| Summary: | 碩士 === 國立交通大學 === 應用化學研究所 === 85 ===
X-ray lithography has the advantages of better resolution (limited at 0.05 um and below), larger depth of focus, less diffraction effect, nearly no substrate reflection, nearly no standing wave, and larger exposure area etc. X-ray lithography will be one of the major technologies to fabricate IGbit DRAM (design rule 0.18 um) in the future. In x-ray lithography, mask fabrication is the key issue. This thesis studies the fabrication low stress x-ray mask. Using silicon-rich nitride as membrane and W-Ta-N allov as absorber.
The stress of silicon nitride(Si3N4) is too large to be used as membrane of x-ray mask, hence, by increasing the amount of silicon in silicon nitride the stress could be reduced. Using low pressure chemical vapor deposition (LPCVD) system to deposit silicon-rich nitride, the ratio of gases flow, temperature and pressure of chamber were modified to fabricate low stress, high optical transmittance membranes. Under SiH2Cl2/NH3=98/22 sccm, temperature 900℃, pressure 160 mtorr, low tensile stress of silicon-rich nitride membrane around 50 MPa was obtained.
Sputtering W, Ta in the present of N2 gas to fabricate x-ray mask absorbers can prevent from the problems of unstable W or Ta thin film stress changing time by time. Under DC power, tungsten 150W, tantalum 250 W, sputtering gases Ar/N2=50/10 sccm, chamber pressure 4 mtorr, the film stress is around -250 MPa, after annealing in 250℃ half an hour, W-Ta-N stress reduced to about +20MPa. The alloy thin film could keep about the same stress after rising to 200℃ three times.
In this thesis the control of the stress of membrane and absorber and the fabrication processes of x-ray mask were accomplished.
|
|---|
