JPS63313814A - Device for forming thin film - Google Patents

Abstract

PURPOSE:To contrive increase both in a thin film deposited area and deposition speed by adjusting the angle formed by an irradiation light and a substrate. CONSTITUTION:The title thin film forming device is provided with an electron accumulation ring 1 as the irradiation means which is the generation source of soft X-rays or a vacuum ultraviolet rays, electrons 1a, a mirror chamber 2, a troidal mirror 3 as a beam-concentrating means, an optical propagation path (beam line)4 consisting of a vacuum pipe, a reaction chamber 5, a substrate 6 to be processed, a heater 7 to be used for heating, air exhaust ports 8 and 15, a raw gas nozzle 9 as a gas introducing means, a substrate holder 12 as an inclining means, and a radiant light introducing port 16 having reduced exhaust conductance in order to conduct differential evacuation between the optical propagation path 4 and the reaction chamber. When a thin film is deposited on the substrate 6 provided in the reaction chamber 5 by irradiating the above-mentioned light on the substrate 6 provided in the reaction chamber 5, the oblique incident angle theta formed by the irradiation light and the substrate 6 is to be made small substantially when the pressure of reaction gas is highAs a result, the increase both in speed of deposition and in the deposi tion area of the thin film can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film forming apparatus using a photoexcitation method.

[Conventional technology]

As a prior art, there is a thin film forming apparatus using synchrotron radiation light as an excitation source, as shown in FIG. this is,
For example, it is described in Japanese Patent Application No. 193088/1988.

In FIG. 6, 1 is an electron storage ring, 2 is a mirror chamber,
3 is a toroidal mirror for condensing light, 4 is a beam line (light propagation path), 5 is a reaction chamber, 6 is a substrate, 7 is a heater for heating,
8 is an exhaust port, 9 is a raw material gas nozzle, 10 is a counter electrode, 1
1 is a bias power supply.

The apparatus shown in FIG. 6 configured in this manner guides the emitted light from the electron storage ring l into the reaction chamber 5 as an excitation source, and sets the substrate 6 perpendicular to the emitted light. The method is characterized in that a thin film is deposited on the substrate 6 by flowing a raw material gas through it.

In this type of apparatus, in order to increase the light intensity per unit area in order to increase the deposition rate, for example, the emitted light is focused by a toroidal mirror 3 installed upstream of the beam line 4, or the irradiated light is In order to prevent the irradiation light from being absorbed and attenuated by gas molecules in the gas phase before reaching the substrate 6, a portion (difference A dynamic exhaust section) was installed. However, in this case, there was a drawback that the thin film formation area became narrow. Therefore, in order to expand the thin film formation area, a new mechanism is required for reciprocating the substrate 6 in the direction perpendicular to the irradiation light during deposition, for example. However, the reciprocating motion caused a reduction in the deposition rate.

Another conventional technique is a thin film forming apparatus using an excimer laser 13 as an excitation source, as shown in FIG. For example, the document "Yoshikawa and Monke 1 Japanese Journal of Applied Physics,
Volume 23 (1984) No. L91 (8, Yoshikawa
a and S, Yamaga+Jpn, J, 8p
p1. Phys.

, 23 (1984) L91) J. In this type of device, a window material (such as quartz or synthetic glass) that allows the excitation light to pass through and insulates the source gas in a vacuum is used.
14 can be used, so there is no need to consider differential pumping, unlike the case where soft X-rays or vacuum ultraviolet light with large gas absorption are used as excitation light, as shown in FIG.

[Problem that the invention seeks to solve]

However, the cross-sectional area of the laser beam is not large at all, approximately 15 x 7 mm2, and when the substrate is tilted to the laser beam in order to form a thin film over a large area, the light intensity per unit area decreases, and therefore the deposition rate decreases. There was a drawback.

The present invention has been made in view of these points, and its purpose is to use soft X-rays or vacuum ultraviolet light as an excitation source, and to increase the product of the deposition rate and the thin film formation area compared to the conventional technology. The goal is to provide a device that is larger than the original.

[Means for solving problems]

In order to achieve such an object, the present invention provides a reaction chamber in which a substrate for depositing a thin film is installed, a gas introduction means for introducing a raw material gas into the reaction chamber, and a soft X-ray or vacuum ultraviolet light source in the reaction chamber. A steep pressure difference is created between the irradiation means that irradiates light as irradiation light, the tilting means that tilts the substrate at an arbitrary angle with respect to the irradiation light, and the beam line that guides the irradiation light from the reaction chamber. In order to achieve this, the beam passing section at the connection of the beam line to the reaction chamber was narrowed and a differential exhaust section was installed to reduce the exhaust conductance, and a focusing means was installed in the middle of the beam line to focus the irradiated light. It is something.

[Effect]

In the thin film forming apparatus according to the present invention, the substrate is installed at an angle with respect to the irradiation light, the incident angle of the irradiation light to the substrate becomes small, and the number of photoelectrons and the amount of reflected light from the substrate increase.
These excite gas molecules in the gas phase, increasing the overall deposition rate.

〔Example〕

The present invention focuses on the fact that the deposition rate increases by increasing the contribution of gas phase reactions among the components that govern the reaction mechanism, and is characterized by forming a thin film by tilting the substrate with respect to the irradiation light. do.

An embodiment of the thin film forming apparatus according to the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is a configuration diagram showing the basic configuration of this device.

In FIG. 1, 1 is an electron storage ring as an irradiation means that is a source of soft X-rays or vacuum ultraviolet light; 1a is an electron;
is a mirror chamber, 3 is a toroidal mirror as a light collecting means,
4 is a light propagation path (beam line) consisting of a vacuum pipe; 5
1 is a reaction chamber, 6 is a substrate to be processed, 7 is a heating heater, 8° 15 is an exhaust port, 9 is a raw material gas nozzle as a gas introducing means, 12 is a substrate holder as a tilting means, 16 is a light propagation path 4 This is a synchrotron radiation introduction port with a small exhaust conductance in order to apply differential exhaust between the reactor and the reaction chamber 5.

In this apparatus configured in this manner, a differential exhaust section consisting of a synchrotron radiation introducing boat 16 and an exhaust port 15 is incorporated in order to provide a steep pressure distribution between the light propagation path 4 and the reaction chamber 5. There is. The opening area of the synchrotron radiation introduction boat 16 is 7X
It was 13 mm2 in length, 18 cm in length, and the evacuation speed of the vacuum pump attached to the exhaust port 15 was 330 A/sec. With this configuration, when the pressure in the reaction chamber 5 is 13 Pa, the pressure immediately above the exhaust port 15 in the light propagation path 4 is 0.36 Pa, which is about 37 times the pressure difference between the two points.

Next, based on FIG. 1, the operating principle, features, and main effects of this device will be described. FIG. 2 shows the dose amount of the deposited film (electron storage ring) using the apparatus shown in FIG. A quantity defined as the product of current and time of 1). The experimental conditions were that the pressure of silane (SiH4) was 2.7 Pa, the pressure of nitrogen (N2) was 60 Pa, and the temperature of the substrate 6 was about 200°C. The current value of the electron storage ring 1 during the experiment was about 100 to 200 mA. Second
In the figure, Sl is the characteristic curve of the grazing incidence angle θ-90 degrees, and S
2 is the characteristic curve of grazing incidence angle θ - 45 degrees, S3 is the grazing incidence angle θ
-30 degree characteristic curve. As is clear from FIG. 2, the smaller the oblique incidence angle θ, the higher the deposition rate.

Figure 3 shows the deposition rate ratio (deposition rate ratio, ratio of deposition rate at a certain oblique incidence angle/deposition rate at an oblique incidence angle of 90 degrees) l/s in θ using the gas pressure conditions during the experiment as parameters.
Show dependencies. Although the 17 sin θ dependence differs depending on the gas pressure conditions, the deposition rate increases as the oblique incidence angle θ decreases.

In Figure 3, S4 is the pressure of silane (SiH4) of 2.
．． 7 Pa, the characteristic curve when the nitrogen (N2) pressure is 13 Pa, S5 is the characteristic curve when the silane (SiH4) pressure is 2.7 Pa,
This is a characteristic curve when the pressure of nitrogen (N2) is 60 Pa. In addition, as can be seen from FIG. 3, the characteristic curve S5 is θ=
It starts to become saturated around 50 degrees, and the deposition rate ratio is θ-50 degrees,
There is no big change at 45 degrees and 45 degrees.

As the oblique incidence angle θ becomes smaller, the irradiation area on the substrate 6 increases and the light intensity per unit irradiation area decreases. Therefore, if the deposition rate is proportional to the light intensity, as described in the prior art section, as the oblique incidence angle θ becomes smaller,
The deposition rate should decrease. Therefore, Figures 2 and 3
Another mechanism must be considered to explain the results shown in the figure.

FIG. 4 is a diagram for explaining the mechanism for emitting photoelectrons from the substrate 6 in order to consider this point.

When synchrotron radiation 17 with a beam cross-sectional area S is obliquely incident on the substrate 6 at an angle of incidence θ, the light is absorbed up to a certain penetration distance l in the substrate 6 determined by the absorption coefficient, and in the process, atoms constituting the substrate 6 are absorbed. excites and generates photoelectrons.

The generated photoelectrons further collide with other atoms and excite them,
While some photoelectrons excite the lattice system and lose energy, some photoelectrons completely lose their energy in the substrate 6, while other photoelectrons fly out of the substrate 6 with a constant kinetic energy. The escape depth dε is a guideline that indicates how deep the photoelectrons jump out from the surface of the substrate 6.
There is.

The escape depth dε varies depending on the kinetic energy of the photoelectrons, but is about 5 to 50 people. This can be seen, for example, in the literature [
Electron Spectroscopy 9 Edited by the Chemical Society of Japan, Society Publishing Center, Tokyo, 19
77.97 pages”.

On the other hand, for example, when the wavelength is 100 people and the substrate is Si, the penetration distance l of the synchrotron radiation is β#100 people because the linear absorption coefficient is about 100 μm −′, and l>dε. Therefore, in such a case, when calculating the number of photoelectrons generated from the substrate 6, as a first approximation, as shown in FIG. Just consider the number of atoms N1. N1 is the atomic density of the substrate n[
/Cm 3 ] is given by the following equation.

N1=S-dε・n/sinθ [pieces]... (l) The number of photoelectrons generated N2 is the incident photon intensity of 1 [photon/(sec・cm")) and the photoionization cross section of σ (cm"). )
is given by the following equation.

N2=I-Nl・σ [pieces/second] (2) That is, (from formula 11,121, when the oblique incidence angle θ becomes small, the number of photoelectrons generated is proportional to l / sin θ For a detailed analysis that takes into account the reflection of synchrotron radiation on the substrate surface and the angular dependence of the direction of photoelectron generation, please refer to the reference [Kobayashi, Record of the 5th Lecture on Accelerator Science and Technology]. , 1984, 250 True (M, Kob
ayashi, Proceedings of the
5th Symposium on Accelera
tor 5science and Technology
, (1984) p. 250) J.

Furthermore, for soft X-rays and vacuum ultraviolet light used as excitation sources in this device, the real part n of the complex refractive index of the substrate is slightly smaller than 1, so the vertical reflectance is extremely low. , as the oblique incidence angle θ is decreased, total reflection will occur at a certain critical angle. On the other hand, for visible light and ultraviolet light, n is generally larger than 1, and although there is some degree of vertical reflectance, total reflection does not occur even if the oblique incidence angle θ is made small. Therefore, in this device, as the oblique incidence angle θ is decreased, the number of photoelectrons from the substrate increases and the reflected light from the substrate also increases, which excites gas molecules in the gas phase, resulting in It is thought that the deposition rate is increasing.

In FIG. 3, the dotted line S6 is a straight line proportional to 1/Stnθ. When the gas pressure in the reaction chamber 5 is high, that is, in the case of characteristic curve S5, when the oblique incidence angle θ is approximately 45 degrees or less, the deposition rate closely matches the straight line l / sin θ, and the reaction is caused by photoelectrons generated from the substrate. This suggests that progress is being made. On the other hand, when the gas pressure is low, that is, in the case of characteristic curve S4, the deposition rate does not increase much even if the oblique incidence angle θ becomes small. By the way, under the conditions of the characteristic curve S4, analysis of the slope of the edge of the deposited silicon nitride film pattern proves that the reaction mechanism is dominated by the substrate surface excitation reaction rather than the gas phase reaction. This can be seen, for example, in the reference "Kuragi and Urisu, 18th Niss Niss DM (1986) A-7-6LN
, 727 pages (H, Kyuragi and T, Uri
su.

18th SSDM (1986) 8-7-6LN, p
, 727) J.

Considering the results of both S4 and S35, when the gas pressure is high, the gas phase excitation reaction becomes dominant, and therefore it is easily influenced by photoelectrons from the substrate and reflected light from the substrate. On the other hand, when the gas pressure is low, it can be interpreted that the substrate surface excitation reaction is the main reaction and is not affected much by photoelectrons or reflected light.

From the above results, in the method of depositing a thin film by irradiating soft X-rays or vacuum ultraviolet light onto a substrate 6 placed in a reaction chamber 5 filled with a reaction gas, it is especially noticeable when the pressure of the reaction gas is high. By decreasing the oblique incidence angle θ, which is the angle between the irradiation light and the substrate 6, it is possible to increase the deposition rate and increase the thin film deposition area. Also,
Even when the pressure of the reaction gas is low, the product of the deposition rate and the thin film deposition area can be increased by reducing the oblique incidence angle θ.

Considering this effect under the condition that the thin film deposition area is constant, it means that the cross-sectional area S of the irradiation light can be narrowed. Therefore, even if the emitted light from the electron storage ring 1 is focused by a toroidal mirror installed upstream of the beam line 4 in order to increase the light intensity per unit area and increase the deposition rate, the thin film deposition area is It can be kept constant. In addition, as shown in FIG. 1, the irradiation light is spatially narrowed between the reaction chamber 5 and the beam line 4 to increase the pressure inside the reaction chamber 5 and to increase the pressure between the reaction chamber 5 and the beam line 4. A steep pressure distribution can be provided. If the pressure inside the reaction chamber 5 is high (if
Naturally, the deposition rate increases.

FIG. 5 explains another effect using the dependence of the deposition rate on the angle of incidence. In FIG. 5, θ1 is the incident angle of the irradiation light 17 on the substrate, and 18 is the deposited film. When the substrate has minute irregularities, for example, when there is a line and space pattern, the irradiation light 17 enters the substrate perpendicularly at the tops of the lines and the valleys of the spaces. However, the light is incident on the side wall of the line portion at an incident angle θ1. Therefore, even if there is such a step difference and the aspect ratio is high, the deposition rate on the side wall portion is high, so it is possible to deposit a thin film with good coverage. Although the normal low-pressure CVD method and plasma CVD method have good coverage, in principle, as long as the deposition is from a gas phase reaction, a certain amount of deposited film is required to cover the steps with a high aspect ratio. However, in the case of this device, the substrate surface excitation reaction is the main reaction and the deposition rate on the sidewalls can be increased, so it is possible to cover the steps even with an extremely thin film thickness.

However, in this case, it is necessary to irradiate the substrate surface with soft X-rays or vacuum ultraviolet light, and if the incident angle θ1 becomes too small, total reflection will occur on the substrate surface, reducing the number of photons penetrating into the substrate. , it must be taken into consideration that the number of photoelectrons generated will decrease. for example,
When light of wavelength 93.4 is incident on the St substrate, θ1
Since total reflection will occur at <5.1 degrees, the inclination α (=90″-θ1) of the convex portion formed on the substrate must be 84.9 degrees or less.Of course, this value depends on the substrate material and It depends on the wavelength of the irradiation.In Fig. 1, an effective wavelength can be selected by installing a spectroscopic element on the optical axis. What is necessary is just to provide it on the optical axis between it and the chamber 5. Moreover, the toroidal mirror 3 may be replaced with a spectroscopic element that also serves as a light condenser.

〔Effect of the invention〕

As explained above, the present invention irradiates soft X-rays or vacuum ultraviolet light onto a substrate to be processed installed in a reaction chamber into which source gas is introduced, and when depositing a thin film on the substrate, the irradiation light and the substrate are By adjusting the angle formed by the tilting means,
Since the product of the thin film deposition area and the deposition rate can be increased, there is an effect that the thin film can be deposited uniformly and at a high throughput.

In addition, the thin film formation area is fixed and the irradiation light can be focused, or a differential exhaust section can be installed between the reaction chamber and the beam line to increase the pressure inside the reaction chamber, so further increases in deposition rate can be expected. effective.

Furthermore, if applied to the case of depositing a thin film on a substrate with unevenness, it is possible to form a thin film with excellent coverage with an extremely thin film even on steps with a high aspect ratio.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of a thin film forming apparatus according to the present invention, Fig. 2 is a graph showing the dose dependence of the deposited film thickness, and Fig. 3 is a graph showing the dependence of the deposition rate on the incident angle. , FIG. 4 is an explanatory diagram for explaining the mechanism of photoelectron emission from the substrate, FIG. 5 is an explanatory diagram showing the case where the present invention is applied to a substrate with unevenness, and FIGS. FIG. 1 is a configuration diagram showing a thin film forming apparatus. l...electron storage ring, 2...mirror chamber, 3...
Toroidal mirror, 4... Light propagation path (beam line)
, 5... reaction chamber, 6... substrate, 7 is a heating heater,
8゜15...Exhaust port, 9...Material gas nozzle, 12
... Substrate holder, 16... Synchrotron radiation introduction boat.

Claims (4)

[Claims] (1) A reaction chamber in which a substrate for depositing a thin film is installed, a gas introduction means for introducing a raw material gas into the reaction chamber, and an irradiation means for irradiating the reaction chamber with soft X-rays or vacuum ultraviolet light as irradiation light. a tilting means for tilting the substrate at an arbitrary angle with respect to the irradiation light, and a beam line for creating a steep pressure difference between the reaction chamber and the beam line guiding the irradiation light. and a differential pumping section in which a beam passing section of the connecting section to the reaction chamber is narrowed to reduce the pumping conductance, and a focusing means for focusing the irradiation light is installed in the middle of the beam line. A thin film forming device featuring: (2) The thin film forming apparatus according to claim 1, wherein the irradiation means is an electron storage device. (3) The tilting means adjusts the angle of oblique incidence between the irradiation light and the substrate by 5
The thin film forming apparatus according to claim 1, characterized in that the temperature is 0 degrees or less. (4) The thin film forming apparatus according to claim 1, wherein the beam line is provided with a spectroscopic element for selecting the wavelength of the irradiated light.