Negative-type Photoresist Research Articles

Photolithographic process of microcapsule sheet for electrophoretic display

A new method of fabricating electrophoretic display sheet was developed utilizing a photolithographic process. In this method, stripe-type barrier ribs with height of 50–80 μm and gap between ribs of 100–150 μm were patterned on the transparent electrode substrate by photolithographic process using a negative-type photoresist. Microspheres dispersed in UV curable monomer system were closely packed into the spaces between the barrier ribs. After laminating the upper ITO film, the resulting sheet was UV-irradiated to give an electrophoretic display panel with uniform packing of microspheres.

High-Resolution Pattern Reproduction by Cold Ultra Violet Stamping in Optical Polymeric Films

In this paper, we present a new method of waveguide-type device fabrication using an optical polymer. This method is applied to the fabrication of a grating on top of a polymeric waveguide film where, we used a mixture of pentaerythritol triacrylate, N-methyldiethanolamin, and eosin as a polymer material. This mixture, called henceforward PNME, acts as a negative-type photoresist polymeric material. Exposure of the material to light of specific wavelength makes the material solidify. Using this particular property of PNME and the fact that before the solidification PNME material is liquid, and thus copies the volume of the vessel where it is contained, we were able to fabricate polymeric films and waveguides with a relief grating on their surfaces. It was also determined that the interface between the side walls of the vessel and the PNME material plays a vital role in the fabrication process. Moreover, the presented method of fabrication is a high-resolution, high-output, and low-cost method of optical device fabrication and thus it is particularly suitable for commercial use.

A new photoresist based on hyperbranched poly(ary1ene ether phosphine oxide)

Hydroxy-terminated hyperbranched poly(ary1ene ether phosphine oxide) (P2) was synthesized via nucleophilic aromatic substitution reaction of AB, monomer, bis(4-hydroxyphenyl)-4'-fluorophenylphosphine oxide with K2CO3 as a base in NMP. The obtained polymer was dissolved well in NMP and DMSO, and casting of the solution gave a transparent film. The study on dissolution behavior of the film containing 10 wt% of diphenyliodonium-9,l0-dimethoxyanthracene-2-sulfonate (DIAS) as a photoacid generator and 25 wt% of 4,4'-methylenebis-[2,6-bis(hydroxymethylphenyl) phenol] (MBHP) as a cross linker revealed that 0.5 wt% aqueous tetramthylammonium hydroxide (TMAH) solution was a suitable developer for this negative-type photoresist system. The photoresist system containing 10 wt% of DIAS and 25 wt% of MBHP showed the sensitivity of 9 mJ/cm2 and the contrast of 1.6 when it was exposed to 365 nm light and postbaked at 12O°C, followed by developing with 0.5 wt% aqueous TMAH solution at room temperature. The heat-treated (300°C, 30 min) negative image did not show any distortion.

Application of an Anthracene Containing Polymer to a Negative Type Photoresist

Yong Woon Kim, and Taek Hyeon KimFaculty of Applied Chemistry and The Polymer Science & Technology Research Center,Chonnam National University, Gwangju 500-757, KoreaReceived February 19, 2002Key Words : Anthracene polymer, Photoresist, Photo-crosslinkingPhotoresists are very important materials for the photo-fabrication process. They are widely used for the manu-facture of microelectronics, printed circuit boards, silkscreen printing, optical disks, black matrix of color cathod-ray tubes, and so on. They can be classified into two types onthe basis of the solubility changes upon irradiation with UVlight, i.e., positive or negative types. The negative type ofphotoresist is generally more sensitive than the positive one. It is well known that anthracene or its derivatives dimerizephotochemically to give [4+4] cycloadducts across the 9,10-positions of anthracene,

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.

Solid-state photochemistry of π-conjugated poly(3-alkylthiophenes)

Films of poly(3-alkylthiophenes) undergo simultaneous photobleaching, cross-linking, and chain scission when irradiated in air with UV or visible light. The quantum yields of the latter two processes were determined using Chalesby–Pinner theory. Under the irradiation conditions employed the cross-linking density is ~ 4.5 times greater than the fracture density (chain scission). This corroborates the observation that poly(3-alkylthiophenes) are negative-type photoresists. Although the quantum yield of cross-linking is relatively low, the polymer maintains a relatively high degree of π-conjugation following irradiation. The mechanism of cross-linking and insolubilization proceeds via a classical photooxidation route that is initiated by photolysis of residual iron impurities. Photobleaching involves photosensitization, and reaction of singlet oxygen. 1O2 undergoes a 1,4 Diels–Alder addition to thienyl units which results in a loss of π-conjugation, a blue shift in the absorption spectrum of the polymer, and a decrease in the optical density. Photobleaching, cross-linking, and chain scission are considerably reduced in the absence of oxygen. Keywords: photochemistry, polymers, thin films, degradation, cross-linking.

核酸塩基を用いる高性能フォトレジストの合成

Pyrimidine derivatives were found to be applicable to photoresists for microelectronics. This paper deals with synthesis and photochemistry of pyrimidine derivatives, and application to photoresists. Intermolecular photodimerization of pyrimidine bases in the side chains of various polymeric and dimeric compounds upon irradiation of UV light (270 nm) led to photocrosslinking of the polymer chains or photopolymerization of the dimeric compounds. These materials can be used as deep-UV negative type photoresists. On the other hand, the polymers containing thymine photodimers in the main chain underwent dissociation of the thymine photodimers upon irradiation to UV light (250 nm), leading to breakage of the polymer chains. These polymers could be used as positive type photoresists and high resolution (0.3μm) was demonstrated. Tautomerism of pyrimidine was also applied to a chemical amplification photoresist system. Polymers containing 2, 4-dialkoxypyrimidine derivatives that is an enol form of uracil were high sensitive deep-UV, and EB chemical amplification resists.

Si-containing copolymer of 2,3-epoxypropyl-1-methacrylate

Poly-p-trimethylsilylphenylmethacrylate(75)-co-glycidylmethacrylate (25) containing aromatic bisazides exhibits uv sensitivity as a negative type photoresist. Sensitometric data have been evaluated. The pressure-dependant reactivity under the conditions of oxygen reactive ion etching was determined.

Functional Monomers and Polymers CLXVIII. Syntheses and Photoreactions of Poly(methacrylate)s Containing Thymine Bases

Poly(methacrylate)s having thymine derivatives were studied for photodimerizations of thymine units in solution and in the film state, and photolithographic sensitivity tests for their applicability to negative type photoresists. In these homopolymers and copolymers, thymine bases were attached to the polymer chain at positions N1 or N3. Among these polymers, the alternate copolymer indicated the highest photosensitivity. The results are discussed from the viewpoint of intra- and/or intermolecular photodimerization and the quantum yields in solution and in the film state.

Pyrimidine Polymers as High Resolution, High Sensitivity Deep-UV Photoresists

Polymethacrylates containing pyrimidine base derivatives, and copolymers of butadiene with methacrylate monomer containing pyrimidine bases were prepared and studied for photodimerization of pyrimidine base units, grafted to the polymer chain. These polymers were found to be applicable as negative type photoresists. Photolysis of the polymers caused dimerization of pyrimidine bases and leaded to the photocrosslinking of the polymer chains. The photolithographic evaluation of these polymers showed high sensitivity, high resolution values of ever 1μm.On the other hand, the application of polyamides synthesized by polycondensation of the thymine photodimer and various diamines into positive resists were studied. The photolysis of these polymers caused dissociation of the thymine photodimers, leading to the breakage of the polymer chains. These polymer indicated very high resolution values of even 0.3μm.

New Application of Se–Ge Glasses to Silicon Microfabrication Technology

A novel inorganic photoresist using Se–Ge glass films is proposed. Fundamental functions of this photoresist are based upon two types of distinct changes in the chemical solubility induced by irradiation of light. One of those is a phenomenon that the light exposure increases dissolution rate in alkaline solutions (positive type), and the other that chalcogenide glasses become almost insoluble into alkaline solutions by photodoping of silver (negative type). Suitable processing techniques and exposure characteristics are investigated. It is shown that the Se–Ge glass films can be used as a positive- or a negative-type photoresist by a slight change in the process of photoetching and that fine pattern photoetching of less than 1 µm linewidth in SiO2 is easily achieved. This photoresist has many potential advantages in high resolution, contrast, etch resistance and its processings.

A novel inorganic photoresist utilizing Ag photodoping in Se-Ge glass films

By ’’photodoping’’ with silver, chalcogenide glasses become almost insoluble in alkaline solutions. This letter examines the applicability of this effect to silicon microfabrication technology. Suitable processing techniques and exposure characteristics are investigated. It is shown that the (Ag) -Se-Ge glass system can be used as a negative-type photoresist; fine pattern photoetching of less than 1 μm line width in SiO2 is easily achieved. This inorganic photoresist has some advantages over the conventional polymer-type photoresists in resolution, etch resistance to acid solutions, and process reproducibility.

Microlenses for Coupling Junction Lasers to Optical Fibers

Microscopic lenses, fabricated on optical fiber surfaces, have quadrupled the efficiency for coupling astigmatic beams from GaAs junction lasers into 4-microm cores of single-mode fibers. A novel photolithographic technique was used to make hemispherical and hemicylindrical microlenses, with diameters between 4 microm and 10 microm, from commercially available negative type photoresist that is transparent at ir laser wavelengths. Geometrical profiles of photoresist lenses, documented with scanning electron photomicrographs, were remarkably smooth even though their dimensions were more than an order of magnitude smaller than other known lenses.