Development of Innovative Self-Aligned SSL Mold (SASM) Scheme with Remarkable Reduction of Chip Size

We developed a Self-Aligned String-Select-Line (SSL) Mold (SASM) scheme where the SSL transistors are independently formed after the main word-line structure, which doesn’t need any dummy hole strings for SSL separation process. The SASM scheme can maximize the gross die by more than 11% by enabling higher density of cell array in the lateral direction. Critical cell characteristics such as erase efficiency, SSL operation window, SSL HCI, cell current, and SSL resistance (SSL RS) are optimized by improving fabrication and operation conditions. The SASM scheme has been successfully integrated in the 9th-generation Vertical NAND (V-NAND) product, suggesting novel memory cell design for next generation V-NAND product with higher bit density and reduced chip size.