The Silicon Precursor Toolbox for Low-Temperature Deposition
The drive toward making electronics faster, denser, and cheaper continues unabated. Shrinking device dimensions and changes in structure place additional demands on the materials used in all steps of semiconductor processing, including depositing silicon nitride (SixNy, or SiN) and silicon oxide (SiO2) films. With horizontal dimensions of transistors already near their lower limit, the path forward for Moore’s Law requires building upward. Increasing use of FinFET transistor structures and 3D NAND memory devices is driving the move from planar coatings on horizontal surfaces to conformal coatings on vertical and topologically complex surfaces. Aspect ratios are growing to the point where conformal coating performance is becoming a potential roadblock.
Silicon nitride and oxide films serve two primary types of functions in semiconductor device fabrication. Some are used for patterning, and others are used for electrical insulation. Within these broad categories, each application comes with a slightly different set of challenges. In this white paper, we explain the role of precursors in depositing high quality silicon-containing films under a wide range of challenging conditions.
SILICON-CONTAINING FILMS USED FOR PATTERNING
SiN and SiO2 function as disposable films for patterning layers in semiconductor devices. Self-aligned double and quadruple patterning, which is becoming increasingly common, is an effective method of creating extremely fine lines. This approach uses films deposited on the side-walls of patterned structures to circumvent the dimensional limitations of photolithography, fabricating narrower lines than individually patterned layers can achieve using 193 nm photolithography. The deposited side-wall layer is used as a mask to pattern underlying layers during subsequent etch steps. When the sacrificial layer is etched away, whether by a dry or wet etch process, the underlying layer has received the pattern at twice the spatial density of the structure before deposition of the patterning film. With quadruple patterning, line widths are one-quarter of the width that would be possible without implementing multiple patterning steps.