Improved Etch and CMP Process Control Using In-Line AFM

摘要

As aspect ratios become higher, features become smaller, and requirements for planarity tighten, Atomic Force Microscopy (AFM) has begun to replace profilometry for topographic measurements such as trench and via depths, step height, and micro-planarity measurements, both in development and in production. In this paper, we describe the application of a new, high throughput AFM for line monitoring in the STI and trench capacitor modules. We focus on two key applications: the post-CMP height difference between the active area and the isolation area in the STI module, and the post-etch depth of a DRAM trench capacitor. We begin by describing the two initial AFM applications. Next, we introduce a statistical approach for determining optimal lot sampling for these applications. From the gap between throughput of our current AFMs, and statistically determined sampling requirements, we validate the need for a high throughput AFM. Next, we describe the design of such an AFM, recently developed by KLA-Tencor, and its expected benefits. Finally, we discuss the economic benefit to Infineon of detecting metrology problems in-line, without the delay and cost of cross-sectional SEM analysis.