Self-Aligned Via Contact Structure to Prevent Overlay Shorts
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Solution Overview
Problem
High-density semiconductor devices face increased likelihood of electrical shorts due to overlay inaccuracies, leading to bridge formation and 'tiger tooth' conditions, which cause voltage breakdown failures, especially with thick contact etch stop layers.
Innovation Solution
Implementing a tri-layered interlayer dielectric (ILD) structure comprising a planar dielectric spacer liner with aligned openings and a self-aligned etch stop dielectric liner, using a two-step etching process to form contact and interconnect via structures, mitigating bridge and tiger tooth issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device density is increased to improve productivity, then more devices can be manufactured per unit area, but the likelihood of unintentional electrical connection (shorts) increases due to reduced spacing between devices
Solution Approach 1:
The patent segments the contact etch stop layer into multiple thinner layers (first contact etch stop layer and second contact etch stop layer) separated by an intermediate layer. This segmentation reduces the risk of overlay-induced shorts by distributing the stop function across multiple layers, making it less sensitive to overlay errors while maintaining device density.
Solution Approach 2:
The patent introduces an intermediate layer between the first and second contact etch stop layers that acts as a mediator. This intermediate layer provides an additional protective barrier that reduces the likelihood of electrical shorts, allowing higher device density without proportionally increasing short risk.
2Reliability
If a thick contact etch stop layer is used to prevent electrical shorts, then reliability improves, but overlay inaccuracies cause bridge formation and tiger tooth conditions leading to voltage breakdown
Solution Approach 1:
The thick contact etch stop layer is segmented into multiple thinner layers (first contact etch stop layer and second contact etch stop layer) separated by an intermediate layer. This segmentation maintains the total thickness for reliable short prevention while reducing sensitivity to overlay errors, as each individual layer is thinner and less prone to bridge formation and tiger tooth conditions.
Solution Approach 2:
The patent addresses the overlay accuracy problem by transitioning from a single-layer approach to a multi-layer vertical structure. By distributing the etch stop function across multiple layers in the vertical dimension, the system reduces the impact of horizontal overlay inaccuracies that cause bridge formation and tiger tooth conditions.
3Ease of manufacture
If conventional single-layer contact etch stop structure is used to simplify manufacturing, then ease of manufacture is improved, but electrical shorts and tiger tooth issues increase due to overlay variations
Solution Approach 1:
The contact etch stop structure is segmented into multiple layers with an intermediate layer, which provides robust electrical short prevention. While the structure becomes more complex, the segmentation approach actually simplifies the etching process by allowing selective removal of the intermediate layer to define contact openings, reducing the risk of tiger tooth issues compared to etching through a single thick layer.
Data Source
AI summary
A planarization dielectric layer is formed over the semiconductor device on a semiconductor substrate. A device contact via structure is formed through the planarization dielectric layer. A planar dielectric spacer liner is formed over the planarization dielectric layer, and is patterned to provide an opening over the device contact via structure. An etch stop dielectric liner and a via-level dielectric layer are formed over the planar dielectric spacer liner. An interconnect via cavity may be formed through the via-level dielectric layer by a first anisotropic etch process that may be selective to the etch stop dielectric liner, and may be subsequently extended by a second anisotropic etch process that etches the etch stop dielectric liner. An interconnect via structure may be formed in the interconnect via cavity. A bottom periphery of the interconnect via structure may be self-aligned to the opening in the planar dielectric spacer liner.