Semiconductor devices including voltage switchable materials for over-voltage protection

• US 20070114640A1
• Filed: 11/21/2006
• Published: 05/24/2007
• Est. Priority Date: 11/22/2005
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Shocking Technologies, Inc.
• Inventors: Kosowsky, Lex
• Granted Patent: US 7,923,844 B2
• Time in Patent Office: Days
• US Class Current: 257/666
• CPC Class Codes: H01L 21/563 Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
• CPC Class Codes: H01L 2224/1132 Screen printing, i.e. using a stencil
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/131 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/274 by blanket deposition of the material of the layer connector
• CPC Class Codes: H01L 2224/32013 the layer connector being larger than the bonding area, e.g. bond pad
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• CPC Class Codes: H01L 2224/83102 using surface energy, e.g. capillary forces
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 2224/92125 the second connecting process involving a layer connector
• CPC Class Codes: H01L 23/3128 the substrate having spherical bumps for external connection
• CPC Class Codes: H01L 23/60 : Protection against electrostatic charges or discharges, e.g. Faraday shields
• CPC Class Codes: H01L 23/62 : Protection against overvoltage, e.g. fuses, shunts
• CPC Class Codes: H01L 24/11 : Manufacturing methods for bumps on insulating substrates H01L21/4853
• CPC Class Codes: H01L 24/13 : of an individual bump connector
• CPC Class Codes: H01L 24/48 : of an individual wire connector
• CPC Class Codes: H01L 24/73 : Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• CPC Class Codes: H01L 24/81 : using a bump connector
• CPC Class Codes: H01L 24/83 : using a layer connector
• CPC Class Codes: H01L 24/94 : at wafer-level, i.e. with connecting carried out on a wafer comprising a plurality of undiced individual devices
• 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 2924/0001 : Technical content checked by a classifier
• CPC Class Codes: H01L 2924/00012 : Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 : Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01015 : Phosphorus [P]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/0103 : Zinc [Zn]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/0104 : Zirconium [Zr]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/12044 : OLED
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15183 : in a single layer of the multilayer substrate
• CPC Class Codes: H01L 2924/15311 : being a ball array, e.g. BGA
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/207 : Diameter ranges

Abstract

Semiconductor devices are provided that employ voltage switchable materials for over-voltage protection. In various implementations, the voltage switchable materials are substituted for conventional die attach adhesives, underfill layers, and encapsulants. While the voltage switchable material normally functions as a dielectric cmaterial, during an over-voltage event the voltage switchable material becomes electrically conductive and can conduct electricity to ground. Accordingly, the voltage switchable material is in contact with a path to ground such as a grounded trace on a substrate, or a grounded solder ball in a flip-chip package.

Claims

1. A semiconductor device comprising:

a dielectric substrate including, on one surface thereof, a die bonding pad and a plurality of conductive traces; and

a semiconductor die attached to the die bonding pad with a die attach adhesive comprising a first voltage switchable material, the die attach adhesive contacting a conductive trace of the plurality of conductive traces.

2. The semiconductor device of claim 1 wherein the die attach adhesive at least partially overlays the conductive trace.

3. The semiconductor device of claim 1 wherein the conductive trace extends between the semiconductor die and the die bonding pad.

4. The semiconductor device of claim 1 wherein the die attach adhesive extends beyond the die bonding pad to contact the conductive trace.

5. The semiconductor device of claim 1 further comprising an encapsulant comprising a second voltage switchable material.

6. The semiconductor device of claim 5 wherein the first and second voltage switchable materials are the same.

12. The semiconductor device of claim 11 further comprising a ground trace disposed on a surface of the substrate and in contact with the encapsulant.

7. A semiconductor device comprising:

a dielectric substrate including, on one surface thereof, a die bonding pad and a plurality of conductive traces;

a semiconductor die attached to the die bonding pad; and

an encapsulant comprising a first voltage switchable material that overlies the semiconductor die and at least part of the dielectric substrate.

8. The semiconductor device of claim 7 wherein the semiconductor die is attached to the die bonding pad with a die attach adhesive.

9. The semiconductor device of claim 8 wherein the die attach adhesive comprises a second voltage switchable material.

10. The semiconductor device of claim 9 wherein the first and second voltage switchable materials are the same.

11. The semiconductor device of claim 7 wherein the semiconductor die is flip-chip bonded to the die bonding pad and the semiconductor device further comprises an underfill layer disposed between the die bonding pad and the semiconductor die.

13. The semiconductor device of claim 11 wherein the underfill layer comprises a second voltage switchable material.

14. The semiconductor device of claim 13 wherein the first and second voltage switchable materials are the same.

15. A semiconductor device comprising:

a dielectric substrate including, on one surface thereof, a die bonding pad including a bond pad for ground;

a semiconductor die flip-chip bonded to the die bonding pad by a plurality of solder balls; and

a ball formed of a first voltage switchable material, disposed between the semiconductor die and the substrate, and contacting the bond pad for ground.

16. The semiconductor device of claim 15 further comprising an encapsulant comprising a second voltage switchable material.

17. A semiconductor device comprising:

a dielectric substrate including a die bonding pad on one surface thereof;

a semiconductor die attached to the die bonding pad; and

an encapsulant including a first conformal layer comprising a first voltage switchable material that conforms to the semiconductor die and at least part of the dielectric substrate, and a second layer that overlies the first conformal layer.

18. The semiconductor device of claim 17 wherein the semiconductor die is attached to the die bonding pad with a die attach adhesive comprising a second voltage switchable material.

19. The semiconductor device of claim 17 wherein the semiconductor die is flip-chip bonded to the die bonding pad and the semiconductor device further comprises an underfill layer comprising a second voltage switchable material disposed between the die bonding pad and the semiconductor die.

20. A wafer-scale package comprising:

a semiconductor die including a plurality of bond pads on a surface thereof, at least one of the bond pads being a bond pad for ground;

solder balls disposed on the bond pads; and

an encapsulant comprising a voltage switchable material encasing the semiconductor die and contacting a solder ball disposed on the bond pad for ground, the solder balls protruding through the encapsulant.