Low-temperature thin film encapsulation for MEMS with silicon nitride/chromium cap

In this work, a low-temperature fabrication process of thin film encapsulation (TFE) with silicon nitride/chromium cap is proposed for large-size (750 μm x 300 μm) packaging of microelectromechanical systems (MEMS). A FEM model was developed to evaluate the shape of TFE as a function of the residual stress and the thickness of the sealing layer, providing useful guidelines for the fabrication process. The low temperature of 200 °C, which was used in the plasma-enhanced chemical vapor deposition of the silicon nitride capping layer, allowed an organic sacrificial material to be employed for the definition of the encapsulation area. Silicon nitride/chromium (1 μm/20 nm) bilayer was demonstrated to be successful to overcome the technological limitations that affect the creation of cap holes with size of ~2 μm on high topography substrates, as in the case of MEMS. Plasma focused ion beam (PFIB) and scanning electron microscopy (SEM) techniques were used in combination to gain deeper insight into the sealing process of cap holes. Specifically, a PFIB-SEM serial section procedure was developed, resulting to be a powerful tool to directly observe the sealing profile above cap holes. Hence, the presented results greatly contribute to overcome the main technological/reliability issues of TFE, paving the way for the widespread application of the proposed encapsulation methodology to the most used MEMS devices, as radio-frequency (RF) switches, transducers, actuators, sensors and resonators

Right hemicolectomy with complete mesocolic excision is safe, leads to an increased lymph node yield and to increased survival: results of a systematic review and meta-analysis.

Funder: Università degli Studi di PerugiaBACKGROUND: The introduction of complete mesocolic excision (CME) for right colon cancer has raised an important discussion in relation to the extent of colic and mesenteric resection, and the impact this may have on lymph node yield. As uncertainty remains regarding the usefulness of and indications for right hemicolectomy with CME and the benefits of CME compared with a traditional approach, the purpose of this meta-analysis is to compare the two procedures in terms of safety, lymph node yield and oncological outcome. METHODS: We performed a systematic review of the literature from 2009 up to March 15th, 2020 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Two hundred eighty-one publications were evaluated, and 17 met the inclusion criteria and were included. Primary endpoints analysed were anastomotic leak rate, blood loss, number of harvested lymph nodes, 3- and 5-year oncologic outcomes. Secondary outcomes were operating time, conversion, intraoperative complications, reoperation rate, overall and Clavien-Dindo grade 3-4 postoperative complications. RESULTS: In terms of safety, right hemicolectomy with CME is not inferior to the standard procedure when comparing rates of anastomotic leak (RR 0.82, 95% CI 0.38-1.79), blood loss (MD -32.48, 95% CI -98.54 to -33.58), overall postoperative complications (RR 0.82, 95% CI 0.67-1.00), Clavien-Dindo grade III-IV postoperative complications (RR 1.36, 95% CI 0.82-2.28) and reoperation rate (RR 0.65, 95% CI 0.26-1.75). Traditional surgery is associated with a shorter operating time (MD 16.43, 95% CI 4.27-28.60) and lower conversion from laparoscopic to open approach (RR 1.72, 95% CI 1.00-2.96). In terms of oncologic outcomes, right hemicolectomy with CME leads to a higher lymph node yield than traditional surgery (MD 7.05, 95% CI 4.06-10.04). Results of statistical analysis comparing 3-year overall survival and 5-year disease-free survival were better in the CME group, RR 0.42, 95% CI 0.27-0.66 and RR 0.36, 95% CI 0.17-0.56, respectively. CONCLUSIONS: Right hemicolectomy with CME is not inferior to traditional surgery in terms of safety and has a greater lymph node yield when compared with traditional surgery. Moreover, right-sided CME is associated with better overall and disease-free survival

Prototype ATLAS IBL Modules using the FE-I4A Front-End Readout Chip

The ATLAS Collaboration will upgrade its semiconductor pixel tracking detector with a new Insertable B-layer (IBL) between the existing pixel detector and the vacuum pipe of the Large Hadron Collider. The extreme operating conditions at this location have necessitated the development of new radiation hard pixel sensor technologies and a new front-end readout chip, called the FE-I4. Planar pixel sensors and 3D pixel sensors have been investigated to equip this new pixel layer, and prototype modules using the FE-I4A have been fabricated and characterized using 120 GeV pions at the CERN SPS and 4 GeV positrons at DESY, before and after module irradiation. Beam test results are presented, including charge collection efficiency, tracking efficiency and charge sharing.Comment: 45 pages, 30 figures, submitted to JINS

Laparoscopic right hemicolectomy: a SICE (Società Italiana di Chirurgia Endoscopica e Nuove tecnologie) network prospective study on the approach to right colon lymphadenectomy in Italy: is there a standard?—CoDIG 2 (ColonDx Italian Group)

Background: Colon cancer is a disease with a worldwide spread. Surgery is the best option for the treatment of advanced colon cancer, but some aspects are still debated, such as the extent of lymphadenectomy. In Japanese guidelines, the gold standard was D3 dissection to remove the central lymph nodes (203, 213, and 223), but in 2009, Hoenberger et al. introduced the concept of complete mesocolic excision, in which surgical dissection follows the embryological planes to remove the mesentery entirely to prevent leakage of cancer cells and collect more lymph nodes. Our study describes how lymphadenectomy is currently performed in major Italian centers with an unclear indication on the type of lymphadenectomy that should be performed during right hemicolectomy (RH). Methods: CoDIG 2 is an observational multicenter national study that involves 76 Italian general surgery wards highly specialized in colorectal surgery. Each center was asked not to modify their usual surgical and clinical practices. The aim of the study was to assess the preference of Italian surgeons on the type of lymphadenectomy to perform during RH and the rise of any new trends or modifications in habits compared to the findings of the CoDIG 1 study conducted 4 years ago. Results: A total of 788 patients were enrolled. The most commonly used surgical technique was laparoscopic (82.1%) with intracorporeal (73.4%), side-to-side (98.7%), or isoperistaltic (96.0%) anastomosis. The lymph nodes at the origin of the vessels were harvested in an inferior number of cases (203, 213, and 223: 42.4%, 31.1%, and 20.3%, respectively). A comparison between CoDIG 1 and CoDIG 2 showed a stable trend in surgical techniques and complications, with an increase in the robotic approach (7.7% vs. 12.3%). Conclusions: This analysis shows how lymphadenectomy is performed in Italy to achieve oncological outcomes in RH, although the technique to achieve a higher lymph node count has not yet been standardized. Trial registration (ClinicalTrials.gov) ID: NCT05943951

Holocene demographic fluctuations, climate and erosion in the Mediterranean: A meta data-analysis

As part of the Changing the Face of the Mediterranean Project, we consider how human pressure and concomitant erosion has affected a range of Mediterranean landscapes between the Neolithic and, in some cases, the post-medieval period. Part of this assessment comprises an investigation of relationships among palaeodemographic data, evidence for vegetation change and some consideration of rapid climate change events. The erosion data include recent or hitherto unpublished work from the authors. Where possible, we consider summed probabilities of 14C dates as well as the first published synthesis of all known optically stimulated luminescence dated sequences. The results suggest that while there were some periods when erosion took place contemporaneously across a number of regions, possibly induced by climate changes, more often than not, we see a complex and heterogeneous interplay of demographic and environmental changes that result in a mixed pattern of erosional activity across the Mediterranean

STRESS-STRAIN BEHAVIOUR OF ELECTROPLATED GOLD THIN FILMS

This work presents the characterization of the stress-strain behavior of an electroplated gold layer deposited on thin chromium layer (thickness: 1500nm, 10nm respectively). The stress of the composite layer is measured by wafer curvature. The strain is applied through a series of thermal cycles at temperatures ranging from 50 to 240°C. The sample stays at high temperature for a long time (18h) to let its structure plastically flow and release all extrinsic stress. After this, the ramp down step induces a known strain due to the mismatch between film’s and substrate’s TCE. From studies on gold [1] it is documented that crystal grain growth activates at temperatures of about 300°C: this leads to the assumption that grain growth is not relevant in the examined temperature range and therefore the intrinsic stress at curing temperature has to be constant. By consequent correction of the calculated thermal stress we obtain a stress-strain curve for our material, which is consistent with literature [4]. A Young’s modulus of about 108 GPa, yield strength of 160 MPa and tensile strength of 190 MPa are calculated. The obtained stress-strain behavior is employed in the modeling of diagnostic test structures, leading to consistent results

A single metal layer MEMS self-assembling coplanar structure

Self-assembling perforated microplates modeled and fabricated on silicon wafers by means of surface micromachining are presented. The structures consist of a single Cr/Au metal layer and are set into position by the residual tensile in-plane stress of the material; the geometry is designed to obtain a lifted microplate coplanar to the surface of the wafer. The structures are modeled both analytically and by finite element simulation to correlate the displacement with the strain of the structural material. Samples are fabricated using IC technology on standard 4-inch silicon wafers by surface micromachining; a photoresist is used as a sacrificial layer and electroplated gold is used as a structural layer on a chromium-gold PVD seedlayer. The fabricated structures exhibit a vertical displacement of 38 μm. The resulting estimated strain is 0.001 66, which corresponds to a tensile stress of 173 MPa and is consistent with thermal residual strain

Design and simulation of a MEMS device to investigate the strain engineering properties of 2D nanomaterials

This paper presents the design and simulation of a novel MEMS device enabling the investigation of the strain engineering properties of 2D materials, like graphene. The novel MEMS device consists of a double set of opposed v-shaped thermal actuators, each provided with heat sink beams, and capacitive readout in order to electrically measure the displacement applied to the nanomaterial sample. The device was designed by means of both analytical modelling and finite element based multiphysics simulations. A displacement capacitive sensor was developed to measure the specimen deformation with high accuracy. The calculated sensitivity is 5.2 fF/nm, and the total stiffness of the device is 40253.6 N/m. The device structure was designed with a compact footprint in order to be compatible with other physical characterization instruments, such as electronic microscopy chambers

Novel Test structures for stress diagnosis in micromechanics

A novel set of microstructures for on-wafer stress measurement is prensented, based on a lancet principle, with dedicated design for the amnplification of the dimensinal variations indced by the internal stress of the structural material. A tilted arm geometry was adopted in order to maximize the strain induced movement, keeping the design relatively simple and robust and the lancet ont he wafer plane. A set of simulations, as well as an analytical examination of the structure was performed to establish the optimal geometry: different tilt angles were simulated in a range between -200 and 200 MPa internal stress. Test structures were then realized by means of surface micromachining, adopting photoresist as sacrifical layer and electroplated gold as structural layer: the novel gemetry was sided by traditional rotating structures [Sens. Actuators A 37/38 (1993) 256] and wafer curvature measurements to confirm the readout. Plastic regime simulations were adopted to analyze the behavior of the gold structures, based on a stress-strain curve obtained experimentall