Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D64/00—Electrodes of devices having potential barriers
  • H10D64/60—Electrodes characterised by their materials
  • H10D64/66—Electrodes having a conductor capacitively coupled to a semiconductor by an insulator, e.g. MIS electrodes
  • H10D64/68—Electrodes having a conductor capacitively coupled to a semiconductor by an insulator, e.g. MIS electrodes characterised by the insulator, e.g. by the gate insulator
  • H10D64/693—Electrodes having a conductor capacitively coupled to a semiconductor by an insulator, e.g. MIS electrodes characterised by the insulator, e.g. by the gate insulator the insulator comprising nitrogen, e.g. nitrides, oxynitrides or nitrogen-doped materials
• • 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
  • H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
  • H01L21/283—Deposition of conductive or insulating materials for electrodes conducting electric current
  • H01L21/285—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation
  • H01L21/28506—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers
  • H01L21/28575—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds
  • H01L21/28587—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds characterised by the sectional shape, e.g. T, inverted T
• • 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
  • H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
  • H01L21/283—Deposition of conductive or insulating materials for electrodes conducting electric current
  • H01L21/285—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation
  • H01L21/28506—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers
  • H01L21/28575—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds
  • H01L21/28587—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds characterised by the sectional shape, e.g. T, inverted T
  • H01L21/28593—Deposition of conductive or insulating materials for electrodes conducting electric current from a gas or vapour, e.g. condensation of conductive layers on semiconductor bodies comprising AIIIBV compounds characterised by the sectional shape, e.g. T, inverted T asymmetrical sectional shape
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/01—Manufacture or treatment
  • H10D30/015—Manufacture or treatment of FETs having heterojunction interface channels or heterojunction gate electrodes, e.g. HEMT
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/60—Insulated-gate field-effect transistors [IGFET]
  • H10D30/67—Thin-film transistors [TFT]
  • H10D30/674—Thin-film transistors [TFT] characterised by the active materials
  • H10D30/675—Group III-V materials, Group II-VI materials, Group IV-VI materials, selenium or tellurium
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D30/00—Field-effect transistors [FET]
  • H10D30/80—FETs having rectifying junction gate electrodes
  • H10D30/801—FETs having heterojunction gate electrodes
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
  • H10D62/10—Shapes, relative sizes or dispositions of the regions of the semiconductor bodies; Shapes of the semiconductor bodies
  • H10D62/17—Semiconductor regions connected to electrodes not carrying current to be rectified, amplified or switched, e.g. channel regions
  • H10D62/351—Substrate regions of field-effect devices
  • H10D62/357—Substrate regions of field-effect devices of FETs
  • H10D62/364—Substrate regions of field-effect devices of FETs of IGFETs
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D62/00—Semiconductor bodies, or regions thereof, of devices having potential barriers
  • H10D62/80—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials
  • H10D62/85—Semiconductor bodies, or regions thereof, of devices having potential barriers characterised by the materials being Group III-V materials, e.g. GaAs
  • H10D62/8503—Nitride Group III-V materials, e.g. AlN or GaN

Definitions

• the present invention involves the structure and formation of high voltage semiconductor devices which in particular have GaN or AIN based p-n junction features.
• Silicon based semiconducting devices have been around for some time for defining p-n structures, such as used in diodes, bipolar transistors and high voltage transistors. Silicon structures have limitations in electrical and optical properties.
• Recent efforts have been made in obtaining semiconductor devices that do not rely on the properties of silicon. Particularly, attention has been directed to III-V compounds, and more particularly, attention has recently been directed at Galium Nitride (GaN) compounds.
• GaN Galium Nitride
• the presently claimed invention seeks to provide semiconductor devices that can also be used at optical wavelengths for specific purposes, such as high power, high voltage devices.
• AIN Aluminium Nitride
• This gate insulating material of AIN is formed on the p-type GaN, while n-type GaN is formed at opposite sides of the gate and over the p-type material.
• the resulting p-n junctions establish high breakdown voltages, enabling larger values of source and drain voltages in transistor structures, for example.
• the AIN, grown on the p-type GaN layer, is semi-insulating, and its thickness is less than critical layer thickness, i.e. around a couple of thousand angstroms.
• the gate dielectric of AIN is defined by etching around a mask of different mask materials, such as SiO 2 , Al 2 O 3 , or preferably Si 3 N 4 , by a reactive ion etch (RIE), for example.
• RIE reactive ion etch
• a selective ion etch is used to form vertical sidewalls of the AIN gate dielectric. While a wet etch might be used, such as KOH, it would be at the expense of avoiding underetching of the AIN gate dielectric.
• source and drain regions can be formed at opposite sides of and below the gate dielectric. This forms and essential gate- source, drain overlap to define a shortened channel length below the gate dielectric.
• the source and drain regions are formed by regrowth of either n+ of n- type GaN, or both, on the p-type GaN layer.
• the growth rate at the sidewall of AIN would determine the geometry of the source, drain overlap with the gate.
• the formation of the source and drain regions can also be carried out by either ion implantation or diffusion, such as with Group VI elements of S or Se, or Group VI elements of Si or Ge, for example.
• LDMOS type devices can be formed by using n-type GaN regrowth on the p-type GaN layer.
• LDMIS devices for example, first a n-type GaN layer is formed at one side of the AIN gate dielectric followed by the formation of a n- - type GaN layer at the opposite side of the gate dielectric. Both layers would be formed partially below the gate dielectric. A subsequent regrowth of a n+ type GaN layer over part of the n- type GaN layer would lead to the LDMIS device with the appropriate electrode attachment.
• insulating sapphire A O 3
• insulating sapphire substrates also offers the advantages of SOI devices.
• both GaN and sapphire have reasonably good values good values of thermal conductivity which is an advantage for good thermal dissipation in devices.
• the visible light transparency of GaN would eliminate adverse effects from visible illumination incident on these devices, such as leakage currents, because of the sub-band gap nature of the light.
• substrates of SiC may be used for its electrical and thermal properties to permit the advantages of a conducting, thick substrate which may be important in suppressing ESD.
• the use of an AIN buffer layer between a SiC substrate and the GaN layer would permit device designs similar to Si based SOI devices using a thick oxide.
• GaN has a band-gap energy of about 3.4 eV while AIN has a bandgap energy of about 6.2 eV.
• the system of GaN-AlN thus has a band-gap that can be varied from about 3.4 to 6.2 eV.
• a close lattice match also results with these two materials over the entire composition range, especially with the addition of a small fraction of In.
• the energy band-gap difference manifests itself as both conduction and valence band discontinuity. Because of the energy band-gap values, the material system is transparent to light in the visible range.
• the large band-gap results in GaN having higher value of breakdown electric field for avalanching, i.e. 2 to 5xl0 6 V/cm, compared to 5xl0 5 V/cm for Si, for example. This enables the p-n junctions on GaN to have larger values of doping.
• the large energy band gap values and relatively stable nature of GaN and AIN would permit operation at elevated temperatures with lower leakage currents then available with Si.
• the carrier transport properties under high field conditions are an important consideration.
• the forward saturation current would be determined by the carrier saturation velocity at high electric fields in a FET.
• GaN has an electron saturation velocity of 2xl0 7 that compares favorably with the value for Si.
• the material AIN with a 6.2 eV band-gap can be grown with semi- insulating properties by MOCVD.
• the AIN layer grown on GaN would be used as the insulating gate dielectric for IGFET devices.
• the AIN/GaN heterostructure has good interface properties with the AIN thickness less than the critical layer thickness or by adding In, and can be used in conjunction with a gate electrode to induce an inversion layer in GaN.
• the resulting MISFET structure is capable of being operated at high voltages.
• Other variations for LDMOS devices can also be inco ⁇ orated.
• the good thermal conductivity values of GaN and sapphire, as well as SiC, for the substrate is an advantage from standpoint of using devices according to the present invention for high power application.
• the use of a sapphire substrate offers the same advantages as Si in SOI devices.
• the reverse leakage current in p-n junctions would not be significantly effected by visible light incident on the device because of the below band-gap nature. Accordingly, the devices according to the present invention can be used in the presence of illumination. Further, the use of transparent ITO contact materials for the gate, source and drain electrodes enables further use in device structures transparent to visible light.
• An alternative process of the present invention involves forming the p- type GaN on a substrate, forming a layer of n-type GaN on the p-type layer, etching through a part of the n-type layer into a part of the p-type layer, and then forming a layer of AIN over the etched parts of the n- and p-layers to provide the gate dielectric. Subsequent device formation can then be carried out to provide a device according to the present invention.
• Figure 1 illustrates a MISFET according to the present invention
• Figure 2, 3, 4 and 5 show different stages in the manufacture of the device in Figure 1 ;
• Figure 6 illustrates a LDMIS-FET according to the present invention
• FIGs 7, 8, 9 and 10 show different stages in the manufacture of the device in Figure 6;
• Figures 11 A, 1 IB and 1 IC show different stages in an alternate technique according to the present invention.
• a transistor of the MIS type according to the present invention is shown in Figure 1.
• This structure includes a p-type layer 2 of GaN on a substrate 1, which may be of a sapphire material.
• a gate dielectric 3 of AIN is provided on a layer 2 with a layer 4, 5 of n+ type GaN at opposite sides of the gate dielectric 3.
• the n+ type GaN portions 4 and 5 form source and drain regions of the transistor structure with the accompanying electrode contacts 6 and 8 of a conductive material, such as ITO, being provided at ends of insulating extensions 12 at opposite sides of the gate dielectric 3 of AIN.
• the gate contact 7 is provided in contact with the gate dielectric 3 of AIN.
• This semiconductor structure is manufactured according to the present invention as shown in Figures 2-5.
• a p-type layer 2 of GaN is formed on a substrate 1, and overlying layer 3 of at least semi-insulating AIN is formed over the layer 2.
• the undoped AIN dielectric and the p-type GaN form a heterostructure where the AIN layer is formed to a thickness less than its critical layer thickness.
• the AIN layer 3 is masked with a layer of Si 3 N 4 and subsequent etching is carried out to provide a vertical wall gate dielectric 13.
• a reactive ion etching technique will form the vertical walls although a wet etch could be used at the expense of an undercut under the gate dielectric 13.
• the p-type layer 2 of GaN is etched down to the line 10 in order to provide a subsequent underetch 11 of the layer 2 of GaN beneath the gate dielectric 13, as shown in Figure 4.
• the channel region dimension below the gate dielectric 13 is controlled to obtain an overlap of the gate region with the source drain regions.
• the source and drain regions 4, 5 are grown by forming layers of n-f type GaN both beneath the gate dielectric portions and over the p-type GaN at opposite sides of the gate dielectric 13.
• the growth rate of the n+ type GaN on the sidewalls of the gate dielectric and the undercut p-type GaN determines the geometry of the source, drain-gate overlap.
• n-type GaN adjacent to the drain area is carried out to form a n- drift region 25 at a side of the gate dielectric 23, as is shown in Figure 6.
• the source and drain regions 24 and 26 are then formed of n+ type GaN at sides of the gate dielectric and the drift region, as is shown in Figure 6.
• Figure 7, 8, 9 and 10 after the gate dielectric 23 is formed, one side of the device is masked together with the gate dielectric by a mask 33. Etching and undercutting is then carried out at one side of the gate dielectric as shown in Figure 7.
• the n-type layer 35 of GaN is formed at that side of the gate dielectric 23 and over the p+ type layer 22 of GaN at that side of the gate dielectric, as is shown in Figure 8. Then the masking layer 33 overlying the one side of the layer and the gate dielectric is removed and a second masking layer 34, covering the gate dielectric and part of the n-layer 35, is formed. Etching is then carried out of the unmasked portions of the p-type
• GaN layer 22 to undercut the gate dielectric at the side opposite to the n-layer 35 and the uncovered portion of the layer 35, as is shown in Figure 9.
• n+ portions 36 of GaN are formed both adjacent to the gate dielectric 23 and over the undercut part of the n-layer 35, shown in Figure 10.
• Appropriate source and drain electrical contacts 27, 29 are formed, together with gate contact 28, relative to insulating portions 32 extending from the gate dielectric, as seen in Figure 6.
• an n+ type layer 43 of GaN can be grown over a p-type layer 42 on a substrate 41, as seen in Figure 11 A.
• etching is carried out through the n+ layer 43 into the p-type layer 42, such as seen in Figure 11B, to form the cavity 44.
• a layer 45 of AIN is grown in the cavity and over the exposed surfaces of the n+ layer 43. Formation of contacts can be further carried out along the lines shown with respect to the devices of Figure 1 and 6.
• ion implantation or diffusion processes can be carried out to form the source and drain regions.
• transparent contact materials such as ITO, would make the present invention transparent to visible light.

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• Engineering & Computer Science (AREA)
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• General Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Thin Film Transistor (AREA)
• Insulated Gate Type Field-Effect Transistor (AREA)
• Formation Of Insulating Films (AREA)

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• 1995
  • 1995-12-28 US US08/583,148 patent/US5915164A/en not_active Expired - Fee Related
• 1996
  • 1996-12-06 JP JP9524138A patent/JPH11501463A/ja not_active Ceased
  • 1996-12-06 EP EP96939258A patent/EP0812468B1/en not_active Expired - Lifetime
  • 1996-12-06 DE DE69625045T patent/DE69625045T2/de not_active Expired - Fee Related
  • 1996-12-06 WO PCT/IB1996/001377 patent/WO1997024752A2/en not_active Ceased
• 1997
  • 1997-11-12 US US08/968,680 patent/US5990531A/en not_active Expired - Fee Related

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