J Schneir

Conformal oxides on Si surfaces

The characteristics of the Si–vacuum interface were compared with the characteristics of the oxide–air interface formed following room temperature oxidation for a variety of samples. Scanning tunneling microscopy was used to measure the surface structure following vacuum preparation, and atomic force microscopy was used to measure the oxide surface on the same samples following exposure to air. Samples investigated included nominally flat Si(111) with equilibrated and quenched surface configurations, Si(111) miscut by 1.25° toward the [211] and equilibrated to yield the faceted structure, and nominally flat Si(001) wafers. In all cases, the step morphology of the clean surfaces was duplicated on the surface of the oxide.

Increasing the value of atomic force microscopy process metrology using a high‐accuracy scanner, tip characterization, and morphological image analysis

Atomic force microscopes are being used increasingly for process metrology. As a case study, the measurement by atomic force microscope of a soda lime glass optical disk patterned using optical lithography and reactive plasma etching is examined. The atomic force microscope used for this measurement has a highly accurate scanner system. The X, Y, and Z axes are calibrated using laser interferometry. To determine the shape of the tip used a commercially available tip calibration artifact was imaged both before and after the measurement. The image was corrected for the tip shape using mathematical morphology. The value of the atomic force microscope measurement is defined to be the impacts of the metrology on the product or process. It is shown that the value of atomic force microscopy process metrology on an optical disk is increased by using an accurate scanner, tip characterization, and morphological image analysis; however, the cost per measurement is increased as well. In general, the characteristics o...

100-nm-pitch standard characterization for metrology applications

In this paper we present and characterize a NIST-traceable, all-silicon, 100 nm pitch structure with the necessary quality attributes to calibrate CD-SEM tools used for metrology of sub-0.25 micron semiconductor process technology.

Progress on accurate metrology of pitch, height, roughness, and width artifacts using an atomic force microscope

NIST personnel (J.S. and T.M.) visited 23 IC manufacturing companies and equipment suppliers during 1994 to determine semiconductor industry needs for scanned probe metrology. NIST has initiated projects addressing some of the need identified. When complete these projects will enable improved metrology using the scanned probe microscope. Industry needs include pitch, height, angle, and width calibration artifacts, and understanding of the effect of humidity on AFM measurements, and tip metrology techniques. To meet these needs we have designed and built a Calibrated Atomic Force Microscope (C-AFM) with interferometric position control. This AFM is capable of making accurate measurements. We present the operational characteristics of the instrument, accurate X, Y, and Z pitch measurements on a commercially available artifact, measurements on a prototype surface roughness artifact, and a promising technique by which to make accurate linewidth measurements.

Measurement of a CD and sidewall angle artifact with two-dimensional CD AFM metrology

Despite the widespread acceptance of SEM metrology in semiconductor manufacturing, there is no SEM CD standard currently available. Producing such a standard is challenging because SEM CD measurements are not only a function of the linewidth, but also dependent on the line material, sidewall roughness, sidewall angle, line height, substrate material, and the proximity of other objects. As the presence of AFM metrology in semiconductor manufacturing increases, the history of SEM CD metrology raises a number of questions about the prospect of AFM CD artifacts. Is an AFM CD artifact possible? What role would it play in the manufacturing environment? Although AFM has some important advantages over SEM, such as relative insensitivity to material differences, the throughput and reliability of most AFM instruments is not yet at the level necessary to support in-line CD metrology requirements. What, then, is the most useful relationship between AFM and SEM metrology? As a means of addressing some of these questions, we have measured the CD and sidewall angle of 1.2 micrometer oxy-nitride line on Si using three different techniques: optical microscopy (with modeling), AFM, and cross sectional TEM. Systematic errors in the AFM angle measurements were reduced by using a rotational averaging technique that we describe. We found good agreement with uncertainties below 30 nm (2 sigma) for the CD measurement and 1.0 degrees (2 sigma) for the sidewall angles. Based upon these results we suggest a measurement procedure which will yield useful AFM CD artifacts. We consider the possibility that AFMs, especially when used with suitable CD artifacts, can effectively support SEM CD metrology. This synergistic relationship between the AFM and SEM represents an emerging paradigm that has also been suggested by a number of others.

Instrument for calibrating atomic force microscope standards

To facilitate the use of AFMs for manufacturing we have initiated a project to develop and calibrate artifacts which can in turn be used to calibrate a commercial AFM so that subsequent AFM measurement are accurate and traceable back to the wavelength of light. We plan to calibrate our artifacts using a specially designed AFM system which we call the Calibrated AFM (C-AFM). The C-AFM has been constructed as much as possible out of commercially available components. We use a flexure stage driven by piezoelectric transducers for scanning; a heterodyne interferometer to measure the X-Y position of the sample; a capacitance sensor to measure the Z position of the sample; and a commercially available AFM control system. The control system has two feedback loops which read from the X and Y interferometers, respectively, and adjust the piezoelectric voltages to keep the X-Y scan position accurate. The critical electromechanical and metrology issues involved in the construction and operation of such a system are discussed in detail.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.