Replacing Boron with Gallium Maureen K Petterson Applied

Replacing Boron with Gallium Maureen K. Petterson Applied Materials N. Y. , USA Hartmut F. -W. Sadrozinski SCIPP, UC Santa Cruz, CA 95064 1

LGAD: Stack Doping p bulk: FZ Np=1 e 12 cm^-3 n cathode: Phosphorus Nn~1 e 19 cm^-3 Surface passivation bi-layer (from silicon surface to top: 800 nm thermal oxide + 40 nm deposited alumina). Phosphorous implantation: First: Energy: 70 Ke. V. Dose: 1 E 15 atm/cm 2; Second: Energy: 150 Ke. V. Dose: 5 E 14 atm/cm 2 Post P implant anneal: 1000 Celsius degrees for 44 min A few wafers had Boron replaced by Gallium C-V on Ga implanted structures reveal the absence of the gain-layer Maureen Petterson performed simulations with SRIM 2013 using two implantation energies (including 400 nm thermal oxide) Original Gallium implantation: Alternative Gallium Implantation: Energy: 60 Ke. V. Dose: 1. 4 E 13 atm/cm 2 Energy: 1500 Ke. V. Dose: 1. 4 E 13 atm/cm 2 2

60 ke. V Ga into Si: Cascades A few selected events shown SRIM 2013: Stopping Ranges of Ions in Matter Damage Calculation: Full Cascades 3

Ga into Si/Si. O 2: Ion Distribution 60 ke. V Ga into Si Mean ≈ 0. 05µm Max ≈ 0. 1µm 60 ke. V Ga into Si. O 2 Mean ≈ 0. 04µm Max ≈ 0. 08µm 1500 ke. V Ga into Si Mean ≈ 1µm Max ≈ 1. 4µm 4

Ga into LGAD: Ion Distribution Ion Penetration: 60 ke. V Ga into Si. O 2 Max Depth ≈ 0. 1µm i. e. all end up within Si. O 2 Ion Penetration: 1500 ke. V Ga into Si. O 2/Si Max Depth ≈ 2 µm i. e. Large fraction ends up within Si 5

Annealing of B/Ga in Si/Si. O 2 Diffusion Constant D for Si/Si. O 2 1000 C D(1000 o. C) [cm^2/sec] Si. O 2 Si B: < 6 e-18 2 e-14 Ga: < 6 e-18 3 e-14 In Si, 1000 o. C: D(B, Si)) ≈ D(Ga, Si) Si vs. Si. O 2: D(B, Si. O 2) < 3*10 -4 D(B, Si) D(Ga, Si. O 2) < 2*10 -4 D(Ga, Si) Ions implanted in Si. O 2 can’t anneal out! -> Ga implantation needs to be made at higher Energy (~1500 ke. V) Si. O 2 data from H. G. Francois-Saint-Cyr et al. JOURNAL OF APPLIED PHYSICS, VOLUME 94, No 12 15 DEC. 2003 -> Doping Concentration Test structures need to include the entire stack (Si. O 2 & Si)

Specific Test Structure. SRP, SIMS, XPS 2. 75 mm 3. 65 mm o+ o o o L 1 P-Stop, C-Stop Well OL 2 x. P-Well (P Multiplication) ide L 3 JTE +A L 4 N-Well luover L 4 + L 2 N-Well mi P-Well L 4 + L 3 N-Well overn. JTE a The bevel angle determins the depth d of probing: =1 deg d= 3 mm*0. 017 = 50 µm =4 deg d= 200 µm N-Well Field Plate