Feasibility of Etching Studies on BCN Thin Films

Abstract

Investigation of wet chemical etching Boron carbon nitride (BCN) thin films deposited by dual magnetron sputtering of B 4 C (DC) and BN (RF) targets was conducted. BCN, a low-k dielectric material, is a potential candidate as inter-layer dielectric (ILD) in VLSI process. A common aluminum etchant consisting of phosphoric acid (H 3 PO 4 ), nitric acid (HNO 3 ) and acetic acid (CH 3 COOH) was tested for its feasibility as a good etchant for BCN thin films. The etching studies were performed on BCN films that were deposited at room temperature, 200 • C and 300 • C as a function of various N 2 /Ar gas flow ratios in an rf sputtering technique. It was found that the film deposited at higher temperatures shows lower etching rate trends. Activation energies (E a ) were calculated for each N 2 /Ar gas flow ratio with the help of Arrhenius plots and compared with respect to elemental compositions of the films. Boron carbon nitride compounds are emerging as the potential candidates of great technological importance due to their favorable electronic, mechanical and optical properties for various device applications.1-3 BCN films with high density, hardness and Young's modulus in the range of 2.0-2.5 g/cm 3 , 5-13 GPa and 110-150 GPa, respectively, have been reported.4 Umeda et al. were able to deposit non-porous BCN films with dielectric constant as low as 1.9.5 A low dielectric constant (i.e. low-k) value of 2.13 with high breakdown strength, resistivity of 3.4 MV/cm and 3E12 .cm have been reported which strengthens the claim that BCN is a robust material in terms of device processing in VLSI integration. 6 The burning issue is integration of uniform, thin low-k film into manufacturing processes like damascene structures for interconnections.7 It has been demonstrated that copper diffuses faster in oxide based low-k films.8 This creates serious reliability problems. Recently, we demonstrated that BCN is robust to the copper diffusion even at higher annealing temperatures of 400• C. 9 BCN with high density and low porosity is expected to be a good candidate as ILD.The technique, etch rate and selectivity to the low-k materials and the characterization of the by-product during etching have attracted great attention to researchers and scientists recently. BN was tested as a potential low-k material before BCN. BN films deposited by plasma-assisted chemical vapor deposition (PACVD) have reliability issues like cracking and film peeling off the substrate as reported by Kimura et al. It has been found that adding carbon atoms to BN films is effective in resolving these issues. 10 Device processing requires steps such as wet chemical etching, electro chemical plating and chemical mechanical polishing (CMP). Watanabe et al. established that BCN film with lower oxide composition is robust to such wet chemical influences.11 In case of similar materials like boron nitride (BN), the sp 2 bonds are preferentially etched than the sp 3 ones. 12Based on the limited knowledge of different etching techniques of BN and B 4 C thin films, fur...

(Invited) NiO/ β-(Al x Ga1-x )2O3 /Ga2O3 Heterojunction Lateral Rectifiers with Reverse Breakdown Voltage > 7kV

“…The β-(Al x Ga 1−x ) 2 O 3 /β-Ga 2 O 3 heterostructures were grown in an Agnitron Agilis 500 MOCVD reactor with trimethylaluminum (TMAl), triethylgallium (TEGa), and oxygen (5N) as precursors, and argon (6N) as carrier gas (19,20) . The TMAl and TEGa precursors were used to grow 70 nm thick Si doped β-(Al x Ga 1−x ) 2 O 3 layer on ~300 nm UID β-Ga 2 O 3 buffer layer, respectively, on a Fe doped (010) β-Ga 2 O 3 1" substrate (Synoptics).…”

“…An additional advance comes from use of the wider bandgap alloy (Al x Ga 1−x ) 2 O 3 in place of Ga 2 O 3 . (Al x Ga 1−x ) 2 O 3 alloys with compositions up to x = 40% have been grown with good crystalline quality on (010)-oriented β-Ga 2 O 3 substrates, and x ≥ 50% can be obtained on (100) and (−201) β-Ga 2 O 3 substrates when the layers are grown by Metal Organic Chemical Vapor Deposition (MOCVD) (18)(19)(20)(21)(22)(23) . Phase pure β-(Al x Ga 1−x ) 2 O 3 films with Al content up to 27% have been grown with this technique (21)(22)(23) , which is promising from the viewpoint that this is the standard epitaxial growth method for most compound semiconductors.…”

“…While most Ga 2 O 3 -based rectifiers to date have been vertical geometry to increase the current-carrying capability (24)(25)(26)(27)(28)(29)(30)(31)(32) , there is also interest in lateral geometry devices (33) , whose breakdown voltage can be more easily scaled by increasing the contact separation distance. Sundaram et al (20) showed that addition of a 30 nm-thick β-(Al 0.22 Ga 0.78 ) 2 O 3 cap to an n-type β-Ga 2 O 3 layer grown by metal organic chemical vapor deposition increased the breakdown voltage by ~20%. The cap increased the surface Schottky barrier with Pt metal, resulting in reduced carrier injection under reverse bias.…”

A brief overview of RF sputtering deposition of boron carbon nitride (BCN) thin films

“…Prakash et al investigated the wet chemical etching of BCN thin films deposited using dual magnetron sputtering of B 4 C (DC) and BN (RF) targets in a mixture of N 2 /Ar ambient using [111]. They used a combination of H 3 PO 4 , HNO 3, and CH 3 COOH as a typical aluminum etchant to test its feasibility as a good etchant for BCN thin films.…”