A Dry Etch Approach To Reduce Roughness And Eliminate Visible Grind Marks In Silicon Wafers Post Back-grind

3D wafer packaging represents a significant component of the total wafer level processing cost. Replacement of the Chemical Mechanical Polishing (CMP) process step with a corresponding dry etch can yield significant time and cost savings. Incorporating equipment already utilized in the 3D integrated wafer packaging process during the subsequent Through Silicon Via (TSV) reveal step, process efficiencies can be achieved, with overall die yields being maintained. Using dry etch technology to treat a 200nm rough back-ground silicon surface, a smooth surface with a peak to valley roughness of less than 6nm is demonstrated. This patented process differs from other dry etch smoothing techniques in that it aims to eliminate any visual grind marks rather than just reducing the surface roughness. The elimination of visible grind marks is critical in later optical inspection where they are falsely identified as defects. The quality of the surface is equivalent to that of a CMP processed wafer and as such, this process has been implemented in manufacturing replacing the CMP step. The novel process described combines a surface modification followed by a roughness reduction in an iterative manner to produce a smooth surface without visible grind marks post processing

Electrochemical Biofunctionalization of Highly Oriented Pyrolytic Graphite for Immunosensor Applications

The present research demonstrates a procedure for surface modification of Highly Oriented Pyrolytic Graphite (HOPG) electrodes intended for use as immunosensors. The HOPG surface is linked to the molecule 8-hydroxydeoxyguanosine (8-OHdG), an oxidative stress biomarker for DNA damage, though the aniline mediator covalently bonded to electrode and biomarker. An electrochemical procedure to graft the mediator is described and the presence of biomarker at surface is demonstrated by using a fluorescence-labeled immune-reagent. An electrochemical functionalization process has been employed for attachment of functional aminie (NH2) linking groups to graphitic surfaces, which consists of two stages: (i) a reaction with a diazonium salt to covalently bond nitrobenzene groups to the surface and (ii) electrochemical reduction of the nitro group (–NO2) to an amine group (–NH2). The shape of the CV curve indicates that the redox reactions are taking place at the HOPG electrode surface. The amine group can subsequently be used to covalently link to an antibody biorecptor. The presence of 8-OHdG, indicative of DNA damage, has been linked to increased cancer risk. Detection of this oxidative stress biomarker is an important tool for the early diagnosis of disease

Graphene Field Effect Transistors for Biomedical Applications: Current Status and Future Prospects

Since the discovery of the two-dimensional (2D) carbon material, graphene, just over a decade ago, the development of graphene-based field effect transistors (G-FETs) has become a widely researched area, particularly for use in point-of-care biomedical applications. G-FETs are particularly attractive as next generation bioelectronics due to their mass-scalability and low cost of the technology’s manufacture. Furthermore, G-FETs offer the potential to complete label-free, rapid, and highly sensitive analysis coupled with a high sample throughput. These properties, coupled with the potential for integration into portable instrumentation, contribute to G-FETs’ suitability for point-of-care diagnostics. This review focuses on elucidating the recent developments in the field of G-FET sensors that act on a bioaffinity basis, whereby a binding event between a bioreceptor and the target analyte is transduced into an electrical signal at the G-FET surface. Recognizing and quantifying these target analytes accurately and reliably is essential in diagnosing many diseases, therefore it is vital to design the G-FET with care. Taking into account some limitations of the sensor platform, such as Debye–Hükel screening and device surface area, is fundamental in developing improved bioelectronics for applications in the clinical setting. This review highlights some efforts undertaken in facing these limitations in order to bring G-FET development for biomedical applications forward

Transcript of Oral History Interview with Guy and Bess Scruggs

Transcript of an oral history interview of Guy and Bess Scruggs conducted by Owen Glen Cosgrove on 21 August 1975. This interview was digitized from cassette format. The Scruggs family was working with Abilene Christian College during its expansion during the 1920s and through the time of the college\u27s dire financial struggles in the 1930s. Mr. Scruggs\u27 thesis on the history of Abilene Christian College is an extensive study of the college during those years. Scruggs and Morris also worked together for many years. Mrs. Scruggs\u27 father was S. N. Allen, for many years a member of the Board of Trustees at Abilene Christian College. Mr. and Mrs. S. N. Allen donated a one-hundred-and-twelve-acre farm to Abilene Christian College in 1944 to help establish the college\u27s agriculture department

Generic epitaxial graphene biosensors for ultrasensitive detection of cancer risk biomarker

A generic electrochemical method of 'bioreceptor' antibody attachment to phenyl amine functionalized graphitic surfaces is demonstrated. Micro-channels of chemically modified multi-layer epitaxial graphene (MLEG) have been used to provide a repeatable and reliable response to nano-molar (nM) concentrations of the cancer risk (oxidative stress) biomarker 8-hydroxydeoxyguanosine (8-OHdG). X-ray photoelectron spectroscopy, Raman spectroscopy are used to characterize the functionalized MLEG. Confocal fluorescence microscopy using fluorescent-labelled antibodies indicates that the anti-8-OHdG antibody selectively binds to the phenyl amine-functionalized MLEG's channel. Current–voltage measurements on functionalized channels showed repeatable current responses from antibody–biomarker binding events. This technique is scalable, reliable, and capable of providing a rapid, quantitative, label-free assessment of biomarkers at nano-molar (<20 nM) concentrations in analyte solutions. The sensitivity of the sensor device was investigated using varying concentrations of 8-OHdG, with changes in the sensor's channel resistance observed upon exposure to 8-OHdG. Detection of 8-OHdG concentrations as low as 0.1 ng ml−1 (0.35 nM) has been demonstrated. This is five times more sensitive than reported enzyme linked immunosorbent assay tests (0.5 ng ml−1)

Epitaxial graphene immunosensor for human chorionic gonadotropin

Human chorionic gonadotropin (hCG), a 37 kDa glycoprotein hormone, is a key diagnostic marker of pregnancy and has been cited as an important biomarker in relation to cancerous tumors found in the prostate, ovaries and bladder.A novel chemically-modified epitaxial graphene diagnostic sensor has been developed for ultrasensitive detection of the biomarker hCG. Multi-layer epitaxial graphene (MEG), grown on silicon carbide substrates, was patterned using electron beam lithography to produce channel based devices. The MEG channels have been amine terminated using 3-Aminopropyl-triethoxysilane (APTES) in order to attach the anti-hCG antibody to the channel.Detection of binding of hCG with its graphene-bound antibody was monitored by measuring reduction of the channel current of the graphene biosensor. The sensitivity of the sensor device was investigated using varying concentrations of hCG, with changes in the channel resistance of the sensor observed upon exposure to hCG. The detection limit of the sensor was 0.62 ng/mL and the sensor showed a linear response to hCG in the range 0.62–5.62 ng/mL with a response of 142 Ω/ng/mL. At concentrations above 5.62 ng/mL the sensor begins to saturate

Fundamental experimental and theoretical studies on the lightfastness of azo dyes.

Photo-degradation reactions of donor acceptor azo dyes in methanol solution have been investigated. Irradiation of the second absorption band was confirmed to be the predominant cause of permanent photo-fading under anaerobic and oxygenated conditions. Under anaerobic conditions, 2'-nitro substituted azobenzenes and azothiophene dyes were the least lightfast, with half-lives of under one hour, whilst 4'-nitro substituted dyes had half-lives of between 1 and 1.5 hours. Photo-degradation was retarded in the presence of oxygen by between 4 and 16 times relative to fading under anaerobic conditions. The photo-fading of dyes deposited on various substrates exhibited similar behaviour to dyes in methanol solution. UV/visible spectra showed that 2'-nitro substituted dyes underwent complete loss of intensity of the visible absorption peak and a corresponding increase in the absorption in the UV region of the spectrum when irradiated under anaerobic conditions, indicating cleavage at the azo bridge and subsequent formation of mono-phenyl derivatives. In contrast, under oxygenated conditions, a gradual loss of intensity at the visible absorption maximum was observed, with no notable newly formed peaks are detected in the UV region suggesting that cleavage at the azo bridge is less significant. The photoproducts of the reaction are suggested to include the reduced form of azo dyes containing nitro groups. Theoretical semi-empirical AMI and ab initio calculations using the 3-21G basis set, predicted reasonable structures for the ground states of dyes. Spectroscopic calculations using a version of the CNDO/S method gave good correlations between calculated transition energies and experimental data obtained in cyclohexane. The results of a multi electron configuration interaction treatment of AMI structures in the gas phase were inconsistent with experimental spectral data obtained in cyclohexane but improved correlations were obtained between calculated transition energies and experimental data in methanol. The structures and energies of excited singlet and triplet states have also been calculated by the AMI method but no apparent correlation of these energies with the lightfastness of azo dyes could be identified. A tentative relationship between calculated distributions of the unpaired electrons in the second excited triplet state and the site of reactivity in the dyes was proposed