Prediction of Abnormal Etching Profile in High-Aspect-Ratio Via/Hole Etching Using On-Wafer Monitoring System

Abstract

For the prediction of abnormal etching profiles, an ion trajectory prediction system has recently been developed. In this system, sheath modeling was combined with the on-wafer monitoring technique for accurate prediction. This system revealed that sidewall conductivity strongly affects the charge accumulation and ion trajectory in high-aspect-ratio holes. It was also found that the accumulated charge in adjacent holes is one of the reasons for the generation of twisting profiles according to analysis using the system. We presume that the prediction system is an effective tool for developing nanoscale fabrication.

Modeling of Charging on Unconventional Surface Morphologies of PMMA Substrates During Ar Plasma Etching

“…The first is the surface currents which have been attributed either to subsurface conduction in SiO 2 layers [37,47] or to the conduction in a thin fluorocarbon layer formed on the dielectric surface during etching with fluorocarbon chemistries. [26,42] The case study in this work is Ar þ sputtering of PMMA, i.e., no fluorocarbon chemistry is employed; additionally no subsurface conduction has been reported for PMMA. The second is the secondary electron emission; even if it exists, in the great majority of charging models in the literature is not considered.…”

“…Consequently, the ion deflection caused by surface charging, lead to profile irregularities such as notching, [22] microtrenching, [23] etching lag, [24] and twisting. [25,26] The notching effect describes the formation of long narrow wedge in a conductive material at the interface with an underlying insulator. It commonly appears at the inner sidewall foot of the outermost feature in a line and space pattern adjacent to an open area.…”

“…Owning to the electrostatic repulsion, ultimately, a vast amount of ions impinge at the trench sidewall surface or even return to the plasma bulk. Consequently, the ion deflection caused by surface charging, lead to profile irregularities such as notching, microtrenching, etching lag, and twisting . The notching effect describes the formation of long narrow wedge in a conductive material at the interface with an underlying insulator.…”

“…Park et al studied the impact of pressure on the microstructure charging during the etching of SiO 2 trenches. Ohtake et al implemented a charging model in which actual data from on‐wafer monitoring sensors was involved in the computation; the focus was on the investigation of twisting during plasma etching of high aspect ratio (AR) SiO 2 holes. Kenney and Hwang investigated the stochastic behavior of charging by studying the oscillation of charging potential in high AR dielectric nanostructures.…”

Feature Profile Evolution in Plasma Processing Using On-wafer Monitoring System

“…Measured data are stored in a memory in the circuit, and then, after unloading the sensor and the circuit, the measured data can be transferred to a PC with infra-red communication. Thirdly, prediction of damage distribution and etching profile is possible by fusion of measurement and simulation 47,48 .…”