Polymers plasma-developable

Fig. 37. Resist images obtained with a cross-linking monocomponent TSI resist (PHOST polymer), cross-linked by photo-oxidation using light at 193-nm wavelength. After exposure, the film was treated with a vapor of dimethyl silyl dimethyl amine and then plasma developed using O2—RIE (122).

Figure 44. A schematic representation of the plasma developed x-ray resist process. Exposure serves to covalenty bind the monomer (m) into the polymer matrix (p). Heating (fixing) drives out (volatilizes) the monomer except where it is "locked in place" by exposure. Plasma treatment converts the silicon to Si02 which retards the etch rate in the exposed areas through formation of a metallic oxide (MO) layer.

Figure 13. Schematic of plasma-developed resist film composed of polymer host (P) and volatile monomer (m). Processing steps are (a) exposure which locks monomer in place, (b) fixing which removes unlocked monomer, (c) plasma development. (Reproduced with permission from...

In formulating a plasma developable electron resist (PDE), NVC, DPAE, MAM and ODMA have been evaluated as monomers along with PC1S, PS, PBD and PTCEM as base polymers. Aside from lithographic performance, the main issues concerning the formulation of PDE are the sublimation or vaporization of monomers under vacuum and the compatibility of the monomer with the base polymer. 

The development process converts the latent image in the polymer into the final 3-D relief image. This process is perhaps the most complex of resist technology. It can generally be achieved by either liquid development or dry (plasma) development. Numerous considerations are critical to either alternative. We will first focus on the wet development process. Plasma development will be discussed in a later section. 

A novel microlithographic application for photoinitiated polymerization involves the polymerization of a monomer and the locking-in of a plasma-sensitive host polymer so that plasma techniques can be used to carry out all-dry development, thus avoiding the problems of swelling and resolution limitation associated with standard resists. Some plasma-developable resists are described later in this section. 

Poly(vinyl pyrrolidone). Another commercial polymer with significant usage is PVP (7). It was developed ia World War II as a plasma substitute for blood... 

The realization of sensitive bioanalytical methods for measuring dmg and metaboUte concentrations in plasma and other biological fluids (see Automatic INSTRUMENTATION BlosENSORs) and the development of biocompatible polymers that can be tailor made with a wide range of predictable physical properties (see Prosthetic and biomedical devices) have revolutionized the development of pharmaceuticals (qv). Such bioanalytical techniques permit the characterization of pharmacokinetics, ie, the fate of a dmg in the plasma and body as a function of time. The pharmacokinetics of a dmg encompass absorption from the physiological site, distribution to the various compartments of the body, metaboHsm (if any), and excretion from the body (ADME). Clearance is the rate of removal of a dmg from the body and is the sum of all rates of clearance including metaboHsm, elimination, and excretion. 

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