Triggered Gain Scheduling for Gas Pulse Pressure Control
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Solution Overview
Problem
Existing gas delivery systems in semiconductor fabrication, such as those used in atomic layer deposition, face challenges in accurately and consistently delivering gas pulses due to limitations in pressure control, particularly during rapid pressure changes associated with the opening and closing of shutoff valves, leading to inaccurate gas dosing in process chambers.
Innovation Solution
A pressure controller system that operates using multiple gain schedules, switching between them based on an external trigger signal indicating the state of the shutoff valve, allowing for optimized control during both pulse delivery and steady-state conditions, thereby improving the accuracy and repeatability of gas delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single gain schedule is used for pressure control, then the system is simple to operate, but the pressure control accuracy deteriorates during rapid pressure changes
Solution Approach 1:
The pressure controller dynamically switches between different gain schedules based on the operational state (triggered vs. non-triggered modes). The control gain is adjusted in real-time: a first gain schedule is applied during rapid pressure changes when the shutoff valve actuates, and a second gain schedule is applied during steady-state conditions. This dynamic adaptation resolves the contradiction by maintaining high pressure control accuracy during transitions without requiring a completely complex control architecture.
Solution Approach 2:
The system changes the control parameter (gain schedule) based on the operational phase. An external trigger signal detects when the shutoff valve actuates, and the controller switches between at least two different gain schedules. This parameter change allows optimal pressure control accuracy during both dynamic transitions and steady-state operation, resolving the contradiction between maintaining simple operation and achieving high precision during rapid pressure changes.
2Manufacturing precision
If the pressure controller responds rapidly to shutoff valve actuation, then gas delivery accuracy improves, but pressure instability increases during transitions
Solution Approach 1:
The controller dynamically adjusts its response characteristics by switching between gain schedules. During rapid pressure changes (when the trigger signal is active), a first gain schedule provides rapid response for accurate gas delivery. When the system returns to steady-state (trigger signal inactive), a second gain schedule maintains pressure stability. This dynamic behavior resolves the contradiction between rapid response and stability.
Solution Approach 2:
The system employs periodic switching between different control modes synchronized with the shutoff valve actuation cycles. The external trigger signal generates periodic triggered modes that coincide with valve actuation, allowing the controller to apply appropriate control strategies at the right moments. This periodic action ensures accurate gas delivery during each pulse while maintaining overall pressure stability through the non-triggered mode between pulses.
3Measurement precision
If multiple gain schedules are implemented, then pressure control precision during transitions improves, but the device complexity increases
Solution Approach 1:
The system implements multiple gain schedules in a dynamic, state-dependent manner rather than requiring multiple independent control systems. The external trigger signal serves as a simple state indicator that switches between pre-configured gain schedules. This approach achieves high pressure control precision during transitions while keeping the overall device complexity manageable through centralized control logic.
Solution Approach 2:
The controller changes internal parameters (gain schedule selection) based on the trigger signal state without adding significant external hardware complexity. The system maintains a library of pre-configured gain schedules and selects the appropriate one based on whether the shutoff valve is actuating. This parameter change strategy achieves high precision while minimizing the increase in device complexity.
Data Source
AI summary
A gas delivery system and associated method includes a flow channel, a control valve, a downstream pressure sensor, and a controller. The control valve controls flow of gas in the flow channel. The downstream pressure sensor, located downstream of the control valve, measures gas pressure in the flow channel. The controller has an external trigger input to receive a trigger signal applied to a shutoff valve downstream from the control valve. The controller operates in separate modes based on a state of the trigger signal. In a non-triggered mode, the controller controls pressure at the pressure sensor via the control valve in accordance with a first gain schedule. In the triggered mode, the controller controls the pressure at the pressure sensor via the control valve in accordance with a second gain schedule that is distinct from the first gain schedule.