JP3561057B2 - Light emitting device manufacturing method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for etching a group III nitride semiconductor in which damage due to etching is prevented, and a method for manufacturing a group III nitride semiconductor light emitting device using the etching method.
[0002]
[Prior art]
Conventionally, dry etching has been used for etching a group III nitride semiconductor. In this method, a reactive gas is introduced into a chamber, a discharge is generated by a method such as RF or ECR to generate a plasma state, and ions in the plasma are accelerated by a potential difference generated between the plasma and a sample. Then, the sample surface is etched by colliding with the sample surface.
[0003]
[Problems to be solved by the invention]
However, there is a problem that the sample is damaged due to the accelerated collision of the ions with the sample surface as described above, the crystallinity of the layer functioning as an element is reduced, and the element performance is reduced.
[0004]
The present invention has been made to solve the above problems, and an object of the present invention is to prevent each layer from being damaged in etching of a group III nitride semiconductor.
[0005]
[Means for Solving the Problems]
Feature of the present invention relates to a method of manufacturing a light emitting device having a substrate and a group III nitride n conduction type n layer consisting of a semiconductor and a p conductivity type p-layer of, when etching the group III nitride semiconductor, chlorine Exposure in a high-temperature atmosphere of a gas is to etch the group III nitride semiconductor.
According to this method, since the plasma ions do not collide with the group III nitride semiconductor, the crystallinity of the layer of the element portion of the group III nitride semiconductor does not decrease, and the element performance can be improved. it can. That is, damage to the p-layer and the n-layer functioning as a light-emitting element can be prevented, the emission luminance can be improved, and the life can be prolonged. By this etching, electrodes for the p layer and the n layer can be formed with good ohmic properties.
In addition, since the p-type activation treatment of the p-layer can also be performed, the manufacturing process of the light-emitting element is simplified.
[0006]
Further, by setting the temperature of the gas atmosphere to 800 to 1200 ° C., the etching rate could be set to 10 to 1000 ° / min.
As in claim 3, as the group III nitride _{semiconductor, A l x Ga y In 1} -Xy N: 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1 are applicable , Blue light emitting diodes and laser diodes.
Further, the protective film, by a SiO ₂ or Si ₃ N _4, can have a resistance to etching resistance against chlorine, only removing the protective film by BHF without damaging the group III nitride semiconductor can do.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment In FIG. 1, a light emitting diode 10 has a sapphire substrate 1 on which a buffer layer 2 of AlN 2 of 500 ° is formed. Of On the buffer layer 2, in turn, a film thickness of about 2.0 [mu] m, the electron concentration of 2 × ¹⁰ 18 / cm high carrier concentration comprising a silicon-doped GaN of ^{3 n +} layer 3, the thickness 3000 Å, the electron concentration of 1 × 10 ¹⁷ / cm ³ n-layer 4 made of silicon-doped GaN, light-emitting layer 5 made of In _0.08 Ga _0.92 N with a thickness of about 0.05 μm, film thickness of about 1.0 μm, hole concentration 5 × A p layer 61 of Al _0.08 Ga _0.92 N doped with magnesium at 10 ¹⁷ / cm ³ and a concentration of 1 × 10 ²⁰ / cm ³ , a film thickness of about 0.2 μm, and a hole concentration of 7 × 10 ¹⁷ / cm ³ A contact layer 62 made of magnesium-doped GaN having a density of ³ cm 2 and a magnesium concentration of 2 × 10 ²⁰ / cm ³ is formed. Then, on the contact layer 62, an electrode 7 made of Ni and joined to the layer 62 is formed. Further, part of the surface of the high carrier concentration n ⁺ layer 3 is exposed, and an electrode 8 made of Ni to be joined to the layer 3 is formed on the exposed portion.
[0010]
Next, a method for manufacturing the light emitting diode 10 having this structure will be described.
The light emitting diode 10 was manufactured by vapor phase growth by a metal organic compound vapor phase epitaxy method (hereinafter, referred to as “MOVPE”).
The gases used were NH ₃ and carrier gas H ₂ or N ₂ and trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”) and trimethylaluminum (Al (CH ₃ ) ₃ ) (hereinafter “TMA”). ), Trimethylindium (In (CH ₃ ) ₃ ) (hereinafter referred to as “TMI”), silane (SiH ₄ ), and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter “CP”). ₂ Mg ").
[0011]
First, a single-crystal sapphire substrate 1 having a thickness of 100 to 400 μm and having a main surface cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of an M0VPE apparatus. Next, the sapphire substrate 1 was subjected to gas phase etching at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at a flow rate of 2 liter / min under normal pressure.
[0012]
Next, the temperature was lowered to 400 ° C., H ₂ was supplied at 20 liter / min, NH ₃ was supplied at 10 liter / min, and TMA was supplied at 1.8 × 10 ⁻⁵ mol / min to form the AlN buffer layer 2. It was formed to a thickness of about 500 mm. Next, the temperature of the sapphire substrate 1 was maintained at 1150 ° C., H ₂ was 20 liter / min, NH ₃ was 10 liter / min, TMG was 1.7 × 10 ⁻⁴ l / min, and H ₂ gas was used. A silane diluted to 86 ppm is supplied at 20 × 10 ⁻⁸ mol / min for 30 minutes to provide a high carrier concentration n of silicon-doped GaN having a film thickness of about 2.2 μm and an electron concentration of 2 × 10 ¹⁸ / cm ^{3. +} Layer 3 was formed.
[0013]
Next, the temperature of the sapphire substrate 1 is maintained at 1150 ° C., N ₂ or H ₂ is 10 liter / min, NH ₃ is 10 liter / min, TMG is 1.12 × 10 ⁻⁴ mol / min, and H ₂ Silane diluted to 0.86 ppm by gas is supplied at 1 × 10 ⁻⁸ mol / min for 4 minutes to provide an n-layer 4 made of silicon-doped GaN having a thickness of about 3000 ° and a concentration of 1 × 10 ¹⁷ / cm ^3. Was formed.
[0014]
Subsequently, the temperature was maintained at 850 ° C., N ₂ or H ₂ was 20 liter / min, NH ₃ was 10 liter / min, TMG was 1.53 × 10 ⁻⁴ mol / min, and TMI was 0.02 / min. X 10 ^-4 mol / min was supplied for 6 minutes to form a light emitting layer 5 of 0.05 μm In _0.08 Ga _0.92 N.
[0015]
Subsequently, the temperature was maintained at 1100 ° C., N ₂ or H ₂ was 20 liter / min, NH ₃ was 10 liter / min, TMG was 1.12 × 10 ⁻⁴ mol / min, and TMA was 0.47 × 10 4 ^-4 mol / min and CP ₂ Mg were introduced at 2 × 10 ^-4 mol / min for 60 minutes, and from a magnesium (Mg) -doped Al _0.08 Ga _0.92 N film having a thickness of about 1.0 μm. A p layer 61 was formed. The concentration of magnesium in p layer 61 is 1 × 10 ²⁰ / cm ³ . In this state, the p layer 61 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.
[0016]
Subsequently, the temperature was maintained at 1100 ° C., N ₂ or H ₂ was 20 liter / min, NH ₃ was 10 liter / min, TMG was 1.12 × 10 ⁻⁴ mol / min, and CP ₂ Mg was 4 liter. It was introduced at a rate of × 10 ⁻⁴ mol / min for 4 minutes to form a contact layer 62 of magnesium (Mg) -doped GaN having a thickness of about 0.2 μm. The concentration of magnesium in the contact layer 62 is 2 × 10 ²⁰ / cm ³ . In this state, the contact layer 62 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.
[0017]
Next, as shown in FIG. 3, an SiO ₂ layer 9 was formed to a thickness of 2000 ° on the contact layer 62 by sputtering, and a photoresist 10 was applied on the SiO ₂ layer 9. Then, by photolithography, as shown in FIG. 3, on the contact layer 62, the photoresist 10 at the electrode formation site A ^′ for the high carrier concentration n ⁺ layer 3 was removed. Next, as shown in FIG. 4, the SiO ₂ layer 9 not covered with the photoresist 10 was removed with a hydrofluoric acid-based etchant such as BHF. Subsequently, the photoresist 10 was removed.
[0018]
Next, the sample was placed in an annealing furnace, heated by flowing chlorine gas at 1000 ° C. for 60 minutes. As a result of this processing, the contact layer 62, the p layer 61, the light emitting layer 5, and the n layer 4 were etched, and as shown in FIG. 5, holes A for taking out electrodes from the high carrier concentration n ⁺ layer 3 were formed.
[0019]
By this treatment, the contact layer 62 and the p-layer 61 became p-type semiconductors having hole concentrations of 7 × 10 ¹⁷ / cm ³ and 5 × 10 ¹⁷ / cm ³ and resistivity of 2 Ωcm and 0.8 Ωcm, respectively.
[0020]
Next, Ni is uniformly deposited on the entire upper surface of the sample, and through a photoresist coating, a photolithography process, and an etching process, as shown in FIG. 1, the high carrier concentration n ⁺ layer 3 and the contact layer 62 are formed. Electrodes 8 and 7 were formed. Thereafter, the wafer processed as described above was cut into chips to obtain light emitting diode chips.
[0021]
The emission spectrum of the light-emitting device thus obtained was measured. As a result, the drive current was 20 mA, the emission peak wavelength was 450 nm, and the emission intensity was 1000 mcd.
[0022]
In the above-described embodiment, a chlorine gas atmosphere at 1000 ° C. was used in the etching, but hydrogen gas and hydrogen chloride gas can be used in addition to chlorine gas. Further, two or three types of mixed gas of chlorine gas, hydrogen gas and hydrogen chloride gas may be used. In the temperature range of the gas atmosphere, a high etching rate of 10 to 1000 ° / min was obtained at 800 to 1200 ° C.
Although SiO ₂ was used for the protective film, Si ₃ N ₄ may be used.
[0023]
The double hetero junction is formed such that the band gap of the light emitting layer 5 is smaller than the band gap of the p layer 61 and the n layer 4 existing on both sides. The component ratio between the light emitting layer 5 and the p layer 61 is selected so as to match the lattice constant of the high carrier concentration n ⁺ layer of GaN.
In the above embodiment, the double hetero junction structure is used, but a single hetero junction structure may be used.
Further, in the above-described embodiment, the example of the light emitting diode is described, but a laser diode may be similarly configured.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a specific first embodiment of the present invention.
FIG. 2 is a sectional view showing a manufacturing step of the light-emitting diode of the embodiment.
FIG. 3 is a sectional view showing a step of manufacturing the light-emitting diode of the example.
FIG. 4 is a sectional view showing the manufacturing process of the light-emitting diode of the embodiment.
FIG. 5 is a sectional view showing the manufacturing process of the light emitting diode of the same embodiment.
[Explanation of symbols]
Reference Signs List 10 light emitting diode 1 sapphire substrate 2 buffer layer 3 high carrier concentration n ⁺ layer 4 n layer 5 light emitting layer 61 p layer 62 contact layer 7, 8 electrode

Claims (3)

In a method for manufacturing a light emitting device having an n-type n-type layer made of a substrate and a group III nitride semiconductor and a p-type p-type layer,
The n layer and the p layer are stacked on the substrate,
Covering the surface of the first layer present on the surface of the n layer and the p layer with a protective film having etching resistance;
Forming an opening by removing the protective film in a portion of the group III nitride semiconductor to be etched;
By exposing the Group III nitride semiconductor having the protective film with the opening formed therein to a high-temperature atmosphere of chlorine gas , etching the Group III nitride semiconductor in the opening to form the n-layer. And exposing a part of the second layer closer to the substrate in the p-layer and simultaneously performing p-type activation of the p-layer,
Removing the protective film,
A method for manufacturing a light emitting device, comprising forming electrodes on the surface of the first layer and the surface of the second layer. The method according to claim 1 , wherein the high-temperature atmosphere is 800 to 1200C. 2. The light emission according to claim 1 , wherein the group III nitride semiconductor is Al _x Ga _y In _1-Xy N: 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1. 3. Device manufacturing method.

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