Electrical and Computer Engineering ETDs

Publication Date

11-14-1973

Abstract

Aluminum oxide films prepared by the electron beam evaporation of Al2O3 tablets have been studied in metal-insulator-semiconductor devices. The structure of Al2O3 films is amorphous with a density os 2.25 gm/cm3. The film conductivity is smaller than 5x10^14 (ohm-cm)^-1 and the breakdown strength is higher than 1.3x10^6 V/cm. The transport mechanisms in the film are believed to be impurity-induced flow at room temperature and Poole-Frenkel emission at higher temperatures.

The average relative dielectric constant is about 7. The interface surface states of the MIS sample are small in the middle of the forbidden band, gradually increasing toward the band edges. The MIS devices have interface surface state densities larger 3.4x10^10 states/cm^+2.

Both n- and p-channel MOSFETs with electron beam evaporated Al2O3 as the gate insulator have been fabricated successfully. The n-channel MOSFET has an average threshold voltage of -2.3 volts and an average channel mobility of 207 cm^2/V-sec. The p-channel MOSFET has an average threshold voltage of -1.5 volts and an average channel mobility of 103.5 cm^2/V-sec.

The radiation resistance of the fabricated n- and p-channel MOSFETs was tested with neutrons, gamma rays, and electrons. At 1x10^16 n/cm^2, the degradation of Id-Vd characteristics of the n-channel devices is from 19.5 to 45 percent, while that of the p-channel devices is from 0 to 53 percent. These devices show some dose rate dependence when the results of gamma ray and electron radiation are compared. From Id-Vd characteristic measurements before and after radiation, it can be concluded that using electron beam deposited Al2O3 as the gate insulator remarkably increases the radiation hardness of a field-effect transistor.

Document Type

Dissertation

Language

English

Degree Name

Electrical Engineering

Level of Degree

Doctoral

Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

Wayne Willis Grannemann

Second Committee Member

Lewellyn Boatwright Jr

Third Committee Member

Harold Dean Southward

Fourth Committee Member

William Jackson Byatt

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