Gas Mixture Distribution Plant for Silicon Wafer Doping
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Solution Overview
Problem
Current methods for packaging gas mixtures for silicon wafer doping in semiconductor production face challenges in achieving precise concentration control, stability, and flexibility, particularly with flammable, pyrophoric, and toxic dopant gases, leading to variability in results and logistical complexities.
Innovation Solution
A plant comprising a source of dopant and carrier gases, a mixer, flow regulators, and a control unit that adjusts flow rates based on target concentrations and consumption rates, with feedback loops and analysis units to ensure accurate and flexible delivery of gas mixtures directly to the doping unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gas mixtures are packaged in compressed or liquefied form in gas cylinders using sequential filling, then the gas mixture can be stored and transported, but the precision of concentration control deteriorates due to limited monitoring accuracy and temperature variations affecting pressure-based measurement
Solution Approach 1:
The patent replaces mechanical pressure-based monitoring with mass flow controllers that use electrical/control mechanisms to regulate gas flow. The MFCs provide precise electronic control of gas mixture composition by monitoring and adjusting flow rates based on setpoints, eliminating the imprecision of pressure-based methods while accounting for temperature variations through controlled regulation rather than passive measurement.
Solution Approach 2:
The patent implements feedback control through mass flow controllers that continuously monitor actual flow rates and adjust them to match desired setpoints. The system compares actual gas mixture composition with target values and makes real-time adjustments to maintain precision within tight tolerances (less than 1%, 0.5%, or 0.1% relative variation), providing closed-loop concentration control that compensates for disturbances.
2Duration of action of stationary object
If gas cylinders are used for delivering gas mixtures, then the gas mixture can be stored for extended periods, but the reliability of concentration stability deteriorates due to uncontrolled evaporation and temperature variations
Solution Approach 1:
The patent implements continuous production of gas mixtures through a flow system that continuously regulates and delivers the desired composition to the doping unit. Rather than relying on pre-packaged cylinders that sit idle and degrade, the system continuously generates fresh gas mixtures with controlled composition, ensuring concentration stability is maintained throughout the doping process without the interruptions and variations associated with cylinder changes.
Solution Approach 2:
The patent replaces passive pressure-driven flow from cylinders with an active controlled flow system using mass flow controllers. These devices use electronic control mechanisms to maintain precise flow rates and composition ratios regardless of temperature variations or pressure changes, eliminating the uncontrolled evaporation and concentration drift that occur in traditional cylinder-based systems.
3Ease of manufacture
If manual filling and monitoring of gas cylinders is performed, then the packaging process can be completed, but the productivity deteriorates due to sequential operations and frequent cylinder changes
Solution Approach 1:
The patent eliminates interruptions in gas supply by implementing a continuous flow system that produces and delivers gas mixtures without stopping for cylinder changes. The system maintains uninterrupted delivery to the doping unit, with the gas generation and delivery process continuing continuously rather than being interrupted by manual cylinder replacement operations, thereby significantly improving productivity.
Solution Approach 2:
The patent pre-configures the gas delivery system with multiple gas sources and a mixing apparatus that is ready to produce the desired gas mixture composition before it is needed. The mass flow controllers are pre-programmed with setpoints for the required gas ratios, allowing the system to immediately begin producing the correct mixture without manual filling operations when production starts or resumes.
4Device complexity
If pressure-based monitoring is used for filling gas cylinders, then the packaging process is simple, but the manufacturing precision deteriorates due to intrinsic limitations of pressure sensor accuracy and temperature variations
Solution Approach 1:
The patent replaces mechanical pressure-based monitoring and control with electronic mass flow control systems. The mass flow controllers use electrical signals and electronic sensing mechanisms to measure and regulate gas flow rates, providing superior precision in composition control. This substitution of mechanical systems with electronic/control-based systems eliminates the intrinsic accuracy limitations of pressure sensors while adding temperature compensation capabilities through electronic regulation.
Solution Approach 2:
The patent implements feedback control loops in the mass flow controllers that continuously monitor actual gas flow and composition, comparing them with target setpoints and making automatic adjustments to maintain precision within tight tolerances. This closed-loop control system compensates for temperature variations and other disturbances, achieving manufacturing precision of less than 1%, 0.5%, or 0.1% relative variation in gas mixture composition, far exceeding what simple pressure-based methods can achieve.
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
The solution enables precise control of gas mixture composition, ensuring high accuracy and stability, flexibility in delivery, and reduced logistical burdens by continuously adapting to consumption rates, thereby improving the reliability and efficiency of silicon wafer doping processes.
Implementation Method 1
a mixer device fluidically connected to the container of dopant gas and to the source of carrier gas, said mixer device being configured to produce, at an outlet, a gas mixture comprising the dopant gas and the carrier gas
Implementation Method 2
a first flow regulator member and a second flow regulator member which are configured to regulate respectively the flow of the dopant gas and the flow of the carrier gas flowing towards the mixer device according to a first flow rate setpoint and a second flow rate setpoint
Implementation Method 3
at least one measurement sensor configured to measure a physical quantity, the variation of which is representative of a variation in the consumption flow rate delivered by the delivery line
Implementation Method 4
the control unit being connected to the measurement sensor and configured to produce a first control signal from the first measurement signal, the flow regulator members being configured to adjust the first flow rate setpoint and the second flow rate setpoint in response to said first control signal
Data Source
AI summary
Plant for delivering a gas mixture to a silicon wafer doping unit comprising a source of a dopant gas (1), a source of a carrier gas (2), a mixer device (3) connected to the container of dopant gas (1) and to the source of carrier gas (2), a first flow regulator member (41) and a second flow regulator member (42) for regulating the flows of the dopant gas (1) and of the carrier gas (2) towards the mixer device (3), a control unit (5) for controlling the first and second flow regulator members (41, 42) so as to adjust the first flow rate setpoint (D1) and the second flow rate setpoint (D2) in proportions determined as a function of at least one target content (C1, C2) of dopant gas (1) and/or carrier gas (2) in the mixture, a buffer tank (7), a delivery line (6) for delivering the mixture to a doping unit (10) with a consumption flow rate (DC), at least one measurement sensor (8) for measuring a physical quantity, the variation of which is representative of a variation in the consumption flow rate (DC) and for providing a first measurement signal, the control unit (5) being connected to the sensor (8) and configured to produce a first control signal from the first measurement signal, the flow regulator members (41, 42) being configured to adjust the first and second flow rate setpoints (D1, D2) in response to said first control signal.