JP2012099617A - Compound semiconductor device and method for manufacturing compound semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound semiconductor device capable of reducing an interface state between a GaN layer and an insulating layer, and realizing good electric characteristics by improving a mobility, and a method for manufacturing the device.SOLUTION: A base layer 12, a superlattice buffer layer 13, a GaN layer 14 and a coating layer 15 are sequentially stacked on a substrate 11. The coating layer 15 comprises AlGaGdN as a mixed crystal of a nitride of a group III element (for example, AlGaN) and a nitride of lanthanoid (for example, GdN), and has a thickness of 20 nm. An insulating layer 16 arranged between a source region 17 and a drain region 18 is an oxynitride formed by oxidizing the coating layer 15 covering the GaN layer 14.

Description

  The present invention relates to a III-V nitride-based compound semiconductor device including a GaN layer and a method for manufacturing the same.

  Nitride III-V compound semiconductors are being applied to various semiconductor devices because they have a larger band gap than silicon, can operate at high temperatures, and can withstand high voltages. . For example, application to a field effect transistor has been proposed.

  When applied to a field effect transistor, a gate insulating film is required. Various oxide films have been proposed as gate insulating films in field effect transistors to which nitride-based III-V group compound semiconductors are applied (see, for example, Patent Documents 1 to 8).

Patent Document 1 discloses a Ga ₂ O ₃ layer obtained by oxidizing a GaN layer, and Patent Document 2 discloses an oxide of Al containing nitrogen (AlON). That is, in the case of Patent Document 1 and Patent Document 2, Ga ₂ O ₃ and AlON are formed by oxidizing GaN or AlN on the outermost surface after forming a nitride-based III-V compound semiconductor. . However, in order to oxidize GaN and AlN, high energy (high temperature) is required, and since the dislocation portion is easily oxidized selectively, a steep interface between the oxide layer and the nitride semiconductor layer is not formed. There is a problem that the expected effect cannot be obtained.

Patent Document 3 discloses a high dielectric material having a relative dielectric constant of 10 or more, Patent Document 4 discloses a SiO ₂ film obtained by oxidizing a Si single crystal thin film, and Patent Document 5 discloses Ta, An oxide of Hf, HfAl, La, and Y is disclosed, Patent Document 6 discloses a halide, and Patent Document 7 discloses an oxide having a work function of 5.6 eV or more and conductivity. Patent Document 8 discloses a dielectric (HfAlO) having a relative dielectric constant of 9 or more and 22 or less.

  In other words, in the case of Patent Documents 3 to 8, oxides are deposited by another method (for example, a sputtering method or the like) after forming a nitride-based III-V compound semiconductor. However, since the process is discontinuous, there is a problem that the interface state cannot be sufficiently reduced.

JP 2002-329863A JP 2005-183597 A JP 2002-324813 A JP 2005-268507 A JP 2006-245317 A JP 2007-81346 A JP 2007-149794 A JP 2007-281453 A

The conventional field effect transistor as described above has a problem that sufficient mobility cannot be obtained and necessary electrical characteristics cannot be obtained. The reason why sufficient mobility cannot be obtained is that the interface state is large at the interface between the nitride III-V compound semiconductor (eg, GaN) and the insulating film (eg, SiO ₂ ) formed on the surface thereof. Can be considered.

  The present invention has been made in view of such a situation, and by applying an insulating layer formed of an oxynitride obtained by oxidizing a mixed crystal of a nitride of a group III element and a nitride of a lanthanoid, a GaN layer An object of the present invention is to provide a compound semiconductor device that realizes excellent electrical characteristics by reducing the interface state between the insulating layer and the insulating layer and improving mobility.

  Further, the present invention forms an insulating layer in which a mixed crystal of a group III element nitride and a lanthanoid nitride is oxidized to form an oxynitride in the GaN layer. Another object of the present invention is to provide a method of manufacturing a compound semiconductor device having excellent electrical characteristics by suppressing generated interface states and increasing carrier mobility in a GaN layer.

  The compound semiconductor device according to the present invention is a group III-V nitride compound semiconductor device including a GaN layer and an insulating layer stacked on the GaN layer, wherein the insulating layer is a nitride of a group III element. It is characterized in that it is formed of an oxynitride obtained by oxidizing a mixed crystal of an oxide and a lanthanoid nitride.

  Therefore, in the compound semiconductor device according to the present invention, the insulating layer covering the GaN layer is an acid obtained by oxidizing a mixed crystal of a nitride of a group III element and a lanthanoid nitride that is easily oxidized as compared with the group III element. Since it is formed of nitride, the insulating layer stacked on the GaN layer can be formed with less energy, and the function as a semiconductor layer is realized by suppressing the number of interface states generated between the GaN layer and the insulating layer. In this case, the mobility required for this is greatly improved, and the electrical characteristics are improved to realize excellent electrical characteristics.

  In the compound semiconductor device according to the present invention, the band gap of the insulating layer is larger than the band gap of the GaN layer.

  Therefore, the compound semiconductor device according to the present invention reliably realizes the insulating property of the insulating layer with respect to the GaN layer.

  In the compound semiconductor device according to the present invention, the oxynitride is formed by oxidizing a multilayer structure film in which the nitride of the group III element and the lanthanoid nitride are alternately stacked, and nitriding the lanthanoid The product is characterized by being formed of 4 molecular layers or less.

  Therefore, the compound semiconductor device according to the present invention can be an oxynitride in a state in which the crystal structure of the nitride of the group III element is secured by preventing the influence of the crystal structure of the lanthanoid nitride.

  In the compound semiconductor device according to the present invention, the lanthanoid includes at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. It is characterized by that.

  Therefore, since the compound semiconductor device according to the present invention includes at least one of the lanthanoid elements, the insulating layer stacked on the GaN layer is reliably formed with less energy.

  In the compound semiconductor device according to the present invention, the nitride of the group III element is AlGaInN.

  Therefore, since the compound semiconductor device according to the present invention includes In as a group III element nitride, the compound semiconductor device is oxidized at a lower oxidation temperature than that of a group III element nitride not including In, and has an interface state. Further suppress the occurrence.

  The compound semiconductor device according to the present invention further includes a source region or a drain region formed by an impurity region reaching the GaN layer from the surface side, and the insulating layer is gate-insulated between the source region and the drain region. It is arranged as a film, and a channel is formed in the GaN layer between the source region and the drain region.

  Therefore, the compound semiconductor device according to the present invention has excellent electrical characteristics such as mobility, and functions as a normally-off field effect transistor.

  A method for manufacturing a compound semiconductor device according to the present invention is a method for manufacturing a group III-V nitride-based compound semiconductor device including a GaN layer and an insulating layer stacked on the GaN layer, the method comprising: Forming the GaN layer through a buffer layer; forming a coating layer composed of a mixed crystal of a nitride of a group III element and a lanthanoid nitride on the GaN layer; and an oxidation having an opening. A step of forming a protective film on the surface of the covering layer; and a step of oxidizing the covering layer exposed in the opening to form an insulating layer of oxynitride.

  Therefore, in the method for manufacturing a compound semiconductor device according to the present invention, a mixed crystal of a nitride of a group III element and a lanthanoid nitride that is easily oxidized as compared with the group III element is stacked on the GaN layer. Since the mixed crystal is oxidized with less energy to form an insulating layer as an oxynitride, the number of interface states generated between the GaN layer and the insulating layer is suppressed, and carriers move in the GaN layer. It is possible to manufacture a compound semiconductor device having a large degree and excellent electrical characteristics.

  Further, in the method for manufacturing a compound semiconductor device according to the present invention, the step of forming the coating layer is a step of alternately laminating group III element nitrides and lanthanoid nitrides to form a multilayer structure film. The step of forming the insulating layer is a step of oxidizing the multilayer structure film.

  Therefore, in the method for manufacturing a compound semiconductor device according to the present invention, a mixed crystal of a group III element nitride and a lanthanoid nitride has a multi-layer structure, so that the group III element nitride and the lanthanoid nitride are mixed. Since the oxidation rate is increased as compared with the case where the mixed crystal is oxidized without having a multilayer structure, the mixed crystal is easily oxidized to oxynitride in a short time.

  In the method for manufacturing a compound semiconductor device according to the present invention, one layer of the lanthanoid nitride is formed of four or less molecular layers.

  Therefore, the method for manufacturing a compound semiconductor device according to the present invention prevents the lanthanoid nitride crystal structure from stabilizing and prevents the influence of the group III element nitride on the crystal structure. Improves the crystallinity of the nitride.

  A compound semiconductor device according to the present invention is a group III-V nitride compound semiconductor device including a GaN layer and an insulating layer stacked on the GaN layer, the insulating layer including a nitride of a group III element It is formed of an oxynitride obtained by oxidizing a mixed crystal with a lanthanoid nitride.

  Therefore, since the insulating layer covering the GaN layer is formed of an oxynitride obtained by oxidizing a mixed crystal of a nitride of a group III element and a lanthanoid nitride that is easily oxidized as compared with the group III element, the GaN layer Can be formed with less energy, and the mobility required to realize the function as a semiconductor layer by suppressing the number of interface states generated between the GaN layer and the insulating layer is increased. Improve and improve electrical characteristics to realize superior electrical characteristics.

  A method for manufacturing a compound semiconductor device according to the present invention is a method for manufacturing a group III-V nitride compound semiconductor device including a GaN layer and an insulating layer stacked on the GaN layer, the buffer being formed on the substrate. A step of forming a GaN layer through the layer, a step of forming a coating layer composed of a mixed crystal of a group III element nitride and a lanthanoid nitride on the GaN layer, and an antioxidant film having an opening. A step of forming on the surface of the coating layer, and a step of oxidizing the coating layer exposed in the opening to form an insulating layer of oxynitride.

  Therefore, a mixed crystal of a nitride of a group III element and a lanthanoid nitride that is easily oxidized as compared with a group III element is stacked on the GaN layer, and the stacked mixed crystal is oxidized with less energy to oxynitride. As an insulating layer is formed, the number of interface states generated between the GaN layer and the insulating layer is suppressed, the carrier mobility in the GaN layer is increased, and excellent electrical characteristics are obtained. A compound semiconductor device can be manufactured.

It is sectional drawing which shows the cross section of the compound semiconductor device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the cross section of the compound semiconductor device which concerns on Embodiment 2 of this invention. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state in which the coating layer was formed. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state which formed the surface protective film in the coating layer. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state which formed the photoresist film in the surface protective film. FIG. 2 is a process diagram illustrating a state in a manufacturing process of the method for manufacturing the compound semiconductor device illustrated in FIG. 1, in which an impurity region is formed by ion implantation to positions corresponding to a source region and a drain region using a photoresist film as a mask. Indicates. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state which activates the implanted ion. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state which removed the surface protective film. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state in which the antioxidant film | membrane was formed. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state which formed the photoresist film in antioxidant film | membrane. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state which formed the opening part in antioxidant film | membrane. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state which oxidized the coating layer and formed the insulating layer. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state in which the photoresist film was formed in order to form a source electrode and a drain electrode. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state in which the source electrode and the drain electrode were formed. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state which formed the photoresist film in order to form a gate electrode. It is process drawing which shows the state in the manufacturing process of the manufacturing method of the compound semiconductor device shown in FIG. 1, and shows the state in which the gate electrode was formed.

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

<Embodiment 1>
A compound semiconductor device 1 according to the present embodiment will be described with reference to FIG.

  FIG. 1 is a cross-sectional view showing a cross section of a compound semiconductor device 1 according to Embodiment 1 of the present invention. Note that hatching is partially omitted in consideration of the visibility of the drawings.

  In the compound semiconductor device 1 according to the present embodiment, a Si substrate having a thickness of about 600 μm is applied as the substrate 11. A base layer 12, a superlattice buffer layer 13, a GaN layer 14, and a coating layer 15 are sequentially stacked on the substrate 11 at a substrate temperature of 1100 ° C. by MOCVD (metal organic chemical vapor deposition). Since the superlattice buffer layer 13 may be a simple buffer layer without being a superlattice, it may be simply a buffer layer 13. In addition, since the base layer 12 to the coating layer 15 are continuously formed, the interface can be controlled with high accuracy.

The underlayer 12 has a laminated structure of AlN / Al _0.2 Ga _0.8 N and has a thickness of 100 nm / 40 nm. The superlattice buffer layer 13 is a GaN / AlN superlattice layer formed subsequent to the base layer 12 (one GaN layer is 20 nm thick, one AlN layer is 5 nm thick, and each layer is repeated 20 layers). And a superlattice layer having a thickness of 500 nm with a repetition period of 20).

The GaN layer 14 is increased in resistance by, for example, carbon doping, and has a thickness of 1 μm. The covering layer 15 is Al _0.3 Ga _0.6 Gd _0.1 N as a mixed crystal of a group III element nitride (eg, AlGaN) and a lanthanoid nitride (eg, GdN), and has a thickness of 20 nm.

  AlGaN is exemplified as the group III element nitride, but AlN, GaN, AlGaInN, or the like may be used. Moreover, although GdN was illustrated as a lanthanoid nitride, other lanthanoids (for example, DyN) have similar properties, and therefore other lanthanoid nitrides may be used.

  The compound semiconductor device 1 according to the present embodiment is formed as a field effect transistor, for example. However, the present invention is not limited to the field effect transistor, and can be applied to, for example, a diode.

  In the present embodiment, since the compound semiconductor device 1 is a field effect transistor, the insulating layer 16 that functions as a gate insulating film, the source region 17 and the drain region that are disposed opposite to both sides of the insulating layer 16 are used. 18 is provided. A source electrode 21 is formed in the source region 17, a drain electrode 22 is formed in the drain region 18, and a gate electrode 23 is disposed in the insulating layer 16. The gate electrode 23 becomes a Schottky electrode.

  The insulating layer 16 located between the source region 17 and the drain region 18 is an oxynitride formed by oxidizing the covering layer 15 that covers the GaN layer 14. The source region 17 and the drain region 18 are made n-type by ion implantation of, for example, silicon (Si). Therefore, since the compound semiconductor device 1 includes the n-type source region 17 and the drain region 18 with respect to the p-type GaN layer 14, a channel is formed in the GaN layer 14 by controlling the voltage applied to the gate electrode 23. Thus, a field effect transistor is obtained.

The compound semiconductor device 1 is a group III-V nitride-based compound semiconductor device including a GaN layer 14 and an insulating layer 16 stacked on the GaN layer 14. The insulating layer 16 is a nitride of a group III element. It is made of an oxynitride (AlGaGdON) obtained by oxidizing a mixed crystal (eg, Al _0.3 Ga _0.6 Gd _0.1 N) of (for example, AlGaN) and a lanthanoid nitride (eg, GdN). If Gd of AlGaGdON is replaced with RE (rare earth element lanthanoid) as a general formula, AlGaGdON is expressed as AlGaREON.

  Therefore, in the compound semiconductor device, the insulating layer 16 covering the GaN layer 14 is an oxynitride obtained by oxidizing a mixed crystal of a nitride of a group III element and a lanthanoid nitride that is easily oxidized as compared with the group III element. Therefore, the insulating layer 16 stacked on the GaN layer 14 can be formed with low energy (low temperature), and the number of interface states generated between the GaN layer 14 and the insulating layer 16 can be suppressed to reduce the number of semiconductors. The mobility necessary for realizing the function as a layer is greatly improved, and the electrical characteristics are improved to realize excellent electrical characteristics.

  The present inventor has found that lanthanoids are more easily oxidized than group III elements in various studies of insulating films and oxide films. The compound semiconductor device 1 according to the present embodiment is based on this knowledge. In other words, by using a mixed crystal (covering layer 15) of a group III element nitride and a lanthanoid nitride, the group III elements disclosed in Patent Document 1 and Patent Document 2 are oxidized as they are. Therefore, oxidation with less energy becomes possible. Therefore, it is possible to form an oxide film (oxynitride: insulating layer 16) having a reduced interface state with little influence on the GaN layer 14 formed in the lower layer, and improved mobility and excellent electrical characteristics. Is realized.

  If the nitride of the group III element is, for example, AlN, GaN, or AlGaInN, and the lanthanoid nitride is, for example, GdN, an oxynitride obtained by oxidizing a mixed crystal of the nitride of the group III element and the lanthanoid nitride (. REON) is represented as AlGdON, GaGdON, AlGaInGdON.

  In the compound semiconductor device 1, the band gap of the insulating layer 16 is preferably larger than the band gap of the GaN layer 14. With this configuration, the insulating property of the insulating layer 16 with respect to the GaN layer 14 is reliably realized.

  In other words, the compound semiconductor device 1 may require a condition for the band gap. Specifically, this is a case where the insulating layer 16 contains In. When In is included, oxidation at a lower temperature is possible than when In is not included. However, if the In addition amount increases and the band gap of the oxynitride obtained by oxidizing the mixed crystal of the group III element nitride and the lanthanoid nitride becomes smaller than the band gap of the GaN layer 14, it does not function as a field effect transistor.

  The compound semiconductor device 1 includes a source region 17 or a drain region 18 formed from an impurity region reaching the GaN layer 14 from the surface side, and the insulating layer 16 is disposed as a gate insulating film between the source region 17 and the drain region 18. Thus, a channel is formed in the GaN layer 14 between the source region 17 and the drain region 18. With this configuration, the compound semiconductor device 1 is excellent in electrical characteristics such as mobility and functions as a normally-off type field effect transistor.

  Note that reaching the GaN layer 14 from the surface side means from the surface side of the compound semiconductor device 1. That is, in the vertical direction. Therefore, the compound semiconductor device 1 may be provided with a surface protection film (not shown) and the like, and impurity regions (source region 17 and drain region 18) may be arranged from the surface protection film (not shown). Further, the impurity region may be etched and extended from the middle of the insulating layer 16 toward the GaN layer 14, for example.

  The lanthanoid applied to the compound semiconductor device 1 desirably includes at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. With this configuration, since at least one of the lanthanoid elements is included, the insulating layer 16 stacked on the GaN layer 14 is reliably formed with less energy.

  The group III element nitride applied to the compound semiconductor device 1 is preferably AlGaInN. With this configuration, since Group III element nitride contains In, it is oxidized at a lower oxidation temperature than Group III element nitrides not containing In, and AlGaInREON as insulating layer 16 is easily formed. For this reason, the generation of interface states is further suppressed.

In the compound semiconductor device 1 of the present embodiment, the insulating layer 16 oxidizes the coating layer 15 with low energy (for example, an oxidation temperature of 500 ° C .; see Embodiment 3), so that SiO ₂ is heated to a high temperature (for example, It is possible to reduce the interface state between the GaN layer 14 and the insulating layer 16 from about 5 × 10 ¹² to about 4 × 10 ¹⁰ compared to the conventional case of heating at about 1000 ° C. This is a two-digit improvement.

<Embodiment 2>
With reference to FIG. 2, the compound semiconductor device 1s according to the present embodiment will be described.

  FIG. 2 is a sectional view showing a section of the compound semiconductor device 1s according to the second embodiment of the present invention. Note that hatching is partially omitted in consideration of the visibility of the drawings.

  Since the basic configuration of the compound semiconductor device 1s according to the present embodiment is the same as that of the compound semiconductor device 1 according to the first embodiment, the different points will be mainly described using the reference numerals. The main difference is that the coating layer 15 in the first embodiment is the coating layer 15s, and the insulating layer 16 in the first embodiment is the insulating layer 16s.

  In the compound semiconductor device 1 s according to the present embodiment, a base layer 12, a superlattice buffer layer 13, a GaN layer 14, and a coating layer 15 s are stacked on a substrate 11. Since the superlattice buffer layer 13 may be a simple buffer layer without being a superlattice, it may be simply a buffer layer 13.

The underlayer 12 has a laminated structure of AlN / Al _0.2 Ga _0.8 N and has a thickness of 100 nm / 40 nm. The superlattice buffer layer 13 is a GaN / Al _0.8 Ga _0.2 N superlattice layer (one GaN layer has a thickness of 20 nm, one AlGaN layer has a thickness of 5 nm, and each layer is repeated 10 times. A superlattice layer with a thickness of 2500 nm.). The repetition period can be changed according to the desired total film thickness.

The GaN layer 14 is increased in resistance by, for example, carbon doping, and has a thickness of 1 μm. The covering layer 15s is a DyN / Al _0.2 Ga _0.8 N superlattice layer (one DyN layer is 0.5 nm thick, one AlGaN layer is 1 nm thick, and each layer is repeated 10 times). A superlattice layer with a thickness of 15 nm.). Note that each lanthanoid nitride (for example, DyN) in each layer is desirably four molecular layers or less in order to improve the crystallinity of the nitride of the group III element.

  The reason why the covering layer 15s is the superlattice layer is that the lanthanoid nitride that is easily oxidized by disposing the superlattice is dispersed and disposed, which facilitates the oxidation and facilitates the oxidation of the entire covering layer 15s. Because.

In the present embodiment, the insulating layer 16 s located between the source region 17 and the drain region 18 is an oxynitride formed by oxidizing the covering layer 15 s that covers the GaN layer 14. The oxynitride (insulating layer 16s) according to the present embodiment has a multilayer structure in which a group III element nitride (for example, Al _0.2 Ga _0.8 N) and a lanthanoid nitride (for example, DyN) are alternately stacked. It is desirable that the film (coating layer 15s) is formed by oxidation.

  With this structure, the coating layer 15s is made a multilayer structure film of a nitride of a group III element and a nitride of a lanthanoid, thereby further facilitating the oxidation, thereby reliably suppressing the interface state and forming a stable interface. To do.

  Further, each of the lanthanoid nitrides in the multilayer structure film (covering layer 15s) is preferably formed of four or less molecular layers. This structure suppresses the determination of the crystal structure of the lanthanoid nitride, prevents the influence of the group III element nitride on the crystal structure, and stabilizes the crystallinity of the group III element nitride. It can be.

  In addition, although DyN was illustrated as a lanthanoid nitride, since other lanthanoids (for example, GdN) have the same property, other lanthanoid nitrides may be used. The lanthanoid nitride may be at least one molecular layer. Since a lanthanide nitride crystal (rock salt structure) becomes stable when it has a stacked structure of four or more molecules, it affects the crystallinity of the nitride of the group III element, and the required single crystal (for example, AlGaN, AlGaInN) Wurtzite structure) cannot be obtained.

The compound semiconductor device 1 s is a group III-V nitride-based compound semiconductor device 1 s including a GaN layer 14 and an insulating layer 16 s stacked on the GaN layer 14, and the insulating layer 16 s is a nitride of a group III element It is formed of an oxynitride (AlGaDyON) obtained by oxidizing a mixed crystal of a material (for example, Al _0.2 Ga _0.8 N) and a lanthanoid nitride (for example, DyN).

  Therefore, in the compound semiconductor device 1 s, the insulating layer 16 s covering the GaN layer 14 is an oxynitride obtained by oxidizing a mixed crystal of a nitride of a group III element and a lanthanoid nitride that is easily oxidized as compared with the group III element. Therefore, the insulating layer 16s stacked on the GaN layer 14 can be formed with less energy, and the number of interface states generated between the GaN layer 14 and the insulating layer 16s can be suppressed, thereby serving as a semiconductor layer. The mobility required for realizing the functions is greatly improved, and the electrical characteristics are improved to realize excellent electrical characteristics.

  In the compound semiconductor device 1 s, the band gap of the insulating layer 16 s is preferably larger than the band gap of the GaN layer 14. With this configuration, the insulating property of the insulating layer 16s with respect to the GaN layer 14 is reliably realized.

  The compound semiconductor device 1 s includes a source region 17 or a drain region 18 formed from an impurity region reaching the GaN layer 14 from the surface side, and the insulating layer 16 s is disposed as a gate insulating film between the source region 17 and the drain region 18. Thus, a channel is formed in the GaN layer 14 between the source region 17 and the drain region 18. With this configuration, the compound semiconductor device 1s has excellent electrical characteristics such as mobility, and functions as a normally-off field effect transistor.

  The lanthanoid applied to the compound semiconductor device 1s preferably includes at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. With this configuration, since at least one lanthanoid element is included, the insulating layer 16s stacked on the GaN layer 14 is reliably formed with less energy.

  The group III element nitride applied to the compound semiconductor device 1s is desirably AlGaInN. With this structure, since Group III element nitride contains In, it is oxidized at a lower oxidation temperature than Group III element nitrides not containing In, thereby further suppressing the generation of interface states.

Note that the interface state in the compound semiconductor device 1 of the present embodiment is about 4 × 10 ¹⁰ compared to 5 × 10 ¹² in the conventional case where SiO ₂ is heated at a high temperature (eg, about 1000 ° C.). This is a two-digit improvement.

<Embodiment 3>
With reference to FIGS. 3A to 3P, a method for manufacturing compound semiconductor device 1 (a field effect transistor as an example) shown in the first embodiment will be described as a method for manufacturing a compound semiconductor device according to the present embodiment.

  FIG. 3A is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1, and shows a state in which the covering layer 15 is formed. In the following drawings, hatching is partially omitted in consideration of easy viewing of the drawings. Moreover, it shows as the compound semiconductor device 1 including the middle of a process.

  In the compound semiconductor device 1, the base layer 12, the superlattice buffer layer 13 (buffer layer 13), the GaN layer 14, and the coating layer 15 are sequentially stacked on the substrate 11.

  The main conditions are as described in the first embodiment. As the source gas, a commonly used material can be applied. The superlattice buffer layer 13 and the GaN layer 14 are laminated (grown) under reduced pressure conditions (13.3 kPa (pascal)). The carbon-doped GaN layer 14 is formed by adjusting the growth pressure.

  The superlattice buffer layer 13 is inserted in order to alleviate the warp when the thick GaN layer 14 is grown on the substrate 11 to prevent the occurrence of dislocations and improve the crystallinity.

For the growth of the coating layer 15, tricyclopentadienyl gadolinium ((Cp) ₃ Gd) was used as a source gas in addition to the organometallic gas. The composition can be controlled by adjusting the flow rate of the organometallic gas.

In the present embodiment, a mixed crystal (Al _0.3 Ga _0.6 Gd _0.1 N) of a group III element nitride (AlGaN) and a lanthanoid nitride (GdN), that is, a mixed crystal state of AlGaGdN is used as the coating layer 15. Formed.

  In the manufacturing method of the compound semiconductor device 1 according to the present embodiment, the step of forming the GaN layer 14 on the substrate 11 via the buffer layer 13, the nitride of the group III element and the lanthanoid nitride on the GaN layer 14 And forming a coating layer 15 composed of the mixed crystal.

  FIG. 3B is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1 and shows a state in which the surface protective film 31 is formed on the coating layer 15.

A surface protective film 31 is formed on the surface of the coating layer 15 in order to cope with subsequent process treatments. The surface protective film 31 is a silicon nitride film (SiNx film) or a silicon oxide film (SiO ₂ ) film formed by a CVD method or a sputtering method. In the present embodiment, the surface protection film 31 is formed by depositing a 100 nm SiNx film by plasma CVD.

  FIG. 3C is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1 and shows a state in which the photoresist film 32 is formed on the surface protective film 31.

  A photoresist film 32 having an opening 32 w is formed on the surface protective film 31 by patterning. The opening 32 w is a region patterned (opened) corresponding to the source region 17 and the drain region 18.

  FIG. 3D is a process diagram illustrating a state in the manufacturing process of the manufacturing method of the compound semiconductor device 1 illustrated in FIG. 1, and ions to positions corresponding to the source region 17 and the drain region 18 using the photoresist film 32 as a mask. A state in which an impurity region is formed by implantation is shown.

  Si ion implantation SI is performed using the surface protective film 31 as a through film. The photoresist film 32 has a masking action on Si ions. Therefore, since Si ions are implanted only into the region corresponding to the opening 32w, the Si ions are implanted into regions corresponding to the source region 17 and the drain region 18. The depth of the source region 17 and the drain region 18 by ion implantation SI was about 200 nm.

  FIG. 3E is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1, and shows a state in which implanted ions are activated.

  The photoresist film 32 is removed, and an activation process for Si ions is performed in a nitrogen atmosphere at a temperature of 1200 ° C. with the surface protective film 31 laminated. By activation, the source region 17 and the drain region 18 are in a state of functioning as a source and a drain, respectively.

  FIG. 3F is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1, and shows a state where the surface protective film 31 is removed.

  After completing the Si ion activation process, the surface protective film 31 is removed with a hydrofluoric acid-based etchant to expose the coating layer 15 again.

  FIG. 3G is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1, and shows a state in which the antioxidant film 33 is formed.

  In order to prevent oxidation of the coating layer 15 in a subsequent process, an antioxidant film 33 is formed on the surface of the coating layer 15. The antioxidant film 33 is, for example, a silicon nitride film (SiNx).

  FIG. 3H is a process diagram showing a state in the manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1 and shows a state in which the photoresist film 34 is formed on the antioxidant film 33.

  A photoresist film 34 having an opening 34 w corresponding to the gate region (a region sandwiched between the source region 17 and the drain region 18 disposed so as to face each other) is formed on the antioxidant film 33. That is, the opening 34 w is disposed between the source region 17 and the drain region 18, and the other region is covered with the photoresist film 34.

  FIG. 3J is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1, and shows a state in which the opening 33 w is formed in the antioxidant film 33.

  An opening 33 w is formed in the antioxidant film 33 using the opening 34 w as a mask. The opening 33w is formed by etching the antioxidant film 33 with hydrofluoric acid or buffered hydrofluoric acid. Since the opening 34w corresponds to the gate region, the opening 33w is formed to correspond to the gate region. That is, the antioxidant film 33 becomes an antioxidant mask film 33p that is patterned to prevent oxidation of regions other than the gate region.

  The manufacturing method of the compound semiconductor device 1 according to the present embodiment includes a step of forming the antioxidant film 33 having the opening 33 w on the surface of the coating layer 15.

  FIG. 3K is a process diagram illustrating a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 illustrated in FIG. 1, and illustrates a state in which the insulating layer 16 is formed by oxidizing the covering layer 15.

  The photoresist film 34 is removed, and the coating layer 15 is oxidized using the antioxidant mask film 33p as an oxidation mask. The oxidation was performed in an atmosphere of a temperature of 500 ° C., 50% oxygen, and 50% inert gas.

  The antioxidant mask film 33p has an opening 33w corresponding to the gate region and covers the others. That is, the covering layer 15 is exposed between the source region 17 and the drain region 18 in the opening 33w.

The exposed coating layer 15 is oxidized to become the insulating layer 16. In the present embodiment, the coating layer 15 is a mixed crystal (Al _0.3 Ga _0.6 Gd _0.1 N) of a group III element nitride (AlGaN) and a lanthanoid nitride (GdN). Therefore, the insulating layer 16 is an oxynitride (AlGaGdON) obtained by oxidizing a mixed crystal of a group III element nitride and a lanthanoid nitride.

  As described in the first embodiment, the composition of the mixed crystal of the nitride of the group III element and the nitride of the lanthanoid forms the oxynitride in the case other than this embodiment. The insulating layer 16 functions as a gate insulating film because it is formed between the source region 17 and the drain region 18.

  The manufacturing method of the compound semiconductor device 1 according to the present embodiment includes the step of forming the insulating layer 16 of oxynitride (covering layer 15) by oxidizing the covering layer 15 exposed in the opening 33w.

  FIG. 3L is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1, and shows a state in which the photoresist film 35 is formed to form the source electrode 21 and the drain electrode 22. Show.

  A photoresist film 35 having openings 35 w corresponding to the source electrode 21 and the drain electrode 22 is formed.

  FIG. 3M is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1, and shows a state in which the source electrode 21 and the drain electrode 22 are formed.

  Ohmic metal is deposited by vacuum evaporation or sputtering using the photoresist film 35 as a mask. The ohmic metal is deposited on the source region 17 and the drain region 18 through the opening 35w. Therefore, the source electrode 21 and the drain electrode 22 are formed by removing (lifting off) the photoresist film 35.

  The ohmic metal has a laminated structure of Ti / Al / Mo / Au (thickness 15/60/35/50 nm) from the lower layer side to the upper layer side. Note that the ohmic characteristics can be obtained by annealing at a temperature of 800 ° C. for 1 minute in a nitrogen atmosphere.

  As other materials, Hf / Al / Hf / Au (thickness 10/60/10/60 nm) can be used. The annealing condition is a temperature of 800 ° C. for 1 minute in a nitrogen atmosphere, and ohmic characteristics are obtained. can get.

  Further, Ti / Au (16/200 nm) can be used, and since the source region 17 and the drain region 18 are ion-implanted, the annealing conditions are ohmic characteristics at a temperature of 550 ° C. for 10 minutes in a nitrogen atmosphere. Is obtained.

  FIG. 3N is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1 and shows a state in which a photoresist film 36 is formed to form the gate electrode 23.

  A photoresist film 36 having an opening 36w formed corresponding to the gate electrode 23 is formed. The photoresist film 36 is formed so as to cover the entire area except for the region corresponding to the gate electrode 23. The opening 36 w is opened so as to form the gate electrode 23 corresponding to a partial region of the insulating layer 16.

  3P is a process diagram showing a state in a manufacturing process of the manufacturing method of the compound semiconductor device 1 shown in FIG. 1, and shows a state in which the gate electrode 23 is formed.

  A gate electrode material is deposited using the photoresist film 36 as a mask. The gate electrode material is deposited on the insulating layer 16 through the opening 36w. Therefore, the gate electrode 23 is formed by removing (lifting off) the photoresist film 36.

As the gate electrode material, WN (tungsten nitride), Ni, Pt, or Pd can be applied. In this embodiment, 100 nm of WN was deposited by reactive sputtering using Ar: N ₂ = 16.8: 50 (sccm), pressure P = 5 Pa (pascal), and input Pin = 300 W (watts). When depositing a normal metal (Ni, Pt, Pd, etc.), the EB vapor deposition method can be applied.

  As described above, the method for manufacturing the compound semiconductor device 1 according to the present embodiment manufactures the group III-V nitride compound semiconductor device 1 including the GaN layer 14 and the insulating layer 16 stacked on the GaN layer 14. A method of forming a GaN layer 14 on a substrate 11 via a buffer layer 13 and a coating layer 15 composed of a mixed crystal of a nitride of a group III element and a nitride of a lanthanoid on the GaN layer 14. Forming an anti-oxidation film 33 having an opening 33w on the surface of the coating layer 15, and oxidizing the coating layer 15 exposed in the opening 33w to form the insulating layer 16 of oxynitride. A process.

  Therefore, in the method for manufacturing the compound semiconductor device 1 according to the present embodiment, a mixed crystal (covering) of a nitride of a group III element and a nitride of a lanthanoid that is easily oxidized as compared with the group III element is applied to the GaN layer 14. Since the layer 15) is stacked and the stacked mixed crystal is oxidized with a small amount of energy to form the insulating layer 16 as an oxynitride, generation of an interface state generated between the GaN layer 14 and the insulating layer 16 occurs. The compound semiconductor device having excellent electrical characteristics can be manufactured by suppressing the number and increasing the carrier mobility in the GaN layer 14.

<Embodiment 4>
A method of manufacturing the compound semiconductor device 1s (field effect transistor as an example) shown in the second embodiment will be described as a method of manufacturing the compound semiconductor device according to the present embodiment. The basic configuration of the method for manufacturing compound semiconductor device 1s according to the present embodiment is the same as the method for manufacturing compound semiconductor device 1 according to the third embodiment. explain.

  The main difference is that the coating layer 15 in the first embodiment is the coating layer 15s, and the insulating layer 16 in the first embodiment is the insulating layer 16s. That is, in the manufacturing method of the compound semiconductor device 1s according to the present embodiment, the manufacturing process of the covering layer 15s and the insulating layer 16s is different from that in the third embodiment. In the following description, the compound semiconductor device 1s including the middle of the process is shown.

  In the compound semiconductor device 1 s, the base layer 12, the superlattice buffer layer 13 (buffer layer 13), the GaN layer 14, and the coating layer 15 s are stacked on the substrate 11.

The underlayer 12 has a laminated structure of AlN / Al _0.2 Ga _0.8 N and has a thickness of 100 nm / 40 nm. The superlattice buffer layer 13 is a GaN / Al _0.8 Ga _0.2 N superlattice layer (one GaN layer has a thickness of 20 nm, one AlGaN layer has a thickness of 5 nm, and each layer is repeated 10 times. A superlattice layer with a thickness of 2500 nm.). The repetition period can be changed according to the desired total film thickness.

The GaN layer 14 is increased in resistance by, for example, carbon doping, and has a thickness of 1 μm. The covering layer 15s is a DyN / Al _0.2 Ga _0.8 N superlattice layer (one DyN layer is 0.5 nm thick, one AlGaN layer is 1 nm thick, and each layer is repeated 10 times). A superlattice layer with a thickness of 15 nm.).

For the growth of the coating layer 15s, tricyclopentadienyl dysprosium ((Cp) ₃ Dy)) was used as a source gas in addition to the organometallic gas. The composition can be controlled by adjusting the flow rate of the organometallic gas.

  As described above, the method for manufacturing the compound semiconductor device 1 s according to the present embodiment manufactures the III-V group nitride compound semiconductor device 1 s including the GaN layer 14 and the insulating layer 16 s stacked on the GaN layer 14. A method of forming a GaN layer 14 on a substrate 11 via a buffer layer 13 and a coating layer 15 composed of a mixed crystal of a nitride of a group III element and a nitride of a lanthanoid on the GaN layer 14. Forming an anti-oxidation film 33 having an opening 33w on the surface of the mixed crystal, and oxidizing the coating layer 15s exposed in the opening 33w to form an oxynitride insulating layer 16s. With.

  Therefore, in the method of manufacturing the compound semiconductor device 1 s according to the present embodiment, the mixed crystal (covering) of the nitride of the group III element and the lanthanoid nitride that is easily oxidized as compared with the group III element in the GaN layer 14 is performed. The layer 15s) is stacked, and the stacked mixed crystal is oxidized with a small amount of energy to form the insulating layer 16s as an oxynitride. Therefore, generation of an interface state generated between the GaN layer 14 and the insulating layer 16s occurs. The compound semiconductor device having excellent electrical characteristics can be manufactured by suppressing the number and increasing the carrier mobility in the GaN layer 14.

In addition, the interface state in the compound semiconductor device 1 of the present embodiment is about 4 × 10 ¹⁰ compared to 5 × 10 ¹² in the conventional case, which is a two-digit improvement.

Further, in the manufacturing method according to the present embodiment, the step of forming the coating layer 15 is performed by alternately laminating group III element nitrides (Al _0.2 Ga _0.8 N) and lanthanoid nitrides (DyN). The step of forming the structure film, and the step of forming the insulating layer 16s is a step of oxidizing the multilayer structure film (covering layer 15s).

  Therefore, in the method for manufacturing the compound semiconductor device 1s according to the present embodiment, the mixed crystal (covering layer 15s) of the nitride of the group III element and the nitride of the lanthanoid is formed as a multilayer structure film, thereby Since the oxidation rate is increased as compared with the case where the mixed crystal of nitride and lanthanoid nitride is oxidized without forming a multilayer structure (Embodiment 3), the mixed crystal (covering layer 15s) can be easily formed in a short time. Oxidized to oxynitride (insulating layer 16s).

Further, in the manufacturing method according to the present embodiment, each one layer of the lanthanoid nitride is preferably formed of four or less molecular layers. That is, the manufacturing method of the compound semiconductor device 1s according to the present embodiment prevents the stabilization of the crystal structure of the lanthanoid nitride (for example, DyN) and the group III element nitride (for example, Al _0.2 Ga _0.8 N). ) To the crystal structure of the nitride of the group III element.

  As described in the second embodiment, the nitride of the group III element applied to the compound semiconductor device 1s (covering layer 15s) is preferably AlGaInN. With this structure, since Group III element nitride contains In, it is oxidized at a lower oxidation temperature than Group III element nitrides not containing In, thereby further suppressing the generation of interface states.

1, 1s compound semiconductor device 11 substrate 12 underlayer 13 superlattice buffer layer (buffer layer)
14 GaN layer 15, 15s Cover layer 16, 16s Insulating layer (gate insulating film)
17 Source region (impurity region)
18 Drain region (impurity region)
21 Source electrode 22 Drain electrode 23 Gate electrode 31 Surface protective film 32 Photoresist film 32w Opening 33 Antioxidation film 33p Antioxidation mask film 33w, 34w, 35w, 36w Openings 34, 35, 36 Photoresist film SI Ion implantation

Claims (9)

A III-V group compound semiconductor device comprising a GaN layer and an insulating layer stacked on the GaN layer,
The compound semiconductor device, wherein the insulating layer is formed of an oxynitride obtained by oxidizing a mixed crystal of a nitride of a group III element and a nitride of a lanthanoid. The compound semiconductor device according to claim 1,
The compound semiconductor device, wherein a band gap of the insulating layer is larger than a band gap of the GaN layer. The compound semiconductor device according to claim 1, wherein:
The oxynitride is formed by oxidizing a multilayer structure film in which the nitride of the group III element and the lanthanoid nitride are alternately laminated, and each layer of the lanthanoid nitride is four molecular layers or less. A compound semiconductor device comprising: A compound semiconductor device according to any one of claims 1 to 3, wherein
The lanthanoid includes at least one of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. A compound semiconductor device according to any one of claims 1 to 4, wherein
The compound semiconductor device, wherein the nitride of the group III element is AlGaInN. A compound semiconductor device according to any one of claims 1 to 5,
A source region or a drain region formed of an impurity region reaching the GaN layer from the surface side;
The compound semiconductor device, wherein the insulating layer is disposed as a gate insulating film between the source region and the drain region, and a channel is formed in the GaN layer between the source region and the drain region. A manufacturing method of a group III-V nitride compound semiconductor device comprising a GaN layer and an insulating layer laminated on the GaN layer,
Forming the GaN layer on the substrate via a buffer layer;
Forming a coating layer composed of a mixed crystal of a group III element nitride and a lanthanoid nitride on the GaN layer;
Forming an antioxidant film having an opening on the surface of the coating layer;
And a step of oxidizing the coating layer exposed in the opening to form an insulating layer of oxynitride. It is a manufacturing method of the compound semiconductor device according to claim 7,
The step of forming the coating layer is a step of alternately laminating a nitride of a group III element and a nitride of a lanthanoid to form a multilayer structure film,
The method of manufacturing a compound semiconductor device is characterized in that the step of forming the insulating layer is a step of oxidizing the multilayer structure film. A method of manufacturing a compound semiconductor device according to claim 8,
Each layer of the lanthanoid nitride is formed of four or less molecular layers. A method for manufacturing a compound semiconductor device, comprising:

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