In industrial laser micro processing, throughput is as important as process quality. Treating large areas in minimum time is pivotal in achieving reduced unit costs in high-volume production. Excimer lasers meet the requirements for clean and precise structuring and enable the smallest structures in an efficient way. The latest technical developments in high power excimer lasers is bound to take cost-efficient UV-laser micro processing to the next level and bridges the gap between achievable precision and achievable throughput. New excimer laser developments and beam concepts together with latest performance data for upscaling both UV power and UV pulse energy will be the topic of this paper against the background of upcoming market trends and high volume applications.
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.
High power excimer lasers are well established as work horses for various kinds of micro material processing. The
applications are ranging from drilling holes, trench formation, thin film ablation to the crystallization of amorphous-Si
into polycrystalline-Si. All applications use the high photon energy and large pulse power of the excimer technology.
The increasing demand for micro scale products has let to the demand for UV lasers which support high throughput
We report the performance parameters of a newly developed XeCl excimer laser with doubled repetition rate compared
to available lasers. The developed laser system delivers up to 900 mJ stabilized pulse energy at 600 Hz repetition rate.
The low jitter UV light source operates with excellent energy stability. The outstanding energy stability was reached by
using a proprietary solid-state pulser discharge design.
We report performance parameters of a robust, 50 W, high repetition rate amplified ArF excimer laser system with FWHM bandwidth of less than 0.25 pm, 95% energy content bandwidth of less than 0.55 pm, and ultra-low ASE level. Proprietary design solutions enable stable operation with a substantial reliability margin at this high power level. We report on characterization of all the key parameters of importance for the next generation microlithography tools, such as spectrum and dose control stability, in various operating modes.
Today the molecular fluorine (F2) laser emitting at a wavelength of 157 nm represents the strongest commercially available coherent light source in the vacuum-ultraviolet spectral range. Lambda Physik produces a broad variety of F2-Lasers which cover a wide range of output power (from less than 1 W to more than 20 W), repetition rate (from less than 100 Hz to more than 4 kHz) and single pulse energy (from less than 1 mJ to more than 30 mJ). The parameters of each of these kinds of F2-lasers are designed and suitable for specific fields of application. In the paper we will review the main parameters of these different types of F2-lasers, compare their special features and discuss the principle applications they are used for. The low energy, medium repetition rate is basically used for metrology and calibration tasks, the high energy or high repetition rate and high power F2-laser systems are mainly used for material investigations and in a growing extent for 157 nm-micromachining. Lithography tools use the high repetition rate, high power single-line F2-laser systems. All of these scientific or industrial applications take advantage of the unique properties of the 157 nm radiation, i.e. the ultra-short wavelength of emission and the very high photon energy of nearly 8 eV. Thus, very precise and fine microstructuring in the micrometer range is possible and the 157 nm optical lithography is on target for critical dimensions of integrated circuits below 70 nm. The short pulse duration and high photon energy also enables efficient and exactly located icroscopic ablation of most critical materials without thermal impact on the surrounding area. In the last part of the paper some recent results on F2-laser development and an outlook on future products will be given.
Excimer lasers are widely used as the light source for microlithography scanners. The volume shipment of scanner systems using 193nm is projected to begin in year 2003. Such tools will directly start with super high numerical aperture (NA) in order to take full advantage of the 193nm wavelength over the advanced 248nm systems. Reliable high repetition rate laser light sources enabling high illumination power and wafer throughput are one of the fundamental prerequisites. In addition these light sources must support a very high NA imaging lens of more than 0.8 which determines the output spectrum of the laser to be less than 0.30 pm FWHM. In this paper we report on our recent progress in the development of high repetition rate ultra-narrow band lasers for high NA 193nm microlithography scanners. The laser, NovaLine A4003, is based on a Single Oscillator Ultral Line-narrowed (SOUL) design which yields a bandwidth of less than 0.30pm FWHM. The SOUL laser enables superior optical performance without adding complexity or cost up to the 4 kHz maximum repetition rate. The A4003's high precision line-narrowing optics used in combination with the high repetition rate of 4 kHz yields an output power of 20 W at an extremely narrow spectral bandwidth of less than 0.30 pm FWHM and highest spectral purity of less than 0.75 pm for the 95% energy content. We present performance and reliability data and discuss the key laser parameters. Improvements in the laser-internal metrology and faster regulation control result in better energy stability and improved overall operation behavior. The design considerations for line narrowing and stable laser operation at high repetition rates are discussed.
According to the ITRS-Roadmap, the 157 nm wavelength of the F2-laser is the most likely solution to extend the optical lithography for production of ICs with critical dimensions below 70 nm down to the 50 nm node. This requires high power, high repetition rate F2-lasers with highest reliability, operating in the power range of more than 40 W at repetition rates of at least 4 kHz. In the recent three years strong efforts have been done in order to investigate and develop all kind of materials, technologies and devices which are necessary to introduce the 157 nm lithography for high volume mass production in the year 2004/5. Towards this road Lambda Physik has developed a 4 kHz line selected F2-laser with an output power of 20 W meeting the spectral performance requirements and therefore suitable for pilot 157 nm scanner. In order to reach an output power of 40 W under retention of the required spectral performance, we are now concentrating on the output power increase which comprises a new tube design, a modified discharge and charging circuit. In this paper the laser performance data which has been verified and measured by existing and improved 157 nm metrology as well as new findings on general F2-laser properties at high repetition rate, high power operation will be discussed. The prototype 4 kHz line selected F2-laser gains benefit from the outstanding long term reliability of the resonator optics. The field proven NovaLine F2020 optics modules are only slightly modified for 4 kHz operation. Lambda Physik will present appropriate reliability data which had been confirmed from field application showing laser tube and optical modules life times passing 5 Bio shots at 2 kHz repetition rate operation.
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.
Capital costs and economical efficiency is becoming the most important criteria for any decision on lithography tools for an advanced IC fabrication facility. Each lithography wavelength has to compete for productivity, cost efficiency and return of investment. Reliable high repetition rate laser light sources enabling high illumination power and wafer throughput are one of the fundamental prerequisites. In this paper we report on our recent progress in development of high repetition rate ultra-narrow line and semi-narrow band ArF lasers for advanced 193nm lithography. These lasers are designed for high NA refractive and catadioptic scanner tools targeting the 100 nm node and below. We present key performance data of our high repetition rate ArF- lasers which currently operate at 4 kHz with a spectral bandwidth of < 0.35 pm or 25 pm, and 20 W or 40 W, respectively. Improvements in the laser-internal metrology and faster regulation control result in better energy and wavelength stability, dose control and improved overall operation behavior. Ultra-narrow bandwidth emission combined with an extra ordinary high spectral purity E(95%) < 0.8 pm is achieved by a new design of the optical line narrowing module implemented into the A4005. Improvements in the tube design support a laser operation with repetition rates of greater than > 4kHz and with 75% duty cycle. Data on the main laser parameters in dependence on repetition rate are presented. These results indicate the robust performance of the A4005 for all operation conditions and suitable reliability and lifetime of the modules.
High output power and ultra-narrow bandwidth has been the development goals for the 193 nm lithography excimer lasers in the last years to support the throughput and requirements of advanced 193 nm wafer scanner. Cost of ownership comparable to current 248 nm lithography wafer scanner is one of the important prerequisites for the economic implementation of 193 nm lithography in production. In this paper we present the performance results of our new high power ArF lithography excimer lasers with repetition rate of 4 kHz. The laser delivers a stabilized output power of up to 40 W. The spectral laser output is matched to the requirements of high NA catadioptric imaging lenses with a bandwidth of less than 25 pm, FWHM. The new laser delivers energy dose stability of less than 0.35% for a 50 pulse dose window. Second part of the paper gives the status of the ultra-narrow bandwidth 193 nm excimer laser for refractive imaging lenses. A spectral bandwidth of less than 0.35 pm, FWHM, has been achieved with a spectral purity of less than 0.95 pm. Results from the laser operating at 2 kHz are presented. The performance characteristics at of he line-narrowed 193 nm laser with 4 kHz repetition rate are presented. Finally an outlook on the achievement of ultra-narrow-bandwidth 193 nm excimer lasers for micro-lithography will be given.
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.
The demand of high throughput and good energy dose stability of DUV scanner systems result in the requirement of laser repetition rates above 2 kHz for lithography production tools at 193 nm and 157 nm. Also in 248 nm lithography, dose energy stability could be improved by higher repetition rates from the laser. We have investigated the possibilities and limits of high repetition rate performance of laser discharge units for DUV lithography lasers. A new chamber has been developed with electrode configuration, pre- ionization system and high speed gas flow system for very high repetition rate operation. Acoustic resonances in the frequency range of interest have been prevented by design. With new solid-state pulsed power modules which support long pulse gain modulation and high precision high voltage power supplies very high repetition rates have been demonstrated. For 248 nm lasers repetition rates above 5 kHz have been achieved, for 193 nm laser above 4.5 kHz. 157 nm lasers can be operated above 2.5 kHz. Data of the laser performance as e.g. power and energy stability are given for the various wavelengths.
We have developed a KrF excimer laser with ultra narrow linewidth and high repetition rate applicable for optical lithography using DUV wafer scanners with highest numerical aperture (NA) of more than 0.8. A laser bandwidth of less than 0.4 pm, full width half maximum, is achieved by our new design of the laser resonator, which is based on out patented polarization coupled resonator. The new resonator design increase the efficiency of ht laser optics and improves the wavelength stability. The laser tube and solid sate pulser have been adapted to the new laser resonator. As a result, another step in the reduction of the cost of operation is achieved. The laser operates with a repetition rate of 2 kHz and gives a large operation range with respect to wavelength and energy range. The characteristic performance of this new excimer laser is presented.
Results on the feasibility of highest repetition rate ArF lithography excimer lasers with narrow spectral bandwidth of less than 0.4 pm are presented. The current 193 nm lithography laser product NovaLine A2010 delivers output power of 10W at 2 kHz repetition rate with energy dose stability of +/- 0.5 percent. A novel 193 nm absolute wavelength calibration technique has ben incorporated in the laser which gives absolute wavelength accuracy better than 0.5 pm. Long-term results of optical materials, coatings and laser components give insight into estimated cost of ownership developments for the laser operation over the next years. Progress in pulse stretching approaches to achieve lower stress of the wafer scanner illumination optics and lens allow optimistic estimates of total system CoO. Initial results on the laser operation at 4 kHz in order to reach 20W output power are discussed.
According to the SIA-Roadmap, the 157 nm wavelength of the F2 laser emission will be used for chip production with critical dimensions of 100 nm down tot eh 70 nm node. Currently al basic technologies for 157 nm lithography are under investigation and development at material suppliers, coating manufacturers, laser suppliers, lens and tool manufacturers, mask houses, pellicle manufacturers, and resist suppliers.
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 laser's 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.
Optical deep UV (DUV) lithography is aiming to reach feature sizes of below 100 nm. The likely choice of the exposure wavelength will be 157 nm, which is emitted by the F2 excimer laser. Experience with this laser type in a variety of applications has been gained at Lambda Physik for the past 20 years. A major breakthrough in performance, in particular laser efficiency and durability, was achieved with the introduction of our metal ceramic laser tube in 1996. In this paper, we report on the progress in the development of the F2 laser light source. A major advance in narrowing the bandwidth of a 10W laser is the achievement of output spectral width of about 1 pm. With a newly developed NovaTube based F2 discharge chamber we show more than 19 million pulses gas lifetime without any additional gas actions. The laser achieves up to 1 kHz repetition rate. Energy stability sigma is 1 percent, dose energy stability 0.5 percent. The performance characteristics as temporal and spatial beam profile and the suitability the laser for microlithography are discussed. Typical lifetimes of the key components and a projection of the present and future cost of operation are presented.
A review of recent achievements and new tendencies in the development high energy, high repetition rate excimer lasers will be presented. The paper mainly focuses on the features of KrF, XeCl lasers with different combinations of output energy x pulse repetition frequency, for example: 1 J X 600 Hz (KrF); 3 J X 200 Hz or 10 J X 100 Hz (XeCl), which have been developed as candidates for industrial applications.
Considerable progress has been made in the development of the major components for 193 nm lithography tools. Here we describe the parameters of a line-narrowed ArF excimer laser for microlithography. With a specified FWHM bandwidth of less than 0.7 pm, the laser is applicable for refractive steppers and scanners which utilize some degree of achromatization. Prototype lasers have been built to study the optimum parameters. The main challenge of the development was the achievement of high efficiency in the conversion from the laser's broadband emission into line-narrowed emission. The lasers are operated at up to 1 kHz repetition rate with a maximum power of 10 W. This paper provides an overview of the currently achievable power levels, energy stability and bandwidths and discusses future trends.
The ArF excimer laser light source will extend the optical lithography to below 0.18 micrometers design rules. Still under discussion is the most effective layout of the stepper or scanner imaging optics. The decision for an all-fused-silica lens, an achromatic lens using CaF2, or a catadioptric imaging system has great impact on the laser-bandwidth requirement. In addition, the potential performance and perspective of the laser must be considered in the system layout of the production stepper or step and scan tool. Cost effective operation of such a lithography tool requires a 193 nm excimer laser with high power and repetition rates in the order of 1 kHz or higher. Precise dose control of the exposure demands high repetition rate and excellent stability of the laser output energy. We have developed an ArF laser which can be operated with up to 800 Hz repetition rate based on NovaTubeTM technology. Optimized materials and discharge configurations have been used to achieve laser tube lifetimes above 109 pulses. Up to 4 X 109 pulses tube lifetime have been achieved in beta-site tests. Gas lifetime of several 107 laser pulses is obtained. A solid-state switch has been adapted for the reliable and cost efficient excitation of the 193 nm lithography laser. To achieve laser output of different bandwidths various resonator arrangements have been investigated. The paper gives an overview of the currently achievable power levels at different bandwidths and discusses future trends.
The paper reviews recent developments in high power excimer laser technology driven by industrial requirements. Technological achievements as NovaTubeTM laser tube technology and HaloSafeTM halogen generator technology are discussed. Experimental results are presented for various lasers at the most important excimer wavelengths 351 nm (XeF), 308 nm (XeCl), 248 nm (KrF), 193 nm (ArF) and 157 nm (F2) which have been designed for application in micromachining, thin-film-transistor annealing, marking as well as lithography.
Industrial applications of excimer laser include fabrication of multi-chip modules, ink jet nozzles and TFT annealing of flat panel displays. For more than a decade these applications and the deep-UV-lithography pushed the excimer laser technology to improved performance and lower cost. As a result, highly reliable laser systems have been developed, which utilize state of the art technologies like metal ceramic laser tubes, solid state switching circuits and solid state halogen generation.High repetition rate lasers are suitable for micromachining applications especially in the direct structuring mode. Depending on the processing parameter the throughput and operating cost of such a high repetition rate system will be advantageous compared to standard laser systems. In the absence of other process inherent limitations, the processing time both for 2D and 3D laser ablation are proportional to the lasers pulse repetition rate. While most industrial lasers are limited to 300 Hz repetition rate, the developed laser operates up to 1.5 kHz.
A new high repetition rate laser module on the basis of our latest metal-ceramic laser tube technology is developed. This laser can be operated up to 1 kHz with practically constant output energy of 30 mJ at 248 nm and up to 15 mJ for ArF and XeF. Gas lifetime and window cleaning interval can be extended to 500 million pulses. We present our latest test results for ArF, KrF, and XeF operation. All industrial applications require excellent pulse energy stability. In order to meet this demanding feature we modified the power supply and the high voltage circuit with respect to pulse energy stability. We achieved excellent pulse energy stability at all important laser wavelength with our new high repetition rate laser module, for example a pulse energy fluctuations of Sigma 0.8% at 1 kHz KrF operation.