JPH0772353B2 - Thin film deposition method and apparatus - Google Patents

Description

The present invention relates to a method for depositing a thin film of a semiconductor, an insulator or a conductor on a substrate by exciting, decomposing or ionizing gas molecules in a reaction chamber. And the device.

[Conventional technology]

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

Fig. 12 shows the typical device configuration. As is well known, this is because a high frequency electric field is applied to the reaction chamber 1 by the coil 3 to decompose or ionize the gas introduced from the gas introduction nozzle 2 by the high frequency discharge to support the substrate in the reaction chamber. It is deposited as a thin film on the surface of the substrate 5 placed on the table 4, and in this example, the magnet 6 is used to improve the ion generation efficiency.

[Problems to be solved by the invention]

In the above conventional technique, it is difficult to limit the discharge region in the reaction chamber, that is, the excitation region where the gas is decomposed or ionized, to a predetermined space. Impurities are mixed in the gas, and the generated plasma (aggregation of ions and electrons) comes into contact with the substrate and the deposited thin film to cause damage, which causes the deterioration of the quality of the thin film.

Further, in the above-mentioned conventional technique, it is difficult to control the kinetic energy of the ions in the plasma to be distributed over a wide range and to have a desired constant value of kinetic energy that contributes to the deposition of the thin film. In addition, the kind of ion species to be generated and its excitation level, that is, the internal energy is also distributed over a wide range, and a specific kind of ion species or a specific excited state ion species that contributes to the deposition of a thin film is concentrated. It was difficult to generate.

An object of the present invention is to provide a new thin film deposition method and apparatus that solves the above-mentioned problems of the prior art.

[Means for solving problems]

In the thin film deposition method of the present invention, a substrate for depositing a thin film is placed in a reaction chamber, the reaction chamber is filled with a gas, and the reaction chamber is filled with soft X-rays or vacuum ultraviolet light emitted from an electron synchrotron radiation device. A beam is radiated parallel to the substrate to decompose or ionize a gas in a limited region in the reaction chamber, and apply an electric field between the region decomposed or ionized with the gas and the substrate, Decomposition products or product ions are deposited on the substrate.

Further, it is characterized in that two or more kinds of gases containing an element forming a deposited film are introduced into the reaction chamber.

Further, the thin film deposition apparatus of the present invention comprises a reaction chamber in which a substrate for depositing a thin film is placed, an electrode placed in the reaction chamber so as to face the substrate, and means for applying a voltage to the substrate and the electrode. A means for introducing gas into the reaction chamber, a soft X-ray or vacuum ultraviolet light beam emitted from an electron synchrotron radiation device into the reaction chamber, and a flat shape of the soft X-ray or vacuum ultraviolet light beam. And a means for introducing the light in parallel to the substrate via a light collecting means for performing the above.

[Action]

In the thin film deposition method and apparatus of the present invention, soft X-rays or vacuum ultraviolet light emitted from an electron synchrotron radiation apparatus to efficiently ionize gas is irradiated parallel to the substrate, and the gas in a limited area is irradiated. By decomposing or ionizing, depositing a thin film by applying an electric field between the excitation region and the substrate, the effect of the electric field is uniformly received, and the substrate is irradiated with ions with uniform kinetic energy controlled with high precision. It is possible to form a high quality thin film.

〔Example〕

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

FIG. 1 is a diagram showing an embodiment of the present invention and shows a basic device configuration.

In FIG. 1, reference numeral 7 schematically shows an electron synchrotron radiation device which is a soft X-ray or vacuum ultraviolet light source. For the electron synchrotron radiation device, refer to (1) [edited by C. Kunz, Synchrotron radiation (Techni
ques and Appli-cations), Springer-Verlag, 1979)
Have been introduced in detail.

8 is a beam propagation path consisting of a vacuum pipe, 9 is a reaction chamber, 10
Is a gas introduction nozzle, 11 and 12 are counter electrodes, 13 is a DC bias power source, 14 is a substrate, and 15 is an excitation region where the gas is decomposed or ionized by the soft X-rays or the vacuum ultraviolet light beam L incident on the reaction chamber 9. Shows.

Next, the operating principle, features and main effects of the device of the present invention will be described with reference to FIG.

FIG. 2 shows the wavelength distribution of the emitted light of the electron synchrotron radiation device (upper figure) and the spectrum of the absorption cross sections of methane (CH ₄ ) and silane (SiH ₄ ) gas with respect to the emitted light (lower figure). Many other gas molecules also show absorption spectra similar to those in this figure, and the gas molecules are ionized by this light absorption. That is, this figure shows that the emitted light of the electron synchrotron radiation device is light having a wavelength distribution with a high absorptivity that efficiently ionizes gas molecules.

The wavelength components with high absorptance are distributed in the range of 10 Å to 2000 Å.

Further, the intensity distribution of the emitted light of the electron synchrotron radiation device is given by Schwinger's equation in the above-mentioned document (1),
According to this equation, as shown in FIG. 3, the vertical spread of the soft X-ray or vacuum ultraviolet light beam L emitted from the electron synchrotron radiation device is (V is the speed of electrons and 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 counter electrodes 11 and 12 of the reaction chamber 9, and this is irradiated with the soft X-ray or vacuum ultraviolet light beam L from the electron synchrotron radiation device 7. , The gas is decomposed or ionized between the counter electrodes 11 and 12, and the counter electrodes 11 and 12, for example, the electrode 11
By applying a predetermined voltage (a voltage that does not cause discharge) so that the anode is the anode and the electrode 12 is the cathode, positive ions of the generated ions are deposited on the substrate 14 by the action of the electric field to form a thin film. It is clear to do.

Here, since the reaction chamber 9 is irradiated with the soft X-rays or the vacuum ultraviolet light beam L having good directivity, the excitation region where the gas is decomposed or ionized by the irradiation of the soft X-rays or the vacuum ultraviolet light beam, That is, the region 15 where plasma is formed
Is limited to a part of the space inside the reaction chamber 9, and the gas around the excitation region 15 still contains unexcited gas.
Therefore, the collision between the generated ions and electrons does not impair the purity of the thin film deposited on the substrate 14 due to the impurities mixed into the gas from the chamber wall or the electrode, and the substrate and the deposited thin film contact the plasma. And will not be damaged.

That is, the apparatus 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 an apparatus according to another embodiment of the present invention.

In this embodiment, the emitted light of the electron synchrotron radiation device 7 is flattened in parallel with the electrode surfaces of the counter electrodes 11 and 12 by a cylindrical mirror (a toroidal mirror, a hyperbolic mirror or the like may be used) 16 provided in the beam propagation path 8. FIG. 5 shows the relative positional relationship between the flat soft X-rays or the vacuum ultraviolet light beam L and the counter electrodes 11 and 12 in the reaction chamber. Shown in.

As described above, the radiated light from the electron synchrotron radiation device 7 has a good directivity. Therefore, it is condensed by a cylindrical mirror, a toroidal mirror, a hyperbolic mirror, etc. It is possible to easily obtain a different beam. Using such a flat beam is not only in line with the gist of the present invention to limit the excitation region 15 in the reaction chamber, but since the entire excitation region is approximately equidistant from the electrode surface, generated by excitation Since the ions are almost evenly affected by the electric field, it is possible to control the kinetic energy of the ions contributing to the deposition of the thin film with high accuracy by changing the strength of the electric field. The kinetic energy of sapphire can be given to all ions.

FIG. 6 and FIG. 7 show another embodiment of the present invention in which a wavelength selecting means for irradiating a soft X-ray or a vacuum ultraviolet light beam having a specific wavelength component is added.

In FIG. 6, the beam propagation path 8 is shown as an example of wavelength selecting means.
A spectroscope 17 consisting of a diffraction grating is installed in the middle of, and only a specific wavelength component of the emitted light of the electron synchrotron radiation device 7 is selected by the spectroscope 17, and this is condensed by the cylindrical mirror 16 and reacted. It is configured to be incident on the chamber 9.

When gas molecules are ionized, the soft X involved in ionization
The energy of the line or vacuum ultraviolet light, that is, the type of io generated with respect to the wavelength (for example, SiH ₄ , Si ⁺ , SiH
⁺ , SiH ₂ ⁺ , SiH ₄ ⁺ , Si ^2+, etc.) and their excitation levels are known to have a certain relationship. Therefore, by selecting the wavelength of the soft X-ray or the vacuum ultraviolet light beam with which the reaction chamber 9 is irradiated by using the apparatus of the embodiment shown in FIG. 6, a specific kind of ion species or a specific excited level ion species is selected. It is possible to selectively generate. In general, the properties of the thin film are greatly affected by the substrate temperature and the internal energy of the active species to be deposited, 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 selected. By controlling
A good quality thin film can be formed at a relatively low substrate temperature.

FIG. 7 shows, as a wavelength selection means, a cylindrical mirror with a multilayer film having a multilayer film 18 in which thin films of, for example, tungsten and carbon are alternately laminated on the surface, not as a spectroscope.
An example using 19 is shown.

It is well known that the reflectance of a multilayer mirror has a certain wavelength selectivity and can be used in place of a spectroscope, but by attaching a multilayer film to a mirror having a condensing function as shown in FIG. Since the functions of the spectroscope 17 and the condenser 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.

If an undulator [a device that causes the electron orbit to meander and is introduced in reference (1)] is attached to the electron synchrotron radiation device, the wavelength distribution of the synchrotron radiation shown in FIG. 2 will be near a specific wavelength λ ₀ . By concentrating and increasing the intensity by almost two orders of magnitude, and further changing the strength of the magnetic field, the wavelength λ ₀ can be changed over a wide range. Therefore, by using the electron synchrotron radiation device equipped with the undulator as the soft X-ray or vacuum ultraviolet light source in the embodiment apparatus of FIG. 1 or FIG. A high intensity soft X-ray or vacuum ultraviolet light beam can be obtained.

Although illustration is omitted, in each of the apparatus 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 acting, the deposition rate of the thin film can be improved. It is also possible to deposit the thin film using only the magnetic field instead of the electric field. Note that a means for forming an electric field or a magnetic field in the reaction chamber is not necessarily required for film deposition. However, it is effective to provide these means in order to increase the film deposition rate.

Hereinafter, experimental examples of the present invention will be described with reference to FIGS.

Figure 8 shows the experimental setup for thin film deposition (hereinafter referred to as SR excited CVD) using electron synchrotron radiation at the Photon Factory facility of the High Energy Physics Laboratory.

The beam propagation path is maintained at a high vacuum by a differential vacuum pumping device (not shown), and as a result, the pressure in the mirror chamber 22 is reduced to 3
The pressure in the reaction chamber 23 was 2 × 10 ^-2 Torr or higher while the pressure was kept lower than × 10 ^-9 Torr. The source gas (100% SiH or 100% SiH ₄ + N ₂ ) 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, SR radiation from the 2.5GeV storage ring 20 is collected by the toroidal mirror 21 and the small chamber
Irradiate 24 to deposit a thin film on the substrate 27. in this case,
The typical partial pressure of SiH ₄ gas was 3 × 10 ⁻³ Torr.

Reference numeral 28 in the figure denotes a heater for heating the substrate.

The experimental results are as follows.

The thickness of the deposited film was measured by the Talystep measuring method. The deposition rate was always constant in the range of the substrate temperature T _S in this experiment (Fig. 9). When a bias voltage (200 V in this case) was applied, the deposition rate increased significantly (Fig. 9). This means that the reaction gas is effectively ionized by SR synchrotron radiation and the ionized species.
Suggest that they are collected on the substrate by the application of an electric field.

The IR absorption spectrum of the deposited a-Si: H (Note, silicon amorphous containing hydrogen) film is shown in FIG. In Fig. 10, the peak near the wave number of 2000 cm ^-1 is the Si-H stretching vibration (st
Although it corresponds to retching vibration), only a weak peak is observed for Si—H ₂ bending vibration. As a result, in the deposited a-Si: H film, Si-
It was inferred that the H-bond was dominant.

Auger depth profile of deposited Si _x N _y H _z film (Auger
The in-depth profile) is shown in Fig. 11. The pressure ratio of nitrogen and silane (P _N2 / P _SiH4 = 1) _{depends on the} glow discharge method [Reference (2)
D. Haiping et al., J. Electrochem. Soc., 128 (1981) 155
Nitrogen atoms are effectively incorporated into the film (N / Si0.8), even though it is considerably lower than that in 5]. From the IR spectrum, it was confirmed that these nitrogen atoms bond to Si and H. Since the binding energy of N ₂ (9.8 eV) and the first ionization potential of N ₂ (15.6 V) are substantially larger than the average electron energy in the glow discharge plasma, the generation rate of N ₂ radicals and ions in the glow discharge plasma is Very low. In contrast, SR radiation has sufficient light energy to decompose or ionize N ₂ gas. Further, the light absorption sectional area of higher N ₂ than the ionization threshold (~20Mb) have it (~40-50Mb) the same order of magnitude of the SiH _4. Therefore, SR synchrotron radiation generates nitrogen ions (N ⁺ , N ²⁺ , N ₂ ⁴⁺ ) in an amount comparable to that of SiHm ions.
The generation of these active ions is one of the interesting features of SR-enhanced CVD, which offers the possibility to open a way for the formation of new materials.

〔The invention's effect〕

As described above, according to the thin film deposition method and apparatus of the present invention, the electron is emitted from the electron synchrotron radiation device,
The substrate is irradiated with soft X-rays or vacuum ultraviolet light, which efficiently ionizes the gas, parallel to the substrate, to decompose or ionize the gas in a limited region, and apply an electric field between the excited region and the substrate to form a thin film. By depositing, the effect of the electric field is evenly applied, and the substrate can be irradiated with ions having a uniform kinetic energy controlled with high accuracy, and a good quality thin film can be formed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the basic device configuration of the present invention, and FIG.
The figure shows the wavelength distribution of electron synchrotron radiation and the spectrum distribution of the absorption cross section of gas molecules, and FIG. 3 shows the radiation angle distribution of electron synchrotron radiation.
FIG. 6 is a schematic view showing another example of the device configuration of the present invention to which a condensing means is added, FIG. 5 is a schematic view showing the relative positional relationship between the counter electrode and the soft X-ray or vacuum ultraviolet light beam, and FIG. FIG. 7 is a schematic view showing another example of the apparatus configuration of the present invention in which a condensing means and a wavelength selecting means are used in combination, FIG. 8 is a schematic diagram showing the configuration of an 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 mirror for condensing, 17 …… Spectroscope for wavelength selection, 18 …… Multilayer film for wavelength selection, 19 …… Cylindrical mirror with multilayer film） 9 …… Reaction chamber, 10… ... Nozzles which are gas introduction means 11, 12, 13 ... Electric field forming means (11, 12 ... counter electrodes, 13
...... DC bias power supply) 14 …… Substrate 15 …… Excitation region L …… Soft X-ray or vacuum ultraviolet light beam

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toyoki Kitayama 3-1, Morinosato Wakamiya, Atsugi City, Kanagawa Pref. Atsugi Telecommunications Research Laboratories, Nippon Telegraph and Telephone Corporation (56) Reference JP-A-59-9164 (JP, A) Kai 59-140368 (JP, A) JP-A-60-121272 (JP, A)

Claims (3)

[Claims] 1. A substrate for depositing a thin film is placed in a reaction chamber, the reaction chamber is filled with a gas, and a soft X-ray or a vacuum ultraviolet light beam emitted from an electron synchrotron radiation device is emitted into the reaction chamber. The substrate is irradiated substantially parallel to decompose or ionize a gas in a limited region in the reaction chamber, and an electric field is applied between the region in which the gas is decomposed or ionized and the substrate. A method of depositing a thin film, characterized in that generated ions are deposited on the substrate. 2. The thin film deposition method according to claim 1, wherein two or more kinds of gases containing an element forming a deposited film are introduced into the reaction chamber. 3. A reaction chamber in which a substrate for depositing a thin film is placed, an electrode placed in the reaction chamber so as to face the substrate, a means for applying a voltage to the substrate and the electrode, and the reaction chamber. Means for introducing a gas into the reaction chamber, and a light X-ray or vacuum ultraviolet light beam emitted from an electron synchrotron radiation device into the reaction chamber for condensing the soft X-ray or vacuum ultraviolet light beam into a flat shape. A thin film deposition apparatus having a means for introducing the substrate parallel to the substrate through a means.