LASER MATERIAL REMOVAL METHODS AND APPARATUS

• US 20100055901A1
• Filed: 08/21/2009
• Published: 03/04/2010
• Est. Priority Date: 08/26/2008
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Zhang, Zhenhua, Shah, Vinay K., Rana, Virendra V.S., Eberspacher, Chris
• Granted Patent: US 8,258,426 B2
• Time in Patent Office: Days
• US Class Current: 438/669
• 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 26/06 Shaping the laser beam, e.g. by masks or multi-focusing
• 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 26/364 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: H01L 31/022441 Electrode arrangements specially adapted for back-contact solar cells
• CPC Class Codes: H01L 31/0682 back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-junction cells
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

Embodiments of the present invention generally provide methods and apparatus for material removal using lasers in the fabrication of solar cells. In one embodiment, an apparatus is provided that precisely removes portions of a dielectric layer deposited on a solar cell substrate according to a desired pattern and deposits a conductive layer over the patterned dielectric layer. In one embodiment, the apparatus also removes portions of the conductive layer in a desired pattern. In certain embodiments, methods for removing a portion of a material via a laser without damaging the underlying substrate are provided. In one embodiment, the intensity profile of the beam is adjusted so that the difference between the maximum and minimum intensity within a spot formed on a substrate surface is reduced to an optimum range. In one example, the substrate is positioned such that the peak intensity at the center versus the periphery of the substrate is lowered. In one embodiment, the pulse energy is improved to provide thermal stress and physical lift-off of a desired portion of a dielectric layer.

Claims

1. An apparatus for material removal, comprising:

a first robot configured to transfer a substrate having a dielectric layer deposited on a first surface thereof from an input region to one of a plurality of support features on a substrate transport surface;

a vision system configured to detect an actual position of the substrate and communicate information regarding the actual position to a system controller;

a first laser scanner positioned to remove a portion of the dielectric layer in a desired pattern, wherein the system controller is configured to determine an offset of the actual position with respect to an expected position of the substrate and adjust either the first robot or the laser scanner to correct for the offset; and

an automation system configured to transport the substrate having a patterned dielectric layer from the first laser scanner to a deposition chamber configured to deposit a conducting layer over the dielectric layer.

2. The apparatus of claim 1, wherein the substrate is positioned such that a portion of light emitted from the first laser scanner strikes the substrate beneath the ablation threshold while the portion of the dielectric material is removed without damaging the underlying substrate.

3. The apparatus of claim 1, wherein the first laser scanner thermally stresses the portion of the dielectric layer by focusing light on the portion and physically removes the portion of the dielectric layer without evaporating the dielectric material.

4. The apparatus of claim 1, further comprising a second laser scanner positioned to remove a portion of the conducting layer in a desired pattern.

5. The apparatus of claim 4, further comprising a second robot configured to transfer the substrate from the substrate transport surface to an exit region.

6. The apparatus of claim 1, wherein the first robot is configured to hold the substrate with the first surface facing downwardly while the first laser scanner removes the portion of the dielectric layer.

7. The apparatus of claim 6, wherein the system controller is configured determine an offset of the actual position with respect to an expected position of the substrate and adjust either the first robot or the laser scanner to correct for the offset.

8. The apparatus of claim 7, further comprising a second laser scanner configured to remove a portion of the conducting layer while the substrate is held by a second robot.

9. The apparatus of claim 1, further comprising a first substrate holder configured to hold the substrate while the laser scanner removes the portion of the dielectric layer.

10. The apparatus of claim 9, further comprising a second substrate holder configured to hold the substrate while a second laser scanner to removes a portion of the conducting layer.

11. The apparatus of claim 1, wherein the laser scanner is positioned to remove a portion of the dielectric layer from the substrate while the substrate is positioned in the support feature of the substrate transport surface.

12. The apparatus of claim 11, further comprising a second laser scanner configured to remove a portion of the conducting layer from the substrate while the substrate is positioned in the support feature of the substrate transport surface.

13. A laser material removal method, comprising:

determining a laser ablation threshold of a material deposited on a substrate;

altering either a position of the substrate or parameters of a laser by defocusing the laser such that a portion of light emitted from the laser strikes the substrate beneath the ablation threshold; and

ablating the material without damaging the underlying substrate.

14. A method of laser material removal, comprising:

thermally stressing a region of dielectric material deposited on a substrate by focusing light emitted from a laser on the region; and

physically removing material from the region without evaporating the material.

15. A processing apparatus, comprising:

a first robot configured to transfer a substrate from an input region to one of a plurality of support features on a substrate transport surface;

a vision system configured to detect an actual position of the substrate and communicate information regarding the actual position to a system controller;

a first deposition chamber configured to deposit a dielectric layer onto the substrate;

a first laser scanner positioned to remove a portion of the dielectric layer from the substrate in a desired pattern while the substrate is positioned on the substrate transport surface, wherein the system controller is configured to determine an offset of the actual position with respect to an expected position of the substrate and adjust the laser scanner to correct for the offset;

a second deposition chamber configured to deposit a conducting layer over the patterned dielectric layer; and

an automation system configured to transport the substrate between the first deposition chamber, the first laser scanner, and the second deposition chamber.

16. The apparatus of claim 15, wherein the substrate is positioned such that a portion of light emitted from the first laser scanner strikes the substrate beneath the ablation threshold while the portion of the dielectric material is removed without damaging the underlying substrate.

17. The apparatus of claim 15, wherein the first laser scanner is configured to thermally stress the portion of the dielectric layer by focusing light on the portion and physically removing the portion of the dielectric layer without evaporating the dielectric material.

18. The apparatus of claim 15, further comprising a second laser scanner positioned to remove a portion of the conducting layer in a desired pattern.

19. The apparatus of claim 18, further comprising a second robot configured to transfer the substrate from the substrate transport surface to an exit region.

20. A method for processing a substrate comprising:

detecting an actual position of a substrate having a dielectric material deposited on a surface thereof;

determining an offset of the actual position with respect to an expected position of the substrate;

transferring the substrate to one of a plurality of support features on a substrate transport surface via a robot;

adjusting a first laser based on the offset;

removing a portion of the dielectric material in a desired pattern from the surface of the substrate via the first laser;

moving the substrate into a deposition chamber;

depositing a conducting layer over the patterned dielectric layer;

adjusting a second laser based on the offset; and

removing a portion of the conducting layer in a desired pattern via the second laser.

21. The method of claim 20, wherein removing a portion of the dielectric material comprises positioning the substrate such that a portion of light emitted from the first laser strikes the substrate beneath the ablation threshold while the portion of the dielectric material is removed without damaging the underlying substrate.

22. The method of claim 20, wherein removing a portion of the dielectric material comprises thermally stressing the portion of the dielectric material by focusing light on the portion and physically removing the portion of the dielectric material without evaporating the dielectric material.

23. The method of claim 20, further comprising holding the substrate with the robot while removing a portion of the dielectric material.

24. The method of claim 20, further comprising transferring the substrate to a substrate holder prior to transferring the substrate to one of a plurality of support features, wherein the substrate is located on the substrate holder during the removing a portion of the dielectric material.

25. The method of claim 20, wherein the substrate is positioned on one of the plurality of support features while removing a portion of the dielectric material.