Hafnium diboride thin films by chemical vapor deposition from a single source precursor

Abstract

High quality, stoichiometric thin films of hafnium diboride are deposited by chemical vapor deposition from the precursor Hf͓BH 4 ͔ 4 at deposition temperatures as low as 200°C. An activation energy of 0.43 eV͑41 kJ/ mol͒ is obtained for the overall process as monitored by temperature programmed reaction studies. Films deposited at low temperatures ͑Ͻ500°C͒ are structurally amorphous to x-ray diffraction; a 12 nm thick film is sufficient to prevent copper diffusion into silicon during a 600°C anneal for 30 min. Films deposited above 500°C are crystalline, but have a columnar microstructure with low density. All the films are metallic, but the low temperature amorphous films have the lowest resistivity ϳ440 ⍀ cm. The process is also highly conformal, e.g., a 65 nm wide trench with a 19:1 depth-width aspect ratio was coated uniformly.

Crystalline texture in hafnium diboride thin films grown by chemical vapor deposition

“…Hu et al [21] observed the presence of Si on the top of epitaxial ZrB 2 films grown at similar temperatures. We previously demonstrated that there is a reaction barrier for the precursor Hf(BH 4 ) 4 to react with a fresh silicon surface [14]; here, we interpret that Si diffuses to the film surface at high growth temperatures and reduces the precursor reaction probability or otherwise interferes with HfB 2 growth. The low growth rate and the high silicon diffusivity are potential problems for using MB 2 films as buffer layers for growing GaN epitaxially on Si, especially because Si is a dopant in GaN [23].…”

“…The deposition system and the growth procedure are described in detail elsewhere [14]. Unless specified, films were grown with a fixed precursor feed rate of 3.2 Â 10 16 molecules/s, for which the precursor partial pressure is estimated to be 10 À5 À10 À6 Torr inside the chamber; films were grown to $300 nm thick by controlling the growth time.…”

“…In contrast, the textures of transition metal diboride thin films have received much less attention [12,13]. We recently reported that stoichiometric and impurity-free HfB 2 thin films can be grown by thermal chemical vapor deposition (CVD) from the single-source precursor Hf(BH 4 ) 4 , which is halogen-, oxygen-, and carbon-free [14]. From temperature programmed reaction studies, we found that the apparent activation energy of the deposition process is only 0.43 eV (41 kJ/mol) and that the growth transits from reaction-limited to flux-limited at $350 1C.…”

Three-dimensional self-assembled photonic crystals with high temperature stability for thermal emission modification

“…A static CVD system, operating at high precursor pressures (15 Torr), was built to achieve conformal coatings on silica colloidal crystal templates. Hafnium borohydride (solid at room temperatures with a 15-Torr vapour pressure) was used as a single source precursor for HfB 2 CVD and was prepared in an inert atmosphere 36,41,42 . Equipment needed for the static CVD included a rough vacuum pump, ultra high purity argon, tube furnace, two glass tubes (0.75 inches in diameter connected by an on/off valve with ground glass joints).…”

Chemical Vapor Deposition of Copper: Use of a Molecular Inhibitor to Afford Uniform Nanoislands or Smooth Films

“…42 The substrate is heated radiatively with a tungsten filament; the substrate temperature is measured with a K-type thermocouple clamped on top of the mounting platen. A reference thermocouple at the back of heating stage is also used to monitor the temperature.…”