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FABRICATION AND CHARACTERIZATION OF Au/n-Si/Au METAL SEMICONDUCTOR METAL STRUCTURE By SOUMO GHOSAL SHRABANI SAMADDAR
10/16/08
1
Detector Technologies Layer Structure
MSM
( Metal Semiconductor Metal)
Semiinsulating GaAs Contact Absorption Contact
PIN
InGaAsP p 5x1018 InGaAs n- 5x1014 InP n 1x1019
Contact Multiplication Transition Absorption Contact Substrate
APD
Waveguide
InP InP InGaAsP InGaAs InP InP
Absorption Layer
10/16/08
Absorption Layer
Simple, Planar, Low Capacitance Low Quantum Efficiency Trade-off Between Quantum efficiency and Speed
Gain-Bandwidth: p 1x1018 n 5x1016 120GHz Low Noise n 1x1016 14 Difficult to make n 5x10 Complex n 1x1018 Semi insulating
Guide Layers
Key:
Features
High efficiency High speed Difficult to couple into
Contact layers 2
MSM Detectors Simple to fabricate
Light
Quantum efficiency: Medium Problem: Shadowing of absorption region by contacts
Semi insulating GaAs Simplest Version
Capacitance: Low Bandwidth: High Can be increased by thinning absorption layer and backing with a non absorbing material. Electrodes must be moved closer to reduce transit time.
Compatible with standard electronic processes GaAs FETS and HEMTs InGaAs/InAlAs/InP HEMTs
10/16/08
Schottky barrier gate metal
To increase speed decrease electrode spacing and absorption depth
Absorption layer E Field Non absorbing substratepenetrates for ~ electrode spacing into material
3
Schottky Contacts and Ohmic Contacts Compared Contacts satisfy Ohm's law. Semiconductor is very highly doped. Schottky barrier depletion region very thin depletion layer becomes quite transparent for electron tunneling. Better to use a metal with a work function m, which is equal to or smaller than the work function of a semiconductor,
s
.
Schottky contact is to GaAs doped at 1015 cm-3 Ohmic contact resistance is 104 Ωcm2.
10/16/08
4
A Comparative Study of Si and GaAs Metal-Semiconductor-Metal Photodetectors
10/16/08
5
BEAKER CLEANING
WAFER CLEANING DI water and ultrasonically agitation. Boiled with hot (TCE) at 80 to 850C for 10-15min. TCE is removed by acetone. Acetone is removed by rinsing with DI water. Soln of NH4OH , H2O2 and H2O at the ratio of 1:1:8 , and kept it for 10-15 minutes at 80 to 850C & then rinsed with DI water A solution (8 : 2 : 1 parts by volume of H2O : H2O2 : HCl ) at 60-70oC for about 10 minutes to remove heavy metals. Dipped for few seconds in 10% solution of HF to remove the SiO2 layer. Cleaned with DI water to make it hydrophobic.
10/16/08
6
WAFER SPECIFICATIONS : Crystal Orientation: <111>[n-type] Substrate resistivity: 1.5 ohm cm Wafer thickness: 300 + - 25 μm
The Ultrasonic Vibrator
10/16/08
7
METALLIZATION HIGH VACUUM CREATION DEPOSITION OF METAL ON ONE SIDE RETURNING TO NORMAL CONDITIONS DEPOSITION OF METAL ON OTHER SIDE
10/16/08
8
Electron Beam Generator
Penning Gauge
Vacuum Measuring Gauges 10/16/08
Metallization Unit
Vacuum Chamber 9
PHOTOLITHOGRAPHY & ETCHING Wafer is subjected to photoresist(-ve) and then it was rotated at 2500rpm in a photoresist spinner . Wafer heated at a temperature of 100 ºC for 15 min in a hot air oven to increases the resist adhesion to wafer. Exposed to U-V light through a photomask for 5 mins. Under exposition of light, the wafer became hard. Dissolved in developer solution Removal of the developer by rinsing . Post-baked in order to dry-out for at least 20 min at 125ºC. Post- baking makes the image permanent.
10/16/08
10
The Circuit set up for I-V Measurement
10/16/08
11
IV Characteristics of MSM structure with and without Illumination 80
Current (mA)
60
40
20
0 -0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Voltage (V) -20
-40
-60
-80
10/16/08
12
Characterization 1200
CV Characteristics 1000
Capacitance (pF)
800
600
400
200
0 0
2
4
6
8
10
12
14
16
18
20
Bias Voltage (volts)
10/16/08
13
The FESEM Instrument used at IACS, Jadavpur for study of surface morphology
10/16/08
14
10/16/08
15
Surface Characterisation
10/16/08
16
Cross Sectional SEM
10/16/08
17
Cross Sectional View of the lower junction
10/16/08
18
EDAX analysis of Pos1 showing presence of Au,Cr and Si
10/16/08
19
Qualitative and Quantitative Analysis of Pos1 of the Sample
10/16/08
20
Bibliography 1. Chou, S. Y., Liu, Y. and Fischer, P. B., Appl. Phys. Lett. 61,477 (1992). 2. Physics of Semiconductor Devices, Second edition, S. M. Sze, Wiley & Sons, 1981, Chapter 5. 3. Device Electronics for Integrated Circuits, Second edition, R.S. Muller and T. I. Kamins, Wiley & Sons, 1986, Chapter 3. 4. Physica Scripta. Vol. T69, 163-166, 1997 A Comparative Study of Si and GaAs Metal-Semiconductor-Metal Photodetectors K. Honkanen,' T. Siirtola,' T. Majamaa,' A. Hovinen' and P. Kuivalainen',' 5. “Fabrication and modelling of SOI and GaAs MSM Photodetectors and GaAs based photreceivers.” - Dissertation for the degree of Doctorate in Technology by Katri. Honkanen, Helsinki University of of Technology. 6. “Current transport in Metal – semiconductor Barriers”-C. R. Crowell & S. M. Sze solid state electronics , 9, 1035 . ( 1966 ) 7.Solid State Electronic Devices. B .G .Streetman 8. Semiconductor Opto-Electronic Devices .Pallab Bhattacharya
10/16/08
21
10/16/08
22
10/16/08
1
Detector Technologies Layer Structure
MSM
( Metal Semiconductor Metal)
Semiinsulating GaAs Contact Absorption Contact
PIN
InGaAsP p 5x1018 InGaAs n- 5x1014 InP n 1x1019
Contact Multiplication Transition Absorption Contact Substrate
APD
Waveguide
InP InP InGaAsP InGaAs InP InP
Absorption Layer
10/16/08
Absorption Layer
Simple, Planar, Low Capacitance Low Quantum Efficiency Trade-off Between Quantum efficiency and Speed
Gain-Bandwidth: p 1x1018 n 5x1016 120GHz Low Noise n 1x1016 14 Difficult to make n 5x10 Complex n 1x1018 Semi insulating
Guide Layers
Key:
Features
High efficiency High speed Difficult to couple into
Contact layers 2
MSM Detectors Simple to fabricate
Light
Quantum efficiency: Medium Problem: Shadowing of absorption region by contacts
Semi insulating GaAs Simplest Version
Capacitance: Low Bandwidth: High Can be increased by thinning absorption layer and backing with a non absorbing material. Electrodes must be moved closer to reduce transit time.
Compatible with standard electronic processes GaAs FETS and HEMTs InGaAs/InAlAs/InP HEMTs
10/16/08
Schottky barrier gate metal
To increase speed decrease electrode spacing and absorption depth
Absorption layer E Field Non absorbing substratepenetrates for ~ electrode spacing into material
3
Schottky Contacts and Ohmic Contacts Compared Contacts satisfy Ohm's law. Semiconductor is very highly doped. Schottky barrier depletion region very thin depletion layer becomes quite transparent for electron tunneling. Better to use a metal with a work function m, which is equal to or smaller than the work function of a semiconductor,
s
.
Schottky contact is to GaAs doped at 1015 cm-3 Ohmic contact resistance is 104 Ωcm2.
10/16/08
4
A Comparative Study of Si and GaAs Metal-Semiconductor-Metal Photodetectors
10/16/08
5
BEAKER CLEANING
WAFER CLEANING DI water and ultrasonically agitation. Boiled with hot (TCE) at 80 to 850C for 10-15min. TCE is removed by acetone. Acetone is removed by rinsing with DI water. Soln of NH4OH , H2O2 and H2O at the ratio of 1:1:8 , and kept it for 10-15 minutes at 80 to 850C & then rinsed with DI water A solution (8 : 2 : 1 parts by volume of H2O : H2O2 : HCl ) at 60-70oC for about 10 minutes to remove heavy metals. Dipped for few seconds in 10% solution of HF to remove the SiO2 layer. Cleaned with DI water to make it hydrophobic.
10/16/08
6
WAFER SPECIFICATIONS : Crystal Orientation: <111>[n-type] Substrate resistivity: 1.5 ohm cm Wafer thickness: 300 + - 25 μm
The Ultrasonic Vibrator
10/16/08
7
METALLIZATION HIGH VACUUM CREATION DEPOSITION OF METAL ON ONE SIDE RETURNING TO NORMAL CONDITIONS DEPOSITION OF METAL ON OTHER SIDE
10/16/08
8
Electron Beam Generator
Penning Gauge
Vacuum Measuring Gauges 10/16/08
Metallization Unit
Vacuum Chamber 9
PHOTOLITHOGRAPHY & ETCHING Wafer is subjected to photoresist(-ve) and then it was rotated at 2500rpm in a photoresist spinner . Wafer heated at a temperature of 100 ºC for 15 min in a hot air oven to increases the resist adhesion to wafer. Exposed to U-V light through a photomask for 5 mins. Under exposition of light, the wafer became hard. Dissolved in developer solution Removal of the developer by rinsing . Post-baked in order to dry-out for at least 20 min at 125ºC. Post- baking makes the image permanent.
10/16/08
10
The Circuit set up for I-V Measurement
10/16/08
11
IV Characteristics of MSM structure with and without Illumination 80
Current (mA)
60
40
20
0 -0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Voltage (V) -20
-40
-60
-80
10/16/08
12
Characterization 1200
CV Characteristics 1000
Capacitance (pF)
800
600
400
200
0 0
2
4
6
8
10
12
14
16
18
20
Bias Voltage (volts)
10/16/08
13
The FESEM Instrument used at IACS, Jadavpur for study of surface morphology
10/16/08
14
10/16/08
15
Surface Characterisation
10/16/08
16
Cross Sectional SEM
10/16/08
17
Cross Sectional View of the lower junction
10/16/08
18
EDAX analysis of Pos1 showing presence of Au,Cr and Si
10/16/08
19
Qualitative and Quantitative Analysis of Pos1 of the Sample
10/16/08
20
Bibliography 1. Chou, S. Y., Liu, Y. and Fischer, P. B., Appl. Phys. Lett. 61,477 (1992). 2. Physics of Semiconductor Devices, Second edition, S. M. Sze, Wiley & Sons, 1981, Chapter 5. 3. Device Electronics for Integrated Circuits, Second edition, R.S. Muller and T. I. Kamins, Wiley & Sons, 1986, Chapter 3. 4. Physica Scripta. Vol. T69, 163-166, 1997 A Comparative Study of Si and GaAs Metal-Semiconductor-Metal Photodetectors K. Honkanen,' T. Siirtola,' T. Majamaa,' A. Hovinen' and P. Kuivalainen',' 5. “Fabrication and modelling of SOI and GaAs MSM Photodetectors and GaAs based photreceivers.” - Dissertation for the degree of Doctorate in Technology by Katri. Honkanen, Helsinki University of of Technology. 6. “Current transport in Metal – semiconductor Barriers”-C. R. Crowell & S. M. Sze solid state electronics , 9, 1035 . ( 1966 ) 7.Solid State Electronic Devices. B .G .Streetman 8. Semiconductor Opto-Electronic Devices .Pallab Bhattacharya
10/16/08
21
10/16/08
22
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