Selective Dry Etching of HfO₂ in CF₄ and Cl₂/HBr-Based Chemistries

Abstract

We investigated HfO2 etching characteristics in conventional Si gate etching chemistries, namely, CF4 and Cl2/HBr/O2-based chemistries. We obtained an adequate etch rate of 2.0 nm/min for both chemistries and a selectivity of 1.9 over SiO2 for Cl2/HBr/O2-based chemistry. We examined the etch rate dependence on source power, bias power, O2 flow rate, and Cl2 flow rate in the Cl2/HBr/O2 chemistry. It was clarified that a physical component is dominant in HfO2 etching in this chemistry. The possibilities of achieving a higher HfO2/SiO2 selectivity and of controlling the anisotropic/isotropic component in HfO2 patterning were also discussed. Moreover, it was clarified that the surface portion of the damaged layer created by the dry-etching step can be removed by a subsequent wet etching. Based on these results, the sub-100 nm patterning of poly-Si/HfO2 gate stacks was successfully demonstrated.

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

“…Dry etching of HfO 2 films deposited on silicon has been studied using several plasma chemistries based on fluorine (F), chlorine (Cl), bromine (Br), and methane (CH 4 ). [4][5][6][7][8][9][10] These studies show that both F-and Cl-based plasmas are suitable for selective dry etching of HfO 2 /Si structures. However, the literature on the dry etching characteristics of HfO 2 /GaAs structures is scarce with the exception of the work by Koester et al, 11) where HfO 2 gate patterning by dry etching is mentioned as part of the fabrication process of GaAs selfaligned MOSFETs (L g ¼ 100 mm) without providing details on the method employed or the resulting pattern morphology.…”

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

“…15 In this paper we present results of the etching of HfO 2 thin films on Si substrates in inductively coupled fluorocarbon ͑CF 4 /Ar and C 4 F 8 /Ar͒ plasmas. The thickness of the gate dielectrics for next-generation CMOS devices ͑in the 65 nm technology node and beyond͒ will be several nm.…”

Selective Etching of High-kDielectric HfO2Films over Si in BCl3-Containing Plasmas without rf Biasing

“…1,2) For the integration of high-k dielectric materials in device fabrication, highly selective etching over underlying Si is indispensable for their removal prior to forming source and drain contacts. Plasma etching of high-k dielectrics has used not only chlorine-based gases such as Cl 2 , 3,4) BCl 3 , [5][6][7][8] BCl 3 / Cl 2 , [5][6][7][8] and Cl 2 /HBr, 9,10) but also fluorine-based gases such as SF 6 , 4) CF 4 , 9,10) and CHF 3 . 10,11) However, the etch selectivity for high-k/Si was not so high (often up to 3 -5), due to the highly volatile halogen compounds of Si, and also to the strong metal-oxygen bonds of high-k dielectrics and less volatile metal-halogen compounds.…”