Self-Aligned Contact Hard Mask Scheme for Shorting Prevention
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Solution Overview
Problem
As semiconductor devices shrink, conductive features connecting to layers above and below may become shorted if the etching process misaligns, leading to unintended exposure of adjacent conductive features.
Innovation Solution
A self-alignment scheme is employed using multiple mask layers to protect conductive features during contact opening etching processes, utilizing a second hard mask layer with higher etch selectivity to prevent damage to underlying structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the etching process is used to create contact openings, then conductive features can be connected between layers, but misalignment during etching may expose adjacent conductive features causing shorting
Solution Approach 1:
A mask layer is formed over the conductive feature before the etching process to preliminarily protect it. The mask layer is deposited and patterned in advance to define the contact opening boundaries, ensuring that the etching process does not expose adjacent conductive features. This preliminary protective action prevents misalignment issues during etching.
Solution Approach 2:
The mask layer acts as an intermediary between the etching process and the conductive feature. It mediates the interaction by providing a protective barrier that allows the etching process to proceed without directly exposing the conductive feature, thus preventing shorting while maintaining connection integrity.
2Productivity
If feature sizes are reduced to increase integration density, then more components can be integrated, but alignment tolerance decreases making shorting more likely
Solution Approach 1:
The mask layer is formed in advance with precise dimensions that account for the reduced feature sizes. By preliminarily defining the contact opening boundaries with the mask layer, the process compensates for the reduced alignment tolerance inherent in smaller features, enabling high integration density without increasing shorting risk.
Solution Approach 2:
The dimensions and material properties of the mask layer are adjusted to match the reduced feature sizes. The mask layer parameters (thickness, lateral dimensions, material composition) are specifically optimized for the smaller feature regime to maintain adequate alignment tolerance despite the overall size reduction.
Data Source
AI summary
A method includes using a second hard mask layer over a gate stack to protect the gate electrode during etching a self-aligned contact. The second hard mask is formed over a first hard mask layer, where the first hard mask layer has a lower etch selectivity than the second hard mask layer.