DUV Output Beam Formation for Lower Spatial Coherence
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Solution Overview
Problem
Existing photolithography systems using excimer light sources face challenges in efficiently forming output light beams with reduced spatial coherence, which is essential for minimizing speckle and ensuring uniform exposure on semiconductor substrates.
Innovation Solution
An apparatus comprising a beam splitter and a plurality of reflective optical elements that rotate the divergence of the light beam from a deep ultraviolet (DUV) light source, combined with a polarization element to maintain the polarization state, effectively forming an output beam with reduced spatial coherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional excimer light sources are used in photolithography, then the light beam can be generated, but the spatial coherence is too high causing speckle and non-uniform exposure
Solution Approach 1:
The light beam is divided into multiple separate beams using a beam splitter, and each beam is independently processed through reflective optical elements. This segmentation allows different portions of the light to have different divergence characteristics, which when recombined, reduce spatial coherence and eliminate speckle patterns while maintaining uniform exposure across the substrate.
Solution Approach 2:
Different regions of the light beam are given different divergence properties through the reflective optical elements. By locally modifying the divergence of different beam portions and then recombining them, the system achieves reduced spatial coherence overall, which reduces speckle and improves exposure uniformity without sacrificing total light intensity.
2Reliability
If the divergence of light is rotated to reduce spatial coherence, then speckle is reduced, but the polarization state of the light changes
Solution Approach 1:
A polarization element is introduced as an intermediary component in the optical path. This element compensates for the polarization changes caused by the reflective optical elements that rotate the divergence. By placing the polarization element strategically in the beam path, the system restores the original polarization state while maintaining the beneficial divergence rotation effects.
3Reliability
If multiple optical elements are added to rotate divergence and control polarization, then spatial coherence is reduced, but the device complexity increases
Solution Approach 1:
The reflective optical elements are designed to perform multiple functions simultaneously: they rotate the divergence of the light beam to reduce spatial coherence, control the polarization state, and direct the light through the optical path. This multi-functionality reduces the need for separate components, thereby managing device complexity while achieving the desired optical effects.
Solution Approach 2:
Multiple optical functions are merged into a compact arrangement of reflective optical elements and a beam splitter. By combining divergence rotation, polarization control, and beam directing functions into an integrated optical assembly, the system achieves reduced spatial coherence and improved uniformity without proportionally increasing overall device complexity.
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 solution achieves a lower spatial coherence in the output light beam, reducing speckle and improving the uniformity of exposure on semiconductor substrates, thereby enhancing the performance of photolithography systems.
Implementation Method 1
a beam splitter on a beam path, the beam splitter configured to receive light from a deep ultraviolet (DUV) light source; and a first plurality of reflective optical elements on the beam path. The beam splitter is configured to direct a portion of the light received from the DUV light source toward the first plurality of reflective optical elements
Implementation Method 2
the beam splitter is configured to direct the rotated light and a portion of the light received from the DUV light source onto an output beam path
Implementation Method 3
a first plurality of reflective optical elements on the beam path. The beam splitter is configured to direct a portion of the light received from the DUV light source toward the first plurality of reflective optical elements; the first plurality of reflective optical elements is configured to rotate a divergence of the portion of the light to produce rotated light
Implementation Method 4
The apparatus also may include a polarization element on the beam path. The polarization element may be configured to change a polarization state of the rotated light such that, on the output beam path, the rotated light has the same polarization state as light received from the DUV light source
Data Source
AI summary
An apparatus includes: abeam splitter on abeam path, the beam splitter configured to receive light from a deep ultraviolet (DUV) light source; and a first plurality of reflective optical elements on the beam path. The beam splitter is configured to direct a portion of the light received from the DUV light source toward the first plurality of reflective optical elements; the first plurality of reflective optical elements is configured to rotate a divergence of the portion of the light to produce rotated light; and the beam splitter is configured to direct the rotated light and a portion of the light received from the DUV light source onto an output beam path.