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Sunday, November 10, 2019

#414 Some more about substrates

Most commonly, a piece of semiconductor material used to fabricate functional devices is in a form of a thin wafer featuring single-crystal structure and typically thinner than 1 mm. A distinction needs to be made between small and large wafers as well as square/rectangular and circular wafers all with the choice of desired surface orientation. In terms of size, commercial circular wafer substrates can be as small as 20 mm in diameter in the case of some II-VI compound semiconductors, and as large as 450 mm in diameter in the case of silicon wafers.


Clearly, while the nature of processes wafers are subjected to in the course of device manufacturing remains the same regardless of the size of the wafer, the way various operations are implemented, and the way wafers are handled, depend on the size and the shape of the wafers. For instance, square, and as thin as some 50 μm Si wafers used in the manufacture of solar cells, where cost of material rather than mechanical stability of the substrate is an issue, are subject to different handling procedures than close to 1000 μm thick, 450 mm in diameter circular Si wafers where mechanical rigidity of the substrate is a prime concern.

Posted by Jerzy Ruzyllo at 10:59 AM | Semiconductors | Link

Sunday, October 27, 2019

#413 A word about substrates

Semiconductor process technology, understood as a technology developed and used for the purpose of manufacturing semiconductor devices, involves complex tools, methods, and procedures devised specifically for semiconductor device fabrication. Semiconductor manufacturing is unique as some devices, for instance cutting edge logic integrated circuits, are among very few mass-produced objects manufactured with truly atomic scale precision.


While discussing semiconductor manufacturing processes it is typically assumed that the substrate into which, or onto which devices are built is a rigid semiconductor wafer. What needs to be recognized, however, is that the way various processing step involved in the manufacture of semiconductor devices are implemented depends of the size, shape, degree of flexibility, and chemical makeup of materials used to construct such devices, and commonly referred to as “substrates”.

Posted by Jerzy Ruzyllo at 10:26 AM | Semiconductors | Link

Sunday, October 6, 2019

#412 236th ECS Meeting

As a reminder, the Fall meeting of the Electrochemical Society (ECS) will be held Oct.13-17, 2019 in Atlanta, GA. Although the name of the Society may not indicate it, the ECS is heavily involved with semiconductor science and engineering.


Consider titles of some symposia to be held during the meeting in Atlanta: International Symposium of Semiconductor Cleaning Science and Technology, Atomic Layer Deposition Applications, Semiconductor Process Integration, Low-dimensional Nanoscale Electronic and Photonic Devices, and Gallium Nitride and silicon Carbide Power Techmologies to mention just a few examples.

Posted by Jerzy Ruzyllo at 05:01 PM | Semiconductors | Link

Sunday, September 22, 2019

#411 More than wearable: implantable

Responding to the needs of portability, mobility, and on-the-go accessibility, permanent or temporary integration of ultra-light and ultra-low power, high-end semiconductor-based electronic and photonic devices and systems with our bodies and clothes we are wearing continues to expand. It goes beyond what we can carry in our pockets (smartphones, notebooks, etc.) and is concerned with instrumentation that is actually integrated with our clothes or attached to our body for the purposes of interacting with our bodies.


Going even further, there is a class of implantable devices based on semiconductor electronics which are installed in our bodies for the purpose of monitoring and/or stimulating certain vital bodily functions. Among the range of implantable electronic devices, the cardiac pacemakers and hearing aids in the form of inner ear implants are the common examples. The trend is bound to continue which means that in the future we will carry more and more semiconductors implanted in our bodies.

Posted by Jerzy Ruzyllo at 09:30 PM | Semiconductors | Link

Sunday, September 8, 2019

#410 What makes university a research university?

It may come as a surprise, but there seems to be no universally accepted answer to the question what makes the university a research university. The same set of criteria is used pretty much all over the world, but emphasis on what is a truly defining factor vary depending on the local circumstances.


No measure is perfect, no raw numbers can fully define quality of education and research in an institution of higher education. Is it a number of publications, amount of funding, or number of Ph.Ds. graduated annually? In addressing this issue, Carnegie Foundation got it right by using number of doctoral degrees granted per year as a lead criterion distinguishing between R1, R2, and R3 research universities. Why Ph.D. degrees weight so much? Because it is in the Ph.D. process where the educational and research missions of the university come together.


And by the way, another term for the research university is a doctoral university in which research funding is an engine driving a Ph.D. process, and publications are the results of such process and its goal.

Posted by Jerzy Ruzyllo at 02:55 AM | Semiconductors | Link

Sunday, August 25, 2019

#409 Silicon makes MEMS possible

A very distinct class of semiconductor devices is represented by Micro-Electro-Mechanical Systems (MEMS), also referred to as Nano-Electro-Mechanical Systems (NEMS) depending on the size of device features. The electro-mechanical semiconductor devices were conceived as a way to exploit excellent mechanical properties of silicon which allows literally endless possibilities for integration of electronic and mechanical functions within a single material system.


MEMS (Micro-Electro Mechanical System) and NEMS (Nanp-Electro Mechanical System) devices integrate mechanical and electrical functions using somewhat modified, but otherwise standard semiconductor device manufacturing technology. Such functional integration is possible only because silicon, besides advantageous electrical and cost/manufacturing related characteristics, also features outstanding mechanical properties. This combination is unique to silicon and cannot be reproduced using any other material. In broad terms, MEMS/NEMS devices fall into two categories of microsensors and microactuators. In the former case mechanical motion of the parts of the MEMS device caused for instance by acceleration (accelerometers), or pressure (pressure sensors) is converted into electrical signal. In the latter case, MEMS device is converting electrical signal into mechanical motion by engaging micro-motors, micro-gears, and other mechanical parts comprising its structure.

Posted by Jerzy Ruzyllo at 04:21 PM | Semiconductors | Link

Sunday, August 11, 2019

#408 Thin-Film Transistor: unsung hero of transistor technology

A Thin-Film Transistor (TFT) is a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) fabricated using thin-film technology rather than conventional technology which forms MOSFETs on the bulk wafers. Unlike in the case of the bulk MOSFET, where channel is formed in the single crystal semiconductor, the channel in TFTs is most commonly formed using non-crystalline, amorphous semiconductor. By definition then, TFT features inferior to conventional MOSFET electronic properties because of the much higher electron mobility in the single-crystal semiconductor as compared to the amorphous semiconductor.


In spite of their performance limiting features, TFTs are among the most important semiconductor devices primarily because of the role they play in flat panel display technology. Whether it is a Liquid Crystal Display (LCD) or emissive display based on Light Emitting Diodes (LED) the best resolution, highest contrast, and significantly improved addressability is achieved when each pixel in individually powered up by the transistor integrated into the pixel’s structure. Displays incorporating TFTs are known as Active Matrix displays and offer the best rendering of images and colors.

Posted by Jerzy Ruzyllo at 05:34 PM | Semiconductors | Link

Sunday, July 28, 2019

#407 Here comes "quantum"

Quantum computing was alluded to in the blog #402 posted on 3/31/19. In the context of the alternative transistor solutions considered in the last few entries, there is a need to mention quantum transistor. With quantum computing we are venturing beyond a realm of the binary system and conventional computers.


The device used to carry out quantum computing operations is referred to as quantum transistor in spite of the fact that its operation is based on the entirely different principles than the operation of the conventional field-effect transistor for instance. What these two types of drastically different in terms of principles of operation transistors have in common, is the fact that both are constructed using primarily semiconductor materials, and fabricated using methods which rely heavily on semiconductor nanotechnology

Posted by Jerzy Ruzyllo at 12:57 PM | Semiconductors | Link

Sunday, July 14, 2019

#406 Photonic alternative

In another solution, electron as an information carrier is replaced by the photon, representing quantum of light. Photon is more efficient than electron information carrier as it can cover distances in the waveguides with very little losses, which is in stark contrast to electron moving in semiconductors and metals with significant losses.


With short wavelength laser diodes and detectors available, and optical waveguides technology being well develop, a still missing link in this “all photonics” scenario is a high-performance optical transistor needed to turn light “on” and “off”.

Posted by Jerzy Ruzyllo at 11:46 AM | Semiconductors | Link

Sunday, June 16, 2019

#405 MOSFET evolution - alternative solutions

As indicated in the previous blog, solutions concerned with materials and architecture modifications of the MOSFET may not be enough to meet anticipated future needs with regard to the performance of devices designed to carry out logic functions. Therefore, alternative solutions radically departing from the mainstream approaches to transistors’ performance improvements are pursued.


Logic circuits carrying out computational operations, operate based on the binary system needed to code and process information which basically comes to switching the system from one state to another. In electronic devices this function is very efficiently carried out by transistors which turn flow of electrons (current) on and off. The problem is that scattering of electrons moving through the solid accounts for the significant signal losses, and thus, electrons as the carriers of electric charge may not be able to support long-term needs of information processing systems.


One of the solutions being explored is concerned with transistors in which magnetic rather than electric field controls device operation and exploits the fact that in addition to electric charge, electron also features an angular momentum known as electron spin. The spin of the electron can be directed by the magnetic field either up or down. In the sense then, it represents an inherently binary system which spintronics attempts to use in a magnetically sensitive transistor, called a spin transistor, to perform logic functions.

Posted by Jerzy Ruzyllo at 07:17 PM | Semiconductors | Link

‹‹ ›› is a personal blog of Jerzy Ruzyllo. He is Distinguished Professor Emeritus in the Department of Electrical Engineering at Penn State University. With over forty years' experience in academic research and teaching in semiconductor engineering he has a unique perspective on the developments in this technical domain and enjoys blogging about it.

This book gives a complete account of semiconductor engineering covering semiconductor properties, semiconductor materials, semiconductor devices and their uses, process technology, fabrication processes, and semiconductor materials and process characterization.

With over 2000 terms defined and explained, Semiconductor Glossary is the most complete reference in the field of semiconductors on the market today.


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