Study on machining characteristics of magnetically controlled laser induced plasma micro-machining single-crystal silicon

Abstract

Introduction: Laser induced plasma micro-machining (LIPMM) has proved its superiority in micro-machining of hard and brittle materials due to less thermal defects, smaller heat affected zone and larger aspect ratio compared to conventional laser ablation. Objectives: In order to improve characteristics and stability of induced plasma, this paper proposed magnetically controlled LIPMM (MC-LIPMM) to achieve a good performance of processing single-crystal silicon which is widely used in solid state electronics and infrared optical applications. Methods: A comprehensive study on surface integrity and geometrical shape was conducted based on the experimental method. Firstly, the mechanism of MC-LIPMM including laser-plasma, laser-materials interactions and transport effects was theoretically analyzed. Then a series of experiments was conducted to completely investigate the effect of magnetic field intensity, pulse repetition frequency, and bubble behavior on surface integrity and geometrical shape of micro channels. Results: It revealed that magnetic field contributed to maximum reduction of 12.64% for heat affected zone and 62.57% for width while maximum increase of 26.23% for depth and 90.26% for aspect ratio. Conclusion: This research confirms that MC-LIPMM can improve the machining characteristics of silicon materials and cavitation bubbles shows an apparently negative impact on the surface morphology.

Keywords

• Laser induced plasma micro-machining (LIPMM)
• Surface integrity
• Geometrical shape
• Bubble behavior
• Magnetic field assisted technique
• Single-crystal silicon