Lateral bipolar photoresistance effect in the CIGS heterojunction and its application in position sensitive detector and memory device

Cu(In,Ga)Se2(CIGS) based multilayer heterojunction, as one of the best high efficiency thin film solar cells, has attracted great interest due to its outstanding features. However, the present studies are primarily focused on the structure optimization and modulation in order to enhance the photoelectric conversion efficiency. Here, we exploit another application of this multilayer heterostructure in photoresistance-modulated position sensitive detector by introducing lateral photoresistance effect.The lateral photoresistance measurements show that this multilayer heterojunction exhibits a wide spectral response(~330 to ~1150 nm) and excellent bipolar photoresistance performances(position sensitivity of ~63.26 X/mm and nonlinearity <4.5%), and a fast response speed(rise and fall time of ~14.46 and^14.42 ms, respectively). More importantly, based on the lateral photoresistance effect, the CIGS heterostructure may also be developed as a position-dependent resistance memory device, which can be modulated by changing laser intensity, wavelength, and bias voltage with excellent stability and repeatability, and the position resolution reaches up to 1 lm. These results can be well explained by considering the diffusion and the drift model of carriers in the CIGS multilayer heterojunction. This work provides a new approach of achieving novel photoelectric sensors and memory devices based on the traditional photovoltaic heterostructures.

Giant negative photoresistance of epitaxial manganite La_(2/3)Ca_(1/3)MnO_(3-δ) film

The La2/3Cal/3Mn03_σ film has been deposited on the （001） SrTiO3 substrate and its temper- ature-dependent photoconductive properties have been investigated from 80 to 300 K. The La2/3Cal/3MnO3-σ film has a novel photoelectric property due to its oxygen-deficient structure. We observed laser-induced giant negative photoresistance of the sample in a wide temperature range. The change rate of negative photoresistance was nearly 100% at the low temperature when the sample was irradiated by 532 nm laser. In addition, this effect was sensitive to the power of laser irradiation. The oxygen-deficiency of La2/3Cal/3Mn03-σ film seems to have an impact on the laser-induced resistance variation. The experimental results made the La2/3Cal/3MnO3_σ film a promising application as a photoswitch device.

A Transparent Photoresist Made of Titanium Dioxide Nanoparticle-Embedded Acrylic Resin with a Tunable Refractive Index for UV-Imprint Lithography

Transparent photoresists with a high refractive index(RI)and high transmittance in visible wavelengths have promising functionalities in optical fields.This work reports a kind of tunable optical material composed of titanium dioxide nanoparticles embedded in acrylic resin with a high RI for ultraviolet(UV)-imprint lithography.The hybrid film exhibits a tunable RI of up to 1.67(589 nm)after being cured by UV light,while maintaining both a high transparency of over 98%in the visible light range and a low haze of less than 0.05%.The precision machining of optical microstructures can be imprinted easily and efficiently using the hybrid resin,which acts as a light guide plate(LGP)to guide the light from the side to the top in order to conserve the energy of the display device.These preliminary studies based on both laboratory and commercial experiments pave the way for exploiting the unparalleled optical properties of nanocomposite resins and promoting their industrial application.

A new metallization method of modified tannic acid photoresist patterning

Metal patterning from a modified tannic acid(TA-Boc-MA)photoresist and the processes are designed using protection of hydroxyl groups in tannic acid,formulation into a photoresist,an exposure and pattern treatment process,and metallization by electroless Ag deposition with silver ion solution.

Use of Cucurbita pepo Oil to Fight against the UV Action on the Skin

Skin aging is a process most often attributed to UV [1] and also to the use of creams and other cosmetic products low in antioxidant compounds [2]. Photochemically stable pepo Cucurbita oil can be used as an exogenous cosmetic supplement due to its high antioxidant content. Incorporated in an agar, media containing a synthetic melanin solution with added pumpkin oil are subjected to UV light, the aging thus modeled is followed by the measurement of photoresistance values correlated with chemical and spectrophotometric analyses. This study confirms that pumpkin oil is highly effective in protecting the skin, especially the most sensitive skins such as babies’ skin [3] by reinforcing the action of melanin and also that of albinos without melanin. Indeed its SPF (Significant Sun Protection Factor) index estimated during this work is very consistent, i.e. more than 22% of UVB (280 - 315 nm) radiations are suppressed.

HYPERBRANCHED CONJUGATIVE MACROMOLECULES CONSTRUCTED FROM TRIPLE-BOND BUILDING BLOCKS

Polycyclotrimerization and polycoupling of acetylenic monomers respectively furnish hyperbranched polyarylenes and polyynes with high molecular weights （up to 1 × 10^6） in high yields （up to 99.9%）. The polymers possess low intrinsic viscosities and high thermal stabilities, losing little of their weights when heated to 〉 400℃. Upon pyrolysis at 〉 800℃, the polymers graphitize with high char yields （up to 86%）. Hyperbranched polyarylenes efficiently emit deep-blue to blue-green lights with fluorescence quantum yields up to 98% and strongly attenuate intense laser pulses with optical power-limiting performances superior to that of C60, a well-known optical limiter. Poly（alkenephenylenes）, poly（aroylarylenes） and polyynes are readily cross-linkable by UV irradiation, serving as excellent photoresist materials for the generation of patterns with nanometer resolution. Thin films of hyperbranched polyynes exhibit very high refractive indexes （n up to 1.86）. The internal and terminal acetylene moieties of the polyynes readily form complexes with cobalt carbonyls, which can be transformed into soft ferromagnetic ceramics with high magnetic susceptibilities （Ms up to ca. 118 emu/g） and near-zero magnetic losses.

Research on the process of fabricating a multi-layer metal micro-structure based on UV-LIGA overlay technology

In this paper,we report the study of the process of fabricating a multi-layermetal micro-structure using UV-LIGA overlay technology,includingmask fabrication,substrate treatment,and UV-LIGA overlay processes.To solve the process problems in the masking procedure,the swelling problemof the first layer of SU-8 thick photoresist was studied experimentally.The 5μmline-width compensation and closed 20μmand 30μmisolation strips were designed and fabricated around the micro-structure pattern.The pore problemin the Ni micro-electroforming layer was analyzed and the electroforming parameters were improved.The pH value of the electroforming solution should be controlled between 3.8 and 4.4 and the current density should be below 3 A/dm^2.To solve the problems of high inner stress and incomplete development of the micro-cylinder hole array with a diameter of 30μm,the lithography process was optimized.The pre-baking temperature was increased via gradient heating and rose every 5℃ from 65℃ to 85℃ and then remained at 85℃ for 50 min–1 h.In addition,the full contact exposure was used.Finally,a multi-layer metal micro-structure with high precision and good quality of microelectroforming layer was fabricated using UV-LIGA overlay technology.

Synthesis and Properties of UV-curable Hyperbranched Polyurethane and Its Application in the Negative-type Photoresist

UV-curable hyperbranched polyurethane （UV-HBPU） containing carboxyl groups was synthesized from isophorone diisocyanate （IPDI）, diethanolamine （DEOA）, polyethylene glycol （PEG-400）, hydroxyethyl acrylate （HEA）, and 2,2-his （hydroxymethyl） propionic acid （DMPA）. The UV-HBPU was used as a negative-type photoresist for a printed circuit board （PCB）. Fourier-transform infrared spectroscopy （FTIR） and proton nuclear magnetic resonance （1HNMR） spectroscopy of UV-HBPUs indicated that the synthesis was successful. Differential scanning calorimetry （DSC） and thermogravimetric analysis （TGA） showed that the thermal stability of the UV-HBPUs decreased as the HEA content increased. The polymer exhibited excellent photoresist properties, and the resolution of circuits based on this negative-type photoresist reached 10 μm.

Simulations of Ion Behaviors in a Photoresist Trench During Plasma Etching Driven by a Radio-Frequency Source

Ion＇s behavior plays an important role in plasma etching processes and is determined by the local electric potential in the etched trenches. In this study, with the trench powered by a radio frequency （rf） source, the Laplace equation is solved to obtain the electric potential. The ion trajectories and the ion energy distribution （IED） at the bottom of the trench are obtained self-consistently by tracking the ions in the trench. The results show that the aspect ratio of depth- to-width of the photoresist trench and the voltage amplitude of the rf source applied to the electrode are important parameters. The larger the aspect ratio and the smaller the amplitude are, the more ions hit the sidewalls, which results in a notching phenomenon. Meanwhile, there are a higher high-energy peak and a lower low-energy peak in the IED with the increase in aspect ratio.

Latest developments in EUV photoresist evaluation capability at Shanghai Synchrotron Radiation Facility

Evaluating the comprehensive characteristics of extreme ultraviolet(EUV)photoresists is crucial for their application in EUV lithography,a key process in modern technology.This paper highlights the capabilities of the Shanghai Synchrotron Radiation Facility(SSRF)08U1B beamline in advancing this field.Specifically,it demonstrates how this beamline can create fringe patterns with a 15-nm half-pitch on a resist using synchrotron-based EUV lithography.This achievement is vital for evaluating EUV photoresists at the advanced 5-nm node.We provide a detailed introduction to the methods and experimental setup used at the SSRF 08U1B beamline to assess an EUV photoresist.A significant part of this research involved the fabrication of high-resolution hydrogen silsesquioxane mask gratings.These gratings,with an aspect ratio of approximately 3,were created using electron beam lithography on an innovative mask framework.This framework was crucial in eliminating the impact of zeroth-order light on interference patterns.The proposed framework propose offers a new approach to mask fabrication,particularly beneficial for achromatic Talbot lithography and multicoherent-beam interference applications.

Recent Advances in Organic-inorganic Hybrid Photoresists

Photoresists are radiation-sensitive materials used for forming patterns to build up IC devices.To date,most photoresists have been based on organic polymers,which have been dominating the semiconductor industries over the past few decades.It is obvious that extreme ultraviolet(EUV)lithography has become the next-generation lithography technology.The development of comprehensive performance EUV resist is one of the most critical issues.However,organic polymeric photoresists are difficult to meet the harsh requirements of EUV lithography.Pure inorganic photoresists such as metal salts,hydrogen silsesquioxane(HSQ)are expected for EUV lithography due to their high resistance and high resolution.But the low sensitivity makes them not suitable for high volume manufacturing(HVM).Organic-inorganic hybrid photoresists,containing both organic and inorganic components,are regarded as one of the most promising EUV resists.They combine both merits of organic and inorganic materials and have significant advantages in machinability,etching resistance,EUV absorption,and chemical/thermal stability.Organic-inorganic hybrid photoresists are considered as ideal materials for realizing industrialgrade patterns below 10 nm.This review mainly focuses on the development of organic-inorganic hybrid photoresists over the past decade.

The Variables and Invariants in the Evolution of Logic Optical Lithography Process

Photolithography has been a major enabler for the continuous shrink of the semiconductor manufacturing design rules.Throughout the years of the development of the photolithography,many new technologies have been invented and successfully implemented,such as image projection lithography,chemically amplified photoresist,phase shifting mask,optical proximity modeling and correction,etc.From 0.25μm technology to the current 7 nm technology,the linewidth has been shrunk from 250 nm to about 20 nm,or 12.5 times.Although imaging resolution is proportional to the illumination wavelength,with the new technologies,the wavelength has only been shrunk from 248 nm to 134.7 nm(193 nm immersion in water),less than 2 times.Would it mean that the imaging performance has been continuously declining?Or we have yet fully utilized the potential of the photolithography technology?In this paper,we will present a study on the key parameters and process window performance of the image projection photolithography from 0.25μm node to the current 7 nm node.

Acidic Polyester Imides as Thermally Stable Binder Polymers for Negative-Tone Black Photoresist

Polyimides are well-known for their high chemical inertness and thermal stability. However, it is usually challenging to synthesize UV-curable polyimides since the imidization reaction requires such harsh conditions that acrylate type double bonds cannot withstand. In this work, synthetic methods are developed to obtain polyester-imide type binder polymers with high thermal stability, high compatibility with the other components of the black photoresist, and fine photolithographic patterning property for the negative-tone black photoresist. The syntheses of diimide-diacid or diimide-diol intermediates for the polyesterification with dianhydride gave polyester imides which meets this requirement. The photolithographic tests have shown that the patterning of the micron-sized PDL of the organic light emitting diode (OLED) panel could be obtained. This work will interest the researchers working on the design and optimization of thermally stable binder polymers.

COPOLYMERS OF CHLOROETHYL METHACRYLATE, GLYCIDYL METHACRYLATE, AND METHYL METHACRYLATE AS SYNCHROTRON RADIATION x-RAY PHOTORESISTS

The copolymers of chloroethyl methacrylate (CMA), glycidyl methacrylate (GMA), and methyl methacrylate (MMA) were synthesized in benzene solution. Their breadths of the molecular weight distributions are 2.1 and 2.3, respectively. The thermal stability of P(GMA-CMA) is superior to that of P(CMA-MMA). The resolutions of P(CMA-MMA) and P(GMA-CMA) photoresists were found to be 0.1-0.16 mu m and 0.17-0.2 mu m, respectively. (Author abstract) 9 Refs.

SYNTHESIS AND THERMAL PROPERTIES OF A NEW CHOLIC ACIDCONTAINING COPOLYMER

A new copolymer was synthesized by free radical polymerization in solution from methyl 3α-methylacryloyl-7α, 12α-dihydroxy-5β-cholan-24-oate (MACAME) and maleic anhydride (MAN). The copolymer was characterized by FT-IR and functional group analysis. The reactivity ratios of the two monomers were estimated [r_1 = 11.6 (MACAME), r_2 = 0.01(MAN)] by conducting a series of copolymerizations with a variety of monomer feed compositions and analyzing thecopolymer composition. Thermogravimetric and differential scanning calorimetric analyses of the samples indicate that thecopolymer possesses good thermal stability. The temperature at which the copolymer samples experienced a 10% weight loss(T_(WL)) is over 287℃, and the T_g ranged from 174 to 185℃ for the copolymers.

Research on the Mechanism of Multilayer Reactive Ion Etching

Dry etching has now become one of the key processes of high ratio of depth to width microstructure and fine patterning. This paper presents a new dry etching technology - multilayer reactive ion etching technology （MRIE）. By taking full advantage of the spatial layout of the chamber, arranging multi-layer electrodes and transporting the discharged gas by a layered air supply device, the function of simultaneous etching in every reaction chamber （layer） is realized. This method can significantly enhance the productivity. Taking the photoresist etching by MRIE as an example, the law and mechanism influencing the etching rate and uniformity were analyzed for different conditions. The result shows that when plate distance is 50/55/60 mm （from bottom to top）, and vacuum degree, ratio of O2 to Ar, RF source power, and continuous etching time are respectively 40 Pa, 1/2, 600 W, and 20 min, the optimal process is achieved. The average etching rate and uniformity are 143.93 A/min and 9.8%, respectively.

Optimum design of photoresist thickness for 90-nm critical dimension based on ArF laser lithography

In this work, a 90-nm critical dimension （CD） technological process in an ArF laser lithography system is simulated, and the swing curves of the CD linewidth changing with photoresist thickness are obtained in the absence and presence of bottom antireflection coating （BARC）. By analysing the simulation result, it can be found that in the absence of BARC the CD swing curve effect is much bigger than that in the presence of BARC. So, the BARC should be needed for the 90-nm CD manufacture. The optimum resist thickness for 90-nm CD in the presence of BARC is obtained, and the optimizing process in this work can be used for reference in practice.

Synthesis and characterization of methacrylate matrix resin bearing o-nitrobenzyl group

The matrix polymer PTBCHNB bearing o-nitrobenzyl group was successfully synthesized by copolymerization of tertiary-butyl methacrylate(TBMA), cyclohexyl methacrylate(CHMA) and o-nitrobenzyl methacrylate(NBMA) via reversible addition fragmentation chain transfer(RAFT) polymerization method. PTBCHNB was characterized by FTIR, 1HNMR, GPC and DSC. After UV irradiation, the o-nitrobenzyl groups of PTBCHNB were photocleaved and the resulting carboxyl groups were highly alkali soluble, and PTBCHNB was converted to PCHIBMA bearing carboxyl groups. So, the matrix polymer could be etched by mild alkali solution with no requirements of photoacid generators and other diverse additives. The photocleavable behaviors of PTBCHNB were determined by FTIR, 1H NMR and TGA analysis. The resist formulated with PTBCHNB and cast in THF solution showed square pattern of 10 μm×10 μm using a mercury-xenon lamp in a contact printing mode and tetramethyl-ammonium hydroxide aqueous solution as a developer.

Fabrication of Diffraction-limited Full Aperture Microlens Array by Melting Photoresist

A further study on the fabrication of diffraction--limited full aperture microlens array by melting photoresist is described. The formation of aspherical surface is considered. The parameters for controlling the process of lens production, the height of original photoresist cylinders and the angle of contact between the melted photoresist and the substrate, are discussed in detail. The diffraction limited full--aperture microlens arrays have been obtained,and some measurement results are shown in the paper. A method of controlling the formation of quality microlens array in real time is suggested.

10 W QCW operation of a proton implanted GaAlAs diode laser array

We report one thick layer of hard-baked photoresist mask.The laser array stripe pattern was defined by standard wet lithography.With this mask, a 10 W QCW(quasi-continuous wave) operation of a narrow proton implanted multiple stripe conventional single quantum well separate confinement heterostructure(SQW-SCH) GaAlAs diode laser array has been realized.These devices exhibit the lateral far-field radiation pattern of a phase-locked array of gain-guided semiconductor injection laser array.The twenty stripe laser array has a lateral far-field beam divergence full width at half maximum(FWHM) of less than 3°,and three twenty stripe laser array has a beam divergence in the plane of the junction of about 9°.