Rounded Hard Mask Trench Formation for Sidewall Overhang Control
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Solution Overview
Problem
Traditional methods for forming trenches in semiconductor devices result in large overhangs on sidewalls due to critical dimension miniaturization, affecting yield and leakage control, and are inefficient in achieving precise trench dimensions.
Innovation Solution
The use of rounded hard masks with a passivation layer formed during etching, which controls etch rates to achieve a rounded profile in the hard mask and a perpendicular profile in the dielectric layer, allowing for improved trench formation and filling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional photolithography and etching methods are used with smaller critical dimensions, then trench width and spacing are reduced, but large overhangs form on sidewalls affecting yield and leakage control
Solution Approach 1:
The patent applies curvature by rounding the top corners of the hard mask pattern before etching. This rounded hard mask profile transfers to the trench sidewalls, eliminating the traditional sharp-cornered overhangs and producing cleaner vertical sidewalls that improve yield and leakage control.
Solution Approach 2:
The patent performs preliminary rounding of the hard mask pattern corners before the main etching process. This preliminary action modifies the mask geometry in advance, ensuring that the subsequent etching process produces trenches with the desired profile without sidewall overhangs, rather than attempting to correct overhangs after etching.
2Ease of manufacture
If traditional patterning methods are used, then process simplicity is maintained, but yield and leakage control are negatively affected
Solution Approach 1:
The rounding step is integrated into the existing photolithography and etching workflow, adding only minimal process complexity. The curved profile transformation is achieved through standard lithographic techniques, maintaining ease of manufacture while dramatically improving reliability by eliminating sidewall overhangs that cause yield and leakage issues.
3Productivity
If smaller critical dimensions are pursued, then trench density increases, but overhang formation and process defects increase
Solution Approach 1:
As critical dimensions shrink and trench density increases, the rounded hard mask approach becomes increasingly beneficial. The curvature prevents the formation of narrow bridges and overhangs that are more likely to occur at smaller dimensions, maintaining precise trench profile control even as trench density increases and productivity improves.
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 reduces overhang formation, enhances process robustness, and increases the process window for trench filling, achieving precise critical dimensions and improved leakage control without increasing pitch.
Implementation Method 1
forming a passivation layer on sidewalls of the opening
Data Source
AI summary
A method embodiment includes forming a hard mask over a dielectric layer, patterning the hard mask to form an opening, forming a passivation layer on sidewalls of the opening, and forming a trench in the dielectric layer by extending the opening into the dielectric layer using an etching process. The sidewalls of the opening are etched to form a rounded profile in the hard mask and a substantially perpendicular profile in the dielectric layer.