Experimental investigation of solid immersion lens lithography

There are several next generation technologies for high resolution lithography, such as ArF wet immersion, F2, EUV, etc. However, these technologies are very expensive because of projection lens and mask costs. Near-field optics using a solid immersion lens (SIL) can meet the requirement of high resolution in a cost-effective way. In this paper, a very compact and inexpensive high resolution system using a SIL is introduced and preliminary experimental results are presented using a 405nm laser diode system. The SIL is used with a modified conventional inverted microscope. The air gap between the SIL flat bottom surface and the wafer is kept less than 50nm. Optical reflected power from SIL bottom and wafer interface is used to control the gap. A high resolution experiment with 405nm wavelength is discussed.