Bit Line Contact Undercut Structure for Misalignment Tolerance
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Solution Overview
Problem
The challenge in semiconductor memory device manufacturing is the occurrence of short circuits due to misalignment during the formation of bit line contact openings, which narrows the process window and reduces manufacturing yield.
Innovation Solution
The solution involves creating an under-cut structure at the edge of the bit line contact opening, which increases the bottom width of the opening compared to the top width, thereby reducing the risk of short circuits and expanding the process window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bit line contact opening is formed with vertical walls, then the manufacturing process is simple, but misalignment occurs leading to short circuits
Solution Approach 1:
The bit line contact opening is designed with an asymmetric under-cut structure where the top width is smaller than the bottom width. This asymmetric geometry creates a self-aligning feature that tolerates misalignment during manufacturing, preventing short circuits while maintaining process simplicity
Solution Approach 2:
The under-cut structure is formed in advance during the contact opening formation process, creating a built-in tolerance zone that cushions against subsequent misalignment. This preemptive structural design ensures that even if alignment drifts occur during later processing steps, the asymmetric geometry prevents harmful short circuits
2Length of moving object
If the process window is narrowed due to continuous miniaturization, then product specification is met, but manufacturing yield decreases
Solution Approach 1:
The invention changes the geometric parameters of the bit line contact opening from a conventional vertical-walled cylinder to an under-cut structure with specific width ratios. By optimizing the top and bottom width parameters, the design achieves both miniaturization and increased process tolerance, thereby maintaining high manufacturing yield at smaller device dimensions
Data Source
AI summary
A semiconductor memory device and a manufacturing method thereof are provided in the present invention. An under-cut structure is formed at an edge of a bit line contact opening in the process of forming the bit line contact opening for avoiding short problems caused by alignment shifting, and the process window of the process of forming the bit line contact opening may be improved accordingly.