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Electrothermal Correction of Low-Threshold Voltages in FET Product

IP.com Disclosure Number: IPCOM000074232D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Kaplan, LH: AUTHOR [+2]

Abstract

Integrated circuit wafers which have been fabricated with a low threshold voltage may be brought into proper specification, after the fact, and almost without regard to cause by use of the following procedure. After the value of the threshold voltage has been determined by quality control testing, the aluminum interconnection metallurgy is removed by chemical etching. Wafers are then exposed to an oxygen ambient at a temperature and for a time determined by the threshold voltage shift desired. They are then covered with an aluminum film more than 5000angstroms thick. Each wafer is then subjected to electrothermal stress, the field, time and temperature depending again upon the desired threshold voltage shift. Finally, the aluminum film is patterned into the final metallurgy by photolithography.

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Electrothermal Correction of Low-Threshold Voltages in FET Product

Integrated circuit wafers which have been fabricated with a low threshold voltage may be brought into proper specification, after the fact, and almost without regard to cause by use of the following procedure. After the value of the threshold voltage has been determined by quality control testing, the aluminum interconnection metallurgy is removed by chemical etching. Wafers are then exposed to an oxygen ambient at a temperature and for a time determined by the threshold voltage shift desired. They are then covered with an aluminum film more than 5000angstroms thick. Each wafer is then subjected to electrothermal stress, the field, time and temperature depending again upon the desired threshold voltage shift.

Finally, the aluminum film is patterned into the final metallurgy by photolithography.

The various parameters used in the above treatment (e.g., time and temperature of oxygen treatment, stressing voltage, etc.) are mutually dependent and, therefore, no one process can be considered optimum. However, satisfactory combinations include an oxygen treatment of between 600 degrees C and 700 degrees C for a ten minute exposure. The electrothermal stress may be carried out in the range of 250degrees C - 350degrees C for times up to ten minutes.

The effect cited above is presumed to arise from the trapping of electrons in sites at the silicon - silicon dioxide interface. These traps are normally remo...