Distinguished University Professor S.V. Babu has led two decades of chemical-mechanical planarization (CMP) research and development at Clarkson University's Center for Advanced Materials Processing (CAMP).
Babu, the CAMP director since 1999, has helped guide the research of this crucial enabling technology for the fabrication of complex logic and memory devices and other integrated circuit structures.
CMP is used to planarize unwanted topographical features by selective material removal at each metallization level during the fabrication of these devices. This is necessary because of the limitations caused by the shallow depth of focus of the optical lithography tools used to create the ever shrinking features of present and future generation semiconductor devices.
The CMP process requires the use of slurry and a polymeric polishing pad. The polishing slurry typically contains abrasive particles dispersed in a liquid carrier and is applied to the substrate’s surface using the polishing pad, mounted on a rotating platen in a polishing tool. A rotating head holds the wafer substrate face down against the rotating polishing pad while the uneven topography is planarized.
CMP began at CAMP as a result of two white papers written in 1993. These papers were developed through the discussions of CAMP Professors S.V. Babu, Ahmed Busnaina, Raymond Mackay, Egon Matijevic, Richard Partch and Don Rasmussen, with two former IBM technical managers and researchers Mike Fury and Frank Kaufman. The white papers addressed the multiple problems and challenges in understanding and improving the CMP processes being developed and used in the semiconductor industry.
The technical directions proposed in these documents exploited the expertise existing at CAMP in thin film processing, particle synthesis, particle coatings, colloidal chemistry, surfactants, process control instrumentation, and in the removal of particles from finished surfaces. The startup CMP activity, which involved the combined efforts of all these CAMP researchers, took place in Babu’s laboratory using a polishing tool donated to CAMP by Strasbaugh and test wafers for experimental trials donated by IBM. The initial experimental efforts at CAMP on CMP were expertly led by David Campbell, a retired senior IBM engineer and manager.
At various stages throughout the years, the research projects involved many CAMP professors, including Shankar Subramanian, Goodarz Ahmadi, Yuzhuo Li, Dipankar Roy, Sitaraman Krishnan, Cetin Cetinkaya, Ian Suni, Igor Sokolov, Devon Shipp and Dan Goia.
At the urging of then-CAMP Deputy Director Ed McNamara after these initial efforts, CAMP sponsored its first CMP conference: a three-day symposium and workshop jointly organized by Kaufman, Fury and Babu in August 1996 in Lake Placid, N.Y. With the success of the conference, representatives from academia and industry decided to work together to better understand the multitude of CMP processes, and the CMP Symposium became an annual event that continues today.
Babu, representing CAMP, has served as the lead symposium organizer for 19 consecutive years. He was supported by many co-organizers during that time, including Frank Kaufman, Mike Fury, Ara Philipossian (Intel), James Ryan (IBM), Manabu Tsujimura (Ebara Corporation, Japan), Kathleen Perry (Applied Materials), Rajesh Tiwari (Texas Instruments), Dan Heenan (IBM), Robert Her (Ferro), Michael Oliver (Rodel), Charles Davis (IBM), CAMP Professor Yuzhuo Li (Clarkson University & R&D Head for special Global Business Unit at BASF), Paul Fischer (Intel), Gundu Sabde (Micron), Laertis Economikos (IBM), Mansour Moinpour (Intel), Mahadevaiyer Krishnan (IBM), Lee Cook (Dow Electronic Materials), Jin-Goo Park (Hanyang University, Korea), Donald Canaperi (IBM), Joseph Steigerwald (Intel), Jihong Choi (GlobalFoundries), Matt Prince (Intel), Anurag Jindal (Micron), Charan Surisetty (IBM), Hirokuni Hiyama (Ebara Corporation, Japan), Rajeev Bajaj (Applied Materials), Robert Rhoades (Entrepix) and Shyan Ramalingam (Micron).
Manabu Tsujimura of Ebara Corporation played a crucial role in the success of many of these conferences and arranged for several Japanese speakers to participate every year. Clarkson University President Tony Collins presented Tsujimura with a special award at the 2012 CMP Symposium.
The symposium continues to attract participants from around the world. More than 100 researchers from several high technology companies, suppliers and universities from the United States, Japan, Korea, China, Taiwan, Germany and Belgium gathered in August 2014 in Albany, N.Y., for the CMP 19th Annual International Symposium. The event was sponsored by Clarkson's CAMP and the CMP Users Group of North America.
Speakers included engineers and scientists from IBM, Intel, Micron, GlobalFoundries, Samsung, SEMATECH, Ebara, Dow Electronic Materials, Cabot Microelectronics, Applied Materials, Ferro, BASF, Hitachi Chemical Company, Texas Instruments, 3M, Air Products, Fujimi and IMEC in Belgium. University speakers attended from Kyushu University and Kyushu Institute of Technology, and Shizuoka and Yamanashi University of Japan, National Taiwan University, Fudan University of China, Hanyang University of Korea, and the College of Nanoscale Science and Engineering also participated.
The 2015 International Conference on Planarization/CMP Technology (2015 ICPT) will be held from Sept. 30 to Oct. 2., at the Wild Horse Pass Hotel & Casino in Chandler, Ariz. ICPT 2015 is jointly hosted by CMP User’s Group of the Northern California Chapter of the American Vacuum Society and Clarkson's CAMP.
The late CAMP professor Yuzhuo Li was integral to the growth of CMP expertise and reputation at CAMP. Besides serving as a co-organizer for numerous symposia on chemical-mechanical planarization, he delivered several keynote talks and carried out innovative research along with his many graduate students and research associates. Among his notable projects were studies of novel pure organic particles as abrasives at low down force, "smart" abrasive particles, abrasive-free systems, edge over erosion using conventional and some novel pads, "reactive" pads, correlation between pad structures and planarization performance, and various aspects of post-CMP cleaning. He edited a well-received book, titled Microelectronic Applications of Chemical Mechanical Planarization, which was published by Wiley Interscience in 2007. While on leave from Clarkson, he led the Research and Development Group for Global Business Electronic Materials at BASF in Ludwigshafen, Germany till his death. The poster session held at the CMP 18th Annual International Symposium was dedicated to his memory.
CAMP has collaborated on CMP projects with various consumable suppliers and other companies, including Micron, IBM, Intel, GlobalFoundries, Ferro, IMEC and Ebara. Over the past decade, Clarkson received more than $1.4 million in funding from Intel. Intel donated silicon wafer polishing equipment and supported CAMP professors working on CMP research. Clarkson also received more than $830,000 in royalties from Ferro Corporation to cover licenses for a CMP slurry formulation developed in Babu’s laboratory by Ramanathan Srinivasan and William America. William America, a late deputy director of CAMP, along with Jack Prendergast, a former employee of Ferro and a past deputy director of CAMP, contributed enormously to this successful effort. Ferro licensed the patents and commercialized, qualified, and marketed the slurry after further considerable development work. Ferro, a world leader for products used in polishing markets, is a former corporate sponsor for CAMP.
Babu currently is editing a book, titled Advances in Chemical Mechanical Planarization, to be published by Woodhead Publishing this year. He also is serving as a guest editor for the Electrochemical Society’s Journal of Solid State Science and Technology for a 2015 focus issue on "Chemical Mechanical Planarization: Advanced Material and Consumable Challenges." For more information about the publication, visit http://jss.ecsdl.org/site/focus_issues/chemical_planarization.xhtml .
Additionally, Babu has supervised 41 doctoral and 38 master of science students so far. Many of these degree recipients wrote their theses on some aspect of CMP. Most of these former students are working and managing in the area of CMP at Micron, GlobalFoundries, Intel and IBM. They showcase the enormous contributions made by Clarkson to the growth of the science and technology of CMP globally.
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