Delineation of Crystalline Defects in Semiconductor Substrates and Thin Films by Chemical Etching Techniques

Abstract

Successful implementation of novel materials like SOI and sSOI into the mass production of advanced devices requires monitoring of their crystal quality and defect densities. Preferential etching techniques in combination with light optical microscopy are still the workhorse for a quick and simple evaluation of defect types and area densities.Classical etching recipes applied to SOI and sSOI substrates reveal certain limitations and the most common recipes are based on toxic Cr(VI). Therefore there is a need for alternative Cr-free recipes with adequate or superior performance for application to SOI and sSOI. We discuss some basic aspects of preferential etching and present two different types of novel Cr-free preferential etching chemistries which are suitable for the application on SOI. Organic peracid etches consist of hydrofluoric acid, an organic acid and hydrogen peroxide which reacts with the organic acid forming the corresponding organic peracid which then acts as the oxidizing agent. These etch solutions have very low removal rates (0.4 -1.5 nm/min at 25{degree sign}C), are very defect sensitive and are suitable for the application on SOI films as well as on CZ bulk material where they reveal vacancy agglomerates (D defects, COPs) with high sensitivity.