DNQ–novolac photoresists revisited: 1H and 13C NMR evidence for a novel photoreaction mechanism

Photoactive compounds, such as diazonaphthoquinone (DNQ) esters, blended with novolac resins, solvents and certain additives, serve as photoresists. These are used for printing of electronic circuits at the micron or sub‐micron level. Patterns are generated based on changes in the physical and chemical properties of the exposed and unexposed photoresist surfaces (printed circuit boards). The huge polarity change between the exposed and unexposed photoresists is exploited in the technique of microlithography. It is believed that the large polarity difference is due to acid formation in the exposed photoresist by a photochemical reaction of DNQ on exposure to light. However, it has also been suggested that in the unexposed part of a photoresist, the novolac resin undergoes an azo coupling reaction with DNQ, leading to an increase in the molecular weight of the resin, rendering it more insoluble in base. The protons in the para positions of the m‐cresol units incorporated in the novolac resin are believed to take part in this azo coupling reaction with DNQ. In this paper, we propose a novel mechanism of action of positive photoresists in the unexposed part of photoresists for dissolution inhibition using molecular modelling, ¹H NMR, ¹³C NMR and DEPT‐135 NMR spectroscopic techniques. Our results enable us to propose that the diazo group of DNQ attacks the methylene bridges rather than the aromatic moiety of the resin. This mechanism explains the pattern formation observed using even p‐cresol‐based resins, where no free para positions are present in the aromatic ring. Copyright © 2003 John Wiley & Sons, Ltd.     

Fabrication of complex multilevel microchannels in PDMS by using three-dimensional photoresist masters

This paper demonstrates a new method of implementing complex microchannels in PDMS, which is simply constructed using three-dimensional photoresist structures as a master mold for the PDMS replica process. The process utilizes UV-insensitive LOR resist as a sacrificial layer to levitate the structural photoresist. In addition, the thickness of photoresist structures can be controlled by multi-step UV exposure. By using these techniques, various three-dimensional photoresist structures were successfully implemented, including the recessed cantilevers, suspended bridges, and the complex plates with micro-pits or micro-villi. We demonstrate that the three-dimensional photoresist structures are applicable to implementing complex multiple microchannels in PDMS by using the PDMS replica method.     

RAFT聚合法合成甲基丙烯酸酯共聚物及其在负性光致抗蚀剂中的应用

以甲基丙烯酸(MAA)、甲基丙烯酸苄基酯(BZMA)、甲基丙烯酸羟乙酯(HEMA)和丙烯酸正丁酯(BA)为共聚单体,偶氮二异丁腈(AIBN)为引发剂,2-(十二烷基三硫代碳酸酯基)-2-甲基丙酸(DMP)为链转移试剂,采用可逆加成-断裂链转移聚合(RAFT)制备了甲基丙烯酸酯共聚物(PMBBH)。利用傅立叶红外光谱(FT-IR)、核磁共振氢谱(¹HNMR)和凝胶渗透色谱(GPC)对共聚物的结构进行了表征。以共聚物PMBBH为基体树脂制备了负性光致抗蚀剂,考察了PMBBH的分子量对光致抗蚀剂分辨率的影响。结果表明,以数均分子量为5.45×10³ g/mol,重均分子量为7.79×10³ g/mol的PMBBH-2作为基体树脂时,该光致抗蚀剂得到的图像轮廓清晰,图形分辨率可达50 μm。     

Tetraindole Derivatives of Porphyrins as Building Blocks in the Synthesis of Monodisperse Polyphenols

A new strategy for the synthesis of monodisperse polyphenols chemically bound to a rigid thermally stable molecular platform has been suggested. The platform has been prepared by the Suzuki–Miyaura reaction of a tetraboryl porphyrin derivative and 3-(4′-bromophenyl)-4,6-dimethoxyindole. Subsequent reactions of complete demethylation of obtained tetraindole and partial blocking of the corresponding phenolic hydroxyls by acid-labile protective groups have led to the formation of a final modified polyphenol compound of the porphyrin series. On the basis of the this polyphenol, a positive photoresist for lithography with exposure radiation at a wavelength of 13.5 nm has been developed; the photoresist affords the fabrication of topological structures with 16-nm resolution.     

酚醛-重氮萘醌正性抗蚀剂溶解抑制机理

本文综述了酚醛 重氮萘醌正性抗蚀剂的溶解抑制机理,主要包括(1)分子间氢键作用机理;(2)偶联反应机理;(3)两步即静态、动态溶解抑制机理;(4)表面沉积溶解抑制机理;(5)酚醛树脂的分子溶解及相关的抑制机理.     

Negative‐working photoresist based on a first‐generation dendrimer consisting of 4,4‐diphenylpentyloxy units

A first‐generation dendrimer ( 2 ), containing phenol groups in the exterior for solubilization in aqueous alkaline solutions, was evaluated as a new negative‐working, alkaline‐developable photoresist material. A negative‐working photoresist based on 2 , 4,4′‐methylenebis[2,6‐bis(hydroxymethyl)phenol] as a crosslinker, and diphenyliodonium 9,10‐dimethoxyanthracene‐2‐sulfonate as a photoacid generator was demonstrated. This resist gave a clear negative pattern through postbaking at 90 °C after exposure to UV light, which was followed by development with a 2.38% aqueous tetramethyl ammonium hydroxide solution at room temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1210–1215, 2005     

一种248 nm光刻胶成膜树脂的合成及相关性能研究

通过自由基共聚合,制备了前驱体共聚物聚对特丁氧酰氧基苯乙烯-共-N-羟基-5-降冰片烯-2,3-二甲酰亚胺甲基丙烯酸酯,该共聚物可以通过热解而部分脱除酚羟基上的保护基,得到目标共聚物聚对羟基苯乙烯-共-N-羟基-5-降冰片烯-2,3-二甲酰亚胺甲基丙烯酸酯-共-对特丁氧酰氧基苯乙烯.通过对具有合适分子量的目标共聚物的有机溶剂溶解性、热性能、成膜性、抗干蚀刻能力和在248 nm处光学吸收(为0.212 μm^-1)性能进行研究,表明该聚合物能满足248 nm光刻胶成膜树脂的要求;此外,目标共聚物还具有酸致脱保性能.具有合适分子量和脱保率的目标共聚物,通过对其酸解留膜率的测试,推测其可能满足248 nm光刻胶的曝光显影工艺过程.     

New Positive‐Type Photoresists Based on Enzymatically Synthesized Polyphenols

Summary: New positive‐type photoresist systems based on enzymatically synthesized polyphenols have been developed. The photoresist thin film consisting of the polyphenol and a diazonaphthoquinone derivative was prepared on copperfoil‐coated epoxy resins and exposed to UV light with different doses. The polyphenols from the bisphenol monomers exhibited high photosensitivity, comparable with a conventional cresol novolac. The sensitivity could be controlled by changing the structure of the polyphenols. Furthermore, the present photoresist showed excellent etching resistance.

Characteristic exposure curves of poly( 1 )/DNQ and poly( 5 )/DNQ (both 70:30 wt.‐%) with different phenylene unit contents.     

Study of SU-8 to make a Ni master-mold: Adhesion, sidewall profile, and removal

For disposable microfluidic devices, easy and inexpensive fabrication is essential. Consequently, replication of microfluidic devices, using injection molding or hot embossing, from a master-mold is widely used. However, the conventional master-mold fabrication technique is unsatisfactory in terms of time and costs. In this regard, direct Ni growth (electroplating) from a back plate is promising when the photoresist is well-defined. Here, we demonstrate the use of SU-8 as a photoresist to define the Ni-growth region. We accomplish this application by focusing on the adhesion, the sidewall profile, and the removal of SU-8: the adhesion is enhanced by controlling the exposure dose, the soft-baking time, and by choosing the adhesion-promoting layer; the sidewall profile is regulated by selecting the intensity of each exposed wavelength, showing an aspect ratio of up to 20.9; and, easy removal is achieved by choosing a proper photoresist-stripper. Using the master-mold fabricated by this method, we test the mechanical stability of the features according to the aspect ratio and length; in the hot embossing process, the features are stable in the aspect ratio of up to 5.8 at a length of 200 microm. In addition, the plastic devices fabricated from this method are applied to the passive stop valves, showing a capillary pressure (-0.2 to -7.2 kPa).     

水溶性丙烯酸酯类感光干膜的制备及其性能研究

用溶液聚合法合成了水溶性丙烯酸树脂,并以该树脂为成膜物质制备了水溶性感光干膜。傅立叶-红外光谱和¹HNMR分析表明,丙烯酸树脂中不含CC不饱和双键,基本不参与紫外光固化反应。感光干膜性能测试表明,干膜中丙烯酸树脂的酸值及重均分子量会影响干膜的解析度和附着力等性能。进一步的研究表明,曝光能量、感光级数和显影时间也会直接影响干膜的性能。以30 μm厚度干膜Ⅱ为例,为获得较好的性能,丙烯酸树脂中甲基丙烯酸含量范围为21.5%~23.8%,重均分子量范围为6.00×10⁴~7.54×10⁴,曝光能量设定40~60 mJ/cm²,感光级数为18~23/41^ST,显影时间40~50 s,在此条件下,干膜的解析度可以达到30 μm,附着力为20 μm,干膜线路的侧边形貌和尺寸稳定性良好。此外,感光干膜中丙烯酸酯的比例和种类也会影响干膜的各方面性能,通过调节干膜中各组分含量的比例可以优化干膜性能。     

Dill’s parameter measure in liquid photosensitive materials via interferometric method

In this work, we have studied the behavior of photosensitive materials in the liquid state when exposed to light with the aim of measuring the chemical kinetics in such state. The chemical kinetics is found determining the Dill’s parameter through the fit of the refractive index variations with energy per exposed area, based on a model proposed by Dill. The measurements were performed during a blue light exposure process of using a high precision Michelson Interferometer in liquid AZ-1518 photoresist.     

一种可以正负互用的水型化学增幅抗蚀剂的研究

研究了一种由甲酚醛树脂、六甲氧基甲基三聚氰胺(HMMM)、六氟磷酸根二苯碘盐和光敏剂组成的水型紫外化学增幅抗蚀剂,发现二苯基碘盐不仅可以作为光敏产酸物,而且可以作为阻溶剂.用碘盐作为光敏产酸物,光解产生的酸可以在中烘时催化甲酚醛树脂与HMMM的交联反应;用氢氧化钠-乙醇水溶液显影可以得到负性光刻图形;采用碘盐作为阻溶剂,可阻止非曝光区的胶膜溶解在显影液中,用稀的氢氧化钠水溶液显影可以得到正性光刻图形.通过优化后的光刻工艺条件,采用不同的显影液和光刻工艺流程,实现了同一光致抗蚀剂的正负性反转,并分别得到负性和正性光刻图形.     

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.     

AZ-1518 Photoresist analysis with synchrotron radiation using high-resolution time-of-flight mass spectrometry

With the aim of identifying molecular modifications among photoresists unexposed and previously exposed to the ultraviolet light the photon stimulated ion desorption (PSID) technique was employed in the study of the AZ-1518 photoresist. Data acquisition was performed at the Brazilian Synchrotron Light Source (LNLS), during a single-bunch operation mode of the storage ring and using high-resolution time-of-flight mass spectrometry (TOF-MS) for ion analysis. PSID mass spectra on both photoresists (unexposed and exposed) were obtained following the S K-shell photoexcitation and desorption ion yield curves have been determined for the main fragments as a function of the photon energy. The AZ-1518 photoresists presented different PSID spectra, showing characteristic fragments. Most of the analyzed ions showed larger relative yields for the exposed photoresist. Fragments related to the photochemical decomposition of the photoresist could be clearly identified. These results showed that the PSID technique is adequate to investigate structural changes in molecular level in unexposed and exposed photoresists.     

Pyrromethene dye sensitized photopolymer—photochemical behavior in polymer matrix and application to photoresist for printed circuit board

The photochemical behavior of the visible light initiating system that consists of a sensitizing dye, 2,6‐diethyl‐8‐phenyl‐1,3,5,7‐tetramethylpyrromethene BF₂ complex (EPP), and a photoacid generator, N‐trifluoromethylsulfonyloxy‐1,8‐naphthalimide (NIOTf), was studied mainly by means of absorption and fluorescence spectrometry not in solution but in a polymer matrix which is a closer medium to the one currently employed in the field of photoresists. Excited singlet electron transfer from EPP to NIOTf was considered as the main reaction pathway in this system. The EPP/NIOTf system was applied to a photoresist for printed circuit board with an appropriate binder polymer which contains an acetal protection group. A pattern profile of the photoresist was exceedingly affected by the amount of photogenerated acids, their diffusion, and amine in the atmosphere. Finally, by controlling exposure energy and the post‐exposure bake (PEB) process, a photoresist with a high resolution (8 µm line and space) was obtained under argon ion laser irradiation. Copyright © 2006 John Wiley & Sons, Ltd.     

248 nm深紫外光刻胶用成膜树脂的研究进展

综述了用于248 nm化学增幅型深紫外光刻胶的不同种类和结构的成膜树脂,以及所使用单体的研发进展,包括聚甲基丙烯酸甲酯及其衍生物、聚对羟基苯乙烯及其衍生物、N取代的马来酰亚胺衍生物,以及其他聚合物等,对不同结构成膜树脂的曝光条件、对光刻胶性能的影响进行了介绍。     

Novel One-component Positive-tone Chemically Amplified I-Line Molecular Glass Photoresist Based on Tannic Acid

Molecular glass resist has been considered as one of the best choices for a new generation of lithography. In this work, a new type of photoactive compound was obtained by the esterification of tannic acid with 2-diazo-1- naphthoquinone-4-sulfonyl chloride(2,1,4-DNQ-Cl) and ditertbutyl dicarbonate. The new obtained compound possessed both a photosensitive group of diazonaphthoquinone sulfonate(2,1,4-DNQ) and a group of acidolytic protection. Upon the irradiation of the compound under 365 nm light, the former group was photolyzed and converted into indene carboxylic acid along with a small amount of sulfonic acid, which could lead to the deprotection of the latter group. As a result, a novel i-line molecular glass photoresist was formed with the chemical modification of tannic acid. The experimental results show that the modificated compound had a fair solubility in many organic solvents. The lithographic performance of the resist was evaluated on an i-line exposure system with high photosensitivity and resolution as well.     

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     

Vis‐sensitive photopolymer containing vinyl ether compound and pyrromethene dye

A visible light(vis)‐sensitive photoresist based on the concept of chemical amplification was developed utilizing poly(p‐hydroxystyrene) (PHS), 2,2‐bis[4‐(2‐(vinyloxy)‐ethoxy)phenyl]propane (BPA‐DEVE) as a crosslinking agent, N‐trifluoromethylsulfonyloxy‐1,8‐naphthalimide (NIT) as a photoacid generator (PAG) and pyrromethene dyes such as 1,3,5,7,9‐pentamethylbipyrromethene difluoroborate (PRH) and 2,8‐diethyl‐1,3,5,7,9‐pentamethylbipyrromethene difluoroborate (PRE) and 3,3′‐carbonylbis(7,7′‐diethylaminocoumarin) (KCD). On irradiation with an argon ion laser, the photopolymer comprising PRH and PRE exhibited a high sensitivity of 65 and 46 mJ cm^?2, respectively. It is suggested that the sensitization mechanism of the pyrromethene dye/PAG system involves singlet electron transfer. The sensitivity of the photoresist increased with the decreasing molecular weight of PHS because of the high dissolution rate. Copyright © 2002 John Wiley & Sons, Ltd.     

Photogenerated polyelectrolyte bilayers from an aqueous-processible photoresist for multicomponent protein patterning

A novel photoresist (PR) that can be processed under mild aqueous conditions was synthesized and used to create photogenerated polyelectrolyte bilayers. Thin films of the PR cast on polycation-coated substrates were exposed to UV irradiation to generate carboxylate groups in the photoresist. The bulk of the UV-exposed PR film was dissolved by rinsing with pH 7.4 phosphate-buffered saline, but a polyelectrolyte bilayer formed in situ at the PR/polycation interface on exposure remained bound to the substrate. The UV-exposed photoresist also exhibited pH-dependent solubility; it was soluble in water above pH 6.6, but insoluble at lower pHs. Using these unique properties, two-component protein patterning was achieved using biotinylated PR films under conditions that avoid exposing the proteins to conditions outside the narrow range of physiological pH, ionic strength, and temperature where their stability is greatest.