Advanced Soft Defect Screen Methodology for Nano-Scale SRAM Yield Improvement

As technology scales down, the density of Static Random Access Memory (SRAM) devices increases drastically, and their storage capacity grows at the same time. Moreover, SRAMs become more prone to physical defects in each technology node. In addition, resistive defects and parametric defects are increasing which are hard to detect by the conventional test. Thus, the need of effective tests with high fault coverage and low cost increases. In this work, we study the reuse of assist technique (read and write assist) and timing margin control technique, commonly applied to improve the functional margins of SRAM core-cells, to improve the coverage of hard-to-detect marginal defects. This analysis is based on extensive injection of resistive bridging defects in core-cells of a commercial low-power SRAM. We show that assist circuits and timing control circuits can be leveraged to increase the defect coverage can be increases up to 28% at nominal operation voltage by simulation. Some successful case studies are also discussed to demonstrate the efficiency of the proposed electrical stress test methodology.

Muffin Technique Micrographic Surgery for Non-melanoma Skin Cancer

Background: Mohs micrographic surgery (MMS) is the gold standard treatment for high-risk facial non-melanoma skin cancer. However, patients' access to MMS is limited by cost. The muffin technique micrographic surgery (MTMS) is an alternative micrographic technique wherein the entire excised margin is evaluated post-operatively by a pathologist using paraffin-embedded material. Herein, we describe the implementation and the preliminary results of MTMS in an academic dermatology center.Objective: To describe the MTMS and outline its efficacy and safety in a real-world clinical academic setting.Methods: A retrospective chart review was conducted of all patients with basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) who underwent MTMS at the University of Alberta Dermatology Center from June 2016 until July 2019.Results: A total of 69 patients were included (64 BCCs and 5 SCCs). 68.1% of surgeries had clear margins following the first incision, 100% after second round re-excisions. There were no observed cases of tumor recurrence after a median 40 months of follow-up. There were no major adverse events or complications.Conclusions: MTMS is a superior alternative to simple excision of skin cancer by providing full margin control and residual tumor mapping.

Outcomes of Staged Excision With Circumferential en Face Margin Control for Lentigo Maligna of the Head and Neck

Background Treatment practices vary for lentigo maligna (LM). Staged excision with circumferential margin control (SECMC) has the potential to achieve low recurrence rates. Objectives To evaluate the clinical outcomes of SECMC using permanent, paraffin-embedded sections and delayed reconstruction. Methods We conducted a retrospective, uncontrolled, observational cohort study involving patients who underwent staged excision for LM of the head and neck at Women’s College Hospital in Toronto, Canada, from September 2010 to March 2013. Recurrence and infection rates were ascertained from patient charts and postal surveys. Results One hundred and two patients (45 female, 57 male) were included with a median follow-up time of 1410.5 (IQR 260-1756) days. The median age was 69 (IQR 61-79) years. Approximately one-fifth (21%, 21/102) of patients required greater than 0.5 cm margins to achieve histological clearance. One patient (1/102) upstaged to invasive melanoma based on the initial stage of excision. The infection rate was 6% (6/102) and the 5-year cumulative recurrence rate was 1.4% (95% CI 0.2-9.6%). Conclusion SECMC using permanent sections and delayed reconstruction appears to be a safe and effective treatment method for LM on the head and neck. Randomized trials are needed to help define the optimal treatment.

The Influence of VSC–HVDC Reactive Power Control Mode on AC Power System Stability

Voltage source converter-based high-voltage direct current (VSC-HVDC) has the advantage of fast and independent controllability on active and reactive power. This paper focuses on effects of commonly proposed reactive power control modes, constant reactive power control and AC voltage margin control. Based on the mathematical model of single machine infinity equivalent system with embedded VSC-HVDC, the influence of VSC-HVDC with different reactive power control strategies on transient stability and dynamic stability of the AC system is studied. Then case studies were conducted with a realistic model of grid. The dynamic responses of AC/DC systems for different VSC-HVDC reactive power control modes were compared in detail. It is shown that compared to constant reactive power control, AC voltage margin control can provide voltage support to enhance the transient angle stability of an AC system. However, the fluctuant reactive power injected into a weak AC system may adversely affect power system oscillation damping for VSC-HVDC with AC voltage margin control, if the parameters of the controller have not been optimized to suppress the low-frequency oscillation. The results of this paper can provide certain reference for the decision of an appropriate VSC-HVDC reactive power control mode in practice.