In this work, a novel fabrication method for VOx-ZnO multilayers with mixed phase of the VO2 and V2O3 through the diffusion of oxygen by annealing at low temperature is presented. A stable sandwich structure of a VOx/ZnO/VOx multilayer was deposited at room temperature, through the oxygen gas flow rate, by RF sputtering system, and the mixed phase was formed through oxygen diffusion by annealing at O2 atmosphere. The results show that the single phase like multilayer formed by this process has a high TCR of more than -2.5%/K and low resistance of about 100 kohm at room temperature. XRD results for the as-deposited VOx/ZnO/VOx multilayer.
This paper presents a 32x32 microbolometer thermal imaging sensor for human body temperature measurement. Waferlevel
vacuum packaging technology allows us to get a low cost and compact imaging sensor chip. The microbolometer
uses V-W-O film as sensing material and ROIC has been designed 0.35-um CMOS process in UMC. A thermal image of
a human face and a hand using f/1 lens convinces that it has a potential of human body temperature for commercial use.
We have proposed a novel encapsulation method with simple process in comparison with conventional encapsulation
technique. Here, the encapsulation film of silicon dioxide is steady for external environment because this can be
designed to cover the emitting organic material from air. Silicon dioxide of 220 nm was deposited by plasma enhanced
chemical vapor deposition and etched by reactive ion etching system. Then, Alq3 was used as a material to emitting layer
in the green (organic light emitting device) OLED and TPD in the hole transportation layer was used for the harmonious
transportation of hole. Luminance was measured with 40 hour intervals at the air-exposed condition. After 400, 1,000,
1,600, and 2,000 hours, luminance of green OLED were 7,366, 7,200, 6,210, and 5,100 cd/m2, respectively. Luminance
of green OLED doesn't decrease until 2,000 hours. As a results, proposed encapsulation technique can increase the life
time of green OLED.
We studied the energy states in In0.8Ga0.2As SAQDs (self-assembled quantum dots) which depended on W(001) and
the misorientation angle of the substrate. Starting materials used in this study were SiO2-patterend exact and 5 degree -
off (001) GaAs substrates. In0.8Ga0.2As SAQDs had only ground state emissions for SiO2-patterned exact (001) GaAs
substrate, whereas those had ground and excited state emissions for SiO2-patterned 5 degree-off (001) GaAs substrate.
These results suggest that discrete nature of the density of states in SAQDs was improved by using SiO2-patterned
vicinal (001) GaAs substrate with higher misorientation angle of substrate.
Titanium dioxide (TiO2) thin films were prepared by ion-assisted electron-beam deposition on glass at room
temperature and were annealed by rapid thermal annealing in O2 and N2 gas flow. TiO2 thin films annealed in N2 gas
flow are (110) rutile phase and (101) anatase phase, but in O2 gas flow are (110) rutile phase. The optical band gaps of
the TiO2 thin films are increased to 3.281 eV with annealing treatment of 300 ~ 500 °C in O2 gas flow and to 3.271 eV in
N2 gas flow. However, the band gap begins to decrease to 3.277 eV at the annealing temperature of 600 °C in O2 gas
flow and to 3.257 eV in N2 gas flow, respectively.
We proposed the grating coupled surface plasmon resonance (GC-SPR) sensors using ZnO and metallic nanograting
structures to enhance the sensitivity of an SPR sensor. The GC-SPR sensors were analyzed using the finitedifference
time-domain method. The optimum resonance angles of 49 and 55.5 degrees are obtained in the 150 nm wide
grating structure with a period of 300 nm for the ZnO thickness of 30 and 50 nm, respectively. Here, an enhanced
evanescent field is obtained due to the surface plasmon on the edge of the bandgap when the ZnO and metallic grating
structures are used to excite the surface plasmon.
In Korea, Japan and China, the measurement of surface temperature profile shown in abnormalities in neural and vascular functions, facial lesions, changes of blood stream in peripheral tissues (breast cancer, etc.), and psychosomatic problems is widely used for the diagnosis and the progress monitor of disease and symptoms (pains). For this application, single element LWIR Hg0.78Cd0.22Te photo-conductive (PC) detectors were fabricated with the wafers having a cutoff wavelength larger than 12.5 mm. The optical characteristics such as responsivity and detectivity were tested and the operation of the detectors was proved by the thermal imaging system IRIS5000. It was found that the 1/f noise makes lines and seriously degrades the thermal images. MWIR Hg0.70Cd0.30Te photo-voltaic (PV) detectors were also fabricated and tested for the medical application. However, owing to the low signal, the results were far from satisfactory. It is supposed that the integration methods are required for the single element MWIR detector.
Long wavelength infrared (LWIR) photoconductive (PC) detectors of single element Hg0.79Cd0.21Te (MCT) on sapphire substrate were fabricated, using three kinds of MCT etching processes, such as wet only, wet & dry mixed, and dry only process. The ohmic contact metals, which were used to the first contact layer in the IR detector fabrication, were Au, Ni, and Ti. The performance test of the fabricated IR detectors showed the good results in the wet etched MCT IR detectors with the detectivities (D*) of (1-3) X 1010 cmHz1/2W-1 and the responsivities of (2-3) X 104 VW-1 at field of view (FOV) of 180 degrees.
The capacitance-voltage (C-V) and the Hall effect measurements were used, in order to study electron cyclotron resonance (ECR) plasma damage in HgCdTe (MCT). In this study using ECR treatments of MCT and C-V measurements, we observed that the type conversion of MCT surface largely depended on the ECR etching conditions, when MCT was etched by ECR plasma as a function of the ECR power and dc bias. The n-type conversion was not observed when the p-type MCT was etched under the condition of ECR power 150 W and dc bias -20 V. As dc bias of ECR increased over -40 V at the constant ECR power 150 W, the p-type MCT was converted to n-type. The p-type MCT was also converted to n-type when ECR power increased to 500 W at the constant dc bias -20 V. These results probably were due to the inter-diffusion of a large amount of excess mercury, liberated during the ECR treatment, into MCT, which were similar to the results of ion milling process. Another interesting result, observed in C-V measurements, was the p- type conversion from n-type MCT when the n-type MCT was etched under the condition of ECR power 150 W and dc bias -20 V. As dc bias of ECR increased over -40 V, the C-V curve was the results of n-type MCT characteristics. We considered that a low dc bias of -20 V, the hydrogen passivation and the deficiency of mercury in the etched surface were dominant and resulted in conversion to p-type. As dc bias increased over -40 V, the inter-diffusion of excess mercury into MCT was dominant and associated with keeping the n-type characteristics.
We obtained the photoluminescence spectra for CdTe(111) grown on Si(100) tilted toward <011> 1 degree, 2 degrees, 4 degrees and 8 degrees by MBE before and after RTA. It is caused by the strain due to the lattice mismatch between CdTe epitaxial layer and the substrate that the shift of peaks form CdTe(111)/Si(100) epitaxial layer was observed comparing with that of bulk. We could guess the crystal structures of the CdTe(111) epitaxial layers from the strains calculated from the quantity of the shifts. We found that the crystal structure of CdTe changed from the cubic in bulk to the tetragonal in strained as-grown samples, and from the tetragonal to the trigonal after RTA. It is caused by the different strain type that the structures are different before and after RTA because the misfit for atomic distance is dependent on the direction between CdTe(111) and Si(100). We found that the inplain compressive strains change from asymmetry to symmetry about (111) direction in CdTe(111) epitaxial layer after RTA.
As the integration density in the manufacturing of IC's increases and tighter design rules are implemented, the accuracy of overlay in the photolithography process is becoming all the more important. Consequently, investigation and characterization of the accuracy (as well as precision) of the overlay measurement are being required to insure that the overlay metrology tool qualifies for the new technologies. In this paper, we analyze the relationship between wafer substrate types and the respective characteristic overlay measurement errors associated with them. We compare results using different illumination wavelengths in the overlay tool. We define the Wafer Induced Shift (WIS) contribution to the measurement accuracy error and introduce a metric for it. And we analyze the relationship between the TIS and WIS. We show that the wavelength of the optical overlay measurement (OL, for short) should be fitted separately to each of the various kinds of overlay measurement targets, or marks. Buried type targets, covered by transparent materials, for which the measurement is made through the transparent interlayer, benefit from wavelength selection due to the possible improvement in contrast associated with an interference effect. Open type targets, on the other hand, in which the measurement signal is collected off the substrate shape itself, do not benefit from that. There is another problem to consider, however. Such targets may show a considerable WIS, even thought TIS and precision are good both before and after etch. The WIS error can be as high as 100 nm. This could create serious OL problem and it means that TIS and precision are not enough to characterize the quality of measurement, and WIS is equally important, it not more so. We look into the causes of WIS in the substrate shape, overlay mark design and fabrication method. We show that with careful selection of illumination wavelength, some layers produce no WIS. On the other layers WIS remains a problem and other methods are still required to control it.