Adhesion of chemical vapor deposited boron carbo-nitride to dielectric and copper films
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K.H. Junker Freescale Semiconductor, Austin, Texas 78721
Y-M. Sun and J.M. White Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712
J.G. Ekerdtb) Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (Received 26 January 2005; accepted 12 May 2005)
The interfacial adhesion energy was studied using the four-point bend method for boron carbo-nitride (BCxNy) deposited on dielectric and copper films. Twenty-five nanometer BCxNy films were deposited by chemical vapor deposition at 360 °C and 1 Torr using dimethylamine borane with no coreactant, NH3, or C2H4, producing different composition films, BC0.37N0.15, BC0.11N0.49, BC0.92N0.07, with dielectric constants of 4.1, 4.2, and 3.8, respectively. BCxNy films were deposited on dense and porous dielectrics, and copper. BCxNy films adhered strongly to the dielectric films and the composite beams snapped before debonding, revealing that the critical debond energy Gc exceeded 10 J/m2. The adhesion of BCxNy to oxidized copper increased with carbon content in the film, with the BC0.92N0.07 film beams snapping, and is possibly related to covalent bonding between surface oxygen and carbon in the film.
I. INTRODUCTION
The semiconductor industry is investigating many new materials to improve device performance, including low-k dielectrics and diffusion barriers to reduce the resistance–capacitance delay associated with copperbased interconnects.1 Boron carbo-nitride (BCxNy) is a potential insulating diffusion barrier; films with dielectric constant (k) less than 4 can be deposited by thermal chemical vapor deposition (CVD) at 360 °C.2 Current Si-based insulating barrier films (silicon nitride, silicon carbo-nitride, and silicon carbide), with k ranging from 4 to 7,3–6 are deposited by plasma enhanced CVD (PECVD), a deposition process that can potentially damage the more fragile porous ultra-low-k (ULK) films (k < 2.6).7 Any insulating diffusion barrier must meet many requirements, including thermal and chemical stability, excellent barrier properties, low leakage current, etch selectivity, and adhesion to the other interconnect materials.1 Good adhesion to both the interlayer dielectric (ILD) and copper is needed to prevent delamination a)
Present address: Texas Instruments, 13560 North Central Expressway, Dallas, TX 75243. b) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0279 2218
http://journals.cambridge.org
J. Mater. Res., Vol. 20, No. 8, Aug 2005 Downloaded: 30 Mar 2015
during chemical mechanical polishing (CMP). Additionally, poor adhesion can contribute to higher electromigration of copper at the copper/insulating barrier interface, which is a common interconnect reliability failure.8 The work of adhesion at an interface is a complex phenomenon that encompasses different mechanisms, such as molecular attraction, interdiffusion, mechanical interlocking, and electrostatic attraction.9 The four-point bend method has emerged as a common tec
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