Monocrystal Interface Shape Control via Load Cell and Camera
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Solution Overview
Problem
Current silicon monocrystal growth methods, such as the Czochralski process, lack the ability to control the interface shape of the ingot during growth, which affects the quality of the final silicon wafer and growth rate, as the shape is only confirmed after completion.
Innovation Solution
A system and method that predict and control the interface shape of the ingot by measuring the ingot's weight using a load cell and diameter using a camera, comparing actual and theoretical values to adjust process conditions in real-time, allowing for targeted interface shape control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the interface shape of the ingot is not monitored during growth, then the measurement system remains simple, but the manufacturing precision of the silicon ingot deteriorates
Solution Approach 1:
The patent introduces an intermediary measurement system consisting of a camera and load cell that indirectly measures the interface shape by capturing images of the meniscus and measuring weight changes. This intermediary approach allows precise interface shape control without requiring direct physical contact or complex in-situ sensors within the crucible environment
Solution Approach 2:
The patent replaces complex mechanical interface shape sensors with an optical measurement system (camera) and weight measurement system (load cell). The camera captures optical images of the meniscus, and the load cell measures weight changes, substituting direct mechanical measurement of the interface with indirect optical and gravitational measurement methods
2Manufacturing precision
If real-time interface shape measurement is implemented, then the manufacturing precision improves, but the device complexity increases
Solution Approach 1:
The measurement system serves multiple functions: the camera not only measures interface shape but also monitors ingot diameter, and the load cell measures both weight and derives growth rate. This multi-functionality reduces the need for separate specialized sensors for each measurement parameter, thereby limiting the increase in device complexity
Solution Approach 2:
The patent implements a feedback control system where the measured interface shape and diameter are continuously compared with target values, and the pulling speed is automatically adjusted to maintain the desired interface shape. This closed-loop feedback enables precise control using a relatively simple measurement system
3Productivity
If the interface shape is only checked after growth completion, then the measurement system remains simple, but the productivity deteriorates due to inability to adjust during growth
Solution Approach 1:
The patent performs preliminary measurement of the interface shape and diameter during the growth process, allowing adjustments to be made before the growth is completed. This preliminary detection enables optimization of the growth rate and interface shape control during the actual growth process, improving productivity
Solution Approach 2:
The real-time feedback from the measurement system allows dynamic adjustment of growth parameters during the process, enabling optimization of the growth rate while maintaining quality standards. This feedback mechanism transforms the growth process from a static post-check system to a dynamic real-time optimization system
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
Enables real-time prediction and control of the ingot interface shape, improving the RRG or ORG quality of the silicon ingot and enhancing the growth rate, resulting in silicon wafers that meet customer needs.
Implementation Method 1
deriving a measurement value by measuring the weight of the ingot grown for a predetermined time by means of a load cell disposed on an upper portion the monocrystal ingot
Implementation Method 2
deriving a theoretical value of the weight of the monocrystal ingot through a diameter of the monocrystal ingot measured by a diameter measuring camera disposed outside of a process chamber
Data Source
AI summary
The present invention relates a method for controlling a growth interface shape while growing a monocrystal ingot by a Czochralski method, the method including a step of starting a growth of the monocrystal ingot after setting a control condition of a monocrystal growing process so that an interface of the ingot becomes a target shape; a step of deriving a measurement value by measuring a weight of the ingot grown for a predetermined time by means of a load cell disposed on an upper portion the monocrystal ingot; a step of deriving a theoretical value of the weight of the monocrystal ingot through a diameter of the monocrystal ingot measured by a diameter measuring camera disposed outside of a process chamber for a predetermined time and a height of the monocrystal ingot grown for the predetermined time; a step of predicting a growth interface shape of a growing monocrystal ingot by deriving a difference between the measurement value and the theoretical value; and changing process conditions during growth of the monocrystal ingot by comparing the predicted interface shape of the monocrystal ingot with the targeted interface shape of the monocrystal ingot. Therefore, the interface shape of the growing ingot may be predicted during the growing process of the monocrystal ingot, and the process conditions may be controlled to grow the silicon ingot in the targeted interface shape.