Multi-Mask Contact-Line-Blocking in FinFET SRAM Fabrication
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Solution Overview
Problem
Existing FinFET SRAM devices face challenges with contact bridging and fin-landing issues due to shrinking semiconductor feature sizes, leading to performance degradation and potential device failures, as the process windows for lithography patterning become increasingly difficult to control.
Innovation Solution
The use of additional masks to define SRAM contacts, with mask patterns split across multiple lithography masks to improve contact definition accuracy and reduce bridging risks, allowing for more flexible tuning and better pattern uniformity, thereby enhancing the separation and alignment of contact lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography patterning is used for contact definition, then manufacturing simplicity is maintained, but contact bridging occurs and manufacturing precision deteriorates
Solution Approach 1:
The contact definition process is segmented into multiple lithography masks, where each mask defines specific contact lines. This segmentation allows for independent optimization of each contact line's positioning and dimensions, thereby improving contact definition accuracy and reducing bridging risks between adjacent contacts.
Solution Approach 2:
Mandrel structures are introduced as intermediary elements to facilitate contact line formation. These mandrels serve as templates that guide the subsequent material deposition and patterning processes, enabling precise contact definition while maintaining process control.
2Area of moving object
If feature sizes are reduced to shrink SRAM cell dimensions, then device density increases, but process window control becomes difficult and manufacturing precision deteriorates
Solution Approach 1:
The SRAM cell structure is segmented into multiple independently patterned components using separate lithography masks. This approach allows each component (contact lines, fin structures, gate regions) to be optimized and controlled independently, maintaining manufacturing precision even as overall cell dimensions are reduced.
Solution Approach 2:
The patent employs parameter changes in the lithography process, including varying mask patterns, etch conditions, and material properties, to achieve precise patterning at reduced feature sizes. By adjusting these parameters for each specific structure, the process window is effectively expanded despite smaller dimensions.
3Manufacturing precision
If additional lithography masks are used to define contact lines, then contact definition accuracy improves, but manufacturing complexity increases
Solution Approach 1:
The fabrication process is segmented into distinct lithography steps, each handled by a specialized mask. While this increases the number of process steps, it enables automated mask alignment and reduces manual intervention, thereby improving precision without proportionally increasing overall manufacturing complexity.
Solution Approach 2:
The multiple lithography masks are designed to work within a universal process framework that uses consistent alignment references and standardized deposition/etch procedures. This multi-functionality approach allows the same equipment and process tools to handle all masks, reducing the complexity increase that would otherwise result from additional specialized equipment.
Data Source
AI summary
A plurality of gate stacks is formed over a substrate. The gate stacks are surrounded by a dielectric structure. A plurality of contact-line-blocking patterns is formed over the dielectric structure. The contact-line-blocking patterns are formed using three or more lithography masks. A plurality of trenches is formed in the dielectric structure. The contact-line-blocking patterns serve as protective masks for the dielectric structure to prevent trenches from being formed in portions of the dielectric structure underneath the contact-line-blocking patterns. The trenches are filled with a conductive material to form a plurality of contact lines of the SRAM device.