An Overview of Dry Etching Damage and Contamination Effects

Plasma or dry etching techniques, such as reactive ion etching, magnetron reactive ion etching, electron cyclotron resonance etching, ion beam etching, and plasma etching, can result in damage and contamination of the materials used in device structures and interconnects. The damage that can take place occurs because of ion bombardment, radiation‐induced bonding changes, and charge buildup. If not removed, damage can have effects which vary from gettering to creating traps in insulators and gap states in semiconductors. The contamination that can take place can have two forms: residue layers and permeation. The former are ultrathin layers of reaction products that can coat surfaces whereas the latter is the embedding or implantation, and perhaps subsequent diffusion, of impurities. These impurities can range from metals whose source is the processing chamber to hydrogen which is often found in the etch recipe or may even be found due to the presence of water in the processing chamber. If not removed, residues can interfere with subsequent processing such as oxidation and can cause series resistance in contacts. Impurities, if not removed, can have a range of effects from modifying carrier lifetimes to interfering with subsequent processing. Hydrogen, in particular, can affect materials in a number of ways including modifying doping activation.