Gunar Lorenz, PhD
Director, System Level Simulation
We just rolled out MEMS+ 5.0 with lots of new capabilities for our users. I discussed some of the new features, support of scanning mirrors in particular, in a previous post. This time I would like to focus on the new capabilities for exporting reduced order models (ROMs) of MEMS devices that system engineers can place in their Simulink schematics and IC designers can place in their circuit schematics.
Before getting into the technical stuff, allow me to provide some motivation. To design the control and signal processing electronics that go around every MEMS device, system engineers usually work in Simulink while circuit designers work in schematic entry tools such as Cadence Virtuoso. There’s a MEMS block in their flow diagram or schematic with an underlying model that captures the coupled electromechanical behavior of the MEMS device. It’s common practice to “hand craft” the MEMS behavioral model, but hand crafted models have many shortcomings: they’re usually over simplified, capturing only one degree of freedom and omitting nonlinear effects. Furthermore, it’s difficult to keep hand crafted models in sync with evolving device designs. All of these shortcomings can be avoided by using ROMs exported from MEMS+ instead of hand-crafted models.
By Steve Breit, Vice President Engineering
The CoventorWare 2014 release has been announced and is now available to customers. I presided over the first release of CoventorWare in 2001 and eight major releases since then with numerous updates in between. With each release, we added new capabilities, and capacity, speed, and accuracy improvements to address the ever more demanding requirements of our users. The new capabilities and performance improvements in each release are easy to talk about and receive all the glory. In this respect, CoventorWare 2014 is no different: the highlights are covered in our press release and a What’s New page elsewhere on our site; I won’t repeat them here. Instead, I want to talk about the steady improvements in the usability, robustness and quality of the software and the documentation. These improvements aren’t as glamorous as the shiny new stuff, but I believe they really matter to users. Our quality assurance team and our documentation team deserve a lot of credit for these improvements. They’re the unsung heroes of CoventorWare.
Semicon West is one of the iconic conferences in the semiconductor industry and annually attracts the key movers and shakers who are involved with how we are going to keep Moore’s Law moving forward, among other things. It’s known rightfully so, as a ‘big iron’ show with the top manufacturing equipment companies showing off their newest machines for the major steps in the manufacture of semiconductors – wafer processing, assembly packaging and test.
It’s not all about the equipment of course, or even just manufacturing. The show has done a good job of expanding to include a wider ecosystem of companies, products and topics that impact chip design as well. So while the majority of attendees come from companies that produce chips – foundries and IDMs – as well as the supporting production services, Semicon visitors also include the fabless companies who really aren’t in the market for manufacturing equipment. read more…
By David M. Fried
Today we officially released SEMulator3D 2014.100. Typically, I wouldn’t be so excited about a “point release”, but this is clearly the biggest interim software release in recent SEMulator3D memory. We’ve added significant capability to an already industry-leading virtual fabrication platform. Many of the features of recent SEMulator3D releases have been focused on Etch enhancements. To complement these enhancements, we’ve stepped up the predictive accuracy of several other process models in SEMulator3D 2014.100, including Deposition and CMP.
The highlight of this release is a new Visibility-Limited Deposition model. This model dramatically improves the predictive accuracy for directional depositions, like Physical Vapor Deposition (PVD) and other plasma enhanced deposition processes. As with other process models in SEMulator3D, we’ve made this process simple to implement and calibrate using a reduced set of process parameters. The key features of this Visibility-Limited Deposition model are the “Source Sigma”, reflecting the directional distribution of the process, and the “Isotropic Ratio”, reflecting the non-visibility-limited component of the deposition process. This model enables a large variety of processes, with a wide range of results.
By Mike Hargrove
Most process/device simulation tools are TCAD-based. By this, I mean they share a common platform which connects the process simulator to the device simulator, usually using the same mesh structure. Most all of these TCAD tools are finite-element based, and the 3D final mesh structure is tetrahedral in nature. The mesh structure contains many nodes which define solution points for the numerous complex set of equations required to create the physical structure, in most cases a transistor, and solve for the electrical characteristics of the device. One of the drawbacks of TCAD is the computational time required to arrive at a solution – both process model solution and device electrical solution. A larger modeled area (e.g. multiple transistors and/or an SRAM cell) usually means longer simulation time.
Coventor’s virtual wafer fabrication approach addresses this challenge. Our process modeling platform combines with the statistical device TCAD suite of tools from Gold Standard Simulations, LTD. (GSS) to produce SRAM device-level simulation capability capturing real process-induced statistical variation. The ultimate objective of statistical device modeling is to capture the intrinsic variation of physically relevant process parameters. The combination of Coventor SEMulator3D process modeling capability and GSS statistical TCAD simulator GARAND fulfills this objective.
Steve Breit, VP Engineering
Coventor attended the Solid State Sensors, Actuators and Microsystems Conference last week, known simply as “Hilton Head” to the North American MEMS and nanotechnology community. This is a delightful conference held every two years at the same beachfront resort on Hilton Head Island, South Carolina. The location and single track of oral presentations create a congenial atmosphere for engaging with other participants.
At the opening, the conference chair Professor Mehran Mehregany of Case Western Reserve noted that this was the 30th anniversary of the conference and remarked on the incredible technical progress over that period. In 1984, the year of the first conference, MEMS products were only a gleam in the eyes of a select group of researchers. Today, MEMS ship in the billions and are ubiquitous in automobiles, mobile devices, and many other products. Professor Mehregany then asked the assembled micro- and nanotechnology research community a provocative question: Now that MEMS have become a reality, what should we do for the next 30 years? To help the research community answer this question, the organizers assembled a panel of four science fiction writers who shared their speculations on what might be possible in 30 years.
With 2D planar NAND flash hitting scaling issues at sub-20nm technology nodes, 3D NAND flash has become all the rage. Instead of restricting memory cells to a single plane and scaling the devices horizontally, memory cells can also be stacked vertically, allowing high cell density while side-stepping scaling issues (for now). Major NAND flash manufacturers have each developed their own designs and technology for 3D NAND flash, and with the addition of vertical cell stacking, new issues in 3D process integration arise.
For instance, in Samsung’s Terabit Cell Array Transistor (TCAT) technology , a memory cell array is formed of NAND flash strings with vertically-oriented channels and word lines arranged in planes. Of particular interest is the gate integration scheme: TCAT uses charge-trapping (SONOS/TANOS) with metal replacement gates, the combination which is expected to result in faster erase speed, wider threshold voltage margins, etc. The cell gates are created using a sacrificial nitride layer combined with a damascene process: the entire stack of SiO2/SiN layers is etched (“word line cut”) after staircase formation, then nitride is removed through wet etching with hot phosphoric acid, leaving behind gaps separated by the oxide. These gaps are then filled with dielectric and gate metal to create gate-all-around structures.
Coventor tells me that they are the leading supplier of 3D modeling and simulation software for MEMS, virtual fabrication of MEMS, and semiconductors, providing software and expertise to help customers predict the structures and behavior of their designs before they commit to actual fabrication. This video attests to the company’s strengths in that area.
As it stands today, the video is a very simple 2-minute animation with no sound, running through all the steps of the 3D BiCS process without any explanation. At some future point I hope to add annotation and pauses at reasonable times so that it makes more sense to those who don’t have the process memorized. Even without this finessing, it’s a pretty compelling video to watch, and it underscores the sheer complexity of this new process.