Stray field shielding structure for semiconductors

• US 20060205177A1
• Filed: 03/08/2005
• Published: 09/14/2006
• Est. Priority Date: 03/08/2005
• Status: Active Grant

• Current Assignee: Everspin Technologies Incorporated
• Original Assignee: David Walter Smith
• Inventors: Smith, David Walter
• Granted Patent: US 7,205,643 B2
• Time in Patent Office: Days
• US Class Current: 438/455
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/32145 the bodies being stacked
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• 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 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 23/5225 Shielding layers formed together with wiring layers
• CPC Class Codes: H01L 23/552 Protection against radiation, e.g. light or electromagnetic waves
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• 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 2924/00014 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 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/10253 Silicon [Si]
• CPC Class Codes: H01L 2924/15153 the die mounting substrate comprising a recess for hosting the device
• CPC Class Codes: H01L 2924/15157 Top view
• CPC Class Codes: H01L 2924/15165 Monolayer substrate
• CPC Class Codes: H01L 2924/19041 being a capacitor
• CPC Class Codes: H01L 2924/3025 Electromagnetic shielding

Abstract

A stray field shielding structure for die attaching onto a magnetic random access memory chip or to other chips to prevent loss of memory due to magnetic fields or radiation is made by a method which provides a thick layer of magnetic material which is precise in its dimensions and adapted for placement on individual die by existing pick and place machines and die attach bonders. The magnetic shielding material is cut to a desired size by etching to remove all burrs and debris and is then attached only to good die using a die attach film of thermoset plastic or a gob of epoxy adhesive.

Claims

1. A method of making a stray field shielding structure comprising the steps of:

bonding a sheet of stray field shielding material to a stable host carrier to provide a laminated panel,

applying a photo-resist film onto the top of said stray field shielding material to provide an array pattern of a plurality of individual shielding structures and expose streets of shielding material,

removing said exposed streets of shielding material separating individual shielding structures,

removing said photo-resist film from the top of said individual shielding structures,

bonding an adhesive film supported on a flexible wafer film to the top of the individual shielding structures that are supported by the stable host carrier, and

removing said stable host carrier to provide a plurality of inverted individual shielding structures that are removable from said flexible wafer film by bonding means.

2. A method as set forth in claim 1 which further includes the step of die bonding said stray field magnetic material onto individual die to form said stray field shielding structure on said die.

3. A method as set forth in claim 2 wherein said step of die bonding comprising attaching said stray field semiconductor material to1 said die with gobs of adhesive.

4. A method as set forth in claim 2 wherein said step of die bonding said stray field magnetic material comprises attaching a layer of die attach film on said stray field magnetic material.

5. A method as set forth in claim 1 wherein the step of removing said exposed streets of shielding material comprises etching.

6. A method as set forth in claim 5 wherein the step of etching comprises plasma etching or sprayed acid etching.

7. A method as set forth in claim 6 wherein said step of attaching comprises attaching a layer of thermoset plastic.

8. A method as set forth in claim 7 wherein said thermoset plastic comprises an insulated polyimide plastic.

9. A method as set forth in claim 1 which further comprises the step of bonding said individual shielding structures to a magnetoresistive random access memory (MRAM).

10. A method as set forth in claim 1 further comprises bonding individual shielding structures to a computer chip having an onboard MRAM.

11. A stray field shielding structure for die attaching onto a magnetorestrictive random access memory (MRAM) chip to prevent loss of memory due magnetic stray fields comprising:

a layer of individual magnetic shielding material adapted for placement by pick and place machines and/or die bonders,

said magnetic shielding material being cut to a precise desired size by etching to remove all burrs and debris in the streets between blocks of shielding material, and

an attaching layer for bonding said magnetic material to individual die.

12. A stray field shielding structure as set forth in claim 11 wherein said streets between magnetic material blocks is acid or plasma etched to remove all burrs and maintain precise dimensions.

13. A stray field shielding structure for attachment to magnetic random access memory chips as set forth in claim 11 wherein said magnetic shielding material comprises nickel or nickel alloy.

14. A stray field shielding structure as set forth in claim 11 wherein said magnetic shield material further comprises a metal radiation shield.

15. A stray field shielding structure as set forth in claim 11 wherein said magnetic random access memory chip comprises a non-volatile magnetoresistive random access memory (MRAM).

16. A stray field shielding structure for die attaching onto an MRAM chip as set forth in claim 11 wherein said attaching layer comprises a polyimide die attach film (DAF).

17. A stray field shielding structure for die attaching onto MRAM chips as set forth in claim 11 wherein said layers of magnetic shielding material is three to eight one thousandths of an inch thick.