Forming holes using laser energy

• US 20070092637A1
• Filed: 09/15/2006
• Published: 04/26/2007
• Est. Priority Date: 09/15/2005
• Status: Active Grant

• Current Assignee: FlexEnable Limited (Plastic Logic JSC)
• Original Assignee: Plastic Logic Limited (Plastic Logic JSC)
• Inventors: Hayton, Carl, Brown, Thomas
• Granted Patent: US 8,546,723 B2
• Time in Patent Office: Days
• US Class Current: 427/97.7
• CPC Class Codes: B23K 2101/42 Printed circuits
• CPC Class Codes: B23K 2103/08 Non-ferrous metals or alloys
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 2103/12 Copper or alloys thereof
• 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 2103/54 Glass
• CPC Class Codes: B23K 26/0006 taking account of the properties of the material involved B23K26/32, B23K26/40 take precedence
• CPC Class Codes: B23K 26/382 by boring
• CPC Class Codes: B23K 26/389 of fluid openings, e.g. nozzles, jets laser machining of inkjet nozzles B41J2/1634
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: B23K 26/55 for creating voids inside the workpiece, e.g. for forming flow passages or flow patterns
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/31138 by dry-etching
• CPC Class Codes: H01L 21/76802 by forming openings in dielectrics
• CPC Class Codes: H10K 10/464 Lateral top-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 71/60 Forming conductive regions or layers, e.g. electrodes

Abstract

A method for generating via-hole interconnections by laser ablation, wherein the layers to be removed and ablated from the substrate are essentially transparent to the laser radiation, but the laser light is absorbed in an underlying absorbing layer with a sufficiently high optical density at the laser wavelength.

Claims

1. A method of producing an electronic device, including:

providing a stack including an absorbing element and a first layer provided over said absorbing element;

using laser energy to create a hole through at least said first layer and expose one or more conductive elements; and

providing conductive material within said hole;

wherein more of the laser energy is absorbed by said absorbing element than is absorbed by said first layer, and said hole in said first layer is created predominantly by the action of energy generated within said absorbing element.

2. A claim as claimed in claim 1, wherein the laser fluence used is greater than the ratio of the ablation threshold of the absorbing element to the transmittance of the first layer.

3. A claim as claimed in claim 1, wherein the laser fluence is less than the ablation threshold of the first layer.

4. A method according to claim 1, wherein said absorbing element is provided in a layer having a thermal conductivity lower than that of said absorbing element.

5. A method according to claim 1, wherein said absorbing element is provided on a further element having a thermal conductivity lower than that of the absorbing element.

6. A claim as claimed in claim 1, wherein the ablation threshold of the first layer is greater than the ratio of the ablation threshold of the absorbing element to the transmission of the first layer.

7. A method according to claim 1, wherein said laser energy is provided in one or more pulses of duration of less than 1 microsecond, preferably less than 100 nanoseconds.

8. A method according to claim 1, wherein said laser energy is provided at a wavelength of greater than 300 nm.

9. A method according to claim 1, wherein said stack includes a second layer below said absorbing element and a further absorbing element below said second layer, wherein said hole is created through at least said first layer, said absorbing element and said second layer, and wherein more of the laser energy is absorbed by said further absorbing element than is absorbed by said second layer, and said hole in said first and second layers is created predominantly by the action of heat generated within said absorbing element and said further absorbing element.

10. A method according to claim 1, wherein the stack includes at least one semiconducting layer and at least one insulating layer provided over the absorbing element;

wherein said hole is created through said at least one semiconducting layer and said at least one insulating layer; and

wherein the amount of laser energy absorbed by said absorbing element is greater than the sum of the amounts of energy absorbed by said at least one semiconducting layer and said at least one insulating layer, and said hole through said at least one semiconducting layer and said at least one insulating layer is created predominantly by the action of heat generated within said absorbing element.

12. A method according to claim 1, including exposing via the hole a conductive element surface facing in the direction of the axis of the hole, and providing said conductive material within said hole such that said conductive material makes contact with said conductive element surface.

13. A method according to claim 1, wherein said absorbing element is a conductive element and wherein said hole is created so as not to extend through the entire thickness of the absorbing element.

14. A method according to claim 13, wherein said absorbing element has a thickness of greater than 50 nm before creating said hole.

15. A method according to claim 14, wherein said absorbing element has a thickness of greater than 100 nm before creating said hole.

16. A method according to claim 1, wherein the absorbing element is a conducting polymer.

17. A method according to claim 1, wherein at least one of said one or more conductive elements is a metallic element.

18. A method according to claim 1, wherein said at one or more conductive elements includes said absorbing element.

19. A method according to claim 1, wherein the first layer is a dielectric layer.

11. A method including:

providing a stack including an absorbing element and a first layer provided over said absorbing element;

using laser energy to create a hole through at least said first layer, wherein more of the laser energy is absorbed by said absorbing element than is absorbed by said first layer and said hole in said first layer is created predominantly by the action of heat generated within said absorbing element.