Etching properties of Pt thin films by inductively coupled plasma

Abstract

The inductively coupled plasma etching of platinum with Ar/Cl2 gas chemistries is described. X-ray photoelectron spectroscopy (XPS) is used to investigate the chemical binding states of the etched surface with various Ar/(Ar+Cl2) mixing ratios. Atomic percentage of Cl element increases with increasing Ar/(Ar+Cl2) mixing ratio with the exception of Ar/(Ar+Cl2) mixing ratio of 1. At the same time, the peaks that seem to be subchlorinated Pt at XPS narrow scan spectra are found and Cl–Pt bonds rapidly increase at Ar/(Ar+Cl2) mixing ratio of 0.62. Quadrupole mass spectrometry (QMS) is used to examine the variations of plasma characteristics with various Ar/Cl2 gas chemistries. QMS results show that Cl2 molecules are converted to Cl radicals with adding Ar gas to Cl2 plasma. QMS results support the increased atomic percentages of Cl elements on the etched Pt surface. Single Langmuir probe measures ion current density with various Ar/Cl2 gas plasma. Ion current densities are used to investigate the ion bombardment effects on the etched surface. Thin film thickness measuring system, scanning electron microscope and a four-point probe are used to extract the Pt etching characteristics. The maximum etch rate of Pt is approximately 140 nm/min at the Ar/(Ar+Cl2) mixing ratio of 0.9. These results are consistent with XPS, QMS, and Langmuir probe data.