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Metrology of electron‐beam lithography systems using holographically produced reference samples

 

作者: Erik H. Anderson,   Volker Boegli,   Mark L. Schattenburg,   Dieter Kern,   Henry I. Smith,  

 

期刊: Journal of Vacuum Science&Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena  (AIP Available online 1991)
卷期: Volume 9, issue 6  

页码: 3606-3611

 

ISSN:1071-1023

 

年代: 1991

 

DOI:10.1116/1.585854

 

出版商: American Vacuum Society

 

关键词: LITHOGRAPHY;ELECTRON BEAMS;SPATIAL RESOLUTION;GRATINGS;HOLOGRAPHY;PHOTORESISTS;REFERENCE SYSTEMS;POSITIONING;IMAGE PROCESSING

 

数据来源: AIP

 

摘要:

Metrology in an electron‐beam lithography system is typically carried out by a combination of beam scan and laser‐interferometer‐controlled sample motion. The high‐resolution technique presented in this paper avoids the stage motion by using a holographically produced grid, which is essentially a permanently recorded interference pattern. This grid can be at least as accurate as the interferometer, and no stage motion, with the potential for additional error sources, is required to map out the distortion in the deflection field. The quality of the grid is critical since it is the reference to which the distortion is compared. With careful control of the holographic exposure system, high‐quality low‐distortion orthogonal grids were fabricated. We have produced grids with a period of 200 nm and orthogonality of a few arc seconds using an UV laser holographic system. Once the grid is processed to produce a high‐contrast signal for either back‐scattered or transmitted electrons, both scanning and signal‐processing techniques are needed to measure the distortion. If the errors are larger or similar in size to the grating period a moiré technique can be used. Unfortunately, when the distortion is much less than the period this technique does not have the required resolution. Therefore, two new techniques have been developed. The first uses a lock‐in amplifier to measure the phase difference between the expected signal and the actual measured signal. The second uses digital image processing to compare the expected and measured images. With both of these techniques resolution of about one beam step (≊6 nm) has been achieved.

 

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