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Steady State Total Dose Irradiation
Test Report Disposition
FBG20N18
ABSTRACT
August 2nd , 2016
Copyright (C) 2017 Freebird Semiconductor
This document contains information proprietary to Freebird Semiconductor, and it is issued on condition that it is received and held in confidence.
Neither it nor the information herein shall be reproduced, sold, lent, disclosed or used for any purpose other than that for which it has been issued
without written authority of Freebird Semiconductor.
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Contents
1.0 Executive Summary ........................................................................................................................................................... 3
1.1 Test Results Summary ................................................................................................................................................... 3
2.0 Background ....................................................................................................................................................................... 4
3.0 References ........................................................................................................................................................................ 4
4.0 Handling Precautions. ....................................................................................................................................................... 5
5.0 Procedure .......................................................................................................................................................................... 5
6.0 Dosimetry. ......................................................................................................................................................................... 6
Fig 3. Dosimeter Prototype Board .......................................................................................................................................... 6
Table 2. Dose Rate and Uniformity ......................................................................................................................................... 6
7.0 Gamma Test Results.......................................................................................................................................................... 7
7.1 Bias Circuit..................................................................................................................................................................... 7
7.2 Total Dose Response. .................................................................................................................................................... 8
7.2.1
Gate-to-Source leakage Current (IGSSF & IGSSR ) Responses ................................................................................ 8
7.2.2
Drain-to-Source Leakage Current (IDSS) Response ......................................................................................... 10
7.2.3
Threshold Voltage (VTH) Response............................................................................................................... 11
7.2.4
On-State Resistance (RDSON) Response .......................................................................................................... 12
8.0 Summary ......................................................................................................................................................................... 13
Appendix A – Notes and Setup Information ......................................................................................................................... 14
Appendix B Test result tables............................................................................................................................................... 15
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1.0 Executive Summary
Freebird evaluated the radiation performance of the FBG20N18X 200 Volts 18 Ampere Enhancement
Gallium Nitride power switching HEMT FET at VPTRad according to the test plan. This report covers the
total dose (Gamma) characterization portion of the test plan for the FBG20N18. Section 5 discusses the test
procedure; and Section 6.0 discusses the test results. Appendix A provides test notes and setup information
from VPTRad.
Freebird Semiconductor performed gamma irradiations under two different bias conditions:
Bias 1: VGS = 5 V and VDS = 0 V (On-State Bias)
Bias 2: VGS = 0 V and VDS = 160 V (Off-State Bias)
Bias 3: VGS = 0 V and VDS = 0 V (No Bias)
1.1 Test Results Summary
Two samples per bias and per wafers were characterized in accordance with Freebird test plan. The wafers
were exposed to an accumulated ionizing dose of 300 krad using a nominal dose rate of 128rad/sec.
The following electrical parameters were measured after each incremental dose to determine a pass-fail
criteria.
-
Gate-to-Source leakage current (IGSSF, IGSSR)
Drain-to-Source leakage current (IDSS)
Threshold voltage (VTH)
On-state resistance (RDSON)
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2.0 Background
The FBG20N18 is an enhancement mode Gallium Nitride High Electron Mobility Transistor (HEMT)
developed by EPC for Freebird under a dedicated source controlled and in Fab screening. The FBG20N18 is
the larger size die of Freebird 200V platform and was screened to a total dose level of 300 krad.
3.0 References
The major applicable documents, used to perform this gamma irradiation characterization are:
MIL-PRF-19500
General Specifications for Semiconductor Devices
MIL-STD-750D
Test Methods for Semiconductor Devices
Method 1019
Steady State Total Dose Irradiation Procedure
Method 3421
On-State Resistance
Method 3403
FET Threshold Voltage Measurement
Method 3405
Drain to Source On-State Voltage
Method 3411
Gate to Source Leakage Current
Method 3415
Drain to Source Leakage current
Test Plan rev 1
FBS20N18
VPTRad XXXX
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Freebird Semiconductor Test Plan
Freebird Datasheet Rev Q
VPTRad operating instructions
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4.0 Handling Precautions.
The following handling precautions were observed:.
4.1 Proper ESD handling the devices according to their rating
4.2 Maximum rated voltages during irradiation were not exceeded
4.3 Devices were stored within antistatic boxes
5.0 Procedure
Test conditions were performed as specified by Freebird Test Plan XXXX using the applicable test circuit.
Irradiations were performed at the ambient temperature of the irradiator system. Figure 1 shows the
insitu bias circuits as defined in the test plan.
Bias 1: VGS = 5 V and VDS = 0 V (On-State Bias)
Bias 2: VGS = 0 V and VDS = 160 V (Off-State Bias)
Bias 3: VGS = 0 V and VDS = 0 V (No Bias)
Figure 1. Test circuit for insitu TID testing
Devices were placed in the (Co-60 Gamma Cell) irradiator with the appropriate bias applied. The devices
were then irradiated to the following accumulated dose levels.
a) 0 krad
b) 100 krad
c) 300 krad
d) 500 krad
Upon completion of each exposure level, the devices were removed from the irradiator, electrically tested,
and returned to the gamma irradiator for the next exposure level.
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6.0 Dosimetry.
Radiation dosimetry at VPT Rad is performed using an alanine Electron Paramagnetic Resonance (EPR)
dosimetry system. The EPR spectrometer uses a variable magnetic field to detect the energy level
transitions of unpaired electrons at specific resonant frequencies. The radiation dosimeters for the EPR
system incorporate the amino acid alanine. When alanine is exposed to ionizing radiation, the molecule
forms a very stable free radical that is detectable by the EPR system. The EPR signal is correlated to
dose by a fitting function based on the system response to the National Institute of Technology (NIST)
certified dosimeters. Table 2 lists the response of the dosimeters for two back-to-back prototype boards
as shown in Figure 3. The calculated average dose rate for this geometry was 128 rad/sec for the testing
on August 2nd 2016.
Fig 3. Dosimeter Prototype Board
Table 2. Dose Rate and Uniformity
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7.0 Gamma Test Results
7.1 Bias Circuit.
Freebird used VPTRad the Standard TO-254 irradiation board which is illustrated in Fig 2 and conforms
to the test circuit shown in figure 1. Figure 2 shows a picture of the VPTRad To-254 test board.
Figure 2. Photograph of TO-254 Bias Board Used during TID Irradiations and Freebird test coupon.
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7.2 Total Dose Response.
Four devices per wafer were exposed to Gamma radiation using a Co-60 Gamma Cell Irradiator at
VPTRad. A nominal dose rate of 128 rad/sec was used to calculate the exposure length for each
incremental dose level. The sections below will discuss the testing of each of the four electrical
parameters and their test results.
7.2.1 Gate-to-Source leakage Current (IGSSF & IGSSR ) Responses
The average gate-to-source leakage current response of all the wafer samples is shown in
Figures 4a and 4b. Figure 4a depicts the forward leakage current with an applied gate of +5V and
Figure 4b depicts the reverse gate to source leakage current with an applied gate of -4V. This measured
response showed that, for any of the two bias conditions, the gate-to-source leakage current remained
below the 3mA and 150µA specification limit up to a total ionizing dose of 500krads.
Figure 4a. Forward Gate-to-Source Leakage Current Response to Total Ionizing Dose
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Figure 4b. Reverse Gate-to-Source Leakage Current Response to Total Ionizing Dose
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7.2.2 Drain-to-Source Leakage Current (IDSS) Response
The average drain-to-source leakage current response of all the wafer samples is shown in
Figure 5. The drain-to-source leakage current was measured at a drain voltage of 200 volts. The
measured response clearly showed that, for all bias conditions, the drain-to-source leakage current did
not exceed the 150 µA specification limit up to a total ionizing dose of 500krads.
Figure 5. Drain-to-Source Breakdown Voltage Response to Total Ionizing Dose
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7.2.3 Threshold Voltage (VTH) Response
Figure 6 shows the average measured threshold voltage response of all the wafer samples. Threshold
voltage was measured at a drain current of 3 mA for all bias conditions. The measured response
showed that the threshold voltage was within the specify limits of the datasheet up to 500krad. The
No Bias condition showed a larger downward shift but stabilized post 100Krad and within specification.
Figure 6. Threshold Voltage Response to Total Ionizing Dose
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7.2.4 On-State Resistance (RDSON) Response
The average ON-state Resistance response of all the wafer samples is shown in figure 7. The ON
Resistance was measured at a gate voltage of 5 V and a drain current of 18 A. The measured response
shows an increase of the on-state resistance under a VDS bias up to 300krad and stabilizing. This
increase in rdson is expected for GaN material as it is mostly attributed to the dynamic rdson of the
HEMT devices. The majority of the wafers did not exceed the 26mΩ specification limit with a total
ionizing dose up to 500 krads.
Figure 10. On-State Resistance Response to Total Ionizing Dose
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8.0 Summary
Four sample per wafers were characterized for the FBG20N18x. No significant wafer fall out was observed
up to an accumulated ionizing dose of 500 krads using a nominal dose rate of 128 rad/sec. Measured
electrical parameters after each incremental dose did not exceed the specified electrical parameters in the
datasheet.
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Appendix A – Notes and Setup Information
A1.0 TEST SETUP CONNECTIONS
Equipment List:
Insitu bias Irradiation:
Keithley 2410
Keithley 2400
(Drain Bias Voltage)
(Gate Bias Voltage)
Electrical Measurements
STI 5300C
Custom Boards
VPTRad custom Insitu Bias Board
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Appendix B Test result tables.
Available with Datapak
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Appendix C:
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