Laser processing method and laser processing apparatus

• US 7,732,730 B2
• Filed: 04/15/2005
• Issued: 06/08/2010
• Est. Priority Date: 09/13/2000
• Status: Expired due to Fees

• Current Assignee: Hamamatsu Photonics KK
• Original Assignee: Hamamatsu Photonics KK
• Inventors: Wakuda, Toshimitsu, Uchiyama, Naoki, Fukumitsu, Kenshi, Fukuyo, Fumitsugu
• Primary Examiner(s): ELVE, MARIA ALEXANDRA
• Application Number:
  US11/106,643
• Publication Number:
  US 20050181581A1
• Time in Patent Office: 1,880 Days
• Field of Search: 219/121.65, 219/121.82, 219/121.83, 219/121.78, 219/121.64, 219/121.6
• US Class Current: 219/121.65
• CPC Class Codes: B23K 20/023 Thermo-compression bonding
• CPC Class Codes: B23K 20/16 with interposition of special material to facilitate connection of the parts, e.g. material for absorbing or producing gas
• CPC Class Codes: B23K 20/233 without ferrous layer
• CPC Class Codes: B23K 20/26 Auxiliary equipment
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 26/03 Observing, e.g. monitoring, the workpiece
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/034 Observing the temperature of the workpiece
• CPC Class Codes: B23K 26/046 Automatically focusing the laser beam
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: B23K 26/066 by using masks
• CPC Class Codes: B23K 26/073 Shaping the laser spot
• CPC Class Codes: B23K 26/0853 Devices involving movement of the workpiece in at least in two axial directions, e.g. in a plane
• CPC Class Codes: B23K 26/16 Removal of by-products, e.g. particles or vapours produced during treatment of a workpiece by a fluid stream B23K26/142
• CPC Class Codes: B23K 26/364 for making a groove or trench, e.g. for scribing a break initiation groove
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/53 for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
• CPC Class Codes: B28D 5/0011 with preliminary treatment, e.g. weakening by scoring
• CPC Class Codes: B65G 2249/04 Arrangements of vacuum systems or suction cups
• CPC Class Codes: C03B 33/023 : the sheet or ribbon being in a horizontal position
• CPC Class Codes: C03B 33/082 : using a focussed radiation beam, e.g. laser C03B33/0855 takes precedence
• CPC Class Codes: C03B 33/102 : involving a focussed radiation beam, e.g. lasers
• CPC Class Codes: C03C 23/0025 : by a laser beam
• CPC Class Codes: G02F 1/1368 : in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H01L 21/6836 : Wafer tapes, e.g. grinding or dicing support tapes adhesive tapes in general C09J7/20
• CPC Class Codes: H01L 21/78 : with subsequent division of the substrate into plural individual devices cutting to change the surface-physical characteristics or shape of semiconductor bodies H01L21/304
• CPC Class Codes: H01L 2221/68327 : used during dicing or grinding
• CPC Class Codes: Y02P 40/57 : Improving the yield, e-g- reduction of reject rates
• CPC Class Codes: Y10T 29/49144 : by metal fusion
• CPC Class Codes: Y10T 83/0341 : Processes

Abstract

A laser beam machining method and a laser beam machining device capable of cutting a work without producing a fusing and a cracking out of a predetermined cutting line on the surface of the work, wherein a pulse laser beam is radiated on the predetermined cut line on the surface of the work under the conditions causing a multiple photon absorption and with a condensed point aligned to the inside of the work, and a modified area is formed inside the work along the predetermined determined cut line by moving the condensed point along the predetermined cut line, whereby the work can be cut with a rather small force by cracking the work along the predetermined cut line starting from the modified area and, because the pulse laser beam radiated is not almost absorbed onto the surface of the work, the surface is not fused even if the modified area is formed.

Claims

1. A laser processing apparatus for forming a modified region which functions as a starting point for cutting within an object to be cut, comprising:

a stage adapted for mounting the object;

a laser source for emitting a pulsed laser light along an optical axis, the object being transparent to the pulsed laser light;

an observation light source for illuminating a surface of the object with a visible observation light having a different wavelength from that of the laser light;

an image pick-up element for imaging the surface of the object illuminated by the observation light source;

a converging lens for converging the pulsed laser light emitted from the laser source within the object mounted on the stage, to form the modified region at a position of the converging point of the pulsed laser;

a controller for controlling movement of at least one of the converging lens and the stage to focus the observation light through the converging lens at a reference position on the surface of the object, to thereafter move at least one of the converging lens and the stage in a direction along the optical axis of the pulsed laser light by an amount of movement corresponding to predetermined displacement data for determining a position of the converging point of the pulsed laser light to be arranged within the object, to cause the converging point of the pulsed laser light to be positioned within the object at a location spaced from the reference position by the amount of movement corresponding to the predetermined displacement data, and to thereafter to initiate irradiation by the pulsed laser light and movement of the stage along a line along which the object is intended to be cut in order to form a modified region within the object along the line along which the object is intended to be cut.

2. The laser processing apparatus according to claim 1, wherein the controller controls the movement of at least one of the converging lens and the stage to position the converging point of the pulsed laser light within the object at a location spaced from the reference position by a first predetermined distance in a thickness direction of the object and to thereafter move the converging point of the laser light within the object along the line along which the object is intended to be cut;

and to thereafter position the converging point of the pulsed laser light within the object at a location spaced from the reference position by a second predetermined distance in the thickness direction of the object and to thereafter move the converging point of the laser light within the object along the line along which the object is intended to be cut.

3. The laser processing apparatus according to claim 1, wherein the predetermined displacement data is determined based on at least one of a thickness and a refractive index of the object.

4. The laser processing apparatus according to claim 1, further comprising an image pick up data processing unit for obtaining a position of the converging lens with respect to the object at which the observation light focuses on the surface of the object.

5. The laser processing apparatus according to claim 1, wherein an optical axis of the converging lens is matched with an optical axis of the observation light emitted from the observation light source and the optical axis of the pulsed laser light.

6. The laser processing apparatus according to claim 1, further comprising a power adjustor for adjusting power of the pulsed laser light and numerical aperture adjusting means arranged on the optical axis of the pulsed laser light between the laser source and the converging lens.

7. The laser processing apparatus according to claim 6, wherein the numerical aperture adjusting means comprising a beam expander.