This thesis presents the development of electrochemical etch-stop techniques (ECES) to achieve high precision 3-dimensional integrated MEMS sensors with wet anisotropic etching by applying proper voltages to various regions in silicon. The anisotropic etchant is selected as tetra methyl ammonium hydroxide, TMAH, considering its high silicon etch rate, selectivity towards SiO2, and CMOS compatibility, especially during front-side etching of the chip/wafer. A number of parameters affecting the etching are investigated, including the effect of temperature, illumination, and concentration of the etchant over the etch rate of silicon, surface roughness, and biasing voltages. The biasing voltages for passivating the n-well and enhancing the etching reactions on p-substrate are determined as -0.5V and -1.6V, respectively, after a series of current-voltage characteristic experiments. The surface roughness due to TMAH etching is prevented with the addition of ammonium peroxodisulfate, AP. A proper etching process is achieved using a 10wt.% TMAH at 85&deg / C with 10gr/lt. AP. Different silicon etch samples are produced in METU-MET facilities to understand and optimize ECES parameters that can be used for CMOS microbolometers. The etch samples are fabricated using various processes, including thermal oxidation, boron and phosphorus diffusions, aluminum and silicon nitride layer deposition processes. Etching with the prepared samples shows the dependency of the depletion layer between p-substrate and n&amp / #8209 / well, explaining the reason of the previous failures during post-CMOS etching of CMOS microbolometers from the front side. Succesfully etched CMOS microbolometers are achieved with back side etching in 6M KOH at 90 &deg / C, where &amp / #8209 / 3.5V and 1.5V are applied to the p-substrate and n-well. In summary, this study provides an extensive understanding of the ECES process for successful implementations of integrated MEMS sensors.

Zinc oxide (ZnO) has higher exiton binding energy (60 meV) and high band gap (~3.4 eV) that can provide efficient ultraviolet (UV) light at room temperature (RT). The easily etched in acids and alkalis that provides the fabrication of small-size ZnO-based devices. Electrodeposition is the growth method that can deposit high quality film and modify the characterizations of film by changing its deposition electrolyte concentration, temperature, and current density. Firstly, the ZnO is deposited on n-type Si substrate by electrodeposition by different deposited temperature, electrolyte concentration, and current density. The deposited films contain zinc nitrate, metal Zn, and ZnO while electrodeposited at various deposition parameters. For the deposited film contains only ZnO, no UV light is found measured by macroscopic photoluminescent analysis even annealed at different ambient and temperature. According to previous papers, an ideal UV light intensity can be obtained by thermal treated metal Zn or Zn ion implantation into oxide materials after annealing. Annealing the Zn-ZnO structure formed in 30oC by electrodeposition can observe intense UV light. This method improves the disadvantages of insufficient light intensity and no UV light observation from conventionally electrodeposited ZnO. The variation of UV light wavelength of ZnO oxidized from metal Zn is associated with the quantum-confinement effect that was discussed by previous papers. It is found that the size of ZnO is not small enough to realize the quantum-confinement effect, herein, we suggest that the variation of UV light wavelength is affected by the metal Zn resides in ZnO. Otherwise, the electrodeposition of ZnO is not easily performed on p-type substrate, an aluminum film on the back side of p-type Si can deposit ZnO by smaller potential, and different ZnO nanostructures are obtained by modifying the current density. Recently, different characteristics were found in nano-size noble metal crystals. In this thesis, the porous structure of Au-ZnO and Pt-ZnO were co-deposited by electrodeposition to enhance the photocatalytic activity. Si is the dominant material in semiconductor technology, but its indirect band gap property makes it not allowed in optoelectronics application. However, since 1990, the visible light is observed from porous Si fabricated by electrochemically etching of Si; though the light mechanism of porous Si is not clear, it can be divided into two parts, the quantum-confinement effect of Si nanocrystals and surface states on porous Si. Porous Si emits efficient visible light, but its light wavelength is readily influence by environment. We developed three methods, electrochemically etching the pre-treated Si substrate, adding chemical solution into electrolyte during etching process, and post-treatment of Si substrate after etching to prevent the emission of porous Si from being affected by environment.

This study utilizes a modified LIGA process to fabricate a high aspect ratio aspherical micro lens array, which improves low light output of OLED due to its intrinsic total internal reflection. Presently typical OLED extraction efficiency is not high. How to increase OLED extraction efficiency is a valuable topic to discuss. This study analyzes related parameters that influence the formation of micro lenses, for example, the influence of variation of diametric dimension, dry etching parameters and electroforming rate. The experimental results indicate that the tolerance of dimensional variation of the diameter is about 5% during the thermal reflow and dry etching stage. The oxygen content and the photoresist surface during dry etching influence the result. A high electroforming rate is helpful for covering the surface defects on photoresist. An undercut caused by dry etching will discontinue the initial electroformed layers. A apherical microens array can raise the luminance to a maximum of 15 times higher.

With the raise of nanotechnology researching, many special physical and chemical properties were found gradually in nanoscale. Among them, the one-dimension nanostructure owns high specific surface area and excellent electron emission properties. Moreover, the two-dimension arrayed nanostructure has the characteristics of photonic crystal and moth-eye effect. Currently, advanced lithographic methods such as electron beam (E-beam) or deep ultraviolet (DUV) lithography and X-ray lithography are adopted to define periodic nanoscale patterns. But these lithographic equipment are too expensive. Moreover, costly etching methods such as inductively coupled plasma reactive ion etching (ICP-RIE) or electron cyclotron resonance reactive ion etching (ECR-RIE) must be used to form arrayed silicon nanostructure with high aspect ratios. The nanoscale array patterns can be defined on the surface of the silicon wafer by the self-assembly of a polystyrene nanosphere. The photo-assisted electrochemical etching (PAECE) has the advantage of forming nanopore, and the aspect ratio of etched nanopores can be as high as 50:1 which is better than ICP-RIE. Therefore, PAECE is very suitable to fabricate nanostructure. This high-cost drawback makes most of academias and small/medium enterprises hard to invest in nanotechnology. This study combines the self-assembly nanosphere lithography (SANSL) process and photo-assisted electrochemical etching to fabricate a nanostructure array with a high aspect ratio on the surface of a silicon wafer. Experimental results show that the nanosphere array with a nearly perfect arrangement can be obtained in the sample of 1.8 ∗1.8 cm2 by spin coating and vibration coating. Using reactive ion etching (RIE) can transfer the nanosphere array pattern to the silicon nitride layer, and form the etching window of PAECE. The concentration of the HF electrolyte used in PAECE was 2.5 wt%. When PAECE was performed with etching mask can produce deeper and periodic nanopores. The surfactant of SDSS added in the HF electrolyte of PAECE can reduce the contact angle of electrolyte and avoid the phenomenon of hole-reaming. When the voltage of 1 V is used to etch for 12.5 min, the etching depth of the nanopore array structure is about 5.69 £gm and its diameter is about 90 nm, such that the aspect ratio of the pore can reach about 63:1. If the etching voltage was increased, the width of pore will be increased and the depth of pore will be reduced gradually at the same time. When the etching voltage of 2 V is applied to etch for 5 min, the etching height of the nanopillar is about 2 £gm and its diameter is about 100 nm, such that the aspect ratio of the pillar can reach about 20:1. The nanopillar was arranged periodically according to the definition of nanosphere, therefore the arrayed nanopillar can be realized successfully. Dropping the solution which has biological samples into the gap of nanopillar, it will affect the light which goes through the nanostructure and produce specific parameters of polarization. The results showed that when the DI water was dropped into the nanopillar structure, the degree of polarization (DOP) is 0.981, azimuth is 4.86¢X and ellipticity is 2.83¢X. When the solution which has alkaline lysis plasmid of 5 £gg/ml was dropped into the nanopillar structure, the DOP is 0.957, azimuth is 7.7¢X and ellipticity is 3.99¢X. The result shows that the change of polarization parameter has the relations with the concentration of biological samples in solution. Therefore, the measure system can be combined with nanopillar array to develop the photonic crystal biosensor. This study also applies the developed nanopore nanostructure array to fabricate sub-wavelength antireflection structure of solar cell. Experimental results show that the deeper in structure and then the better in antireflective effect. After performing 1 V PAECE for 5 min, the weighted mean reflectance can be reduced to 1.73% under the wavelength range of 280¡V890 nm. Further coating of a silicon nitride layer on the surface of a nanostructure array reduces the weighted mean reflectance even to 0.878 %. Finally, this study also uses various voltage of PAECE to produce nanostructure array with different surface area for the electrode fabrication of fuel cell. Experimental results show that the larger in surface area of sample and then the better in catalysis effect. Two-staged PAECE of 1.5 V and 1.75 V can yield nanopillar with surface area of 14.2 cm2 , which is about 50.2 times higher than a planar electrode. When the surface of such a nanopillar array is coated with platinum of 1000 Å, the reaction current of nanopillar array is 10.2 mA, which is 72.9 times higher than that obtained by only a planar electrode.

Although copper (Cu) is the preferred interconnect material due to its lower resistivity than aluminum (Al), Cu subtractive etching processes have not been developed at temperatures less than 180 °C, primarily due to the inability to form volatile etch products at low temperature. The conventional damascene technology avoids the need for subtractive etching of Cu by electroplating Cu into previously etched dielectric trenches/vias, followed by a chemical/mechanical planarization (CMP) process. However, a critical "size effect" limitation has arisen for damascene technology as a result of the continuing efforts to adhere to "Moore's Law". The size effect relates to the fact that the resistivity of damascene-generated lines increases dramatically as the line width approaches the sub-100 nm regime, where feature size is similar to the mean free path of electrons in Cu (40 nm). As a result, an alternative Cu patterning process to that of damascene may offer advantages for device speed and thus operation. This thesis describes investigations into the development of novel, fully-plasma based etch processes for Cu at low temperatures (10 °C). Initially, the investigation of a two-step etch process has been studied. This etch approach was based on a previous thermodynamic analysis of the Cu-Cl-H system by investigators at the University of Florida. In the first step, Cu films are exposed to a Cl₂ plasma to preferentially form CuCl₂, which is believed to be volatilized as Cu₃Cl₃ by subsequent exposure to a hydrogen (H₂) plasma (second step). Patterning of Cu films masked with silicon dioxide (SiO₂) layers in an inductively coupled plasma (ICP) reactor indicates that the H₂ plasma step in the two-step process is the limiting step in the etch process. This discovery led to the investigation of a single step Cu etch process using a pure H₂ plasma. Etching of blanket Cu films and Cu film patterning at 10°C, display an etch rate ~ 13 nm/min; anisotropic etched features are also observed. Comparison of H₂ plasma etching to sputtering of Cu films in argon (Ar) plasmas, indicates that both a chemical component and a physical component are involved in the etching mechanism. Additional studies using helium plasmas and variation of power applied to the plasma and etching surface demonstrate that the etch rate is controlled by reactive hydrogen species, ion bombardment flux and likely photon flux. Optical Emission Spectroscopy (OES) of the H₂ plasma during the Cu etching process detects Cu emission lines, but is unable to identify specific Cu etch products that desorb from the etching surface. Variation of Cu etch rates as a function of temperature suggests a change in mechanism for the removal of Cu over the temperature of -150 °C to 150 °C. OES analyses also suggest that the Cl₂ plasma step in the two-step process can inhibit Cu etching, since the subsequent H₂ (second) plasma step shows a time delay in film removal. Preliminary results of the etching of the SiO₂ mask material in H₂ plasmas with various intentionally introduced contaminants demonstrate the robustness of the H₂ plasma Cu etch process.

Thesis (M.S.D.)--Indiana University School of Dentistry, 2009. / Title from PDF t. p. (viewed Feb. 10, 2010) Advisor(s): Masatoshi Ando, Chair of the Research Committee, Carlos Gonzalez-Cabezas, Melvin Lund, Tien-Min Gabriel Chu, Michael Cochran. Curriculum vitae. Includes abstract. Includes bibliographical references (leaves 64-70).

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Title from PDF title page (viewed on Feb. 3, 2010). Includes bibliographical references (p. 52-57).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 187-201). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Evaluation of the wet etching properties of several different thin film oxidesgrown by physical vapour deposition was performed in this work. MgO, Al2O3,SiO2, TiO2, HfO2 ZrO2 and Y2O3 were coated on two types of substrates; Si andborosilicate glass and etching tests were performed in different etchingsolutions. MgF2 thin films have also been evaluated. Important aspects of the choice of the thin films was taken into account in orderto match to good optical properties such as refractive index (n), extinction coefficient (k) and optical thickness (TP) as well as good chemical properties in the wet etching process. A description is made of the physics of optical filters and how a combination of different oxides stacked onto each other can create interference filters. A description of the manufacturing process of the thin films where physical vapour deposition (PVD) was used is presented. Thermal shift of the optical spectra caused by porous coatings was investigated and analyses of the thin films by ellipsometry, surface profilometry and transmission spectrophotometry have been performed. The wet etching properties were evaluated by monitoring the transmission insituon transparent borosilicate glass substrates. A method of how to measure the wet etching rate for different thin films is described. A computer software was used to calculate the Pourbaix diagrams in order to understand the chemical behaviour of the etching solutions. The pH can have a significant impact on the etching behaviour. In case of TiO2, it can be dissolved in an alkaline solution of H2O2. The catalytically process behind this is evaluated. Etching rate for both Y2O3 andSiO2 were matched by adjusting the etchant concentration as a case example. The group IVB oxides are difficult to etch. The catalytic etching of TiO2 with peroxide is slow but detectable. Al2O3, Y2O3 and MgO are reasonably easy to etch but have too low refractive indices to be useful in multilayer optical filters. The In-situ etching instrument was found to be very useful for measuring etching rates. / Utvärdering av våtkemiska egenskaper för flera olika oxidtunnfilmer utfördes idetta arbete på tunnfilmer av MgO, Al2O3, SiO2, TiO2, HfO2 ZrO2 and Y2O3 vakuumdeponerade på både kiselwafers och borosilikatglas. Etstester gjordes med ett flertal etslösningar. Även MgF2-tunnfilmer utvärderades. Både optiska och kemiska egenskaper togs i beaktande vid utvärderingen av tunnfilmerna. De optiska lagar som gäller för tunnfilmer redovisas, bl a hur kombinationer av olika oxider kan skapa interferrensfilter. En beskrivning av tillverkningsprocessen varvid PVD användes presenteras. Termiskt skift av det optiska transmissionsspektrat orsakat av porositet undersöktes. Analyser av tunnfilmerna med ellipsometri, profilometri och transmissions spektroskopi utfördes. Våtetsningsegenskaperna utvärderades genom att mäta in-situ vid etsprocessen på transparenta borosilikatglassubstrat. Metoden för att mäta etshastigheten för olika oxider är beskriven. Datorberäkningar av pourbaixdiagram användes för att skapa en förståelse av de kemiska egenskaperna för etslösningarna. Etsegenskaperna påverkas till stordel av lösningens pH. TiO2 kan etsas i basisk lösning av peroxid. Denna process utvärderades, likaså utvärderades etshasigheten för Y2O3 och SiO2 för att erhålla matchande par avoxider som en fallstudie. Grupp IVB oxiderna är mycket svåra att etsa. Katalytisk etsning av TiO2 med peroxid är detekterbar men långsam. Al2O3, Y2O3 och MgO är förhållandevis enkla att etsa men har för låga brytningsindex för att var praktiskt använbara i optiska multilagerfilter. In-situ etsinstrumentet befanns vara ett utmärkt verktyg för att mäta etshastigheten för tunnfilmer.