Paper TF1-FrM6
Conformal CVD of MgO from Mg(H3BNMe2BH3)2 and Water: A New Process for Dielectric Barrier Layers in Plasma Display Panels

Friday, October 19, 2007, 9:40 am, Room 602/603

MgO is an attractive material for use as a dielectric barrier layer: it is a refractory oxide with a high melting point (2852 °C), high dielectric constant (9.8), wide bandgap (7.2 eV), and high secondary electron emission coefficient. These properties, combined with a good resistance to plasma erosion, make it suitable for use in AC plasma display panels, with the potential to significantly lower the firing voltage. Chemical vapor deposition affords simplicity, high deposition rate, and the ability to produce conformal coatings in deep features such as cylindrical vias. However, previous efforts to deposit MgO by CVD have not been satisfactory due to low deposition rate (~ nm/min), high deposition temperature (> 400 °C), or the presence of carbon or halogen impurities. Such issues derive from the lack of a suitable Mg-containing precursor molecule. We recently developed a completely new type of Mg precursor, bis(N,N,-dimethyldiboranamido)magnesium, here termed Mg(DMDBA)2. The vapor pressure of this precursor at room temperature is remarkably high, ~ 0.8 Torr, such that no carrier gas or heated delivery lines are required. The precursor is thermally stable but reacts readily with water to produce MgO films at temperatures as low as 225 °C. The high vapor pressure of the precursor allows us to achieve extreme conformality, e.g. a completely uniform film on a trench with depth/width ratio of 35:1, or a very rapid growth, e.g. deposition rate of a few hundred nm/min, or any compromise in between. We will present the CVD kinetics and the microstructure, crystallinity, electrical, and optical properties of MgO films grown from Mg(DMDBA)2 and H2O. Films grown at T > 500 °C on Si(100) or glass substrates are crystalline with a (002) texture; films grown at T > 400 °C are columnar; and films grown a lower temperatures are dense and smooth. The refractive index is 1.69-1.72 and the dielectric constant is 9.5, both of which are very close to the values for bulk MgO. The excellent CVD process characteristics and excellent film quality makes this an attractive new means to deposit the dielectric barrier layers in PDPs.