Muneki Hamashima

First dynamic exposure results from an electron projection lithography tool

Electron projection lithography (EPL) is one of the promising technologies below the 65 nm node, especially for contact hole and gate layers. Nikon is developing an EPL exposure tool as an electron beam (EB) stepper and the first generation EB stepper is now being manufactured. The voltage of 100 kV is adopted for electron beam acceleration. The subfield size is 0.25 mm×0.25 mm on the wafer and the deflection width of the electron beam is 5 mm on the wafer. The magnification of the projection optics is 1/4. A 5 mm×25 mm area from the φ200 mm reticle can be exposed by the combination of beam deflection and stage scanning motion (dynamic exposure). This area is called “a mechanical stripe.” After one mechanical stripe exposure, the reticle and wafer stages turn around and the next exposure of the adjacent mechanical stripe starts as a scan and stitch stage motion. Finally, a 20 mm×25 mm exposure field from the φ200 mm reticle is exposed. We report the first dynamic exposure in the history of EPL although on...

EPL electron optics performance on test stand: 1. resolution results

The performance of the electron optical (EO) column of Nikons EB-stepper mounted on its test stand is reported, mainly focusing on the subject of resolution as preliminary results. Stitching data will be presented in the next paper at MNE2002. Resolution performance data are presented with SEM photos of line/space patterns and contact hole features, printed in both positive and negative resists. EO adjustment techniques were established to obtain the maximum resolution with best trajectory optimisation so that both resolution and distortion can meet their specifications. It is essential to have a metrology capability to measure, distortion as well as resolution. Good resolution results have been achieved over the large deflection (5 mm) field of the EO column using the curvilinear variable axis lens (CVAL) concept, which has been demonstrated by IBM theoretically and experimentally. Current beam blur, depth of focus (DOF) and some characteristic features of the EO conditions are also demonstrated. Image blur at small-deflected positions has also been determined by a direct measurement method. The minimum feature size of 50 nm and a large depth of focus over 5 µm, have been obtained. Overall performance over the whole 5 mm deflected range has not been accomplished yet due to stability limitations of the test stand stage, but good 80-nm line and space resist images have been obtained for the whole deflected range.

PREVAIL - Latest electron optics results

The PREVAIL electron optics subsystem developed by IBM has been installed at Nikons facility in Kumagaya, Japan, for integration into the Nikon commercial EPL stepper. The cornerstone of the electron optics design is the Curvilinear Variable Axis Lens (CVAL) technique originally demonstrated with a proof of concept system. This paper presents the latest experimental results obtained with the electron optical subsystem at Nikons facility. The results include micrographs illustrating proper CVAL operation through the spatial resolution achieved over the entire optical field of view. They also include data on the most critical issue of the EPL exposure approach: subfield stitching. The methodology of distortion correction will be described and both micrographs and metrology data of stitched subfields will be presented. This paper represents a progress report of the IBM/Nikon alliance activity on EPL.

Progress and preliminary results on EB stepper

As Next Generation Lithography (NGL) systems, several systems are proposed. EPL (Electron Beam Projection Lithography) system, which is one of NGL systems using electron beam (EB), is expected to be a most promising candidate, which has a high throughput (>20 wph of a 300 mm wafer) and a high resolution (<70 nm). Many studies on NGL systems have been reported but most of them were limited to basic scientific discussions on the research level. There are few discussions on technical issues on each system. Nikon has developed EPL system (EB Stepper) in collaboration with IBM. The development moves to the system evaluation phase. Discussions on EB Stepper must be technical rather than scientific. In this paper recent progress on EB Stepper will be discussed.

Electron Optics Properties of Electron Beam Stepper

Electron projection lithography (EPL) is one of the most reliable lithography tools for 65 nm node generation and below. An electron optics (EO) subsystem, which has been developed in collaboration with IBM, and Nikons original stage/body are integrated into an electron beam (EB) stepper. The latest EO properties of the EB stepper are discussed. Experimentally, the curvilinear variable axis lens (CVAL) adjustment is established. Therefore, good resolution (better than 80 nm) and low nonlinear distortion (approximately 10 nm) is obtained at the maximum (2.5 mm) deflected sub-field on the test stand. After docking with body and stages, good resolution (better than 90 nm) is achieved for the on-axis beam.