Plasma Etching of Metals

• Metal etch is used to form the interconnection lines for an integrated circuit to connect transistors and circuits units.

• The most commonly used chemical for metal etch is chlorine.

• In plasma, Cl₂ breaks into Cl free radicals that can react with TiN, Al and Ti to form volatile byproducts TiCl₄ and AlCl₃.

Cl₂ ® Cl + Cl (plasma)

3Cl + Al ® AlCl₃ (plasma)

4Cl + TiN ® TiCl₄ + N (plasma)

4Cl + Ti ® TiCl₄ (plasma)