By Peter Vanderlee
TNAZ In-Business Correspondent
Editor's Note: Mr. Vanderlee, a business development consultant for EMC, has more than two decades experience as a journalist and fact-reliant writer. Contact him via TheEditors@technewsarizona.com.
The development and commercial refinement of a breakthrough electro-chemical residue sensor (ECRS) by Tucson, AZ-based Environmental Metrology Corporation (EMC) will enable semiconductor manufacturers to optimize a critical stage of fabrication – surface preparation – reducing the use of water, energy and chemicals to provide annual savings of up to 50% while increasing yield and throughput.
Currently, a wireless version of the sensor is being jointly developed by EMC and the ConnectionOne Industry-University Research Center located at Arizona State University.
The technology, based on science developed at the University of Arizona, has been thoroughly tested at the facilities of two major semiconductor manufacturers. In addition to facilitating optimization of the wafer rinsing process, testing at these facilities have also proven that the ECRS can detect very small quantities of impurity left after an incomplete cleaning procedure. As a result of these test results and the strong advocacy of its customers, EMC was awarded a 2009 Editors' Choice Best Product Award from Semiconductor International.
One of the most important stages of semiconductor manufacturing – surface preparation of wafers through clean rinsing – has also proven to be one of the most elusive to make more efficient.
The cleaning and drying of micro- and nano-structures typically account for up to 65% of the total manufacturing process and consumes more than 80% of the ultra-pure water used in semiconductor fabrication. This is because wafers, whether prepared individually or in batches, are cleaned and rinsed up to 400 times to ensure elimination of any impurities.
As a result there have been many efforts made over the years to develop more effective cleaning methods that consume less chemicals, energy and water, including recycling and reusing the rinse water. To date, unfortunately, these attempts have shown limited results or have proven ineffective as technology increasingly scales down from micro- to nano-size. In fact, resource use usually increases more rapidly as the device size deceases.
This is because improving batch or single-wafer process efficiencies requires the availability of an in situ and real-time metrology technology. Without knowing the amount of chemical residue in the fine structures of patterned wafers, the end point in a rinse process is usually determined by recipes that are typically based on external measurements that offer limited data for a best guess estimate. This approach is indirect, unreliable, and expensive.
"You can't optimize what you can't measure, and ECRS is the first tool the industry can use that performs in situ and real-time measurement of cleanliness inside high-aspect-ratio features while the wafer is being cleaned, rinsed or dried," said Doug Goodman, Chairman of EMC.
He also points out that conservation is becoming a major concern for semiconductor manufacturers with respect to resource availability, cost reduction and waste disposal. "Manufacturing sustainability based on resource usage is becoming more critical as the technology scales to smaller features," Goodman said.
To date, ECRS has been awarded three patents, with another pending.
The technology is a combination of hardware and software. The hardware is a unique sensor that has been designed, fabricated, and tested for rinsing. The software is a comprehensive process model that includes surface interactions, charge effects, and transport processes that take place in fine structures of patterned wafers. The model, in testing, has proven a powerful method for predicting the rinse behavior where data is not available through conventional means.
Testing results of the ECRS also show that the conventional method of monitoring the progress of rinse through measurement of bulk water resistivity in the tank is neither accurate nor adequate for determining the process end point and optimizing rinse steps.
Indeed, ECRS has proven to be the only technology currently available that enables in situ and real-time monitoring of the residual surface contamination in microstructures. As a result, it is proving uniquely effective as a means of generating rinse guidelines and new recipes for dramatically lowering water, chemical and energy use during the rinse process.
The commercial availability of ECRS comes at a key time. After a decline through the past three years, the semiconductor industry is now beginning to ramp up production to meet demand generated by growth in the PC, smart phone and electronic device markets. Industry research firm Gartner, Inc. predicts a 20.9% increase in capital spending to $29.4 billion in 2010, growing to annual capital spending of $42.6 billion by 2012.
"We've invested heavily and worked hand-in-hand with semiconductor manufacturing customers to prove the efficacy of the technology and quantify its benefits," said Goodman. "With the semiconductor industry now beginning to rebound, we believe it's an optimum time to seek either a commercial partner or buyer for this technology that can sell and support ECRS on a broad international scale as an integral part of the semiconductor manufacturing process," he added.
So far, the path to market for the ECRS has been a model of collaboration. The fundamental science was developed at the University of Arizona's Engineering Research Center for Environmentally Benign Semiconductor Manufacturing with support and mentoring from the Semiconductor Research Corporation. Spun out from the center in 2003 as EMC, a prototype was designed, built and tested under the National Science Foundation's Small Business Innovation Research program. Later, supported by private investment, a commercial version of the sensor was developed to undergo successful testing in real-world semiconductor manufacturing facilities.