Plasma Etch Uniformity Control Using Localized Gas Pulsing
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Solution Overview
Problem
Plasma etching processes face challenges in achieving uniformity and repeatability, particularly at atomic scale dimensions, due to non-uniform distribution of etchant and passivating species across the substrate, leading to issues like footing at the center and bowing at the edge, which affect wafer yield and critical dimension control.
Innovation Solution
The method involves pulsing additional gases using effusive gas injectors to localize the flux of etchants and passivants, adjusting the plasma composition locally to enhance uniformity by synchronizing or asynchronizing RF power and gas pulsing, thereby compensating for non-uniform etch rates and profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a steady state flow of process gas is maintained in the plasma processing chamber, then the plasma generation and etching process can be sustained, but non-uniform distribution of etchant and passivating species occurs across the substrate
Solution Approach 1:
The patent applies periodic action by pulsing additional process gas in cyclic intervals during the etching process. This periodic gas pulsing creates time-varying plasma conditions that redistribute etchant and passivating species across the substrate, converting a static non-uniform distribution into a dynamically controlled process that achieves uniform etching results while maintaining plasma stability.
2Manufacturing precision
If additional gas is pulsed using effusive gas injector to disrupt steady state flow, then local plasma composition is changed to improve uniformity, but device complexity increases
Solution Approach 1:
The patent uses an effusive gas injector as an intermediary device to deliver additional process gas into the plasma chamber. This intermediary component enables precise local injection of gas that disrupts the steady state flow and modifies plasma composition in specific regions, achieving uniform etching without requiring complete system redesign. The effusive injector acts as a mediator between the gas source and the plasma environment.
3Manufacturing precision
If effusive gas injector is used to pulse additional gas towards substrate, then etchant and passivant flux is localized to control etch profile, but loss of time occurs during gas pulsing cycles
Solution Approach 1:
The patent implements periodic gas pulsing where additional process gas is injected in controlled cycles during the etching process. This periodic action allows the system to achieve uniform etch profiles and precise critical dimension control by redistributing reactive species across the substrate. The cyclic nature of the process enables time for gas injection, plasma adjustment, and etching to occur in organized intervals, optimizing both precision and throughput.
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 improves plasma etching uniformity by localizing gas flux, reducing or eliminating footing and bowing issues, ensuring consistent etch rates across the substrate, thereby enhancing wafer yield and critical dimension control.
Implementation Method 1
pulsing an additional gas, using an effusive gas injector, towards a region of the substrate to disrupt the steady state flow of the process gas over the region
Implementation Method 2
providing a pulsed RF source power to a first electrode of the plasma processing chamber to generate a plasma in the plasma processing chamber
Data Source
AI summary
A method of processing a substrate that includes: loading the substrate in a plasma processing chamber, the substrate including an underlying layer; maintaining a steady state flow of a process gas into the plasma processing chamber in the plasma processing chamber; generating a plasma in the plasma processing chamber; exposing the substrate to the plasma to etch the underlying layer; and pulsing a first additional gas, using a first effusive gas injector, towards a first region of the substrate to disrupt the steady state flow of the process gas over the first region, the pulsing locally changing a composition of the plasma near the first region.