Single-mask, three-dimensional microfabrication of high-aspect-ratio structures in bulk silicon using reactive ion etching lag and sacrificial oxidation

Abstract

This letter describes a simple method for three-dimensional microfabrication of complex, high-aspect-ratio structures with arbitrary surface height profiles in bulk silicon. The method relies on the exploitation of reactive ion etching lag to simultaneously define all features using a single lithographic masking step. Modulation of the mask pattern openings used to define the features results in etch depth variation across the pattern, which is then translated into surface height variation through removal of the superstructure above the etched floors. Utilization of a nonisotropic superstructure removal method based on sacrificial oxidation enables definition of high-aspect-ratio structures with vertical sidewalls and fine features. The utility of the approach is demonstrated in the fabrication of a sloping electrode structure for application in a hybrid micromirror device.

Fabrication of photonic crystals and Nanocavities

“…Figure 4.6(C) confirms that although initially the aspect ratio increases rapidly, the increase in aspect ratio levels off as etching progresses. At etching durations below 12 minutes we observe that narrower pores have higher aspect ratios, similar to results reported for large one-dimensional trenches [160,176]. At etching durations exceeding t = 12 minutes the aspect ratio appears to reach a maximum.…”

“…Since deep reactive ion etching (DRIE), and more specifically the Bosch process [126], is already used in the semiconductor industry, it is interesting to consider this process for etching nanopores. The use of the Bosch process in the semiconductor industry is exemplified by the fabrication of sloping electrodes [160], antireflection structures [161], and high-speed electronics [154]. Recently the Bosch process has also been used to etch high aspect ratio pores with large diameters of 6 µm and interpore distances exceeding 9 µm in silicon [162], and pores with diameters of 1 µm with interpore distances of around 2.3 µm [158].…”

A Titanium Based Flat Heat Pipe

“…Bulk titanium processing techniques have been developed since 2001 for harsh environment microsystems such as mirrors [2], electrodes [6] and relays [7]. Argon and chlorine are usually utilized for dry etching of Ti [2,8].…”

Mask-shift filtering for forming microstructures with irregular profile

“…5 The half-tuning mask method is the other approach to form the irregular continuous relief. Other gray scale techniques such as high-energy beam sensitive glass process [8][9][10] need exposure under the E-beam, and have the disadvantages of limited fabrication area and high cost. Then relief depth of the sampled areas is encoded by means of tuning pixel space or pixel size.…”