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High-Pressure Oxidized Tantalum Pentoxide Films on Silicon With Improved Leakage

IP.com Disclosure Number: IPCOM000041923D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Merz, CJ: AUTHOR [+3]

Abstract

Ta2O5 films on Si are presently of interest as alternative dielectric layers for high-capacitance density storage capacitors. A major problem with Ta2O5 thin films is the high leakage current observed, which is most likely due to non-stoichiometry of the dielectric films. A method of producing Ta2O5 thin films on Si with improved stoichiometry and improved leakage is described herein. First, 20 nm thick Ta films are deposited by electron-beam evaporation on clean Si wafers. Next, the metal films are oxidized at about 525ŒC for 1 hour at 40 atmospheres dry O2 pressure. This converts the Ta layer into a Ta2O5 film of about 50 nm thickness.

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High-Pressure Oxidized Tantalum Pentoxide Films on Silicon With Improved Leakage

Ta2O5 films on Si are presently of interest as alternative dielectric layers for high-capacitance density storage capacitors. A major problem with Ta2O5 thin films is the high leakage current observed, which is most likely due to non- stoichiometry of the dielectric films. A method of producing Ta2O5 thin films on Si with improved stoichiometry and improved leakage is described herein. First, 20 nm thick Ta films are deposited by electron-beam evaporation on clean Si wafers. Next, the metal films are oxidized at about 525OEC for 1 hour at 40 atmospheres dry O2 pressure. This converts the Ta layer into a Ta2O5 film of about 50 nm thickness. The results of ellipsometry measurements performed on the Ta2O5 films show that the ratio of O/Ta is improved in high-pressure oxidized Ta2O5 films as compared to Ta2O5 films obtained by oxidation at atmospheric pressure. Furthermore, electrical measurements on Al/Ta2O5/p-Si capacitors show decreased leakage. We find, for example, that the leakage current with -5 V applied to the Al-gate (500 nm thick, 0.81 nm diameter dot) is about 7 x 10-9 A. For Ta2O5 films oxidized at atmospheric pressure (under a great variety of heat treatment parameters like temperature, time, etc.), it is in the best case 2 x 10-7A for the same applied field. Also, with the Al-gate positive the high-pressure oxidized Ta2O5 films show significantly improved leakage.

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