Delayed RF Pulsing in Plasma Etching for Uniform Wafer Processing
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Solution Overview
Problem
Current semiconductor fabrication processes face challenges in achieving uniformity and selectivity in plasma etching, particularly at the nanometer scale, due to aspect ratio-dependent etch effects, which result in non-uniform etching rates and profiles across features of varying dimensions.
Innovation Solution
Implementing delayed pulsing of RF source and bias power in a plasma processing system, where RF source power is applied for a first period, followed by a delay before applying an RF bias signal, and then both are removed before the next pulse period, allowing control over the neutral to ion density ratio and ion energy of the plasma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used, then etching process is simple and fast, but etching uniformity and selectivity deteriorate due to aspect ratio-dependent etch effects
Solution Approach 1:
The patent applies periodic pulsed RF power to the plasma generating element, alternating between plasma generation phases and non-plasma phases. This periodic action allows control over the neutral to ion density ratio by adjusting pulse width, duty cycle, and frequency, thereby improving etching uniformity across features with different aspect ratios while managing process complexity through programmable control.
2Productivity
If higher RF power is applied to increase etching rate, then productivity improves, but etching selectivity and uniformity worsen due to increased ion bombardment
Solution Approach 1:
By using pulsed RF power with variable duty cycles, the system can deliver high power during plasma generation phases to maintain high etching rates, then reduce or eliminate power during non-plasma phases to allow neutral density to dominate. This periodic modulation enables high productivity while preserving selectivity and uniformity by controlling the timing and duration of high-power application.
Solution Approach 2:
The patent changes the temporal parameters of RF power application (pulse width, duty cycle, frequency) to independently control plasma chemistry and ion flux. By adjusting these parameters, the system can optimize etching rate while maintaining selectivity and uniformity, resolving the contradiction between productivity and manufacturing precision.
3Quantity of substance
If continuous RF power is applied, then plasma density is high and etching is fast, but control over neutral and ion density ratios is lost
Solution Approach 1:
The pulsed RF power system maintains high average plasma density through high-power plasma generation phases while providing control over the neutral to ion density ratio by adjusting the duty cycle. During plasma phases, ion density increases; during non-plasma phases, neutral density is preserved. This periodic action enables both high plasma density and fine process control.
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 etching selectivity and uniformity by maintaining higher neutral density and controlling ion energy independently, leading to improved etching performance across features with different aspect ratios and materials, reducing loading deficiencies and aspect ratio-dependent etch effects.
Implementation Method 1
The plasma is often generated by applying radiofrequency (RF) power to a process gas in a controlled environment, such that the process gas becomes energized and transforms into the desired plasma
Implementation Method 2
a bias voltage applied to attract charged constituents of the plasma toward the substrate
Data Source
AI summary
A method, apparatus and system for processing a wafer in a plasma chamber system, which includes at least a plasma generating element and a biasing electrode, include generating a plasma in the plasma chamber system by applying a source RF source power to the plasma generating element for a first period of time of a pulse period of the RF source power, after the expiration of the first period of time, removing the source RF source power, after a delay after the removal of the RF source power, applying an RF bias signal to the biasing electrode for a second period of time to bias the generated plasma towards the wafer, and after the expiration of the second period of time, removing the RF bias signal from the biasing electrode before a next pulse period of the RF source power. The generated plasma biased toward the wafer is used to process the wafer.