Application of a gate blocking layer on glass by using TiO₂ as a high-k material for a nonvolatile memory

Thin films of high dielectric constant materials, specifically titanium dioxide, were investigated as potential replacements for silicon dioxide, which is generally used as a blocking layer for nonvolatile memory devices. A silicon-oxynitride layer using nitrous-oxide plasma as a tunneling layer and using titanium-dioxide as a blocking layer was deposited to fabricate nonvolatile memory on rough poly-silicon. Titanium dioxide thin films were deposited using atmospheric pressure chemical vapor deposition and spectroscopic ellipsometry and scanning electron microscopy were used to measure the physical properties. A metal-insulator-semiconductor device was fabricated to measure the current density-electric field and a nonvolatile memory device on glass was fabricated to measure the gate voltage - drain current, drain voltage - drain current and retention characteristics. The leakage current density of the sample deposited at 250°C was the lowest (1.4 × 10^-9 A/mm ² at 2 MV/cm). The threshold voltage shift of the nonvolatile memory device on glass was 1.6 V and the subthreshold swing (∼270 mV/decade based on the maximum slope in the transfer curve) and the on/off current ratio (∼10⁶) remained nearly constant during the programming/erasing operations.