Tri-Step Etching for Semiconductor Laser Diode Resin Protection
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Solution Overview
Problem
The existing methods for manufacturing semiconductor laser diodes with ridge waveguide structures face challenges in protecting the striped structure during processing, leading to damage and inaccuracies in photo-resist patterning, and the formation of deep openings in resin layers can cause breakage of wiring at the corners.
Innovation Solution
A method involving tri-step etching using a mixed gas of CF4 and O2 with varying partial pressures to form a dulled side surface in the openings, where the resin layer contains silicon and the photo-resist is free from silicon or has a lower silicon concentration, effectively preventing wiring breakage by expanding the opening and smoothing the side walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resin layer is used to planarize the top surface and protect the striped structure, then the protection of the striped structure is improved, but the opening depth increases causing wiring breakage at corners
Solution Approach 1:
The patent changes the chemical composition parameter of the resin layer by incorporating silicon-containing compounds (such as silane-modified polymers or colloidal silica) into the resin. This modification alters the etching characteristics of the resin, enabling selective removal during RIE processing while maintaining adequate protection depth. The silicon concentration in the resin is specifically controlled to achieve optimal balance between protection and etchability.
2Reliability
If protrusions are formed to protect the striped structure, then the protection is improved, but the device complexity and process steps increase
Solution Approach 1:
The patent extracts the protection function from the structural protrusions and transfers it to a planar resin layer that uniformly covers the entire surface. This eliminates the need for complex lithography and etching steps to create protrusions, while still providing effective protection. The protection mechanism is simplified from geometric shielding to chemical/physical cushioning by the resin layer.
3Manufacturing precision
If the photo-resist contains silicon at substantial concentration like the resin, then the etching selectivity is improved, but the ability to form precise patterns is reduced
Solution Approach 1:
The patent applies local quality by creating a dual-layer resist system where the lower layer (adhesion promoter) contains silicon at substantial concentration for selective etching, while the upper layer (pattern definition layer) is free from silicon or contains silicon at low concentration for precise patterning. This spatial differentiation of material composition allows each layer to perform its specific function optimally without interfering with the other.
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 dulled side surface of the openings in the resin layer prevents wiring breakage at the edges, ensuring reliable electrical contact and reducing the risk of damage during the manufacturing process.
Implementation Method 1
first etching of the resin partially by the RIE (Reactive Ion Etching) with a mixed gas of carbon fluorine (CF4) and oxygen (O2)
Implementation Method 2
second etching of the photo-resist by the RIE using a mixed gas of CF4 and O2 under the second partial pressure of CF4 with respect to O2
Data Source
AI summary
A method for manufacturing an LD is disclosed. The LD has a striped structure including an optical active region. The striped structure is buried with resin, typically benzo-cyclo-butene (BCB). The method to form an opening in the BCB layer has tri-steps etching of the RIE. First step etches the BCB layer partially by a mixed gas of CF4 and O2, where CF4 has a first partial pressure, second step etches the photo-resist patterned on the top of the BCB layer by a mixed gas of CF4 and O2, where CF4 in this step has the second partial pressure less than the first partial pressure, and third step etches the BCB left in the first step by mixed gas of CF4 and O2, where CF4 in this step has the third partial pressure greater than the second partial pressure.