Sanjay K. Yedur

Specular spectroscopic scatterometry in DUV lithography

Scatterometry is a one of the few types of metrology that has true in-situ potential for deep submicron CD and profile analysis. To date, commercial prototypes have been used to establish scatterometry based on single wavelength, multiple incident angle inspection. We extend this idea by deploying specular spectroscopic scatterometry (SSS). Conventional scatterometry is designed to measure either many diffraction orders or variable incident/collection angle at a single wavelength. Specular spectroscopic scatterometry is designed to measure the 0th order diffraction responses at a fixed angle of incidence. Specular spectroscopic scatterometry can make direct use of the existing spectroscopic ellipsometry equipment. We show that SSS provides an accurate, inexpensive, and non-destructive CD metrology solution.

Phase Profilometry for the 193 nm lithography gate stack

Phase Profilometry (PP) has been proposed for in-situ/in-line critical dimension and profile measurements. This is usually accomplished by using rigorous electromagnetic theory to simulate the optical responses of gratings with different profiles, and by using spectroscopic ellipsometry/reflectometry to measure 1-D gratings. In this paper, phase profilometry is applied to the lithography process for cross-sectional profile extraction metrology. A focus-exposure experiment was conducted using Sematechs 193 nm lithography tool. Comparison between the measurements from CD-SEM, CD-AFM and PP are discussed and explained.

Evaluation of atomic force microscopy: comparison with electrical CD metrology and low-voltage scanning electron microscopy

With the increasing move towards measurement of smaller and smaller dimensions, the reliability of existing metrology approaches is begin called into question. The most widely used approach for CD measurement in a fabrication environment is the use of Low Voltage Scanning Electron Microscopy. SEMs are routinely used in industry for top-down measurements of lines, spaces, and contacts in the production line. The destructive approach of cross section SEMs is used for trouble shooting and analysis. Electrical CD measurements are also routinely used to measure the CDs of conducting layers in the production environment. However, electrical CD metrology is not appropriate for the majority of surfaces that are non-conductive, such as those with photoresist. It has been speculated for a while n ow that the AFM can provide a viable alternative by overcoming all the drawbacks of the other metrology techniques. This paper address this issue and discusses the relative merits of the AFM as compared to the others. The measurement bias between the three techniques on isolated line features ranging from 0.1 to 0.3 microns is compared. The ability of the AFM to measure profiles is discussed.

Specular spectroscopic profilometry for the sub-0.18-um polySi-gate processes

Specular Spectroscopic Profilometry (SSP), or Phase Profilometry (PP), has been proposed for in-situ/in-line patterned thin-film measurements. This is usually accomplished by using a rigorous electromagnetic theory to simulate the optical responses of gratings with different profiles, and by using spectroscopic ellipsometry/reflectometry to measure 1-D gratings. In this paper, specular spectroscopic profilometry is applied in DUV lithography and etch processes as a profile extraction metrology. One focus-exposure experiment is conducted by using 0.18 micrometer lithography technology, another focus-exposure experiment is conducted by using 0.18 micrometer lithography and etch technology. Comparison between the measurement from CD-SEM, CD-AFM and PP are discussed and explained.