Polycrystalline-silicon etch with low-peroxide apm
AssigneeIntermolecular, Inc.
InventorGregory Nowling
Life of this patent
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Abstract
Polycrystalline silicon (poly-Si) can be thoroughly removed without significant effect on adjacent oxides by an aqueous solution of ammonium hydroxide with smaller concentrations of hydrogen peroxide than are normally used in ammonia-peroxide mixture (APM) formulations used for cleaning. The etching selectivity of poly-Si relative to oxides can be widely tuned by varying the hydrogen-peroxide concentration. Compared to other formulations used to remove poly-Si dummy gates in logic-node fabrication, such as TMAH, these aqueous solutions are less hazardous to workers and the environment.
Claims19
A method of etching polycrystalline silicon on a substrate, the method comprising:
- preparing an aqueous solution comprising ammonium hydroxide and hydrogen peroxide, where a ratio of the ammonium hydroxide to the hydrogen peroxide is within a range of about 10:1-1000:1, and
- exposing the polycrystalline silicon to the aqueous solution at a temperature between about 25 C and 80 C.
An etchant for polycrystalline silicon, the etchant comprising:
- an aqueous solution comprising ammonium hydroxide and hydrogen peroxide,
- where a ratio of the ammonium hydroxide to the hydrogen peroxide is within a range of about 10:1-1000:1.
A method of replacement-metal-gate integration, the method comprising:
- depositing a gate oxide,
- depositing polycrystalline silicon over the gate oxide,
- selectively patterning the polycrystalline silicon to create a dummy gate,
- depositing an interlayer dielectric over and around the dummy gate,
- removing the interlayer dielectric from a surface of the dummy gate, and
- exposing the dummy gate and the interlayer dielectric to an aqueous solution at a temperature between about 25 C and about 8° C. until the polycrystalline silicon of the dummy gate is etched away, creating an opening in the interlayer dielectric with a surface of the gate oxide comprising a bottom of the opening,
- where the aqueous solution comprises ammonium hydroxide and hydrogen peroxide in a ratio between about 10:1 and 1000:1.
Dependencies are inferred from the claim text.