Dry etching of Si is critical in satisfying the demands of the
micromachining industry. The micro-electro-mechanical systems (MEMS) community
requires etches capable of high aspect ratios, vertical profiles, good feature
size control and etch uniformity along with high throughput to satisfy
production requirements. Surface technology systems' (STS's) high-density
inductively coupled plasma (ICP) etch tool enables a wide range of
applications to be realized whilst optimizing the above parameters.
Components manufactured from Si using an STS ICP include accelerometers and
gyroscopes for military, automotive and domestic applications. STS's advanced
silicon etch (ASETM) has also allowed the first generation of
MEMS-based optical switches and attenuators to reach the marketplace. In
addition, a specialized application for fabricating the next generation
photolithography exposure masks has been optimized for 200 mm diameter wafers,
to depths of ~750 µm.
Where the profile is not critical, etch rates of greater than
8 µm min-1 have been realized to replace previous methods such as wet
etching. This is also the case for printer applications. Specialized
applications that require etching down to pyrex or oxide often result in the
loss of feature size control at the interface; this is an industry wide
problem. STS have developed a technique to address this.
The rapid progression of the industry has led to development of the STS ICP etch tool,
as well as the process.
High density plasmas are beginning to dominate the market for advanced anisotropic silicon etching for MEMS applications. This paper looks at the reasons behind this dominance for high etch rate, deep anisotropic etching. A discussion of anisotropic etch mechanisms highlights the need for sidewall passivation to meet these requirements. Results are presented of a novel room temperature advanced silicon etch process : 2 p.m/mm; selectivity to resist (and 1 50:1 to oxide); up to 30: 1 aspect ratio; 500 im depth capability; using a non-toxic non-corrosive environmentally acceptable fluorine based chemistry.
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