JP2566800B2 - Light emitting device manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a light emitting device such as an LED.

[Conventional technology and its problems]

Recently, light emitting devices have been used in various fields, and accordingly, light emitting devices having excellent environmental resistance are required. For example, when the light emitting side surface is used in an environment that is easily affected physically or chemically, a translucent protective member having excellent corrosion resistance, heat resistance, mechanical strength, etc. must be formed on the light emitting side surface. .

The light emitting element has a structure in which a light emitting diode made of Ga _1-x Al _x As / GaAs or the like is formed on a silicon (Si) substrate or a gallium arsenide (GaAs) substrate. The optical energy band of the substrate and Si substrate is
The emission energy is smaller than that of Ga _1-x Al _x As / GaAs, and thus the emitted light is absorbed by the substrate. Therefore, the light emitted from the light emitting diode is projected on the opposite side to the substrate and is irradiated through the translucent protective member and the like.

On the other hand, Ga _1-X Al _X As
To a thickness of about 300 μm, then: G on top of that layer
It has been proposed to form an a _1-y Al _y As layer, thereby forming a PN junction between them, and then removing the GaAs substrate by polishing.

However, according to the light emitting device manufactured as described above, the GaAlAs layer is inferior in strength, and thus the reliability of the light emitting device is deteriorated.

Moreover, there is a problem that the manufacturing cost is significantly increased when the above manufacturing method is used.

[Object of the Invention]

Therefore, the present invention has been completed in view of the above circumstances, and an object thereof is to provide a method for manufacturing a light emitting element capable of emitting light from the substrate side.

Another object of the present invention is to provide a method for manufacturing a light emitting device having excellent environment resistance and reliability.

Still another object of the present invention is to eliminate the need for a translucent protective member,
It is an object of the present invention to provide a method for manufacturing a light emitting device that can reduce the manufacturing cost.

[Means for solving problems]

According to the present invention, a silicon layer having a thickness of 2 μm or less is vapor-deposited on an alumina single crystal substrate, and then an organometallic pyrolysis gas comprising the following steps (A) and (B) is sequentially formed on the silicon layer. Phase III with PN junction by phase growth method
A method for manufacturing a light-emitting device is provided, wherein a group V compound semiconductor layer is epitaxially grown and light emitted from the semiconductor layer can be projected through the silicon layer and the substrate.

(A) ... The substrate is set in a temperature range of 370 to 470 ° C., a group III element-containing gas and a group V element-containing gas are introduced into the reaction chamber, and the silicon layer is formed by vapor phase epitaxy. A group III / V compound is formed on the substrate (B) ... The substrate is set within a temperature range of 550 to 750 ° C., and the group III element-containing gas and the group V element-containing gas are placed inside the reaction chamber. Introduced into the
Production of Group V Compound Hereinafter, the present invention will be described in detail by taking the case where the group III / V compound is GaAs as an example.

According to the manufacturing method of the present invention, a silicon (Si) layer is formed on an alumina single crystal substrate, and then the steps (A) and (B) are performed.
Metal-organic pyrolysis vapor phase growth method (Metal-Organ
ic chemical vapor deposition (abbreviated as MOCVD method for short) is used to form a GaAs semiconductor layer on the Si layer, and the semiconductor layer is formed into a P-N junction to form a light emitting diode. Then, the light emitted from the light emitting diode is made to be able to emit light through the Si layer and the substrate, whereby a light emitting element having excellent environment resistance and reliability and capable of reducing manufacturing cost can be obtained.

When a substrate having a Si layer formed on an alumina single crystal substrate in this way, that is, a substrate called a SOS substrate (Silicon on Sapphire substrate) is used, the alumina single crystal substrate without the Si layer is used to obtain the substrate. The crystallinity is improved as compared with the case where a GaAs semiconductor layer is formed on the GaAs semiconductor layer, and as a result, the light emission characteristics and reliability are improved, and moreover, the (100) plane orientation can be obtained.

First, the Si layer is formed by a conventionally known CVD method in which silane gas or the like is thermally decomposed.

The thickness of the Si layer may be set to 2 μm or less, preferably 1 μm or less.

That is, since the Si layer has a smaller bad gap than the GaAs layer, the light emitted from the GaAs layer is absorbed by the Si layer. Therefore, the absorption amount can be reduced by reducing the thickness of the Si layer. According to experiments conducted by the inventors of the present invention, when the thickness of the Si layer is set to 2 μm or less, about 60% or more of the emitted light is emitted from the alumina single crystal substrate, which causes no practical problem. It was confirmed that it could be an element.

Next, a GaAs semiconductor layer is formed on the Si layer by MOCVD.

The MOCVD method sequentially comprises the following steps (A) and (B).

In the step (A), the temperature of the SOS substrate is set lower than the substrate temperature set in the step (B), and a Ga element-containing gas and an As element-containing gas are introduced into the reaction chamber to generate a nucleus required for crystal growth. To form. For that, SOS substrate is 370 to 470
The temperature may be set to ℃, preferably 400 to 450 ℃. 37
It was experimentally confirmed that GaAs nuclei do not grow at temperatures lower than 0 ° C. On the other hand, when the temperature exceeds 470 ° C., uniform and favorable island-shaped growth is not performed, and the reason for this is that the inventors of the present invention have a defect in the interface.

The thickness of the GaAs film produced by this (A) process is 100
It is recommended to set it in the range of ~ 500Å. When it is set within this range, the film which is not sufficiently crystallized may be easily crystallized in the next step (B).

The next (B) step is a step of growing GaAs crystal,
When a Ga element-containing gas and an As element-containing gas are introduced into the reaction chamber and the base temperature is set within the range of 550 to 750 ° C, preferably 570 to 730 ° C, these gases are thermally decomposed, and (A )
GaAs can be epitaxially grown on the GaAs thin film formed in the process.

The Ga element-containing gas used in the above steps (A) and (B) includes Ga (CH ₃ ) ₃ , Ga (C ₂ H ₅ ) _{3 and the} like, while one As element-containing gas includes AsH ₃ etc. is there. The carrier gas for these gases is H ₂ or an inert gas (Ar, N ₂ , H
e, Ne, etc.)

In order to control the conductivity type of the GaAs semiconductor layer thus formed, the following impurities may be doped.

To make an n-type semiconductor, Si, Se, S, etc. may be doped, and the dopant used for that purpose is Si.
H ₄ , Si ₂ H ₆ , H ₂ Se, H ₂ S, etc.

In order to obtain a P-type semiconductor, Zn, Mg, etc. may be doped, and the dopants used for this purpose include dimethyl zinc (DMZn), hiscylco pentenyl magnesium (Cp ₂ Mg) and the like.

Then, a part of Ga element in the GaAs semiconductor layer is Al,
It is also possible to substitute P, In or the like to form a ternary mixed crystal such as GaAlAs, GaPAs, GaInAs, etc., whereby the band gap size can be changed. The gas used for that is (CH
₃ ) ₃ Al, (C ₂ H ₅ ) ₃ Al, (isoC ₄ H ₉ ) ₃ Al, (C ₂ H ₅ ) ₃ In, PH ₃
and so on.

Further, in the manufacturing method of the present invention, it is preferable to form a GaAs semiconductor layer having surface smoothness on the SOS substrate.
Luminous efficiency is remarkably increased, and fine processing of the semiconductor surface becomes possible.

In order to obtain such surface smoothness, the off angle of the Si layer surface may be set within the range of 1 to 8 °, preferably 3 to 6 ° from the (100) plane toward the (011) plane. Such range setting corresponds to the off-angle of the R plane of the alumina single crystal substrate, and by determining this off-angle, the off-angle of the surface of the Si layer is determined as a predetermined value.

The minimum thickness of this Si layer is determined so that the crystallinity of the GaAs layer is improved. Regarding the thickness, the present inventors consider that 0.05 μm or more is preferable.

Thus, according to the production method of the present invention, the above (A)
By setting the step and the step (B) and the off angle of the SOS substrate surface, a semiconductor element having surface smoothness, excellent crystallinity, and a (100) plane orientation on the layer surface can be obtained. Provided.

According to experiments repeatedly conducted by the present inventors, the surface smoothness is set to a surface roughness of 0.1 S or less, 0.05 S or less, and 0.03 S or less.

In manufacturing such a semiconductor device, the inventors of the present invention can more advantageously achieve the object of the present invention by pretreating the substrate as follows before the steps (A) and (B). I also found out.

That is, the SOS substrate is installed in the MOCVD reaction chamber, an As element-containing gas such as AsH ₃ and a carrier gas such as H ₂ are introduced, and the substrate is heated to 850 ° C. or higher by a normal heating means, preferably 1000 ° C. or higher. Heating until the oxides adhering to the surface of the Si layer can be removed.
Further, a GaAs semiconductor layer having improved crystallinity can be formed.

Further, according to the manufacturing method of the present invention, the gas ratios in the steps (A) and (B) may be set as follows in order to improve the crystallinity of the GaAs semiconductor layer.

That is, the molar volume ratio of the As element-containing gas to the molar volume of the Ga element-containing gas may be set to 10 or more, preferably 30 to 100.

Next, a high frequency induction heating type MOCVD apparatus will be described with reference to FIG.

In the figure, 1 is a reaction chamber, in which a susceptor 2 is installed, and for growing a GaAs film on the susceptor 2.
The SOS substrate 3 is installed. A high frequency coil 4 is wound around the reaction chamber 1, a high frequency power source (not shown) is connected to the high frequency coil 4, and the susceptor 2 is induction-heated as high frequency power is applied to the high frequency coil 4. And
The reaction chamber 1 has an ultra-high vacuum exhaust device 5 and an exhaust gas treatment device 6
Before the film formation, the inside of the reaction chamber 1 is evacuated by the ultra-high vacuum exhaust device 5 to remove the residual gas therein, and the exhaust gas treatment device 6 removes the As compound in the exhaust gas. To do.

AsH ₃ gas in the first tank 7 and (CH
₃ ) ₂ Zn gas (which is diluted with H ₂ gas and its concentration is set to 0.1 mol%) is stored in the third tank 9
Si ₂ H ₆ gas is sealed in, and the flow rates discharged from the respective tanks are adjusted by the mass flow controllers 10, 11 and 12, and both gases are supplied to the first main pipe 13.

Further, H ₂ gas is hermetically sealed in the fourth tank 14, and this gas is highly purified as a carrier gas through a purifier 15 and is then supplied to the first main pipe 13, and the gas flow rate thereof is a mass flow controller. Adjusted by 16,24.

17 is the first bubbler containing the Ga (CH ₃ ) ₃ liquid, 18 is the second bubbler containing the Al (CH ₃ ) ₃ liquid, and 19 and 20 require the respective bubblers 17 and 18. It is a constant temperature bath for setting the temperature of. The high-purity H ₂ gas supplied from the fourth tank 14 through the purifier 15 is the first bubbler 1
7, the liquid is introduced into the second bubbler 18, whereby the liquid in the bubbler is gasified and introduced into the second main pipe 21. The gas introduced into the second main pipe 21 is adjusted by the mass flow controllers 22 and 23, and moreover, the fourth tank 14
The high-purity H ₂ gas supplied through the purifier 15 by the second main pipe while being adjusted by the mass flow controller 24.
The H ₂ gas is introduced into Ga (CH
₃ ) It also serves as a carrier gas for ₃ gas and Al (CH ₃ ) ₃ gas.

Thus, AsH ₃ gas, (CH ₃ ) ₂ Zn gas and Si ₂ H ₆ gas are supplied from the first main pipe 13 and Ga (CH ₃ ) _{3 is} supplied from the other second main pipe 14.
Gas and Al (CH ₃ ) ₃ gas are carried and introduced into the reaction chamber 1. In addition, 25,26,27,28,29,30,31,32,33,34,35,36,37,38,
39 and 40 are valves.

In the MOCVD apparatus configured as described above, the SOS substrate 3 is fixed on the susceptor 2, and the AsH ₃ gas from the first tank 7 and the H ₂ gas from the fourth tank 14 are introduced into the reaction chamber 1, respectively. The substrate 3 is induction-heated at a temperature of about 950 ° C. by the coil 4 to remove the deposits on the substrate surface and perform a cleaning process.

Next, the inside of the reaction chamber 1 was heated to 10 ^-7 To
The substrate 3 is induction-heated by the high-frequency coil 4 to a vacuum of rr, and this temperature is maintained when a predetermined temperature is reached. Then, the valves 34 to 40 are fully opened, and the fourth tank 14 is opened.
High-purity H ₂ gas is introduced into the reaction chamber 1 via the purifier 15.

First, in step (A), the valve 25 is fully opened to release AsH ₃ gas from the first tank 7, and the released amount is introduced into the first main pipe 13 while adjusting the mass flow controller 10. Also, close valve 30 and fully open valves 28 and 29,
₂ gas is introduced into the bubbler 17 to obtain Ga (CH ₃ ) ₃ gas. The supply amount of this gas is set by the temperature of the constant temperature bath 19 and the mass flow controller 22, and is introduced into the second main pipe 21.

In the next step (B), the substrate temperature is set within a predetermined range, and Ga (CH ₃ ) ₃ gas and AsH ₃ gas are introduced into the reaction chamber in the same manner as described above to grow GaAs crystals. This GaAs layer has semiconducting properties and its conductivity type is determined by doping with Si or Zn. Therefore, in this step (B), the valve 26 or the valve 27 is fully opened and the second tank 8 is opened.
Alternatively, Zn (CH ₃ ) ₃ gas or Si ₂ H ₆ gas may be released from the third tank 9 and introduced into the reaction chamber 1 together with AsH ₃ gas.

In the case of crystal growth of the GaAlAs layer in the step (B), the valve 33 is closed and the valves 31 and 32 are fully opened.
₂ gas is introduced into the bubbler 18 to obtain Al (CH ₃ ) ₃ gas. The amount of this gas supplied is also set by the temperature of the thermostatic chamber 20 and the mass flow controller 23, and the amount of gas supplied together with the Ga (CH ₃ ) ₃ gas
It is introduced into the main pipe 21 and supplied to the reaction chamber 1.

Thus, according to the manufacturing method of the present invention, the GaAs semiconductor layer or the GaAlAs semiconductor layer can be formed on the SOS substrate using the MOCVD apparatus, and the conductivity type of the semiconductor layer can be controlled to control the P type.
-N junctions can also be formed.

A typical structure of the light emitting device obtained by the manufacturing method of the present invention is as shown in FIG.

According to the figure, the Si layer 41b is formed on the alumina single crystal substrate 41a.
N-type Ga _1-x Al _x As layer 42 on the SOS substrate 41 formed by
(Thickness 1 to 3 μm), P-type Ga _1-y AlyAs layer 43 (thickness 1 to 3 μm)
μm) and a P ^{+ -type} GaAs layer 44 are sequentially stacked, 45 is a protective layer made of SiN, 46 is a first electrode made of Ag / Zn alloy, and 47 is made of Au / Ge / Ni alloy Second
Electrodes, 48 are solders for connecting lead wires.

The above-mentioned x value and y value have a relationship of x> y so that the Ga _{1 -x} Al _x As layer does not absorb light emission by making a difference in the bad gap between the layers 42 and 43.

In addition, the above-mentioned light emitting device is formed into a layer by the manufacturing method described below.
43, 44, and 45 are divided into two, and the area A is used as a light emitting portion and the other area B is used as an electrode lead portion.

The light emitting device is sequentially manufactured by the following first to sixth steps.

First step: n-type Ga _1-x A on SOS substrate 41 by MOCVD method
The l _x As layer 42, the P-type Ga _1-y AlyAs layer 43, and the P ⁺ -type GaAs 44 are sequentially formed (see FIG. 3).

Second step ... As shown in FIGS. 4 to 6, each layer
Predetermined portions of 42, 43 and 44 are sequentially and selectively etched. This etching may be either wet etching or dry etching, and the etching component is determined by the material of each layer. For example, the etching component for GaAs and GaAlAs may _{H 2 SO 4 -H 2 O 2} -H 2 O, the selective etching component to GaAs has H ₂ O ₂ -NH ₄ OH, and, GaAlA
The selective etching component for s includes HF-H ₂ O ₂ .

Third step ... As shown in FIG. 7, a SiN protective layer 45 is formed over the entire surface by a plasma CVD method.

Fourth step ... As shown in FIG. 8, the SiN protective layer 45 is selectively removed by photoetching.

Fifth step ... As shown in FIG. 9, the first electrode 46 is formed by vapor deposition and photo process.

Sixth step ... As shown in FIG. 10, the second electrode 47 is formed by vapor deposition and photo process.

Thus, a Si layer is formed on the alumina single crystal substrate, and then a GaAs semiconductor layer is formed by MOCVD to form a P-N junction, and thereafter, the first to sixth steps are sequentially performed. The light emitting device shown in FIG. 2 is manufactured.

〔The invention's effect〕

As described above, according to the manufacturing method of the present invention, it is possible to form a semiconductor layer controlled to have a required conductivity type on the SOS substrate by the MOCVD method, and thus, a PN junction semiconductor for light emission can be formed, and By setting the thickness of the Si layer of the SOS substrate within a predetermined range, the translucency of the SOS substrate itself can be remarkably enhanced, and as a result, it is possible to provide a light emitting element capable of emitting light from the substrate side.

Further, according to the manufacturing method of the present invention, since it was possible to project light from the SOS substrate side, it becomes a light emitting element excellent in corrosion resistance, heat resistance, scratch resistance, mechanical strength, etc., thereby, environmental resistance and reliability An excellent light emitting device can be provided.

Further, according to the manufacturing method of the present invention, a light-transmitting protective member is not required, and further, polishing removal of the substrate is not required, whereby an inexpensive light emitting element can be provided.

In the production method of the present invention, the group III / V compound is G
Although the case of aAs is described as an example, the present inventors have found that other group III / V compounds such as InP and InAs are used.
We believe that similar effects can be obtained with compounds such as P, GaP, and GaN.

[Brief description of drawings]

FIG. 1 is a schematic view of a MOCVD apparatus, FIG. 2 is a cross-sectional view of a light emitting device obtained by the manufacturing method of the present invention, and FIG.
FIG. 4, FIG. 5, FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 8, FIG. 9 and FIG. 10 show the manufacturing sequence of the above light emitting device, and each drawing is a sectional view showing each process. is there. 41a …… Alumina single crystal substrate 41b …… Silicon layer 42 …… n type Ga _1-x Al _x As layer 43 …… P type Ga _1-y Al _y As layer 44 …… P ^{+ type} GaAs layer 45 …… Protection layer

Claims (1)

(57) [Claims] 1. A metal layer having a thickness of 2 .mu.m or less is vapor-deposited on an alumina single crystal substrate, and the organometallic pyrolysis vapor phase is formed on the silicon layer by the following steps (A) and (B). A light emitting device characterized in that a group III / V compound semiconductor layer having a P-N junction can be epitaxially grown by a growth method and light emitted from the semiconductor layer can be projected through the silicon layer and the substrate. Manufacturing method. (A) ... The substrate is set in a temperature range of 370 to 470 ° C., a group III element-containing gas and a group V element-containing gas are introduced into the reaction chamber, and the silicon layer is formed by a vapor phase growth method. A Group III / V compound is formed on the substrate (B) ... The substrate is set within a temperature range of 550 to 750 ° C., and the Group III element-containing gas and the Group V element-containing gas are placed inside the reaction chamber. Introduced into the
Produces Group V compounds