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Screening of Dielectric Defects in Memory Devices

IP.com Disclosure Number: IPCOM000048412D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Anolick, ES: AUTHOR [+3]

Abstract

Substantially all failures of dielectrics in memory devices are related to defects which existed during the manufacturing process. For this reason, heavy stressing of dielectrics during the manufacturing process will screen out many potential failures without affecting the structures which have no dielectric defects.

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Screening of Dielectric Defects in Memory Devices

Substantially all failures of dielectrics in memory devices are related to defects which existed during the manufacturing process. For this reason, heavy stressing of dielectrics during the manufacturing process will screen out many potential failures without affecting the structures which have no dielectric defects.

In essence, the screening technique is as follows:
1. After the wafer is developed through to the

second level of polysilicon, but prior to

etching the second level pattern, provide a

pad having access to all first level

polysilicon. This can be accomplished by a

simple etch step.
2. Apply an excess potential (that is, a more

negative potential) on the first level

polysilicon relative to both the second level

and the substrate.
3. Apply an excess potential (that is, a more

negative potential) on the second level

relative to the substrate.

After the above steps, normal wafer processing is continued.

The screening can be done at room temperature, and will effectively screen out wafers that would be prone to early failure over a range of temperatures. However, as temperature increases, time to fail decreases. Therefore, the screening should reflect product life over the entire range of temperature. For example, a product could be stressed for one second at ten volts above its intended use voltage, at 25 degrees C. This is equivalent to 2x10/7/ hours at 25 degrees C at the intended use voltage. Stressing...