Comparison of high-density electron cyclotron resonance and inductively coupled plasma sources for etching of electronic materials: New plasma etch regimes for electronic materials

The requirement for sub-micron semiconductor device fabrication has brought unprecedented demands for process optimization and control which, in turn, have led to improved plasma reactors for the dry etching, passivation and deposition of thin films.;The plasma etching processing investigated here is based on a comparison of older techniques, such as conventional reactive ion (RIE) etching and reactive ion beam etching (WBE) with newer high ion density processes involving electron cyclotron resonance (ECR) and inductively coupled plasma (ICP) sources. Especially, strong attention has been paid to the performance of the high ion current ECR and ICP sources. These sources will compete each other for etching of next generation devices. However, thus far, there have been few data showing a direct comparison of the performance of these two plasma sources.;The work has focused mainly on GaAs and InP due to their applications in electronic and photonic devices. Especially, advanced plasma etching processes for InP and its related compounds are necessary because of low etch rates for these compounds with conventional techniques. Therefore, one definite goal of this research is to find new etch regimes to obtain smooth, high-rate etching for InP and related materials, and to establish the etch mechanism.;Measurements of etch yields for InP, GaAs and their compounds were performed to understand plasma etching mechanism. Data for both existing RIE and pure Ar sputtering were compared to determine the mechanism for etch rate enhancement in high ion density plasmas. Also, the etch products for Cl;The mechanism of fast and smooth etching of In and Ga-based materials in high-density plasma sources (i.e., ECR or ICP) was found to be related to finding ion-to- neutral ratios (typically ;To ensure that the new etch modes we developed are realistic, we studied degradation of electrical properties of devices such as Schottky diodes, heterojunction bipolar transistors (HBTs) and metal semiconductor field effect transistors (MESFETs) after plasma etching by simulating physical Ar bombardments on the devices. The results showed that a balanced condition of ion current and ion energy could make it possible to obtain damage-free process regions for high-ion-density plasma etching or deposition.;Finally, a simple model was developed to calculate etch yield, and was found to fit to experimental data and to guide us in explaining the mechanism of plasma etching in high-density plasma sources. This model is also applicable to other materials which have poor etch yields under normal conditions, such as Cu.