Anisotropic Dry Etching of S1O₂ on Si and its Impact on Surface and Near-Surface Properties of the Substrate.

Abstract

In the present paper structural and chemical changes which can occur in the surface and near-surface properties of the substrate during anisotropic dry etching of SiO2 on Si will be reviewed.Silicon specimens which had been etched in CF4/X%H2 (X≤40) have been characterized by X-ray photoelectron emission spectroscopy, He ion channeling, H profiling and Raman scattering techniques.Key results of our studies are summarized as follows: Plasma exposure of a Si surface leads to the deposition of a thin (≤50Å thick) C,F-film.A Si-carbide containing Si region is formed during RIE which is localized near the fluorocarbon-film/Si interface.The near-surface region (∼30–50Å) of the Si substrate is also heavily disordered as found by ion channeling and Raman scattering.A modified, less damaged Si region has been found in the case of hydrogen-based etching gases, which extends from about 30–50Å from the surface to a depth in extent of 250Å and contains a high concentration (∼ 5 at.%) of H as shown by hydrogen profiling techniques.From the observation of Si-H and Si-H2 vibrational modes by Raman scattering it has been shown that some of the H is bonded to the Si lattice.

Evolution of Damage, Dopant Deactivation, and Hydrogen‐Related Effects in Dry Etch Silicon as a Function of Annealing History

“…The primary thermal donors which are commonly observed in as-grown silicon are related to oxygen. These thermal donors, referred to as "oxygen thermal donors," form in the temperature range between 400 ~ and 550~ Annihilation of the oxygen thermal donors occurs after a short anneal at 650~ Although the exact microscopic structure of the oxygen thermal donors is still being debated (3), it is well established that this type of defect gives rise to photoluminescence (PL) at the photon energy of 0.767 eV (4)(5).…”

“…The extent of this bonding damaged layer in the etched material is also dependent on both the chemical and physical aspects of plasma-based etch processes. The physical ion bombardment present during the etch can create bonding (lattice) damage to depths of 100s of angstroms as it disarranges some of the atoms in the etched material (3)(4)(5).…”

Highly Selective Etching of SiO2 over Si3N4 and Si in Capacitively Coupled Plasma Employing C5HF7 Gas

“…Thus, the deep straight profile of HARC and selectivity of SiO 2 etching employing fluorocarbon plasmas over the photoresist (PR) mask and underlying materials such as silicon nitride (SiN) and Si need to be improved for a commercially viable manufacturing technology. [1][2][3][4][5][6][7][8][9][10] For highly selective SiO 2 /SiN and SiO 2 /Si etching using fluorocarbon plasmas, it is well known that the primary mechanism is the selective formation of a thick fluorocarbon film passivated on the surface of the underlying materials such as SiN and Si. In the steady state during etching, Si etch rate is regulated by preventing spontaneous reactions and diffusion of atomic fluorine with the passivated film.…”

Substrate Trenching Mechanism during Plasma and Magnetically Enhanced Polysilicon Etching

“…The etch process used to fabricate this structure must achieve these objectives while maintaining high selectivity to the underlying gate oxide, low dimensional loss, and minimal substrate damage. Conventional RIE processes are inadequate for this application primarily due to the gate oxide and substrate damage caused by high energy charge particle bombardment during processing (2). Our study shows that MERIE with chlorine gas can be used to fabricate sub-half micron polysilicon-gate electrodes without significant ion bombardment damage to the silicon substrate (1).…”