Aluminum Nitride Contour Mode Resonators

Resonators are a major component in RF electronic products. They are used in a host of ways to filter radio signals. Modern and Future RF communications have placed high demands on the industry; requiring low power usage, wide array of applications and resistance to noise. In this thesis, a discussion of the motivation for RF MEMS filters and basic theory is given with an explanation of the concepts of Q factor, piezoelectricity, acoustics theory, the major types of resonators (SAW, BAW, CMR or LAMB), apodization theory and techniques as well as design, simulation of CMR and BAW devices, testing and process development of aluminum nitride by RF reactive sputtering at RIT. Finite element analysis was performed on a number of factors of aluminum nitride contour mode resonators (CMR) from piezoelectric film thickness, to electrode pitch, electrode thickness and electrode configuration; to understand the effects. First order and second order vibration modes were seen including symmetric S0, S1 and antisymmetric A0, A1 resonant modes in the pizeoacoustic devices and higher. A series of time dependent video simulations of SAW, BAW and LAMB wave resonators were also performed, perhaps the first of their kind. The RF reactive sputtering deposition for aluminum nitride was developed at RIT by a fractional factorial experiment with the factors being RF power, nitrogen to argon flow rate ratios, changing the distance of the wafer to the platen from 5 to 4 cm, use of a aluminum, molybdenum or virgin silicon seed layer and chamber pressure. In nearly all cases it was found that an RF power of 1000W is the most important factor contributing to the〈002〉orientation. The decreasing of the target distance may inhibit a reaction mechanisms in the plasma resulting in a more amorphous deposition. It may be due to the increase in temperature resulting from the higher RF power that promotes the growth of〈002〉oriented aluminum nitride. A molybdenum seed layer tends to have a stronger〈002〉peak relative to aluminum and a chamber pressure of 3mT was found to exhibit a deposition that most favors the〈002〉oriented aluminum nitride. It was found that molybdenum is not consumed in a wet etch of KOH. Molybdenum is oxidized during photo resist ashing. The Contact Vias were necessarily over retched in order to ensure complete removal of Al-N over the Bottom Electrode. C-V measurements were done on the aluminum nitride to determine its quality, the measured extensional piezoelectric coefficient d33 is -0.000108716nm/V, which is -0.108716pm/V lower than 8pm/V typically reported. The lower piezo electric coefficient measured as compared with typical values, may be due to low film density a result of the high power used in the RF reactive sputtering that was used to heat the platen to a high enough temperature to promote the〈002〉oriented growth of AlN. A series of iterations were designed and S11 frequency response measured. The electrode overlap from 25 to 50 to 75μm, it does not appear to have an effect on the resonant frequency, but does increase the amplitude of the response at that die\u27s given frequency. Increasing the anchor width from 5μm to 10μm to 20μm lowers the relative amplitude of the response therefore lowering the Q of the resonator. It may be that the increasingly wide anchor, increases the mechanical resistances within the device and thereby lowers the Q factor of the resonator. Increasing the number of electrodes increases the relative amplitude of the response. Increasing pitch from 5μm to 6μm seems to have a small effect on the resonant frequency of the devices, shifting them from 4.57 to 4.59 GHz. A quality factor was measured, with an anchor width of 5μm, pitch of 5μm, 24 electrodes and an electrode overlap of 75μm had a measured Q value of 98.8

Quality of Neonatal Health Care: Learning From Health Workers’ Experiences in Critical Care in Kilimanjaro Region, Northeast Tanzania

Neonatal deaths are generally attributed to suboptimal standards of health care. Health care worker motivation and adherence to existing guidelines are rarely studied. To assess the performance of health workers for neonatal health care in the hospitals of Kilimanjaro region. A descriptive study using a semi-structured interview for health care workers at a tertiary referral hospital and peripheral health facilities (regional referral, district hospitals and health centres).was used. Health Care Workers (HCW) were asked to recall a scenario of a critically ill neonate admitted in the wards and the treatment that was provided. The WHO Emergency Triage Assessment and Treatment (ETAT) guidelines were used as a standard reference for knowledge of critical care. Birth asphyxia was the most recalled health problem requiring critical care, reported by 27.5% of 120 HCW at both peripheral hospitals and by 46.4% of 28 health workers in tertiary referral centres. Half of the HCW commented on their own performance (47.5%, n=140). HCW presented with low to moderate levels of knowledge for critical care were at 92%. Supplementary training was associated with a higher levels of knowledge of neonatal critical care (p value = 0.05). HCW in peripheral hospital had lower levels of knowledge (only 44.7% at peripheral hospitals had sufficient ratings compared to 82.1% at the referral centre). [Pearson χ2 (2) = 12.10, p value = 0.002]. Guided Practical-Competence Diagnostic Specific neonatal health care training is highly needed in the peripheral facilities of rural Kilimanjaro region

Worlds Beyond: A Strategy for the Detection and Characterization of Exoplanets Executive Summary of a Report of the ExoPlanet Task Force Astronomy and Astrophysics Advisory Committee Washington, DC June 23, 2008

[No abstract

International evaluation of an AI system for breast cancer screening.

Screening mammography aims to identify breast cancer at earlier stages of the disease, when treatment can be more successful1. Despite the existence of screening programmes worldwide, the interpretation of mammograms is affected by high rates of false positives and false negatives2. Here we present an artificial intelligence (AI) system that is capable of surpassing human experts in breast cancer prediction. To assess its performance in the clinical setting, we curated a large representative dataset from the UK and a large enriched dataset from the USA. We show an absolute reduction of 5.7% and 1.2% (USA and UK) in false positives and 9.4% and 2.7% in false negatives. We provide evidence of the ability of the system to generalize from the UK to the USA. In an independent study of six radiologists, the AI system outperformed all of the human readers: the area under the receiver operating characteristic curve (AUC-ROC) for the AI system was greater than the AUC-ROC for the average radiologist by an absolute margin of 11.5%. We ran a simulation in which the AI system participated in the double-reading process that is used in the UK, and found that the AI system maintained non-inferior performance and reduced the workload of the second reader by 88%. This robust assessment of the AI system paves the way for clinical trials to improve the accuracy and efficiency of breast cancer screening.Professor Fiona Gilbert receives funding from the National Institute for Health Research (Senior Investigator award)

Quality of Neonatal Healthcare in Kilimanjaro Region, Northeast Tanzania: Learning from Mothers' Experiences.

With a decline of infant mortality rates, neonatal mortality rates are striking high in development countries particularly sub Saharan Africa. The toolkit for high quality neonatal services describes the principle of patient satisfaction, which we translate as mother's involvement in neonatal care and so better outcomes. The aim of the study was to assess mothers' experiences, perception and satisfaction of neonatal care in the hospitals of Kilimanjaro region of Tanzania. A cross sectional study using qualitative and quantitative approaches in 112 semi structured interviews from 14 health facilities. Open ended questions for detection of illness, care given to the baby and time spent by the health worker for care and treatment were studied. Probing of the responses was used to extract and describe findings by a mix of in-depth interview skills. Closed ended questions for the quantitative variables were used to quantify findings for statistical use. Narratives from open ended questions were coded by colours in excel sheet and themes were manually counted. 80 mothers were interviewed from 13 peripheral facilities and 32 mothers were interviewed at a zonal referral hospital of Kilimanjaro region. 59 mothers (73.8%) in the peripheral hospitals of the region noted neonatal problems and they assisted for attaining diagnosis after a showing a concern for a request for further investigations. 11 mothers (13.8%) were able to identify the baby's diagnosis directly without any assistance, followed by 7 mothers (8.7%) who were told by a relative, and 3 mothers (3.7%) who were told of the problem by the doctor that their babies needed medical attention. 24 times mothers in the peripheral hospitals reported bad language like "I don't have time to listen to you every day and every time." 77 mothers in the periphery (90.6%) were not satisfied with the amount of time spent by the doctors in seeing their babies. Mothers of the neonates play great roles in identifying the illness of the newborn. Mother's awareness of what might be needed during neonatal support strategies to improve neonatal care in both health facilities and the communities

Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie

Aluminum Nitride Countour Mode Resonators

Resonators are a major component in RF electronic products. They are used in a host of ways to filter radio signals. Modern and Future RF communications have placed high demands on the industry; requiring low power usage, wide array of applications and resistance to noise. In this thesis, a discussion of the motivation for RF MEMS filters and basic theory is given with an explanation of the concepts of Q factor, piezoelectricity, acoustics theory, the major types of resonators (SAW, BAW, CMR or LAMB), apodization theory and techniques as well as design, simulation of CMR and BAW devices, testing and process development of aluminum nitride by RF reactive sputtering at RIT. Finite element analysis was performed on a number of factors of aluminum nitride contour mode resonators (CMR) from piezoelectric film thickness, to electrode pitch, electrode thickness and electrode configuration; to understand the effects. First order and second order vibration modes were seen including symmetric S0, S1 and antisymmetric A0, A1 resonant modes in the pizeoacoustic devices and higher. A series of time dependent video simulations of SAW, BAW and LAMB wave resonators were also performed, perhaps the first of their kind. The RF reactive sputtering deposition for aluminum nitride was developed at RIT by a fractional factorial experiment with the factors being RF power, nitrogen to argon flow rate ratios, changing the distance of the wafer to the platen from 5 to 4 cm, use of a aluminum, molybdenum or virgin silicon seed layer and chamber pressure. In nearly all cases it was found that an RF power of 1000W is the most important factor contributing to the ⟨002⟩ orientation. The decreasing of the target distance may inhibit a reaction mechanisms in the plasma resulting in a more amorphous deposition. It may be due to the increase in temperature resulting from the higher RF power that promotes the growth of ⟨002⟩ oriented aluminum nitride. A molybdenum seed layer tends to have a stronger ⟨002⟩ peak relative to aluminum and a chamber pressure of 3mT was found to exhibit a deposition that most favors the ⟨002⟩ oriented aluminum nitride. It was found that molybdenum is not consumed in a wet etch of KOH. Molybdenum is oxidized during photo resist ashing. The Contact Vias were necessarily over retched in order to ensure complete removal of Al-N over the Bottom Electrode. C-V measurements were done on the aluminum nitride to determine its quality, the measured extensional piezoelectric coefficient d 33 is -0.000108716 nm/V, which is -0.108716 pm/V lower than 8pm/V typically reported. The lower piezo electric coefficient measured as compared with typical values, may be due to low film density a result of the high power used in the RF reactive sputtering that was used to heat the platen to a high enough temperature to promote the?002?oriented growth of AlN. A series of iterations were designed and S11 frequency response measured. The electrode overlap from 25 to 50 to 75μm, it does not appear to have an effect on the resonant frequency, but does increase the amplitude of the response at that die's given frequency. Increasing the anchor width from 5μm to 10μm to 20μm lowers the relative amplitude of the response therefore lowering the Q of the resonator. It may be that the increasingly wide anchor, increases the mechanical resistances within the device and thereby lowers the Q factor of the resonator. Increasing the number of electrodes increases the relative amplitude of the response. Increasing pitch from 5μm to 6μm seems to have a small effect on the resonant frequency of the devices, shifting them from 4.57 to 4.59 GHz. A quality factor was measured, with an anchor width of 5μm, pitch of 5μm, 24 electrodes and an electrode overlap of 75μm had a measured Q value of 98.8