Method and apparatus for separating non-metallic substrates utilizing a laser initiated scribe

• US 6,211,488 B1
• Filed: 01/29/1999
• Issued: 04/03/2001
• Est. Priority Date: 12/01/1998
• Status: Expired due to Fees

• Current Assignee: Laserdyne Labs, Inc.
• Original Assignee: Accudyne Display And Semiconductor Systems, Inc.
• Inventors: Hoekstra, Brian L, Efimov, Oleg M., Glebov, Leonid B.
• Primary Examiner(s): Evans, Geoffrey S.
• Application Number:
  US09/240,057
• Time in Patent Office: 795 Days
• Field of Search: 225/1, 225/2, 225/93.5, 219/121.76, 219/121.67, 219/121.72, 219/121.68, 219/121.69
• US Class Current: 219/121.72
• 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 26/0604 by a combination of beams
• CPC Class Codes: B23K 26/0608 in the same heat affected zone [HAZ] B23K26/0613, B23K26/0619 take precedence
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: B23K 26/064 by means of optical elements, e.g. lenses, mirrors or prisms
• CPC Class Codes: B23K 26/0648 comprising lenses
• CPC Class Codes: B23K 26/067 Dividing the beam into multiple beams, e.g. multifocusing
• CPC Class Codes: B23K 26/0736 into an oval shape, e.g. elliptic shape
• CPC Class Codes: B23K 26/123 in an atmosphere of particular gases
• CPC Class Codes: B23K 26/125 of mixed gases
• CPC Class Codes: B23K 26/14 using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor B23K26/12 takes precedence
• CPC Class Codes: B23K 26/146 the fluid stream containing a liquid
• CPC Class Codes: B23K 26/1462 Nozzles; Features related to nozzles
• 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: C03B 33/093 using two or more focussed radiation beams
• CPC Class Codes: H01L 21/3043 Making grooves, e.g. cutting
• CPC Class Codes: H05K 3/0029 of inorganic insulating material
• CPC Class Codes: H05K 3/0052 Depaneling, i.e. dividing a panel into circuit boards; Working of the edges of circuit boards
• CPC Class Codes: Y10T 225/12 : With preliminary weakening
• CPC Class Codes: Y10T 225/304 : Including means to apply thermal shock to work

Abstract

An apparatus and method for physically separating non-metallic substrates forms a microcrack in the substrate and controllingly propagates the microcrack. An initial mechanical or pulsed laser scribing device forms a microcrack in the substrate. If a pulsed laser is used, it forms a crack inside the substrate that does not extend to either the upper or lower surface. A scribe beam is applied onto the substrate on a separation line. A coolant stream intersects with, or is adjacent to, the trailing edge of the scribe beam. The temperature differential between the heat affected zone of the substrate and the coolant stream propagates the microcrack. Two breaking beams on opposing sides of the separation line follow the coolant stream. The breaking beams create controlled tensile forces that extend the crack to the bottom surface of the substrate for full separation. The scribe and break beams and coolant stream are simultaneously moved relative to the substrate. A preheat beam preheats the heat affected area on the substrate. The beams are formed by an arrangement of lasers and mirrors and lenses. A movable mirror selectively diverts a beam to form either the preheat beam or one or more of the break and scribe beams. Spherical aberration is introduced in the break and scribe beams to flatten their energy distribution profiles and evenly apply the beam energy.

Claims

1. A method for separating a non-metallic substrate having an upper surface and a lower surface, the method comprising:

forming a crack in the substrate between the upper surface and the lower surface that does not extend vertically to either the upper surface or the lower surface;

propagating the crack, including directing a scribe beam of coherent radiation onto the substrate and applying a stream of coolant onto the substrate; and

separating the substrate.

2. The method of claim 1, further comprising the step of simultaneously moving the scribe beam and the coolant stream relative to the substrate.

3. The method of claim 1, wherein said forming a crack step includes pulsing a laser to apply a beam to the substrate such that the beam has a focal point located between the upper and lower surfaces of the substrate, said method further comprising the step of simultaneously moving the beam from the pulsed laser, the scribe beam and the coolant stream relative to the substrate.

4. The method of claim 1, further comprising the step of directing a plurality of break beams of coherent radiation onto the substrate.

5. The method of claim 4, wherein the break beams directing step includes directing a plurality of break beams of coherent radiation onto the substrate to impinge behind and laterally offset from an impingement spot of the scribe beam.

6. A method for separating a non-metallic substrate by propagating a microcrack, the substrate having an upper surface and a lower surface, the method comprising:

directing a pulsed laser towards the substrate so that the focal point of the laser is between the upper and lower surfaces of the substrate;

pulsing the laser to form a microcrack;

directing an incident beam of coherent radiation onto the substrate to impinge at a spot positioned at least behind the focal point of the pulsed laser; and

applying a stream of coolant onto the substrate at a location behind at least a portion of the spot caused by the incident beam.

7. The method of claim 6, wherein said directing step includes directing a pulsed laser towards the substrate so that the focal point of the laser is 5%-50% of the thickness of the substrate from the upper surface of the substrate.

8. The method of claim 6, wherein said incident beam of coherent radiation is a first beam of coherent radiation, said method further comprising the step of directing a second incident beam of coherent radiation onto the substrate to impinge at a spot positioned at least partially behind and laterally offset from the impingement spot of the first beam.

9. The method of claim 8, further comprising the step of directing a third incident beam of coherent radiation onto the substrate to impinge at a spot positioned at least partially behind and laterally offset from the impingement spot of the first beam.

10. A The method of claim 6, wherein said substrate has a first end and a second end, said substrate to be separated along a line between the first and second ends, said method comprising applying the pulsed laser at the first end and the second end and not applying the pulsed laser for a distance along the line between the first and second ends.

11. The method of claim 6, wherein said substrate has a first end and a second end, said substrate to be separated along a line between the first and second ends, said method comprising constantly applying the pulsed laser along the line from the first end to the second end.

12. The method of claim 6, further comprising the step varying the polarization of the pulsed laser.

13. The method of claim 6, further comprising the step varying the pulse width of the pulsed laser.

14. The method of claim 6, further comprising the step varying the mode of the pulsed laser.

15. The method of claim 6, wherein said method for separating a substrate includes separating a glass sheet.

16. An apparatus for separating a non-metallic substrate by propagating a microcrack, the substrate having an upper surface and a lower surface, the apparatus comprising:

a first laser, said first laser being a pulsed laser to emit a pulsed first beam to be directed at the substrate, wherein said pulsed first beam has a focal point located between the upper and lower surfaces of the substrate; and

an incident second beam of coherent radiation, said second beam positioned to impinge on the substrate at a location at least partially behind the pulsed first beam.

17. An apparatus for separating a non-metallic substrate by propagating a microcrack, the substrate having an upper surface and a lower surface, the apparatus comprising:

a first laser, said first laser being a pulsed laser to emit a pulsed first beam to be directed at the substrate;

an incident second beam of coherent radiation, said second beam positioned to impinge on the substrate at a location at least partially behind the pulsed first beam; and

a quenching device, said quenching device imparting coolant directed at the substrate at a position behind at least a portion of the impingement location of the second beam.

18. The apparatus of claim 17, further comprising third and fourth beams of coherent radiation, said third and fourth beams positioned behind at least a portion of the impingement location of the second beam.

19. The apparatus of claim 18, further comprising a second laser, said second laser emitting an initial beam that is split to produce said second, third, and fourth beams.

20. The apparatus of claim 18, further comprising a second laser, said second laser emitting producing said second beam, and a third laser, said third laser emitting an initial beam that is split to produce said third and fourth beams.

21. The apparatus of claim 18, wherein said substrate is divided along a separation line, said third and fourth beams positioned laterally offset from the separation line, and on opposite sides thereof.

22. An apparatus for separating a non-metallic substrate by propagating a microcrack, the substrate having an upper surface and a lower surface, the apparatus comprising:

a pulsed laser, said pulsed laser emitting a pulsed beam,

at least one optical element, said at least one optical element directing the focal point of the beam emitted by the pulsed laser to lie between the upper and lower surfaces of the substrate at a first spot;

a second laser capable of emitting an incident beam of coherent radiation positioned to impinge on the substrate at a second spot positioned at least partially behind the first spot; and

a quenching device, the quenching device projecting a steam of coolant onto the substrate at a location behind the first spot and behind at least a portion of the second spot.

23. The apparatus of claim 22, further comprising means for simultaneously moving said first and second spots and the location of the projection of the coolant relative to the substrate.

24. The apparatus of claim 22, wherein said at least one optical element is vertically adjustable relative to said pulsed laser for adjusting the location focal point of the pulsed first beam between the upper and lower surfaces of the substrate.