No abstract

In the stress control of an X-ray mask absorber, the repeatability of control and stability are important. We found that the change in the stress in a Ta film resulting from annealing depends on the oxygen concentration in the film; the magnitude of the stress change is determined by the annealing temperature and time. Using this characteristic of Ta film, we have successfully controlled the stress in the Ta absorber to less than 5 MPa with good repeatability. In our mask fabrication process, Al2O3 film was used as an etching mask. We found that the Al2O3 film prevented the Ta absorber stress from changing in high-temperature atmospheres because the Al2O3 film prevented oxygen diffusion into the Ta film. Utilizing Al2O3 films, we succeeded in preventing changes in Ta absorber stress in the thermal processes after Ta stress control, such as frame bonding and resist baking. Consequently, we were able to precisely control the Ta absorber stress in X-ray masks with good repeatability and stability in a realistic X-ray mask fabrication process.

We investigated the effects of etch rate on low-k damage induced by dry etching under CF 4 , CF 4 /O 2 , and C 4 F 6 /O 2 /Ar chemistry conditions. The amount of damage increases with decreasing etch rate in all chemistries. This is because the amount of fluorine or oxygen radical diffusion increases with plasma exposure time. These radicals extract CH 3 groups from the low-k film or oxidize the film. To reduce damage to the lowest level possible, it is necessary to suppress the effect of the damage diffusion using etching conditions where the etching speed is higher than the diffusion speed of the damage.

No abstract

Effective charges of the constituents of NaN02, NaNO,, KNOi and CaCO, are calculated from the splitting of polar optical modes into transverse and longitudinal components, obtained from the simulation of the infrared reflectivity spectra polarised along the different crystallographic directions. Effective charges within planar molecular ions are found to be highly anisotropic, whereas the effective charge of external cations depends little on polarisation. The temperature dependence of the effective charges is reported in NaNO,, NaN03 and KN03. The dependences are discussed in terms of correlation of the cationanion distance with the iono-covalent character of the bond, in particular near structural phase transitions where the cation-anion distances may change.