Deep Reactive Ion Etching (DRIE) Electrical and （深反应离子刻蚀(冲动)电气和）.pdf

Deep Reactive Ion Etching (DRIE) ENEE416 03/16/2004 Alexandre Reis Raj Bhattacharya The etching approach described herein is counted among the present state of the art techniques utilized in the current trend toward miniaturization of sensors and actuators. The ability to microfabricate deep trenches in silicon substrates while maintaining high selectivity to masking material, good profile control and low nonuniformity across a wafer has been revolutionized with the current generation of deep-reactive-ion-etching (DRIE) tools. These deep-silicon-etching machines can easily achieve rates in the excess of 3µm/min, selectivities to photomasking materials greater than 70:1 (at least twice as much for silicon dioxide), excellent profile control (see figure 1) and non-uniformities across the wafer of 5% of less. These high-density plasma tools can use two distinct gas-feeding approaches: standard and time multiplexing. The standard approach, all gas species are flowed at the same time, and the etching results depend on the glow discharge having both one species of radicals to proceed with the etch, and another species of radicals for protecting the sidewalls during operation. In the time-multiplexing scheme, the etching and passivating gases used are flowed independently one at a time (see figure 2), and the machine alternates between an etching cycle and a passivating cycle. During the etching cycle step a shallow trench is formed in the silicon substrate, with an isotropic profile characteristic of fluorine-rich glow discharges. The typical duration of these steps is ≤12s. During the passivation cycle, a protective fluorocarbon film is deposited on all surfaces. The duration of the step is usually ≤10s and shorter than the etching cycle. In the subsequent etch step, ion bomb