Exposure characteristics

No tests available, but history may help to identify source and exposure characteristics (majority of incidents generating exposures to humans involve trucking with labels on vehicle). 

Table IV compares the X-ray exposure characteristics (at 8.3 X, Al Kai,2 emission line) of the halogenated resists and of PMMA Elvacite 20U1. It can be seen that poly(2-ehloroethyl methacrylates) and poly(2-bromoethyl methacrylates) exhibit a low sensitivity unlike poly(2-fluoroethyl methacrylates) and poly(2-, 2-,2-trifluoroethyl methacrylates) which are more sensitive than PMMA as shown in Figures 2a, 2b, 2c, 2d where the dose-thickness curves of these resists are plotted. The low sensitivity of the PC1EMA and PBrEMA samples may be explained by some competing crosslinking reactions which could occur during exposure as a result of C-Cl and C-Br homolytic bond scissions as noted by Tada...

Table IV. X-ray Exposure Characteristics (at 8.34 A A1 Ka,2 emission line) of the Poly(haIogenoalkyl methacrylates) and of PMMA Elvacite 2041"...

Delayed neurologic and psychiatric disorders following acute arsine exposures have been reported (Frank 1976). Exposure concentrations were not provided, but duration of exposure ranged from 10 to 90 min. Within hours after the exposures, characteristic signs of arsine poisoning (e.g., hemolysis and hematuria) were observed. Polyneuropathies and neuropsychiatric syndromes were detected at 1-36 mon after the acute exposures to arsine. 

Figure 2 shows the exposure characteristics for azide-styrene resin resist film with an azide concentration from 10 to 40 wt% (based on the styrene resin weight) and Figure 3 shows the contrast of the resist films as a function of the azide concentration. Development was done with a 60s immersion in 0.83% TMAH solution. The styrene resin matrix alone has been found to be a negative deep UV resist. However, rather low contrast (1.48) and low sensitivity (2.5 J/cm2) are observed. The contrast and the sensitivity of the styrene resin is remarkedly increased by adding the azide, as shown in Figures 2 and 3. 

Figure 2. Effect of azide concentration on exposure characteristics for azide-styrene resin resist of 1.0 micron film thickness.

Two component, positive photoresists (see Section 3.5.b) represent systems with unusual exposure characteristics caused by the standing wave effect (see Section 2.1.f) and "bleaching" or change in optical density during exposure (see Sections 3.5 and 3.9). Both of these phenomena result in nonlinear exposure throughout the thickness of the resist film, and result in uneven developing rates as a function of film thickness, making evaluation of these systems difficult. 

A number of approaches have been suggested to combine the exposure to chemicals that act by a similar mechanism of action but have different potencies and exposure characteristics (US-EPA 1999, 2000a,b). Wilkinson et al. (2000) have critically evaluated these approaches. 

Figure 1 shows the exposure characteristics of atactic and isotactic poly(a,a-dimethylbenzyl methacrylate) resists with CH3ONa development together with those of the poly (methyl methacrylate) resist with MIBK/IPA development. Poly(a,a-dimethylbenzyl methacrylate) s showed high sensitivity and very good contrast between exposed and unexposed areas. The atactic polymer with alkaline development was improved in the sensitivity and 7-value by a factor of more than three over poly(methyl methacrylate) with MIBK/IPA development. 

Figure 1. Exposure characteristics of poly (methyl methacrylate) (PMMA), and atactic and isotactic poly(a,

Table IV. Electron-beam Exposure Characteristics of Copolymers of a,a-Diphenylethyl Methacrylatef ) with Methyl Methacrylate ( /2) ...

Table VII. Electron-beam Exposure Characteristics of Copolymers...

Table VII the electron-beam exposure characteristics are given for the soluble poly (triphenylmethyl methacrylate-co-methyl methacrylate)s. The sensitivity on alkaline development was strongly influenced by the copolymer composition. The highest sensitivity was obtained on the copolymer containing 93.7 mol% methyl methacrylate. The copolymer of highest sensitivity showed the 7-value of 6.3, which was nearly twice as large as that for poly(methyl methacrylate). Formation of methacrylic acid units on exposure is obvious from the infrared spectrum. However, the mechanism of the occurrence should be different from the case of the a,a-dimethylbenzyl methacrylate polymer since there are no /3-hydrogen atoms in the triphenylmethyl group, and may be similar to the case of poly (methyl methacrylate). This will be explored in the near future.

Aldehyde Copolymer Self Developing Electron-beam Resists. The ceiling temperature for the copolymerization of aliphatic aldehydes is usually below 0°C and the copolymers are easily depolymerized into monomeric aldehydes above 150°C under vacuum. This depolymerization into monomers also occurs on electron-beam or X-ray exposure as evidenced by combined gas-liquid partition chromatography-mass spectrometry. As a result, the copolymers of aldehydes behaved as self-developing positive resists and almost complete development was accomplished without any solvent treatment. Electron-beam exposure characteristics of the aliphatic aldehyde copolymers studied here are... 

Figure 1. Exposure characteristics of EP resist, (a) no curing, (b) cured in...

Langard S. 1993. Role of chemical species and exposure characteristics in cancer among persons occupationally exposed to chromium compounds. Scand J Work Environ Health Suppl 1 81-89. 

The two basic types of analytical studies are the cohort and the case-control study. Each lias strengths and weaknesses as well as different resource and time requirements. The cohort study involves the study of individuals classified by exposure characteristics, e.g., a group of welders. The study then follows the development of disease in the welders group as well as in an unexposed comparison population. The mciisure that assesses the magnitude of... 

Novolac- or phenolic resin-based resists usually show no pattern deformation induced by swelling during development in aqueous alkaline solution. Examples of such resists are naphtho-quinonediazide/novolac positive photoresists, novolac-based positive electron-beam resist (NPR) (1), and azide/phenolic negative deep-UV resist (MRS) (2). Iwayanagi et al.(2) reported that the development of MRS proceeds in the same manner as the etching process. This resist, consisting of a deep-UV sensitive azide and phenolic resis matrix, is also sensitive to electron-beams. This paper deals with the development mechanism of non-swelling MRS and its electron-beam exposure characteristics. 

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