Dry Stripping & Cleaning

As chip node dimensions continuously shrink, wafer cleanliness is becoming very important. Through the device manufacturing cycle, wafer surfaces are required to be regularly cleaned from any residues that may impact its performance. Most common stripping application consists of removal of photoresist, either through wet process or dry plasma process under vacuum (also named ashing). Other cleaning processes (commonly named descum) consist of removing polymer residues in device trench after etch process.

Application requirements

  • Vacuum performance stability over time for optimized yield
  • High pumping speed and fast pump down time for high throughput
  • High process lifetime at low operating costs: Low power consumption, low repair cost
  • Low footprint dry pumps

How does it work?
Using a plasma source, reactive species are generated, commonly oxygen or fluorine. For advance nodes manufacturing, trend is to replace oxygen by hydrogen to reduce wafer surface oxidation.
As the plasma is formed, many free radicals are created which could damage the wafer. In order to reduce wafer damage, most stripping equipment use a remote or downstream plasma configuration. Reactive species combine with the photoresist to form volatile byproduct which is evacuated by a vacuum pump.

Vacuum requirements
Dry ashing or stripping process operates at a working pressure in the range of 1 mbar and typically requires dry pumps with pumping speeds in the range of 600 to 1,800 m3/h, with emerging needs up to 3,000 m3/h. As some equipment are not equipped with Load Lock chambers, fast pump down times are required for high throughput.

Product portfolio
Byproducts, consisting mainly of carbon oxides and polymers, are not critical for vacuum pumps. Our A4H dry pumps are well adapted to this application, featuring long lifetimes & low operating costs.

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