Plasma Stage Voltage Waveform for Wafer Charge Removal Control
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Solution Overview
Problem
Conventional plasma etching technologies face challenges in efficiently removing charges from the wafer surface while maintaining precision, leading to electron shading effects that degrade the perpendicularity of trench sidewalls in semiconductor manufacturing.
Innovation Solution
A plasma processing apparatus and method that employs a voltage waveform with a positive ramp period, a negative ramp period, and a removal amount control period to manage the removal of charged particles, using a DC power supply to alternate phases with varying and constant voltage regions, optimizing the removal process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear triangular wave voltage or curved triangular wave voltage is applied to the stage to remove charged particles, then the charge removal effectiveness is improved, but the device complexity increases
Solution Approach 1:
The voltage waveform is segmented into distinct functional periods: a positive ramp period for charge removal, a negative ramp period for charge accumulation control, and a removal amount control period for precision adjustment. This segmentation allows independent optimization of each function while simplifying the overall control system compared to complex continuous waveforms.
Solution Approach 2:
The power supply applies periodic voltage waveforms with alternating positive and negative ramp periods to the sample stage. This periodic action creates time-varying electric fields that effectively remove charged particles while maintaining simple waveform generation through repetitive cycles rather than complex continuous control.
2Productivity
If the amplitude of the triangular wave voltage is increased to increase charge mobility, then the charge removal efficiency is improved, but the charge accumulation on the capacitor increases
Solution Approach 1:
The power supply alternates between positive ramp periods (removing charges) and negative ramp periods (controlling charge accumulation) in a periodic manner. This allows high amplitude voltages to be applied temporarily for efficient charge removal while the negative ramp period prevents excessive charge accumulation on the capacitor, maintaining productivity without harmful side effects.
Solution Approach 2:
The voltage waveform dynamically transitions between positive and negative ramp periods, allowing the system to adapt the electric field direction and magnitude over time. This dynamic control enables efficient charge removal during positive ramps while preventing capacitor charge saturation through negative ramps, optimizing both productivity and charge management.
3Reliability
If voltage is continuously applied to remove charges, then the charge removal effectiveness is improved, but the damage to the wafer surface increases
Solution Approach 1:
The power supply applies voltage in periodic cycles with positive ramp periods for charge removal and negative ramp periods for recovery. This periodic application removes charges effectively during active periods while allowing the wafer surface to recover during negative ramp periods, reducing cumulative damage compared to continuous voltage application.
Solution Approach 2:
The negative ramp period serves as a preliminary anti-action that counteracts the potential harmful effects of the positive ramp period. By applying reverse voltage after charge removal, the system prevents excessive charge accumulation and reduces wafer surface damage before it can occur, maintaining effectiveness while minimizing harm.
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 maintains efficient charge removal from the wafer surface, reducing electron shading effects and enhancing the precision of plasma processing by minimizing damage to the wafer surface.
Implementation Method 1
a cycle of a waveform of the voltage has a positive ramp period during which the voltage rises, a negative ramp period during which the voltage falls, and a removal amount control period during which an amount of charged particles removed from the sample per unit time is controlled
Implementation Method 2
a first high frequency power supply that supplies high frequency power for plasma generation
Data Source
AI summary
A high-precision plasma processing apparatus configured with: a processing chamber in which a sample undergoes plasma processing; a first radio frequency power supply that supplies radio frequency power for plasma generation; a sample stage on which a sample is loaded; a second radio frequency power supply that supplies radio frequency power to the sample stage; a power supply that applies voltage to the sample stage; and a control unit that controls the power supply. In the plasma processing apparatus, a cycle of a waveform of the voltage has a positive ramp period during which the voltage rises, a negative ramp period during which the voltage falls, and a removal amount control period during which the amount of charged particles removed from the sample per unit time is controlled.