Oblique-Directional Plasma Etching of Si Using a Faraday Cage

Abstract

A method for controlling the direction of Si etch profiles was developed using a Faraday cage system and a conventional gas-chopping process. The gas-chopping process consisted of sequentially alternating etching and deposition steps using SF6 and normalC4normalF8 plasmas, respectively. The single-directional oblique etching was achieved using a Faraday cage having a top horizontal grid plane, inside of which a tilted substrate holder was placed. The double-directional etching was also obtained using a cage having two slanted grid planes. The double-directional etch profiles were either symmetrically or asymmetrically oblique according to the angle of the sample holder. During the oblique-directional etching, the shadowing effect by the bombardment of tilt-angled ions was found to affect etch profiles. Due to the shadowing effect, the top width of the pattern and the etch depth decreased as the ion-incident angle increased, and a fluorocarbon film accumulated in the shadow area. By regulating the process conditions to allow a higher mask selectivity, an oblique Si etch profile with a high aspect ratio (etch depth=5700nm and aspect ratio=9.5 ) was obtained.

Tipping solutions: emerging 3D nano-fabrication/ -imaging technologies

“…Recently, researchers have begun to reconsider the venerable Faraday cage angled-etching (FCAE) technique [101] as it has proven itself to be suitable method to adjust etch angle during dry plasma etching [102]. This method was used to produce free-standing cantilievers, ring resonators [103], and other photonic nanostructures [104] in silicon [102,103], diamond [104] or even quartz [103]; thus, FCAE should work virtually on any material that can be etched by RIE.…”

“…This method was used to produce free-standing cantilievers, ring resonators [103], and other photonic nanostructures [104] in silicon [102,103], diamond [104] or even quartz [103]; thus, FCAE should work virtually on any material that can be etched by RIE. A schematic representation of FCAE setup and several nano-fabrication examples are shown in Figure 11. …”

Device-level and module-level three-dimensional integrated circuits created using oblique processing

“…Using a Faraday cage, the direction of the ion acceleration can be altered so that oblique etching will occur. [14][15][16][17] We have demonstrated patterned oblique etching using both reactive ion etch and inductively coupled plasma etch systems using a Faraday cage to direct the etchant species obliquely. Our Faraday cage was machined into a 45∕45∕90 wedge out of a solid stainless steel block.…”

Semi-isotropic surface etching of diamond using a Faraday cage

“…This etching technique can also be applied to etch other semiconductor materials and no additional mask is required to be deposited on the substrates. There are a few reports of using the Faraday cage to etch Si [18,19], oblique incident angle etching of SiO 2 , Si 3 N 4 [20] and to etch diamond at certain angles [21]. Detailed modelling and functionality of Faraday cages in plasma etching can be found in [18][19][20][22][23][24][25].…”

“…There are a few reports of using the Faraday cage to etch Si [18,19], oblique incident angle etching of SiO 2 , Si 3 N 4 [20] and to etch diamond at certain angles [21]. Detailed modelling and functionality of Faraday cages in plasma etching can be found in [18][19][20][22][23][24][25]. Furthermore, to etch deeper structures with isotropic profile, selection of a suitable masking material is difficult as photoresist has a very low etching selectivity [26].…”