JPH09309793A - Production of epitaxial wafer and single crystal substrate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit an epitaxial wafer from being broken or chipped, which is prepared by vapor-phase growth of an epitaxial layer on a single crystal substrate having a crystalline structure of sphalerite type. SOLUTION: After an epitaxial layer is grown in the vapor phase on a single crystal substrate that has a crystalline structure of sphalerite type and the surface deviating from the face 100} by 1-16 deg. in an arbitrary direction with an outer diameter of D where an orientation flat satisfying the length L>D×0.18 is not formed, the main orientation flat is formed. In this single crystal substrate, the epitaxial layer is grown in the vapor phase on a single crystal substrate that has a crystalline structure of sphalerite type and the surface deviating from the face 100} by 1-16 deg. in an arbitrary direction with an outer diameter of D in which an orientation flat satisfying the length L>D×0.18 is not formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epitaxial wafer which can be suitably used for a light emitting diode (LED) and the like and a single crystal substrate used for the epitaxial wafer.

[0002]

2. Description of the Related Art In recent years, compound semiconductors have been widely used as optical semiconductor device materials. As this semiconductor material, a material obtained by epitaxially growing a desired semiconductor crystal layer on a single crystal substrate is used. This is because currently available crystals used as a substrate have many defects and low purity, so that it is difficult to use them as they are as light emitting elements. Therefore, a layer having a composition for obtaining a desired emission wavelength is epitaxially grown on the substrate.
A ternary mixed crystal layer is mainly used as the epitaxial growth layer. And for epitaxial growth,
Vapor or liquid phase growth methods are used. In the vapor phase growth method, a graphite or quartz holder is placed in a quartz reactor, and epitaxial growth is performed by flowing a raw material gas and heating. Epitaxial wafers for LEDs generally have zinc-zinc structure II
I-V group compound semiconductors have been put into practical use, and they have a cleavage property and are easily cracked. Normally, in the case of GaP substrate, [0
The (100) plane has an angle (off-angle) deviated by several degrees in the (-1-1) direction, preferably 3 to 10 °. Ga
In the case of P, the substrate thickness is about 300 μm and the diameter is about 45 to 55.
It is common to use a circular substrate of mm. This Ga
An epitaxial wafer with a GaAsP epitaxial layer grown on a substrate such as P is a light emitting diode (LED)
It is processed for use. In order to finally use LED,
The processed epitaxial wafer is separated into elements by dicing. Dicing is to directly cut the epitaxial wafer with a rotary blade. In the case of a cleavable epitaxial wafer, it is necessary to match the dicing direction with the crystal orientation of the epitaxial wafer, that is, the cleavable direction when cleavable. If they are not matched, LED chips may be chipped after dicing, resulting in defective products. Usually, when a single crystal ingot for manufacturing a substrate is manufactured, the orientation of the crystal is determined by X-rays or the like, and then the surface of the cylindrical ingot is ground parallel to the cleavage direction of the crystal, and then the substrate is cut out. A single crystal substrate having a main orientation flat formed by removing a part of a circular substrate parallel to the cleavage direction in an arcuate shape is used, and an epitaxial layer is vapor-phase grown thereon. This makes it possible to accurately and easily determine the cleavable direction in the subsequent steps. The length of the main orientation flat is generally 10 to 22 mm in order to determine such a direction precisely and easily. Normally, the cleavage direction is aligned with the main orientation flat surface, so the dicing direction is determined by this main orientation flat.

Incidentally, the epitaxial wafer is naturally provided with a main orientation flat after the growth, (10
0) If a substrate having a plane orientation of a plane system has a main orientation flat in the cleavage direction, it also changes in a direction substantially perpendicular to the main orientation, although it changes depending on the off-angle direction and the angle. Further, in the past, many LED processing steps were manually performed and epitaxial wafers were handled carefully, but in recent years, automation of all processing steps has been promoted to reduce the cost of LEDs. Became. In order to be able to handle epitaxial wafers with automated processing equipment, the substrate has a fixed shape with a main orientation flat,
It is important to know the cleavage direction accurately. Furthermore, apart from the main orientation flat,
A smaller orientation flat is provided in an arbitrary direction that is not parallel to the main orientation flat to distinguish the front and back of the substrate, and such a length L is 18% or less of the outer diameter D of the substrate. An orientation flat that is only long is called a sub-orientation flat.

[0004]

A wafer that has been epitaxially grown is often cracked or chipped during temperature increase or decrease or during processing for removing the outer periphery of the wafer. If it breaks during the process, it will increase the cost. Furthermore, there is a demand for an epitaxial wafer that is even more resistant to breakage during LED processing.

[0005]

Therefore, as a result of intensive studies to solve the above problems, the present inventor has noticed that the above-mentioned cracks and chips of the epitaxial wafer often occur near the main orientation flat. It was presumed that stress was likely to be concentrated in the main orientation flat where the main orientation flat had a cleavability in the direction perpendicular thereto, and that the epitaxial wafer was easily broken from the main orientation flat. When vapor phase growth of the epitaxial layer was performed using a single crystal substrate without a main orientation flat, the occurrence of cracks and chips could be significantly reduced, and the epitaxial wafer with a zinc-zinc structure had cleavability. From the above, they have found that the main orientation flat can be easily formed after the epitaxial growth, and arrived at the present invention. That is, the gist of the present invention is to have a zinc blende type crystal structure,
A single crystal substrate having an outer diameter D, whose surface is displaced from the {100} plane by 1 to 16 ° in an arbitrary direction, and has a length L of L>
A method for producing an epitaxial wafer, which comprises vapor-depositing an epitaxial layer on a single crystal substrate on which a main orientation flat satisfying D × 0.18 is not formed, and then forming the main orientation flat. , And a sphalerite type crystal structure, the surface of which is a plane deviated from the {100} plane by 1 to 16 ° in an arbitrary direction, and has a diameter L of L > D ×
A single orientation substrate for an epitaxial wafer is characterized in that a main orientation flat satisfying 0.18 is not formed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The single crystal substrate of the present invention has a zinc blende type crystal structure. If the surface of the single crystal substrate has a surface orientation of too low order, when an epitaxial layer is grown thereon,
Since the growth rate becomes low, when it is desired to obtain a plane having a low-order plane orientation such as (100), the plane intentionally deviated from the (100) plane by several degrees is used as the surface. The difference between the angle of the low-order surface and the actual surface is called an off-angle, and in the present invention, the surface is 1 to 1 in any direction from the {100} plane.
A surface deviated by 16 °, that is, a single crystal substrate having an off angle of 1 to 16 ° is used. The off-angle is 5 to 11 ° when the single crystal substrate is gallium phosphide (GaP), and is 1 to 7 ° when the single crystal substrate is gallium arsenide (GaAs). It is preferable because it is possible. The off-angle direction is basically arbitrary, but in order to grow an epitaxial layer with better crystallinity on the substrate, the surface of the single crystal substrate is preferably one of the following planes. The effect of preventing cracking and chipping of the present invention is greater when a good epitaxial layer is grown. From the (100) plane, [001], [010], [00-
1] or a plane deviated by 1 to 16 ° in the [0-10] direction [011] or [0-1-1] from the (100) plane
A plane deviated by 1 to 16 ° from the (100) plane to [01-1] or [0-11]
A plane deviated by 1 to 16 ° in the direction or a plane crystallographically equivalent to the above planes. Of these, in the case of, the off-angle is preferably 6 to 12 °, and in the case of, the off-angle is preferably 4 to 12 ° in terms of crystallinity.

In the case of sphalerite type crystals, (10
The planes crystallographically equivalent to the (0) plane are (100), (01
0), (001), (-100), (0-10), (0
There are six types of planes, 0-1), and these are collectively referred to as {100} planes. Further, the planes crystallographically equivalent to the above planes 1 to 16 are from the planes crystallographically equivalent to the (100) plane.
The surface is deviated, and the direction of the deviation may be a direction that preserves the relative positional relationship between each of the above-mentioned directions (1) to (100). Specifically, for example, (010)
Regarding the planes, from the (010) plane to [100], [001], [-10
0] or a plane deviated by 1 to 16 ° in the [00-1] direction [101] or [-10-1] from the (010) plane
A plane deviated by 1 to 16 ° from the (010) plane to [-101] or [10-1]
The planes deviated by 1 to 16 ° in the direction are crystallographically equivalent to the above planes. According to the present invention, such a single crystal substrate is not formed with a main orientation flat having a length L satisfying L> D × 0.18, and more preferably any orientation flat satisfying L> D × 0.14. Is also not formed.

At the outer peripheral edge of the epitaxial wafer, the growth rate is already high, the crystallographic plane orientation changes at the outer peripheral edge, and generally there is processing damage at the outer peripheral edge of the wafer. In addition, the source gas directly enters between the substrate and the holder, and the epitaxial layer is polycrystallized due to the growth of the epitaxial layer on the back surface side at the end of the single crystal substrate. Then, since the epitaxial layer becomes thicker in the outer peripheral portion, the internal stress becomes particularly large, and polycrystallization occurs in a crack shape at the edge of the epitaxial wafer. When the main orientation flat is formed in advance, the main orientation flat has a cleavage property in the direction perpendicular to it, and since the linear end shape tends to concentrate internal stress, it is easy for cracks to be introduced. Is likely to become thick and become polycrystalline.

In order to make the epitaxial wafer less likely to break during growth, it is best not to give the orientation flat to the single crystal substrate. However, in the present invention, in order to facilitate the use in an automated device during the LED processing step of the epitaxial wafer, the outer diameter of the single crystal substrate, that is, even in the case of a circular shape, an elliptical shape or an incomplete circular shape lacking a part of the circular shape Also in the case where the maximum outer diameter is D,
Length L is L ≦ D × 0.18, preferably L ≦ D × 0.1
A sub-orientation flat that satisfies 4 may be provided as a mark in the cleavage direction. The sub-orientation flat is originally for identifying the front and back of the substrate, and it is difficult to accurately determine the cleavage direction because the length is too short, but it is sufficient as a guide. For that purpose, L is preferably large to some extent or more, and D × 0.07 or more is preferable. However, for example, when two or more sub-orientation flats are used for the purpose of discriminating between the front and back of the substrate, the length L of one sub-orientation flat is
It does not need to be so large, D × 0.05 ≦ L ≦ D
It is preferably about × 0.12. As an example, G on a GaP substrate
It will be described in the manufacture of an epitaxial wafer on which an aAsP epitaxial layer is grown. GaP substrate diameter is about 50m
m. After the epitaxial growth is performed using a substrate having no main orientation flat or a sub-orientation flat of 9 mm or less, preferably 7 mm or less, the main orientation flat is formed.

The main orientation flat does not necessarily have to be parallel to the cleavage and can be formed in any direction as needed by a method such as grinding using a beveling machine. However, it is preferable to utilize the cleavage because it is easy to use. . In particular, on the surface of the GaAsP epitaxial wafer, two striped patterns overlapping with crosses due to unevenness parallel to the <110> direction called cross hatch, which can be sufficiently identified by the naked eye, appear, and the cleavage plane is parallel or perpendicular to this striped pattern. So
In accordance with this, the main orientation flat can be easily formed by cleavage manually. In GaAsP, there is a difference in the stripe pattern between the [011] direction and the [01-1] direction,
For example, in a substrate deviated by 6 ° in the [0-1-1] direction on the (100) plane, a striped pattern parallel to the [01-1] direction always appears stronger. As a result, by cleaving on the (0-11) plane or the (0-1-1) plane, the direction of the main orientation flat can be surely formed in the cleavage direction.

On the gas upstream side of the epitaxial wafer, there is a very thick portion of the epitaxial layer, usually called a crown. Since the crown also causes cracks during the LED processing process, the crown can be removed by subjecting the crown portion to main orientation flat processing. If the direction of the substrate is determined beforehand and epitaxial growth is performed, the crown can be easily removed by cleavage.

The method for manufacturing the epitaxial substrate or the epitaxial wafer used in the present invention is not particularly limited, and various thermal decomposition methods, halogen transport methods, MOCVD, MBE methods and the like can be mentioned, but they are generally popular. Therefore, it is preferable to use the halogen transport method with good productivity. Needless to say, the epitaxial wafer has the same off-angle after the epitaxial growth. In this specification, the off-angle direction is a line of intersection of the normal line of the (100) plane, the plane including the normal line of the actual surface, and the actual surface, which is (100 ) The direction from the surface normal to the actual surface normal. If the main orientation flat is an epitaxial substrate or an epitaxial wafer having a zinc-zinc structure, it represents the plane orientation of the substrate and the epitaxial wafer in a direction perpendicular to the plane, and is usually a cleavage plane of the (110) plane system. Often shows parallel planes.

[0013]

【Example】

 (Example 1) GaP substrate and high-purity gallium (Ga)
Epitaxial rear with quartz boat for Ga storage
Each of them was installed at a predetermined place in the doctor. GaP group
The plate contains 3 to 10 x 10 sulfur (S)¹⁷Atom / cm^ThreeAddition
It is a circle with a diameter of 50 mm and has a sub-orientation
Is parallel to the plane cleaved by the (011) plane and has a length of about 3 mm.
A plane that is 6 degrees away from the (100) plane in the [001] direction
The GaP substrate with the (100) plane is deviated by 6 ° in the [011] direction.
GaP substrate with a plane deviated by 6 ° in the [01-1] direction from the (100) plane
A GaP substrate having These were placed on the holder at the same time. E
Ruder rotated 3 revolutions per minute. Next, nitrogen (N_Two) The gas
Introduced into the reactor for 15 minutes to sufficiently remove air.
Later, high-purity hydrogen (H_Two) 9 per minute
Introduce 600cc, N_TwoFlow is stopped and the temperature rise process begins
Was. The above-mentioned Ga-containing quartz boat installation portion and GaP single crystal
The temperature of the board installation part is 800 ℃ and 930 ℃, respectively.
After confirming that it is held constant at
630 ± 10 nm long GaAs_1-xP _xEpitaxial
The vapor phase growth of the film was started. First, hydrogen to a concentration of 50 ppm
Diethyl tellurium ((C
_TwoH_Five)_TwoTe) is introduced at a rate of 15 cc / min, and Periodic Table II
Generates 369 cc / min of GaCl as a group I element component
High purity hydrogen chloride gas (HCl) is added to the quartz
369cc per minute is blown into the Ga reservoir in the container, and the Ga reservoir top table
It was blown out from the surface. On the other hand, as a group V element component of the periodic table
And H_TwoHydrogen phosphide diluted to 10% concentration with_Three)
Introducing 910 cc / min for 20 minutes
A GaP layer as a layer was grown on a GaP single crystal substrate.
Next, (C_TwoH_Five)_TwoTe, HCl, PH_ThreeOf each gas
H without changing the introduction amount_TwoDiluted to 10% with
Hydrogen arsenide (AsH_Three) Introduction amount from 0 cc per minute
Gradually increase to 431cc, and at the same time, increase the temperature of the GaP substrate.
Gradually lower the temperature from 930 ℃ to 870 ℃ for 90 minutes
Second GaAs _1-xP_xEpitaxial layer
Were grown on the first Gap epitaxial layer. next
For 30 minutes, (C_TwoH_Five)_TwoTe, HCl, PH_Three, A
sH_ThreeWithout changing the introduction amount, that is, each minute
Hold at 15cc, 369cc, 910cc, 431cc
While the third GaAs_1-xP_xEpitaxial layer
2 GaAs_{1- x}P_xGrown on the epitaxial layer
Was. For the last 50 minutes (C_TwoH_Five)_TwoTe, HCl, P
H_Three, AsH_ThreeWhile introducing without changing the amount of
For adding nitrogen iso-electronic trap
High-purity ammonia gas (NH 3)_Three)
Addition of 4th GaAs_1-xP_xEpitaxial layer
Third GaAs_1-xP_xGrown on an epitaxial layer
Then, the vapor phase growth was completed. Epitaxial film first, first
The film thickness of each of the second, third and fourth epitaxial layers is 5
μm, 40 μm, 16 μm, 26 μm, fourth epitaxy
The mixed crystal ratio x of the Charl layer is 0.67, and the n-type carrier
Concentration is 0.7 × 10¹⁶cm^-3Met.

The cleavage direction was determined by observing the cross-hatch pattern on the surface of the epitaxial layer by observing with a naked eye without using a microscope, and was formed by cleavage. Although it was difficult to determine the cleavage direction with the sub-orientation flat alone,
This made it easy to form. Further, epitaxial growth was repeated to examine the occurrence of cracks. There was almost no difference between all the substrates, and there was no single crack in 25 substrates. Next, using ZnAs ₂ as a diffusion source, an epitaxial wafer not coated with Zn, which is a p-type impurity, was encapsulated in a quartz ampoule, diffused at a temperature of 760 ° C., and a pn junction was formed at a depth of 4 μm from the surface. Was formed.
Subsequently, an LED process such as electrode formation by vacuum vapor deposition was performed to prepare a 300 μm square mesa-type LED chip, and the emission output, wavelength, and electrical characteristics were measured for all LEDs. The emission wavelength was 631 ± 3 nm and did not change due to the difference in off angle. There was no difference in electrical characteristics.

Example 2 Using a GaP substrate having no sub-orientation flat on the GaP substrate, the same as in Example 1 except that the occurrence of cracks was examined. None of the 25 substrates had cracks. (Comparative Example) A GaP substrate having a circular shape with a diameter of 50 mm and a main orientation flat having a length of 16 mm in parallel with the plane cleaved by the (01-1) plane were used. Everything else was the same as in Example 1. 25 cracks occur on the substrate
2 out of 25, 2 out of 25 on board, 3 out of 25 on board
It was a sheet.

[0016]

According to the present invention, a single crystal substrate having a surface having a specific off-angle and not having a main orientation flat is used, and an epitaxial layer is vapor-phase grown on the single crystal substrate. By forming a main orientation flat later, the cracking and chipping of the epitaxial wafer can be significantly suppressed. The main orientation flat can be easily formed by observing and cleaving the cross-hatch pattern with the naked eye without using an advanced technique. The epitaxial wafer thus grown is not easily cracked, and since the number of cracks in the LED processing step is extremely small, the epitaxial wafer can be easily processed later. Therefore, the yield of the LED processing step can be improved.

Claims (16)

[Claims] 1. A single crystal substrate having an outer diameter D, which has a zinc blende type crystal structure and whose surface is displaced from the {100} plane by 1 to 16 ° in an arbitrary direction, and has a length of L is L> D ×
A method for producing an epitaxial wafer, comprising forming an epitaxial layer on a single crystal substrate on which a main orientation flat satisfying 0.18 is not formed, and then forming the main orientation flat. 2. The surface of the single crystal substrate is [001], [010], [00-
1] or a plane deviated by 1 to 16 ° in the [0-10] direction [011] or [0-1-1] from the (100) plane
A plane deviated by 1 to 16 ° from the (100) plane to [01-1] or [0-11]
The method according to claim 1, which is a plane deviated by 1 to 16 ° in the direction or a plane crystallographically equivalent to the above planes. 3. The surface of the single crystal substrate is [001], [010], [00-1] or [0] from the (100) plane.
3. The method according to claim 2, which is a plane deviated by 6 to 12 ° in the −10] direction or a plane crystallographically equivalent thereto. 4. The method according to claim 1, wherein the single crystal substrate is a substrate on which a sub-orientation flat satisfying L ≦ D × 0.18 is formed. 5. The single crystal substrate is formed from the {100} plane by 5
Gallium phosphide (Ga) with a surface offset by ~ 12 °
The method of claims 1 to 4 which is a P) substrate. 6. The single crystal substrate is 1 from the {100} plane.
Gallium arsenide (GaAs) with a surface offset by ~ 7 °
A method according to claims 1 to 4 which is a substrate. 7. The method according to claim 1, wherein the epitaxial layer is gallium arsenide phosphide (GaAsP). 8. The method according to claim 1, wherein the vapor phase growth method of the epitaxial layer is a hydride transport method. 9. The method according to claim 1, wherein the main orientation flat is provided parallel or perpendicular to the crosshatch pattern on the surface of the epitaxial layer. 10. The method according to claim 1, wherein the main orientation flat is formed by cleavage. 11. A single crystal substrate having an outer diameter D, which has a zincblende type crystal structure and whose surface is displaced from the {100} plane by 1 to 16 ° in an arbitrary direction, and has a length of L is L> D ×
A single crystal substrate for an epitaxial wafer, in which a main orientation flat satisfying 0.18 is not formed. 12. The surface is [001], [010], [00-] from the (100) plane.
1] or a plane deviated by 1 to 16 ° in the [0-10] direction [011] or [0-1-1] from the (100) plane
A plane deviated by 1 to 16 ° from the (100) plane to [01-1] or [0-11]
The single-crystal substrate according to claim 11, which is a plane deviated by 1 to 16 ° in the direction or a plane crystallographically equivalent to the above planes. 13. The surface is (100) to [001],
The single crystal substrate according to claim 12, which is a plane deviated by 6 to 12 ° in the [010], [00-1] or [0-10] direction or a plane crystallographically equivalent thereto. 14. The single crystal substrate according to claim 11, wherein a sub-orientation flat satisfying L ≦ D × 0.18 is formed. 15. A method comprising gallium phosphide (GaP),
The single crystal substrate according to any one of claims 11 to 14, which has a surface displaced by 5 to 12 ° in any of the directions. 16. A method comprising gallium arsenide (GaAs),
15. The single crystal substrate according to claim 11, which has a surface displaced by 1 to 7 degrees in any of the directions.