Wet Process for Highly Uniform Oxide Etching

Wet etching for oxide thin films is superior to dry processes because it has extremely low contamination, eliminates water markes from the wafers, provides a high degree of process flexibility and control, has better cleanliness, and the equipment is compact. However, wet etching has had limited application because the etch uniformity is difficult to control. We propose to develop an innovative mixer which operates inside a wet etching chamber to provide extremely uniform conditions to all wafers to produce very uniform etch results. The innovation is the use of non-contacting, hydrodynamic bearings to support the mixing impeller without any solid-to-solid contact between the impeller and the chamber walls, so that no particulate contamination is generated. In Phase I we will perform flow tests to measure loads on the impeller shaft during operation and to show that the mixing impeller provides uniform conditions in the etching chamber. A prototypical hydrodynamic bearing will be fabricated and tested for load bearing capacity. In Phase II we will design and build the drive system for the mixer and test it in actual wafer etching chambers and evaluate its effectiveness by measuring the uniformity of etched silicon wafers. Anticipated Benefits: The proposed wet etching process will have extremely low contamination and excellent control of etch uniformity. The mixing unit will be inexpensive and reliable because there are no contacting, moving parts. The primary application is etching of thin film, mutli-component oxides used in electronics, photonics, sensors, and micro-electro mechanical systems.