Oxidation-induced stacking faults in silicon. II. Electrical effects in P N diodes

Abstract

The electrical characteristics of boron‐diffused P⁺N diodes containing electrically active stacking faults (EASF) are investigated. The method combines an analysis of the I‐V characteristics of the diodes with information derived from a scanning‐electron‐beam technique, the electron‐beam‐induced current (EBIC) mode. Stacking faults (SF) measuring 1–2 μm in length nucleate and develop in the near‐surface region of the silicon slice during the initial oxidation process. Subsequent to the boron diffusion, the SF are heavily decorated with impurity precipitates. Excess reverse currents are measured at room temperature over a broad range of voltage from the very‐low‐voltage region where V_R < kT/q to the high‐voltage preavalanche region where $V_R\mathrm{\gg kT/q}$ . Two distinct regions are observed in the I‐V characteristics of all diodes containing EASF's. These regions are separated by an effective threshold voltage V_THE, which is characteristic of the EASF's in the particular diode. For typical diodes with a junction depth X_j=0.4 μm, experimentally determined values for V_THE are in the range 0.1–10.0 V. When the applied reverse voltage V_R < V_THE the diode exhibits the two regions characteristic of silicon diodes at room temperature; a low‐field Ohmic conductance region when V_R < k T/q and a space‐charge‐generation region when V_R > k T/q, which is similiar to a modified form of SNS theory. In this region, the excess generation currents are found to correlate with the threshold voltage of the EASF's. When V_R > V_THE a voltage power‐law dependence is observed where I_RαVⁿ, n≈4.75±0.25. This carrier‐generation effect results from the interaction between the strain field and/or the impurity atmosphere surrounding the EASF and the depletion field of the P N junction. The composite defect introduces a local high‐density zone of g‐r centers which reduce the effective lifetime of minority charge carriers in the region of the SF. The localized g‐r zones are typically 20 μm² in cross‐sectional area with an effective lifetime of 4 – 400 ps. They are distributed nonuniformly, and are the direct source of excess I_R currents measured at room temperature.