Gas Flow Ratio Control Using Manifold Back Pressure
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Solution Overview
Problem
Existing gas delivery assemblies for semiconductor processing chambers face challenges in achieving precise flow ratio control, leading to variations and non-uniformity in process outcomes due to competition among mass flow controllers for gas flow, resulting in undesirable flow variations and potential impacts on etch or deposition quality.
Innovation Solution
A gas flow control assembly that includes a distribution manifold, mass flow controllers, and a back pressure controller, which dynamically controls flow set points and back pressure to eliminate competition among mass flow controllers, ensuring precise flow ratio control and reducing flow variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple mass flow controllers are used to control gas flow to multiple input ports, then flow ratio control is improved, but flow variations and starvation issues occur due to competition among controllers
Solution Approach 1:
A common upstream pressure control point is introduced as an intermediary element that all mass flow controllers access. This mediator ensures that each controller receives adequate gas flow pressure, preventing starvation and competition effects while maintaining precise flow ratio control across multiple input ports.
Solution Approach 2:
The system equalizes the upstream pressure conditions for all mass flow controllers by providing a common pressure control point. This creates equipotential flow conditions where each controller operates under identical pressure conditions, eliminating competitive interactions and ensuring stable, reliable flow delivery.
2Manufacturing precision
If flow-splitting methods are used with multiple mass flow controllers, then flow ratio accuracy is improved, but device complexity increases
Solution Approach 1:
The common upstream pressure control point serves multiple functions simultaneously: it provides pressure regulation for all mass flow controllers, eliminates flow competition, ensures adequate flow delivery to each controller, and simplifies the overall system architecture. This multi-functional element reduces complexity while maintaining high flow ratio accuracy.
3Manufacturing precision
If mass flow controllers actively control relative flow rates, then flow ratio control is achieved, but flow variations occur due to competition for gas flow
Solution Approach 1:
The system establishes preliminary pressure conditions at a common upstream control point before gas flow reaches the individual mass flow controllers. This preliminary pressure equalization ensures that each controller starts from the same pressure baseline, preventing flow variations and composition instability that would otherwise result from competitive flow dynamics.
Data Source
AI summary
A master controller determines a first flow setpoint for a process flow gas and/or a carrier gas flow through a first mass flow controller. The master controller obtains a back pressure setpoint of a distribution manifold and determines a second flow setpoint for the process gas flow and/or the carrier gas flow through a second mass flow controller or a back pressure controller based on the determined first flow setpoint and the obtained back pressure setpoint. The master controller controls the process gas flow and/or the carrier gas flow through the first mass flow controller to the first flow setpoint and the second mass flow controller and/or the back pressure controller to the second flow setpoint. The master controller controls the back pressure of the distribution manifold to the back pressure set point in view of a back pressure reading from a back pressure sensor of the distribution manifold.