STRUCTURE AND METHOD OF USING OXIDIZED SILICON NITRIDE AS AN ETCH-STOP LAYER FOR WET CHEMISTRY ETCHING OF SILICON NITRIDE
Publication Date: 2003-Sep-04
The IP.com Prior Art Database
Stacked silicon nitride layers are commonly used to produce various semiconductor devices and electrical components. When stacking a first layer of silicon nitride upon a second layer of silicon nitride, an intermediary layer of deposited polysilicon has been used as a means for providing an etch stop for dry etch chemistries. The intermediary deposited polysilicon layer provides a means to stop dry etch chemistry removal of the overlying silicon nitride without continuing through the etch stop layer (polysilicon) into the underlying silicon nitride. While deposited polysilicon provides adequate etch selectivity for common dry etch chemistries to function as a dry etch chemistry etch stop layer, dry etch chemistry processing is more expensive and complicated in comparison to wet etch processing. Additionally, deposition of polysilicon is slow and expensive. Moreover, deposited polysilicon cannot be selectively deposited on silicon nitride; therefore additional masking steps are required to restrict deposition to the underlying silicon nitride layer as is common when forming devices or components. Thus, it would be advantageous to form an etch stop layer between silicon nitride layers that would enable the use of low cost wet etch, wherein the etch stop layer material is inexpensive to form, has high etch selectivity to silicon nitride and can be selectively formed on underlying silicon nitride.