Etch depth determination

Srinivasan etal.,64 in a phenomenological development, split the etch rate into thermal and photochemical components and used zeroth-order kinetics to calculate the thermal contribution to the etch rate. An averaged time-independent temperature that is proportional to the incident fluence was used to determine the kinetic rate constant. The photochemical component of the etch rate was modeled using, as previously discussed, a Beer s law relationship. The etch depth per pulse is expressed, according to this model, in the form... 

Deviations between the actual ablation rates and those predicted using Eq. (2) occur at higher fluences. 64 65 Hence, a different rate equation is required to determine the relationship between amax and fluence. According to a rate model proposed by Sauerbrey and Pettit,46 the etch depth per pulse is given by... 

Figure 18. Experimental procedure (a) and stylus thickness measurement (b) for determining etch depth.

This conclusion was tested with a practical experiment in which the erosion yield of polystyrene under exposure to the effusive plasma source was measured with and without the addition of the pulsed hyperthermal Ar beam. In this experiment, the Ar beam pulse was not chopped, so the entire beam pulse produced from the laser detonation source was allowed to strike the surface. The erosion yield was determined by placing a screen over the samples during exposure and measuring the etch depth... 

The threshold fluence (FTh) was specifically determined for thin films, because for the transmission measurements thin films were used. The threshold fluence is normally determined from a linear plot of the etch depth d(F) vs In F according to Eq. 1. 

Ar etching rate of organic and inorganic is anticipated to be different, which results in preferential removal of organic and enrichment of inorganic with etch depth thus conq>romising the absolute determination of elemental composition with depth. 

The determination of oxygen in tungsten by helium-3 activation is described by Vandecasteele et al. (247) and by Revel and Albert (240). Vandecasteele et al. (247) irradiated for 20 min with a 1.5 mA beam of 20 MeV helium-3. The sample was chemically etched in a 1/1 mixture of hydrofluoric and nitric acids, rinsed and dried. The energy corresponding to the etched depth was 13.5 - 14.2 MeV. The sample was dissolved in a mixture of 10 g of sodium hydroxide, 400 mg of sodium fluoride and 2.5 g of sodium nitrate in a nickel crucible. The melt was dissolved in nitric acid and F was... 

Surface features can also be revealed by etching, which permits identification of points of intersection of line dislocations with the surface, and this is valuable in determining the role of these imperfections in chemical processes [45,214] and, in particular, nucleus formation. Smaller topographical details can be rendered visible by the evaporation of a thin (<0.5 nm) film of gold onto the surface [215,216]. Heights and depths of surface features can be determined by interferometry [203—205]. Microcinematography has also been used [217] to record the progress of solid phase reactions. 

Silicon-based pressure sensors are amongst the most common devices making use of this process. A thin low-n-doped epitaxial layer on the wafer determines an etch stop depth and thus the thickness of e.g. the pressure sensor membrane. 

Depth profile and total content of oxygen in PE was determined by RBS method. The profiles of plasma-treated sample and that subsequently etched in water are compared in Figure 9. The mean oxygen contents in the surface layer accesible by RBS, ca 140 nm thick, are (39 5) and (28 3).10 cm" for plasma-treated and water etched samples respectively. Both concentration profiles exhibit a maximum at the depth of ca 20 nm, further the concentration decreases slowly, falling to negligible concentrations at 60 nm. Similar trend was observed in previous report dealing with PE exposed to Ar plasma at the power of 1.7 W [70]. 

The quality of the relief thus obtained can be determined directly in the course of etching because the light reflected from the etched grating produces a diffraction pattern that characterizes the depth and shape of the grating profile at any given moment. To this end, one has just to measure the intensity of the reflected light. The method possesses a high sensitivity the occurrence of the relief can be detected when its depth is only of the order of 0.01 /an. 

The determination of structure and bonding of polymer anchored catalysts is another area where the insolubility of the materials often precludes solution spectroscopic studies and one is limited to techniques that can be applied to irregular solids (57). In addition, combining oxygen plasma etching and surface analysis allows investigation of the depth of penetration of the metal into the polymer and allows detection of components that require concentration to allow detection. 

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