John Patrick Holland

A three‐dimensional model for inductively coupled plasma etching reactors: Azimuthal symmetry, coil properties, and comparison to experiments

Inductively coupled plasma (ICP) etching reactors are rapidly becoming the tool of choice for low gas pressure, high plasma density etching of semiconductor materials. Due to their symmetry of excitation, these devices tend to have quite uniform etch rates across the wafer. However, side to side and azimuthal variations in these rates have been observed, and have been attributed to various asymmetries in pumping, reactor structure and coil properties. In this article, a three‐dimensional computer model for an ICP etching reactor is reported whose purposes is to investigate these asymmetries. The model system is an ICP reactor powered at 13.56 MHz having flat coils of nested annuli powering Ar/N2 and Cl2 plasmas over a 20‐cm diam wafer. For demonstration purposes, asymmetries were built into the reactor geometry which include a wafer‐load lock bay, wafer clamps, electrical feeds to the coil, and specifics of the coil design. Comparisons are made between computed and experimentally measured ion densities an...

Interactions between arrayed hollow cathodes

An array of novel hollow cathode plasma sources of 4 mm diameter and driven by up to 500 W of 13.56 MHz rf power was constructed. It was investigated using spatially resolved Langmuir probe measurements in the plasma expansion region. Initial results suggest the plasma observed downstream is the combination of a diffusion from the exit orifice of the 30 mm long cylindrical source region and a uniform plasma created in the expansion region. By measuring the ion density of the plasma plumes produced by two or more active hollow cathode sources, their mutual interaction has been inferred with the aim of determining whether a much larger array of sources could be envisioned. The effectiveness of the plasma in dissociating reactive species was tested using SF6 and measuring etch rates on unbiased silicon wafers. The results have been modelled and show that it is possible to produce a uniform spread of ±5%.

Transformer-coupled plasma technology for sub-half-micron etching

A transformer coupled plasma (TCP) source has been developed for use in the etching of polysilicon films. The TCP is a planar, inductive source which can achieve high density operation (> 1012 cm-3) over a large pressure range (1 - 100 mT). The etching characteristics of this source are described and process trends for etch rate, selectivity, and profile microloading are presented. Process requirements for polysilicon films with sub- half micron features are achieved using the TCP source by separately controlling the plasma parameters and the wafer bias.