Preventing fin bending in humid conditions

As semiconductors get smaller, so do their individual parts. Fin field-effect transistors (FinFETs) are commonly used in semiconductors, allowing the electric current to flow through a silicon fin and enabling better control than other transistors.

Keeping the microscopic fins spaced perfectly can be tricky, so Satake et al. studied the humidity conditions surrounding the FinFET lifecycle and how this excess water can cause fin bending.

“Silicon fin bending is a phenomenon in which the narrow silicon fins used in FinFET devices become deformed and lean toward neighboring fins,” said author Makoto Satake.

It can occur in wet environments from capillary action or after film deposition due to mechanical stress. When the tiny fins touch, the defect runs the risk of rendering the entire device unusable.

“In our work, we focused on a different mechanism: fin bending that occurs after dry etching simply through exposure to humid air,” Satake said.

The researchers studied silicon fin structures created by dry etching, then exposed the structures to different humidity levels. They analyzed the structures to compare the capillary force from the humidity with the elastic restoration force inherent to the fin and found that bending occurs when the relative humidity exceeds approximately 60%.

“Our study suggests that humidity control during wafer storage and transportation is important for preventing fin bending,” Satake said. “Without proper humidity control, fin bending may be mistaken for a dry-etching defect.”

The researchers hope to establish more effective methods for preventing pattern collapse in high-aspect-ratio device architectures, including FinFET devices.

Source: “Mechanism of silicon fin bending during air exposure after dry etching,” by Makoto Satake, Takeshi Ohmori, and Naoyuki Kofuji, Journal of Vacuum Science & Technology B (2026). The article can be accessed at https://doi.org/10.1116/6.0005733 .