Micro-features of ambipolar snapback behaviour under high current injection to design capacitorless memory device

2021 ◽  
Vol 96 (12) ◽  
pp. 124069
Author(s):  
Pragati Singh ◽  
Rudra Sankar Dhar ◽  
Srimanta Baishya
Keyword(s):  
Flow Line ◽  
Memory Cell ◽  
Memory Device ◽  
Storage Capacitor ◽  
High Current ◽  
Current Crowding ◽  
Current Ramp ◽  
Operational Window ◽  
Micro Features ◽  
The Impact

Abstract This paper presents micro-features of capacitorless memory cells based on snapback phenomenon and modeling of space-charges. 2—Dimensional gate grounded NMOS structure is specified and its operational window of the memory cell is inspected using the Synopsys TCAD tool. This work examines snapback behaviour in one transistor DRAM memory cell in the absence of a storage capacitor under zero gate bias and applied ramp of high current at the drain terminal. Carrier electrostatics and memory cell mechanisms are also explored by adjusting the slope of the high current ramp. The process variation is examined for different parameters in the device. The current crowding phenomenon due to the injection of electrons and holes is investigated, giving rise to ambipolar behaviour. Due to the snapback, redistribution of electron and hole current is investigated. This work also evaluates the impact on electrostatic potential along channel and bulk under the snapback. It explains the dependency of snapback on potential build-up. Post-snapback electron current flipping presents the flow line near the gate region. The bipolar activity is manifested in surface and bulk regions to show its impact through analytics. The effect of gate biasing is also examined under the applied current ramp.

Carrier Profiling of the 10-nm-order Structure in a 3D Flash Memory Cell Using Scanning Nonlinear Dielectric Microscopy

2019 ◽  
Author(s):  
Jun Hirota ◽  
Ken Hoshino ◽  
Tsukasa Nakai ◽  
Kohei Yamasue ◽  
Yasuo Cho
Keyword(s):  
Spatial Resolution ◽  
Flash Memory ◽  
Analytical Techniques ◽  
Memory Cell ◽  
Memory Device ◽  
Floating Gate ◽  
Order Structure ◽  
Carrier Distribution ◽  
Nonlinear Dielectric ◽  
Flash Memory Cell

Abstract In this paper, the authors report their successful attempt to acquire the scanning nonlinear dielectric microscopy (SNDM) signals around the floating gate and channel structures of the 3D Flash memory device, utilizing the custom-built SNDM tool with a super-sharp diamond tip. The report includes details of the SNDM measurement and process involved in sample preparation. With the super-sharp diamond tips with radius of less than 5 nm to achieve the supreme spatial resolution, the authors successfully obtained the SNDM signals of floating gate in high contrast to the background in the selected areas. They deduced the minimum spatial resolution and seized a clear evidence that the diffusion length differences of the n-type impurity among the channels are less than 21 nm. Thus, they concluded that SNDM is one of the most powerful analytical techniques to evaluate the carrier distribution in the superfine three dimensionally structured memory devices.

scholarly journals Pre-Emphasis Pulse Design for Random-Access Memory

Electronics ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1454
Author(s):  
Yoshihiro Sugiura ◽  
Toru Tanzawa
Keyword(s):  
Time Constant ◽  
Random Access ◽  
Memory Cell ◽  
Random Access Memory ◽  
Memory Access ◽  
Access Time ◽  
Access Memory ◽  
Delay Times ◽  
Cell Current ◽  
The Impact

This paper describes how one can reduce the memory access time with pre-emphasis (PE) pulses even in non-volatile random-access memory. Optimum PE pulse widths and resultant minimum word-line (WL) delay times are investigated as a function of column address. The impact of the process variation in the time constant of WL, the cell current, and the resistance of deciding path on optimum PE pulses are discussed. Optimum PE pulse widths and resultant minimum WL delay times are modeled with fitting curves as a function of column address of the accessed memory cell, which provides designers with the ability to set the optimum timing for WL and BL (bit-line) operations, reducing average memory access time.

RIB/Channel Effect on Cell Performance Under High Current Density Operation

2010 ◽  
Author(s):  
Yuichiro Tabuchi ◽  
Takeshi Shiomi ◽  
Osamu Aoki ◽  
Norio Kubo ◽  
Kazuhiko Shinohara
Keyword(s):  
Water Transport ◽  
Current Density ◽  
Liquid Water ◽  
Water Distribution ◽  
Numerical Study ◽  
High Current Density ◽  
Cell Performance ◽  
High Current ◽  
Numerical Validation ◽  
The Impact

Heat and water transport in polymer electrolyte membrane fuel cell (PEMFC) has considerable impacts on cell performance under high current density which is desired in PEMFC for automobiles. In this study, the impact of rib/channel, heat and water transport on cell performance under high current density was investigated by experimental evaluation of liquid water distribution and numerical validation. Liquid water distribution between rib and channel is evaluated by Neutron Radiography. In order to neglect the effect of liquid water in channel and the distribution of oxygen and hydrogen concentration distribution along with channel length, the differential cell was used in this study. Experimental results show that liquid water under channel was dramatically changed with Rib/Channel width. From numerical study, it is found that the change of liquid water distribution was strongly affected by temperature distribution between rib and channel. In addition, not only heat transport but also water transport through membrane also significantly affected cell performance under high current density operation. From numerical validation, it is concluded that this effect on cell performance under high current density could be due to the enhancement of back-diffusion of water through membrane.

scholarly journals Thermal and Chemical Integrity of Ru Electrode in Cu/TaOx/Ru ReRAM Memory Cell

2019 ◽  
Vol 8 (12) ◽  
pp. N220-N233
Author(s):  
Mohammad Al-Mamun ◽  
Sean W. King ◽  
Marius Orlowski
Keyword(s):  
Memory Cell ◽  
Operating Conditions ◽  
Electrical Performance ◽  
Pt Electrode ◽  
Switching Performance ◽  
Inert Electrode ◽  
Work Function Difference ◽  
The Impact ◽  
Si Wafer

A good candidate for replacing the inert platinum (Pt) electrode in the well-behaved Cu/TaOx/Pt resistive RAM memory cell is ruthenium (Ru), already successfully deployed in the CMOS back end of line. We benchmark Cu/TaOx/Ru device against Cu/TaOx/Pt and investigate the impact of embedment of Cu/TaOx/Ru on two different substrates, Ti(20nm)/SiO2(730nm)/Si and Ti(20nm)/TaOx(30nm)/SiO2(730nm)/Si, on the cell's electrical performance. While the devices show similar switching performance at some operating conditions, there are notable differences at other operation regimes shedding light on the basic switching mechanisms and the role of the inert electrode. The critical switching voltages are significantly higher for Ru than for Pt devices and can be partly explained by the work function difference and different surface roughness of the inert electrode. The poorer switching properties of the Ru device are attributed to the degraded inertness properties of the Ru electrode as a stopping barrier for Cu+ ions as compared to the Pt electrode. However, some of the degraded electrical properties of the Ru devices can be mitigated by an improved integration of the device on the Si wafer. This improvement is attributed to the suppression of crystallization of Ru and its silicidation reactions that take place at elevated local temperatures, present mainly during the reset operation. This hypothesis has been corroborated by extensive XRD studies of multiple layer systems annealed at temperatures between 300K and 1173K.

Current crowding as a major cause for InGaN LED degradation at extreme high current density

2021 ◽  
Author(s):  
Nicola Trivellin ◽  
Matteo Buffolo ◽  
Carlo De Santi ◽  
Enrico Zanoni ◽  
Gaudenzio Meneghesso ◽  
...  
Keyword(s):  
Current Density ◽  
High Current Density ◽  
High Current ◽  
Current Crowding

Improved Heat Dissipation and Optical Performance of High-power LED Packaging with Sintered Nanosilver Die-attach Material

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001585-001605 ◽  
Author(s):  
Paul Panaccione ◽  
Tao Wang ◽  
Guo-Quan Lu ◽  
Xu Chen ◽  
Susan Luo
Keyword(s):  
Thermal Resistance ◽  
High Power ◽  
Heat Removal ◽  
High Current ◽  
Die Attach ◽  
High Power Led ◽  
Silver Epoxy ◽  
The Difference ◽  
Nanosilver Paste ◽  
The Impact

Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED's lifetime at a given photometric flux (brightness). Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable Tj for a given lifetime. A significant portion of the junction-to-case thermal resistance comes from the joint between chip and substrate, or the die-attach layer. In this study, we evaluated three different types of leading die-attach materials; silver epoxy, lead-free solder, and an emerging nanosilver paste. Each of the three was processed via their respective physical and chemical mechanisms: epoxy curing by cross-linking of polymer molecules; intermetalic soldering by reflow and solidification; and nanosilver sintering by solid-state atomic diffusion. High-power LED chips with a chip area of 3.9 mm2 were attached by the three types of materials onto metalized aluminum nitride substrates, wire-bonded, and then tested in an electro-optical setup. The junction-to-heatsink thermal resistance of each LED assembly was determined by the wavelength shift methodology, described in detail in this paper. We found that the average thermal resistance in the chips attached by the nanosilver paste was the lowest, and it is the highest from the chips attached by the silver epoxy: the difference between the two was about 0.7°C/W, while the difference between the sintered and soldered was about 0.3°C/W. The lower thermal resistance in the sintered joints is expected to significantly improve the photometric flux from the device. Simple calculations, excluding high current efficiency droop, predict that the brightness improvement could be as high as 50% for the 3.9 mm2 chip. The samples will be functionally tested at high current, in both steady-state and pulsed operation, to determine brightness improvements, including the impact of droop. Nanosilver die-attach on a range of chip sizes up to 12 mm2 are also considered and discussed.

Bump Electromigration and Back End Design Rules

2007 ◽  
Author(s):  
Vishal Nagaraj ◽  
Saket Karajgikar ◽  
Dereje Agonafer ◽  
Senol Pekin
Keyword(s):  
Flip Chip ◽  
Heat Dissipation ◽  
High Current Density ◽  
Electrical Performance ◽  
High Current ◽  
Current Crowding ◽  
Element Analysis ◽  
Chip Technology ◽  
Flip Chip Packaging ◽  
Current Densities

As there is continuous demand for miniaturization of electronic devices, flip chip technology is predominantly used for high density packaging. The technology offers several advantages like excellent electrical performance and better heat dissipation ability. Original invention of flip chip packaging utilized ceramic substrates and high lead bumps. Low cost commercialization of this packaging technology, however, required organic laminate substrates coupled with SnPb eutectic bumped interconnects on the die side. While organic laminate flip chip packaging may be a good option for many low power applications, current carrying capability of the eutectic bumped interconnect causes a catastrophic failure mechanism called electromigration. Previously, researchers have identified and addressed few issues regarding electromigration. Electomigration leads to the formation of metal voids in the conductors which eventually increases the resistance drop across the conductor causing electrical opens. Electromigration is very significant at high current densities. Temperature is the other parameter of concern for electromigration. High current density causes temperature to rise due to Joule heating, there by reducing the life of package. In order to determine the factors responsible for high current densities, we formed a full factorial design of experiments (DOE) that contained parameters such as passivation opening, UBM size, UBM thickness and trace width. Finite Element Analysis (FEA) was performed in order to study the effect of above parameters on current crowding and temperature in the bumped interconnects. Based on the results, hierarchy of the most important parameters to be considered while selecting the appropriate flip chip technology is proposed.

scholarly journals Impact of an Antiresonant Oxide Island on the Lasing of Lateral Modes in VCSELs

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2195
Author(s):  
Marta Więckowska ◽  
Robert P. Sarzała ◽  
Rafał Ledzion ◽  
Maciej Dems
Keyword(s):  
Numerical Analysis ◽  
Current Crowding ◽  
Crowding Effect ◽  
Factors Influencing ◽  
Mode Selectivity ◽  
Lateral Mode ◽  
Mode Discrimination ◽  
Lateral Modes ◽  
The Impact ◽  
Side Mode

Use of antiresonant structures is a proven, efficient method of improving lateral mode selectivity in VCSELs. In this paper, we analyze the impact of a low-refractive antiresonant oxide island buried in a top VCSEL mirror on the lasing conditions of lateral modes of different orders. By performing comprehensive thermal, electrical, and optical numerical analysis of the VCSEL device, we show the impact of the size and location of the oxide island on the current-crowding effect and compute threshold currents for various lateral modes. If the island is placed close to the cavity, the threshold shows strong oscillations, which for moderate island distances can be tuned to increase the side mode discrimination. We are therefore able to pinpoint the most important factors influencing mode discrimination and to identify oxide island parameters capable of providing single-lateral-mode emission.

Improved Heat Dissipation and Optical Performance of High-Power LED Packaging with Sintered Nanosilver Die-Attach Material

2010 ◽  
Vol 7 (3) ◽  
pp. 164-168 ◽  
Author(s):  
Paul Panaccione ◽  
Tao Wang ◽  
Xu Chen ◽  
Susan Luo ◽  
Guo-Quan Lu
Keyword(s):  
Thermal Resistance ◽  
High Power ◽  
Heat Removal ◽  
High Current ◽  
Die Attach ◽  
High Power Led ◽  
Silver Epoxy ◽  
The Difference ◽  
Nanosilver Paste ◽  
The Impact

Heat removal in packaged high-power light-emitting diode (LED) chips is critical to device performance and reliability. Thermal performance of LEDs is important in that lowered junction temperatures extend the LED's lifetime at a given pho-tometric flux (brightness). Optionally, lower thermal resistance can enable increased brightness operation without exceeding the maximum allowable Tj for a given lifetime. A significant portion of the junction-to-case thermal resistance comes from the joint between chip and substrate, or the die-attach layer. In this study, we evaluated three different types of leading die-attach materials; silver epoxy, lead-free solder, and an emerging nanosilver paste. Each of the three was processed via their respective physical and chemical mechanisms: epoxy curing by cross-linking of polymer molecules; intermetalic soldering by reflow and solidification; and nanosilver sintering by solid-state atomic diffusion. High-power LED chips with a range of chip areas from 3.9 mm2 to 9.0 mm2 were attached by the three types of materials onto metalized aluminum nitride substrates, wire-bonded, and then tested in an electro-optical setup. The junction-to-heatsink thermal resistance of each LED assembly was determined by the wavelength shift methodology. We found that the average thermal resistance in the chips attached by the nanosilver paste was the lowest, and it was highest from the chips attached by the silver epoxy. For the 3.9 mm2 die, the difference was about 0.6°C/W, while the difference between the sintered and soldered was about 0.3°C/W. The lower thermal resistance in the sintered joints is expected to significantly improve the photometric flux from the device. Simple calculations, excluding high current efficiency droop, predict that the brightness improvement could be as high as 50% for the 3.9 mm2 chip. The samples will be functionally tested at high current, in both steady-state and pulsed operation, to determine brightness improvements, including the impact of droop. Nanosilver die-attach on a range of chip sizes up to 12 mm2 are also considered and discussed.

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