K. Bolan

Fundamental studies of dissolution inhibition in poly(norbornene-alt-maleic anhydride) based resins

Abstract The dissolution inhibition mechanism for tert-butylcarboxylate (e.g. tert-butyl cholate) dissolution inhibitors and onium salt photoacid generators (PAGs) were examined in terpolymers of poly(norbornene-maleic anhydride-acrylic acid) (P(NB/MA/AA)). For tert-butyl carboxylates, increasing hydrophobicity increased the dissolution inhibition ability. Dissolution promotion tracked with the number of carboxylic acid moieties and the hydrophobicity of carboxylic acids moieties released upon acidolytic cleavage of the tert-butyl carboxylate. For onium salt PAGs, increasing the hydrophobicity and size of fluorinated anions decreased dissolution inhibition.

Precise measurement of the effective backscatter coefficient for 100‐keV electron‐beam lithography on Si

A technique has been developed to measure the effective backscatter coefficient in resist that is more reliable than conventional techniques since (1) it does not require precise information about the form of the backscatter profile, and (2) it makes use of the complete resist exposure response function. The estimated backscatter coefficient on Si for 100 keV electrons has been found to be 0.38±0.05, significantly lower than other published values determined at this energy. Within the accuracy of the measurement, the backscatter coefficient is the same for tests determined by scattering with angular limitation projection electron lithography and direct write exposures.

Mechanism of single-layer 193-nm dissolution inhibition resist

We have found that the progress of developer base into films of terpolymers of norbornene (NB)-maleic anhydride (MA) and acrylic acid (AA) is a percolation process with a critical site concentration of x(c) equals 0.084 which suggests that every acrylic acid site in the terpolymer of norbornene-maleic anhydride-acrylic acid can make 12 monomer units of the polymer water compatible. In practice these systems are being used with various tert-butyl esters of cholic acid as dissolution inhibitors. The cholates differ very much in their dissolution inhibition factors (lowest t-butyl cholate (1.3) to highest t-butyl lithocholate glutarate dimer (7.4). The change in these factors corrected for molarity follow the hydrophobic character of the dissolution as measured by log(p). A quick screening method has also been established to evaluate dissolution inhibitors based on our observation that the cloud point (the volume % acetone in a water/acetone which gives persistent cloudiness) parallels the dissolution inhibiting power as measured by the dissolution inhibition factor. For dissolution promotion, optimal results are obtained with t-butyl 1,3,5-cyclohexanetricarboxylate (f equals -6.3) and poorest results with t-butyl lithocholate (f equals -2.8); this appears to track with the number of carboxyl groups and the hydrophobicity of the carboxylic acids. The Rmax found for resist formulations tracks well with these findings. Another factor in determining the ultimate achievable contrast is the degree of acidolytic deprotection achieved by the material. It appears that acidolyticaly cleaveable carboxylate esters with a higher concentration of electron withdrawing groups such as t-butyl 1,3,5-cyclohexanetricarboxylate are more effective.

Lithographic behavior of carboxylate-based dissolution inhibitors and the effect of blending

We report on a lithographic study of the behavior of non- cholate tert-butylcarboxylate dissolution inhibitor (DIs) formulated in a poly(norbornene/maleic anhydride/acrylic acid/tert-butyl acrylate) 193 nm single layer resin. A comparision is made between formulations containing non- cholate DIs, cholate based DIs and formulations containing blends of the two different types of DIs. It was found that formulations containing the non-cholate materials tended to give T-topped profiles while the formulations containing cholate based materials and blends containing as little as 1% cholate based DI did not.

High-density lithography using attenuated phase-shift mask and negative resist

We demonstrate a technique to print. high-density windows using attenuated phase shift mask, negative photoresist and ArF exposure tool and compare our result with that obtained using a binary mask and positive photoresists.

A 2 million transistor digital processor with 120 nm gates fabricated by 248 nm wavelength phase shift technology

Abstract Alternating phase shift technology has been shown to substantially improve focus latitude and resolution for several years. However, the use of phase shift masks to improve the process latitude in gate level lithography has been hindered by the lack of commercially available tools that can convert conventional gate layouts into phase shift mask patterns. A software package has recently become available that allows a user to create phase shift masks to reduce the gate length of features in existing circuit layouts. A digital signal processing chip with 2 million gates has been used as a test vehicle to evaluate the feasibility of phase shifting and processing a large number of devices in a complete circuit. Three wafer lots have been processed with a target feature size of 120 nm with a variation of 25 nm 3σ. The timing circuits of the chips have been tested; those with 120 nm gates showed a nearly fourfold improvement in speed when compared to 240 nm gate circuits at 1 volt operation.

Shape engineering: A novel optical proximity correction technique for attenuated phase-shift mask

Modifications of the shapes and relative orientations of contact windows in attenuated phase shifting mask are studied theoretically and experimentally to maximize process latitude and resolution and to minimize sidelobe printability. By utilizing a non-square contact window shape and maintaining the overall pattern transmission, we achieve considerable sidelobe suppression with no loss in process latitude and resolution.

Lithographic evaluation of a positive‐acting chemically amplified resist system under conventional and projection electron‐beam exposures

New resist materials and processes are necessary to pattern sub‐0.18 μm design rule circuits with advanced x‐ray and electron‐beam lithographic technologies. We have evaluated a new deep‐ultraviolet multicomponent positive‐acting chemically amplified resist (ARCH: advanced resist chemically amplified), that exhibits excellent resolution under deep‐ultraviolet exposure, and furthermore an overcoat is not used to protect against any basic airborne contaminants. Different formulations of the resist system were studied with electron‐beam lithography in an attempt to enhance sensitivity and maintain wide process latitude and high resolution. In our study we compare the lithographic characteristics of the resist under electron‐beam exposure, with either a Cambridge EBMF vector scan system operating at 40 keV or a JEOL JBX‐5DII system operating at 50 keV, to those obtained at 100 keV with a scattering with angular limitation projection electron lithography (SCALPEL) experimental tool. Using the direct write expo...

Lithographic performance of a negative resist under scattering with angular limitation for projection electron lithography exposure at 100 keV

Scattering with angular limitation for projection electron lithography (SCALPEL)TM [S. D. Berger and J. M. Gibson, Appl. Phys. Lett. 57, 153 (1990)] has been used to evaluate the lithographic performance of a negative‐acting silicon containing chloromethylstyrene resist at 100 keV [A. E. Novembre, M. J. Jurek, A. Kornblit, and E. Reichmanis, Polym. Eng. Sci. 29, 920 (1989)]. This article presents the preliminary evaluation of the resist in a small field of view SCALPEL machine using masks with a membrane area of 1 mm2. A resolution of 0.15 μm was obtained at 61 μC/cm2. Furthermore, the good electron‐beam sensitivity of this well‐characterized negative resist has allowed us to optimize the alignment, astigmatism, and focus of the experimental tool.