Plasma Etching Electrode Bias Switching for Substrate Charge Control
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Solution Overview
Problem
During plasma etching, substrates become charged, leading to reduced etching rates and shape abnormalities in the formed openings, as the amount of positive ions supplied into the openings decreases.
Innovation Solution
A plasma processing apparatus with a power supply unit that generates both positive and negative DC voltages, which are applied to the lower electrode in specific time periods to manage the charge on the substrate and enhance etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positive DC voltage is applied to the lower electrode to reduce substrate positive charge, then the substrate charge is reduced, but the etching rate decreases due to reduced positive ion supply
Solution Approach 1:
The patent applies periodic switching between positive and negative DC voltages to the lower electrode. During etching, the voltage is switched: positive voltage is applied to remove excess positive charge from the substrate, then negative voltage is applied to restore positive ion supply for etching. This periodic action resolves the contradiction by temporarily accepting reduced etching rate to maintain substrate charge balance, then restoring etching capability.
Solution Approach 2:
The patent dynamically adjusts the DC voltage polarity and magnitude based on real-time substrate charge state. The power supply unit continuously monitors and modifies the voltage applied to the lower electrode, transitioning from static voltage application to dynamic control. This allows the system to adaptively balance substrate charge management with maintaining adequate etching rate.
2Productivity
If a negative DC voltage is applied to the lower electrode to enhance positive ion supply, then the etching rate improves, but the substrate becomes overly charged causing shape abnormalities
Solution Approach 1:
The patent uses periodic voltage switching to prevent excessive substrate charging. After applying negative voltage to enhance etching, the system periodically switches to positive voltage to remove accumulated positive charge. This periodic correction prevents shape abnormalities while maintaining high etching rates during the negative voltage phases.
Solution Approach 2:
The patent implements feedback control where the power supply unit monitors the substrate charge state and adjusts the DC voltage accordingly. When substrate charge reaches a threshold that may cause shape abnormalities, the system automatically switches voltage polarity to correct the charge balance, thereby maintaining opening shape accuracy while preserving etching efficiency.
3Ease of operation
If DC voltage is continuously applied during plasma generation, then charge control is simplified, but ion energy becomes uncontrolled leading to etching rate instability
Solution Approach 1:
The patent applies periodic switching of DC voltage during plasma generation rather than continuous application. The voltage alternates between positive and negative polarities at controlled intervals, which maintains ion energy within an optimal range for stable etching while still providing effective substrate charge control. This resolves the contradiction by making the system slightly more complex in operation but significantly improving etching stability.
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
The continuous switching of DC voltages from positive to negative during plasma generation enhances the energy of positive ions colliding with the substrate, thereby improving the etching rate and reducing charge-related issues.
Implementation Method 1
The radio-frequency power supply is configured to supply a radio-frequency power to generate plasma from a gas in the chamber
Implementation Method 2
The power supply unit applies a second DC voltage to the lower electrode in a third time period during which the plasma is being generated from the etching gas in the chamber after the second time period, in order to etch the substrate placed on the substrate support
Implementation Method 3
The substrate is charged as the etching of the substrate with the positive ions is progressed
Implementation Method 4
The substrate is etched by the positive ions from the plasma, and openings are formed in the substrate
Data Source
AI summary
A plasma processing apparatus includes a chamber and a substrate support provided in the chamber. A power supply unit is connected to a lower electrode of the substrate support. The power supply unit applies a first DC voltage to the lower electrode during generation of plasma from an etching gas in the chamber. The first DC voltage is a positive DC voltage. The power supply unit applies a second DC voltage to the lower electrode during the generation of plasma from the etching gas in the chamber, to etch the substrate placed on the substrate support. The second DC voltage is a negative DC voltage. The DC voltage output by the power supply unit is continuously switched from the first DC voltage to the second DC voltage.