A review is presented of the recent advances in the study of oxygen precipitation and of the main properties of oxide precipitates in silicon. After a general overview of the system ‘‘oxygen in silicon,’’ the thermodynamics and the kinetics of the precipitate formation are treated in detail, with major emphasis on the phenomenology; subsequently, the most important techniques for the characterization of the precipitates are illustrated together with the most interesting and recent results. Finally, the possible influence of oxygen precipitation on technological applications is stressed, with particular attention to recent results regarding device yield. Actually, the essential novelty of this review rests on the attempt to give an extended picture of what has been recently clarified by means of highly sophisticated diagnostic methods and of the influence of precipitation on the properties of semiconductor devices.

Oxygen precipitation in silicon

The present invention is directed to a process for device fabrication and resist materials that are used in the process. The resist material contains a polymer that contains monomeric units that contain alicyclic formate moieties, and at least one other type of monomeric unit. The polymer may be formed by polymerization or by polymer modification of an existing polymer, and the resulting polymer either has alicyclic moieties incorporated into the polymer backbone or pendant to the polymer backbone via saturated hydrocarbon linkages. A preferred polymerization process is free radical polymerization, in which other monomers are selected for polymerization with the alicyclic moiety-containing monomer on the basis of the ability of the monomer to copolymerize by free radical polymerization. Although the polymers are contemplated as useful in resist materials that are sensitive to radiation in the ultraviolet, and x-ray wavelengths as well as sensitive to electron beam radiation, the polymers are particularly advantageous for use in process in which the exposing radiation is 193 nm, because the amount of ethylenic unsaturation in these resist materials is low.

Energy-sensitive resist material and a process for device fabrication using an energy-sensitive resist material

Photolithographic patterning of organic materials and plasma-based transfer of photoresist patterns into other materials have been remarkably successful in enabling the production of nanometer scale devices in various industries. These processes involve exposure of highly sensitive polymeric nanostructures to energetic particle fluxes that can greatly alter surface and near-surface properties of polymers. The extension of lithographic approaches to nanoscale technology also increasingly involves organic mask patterns produced using soft lithography, block copolymer self-assembly, and extreme ultraviolet lithographic techniques. In each case, an organic film-based image is produced, which is subsequently transferred by plasma etching techniques into underlying films/substrates to produce nanoscale materials templates. The demand for nanometer scale resolution of image transfer protocols requires understanding and control of plasma/organic mask interactions to a degree that has not been achieved. For manufa...

Plasma-polymer interactions: A review of progress in understanding polymer resist mask durability during plasma etching for nanoscale fabrication

The behavior of poly(ferrocenyldimethylsilane) (PFS) under reactive ion etching conditions was investigated. Due to the presence of iron and silicon in the main chain, the polymer was found to be relatively stable toward oxygen plasma etching compared to common organic polymers. Depending on the conditions employed, the etching rate ratio for poly(isoprene) vs poly(ferrocenyldimethylsilane) ranged from 20:1 to 50:1. During etching, a thin iron- and silicon-containing oxide layer was formed at the surface of the organometallic polymer. The oxide layer was characterized by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) using depth profiling. Iron was found to be more resistant toward removal by oxygen plasma compared to silicon. Iron in the polymer also makes it resistive to CF4/O2 etching. A regular pattern consisting of parallel lines of PFS on a solid substrate was obtained by micromolding in capillaries (MIMIC) (a microcontact printing technique), which could be transferred...

Poly(ferrocenyldimethylsilanes) for Reactive Ion Etch Barrier Applications

The implementation of high-resolution polymer templates fabricated by capillary force lithography (CFL) is explored both in nanoimprint lithography (NIL) and in the wet-etching of metals. Several different thermoplastic and UV-curable polymers and types of substrates are incorporated into the general CFL procedure to meet the diverging requirements of these two applications. The mechanical stability of UV-curable templates for imprinting in polymers, as examined by atomic force microscopy (AFM), and their anti-adhesive properties are excellent for application in NIL. The conditions for curing the UV-curable polymer are optimized in order to obtain high-stability polymer templates. Gold patterns on silicon with a lateral resolution of 150 nm are fabricated by subsequent lift-off in acetone. Similar patterns with a lateral resolution of 100 nm are fabricated using templates of thermoplastic polymers on gold layers on silicon as an etch mask. The transfer of stamp residues during CFL with these polymer templates is proven by X-ray photoelectron spectroscopy (XPS) and AFM friction analysis. For poly(methylmethacrylate) (PMMA), the presence of large amounts of silicon-containing residues is found to compromise the processability of the resulting template in subsequent O2 reactive-ion etching (RIE) treatment. The extent of silicon contamination is up to six times less for polystyrene (PS). At this level, the etch performance of the PS etch mask is not affected, as was the case for PMMA. Accurate downscaling of the lateral dimensions of the resulting metal patterns by several factors with respect to the dimensions of the PS etch mask is achieved by over-etching of the gold. Overall, the results in this paper demonstrate the potential of CFL templates as tools for high-resolution soft lithography.

Capillary Force Lithography: Fabrication of Functional Polymer Templates as Versatile Tools for Nanolithography

Proprietes de corrosion de polymeres organosilicies, caracteristiques d'exposition a un faisceau d'electrons et aux UV lointains des homo- et copolymeres de trimethylsilylstyrene. Application du copolymere d'un systeme resist bicouches

Copolymers of Trimethylsilylstyrene with Chloromethylstyrene for a Bi‐Layer Resist System

It is shown that interstitial oxygen infrared (IR) absorption at 515 cm−1 decreases anomalously compared with the absorption at 1106 cm−1 in heat‐treated Czochralski‐grown silicon wafers. This phenomenon is described by the close correlation between the absorption coefficient ratio αr (α1106/α515), the half‐bandwidth of the 1106‐cm−1 peak, and the precipitated oxygen content during heat treatments. As a result, it is suggested that on the basis of IR absorption spectrum data interstitital oxygen atoms distribute heterogeneously in a silicon matrix as the forestage of Si‐0 complex precipitation.

Heterogeneous distribution of interstitial oxygen in annealed Czochralski‐grown silicon crystals

http://jes.ecsdl.org/content/132/4/909.full.pdf

A Silicon Containing Positive Photoresist (SIPR) for a Bilayer Resist System

Disclosed is a novel novolak resin comprising structural units having a trimethylsilyl group. A resist material highly resistive to dry etching is obtained by adding a photosensitive diazo compound to this novolak resin. The resist material is useful in various lithography methods to form a positive resist pattern. This resist material is used in a pattern forming method of a two-layer type, in which a fine pattern is formed in a thin film of the resist material by lithography and then transferred into an underlying thick organic polymer layer by dry etching of the underlying layer with the resist pattern as mask. Curing of the resist pattern by irradiation with deep UV rays is effective for further improvement in the precision of the transferred pattern.

Silicon-containing novolak resin and resist material and pattern forming method using same

A liquid crystal composition having long-life dynamic light scattering properties under application of DC or AC voltage, comprising (1) at least one liquid crystalline substance selected from the group consisting of nematic and cholesteric, and (2) at least one additive selected from the group consisting of (A) mixtures of at least one first organic cyclic compound selected from the group consisting of quinone compounds, quinoneimine compounds, imino compounds, desoxybenzoin compounds, dibenzyl methane compounds and triphenyl methane compounds, with at least one second organic cyclic compound selected from the group consisting of hydroquinone compounds, aromatic amino compounds, heterocyclic amino compounds and alicyclic amino compounds, and (B) aromatic, heterocyclic and alicyclic compounds having at least one radical selected from the group consisting of carbonyl and imino radicals and at least one radical selected from the group consisting of hydroxyl and amino radicals

Yoshitake Ohnishi

Papers

Copolymers of Trimethylsilylstyrene with Chloromethylstyrene for a Bi‐Layer Resist System

Heterogeneous distribution of interstitial oxygen in annealed Czochralski‐grown silicon crystals

A Silicon Containing Positive Photoresist (SIPR) for a Bilayer Resist System

Silicon-containing novolak resin and resist material and pattern forming method using same

Liquid crystal composition