In this study we have investigated the reactive ion etching of 60 μm diam, 200 μm deep holes in 3 in. diam semi-insulating GaAs wafer using a combination of CCl2F2 and CCl4 gases for fabrication of through substrate via holes for grounding in monolithic microwave integrated circuits (MMICs). The effect of process parameters viz. pressure, CCl4/CCl2F2 ratio, and power on GaAs etch rate and resultant etch profile was investigated. Two kind of masks, photoresist and Ni, were used to etch GaAs and their performance was compared by investigating effect on etch rate, etch depth, etch profile, and surface morphology. The etch profile, etch depth, and surface morphology of as-etched samples were characterized by scanning electron microscopy. The desired 200 μm deep strawberry profile, with a top normaldiam=60±10 μm and bottom normaldiam=180±10 μm, was obtained at 40 mTorr process pressure with an average etch rate ∼1.3 μm/min using Ni mask. The vias were then metallized by depositing a thin seed layer of Ti/Au (1000 Å) using radio frequency sputtering and Au (5 μm) electroplated to connect the front side pad and back side ground plane. The parasitic inductance offered by these vias was ∼76 pH. The developed process was then integrated into the MMIC process line and a 16-18 GHz amplifier was fabricated using grounding vias with yield >90%. © 2003 The Electrochemical Society. All rights reserved.

No abstract

A Gunn diode is a simple two terminal source of low-noise, high frequency microwave power. It is most commonly used as local oscillator in critical microwave and mm-wave systems. The system requirement of frequency agility and temperature stability impose stringent demands on the device performance and hence on its material and fabrication technology. The present paper discusses some of the technological innovations attempted in this direction along with results obtained. Some of the issues addressed are carrier concentration ramping to check velocity degradation in the active layer, power optimisation by in-situ etching, minimisation of dead zone and thermal management. Physics, design and fabrication technology and testing of Gunn diodes is also briefly described in this article.

Introduction Amyloidosis is brought about by intracellular and/or extracellular accumulation of insoluble abnormal amyloid fibrils that alters the normal function of the tissues. Localized laryngeal amyloidosis is a rare disease which lacks long-term follow-up studies. It is prone to recurrence; hence meticulous excision is required. We are doing this study to analyse clinical features of primary laryngeal amyloidosis, the subsites commonly found in, and the effectiveness of CO2 laser as treatment modality. Materials and Methods It is a retrospective study of 13 patients diagnosed as Primary Laryngeal Amyloidosis in between 2005 to 2018, where clinical features, histologic and immuno-histochemical patterns of the patients were evaluated. Systemic amyloidosis was ruled out by the non-appearance of Bence-Jones proteins in urine and serum electrophoresis examination. Systemic workups were pursued during the follow-up. The patients were followed up 3 monthly for the first year, then 6 monthly after that, for 3 years. The last patient who underwent the surgery was in the 2018 and had just finished his 2nd follow up, while the rest have been followed up for 3 years. Results Hoarseness was the most common complaint in all the patients. The subsites most common for amyloid deposition were seen in the true vocal cords followed by supraglottis, anterior commissure, ventricle and the subglottis. Microscopically, the amyloid was deposited within the submucosa surrounded by lymphoplamocytic infiltration. All cases were treated with microlaryngoscopic CO2 Laser excision. With the exception of one patient, the rest had no recurrence. Conclusion Primary Laryngeal Amyloidosis is an uncommon benign disease that has a predisposition for recurrence. With use of CO2 laser as the primary treatment modality, the percentage of recurrence has drastically reduced. Systemic involvement should be ruled out. A frequent follow-up of the patients is desirable for early detection of recurrences. Laser is a novel treatment of laryngeal amyloidosis.

No abstract