JP3620923B2 - Group 3 nitride semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device using a group 3 nitride semiconductor. In particular, the present invention relates to a semiconductor element having excellent element characteristics and reliability.
[0002]
[Prior art]
Conventionally, a material using an AlGaInN based compound semiconductor is known as a material for a light emitting element in a blue or short wavelength region. Since the compound semiconductor is a direct transition type, it has attracted attention because of its high emission efficiency and the use of blue and green as one of the three primary colors of light.
[0003]
Recently, it has become clear that AlGaInN based semiconductors can also be made p-type by doping Mg and irradiating an electron beam or by heat treatment. As a result, an AlGaN p layer, a Zn-doped InGaN light emitting layer, and an AlGaN n layer were used instead of the conventional MIS type structure in which an n layer and a semi-insulating layer (i layer) were joined. A semiconductor device having a double hetero structure or a single quantum well structure has been proposed.
[0004]
The AlGaInN 2 -based semiconductor of the semiconductor element having the above structure is formed on a semiconductor or insulator substrate by epitaxial growth using an organic metal compound vapor phase growth method or a molecular beam growth method.
[0005]
Ideally, a material whose lattice constant and thermal expansion coefficient substantially coincide with those of an AlGaInN-based semiconductor and that is stable even at high temperatures during epitaxial growth is suitable for the substrate. From this point of view, it is optimal to use an AlGaInN semiconductor of the same material as the element layer for the substrate. However, in practice, it is difficult to obtain an AlGaInN semiconductor single crystal having a large area that can be used as a substrate because the equilibrium vapor pressure of nitrogen, which is a constituent element, is extremely high. Moreover, in other materials, a lattice constant and a thermal expansion coefficient are close to those of an AlGaInN-based semiconductor, and stable materials are not found even at high temperatures during epitaxial growth.
Therefore, as shown in FIG. 5, in the conventional light emitting diode 20, sapphire 21 or silicon carbide having a lattice constant and a thermal expansion coefficient different from those of an AlGaInN semiconductor are sequentially formed on a substrate, a buffer layer 22, and a GaN n ⁺ layer 23. GaN n layer 24, InGaN active layer 25, AlGaN p layer 26, GaN contact layer 27, and electrode layers 28 and 29 are formed.
[0006]
[Problems to be solved by the invention]
However, in the above element, thermal stress is generated due to the difference in thermal expansion coefficient between the substrate and the AlGaInN semiconductor in the process of lowering the temperature to room temperature after the epitaxial growth of the AlGaInN semiconductor at a high temperature is completed. Due to this thermal stress, crystal defects, cracks, and warpage are likely to occur in the substrate or the AlGaInN semiconductor, resulting in a problem.
[0007]
The occurrence of such crystal defects and cracks deteriorates the electrical characteristics of the device and greatly reduces the yield. Furthermore, it causes deterioration of the device and shortens the device life.
[0008]
In addition, the occurrence of warpage is a factor that deteriorates the accuracy of microfabrication such as etching and electrode formation at the time of device fabrication to deteriorate device characteristics, or causes device electrodes and protective films to be easily peeled off, thereby reducing reliability. Further, when the light emitting element is a laser, an optical resonator is configured with both end faces of the light emitting layer as mirror surfaces and light amplification is performed by stimulated emission. However, warping in the light emitting layer causes loss of light. As a result, the amplification gain of light is lowered.
[0009]
Accordingly, an object of the present invention is to provide a group III nitride semiconductor device that is free from crystal defects and cracks and has no warping, and as a result has excellent device characteristics and reliability.
[0010]
[Means for Solving the Problems]
A feature of the first invention is that a substrate made of a semiconductor or an insulator, and a group III nitride semiconductor (Al _x Ga _Y In _1-XY N; 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1) formed thereon. , 0 ≦ X + Y ≦ 1), a positive and negative electrode provided on the light emitting device layer, and a surface of the substrate opposite to the surface on which the light emitting device layer is formed. wherein the order is formed of semiconductor layers and SiO ₂ having a back surface layer composed of an insulator layer.
[0011]
A feature of the second invention is that the semiconductor layer forming the back layer is a group III nitride semiconductor (Al _x Ga _Y In _1-XY N; 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1) It is a layer which consists of.
A feature of the third invention is that the substrate is sapphire or silicon carbide.
A feature of the fourth invention is that the thickness of the substrate is 30 to 300 μm.
[0012]
[Action and effect of the invention]
In the above light emitting device, a back surface layer composed of a semiconductor layer and an insulating layer made of SiO ₂ is formed on the substrate surface opposite to the surface on which the light emitting device layer provided with the positive and negative electrodes is formed. By adjusting the film thickness, layer structure, film formation temperature, and the like of the layers, thermal stress applied to the light-emitting element layer can be reduced and warpage of the light-emitting element can be eliminated. As a result, the occurrence of crystal defects and cracks in the substrate and the light emitting element layer of the semiconductor light emitting element can be suppressed, the electrical characteristics of the light emitting element layer can be improved, and the yield can be improved. Further, the light emitting element is hardly deteriorated and the life is extended. Further, since warpage caused by thermal stress is eliminated, there are no problems in microfabrication at the time of manufacturing a light emitting element, peeling of an electrode or a protective film, and the light emitting element characteristics and reliability are excellent. Further, since there is no warp of the light emitting layer of the light emitting element, the parallelism of the mirror surfaces at both end faces is increased and the loss of light is reduced. Therefore, it becomes easy to produce a resonator structure with the end face of the light emitting layer as a mirror surface, the amplification gain of light by stimulated emission can be increased, and a high-density optical output can be obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on specific examples. The present invention is not limited to the following examples.
First embodiment In Fig. 1, a light emitting diode 10 has a sapphire substrate 1, and an AlN buffer layer 2 having a thickness of 0.05 m is formed on the sapphire substrate 1. On the buffer layer 2, in turn, a film thickness of about 2.5 [mu] m, an electron concentration 2 × ¹⁰ 18 / cm ³ of silicon (Si) of doped GaN high carrier concentration ^{n +} layer 3, a thickness of about 0. High carrier concentration n layer 4 made of silicon (Si) -doped (Al _x1 Ga _1-x1 ) _y1 In _1-y1 N with an electron concentration of 5 × 10 ¹⁷ / cm ³ , a film thickness of about 0.05 μm, Al _x2 Ga _1-x2 ) _y2 In _1-y2 N, silicon (Si) and zinc (Zn) added to 1 × 10 ¹⁸ / cm ³ , respectively, active layer 5, film thickness of about 1.0 μm, p-layer composed of magnesium (Mg) -doped (Al _x3 Ga _1-x3 ) _y3 In _1-y3 N with a hole concentration of 5 × 10 ¹⁷ / cm ³ , film thickness of about 0.2 μm, hole concentration of 7 × 10 of ¹⁷ / cm ³ magnesium Contact layer 7 made of GaN of beam (Mg) doped is formed. Furthermore, a metal electrode 8 connected to the contact layer 7 and a metal electrode 9 connected to the n ⁺ layer 3 are formed. On the back surface of the sapphire substrate, in order from the side closer to the substrate, a back buffer layer 12 of 0.05 μm AlN, a back surface GaN layer 13 made of GaN having a film thickness of about 4.3 μm, and SiO film having a film thickness of about 0.15 μm. _Two layers 14 are formed.
[0014]
The element layer is composed of a buffer layer 2, an n ⁺ layer 3, an n layer 4, an active layer 5, a p layer 6, and a contact layer 7. The back layer is a back buffer layer 12, a back GaN layer 13, and SiO _2. It is composed of layer 14.
[0015]
Next, a method for manufacturing the semiconductor element having this structure will be described.
The light emitting diode 10 was manufactured by vapor phase growth by metal organic chemical vapor deposition (hereinafter referred to as MOVPE).
The gases used were ammonia (NH ₃ ), carrier gas (H ₂ ), trimethyl gallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”), trimethyl aluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”). referred to as "TMA"), trimethylindium _{(In (CH 3) 3)} ( hereinafter referred to as "TMI"), silane _(SiH 4), diethylzinc _{(Zn (C 2 H 5)} 2) ( hereinafter, "DEZ" And cyclopentadienylmagnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter referred to as “CP ₂ Mg”).
[0016]
First, a single crystal sapphire substrate 1 having a thickness of 30 to 300 μm with the a-side cleaned by organic cleaning and heat treatment as the main surface and mirror-finished on both front and back surfaces is placed on the back surface of the susceptor mounted in the reaction chamber of the M0VPE apparatus. Wear with the face up. Next, the sapphire substrate 1 was baked at a temperature of 1100 ° C. while flowing H ₂ at normal pressure and a flow rate of 2 liters / minute into the reaction chamber for about 30 minutes.
[0017]
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 for about 90 seconds to make the back side of AlN The buffer layer 12 was formed to a thickness of about 0.05 μm. Next, the temperature of the sapphire substrate 1 is maintained at 1150 ° C., H ₂ is introduced at 20 liter / min, NH ₃ is introduced at 10 liter / min, and TMG is introduced at 1.7 × 10 ⁻⁴ mol / min for about 7 minutes, A back GaN layer 13 having a thickness of about 4.3 μm was formed. Next, a SiO ₂ layer 14 having a thickness of 0.15 μm was formed on the back GaN layer 13 by plasma CVD to obtain a structure as shown in FIG.
[0018]
Next, the sample was again mounted on the susceptor placed in the reaction chamber of the M0VPE apparatus with the surface facing up. Subsequently, the sapphire substrate 1 was baked at a temperature of 1100 ° C. while flowing H ₂ at normal pressure and a flow rate of 2 liters / minute into the reaction chamber for about 30 minutes.
Next, the temperature was lowered to 400 ° C., and H ₂ was supplied at 20 liters / minute, NH ₃ at 10 liters / minute, and TMA at 1.8 × 10 ⁻⁵ moles / minute for about 90 seconds to supply AlN 3. The buffer layer 2 was formed to a thickness of about 0.05 μm. Next, the temperature of the sapphire substrate 1 is maintained at 1150 ° C., H ₂ is 20 liters / minute, NH ₃ is 10 liters / minute, TMG is 1.7 × 10 ⁻⁴ mol / minute, and H ₂ gas is reduced to 0. Silane diluted to 86 ppm is introduced at 20 × 10 ⁻⁸ mol / min for 40 minutes, and a high carrier concentration of silicon (Si) -doped GaN having a film thickness of about 2.5 μm and an electron concentration of 2 × 10 ¹⁸ / cm ^3. An n ⁺ layer 3 was formed.
[0019]
After the high carrier concentration n ⁺ layer 3 is formed, the temperature is subsequently maintained at 1150 ° C., N ₂ or H ₂ is 10 liters / minute, NH ₃ is 10 liters / minute, and TMG is 1.12 × Silane diluted to 10 ⁻⁴ mol / min and 0.86 ppm from H ₂ gas was introduced at 1 × 10 ⁻⁸ mol / min for 7 minutes, and the film thickness was about 0.5 μm and the concentration was 5 × 10 ¹⁷ / cm. ^An n layer 4 made of ³ silicon-doped GaN was formed.
[0020]
Subsequently, the temperature is maintained at 850 ° C., N ₂ or H ₂ is 20 liters / minute, NH ₃ is 10 liters / minute, TMG is 1.53 × 10 ⁻⁴ mol / minute, and TMI is 0.02 × 10. ^-4 mol / min, silane diluted to 0.86 ppm with H ₂ was introduced at 10 × 10 ⁻⁸ mol / min and DEZ at 2 × 10 ⁻⁴ mol / min for 7 minutes, and the film thickness was about 0.05 μm. An active layer 5 made of In _0.08 Ga _0.92 N was formed. The active layer 5 has a Si and Zn concentration of 1 × 10 ¹⁸ / cm ³ and a carry concentration of 1 × 10 ¹⁸ / cm ³ .
[0021]
Subsequently, the temperature is maintained at 1100 ° C., N ₂ or H ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG is 1.12 × 10 ⁻⁴ mol / min, and TMA is 0.47 × 10. ^-4 mol / min and CP ₂ Mg were introduced at 2 × 10 ⁻⁴ mol / min for 60 minutes, and from about 0.0 μm magnesium (Mg) -doped Al _0.08 Ga _0.92 N A p-layer 6 was formed. The magnesium concentration of the p layer 6 is 1 × 10 ²⁰ / cm ³ . In this state, the p layer 6 is still an insulator having a resistivity of 10 ⁸ Ωcm or more. Next, the temperature is maintained at 1100 ° C., N ₂ or H ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG is 1.12 × 10 ⁻⁴ mol / min, and CP ₂ Mg is 2 A contact layer 7 made of GaN doped with magnesium (Mg) having a film thickness of about 0.2 μm was formed by introducing it at 4 × ^{4 −4} mol / min for 4 minutes. The magnesium concentration of the contact layer 7 is 2 × 10 ²⁰ / cm ³ . In this state, the contact layer 7 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.
[0022]
Next, the electron beam was uniformly irradiated to the contact layer 7 and the p layer 6 using the electron beam irradiation apparatus. The electron beam irradiation conditions are an acceleration voltage of about 10 KV, a data current of 1 μA, a beam moving speed of 0.2 mm / sec, a beam diameter of 60 μmφ, and a degree of vacuum of 5.0 × 10 ⁻⁵ Torr. By this electron beam irradiation, the contact layer 7 and the p layer 6 are formed into p-conductivity type semiconductors having a hole concentration of 7 × 10 ¹⁷ / cm ³ , 5 × 10 ¹⁷ / cm ³ , and resistivity of 2 Ωcm and 0.8 Ωcm, respectively. became. In this way, a wafer having a multilayer structure as shown in FIG. 3 was obtained.
[0023]
Subsequently, as shown in FIG. 4, in order to form the electrode 9, a part of the contact layer 7, p layer 6, active layer 5, and n layer 4 corresponding to that portion was removed by etching. Next, nickel (Ni) is uniformly deposited on the entire upper surface of the sample, and the electrodes 8 and 9 of the contact layer 7 and the n ⁺ layer 3 are formed through a photoresist coating, a photolithography process, and an etching process, respectively. did. Thereafter, the wafer processed as described above was cut for each element to obtain a light emitting diode having the structure shown in FIG. The light emitting diode 10 had a driving current of 20 mA, an emission peak wavelength of 430 nm, and an emission intensity of 1000 mcd.
[0024]
Next, the measurement result of the curvature of the sample when the back layer is formed and when it is not formed will be described. 6 shows the warpage of the sample when the back layer is not formed, and FIG. 7 shows the warp of the sample when the back layer is formed. When the back layer is not formed, it can be seen that the sample is greatly warped. Such warpage increases thermal stress, particularly stress at the interface between the element layer and the substrate, and crystal defects and cracks are liable to occur, adversely affecting element characteristics. As shown in FIG. 7, by forming the back surface layer, such warpage is almost eliminated, and generation of crystal defects and cracks can be suppressed.
[0025]
In this embodiment, a single layer is used as the active layer 5, but a single quantum well structure or a multiple quantum well structure may be used instead. Further, although GaN is used for the back layer, a semiconductor such as AlGaInN, GaAs, Si, ZnO ₂ , or an insulator such as SiO ₂ or Si ₃ N ₄ may be used.
[0026]
Further, sapphire and silicon carbide can be preferably used as the substrate, but ZnO and MgAl ₂ O ₄ can also be used.
The thickness of the substrate is preferably 30 to 300 μm. If it is thicker than 300 μm, it is difficult to cut each element, and if it is thinner than 30 μm, mechanical strength is small and handling is difficult.
Although the above embodiment has been described with respect to a light emitting diode, it can also be applied to laser diodes, photoelectric conversion elements, FETs, and other semiconductor elements.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a specific embodiment 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 configuration diagram showing a configuration of a conventional light emitting diode.
FIG. 6 is a measurement diagram in which the warpage of a sample when a back layer is not formed is measured.
FIG. 7 is a measurement diagram in which warpage of a sample when a back layer is formed is measured.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration n ⁺ GaN layer 4 ... GaN layer 5 ... Active layer 6 ... p layer 7 ... Contact layer 8, 9 ... Metal electrode 12 ... Back surface buffer layer 13 ... Back GaN layer 14 ... SiO ₂ layer

Claims (4)

A substrate made of a semiconductor or an insulator;
A light emitting device comprising a multi-layer formed of a group III nitride semiconductor (Al _x Ga _Y In _1-XY N; 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1) formed thereon Layers,
Positive and negative electrodes provided in the light emitting element layer;
A semiconductor light emitting device comprising: a semiconductor layer formed in order on a surface opposite to the surface on which the light emitting device layer is formed in the substrate ; and a back layer made of an insulating layer made of SiO ₂ . Semiconductor layer group III nitride semiconductor for forming the back surface layer; is a layer made of _{(Al x Ga Y In 1-} XY N 0 ≦ X ≦ 1,0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1) The semiconductor light emitting element according to claim 1. The semiconductor light-emitting element according to claim 1, wherein the substrate is sapphire or silicon carbide. The semiconductor light emitting element according to claim 1, wherein the substrate has a thickness of 30 to 300 μm.

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