Effect of C2H2F4/CF4O with low global warming potentials on SiNx etching as a CHF3 replacement

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.