P-doped poly

Layers Typical materials for which CMP processes originally have been developed for microelectronic applications include various types of silicon dioxide such as thermal oxide, TEOS, HDP, BPSG, and other B- or P-doped oxide films. These films are used for various isolation purposes including interlevel dielectric (ILD), intermetal dielectric (IMD), or shallow trench isolation (STI). In addition, n- or p-doped poly-Si, which is a semiconducting material used as capacitor electrode material for DRAMS or gate electrode for MOS applications (CMOS as well as power MOS devices), also has to be polished. Metals for which CMP processes have emerged over the last 10-15 years are W for vertical interconnects (vias) and most importantly Cu as a low-resistivity replacement for aluminum interconnects, employed in the damascene or dual-damascene processing scheme. Other metals that are required for future nonvolatile memories are noble metals like Pt or Ir for which CMP processes have been explored. 

FIGURE 5.22 Band structure of the p-doped poly(p-phenylene). 

Bhat D. K, Kumar M. S., N and p doped poly[3,4-ethylenediox34hi-ophene] electrode materials for symmetric redox supercapacitors,/ Mater. Sci., 2007,42,8158-8162. 

Arbizzani, C., M. Catellani, M. Mastragostino, and C. Mingazzini. 1995. N- and p-doped poly-dithieno[3,4-B 3, 4 -D] thiophene A narrow band gap polymer for redox supercapacitors. Electro-chim Acta 40 1871-1876. 

Borjas, R., and D.A. Buttry. 1991. EQCM studies of film growth, redox cycling, and charge trapping of n-doped and p-doped poly(thiophene). Chem Mater 3 872. 

H. Randriamahazaka, V. Noel and C. Chevrot, Fractal dimension of the active zone for a p-doped poly(3,4-ethylenedioxvthiophene) modified electrode towards a ferrocene probe, J. Electroarud. Chem. 521, 107-116 (2002). 

The solid contact for plastic ISE membranes, made by applying conducting polymer (CP) and supported by a comprehensive theoretical model, was introduced by Lewenstam group [4, 10]. The CP used was poly(pyrrole) doped deliberately with tetrafluoride anions [see Eq. (10.10) and adjacent comment]. Since then different conducting polymers were used by numerous authors, mainly conjugated p-doped poly(tiophene), poly (aniline) and poly (pyrrole), and their derivates were applied [11, 12]. 

The polymers which have stimulated the greatest interest are the polyacetylenes, poly-p-phenylene, poly(p-phenylene sulphide), polypyrrole and poly-1,6-heptadiyne. The mechanisms by which they function are not fully understood, and the materials available to date are still inferior, in terms of conductivity, to most metal conductors. If, however, the differences in density are taken into account, the polymers become comparable with some of the moderately conductive metals. Unfortunately, most of these polymers also have other disadvantages such as improcessability, poor mechanical strength, instability of the doped materials, sensitivity to oxygen, poor storage stability leading to a loss in conductivity, and poor stability in the presence of electrolytes. Whilst many industrial companies have been active in their development (including Allied, BSASF, IBM and Rohm and Haas,) they have to date remained as developmental products. For a further discussion see Chapter 31. 

The stoichiometry of the redox reactions of conducting polymers (n and m in reactions 1 and 2) is quite variable. Under the most widely used conditions, polypyrroles and polythiophenes can be reversibly oxidized to a level of one hole per ca. 3 monomer units (i.e., a degree of oxidation, n, of ca. 0.3).7 However, this limit is dictated by the stability of the oxidized film under the conditions employed (Section V). With particularly dry and unreactive solvents, degrees of oxidation of 0.5 can be reversibly attained,37 and for poly-(4,4 -dimethoxybithiophene), a value of n = 1 has been reported.38 Although much fewer data are available for n-doping, it appears to involve similar stoichiometries [i.e., m in Eq. (2) is typically ca. 0.3].34,39"41 Polyanilines can in principle be reversibly p-doped to one... 

Figure 4 compares cyclic voltammograms for a redox polymer (poly-[Fe(5-amino-1,10-phenanthroline)3]3+/2+)91 and p-doping and undoping of a conducting polymer (polypyrrole).92 The voltammogram for the redox... 

Figure 4. (A) Cyclic voltammograms over a range of scan rates for a redox polymer (poly-[Fe 5-amino-1,10-phenanthrotme)3]3+/>)91 and (B) p-doping and undoping of a conducting polymer (polypyrrole) (B). [(A) Reprinted from X. Ren and P. O. Pickup, Strong dependence of the election hopping rate in poly-tris(5-amino-1,10-phenan-throline)iron(HI/II) on the nature of the counter-anion J. Electroanal. Chem. 365, 289-292,1994, with kind permission from Elsevier Sciences S.A.]...

Mulder, J., Eppenga, P., Hendriks, M., and Tong, J., An Industrial LPCVD Process for In Situ Phosphorus-Doped Poly silicon, /. Electrochem. Soc., 137(l) 273-279(Jan. 1990)... 

Most conducting polymers, such as doped poly(acetylene), poly(p-pheny-lene), and poly(/ -phenylene sulfide), are not stable in air. Their electrical conductivity degrades rapidly, apparently due to reaction with oxygen and/or water. Poly(pyrrole) by contrast appears to be stable in the doped conductive state. 

Table 5.3 Examples of electronically conducting polymers, y is the level of electrochemical doping and k is the maximum electrical conductivity. Except for poly acetylene and polyparaphenylene, only p-doping is considered... 

The dynamic viscoelasticity of particulate gels of silicone gel and lightly doped poly-p-phenylene (PPP) particles has been studied under ac excitation [55]. The influence of the dielectric constant of the PPP particles has been investigated in detail. It is well known that the dielectric constant varies with the frequency of the applied field, the content of doping, or the measured temperature. In Fig. 11 is displayed the relationship between an increase in shear modulus induced by ac excitation of 0.4kV/mm and the dielectric constant of PPP particles, which was varied by changing the frequency of the applied field. AG increases with s2 and then reaches a constant value. Although the composite gel of PPP particles has dc conductivity, the viscoelastic behavior of the gel in an electric field is qualitatively explained by the model in Sect. 4.2.1, in which the effect of dc conductivity is neglected. 

Recently, intense interest has been paid on doped poly(acetylene) because its film 68) showed markedly high conductivity on doping69 70 71 and the n- and p-type conductivities are depending on the dopants. The confirmation of p-n junction formation with the p- and n-type -fCH T, has roused great expectations to produce a polymer film solar cell.72a)... 

The doped poly(acetylene) forms various junctions such as a) a p-n junction from p- and n- -f CH, b) a hetero-Schottky junction from the inorganic semiconductor and metalic -f CH-, and c) a heterojunction from the inorganic semiconductor and semiconducting The bandgaps of -(-CH (trans- 0.6 eV, cis- 0.9 eV)... 

In poly[2,5-bis(3,4-ethylene-dioxy-2-thienyl)pyridine], a copolymer of thiophene and pyridine in a 2 1 ratio, the effective HOMO and LUMO energy levels of the ir-system are controlled in such a way that both p-doped and n-doped states are accessible (Scheme 9) [43]. The thin fdms display multicolor... 

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