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© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 1
Rochester Institute of TechnologyMicroelectronic Engineering
ROCHESTER INSTITUTE OF TECHNOLOGYMICROELECTRONIC ENGINEERING
Testing of Semiconductor Devices and Sensors
Dr. Lynn Fuller Webpage: http://people.rit.edu/~lffeee Microelectronic Engineering
Rochester Institute of Technology 82 Lomb Memorial Drive Rochester, NY 14623-5604 Tel (585) 475-2035 Fax (585) 475-5041
Email: LFFEEE@rit.edu Department webpage: http://www.microe.rit.edu
11-16-2007 Intro_Test.ppt
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 2
Rochester Institute of TechnologyMicroelectronic Engineering
OUTLINE
IntroductionDefinition of TermsCharacterization of Electronic DevicesElectronic Device ClassificationI-V CharacteristicsTesting Resistors
Resistor Temperature SensorResistor Chemical Sensor
Testing DiodesDiode Temperature SensorDiode Light SensorDiode Light Source
Testing TransistorsBJTMOSFET
ReferencesReview Questions
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 3
Rochester Institute of TechnologyMicroelectronic Engineering
INTRODUCTION
This is a laboratory guide that will introduce the reader to testing of semiconductor devices and sensors. Most devices are tested by measuring voltages across a device and the resulting current through a device. This can be done manually with variable voltage sources, voltmeters and current meters. A programmable test instrument called “Semiconductor Parameter Analyzer” could also be used and can provide equivalent results with easier and more flexible setup.
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 4
Rochester Institute of TechnologyMicroelectronic Engineering
DEFINITION OF TERMS
DUT - Device Under TestOhm’s Law – Fundamental Relationship between current through
and voltage across a resistor.Charge – created by the presence or absence of electronsCurrent – movement of chargeVoltage – potential to move chargeResistor – opposition to the movement of chargeLED – Light Emitting DiodeDiode – device that allows current to flow in one direction onlyBJT – Bipolar Junction TransistorMOSFET – Metal Oxide Semiconductor Field Effect Transistor
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 5
Rochester Institute of TechnologyMicroelectronic Engineering
CHARACTERIZATION OF ELECTRONIC DEVICES
Electronic devices are classified by their current-voltage (I-V) characteristics. The I-V characteristics could be measured experimentally or derived theoretically. The experimental approach would involve applying several voltages and measuring the corresponding current. The current vs. voltage is plotted and compared with known classifications. For example: a variable voltage supply Vs is used to apply different voltages to the Device Under Test (DUT) while a current meter (I) and Digital Multimeter(DMM) is used to measure I and V
DUTVs
I
+
-DMM
I
V
Data is collected for I and V(shown on the next page)
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 6
Rochester Institute of TechnologyMicroelectronic Engineering
DEVICE CLASSIFICATIONS
I
V1 2 3 4
-4 -3 -2 -1
R = 1000 ohms
R = 4000 ohms
Resistors have linear I-V characteristics that go through the origin.
Battery has linear I-V characteristics with constant voltage at any current
Diode has exponentially increasing current in the first quadrant and ~ zero current in the third quadrant (until breakdown).
3.5 VoltBattery
Diode0.0040.0030.002
Resistor Symbol
RI
V -+
+
-VB
Battery Symbol
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 7
Rochester Institute of TechnologyMicroelectronic Engineering
HP4145 – SEMICONDUCTOR PARAMETER ANALYZER
On ButtonMeasurement LED
(turns on when measurement is in progress)
Screen(Displays useful information
and options)
Data Transfer & Standby LED’s
Press the On Button to Power Up
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 8
Rochester Institute of TechnologyMicroelectronic Engineering
RESISTOR TEST DATA
30.00320.00210.00100-1-0.001-2-0.002-3-0.003
V (volts)I (amps)
Y = mX + B0
I = slope V + 0
I = (1/R) V Ohm’s Law
I
V
Data in Table Form Data in Graph Form
1 2 3 4
-4 -3 -2 -1
-0.002-0.003-0.004
0.0040.0030.002
Slope = 0.002/2R = 1000 ohms
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 9
Rochester Institute of TechnologyMicroelectronic Engineering
TESTING RESISTORS
Resistor I-V CharacteristicsResistor as a Light Sensor
Resistor as a Temperature SensorTesting of a Resistive Chemical Sensor
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 10
Rochester Institute of TechnologyMicroelectronic Engineering
RESISTOR I-V CHARACTERISTICS
R = Rhos L/Wfind Rhos R= 1/1.44e-3
= 694 ohms
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 11
Rochester Institute of TechnologyMicroelectronic Engineering
RESISTOR LIGHT RESPONSE
No lightFull light
R = ρ L/(W xj) ohms
ρ = 1/( qµnn + qµpp)
L,W,xj do not change with light, µn and µp does not change with light but can change with temperature, n and p does not change much in heavy doped semiconductors (that is, n and p is determined by doping)
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 12
Rochester Institute of TechnologyMicroelectronic Engineering
RESISTOR TEMPERATURE RESPONSE
I
V1 2 3 4
-4 -3 -2 -1
-0.002-0.003-0.004
0.0040.0030.002
Cold
Hot
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 13
Rochester Institute of TechnologyMicroelectronic Engineering
TESTING RESISTOR CHEMICAL SENSORS
Upper Left: Finished Sensor with chip pinsUpper Right: Close up of interdigitated gold fingers
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 14
Rochester Institute of TechnologyMicroelectronic Engineering
COMPLETED POLYMER/CARBON BLACK RESISTORS
Mix a polymer with Carbon Black and apply a thin coating over the interdigitated gold fingers.
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 15
Rochester Institute of TechnologyMicroelectronic Engineering
MANUAL TESTING
Micro Sensor Resistence (ohms)
0
50
100
150
200
250
300
350
400
450
500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Time
Res
iste
nce
The resistance is measured using an ohmmeter. Measurements are taken every 15 seconds. Chemical fumes are presented to the sensor after 60 seconds causing an increase in resistance
time
Res
ista
nce
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 16
Rochester Institute of TechnologyMicroelectronic Engineering
AUTOMATED TESTING
Computer controlled ohmmeter measures resistance every second for 3 min. Output is plotted versus time.
30s off, 30s on, 60s off, 30s on, 30s off
Off means no chemical vaporsOn means chemical vapor exists
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 17
Rochester Institute of TechnologyMicroelectronic Engineering
MORE CHEMICAL SENSOR TEST RESULTS
30s off, 30s on, 60s off, 30s on, 30s off0.5 ml Acetone/ 125 ml bottle = 4000 ppmResistance goes from ~100 ohms (no vapor) to ~ 100,000 ohms (with vapor)
30s off, 30s on, 60s off, 30s on, 30s offIsopropanol ~ 10,000 ppmNo Response
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 18
Rochester Institute of TechnologyMicroelectronic Engineering
MORE CHEMICAL SENSOR TEST RESULTS
30s off, 120s on, 60s off, 120s on, 30s off 0.1 ml Acetone/ 125 ml bottle = 800 ppmResistance goes from ~100 ohms (no vapor) to ~ 4,000 ohms (with vapor)
Sensor shows no response to 1 ppm acetone (just measurement noise)
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 19
Rochester Institute of TechnologyMicroelectronic Engineering
DIODES - THEORY
VD
ID
1.0-
+
SYMBOL
Diodes are like check valves. Current only flows in one direction (as shown by arrow in the symbol)
Anode (p-side)
Cathode (n-side)
ID = Io [EXP( –VD/Vth) -1 ]Io is a constant eg 1E-9 AmpsVth is ~ 0.026 at room temperture
Ideal Diode Equation
ID
VD
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 20
Rochester Institute of TechnologyMicroelectronic Engineering
TESTING DIODES
Diode I-V CharacteristicsTesting a Diode as a Temperature Sensor
Testing a Diode as a Light SensorTesting a Diode as a Light Source (LED)
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 21
Rochester Institute of TechnologyMicroelectronic Engineering
DIODE I-V CHARACTERISTICS
Nearby N++ contact to n type substrate allows us to use the resistor as a photo diode
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 22
Rochester Institute of TechnologyMicroelectronic Engineering
DIODE TEMPERATURE SENSOR
Compare with theoretical -2.2mV/°C
Gnd
~20Volts
Vout+-
R=22K I
Gnd
Idea is to keep the current constant and measure Vout vs T
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 23
Rochester Institute of TechnologyMicroelectronic Engineering
DIODE TEMPERATURE TEST DATA
Temperature vs Dial Setting
0
20
40
60
80
100
120
0 1 2 3 4 5 6
Dial Setting
Tem
per
atu
re (
°C0
Diode Voltage vs Temperature
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 20 40 60 80 100 120
Temperature (°C)
Dio
de
Vo
ltag
e (V
olt
s)
I
V
T1T2
T1<T2
Dial Vdiode Temp0 0.6539 20
0.51
1.52 0.601 54.5
2.53 0.5747 71
3.5 0.556 834 0.543 90
4.5 0.5246 1005 0.51 108.5
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 24
Rochester Institute of TechnologyMicroelectronic Engineering
DIODE RESPONSE TO LIGHT
No light
Full light
Medium light
~ Max Power Out
P=IV = (9.97e-6)( 0.32)=3.19µwatts
P/unit area =3.18e-6/500e-6/100e-6
= 63.8watt/m2
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 25
Rochester Institute of TechnologyMicroelectronic Engineering
TESTING LIGHT EMITTING DIODES
VD
ID
2.0
LED
-10.0
Light
Flat
np
Light Emitting Diode -LED
- Va +
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 26
Rochester Institute of TechnologyMicroelectronic Engineering
TESTING TRANSISTORS
Theoretical BJT I-V CharacteristicsTesting a BJT
Theoretical MOSFET I-V CharacteristicsTesting a MOSFET
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 27
Rochester Institute of TechnologyMicroelectronic Engineering
THEORETICAL BJT I-V CHARACTERISTICS
npn
Schematic Symbol
Base - p
Collector - n
Emitter - n
10 µA increments
1 mA2 mA3 mA4 mA5 mA
7 mA8 mA9 mA
10 mA
∆IC = 5 mA
VCE
IC
6 mA
IB = 10 µA
IB = 20 µA
IB = 30 µA
Steps of base current - IB
βdc
Current Gain (Beta)Βdc = IC / IB = 5 mA / 20 µA = 250
IB = 0 µA
IC
VCE
+-IB
p nnEmitterLead
BaseLead
CollectorLead
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 28
Rochester Institute of TechnologyMicroelectronic Engineering
DEFINITIONS
§ Bipolar Junction Transistor - (BJT) Both holes and electrons participate in the conduction of current, hence the name bipolar.
§ Minority carrier - In a p-type semiconductor electrons are the minority carrier type, in an n-type semiconductor holes are the minority carrier type.
§ Emitter - Emits minority carriers into the base region of a BJT. For example, in an NPN BJT the n-type emitter, emits electrons into the p-type base. The emitter usually has the highest doping levels of the three regions of a BJT.
§ Base - Thin region (<1µm) which is used to control the flow of minority carriers from the emitter to the collector
§ Collector - Collects the minority carriers that make it through the base from the emitter. The collector usually has the lightest doping concentrations of the three regions.
§ DC Beta ( βdc ) - The ratio of the steady-state collector current to the base current. (Current Gain)
βdc = IC / IB
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 29
Rochester Institute of TechnologyMicroelectronic Engineering
BIPOLAR JUNCTION TRANSISTORS
Flat
12 3
Discrete Packaged BJTLabel
2N39
04
1 2 3
Bottom View
2N3904NPNGain ~200Maximum VCE = 30VMaximum IC = 800mAMaximum Power = 1.8watts
emitterbase collector
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 30
Rochester Institute of TechnologyMicroelectronic Engineering
TESTING A BJT
VD
ID
1.0VD
ID
1.0
V
I
1.0
Base - EmitterBase - Collector
Collector to Emitter
-7.0
-7.0
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 31
Rochester Institute of TechnologyMicroelectronic Engineering
TESTING A BJT
General purpose npn 2N3904
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 32
Rochester Institute of TechnologyMicroelectronic Engineering
THEORETICAL MOSFET I-V CHARACTERISTICS
Id (Amps)
10-5
VgsVt
Sub Vt Slope (mV/dec)
10-410-310-2
10-1010-910-810-710-6
10-11
10-12
G
D
S
Vgs=VdsId
+
-
+Ids+Vgs
+Vds
+5+4+3+2
+Vgs
+Id
Vto
Vsub = 0
-2-1
-3 volts
G
D
S
Vgs
Id+
-Vsub
Vd = 0.1 Volt
Family of Curves
Ids vs Vgs
Subthreshold
Saturation Region Non SaturationRegion
Non SaturationRegion
Saturation Region
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 33
Rochester Institute of TechnologyMicroelectronic Engineering
TESTING A MOSFET
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 34
Rochester Institute of TechnologyMicroelectronic Engineering
REFERENCES
1. Dr. Fuller’s webpage http://www.rit.edu/~lffeee2. more
© November 16, 2007 Dr. Lynn Fuller
Testing Devices and Sensors
Page 35
Rochester Institute of TechnologyMicroelectronic Engineering
REVIEW QUESTIONS
1. A 220 ohm resistor has 1.5 volts across it. The current through the resistor is a)1.5A b) 0.0068A c) 68mA d) 0.147A
2. A diode has voltage of -1.5 volts applied to it. The current isa) zero b) infinite c) 1A d) 68 mA
3. An npn BJT biased in the forward active mode has base currentof 20 µA and current gain of 150. What is the collector current?a) zero b) infinite c)300 µA d)3 mA
4. A nMOSFET has 5 volts on the gate. The transistor is:a) On b) Off c) saturated d) subthreshold
5. A diode can be used to sense temperature. If the temperature increases the voltage VD: a) increases b) decreases c) stays the same d) none of above
6. A resistor can be used to sense temperature. If the temperature increases the resistance value will: a) increases b) decreases c) stay the same d) none of above
-
+ ID
VD