Provided is a positive working photoresist composition comprising (A) an alkali-soluble novolak resin obtained by condensation reaction of a mixture of phenols, which are constituted of specified proportions of m-cresol and two kinds of specific phenols, with an aldehyde and having a Mw/Mn ratio of from 1.5 to 4.0 (wherein Mw stands for a weight-average molecular weight, and Mn stands for a number-average molecular weight); (B) a 1,2-naphthoquinonediazide-5-(and/or -4-)sulfonic acid ester as a photosensitive material; and (C) a low molecular weight compound having from 12 to 50 carbon atoms per molecule and from 2 to 8 phenolic hydroxy groups per molecule.

Positive-working photoresist composition

Methods for the preparation of multilayered resists include exposure of the a first layer to radiation followed by exposure to an oxidizing agent. The oxidizing agent alters the surface characteristics of the first resist layer such that it is rendered more hydrophilic than the original resist layer. A second layer of resist is then applied to the oxidized surface of the first resist layer and exposed to radiation. This process can be repeated for thousands of coating layers, thereby permitting stereolithographic patterning of parts and construction of micromachines. A final treatment with a dissolution solution will dissolve unwanted resist material. Dependent upon the type of resist material used in the multilayered resist, the dissolution solution can remove the radiation exposed areas, e.g., a positive resist, or remove unexposed areas, e.g., a negative resist.

Stereolithographic patterning with interlayer surface modifications

Methods for the preparation of multilayered resists are described. A first layer of photoresist is deposited onto a substrate. First portions of the first layer are exposed to a first dose of radiant energy. A second layer of photoresist is deposited at atop the first layer and second portions of the second layer are exposed to a second varied dose of radiant energy. The dose is modulated over different portions of a layer to preferentially enhance development within the interior of the structure to reduce total development times.

Stereolithographic patterning by variable dose light delivery

We demonstrate carbon nanotube (CNT) field-effect transistors (CNFETs) with the highest current drive (per unit layout width)1 to-date (>100 µA/µm at 400 nm channel length and 1V V DS ), while simultaneously achieving high I ON /I OFF (>5,000). This is the first demonstration of CNFETs with CNT density above 100 CNTs/µm consisting of highly-aligned CNTs and achieving both high current drive and high I ON /I OFF . The current drives of the demonstrated CNFETs approach that of similarly-scaled and similarly-biased silicon-based field-effect transistors in production in major semiconductor foundries.

High-performance carbon nanotube field-effect transistors

Methods for the preparation of multilayered resists are described. To efficiently pattern large contiguous areas rapidly, a procedure has been developed using spot-size modulation of the focused laser beam to more efficiently pattern interior portions. Critical portions at the perimeter are patterned at high resolutions. The spot-size is progressively increased towards the interior allowing a controlled transition to coarser spot-sizes without impacting the exposure dose in critical portions. Patterning times are significantly reduced since in effect shells are patterned. An algorithm is defined to subdivide a layer into different zones, determine the appropriate focused spot-sizes used for each zone, and define the laser scan trace within a zone to enable efficient patterning of broad areas in positive tone resists.

Stereolithographic patterning with variable size exposure areas

The invention is for a developer for a bilayer photoresist film comprising a first relatively thick layer of a polyglutarimide and a second relatively thin layer of a diazo sensitized novolak resin. The developer is an aqueous solution of a tetra alkyl ammonium hydroxide where at least two of the alkyl groups have two or more carbon atoms. The developer of the invention permits development of the bottom resist layer without erosion of the top resist layer.

Positive acting bilayer photoresist development

An aqueous developable two layer resist system has been developed using a poly(dimethylglutarimide) (PMGI) based planarizing layer. This material offers better resistance to dry etching and thermally induced flow than PM M A. The PMGI layer is highly solvent resistant so no interfacial mixing with conventional positive resist top layers is observed. The pattern transfer exposure wavelengths for the PMGI are 240 - 280 nm. Dyes were added to the novolak based top layer to ensure optimum deep UV masking for thicknesses less than one micron.

A Totally Aqueous Developable Bilayer Resist System

PMGI is a recently developed polymer which has features that make it of interest to the semiconductor industry. Some recent work and applications of this polymer are presented. Emphasis is placed on incremental results and on the achievement of consistency in the behavior of the polymer. The material is currently under evaluation at a number of different sites.

Polydimethylglutarimide (PMGI) Resist - A Progress Report

A new resin system, comprising a thermoplastic polymer backbone with chemically stable imide functionality, has been adapted for use in three different positive resist product types. These include an advanced bilayer system, a near, mid and deep UV monolevel resist; and an antireflective coating. The key features of the imide polymer system which are utilized for the new resist products are: 1. Novolac-like solubility in aqueous base. This property allows formulation of resists, including the planarizing layer of a bilevel system, with conventional types of positive resist photoactive compounds and aqueous base developers, unlike the situation with PMMA which is not base soluble. 2. Transparency to wavelengths above 260nm. This permits use of the polymer as the matrix for systems which utilize mid and deep UV exposure, including the planarizing layer for a bilevel system and mid and deep UV monolayer resists. This is in contrast to novolac resin wHch absorbs strongly in the deep UV region. 3. Insolubility in solvents used for conventional positive resists. This property is critical to use of the resin in planarizing layers of bilevel systems, including antirefiective coatings. It eliminates the intermixing problems which represent a major problem in conventional PMMA bilevel systems. 4. High Tg (185°C). This value is about 80°C higher than that of PMMA and allows higher temperature processing without pattern distortion. 5. Chemical stability and plasma resistance. Unlike conventional reactive polyimide resins the subject polymer is chemically unreactive and is stable to temperatures above 300°C. Further, the polymer has significantly greater resistance to plasma than does PMMA.

Michael W. Legenza

Papers

Positive acting bilayer photoresist development

A Totally Aqueous Developable Bilayer Resist System

Polydimethylglutarimide (PMGI) Resist - A Progress Report

A New Class Of Bilevel And Mono-Level Positive Resist Systems Based On A Chemically Stable Imide Polymer

Bilayer photoresist development