Flow Ratio Controller Settling Time Reduction
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Solution Overview
Problem
Existing gas delivery systems for semiconductor processing struggle with achieving precise and rapid gas flow rate control, leading to transient states and perturbations that hinder the attainment of desired steady-state conditions, especially as technology advances to smaller critical dimensions.
Innovation Solution
The method involves deactivating ratio setpoint feedback control in a flow ratio controller, initiating gas flow, moving valves to predetermined positions based on stored values from prior runs when upstream pressure is reached, and activating feedback control once steady-state flow is determined, utilizing a combination of mass flow sensors and adjustable valves to achieve precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional feedback control is continuously active in a flow ratio controller, then steady-state flow accuracy is maintained, but settling time increases and transient flow perturbations occur
Solution Approach 1:
The system performs preliminary action by storing valve positions and upstream pressure values from a prior process run during which steady-state flow was achieved. When a new process run begins, the controller deactivates feedback control and directly positions valves based on pre-stored optimal values, eliminating the transient period required for feedback control to converge to steady state.
Solution Approach 2:
The system creates a copy of the successful valve positions and pressure conditions from a prior process run. By copying these stored values and applying them at the start of a new process run, the system reproduces the steady-state conditions without going through the transient phase, thus reducing settling time while maintaining flow rate precision.
2Loss of time
If feedback control is deactivated and valve positions are set based on stored values, then settling time is reduced and transient flow is minimized, but control precision during transient states may be compromised
Solution Approach 1:
The system performs preliminary action by performing a calibration run where feedback control is active to establish accurate stored valve positions and upstream pressure values. This preliminary calibration ensures that the stored values represent reliable steady-state conditions, which are then copied to subsequent process runs to achieve fast settling without sacrificing control stability.
Solution Approach 2:
The system uses feedback control during the initial calibration phase to accurately determine and store the optimal valve positions and pressure values. This feedback mechanism ensures that the stored reference values are reliable, and subsequent process runs benefit from this pre-established accuracy while achieving faster settling times.
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 significantly reduces settling time, minimizes transient flow, and enables tighter process control by ensuring faster and more precise gas delivery to semiconductor processing chambers, potentially reaching steady-state flow rates up to 100% faster than conventional systems.
Implementation Method 1
a pressure sensor coupled to the input gas line and adapted to sense an up-stream gas pressure in the input gas line
Implementation Method 2
a plurality of mass flow sensors, each mass flow sensor operatively coupled to a different one of the plurality of outputs of the fan-out manifold and adapted to sense gas flow through a respective output
Data Source
AI summary
The present invention provides methods and apparatus for controlling gas flow to a semiconductor-processing chamber. The invention includes deactivating ratio setpoint feedback control in a flow ratio controller; initiating gas flow through the flow ratio controller; moving valves of the flow ratio controller to a preset position based on a stored position when an upstream pressure reaches a stored upstream pressure value, wherein the stored position and the stored upstream pressure value were stored during a prior process run; determining that steady state flow ratio controller output flows have been reached; and activating ratio setpoint feedback control in the flow ratio controller. Numerous additional features are disclosed.