Intermediate Separation Layer for BEOL Patterning Reduction
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Solution Overview
Problem
The current semiconductor fabrication process for back-end-of-line (BEOL) processing is costly due to the need for extra patterning steps to access memory arrays, as separation layers interrupt logic connections and require additional processing.
Innovation Solution
An intermediate separation layer is formed within the inter-level dielectric (ILD) layer, which is shorter than the normal ILD layer, allowing access to both the under and top layers with a single patterning step, thereby reducing the number of required patterning steps and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a full-height separation layer is used to seal devices in the memory array, then device isolation is improved, but the number of patterning steps increases and fabrication cost increases
Solution Approach 1:
The separation layer is segmented in height rather than extending through the full height of the ILD layer. The intermediate separation layer is formed only in a first portion of the ILD layer height, leaving the second portion without the separation layer. This segmentation allows different regions to have different isolation characteristics, providing device isolation where needed while maintaining access pathways where required, thereby reducing the number of patterning steps needed.
Solution Approach 2:
The separation layer is applied locally rather than uniformly across the entire ILD layer height. By forming the intermediate separation layer only in a portion of the ILD layer, the structure achieves local device isolation in the memory array region while maintaining open access pathways in other regions. This local quality approach eliminates the need for additional full-height separation layers and associated patterning steps.
2Ease of operation
If extra patterning steps are added to access memory arrays through separation layers, then logic connection access is improved, but fabrication cost increases
Solution Approach 1:
The intermediate separation layer is segmented both in height and in lateral extent, creating a structure that provides logic connection access without requiring additional patterning steps. The separation layer is present only in specific regions and heights, allowing underlying structures to be accessed through openings in the ILD layer without needing separate patterning operations for full-height separation layers.
3Reliability
If the separation layer extends through the full ILD layer height, then complete device sealing is achieved, but the number of required openings and patterning steps increases
Solution Approach 1:
The separation layer is segmented vertically, extending only through a first portion of the ILD layer height rather than the full height. This vertical segmentation provides sufficient device sealing for the memory array devices while leaving the upper portion of the ILD layer open for access pathways, eliminating the need for multiple patterning steps to create openings through full-height separation layers.
Solution Approach 2:
Instead of forming a separation layer through the full ILD layer height, the intermediate separation layer is formed only to the extent necessary for device sealing. This partial action approach provides adequate sealing functionality without the excessive action of creating a full-height separation layer that would require additional openings and patterning steps, thereby improving fabrication efficiency.
Data Source
AI summary
Embodiments herein describe techniques for a semiconductor device having an interconnect structure including an inter-level dielectric (ILD) layer between a first layer and a second layer of the interconnect structure. The interconnect structure further includes a separation layer within the ILD layer. The ILD layer includes a first area with a first height to extend from a first surface of the ILD layer to a second surface of the ILD layer. The ILD layer further includes a second area with a second height to extend from the first surface of the ILD layer to a surface of the separation layer, where the first height is larger than the second height. Other embodiments may be described and/or claimed.