Fluorinated gases for semiconductor manufacture: process advances in chemical vapor deposition chamber cleaning

In the past several years, the semiconductor industry has been presented with various options for cleaning of plasma enhanced chemical vapor deposition (PECVD) tool chambers. In this paper, we assess the relative merits of the latest chamber cleaning processes. These processes will be compared on the overall cleaning performance (process throughput, efficiency of clean) the economic performance (gas usage, costs) and the environmental performance (perfluorocarbon (PFC) emissions). Direct comparisons between chemistries will be made whenever relevant process factors (e.g. tool type, film, analysis methods) are held constant.We have previously reported both laboratory and commercial CVD tool results comparing different chamber cleaning gases. These studies using both Novellus Concept-1 and AMAT P-5000 tools, indicated that a “drop-in” alternative such as octafluorocyclobutane (c-C₄F₈) would significantly lower PFC emissions (up to 85%) as well as decrease process costs through reductions in gas consumption. In this paper, we further extend this work to include qualification and implementation at chipmakers on a variety of tools, wafer sizes, and films. Key process data on film properties such as uniformity, number of particles, and thickness is also presented.The overall results support and extend the basic conclusions reached earlier: c-C₄F₈ has the lowest process cost of any cleaning gas, without any penalty in cleaning performance (process throughput) but most importantly, it also offers the lowest PFC emissions of any fluorocarbon-based process. It is a true drop-in alternative offering the unique win-win combination of improved environmental performance while also reducing processing costs.