TCAD Simulation of Total Ionization Dose Response on DSOI nmosfet Huang Yang Institute of Microelectronics of Chinese Academy of Sciences Co Authors: Li Binhong (IMECAS), Liu Bing (BISLMV), Shen Chen (Cogenda), Song Yanfu (Cogenda), Li Bo (IMECAS), Han Zhengsheng (IMECAS), Luo Jiajun (IMECAS) @IMECAS 1
Contents I. Radiation Environment II. SOI vs. DSOI III. TCAD model for DSOI IV. TID response of DSOI nmosfet @IMECAS 2
Radiation Environment Radiation Effect: Total Ionization Dose- TID trapped holes in the oxide and interface traps at the Silicon-oxide interface will affect the device performance parameters Single Event Upset-SEU the state change caused by one single ionizing particle striking the sensitive node of a device @IMECAS 3
SOI vs DSOI SOI Advantages: ü good SEU suppression because of the buried oxide isolation(box) ST I Vsource FD-SOI Vsub Vgate BOX Vdrain ST I Gate ox + + X X X Body X X X X + + + + + BOX positive oxide trapped charges interface traps STI Vsource FD-SOI Vsub Vgate BOX Vdrain Sub STI Disadvantages: ü the TID effect is even worse in FDSOI because of the introduction of the buried oxide layer(box) and the coupling effect between the front and back gate @IMECAS 4
SOI vs DSOI DSOI has an additional Si layer (SOI2) STI N+ P N+ BOX1 SOI2 BOX2 STI P+ N P+ BOX1 SOI2 BOX2 STI Sub With SOI2 (Advantages): compensation of TID effect VSOI2 controls the positive trapped charges in the oxide compensate NMOS and PMOS seperately the compensation voltages needed for NMOS and PMOS are different reduction of back-gate effect the back-gate effect can be suppressed with SOI2 biased at a constant voltage @IMECAS 5
SOI vs DSOI TID Experimental Results of DSOI(0.2μm FD NMOS) ü Irradiation state: OFF ü Irradiation dose rate: 50rad(Si)/s ü Irradiation dose: high up to 5Mrad(Si), by 60 Co γ-ray 10-4 10-4 10-6 Vth V SOI2 =0V 10-6 V SOI2 =-7V ID (A) 10-8 10-10 10-12 Ioff 0Krad(Si) 100Krad(Si) 300Krad(Si) 500Krad(Si) 1Mrad(Si) 2Mrad(Si) 3Mrad(Si) 4Mrad(Si) 5Mrad(Si) ID(A) 10-8 10-10 10-12 0 Krad(Si) 500 Krad(Si) 1 Mrad(Si) 2 Mrad(Si) 3 Mrad(Si) 4 Mrad(Si) 5 Mrad(Si) -0.5 0.0 0.5 1.0 1.5 2.0 VG (V) IV shift negatively due to radiation induced holes. By applying V SOI2 properly, IV curves can be recovered. -0.5 0.0 0.5 1.0 1.5 2.0 VG(V) @IMECAS 6
TCAD model for DSOI Software used: Cogenda TCAD device modeling tool(focus on radiation effect simulation) Main characteristics of DSOI(NMOS) FDSOI technology; floating body device üsoi1 thickness: 46.7nm übox1 thickness:158.7nm üsoi2 thickness: 84nm übox2 thickness:156nm ücore gate oxide thickness: 5.6nm üsubstrate: p type, resistivity >1000 ohm-cm üsoi2: n type, resistivity ~10ohm-cm V S V D V SOI2 üchannel stop implant: 15nm to 46.7 nm below SOI1 top surface with peak conc. 5e15cm^-3. üvt implant: 0~12nm below SOI1 top surface with peak conc. 1.6e18cm^-3. üldd implant: peak conc. 9e18cm^-3 at SOI1 top surface. Offset to Poly edge is zero. üs/d implant: 0~15nm below SOI1 top surface with peak conc. 2.0e20cm^-3. Offset spacer distance is 100nm. V G SOI1 SOI2 @IMECAS 7
TCAD model for DSOI Physical models used for TCAD modeling Physical Model Mobility model Impact ionization model Tunneling model DSOI Lucent High field saturation model Selberherr BBT model low field mobility model ü Lucent High Field Mobility Model This model incorporates Philips Unified Mobility model and the Lombardi Surface Mobility model, as well as accounting for Caughey-Thomas model. mobility in the (MOS) inversion layer high field velocity saturation suitable for MOS simulation! Philips Lombardi @IMECAS 8
TCAD model for DSOI ü Selberherr Impact ionization model default avalanche model The generation rate of electron-hole pairs due to the carrier Impact Ionization (II) is generally modeled as: ionization coefficients Selberherr ü Band-to-band tunneling model Many studies have shown that the combined impact of BBT and positive trapped charge in the buried oxide is a significant factor in the radiation response of floating body FDSOI NMOS. @IMECAS 9
TCAD model for DSOI TCAD simulation results vs. experimental results DSOI NMOS (W/L=8/1) Solid lines: simulated curves Dotted lines: experimental curves Kink effect because of floating body Vg=1.8V Vg=1.5V Vd=0.95V Vg=1.2V Vd=0.1V Vg=0.6V good correspondence! @IMECAS 10
TCAD model for DSOI TCAD simulation results of DSOI NMOS Suppression of back-gate effect V SOI2 =0V, IDVG curves with different Sub voltages. V S V G V D V SOI2 BOX1 V SOI2 =0V BOX2 SOI2 works as a good shield! V Sub =5V V Sub @IMECAS 11
TCAD model for DSOI TCAD simulation results of DSOI NMOS I D V G curves with different V SOI2 front VG=-0.6V back Vsoi2=15V, E V and E C TCAD Results ID 5.0x10-5 4.5x10-5 4.0x10-5 3.5x10-5 3.0x10-5 2.5x10-5 2.0x10-5 1.5x10-5 1.0x10-5 5.0x10-6 Vsoi2=-15V Vsoi2=-10V Vsoi2=-5V Vsoi2=0V Vsoi2=5V Vsoi2=10V Vsoi2=15V Vsoi2=15V Experimental Results Vsoi2=-15V 0.0-1.0-0.5 0.0 0.5 VG 1.0 1.5 2.0 ID/A Vsoi2=15V VG=1V VG=0.2V VG=-0.6V VG=0.2V Vsoi2=-15V VG=1V VG/V @IMECAS 12
TID response of DSOI NMOS TID simulation method of Cogenda Difficult to implement Method proposed by N.L. Rowsey (2012) and I.S. Esqueda (2011) energetic particle transport Easy to implement Monte Carlo particle simulation @IMECAS 13
TID response of DSOI NMOS Bias configurations during irradiation and measurement Bias applied during irradiation V G V S V D V SOI2 V sub OFF 0V 0V 1.8V 0V 0V Bias applied during measurement Id-Vg curve V G V S V D V SOI2 V sub V SOI2 =0V V SOI2 =-5V Sweep 0V to 1.98V Sweep 0V to 1.98V 0V 0.1V 0V 0V 0V 0.1V -5V 0V DSOI nmosfets are irradiated up to 1Mrad(Si) by 60 Co γ-ray at a dose rate of 50rad(Si)/s. Irradiation Dose:0rad(Si) 100Krad(Si) 300Krad(Si) 500Krad(Si) 1Mrad(Si) @IMECAS 14
TID response of DSOI NMOS TCAD simulation results vs. experimental results DSOI NMOS (W/L=8/1) Irradiation State: OFF V SOI2 =0V Irradiation Dose: 0rad(Si) 100Krad(Si) 300Krad(Si) 500Krad(Si) 1Mrad(Si) Dose/krad(Si) Threshold (Vth): Vg@Id=(0.1μA)x(W/L) Vth shift/v ~0.6µs ~0.6µs ~1.8V @IMECAS 15
TID response of DSOI NMOS Simulated trapped holes in the BOX1 layer Irradiation Dose: 1Mrad(Si) front interface Source LDD Channel LDD Drain BOX1 V S =0V V G =0V V D =1.8V V SOI2 =0V cutline cutline V Sub =0V back interface @IMECAS 16
TID response of DSOI NMOS Compensation of TID effect with VSOI2 Different V SOI2 during measurement 5.0x10-4 4.5x10-4 4.0x10-4 3.5x10-4 pre Vsoi2=0V 1Mrad(Si) Vsoi2=0V 1Mrad(Si) Vsoi2=-5 Experimental Results Irradiation Bias: OFF V SOI2 =0V TCAD Results ID/A 3.0x10-4 2.5x10-4 2.0x10-4 1.5x10-4 1.0x10-4 Shift back after Vsoi2=-5V Shift negatively after 1Mrad(Si) 5.0x10-5 Irradiation Dose: 1Mrad(Si) Measurement Bias: IDVG curve with V SOI2 =0V and V SOI2 =-5V respectively V D =0.1V 0.0-1.0-0.5 0.0 0.5 1.0 1.5 2.0 VG/V V SOI2 =0V pre V SOI2 =-5V I D V G curve is recovered by V SOI2 after 1Mrad(Si)! @IMECAS 17
TID response of DSOI NMOS Compensation of TID effect with VSOI2 Different V SOI2 during measurement Source Channel Drain Electrical Field VSOI2=0V cutline BOX1 top Electrical Field VSOI2=-5V cutline BOX1 top @IMECAS 18
Summary Background Advantages of DSOI compared with SOI. Successful TID compensation. TCAD model for DSOI Physical model. Good correspondence with experimental results. TCAD simulation results and explanation TCAD simulation before and after irradiation. Impact of V SOI2 before and after irradiation. @IMECAS 19
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