Study of layered diamond like carbon and PECVD fluorocarbon films for ultra low dielectric constant interlayer dielectri
- PDF / 1,023,775 Bytes
- 11 Pages / 584.957 x 782.986 pts Page_size
- 43 Downloads / 219 Views
etharaman Ramachandran Lam Research Corporation, Fremont, California 94538, USA
Lawrence Overzet, Matthew Goeckner, and Gil-Sik Lee The University of Texas at Dallas, Richardson, Texas 75083, USA (Received 11 July 2015; accepted 25 February 2016)
Diamond like carbon (DLC) films deposited using CH4 and Ar and amorphous fluorocarbon (a:C-F) films deposited using CF4 and Si2H6 as precursors were optimized for ultra-low dielectric constant applications by tuning pressure, substrate temperature, and flow rate ratio. Sixty three films belonging to three stack configurations possessed good morphology and adhesion post DLC deposition. Structural and mechanical properties with respect to film integrity, adhesion, roughness, and shrinkage rate were studied. Internal and interface stress distribution results in the increased stability of as deposited DLC–a:C-F–DLC sandwich layers in comparison to a:C-F–DLC stacks. Annealed a:C-F with DLC top coat and As deposited a:C-F are similar in bonding structure. Failure mode is buckling delamination failure with increasing severity in films with higher oxygen incorporation and can be preserved by annealing the fluorocarbon component or providing a DLC base coat. Effect of process parameters on properties relevant to integration has been determined.
I. INTRODUCTION
As semiconductor device dimensions continue to shrink, interconnect delays have become significant in comparison to transistor performance delays. The 2013 update to the ITRS roadmap details the difficult challenges for .22 nm node as the introduction of new dielectric materials to meet conductivity challenges and reduce dielectric permittivity.1 For the 10 nm node, materials with k-values between 2.4 to 2.5 may still be utilized while retaining currently used integration scheme. However, a materials solution for the sub-7 nm node, that requires materials with a k value of 2.2, is not yet available.2 Amorphous fluorocarbon (a:C-F), amorphous hydrogenated carbon (a:C-H), DLC, and fluorinated DLC films have previously been individually evaluated as potential candidates for ultra-low-k dielectric applications. DLC is typically defined as “amorphous carbon (a:C) or hydrogenated amorphous carbon (a:C-H) with a significant fraction of sp3 bonds”.3 The three kinds of electronic hybridizations possible in C, namely, sp3, sp2, and sp1 (Ref. 4) impart to DLC an entire range of chemical,
Contributing Editor: Mauricio Terrones a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.97
mechanical, electrical, and electrochemical properties. Figure 1 shows that DLC films can be comprised of a combination of these three types of bond hybridizations without being limited by the properties of any one type of allotrope. While DLC has properties similar to diamond in terms of its hardness, elastic modulus, and resistance to chemical attack, it is a completely amorphous thin film with no grain boundaries.5 It is possible to deposit a-C:H films with higher sp2 and hydrogen contents using plasma-enhanced chemical vapor
Data Loading...
