Etching Of Silicon In Plasmas Research Articles

Effect of oxygen plasma cleaning on nonswitching pseudo-Bosch etching of high aspect ratio silicon pillars

In dry plasma silicon etching, it is desired to have a high etching rate, a high etching selectivity to mask material, a vertical or controllable sidewall profile, and a smooth sidewall. Since the standard Bosch process (switching between SF6 and C4F8 gases) leads to a wavy/rough sidewall profile, the nonswitching pseudo-Bosch process is developed to give a smooth sidewall needed for nanostructure fabrication. In the process, SF6 and C4F8 gases are introduced to the chamber simultaneously. Here, the authors show that by introducing a periodic oxygen (O2) plasma cleaning step, that is, switching between SF6/C4F8 etching and O2 cleaning, the silicon etching rate can be significantly improved (by up to ∼55%, from 139 to 216 nm/min) without any adverse effect. This is mainly because O2 plasma can remove the fluorocarbon polymer passivation layer at the surface. The etching and cleaning step durations were varied from 5 s to 40 min and from 0 to 60 s, respectively. The fastest etching rates were obtained when the cleaning step takes roughly 10% of the total etching time.

Interfacial Contact is Required for Metal-Assisted Plasma Etching of Silicon.

For decades, fabrication of semiconductor devices has utilized well-established etching techniques to create complex nanostructures in silicon. The most common dry process is reactive ion etching which fabricates nanostructures through the selective removal of unmasked silicon. Generalized enhancements of etching have been reported with mask-enhanced etching with Al, Cr, Cu, and Ag masks, but there is a lack of reports exploring the ability of metallic films to catalytically enhance the local etching of silicon in plasmas. Here, metal-assisted plasma etching (MAPE) is performed using patterned nanometers-thick gold films to catalyze the etching of silicon in an SF6/O2 mixed plasma, selectively increasing the rate of etching by over 1000%. The catalytic enhancement of etching requires direct Si-metal interfacial contact, similar to metal-assisted chemical etching (MACE), but is different in terms of the etching mechanism. The mechanism of MAPE is explored by characterizing the degree of enhancement as a function of Au catalyst configuration and relative oxygen feed concentration, along with the catalytic activities of other common MACE metals including Ag, Pt, and Cu.

Experiment and numerical simulation of melt convection and oxygen distribution in 400-mm Czochralski silicon crystal growth

Single-crystalline silicon materials with large dimensions have been widely used as assemblies in plasma silicon etching machines. However, information about large-diameter low-cost preparation technology has not been sufficiently reported. In this paper, it was focused on the preparation of 400-mm silicon (100) crystal lightly doped with boron from 28-in. hot zones. Resistivity uniformity and oxygen concentration of the silicon crystal were investigated by direct-current (DC) four-point probes method and Fourier transform infrared spectroscopy (FTIR), respectively. The global heat transfer, melt flow and oxygen distribution were calculated by finite element method (FEM). The results show that 28-in. hot zones can replace conventional 32 in. ones to grow 400-mm-diameter silicon single crystals. The change in crucible diameter can save energy, reduce cost and improve efficiency. The trend of oxygen distribution obtained in calculations is in good agreement with experimental values. The present model can well predict the 400-mm-diameter silicon crystal growth and is essential for the optimization of furnace design and process condition.

Research and development of deep anisotropic plasma silicon etching process to form MEMS structures

Process characteristics of deep silicon etching as a function of its operational parameters are investigated. A process of deep anisotropic plasma etching process is developed and optimized to form MEMS silicon structures. The results of the work are used in forming MEMS working structures.

A Bird's Beak Free Local Oxidation Technology Feasible for VLSI Circuits Fabrication

This paper presents a bird's beak free and fully recessed local oxidation-isolation structure employing only conventional LSI processing techniques; no additional masking step is required. A SideWAll Masked Isolation (SWAMI) process employing anisotropic plasma silicon etching and anisotropic plasma silicon nitride etching was implemented to form this new isolation structure. The SWAMI isolation scheme almost completely eliminates the reduction in effective channel width from drawn mask dimensions. The effective channel width obtained with the SWAMI isolation structure is independent of field-oxide thickness unlike the conventions LOCOS process. Fabrication technology and device characteristics of MOSFET's fabricated with the SWAMI isolation structure will be compared with the conventional LOCOS isolated MOSFET's.

A bird's beak free local oxidation technology feasible for VLSI circuits fabrication

This paper presents a bird's beak free and fully recessed local oxidation-isolation structure employing only conventional LSI processing techniques; no additional masking step is required. A SideWAll Masked Isolation (SWAMI) process employing anisotropic plasma silicon etching and anisotropic plasma silicon nitride etching was implemented to form this new isolation structure. The SWAMI isolation scheme almost completely eliminates the reduction in effective channel width from drawn mask dimensions. The effective channel width obtained with the SWAMI isolation structure is independent of field-oxide thickness unlike the-conventional LOCOS process. Fabrication technology and device characteristics of MOSFET's fabricated with the SWAMI isolation structure will be compared with the conventional LOCOS isolated MOSFET's.