Wafer processing apparatus

A laser processing apparatus comprising:

• a chuck table for holding a wafer;
• laser beam applying means for applying a laser beam to said wafer held on said chuck table;
• and
• a feeding mechanism, for relatively feeding said chuck table and said laser beam applying means;
• said laser beam applying means including
• a laser oscillator for oscillating said laser beam, and
• a condenser having a focusing lens for focusing said laser beam oscillated by said laser oscillator and applying said laser beam focused to said wafer held on said chuck table;
• said condenser having a function of spherical aberration such that a focal point to be formed by said laser beam passing through a radially inner portion of said condenser is continuously changed in position toward said chuck table from a focal point to be formed by said laser beam passing through a radially outer portion of said condenser;
• said laser beam being applied to said wafer in the condition where the focal point of said laser beam is set inside said wafer, so as to be continuously changed in position along the thickness of said wafer, thereby forming a shield tunnel inside said, wafer, said shield tunnel being composed of a fine hole and an amorphous region surrounding said fine hole.