JPS62154723A - Thin film vapor growth by light irradiation - Google Patents

Abstract

PURPOSE:To grow single crystal Si, polycrystalline Si, thin film of amorphous Si etc. or compound thin film containing Si at low temperature by a method wherein SiH4 is irradiated with light in the region of vacuum ultraviolet radiation to be photodissociated efficiently and then the gas containing silane ion produced by the photodissociation is used for film formation. CONSTITUTION:When SiH4 is irradiated with light in the region of vacuum ultraviolet radiation, SiH4 is photodissociated simultaneously subject to photoionizing reaction and the fragments produced by this reaction are composed of Si such as Si, SiH2+, SiH3+ etc. and silane ion effective for film formation. The wavelength range is 500-1,050Angstrom . For example, an Si wafer 109 is heated up to 700-800 deg.C to be irradiated horizontally to 109 surface with the spectral light with wavelength of 800-1,000Angstrom . The light on the Si wafer 109 surface is beams 2mm long in the vertical direction and 6mm wide in the horizontal direction to the wafer surface. Resultantly, an Si with excellent quality even at low temperature is epitaxially grown on the part irradiated with the beams better than on the part not irradiated with the beams.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method of vapor phase growth of thin films by light irradiation, and in particular,
Si or S
The present invention relates to a method of vapor phase growth of a thin film suitable for forming a thin film of a compound containing i.

[Background of the invention]

Conventionally, as a method for growing Si using a photoexcitation reaction using a vapor phase growth method, there is a method in which H2 is used as a carrier gas, Si(, Q+ is used as a raw material gas, and epitaxial growth is performed by irradiating a mercury lamp. As a method for vapor phase growth, SiH4 is used as one reaction gas.
and N z O using a mercury lamp or A
A method of growing the film by irradiating it with an rF excimer laser, or a method of depositing a film by irradiating it with an Hg lamp using a mixed gas of 5izH6 and 02 as a reactive gas has been proposed.

The wavelength of low-pressure mercury lamp is 1849 Å or more, A r F
.

Even for KrF excimer laser, the wavelength is 1930, 24
90 people, the wavelength is relatively long and the irradiation energy is small, so SiH4 absorbs little light and the decomposition reaction does not proceed. Furthermore, since the light energy is small, the decomposed species are neutral molecules.

Therefore, there was a problem that the rate of film formation (vapor phase growth) was slow and a high quality film could not be obtained.

Note that the following documents are available as examples of these conventional techniques.

1) Journal of the Institute of Electronics and Communication Engineers (9) P991-997 (19
84) Application of r-excimer laser to semiconductor process” 2) Proceedings of the Institute of Electrical Engineers of Japan EDD-84-61 (1984゜7
) "Photo-CVD film" 3) Proceedings of the 22nd Semiconductor Specialized Seminar (1984, August).

20) “Optical CVDJ of silicon film [Object of the invention] The object of the present invention is to efficiently photodissociate 5iHi by irradiating it with light in the vacuum ultraviolet region, and to perform monolithic CVDJ using a gas containing silane ions generated by the photodissociation. An object of the present invention is to provide a method for growing thin films of crystalline Si, polycrystalline Si, amorphous Si, etc., or compound thin films containing Si at low temperatures.

[Summary of the invention]

The ultraviolet absorption of SiH4 is between 1100 and 1600.
For 1470 people, a) S iHi + h v (
It is conventionally known that the following reaction occurs: 1470 people) → 5iHz +2H, b) SiHa 10hν (1470 people) → SiH+H. Using photoexcitation reaction of SiH,
When depositing a thin film of Si or a thin film of a compound containing Si.

It is necessary to decompose 5iI-I4 with light. When depositing single crystal Si or polycrystalline Si, the decomposed products must undergo further reaction on the substrate surface. Conventionally, in photo-excited CVD using SiHa, SiH is converted into C
A method of decomposition by thermal vibrational excitation using an Oz laser is known, but since this method only decomposes SiH, the deposited thin film is an amorphous film.

The inventors have developed thin films of single crystal Si, polycrystalline Si, amorphous Si, and compounds containing Si.

To grow from SiHa by photoexcitation reaction.

The basic properties of photodissociation of SiHa are 5OR (Sync
hrotron Orbital Radiation
, synchrotron radiation). As a result, when 51g4 is irradiated with light in the vacuum ultraviolet region, SiH4 is photodissociated and a photoionization reaction occurs, and the fragments produced by this reaction are Sin.

These are Si and silane ions such as S i Hz+ and S i Ha+, and it was found that these ions have a remarkable effect on film formation. The wavelength range is from 500 to 1,050 people.2Normally, measurements cannot be performed in such a vacuum ultraviolet region because there is no light source with continuous wavelengths, but measurements have become possible by using SOR as a light source. For measurement, S.O.
The R beam was separated into spectra by an optical system consisting of a front mirror, a Seya spectrometer, a Namioka spectrometer, and a rear mirror, and the following measurements were performed using the separated light. The concave diffraction grating used (Bausch & L.
(manufactured by omb) has a radius of curvature of 998.4 mm and the number of scored lines is 24.
The 0-minute light of 00 Q/m+m has a cross section perpendicular to the traveling direction of approximately 2 mm x 10III11. Immediately below the progress of the light, from a nozzle made of a stainless steel pipe with an inner diameter of 0.5 Illlφ, the vacuum level of the optical system such as a Ti mirror after the spectrometer is 5 x 10-9 Torr or less, and the time
The ultimate vacuum level of the mass spectrometry measurement chamber of Flight is 5
X 10-9 Torr, the pressure at the time of measurement is 2 X 1
It was 0-6 Torr. FIG. 3 shows the wavelength dependence of the photoionization cross section of S i H4. Curve A is the ionization cross section of all ions generated by photoionization. Curves B, C,
D is the ionization cross section of the fragment ion separated in the time of flight spectrum (Figure 4), and shows the wavelength dependence of the ionization cross section of SiH"+S i Hz+ and S i ÷, respectively. That is,
When 5iHi is irradiated with light of 1050 Å or less, a photoionization reaction occurs at the same time as photodissociation as shown below, and the fragment ions generated by dissociation are SiH÷+
It was found that S iH2+tSi+.

S i H4+ h v-+S i Hs++ H+ e
-→5iHz++Hz+e- 8iHa +h v+S i++2Hz+e-SiH+
, S iHz+, A ppaavenc of S i+
aP otantial are 12.2 sV and 1, respectively.
1.6eV, 13. OeV, S i Had,
S i Hz+.

The photoionization cross section of the Si film has a wavelength of 850-1 in both cases.
ooo It grows in the realm of humans. In the presence of neutral silane molecules, the silane ions generated by the photoionization reaction will undergo a secondary reaction as shown in the example below, causing a chain reaction of ionization, dissociation, and decomposition of the neutral molecules. It happens.

S i Hz++ S i H4→S i zHz4+
2 H2S1Hz++SiH number → S i z
H+++ HzS i Ha++ S i H4→5i
2H+s++HS i H! ++ S i Ha→S
i HadS i HadS i Hs++ S
i H number → S i H4+ S i Had These photodissociated ions and electrons contribute to the surface reaction on the substrate surface, and when a Si film is formed using the photodissociation reaction of SiH4 according to the present invention, crystallinity A good film can be obtained. Furthermore, since there is no electric or magnetic field in the reaction apparatus for these ions and electrons, there is no damage to the substrate due to acceleration of the ions, unlike in conventional so-called plasma CVD.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on examples with reference to the drawings. FIG. 1 is a schematic diagram of an apparatus that takes in vacuum ultraviolet light using synchrotron orbital radiation as a light source, photo-ionizes SiH, and deposits a film on a substrate. 101 is storage
102 is a front mirror, 103 is an entrance slit, 104 is a Seya wave spectrometer consisting of a concave diffraction grating, and 105 is an output light source, which isolates the radiation source from the ring from the spectrometer and the film vapor growth chamber. The slit 106 is a toroidal mirror (rear mirror). 107 is an inlet for SiH4 gas, 108 is a film growth chamber 5109, a substrate (Si wafer) on which a film is deposited, and 110 is a substrate.

This is a heater that heats 109. Prefix fi1 in the device
02 chamber is a turbo molecular pump with 2×10''T
orr, the chamber of the spectrometer 104 is powered by an ion pump.
The chamber of the rear mirror 106 is maintained at a vacuum level of 5 x 10-OTorr by a turbo molecular pump. Further, the growth chamber 108 and the chamber of the rear mirror 106 are differentially evacuated by a pump located between them. The film growth chamber 108 has a pressure of 1 to 100 T during vapor phase growth of the film.
It is orr.

In the apparatus described above, the Si wafer 109 is
The Si wafer was heated to ~800° C., and 109 sides of the Si wafer were irradiated horizontally with light having a wavelength of 800 to 1,000. Si
The light on the wafer 109 surface is:

2IOI11 perpendicular to the wafer surface, 6mm horizontally
The width of the beam is . As a result, higher quality Si was epitaxially grown in the beam-irradiated portions than in the beam-unirradiated portions even at lower temperatures.

In the above example, the synchrotron radiation is divided and irradiated.

A light source in the wavelength range in which SiH4 is photoionized may be directly irradiated without spectroscopy.The wavelength range for photoionization of SiH extends from 500 to 1100 people.

If the same light source is used for light including the above-mentioned wavelength range, it is better to use light that is not separated into lights rather than separated into lights.

In particular, when the light intensity is /JN low, the use of non-spectral light increases the production efficiency of silane ions generated by photodissociation of SiH+ and increases the growth rate.

In the above example, monocrystalline Si was formed on the Si wafer, but polycrystalline Si is formed when the temperature of the Si wafer is set to 500-700'C, and amorphous silicon is formed when the temperature is set to 200-500'C.

In the present invention, when performing vapor phase growth of a film using SiH gas, the wavelength of the irradiated light is limited, but when using a mixture of 5iHi and other reactive gases, the wavelength of the irradiated light is limited. Light in a wavelength range that promotes dissociation, decomposition, and photoreaction between the photodissociated fragments of S i H4 and SiH4 and other reactive gases can be synergized.

For example, when forming a SiO2 film from 5iHi and N20, the light with a wavelength of 1050 Å or less required for photoionization of 5iHi and the low pressure mercury lamp required for decomposition of N20 are used.
It is possible to synergistically irradiate light in the vicinity of 849 people and the Kr resonance line 1236 people. In addition, when forming a SiC film from S i H4 and CH4 gas, light near the Kr resonance line 1236 necessary for photodecomposition of CH4 gas or C
Light of 950 Å or less, which is necessary for photoionization (photodissociation) of Hh gas, may be irradiated in combination.

Figure 2 shows a light source using a He or Ne discharge tube and a Si
1 is a schematic diagram of an apparatus for photoionizing H+ to deposit a film on a substrate. Both 201 and 202 are fans for cooling the discharge tube, 203 is a cathode, and 204 is an anode, and both are AQ or Niv! This is a discharge electrode. 205 is a π-type discharge tube made of a quartz tube, 206 is a valve for introducing Ha or Ne discharge gas, 2o7 is a discharge gas exhaust port, and 208 is a π-type discharge tube.
A cooling water intake is provided on the outer wall of the discharge tube 205, 209 is a discharge transformer, and 210 is a slide transformer.

The pressure of the discharge gas in the π-type discharge tube 205 is 4O at I-1e.
-60 Torr, and about 300 Torr for Ne.

211 is an inlet for SiH4 gas, 212 is a substrate (Si wafer), and 213 is a heater for heating the substrate. The film growth chamber 214 and the π-type discharge tube 205 are differentially pumped by a turbo molecular pump located therebetween.

The film growth chamber 214 itself is also evacuated by a turbo molecular pump,
In the above apparatus in which the pressure during vapor phase growth of the film is 1 to 100 Torr, when He is used as the discharge gas, the pressure is 680 Torr.
600-1100, with a maximum around 850 people and 600-1100 people.
It has an emission spectrum with a continuous band in the human region. In the above apparatus, the Si wafer 212 is heated to 700 to 800°C and irradiated with light emitted from the He discharge tube 205 to provide 3i
By decomposing H4, Si was grown in a vapor phase on the Si wafer 212. As a result, by irradiating the light emitted from the Hs discharge tube 205, Si epitaxially grew at a lower temperature than when no light was irradiated.

〔Effect of the invention〕

According to the present invention, high-quality Si single crystals, Si polycrystals, etc. can be formed at low temperatures, so it can be applied to submicron processes for LSIs, resulting in higher integration and higher functionality of LSIs. Furthermore, since polycrystalline Si and amorphous silicon can be formed at low temperatures and grown at high speed, inexpensive glass substrates can be used as liquid crystal active matrix substrates, so active matrix substrates can be formed at low cost.

Furthermore, by narrowing down the irradiated light beam, it is possible to directly write film growth, which has the effect of increasing the functionality of LSIs and new conductor elements.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the present invention, and is an explanatory diagram of the outline of a film growth apparatus by light irradiation using synchrotron radiation light as a light source. FIG. 2 shows another embodiment of the present invention. Figure 3 is a diagram showing the wavelength dependence of the photoionization cross section of SiH4, The diagram is
Time of fl of photoionization of S i i-14
It is a figure which shows the light spectrum. 101...Shutoff valve for synchrotron radiation light source,
102... front mirror, 103... entrance slit, 10
4... Diffraction grating, 105... Output slit, 106
...1i left! Mirror (Toroidal Mirror), 107...
SiH number or its mixed gas inlet, 108...
Membrane Growth /In Hayabusa 2 Figure 20'/

Claims (1)

[Claims] 1. In a method of forming a thin film of Si or a compound containing Si by irradiating monosilane gas with light, the irradiating 5
Absorption of light with a wavelength of 00 to 1050 Å causes photodissociation and photoionization reactions of monosilane gas, resulting in photodissociation and photoionization.
A thin film vapor phase growth method using light irradiation, in which a gas containing silane molecules and silane ions produced by photoionization is guided onto a substrate to form a thin film. 2. In claim 1, 850 to 1000
irradiated with light of Å, and Si+, S dissociated by light irradiation.
A thin film vapor phase growth method using light irradiation in which silane ions generated by iH+, SiH_2+, and SiH_3+ and a gas containing these silane ions are introduced onto a substrate to form a thin film. 3. A thin film vapor phase growth method using light irradiation, in which a gas containing silane ions is introduced onto a Si substrate to form a Si single crystal thin film, as set forth in claim 1. 4. A thin film vapor phase growth method using light irradiation according to claim 1, in which monosilane gas is irradiated with synchrotron radiation light or light obtained from a rare gas discharge tube to form a thin film.