Plasma Etching with Sub-1 MHz DC Pulses to Limit Contamination
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Solution Overview
Problem
In plasma processing apparatuses, high potential differences between the chamber body and plasma lead to increased ion energy on the inner wall, causing particle release and substrate contamination, while existing DC voltage techniques at 1 MHz or higher increase ion energy to the chamber body, accelerating contamination and reducing etching rates.
Innovation Solution
Applying a negative DC voltage to the lower electrode with a frequency below 1 MHz and regulating the duty ratio to 50% or less, cyclically applying the DC voltage to control ion movement and reduce plasma potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a negative DC voltage is applied to the lower electrode with frequency of 1 MHz or higher to increase ion energy for etching, then the etching rate increases, but the ion energy on the chamber body wall increases causing particle release and substrate contamination
Solution Approach 1:
The patent applies periodic DC voltage pulses to the lower electrode instead of continuous DC voltage. By controlling the duty ratio (ratio of pulse width to period) to be 50% or less, the method periodically accelerates ions toward the substrate for etching while allowing sufficient time for ion energy to dissipate before ions reach the chamber body wall, thereby preventing particle release and substrate contamination while maintaining etching efficiency
Solution Approach 2:
The patent changes the frequency parameter of the applied DC voltage to be below 1 MHz (specifically 100 kHz to 500 kHz) and adjusts the duty ratio to 50% or less. This parameter optimization allows sufficient time for ion energy dissipation during each cycle, preventing excessive ion energy from reaching the chamber body wall while still achieving effective etching on the substrate during the pulse periods
2Productivity
If the potential difference between chamber body and plasma is large to increase ion energy for etching, then the etching rate increases, but particles are released from the chamber body and contaminate the substrate
Solution Approach 1:
The periodic application of DC voltage pulses creates controlled potential differences between the chamber body and plasma only during the pulse periods. This allows ion acceleration for etching while preventing sustained high potential differences that would cause excessive ion energy on the chamber body wall and subsequent particle release
Solution Approach 2:
By setting the frequency below 1 MHz and duty ratio to 50% or less, the patent optimizes the timing and magnitude of potential difference application. This ensures that ion energy remains sufficient for etching during pulse periods while allowing energy dissipation during off-periods, preventing particle release from the chamber body
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 suppresses substrate deterioration and reduces ion energy on the chamber body, minimizing contamination and maintaining etching efficiency.
Implementation Method 1
a radio-frequency power supply configured to supply radio-frequency waves for generating plasma of a gas supplied to the chamber
Implementation Method 2
the ions are accelerated by a potential difference between the potential of the lower electrode and the potential of the plasma, and the accelerated ions are radiated onto the substrate
Data Source
AI summary
A plasma processing method includes providing a plasma processing apparatus; supplying radio-frequency waves from a radio-frequency power supply; and applying a negative DC voltage to a lower electrode from the at least one DC power supply. In the applying the DC voltage, the DC voltage is cyclically applied to the lower electrode, and in a state where a frequency defining each cycle in which the DC voltage is applied to the lower electrode is set to be lower than 1 MHz, a ratio occupied by a period during which the DC voltage is applied to the lower electrode in the each cycle is regulated.