E C. Teague

Optical techniques for on-line measurement of surface topography

Abstract Optical techniques have great potential for non-destructive and on-line measurements of surface roughness during manufacturing. This paper reviews the state-of-the-art in a number of optical techniques including specular reflectance, total integrated scatter, diffuseness, angular scattering distributions, speckle, ellipsometry, and interferometry. The distinction is drawn between the more quantitative but slower profiling techniques and less quantitative, parametric techniques, which are faster and hence more useful for high-speed monitoring of surfaces. Overall, no currently available technique combines accuracy and speed and is therefore suitable as an on-line metrological tool for roughness measurement of engineering surfaces. Speckle techniques hold perhaps the greatest potential as accurate, high-speed metrological tools

Electronic limitations in phase meters for heterodyne interferometry

Abstract Limitations imposed by the phase meters used in heterodyne interferometers are evaluated. These instruments measure the phase relationship between electrical signals generated by the heterodyning process, allowing the interferometers to resolve fractions of an optical fringe. Measurements indicate that the phase meters used in currently available heterodyne interferometers probably limit achievable accuracy to a greater extent than barriers imposed by the optics. We show that a new class of time interval counters offers a means of greatly improving accuracy in these instruments.

Measurement of patterned film linewidth for interconnect characterization

Test results from high-quality electrical and physical measurements on the same cross-bridge resistor test structure with approximately vertical sidewalls have shown differences in linewidth as great as 90 nm for selected conductive films. These differences were independent of design linewidth. As dimensions become smaller, the accurate measurement of the patterned conductor width is necessary to assure predictable timing performance of the interconnect system as well as control of critical device parameters.

Test structure for the in-plane locations of project features with nanometer-level accuracy traceable to a coordinate measurement system

A new test structure is reported. It is designed to measure the positions of the images of an array of features projected from a mask into a resist film on substrate with accuracy better than 10 nm. The resist film on the substrate covers a nominally matching array of partially formed versions of the test structure prepatterned in a conducting film. Instances of the finished structure are formed on the substrate by further selective removal of conducting material from the partially formed test structures where they are overlaid by images of the fiducial marks on the mask. At each array point, the feature of the completed test structure that is defined by the overlay of the image of the fiducial marks on the mask is called the pointer. The part of the partially formed test structure that is unaffected by the overlay of the images of the fiducial marks on the mask serves as a ruler. Electrical testing accurately provides the precise location of the pointer relative to the ruler within each test structure. The locations of the rulers prepatterned on the substrate are determined with a coordinate measurement system (CMS) called the NIST (National Institute of Standards and Technology) Molecular Measuring Machine (M-Cubed).<<ETX>>

A new method to measure the distance between graduation lines on graduated scales

Line scales are used throughout industry for a variety of applications. The most common is the stage micrometer, a small, graduated glass scale for the calibration of optical instruments such as microscopes. However, stage micrometers are generally not calibrated, except for critical applications, due to the time and cost of optical calibration techniques. A method for calibrating line scales is presented which uses electrical test structure metrology. A description of the technique as well as examples of results from this technique are presented.

Metrology standards for advanced semiconductor lithography referenced to atomic spacings and geometry

It is shown how the needs for calibrating the positional accuracy of features of an X-ray mask membrane or an optical reticle can be addressed by application of a high-accuracy coordinate metrology system known as the Molecular Measuring Machine (M-Cubed). Based on scanning tunneling microscopy and state-of-the-art heterodyne optical interferometry, the measurements of M-Cubed are referenced to fundamental standards of length and angle and with the atomic-resolution of its scanning tunneling microscope probe are validated against the interatomic spacings and geometry of single crystal surfaces. Through the use of a stable reference grid, serving as an intermediate calibration artifact, the positional accuracy of features on an X-ray mask membrane or an optical reticle can be referenced to fundamental standards of length and angle by means of the metrology system of M-Cubed.<<ETX>>