An Overview of Dry Etching Damage and Contamination Effects

Abstract

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, radiationinduced 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.

(Invited) Towards a Vertical and Damage Free Post-Etch InGaAs Fin Profile: Dry Etch Processing, Sidewall Damage Assessment and Mitigation Options

“…(14,(16)(17)(18)(19)(21)(22)(23)(24)(25)(30)(31)(32)(33) have been used to yield structural, chemical and electrical information relating to etch-induced damage. Our concern here is the extent of electrical damage to the dielectric/sidewall interface.…”

“…The choice of gas chemistry and the control of process parameters dictate the quality of the etch process in terms of selectivity, anisotropy, etch rate and uniformity (14)(15)(16)(17)(18)(19)(20). The utilization of dry etch processing, however, carries with it the inherent risk of damage to the semiconductor due to energetic ion bombardment and the presence of reactive ion species (18,19,21). Etch-induced damage can manifest in various forms such as lattice defects (traps, vacancies and interstitials), lattice disordering (amorphisation) and surface roughness due to ion bombardment (19,21,22), surface contamination resulting from polymer deposition (21), dopant passivation by atomic hydrogen (21)(22)(23) and changes in surface stoichiometry due to preferential etching or layer intermixing (23)(24)(25).…”

“…The utilization of dry etch processing, however, carries with it the inherent risk of damage to the semiconductor due to energetic ion bombardment and the presence of reactive ion species (18,19,21). Etch-induced damage can manifest in various forms such as lattice defects (traps, vacancies and interstitials), lattice disordering (amorphisation) and surface roughness due to ion bombardment (19,21,22), surface contamination resulting from polymer deposition (21), dopant passivation by atomic hydrogen (21)(22)(23) and changes in surface stoichiometry due to preferential etching or layer intermixing (23)(24)(25). These effects can degrade the optical and electrical properties of the semiconductor, of detriment to the final device performance.…”

“…However, satisfying both criteria is a challenging prospect. Highly anisotropic dry etching required for sidewall verticality is more damaging due to the physical nature of the process (21). Unlike Si, the induced damage cannot be cured by post etch annealing in III-Vs (1,19).…”

Top down nano technologies in surface modification of materials

“…Often, anisotropic (vertical) sidewall profiles are required, perhaps with some roundness at the bottom of the feature. Radiation damage refers to structural damage of the crystal lattice or, more importantly, to electrical damage of sensitive devices caused by plasma radiation (ions, electrons, UV and soft X-ray photons) [45]. Charging of insulating materials within a micro feature can lead to pattern distortion (notching), or highenergy ion bombardment can lead to structural damage of the top atomic layers of the etched film.…”