Hideki Morishima

Off-axial HMD optical system consisting of aspherical surfaces without rotational symmetry

An off-axial optical system is desirable for a see-through head mounted display (HMD) with a wide field of view (FOV). Using our new off-axial paraxial theory and the fabricating methods, we have achieved to correct the off-axial aberrations of the optical systems which consists of an aspherical surfaces without rotational symmetry. In this paper, we describe 3 types of off-axial HMD optical systems. (1) The first one is a hologram for a monochromatic HMD. The hologram has been recorded the wavefront generated by computer generated hologram. The image spot size is about 15 micrometers over 9 degree FOV. (2) The second one is an aspherical mirror system for a color HMD. The designed image spot size is less than 30 micrometers over 43.5 degree FOV. The shape error of the fabricated mirror is measured by a contact probing from 1.0 micrometers to 1.9 micrometers . The maximum resolution is 36 lp/mm. (3) The last one is a prism with aspherical surfaces, 34 degree FOV and less than 15 mm thickness. The monocular HMD with only 80 g weight has been developed. The line of sight detecting device has been applied as an interactive man-machine interface.

Study of system performance in SFET

We shipped a small field exposure tool (SFET) to Selete (Semiconductor Leading Edge Technologies, Japanese Consortium) in 2006. The SFET was founded for the purpose of EUVL mask and resist development. We have been working on the exposure test and the tool evaluation in collaboration with Selete. In the development of the SFET, We have experienced to connect two types of light source to the SFET, LPP light source and DPP light source. And now we operate the SFET with DPP light source. On exchanging light source for DPP light source from LPP light source, we planed to apply the new illuminator unit optimized for DPP light source. The new illuminator unit of the SFET will improve dose uniformity on the imaging surface. We have installed the new illuminator unit of the SFET at Selete in 2007, and evaluated the effects of dose uniformity. In EUV lithography, the system performance reflects sensitively to the exposure results. We have been evaluating the SFET quantitatively on mainly sensitive factors, in the system performance, to exposure result. We try to take a correlation between the system performance and exposure results. In the system performance, the synchronization error between the wafer and mask stages is one of the main factors to exposure sensitivity. We continue to evaluate the relations between the system performance and the exposure results.

Canon's development status of EUVL technologies

Canon has been developing the EUVL technologies for more than ten years. The current development status of EUVL technologies is presented. The small field exposure tool (SFET) is positioned as a cornerstone of the manufacturing technologies for the EUVL beta tool. LPP source and the DPP source are the most expecting methods for the EUVL beta tools.

Development status of Canon's full-field EUVL tool

EUVL is the most promising candidate of 32 nm generations and beyond. In this paper, we present Canons development status of EUVL technologies. The system design of the EUV full field high volume manufacturing tool (VS2) is under way. The specification of VS2 is presented in this paper. The fabrication of six-aspheric-mirror prototype projection optics (PO1) of NA 0.3 has been started. The PO1 is fabricated to evaluate and improve our technologies of polishing and measuring the figure of mirrors. We present some results of the figuring accuracy of the mirror. EUVL will be required to resolve sub-twenty nm L&S patterns. We are studying off-axis illumination technologies and high- NA technologies. The simulation results of the resolution capability and the DOF are presented.

Performance estimation of EUV exposure optics for below 32-nm node in consideration of Mo/Si multilayer coating

The EUV lithography is the most promising candidate for the next generation semiconductor exposure technology to fabricate fine patterns of 32nm and below 32nm, now that ArF immersion technology is expected to cover the 45 nm node these days. This paper focuses on the optical performance of EUV projection optics that will be the lithography tool under 32nm node. EUV projection optics is consists only of the mirrors, and the number of mirrors varies depending on the numerical aperture (NA) of projection optics. As the NA becomes higher, more mirrors are required. For example, it is expected that 6-mirror projection optics (6M-PO) could have 0.25NA, and 8-mirror projection optics (8M-PO) could have over 0.35NA. Assuming a process factor K1 of 0.6, EUV projection optics with NA of 0.25 can achieve 32nm resolution, and projection optics with NA of 0.35 can achieve 22nm resolution. Therefore, 6M-PO and 8M-PO are suitable for 1st EUV generation and 2nd EUV generation, respectively. In EUV optics, each mirror has multi-layered Mo/Si coating to get high reflectivity. The reflectivity is extremely sensitive to the layer thickness of coating, the exposure wavelength, and the ray incidence angle, so the multilayer coating is designed to give a best performance at exposure wavelength of 13.5nm. This means that thickness and optical indices in the multilayer coating cause serious degradations on the imaging performance. Therefore, more mirrors might cause greater degradation on the image performance. This paper discusses the relationships between the multilayer coatings and the imaging performance in order to apply EUV lithography for below HP32nm technology node. We compare 6M-PO to 8M-PO from the point of view of the multilayer coatings numerically. 1. Imaging performance with error-less multilayer coating in consideration of chromatic aberration Even If the multilayer coating without any coating errors can be coated on all of the mirrors, the chromatic aberration cannot be avoided. We compare the imaging performance of 6M-PO to 8M-PO in consideration of chromatic aberration. 2. Influence of multilayer coating errors on transmittance of optical system and aberration There are some kinds of multilayer coating errors. In this paper, we discuss thickness errors that have a great influence on transmittance and aberration. 3. Influence of contamination on aberration We discuss the influence of carbon contamination films that deposit on the top surface of the multilayer coatings.