深紫外euv光刻源 euv sources for lithography-2

1、Star Pinch EUV Source 465Figure 15.8 Spectrum from Star Pinch with xenon, optimized for 13.5-nm output.Figure 15.9 Optimization of 13.5-nm signal with gas flow rate as a function of repetition frequency.15.3 Current Star

2、 Pinch PerformanceThe following data, coming from tests in early 2004, represent an intermediate stage in the development of this source, the ultimate limits of which are discussed in Sec. 15.4.1 below. A comprehensive m

3、easurement set was taken on the Star Pinch in December 2003 by the Flying Circus standards team and has been pub-Star Pinch EUV Source 46715.3.2 Plasma size and stabilityPlasma size and positional stability are very impo

4、rtant parameters entering into the usable source etendue that determines what fraction of the 13.5-nm energy mea- sured from the whole plasma can be used in the illuminator optic and projection optic of the scanner. We h

5、ave used a 13.5-nm imaging tube26 that reimages at 1:1 magnification, via two reflections off 13.5-nm mirrors, onto a Ce-doped YAG crystal. The crystal is in the form of a 15-mm-diameter, 0.5-mm-thick disk with a 200-nm

6、overcoating of Zr on the incident face to block visible light. This crystal is an efficient fluorescer,27 giving a yellowish-green fluorescence that allows real- time plasma observation at 13.5 nm, a feature that has pro

7、ved extremely useful in the development process. We usually observe the plasma at 40 deg to the axis so as to obtain both length and diameter information from one measurement. Typical views of the plasma at 1.0, 1.5, and

8、 2.0 kHz are shown in Fig. 15.10. The dark central disk is the outline of the Zr coating, which is 14.5 mm in diameter. Each image in Fig. 15.10 was exposed for 14 s, resulting in the superposition of 250, 375, and 500 p

9、ulses. This set of images had the plasma dimensions shown in Table 15.3, as measured in 13.5-nm emission. An improved design has an axial length of 4.0 mm at full power and 2.0 mm at half power. It is found that increasi

10、ng the xenon density above the optimum for 13.5-nm emission reduces the plasma length significantly, but at the cost of aFigure 15.10 Images of xenon Star Pinch plasma at 40 deg in fluorescence from 13.5-nm light. Left t

11、o right, 1.0, 1.5, and 2.0 kHz at 0.25-s exposure in each case.Table 15.3 Measurements of plasma size in xenon 13.5-nm emission.Repetition rate (kHz) Diameter (μm, Apparent length True axial length FWHM) (mm, FWHM) (mm,