Ingo Klaft

Advanced F2-lasers for 157-nm lithography

According to the SIA-Roadmap, the 157 nm wavelength of the F2 laser is the most likely solution to extend the optical lithography for chip production from the critical dimensions of 100 nm down to the 50 nm node. The introduction of the 157 nm lithography for high volume mass production requires high power, high repetition rate F2 lasers operating in the power range of more than 40 W or at repetition rates of more than 4 kHz. These leading specifications are combined with other challenging laser specifications on dose stability and bandwidth which must be realized within a very aggressive time line for the introduction of the full-field scanner systems in the year 2003. According to this roadmap of the tool suppliers Lambda Physik has now introduced a 2 kHz lithography-grade F2 laser F2020 for further pilot scanner systems. In this report we present basic performance data of this single line 2 kHz F2 laser and some typical results on key laser parameters which had been measured with new and improved metrology equipment. We demonstrate for the first time precise measurements on the correlation of the natural bandwidth versus pressure which had been performed with an ultrahigh resolution VUV spectrometer. In addition a new compact and transportable high resolution VUV spectrometer was used for analyses of spectral purity and line suppression ratio of the laser emission. The experimental setup and result of an absolute calibration of a power meter, for the first time directly performed at the true 157 nm wavelength, are presented.

High-power high-repetition-rate F2 lasers for 157-nm lithography

According to the ITRS-Roadmap, the 157nm wavelength of the F2-laser is the most likely solution to extend the optical lithography for production of ICs with critical dimensions below 70nm down to the 50nm node. The introduction of the 157nm lithography for high volume mass production requires high power, high repetition rate F2-lasers operating in the power range of more than 40W or at repetition rates of more than 4kHz. To meet the narrow time gap for an introduction of the full-field 157nm-scanner systems for real production in the year 2004/5 the community have to solve several challenging issues even in the laser section. F2-laser systems are needed which completely fulfill all specifications of a lithography light source, either for a refractive or a catadioptic projection optics. Verification and precise measurement of the key laser parameters in the VUV usually requires a specific development of the metrology, necessary for this task. In this report we present the progress which had been achieved in the development of high repetition rate high power single-line F2 lasers for catadioptic lithography application. The key features of a F2-laser > 4kHz will be demonstrated. We will also review the main parameters and the performance data from the field of the standard lithography-grade F2020 a 2kHz system which is already applied for pilot scanner tool design. Some improvements of these systems with regard to single line power, dose stability, polarization and gas life will be shown and reliability data from the field will be reviewed. Critical dependence of the spectral properties of the F2-laser emission at 2 kHz and 4 kHz will be discussed. Some new investigations on the coherence properties of the Fluorine laser are also implemented.

High-repetition-rate excimer lasers for DUV lithography

With the transition of DUV lithography into mass production, the economics of the excimer laser light sources is getting more important. The efforts in the development are directed towards an increase of the lasers repetition rate and output power for higher wafer throughput and an improvement of the component lifetime in order to reduce the cost of laser operation. Here we describe advanced 248 nm and 193 nm laser systems which operate with repetition rates of 2 kHz to be used in conjunction with refractive, partially achromatic refractive and catadioptric lithographic lenses, respectively.

Advances in industrial high-power excimer laser technology

The paper presents a review of the most recent achievements in the development of the industrial high power excimer lasers. The results of the development of a XeCl laser with the output energy above 900mJ and the pulse repetition frequency up to 600Hz will be demonstrated. The system performance such as energy, stability, spatial and temporal properties of the laser pulse as well as the extended maintenance cycles and finally low cost of operation in industrial applications will be discussed. Special emphasis will be placed on the design of the laser chamber and the pulsed power module, enabling the generation of a reproducible and homogeneous gas discharges which is indispensable for the required laser performance over the whole range of the laser output power.

Long-term test and characterization of optical components at 193 nm and 157 nm

We have investigated bulk and coated optical elements as well as UV detectors and CCD cameras in long term exposure experiments using 193 nm and 157 nm continuously pulsed laser irradiation at high fluence levels up to 10 mJ/cm2 and at repetition rates of 1 kHz. The irradiation is performed in nitrogen purged exposure chambers. The samples accumulate several billion of laser shots up to total dose values above 100 kJ/cm2. In this report we present some recent results on optical elements and UV- detectors each of several different suppliers which are illuminated by more than 2.4 billion shots of 157 nm laser radiation. The original and final properties are compared.