A solid immersion lens (SIL) is described with NA = 2.64 that is fabricated
from a two-step process using a large BK7 glass hemisphere and a small GaP hemisphere.
The Gallium Phosphide (GaP) hemisphere has a radius 114μm, and is cemented in the
center of BK7 SIL with index-matching epoxy. The BK7 SIL thickness is accommodated
to have both BK7 SIL and GaP SIL in an image centric configuration. The two-step GaP
SIL is tested on an induced polarization imaging system. Induced polarization pupil
images, the native polarization image and induced polarization image of a DVD RW
sample are given in this paper.
Near-field induced polarization imaging with a solid immersion lens (SIL) is used to provide high lateral resolution for both native and induced polarization (cross polarized) images. A new technique is used to obtain height information from the near-field induced polarization image. An AltPSM mask sample is studied with this imaging technique, and compared to imaging with an AFM and a PSI interferometer. Topological data from the near-field induced polarization image are within a few nanometer of the AFM result, without contacting surface. In addition, features due to undercutting the Cr are observable in the induced polarization image.
A compact mechanical package is developed for a standard microscope that implements a solid immersion lens (SIL) on a retractable bimorph swing arm. With the compact package mounted on an inverted microscope, far-field and near-field images are obtained at the same location by moving the SIL with the swing arm. With white-light incoherent illumination, the resolution of this system for observing digital versatile discs is around 200 nm with an effective numerical aperture of 1.5. Imaging with the SIL is compared with an atomic force microscopy scan.
Near-field induced polarization imaging with a solid immersion lens (SIL) is used to provide high lateral resolution compared with conventional far-field microscopy. In addition, a new technique is used to obtain height information from the near-field induced polarization (cross polarized) image. Several optical data storage samples, including DVD-R, DVD-RW, BD-RW, are studied with this imaging technique. A calibration target indicates an accuracy of ±2nm for obtaining height information.
Image contrast enhancement, resolution improvement and accurate height information are obtained by near-field induced polarization imaging using a solid immersion lens (SIL) microscopy. A semiconductor PC processor is investigated by this imaging technology. With 520nm linear polarization illumination, around 100nm feature size is resolvable, and topographical information is also achieved from this induced polarization image. We demonstrate this near-field induced polarization imaging is a fast acquisition, large field and high resolution metrology solution.
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.
ArF technology is currently being used for 80nm resolution in the photo-lithography field, and ArF wet immersion technology is expected to be used for high resolution systems down to 50nm. Between ArF wet immersion technology and EUV technology, there is no proper technology that can cover the resolution range from 50nm to 30nm. In this paper, a new lithography technology using a Solid Immersion Lens (SIL) is introduced as an idea for very high resolution, and its resolution achievement is estimated through simulation. SIL technology is a near-field optics technology that achieves high resolution. A SIL is a hemispherical lens, and the incident beam is normal with respect to the surface of the lens. Because a high refractive index material is used for the SIL, very high numerical aperture provides high resolution. The resolution limit is estimated by calculating the vector irradiance inside the thin-film stack composed of the SIL, air gap, photoresist, anti-reflection layer and substrate. Feature size is estimated over reasonable exposure latitude at 20nm depth in the resist. Results show that, using a 365nm wavelength source, 70nm resolution is expected, and 50nm resolution is expected with a 248nm wavelength source. With a shorter wavelength light source and a proper SIL material of high refractive index for the wavelength, higher resolution can be achieved.
The International Technology Roadmap for Semiconductors (ITRS) shows that 45 nm and lower feature sizes are required in lithographic production before the year 2007. Both immersion lithography and EUV lithography can play major roles in realizing this goal. However, a maskless lithography system capable of producing 45 nm features is an attractive option for small-volume semiconductor fabrication, such as with ASIC manufactures. Compared with a conventional lithography system, the maskless feature of the system allows the chip designer to be free of the very expensive process of mask fabrication and to shortcut development time. In this paper, we discuss a new maskless lithography concept employing an array of solid immersion lens (SIL) nano-probes. The nano-probes are efficient near-field transducers. Each transducer is the combination a SIL, a dielectric probe tip and an antenna structure. The nano-probes are fabricated in arrays that dramatically improve throughput. By combining these technologies, it should be possible to fabricate an efficient array of near-field transducers with optical spot dimensions of around 20 nm when illuminated by a 405 nm laser diode source. This paper plans to address, for the first time, the efficient generation of an array of light spots with dimensions of λ/20 or less that couple efficiently into dielectric films, like photoresist.