Sacrificial-Block Reflow for Uniform Embedded Micro Lenses
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Solution Overview
Problem
Existing micro lens formation methods using hard masks result in non-uniformity of micro lens size and shape due to thickness variations, leading to inconsistencies in optical signal convergence.
Innovation Solution
A two-step etching process is employed without the use of a hard mask, involving the formation of sacrificial blocks, their reflowing, and subsequent etching to create micro lenses embedded in a substrate, followed by a second etching step to recess them, ensuring uniformity and precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hard mask is used in micro lens formation, then the manufacturing process is simplified, but the micro lens size and shape become non-uniform due to thickness variations
Solution Approach 1:
The patent removes the hard mask layer from the micro lens formation process. By extracting this intermediate layer, the invention eliminates the source of non-uniformity caused by thickness variations, while the process is maintained through direct patterning of the lens structure itself
Solution Approach 2:
The patent performs preliminary patterning of the lens structure before formation. By pre-defining the exact shape and position of micro lenses through lithography, the invention ensures uniformity is built into the structure from the start, eliminating the need for hard mask thickness control
2Device complexity
If traditional etching methods are used, then the process is simpler, but the micro lenses exhibit non-uniform shapes and sizes
Solution Approach 1:
The patent divides the etching process into multiple sequential steps with different selectivity ratios. By segmenting the etching into distinct phases (first etching with lower selectivity, second etching with higher selectivity), the invention achieves precise control over lens shape uniformity while managing process complexity
Solution Approach 2:
The patent changes the etching parameters (selectivity ratio, etching rate) between different process steps. By adjusting these parameters to achieve specific lens geometries, the invention transforms a potentially complex single-step process into controlled multi-step processes that guarantee uniformity
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 method eliminates non-uniformity issues, resulting in uniformly shaped micro lenses that effectively converge optical signals without the need for a hard mask, enhancing the consistency and performance of optical devices.
Implementation Method 1
reflowing the sacrificial blocks
Implementation Method 2
performing a first etching process to etch both of the sacrificial blocks and the substrate
Data Source
AI summary
A method includes forming sacrificial blocks on a substrate, reflowing the sacrificial blocks, performing a first etching process to etch both of the sacrificial blocks and the substrate until parts of the substrate that are etched to form micro lenses, forming a patterned etching mask, and performing a second etching process to etch the substrate. At a time after both of the first etching process and the second etching process have been performed, the micro lenses are in recesses of the substrate.