Michael Barnes

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...

Studies of the low-pressure inductively-coupled plasma etching for a larger area wafer using plasma modeling and Langmuir probe

As semiconductor wafer size increases (from the current 200 to 300 mm), scaling up a process chamber to meet the same or even more stringent requirements becomes difficult due to complexity of the nonequilibrium plasmas. Designing 300 mm etching reactors can be costly and time consuming for developers without an understanding of fundamental physical and chemical processes. To expedite development and reduce cost, plasma modeling and plasma diagnostics are used to gain insight and assist the 300 mm etching reactor development. In this article, it is demonstrated that plasma modeling and Langmuir probe measurement can be used to study various plasma properties including the effects of inductively coupled power, chamber pressure, aspect ratio, and coil configuration, for a planar inductively-coupled plasma. The results from these studies are used to optimize an inductively-coupled plasma R&D chamber capable of etching 300 mm wafers.