Overview

To facilitate replacement of hazardous substances, UMC is committed to developing and promoting environmentally friendly and recyclable chemicals for use in semiconductor processes, and has already achieved fruitful results.

UMC is the first semiconductor manufacturer worldwide to achieve IECQ QC 080000 HSPM certification for all fabs and also the first to replace perfluorooctanoic acid (PFOA) related hazardous substances in the Company's manufacturing process in Taiwan, demonstrating compliance with internationally recognized standards for management of hazardous substances. Moreover, all of UMC's fabs in Taiwan have been awarded the Certificate of Cleaner Production Assessment by the Industrial Development Bureau of Taiwan's Ministry of Economic Affairs.

Reduction at the source instead of end-of-pipe treatment
To mitigate the environmental impact of our semiconductor manufacturing activities, UMC adopts a strategy of reduction at the source instead of end-of-pipe treatment. In the early days of the semiconductor industry, cleaning solvents were mixed with fluorinated compounds to improve cleaning efficiency, but fluorinated compounds have been found to be harmful for both humans and the environment. However, to reduce, recycle, or replace these solvents is not an easy task, as their formulations are owned by large international suppliers. Therefore, rather than treating the chemical waste at the end of the process, UMC has taken the initiative to reduce the volume of harmful chemicals at the beginning of the process.

One method of source reduction is to optimize cleaning efficiency. UMC employs nano-surface analysis (SEM/TEM/EDX) to inspect residue created by etching from the previous step in the manufacturing process, then adjusts the parameters of the etching equipment to reduce residue or destabilizing their structure to make it easier to remove. In the subsequent cleaning step, the composition, concentration, and temperature setting of the cleaning solvent are optimized to enhance its capability to remove residue thoroughly. For example, in the backend-of-the-line (BEOL) stage of forming copper interconnects, the wafer is soaked in a cleaning solvent. Through the method introduced above, the replacement cycle of the solvent can be extended, reducing the amount used by over 70%.

Another method is to customize cleaning solvents. In order to reduce dependence on foreign suppliers, UMC has collaborated with domestic chemical companies to jointly develop proprietary green solvent chemicals based on the characteristics of etching residues. Through the use of these replacements, UMC successfully phased out PFOS (Perfluorooctanesulfonic acid) in 2015, and in 2017, it led the industry in phasing out PFOA (Perfluorooctanoic acid).

Developing green chemicals
Since 2018, UMC has completed the development of one green chemical every year. In 2018, UMC independently developed a new green chemical using biodegradable and environmentally friendly materials. This chemical was officially launched at our Fab 12i in Singapore, where it was applied to the 40nm process, reducing costs by up to NT$40 million. In 2019, UMC replaced traditional alkaline and fluorine-containing cleaning agents with biologically derived acids from the tricarboxylic acid (TCA) cycle. This recyclable chemical was introduced to our Fab 12A in Tainan, and applied to the 14nm process, reducing the use of fluorine-containing solvents by 10 tons per year.

In 2020, UMC utilized a redox reaction process to recycle its cleaning solution while maintaining its halogen-free characteristics. This process, which is applicable to the BEOL of the 14nm and 22nm processes, reduces cleaning costs by 50% and prevents the generation of environmentally harmful fluorine-containing substances. In 2021, UMC developed a special green chemical using the tricarboxylic acid cycle, thus reducing the use of fluoride in the original cleaning solution by 98%. In 2022, UMC completed development of a critical BEOL metal cleaning process that complies with the EU environmental regulations, replacing traditional cleaning solvents with NMP-free (N-Methylpyrrolidinone-free) hydrophilic solvents. This special green chemical was successfully tested and applied at Fab 12A, reducing the use of chemical solvents containing NMP by approximately 13 tons in 2022 in comparison to 2021 under the same production capacity. UMC will gradually apply the NMP-free cleaning solvents to various processes at Fab 12A, and will continue to promote the NMP-free cleaning process at all fabs.

Implementing UMC's environmental sustainability commitment

UMC has been widely recognized for our achievements in green chemistry education, green safety substitution, chemical management, disaster prevention, and rescue readiness. UMC is the only company in Taiwan to win the Environmental Protection Administration’s "Green Chemistry Application and Innovation Award" in both the group and individual categories consecutively since the award was started in 2019.

Not to be content with our previous achievements, UMC's push for a revolution in greenhouse gas replacement continues. We aim to remain at the forefront of the industry in 2023 by developing a frontend-of-line (FEOL) process that reduces the use of nitrous oxide (N2O). The process is expected to reduce N2O usage by 9.63 metric tons annually, which is equivalent to a reduction of 2,551 metric tons of CO2. After development is complete, the process will be applied to various 22nm processes and other mature processes. This will enhance the UMC's competitiveness and will also be more environmentally friendly, reducing semiconductor manufacturing's impact on the planet and achieving our goal of minimizing our environmental footprint.