JPS6251210A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent light deterioration action from resulting under actual employment conditions, by adding a neutralizing additive of hydrogen or deuterium to unpaired coupling hands resulting from light irradiation, and by neutralizing and stabilizing by coupling with the unpaired coupling hands, in non-single- crystalline semiconductors. CONSTITUTION:On a synthetic quartz substrate 10, a pair of electrodes 24, 24' are formed, on which amorphous semiconductor 26 being non-single- crystalline semiconductor having hydrogen or halogen elements added is formed. Light conductivity and dark conductivity are measured by contacting probes 17, 17' to the electrodes 24, 24'. After light irradiation annealing is done in vacuum, additive for neutralizing recombination centers of hydrogen or deuterium is added into the semiconductor. The additive introduced for neutralizing hydrogen or deuterium, or oxygen as well as the additive invades into the inside from the surface or vacant holes of the semiconductor to deposit there, and couples with the unpaired coupling hands of silicon preliminarily formed with light irradiation, forming Si-H coupling, Si-D coupling, or Si-T coupling, or Si-O coupling, and is neutralized and stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves the steps of forming a semiconductor material containing hydrogen or a halogen element, holding this semiconductor under reduced pressure and photo-annealing it, and after this step, forming a semiconductor material (
The present invention relates to reducing or eliminating the Stebler-Lonski effect by adding hydrogen or deuterium to a semiconductor (hereinafter simply referred to as "inside" a semiconductor), thereby obtaining high-fidelity characteristics. The present invention is an active semiconductor layer that generates a photovoltaic force upon irradiation with light.
xlQ14~5 For semiconductors to which hydrogen or halogen elements (artificially mixed into the concentration of Xl017cm-3 or mixed at background level) are added, the semiconductors are kept in a reduced pressure state without being exposed to the atmosphere. Alternatively, by performing photoannealing in this atmosphere, dangling bonds generated by light irradiation are sufficiently generated. Thereafter, the purpose is to neutralize the generated dangling bonds by adding hydrogen or deuterium into the semiconductor.

For this purpose, the present invention provides plasma Cvn on a substrate.
A non-single crystal semiconductor (hereinafter simply referred to as a semiconductor) containing hydrogen or a halogen element is heated at a temperature of 500°cll or less, generally at 150
~30 (formed under reduced pressure of 1'c).

In particular, the present invention provides that in one layer, which is the active semiconductor layer,
Oxygen concentration in the lowest concentration region in a semiconductor (SIMS
(minimum concentration when measured at 5 x 1018 cm)
A non-single crystal semiconductor, such as a silicon semiconductor, to which hydrogen or a halogen element containing less than -3, preferably less than IXl018 cm-3 is added is used.

Then, the density of recombination centers in such a semiconductor, especially the recombination centers generated by light irradiation, is calculated from IXIOcm-3 to l
Xl017cm-3 or less, preferably approximately 5 Xl01
The aim is to lower the height to about 6 cm-3.

However, conventionally, when such a highly purified semiconductor is taken out into the atmosphere immediately after film formation and irradiated with light at atmospheric pressure, the electrical conductivity deteriorates, and the electrical conductivity is restored by thermal annealing. The Stebla-Lonski effect is observed.

On the other hand, the present inventor has found that after forming such a high-purity semiconductor, this semiconductor is held in an ultra-high vacuum atmosphere without being exposed to the atmosphere, and when light irradiation (photoannealing) and thermal annealing are performed in this vacuum, this The so-called SEL (Sta te Excited b
y Light) effect was observed.

As a result, it was found that the conventionally known Stebla-Lonski effect can only be observed when a semiconductor is formed and then exposed to the atmosphere. It has been concluded that the reason for this is that the atmosphere, particularly oxygen, is impregnated into the semiconductor. It takes St'! Regarding the L effect and its countermeasure, returning the formed semiconductor to atmospheric pressure in an oxygen-free atmosphere, the patent filed by the present inventor (Japanese Patent Application No. 60-120881, June 3, 1985) (Applications filed in Japan).

The present invention actively utilizes the SEL effect discovered by the present inventors to prevent photodegradation effects from occurring under actual use conditions. In other words, due to the SEL effect, a sufficient amount of dangling bonds (called recombination centers in electrical terms or recombination centers with units at deep levels in terms of energy hands) generated by light irradiation is generated in a non-single crystal semiconductor. I'll let you. Then, in addition to an additive for neutralizing hydrogen or deuterium or an element selected from oxygen, fluorine, chlorine, and nitrogen in addition to the alkali metal element, an element selected from oxygen, fluorine, chlorine, and nitrogen is added to the dangling bonds sufficiently generated by light irradiation. It combines with the unpaired bond, neutralizing and stabilizing it. In this way, all halfway weak bonds are cut once to create unpaired bonds, and these unpaired bonds are neutralized after a sufficient period of time. As a result, in actual use, even if light is irradiated again, this irradiation will generate unpaired bonds and, as a result, the Stebla-Lonski effect, which is observed due to an increase in recombination centers, will not occur. be.

The present invention will be illustrated below according to the drawings.

FIG. 1 shows an outline of the manufacturing equipment used for manufacturing the semiconductor device of the present invention.

FIG. 1 shows a block diagram of an ultra-high vacuum device (UHV device) used in the present invention.

The substrate (10') is arranged below the heater (indicated by (12') in the drawing) in the first preliminary chamber (1). This substrate has in advance a pair of electrodes for measuring electrical conductivity (shown in FIG. 2 (24) and (24')). When measuring electrical properties, a pair of probes (17) are attached to this electrode from the outside after the coating is formed.

(17") can be moved and brought into contact with each other (see Figure 2), and after the semiconductor coating is formed, the optical conversion conductivity and dark conversion conductivity can be determined by the presence or absence of light irradiation (20) without exposing the coating to the atmosphere. In other words, it enables evaluation under IN 5 ITU conditions in vacuum.

It has a first preliminary chamber (1) for inserting and removing a substrate (10 degrees) and a second preliminary chamber (2) connected to this preliminary chamber by a gate valve (3). In this first preliminary chamber, a heater (12') which also serves as a substrate stand is attached.

The second preliminary chamber is separated from the cryopump (6) by a second gate valve (5) and also from the turbomolecular pump (8) by a third gate valve (7).

Then, the substrate (10') and the heater (12') are connected to the first
After inserting it into the preliminary chamber, open the gate valves (3) and (7), close the gate valves (5) and (4), and vacuum the first and second preliminary chambers with the turbo molecular pump (8). Pull. Furthermore, after reducing the pressure to 10-6 torr or less, the substrate (10") and the heater (12') are moved from the first preliminary chamber (1) to the second preliminary chamber using the moving mechanism (19), and the gate valve (3) is moved to the second preliminary chamber using the moving mechanism (19). )
is closed. Then open the gate valve (5) and open the gate valve (7).
), and evacuated to the order of 10-10 torr using a cryopump.

Furthermore, the fourth gate valve (4) is opened, and the substrate (10) and heater (12) are transferred to the reaction chamber (11) using the moving mechanism (19°). The reaction chamber (11) is also pumped with a cryopump (6) from 10-9 to 10-” to
The back pressure is set to rr. Furthermore, the gate valve (4) is closed.

In the drawing, a substrate (10) and a heater (
12) is installed. A pair of electrodes (,14), (,
15) Plasma discharge can be generated between the two. In addition to this plasma CVD method, ultraviolet light and excimer laser light can be used as a window (16).
The semiconductor film may be formed by a photo-CVD method or a photo-plasma CVD method in which high-frequency energy is added to the photo-CVD method.

Reactive gas is added from a doping system (21), and unnecessary substances from the plasma CVD method are exhausted by another turbo-molecular pump (9) while the pressure is controlled by a control valve (22).

The pressure inside the reactor is reduced to 0 by the control valve (22).
．． 001~10torr10torr, 05~0.1t
It was controlled to orr. A non-single crystal semiconductor film, here an amorphous silicon film doped with hydrogen, was formed by applying high frequency energy from (13) (13.56 MHz output 10-) and plasma CVD. Thus, 0.
A non-single crystal semiconductor having a thickness of 6 μm without addition of P or N type impurities was formed at a temperature of 500° C. or less, for example, 250° C.

Reactive gas and carrier gas contain zero impurities of oxygen and water.
．． It was introduced from 21) with a high purity of IPPM or lower, preferably IPPB. Furthermore, when attempting to form a silicon film, silane, which is a silicide gas purified by liquefaction to ultra-high purity, was used.

When constructing a photoelectric conversion device, this doping number is increased, and diborane, which is an impurity for P-type, is mixed with silane by 500%.
It may be diluted to ~5000 PPM and introduced from (21''). Also, phosphin, which is an N-type impurity, may be diluted to 5000 PPM with silane and introduced from (21'').

After the semiconductor film was thus formed in the reaction chamber, the supply of reactive gas was stopped, and unnecessary substances in the reaction chamber were removed by the turbo molecular pump (9). □When adding oxygen, fluorine, chlorine, or nitrogen as a neutralizing additive, these gases were introduced into the preliminary chamber from the doping system (25) in FIG.

After this, the reaction chamber is evacuated using a turbo molecular pump (9).
This was done by Furthermore, the semiconductor (26) on the substrate (10)
, the heater (12) is moved into the first preliminary chamber (1) by opening the gate valves (4), (3) and using the moving mechanisms (19'), (19). Further, the gate valve (4) was closed, the gate valve (5) was opened, and the first preliminary chamber was maintained under reduced pressure by the cryopump (6). The degree of this pressure reduction is at least 10-'' torr or less, and generally 1
The pressure was set at 0-' to 10-9 torr. A semiconductor (26) is held in this preliminary chamber.

The substrate (10) was kept at a temperature of 50° C. or lower that would not induce thermal annealing effects, and after the semiconductor film was formed, it was irradiated with light without being exposed to the atmosphere at all. Furthermore, we performed a step of adding an additive for neutralizing dangling bonds into the semiconductor, and a step of examining changes in electrical conductivity after photo-annealing and thermal annealing. Optical annealing was performed by irradiating visible light such as xenon light (100 mW/c11) through a window (20), and thermal annealing was performed by supplying electricity to a heater (12'').

In Figure 2, a pair of electrodes (chromium is used here) (24) and (24') are formed on a synthetic quartz substrate (10), and the upper surface is covered with intrinsic or substantially intrinsic hydrogen or An amorphous semiconductor (26), which is a non-single-crystal semiconductor doped with a rogen element, was formed. Then, the optical conductivity and optical conductivity were measured at IN 5 in the first preliminary room shown in Figure 1.
ITU, that is, after the film was formed, the probes (17) and (17') were set up on the pair of electrodes (24) and (24''), and the measurement was carried out by the contact method without changing the atmosphere from vacuum.

In the present invention, after light irradiation annealing was performed in a vacuum, an additive for neutralizing hydrogen or deuterium recombination centers was added to the semiconductor.

In addition, the introduced neutralizing additives such as hydrogen or deuterium or their oxygen and oxygen permeate into the interior of the semiconductor through the surface and holes, and combine with the dangling bonds of silicon that have been created in advance by light irradiation. , 5i-H bond, 5t-D bond, 5i-T
bonds or create 5i-0 bonds with these to neutralize and stabilize.

FIG. 3 shows an amorphous silicon semiconductor film formed using a conventionally known apparatus, and then its electrical conductivity measured and evaluated in the atmosphere.

Light irradiation when a silicon semiconductor layer is formed to a thickness of 0.6μ on quartz glass as a substrate (old A) (
The photoconductivity (28) and dark conductivity (2B') at 100 mW/cm'') are shown.

That is, the initial state photoconductivity (28-1) and dark conductivity (28
After measuring ゛-1), AMI (100mW/cm2)
The sample was irradiated with light for 2 hours, and the photoconductivity (28-2) and dark conductivity (28''-2) were then measured and evaluated.Furthermore, this sample was thermally annealed at 150''C for 12 hours, and the same process was performed again. photoconductivity (28-3), dark conductivity (28°-3)
was measured. When this process was repeated, a reversible characteristic was observed as shown in FIG. 3, in which the electrical conductivity decreased due to light irradiation and was recovered by thermal annealing. This repeatability is called the Stebla-Lonski effect.

FIG. 4 shows the electrical characteristics for achieving the present invention, including SEI,
It shows the effectiveness. A semiconductor film is formed using the UHV apparatus shown in FIG. Thereafter, the reaction chamber was evacuated without going through the step of adding additives into the semiconductor.

Furthermore, the substrate (10') on which the semiconductor (22) is formed is held under this heater (12°) in the first preliminary chamber (1).
Changes in electrical conductivity (29), (29') with or without light irradiation (20) and thermal annealing (12') under ultra-high vacuum without exposing it to the atmosphere can be measured IN 5IT.
It was measured in U.

That is, the initial dark conductivity (29'-1) of 1.5 xlO-'Scm-' and the photoconductivity of 9 x10-'Scm-' were measured at a temperature of 25°C and a vacuum of 4 x 10-'torr. (29-1) (using a xenon lamp) was obtained. When this was irradiated with a xenon lamp (100 mW/cm2) for 2 hours, the electrical conductivity was (29-2), (29°-2
), the photoconductivity decreased to 3.5 XIOXlo-5S', and the dark conductivity decreased to 6 x 10-95 cm-'. This sample was then subjected to heat treatment at 150°C for 3 hours. Then,
Conventionally, the electrical conductivity should recover to the initial state value as shown in Figure 3 (28-3) and (28'-3), but in the IN 5rTU measurement method under UHV of the present invention, , as shown in FIG. 4 (29-3) and (29'-3), further decreases. 2 again with the xenon lamp
29-4), (29''-4) was obtained by time irradiation, and (29-5) was obtained by thermal annealing at 150°C for 3 hours.

(29'-5) is obtained. Further, (29-6) and (29'-6) are obtained by xenon lamp annealing. Further, (29-7) and (29°-7) are obtained by thermal annealing. Even if these heat irradiation and thermal annealing were repeated, the photoconductivity (29) and dark conductivity (29°) simply tended to decrease, resulting in characteristics completely different from those in FIG. 3.

This is because the electrical conductivity decreases when the unit is induced by light irradiation, and the inventors believe that 5EL
(State Excited by Light)
It is called an effect.

FIG. 5 shows other electrical characteristics produced by the method of the present invention.

That is, a semiconductor film was formed using the apparatus shown in FIG. The photoconductivity of this semiconductor film is (30), and the dark conductivity is (30).
The electrical conductivity immediately after the film is formed is shown in (30
-1) and (30'-1). Thereafter, the reaction chamber or the first preparatory chamber is kept in vacuum for a sufficient period of time (more than 3 hours, here 48 hours), and visible light (100 mW/cm2) is applied.
), and St! A recombination center is induced by the L effect, and its electrical conductivity becomes (30-2) and (30'-
2).

Furthermore, for semiconductors in which this SEL effect occurs, the system (2
5) Add hydrogen or deuterium to the preliminary chamber.

This hydrogen or deuterium is heated and added to the semiconductor surface and the semiconductor held under reduced pressure, and the electrical conductivity after about 48 hours is shown in (30-3) and (30'-3). Then, this impregnated hydrogen or deuterium combines with the dangling bond of Si- in the semiconductor to form Si-1 H-5i-H 5i-+ D-5i-D SL-10 T-5i-T. This Si--Li bond is expected to be stable even if the semiconductor device is subsequently placed in the atmosphere. Thus, the semiconductor formed by the method of the present invention has an IN 5 ITU
A cycle of light irradiation and thermal annealing in vacuum was simultaneously performed as shown in FIG. However, as shown in FIG. 5, there was almost no change.

That is, 6. in the initial state. The light irradiation (2 hours) (30-
4) , (30”-4) , (30-6) , (
30'-6) is obtained. Furthermore, (30-5) and (30'-5) were obtained by thermal annealing at 150° C. for 3 hours. Although this electrical conductivity changes slightly, there is almost no change, and it can be seen that almost no new recombination centers are generated by this light irradiation and thermal annealing.

From the results of the above experiments, the Stebla-Lonski effect is observed only in photo-annealing and thermal annealing in the atmosphere of a sample in which a semiconductor is formed, the semiconductor device is exposed to the atmosphere, and oxygen is adsorbed or reacted with the semiconductor. It turns out that this is a phenomenon that occurs. And SIl discovered by the inventor
The L effect is observed by performing optical annealing and thermal annealing to form a semiconductor film, and then evaluating the electrical characteristics of the semiconductor film under ultra-high vacuum without exposing it to the atmosphere.

Furthermore, after forming the semiconductor film shown by the present inventor, the SEL effect is induced under ultra-high vacuum, and by adding an additive for neutralizing recombination centers to this semiconductor, unstable dangling bonds are removed. By combining with additives and stabilizing it, it is possible to prevent property deterioration due to light irradiation.

Furthermore, after forming the semiconductor, the present invention uses an ultra-high purity inert gas (Ar+He+Ne or N
z) Atmospheric pressure inside. Furthermore, this semiconductor is transferred to a different vacuum container, kept under ultra-high vacuum again, heated (at or above the film formation temperature), degassed, induces the SEL effect, and is removed by light irradiation. It is also effective to generate a sufficient amount of stable dangling bonds and then add an additive to the semiconductor without mechanically damaging stress to neutralize the unstable dangling bonds. However, it is estimated that the change in electrical conductivity of the semiconductor device manufactured by this process is slightly more degraded than the results shown in FIG.

Furthermore, in the method of the present invention, the substrate is held in this mixed gas of hydrogen and oxygen, and the pressure is brought to atmospheric pressure.
It is also possible to perform heat treatment at 500° C., typically 250 to 300° C., to diffuse the active H,0 element into the semiconductor and neutralize the dangling bonds.

The method of the present invention described above is similar to the conventional method (for example, USP 4226898S) in which, when forming a semiconductor film, the film is formed in an atmosphere containing impurities such as fluorine, and these additives are added at the same time as the film is formed. , R. Optinski), its technical philosophy is fundamentally different.

The film formed in the present invention mainly consisted of an amorphous silicon semiconductor doped with hydrogen. However, fluorinated amorphous silicon, 5iXCt-x (0<X<1), 5i
xGe+-x(0<X<1), 5ixSn+-x(0<
X<1) It goes without saying that the present invention can also be applied to non-single crystal semiconductors in which other Stebla-Wronski effects are normally observed.

In the present invention, the addition of hydrogen or deuterium is not limited to the examples only, and addition of other hydrides (e.g. Hz
O, HF, IIcI, NHs, DzO, HD, D□, T
2□ etc.) may be used. It was also effective to simultaneously add oxygen, fluorine, chlorine, and nitrogen.

[Brief explanation of the drawing]

FIG. 1 shows an outline of a plasma vapor phase reactor for manufacturing a semiconductor device according to the present invention. FIG. 2 shows a longitudinal cross-sectional view of a system for measuring electrical conductivity. FIG. 3 shows the electrical characteristics of conventionally known intrinsic semiconductors. FIG. 4 shows the electrical characteristics of an intrinsic semiconductor for implementing the present invention. FIG. 5 shows the electrical characteristics of an intrinsic semiconductor produced by the method of the present invention.

Claims (1)

[Claims] 1. A step of forming a non-single crystal semiconductor containing hydrogen or a halogen element on a substrate, and holding the semiconductor under reduced pressure,
A method for manufacturing a semiconductor device, comprising the steps of performing photo-annealing and, after the step, adding hydrogen or deuterium as an additive into or on the surface of the semiconductor. 2. A method for manufacturing a semiconductor device according to claim 1, wherein the reduced pressure state in which the semiconductor is maintained is 10^-^3 torr or less, and the temperature is maintained at 50°C or less. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the additive is selected from oxygen, fluorine, chlorine, and nitrogen in addition to hydrogen or deuterium.