Patent ID: 7728257
Filing Date: 2010-06-01
Classification: B23K,H01L

Abstract:
1. A method of forming embrittled areas inside a wafer for dividing the wafer that positions a focal point of a laser beam having a wavelength capable of penetrating the wafer having predetermined division lines of a first direction and predetermined division lines of a second direction that intersect the predetermined division lines of the first direction, irradiates inside the wafer at the predetermined division lines of the first direction and the predetermined division lines of the second direction, and moves the wafer and the laser beam relative to each other, forming embrittled areas in multiple layers inside the wafer at the predetermined division lines of the first direction and the predetermined division lines of the second direction, the method comprising: first direction embrittling by forming embrittled areas in a first direction inside the wafer at the predetermined division lines of the first direction in multiple layers by stacking first direction embrittled areas on a bottom layer one by one; and second direction embrittling by forming embrittled areas inside the wafer at the predetermined division lines of the second direction in multiple layers by stacking second direction embrittled areas on the bottom layer one by one; wherein the first direction embrittling and the second direction embrittling are alternately executed so that lengths of unprocessed areas remaining at positions where layers of embrittled areas in the first and second directions cross each other are made minimum and kept within a range such that said lengths do not interfere with division of the wafer, wherein when the wafer thickness is T μm, and a thickness of each embrittled area formed by irradiation by the laser beam is h μm, forming a predetermined number of layers of embrittled areas by execution of the first and second direction embrittling, and T≧2h by,