JPH07111249A - Manufacture of semiconductor epitaxial wafer - Google Patents

Abstract

PURPOSE:To suppress cracks and flaws of an epitaxial wafer by a method wherein a single crystal semiconductor substrate surface has the face azimuth of a face having an off-angle and raw gas is supplied in the off-angle direction or a direction having an angle within a specific range from the off-angle direction. CONSTITUTION:A single crystal semiconductor substrate surface has the face orientation of a (100) face having an off-angle. The direction in which raw gas for epitaxial growth is supplied is the off-angle direction or a direction having an angle smaller than 30 deg. to the 180 deg.-direction of the off-angle direction. If a semiconductor substrate is set in this direction, the off-angle direction of the substrate is the upstream direction of a gas flow and a facet is produced on the end surface of the epitaxial wafer and the growth on the rear is not produced at an abnormally high speed. Therefore, the growth on the backside of the substrate hardly occurs. As a result, the substrate does not adhere to the holder, so that cracks produced after the epitaxial growth can be reduced substantially.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor epitaxial wafer.

[0002]

2. Description of the Related Art In recent years, compound semiconductors have been widely used as materials for optical semiconductor devices. As the semiconductor material, a material obtained by epitaxially growing a desired layer on a single crystal substrate is used. This is because the crystal used as the substrate has many defects and low purity, and it is difficult to use it as it is as a light emitting element. Then, 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 for this epitaxial growth layer. For the epitaxial growth, a vapor phase growth method or a liquid phase growth method is usually used.

An ordinary vapor phase growth method will be described with reference to FIG. In the vapor phase growth method, a holder made of graphite or quartz is placed in a quartz reactor, and epitaxial growth is performed by a method of flowing a source gas and heating. On a normal holder, it is common to arrange the substrate with a few degrees of inclination with respect to the gas flow.

This will be explained by taking the growth of an epitaxial wafer of a GaP substrate GaAsP as an example. Ga
The orientation flat of the P substrate is (0, -1,
The (100) plane is parallel to the cleavage plane of the 1) plane and has an angle (off-angle) shifted by 6 ° in the [0, -1, -1] direction. Normally, [0,
It is arranged so that the [-1, -1] direction is on the gas upstream side. G
In the case of aP, a substrate thickness of about 300 μm is used.

[0005]

The wafer epitaxially grown by such a method is often cracked or chipped when the temperature is raised or lowered. This is because the source gas directly enters between the substrate and the holder during the growth, and the epitaxial layer grows on the back surface side at the end of the single crystal substrate. That is, during vapor phase growth, 50 to 2
An epitaxial layer of 00 μm grows on the edge of the wafer. This epitaxial layer often reaches the holder surface and bonds the holder surface to the substrate. After the temperature rising process after the epitaxial growth, when the temperature was raised to room temperature, the adhered portion was cracked due to the difference in the thermal expansion coefficient, and the whole wafer was cracked. Furthermore, even if a slight defect remains after the epi growth, some cracks are present in that part.Therefore, if the outer peripheral processing is performed after the epi growth, the wafer is broken at that time, which causes a decrease in yield. There were challenges.

[0006]

Therefore, as a result of intensive studies to solve the above problems, the present inventor has utilized the anisotropy of the growth rate due to the fact that the edges of the substrate have various orientations. As a result, they have found that such problems can be solved, and have reached the present invention. That is, the object of the present invention is that in the epitaxial growth step of the compound semiconductor epitaxial wafer, the epitaxial wafer grows on the back surface of the end portion on the upstream side of the source gas, and the epitaxial layer grows.
The purpose is to suppress the occurrence of cracks or scratches on the epitaxial wafer.
In a method for manufacturing a semiconductor epitaxial wafer in which a single crystal semiconductor epitaxial layer having a zinc-zinc structure type is grown on a single crystal semiconductor substrate having an inclende structure type by a vapor phase method, the surface of the single crystal semiconductor substrate has an off-angle. A method of manufacturing a semiconductor epitaxial wafer, characterized in that it has a (100) plane orientation and a source gas is supplied from the off-angle direction or a direction within 30 ° from the 180 ° direction thereof. To be done. The present invention will be described in more detail below.

The gas phase method used in the present invention is not particularly limited, and various thermal decomposition methods, halogen transport methods, MDCVD methods, MBE methods and the like can be mentioned. It is preferable to use a halogen transport method with good performance. The substrate used in the present invention is not particularly limited as long as it has a zinc-zinc structure type, but from the viewpoint that a material with few surface defects is easily available, gallium arsenide-based or gallium phosphorus-based is preferable. A semiconductor substrate of zinc selenide type or the like can be used.

It is essential that this substrate has a surface orientation of (100) having an off-angle. The off-angle means that if the substrate surface has a plane orientation of too low order, the growth rate will be low,
When it is desired to obtain a plane with a low plane orientation such as (100), the plane intentionally shifted by several degrees from the (100) plane is used as the surface, and the angle is grown between the low plane and the actual surface. The difference between is called off angle. In this specification, the off-angle direction means the normal line of the (100) plane,
It is the line of intersection of the surface including the actual surface normal and the actual surface, and the direction from the normal of the (100) surface on the surface side to the actual surface normal.

The off-angle direction is usually [01
1], [01-1], [0-11], [0-1-1], or [001], [010], [00]
It is often performed by shifting in the −1] and [0-10] directions. The preferred angle of this off-angle varies depending on each direction and the type of the substrate, but the preferred range is Ga.
In the case of a P substrate, [011], [0] for the (100) plane
1-1], [0-11], and [0-1-1] directions are 3 to 10 °, preferably 3 to 7 °, and [00
1], [010], [00-1], and [0-10] directions are 4 to 15 °, preferably 5 to 11 °.
And in the case of GaAs substrate, [0
11], [01-1], [0-11], [0-1-1]
In the direction, it is 1 to 7 °, preferably 1 to 5 °, and [001], [010], [00-1], [0-1
0] direction, 1 to 15 °, preferably 1 to 5 °
Is.

Among these, the effect of the present invention is particularly remarkable when the direction of the off angle is [011] on the GaP substrate.
[0-1-1], the off-angle direction on the GaAs substrate is [001], [010], [00-1],
It is in the [0-10] direction.

The most important feature of the present invention is that the direction in which the source gas is supplied during the epitaxial growth is within 30 ° from the off-angle direction or the 180 ° direction. More preferably, it is within 10 ° from the off-angle direction or the 180 ° direction. The reason for the direction of the raw material supply at this time is not clear, but even if the table on which the substrate is placed is rotated, it is not necessary to consider the deviation of the direction of the raw material supply due to the rotation. . Therefore, as shown in FIG. 1, if the barrel type is used, the upper side of the barrel is in the direction of the raw material supply,
In the case of the flat type as shown in, the direction of the center of the plane is obtained.

When the substrate is set in this direction, the off-angle direction of the substrate becomes upstream of the gas, and facet growth occurs on the end surface of the epi-wafer, which causes the growth of polycrystals to the back surface at an abnormally fast rate. Because no growth occurs,
Growth is unlikely to occur on the back surface side of the substrate, and as a result, adhesion between the substrate and the holder surface does not occur, and the occurrence of cracks after epi growth can be minimized.

[0013]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded.

(Example 1) Sulfur (S) is 2 to 10 × 10
¹⁷ atoms / cm ^{3 was} added, and the crystallographic plane orientation was (10
A GaP-edge crystal substrate deviated by 6 ° from the (0) plane in the [0-1-1] direction and high-purity Ga were placed at predetermined positions in an epitaxial reactor equipped with a Ga storage quartz boat. The GaP substrate was arranged so that the upstream side of the gas in the quartz holder was in the [0-1-1] direction. The holder was rotated 3 times per minute. Next, nitrogen (N ₂ ) gas was introduced into the reactor for 15 minutes to sufficiently replace and remove air, and then high-purity hydrogen (H ₂ ) was introduced as a carrier gas at 9500 cc / min to stop the N ₂ flow and rise. The warm process started. The temperatures of the Ga-containing quartz boat installation portion and the GaP single crystal substrate installation portion are 800 ° C. and 93 ° C., respectively.
After confirming that the temperature was kept constant at 0 ° C., vapor phase growth of a GaAs _1-X P _X (x = 0.9) epitaxial layer having a peak emission wavelength of 590 ± 5 nm was started. First, concentration 50
n-type impurity tellurium (T) diluted with hydrogen gas to ppm
e) a dopant gas of diethyl tellurium ((C
₂ H ₅ ) ₂ Te) was introduced at a rate of 30 cc / min and the periodic table II
GaCl as a group I element component was introduced by blowing high purity hydrogen chloride gas (HCl) into the Ga reservoir in the quartz boat at 380 cc per minute in order to generate 380 cc per minute and blown out from the upper surface of the Ga reservoir. At the same time, while introducing 1190 cc / min of hydrogen phosphide (PH ₃ ) diluted with H ₂ to a concentration of 10% as a Group V element component of the periodic table, the GaP layer as the first layer was changed to a GaP single crystal substrate for 20 minutes. Grown up. Next, the introduction amount of hydrogen arsenide (AsH ₃ ) diluted with H ₂ to a concentration of 10% was changed from 0 cc / min without changing the introduction amount of each gas of (C ₂ H ₅ ) ₂ Te, HCl, and PH _3. The temperature of the GaP substrate is gradually decreased from 910 ° C to 860 ° C by gradually increasing it to 140 cc / min.
A second GaAs _1-X P _X epitaxial layer was grown on the first GaP epitaxial layer for 0 minutes. (C ₂ H ₅ ) ₂ Te, HCl, PH ₃ , AsH for the next 30 minutes
30cc each minute without changing the introduction amount of ₃ ,
A third GaAs _1-X P _X epitaxial layer was grown on the second GaP epitaxial layer while holding at 380 cc, 1190 cc, and 140 cc. Finally 50 minutes (C ₂
H ₅ ) ₂ Te, HCl, PH ₃ and AsH ₃ are introduced without changing the introduction amount thereof, and nitrogen (N) of a nitrogen iso-electronic trap is added to this at 320 min / min.
High purity ammonia gas (NH ₃ ) of cc was added to grow a fourth GaAs _1-X P _X epitaxial layer on the third GaP epitaxial layer, and vapor phase growth was completed. The film thicknesses of the first, second, third and fourth epitaxial layers of the epitaxial film are 5 μm, 39 μm and 15 μm, respectively.
It was 27 μm, and the n-type carrier concentration of the fourth epitaxial layer was 1.2 × 10 ¹⁶ cm ⁻³ .

Next, Zn, which is a p-type impurity, is diffused by using ZnAs ₂ as a diffusion source, and p− is formed at a depth of 6 μm from the surface.
An n-junction was formed. The sheet resistance of this product is 15Ω / cm
^{Was 2} . Subsequently, photolithography, electrode formation by vacuum deposition, etc. were performed to form a prism-shaped light emitting diode of 500 μm × 500 μm × 180 μm (thickness) having a mesa type pn junction having a diameter of 180 μm. Initial brightness value is current 15
It was 5200 ftL at mA with no epoxy coat.
There was no problem in quality. Furthermore, epitaxial growth was repeated. As a result, the number of adhesion cracks was 0 out of 35.
It was a sheet. The thickness of the epitaxial layer on the back surface of the raw material gas upstream side end of the epitaxial wafer is about 60 μm.
There were few scratches on the layer due to adhesion.

(Embodiment 2) In carrying out the present invention, everything was the same as in Embodiment 1 except that [011] of the GaP substrate was placed on the upstream side of the source gas. As a result, the number of adhesion cracks was 0 out of 12. The thickness of the epitaxial layer on the back surface of the end portion on the upstream side of the raw material gas of the epitaxial wafer was about 50 μm, and there were almost no scratches due to adhesion to the layer.

(Comparative Example) In the implementation, all were the same as in Example 1 except that [01-1] of the GaP substrate was arranged on the upstream side of the source gas. As a result, the number of adhesion cracks was 5 out of 24. The thickness of the epitaxial layer on the back surface of the end portion on the upstream side of the raw material gas of the epitaxial wafer was about 150 μm, and all scratches due to adhesion were generated on the layer.

[0018]

According to the present invention, by optimizing the crystal orientation of the wafer and the direction of the gas flow, it is possible to prevent the growth of the epitaxial layer on the back surface of the substrate from being most attached to the holder surface. It goes without saying that exactly the same effect can be obtained by growing a GaAs substrate. The epitaxial wafer thus grown has no cracks or scratches and becomes an epitaxial wafer that can be easily processed later. As a result, the yield of the epitaxial process can be improved and the quality can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a barrel type holder for growing a wafer.

FIG. 2 is an explanatory diagram showing an example of a flat type holder for growing a wafer.

Claims (3)

[Claims] 1. A method for producing a semiconductor epitaxial wafer in which a single crystal semiconductor epitaxial layer having a zinc-free structure type is grown on a single-crystal semiconductor substrate having a zinc-free structure type by a vapor phase method. The substrate surface has a plane orientation of (100) plane with an off angle,
30 ° from the off-angle direction or its 180 ° direction
A method of manufacturing a semiconductor epitaxial wafer, characterized in that the source gas is supplied from within the direction. 2. The direction of the off-angle is [0, -1,
-1] or [0,1,1] to 3 to 10 [deg.], The method for producing a semiconductor epitaxial wafer according to claim 1. 3. The method for producing a semiconductor epitaxial wafer according to claim 1, wherein the single crystal semiconductor substrate is gallium arsenide or gallium phosphide.