Raw Material Gas Supply Apparatus for ALD Film Thickness Control
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Solution Overview
Problem
In the Atomic Layer Deposition (ALD) method, precise control of the vaporized raw material flow rate in the raw material gas is challenging due to variations in raw material state (solid or liquid), grain size, and temperature distribution, leading to unstable film thickness and quality.
Innovation Solution
A raw material gas supply apparatus with a mass flow controller for the carrier gas, a flow rate measurement unit, and a dilution gas supply line, which uses a PID operation unit to adjust the carrier and dilution gas flow rates based on measured vaporization amounts, ensuring a stable vaporized raw material supply by intermittently repeating supply and pause periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a densitometer is used to measure raw material concentration in the mixed gas, then measurement capability is provided, but precise detection is not achieved due to the short supply time of the raw material gas in ALD processes
Solution Approach 1:
The patent introduces a pre-mixing chamber where the carrier gas and raw material vapor are mixed before entering the measurement section. This preliminary mixing action ensures that the raw material concentration is already established and stable before the brief ALD supply period begins, allowing the densitometer to accurately measure the concentration during the short available time window.
Solution Approach 2:
The system maintains continuous flow of carrier gas through the raw material container and pre-mixing chamber, ensuring that the raw material vaporization and mixing process continues uninterrupted. This continuous action guarantees that whenever the valve opens for the short ALD supply period, the raw material gas is already properly formed and ready for immediate measurement and deposition.
2Temperature
If the raw material is heated for vaporization, then vaporized raw material is produced, but temperature distribution becomes non-uniform due to heat loss from sublimation
Solution Approach 1:
The patent employs a heater that selectively heats specific regions of the raw material container where raw material is present. By concentrating heating power in localized areas rather than attempting to heat the entire container uniformly, the system compensates for heat loss from sublimation in those specific zones, maintaining consistent vaporization temperature and preventing cold spots that would cause non-uniform temperature distribution.
Solution Approach 2:
The system uses temperature sensors to monitor the temperature within the raw material container and feeds this information back to the heater control. Based on the feedback signal, the heater automatically adjusts its power output to maintain the desired temperature, compensating for heat loss from sublimation and ensuring uniform temperature distribution throughout the raw material.
3Productivity
If the carrier gas flow rate is increased to improve mixing, then vaporized raw material transport is enhanced, but control precision of the vaporized raw material amount decreases
Solution Approach 1:
The patent divides the gas flow control into two independent segments: the carrier gas flow rate is optimized for efficient transport of vaporized raw material, while the raw material vaporization rate is separately controlled through precise temperature management of the raw material container. This segmentation allows each parameter to be optimized independently without compromising the other, achieving both high transport efficiency and precise control of the vaporized raw material amount.
Solution Approach 2:
The pre-mixing chamber acts as an intermediary between the raw material vaporization source and the deposition chamber. In this intermediate zone, the carrier gas and raw material vapor are thoroughly mixed, and the total flow rate is regulated before entering the ALD process. This intermediary stage decouples the transport efficiency function from the control precision function, allowing optimal performance of both.
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 allows for precise control of the vaporized raw material flow, stabilizing the film formation process and maintaining consistent film thickness and quality by compensating for variations in raw material distribution and temperature.
Implementation Method 1
By heating a raw material container accommodating the raw material, the raw material is vaporized to a raw material gas
Implementation Method 2
A carrier gas is supplied into the raw material container. The raw material is supplied into the processing chamber by the carrier gas
Data Source
AI summary
A raw material gas supply apparatus is configured to obtain a difference between a set value and a measured value of a vaporized raw material, add the difference as a correction value to the set value of the flow rate of the carrier gas to maintain an amount of the vaporized raw material at the set value, and subtract a difference from a set value of a flow rate of the dilution gas to maintain a total flow rate of the carrier gas and the dilution gas at a constant level. The amount of the vaporized raw material is calculated by subtracting an integration value of a measured value of the flow rate of the inert gas in the supply period of the raw material gas from an integration value of the flow rate of the raw material gas which is measured in the supply period.