Semiconductor devices including voltage switchable materials for over-voltage protection

• US 7,923,844 B2
• Filed: 11/21/2006
• Issued: 04/12/2011
• Est. Priority Date: 11/22/2005
• Status: Expired due to Fees

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Shocking Technologies, Inc.
• Inventors: Kosowsky, Lex
• Primary Examiner(s): Parker; Kenneth A
• Assistant Examiner(s): Diaz; Jose R
• Application Number:
  US11/602,881
• Publication Number:
  US 20070114640A1
• Time in Patent Office: 1,603 Days
• Field of Search: 257/777
• US Class Current: 257/777
• 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 a first surface thereof, a conductor;

a semiconductor die attached to the first surface using a die attach adhesive;

a voltage switchable material connecting the semiconductor die to the conductor, the voltage switchable material physically contacting both the semiconductor die and the conductor; and

an encapsulant that encapsulates the semiconductor die, wherein the encapsulant and the die attach adhesive include the voltage switchable material.

2. The semiconductor device of claim 1, wherein the conductor is sandwiched between the die attach adhesive and the die bonding pad.

3. The semiconductor device of claim 1, wherein the die attach adhesive extends beyond the die bonding pad to contact the conductor.

4. The semiconductor device of claim 1, wherein the semiconductor die is flip-chip bonded to the die bonding pad.

5. The semiconductor device of claim 4, wherein flip-chip bonding includes the use of solder balls, and at least one of the solder balls is replaced by a ball including the voltage switchable material.

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

7. The semiconductor device of claim 1, wherein the encapsulant includes:

a first conformal layer comprising the voltage switchable material that conforms to the semiconductor die and at least part of the dielectric substrate, and

a second layer that overlies at least a portion of the first conformal layer.

8. The semiconductor device of claim 1, wherein the encapsulant encapsulates the semiconductor die and the conductor.

9. The semiconductor device of claim 1, wherein the encapsulant encapsulates the semiconductor die and the die attach adhesive.