Mass Flow Controller Timing for Fast ALD Gas Delivery
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Solution Overview
Problem
The delay and slowdown in the rise of the flow rate of material gas at the substrate position due to piping delays and viscosity effects reduce the production efficiency and quality of semiconductors produced by Atomic Layer Deposition (ALD).
Innovation Solution
A mass flow controller that performs flow rate control at different rates during distinct periods: a transitional period with an increased flow rate to quickly fill the piping, a steady flow period to maintain the target rate, and a stop period to ensure precise and timely adjustments to the substrate. The control mechanism includes a display means that provides real-time feedback and an abnormality handling mechanism to prevent incorrect readings and unnecessary operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the flow rate control valve repeatedly opens and closes to supply material gas in short cycles, then the responsiveness in flow rate control is maintained, but the valve becomes fatigued and performance degrades
Solution Approach 1:
The system performs preliminary actions by pre-positioning the valve and preparing the flow path before the actual short-cycle operation begins. The valve is kept in a predetermined state and the system is pre-configured to minimize the number of actual opening/closing operations needed during ALD cycles, thereby reducing fatigue while maintaining responsiveness.
2Ease of operation
If the material gas flows through long piping to reach the substrate, then the gas can be supplied to the reaction chamber, but the flow rate rises with delay and slowdown due to piping delays and viscosity effects
Solution Approach 1:
The flow path is segmented into multiple sections with control valves positioned at different locations along the piping. This allows independent control of different segments, enabling faster response by controlling flow locally rather than through the entire piping length, thereby reducing the delay and slowdown effects.
Solution Approach 2:
A bypass line with a bypass valve is introduced as an intermediary path that allows material gas to reach the reaction chamber more quickly by circumventing parts of the main piping. This mediator path reduces the effective flow path length and minimizes viscosity-related delays.
3Loss of time
If the flow rate is increased to quickly fill the piping, then the delay is reduced, but the flow rate control precision may be compromised
Solution Approach 1:
The control system dynamically adjusts the flow rate based on real-time feedback from the flow sensor. During the initial filling phase, a higher flow rate is permitted to reduce delay, but as the system reaches the target flow rate, the control automatically transitions to precise regulation mode, maintaining manufacturing precision while minimizing time loss.
Solution Approach 2:
A flow sensor provides real-time feedback to the control system, enabling closed-loop control that can quickly respond to flow rate changes. This feedback mechanism allows the system to temporarily exceed target flow rates during piping filling while automatically correcting to maintain precise flow rate control once the substrate area is reached, thereby resolving the contradiction between speed and precision.
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 reduces the delay and slowdown in the flow rate at the substrate, improving the quality and production efficiency of semiconductors by ensuring the fluid reaches the substrate quickly and accurately, minimizing wastage and preventing false alarms.
Implementation Method 1
a flow sensor which outputs a flow rate signal corresponding to a flow rate of a fluid
Implementation Method 2
a flow control valve which controls the flow rate of the fluid by adjusting an opening degree of the valve
Data Source
AI summary
A mass flow controller performs flow rate control depending on supply periods. In a period from a first time point to a second time point t, a valve opening degree signal is output to a flow rate control valve such that a flow rate measured value determined based on a flow rate signal is larger than the first setting value. In a period from the second time point to a third time point, the valve opening degree signal is output to the flow rate control valve such that the flow rate measured value coincides with the first setting value, and in a period from the third time point to a time point when the first setting value is next input, the valve opening degree signal is output to the flow control valve such that the flow rate measured value coincides with the second setting value.