Lithographic evaluation

Lithographic Evaluation of Phenolic Resin—Dimethyl Siloxane Block Copolymers... 

In this paper, the material characteristics and lithographic evaluation of this new resist are demonstrated. The resist meets the requirements for KrF excimer laser lithography, which exhibits high sensitivity, high resolution and high aspect ratio pattern profiles. 

Figure 8 shows the effect of the alkaline concentration in TMAH solutions on the contrast and sensitivity of the new resist. Sensitivity of the resist increases as the alkaline concentration increases, however, the contrast is maxima (4.72) at 0.83% TMAH solution. This means that the higher concentration over 0.83% cannot distinguish the difference of the dissolution rate between the unexposed and exposed resist film. For instance, the higher concentrated developer also attacks the exposed areas and the loss of resist thickness occurs. The alkaline concentration in TMAH solution, therefore, is optimized at 0.83%. This developer concentration was subjected to the following lithographic evaluation. 

Table I. Quantum Yields in Solution and Lithographic Evaluation of Poly methacrylates with Pendant Pyrimidine bases...

Table II. Lithographic Evaluation of Polymethacrylates with Pendant Thymine bases...

Wilkins, C. W., Jr. Reichmanis, E. Chandross, E. A. "Lithographic Evaluation of an o-Nitrobenzyl Ester Based DUV Resist System," J. Electrochem. Soc., in press. 

ODUR-110-WR, but no detailed lithographic evaluation has been published. Since the matrix resin is cyclized rubber, one would expect the same swelling limitation on resolution evident in conventional negative photoresists. 

An electron beam exposure machine ELS-5000 (Elionix) operated at 20 kV was used for lithographic evaluation. Sensitivity curves to X-ray and deep UV (254 nm) were determined with a X-ray exposure machine SR-1 (Mo target), developed in our laboratory 12) and a Spectro Irradiator, CRM-FA (JASCO), respectively. After exposure, SNR was developed with (3/1) methylethylketone-isopropanol solvent mixture and rinsed with isopropanol. 

Films for lithographic evaluation were cast from methyl cellosolve acetate, and prebaked at 120°C in a vacuum oven for one hour. Patterns were developed using mixtures of ethyl cellosolve acetate and methyl cellosolve acetate. Areas exposed at a dose of 80 / 2 (20 keV) were developed with about 10% thinning of the unexposed resist. For development at 100 / 2, a contrast of 2.1 was observed (Figure 2), and the resolution at this dose was limited to about one micron. Superior sensitivity and resolution were obtained using a MA-AMS copolymer formed on the wafer by prebaking a copolymer of the methyl half ester of maleic acid with alphamethylstyrene. This latter resist system is discussed a little later. 

For lithographic evaluation, films of P(MM-AMS) were cast from solutions in 2-ethoxyethanol and prebaked one hour at 150°C. Under these prebake conditions, the ester was converted largely back to the anhydride as... 

Synthesis, Characterization and Lithographic Evaluation of Chlorinated Polymethylstyrene... 

The work reported in this paper concerns the synthesis of a series of chlorinated polymethylstyrenes, prepared by chlorination of both anionically and free radically synthesized polymethylstyrene, and their subsequent characterization by H NMR, 13C NMR, IR and elemental analysis. The preliminary lithographic evaluation of the chlorinated materials is also discussed. 

Lithographic Evaluation. Films were spin-coated onto silicon substrates from 10% solutions in chlorobenzene and prebaked at temperatures between 90 °C and 100°C for 1 hour to ensure solvent removal. The thickness of each film was about 5000 A. Electron beam exposures were performed on the AT T Bell Laboratories electron beam exposure system (EBES-I) operating at 20 kV with a beam adress and spot size both equal to 0.25 . A minimal cure time was required since there is no post-exposure reaction (4,16). 

Resolution between 0.75 and 1.0 (equal lines and spaces), was obtained in preliminary lithographic evaluation of chlorinated PMS and P-p-MS. Typical patterns are shown in Figure 23. The small amount of residual material could be removed by descumming if desired. 

Lithographic Evaluation of Poly(methyl methacrylate)-gra/t-poly(dimethylsiloxane) Copolymers... 

Recently, we reported (ii) the synthesis and preliminary characteristics of the first poly (acylsilane), poly(l-trimethylsilyl-2-propen-l-one) (PVTMSK), which was obtained by a free-radical polymerization of 1-tri-methylsilyl-2-propen-l-one (12) (vinyl trimethylsilyl ketone [VTMSK], III). In this chapter, we report the lithographic evaluation of PVTMSK and our attempts to synthesize an a-methyl derivative of PVTMSK, poly(l-trimeth-ylsilyl-2-methyl-2-propen- 1-one) (poly[isopropenyl trimethylsilyl ketone] [PIPTMSK], IV). 

Lithographic Evaluation. Films of PVTMSK were spin coated on polished silicon wafers by using 5 or 10% solutions in chlorobenzene. The lithographic sen-... 

The structure of itaconic acid bears some resemblance to methacryllc acid. While It Is know that methacryllc acid and methacrylic anhydride do enhance sensitivity when copolymerized with methyl methacrylate, some of the Increase In speed may be due to porosity (7,12). The gas formation may cause a higher rate of dissolution then can be attributed to chain scission alone. Pittman and co-workers have reported G(s) values for poly(methacryllc anhydride) of 0.4 (10) and 1.8 and 2.9 (14) based on gamma radiation experiments. Hiroaka (12) measured G(s) by gas evolution on Irradiation of films with electron beams and established values In the ration 1 2 6 for the methyl methacrylate. A terpolymer with the three components In the molar ratio of 70 15 15 (same three monomers) was selected by Moreau et al (13) on the basis of complete lithographic evaluation. The speed Is 4 to lOx that of PMMA. As aforementioned, an Increase In G(s) may be only partially responsible. 

Although chain scissioning yields are only a secondary measure of sensitivity, the high G(s) values reported here for MMA-itaconlc acid copolymers have been supported by the good electron-beam sensitivities determined from a complete lithographic evaluation of these copolymers. A full discussion of these results Is beyond the scope of this paper but they have been reported elsewhere (15). 

There are numerous analytical and characterization steps in resist formulation and lithographic evaluation processes. First of all, each component of a resist formulation, polymer, acid generator, and additives, must be synthesized as... 

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