JP2000044391A - Single crystal material and its production and substrate for film formation and electronic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive, large-diameter oxide single crystal substrate easy to work by subjecting at least one of CaCO3, SrCO3 and BaCO3 and Al2O3 to decarbonation treatment followed by baking to afford a feedstock which is then melted and pulled up into a single crystal. SOLUTION: The subject single crystal material consisting of a single crystal body 7 is obtained according to the following procedure: at least one kind of powder selected from CaCO3 powder, SrCO3 powder and BaCO3 powder and Al2O3 powder are mixed with each other so as to effect a composition of the formula (CaaBabSr1-a-b)pAl2qOp+3q (0<=(a+b)<=1; 1/12<=p/q<=3/2), which is then subjected to decarbonation treatment at >=900 deg.C and subsequently baked under heating at >=1,300 deg.C followed by crystallization by a melting method such as Bernoulli method to afford a granular feedstock; the feedstock is then melted under heating into a melt 5, which, in turn, is filled in a crucible 3 with a molybdenum die 4 set up therein, and pulled up using a seed crystal 6. The 2nd objective substrate consists of the above single crystal material. The 3rd objective electronic device is obtained by forming a compound semiconductor on the surface of the above-mentioned substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film-forming substrate for forming a compound semiconductor thin film such as gallium nitride, mercury cadmium tellurium, zinc oxide, aluminum nitride single crystal, etc.
And a single crystal material therefor.

[0002]

2. Description of the Related Art Since it is difficult to prepare a bulk body of a compound semiconductor material, a material formed by epitaxial growth on the surface of a film forming substrate is used.

For example, a gallium nitride thin film single crystal, which is a compound semiconductor material used for a light emitting device or the like, is most commonly formed on a surface of a film forming substrate made of single crystal sapphire. . Alternatively, as another film formation substrate, a single crystal spinel, a single crystal silicon carbide, or a single crystal gallium nitride substrate is also used.

Similarly, as a compound semiconductor material, a mercury-cadmium tellurium thin film single crystal used for a sensor or the like is generally formed on the surface of a single crystal sapphire film forming substrate.

[0005] In general, zinc oxide and aluminum nitride thin film single crystals, which are compound semiconductor materials used as piezoelectric materials and semiconductor materials, use a glass or single crystal sapphire film-forming substrate.

[0006]

Among the substrates on which the gallium nitride single crystal film is formed, a single crystal spinel (MgAl
₂ O ₄ ), single crystal silicon carbide (SiC), single crystal gallium nitride (Ga
N), single crystal zinc oxide (ZnO), single crystal aluminum nitride
(AlN) has a problem that the cost of the substrate is very high, and it is difficult to produce a high-quality crystal substrate, and it is difficult to produce a large-diameter substrate.

In contrast to the above substrates, single crystal sapphire is most commonly used as a substrate for forming a gallium nitride single crystal film, but has a high hardness and is difficult to process.
Since it is easy to chip, it is necessary to carefully process under conditions of low productivity, resulting in poor production efficiency. In addition, since single crystal sapphire has extremely high chemical resistance, advanced technology is required for general chemical polishing, and dangerous phosphoric acid and phosphoric acid-sulfuric acid mixed solution are boiled in corrosion processing performed in the device process. There was a problem that had to be.

Further, single crystal sapphire has a melting point of 20
Since the temperature exceeds 00 ° C., the furnace material becomes expensive, and there is a problem that a large amount of energy is required to raise the temperature to the melting point.

On the other hand, other than the gallium nitride single crystal film, the same problem as described above also occurs in a substrate for forming a mercury cadmium tellurium, zinc oxide, aluminum nitride single crystal thin film or the like.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an oxide single crystal substrate which is inexpensive, has a large diameter, and is easy to process.

[0011]

SUMMARY OF THE INVENTION The present invention relates to (Ca _a Ba _b Sr
_1-ab ) _p Al _2q O _{p + 3q} , 0 ≦ a + b ≦ 1, and 1 / _ab
A single crystal material having a composition satisfying 12 ≦ p / q ≦ 3/2 is characterized.

Further, the present invention provides a process of mixing raw materials having the above composition, decarboxylating at 900 ° C. or more, firing at 1300 ° C. or more, melting the obtained raw material, and pulling up a single crystal. The method is characterized by a method for producing a single crystal material comprising:

Further, the present invention is characterized by a film-forming substrate formed of the above-mentioned single crystal material and having a compound semiconductor film formed on the surface thereof.

Further, the present invention is characterized by an electronic device in which a compound semiconductor film is formed on a surface of a substrate made of the above-mentioned single crystal material.

[0015]

The single crystal material having the above composition is easy to manufacture, for example, it can be pulled at a lower temperature than single crystal sapphire. Therefore, it is possible to cope with a large diameter, and mass production is easy. In addition, the single crystal material can be easily machined or etched, and when used as a film formation substrate, can be easily ground or cut out after film formation.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail.

The film-forming substrate 1 shown in FIG. 1 is a plate-like body made of a single crystal material, which will be described in detail later, and has a surface on which a compound such as gallium nitride, mercury cadmium tellurium, zinc oxide, or aluminum nitride thin film single crystal is formed. This is for epitaxially growing the semiconductor film 2.

After these compound semiconductor films are formed, they are ground or cut out into a predetermined shape.
An electronic device such as a light emitting device, a light receiving device, and a piezoelectric electronic component can be used.

The film forming substrate 1 is made of (Ca _a Ba _b S
r _1-ab ) _p Al _2q O _{p + 3q} , 0 ≦ a + b ≦ 1 and 1 /
It is made of a single crystal material having a composition satisfying 12 ≦ p / q ≦ 3/2.

The single crystal material having the above composition can be easily manufactured, for example, it can be pulled up at a relatively low temperature. Therefore, it is possible to cope with a large diameter, and mass production is easy. In addition, since the single crystal material can be easily machined and etched, grinding and cutting after film formation can be easily performed.

In order to stably produce the single crystal material, p and q are as follows: (1) p = 3, q = 2 (2) p = 12, q = 14 (3) p = 1 , q = 2 (4) p = 1, q
= 4 (5) It is preferable that either p = 1 or q = 12, and particularly the compositions (3) and (4) are the most stable.

The values of a and b are not particularly limited, but are preferably composed of any one of Ca, Ba, and Sr from the viewpoint of production stability. That is, it is preferable that either (1) a = 1, b = 0, (2) a = 0, b = 1, (3) a = b = 0.

Further, preferably, a = 1, b = 0, p = 1, q = 2, that is, a composition represented by CaAl ₄ O ₇ is optimal.

Next, a method for producing the single crystal material will be described.

First, a raw material is mixed with at least one of CaCO ₃ powder, SrCO ₃ powder and BaCO ₃ powder and Al ₂ O ₃ powder so as to have the above composition range, and the raw material is decarbonated at 900 ° C. or more. After performing the treatment and firing at 1300 ° C. or more, the particles are once crystallized by a melting method such as the Bernoulli method to be granular. Using the raw material after this treatment, Czochralski method, E
A single crystal material is manufactured by a melting method such as the FG method and the Bernoulli method.

Specifically, as shown in FIG. 2, a crucible 3 made of molybdenum is provided with a die 4 made of molybdenum, a raw material melt 5 is filled, and a single crystal is pulled up by using a seed crystal 6. The body 7 can be obtained.

At this time, by performing the above-mentioned melting treatment after firing on the raw material, the filling efficiency into the crucible 3 and the melting rate can be increased. Moreover, the raw material subjected to the above treatment can be easily melted in the crucible 3 made of molybdenum or iridium irrespective of powdery or granular form.

As described above, by using the raw material having the composition according to the present invention and performing pulling by the method of the present invention, it is possible to produce with less heating energy than pulling single crystal sapphire. It can be used as a furnace material, and a large single crystal can be easily obtained.

The single crystal material pulled up by the melting method can be processed more easily than single crystal sapphire, and can be polished on a wafer.

When the single-crystal material thus obtained is used to form the film-forming substrate 1 shown in FIG. 1, it is stable at high temperature, in a vacuum and in a reducing atmosphere, and is therefore made of gallium nitride, mercury cadmium telluride, zinc oxide. In addition, an aluminum nitride single crystal film can be favorably grown epitaxially.

Although the substrate for film formation has been described above, the single crystal material of the present invention can be used for various applications such as window materials and structural materials.

[0032]

EXAMPLES Example 1 (Ca _a Ba _b Sr _1-ab ) _p Al _2q O _{p + 3q} , a = 1, b = 0, p =
Calcium carbonate and alumina powders were mixed so that 1, q = 2. Carbon dioxide contained in calcium carbonate is
Calculated as volatilizing during firing. The particle size of the raw material powder is 3 μm for both calcium carbonate and alumina, mixed in a wet mill for 8 hours, and dried by boiling.
It was kept at 0 ° C. for 3 hours, decarbonated, and fired at 1300 ° C.

Regarding the phase change temperature, crystallization of the starting material phase was confirmed at 1100 ° C., and even at 1300 ° C., if the temperature was not maintained for 3 hours or more, a different phase was crystallized and did not become a single phase.

This raw material was filled in a molybdenum crucible and heated and melted at 1800 ° C. in a high-frequency heating furnace in an argon atmosphere. Under the conditions using a molybdenum crucible and an argon atmosphere, no reaction was confirmed between the raw material melt and the crucible. The electric power required for heating to 1800 ° C. in the high-frequency induction heating furnace is 2000 times required for melting sapphire.
An electric power lower by 30% or more than the electric power required for the temperature condition of slightly over ℃ was sufficient.

A seed crystal was brought into contact with the liquid surface of the melt in a molten state heated to 1740 to 1770 ° C., and the temperature was lowered by a Czochralski method at a rate of 2 mm per hour while lowering the temperature. Lifting speed is 0 per hour
Pulling was possible at a speed of about 5 mm, and pulling could be performed at a speed higher than that of a sapphire single crystal.

As a result, a diameter of 52 mm and a length of 120 mm
Was pulled out, a substrate having a thickness of 0.5 mm and a diameter of 50 mm was cut out, and the obtained substrate was mirror-finished by chemical polishing.

The substrate thus obtained was acid-treated with sulfuric acid and used as a substrate for forming a gallium nitride single crystal film. In addition, 4 ~ 5 in sulfuric acid of pH2 at normal temperature
The surface could be easily etched by impregnating for a time.

For the gallium nitride film formation, an organometallic compound vapor deposition method using trimethylgallium is used,
Alternatively, a uniform gallium nitride single crystal film could be obtained via a low-temperature buffer phase of GaN.

Example 2 In the same manner as described above, as a result of using the EFG method, a plate-like single crystal substrate having a width of 50 mm and a length of 150 mm in a predetermined orientation could be produced. Molybdenum was used for the crucible and the die, but no reaction with the melt was observed.

However, regarding the composition ratio of the melt, CaO: Al ₂ O ₃
With a molar ratio of 1/12 to 3/2 and a composition other than pure alumina, a reaction was observed between molybdenum and the melt, and pure crystals could not be drawn.

In the case where iridium is used for the crucible material without using molybdenum, the composition ratio of the melt is
When the molar ratio of CaO: Al ₂ O ₃ was set in the range of 1/12 to 3/2, it was confirmed that crystal growth was possible.

Also, in the case of powder raw materials, (Ca _a Ba _b Sr
_1-ab ) _p Al _2q O Mix the calcium carbonate and alumina powders so that a = 1, p = 1, q = 2 in _{p + 3q} ;
Decarbonation treatment at 00 ° C, powdered material that has been baked at 1300 ° C, once melted and solidified by the Bernoulli method, and when the raw material ground to about 5 mm is used, the filling amount in the crucible is more than twice the powder. In addition, since the melting time was shortened, melting was possible in a short time, and a very useful raw material for crystal pulling of the present invention was produced.

[0043]

According to the present invention, (Ca _a Ba _b Sr _1-ab )
_p Al _2q O _{p + 3q} , 0 ≦ a + b ≦ 1, and 1/12 ≦ p / q
By using a single crystal material having a composition that satisfies ≦ 3/2, it is stable in a high-temperature reducing atmosphere, can be easily machined and etched, and is easy to manufacture. It can handle large diameters.

In addition, when a substrate for film formation is formed using the single crystal material according to the present invention, the substrate itself can be easily formed and processed. Both the cutting process can be easily performed with good yield. As a result, the electronic device of the present invention can be mass-produced at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a film formation substrate of the present invention.

FIG. 2 is a diagram for explaining a method for producing a single crystal material according to the present invention.

[Explanation of symbols]

 1: film formation substrate 2: compound semiconductor film 3: crucible 4: die 5: raw material melt 6: seed crystal 7: single crystal

Claims (5)

[Claims] 1. A composition represented by (Ca _a Ba _b Sr _1-ab ) _p Al _2q O _{p + 3q} and satisfying 0 ≦ a + b ≦ 1 and 1/12 ≦ p / q ≦ 3/2. Single crystal material. 2. A composition represented by (Ca _a Ba _b Sr _1-ab ) _p Al _2q O _{p + 3q} which satisfies 0 ≦ a + b ≦ 1 and 1/12 ≦ p / q ≦ 3/2. Raw materials are mixed and decarbonated at 900 ° C. or higher,
A method for producing a single crystal material, comprising a step of baking at 1300 ° C. or higher, melting the obtained raw material and pulling up a single crystal. 3. A composition represented by (Ca _a Ba _b Sr _1-ab ) _p Al _2q O _{p + 3q} and satisfying 0 ≦ a + b ≦ 1 and 1/12 ≦ p / q ≦ 3/2. A film formation substrate comprising a single crystal material and a compound semiconductor film formed on a surface thereof. 4. The film forming substrate according to claim 3, wherein a = 1, b = 0, p = 1, and q = 2 are satisfied. 5. A composition represented by (Ca _a Ba _b Sr _1-ab ) _p Al _2q O _{p + 3q} and satisfying 0 ≦ a + b ≦ 1 and 1/12 ≦ p / q ≦ 3/2. An electronic device in which a compound semiconductor film is formed on a surface of a substrate made of a single crystal material.