Investigation of Compact Hollow-Anode Discharge Source for Copper Thin Films by Sputtering Processes

In-Je Kang,Kyu-Sun Chung,In-Sun Park,Ji-Hun Kim

doi:10.3390/en14113138

Abstract

A compact hollow-anode discharge (HAD) source with a size of 60 mm in radius and 70 mm in length has been developed to stably generate plasma jets for various sputtering processes in semiconductor and display fabrications. A developed HAD plasma source has been investigated by cylindrical electric probes, and the experimental results were compared to the values of numerical calculations. A uniform density discharge model with a geometry factor was proposed to estimate the profiles of plasma parameters. Owing to the difference of absolute magnitude, even with the similar trend of spatial variation, plasma parameters such as electron temperature (Te) and plasma density (ne) measured at z = 3 cm have been calibrated by the values of numerical calculations at the nozzle entrance (z = 0 cm, at the throat of the jet), and the calibration factors for Te and n0 have been deduced by comparing the experimental values to numerical calculations. These are to be explained by the decay mechanism along the axis of the jet with elastic collisions in terms of the mean free path. The developed HAD plasma source was tested for the deposition of Cu thin films with an optimized condition as a plausible application to sputtering processes.

Highlights

Plasma jets or ion beam sources have been developed for various material applications, such as plasma enhanced chemical vapor deposition (PECVD), dry etching and plasma surface treatments to improve qualities of substrates and efficiency of processing [1,2,3,4]
Applied voltages were maintained as almost constant, even when discharge currents increased up to 150 mA, showing fully developed state plasmas between the electrodes. This may be explained by a “layered-glows mode” which plays a crucial role on the relation of higher discharge currents with applied voltages only at a hollow-anode plasma source [9]
A new compact plasma jet with the concept of a hollow-anode discharge (HAD) structure has been developed for an application to sputtering processes

Summary

Introduction

Plasma jets or ion beam sources have been developed for various material applications, such as plasma enhanced chemical vapor deposition (PECVD), dry etching and plasma surface treatments to improve qualities of substrates and efficiency of processing [1,2,3,4]. A hollow-anode discharge (HAD) source invented by Miljevic [5] was proposed as a plasma source for generating plasma jets It has provided high-density and high-energy electrons in the hollow-anode region. To estimate electron temperature (Te ) and plasma density (ne ) in a cylindrical discharge reactor, a uniform density discharge model by Lieberman is considered [10]. Assuming uniform energy loss at all surfaces, plasma density (n0 , in the central region of plasma source) from the energy balance can be calculated by equating the total power generation (Pg ), which is absorbed into the electrons [10]: Pg = n0 u B Ae f f ET ,.

Experiment

Results

Conclusions