AVS 45th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThP

Paper PS-ThP2
Tantalum Film for X-ray Lithography Mask Deposited by Electron Cyclotron Resonance Plasma Source Coupled with Divided Microwaves

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Plasma Science and Technology Division Poster Session
Presenter: H. Nishimura, NTT System Electronics Laboratories, Japan
Authors: H. Nishimura, NTT System Electronics Laboratories, Japan
T. Ono, NTT System Electronics Laboratories, Japan
M. Oda, NTT System Electronics Laboratories, Japan
S. Matsuo, NTT System Electronics Laboratories, Japan
Correspondent: Click to Email
An advanced ECR plasma source by which a conductive film can be stably formed has been developed and applied to Ta film formation.@footnote 1@ We investigate the applicability of ECR-Ta as absorbers of x-ray masks. It is found from TEM observation that an ECR-Ta film is a polycrystal film that has a large grain size of (>0.5 µm) and a dense microstructure. The x-ray absorber material must satisfy several conditions, such as low, uniform, and stable stress. The stress change of ECR-Ta film is rarely observed not only in the air but also under the SR irradiation condition. In order to control film stress, we have investigated the stress-depth distribution. The stress is analyzed to be a sum of an interfacial stress (retained near the film-substrate interface) and a bulk stress (retained in the film bulk). These individual stresses can be independently controlled. The interfacial stress depends on the substrate temperature, working-gas pressure, and deposition rate. The bulk stress varies toward compressive by adding Ar to the sputtering gas (Xe). A low stress film with no stress-depth distribution (15 MPa at 200-400 nm) is obtained by optimizing deposition parameters. A highly accurate x ray mask is achieved by using an ECR-Ta film. These results show that the dense microstructure including the grain boundary rather than the film structure (polycrystal or amorphous) is important for a highly accurate x-ray mask. The ECR sputter method is suitable for depositing dense microstructure film because of the enhancement of film formation reaction on the surface by low energy (10-30 eV) ion irradiation. @FootnoteText@ @footnote 1@ H. Nishimura, et al., J. Vac. Sci. Technol. A15 (19 97) 707.