JP7290217B2 - Thin films, substrates with thin films and semiconductor devices - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act applies Publisher name: International Workshop on Nitride Semiconductors 2018, Publication name: International Workshop on Nitride Semiconductors 2018 Proceedings pp. GR11-5, Publication date: Nov. 2018 11th of the month website Address: https://aip. sitation. org/doi/10.1063/1.5053147 Posted: November 13, 2018 Assembly name: International Workshop on Nitride Semiconductors 2018 Date: November 15, 2018 Venue: ANA Crowne Plaza Hotel Kanazawa

The present invention relates to a thin film, a substrate with a thin film, and a semiconductor device.

Light in the deep ultraviolet wavelength region from 200 nm to 300 nm is used for sterilization, water and air purification applications. Light sources currently used for these purposes are mercury UV lamps, metal halide UV lamps, etc., and use emission lines (wavelength of 254 nm, etc.) of a gas enclosed in a quartz tube. These have the problems of high power consumption, short life, and large light sources. Therefore, researches are actively conducted to realize deep ultraviolet light emission by LEDs (Light Emitting Diodes) that consume less power, have a longer life, and can be made into a very small light source.

LEDs with wavelengths such as near-ultraviolet and blue have been put into practical use with III-nitrides such as GaN and InGaN, and are used as light sources for white lamps (light sources for excitation of phosphors), decorations, light sources for curing ultraviolet curing resins, and for inspection. Used as a light source. However, since GaN and InGaN cannot provide deep ultraviolet light emission effective for sterilization, etc., in order to realize LEDs in the deep ultraviolet wavelength range, it is necessary to use AlN or AlN with a high molar concentration in the same Group III nitride semiconductor. AlGaN is required.

AlN, GaN, InN, and group III nitrides, which are mixed crystals thereof, have a wurtzite crystal structure. When a group III nitride thin film having this wurtzite crystal structure is produced, the thin film tends to grow so that the film thickness direction of the thin film is the c-axis direction, ie, the preferential orientation axis is the c-axis. Group III nitrides with a wurtzite crystal structure have c Electrical polarity occurs in the axial direction. Therefore, when a plurality of group III nitride thin films having a wurtzite crystal structure are stacked, polarization occurs along the stacking direction of the thin films, and an internal electric field is generated at the hetero interface between the thin films adjacent in the stacking direction. occur. This problem is a hindrance to improving the efficiency of GaN-based LEDs that have already been realized, but it is thought to become a more serious problem for AlN-based semiconductors, which have a larger electronegativity difference. there is

In the case where the light-emitting layer of the aforementioned LED is composed of a plurality of group III nitride thin films having a wurtzite crystal structure stacked in a direction coinciding with the c-axis, the hetero interface between adjacent thin films A relatively large internal electric field is generated. As a result, the electrons and holes present in the light-emitting layer are spatially separated, and the recombination efficiency of the electrons and holes is reduced. In addition, the light extraction efficiency in the c-axis direction is low, and therefore the light extraction efficiency from the plane (c-plane) perpendicular to the c-axis in the light-emitting layer of the LED is lowered.

Also, this electrical polarity problem is also a factor impeding the realization of performance in transistors made of group III nitrides. For example, it is very difficult to fabricate a normally-off transistor.

On the other hand, a technique has been provided for fabricating LEDs and transistors using a substrate on which a crystal plane on which a thin film is grown whose preferential orientation axis is electrically non-polar a-axis or m-axis is exposed ( For example, see Patent Documents 1 to 4).

JP-A-2008-091598 JP 2009-099774 A JP 2010-232425 A JP 2010-251660 A

As a method of epitaxially growing a group III nitride thin film having a non-polar wurtzite crystal structure of a-axis or m-axis, a single crystal ingot of the group III nitride itself is prepared and cut on the a-plane or the m-plane. Therefore, a method of homoepitaxially growing thereon can be considered. However, unlike other III-V semiconductors, such as GaAs, for which large single crystal ingots can be produced relatively easily, it is extremely difficult to synthesize large single crystal ingots of Group III nitrides. This is because GaAs or the like can be easily melted at a high temperature and can be single-crystallized during its solidification process, whereas GaN or the like does not melt at a high temperature and nitrogen is separated. Therefore, even if a single crystal ingot of group III nitride is produced, the manufacturing method thereof is extremely special, and as a result, the single crystal ingot becomes expensive. Therefore, r-plane sapphire substrates, a-plane SiC substrates, m-plane SiC substrates, etc. are being studied for heteroepitaxial growth. However, in this case, there is a problem that many defects are generated when a single crystal ingot of sapphire, SiC, or the like is cut so that the r-plane, a-plane, and m-plane are exposed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thin film, a substrate with a thin film, and a semiconductor device having a non-polar wurtzite crystal structure independent of the type of substrate or the crystal state of the substrate. With the goal.

In order to achieve the above object, the thin film according to the present invention is
A thin film formed of a nitride represented by (Al1 _{- yGay} ) _{1- xTxN} (0≤x≤1, 0≤y≤1) where T is a 3d transition metal. hand,
The nitride has a wurtzite crystal structure and a preferred orientation axis in the film thickness direction is the a-axis or the m-axis,
the 3d transition metal is Fe,
When the nitride is expressed as (Al1 _-yGay ) 1 _{- xFexN ,} y is within the range of 0≤y≤1.0 and x is 0.081<x≤0.261 . Within range .

A substrate with a thin film according to the present invention viewed from another point of view is
a substrate;
It is formed from a nitride represented by (Al1 _{- yGay} ) _{1- xTxN} (0≤x≤1, 0≤y≤1) where T is a 3d transition metal, and is formed on the substrate a thin film provided in
The substrate is formed of a crystalline or amorphous metal, semimetal, semiconductor or insulator,
The nitride has a wurtzite crystal structure and a preferred orientation axis in the film thickness direction is the a-axis or the m-axis,
the 3d transition metal is Fe,
When the nitride is expressed as (Al1 _-yGay ) 1 _{- xFexN ,} y is within the range of 0≤y≤1.0 and x is 0.081<x≤0.261 . Within range .

A semiconductor device according to the present invention viewed from another point of view includes:
a substrate;
On the substrate, a first nitride represented by (Al1 _{- yGay} ) _{1-xTxN (} 0≤x≤1, 0≤y≤1) where T is the 3d transition metal a thin film formed from
a multiple quantum well structure formed from a second nitride represented by In _z (Al _1-y Ga _y ) _1-z N (0≦y≦1, 0≦z≦1) above the thin film; and a light-emitting layer having
The first nitride and the second nitride have a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction is the a-axis or the m-axis,
the 3d transition metal is Fe,
When the first nitride is expressed as (Al1 -yGay)1-xFexN _, y is _{within the range} of 0≤y≤1.0, and x is 0.081<x≤0. 261 range .

According to the present invention, a nitride represented by (Al _{1-y Gay} ) _1-x T _x N (0 ≤ x ≤ 1, 0 ≤ y ≤ 1), where T is the 3d transition metal T The nitride has a wurtzite crystal structure and the preferential orientation axis in the film thickness direction is the a-axis or the m-axis. As a result, when a thin film is grown on a substrate, regardless of the type of surface on which the thin film is grown on the substrate, the substrate has a wurtzite crystal structure and the preferential orientation axis in the film thickness direction is the a-axis. Alternatively, a thin film can be grown that is m-axis. In other words, a thin film having a nonpolar wurtzite crystal structure can be realized without depending on the type of substrate or the crystal state of the substrate.

(A) is a diagram showing an example of a substrate according to an embodiment of the present invention, and (B) is a diagram for explaining a wurtzite crystal structure. 1 is a schematic configuration diagram showing an example of a high-frequency sputtering apparatus used for producing a thin film according to Embodiment 1; FIG. It is a figure which shows an example of the semiconductor device which concerns on Embodiment 2 of this invention. FIG. 4 is a diagram showing Fe concentration dependence of X-ray diffraction profiles of thin films according to Examples and Comparative Examples. FIG. 4 is a diagram showing the degree of orientation of thin films according to Examples and Comparative Examples; (A) is a diagram showing lattice constants and full widths at half maximum of diffraction peaks corresponding to c-planes of thin films according to Examples and Comparative Examples, and (B) corresponds to a-planes of thin films according to Examples and Comparative Examples. FIG. 4 is a graph showing lattice constants and full widths at half maximum of diffraction peaks; It is a figure which shows the X-ray-diffraction profile of the thin film which concerns on an Example.

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

(Embodiment 1)
A substrate 1 with a thin film according to the present embodiment includes a substrate 11 and a thin film 12 grown on the substrate 11, as shown in FIG. 1(A). As the substrate 11, a substrate selected from a quartz glass substrate, a metal plate, a sapphire substrate, and a Si substrate can be adopted. The substrate 11 may be made of other crystalline or amorphous metals, semimetals, semiconductors, or insulators.

The thin film 12 is formed from a nitride represented by (Al1 _{- yGay} ) _{1- xTxN} (0≤x≤1, 0≤y≤1) where T is the 3d transition metal T. It is In other words, the thin film 12 is a nitride represented by Al _1-y Ga _y N (0 ≤ y ≤ 1) in which at least one of Al and Ga of the nitride is partially substituted with a 3d transition metal. formed. The nitride has a wurtzite crystal structure as shown in FIG. 1(B). Here, among the atoms represented by circles in FIG. 1B, for example, the larger one is Al, Ga or 3d transition metal, and the smaller one is nitrogen. In the thin film 12, the preferential orientation axis in the film thickness direction indicated by the arrow AR1 in FIG. 1A is the a-axis or the m-axis shown in FIG. 1B.

As the 3d transition metal, one or more metals selected from Fe, Co, Ni and Cu are preferably employed. Ti, V, Cr, and Mn, which are the same 3d-transition metals as these, are known to easily take a c-axis-oriented wurtzite crystal structure in a concentration range of up to about 13% (Non-Patent Document: N. Tatemizo, S. Imada, Y. Miura, K. Nishio, and T. Isshiki, “Chemical trend in band structure of 3d-transition-metal-doped AlN films” Materials Science Forum, 924, 322 (2018). Non-patent literature: N. Tatemizo, Y. Miura, K. Nishio, S. Hirata, F. Sawa, K. Fukui, T. Isshiki and S. Imada, “Band structure and photoconductivity of blue-green light absorbing AlTiN films” , Journal of Material Chemistry A, 5, 20824 (2017).). However, when the concentration is higher than this, it is difficult for the crystals forming the thin film 12 to maintain the wurtzite crystal structure. Under most of the film forming conditions, polycrystalline non-oriented microcrystals are formed in a higher concentration region, and when the concentration is further increased, a structure other than the wurtzite crystal structure is formed. This may be because TiN, VN, CrN, and MnN, which are nitrides of Ti, V, Cr, and Mn, tend to have a so-called rock salt crystal structure. The wurtzite crystal structure has a 3d transition metal element coordinated to four nitrogens, whereas the rocksalt crystal structure has a 3d transition metal element coordinated to six nitrogens. . Therefore, in the case of nitrides of Ti, V, Cr, and Mn, when the concentrations of Ti, V, Cr, and Mn become high, they try to adopt the stable 6-coordinate structure of these nitrides. For this reason, it is predicted that, for example, the same crystal structure cannot be maintained in the entire TiN--AlN mixed crystal. Furthermore, in the case of high concentrations of Ti and Cr, it is known that a rock salt structure is formed in a region where the composition of Ti and Cr in TiAlN, CrAlN, etc. is larger than the composition of Al.

On the other hand, nitrides FeN and CoN of Fe and Co are known to have a stable sphalerite crystal structure. NiN and CuN have almost no experimental reports, but it is reported that the zinc-blende crystal structure can theoretically exist stably. The zincblende crystal structure is basically a four-fold nitrogen structure similar to the wurtzite crystal structure. As a result, it is predicted that a wurtzite crystal structure could be formed in a wide concentration range.

Further, when the nitride is expressed as (Al _{1-y Gay} ) _1-x Fe _x N, y is within the range of 0 ≤ y ≤ 1.0, and x is 0.05 < x ≤ 0.261. is preferably within the range of Further, it is more preferable that y is 0 and x is in the range of 0.11≦x≦0.218 for the above-mentioned nitrides.

The nitride according to this embodiment can be produced, for example, by a sputtering method using a high-frequency sputtering apparatus 900 as shown in FIG. A high-frequency sputtering apparatus 900 includes a chamber 901, a high-frequency power supply RF, a matching unit 902, a holder 904 holding a substrate W, a holder 905 holding a target material TG, a heater 903 for heating the substrate W, Prepare. The chamber 901 is provided with a supply port 911 for supplying material gas into the chamber 901. For example, a mixed gas of Ar and nitrogen is supplied into the chamber 901 through the supply port 911 as indicated by an arrow AR91. be. Further, the chamber 901 is provided with an exhaust port 912 for exhausting the gas inside the chamber 901, and an exhaust rate set in advance by a vacuum pump (not shown) connected to the exhaust port 912 is set by an arrow AR92. The pressure in the chamber 901 is maintained at the set value by exhausting as shown in . A shutter 906 is arranged between the holders 904 and 905 . A cooling mechanism 941 having a flow path 941a through which a coolant flows is arranged vertically above the holder 904 . Then, heat is exchanged between the coolant that flows into the flow path 941a as indicated by an arrow AR93 and flows out from the flow path 941a as indicated by an arrow AR94 and the portion of the holder 904 that is not on the substrate W side. The portion not on the W side is cooled. Further, vertically below the holder 905, a cooling mechanism 951 having a flow path 951a through which a coolant flows and for cooling the target material TG is arranged. The target material TG is cooled by heat exchange between the target material TG and the coolant flowing into the flow path 951a as indicated by an arrow AR95 and flowing out from the flow path 951a as indicated by an arrow AR96.

A method for fabricating the aforementioned nitride thin film using this high-frequency sputtering apparatus 900 will now be described. First, in the chamber 901, the substrate W is held by the holder 904 so that the surface on which the thin film is to be grown faces vertically downward. Also, the target material TG is held by the holder 905 vertically below the substrate W in the chamber 901 . As the target material TG, for example, the sintered body of the aforementioned nitride is adopted. Also, on the target material TG, at least one piece CP of 3d transition metal to replace Al or Ga is placed. Here, by changing the area, number, or arrangement of the individual pieces CP placed on the target material TG, it is possible to adjust the amount of the 3d transition metal to be incorporated into the thin film to be produced.

Next, with the shutter 906 closed, the gas remaining in the chamber 901 is discharged out of the chamber 901, and then a mixed gas of Ar (argon) and nitrogen is introduced into the chamber 901 through the supply port 911. Introduce. Here, the partial pressure ratio of nitrogen to Ar in the mixed gas may be in the range of 0.25 to 1.0. Subsequently, in a mixed gas atmosphere, the heater 903 heats the substrate W to a preset film formation temperature. Here, the film formation temperature is a temperature within the range of 200° C. or higher and 400° C. or lower. The timing of introducing the mixed gas into the chamber 901 may be before or after the heating of the substrate W by the heater 903 is started.

Thereafter, by supplying high-frequency power from the high-frequency power supply RF into the chamber 901 through the matching unit 902, plasma is induced in the vicinity of the target material TG to sputter the target material TG. Here, if the shutter 906 is kept open, the atoms ejected by the sputtering of the target material TG reach the substrate W, and nitride crystals grow on the substrate W. As shown in FIG. At this time, the Fe pieces CP are sputtered at the same time as the target material TG, react with nitrogen contained in the mixed gas introduced into the chamber 901, and are incorporated into the thin film formed on the substrate W. FIG. Before forming a thin film on the substrate W, the surface of the substrate W and the surface of the target material TG may be cleaned by exposing the surface of the substrate W and the surface of the target material TG to plasma. By using this sputtering method, the composition of the thin film grown on the substrate W can be changed by changing the area, number, or arrangement of the individual CPs.

In this embodiment, an example of performing the sputtering method using the high-frequency sputtering apparatus 900 has been described, but means for performing the sputtering method is not limited to this. For example, a magnetron sputtering device, an ECR (electron cyclotron resonance) sputtering device, or an ion beam sputtering device may be used.

As described above, the thin film according to the present embodiment has (Al _{1-y Gay} ) _1-x T _x N (0≦x≦1, 0≦y It is made of a nitride represented by ≦1). The nitride has a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction is the a-axis or the m-axis. As a result, when the thin film 12 is grown on the substrate 11, regardless of the type of the substrate 11, the substrate 11 has a wurtzite crystal structure and the preferential orientation axis in the film thickness direction is the a-axis or the m-axis. Thin films that are axial can be grown. In other words, the thin film 12 having a nonpolar wurtzite crystal structure can be realized without depending on the type of the substrate 11 or the crystal state of the substrate 11 .

Further, the substrate 11 according to the present embodiment is selected from among substrates formed from crystalline or amorphous metals, semimetals, semiconductors or insulators, including quartz glass substrates, metal plates, sapphire substrates, and Si substrates. selected. As a result, there is more room for selection of the substrate 11 that can be used to fabricate the substrate 1 with the thin film, so there is an advantage that the range of application of the substrate 1 with the thin film is expanded accordingly.

(Embodiment 2)
The semiconductor device according to this embodiment is a so-called LED (Light Emitting Diode) element. For example, as shown in FIG. 3, a semiconductor device 100 according to this embodiment includes a substrate 11, a thin film 12 grown on the substrate 11, clad layers 21 and 23, a light emitting layer 22, and electrodes 31 and 32. , provided. As the substrate 11, a substrate selected from a quartz glass substrate, a polycrystalline metal plate, a sapphire substrate, and a Si substrate can be adopted. The substrate 11 may be made of other crystalline or amorphous metals, semimetals, semiconductors, or insulators.

The thin film 12 is a first nitride represented by (Al1 _{- yGay} ) _{1- xTxN} (0≤x≤1, 0≤y≤1) where T is the 3d transition metal T is formed from The thin film 12 has a wurtzite crystal structure, and the preferred orientation axis in the film thickness direction indicated by the arrow AR1 in FIG. 3 is the a-axis or the m-axis described in the first embodiment. That is, the crystal planes on both sides in the thickness direction of the thin film 12 are a-planes or m-planes in the wurtzite crystal structure. Here, the 3d transition metal is preferably at least one selected from Fe, Co, Ni, and Cu, and more preferably Fe. Further, when the 3d transition metal is Fe, when the above-mentioned first nitride is expressed as (Al1 _{- yGay} ) _{1-xFexN ,} y is within the range of 0 ≤ y ≤ 1.0 and x is in the range of 0.05<x≦0.261.

Cladding layer 21 is made of a nitride of n-type conductivity. As the n-type nitride, for example, a nitride represented by In _z (Al _1-y Ga _y ) _1-z N (0≦y≦1, 0≦z≦1) doped with a donor impurity is used. Adopted. Donor impurities may be selected from Si, O, and H, for example. The clad layer 21 also has a wurtzite crystal structure, and the preferred orientation axis in the film thickness direction indicated by the arrow AR1 in FIG. 3 is the a-axis or the m-axis described in the first embodiment. An electrode 31 is provided on the clad layer 21 .

A light-emitting layer 22 is formed on the clad layer 21 above the thin film 12 . The light emitting layer 22 is a semiconductor layer formed of a plurality of second nitrides represented by, for example, In _z (Al _1-y Ga _y ) _1-z N (0≦y≦1, 0≦z≦1). It has a stacked multiple quantum well structure. Each semiconductor layer forming the light-emitting layer 22 also has a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction of each semiconductor layer indicated by the arrow AR1 in FIG. 3 is the a-axis or the m-axis.

The cladding layer 23 is made of a p-type nitride. As the n-type nitride, for example, a nitride represented by In _z (Al _1-y Ga _y ) _1-z N (0≦y≦1, 0≦z≦1) doped with an acceptor impurity is used. Adopted. Acceptor impurities may be selected from Mg, Ca, and C, for example. The clad layer 23 also has a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction indicated by the arrow AR1 in FIG. 3 is the a-axis or m-axis described in the first embodiment. An electrode 32 is provided on the clad layer 23 . In this embodiment, the case where the conductivity type of the cladding layer 21 is the n-type and the conductivity type of the cladding layer 23 is the p-type has been described. It may be p-type and the conductivity type of the cladding layer 23 may be n-type.

As described above, in the semiconductor device 100 according to the present embodiment, the thin film 12 has (Al _{1-y Gay} ) _1-x T _x N (0≦x ≤ 1, 0 ≤ y ≤ 1). The nitride has a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction is the a-axis or the m-axis. As a result, a semiconductor layer having a wurtzite crystal structure and a preferential orientation axis in the film thickness direction being the a-axis or the m-axis can be grown on the thin film 12 . Therefore, the light-emitting layer 22 can be formed by laminating a plurality of semiconductor layers having electrically non-polar a-axis or m-axis preferential orientation axes in the film thickness direction. The electric field magnitude is reduced. Thereby, the recombination efficiency of electrons and holes present in the light-emitting layer 22 can be improved. In addition, since the m-plane or a-plane in the light-emitting layer 22 of the LED has higher light extraction efficiency than the c-plane, there is an advantage that the efficiency of light extraction from the light-emitting layer 22 is increased accordingly.

Although each embodiment of the present invention has been described above, the present invention is not limited to the configuration of each of the above-described embodiments. For example, in Embodiment 1, the thin film 12 may be produced by a molecular beam epitaxy method (MBE method). In this case, a nitrogen-containing atomic gas is introduced into a chamber in a vacuum atmosphere, and while the nitrogen-containing atomic gas is photolyzed or thermally decomposed on or near the surface of a substrate placed in the chamber, molecular beams of Ga are emitted onto the substrate surface. and the molecular beam of the 3d transition metal, the thin film 12 is grown. Here, nitrogen molecules (N2), ammonia (NH3), etc. are employed as the nitrogen-containing atomic gas. Also, the method of decomposing the nitrogen-containing atomic gas to obtain nitrogen atoms is not particularly limited. For example, a method of decomposing nitrogen molecules by applying high-frequency energy to the nitrogen molecules using a plasma gun may be employed. At this time, the composition of the nitride can be changed by changing the supply amount of the 3d transition metal to the substrate surface by increasing or decreasing the cell temperature of the Al, Ga and 3d transition metal molecular beam cell.

Although the embodiments and modifications of the present invention (including those described in the notes, the same applies hereinafter) have been described above, the present invention is not limited to these. The present invention includes appropriate combinations of the embodiments and modifications, and appropriate modifications thereof.

A thin film and a method for manufacturing a thin film according to the present invention will be described based on examples.

A high-frequency sputtering apparatus 900 shown in FIG. 2 was used to fabricate Al _1-x Fe _x N (0≦x≦1) thin films according to Examples and Comparative Examples, and the properties of the fabricated thin films were evaluated. A mixed gas of Ar and nitrogen was introduced into the chamber 901 when the thin film was formed. As the target material TG, a sintered body of AlN (99% purity: manufactured by Furuuchi Chemical Co., Ltd.) was used. Then, individual pieces CP made of Fe (99.9% purity: manufactured by Furuuchi Chemical Co., Ltd.) were placed on the target material TG. As the substrate W, a quartz glass substrate and a sapphire substrate were used. First, the air remaining in the chamber 901 was discharged with the shutter 906 closed, and then the temperature of the substrate W was raised to 300° C. by the heater 903 . Next, a mixed gas of Ar and nitrogen was introduced into the chamber 901 . The partial pressure ratio of nitrogen to Ar in the mixed gas was set to 0.5, and the internal pressure of the chamber 901 was set to 0.65Pa. Subsequently, plasma was generated in the chamber 901 by supplying high frequency power from the high frequency power supply RF into the chamber 901 . The high frequency power at this time was set to 200W. After that, the thin film was grown on the substrate W with the shutter 906 opened. The thin film growth rate was 0.5 μm/hr.

In the method for producing a thin film described above, the substrate W is a quartz glass substrate and the thin film is produced while changing the amount of the individual pieces CP formed of Fe placed on the target material TG. Seventeen kinds of thin films according to Comparative Examples 1 to 7 were produced. The thin films according to Examples 1 to 10 and Comparative Examples 1 to 7 have different Fe concentrations in the thin films. Table 1 shows the concentration of Fe in each of the thin films according to Examples 1 to 10 and Comparative Examples 1 to 7. The thin film according to Comparative Example 1 was produced by carrying out the above-described method for producing a thin film without placing individual pieces CP made of Fe on the target material TG.

Next, FIG. 4 shows profiles measured by an X-ray diffraction method (XRD method) for each of the thin films according to Examples 1 to 10 and Comparative Examples 1 to 7. FIG. As shown in FIG. 4, in the case of Comparative Examples 1 to 5, that is, in the case of thin films with a Fe concentration of less than 5%, the (0002) plane, that is, the diffraction angle (36° A sharp peak was observed in the vicinity). From this, it was found that the preferential orientation axis in the thickness direction of the thin film with an Fe concentration of less than 5% is the c-axis. On the other hand, in the case of Examples 1 to 10, that is, the thin films having an Fe concentration of 8.1% or more and 26.1% or less, the (11-20) plane, that is, the diffraction corresponding to the a-plane of the wurtzite crystal structure A sharp peak was observed at an angle (near 58°). From this, it was found that the preferential orientation axis in the thickness direction of the thin film with the Fe concentration of 8.1% or more and 26.1% or less was the a-axis. In particular, in the case of the thin films according to Examples 3 to 9, that is, when the Fe concentration in the thin film is more than 10.2% and 24.8% or less, the peak value of the diffraction angle corresponding to the (11-20) plane is got bigger. In Example 7, that is, when the Fe concentration in the thin film was 19.4%, the peak value of the diffraction angle corresponding to the (11-20) plane was the largest. In Comparative Example 6, that is, in the case of a thin film having an Fe concentration of about 7%, the diffraction angle peaks corresponding to the (0002) plane and the (11-20) plane were weak and hardly observed. In Comparative Example 7, that is, in the case of the thin film having an Fe concentration of 30.7%, no diffraction angle peaks corresponding to the (0002) plane and the (11-20) plane were observed.

ここで、Ｉ_ｅｘｐ．（ｈｋｉｌ）は、図４に示すプロファイルから得られる（ｈｋｉｌ）面に対応するピークの強度を示し、Ｉ_ＰＤＦ（ｈｋｉｌ）は、特定の配向を持たないＡｌＮ結晶の試料（たとえば多結晶非配向膜）についてＸＲＤ法により測定を行った場合の（ｈｋｉｌ）面に対応するピークの強度、或いは、ＡｌＮの多結晶非配向膜を想定したときの理論ピーク強度を示す。 Next, FIG. 5 shows the results of calculating index values indicating the degree of crystal orientation for the thin films according to Examples 1 to 10 and Comparative Examples 1 to 7, respectively. The index value indicating the degree of orientation was calculated from the profile shown in FIG. 4 using the following relational expression (1).

Here, I _exp. (hkil) indicates the intensity of the peak corresponding to the (hkil) plane obtained from the profile shown in _FIG . ) is measured by the XRD method, or the peak intensity corresponding to the (hkil) plane, or the theoretical peak intensity assuming a polycrystalline non-oriented film of AlN.

As shown in FIG. 5, when the Fe concentration in the thin film is less than 5%, the index value indicating the degree of orientation in the [0001] direction, that is, in the c-axis direction is "1". From this, it was found that the preferential orientation axis in the thickness direction of the thin film with the Fe concentration of less than 5% was the c-axis. In addition, from the Fe concentration dependence of the magnitude of the index value corresponding to each of the [0001] direction and the [11-20] direction in FIG. It was also found that the preferential orientation axis in the film thickness direction of was switched from the c-axis to the a-axis. Furthermore, when the Fe concentration in the thin film is 8.1%, the index value corresponding to each of the [10-10] direction, [10-11] direction, and [10-12] direction is "0.15" or less. While the levels are the same, the index value corresponding to the [11-20] direction, that is, the a-axis direction exceeds "0.6". When the Fe concentration in the thin film is 19.6%, the index values corresponding to each of the [10-10] direction, [10-11] direction, and [10-12] direction are less than "0.1". On the other hand, the index value corresponding to the [11-20] direction, that is, the a-axis direction, is extremely close to 1. That is, when the concentration of Fe in the thin film was 19.6%, it was found that the degree of orientation in the a-axis direction was the highest.

Next, for each of the thin films according to Examples 1 to 10 and Comparative Examples 1 to 7, the results of calculating the lattice constant of the thin film in the (0002) plane and the full width at half maximum of the peak corresponding to the (0002) plane are shown in FIG. A). As shown in FIG. 6A, as the Fe concentration increases, both the lattice constant of the thin film in the (0002) plane and the full width at half maximum of the peak corresponding to the (0002) plane increase. Further, for each of the thin films according to Examples 1 to 10 and Comparative Examples 1 to 7, the results of calculating the lattice constant of the thin film in the (11-20) plane and the full width at half maximum of the peak corresponding to the (11-20) plane are shown. It is shown in FIG. As shown in FIG. 6A, as the Fe concentration increases, the lattice constant of the thin film in the (11-20) plane increases, while the full width at half maximum of the peak corresponding to the (11-20) plane decreases. found to do. This result indicates that the ionic radius of Fe ions is larger than the ionic radius of Al ions, so the lattice constant increases as the concentration of Fe increases and the amount of substitution from Al to Fe increases. It is considered that there are The change in the full width at half maximum shown in FIG. 6A indicates that the grain size of the c-axis oriented single crystal in the thin film decreases as the Fe concentration increases, and FIG. It can be considered that the change in the full width at half maximum shown in (1) indicates that the grain size of the a-axis oriented single crystal in the thin film increases as the Fe concentration increases.

In addition, the thin film according to Example 11 formed on the quartz glass substrate and the thin film according to Example 12 formed on the (0001) plane of the sapphire substrate are shown in FIG. 7. Here, the Fe concentrations of the thin films according to Examples 11 and 12 were both set to 14.5%. Other film forming conditions are the same as in Examples 1-10.

As shown in FIG. 7, in both Examples 11 and 12, a peak corresponding to the a-plane was observed near the diffraction angle of 58°. In the case of the thin film according to Example 12, a peak corresponding to the (0002) plane of the sapphire substrate is observed near the diffraction angle of 40°. From this fact, even if the surface of the substrate on which the thin film is grown is the (0001) plane, that is, the c-plane or a plane having an amorphous structure, the thin film has a preferential orientation axis in the film thickness direction of a turned out to be the axis

The thin film of the present invention is suitable as a material for use in LED light emitting devices, transistors, or surface acoustic wave filters.

1: Substrate with thin film, 11: Substrate, 12: Thin film, 21, 23: Cladding layer, 22: Light emitting layer, 31, 32: Electrode, 100: Semiconductor device, 900: High frequency sputtering device, 901: Chamber, 902: Matching Part 903: Heater 904, 905: Holder 906: Shutter 911: Supply port 912: Exhaust port 941, 951: Cooling mechanism 941a, 951a: Flow path CP: Individual piece TG: Target material W: Substrate

Claims (9)

A thin film formed of a nitride represented by (Al1 _{- yGay} ) _{1- xTxN} (0≤x≤1, 0≤y≤1) where T is a 3d transition metal. hand,
The nitride has a wurtzite crystal structure and a preferred orientation axis in the film thickness direction is the a-axis or the m-axis,
the 3d transition metal is Fe,
When the nitride is expressed as (Al1 _-yGay ) 1 _{- xFexN ,} y is within the range of 0≤y≤1.0 and x is 0.081<x≤0.261 . is in range ,
Thin film. When the 3d transition metal is T, (Al _1-y Ga _y ) _1-x T. _x A thin film formed of a nitride represented by N (0 ≤ x ≤ 1, 0 ≤ y ≤ 1),
The nitride has a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction is the a-axis.
Thin film. The 3d transition metal is at least one selected from Fe, Co, Ni, and Cu.
The thin film of claim 2 . a substrate;
It is formed from a nitride represented by (Al1 _{- yGay} ) _{1- xTxN} (0≤x≤1, 0≤y≤1) where T is a 3d transition metal, and is formed on the substrate a thin film provided in
The substrate is formed of a crystalline or amorphous metal, semimetal, semiconductor or insulator,
The nitride has a wurtzite crystal structure and a preferred orientation axis in the film thickness direction is the a-axis or the m-axis,
the 3d transition metal is Fe,
When the nitride is expressed as (Al1 _-yGay ) 1 _{- xFexN ,} y is within the range of 0≤y≤1.0 and x is 0.081<x≤0.261 . is in range ,
Substrate with thin film. a substrate;
When the 3d transition metal is T, (Al _1-y Ga _y ) _1-x T. _x a thin film formed of a nitride represented by N (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and provided on the substrate;
The substrate is formed of a crystalline or amorphous metal, semimetal, semiconductor or insulator,
The nitride has a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction is the a-axis.
Substrate with thin film. The 3d transition metal is at least one selected from Fe, Co, Ni, and Cu.
A substrate with a thin film according to claim 5. a substrate;
On the substrate, a first nitride represented by (Al1 _{- yGay} ) _{1-xTxN (} 0≤x≤1, 0≤y≤1) where T is the 3d transition metal a thin film formed from
a multiple quantum well structure formed from a second nitride represented by In _z (Al _1-y Ga _y ) _1-z N (0≦y≦1, 0≦z≦1) above the thin film; and a light-emitting layer having
The first nitride and the second nitride have a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction is the a-axis or the m-axis,
the 3d transition metal is Fe,
When the first nitride is expressed as (Al1 -yGay)1-xFexN _, y is _{within the range} of 0≤y≤1.0, and x is 0.081<x≤0. 261 within the range of
semiconductor device. a substrate;
On the substrate, when the 3d transition metal is T, (Al _1-y Ga _y ) _1-x T. _x a thin film formed of a first nitride represented by N (0≤x≤1, 0≤y≤1);
Above the thin film, In _z (Al _1-y Ga _y ) _1-z a light-emitting layer having a multiple quantum well structure formed from a second nitride represented by N (0 ≤ y ≤ 1, 0 ≤ z ≤ 1);
The first nitride and the second nitride have a wurtzite crystal structure, and the preferential orientation axis in the film thickness direction is the a-axis.
semiconductor device. The 3d transition metal is at least one selected from Fe, Co, Ni, and Cu.
9. The semiconductor device according to claim 8 .

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