Novolak Photoresist Research Articles

Photo-Wolff Rearrangement of 2-Diazo-1,2-naphthoquinone: Stern-Volmer Analysis of the Stepwise Reaction Pathway.

2-Diazo-1,2-naphthoquinone (1) and its derivatives are the photoactive components in Novolak photoresists. A femtosecond infrared study has established that the photoreaction of 1 proceeds largely by a concerted Wolff rearrangement yielding the ketene 1H-inden-1-ylidene-methanone (3) within 300 fs after excitation, but earlier trapping studies gave evidence for a minor reaction path via a carbene intermediate 1-oxo-2(1H)-naphthalenylidene (2) with a lifetime of about 10 ps. Here, we provide a quantitative assessment of the stepwise pathway by Stern-Volmer analysis of the trapping of 2 by methanol to yield 2-methoxy-1-naphthol (4). We conclude that the lifetime of the carbene 2 is at least 200 ps. Moreover, [3 + 2]cycloaddition of 2 and acetonitrile yielding 2-methylnaphth[2,1-d]oxazole (5) was observed. A comparison of the yields of 5 formed upon photolysis and upon thermolysis of 1 in acetonitrile provides evidence that a substantial part of the hot nascent carbene 2 formed photolytically rearranges to the ketene 3 during its vibrational relaxation (hot ground-state reaction).

The Study of X-ray Lithography Using the DNQ-Novolak Type Photoresist

As a result of the rapid development of lithography, it enables semiconductor technology to design more devices in the same area, which therefore makes electronic products faster, more functional, and hold more components. The photoresist, playing an important role in lithography, constantly develops with a light wavelength used for exposure from early entire wavelengths to present optical and non-optical lithography. The light sources of optical lithography have moved from the early 436nm and 365nm wavelength to short-wavelength light gradually. It is a big issue to find a suitable photoresist under the exposure of 0.578nm X-Ray light source. In this paper we first proposed to use DNQ / Novolak photoresist sold in the market for the 0.578nm X-Ray lithography. In the experiment, it is discovered that the exposure amount of X-Ray can determine if the photoresist is positive or negative; in low doses, when the photoresist film thickness is increased with the reduced exposure time, and a critical level is reached, the Novolak liquid will become positive photoresist after it is exposed in certain time. The high-dose X-Ray beam will make Novolak resin bond break and result in free radicals, which, through resin crosslinking, can improve the internal strength, and reduce developer solubility so the Novolak liquid can become a negative photoresist. By using synthesized DNQ / Novolak photoresist under X-Ray exposure, we can reduce the process line width, and explore principles of photoresist imaging analysis under the different exposure doses.

Patterning of Conducting Polymers Using UV Lithography: The in-Situ Polymerization Approach

We report on the in-situ polymerization of 3T with Cu(ClO4)2 inside several host polymers such as Novolak-based negative-tone photoresist, polystyrene (PS), poly(4-vinylphenol) (P4VP), poly(methyl methacrylate) (PMMA), and poly(4-vinylphenol)-co-(methyl methacrylate) (P4VP-co-MMA) to form an interpenetrating polymer network (IPN). Conducting IPN films in the order of 10–4–150 S/cm are obtained depending on the specific IPN composition. Moreover, the convenience of this synthetic approach has been demonstrated using a commercially available negative-tone photoresist based on Novolak as a host polymer. Novolak photoresist was properly formulated with 3T and Cu(ClO4)2 to preserve as far as possible the negative lithographic characteristics of Novolak-based photoresist and generate conductive micropatterns by means of UV lithography. The CP is in situ synthesized into the Novolak matrix by a postbake after the lithography process (exposure + development). The electrical conductivity of the patterned film is 10–2 S/cm. We accurately patterned three different types of microstructures with different resolutions: interdigitated structures with a width of 100 μm, 200 μm side squares, and a 20 μm wide cross. We believe this synthetic approach is of potential application to modify the conductivity of numerous insulating polymers while preserving their physical and chemical properties.

Evaluation of a novolak based positive tone photoresist as NanoImprint Lithography resist

Motivated by the high etch selectivity obtained with novolak based UV photoresists masks in the pattern transfer to silicon, we have studied the conditions under which a novolak photoresist may be also patterned by NanoImprint Lithography (NIL). The present study is specifically carried out on MICROPOSIT S1800, for which we have identified a suitable NIL process window. The overall quality of the produced nanopatterns depends strongly on the thermal history of the photoresist film. In particular, residuals of solvent in the film are essential to obtain thin residual layers and to avoid cracks during stamp separation, which otherwise easily occur in fully dried material owing to an increase of brittleness. Infrared spectroscopy is applied to determine the relative amount of solvent for different processes and to correlate it to the optimal imprinting conditions. Finally, high-aspect-ratio pattern transfer has been demonstrated in an Inductively Coupled Plasma (ICP) etching system using NIL nanopatterned S1800 resist as a mask.

Removal of Ion-Implanted Photoresists Using Atomic Hydrogen

In this paper, we investigated the removal characteristic of positive-tone novolak photoresists into which B, P, and As ions were implanted with doses of at an acceleration energy of 70 keV using atomic hydrogen, and the hardening mechanisms for the photoresists. All of the ion-implanted photoresists with doses up to were removed without regard for ion species. The removal rates of the photoresists decreased with increasing ion-implantation dose due to hardening of the photoresist surfaces with implantation. The thickness of the surface-hardened layer of the photoresists decreased in the order of , and the removal rate increased with decreasing thickness. The energy supplied from the ions to the photoresist concentrated on the surface side in the order of , and the impact of the heavier ion on the photoresist was greater than that of the lighter ion. We deduced that the photoresists exhibited carbonization and cross-linkage attributable to the decrease in OH, CH, and O 1s and the increase in , C 1s, and π-conjugated systems.

Removal of Ion-Implanted Photoresists Using Wet Ozone

Using environmentally friendly wet ozone instead of chemicals, we removed B-, P-, and As-ion-implanted positive-tone novolak photoresists with an implantation dose of at an acceleration energy of 70 keV. Ion-implanted photoresists with an implantation dose exceeding could not be removed, but photoresists implanted at doses below could be removed. Photoresist implanted with B ions at was removed slowly, but photoresists implanted with P and As ions were not removed at all. The hardness of the photoresist with B ions implanted at was 1.8 times greater than that of the nonimplanted photoresist (AZ6112), that of the P-ion-implanted photoresist was eight times greater, and that of the As-ion-implanted photoresist was five times greater. The B-ion-implanted photoresist was softer than the P- and As-ion-implanted photoresists. We also obtained the calculation results in which the energy supplied from the B ions to the photoresist was lower than that from P and As ions. We assumed that the ion-implanted photoresists were hardened by cross-linkage due to the energies supplied to the photoresists from the ions. Therefore, we determined that the hardness threshold of the photoresist that could be removed by using wet ozone was twice the hardness of AZ6112.

Photoresist Removal Using Atomic Hydrogen Generated by Hot-Wire Catalyzer and Effects on Si-Wafer Surface

We investigated an environmentally friendly method using atomic hydrogen generated by contact catalysis on a tungsten hot-wire catalyzer to remove photoresist instead of using chemicals and its effects on a Si-wafer surface. We eventually obtained a photoresist removal rate of 2.5 µm/min attributable to a reaction of atomic hydrogen with a positive-tone novolak photoresist, without thermal shrinkage of the photoresist film during atomic hydrogen irradiation because the photoresist shrank only under the influence of substrate heating by the catalyzer. The effects of atomic hydrogen irradiation on the substrate surfaces cannot be confirmed.

Femtosecond midinfrared study of the photoinduced Wolff rearrangement of diazonaphthoquinone

Time-resolved vibrational femtosecond spectroscopy is employed to investigate the photoinduced Wolff rearrangement reaction of diazonaphthoquinone (DNQ) dissolved in different solvents (methanol and water). DNQ is an important compound in commercial Novolak photoresists. Upon photoexcitation the ketene intermediate appears within 300 fs, indicating that the ketene is formed in a very fast concerted process involving N(2) loss and rearrangement. The strong shift of the vibrational band, assigned to the ketene by density functional theory calculations and experimental infrared spectra, toward higher wavenumbers is attributed to vibrational cooling. The relaxation time depends on the solvent (10 ps in methanol and 3 ps in water). However, the spectroscopic data show that the indirect ketene formation via a carbene intermediate might also be involved in the reaction process contributing to the ketene formation on the 10 ps time scale.

Behavior of Reaction Products during Puddle Development in Fabrication of Ultralarge-Scale Integrations

The behavior of reaction products during puddle development was investigated in ultralarge-scale integration (ULSI) lithography. The concentration of reaction products originating from novolak photoresist was optically measured. Reaction products during puddle development migrated with time and gathered into cell-like structures. After from the developer puddle formation, the dissolution rate of photoresist at the cellular structures was about 10% lower than that in other areas. We examined two modified methods of puddle development in order to control the gathering phenomenon of reaction products: one is a method of agitating the reaction product by rocking the wafer, and the other is a method of heating the upper side of the developer solution. The distributions of the dissolution rate for the former and latter methods were 5.9 and , respectively. Compared with the distribution of the dissolution rate of for conventional puddle development, both modified methods can improve the distribution of the dissolution rate. The migration of reaction products was large when the wafer temperature was high, and the Marangoni number was consistent with the critical value. Therefore, the cellular structures seem to be caused by Marangoni convection.

Development of a high-selectivity process for electron cyclotron resonance plasma etching of II-VI semiconductors

The erosion rate of resist during electron cyclotron resonance (ECR) plasma etching of II-VI semiconductors is the limiting factor for the selectivity (values range from 5:1 to 10:1). We have measured the erosion rates of AZ 1529, a commercially available diazonaphthoquinone (DNQ) novolak photoresist, under plasma conditions optimized for etching of the underlying semiconductor and have developed an in-situ technique to "harden" the resist by exposing it to an argon-only ECR plasma. A subsequent standard plasma process can then be used to etch the II-VI material, thereby achieving selectivity values greater than 50:1.

TOF-SIMS analysis of chemical state changes in cresol–novolak photoresist surface caused by O 2 plasma downstream

The chemical state changes on cresol–novolak photoresist surfaces caused by O 2 plasma exposure were investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). TOF-SIMS spectra were measured at the surface of the photoresist samples which were exposed to the O 2 plasma downstream for various exposure times and the spectral intensity changes of characteristic secondary ion species with respect to O 2 plasma conditions were quantitatively evaluated. Oxidation and decomposition of the polymer were observed from analysis of the changes in the peaks originating from the chemical structure of the polymer, both in positive and negative mass spectra. It was clarified that oxidation and vaporization attain a balance within a thin altered layer. In addition, depletion of photosensitive additive at the surface was confirmed and the usefulness of TOF-SIMS for predicting the reaction occurring on photoresist surfaces was successfully demonstrated.

Development of a multideveloping photoresist and its application to make liquid crystal display color filter

AbstractThis paper reports the fabrication of a single expose multideveloping positive Diazonaphthoquinone (DNQ) /Novolak photoresist capable of simplifying the fabrication process of color filter plates composed of red, green, blue pixels and black matrix. Film thickness retention was measured on multideveloping photoresist(MDPR) containing novolak resins made from various phenolic compounds including cresols, xylenols, trimethylphenol, resorcinol and their copolymers. It was found that there were suitable combinations of phenolic compounds to exhibit appropriate thermal stability, wide process window as well as compatibility to electrodeposition of color films.

The relation between lift-off of photoresist and the surface coverage of trimethylsiloxy groups on silicon wafers: A quantitative time-of-flight secondary ion mass spectrometry and contact angle study

In this paper the interaction between a trimethylsilylated silicon substrate and diazonaphthoquinone–novolak photoresist material has been examined. Time-of-flight secondary ion mass spectrometry (TOF SIMS) and contact angle measurements of water have been used to determine the surface coverage of trimethylsiloxy (TMS) groups on cleaned and subsequently treated silicon wafers. A linear relation is obtained between the relative surface coverage as measured by TOF SIMS and the cosine value of the contact angle. The surface coverage of the TMS groups has to exceed a value of about 50% of a monomolecular layer to assure the absence of lift-off of photoresist. Contrary to the common belief that trimethylsilylation of silicon substrates improves the adhesion between photoresist and the silicon substrate, it rather deteriorates the adhesion. This is further corroborated by experiments on silica particles. It is proposed that the low-surface energy of the trimethylsilylated surface prevents the penetration of the alkaline developer solution into the interface of the silicon substrate and the photoresist material.