22 nm technology node active layer patterning for planar transistor devices

摘要

As the semiconductor device size shrinks without concomitant increase of the numerical aperture (NA=1.35) or index of the immersion fluid from 32 nm technology node, 22 nm patterning technology presents challenges in resolution as well as process window. Therefore, aggressive Resolution Enhancement Technique (RET), Design for Manufacturability (DFM) and layer specific lithographic process development are strongly required. In order to achieve successful patterning, co-optimization of the design, RET and lithographic process becomes essential at the 22 nm technology node. In this paper, we demonstrate the patterning of the active layer for 22 nm planar transistor device and discuss achievements and challenges in 22 nm lithographic printing. Key issues identified include printing tight pitches and 2-D features simultaneously without sacrificing the cell size, while maintaining large process window. As the poly-gate pitch is tightened, the need for improved corner rounding performance is required inorder to ensure proper gate length across the entire gate width. Utilizing water immersion at NA=1.2 and 1.35, we will demonstrate patterning of the active layer in a 22 nm technology node SRAM of a bit-cell having a size of 0.1 μm~2 and smaller while providing large process window for other features across the chip. It is shown that highly layer-specific and design-aware RET and lithographic process developments are critical for the success of 22 nm node technology.