Optimum Exposure Dose Research Articles

Patterning characteristic control of sol-gel-derived random-structure oligomeric silsesquioxanes having a diazonaphthoquinone derivative

Positive photosensitive materials prepared by adding a diazonaphthoquinone (DNQ) derivative to matrices of oligomeric silsesquioxanes (oligo-SQs) with random structures, including only a phenyl (Ph) substituent or both Ph and methyl (Me) substituents (wherein the Ph group content is over 50 mol. %), exhibit a high patterning ability (i.e., a high-resolution pattern formation under 10 μm). One cause of such a high patterning ability is the particularly low solubility of unexposed areas in an alkaline developer, caused by the DNQ derivative-containing oligo-SQs having over 50 mol. % of Ph group content. However, the effects of the exposed areas on the alkaline dissolution behavior, which can be another factor of high patterning ability, have not been examined yet. In this study, the effects of the Me group content on the alkali solubility of the exposed areas on the optimum exposure dose (Eop), the resolution limit, and the pattern shape were examined for a positive photosensitive material having over 50 mol. % of Ph group content. As a result, the resolution did not change with increasing Me group content but the Eop decreased, and the pattern shape tended to change from showing a protruding defect in the central portion to having a normal taper shape. Furthermore, density functional theory calculations for the oligo-SQ model compounds suggested the formation of a new hydroxyl (OH) group domain that includes Me groups in oligo-SQs with increasing Me group content. This new type of OH group domain differs from that derived from oligo-SQs possessing only Ph groups. Moreover, the results suggested that the intramolecular hydrogen bonding was weaker in the new domain than in the domain from oligo-SQs containing only the Ph groups and that the intermolecular interaction between the domain and the DNQ was also weak. The weak intermolecular interaction seemed to be the cause of the high alkali solubility in the exposed areas.

Silicon Nanohole Arrays Fabricated by Electron Beam Lithography and Reactive Ion Etching

The fabrication of silicon nanohole (SiNH) using a combination of electron beam lithography (EBL) and reactive ion etching (RIE) processes is reported. The optimum exposure dose of EBL process was found to be in the range of 210-240 µC/cm2 due to small enlargement of hole diameter after pattern development process. The anisotropic etching and isotropic etching was achieved at low and high reaction pressures, respectively. As expected, the etching rate increase with time and RF power. A relatively smooth and well-defined NH has been obtained at RF power of 100 W and reaction pressure of 0.08 Torr, which is suitable to be applied for optical waveguide.

A user-friendly guide to the optimum ultraviolet photolithographic exposure and greyscale dose of SU-8 photoresist on common MEMS, microsystems, and microelectronics coatings and materials

We provide here a user-friendly guide to find the optimumi-line (365 nm) photolithographic exposure dose of an arbitrary thickness of SU-8 on various substrate materials and thin film coatings used in MEMS, microsystems and microelectronics technologies: semiconductors, 2D materials (graphene and MoS2) plastics, glass, metals and ceramics.

Design and development of low activation energy based nonchemically amplified resists (n-CARs) for next generation EUV lithography

The rendition of EUV resists is one of the major challenges for high volume production and cost-effective realization of next generation (NG) EUV technology. EUV lithography (EUVL) is a promising technique which has been predicted to print 16nm line patterns and beyond. Thus EUV resists must have exceptionally higher sensitivity and resolution than current resists, because IC technology scaling of isolated resist lines and LWR have been set to ~15nm and ~1.5nm, respectively. There is everlastingly, contest to meet photosensitivity and resolution simultaneously with the traditional chemically amplified resists (CARs) due to random walk nature of photo-acid diffusion and minimal control over critical dimension (CD), which eventually confines its adeptness to be front end EUV resists. The present study demonstrates the development of a new non-chemically amplified negative tone resist (n-CARs), MAPDST–i-PrMA [Mw=14,000g/mol] using suitable monomer, bearing radiation sensitive trifluoromethanesulfonate functionality. EUV sensitivity (E0) and optimum exposure dose (Eox) for this newly designed and developed resist have been experimentally calculated to be 11.3mJ/cm2 and 26.6399mJ/cm2 respectively. Similarly, EBL sensitivity (E'0), contrast (γ) and reactive ion etching (RIE) selectivity (S) (CHF3/O2 @35/4 SCCM) of the developed resist formulation are computed as 2.14μC/cm2, 0.66±0.04 and 1.77, respectively. The Derjaguin-Muller-Toporov (DMT) modulus and adhesion for EUV exposed line patterns of 20, 25, 30, 35, 40, 45 & 50nm with various L/S characteristics are ~3.2±0.16GPa and ~33±4nN, respectively. Thus, the significantly low activation energy (11.3mJ/cm2) of the newly developed resist formulation and manifestation of all the polarity switching during radiation exposure avoid acid diffusion, blurring of resist patterns and anticipated to meet the stringent requirements of EUVL for sub-20nm node.

Estimating the optimum dose for arbitrary substrate materials based on Monte Carlo simulated point spread functions

In electron beam lithography (EBL), determining the optimum exposure dose is a key factor for a successful exposure when using a new substrate or changing the acceleration voltage. It is well known that the optimum dose in EBL depends on the exposed material stack as well as the energy of the injected electrons. An experimental dose calibration is usually necessary to establish the optimum process conditions for new materials. In this study we will calculate the optimum dose employing simulations and attempt to verify the results experimentally. Monte Carlo simulations were performed in order to determine the point-spread function (PSF) for a set of commonly used substrate materials. The optimum dose for each of the material stacks was calculated by comparing the simulated PSFs. Numeric integration of the individual PSFs was used to determine the total energy deposited in a specific layer of the resist. The ratio of the total energies is equal to the ratio of the optimum doses.To verify our calculation results experimentally, we exposed dose calibration tests using contrast curves and device patterns. The tests were repeated on different substrates with different material properties to determine the range of validity of our method. A comparison of the calculated and measured optimum doses is presented, showing a good agreement in the range of 10% except for samples suffering from heavy charging. This limitation might be explained by the neglect of charging effects in the simulation model. It was shown that Monte Carlo simulations can be used to calculate the optimum doses for new substrate materials which reduces the need for extensive experimental dose calibration, saving time and cost.

Wafer scale interdigitated nanoelectrode devices functionalized using a MEMS-based deposition system

This paper reports on a methodology to elaborate interdigitated nanoelectrode devices (INDs) at the wafer scale, relying on a mix-and-match process which combines proximity optical lithography and electron beam lithography. An optimum exposure dose allowed fabricating nanodevices, at the wafer level, with a successful yield of 97%. The final devices are bonded onto conventional TO-8 packages. Electrical characterization in a short-circuited nanoelectrode is performed, revealing a 230 µΩ cm resistivity value at 23 °C. A MEMS-based spotter made of cantilevers (called Bioplume) has been used to obtain precise functionalization of the INDs with sub-picoliter volume solutions. These INDs are the basis of multiple tunnel junction nanodevices, intended to serve as novel highly sensitive nanobiosensors.

Interdependence of optimum exposure dose regimes and the kinetics of resist dissolution for electron beam nanolithography of polymethylmethacrylate

The authors report a systematic experimental study of dense nanostructures in polymethylmethacrylate (PMMA) created by low-energy electron beam lithography (EBL) with varying duration and temperature of the resist dissolution. They observe that decreasing the development temperature not only yields the widest favorable exposure dose regimes but also requires highest exposure doses to fabricate dense nanopatterns. They interpret the observed interdependence of the exposure doses and the development temperatures in terms of a simple kinetic model describing the diffusion mobility of fragments in exposed PMMA during dissolution and discuss the corresponding molecular mechanisms that determine the resolution and sensitivity of EBL nanofabrication.

High-power laser interference lithography process on photoresist: Effect of laser fluence and polarisation

High throughput and low cost fabrication techniques in the sub-micrometer scale are attractive for the industry. Laser interference lithography (LIL) is a promising technique that can produce one, two and three-dimensional periodical patterns over large areas. In this work, two- and four-beam laser interference lithography systems are implemented to produce respectively one- and two-dimensional periodical patterns. A high-power single pulse of ∼8 ns is used as exposure process. The optimum exposure dose for a good feature patterning in a 600 nm layer of AZ-1505 photoresist deposited on silicon wafers is studied. The best aspect ratio is found for a laser fluence of 20 mJ/cm 2. A method to control the width of the sub-micrometer structures based on controlling the resist thickness and the laser fluence is proposed.

Focus and Dose Measurement Method in Volume Production

We propose a new inspection method of in-line focus and dose control for semiconductor volume production. We refer to this method as the focus and dose line navigator (FDLN). Using FDLN, the deviations from the optimum focus and exposure dose can be obtained by measuring the topography of the resist pattern on a process wafer that was made under a single-exposure condition. Generally speaking, FDLN belongs to the technology of solving the inverse problem as scatterometry. The FDLN sequence involves following the two steps. Step 1: creating a focus exposure matrix (FEM) using a test wafer for building the model as supervised data. The model means the relational equation between the topography of resist patterns (critical dimension (CD), height, sidewall angle) and FEM's exposure conditions. Step 2: measuring the topography of resist patterns on a production wafers and feeding the topography data into the library to extrapolate focus and dose. To estimate the accuracy of FDLN, we performed some experiments. We developed a FEM with an ArF lithography tool and measured the topography of the FEM with an optical CD measurement tool. Using the topography data, we obtained the following results. Focus: 27.0 nm (5.2 nm) and Dose: 1.8% (1.4 nm). The numerical value in a parenthesis shows the value of the estimated accuracy with changing CD. We also show other experimental results and some simulation results in this paper.

Recording performance of holographic diffraction gratings in dry films containing hyperbranched polyisophthalesters as polymeric binders.

By use of a photopolymerization-diffusion model, the diffraction efficiency of photopolymerizable recording dry films prepared from hyperbranched polyisophthalesters as polymeric binders was investigated. The recording characteristics of these films, i.e., spatial frequency, polymeric binder structure, exposure intensity, and modulation depth, are discussed in detail. For a given total exposure dose the diffraction efficiency first increases and then decreases with increasing exposure intensity, and this effect becomes more remarkable as the unsaturated concentration of polymeric binder increases. An optimum total exposure dose of 36 mJ cm(-2) and an exposure intensity of 0.4 mW cm(-2) were determined. A modulation depth of 1 was found to produce the highest diffraction efficiency. Longer-lasting gratings could be obtained by use of polymeric binders with higher cross-linking densities.

Contrast Enhancement based on Acid Equilibrium for Chemically Amplified Resists

We have developed a method of enhancing the resist contrast governed by the hydrogen-ion concentration in chemically amplified resist films. We consider the distribution of permittivity and the equilibrium constants of acids generated by photoirradiation. The hydrogen-ion concentration in a resist film containing a weak acid increases with increasing permittivity. If the permittivity of exposed areas is higher than that of unexposed areas, the resist contrast is greater than that of resist films whose permittivity is the same in both exposed and unexposed areas. Accordingly, the resolution capability is enhanced and the depth of focus is increased. Calculations based on a model in which an additive whose polarizability is increased by photoirradiation is mixed within the resist, indicated that (1) the resist contrast depends on the amount of polarizability change and the concentration of the additive, (2) the resist contrast takes a maximum value at an optimum exposure dose, and (3) an appropriate combination of available additives and available exposure doses can result in a resist contrast higher than that obtained when strong acids are generated and also higher than the optical contrast.

Phantom exposures of chemically amplified resists caused by acids generated in environmental air in synchrotron radiation lithography

In this article, we discuss the phantom exposure of chemically amplified resists in x-ray lithography, which is attributable to acids in environmental air induced by x-ray irradiation. Since the acids generated in the air diffuse into the resist film from the top to the bottom like so many catalytic acids, they cause cross linking in a negative resist and decomposition in a positive resist. The phantom exposure in flood exposures of a 20 mm square increases as the exposure dose increases, and expands more than 10 mm outside the exposure field when the exposure dose is ten times greater than the optimum exposure dose for patterning. Dependence of the phantom exposure on the exposure dose and resist material are evaluated.

Patterning Characteristics of Hole Patterns in Synchrotron Radiation Lithography

The patterning characteristics of synchrotron radiation lithography for hole patterns using a low-contrast mask (contrast: 3.5) are investigated. A resolution of 110 nm provides a large exposure dose latitude of more than 10% when the proximity gap is less than 15 µm, and the replicated minimum hole size is 70 nm with a 10-µm gap. Resist pattern sizes from 110 to 360 nm are kept within ±10% with proximity gaps of less than 20 µm. However, the exposure dose margin to guarantee mask linearity decreases to several percent because of the different optimum exposure dose for each pattern. Pattern size correction using mask bias to improve the mask linearity and exposure dose margin is proposed.

Investigation of the notching effect for single layer deep ultraviolet resist processing

In order to extend the application limit of single layer resist processing to 0.25 μm pattern formation, the influence of resist thickness on reflective notching effects was investigated, using a two-dimensional resist profile simulator with the vector model. As the resist thickness increased, the reflective notching was varied periodically. Resist profile degradation due to reflective notching was maximum at the resist thickness where resist sensitivity was maximum (Emax), and was minimum at the resist thickness where resist sensitivity was minimum (Emin). The reflective notching was strongly dependent on the effective exposure dose Eeff at the bottom of the resist film, defined as the product of resist transmittance and optimum exposure dose Eopt. These simulation results were verified experimentally. It was concluded that the resist thickness should be set to minimize exposure dose for the reduction of reflective notching effects.

Extendibility of synchrotron radiation lithography to the sub-100 nm region

This article discusses the resolution of synchrotron radiation lithography in the sub-100 nm region, taking into consideration the mass production of large-scale integrated circuits, under attainable conditions for the x-ray mask, proximity gap, and resist processes. Resolution and exposure latitude for line-and-space patterns are markedly improved by using a mask with a contrast of only 2.5. Resolutions of 90, 80, 70, and 60 nm can be achieved with proximity gaps of 30, 20, 15, and 10 μm if a high-contrast resist and a low-surface tension developer are used. The latitude will be 10% for pattern sizes as small as 70 nm when the proximity gap is narrower than 15 μm. The effects of mask duty [which is defined to be the ratio of the absorber (line) width to the pattern pitch, i.e., duty cycle] on the optimum exposure dose and mask linearity are also evaluated.

437. CRにおける最適な低被曝線量撮影系の検討

437. CRにおける最適な低被曝線量撮影系の検討

209.CRの適正線量の検討 : 骨折の診断に際しての線量について

209.CRの適正線量の検討 : 骨折の診断に際しての線量について

375. CR の適正線量について (第 5 報) : 低線量撮影の可能性について(CR 被曝低減)

375. CR の適正線量について (第 5 報) : 低線量撮影の可能性について(CR 被曝低減)

426. CR の適正線量について (第 4 報)(第 49 回総会学術大会一般研究発表予稿)

426. CR の適正線量について (第 4 報)(第 49 回総会学術大会一般研究発表予稿)

426. CR の適正線量について (第 4 報)(DR-6 画像評価)

426. CR の適正線量について (第 4 報)(DR-6 画像評価)