AVS 49th International Symposium
    Thin Films Monday Sessions
       Session TF-MoM

Paper TF-MoM4
Electron Cyclotron Resonance Sputtering Apparatus for Optical Band-pass Filters for Wavelength Division Multiplexing

Monday, November 4, 2002, 9:20 am, Room C-101

Session: Optical Thin Films
Presenter: Y. Jin, NTT Telecommunications Energy Laboratories, Japan
Authors: Y. Jin, NTT Telecommunications Energy Laboratories, Japan
M. Shimada, NTT Telecommunications Energy Laboratories, Japan
Correspondent: Click to Email
We have developed a new apparatus for fabricating narrow band-pass multilayer filters for dense wavelength division multiplexing (DWDM) that uses electron cyclotron resonance (ECR) sputtering with two plasma sources. ECR sputtering with Ar/O@sub 2@ gas and a metallic target has a stable metal-mode deposition. The target is sputtered in a metallic state, and this is followed by oxide film formation, which is enhanced by ECR plasma irradiation on the substrate.@footnote 1@ The ECR sputtering of metal-mode SiO@sub 2@ and Ta@sub 2@O@sub 5@ films is suitable for the fabrication of optical multilayer filters because it provides surface smoothness, low optical loss, and stability of the refractive index. These depositions were carried out at room temperature. The sputtering system consists of two ECR plasma sources, which are coupled with divided microwaves (2.45 GHz), and cylindrical sputtering targets (Si: 99.999%, Ta: 99.99%) biased by using rf-power (13.56 MHz). The deposition-thickness uniformities are ±0.65% for SiO@sub 2@ and ±0.44% for Ta@sub 2@O@sub 5@ over a 200-mm diameter. The refractive indices of the SiO@sub 2@ and Ta@sub 2@O@sub 5@ films are 1.47 and 2.10 at a wavelength of 1550 nm. This technique produces a typical surface roughness of 0.12-nm rms. To achieve precise deposition of these films, a new optical thickness monitoring system was developed. This system directly measures spectral transmission curves during film deposition using incandescent light and an infrared spectrometer, and detects the endpoint of the demanded thickness. Using this method, we fabricated a narrow band-pass filter with 43 layers on a 100-mm quartz substrate, and obtained a half bandwidth with 0.27-nm ±0.0253-nm band-pass filtering characteristics with low optical loss over the whole 100-mm diameter. ECR sputtering deposition in the metal mode is thus effective for DWDM optical band-pass filter fabrication. @FootnoteText@ @footnote 1@ M. Shimada et al., Vacuum 59, 727 (2000).