JP2000211998A - Oxidation of silicon and production of single crystal silicon oxide film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce electrons existing in a film or concentration of positive hole trapping center, to improve interfacial characteristics and to attain high integration and speed-up of circuit by bringing silicon supported on a single crystal substrate into contact with oxygen in the presence of atomic hydrogen to form an oxide film. SOLUTION: A single crystal substrate 2 is arranged in an ultrahigh vacuum apparatus 1. Silicon supplied from a silicon evaporation source is deposited on the surface of the single crystal substrate to form the single crystal substrate supporting a silicon film. Atomic hydrogen is supplied from a hydrogen atom source 3 and an oxygen gas from an oxygen feed opening 4 to the apparatus. The silicon film is oxidized at about 300-500 deg.C while exhausting from an exhaust vent 5. The obtained silicon film is annealed at about 800-1,200 deg.C to from a single crystal silicon oxide film. A hydroxyl group is bonded to the surface of silicon once by using both an oxygen gas and atomic hydrogen and is decomposed to form a high-quality silicon oxide film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing silicon oxide, and more particularly, to a novel method for producing a single crystal silicon oxide film.

[0002]

2. Description of the Related Art In recent years, demands for higher integration and higher speed of silicon integrated circuits using MOS transistors have been further increased. For this, it is essential to reduce the thickness of a gate oxide film, and a high quality gate of 5 nm or less is required. A method for obtaining an oxide film is a major issue in this field. Heretofore, a gate oxide film in a MOS transistor has generally been obtained by cleaning a cleaned silicon crystal in a dry oxygen atmosphere for 100 hours.
It was manufactured by heating to 0 to 1200 ° C and oxidizing. However, when the gate oxide film obtained in this manner is made thinner, the gate leakage current increases and the electrical characteristics become unstable. Electron or hole trapping centers also have a significant effect on electrical properties. Many of the problems associated with thinning the gate oxide film are due to the fact that the conventional gate oxide film has not been formed of a single crystal. , A high-performance ultra-fine MOS transistor can be obtained.

[0003]

SUMMARY OF THE INVENTION According to the present invention, the concentration of electron or hole trapping centers existing in a silicon oxide film as a gate oxide film, which has not been realized until now, is greatly increased by single crystallization. The object of the present invention is to achieve high integration, high speed, and high reliability of a silicon integrated circuit by reducing the interface characteristics and improving the interface characteristics.

[0004]

The present inventors have conducted various studies on the formation of a silicon oxide film. As a result, by oxidizing silicon in the presence of hydrogen atoms at a relatively low temperature, That a silicon oxide that easily undergoes a phase transition can be obtained, and that a silicon oxide thin film thus formed on a single crystal substrate is further annealed to cause a phase transition to obtain a high-quality single crystal silicon oxide film And found the present invention based on this finding.

That is, the present invention provides a method for oxidizing silicon, comprising contacting silicon with oxygen in the presence of atomic hydrogen, and oxidizing a silicon film carried on a single crystal substrate in the presence of atomic hydrogen. And forming a silicon oxide film, followed by annealing to form a single crystal, thereby providing a method of manufacturing a single crystal silicon oxide film.

[0006]

Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing an example of an apparatus for performing the method of the present invention, in which a single crystal substrate 2 is arranged at an appropriate position in an ultrahigh vacuum apparatus 1 and silicon supplied from a silicon evaporation source is supplied. A single crystal substrate carrying a silicon film is formed by vapor deposition on the surface. Next, a silicon oxide film is obtained by supplying atomic hydrogen from the hydrogen atom source 3 and supplying oxygen gas from the oxygen supply port 4 and oxidizing the silicon film while exhausting from the exhaust port 5. If the silicon oxide film thus obtained is further annealed,
Single crystallization occurs to form a single crystal silicon oxide film. It is preferable to use silicon as the single crystal substrate in the method of the present invention, but it is also possible to use a metal single crystal having compatibility with silicon. Here, having matching means that the symmetry and the crystal lattice spacing of the silicon single crystal match, or even if they do not match, the difference is within 5%. Such metals include
Nickel and cobalt are mentioned, but nickel is particularly preferable because it is easily compatible with silicon.

When used in the method of the present invention, it is necessary to clean the surface of the single crystal substrate. Next, the silicon wafer heated to 1200 to 1300 ° C. is thermally vapor-deposited on the surface of the cleaned single crystal substrate using the silicon wafer as an evaporation source. An appropriate thickness of this silicon layer is about 10 to 40 °.

[0008] The substrate on which silicon has been deposited in this manner is then brought into contact with oxygen while being irradiated with atomic hydrogen, thereby being completely oxidized. Atomic hydrogen at this time can be produced by a method conventionally used for producing atomic hydrogen, for example, 14
It is formed by a method in which hydrogen gas is brought into contact with tubular or reticulated tungsten heated to 00 to 1500 ° C. The ratio of atomic hydrogen and oxygen gas introduced into the reaction zone is
The volume ratio is selected in the range of 1: 1 to 10: 1. This oxidation is performed by heating the substrate to a temperature in the range of 300 to 500C.

As described above, by using oxygen gas as an oxidizing agent and atomic hydrogen together, a hydroxyl group (OH) is once bonded to the surface of silicon, and this is decomposed to form a high quality silicon oxide film. I do.

[0010] The silicon oxide film thus obtained is then annealed at a temperature in the range of 800 to 1200 ° C to make it a single crystal. This annealing
This is performed in an oxygen atmosphere or a mixed atmosphere of oxygen and hydrogen. Thus, a single-crystal silicon oxide film of 1 to 5 mm is formed on the single-crystal substrate.

In the present invention, the formation of the silicon oxide film is performed as follows.
It can be confirmed by an Auger electron spectrum, and the formation of the single crystal silicon oxide film can be confirmed by low-speed electron diffraction or observation with a scanning tunneling microscope.

[0012]

The single crystal silicon oxide film obtained according to the present invention has a very high quality even though the whole film is formed of a single domain crystal and has a thickness of 5 nm or less. Therefore, it is suitable as a gate oxide film of a MOS transistor constituting a silicon integrated circuit, and can also be used as an element material having other new functions.

[0013]

Next, the present invention will be described in more detail with reference to examples.

Example 1 A chamber equipped with an Auger low-energy electron diffraction spectrometer was kept at 10 ^-9 Torr or less, and cobalt having good lattice matching with quartz was disposed therein as a metal substrate. This metal substrate was prepared from an oriented crystal rod (000
1) It was cut along the surface and polished. The cobalt surface was first bombarded with argon ions and then cleaned by annealing at 800 ° C. in a chamber. Next, the silicon wafer heated to 1250 ° C. was evaporated on the cleaned cobalt surface to deposit about 2 ML of silicon. The silicon-supported cobalt substrate thus obtained was then oxidized in the presence of atomic hydrogen while heating to 350 ° C. At this time, the atomic hydrogen partial pressure was 2 × 10 ⁻⁶ Torr, and the oxygen partial pressure was 2 × 10 ⁻⁷ Torr.
Torr. In the low-speed electron diffraction pattern, the amorphous nature was not recognized in the silicon oxide film formed on the cobalt surface. Next, the silicon oxide film was annealed in an oxygen atmosphere at 1100 ° C. for 2 minutes to grow a single crystal on the cobalt (0001) plane. To obtain this single crystal silicon oxide film, the annealing temperature is set to 11
It is necessary to be 00 ° C. For unknown reasons,
Although the melting point of cobalt is 1494 ° C., at 1100 ° C. or higher, cobalt becomes polycrystalline.

Example 2 A single crystal silicon oxide film was manufactured in the same manner as in Example 1 except that a Ni (111) plane was used as a substrate instead of a cobalt (0001) plane. FIG. 2 is an Auger electron spectrum of a clean surface of the nickel substrate used at this time, and FIG.
4 is an Auger electron spectrum when a silicon film is deposited. As can be seen from these figures, the nickel-derived spectrum appearing at 61 eV by depositing silicon in FIG. 2 is reduced in FIG. 3, and the silicon-derived spectrum appears at 91 eV instead.
Next, FIG. 4 is an Auger electron spectrum of the silicon oxide film when the deposited silicon is completely oxidized while irradiating atomic hydrogen at 350 ° C. in an oxygen atmosphere. As can be seen from this figure, the spectrum of silicon appearing at 91 eV completely disappears, and the Auger electron spectrum of SiO ₂ generated by newly oxidizing silicon at 80 eV appears. At this time, the formation of foreign substances such as nickel silicide and the phenomenon of segregation of nickel on the surface were not observed at all. Thus, a silicon oxide film having a thickness of about 3 nm was obtained. Next, this silicon oxide film is
By performing the heat treatment for 2 minutes, a single crystal silicon oxide film could be manufactured.

Example 3 Using a single crystal silicon (001) plane as a substrate, about 2 ML of silicon was deposited thereon in the same manner as in Example 1. Next, the substrate was oxidized in the presence of atomic hydrogen while heating the substrate to 350 ° C. under the same conditions as in Example 1. When the low-speed electron diffraction pattern of the silicon oxide film on the substrate thus obtained was observed, no amorphousness was observed. Next, this silicon oxide film is
Heating at 2 ° C. for 2 minutes and annealing in an oxygen atmosphere resulted in single crystallization, and an ultra-thin single crystal silicon oxide film was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of an apparatus used in the method of the present invention.

FIG. 2 is an Auger electron spectrum of a clean nickel surface obtained in Example 2.

FIG. 3 is an Auger electron spectrum of a nickel surface on which a silicon film obtained in Example 2 is deposited.

FIG. 4 is an Auger electron spectrum of the silicon oxide film obtained in Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultra high vacuum apparatus 2 Single crystal substrate 3 Hydrogen atom source 4 Oxygen supply port 5 Exhaust port

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masashi Ozeki 1-1-4 Higashi, Tsukuba, Ibaraki Pref. BC01 BC02 BE01 BE04 BF51 BF52 BF53 BF54 BF55 BF57 BF60 BF61 BF62 BF63 BH01 BH02 BH03 BJ01

Claims (6)

[Claims] 1. A method for oxidizing silicon, comprising bringing silicon into contact with oxygen in the presence of atomic hydrogen. 2. The oxidation method according to claim 1, wherein the silicon is a film supported on a single crystal substrate. 3. The oxidation method according to claim 1, wherein the oxidation is carried out at a temperature of 300 to 500 ° C. with oxygen. 4. A single crystal silicon oxide, wherein a silicon film supported on a single crystal substrate is oxidized in the presence of atomic hydrogen to form a silicon oxide film, and then annealed to form a single crystal. Manufacturing method of membrane. 5. The method according to claim 4, wherein the oxidation is carried out at a temperature of 300 to 500 ° C. by contacting with oxygen. 6. The method according to claim 4, wherein the annealing is performed while maintaining the temperature at 800 to 1200 ° C.