Heated Wafer Carrier Profiling for CVD Uniformity
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Solution Overview
Problem
Chemical vapor deposition processes face challenges in maintaining uniform conditions across multiple wafers, leading to variations in semiconductor device properties due to minor temperature and gas composition differences, affecting the emission wavelength of LEDs and other optoelectronic devices.
Innovation Solution
A system comprising a rotatable wafer carrier with a surface characterization tool that moves over multiple positions to measure temperature, reflectance, photoluminescence, and emissivity, providing position-dependent parameters to adjust heaters and gas sources in real-time, ensuring uniform conditions and optimizing the chemical vapor deposition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heating elements are used to maintain elevated temperature of the wafer carrier, then the desired reaction temperature is achieved, but temperature non-uniformity across the wafer surface occurs
Solution Approach 1:
The heating system is divided into multiple independent heating zones across the wafer carrier surface. Each zone can be independently controlled to compensate for local temperature variations, ensuring uniform temperature distribution across the entire wafer surface during chemical vapor deposition
Solution Approach 2:
Infrared sensors continuously monitor the temperature distribution across the wafer surface and provide real-time feedback to the control system. The control system adjusts the heating power in each zone based on the measured temperature deviations, maintaining uniform temperature despite variations in gas flow or environmental conditions
2Quantity of substance
If gas distribution elements are positioned to deliver reactant gases to the wafer surface, then chemical vapor deposition occurs, but non-uniform gas composition causes variations in deposited layer properties
Solution Approach 1:
The gas distribution element is segmented into multiple independent gas delivery zones corresponding to different regions of the wafer surface. Each zone can be independently controlled to deliver precise amounts of reactive gases, ensuring uniform composition of the deposited layer across the entire wafer
Solution Approach 2:
Different regions of the gas distribution element are designed with locally optimized characteristics, such as varying pore sizes or flow rates, to compensate for position-dependent variations in gas flow patterns and ensure uniform reactive gas composition across the wafer surface
3Productivity
If a large disc-shaped wafer carrier is used to hold numerous wafers, then productivity is increased, but maintaining uniform conditions across all wafers becomes more difficult
Solution Approach 1:
The large disc-shaped wafer carrier is divided into multiple independently controlled heating zones and gas distribution zones. This segmentation allows each region to be optimized and controlled separately, maintaining uniform temperature and gas composition across all wafers even as the total number of wafers increases
Solution Approach 2:
The system employs dynamic control of heating and gas distribution based on real-time sensor feedback from each wafer position. This allows the system to adapt to variations in thermal mass, gas flow patterns, and environmental conditions for each individual wafer, ensuring uniform processing conditions across the entire carrier
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 solution ensures uniformity across wafers, improving the yield and consistency of semiconductor devices by regulating temperature and gas distribution, thereby minimizing variations in device properties and enhancing the quality of LEDs and other optoelectronic devices.
Implementation Method 1
a surface characterization tool which is operative to move over a plurality of positions relative to the top surface of the carrier and/or the wafer transverse to the axis of rotation and is further adapted to produce characterization signals
Implementation Method 2
A surface characterization tool is moved over a plurality of positions relative to the top surface of the carrier, where a measurement location over the top surface of the carrier is changed while said top surface of the carrier is heated to a predetermined temperature
Implementation Method 3
heat is transferred from the heating elements to the bottom or second surface of the wafer carrier (the surface facing in the opposite direction from the top surface) and flows upwardly through the wafer carrier to the individual wafers
Implementation Method 4
The wafer carrier is maintained at the desired elevated temperature by heating elements, typically electrical resistive heating elements disposed below the wafer carrier
Implementation Method 5
Chemical vapor deposition is a process in which layers of one or more materials are deposited on a substrate by reaction of materials supplied as gasses or vapors
Data Source
AI summary
A method for characterizing a surface comprises rotating a carrier about an axis of rotation where the carrier has a top surface adapted to hold at least one semiconductor wafer with a major surface of the wafer extending generally transverse to the axis of rotation. A surface characterization tool is moved over a plurality of positions relative to the top surface of the carrier, where a measurement location over the top surface of the carrier is changed while said top surface of the carrier is heated to a predetermined temperature. Characterization signals over the plurality of positions with the surface characterization tool are produced and contain information about the heated top surface of the carrier, or when semiconductor wafers are held on the carrier, information about the semiconductor wafer can also be obtained.