Presentation Information
[10p-S1-5]Suppression of SiO2 Deformation and Warpage in 3D Flash Memory Stacked Structures through Investigated Drying Processes
〇Shunsuke Aita1, Kazutaka Suzuki1, Katsuhiro Sato1, Takatsugu Sakai2, Shunsuke Saito2 (1.KIOXIA Corp., 2.Sandisk GK)
Keywords:
3D flash memory,deflection,drying process
This study investigates drying conditions to suppress SiO2 bending in the WL Replace process for 3D flash memory, where reduction of the staircase contact region is essential for chip area scaling. In the WL Replace process, an ON stack composed of SiO2 and SiN is patterned, the SiN is removed by phosphoric acid etching, and the structure is then filled with tungsten (W). However, during drying after etching, capillary force-related Laplace pressure can deform the SiO2 dielectric, leading to WL closure and subsequent metal fill defects. To evaluate bending suppression performance, three drying conditions were compared: conventional drying method A, Laplace pressure-reducing condition B, and adhesion-reducing condition C. An ON stack of about 2.4 μm was formed on a Si substrate, and slit and pillar hole patterns were fabricated to simulate anti-bending supports. After phosphoric acid etching and drying, W was deposited, and cross-sectional SEM observations were used to quantify WL closure frequency. SSPI was also calculated from the etched cross-sectional profile. The results showed that condition A caused SiO2 bending and incomplete W filling, while condition B effectively suppressed closure and enabled defect-free W deposition. Condition B achieved an SSPI of 24.7 mN/m, indicating significantly better bending suppression than condition A (136 mN/m or less). These findings demonstrate that optimizing drying conditions, especially by reducing Laplace pressure, is highly effective for preventing structural collapse and improving process margin in staircase scaling for 3D flash memory.