JPS589320A - Manufacture of silicon thin-film - Google Patents

Abstract

PURPOSE:To reduce primitive additive impurity to a certain depth and perform replacement, by placing a doped Si thin-film in a sort of plasma of F, Cl, H. CONSTITUTION:A P or N type Si thin-film of single crystal, amorphous, or mixture of fine crystal powder in amorphous is placed in a sort of plasma of F, Cl, H. The plasma discharge is made by adjusting the pressure to a degree of 1.5X10<-2>-3 Torr, keeping the flow in a viscosity range within a container, and varying the power range within 0.5-50W/cm<3>. As a result, a primitive additive impurity can be replaced by a plasm element at a certain depth from the thin- film substrate surface to 5,000Angstrom deep at maximum. Another N or P type Si thin- film is accumulated thereupon or through an i layer. This method maintain the release of the additive impurity at little value even being exposed to an arbitrary plasma, thereby obtaining the Si thin-film of good property.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a silicon thin film that can be applied to diodes, solar cells, photoconductors for both image formation, photoelectric conversion elements for continuous NIL devices, and the like.

Conventionally, a silicon thin film has been used alone or as a general (pin junction element or pniI junction element) to achieve a desired purpose. In an atmosphere, for example, a PL silicon thin film doped with B (boron) as an impurity is formed, and then an undoped type 1 silicon thin film serving as an active layer and an n-type silicon film doped with P (phosphorus) are formed on the p-type silicon thin film. type silicon thin film or the NLL silicon thin film directly on the p-type silicon thin film using two or three 1 mK deposition steps. Alternatively, first the n-layer film and then the 111-layer film are grown. A method of forming a p-layer film or a p-layer film directly on the n-layer film was also carried out in the same way. However, devices fabricated by such a film-forming method are Forming a new upper layer on top of the lVc film has the disadvantage that impurities in the lower (already grown) film are released in a plasma atmosphere and are mixed into the upper layer.As a result, the film grown on a substrate that does not contain impurities A film grown on a film containing impurities has lower photoelectric conductivity and positive conductivity compared to
If a pin junction semiconductor device is manufactured for the purpose of solar cells, if the device is manufactured using a substrate, a p-layer film, a single-layer film, and an n-layer film, p*111 in the single-layer film.
Due to the contamination of the impurities added to II, the photoelectric conductivity and positive electrical conductivity are reduced, and a good bond is not formed. On the other hand, for devices fabricated using a substrate, an n-layer film, a five-layer film, and a p-layer film (for example, impurities added to the n-layer film are mixed into the first-layer film and moved from the 7-hermi level). As a result, it is not possible to obtain a sufficient open-circuit voltage.This ultimately means that the light energy conversion efficiency decreases, which reduces the performance of solar cells and makes them difficult to use for various applications. Even in this case, the performance deteriorated.

The present inventors have proposed that a pm[silicon thin film or n1M silicon thin film doped with impurity elements is subjected to a plasma discharge state of a gas containing at least the same number of elements as fluorine, chlorine, bromine, iodine, and hydrogen. The silicon thin film has a reduced amount of impurities at a depth of 5oooi from its surface, and the dangling bonds created by the removal of impurities in the p II or nll silicon thin film are replaced by plasma discharge gas, thereby increasing the plasma It has been discovered that a barrier layer can be formed to prevent further release of impurities from a silicon thin film in an atmosphere.

Additionally, it has been found that the degree of destruction and the depth of reduction of impurities from the silicon thin film can be varied by adjusting the pressure and time during plasma discharge in the vacuum vessel, as well as the force density during plasma discharge.

The discharge pressure itt, which is one of the important parameters mentioned above when implementing the manufacturing method according to the present invention, is 5x1 G-”
It is preferable to control the temperature between Torr and 3 Torr.

In other words, if the discharge pressure is below 1.5810 Torr, the flow inside the vacuum vessel becomes a diffusion flow, and there is a high possibility that impurities released from the silicon thin film substrate will mix into the silicon thin film substrate again. , to make the flow inside the vacuum container a viscous flow, the pressure during discharge is 1.5
It is necessary that the value is at least Torr.

Further, the pressure at the time of discharge of 3 Torr is for preventing discharge between the electrode and the earth shield, and is mainly due to equipment factors. Also, the discharge power level varies depending on the nature of the Blaz i gas used, but it is 0.5 to 50 W/
cJam is suitable. The discharge time under such conditions can vary from 1 second to 5 hours.

Also, regarding the relationship between discharge power density and discharge time,
Generally, it can be said that the discharge power density is involved in the depth of reduction of the originally added impurity element, and the discharge time affects the amount of reduction of the originally added impurity element.

In addition, the flow rate of the plasma element gas brought into the plasma state into the vacuum chamber is adjusted to keep the plasma state stable.
Good results were obtained at 0.5 to 11008 CC.

The present invention has been made based on the above-mentioned new findings. That is, the method for producing a silicon thin film according to the present invention provides Kpm silicon yi in a gas discharge state of at least one element of fluorine, chlorine, bromine, iodine, and hydrogen.
** or nl [A silicon thin film is deposited, and the amount of impurities is reduced from the surface of the p-type or nll silicon thin film to an arbitrary depth of 5,000 mm.The dumplin 2 bond produced by removing the impurities is then exposed to plasma. A notable feature is that it is replaced by discharge gas.

Therefore, the pm! produced according to the invention! Alternatively, even if a silicon thin film is exposed to a low-power electric discharge, as in the case of forming a single-layer film on top of an iron thin film in an artificial process, the impurities in the thin film will be re-released into the single-layer film. There's nothing to do.

That is, when another film is grown in a plasma atmosphere on an NFJ or 9M thin film substrate prepared by the conventional method, the impurities of the film used as the substrate are contained in the film at 1016 atoms/cm.
``Nl produced by the production method of the present invention compared to the above
When another film is grown on a 1 or pW1 thin film as a substrate, it is possible to suppress the amount of impurities released into this film from the film that served as the substrate to 101@atoms/rs” or less. It is possible.

Therefore, the main object of the present invention is to prevent the added impurities from being released to the outside (or even if they are released, it is assumed to be extremely small) even if Kth is performed in any plasma atmosphere. Another object of the present invention is to provide a method for manufacturing an NLL silicon thin film.

Another object of the present invention is to provide a solar cell, a photoconductor for image formation, a photoelectric conversion element for an 11IIIL device, or a solar cell having good photoelectric conductivity and dark electric conductivity and improved light energy conversion efficiency. An object of the present invention is to provide a method for manufacturing a silicon thin film that can be used for manufacturing diodes and the like.

In the manufacturing method according to the present invention, an amorphous silicon semiconductor film is formed on an arbitrary substrate in a plasma atmosphere using a silicon single crystal semiconductor and a mixture of silane (81Ha) and a dopant gas as raw material gases. In addition, silicon thin films such as those described in the applicant's patent application (Japanese Patent Application No. 55-143010), i.e., Si 8
iH4 or halogenated silane 81H, ~, x4~t
(X: Haloken element 11) or a mixture of two or more thereof is used as a raw material gas, a dopant gas is mixed with this, and a crystalline and amorphous mixed layer is generated by sufficiently controlling the film formation mode. For the purpose of
When diluted with a diluted oxide such as agonist or hydrogen fat at a ratio of about 1:1 or more, silicon is deposited while applying power with a plasma discharge power density of 4k, about 0.2 W/(J" or more). Thin films may also be conveniently applied.

Next, the method for manufacturing a silicon thin film according to the present invention will be described in Example K.
I will explain.

Embodiment 1 In FIG. 1, the entire equipment system including the mixing vessel 1 is pumped approximately 10-a'' using an oil rotary pump 2 and an oil diffusion pump 3.
The degree of vacuum is set to I'orr, and then gases are introduced from the silane cylinder 4, the hydrogen cylinder 5, and the dopant gas (ciborane or sphin) cylinder 6 or 7 at a required ratio into the mixing container 11C and mixed.

The mixed gas is introduced into the vacuum vessel 9 through the flow meter 8 at a constant flow rate. The main pulp 10 is operated to maintain the required pressure while monitoring the degree of vacuum in the vacuum container 9 with a vacuum gauge 11. Electrodes 13 and 13' with high frequency oscillation @12
A goo discharge is generated by applying a high frequency voltage to the gate. The substrate 15 is placed on a substrate heated by the heater 14,
This substrate 15 is heated to the required temperature with a heater.
A doped silicon thin film is deposited thereon.

In this practical example, the raw material gas is 84H,s H,=1:
Siborane (BII) was used as a dopant using a mixed gas of
It was a mixture of 8 tH and 2% (volume basis) of 8 tH and V. Hydrogen stuff again! The deposition conditions for the pli silicon thin film before processing in the atmosphere are a plasma applied power density of 0. I W/cI1m, raw material gas flow rate 158CC
M, substrate temperature 300°C, film formation pressure S X 10-”7o
It was rr.

After forming the resilicon thin film as described above, the entire equipment system including the mixed customer gs1 is again evacuated to a vacuum level of approximately 10-' Torr using bonders 2 and 3, and water bulk gas is piped from the hydrogen cylinder 5. It is fed directly via line 16 to meter 8 and then at a constant flow rate into vacuum vessel 9. Manipulate the main pulp 10 to measure the degree of vacuum in the vacuum chamber 9 with a vacuum gauge 11.
Adjust to ITorr while monitoring. Next, the high frequency oscillator 12 applies a high frequency voltage of 13 to 56 MHz to the voltages 1ii13 and 13/ to generate a hydrogen plasma goo discharge. An amorphous silicon thin film having a pH in which impurities were removed from the surface and the resulting dangling bonds were replaced by hydrogen was fabricated.

Four types of p were prepared by changing the hydrogen plasma discharge conditions, that is, the discharge time.
l [An amorphous silicon thin film was produced. The result is the 11th HC
shown. In this table, AI is a p-silicon thin film manufactured by a conventional method without hydrogen gas discharge treatment. 12 to 5 are examples of pH silicon thin films produced according to the present invention, and by adjusting the hydrogen A gas flow rate and the pressure during hydrogen plasma discharge, the flow in the device is made into a viscous flow region, and the Is the radiation released from the silicon thin film contained in the silicon thin film? ! Operations were carried out to prevent contamination.

No. 250 shows the electrical conductivity of silicon thin films made according to the present invention as a function of hydrogen plasma treatment time. From FIG. 2, it can be considered that the amount of boron atoms in the silicon thin film is reduced from the surface by the manufacturing method of the present invention. Furthermore, it was determined by the 8IM8jl determination that the dart atoms from the surface m to a depth of 10001 in the PM thin film according to the present invention were removed to a depth of 51-.
Please refer to the figure).

Example 2 A -Cng silicon thin film was prepared in the same manner as in Example 1 except that phosphine (Paa) was used as the dopant, and then the wrinkled nil silicon thin film was subjected to hydrogen plasma treatment in the same manner as in Example 1. discussed.

8MM8 measurements confirmed that the phosphorus atoms were completely removed from the nl thin film from the surface to a depth of 5001 kW.

pm produced by the production method of the present invention as described above
! Alternatively, it will be appreciated that n-type silicon thin films can be fabricated using conventional deposition techniques such as pnll or pin II (#) 41 composite devices. On the pl[(or nl[)ill] film formed according to the present invention, it is possible to
i1m! , n-type (or p If ) H films have a better pi (or ni ) junction than the conventional pin-class hybrid semiconductor device, and similarly, the pin junction semiconductor device fabricated by forming n-type (or p If ) H films has a better pi (or ni ) junction than the conventional pin-class hybrid semiconductor device. Membrane pH (or n Ii!)
PN with n1M (or p II ) film deposited on 1M
*It has better pnm matching than the pn junction semiconductor iris which is a hybrid conductor element. In addition, the present invention can be applied to a pH film substrate to sufficiently remove impurities from the pH film surface to form a pill silicon thin film. You can also make Ushihiro body elements.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an apparatus for implementing the silicon thin film manufacturing method according to the present invention. The second wJ is a graph showing the electrical conductivity of a silicon thin film produced by the production method according to the present invention as a function of plasma discharge time. Figure 3 is a graph showing the measurement results of SIM8 of a silicon thin film manufactured by the manufacturing method according to the present invention. 1: Mixing container 4.5.6, 7: Gas pump 92 Vacuum container 13.13': Electrode 15: Substrate

Claims (1)

[Claims] 1) The pal father places a nil silicon thin film under a plasma atmosphere of at least one element selected from the group of fluorine, chlorine, bromine, iodine, and hydrogen, so that the surface of the silicon thin film is 1. A method for manufacturing a silicon thin film, characterized in that the amount of impurity elements is reduced over a predetermined depth, and plasma elements are substituted for cough impurity elements. 2) The manufacturing method according to claim 1, characterized in that the pressure during plasma discharge of fluorine, chlorine, bromine, iodine, or water gas is adjusted so that the flow within the container is in a viscous flow region. 3) The manufacturing method according to item 2 of the patent-requested scope, characterized in that the pressure when applying the plasma of fluorine, chlorine, bromine, iodine or water bulk gas is 1.5 x 10-'' to 3 Torr. ) The manufacturing method according to claim 3, characterized in that the impurity reduction depth is adjusted by changing the power density in the range of 0.5 to 7 ams. 5) The amount of impurities is determined by the surface of the silicon thin film. up to 5,000
5. A manufacturing method according to claim 4, characterized in that the depth decreases over a depth of λ. 6) The manufacturing method according to claim 8, wherein the silicon thin film is a single crystal silicon semiconductor. 7) The manufacturing method according to claim 8, wherein the silicon thin film is an amorphous silicon semiconductor. 8) Claim Ii! The silicon thin film is a silicon semiconductor in which microcrystalline grains are mixed in an amorphous layer! 1tsThe manufacturing method described in item 1. 9) Placing a PAL or NIL silicon thin film in a plasma atmosphere of at least one element selected from the group of fluorine, chlorine, bromine, iodine and hydrogen, thereby extending a predetermined edge K from the surface of the silicon thin film. 41 - A method for manufacturing a silicon thin film, characterized in that the amount of impurity element is reduced and the plasma element replaces the cough impurity element, and then a K n M or Pi1 silicon thin film is deposited on the thin film. 1u) pH or nal silicon # membrane with at least one ear of elemental goodness selected from the group of fluorine, chlorine, bromine, iodine and hydrogen! 11! - placed under air, thereby reducing the amount of impurity elements over a predetermined depth from the surface of the silicon thin film and allowing plasma elements to replace the impurity elements, and then placing the Ki-type silicon thin film on the wrinkled thin film.
I! A method for producing a silicon thin film, characterized by forming a thin NLL or P silicon film.