Digital Etch for InGaSb p-Channel FinFETs with 10-nm Fin Width - PowerPoint PPT Presentation

Digital Etch for InGaSb p-Channel FinFETs with 10-nm Fin Width Wenjie Lu and Jesús A. del Alamo Massachusetts Institute of Technology CSW, May 30, 2018 Sponsors: KIST, SRC, DTRA, Lam Research Acknowledgment: KIST, NRL, Sandia, MTL, SEBL

Outline • Motivation • InGaSb Digital Etch • InGaSb p‐channel FinFET • Off‐state Current • Conclusions 2

Reported Mobility in InGaSb High electron mobility 3 del Alamo, Nature 2011

Reported Mobility in InGaSb InGaSb CMOS High hole mobility & strain effect 4 del Alamo, Nature 2011

Digital Etch Ramesh, IEDM 2017 Zhao, IEDM 2017 Kilpi, IEDM 2017 Vardi, IEDM 2017 Digital Etch: standard in InGaAs VNW/FinFET process 5

Digital Etch in InGaSb Fin etch Oxidation Oxide Etch O 2 plasma H 2 SO 4 :H 2 O O 3 HCL:H 2 O H 2 O 2 6

Key: Water Damages Antimonides Dip in DI water for 2 min  Must remove water 7 Lu, EDL 2017

Alcohol-based Treatment After RIE 10% HCl:IPA 2 min No sidewall damage Lu, EDL 2017 8

Digital Etch in InGaSb Fin etch Oxidation Oxide Etch O 2 plasma HCl:IPA O 3 H 2 O 2 9

O 2 Plasma + HCl:IPA 3 cycles 10 cycles (r = 1 nm/cycle) (r = 0.2 nm/cycle) After RIE HSQ 10 nm InAs InGaSb 25 nm 19 nm 16 nm AlGaSb r (III-Sb) ↓ after 3 cycles r (III-As) > r (III-Sb) 10

Oxidation of GaSb • In air: ‒Ga 2 O 3 , Sb 2 O 3 • In strong oxidation agents: ‒Ga 2 O 3 , Sb 2 O 3 ‒Sb 2 O 5 (insoluble in common aqueous acid/alkali) Must avoid formation of Sb 2 O 5 11 Liu, JVST B. 2002

Experiments of InGaSb DE RT O 2 Best results: RT O 2 atmosphere + HCl:IPA 12

RT O 2 + HCl:IPA 2 cycles 4 cycles r = 2 nm/cycle r = 2 nm/cycle No DE HSQ InAs 25 nm 17 nm 9 nm InGaSb AlGaSb • Stable etching rate • Identical etch rate for InAs and antimonides 13

InGaSb p-Channel FinFETs Fin InAs/InAsSb InAlSb Heterostructure grown by KIST 14

InGaSb p-Channel FinFETs G3 FinFET • 3 Generations ‒G1: No sidewall treatment ‒G2: HCl:IPA treatment ‒G3: HCl:IPA + digital etch Minimum W f = 10 nm Lu, IEDM 2017 15

Minimum-size Devices G1 G2 G3 W f = 30 nm, L g = 100 nm W f = 18 nm, L g = 20 nm W f = 10 nm, L g = 20 nm 200 200 V GS = 0.5 V to -1 V 200 V GS = 1 V to -1 V V GS = 1 V to -1 V 150 150 150 -I D (  A/  m) -I D (  A/  m) -I D (  A/  m) 100 100 100 50 50 50 0 0 0 -0.8 -0.4 0.0 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 V DS (V) V DS (V) V DS (V) Lu, IEDM 2015 Lu, CSW 2017 Lu, IEDM 2017 16

Off-state Current • G2: W f = 20 nm, L g = 100 nm 2 fins Same total mesa width 200 150 W m -I D (  A) 1 fin 100 50 0 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 V DS (V) Presence of leakage paths outside the fins 17

Off-state Current • G2: V gt = 0.6 V, V ds = ‐ 50 mV HSQ 10 8 InGaSb W m -I D  L G /W m (nA) 6 ~W f 4 AlGaSb 2 0 0 50 100 W f (nm) 18

Off-state Current • G3: W f = 20 nm, L g = 1 µm, V DS = ‐50 mV 2 10 0 DE cycle 1 10 -I D (  A/  m) 0 10 1 DE cycle -1 10 -2 10 -1.0 -0.5 0.0 0.5 1.0 V GS (V) 1 DE cycle significantly improves off current More improvement needed 19

Benchmark Gen 3 800 1000 Gen 3 DE 600 g m /W f (  S/  m) g m /W f (  S/  m) Gen 2 400 100 HCl:IPA FinFETs Gen 1 200 Gen 2 Planar Gen 1 ddd 10 0 0 500 1000 1500 2000 2500 Planar 0 50 100 150 200 S lin (mV/dec) W f (nm) ddd g m /W f = 704 μS/μm at W f = 10 nm 20

Conclusion • Digital Etch ‒ Alcohol‐based HCl treatment ‒ O 2 for oxidation at RT ‒ Compatible to InGaSb and InAs • InGaSb p‐Channel FinFETs ‒ Minimum W f = 10 nm, L g = 20 nm ‒ HCl:IPA and DE improves I off ‒ Record device performance 21

Off-state Current • G3: W f = 20 nm, L g = 1 µm, V DS = ‐50 mV 2 10 0 DE cycle 1 10 I D (  A/  m ) 4 DE cycle 0 10 1 DE cycle -1 10 -2 10 -1.0 -0.5 0.0 0.5 1.0 V GS (V) 22

Off-state Current 3 DE cycle 10 min air exposure 2 10 0 DE cycle 1 10 I D (  A/  m ) 4 DE cycle 0 10 1 DE cycle -1 10 -2 10 -1.0 -0.5 0.0 0.5 1.0 V GS (V) • Buffer is damaged after multiple DE cycles • Al 0.93 Ga 0.07 Sb is too reactive 23

Off-state Current • G2: V gt = 0.6 V, V ds = ‐ 50 mV G2 HSQ HCl:IPA 1 min 0.2 InGaSb -I D  L g (  A  m) 0.1 AlGaSb 0.0 0 20 40 60 80 100 W f (nm) HCl:IPA  Super-linear dependency on W f 24

Off-state Current • G3: V gt = 0.6 V, V ds = ‐ 50 mV G2 HCl:IPA 1 min G3 0.2 HCl:IPA 1 min -I D  L g (  A  m) + 1 DE 0.1 0.0 0 20 40 60 80 100 W f (nm) + 1 DE  More linear dependency on W f 25