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Laser annealing of sputtered silicon for wafer-bonding applications

R. E. HURLEY1,* , H. S. GAMBLE1, M-H. JIN1, B. M. ARMSTRONG1, M. GHITA2, R.W. McCULLOUGH2, A. A. D. T. ADIKAARI3, S. J. HENLEY3, S. R. P. SILVA3

Affiliation

  1. Northern Ireland Semiconductor Research Centre, School of Electrical & Electronic Engineering, Queen's University Belfast, Belfast, BT9 5AH, UK
  2. School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, UK
  3. Advanced Technology Institute, School of Electronics and Physical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK

Abstract

Sputtered silicon is investigated as a bonding layer for transfer of pre-processed silicon layers to various insulating substrates. Although the material appears suitable for low temperature processing, previous work has shown that gas trapped in the pores of the sputtered material is released at temperatures above 350 0C and further increases of temperature lead to destruction of any bonded interface. Pre-annealing at 1000 0C before bonding drives out gas and/or seals the surface, but for device applications where processing temperatures must be kept below about 300 0C, this technique cannot be used. In the current work, we have investigated the effect of excimer laser-annealing to heat the sputtered silicon surface to high temperature whilst minimising heating of the underlying substrate. Temperature profile simulations are presented and the results of RBS, TEM and AFM used to characterise the annealed layers. The results verify that gases are present in the sub-surface layers and suggest that while sealing of the surface is important for suppression of the out-diffusion of gases, immediate surface gas removal may also play a role. The laser-annealing technique appears to be an effective method of treating sputtered silicon, yielding a low roughness surface suitable for wafer bonding, thermal splitting and layer transfer..

Keywords

Silicon, Sputter, Laser anneal, Excimer, Wafer bonding, Layer transfer.

Submitted at: Nov. 28, 2006
Accepted at: Jan. 15, 2007

Citation

R. E. HURLEY, H. S. GAMBLE, M-H. JIN, B. M. ARMSTRONG, M. GHITA, R.W. McCULLOUGH, A. A. D. T. ADIKAARI, S. J. HENLEY, S. R. P. SILVA, Laser annealing of sputtered silicon for wafer-bonding applications, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 1, pp. 121-126 (2007)