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Metallurgy Structure For Insuring Threshold Stability Of FET Devices Under A Solder Terminal

IP.com Disclosure Number: IPCOM000048791D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Hu, CC: AUTHOR [+2]

Abstract

In integrated circuit devices utilizing FET transistors, the transistors located beneath a solder terminal are vulnerable to leakage induced threshold shift. This structure provides protection for FET devices located beneath the solder terminal.

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Metallurgy Structure For Insuring Threshold Stability Of FET Devices Under A Solder Terminal

In integrated circuit devices utilizing FET transistors, the transistors located beneath a solder terminal are vulnerable to leakage induced threshold shift. This structure provides protection for FET devices located beneath the solder terminal.

A leakage-induced threshold shift is one of the threshold stability concerns in double polysilicon double conductive metallurgy systems. Its mechanism involves the trapping of electrons injected into the insulator that leads to a positive shift in the threshold voltage. The shift depends on the quality of the oxide, i.e., the trapping density, etc. Devices under the solder terminal are vulnerable to leakage induced threshold shift effect due to the exposure to sputter cleaning during the fabrication of the solder terminals. This process step may induce more traps or surface states in the insulator, and thus lead to larger threshold shift.

In the figure, a conventional polysilicon gated field-effect transistor is shown on the left hand side. On the right hand side, the structure described in the text is shown.

In this structure there is provided a first metal plate 10 over polygate region 12 associated with source and drain regions 14 and 16, respectively. Metal plates 10 are located over the gate regions of the FETs whenever the FETs sre located beneath the solder terminal 18. A dielectric layer 20 electrically isolates the second...