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Sloped via holes (45 degrees-50 degrees sidewalls) are etched in SiO(2) with a standard isotropic etch by depositing a thin blanket layer of plasma deposited oxide on the SiO(2) prior to etching.
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Controllable Method of Etching Openings into SiO(2) with a 45 Degree
Sloped via holes (45 degrees-50 degrees sidewalls) are etched in SiO(2)
with a standard isotropic etch by depositing a thin blanket layer of plasma
deposited oxide on the SiO(2) prior to etching.
In semiconductor microlithography, one routinely etches openings into SiO(2)
(sputtered or thermally grown). While it is easy to etch holes with relatively steep
sidewalls, it is often desired that the sidewalls be more gently tapered. An
example is the case where metallization (wiring) is to be deposited into the hole
and leading out of it. Since with the methods of metallization commonly used the
metallization thins out as it climbs over a steep sidewall, one can expect reliability
problems unless the size of the wiring is increased, which is also undesirable.
For heavy current densities, sidewall angles around 45-50 degrees are desired to
minimize the thinning out of metallization.
This method controllably etches holes into SiO(2) with 45-50
degrees sidewall angles. The process is as follows: 1. Just prior to resist coating, blanket deposit a thin (2000
Angstroms or less) layer of plasma deposited SiO(x). 2. Resist coat, bake, expose, develop, etc., as normally is
done for wet etching of SiO(2). 3. Etch openings (buffered HF, for example). 4. Strip resist. 5. Plasma SiO(x) can be left in place, or, if no allowance was
made for a very slight extra thickness in the topology, it can