Development of Reflow Fill of CGeSbTe Films for Sub-20 nm Cells in 3D Cross-Point Memory

To obtain reliable and scalable cells in 3D cross-point memory, endurance failures caused by voiding from etching damage to memory cells should be resolved to preserve the properties of GeSbTe (GST) phase-change materials. Herein, the fabrication of a damascene cell without patterning, which relies on the bottom-up fill of carbon-doped GST layers into confined cells, is proposed as a promising solution. The reflow fill of the sputtered carbon-doped GST films into confined cells at high-temperature and low-power conditions is demonstrated, and a mechanism in which Sb and Te transfer into the cell through vapor transfer and viscous flow due to capillary pressure is verified. The aspect ratio increases from 2 to 7.7 under enhanced vaporization of Sb and Te as well as the capillary force. The advanced reflow-fill process using a laser can overcome the limit of the conventional reflow-fill technology by increasing the atomic mobility above the melting temperature. Based on the proposed method, 19 nm cross-point memory devices are successfully integrated together with the Ovonyx threshold switch and appropriate memory windows are secured. Furthermore, the 9 nm cells exhibit reliable endurance cycles over 10(8).

Automated summary

In order to address endurance failures caused by etching damage in 3D cross-point memory, a non-patterning filling method is proposed, which involves the reflow fill of carbon-doped GST films into confined cells. This method successfully resolves endurance failures caused by voiding and allows for the preservation of the properties of GST phase-change materials.