High-Aspect Ratio Silicon Etching Shape Control
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Solution Overview
Problem
High-aspect ratio etching of silicon films often results in 'twisting' phenomena, leading to degradation of etched hole shapes, particularly as devices become smaller and more complex, with existing methods failing to maintain shape integrity beyond aspect ratios of 15.
Innovation Solution
The method involves supplying HBr, NF3, and O2 gases into a plasma chamber and gradually reducing the HBr gas flow rate while increasing the O2 gas flow rate relative to HBr, across multiple etching steps, to control ion direction and prevent twisting and bowing in high-aspect ratio etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional etching methods are used for high-aspect ratio holes, then etching depth can be achieved, but twisting occurs and shape integrity is degraded
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the HBr gas flow rate during the etching process. The HBr flow rate is gradually reduced from an initial high value to a final low value over multiple etching steps, transforming the static etching process into a dynamic one that adapts to the changing aspect ratio during etching, thereby preventing twisting while achieving high etching depth
Solution Approach 2:
The patent implements parameter changes by modifying the HBr gas flow rate parameter throughout the etching process. The flow rate is changed from a constant value to a varying value that decreases over time, and the O2 gas flow rate is adjusted in response to HBr flow rate changes, allowing the etching process to maintain shape integrity while achieving high aspect ratios
2Shape
If HBr gas flow rate is reduced to prevent twisting, then shape integrity is maintained, but etching speed may be affected
Solution Approach 1:
The patent applies preliminary action by performing multiple etching steps with progressively reduced HBr flow rates. The process starts with high HBr flow rate to achieve rapid initial etching, then gradually reduces the flow rate in subsequent steps to prevent twisting as the aspect ratio increases, thereby maintaining both high etching speed and shape integrity through staged etching
Solution Approach 2:
The patent implements periodic action by dividing the etching process into multiple discrete steps with periodic adjustment of gas flow rates. Each etching step involves supplying gases at specific flow rates, then pausing to adjust the HBr flow rate before the next step, creating a periodic cycle of etching and adjustment that maintains both productivity and shape control
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 maintains a satisfactory etching shape even at high aspect ratios (up to 25 or more), preventing twisting and bowing, and ensuring verticality of etched holes in silicon films.
Implementation Method 1
performing a plurality of etching processes on the silicon film with a plasma generated by the supplied HBr gas, NF3 gas, and O2 gas
Implementation Method 2
etching a target etching layer containing polycrystalline silicon by using plasma generated by supplying HBr (hydrogen bromide) gas, NF3 (nitrogen trifluoride) gas, and O2 (oxygen) gas
Data Source
AI summary
A method for etching a silicon film formed on a substrate includes supplying HBr gas, NF3 gas, and O2 gas into a chamber and performing a plurality of etching processes on the silicon film with a plasma generated by the supplied HBr gas, NF3 gas, and O2 gas, gradually reducing a flow rate of the HBr gas during the plurality of etching processes, and adjusting a flow rate of the O2 gas according to the reduction of the HBr gas.