JPH0338756B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves forming a transparent electrode in close contact with one surface of a semiconductor, and optically annealing the conductive electrode and the semiconductor by irradiating the conductive electrode and the semiconductor with laser or similar strong light energy. The purpose is to do the following.

The object of the present invention is to perform such photoannealing on a non-single crystal semiconductor made of silicon, germanium, or one of them to which oxygen, nitrogen, carbon, tin, or lead is added. .

The present invention relates to a semiconductor device having a non-single-crystal semiconductor mainly composed of group elements and a transparent electrode mainly composed of an oxide or nitride containing an additive provided on the upper or lower surface of the semiconductor. The purpose is to dope the elements or additives constituting the non-single crystal semiconductor with each other so that the semiconductor and the electrode are integrated or substantially integrated.

Conventionally, thermal annealing has been known as a method for reducing the density of recombination centers or levels generated in semiconductor devices. This is 300~700℃
By annealing (heat slowing) in hydrogen or inert gas at a temperature of silicon oxide - semiconductors, especially silicon)
In semiconductor devices, it has been used to cancel slow levels at interfaces or remove lattice distortion in single crystal semiconductors.

For high temperature annealing, e.g. 700~1200℃
Boron (B), phosphorus (P), arsenic (As), etc. are implanted into a single crystal semiconductor at 1000°C, and through subsequent annealing, the amorphous state generated by this implantation is transformed into a single crystal as if it were warm. It was known that

However, in all of these, the basic idea is to eliminate dangling bonds or vacancies in the crystal by making it more monocrystalline.

Rather than using such conventionally known thermal annealing methods, the present invention applies laser light or similar intense light energy (hereinafter collectively referred to as L-annealing) to a semiconductor, and as a result, This is what I wanted to do.

Further, the present invention provides that such L-annealing is more effective for non-single crystals than for single crystals, and for non-single crystals, that is, polycrystalline or amorphous semiconductors formed on a substrate by a method such as a CVD method, or a glow discharge method. , hydrogen-containing amorphous amorphous or crystal grain size formed by plasma CVD method etc.
It is particularly effective for polycrystals with microscopic diameters of ~100 Å.

Such non-single crystal semiconductors generally have an extremely large number of dangling bonds, so impurities in the range of 10 ¹⁹ to
10 ²¹ cm ^-3 when used as a substantially doped conductor, or by simultaneously forming the film in such a non-single-crystal semiconductor and simultaneously bonding the unpaired junction with hydrogen to neutralize it. It is known that it is used as a semiconductor. However, regarding the former, when the impurity is doped in a large amount of 10 ²⁰ cm ^-3 to 50 atomic %, the impurity precipitates, causing so-called segregation, and a lump of impurity is generated in the semiconductor.
It becomes no longer electrically active. That is, its activity in the semiconductor (the amount of active P or N type in the semiconductor/the amount of impurities mixed in the semiconductor) has become extremely low, at 0.1 to 10 atomic percent. On the other hand, in the case of hydrogen-doped non-single crystal semiconductors, if electrodes are formed in the system or annealing is performed at a lower temperature of 300 to 700°C, the hydrogen in the semiconductor is converted into hydrides such as Si.
It was liberated from the -H bond and released from the semiconductor as H ₂ , and the density of recombination centers increased due to thermal annealing.

The present invention eliminates such drawbacks, and when an additive having a P or N type above its solid solubility limit is added to a semiconductor, its activity is increased by increasing crystallization. 100
% and thus increase its electrical conductivity in the semiconductor, and this treatment or 300 ~
Due to the low-temperature annealing at 700°C, the neutralized recombination centers such as hydrogen or halogen elements are added back into the semiconductor in a chemically active state and bonded to the dangling bonds to form a semiconductor. The density of the recombination centers inside is lowered.

In addition, the present invention moves some of the additives or constituent elements of the electrode, particularly the transparent electrode, formed on the upper surface of the semiconductor into the semiconductor during L-annealing, and the boundary is changed from the conventional surface concept. It is characterized by its expansion to include the concept of territory. As a result, the impurity activity of the semiconductor under the electrode is increased, and its electrical conductivity is extremely high and has a conductivity close to that of metal. That is, it has been found that the Fermi level can be brought to a substantially degenerate state.

Embodiments of the present invention used in the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a semiconductor device used in the present invention.

A semiconductor substrate 1 is shown in FIG. 1A. A typical example of this semiconductor substrate is a single crystal semiconductor such as silicon. This single-crystal semiconductor may have an MIS structure on its upper surface, or a portion of the semiconductor substrate may be doped with impurities by ion implantation or the like to become partially non-single-crystal. In the present invention, such a semiconductor was subjected to L-annealing. The laser used for L-annealing was a CW laser. The output was 10-70W. In this way, the semiconductor layer near the surface of the semiconductor substrate at a depth of 0.1 to 3 μm was annealed. However, this L-annealing was not very effective in eliminating the interface states at or near the semiconductor-insulating film interface. In addition, it is not very effective in preventing leakage of minute currents due to minority carriers flowing in semiconductors.

In order to eliminate such drawbacks, the present invention immerses this semiconductor in an atmosphere maintained at one atmospheric pressure or less that contains neutralized recombination centers such as hydrogen in a chemically active state excited by radio frequency induction. (hereinafter referred to as induction annealing) The temperature of this atmosphere is room temperature (-70~+
(200℃) is also possible. Hydrogen or an inert gas such as helium or a portion of halogen elements such as chlorine and fluorine are mixed to a concentration of 0.01 to 3 atomic % in a reduced pressure furnace from the outside at 0.1 to 100 MHz, for example 13.5 MHz, by high frequency induction. Excited atmosphere. Therefore, for example, hydrogen is more H than _H2 , H ^*
Or H ⁺ and chemically active generating group hydrogen, that is, it can be in a plasma state. This hydrogen penetrates into semiconductors or insulators without any hindrance, and can be dangling bonds in semiconductors, insulators, or semiconductors such as silicon that exist at their interfaces, or dangling bonds in insulators such as silicon or oxygen in silicon oxide. It combined with the pair bond and electrically neutralized it.

As a result, the defect density of the semiconductor layer, which had been destroyed by ion implantation, decreased from 10 ²² cm ^-3 to 10 ¹⁹ to 10 ¹⁷
cm ^-3 , which can be further reduced to 1/10
I was able to lower it to ~1/50. In particular, while laser annealing can reduce the defect density of the impurity layer that constitutes the source and drain of MIS.FET without widening the junction, induction annealing can reduce the defect density in the impurity layer that constitutes the source and drain of MIS. This was effective in reducing the number of dangling bonds and levels at the interface. In addition, while laser annealing anneals areas closer to the interface, L-annealing neutralizes and anneals defects at a depth of 3 to 10 μm from the semiconductor surface, which cannot be processed. Induction annealing was extremely effective.

FIG. 1B shows a semiconductor layer 1 formed on a substrate 3. In FIG. This semiconductor or semiconductor layer is produced by using a thermal decomposition method using a whole silicide such as silane.
It was formed at a temperature of 900℃. In order to fabricate this semiconductor layer, CVD (Chemical Vapor
Deposition) was invented by the present inventor in 1973.
1389. Furthermore, the invention was carried out based on the glow discharge method, plasma CVD method, etc. patent application No. 53-067507 (filed on June 5, 1978) filed by the inventor. The semiconductor layer 1 formed by this method is made of a non-single crystal semiconductor, and PN is selectively formed in the semiconductor or approximately parallel to the substrate surface.
Multiple junctions such as junctions, PIN junctions, PNPN .
For example, it is described in Application No. 53-124022 (October 7, 1978), which is an invention of the present inventor.

When such a non-single crystal semiconductor is selectively or entirely subjected to L-annealing similar to that shown in FIG. 1A,
The density of lattice defects on the semiconductor surface or at a depth of 2 to 3 μm from the surface can be reduced to 1/10 ³ to 1/10 ⁵ by bonding the elements constituting the lattice. However, at the same time, the elements constituting the semiconductor combine with hydrogen, etc. and are neutralized, and some of the dangling bonds change from Si-H bonds to Si-, creating dangling bonds instead. I let it happen. At this time, hydrogen bonds with each other through Si-H,
It was found that only H ₂ remained in a stable state in the semiconductor. That is, Process 1 Si-H+H-Si→Si-Si+H ₂ Process 2 Si-H+H-Si→2Si-+H If this process 2 occurs more often, crystallization will be promoted more and the density of recombination centers will be simpler than in process 1. It was found that even though it approached crystallization, it increased the amount. In other words, in process 1, silicon atoms form covalent bonds with each other, approaching a single crystal, and the electrical conductivity increases by approximately 100 times.
The density of recombination centers is 10 18 ^to 10 ¹⁹ cm -3 in films made by glow discharge, etc., compared to 10 ¹⁷ to 10 ¹⁸ cm ^-3 before L-annealing, which is due to ^the hydrogen content in this semiconductor. It was found that although the amount remained unchanged at about 20 to 30 mol%, it increased by an order of magnitude. In other words, this fact indicates that free hydrogen bonds with itself, and that the hydrogen cannot fully bond with the dangling bonds of silicon in an extremely short period of time.

FIG. 2 shows another embodiment of the present invention, in which a transparent electrode is formed on a semiconductor.

In FIG. 2A, the substrate 3 is an insulating substrate made of glass, a composite material such as ceramic or glass epoxy, an organic material such as Kapton or polyimide, or a stainless steel substrate.
It may be a conductor substrate made of steel, titanium, titanium nitride, or the like, or a composite substrate in which a conductor is selectively provided on the above-mentioned insulating substrate. A semiconductor layer 1 having a non-single crystal structure was formed on these substrates. This semiconductor was manufactured using a plasma CVD method using silicide as the main component. This semiconductor contains a PN junction,
PIN junction or PNPN…PN multiple junction, PINI…
IPIN multiple junctions were formed. The thickness of the semiconductor layer is 0.5
~5μ thick. Furthermore, tin oxide is added to this top surface.
A conductive film 2 further made of indium oxide, antimony oxide, or a mixture thereof or a nitride of tin, indium, antimony, or a mixture thereof is made into a single-layer or multilayer electrode with a thickness of 0.05 to 3μ by the same plasma CVD method. Created.
This conductive film is optically transparent and is characterized by low absorption of laser light and visible light. Furthermore, L-annealing is added to this FIG. 2A, and a transition region 5 is provided at the boundary between the transparent electrode 2 and the semiconductor layer 1 as shown in FIG. 2B. Oxygen or nitrogen, and indium (In), which exhibits P-type conductivity in semiconductors,
Gallium (Ga), aluminum (Al), boron (B), zinc (Zn), and cadmium (Cd) were added as additives. In particular, when used alone, metals have characteristics, and in semiconductors, In or a mixture of In and B, which has P-type conductivity, is a P-type additive in this transition region.
This was effective in making the conductivity of the mold extremely high. This L-annealing increases the melting amount of In and B by 10 to 10 ³ times the concentration of 10 ²⁰ cm ^-3 which is the melting limit,
It has the characteristics of being in a supersaturated state and not causing segregation, and is 10 ²⁰ cm ^-3 to 30 at.
The addition of was extremely effective in increasing conductivity without causing scattering of impurities with respect to holes. In the present invention, the diameter of the crystal grain boundary of the non-single crystal semiconductor is further reduced to 10 to 1000 Å by this L-annealing.
By increasing the size to 1 to 50 μm and approaching a single crystal, the conductivity could be increased by 10 to 10 ³ times. However, in order to prevent the generation of dangling bonds due to this L-annealing, induction annealing was further performed on Figure 2B, and hydrogen in an active state was added to the dangling bonds to electrically neutralize them. It made me feel at ease. By doing so, it is possible to improve the photoelectric conversion efficiency in the short wavelength region on the light transmitting side of a photoelectric conversion device, especially a solar cell, etc., and ultimately increase the collection effect in the 0.3 to 0.5 μ wavelength region to 95 to 100%. I was able to do that.

Also, if you want to make the semiconductor under the transparent electrode N-type, add antimony (Sb) as an additive to the transparent electrode.
Additives such as arsenic (As), phosphorus (P) or tellurium (Te), selenium (Se) to transparent electrodes of tin oxide or nitrides such as tin nitride or antimony nitride ^. It may be added at a concentration of cm ^-3 to 30 atomic %. Among these additives, particularly Sb or a mixture of Sb and P, the semiconductor layer directly under the electrode is similarly made N-type by L-annealing.
And N has an activity close to 100% without causing segregation at a concentration exceeding the solid solubility limit of the added amount.
I was able to make it into a mold.

By such L-annealing, a non-single crystal semiconductor can be made into a single crystal, and some components or additives of the transparent electrode can be doped to a very shallow depth of 50 to 5×10 ³ Å, especially 500 Å. Ta. This doped surface is a transition region that can be in close contact with both electrodes and semiconductors, and its resistivity is 10 ^-1 to 10 ^-4 Ωcm ^-1 , which is close to that of metals, and in terms of quantum theory, it is in a degenerate state at the Fermi level. It is estimated to be. In addition, since this transition region is thin, in photoelectric conversion devices, short-wavelength light is used to cause excitation to generate electron-hole pairs, and the recombination center of both is neutralized with a neutralizing substance such as hydrogen. Therefore, it was possible to guide it to the electrode without recombining.

In addition, in the present invention, since the annealing is forcibly performed by L-annealing, some elements, such as oxygen or nitrogen, may locally react with the elements constituting the semiconductor to form local lower silicon oxide or silicon nitride. 100~150℃ to prevent failure mode such as making insulating film
It was extremely reliable as it did not cause any problems such as when left at high temperatures.

FIG. 2C shows a case where the transparent electrode 2 is formed on the lower side and the semiconductor layer 1 is formed on the upper side. In such a case, if the substrate 3 is made of glass or the like, annealing using laser light incident from the lower glass side is preferable. However, if the semiconductor layer is as thin as 0.05-2μ, L-annealing may be performed through the semiconductor layer from above.

As a result, a transition region 5 was formed as shown in FIG. 2D, similar to FIG. 2B. Depending on the direction of laser light irradiation, the crystal grain size of the semiconductor layer increases; when irradiated from below, the lower part of the semiconductor layer is large and the upper part is small; when irradiated from above, as shown in Figure 2B, The upper part of the semiconductor layer 1 becomes larger and the lower part becomes smaller as a crystal. From this, it was found that the crystal grain size in the depth direction can be controlled by the irradiation direction, intensity, and irradiation time of the laser beam.

FIG. 2E shows a case where a transparent electrode is formed on the upper side 2 and further on the lower side 4 with a semiconductor layer 1 sandwiched therebetween. As a result, the transition region 3 is made to be P type and the transition region 6 is made to be N type by L-annealing, so that a so-called P-N junction can be suitably made. Of course, in the embodiment shown in the drawings, the lower electrode 4 is formed by forming a conductive electrode made of a compound of Sn and Sb on the base metal on the substrate, and utilizing the reflection of the laser beam from the upper side of the lower electrode. A method may be used in which a part of this electrode is added to the semiconductor layer. Conversely, it is also possible to create a NIP junction where the upper electrode has a valent additive, and the lower electrode has a valent additive.

In Figures 2A and 2C, it is not specified that a semiconductor layer of N or P type conductivity is formed on the substrate or semiconductor layer, and that a PN junction or other junction is formed within this semiconductor layer. . However, the CVD method
In plasma CVD method, glow discharge method, etc.
Semiconductors of these conductivity types may be manufactured by adding B as an impurity for a P type and P as an impurity for an N type at the same time as the semiconductor layer is formed. Furthermore, since this concentration exceeds the solid solubility limit and its activity is only 3 to 30% in non-single crystal semiconductors, it can be increased to 90 to 100% by performing L-annealing, making it extremely suitable for semiconductors. It has become possible to have structural sensitivity as

FIG. 2G is an example in which transparent electrodes are selectively provided on the conductor layer.

As a result, the shear-low junction (5 to 200 Å) was
It can be made as 5, 5' as shown in Figure H.

FIG. 3 is an example of a manufacturing apparatus for carrying out the present invention. The outline of the device will be explained based on the drawings and the description as before.

A substrate 11 on which a semiconductor is formed is delivered from an input chamber 20 to an output chamber 21 by a loader 28 . Chamber 23 is especially 0.01~100torr
Since the reaction is carried out under a reduced pressure of 0.1 to 10 torr, hydrogen as a neutralization gas is introduced from 15, an inert gas such as helium is introduced from 16, and a halogen element such as HCI is introduced from 17. Further, the exhaust gas is exhausted by a vacuum pump 19 via a needle valve 18. The laser beam is scanned from the laser 12 through the mirror 13 onto the substrate.
- Annealing is performed. In this device, a high frequency induction furnace is installed outside the chamber at the same position where the laser is irradiated. This high frequency induction furnace 22 uses a voltage heating method and has a 13.6MHz,
100W to 1KW was used. After this, all these are 300
A furnace 25 for low-temperature annealing at ~700°C is provided, and a special high-frequency induction furnace 24 is provided independently behind the furnace 25. This induction furnace may also be of a parallel plate type so as to face the substrate 11. This caused a discharge in the chamber, and hydrogen and other chemically active groups of the generated groups (radicals) were doped into the semiconductor, bonding with the dangling bonds and neutralizing them. In addition, conventionally, L-annealing could only be performed in air, but by doing so, it can be performed in hydrogen, an inert gas, especially helium, and as a result, a characteristic of ring-shaped L-annealing on the irradiated surface is achieved. It was possible to reduce the occurrence of striped patterns.

In the present invention, a Q-switched pulse oscillation laser or a CW laser was used for L-annealing, but it is also possible to generate flash etc. using a xenon lamp or the like to produce similar effects. Good too. The temperature of the substrate is raised and cooled extremely rapidly, and even though microscopic movement of the semiconductor or additives in the semiconductor can be carried out at high temperatures and in a substantially molten state, large movements such as segregation of impurities cannot occur, and heat A feature of this method is that impurities or additives with a concentration higher than the solid solubility limit in the annealing method are added to the semiconductor without precipitation.

In previous embodiments of the invention, the transparent electrodes were left in place. However, it goes without saying that this electrode may be removed once with an etching solution and a new transparent electrode may be formed again. In addition, the first transparent electrode is made of nitride, for example, to
After forming the electrode to a thickness of 0.1 Å, photoannealing may be performed, and a second transparent electrode may be further formed from an oxide to a thickness of 0.1 to 2 μm.

Furthermore, in the previous embodiments of the present invention, silicon was mainly used as the semiconductor. However, SixGe _1-X (0<X
<1), SixSn _1-X (0<X<1), SixC _1-X (0.5<X
<1) or a semiconductor of the group such as Sn or
Group compound semiconductors such as GaAs and GaAlAs,
Furthermore, or in a part of the semiconductor, SixO _2-X (0<X<
2) A semiconductor in which a part of such a semiconductor is formed of a lower oxide or lower nitride such as SixN _4-X (0<X<4), and its energy band width is continuously changed to a W-N structure. It goes without saying that you may also use .

In the embodiments of the present invention, the transparent electrode is mainly an oxide conductive transparent electrode made of tin oxide, indium oxide, antimony oxide, or the like. However, tin nitride, indium nitride, and antimony nitride may be used as conductive transparent electrodes of chemically more stable nitrides, and silicon nitride and mixtures thereof may also be used as conductive transparent electrodes.

In addition, at the boundary between the semiconductor layer and the oxide transparent electrode, 10
It goes without saying that the present invention can also be applied to a semiconductor device provided with an extremely thin nitride film that allows a tunnel current of ~50 Å to flow.

Furthermore, it goes without saying that the semiconductor device of the present invention can be applied not only to photoelectric conversion devices, especially solar cells, but also to all semiconductor devices such as integrated circuits using MIS.FET, light emitting elements, semiconductor lasers, other transistors, and diodes. .

[Brief explanation of the drawing]

FIG. 1 shows an example of a semiconductor device for implementing the present invention. FIG. 2 shows an example of a semiconductor device for illustrating another embodiment of the present invention. FIG. 3 is an example of a manufacturing apparatus for carrying out the present invention.

Claims (1)

[Claims] After performing optical annealing by irradiating one principal surface of a non-single-crystal semiconductor mainly composed of Group 1 elements with a laser or similar intense light energy, the semiconductor is heated with hydrogen in a plasma state by radio frequency or microwave. A method for manufacturing a semiconductor device characterized by placing the device in a halogen element or inert gas atmosphere.