Mandrel Bridge Etching for Reduced Interconnect Line-End Spacing
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Solution Overview
Problem
Current methods for forming interconnect structures with metal lines and vias face challenges in reducing line-end spacing while maintaining control over the scale of metal lines and vias.
Innovation Solution
The method involves forming mandrels with spacers of different materials, where the mandrel etching rate is significantly higher than the spacer etching rate, allowing for lateral etching of the bridging portion to reduce line-end spacing without increasing the width of the metal lines, using a two-step etching process with high selectivity to achieve precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form metal lines and vias, then the manufacturing process is simpler, but the line-end spacing cannot be reduced below a certain minimum
Solution Approach 1:
The mandrel structure is segmented into a body portion and a bridging portion, with the bridging portion being laterally recessed relative to the body portion. This segmentation allows independent control of the bridging portion through selective etching, enabling reduced line-end spacing while maintaining the overall mandrel structure integrity.
Solution Approach 2:
Different regions of the mandrel are given different properties: the body portion maintains full width to support the metal line formation, while the bridging portion is laterally recessed to reduce the spacing between adjacent metal lines. This local differentiation resolves the contradiction by allowing precise control of line-end spacing without compromising the structural support function.
2Manufacturing precision
If the bridging portion is laterally etched to reduce line-end spacing, then the spacing between metal lines decreases, but the line width may increase
Solution Approach 1:
The mandrel is divided into a body portion and a bridging portion that can be independently processed. The lateral etching is applied only to the bridging portion, which does not directly determine the metal line width. This segmentation allows the bridging portion to be recessed (reducing line-end spacing) while the body portion maintains its original dimensions (controlling line width).
Solution Approach 2:
The bridging portion acts as an intermediary structure between adjacent mandrels. By laterally recessing only this intermediary portion, the spacing between metal lines is reduced without affecting the critical dimensions of the metal lines themselves, thus resolving the contradiction between line-end spacing and line width.
3Manufacturing precision
If high selectivity etching is used to laterally recess the bridging portion, then the control over line-end spacing improves, but the process complexity increases
Solution Approach 1:
The etching process parameters are changed to achieve high selectivity between the bridging portion and other structures. By adjusting etching gas composition, power, pressure, or other parameters, the process selectively removes material from the bridging portion while leaving the body portion and surrounding structures intact. This parameter optimization enables precise line-end spacing control without requiring excessively complex multi-step processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces line-end spacing below the minimum achievable by conventional methods without increasing the width of the metal lines, thereby improving the density and efficiency of interconnect structures.
Implementation Method 1
the etching gas is selected so that a first etching rate of the mandrel is significantly higher than a second etching rate of the spacers
Data Source
AI summary
A method includes forming an etching mask to cover a mandrel, a first spacer, and a second spacer, and the first spacer and the second spacer are in contact with opposing sidewalls of the mandrel. The etching mask is then patterned, and includes a first portion covering the first spacer, a second portion covering the second spacer, and a bridge portion connecting the first portion to the second portion. The bridge portion has first sidewalls. A first etching process is performed on the mandrel using the etching mask to define pattern, and after the first etching process, the mandrel includes a second bridge portion having second sidewalls vertically aligned to corresponding ones of the first sidewalls. After the mandrel is etched-through, a second etching process is performed to laterally recess the second bridge portion of the mandrel.