JP2009272316A - Nitride-based semiconductor element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride-based semiconductor element for highly activating a p-type nitride-based semiconductor element with high reproducibility, and to provide a manufacturing method thereof. <P>SOLUTION: This method for manufacturing a nitride-based semiconductor element includes: a step of forming at least a single-layer nitride-based semiconductor layer (2, 3) on a substrate 1; a step of forming a p-type nitride-based semiconductor layer 4 doped with magnesium on the nitride-based semiconductor layer (2, 3); and a step of annealing the p-type nitride-based semiconductor layer 4 at 800-920°C in a nitride atmosphere. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nitride-based semiconductor device and a method for manufacturing the same, and more particularly to a nitride-based semiconductor device in which a p-type nitride-based semiconductor layer is highly activated and a method for manufacturing the same.

  Conventionally, nitride-based semiconductors have attracted attention as a material for light-emitting elements having a short wavelength because of the size of the band gap. In particular, compound semiconductors centered on gallium nitride (GaN) have been studied extensively and put into practical use as blue light emitting diodes and white light emitting diodes combined with phosphors.

  A semiconductor light emitting element such as a light emitting diode element or a laser element has a pn junction structure in which electrons and holes are recombined and light is emitted by the recombination. As conventionally known, a p-type nitride-based semiconductor layer obtained by containing Mg as a p-type impurity has a remarkably low Mg activation rate. It was not easy to obtain a layer.

As a method of manufacturing a p-type GaN-based semiconductor layer, after growing a GaN-based semiconductor layer doped with a p-type impurity, 400 atmosphere in an atmosphere that does not contain hydrogen gas, ammonia, or the like, that is, substantially does not contain hydrogen. A method of obtaining a low-resistance p-type GaN-based semiconductor layer by performing a heat treatment at a temperature equal to or higher than ° C. is known (see, for example, Patent Document 1). This method activates the p-type impurity by driving out hydrogen bonded to the p-type impurity from the GaN-based semiconductor layer doped with the p-type impurity, thereby reducing the resistance.
Japanese Patent Laid-Open No. 6-314821

  However, it has been found that even when the heat treatment temperature is 400 ° C. or higher, the degree of activation, for example, carrier concentration, mobility, or resistivity, is completely different depending on a certain temperature. That is, there is a problem that an activated p-type GaN-based semiconductor layer having a high carrier concentration cannot always be obtained with good reproducibility under conventional temperature conditions.

  An object of the present invention is to provide a nitride semiconductor device capable of activating a p-type nitride semiconductor layer with high reproducibility and a method for manufacturing the same.

  According to one aspect of the present invention for achieving the above object, a step of forming at least one nitride-based semiconductor layer on a substrate, and p-type nitridation doped with magnesium on the nitride-based semiconductor layer Provided is a method for manufacturing a nitride semiconductor device, comprising: a step of forming a physical semiconductor layer; and a step of annealing the p-type nitride semiconductor layer at 800 to 920 ° C. in a nitrogen atmosphere. Is done.

  According to another aspect of the present invention, a p-type nitride semiconductor layer annealed at 800 to 920 ° C. in a nitrogen atmosphere is provided on at least one nitride semiconductor layer disposed on a substrate. A nitride-based semiconductor device is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the nitride type semiconductor element which can highly activate a p-type nitride type semiconductor layer with high reproducibility, and its manufacturing method can be provided.

  A nitride semiconductor device and a method for manufacturing the same according to embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, differ from actual ones, and also include portions having different dimensional relationships and ratios between the drawings.

[First embodiment]
(Structure of nitride semiconductor device)
A nitride-based semiconductor light-emitting device as a nitride-based semiconductor device according to the first embodiment of the present invention will be described with reference to FIG.

  The nitride-based semiconductor device 10 according to the first embodiment of the present invention has a temperature of 800 to 920 ° C. in a nitrogen atmosphere on at least one nitride-based semiconductor layer (2, 3) disposed on the substrate 1. The p-type nitride-based semiconductor layer 4 is annealed in FIG.

  As shown in FIG. 1, a nitride semiconductor device 10 according to the present embodiment includes a substrate 1, an n-type nitride semiconductor layer 2, a light emitting layer 3, and a p-type nitride system formed on the substrate 1. Semiconductor layers 4 are sequentially stacked. An n-side electrode 5 is disposed on the upper surface of the n-type nitride-based semiconductor layer 2, and a p-side electrode 6 is disposed on the upper surface of the p-type nitride-based semiconductor layer 4 via the transparent electrode layer 7. Has been placed.

The substrate 1 is a substrate for growing a nitride-based semiconductor layer (2-4). Examples of the material of the substrate 1 include sapphire (Al ₂ O ₃ ), Si, SiC, GaAs, MgO, ZnO, spinel, and GaN.

The n-type nitride semiconductor layer 2 is for injecting electrons into the light emitting layer 3, and is formed on the substrate 1. The n-type nitride semiconductor layer 2 has a thickness of about 3 to 5 μm, for example, and is made of, for example, n-type GaN doped with Si having a carrier concentration of about 6 to 8 × 10 ¹⁷ atoms / cm ^3. .

  Between the substrate 1 and the n-type nitride-based semiconductor layer 2, a buffer layer 8 made of a thin amorphous or polycrystalline AlN or GaN film may be disposed in order to reduce the influence of lattice mismatch.

The light emitting layer 3 is for emitting blue light, for example, and is disposed on the n-type nitride semiconductor layer 2. Emitting layer 3 is, for example, a plurality of well layers consisting of about 2~3nm a thickness of about _{In X Ga 1-X N (} 0.05 ≦ X ≦ 0.2) ( not shown), for example, about 20nm From an MQW (Multi Quantum Well) structure having a thickness of about 0.05 to 0.15 μm, for example, in which a plurality of barrier layers (not shown) made of GaN having the following thicknesses are alternately stacked. Become.

The p-type nitride semiconductor layer 4 is for injecting holes into the light emitting layer 3 and is formed on the light emitting layer 3. The thickness is, for example, about 0.3 to 0.5 μm, and is made of, for example, p-type GaN doped with Mg having a carrier concentration of about 6 to 8 × 10 ¹⁷ atoms / cm ³ .

  In addition, although each nitride-based semiconductor layer uses a nitride-based semiconductor layer including a layer made of GaN or InGaN, the present invention is not limited to this, and a nitride-based semiconductor including a layer other than a layer made of GaN or InGaN A semiconductor layer, for example, a layer made of AlGaN, AlInGaN, or the like may be further used.

  The n-side electrode 5 is formed on the n-type nitride-based semiconductor layer 2 and has a thickness of about 0.1 to 0.3 μm, for example, and is made of, for example, aluminum (Al). The n-side electrode 5 is ohmically connected to the upper surface of the n-type nitride semiconductor layer 2. The n-side electrode 5 is disposed at a predetermined interval from the light emitting layer 3 and the p-type nitride-based semiconductor layer 4 in plan view.

  The p-side electrode 6 is disposed on the p-type nitride semiconductor layer 4 and is electrically connected to the p-type nitride semiconductor layer 4. The p-side electrode 6 may be connected to the p-type nitride semiconductor layer 4 through a transparent electrode layer 7 made of, for example, ITO (indium-tin oxide), MgO, ZnO, or the like. In this case, the light emitted from the light emitting layer 3 can be efficiently extracted from the p-side electrode 6 side. The p-side electrode 6 has a thickness of about 0.06 to 0.4 μm, for example, for example, Pa / Au having a thickness of about 0.01 to 0.2 μm and about 0.05 to about 0. It consists of a Ti / Au metal laminate structure with a thickness of 2 μm.

(Operating principle)
The operation principle of the nitride semiconductor device according to the embodiment of the present invention is as follows.

  First, when a forward voltage is applied between the n-side electrode 5 and the p-side electrode 6 via the n-side external electrode portion (not shown) and the p-side external electrode portion (not shown), the n-side Electrons are injected into the electrode 5 and holes are injected into the p-side electrode 6. The electrons injected into the n-side electrode 5 are injected into the light emitting layer 3 through the n-type nitride semiconductor layer 2. Holes injected into the p-side electrode 6 are injected into the light emitting layer 3 through the p-type nitride semiconductor layer 4. The electrons and holes injected into the light emitting layer 3 are recombined in the well layer to emit blue light of about 450 nm, for example. The emitted light is transmitted to the outside through the substrate 1.

(Nitride semiconductor device manufacturing method)
The nitride semiconductor device manufacturing method according to the first embodiment of the present invention includes at least one nitride semiconductor layer (2, 3) formed on a substrate 1, as shown in FIGS. A step of forming, a step of forming a p-type nitride-based semiconductor layer 4 doped with magnesium on the nitride-based semiconductor layer (2, 3), and a step of forming the p-type nitride-based semiconductor layer 4 in a nitrogen atmosphere. Annealing at 800-920 ° C.

  Below, a manufacturing process is explained in full detail.

(A) First, as shown in FIG. 2 (a), a substrate 1 made of a sapphire substrate is introduced into a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus (not shown) to form a substrate 1 The buffer layer 8 made of AlN is grown on the substrate 1 while maintaining the temperature of about 400 to 700 ° C. Next, the growth temperature is set to about 1050 ° C., and in this state, silane gas, trimethyl gallium (hereinafter referred to as TMG) gas and ammonia gas are supplied by a carrier gas, and from the n-type GaN doped with Si An n-type nitride semiconductor layer 2 is formed on the buffer layer 8.

(B) Next, as shown in FIG. 2B, in a state where the growth temperature is set to about 760 ° C., trimethylindium (hereinafter referred to as TMI) gas, TMG gas, and ammonia gas are mixed with the carrier gas. Then, a well layer made of non-doped InGaN is formed on the n-type nitride semiconductor layer 2. Next, with the growth temperature maintained at about 760 ° C., TMG gas and ammonia gas are supplied by a carrier gas to form a barrier layer made of non-doped GaN on the well layer. Thereafter, a plurality of well layers and barrier layers are alternately stacked under the same conditions to form the light emitting layer 3.

(C) Next, as shown in FIG. 2 (c), the process pressure is, for example, about 26.7 kPa (about 200 Torr) in a nitrogen atmosphere with the growth temperature maintained at about 1010 ° C., for example. ) TMG flow rate, for example, about 14 sccm [sccm: standard cc / min, that is, about 1 atm (atmospheric pressure 1,013 hPa), ccm = cm ³ / min normalized at 0 ° C.], and screw A p-type nitride semiconductor layer made of p-type GaN doped with Mg on the light emitting layer 3 by supplying a flow rate of ethylcyclopentadienylmagnesium (hereinafter referred to as EtCp2Mg) gas, for example, about 30 sccm. 4 is formed.

  Next, the p-type nitride semiconductor layer 4 is annealed at a temperature of about 800 to 920 ° C., preferably about 820 to 910 ° C., and more preferably about 840 to 910 ° C. The annealing time is, for example, about 5 to 15 minutes, preferably about 10 minutes.

  Thereby, the hole concentration in the p-type nitride semiconductor layer 4 can be increased. As the hole concentration increases, the resistivity also decreases, and the activation of the p-type nitride semiconductor layer 4 can be increased.

  The hole concentration of the p-type nitride semiconductor layer 4 is affected by the growth temperature of the p-type nitride semiconductor layer 4. The growth temperature of the p-type nitride-based semiconductor layer 4 is about 980 to 1040 ° C., preferably about 1000 to 1020 ° C., and more preferably about 1010 ° C. as described above. Thereby, the hole concentration in the p-type nitride semiconductor layer 4 can be increased.

The hole concentration of the p-type nitride semiconductor layer 4 is affected by the EtCp2Mg gas flow rate. The EtCp2Mg gas flow rate is about 20 to 40 sccm, preferably about 25 to 35 sccm, and more preferably about 30 sccm as described above. The number of moles of inflow varies depending on the temperature of the Mg raw material container (vapor pressure of the Mg raw material) and the pressure when the container is used (hydrogen inflow pressure) even if the flow rate sccm is constant. In the apparatus environment in the present embodiment, the flow rate of about 30 sccm was about 3 × 10 ⁻⁸ mol / min. Thereby, the hole concentration in the p-type nitride semiconductor layer 4 can be increased. At that time, the EtCp2Mg gas / TMG flow ratio is preferably about 30/14. Thereby, the hole concentration can be further increased. When the ratio of the EtCp2Mg gas flow rate is increased, the crystallinity is deteriorated. On the other hand, when the ratio of the EtCp2Mg gas flow rate is decreased, the hole concentration is decreased, which is not preferable.

(D) Next, as shown in FIG. 3D, an etching mask layer 20 is formed on a predetermined region of the p-type nitride semiconductor layer 4, and this etching mask layer 20 is used to form a p-type nitride system. A predetermined region of the semiconductor layer 4, the light emitting layer 3, and the n-type nitride semiconductor layer 2 is etched using, for example, plasma containing chlorine using a plasma processing apparatus such as an RIE (Reactive Ion Etching) apparatus. . As a result, a ridge composed of the p-type nitride semiconductor layer 4, the light emitting layer 3, and the n-type nitride semiconductor layer 2 is formed. After the etching, the etching mask layer 20 is removed.

(E) Next, as shown in FIG. 3E, a transparent electrode layer 7 made of, for example, ZnO is formed on the p-type nitride semiconductor layer 4 by vapor deposition. Next, after forming a resist film so that a part of the transparent electrode layer 7 is exposed, a p-side electrode 6 made of a Pa / Au film and a Ti / Au film is formed by a vapor deposition method or the like. Thereafter, the Pa / Au film and the Ti / Au film on the resist film are removed together with the resist film while leaving the p-side electrode 6. Next, in the same manner, an n-side electrode 5 made of Al is formed by vapor deposition or the like, and the nitride semiconductor device 10 shown in FIG. 1 is completed.

  The method for crystal growth of each nitride-based semiconductor layer is not limited to the method using the MOCVD apparatus described above. The nitride semiconductor layers may be crystal-grown using HVPE (Hydride Vapor Phase Epitaxy), gas source MBE (Molecular Beam Epitaxy), or the like.

(Example)
As an example, the nitride semiconductor device 10 manufactured by the nitride semiconductor device manufacturing method according to the present embodiment is characterized by the characteristics of the hole concentration and resistivity with respect to the annealing temperature of the p-type nitride semiconductor layer 4. Is shown in FIG.

  In the embodiment, in the production of the p-type nitride semiconductor layer 4, the growth conditions of the p-type nitride semiconductor layer 4 are as follows: growth temperature = about 1010 ° C., growth process pressure = about 200 Torr, reaction gas flow rate: TMG = about 14 sccm and EtCp2 = about 30 sccm, and the annealing conditions were an annealing time of about 10 minutes in a nitrogen atmosphere. On the other hand, as a comparative example, except that annealing was performed in a nitrogen / oxygen atmosphere instead of a nitrogen atmosphere, the conditions were the same as described above, and the results are shown in FIG. However, the flow rate ratio of nitrogen / oxygen was about 1 slm (slm: standard liter / min) /0.2 slm.

As shown in FIG. 4A, the hole concentration in the p-type nitride-based semiconductor layer 4 shows a peak when the annealing temperature is about 850 ° C., and shows a high concentration of about 7.3 × 10 ¹⁷ / cm ^3. It was. The hole concentration is high when the annealing temperature is in the range of about 800 to 920 ° C., particularly in the range of about 840 to 910 ° C. When the annealing temperature is outside the range of about 800 to 920 ° C., the hole concentration is lowered. Moreover, as shown in FIG.4 (b), in the range whose annealing temperature is about 800-920 degreeC, the resistivity showed a favorable value compared with other temperature.

On the other hand, in the comparative example, as shown in FIG. 5A, the hole concentration in the p-type nitride-based semiconductor layer 4 is about 5.8 × 10 ¹⁷ / cm ³ when the annealing temperature is about 850 ° C. Also, at other annealing temperatures, the concentration was lower than the peak concentration in the example (broken line in FIG. 5A). Moreover, as shown in FIG.5 (b), in the range whose annealing temperature is about 800-920 degreeC, the resistivity showed a high value compared with the Example.

  According to the method for manufacturing a nitride-based semiconductor element according to the present embodiment, carrier concentration and resistance are obtained by annealing the p-type nitride-based semiconductor layer 4 within a range of 800 to 920 ° C. in a nitrogen atmosphere. A nitride-based semiconductor element 10 having a good rate can be obtained.

  According to nitride-based semiconductor element 10 according to the present embodiment, the carrier concentration of p-type nitride-based semiconductor layer 4 is increased, so that the hole injection efficiency is increased and the luminance can be increased. Further, since the resistivity decreases, it is possible to drive with a low driving voltage.

  According to the nitride semiconductor device and the manufacturing method thereof according to the present embodiment, the p-type nitride semiconductor layer 4 can be activated with high reproducibility.

[Other embodiments]
As described above, the present invention has been described in detail according to the above-described first embodiment. However, for those skilled in the art, the present invention is not limited to the first embodiment described in this specification. Is clear. The present invention can be implemented as modifications and changes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention. Hereinafter, a modified embodiment in which the first embodiment described above is partially modified will be described.

  For example, it is possible to change the thickness of each layer of the nitride-based semiconductor layer and the constituent material.

  In the method for manufacturing the nitride semiconductor device 10 according to the first embodiment described above, the method for manufacturing a semiconductor light emitting device using light emitted from the light emitting layer 3 of the nitride semiconductor layer has been described. However, the present invention is not limited to this, and the present invention can also be used for manufacturing a light emitting element that combines a semiconductor laser and a phosphor that uses emission light from these light emitting elements as excitation light. Further, it can be applied to a power device having a nitride-based semiconductor layer and an electronic device such as a HEMT (High Electron Mobility Transistor).

1 is a schematic cross-sectional structure diagram of a nitride-based semiconductor device according to a first embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of the manufacturing method of the nitride-type semiconductor element which concerns on the 1st Embodiment of this invention, Comprising: (a) Process drawing which forms the n-type nitride-type semiconductor layer 2 on the board | substrate 1, (b) FIG. 5 is a process diagram for forming the light emitting layer 3 on the n-type nitride semiconductor layer 2; and (c) a process diagram for forming the p-type nitride semiconductor layer 4 on the light emitting layer 3. It is explanatory drawing of the manufacturing method of the nitride-type semiconductor element which concerns on the 1st Embodiment of this invention, Comprising: (d) The process of etching the n-type nitride-type semiconductor layer 2 in order to form the n side electrode 5 FIG. 4E is a process diagram for forming an n-side electrode 5 and a p-side electrode 6. It is a figure which shows the characteristic of the nitride type semiconductor element which concerns on the 1st Embodiment of this invention, Comprising: (a) The characteristic figure which shows the relationship between annealing temperature and hole concentration, (b) Annealing temperature and resistivity The characteristic view which shows the relationship. It is a figure which shows the characteristic of the nitride type semiconductor element of a comparative example, Comprising: (a) The characteristic figure which shows the relationship between annealing temperature and hole concentration, (b) The characteristic figure which shows the relationship between annealing temperature and resistivity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... N-type nitride semiconductor layer 3 ... Light emitting layer 4 ... P-type nitride semiconductor layer 5 ... N side electrode 6 ... P side electrode 7 ... Transparent electrode layer 8 ... buffer layer 10 ... nitride semiconductor element

Claims (3)

Forming at least one nitride-based semiconductor layer on the substrate;
Forming a magnesium doped p-type nitride semiconductor layer on the nitride semiconductor layer;
Annealing the p-type nitride-based semiconductor layer at 800-920 ° C. in a nitrogen atmosphere.   The method of manufacturing a nitride semiconductor device according to claim 1, wherein the annealing time is 5 to 15 minutes.   A nitride semiconductor device comprising a p-type nitride semiconductor layer annealed at 800 to 920 ° C. in a nitrogen atmosphere on at least one nitride semiconductor layer disposed on a substrate.

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