Damage induced in Si by ion milling or reactive ion etching

Abstract

Surface damage in Si substrates created by Ar-ion milling or by reactive-ion etching in CF4, CHF3, Cl2, SiCl4, or SiF4 has been investigated. Metal-oxide-semiconductor capacitors were fabricated on the etched Si substrates, and the interface-state densities were obtained from capacitance-voltage measurements. Interface states generated by the dry etching processes were strongly dependent on the etching gas and the bias voltage. Carbon-based gases (CF4, CHF3) induced more interface states than those without carbon. For the carbon-based gases, Si samples etched in CHF3 showed lower densities of interface states than samples etched in CF4 under the same conditions. Generation lifetime measurements indicated that samples with large densities of interface states also had short lifetimes. Measurements of oxidation-induced stacking faults caused by dry etching were consistent with both the interface-state and lifetime measurements. Thermal annealing of the etched wafers was not effective in reducing the surface damage. The measured interface states on the dry etched Si substrates could be lowered to their pre-etched levels by removing at least 500 Å of the etched surface by wet chemical etching.

An Assessment of ECR Argon Plasma Etching Damage on Si and SiO2 Interfaces

“…It has earlier been shown that the interface state density increases as the incident ion energy increases. 6 The high frequency C-V curve of our Ar etched sample shows a hysteresis effect, confirming that there is some degree of damage at the Si/Si02 interface during the etching. A negative flatband voltage shift of 2.5 V was also observed for the etched sample relative to the control.…”

Effect of reactive ion etch-induced damage on the performance of 4H-SiC schottky barrier diodes

“…The high leakage current in the diodes with CF 4 /O 2 etched surfaces is attributed to the incomplete removal or reformation of oxide layer on the surface during RIE. Also, CF 4 based discharges are known to create higher degree of damage and surface roughness as observed in Si, 32,33 which may also explain the higher leakages observed in diodes with CF 4 /O 2 etched surfaces. The interfacial layer capacitance (C i = ε/δ) for the surfaces etched in CHF 3 /O 2 , CF 4 /O 2 , and CHF 3 / CF 4 were estimated to be 2.3, 1.5, and 25 µF/cm 2 , respectively.…”

Minimising bulk lifetime degradation during the processing of interdigitated back contact silicon solar cells

“…RIE‐induced damage of the patterned area was therefore suspected. Shallow implantation of reactive ions as well as lattice damage has been shown to produce surface degradation in silicon . The right‐hand image in Figure C shows a PL image of a test wafer patterned using RIE, then doped using BBr 3 diffusion and finally passivated with ALD Al 2 O 3 .…”