A New Ultra-Low K ILD Material Based On Organic-Inorganic Hybrid Resins
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A New Ultra-Low K ILD Material Based On Organic-Inorganic Hybrid Resins Ben Zhong1, Herman Meynen2, Francesca Iocopi3,4, Ken Weidner1, Stephane Mailhouitre3,4, Eric Moyer1, Cory Bargeron1, Paul Schalk1, Alan Peck1, Marleen Van Hove3, Karen Maex3,4, 1 Dow Corning Corporation, Midland, MI, USA 2 Dow Corning Corporation, Seneffe, Belgium 3 IMEC, Heverlee, Belgium 4 Katholieke Universiteit Leuven, Belgium. ABSTRACT A ULK material based on a siloxane resin has been developed that can be processed using spin-coating and thermal cure to yield porous low-k films. The chemical bonds between the resin and porogen groups prevent the phase separation of the porogen from the resin during curing and lead to extremely small pores. The highly hydrophobic thin films made from this material displayed dielectric constant of 1.8, breakdown voltage of 4 MV/cm, a cohesive strength > 60 MPa, excellent crack resistance, and an average pore size of 2.2 nm by Positron Annihilation Lifetime Spectroscopy (PALS) and 2.5-3.0 nm by Ellipsometric Porosimetry (EP). In this paper, our strategy for designing low-k materials, the material properties and initial integration results for this new material will be discussed. INTRODUCTION ILD materials with low dielectric constants are needed by electronic industry in order to reduce the IC interconnect delay, which is a major factor limiting the overall chip performance. An effective way to reduce the dielectric constant of a given material is to make it porous. Control over the pore size and distribution is critical to obtain films with suitable electrical properties and well-defined features. One of the approaches for producing porous films utilizes a blend of a curable resin with a removable porogen [1]. Dow Corning XLKTM technology [2] uses ammonia treatment to render H-resin a rigid porous structure, where a solvent serves as the porogen. In both cases, a good compatibility between the resin and the porogen is critical to achieve small pore size and narrow distribution. Here, we are presenting Dow Corning BOSS technology (Burning Out Sacrificial Spacers), which utilizes a porogen chemically linked to the resin, allowing the control of pore sizes in molecular levels. EXPERIMENTAL DETAILS BOSS resin samples in this study were prepared using the methods previously disclosed [3]. For nitrogen adsorption studies, bulk resin samples were cured at 470 °C for 1 h in a nitrogen stream in a muffler furnace. Nitrogen adsorption analysis on the cured solids was done on a Micromeritics ASAP2000 Analyzer. Thin film processing consisted of spin coating of resins on silicon wafers followed by thermal cure in nitrogen in a QTF furnace. The thickness the films was measured on a Woollam M-2000D Ellipsometer. For dielectric measurements, 20 nm of Ti and 1 µm of Al were deposited on the films using a Denon Sputter tool, the films were then annealed at 400 °C in nitrogen for 1 hour, and dot-to-dot capacitance was tested to obtain dielectric constants. Modulus and hardness were measured on a Digital5000 AFM along with a B1
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