Effect of dual frequency on the plasma characteristics in an internal linear inductively coupled plasma source

Abstract

An internal-type linear inductive antenna, referred to as a “double comb-type antenna,” was used as a large area plasma source with a substrate size of 880×660mm2 (fourth generation glass size). The effects of the dual frequency (2 and 13.56MHz) radio frequency (rf) power to the antenna as well as the power ratio on the plasma characteristics were investigated. High-density plasma on the order of 1.7×1011cm−3 could be obtained with a dual frequency power of 5kW (13.56MHz) and 1kW (2MHz) at a pressure of 15mTorr Ar. This plasma density was lower than that obtained for the double comb-type antenna using a single frequency alone (5kW, 13.56MHz). However, the use of the dual frequency with a rf power ratio of approximately 1(2MHz):5(13.56MHz) showed better plasma uniformity than that obtained using the single frequency. Plasma uniformity of 6.1% could be obtained over the substrate area. Simulations using FL2L code confirmed the improvement in the plasma uniformity using the dual frequency to the double comb-type antenna.

Electron density modulation in a pulsed dual-frequency (2/13.56 MHz) dual-antenna inductively coupled plasma discharge

“…Another possible reason is the higher power absorption at low (2 MHz) driving frequency. It is well known that ohmic heating in the plasma volume is proportional to the electric field strength which is inversely proportional to the driving frequency; 22 thus, a higher electric field is expected at 2 MHz driving frequency compared to 13.56 MHz, which produces a higher plasma density. Previously, in Ar discharge and in the same set-up, it was shown that a higher plasma density is produced by two antennae energized by 2 and 13.56 MHz when compared to a single coil energized by 13.56 MHz for the same total input power.…”

“…Multiple antenna ICPs are proposed and designed in order to scale up the conventional single frequency ICPs for largearea device fabrication. [21][22][23] The rationale of multipleantenna ICPs is to increase the coil area by keeping the coil inductance low enough to enable efficient RF matching and uniform plasma over the large-area substrate size. Based on this concept, a dual-frequency (2/13.56 MHz), dual-antenna ICP (12 turn inner coil powered by 2 MHz and three turn outer coil powered by 13.56 MHz) has been designed.…”

Plasma Characteristics of a Ni–Zn Ferrite Enhanced Internal-Type Inductively Coupled Plasma Source Operated at 2 and 13.56 MHz

“…This can result in intensive ion bombardment of the ICP source antenna causing erosion of the dielectric material on the antenna and contamination by the sputtered dielectric materials. In addition, non-uniform rf voltage developing along the long antenna caused by a standing wave effect may also deteriorate plasma uniformity over the substrate surface [8][9][10][11].…”

Ion energy distributions in a pulsed dual frequency inductively coupled discharge of Ar/CF4 and effect of duty ratio

“…Many schemes, based on multiple frequencies, power splitting mechanism, pulse shape tailoring, and customized shape of bias power, have been proposed. [16][17][18][19][20][21][22][23][24][25][26][27][28][29] Recently, a new approach, based on using dual frequency and power splitting mechanism in ICP source, has been proposed to provide a good discharge uniformity and control on discharge parameters. 30,31 Pulsing the plasma source provides an added flexibility in controlling the discharge parameters and proves to be an important tool for tailoring discharge parameters specific to a particular application.…”