February 7, 2012 — Novellus Systems (NASDAQ:NVLS) debuted the VECTOR Strata dielectric deposition tool for high-volume manufacturing of vertically integrated memory (VIM) Flash devices. VECTOR Strata aims for ultra-smooth films with exceptional defect performance, enabling in-situ deposition of the alternating silicon-based layers used in the formation of the VIM structure.
It joins the ALTUS ExtremeFill tungsten chemical vapor deposition (CVD) system for this emerging semiconductor manufacturing market.
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| Figure 1a) VECTOR Strata’s ultra-smooth films deposited in an alternating layer film stack in comparison to | b) conventional PECVD films. |
VIM is an alternative to planar NAND Flash devices, which experience parasitic inter-wire capacitance issues and shifts in the threshold value of a memory cell during programming at small geometries. At sub-20nm dimensions, the number of electrons in the floating gate of a traditional planar NAND flash device is reduced to the point where multiple bits per cell are no longer possible. Different 3D VIM designs require specific materials, all made with alternating layers of silicon-based films. Each pair of alternating layers is used to form a memory cell, and up to 64 pairs of alternating layers are expected to be used in the formation of a VIM chip.
Novellus designed the VECTOR Strata film tool for this manufacturing process, where underlying film roughness and defects within each layer can be magnified while building up the VIM structure. It targets exceptional nano-particle control and ultra-smooth film deposition to avoid word line edge variability. The system optimizes gas delivery and RF distribution.
The VECTOR’s multi-station sequential processing (MSSP) architecture enables high-volume production of VIM Flash in a lower-cost process. The MSSP architecture allows for independent temperature and flow control to deposition stations.
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| Figure 2. Atomic force microscope (AFM) images of ultra-smooth VECTOR Strata films, showing film roughness that is comparable to the underlying substrate. | |
Leading memory manufacturers are using VECTOR Strata for VIM development.
Novellus Systems Inc. (Nasdaq:NVLS) provides advanced process equipment for the global semiconductor industry. For more information, please visit www.novellus.com.