Future trends of cross-sectional transmission electron microscopy for electronic and photonic devices

Abstract

Cross-sectional transmission electron microscopy (XTEM) has played an important role in silicon very large scale integration (VLSI) device development, process evalution and failure analysis. More recently, XTEM has also been applied to photonic device evaluation and diagnosis. Most diffuculties in XTEM sample preparation for both silicon VLSI and photonic devices have been overcome. Sample preparation time is now limited by the nature of ion milling. It is clear that XTEM is more time consuming and expensive than other analytical techniques (Auger spectroscopy, secondary ion mass spectrometry, Rutherford backscattering etc.) and considerable development and refinements of preparation techniques will occur. In this paper new preparation methods are discussed including (1) polyimides both to bond and to protect specimens at elevated temperatures for in situ studies, (2) selective dry ethcing prior to ion milling in order to reduce the effects of preferential sputtering rates, (3) oxide and junction delineation techniques and (4) a precision cross-section method to aid in the diagnosis of specific predefined areas.