JPH0525394B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a structure that is intermediate between an amorphous structure and a crystalline structure (including single crystals and polycrystals) and is stable in terms of free energy. The present invention relates to an MIS type semiconductor device using semi-amorphous amorphous material (hereinafter referred to as SAS) having a third state.

[Conventional technology and its problems]

Conventionally, amorphous silicon semiconductors (hereinafter referred to as AS) have been defined as having random interatomic distances and random crystallographic coordination.

In addition, due to this randomness in every sense, in terms of free energy, it is similar to a crystalline semiconductor
It cannot be said that it is necessarily more stable than AS, and because of its randomness, there are many unpaired bonds in such AS that do not scientifically bond with others. This unpaired bond becomes the center of recombination and extremely shortens the lifetime of the carrier, making it the most anticipated carrier killer to eliminate. As a method for removing these dangling bonds, it has recently been known to neutralize with hydrogen or halogen, i.e., assuming the semiconductor is silicon, Si・+H・→Si−H Si・+F・→Si−F . The film produced by using glow discharge or plasma CVD method for silane (SiH ₄ ), silicon tetrafluoride (SiF ₄ ), or a mixture thereof has a recombination center density similar to that of AS without the addition of hydrogen or halogen. has a density of recombination centers of 10 ²⁰ to 10 ²² cm ^-3 , whereas 10 ¹⁷ to 10 ¹⁹ cm ^-3 and 10 ⁴
It is attracting attention as a method that can reduce the density of recombination centers by ~ ¹⁰⁶ times.

However, such a density was not sufficient for a semiconductor. Therefore, AS was not suitable for semiconductors. The present invention reduces the density of such recombination centers to 10 ¹³ to 10 ¹⁶ cm ^-3 and further to 1/10 ² to 1/10 ⁴
and the electrical conductivity is 10 ^-6 to 10 ^-4 Ωcm ^-1 and 10 ⁴
It can be increased by ~10 ⁶ times, bringing it even closer to an ideal semiconductor, and as a result, the mobility of electrons and holes is 300 Å for AS and ~10 ³ μ for CS.
It was possible to obtain an intermediate value of m between 1 and 50 μm.

The object of the present invention is to apply a semi-amorphous semiconductor having the above properties to an MIS type semiconductor.

[Means to solve the problem]

In the present invention, the source region, the drain region, and the channel forming region are formed of a semi-amorphous semiconductor, and the isolation region is formed of an amorphous semiconductor. It is capable of forming an isolation region and has the following features.

The present invention is a semi-amorphous semiconductor (semi-amorphous)
Regarding semiconductor devices that are defined as a semiconductor having a structure and in which such a semiconductor and an amorphous semiconductor are placed adjacent to each other, a semiconductor with such an intermediate structure is referred to as a semi-amorphous semiconductor (hereinafter referred to as SAS) and an amorphous semiconductor (hereinafter referred to as AS). be controlled,
In particular, it is characterized in that the conductivity of SAS is greater than that of AS.

The present invention allows AS to pass a pulsed current to a specific path in conjunction with the energy of optical excitation by light irradiation or thermal excitation by heating, thereby allowing the current to pass through recombination centers due to dangling bonds. The feature is that the state of the material is frozen (quinched) by local multi-heating and rapid cooling at such locations due to recombination of the two, especially by this extremely rapid cooling when the current is stopped. That is, by activating this unpaired bond,
By combining this dangling bond with another dangling bond nearby or with a bond neutralized by other hydrogen, etc., a normal interatomic distance is maintained and the dangling bond cancels out the dangling bond. semi-amorphous semiconductor (SEMI-AMORPHOUS), which freezes the neutralized state.
SEMICONDUCTOR (SAS).

The present invention physically causes reactions such as Si・+Si・→Si−Si Si・+Si−H→Si−Si+H・ in a semiconductor, for example, silicon, by using an overcurrent, thereby reducing the density of dangling bonds. In addition to this, the heat generated by this reaction promotes the rearrangement of atoms in the short range order.

Examples of the present invention are shown below.

[Example 1]

This example shows the present invention and mainly describes the manufacturing principle and existence theory of SAS.

In FIG. 1, a conductor or semiconductor electrode 3 (referred to as M) is selectively formed in an amorphous structure on an insulating substrate 4 having an amorphous structure, and a semiconductor 1
(Semiconductors are collectively referred to as S) i.e. AS or SAS
2 shows a vertical cross-sectional view of an MSM structure in which a counter electrode 2 (hereinafter referred to as M) is composed of a translucent metal or a transparent electrode such as ITO.

In the drawings, this embodiment relates to a semiconductor 1 mainly composed of silicon, and first, a silicide gas such as silane (SiH ₄ ), SiF ₄ , SiH ₂ Cl ₂ is heated to a thickness of 0.1 to 10 μm by a glow discharge method or a plasma CDV method. ,
In particular, it was formed to have a thickness of 1 to 5 μm. The semiconductor film may be formed using a sputtering method, a vacuum evaporation method, or a reduced pressure CDV method. Also, in AS GROWN state, SAS is 1~
To mix in 50% amount AS, or to approach 100% SAS, or to make part of it into SAS, the temperature is 30~150℃ lower than the crystallization temperature, which is 450 ~
Heated at a temperature of 700℃, and the atmosphere was H and He.
For example, SiH ₄ : 10-30%, H ₂ : 0
~10%, He: 90~60% at 1~100MHz or 1~
It was sufficient to generate plasma using induction energy with an output of 300W to 3KW at a frequency of 10GHz. He has the highest ionization voltage of all atoms, and for connection in the plasma state, it also has a high thermal conductivity.
0.123Kcal/mHrC and neon 0.0398, argon
0.0140, and nitrogen 0.0206, which is the largest of all gaseous elements, so it was particularly important for performing isothermal reactions.

The present invention further improves the probability of the existence of SAS in this AS and achieves an AS GROWN of 95% or more, approximately 100%.
The aim is to make it into a semiconductor.

Furthermore, before and after the process of forming this semiconductor,
A semiconductor electrode doped with a large amount of metal or an impurity, or an impurity electrode, is used to form the electrodes 3 and 2 using a vacuum evaporation method, plasma CVD method, or reduced pressure.
The structure shown in FIG. 1 was obtained by forming by CVD method. Furthermore, apply a voltage of 1.0 in the forward direction to these two electrodes.
100 seconds in the range of Å/cm ² to 5×10 ⁴ Å/cm ² , especially 0.01
Current, particularly pulsed current, was applied by applying for ~2 seconds.

This current may be applied multiple times between the electrodes 3 and 2 by charging a capacitor of 10 to 10 PF and discharging it.

At this time, when AS is not doped with impurities, its electrical conductivity (referred to as σ) is 10 ^-9 to ^{10 -12} Ωcm ^-1 , which is equivalent to insulating property. However, in particular, light irradiation is applied to a predetermined area in the form of a spot with a size of 1μφ to 1mmφ.
If the illuminance is 10 ⁴ LX or higher, the electrical conductivity σ at that location increases by ^a factor of 10 ⁶ to 10 -1 to 10 ^-6 Ωcm ^-1 .
By using this optical carrier, a large current can be passed only in this part, making it an SAS, and furthermore, since no current flows in the surrounding area, an AS
It was found that the structure of

Furthermore, regarding the characteristics of this SAS, an example will be shown.

In Figure 2, the vertical axis shows the electric conductivity σ in LOG coordinates, and the horizontal axis shows the absolute temperature.

Curve 10 is the electrical conduction characteristic of AS, and 3
When ×10 A/cm ² and 10 ³ A/cm ² are applied for 0.5 seconds, the curves change to 11 and 12, respectively, and the electrical conductivity is 10 ^-10 Ωcm ^-1 for AS at room temperature. ^-6 ～
It was found that it can be increased by 10 ⁴ to 10 ⁶ times to 10 ^-4 Ωcm ^-1 .

Furthermore, it is a metallic impurity for this AS.
V value impurities such as AS and sb, value impurities such as Ga and In, and value impurities such as Sn and Pb from 0.1 to 10
Characteristics of AS added with mol% e.g. 1.2 mol% 10'
Curves 13 and 14 were obtained when a current for SAS conversion was applied to the sample.

Therefore, valent metallic elements serve as adjuvants to promote SAS.
The properties were quite different from impurities such as B and P, which do not have any auxiliary effect.

Furthermore, the increase in electrical conductivity due to SAS
According to the results of measuring the spin density of unpaired bonds using ESR (electron spin resonance), when the application time is changed to 0.1 seconds17, 0.5 seconds16, and 2.5 seconds18, the results are as shown in Figure 3. , we were able to obtain curves that all gradually decreased with respect to current density.

That is, it was found that the number of dangling bonds was reduced by forming SAS, the electrical conductivity was further improved, and the carrier mobility was also improved by 10 ³ to 10 ⁶ times.
However, when electron beam diffraction images are taken of these semiconductor films, no crystallized structure can be discerned, and from a crystallographic point of view, it can be said that they do not have a crystal structure and are amorphous.

Further, although the hydrogen content was 20 mol% in AS, the amount decreased to only about 0.1 to 5 mol%. Therefore, the ESR result is thought to be due to the fact that the unpaired bonds were not neutralized by hydrogen, but were neutralized by Si bonding with each other.

From the above characteristics, the interlattice distances and positions of the so-called AS film are random, which is different from the crystalline structure which is stable in free energy and stable in terms of thermal energy. It is assumed that it has a third stable point in terms of free energy. Figure 4 shows this relationship, and the concept is a general one.
CONFIGURATIONAL COODINATE (phase space coordinates) The vertical axis shows free energy. In the drawing, it was found that there are three states: AS21, 21', SAS22, and CS23, and SAS is the third stable state rather than a metastable state that changes from AS to CS.

In addition, in this figure 2, the substrate temperature is lower than room temperature.
Assuming 200℃ and 400℃, room temperature graphs 11 and 12
could be obtained at low current densities 11 of 3 A/cm ² or 10 ² A/cm ² , respectively. Generating a photo carrier by localized light irradiation when applying electric current, and scanning this light spot, following the scanned optical path.
The ability to create SAS is a feature of the present invention. Further, at this time, it was not difficult in practice to promote thermal excitation by heating at the same time, and it was extremely effective for uniformly applying current to a wide area.

This current density means the average current in this area. Since it refers to the current density in a region where the current flows locally under the electrode, it can be applied not only to a small area of 1 mm□ or less but also to a large area such as 10 cm□.

In FIG. 1, the semiconductor 20 directly below the electrode 2 becomes the SAS, and since the region 19 also has no lower electrode, it is not the AS or AS of the AS GROWN.
Semiconductor mixed with SAS, area 19' is AS
It has an intermediate structure between the GROWN semiconductor and the region 20 semiconductor.

This figure 1 shows the case of amorphous silicon.
Ge, GeSix (0<X<1), SiO _2-X (0<X<2),
Compounds or mixtures such as SiC _1-X (0<X<1) and Si ₃ N _4-X (0<X<4) can also be used in the same manner. It goes without saying that it also includes semi-insulators within the limits of flowability.

Thus, in silicon, which is AS, the carrier mobility was only about 300 Å, but it was 1 to 50 μm.
The crystallinity was ¹⁰⁴ times that of a single crystal, making it close to 1/10 to 1/1000 of that of a single crystal.

In addition, when semi-amorphous semiconductors were examined using electron beam diffraction, the interatomic distance was 2.2 to 2.2 in silicon.
It was 2.5 Å, which roughly matched the 2.3 Å of a single crystal. However, this distance does not necessarily have a crystalline diamond structure like a single crystal, and even if it can have a diamond structure in the short range order, it has a lot of lattice distortion in the range examined by diffraction.

Due to this lattice strain, the transition of light is different from the indirect transition of single-crystal silicon, and like AS, it is a direct transition, indicating that semi-amorphous semiconductors have an ideal semiconductor structure.

[Example 2] The longitudinal cross-sectional view of this Example 2 is shown in Fig. 5.
This is related to MIS-FET.

The drawing shows an SOS type, in which an AS semiconductor layer is formed on an insulating substrate 40 having a so-called amorphous surface, which is an oxide film formed to a thickness of approximately 1 μm on a glass, ceramic, or silicon substrate. Selectively convert a part into SAS and convert this SAS into MIS−FET
41, and AS is used as isolation regions 46, 46'.

That is, silicon nitride 42 was applied to the AS with a thickness of 0.3 to 1 μm produced by the method shown in Example 1.
It was formed to a thickness of 0.2 to 0.5 μm and used as a mask coating. This silicon nitride is a film that selectively acts as a mask against oxidizing gases.

Next, AS was oxidized and stored to form a selective oxide film 49.

After that, remove this mask coating and try again.
Gate insulating films 42 and 42' were formed to a thickness of 50 to 100 Å using AS at high pressure or plasma oxidation.
Further, gate electrodes 41, 41' were formed as AS or SAS. In particular, in the case of SAS, conductive metals such as Sb and As are used to make N-type, and Sb and As are used to make P-type.
In and Ga were added in an amount of 0.1 to 5 mol%. Thereafter, this semiconductor layer was photo-etched to produce source and drain electrode leads 50, 50', 5''.
Thereafter, in the case of an N-channel MIS-FET, AS was doped into the source 43, 43' and drain 44, 44' regions by ion implantation. _VDD
An output (drain) electrode lead 48 for the lead 50 is formed on the overcoat film (interlayer insulating film), and a pulse current is passed in accordance with Example 1, and the channel forming regions 45 and 45' are made into SAS. At the same time, sources 43, 43', drain 44,
44' was also converted into SAS. However, AS46, 46' under the insulating film 49 through which current does not flow remains as AS, and AS and SAS can be selectively formed in the same semiconductor layer, and SAS acts as a semiconductor.
essentially acted as an insulator.

In order to make the load 41' a depletion type, the gate of the driver 41' is of N ⁺ type, and the gate of the driver 41 is of P ⁺ type, which is different from the conductivity type of the source and drain. It shows.

When using a small number of carriers, use N-channel MIS-
In the FET, the channel forming regions 45, 45' are preferably of P type.

This example is an example of an MIS-FET inverter, but this is integrated and a bipolar type
It is also possible to apply the present invention to IC, SIT, IIL, etc.
In that case, the transistor and diode areas are SAS
Then, part or all of the surrounding isolation area may be set as AS.

According to the present invention, it is possible to easily change from AS to SAS by simply applying light and electric current, so regions with different conductivities can be easily formed.

Therefore, an isolation region can be easily formed.

As is clear from the above explanation, the AS of the present invention
Providing SAS in the same semiconductor is the implementation specification of MIS type photoelectric conversion device, MIS-FET.
It can be applied to integrated circuits, optical memories, etc. using the same technology, and many other applications based on the same technical idea are also possible.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a semiconductor device for explaining the principle of the present invention. Figure 2 shows the resulting electrical conductivity. Figure 3 shows the ESR results. Figure 4 shows free energy in terms of AS, SAS, and CS. Figure 5 shows the MIS-FET of the present invention.
are arranged in an inverter structure on the same substrate.

Claims (1)

[Claims] 1. A MIS type semiconductor device characterized in that a source region, a drain region, and a channel forming region are made of a semi-amorphous semiconductor, and an isolation region is made of an amorphous semiconductor.