Ion Beam Sputter Deposition of Dielectric Films on Large Optical Substrates
Homogeneous deposition on large, planar optical substrates using state of the art electron beam evaporation sources has been challenging due to the point-type sources and the lack of a sophisticated movement system of the mass production capable evaporation sources. Alternatively, the utilization of Ion Beam Sputter Deposition (IBSD) has the advantage of higher energy of the sputtered material (i.e. temperature) arriving at the substrate, compared to competing techniques. Therefore IBSD commonly yields denser films with properties closer to the respective bulk materials.
Al2O3 was deposited as an anti-reflective coating on an optical glass. The process was conducted reactively from the metallic Aluminum target. Oxygen was added as a reactive background gas.
The substrates dimension was 500 mm x 300 mm. Homogeneity was controlled by constant velocity linear movement of the substrate stage and shapers. Static deposition rate of Al2O3 was 7 nm/min. Deposited film thickness was in-situ monitored by a software integrated quartz crystal oscillator and used as an endpoint signal. Film thickness measurements were conducted on a Sentech SE400 ellipsometer. Measurement of the large sample area was done on five 150 mm substrates. Reproducibility was determined from three subsequently process runs.
Static deposition rates of different materials
- Si: 3,0 [nm/min]
- Al: 5,5 [nm/min]
- Mo: 3,5 [nm/min]
- Ti: 2,8 [nm/min]
- Al2O3: 7,0 [nm/min]
- IBSD on large substrates up to 500 mm x 300 mm or 300 mm diameter
- Translation and/or rotation of substrate stage fully CAM controlled for creation of gradient layers etc.
- Target drum for 6 water cooled target for automated deposition of multilayer films
- Recipe selectable shaper for target specific control of homogeneity
- Homogeneity up to 2 % on large substrates and 0.5 % on 200 mm wafers