About 10 years ago, copper replaced aluminum for back end of line (BEOL) interconnects in the semiconductor industry. This was due mainly because of some key features of copper compared to their aluminum counterparts:
The downside of using copper for improved semiconductor performance is that it created a copper rich effluent from electroplating that is considered hazardous waste. This copper rich waste stream also contains high levels of hydrogen peroxide that in most cases cannot be treated onsite using conventional effluent treatment processes. The result is that most semiconductor manufacturers resort to having a certified waste contractor take and treat the plating solutions offsite. All companies have a social and ethical responsibility to treat wastes generated by their operations using best availability technologies (BAT) and most take this very seriously.
To that end, to ship hazardous material offsite is not considered an environmentally sustainable practice and moreover it has a considerable financial implication to their bottom line. Semiconductor manufacturers like Samsung, Intel and others are keen to invest in green technologies that enable them to treat hazardous wastes onsite in order to achieve their strict sustainability and environmental objectives.
Fortunately, many semiconductor manufacturers have taken the initiative to utilize metal recovery techniques such as electrowinning to quantitatively remove the copper from the waste effluent and destroy the hydrogen peroxide. Electrowinning has been used in the mining and metals industry for over a century but is now being embraced by the hi-tech industry as well. The result is an effluent that can now be easily treated by their existing effluent treatment facility.
Not only does this eliminate the increasingly expensive disposal fees of copper liquid waste, but also produces saleable copper as additional revenue or recycle.
While the amount of saleable copper generated does not justify the capital expenditure of a new electrowinning process, the hundreds of thousands of dollars saved from paying waste disposal contractors to treat the waste more than justifies the investment. In most cases the financial payback can be 6-12 months while the sustainability and good karma lasts forever.
In one example, by investing in a small custom design electrowinning plant to treat copper plating waste, a leading semiconductor manufacturer achieved:
Certainly, examples such as this one clearly show that the semiconductor industry is leading by example by embracing green technologies to overcome environmental, technical and financial challenges.
Image credit: "wafer - 2," Windell Oskay © 2009, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/