JP2006222225A - Method of manufacturing p-type nitride semiconductor and semiconductor apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a p-type nitride semiconductor capable of activating p-type impurities while controlling the shortage of nitrogen, and to provide a method of manufacturing a semiconductor apparatus using it. <P>SOLUTION: After forming a nitride semiconductor 12 including p-type impurities, the p-type impurities are activated by heat treatment in atmosphere containing such a halogenated nitrogen gas as NF<SB>3</SB>. Since the halogenated nitrogen gas is decomposed at low temperature of 200°C or less so that nitrogen and halogen may be produced, the discharge of hydrogen can be promoted by making halogen draw hydrogen contained in the nitride semiconductor 12, while enabling it to suppress the coming-off of nitrogen from the nitride semiconductor 12 caused by nitrogen. Therefore, the p-type impurities can be activated, while controlling the shortage of nitrogen. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a p-type nitride semiconductor including a step of activating p-type impurities, and a method for manufacturing a semiconductor element using the same.

  GaN, AlGaN mixed crystals, GaInN mixed crystals, or nitride semiconductors added with any amount of boron (B) to these can be used from the far infrared region to the ultraviolet region by using a quantum cascade structure or quantum well structure for the light emitting layer. It is promising as a constituent material of a light-emitting element capable of obtaining a wide emission wavelength band up to a region or as a constituent material of an electronic element. In particular, light emitting diodes (LEDs) using nitride semiconductors have already been put into practical use and are attracting great attention. In addition, the realization of a semiconductor laser (LD; Laser Diode) using a nitride semiconductor has been reported, and applications such as a light source of an optical disk device are expected.

  By the way, in order to obtain excellent characteristics in such an element, it is important that the electrode is satisfactorily in ohmic contact with the semiconductor to reduce the contact resistance. For example, for an n-type semiconductor, a relatively high carrier concentration can be obtained by adding an n-type impurity such as silicon (Si), but for a p-type semiconductor, a p-type impurity such as magnesium (Mg) is added. Even if it is added, since it is bonded to hydrogen (H), the activation rate is low, and it is difficult to obtain a sufficient carrier concentration. Therefore, it is necessary to activate the p-type impurity.

As a method for activating the p-type impurity, a method of performing heat treatment at a temperature of 400 ° C. or higher in a nitrogen atmosphere or the like (see Patent Document 1), a method of irradiating an electron beam in a vacuum (see Patent Document 2), or nitrogen A method of applying a high-frequency electric field in an atmosphere or the like (see Patent Document 3) has been reported.
Japanese Patent No. 2540791 Japanese Patent No. 2587825 JP 2001-351925 A

  However, although these methods can activate p-type impurities, it takes time for p-type activation, or nitrogen (N) escapes from the nitride semiconductor and crystallinity decreases. There was a problem that it might end.

  The present invention has been made in view of such problems, and an object of the present invention is to produce a p-type nitride semiconductor capable of activating p-type impurities while suppressing escape of nitrogen, and a semiconductor using the same. The object is to provide a method for manufacturing an element.

  The method for producing a p-type nitride semiconductor according to the present invention performs a process of activating a p-type impurity in an atmosphere containing a nitrogen halide gas for a nitride semiconductor containing a p-type impurity.

  The method for manufacturing a semiconductor device according to the present invention includes a step of performing a process of activating a p-type impurity in an atmosphere containing a nitrogen halide gas for a nitride semiconductor containing the p-type impurity.

  According to the method for manufacturing a p-type nitride semiconductor of the present invention and the method for manufacturing a semiconductor device according to the present invention, a p-type impurity is activated in an atmosphere containing a nitrogen halide gas. It is possible to prevent nitrogen from being released from the nitride semiconductor due to the nitrogen generated by the decomposition of. In addition, the halogen generated by the decomposition of the nitrogen halide gas can attract hydrogen contained in the nitride semiconductor and promote the release of hydrogen. Therefore, the p-type impurity can be activated while suppressing the escape of nitrogen.

  In particular, since the nitrogen halide gas is decomposed even at a low temperature, when the p-type impurity is activated by heat treatment, the p-type impurity can be easily activated even at a low temperature of, for example, 600 ° C. or lower. Therefore, it is possible to further suppress the escape of nitrogen, and it is possible to suppress the deterioration even when a layer having a large deterioration due to heat is included. Therefore, the performance and reliability of the semiconductor element can be improved.

  Further, if the treatment is performed in an atmosphere containing a nitrogen halide gas and an inert gas, it is possible to suppress the formation of a halide on the surface of the nitride semiconductor.

  Furthermore, if the treatment is performed in an atmosphere containing at least one of oxygen gas and carbon dioxide gas in addition to nitrogen halide gas or nitrogen halide gas and inert gas, the type of nitride semiconductor crystal Accordingly, the force of attracting hydrogen contained in the crystal can be finely controlled to drive out hydrogen or hydrogen ions out of the crystal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows one step in a method for manufacturing a p-type nitride semiconductor according to an embodiment of the present invention. Note that a nitride semiconductor means at least one of group 13 elements of a long-period periodic table made of gallium (Ga), aluminum (Al), indium (In), boron, and the like, nitrogen, arsenic (As ) And phosphorus (P), etc., and those containing at least nitrogen among group 15 elements of the periodic table. Specifically, there are GaN, AlGaN mixed crystal, GaInN mixed crystal, AlGaInN mixed crystal, GaNAs mixed crystal, AlGaNAs mixed crystal, GaInNAs mixed crystal, AlGaInNAs mixed crystal, or a mixed crystal obtained by adding an arbitrary amount of boron to these. is there.

First, as shown in FIG. 1, for example, magnesium is formed on the c-plane of the substrate 11 made of sapphire (α-Al ₂ O ₃ ) by MOCVD (Metal Organic Chemical Vapor Deposition) method. The nitride semiconductor 12 containing the p-type impurity is grown.

At that time, for example, trimethyl gallium ((CH ₃ ) ₃ Ga) or triethyl gallium ((C ₂ H ₅ ) ₃ Ga) is used as a gallium source gas, and trimethyl aluminum ((CH ₃ ) ₃ Al is used as an aluminum source gas. ), For example, trimethylindium ((CH ₃ ) ₃ In) for a source gas of indium, for example, trimethylboron ((CH ₃ ) ₃ B) for a source gas of boron, for example, ammonia (NH ₃ ) for a source gas of nitrogen Examples of magnesium source gas include bis = cyclopentadienyl magnesium ((C ₅ H ₅ ) ₂ Mg), methyl cyclopentadienyl magnesium ((CH ₃ ) (C ₅ H ₅ ) Mg), or ethyl cyclopentadi Enilmagnesium ((C ₂ H ₅ ) (C ₅ H ₅ ) Mg) is used.

  The grown nitride semiconductor 12 contains hydrogen atoms, and activation of the p-type impurity is inhibited by the bond with the hydrogen. In addition to magnesium, examples of p-type impurities include beryllium (Be), calcium (Ca), and zinc (Zn), and a mixture of two or more of these may be used.

  Next, the nitride semiconductor 12 is heat-treated in an atmosphere containing a nitrogen halide gas to activate p-type impurities. At that time, the nitrogen halide gas is decomposed to generate nitrogen and halogen, which suppresses the escape of nitrogen from the nitride semiconductor 12 by nitrogen and attracts the hydrogen contained in the nitride semiconductor 12 by the halogen to promote the release. . Nitrogen halide gas is decomposed even at a low temperature of 200 ° C. or lower, and the release of hydrogen can be promoted by halogen, so that the p-type impurity is easily activated even when the heat treatment temperature is as low as 600 ° C. or lower. . Therefore, when the p-type impurity is activated by heat treatment, the activation rate of the p-type impurity is high when the processing temperature is increased, but nitrogen is released from the nitride semiconductor 12, and when the processing temperature is lowered, the nitrogen is released. However, there is a problem that the activation rate of the p-type impurity decreases, but the activation rate of the p-type impurity can be increased even when the processing temperature is lowered by using a nitrogen halide gas. In addition, nitrogen escape can be further suppressed.

Examples of the halogenated nitrogen gas include nitrogen trifluoride (NF ₃ ) gas, nitrogen trichloride (NCl ₃ ) gas, and bromine trichloride (NBr ₃ ) gas. As the halogenated nitrogen gas, one kind may be used alone, or two or more kinds may be mixed and used, and among these, nitrogen fluoride gas is preferable. This is because halogen is an element having a high electronegativity, but fluorine has the highest electronegativity not only in the halogen but also in other elements, and therefore has a large power to attract hydrogen.

The atmosphere during the heat treatment may be only nitrogen halide gas, but it is preferable to use a mixed gas of nitrogen halide gas and inert gas. In this case, the concentration of nitrogen halide gas is, for example, 0.1 mol% to 50 mol. % Is preferable. This is because the effects described above can be obtained even with a small amount of nitrogen halide gas, and if the concentration of the nitrogen halide gas is high, a film of halide may be formed on the surface of the nitride semiconductor 12. Examples of the inert gas include nitrogen (N ₂ ) gas, helium (He) gas, argon (Ar) gas, and neon (Ne) gas. Among these, nitrogen gas is preferable from the viewpoint of versatility.

In addition, oxygen (O ₂ ) gas, carbon dioxide (CO ₂ ) gas, or both may be mixed in a halogenated nitrogen gas or a mixed gas of a halogenated nitrogen gas and an inert gas. Oxygen gas and carbon dioxide gas also have an action of attracting hydrogen contained in the nitride semiconductor 12, but the force differs depending on the substance, so that it can be used depending on the type of crystal of the nitride semiconductor 12. This is because the force of attracting hydrogen in the crystal can be finely controlled. In this case, the concentration of oxygen gas or carbon dioxide gas is preferably 0.1 mol% to 50 mol%, for example.

  The heat treatment temperature is preferably 250 ° C. or more and 600 ° C. or less, for example, and the treatment time is preferably about 5 to 60 minutes. In the case of a nitride semiconductor that is not significantly deteriorated by heat, it may be processed at a temperature higher than this, but a nitride semiconductor containing indium that is greatly deteriorated by heat, for example, GaInN mixed crystal, InN mixed crystal, GaInNAs In the case of a mixed crystal, an AlGaInNAs mixed crystal, an AlGaInN mixed crystal, a BGaInN mixed crystal, a BInN mixed crystal, a BInNAs mixed crystal, a BAlInN mixed crystal, a BAlGaInNAs mixed crystal, or a BAlGaInN mixed crystal, such a low temperature is preferable. . However, if the temperature is too low, it takes time to activate the p-type impurity, and therefore, if it is in the range of 500 ° C. or higher and 600 ° C. or lower, the processing time can be shortened, which is preferable.

  Thereby, a p-type nitride semiconductor is obtained.

  Next, a method for manufacturing a semiconductor element using this method for manufacturing a p-type nitride semiconductor, specifically, a method for manufacturing a light emitting element such as an LED or an LD will be described.

  FIG. 2 shows a layer structure of a light-emitting element manufactured using the method for manufacturing a p-type nitride semiconductor according to the present embodiment. First, for example, a substrate 21 made of sapphire is prepared, and each layer that is an n-type nitride semiconductor layer is grown on the c-plane of the substrate 21 by MOCVD. Specifically, for example, an n-type first contact layer 22 made of an n-type GaN or n-type AlGaN mixed crystal to which silicon as an n-type impurity is added, an n-type GaInN mixed crystal or an n-type AlGaInN mixed crystal to which silicon is added. N-type second contact layer 23 made of silicon, n-type cladding layer 24 made of silicon-doped n-type GaN or n-type AlGaN mixed crystal, silicon-doped n-type GaN, n-type GaInN mixed crystal or n-type AlGaInN mixed crystal The first guide layer 25 made of these is sequentially grown. Note that boron may be added to at least one of these layers, and the first guide layer 25 may not be n-type without adding n-type impurities. Further, only one of the n-type first contact layer 22 and the n-type second contact layer 23 may be formed. In the case of an LED, the n-type cladding layer 24 may not be formed. .

Then, on the n-type nitride semiconductor layer, for example, different B _x compositions by MOCVD _{Al y Ga z In 1- (x} + y + z) N mixed crystal layer (where, 1 ≧ x ≧ 0, 1 An active layer 26 having a multiple quantum well structure laminated by combining ≧ y ≧ 0, 1 ≧ z ≧ 0, x + y + z = 1) is grown. At that time, at least indium is added to the well layer.

  Subsequently, each layer, which is a nitride semiconductor layer containing a p-type impurity, is grown on the active layer 26 by, for example, MOCVD. Specifically, for example, a second guide layer 27 made of GaN, GaInN mixed crystal or n-type AlGaInN mixed crystal to which magnesium is added, a p-type cap layer made of AlGaN mixed crystal or n-type AlGaInN mixed crystal to which magnesium is added ( p-type barrier layer) 28, p-type cladding layer 29 made of GaN or AlGaN mixed crystal to which magnesium is added, p-type first contact layer 30 made of GaN or GaNAs mixed crystal to which magnesium is added, GaInN mixed crystal to which magnesium is added , GaInNAs mixed crystal or AlGaInNAs mixed crystal is sequentially grown. Note that boron may be added to at least one of these layers, and the second guide layer 27 may not be p-type without adding p-type impurities. Only one of the p-type first contact layer 30 and the p-type second contact layer 31 may be formed. In the case of an LED, the p-type cladding layer 29 may not be formed. .

  Thereafter, in the same manner as in the above-described method for manufacturing a p-type nitride semiconductor, heat treatment is performed in an atmosphere containing a nitrogen halide gas, and the second guide layer 27, the p-type cap layer 28, the p-type cladding layer 29, The p-type impurities contained in the p-type first contact layer 30 and the p-type second contact layer 31 are activated. At that time, the active layer 26 in which the well layer is composed of a nitride semiconductor containing indium is greatly deteriorated by heat, but according to the present embodiment, it can be processed at a low temperature of 600 ° C. or lower. Deterioration can be suppressed.

  Further, a resist pattern (not shown) having a stripe shape is formed on the p-type second contact layer 31 in correspondence with a formation position of an n-side electrode 32 described later. Thereafter, the p-type second contact layer 31, the p-type first contact layer 30, the p-type cladding layer 29, and the p-type cap layer are formed by, for example, RIE (Reactive Ion Etching) using this resist pattern as a mask. 28, the second guide layer 27, the active layer 26, the first guide layer 25, and the n-type cladding layer 24 are selectively removed in order, and the n-type second contact layer 23 is exposed. Next, the resist pattern (not shown) is removed, and the n-side electrode 32 is formed on the exposed n-type second contact layer 23. A p-side electrode 33 is formed on the p-type second contact layer 31. Thereby, the light emitting element shown in FIG. 2 is completed.

  As described above, according to the present embodiment, since the p-type impurity is activated in the atmosphere containing the nitrogen halide gas, the nitrogen generated by the decomposition of the nitrogen halide gas causes the nitride semiconductor to be activated. The release of nitrogen can be suppressed, and the halogen generated by the decomposition of the nitrogen halide gas can attract the hydrogen contained in the nitride semiconductor and promote the release of hydrogen. Further, since the nitrogen halide gas is decomposed even at a low temperature, the p-type impurity can be easily activated even at a low temperature of, for example, 600 ° C. or lower.

  Therefore, it is possible to suppress the escape of nitrogen, and it is possible to suppress the deterioration even when a layer having a large deterioration due to heat is included. In particular, in the manufacture of a semiconductor device, there is a case where a layer that is greatly deteriorated by heat is already formed before forming the p-type nitride semiconductor layer. However, the present invention is not limited to the p-type nitride semiconductor layer. Degradation can also be suppressed for the layer. Therefore, the performance and reliability of the semiconductor element can be improved.

  Further, if the treatment is performed in an atmosphere containing a nitrogen halide gas and an inert gas, it is possible to suppress the formation of a halide on the surface of the nitride semiconductor.

  Furthermore, if the treatment is performed in an atmosphere containing at least one of a nitrogen halide gas or a nitrogen halide gas and an inert gas and at least one of an oxygen gas and a carbon dioxide gas, the type of nitride semiconductor crystal can be reduced. Accordingly, the force that attracts hydrogen contained in the crystal can be finely controlled to drive out hydrogen or hydrogen ions to the outside of the crystal.

  While the present invention has been described with reference to the embodiment and examples, the present invention is not limited to the above embodiment and can be variously modified. For example, in the above embodiment, the case where the p-type impurity is activated by the heat treatment has been described. However, the p-type impurity may be activated by another method. Other methods for activating the p-type impurity include, for example, irradiation with an electron beam (see Patent Document 2) or application of a high-frequency electric field (see Patent Document 3), which also includes an atmosphere containing a nitrogen halide gas. If the treatment is performed inside, it is possible to suppress the escape of nitrogen from the nitride semiconductor.

  In the above embodiment, the case where the nitride semiconductor 12 is grown by the MOCVD method has been described. However, the MBE (Molecular Beam Epitaxy) method, the MOMBE (Metal Organic Molecular Beam Epitaxy) method, and the like. It may be formed by other methods such as a method, a hydride vapor phase growth method or a halide vapor phase growth method. The hydride vapor phase growth method is a vapor phase growth method in which hydride (hydride) contributes to the reaction or transport of the source gas, and the halide vapor phase growth method is a reaction in which the halide (halide) is reacted or the source gas. It is a vapor phase growth method that contributes to the transport of methane.

Further, in the above embodiment, the substrates 11 and 21 made of planar (planar) sapphire are used, but ZnO, AlN, Si, spinel (MgAl ₂ O ₄ ), GaN, SiC, GaAs, GaP or A substrate made of another material such as InP may be used. Further, a recess type substrate in which a concave portion is formed by etching the planar type substrate with an arbitrary mask pattern may be used.

  In addition, in the above-described embodiment, a method for manufacturing a light emitting device such as an LED or LD has been described as a specific example of a method for manufacturing a semiconductor device. The present invention can also be applied to the case of manufacturing other semiconductor elements that require a type nitride semiconductor.

It is sectional drawing showing 1 process of the manufacturing method of the p-type nitride semiconductor which concerns on one embodiment of this invention. It is sectional drawing showing the structure of the semiconductor laser produced using the manufacturing method of the p-type nitride semiconductor which concerns on one embodiment of this invention.

Explanation of symbols

11, 21 ... substrate, 12 ... nitride semiconductor, 22 ... n-type first contact layer, 23 ... n-type second contact layer, 24 ... n-type cladding layer, 25 ... first guide layer, 26 ... active layer, 27 2nd guide layer, 28 ... p-type cap layer, 29 ... p-type cladding layer, 30 ... p-type first contact layer, 31 ... p-type second contact layer, 32 ... n-side electrode, 33 ... p-side electrode.

Claims (12)

  A method for producing a p-type nitride semiconductor, comprising: performing a treatment for activating a p-type impurity in an atmosphere containing a nitrogen halide gas for a nitride semiconductor containing a p-type impurity.   The method for producing a p-type nitride semiconductor according to claim 1, wherein a treatment for activating the p-type impurity is performed in an atmosphere containing an inert gas in addition to the halogenated nitrogen gas.   The method for producing a p-type nitride semiconductor according to claim 2, further comprising a step of activating the p-type impurity in an atmosphere containing at least one of oxygen gas and carbon dioxide gas.   2. The p-type nitride semiconductor according to claim 1, wherein a treatment for activating the p-type impurity is performed in an atmosphere containing at least one of oxygen gas and carbon dioxide gas in addition to nitrogen halide gas. Manufacturing method.   2. The production of a p-type nitride semiconductor according to claim 1, wherein at least one selected from the group consisting of nitrogen trifluoride gas, nitrogen trichloride gas and bromine trichloride gas is used as the nitrogen halide gas. Method.   As the p-type impurity, a nitride semiconductor including at least one selected from the group consisting of magnesium (Mg), beryllium (Be), calcium (Ca), and zinc (Zn) is activated. The method for producing a p-type nitride semiconductor according to claim 1.   A method of manufacturing a semiconductor device, comprising: a step of activating a p-type impurity in an atmosphere containing a nitrogen halide gas for a nitride semiconductor containing a p-type impurity.   8. The method of manufacturing a semiconductor device according to claim 7, wherein a treatment for activating the p-type impurity is performed in an atmosphere containing an inert gas in addition to the halogenated nitrogen gas.   9. The method of manufacturing a semiconductor element according to claim 8, further comprising a step of activating the p-type impurity in an atmosphere containing at least one of oxygen gas and carbon dioxide gas.   8. The method of manufacturing a semiconductor device according to claim 7, wherein a treatment for activating the p-type impurity is performed in an atmosphere containing at least one of oxygen gas and carbon dioxide gas in addition to nitrogen halide gas. .   8. The method of manufacturing a semiconductor element according to claim 7, wherein at least one selected from the group consisting of nitrogen trifluoride gas, nitrogen trichloride gas, and bromine trichloride gas is used as the nitrogen halide gas. As the p-type impurity, a nitride semiconductor including at least one selected from the group consisting of magnesium (Mg), beryllium (Be), calcium (Ca), and zinc (Zn) is activated. 8. A method of manufacturing a semiconductor device according to claim 7, wherein:

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