Plasma Assisted Oxidation of Si at Temperatures below 800°C

Abstract

A system for plasma assisted oxidation of Si at temperatures below 800°C is described. Oxides grown in this system have an unusual thickness versus time relationship. The first 110 nm of oxide exhibit a t 1 1 2 dependence. Any additional growth shows a t 1 13 dependence. Pressure, oxygen concentration, and rf power are all important parameters in determining the growth rate and uniformity of the oxide layers. Breakdown measurements on these oxide layers show that post oxidation annealing is necessary if these oxides are to compete with thermal oxides. The type of annealing is very important in determining the breakdown voltage. The results of various annealing procedures are described. The effects of heating the wafers independent of the heat generated by the plasma, and the frequency dependence of the growth are discussed.

Species Charge and Oxidation Mechanism in the “Cathodic” Plasma Oxidation of Silicon

“…In one case, the sample is externally biased positively during oxidation and the process is termed "plasma anodization," while in the second case the sample is at floating potential and the process is termed "plasma oxidation" (1)(2)(3)(4)(5). In a third kind of oxidation of silicon in a plasma, the silicon is at the plasma floating potential, but because of confinement of the plasma, oxidation occurs on the silicon surface facing away from the plasma (6)(7)(8)(9). It has been found by Ray and Reisman (10) that this oxidation process is field-assisted via the floating potential established in the wafer.…”

“…In the present study, two aspects of the third type of plasma oxidation in an RF system based on earlier designs (6)(7)(8)(9) are presented. First, the sign of the charge of the species present in the gas phase responsible for oxide growth has been determined.…”