Electrical die contact structure and fabrication method

• US 7,795,126 B2
• Filed: 01/04/2008
• Issued: 09/14/2010
• Est. Priority Date: 05/13/2002
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Prabhu, Ashok, Owens, Alexander H., Patil, Sadanand R., Lee, Shaw Wei
• Primary Examiner(s): Landau; Matthew C
• Assistant Examiner(s): Mitchell; James M
• Application Number:
  US11/969,756
• Publication Number:
  US 20080102604A1
• Time in Patent Office: 984 Days
• Field of Search: 438/33, 438/108, 438/598, 438/612
• US Class Current: 438/612
• CPC Class Codes: H01L 23/482 consisting of lead-in layers inseparably applied to the semiconductor body electrodes H01L29/40
• CPC Class Codes: H01L 23/4827 Materials
• CPC Class Codes: H01L 27/14618 Containers
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A semiconductor device of the invention includes an integrated circuit formed on a semiconductor substrate having first and second surfaces and a notch region along the edges. The first surface includes electrical contact pads electrically connected with the integrated circuit. The first surface of the semiconductor substrate includes a top protective layer that has a surface portion extending beyond the edges of the semiconductor substrate. The second surface of the semiconductor substrate includes a bottom protective layer with electrical connectors. The surface portion of the top protective layer includes electrical contact pads that are electrically interconnected with electrical contact pad extensions. The electrical contact pad extensions are interconnected with electrical connectors via a backside electrical connector that overlaps the electrical contact pad extensions forming a lap connection. Methods for constructing such devices and connections are also disclosed.

Claims

1. A method for producing electrical die contact structures for integrated circuit devices, the method including the steps of:

providing a plurality of integrated circuits on a semiconductor wafer having a front side and a backside, each of the integrated circuits being delineated from other integrated circuits on the wafer by a plurality of saw streets and each integrated circuit including a multiplicity of electrical contact pads with contact pad extensions that extend into the saw streets;

attaching a front side protective layer to a front side surface of the wafer and wherein the electrical contact pads are electrically isolated from the contact pad extensions by a passivation material and then electrically interconnecting the contact pads and the pad extensions using an overlying bridge of conducting material;

removing material from the backside of the wafer in the saw streets until a bottom surface of the contact pad extensions is exposed, thereby defining notches along edges of the integrated circuit devices;

forming electrical connections on the backside of the semiconductor substrate;

forming a backside metal layer such that a tail portion of the metal layer overlaps the bottom surface of one of the contact pad extensions in one of said notches, the tail portion extending along a side edge of the notch and including a bend at a bottom of the notch such that the tail portion extends from the bend in a direction substantially parallel to the pad extension forming a parallel electrical connection between said contact pad extension and said tail portion such that the contact pad extensions are electrically interconnected with electrical connections; and

separating the plurality of integrated circuit devices into individual devices.

2. The method of claim 1, wherein the providing step includes providing the semiconductor wafer wherein the integrated circuits comprise optical devices;

and

wherein attaching the front side protective layer comprises attaching an optically transmissive protective layer to a front side surface of the wafer using an optically transmissive adhesive material.

3. The method of claim 1, wherein the step of removing material from the backside of the wafer includes the step of thinning the wafer by removing material from the backside of the wafer.

4. The method of claim 1, wherein the step of forming electrical connections on the backside of the semiconductor substrate includes:

attaching a backside protective layer to a backside surface of the wafer with a backside adhesive,

forming electrical connections on a surface of the backside protective layer; and

wherein the step of forming a backside metal layer includes, removing the backside adhesive material and backside protective layer material in the saw streets and in the notches until a bottom surface of the contact pad extensions is exposed,

and forming the backside metal layer such that the tail portion of the metal layer overlaps the bottom surface of the contact pad extensions and such that the contact pad extensions are electrically interconnected with electrical connections on the backside protective layer.

5. The method of claim 1, wherein the step of forming electrical connections on the backside of the semiconductor substrate includes forming low modulus pads of material having a low coefficient of thermal expansion and forming solder balls on the low modulus pads.

6. The method of claim 1, wherein the step of forming the backside metal layer includes forming a layer of sealing material in the notch over the backside metal layer.

7. The method of claim 1, wherein the step of forming the backside metal layer includes:

forming the backside metal layer such that it includes an opening in the notch, thereby separating a backside metal layer of one integrated circuit from a backside metal layer of another adjacent integrated circuit, and includes forming a layer of sealing material in the notch over the backside metal layers such that is fills the opening.

8. A method for producing electrical die contact structures for integrated circuit devices, the method including the steps of:

providing a plurality of integrated circuits on a semiconductor wafer having a front side and a backside, each of the integrated circuits being delineated from other integrated circuits on the wafer by a plurality of saw streets and each integrated circuit including a multiplicity of electrical contact pads with contact pad extensions that extend into the saw streets; and

wherein the electrical pads are isolated from the contact pad extensions by a passivation material and then electrically interconnecting the contact pads and the pad extensions using an overlying bridge of conducting material;

removing material from the backside of the wafer in the saw streets until a bottom surface of the contact pad extensions is exposed, thereby defining notches along edges of the integrated circuit devices;

forming electrical connections on the backside of the semiconductor substrate;

forming a backside metal connector on an edge of an integrated circuit device, the connector having a first end and a second end,

the first end comprising an angled portion that directs the connector away from the edge and extends into a tail portion that overlaps and extends substantially parallel to the bottom surface of the contact pad extensions to generate an extended contact surface between the tail portion and the contact pad extensions to generate an extended contact surface and such that the second end is in electrical contact with an electrical connection on said contact pad extensions are electrically interconnected with electrical connections; and

separating the plurality of integrated circuit devices into individual devices.

9. The method of claim 8 wherein

said removing material from the backside of the wafer is conducted such that said notches have sidewalls and floor surfaces at the bottom of the notches;

and

said forming of the backside metal connector includes the formation of the tail portion that bends and extends away from the notch sidewall in a direction substantially parallel to a lower surface of the contact pad extension, the tail portion having an upper surface and an opposing lower surface on an opposite surface of the tail portion, the upper surface of the tail portion overlaps and extends substantially parallel to the bottom surface of the contact pad extensions providing an extended bond structure between the upper surface of the tail portion and the bottom surface of the contact pad extensions.

10. A method of forming a backside contact, comprising:

forming a portion of a contact in an active portion of a substrate, the contact comprising electrical contact pads and electrical contact pad extension extending into a region of the substrate; and

wherein the electrical pads are isolated from the contact pad extensions by a passivation material and then electrically interconnecting the contact pads and the pad extensions using an overlying bridge of conducting material;

including a boundary region between two die of the substrate;

removing material from a backside of the substrate to form an opening in said boundary region, the opening exposing a portion of the contact at a bottom surface of the opening;

forming a conductive line on the backside of the substrate such that the conductive line extends down into the opening and contains a bend at the bottom of the opening which alters the orientation of the conductive line relative to the contact such that it extends a distance directly adjacent to and substantially parallel with the contact in an overlapping configuration to create an electrical lap joint connection between the conductive line and the contact, the conductive line also in electrical contact with an electrical connection on the backside of the substrate; and

separating the two die along the boundary through a portion of the contact.

11. A method as recited in claim 10 wherein the boundary between the two die comprises a saw street and wherein separating the two die comprises cutting the die apart using a saw to cut in the saw street.

12. A method as recited in claim 10 wherein removing material from a backside of the substrate to form an opening comprises etching the backside of the substrate to form the opening.

13. A method as recited in claim 12 wherein said etching forms an opening having sloped sidewalls.

14. A method as recited in claim 10 wherein separating the die is followed by a step of sealing edges formed by such separation.

15. A method as recited in claim 10 wherein the lap joint comprises a connection formed of a single alloyed material.

16. A method as recited in claim 10 wherein the method further includes treating the electrical connection on the backside of the substrate with a solder process to form a solder ball on the electrical connection.

17. A method as recited in claim 10 wherein removing material from a backside of the substrate to form a opening comprises etching the backside of the substrate to form the opening.

18. A method as recited in claim 17 wherein said etching forms an opening having sloped sidewalls.

19. A method of forming a backside contact, comprising:

forming a pair of contacts on an upper portion of a substrate, wherein each of the contacts comprising electrical contact pads and electrical contact pad extensions a first contact electrically connected with a first integrated circuit of the substrate and the second contact electrically connected with a second integrated circuit of the substrate, each contact extending into a region of the substrate between said integrated circuits; and

wherein the electrical pads are isolated from the contact pad extensions by a passivation material and then electrically interconnecting the contact pads and the pad extensions using an overlying bridge of conducting material;

removing material from the backside of the substrate to form an opening in the backside of the substrate exposing a portion of each contact;

forming a conductive line in the opening, said line extending between the first and the second contacts across a bottom surface of the opening and overlaps at least some of the exposed portions of both the first and the second contacts, said conductive line also extending toward and electrically connecting with electrical connectors formed on a bottom surface of each die; and

separating the first and second integrated circuits along a boundary in said region of between the said integrated circuits.

20. A method as recited in claim 19 wherein the region of the substrate between said integrated circuits comprises a saw street and wherein separating the integrated circuits comprises cutting the die apart using a saw to cut in the saw street.

21. A method as recited in claim 19 wherein separating the die is followed by a step of sealing edges formed by such separation.

22. A method as recited in claim 19 wherein the portion of the conductive line over laps the contact comprises a lap joint and wherein the lap joint is formed of a single alloyed material.

23. A method as recited in claim 19 wherein the method further includes treating the electrical connectors on the backside of the substrate with a solder process to form a solder balls on the electrical connectors.

24. A method for producing electrical die contact structures for integrated circuit devices, the method including the steps of:

providing a semiconductor wafer having a front side and a back side surface, the wafer including an integrated circuit die delineated from other integrated circuit dice on the wafer by a plurality of saw streets, the wafer including a plurality of contacts comprising electrical contact pads and electrical contact pad extensions wherein at least a portion of the contacts extend into the saw streets; and

wherein the electrical pads are isolated from the contact pad extensions by a passivation material and then electrically interconnecting the contact pads and the pad extensions using an overlying bridge of conducting material;

removing material from the back side of the wafer in the saw streets to form an opening having sidewalls and a floor, and further exposes said contact;

forming a bond pad on the backside surface of the die;

forming a backside metal line that electrically connects said bond pad with a portion of said contact, the backside metal line extending from the bond pad up the sidewall of the opening and having a bend at the floor of the opening, the bend changing the direction of the metal line such that extends along the floor, the metal line extending from the bend so that it is substantially parallel with the contact and in conductive contact with the contact thereby establishing electrical contact between said bond pad and outer contact; and

separating the plurality of integrated circuit dice into individual devices.