ELECTRICAL CHARACTERIZATION AND SURFACE-ANALYSIS OF DRY ETCH-INDUCED DAMAGE ON SI AFTER ETCHING IN ON ECR SOURCE

Si was etched with a Cl-2 plasma generated by an electron cyclotron resonance (ECR) source and the effects of etch-induced damage were studied. Surface damage was evaluated by electrical characterization and surface analysis. Low ion energy and optimized reactive species concentration are necessary to minimize etch-induced damage. The reactive species concentration is optimized when the etch conditions provide high concentration of reactive species and high etch rate. As RF power was increased from 20 to 250 W, the ideality factor for Schottky diode increased from 1.08 to 1.90 and the breakdown voltage decreased from 60 to 6 V. Using transmission electron microscopy, defect density increased from 3.6 X 10(10) to 1.0 X 10(11) cm(-2) while the damage layer thickness decreased from 134 to 91 nm as RF power was increased from 50 to 500 W. The etch-induced defects are mainly dislocation loops ranging from 1.2 to 2.4 nm. Higher RF power also caused an increase in thermal wave signal. At low self-induced bias voltage (-50 V), leakage current and thermal wave signal increased with increasing microwave power. However, Schottky diode characteristics improved at higher microwave power when high self-induced bias voltage (-150 V) was used. Addition of Ar degraded the Schottky diode performance and increased thermal wave signal. After removing 60 nm from the etched surface using low energy chlorine species, full recovery in the device performance is observed as indicated by the electrical and thermal wave measurements. A new damage model is proposed to relate the generation of defects to the etch conditions by comparing the increase in leakage current of the Schottky diodes after dry etching. The defect density is found to increase with self-induced bias voltage and microwave power, but to decrease with etch rate and distance from the etched surface. Good agreement is obtained between the measured and the predicted Schottky diode characteristics.