ULSI stands for Ultar Large Scale Integration

Very-large-scale integration (VLSI) is the process of creating integrated circuits by combining thousands of transistor-based circuits into a single chip. Etching is used to create ultra-fine circuit pathways in silicon wafers. While early techniques used a "wet" fluid to dissolve the unwanted material, newer techniques use "dry" plasma etching to remove wafer material.

Medium scale integration

Ultra Large Scale Integration