A new type of eco‐friendly resist based on nonchemically amplified system

Novel water‐processable photopolymers were designed to be useful as environment‐friendly photolithographic materials. By copolymerization of 2‐(2‐diazo‐3‐oxo‐butyryloxy)ethyl methacrylate (DOBEMA), hydroxyethyl methacrylate (HEMA), methacryllic acid (MAA), and sodium 4‐vinylbenzenesulfonate (SVBS), two kinds of polymers, poly(DOBEMA‐co‐HEMA‐co‐SVBS) for negative‐tone resist and poly(DOBEMA‐co‐MAA) for positive‐tone resist, were synthesized and their photolithographic properties were investigated. The single component negative‐tone resist produced 0.8 μm line and space patterns using a mercury‐xenon lamp in a contact printing mode using pure water as casting and developing solvent at a exposure dose of 25 mJ cm^?2. On the other hand, the single component positive‐tone resist produced 0.8 μm line and space patterns at a much higher dose of 150 mJ cm^?2. Thus, the negative resist showed much improved sensitivity when compared with the positive resist and the reported nonchemically amplified resists. This sensitivity is comparable with those of typical chemically amplified resists. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7534–7542, 2008     

A New Method of Photopatterning with LB Films Based on a Chemically Amplified Mechanism

IntroductionDeep-UV lithography is generally recognized asthe most promising lithographic technology, for the pro-duction of high-resolution devices. However, lithogra-phy requires high sensitivity, high resolution, and highresistance. To make this techno…     

Chemical amplification resists: Inception,implementation in device manufacture,and new developments

The chemical amplification concept aimed at dramatically boosting the resist sensitivity was invented at IBM Research in San Jose, CA, in 1980. The sensitivity enhancement is achieved by generating acid by irradiation, which induces a cascade of chemical transformations in a resist film. A chemically amplified resist based on acid‐catalyzed deprotection was quickly employed in the mid‐80s in manufacture of 1 megabit (Mbit) dynamic random access memory (DRAM) devices by deep ultraviolet (UV) (～250 nm) lithography in IBM. The unexpectedly high‐resolution capability of chemical amplification resists promoted their acceptance in the resist community and the microelectronics industry. All the advanced lithographic technologies (current workhorse 248 nm, maturing 193 nm, and emerging 157 nm, extreme UV, and projection electron beam) depend on chemical amplification resists. This article describes the invention, implementation in device manufacturing, current status, and future perspective of chemical amplification resists. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3863–3870, 2003     

Methacrylic silicon-containing tercopolymers for chemically amplified resists

Tercopolymers of methyl methacrylate with methacrylic acid and dimethylphenyl (methyldiphenyl)silyl methacrylates are synthesized and investigated as components of chemically amplified resistive formulations with sulfonium and iodonium salts as photoacid generators for UV lithography in the 254-nm range. The surface behavior and the kinetics of dissolution of resistive films in an aqueous solution of tetraethylammonium hydroxide in relation to the concentration of onium salts and the temperatures of postapply and postexposure bakes are studied. The introduction of sulfonium salt into the resistive formulation brings about an increase in the solubility of unexposed films, thereby erasing the difference in dissolution rates of exposed and unexposed areas of a resist and preventing image formation. The iodonium salt plays the role of an inhibitor for dissolution of unexposed films of both copolymers, which makes it possible to obtain a high-contrast positive image in resists.     

Alkaline-developable positive-type photosensitive polyimide with high mechanical strength and high resolution based on chain extendable poly(amic acid), thermally degradable cross-linker and photoacid generator

A positive-type photosensitive polyimide ( PSPI ) based on a chain extendable poly(amic acid) ( PAA ), a thermally degradable cross-linker 1,3,5-tris[(2-vinyloxy)ethoxy]benzene ( TVEB ), and a photoacid generator (PAG) (5-propylsulfonyloxyimino-5H-thiophene-2-ylidene)-(2-methylphenyl)acetonitrile ( PTMA ) has been developed. The chain extendable PAA was prepared from 3,3′,4,4′-biphenyltetracarboxylic dianhydride ( BPDA ) and 4,4′-oxydianiline ( ODA ) and end-capped with di-tert-butyl dicarbonate ( DIBOC ) in N-methyl-2-pyrrolidone (NMP), which has a controlled molecular weight for developing in a 2.38 wt% tetramethyl ammonium hydroxide aqueous solution ( TMAH _aq ) and undergoes a chain extending reaction during curing stage. The photosensitive resist solution was formulated with the polymerization solution (30 wt% in NMP), TVEB (15 wt% for the polymer), and PAG (4.5 wt% for the polymer). The PSPI showed a sensitivity of 47 mJ cm⁻² and a contrast of 5.8 when exposed to 365-nm light, followed by postexposure baking at 90 °C for 10 min and development with the 2.38 wt% TMAH _aq at room temperature. A fine-positive image with 3-μm line-and-space patterns was obtained on a 3-μm thick film exposed to UV light at 365 nm in the contact-printed mode. After thermal curing at 350 °C for 1 hr, the resulting PSPI features excellent mechanical strength and elongation.     

Retrospective of work at Bell Laboratories on the effect of fluorine substitution on the properties of photoacid generators

An overview is given on the work done at Bell Laboratories in which fluorine substitution was employed to tune the structure property relationships of chemically amplified resists. In particular, this paper will detail how structural changes in 2-nitrobenzyl photoacid generator (PAG) affect molecular properties such as quantum yield, thermal stability, and in turn also influence the lithographic characteristics of photoresist formulations such as sensitivity and post-exposure bake (PEB) and post-exposure delay (PED) latitude.     

248nm深紫外光刻胶

本文从化学增幅技术的产生,深紫外248nm胶主体树脂及PAG发展历程、溶解抑制剂、存在的工艺问题及解决途径多个方面综述了深紫外248nm胶的发展与进步.     

Electron-beam and x-ray resists for microlithography

Firstly, general considerations about microlithography and resists were presented, leading to the conclusion that positive resists seemed to be more suitable than negative resists to provide high resolution in electron-beam lithography and in X-ray lithography. Therefore, parameters affecting the sensitivity of positive resists to such types of radiation were outlined. Among these positive resists, poly (fluoroalkyl methacrylates) were shown to be interesting candidates, due to their enhanced radiation absorption. Thus, poly(1-, 1- dimethyl 2, 2, 3, 3-tetrafluoropropyl methacrylate) (called FBP resist) was synthesized and physico-chemically characterized. The lithographic performances of such a resist were evaluated both upon electron-beam and X-ray exposures. Its dry-etch resistance was also studied. Furthermore, fabrication of Field-Effect Transistors using this resist was demonstrated.     

The molecular mechanism of novolak-diazonaphthoquinone resists

Novolak-diazonaphthoquinone (DNQ) resists are photosensitive varnishes that are used in the fabrication of more than 80% of today's integrated circuits. They have played a crucial role in an unprecedented technical revolution, yet until quite recently nobody really knew how they work. We have been concerned with this problem for some time and we realize now that the principal functions of novolak resists, namely the inhibition by DNQ derivatives of the dissolution of novolak films, and the cessation of inhibition on exposure to radiation, are essentially physical phenomena. Dissolution inhibition is caused by an electric stress imposed on the phenol groups of the resin by the inhibitor. This effect penetrates deep into the material through the formation of hydrogen-bonded phenolic strings. Exposure relieves the stress by uncoupling the strings from the source of induction. The concept of phenolic strings is new and unusual, but it is essential for the understanding of dissolution inhibition. With it, all the many aspects of novolak resists can be interpreted in a unified manner.     

Poly(silamine)s as new electron-beam resist materials

Several types of poly(silamine)s were prepared and their structure-characteristics relationships were investigated. When a phenyl ring in the organosilyl unit and/or a cyclic structure in the amino unit was introduced, the glass transition temperatures were increased significantly in order to increase film formability. From the thermogravimetric analysis of the poly(silamine)s, it was found that the thermal decomposition of poly(silamine)s starts at ca. 380–400°C. On electron-beam irradiation of the poly(silamine) films, degradation of the polymer took place. On the basis of these results, poly(silamine)s can be one of the candidates for new positive-type polymeric resists.     

多光子光刻用的杯[4]芳烃分子玻璃正性光刻胶

分子玻璃材料和多光子光刻技术分别是近年来光刻胶和光刻技术领域的研究热点.本文对分子玻璃正性光刻胶在多光子光刻中的应用进行了探索,设计合成了叔丁氧基羰基保护的杯[4]芳烃衍生物分子玻璃材料,将其作为主体材料与光生酸剂三氟甲磺酸三苯锍鎓盐进行复配,制备了分子玻璃正性光刻胶,探讨并优化了光刻胶的成分配比及其在紫外光曝光下的显影工艺.利用780nm波长飞秒激光对所制备的分子玻璃正性光刻胶进行了多光子光刻特性的评价,实验得到了最低线宽180nm的线条和复杂的二维微结构图形,结果表明杯[4]芳烃衍生物分子玻璃正性光刻胶有望应用于多光子光刻技术.     

Octadecyltrichlorosilane (OTS): a resist for OMCVD gold nanoparticle growth

One application of octadecyltrichlorosilane (OTS) self‐assembled monolayers (SAMs) is its use as thin film resists. In this work, we demonstrated that OTS SAMs can be reliable resists for organo‐metallic chemical vapor deposition (OMCVD) grown gold nanoparticles (Au NPs). In optical sensing applications based on Au NPs, one candidate system consists of patterned OTS SAMs and precisely grown OMCVD Au NPs for achieving a high sensitivity. As an initial step, the OTS SAMs need to perfectly resist the OMCVD Au NP growth. Hence the optimized formation of the OTS SAMs affected by different assembly times and baking temperatures was studied by contact angle, ellipsometry, XPS, SEM, and atomic force microscopy (AFM). To demonstrate the ability of the OTS SAMs to resist OMCVD Au NP growth, the OMCVD process was carried out on two sets of samples: OTS SAMs fabricated under optimized conditions on one set and the other set without OTS SAMs. High‐resolution XPS, RBS, SEM, and ultraviolet‐visible (UV‐Vis) spectroscopy were applied to study the growth of Au NPs on the samples with and without OTS SAM resists. Copyright © 2009 John Wiley & Sons, Ltd.     

Fluorine-contained photoacid generators (PAGs) and corresponding polymer resists

A new series of fluorinated anionic photoacid generators (PAGs) (F4-MBS-TPS, F4VBzBS-TPS, F4-IBBS-TPS, CF3 MBS-TPS, MTFBS-TPS and VBzTFBS-TPS), and corresponding PAG bound polymeric resists (HS-EA-PAG) based on hydroxystyrene (HOST) and 2-ethyl-2-adamantyl methacrylate (EA), (GB-EA-PAG) based on γ-butyrolactone methacrylate (GBLMA) and 2-ethyl-2-adamantyl methacrylate (EA) were prepared and characterized. The acid generating efficiency of PAG bound polymers (HS-EA-PAG) series was in the range of 54-81%, which agrees well with the electron withdrawing effect of the substituents. With regard to the referenced F4-PAG bound polymer with 68% acid generating efficiency, and our previously reported EUVL results of F4-MBS-TPS bound polymer photoresists, these new PAG bound polymers should be effective resists for 193 nm or EUV lithography.     

The synthesis and lithographic evaluation of a new organosilicon novolac-based resist

A novel material, bis(trimethylsilylmethoxy resorcinol) was synthesized by a phenoxide alkylation method. The new substituted resorcinol was then terpolymerized with 2-methyl resorcinol and formaldehyde. We evaluated the preparation of this new polymer in terms of feed ratio of the reactants, reaction time, and temperature; and prepared a series of materials with different silicon content. Polymers which retained base solubility at high silicon content were blended with a dissolution inhibitor, and studied for their lithographic capabilities as positive, photo- or electron-beam bilevel resists. When used in a photoresist formulation a dose of 120 mJ/cm² allowed formation of submicron features. When used in an electron-beam resist formulation 0.5 μm line/space patterns were obtained at a dose of 10 μC/cm². Furthermore, these materials displayed etching ratios relative to hardbaked HPR206 of ? 1 : 10. This value is believed to be large enough to allow these resists to withstand reactive ion etching conditions for pattern transfer in a bilevel scheme.     

一种高感度深紫外正性化学增幅型抗蚀剂的制备

聚对羟基苯乙烯和环己基乙烯基醚反应得到缩醛保护的聚合物.该聚合物易溶于常见的有机溶剂,具有较好的热稳定性,在248 nm处透明性良好.该聚合物可与聚对羟基苯乙烯-甲基丙烯酸金刚烷基酯及二砜光产酸剂等组成一种三组分正性化学增幅型深紫外光致抗蚀剂,初步研究了该抗蚀剂的感光成像性能.采用KrF激光（248 nm）曝光,在较低的后烘温度下,显影得到分辨率为180 nm的线条图形.显影后的留膜率在99%以上.在光致抗蚀剂体系中引入对羟基苯乙烯-金刚烷基甲基丙烯酸酯共聚物,可提高光刻胶材料的玻璃化转变温度,有利于其实际应用.     

A novel photo‐acid generator bound molecular glass resist with a single protecting group

A novel photo‐acid generator (PAG) bound molecular glass photoresist with a single protecting group has been developed as a promising resist material for use in microelectronics. This single component molecular resist was prepared in four steps starting from 9,9‐bis(4‐hydroxyphenyl)fluorene. The single component molecular resist exhibited good thermal properties, such as a 10% weight loss temperature of 200 °C and a glass transition temperature of 91 °C. This resist showed a good sensitivity of 60 μC/cm² with e‐beam exposure (50 keV). On the other hand, the fine pattern with a half‐pitch of 50 nm in the presence of 4 wt % quencher, trioctylamine, was obtained using electron‐beam (100 keV) lithography. The LER value was 8.2 nm (3σ, 60 nm half‐pitch patterns). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

含碘鎓盐光产酸剂和增感染料的化学增幅型i-线正性光致抗蚀剂

4,4’-二甲苯基三氟甲磺酸碘鎓盐可以被染料增感,在365 nm光照时分解产酸.尽管产生的酸与染料的胺基发生作用,依然能在后烘过程中催化缩醛聚合物酸敏基团的分解,但需要稍高的后烘温度和稍长的后烘时间.基于此,本文将酚醛树脂、缩醛聚合物、碘鎓盐产酸剂和染料组成了一种新型的化学增幅型i-线正性光致抗蚀剂材料,在曝光量为10...     

Preparation of trimethylsilyl group containing copolymer for negative-type photoresists that enable stripped by an alkaline solution

A series of four trimethylsilyl group containing copolymers were synthesized using the solution free-radical copolymerization with azobisisobutyronitrile (AIBN) in 1,4-dioxane at 60 °C. The photoresists were prepared by dissolving copolymer, one of two kind photosensitizer (dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate) and Michler's ketone in tetrahydrofuran (THF). The cyclic maleimide group was responsible for the high thermal stabilities. After irradiation by a deep-ultraviolet light and development with mixed solvent (methyl isobutyl ketone:2-propanol=1:3), the developed patterns showed negative images and exhibited good adhesion to the silicon wafer without using any adhesion promoter. The resolution of the resists was at least 1.75 μm and the oxygen plasma etching rate was 1/6 of hard-baked HPR-204, which can be also used as the top-imaging layer of a bilayer resist for microlithographic application. These photoresists can be stripped by week alkaline solution such as sodium carbonate solution (0.01 wt.%) after exposure.     

Oxidation of elemental gold in alcohol solutions

Gold is designated as the noblest metal because of its chemical inertness. It is known to dissolve in cyanide solutions in the presence of air or H2O2 or in halogen-containing solutions, aqua regia being the most famous example. Herein, we report a unique thiol, especially 4-pyridinethiol (4-PS), assisted dissolution of Au in alcohol solutions. Although dissolution was found to be very selective for pyridinethiols, such a phenomenon is astonishing since thiols are commonly used as etch resists for Au and even 4-PS is extensively used as a surface modifier for Au. To gain further understanding of the dissolution process, the influence of the reaction conditions was extensively studied. On the basis of the obtained results, a mechanism for the dissolution reaction is proposed. Fascinatingly, by tuning of the reaction conditions, this phenomenon can be applied in selective preparation of self-supporting nanometer-thick Au foils.     

Acid generation and deprotecting reaction by diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate in a novolak positive photoresist based on chemical amplification

In a positive photoresist composed of diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate as a novel photoacid generator, bisphenol A protected with tertbutoxycarbonyl group as a dissolution inhibitor, and a novolak resist matrix, the efficiency of photo-acid generation and deprotective reaction were investigated by means of UV-visible and IR spectroscopies. The quantitative measurement of photogenerated acid by using the acid-sensitive dye exhibited 0.18 as the quantum yield of acid generation in novolak resin film. The lithographic evaluation of this system as a chemically amplified resist was studied. The catalytic chain length for the acid-catalyzed deprotection step was determined as about 100 when 10 min post-exposure bake (PEB) at 80°C was given. The sensitivity and the resolution as a positive resist are 180 mJ/cm² and higher than 1 μm, respectively under the PEB conditions mentioned above.