Fabrication of Nanometer Scale Patterns with Polymer Langmuir-Blodgett Films

The continuing trend toward higher circuit density in microelectronic devices has motivated research efforts in varieties of high-resolution lithography techniques, including electron beam (EB), X-ray, and deep UV irradiation.已经提出了使用超薄薄膜和新材料作为改善光刻分辨率的方法。亚博网站下载Langmuir-Blodgett（LB）技术是非常有效的方法，用于制备具有受控厚度和分子水平的厚度和取向的明确定义的超薄膜。因此，预期LB薄膜将实现超高分辨率光刻[1-4]。

在以前的研究中，[5-7]我们已经发现了N- 用高度有序的结构形成均匀的LB膜，并通过光聚合产生微量的阴性图案。Furthermore, we have also succeeded in the preparation of preformed polymer LB film that has a cross-linking group [8].通过与深UV和电子束照射的交联反应，我们获得了由二维网络组成的细负面图案。一种ll of these polymer LB films resulted in negative-tone photopatterns.另一方面，我们也使用Poly获得正型PhotoPatterns（N-tetradecylmethacrylamide)(p(TDMA)) LB films without any development process (self-development) [9, 10].It was found that the higher sensitivity could be obtained by changing the alkyl side chain to the short-branched type [11].此外，脱保护反应t- 丁氧基羰基氧基也已用于聚合物LB膜的正图案化[12-14]。Combining these interesting properties, the improvement of not only the sensitivity but also the imaging quality can be expected.In this work, we prepared the copolymers of photodegradableN-tetradecylmethacrylamide (TDMA) witht- 丁基4-乙烯基苯基酯（tBVPC) (Figure 1) aiming at the fabrication of a new type of positive resist taking place both main chain scission and polarity change caused byt-butoxycarbonyloxy group deprotection.

Figure 1.Chemical structure of p(TDMA-tBVPC).

Experimental

共聚物（P（TDMA-tBVPC)) was prepared by free-radical copolymerization ofN-tetradcylmethacrylamide (TDMA) witht- 丁二丁丁基碳酸丁酯（tBVPC）在60℃的甲苯中。测量表面压力（π） - 区域 （一种）isotherm and deposition of monolayers were carried out at 15˚C with a Langmuir trough system (FSD-50 and 51, USI) with a compression speed of 14 cm²/分钟。在上下行程中，沉积速率设定为10mm / min。将去离子纯水（Milli-QII，Millipore）用作亚相。将共聚物以浓度溶于氯仿中加利福尼亚州。1毫米，溶液在水面上涂布。沉积玻璃，石英和硅载玻片，最初通过UV-O3清洁剂（NL-UV253，Nippon激光电子）清洗液体;然后用正辛基三氯硅烷制成疏水。用Hitachi U-3000 uV-Vis分光光度计记录UV吸收测量。The molar ratio of thet共聚物中的BCPV¹H NMR of p(TDMA-tBVPC）。Molecular weight was determined with a Toyo Soda gel permeation chromatography (GPC) using a polystyrene standard.IR spectra were measured with a JASCO-IR 230 spectrometer.通过IR-CUT过滤器，用深紫外灯（UXM-501MA，USHIO）进行深紫外线照射。使用Sloan Dektak 3st，用表面轮廓测定共聚物LB膜的厚度。Gold film was deposited onto a glass substrate with a vacuum evaporator (V-KS200, Osaka Vacuum, Ltd).

Results and Discussion

Formation of Copolymer LB Films

p的分子量（tdma-tBVPC) are summarized in Table 1.共聚物（P（TDMA-tBVPC））从氯仿溶液中涂在水亚相（加利福尼亚州。1mm）测量表面压力（π）- 区域（一种）isotherms (Figure 2).共聚物p（TDMA-tBVPC) monomers have collapse pressure.Their curves stand sharply.我们可以得出结论，它们可以在水亚相的凝聚的单体形成。The p(TDMA-tBVPC) monolayer could be transferred onto a solid substrate with a transfer ratio of almost unity.P的紫外线吸收光谱（TDMA-t在石英上的BVPC56）LB膜作为层数的函数测量（图3）。193nm处的吸光度显然随着沉积的层数线性增加，表明共聚物单层的正则沉积在固体基质上。

Table 1.TDMA的各种共聚物tBVPC。

p的光刻性能（TDMA-tBVPC) LB Films

The p(TDMA-tBVPC56）具有60层的LB膜直接暴露于深紫色灯（86mW / cm²）through a photomask without no monochromatic filter in the air for 60 min and then developed with 1% tetramethylammonium hydroxide (TMAH) aqueous solution.如图4所示，我们获得了一个明确的正音模式，分辨率为0.75µM，这是本作中采用的光掩模的分辨率限制。在LB膜（20,40,60和80层）的光图中，具有60层的LB膜在本条件下给出了最优质的分辨率。Therefore, the subsequent experiments for the sensitivity were carried out with 60 layers of LB films.

Figure 4.P（TDMA-TBVPC56）光学显微照片（TDMA-TBVPC56）LV薄膜，具有60层，在空气中进行60分钟，随后用1％TMAH水溶液进行20多次

为了估计LB膜的光刻性能的灵敏度，以暴露时间的函数测量暴露部分中的LB膜的残留厚度（图5）。It should be noted that the p(TDMA-tBVPC56）LB膜比均聚物[P（TDMA）] LB膜更敏感（图5）[11]。此外，P的厚度下降显然有两个步骤（TDMA-tBVPC56) LB film,虽然在接受主要链群的所有聚（烷基甲基丙烯酰胺）LB膜的敏感性曲线中观察到厚度的单调减少[11]。Since the light intensity at 193 nm (λ_最大限度of the copolymers) from the deep UV lamp was very weak and was not able to be estimated exactly, the quantitative analysis of the sensitivity of the LB films could not be determined.From the shape of the sensitivity curve of p(TDMA-t然而，BVPC56）LB膜，光电二聚体过程中有两个步骤是显而易见的;去的去脱离t-butoxycarbonyloxy group is predominant in the initial region and consequently the main chain scission due to the TDMA fragmentation occurs.归一化膜厚度随曝光时间减少，即，LB膜中的共聚物通过深紫色辐射有效地分解并与碱性溶液的发育完全除去。

Figure 5.P（TDMA-TBVPC56）和P（TDMA）LB膜的敏感性曲线。

Etching Resistance

蚀刻p（TDMA-tBVPC56) LB film against wet etching was also investigated as follows: the p(TDMA-tBVPC56）具有20层的LB膜沉积在金基底上;然后，通过具有深紫外灯的光掩模照射它（86 nW / cm²）; finally, it was developed with alkaline solution.接下来，将正色调图案化底物浸入碘化铵，碘化物，乙醇和水（蚀刻剂）的混合溶液中。Finally the LB film on gold film was removed with chloroform.Figure 6 shows the patterns of gold film after the etching.Resolution of 1.0µ获得用于金膜的m。This indicates that the copolymer p(TDMA-t具有至少20层的BVPC56）LB膜具有蚀刻剂的高抗蚀刻性。

共聚物LB膜的光分解

The photopattern formation in copolymer LB films was investigated for the photodecomposition mechanism.获得实验数据的显着变化，p（TDMA-tBVPC56) LB film with 40 layers were used for UV and IR spectra, and p(TDMA-tBVPC56) cast film was utilized for GPC measurements.First, absorption spectra change of p(TDMA-tBVPC56) LB film with 60 layers under deep UV irradiation was measured (Figure 7).193纳米的吸收带是分配给一个mide group and the group oft- 丁氧基羰基氧基。193nm处的吸光度降低表明主链体裂变，芳香环的光分解或t-butoxycarbonyloxy group occurs by UV light irradiation, leading to the formation of volatile low molecular weight compounds such as carbon dioxide, isobutylene [16], or form conjugated structure because of the presence of a broad absorptive tail at wavelength above 230 nm.

In addition, the GPC measurement of the p(TDMA-tBVPC56）进行铸造膜以确认在深紫色辐照期间的分子量变化。一种s clearly shown in Figure 8, the molecular weight decreased with irradiation time, and the curve became broader, indicating that the molecular distribution is larger than that of the initial state.These findings suggest that the main chain scission also takes place.

吸光度在3350厘米处^-1在羟基的拉伸振动的LB膜的IR光谱中，照射后增加（图9），这是通过UV辐射产生羟基的证据[11,17]。频段为1750厘米^-1, which is assigned to carbonyl group, is attenuated by deep UV irradiation.This also means that thet将丁氧基羰基氧基从侧链中除去，得到苯酚，其可以溶解在碱性溶液中[15]。而且，2910厘米处的吸光度^-1assigned to the alkyl group is drastically decreased after 30 min irradiation.This implies that the LB film is more dissolved in alkaline solution due to the change of the molecular weight.一种lthough the difficulty still remains in distinguishing the difference between main chain and side chain scissions, these findings support the above discussion in the sensitivity curve for p(TDMA-tBVPC56) LB film.

结论

共聚物[P（TDMA-tBVPC)] were prepared by free radical copolymerization.The copolymer has a structure being subjected to decomposition in main chain scission and side chain cleavage.聚合物在水亚相的稳定单层形成稳定的单层，并且可以将单层转移到固体基质上。在LB膜上的深紫色光照射的情况下，用碱性水溶液显影后可以获得正色调图案。We also investigated the etching property of the underling gold.The p(TDMA-tBVPC56) LB films with 20 layers have a high etching resistance with a resolution of 1.0µm。从结果我们期望新的共聚物[p（tdma-tBVPC56)] can be used in the lithographic process in future.

一种cknowledgements

We would like to thank Prof. T. Miyazaki, and Dr. Y. Ando, Department of Applied Physics, Graduate School Engineering, Tohoku University, for the use of the surface profilometry.从日本促进科学协会的“未来”计划（JSPS-RFTF97P00302）的“对未来”计划（JSPS-RFTF97P00302）的授予，部分支持这项工作。亚博老虎机网登录

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This paper was also published in print form in “Advances in Technology of Materials and Materials Processing”, 7[2] (2005) 209-214.