ON Semiconductor (Canada)

Bias Temperature Instability (BTI) measurements were performed on SiC n-channel DMOSFETs. The effects of the BTI stress on the electrical characteristics of the device were studied using slow and fast measurements. The slow Measurements show that the change in threshold voltage (Vth) can be attributed to charge carrier trapping/de-trapping at border traps, while interface trapped charge density is found to be unaffected. The fast measurements, however, shows significant Vth recovery taking place in-situ during measurement. Moreover, Vth shift is observed to decrease with increasing temperature for the same stress level suggesting that Vth recovery is temperature activated.

The Silicon Carbide power device industry continues to experience very robust increases and adoption in many long-term growth markets like renewables, cloud and electric vehicles. The continuous year over year increases in demand has led to widespread raw material shortages of substrates and epi wafers. This has resulted in incumbent manufacturers putting in more capacity and the emergence of many new SiC substrate manufacturers. With many supply sources, there is also a wide variety of quality in the material. In some of our previous works, we have looked at some of the issues arising from immature crystal quality. However, often overlooked as a source of defects and surface quality, is the damage left over from wafering, grinding and CMP. In this work, we observe the effects of sub-surface damage and how it affects epitaxial layer quality. We also look at ways to minimize this effect both at the CMP stage and at the epi growth stage. Defect metrology tools for Silicon Carbide wafers have seen great improvements in capability and throughput. As wafers are measured both pre-epi and post-epi, a wide category of defects are identified and classified. Full wafer scans for substrates yield several defect categories like micropipes, bumps/particles as well as shallow and deep scratches. Recent tools with photoluminescence (PL) are also able to detect crystal defects like grain boundaries and bar stacking faults among others. All of these defects have an effect on the epitaxial layers either nucleating or transforming into other defects. However, none of the detection methods are able to detect residual damage left over from the wafering/grind process. This damage can be present just below the surface even if the surface is extremely smooth and scratch free. We detect the presence of these damage layers after epitaxial growth. Depending on the amount of damage present a very high density of stacking faults and triangular defects (and partials) are seen in the epitaxial layers. To remove the damage layers, a higher amount of CMP removal was used. As the damaged layer is reduced, the nucleation of the stacking faults and triangular defects also reduce. In some wafers, we observe some residual damage layers present near the wafer edges and flats where the CMP process is not uniform. Moreover, even when the nucleation of the defects are suppressed, the resulting epi is much rougher than epi grown on a substrate without any sub-surface damage. Wafers that displayed sub-surface damage were re-polished back to the substrate using a known good process. These wafers did not show the nucleation of defects. The suppression of the nucleation of defects was also attempted by enhanced in-situ etching before epi growth. Though this resulted in suppression of nucleated defects, by removal of the damage layer, it also resulted in much rougher epitaxial layers. The characterization results and processes from these experiments will be presented. Additional methods to detect these damage layers will be discussed.

Artificial Intelligence (AI) has made many significant advances over recent years. Starting out as mainly university research endeavors, recent significant breakthroughs have pushed the practicality of AI to the forefront. It is making fast inroads to traditional industrial applications and it is clear that given sufficient computing resources, AI is applicable to almost anything.The breakthrough referenced is mostly the result of the diligent persistence of a number of AI researchers in combination with large increases in available computation power to reconsider much deeper neural networks than previously used which were consistently rejected because of their large complexity reasons. Deep Neural Nets have proven to be an adept framework and up to solving the difficult challenges proven previous machine learning approaches could not solve.Recently, driven by enhanced computational power and necessity, edge applications have arisen to the forefront. Generally, now that cloud computing is available, a choice may be made where to locate the recognition engine, local to the data source or on the cloud where considerable computing resources are available.Hearing aids, a product on the edge now connected via one or more wireless links and fully immersed in IoT are the subject and consideration of this paper. It is natural to consider whether, via these links, remote computation is possible and appropriate for hearing aid applications. Difficulties arise when remote computation is attempted simply because the local data to be inferenced must be transmitted. Summarizing, utilizing remote computing for local recognition creates, two immediate problems: 1) the transmission of possibly private data across an insecure channel, and 2) the channel may not exist in remote or adverse transmission environments. Two further difficulties emerge in an important subset of applications, including hearing aids and hearable products: 1) Delay from the transmission latency required to obtain Cloud computation – although fast and capable – once the information is obtained and 2) Transmission power.

The scanning of Silicon Carbide (SiC) epitaxy wafers for defects by ultraviolet (UV) laser or lamps is widely prevalent. In this work, we document the effects of UV light excitation on the SiC epitaxy material. An increase in background photoluminescence (PL) is observed after repeated scans. The effect of this increase on defect detection is shown. Optimal surface treatments to recover the material back to the original state are demonstrated. Further, some surface treatments are proposed which reduce the effect of the UV light excitation and prevent to a large extent the rise in background PL.

A tunable bandstop filter (BSF) with a wideband balun using integrated passive devices (IPDs) technology for multichip module is proposed. The compact tunable BSF uses barium strontium titanate (BST) varactors demonstrating a tuning range of 55% from 1.3 to 2.3 GHz with a 20-dB rejection level. The performance of the filter is optimized by applying asynchronous biases to the BST varactors, leading to bandwidth and rejection level improvement. High-power test results show that the filter exhibits a third-order input intercept point of more than 40 dBm. An IPD wideband balun (0.5–2.5 GHz with ±1 dB amplitude imbalance and 180° ± 20°) using a wideband phase inverter is also presented. The design considerations of the wideband phase inverter (1.5–8 GHz) are addressed in this paper. Design and measured results are also presented for a fixed IPD bandpass filter, and an IPD bandpass filter with a tunable transmission zero to demonstrate the reconfigurability in frequency agile applications.

Abstract This paper continues the work of reference [1], evaluating shear test results of Cu ball bonds over a variety of probe marks in two different pad aluminum (Al) thicknesses (0.8μm and 3μm). The presence of invasive probe marks on thick Al bond pads lowers certain shear force results.. Lower values of shear force imply reduced Cu bond reliability. Physical factors are investigated relating to poor intermetallic (IMC) formation in the Cu wirebond and bond shear force. Optical microscopic image analysis of Cu bonds, bond contact areas and Al “splash” are studied for correlation with the shear test results. Percent IMC coverage of bond contact areas decrease when invasive probe marks are present beneath the bond, which in turn may reduce the shear force. Probe mark features are studied to discover the characteristics of greatest influence on % IMC coverage and shear test values in each of the pad metal thicknesses.

This IEEE Signal Processing Magazine forum discusses the latest advances and challenges in ultra-low power (ULP) signal processing (SP). The forum members bring their expert insights to issues such as design requirements and future applications of ULP SP systems.

This study reports a number of experiments that were designed to characterize aluminum bond pad surfaces prior to electroless nickel immersion gold (ENIG). In the ENIG process, aluminum bond pads need special treatment to achieve successful nickel deposition and provide reliable interconnection of under bump metallurgy in advanced packaging. During this treatment process, the aluminum pad was cleaned, activated and then coated with a layer of zinc. Systematic study was carried out to determine the best parameters, through multiple and various exposure times of the zincation process and zincation solution concentration effect on the Ni/Au surface roughness and aluminum dissolution rate on the bond pad during multiple zincation process. The ball shear strength was evaluated between eutectic 37Pb/63Sn solder ball and under bump metallurgy (UBM) interfaces across multiple zincation process. Scanning Electron Microscope (SEM), Energy Dispersive X-Ray (EDX), Atomic Force Microscopy (AFM), Focused Ion Beam (FIB) and ball shear tester were used as analytical tools. The results suggest that the multiple zincation process consistently produces a smoother surface of ENIG UBM and consequently provides a better shear strength.

Abstract A 1.3‐GHz Sallen and Key filter, based on a voltage amplifier designed with an original topology, is presented. SiGe realization showed good agreement between simulation and measurement. In particular, the amplifier gain and the filter selectivity can be tuned and Q factors of up to 60 were measured. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 22–24, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11115