Beam Homogenization for Uniform Semiconductor Annealing
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Solution Overview
Problem
Current thermal processing techniques for semiconductor wafers, such as Rapid Thermal Processing (RTP), struggle to achieve rapid temperature ramp-up and ramp-down rates, leading to inefficient annealing processes that expose wafers to elevated temperatures for too long, causing damage and non-uniform energy delivery, especially with shrinking device sizes and stringent uniformity requirements.
Innovation Solution
A system comprising an energy source, micro-lens arrays, beam splitting and combining devices, and a random diffuser to deliver a composite energy pulse with optimized pulse width and uniformity, minimizing damage and ensuring precise energy distribution across the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional RTP processes heat the entire wafer, then the wafer reaches elevated temperature for annealing, but the temperature ramp-up and ramp-down rates are limited and the wafer is exposed to elevated temperatures for too long
Solution Approach 1:
The patent segments the heating process by using multiple independent energy delivery zones across the wafer surface. Instead of heating the entire wafer uniformly, the system divides the wafer into multiple regions that can be heated independently and simultaneously, enabling faster overall heating while reducing the time each region spends at elevated temperature.
Solution Approach 2:
The patent employs pulsed energy delivery rather than continuous heating. By delivering energy in rapid pulses with controlled duration and repetition rates, the system achieves fast temperature ramps while allowing precise control over the total thermal exposure time, thereby reducing thermal budget damage.
2Manufacturing precision
If scanning laser anneal techniques deliver constant energy flux to small regions, then localized annealing is achieved, but the complexity of minimizing overlap and ensuring uniformity increases significantly
Solution Approach 1:
The patent merges multiple energy delivery zones into a single integrated system that processes multiple wafer regions simultaneously. By combining several heating zones into one coordinated system, it achieves uniform annealing across the wafer without requiring complex sequential scanning and overlap control, thereby reducing process complexity while maintaining precision.
Solution Approach 2:
The patent applies energy delivery that extends slightly beyond the immediate annealing region to ensure uniformity, using overlapping energy zones that are carefully controlled. This partial excess action compensates for edge effects and ensures consistent annealing across the entire wafer surface without requiring precise boundary control.
3Speed
If pulsed laser anneal delivers high energy in short pulses, then rapid heating is achieved, but damage to the substrate or optical components may occur
Solution Approach 1:
The patent segments the high-energy pulse into multiple lower-energy sub-pulses delivered to different zones. This segmentation allows rapid heating of each zone while distributing the peak energy load, thereby achieving fast heating rates without concentrating enough energy in a single location to cause substrate damage or optical component failure.
Solution Approach 2:
The patent introduces intermediate energy delivery steps between the source and the substrate. By using multiple energy delivery zones as intermediaries that distribute and moderate the energy flow, the system achieves rapid heating while preventing excessive energy concentration that would cause damage to either the substrate or optical components.
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
The system enables rapid and uniform thermal processing of semiconductor substrates, reducing damage and extending the lifetime of optical components while maintaining high energy delivery efficiency and uniformity, addressing the limitations of existing RTP techniques.
Implementation Method 1
a first micro-lens array having a plurality of micro-lenses that are adapted to receive at least a portion of the first energy pulse transmitted from the output of the energy source, a second micro-lens array having a plurality of micro-lenses that are adapted to receive the at least a portion of the energy transmitted from the first micro-lens array
Implementation Method 2
a second lens that is positioned to receive the at least a portion of the first energy pulse and cause the image received by two or more micro-lenses in the first micro-lens array to be at least partially different, wherein the second lens is adapted to improve the uniformity of the at least a portion of the first pulse transmitted by the first lens
Data Source
AI summary
The present invention generally relates to an optical system that is able to reliably deliver a uniform amount of energy across an anneal region contained on a surface of a substrate. The optical system is adapted to deliver, or project, a uniform amount of energy having a desired two-dimensional shape on a desired region on the surface of the substrate. Typically, the anneal regions may be square or rectangular in shape. Generally, the optical system and methods of the present invention are used to preferentially anneal one or more regions found within the anneal regions by delivering enough energy to cause the one or more regions to re-melt and solidify.