JPH09106947A - Thin film growth method - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: By synchrotron radiation excited reaction using semiconductor gas,
To provide a thin film growth method for selectively growing a thin film directly only on a radiant light irradiation portion. To solve the above problem, a semiconductor substrate placed in a vacuum is cooled to a temperature equal to or lower than a freezing point of a material gas composed of constituent elements of a thin film to be deposited, and the material gas is introduced to the substrate. After forming the adsorption layer of the molecular solid, the gas was exhausted, and then the photochemical reaction was caused by irradiating the molecular solid layer with synchrotron radiation. Then, the substrate was returned to room temperature and the synchrotron was added. This can be solved by using a thin film growth method in which a substrate having a thin film grown only on the radiant light irradiation portion is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a thin film on a semiconductor substrate, and in particular, it selectively grows a thin film directly on a radiant light irradiation portion by a radiant light excited reaction using a semiconductor gas. The present invention relates to a thin film growth method.

[0002]

2. Description of the Related Art X-ray lithography is known as an application of synchrotron radiation to a semiconductor process.
In this case, usually, a substrate surface coated with a resist material is irradiated with X-rays through an X-ray mask, the resist is exposed to light to obtain a predetermined pattern, and the resist pattern is used as a mask. With the LSI process,
A step of performing film formation or etching on a portion without a resist and finally removing the resist is performed. However, in this method, the resolution of the pattern is limited due to the multi-step process and the large amount of secondary electrons generated inside the resist.

On the other hand, it is known that when a substrate is irradiated with radiant light while a reaction gas is introduced into a vacuum chamber, etching and thin film growth occur due to a photochemical reaction.
A problem of such thin film deposition by a direct reaction process that does not use a resist is that ions and radicals generated by photolysis of gas also fly to and be adsorbed on the non-irradiated portion. Of course, the growth rate of the irradiated part is significantly higher than that of the non-irradiated part, but the selection ratio of the growth between the irradiated part and the non-irradiated part is not infinite. Therefore, as a method of causing only the irradiated part to grow. Was unsuitable.

On the other hand, it is possible to grow only in the irradiated portion by a so-called synchrotron radiation excited atomic layer growth method, in which the step of exposing the substrate to gas and then exhausting it and the step of irradiating X-rays in a vacuum are alternately repeated. It has been known. However, in this case, since the molecules excited by X-rays are limited to the chemisorption layer of one atomic layer or less existing on the substrate surface,
The reaction efficiency is extremely low, and therefore, it takes a long time to deposit a thick film.

[0005]

The problem to be solved in order to carry out the vacuum integrated process by the photochemical reaction using X-rays is to solve the problem of how to grow the film with high reaction efficiency and only in the light irradiation part. The question is whether it can be done. Furthermore, in order to actually perform patterning, it is necessary to adopt a method that allows the X-ray mask used in X-ray lithography to be applied as it is.

The object of the present invention is to solve the problems of the prior art described above, and to selectively form a thin film only on the radiant light irradiation portion by a radiant light excited reaction using a semiconductor gas. It is to provide a thin film growth method capable of growing.

[0007]

The above object can be solved by the following method. That is,
A semiconductor substrate placed in a vacuum is cooled to a temperature below the freezing point of the material gas consisting of the constituent elements of the thin film to be deposited, and the material gas is introduced to form a molecular solid adsorption layer on the substrate. After evacuating the gas, and then causing a photochemical reaction by irradiating the molecular solid layer with synchrotron radiation, the substrate is returned to room temperature,
A thin film growth method for producing a substrate in which a thin film is grown only on the synchrotron radiation irradiation part, or
A semiconductor substrate placed in a vacuum is cooled to a low temperature, a material gas consisting of the constituent elements of the thin film to be deposited is introduced, and a sufficient thickness that is in adsorption-desorption equilibrium with the gas phase gas on the substrate surface. A liquid layer is formed, and then a photochemical reaction is caused by irradiating the liquid layer with synchrotron radiation, and then the substrate is returned to room temperature to grow a thin film only on the synchrotron radiation irradiation portion. The problem can be solved by using a thin film growth method for producing a different substrate.

The operation and effect of the method of the present invention will be described below in brief. Whatever the material gas is, with varying degrees of temperature, it becomes liquid at low temperatures and solid at further cooling. A similar phenomenon is observed when the temperature of the substrate placed under the material gas atmosphere in the chamber is lowered. At this time, first, the gas becomes a liquid state and is adsorbed in multiple layers on the substrate. At equilibrium, the liquid layer thickness is a function of gas pressure and substrate temperature,
If the gas pressure is low and the temperature is low, a liquid layer having a sufficient thickness can be formed on the substrate. When the temperature is further lowered, the liquid layer changes into a solid layer in which molecules are oriented.

If the molecular weight of the material gas used is sufficiently large so that a condensed solid in which multiple layers of gas are adsorbed on the surface of the substrate can be easily realized without much cooling, the story is simple and the solid layer After forming the gas, the gas may be exhausted and then X-ray irradiation may be performed in a vacuum. As a result, a photochemical reaction occurs, and the condensed solid layer in the irradiation section is changed into a chemically bonded thin film. In this case, after preparing a solid layer having a predetermined thickness, setting an X-ray mask on the substrate and irradiating,
Film growth and patterning can be done simultaneously.

Although it is difficult to realize a condensed solid layer because of its low freezing point, for a material gas that can be realized in a liquid layer state, a predetermined thickness is obtained by adsorption-desorption equilibrium with the gas phase. The liquid adsorption layer is formed beforehand, and X-ray irradiation is performed in the presence of gas. At this time, in the irradiation section, as in the case of the condensed solid, the decomposition and recombination of molecules occur, and the liquid layer changes into a thin film. At this time, photoactive decomposition of the gas produces reactive ions and radicals, and the non-irradiated area is also covered with the liquid layer, so the active reactive species are adsorbed on the liquid. If the layer is thick enough, the adsorbate is lost in the vacuum when the substrate is returned to room temperature and the liquid in the non-irradiated area evaporates. Therefore, the effect of the photochemical reaction actually works only in the irradiation part.

When a molecule condensed on the surface of a substrate is irradiated with X-rays, light is first absorbed by the constituent atoms, and photoelectrons, Auger electrons, secondary electrons, etc. are emitted along with it. Excitation of atoms by various light absorptions or excitation by the above-mentioned emitted electrons breaks the chemical bonds constituting the molecule. Since the ions and radicals that are cut and released to the interstitial sites have dangling bonds, they recombine with each other to form a solid network in which molecules are connected to each other, although it is extremely incomplete. The penetration depth of X-rays into the solid varies depending on the substance, but as a rough guide, it is 1μ for light with a wavelength of 10Å.
It is about 0.1 μm for light with a wavelength of about 100 m. Within such a depth that light can enter, the intramolecular bonds are broken and recombined at once over the entire film, so that the condensed layer is directly converted into a thin film. That is, the reaction efficiency is remarkably higher than that in the case where the layers are grown one by one by the surface reaction. In addition, since the layer in which the material gas is condensed is basically regarded as an inorganic material, the emission of secondary electrons is much smaller than that in the case of irradiating the resist with X-rays, and as a result, the pattern is blurred. Remarkably suppressed.
Further, since the photochemical reaction inside the condensed solid is used, it is also advantageous that the X-ray mask used in X-ray lithography can be used as it is.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the constitution of the method of the present invention will be specifically described with reference to embodiments of the invention.

[0013]

First Embodiment An example of the first embodiment will be described with reference to FIG. First, the semiconductor substrate 1 stored in a vacuum chamber is cooled to a low temperature. Next, a material gas is introduced into the chamber and the substrate is exposed to the material gas to form the condensed solid layer 2 on the surface of the substrate (b). Since the thickness of the solid layer can be monitored by ellipsometry or the like, when the solid layer having a predetermined thickness is obtained, the solid layer is evacuated. Here, after aligning the X-ray mask 3 with the substrate 1, radiant light is irradiated from the vertical direction to cause a reaction (c). When the mask 3 is removed after sufficient irradiation, as shown in (d), the thinned region 4 made of the constituent material is formed only in the irradiated portion. When this substrate is returned to room temperature, the solid condensed in the non-irradiated part evaporates, leaving a thin film only in the irradiated part.
(e). Often, this film is amorphous,
When this thin film can be a crystal, the crystallized thin film 5 can be obtained by heating this substrate (f).

[0014]

Embodiment 2 of the Invention An example of the second embodiment will be described with reference to FIG. First, the semiconductor substrate 1 stored in a vacuum chamber is cooled to a low temperature. Next, a material gas is introduced into the chamber and the substrate is exposed to the material gas to form the condensed solid layer 2 on the surface of the substrate (b). Since the thickness of the liquid layer can be monitored by ellipsometry or the like, when the liquid layer having a predetermined thickness is obtained, the X-ray mask 3 is placed on the substrate 1.
After aligning with, the radiant light is irradiated from the vertical direction to cause the reaction (c). When the mask 3 is removed after sufficient irradiation, as shown in (d), the liquid layer in the irradiated portion is changed into a thin film region of the constituent substance by a photochemical reaction.
Furthermore, a deposition layer 5 made of a product formed by ionizing the gas during irradiation is formed thereon. A small amount of the deposit 6 may be formed on the liquid layer in the non-irradiated portion, although the amount is small. When this substrate is returned to room temperature, the liquid condensed in the non-irradiated part evaporates with the deposits on it, leaving a thin film only in the irradiated part (e). In many cases, this thin film is amorphous, but when this thin film can be crystalline, the crystallized thin film 7 can be obtained by heating this substrate.

[0015]

As described above, by using the method of growing a thin film on a semiconductor substrate as the method of the present invention, the problems of the prior art can be solved and radiation using semiconductor gas can be achieved. It has been possible to provide a thin film growth method in which a thin film is directly grown only on a radiant light irradiation portion by a photoexcitation reaction.

[Brief description of the drawings]

FIG. 1 is a process diagram showing the procedure of the thin film growth method described in the first embodiment of the invention.

FIG. 2 is a process drawing showing a procedure of the thin film growth method described in the second embodiment of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Condensed solid (liquid) body layer, 3 ... X-ray mask, 4 ... Thin film region, 5 ... Crystallized thin film, 6 ... Deposition layer (irradiation part), 7 ... Deposition layer (non-irradiation part) ), 8 ... Crystallized thin film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/28 H01L 21/26 Z

Claims (2)

[Claims] 1. A semiconductor substrate placed in a vacuum is cooled to a temperature below a freezing point of a material gas consisting of constituent elements of a thin film to be deposited, and the above material gas is introduced to introduce a molecular solid on the substrate. After forming the adsorption layer, the gas is exhausted, and then the molecular solid layer is irradiated with synchrotron radiation to cause a photochemical reaction, and then the substrate is returned to room temperature and irradiated with the synchrotron radiation. A method for growing a thin film, which comprises producing a substrate in which a thin film is grown only on a portion. 2. A semiconductor substrate placed in a vacuum is cooled to a low temperature, a material gas consisting of constituent elements of a thin film to be deposited is introduced, and a vapor phase gas and adsorption-desorption equilibrium are provided on the substrate surface. After forming a liquid layer having a sufficient thickness and then inducing a photochemical reaction by irradiating the liquid layer with synchrotron radiation, the substrate is returned to room temperature and only the synchrotron radiation irradiation part is formed. A method for growing a thin film, which comprises producing a substrate on which a thin film is grown.