Characterisation and Reliability testing of THz Schottky diodes. By Chris Price [email protected]...
-
date post
19-Dec-2015 -
Category
Documents
-
view
218 -
download
0
Transcript of Characterisation and Reliability testing of THz Schottky diodes. By Chris Price [email protected]...
![Page 1: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/1.jpg)
Characterisation and Reliability testing of THz
Schottky diodes.
By Chris [email protected]
Supervisor: Dr Byron Alderman
December 2006
Preliminary Presentation
![Page 2: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/2.jpg)
Contents• Problems with THz technology
• What is a Schottky diode
• What are Schottky diodes used for
• The fabrication method
• European situation
• Characterisation
• Reliability
• Summarise current position
• Future plans
• Questions ???
Probe station (Pegasus s200)
![Page 3: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/3.jpg)
Problems with THz Technology
• THz frequencies are loosely defined in the range of 0.1-10 THz
• There is an absence of low cost, miniaturised solid state power supplies
10-3 10-2 10-1 1 10Frequency (THz)
![Page 4: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/4.jpg)
Problems with THz Technology
• Transit Time Devices (up to 170 GHz)
• Advanced electronics
• Equivalent to commercially available
devices with reduced dimensions
• Maximum frequency determined by;
• Time taken for a carrier to move a characteristic distance
• And to a lesser extent the RC time constant
![Page 5: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/5.jpg)
Problems with THz Technology
• Energy Transition Devices– Charge carriers undergo a transition between
energy states– Frequency given by (E2 – E1)= h f
• Problems;– Cannot get population inversion at room
temperatures– Photon density of states α Frequency^2
E2
E1
PhotonFrequency, f
![Page 6: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/6.jpg)
Recombination of electrons and holes occurs creating a depletion zone
What is a Schottky diode
• P-N diode• is a combination to two oppositely doped semi-conductors
P- Type N- Type
Energy Band
diagram of
P-N junction
![Page 7: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/7.jpg)
What is a Schottky diode
• Combination of metal and a semi-conductor• This creates;
– Lower junction voltage– Almost non-existent depletion width in metal
• Another property of Schottky diodes;– Majority carrier
• No slow random recombination
Energy band
diagram of
Schottky
junction
![Page 8: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/8.jpg)
Planar Schottky diode
Air BridgeSchottky Contact
Ohmic
)1)(exp(0 Tk
qVIi
B
d
• Diode current voltage relationship is given by; i is the current
I0 is reverse saturation currentq is the charge on an electronVd is voltage across the diodekb is the Boltzmann constantT is the temperature in kelvinη is the ideality
![Page 9: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/9.jpg)
What diodes are used for
• Two devices that use the non-linear properties are;
• Multipliers (diode used as a varactor)– High frequency multipliers use the
nonlinear capacitance property, and a filter to eliminate specific harmonics and produce an output that is a multiple of the input frequency
...)( 33
2210 VaVaVaaVVI B
![Page 10: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/10.jpg)
•Mixers (diode used as a varistor)• A mixer is a non linear circuit that receives two input signals and outputs a signal equal to the difference and to the sum of the two input frequencies
What diodes are used for
)]][2cos()][2[cos(2
.. 2121
2121 tfftff
AAvv
![Page 11: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/11.jpg)
The creation of these diodes can be broken down into four stages:
1) Making the ohmic
2) Making the Schottky contact
3) Making the finger
4) Making the air gap
12
3
4 12
3
4
Fabrication Process
![Page 12: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/12.jpg)
Preparing the ohmic
Annealer
Thermal evaporator
![Page 13: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/13.jpg)
Schottky Contact
E- beam evaporator
![Page 14: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/14.jpg)
Anode Finger
![Page 15: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/15.jpg)
Air Gap
![Page 16: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/16.jpg)
• Virginia Diodes Inc. (VDI)– Leading supplier of Schottky diodes– Concerns over future availability
• University of Bath– Made limited progress
• Darmstadt– Are developing a novel approach
• UMS – Provide commercial diodes, but no influence
over design• RAL
– Produced leading mixer results at 200 GHz– Very much at the forefront of technology
Supply Situation in Europe
![Page 17: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/17.jpg)
• Two methods:– Current Voltage (IV)
• Measures DC characteristics • Useful for mixers
– Capacitance Voltage (CV)• Measures AC characteristics• Useful for multipliers
Probe station (Pegasus S200)
Characterisation
![Page 18: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/18.jpg)
IV setup
Basic Circuit
![Page 19: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/19.jpg)
Calculating Parameters
• Parameters Interested in;– Spreading Resistance Rs,
– Ideality η and – Reverse saturation current I0
• Two methods of calculations:– Standard formulae on current
point measurements– Curve fitting the IV
characteristics at arbitrary measurement points
![Page 20: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/20.jpg)
Calculating Parameters
• Standard formula• ΔV = V3 – V4
• Rs = 1000 ((V5 – V4) – ΔV• η = q ΔV log10 (e) / (kB T)• I0 = i1 / (exp ((q V1) /(η kB T))
– 1)• Allows comparison between measurements• Good heritage for comparisons with
previously used diodes but• If two or more points are missed
comparison is no longer valid
![Page 21: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/21.jpg)
• Curve fitting– Derived from IV equation and – assumes there is a constant
spreading resistance also– Assuming that i >> I0
– Substituting in Vd = V – i Rs
– V = a ln(i) + b i + c– Least square fits is performed
to calculate the coefficients
Calculating Parameters
)1)(exp(0 Tk
qVIi
B
d
q
Tka B
sRb q
ITkc b )ln( 0
![Page 22: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/22.jpg)
Results
![Page 23: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/23.jpg)
1 2 3 4 5 6 7 8 9 10
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
Ideality
X coordinate
Y coordinate
Surface Plot of ideality, P8.1 1um single anode
1.40-1.50
1.30-1.40
1.20-1.30
1.10-1.20
1.00-1.10
0.90-1.00
1 2 3 4 5 6 7 8 9 10
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
Resistance (ohms)
X coordinate
Y coordinate
Surface map of spreading resistance
16.00-20.00
12.00-16.00
8.00-12.00
4.00-8.00
Results
![Page 24: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/24.jpg)
Scanning electron microscope (SEM)
IV setup• Problem;
![Page 25: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/25.jpg)
Reliability Tests
• Defined as how resistant it is to failure• Failure criteria;
– A 10% deviation from original measurements.
• Simple tests– Repeatability – Soldering – Thermal Cycling
• Accelerated Life tests– Thermal – Humidity– Electrical Biasing
![Page 26: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/26.jpg)
Summary
• Current Situation:– Understood how the IV
characterisation calculations are done and
– how the Probe Station works– I have separated the diodes and
currently building the basic circuit for the reliability tests and
– I am currently learning LabView
Above: Diced diode from a wafer
Left: dicing saw
![Page 27: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/27.jpg)
Future plans
• Remove bugs from the probe station and calibrate with new heads
• Develop the software necessary
• Build thermal experiment• Perform repeatability test• Perform soldering test• Analyse data collected
![Page 28: Characterisation and Reliability testing of THz Schottky diodes. By Chris Price C.M.Price@rl.ac.uk Supervisor: Dr Byron Alderman December 2006 Preliminary.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d395503460f94a13ecc/html5/thumbnails/28.jpg)
Any Questions???