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FET Gate Integrity by Ion Implantation

IP.com Disclosure Number: IPCOM000079235D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Double, GP: AUTHOR [+2]

Abstract

Ion implantation through the gate insulator of field-effect transistors (FET's) is known for adjusting threshold voltage. Proper adjustment of ion implantation process parameters achieves not only threshold voltage adjustment, but also increases the reliability against failure of the gate dielectric.

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FET Gate Integrity by Ion Implantation

Ion implantation through the gate insulator of field-effect transistors (FET's) is known for adjusting threshold voltage. Proper adjustment of ion implantation process parameters achieves not only threshold voltage adjustment, but also increases the reliability against failure of the gate dielectric.

In this technique, preferably phosphorus ions are implanted in about the first 300 angstroms of a silicon substrate to a peak concentration in the range from about 10/11/ to 10/13/ atoms per cc, as shown in the figure. The silicon substrate is covered by a first 300 angstrom layer of silicon dioxide and a second 300 angstrom layer of silicon nitride. Approximately two to three percent of the total peak concentration of the phosphorus ions in the silicon substrate extends into the silicon dioxide layer, as shown by portion 1 of the initially implanted impurity profile 2. The composite structure after implantation is subjected to an annealing step of, for example, 1050 degrees C for one-half hour in a nitrogen atmosphere. The annealing step causes the redistribution of the phosphorus ions, as represented by the impurity profile 3. Profile 3 shows that the phosphorus ions out-diffuse into the silicon dioxide layer, but do not penetrate into the silicon nitride layer.

The phosphorus ions represented by the area under the profile curve 3 in the silicon dioxide layer, improve the oxide integrity against early failure (under 300 hours)...