Laser processing apparatus

Abstract

Provided is a laser processing apparatus which does not damage a device even if a laser beam is irradiated to form a modified layer by positioning a focal point inside a relatively narrow division line. A laser beam applying unit (6) of the laser processing apparatus includes a laser oscillator (30) for emitting a pulsed laser beam (LB) having a wavelength transmittable through a wafer (72), a beam condenser (32) for converging the pulsed laser beam (LB) emitted from the laser oscillator (30) onto the wafer (72) held on a chuck table (4), a beam splitter assembly (34) disposed between the laser oscillator (30) and the beam condenser (32), for splitting the pulsed laser beam (LB) emitted from the laser oscillator (30) to form at least two converged spots in X-axis directions, and a mask assembly (36) disposed between the laser oscillator (30) and the beam condenser (33), for reducing the width of the converged spots of the pulsed laser beam (LB) emitted by the laser oscillator (30) in Y-axis directions to keep the converged spots within the width of the projected dicing lines (74).

Description

technical field [0001] The present invention relates to a laser processing apparatus for forming a modified layer inside a wafer divided by a plurality of dividing lines intersecting each other and having a plurality of devices formed on the front surface. Background technique [0002] A wafer divided by a plurality of dividing lines intersecting each other and formed with multiple devices such as ICs and LSIs on the front side is divided into individual device chips by a dicing device (dicing machine), and the divided device chips are used in mobile phones, Electronic equipment such as personal computers. [0003] A technique has been proposed in which laser light is irradiated onto a wafer by irradiating a laser beam with a laser light converging point positioned inside a planned dividing line, and a modified layer is formed inside the wafer along the planned dividing line to divide the wafer into individual device chips (e.g., , refer to Patent Document 1). The above te...

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Problems solved by technology

[0005] However, when the laser beam is irradiated from the front surface of the wafer to form a converging spot inside, there is a problem that the spot of the laser beam irradiated to the front surface is positioned beyond the width of the planned dividing line, so that damage is adjacent to the planned dividing line. device

[0006] In addition, when the laser beam is irradiated from the back surface of the wafer to the area corresponding to the planned division line with the laser beam condensed at the inside, there is a problem that the light leakage after the modified layer is formed will damage the formed layer. Devices on the front

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