Silicon Oxide-Nitride-Oxide Via Patterning With Single-Step Etching
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Solution Overview
Problem
Existing microfabrication methods for patterning silicon oxide-silicon nitride-silicon oxide stacks are inefficient, requiring multiple etch processes and masks, which increases processing time and cost.
Innovation Solution
A method involving a single isotropic etch process using a buffered oxide etch solution to pattern a silicon oxide-silicon nitride-silicon oxide stack, allowing for the formation of a via cavity with controlled sidewall profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple etch processes and masks are used to pattern the silicon oxide-silicon nitride-silicon oxide stack, then the patterning can be achieved with conventional methods, but the processing time and cost increase significantly
Solution Approach 1:
The patent combines multiple etch processes into a single isotropic etch process that simultaneously patterns all three layers (silicon oxide, silicon nitride, and silicon oxide) of the stack. This merging of processes eliminates the need for sequential etching steps and multiple masks, directly reducing processing time while maintaining patterning precision through the selective etch rates of the different materials in the buffered oxide etch solution.
2Manufacturing precision
If multiple etch processes and masks are used to pattern the silicon oxide-silicon nitride-silicon oxide stack, then the patterning can be achieved with conventional methods, but the processing cost increases
Solution Approach 1:
The patent merges multiple etch processes and masks into a single isotropic etch process using a buffered oxide etch solution. This consolidation eliminates the need for multiple process steps, masks, and associated cleaning and preparation operations, directly reducing manufacturing cost while maintaining the ability to achieve precise patterning through the inherent selectivity of the etch solution对不同材料的差异化蚀刻速率.
3Productivity
If dry etching processes are used to pattern the silicon oxide-silicon nitride-silicon oxide stack, then the etching can be performed with standard equipment, but potential damage occurs to the structure
Solution Approach 1:
The patent replaces the mechanical/physical dry etching process with a chemical wet etching process using a buffered oxide etch solution. This substitution eliminates the mechanical stress and potential damage associated with dry etching while maintaining high etching efficiency through the chemical reactivity of the buffered solution with the silicon oxide and silicon nitride layers, thereby preserving structure integrity.
4Productivity
If a single isotropic etch process is used to pattern the silicon oxide-silicon nitride-silicon oxide stack, then the processing steps are reduced and throughput is enhanced, but precise control of sidewall profiles is required
Solution Approach 1:
The patent utilizes parameter changes in the form of different etch rates for different materials within the same isotropic etch process. The buffered oxide etch solution is formulated to etch silicon oxide and silicon nitride at different rates, allowing precise control of sidewall profiles to form the desired hourglass shape. This parameter-based control enables single-step processing with high throughput while maintaining manufacturing precision through the inherent material selectivity of the etch chemistry.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces processing steps and costs, enhances throughput, and avoids potential damage from dry etching processes, while achieving precise sidewall profiles for microfabricated structures.
Implementation Method 1
forming a via cavity extending through the layer stack and down to a top surface of the conductive material portion by isotropically etching portions of the second silicon oxide layer, the silicon nitride layer, and the first silicon oxide layer
Implementation Method 2
A method involving a single isotropic etch process using a buffered oxide etch solution to pattern a silicon oxide-silicon nitride-silicon oxide stack
Data Source
AI summary
A layer stack is formed over a conductive material portion located on a substrate. The layer stack contains a first silicon oxide layer, a silicon nitride layer formed by chemical vapor deposition, and a second silicon oxide layer. A patterned etch mask layer including an opening is formed over the layer stack. A via cavity extending through the layer stack and down to the conductive material portion is formed by isotropically etching portions of the layer stack underlying the opening in the patterned etch mask layer using an isotropic etch process. A buffered oxide etch process may be used, in which the etch rate of the silicon nitride layer is less than, but is significant enough, compared to the etch rate of the first silicon oxide layer to provide tapered straight sidewalls on the silicon nitride layer. An optical device including a patterned layer stack can be provided.