WO2024082636A1 - 一种肖特基势垒二极管 - Google Patents

一种肖特基势垒二极管 Download PDF

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WO2024082636A1
WO2024082636A1 PCT/CN2023/096765 CN2023096765W WO2024082636A1 WO 2024082636 A1 WO2024082636 A1 WO 2024082636A1 CN 2023096765 W CN2023096765 W CN 2023096765W WO 2024082636 A1 WO2024082636 A1 WO 2024082636A1
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Prior art keywords
semiconductor layer
layer
schottky
sno2
barrier diode
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PCT/CN2023/096765
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English (en)
French (fr)
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尹向阳
谢弟银
李静
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广州华瑞升阳投资有限公司
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Publication of WO2024082636A1 publication Critical patent/WO2024082636A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
    • H01L29/861—Diodes
    • H01L29/872—Schottky diodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
    • H01L29/24—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/66007—Multistep manufacturing processes
    • H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
    • H01L29/66083—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by variation of the electric current supplied or the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched, e.g. two-terminal devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
    • H01L29/861—Diodes

Definitions

  • the invention relates to the technical field of semiconductor devices, and in particular to a Schottky barrier diode.
  • Semiconductor materials have been developed for decades, from the first generation of semiconductor materials such as germanium and silicon, to the second generation of semiconductor materials such as gallium arsenide and indium phosphide, to the third generation of semiconductor materials such as silicon carbide, gallium nitride, boron nitride, etc., and oxide semiconductor materials including gallium oxide, zinc oxide, tin oxide, etc.
  • semiconductor materials such as germanium and silicon
  • gallium arsenide and indium phosphide such as silicon carbide, gallium nitride, boron nitride, etc.
  • oxide semiconductor materials including gallium oxide, zinc oxide, tin oxide, etc.
  • Silicon is currently the most commonly used material for semiconductor devices and power devices. Its raw material reserves are abundant, and the crystal growth process is mature and efficient; however, the band gap of silicon material is 1.1eV, and the breakdown field strength is only 40V/ ⁇ m. In some high-voltage and high-temperature fields, its application has great limitations.
  • the third-generation semiconductor materials that are in full swing at present have significantly improved material properties compared to silicon.
  • the band gap width of silicon carbide is about 3.3eV, which is three times that of silicon; the breakdown field strength is about 300V/ ⁇ m, which is more than seven times that of silicon.
  • the band gap width of gallium nitride is about 3.44eV, which is more than three times that of silicon; the breakdown field strength is about 500V/ ⁇ m, which is more than 10 times that of silicon.
  • the mainstream preparation process of silicon carbide single crystals adopts physical vapor transport [PVT], which has a relatively slow crystal growth efficiency, and because silicon carbide has more than 200 isomers, its crystal growth yield is very low.
  • PVT physical vapor transport
  • the mainstream preparation process of gallium nitride single crystals adopts halide vapor phase epitaxy [HVPE], which uses epitaxy to grow crystals, making its crystal growth efficiency slower than silicon carbide, and coupled with the more expensive source materials, the cost of gallium nitride single crystals is more than three times that of silicon carbide single crystals.
  • the technical problem to be solved by the present invention is to provide a Schottky barrier diode, which can be applied to higher reverse withstand voltage scenarios and can suppress the increase of forward voltage.
  • the Schottky barrier diode provided by the present invention is as follows:
  • a Schottky barrier diode comprising:
  • a second semiconductor layer wherein a lower surface of the second semiconductor layer forms an ohmic contact with an upper surface of the ohmic electrode layer, the second semiconductor layer is an n-type semiconductor layer, and the second semiconductor layer includes a SnO2- based compound semiconductor material;
  • the first semiconductor layer is an n-type semiconductor layer, including a SnO 2 compound semiconductor material, the concentration of electron carriers of which is less than or equal to 5 ⁇ 10 17 /cm 3 , when the reverse withstand voltage of the Schottky barrier diode is set to 10-10000V, the thickness of the first semiconductor layer is greater than or equal to 0.18 ⁇ m and less than or equal to 112 ⁇ m, and the concentration of electron carriers in the first semiconductor layer is lower than the concentration of electron carriers in the second semiconductor layer;
  • a Schottky electrode layer wherein a lower surface of the Schottky electrode layer forms a Schottky contact with an upper surface of the first semiconductor layer.
  • a dielectric layer is stacked on the upper surface of the first semiconductor layer, a window is provided on the dielectric layer, thereby partially leaking out the upper surface of the first semiconductor layer, the Schottky electrode layer is filled in the window, and extends along the side wall of the window to the upper surface of the dielectric layer.
  • the concentration of electron carriers in the second semiconductor layer is more than 10 times higher than the concentration of electron carriers in the first semiconductor layer.
  • the thickness of the first semiconductor layer is greater than or equal to the width of the depletion layer corresponding to the reverse withstand voltage.
  • the concentration of electron carriers in the first semiconductor layer is less than or equal to 5 ⁇ 10 16 /cm 3 ; or the concentration of electron carriers in the first semiconductor layer is 5 ⁇ 10 15 /cm 3 .
  • the electron carrier concentration of the second semiconductor layer is greater than or equal to 5 ⁇ 10 17 /cm 3 .
  • the electron carrier concentration of the second semiconductor layer is greater than or equal to 5 ⁇ 10 17 /cm 3 .
  • the Schottky diode based on SnO2 semiconductor material provided by the present invention has the following two effects:
  • Schottky diodes based on SnO2 semiconductor materials can be used in higher reverse voltage withstand scenarios, and their voltage withstand capability can be as high as several thousand volts. It can also suppress the increase of forward voltage, reduce device loss and reduce device heating.
  • the single crystal preparation of Schottky diodes based on SnO2 semiconductor materials adopts the physical vapor transport method [PVT].
  • PVT physical vapor transport method
  • the preparation efficiency of SnO2 single crystals is higher than that of gallium nitride single crystals, and the source material cost of SnO2 single crystals is lower than that of gallium nitride single crystals, which has greatly reduced the cost of SnO2 single crystals compared with gallium nitride single crystals.
  • the reduction in single crystal costs allows SnO2 -based Schottky diodes to be used in a wider range.
  • FIG. 1 is a cross-sectional structural diagram of a Schottky barrier diode according to a first embodiment of the present invention
  • 2A is a comparative table showing the relationship between the electron carrier concentration, resistivity , thickness and voltage drop of the n- semiconductor layer and the n+ semiconductor layer when the reverse withstand voltage is set to 100V for the case where Si is used as the semiconductor material and the case where SnO 2 is used as the semiconductor material in the present invention;
  • 2B is a comparison table showing the relationship between the electron carrier concentration, resistivity , thickness and voltage drop of the n- semiconductor layer and the n+ semiconductor layer when the reverse withstand voltage is set to 600V for the case where SiC is used as the semiconductor material and the case where SnO 2 is used as the semiconductor material in the present invention;
  • 2C is a comparison table showing the relationship between the electron carrier concentration, resistivity, thickness and voltage drop of the n- semiconductor layer and the n+ semiconductor layer when the reverse withstand voltage is set to 1000V for the case where SiC is used as the semiconductor material and the case where SnO2 is used as the semiconductor material in the present invention;
  • 2D is a comparative table showing the relationship between the electron carrier concentration, resistivity, thickness and voltage drop of the n- semiconductor layer and the n+ semiconductor layer when the reverse withstand voltage is set to 10000V for the case where SiC is used as the semiconductor material and the case where SnO 2 is used as the semiconductor material in the present invention;
  • FIG. 3 is a cross-sectional structural diagram of a Schottky barrier diode according to a second embodiment of the present invention.
  • the above drawings include the following reference numerals: 1. Schottky electrode layer, 2. dielectric layer, 3. n-type semiconductor layer, 31. first semiconductor layer, 32. second semiconductor layer, 4. ohmic electrode layer.
  • the layer/region when a layer/region is described as being “disposed/stacked” on another layer/region, the layer/region may be “directly disposed/stacked” on the other layer/region, or be “disposed/stacked” on the other layer/region through a third layer/region; when a process step is described as being continued to another process step, the process step may be directly continued to the other process step, or be continued to the other process step through a third process step.
  • FIG. 1 is a cross-sectional structural diagram of a Schottky barrier diode according to a first embodiment of the present invention, wherein the Schottky barrier diode comprises: an ohmic electrode layer 4; a second semiconductor layer 32, wherein the lower surface of the second semiconductor layer 32 forms an ohmic contact with the upper surface of the ohmic electrode layer 4, and the second semiconductor layer 32 is an n-type semiconductor layer, and the second semiconductor layer 32 comprises a SnO2 compound semiconductor material; a first semiconductor layer 31, which is an n-type semiconductor layer, and comprises a SnO2 compound semiconductor material, and the concentration of electron carriers thereof is less than or equal to 5 ⁇ 10 17 /cm 3 , and when the reverse withstand voltage of the Schottky barrier diode is set to 10-10000V, the thickness of the first semiconductor layer 31 is greater than or equal to 0.18 ⁇ m and less than or equal to 112 ⁇ m, and the concentration of electron carriers of the first semiconductor layer 31 is lower than the concentration of electron carriers of the
  • the second semiconductor layer 32 is equivalent to an n-type heavily doped [n+] SnO 2 substrate layer, which contains conductive impurities such as Nb or Sb; the SnO 2 substrate layer is formed by slicing, thinning and grinding a bulk single crystal of a SnO 2 single crystal grown by physical vapor transport [PVT].
  • the first semiconductor layer 31 is equivalent to an n-type lightly doped [n-] SnO 2 epitaxial layer, which contains Nb or Sb Conductive impurities such as SnO2 epitaxial layer are grown by vapor phase epitaxy methods such as MOCVD [Metal Organic Chemical Vapor Epitaxy], and a SnO2 semiconductor layer with a lightly n-type doping is epitaxially grown on one side of the SnO2 substrate layer.
  • MOCVD Metal Organic Chemical Vapor Epitaxy
  • the breakdown field strength of Si is about 40V/ ⁇ m, and the breakdown field strength of SiC is about 300V/ ⁇ m.
  • the breakdown field strength of SnO2 is about 430V/ ⁇ m, which is higher than both Si and SiC.
  • the reverse withstand voltage of a Schottky diode is positively correlated with the square of the breakdown electric field strength and inversely correlated with the electron carrier concentration. Therefore, if the breakdown electric field strength increases, the reverse withstand voltage will also increase when the electron carrier concentration remains the same. If the same reverse withstand voltage is required, the forward resistance will decrease and the forward voltage drop [V F ] will decrease by increasing the breakdown electric field strength and thus the electron carrier concentration.
  • Fig. 2A to Fig. 2D are comparison tables showing the relationship between the electron carrier concentration, resistivity , thickness of the first semiconductor layer (31) [epitaxial layer] and the second semiconductor layer (32) [substrate] and the voltage drop when the current density is set to 200A/ cm2 , for the case where Si or SiC is used as the semiconductor material and the case where SnO2 is used as the semiconductor material in the present invention.
  • Fig. 2A is a comparison table when Si and SnO2 are used and the reverse withstand voltage is set to 100V
  • Fig. 2B is a comparison table when SiC and SnO2 are used and the reverse withstand voltage is set to 600V
  • 2C is a comparison table when SiC and SnO2 are used and the reverse withstand voltage is set to 1000V [1kV]
  • Fig. 2D is a comparison table when SiC and SnO2 are used and the reverse withstand voltage is set to 10000V [10kV].
  • the electron carrier concentration and thickness of the n- semiconductor layer are 2.47x10 15 /cm 3 and 7.5 ⁇ m in Si, while they are 2x10 17 /cm 3 and 0.923 ⁇ m in SnO 2 of the first embodiment. Therefore, the voltage drop in the n- semiconductor layer is 0.1955 V in Si, while it is 0.0026 V in SnO 2. As a result, the total voltage drop including the n- semiconductor layer and the n+ semiconductor layer is 0.2226 V in Si and 0.0919 V in SnO 2 , which can reduce the voltage drop by about 59%.
  • the electron carrier concentration and thickness of the n- semiconductor layer are 2.16x10 16 /cm 3 and 5.46 ⁇ m in SiC, while they are 4x10 16 /cm 3 and 3.07 ⁇ m in SnO 2 of the first embodiment.
  • the voltage drop in the n- semiconductor layer is 0.0345 V in SiC, while it is 0.0369 V in SnO 2.
  • the total voltage drop including the n- semiconductor layer and the n+ ... SnC while it is 0.0369 V in SnO 2.
  • the total voltage drop including the n- semiconductor layer and the n+ semiconductor layer is 0 0.0546V, in the case of SnO2 it is 0.0667V, the voltage drop has increased to a certain extent, about 22%. However, because the value itself is very small, the absolute value of the voltage drop is only increased by 0.0121V.
  • SiC single crystal and SnO2 single crystal also use physical vapor transport [PVT] to grow crystals. Since SnO2 has only one phase [tetragonal rutile phase] that is stable under the crystal growth environment conditions, and SiC has multiple isomers coexisting under the crystal growth conditions, the growth yield of SnO2 single crystal will be much higher than that of SiC single crystal.
  • SnO2 single crystal is much lower than that of SiC single crystal.
  • the cost of SnO2- based Schottky diodes will also be much lower than that of SiC-based Schottky diodes.
  • SnO2 -based Schottky diodes Under the condition of equivalent device performance, SnO2 -based Schottky diodes, with lower costs, can have a wider range of uses.
  • the electron carrier concentration and thickness of the n- semiconductor layer are 1.3x10 16 /cm 3 and 9.1 ⁇ m in SiC, while they are 2.7x10 16 /cm 3 and 5.12 ⁇ m in SnO 2 of the first embodiment.
  • the voltage drop in the n- semiconductor layer is 0.0914 V in SiC, while it is 0.0911 V in SnO 2.
  • the total voltage drop including the n- semiconductor layer and the n+ semiconductor layer is 0.1115 V in SiC and 0.1209 V in SnO 2 , and the voltage drop increases to a certain extent, about 8%.
  • SnO2- based Schottky diodes Based on the Schottky diodes made of them as substrates, the cost of SnO2- based Schottky diodes will also be much lower than that of SiC-based Schottky diodes. Under the condition of equivalent device performance, SnO2 -based Schottky diodes, with lower costs, can have a wider range of uses.
  • the electron carrier concentration and thickness of the n- semiconductor layer are 1.3x10 15 /cm 3 and 90.9 ⁇ m in SiC, while they are 2.7x10 15 /cm 3 and 51.2 ⁇ m in SnO 2 of the first embodiment. Therefore, the voltage drop in the n- semiconductor layer is 8.1118 V in SiC, while it is 9.1168 V in SnO 2.
  • the total voltage drop including the n- semiconductor layer and the n+ semiconductor layer is 8.1319 V in SiC and 9.1466 V in SnO 2 , and the voltage drop increases to a certain extent, about 12%, and the absolute value of the voltage drop increases only by 1.0147 V.
  • SiC single crystal and SnO2 single crystal also use physical vapor transport [PVT] crystal growth. Since SnO2 has only one phase [four Rutile phase] exists stably, while SiC has multiple isomers coexisting under crystal growth conditions. Therefore, the growth yield of SnO2 single crystal will be much higher than that of SiC single crystal.
  • the cost of SnO2 single crystal is much lower than that of SiC single crystal.
  • the cost of SnO2 -based Schottky diodes will also be much lower than that of SiC-based Schottky diodes. Under the condition of equivalent device performance, SnO2 -based Schottky diodes have a lower cost and can have a wider range of applications.
  • the electron affinity of the semiconductor must be smaller than the work function of the metal that serves as the electrode.
  • Metals that satisfy this relationship include Pt, Pd, Ni, and the like.
  • the ohmic electrode layer is formed on the surface of the second semiconductor layer 32 by vacuum evaporation or sputtering.
  • the material of the ohmic electrode for example, Ti is selected.
  • other elements can be used as the material of the ohmic electrode layer as long as the metal has a work function smaller than the electron affinity of SnO2 .
  • FIG. 3 is a cross-sectional structural diagram of the Schottky barrier diode of the second embodiment.
  • the Schottky barrier diode in this embodiment is different from the Schottky barrier diode in FIG. 1 in that a dielectric layer 2 is stacked on the upper surface of the first semiconductor layer 31, and a window is provided on the dielectric layer 2 so that the upper surface of the first semiconductor layer 31 is partially leaked out.
  • the Schottky electrode layer 1 is filled in the window and extends along the side wall of the window to the upper surface of the dielectric layer 2.
  • Example 2 can effectively alleviate the electric field concentration effect in Example 1.
  • the electric field lines are densely distributed at the edges and corners where the Schottky electrode contacts the first semiconductor layer 31, so that when the diode is reverse biased, the electric field distribution in the above area is uneven, and there is a possibility of premature breakdown. At the same time, the leakage current will increase.
  • Example 2 through the relative action of the Schottky electrode and the dielectric layer, makes the electric field distribution in the above area relatively uniform, improves the reverse characteristics and voltage resistance of the diode, and makes the Baliga figure of merit BFOM of the tin oxide diode device approach the ideal value.
  • the Schottky diode based on SnO2 material can also be a horizontal structure in which a Schottky electrode layer (1) and an ohmic electrode layer (4) are vapor-deposited on the same side of the n-type semiconductor layer (3) in addition to the structure [vertical] of the above embodiment.
  • the concentration of electron carriers in the second semiconductor layer 32 is more than 10 times higher than that in the first semiconductor layer 31, and the overall resistance of the n-type semiconductor layer 3 is reduced;
  • the thickness of the first semiconductor layer 31 is ⁇ the width of the depletion layer corresponding to the reverse withstand voltage. Considering that the reverse withstand voltage and the electron carrier concentration of the first semiconductor layer 31 determine the width of the SnO2 semiconductor depletion layer, for the required withstand voltage, the thickness of the first semiconductor layer 31 needs to be formed to be wider than the depletion layer width corresponding to the reverse withstand voltage;
  • the electron carrier concentration of the first semiconductor layer 31 is set according to the reverse withstand voltage required by the Schottky barrier diode and the breakdown electric field strength of SnO 2.
  • the electron carrier concentration of the first semiconductor layer 31 of the present invention can be set within a range lower than 5 ⁇ 10 17 /cm 3. Further, the electron carrier concentration of the first semiconductor layer 31 can be set to be less than or equal to 5 ⁇ 10 16 /cm 3. Further, the electron carrier concentration of the first semiconductor layer 31 can be set to be less than or equal to 5 ⁇ 10 15 /cm 3 .
  • the electron carrier concentration of the second semiconductor layer 32 is greater than or equal to 5 ⁇ 10 17 /cm 3 .
  • the setting value depends on the required forward voltage of the Schottky barrier diode. The higher the electron carrier concentration of the second semiconductor layer 32 , the smaller the overall resistance of the n-type semiconductor layer 3 and the smaller the forward voltage.
  • a Schottky diode based on SnO2 semiconductor material can be provided.
  • the Schottky diode can be applied to higher reverse withstand voltage scenarios and can suppress the increase of forward voltage; compared with the Schottky diode based on SiC-based semiconductor material, the Schottky diode can have a lower device cost under the premise of comparable device performance.

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Abstract

本发明提供了一种肖特基势垒二极管，具有：欧姆电极层4；第二半导体层32，下表面与欧姆电极层4上表面形成欧姆接触，为n型半导体层，包括SnO2类化合物半导体材料；第一半导体层31，为n型半导体层，包括SnO2类化合物半导体材料，其电子载流子浓度≤5×1017/cm3，当肖特基势垒二极管设定的反向耐压为10-10000V时，厚度为≥0.18μm且≤112μm，电子载流子浓度低于第二半导体层32的电子载流子浓度；肖特基电极层1，下表面与第二半导体层31的上表面形成肖特基接触。本发明相较于Si基半导体材料的肖特基二极管，可以应用于更高的反向耐压场景且能够抑制正向电压的增大；相较于SiC基半导体材料的肖特基二极管，可以在器件性能相当的前提下有着更低的成本。

Description

一种肖特基势垒二极管 技术领域
本发明涉及半导体器件技术领域，具体涉及一种肖特基势垒二极管。
背景技术
半导体材料经过几十年的发展，从第一代的半导体材料锗和硅，到第二代的半导体材料砷化镓和磷化铟，再到第三代的半导体材料如碳化硅、氮化镓、氮化硼等，以及氧化物半导体材料包括氧化镓、氧化锌、氧化锡等。材料的发展迭代，使得半导体的性能越来越优，半导体的尺寸越来越小。
硅是目前最常用的用于半导体器件和功率器件的材料。其原材料储量丰富，晶体生长工艺成熟且高效；然而硅材料的禁带宽度为1.1eV，且击穿场强仅为40V/μm，在一些高电压、高温度的领域，其应用存在较大的局限性。
当下如火如荼的第三代半导体材料例如碳化硅、氮化镓，其材料特性相对于硅而言，有较大幅度的提升。例如碳化硅的禁带宽度约为3.3eV，是硅的3倍；击穿场强约为300V/μm，是硅的7倍有余。例如氮化镓的禁带宽度约为3.44eV，是硅的3倍有余；击穿场强约为500V/μm，是硅的10倍有余。这些材料特性的提升，使得碳化硅和氮化镓能够使用于更高压、更高温的应用场景，扩宽半导体材料的应用边界。
然而，不论是碳化硅，亦或是氮化镓，它们的晶体制备都十分困难。例如碳化硅单晶的主流制备工艺采用物理气相输运法【PVT】，其长晶效率相对较慢，且由于碳化硅有超过200种的同分异构体，使得其长晶良率很低，这两部分因素，使得碳化硅单晶的成本居高不下。例如氮化镓单晶的主流制备工艺采用卤化物气相外延法【HVPE】，采用外延的方式来长晶，使得其长晶效率相对碳化硅更慢，且加之较为昂贵的源料，使得氮化镓单晶的成本，更是碳化硅单晶成本的3倍以上。这些因素，在很大程度上影响了碳化硅和氮化镓在更大范围内的应用。
发明内容
有鉴如此，本发明要解决的技术问题是提供一种肖特基势垒二极管，其可以应用于更高的反向耐压场景且能够抑制正向电压的增大。
为实现上述目的，本发明所提供的肖特基势垒二极管实施例如下：
一种肖特基势垒二极管，包括自下至上依次堆叠的：
欧姆电极层；
第二半导体层，所述第二半导体层的下表面与所述欧姆电极层的上表面形成欧姆接触，所述第二半导体层为n型半导体层，所述第二半导体层包括SnO2类化合物半导体材料；
第一半导体层，为n型半导体层，包括SnO2类化合物半导体材料，其电子载流子的浓度小于或等于5×1017/cm3，当所述肖特基势垒二极管设定的反向耐压为10-10000V时，所述第一半导体层的厚度为大于或等于0.18μm且小于或等于112μm，所述第一半导体层的电子载流子的浓度低于所述第二半导体层的电子载流子的浓度；
肖特基电极层，所述肖特基电极层的下表面与所述第一半导体层的上表面形成肖特基接触。
进一步地，在所述第一半导体层上表面堆叠有介质层，所述介质层上设置有一窗口，从而部分漏出所述第一半导体层的上表面，所述肖特基电极层填充在所述窗口之中，并沿所述窗口的侧壁延伸至所述介质层的上表面。
所述第二半导体层的电子载流子的浓度比所述第一半导体层的电子载流子的浓度高10倍以上。
进一步地，所述第一半导体层的厚度≥反向耐压对应的耗尽层的宽度。
进一步地，所述第一半导体层的电子载流子的浓度为小于或等于5×1016/cm3；或者所述第一半导体层的电子载流子的浓度为5×1015/cm3。
基于上述第一半导体层的电子载流子的浓度的取值范围，进一步地，所述第二半导体层的电子载流子的浓度大于或等于5×1017/cm3。
未基于上述第一半导体层的电子载流子的浓度的取值范围，进一步地，所述第二半导体层的电子载流子的浓度大于或等于5×1017/cm3。
本发明提供的基于SnO2类半导体材料的肖特基二极管，其发明效果体现在如下两点：
第一，相对于硅基肖特基二极管而言，基于SnO2类半导体材料的肖特基二极管，既能够应用于更高的反向耐压场景，其耐压能力可以高达数千伏。同时 又能够抑制正向电压的增大，降低器件损耗，减少器件发热。
第二，相对于碳化硅基肖特基二极管而言，基于SnO2半导体材料的肖特基二极管，其单晶制备采用物理气相输运法【PVT】，然在长晶条件下，其稳定存在的同分异构体仅有一种【四方金红石相】，因此其长晶良率可大幅提升。使得其单晶成本相对于碳化硅单晶有大幅度的下降。相对于氮化镓基肖特基二极管而言，SnO2单晶的制备效率高于氮化镓单晶的制备效率，SnO2单晶的源料成本低于氮化镓单晶的源料成本，这都使得SnO2单晶成本相对于氮化镓单晶有大幅度的下降。单晶成本的下降，使得SnO2基肖特基二极管，可以在更大的范围内得到应用。
附图说明
图1是本发明第一实施例的肖特基势垒二极管的剖面结构图；
图2A是表示针对使用Si作为半导体材料的情况与本发明使用SnO2作为半导体材料的情况，在将反向耐压设定为100V的情况下，n-半导体层以及n+半导体层的电子载流子浓度、电阻率、厚度与电压降的关系的比较表；
图2B是表示针对使用SiC作为半导体材料的情况与本发明使用SnO2作为半导体材料的情况，在将反向耐压设定为600V的情况下，n-半导体层以及n+半导体层的电子载流子浓度、电阻率、厚度与电压降的关系的比较表；
图2C是表示针对使用SiC作为半导体材料的情况与本发明使用SnO2作为半导体材料的情况，在将反向耐压设定为1000V的情况下，n-半导体层以及n+半导体层的电子载流子浓度、电阻率、厚度与电压降的关系的比较表；
图2D是表示针对使用SiC作为半导体材料的情况与本发明使用SnO2作为半导体材料的情况，在将反向耐压设定为10000V的情况下，n-半导体层以及n+半导体层的电子载流子浓度、电阻率、厚度与电压降的关系的比较表；
图3是本发明第二实施例的肖特基势垒二极管的剖面结构图。
其中，上述附图包括以下附图标记：
1.肖特基电极层，2.介质层，3.n型半导体层，31.第一半导体层，32.第
二半导体层，4.欧姆电极层。
具体实施方式
为使本发明的上述目的、特征和优点能够更加明显易懂，下面结合附图对本发明的具体实施方式做详细的说明，显然，所描述的实施例是本发明一部分实施例，而不是全部实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都应当属于本申请保护的范围。
需要说明的是，本申请的说明书和权利要求书中描述的术语“包括”和“具有”以及他们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列层、区或工艺步骤不必限于清楚地列出的那些层、区或工艺步骤，而是可包括没有清楚地列出的或对于这些结构固有的层、区或工艺步骤。
另外，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。
应该理解的是，在说明书以及权利要求书中，当描述有层/区“设置/堆叠”于另一层/区时，该层/区可“直接设置/堆叠”至该另一层/区，或者通过第三层/区“设置/堆叠”于该另一层/区；当描述有工艺步骤接续至另一工艺步骤时，该工艺步骤可直接接续至该另一工艺步骤，或者通过第三工艺步骤接续至该另一工艺步骤。
图1是本发明第一实施例方式的肖特基势垒二极管的剖面结构图，其中，肖特基势垒二极管具有：欧姆电极层4；第二半导体层32，第二半导体层32的下表面与欧姆电极层4的上表面形成欧姆接触，第二半导体层32为n型半导体层，第二半导体层32包括SnO2类化合物半导体材料；第一半导体层31，为n型半导体层，包括SnO2类化合物半导体材料，其电子载流子的浓度小于或等于5×1017/cm3，当肖特基势垒二极管设定的反向耐压为10-10000V时，第一半导体层31的厚度为大于或等于0.18μm且小于或等于112μm，第一半导体层31的电子载流子的浓度低于第二半导体层32的电子载流子浓度；肖特基电极层1，肖特基电极层1的下表面与第一半导体层31的上表面形成肖特基接触。
在图1的示例中，第二半导体层32相当于n型重掺杂【n+】的SnO2衬底层，其含有Nb或Sb等导电性杂质；SnO2衬底层是采用物理气相输运法【PVT】培育的SnO2单晶的体单晶进行切片并对其进行减薄和研磨形成。
第一半导体层31相当于n型轻掺杂的【n-】SnO2外延层，其含有Nb或Sb 等导电性杂质；SnO2外延层是采用MOCVD法【金属有机化学气相外延法】等气相外延法，在SnO2衬底层的一面上，外延生长具有n型轻掺杂的SnO2半导体层。
不同的半导体材料有着不同的击穿电场强度Ec，Si的击穿场强约为40V/μm，SiC的击穿场强约为300V/μm，与其相比，SnO2的击穿场强约为430V/μm，比Si和SiC都要高。
一般地，肖特基二极管的反向耐压与击穿电场强度的平方成正相关，与电子载流子浓度成反相关。因此，若击穿电场强度增大，在电子载流子浓度相同的情况下，反向耐压也增加。若要求相同的反向耐压，则能够通过增大击穿电场强度，进而提高电子载流子浓度，则正向导通电阻会随之变小，正向导通压降【VF】随之变小。
图2A～图2D是表示针对使用Si或者SiC作为半导体材料的情况与本发明使用SnO2作为半导体材料的情况，第一半导体层(31)【外延层】以及第二半导体层(32)【衬底】的电子载流子浓度、电阻率、厚度与将电流密度设定为200A/cm2的情况下的电压降的关系的比较表。其中，图2A是使用Si以及SnO2并将反向耐压设定为100V的情况下的比较表，图2B是使用SiC以及SnO2并将反向耐压设定为600V的情况下的比较表，图2C是使用SiC以及SnO2并将反向耐压设定为1000V【1kV】的情况下的比较表，图2D是使用SiC以及SnO2并将反向耐压设定为10000V【10kV】的情况下的比较表。
如图2A所示，在将反向耐压设定为100V的情况下，n-半导体层的电子载流子浓度以及厚度在Si中为2.47x1015/cm3、7.5μm，与此相对，在第一实施方式的SnO2中为2x1017/cm3、0.923μm。由此，在n-半导体层中的电压降在Si的情况下为0.1955V，与此相对，在SnO2的情况下为0.0026V。其结果是，包括n-半导体层以及n+半导体层在内的总电压降在Si的情况下为0.2226V，在SnO2的情况下为0.0919V，能够降电压降降低约59％。
另外，如图2B所示，在将反向耐压设定为600V的情况下，n-半导体层的电子载流子浓度以及厚度在SiC中为2.16x1016/cm3、5.46μm，与此相对，在第一实施方式的SnO2中为4x1016/cm3、3.07μm。由此，在n-半导体层中的电压降在SiC的情况下为0.0345V，与此相对，在SnO2的情况下为0.0369V。其结果是，包括n-半导体层以及n+半导体层在内的总电压降在SiC的情况下为 0.0546V，在SnO2的情况下为0.0667V，压降有一定程度的升高，约22％。然而，因为数值本身很小，压降的绝对值提高仅为0.0121V。此时，需考虑到SiC单晶和SnO2单晶，同样采用的是物理气相输运法【PVT】长晶，由于SnO2在长晶环境条件下仅有一种相【四方金红石相】稳定存在，而SiC在长晶条件下存在多种同分异构体并存，因此，SnO2单晶的长晶良率会远高于SiC单晶。从而使得SnO2单晶的成本远低于SiC单晶，基于它们为衬底制作的肖特基二极管，SnO2基肖特基二极管的成本也会远低于SiC基肖特基二极管。在器件性能相当的情况下，SnO2基肖特基二极管，成本更低，则能够有着更大的使用范围。
另外，如图2C所示，在将反向耐压设定为1000V的情况下，n-半导体层的电子载流子浓度以及厚度在SiC中为1.3x1016/cm3、9.1μm，与此相对，在第一实施方式的SnO2中为2.7x1016/cm3、5.12μm。由此，在n-半导体层中的电压降在SiC的情况下为0.0914V，与此相对，在SnO2的情况下为0.0911V。其结果是，包括n-半导体层以及n+半导体层在内的总电压降在SiC的情况下为0.1115V，在SnO2的情况下为0.1209V，压降有一定程度的升高，约8％。然而，因为数值本身很小，压降的绝对值提高仅为0.0094V。此时，需考虑到SiC单晶和SnO2单晶，同样采用的是物理气相输运法【PVT】长晶，由于SnO2在长晶环境条件下仅有一种相【四方金红石相】稳定存在，而SiC在长晶条件下存在多种同分异构体并存，因此，SnO2单晶的长晶良率会远高于SiC单晶。从而使得SnO2单晶的成本远低于SiC单晶，基于它们为衬底制作的肖特基二极管，SnO2基肖特基二极管的成本也会远低于SiC基肖特基二极管。在器件性能相当的情况下，SnO2基肖特基二极管，成本更低，则能够有着更大的使用范围。
另外，如图2D所示，在将反向耐压设定为1000V的情况下，n-半导体层的电子载流子浓度以及厚度在SiC中为1.3x1015/cm3、90.9μm，与此相对，在第一实施方式的SnO2中为2.7x1015/cm3、51.2μm。由此，在n-半导体层中的电压降在SiC的情况下为8.1118V，与此相对，在SnO2的情况下为9.1168V。其结果是，包括n-半导体层以及n+半导体层在内的总电压降在SiC的情况下为8.1319V，在SnO2的情况下为9.1466V，压降有一定程度的升高，约12％，压降的绝对值提高仅为1.0147V。此时，需考虑到SiC单晶和SnO2单晶，同样采用的是物理气相输运法【PVT】长晶，由于SnO2在长晶环境条件下仅有一种相【四 方金红石相】稳定存在，而SiC在长晶条件下存在多种同分异构体并存，因此，SnO2单晶的长晶良率会远高于SiC单晶。从而使得SnO2单晶的成本远低于SiC单晶，基于它们为衬底制作的肖特基二极管，SnO2基肖特基二极管的成本也会远低于SiC基肖特基二极管。在器件性能相当的情况下，SnO2基肖特基二极管，成本更低，则能够有着更大的使用范围。
一般地，为了能够实现在半导体与金属之间产生整流作用的肖特基接触，半导体的电子亲和势需小于成为电极的金属的功函数。作为满足该关系的金属，包括Pt、Pd、Ni等。
欧姆电极层是通过真空蒸镀法或者溅射法形成在第二半导体层32的表面。作为欧姆电极的材料，例如选择Ti。此外，只要是功函数比SnO2的电子亲和势小的金属，使用其它元素作为欧姆电极层的材料也可。
图3是第二实施例肖特基势垒二极管的剖面结构图，本实施例中的肖特基势垒二极管与图1中的肖特基势垒二极管不同之处在于：在第一半导体层31上表面堆叠有介质层2，介质层2上设置有一窗口，从而部分漏出第一半导体层31的上表面，肖特基电极层1填充在窗口之中，并沿窗口的侧壁延伸至介质层2的上表面。
实施例二相比于实施例一，其可以有效缓解实施例一中的电场集中效应，实施例一中电场线在肖特基电极与第一半导体层31接触的边、角处的分布密集，使得二极管在反向偏置时，在以上区域电场分布不均匀，存在被提前击穿的可能，同时漏电流会增加，实施例二通过肖特基电极与介质层的相对作用，使得电场在上述区域中的分布相对均匀，提高二极管的反向特性和耐压能力，使氧化锡二极管器件的巴利加优值BFOM趋于理想值。
以上，对本发明优选的实施方式进行说明，但本发明不限定于上述的实施方式，可在不脱离本发明主旨的范围进行各种变更，当然这些也包含于本发明的范围内。例如基于SnO2材料的肖特基二极管除了上述实施方式的结构【纵型】以外，也可以是在n型半导体层(3)的相同面侧蒸镀有肖特基电极层(1)以及欧姆电极层(4)的横型结构。
为了获得较好的器件特征，本申请的发明人经过设计验证，获得如下优选的参数特性：
(1)第二半导体层32的电子载流子的浓度比第一半导体层31的电子载流子浓度高10倍以上，此时n型半导体层3的整体电阻变小；
(2)第一半导体层31的厚度≥反向耐压对应的耗尽层的宽度，考虑到反向耐压和第一半导体层31的电子载流子浓度决定了SnO2半导体耗尽层的宽度，因此对于需求耐压，第一半导体层31的厚度需要形成为比对应反向耐压的耗尽层宽度宽；
(3)第一半导体层31的电子载流子浓度根据肖特基势垒二极管所要求的反向耐压和SnO2的击穿电场强度来设定，本发明第一半导体层31的电子载流子浓度可以设定在比5×1017/cm3低的范围内，进一步地，第一半导体层31的电子载流子浓度可以设定为小于或等于5×1016/cm3，进一步地，第一半导体层31的电子载流子浓度可以设定为小于或等于5×1015/cm3；
(4)第二半导体层32的电子载流子浓度大于或等于5×1017/cm3，其设定值取决于需求的肖特基势垒二极管的正向电压的大小，第二半导体层32的电子载流子浓度高，n型半导体层3的整体电阻小，正向电压小。
根据本发明，可提供一种基于SnO2半导体材料的肖特基二极管，相较于Si基半导体材料的肖特基二极管，其可以应用于更高的反向耐压场景且能够抑制正向电压的增大；相较于SiC基半导体材料的肖特基二极管，其可以在器件性能相当的前提下，有着更低的器件成本。

Claims (7)

  1. 一种肖特基势垒二极管，其特征在于，包括自下至上依次堆叠的：
    欧姆电极层(4)；
    第二半导体层(32)，所述第二半导体层(32)的下表面与所述欧姆电极层(4)的上表面形成欧姆接触，所述第二半导体层(32)为n型半导体层，所述第二半导体层(32)包括SnO2类化合物半导体材料；
    第一半导体层(31)，为n型半导体层，包括SnO2类化合物半导体材料，其电子载流子的浓度小于或等于5×1017/cm3，当所述肖特基势垒二极管设定的反向耐压为10-10000V时，所述第一半导体层(31)的厚度为大于或等于0.18μm且小于或等于112μm，所述第一半导体层(31)的电子载流子的浓度低于所述第二半导体层(32)的电子载流子的浓度；
    肖特基电极层(1)，所述肖特基电极层(1)的下表面与所述第一半导体层(31)的上表面形成肖特基接触。
  2. 根据权利要求1所述肖特基势垒二极管，其特征在于：在所述第一半导体层(31)上表面堆叠有介质层(2)，所述介质层(2)上设置有一窗口，从而部分漏出所述第一半导体层(31)的上表面，所述肖特基电极层(1)填充在所述窗口之中，并沿所述窗口的侧壁延伸至所述介质层(2)的上表面。
  3. 根据权利要求1所述肖特基势垒二极管，其特征在于：所述第二半导体层(32)的电子载流子的浓度比所述第一半导体层(31)的电子载流子的浓度高10倍以上。
  4. 根据权利要求1所述的肖特基势垒二极管，其特征在于，所述第一半导体层(31)的厚度≥反向耐压对应的耗尽层的宽度。
  5. 根据权利要求1至4任一项所述的肖特基势垒二极管，其特征在于，所述第一半导体层(31)的电子载流子的浓度为小于或等于5×1016/cm3；或者所述第一半导体层(31)的电子载流子的浓度为5×1015/cm3。
  6. 根据权利要求5所述的肖特基势垒二极管，其特征在于，所述第二半导体层(32)的电子载流子的浓度大于或等于5×1017/cm3。
  7. 根据权利要求1至4任一项所述肖特基势垒二极管，其特征在于，所述第二半导体层(32)的电子载流子的浓度大于或等于5×1017/cm3。
PCT/CN2023/096765 2022-10-19 2023-05-29 一种肖特基势垒二极管 WO2024082636A1 (zh)

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CN105453272A (zh) * 2013-08-19 2016-03-30 出光兴产株式会社 氧化物半导体基板及肖特基势垒二极管元件
CN105474397A (zh) * 2013-08-19 2016-04-06 出光兴产株式会社 氧化物半导体基板及肖特基势垒二极管

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Publication number Priority date Publication date Assignee Title
US20110156020A1 (en) * 2009-12-24 2011-06-30 Sang-Hun Jeon Transistor
CN103918082A (zh) * 2011-11-09 2014-07-09 株式会社田村制作所 肖特基势垒二极管
CN105453272A (zh) * 2013-08-19 2016-03-30 出光兴产株式会社 氧化物半导体基板及肖特基势垒二极管元件
CN105474397A (zh) * 2013-08-19 2016-04-06 出光兴产株式会社 氧化物半导体基板及肖特基势垒二极管

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