Analysis of electrical properties of buried nitride formed by high dose N + implantation

Abstract

N-type 〈100〉 crystalline silicon wafers were implanted by N + at 170 keV with doses ranging from (0.5–2.2) × 10 18/cm 2. All these implanted wafers were annealed at 1200°C for 2 h in dry-N 2 ambient. Infrared (IR) transmission spectroscopic measurements showed that a buried α-Si 3N 4 layer was formed for those wafers in which the dose of implanted N + was higher than 1 × 10 18/cm 2. B +, Si + and Ar + were implanted into these wafers to amorphize the buried α-Si 3N 4 in order to improve its insulating properties. IR measurements indicated that Si + and Ar + implantations can amorphize the buried α-Si 3N 4. Though the deposited energy density of B + was higher than that of Si + and Ar +, buried α-Si 3N 4 cannot be amorphized by B + implantation. These wafers were annealed at 900 and 1150°C for 45 min. Amorphized nitride recrystallized to form α-Si 3N 4 after annealing at 1150°C. Ohmic contacts were fabricated at front and back sides for all wafers by As + implantation and aluminium evaporation. I–V characteristics were measured and the effect of B +, Si +, and Ar + implantations on insulating properties of the buried insulator was studied for all samples.