Depth-dose model

The depth-dose model allows the gel energy Eg of a resist to be calculated from an observed interface gel dose Dg under conditions of zero backscatter and predicts a dependence of Dg on accelerating voltage going as which agrees reasonably well with experiments. Calculations of... 

Calculation of G -values from the results shown in Figures 2 and 3 requires determining the amount of dose absorbed in the film for a given incident dose. Bowden (7) has shown, using the depth-dose model of Heidenreich, (9) an accurate measure of the energy absorbed in a polymer film can be determined. An example of such a calculation for polystyrene is given in the appendix. 

Electron beam irradiation has been carried out with an electrocurtain accelerator manufactured by Energy Sciences, lnc.(model CB/150/15/180). The samples were placed on steel plates in aluminum trays and passed through the conveyor system of the electron beam apparatus. The maximum available dose per pass was 20 Mrad, hence, for the highest dose used in this study(40 Mrad), two passes were utilized. In light of the depth-dose profile at 175 kilovolts electron energy level of the EB system, the radiation dose will be nearly unifiorm throughout the sample thickness(3 mil). 

The depth profiles in Fig. 3.26 show that the typical flat channeling implantation profile is generated with low doses only. Increasing the dose superimposes the normal implantation profile shape. Undertaking such experiments with homogeneous wafers enables the production of calibrating models for semiconductor production. 

Figure 6. From figure 11 of Kylling et al. 1998. The ratio between simulated Brewer and Bentham UVB dose rates with and without aerosols as a function of the aerosol optical depth at 355 nm. Ratios of model results with aerosol single scattering albedo of (0.95 solid line), 0.87(dotted line) and 0.80 (dashed line) versus aersosol free model results are shown for solar zenith angle of 10° and an ozone column of 340 DU.

There was one report that at very high doses some central effects were indeed observed. With quantities in the several hundreds of milligrams a picture emerged of changes in perceived color and depth perception, but without euphoria. It was said to resemble a mild dose of ketamine. This is an interesting comment, in that ketamine has found its major medical use as an anesthetic, and MDHOET is among the most effective of all the N-substituted MDA derivatives assayed in several animal analgesia models. 

Gas bubble formation and blistering effects have been widely observed in high-dose implantations of inert-gas ions. Backscattering measurements of depth distributions often show very low concentrations of implanted species in the nearsurface region. This indicates that the inert-gas atoms can escape from the material even without sputtering. In these cases, the simple model described in the previous sections does not apply. 

Another exposure model was proposed by Byers et al. In this model, the exposure dose is first converted into an effective dose, which is coupled into the resist as a function of depth. The depth dependence of the exposure dose D(z) is expressed in terms of a simplified form of the full standing wave equation, given by... 

Validity. To prove the applicability of the model, the first in situ measurements were performed in the Neckar, an impounded river, under almost stationary flow conditions. A tracer (Rhodamine B) was dosed into the eflluent of a sewage treatment plant. The outlet of the channel was situated at the right bank of the river with an angle of 35° between the river axis and the channel. The concentration proflles in a transverse direction were measured with a fluorometer installed on a boat. Preliminary measurements showed that the river is well-mixed along the depth, so that a sample taken at a depth of 1 m could be considered representative. The discharge of the river was 51 m /sec and the discharge of the treatment plant was 1.2 m /sec. 

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