High dose p+ buried layers for reduced diode leakage

We report on the effectiveness of moderate to high dose (1×10¹⁴ cm^-2-1×10¹⁵ cm^-2) blanket boron implants (1.8 MeV) at reducing diode leakage and gettering surface oxygen. Diode leakage correlates strongly with the near surface defect density resulting from the buried layer implant. This leakage decreases by orders of magnitude as the buried layer dose increases from 3×10¹⁴ cm^-2 to 1×10¹⁵ cm^-2. The reduction depends on the post-buried layer implant annealing conditions at moderate doses. For a 3×10¹⁴ cm^-2 dose, a two-step annealing process (RTA followed by furnace annealing) produced lower leakage than either furnace or RTA annealing alone. TEM micrographs indicate that the best leakage is obtained for minimum widths of the damage band at the projected range of the buried layer implant. High dose buried layers also getter oxygen effectively. Oxygen levels from the surface down to 2 μm are reduced below 2×10¹⁷ cm^-3 by buried layer implants using a dose of 3×10¹⁴ cm^-2 and a 1000°C furnace anneal, increasing the buried layer dose above this level has little effect on oxygen SIMS profiles, but GOI performance continues to improve