Ari Aviram

New high‐resolution charge transfer x‐ray and electron beam negative resist

A new class of polymeric negative x‐ray and electron beam resists is described. Polystyrene‐tetrathiafulvalene films doped with a halocarbon acceptor show good sensitivity to x‐rays (D1/2=44 mJ/cm2) and electron beams (D1/2=6 μC/cm2), with high contrast values γ≳2.5, and with no evidence for the classical swelling phenomena. In electron beam exposures at 10 μC/cm2, parallel wall patterns are produced with pattern resolution of 1000 A or better. Reasons for the improvement in lithographic parameters relative to previous negative resists are briefly discussed.

A View of the Future of Molecular Electronics

Abstract The article describes some prevailing thoughts and an approach to the development of molecular circuit elements for molecular electronics. Three basic principles are proposed and exemplified by a particular example of a suitable molecule. The model relies upon the current state of the art in science and technology.

Application of 4-methyl-1-acetoxycalix[6]arene resist to complementary metal–oxide–semiconductor gate processing

Gate lengths from 10 to 30 nm are beyond the reproducible limits of chemically amplified negative resists. Gate stack etching, the most challenging step, requires a negative, nonmetallic resist capable of withstanding enhanced etching with fluorine plasmas. This paper describes a new negative resist, 4-methyl-1-acetoxycalix[6]arene (MAC) which has demonstrated 10 nm scale resolution and etch resistance matching that of novolaks. Because increased etch resistance is required to allow reasonable resist aspect ratios, this work addresses techniques for increasing the etch resistance of MAC resist. The major disadvantage of MAC is its very low sensitivity; to address this we present a technique for combining the use of UVN with MAC.

New family of non-chemically amplified resists

Non-chemically amplified resists offer advantages over chemically-amplified (CA) resists because they are less susceptible to temperature variations and contaminants. In order for non-CA resists to be viable, they have to perform lithographically at an equivalent level with the CA resists from the point of view of quantum yield, resolution and etch resistance. We report here on new non-CA resists based on polymer esters that undergo deesterification to the corresponding acids upon exposure to UV, x-ray and e-beam radiation. The efficiency of the radiation reaction is surprisingly high. The resulting poly acids are base soluble and can be employed as positive working resists. The resists are composed of polymers and copolymers of methacrylate esters. The sensitivity of one derivative to x-ray is 75 mJ/cm2 and to e-beam is 1.0 (mu) C/cm2 at 10 KV. Best resolution obtained was 125 nm with x-ray radiation.

A New High Performance CA Resist for E-beam Lithography

Three major lithographic applications have emerged for electron beam exposure tools: optical mask fabrication, direct writing for device fabrication, and more recently projection e-beam printing. The traditional mask making process uses poly(butenesulfone) resist. A wet etch process was adopted to generate patterns on chrome. Recently, shrinking dimensions, optical proximity correction features, and the complexity of phase shift masks have forced the industry to a chrome dry etch process. ZEP, a poly(methyl α-chloroacrylate-co-α-methylstyrene) based resist, has been well accepted for most of the >180 nm device mask making. The acceptance of ZEP comes in spite of its low contrast, marginal etch resistance, organic solvent development, and concerns of resist heating associated with its high dose requirements. These issues have spawned interest in using chemically amplified resist (CAR) systems for direct write and mask making applications. We have developed a high contrast resist based on ketal protecting groups, KRS-XE, which is robust against airborne contamination and can be used for all forms of e-beam exposure in both chrome mask and silicon processing. This high contrast resist is processed with aqueous base developer and has a wide bake latitude. The development of KRS-XE has provided the capability of fabricating chrome masks for future generation (

High-performance e-beam resist coupling excellent dry etch resistance and sub-100-nm resolution for advanced mask making

Recently, there is a significant interest in using CA resists for electron beam (E-beam) mask making application. CA resists provide superior lithographic performance in comparison to traditional non CA E-beam resists in particular high contrast, resolution, and sensitivity. However, most current CA resists exhibit very large sensitivity to PAB and/or PEB temperatures resulting in significant impact on CD. In addition, image collapse issues associated with high aspect ratio patterning as well as electron scattering effects in low KeV tools necessitate thinner resists. Therefore, there is a need to have a high etch resistant resist system which can withstand the demanding chrome etch process. Previously, we reported on the KRS-XE resist which exhibits dry etch resistance comparable to the best deep UV resist and excellent lithographic performance and bake latitudes. No PEB is needed for this resist. In this paper, we report on an advanced KRS-XE resist formulation which exhibits dry etch resistance surpassing the industry standard, novolak, in the chrome etch process. This new resist also exhibits excellent lithographic performance - 50nm lines/space delineated and requires no PEB. This paper will highlight the lithographic and etch performance of this new resist.

Nonchemically amplified positive photoresist for synchrotron radiation x-ray lithography

Iodine containing diazoquinone photoactive compounds (PAC) were synthesized and formulated with novolak and other resins in an effort to develop a positive photoresist for the synchrotron beam line at IBMs Advanced Lithography Facility. The studies focused on the effect of synchrotron radiation on the PACs themselves and in various halogenated resins. These materials were tested by exposing the resist materials to various doses of radiation and then measuring the loss of diazo from the PAC. An enhanced sensitivity x-ray (ESX) photoresist system was developed by combining an iodinated PAC with a novolak resin. ESX was compared to a conventional DQ/novolak photoresist system TNS. ESX was able to print at approximately half the dose needed for TNS. Features as small as 175 nm resolved. These set of experiments demonstrate the potential of significantly improving the photospeed of DQ/novolak photoresist system by utilizing a more x-ray efficient PAC.

A diazoquinone positive photoresist for x‐ray lithography

Diazoquinone photoresists are very reliable materials for photolithography. They have been used extensively by the electronic industry because of their reliability, stability, and ease of operation; and a large body of information has been gathered regarding their application and use. Therefore, it would be natural to extend their use to the field of x‐ray lithography. Unfortunately, the response of these resists to x‐ray radiation is poor, and requires 1.2 J/cm2. Such a dose is too high for practical applications. Amplified resists have been used successfully in x‐ray lithography, but this came with the usual environmental sensitivity of the amplified resists. Here we report the modification of diazoquinone resists for x‐ray lithography. This was accomplished by substituting hydrogen atoms in the photoactive compound (PAC) by iodine. The attachment was carried out in two ways. In the first approach, we used iodine containing moieties to bridge several conventional diazonaphthoquinone sulfonates. Some of ...

Thermal transfer printing with heat amplification

A major advance in the field of thermal printing was the introduction of the QuietwriterR marketed by IBM which is based on resistive ribbon and utilizes the most advanced thermal printing technology. This printing technology is also termed Resistive Ribbon Thermal Transfer (R2T2) printing (1), because it is based on an electrically conductive ribbon. A recent detailed review of resistive ribbon printing is provided in ref. 2. In conventional thermal printing processes (3), the gating factor for the speed is the time it takes for the print head to cool down between cycles. Due to this limitation, the printing cycle for each successive printing element is about 2m seconds. A further drawback of this thermal printing technology, is the dependence of print quality on the type of paper used requiring very smooth paper for reasonable quality printing. This is probably due to inadequate heating of the ink resulting in high melt viscosity and consequently poor ink flow from ribbon to paper. This problem is alleviated in resistive printing where ink transfer temperatures are much higher than in the case of thermal head printing (4). In this technology the ink reaches temperatures far above the melting point of the ink. This is achieved by pumping enough energy into the ribbon to reach the necessary threshold temperature. however, there is a practical limit to the energy that the ribbon can withstand in a certain pulse without undergoing decomposition. Therefore, a need was recognized for approaches to improve thermal printing efficiency while minimizing the input energy requirement.