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In the process of this invention the high level of selectivity of the silicon dioxide(SiO2) etch rate with respect to said Si3 N4 etch rate is preferably at least about 10:1, more preferably at least about 20:1, and most preferably at least about 50:1. The process also produces a preferred high SiO2 etch rate which is at least about 2500 angstroms of SiO2 per minute, more preferably at least about 3000 angstroms of SiO2 per minute, and most preferably at least about 4000 angstroms of SiO2 per minute. Furthermore, the selectivity of the SiO2 etch rate with respect to the Si3 N4 etch rate for etching the silicon dioxide outer layer to the silicon nitride stop layer, employing a fluorinated chemical etchant system including an etchant material and an additive material, is preferably at least about 500%, more preferably at least about 1000%, and most preferably at least about 1500%, higher than the selectivity of said SiO2 etch rate with respect to said Si3 N4 etch rate for etching the silicon dioxide outer layer to the silicon nitride stop layer, employing a fluorinated chemical etchant system including the above-described etchant material, but without the subject additive material.

The process of the present invention preferably includes the step of etching the exposed areas of the silicon dioxide outer layer down to the silicon nitride stop layer employing a dry etching process conducted in a magnetically-enhanced etching chamber, more preferably an RIE or an MERIE etching chamber. The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment which proceeds with reference to the drawings.

Internationally renowned industry advisory body "Transparency Market Research" recently released research report, 2014 Global precipitated silicon dioxide market capitalization of $ 2.11 billion, is expected to in 2023 is expected to climb to $ 3.49 billion in 2015 ~ 2023 year average annual growth rate of 5.8%. Scale industrial production of precipitated silica used in raw materials, including sodium silicate, silica sand, sulfuric acid and hydrochloric acid. And other tires, footwear and toothpaste variety of products, often need to use precipitated silica as an additive. Precipitated silica is widely used in rubber, personal care, agricultural chemicals (such as pesticides, fertilizers) and coatings and many other areas. 


 

 

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