Multi-stage Optical Homogenization for Rapid Thermal Processing
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Solution Overview
Problem
Rapid thermal processing systems face challenges in achieving uniform substrate heating due to inhomogeneous light pulses, which can lead to thermal non-uniformities and impact wafer yields during processes like dopant diffusion and chemical alterations.
Innovation Solution
The use of multiple optical homogenizers, specifically a first and second optical homogenizer with micro-lens arrays and Fourier lenses, to process light and achieve a uniform illumination across the substrate, reducing inhomogeneity by a factor of 64 or less, thereby improving thermal processing uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If short pulse duration light sources are used to rapidly heat the substrate, then heating speed is improved, but illumination uniformity deteriorates
Solution Approach 1:
The patent divides the illumination system into multiple optical homogenizers (first and second homogenizers) that segment and redistribute the light from the flash lamp. Each homogenizer contains multiple optical elements that split and recombine light paths, creating a more uniform illumination profile across the substrate while maintaining short pulse durations for rapid heating.
Solution Approach 2:
The patent introduces optical homogenizers as intermediary components between the flash lamp and the substrate. These homogenizers act as mediators that transform the inhomogeneous light distribution from the lamp into a uniform illumination pattern, allowing short pulse duration light sources to achieve both rapid heating and uniform illumination.
2Duration of action of moving object
If flash lamps are used to provide short pulse durations, then heating time is reduced, but thermal non-uniformities increase
Solution Approach 1:
The illumination system is segmented into multiple optical homogenizers that independently process different portions of the light beam. This segmentation allows each homogenizer to correct specific non-uniformities while maintaining the short pulse duration characteristic of flash lamps, thereby achieving both rapid heating and thermal uniformity.
Solution Approach 2:
The patent changes the optical parameters of the illumination system by introducing homogenizers with specific numerical apertures and optical configurations. These parameter changes transform the temporal and spatial characteristics of the light pulses, maintaining short duration while improving spatial uniformity to reduce thermal non-uniformities.
3Manufacturing precision
If multiple optical homogenizers are used to improve illumination uniformity, then thermal uniformity is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple optical homogenizers into a single integrated optical train between the flash lamp and substrate. By merging the functions of multiple homogenizing stages into a coordinated system with matched numerical apertures, the design achieves improved thermal uniformity while managing overall system complexity through functional integration.
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 enhances the uniformity of substrate heating, ensuring consistent thermal treatment and improving wafer yields by maintaining high optical efficiency and reducing thermal non-uniformities across the substrate.
Implementation Method 1
a first optical homogenizer with an output numerical aperture and a second optical homogenizer with an input numerical aperture. The first optical homogenizer includes a first micro-lens array, a second micro-lens array, and a first Fourier lens. The second optical homogenizer includes a third micro-lens array, a fourth micro-lens array, and a second Fourier lens.
Implementation Method 2
For many substrates, like silicon substrates as commonly used in the manufacture of integrated circuits, optical absorption is higher for shorter wavelengths especially at the beginning of a heating cycle when the substrate is closer to room temperature.
Data Source
AI summary
Substrate processing equipment and methods are used to improve the uniformity of illumination across an illuminated portion of a substrate by processing light with multiple optical homogenizers. The multiple optical homogenizers each include micro-lens arrays and Fourier lens. The multiple optical homogenizers are arranged so that the output numerical aperture of one of the optical homogenizers is within 5% of the input numerical aperture of another optical homogenizer.