1 research outputs found
Self-Anchored Catalyst Interface Enables Ordered Via Array Formation from Submicrometer to Millimeter Scale for Polycrystalline and Single-Crystalline Silicon
Defying
text definitions of wet etching, metal-assisted chemical etching (MacEtch),
a solution-based, damage-free semiconductor etching method, is directional,
where the metal catalyst film sinks with the semiconductor etching
front, producing 3D semiconductor structures that are complementary
to the metal catalyst film pattern. The same recipe that works perfectly
to produce ordered array of nanostructures for single-crystalline
Si (c-Si) fails completely when applied to polycrystalline Si (poly-Si)
with the same doping type and level. Another long-standing challenge
for MacEtch is the difficulty of uniformly etching across feature
sizes larger than a few micrometers because of the nature of lateral
etching. The issue of interface control between the catalyst and the
semiconductor in both lateral and vertical directions over time and
over distance needs to be systematically addressed. Here, we present
a self-anchored catalyst (SAC) MacEtch method, where a nanoporous catalyst film is used to produce nanowires through the pinholes, which in turn
physically anchor the catalyst film from detouring as it descends.
The systematic vertical etch rate study as a function of porous catalyst
diameter from 200 to 900 nm shows that the SAC-MacEtch not only confines
the etching direction but also enhances the etch rate due to the increased
liquid access path, significantly delaying the onset of the mass-transport-limited
critical diameter compared to nonporous catalyst c-Si counterpart.
With this enhanced mass transport approach, vias on multistacks of
poly-Si/SiO<sub>2</sub> are also formed with excellent vertical registry
through the polystack, even though they are separated by SiO<sub>2</sub> which is readily removed by HF alone with no anisotropy. In addition,
320 μm square through-Si-via (TSV) arrays in 550 μm
thick c-Si are realized. The ability of SAC-MacEtch to etch through
poly/oxide/poly stack as well as more than half millimeter thick silicon
with excellent site specificity for a wide range of feature sizes
has significant implications for 2.5D/3D photonic and electronic device
applications