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Reducing Radiation Damage in In Channel IGFET's

IP.com Disclosure Number: IPCOM000074276D
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

Gregor, LV: AUTHOR [+3]

Abstract

In the fabrication of insulated gate field-effect transistors, the passivation of these transistors with sputtered quartz results in a shift in the threshold voltage (V(T)) of these devices. The models proposed involve radiation damage and the activation of defects or "traps" in the thermal oxide immediately adjacent to the silicon surface. The traps are such that they retain positive charge in the oxide. These positive charges decrease the absolute value of the threshold voltage.

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Reducing Radiation Damage in In Channel IGFET's

In the fabrication of insulated gate field-effect transistors, the passivation of these transistors with sputtered quartz results in a shift in the threshold voltage (V(T)) of these devices. The models proposed involve radiation damage and the activation of defects or "traps" in the thermal oxide immediately adjacent to the silicon surface. The traps are such that they retain positive charge in the oxide. These positive charges decrease the absolute value of the threshold voltage.

The present process minimizes the amount of acceptors present at the silicon-silicon dioxide interface to minimize the shift in threshold voltage arising from the sputtering passivation step or from any other source of radiation. Specifically, the initial processing steps of the field-effect transistors are designed to maximize boron depletion and thereby minimize boron out diffusion during the growth of the gate oxide. Thus, instead of cleaning the surface of a silicon wafer with a H(2)O(2) - NH(4)OH solution and growing the initial oxide at a temperature of 970 degrees in oxygen, water, and oxygen for times of 15 minutes, 75 minutes, and 30 minutes, respectively, the present process contemplates depositing an oxide (e.g. at 1000 degrees C), stripping the oxide and then growing the initial oxide (e.g. at 1100 degrees C for 16 hours).

The higher oxide growth temperature and longer times result in maximum boron depletion from the silicon an...