The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 29, 2014
Filed:
Jul. 08, 2011
Alvin Gabriel Stern, Newton, MA (US);
Alvin Gabriel Stern, Newton, MA (US);
Other;
Abstract
A high purity, non-toxic, environmentally friendly method for anisotropically etching single crystal silicon and etching polysilicon, suitable for microelectronics, optoelectronics and microelectromechanical (MEMS) device fabrication, using high purity aqueous ammonium hydroxide (NHOH) solution generated at the point of use, is presented. The apparatus of the present invention supports generation of high purity aqueous NHOH solution from ammonia NHgas dissolved into distilled/deionized water and maintained in equilibrium with an overpressure of NH, within a hermetically enclosed chamber at the optimal temperature between 70-90° C., preventing evaporation of NHgas from aqueous NHOH solution for achieving a high anisotropic etching rate. Other liquid anisotropic etching methods for silicon may use tetramethylammonium hydroxide (TMAH). In contrast to carbon containing TMAH, the NHgas and HO precursors of NHOH etchant eliminate risk for solid residues to be deposited on silicon due to being composed entirely of elements having a gaseous form at room temperature.