Shinichi Imai

Third‐harmonic generation of an alexandrite laser in β‐BaB2O4

We report the first cascading third‐harmonic generation by light from an alexandrite laser in β‐BaB2O4. Ultraviolet (UV) light was generated by mixing the fundamental laser light with the second‐harmonic light. The calculated effective nonlinear constant for type I mixing is nearly three times larger than that for type II. Using type I mixing we demonstrated UV light generation in the wavelength region 244–259 nm with 24% mixing efficiency at maximum.

Deep UV light generation by a fiber/bulk hybrid amplifier at 199 nm

A high-pulse-repetition-frequency (PRF) pulsed light source in the deep ultraviolet region has been realized by a multiple wavelength conversion technique using a hybrid fiber/bulk amplifier system. Output of 199 nm with a power of 50 mW was achieved at 2.4 MHz PRF. The 1 microm amplifier consisted of a Yb-doped fiber amplifier and a Nd-doped YVO(4) amplifier. A 1.5 microm fiber master-oscillator power amplifier was employed as the other fundamental source. The amplifiers exhibited good amplification properties in pulse energy, polarization extinction ratio, and spectrum for nonlinear wavelength conversion.

Highly Reliable 198 nm Light Source for Semiconductor Inspection Based on Dual Fiber Lasers

Highly reliable DUV light sources are required for semiconductor applications such as a photomask inspection. The mask inspection for the advanced devices requires the UV lightning wavelength beyond 200 nm. By use of dual fiber lasers as fundamental light sources and the multi-wavelength conversion we have constructed a light source of 198nm with more than 100 mW. The first laser is Yb doped fiber laser with the wavelength of 1064 nm; the second is Er doped fiber laser with 1560 nm. To obtain the robustness and to simplify the configuration, the fundamental lights are run in the pulsed operation and all wavelength conversions are made in single-pass scheme. The PRFs of more than 2 MHz are chosen as an alternative of a CW light source; such a high PRF light is equivalent to CW light for inspection cameras. The light source is operated described as follows. Automatic weekly maintenance within an hour is done if it is required; automatic monthly maintenance within 4 hours is done on fixed date per month; manufacturers maintenance is done every 6 month. Now this 198 nm light sources are equipped in the leading edge photomask inspection machines.

Development of advanced reticle inspection apparatus for hp 65 nm node device and beyond

The usage of ArF immersion lithography for hp 65nm node and beyond leads to the increase of mask error enhancement factor in the exposure process. Wavelength of inspection tool is required to consistent with wavelength of lithography tool. Wavelength consistency becomes more important by the introduction of phase shift mask such as Tri-tone mask and alternating phase shift mask. Therefore, mask inspection system, whose inspection light wavelength is 199nm, has been developed. This system has transmission and reflection inspection mode, and throughput, using 70 nm pixel size, were designed within 2hours per mask. The experimental results show expected advantages for Die-to-Die and Die-to-Database inspection compared with the system using 257nm inspection optics. Shorter wavelength effect makes transmission inspection sensitivity increase, and realizes 40nm size particle inspection. As for the phase shift mask, the difference of gray value between the area with phase defect and without phase defect was clear relatively. In this paper, specifications and design, experimental results are described.

CW 198.5-nm light generation in CLBO

A continuous-wave 198.5-nm light is produced by sum-frequency generation in CLBO for advanced photolithography mask inspections. Two fundamental lights are frequency-stabilized and mixed in an external cavity. The output power of 50mW was demonstrated with a single-resonance cavity.

Long-pulse ultraviolet-laser sources based on tunable alexandrite lasers

A long-pulse ultraviolet (UV) laser source has been demonstrated. It was obtained by the harmonic generator of a flashlamp-pumped alexandrite laser operating in the normal-pulse mode. We obtained tunable UV light in the wavelength region 365-390 nm. A 375-nm output generated 90 mJ. The pulsewidth was 240 /spl mu/s. The UV-laser output was successfully transmitted through a 3-m-long step-index-type silica fiber with a core diameter of 600 /spl mu/m.

Advanced mask inspection optical system (AMOS) using 198.5-nm wavelength for 65-nm (hp) node and beyond: system development and initial state D/D inspection performance

A novel high-resolution mask inspection platform using DUV wavelength has been developed. This platform is designed to enable the defect inspection of high quality masks for 65nm node used in 193nm lithography. In this paper, newly developed optical system and its performance are reported. The system is operated at wavelength of 198.5nm, which wavelength is nearly equal to 193nm-ArF laser exposure tool. Some defect image data and defect inspection sensitivity due to simulation-base die-to-die (D/D) inspection are shown on standard programmed defect test mask. As an initial state D/D inspection performance, 20-60 nm defects are certified. System capabilities for 65nm node inspection and beyond are also discussed.

A 20 W Cr3+, Tm3+, Ho3+: YAG laser

Abstract A 2.1 μm Cr 3+ , Tm 3+ , Ho 3+ : YAG laser is operated with an output power of 20 W at 12 Hz. The laser output is successfully transmitted through a silica fibre. The laser system was designed based on the technology of an alexandrite laser oscillator.

Characterization of CsLiB 6 O 10 crystals grown in dry atmosphere

We attempted the growth of CsLiB 6 O 10 in dry atmosphere. Devices fabricated from dry-grown crystal had demonstrated 1 week of continuous operation without shifting the crystal at the output power of 100 mW at 199 nm.

Polarization-Maintaining 1064 nm Fiber MOPA System with Narrow Bandwidth for Wavelength Conversion

A seeded pulsed diode oscillator and fiber amplifiers are used to obtain a polarized single-mode output with 750 MHz linewidth and over 1 kW peak power with low-nonlinearity for wavelength conversion applications.