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The system concepts used in a novel approach for a high throughput maskless lithography system called reflective electron beam lithography (REBL) are described. The system is specifically targeting five to seven wafer levels per hour throughput on average at the 45nm node, with extendibility to the 32nm node and beyond. REBL incorporates a number of novel technologies to generate and expose lithographic patterns at estimated throughputs considerably higher than electron beam lithography has been able to achieve as yet. A patented reflective electron optic concept enables the unique approach utilized for the digital pattern generator (DPG). The DPG is a complementary metal oxide semiconductor application specific integrated circuit chip with an array of small, independently controllable metallic cells or pixels, which act as an array of electron mirrors. In this way, the system is capable of generating the pattern to be written using massively parallel exposure by ∼1×106 beams at extremely high data rates (∼1Tbit∕s compressed data). A rotary stage concept using a rotating platen carrying multiple wafers optimizes the writing strategy of the DPG.

Multiaxis and multibeam technology for high throughput maskless E-beam lithography J. Vac. Sci. Technol. B 30, 06FC01 (2012); 10.1116/1.4767275 High-current electron optical design for reflective electron beam lithography direct write lithography J. Vac. Sci. Technol. B 28, C6C1 (2010); 10.1116/1.3505130 REBL: A novel approach to high speed maskless electron beam direct write lithographyReflective electron beam litography ͑REBL͒ utilizes several novel technologies to generate and expose lithographic patterns at throughputs that could make ebeam maskless lithography feasible for high volume manufacturing. The REBL program was described in a previous article ͓P. Petric et al., J. Vac. Sci. Technol. B 27, 161 ͑2009͔͒ 2 years ago. This article will review the system architecture and the progress of REBL in the past 2 years. The main technologies making REBL unique are the reflective electron optics, the rotary stage, and the dynamic pattern generator ͑DPG͒. Changes in how these concepts have been implemented in a new design will be discussed. The main disadvantage of today's electron beam direct write is low throughput; it takes many tens of hours to expose a 300 mm wafer today using ebeam lithography. The projected system throughput performance with the integrated technology of the reflective optics, DPG, and a multiple wafer rotary stage will be shown incorporating the performance data for the new column design. C6C10 Petric et al.: Reflective electron beam lithography: A maskless ebeam direct write lithography C6C10 J.

REBL (Reflective Electron Beam Lithography) is being developed for high throughput electron beam direct write maskless lithography. The system is specifically targeting 5 to 7 wafer levels per hour throughput on average at the 45 nm node, with extendibility to the 32 nm node and beyond. REBL incorporates a number of novel technologies to generate and expose lithographic patterns at estimated throughputs considerably higher than electron beam lithography has been able to achieve as yet. A patented reflective electron optic concept enables the unique approach utilized for the Digital Pattern Generator (DPG). The DPG is a CMOS ASIC chip with an array of small, independently controllable cells or pixels, which act as an array of electron mirrors. In this way, the system is capable of generating the pattern to be written using massively parallel exposure by ~1 million beams at extremely high data rates (~ 1Tbps). A rotary stage concept using a rotating platen carrying multiple wafers optimizes the writing strategy of the DPG to achieve the capability of high throughput for sparse pattern wafer levels. The exposure method utilized by the DPG was emulated on a Vistec VB-6 in order to validate the gray level exposure method used in REBL. Results of these exposure tests are discussed.

Projection reduction exposure with variable axis immersion lenses (PREVAIL) represents the high throughput e-beam projection approach to NGL, which IBM is pursuing in cooperation with Nikon as alliance partner; another e-beam projection approach is SCALPEL pursued by Lucent Technologies. This article discusses the challenges and accomplishments of the PREVAIL project. It will focus on the results obtained with the proof of concept (POC) system. This system was developed to demonstrate key technical building blocks required for high throughput, high resolution e-beam step, and scan projection lithography. The supreme challenge facing all e-beam lithography approaches has been and still is throughput. Since the throughput of e-beam projection systems is severely limited by the available optical field size, the key to success is the ability to overcome this limitation. The PREVAIL technique overcomes field-limiting off-axis aberrations through the use of variable axis lenses, which electronically shift the optical axis simultaneously with the deflected beam, so that the beam effectively remains on axis. This technique developed by IBM has been successfully applied to probe-forming shaped beam systems (EL-4). It had to be modified and extended to provide the larger beam deflections and the wider beam images at the wafer plane used in projection reduction systems. The POC system projects sequentially 1×1 mm2 subfields, selected at the reticle, in 4:1 reduction mode onto the wafer, exposing and resolving patterns of 80 nm lines and spaces in resist; each subfield contains 107 pixels. The deflection capability demonstrated permits electronic selection of 20 1 mm subfields at the reticle and projection of these 20 subfields onto the wafer exposing a field with 5 mm scan length. The resist images provide proof that PREVAIL effectively eliminates off-axis aberrations affecting resolution, since the deflected and undeflected images are indistinguishable. PREVAIL also controls off-axis aberrations affecting placement accuracy of pixels, since distortions of the deflected subfield are corrected to within 12 nm. A high emittance gun has been developed to provide uniform illumination of the patterned subfield, and to fill the large numerical aperture of the projection optics required to significantly reduce beam blur caused by Coulomb interaction.