In this study, we demonstrated the textured structure on silicon surface by metal assisted etching method, using Au
nanoparticles as catalysts in HF and H2O2 solution. The size and density of the nanoparticles could be tuned easily. The
porous layers filled with cylinder- or cone-shaped were uniformly formed by immersing the gold deposited silicon
wafers in a mixed solution containing HF and H2O2 under different etching conditions. The optimized textured structure
was close-packed pyramids-like surface in subwavelength scale and showed the lowest reflectance less than 0.5% over
whole visible and near IR wavelengths. The large reduction of reflectance was attributed from the gradient refractive
index of the silicon surface with the depth along the light propagation.
In this work, we present the evolution of optical constants varying with distinct annealing temperature for poly (3-
hexylthiophene) (P3HT) and 6,6-phenyl C61-butyric acid methyl ester (PCBM). With calculation of the transmission and
reflection spectra in P3HT:PCBM photovoltaic device , the optical properties correlation to annealing temperature is
studied. The solar cell power conversion efficiency and optical absorption is compared simultaneously. Finally, the
electric field amplitude in the device is discussed for detailed explanation of thermal annealing effects on the organic
photovoltaic device performance.
In this paper, we have demonstrated a low-reflectance organic light-emitting device (OLED) by inserting a perylene
diimide derivative between the emitting layer (EML) and the cathode. Such a material exhibits a good electron transport
capability and good photoconductivity which absorbs light. A semi-transparent layer composed of thin aluminum (Al)
and silver (Ag) was used between the EML and the n-type organic material, a perylene diimide derivative, for better
electron injection and efficient destructive interference. The J-V characteristics of our low reflection and the control one
are nearly identical which shows the superior conductivity of this material. In addition, the absorption peak of this ntype
organic material is near 550 nm which can eliminate most of the ambient visible light. And the potocurrent is
generated from self-absorption by this material. Thus, this device can also be applied as a photodetector or the
applications of the self-adjustable display under different ambient illumination with suitable driving scheme.
In the recent ITRS roadmap, the ArF lithography combining with resolution enhancement techniques have great potential to lead IC technologies to the generation less than 100nm. The problems of critical dimension control caused by highly reflective substrates are far more serious in the ArF regime than in the longer wavelengths. It is therefore important to find a high performance antireflective coating layer working in this spectral regime. For increasing resolution of optical lithography, expose systems with high numerical aperture (NA) are essential. The efficiency of conventional single layer BARC structure will degrade as the incident angle increased. It is due to the reflectance at resist/BARC interface increased in high incident angle regimes. Here we demonstrate a multi-layer bottom antireflective coating (BARC) layer for high NA ArF lithography. The multi-layer antireflective structure is composed of conventional SiON films. In a multi-layer BARC, the extinction coefficient of each BARC layer is gradually increased layer by layer, an dis the highest at the bottom. By adding an optimized structure, the reflectance can be remained less than 2% at resist/silicon substrate interface as the incident angle from 0 to 60 degrees (i.e. NA ~ 0.85). The swing effect in the resist is also shown significantly reduced. It also has a great potential to be used as BARC layer on other highly reflectance substrate such as copper, aluminum silicon (Al-Si), poly-silicon, tungsten silicide (W-Si), which are commonly used in IC processes.
A high-throughput, one-step microwave technique was developed for the dissolution of photolithographic materials. The effects of dissolution temperature and digestion acid volume on the dissolution efficiency were systematically evaluated. By combining the proposed microwave digestion and inductively coupled plasma mass spectrometry techniques, the detection limits int the sub- ppb level and the analytical throughput up to 14 samples per hour were achieved for the analysis of nine metals. The novel process of using the identical bottom antireflective coating (BARC) material was applied to the KrF and ArF photoresist systems to reduce swing effect and surface reflectance on the substrate. It was found that the optimal thickness of the BARC film for the KrF and ArF photoresist systems were 62.5 nm and 119 nm, respectively.
A novel bilayer bottom antireflective coating (BARC) structure composed of a commercial KrF lithography resist and an organic BARC film is demonstrated for ArF lithography. The diluted deep ultraviolet (248 nm) resist is high absorption at the 193 nm regime, which is suitable as bottom layer of bilayer BARC structures. While the deep ultraviolet organic BARC material is low absorption at the 193 nm regime, which is suitable as top layer of bilayer BARC structures. Such a bilayer BARC can have large thickness control tolerances over various highly reflective substrates. The measured swing effect is found significantly reduced by adding such a bilayer BARC on both aluminum and silicon crystal substrates. Reflectance can be reduced to less than 2% on other highly reflectance substrates such as copper, poly-silicon, tungsten silicide, and aluminum silicon. Such a process has several advantages: high performance, relatively inexpensive, large thickness control tolerance, low contamination, and easy film removal.
Polymeric optical waveguides are fabricated by using optical polymer benzocyclobutene BCB). The properties of BCB include good thermal stability and high optical transmission. Anisotropic etching of BCB has been characterized by reactive ion etching. The output mode distribution has been examined by CCD measurement system. Also, an optical coupler based on multimode interference (MMI) effect has been designed and fabricated. We show that such MMI couplers can offer superior properties such as low excess loss and good tolerance to the variation of wavelength. The measurement results are presented.
Characterization results of cladding layer for photonic integrated circuits are present. The silicon oxide films were deposited by various methods. The mechanical stress, depending upon the methods of film deposition, had been measured. TEOS silicon oxide exhibited large mechanical stress. The stress of polymer benzocyclobutene (BCB) was also measured. Its stress is only 29 MPa. The roughness of BCB surface is 1.18 nm. The mode profiles of planar waveguide were calculated.
We demonstrate a new bottom antireflective coating (BARC) layer for ArF lithography. The antireflective layers are composed of a low dielectric constant FLARE 2.0 film and its etching hard mask layer, such as oxide or nitride. By adding an optimized thin oxide or nitride layer, the reflectance of less than 1% at resist/silicon substrate interface can be achieved. The swing effect in the resist is also shown significantly reduced. It also has a great potential to be used as BARC layer on other highly reflectance substrate such as copper, aluminum, tungsten, titanium nitride, and tantalum nitride, which are commonly used in metal interconnect. Since it is easy to reduce reflectance by adding a FLARE film and its etching hard mask layer without adding an extra BARC layer. It is convenient to use this structure for patterning low dielectric materials in ArF lithography. Suitable etching characteristics and thermal stability of FLARE 2.0 based BARC layers are also shown in this paper.
In this paper, we demonstrated a novel anti-reflective coating structure for deep ultraviolet binary mask, which is based on three-layer Fabry-Perot Structure. The anti- reflective coating structure is composed of the chrome/oxide/chrome stack. By adding different optimized structures, reflectance of less than 2% at both 248nm and 193nm have been achieved. The results are also agreed well with simulated ones. At the three-layer Fabry-Perot structure, the thickness of bottom chrome layer should be larger than 100 nm to provide suitable absorption. By controlling the thickness of the intermediate oxide layer, we can tune the minimum reflection regime to the desired exposure wavelength. The thickness of top chrome layer should be well controlled in order to optimize transmission light into Fabry-Perot structures. In general, the mask layer should have good electrical conductivity for e-beam writing in order to prevent writing errors due to charging effects. In the Fabry-Perot structure, the top metal layer can also prevent charge accumulation during e-beam writing.
The optical behavior of semiconductor bottom antireflective coating (BARC) material was investigated by both the measurement and simulation methods. The effects of spin- coating rate, interface reflection, BARC layer thickness and photoresist layer thickness were studied. Our results indicated that the 62.5 nm of BARC layer had strong effect on suppressing the light reflection of wavelength of 248 nm form the wafer surface, irrespective of the photoresist layer thickness. Based on the gravimetric method, a high throughput and one-step microwave digestion procedure was developed for the BARC materials. The digestion efficiency increased with the digestion duration and the temperature. By following the established one-step microwave digestion method and inductively coupled plasma mass spectrometry determination, the detection limits obtained for Cr, Ni, Cu, An and Pb were in 0.1 to 1.11 ppb levels. The spike recoveries of the metallic impurities were in the range 86- 102% for the BARC materials. The analytical results of the BARC samples were found to be in reasonably good agreement with our previous method, and the analytical throughput can achieve up to 20 samples per hour for the analysis of 5 elements.
KEYWORDS: Deep ultraviolet, Electron beam lithography, Etching, Lithography, Oxides, Chemically amplified resists, Process control, Electron beams, Optical lithography, Polymethylmethacrylate
Chemically amplified resists have been widely used in deep UV optical lithography. In this paper, we characterized positive deep UV resists for high-resolution electron beam lithography applications. Results indicate this deep UV resist is very high sensitive and suitable for high throughput e-beam lithography applications. In general, deep UV resists are not suitable for sub-100 nm resolution lithography, except for strictly process control. After a simple thermal flow procedure, the trench-width can be easily down to 70 nm. It is also convenient to get a sub-70 nm contact hole pattern by utilizing commercial deep UV resists with this strategy. Many factors influence performance or resists such as soft bake, post exposure bake, exposure dose, and thermal flow, which are discussed and optimized. Suitable dry etching properties of deep UV resists are also characterized for pattern transfer.
Suitable silicon-oxynitride films for constructing the attenuated phase shifting masks to be operated in the 157 nm excimer laser regime are obtained by varying the gas flow rations in a RF sputtering process. Characteristics of the films such as optical constants, material compositions, etching selectivity, surface profiles, and adhesion strength are experimentally analyzed. These results indicate that he silicon-oxynitride films thus fabricated can meet the requirements for building such APSM's working in the wavelength of 157 nm.
We have simulated the optical behavior of a new reflective APSM by utilizing the optical multilayer thin film theory. In a typical Mo/Si multilayer structure, we show that the requirement of a reflective APSM can be met simply by adjusting the thickness of the over-coated Ge layer. A phase shift of 180 degrees results when compared light reflected from a Ge absorption layer to that form a Mo/Si multilayer, and the resultant reflectance ratio is in the range of 4-15 percent. No additional phase shifting layer is needed.
Fiber Bragg gratings were fabricated by utilizing high pressure deuterium loading for photosensitivity enhancement and a phase mask for holographic exposure. The absorption peak near 1.71 micrometers was used as an indicator to monitor the evolution of deuterium diffusion into and out of a fiber, and the results were consistent with the theoretical modeling. Thermal hysteresis of the fiber Bragg grating was greatly reduced and thermal reliability was increased when annealing was applied.
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