WO2018066289A1 - Semiconductor element substrate, etching method, and etching solution - Google Patents

Semiconductor element substrate, etching method, and etching solution Download PDF

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WO2018066289A1
WO2018066289A1 PCT/JP2017/031845 JP2017031845W WO2018066289A1 WO 2018066289 A1 WO2018066289 A1 WO 2018066289A1 JP 2017031845 W JP2017031845 W JP 2017031845W WO 2018066289 A1 WO2018066289 A1 WO 2018066289A1
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layer
etching
nitride semiconductor
semiconductor element
semiconductor device
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French (fr)
Japanese (ja)
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達慶 河本
達也 山中
金子　尚史
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Jsr株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/20—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/3065—Plasma etching; Reactive-ion etching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/308—Chemical or electrical treatment, e.g. electrolytic etching using masks

Definitions

  • the present invention relates to a semiconductor element substrate, an etching method, and an etching solution.
  • AlGaN nitride semiconductor element represented by Al x Ga (1-x) N (0 ⁇ x ⁇ 1)
  • the nitride-based compound semiconductor layer is often processed by etching.
  • etching In general, there are wet etching and dry etching, but the nitride semiconductor layer is physically and chemically stable, and it is difficult to perform wet etching on the semiconductor layer. Therefore, conventionally, when manufacturing a nitride semiconductor device, dry etching is used in which etching is performed in a reactive gas atmosphere such as Cl 2 or HCl or in a plasma atmosphere (see, for example, Patent Documents 1 and 2).
  • some aspects of the present invention provide a nitride semiconductor device that can efficiently remove the altered layer formed by dry etching on the nitride semiconductor layer by solving at least a part of the above-described problems.
  • a manufacturing method is provided.
  • some embodiments according to the present invention provide a nitride semiconductor device manufactured by the manufacturing method.
  • the present invention has been made to solve at least a part of the above-described problems, and can be realized as the following aspects or application examples.
  • One aspect of the substrate for a semiconductor element according to the present invention is: An Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer, The ratio MA / MG of the Al content (MA) and the Ga content (MG) measured by XPS on the surface of the Al x Ga 1-x N (0 ⁇ x ⁇ 1) layer is 0.45 to 0 .55.
  • One aspect of the AlGaN layer etching method according to the present invention is as follows.
  • the ratio of Al loss measured by fluorescent X-ray is 5% or more.
  • AlGaN layer etching method is as follows. Wet etching is performed after dry etching.
  • AlGaN layer etching method is as follows. After contacting with water, it is contacted with an acid or alkaline aqueous solution.
  • the pH adjuster contains at least one selected from sulfuric acid, hydrofluoric acid, and ammonia.
  • the altered layer formed by dry etching on the nitride semiconductor layer can be efficiently removed, so that productivity is improved and electrical characteristics and A nitride semiconductor device having excellent optical characteristics can be manufactured.
  • FIG. 1 is a cross-sectional view schematically showing a manufacturing process of the method for manufacturing a nitride semiconductor device according to this embodiment.
  • FIG. 2 is a cross-sectional view schematically showing a manufacturing process of the method for manufacturing a nitride semiconductor device according to this embodiment.
  • FIG. 3 is a cross-sectional view schematically showing a manufacturing process of the method for manufacturing a nitride semiconductor device according to this embodiment.
  • the “nitride semiconductor layer” refers to a layer made of a nitride semiconductor in which the structure and shape of the element have not yet been formed.
  • the “nitride semiconductor element” refers to a structure in which the structure and shape of the element are formed by subjecting the nitride semiconductor layer to processing such as etching.
  • a method for manufacturing a nitride semiconductor device according to the present embodiment includes performing dry etching on an Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer to provide a device and an altered layer. And a step of removing the deteriorated layer by wet etching.
  • a method for manufacturing a nitride semiconductor device according to the present embodiment will be described with reference to cross-sectional views of manufacturing steps shown in FIGS.
  • an Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 is formed on a substrate 10.
  • a substrate such as sapphire, Si, SiC, ZnB 2 , GaN, Ga 2 O 3 , MgAlO 2 , or ZnO can be used for the substrate 10.
  • a method for forming the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 on the substrate 10 for example, a sublimation method, an HVPE (hydride vapor phase epitaxy) method, an MBE (MBE) method is used.
  • Examples include a vapor phase growth method such as a molecular beam epitaxy (MOB) method, a MOCVD (metal organic chemical vapor deposition) method, a liquid phase method such as a flux method and a high nitrogen pressure solution method.
  • a vapor phase growth method such as a molecular beam epitaxy (MOB) method, a MOCVD (metal organic chemical vapor deposition) method, a liquid phase method such as a flux method and a high nitrogen pressure solution method.
  • MOB molecular beam epitaxy
  • MOCVD metal organic chemical vapor deposition
  • Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 may be formed on the whole or part of the surface of the substrate 10, or may be a plurality of layers be a single layer. Further, the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 has, for example, a ⁇ 1000 ⁇ plane (c plane), a ⁇ 11-20 ⁇ plane (a plane), or a ⁇ 1-100 ⁇ plane ( m-plane). In addition, ⁇ indicates a collective surface, and for negative indices, “ ⁇ ” (bar) is attached on the number in terms of crystallography. It has a negative sign.
  • the nitride semiconductor layer is made of at least one of GaN, AlN, InN, and mixed crystals thereof. A layer may be formed.
  • a dry etching mask layer may be formed on the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12.
  • This dry etching mask layer acts as a mask when subsequent dry etching is performed. Therefore, the dry etching mask layer is not particularly limited as long as it is a material that is resistant to an etching agent for dry etching. Examples of the material for the dry etching mask layer include nickel, tungsten, molybdenum, and SiO 2 .
  • the dry etching mask layer is removed after the dry etching process.
  • Al x Ga (1-x) N (0 ⁇ x ⁇ 1) is obtained by ECR plasma or ICP plasma using a gas containing chlorine atoms such as chlorine gas (Cl 2 ). Dry etching is performed on the layer 12. By this dry etching process, a semiconductor element is formed in the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 and the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer. The altered layer 14 is formed on the surface 12.
  • This altered layer 14 is a defective part of the crystal structure and has been confirmed to have a thickness of about 1 to 30 nm.
  • the electrical characteristics and optical characteristics such as the band gap of the altered layer 14 are the same as the electrical characteristics and optical characteristics of the internal Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12. Behave differently. Therefore, if the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer portion is used as a semiconductor element without removing the altered layer 14, the performance as the semiconductor element may be impaired.
  • the re-grown nitride semiconductor layer is affected by the deteriorated layer 14 and is defective. A high crystal structure may be formed and the performance as a semiconductor element may be impaired. Therefore, it is desirable to remove the altered layer 14 without affecting the semiconductor element formed in the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12.
  • wet etching is performed in order to remove the altered layer 14 formed in the dry etching process.
  • the nitride semiconductor element can be immersed in an etching solution and irradiated with ultrasonic waves as necessary.
  • the temperature of the etching solution is preferably 30 to 100 ° C., more preferably 35 to 90 ° C., and more preferably 40 to 85 It is particularly preferable that the temperature is set to ° C.
  • immersion time is not specifically limited, For example, 10 seconds or more and 1000 seconds or less are preferable, and 20 seconds or more and 600 seconds or less are more preferable.
  • the removal rate is preferably 1 to 100 nm / min, and more preferably 5 to 50 nm / min.
  • an acidic aqueous solution having a pH of 1 to 4 or an alkaline aqueous solution having a pH of 9 to 14 can be used.
  • the etching solution can contain a pH adjuster.
  • the acidic aqueous solution preferably contains at least one of sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid and phosphoric acid as a pH adjuster, and at least one of sulfuric acid and hydrofluoric acid is used. It is more preferable to contain.
  • the alkaline aqueous solution preferably contains at least one of ammonia, tetramethylammonium hydroxide (salt), methanolamine, triethylenetetramine, and choline as a pH adjuster. And tetramethylammonium hydroxide (salt) are more preferable, and ammonia is particularly preferable.
  • the etching solution contains these components, it becomes easy to adjust the etching solution to a desired pH, and a clean nitride semiconductor device can be easily manufactured by cleaning the surface to be etched with pure water or the like. Can do.
  • the content of the pH adjusting agent in the etching solution is not particularly limited, and the pH adjusting agent can be contained so as to have a desired pH.
  • the etching solution further contains an oxidizing agent.
  • an oxidizing agent By containing the oxidizing agent, the removal rate of the altered layer 14 is improved.
  • examples of such an oxidizing agent include hydrogen peroxide and ammonium persulfate, and it is preferable to contain at least one of them.
  • the content of the oxidizing agent in the etching solution is not particularly limited, but is preferably 1 to 20 parts by mass, more preferably 3 to 15 parts by mass, particularly preferably when the total mass of the etching solution is 100 parts by mass. 5 to 10 parts by mass.
  • the wet etching process may be performed in one step, or may be performed in two or more stages.
  • the first wet etching step in which the nitride semiconductor element is immersed in water after the dry etching step, and the first wet etching step. It is preferable to perform two-stage wet etching including a second wet etching process in which the nitride semiconductor element is immersed in an etching solution after the etching process.
  • the nitride semiconductor element is simply immersed in water for a predetermined time after the dry etching process.
  • halogens such as F, Cl, and Br contained in the etching gas react with water
  • the removal rate (etching rate) of the altered layer 14 is improved, and the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 after the etching process is improved. Good surface roughness.
  • the nitride semiconductor device 100 including the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 in which the semiconductor device is formed on the substrate 10 is formed.
  • the nitride semiconductor device 100 thus obtained has an Al content (MA) and a Ga content (the surface of the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 measured by XPS) and the Ga content (
  • the ratio MA / MG to MG) is 0.45 to 0.55.
  • This ratio MA / MG is preferably 0.47 to 0.52.
  • the ratio MA / MG is within the above range, the element ratio in the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer 12 is maintained, whereby a predetermined band gap value can be obtained. As a result, a semiconductor element with good desired performance can be manufactured.
  • the nitride semiconductor element 100 obtained in this way preferably has a thickness of 1 mm or more, and more preferably has a thickness of 2 mm or more.
  • the nitride semiconductor element 100 having a thickness of 1 mm or more is preferable because it is difficult to break.
  • the ratio of Al loss measured by fluorescent X-ray is 5% or more.
  • Al loss is an Al decrease amount obtained by quantifying the Al amount on the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer before and after the etching process by fluorescent X-rays. It can be calculated by an equation.
  • Al loss ((Al amount before etching) ⁇ (Al amount after etching) / (Al amount before etching)) ⁇ 100
  • the ratio of Al loss is small, the element composition of the Al x Ga (1-x) N (0 ⁇ x ⁇ 1) layer before and after the etching process does not vary, and therefore Al x Ga (1-x) N before and after the etching process. (0 ⁇ x ⁇ 1) This is an indicator that a change in electrical characteristics of the layer is suppressed.
  • the nitride semiconductor device 100 thus obtained includes, for example, light-emitting devices such as light-emitting diodes and laser diodes; electrons such as rectifiers, bipolar transistors, field-effect transistors, and HEMTs (High Electron Mobility Transistors). Element; Semiconductor sensor such as temperature sensor, pressure sensor, radiation sensor, visible-ultraviolet light detector; SAW device (Surface Acoustic Wave Device), vibrator, resonator, oscillator, MEMS (Micro Electro Mechanical System) ) It can be suitably used for components and substrates for devices such as piezoelectric actuators.
  • light-emitting devices such as light-emitting diodes and laser diodes
  • electrons such as rectifiers, bipolar transistors, field-effect transistors, and HEMTs (High Electron Mobility Transistors). Element; Semiconductor sensor such as temperature sensor, pressure sensor, radiation sensor, visible-ultraviolet light detector; SAW device (Surface Acoustic Wave Device), vibr
  • Example 1 Preparation of etching solution> Ion-exchanged water 50 mass parts, 55 mass% hydrofluoric acid aqueous solution converted to hydrofluoric acid, equivalent to 0.5 mass parts (0.91 mass parts), 30 mass% hydrogen peroxide solution converted to hydrogen peroxide Then, an amount corresponding to 10 parts by mass (33.3 parts by mass) was added, and these were stirred for 15 minutes. Finally, ion-exchanged water was added so that the total amount of all components was 100 parts by mass, and then the solution was filtered with a filter having a pore diameter of 1 ⁇ m to prepare an etching solution.
  • the AlGaN film-coated wafer was dipped in the etching solution prepared above at a liquid temperature of 40 ° C. for 5 minutes for wet etching.
  • the AlGaN film-coated wafer was washed with distilled water and dried to produce a nitride semiconductor element.
  • the produced nitride semiconductor device is cut into a 5 cm square, and a film thickness of an arbitrary portion of the AlGaN film is formed using a wavelength dispersive X-ray fluorescence (WDXRF) wafer analyzer (product name “2830ZT”, manufactured by Panalytical). Three points were measured, the average value was obtained, and the AlGaN film thickness after the etching solution treatment was calculated. Then, the removal rate of the AlGaN film was calculated from the change in the AlGaN film thickness before and after the etching solution treatment and the immersion time in the etching solution. It can be determined that the removal rate of the AlGaN film is good if it is 5 nm / min or more. The results are shown in Table 1.
  • Example 2 to 4 and Comparative Examples 1 to 5 A nitride semiconductor device was fabricated and evaluated in the same manner as in Example 1 except that the etching solution having the composition shown in Table 1 was prepared and used, and the wet etching temperature was changed to the temperature shown in Table 1. The results are shown in Table 1.
  • Example 5 Preparation of etching solution> An etching solution was prepared in the same manner as in Example 1 except that the etching solution composition shown in Table 2 was changed.
  • the AlGaN film-coated wafer was dipped in 18 M ⁇ Siemens ultrapure water for 5 minutes for wet etching.
  • a nitride semiconductor device was produced and evaluated in the same manner as in Example 1 except that the etching temperature was changed to the temperature shown in Table 2 using the etching solution prepared above. The results are shown in Table 2.
  • Example 6-8 Comparative Examples 6-10 A nitride semiconductor device was fabricated and evaluated in the same manner as in Example 5 except that an etchant having the composition shown in Table 2 was prepared and used, and the wet etching temperature was changed to the temperature shown in Table 2. The results are shown in Table 2.
  • a first wet etching step is performed in which the AlGaN film on which the altered layer is formed is immersed in water, and then the AlGaN film is immersed in an etching solution. It was found that the two-stage wet etching (Examples 5 to 8 in Table 2) in which the second wet etching process is performed is superior to the one-stage wet etching (Examples 1 to 4 in Table 1).
  • the nitride semiconductor devices obtained by the manufacturing methods of Examples 1 to 8 have the Al content (MA) and Ga content (MG) on the surface of the Al x Ga 1-x N (0 ⁇ x ⁇ 1) layer.
  • the ratio MA / MG was in the range of 0.45 to 0.55.
  • the etching solution according to the present invention used in Examples 1 to 8 allows the Al loss ratio measured by fluorescent X-rays to be 5% or more, and by removing the altered layer, crystals on the wafer can be obtained. It was possible to produce a nitride semiconductor device having a ratio MA / MG of 0.45 to 0.55 with reduced defects and electrical characteristics suitable for a power semiconductor.
  • the present invention is not limited to the above embodiment, and various modifications can be made.
  • the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects).
  • the present invention also includes a configuration in which a non-essential part of the configuration described in the above embodiment is replaced with another configuration.
  • the present invention includes a configuration that achieves the same effects as the configuration described in the above embodiment or a configuration that can achieve the same object.
  • the present invention includes a configuration obtained by adding a known technique to the configuration described in the above embodiment.

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Abstract

Provided is a nitride semiconductor element manufacturing method wherein an altered layer formed to a nitride semiconductor layer by dry etching can be efficiently removed. A nitride semiconductor element manufactured by the manufacturing method is also provided. A semiconductor element substrate relating to the present invention is characterized in that: the semiconductor element substrate is provided with an AlxGa(1-x)N (0<x≤1) layer; and the value of MA/MG, i.e., the ratio between an Al content (MA) and a Ga content (MG), which are obtained by measuring the surface of the AlxGa(1-x)N (0<x≤1) layer by means of X-ray photoelectron spectroscopy (XPS), is 0.45-0.55. Furthermore, an AlGaN layer etching method relating to the present invention is characterized in that wet etching is performed after performing dry etching.

Description

半導体素子用基板、エッチング方法、及びエッチング液Semiconductor device substrate, etching method, and etchant
　本発明は、半導体素子用基板、エッチング方法、及びエッチング液に関する。 The present invention relates to a semiconductor element substrate, an etching method, and an etching solution.
　ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）（以下、単に「ＡｌＧａＮ」ともいう。）で表される窒化物半導体素子を用いた電子デバイスは、高い破壊電解強度と二次元電子ガスチャネルの高い移動度から、モータ駆動や電源回路に用いるパワー半導体デバイスとして期待されている。 An electronic device using a nitride semiconductor element represented by Al x Ga (1-x) N (0 <x ≦ 1) (hereinafter also simply referred to as “AlGaN”) has high breakdown electrolysis strength and two-dimensional electron. Due to the high mobility of the gas channel, it is expected as a power semiconductor device used for motor driving and power supply circuits.
　このような窒化物半導体素子を製造する場合、その素子を形成するために、窒化物系化合物半導体層をエッチングにより加工することが多い。一般に、エッチングには、ウエットエッチングとドライエッチングがあるが、窒化物半導体層は物理的・化学的に安定なため、この半導体層に対してウエットエッチングを行うことは困難である。そのため、従来、窒化物半導体素子を製造する場合には、Ｃｌ２やＨＣｌなどの反応性ガス雰囲気下やプラズマ雰囲気下においてエッチングを行うドライエッチングが使用される（例えば特許文献１～２参照）。 When manufacturing such a nitride semiconductor device, in order to form the device, the nitride-based compound semiconductor layer is often processed by etching. In general, there are wet etching and dry etching, but the nitride semiconductor layer is physically and chemically stable, and it is difficult to perform wet etching on the semiconductor layer. Therefore, conventionally, when manufacturing a nitride semiconductor device, dry etching is used in which etching is performed in a reactive gas atmosphere such as Cl 2 or HCl or in a plasma atmosphere (see, for example, Patent Documents 1 and 2).
特開平０８－１７８０３号公報Japanese Patent Laid-Open No. 08-17803 特開２０００－２３２０９４号公報Japanese Patent Laid-Open No. 2000-232094
　しかしながら、窒化物半導体層に対してドライエッチングを行うと、窒化物半導体層の表面がダメージを受けて、変質層が形成されるという問題があった。この変質層は、結晶構造の欠陥部である。この変質層の電気的特性及びバンドギャップなどの光学的特性は、内部の窒化物半導体層の電気的特性及び光学的特性とは異なる挙動を示す。そのため、窒化物半導体層に対してドライエッチングにより形成された変質層を効率的に除去することにより、窒化物半導体素子を製造する方法が要求されていた。 However, when dry etching is performed on the nitride semiconductor layer, the surface of the nitride semiconductor layer is damaged and a deteriorated layer is formed. This altered layer is a defect in the crystal structure. The electrical characteristics of the altered layer and optical characteristics such as a band gap behave differently from the electrical characteristics and optical characteristics of the internal nitride semiconductor layer. Therefore, there has been a demand for a method for manufacturing a nitride semiconductor element by efficiently removing the altered layer formed by dry etching on the nitride semiconductor layer.
　そこで、本発明に係る幾つかの態様は、前記課題の少なくとも一部を解決することで、窒化物半導体層に対してドライエッチングにより形成された変質層を効率的に除去できる窒化物半導体素子の製造方法を提供する。また、本発明に係る幾つかの態様は、前記製造方法により製造された窒化物半導体素子を提供する。 Accordingly, some aspects of the present invention provide a nitride semiconductor device that can efficiently remove the altered layer formed by dry etching on the nitride semiconductor layer by solving at least a part of the above-described problems. A manufacturing method is provided. In addition, some embodiments according to the present invention provide a nitride semiconductor device manufactured by the manufacturing method.
　本発明は上述の課題の少なくとも一部を解決するためになされたものであり、以下の態様または適用例として実現することができる。 The present invention has been made to solve at least a part of the above-described problems, and can be realized as the following aspects or application examples.
　［適用例１］
　本発明に係る半導体素子用基板の一態様は、
　ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層を備え、
　該ＡｌｘＧａ１－ｘＮ（０＜ｘ≦１）層の表面をＸＰＳで測定したＡｌ含有量（ＭＡ）とＧａ含有量（ＭＧ）との比ＭＡ／ＭＧの値が０．４５～０．５５であることを特徴とする。 [Application Example 1]
One aspect of the substrate for a semiconductor element according to the present invention is:
An Al x Ga (1-x) N (0 <x ≦ 1) layer,
The ratio MA / MG of the Al content (MA) and the Ga content (MG) measured by XPS on the surface of the Al x Ga 1-x N (0 <x ≦ 1) layer is 0.45 to 0 .55.
　［適用例２］
　本発明に係るＡｌＧａＮ層のエッチング方法の一態様は、
　蛍光Ｘ線で測定したＡｌ　ｌｏｓｓの比率が５％以上であることを特徴とする。 [Application Example 2]
One aspect of the AlGaN layer etching method according to the present invention is as follows.
The ratio of Al loss measured by fluorescent X-ray is 5% or more.
　［適用例３］
　本発明に係るＡｌＧａＮ層のエッチング方法の一態様は、
　ドライエッチングした後にウエットエッチングを行うことを特徴とする。 [Application Example 3]
One aspect of the AlGaN layer etching method according to the present invention is as follows.
Wet etching is performed after dry etching.
　［適用例４］
　本発明に係るＡｌＧａＮ層のエッチング方法の一態様は、
　水に接触させた後に、酸またはアルカリ性水溶液に接触させることを特徴とする。 [Application Example 4]
One aspect of the AlGaN layer etching method according to the present invention is as follows.
After contacting with water, it is contacted with an acid or alkaline aqueous solution.
　［適用例５］
　本発明に係るＡｌＧａＮ層のエッチング液の一態様は、
　ｐＨ調整剤として、硫酸、フッ酸、アンモニアから選ばれる少なくとも一種を含有することを特徴とする。 [Application Example 5]
One aspect of the etching solution for the AlGaN layer according to the present invention is:
The pH adjuster contains at least one selected from sulfuric acid, hydrofluoric acid, and ammonia.
　［適用例６］
　適用例５のエッチング液において、
　さらに酸化剤を含むことができる。 [Application Example 6]
In the etching solution of Application Example 5,
Further, an oxidizing agent can be included.
　本発明に係る窒化物半導体素子の製造方法によれば、窒化物半導体層に対してドライエッチングして形成された変質層を効率的に除去できるので、生産性が向上するとともに、電気的特性及び光学的特性に優れた窒化物半導体素子を製造することができる。 According to the method for manufacturing a nitride semiconductor device according to the present invention, the altered layer formed by dry etching on the nitride semiconductor layer can be efficiently removed, so that productivity is improved and electrical characteristics and A nitride semiconductor device having excellent optical characteristics can be manufactured.
図１は、本実施形態に係る窒化物半導体素子の製造方法の製造工程を模式的に示す断面図である。FIG. 1 is a cross-sectional view schematically showing a manufacturing process of the method for manufacturing a nitride semiconductor device according to this embodiment. 図２は、本実施形態に係る窒化物半導体素子の製造方法の製造工程を模式的に示す断面図である。FIG. 2 is a cross-sectional view schematically showing a manufacturing process of the method for manufacturing a nitride semiconductor device according to this embodiment. 図３は、本実施形態に係る窒化物半導体素子の製造方法の製造工程を模式的に示す断面図である。FIG. 3 is a cross-sectional view schematically showing a manufacturing process of the method for manufacturing a nitride semiconductor device according to this embodiment.
　以下、本発明に係る好適な実施形態について詳細に説明する。なお、本発明は、以下に記載された実施形態のみに限定されるものではなく、本発明の要旨を変更しない範囲において実施される各種の変形例も含むものとして理解されるべきである。なお、以下の図面の説明において同一または相当する部分には、同一の参照符号を付す。 Hereinafter, preferred embodiments according to the present invention will be described in detail. It should be understood that the present invention is not limited only to the embodiments described below, and includes various modifications that are implemented within a scope that does not change the gist of the present invention. In the following description of the drawings, the same or corresponding parts are denoted by the same reference numerals.
　本発明において「窒化物半導体層」とは、未だ素子の構造や形状が形成されていない窒化物半導体からなる層のことをいう。 In the present invention, the “nitride semiconductor layer” refers to a layer made of a nitride semiconductor in which the structure and shape of the element have not yet been formed.
　本発明において「窒化物半導体素子」とは、窒化物半導体層にエッチング等の加工処理を施すことにより素子の構造や形状が形成されたものをいう。 In the present invention, the “nitride semiconductor element” refers to a structure in which the structure and shape of the element are formed by subjecting the nitride semiconductor layer to processing such as etching.
　１．窒化物半導体素子の製造方法
　本実施形態に係る窒化物半導体素子の製造方法は、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層に対してドライエッチングを行って素子及び変質層を形成する工程と、前記変質層をウエットエッチングによって除去する工程と、を含むことを特徴とする。以下、本実施形態に係る窒化物半導体素子の製造方法について、図１～図３の製造工程断面図を参照しながら説明する。 1. Method for Manufacturing Nitride Semiconductor Device A method for manufacturing a nitride semiconductor device according to the present embodiment includes performing dry etching on an Al x Ga (1-x) N (0 <x ≦ 1) layer to provide a device and an altered layer. And a step of removing the deteriorated layer by wet etching. Hereinafter, a method for manufacturing a nitride semiconductor device according to the present embodiment will be described with reference to cross-sectional views of manufacturing steps shown in FIGS.
　まず、図１に示すように、基板１０上にＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２を形成する。基板１０には、サファイア、Ｓｉ、ＳｉＣ、ＺｎＢ２、ＧａＮ、Ｇａ２Ｏ３、ＭｇＡｌＯ２、ＺｎＯなどの基板を用いることができる。基板１０上にＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２を形成する方法としては、例えば、昇華法、ＨＶＰＥ（Ｈｙｄｒｉｄｅ　Ｖａｐｏｒ　Ｐｈａｓｅ　Ｅｐｉｔａｘｙ：ハイドライド気相成長）法、ＭＢＥ（Ｍｏｌｅｃｕｌａｒ　Ｂｅａｍ　Ｅｐｉｔａｘｙ：分子線エピタキシ）法、ＭＯＣＶＤ（Ｍｅｔａｌ　Ｏｒｇａｎｉｃ　Ｃｈｅｍｉｃａｌ　Ｖａｐｏｒ　Ｄｅｐｏｓｉｔｉｏｎ：有機金属化学気相堆積）法などの気相成長法、フラックス法、高窒素圧溶液法などの液相法などが挙げられる。 First, as shown in FIG. 1, an Al x Ga (1-x) N (0 <x ≦ 1) layer 12 is formed on a substrate 10. A substrate such as sapphire, Si, SiC, ZnB 2 , GaN, Ga 2 O 3 , MgAlO 2 , or ZnO can be used for the substrate 10. As a method for forming the Al x Ga (1-x) N (0 <x ≦ 1) layer 12 on the substrate 10, for example, a sublimation method, an HVPE (hydride vapor phase epitaxy) method, an MBE (MBE) method is used. Examples include a vapor phase growth method such as a molecular beam epitaxy (MOB) method, a MOCVD (metal organic chemical vapor deposition) method, a liquid phase method such as a flux method and a high nitrogen pressure solution method. .
　ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２は、基板１０の表面の全部もしくは一部に形成されていればよく、また単層でも複層でもよい。また、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２は、例えば｛１０００｝面（ｃ面）、｛１１－２０｝面（ａ面）または｛１－１００｝面（ｍ面）のいずれかであることが好ましい。なお、｛｝は、集合面を示し、負の指数については、結晶学上、“－”（バー）を数字の上に付けることになっているが、本明細書中では、数字の前に負の符号を付けている。 Al x Ga (1-x) N (0 <x ≦ 1) layer 12 may be formed on the whole or part of the surface of the substrate 10, or may be a plurality of layers be a single layer. Further, the Al x Ga (1-x) N (0 <x ≦ 1) layer 12 has, for example, a {1000} plane (c plane), a {11-20} plane (a plane), or a {1-100} plane ( m-plane). In addition, {} indicates a collective surface, and for negative indices, “−” (bar) is attached on the number in terms of crystallography. It has a negative sign.
　また、基板１０とＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２との間には、窒化物半導体層としてＧａＮ、ＡｌＮ、ＩｎＮ及びそれらの混晶の少なくともいずれかからなる層を形成してもよい。 Further, between the substrate 10 and the Al x Ga (1-x) N (0 <x ≦ 1) layer 12, the nitride semiconductor layer is made of at least one of GaN, AlN, InN, and mixed crystals thereof. A layer may be formed.
　次に、必要に応じて、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２上にドライエッチングマスク層を形成してもよい。このドライエッチングマスク層は、後続のドライエッチングを行う際にマスクとして作用する。そのため、ドライエッチングマスク層は、ドライエッチングのエッチング剤に対して耐性を示す材質であれば特に限定されない。ドライエッチングマスク層の材質としては、例えばニッケル、タングステン、モリブデン、ＳｉＯ２等が挙げられる。なお、このドライエッチングマスク層は、ドライエッチング工程の後に除去される。 Next, if necessary, a dry etching mask layer may be formed on the Al x Ga (1-x) N (0 <x ≦ 1) layer 12. This dry etching mask layer acts as a mask when subsequent dry etching is performed. Therefore, the dry etching mask layer is not particularly limited as long as it is a material that is resistant to an etching agent for dry etching. Examples of the material for the dry etching mask layer include nickel, tungsten, molybdenum, and SiO 2 . The dry etching mask layer is removed after the dry etching process.
　次に、図２に示すように、塩素ガス（Ｃｌ２）などの塩素原子を含むガスを用いたＥＣＲプラズマやＩＣＰプラズマなどにより、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２に対してドライエッチングを行う。このドライエッチング工程により、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２に半導体素子が形成されるとともに、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２の表面に変質層１４が形成される。 Next, as shown in FIG. 2, Al x Ga (1-x) N (0 <x ≦ 1) is obtained by ECR plasma or ICP plasma using a gas containing chlorine atoms such as chlorine gas (Cl 2 ). Dry etching is performed on the layer 12. By this dry etching process, a semiconductor element is formed in the Al x Ga (1-x) N (0 <x ≦ 1) layer 12 and the Al x Ga (1-x) N (0 <x ≦ 1) layer. The altered layer 14 is formed on the surface 12.
　この変質層１４は、結晶構造の欠陥部であり、１～３０ｎｍ程度の厚みを有していることが確認されている。この変質層１４の電気的特性及びバンドギャップなどの光学的特性などは、内部のＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２の電気的特性及び光学的特性などとは異なる挙動を示す。したがって、この変質層１４を除去することなくＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層の部分を半導体素子として使用すると、半導体素子としての性能が損なわれるおそれがある。また、この変質層１４の表面にさらに別の窒化物半導体層を再成長させて半導体素子を製造する場合、再成長させた別の窒化物半導体層が変質層１４の影響を受けて欠陥性の高い結晶構造を形成し、半導体素子としての性能が損なわれるおそれがある。そのため、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２に形成された半導体素子に影響を及ぼすことなく、変質層１４を除去することが望ましい。 This altered layer 14 is a defective part of the crystal structure and has been confirmed to have a thickness of about 1 to 30 nm. The electrical characteristics and optical characteristics such as the band gap of the altered layer 14 are the same as the electrical characteristics and optical characteristics of the internal Al x Ga (1-x) N (0 <x ≦ 1) layer 12. Behave differently. Therefore, if the Al x Ga (1-x) N (0 <x ≦ 1) layer portion is used as a semiconductor element without removing the altered layer 14, the performance as the semiconductor element may be impaired. When a semiconductor device is manufactured by re-growing another nitride semiconductor layer on the surface of the deteriorated layer 14, the re-grown nitride semiconductor layer is affected by the deteriorated layer 14 and is defective. A high crystal structure may be formed and the performance as a semiconductor element may be impaired. Therefore, it is desirable to remove the altered layer 14 without affecting the semiconductor element formed in the Al x Ga (1-x) N (0 <x ≦ 1) layer 12.
　そこで、次に、ドライエッチング工程において形成された変質層１４を除去するためにウエットエッチングを行う。ウエットエッチング工程では、窒化物半導体素子をエッチング液に浸漬させ、必要に応じて超音波照射させながら行うことができる。 Therefore, next, wet etching is performed in order to remove the altered layer 14 formed in the dry etching process. In the wet etching step, the nitride semiconductor element can be immersed in an etching solution and irradiated with ultrasonic waves as necessary.
　ウエットエッチング工程では、変質層１４の除去速度（エッチング速度）を向上させるために、エッチング液の温度を３０～１００℃とすることが好ましく、３５～９０℃とすることがより好ましく、４０～８５℃とすることが特に好ましい。また、浸漬時間は特に制限されないが、例えば１０秒以上１０００秒以下が好ましく、２０秒以上６００秒以下がより好ましい。 In the wet etching step, in order to improve the removal rate (etching rate) of the deteriorated layer 14, the temperature of the etching solution is preferably 30 to 100 ° C., more preferably 35 to 90 ° C., and more preferably 40 to 85 It is particularly preferable that the temperature is set to ° C. Moreover, although immersion time is not specifically limited, For example, 10 seconds or more and 1000 seconds or less are preferable, and 20 seconds or more and 600 seconds or less are more preferable.
　ウエットエッチングにより変質層１４を除去する場合、その除去速度は１～１００ｎｍ／分であることが好ましく、５～５０ｎｍ／分であることがより好ましい。前記範囲の除去速度で変質層１４を除去することにより、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２に形成された半導体素子への影響を大幅に抑制することができ、良好な電気的特性及び光学的特性を示す半導体素子を作製することができる。 When the altered layer 14 is removed by wet etching, the removal rate is preferably 1 to 100 nm / min, and more preferably 5 to 50 nm / min. By removing the altered layer 14 at a removal rate in the above range, the influence on the semiconductor element formed in the Al x Ga (1-x) N (0 <x ≦ 1) layer 12 can be significantly suppressed. Thus, a semiconductor element exhibiting favorable electrical characteristics and optical characteristics can be manufactured.
　エッチング液としては、ｐＨが１～４の酸性水溶液あるいはｐＨ９～１４のアルカリ性水溶液を用いることができる。エッチング液は、ｐＨ調整剤を含有することができる。エッチング液として酸性水溶液を用いる場合には、酸性水溶液はｐＨ調整剤として、硫酸、塩酸、硝酸、フッ酸及びリン酸の少なくともいずれかを含有することが好ましく、硫酸及びフッ酸の少なくともいずれかを含有することがより好ましい。エッチング液としてアルカリ性水溶液を用いる場合には、アルカリ性水溶液はｐＨ調整剤として、アンモニア、水酸化テトラメチルアンモニウム（塩）、メタノールアミン、トリエチレンテトラミン及びコリンの少なくともいずれかを含有することが好ましく、アンモニア及び水酸化テトラメチルアンモニウム（塩）の少なくともいずれかを含有することがより好ましく、アンモニアを含有することが特に好ましい。エッチング液がこれらの成分を含有することにより、エッチング液を所望のｐＨに調整することが容易となり、被エッチング面を純水等で洗浄することにより清浄な窒化物半導体素子を容易に作製することができる。 As the etching solution, an acidic aqueous solution having a pH of 1 to 4 or an alkaline aqueous solution having a pH of 9 to 14 can be used. The etching solution can contain a pH adjuster. When an acidic aqueous solution is used as the etching solution, the acidic aqueous solution preferably contains at least one of sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid and phosphoric acid as a pH adjuster, and at least one of sulfuric acid and hydrofluoric acid is used. It is more preferable to contain. When an alkaline aqueous solution is used as the etching solution, the alkaline aqueous solution preferably contains at least one of ammonia, tetramethylammonium hydroxide (salt), methanolamine, triethylenetetramine, and choline as a pH adjuster. And tetramethylammonium hydroxide (salt) are more preferable, and ammonia is particularly preferable. When the etching solution contains these components, it becomes easy to adjust the etching solution to a desired pH, and a clean nitride semiconductor device can be easily manufactured by cleaning the surface to be etched with pure water or the like. Can do.
　エッチング液中のｐＨ調整剤の含有量は、特に制限されず、所望のｐＨとなるようにｐＨ調整剤を含有させることができる。 The content of the pH adjusting agent in the etching solution is not particularly limited, and the pH adjusting agent can be contained so as to have a desired pH.
　また、エッチング液には、さらに酸化剤を含有させることが好ましい。酸化剤を含有させることで、変質層１４の除去速度が向上する。このような酸化剤としては、過酸化水素及び過硫酸アンモニウムが挙げられ、これらの少なくともいずれかを含有することが好ましい。エッチング液中の酸化剤の含有量は、特に制限されないが、エッチング液の全質量を１００質量部としたときに、好ましくは１～２０質量部、より好ましくは３～１５質量部、特に好ましくは５～１０質量部である。 Further, it is preferable that the etching solution further contains an oxidizing agent. By containing the oxidizing agent, the removal rate of the altered layer 14 is improved. Examples of such an oxidizing agent include hydrogen peroxide and ammonium persulfate, and it is preferable to contain at least one of them. The content of the oxidizing agent in the etching solution is not particularly limited, but is preferably 1 to 20 parts by mass, more preferably 3 to 15 parts by mass, particularly preferably when the total mass of the etching solution is 100 parts by mass. 5 to 10 parts by mass.
　ウエットエッチング工程は、１段階で行ってもよく、２段階以上の多段階で行ってもよいが、ドライエッチング工程後に窒化物半導体素子を水に浸漬させる第１ウエットエッチング工程と、前記第１ウエットエッチング工程後に窒化物半導体素子をエッチング液に浸漬させる第２ウエットエッチング工程とを含む２段階ウエットエッチングを行うことが好ましい。 The wet etching process may be performed in one step, or may be performed in two or more stages. The first wet etching step in which the nitride semiconductor element is immersed in water after the dry etching step, and the first wet etching step. It is preferable to perform two-stage wet etching including a second wet etching process in which the nitride semiconductor element is immersed in an etching solution after the etching process.
　第１ウエットエッチング工程では、ドライエッチング工程後に窒化物半導体素子を所定時間水に浸漬させるだけであるが、エッチングガスに含まれているＦ、Ｃｌ、Ｂｒ等のハロゲンが水と反応することにより、変質層１４に対するエッチング作用が生じるとともに、変質層１４の表面を酸化させて酸化物層を形成できることが明らかとなった。これにより、後続する第２ウエットエッチング工程において、変質層１４の除去速度（エッチング速度）が向上するとともに、エッチング処理後のＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２の表面ラフネスが良好となる。 In the first wet etching process, the nitride semiconductor element is simply immersed in water for a predetermined time after the dry etching process. However, when halogens such as F, Cl, and Br contained in the etching gas react with water, It has been clarified that an etching action occurs on the altered layer 14 and that the oxide layer can be formed by oxidizing the surface of the altered layer 14. Thereby, in the subsequent second wet etching step, the removal rate (etching rate) of the altered layer 14 is improved, and the Al x Ga (1-x) N (0 <x ≦ 1) layer 12 after the etching process is improved. Good surface roughness.
　このようにして、図３に示すように、基板１０の上に半導体素子が形成されたＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２を備えた窒化物半導体素子１００を製造することができる。 Thus, as shown in FIG. 3, the nitride semiconductor device 100 including the Al x Ga (1-x) N (0 <x ≦ 1) layer 12 in which the semiconductor device is formed on the substrate 10 is formed. Can be manufactured.
　このようにして得られた窒化物半導体素子１００は、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２の表面をＸＰＳで測定したＡｌ含有量（ＭＡ）とＧａ含有量（ＭＧ）との比ＭＡ／ＭＧの値が０．４５～０．５５となる。この比ＭＡ／ＭＧは、０．４７～０．５２であることが好ましい。比ＭＡ／ＭＧの値が前記範囲であると、ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層１２中の元素比が維持されることにより、所定のバンドギャップ値を得られるようになり、所望の性能の良好な半導体素子を作製することができる。 The nitride semiconductor device 100 thus obtained has an Al content (MA) and a Ga content (the surface of the Al x Ga (1-x) N (0 <x ≦ 1) layer 12 measured by XPS) and the Ga content ( The ratio MA / MG to MG) is 0.45 to 0.55. This ratio MA / MG is preferably 0.47 to 0.52. When the ratio MA / MG is within the above range, the element ratio in the Al x Ga (1-x) N (0 <x ≦ 1) layer 12 is maintained, whereby a predetermined band gap value can be obtained. As a result, a semiconductor element with good desired performance can be manufactured.
　また、このようにして得られた窒化物半導体素子１００は、１ｍｍ以上の厚みを有することが好ましく、２ｍｍ以上の厚みを有することがより好ましい。窒化物半導体素子１００が１ｍｍ以上の厚みを有することで、破損し難くなるので好ましい。 Further, the nitride semiconductor element 100 obtained in this way preferably has a thickness of 1 mm or more, and more preferably has a thickness of 2 mm or more. The nitride semiconductor element 100 having a thickness of 1 mm or more is preferable because it is difficult to break.
　本実施形態に係る窒化物半導体素子の製造方法において、蛍光Ｘ線で測定したＡｌ　ｌｏｓｓの比率は５％以上となる。ここで、「Ａｌ　ｌｏｓｓ」とは、エッチング処理前後のＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層上のＡｌ量を蛍光Ｘ線で定量したＡｌ減少量であり、下記計算式により算出することができる。
Ａｌ　ｌｏｓｓ＝（（エッチング前のＡｌ量）－（エッチング後のＡｌ量）／（エッチング前のＡｌ量））×１００
　Ａｌ　ｌｏｓｓの比率が小さい場合、エッチング処理前後のＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層の元素組成に変動がないため、エッチング前後でＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層の電気特性の変化が抑制されているという指標となる。 In the method for manufacturing a nitride semiconductor device according to the present embodiment, the ratio of Al loss measured by fluorescent X-ray is 5% or more. Here, “Al loss” is an Al decrease amount obtained by quantifying the Al amount on the Al x Ga (1-x) N (0 <x ≦ 1) layer before and after the etching process by fluorescent X-rays. It can be calculated by an equation.
Al loss = ((Al amount before etching) − (Al amount after etching) / (Al amount before etching)) × 100
When the ratio of Al loss is small, the element composition of the Al x Ga (1-x) N (0 <x ≦ 1) layer before and after the etching process does not vary, and therefore Al x Ga (1-x) N before and after the etching process. (0 <x ≦ 1) This is an indicator that a change in electrical characteristics of the layer is suppressed.
　このようにして得られた窒化物半導体素子１００は、たとえば発光ダイオード、レーザダイオードなどの発光素子；整流器、バイポーラトランジスタ、電界効果トランジスタ、ＨＥＭＴ（Ｈｉｇｈ　Ｅｌｅｃｔｒｏｎ　Ｍｏｂｉｌｉｔｙ　Ｔｒａｎｓｉｓｔｏｒ；高電子移動度トランジスタ）などの電子素子；温度センサ、圧力センサ、放射線センサ、可視－紫外光検出器などの半導体センサ；ＳＡＷデバイス（Ｓｕｒｆａｃｅ　Ａｃｏｕｓｔｉｃ　Ｗａｖｅ　Ｄｅｖｉｃｅ；表面弾性波素子）、振動子、共振子、発振器、ＭＥＭＳ（Ｍｉｃｒｏ　Ｅｌｅｃｔｒｏ　Ｍｅｃｈａｎｉｃａｌ　Ｓｙｓｔｅｍ）部品、圧電アクチュエータ等のデバイス用の基板などに好適に用いることができる。 The nitride semiconductor device 100 thus obtained includes, for example, light-emitting devices such as light-emitting diodes and laser diodes; electrons such as rectifiers, bipolar transistors, field-effect transistors, and HEMTs (High Electron Mobility Transistors). Element; Semiconductor sensor such as temperature sensor, pressure sensor, radiation sensor, visible-ultraviolet light detector; SAW device (Surface Acoustic Wave Device), vibrator, resonator, oscillator, MEMS (Micro Electro Mechanical System) ) It can be suitably used for components and substrates for devices such as piezoelectric actuators.
　２．実施例
　以下、本発明を実施例に基づいて具体的に説明するが、本発明はこれらの実施例に限定されるものではない。実施例、比較例中の「部」および「％」は、特に断らない限り質量基準である。 2. EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. “Part” and “%” in Examples and Comparative Examples are based on mass unless otherwise specified.
　２．１．実施例１
＜エッチング液の調製＞
　イオン交換水５０質量部、５５質量％フッ酸水溶液をフッ酸に換算して０．５質量部に相当する量（０．９１質量部）、３０質量％過酸化水素水を過酸化水素に換算して１０質量部に相当する量（３３．３質量部）を添加し、これらを１５分間撹拌した。最後に、全成分の合計量が１００質量部となるようにイオン交換水を加えた後、孔径１μｍのフィルターで濾過することにより、エッチング液を調製した。 2.1. Example 1
<Preparation of etching solution>
Ion-exchanged water 50 mass parts, 55 mass% hydrofluoric acid aqueous solution converted to hydrofluoric acid, equivalent to 0.5 mass parts (0.91 mass parts), 30 mass% hydrogen peroxide solution converted to hydrogen peroxide Then, an amount corresponding to 10 parts by mass (33.3 parts by mass) was added, and these were stirred for 15 minutes. Finally, ion-exchanged water was added so that the total amount of all components was 100 parts by mass, and then the solution was filtered with a filter having a pore diameter of 1 μm to prepare an etching solution.
＜窒化物半導体素子の作製＞
　ＮＴＴアドバンステクノロジ株式会社製のシリコンウエハ上に２μｍのＧａＮ膜を形成し、さらにその上にＡｌＧａＮ膜を３０ｎｍの厚さとなるようにエピタキシャル成長させたＡｌＧａＮ膜付きウエハを、圧力１０ｍＴｏｒｒのＢＣｌ３とＣｌ２の１：１混合ガスプラズマに暴露し、ドライエッチングを行った。その後、ＡｌＧａＮ膜付きウエハを、液温４０℃の上記で調製したエッチング液に５分間浸漬しウエットエッチングを行った。その後、ＡｌＧａＮ膜付きウエハを蒸留水で洗浄し、乾燥することにより、窒化物半導体素子を作製した。 <Production of nitride semiconductor device>
A wafer with an AlGaN film, in which a 2 μm GaN film is formed on a silicon wafer manufactured by NTT Advanced Technology Corporation and an AlGaN film is epitaxially grown so as to have a thickness of 30 nm, is formed on BCl 3 and Cl 2 at a pressure of 10 mTorr. Were subjected to dry etching by exposure to 1: 1 mixed gas plasma. Thereafter, the AlGaN film-coated wafer was dipped in the etching solution prepared above at a liquid temperature of 40 ° C. for 5 minutes for wet etching. Thereafter, the AlGaN film-coated wafer was washed with distilled water and dried to produce a nitride semiconductor element.
＜窒化物半導体素子の評価＞
　作製した窒化物半導体素子を３ｃｍ角にカットし、走査型Ｘ線光電子分光分析装置（ＸＰＳ、アルバックファイ社製、製品名「ＰＨＩ　Ｑｕａｎｔｅｒａ　ＩＩ」）を用いてＡｌＧａＮ膜表面の組成を評価した。その結果を表１に示す。 <Evaluation of nitride semiconductor device>
The produced nitride semiconductor device was cut into a 3 cm square, and the composition of the AlGaN film surface was evaluated using a scanning X-ray photoelectron spectrometer (XPS, product name “PHI Quantera II” manufactured by ULVAC-PHI). The results are shown in Table 1.
　作製した窒化物半導体素子を５ｃｍ角にカットし、波長分散型蛍光Ｘ線（ＷＤＸＲＦ）ウェハーアナライザ（パナリティカル社製、製品名「２８３０ＺＴ」）を用いて、ＡｌＧａＮ膜の任意の箇所の膜厚を３点測定し、その平均値を求めてエッチング液処理後のＡｌＧａＮ膜厚を算出した。そして、エッチング液処理前後のＡｌＧａＮ膜厚の変化とエッチング液への浸漬時間からＡｌＧａＮ膜の除去速度を算出した。ＡｌＧａＮ膜の除去速度は、５ｎｍ／分以上であれば良好であると判断することができる。その結果を表１に示す。 The produced nitride semiconductor device is cut into a 5 cm square, and a film thickness of an arbitrary portion of the AlGaN film is formed using a wavelength dispersive X-ray fluorescence (WDXRF) wafer analyzer (product name “2830ZT”, manufactured by Panalytical). Three points were measured, the average value was obtained, and the AlGaN film thickness after the etching solution treatment was calculated. Then, the removal rate of the AlGaN film was calculated from the change in the AlGaN film thickness before and after the etching solution treatment and the immersion time in the etching solution. It can be determined that the removal rate of the AlGaN film is good if it is 5 nm / min or more. The results are shown in Table 1.
　２．２．実施例２～４、比較例１～５
　表１に記載の組成のエッチング液を調製して使用し、ウエットエッチング温度を表１の温度に変更した以外は実施例１と同様にして窒化物半導体素子を作製して評価した。その結果を表１に示す。 2.2. Examples 2 to 4 and Comparative Examples 1 to 5
A nitride semiconductor device was fabricated and evaluated in the same manner as in Example 1 except that the etching solution having the composition shown in Table 1 was prepared and used, and the wet etching temperature was changed to the temperature shown in Table 1. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　２．３．実施例５
＜エッチング液の調製＞
　表２に記載のエッチング液組成に変更した以外は実施例１と同様にしてエッチング液を調製した。 2.3. Example 5
<Preparation of etching solution>
An etching solution was prepared in the same manner as in Example 1 except that the etching solution composition shown in Table 2 was changed.
＜窒化物半導体素子の作製及び評価＞
　ＮＴＴアドバンステクノロジ株式会社製のシリコンウエハ上に２μｍのＧａＮ膜を形成し、さらにその上にＡｌＧａＮ膜を３０ｎｍの厚さとなるようにエピタキシャル成長させたＡｌＧａＮ膜付きウエハを、圧力１０ｍＴｏｒｒのＢＣｌ３とＣｌ２の１：１混合ガスプラズマに暴露し、ドライエッチングを行った。その後、ＡｌＧａＮ膜付きウエハを、１８ＭΩジーメンスの超純水に５分間浸漬しウエットエッチングを行った。その後、上記で調製したエッチング液を用いて、エッチング温度を表２の温度に変更した以外は実施例１と同様にして窒化物半導体素子を作製して評価した。その結果を表２に示す。 <Production and Evaluation of Nitride Semiconductor Device>
A wafer with an AlGaN film, in which a 2 μm GaN film is formed on a silicon wafer manufactured by NTT Advanced Technology Corporation and an AlGaN film is epitaxially grown so as to have a thickness of 30 nm, is formed on BCl 3 and Cl 2 at a pressure of 10 mTorr. Were subjected to dry etching by exposure to 1: 1 mixed gas plasma. Thereafter, the AlGaN film-coated wafer was dipped in 18 MΩ Siemens ultrapure water for 5 minutes for wet etching. Thereafter, a nitride semiconductor device was produced and evaluated in the same manner as in Example 1 except that the etching temperature was changed to the temperature shown in Table 2 using the etching solution prepared above. The results are shown in Table 2.
　２．４．実施例６～８、比較例６～１０
　表２に記載の組成のエッチング液を調製して使用し、ウエットエッチング温度を表２の温度に変更した以外は実施例５と同様にして窒化物半導体素子を作製して評価した。その結果を表２に示す。 2.4. Examples 6-8, Comparative Examples 6-10
A nitride semiconductor device was fabricated and evaluated in the same manner as in Example 5 except that an etchant having the composition shown in Table 2 was prepared and used, and the wet etching temperature was changed to the temperature shown in Table 2. The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　２．５．評価結果
　ＡｌＧａＮ膜をエッチング液に浸漬させてウエットエッチングを行っても、ＡｌＧａＮ膜は物理的・化学的に安定なため、エッチングすることは困難である。しかしながら、実施例１～８で示されるように、ドライエッチングを行った後、所定の組成を有するエッチング液を用いたウエットエッチングを行うことにより、ドライエッチングにより形成されたＡｌＧａＮ膜の変質層を除去できることが判明した。 2.5. Evaluation Result Even when wet etching is performed by immersing the AlGaN film in an etching solution, it is difficult to etch because the AlGaN film is physically and chemically stable. However, as shown in Examples 1 to 8, after performing dry etching, wet etching using an etching solution having a predetermined composition is performed to remove the altered layer of the AlGaN film formed by dry etching. It turns out that you can.
　また、ＡｌＧａＮ膜の変質層をより効率的に除去するためには、まず変質層が形成されたＡｌＧａＮ膜を水に浸漬させる第１ウエットエッチング工程を行い、その後該ＡｌＧａＮ膜をエッチング液に浸漬させる第２ウエットエッチング工程を行う、２段階ウエットエッチング（表２の実施例５～８）の方が１段階ウエットエッチング（表１の実施例１～４）よりも優れていることが判明した。 In order to more efficiently remove the altered layer of the AlGaN film, first, a first wet etching step is performed in which the AlGaN film on which the altered layer is formed is immersed in water, and then the AlGaN film is immersed in an etching solution. It was found that the two-stage wet etching (Examples 5 to 8 in Table 2) in which the second wet etching process is performed is superior to the one-stage wet etching (Examples 1 to 4 in Table 1).
　実施例１～８の製造方法により得られた窒化物半導体素子は、ＡｌｘＧａ１－ｘＮ（０＜ｘ≦１）層の表面のＡｌ含有量（ＭＡ）とＧａ含有量（ＭＧ）との比ＭＡ／ＭＧの値が０．４５～０．５５の範囲内にあった。ＡｌＧａＮ膜中の元素比が前記範囲であることにより、所定のバンドギャップ値を得られるようになり、所望の性能のパワー半導体デバイスを得られると推測される。また、実施例１～８で使用した本願発明に係るエッチング液により、蛍光Ｘ線で測定したＡｌ　ｌｏｓｓの比率を５％以上とすることができ、変質層を除去することにより、ウエハ上の結晶欠陥を低減し、パワー半導体に適した電気特性を有する比ＭＡ／ＭＧの値が０．４５～０．５５の窒化物半導体素子を作製することができた。 The nitride semiconductor devices obtained by the manufacturing methods of Examples 1 to 8 have the Al content (MA) and Ga content (MG) on the surface of the Al x Ga 1-x N (0 <x ≦ 1) layer. The ratio MA / MG was in the range of 0.45 to 0.55. When the element ratio in the AlGaN film is within the above range, a predetermined band gap value can be obtained, and it is estimated that a power semiconductor device having a desired performance can be obtained. In addition, the etching solution according to the present invention used in Examples 1 to 8 allows the Al loss ratio measured by fluorescent X-rays to be 5% or more, and by removing the altered layer, crystals on the wafer can be obtained. It was possible to produce a nitride semiconductor device having a ratio MA / MG of 0.45 to 0.55 with reduced defects and electrical characteristics suitable for a power semiconductor.
　本発明は、上記の実施形態に限定されるものではなく、種々の変形が可能である。本発明は、実施形態で説明した構成と実質的に同一の構成（例えば、機能、方法および結果が同一の構成、あるいは目的および効果が同一の構成）を包含する。また本発明は、上記の実施形態で説明した構成の本質的でない部分を他の構成に置き換えた構成を包含する。さらに本発明は、上記の実施形態で説明した構成と同一の作用効果を奏する構成または同一の目的を達成することができる構成をも包含する。さらに本発明は、上記の実施形態で説明した構成に公知技術を付加した構成をも包含する。 The present invention is not limited to the above embodiment, and various modifications can be made. The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). The present invention also includes a configuration in which a non-essential part of the configuration described in the above embodiment is replaced with another configuration. Furthermore, the present invention includes a configuration that achieves the same effects as the configuration described in the above embodiment or a configuration that can achieve the same object. Furthermore, the present invention includes a configuration obtained by adding a known technique to the configuration described in the above embodiment.
１０…基板、１２…ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層、１４…変質層、１００…窒化物半導体素子 10 ... substrate, 12 ... Al x Ga (1 -x) N (0 <x ≦ 1) layer, 14 ... altered layer, 100 ... nitride semiconductor device

Claims (6)

  1. 　ＡｌｘＧａ（１－ｘ）Ｎ（０＜ｘ≦１）層を備え、
    　該ＡｌｘＧａ１－ｘＮ（０＜ｘ≦１）層の表面をＸＰＳで測定したＡｌ含有量（ＭＡ）とＧａ含有量（ＭＧ）との比ＭＡ／ＭＧの値が０．４５～０．５５である、半導体素子用基板。     An Al x Ga (1-x) N (0 <x ≦ 1) layer,
    The ratio MA / MG of the Al content (MA) and the Ga content (MG) measured by XPS on the surface of the Al x Ga 1-x N (0 <x ≦ 1) layer is 0.45 to 0 .55 for a semiconductor device.
  2. 　蛍光Ｘ線で測定したＡｌ　ｌｏｓｓの比率が５％以上である、ＡｌＧａＮ層のエッチング方法。 An AlGaN layer etching method in which the Al loss ratio measured by fluorescent X-ray is 5% or more.
  3. 　ドライエッチングした後にウエットエッチングを行うことを特徴とするＡｌＧａＮ層のエッチング方法。 An etching method for an AlGaN layer, characterized by performing wet etching after dry etching.
  4. 　水に接触させた後に、酸またはアルカリ性水溶液に接触させることを特徴とするＡｌＧａＮ層のエッチング方法。 An etching method for an AlGaN layer, characterized by contacting with water and then with an acid or alkaline aqueous solution.
  5. 　ｐＨ調整剤として、硫酸、フッ酸、アンモニアから選ばれる少なくとも一種を含有するＡｌＧａＮ層のエッチング液。 An etching solution for an AlGaN layer containing at least one selected from sulfuric acid, hydrofluoric acid, and ammonia as a pH adjuster.
  6. 　さらに酸化剤を含む、請求項５に記載のＡｌＧａＮ層のエッチング液。 The etching solution for an AlGaN layer according to claim 5, further comprising an oxidizing agent.
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