Etching characteristics of high-k dielectric HfO2 thin films in inductively coupled fluorocarbon plasmas

Abstract

Formation of polycrystalline silicon germanium/HfO 2 gate stack structure using inductively coupled plasma etching J.Inductively coupled fluorocarbon ͑CF 4 / Ar and C 4 F 8 /Ar͒ plasmas were used to etch HfO 2 , which is a promising high-dielectric-constant material for the gate of complementary metal-oxide-semiconductor devices. The etch rates of HfO 2 in CF 4 / Ar plasmas exceeded those in C 4 F 8 / Ar plasmas. The tendency for etch rates to become higher in fluorine-rich ͑high F / C ratio͒ conditions indicates that HfO 2 can be chemically etched by fluorine-containing species. In C 4 F 8 /Ar plasmas with a high Ar dilution ratio, the etch rate of HfO 2 increased with increasing bias power. The etch rate of Si, however, decreasd with bias power, suggesting that the deposition of carbon-containing species increased with increasing the power and inhibited the etching of Si. The HfO 2 / Si selectivity monotonically increased with increasing power, then became more than 5 at the highest tested bias power. The carbon-containing species to inhibit etching of Si play an important role in enhancing the HfO 2 / Si selectivity in C 4 F 8 / Ar plasmas.

Ion-radical synergy in HfO2 etching studied with a XeF2/Ar+ beam setup

“…Furthermore, the ion energy in a conventional plasma reactor is not very well defined and often has a bimodal energy distribution due to the applied radio frequency voltage. 32 These effects might explain why not all etch rate data 4,5,8,9 agree well with Eq. ͑2͒, while the etch yield may still follow this ion energy dependence.…”

“…A wide variety of chemistries have been tried for the etching of high-k metal oxides such as HfO 2 and ZrO 2 . [4][5][6][7][8][9][10][11][12] These studies have revealed that etching of these materials is dominated by momentum transfer from the ions to the surface atoms in most cases. [7][8][9] An etch selectivity toward Si of 10 and higher has been reported.…”

“…[4][5][6][7][8][9][10][11][12] These studies have revealed that etching of these materials is dominated by momentum transfer from the ions to the surface atoms in most cases. [7][8][9] An etch selectivity toward Si of 10 and higher has been reported. 12,13 Furthermore, Sha et al 5 have reported that a functional transistor could be built with HfO 2 as a gate dielectric with the pattern transferring using a BCl 3 plasma.…”

Selective Removal of High-k Dielectrics

“…Moreover, after etch a lot of non-volatile etch products (fluorides) were observed on the surface. 9 , 10 One can conclude that fluorine can break a metal-oxygen bond and a form a fluoride, but these fluorides are usually not volatile enough to be removed from the surface. Another concern for the fluorine-based chemistry is selectivity over the substrate.…”

On the Etching Characteristics and Mechanisms of HfO<SUB>2</SUB> Thin Films in CF<SUB>4</SUB>/O<SUB>2</SUB>/Ar and CHF<SUB>3</SUB>/O<SUB>2</SUB>/Ar Plasma for Nano-Devices

“…Currently, there are many published works on the investigation of the HfO 2 etch process in fluorinebased, [3][4][5][6][7][8][9] chlorine-based, 3 6 7 9−12 bromine-based 6 10 13 and hydrogen-based 3 gas chemistries. The results of these works can be summarised as follows: (1) The chemical enhancement of the HfO 2 etching rate over the pure ion etching in Ar plasma is maximum for the Cl-and Br-based gas chemisties and minimum for the fluorine-based ones.…”