Laser Annealing Focus Correction via Dynamic Beam Width Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Laser annealing methods face challenges in correcting focus position and beam size adjustments due to positional variations of semiconductor films, particularly in the minor axial direction, which affect annealing performance and energy density, especially with solid green laser systems having lower power and narrower beam sizes.
Innovation Solution
A laser annealing method and apparatus that utilize a minor-axis condenser lens and cylindrical lens arrays to detect and correct positional variations, adjusting the focus position and beam size automatically through feedback control, ensuring consistent energy distribution across the semiconductor film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid green laser is used to achieve higher process margin, then carrier mobility control is improved, but beam size must be narrowed to 100 μm or below which decreases depth of focus and makes annealing performance sensitive to positional variation
Solution Approach 1:
The patent makes the beam size dynamic by introducing a variable beam width mechanism that adjusts the minor axis beam width based on the detected positional variation of the semiconductor film. When positional variation is large, the beam width is increased to maintain sufficient depth of focus; when positional variation is small, the beam width is decreased to maintain high carrier mobility. This dynamic adjustment resolves the contradiction between process margin and annealing performance consistency.
2Power
If beam size is narrowed to increase power density, then carrier mobility is improved, but depth of focus decreases making the system sensitive to positional variation of semiconductor film
Solution Approach 1:
The patent implements a feedback control system that detects the positional variation of the semiconductor film and automatically adjusts the beam size accordingly. The detection unit measures positional variation, and the control unit modifies the minor axis beam width of the rectangular beam based on this measurement. This feedback mechanism ensures that the system maintains optimal power density while compensating for positional variations, thereby resolving the contradiction between power density and focus position sensitivity.
3Manufacturing precision
If excimer laser is used with large beam width, then depth of focus is large reducing sensitivity to positional variation, but carrier mobility is greatly changed depending on irradiation energy
Solution Approach 1:
The patent applies local quality by using a rectangular beam with different width characteristics in major and minor axes. The minor axis beam width is specifically controlled and dynamically adjusted based on positional variation, while the major axis maintains sufficient width for adequate depth of focus. This localized control of beam dimensions allows the system to simultaneously achieve positional variation tolerance and carrier mobility control that excimer lasers cannot provide.
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 correction of focus position and beam size adjustments in the minor axial direction, enhancing the stability and efficiency of the laser annealing process by maintaining consistent energy density and reducing interference fringes, even with positional variations.
Implementation Method 1
forming a polycrystalline silicon film by melting and solidifying an amorphous silicon film deposited on a substrate by irradiating to the amorphous silicon film with a laser beam
Implementation Method 2
focusing the shaped laser beam as a rectangular beam on a surface of a semiconductor film
Data Source
AI summary
In laser annealing using a solid state laser, a focus position of a minor axial direction of a rectangular beam is easily corrected depending on positional variation of a laser irradiated portion of a semiconductor film. By using a minor-axis condenser lens 29 condensing incident light in a minor axial direction and a projection lens 30 projecting light, which comes from the minor-axis condenser lens 29, onto a surface of a semiconductor film 3, laser beam 1 is condensed on the surface of the semiconductor film 3 in the minor axial direction of a rectangular beam. The positional variation of a vertical direction of the semiconductor film 3 in a laser irradiated portion of the semiconductor film 3 is detected by a positional variation detector 31, and the minor-axis condenser lens 29 is moved in an optical axis direction based on a value of the detection.