Surface Emitting Laser Mesa Taper Angle Control
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Solution Overview
Problem
The manufacturing of surface emitting laser elements faces challenges such as disconnection and reduced yield due to insufficient step coverage of wiring, particularly at the taper angles and slope angles of the mesa, leading to non-uniformity and stress-induced variations in laser characteristics.
Innovation Solution
The method involves controlling the taper angle of the dielectric layer through wet etching and the slope angle of the mesa through dry etching, ensuring the taper angle is less than the slope angle, which improves the thickness and reliability of the wiring, preventing disconnection and enhancing manufacturing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mesa is formed with a taper shape to improve step coverage, then the wiring reliability is improved, but the angle of the peripheral part of the top end becomes close to a right angle causing wiring disconnection
Solution Approach 1:
The patent divides the mesa structure into multiple sections with different taper angles. The lower part of the mesa has a larger taper angle to improve step coverage, while the upper part has a smaller taper angle to prevent wiring disconnection. This segmentation allows each part to optimize for its specific function.
Solution Approach 2:
Different regions of the mesa are given different geometric properties. The lower mesa region has a steeper taper angle for better wiring coverage, while the upper mesa region has a gentler taper angle for wiring stability. This local differentiation resolves the contradiction between coverage and connection reliability.
2Reliability
If multiple stages of taper are formed to improve step coverage, then the wiring coverage is improved, but the in-plane distribution of etching shape becomes non-uniform reducing manufacturing yield
Solution Approach 1:
The patent extracts the taper formation process from a complex multi-stage etching process and implements it through a single wet etching step that naturally produces the desired tapered profile. This simplifies the process and ensures uniform etching across the wafer while achieving the required step coverage.
Solution Approach 2:
The patent changes the etching parameters by using wet etching instead of dry etching, and by controlling the etching conditions to achieve a specific taper angle distribution. This parameter optimization allows simultaneous achievement of good step coverage and uniform in-plane distribution.
3Reliability
If the wiring width on the side wall of the mesa is increased to improve step coverage, then the wiring coverage is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent performs preliminary action by forming the tapered mesa structure before wiring deposition. This pre-formed taper naturally provides the required step coverage, eliminating the need for subsequent wiring width adjustments or additional process steps to achieve adequate coverage.
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 allows for the stable and precise manufacturing of surface emitting laser arrays with improved reliability and high yield, enabling high-quality optical scanning and image formation in devices like laser printers.
Implementation Method 1
controlling the taper angle of the dielectric layer through wet etching
Implementation Method 2
controlling the slope angle of the mesa through dry etching
Data Source
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AI summary
A surface emitting laser element includes a light emission part (100a) having a mesa structure. The light emission part includes a lower reflector (103), a resonator structure including an active layer (105) and an upper reflector (107). The lower reflector, the resonator structure and the upper reflector are laminated on a substrate (101). A peripheral part of a top surface of the mesa structure is covered by a dielectric layer (111a) that has a tapered surface such that a thickness decreases in a direction toward an outermost part, a taper angle (δ) of the tapered surface with respect to a surface of the substrate is smaller than a slope angle (θ) of a side wall of the mesa structure with respect to the surface of the substrate, and an end part of the dielectric layer coincides with an end part of the upper reflector.