Shaped Bulb Wall Thickness for Uniform Pupil Fill
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Solution Overview
Problem
Broadband light sources used in semiconductor processing, such as plasma-based arc lamps, often suffer from non-uniform pupil fill due to the geometry of the bulb, leading to inefficient light distribution and reduced optical power at certain numerical aperture values.
Innovation Solution
The bulb thickness is strategically varied with increasing azimuthal angle to optimize the pupil fill, ensuring that the thickness at the cathode cutoff is between 0.8 and 0.9 times the equatorial thickness, and following a specific thickness profile (Y=Ax+B) to enhance the 0.24/0.13 NA power ratio, thereby improving light distribution and optical power across a range of numerical apertures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the bulb has a uniform thickness, then the manufacturing is simple, but the pupil fill is non-uniform leading to inefficient light distribution
Solution Approach 1:
The bulb wall thickness is made non-uniform with specific variation along the azimuthal angle, creating different optical paths in different regions. The thickness at cathode cutoff is designed to be 0.8-0.9 times the equatorial thickness, optimizing light distribution efficiency while maintaining manufacturing feasibility through controlled geometric variation.
2Productivity
If the bulb thickness is varied to optimize pupil fill, then the light distribution improves, but the manufacturing complexity increases
Solution Approach 1:
The bulb wall thickness parameter is systematically varied as a function of azimuthal angle, with the thickness at cathode cutoff set to 0.8-0.9 times the equatorial thickness. This controlled parameter variation achieves uniform pupil fill and optimizes the 0.24/0.13 NA power ratio to 3.0-3.3 while maintaining a manageable geometric complexity.
3Productivity
If the bulb thickness follows the specified profile, then the 0.24/0.13 NA power ratio is optimized, but the manufacturing precision requirements increase
Solution Approach 1:
The thickness variation is localized to specific regions of the bulb, with the critical parameter being the ratio of thickness at cathode cutoff to equatorial thickness (0.8-0.9). This localized quality control optimizes the 0.24/0.13 NA power ratio to 3.0-3.3 while concentrating precision requirements on key dimensional ratios rather than the entire surface.
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 results in a more uniform and efficient pupil fill, achieving a desired 0.24/0.13 NA power ratio between 3.0 and 3.3, enhancing the performance of broadband light sources in semiconductor wafer inspection tools by ensuring proper illumination over a range of incident angles.
Implementation Method 1
The bulb includes a wall made of an optically refractive material... the thickness of the wall is adjusted so that a thickness of the wall at a cathode cutoff is between about 0.8 and about 0.9 times a thickness of the wall at an equatorial plane
Data Source
AI summary
A lamp, a method of making a bulb for a lamp and an optical apparatus are disclosed. The lamp may include an anode and cathode disposed within a bulb. The bulb may include an optically refractive wall that is rotationally symmetric about an axis. A thickness of the wall may decrease with increase in azimuthal angle between an equatorial plane of the bulb and a point on the bulb's surface. The apparatus may include the lamp and an ellipsoidal reflecting surface. An alternative apparatus may include an ellipsoidal reflecting surface and a lamp having an anode and cathode within a bulb. A gap between the anode and cathode may be proximate a focus of the reflecting surface. The bulb may include an optically refractive wall configured such that a 0.24/0.13 NA power ratio for bulb light coupled to the interior ellipsoidal reflecting surface is between about 3.0 and about 3.3.