WO2013176905A1 - A high electron mobility field effect transistor and method of manufacturing the same - Google Patents

A high electron mobility field effect transistor and method of manufacturing the same Download PDF

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Publication number
WO2013176905A1
WO2013176905A1 PCT/US2013/040441 US2013040441W WO2013176905A1 WO 2013176905 A1 WO2013176905 A1 WO 2013176905A1 US 2013040441 W US2013040441 W US 2013040441W WO 2013176905 A1 WO2013176905 A1 WO 2013176905A1
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Prior art keywords
layer
gate
drain
drift region
hemt
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PCT/US2013/040441
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French (fr)
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WO2013176905A4 (en
Inventor
Sameh Khalil
Karim S. Boutros
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Hrl Laboratories, Llc
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Priority claimed from US13/478,402 external-priority patent/US9000484B2/en
Priority claimed from US13/479,018 external-priority patent/US8680536B2/en
Priority claimed from US13/478,609 external-priority patent/US9379195B2/en
Application filed by Hrl Laboratories, Llc filed Critical Hrl Laboratories, Llc
Priority to CN201380024745.5A priority Critical patent/CN105103296B/en
Priority to EP13793952.6A priority patent/EP2852979A4/en
Publication of WO2013176905A1 publication Critical patent/WO2013176905A1/en
Publication of WO2013176905A4 publication Critical patent/WO2013176905A4/en

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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00Semiconductor 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
    • H01L29/66Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/66007Multistep manufacturing processes
    • H01L29/66075Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
    • H01L29/66227Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
    • H01L29/66409Unipolar field-effect transistors
    • H01L29/66446Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET]
    • H01L29/66462Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET] with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00Semiconductor 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
    • H01L29/02Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/30Semiconductor bodies ; Multistep manufacturing processes therefor characterised by physical imperfections; having polished or roughened surface
    • H01L29/34Semiconductor bodies ; Multistep manufacturing processes therefor characterised by physical imperfections; having polished or roughened surface the imperfections being on the surface
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00Semiconductor 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
    • H01L29/66Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/76Unipolar devices, e.g. field effect transistors
    • H01L29/772Field effect transistors
    • H01L29/778Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface
    • H01L29/7786Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04Manufacture 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
    • H01L21/18Manufacture 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
    • H01L21/30Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/31Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
    • H01L21/3105After-treatment
    • H01L21/311Etching the insulating layers by chemical or physical means
    • H01L21/31144Etching the insulating layers by chemical or physical means using masks
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00Semiconductor 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
    • H01L29/02Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/12Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
    • H01L29/20Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIIBV compounds
    • H01L29/2003Nitride compounds
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00Semiconductor 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
    • H01L29/40Electrodes ; Multistep manufacturing processes therefor
    • H01L29/41Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions
    • H01L29/423Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions not carrying the current to be rectified, amplified or switched
    • H01L29/42312Gate electrodes for field effect devices
    • H01L29/42316Gate electrodes for field effect devices for field-effect transistors
    • H01L29/4232Gate electrodes for field effect devices for field-effect transistors with insulated gate
    • H01L29/42356Disposition, e.g. buried gate electrode
    • H01L29/4236Disposition, e.g. buried gate electrode within a trench, e.g. trench gate electrode, groove gate electrode

Definitions

  • This disclosure presents a high electron mobility transistor (HEMT) having a controlled lateral two-dimensional electron gas in type III nitride devices using ion
  • This disclosure relates to type III - nitride HEMT devices and in particular to two dimensional electron gas (2DEG) in the drift region.
  • 2DEG two dimensional electron gas
  • a high electron mobility transistor is a field effect transistor incorporating a junction between two materials with different band gaps (i.e., a heteroj unction) .
  • Gallium nitride (GaN) HEMTs have attracted attention due to their high-power performance.
  • type Ill-nitride HEMT devices used in power applications there is a design tradeoff between the on-state resistance and breakdown voltage
  • field plate and multistep field plates are some of the techniques that are used to improve the electric field distribution. However, field plates typically result in multiple peaks and suffer from less than ideal flat field distribution, and may exhibit a saw tooth profile. Field plates also add to the gate to drain capacitance. In
  • a high electron mobility field effect transistor comprises a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
  • 2DEG two dimensional electron gas
  • a high electron mobility field effect transistor comprises lattice damage in a drift region of a carrier supply layer between a gate and a drain, wherein the lattice damage decreases in a direction in the drift region from the gate to the drain.
  • a method of fabricating a high electron mobility field effect transistor comprises forming a channel carrier traveling layer on a substrate, forming a carrier supply layer on the channel carrier traveling layer, forming a mask layer on the carrier supply layer, the mask layer configured to be aligned with a drift region from a gate to a drain, and configured to have a lateral variation in a direction from the gate to the drain, and implanting ions through the mask layer into the carrier supply layer.
  • HEMT high electron mobility field effect transistor
  • FIG. 1 shows the use of a gray scale mask to control ion implantation to be tapered in a drift region in accordance with the present disclosure
  • FIG. 2 shows a tapered two dimensional electron gas (2DEG) charge density in a type III Nitride device in accordance with the present disclosure
  • FIGs. 3A-3C are flow diagrams for methods of fabricating a HEMT device in accordance with the present disclosure.
  • a field effect transistor (FET) device structure 10 is shown.
  • the FET device structure 10 is composed of a stack of III-V layers, such as GaN layer 14 and AlGaN layer 16, grown on a substrate 12 that can be any of the suitable substrates that are commonly used to grow type Ill-nitride materials.
  • Suitable substrates include but are not limited to silicon (Si), Sapphire, silicon carbide (SiC) , and bulk single crystal gallium nitride (GaN) .
  • the stack of III-V layers may include a buffer layer of GaN or aluminum gallium nitride (AlGaN) grown on the substrate 12. Then a channel layer also known as a channel carrier travelling layer, such as GaN layer 14, is grown on the buffer layer. Then a barrier layer also known as a carrier supplying layer, such as AlGaN layer 16, is grown on top of the GaN layer 14. An A1N spacer layer may be between the GaN layer 14 and the AlGaN layer 16 to improve device electrical performance.
  • AlGaN aluminum gallium nitride
  • a suitable masking layer 50 which may be Si 3 N 4 , is grown.
  • the masking layer 50 is used as a masking layer to stop the majority of the ions implanted via ion implantation 52 from reaching the AlGaN layer 16. Only a small fraction of the implanted ions, the tail of the Gaussian distribution, are intended to reach the AlGaN layer 16 to cause damage to the lattice. The small fraction of ions that succeed in reaching the AlGaN layer 16 ideally do not penetrate deep into the AlGaN layer 16.
  • the masking layer 50 is configured to vary the density of ions implanted along the drift region between a gate and a drain of a field effect transistor (FET) .
  • a mask layer 50 may be used, as shown in FIG. 1, to form a tapered mask layer 60 in the drift region between points 62 and 64.
  • the tapered mask layer 60 has a lateral profile and has a height that increases towards the drain.
  • a mask may be used that has with various size openings to vary the density of ions implanted along the drift region. Either type of mask modulates the ion
  • the mask layer 50 may be configured to provide a lattice damage that linearly increases from point 64, along the drift region from near the drain 20, to point 62 near the gate 22.
  • the source contact 18 and drain contact 20 shown in FIG. 2 may be formed by metal evaporation or metal
  • a passivation layer 24 may be deposited between the source 18 and the drain 20.
  • a gate region is then formed by etching through the passivation layer 24 in a gate area between the source 18 and drain 20 and into the AlGaN layer 16. In another embodiment the etch may extend through the AlGaN layer 16 and partially into the GaN layer 14 to an appropriate depth.
  • a gate dielectric 26 is then deposited over the area between the source 18 and gate 22 and the gate 22 and the drain 20, and also deposited to line the etched trench that extends into the AlGaN layer 16. If the etched trench extends into the GaN layer 14, then the gate dielectric 26 also lines the etched trench that extends into the GaN layer 14.
  • gate metal 22 is formed by evaporation or sputtering and fills the etched trench.
  • alternating passivation and metallization layers may be formed as a part of back-end processing to improve the parasitic resistance of the device and provide connection to device pads and/or a package.
  • the distribution of lattice damage in the drift region of the AlGaN layer 14 provides a significant improvement of the figure of merit (FOM) in type III Nitride HEMT devices by achieving flat electric field distribution in the drift region between the gate 22 and the drain 20.
  • FOM figure of merit
  • the 2DEG 42 is varied in the drift region to form a non-uniform lateral 2DEG distribution 44. As shown in the embodiment of FIG. 2, the 2DEG increases in the drift region in the direction from the gate 22 towards the drain 20.
  • the stress in the AlGaN layer 16 may be varied by opening windows in the photo resist with varying size where the size of the opening is a function of the lateral distance from the gate to the drain.
  • the size of the openings may be larger or smaller in the drift region near the gate and decrease or increase, respectively, in the drift region in the direction of the drain.
  • the 2DEG 44 density increases as a function of distance from the gate region along the drift region, as shown in FIG. 2.
  • FIGs. 3A-3C are flow diagrams for methods of fabricating a HEMT a type III Nitride device in accordance with the present disclosure.
  • a channel carrier traveling layer 14 is formed on a substrate 12. Then in step 102 a carrier supply layer 16 is formed on the channel carrier traveling layer 14.
  • the layers 14 and 16 are formed by an epi manufacturer .
  • a mask layer 50 is formed on the carrier supply layer 16.
  • the mask layer is configured to be aligned with a drift region from a gate to a drain, and configured to be have a lateral variation in a direction from the gate to the drain.
  • ions 52 are implanted through the mask layer 50 into the carrier supply layer 16.
  • the mask layer is formed in step 108 by forming a tapered section on the mask layer that has a thickness that increases in the direction from the gate to the drain by using gray scale photolithography and then in step 110 etching the mask layer to form the tapered section.
  • the mask layer is formed by coating the carrier supply layer with photoresist in step 112 and then in step 114 opening windows in the photoresist of varying size such that the size of the openings decrease in the direction from the gate to the drain.
  • a high electron mobility field effect transistor comprising:
  • a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
  • concept 2 The HEMT of concept 1 further comprising:
  • the lattice damage decreases in a direction in the drift region from the gate to the drain.
  • the HEMT of concept 1 further comprising:
  • a channel carrier traveling layer on the substrate a channel carrier traveling layer on the substrate; and a carrier supply layer on the channel carrier traveling layer .
  • the substrate comprises silicon (Si) , sapphire, silicon carbide (SiC) , OR bulk single crystal gallium nitride (GaN) ;
  • the channel carrier traveling layer comprises a GaN layer;
  • the carrier supply layer comprises a AlGaN layer.
  • the HEMT of concept 4 further comprising:
  • a gate dielectric layer surrounding the gate metal extending through the passivation layer and into the AlGaN layer .
  • the HEMT of concept 4 further comprising:
  • the gate comprises:
  • a gate dielectric layer surrounding the gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer.
  • a high electron mobility field effect transistor comprising:
  • the lattice damage decreases in a direction in the drift region from the gate to the drain.
  • a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
  • a channel carrier traveling layer on the substrate a channel carrier traveling layer on the substrate; and a carrier supply layer on the channel carrier traveling layer .
  • the substrate comprises silicon (Si) , sapphire, silicon carbide (SiC) , or bulk single crystal gallium nitride (GaN) ;
  • the channel carrier traveling layer comprises a GaN layer;
  • the carrier supply layer comprises a AlGaN layer.
  • the HEMT of concept 10 further comprising:
  • the gate comprises:
  • a gate dielectric layer surrounding the gate metal extending through the passivation layer and into the AlGaN layer .
  • the HEMT of concept 10 further comprising:
  • the gate comprises:
  • a gate dielectric layer surrounding the gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer.
  • a method of fabricating a high electron mobility field effect transistor (HEMT) comprising:
  • the mask layer configured to be aligned with a drift region from a gate to a drain, and configured to have a lateral variation in a direction from the gate to the drain;
  • the method concept 13 further comprising:
  • the substrate comprises silicon (Si) , sapphire, silicon carbide (SiC) , or bulk single crystal gallium nitride (GaN) ;
  • the channel carrier traveling layer comprises a GaN layer;
  • the carrier supply layer comprises a AlGaN layer.
  • forming a passivation layer over the AlGaN layer; and forming a gate comprising the steps of:
  • 2DEG two dimensional electron gas

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  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
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Abstract

A high electron mobility field effect transistor (HEMT) includes a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.

Description

HIGH ELECTRON MOBILITY FIELD EFFECT TRANSISTOR
AND METHOD OF MANUFACTURING THE SAME
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to US Patent
Application Serial No. 13/478,609 filed May 23, 2013 and entitled "HEMT GaN Device with a Non-Uniform Lateral Two- Dimensional Electron Gas Profile and Process for
Manufacturing the Same" and to US Patent Application Serial No. 13/479,018 filed May 23, 2012 and entitled "Non-Uniform Two-Dimensional Electron Gas Profile in Ill-Nitride HEMT Devices", which are hereby incorporated by reference as though set forth in full. Furthermore, this application is related to and claims priority to US Patent Application Serial No. 13/478,402 filed May 23, 2013 and entitled "Controlling
Lateral Two-Dimensional Electron Hole Gas HEMT in Type III Nitride Devices Using Ion Implantation Through Gray Scale Mask", which is hereby incorporated by reference in its entirety.
TECHNICAL FIELD
[0002] This disclosure presents a high electron mobility transistor (HEMT) having a controlled lateral two-dimensional electron gas in type III nitride devices using ion
implantation through a gray scale mask and a method of manufacturing the same. This disclosure relates to type III - nitride HEMT devices and in particular to two dimensional electron gas (2DEG) in the drift region.
BACKGROUND
[0003] A high electron mobility transistor (HEMT) is a field effect transistor incorporating a junction between two materials with different band gaps (i.e., a heteroj unction) . Gallium nitride (GaN) HEMTs have attracted attention due to their high-power performance. In type Ill-nitride HEMT devices used in power applications there is a design tradeoff between the on-state resistance and breakdown voltage
(BV) . Since the relation between the BV and on resistance is at least quadratic, improvement in the BV for a given drift region length results in a significant improvement in the FOM of the device, defined as BV2/Ron.
[0004] In the prior art type Ill-nitride HEMT devices have a uniform 2DEG density which results in a peak electric field under or near the gate region. The electric field
distribution tends to be closer to a triangular shape than to the desired trapezoidal shape which reduces the breakdown voltage per unit drift region length of the device. The use of field plate and multistep field plates are some of the techniques that are used to improve the electric field distribution. However, field plates typically result in multiple peaks and suffer from less than ideal flat field distribution, and may exhibit a saw tooth profile. Field plates also add to the gate to drain capacitance. In
addition, process complexity and cost typically increase with the number of field plate steps. [ 0005 ] U.S. Patent No. 7,038,253 to Furukawa describes a GaN based device on silicon (Si) technology which uses a uniform 2DEG profile in the drift region. Because of the absence of any field shaping technique in the Furukawa device, the breakdown voltage and dynamic on resistance from drain to source is limited by a localized increase in the electric field under the gate region thus requiring over design of the device which degrades the figure of merit (FOM) that such a device can achieve.
[ 0006] In "High Breakdown Voltage AlGaN/GaN HEMTs Achieved by Multiple Field Plates" by H. Xing et . Al, a field shaping technique that uses multiple field plates is described to improve the electric field distribution. However, multiple field plates do not achieve a uniform electric field, may have a saw tooth type distribution, and introduce gate to drain capacitance. Implementing such a device structure also increases device complexity and cost.
[ 0007 ] What is needed is a significant improvement in the FOM in type III nitride HEMT devices, and in particular an improvement in the breakdown voltage for a given drift region length, so that the FOM of the device, defined as BV2/Ron, improves. The embodiments of the present disclosure answer these and other needs.
SUMMARY
[ 0008 ] In a first embodiment disclosed herein, a high electron mobility field effect transistor (HEMT) comprises a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
[ 0009] In another embodiment disclosed herein, a high electron mobility field effect transistor (HEMT) comprises lattice damage in a drift region of a carrier supply layer between a gate and a drain, wherein the lattice damage decreases in a direction in the drift region from the gate to the drain.
[ 0010 ] In yet another embodiment disclosed herein, a method of fabricating a high electron mobility field effect transistor (HEMT) , the method comprises forming a channel carrier traveling layer on a substrate, forming a carrier supply layer on the channel carrier traveling layer, forming a mask layer on the carrier supply layer, the mask layer configured to be aligned with a drift region from a gate to a drain, and configured to have a lateral variation in a direction from the gate to the drain, and implanting ions through the mask layer into the carrier supply layer.
[ 0011 ] These and other features and advantages will become further apparent from the detailed description and
accompanying figures that follow. In the figures and
description, numerals indicate the various features, like numerals referring to like features throughout both the drawings and the description.
BRIEF DESCRIPTION OF THE DRAWINGS
[ 0012 ] FIG. 1 shows the use of a gray scale mask to control ion implantation to be tapered in a drift region in accordance with the present disclosure; [ 0013 ] FIG. 2 shows a tapered two dimensional electron gas (2DEG) charge density in a type III Nitride device in accordance with the present disclosure; and
[ 0014 ] FIGs. 3A-3C are flow diagrams for methods of fabricating a HEMT device in accordance with the present disclosure.
DETAILED DESCRIPTION
[ 0015 ] In the following description, numerous specific details are set forth to clearly describe various specific embodiments disclosed herein. One skilled in the art, however, will understand that the presently claimed invention may be practiced without all of the specific details
discussed below. In other instances, well known features have not been described so as not to obscure the invention.
[ 0016] Referring now to FIG. 1, a field effect transistor (FET) device structure 10 is shown. The FET device structure 10 is composed of a stack of III-V layers, such as GaN layer 14 and AlGaN layer 16, grown on a substrate 12 that can be any of the suitable substrates that are commonly used to grow type Ill-nitride materials. Suitable substrates include but are not limited to silicon (Si), Sapphire, silicon carbide (SiC) , and bulk single crystal gallium nitride (GaN) .
[ 0017 ] The stack of III-V layers may include a buffer layer of GaN or aluminum gallium nitride (AlGaN) grown on the substrate 12. Then a channel layer also known as a channel carrier travelling layer, such as GaN layer 14, is grown on the buffer layer. Then a barrier layer also known as a carrier supplying layer, such as AlGaN layer 16, is grown on top of the GaN layer 14. An A1N spacer layer may be between the GaN layer 14 and the AlGaN layer 16 to improve device electrical performance.
[ 0018 ] On top of the AlGaN layer 16 a suitable masking layer 50, which may be Si3N4, is grown. The masking layer 50 is used as a masking layer to stop the majority of the ions implanted via ion implantation 52 from reaching the AlGaN layer 16. Only a small fraction of the implanted ions, the tail of the Gaussian distribution, are intended to reach the AlGaN layer 16 to cause damage to the lattice. The small fraction of ions that succeed in reaching the AlGaN layer 16 ideally do not penetrate deep into the AlGaN layer 16.
[ 0019 ] Further, the masking layer 50 is configured to vary the density of ions implanted along the drift region between a gate and a drain of a field effect transistor (FET) . A mask layer 50 may be used, as shown in FIG. 1, to form a tapered mask layer 60 in the drift region between points 62 and 64. The tapered mask layer 60 has a lateral profile and has a height that increases towards the drain. In another embodiment a mask may be used that has with various size openings to vary the density of ions implanted along the drift region. Either type of mask modulates the ion
implantation between points 62 and 64, such that lattice damage due to ion implantation in the AlGaN layer 16 is greater at the point 62, near the edge of gate region 22, as shown in FIG. 2, and less at point 64 along the drift region towards the drain 20, as shown in FIG. 2. The mask layer 50 may be configured to provide a lattice damage that linearly increases from point 64, along the drift region from near the drain 20, to point 62 near the gate 22. After ion
implantation the masking layer is etched and removed. [ 0020 ] The source contact 18 and drain contact 20 shown in FIG. 2 may be formed by metal evaporation or metal
sputtering. Then a passivation layer 24 may be deposited between the source 18 and the drain 20.
[ 0021 ] A gate region is then formed by etching through the passivation layer 24 in a gate area between the source 18 and drain 20 and into the AlGaN layer 16. In another embodiment the etch may extend through the AlGaN layer 16 and partially into the GaN layer 14 to an appropriate depth. A gate dielectric 26 is then deposited over the area between the source 18 and gate 22 and the gate 22 and the drain 20, and also deposited to line the etched trench that extends into the AlGaN layer 16. If the etched trench extends into the GaN layer 14, then the gate dielectric 26 also lines the etched trench that extends into the GaN layer 14.
[ 0022 ] After deposition of the gate dielectric 26, gate metal 22 is formed by evaporation or sputtering and fills the etched trench.
[ 0023 ] Various alternating passivation and metallization layers may be formed as a part of back-end processing to improve the parasitic resistance of the device and provide connection to device pads and/or a package.
[ 0024 ] The use of the mask layer 50 with tapered mask layer 60 or in another embodiment a mask with various size openings to control ion implantation and thereby the
distribution of lattice damage in the drift region of the AlGaN layer 14 provides a significant improvement of the figure of merit (FOM) in type III Nitride HEMT devices by achieving flat electric field distribution in the drift region between the gate 22 and the drain 20. By controlling the ion implantation and thereby the lattice damage in the drift region from the gate to the drain, the 2DEG 42 is varied in the drift region to form a non-uniform lateral 2DEG distribution 44. As shown in the embodiment of FIG. 2, the 2DEG increases in the drift region in the direction from the gate 22 towards the drain 20. A flat electric field
distribution results from the non-uniform lateral 2DEG distribution 44 along the drift region which provides the improvement in the figure of merit (FOM) .
[ 0025 ] Implementing a non-uniform lateral 2DEG profile 44 along the drift region by causing tapered lattice damage to the carrier supplying layer, such as AlGaN layer 16, controls the level of damage or stress in that layer. The lateral control of the damage in the carrier supplying layer is achieved by means of ion implantation of a suitable ion specie through a masked layer, such as mask layer 50, that has a tapered profile, where the vertical height of the masking layer determines the stopping power of the implanted projectiles and hence their projected range. The tapered profile of the masking layer may be produced by gray scale photolithography followed by an etch step.
[ 0026] Alternatively the stress in the AlGaN layer 16 may be varied by opening windows in the photo resist with varying size where the size of the opening is a function of the lateral distance from the gate to the drain. The size of the openings may be larger or smaller in the drift region near the gate and decrease or increase, respectively, in the drift region in the direction of the drain.
[ 0027 ] Since the density of charge in the 2DEG region is determined locally by the magnitude of the damage induced by ion implantation, a non-uniform 2DEG distribution 44 is achieved by varying the lattice damage laterally over the drift region. If the lattice damage caused by ion
implantation is reduced as a function of a distance from the gate region along the drift region by increasing the height of the mask layer 50 or by reducing the size of openings in the mask, the 2DEG 44 density increases as a function of distance from the gate region along the drift region, as shown in FIG. 2.
[ 0028 ] FIGs. 3A-3C are flow diagrams for methods of fabricating a HEMT a type III Nitride device in accordance with the present disclosure.
[ 0029 ] In step 100 a channel carrier traveling layer 14 is formed on a substrate 12. Then in step 102 a carrier supply layer 16 is formed on the channel carrier traveling layer 14. In an embodiment, the layers 14 and 16 are formed by an epi manufacturer .
[ 0030 ] Next in step 104 a mask layer 50 is formed on the carrier supply layer 16. The mask layer is configured to be aligned with a drift region from a gate to a drain, and configured to be have a lateral variation in a direction from the gate to the drain. Then ions 52 are implanted through the mask layer 50 into the carrier supply layer 16.
[ 0031 ] In one embodiment the mask layer is formed in step 108 by forming a tapered section on the mask layer that has a thickness that increases in the direction from the gate to the drain by using gray scale photolithography and then in step 110 etching the mask layer to form the tapered section.
[ 0032 ] In another embodiment the mask layer is formed by coating the carrier supply layer with photoresist in step 112 and then in step 114 opening windows in the photoresist of varying size such that the size of the openings decrease in the direction from the gate to the drain.
[ 0033 ] Having now described the invention in accordance with the requirements of the patent statutes, those skilled in this art will understand how to make changes and modifications to the present invention to meet their specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention as disclosed herein.
[ 0034 ] The foregoing Detailed Description of exemplary and preferred embodiments is presented for purposes of
illustration and disclosure in accordance with the
requirements of the law. It is not intended to be exhaustive nor to limit the invention to the precise form(s) described, but only to enable others skilled in the art to understand how the invention may be suited for a particular use or implementation. The possibility of modifications and variations will be apparent to practitioners skilled in the art. No limitation is intended by the description of exemplary embodiments which may have included tolerances, feature dimensions, specific operating conditions,
engineering specifications, or the like, and which may vary between implementations or with changes to the state of the art, and no limitation should be implied therefrom.
Applicant has made this disclosure with respect to the current state of the art, but also contemplates advancements and that adaptations in the future may take into
consideration of those advancements, namely in accordance with the then current state of the art. It is intended that the scope of the invention be defined by the Claims as written and equivalents as applicable. Reference to a claim element in the singular is not intended to mean "one and only one" unless explicitly so stated. Moreover, no element, component, nor method or process step in this disclosure is intended to be dedicated to the public
regardless of whether the element, component, or step is explicitly recited in the Claims. No claim element herein is to be construed under the provisions of 35 U.S.C. Sec. 112, sixth paragraph, unless the element is expressly recited using the phrase "means for. . ." and no method or process step herein is to be construed under those provisions unless the step, or steps, are expressly recited using the phrase "comprising the step(s) of. .
CONCEPTS
At least the following concepts have been disclosed.
Concept 1. A high electron mobility field effect transistor (HEMT) comprising:
a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
Concept 2. The HEMT of concept 1 further comprising:
lattice damage in a drift region of a carrier supply layer between the gate and the drain;
wherein the lattice damage decreases in a direction in the drift region from the gate to the drain.
Concept 3. The HEMT of concept 1 further comprising:
a substrate;
a channel carrier traveling layer on the substrate; and a carrier supply layer on the channel carrier traveling layer .
Concept 4. The HEMT of concept 3 wherein:
the substrate comprises silicon (Si) , sapphire, silicon carbide (SiC) , OR bulk single crystal gallium nitride (GaN) ; the channel carrier traveling layer comprises a GaN layer; and
the carrier supply layer comprises a AlGaN layer.
Concept 5. The HEMT of concept 4 further comprising:
a passivation layer over the AlGaN layer; and wherein the gate comprises:
gate metal extending through the passivation layer and into the AlGaN layer; and
a gate dielectric layer surrounding the gate metal extending through the passivation layer and into the AlGaN layer .
Concept 6. The HEMT of concept 4 further comprising:
a passivation layer over the AlGaN layer; and
wherein the gate comprises:
gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer; and
a gate dielectric layer surrounding the gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer.
Concept 7. A high electron mobility field effect transistor (HEMT) comprising:
lattice damage in a drift region of a carrier supply layer between a gate and a drain;
wherein the lattice damage decreases in a direction in the drift region from the gate to the drain.
Concept 8. The HEMT of concept 7 further comprising:
a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
Concept 9. The HEMT of concept 7 further comprising:
a substrate;
a channel carrier traveling layer on the substrate; and a carrier supply layer on the channel carrier traveling layer .
Concept 10. The HEMT of concept 9 wherein:
the substrate comprises silicon (Si) , sapphire, silicon carbide (SiC) , or bulk single crystal gallium nitride (GaN) ; the channel carrier traveling layer comprises a GaN layer; and
the carrier supply layer comprises a AlGaN layer.
Concept 11. The HEMT of concept 10 further comprising:
a passivation layer over the AlGaN layer; and
wherein the gate comprises:
gate metal extending through the passivation layer and into the AlGaN layer; and
a gate dielectric layer surrounding the gate metal extending through the passivation layer and into the AlGaN layer .
Concept 12. The HEMT of concept 10 further comprising:
a passivation layer over the AlGaN layer; and
wherein the gate comprises:
gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer; and
a gate dielectric layer surrounding the gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer.
Concept 13. A method of fabricating a high electron mobility field effect transistor (HEMT) , the method comprising:
forming a mask layer on a carrier supply layer, the mask layer configured to be aligned with a drift region from a gate to a drain, and configured to have a lateral variation in a direction from the gate to the drain; and
implanting ions through the mask layer into the carrier supply layer.
Concept 14. The method concept 13 further comprising:
forming a channel carrier traveling layer on a
substrate; and
forming a carrier supply layer on the channel carrier traveling layer.
Concept 15. The method of concept 13 wherein forming a mask layer on the carrier supply layer comprises:
forming a tapered section on the mask layer that has a thickness that increases in the direction from the gate to the drain by
using gray scale photolithography; and
etching the mask layer to form the tapered section.
Concept 16. The method of concept 13 wherein forming a mask layer on the carrier supply layer comprises:
coating the carrier supply layer with photoresist; and opening windows in the photoresist of varying size wherein the size of the openings decrease in the direction from the gate to the drain.
Concept 17. The method of concept 13 wherein implanting ions comprises:
damaging a lattice of the carrier supply layer;
wherein the lattice damage decreases in a direction in the drift region from the gate to the drain. Concept 18. The method of concept 17 wherein:
the substrate comprises silicon (Si) , sapphire, silicon carbide (SiC) , or bulk single crystal gallium nitride (GaN) ; the channel carrier traveling layer comprises a GaN layer; and
the carrier supply layer comprises a AlGaN layer.
Concept 19. The method of concept 18 further comprising:
forming a passivation layer over the AlGaN layer; and forming a gate comprising the steps of:
forming a trench extending through the passivation layer and into the AlGaN layer; and
depositing a gate dielectric layer in the trench; and
forming gate metal on the gate dielectric.
Concept 20. The method of concept 19 wherein forming a trench extending through the passivation layer and into the AlGaN layer further comprises:
forming the trench to extend into the GaN layer.
Concept 21. The method of concept 19 wherein the lattice damage decreases in a direction in the drift region from the gate dielectric layer to the drain.
Concept 22. The method of concept 17 wherein damaging a lattice of the carrier supply layer further comprises:
forming a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non¬ uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.

Claims

WHAT IS CLAIMED IS:
1. A high electron mobility field effect transistor (HEMT) comprising :
a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
2. The HEMT of claim 1 further comprising:
lattice damage in a drift region of a carrier supply layer between the gate and the drain;
wherein the lattice damage decreases in a direction in the drift region from the gate to the drain.
3. The HEMT of claim 1 further comprising:
a substrate;
a channel carrier traveling layer on the substrate; and a carrier supply layer on the channel carrier traveling layer .
4. The HEMT of claim 3 wherein:
the substrate comprises silicon (Si) , sapphire, silicon carbide (SiC) , OR bulk single crystal gallium nitride (GaN) ; the channel carrier traveling layer comprises a GaN layer; and
the carrier supply layer comprises a AlGaN layer.
5. The HEMT of claim 4 further comprising:
a passivation layer over the AlGaN layer; and
wherein the gate comprises: gate metal extending through the passivation layer and into the AlGaN layer; and
a gate dielectric layer surrounding the gate metal extending through the passivation layer and into the AlGaN layer .
6. The HEMT of claim 4 further comprising:
a passivation layer over the AlGaN layer; and
wherein the gate comprises:
gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer; and
a gate dielectric layer surrounding the gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer.
7. A high electron mobility field effect transistor (HEMT) comprising :
lattice damage in a drift region of a carrier supply layer between a gate and a drain;
wherein the lattice damage decreases in a direction in the drift region from the gate to the drain.
8. The HEMT of claim 7 further comprising:
a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a non-uniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
9. The HEMT of claim 7 further comprising:
a substrate;
a channel carrier traveling layer on the substrate; and a carrier supply layer on the channel carrier traveling layer .
10. The HEMT of claim 9 wherein:
the substrate comprises silicon (Si), sapphire, silicon carbide (SiC) , or bulk single crystal gallium nitride (GaN) ; the channel carrier traveling layer comprises a GaN layer; and
the carrier supply layer comprises a AlGaN layer.
11. The HEMT of claim 10 further comprising:
a passivation layer over the AlGaN layer; and
wherein the gate comprises:
gate metal extending through the passivation layer and into the AlGaN layer; and
a gate dielectric layer surrounding the gate metal extending through the passivation layer and into the AlGaN layer .
12. The HEMT of claim 10 further comprising:
a passivation layer over the AlGaN layer; and
wherein the gate comprises:
gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer; and
a gate dielectric layer surrounding the gate metal extending through the passivation layer and the AlGaN layer and into the GaN layer.
13. A method of fabricating a high electron mobility field effect transistor (HEMT) , the method comprising:
forming a mask layer on a carrier supply layer, the mask layer configured to be aligned with a drift region from a gate to a drain, and configured to have a lateral variation in a direction from the gate to the drain; and
implanting ions through the mask layer into the carrier supply layer.
14. The method claim 13 further comprising:
forming a channel carrier traveling layer on a
substrate; and
forming a carrier supply layer on the channel carrier traveling layer.
15. The method of claim 13 wherein forming a mask layer on the carrier supply layer comprises:
forming a tapered section on the mask layer that has a thickness that increases in the direction from the gate to the drain by
using gray scale photolithography; and
etching the mask layer to form the tapered section.
16. The method of claim 13 wherein forming a mask layer on the carrier supply layer comprises:
coating the carrier supply layer with photoresist; and opening windows in the photoresist of varying size wherein the size of the openings decrease in the direction from the gate to the drain.
17. The method of claim 13 wherein implanting ions
comprises :
damaging a lattice of the carrier supply layer;
wherein the lattice damage decreases in a direction in the drift region from the gate to the drain.
18. The method of claim 17 wherein:
the substrate comprises silicon (Si) , sapphire, silicon carbide (SiC) , or bulk single crystal gallium nitride (GaN) ; the channel carrier traveling layer comprises a GaN layer; and
the carrier supply layer comprises a AlGaN layer.
19. The method of claim 18 further comprising:
forming a passivation layer over the AlGaN layer; and forming a gate comprising the steps of:
forming a trench extending through the passivation layer and into the AlGaN layer; and
depositing a gate dielectric layer in the trench; and
forming gate metal on the gate dielectric.
20. The method of claim 19 wherein forming a trench extending through the passivation layer and into the AlGaN layer further comprises:
forming the trench to extend into the GaN layer.
21. The method of claim 19 wherein the lattice damage decreases in a direction in the drift region from the gate dielectric layer to the drain.
22. The method of claim 17 wherein damaging a lattice of the carrier supply layer further comprises:
forming a two dimensional electron gas (2DEG) in the drift region between the gate and the drain that has a nonuniform lateral 2DEG distribution that increases in a direction in the drift region from the gate to the drain.
PCT/US2013/040441 2012-05-23 2013-05-09 A high electron mobility field effect transistor and method of manufacturing the same WO2013176905A1 (en)

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US13/478,402 US9000484B2 (en) 2012-05-23 2012-05-23 Non-uniform lateral profile of two-dimensional electron gas charge density in type III nitride HEMT devices using ion implantation through gray scale mask
US13/479,018 US8680536B2 (en) 2012-05-23 2012-05-23 Non-uniform two dimensional electron gas profile in III-Nitride HEMT devices
US13/479,018 2012-05-23
US13/478,609 US9379195B2 (en) 2012-05-23 2012-05-23 HEMT GaN device with a non-uniform lateral two dimensional electron gas profile and method of manufacturing the same
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EP2852979A1 (en) 2015-04-01

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