JPS6244575A - Method and apparatus for depositing thin film - Google Patents

Abstract

PURPOSE:To prevent the entering of impurities into a thin film and the damage of the thin film by exciting gaseous molecules by the irradiation of soft X-rays or ultraviolet rays so as to deposit the thin film on a substrate. CONSTITUTION:Soft X-rays or ultraviolet rays L having a specified wavelength range are irradiated on the inside of a reaction chamber 9 filled with a gas 10 to decompose or ionize the gas 10 in a limited region in the chamber 9. The resulting decomposition products or produced ions are deposited on a substrate 14 placed in the chamber 9.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for depositing a thin film of a semiconductor, insulator or conductor on a substrate by exciting, decomposing or ionizing gas molecules in a reaction chamber. and equipment.

[Conventional technology]

As a conventional technique in this field, there is a plasma CVD apparatus that excites gas molecules by electric discharge.

FIG. 12 shows a typical device configuration. As is well known, this method applies a high-frequency electric field to the reaction chamber 1 using the coil 3, decomposes or ionizes the gas introduced from the gas introduction nozzle 2 by high-frequency discharge, and supports the substrate inside the reaction chamber. It is deposited as a thin film on the surface of a substrate 5 placed on a table 4, and in this example, a magnet 6 is used to improve the ion production efficiency.

[Problem that the invention seeks to solve]

In the above conventional technology, it is difficult to limit the discharge region in the reaction chamber, that is, the excitation region where gas is decomposed or ionized, to a predetermined space. Impurities were mixed into the gas, and the generated plasma (a collection of ions and electrons) came into contact with the substrate and the deposited thin film, causing damage, resulting in a decline in the quality of the thin film.

Furthermore, in the above conventional technology, the kinetic energy of ions in the plasma is distributed over a wide range, and it is difficult to control this so that the kinetic energy has a desired constant value that contributes to the deposition of a thin film. Furthermore, the types of ion species generated and their excited levels, that is, their internal energies, are distributed over a wide range. It is an object of the present invention to provide a new thin film deposition method and apparatus which solves the problems of the above-mentioned prior art.

[Means for solving problems]

In the thin film deposition method of the present invention, a soft X
line or vacuum ultraviolet light beam (preferably wavelength 10~2
000 people) to decompose or ionize the gas in a limited area within the reaction chamber, and deposit the decomposition products or generated ions on a substrate placed within the reaction chamber.

The thin film deposition apparatus of the present invention also includes a reaction chamber in which a substrate for depositing a thin film is installed, a means for introducing gas into the reaction chamber, and a soft X-ray or vacuum ultraviolet light beam (preferably wavelength a means for irradiating 1000 to 2000 people;
Either or both of an electric field and a magnetic field for depositing decomposition products or generated ions on the substrate in an excitation region where gas is decomposed or ionized by irradiation with the soft X-rays or vacuum ultraviolet light beam as necessary. The soft X-ray or vacuum ultraviolet light beam irradiation means is characterized in that it uses an electron synchrotron radiation device as a soft X-ray or vacuum ultraviolet light generation source.

[Effect]

In the thin film deposition method of the present invention, gas molecules are excited only in a limited area within the reaction chamber by irradiation with soft X-rays or vacuum ultraviolet light beams. Plasma can be generated without contact, thereby avoiding contamination of the deposited thin film with impurities and damage to the substrate or thin film caused by the plasma. In addition, because the excitation region is limited, the kinetic energy of the generated ions can be easily controlled, and by using soft X-rays or vacuum ultraviolet light beams of specific wavelengths, specific types or specific Excited ion species can be selectively generated, and the internal energy of the ions can be easily controlled. This allows the properties of the deposited thin film to be varied as desired.

The thin film deposition apparatus of the present invention excites gas molecules in a limited region by irradiating a reaction chamber with highly directional, high-intensity soft X-rays or vacuum ultraviolet light beams generated from an electron synchrotron radiation device. This can be carried out efficiently, and the generated ions can be efficiently deposited on the substrate by one or both of the electric field and magnetic field applied to the excitation region. Furthermore, if a wavelength selection means is used in conjunction with an electron synchrotron radiation device that is a source of soft X-rays or vacuum ultraviolet light, a soft X-ray or vacuum ultraviolet light beam having the specific wavelength can be easily obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 1 is a diagram showing one embodiment of the present invention, showing the basic device configuration.

In FIG. 1, numeral 7 schematically shows an electron synchrotron radiation device which is a source of soft X-rays or vacuum ultraviolet light. Regarding the electron synchrotron radiation device, see the literature (
1) (edited by C. Kunz, 5ynchrotron
radiation (Techniques and
d Applications), Spring
r-Verlag, 1979].

8 is a beam propagation path consisting of a vacuum pipe, 9 is a reaction chamber, 1
0 is a gas introduction nozzle, 11.12 is a counter electrode.

13 is a DC bias power supply, 14 is a substrate, and 15 is a reaction chamber 9.
It shows an excitation region in which gas is decomposed or ionized by soft X-rays or vacuum ultraviolet light beam L incident on it.

Next, the operating principle, features, and main effects of the device of the present invention will be described based on FIG.

Figure 2 shows the wavelength distribution of the emitted light from the electron synchrotron radiation device (upper figure) and the spectrum of the absorption cross section of methane (CH4) and silane (SiH) gases for the emitted light (lower figure). Many other gas molecules also exhibit absorption spectra roughly similar to this diagram, and gas molecules are ionized as a result of this light absorption. In other words, this figure shows that the emitted light from the electron synchrotron radiation device is light that efficiently ionizes gas molecules and has a wavelength distribution with a high absorption rate.

This wavelength component with high absorption rate is distributed in a range of about 10 to 2000.

Furthermore, the intensity distribution of synchrotron radiation from an electron synchrotron radiation device is given by the Schwinger formula in the above-mentioned document (1),
According to this formula, as shown in FIG. 3, the soft X-ray or vacuum ultraviolet light beam L emitted from the electron synchrotron radiation device is expressed by the upper and lower particles (C is the speed of light).

From this, it can be seen that a soft X-ray or vacuum ultraviolet light beam with good directivity is generated.

Therefore, in FIG. 1, if gas is filled between the gas introduction nozzle 10 and the opposing electrodes 11 and 12 of the reaction chamber 9, and the space is irradiated with soft X-rays or vacuum ultraviolet light beam L from the electron synchrotron radiation device 7, , the gas is decomposed or ionized between the opposing electrodes 11 and 12, and a predetermined voltage (a voltage that does not cause discharge) is applied to the opposing electrodes 11 and 12, for example, so that the electrode 11 becomes an anode and the electrode 12 becomes a cathode. Therefore, it is clear that among the generated ions, positive ions are deposited on the substrate 14 by the action of the electric field to form a thin film.

Here, since the interior of the reaction chamber 9 is irradiated with soft X-rays or vacuum ultraviolet light beam L with good directionality, an excitation region where gas is decomposed or ionized by irradiation with the soft X-rays or vacuum ultraviolet light beam, That is, region 1 where plasma is formed
5 is limited to a part of the space within the reaction chamber 9, and the excitation region 1
There is still unexcited gas in the space around 5. Therefore, the purity of the thin film deposited on the substrate 14 will not be impaired due to impurities mixed into the gas from the vessel walls or electrodes due to the collision between the generated ions and electrons, and the substrate and the deposited thin film will not come into contact with the plasma. It will not cause any damage.

That is, the apparatus of the embodiment shown in FIG. 1 can be used as an apparatus for carrying out the thin film deposition method of the present invention.

FIG. 4 shows another embodiment of the present invention.

In this embodiment, a cylindrical mirror (
The light beam is condensed into a flat shape parallel to the electrode surfaces of the counter electrodes 11 and 12 by a toroidal mirror, a hyperbolic mirror, etc.) and is incident on the reaction chamber 9. line or vacuum ultraviolet light beam L
The relative positional relationship between the electrodes 11 and 11 and the counter electrodes 11 and 12 is shown in FIG.

As mentioned above, the emitted light from the electron synchrotron radiation device 7 has good directivity, so it can be collected into a flat surface with a thickness of about 1 mm by condensing it with a cylindrical mirror, toroidal mirror, hyperbolic mirror, etc., or focusing it with a slit. You can easily obtain a beam of Using such a flat beam not only meets the purpose of the present invention to limit the excitation region 15 inside the reaction chamber, but also because the entire excitation region is approximately equidistant from the electrode surface. Since the generated ions are almost equally affected by the electric field, by changing the electric field strength, it is possible to control with high precision the kinetic energy of the ions that contribute to thin film deposition. A desired amount of kinetic energy can be imparted to all ions.

FIGS. 6 and 7 show another embodiment of the present invention, which is equipped with wavelength selection means for irradiating soft X-rays or vacuum ultraviolet light beams of specific wavelength components.

In FIG. 6, a beam propagation path 8 is shown as an example of wavelength selection means.
A spectroscope 17 consisting of a diffraction grating is installed in the middle of the electron synchrotron radiation device 7, and only a specific wavelength component is selected by the spectrometer 17, which is focused by the cylindrical mirror 16 and reacted. The configuration is such that the light enters the chamber 9.

When gas molecules are ionized, the soft X involved in ionization
The type of ions produced (for example, SL
", S i H", SiH2", SiH4", Sj2+
) and their excited levels are known to have a certain relationship. Therefore, by selecting the wavelength of the soft X-ray or vacuum ultraviolet light beam irradiated to the reaction chamber 9 using the embodiment apparatus shown in FIG. This enables selective generation. In general, the properties of thin films are greatly affected by the substrate temperature and the internal energy of the deposited active species, so the wavelength of the soft X-ray or vacuum ultraviolet light beam is selected as described above, and the internal energy of the generated ions is By controlling.

It becomes possible to form high-quality thin films at relatively low substrate temperatures.

FIG. 7 shows an example in which a multilayered cylindrical mirror 19 having a multilayered film 18 on the surface of which thin films of tungsten and carbon are alternately laminated, for example, is used instead of a spectroscope as the wavelength selection means.

It is well known that the reflectance of a multilayer mirror has a certain wavelength selectivity and can be used in place of a spectrometer. Since the functions of the spectroscope 17 and the condensing mirror 16 shown in the embodiment of FIG. 6 can be realized by one mirror, the loss of the soft X-ray or vacuum ultraviolet light beam can be reduced.

When an undulator (a device that makes electron orbits meander and is introduced in Reference (1)) is attached to an electron synchrotron radiation device, the wavelength distribution of the emitted light shown in Fig. 2 will change to a specific wavelength λ. The intensity increases by nearly two orders of magnitude, and by further changing the strength of the magnetic field, the wavelength λ. can vary widely. Therefore, in the embodiment apparatus shown in FIG. 1 or 4, by using an electron synchrotron radiation device equipped with an undulator as a soft A certain high intensity soft X-ray or vacuum ultraviolet light beam can be obtained.

Although not shown, in each of the embodiment apparatuses shown in FIGS. 1, 4, 6, and 7, a magnet is installed at a predetermined position in the reaction chamber 9, and a magnetic field is applied to the excitation region 15. By allowing this to occur, it is possible to improve the deposition rate of the thin film. It is also possible to deposit thin films using only a magnetic field instead of an electric field. Note that for film deposition, means for forming an electric or magnetic field in the reaction chamber is not necessarily required).

However, providing these means is effective in increasing the film deposition rate.

Experimental examples of the present invention will be explained below with reference to FIGS. 8 to 11.

Figure 8 shows thin film deposition using electron synchrotron radiation at the Photon Factory facility of the High Energy Physics Research Institute.
An experimental setup for SR excitation CVD (hereinafter referred to as SR excitation CVD) is shown below.

The beam propagation path is maintained at a high vacuum by a differential evacuation device (not shown), and as a result, while the pressure inside the mirror chamber 22 is kept lower than 3 x 10-9T orr,
The pressure inside the reaction chamber 23 was 2×10-” Torr or more.The source gas (100% SiH or 100%
SiH, +N2) was supplied to the small chamber 24 in the reaction chamber 23, and a DC bias voltage was applied between the electrode 25 and the substrate support 26. In this state, the SR radiation from the 2.5 GeV storage link 20 was focused by the toroidal mirror 21 and irradiated into the small chamber 24 to deposit a thin film on the substrate 27. In this case, the typical partial pressure of SiH4 gas is 3
X IF' Torr.

Note that 28 in FIG. 1 indicates a heater for heating the substrate.

The experimental results are as follows.

The thickness of the deposited film is Talystep f
It was measured by the fi'l standard method. The deposition rate was always constant within the range of substrate temperature Ts in this experiment (FIG. 9). Adding a bias voltage (200V in this case) greatly increased the deposition rate (Figure 9). This suggests that the reactant gas is effectively ionized by the SR radiation and that the ionized species are collected on the substrate by the application of the electric field.

The IR absorption spectrum of the deposited a-3i:H (note: silicon amorphous containing hydrogen) film is shown in FIG. In Fig. 10, the peak near the wave number 2000 cm-1 is the Si-H stretching vibration (stretching vibration).
5i-N2 bending vibration (b
(endingvibration), only a weak peak is observed. As a result, the deposited a-5i:
It was inferred that 5i-H bonds were dominant within the H film.

The Auger 1n-depth profile of the deposited 5ixN, Hz film is shown in FIG.

Pressure ratio of nitrogen and silane (PN2/ps; H4: 1
) is the glow discharge method [Reference (2) D, Haiping
et al., +J.

Electrochem, Soc, 128 (1
981) Even though it is considerably lower than that in 1555),
Nitrogen atoms are effectively incorporated into the film.
0.8). From the IR spectrum, these nitrogen atoms are S
It was confirmed that it binds to i and H. Since the binding energy of N2 (9,8 eV) and the first ionization potential of N2 (15,6 eV) are substantially larger than the average electron energy in glow discharge plasma, the generation rate of N2 radicals and ions in glow discharge plasma is very high. low. In contrast, SR synchrotron radiation has sufficient optical energy to decompose or ionize N2 gas. Furthermore, the optical absorption cross section of N2 (~20 Mb) higher than the ionization threshold is that of SiH (~40-40-5
It has the same size as O.

Therefore, the SR synchrotron radiation generates nitrogen ions (N+, NZ+, N24+) in an amount comparable to S i Hm ions.

The generation of these active ions is one of the interesting features of SR-excited CVD, which offers the possibility of opening an avenue for the formation of new materials.

〔Effect of the invention〕

As described above, the thin film deposition method of the present invention excites gas molecules in a limited area within a reaction chamber by irradiation with soft X-rays or vacuum ultraviolet light beams, and deposits a thin film on a substrate placed within the reaction chamber. Therefore, it is possible to avoid the contamination of impurities from the vessel walls and electrodes and damage to the substrate and thin film due to contact with plasma, which are disadvantages of the conventional plasma CVD method, and it is possible to form a thin film with better characteristics.

Further, according to the thin film deposition apparatus of the present invention, gas molecules in a limited area are excited and A thin film can be efficiently deposited on a substrate.

The unique effects of each embodiment other than the above are as described in the Examples section.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the basic device configuration of the present invention;
Figure 3 shows the wavelength distribution of electron synchrotron radiation and the spectral distribution of the absorption cross section of gas molecules, Figure 3 shows the radiation angle distribution of electron synchrotron radiation, and Figure 4 shows the radiation angle distribution of electron synchrotron radiation.
The figure is a schematic diagram showing another example of the device configuration of the present invention in which a condensing means is added; FIG. 5 is a schematic diagram showing the relative positional relationship between the counter electrode and the soft X-ray or vacuum ultraviolet light beam; 7 is a schematic diagram showing another example of the configuration of the apparatus of the present invention using both a condensing means and a wavelength selection means, FIG. 8 is a schematic diagram showing the configuration of the experimental apparatus of the present invention, and FIGS. FIG. 11 is a graph showing experimental data, and FIG. 12 is a schematic diagram showing a conventional plasma CVD apparatus. 7.8.16.17, 18.19... Soft X-ray or vacuum ultraviolet light beam irradiation means (7... Electron synchrotron radiation'! device, 8 Beam propagation path, 16... Cylindrical for focusing Mirror, 17... Spectrometer for wavelength selection, 18
...Multilayer film for wavelength selection, 19...Cylindrical mirror with multilayer film) 9...Reaction chamber, 10...Nozzles 11, 12, which are gas introducing means.13...Electric field forming means (11, 12...
・Counter electrode, 13...DC bias power supply) 14...Substrate 15...Excitation region L...Soft X-ray or vacuum ultraviolet light beam Patent applicant Junnosuke Nakamura, patent attorney for Nippon Telegraph and Telephone Corporation Happy 1 Illustration 2 '□ t 3 Congratulations and condolences (A) Spear 4 Illustration

Claims (7)

[Claims] (1) A reaction chamber filled with gas is irradiated with a soft X-ray or vacuum ultraviolet light beam to decompose or ionize the gas in a limited area within the reaction chamber, and the decomposition products or generated ions are placed inside the reaction chamber. A method for depositing a thin film, characterized by depositing the film on a substrate. (2) The soft X-ray or vacuum ultraviolet light beam consists of a specific wavelength component, and the specific wavelength component ionizes the gas into a specific type of ion species. Thin film deposition method described in section. (3) The thin film deposition method according to claim 1 or 2, wherein the soft X-ray or vacuum ultraviolet light beam has a flat shape. (4) A reaction chamber in which a substrate for depositing a thin film is installed, a means for introducing gas into the reaction chamber, and a soft X
rays or vacuum ultraviolet light beam, and the soft X-ray or vacuum ultraviolet light beam irradiation means has a configuration using an electron synchrotron radiation device as a soft thin film deposition equipment. (5) The soft X-ray or vacuum ultraviolet light beam irradiation means:
5. The thin film deposition apparatus according to claim 4, further comprising wavelength selection means for making the soft X-ray or vacuum ultraviolet light beam a specific wavelength component. (6) The soft X-ray or vacuum ultraviolet light beam irradiation means:
6. The thin film deposition apparatus according to claim 4, further comprising condensing means for flattening the soft X-ray or vacuum ultraviolet light beam. (7) A reaction chamber in which a substrate for depositing a thin film is installed, a means for introducing gas into the reaction chamber, and a soft X
means for irradiating a soft X-ray or vacuum ultraviolet light beam, and an electric field for depositing decomposition products or product ions on the substrate in an excitation region where the gas is decomposed or ionized by the irradiation with the soft x-ray or vacuum ultraviolet light beam; and a means for forming either or both of a magnetic field and a magnetic field, and the soft X-ray or vacuum ultraviolet light irradiation means has a configuration using an electron synchrotron radiation device as a soft X-ray or vacuum ultraviolet light generation source. Characteristic thin film deposition equipment.