Wafer inspection

In this chapter we discuss double-crystal topography, in which we obtain a map of the diffracting power of a crystal compared to that of a reference. We first treat the principles and geometries, the mechanisms of image contrast and resolution and the ttse of laboratory and synchrotron radiation. We then discuss applicatiorrs wafer inspection, strain contour mapping, topography of curved crystals. 

Matthew Marcus (center) received his PhD. in 1978from Harvard and joined Bell laboratories the same year. At Bell Labs, he worked on a variety of problems in materials science, with an emphasis on structure. Some of these problems include the structure of the liquid crystal blue phase, the precipitation kinetics of in Al films (probed by EXAFS), the relation between local structure and luminescence of Er in silica and silicon, and the structure and vibrations of nanoparticles of Au and CdSe. His contributions to EXAFS technique include methods for preparing samples and improved methods for fitting sets of data taken at different temperatures. In 1998, he left Bell Labs to work for KLA-Tencor, helping develop a new kind of PEEM-related electron microscope for wafer inspection. In 2001 he took on the position of Beamline Scientist at the Advanced Light Source, where he collaborates on environmental and materials problems using an X-ray microprobe. 

In order to avoid the specimen size limitations imposed by both the DS-130 top stage and SS-series HR operating mode (8mm diameter X 5mm high), a new objective lens, in which the magnetic center lies outside the polepiece gap, has been developed. Cg and values obtained at a working distance of 3mm are similar to those of the SS-series in the HR mode. This lens is incorporated in the ISI IC-130 semiconductor wafer inspection SEM, which has recently been introduced. 

After appropriate annealing, each LEC and VGF crystal is subjected to an intensive seed- and tail-end wafer inspection program that includes structural control, measurement of electrical parameters and other physical and chemical properties relevant for device manufacturing. Spot checks of wafers between seed and tail are carried out additionally. All data are stored in a data base for continuous and detailed evaluation in relation to technological synthesis, crystal growth and watering parameters. 

The following sections give examples of a number of applications ofX-ray diffraction imaging and wafer inspection (XRDI). 

SAM) and TEM. An Auger electron spectrometer with high spatial resolution imaging capability was developed especially for the detection of small particles and defects which might be present in the ULSI regime this enabled the inspection of wafers up to 200 mm in diameter [2.150]. 

Single etch pits can be inspected and counted under an optical microscope, as shown in Fig. 2.7b. The scattering of light shining onto a wafer surface under a... 

Raman samples were prepared by peeling SiNW thin films off the silicon wafers to avoid Raman signals from the silicon substrate. A razor blade was used to shave the thin films on top of the silicon wafers. The thin films were mounted on a carbon tape for SEM and Raman inspection, or on a transparent Mylar film for Raman measurements. 

The n-type GaP used was a single crystal in the form of wafers, 99.999%pure and doped with sulfur to the concentration of 2 to 3 x 1017 cm-3 (Yamanaka Chemical Industries Ltd.). The p-type GaP used was doped with zinc to 3.7 x 10 cm 3 (Sanyo Electric Co., Ltd.). Both were cut perpendicular to the [lll]-axis. The ohmic contact was made by vacuum deposition of indium on one face of the crystal, followed by heating at ca. 500 °C for 10 min. The side connected with a wire was covered with epoxy resin. Before the experiment, the crystals were polished and etched with warm aqua regia. The (lll)-face (Ga face) and the (lll)-face (P face) were distinguishable by microscopic inspection of the etched surfaces, the former very rough and the latter smooth. 

One lot of 25 wafers has been polished on two different oxide CMP tools using two different oxide CMP slurries. The 13 wafers polished on the second CMP tool show zero final test yield. You have inspected the wafers and even did defect classification and have not seen any difference at the time and still see no difference in revisiting all the data you have collected. What could have happened Find and explain two different possible scenarios. 

The metal films polish rates (Ti, TiN, and W) were measured on Prometrix 4-point resistivity probe. Oxide loss on blanket and fully integrated wafers were measured on KLA-Tencor UV1280. In-line SEM was used for defect inspection. 

First, no planarization is achieved for feature sizes above 4.5 mm. For feature sizes 1.0 mm to 4.5 mm, only partial planarization is possible, and with the exception of the 3, 3.5 and 4 mm structures, its effectiveness increases monotonically with feature size reduction. And finally, for feature sizes 1.0 mm and below, nearly constant planarization efficiency was achieved, as the trench depth was reduced from 0.8 pm to zero. We believe that the irregularity in our experimental data for 3-4 mm feature sizes was caused by an error in the exposure. This caused each of these structures on wafers from this particular lot to be actually composed of two smaller trenches with slight separation, as evidenced from visual inspection of the pre-polished wafers. 

This system employs a simultaneous film thickness measurement method, which incorporates a two-dimensional CCD camera detector , a variable wavelength light source, and an analyzer for the captured image data. With this configuration the system can, not only measure test pattern film thickness but also be used for a variety of visual wafer checks and film data inspections for Cu and other metal films during metal CMP. Moreover, we now have evidence that the system may even be able to handle moving wafers. With such potential, this system could evolve into a true In-Situ Monitor which measures film thickness inside the CMP unit itself with the same precision and accuracy. 

Most electrical characterization techniques require physical contacts between the wafer and the measuring instrument. They can be nonpermanent contacts (e.g. four-point probe) or permanent contacts (e.g. evaporated metal). For some applications such permanent contacts are not permissible. They may, for example, create damage or leave residues that are deleterious during subsequent processing. Non-contacting methods allow complete inspection of all wafers because no physical contact is made. 

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