Stacked Contact Plug with Low Aspect Ratio
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Solution Overview
Problem
Conventional contact plugs in integrated circuits face issues with increasing aspect ratios due to unscaled thickness of inter-layer dielectric, leading to top corner shortening and uncontrollable bottom profiles, causing circuit degradation and potential device failure.
Innovation Solution
A dual damascene structure with a contact plug having a lower portion in the first dielectric layer and an upper portion in a second dielectric layer, separated by a diffusion barrier layer, and a novel stacked contact plug structure with reduced aspect ratios, formed using a dual or single damascene process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of inter-layer dielectric is not reduced with down-scaling, then the aspect ratio of contact plugs increases, but this causes top corner shortening and uncontrollable bottom profiles
Solution Approach 1:
The contact plug is divided into two separate plugs: a first contact plug in the first dielectric layer and a second contact plug in the second dielectric layer. This segmentation reduces the aspect ratio of each individual plug while maintaining the overall vertical connection, thereby improving profile control and reducing top corner shortening issues
Solution Approach 2:
The solution introduces a vertical stacking dimension by creating multiple dielectric layers with contact plugs at different heights. This dimensional approach allows the contact structure to achieve the necessary electrical connection while maintaining lower aspect ratios in each layer, solving the profile control problem
2Device complexity
If conventional single contact plug structure is used, then the structure is simple, but top corners may be shortened due to optical proximity effects and etching process inaccuracies
Solution Approach 1:
By segmenting the contact plug into first and second contact plugs at different vertical levels, the manufacturing process can better control the top width of each plug. The separation allows for more precise patterning and etching control, reducing top corner shortening caused by optical proximity effects
Solution Approach 2:
The first dielectric layer acts as an intermediary between the semiconductor device and the second dielectric layer. This intermediate layer provides a buffer zone that helps control the transition and profile of the contact plugs, improving manufacturing precision
Data Source
AI summary
An integrated circuit structure includes a semiconductor substrate; a metallization layer over the semiconductor substrate; a first dielectric layer between the semiconductor substrate and the metallization layer; a second dielectric layer between the semiconductor substrate and the metallization layer, wherein the second dielectric layer is over the first dielectric layer; and a contact plug with an upper portion substantially in the second dielectric layer and a lower portion substantially in the first dielectric layer. The contact plug is electrically connected to a metal line in the metallization layer. The contact plug is discontinuous at an interface between the upper portion and the lower portion.