半導體業全氟化合物溫室氣體排放量計算盤查公式差異比較及減量評估

Abstract

近幾年之氣侯環境變遷等問題已使溫室氣體排放減量躍升為國際各界矚目議題。半導體業於乾蝕刻(Dry Etch)及化學氣相沉積(Chemical Vapor Deposition, CVD)製程所使用之全氟化合物(PFCs)氣體， 是一種高暖化潛勢的溫室氣體，其在對溫室效應的貢獻量雖然較其他產業為小，但也不容忽視。 本研究以晶圓代工半導體廠為例，對乾蝕刻與化學氣相沉積製程中所使用之全氟化合物氣體，依據2006 IPCC Guidelines的 Tier 2a 與Tier 2b盤查公式進行排放量計算差異比較，此外亦進行化學氣相沉積製程清潔氣體以C4F8進行取代時之排放減量效益評估。針對某半導體廠之案例研究結果顯示，由Tier 2a所計算的排放量約35,999 ton CO2e /年，較Tier 2b多出1,155 ton CO2e /年，總排放當量約增加3%，因此採用Tier 2b公式對廠區排放量計算會較有利。而安裝不同製程尾氣處理設備對排放量差異比較結果顯示，採用燃燒式尾氣處理設備可較電熱式少132,005 ton CO2e /年排放量，因此燃燒式尾氣處理設備對PFCs削減成效較佳。另製程氣體若以C4F8取代C3F8，因氣體使用率(Ui值)較高可降低製程過程耗用量，對於整體全氟化合物溫室氣體排放當量約可減少29.8%，相當於10,389 ton CO2e /年 排放量；且使用之含氟氣體可減量達39.4%，相當於每年約減少15,154kg使用量，每年亦可節省約247萬元成本支出，因此證明C4F8取代C3F8氣體對溫室氣體排放減量是一種有效之方法。

In recent years, the global climate change caused by the greenhouse gas emission has gained worldwide attention. The CVD and Dry Etch process in semiconductor industry use a significant amount of PFCs (Perfluorinated Carbons) gases. They are high global warming potenitial gases and thus their effects can not be neglected. This research focuses on the comparison of PFCs emission estimation methods and reduction potential of semiconductor factory based on the 2006 IPCC Guidelines Tier 2a and Tier 2b calculation methods. The results reveal that the PFCs emission of greenhouse gas is 35,999 ton CO2e/year according to Tier 2a method, which is 3% (1,155 ton CO2e/year) higher than that based on Tier 2b emission estimation. Thus adopting Tier 2b method to calculate the PFCs emission is more beneficial for the semiconductor industry. On comparing the local scrubber devices for PFCs emission control, by adopting fuel combustion based scrubbers the PFCs emissions can be less than that by adopting electric heating scrubber, which is 29.8% in reduction (132,005 ton CO2e/year). For the emission estimation of substituting PFCs from C3F8 to C4F8, it reveals that the utilization rate of PFCs can be increased and thus the overall PFCs emission can be reduced by 29.8% in terms of CO2 equivalent emission (10,389 ton CO2e/year). And the PFCs gas use can be reduced by 39.4% (15,154 kg PFCs). This corresponds to a cost benefit of $2.47 million NTD/year.