Multiheight Contact Via Structures for Multilevel Interconnects
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Solution Overview
Problem
Existing methods for forming multilevel metal interconnect structures with electrically conductive via contacts of different heights are limited by the requirement for lateral discontinuity of electrodes and restrict design density and processing complexity.
Innovation Solution
A method involving a stack of alternating sacrificial layers and insulating layers over a substrate, where contact openings are formed perpendicular to the substrate, and sacrificial layers are removed to create recesses for via contacts, allowing for self-aligned insulating liners and simultaneous deposition of via contacts and electrodes, enabling high-density interconnects without significant design restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lateral discontinuity of electrodes is required to form via contacts of different heights, then via contact height differentiation is achieved, but design density and processing complexity are restricted
Solution Approach 1:
The patent segments the electrode formation process by introducing sacrificial layers at different heights within the stack. These sacrificial layers are selectively removed to create recesses, allowing via contacts to be formed at different levels without requiring lateral discontinuity of the electrodes themselves. This segmentation enables independent control of via contact heights while maintaining continuous electrode structures.
Solution Approach 2:
The patent uses sacrificial layers as intermediary structures to achieve via contact height differentiation. These temporary structures are deposited conformally over the electrode stack, then selectively removed to create the desired recesses. The sacrificial layers mediate between the continuous electrode structure and the differentiated via contact heights, eliminating the need for lateral electrode discontinuity.
2Adaptability or versatility
If continuous electrode structures are used, then design flexibility is improved, but via contact height differentiation becomes difficult
Solution Approach 1:
The patent applies preliminary action by depositing sacrificial layers conformally over the continuous electrode structure before via contact formation. These pre-deposited sacrificial layers are then selectively removed to create recesses, enabling via contact height differentiation while preserving the continuity of the underlying electrode structures. This preliminary placement of sacrificial layers allows flexible electrode design without compromising via contact height control.
Data Source
AI summary
Contact openings extending to sacrificial layers located at different depths can be formed by sequentially exposing a greater number of openings in a mask layer by iterative alternation of trimming of a slimming layer over the mask layer and an anisotropic etch that recesses pre-existing contact openings by one level. In one embodiment, pairs of an electrically conductive via contact and electrically conductive electrodes can be simultaneously formed as integrated line and via structures. In another embodiment, encapsulated unfilled cavities can be formed in the contact openings by non-conformal deposition of a material layer, electrically conductive electrodes can be formed by replacement of portions of the sacrificial layers, and the electrically conductive via contacts can be subsequently formed on the electrically conductive electrodes. Electrically conductive via contacts extending to electrically conductive electrodes located at different level can be provided with self-aligned insulating liner.