JP3672585B2 - Method for manufacturing group 3 nitride semiconductor - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a vapor phase growth method for a group 3 nitride semiconductor (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0).
[0002]
[Prior art]
Conventionally, a blue light emitting diode using a pn junction of a GaN compound semiconductor is known. Since the compound semiconductor is a direct transition type, it has been attracting attention because of its high luminous efficiency and the fact that one of the three primary colors of light is blue.
[0003]
In the above light emitting device, the p layer is obtained by doping the GaN with magnesium (Mg), and then irradiating with an electron beam or heat treatment to obtain a p-conductivity type.
[0004]
[Problems to be solved by the invention]
However, the above light-emitting element releases hydrogen present in a large amount in the film by heat treatment. However, since nitrogen is also released at the same time as hydrogen is released, there is a problem that crystallinity is lowered by heat treatment.
Therefore, the light emitting element manufactured by this method also has a problem that the light emission intensity is low.
[0005]
The present invention has been made to solve the above-described problems, and its purpose is to improve the crystallinity of a semiconductor thin film using AlGaInN and to improve the light emission intensity of a light-emitting element using the semiconductor. It is.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is a method for producing a group III nitride semiconductor (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0). After vapor phase growth of semiconductors (including Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0), heat treatment is performed in a plasma discharge region where nitrogen radicals exist at a pressure of 100 torr or less It is characterized by doing.
[0007]
According to a second aspect of the present invention, there is provided a light emitting device made of a group III nitride semiconductor (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0). Nitrogen radicals exist at a pressure of 100 torr or less after vapor phase growth of the added group III nitride semiconductor (Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0) It is formed by heat treatment in the plasma discharge region .
[0008]
[Action and effect of the invention]
Plasma discharge region where nitrogen radicals exist at a pressure of 100 torr or less after vapor phase growth of group III nitride semiconductors (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0) By performing the heat treatment therein , hydrogen present in a large amount in the thin film is released from the film and nitrogen is prevented from being released from the thin film due to the presence of nitrogen plasma.
[0009]
As a result, the crystallinity of the group 3 nitride semiconductor (Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0) is improved. In addition, the light emitting device manufactured in this manner has improved light emission intensity because the crystallinity of each layer is improved.
[0010]
【Example】
First embodiment In Fig. 1, a light emitting diode 10 has a sapphire substrate 1, and a 500 サ フ ァ イ ア AlN buffer layer 2 is formed on the sapphire substrate 1. 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, a thickness of about 2.0 [mu] m, an electron concentration 2 × High carrier concentration n ⁺ layer 4 consisting of 10 ¹⁸ / cm ³ silicon-doped (Al _x2 Ga _1-x2 ) _y2 In _1-y2 N, about 0.5 μm thick, zinc and magnesium doped (Al _x1 Ga _{1- x1} ) Light-emitting layer 5 made of _y1 In _1-y1 N, p film made of magnesium-doped (Al _x2 Ga _1-x2 ) _y2 In _1-y2 N with a film thickness of about 1.0 μm and a hole concentration of 2 × 10 ¹⁷ / cm ³ Layer 6 is formed. An electrode 7 made of nickel connected to the p layer 6 and an electrode 8 made of nickel connected to the high carrier concentration n ⁺ layer 4 are formed. The electrode 7 and the electrode 8 are electrically insulated and separated by the groove 9.
[0011]
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 using a metal organic compound vapor phase growth method (hereinafter referred to as “M0VPE”).
[0012]
The gases used were NH ₃ and carrier gas H ₂ or N ₂ , trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”) and trimethylaluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as “TMA”). ), Trimethylindium (In (CH ₃ ) ₃ ) (hereinafter referred to as “TMAI”), diethylzinc ((C ₂ H ₅ ) ₂ Zn) (hereinafter referred to as “DEZ”) and silane (SiH ₄ ) and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter referred to as “CP ₂ Mg”).
[0013]
First, the single crystal sapphire substrate 1 having the a-plane as a main surface cleaned by organic cleaning and heat treatment is mounted on a susceptor mounted in the reaction chamber of the M0VPE apparatus. Next, the sapphire substrate 1 was vapor-phase etched at a temperature of 1100 ° C. while flowing H ₂ at normal pressure and a flow rate of 2 liter / min into the reaction chamber.
[0014]
Next, the temperature is lowered to 400 ° C., H ₂ is supplied at 20 liter / min, NH ₃ is supplied at 10 liter / min, and TMA is supplied at 1.8 × 10 ⁻⁵ mol / min. The thickness was formed. Then, maintaining the temperature of the sapphire substrate 1 to 1150 ° C., to form a film thickness of about 2.2 [mu] m, an electron concentration of 2 × 10 ¹⁸ / cm high carrier concentration n ⁺ layer 3 made of GaN of silicon doped ^3.
[0015]
Examples of composition ratios and crystal growth conditions of the light emitting layer 5 (active layer) and the cladding layers 4 and 6 when zinc (Zn) is the emission center and the emission peak wavelength is set to 450 nm will be described below. After the above high carrier concentration n ⁺ layer 3 is formed, the temperature of the sapphire substrate 1 is maintained at 1150 ° C., N ₂ is 20 liter / min, NH ₃ is 10 liter / min, and TMG is 1.12 × 10 ^{− 4} mol / min, TMA 0.47 × 10 ⁻⁴ mol / min, TMI 0.1 × 10 ⁻⁴ mol / min, and silane introduced, with a film thickness of about 2.0 μm and a concentration of 2 × 10 ¹⁸ / cm ³ A high carrier concentration n ⁺ layer 4 made of doped (Al _0.3 Ga _0.7 ) _0.94 In _0.06 N was formed.
[0016]
Subsequently, the temperature is maintained at 860 ° C., N ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG is 1.53 × 10 ⁻⁴ mol / min, TMA is 0.47 × 10 ⁻⁴ mol / min, TMI Was introduced at a rate of 0.02 × 10 ⁻⁴ mol / min and DEZ at 2 × 10 ⁻⁴ mol / min for 7 minutes, and was doped with zinc (Zn) with a film thickness of approximately 0.3 μm (Al _0.09 Ga _0.91 ) _0.99 In _0.01 N A light emitting layer 5 made of was formed. The light emitting layer 5 is still an insulator having a resistivity of 10 ⁸ Ωcm or more in this state. The concentration of zinc (Zn) in the light emitting layer 5 is 5 × 10 ^{17 to} 3 × 10 ¹⁹ / cm ³ .
[0017]
Subsequently, the temperature is maintained at 1100 ° C., N ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG is 1.12 × 10 ⁻⁴ mol / min, TMA is 0.47 × 10 ⁻⁴ mol / min, TMI From 0.1 × 10 ⁻⁴ mol / min and CP ₂ Mg of 2 × 10 ⁻⁴ mol / min, and about 1.0 μm magnesium (Mg) -doped (Al _0.3 Ga _0.7 ) _0.94 In _0.06 N A p-layer 6 was formed. The concentration of magnesium in the p layer 6 is 1 × 10 ¹⁹ / cm ³ . In this state, the p layer 6 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.
[0018]
Next, the reaction chamber is once evacuated to make the remaining gas only N ₂ gas. Thereafter, N ₂ gas was introduced, and the pressure in the reaction chamber was adjusted to 100 torr or less. Next, plasma discharge is performed at a power of 10 to 100 W in the reaction chamber, and then the temperature of the substrate is heated to 500 to 900 ° C. and plasma annealed for 5 to 60 minutes. This discharge may be any means such as high frequency, microwave, and direct current. The substrate is placed either in a plasma discharge region where N (radicals) exist, or in a region where there are no long-lived radical species called afterglow, but no long-lived ion species exist. By the above treatment, the p-layer 6 became a p-conduction type semiconductor having a hole concentration of 6 × 10 ¹⁷ / cm ³ and a resistivity of 2 Ωcm. In this way, a wafer having a multilayer structure as shown in FIG. 2 was obtained.
[0019]
Here, various experiments for confirming the effect of the plasma treatment will be described below. In this experiment, the PL intensity of the thin film after various treatments was measured for the (Al _0.09 Ga _0.91 ) _0.99 In _0.01 N thin film without addition of impurities. The measurement results are shown in FIGS. FIG. 8 shows the PL intensity of 360 nm, 380 nm, and 540 nm of the thin film after being treated with plasma untreated, afterglow, and 40 W plasma. It can be seen that the PL intensity is most improved in the thin film after being treated with 40 W plasma.
[0020]
Further, after the thin film was formed by changing the substrate temperature during the plasma treatment, the PL intensity at 360 nm, 380 nm, and 540 nm of the thin film was measured. The measurement results are shown in FIG. It is understood that the PL intensity is highest at 750 ° C. in the range of 500 to 900 ° C.
[0021]
Further, the PL intensity at 360 nm, 380 nm, and 540 nm of the thin film after the plasma treatment for 5 minutes with various changes in plasma power with the substrate temperature set to 700 ° C. was measured. The measurement results are shown in FIG. It is understood that the maximum PL intensity is shown when the plasma power is 40 W.
[0022]
In addition, the PL intensity at 360 nm, 380 nm, and 540 nm of the thin film after the plasma treatment with the substrate temperature set to 700 ° C., the plasma power set to 40 W, and the treatment time changed was measured. The measurement results are shown in FIG. It can be seen that at 60 minutes or less, the PL intensity increases as the plasma treatment time increases.
[0023]
Next, the continuation of the manufacturing method of a light emitting element is demonstrated. 3 to 7 described below are cross-sectional views showing only one element on the wafer. Actually, processing is performed on a wafer in which this element is continuously repeated, and thereafter, for each element. Disconnected.
[0024]
As shown in FIG. 3, the SiO ₂ layer 11 was formed on the p layer 6 to a thickness of 2000 mm by sputtering. Next, a photoresist 12 was applied on the SiO ₂ layer 11. Then, by photolithography, the electrode forming portion A corresponding to the hole 15 formed so as to reach the high carrier concentration n ⁺ layer 4 on the p layer 6 and its electrode forming portion are insulated and separated from the electrode of the p layer 6. The photoresist at the site B where the groove 9 is to be formed was removed.
[0025]
Next, as shown in FIG. 4, the SiO ₂ layer 11 not covered with the photoresist 12 was removed with a hydrofluoric acid etching solution. Next, as shown in FIG. 5, the p layer 6 at a portion not covered with the photoresist 12 and the SiO ₂ layer 11, the light emitting layer 5 thereunder, and a part of the upper surface of the high carrier concentration n ⁺ layer 4 are vacuum-treated. After dry etching by supplying 0.04 Torr, high frequency power of 0.44 W / cm ² and BCl ₃ gas at a rate of 10 ml / min, dry etching was performed with Ar. In this step, a hole 15 for extracting an electrode for the high carrier concentration n ⁺ layer 4 and a groove 9 for insulating separation were formed.
[0026]
Next, as shown in FIG. 6, the SiO ₂ layer 11 remaining on the p layer 6 was removed with hydrofluoric acid. Next, as shown in FIG. 7, the Ni layer 13 was formed on the entire upper surface of the sample by vapor deposition. As a result, the Ni layer 13 electrically connected to the high carrier concentration n ⁺ layer 4 is formed in the hole 15. Then, a photoresist 14 is applied on the Ni layer 13, and a pattern is formed in a predetermined shape by photolithography so that the electrode portions of the photoresist 14 with respect to the high carrier concentration n ⁺ layer 4 and the p layer 6 remain. did.
[0027]
Next, as shown in FIG. 7, the exposed portion of the lower Ni layer 13 was etched with a nitric acid-based etchant using the photoresist 14 as a mask. At this time, the Ni layer 13 deposited in the groove 9 for insulation separation is completely removed. Next, the photoresist 14 was removed with acetone, leaving the electrode 8 of the high carrier concentration n ⁺ layer 4 and the electrode 7 of the p layer 6. Thereafter, the wafer processed as described above was cut for each element to obtain a gallium nitride light emitting element having a pn structure shown in FIG.
[0028]
The light-emitting element thus obtained had a drive current of 3.6 V, an emission peak wavelength of 450 nm, and an emission intensity of 1000 mcd.
[0029]
The zinc (Zn) concentration in the light emitting layer 5 is preferably in the range of 1 × 10 ¹⁷ to 1 × 10 ²⁰ in terms of improving the light emission intensity.
[0030]
In the above embodiment, a light emitting element using (Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0) is shown. In general, the present invention can be applied to a vapor phase growth method of a thin film (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0).
[0031]
Although the light emitting element having a pin structure is shown in the above embodiment, a light emitting element having a ppn structure may be used. That is, the p layer may have a double structure of a first p layer doped with Mg and Zn that joins the n layer and a second p layer doped with Mg.
In addition, the heat treatment in nitrogen plasma may be performed only for the p layer, but may be performed every time the n layer and the p layer are formed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a configuration of a light emitting diode according to a first specific example of the present invention.
FIG. 2 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the same example.
FIG. 3 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the example.
FIG. 4 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the same example.
FIG. 5 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the example.
6 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the example. FIG.
7 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the example. FIG.
FIG. 8 is a measurement diagram in which the PL intensity of a thin film after untreated, afterglow, and plasma treatment was measured.
FIG. 9 is a measurement diagram in which the PL intensity of a thin film after plasma treatment is performed while changing the substrate temperature.
FIG. 10 is a measurement diagram in which the PL intensity of a thin film after plasma treatment with varying plasma power is measured.
FIG. 11 is a measurement diagram in which the PL intensity of a thin film after the plasma treatment is performed while changing the plasma treatment time is measured.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration n ⁺ layer 4 ... High carrier concentration n ⁺ layer 5 ... Light emitting layer 6 ... P layer 7, 8 ... Electrode 9 ... Groove

Claims (2)

In a method for manufacturing a group 3 nitride semiconductor (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0),
Plasma discharge region where nitrogen radicals exist at a pressure of 100 torr or less after vapor phase growth of group III nitride semiconductors (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0) The manufacturing method characterized by heat-processing in. In a light emitting device made of a group III nitride semiconductor (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0),
After vapor phase growth of group III nitride semiconductor (Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0) to which acceptor impurities are added, nitrogen radicals at a pressure of 100 torr or less A manufacturing method characterized by being formed by being heat-treated in a plasma discharge region where there is .

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