JPH10120491A - Formation of crystal film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a crystal film excellent in crystallinity, i.e., a polycrystal or single crystal thin film at a low substrate temperature of <=400 deg.C even on a substrate of noncrystalline insulating material. SOLUTION: This method for forming a crystal film comprises heating a quartz substrate 113 to 250-350 deg.C by a heater 114, introducing SiH4 gas and dilution gas H2 into a vacuum vessel 102, setting the inner pressure at 0.1-2.0Torr by adjusting a valve 116, generating plasma between an electrode 103 and grid electrode 118 and forming a 0.3-1nm thick noncrystalline silicon film on the substrate 113. Then, by introducing high-purity He gas from a cylinder 108 into the vacuum vessel, applying high frequency power under a pressure of 0.1-2.0Torr, generating plasma between the electrodes, changing the atomic arrangement of an a-Si:H film to what is much nearer to a crystal by contacting He atoms in a metastable state with the surface of the a-Si:H film and introducing high-purity SiF4 , high purity SiH4 gas and dilution gas H2 into the vacuum vessel, the objective crystalline Si film is grown on the a-Si:H film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a polycrystalline or single-crystal film used for a semiconductor device or a display device using a semiconductor thin film as a component.

[0002]

2. Description of the Related Art As a method of forming a crystalline film on an insulating substrate such as glass or quartz, an amorphous film or a polycrystalline film is first formed, and then a laser or an electron beam is irradiated, or a strip heater is used. A method has been proposed in which a single crystal is formed by heating, or recrystallized into a polycrystal having a larger particle size (grain size).

As a technique for forming a crystal film directly on an insulator substrate, chemical vapor deposition under reduced pressure (decompression CV)
In D), a method of vapor-phase growing a polycrystalline film at a relatively high substrate temperature of 500 ° C. or higher is generally used. Furthermore, in chemical vapor deposition (plasma CVD) using plasma, the raw material gas is highly diluted with hydrogen to form a 200-
It has been reported that a microcrystalline film can be obtained at a lower substrate temperature of 400 ° C. (JP-A-63-16616).

[0004]

In the method of irradiating a laser or an electron beam, only the layer desired to be recrystallized can be heated by adjusting the irradiation energy, so that the underlying or peripheral film or device structure can be heated. The crystal film can be formed without much influence. However, when the area of the substrate is large, there is a problem that it takes a long time to scan the beam and the accuracy of adjusting the irradiation position is deteriorated. On the other hand, in the method of heating with the strip heater, even if the substrate has a large area, if the length of the heater is increased, the crystallization processing time does not need to be increased, but it is not possible to heat only the layer to be recrystallized. Since almost the entire substrate is heated, there is a problem that the underlying substrate and already formed devices are affected.

In the method of forming a crystal film directly on an insulator substrate, a crystal film is formed first and then processed into a device. There is an advantage that it is easy to obtain. However, decompression CV
In the case of D, there is a problem that a single crystal film cannot be formed because the base material is an insulator, and the substrate temperature is relatively low, so that it is difficult to obtain a high quality crystal film having a small polycrystal grain size. Further, the plasma CVD method has a feature that a film can be formed on a large-sized substrate, but epitaxial growth can be performed on a crystal substrate. There is a problem that only a microcrystalline film having a smaller particle size can be obtained.

As described above, according to the conventional method, a crystalline film having excellent crystallinity, that is, a single crystal or a polycrystalline film having a large grain size is formed on an insulating substrate over a large area at a low temperature of 400 ° C. or less. It was impossible.

In order to solve the problems of the prior art, a method of forming a crystal film according to the present invention employs a method of forming a crystal film on an insulating substrate.
It is an object of the present invention to provide a method for forming a crystalline film having excellent crystallinity, that is, a single crystal or a polycrystalline film having a large grain size over a large area at a low temperature of not more than ° C.

[0008]

According to a method of forming a crystalline film of the present invention, a film containing at least an amorphous phase is formed on a substrate, and then at least particles in a metastable state are removed from the amorphous phase. The film containing the amorphous phase to change the atomic arrangement of the film containing the amorphous phase, and bringing the particles containing at least atoms constituting the film containing the amorphous phase into contact with the amorphous phase to form the non-crystalline film. A method for forming a crystal film, comprising forming a crystal film on a film containing a crystalline phase.

In the above method for forming a crystalline film, the thickness of the film containing an amorphous phase is 1 nm or more and 100 nm or less.

In the above-mentioned method for forming a crystalline film, at least hydrogen radicals are brought into contact with the substrate surface before forming the film containing an amorphous phase.

In the above method for forming a crystal film, the particles in a metastable state are rare gas atoms.

Further, in the above-mentioned method for forming a crystal film, before forming the crystal film, formation of a film containing an amorphous phase and contact of particles in a metastable state are repeated a plurality of times.

Further, in the above-mentioned method for forming a crystalline film, the thickness of the film containing the amorphous phase is sequentially reduced or constant.

Further, in the above-described method for forming a crystal film, the atoms constituting the crystal film are silicon.

In the above-mentioned method for forming a crystal film, a cathode electrode to which a high-frequency power source is connected, a substrate disposed apart from the cathode electrode, and a grid grounded or negatively biased between the cathode electrode and the substrate. A crystallization processing gas composed of atoms having a metastable level was introduced into the vacuum vessel in which the electrodes were disposed, and a glow discharge was generated between the cathode electrode and the substrate to generate the crystallization processing gas. Metastable particles are brought into contact with the substrate surface to change the atomic arrangement of the amorphous film.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a schematic view of a forming apparatus showing one embodiment of a method for forming a crystal film according to the present invention. The power supply 101 is a high-frequency (1 kHz to 1 GHz) or microwave (1 GHz or more) power supply.
02 is connected to the electrode 103 in the circuit 102 via a matching circuit 104.

The electrode 103 is provided with a large number of holes in the form of a shower. ) 109-112, 121,
The flow rate is adjusted to a predetermined value by 122 and introduced into the vacuum vessel 102 from these holes (only six gas cylinders and gas systems are shown in FIG. 1, but these increase or decrease according to the type of film to be formed). ).

A substrate 113 for forming a crystal layer is placed on a heater 114 and heated to a predetermined temperature. In FIG. 1, reference numeral 115 denotes a vacuum pump, 116 denotes an exhaust valve, and 117 denotes a water cooling device. The water cooling device 117 is for increasing the cooling rate of the substrate temperature after the formation of the crystal film, and is not always necessary. A mesh-shaped grid electrode 118 connected to an external power supply for adjusting the number of ions incident on the substrate 113 is arranged in the vacuum vessel 102.

Using this apparatus, a silicon crystal film was formed in the following procedure. First, the quartz substrate 113 is
The inside of the vacuum vessel 102 was evacuated to a high vacuum, and the substrate 113 was heated to 250 to 300 ° C. Note that it is desirable to form a crystal film at a substrate temperature of 400 ° C. or lower.

Next, high purity SiH ₄ gas is supplied to the cylinder 105.
Through the MFC 109, H ₂ as a dilution gas is introduced into the vacuum vessel 102 through the MFC 111 by the cylinder 107, and the predetermined pressure (0.1 to
2.0 Torr).

A high frequency power of 13.56 MHz is applied to the electrode 103 in a range of 0.01 to 0.2 W / c per unit area of the electrode 103.
m ² to generate plasma between the electrode 103 and the grid electrode 118, and as shown in FIG.
An amorphous silicon (hereinafter abbreviated as a-Si: H) film 201 was formed thereon in a thickness of 0.3 to 1 nm. At this time, the voltage applied to the grid electrode 118 is -300 to 0 V and a
-The ions were prevented from being incident on the Si: H film 201, and the flow rate ratio SiH ₄ / H ₂ was 5/1 to 1/100.

Next, the introduction of these gases is stopped, and high-purity He gas is introduced from the cylinder 108 through the MFC 112 into the vacuum vessel 102, and the same pressure (0.1 to
High-frequency power is applied at a density of 0.05 to 1 W / cm ² at 2.0 Torr, and plasma is generated between the electrode 103 and the grid electrode 118 for 10 seconds to 10 minutes, and a plasma is generated on the surface of the a-Si: H film 201. Contact a stable He atom with a
The atomic arrangement on the free surface side of the -Si: H film 201 was changed to one closer to a crystal.

Next, the introduction of He gas is stopped and the high purity Si gas is removed.
F ₄ passes through the MFC 110 from the cylinder 106, high-purity SiH ₄ gas passes through the MFC 109 from the cylinder 105, and H ₂ as a dilution gas flows from the cylinder 107 into the MFC 111.
And introduced into the vacuum vessel 102 at a pressure similar to the above (0.1 to 2.0 Torr) and 0.01 to 0.2 W / cm ^2.
A high-frequency power was applied at a density of .mu.m to generate plasma between the electrode 103 and the grid electrode 118, and a crystalline Si film 202 was grown to a thickness of 100 nm to 10 .mu.m as shown in FIG. At this time, the flow ratio SiF ₄ / SiH ₄ is 1/10 to 10
/ 1 and SiH ₄ / H ₂ were 1/10 to 1/100.

When this crystalline Si film 202 was evaluated by Raman spectroscopy and transmission electron microscopy (TEM), a peak due to crystalline Si was observed near 520 cm ^{-1 in} Raman spectroscopy, and the crystal grain size was at least 20 μm. From the above, it was found that a material close to a single crystal was obtained.

For comparison, a test was also performed in the case where the surface of the a-Si: H layer 201 was not brought into contact with any metastable He atoms without generating He plasma.
When the film grown on the i: H layer 201 was evaluated in the same manner as above, no peak near 520 cm ^-1 was observed in Raman spectroscopy, indicating that the film was amorphous.

From the above results, by bringing the He atoms in the metastable state (excitation levels 2 ³ S ₁ , 2 ¹ S ₀ ) into contact with the surface of the amorphous film 201, the energy (19.82 eV, 20.61 eV) is applied to the surface of the film 201, and the surface is effectively heated. Moreover, metastable He atoms are generated in the plasma region that emits light between the grid electrode 118 and the electrode 103, the life is 2 ³ S ₁ at 6 × 10
^{Since -5} seconds and 2 ¹ S ₀ are as long as 2 × 10 ^-2 seconds, they can sufficiently reach the surface of the film 201 by diffusion.

The distance between the grid electrode 118 and the substrate differs depending on the type of metastable atom.
It is desirable that the thickness be not less than mm and not more than 50 mm. As a method of heating the film surface, ions accelerated with an appropriate energy may be incident.However, in the case of ions, there is a problem that the kinetic energy causes the atoms to be repelled or displaced to disturb the atomic arrangement. is there. Therefore, even if an atomic arrangement close to a crystal is formed, the atomic arrangement is disturbed when ions are incident, and as a result, the atomic arrangement does not approach the crystal structure very much. On the other hand, in the case of metastable atoms, since they enter the surface of the film 201 by diffusion, they do not have large kinetic energy and do not disturb the atomic arrangement. Therefore, it is easy to form an atomic arrangement close to the crystal structure.

Also, metastable atoms generated in the plasma region
Of at least 10 to obtain a good crystal structure.
^Tencm^{ー 3}Or more, preferably 10¹²
cm ^{ー 3}It is about.

The substrate 113 is a quartz substrate, a glass substrate, a sapphire substrate, SiO _x , SiN _x , SiC _x ,
GeO _x , GeN _x , GeC _x , AlO _x , AlN _x , B
Si or GaAs on which inorganic insulators such as C _x and BN _x are formed
The same effects as described above can be obtained by using an insulating substrate such as a wafer or a conductive substrate, or a conductive substrate having a transparent conductive film such as ITO or SnO ₂ ZnO formed on a metal substrate or a glass substrate. When the substrate temperature was 150 ° C. or more and 400 ° C. or less, the same result as described above could be obtained.

When controlling the conductivity of the crystal film 202,
PH for imparting n-type conduction_Three, PF_Three, PF_Five, PC
l_TwoF, PCl_TwoF_Three, PCl_Three, PBr_Three, AsH_Three, As
F_Three, AsF_Five, AsCl_Three, AsBr_Three, SbH_Three, Sb
F_Three, SbCl_Three, H_TwoImpurity gas such as Se
It can be supplied at the time of film formation from step 9.
Kiha B_TwoH₆, BF_Three, BCl_Three, BBr_Three, (CH_Three)_ThreeA
l, (C_TwoH_Five)_ThreeAl, (iC_FourH₉)_ThreeAl, (CH_Three)_Three
In, (CH_Three)_ThreeGa, (C_TwoH_Five)_ThreeIn, (C _TwoH_Five)_Three
A gas such as Ga may be supplied from the cylinder 120.

The source gas that can be used is the above-mentioned Si.
H_FourAnd SiF_FourBesides Si_TwoH₆, Si_ThreeH₈, Si
_FourH_Ten, SiH_4-nF_n, SiH_4-nCl_n(However, n = 1,2,
3), Si_TwoF ₆, SiCl_FourSuch as silicon compound gas
No.

In the above example, a silicon crystal film is formed. However, a crystal film can be obtained in the same manner by changing the raw material gas also in the case of diamond, germanium, silicon carbide, and silicon germanium.

In the case of diamond, CH ₄ , C ₂ H ₆ ,
_{C 3 H 8, C 4 H} 10, C 2 H 4, C 3 H 6, C 4 H 8, C 2 H 2,
C ₃ H _4, hydrocarbon gas such as _{C 4 H 6, C 6 H} 6, CH
₃ F, CH ₃ Cl, CH ₃ Br, CH ₃ I, C ₂ H ₅ Cl, C
₂ H ₅ Br, alkyl halides, such as _{C 2 H 5 I, C 3} H 5
Allyl halides such as F, C ₃ H ₅ Cl, C ₃ H ₅ Br,
Source gases include CFC ₃ , CF ₄ , CHF ₃ , C ₂ F ₆ , C ₃ F ₈ and other fluorocarbon gases, and C ₆ H _{6 -m} F _m (m = 1 to 6) such as carbon compound gases such as fluorinated benzene. Just use
In the case of germanium, GeH ₄ , Ge ₂ H ₆ , Ge
₃ H ₈ , GeF ₄ , GeCl ₄ , GeBr ₄ , GeI ₄ , Ge
F ₂ , GeCl ₂ , GeBr ₂ , GeI ₂ , GeHF ₃ , G
eH ₂ F ₂ , GeH ₃ F, GeHCl ₃ , GeH ₂ Cl ₂ , G
eH ₃ Cl, GeHBr ₃ , GeH ₂ Br ₂ , GeH ₃ B
Germanium compound gas such as r, GeHI ₃ , GeH ₂ I ₂ , GeH ₃ I can be used as a source gas.

In the case of silicon carbide, the above-mentioned silicon compound gas and carbon compound gas may be used as source gases, and in the case of silicon germanium, the above-mentioned silicon compound gas and germanium compound gas may be used as source gases.

In the case of compound semiconductors such as GaAs, GaP and GaN, the same effects as described above can be obtained by changing the source gas in the same manner.

The gas that can be used as the crystallization treatment gas may be any gas having a metastable state. For example, in addition to the above He, Ne, Ar, Kr, Xe, H ₂ ,
N ₂ . Further, these gases may be mixed and used. These gases can also be used as a diluting gas.

(Embodiment 2) In the formation of the crystal film described in Embodiment 1, a-Si:
Before forming H201, only H ₂ gas is supplied to the vacuum vessel 10
2 and a high frequency power of 0.01 to 0.1 W / cm ² under a pressure of 0.1 to 1.0 Torr and a power density of 0.01 to 0.1 W / cm ^2.
3 was applied to generate plasma, and hydrogen radicals were brought into contact with the surface of the quartz substrate 113 for cleaning. In this case, the crystalline Si film 2 formed on the a-Si: H layer 201
No. 02 confirmed that the crystal grain size was as large as 50 μm or more.

(Embodiment 3) In the formation of the crystal film described in Embodiment 1, a
The case where the film thickness of the -Si: H layer 201 was sequentially increased from 0.3 nm was examined. As a result, a-Si:
When the thickness of the H layer 201 exceeds 10 nm, it has been found that an amorphous region remains on the quartz substrate 113 side of the a-Si: H layer 201 even after the crystallization treatment by He plasma.

(Embodiment 4) In the formation of the crystal film described in Embodiment 1, a
After setting the film thickness of the -Si: H layer 201 to approximately 10 nm and performing crystallization treatment using He plasma, as shown in FIG.
A crystallization treatment by plasma was performed. In this case, a-S
It was confirmed that the crystalline Si film 202 formed on the i: H layer 201 had a large crystal grain size of 50 μm or more.

It has also been confirmed that the crystal grain size of the crystalline Si film 202 increases as the number of a-Si: H layers stacked increases. Furthermore, it was also confirmed that the crystal grain size was significantly increased by sequentially reducing the film thickness of the stacked a-Si: H. However, the first layer a-Si: H layer 20
When the thickness of one film is 2 nm or less, a-Si is sequentially laminated.
The effect is not remarkable even if the thickness of the H layer is reduced, and the thickness of the laminated a-Si: H layer may be constant.

(Embodiment 5) The liquid crystal display device shown in the sectional view of FIG.
LC). AMLC is a thin film transistor (hereinafter, referred to as TFT) or a diode for driving a liquid crystal layer, or a metal-insulator-metal (MI).
M) An active element such as an element is arranged in each pixel. However, FIG. 3 shows an example using a TFT. In this case, a TFT using a polycrystalline semiconductor (for example, polycrystalline silicon or single crystal silicon) as the semiconductor layer 301 is formed in a matrix on a transparent insulating substrate (for example, a borosilicate glass substrate or a quartz substrate) 302. It was done.

First, the TFT is formed by setting the transparent insulating substrate 30
A gate electrode 303, for example, Cr or Al + Z
r, Al alloy such as Al + Ta, Al-W or Al /
Cr layer, and then the SiN _x gate insulating film 30
4 was formed by a plasma CVD method. Next, a-Si: H
The a-Si: H layer is crystallized by contacting with metastable He atoms in He plasma, and the layer is further subjected to plasma CVD using a mixed gas of SiH ₄ and H _2.
A semiconductor layer 301 having a thickness of 00 nm was formed.

Further, after forming the SiN _x semiconductor protective layer 305 by the plasma CVD method, the semiconductor layer 301 and the semiconductor protective layer 305 were patterned. Next, in order to improve the ohmic property, SiH ₄ and H are used in the plasma CVD method.
After forming an n-type semiconductor layer 306 in the same manner as the semiconductor layer 301 using a mixed gas of ₂ and PH ₃ , the source electrode 30
7. Drain electrode 308 (for example, Al, Mo, Mo / A
l / Mo multi-layer structure), and finally IT
An O transparent electrode 309 was formed, and a TFT was manufactured.

When this TFT was evaluated, the semiconductor layer 3
The electron mobility of 01 was 300 to 500 cm ² / V · s. This was 3 to 5 times higher than a TFT using polycrystalline Si as a semiconductor layer obtained by laser annealing.

Thereafter, an alignment film 310 made of an organic polymer (for example, polyimide or polyvinyl alcohol) was applied to a thickness of 0.01 to 0.5 μm and subjected to an alignment treatment by rubbing. The other transparent insulating substrate 311 is provided with a counter electrode 312 and a black matrix 313 for shielding light, and is similarly coated with an alignment film 314 and subjected to alignment processing. In this case, rubbing is shifted by about 90 ° from the previous substrate. I went in the direction. Subsequently, a twisted nematic liquid crystal 315 is sealed between the two substrates as shown in FIG.
6,317 were arranged to produce a liquid crystal display device.

When the display image of this liquid crystal display device was evaluated, it was possible to operate an XGA class high-definition image with a contrast of 150: 1 without divided driving as in the prior art.

[0048]

As described above, according to the method for forming a crystal film according to the present invention, a crystal film having a large crystal grain size and excellent crystallinity can be formed on a non-crystal insulator substrate at a low substrate temperature. As a result, a semiconductor device or a liquid crystal display device which is inexpensive and can operate at high speed can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a manufacturing apparatus used in a method for forming a crystal film according to the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of a film formed by the method for forming a crystal film according to the present invention.

FIG. 3 is a cross-sectional view showing one embodiment of a liquid crystal display device manufactured by the method for forming a crystal film according to the present invention.

[Explanation of symbols]

 Reference Signs List 101 Power supply 102 Vacuum container 103 Electrode 104 Matching circuit 105, 106 Raw material gas cylinder 107 Dilution gas cylinder 108 Crystallization gas cylinder 109-112 Mass flow controller (MFC) 113 Substrate 114 Heater 115 Vacuum pump 116 Exhaust valve 117 Water cooling device 118 Grid electrode 119, 120 Impurity gas cylinder 121, 122 Mass flow controller 201, 203 Amorphous silicon layer 202 Crystalline Si layer

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/336

Claims (8)

[Claims] After forming a film containing at least an amorphous phase on a substrate, at least particles in a metastable state are brought into contact with the film containing the amorphous phase to form a film containing the amorphous phase. By changing the atomic arrangement, contacting particles containing at least atoms constituting the film containing the amorphous phase with the amorphous phase to form a crystalline film on the film containing the amorphous phase. Characteristic method of forming a crystalline film. 2. The method according to claim 1, wherein the thickness of the film containing the amorphous phase is 0.3 nm or more and 10 nm or less. 3. The method according to claim 1, wherein at least hydrogen radicals are brought into contact with the surface of the substrate before forming the film containing the amorphous phase. 4. The method according to claim 1, wherein the particles in the metastable state are rare gas atoms. 5. The method according to claim 1, wherein the step of forming the film containing the amorphous phase and the contact of the particles in the metastable state are repeated a plurality of times before forming the crystal film. . 6. The thickness of a film containing an amorphous phase decreases in order.
6. The method according to claim 5, wherein the crystal film is constant. 7. The method according to claim 1, wherein atoms constituting the crystal film are silicon. 8. A vacuum vessel having a cathode electrode to which a high-frequency power source is connected and a substrate separated from the cathode electrode, and a grounded or negatively biased grid electrode disposed between the cathode electrode and the substrate. Introducing a crystallization processing gas composed of atoms having metastable levels, generating glow discharge between the cathode electrode and the substrate to generate metastable particles generated from the crystallization processing gas on the substrate surface. 2. The method for forming a crystalline film according to claim 1, wherein the atomic arrangement of the amorphous film is changed by contact.