Niranjan M. Patel

Water soluble conducting polyanilines: Applications in lithography

A new class of water soluble conducting polyanilines has been developed. This is accomplished by oxidatively polymerizing aniline monomers on a template such as a polymeric acid. The resulting polyanilines readily dissolve in water. These materials can be applied as removable discharge layers for electron‐beam lithography and for mask inspection by scanning electron microscopy. They can be spin‐applied directly on top of resists without any interfacial problems. Image distortion as a result of charging during resist exposure is not observed with these materials. After exposure the polyaniline is readily and cleanly removed during the resist develop. By incorporating cross‐linkable functionality on the polyaniline backbone, water soluble polyanilines that are radiation curable are attained. Upon irradiation these materials cross‐link and become insoluble and thus can be utilized as permanent conducting coatings for electrostatic discharge applications. In addition, the cross‐linkable polyanilines can be us...

Water Soluble Polyanilines: Properties and Applications

A new class of water soluble conducting polyanilines have been developed. This is accomplished by oxidatively polymerizing aniline monomers on a template such as a polymeric acid. The resulting polyanilines readily dissolve in water. These Materials can be applied as removable discharge layers for electron-beam (e-beam) lithography and for SEM Mask Metrology. Cross-linkable functionality can be incorporated on the polyanilinc backbone resulting in water soluble polyanilines that are radiation curable. Upon irradiation these materials cross-link and become insoluble and thus can be utilized as permanent conducting coatings for electrostatic discharge (ESD) applications. In addition, the cross-linkable polyanilines can be made into water developable conducting resists. 1.0μm conducting lines have been patterned with e-beam irradiation.

Amic acid doping of polyaniline: Characterization and resulting blends

Abstract Amic acids are found to be dopants for polyaniline (Pani). In particular, polyamic acids, the precursors to polyimides, react with Pani to form an all-polymer conducting matrix composed of protonated Pani and the polyamate counteranion. The acid/base interaction provides the driving force for molecular miscibility. The doping reaction is probed further by using a model system based on a monomeric diamic acid. It is found that the conductivity in the all-polymer matrix is limited by geometric constraints between the two polymers. Upon imidization of the Pani/polyamic acid blend, the doping reaction is reversed resulting in a non-conducting Pani/polyimide blend. However, the miscibility between the two polymers is still retained forming a “frustrated” blend in which the two polymers are frozen into a homogeneous, non-equilibrium state unable to phase separate as a result of physical restrictions.

Edge lithography as a means of extending the limits of optical and nonoptical lithographic resolution

Lithographic scaling entails continuously increasing resolution while at the same time improving the tolerance control on the printed images. Typically, this has been done by using shorter actinic wavelengths, increasing numerical aperture, compensating reticle patterns and similar methods that serve to enhance the fidelity of the aerial image. In some case, this scaling has been achieved by altering the method of image formation, such as with the use of alternating phase shift reticles, in which the width of the aerial image is established by phase interference rather than of a diffraction-limited process of passing light through a dark masking pattern. This paper describes development of a resist material that provides a new way to scale lithographic patterns, one similar to alternating phase shift lithography in the sense that it prints the edge of an aerial image rather than the entire image as a single pattern. Because the edge of the aerial image is of higher resolution, with smaller components of tolerance than the entire image, this type of resist may provide a new method of scaling.

PHS with inert blocking groups for DUV negative resist

The synthesis, characterization, and lithographic evaluation of a polyhydroxystyrene (PHS) modified with isopropyloxycarbonate groups is described. The inert blocking group is attached to the hydroxyl sites on PHS resin to slow the dissolution rate and make the resin useful in resists designed for 0.263 N TMAH developers. A negative tone resist (CGR-IP) that is formulated with the modified polymer is compatible with the industry standard 0.263 N TMAH developer and is capable of resolving 0.22 micrometer L/S features and 0.14 micrometer isolated lines on a 0.50 NA imaging system. Reaction with PHS resin occurs primarily at the phenolic sites as shown by carbon-13 NMR and 10% protection is sufficient to lower the dissolution rate to an acceptable level so that there is less than 50 angstrom film loss in exposed areas. The blocking group described here is not acid labile and reaming intact after the resist film is baked at 150 degrees Celsius.

Important role of hydroxyethyl derivatives of poly(hydroxystyrene) in the development of advanced negative resists

In this paper, we present the synthesis, thermal properties, dissolution characteristics and lithographic potential of a new poly(hydroxystyrene) derivative (PHS-EtOH) obtained by blocking the phenolic functionality with a saturated alcohol moiety through an ether linkage. The replacement of PHS with this modified polymer in a negative resist formulation has resulted in a dramatic improvement in dense line resolution.

Water soluble electrically conducting polymers

Summary form only given. Polyanaline is a family of electrically conducting polymers. Various polyaniline derivatives have been found to be viable in a number of lithographic applications. These have included charge dissipators for electron-beam lithography and SEM mask metrology, conducting resists, and imageable metal seeders. Most of the polyanilines to date have been processed in organic solvents. This paper introduces a novel series of polyaniline derivatives, PanAquas, which are water soluble in the conducting form and thus, eliminate environmental concerns of organic solvents. As these materials can be easily applied and removed in water, they can be used as removable charge dissipators in a number of lithographic areas replacing metals which often need to be sputtered or plated. By incorporating cross-linkable functionality on the backbone of these derivatives , the polyanilines can be made to cure upon irradiation. The cured polymers are no longer soluble and thus can be used as permanent conducting coatings for electrostatic discharge (ESD) protection. They can be applied as coatings on electronic component carriers replacing metals and carbon filled materials. The cross-linkable polyanilines can also be made into water developable conducting resists.<<ETX>>

Applications of Conducting Polyanilines in Computer Manufacturing Processes

Polyaniline is found to be suitable for a number of applications in computer manufacturing processes. In particular, polyaniline can play significant roles in the lithographic processes used to fabricate integrated circuits. Thin films of conducting polyaniline are found to be effective discharge layers for electron-beam lithography. Insulating resist systems charge during electron-beam exposure which results in pattern displacements. When polyaniline is incorporated into the resist process as a thin conducting layer, no pattern displacements are observed. Especially suited for this application is a water soluble polyaniline that we have recently developed. This material is an aqueous based, spin-apply discharge layer that can easily be removed after the resist exposure. Conducting polyaniline is also an effective charge dissipator for the high resolution inspection and dimensional measurements of x-ray and optical masks by scanning electron microscopy (SEM) when used as a coating on top of the mask. In addition, a number of polyanilines are made radiation sensitive and thus can function as conducting resists for electron-beam lithography. In particular, we have developed a water developable conducting resist. Lastly, polyaniline can be utilized for electrolytic and electroless metallization applications.