Nanoscale Selective Plasma Etching of Ultrathin HfO₂Layers on GaAs for Advanced Complementary Metal–Oxide–Semiconductor Devices

Abstract

We present a reliable dry-etch process for patterning deep-submicron structures in ultrathin (16 nm) HfO2 layers deposited on GaAs substrates. Plasma chemistries based on BCl3/O2 and SF6/Ar have been investigated using an inductively-coupled plasma reactive ion etch (ICP-RIE) reactor. The process reliability has been examined in terms of etch rate selectivity, etch time control, anisotropy, and surface roughness of the underlying GaAs substrate for potential application to gate nanopatterning in next-generation field-effect transistor fabrication. We show that a SF6/Ar plasma process provides excellent prospects as a nanopatterning method for subsequent re-growth of GaAs in novel device architectures.

Fabrication of HfO2 patterns by laser interference nanolithography and selective dry etching for III-V CMOS application

“…line roughness ( R a ) measured along the HfO 2 stripes and the etched GaAs trenches were 0.14 ± 0.03 nm and 0.18 ± 0.03 nm, respectively. The value of the GaAs line roughness measured in this work is comparable to that reported previously for HfO 2 etching using a SF 6 /Ar plasma (0.13 nm) [ 8 ]. Etching with a CF 4 plasma chemistry thus provides an atomically smooth GaAs surface, which is a critical requirement for subsequent selective III-V growth during device fabrication.…”

“…This process has been estimated to occur at a rate of 0.06 nm/s. Such slow HfO 2 etching rate is advantageous with respect to previous reports using SF 6 /Ar [ 8 ] from the process control viewpoint, as it allows to process a typical 2-nm-thick gate oxide in a practicable etching time, i.e. approximately 30 s. As shown in the image, a tapered etch profile with a 70° inclination angle is achieved by the formation of a sidewall passivation layer comprised of non-volatile reaction by-products of the CF 4 etching process.…”

“…Comparatively much less attention has been paid to patterning ultrathin layers of HfO 2 deposited on GaAs substrates despite its key role in the fabrication of next generation non-planar high-κ/III-V transistors. In recent papers, we have studied the nanoscale patterning of HfO 2 /GaAs by electron beam lithography and inductively coupled plasma reactive ion etching (ICP-RIE) using BCl 3 /O 2 and SF 6 /Ar chemistries [ 8 , 9 ]. Only the less-reactive F-based chemistry showed good etch selectivity of HfO 2 over GaAs (i.e.…”

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

“…5 The dilution of the fluorocarbon gas by Ar at constant gas pressure results in the non-monotonic (with a maximum) HfO 2 etching rate. Such effect have repeatedly been obtained for C 4 F 8 /Ar 9 and CF 4 /Ar 16 plasmas.…”

“…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.…”