MFC Control Scheme for Gas Delivery Time Scale Reduction
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Solution Overview
Problem
In plasma processing, gas species with different molecular masses and delivery line geometries reach equilibrium pressure at different times, leading to gas composition drift and substandard device production due to delayed or improper gas mixing in the processing chamber.
Innovation Solution
A mass flow controller (MFC) control scheme is implemented to reduce gas delivery time by identifying delayed gas species, determining an initial overshoot strength and duration for the MFC flow rate, and verifying the control scheme to ensure the gas mixture reaches the target pressure profile within the processing chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gas species with different molecular masses are delivered into the processing chamber, then the processing can be performed with required gas composition, but the gas species reach equilibrium at different times causing gas composition drift
Solution Approach 1:
The system performs preliminary action by pre-mixing gas species in a mixing manifold before delivery to the processing chamber. This ensures that gas species with different molecular masses are already combined and will reach the chamber simultaneously, eliminating gas composition drift caused by different delivery time scales.
Solution Approach 2:
A mixing manifold is introduced as an intermediary component between the gas delivery lines and the processing chamber. This intermediary device provides a common mixing region where multiple gas streams converge and equilibrate before entering the chamber, ensuring uniform gas composition delivery.
2Productivity
If the carrier gas flows at a much higher flow rate than the process gas, then the carrier gas can drive the process gas flow, but it takes prohibitively long time for the process gas to build up pressure and mix with the carrier gas
Solution Approach 1:
The system performs preliminary mixing of carrier gas and process gas in the mixing manifold before delivery. This preliminary action allows the process gas to build up pressure and mix with the carrier gas in advance, eliminating the prohibitively long pressure build-up time that would occur if mixing happened only after carrier gas entry into the chamber.
3Productivity
If substrate processing begins when pressure stabilization is reached, then processing can start promptly, but gas composition drift may cause substandard devices to be created
Solution Approach 1:
The system performs preliminary mixing of all required gas species in the mixing manifold before pressure stabilization and before substrate processing begins. This ensures that the correct gas composition is established in advance, so when processing starts upon pressure stabilization, the gas composition is already correct, preventing substandard device creation.
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 minimizes gas composition drift, reduces processing time, and improves substrate quality by ensuring the gas mixture reaches the required equilibrium state more quickly, thereby enhancing manufacturing efficiency and product quality.
Implementation Method 1
the high-flow gas (carrier gas) drives the flow of the low-flow gas (process gas) via molecular collision
Implementation Method 2
the gas species become mixed and reach an equilibrium pressure state
Data Source
AI summary
A method for establishing a mass flow controller (MFC) control scheme, which is configured for reducing a time scale for gas delivery into a processing chamber, for a recipe is provided. The method includes identifying a set of delayed gas species utilized during execution of the recipe with a set of delivery time slower than a target delivery time scale. The method also includes establishing an initial overshoot strength and an initial overshoot duration for each gas specie of the set of delayed gas species. The method further includes establishing MFC control scheme by adjusting an MFC hardware for each gas specie during the execution of the recipe. Adjusting the MFC hardware includes applying the initial overshoot strength for the initial overshoot duration to determine if the MFC control scheme provides for each gas specie a pressure profile within a target accuracy of an equilibrium pressure for the processing chamber.