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?????????? ???? Metal Gate and Ge on Insulator Process

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Title: ?????????? ???? Metal Gate and Ge on Insulator Process


1
?????????? ???? Metal Gate and Ge on Insulator
Process
  • ??????? ??
  • ?????
  • ????????????

2
Outline
  • Introduction
  • The Electrical Characteristics of Tantalum
    Nitride Metal Gate
  • Ge-on-Insulator Substrates Formation by Wafer
  • Bonding and Layer Transfer
  • A Novel 850 nm, 1.3µm and 1.5µm GOI MOS
  • Photodetector for Optical Communication
  • Summary

3
Internl Technology Roadmap for Semiconductors--
ITRS
4
Why metal gate ?
  • Problems in conventional poly silicon gate
    (poly-Si)
  • High gate resistance
  • High gate tunneling leakage current
  • Poly silicon gate depletion
  • Boron penetration into the channel region
  • Solution
  • Metal gate

5
Pure Metal Work Functions
  • The work-function with various pure metals.
  • The band gap of silicon that between the
    conduction band (Ec) and valence band (Ev) is
    1.12eV at room temperature.

6
Why tantalum metal is suitable for semiconductor
industry?
  • Advantages
  • Body-centered-cubic (BCC) crystal structure
  • High melting point(2996?)
  • Low-resistance ohmic contact

Cubic, Body Centered
Cubic, Face Centered For instance, Al, Pt and Cu
7
Outline
  • Introduction
  • The Electrical Characteristics of Tantalum
    Nitride Metal Gate
  • Ge-on-Insulator Substrates Formation by Wafer
    Bonding and Layer Transfer
  • A Novel 850nm, 1.3µm, and 1.5µm GOI MOS
    Photodetector for Optical Communication
  • Summary

8
Alloy Work Functions
9
Experiment Process Flow
10
C-V Curves of TaN with PMA 400?
Before N2 Annealing
After N2 Annealing
  • After PMA 5minutes in 400?, the interface
    traps of TaN gate device
  • are significantly reduced by heat
    treatment.

11
Calculation of Flat-Band Voltage
Cfb
Vfb
  • Cox , Vg, A as known

Vfb
Here LD was the Debye length defined
12
Flat-Band Voltages Versus Silicon Dioxide
Thickness
13
Flat-Band Voltages Versus Nitrogen Flow Ratio
  • The VFB converge to a specific value (i.e.
    -0.42V)
  • when the N2 flow rate is upto abut twenty.

14
Work Functions of Tantalum Nitride
15
The C-V Curves Dispersion After PMA 900? 20sec
  • After PMA 900C 20sec, the Cox of TaN gate
    devices continues
  • to decrease as nitrogen flow ratio.

16
The Value of Cox Dispersion After PMA 900? 20sec
  • If nitrogen gas flow ratio is higher than
    thirteen percents,
  • the Cox dispersion phenomenon is obviously.

17
The TaN Gate Analysis of Auger Microprobe
After PMA 900? 20sec
After PMA 400? 5min
  • With increasing nitrogen gas flow ratio, the
    thermal stability
  • decreased by tantalum diffusion into
    dielectric layer.

18
Outline
  • Introduction
  • The Electrical Characteristics of Tantalum
    Nitride Metal Gate
  • Ge-on-Insulator Substrates Formation by Wafer
    Bonding and Layer Transfer
  • A Novel 850nm, 1.3µm, and 1.5µm GOI MOS
    Photodetector for Optical Communication
  • Summary

19
Roadmap for GOI Process
20
Direct Wafer Bonding
  • Megasonic acoustic cleaning
  • KOH cleaning
  • KOHH20
  • DI water rinse
  • Hydrophilic surface (OH-)
  • SC1 cleaning
  • NH4OHH2O2H2O
  • DI water rinse
  • Hydrophilic surface (OH-)
  • Pre-bonding
  • Alignment
  • Form a single bonding wave
  • High temperature treatment
  • 6500C, O2, 30min
  • Strength the chemical bonds

21
GOI Wafer Formation
  • The scanning electron microscopy (SEM) picture
    of a Ge wafer
  • bonds to another Si wafer capped with 600
    nm BPSG.

22
The hydrogen-induced exfoliation of Germanium
  • Formation of point defect in the lower
    concentration of hydrogen implant.
  • Rearrangement of the defect structure above
    650?.
  • H2 trap in the microvoids.
  • Development of these microvoids into cracks
    leading to complete layer transfer.

23
GOI Smart Cut Process Flow
  • Ion Implant (Hydrogen Dose 1E17)
  • Megasonic acoustic cleaning
  • Direct Wafer Bonding
  • KOH Cleaning
  • SC1 Cleaning
  • Pre-bonding
  • H Induced Layer Transfer
  • High temperature treatment
  • (650? 30min in Oxygen gas)
  • Surface Roughness Reduction
  • High temperature annealing
  • (825? 60min in hydrogen gas)

24
Ion Implantation Depth
  • The hydrogen implant depth in Ge vs. implant
    energy.
  • The longitudinal Straggle in Ge vs. implant
    energy.

25
TRIM Simulation
  • The concentration profile of hydrogen atoms is
    simulated by TRIM.
  • The hydrogen implant into germanium with
    200KeV implant energy.

26
SEM of GOI After Smart Cut Process
  • The surface of GOI substrate is rough after
    smart cut process.
  • The thin germanium layer (i.e. 1.46µm)
    transfers upon BPSG.

27
Microroughness Measurement After Smart-cut
With Annealing in F. G.
No Annealing
After GOI annealed in furnace 825? with forming
gas , GOI surface roughness reduced to RMS27nm.
GOI surface
Roughness-mean-square(RMS)97nm.
28
Microroughness Measurement After Smart-cut
With Annealing in N2
With Annealing in H2
After GOI annealed in furnace 825 ? with N2 gas ,
GOI surface roughness reduced to RMS62nm.
After GOI annealed in RTP 825 ? with H2 gas , GOI
surface roughness reduced to RMS43nm.
29
GOI Surface Roughness Reduction
  • Surface microroughness of Ge-on-insulator with
    different kind of gas,
  • for an hour annealing at 825? in furnace.

30
Outline
  • Introduction
  • The Electrical Characteristics of Tantalum
    Nitride Metal Gate
  • Ge-on-Insulator Substrates Formation by Wafer
    Bonding and Layer Transfer
  • A Novel 850 nm, 1.3µm and 1.5µm GOI MOS
    Photodetector for Optical Communication
  • Summary

31
Roadmap for GOI Photodetector
32
GOI Smart Cut at Low Temperature Splitting
Annealing
  • Ion Implant (Hydrogen Dose 1E17)
  • Megasonic acoustic cleaning
  • Direct Wafer Bonding
  • KOH Cleaning
  • SC1 Cleaning
  • Pre-bonding
  • H Induced Layer Transfer
  • Low temperature splitting annealing
  • (150? 12hr in 10 Oxygen gas)

33
Low Temperature Splitting Annealing
  • After splitting, the microroughness of
    Ge-on-insulator substrate.
  • The cross-section SEM image of Ge-on-insulator
    substrate.

After low temperature splitting annealing 150?
with N2 gas , GOI surface roughness is around
6.6nm (r.m.s).
After splitting annealing, the germanium layer
thickness is 800nm.
34
Current Reduction by Metal Technique
Device Area 3x10-4 (cm2) Pt is good selection
for Ge N(100).
35
GOI Photodetector Process Flow
  • Ion implant (hydrogen
  • dose1E17).
  • Direct Wafer bonding.
  • H induced layer transfer.
  • (150? 12Hr in 10 Oxygen)
  • Liquid Phase Deposition.
  • Gate electrode fabrication.
  • (Pt gate and Al contact)

36
GOI Photodetector Formation
  • The cross-section TEM image of Ge-on-insulator
    PMOS devices.

37
Photocurrent Under 850nm Light Source
  • The dark and photocurrent of the GOI PMOS
    detector exposures
  • to 850nm lightwave with different light
    intensity.

Responsivity 0.2 0.3 (A/W) GOI PMOS
Photodetector
Responsivity 0.2 (A/W) Bulk Ge MOS detector
38
Photocurrent under 1300 and 1550 nm light source
  • The dark and photocurrent of the GOI PMOS
    detector exposures
  • to 1300nm and 1550 nm lightwave with
    different light intensity.

Responsivity 0.2 (A/W)
Responsivity 0.06 (A/W)
39
Responsivity and Efficiency
  • The responsivity of GOI PMOS detector
    exposures to 850nm, 1.3µm, and 1.5µm
  • lightwave with different light intensity.
  • The quantum efficiency (?) of the GOI
    photodetectors versus power under different
  • lasers exposure.

40
Impulse Response Bulk Ge Detector
  • The Full-Width Half-Maximum (FWHM) is 722 ps
    for the typical Ge MOS detector
  • under 850nm pulse measurement.
  • After fast fourier transform (FFT), the -3 dB
    bandwidth can be obtained about
  • 340 MHz.

41
Impulse Response GOI Detector
  • The Full-Width Half-Maximum (FWHM) is 543 ps
    for the typical Ge MOS detector
  • under 850nm pulse measurement.
  • After fast fourier transform (FFT), the -3 dB
    bandwidth can be obtained about
  • 340 MHz.
  • The 60 enhancement is achieved with -3 dB
    bandwidth, comparing to bulk
  • Ge MOS detector.
  • Since some of diffusion current is eliminated
    in GOI MOS photodetectors,
  • the speed and bandwidth of the device
    increases.

42
Outline
  • Introduction
  • The Electrical Characteristics of Tantalum
    Nitride Metal Gate
  • Ge-on-Insulator Substrates Formation by Wafer
    Bonding and Layer Transfer
  • A Novel 850nm, 1.3µm, and 1.5µm GOI MOS
    Photodetector for Optical Communication
  • Summary

43
Summary
  • Tantalum Nitride Metal Gate
  • In experiment, we obtained that the oxide charges
    are positive in TEOS and the flat-band voltages
    concentrated -0.42V at twenty percents nitrogen
    flow ratio.
  • With increasing nitrogen gas flow ratio, the
    thermal stability decreased by tantalum diffusion
    into dielectric layer.
  • If nitrogen gas flow ratio is higher than
    thirteen percents, the tantalum diffusion
    phenomenon is obviously.
  • Ge-on-Insulator substrates Formation
  • The GOI surface roughness is reduced by thermal
    rapid annealing with hydrogen gas in furnace.
  • The bonding condition of low temperature heat
    treatment is at 150? with 10 oxygen flow in
    furnace.

44
Summary
  • GOI MOS Photodetector
  • The leakage current is decreased at inversion
    bias by platinum gate electrode.
  • The novel GOI PMOS photodetectors have high
    responsivity (0.3 A/W) and high quantum
    efficiency of 40 at 850nm (0.25mW).
  • The 60 enhancement is achieved with -3 dB
    bandwidth, comparing to bulk Ge MOS detector.

45
Future Work
  • The RF pattern can be designed to enhance the
    speed (3-dB bandwidth) of GOI MOS photodetectors.
  • The thickness of germanium layer on insulator can
    be designed for fabricating resonant-cavity-enhanc
    ed (RCE) photodetectors to increase the
    bandwidth-efficiency.
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