Silicon Trench Etching with Pulsed Plasma Sidewall Protection
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Solution Overview
Problem
Existing etching methods face challenges in maintaining consistent etching depth and preventing shape abnormalities, such as bowing, particularly in trenches with varying opening sizes and shapes.
Innovation Solution
An etching method utilizing a plasma processing apparatus that forms a protective layer on the side walls of recesses in a silicon layer, followed by controlled application of radio frequency and bias power pulses to etch the bottom of the recesses, ensuring non-overlapping power supply periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching is performed on trenches with varying opening sizes, then etching can be completed, but etching depth varies and shape abnormalities such as bowing occur
Solution Approach 1:
A protective layer is formed on the side walls of trenches before the main etching process. This preliminary protective layer prevents etching solution from attacking the side walls, thereby preventing shape abnormalities such as bowing and ensuring uniform trench shapes even when opening sizes vary
Solution Approach 2:
The protective layer is selectively formed only on the side walls of trenches, providing localized protection where needed. This allows different parts of the structure (side walls vs. bottom) to have different properties, with side walls protected and bottoms etched
2Length of moving object
If etching is performed to create deeper trenches, then trench depth increases, but etching depth variation increases
Solution Approach 1:
The protective layer is formed on side walls before deep etching, enabling the etching process to proceed deeper without causing shape abnormalities or depth variation. This preliminary protection allows consistent depth control even for deep trenches
Solution Approach 2:
The etching process uses periodic pulsed power supply with alternating source RF power and bias power periods. This periodic action allows controlled etching progression while maintaining depth consistency, preventing the depth variation that occurs in continuous etching of deep trenches
3Area of moving object
If smaller openings are used in the mask pattern, then pattern density increases, but bowing and shape abnormalities become more likely
Solution Approach 1:
The protective layer is formed on side walls before etching small-opening patterns. This preliminary protection is particularly important for small openings where bowing is more likely to occur, ensuring uniform trench shapes even in high-density patterns
Solution Approach 2:
The protective layer provides localized protection on side walls of small openings, preventing etching solution from causing bowing. This local protection enables successful etching of dense patterns that would otherwise be prone to shape abnormalities
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 suppresses variations in etching depth and reduces shape abnormalities, achieving high etching consistency and minimizing microloading effects.
Implementation Method 1
forming a recess overlapping an opening of the mask by etching the silicon layer using first plasma generated from a first process gas
Implementation Method 2
supplying a pulse of source radio frequency power from a radio frequency power supply, and supplying a pulse of bias power from a bias power supply
Data Source
AI summary
An etching method includes forming a recess overlapping an opening of a mask by etching a silicon layer, forming a protective layer on at least a side wall of the recess, and etching a bottom of the recess, in which the forming of the protective layer includes forming a precursor layer on at least the side wall of the recess, and modifying the precursor layer into the protective layer, the etching of the bottom of the recess includes supplying a pulse of source radio frequency power from a radio frequency power supply, and supplying a pulse of bias power to a support configured to support the substrate from a bias power supply, and a period during which the forming of the precursor layer is performed does not overlap a period during which the modifying of the precursor layer is performed.