Stijn Willem Herman Karel Steenbrink

Imaging performance of production-worthy multiple-E-beam maskless lithography

E-beam maskless lithography is a potential solution for 32-nm half-pitch (HP) node and beyond. The major concern to implement it for mass production is whether its throughput can reach a production-worthy level. Without violating the law of physics using unrealistic e-beam current, parallelisms in the writing beams and the data path are a few possible solutions to achieve such high productivity. It has been proposed to realize throughput greater than 10 wafers per hour (WPH) from a single column with >10,000 e-beams writing in parallel, or even greater than 100 WPH by further clustering multiple columns within an acceptable tool footprint. The MAPPER concept contains a CMOS-MEMS blanker array supported by high-speed optical data-path architecture to simultaneously control this high number of beams, switching them on and off independently. The MAPPER pre-α tool with a 110-beam 5-keV column and a 300-mm wafer stage has been built and is ready for imaging test. In this paper, the resist imaging results of 110-beam parallel raster-scan writing for 32-nm logic circuit layout on 300-mm wafer is shown. The challenges of implementing multiple e-beam maskless lithography (MEBML2) in mass production environment, including illumination, focusing, and CD uniformity, are discussed.

Performance validation of Mapper's FLX-1200

Mapper has installed its first product, the FLX–1200, at CEA-Leti in Grenoble (France). This is a maskless lithography system, based on massively parallel electron-beam writing with high-speed optical data transport for switching the electron beams. The FLX-1200, containing 65,000 parallel electron beams in a 13mm x 2mm electron optics slit, is capable of patterning any resolution and any different type of structure all the way down to 28 nm node patterns. As of August 2017 the FLX-1200 has a fully operational electron optics column, including a 65,000 beam blanker. In this paper the latest technical achievements of the FLX-1200 have been described: beam current is at 80% of FLX-1300 target (85 minutes per wafer). For 42nm hp dense lines a CDu of 8nm 3σ and a LWR of 5nm 3σ has been demonstrated. The stitching error is 12nm μ+3σ and regarding overlay a 15nm capability demonstrated, provided matching strategy is implemented and the mirror map is calibrated.

Performance validation of Mapper FLX-1200

Operating maskless, massively parallel electron beam direct write (MEBDW) is an attractive alternative to optical lithography in micro and nano device manufacturing. Mapper Lithography develops MEBDW tools able to pattern wafers, for application nodes down to 28nm, with a throughput around one wafer per hour. A prototype tool from this series, named FLX-1200, is installed in the CEA-Leti clean room. This paper reviews the current performances of this prototype and the methodology used to measure them. On standardized exposure, consisting of 100 fields of 5×5mm2 exposed, in less than one hour, on 300mm silicon wafers, we obtained CD uniformity below 10nm (3σ) and LWR of 4.5nm for 60nm half pitch dense lines. We also demonstrate capability of 15nm and 25nm (3σ) for stitching and overlay errors respectively.

Overlay performance assessment of MAPPER's FLX-1200 (Conference Presentation)

Mapper Lithography has introduced its first product, the FLX–1200, which is installed at CEA-Leti in Grenoble (France). This is a mask less lithography system, based on massively parallel electron-beam writing with high-speed optical data transport for switching the electron beams. This FLX platform is initially targeted for 1 wph performance for 28 nm technology nodes, but can also be used for less demanding imaging. The electron source currently integrated is capable of scaling to 10 wph at the same resolution performance, which will be implemented by gradually upgrading the illumination optics. The system has an optical alignment system enabling mix-and-match with optical 193 nm immersion systems using standard NVSM marks. The tool at CEA-Leti is in-line with a Sokudo Duo clean track. Mapper Lithography and CEA-Leti are working in collaboration to develop turnkey solution for specific applications. At previous conferences we have presented imaging results including 28nm node resolution, cross wafer CDu of 2.5nm 3 and a throughput of half a wafer per hour, overhead times included. At this conference we will present results regarding the overlay performance of the FLX-1200. In figure 2 an initial result towards measuring the overlay performance of the FLX-1200 is shown. We have exposed a wafer twice without unloading the wafer in between exposures. In the first exposure half of a dense dot array is exposed. In the second exposure the remainder of the dense dot array is exposed. After development the wafer has been inspected using a CD-SEM at 480 locations distributed over an area of 100mm x 100mm. For each SEM image the shift of the pattern written in the first exposure relative to the pattern written in the second exposure is measured. Cross wafer this shift is 7 nm u+3s in X and 5 nm u+3s in Y. The next step is to evaluate the impact of unloading and loading of the wafer in between exposures. At the conference the latest results will be presented.