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:
Apr. 02, 2013
Filed:
Jan. 25, 2007
Zin-chang Wei, Hsin-Chu, TW;
Tsung-min Huang, Lujhou, TW;
Ming-tsao Chiang Chiang, Jhubei, TW;
Cheng-chen Calvin Hsueh, Linkou, TW;
Zin-Chang Wei, Hsin-Chu, TW;
Tsung-Min Huang, Lujhou, TW;
Ming-Tsao Chiang Chiang, Jhubei, TW;
Cheng-Chen Calvin Hsueh, Linkou, TW;
Taiwan Semiconductor Maufacturing Co., Ltd., Hsin-Chu, TW;
Abstract
A method and system for controlling a silicon nitride etching bath provides the etching bath including phosphoric acid heated to an elevated temperature. The concentration of silicon in the phosphoric acid is controlled to maintain a desired level associated with a desired silicon nitride/silicon oxide etch selectivity. Silicon concentration is measured while the silicon remains in soluble form and prior to silica precipitation. Responsive to the measuring, fresh heated phosphoric acid is added to the etching bath when necessary to maintain the desired concentration and silicon nitride:silicon oxide etch selectivity and prevent silica precipitation. The addition of fresh heated phosphoric acid enables the etching bath to remain at a steady state temperature. Atomic absorption spectroscopy may be used to monitor the silicon concentration which may be obtained by diluting a sample of phosphoric acid with cold deionized water and measuring before silica precipitation occurs.