Laser Annealing Sweep Control for Thin-Wafer Backside Heating
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Solution Overview
Problem
Thin semiconductor wafers experience temperature rises on the surface opposite to the laser irradiation surface during annealing, which is not adequately suppressed by existing laser annealing techniques.
Innovation Solution
An annealing device and method where the laser beam spot is swept in the longitudinal direction, optimizing the sweep speed and aspect ratio of the beam spot to reduce the temperature rise on the back surface while maintaining activation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a pulsed laser beam is irradiated on a surface of an annealed target to perform annealing, then the annealing effect is achieved, but a temperature of a surface opposite to the laser irradiation surface rises due to heat conduction from the laser irradiation surface
Solution Approach 1:
The laser beam is divided into multiple pulses in the time domain, with each pulse separated by a predetermined time interval. This temporal segmentation allows the irradiated surface to cool down between pulses, preventing excessive heat conduction to the opposite surface while maintaining the annealing effect on the irradiation surface.
Solution Approach 2:
The laser beam is applied periodically with a predetermined cycle period, creating a rhythmic heating-cooling pattern. This periodic action ensures that heat accumulates sufficiently for annealing during the laser pulse duration, then dissipates during the interval, preventing thermal buildup that would cause opposite surface heating.
2Area of stationary object
If a beam spot is shaped into a long shape and moved across the annealed target, then annealing coverage is improved, but the sweep operation time increases
Solution Approach 1:
The laser beam is applied periodically with a predetermined cycle period during the sweep operation. This periodic pulsing allows for efficient energy delivery across the extended beam path, maintaining effective annealing treatment while managing the total processing time through optimized pulse timing rather than continuous irradiation.
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
Effectively suppresses the temperature rise on the back surface of the annealed target while achieving the desired activation rate, even with thin wafers, by increasing the sweep speed and optimizing the beam spot's aspect ratio.
Implementation Method 1
A beam spot (39) of a pulsed laser beam output from a laser light source (10) on a surface of an annealed target (60) is shaped into a long shape in one direction by a beam shaping optical element (12)
Implementation Method 2
it has been found that when a pulsed laser beam is irradiated on a surface of an annealed target to perform annealing, a temperature of an opposite surface rises due to heat conduction from a laser irradiation surface
Data Source
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AI summary
The disclosure provides a control device (40) of an annealing device, which is capable of further suppressing a temperature of a surface opposite to a laser irradiation surface from rising. A beam spot (39) of a pulsed laser beam output from a laser light source (10) on a surface of an annealed target (60) is shaped into a long shape in one direction by a beam shaping optical element (12). A movement mechanism (20) moves the beam spot with respect to the annealed target. The control device controls the laser light source and the movement mechanism and performs annealing by performing a sweep operation of moving the beam spot in a longitudinal direction of the beam spot with respect to the annealed target while causing the pulsed laser beam to be incident on the annealed target.