Semiconductor Laser Welding With Focus Delocalization Compensation
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Solution Overview
Problem
Current laser welding technologies cannot effectively bond semiconductor materials with opaque materials, such as silicon with metal, due to the challenges of nonlinear interactions and delocalization of laser energy within semiconductor materials, which results in insufficient energy deposition at the interface.
Innovation Solution
A method and system that utilize pulsed laser radiation to weld semiconductor workpieces by determining and compensating for the delocalization of the laser focus within the semiconductor material, ensuring the intensity maximum is positioned at the interface with the second workpiece, thereby achieving a permanent modification and optimized bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the geometric focus of the laser beam is positioned at the exit surface of the semiconductor workpiece, then the beam can enter through the entrance surface and exit through the exit surface, but the nonlinear interaction causes delocalization of the focus and insufficient energy deposition at the interface
Solution Approach 1:
The patent applies preliminary action by pre-determining the delocalization amount through characterization of the semiconductor material's nonlinear optical properties before the actual welding process. This advance measurement allows the system to compensate for focus shift by adjusting the geometric focus position upstream, ensuring the intensity maximum arrives precisely at the interface during welding, thereby resolving the contradiction between geometric focus positioning and actual energy deposition reliability
Solution Approach 2:
The patent implements feedback by using the determined delocalization amount as a correction parameter for subsequent welding operations. The system measures the actual focus shift caused by nonlinear interactions and uses this information to adjust the geometric focus positioning in real-time, creating a closed-loop control that maintains welding reliability despite the delocalization effect
2Power
If high-power ultrashort pulse lasers are used to irradiate transparent semiconductor materials, then the beam can propagate through the material, but the Kerr-induced self-focusing and plasma absorption cause energy delocalization and saturation
Solution Approach 1:
The patent applies preliminary anti-action by characterizing the delocalization effect caused by Kerr self-focusing and plasma absorption before welding, and then using this knowledge to pre-compensate for the energy spread. By adjusting the geometric focus position upstream based on the determined delocalization amount, the system counteracts the inevitable energy delocalization, concentrating the intensity maximum at the interface and preventing energy loss to surrounding areas
Solution Approach 2:
The patent changes the parameter of geometric focus position based on the optical properties and thickness of the semiconductor workpiece. By dynamically adjusting the focus position upstream according to the workpiece characteristics, the system compensates for nonlinear effects and maintains efficient energy deposition at the interface, transforming the delocalization problem into a controllable parameter adjustment
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 approach enables reliable, repeatable, and reproducible laser welding of semiconductor materials to opaque materials by re-localizing the laser intensity maximum at the interface, maximizing energy absorption and bonding strength between the two workpieces.
Implementation Method 1
the competition between the Kerr-induced self-focusing effect on the one hand, and plasma absorption and defocusing effects on the other hand
Implementation Method 2
the competition between the Kerr-induced self-focusing effect on the one hand, and plasma absorption and defocusing effects on the other hand
Implementation Method 3
irradiating the first workpiece with a beam of pulsed laser radiation
Implementation Method 4
the geometric focus of the beam being positioned in the plane of the exit surface
Data Source
AI summary
The invention relates to a method for welding a first workpiece (11) to a second workpiece (12) by means of a laser. It is an object of the invention to provide a reliable, repeatable and reproducible approach for laser welding of two workpieces one of which consists of a semiconductor material. The method proposed by the invention comprises the following steps: Irradiating the first workpiece (11) with a beam of pulsed laser radiation, wherein the first workpiece (11) consists of a semiconductor material which is transparent at the wavelength of the laser radiation, so that the beam enters the first workpiece (11) through an entrance surface and leaves it through an exit surface, the geometric focus of the beam being positioned in the plane of the exit surface; determining a delocalization of the focus caused by nonlinear interaction of the laser radiation with the semiconductor material; placing the second workpiece (12) against the first workpiece (11); and, again, irradiating the first workpiece (11) with the laser beam of pulsed laser radiation, the focus of the laser radiation being positioned along the beam direction taking into account the determined delocalization so that the intensity maximum is located in the plane of the exit surface forming the interface of the two workpieces (11, 12), whereby the first workpiece (11) is welded to the second workpiece (12). Moreover, the invention relates to a system for welding a first workpiece (11) to a second workpiece (12).