Switch-Mode Bias Waveforms for Wafer Surface Charge Control
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Solution Overview
Problem
Current plasma processing methods lack real-time monitoring and control of surface charge accumulation on wafers, leading to device damage and undesirable etching profiles due to capacitive breakdown and ion deflection, relying on offline empirical data that is prone to errors under varying processing conditions.
Innovation Solution
A system utilizing a switch mode power supply to generate an asymmetric periodic waveform with voltage steps and linearly decreasing voltage to manage charge buildup on a wafer, allowing for real-time monitoring and control of surface charge through ion current measurement, with a controller adjusting the waveform to prevent charge accumulation from exceeding thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If off-line empirical data accumulation and analysis methods are used to monitor surface charge, then device complexity is reduced, but measurement precision and reliability of surface charge monitoring deteriorate due to errors when real-time processing conditions differ from empirical models
Solution Approach 1:
The patent implements a feedback control system where the measured surface charge level is continuously fed back to the power supply controller, which automatically adjusts the RF power level to maintain optimal charge conditions. This closed-loop feedback mechanism enables real-time adaptation to changing processing conditions, resolving the contradiction by providing both high measurement precision through continuous monitoring and automated control without requiring complex empirical models.
Solution Approach 2:
The system enables self-service by allowing the plasma processing system to automatically monitor and regulate its own surface charge conditions through integrated sensors and control algorithms. The system self-adjusts power levels based on real-time charge measurements, eliminating the need for external empirical data analysis and providing both precise measurement and simplified operation.
2Device complexity
If no real-time surface charge control is implemented, then device complexity is reduced, but harmful effects on wafers increase due to charge buildup leading to capacitive breakdown and device damage
Solution Approach 1:
The feedback control system continuously monitors surface charge levels and automatically adjusts RF power to prevent charge buildup that could cause capacitive breakdown or device damage. This real-time feedback mechanism provides protection against harmful effects while maintaining relatively simple system architecture through automated control rather than complex mechanical safeguards.
Solution Approach 2:
The system applies preliminary anti-action by proactively monitoring surface charge levels and adjusting power levels before charge accumulation reaches dangerous thresholds. This preventive approach counteracts potential harmful effects before they occur, protecting wafers from capacitive breakdown and damage while maintaining simple operational procedures.
3Reliability
If real-time ion current monitoring and surface charge control is implemented, then reliability and manufacturing precision of plasma processing improve, but device complexity increases due to additional sensors and control systems
Solution Approach 1:
The patent achieves multi-functionality by integrating surface charge monitoring and RF power control into a single unified power supply system. The same power supply unit that delivers RF power to the plasma also measures surface charge levels and automatically adjusts its output, eliminating the need for separate monitoring and control systems. This universal approach provides both high reliability through real-time control and reduced device complexity by consolidating functions.
Solution Approach 2:
The system merges the functions of RF power delivery, surface charge monitoring, and power level control into a single integrated system. By combining these previously separate functions into one unified power supply unit, the patent achieves both improved reliability through comprehensive real-time control and reduced overall system complexity through functional consolidation.
4Manufacturing precision
If asymmetric periodic voltage waveform with linearly decreasing voltage is applied, then surface charge control precision improves, but use of energy increases due to continuous voltage adjustments
Solution Approach 1:
The patent employs periodic action by applying asymmetric periodic voltage waveforms with linearly decreasing voltage segments to the substrate. This periodic waveform structure enables precise control of surface charge accumulation by systematically varying voltage over time cycles, achieving high manufacturing precision while managing energy consumption through rhythmic rather than continuous adjustment patterns.
Solution Approach 2:
The system implements dynamics by continuously varying the voltage waveform parameters including amplitude, duration, and slope of the linearly decreasing voltage portions. These dynamic adjustments to the voltage profile enable precise real-time control of surface charge levels, optimizing manufacturing precision while the system adapts energy consumption to actual charge control needs rather than maintaining constant high power.
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 provides accurate and real-time monitoring and control of surface charge, preventing structural damage and ensuring precise etching profiles by maintaining optimal charge levels, thereby enhancing the reliability and precision of plasma processing.
Implementation Method 1
The plasma processing chamber can be configured to contain a plasma that includes ions
Implementation Method 2
The power supply can be configured to provide an asymmetric periodic voltage function to an output configured to couple to a substrate support
Implementation Method 3
the periods of linearly decreasing voltage result in a sustained negative voltage at the wafer surface (e.g., a slight voltage slope), which attracts ions to the surface for processing
Data Source
AI summary
Systems, methods and apparatus for regulating ion energies in a plasma chamber and avoiding excessive and damaging charge buildup on the substrate surface and within capacitive structures being built on the surface. An exemplary method includes placing a substrate in a plasma chamber, forming a plasma in the plasma chamber, controllably switching power to the substrate so as to apply a periodic voltage function (or a modified periodic voltage function) to the substrate, and modulating, over multiple cycles of the periodic voltage function, the periodic voltage function responsive to a defined distribution of energies of ions at the surface of the substrate so as to effectuate the defined distribution of ion energies on a time-averaged basis, and to maintain surface charge buildup below a threshold.