Atmospheric He/O2 plasma jet fine etching with a scanning probe microscope

Abstract

In this study, we investigate a maskless fine etching technology using a He/O2 atmospheric pressure plasma jet (APPJ) assisted by a scanning probe microscope (SPM). The APPJ is localized in the submicrometer range by a nanopipette, which is also used as the probe of the SPM. We improve the rate of submicrometer-scale etching by adding O2 gas to the He source gas. The depth and full width at half maximum of a typical etched dot on a polymethylmethacrylate film were 475 nm and 235 nm, respectively. The etching rate was found to be six times faster with the added gas than without it. We also demonstrate line patterning; the width of the line was found to be 281 nm.

Micromachining of polymers using atmospheric pressure inductively coupled helium plasma localized by a scanning nanopipette probe microscope

“…As shown in these figures, the two-line grooves with a depth of 0.3 µm and a width of 0.5 µm were successfully processed with high reproducibility. The drawing speed of 20 µm s −1 was much faster than that obtained with LF-APPJs in our previous studies: the drawing speed of a photoresist film etched by LF-APPJ with He gas was 0.5 µm s −1 [24], and the drawing speed of a PMMA film etched by LF-APPJ with He/O 2 mixed gas was 5 µm s −1 [25]. The plasma density of the ICP jet used in this study is much higher than that of the LF-APPJs in previous reports, allowing for improvement in etching rate of the line groove.…”

“…In this system, the nanopipette was used not only as the discharge nozzle but also as the SPM probe. Furthermore, to improve the etching rate of the system, the APPJ with mixed He/O 2 gas was used for local etching of a polymethyl methacrylate (PMMA) film [25]. However, in these earlier studies, etching was performed using low-frequency APPJs (LF-APPJs) generated by applying low-frequency voltages.…”

Compared discharge characteristics and film modifications of atmospheric pressure plasma jets with two different electrode geometries

“…In recent years, atmospheric pressure plasma jets (APPJ) have garnered significant attention in materials processing, owing to their pivotal role in material surface modification, etching, and film deposition. [1][2][3][4][5][6][7][8][9][10] Li et al [11,12] investigated mechanisms of APPJ plume formation and morphology transition by electrical and spectral measurements as well as fast photography. An APPJ can generate a plasma plume that propagates away from the confinement of electrodes and into the ambient atmosphere.…”

“…APPJ sources have been widely used for this purpose, with different types of devices available based on the electrode structure. The most common ones include single-rod electrode, [11,12,15,16] rod-ring (or needle-ring), [4,6,10,17] singlering, [18] and double-ring. [5,7,8,19] APPJ devices, all of which have been used by researchers for surface modification of polymer films.…”

Sub-micrometer plasma-enhanced chemical vapor deposition using an atmospheric pressure plasma jet localized by a nanopipette scanning probe microscope

“…These microcantilevers require complex microfabrication processes and are difficult to use owing to their high manufacturing costs. Previous studies have developed localized APPJs using a nanopipette that can be easily and inexpensively prepared by thermally pulling a capillary glass tube [36][37][38][39]. A nanopipette with a tip aperture of sub-micrometer diameter was used not only as a nozzle to generate localized APPJs but also as a probe for scanning probe microscopy (SPM).…”