JPH07165499A - Gaas single crystal wafer and its production and method for sorting the same - Google Patents

Abstract

PURPOSE:To provide a method for producing a GaAs single crystal wafer so designed that only wafer having such crystal surface as to easily remove a Ga oxide therefrom is sorted to ensure a thermal cleaning to be carried out stably and easily and enable high-quality epitaxial layer to be grown. CONSTITUTION:The photoelectron spectrum on the surface of a GaAs single crystal wafer is determined by X-ray photoelectron spectroscopy; The conditions for the determination are as follows: AlKalpha-rays are used as X-ray source; the angle of incidence of X-rays with the surface of a test sample is 20 deg.; and, the angle of an analyzer input lens with the surface of the test sample is 75 deg.. Such a GaAs single crystal wafer as to satisfy the following two conditions is sorted; namely: (Ga-O bond peak height)/(Ga-As bond peak height) <=0.05, and (As-As bond peal height)/(As-Ga bond peak height) >=0.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GaAs single crystal wafer, a manufacturing method thereof, and a sorting method.

[0002]

2. Description of the Related Art Compound semiconductors are used in the manufacture of Schottky gate field effect transistors (MESFETs), high mobility transistors (HEMTs), heterojunction bipolar transistors (HBTs), light emitting and receiving devices and the like. These devices are manufactured by epitaxially growing an active layer on the mirror-finished wafer surface by the molecular beam epitaxial growth (MBE) method and the metal organic vapor layer epitaxial growth (MOVPE) method.

Generally, a mirror-finished wafer is produced by the following procedure. Slice the ingot and cut the wafer. This wafer is rough-polished to improve its flatness, and then mirror finished by mechanochemical polishing. Next, degreasing cleaning, cleaning with a cleaning liquid having an extremely slight etching action, and ultrapure water cleaning are performed. Finally, the wafer is dried by an IPA (isopropyl alcohol) drying method or a spin drying method.

For epitaxial growth, this wafer may be used as it is, but in many cases, as a pretreatment before the epitaxial growth, a sulfuric acid type etchant (H ₂ SO ₄ —H ₂ 0 ₂ —H ₂ O) or an ammonia type is used. A wafer whose wafer surface is etched by 1 to 2 μm with an etchant (NH ₄ OH—H ₂ O ₂ —H ₂ O) is used. After etching, heat treatment (thermal cleaning) in the epitaxial growth furnace to sublimate the native oxide on the wafer surface.
Evaporate and clean the surface.

Although not generally used, there is also a method of removing the oxide layer by thermal cleaning in a furnace after forming a thick oxide layer on the surface by forced oxidation by thermal oxidation or ultraviolet irradiation ozone treatment. .

[0006]

However, the above-mentioned prior art has the following drawbacks.

(1) Since it is necessary to perform etching and forced oxidation in addition to thermal cleaning before the epitaxial growth, the economic burden before the epitaxial growth is large.

(2) An oxide layer made of As oxide and Ga oxide is formed on the surface of the GaAs wafer pretreated by etching or forced oxidation. Among these, the As oxide can be removed relatively easily, but the Ga oxide has a high sublimation temperature, so that the temperature and time of thermal cleaning are not stable and are difficult to remove.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art by selecting a wafer having a crystal surface from which Ga oxide can be easily removed, and to perform thermal cleaning in a stable and easy manner. It is an object of the present invention to provide a novel GaAs crystal wafer capable of growing an epitaxial layer, a manufacturing method thereof, and a selection method.

[0010]

[Means for Solving the Problems]

Condition A: (Ga-O bond peak height) / (Ga-As bond peak height) ≦ 0.06 in Ga3d spectrum (As-As bond peak height) / (As-Ga bond) in As3d spectrum Peak height of ≧ 0.47 Condition B: (Ga—O bond peak height) / (Ga—As bond peak height) ≦ 0.05 in Ga3d spectrum (As—As bond peak) Height) / (peak height of As—Ga bond) ≧ 0.5, the photoelectron spectrum of the GaAs single crystal wafer of the first invention satisfies the condition A.

The GaAs single crystal wafer of the second invention is the first
The condition B is satisfied instead of the condition A of the invention.

In the method for producing a GaAs single crystal wafer of the third invention, a semi-insulating GaAs wafer is immersed in a mixed aqueous solution of citric acid or acetic acid and sulfuric acid or hydrofluoric acid, and the spectrum of X-ray photoelectron spectroscopy is conditioned. The surface treatment is performed so as to satisfy A.

The method for producing a GaAs single crystal wafer according to the fourth aspect of the present invention satisfies condition B instead of condition A of the third invention.

In the method for producing a GaAs single crystal wafer of the fifth invention, the composition ratio of the mixed aqueous solution of the third invention and the fourth invention is
_{5% C 6 H 8 O 7} : 49% HF: H 2 O = 1~3: 50
.About.100: 1 to 50.

In the method for producing a GaAs single crystal wafer according to the sixth aspect of the invention, the composition ratio is changed to 5% C instead of the composition ratio of the fifth aspect.
_{H 3 CO 2 H: 49%} HF: H 2 O = 1~3: 50~1
It is set to 00: 1 to 50.

In the method of manufacturing a GaAs single crystal wafer according to the seventh aspect of the invention, the composition ratio is changed to 5% C instead of the composition ratio of the fifth aspect.
_{6 H 8 O 7: 98%} H 2 SO 4: H 2 O = 1~3: 10
It is set to 0: 1 to 5.

In the method for producing a GaAs single crystal wafer according to the eighth aspect of the invention, the composition ratio is changed to 5% C instead of the composition ratio of the fifth aspect.
_{H 3 CO 2 H: 98%} H 2 SO 4: H 2 O = 1~3: 1
It is set to 00: 1 to 5.

In the method for selecting a GaAs single crystal wafer according to the ninth aspect of the invention, the photoelectron spectrum of the GaAs single crystal wafer is measured by X-ray photoelectron spectroscopy, and the measurement conditions are AlKα for the X-ray source and X-rays for the sample surface. Incident angle of 20
, And the photoelectron spectrum obtained when the angle of the analyzer input lens with respect to the sample surface is 75 ° is for selecting a GaAs single crystal wafer that satisfies the condition A.

The method for selecting a GaAs single crystal wafer according to the tenth aspect of the invention is such that the condition B is satisfied instead of the condition A of the ninth aspect.

[0020]

In the present invention, the GaAs single crystal wafer whose photoelectron spectrum is to be measured is a mirror-finished wafer which is pretreated before epitaxial growth.

Among various methods for analyzing the structure of the crystal surface, especially X-ray photoelectron spectroscopy (X-ray Photoelectron spectroscopy)
The reason for measuring the photoelectron spectrum on the surface of a GaAs single crystal wafer by n spectroscopy (XPS) is that it is possible to measure the binding energy of the inner-shell electrons localized in the atoms of the material constituent by using X-rays as the excitation source. This is because the bonding state of elements can be investigated by utilizing this.

The peak height of the Ga—O bond relative to the peak height of the Ga—As bond in the Ga3d spectrum is defined as condition A.
Alternatively, the condition B is adopted because Ga oxide has a high sublimation temperature and is difficult to be removed, and therefore, if it is higher than the condition value, it is difficult to completely remove it.

The As-As bond peak height relative to the As-Ga bond peak height in the As3d spectrum is defined as condition A or condition B because the As3d spectrum As-As bond peak indicates the presence of the As layer. This means that the As layer needs to have a certain thickness in order to prevent the GaAs crystal under the As layer from being oxidized.
This is because the thickness that prevents oxidation cannot be obtained.

However, 0.05 <(Ga-O bond peak height) / (Ga-As bond peak height) ≤ 0.06 0.47 ≤ (As-As bond peak height) / (As-Ga bond peak) Since a wafer having a height of <0.5 has unstable characteristics, it is preferable to satisfy the condition B.

In order to manufacture a GaAs single crystal wafer satisfying such conditions, the semi-insulating GaAs wafer is immersed in various mixed aqueous solutions obtained by combining predetermined solvents and surface-treated. To meet the above conditions. The combination of electrolytes gives good results especially when a mixed aqueous solution of citric acid or acetic acid and sulfuric acid or hydrofluoric acid is used.

If a wafer satisfying the above conditions is selected in advance from the GaAs single crystal wafer whose photoelectron spectrum is measured before epitaxial growth, the selected GaA
The s single crystal wafer does not need to be subjected to etching treatment before epitaxial growth, and thermal cleaning before epitaxial growth can be performed stably and easily.
High quality epitaxial layer can be grown.

[0027]

【Example】

<Example 1> As a sample, a non-doped semi-insulating GaAs crystal wafer manufactured by the LEC method was used. This crystal wafer was used as an anode, Pt as a cathode, and a saturated calomel electrode as a reference electrode. The electrolyte is HCl, H ₂ SO ₄ , H ₂ O ₂ , HF,
Using various mixed aqueous solutions obtained by combining NaOH and mixed aqueous solutions obtained by further combining the various mixed aqueous solutions with citric acid (C ₆ H ₈ O ₇ ) or acetic acid (CH ₃ CO ₂ H), the anode potential with respect to the reference electrode was adjusted. Electrolysis was performed in the range of 0 to 5V.

By adjusting the composition of the electrolytic solution and the anode potential, the XPS spectrum becomes Ga-d in Ga3d.
The ratio of the peak height of the As bond to the peak height of the Ga—O bond is 1: (0 to 0.2), and the ratio of the peak height of the As—Ga bond to the peak height of the As—As bond in As3d is 1 :. 100 wafers of (0-1) were prepared.

Here, the XPS spectrum measurement condition is X
The source is AlKα, and the incident angle of X-ray on the sample surface is 20
The angle of the analyzer input lens with respect to the sample surface was 75 °.

The above wafer was put into an MBE apparatus and epitaxially grown by the process described below. First, thermal cleaning was performed at a substrate temperature of 600 ° C. while irradiating As molecular beams. High-energy electron diffraction (RHEED) observation after the substrate temperature reaches 600 ° C shows the atomic arrangement in which the outermost surface of the substrate becomes the most stable state (2
X4) The time until the pattern appeared was taken as the thermal cleaning time. After that, the temperature is lowered to 520 ° C., undoped GaAs is 0.8 μm, and Si-doped GaAs is 0.2 μm.
μm grown.

The measurement results of the thermal cleaning time with respect to the epitaxial surface characteristics are shown in FIGS. In the plots in the figure, those with a good epitaxial surface are shown as white circles, and those with a surface abnormality such as haze are shown as triangles. (Ga-O bond peak height) / (Ga-A
s bond peak height) ≦ 0.05, and (As-As bond peak height) / (As-Ga bond peak height) ≧ 0.
The wafer No. 5 had a short thermal cleaning time of about 1/10 within 1 minute as compared with the other wafers, and the time was stable. Moreover, the mirror surface state of the epitaxial layer was also good.

Therefore, by adjusting the electrolytic solution composition and the anodic potential during electrolysis of the wafer so as to satisfy the above values, electrolysis is performed, the thermal cleaning time is short and stable, and the wafer is obtained with a good mirror surface condition of the epitaxial layer. .

As the electrolytic solution, among the above-mentioned solvent combinations, good results were obtained when a mixed aqueous solution of citric acid or acetic acid and sulfuric acid or hydrofluoric acid was used. The composition ratio of is as follows.

5% C ₆ H ₈ O ₇ : 49% HF: H ₂ O
= 1~3: 50~100: 1~50 5% CH 3 CO 2 H: 49% HF: H 2 O = 1~3:
_{50~100: 1~50 5% C 6 H} 8 O 7: 98% H 2 SO 4: H 2 O = 1~
3: 100: 1~5 5% CH 3 CO 2 H: 98% H 2 SO 4: H 2 O = 1
~ 3: 100: 1 ~ 5 When using these electrolytes, GaAs is used as the electrolyte.
It is sufficient to immerse the single crystal wafer for a predetermined time to etch the surface, and it is possible to perform the treatment in a shorter time by applying an anode potential of 5 V or less using the above electrode.

If a GaAs single crystal wafer satisfying the above values under the XPS spectrum measurement conditions is selected in advance before the epitaxial growth, the selected GaA
The s single crystal wafer does not need to be subjected to etching treatment before epitaxial growth, and thermal cleaning before epitaxial growth can be performed stably and easily.
High quality epitaxial layer can be grown.

Example 2 Cr-doped semi-insulating Ga
When the same experiment as in Example 1 was performed on the As single crystal wafer, the Si-doped n-type GaAs single crystal wafer, and the Zn-doped p-type GaAs single crystal wafer, the same results as in Example 1 were obtained. It was

[0037]

【The invention's effect】

(1) According to the GaAs single crystal wafers of the first and second aspects, thermal cleaning can be stably performed in a short time, so that the epitaxial growth time by the MBE process can be significantly shortened. Further, since the thermal cleaning can be performed almost completely, a high quality epitaxial layer can be stably grown thereafter, and the yield can be increased.

(2) According to the method for producing a GaAs single crystal wafer according to any one of claims 3 to 8, a simple method of adjusting the composition of the electrolytic solution to perform electrolysis allows the Ga peak to be calculated from the height of the bond peak.
Wafers with less oxide can be manufactured.

(3) According to the method for selecting a GaAs single crystal wafer according to claims 9 and 10, since a wafer containing a small amount of Ga oxide is selected in advance from the bond peak height, it is necessary to perform an etching treatment before epitaxial growth. There is no such thing, and the economical effect is large by omitting the process.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between (Ga—O bond peak height) / (Ga—As bond peak height) and thermal cleaning time.

FIG. 2 (As-As binding peak height) / (As-Ga
FIG. 5 is a characteristic diagram showing the relationship between the thermal cleaning time and the binding peak height).

Claims (10)

[Claims] 1. A GaAs single crystal wafer having a photoelectron spectrum satisfying the following two conditions. In Ga3d spectrum (Ga-O bond peak height) / (Ga-As bond peak height) ≤ 0.06 In As3d spectrum (As-As bond peak height) / (As-Ga bond peak height) Sa) ≧ 0.47 2. A GaAs single crystal wafer having a photoelectron spectrum satisfying the following two conditions. In Ga3d spectrum (Ga-O bond peak height) / (Ga-As bond peak height) ≤0.05 In As3d spectrum (As-As bond peak height) / (As-Ga bond peak height) Sa) ≧ 0.5 3. A semi-insulating GaAs wafer is immersed in a mixed aqueous solution of citric acid or acetic acid and sulfuric acid or hydrofluoric acid,
A method for producing a GaAs single crystal wafer, which is characterized in that surface treatment is performed so that the spectrum of X-ray photoelectron spectroscopy satisfies the following two conditions. In Ga3d spectrum (Ga-O bond peak height) / (Ga-As bond peak height) ≤ 0.06 In As3d spectrum (As-As bond peak height) / (As-Ga bond peak height) Sa) ≧ 0.47 4. A semi-insulating GaAs wafer is immersed in a mixed aqueous solution of citric acid or acetic acid and sulfuric acid or hydrofluoric acid,
A method for producing a GaAs single crystal wafer, which is characterized in that surface treatment is performed so that the spectrum of X-ray photoelectron spectroscopy satisfies the following two conditions. In Ga3d spectrum (Ga-O bond peak height) / (Ga-As bond peak height) ≤0.05 In As3d spectrum (As-As bond peak height) / (As-Ga bond peak height) Sa) ≧ 0.5 5. The composition ratio of the mixed aqueous solution is 5% C ₆ H ₈ O ₇ : 49% HF: H ₂ O = 1 to 3:50.
The method of manufacturing a GaAs single crystal wafer according to claim 3 or 4, wherein: 100: 1 to 50. 6. The composition ratio of the mixed aqueous solution is 5% CH ₃ CO ₂ H: 49% HF: H ₂ O = 1 to 3: 5.
It is 0-100: 1-50, The manufacturing method of the GaAs single crystal wafer of Claim 3 or 4. 7. The composition ratio of the mixed aqueous solution is 5% C ₆ H ₈ O ₇ : 98% H ₂ SO ₄ : H ₂ O = 1 to
The method for producing a GaAs single crystal wafer according to claim 3 or 4, wherein the ratio is 3: 100: 1-5. 8. The composition ratio of the mixed aqueous solution is 5% CH ₃ CO ₂ H: 98% H ₂ SO ₄ : H ₂ O = 1 to
The method for producing a GaAs single crystal wafer according to claim 3 or 4, wherein the ratio is 3: 100: 1-5. 9. A GaAs single crystal wafer is subjected to X-ray photoelectron spectroscopy under the measurement conditions of AlKα as an X-ray source, an incident angle of X-rays with respect to the sample surface of 20 °, and an angle of an analyzer input lens with respect to the sample surface of 75 °. A method for selecting a GaAs crystal wafer, characterized in that a GaAs single crystal wafer satisfying the following two conditions is selected based on a photoelectron spectrum obtained by measurement. In Ga3d spectrum (Ga-O bond peak height) / (Ga-As bond peak height) ≤ 0.06 In As3d spectrum (As-As bond peak height) / (As-Ga bond peak height) Sa) ≧ 0.47 10. The X-ray source is AlKα, and X is for the sample surface.
Under the measurement condition that the incident angle of the line is 20 ° and the angle of the analyzer input lens with respect to the sample surface is 75 °, GaAs
The photoelectron spectrum obtained when a single crystal wafer is measured by X-ray photoelectron spectroscopy is GaAs that satisfies the following two conditions.
A method for selecting a GaAs crystal wafer, which comprises selecting a single crystal wafer. In Ga3d spectrum (Ga-O bond peak height) / (Ga-As bond peak height) ≤0.05 In As3d spectrum (As-As bond peak height) / (As-Ga bond peak height) Sa) ≧ 0.5