Transcript IntelliEPIpaul

Intelligent Epitaxy Technology, Inc.
Presentation: SMU EE 5312/7312 Class
Band Gap Engineering
for
Heterostructure Devices
Grown by
Molecular Beam Epitaxy (MBE)
18 October 2006
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Outline
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Band Gap Engineering & Molecular Beam Epitaxy (MBE)
Company profile & product mix
Company technology
Selected Applications of compound semiconductor
– HBT for high speed electronics
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BandProf* demonstration/open discussion
*BandProf is a Java based device simulation software developed by Prof. Frensley at UT Dallas.
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Compound Semiconductor Band Gap Engineering
Band Gap vs. Lattice Constant
Example of
Epi structure
VCSEL
Band Gap Engineering: Altering properties of layered epitaxy materials while maintaining
crystalline lattice registration
• Band gap
3rd degree of freedom for device design
• Band alignment
based Heterojunction concept!
• Dielectric constant
• Thermal conductivity
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IntelliEPI : MBE Technology for III-V Compound Semiconductor
MBE System
Substrate
Platen
Materials Capability
Substrate: GaAs, & InP
Group III: Al, Ga, & In
Group V: As, P, Sb, & N
N-type Dopant: Si
P-type Dopant: Be, & C (from CBr4)
Molecular
Beam Fluxes
Deposition
Source Materials
UHV Growth Chamber
Molecular Beam Epitaxy (MBE)
• Impinging molecular/atomic beam fluxes are the precursors for the epitaxy growth
process
• Epitaxy growth process maintain lattice registration along the growth direction
• MBE process grows each atomic monolayer at a time
• Ultra high vacuum growth chamber: 10-10 Torr base pressure
• Growth of customized active device/structure on top of crystalline substrate
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IntelliEPI: Thickness Uniformity Across Platen for 7x6” MBE
Riber 7000 thickness uniformity
measured by white light reflection
103.0
Normalized thickness (%)
102.0
Ga
Al
101.0
7X6” platen
100.0
99.0
2,500Å GaAs
Outside wafer
Center wafer
98.0
2,000Å AlAs
97.0
0
50
100
150
200
Platen radial position (mm)
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250
GaAs substrate
Thickness variation across platen < 1% across 7X6” platen configuration
Si doping GaAs layer uniformity by contactless resistivity mapping:
– 6” wafer doping variation < 1%
– Difference from center wafer to outside wafer < 0.5%
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Overview of IntelliEPI in-situ Sensor Technologies
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Substrate temperature
ABES light source:
Light pipe, or
Heater filament
– Pyrometry
– Absorption Band-Edge Spectroscopy
(ABES): band-gap dependence on temp
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Materials composition
– Optical-based Flux Monitor (OFM):
atomic absorption of group III fluxes
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Optical
Pyrometer
OFM
Growth rate
– Optical Reflectometry
– Pyrometric Interferometry
Optical Reflectometry
OFM setup
Absorption Band-Edge Spectroscopy,
Pyrometer, and
Laser Reflection.
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PHEMT In-situ Composition Monitoring with OFM
PHEMT Structure
OFM Profile During PHEMT Growth
atomic abosrption (%)
30
30348D
Al
Ga
In
20
AlGaAs
Gate
GaAs/AlGaAs
SL
10
InGaP
Etch
Stop
InGaAs
Channel
n+ GaAs
Cap
n InGaP
Etch Stop
n AlGaAs
Gate
AlGaAs
Spacer
InGaAs
Channel
AlGaAs
Spacer
Si - delta
AlGaAs
GaAs
AlGaAs
SL
0
2000
2500
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time (sec)
3000
3500
GaAs
Buffer
GaAs
Substrate
Direct composition monitoring for each critical layer
In-situ composition monitoring for key layers:
– InGaAs Channel: Accurate x-ray measurement
– AlGaAs Gate: X-ray represents average of SL and Gate
– InGaP Etch Stop: Very thin layer limits x-ray accuracy
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Absorption Band-Edge Spectroscopy (ABES)
Light from heater
or light source
Substrate
~500 um
EPI
~1 UM
Transmitted light
Through substrate
c
Input light
at different
photon
energies
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Transmitted light has
photon energy
smaller than
substrate band gap
v
ABES measures transmission of light through the substrate
EPI material not the dominate effect when:
– EPI material is not too thick
– EPI material has larger band-gap than substrate
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Substrate semiconductor band-gap shrinks with increase substrate
temperature
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IntelliEPI: ABES Temperature Measurement
InP Band-edge transmission spectra
Band-edge wavelength vs. temperature
transmission Intensity (A.U.)
1250
360 C
450 C
535 C
InP band-edge knee
1200
1150
70283B
1000
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1050
1100
1150
wavelength (nm)
1200
1250
1100
350
400
450
500
substrate temp (C)
550
Determine substrate temperature by monitoring shift in substrate
band gap as a function of temperature.
Measurement range extends to substrate temperature well below the
operating range of optical pyrometer.
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C-doped InP-DHBT: Temperature and Group III flux
control
In-situ flux profile and substrate temperature during growth
Emitter contact (n-InGaAs)
Emitter (n-InP)
Base (p-InGaAs)
InP
Collector
InGaAs Base
InP
Emitter
Collector grade (n-InAlGaAs)
Collector (n-InP)
InP substrate
Data from
Riber6000
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Control of temperature & composition profile critical for HBT device
parameters such as beta, Vbe, Rbs
Substrate temperature: measured by ABES
Group III fluxes: measured by OFM
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IntelliEPI: InP HBT Large Area Device Processing
I-V Characteristics, 50x50 um 2
2.5E-02
2.0E-02
Ic (A)
1.5E-02
1.0E-02
5.0E-03
0.0E+00
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
-5.0E-03
Current Gain
Vce (V)
50
45
40
35
30
25
20
15
10
5
0
• InP/InGaAs SHBTs & DHBTs
• InP/GaAsSb/InP DHBTs
• Be or Carbon-doped base
• 2E19 to 1E20 cm-3 base doping
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
Vbe (V)
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Communications Technology Evolution
III-V semiconductors
from elements of
group III and group V
columns of Periodic
Table
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III
IV
V
B
C
N
Al
Si
P
Ga
Ge
As
In
Sn
Sb
InP and GaAs are key enabling technology for all communications systems
– Wireless, telecomm, satellite, fiber optics, and other high frequency systems such as
collision warning radar system all require faster semiconductors like GaAs and InP
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InP outperforms all existing RF/telecomm technology in terms of speed
– Wireless from 2GHz to 300 GHz with 2x breakdown voltage vs. SiGe, high gain, better
efficiency
– Current fasted flip-flop speed at 150 GHz (from IntelliEPI/Vitesse) vs. 96GHz of SiGe
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Competing Building Blocks - Fiber optic network example
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Internet is the main driving force
– data, speed, bandwidth,
wireless
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Both long-haul and local networks
shift to fiber optic networks
Current 2.5Gbps networks will be
replaced by 10Gbps (OC192)
2004-2005. GaAs is the major
semicon building block
40Gbps network will be the 2nd
largest in 2005 and will be
dominated by InP
Silicon will be dominant for
market adoption in the “late
majority” and “laggard” phases
Fiber optics industry major
recovery expected in 2005-2006
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High Speed Technology Race
InP Heterojunction
Bi-Polar Transistor (HBT)
0.25 m
Base
Emitter
Collector
W. Hafez, et al, IEEE Elect. Dev. Lett.,
Vol 24, #7, pg 346, July 2003.
*Partial slide Source: N. Pan, UCLA.
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Divide by Two Circuit operating at 152 GHz!
IntelliEPI supplied materials.
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Static digital flip-flop circuit fabricated by Vitesse using VIP-2
process (InP DHBT)
*Data courtesy of Vitesse Semiconductor for DARPA-TFAST program.
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Summary of Key Concepts
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Band gap engineering enable the additional degree of
freedom along the growth direction
MBE: ultra high vacuum deposition/crystal growth
process
Compound semiconductor suited for high speed
applications due to fast intrinsic electron mobility
PHEMT analogous to FET
HBT analogous to Si Bi-Polar Junction Transistor
(BJT)
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