Conductor & Polysilicon Etch

Dry conductor etch process consists of selectively removing conductor materials (aluminum, tungsten,...) on the wafer, shaping the electrical interconnections of a semiconductor device. Dry Polysilicon (Poly-Si) etch consists of selectively removing Polysilicon to create the transistor gate. As critical dimensions are continuously shrinking, high uniformity and selectivity are needed to meet required electrical performance on such tiny structures: this is achieved by Plasma or Reactive Ions etching process.

How does it work?

Etching gas, commonly Chlorine or Fluorine based, are injected in the reactor. Plasma generates radicals which react on the wafer surface by creating a volatile by-product. Thanks to device patterning obtained by lithography and through control of plasma reaction and temperature, the material is selectively etched from the surface at the desired rate.

Vacuum requirements

Dry conductor & Poly-Si etch processes operate at low pressure, in the range of 10-2 to 10-3 mbar. In order to maintain a low vacuum, turbopumps are mounted directly on the chamber reactor, backed by primary dry pumps installed in the basement. As gas flows are continuously increasing, required turbopumps pumping capacity vary from 1,600 to 3,000 l/sec on the newest generation reactors. Dry pumps typically require pumping speeds from 600 to 1,200 m3/h.

By-products to be evacuated are condensable and highly corrosive. This represents a great challenge for vacuum pumps, which should be able to operate at high temperature under a very corrosive environment.