Staggered Semiconductor Contacts for Alignment and Resistance
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Solution Overview
Problem
Current semiconductor device fabrication techniques face challenges in decreasing feature dimensions due to limitations in forming contact holes with sufficient dimensions, leading to misalignment and high contact resistance issues.
Innovation Solution
The use of staggered contacts and a dual damascene methodology, where trenches and apertures are formed to multiple fabrication levels and filled with conductive material, allowing for larger conductive plugs and increased alignment tolerances, along with intermediate structures that serve multiple functions like etch stops and polish stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If contact holes are formed in two or more process steps with smaller dimensions at the bottom to prevent misalignment, then alignment precision is improved, but contact resistance increases undesirably
Solution Approach 1:
The contact structure is segmented into two distinct parts: a larger-diameter conductive plug at the bottom and a smaller-diameter contact opening at the top. This segmentation allows each part to optimize its function - the large plug ensures low contact resistance while the small opening maintains alignment precision
Solution Approach 2:
The contact opening is nested within the conductive plug structure, with the smaller top opening positioned above the larger bottom plug. This nested configuration allows the contact hole to be aligned with the plug while maintaining different dimensions at different heights to resolve the contradiction between alignment and contact resistance
2Productivity
If feature dimensions are decreased to increase device density, then device density is improved, but fabrication challenges increase due to etch process limitations
Solution Approach 1:
The solution moves from a single-dimension approach (uniform contact hole diameter) to a multi-dimensional approach by varying the contact structure dimensions along the vertical axis. The contact has different diameters at different heights, allowing the bottom to be larger for manufacturability while the top remains small for high density
3Length of moving object
If the dimensions across the top surface of conductive plugs are made smaller to maintain pitch, then pitch is reduced, but misalignment occurs and electrical communication is compromised
Solution Approach 1:
The contact structure is made asymmetric along the vertical axis, with the bottom diameter being larger than the top diameter. This asymmetric design allows the bottom plug to maintain sufficient size for alignment tolerance while the top opening can be smaller to maintain pitch, resolving the contradiction between pitch reduction and alignment precision
Data Source
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Figure 7~9A
AI summary
A semiconductor device structure includes staggered contacts to facilitate small pitches between active-device regions and conductive lines while minimizing one or both of misalignment during fabrication of the contacts and contact resistance between sections of the contacts. The contacts of one row communicate with every other active-device region and are staggered relative to the contacts of another row, which communicate with the remaining active-device regions. Each contact may include a relatively large contact plug with a relatively large upper surface to provide a relatively large amount of tolerance as a contact hole for an upper portion of the contact is formed. The contact holes may be formed substantially simultaneously with trenches for conductive traces, such as bit lines, in a dual damascene process. Intermediate structures are also disclosed, as are methods for designing semiconductor device structures.