Improving the etching performance of high-aspect-ratio contacts by wafer temperature control: Uniform temperature design and etching rate enhancement

Abstract

A novel wafer temperature control system using direct expansion cycles is developed to improve etching performance. This system enables rapid temperature control of a wafer with low power consumption. In a previous report, we confirmed that the etching rate and mask selectivity of high-aspect-ratio contact etching could be increased by around 6% and 14%, respectively, by controlling the temperature of the wafer during the etching process. In this study, an advanced wafer temperature control system that realizes not only rapid response but also uniform wafer cooling is developed, and a new etching process that controls O2 gas flow rate as well as wafer temperature during etching is evaluated to decrease the etching rate depression of high-aspect-ratio contact etching. As a result, a rate of wafer temperature change of 1°C/s and uniformity of ±0.7% with a coefficient of performance exceeding 3 is achieved over a wafer with a diameter of 300mm during the etching process. Furthermore, etching rate depression in C4F6/Ar/O2 plasma is decreased from 14.4% to 7.8% for a sample with a diameter of 100nm and aspect ratio of 30.