Dry etching with gas chopping without rippled sidewalls

Abstract

In the last years, silicon micromachining techniques based on high aspect ratio reactive ion etching with gas chopping have been developed. There the gas flow of etching and deposition gas precursors is chopped which results in controllable sidewall passivation and high anisotropy. However, the rippled sidewalls are a serious limit for various applications. We report on the development of a novel gas chopping etching technique (GCET) process in order to achieve a smooth (rippled free) sidewall surface. As the direct etch mask, we used a 1 or 2-μm-thick resist layer, which was lithographically patterned. The novelty of the process consists in the replacing of the isotropic etching step by an anisotropic etching step. In this way we omit the main source for sidewall ripples. GCET combined with inductively coupled plasmas and fluorine chemistry provide very high etch rates and good control of the sidewall slope. These techniques also can be applied to conventional reactive ion etching equipment with Cl or F based plasma chemistry. However, the techniques used in this study have lower selectivity (in range of 30) than the conventional GCET. A SiON/Si selectivity as high as 50 has been achieved.

A Gap Reduction and Manufacturing Technique for Thick Oxide Mask Layers With Multiple-Size Sub-<tex>$mu$</tex>m Openings

“…However, the application of recipes developed for m-scale trenches in the sub-m domain may result in excessive undercuts as well as rough and exceedingly scalloped (relative to the gap side) trench sidewalls. Numerous approaches have been studied to reduce the sidewall roughness and increase the aspect ratio of trenches fabricated using the Bosch process [10], [11]. All these efforts target highly anisotropic etching step and efficient sidewall passivation.…”

Fabrication of open stencil masks with asymmetric void ratio for the ion projection lithography space charge experiment

“…The structures in the resist have been transferred into the membrane by reactive ion etching ͑RIE͒ processes using fluorine chemistry, or by inductively coupled plasma ͑ICP͒ etching using a gas chopping process. 7 The fabrication process is shown in Fig. 4.…”

Comparison of deep silicon etching using SF6/C4F8 and SF6/C4F6 plasmas in the Bosch process

“…[3][4][5][6][7][8] However, C 4 F 8 ͑octafluorocyclobutane͒ is perfluoro carbon ͑PFC͒, which is considered to be problematic from an environmental point of view because of its long atmospheric lifetime, high global warming potential, and strong infrared absorption. [9][10][11] Originally, PFCs have been extensively used as etchants for silicon and silicon dioxide in microelectronics industries.…”