Focus latitude

Ultrathin resists have many technological advantages In optical lithography they offer improved exposure and focus latitude (2), and alleviate the problem of... 

Figure 12. KRS 250nm L/S images from 16 to 21 mj/cm with 1.2 micron focus latitude.

Figure 8. Lithographic performance of the resist formulation PHS-BP (12% Mw = 50(X)) Photoacid generator TPS-TF MSII (0.5NA) exposure data Dose and focus latitude for 0.25 pm L/S and the masking linearity.

This presentation focuses on the vertical distribution of halocarbons obtained by analysis of cryogenically collected whole-air samples. The balloon-borne cryogenic samplers developed and flown by the Max-Planck-Institut fur Aeronomie (MPAE) and the Kem-forschungsanlage Jiilich (KFA) are described by Fabian [17] and Schmidt [18]. Between 1977 and 1993, a total of 33 balloon ascents have been carried out by both institutions, 28 at northern midlatitudes (southern France, 44°N), 3 at high latitudes(Kiruna, 69°N) and 2 in the tropics (Hyderabad, 17,5°N). These stratospheric data are limited to balloon altitudes, i.e. up to about 35 km. Tropospheric data were obtained from balloon samples, samples collected aboard aircraft and at ground level. 

Although DNQ-novolac systems were first used more that 40 years ago in the printing-plate industry, they continue to be the focus of significant interest. For example, several recent studies have addressed the optimization of novolac properties through manipulation of molecular weight, isomeric structure of the phenolic starting materials, and methylene bond position (26-28). These changes are reported to influence resist sensitivity, contrast, and process latitude. 

The discussion below specifically focuses on application of the model to low latitude (<35°N or S) examples, in order to further validate the global model. There are several reasons for emphasizing this latitude range and not higher latitudes. First, tropical latitudes are more... 

Note After Bierman (1994), Gosse and Phillips (2001), and Lai (1988). See Gosse and Phillips (2001) for details about radionuclide decay constants and production rate uncertainties. Isotopes in italics are those that have been used routinely in cosmogenic nuclide studies. Stable isotopes will resolve paleoaltimetry for Cenozoic and older rocks. High-latitude, sea-level rates from empirical studies only. Production mostly via neutron spallation unless noted. Recent debate on die half-life of 10Be has focused on whether this number is off by >10%. 

Elastomer materials specifications usually do not focus on the adhesive properties, but mainly address the chemical and physical properties of the rubber. Thus, the supplier has wide latitude within the specification to make changes in the compound formulation that could be disastrous to the adhesive bond. One solution is to qualify every new lot of elastomer material for adhesion as well as the more standard properties. 

Inorganic resists have many advantages over conventional polymeric resists, especially in regard to resolution, linewidth control latitude, focus depth tolerance, and dry processability. These features make them very suitable for application to submicron VLSI fabrication. Efforts to improve processing technologies will open the way for practical use in LSI fabrication. 

All future alternatives will require new resists and processes, and for the first time, manufacturing lines will be using at least two different resists. These new materials must have satisfactory sensitivity, resolution, and process latitude. In addition, the deep-UV tools will have limited depth of focus (1-2 (xm) and will be useful only with relatively planar surfaces. Multilayer-resist schemes have been proposed to overcome these limitations, and the simplest is the bilevel scheme that requires a resist that can be converted, after development, to a mask resistant to O2 reactive ion etching (RIE). Resistance to O2 RIE can be achieved by incorporating an element into the resist structure that easily forms a refractory oxide. Silicon performs this function very well and is relatively easy to include in a wide variety of polymer structures. 

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