Gas Flow Ratio Control Using Manifolded MFC 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 attempted, but competition among MFCs for gas flow causes flow variations and reduces manufacturing precision
Solution Approach 1:
A distribution manifold is introduced as an intermediary component between the gas source and multiple mass flow controllers. The manifold distributes gas flow to multiple MFCs simultaneously, eliminating the competitive struggle for gas flow that occurs when MFCs are connected directly to a common source. This intermediary structure ensures that each MFC receives adequate gas flow while maintaining precise flow ratio control to multiple input ports.
2Measurement precision
If flow splitting methods are used to improve flow ratio accuracy, then repeatability improves, but flow starvation and competition among MFCs still occur
Solution Approach 1:
The gas delivery system is segmented into distinct flow paths through the distribution manifold, which divides the gas flow into multiple independent channels that feed separate mass flow controllers. This segmentation allows each MFC to operate independently with adequate gas supply, eliminating flow starvation conditions while maintaining accurate flow ratio control through the coordinated operation of multiple MFCs.
Data Source
AI summary
A master controller identifies a flow ratio setpoint for at least one of a process gas or a carrier gas flow to a process chamber through a set of mass flow controllers. The master controller determines a flow setpoint for the at least one of the process gas or the carrier gas through the set of mass flow controllers based on the identified flow ratio setpoint. The master controller controls the at least one of the process gas flow or the carrier gas flow through each of the set of mass flow controllers according to the determined flow setpoint for each of the set of mass flow controllers and based on a back pressure reading provided by a back pressure sensor.