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.

ISSN:0734-211X    

DOI:10.1116/1.585854

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

This article describes the extension of atomic force microprobe (AFM) technology to two dimensions (2D) for accurate measurement of submicron critical dimensions (CDs). The system utilizes a vibrating tip with heterodyne‐interferometer sensor similar to that introduced by Martin, Williams, and Wickramasinghe. [Y. Martin, C. C. Williams, and H. K. Wickramasinghe, J. Appl. Phys.61, 4723 (1987)]. However, the tip vibrates in 2D with dual heterodyne detection. The sample is moved relative to the tip by means of coarse‐ and fine‐motion stages whose position is monitored with 3D interferometry. The system does not scan the sample, but operates like a nanorobot sensing the approach of the tip to the surface by means of the vibration damping. A special three‐point tip has been fabricated by Lee [K. L. Lee, D. W. Abraham, F. Serord, and L. Landstein, Proceedings of the 35th ISEIPB Conference, Seattle, WA, May 28–31, 1991 (unpublished), paper K1]with 0.1 μm shank diameter which allows measurement of submicrometer trench widths up to 2 μm in depth with accuracy and repeatability at the nanometer level. Measurements are made under computer control. The system design and operating characteristics are discussed.

ISSN:0734-211X    

DOI:10.1116/1.585855

出版商:American Vacuum Society    

年代:1991

数据来源: AIP