Gradient techniques scanning

In this paper, we report the evolution and quantification of the step-height-reduction-ratio, and subsequently extract the planarization distance for copper CMP for the first time. Conventional profilometry and the InSiteSOO photo-acoustic measurement tool were employed to quantify copper film thickness and topography. The Insite 300 operates upon the transient gradient technique and allows for noncontact, nondestructive metal film thickness measurement [5]. The utility of this metal thickness tool bypasses a number of issues which arise with conventional profilometry. The ability to accurately delineate metal feature edge positions and circumvent stress-induced curvature present in long profilometry scans is of principle importance. 

The limitation of the resolution by signal decay in the absence of a gradient applies only for frequency encoding of the space information, that is for the space dimension which is acquired directly (cf. Section 2.3.4). For indirect detection of the space information by phase encoding with the spin-warp technique, the spatial resolution is unrestricted in theory. It is determined just by the range of gradient values scanned in the experiment. Apodization techniques can be used for giving the voxel the desired shape (cf Section 6.2.4) [Marl]. 

In addition to measuring the distance between peak apex and baseline, a vertical readout also can be taken at any section of the ascending or descending part of a peak. Such an additional peak dimension H = k C) is exploited in the FIA gradient techniques (cf. Sections 2.4 and 2.5). Further information or peak dimensions can be obtained by taking vertical measurements not only at one detector channel, such as a fixed wavelength, but by scanning an entire spectrum. 

Thin-layer chromatography (TLC) is used both for characterization of alcohol sulfates and alcohol ether sulfates and for their analysis in mixtures. This technique, combined with the use of scanning densitometers, is a quantitative analytical method. TLC is preferred to HPLC in this case as anionic surfactants do not contain strong chromophores and the refractive index detector is of low sensitivity and not suitable for gradient elution. A recent development in HPLC detector technology, the evaporative light-scattering detector, will probably overcome these sensitivity problems. 

Wet samples can be analyzed without a previous preparation by the so-called environmental scanning electron microscopy (ESEM). In this technique, instead of the vacuum conditions, the sample chamber is kept in a modest gas pressure (Bache and Donald, 1998). The upper part of the column (illumination source) is kept in high vacuum conditions. A system of differential pumps allows to create a pressure gradient through the column (Bache and Donald, 1998 Stokes and Donald, 2000). The choice of the gas depends on the kind of food hydrated food is kept under water vapor. 

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