Aligned frontside backside laser dicing of semiconductor films

• US 8,361,828 B1
• Filed: 08/31/2011
• Issued: 01/29/2013
• Est. Priority Date: 08/31/2011
• Status: Active Grant

• Current Assignee: Alta Devices Incorporated (He Jun Li,)
• Original Assignee: Alta Devices Incorporated (He Jun Li,)
• Inventors: He, Gang, Patterson, Daniel G., Mattos, Laila
• Primary Examiner(s): MULPURI, SAVITRI
• Application Number:
  US13/222,750
• Time in Patent Office: 517 Days
• Field of Search: 438/57, 438/68, 219/121.72, 257/E21.599
• US Class Current: 438/57
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/172 wherein at least one of the layers is non-metallic
• CPC Class Codes: B23K 2103/42 Plastics B23K2103/16 takes precedence
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/0619 with spots located on opposed surfaces of the workpiece
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: B23K 26/082 Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
• 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 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• 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

Abstract

A method and system for dicing semiconductor devices from semiconductor thin films. A semiconductor film, backed by a metal layer, is bonded by an adhesive layer to a flexible translucent substrate. Reference features define device boundaries. An ultraviolet laser beam is aligned to the reference features and cuts through the semiconductor film, the metal layer and partially into the adhesive layer, cutting a frontside street along a real or imaginary scribe line on the cutting path. An infrared laser beam is aligned to the trough of the frontside street from the back surface of the flexible substrate, or the scribe lines are mapped to the back surface of the flexible substrate. The infrared laser beam cuts through the flexible substrate and the majority of the thickness of the adhesive layer, cutting a backside street along the scribe line. The backside street overlaps or cuts through to the frontside street, thereby separating the semiconductor devices.

Claims

1. A method for dicing semiconductor devices, comprising:

providing a holder supporting a semiconductor film backed by a metal layer having a back surface bonded to a front surface of a substrate by an adhesive layer, the film having semiconductor devices thereupon and having an exposed front surface with reference features defining real or virtual device boundaries, and the flexible substrate having an exposed back surface;

directing an ultraviolet laser beam of a first wavelength to cut from the front surface of the film through the semiconductor film, through the metal layer and partially into the adhesive layer such that a majority of a thickness of the adhesive layer remains intact;

moving the semiconductor film and the ultraviolet laser beam relative to each other to cut using the device boundaries from the front surface of the film to form a first trough;

mapping the real or virtual device boundaries from the front surface of the semiconductor film to corresponding mapped real or virtual device boundaries on the back surface of the flexible substrate;

directing an infrared laser beam of a second wavelength to cut from the back surface of the flexible substrate through the flexible substrate and through the majority of the thickness of the adhesive layer; and

moving the semiconductor film and the infrared laser beam relative to each other to cut using the mapped device boundaries from the back surface of the flexible substrate and form a second trough using the mapped device boundaries meeting or overlapping the first trough thereby separating a one of the semiconductor devices from another of the semiconductor devices.

2. The method of claim 1 wherein the semiconductor devices are electronic chips, opto-electronic devices or solar cells.

3. The method of claim 1 further comprising:

using machine vision to create an image of the front surface of the wafer and data relating thereto; and

determining at least two reference points on the image of the front surface of the wafer, wherein the scribe line as applied to forming the first trough is at least partially based upon the two reference points.

4. The method of claim 1 further comprising:

using machine vision to create an image of the back surface of the flexible substrate and a portion of the first trough visible therethrough, and data relating thereto; and

determining at least two reference points on the image of the front and back surface of the flexible substrate identifying device boundaries.

5. The method of claim 1 wherein testing or semiconductor processing is performed subsequent to the forming of the first trough and prior to the forming of the second trough.

6. A method for dicing solar cells from a semiconductor film, comprising:

providing a semiconductor film that has a plurality of solar cells thereupon and is backed by a metal layer, the semiconductor film having a front surface;

laminating the semiconductor film to a flexible and at least translucent substrate, using an adhesive layer to bond the substrate to the metal layer backing the semiconductor, the adhesive layer having a thickness and the substrate having a back surface;

establishing reference features on the film;

aligning an ultraviolet laser beam to a cutting path based upon the reference features from the front surface of the film;

cutting a frontside street along the cutting path, using the aligned ultraviolet laser beam to cut from the front surface of the film through the film, through the metal layer and partially into the adhesive layer, a trough of the frontside street being visible from the back surface of the substrate through the substrate and through the adhesive layer;

aligning an infrared laser beam to the trough of the frontside street from the back surface of the substrate; and

cutting a backside street, using the aligned infrared laser beam to cut from the back surface of the flexible substrate through the substrate and through a majority of the thickness of the adhesive layer so that a trough of the backside street meets or overlaps the trough of the frontside street, thereby dicing the semiconductor film and substrate and separating a one of the solar cells from another of the solar cells.

7. The method of claim 6 wherein the semiconductor film is a gallium arsenide ELO semiconductor film.

8. The method of claim 6 further comprising:

using machine vision to produce an image of a pre-deposited metal trace on the front surface of the film;

determining reference points on the image of the metal trace and the front surface of the film to define a backside cutting path.

9. The method of claim 6 further comprising imaging from the back surface of the substrate the trough of the frontside street that is visible through the substrate, wherein aligning the infrared laser beam is based upon the imaging of the trough of the frontside street from the back surface of the substrate.

10. The method of claim 6 further comprising testing one or more of the solar cells after cutting the frontside street, with the flexible substrate intact.