Electron-Enhanced Deposition of Titanium-, Silicon- and Tungsten-Containing Films at Low Temperatures Using Volatile Precursors with Various Reactive Background Gases

Electron-enhanced atomic layer deposition (EE-ALD) and electron-enhanced chemical vapor deposition (EE-CVD) can be employed for the low temperature deposition of thin films using volatile precursors with various reactive background gases (RBGs). EE-CVD expands on the previous demonstration of TiN EE-ALD using alternating Ti(N(CH3)2)4 (tetrakisdimethylamino titanium (TDMAT)) and electron beam exposures with NH3 RBG. During EE-CVD, the electron beam and the RBG are present continuously. Together with the RBG and electron beam incident on the surface, the volatile precursor is pulsed into the vacuum chamber to control the film growth. In this survey, the metal or metalloid precursors were TDMAT, Si2H6, and W(CO)6. The RBGs were O2, NH3, CH4, and H2. The study focused on TiO2 EE-ALD and SiN, SiO2, SiCx, SiHx, W2N, WOx, and WCx EE-CVD. Thin film growth was monitored using in situ 4-wavelength ellipsometry. To first illustrate EE-ALD, TiO2 EE-ALD was performed at T < 80 °C using alternating TDMAT and electron beam exposures together with O2 RBG. The growth rate for the TiO2 EE-ALD was ∼0.7 Å/cycle. The TiO2 EE-ALD films were nearly stoichiometric, displayed crystallinity, and were smooth as measured by atomic force microscopy (AFM). Other Ti-containing EE-ALD films were deposited using CH4 and H2 RBGs. Subsequently, to demonstrate EE-CVD, SiCx EE-CVD was performed at T < 100 °C using repeating Si2H6 pulses with continuous electron beam and CH4 RBG exposures. XPS revealed a 1:1 Si/C stoichiometry for a CH4 RBG pressure of 0.45 mTorr and C-rich films for higher CH4 RBG pressures. The SiC EE-CVD growth rate was ∼0.4 Å per Si2H6 pulse. The stoichiometric SiC EE-CVD films were smooth as measured by AFM. Other Si-containing EE-CVD films that were deposited included SiO2, SiN and SiHx. In addition, W2N was deposited with EE-CVD at T < 120 °C using repeating W(CO)6 pulses with continuous electron beam and NH3 RBG exposures. The W2N EE-CVD growth rate was ∼0.17 Å per W(CO)6 pulse. The W2N films had a resistivity of ∼450 μΩ cm. The W2N EE-CVD films also displayed crystallinity and high purity. Other W-containing EE-CVD films that were deposited included WOx and WCx. This survey shows that the EE-ALD technique can be extended to EE-CVD with various RBGs to deposit a broad range of materials at low temperatures including oxides, nitrides and carbides.