Formation and Annihilation of Hydrogen-Related Donor States in Proton-Implanted and Subsequently Plasma-Hydrogenated N-Type Float-Zone Silicon

Formation and Annihilation of Hydrogen-Related Donor States in Proton-Implanted and Subsequently Plasma-Hydrogenated N-Type Float-Zone Silicon Reinhart Job, University of Hagen, Germany Franz-Josef Niedernostheide, Infineon Technologies AG, Germany Hans-Joachim Schulze, Infineon Technologies AG, Germany Holger Schulze, Infineon Technologies Austria AG, Austria High-Purity-Silicon X, PRIME 2008, Joint International Meeting 214th Meeting of the ECS The Electrochemical Society 2008 Fall Meeting of The Electrochemical Society of Japan Honolulu, HI, USA, Oct. 12 th 17 th, 2008

Outline of the talk Introduction Experimental details Results and discussion Summary Folie 2

Outline of the talk Introduction Experimental details Results and discussion Summary Folie 3

Introduction Light ion implantation (H +, He + ): useful tool in semiconductor technology can modify semiconductor properties can influence a wide spatial range within the semiconductor Applications of light ion implantation: H + -, He + -implantation: charge carrier lifetime control H + -implantation: formation of hydrogen related donors after post-implantation annealing procedures Attractive for high-power device technology: formation of deep n-type doped layers penetration depth at a given energy higher than for standard donors (P) proton induced doping requires moderate thermal annealing regimes Folie 4

Introduction In this presentation: investigation of two-step processes in FZ Si wafers successive H + -implantation and H-plasma treatments (temperatures during H-plasma exposures: up to 500 C) formation and annihilation of n-type doping profiles Folie 5

Outline of the talk Introduction Experimental details Results and discussion Summary Folie 6

Experimental details Substrates: - n-type float zone (FZ) silicon wafer, (100)-oriented - ρ = 30 Ωcm, phosphorous doped H + -implantation: - shallow implantation: E = 1 MeV, R p 16.5 µm* D = 1 cm -2 - deep implantation: E = 3 MeV, R p 92.8 µm* D = 1 cm -2 H-plasma: - RF generator: ν = 13.56 MHz - plasma power: P Pl = 150 W -H 2 -flux: F H2 = 50 sccm - Ar-flux*: F Ar = 50 sccm - chamber pressure: p = 7.4 10-3 mbar - process temperatures: T S = 350, 400, 450, 500 C Analyses: - two-point-probe spreading resistance measurements * projected ion ranges R p (SRIM 2008 simulations with full damage cascades) Folie 7

Outline of the talk Introduction Experimental details Results and discussion Summary Folie 8

Spreading resistance analyses H + -implantation: E = 1 MeV D = 1 cm -2 H-plasma treatment at various substrate temperatures: - 350 C - 400 C - 450 C - 500 C t = 15 min Spreading Resistance (Ohm) 10 5 10 5 10 5 H + -Implantation & 15 min H-Plasma 500 C 450 C 400 C 350 C 10 5 Folie 9 0 5 20 25

Spreading resistance analyses Faculty of Mathematics and Computer Science H + -Implantation & 15 min H-Plasma 500 C Transformation of SR profiles into doping concentration profiles Spreading Resistance (Ohm) 10 5 10 5 10 5 10 5 H + -Implantation & 15 min H-Plasma 0 5 20 25 500 C 450 C 400 C 350 C 450 C 400 C 350 C 0 5 20 25 Folie 10

Spreading resistance analyses Faculty of Mathematics and Computer Science H + -Implantation & 15 min H-Plasma 500 C Region deeper than R p : initial n-type doping concentration 450 C of untreated FZ Si material Region close to R p : surplus n-type doping n-type doping concentration 400 C enhanced by one order of magnitude 10 Region towards R p (up to 15 µm 14 depth): 350 C surplus n-type doping profile follows implantation damage profile vacancy concentration profile 0 5 20 25 Folie 11

Spreading resistance analyses Faculty of Mathematics and Computer Science H + -Implantation & 15 min H-Plasma 500 C Region close to the surface: n-type doping is a bit enhanced 450 C (factor of 2) for H-plasma treatment at 350 C and 400 C Region towards the surface: n-type doping towards the surface 400 C more stronger enhanced at 450 C and 500 C 10 Region close to the surface: 14 doping concentration reduced 350 C (H-plasma at 450 C) doping concentration below initial doping n-type level (H-plasma at 500 C) 0 5 20 25 Folie 14

Spreading resistance analyses H + -Implantation & 15 min H-Plasma 500 C Conclusions (I): Region near R p : hydrogen-related shallow donor formation occurs vacancies play a significant role excessive donor concentration vacancy-hydrogen-complexes 450 C 400 C 350 C 0 5 20 25 Folie 17

Spreading resistance analyses H + -Implantation & 15 min H-Plasma 500 C Conclusions (II): Region towards the surface: vacancies diffuse towards the surface during plasma exposure at elevated temperatures enhanced vacancy concentration toward the surface vacancy-hydrogen-complexes excessive donor concentration 450 C 400 C 350 C 0 5 20 25 Folie 18

Spreading resistance analyses H + -Implantation & 15 min H-Plasma 500 C Conclusions (III): Region close to the surface (I): formation of acceptor-like defect complexes acceptor-like defect complexes are passivated by hydrogen at lower temperatures at higher temperatures acceptorlike defect complexes become electrically active again compensation of n-type doping 450 C 400 C 350 C 0 5 20 25 Folie 19

Spreading resistance analyses Faculty of Mathematics and Computer Science H + -Implantation & 60 min H-Plasma 500 C H + -implantation: E = 1 MeV D = 1 cm -2 H-plasma treatment at various substrate temperatures: - 350 C - 400 C - 450 C - 500 C t = 60 min 450 C 400 C 350 C Folie 20 0 5 20 25

Spreading resistance analyses Faculty of Mathematics and Computer Science H + -Implantation & 60 min H-Plasma 500 C Donor states in the subsurface region down to R p disappeared initial homogeneous doping concentration is re-established However, close to the surface n-type doping compensated for by acceptor-like defects 450 C 400 C 350 C Folie 21 0 5 20 25

Spreading resistance analyses H + -Implantation & 60 min H-Plasma 500 C Donor states in the subsurface region down to R p disappeared initial homogeneous doping concentration is re-established However, close to the surface n-type doping compensated for by acceptor-like defects 450 C 400 C 350 C Folie 22 0 5 20 25

Spreading resistance analyses No H + -implantation Only 60 min H-plasma treatment at 400 C substrate temperature No formation of doping profiles! Similar results for H-plasma exposure at other substrate temperatures up to 500 C Doping Concentration (cm -3 ) 60 min H-Plasma (400 C) (no implantation) 0 5 20 25 Folie 23

Spreading resistance analyses H + -Implantation & 60 min H-Plasma 500 C Conclusion: strong injection of hydrogen during long-term plasma treatment transformation of vacancyand hydrogen-related donor states into electrically inactive defects, e. g. V-H 4 acceptor-like defects near the surface hydrogenated vacancy or multi-vacancy complexes, e. g. V 2 -H 2 (?) 450 C 400 C 350 C Folie 25 0 5 20 25

Spreading resistance analyses 3 MeV H + -Implantation & H-Plasma (400 C) 10 16 15 min H-Plasma Deep H + -implantation: E = 3 MeV D = 1 cm -2 H-plasma treatment at 400 C substrate temperature for various duration: - t = 15 min (above) - t = 60 min (below) 10 12 10 16 60 min H-Plasma 10 12 0 20 40 60 80 100 Folie 26

Spreading resistance analyses 3 MeV H + -Implantation & H-Plasma (400 C) 10 16 15 min H-Plasma Region close to R p : surplus n-type doping caused by vacancy-hydrogen-complexes (15 min H-plasma exposure) Region at 30 µm 85 µm depth: strong reduction of n-type carrier concentration implantation damage (15 min H-plasma exposure) 10 12 10 16 60 min H-Plasma 10 12 0 20 40 60 80 100 Folie 27

Spreading resistance analyses Region down to 30 µm depth: indiffusing hydrogen passivates implantation damage toward the surface: initial doping level recovered (15 min H-plasma exposure) surplus n-type doping profile follows the vacancy concentration profile vacancy-hydrogen-defects (15 min H-plasma exposure) at the surface weak reduction of the n-type doping acceptor-like defect states (15 min H-plasma exposure) Faculty of Mathematics and Computer Science 3 MeV H + -Implantation & H-Plasma (400 C) 10 16 15 min H-Plasma 10 12 10 16 10 12 0 20 40 60 80 100 60 min H-Plasma Folie 29

Spreading resistance analyses Region close to R p : surplus n-type doping caused by vacancy-hydrogen-complexes (60 min H-plasma exposure) Subsurface region down to R p : indiffusing hydrogen passivates implantation damage (V-H 4 ) initial n-type doping level (60 min H-plasma exposure) surplus n-type doping follows vacancy concentration profile Close to the surface: acceptor-like defect states compensate for n-type doping (60 min H-plasma exposure) 3 MeV H + -Implantation & H-Plasma (400 C) 10 16 15 min H-Plasma 10 12 10 16 10 12 60 min H-Plasma 0 20 40 60 80 100 Folie 32

Spreading resistance analyses Region close to R p : surplus n-type doping caused by vacancy-hydrogen-complexes (60 min H-plasma exposure) Subsurface region down to R p : indiffusing hydrogen passivates implantation damage (V-H 4 ) initial n-type doping level surplus n-type doping follows vacancy concentration profile (60 min H-plasma exposure) Close to the surface: acceptor-like defect states compensate for n-type doping (60 min H-plasma exposure) 3 MeV H + -Implantation & H-Plasma (400 C) 10 16 15 min H-Plasma 10 12 10 16 10 12 60 min H-Plasma 0 20 40 60 80 100 Folie 33

Outline of the talk Introduction Light ion implantation into silicon Plasma hydrogenation of silicon Hydrogen related donor states in silicon Experimental details Sample preparation Experimental analyses Results and discussion Formation of doping profiles by H + -implantation and subsequent plasma hydrogenation at elevated temperatures Mechanisms of donor states formation Summary Folie 35

Summary Influence of plasma hydrogenation on H + -implanted FZ Si was studied Analysis as done be means of spreading resistance measurements It was observed that surplus n-type doping occurs near R p (one order of magnitude above the initial doping level) surplus n-type doping occurs also towards the wafer surface for 15 min H-plasma exposure (less strong) surface acts as a getter center for vacancies hydrogenated vacancy defect complexes are responsible for surplus n-type doping in the subsurface layer down to R p near the surface (down to a depth of 2 µm) acceptor-like states were created, which compensate for the n-type doping acceptor-like defect states can be attributed to (multi-) vacancyhydrogen complexes Folie 36

Acknowledgements The technical support of Mrs. Renate Bommersbach (Infineon Technologies AG, Munich) & Mr. Josef Niedermeyr (Infineon Technologies AG, Munich) is gratefully acknowledged. Folie 37