Interference design
Work led by Bedford has sought to optimise the multi beam interference geometry through improved system design and understanding the influence of key factors. Several prototype arrangements have been constructed and evaluated.
In the following figure, the LIL design and examination setup is as shown in the previous figure. The incident angle is 58°. The results are all obtained from positive photoresist.
The TE-TE-TE-TE polarisation combination result, as shown in Figure A, is about 200nm.
Figure B is the TE-TE-TM-TM combination result. Significant intensity modulation generated by the initial incident and azimuth angle offset in this mode.
Figure C is the TE-TE-TE-TM combination result. This combination could be a good choice for its relatively high contrast and slight modulation. However, long range intensity modulation still remains a significant issue, despite it being supressed in case C.
To deal with this, we have proposed a novel arrangement using asymmetrical three-beam interference for which the azimuthal angles: 0°, 90°, and 180° and the polarisation mode: TE-TM-TE or TM-TE-TM.
