Embedded Micro Lens Structures With Curvature-Controlled Etching
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Solution Overview
Problem
Existing methods for forming micro lenses on transparent substrates, such as silicon, are inefficient and result in significant thickness loss and roughness, limiting the control over curvature and integration with optical and electronic devices.
Innovation Solution
A single photolithography process followed by an etching process is used to form micro lenses on a transparent substrate, utilizing a gray-tone lithography mask or two binary masks to control curvature and reduce thickness loss, with anisotropic etching to transfer the photoresist shape into the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to form micro lenses on transparent substrates, then micro lenses can be formed, but significant thickness loss and roughness occur
Solution Approach 1:
A sacrificial layer is deposited on the substrate before patterning, and this sacrificial layer is removed after the micro lenses are formed. This preliminary action allows the etching process to remove only the sacrificial layer material rather than substrate material, preventing thickness loss while maintaining lens precision
Solution Approach 2:
The sacrificial layer acts as an intermediary material that facilitates the formation of micro lenses. It is patterned to define lens locations, then removed after transferring the pattern to the substrate through anisotropic etching, enabling precise lens formation without direct substrate material removal
2Manufacturing precision
If conventional etching methods are used to form micro lenses, then micro lenses can be formed, but high roughness is produced
Solution Approach 1:
The sacrificial layer is removed after the etching process completes, leaving a smooth substrate surface. The sacrificial layer's removal occurs after the lens structure is formed, preventing the generation of roughness during the critical lens formation stage
Solution Approach 2:
The sacrificial layer serves as a temporary intermediary that is selectively removed after transferring the lens pattern. This sequence ensures that the substrate surface remains smooth throughout the lens formation process, as the sacrificial layer removal occurs post-etching when surface quality is most critical
3Manufacturing precision
If conventional methods are used, then micro lenses can be formed, but control over curvature is limited
Solution Approach 1:
The desired lens curvature is predetermined by the sacrificial layer thickness profile before etching begins. By controlling the sacrificial layer thickness during deposition, the final lens curvature is precisely controlled without requiring complex post-processing steps
Solution Approach 2:
The sacrificial layer thickness is varied across different regions to control the final lens curvature. By changing the thickness parameter of the sacrificial layer during deposition, precise control over lens curvature is achieved through the anisotropic etching process
4Manufacturing precision
If multiple processing steps are used to form micro lenses, then curvature control is improved, but process complexity and time increase
Solution Approach 1:
The sacrificial layer deposition, patterning, and removal steps are integrated into a streamlined process sequence. The sacrificial layer is deposited, patterned in the same step as the lens structure, and then removed in a single etching operation, combining multiple functions into fewer discrete steps
Solution Approach 2:
The sacrificial layer is prepared in advance before the final etching step, allowing the lens pattern to be transferred in a single anisotropic etching operation. This preliminary preparation eliminates the need for multiple separate patterning and etching steps, reducing overall process 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 method achieves reduced thickness loss, low roughness, and controllable curvature of micro lenses, enhancing integration with optical and electronic devices by forming micro lenses with precise dimensions and shapes.
Implementation Method 1
A single photolithography process followed by an etching process is used to form micro lenses on a transparent substrate, utilizing a gray-tone lithography mask or two binary masks to control curvature
Implementation Method 2
performing an etching process to etch the substrate and the sacrificial layer, wherein the etching process transfers the shape of the photoresist into the substrate
Data Source
AI summary
A method includes forming a sacrificial layer on a substrate, and patterning the sacrificial layer to form a first sacrificial block having a first height, and a second sacrificial block having a second height greater than the first height. The second sacrificial block is spaced apart from the first sacrificial block by a space. The method further includes reflowing the first sacrificial block and the second sacrificial block, and performing an etching process to etch the first sacrificial block, the second sacrificial block, and the substrate. As a result of the etching, a first portion of the substrate directly underlying the first sacrificial block forms a micro lens, and a second portion of the substrate directly underlying the second sacrificial block forms a protection wall.