Buried Alignment Key Structure for Precise Semiconductor Overlay
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Solution Overview
Problem
The increasing complexity of semiconductor manufacturing processes and introduction of new materials have made overlay measurement processes more difficult due to potential damage to alignment keys, affecting yield and productivity.
Innovation Solution
A semiconductor device design featuring a substrate with distinct areas, including a bit-line structure, buried contacts, and alignment key structures with specific height differences, along with a manufacturing method involving conductive material deposition and etch-back processes to form buried patterns and contacts, enhancing precision and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If new materials and complex manufacturing processes are introduced to achieve higher integration, then device functionality is improved, but alignment key damage occurs and overlay measurement difficulty increases
Solution Approach 1:
The patent divides the alignment key into two separate structures: a first alignment key structure formed in the bit line region and a second alignment key structure formed in the pad region. This segmentation allows each alignment key to be independently optimized and protected, preventing damage to the overall alignment system while maintaining functionality in both bit line and pad areas.
Solution Approach 2:
The patent introduces a dummy pad structure as an intermediary element between the alignment key and the complex manufacturing processes. This dummy pad serves as a protective mediator that absorbs process stress and prevents direct damage to the alignment key during subsequent manufacturing steps, thereby maintaining alignment key integrity while allowing advanced process integration.
2Measurement precision
If alignment key is used for overlay measurement, then measurement capability is provided, but alignment key damage increases measurement difficulty
Solution Approach 1:
The patent creates a dummy pad structure that copies the essential geometric features and material composition of a functional pad without containing critical alignment information. This copy serves as a sacrificial element that can be damaged or modified during manufacturing without affecting the actual alignment measurement, thereby maintaining measurement precision while reducing measurement difficulty.
Solution Approach 2:
The patent positions the dummy pad structure in advance to provide cushioning protection for the alignment key. By placing this protective structure beforehand, the alignment key is shielded from damage during subsequent manufacturing processes, ensuring that the alignment key remains intact and measurable throughout the fabrication sequence.
3Ease of manufacture
If conventional alignment key structure is used, then simple fabrication is achieved, but damage to alignment key occurs during manufacturing
Solution Approach 1:
The patent merges the formation of the alignment key with the formation of the dummy pad structure into a single integrated process sequence. Both structures are formed using the same material deposition and patterning steps, eliminating the need for separate alignment key fabrication processes. This merging maintains fabrication simplicity while the dummy pad simultaneously provides protective functionality.
Data Source
AI summary
A semiconductor device includes a substrate that includes a first area and a second area, a first active pattern in the first area, a bit-line structure on the first area, a buried contact that is on a side surface of the bit-line structure and is electrically connected to the first active pattern of the first area, an alignment key structure that is on the second area and defines a key trench, and a buried pattern in at least a portion of the key trench, where the buried contact and the buried pattern include a first conductive material, and where, relative to an upper surface of the substrate and in a direction that is perpendicular to the upper surface of the substrate, a height of an upper surface of the buried pattern is greater than a height of an upper surface of the buried contact.