Microwave Plasma Pulse Control for Uniform Low-Power Etching
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Solution Overview
Problem
Low-power microwave plasma etching results in non-uniform plasma distribution, leading to non-uniform etching on semiconductor surfaces.
Innovation Solution
A plasma processing apparatus and method that uses a first high-power microwave pulse to create a uniformly distributed plasma, followed by a low-power microwave pulse with a wafer bias voltage, and ceases these when the plasma density distribution falls below a criterion, ensuring uniform etching results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low-power microwaves are used for plasma etching, then substrate damage is reduced and etching selectivity is improved, but plasma density becomes low and plasma distribution becomes non-uniform
Solution Approach 1:
The patent applies periodic pulsed microwave power with multiple on-periods and off-periods. The microwave power is applied in a first on-period, then a first off-period, then a second on-period with different power levels. This periodic action allows plasma to be generated and maintained uniformly while controlling the timing and intensity of ion bombardment, thereby reducing substrate damage while maintaining adequate plasma density for uniform distribution.
Solution Approach 2:
The patent changes microwave power parameters by applying different power levels in different time periods. A first microwave power level is used in the first on-period, and a second microwave power level (different from the first) is used in the second on-period. This parameter change allows optimization of plasma density and distribution uniformity while controlling substrate damage, resolving the contradiction between low power benefits and plasma density requirements.
2Manufacturing precision
If low-power microwaves are used for plasma etching, then etching selectivity is improved, but plasma distribution uniformity deteriorates
Solution Approach 1:
The periodic pulsed microwave structure with multiple on-periods and off-periods allows plasma to be generated uniformly throughout the chamber during each on-period, then given time to distribute uniformly during off-periods. This periodic action maintains plasma distribution uniformity while enabling precise control of etching selectivity through timing and power level adjustments.
Solution Approach 2:
The first on-period serves as a preliminary action to generate and distribute plasma uniformly throughout the processing chamber before the actual etching process in the second on-period. This preliminary plasma generation ensures uniform plasma distribution is established before etching begins, maintaining composition stability while preserving etching selectivity.
3Object-affected harmful factors
If low-power microwaves are used for plasma etching, then gentle plasma is created, but plasma does not spread evenly to the outer periphery
Solution Approach 1:
The periodic pulsed microwave structure with multiple on-periods allows plasma to be generated in cycles, giving it time to expand and distribute uniformly to the outer periphery during off-periods before the next generation cycle begins. This periodic action ensures gentle plasma creation while achieving even plasma coverage across the entire processing area.
Solution Approach 2:
The first on-period acts as a preliminary plasma generation phase that allows plasma to spread and establish uniform distribution throughout the chamber, including reaching the outer periphery, before the main etching process begins in the second on-period. This preliminary action ensures adequate plasma coverage area while maintaining gentle plasma characteristics.
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
Achieves uniform etching results by controlling plasma density distribution, reducing substrate damage, and enhancing etching selectivity.
Implementation Method 1
plasma is generated by microwaves in a vacuum container to which an external magnetic field is applied
Implementation Method 2
by creating resonance between the frequency of the magnetic field with the frequency of the microwaves, plasma can be generated
Implementation Method 3
high-frequency power is applied to a sample (for example, a wafer) in a substantially sinusoidal continuous waveform in order to accelerate ions incident on the semiconductor device
Implementation Method 4
Etching progresses by the reaction between the radicals and ions generated by the plasma with the material of the sample
Data Source
AI summary
Aspects relate to providing a plasma processing technique that is capable of facilitating uniform etching results in low-power microwave plasma processing applications. A plasma processing apparatus includes a control unit configured to cause a microwave power supply to output a first microwave pulse having a first power and a first duty ratio to produce a uniformly distributed plasma in a plasma processing chamber; the microwave power supply to output a second microwave pulse having a second power which is less than the first power and a second duty ratio which is greater than the first duty ratio; a RF bias power supply to apply a wafer bias voltage with respect to a substrate stage; and the microwave power supply and the RF bias power supply to cease output of the second microwave pulse and the wafer bias voltage.