Effect of C2H2F4/CF4O with low global warming potentials on SiNx etching as a CHF3 replacement
Kyung Lim Kim1,2, Jong Woo Hong3, Young Woo Jeon4
1Department of Semiconductor and Display Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
None:
As the size of the device continues to decrease due to the increasing demand for faster processing speed and lower power consumption in semiconductor integrated circuit device technology, the double patterning process is widely used. The SiNx used in this double patterning process requires high etch rate and high etch selectivity over SiOx, while at the same time achieving an anisotropic etch profile. In the past, gases such as CHF3/CF4 were used for SiNx etching of double patterning. However, the low etch selectivity of these gases and their high global warming potential (GWP) have led to the need for alternative gases. To address this issue, in this study, the effect of alternative gases instead of CHF3 on SiNx etching characteristics has been investigated. When C2H2F4 was used instead of CHF3, both etch rate and etch selectivity were improved, but issues such as trenching and increased critical dimension (CD) were observed. When CF4O was added to C2H2F4, both etch rate and etch selectivity were further improved while eliminating trenching issue. The analysis showed that C2H2F4 compared to CHF3 promoted stronger polymer formation, thereby improving mask passivation while trenching defects occurred due to polymer deposition. For the C2H2F4 + CF4O mixture, increased fluorine dissociation resulted in higher SiNx etch rates and consequently better etch selectivity, and trenching was eliminated by increasing gas dissociation and decreasing polymer production. Million Metric Tones of Carbon Equivalent (MMTCE) measurements showed that C2H2F4 decreased by approximately ~83.9% and C2H2F4 + CF4O by approximately ~75.2% of greenhouse gas emissions compared to CHF3. Therefore, the results obtained with alternate gases are next-generation eco-friendly etch processes that can be applied to semiconductor devices such as Fin Field Effect Transistor (FinFET), 3D Not-AND (NAND), and other advanced semiconductor and display manufacturing technologies.
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