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The process of the present invention meets the above-described existing needs by forming the above-described etched multilayer structure in which the sidewalls of the Silicon Dioxide layer are substantially upright at a high SiO2 etch rate and at a high selectivity of SiO2 with respect to the underlying Si3 N4. This is accomplished by employing a process for etching the SiO2 layer down to the Si3 N4 stop layer as hereinafter described.

More specifically, a process is provided for etching a multilayer structure to form a predetermined etched pattern therein. The subject process comprises providing the multilayer structure having a plurality of structural layers. The structural layers of the multilayer structure comprise a silicon dioxide outer layer on an underlying silicon nitride stop layer. Then, a chemical etchant protective layer is formed on a major surface of the multilayer structure having a predetermined pattern of openings, thereby exposing areas of the silicon dioxide outer layer corresponding to the predetermined pattern of openings. The exposed areas of the silicon dioxide outer layer are then etched down to the silicon nitride stop layer, at a high Silicon Dioxide etch rate, and at a high level of selectivity of the SiO2 etch rate with respect to the Si3 N4 etch rate, with a fluorinated chemical etchant system. The etching step forms a substantially predetermined etch pattern in the silicon dioxide layer in which the contact sidewalls of said SiO2 are substantially upright.

Here is a news: Yichang fire fog is Silicon Dioxide dust that inhaled suffering from silicosis. The police and fire come to rescue have to wear a gas mask, n-traffic control; advised residents to stay away from the scene as soon as possible. After initial identification: ZTE chemical chlorosilane fires, and chlorosilanes combustion will produce hydrogen chloride gas and Silicon Dioxide. We smell a slight pungent odor is hydrogen chloride, easily soluble in water to produce hydrochloric acid. And what we see is fog Silicon Dioxide dust, if long-term inhalation people, suffering from silicosis. (Three Gorges Evening News)



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