Mandrel Spacer 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 in a controllable manner without increasing the width of the metal lines.
Innovation Solution
The method involves forming mandrels with spacers of different materials, where the mandrel is patterned with a higher etching rate than the spacers, and a bridging portion is laterally etched to reduce the line-end spacing without affecting the line widths, using a combination of anisotropic and isotropic etching processes to achieve precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard lithography processes are used to reduce line-end spacing, then the manufacturing precision is improved, but the line width increases beyond acceptable limits
Solution Approach 1:
The patent segments the mandrel structure by forming spacers on its sidewalls, creating distinct regions (mandrel body and bridging portion) that can be etched at different rates. This segmentation allows the line-end spacing to be reduced through selective etching of the bridging portion while the main mandrel structure remains intact to define the final line width.
Solution Approach 2:
The patent applies local quality by using materials with different etching rates in different regions. The mandrel and spacers are formed of materials where the mandrel has a significantly higher etching rate than the spacers, enabling selective removal of the mandrel's bridging portion while preserving the spacer structure that defines the line width.
2Productivity
If the mandrel is etched with high etching rate to reduce line-end spacing, then the productivity is improved, but the manufacturing precision of line width control deteriorates
Solution Approach 1:
The spacers act as intermediary structures that mediate between the high-rate mandrel etching and the final line width definition. The spacers protect the regions where line width must be maintained while allowing the mandrel to be etched away at high rate in the bridging regions, thus decoupling the etching rate from line width control precision.
3Manufacturing precision
If the bridging portion is laterally etched to reduce line-end spacing, then the line-end spacing is reduced below lithography limits, but the process complexity increases
Solution Approach 1:
The patent changes the material parameters of the mandrel and spacer materials to achieve significantly different etching rates. By selecting materials where the mandrel etches much faster than the spacers, the complex task of precise line-end spacing control is achieved through material property differences rather than complex process steps.
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 standard lithography processes without increasing the width of the metal lines, thereby pushing the limits of line-end spacing while maintaining line width integrity.
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.