Plasma Polymerized Methyl Methacrylate Research Articles

Morphology of plasma polymerized methyl methacrylate films

The surface morphology of plasma polymerized methyl methacrylate films was investigated using atomic force microscopy. It was found that the plasma polymer surfaces consist of nanometer scale growth columns. The average grain size of the growth columns increases with deposition time. For the same deposition time, the average grain size is proportional to pressure and deposition power. It was deduced that microscopic properties of plasma polymers are not uniform through the bulk of the plasma polymer films even though the external deposition parameters are held constant.

A time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy investigation of the structure of plasma polymers prepared from the methacrylate series of monomers

Plasma polymers (PPs) have been prepared from methacrylate precursors and analysed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (X.p.s.). The negative SIMS data for plasma polymerized methyl methacrylate (ppMMA) were compared with that of a low molecular weight oligomer and a high molecular weight conventional poly(methyl methacrylate). This facilitated the interpretation of the SIMS data and has enabled a qualitative structure for ppMMA to be proposed. The secondary ion mass spectra from PPs of ethyl methacrylate and butyl methacrylate are shown to be very similar to ppMMA, where the methyl group is replaced by an ethyl and a butyl group, respectively. The X.p.s. data for ppMMA showed that the PP had retained ∼80% of the oxygen from the monomer. Much of this was present as the ester group which indicates that extensive fragmentation of the monomer had not occurred during plasma polymerization. Evidence that the monomer structure had been retained in the PP was also provided by the SIMS data; a number of negative ions (e.g. at m z = 85, 87, 101 and 187) have structures which contain a complete monomer unit.

Photoluminescence of plasma polymerized methyl methacrylate films

The photoluminescence properties of plasma polymerized methyl methacrylate films are investigated. The photoluminescence is a fluorescence rather than a phosphorescence process with a lifetime on the order of a few nanoseconds. The photoluminescence is a one-photon volume effect. The wavelength span of the photoluminescence using suitable UV excitation can reach over 300 nm with a FWHM exceeding 200 nm. These photoluminescent films may find potential applications in wavelength transformers for solar cells or as a gain medium for tunable solid-state dye lasers.

Improvement in the Sensitivity of PPMMA Electron Beam Resist by S and F Atom Doping

The present work reports the dependence of sensitivity of plasma polymerized methyl methacrylate (PPMMA) as electron beam resist on S and F atom concentration in the films. Plasma polymerization of MMA is carried out in an inductively coupled reactor at different deposition conditions with and without SF6 doping. Ar is used as carrier gas. The bonding characterization of the films is done by IR and X-ray photoelectron spectroscopy (XPS) techniques. XPS data taken on films, deposited under different deposition conditions, is used to estimate the S and F concentrations. The electron beam delineation is done using scanning electron microscope (SEM), modified for electron beam writing. The self development sensitivity of PPMMA films doped with S and F atoms is found to be 2-3 times improved compared to undoped PPMMA and is also dependent on deposition conditions.

Molecular Structure of Plasma-polymerized Methyl Methacrylate and Evaluation as a Resist

種々のキャリヤーガスプラズマ下流にメタクリル酸チルモノマーを混入して重合膜を基板上に形成した。重合速度やエッチング速度のキャリヤーガス依存性を調べるとともに,重合膜のIR,ESCA,NMR測定を行ない,分子構造,反応機構を検討した。さらに,この重合膜を電子線X線で描画し,その潜像をプラズマエッチングによって現嫁し,レジストとしての特性を評価した。この結果・不活性ガスをキャリヤーガスとしたときはラジカル性の反応が主要な反応機構であり,分子構造も通常の高分子に類似したものであることがわかった。他方,酸素などの反応性ガスの場合,イオン性反応が観測され,分子構造も通常の高分子とは異なっていることがわかった。レジストとしての特性は,ドライ現嫁する場合は,プラズマ重合したものが通常の高分子よりも高感度となり,描画パターンの現像ができた。しかし,実用的なレジスト感度を得るためには,さらに増感剤の混入などの対策が必要なことがわかった。

Thin films prepared by plasma polymerization of methyl-methacrylate and their properties as an electron beam resist

Plasma polymerized methyl-methacrylate (PPMMA) thin films were formed under various conditions in an ac glow discharge using a bell-jar type reactor with parallel plate electrodes. It has been found that the deposition rate increases in the frequency range from 10 to 50 kHz. The possibility of using the films as an electron beam resist has been investigated.

Vacuum lithography using plasma polymerization and plasma development

A completely dry lithography has been proposed which involves plasma polymerization of methyl methacrylate (MMA) and plasma development with CCl 4. It was called vacuum lithography because all processes were performed in a vacuum. However, the developed pattern had a lower resolution than patterns produced by conventional lithography with a wet process. After several technical refinements, the quality of the resist and the developed pattern was markedly improved. In this paper, recent results will be reported. A gas-flow-type reactor was used instead of a bell-jar-type reactor because the morphology of plasma-polymerized MMA (PPMMA) varied with each experimental run which was performed with the same gas and discharge parameters. The monomer vapour was introduced downstream of the argon discharge, and the polymerized film was formed on the substrate placed further downstream in the mixed gas. The development of pattern was performed by etching with an Ar-O 2 mixture and with hydrogen gas instead of CCl 4 gas, because the etching rate of the resist was too high in a CCl 4 plasma and a clear pattern was not obtained. The evaluated sensitivity and γ value of PPMMA were 1000 μC cm −2 and 1 respectively. MMA containing 5% tetramethyltin was also used as a monomer gas for plasma polymerization downstream of the argon discharge. In this case the sensitivity and γ value were 10 μC cm −2 and 2 respectively.

Vacuum lithography?A completely dry lithography using plasma processing

The purpose of this paper is to describe a thoroughly dry lithography using plasma polymerization and plasma etching. The new lithography is named vacuum lithography because all processes are performed at reduced pressures. Resist films were formed in bell-jar-type and argon-flow-type reactors. The controllability of plasma polymerization is discussed with respect to the type of reactor and gas mixture. A pattern was delineated in the resist using an electron beam, and it was developed by plasma etching with a mixture of argon and oxygen. It was found that the quality of the plasma-polymerized resist depends strongly on the polymer structure and on the plasma etching conditions. In this experiment, the recorded values of sensitivity and γ value of plasma-polymerized methyl methacrylate were 700 µC/cm2 and 1, respectively.

Plasma polymerized methyl-methacrylate as an electron-beam resist

Plasma polymerized methyl-methacrylate thin film was formed on a glass substrate coated with chromium as a resist for electron-beam lithography. The polymerizations were conducted at two discharge frequencies of 13.56 MHz and 5 KHz using a capacitively coupled discharge electrode system in a bell-jar-type reactor. Delineations were carried out using an electron beam whose diameter and acceleration voltage were 0.5 μm and 20 kV, respectively. As a test pattern, 25 pairs of parallel lines and spaces each having a 10-μm width were delineated in a rectangular area of 0.5×0.5 mm2. Each line of 10-μm width was depicted by sweeping over using the electron beam with 20 repetitions. The patterns were developed on the chromium by CCl4 plasma etching.