Immersion lithography started to become the main workhorse for volume production of 45-nm devices, and while
waiting for EUV lithography, immersion will continue to be the main technology for further shrinks. In a first step
single exposure can be stretched towards the 0.25 k1 limit, after which various double patterning methods are lining up
to print 32-nm and even 22-nm devices. The immersion exposure system plays a key role here, and continuous
improvement steps are required to support tighter CD and overlay budgets. Additionally cost of ownership (COO) needs
to be reduced and one important way to achieve this is to increase the wafer productivity. In this paper we discuss the
design and performance of a new improved immersion exposure system XT:1950i. This system will extend immersion
towards 38-nm half pitch resolution using a 1.35 NA lens and extreme off axis illumination (e.g. dipole). The system
improvements result in better CDU, more accurate overlay towards 4-nm and higher wafer productivity towards 148-
wph. Last but not least a next step in immersion technology is implemented. A novel immersion hood is introduced
giving more robust low and stable defects performance.
This paper shows the improvements in imaging performance on the ASML PAS5500/800<SUP>TM</SUP>, the PAS5500/850B<SUP>TM</SUP> and the TWINSCAN<SUP>TM</SUP> AT:850B<SUP>TM</SUP> Step & Scan systems. During setup, the lens aberrations are measured by the TAMIS technique and optimized. This gives excellent imaging performance for aberration sensitive features such as 'two bar,' the DRAM isolation pattern and isolated lines printed with alternating PSM. Lithographic tests based on these features were developed and tested on a number of 800 and 850 systems and gave results well within specification limits. Consequently, the imaging performance has been improved for a wide range of applications.
An interferometer for VUV wavelengths was realized in order to improve the resolution and the sensitivity of optical metrology. To be able to work at wavelengths 157 nm up to 900 nm an apochromatic design was chosen using reflective optics. For the examination of the influence of the wavelength binary gratings with different periods, aspect ratios and depths, have been selected as test structures. The benefits and also the technological problems which come along with the use of VUV wavelengths are discussed. The design of this interferometer and measuring results with different wavelengths are presented.
To improve the resolution and the sensitivity of optical metrology an interferometer for VUV wavelengths was realized. To examine the influence of the wavelength especially with regard to the period of the object structure, an apochromatic design was chosen. This means an object can be measured with wavelength from 157nm up to 900nm without changing the optical setup. The design of this interferometer will be presented. The benefits and also the technological problems which come along with the use of VUV wavelengths are discussed. Further problems occur when deep binary structures are measured. An overview of those problems will be given and the use of white light interferometric methods to overcome those problems will be discussed. Measurements have been performed with different light sources. The wavelength scale is extended from the visible to the deep UV, the coherence properties of the sources are very dissimilar and the interferograms are evaluated with different techniques. The experimental results will be presented and discussed.