Computer Database-Development of a production EUV source

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					X-Message-Delivery: Vj0xLjE7dXM9MDtsPTA7YT0wO0Q9MTtTQ0w9MA== X-Message-Status: n:0 X-SID-PRA: X-Message-Info: JGTYoYF78jG9eYQUPvT9d+ovqtXbirmUnYbt7dwAoQJ/WecX0CMJ2vI2e/cYHvGTpajURs+8X49C3YRm 0qFEpj9VQuuVIQWQ Received: from ([]) by with Microsoft SMTPSVC(6.0.3790.2668); Fri, 3 Apr 2009 14:41:49 -0700 Received: from tg-pxpres31 ([]) by (PMDF V6.2 #30554) with ESMTP id <> for; Fri, 03 Apr 2009 17:41:49 -0400 (EDT) Date: Fri, 03 Apr 2009 17:41:49 -0400 (EDT) Date-warning: Date header was inserted by From: Subject: Computer Database:Development of a production EUV source. Sender: To: Reply-to: Message-id: <1143596957.1238794909047.JavaMail.galemgr@tg-pxpres31> MIME-version: 1.0 Content-type: multipart/mixed; boundary="Boundary_(ID_RDjpCFEsqxtRKgZW/GH5vw)" Return-Path: X-OriginalArrivalTime: 03 Apr 2009 21:41:49.0728 (UTC) FILETIME=[FEAEE200:01C9B4A4] --Boundary_(ID_RDjpCFEsqxtRKgZW/GH5vw) Content-type: text/plain; charset=us-ascii Content-transfer-encoding: quoted-printable Gale Cengage Learning Farrar, N R, Brandt, D C (Nov 2008). Development of a production EUV source= . Microlithography World, 17, <span class=3D"citation-publication">4. </spa= n>p.3(3). Retrieved April 03, 2009, from Computer Database via Gale:<span i= d=3D"infomarkUrl"> =3Dretrieve&tabID=3DT003&prodId=3DCDB&docId=3DA196383607&source=3Dgale&user= GroupName=3Dmultnomah_main&version=3D1.0</span> Full Text:COPYRIGHT 2008 PennWell Publishing Corp. Laser Produced Plasma (LPP) EUV source technology has advanced towards the = specifications needed for actual chip production. The clear leader for high-power production EUV sources is laser-produced pl= asma (LPP) technology. After investigating alternatives, UP has been Cymer'= s chosen technology path for the last four years. This source architecture = provides key advantages of both high conversion and collection efficiency w= ith intrinsic scalability of output power. Source power and lifetime have been top issues for EUVL development in lith= ography industry surveys for the past three years. This is because the high=

throughput needed to provide competitive cost of ownership (COO) for EUV e= xposure tools is critically dependent on source power and resist sensitivit= y due to the low system transmission, which results from using reflective o= ptics. Since it appears difficult to improve resist sensitivity while simul= taneously maintaining resolution and line-edge roughness (LER) performance,= high source power is essential for high productivity production EUVL. LPP sources use a drive laser to heat a target material to a high-temperatu= re forming plasma which emits at the EUV wavelength-of-interest, 13.5nm. Re= search into different combinations of drive laser wavelength and target mat= erial over the last few years has shown that the optimum combination is a C= OZ drive laser running at 10.6[micro]m wavelength, and tin target material,= which produces the highest conversion efficiency from laser input energy t= o in-band EUV output energy. This energy is emitted isotropically, but must= be collected and transmitted to the intermediate focus (IF), which is the = interface between the source and exposure system. It has been shown that UP= architecture allows much higher collection efficiency of output energy tha= n alternative approaches due to the small source size and largest geometric= collection angle possible.

A key challenge in UP source design is to maintain high collection efficien= cy and consistent power output over long periods of time to meet COO target= s. The proximity of the collector optics to the high temperature plasma exp= oses it to high energy ions and other debris which can damage the reflectiv= e coating and reduce collection efficiency. Minimization of damage from deb= ris requires the use of small droplets of target material. Development of a= source system that can maintain high-conversion efficiency using droplet t= argets implies maximizing the laser input energy that is coupled into the s= mall droplets, which requires complex optimization and control of the laser= beam delivery and focusing optics. Cymer's plasma chamber architecture is shown in Fig. 1. The tin droplets ar= e emitted from a droplet generator in the wall of the vessel. Light from th= e C[0.sub.2] laser is introduced into the chamber through a central hole in= the collector mirror. The laser beam is focused and steered to impinge on = the droplets using closed-loop feedback from the droplet, targeting cameras= that monitor droplet position. A plasma is formed at one focus of the elli= ptical mirror and light is collected and refocused to the second focus of t= he mirror, which is the IF position. Turbo pumps near the IF, and other con= tainment components, prevent molecular transport from the source chamber to= the scanner vacuum chamber. A beam-stop prevents laser light from entering= the scanner. Any non-targeted droplets are collected and may be recycled, = although if the droplet size goal is achieved, only a very small amount of = tin will be required during a year of operation. The plasma chamber will be integrated directly with the scanner body. This = close coupling between the source and scanner is unlike current laser light= sources and has required very close design interaction between Cymer and i= ts direct customers. In the fab environment, the laser and support electron= ics will be installed in the subfab and the output beam will directed throu= gh the fab floor to the plasma chamber.

The initial power requirement for EUV sources is about 100W (in-band at IF)=

. The source design parameters needed to meet this requirement are shown in= the Table. Cymer has demonstrated progress towards achieving these target = performance parameters over the last several years, with a goal of deliveri= ng sources for use in pre-production scanners starting at the end of 2008. = The development program is on track to meeting this goal. The first two sources for delivery have been assembled and are operational.= One of these is shown in Fig. 2. The high-power pulsed C[0.sub.2] laser is= based on production-proven commercial technology, capable of delivering 12= kW of output power at 50kHz, well in excess of the initial target shown in = the Table.

In-band conversion efficiency at the 3% target level has also been demonstr= ated on these systems. Figure 3 shows a demonstration of 100W burst output = power over short periods of time. This has been achieved with extensive dev= elopment of droplet generator technology, which produces highly repeatable = droplet size and spacing, and a closed-loop laser targeting control system = that ensures each laser pulse is optimally focused and accurately targeted = on the corresponding droplet. Currently, development of enhanced thermal co= ntrol of beam delivery and focusing optics is ongoing to extend continuous = operation performance. To date, 25W average power output over 90 minutes op= eration has been achieved (Fig. 3). Currently, power is calculated IF value= based on measurements at the plasma and using the collector characteristic= s shown in the Table. The power output has ramped rapidly over the last two years, as shown in Fi= gure 4. Initially, power scaling was focused on burst power, which was requ= ired to demonstrate that high conversion efficiency could be achieved using= an integrated system of droplet targets. Burst power at low-duty cycle was= scaled by two orders of magnitude over 18 months. Since mid-2007, when it = was clear that burst power was on a trajectory to meet the 100W target, foc= us was shifted to scaling average power with a goal of reaching 100W by the= end of 2008. This work has required the identification of various issues l= imiting high duty cycle operation, and developing engineering solutions, pr= imarily in the area of thermal control. To date, progress is on plan, with = another factor of 3 improvement required to meet the 100W goal. Another integral part of the strategy for high-power output, shown in the T= able, is the high-reflectivity, high-collection-angle mirror. This mirror w= ill have a 5-steradian collection angle and be greater than 600mm in diamet= er. It will be coated with many silicon-molybdenum multilayers, similar to = the scanner optics mirrors, to reflect a small band around the target wavel= ength of 13.5nm. Two key differences in the mirror are the need for a grade= d multilayer spacing from center to edge, to compensate for changing incide= nce angles, and a mutilayer design that will resist interdiffusion (and los= s of reflectivity) at the high temperatures likely to be experienced in the= source chamber. Small diameter (320mm) mirrors with such coatings have bee= n produced and show excellent center-to-edge reflectivity uniformity, which= meets the performance target shown in the Table. Larger mirrors are curren= tly under fabrication for insertion into the prototype systems and have rec= ently completed the polishing step, as shown in Fig. 5.

To deliver acceptable COO for the source, it is essential to maintain high = power, high collection efficiency, and clean transmission over long periods= of time. This requires technology within the plasma chamber that prevents = degradation of mirror reflectivity from three main sources: * Deposition of tin particle debris from the droplets * Erosion of the mirror by high-energy ions and neutral atoms * Deposition of tin from vapor The first is mitigated primarily by the geometric design of the source vess= el. Buffer gas significantly reduces erosion rates by mitigating the ion fl= ux incident at the mirror surface by up to 4 orders of magnitude, and the i= on energy by about one order of magnitude. Buffer gas also offers the advan= tage over electric or magnetic mitigation schemes in that it will also miti= gate neutral atom sputtering of the mirror. Although the erosion rate is si= gnificantly reduced, the targeted collector lifetimes will also require the= addition of hundreds of sacrificial multilayers during the coating step of= collector fabrication. Deposition must be almost entirely eliminated becau= se only about lnm of deposited tin results in unacceptable reflectivity los= s. Cymer has shown that debris mitigation techniques in the chamber can eff= ectively protect the collector from reflectivity degradation and provide a = reliable and robust method of preserving collector lifetime. Cymer's source development and product roadmap is closely aligned with the = scanner manufacturers' roadmap. First-generation prototype EUV sources are = planned to be available in late 2008 for shipment to scanner suppliers. The= technology will be improved during 2009, before exposure systems are deliv= ered to chipmakers in 2010 for process development of next-generation devic= es. By the time EUVL is introduced into production, it is expected that the= technology will meet all of the requirements of the commercial semiconduct= or capital equipment industry. Additionally, later systems for high-volume = production are expected to operate at higher power than these initial proto= types. Further development and engineering of EUV sources is planned for ma= ny years to come, with progressively higher power and lower COO systems bei= ng delivered to support the roadmaps of both the scanner manufacturers and = chipmakers through the next several device nodes. Contact: NigelFarrar, CymerInc., 17075 Thornmint Ct., San Diego, CA 92127 T= el: 858-384-5527; e-mail: nfarrar@cymercom

Table 1. Cymer EUV source power budget and status Roadmap =20 First System =20 (Laser power 10.8kW In-band conversion efficiency 3.00% (Geometric collection efficiency 5sr (Collector average reflectivity 50% (Optical transmission 90% EUV power @ IF (W) 100

Cymer EUV Source Status Confirmed Confirmed In process Confirmed In process

Gale Document Number:A196383607

=20 2009 Gale, Cengage Learning.=20 --Boundary_(ID_RDjpCFEsqxtRKgZW/GH5vw)-</

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