Scatter Melt Detection for Laser Annealing Phase Transition Control
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Solution Overview
Problem
Accurate measurement and control of wafer temperature during pulsed-laser annealing in IC chip fabrication is challenging due to the rapid temperature changes and small surface areas involved, affecting the precision of annealing processes.
Innovation Solution
A scatter melt detection system using a scatter melt detector with a focal plane array (FPA) to capture scatter images, identifying phase transitions by analyzing intensity variations, and calibrating laser power levels based on scatter images to control the annealing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pulsed-laser annealing is used for rapid thermal processing, then productivity and annealing effectiveness are improved, but measurement precision and temperature control accuracy deteriorate due to rapid temperature changes and small surface areas
Solution Approach 1:
The patent utilizes the phase transition of semiconductor material from solid to liquid at the melt threshold temperature. By detecting the optical scattering changes that occur during this phase transition, the system can precisely identify when the wafer surface reaches the critical temperature, thereby enabling accurate temperature measurement during rapid pulsed-laser annealing processes
Solution Approach 2:
The patent detects changes in optical scattering properties (analogous to color/optical property changes) of the semiconductor surface during phase transition. The scatter detector measures variations in light scattering intensity and patterns that occur when the material transitions from solid to liquid phase, providing a visual/optical indicator of temperature reach
2Manufacturing precision
If laser power is increased to achieve melt annealing, then annealing effectiveness is improved, but manufacturing precision deteriorates due to risk of exceeding melt threshold and causing defects
Solution Approach 1:
The patent implements a feedback control system where the scatter detector continuously monitors the semiconductor surface during laser annealing. When the detected scattering pattern indicates approach to the melt threshold phase transition, the system provides feedback to adjust or terminate laser power, preventing overheating and ensuring reliable process control
Solution Approach 2:
The patent uses preliminary calibration processes to establish the specific melt threshold characteristics for different semiconductor materials and conditions. This preliminary characterization allows the system to predict and control the phase transition point, enabling precise power level selection before actual annealing to ensure both effectiveness and reliability
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 precise detection of solid-to-liquid phase transitions and calibrates laser power for consistent annealing, ensuring accurate temperature control and process uniformity in semiconductor manufacturing.
Implementation Method 1
forming a scatter image of a region of the semiconductor surface that includes the annealing image; and identifying a solid to liquid material phase transition of the semiconductor material according to an intensity of light collected in the scatter image
Implementation Method 2
forming an annealing image on a surface of the semiconductor material with an annealing laser beam from an annealing laser
Implementation Method 3
the annealing includes incrementally varying a power level of the annealing laser below and above a melt threshold power level where a solid to liquid phase transition of the semiconductor material occurs
Data Source
AI summary
High bandwidth time-and-space resolved scatter phase transition microscopy systems configured to detect melt onset in a wafer being processed by laser annealing systems with ultra-short dwell times and spot size.