Square-Wave Plasma Etching Signals for Uniform High-Rate Processing
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Solution Overview
Problem
Existing parallel-plate plasma etching apparatuses using radio frequency signals face challenges in achieving optimal etch rates and uniformity on semiconductor substrates due to inefficiencies in ion energy and distribution.
Innovation Solution
Implementing systems that generate and filter square-shaped pulse signals at specific frequencies, which are transmitted through impedance matching circuits and filters to electrodes and edge rings within a plasma chamber, enhancing ion energy and uniformity across the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If radio frequency (RF) signals are used in parallel-plate plasma etching apparatus, then plasma can be formed between electrodes, but the etch rate for etching the predetermined layer cannot be achieved
Solution Approach 1:
The patent applies periodic pulsed RF signals instead of continuous RF signals to create time-varying electric fields that enhance ion acceleration and etch rate. The pulsed nature allows for controlled plasma formation and ion bombardment cycles that improve etching efficiency while maintaining plasma stability.
Solution Approach 2:
The patent modifies RF signal parameters including frequency, pulse width, and duty cycle to optimize etch rate. By changing these electrical parameters and creating non-sinusoidal waveforms, the system achieves higher peak electric fields that accelerate ions more effectively, thereby increasing etch rate without sacrificing plasma quality.
2Manufacturing precision
If conventional RF signals are used, then plasma etching can be performed, but uniformity across the substrate surface is not achieved
Solution Approach 1:
The patent introduces edge rings with independent RF signal control to create localized electric field enhancement at the substrate edges. This allows different regions of the substrate (center vs. edge) to receive optimized RF power, ensuring uniform ion bombardment and etch rate across the entire substrate surface while maintaining high processing rates.
Solution Approach 2:
The patent employs dynamic RF signal modulation with different frequencies and phases applied to different electrode regions. This dynamic control allows real-time adjustment of plasma distribution and ion flux across the substrate, achieving uniform etching while preserving high productivity through optimized signal timing and amplitude variations.
3Use of energy by moving object
If RF signals are applied to electrodes, then plasma is formed, but ion energy and distribution are insufficient for optimal etching
Solution Approach 1:
The patent divides the RF signal generation into multiple independent pulse generators, each controlling specific electrode or edge ring regions. This segmentation allows independent optimization of ion energy delivery to different areas, achieving high ion energy where needed while managing system complexity through modular, independently controllable signal sources.
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 use of square-shaped pulse signals increases processing rates and achieves uniform etching across the substrate surface by optimizing ion energy distribution and directionality, leading to improved etching efficiency.
Implementation Method 1
a first filter that receives the first square wave signal and filters a second frequency from interfering with the first square wave signal to provide a first filter output signal
Implementation Method 2
The RF transmission line combines the first filter output signal and the modified signal to output a combined signal
Implementation Method 3
a radio frequency (RF) signal is applied to at least one of the electrodes to form an electric field between the electrodes. A process gas is turned into plasma by the RF signal, thereby performing plasma etching
Data Source
AI summary
A system for using a square wave signal for processing a substrate is described. The system includes a first pulse generator that generates a first square wave signal of a first frequency. The system further includes a first filter that filters a second frequency from interfering with the first square wave signal to provide a first filter output signal. The first filter provides the first filter output signal via a first transmission line to an electrode of a plasma chamber. The system includes a second pulse generator that generates a second square wave signal of a third frequency. The system also includes a second filter that filters the second frequency from interfering with the second square wave signal to provide a second filter output signal. The second filter provides the second filter output signal via a second transmission line to an edge ring of the plasma chamber.