Sub-100 nm metrology using interferometrically produced fiducials

Abstract

Pattern-placement metrology plays a critical role in nanofabrication. Not far in the future, metrology standards approaching 0.2 nm in accuracy will be required to facilitate the production of 25 nm semiconductor devices. They will also be needed to support the manufacturing of high-density wavelength-division-multiplexed integrated optoelectronic devices. We are developing a new approach to metrology in the sub-100 nm domain that is based on using phase-coherent fiducial gratings and grids patterned by interference lithography. This approach is complementary to the traditional mark-detection, or ''market plot'' pattern-placement metrology. In this article we explore the limitations of laser-interferometer-based mark-detection metrology, and contrast this with ways that fiducial grids could be used to solve a variety of metrology problems. These include measuring process-induced distortions in substrates; measuring patterning distortions in pattern-mastering systems, such as laser and e-beam writers; and measuring field distortions and alignment errors in steppers and scanners. We describe a proposed standard for pattern-placement metrology, which includes both a fiducial grid and market-type marks. Finally, a number of methods through which phase-coherent periodic structures can be patterned are shown, including ''traditional'' interference lithography, achromatic interference lithography, near-field interference lithography, and scanning-beam interference lithography.

Relativistic corrections in displacement measuring interferometry

“…Let us assume that the mask pattern is projected onto a wafer at four-fold reduction. This requires that the reticle stage moves in a highly An example where relativistic corrections are more important is scanning-beam interference lithography (SBIL), [4] which is currently being developed in our laboratory. The challenging goal of this technique is the manufacture of large-area phase-coherent periodic patterns with subnanometer phase error for pattern-placement metrology and other applications.…”

“…For example a recently proposed method for the manufacturing of large-area, fine-period, and low-distortion gratings and grids requires the ability to repeatedly scan a single large wafer many times at high speed with nanometer accuracy under a mm 2 sized interference pattern. [4] In the following we first review the principles underlying heterodyne interferometric displacement measurements. We then calculate the relativistic Doppler shift for the general case of a single reflection from a mirror that moves arbitrarily within a plane.…”

In situ surface topography measurement method of granite base in scanning wafer stage with laser interferometer

“…The less DOF needs more accurate leveling and focusing control method which monitors and adjusts the vertical position of the wafer stage. In order to keep the surface of the wafer stage in the DOF during the scanning, the topography information of the granite base surface is required for the focusing and leveling system [5]. Thus, fast and accurate measurement methods of granite topography become necessary [6].…”

Precision grating for measuring microscope lens distortions

“…In this work, a diffraction grating [9] was chosen for its advantages in measuring a microscope's optical distortion and video camera distortion. Recently, gratings have been fabricated with long range errors less than 2 nm, 3σ, and even more accurate gratings are expected in the future [7]. High precision gratings can be readily utilized in calibration.…”

“…Only the illumination was changed between image of the resist features and image of the grating. Measurements of the patterned level with respect to the grating provide an absolute measurement of the placement of its features, with an accuracy limited by the accuracy of the Correspondence: ljiang@tuskegee.edu diffraction grating -state of art less than 2 nm, 3σ [6,7]. The absolute positional accuracy is required for measuring lithographic tool performance, e.g., distortions in an optical projection lens, or writing errors in an e-beam exposure tool.…”