Plasma Bias Waveform Control for Uniform High-Aspect-Ratio Etching
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Solution Overview
Problem
The increasing complexity of semiconductor device manufacturing due to decreasing line widths and increasing aspect ratios poses challenges in forming microstructures with high reliability, particularly in achieving effective plasma control for etching processes.
Innovation Solution
A voltage waveform control method involving a non-sinusoidal wave with specific adjustments to the pulse and ramp periods, including a negative bias voltage period that is no more than 20% of the total waveform period, and adjusting the slopes of transition and ramp periods to improve etching distribution and selectivity of the etching mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional sinusoidal voltage waveform is used for plasma etching, then the etching process can proceed continuously, but the etching distribution and mask selectivity deteriorate due to inability to control ion flux and energy effectively
Solution Approach 1:
The patent applies periodic action by using a pulsed voltage waveform with distinct pulse periods and ramp periods. The voltage waveform alternates between high voltage states (positive bias) and low voltage states (negative bias) in a periodic manner, enabling cyclic control of ion flux and energy. This periodic modulation allows precise control of etching distribution and mask selectivity by adjusting pulse width, duty cycle, and voltage amplitude, directly resolving the technical contradiction between manufacturing precision and device complexity.
2Manufacturing precision
If the negative voltage period is extended to improve ion energy control, then etching anisotropy improves, but mask selectivity deteriorates due to prolonged ion bombardment
Solution Approach 1:
The patent applies dynamics by implementing a time-varying voltage waveform where the negative voltage period is dynamically optimized. The waveform transitions from static continuous voltage to dynamic pulsed voltage with adjustable parameters including pulse period, duty cycle, and voltage amplitude. This dynamic control enables precise regulation of ion bombardment duration and intensity, achieving both etching anisotropy and mask selectivity by optimizing the negative voltage period to be sufficiently long for anisotropy but not excessively long to damage the mask.
3Productivity
If the voltage waveform slope is increased to improve etching speed, then productivity increases, but etching distribution uniformity deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically optimizing multiple voltage waveform parameters including pulse amplitude, pulse width, duty cycle, and voltage slope. The ramp period slope is specifically optimized to balance etching speed and distribution uniformity. By adjusting these parameters, the patent achieves high etching speed through steeper voltage transitions while maintaining uniform etching distribution through controlled pulse duration and duty cycle, effectively resolving the contradiction between productivity and manufacturing 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 enhances the selectivity and distribution of the etching process, maintaining a constant voltage induced to the substrate, thereby improving the reliability of forming microstructures with high aspect ratios in semiconductor devices.
Implementation Method 1
generating plasma in a processing space inside the chamber by applying a plasma voltage to an upper electrode structure
Data Source
AI summary
Provided is a voltage waveform control method comprising generating a voltage waveform of a non-sinusoidal wave comprising a pulse period having a positive bias voltage, a ramp period having a negative bias voltage, a first transition period changing from the pulse period to the ramp period, and a second transition period changing from the ramp period to the pulse period, adjusting a length of a negative voltage period having the negative bias voltage during a period of the voltage waveform to be at most 20% of a total length of the period, adjusting a slope of the ramp period, and outputting an adjusted voltage waveform based on the adjusted length of the negative voltage period and the adjusted slope of the ramp period, where the adjusting the length of the negative voltage period comprises adjusting a length of the first transition period and a length of the second transition period.