Mechanism of wiggling enhancement due to HBr gas addition during amorphous carbon etching

Abstract

The effect of gas chemistry during etching of an amorphous carbon layer (ACL) on wiggling has been investigated, focusing especially on the changes in residual stress. Although the HBr gas addition reduces critical dimension loss, it enhances the surface stress and therefore increases wiggling. Attenuated total reflectance Fourier transform infrared spectroscopy revealed that the increase in surface stress was caused by hydrogenation of the ACL surface with hydrogen radicals. Three-dimensional (3D) nonlinear finite element method analysis confirmed that the increase in surface stress is large enough to cause the wiggling. These results also suggest that etching with hydrogen compound gases using an ACL mask has high potential to cause the wiggling.

Role of Oxygen in Amorphous Carbon Hard Mask Plasma Etching

“…Additionally, in both current and next-generation semiconductor processing, the ACL hard mask, in conjunction with a complex gas mixed plasma, can be leveraged to achieve high etching selectivity in HAR etching. − In industrial semiconductor plasma etching, three or more complex gas mixtures, which are based on inert gases such as argon and composed of a combination of oxygen, C x F y , and C x H y F z gases, are used to control the etch profile and selectivity. , In a complex gas mixture, inert gas is injected to control the plasma density and degree of dissociation rate, and a trace amount of oxygen gas is injected to control the degree of precursors and deposited polymers produced in the plasma. , However, the high removability of the ACL by oxygen can result in unwanted sidewall etching of the ACL hard mask when exposed to a processing plasma containing oxygen gas, leading to a distorted etch profile and increased pattern opening. Thus, it is imperative to analyze and regulate the etching characteristics of the ACL when using oxygen gas as the profile of the hard mask holds a significant influence on the profile of the bottom layer to be etched, and thus greatly impacts the device quality and performance.. , …”

“…30,33 However, the high removability of the ACL by oxygen can result in unwanted sidewall etching of the ACL hard mask when exposed to a processing plasma containing oxygen gas, leading to a distorted etch profile and increased pattern opening. Thus, it is imperative to analyze and regulate the etching characteristics of the ACL when using oxygen gas as the profile of the hard mask holds a significant influence on the profile of the bottom layer to be etched, and thus greatly impacts the device quality and performance.. 22,34 However, even though the etch characteristics of the ACL hard mask, such as etch rate, etch profile of mask, and mask damage (wiggling, notching, and pattern collapse) may differ caused by the small amount of oxygen gas and inert gas species, prior studies have focused on the etching characteristics of conductive or dielectric underlayers and not on those of the ACL mask. In addition, studies on the etch properties (etch rate, damage, and etch selectivity) of ACL hard masks have been scarce in plasma etching technologies, despite their importance in the manufacturing process of current and nextgeneration devices, such as 3D DRAM and vertical-NAND flash memory with high-aspect-ratio patterns.…”

“… 30 , 33 However, the high removability of the ACL by oxygen can result in unwanted sidewall etching of the ACL hard mask when exposed to a processing plasma containing oxygen gas, leading to a distorted etch profile and increased pattern opening. Thus, it is imperative to analyze and regulate the etching characteristics of the ACL when using oxygen gas as the profile of the hard mask holds a significant influence on the profile of the bottom layer to be etched, and thus greatly impacts the device quality and performance.. 22 , 34 …”