Low-Leakage ESD Power Supply Clamps in General Purpose 65 nm CMOS Technology

Electrostatic discharge (ESD) is a well-known contributor that reduces the reliability and yield of the integrated circuits (ICs). As ICs become more complex, they are increasingly susceptible to such failures due to the scaling of physical dimensions of devices and interconnect on a chip [1]. These failures are caused by excessive electric field and/or excessive current densities and result in the dielectric breakdown, electromigration of metal lines and contacts. ESD can affect the IC in its different life stages, from wafer fabrication process to failure in the field. Furthermore, ESD events can damage the integrated circuit permanently (hard failure), or cause a latent damage (soft failure) [2]. ESD protection circuits consisting of I/O protection and ESD power supply clamps are routinely used in ICs to protect them against ESD damage. The main objective of the ESD protection circuit is to provide a low-resistive discharge path between any two pins of the chip to harmlessly discharge ESD energy without damaging the sensitive circuits. The main target of this thesis is to design ESD power supply clamps that have the lowest possible leakage current without degrading the ESD protection ability in general purpose TSMC 65 nm CMOS technology. ESD clamps should have a very low-leakage current and should be stable and immune to the power supply noise under the normal operating conditions of the circuit core. Also, the ESD clamps must be able to handle high currents under an ESD event. All designs published in the general purpose 65 nm CMOS technology have used the SCR as the clamping element since the SCR has a higher current carrying capability compared to an MOS transistor of the same area [3]. The ESD power supply clamp should provide a low-resistive path in both directions to be able to deal with both PSD and NDS zapping modes. The SCR based design does not provide the best ESD protection for the NDS zapping mode (positive ESD stress at VSS with grounded VDD node) since it has two parasitic resistances (RNwell and RPsub) and one parasitic diode (the collector to base junction diode of the PNP transistor) in the path from the VSS to VDD. Furthermore, SCR-based designs are not suitable for application that exposed to hot switching or ionizing radiation [2]. In GP process, the gate oxide thickness of core transistors is reduced compared with LP process counterpart to achieve higher performance designs for high-frequency applications using 1 V core transistors and 2.5 V I/O option. The thinner gate oxide layer results in higher leakage current due to gate tunneling [4]. Therefore, using large thin oxide MOS transistors as clamping elements will result in a huge leakage. In this thesis, four power supply ESD clamps are proposed in which thick oxide MOS transistors are used as the main clamping element. Therefore, the low-leakage current feature is achieved without significantly degrading the ESD performance. In addition, the parasitic diode of the MOS transistors provides the protection against NSD-mode. In this thesis, two different ESD power supply clamp architectures are proposed: standalone ESD power supply clamps and hybrid ESD power supply clamps. Two standalone clamps are proposed: a transient PMOS based ESD clamp with thyristor delay element (PTC), and a static diode triggered power supply (DTC). The standalone clamps were designed to protect the circuit core against ±125 V CDM stress by limiting the voltage between the two power rails to less than the oxide breakdown voltage of the core transistors, BVOXESD = 5 V. The large area of this architecture was the price for maintaining the low-leakage current and an adequate ESD protection. The hybrid clamp architecture was proposed to provide a higher ESD protection, against ±300 V CDM stress, while reducing the layout area and maintaining the low-leakage feature. In the hybrid clamp structure, two clamps are connected in parallel between the two power supply rails, a static clamp, and a transient clamp. The static clamp triggers first and starts to sink the ESD energy and then an RC network triggers the primary transient clamp to sink most of the ESD stress. Two hybrid designs were proposed: PMOS ESD power supply clamp with thyristor delay element and diodes (PTDC), and NMOS ESD power supply clamp with level shifter delay element and diode (NLDC). Simulation results show that the proposed clamps are capable of protecting the circuit core against ±1.5 kV HBM and at least against ±125 V CDM stresses. The measurement results show that all of the proposed clamps are immune against false triggering, and transient induced latch-up. Furthermore, all four designs have responded favorably to the 4 V ESD-like pulse voltage under both chip powered and not powered conditions and after the stress ends the designs turned off. Finally, TLP measurement results show that all four proposed designs meet the minimum design requirement of the ESD protection circuit in the 65 nm CMOS technology (i.e. HBM protection level of ±1.5 kV )

NASA Tech Briefs, November 2000

Topics covered include: Computer-Aided Design and Engineering; Electronic Components and Circuits; Electronic Systems; Test and Measurement; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Data Acquisition

Topical Workshop on Electronics for Particle Physics

The purpose of the workshop was to present results and original concepts for electronics research and development relevant to particle physics experiments as well as accelerator and beam instrumentation at future facilities; to review the status of electronics for the LHC experiments; to identify and encourage common efforts for the development of electronics; and to promote information exchange and collaboration in the relevant engineering and physics communities

NASA Tech Briefs, December 1989

Topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, and Life Sciences

NASA Tech Briefs, October 1990

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical' Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Development of in vitro and in vivo models to underpin advances in human radiotherapy

Radiotherapy (RT) is commonly used for the local control of many cancer types. Unfortunately, not all patients will achieve a therapeutic benefit, and some will develop loco-regional recurrences and/or metastatic disease. The hypoxic nature of the tumour microenvironment and the development of radioresistant cancer cells can contribute to these treatment failures. Understanding the mechanisms involved in acquired radioresistance and the development of techniques to identify and target hypoxic tumour areas has the potential to improve RT response rates. The first aim of this project was to investigate the development of acquired radioresistance and identify radiation-induced secreted biomarkers which could be used as indicators of a radiation response or radiosensitivity. Human radioresistant (RR) breast cancer cell lines were developed from parental MCF-7, ZR-751 and MDA-MB-231 cells. Parental and RR cells underwent genotypic, phenotypic and functional characterisation. RR cells exhibited enhanced migration and invasion, with evidence of epithelial-to-mesenchymal transition. MCF-7 RR and ZR-751 RR cell lines exhibited significant phenotypic changes, including loss of ERα and PgR expression and increased EGFR expression, which were associated with the down-regulation of ER signalling genes and up-regulation of genes associated with PI3K, MAPK and WNT pathway activation. A change in subtype classification from luminal A to HER2-overexpressing (MCF-7 RR) and normal-like (ZR-751 RR) subtypes was also observed, consistent with radiation and endocrine therapy resistance and a more aggressive phenotype. To identify biomarkers secreted in response to radiation, human and canine breast and ovine lung cancer cell lines were radiated. Secretome samples were analysed by liquid chromatography-mass spectrometry. Using results from the MCF- 7 cell line, 33 radiation-induced secreted biomarkers were identified which had higher (up to 12-fold) secretion levels compared to untreated controls. Based on secretion profiles and functional analysis 9 candidate biomarkers were selected (YBX3, TK1, SEC24C, EIF3G, EIF4EBP2, NAP1L4, VPS29, GNPNAT1 and DKK1) of which the first 4 underwent in-lab validation. To identify biomarkers related to radiosensitivity transcriptomic analysis identified higher expression of genes encoding 7 of the candidate biomarkers in the MCF-7 cell line compared to its radioresistant derivative. WB analysis identified increased levels of the 4 biomarkers in the conditioned media of parental cells 24 h post-radiation which was not seen in the RR cell lines. These biomarkers, which had differential gene expression and secretion profiles between parental and RR cell lines, may be useful for both predicting and monitoring a tumour’s response to RT. A further aim was to investigate the biocompatibility and functionality of an implantable electrochemical sensor, developed within the Engineering and Physical Sciences Research Council funded IMPACT project. This sensor was designed to measure tissue O2 tension (ptO2) within a tumour, enabling the identification and monitoring of radioresistant hypoxic tumour areas. This study developed a novel in vivo tumour xenograft model to evaluate the potential of 6 materials (silicon dioxide, silicon nitride, Parylene-C, Nafion, biocompatible EPOTEK epoxy resin and platinum) used in the construction of the sensor, to trigger a foreign body response (FBR) when implanted into a solid tumour. Following implantation none of the materials affected tumour growth and all mice remained healthy. Immunohistochemistry performed on the tumour showed no significant changes in necrosis, hypoxic cell number, proliferation, apoptosis, immune cell infiltration or collagen deposition around the implant site. The absence of a FBR supports their use in the construction of implantable medical devices. In vivo validation of the O2 sensor to provide real-time measurements on intra-tumoural ptO2 was performed using a novel large animal ovine model. To achieve this aim, we developed a novel computed tomography (CT) guided transthoracic percutaneous implantation technique for the delivery of sensors into naturally occurring ovine pulmonary adenocarcinoma (OPA) tumours. This model successfully integrated techniques such as ultrasound, general anaesthesia, CT and surgery into the OPA model, all of which are techniques commonly used in the treatment of human lung cancer patients. This methodology resulted in the accurate implantation of sensors into OPA tumours with minimal complications and demonstrated the sensor’s ability to detect changes in intra-tumoural ptO2 following manipulation of the inspired fractional O2 concentration (FiO2). To investigate other possible clinical applications, sensors were validated for measuring intestinal ptO2 using a novel rat model. These experiments assessed the potential of the sensor to monitor intestinal perfusion following an intestinal resection and anastomosis. The sensor was placed onto the serosal surface of the small intestine of anaesthetised rats that were subsequently exposed to ischaemic, hypoxaemic and haemorrhagic insults. Decreases in intestinal ptO2 were observed following superior mesenteric artery occlusion and reductions in FiO2; these changes were reversible after reinstating blood flow or increasing FiO2. These results provided evidence that the sensors could detect changes in intestinal perfusion which could be utilised in a clinical setting to monitor peri-anastomotic intestinal ptO2. Overall this PhD project has conducted both in vitro and in vivo work aimed at the investigation of mechanisms of radioresistance, identifying secreted biomarkers of radiosensitivity and validating the ability of an implantable sensor to measure real-time intra-tumoural and visceral surface O2 tension. Identification of factors contributing to poor RT responses, such as radioresistance development and hypoxic tumour areas could provide a means by which RT could become personalised. Patients identified as having radioresistant tumours or those not responding to RT based on radiation-induced secreted biomarkers, could be given higher dose of radiation or radiosensitising agents to improve patient outcomes

Acoustic Waves

The concept of acoustic wave is a pervasive one, which emerges in any type of medium, from solids to plasmas, at length and time scales ranging from sub-micrometric layers in microdevices to seismic waves in the Sun's interior. This book presents several aspects of the active research ongoing in this field. Theoretical efforts are leading to a deeper understanding of phenomena, also in complicated environments like the solar surface boundary. Acoustic waves are a flexible probe to investigate the properties of very different systems, from thin inorganic layers to ripening cheese to biological systems. Acoustic waves are also a tool to manipulate matter, from the delicate evaporation of biomolecules to be analysed, to the phase transitions induced by intense shock waves. And a whole class of widespread microdevices, including filters and sensors, is based on the behaviour of acoustic waves propagating in thin layers. The search for better performances is driving to new materials for these devices, and to more refined tools for their analysis

NASA Tech Briefs, June 1991

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences