JPH05294795A - Production of zinc oxide single crystal thin film - Google Patents

Abstract

PURPOSE:To obtain a ZnO thin film having high purity, excellent crystallinity and large area on a Si substrate by forming the ZnO thin film further on the surface of the Si single crystal substrate on which a SiC thin film is formed. CONSTITUTION:The Si (111) substrate 14 is provided in an apparatus 1 and is heated at 1350 deg.C while allowing a raw material gas (e.g. C3H8) to flow. And beta-SiC thin film is formed on the substrate 14. Or using the ion-polating method or the like, beta-SiC thin film is formed on the Si substrate 14. Next, in the same apparatus, by providing ZnO powder 15 adjacent to the substrate 14 and heating e.g. at 1000 deg.C, the ZnO singlecrystal thin film having a smooth surface is formed on the SiC thin film. Thus, the lattice mismatching of ZnO and SiC is small, ZnO is easily oriented in c axis and the ZnO singlecrystal thin film having high purity and excellent crystallinity is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a zinc oxide single crystal thin film. More specifically, silicon carbide (SiC)
The present invention relates to a method for producing a zinc oxide single crystal thin film on a substrate.

[0002]

2. Description of the Related Art Zinc oxide (ZnO) has a wurtzite structure (crystal symmetry 6 mm) and has a band gap of 3.1.
It is one of the II-VI group compound semiconductors of eV (room temperature). In addition, zinc oxide (ZnO) powder and metallic zinc raw material are inexpensive and abundant, and are stable and safe substances. Therefore, since zinc oxide (ZnO) has a large electromechanical coupling coefficient, a piezoelectric transducer, a surface wave TV-IF filter, a low frequency tuning fork type filter, etc., which utilize the characteristics thereof, are commercially available, and niobate Lithium (L
Active research and development is being carried out toward practical application to functional thin film guides for optical ICs together with iNbO ₃ ) and lithium tantalate (LiTaO ₃ ).

Further, the translucency of this material and aluminum (A
l), lithium (Li), hydrogen (H), etc. are used to reduce the resistance, and therefore, they are promising as a new transparent conductive thin film to replace ITO (Indium Tin Oxide). A zinc oxide (ZnO) thin film can be easily formed on a glass or metal substrate with C-axis orientation and uniform polarity. However, by making the most of the material characteristics of ZnO, the device can be operated more efficiently, and the optical IC
When used as a functional waveguide for a single crystal, a single crystal thin film is required.

[0004]

So far, ZnO thin films have been used for sapphire (Z plane, R plane), quartz (Z plane), MnO.
[(111 plane)], α-ZnS [(110) plane, (11 plane)
It has been reported that heteroepitaxial growth is performed on a (1) plane, (001) plane] single crystal substrate, but it has drawbacks that the substrate itself is very expensive and it is very difficult to form an IC. In addition, it is easy to integrate Z on a single crystal substrate of Si, GaAs, InP, etc., which is relatively inexpensive.
Although there are reports of attempts to grow nO thin films,
The lattice mismatch with ZnO is extremely large (Si: -1
5.4%, GaAs: -18.7%, InP: -21.
However, there is no report that a single crystal thin film has been obtained yet.

[0005]

Thus, according to the present invention, α-silicon carbide or β-silicon carbide can be formed on the surface of a silicon single crystal substrate in the same apparatus without exposing the silicon single crystal substrate to the atmosphere. And a zinc oxide single crystal thin film is formed on the thin film, and a method for producing a zinc oxide single crystal thin film is provided.

In the present invention, a thin film of silicon carbide (SiC) is formed in a desired region on a surface of a silicon single crystal substrate, and subsequently a zinc oxide single crystal thin film is formed, which are exposed to the atmosphere in the same apparatus. Done without. For example SiC
When a thermal carbonization method is used to form a ZnO thin film, a CV
It is possible to combine the D method and the sputtering method and the ion plating method.

In the present invention, as a method for forming a thin film of SiC on a silicon single crystal substrate, a known method such as a CVD method or an ion plating method can be mentioned. The film thickness thereof is 0.2 to 3 μm, preferably 2-3 μm is desirable. When the SiC is formed by the ion plating method, the ion source may be an ECR type, an RF type, or a duoplasmatron type.

As the introduction gas for carbonizing the silicon single crystal thin film, ethylene, propane, acetylene or the like can be mentioned, but any kind of hydrocarbon gas can be used. Furthermore, when depositing a zinc oxide single crystal thin film on β-SiC, β-SiC used at this time is preferably formed by carbonizing the (111) plane of Si.

A known method can be used as a method for forming the zinc oxide single crystal thin film. For example CVD
If the method is used, put zinc oxide in the crucible for heating
By heating to ˜1400 ° C., a zinc oxide single crystal thin film can be formed on the SiC substrate in a thickness of 0.2 to 2 μm. As a method for heating zinc oxide, resistance heating, electron beam heating, Knudsen cell or the like can be used.

[0010]

Function: The lattice mismatch between ZnO and SiC is small (5.4
4%) and ZnO have the property of easily being C-axis oriented, so that a ZnO single crystal thin film having high purity and good crystallinity can be produced.

[0011]

【Example】

Example 1 A Si single crystal surface was once formed with a silicon carbide thin film on the surface with a hydrocarbon gas such as propane (C ₃ H ₈ ), and then zinc vapor and nitrogen (N) were obtained by sublimating zinc oxide (ZnO) as a source gas. The case of the CVD method using a mixed gas of ₂ ) and oxygen (O ₂ ) will be described.

FIG. 1 is a block diagram of a growth apparatus used in an embodiment of the present invention. Water-cooled horizontal double quartz tube 1
A quartz support base 3 on which a graphite sample base 2 is placed is installed, and a high-frequency current is passed through a work coil 4 wound around the outer tube portion of the reaction tube 1 to inductively heat the sample base 2. .. The sample table 2 may be installed horizontally or may be tilted appropriately.
A branch pipe 5 serving as a gas inlet is provided on one side of the reaction pipe 1, and cooling water is supplied to the quartz pipe outside the double quartz pipe 1 through the branch pipes 6 and 7. The other end of the reaction tube 1 is tightly closed by a stainless steel flange 8 and is sealed by a stopper plate 9, a bolt 10, a nut 11 and a rolling 12 which are arranged around the flange. A branch pipe 13 serving as a gas outlet is provided at the center of the flange 8. The following crystal growth was performed using this growth apparatus.

Place the Si (111) substrate 14 on the sample table 2.
To do. Hydrogen (H ₂3.) Gas per minute 3.
0 liter, siliconized silicon surface on Si substrate
Propane (C₃H₈)
Gas is flowed at about 1.0 cc per minute to work coil 4 at high frequency.
The graphite sample stage 2 is heated by passing a wave current, and the Si substrate 14
The temperature of about 1350 ℃, silicon on Si substrate
Form a silicon carbide single crystal thin film on the single crystal surface with a film thickness of 2 μm
To achieve. Next, the supply of propane is cut off, and the Si substrate 14
After lowering the temperature to 300-800 ℃,
Open the valve and flow a mixed gas of nitrogen and oxygen at a rate of 1 to 3 cc per minute.
The amount is introduced from the branch pipe 5. Flow rate of mixed gas of nitrogen and hydrogen
Is introduced from the branch pipe 13 at 0.4 to 0.9 cc per minute,
The ZnO powder placed on the left side of the Si substrate 14 is used as another work.
A high-frequency current is passed through the coil 16 to heat it at 1000 ° C.
By maintaining the above condition for 1 hour, about 2
A μm zinc oxide single crystal thin film can be formed. As a result, X
Oxidation of a flat surface by line diffraction and observation with an electron microscope
A zinc single crystal thin film was obtained on the entire surface of the Si substrate 14. Example 2 By irradiating the surface of a Si single crystal with carbon (C) ions
Then, after forming a silicon carbide thin film on the surface,
In the atmosphere, zinc (Zn) is used as a raw material and evaporated
To form zinc oxide (ZnO).
The plating method will be described.

FIG. 2 is a block diagram of a growth apparatus used in an embodiment of the present invention. Surface washed Si (11
1) The substrate 18 is mounted on the holder 19 and the inside of the vacuum chamber is evacuated to 1.0 × 10 ⁻¹⁰ Torr. The substrate is heated to about 1350 ° C. by the electron beam heater 20. Ethylene gas of 1 to 4 sccm is passed through the gas inlet 22 to the Kauffman type ion source 21, and the acceleration voltage is 100 V.
~ 3kV, Ion current 1μA ~ 2mA, carbon (C)
By irradiating the substrate with ions, a silicon carbide thin film having a film thickness of 2 μm is formed. Then turn off the ion source and turn on S
After the temperature of the i substrate 18 is lowered to 300 to 800 ° C., oxygen gas is supplied from the gas inlet 23 to 1 × 10 ^{−4 to} 5 × 10 ^−4.
Introduced up to Torr, working coil 24 high frequency 1
Apply 3.56 MHz to induce plasma discharge. Then, the emission current of the electron beam heating crucible 25 filled with zinc (Zn) is set to 5 to 50 mA,
The raw material zinc is evaporated. By maintaining the above state for 3 hours, a zinc oxide single crystal thin film of about 0.2 to 2 μm can be formed on the substrate. As a result, the X-ray diffraction and the electron microscope observation revealed that the zinc oxide single crystal thin film having a flat surface was S
It was obtained on the entire surface of the i substrate 18.

[0015]

According to the present invention, it is possible to obtain a large-area ZnO thin film having a high purity and a good crystallinity on a Si substrate, so that an optical IC using a ZnO optical waveguide can be put to practical use. Becomes

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a main part of a growth apparatus of the present invention.

FIG. 2 is a schematic cross-sectional view showing a main part of the growth apparatus of the present invention.

[Explanation of symbols]

 1 Reaction Tube 2 Sample Table 3 Support Table 4 Work Coil 5-7 Branch Tube 8 Flange 13 Branch Tube 14 Si Substrate 15 Crucible 16 Work Coil 17 Branch Tube 18 Si Substrate 19 Substrate Holder 20 Electron Beam Heater 21 Ion Source 22, 23 Gas inlet 24 High frequency work coil 25 Electron beam heating crucible 26 Vacuum tank 27 Vacuum exhaust device 28 Thermocouple 29 Shutter 30 Vacuum gauge

Claims (2)

[Claims] 1. In the same apparatus, a thin film of α-silicon carbide or β-silicon carbide is formed on the surface of a silicon single crystal substrate without exposing the silicon single crystal substrate to the atmosphere, and then on the thin film. A method for producing a zinc oxide single crystal thin film, which comprises forming a zinc oxide single crystal thin film on a substrate. 2. The method for producing a zinc oxide single crystal thin film according to claim 1, wherein the method for forming the β-silicon carbide thin film comprises carbonizing the (111) plane of silicon.