Obtaining high rates for the etching and ashing for large liquid‐crystal display substrates by using a surface‐wave plasma source

Abstract

AbstractIn the manufacture of thin‐film transistor liquid‐crystal displays (TFT‐LCDs), a major goal is to scale up the production of liquid‐crystal panels and lower their production costs. For that reason, we have developed a large‐area high‐density (3.58 × 1011 cm−3) surface‐wave plasma source based on a slot antenna. This source is designed to reduce the number of separate production steps in semiconductor processing, thereby increasing the throughput of large‐area TFT‐LCD substrates. We are convinced that the use of this plasma source will not only increase the etching rate, but also reduce the need for industry‐standard photoresist liftoff processes by enabling an uninterrupted transition after etching to photoresist liftoff (ashing). We found that the etching rate for a 400 × 500 mm2 polysilicon layer on a glass substrate was 58 nm/min with a uniformity of ±6.8% when our source was used. Furthermore, when ashing was carried out in the same chamber immediately after etching, the ashing rate was 1430 nm/min with a uniformity of ±9.3%. We also found that the selectivity ratio for resist versus polysilicon and the SiO2 in an underlayer was higher than 140. This implies that our process outperforms the standard resist liftoff process; indeed, we have realized a high‐uniformity etching process with twice the etching rate of standard methods. In addition, we have made progress toward realizing an ashing process, which is almost ready for practical use. These two processes can be combined into a single integrated etching–ashing process that will reduce the need for a separate liftoff procedure and simplify processing. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(6): 28–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10086