Super Via Structure BEOL Integration via Selective Nitride Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current processes for forming super via structures in back end of line (BEOL) processing often result in necking profiles and incomplete metal filling due to high aspect ratio reactive ion etching, and the presence of multiple nitride layers complicates alignment marker visibility.
Innovation Solution
The method involves forming semiconductor devices with a structure including interconnect levels separated by nitride cap layers, where selected portions of the second nitride cap layer are removed to expose dielectric material, allowing for the deposition and patterning of a third interconnect level to create super via structures that span two interconnect levels without a landing pad, using a high aspect ratio etch recipe focused on dielectric material only, and improved visibility for alignment markers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If high aspect ratio reactive ion etching is used to form super via structures, then via depth is increased to span multiple interconnect levels, but necking profiles and incomplete metal filling occur
Solution Approach 1:
The patent segments the etching process into two distinct stages: first etching through dielectric layers to a stop at the nitride cap layer, then performing a second etch through the nitride cap layer to complete the via. This segmentation prevents necking profiles by avoiding excessive etch depth in a single step, ensuring complete metal filling, and maintaining via profile uniformity throughout the super via structure.
2Device complexity
If multiple nitride cap layers are present between interconnect levels, then interconnect level separation is achieved, but alignment marker visibility is reduced
Solution Approach 1:
The patent extracts or removes portions of the nitride cap layer to create openings that expose underlying alignment markers. This selective removal maintains the nitride cap layer's function of separating interconnect levels while eliminating the obstruction it causes to alignment marker visibility during lithography and alignment processes.
3Productivity
If super via structures are formed to span two interconnect levels without a landing pad, then interconnect density is increased, but etch profile control becomes more difficult
Solution Approach 1:
The patent performs preliminary etching actions to create via openings that extend through dielectric layers to a precise stop at the nitride cap layer before forming the super via structure. This preliminary action establishes controlled etch profiles and precise via geometry, enabling subsequent metal filling while maintaining manufacturing precision and achieving high interconnect density through the super via structure spanning two interconnect levels without a landing pad.
Data Source
AI summary
Semiconductor devices including super via structures and BEOL processes for forming the same, according to embodiments of the invention, generally include removing selected portions of a nitride cap layer intermediate interconnect levels, wherein the selected portions correspond to the regions where the super via structure is to be formed and where underlying overlay alignment markers are located.