A Material Removal Rate Model for Aluminum Gate Chemical Mechanical Planarization

Abstract

In this work, a new aluminum gate chemical mechanical planarization (CMP) model for material removal rate (MRR) is proposed in high-k metal gate (HKMG) process. Using the basic principles of steady-state oxidation reaction and mechanical abrasion mechanism, the combinational interaction of chemical and mechanical coupled effects on MRR was systematically described by process parameters, pad properties and concentration of oxidizer, and then balanced to construct an overall polishing rate. Because of the great significance of the slurry pH on MRR in CMP process, the effects of surface forces, including the influences of van der Waals (vdW) and double-layer (DL) forces simultaneously acted between the wafer and the particles were investigated. Meanwhile, the influence of particle sizes, abrasive loadings and zeta potentials of the wafer and particles on MRR was also analyzed. It is found that the attractive vdW forces strengthen the MRR, while the DL forces, calculated to be repulsive, lower the MRR. The magnitude of surface forces increases with a smaller particle size compared with the pad-particle force. When zeta potentials of the wafer and particles are considered as a function of slurry pH, the experimental trends for the MRR with slurry pH, applied pressure and abrasive loading were predicted well by the present model. Therefore, the governing equation of aluminum removal reveals some insights into the HKMG CMP process and can be utilized for optimizing and controlling the polishing rate of aluminum gate structures and performing sensitivity analyses of operating parameters. With the steady shrinkage of the feature size and device geometry of modern integrated circuits (ICs), chemical mechanical planarization (CMP) has become the most important process choice for the surface planarization in the fabrication of advanced multilever ICs in microelectronic industry.1 A variety of materials and structures, including copper damascene metallization, oxides in shallow trench isolation (STI) and inter-level dielectrics (ILD), replacement metal gate for high-k metal gate (HKMG) structures and fin field effect transistor (FinFET) devices are polished with different slurries. [2][3][4] In CMP process, a rotating wafer with different types of design structures is pushed against a rotating polishing pad which is immersed in slurries containing chemicals and abrasive particles. Pattern structures on the wafer surface are first chemically passivated by slurry chemicals and then removed by effects of contact interactions of abrasive particles which are trapped between the pad and the wafer. The contact mechanism of the particles in the slurry provides the opportunity to remove the material from the wafer surface at an acceptable production rate. 5The material removal rate (MRR) which has been studied extensively from both a modeling and experimental standpoint depends sensitively on pattern geometry, process parameters, chemical reactions, pad properties and mechanical abrasion. If the CMP process is not properly controlled...

A Wafer-Scale Material Removal Rate Model for Chemical Mechanical Planarization

“…Meanwhile, the reversible surface reaction is also ignored in the present modeling. 2,6,7,[10][11][12]19 The detailed modeling parameters are gradually considered as the model develops.…”

“…They are dependent on the polishing pressure and relative speed between the wafer surface and pad. Accordingly to the chemical kinetics modeling method, 7 [ ] Consequently, the total removal rate of the wafer surface can be represented as the following expression:…”

Analysis of interaction between mechanical force and chemical effect in cleaning phenomenon by probability density functional method

“…Researches on jet cleaning have been conducted on an integrated model for predicting dishwasher nozzle performance (Perez‐Mohedano et al, 2017) and on an expression of the relationship between pressure and detergency by the wibble function (Gerhards et al, 2019). In terms of polishing cleaning, the theory of chemical and mechanical action rates in diamond polishing (Yuan et al, 2018), in wafer polishing cleaning (Xu & Chen, 2015), in tantalum polishing cleaning (Gao & Liang, 2009), and in tungsten (Lim et al, 2004) were studied.…”

Chemomechanical magnetorheological finishing: Process mechanism, research trends, challenges and opportunities in surface finishing

“…11 A silicon wafer, shallow trench isolation (STI), an inter-layer dielectric (ILD) and the establishment of interconnects are all CMP processing areas. [12][13][14][15] CMP has recently expanded its applications to include microelectromechanical devices, printed circuit boards and more. [16][17][18][19][20] The CMP process removes material through chemical action including slurry chemicals and abrasives, along with mechanical abrasion.…”