Synchronized Source-Bias RF Pulsing for Vertical Plasma Etching
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Solution Overview
Problem
In plasma processing for high aspect ratio substrates, existing technologies face challenges in maintaining vertical etching accuracy and preventing shape abnormalities due to oblique ion incidence and deposition of reaction products, which affect the control of reaction species and byproducts.
Innovation Solution
A plasma processing method using a pulsed RF signal system where the source RF signal and bias RF signal are synchronized with overlapping operating and non-operating periods, allowing for precise control of ion energy, radical flux, and byproduct management through varying power levels and timing adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If continuous RF signals are used for plasma processing, then plasma generation is maintained, but ion delivery control and shape accuracy deteriorate due to uncontrolled ion incidence angles
Solution Approach 1:
The patent applies periodic pulsing of source RF and bias RF signals with different duty cycles to control plasma generation and ion delivery in distinct phases. The source RF signal is pulsed to control radical generation, while the bias RF signal is pulsed to control ion acceleration timing, achieving periodic control over ion incidence angles and energy delivery to maintain vertical etching accuracy in high aspect ratio features
Solution Approach 2:
The patent dynamically adjusts the timing and duration of source RF and bias RF signal pulses to optimize plasma processing. By varying the duty cycles and phase relationships between source and bias RF pulses, the system dynamically controls ion energy, radical flux, and ion incidence angles throughout the processing cycle, enabling precise control of etching morphology
2Productivity
If high ion energy is used to improve etching rate, then productivity increases, but shape abnormalities occur due to oblique ion incidence
Solution Approach 1:
The patent uses periodic pulsing of bias RF signals synchronized with source RF signals to deliver ion energy in controlled bursts. The bias RF pulse timing is adjusted relative to the source RF pulse to ensure ions are accelerated vertically during the plasma generation phase, maintaining high etching rates while preventing oblique ion incidence that causes shape abnormalities in high aspect ratio features
Solution Approach 2:
The patent changes the timing parameters (duty cycles, phase shifts) of the pulsed RF signals to optimize the balance between ion energy delivery and ion incidence angle control. By adjusting these parameters, the system maintains high ion energy for productive etching while ensuring ions strike the substrate vertically to preserve feature shape uniformity
3Manufacturing precision
If reaction products are not controlled, then processing continues smoothly, but deposition on substrate causes shape distortions
Solution Approach 1:
The patent employs periodic pulsing of source RF signals to control the generation of reaction products. By synchronizing the source RF pulse duration and duty cycle with the bias RF pulse, the system limits reaction product formation to specific phases while enhancing ion-driven removal processes in other phases, preventing deposition on substrate surfaces and maintaining feature shape accuracy
Solution Approach 2:
The patent converts the potentially harmful reaction products into beneficial by utilizing ion bombardment during the biased pulse phase to physically remove deposited reaction products from the substrate surface. This transforms the harmful deposition effect into a controlled process where reaction products are generated and then immediately removed by ion cleaning, preserving feature shape
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 enhances the etching performance by ensuring efficient ion delivery and reducing shape distortions, thereby improving the accuracy and uniformity of high aspect ratio feature formation in plasma processing.
Implementation Method 1
an antenna disposed above the chamber... supplying a pulsed source RF signal to the antenna
Implementation Method 2
supplying a pulsed bias RF signal to the lower electrode... each bias cycle having a bias operating state during a bias operating period
Implementation Method 3
A method for processing a substrate by a plasma processing apparatus... enhances the etching performance by ensuring efficient ion delivery
Data Source
AI summary
A method for processing a substrate includes: supplying a pulsed source RF signal to an antenna disposed above a chamber, the pulsed source RF signal including a plurality of source cycles each having a source operating state and a source non-operating state after the source operating period; and supplying a pulsed bias RF signal to a lower electrode disposed in a substrate support provided in the chamber, the pulsed bias RF signal including a plurality of bias cycles having a same pulse frequency as that of the plurality of source cycles, each bias cycle having a bias operating state during a bias operating period and a bias non-operating state during a bias non-operating period after the bias operating period. A transition timing to the bias operating state in each bias cycle is delayed with respect to a transition timing to the source operating state in a corresponding source cycle.