Plasma Etching Method Using Time-Varying DC Voltage
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Solution Overview
Problem
Conventional plasma etching methods for semiconductor devices and flat panel displays face challenges in achieving precise control over etching shape due to high deposition rates leading to undercut or bowing, and require multi-step processes with different gases, resulting in stepped portions and dimensional inaccuracies.
Innovation Solution
A capacitively coupled plasma etching method using a DC voltage applied to a member away from the substrate, with the voltage varied according to a time-voltage function or switched between values in cycles, allowing continuous control of etching and deposition processes without changing gas types or flow rates, ensuring accurate etching shape control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high deposition rate is used to protect the sidewall from neutral reactive species or ion impact, then undercut or bowing is prevented, but the etching rate decreases causing excessively tapered shape or stop of etching reaction
Solution Approach 1:
The patent applies a time-varying DC voltage to the upper electrode during the etching process. The voltage is dynamically adjusted from an initial value that promotes etching to a later value that promotes deposition, enabling continuous control of the etching-deposition balance without manual intervention or process interruption. This dynamic control allows optimization of both sidewall protection and etching rate throughout the process.
Solution Approach 2:
The patent changes the DC voltage parameter applied to the upper electrode during the etching process. By varying the voltage from a first value (promoting etching) to a second value (promoting deposition), the patent controls the balance between etching rate and deposition rate, preventing both undercut/bowing and excessive tapering while maintaining high productivity.
2Manufacturing precision
If a multi-step method with different etching gases is used to combine etching dominant and deposition dominant processes, then anisotropic processing accuracy is improved, but the apparatus is scaled up and transition between steps is discontinuous causing stepped portions on sidewall
Solution Approach 1:
The patent merges the etching dominant process and deposition dominant process into a single continuous etching step by applying a time-varying DC voltage to the upper electrode. This eliminates the need for multiple gas supply sources and separate process chambers, reducing apparatus complexity while maintaining anisotropic processing accuracy. The continuous voltage variation prevents discontinuous transitions and stepped portions on sidewalls.
Solution Approach 2:
The patent maintains continuous useful action by performing the entire etching process in a single step with continuous DC voltage variation. The voltage is continuously adjusted from the first value to the second value throughout the etching duration, ensuring smooth transition between etching and deposition phases without interruption or stepped portions, thereby simplifying the process while maintaining precision.
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 method enables precise control over etching characteristics, maintaining high etching accuracy and reducing the need for multiple gas sources, by dynamically adjusting the DC voltage to manage etching and deposition processes within a single-step process, thus improving dimensional accuracy and reducing unwanted shape formations.
Implementation Method 1
molecules of a processing gas are ionized by collision with electrons accelerated by the radio wave electric field
Implementation Method 2
thereby generating a plasma of the processing gas
Implementation Method 3
the part being disposed away from the substrate and being etched by reaction with reactant species in the plasma
Data Source
AI summary
A plasma etching method includes disposing a first electrode and a second electrode to face each other; preparing a part in the processing chamber; supporting a substrate; vacuum-evacuating the processing chamber; supplying an etching gas into a processing space between the first electrode and the second electrode; generating a plasma of the etching gas in the processing space by applying a radio wave power to the first electrode or the second electrode; and etching a film to be processed on a surface of the substrate by using the plasma. Further, a DC voltage is applied to the part during the etching process, the part being disposed away from the substrate and being etched by reaction with reactant species in the plasma.