Solid Immersion Lens Toroidal Surface for High NA Optical Coupling
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Solution Overview
Problem
Conventional solid immersion lenses face challenges in achieving high numerical aperture and simplified positional control due to limitations in surface accuracy, manufacturing costs, and potential damage to semiconductor devices during optical coupling, especially with plano-convex and bi-convex lens designs.
Innovation Solution
A solid immersion lens with a toroidal-shaped attaching surface, featuring an aspherical bottom surface that is not optically-axis-symmetric, allowing for a band-like optically coupled region with a high numerical aperture and simplified positional control, reducing the risk of damage during attachment and detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plano-convex lens is used as a solid immersion lens, then the lens can be manufactured with a wide confronting region, but the gap between the lens and semiconductor substrate becomes great, causing transmitted light intensity to sharply decline and effective numerical aperture to be limited
Solution Approach 1:
The patent applies a toroidal surface design instead of a flat plano-convex surface. The toroidal curvature allows the lens to conform to the semiconductor substrate surface, eliminating large gaps while maintaining ease of manufacture. This curved surface design enables effective optical coupling without requiring extremely high surface accuracy, thus resolving the contradiction between manufacturability and precision requirements.
Solution Approach 2:
The patent changes the geometric parameters of the lens surface from a flat plane to a toroidal surface with specific curvature radii. By adjusting these parameters, the lens achieves both ease of manufacture and adequate optical coupling, eliminating the need for extremely high surface accuracy while maintaining effective numerical aperture.
2Reliability
If high surface accuracy is required for the bottom surface of the plano-convex lens and semiconductor substrate, then optical coupling can be achieved, but manufacturing cost increases and pretreatment requires a great deal of labor
Solution Approach 1:
The toroidal surface design inherently provides better conformality to the semiconductor substrate than a flat surface. This curvature allows optical coupling to be achieved with standard manufacturing tolerances, eliminating the need for expensive high-precision machining and labor-intensive polishing treatments, thus reducing manufacturing cost and labor while maintaining reliable optical coupling.
Solution Approach 2:
The patent design allows the use of standard, inexpensive manufacturing processes instead of high-precision, costly processes. The toroidal surface can be produced with conventional machining and polishing, avoiding the need for expensive diamond turning or precision polishing treatments, thereby reducing manufacturing cost and making the process more economically viable.
3Reliability
If air flow resistance is high between the plano-convex lens and substrate, then optical coupling is difficult, but it takes a long time to attain optical coupling
Solution Approach 1:
The toroidal surface reduces the air gap and improves contact between the lens and substrate compared to a flat surface. This curvature design facilitates faster optical coupling by reducing the distance over which air must be displaced, thereby decreasing the time required to achieve optical coupling while maintaining reliable coupling.
4Reliability
If a bi-convex lens is used to make contact with the observed object at a point, then optical connectivity is secured, but the contact area is very small, preventing high NA light flux from passing when substrate thickens
Solution Approach 1:
The toroidal surface provides a distributed contact area rather than a single point contact. This curved surface design maintains optical connectivity while allowing sufficient contact area to transmit high NA light flux, even when the substrate thickness varies, thus resolving the contradiction between optical connectivity and light flux transmission.
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
Enables high-resolution imaging with a high numerical aperture while simplifying the positional control of the lens, reducing the risk of damage to the observed object and the lens itself, and facilitating efficient optical coupling and decoupling.
Implementation Method 1
if the gap between the solid immersion lens and rear surface of the semiconductor substrate becomes equivalent to a light wavelength of the inside of the semiconductor, light can be propagated by evanescent coupling
Implementation Method 2
if a gap occurs between the solid immersion lens and a semiconductor substrate, an incident light with a critical angle or more is totally reflected
Data Source
AI summary
A solid immersion lens 1 comprises a spherical portion 2 and a bottom surface portion 3. The bottom surface portion 3 is attached in close contact with a substrate 10 of a semiconductor device to be an observed object. The bottom surface portion 3 of this solid immersion lens 1 is formed in a cylindrical shape. Thereby, a solid immersion lens which can be easily separated from the observed object after an observation and can, during an observation, allow a light flux with a high NA to pass and a microscope using the same can be obtained.