Thickness dependent dielectric strength of a low-permittivity dielectric film

The dielectric strength of a promising interlevel low relative permittivity dielectric is investigated for various film thicknesses and temperatures by using I-V measurements with metal-insulator-semiconductor (MIS) structures. It is found that the dielectric breakdown mechanism also depends on thickness. For relatively thick films (thickness >500 nm), the dielectric breakdown is electromechanical in origin, i.e. the dielectric strength is proportional to the square root of Young's modulus of the films. By scanning electron microscopy (SEM) observation, a microcrack in thicker films may contribute to a lower value of Young's modulus, which may confirm that the electromechanical breakdown is the dominant mechanism for dielectric breakdown of thicker films. In addition, the thickness dependent dielectric strength can be described by the well-known inverse power-law relation by using different exponents to describe different thickness ranges, However for thinner films, i.e., <500 nm, the experimentally observed relationships among the dielectric strength, Young's modulus, and film thickness cannot be explained by the existing models.

[1]  Paul S. Ho,et al.  Materials Issues and Characterization of Low-k Dielectric Materials , 1997 .

[2]  L. Peters.  Pursuing the perfect low-k dielectric , 1998 .

[3]  Johannes Heitz,et al.  Pulsed-laser deposition of crystalline Teflon (PTFE) films , 1998 .

[4]  Kuniaki Tanaka,et al.  Characteristics of Polytetrafluoroethylene Thin Films Prepared by Ionization-Assisted Deposition , 1998 .

[5]  K. H. Oh,et al.  Variation of trapping/detrapping properties as a function of the insulator size , 1993 .

[6]  Fumihiko Kannari,et al.  Deposition of fluoropolymer thin films by vacuum‐ultraviolet laser ablation , 1994 .

[7]  J. Fothergill.  Filamentary electromechanical breakdown , 1991 .

[8]  V. K. Agarwal,et al.  Thickness dependence of breakdown field in thin films , 1971 .

[9]  F. G. Shi,et al.  Low-k dielectrics for ULSI multilevel interconnections: thickness-dependent electrical and dielectric properties , 2000, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation (Cat. No.00CH37075).

[10]  Alun S. Vaughan,et al.  Morphology and the electro-mechanical breakdown model in polyethylene , 1999, 1999 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (Cat. No.99CH36319).

[11]  P. Bjellheim,et al.  Electric breakdown strength of aromatic polymers: dependence on film thickness and chemical structure , 1991 .

[12]  K. Stark,et al.  Electric Strength of Irradiated Polythene , 1955, Nature.

[13]  John B. Pethica,et al.  The influence of mechanical stress on the dielectric breakdown field strength of thin SiO2 films , 1998 .

[14]  M. Ieda,et al.  High-Field Conduction and Electrical Breakdown of Polyethylene at High Temperatures , 1985 .

[15]  T. J. Lewis.  New electro-mechanical concepts of the primary mechanisms of electrical breakdown in liquids , 1996, ICDL'96. 12th International Conference on Conduction and Breakdown in Dielectric Liquids.

[16]  J. Hammes,et al.  Adhesion and Dielectric Strength of Ultra-Low Dielectric Constant PTFE Thin Films , 1997 .

[17]  Reinhard Schwödiauer,et al.  Charge stability of pulsed-laser deposited polytetrafluoroethylene film electrets , 1998 .

[18]  Takanori Katoh,et al.  Synchrotron radiation ablative photodecomposition and production of crystalline fluoropolymer thin films , 1996 .

[19]  G. Damamme,et al.  Effect of the insulator size on the breakdown strength , 1997, IEEE 1997 Annual Report Conference on Electrical Insulation and Dielectric Phenomena.

[20]  Robert D. Miller.  In Search of Low-k Dielectrics , 1999, Science.

[21]  V. K. Agarwal,et al.  Thickness dependent studies of dielectric breakdown in Langmuir thin molecular films , 1973 .

[22]  U. Dahmen,et al.  High-Resolution-Electron-Microscopy Investigation of Nanosize Inclusions , 1997 .

[23]  Yoshimichi Ohki,et al.  Dielectric breakdown of new type polymerized polyethylene using a single-site catalyst , 1999 .

[24]  Frank G. Shi,et al.  Thickness dependence of morphology and mechanical properties of on-wafer low-k PTFE dielectric films , 2000 .

[25]  David Hsu,et al.  ILD thermal stability in deep-submicron technologies: from thin to ultrathin dielectric films , 1999, Advanced Lithography.

[26]  Frank G. Shi,et al.  Thickness dependence of elastic modulus and hardness of on-wafer low-k ultrathin polytetrafluoroethylene films , 2000 .