Near field scanning optical microscopy of thin birefringent samples is described. The system utilized is the linear polarizing near field microscope, resulting in a pure birefringence image of the sample. The sign of the birefringence is also preserved. Two specific classes of sample are studied. These include thin sections of Kevlar fibers, and polymer dispersed liquid crystals. Results are correlated with simultaneously obtained topographic images. Based on experimental observations, the relative strength of the optical indices of the structures is determined
Images of a microlithographic sample obtained using a new near field scanning optical microscope (NSOM) that uses force regulation of the sample-tip separation are presented. The NSOM is a research instrument fitted with a metal covered glass tip probe that defines a small aperture at the sharp end. The aperture is estimated to be on the order of 100 nanometers in diameter resulting in a resolution exceeding that of diffraction limited systems. This form of microscopy can be done both in the transmission and the reflection modes. The force regulation mechanism produces a simultaneously obtained scanned force microscope image of the topography thus permitting correlative imaging of the sample. The samples are imaged in transmission and reflection near field optical format, with white light and with coherent light. The results are compared with other forms of IC imaging and characterization, namely scanned force microscopy and scanning electron microscopy.
A novel atomic force microscope (AFM) is used to image a microlithographic sample. The AFM operates in the non destructive non-contact mode, uses glass tips as opposed to tungsten or silicon, and has an optical interferometric detection system. Its estimated lateral resolution is under 10 nanometers and much better in the z direction. A sample consisting of chrome features on quartz was produced for measurements using AFM and electric probe techniques. The features are single and grouped lines on the order of 1 micrometers incorporated into an electric probe pad layout. Dimensions of these features are determined from the AFM images by relating their sizes in pixels to the excursions of the scanners during the formation of the images. These results are compared with measurements obtained through electric probing techniques.
Highly sensitive and stable detection of minute ac and pseudo-dc (i.e. , very low frequency) vibrations is performed by means of a differential fiber optic Michelson interferometer. Any residual instabilities are eliminated by means of an ac feedback control loop. The stabilization technique is not affected by the variations in the reflectivity of the sample and by launch inefficiencies into the fiber. This approach also provides a simple, quantitative method for calibrating sample vibrations. Results are presented on the operation of the system in stabilizing its output as well as on the detection of the vibration of a silicon sample.
Near field scanning optical microscopy (NSOM) provides a number of unique capabilities for high resolution imaging. In this regard, a fundamental aspect of the technique is its ability to retain much of the characteristics available in diffraction limited optical probing. Results are presented on the use of near field scanning optical microscopy (NSOM) in imaging a variety of samples, using different contrast mechanisms. The approaches adopted are based on the recently introduced simultaneous, non-contact, near field optical microscope with atomic force regulation. Amongst the techniques discussed are linearized polarizing microscopy, as well as amplitude, and phase, interference contrast imaging modalities.
KEYWORDS: Thin films, Microscopes, Optical microscopes, Blood, Microscopy, Atomic force microscopy, Near field scanning optical microscopy, Integrated circuits, Scanning probe microscopy, Near field optics
The design and theory of operation of a new form of near field scanning optical microscope are presented. In this system, the tip/sample distance regulation is achieved in a feedback system utilizing the topography information derived from the attractive force sensed between the tip and the sample. The technique affords the possibility of correlative microscopy. Results are presented on imaging blood smears and thin film integrated circuits.
Results are reported on the use of the in-situ differential scanning
electron microscope in precision micro-metrology of submicron
features. It is shown that the technique is capable of providing
remarkably stable linescans across etched silicon patterns partially
covered with silicon dioxide on the surface. Results are also
presented on the metrology of photo-resist, showing relative signal
stability even in presence of charging effects. An important ability
of the technique, namely its inherent capability to effect an
ob5ectively defined alignment of the samples, is extensively utilized
in this regard.