Composition and Resistivity of Sputtered Tungsten Silicides

Hara, Tohru; Hayashida, Hiroyuki; Takahashi, Shuya

doi:10.1149/1.2095855

Cited by 6 publications

(1 citation statement)

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“…Such films have been extensively used in polycide gates and interconnections of very large scale integrated circuits (1), Deposition from the reaction between monosilane (Sill4, denoted hereafter as MS) and tungsten hexafluoride (WF6) has been reported by many authors (1,2). However, the high fluorine concentration of MS WSi~ film leads to flatband voltage shifts and a reduction of gate capacitance in CVD WSix polycide gates (3). Film peeling during the oxidation process and microcracking at the inside corner of the step are also serious problems.…”

Section: Discussionmentioning

confidence: 99%

Sputtered Tungsten Silicides Deposited at Different Argon Pressures

Hara

Takahashi

Chen

et al. 1989

J. Electrochem. Soc.

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The argon impurities in sputtered tungsten silicide (WSi=) was measured in 2000/~ thick films deposited by dc magnetron sputtering at Ar pressures ranging from 4 to 20 mtorr. The Ar concentration found by Rutherford backscattering spectrometry was 7.8 • 102~ cm -3 in the film at 4 mtorr. The concentration decreased slowly with increasing Ar pressure and reaches 5.1 • 102~ cm -3 at 20 mtorr. Target voltage changed from 555 to 455V with these Ar pressure changges. Si composition, x, of WSi= changed from 2.46 to 2.61 and the stress of the films deposited on Si changed from 1.7 • 10 to 2.1 • 109 dyne-cm -2 with varying Ar pressure from 4 to 20 mtorr. The resistivity increased slowly with increasing Ar pressure, with an average value of 800 ~-cm. These results indicate that the film properties are not much affected by Ar impurities contained in the film, especially after 1000~ annealing.Tungsten silicide (WSi=) has been extensively used in gates and interconnects of 1 and 4 megabit dynamic random access memories (DRAM). Much better thermal stability can be achieved in this film than in titanium silicide. Better adhesion properties ~br Si and SiO2 can also be attained.Since a large amount ofF impurity, for instance, 1 • 1021 cm -3, is contained in CVD WSix films (1), flatband voltage shift and gate capacitance reduction are serious problems in polycide gate processes as reported by Tamura et al. (2).Process technologies of CVD WSi= polycide gate process are more difficult. Therefore, sputtered WSix is extensively used in this application. Film property differences between CVD and sputtered WSi= have been studied recently (3). Low resistivity films (40 ~-cm) have been obtained in sputtered WSix (3).The higher resistivity of sputtered WSix films may be I" due to Ar impurities incorporated in the film. However, Ar impurity effects on film properties have been little studied.|0 4 Ar spectra of sputtered WSi= films have been measured by Rutherford backscattering spectrometry (RBS). The concentration of Ar in sputtered tantalium silicide was reported by Levy and Gallagher (4).This paper describes Ar impurity concentrations in sputtered WSi~ films, and the effects of Ar impurities on film properties.

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Section: Discussionmentioning

confidence: 99%