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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. Freebird Semiconductor Confidential Page 1 of 17 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 Freebird Semiconductor Confidential Page 2 of 17 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) Freebird Semiconductor Confidential Page 3 of 17 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 Freebird Semiconductor Confidential Freebird Semiconductor Test Plan Freebird Datasheet Rev Q VPTRad operating instructions Page 4 of 17 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. Freebird Semiconductor Confidential Page 5 of 17 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 Freebird Semiconductor Confidential Page 6 of 17 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. Freebird Semiconductor Confidential Page 7 of 17 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 Freebird Semiconductor Confidential Page 8 of 17 Figure 4b. Reverse Gate-to-Source Leakage Current Response to Total Ionizing Dose Freebird Semiconductor Confidential Page 9 of 17 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 Freebird Semiconductor Confidential Page 10 of 17 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 Freebird Semiconductor Confidential Page 11 of 17 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 Freebird Semiconductor Confidential Page 12 of 17 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. Freebird Semiconductor Confidential Page 13 of 17 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 Freebird Semiconductor Confidential Page 14 of 17 Appendix B Test result tables. Available with Datapak Freebird Semiconductor Confidential Page 15 of 17 Appendix C: Freebird Semiconductor Confidential Page 16 of 17 Freebird Semiconductor Confidential Page 17 of 17