Thermal Stability Limits of Thin TiSi2: Effect on Submicron Line Resistance and Shallow Junction Leakage

F. A. Baiocchi, S. Nakahara, N. T. Ha, G. E. Georgiou, H. Abiko

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

TiSi2, the silicide most commonly used for a low resistivity self-aligned salicide process, must become thinner as the junction depth and poly-Si gate height decrease so as not to affect junction leakage and gate work function. The thermal stability of the thinner TiSi2 during the back-end thermal process cycles, is an important concern. We report on the thermal stability of 300 to 700 A thin TiSi2 on As, P, or BF2 doped poly-Si to annealing at 750 to 850°C for 10 to 30 min determined by the increase in the resistance of long 0.3 to 1.5 μm wide poly-Si meander lines. The increase in line resistance is correlated with changes in the TiSi2 microstructure. Poly-Si lines ≤0.5 μm wide with 500 A TiSi2 increase their resistance after annealing at 750°C, 30 min. 500 A TiSi2 is stable on 0.5 μm wide poly-Si lines after annealing at 800°C, 15 min. Silicide instability increases the reverse bias diode leakage measured for —1500 A shallow n+(As + P)/p-well junctions whereas it does not increase diode leakage for —2000 A shallow p+(BF2)/n-well junctions. Increasing TiSi2 thickness improves thermal stability. Dopant type and concentration affect the TiSi2 thermal stability through their effect on the TiSi2 thickness (thinner on As doped Si) sintered with a particular Ti sintering process. We use Rutherford backscattering spectroscopy, transmission electron microscopy, and scanning electron microscopy to correlate the increase in effective sheet resistance of submicron wide poly-Si lines and the increase in ultra shallow junction leakage with an increase in roughness for 700 A thick TiSi2 and agglomeration for ≤500 A thin TiSi2.

Original languageEnglish (US)
Pages (from-to)1351-1356
Number of pages6
JournalJournal of the Electrochemical Society
Volume141
Issue number5
DOIs
StatePublished - 1994
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films
  • Electrochemistry
  • Materials Chemistry

Keywords

  • crystal microstructure
  • electric properties leakage currents
  • high-temperature effects integrated circuit technology
  • p-n junctions
  • thin films

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