Nano-HEMTs Fabricated by utilizing Ne- based Atomic Layer Etching - - PowerPoint PPT Presentation

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Nano-HEMTs Fabricated by utilizing Ne- based Atomic Layer Etching - - PowerPoint PPT Presentation

Oct 02, 2022 278 likes •444 views

Nano-HEMTs Fabricated by utilizing Ne- based Atomic Layer Etching Dong-Hyun Kim S.H. Shin 1 , T.W. Kim 1 , J.I. Song 1 , G.Y. Yeom 2 , and J.H. Jang 1 High Mesa Waveguide Gwangju Institute of Science & Technology Department of Information

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

1 High Mesa Waveguide

Dong-Hyun Kim

Nano-HEMTs Fabricated by utilizing Ne- based Atomic Layer Etching

Gwangju Institute of Science & Technology Department of Information & Communications

S.H. Shin1, T.W. Kim1, J.I. Song1, G.Y. Yeom2, and J.H. Jang1

Department of Materials Science and Engineering SKKU

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Outline

  • Introduction
  • 1. High speed electronic devices
  • 2. Key fabrication processes for Nano-HEMTs
  • 3. Two step recess technology employing atomic layer

etching

  • Atomic Layer Etching

Properties of the etched surface (Selectivity, XPS, and AFM) Characteristics of Vertical Schottky Diodes

  • DC and RF Characteristics of Nano-HEMTs

Depletion-mode InAs Composite Channel p-HEMTs Enhancement-mode InAs Composite Channel p- HEMTs

  • Conclusions
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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Overview of Ultra Overview of Ultra-

  • fast Electronic

fast Electronic Devices Devices

Record High fT of III-V HEMTs

< Ref. : Shinohara et al. (IPRM 2004) >

State of the Art Electronic Devices

1985 1990 1995 2000 2005 2010 200 400 600 800

Cutoff Frequency [GHz] Year

1985 1990 1995 2000 2005 2010 200 400 600 800

Year Cutoff Frequency [GHz]

1985 1990 1995 2000 2005 2010 200 400 600 800

Year Cutoff Frequency [GHz]

1985 1990 1995 2000 2005 2010 200 400 600 800

Cutoff Frequency [GHz] Year

Si CMOS SiGe HBTs III-V HBTs III-V HEMTs

1998 2000 2002 2004 2006 2008 300 400 500 600 700 628 GHz for 30-nm p-HEMTs IEEE EDL, 2008

JJAP, 41, 4B, 437

472 GHz for 30-nm LM-HEMTs

562 GHz for 25-nm P-HEMTs

IEEE EDL, 23, 573 547 GHz for 30-nm P-HEMTs

IEEE EDL, 25, 241

InP-based HEMT

Cutoff frequency fT (GHz) Year

IEEE EDL, 22, 507 400 GHz for 45-nm P-HEMT

610 GHz for 15-nm p-HEMTs IEEE IEDM, 2007

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Gate Recess: Critical Process for Nano Gate Recess: Critical Process for Nano-

  • HEMT

HEMT

Buffer Channel Insulator Cap ZEP Buffer Channel Insulator Cap ZEP

Ar-based plasma & ALET

InP InP

Wet etching

Two-step recess for HEMT fabrication

  • 1st step: wet etch n+ InGaAs/InAlAs multi-layer cap removal
  • 2nd step: dry etch InP etch stop layer removal:
  • Ar-based RIE (Conventional)
  • or Ne-based atomic layer etching (ALET)

<Ref: Suemitsu et al. (IEDM 98)>

  • Problems of Conventional Ar-based RIE
  • Low etch selectivity
  • Electrical & physical damage: Ion bombardment
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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Atomic Layer Etching Technique Atomic Layer Etching Technique (ALET) (ALET)

Reactant Feed

Reactant molecules adsorb onto a substrate surface. The etchant does not spontaneously etch the substrate.

Reactant Purge

Excess reactant is purged

Beam Irradiation

An energetic beam irradiates the surface, and surface atoms bonded with reactant are etched off owing to beam- induced chemical etching.

Product Purge

Etching products are purged after which

  • ne cycle of digital

etching is completed

InP layer Cl2 gas Ne neutron-beam

The expected advantages of Ne-based ALET over Ar-based RIE

  • The higher etch selectivity (ALET)
  • The lower electrical & physical damage Low energy neutral

beam

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Etching Property of ALET Etching Property of ALET

Composition of In0.52Al0.48As surface

50 100 150 200 50 100 150 200 250 300 Etch Depth ( Å )

Number of Etch Cycles

InP Bulk InP (80 Å )/InAlAs Epitaxial Structure

20 40 60 80 100 0.0 0.3 0.6 0.9 1.2 1.5 0.0 0.3 0.6 0.9 1.2 1.5

Al/In ratio As/InAl ratio take-off angle

, Reference , Atomic Layer Etching , Reactive Ion Etching

Very high selectivity of InP over InAlAs (~70) cf) Ar-based RIE (~20) Minimal surface modification

Selectivity of InP over In0.52Al0.48As

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Surface Roughness Surface Roughness

Wet etching RIE ALET 7.77 Å 2.97 Å 1.37 Å

The smallest rms roughness achieved by ALET process

AFM image

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Vertical Schottky Diode Vertical Schottky Diode

  • 1.0
  • 0.8
  • 0.6
  • 0.4
  • 0.2

0.0 0.2 0.4 0.6 0.8 10

  • 12

10

  • 10

10

  • 8

10

  • 6

10

  • 4

10

  • 2

10

I [mA/mm

2]

V [V]

ALET RIE

Ti/Pt/Au Ni/Ge/Au N-type InP sub. In0.52Al0.48As 3000Å

RIE: ΦB = 0.56 eV, η = 1.25 ALET: ΦB = 0.64 eV, η = 1.17

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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The Fabricated Devices The Fabricated Devices

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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60 60-

  • nm Depletion

nm Depletion-

  • Mode p

Mode p-

  • HEMTs

HEMTs

0.0 0.1 0.2 0.3 0.4 0.5 100 200 300 400 500

  • 0.2V
  • 0.1V

0V 0.1V 0.2V 0.3V

ALET RIE

IDS [ mA / mm ] VDS [ V ]

0.4V

  • 0.8
  • 0.6
  • 0.4
  • 0.2

0.0 0.2 100 200 300 400 500 200 400 600 800 1000 1200

GM [ mS / mm ] IDS [ mA / mm ] V

GS [ V ]

ALET RIE

VDS=0.5V

DC Characteristics

  • GM,Max of the p-HEMTs fabricated by the ALET process was larger than that
  • f the p-HEMT fabricated by the Ar-based RIE by 21%

→much lower plasma-induced damage characteristics of the ALET process

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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60 60-

  • nm Depletion

nm Depletion-

  • Mode HEMTs

Mode HEMTs

1E8 1E9 1E10 1E11 1E12 10 20 30 40 50 60 fT=355GHz

ALET RIE H21 [ dB ] Frequency [ Hz ]

398GHz

VGS=0.05V,VDS=0.5V

RF Characteristics

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Enhancement Enhancement-

  • mode HEMT (E

mode HEMT (E-

  • HEMTs)

HEMTs)

  • 0.6
  • 0.4
  • 0.2

0.0 0.2 0.4 0.6 100 200 300 400 500 400 800 1200 1600

GM [ mS / mm ] IDS [ mA / mm ] VGS [ V ]

E-HEMT

VDS = 0.5V

E-HEMTs were fabricated by utilizing buried-Pt gate

  • Gate metal stack: Pt(6 nm)/Ti/Pt/Au
  • Post-annealing was carried out to drive Pt into InAlAs
  • ALET: gM,max = 1.38 S/mm
  • RIE: gM,max = 1.1 S/mm
  • VT = 0.07 V

1 10 100 1000 10 20 30 40 0.0 0.2 0.4 0.6 0.8 1.0 K

Current gain H21 Unilateral gain Ug MAG/MSG

Gain [dB] Frequency [GHz]

fmax = 470 GHz fT = 403 GHz Stability factor K VGS =0.4 V, VDS = 0.6 V

  • FT of 403 GHz
  • Higher fT than D-HEMTs
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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Conclusions Conclusions

The effect of ALET in the two-step gate recess process

  • Higher InP etch selectivity against the underlying

In0.52Al0.48As barrier layer Better uniformity of device characteristics Less plasma-induced damage compared to conventional Ar- based RIE process The smoother etched surface Better gate diode characteristics The higher transconductance The lower subthreshold slope Buried Pt gate

  • The thinner effective Schottky layer thickness

Alleviation of short channel effect Better gate modulation characteristics

  • The higher Schottky barrier height due to the annealed Pt

Positive shift of threshold voltage The smaller gate leakage current

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Other Interesting Stuffs !!! Other Interesting Stuffs !!!

Ring resonator based Optical Filters and Biosensors Oxide Thin Film Transistors Single Photon Detectors

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G Gwangju wangju I Institute of nstitute of S Science and cience and T Technology echnology Department of Information and Communications Department of Information and Communications

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Thank You!!

Gwangju Institute of Science & Technology Department of Information & Communications