Excimer laser induced heating, melting, and mass diffusion in crystal silicon in nanosecond and nanometer scale

X. Zhang, J. R. Ho, Constantine P. Grigoropoulos

Research output: Contribution to journalConference articlepeer-review


Heat and mass transfer at the nanosecond time scale and the nanometer length scale in pulsed laser fabrication of ultra-shallow p+-junction is studied in this work. A technique is developed to fabricate the ultra-shallow p+-junctions with pulsed laser doping of crystalline silicon with a solid spin-on-glass (SOG) dopant, through the nanosecond pulsed laser heating, melting, and boron mass diffusion in the 100 nm thin silicon layer close to the surface. High boron concentration of 1020 atoms/cc and the 'box-like' junction profile are achieved. The key mechanism determining the 'box-like' junction shape is found to be the melt-solid interface limited diffusion. The ultra-shallow p+-junctions with the depth from 30 nm to 400 nm are successfully made by the excimer laser. The optimal laser fluence condition for SOG doping is found about 0.6 - 0.8 J/cm2 by studying the ultra-shallow p+-junction boron profiles measured by the secondary ion mass spectroscopy versus the laser fluence and the pulse number. The 1D numerical analysis agrees reasonably with the experiment, within the available physical picture. Possible mechanisms such as boron diffusivity dependence on the dopant concentration in the molten silicon are proposed.

Original languageEnglish
Pages (from-to)232-241
Number of pages10
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1996
EventLasers as Tools for Manufacturing of Durable Goods and Microelectronics - San Jose, CA, United States
Duration: 29 Jan 199629 Jan 1996


  • Boron diffusion
  • Excimer laser
  • Ultrashallow junction


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