The spherical pinch plasma radiation source (SPX II) for X-ray, UV and deep UV lithography

The method of generation of radiation from UV to soft X-rays in a Spherical Pinch plasma device has been presented elsewhere, and the operational characteristics of the source SPX II have been given. In this paper the authors present the X-ray output power levels at different input electrical energies and times of exposure to attain a given dose level. In addition, they present the radiation flux densities in various spectral ranges for the same source. The broad band radiation emission of SPX II extends from UV (10 eV) to soft X-rays (1.2 keV), and the relative levels of radiation depend upon the electrical energy stored in the condenser bank. By using appropriate filters like beryllium foils, and a radiachromic film detector at 20 cm from the source, they have measured the soft X-ray flux in the 1 keV to 1.2 keV region at various electrical energy levels. SPX II is capable of discharging at a repetition rate of ∼ 0.1 Hz, and therefore a required dose of radiation at the detector can be obtained by choosing the appropriate number of discharges for a given input electrical energy level. The figure below shows the variation of X-ray power and exposure time required to reach a dose level of 10 mJ/sq.cm, as a function of electrical energy input. The first three points on the X-ray power line, at ∼ 8 kJ, 15 kJ, and 18 kJ, respectively, are measured points. The others are projected. Finally, the construction of a new upscale version of a Spherical Pinch X-ray source (SPX III) is underway, which will be an industrial prototype for application in X-ray microlithography