Material removal mechanism in chemical mechanical polishing: theory and modeling

The abrasion mechanism in solid-solid contact mode of the chemical mechanical polishing (CMP) process is investigated in detail. Based on assumptions of plastic contact over wafer-abrasive and pad-abrasive interfaces, the normal distribution of abrasive size and an assumed periodic roughness of pad surface, a novel model is developed for material removal in CMP. The basic model is MRR=/spl rho//sub w/NVol/sub removed/, where /spl rho//sub w/ is the density of wafer N the number of active abrasives, and Vol/sub removed/ the volume of material removed by a single abrasive. The model proposed integrates process parameters including pressure and velocity and other important input parameters including the wafer hardness, pad hardness, pad roughness, abrasive size, and abrasive geometry into the same formulation to predict the material removal rate (MRR). An interface between the chemical effect and mechanical effect has been constructed through a fitting parameter H/sub w/ a "dynamical" hardness value of the wafer surface, in the model. It reflects the influences of chemicals on the mechanical material removal. The fluid effect in the current model is attributed to the number of active abrasives. It is found that the nonlinear down pressure dependence of material removal rate is related to a probability density function of the abrasive size and the elastic deformation of the pad. Compared with experimental results, the model accurately predicts MRR. With further verification of the model, a better understanding of the fundamental mechanism involved in material removal in the CMP process, particularly different roles played by the consumables and their interactions, can be obtained.

[1]  W. Tseng,et al.  Re‐examination of Pressure and Speed Dependences of Removal Rate during Chemical‐Mechanical Polishing Processes , 1997 .

[2]  K. Drescher,et al.  Chemical-mechanical polishing of copper for interconnect formation , 1997 .

[3]  Marius K. Orlowski,et al.  A statistical polishing pad model for chemical-mechanical polishing , 1993, Proceedings of IEEE International Electron Devices Meeting.

[4]  J. Greenwood,et al.  Contact of nominally flat surfaces , 1966, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[5]  Frank G. Shi,et al.  Modeling of chemical-mechanical polishing with soft pads , 1998 .

[6]  Dennis Okumu Ouma,et al.  Modeling of chemical mechanical polishing for dielectric planarization , 1998 .

[7]  R. Scattergood,et al.  Ductile-Regime Grinding: A New Technology for Machining Brittle Materials , 1991 .

[8]  Ronald J. Gutmann,et al.  Chemical Mechanical Planarization of Microelectronic Materials , 1997 .

[9]  S. R. Runnels,et al.  Tribology Analysis of Chemical‐Mechanical Polishing , 1994 .

[10]  M. Pohl,et al.  The Importance of Particle Size to the Performance of Abrasive Particles in the CMP Process , 1996 .

[11]  K. Johnson Contact Mechanics: Frontmatter , 1985 .

[12]  S. Chandrasekar,et al.  Role of indentation fracture in free abrasive machining of ceramics , 1993 .

[13]  Steven Danyluk,et al.  Contact Mechanics and Lubrication Hydrodynamics of Chemical Mechanical Polishing , 1999 .

[14]  F. W. Preston The Theory and Design of Plate Glass Polishing Machines , 1927 .

[15]  B. Bhushan,et al.  Effects of particle size, polishing pad and contact pressure in free abrasive polishing , 1996 .

[16]  Bau-Tong Dai,et al.  Modeling of the Wear Mechanism during Chemical‐Mechanical Polishing , 1996 .

[17]  Marius K. Orlowski,et al.  Combined asperity contact and fluid flow model for chemical-mechanical polishing , 1994, Proceedings of International Workshop on Numerical Modeling of processes and Devices for Integrated Circuits: NUPAD V.

[18]  P. R. Pinnock,et al.  The mechanical properties of solid polymers , 1966 .

[19]  Y. Moon,et al.  Mechanical aspects of the material removal mechanism in chemical mechanical polishing (CMP) , 1999 .

[20]  Srinivasan Chandrasekar,et al.  Polishing and Lapping Temperatures , 1997 .

[21]  Ranga Komanduri,et al.  Magnetic Field Assisted Finishing of Ceramics—Part II: On the Thermal Aspects of Magnetic Float Polishing (MFP) of Ceramic Balls , 1998 .

[22]  T. Cale,et al.  Von Mises Stress in Chemical‐Mechanical Polishing Processes , 1997 .

[23]  R. Dejule CMP challenge below a quarter micron , 1997 .

[24]  N. Chandrasekaran,et al.  Effect of tool geometry in nanometric cutting: a molecular dynamics simulation approach , 1998 .

[25]  Goodarz Ahmadi,et al.  Particle Adhesion and Removal in Chemical Mechanical Polishing and Post‐CMP Cleaning , 1999 .

[26]  Yaw-Terng Su,et al.  Investigation of Removal Rate Properties of a Floating Polishing Process , 2000 .