JPS6347135B2 - - Google Patents

Abstract

PURPOSE:To obtain the wafer with extremely uniform thickness without lowering luminous efficiency by making the ratio of galluium as a gas for gaseous phase growth and arsenic and phosphorus proper. CONSTITUTION:A gallium phosphide arsenide mixed crystal rate varying layer, a gallium phosphide arsenide mixed crystal rate fixed layer and a gallium phosphide arsenide mixed crystal rate fixed layer containing an isoelectronic trap are formed successively onto a single crystal substrate through a gaseous phase epitaxial growth method, and the gallium phosphide arsenide mixed crystal epitaxial wafer is manufactured. The ratio (Ga)/(As+P) of the component concentration of gallium as the gas for the gaseous phase growth of the mixed crystal rate fixed layer containing the isoelectronic trap to the component concentration of phosphorus and arsenic is made within a range of 1.5-5 at that time, and the ratio (Ga)/(As+P) is made within a range of 0.3-1 when growing other layers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to gallium arsenide phosphide mixed crystal (G _a A _s1-x
P _x , x: mixed crystal ratio) The present invention relates to a method for manufacturing an epitaxial wafer.

More specifically, gallium arsenide phosphide mixed crystal containing isoelectronic traps, that is, gallium phosphide mixed crystal containing an epitaxial layer consisting of G _a A _s1-x P _x (0.55≦x≦1) The present invention relates to a method for manufacturing an epitaxial wafer (hereinafter referred to as "G _a A _s1-x P _x ").

In general, the vapor phase growth method, liquid phase growth method, molecular beam method, and vacuum evaporation method are known as methods for growing epitaxial layers of multi-component mixed crystal compound semiconductors such as G _a A _s1-x P _x . However, in particular, the vapor phase growth method is excellent in mass production of epitaxial wafers, and
Impurities (dopants) for planar structure
It has many advantages, including the ability to mass-produce devices such as light-emitting diodes because it can utilize an integrated circuit IC manufacturing process that involves a thermal diffusion process.

Conventionally, when performing the vapor phase growth method for G _a A _s1-x P _x epitaxial films, a group element, ie, gallium ( G _a ) Excessive atmosphere, i.e., the atomic ratio of the group elements, G _a and the group elements, i.e., phosphorus (P) and arsenic (A _s ), contained in the vapor phase growth gas unit volume, i.e., G The ratio of the concentration of _{the a} component [G _a ] to the sum of the concentrations of the A _s component and the P component, [G _a ]/[A _s +
P] was maintained at a constant value in the range of 1.5-2.

However, although the G _a A _{s1- x} P There was a problem that the coating thickness was extremely non-uniform.

As an example, G _a A _s0.35 for orange light emission (peak emission wavelength 630 nm±10 nm) grown in vapor phase on a G _a P substrate.
The case of a P _0.65 epitaxial wafer will be explained as follows.

FIG. 1 is a vertical cross-sectional model diagram of an example of a wafer obtained by a conventional method.

In FIG. 1, 1 is a single crystal substrate. As for the single crystal substrate, the mixed crystal ratio x according to the method of the present invention is
For G _a A _s1-x P _x epitaxial wafers in the range 0.55≦x≦1, gallium phosphide (G _a P)
A single crystal substrate is most suitable, but substrates made of gallium arsenide ( _{GaAs )} , silicon ( _Si ), germanium ( _Ge ), etc. can also be used.

2 is a mixed crystal ratio change layer. For example, in the case of an orange light emitting diode using a _GaP substrate,
G _a A _s0.35 P _0.65 , that is, a layer in which the mixed crystal ratio x is varied from 1 to 0.65. By providing this layer, the occurrence of dislocations due to mismatch in lattice constants can be minimized.

3 is a constant mixed crystal ratio layer. This layer is appropriately selected depending on the desired emission wavelength. x for orange
= 0.65.

4 is a constant mixed crystal ratio layer containing an isoelectronic trap. Mixed crystal ratio x is 0.55 or more
In the case of G _a A _s1-x P _x , since it is an indirect transition type, nitrogen (N) is usually added as an isoelectronic trap for the purpose of improving luminous efficiency. A pn junction is formed in layer 4.

5 is an arrow indicating the direction of air flow during vapor phase epitaxial growth.

As in the conventional method, [G _a ]/[A _s +P] is set from 1.5 to
2, the film thickness of the portion of the wafer on the upstream side of the gas flow for vapor phase growth becomes abnormally thicker than other portions, as shown in FIG. That is, the thickness of the epitaxial film (the sum of the thicknesses of layers 2, 3, and 4) is 2 to 2.5, with a maximum thickness of 200 to 250 μm on the upstream side when the downstream end is 100 μm.
It was customary for it to be twice as thick. Therefore,
When manufacturing wafers such as light emitting diodes from such wafers, there is a step of making the thickness uniform by polishing,
That is, it was necessary to provide a Debur process.

In order to solve the problems of the conventional method, the present inventors have arrived at the present invention as a result of intensive research. The purpose of the present invention is to provide a manufacturing process for G _a A _s1-x P _x wafers.

The above-mentioned object of the present invention is to provide a gallium arsenide phosphide compound containing a gallium arsenide phosphide mixed crystal layer with a variable crystal concentration, a gallium arsenide phosphide constant layer and an isoelectronic trap on a single crystal substrate. In manufacturing a gallium arsenide phosphide mixed crystal epitaxial wafer in which a constant crystallinity layer is formed in the above order by a vapor phase epitaxial growth method, at least a gallium arsenide phosphide containing the above-mentioned isoelectronic trap is used. When growing a constant gallium mixed crystal layer, the sum of the concentration of gallium component [G _a ] and the concentration of phosphorus and arsenic components contained in the gas for vapor phase growth [A _s +
P] (the above concentration is expressed by the number of atoms of each component contained in a unit volume of gas for vapor phase growth), the ratio [G _a ]/[A _s +P] is maintained in the range of 1.5 to 5,
When growing other layers, the above [G _a ]/[A _s
+P] is maintained in the range of 0.3 to 1 by a method for manufacturing a gallium arsenide phosphide mixed crystal epitaxial wafer.

As mentioned above, _GaP is most suitable as the single crystal substrate used in the method of the present invention, _{but GaAsSi ,}
G _e , saphire, spinel, etc. are also used. The board surface is the (100) plane or 1 to 1 from the (100) plane.
A surface tilted approximately 5 degrees in the <110> direction is suitable. In the method of the present invention, when growing layers other than layer 4) of constant mixed crystal content containing at least isoelectronic traps in Figure 1, [G _a ]/
[A _s +P] is maintained at 0.3 to 1, and when growing the layer with a constant mixed crystal ratio, [G _a ]/[A _s +
P] is maintained between 1.5 and 5, preferably between 1.5 and 3. In order to change the value of [G _a ]/[A _s +P], it is preferable to change the value during the growth of layer 3 in Figure 1 or near the boundary between layers 3 and 4. You can also do this after it has grown more than half of its size. Since a pn junction is formed in layer 4, [G _a ]/
Changing [A _s +P] is not preferable because it may reduce luminous efficiency. Further, it is not preferable to change [G _a ]/[A _s +P] at the initial stage of epitaxial growth of layer 2 because the effects of the present invention cannot be fully exhibited.

By carrying out the method of the present invention, wafers with extremely uniform film thickness (ratio of maximum thickness to minimum thickness of 1.1 to 1.3) can be obtained without reducing luminous efficiency, and have extremely high industrial value. It's large.

Next, the present invention will be explained in more detail based on Examples.

[Example 1] Sulfur (S) is added as an n-type impurity, and n
G _a P with a shape carrier concentration of 2.5×10 ¹⁷ cm ^-3 and a crystallographic plane orientation deviated by 4° from the (100) plane to the <110> direction.
Place the single-crystal substrate at a specified location in a horizontal quartz epitaxial reactor with an inner diameter of 60 mm and a length of 95 cm.
In addition, quartz boats containing high-purity _Ga were installed at other predetermined locations within the reactor.

Next, argon (Ar) gas is introduced into the reactor for 15 minutes to sufficiently replace and remove air, and then high-purity hydrogen (H ₂ ) is introduced every minute as a carrier gas.
After introducing 2000ml, the flow of Ar was stopped and the temperature raising process started.
The temperatures of the G _a quartz boat installation area and the G _s P single crystal substrate installation area are 770℃ and 770℃, respectively.
Confirm that the temperature is maintained at a constant temperature of 870°C, and then remove the G _a A _s1-x P _x epitaxial film for orange (peak emission wavelength = 630 nm ± 10 nm) light emitting diode (however, the Vapor phase growth of a constant mixed crystal ratio layer (G _a A _s1-x P _x mixed crystal ratio X = 0.65) to which nitrogen was added as a layer was started.

For the first 150 minutes from the start of vapor phase growth, the concentration
Hydrogen sulfide (H ₂ S), an n-type impurity diluted to 15 ppm, was introduced at 15 ml per minute, and high-purity hydrogen chloride gas (HCl) was introduced to produce 22 ml per minute of _Ga Cl, a group element component. 22 ml per minute was blown into the center bottom of the _Ga reservoir of the quartz boat and blown out from the upper surface of the _Ga reservoir, and on the other hand, the group element component was concentrated with _H2.
Hydrogen phosphide (PH ₃ ) diluted to 11% at 400ml per minute
Introduced by gradually reducing the amount to 240ml per minute.
Hydrogen arsenide (A _s H ₃ ) diluted to a concentration of 11% with H ₂ on the other hand
G a gradually increases from 0 ml per minute to 160 ml per minute, and X gradually changes from 1 to 0.65 _.
An A _s1-x P _x mixed crystal ratio variable layer (corresponding to layer 2 in FIG. 1) was formed. In this case, [G _a ]/[P+A _s ]
=0.5. For the next 60 minutes, H ₂ , H ₂ S, HCl,
Without changing the amounts of PH ₃ and A _s H ₃ introduced, that is, 2000 ml of H ₂ , 15 ml of H ₂ S, 22 ml of HCl,
While holding PH ₃ at 240ml and A _s H ₃ at 160ml,
A layer (corresponding to layer 3 in FIG. 3) with a constant composition of G _a A _s1-x P _x of 0.65 (constant) was formed. in this case,
[G _a ]/[A _s +P]=0.5.

The final 60 minutes consisted of iso-electronic
Ammonia gas (NH ₃ ) was introduced at 180 ml per minute to add trap (N), and H ₂ , H ₂ S,
Among the introduced amounts of HCl, PH ₃ and A _s H ₃ , only HCl was introduced at a rate of 110 ml per minute, and nitrogen addition G _a A _s1-x
P _x constant mixed crystal content layer (corresponds to layer 4 in Figure 1)
was formed. In this case, [G _a ]/[A _s +P] = 2.5
It is.

Each layer of the obtained epitaxial film (2, 3, 4
As a result of chemical staining and microscopic measurement of G _a A _s1-x at the upstream end of the vapor growth gas flow
P _x mixed crystal ratio change layer is 54 μm thick and does not contain nitrogen
G _a A _s1-x P _x Constant mixed crystal content layer is 21μm thick and nitrogen added
The G _a A _s1-x P _x constant mixed crystal content layer is 32 μm thick and is located at the downstream end of the vapor growth gas flow, and the G _a A _s1-x P _x mixed crystal content variable layer is 51 μm thick and does not contain nitrogen. The G _a A _s1-x P _x constant mixed crystal content layer had a thickness of 19 μm, and the nitrogen-added G _a A _s1-x P _x constant mixed crystal content layer had a thickness of 20 μm.

That is, the thickness of the epitaxial film was 107 μm at the upstream end of the vapor growth gas flow, and 90 μm at the downstream end.

[Example 2] In this example, the same epitaxial reactor as described in Example 1 was used.

From the start of vapor phase growth, for the first 150 minutes, 2000 ml of H ₂ per minute, 18 ml of H ₂ S with a concentration of 15 ppm, and 18 ml of _Ga Cl as a group element component are generated per minute.
18ml HCl per minute, 11% concentration as group element component
PH ₃ was gradually decreased from 409 ml per minute to 245 ml per minute, while A _s H ₃ at a concentration of 11% was gradually increased from 0 ml per minute to 164 ml per minute. The mixture was introduced into a reactor to form a layer with variable crystallinity of G _a A _s1-x P _x in which X gradually changed from 1 to 0.64.

For the next 60 minutes, H ₂ , H ₂ S, HCl, PH ₃ , A _s H ₃
without changing the amount of each introduced, i.e., per minute, H ₂
2000ml, _H2S 15ml, HCl 18ml, PH ₃ 245
ml, A _s H ₃ is kept at 164 ml, X is 0.64 (constant)
A layer with a constant mixed crystal content of G _a A _s1-x P _x was formed. The previous [G _a ]/[A _s +P] was kept at 0.4.

The final 60 minutes consisted of iso-electronic
180 ml/min of NH ₃ to add trap (N)
and also H ₂ , H ₂ S, HCl, PH ₃ , A _s H ₃
Among the introduced amounts, only HCl was introduced at a rate of 90 ml per minute to form a layer with a constant nitrogen-added Ga _{A s1-x} P _x mixed crystal ratio. ([G _a ]/[A _s +P] = 2) Each of the obtained epitaxial films (corresponding to 2, 3, and 4) was chemically stained and measured with a microscope, and it was found that the vapor growth gas At the upstream end,
_{G a A S1 - x P _ _} The constant ratio layer is 30 μm thick at the downstream end of the vapor growth gas flow, and the variable _crystal ratio layer is 51 μm thick and G _{a A s1 -x} does not contain nitrogen.
P _x constant mixed crystal layer has a thickness of 18 μm, nitrogen addition G _a A _s1-x
The P _x constant mixed crystal content layer had a thickness of 19 μm.

That is, the epitaxial film thickness at the upstream end of the vapor phase growth gas flow is 103 μm, and the film thickness at the downstream end of the gas flow is 88 μm.
(= 51μ + 18μ + 19μ) and has excellent film thickness uniformity.
It was confirmed that the debar process was not necessary at all.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional model diagram of a wafer obtained by a conventional method. DESCRIPTION OF SYMBOLS 1... Single crystal substrate, 2... Mixed crystal ratio change layer, 3...
...Constant mixed crystal content layer, 4...Constant mixed crystal content layer containing isoelectronic traps, 5...Arrow indicating the direction of air flow.

Claims (1)

[Scope of Claims] 1. A gallium arsenide phosphide mixed crystal containing a gallium arsenide phosphide mixed crystal ratio variable layer, a gallium arsenide phosphide constant mixed crystal ratio layer, and an isoelectronic trap on a single crystal substrate. In manufacturing a gallium arsenide phosphide mixed crystal epitaxial wafer in which the constant rate layers are formed in the above-mentioned order by a vapor phase epitaxial growth method, at least the gallium arsenide phosphide containing the above-mentioned isoelectronic trap is used. When growing a layer with a constant gallium mixed crystal ratio, the concentration of gallium component [G _a ] contained in the vapor phase growth gas and the concentration of phosphorus and arsenic components [A _S + P] (the above concentration is The ratio [G _a ]/[A _s + P] of each component (expressed in the number of atoms of each component contained in a unit volume of gas) is 1.5.
A gallium arsenide phosphide mixed crystal characterized by maintaining the above [G _a ]/[A _s +P] within a range of 0.3 to 1 during growth of other layers. Method for manufacturing epitaxial wafers.