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Sunday, April 19, 2020

#428 Semiconductor clean-rooms, virus protection, cleaning, cont.

Semiconductor clean-room apparel in general, including disposable and sterile clean-room garments, hoods, respirators, masks, gloves, shoes,  etc.,etc. are serving one purpose which is to protect pristinely clean environment from the particles generating people working in the clean-room. In other words, the goal is to protect the environment from us.


In the case of protection against viruses it is the other way around - the goal is to protect us against the contaminated environment. But the tools and means are exactly the same in these two cases.


Another example of semiconductor technology setting a tone for various virus-protection solutions is concerned with aggressively recently pursued use of UV light to clean surfaces and objects we touch in our daily lives. In semiconductor processing UV treatments of solid surfaces were explored (specifically for the purpose of organic contaminants removal) already over thirty years ago. See for instance this research paper: J. Ruzyllo, G, Duranko, and A, Hoff, "Pre-Oxidation UV Treatments of Silicon Wafers", Journal of the Electrochemical Society, vol. 134. p. 2052 (1987).


Posted by Jerzy Ruzyllo at 08:26 PM | Semiconductors | Link

Sunday, April 5, 2020

#427 Can semiconductor clean-rooms provide SARS-Cov-2-free environment?

When not interacting with the living cells aren’t the viruses behaving like independent particles? Aren’t then class sub-1 clean-rooms used in cutting edge semiconductor manufacturing creating a virus-free environment? At least SARS-Cov-2-free environment?


The size of the SARS-Cov-2 virus which is causing coronavirus disease wreaking incredible havoc around the world these days is apparently in the range of 120 nm while the advanced ULPA (Ultra Low Particulate Air) filters are removing from the air particles as small as 100 nm. Besides, air in the clean-rooms is continuously exchanged and ULPA filtered which further limits any potentially harmful interactions with viruses.


People working in semiconductor clean-room are wearing elaborate gowns to protect environment against particle generating people, no other way around. In the case of clean-rooms used for virus protection such a costly  gear wouldn’t be needed.


All in all, I think there is good chance clean-room technology will be spreading in the future well beyond semiconductor labs and fabs. 

Posted by Jerzy Ruzyllo at 08:51 PM | Semiconductors | Link

Sunday, March 29, 2020

#426 Thirty years ago: March 1990

Here are the themes that could be identified in some semiconductors related journal in March 1990. In the Journal of the Electrochemical Society etching appears to be one of the lead themes. Whether it was Reactive Ion Etching (RIE), or ion-milling, silicon or GaAs, etch processes were clearly at the forefront in this particular issue. It is in agreement with what I recall about those times. RIE, RIE-induced damage, and etch related surface contamination were of great interest then. 


As the name of the journal indicates, papers published in the IEEE Transactions on Electron Devices were geared more toward device-related phenomena. Exactly thirty years ago, much attention has been paid to the charge transport phenomena in both field-effect and bipolar devices, charge carrier trapping, etc. 

Posted by Jerzy Ruzyllo at 09:29 PM | Semiconductors | Link

Sunday, March 15, 2020

#425 My new book

The book I was working on during the last three years or so, is now available on the market. It is entitled “Guide to Semiconductor Engineering” and was published by the World Scientific Publishing Company. If interested, you may want to take a look at it here. I do my best to explain premises upon which this book was conceived in the video included. Also, consider exploring the Table of Contents to see a broad range of issues covered in this contribution.


Posted by Jerzy Ruzyllo at 09:16 AM | Semiconductors | Link

Sunday, March 8, 2020

#424 Thin-films

Thin-films are at the core of any semiconductor material systems in which properties of surfaces and interfaces discussed earlier are coming to play. There is a strong correlation between the thickness of any solid, including semiconductors, and its electronic properties. While gradually confining geometry of a solid from the three-dimensional bulk realm to the two-dimensional configuration, basic physical characteristics of material are changing. The changes will occur according to the laws of classical physics up to the point where at the extreme geometrical confinement quantum phenomena take over control of the behavior of electrons which are now subject to the laws of quantum physics.


So, how the concept of the “thin-film” can be defined? Considering resistivity of semiconductor for instance, it displays bulk characteristics as long as continued reduction of its thickness do not alter electrons motion in any of the three directions. At certain thickness, however, resistivity starts increasing as the increasing scattering of strongly 2D confined electrons alters the flow of electrons. This is a point at which material no longer displays bulk properties and assumes properties of a thin-film.  


Posted by Jerzy Ruzyllo at 11:14 AM | Semiconductors | Link

Sunday, February 23, 2020

#423 Thirty years ago: February 1990

Research papers published in February 1990 reflected on the anticipated at that time challenges facing semiconductor technology. In the case of the Journal of Electrochemical Society the issues related to the MOS gate oxide processing in the context of the continued scaling of its thickness are at the forefront. (Quick reminder, the gate oxide thickness was at that time in the range of 8-10 nm and the oxide was either pure or nitrided SiO2). Also of interest were challenges facing etch technology in the case of binary and ternary compound semiconductors material systems.


In the case of IEEE Electron Device Letters similar concerns are on full display, but at the device level. Hot-electron induced degradation in deep-submicrometer MOSFETs, as advanced MOSFETs were referred to at that time, was getting much attention.


The  February 1990 issue of the IEEE Transactions on Electron Devices was a special issue devoted enrtirely to Photovoltaic Materials, Devices, and Technologies. An observation: not much of what's going on in photovotaics now, was entirely unknown 30 years ago.

Posted by Jerzy Ruzyllo at 02:08 PM | Semiconductors | Link

Sunday, February 16, 2020

#422 Interface

Interfaces are the integral part of any material system comprised of two and more materials in which they typically play the role which defines characteristics of the entire system. As in the case of the surfaces (see previous blog), the effect of an interface between two materials expands into the adjacent regions. An interface is essentially a transition region featuring finite thickness that is needed to allow structural transition between two materials featuring different structure and/or chemical transition between two materials featuring different chemical composition. In either case, interface represents a discontinuity of electrical, optical, mechanical, and thermal properties of the material system.


From the point of view crystal structure interface is basically a planar defect severely disrupting integrity of the material system, and hence, altering its characteristics. And by the way, the impact of interface on semiconductor device performance manifest itself differently depending onwhether device current is flowing parallel to the interface or across the interface


Posted by Jerzy Ruzyllo at 05:45 PM | Semiconductors | Link

Sunday, February 9, 2020

#421 Surface-key element of the material system

In general terms, surface is an exterior face of the solid and represents two-dimensional termination of fundamental characteristics displayed by the three-dimensionally distributed atoms in the bulk of the sample. .In the case of crystals, surface also represents an abrupt discontinuity of crystal structure. In practice, a surface can be significantly disturbed by its roughness (even at the nano-scale) as well as process related physical damage.


Considering the above, it is clear that electronic properties of the surface and the near-surface region of any solid, including semiconductors, depart significantly from the same properties in the bulk. For instance, due to the increased scattering of electrons resulting from the defective lattice and electrically charged centers in the near-surface region, transport of electrons close to the surface is significantly disturbed as compared to the transport of electrons in the bulk. This effect has a major adverse effect on the operation of semiconductor devices which depend on the surface and interface related phenomena, e.g., Metal Oxide Semiconductor Field Effect Transistors (MOSFET).

Posted by Jerzy Ruzyllo at 09:41 PM | Semiconductors | Link

Sunday, January 26, 2020

#420 Thirty years ago: January 1990

Following on the previous blog let’s take a quick look at what trends were noticeable in some research papers published exactly 30 years ago.


In the January issue of the IEEE Transactions on Electron Device for instance, my attention attracted papers concerned with 2D quantum wells and 2D electron gas. It shows that already thirty years ago quantum phenomena in the highly geometrically confined structures were the subject of thorough exploration. The January issue of the IEEE Electron Device Letters in turn clearly shows that the complex heterostructures involving binary and ternary III-V compounds, and including strained layer superlattices, were pretty common in the advanced research publications at that time.

Posted by Jerzy Ruzyllo at 07:52 PM | Semiconductors | Link

Sunday, January 19, 2020

#419 Thirty years ago

The idea of going back in time to check on what was going on in various engineering domains in the past is not new. As an example, sometime ago IEEE Spectrum published several articles in the series entitled Thirty Years Ago which were analyzing developments in electrical engineering and electronics three decades earlier.  

Look for the future entries on this blog site that will follow the same idea, except that they will be focusing specifically on semiconductors science and engineering. Various   trends emerging thirty years earlier will be identified based on the research papers published in the IEEE and the Electrochemical Society journals.


As you will see, it is good to look back in time to remind ourselves that in semiconductor science and engineering, just like in all other areas of engineering sciences, things do not happen overnight and that most of what’s being perceived as new and current is deeply rooted in the work done many years ago.



Posted by Jerzy Ruzyllo at 01:06 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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