光技術情報誌「ライトエッジ」No.16
4th International Symposium on 193nm Lithography
(1999年3月)
ArF Excimer Laser for 193 nm Lithography
Takashi Saito, Ken-ichi Mitsuhashi, Motohiro Arai,
Kyouhei Seki, Tatsushi Igarashi, and Kazuaki Hotta
USHIO Research Institute of Technology Inc.
5-2-4 Tokodai, Tukuba, Ibaraki, Japan
Telephone:+81-298-47-9072 Fax:+81-298-47-9076
A line-narrowed ArF excimer laser are being developed as a light source for 193 nm lighography using a refractive lens system. The system is required a narrow spectral bandwidth, high laser output stability and long lifetime. In this laser, we present a newly developed sub-picometer ArF excimer laser for lithography.
The prototype laser, as shown in this paper, utilizes an all solid state pulse power modulator with 2-stage magnetic pulse compressors. A barrier discharge excimer lamp technology 1) developed by USHIO is adopted as a pre-ionization method. The materials that constitute this laser are carefully selected to prevent the impurity generation. A long gas life time of over 4×107 shots has been confirmed in a broad-band operation.
The line-narrowing optics in this laser consists of a combination of prism beam expanders and a grating. Figure 1 shows a spectral profile measured by an etalon system with a FSR of 6 pm and a reflection finesse of about 30. Figure 2 shows an ingegrated energy distribution. More than 5 mJ of pulses with of below 0.6 pm FWHM and 95% of the spectral energy lying within a 2 pm were obtained. The laser output stability and the spectral stability will be also presented.
![](./content_file/file/lightedge_16-07-01.png)
Fig.1 Spectral bandwidth measured by etalon system with a free spectral range of 6 pm
![](./content_file/file/lightedge_16-07-02.png)
Fig.2 Integrated ene rgy Distribution
参考資料
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Table1.Outline
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Table2. USHIO's activities
![](./content_file/file/lightedge_16-07-04.png)
Table3. Characteristics of the ArF excimer laser system
![](./content_file/file/lightedge_16-07-07.png)
Fig.3 Photograph of ArF excimer laser system
![](./content_file/file/lightedge_16-07-05.png)
Fig.4 Schematic view of ArF excimer laser system
![](./content_file/file/lightedge_16-07-08.png)
Fig.5 Gas flow velocity
![](./content_file/file/lightedge_16-07-09.png)
Fig.6 Solid state pulse power module
![](./content_file/file/lightedge_16-07-12.png)
Fig.7 Characteristics of SSPPM
![](./content_file/file/lightedge_16-07-10.png)
Fig.8 Material selection(chamber)
![](./content_file/file/lightedge_16-07-13.png)
Fig.9 Gas lifetime test at 1 kHz in constant voltage mode
![](./content_file/file/lightedge_16-07-11.png)
Fig.10 Gas lifetime test at 1 kHz in stabilized power mode
![](./content_file/file/lightedge_16-07-14.png)
Fig.11 Transmittance of CaF2 windows
![](./content_file/file/lightedge_16-07-17.png)
Fig.12 Optics module
![](./content_file/file/lightedge_16-07-15.png)
Fig.13 Spectrum of the whole laser beam
![](./content_file/file/lightedge_16-07-18.png)
Fig.14 Sepctra of different portions of the laser beams
![](./content_file/file/lightedge_16-07-16.png)
Fig.15 Wavelength stability
![](./content_file/file/lightedge_16-07-19.png)
Fig.16 Average laser output power and stability
![](./content_file/file/lightedge_16-07-20.png)
Table4. Specifications of our prototype laser
![](./content_file/file/lightedge_16-07-22.png)
Table 5. Summary
![](./content_file/file/lightedge_16-07-21.png)
Fig.17 Average laser power and stability