In manufacturing devices used in the data storage, semiconductor, and flat panel display industries, thin layers of materials are deposited on a particular substrate. These films may consist of semiconductors, dielectrics, polymers, dyes, (photoresist, resin, etc.), color filters, and metal films. In addition to silicon, substrates may consist of glass, quartz, poly-carbonate, or PET. In order to optimize the performance of these devices, an effective thin film characterization method is needed that can measure these thin film structures. We will present a technique that determines, thickness, spectra of n and k from 190 to 900 nm, E_g, and interface roughness of the 'film/substrate' combinations used in the aforementioned industries. This technique is based on wide-band spectrophotometry, combined with spectral analysis incorporating the Forouhi-Bloomer dispersion equations for n and k. The technique offers an excellent signal to noise ratio even in the deep UV wavelength range (below 350 nm) and takes 1 second for the entire measurement.

Scanning Reflectance Analysis^TM (SRA^TM) is an emerging technique that has been rapidly gaining acceptance as a powerful tool for the analysis of thin film disks. This is because the technique provides a means to generate high resolution maps of the thickness and composition of lubricant, overcoat, and contaminant films on a disk in about ten seconds. Common quality assurance applications have included overcoat thickness, composition, and uniformity measurements as well as substrate polish quality measurements and stain identification. Applications in failure analysis have included lubricant pooling and degradation, carbon wear, corrosion, and contaminant detection. This paper will focus on the design and principle of operation of a SRA. The discussion will include the general theory that governs the machine's design and the data it produces as well as some details that maximize performance and simplify data interpretation. Following this, a few example applications of the technique will be presented.

Surface Reflectance Analysis (SRA) is an emerging optical inspection technique for studying and quantifying the composition and thickness uniformity of thin films on surfaces. This article will concentrate on measuring the uniformity of amorphous carbon overcoats on thin film magnetic disks. SRA is in essence a high speed ellipsometer with scattered light detection capability. We will show how this technique can be used for mapping the uniformity of deposited film thickness, while simultaneously giving information about the uniformity of the film composition. Composition and thickness variations can be related to the geometry of the sputtering system used to deposit the carbon films. Obviously, variations in sputter conditions also give rise to thickness and composition variations. We will also discuss the application of SRA in the analysis of localized film thickness variations such as defects in the deposition process or local wear of the films. Other applications of SRA include analysis of substrates and oxide films on silicon wafers. The principle of operation, the data interpretation and data analysis procedures of the SRA technique will be discussed in detail.

Organic contaminants can affect semiconductor wafer processing including gate oxide integrity, polysilicon growth, deep ultraviolet photoresist line-width, and cleaning & etching steps. Organophosphates are known to counter dope silicon wafers. Organic contaminants in disk drives can cause failures due to stiction or buildup on the heads. Therefore, it is important to identify organic contaminants adsorbed on wafer or disk surfaces and find their sources so they can be either completely eliminated or at least controlled. Dynamic headspace TD-GC-MS (Thermal Desorption-Gas Chromatography-Mass Spectrometry) methods are very sensitive and can be used to identify organic contaminants on disks and wafers, in air, or outgassing from running drives or their individual components.

In a disk drive magnetic read/write is achieved with a magnetic head flying closely over a magnetic disk. As area 1 recording density is increased to several Gbits/In², the dynamic flying height of the magnetic head is reduced to one (mu) -inch or less. Bumps taller than one (mu) -inch often results in head crash. Since the DLC coating on the magnetic disk surface is less than 10 nanometers in thickness, pits with depth over 10 nanometers cause damage to the magnetic layer. To prevent head crash or missing bit errors, magnetic disk surface needs to be examined for bumps taller than the dynamic flying height and pits deeper than the DLC thickness. In this paper, we report experimental results using a head with an MR sensor flying over a disk with precision bumps and pits micro-fabricated on the disk surface. Non-contact signal disturbances of the MR sensor flown over variable area square pits and bumps on the 2400 Oe media exhibit both magnetic and thermal signal characteristics. The lateral sizes of the pits and bumps obtained using the MR magnetic signal measured from a Phase Metrics MG250 tester agree well with those measured with an Atomic Force Microscope (AFM). The thermal signal characteristics of the pits and bumps are of opposite polarity, and scale in a non-linear fashion with the lateral size of the surface defects. Some preliminary experimental results involving naturally occurring surface defects and Phase Metrics' optical scatterometry tester PS5100 are also discussed for comparison purposes.

This paper briefly reviews the use of a verified model to investigate light scatter metrology to detect the presence of defects in semiconductor circuit vias. Three types of defects are examined. Although defects can be detected, there are practical problems associated with separating defects from acceptable changes in dielectric film thickness.

Accurately sized PSL spheres of several diameters are deposited on disks. Scatter from the depositions is measured and compared to the results of a model for surface bound particles. The results are important for two reasons. The measurements will help provide an early database for determining the smallest detectable particles for a given disk texture. Secondly, the use of these particular PSL spheres, which have been accurately sized to about 1% of their diameter, will be important for establishing particle standards for the disk industry.

Bidirectional ellipsometry has been developed as a technique for distinguishing among various scattering features near surfaces. Employing incident light with fixed polarization, the technique measures the principal angle of polarization and the degree of linear polarization of light scattered into directions out of the plane of incidence. This technique has been previously shown to be successful at distinguishing between subsurface defects and microroughness. Theoretical models have predicted that the polarization of light scattered by particles should also be different than that scattered by subsurface defects and microroughness. In this paper, experimental results will be presented which show good agreement with these models for a range of sizes of polystyrene latex spheres on silicon wafers. The results demonstrate that the polarization of light scattered by particles can be used to determine the size of particulate contaminants on silicon wafers and other smooth surfaces. The model calculations, based on different degrees of approximation, demonstrate that the mean distance of a particle from the surface is the primary determinant of the scattered light polarization for small scattering angles.

Demand for faster disk drives with bigger storage capacity calls for higher quality of aluminum disks used in their production. Accordingly, decreasing tolerances on disk flatness and tighter specifications on defect presence (pockets) must be met by aluminum bland suppliers. At the same time volume of production is growing requiring automated quality control at high speed. Veeco Process Metrology has developed high performance automated 95 mm aluminum blank disk tester based on Twymann-Green interferometer working a wavelength of 10.6 micrometer. It is a fully automated tool for high volume production with throughput of one disk per second. Lateral resolution of 0.6 mm in the disk plane allows flatness and shape testing as well as pocket detection. The use of long wavelength makes interferometer insensitive to environmental vibrations and dust. Vertical accuracy of instrument is 300 nm (PV) and repeatability is 130 nm (RMS). In this paper we present technical design issues and metrological capabilities of the device. The interferometer is supplied with new automated analysis software which automatically detects defects on the disk surface (pockets) as small as 0.5 micrometer in depth and performs shape categorization.

Requirements on wafer flatness, like most semiconductor specifications, are becoming increasingly tight, with greater accuracy and resolution needed for measurements. In addition to traditional peak-to-valley surface deviation and root-mean- square roughness measurements, it is desirable to measure the flatness of silicon wafers over a small area, or site flatness. This involves dividing the wafer into many sub- regions and calculating the surface statistics for these smaller regions in addition to the overall wafer statistics. Veeco Metrology has developed a high-resolution phase-shifting laser Fizeau interferometer for site flatness testing. The system is designed with 40 mm X 40 mm square field and a 1000 X 1000 pixel CCD camera. Features as small as 100 micrometer may be measured by the system with high resolution, repeatability, and accuracy. A motorized stage allows any region of the wafer to be measured by the system such that problem areas do not escape measurement. This paper discusses the overall system design and presents data from the wafer flatness tester developed by Veeco. Data on lateral resolution, vertical repeatability and accuracy are presented. In addition, the site flatness statistics of a silicon wafer measured by the instrument are given.

For quality inspection of polished surfaces as applied in semiconductor and optical industry, various methods are used for a fast detection of microroughness, defects, and contaminations. With the aid of stray light sensors the intensity distribution of the reflected and scattered light, i.e. the BRDF, is measured. The probability distribution of values of a BRDF is parametrized to obtain a measure for roughness and for classes of defects. There is still need for justifying the choice of statistical moments to characterize and finally to classify different surfaces. Of course, a basic quantitative, i.e. metrological understanding of stray light sensors is necessary. The power spectrum of surface topographies sufficiently smooth to obey Rayleigh-Rice approximation is proportional to the BRDF. Therefore a comparison was only carried out with sample surfaces obeying this approximation. Defects and contaminations with lateral sizes smaller than the wavelength of the illuminating light employed in the stray light sensor, however, could not be analyzed within this investigation. We have measured the topography of large areas up to 600 micrometer X 100 micrometer with an AFM by patching several scans (up to 8) with overlap. BRDFs evaluated from AFM measurements agree well with BRDFs measured with a stray light sensor.

The spatial frequency response, height sensitivity and system noise of a scanning common-path interferometer have been studied. The impulse response function and the frequency transfer function of the system are obtained analytically using Fresnel diffraction integral. Experimental results are also given. The results show that the system covers a broad spatial frequency range from 2 X 10^-5/micrometer to 3/micrometer. The height sensitivity of the system is better than 0.01 angstrom. System stationary noise less than 0.1 angstrom RMS is achievable without additional noise reduction post-process. Measurement of an ultra-smooth silicon substrate with a sub-angstrom roughness is successfully demonstrated. Measurement of a smooth glass substrate is also shown.

Roughness on silicon wafers is becoming a critical surface parameter with the advent of improved semiconductor processes. Roughness levels in the order of 1 angstrom are routinely manufactured, challenging the limits of some micro-roughness measurement technologies. Additionally, measurement is moving from R&D and Q.A. areas into the manufacturing line placing more emphasis on speed of analysis, robustness, correlation and repeatability of the various techniques. This paper attempts to identify, review, and correlate suitable techniques for measurement at such low levels of micro- roughness. The strengths and weakness of each technique from a production viewpoint are also touched upon. Wafer roughness measurements were used to characterize a set of semiconductor wafers with a varying dopant and process characteristics. One hundred, 8' bare wafer samples with various dopants were prepared for measurements in the order of 1 angstrom to 2 angstrom. The samples were then measured with different methods using total integrated scatter (TIS), atomic force microscopy (AFM), interferometry (IF) and optical profilometers (OP). These techniques differ in many ways in their assessment of surface roughness and the results from each technique are presented and a discussion of the correlation issues between the different measurement systems is given.

This paper describes the design and performance of a compact new multi-plane scanning slit Beam Profiler. It allows simultaneous real-time measurement of M² beam quality, focus position, beam-waist diameter and axial alignment, solving problems in the active adjustment and verification of tightly focused laser beams. The DataRay BeamM²AP^TM measures preset pass/fail criteria with sub-micron accuracy at greater than 5 Hz update rate. It is suited to the development, QA and production of precision focused laser assemblies for applications such as disk/wafer characterization, laser printing, etc.