Alfred T. Jeffries

Selectively DNQ-esterified PAC for high-performance positive photoresists

DNQ-PACs with varying number of OH groups unesterified were examined for their imaging performance in novolac-based positive resists by means of a dissolution rate study. PACs generally lost dissolution inhibition with increasing numbers of the unesterified OH groups when compared to fully esterified PACs, whereas certain particular PACs still retained strong inhibition even when an OH was left unesterified. Such PACs lost inhibition quickly when one or more OH was left unesterified and gave a large dissolution discrimination upon exposure that resulted in high resolution of the resist. High hydrophobicity and remote DNQ configuration of the PAC molecule, and probably the steric crowding around the OH group appear to be structural requirements for obtaining such a high performance PAC. The PACs also provided an advantage in good solubility to resist solvent, and can be practically made by a proposed selective DNQ esterification.

Studies of dissolution inhibition mechanism of DNQ-novolak resist (II): effect of extended ortho-ortho bond in novolak

A p-cresol trimer sequence was incorporated into a polymeric chain of novolak by copolymerization with m-cresol of a reactive precursor which was prepared by attaching two units of m-cresol to the terminal ortho positions of p-cresol trimer. The resulting novolak was characterized by 13C NMR and FTIR in an attempt to correlate novolak structure with dissolution inhibition function based on physicochemical analysis of molecular interactions between novolak and DNQ-PAC in solid films.

Novolacs With Alternating P-Cresol & Polyhydroxyphenyl Monomer Units: Developer Cationic Effects And Thermal Properties

Novolacs which alternate p-cresol monomer units with polyhydroxyphenyl monomer units have been synthesized by acid catalyzed condensation of 2,6-bis(hydroxymethyl)-p-cresol with polyhydroxybenzenes such as resorcinol or 4-chlororesorcinol. These novolacs are highly alkaline soluble and exhibit improved glass transition temperatures relative to conventional novolacs. Unexpected developer cation effects have been observed on the dissolution times of some of these novolacs. The effect of molecular weight on these effects will be discussed for one system. The dissolution discrimination and inhibition of a 4- chlororesorcinol containing novolac was examined relative to a standard m-,p-cresol novolac and polyvinyl phenol. Images produced from a resist using a p-cresol/ 4-chlororesorcinol novolac showed no significant image degradation at 200 degrees C.

Novel novolac resins produced from 2,6-bishydroxymethyl-p-cresol, p-cresol, and m-cresol: a method to more evenly distribute p-cresol units throughout a novolac resin

In an effort to improve the performance of positive resists by increasing the amounts of o,o- bonding, some m-/p-cresol novolacs were prepared in which a portion of the p-cresol was replaced by 2,6-bishydroxymethyl-p-cresol (BHMPC). This work distinguishes itself from earlier work in which BHMPC was the sole source of p-cresol. Fractionated BHMPC polymers were shown to incorporate more p-cresol into their higher molecular weight portions of the molecules. The parent novolacs possessed lower molecular weights and polydispersivities than conventional m-/p-cresol novolacs of the same composition. The lithographically acceptable polymers were evaluated on an 0.52 NA i-line stepper. The resists made from the fractionated BHMPC polymers exhibited a direct relationship between the amount of p-cresol in the higher molecular weight fractions and resolution. The reasons for the difference in performance are discussed in terms of the m-/p-cresol contents of the fractionated and unfractionated polymers as determined by carbon-13 nmr.

Novel combination of photoactive species: photoresists formed from selectively esterified novolacs and polyfunctional photoactive compounds

The addition of selected PACs to resists comprised of selectively esterified DNQ novolacs improves their performance in terms of side wall angle and resolution compared to resists whose photoactive component is composed of entirely selectively esterified DNQ novolacs. The performance gain is particularly evident for the resists with two selectively esterified fractions. A conventional 60/40 m-cresol/p-cresol novolac was synthesized and fractionated into five nearly equal weight fractions using supercritical fluids (SCF) fractionation technique. Resists were made from either a single esterified fraction [fraction Two, esterification level (EL), 42%] or dual esterified fractions (fractions Two and Four, EL 21% each), a selection of PACs and the remaining unesterified fractions. They were compared to a control containing only the corresponding esterified fraction(s). The PACs A and B were effective at increasing the resist profile angle for 0.50 (mu) features in the singly esterified novalacs in comparison to the control material and exhibited flat tops. The resolution and profiles of dual esterified fraction resists improved significantly when low levels of PACs were added to dual esterified fraction control resist. The comparison was made from 0.40 (mu) features. The resist made using PAC C is the best candidate for photospeed although its profile angle is less in comparison to PACs A and B.

Selectively esterified novolac resins: a study of resist properties as a function of novolac molecular weight and composition

Supercritical fluids were used to fractionate a conventional 60 meta/40 para cresol novolac into five narrow polydispersivity fractions. Single and multiple fractions were esterified with a DNQ moiety and recombined to obtain a resist having essentially the same molecular weight and composition as the original parent novolac. Fractions 1 - 4 were esterified. An experimental design was constructed and the resulting selectively esterified novolacs were used to study resist properties as a function of the molecular weight and composition of the esterified fractions. Positive resists prepared from fraction 2 (MW 870 and 69% m-cresol), and fractions 2 and 4 (MW 3064 and 75% m-cresol) exhibited better performance compared to resists prepared from other selectively esterified fractions and the randomly esterified parent novolac.