Laser machining using an active assist gas

Abstract

A silicon workpiece 5 is machined by a laser 2 with a laser beam 4 with a wavelength of less than 0.55 microns by providing a halogen environment for the silicon workpiece to form an active assist gas for laser machining. The laser beam is focussed onto the silicon workpiece at a power density above an ablation threshold of silicon so that the assist gas reacts with the silicon workpiece at or near a focus of the laser beam such that laser machining speed is increased and strength of the machined workpiece is increased due to an improvement in machining quality. The invention has particular application in the dicing of a silicon wafer in the presence of sulphur hexafluoride (SF6), resulting in increased strength of resultant dies.

Description

technical field [0001] The present invention relates to laser processing using reactive cogas. Background technique [0002] It is known that the silicon wafer substrate in SF 6 Etching in an ambient environment results in a clean and smooth etch of the silicon substrate. [0003] In addition, during laser processing, SF 6 The presence of improves the quality and efficiency of the material removal process. However, while the presence of this gas aids in material removal, it generally prevents laser processing from being able to perform manufacturing processes at sufficiently high throughput rates. [0004] US 3679502 describes a method in SF 6 Method for delocalized etching of silicon wafer substrates heated to temperatures in the range 950 to 1250°C in ambient. The fluorine radicals generated at such high temperatures attack the silicon surface to produce a smooth and clean surface. [0005] In US 3866398, it is disclosed that for example SF 6 The reagent gas is loca...

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Problems solved by technology

However, while the presence of this gas aids in material removal, it often prevents laser processing from being able to perform manufacturing processes at high enough throughput rates.

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