension of the inner circumferential surface of 12. Specifically, the magnetron sputtering device "S-Gun" manufactured by Varian (USA) is used. ” is given as a preferable example.

Further, as shown in FIG. 2, the hydrogen discharge tube 7 includes a discharge space member 24 made of, for example, cylindrical glass, surrounding a discharge space 23 having a cylindrical one electrode member 22 having a gas inlet 21 at one end. , and a ring-shaped other electrode member 26 having an outlet 25 provided at the other end of the discharge space member 24, and a DC or AC voltage is applied between the one electrode member 22 and the other electrode member 26. When applied, the hydrogen gas supplied through the gas inlet 21 generates a glow discharge in the discharge space 23 , whereby active hydrogen and hydrogen ions consisting of hydrogen atoms or molecules activated by electronic energy are transferred to the outlet 25 . It is configured so that it can be discharged more easily.

After forming the antimony layer on the substrate and the a-silicon layer thereon as described above, the operation of the sputtering device 10 was stopped, and the substrate temperature was lowered to 300°C.
The metal evaporation source 12, which uses platinum as the evaporation material, is heated by a resistance heating method to deposit platinum on the a-silicon layer 31 for 10 seconds, thereby forming a transparent metal layer 33 with a thickness of 100 Å. A solar cell was manufactured by forming an electrode layer 34 made of ITO on top of the electrode layer 34, but the photoelectric conversion efficiency of this solar cell was 4%.
It was hot.

On the other hand, in the above manufacturing process, the antimony layer 3
When a solar cell was manufactured in exactly the same manner except that the a-silicon layer 31 was directly formed on the substrate 4 without forming 0, the photoelectric exchange efficiency was as low as 1%.

As described above, according to the present invention, there is no need for a doping process to form a heavily doped layer as in the prior art, and a good interlayer is created by simply providing a deposited layer of a-silicon on the antimony layer of the substrate. Ohmic contact can be formed, thus
Furthermore, a solar cell with good characteristics can be provided.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an apparatus used to carry out the method of manufacturing a solar cell of the present invention, FIG. 2 is an explanatory diagram showing the configuration of a hydrogen gas discharge tube used in the manufacturing apparatus of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing the configuration of a sputtering device used in the manufacturing apparatus of FIG. 1, and FIG. 4 is an explanatory cross-sectional view showing the configuration of a solar cell obtained by the manufacturing method of the present invention. 1... Belgear, 3... Exhaust path, 4... Substrate, 5... Heater, 6... DC power supply, 7... Hydrogen gas discharge tube, 8... Antimony evaporation source, 9...
Argon gas introduction pipe, 10... Silicon sputtering device, 11... Platinum evaporation source, 21... Hydrogen gas inlet, 22, 26... Electrode member, 23... Discharge space, 30... Antimony layer, 31... Amorphous silicon layer, 32... Transparent metal layer, 33...
ITO transparent conductive film.

Claims (1)

[Claims] 1. A step of forming an antimony layer on a substrate, and a step of providing a deposited layer of amorphous silicon on the antimony layer by magnetron sputtering in the presence of hydrogen gas ionized by glow discharge. When providing the deposited layer of amorphous silicon, an ohmic contact is obtained between the antimony layer and the deposited layer of amorphous silicon, and a step of forming the antimony layer; 1. A method for manufacturing a solar cell, characterized in that the step of forming a deposited layer of assilicon can be performed continuously through the same or adjacent vacuum chambers.