Excimer Laser Beam Profile Control via Dual-Beam Overlap
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing excimer-laser annealing process for silicon crystallization is inefficient due to high error margins in energy density, leading to non-uniform crystalline microstructures, and previous methods to compensate for this, such as using absorbers, result in wasteful laser energy usage and potential damage to optical components.
Innovation Solution
The use of two laser beams with different short-axis beam-widths, homogenized and focused to create a step-profile intensity distribution on the silicon layer, allowing for controlled partial overlap to achieve a desired energy density distribution without wasting laser energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If absorbers are used to create step-profile intensity distribution, then energy density uniformity is improved, but laser energy is wasted and absorbers suffer damage at short wavelengths
Solution Approach 1:
The patent divides the single laser beam into two separate beams using beam splitting optics. Each beam is independently homogenized through separate short-axis homogenizers, allowing the creation of a step-profile intensity distribution without energy-wasting absorbers. The segmented beams are then recombined to form the final elongated beam with the desired intensity profile.
Solution Approach 2:
The patent changes the optical parameters of the two beams by adjusting their respective short-axis beam-widths through independent homogenizer settings. By controlling the degree of overlap and the focal positions of the two beams, the system achieves variable step-profile intensity distributions without energy loss, directly addressing the energy wastage problem caused by traditional absorber-based methods.
2Manufacturing precision
If absorbers are used to control intensity profile, then crystalline microstructure uniformity is improved, but absorbers cause damage at short wavelengths
Solution Approach 1:
The patent extracts and eliminates the harmful absorber elements from the optical path. Instead of using absorbers to create the step-profile intensity distribution, the system uses pure optical elements (beam splitters, homogenizers, and focusing lenses) that do not suffer from damage at short excimer laser wavelengths, thereby removing the harmful factor while maintaining the desired crystalline microstructure uniformity.
Solution Approach 2:
The patent introduces intermediary optical elements (beam splitting optics and separate homogenizer systems) to achieve the intensity profile control function previously performed by absorbers. These intermediaries manipulate the beam parameters optically without the harmful side effects of absorber damage, enabling precise control of crystalline microstructure formation.
3Device complexity
If single laser beam is used, then device complexity is reduced, but ability to achieve selective beam profile is limited
Solution Approach 1:
The patent introduces dynamic controllability to the optical system by enabling independent adjustment of parameters for two separate beams. The short-axis homogenizers and focusing optics for each beam can be independently configured, allowing dynamic selection of different beam profiles, overlap degrees, and intensity distributions. This dynamic adaptability compensates for the increased device complexity by providing versatile beam profile control.
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 approach enables precise control of energy density across the silicon layer, reducing the error margin in crystallization and maintaining process throughput while avoiding damage to optical components, resulting in a more uniform crystalline microstructure.
Implementation Method 1
short-axis homogenizer (16) including spaced apart arrays (18A and 18B) of cylindrical lenses (19). These lenses have positive optical power in the short-axis only, having zero optical power in the long axis
Implementation Method 2
Lenses 26 and 32 are configured and arranged such that each diverging beam-part from array 22A is spread to a long-axis pupil of apparatus 10
Implementation Method 3
A favored source of the optical pulses is an excimer laser, which delivers pulses having a wavelength in the ultraviolet region of the electromagnetic spectrum
Implementation Method 4
a thin layer of amorphous silicon on a glass substrate is repeatedly melted by pulses of laser radiation
Implementation Method 5
Melting and re-solidification (re-crystallization) through the repeated pulses take place until a desired crystalline microstructure is obtained in the film
Data Source
AI summary
Apparatus for homogenizing and projecting two laser-beams is arranged such that the projected homogenized beams are aligned parallel to each other in a first transverse axis and partially overlap in second transverse axis perpendicular to the first transverse axis. The projected homogenized laser-beams have different intensities in the second axis and the degree of partial overlap is selected such that the combined intensity of the laser beams in the second axis has a step profile.