The laser interference phase-measuring computer-aided microscope enabling 3-D presentation of surface structure has been developed. Plane and height resolution numbers are 0,1μm and 1 nm. Results using this technics, application area and error sources are discussed.

Measurements with computer phase microscope show feasibility determination the phase object dimensions and coordinates to an accuracy depending S/N ratio δx = (S/N)^-1d_R where d_R - Rayleigh criterion. The resolution achieved in experiment with semiconductor structures is δx = 0.02 μm. Simple theoretic models of phase objects are discussed.

Two methods are described allowing the localization of defects (e.g. hot spots, leakage currents, electrostatic discharge defects) in electric devices using the OBIC (optical beam induced current) signal produced by a laser scan microscope. Knowledges about the generation of the OBIC and the design of the integrated circuit are not needed. In both methods the OBIC signals of a device under test and a good reference device (golden device) are compared. The difference between the two OBIC - images reveals any dissimilarities and in this way localizes defects in a device under test.

Optical beam testing methods offer several advantages with respect to conventional Scanning Electron Microscopy (SEM) techniques for failure analysis of integrated circuits and discrete devices: they do not require vacuum, avoid MOS and oxide damaging in OBIC (Optical Beam Induced Current) tests. This paper describes the application of scanning laser techniques to failure analysis of integrated circuits and discrete devices. Results have been obtained by means of a commercially available laser system (Biorad Lasersharp SOM 150), equipped with a visible (He-Ne 633 nm, 15 mW) and an IR (laser-diode-pumped Nd:YAG 1320 nm, 25 mW) laser source.

New methods of measuring micro-images, needed during the fabrication of integrated optics and semiconductors, are currently receiving much attention. Edge location and linewidth measurements to sub-micron accuracy are required to be made at high speed, but conventional high resolution optical microscopy is not always suitable due to the small depth-of-focus and sensitivity to vibration associated with high numerical aperture lenses. This paper describes the design and performance of a comparator microscope which, although originally suggested for quantifying surface flaws, can also be applied to measuring linewidths and for precise edge location. The technique, which is still under development, shows promise in enabling high precision measurements on some types of image using relatively low aperture, large depth-of-focus lenses.

In micrometrology of thin line structures, in for example the semiconductor wafer fabrication industry, it is necessary to locate accurately the positions of edges in order to provide dimensional information concerning the structure. In some cases all that is required is reproducability, and measurements can be calibrated against known structures. However, in order to extract as much information as possible from the measured profiles, it is necessary to have an accurate model to predict the image profile from the structure. Structures resulting from semiconductor microlithography are often several wavelengths thick, making any attempt at image calculation difficult. Several attempts at the rigorous modelling of thick gratings have been made. This paper will concentrate on providing an overview of the current state of imaging and proposing several simple models for this task. Towards this end, the imaging of a surface-relief square wave dielectric grating of between 0.1 and 20.1 wavelengths (λ) period (Λ) and for 0 to 2 wavelengths thickness (d) are discussed.

A discussion is given of the various factors effecting the minority carrier distribution excited in a semiconducting sample by a focused light beam. Parameters considered include the objective lens numerical aperture, the surface recombination velocity and the exciting beam scan speed. The discussion is aimed at producing a theoretical understanding of the optical beam induced current (OBIC) and photoluminescence (PL) semiconductor imaging techniques.

Techniques for high resolution mapping of chemical and native crystal defects in semiconductor substrates are required for basic materials research as well as for quality control in the industrial manufacturing of wafers for electronic devices. Because of the relative ease of use, near infra-red microscopy has recently become popular. Imaging in 350μm thick wafers at a wavelength of 1.0μm presents special problems, particularly with the refractive index of the material being as high as 3.5. The bright field mode is capable of revealing the larger micro-precipitates of around 1μm in size in GaAs, doped GaAs and InP. An improvement in contrast is achieved with the dark field mode. Phase contrast microscopy can be used to show growth striations in doped GaAs and even the paths of disloca-tion lines under certain conditions. One emerging technique is Laser Scanning Tomography (LST) which uses a scanned Nd-YAG laser beam (1.06μm) to reveal micro-precipitates smaller than the diffraction limit of the imaging system. High contrast images are produced showing a more complete picture of micro-precipitates in GaAs, doped GaAs, InP and Si. Tomography can be used to observe the development of the nucleation of oxide precipitates in silicon, from the embryonic stage of particles as small as 20Å, through to larger particles of the order of 1μm. Some of the problems and latest results using these different techniques in this interesting applications area are presented and discussed.

A system is described, which allows photoluminescence measurements in the spectral region from 400 nm to 1.2 μm with a spatial resolution better than 1 μm and with an energy resolution of about 10 meV. The apparatus is based on a laser scan microscope. The luminescence excited by blue laser light (488nm) at arbitary points of the sample is detected by a photomultiplier positioned at the exit of a monochromator. Some results of investigations on GaAs / GaAlAs - heterostructures are presented.

A laser scanning microscope with an OBIC stage is used to investigate internal binary states of integrated circuits and diffusion parameters of the semiconductor material applying different laser wavelengths. The internal logical states of the circuit could be detected using blue and red laser radiation. Red and IR radiation are used to investigate the depth and location of doped wells. Applying three wavelengths it could be distinguished between surface and bulk recombination in the semiconductor material. The OBIC images of a CMOS inverter and a complete NOR-gate consisting of 10 transistors are analyzed in dependence on the logical input pattern.

For overpassing the classical limit of resolution in optical microscopy, it is necessary to detect the diffracted light from small objects in the near field and not in the far field as in classical microscopy. A particular case is the detection of the evanescent field lying on the surface of a guiding structure. These surface waves interact with the object details and then can be used for determining the topography of the object. The chief problem is the detection because the light beam is confined on the object surface. A solution consists of frustrating the evanescent field by means of a dielectric probe. The conversion of the in-homogeneous waves into homogeneous ones is fundamentally similar to the electronic tunneling effect. Subwavelength resolution can be obtained by placing a suitable optical stylus connected to an optical fibre near the surface. A xyz piezo-electric micropositioning system allows then to scan the object surface under test. A microscope exploiting this principle has been built. Preliminary experimental results are presented and discussed.

We consider the decay rate of an excited molecule near a rough surface. The variations of the decay rate is obtained by summing the contributiorsof the pair interactions between the adsorbed molecule and the roughness considered as small polarizable systems.

We present a new form of optical microscope. An evanescent field is produced in the lower index medium of an ATR system and modulated by a sample deposited on the hypotenuse of the prism. A sharpened fiber optic probes this field and gives information about the topography of the surface.

In the case of weakly absorbing objects and of complete incoherence of the emitted radiation, the three-dimensional image g(r) produced by a Confocal Scanning Laser Microscope (CSLM) is the convolution of the distribution function of the fluorescent material, f(r), with the impulse response function of the instrument, h(r). Since h(r) is band-limited, the image g(r) contains information only about the Fourier components of f(r) in the band of h(r). Moreover, these components are distorted because the Fourier transform of h(r) is not constant over the band. If both g(r) and h(r) are known it is possible to invert the integral relationship indicated above in order to improve the imaging fidelity and the resolution of the microscope. This deconvolution problem is ill-posed and the so-called regularization methods must be used in order to get stable and approximate solutions. In this paper we discuss the potential applications of a very simple regularization technique to the restoration of three-dimensional images produced by the confocal scanning microscope developed at the University of Amsterdam.

The accurate and precise measurement of the critical dimensions of submicron structures is a fundamental aspect of modern integrated circuit fabrication. The limit of optical resolution of classical microscopy has been reached and new, improved methods are needed. Confocal laser scanning microscopy can provide measurement repeatability of well below 10 nm. However, the gathered image is not always a true image of the real structure. The image depends very much on the intricate interaction of the structure with the optical field in the focal region. In particular for the case of semi-transparent structures, such as photoresist, accurate measurement of the size proves to be more difficult. In this case the structure reflects only a fraction of the incoming light and the signal is mainly determined by the underlying layer. If this is a metal layer (e.g. aluminium) which reflects more than 90 % of the incoming light, the influence of this layer is observable even in a region of more than 1.5 micron outside the geometrical focus. Therefore the light reflected by the substrate interferes coherently with the light reflected by the resist structures and both signals cannot be separated. The real shape of the resist edge is not correctly imaged and an accurate measurement is difficult. The purpose of this paper is to analyse this effect in detail and present an optical arrangement in which the reflection of the substrate is suppressed with respect to the reflection from the air-resist interface.

The main purpose of the (TSSM) is to confine illumination, in effect, to just the plane of focus of the specimen, also a major purpose of the tandem scanning microscopes based on pinhole field apertures. However the TSSM achieves this end by a different method, with possible advantages in both cost and performance. It can be thought of as an epiillumination tandem scanning pinhole microscope with substitution of the pinhole apertures by slits, and substitution of the beam splitter (which makes the mirror image of one field aperture coincident with the other) by an opaque mirror. This mirror is placed with an edge in the plane defined by the viewing slit and the center of the objective aperture, so that the mirror reflects light from the illuminated slit onto just one semicircle of the objective aperture, the remaining semicircle used for projecting light from the specimen to the viewing slit. The illuminated volume of the specimen is then non-intersecting with the viewable volume except where these volumes intersect at the image of the illuminated slit, only in the plane of focus. Scanning can be accomplished by reciprocally rotating the two slits and the mirror as a light weight, rigid assembly. Advantages relative to raster scanned confocal microscopes include 1) scanning in just one dimension, 2) no need for electronic sensing and display of the image, 3) production of a real time, actual color, direct optical image, without raster lines or pixel boundaries, and 4) utilization of a single, inexpensive, broadspectrum light source for reflected light and for a wide variety of flourescent dyes. Relative to the Petran/Hadraysky multiple pinhole microscope, advantages include 1) ease of fabricating slit apertures which cause no visible noise in the image, 2) ease of adjusting these apertures to optimize, for each specimen, the tradeoff between image brightness and focal plane specificity, 3) shorter effective photographic exposure times (because with a single sweep, each point in the specimen is exposed just a fraction of the total sweep time) , and 4) better out-of-focus light rejection at large distances from the plane of focus.

A new kind of contrast for an optical microscope is presented. It can be realized by first imaging a rotating grating onto the object and then imaging the grating together with the object to a second rotating grating positioned in an intermediate image plane. The image of the first grating must be congruent with the second one and the rotating velocities of the two gratings have to be slightly different. Hence a beat frequency will occur in those areas where the contrast of the first grating is not diminished too much by the corresponding object fields. This kind of procedure may be called simultaneous heterodyne detection. The "carrier frequency" is presented by the first grating, which is modulated by the optical properties (reflection, transmission, de-fraction etc.) of the object. After mixing the "carrier wave" with the "reference wave" (presented by the second grating) the image intensity varies with the beat frequency which carries the image information. A video camera is synchronized with the beat frequency so that image pick up will take place only at the maximum and minimum of the image intensity. The difference of the two images will finally form the required image. It is proved within the validity of incoherent approximation that super-resolution is possible.

A scanning optical microscope based on the optics and the mechanics of a Compact Disc player has been constructed. The light and simple construction of a CD player offers the possibility of scanning essentially the entire microscope with respect to a stationary object. The microscope is capable of measuring amplitude and phase changes of the light and is equipped with automatic focussing.

A confocal microscope can be considered as a 3-D sampling instrument to collect data from spatial structures, especially biological ones. Optimal performance requires the adaptation of the dimensions of the sampling volume to the lateral and axial raster parameters employed during data collection. It will be shown that the shape of the sampling volume can be controlled through optical means by a combination of specific illumination and detection parameters. The use of these techniques in computer controlled instruments is discussed, especially in relation to operation in fluorescence.

Laser scanning technology is a key technology in optical information systems such as optical disc storage and laser beam printers. Higher speed and higher resolution are always requested. In laser beam printers,dual beam laser scanning with a rotationally asymmetric aspheric surface is introduced to achieve these requirements. In optical disc systems, the mechanical actuator is eliminated and an electronically controlled surface acoustic wave (SAW) deflector is introduced.

The evaluation of magneto-optical thin films in dynamic write-read tests requires an exact knowledge of the noise sources of the system. For common grooved plastic disks there is a superposition of two dominant noise contributions - disk noise and writing noise -which can not simply be distinguished in the signal spectra. A particular measuring method is described which allows the analysis of noise spectra of power and magnetic field scans on unstructured disk regions where the phenomenon of writing noise can easily be studied. A number of noise measurements comparing ungrooved with grooved parts on the same disk are discussed. The effect of writing noise is shown to result from unsmooth boundaries and length variations of thermomagnetically written domains. This effect is most drastically seen near the writing threshold in the bias field scans.

In this paper we are presenting a simple model of an optical tomographic memory. Tomography, which is usually used to obtain the information from the natural object (like human body), is used here to retrieve the information previously artifically stored in a volume media. Memory readout is done in incoherent white light, by detecting the intensity of the radiation transmitted in various directions through the memory.

A flying type optical head on an air bearing slider is proposed for phase-change recording media. Data signals are detected as light output switched by the light reflected back from the medium. The head consists of a beam-converging laser diode and a photodetector. The full widths at the half-maximum of the near field pattern of the laser diode are 0.8 μm and 1 μm. This paper clarifies the head signal detection mechanism. Signal amplitude variation due to the flying height change is reduced to less than 30% and signal-to-noise ratio is sufficiently increased by decreasing the reflectivity of the laser facet facing the medium to less than 5%. Furthermore, OSL head track error signal using the sampled servo method is successfully detected.