Removal Rate In Chemical Mechanical Polishing Research Articles

Effect of CVD Temperature on Orientation, Roughness, and Chemical Mechanical Polish Removal Rate of W Thin Films

The deposition temperature for tungsten films used as interconnects on Si integrated circuits is found to strongly influence the subsequent chemical mechanical polishing (CMP) removal rate. Careful analysis of the films by orientation imaging microscopy showed a direct correlation between the chemical vapor deposition temperature and the area fraction of (114) vs. (110) oriented tungsten grains. The CMP removal rate decreased as the fraction of (114) oriented grains in the film increased. © 2002 The Electrochemical Society. All rights reserved.

Surface Removal Rate in Chemical-Mechanical Polishing

Variation of the surface removal rate with down pressure, pad asperity, and relative velocity in chemical-mechanical polishing (CMP) was studied. A phenomenological model for contact of pad asperities with abrasive particles and wafer is described. The functional dependence of the polishing rate on pressure and velocity was found to be related to the distribution of pad asperities. Simple argument based on the mechanical contact theory suggests that the linear variation predicted by Preston's equation follows when the pad asperities have a random distribution. The sublinear dependence of the removal rate, however, is obtained when the pad asperities have a wavy distribution. The use of the statistical least-square method is suggested as a way to determine the relationship between the removal rate and pressure for different industrial pads used in CMP processes. CMP polishing planarization surface removal

Characterization of methyl-doped silicon oxide film deposited using Flowfill™ chemical vapor deposition technology

In this article, methyl-doped silicon oxide films deposited using Flowfill™ chemical vapor deposition (CVD) technology have been chracterized for use in inter-layer dielectrics application. Films with different methyl concentrations were deposited and characterized in order to study the effect of methyl concentration on film properties. Material properties including chemical composition and bonding structure, density, dielectric constant (κ), refractive index, thermal stability, resistance to moisture absorption, leakage current, and hardness were investigated. The films have a κ as low as 2.7 and were found to be thermally stable up to 550 °C. They show excellent resistance to moisture absorption. Low-leakage current and breakdown voltage higher than 3 MV/cm were obtained. Their hardness is lower than silicon oxide deposited using plasma-enhanced CVD but is higher than most polymer and nanoporous low-dielectric constant (low-κ) materials. The chemical mechanical polishing (CMP) characteristics of these films and their stability under plasma treatments were also studied. Film’s CMP removal rate decreases as the methyl concentration in film increases. An atomically smooth surface with root mean square surface roughness <1 nm over a 10×10 μm area was obtained after CMP. This film remains stable under nitrogen (N2) and hydrogen (H2) plasma but is damaged by oxygen (O2) plasma.

Surface Kinetics Model for SiLK Chemical Mechanical Polishing

The surface mechanism for SiLK removal by chemical mechanical polishing (CMP) is modeled quantitatively using modified Langmuir-Hinshelwood surface reaction kinetics to define the boundary condition on the wafer surface for three-dimensional diffusive mass-transport equations. The model generates slurry concentration distributions between the pad and wafer as well as a CMP removal rate profile along the wafer diameter. Mathematically predicted removal rates of 15-200 nm/min accurately represent experimental data for concentrations of 0.0015-0.024 M potassium-hydrogen phthalate slurry. Three-dimensional model fits to experimental data for a range of velocity and pressure indicate that the SiLK CMP removal rate is controlled by a combination of (i) chemical reaction altering the SiLK surface layer and (ii) physically enhanced desorption of the reacted surface layer into the surrounding slurry. © 2001 The Electrochemical Society. All rights reserved.

Highly reliable chemical–mechanical polishing process for organic low-k methylsilsesquioxane

In this work, chemical–mechanical polishing (CMP) of the organic polymer, methylsilsesquioxane (MSQ), has been investigated. For conventional silicate-based slurry, the CMP removal rate of MSQ is low and many scratches are formed at the surface. Moreover, the dielectric properties of a post-CMP MSQ film are degraded in comparison to the as-cured MSQ. We have proposed a reliable process for the CMP of MSQ which includes a slurry of additive and a post-CMP NH3 plasma treatment. Experimental results show that the modified slurry provides a high polishing rate and uniform surface topography. In addition, the NH3 plasma process can form a thin nitrogen-containing layer on the post-CMP MSQ surface, which enhances the resistance to moisture absorption and copper diffusion.

Effects of alumina and hydrogen peroxide on the chemical-mechanical polishing of aluminum in phosphoric acid base slurry

Abstract The electrochemical behavior of aluminum in phosphoric acid base slurry was investigated under chemical-mechanical polishing (CMP) condition. The effect of alumina and hydrogen peroxide concentration on the CMP metal removal rate was evaluated. The experimental results from potentiodynamic polarization curve measurements indicated that a particle content in the range of 1–15 wt.% greatly modified the electrochemical behavior by decreasing the corrosion potential and increasing the passive current density. The results of electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) examinations showed that the passivation behavior of Al in the testing slurry was affected by hydrogen peroxide. The CMP removal rate was also a strong function of hydrogen peroxide concentration in the phosphoric acid base slurry.

A plasticity-based model of material removal in chemical-mechanical polishing (CMP)

It is well known that the chemical reaction between an oxide layer and a water-based slurry produces a softer hydroxylated interface layer. During chemical-mechanical polishing (CMP), it is assumed that material removal occurs by the plastic deformation of this interface layer. In this paper, the behavior of the hydroxylated layer is modeled as a perfectly plastic, material, and a mechanistic model for material removal rate (MRR) in CMP is developed. The deformation profile of the soft pad is approximated as the bending of a thin elastic beam. In addition to the dependence of MRR on pressure and relative velocity, the proposed plasticity-based model is also capable of delineating the effects of pad and slurry properties. The plasticity-based model is utilized to explore the effects of various design parameters (e.g., abrasive shape, size and concentration, and pad stiffness) on the MRR. Model predictions are compared with existing experimental observations from glass polishing, lapping, and CMP.

Novel Polymeric Surfactants for Improving Chemical Mechanical Polishing Performance of Silicon Oxide

We investigated the impacts of novel surfactants on oxide chemical mechanical polishing (CMP) performance. Silica-based potassium hydroxide was formulated for this study. Two polymeric surfactants, methyl methacrylate (MMA)-based CHE and siloxane-based SHE, were added to the slurry for evaluation. Particle size, viscosity, surface tension, and contact angle of slurries were characterized. Without surfactant, the silica-based slurry withstood up to 8.5 wt % of solid loading before the silica abrasives segregate and settle. With the addition of surfactant, however, the slurry held up to 15 wt % of solids without segregation. The CHE-added slurry yielded higher viscosity and higher oxide CMP removal rate than SHE-added slurry, while the latter exhibited better colloidal dispersion characteristics and lower within-wafer nonuniformity. © 2001 The Electrochemical Society. All rights reserved.

Chemical Mechanical Polishing of Low Dielectric Constant Oxide Films Deposited Using Flowfill Chemical Vapor Deposition Technology

In this work, the properties and chemical mechanical polishing (CMP) characteristics of thin films of a new low dielectric constant (low‐κ) oxide deposited using Flowfill chemical vapor deposition (CVD) technology are presented. This oxide film consists of silicon dioxide network with methyl groups incorporated and has a dielectric constant κ as low as ∼2.7. The film properties were studied using Fourier transform infrared spectroscopy (FTIR),spectroscopic ellipsometry, Rutherford backscattering, atomic force microscopy, and capacitance‐voltage measurements. The refractive index, as low as 1.38, was measured using spectroscopic ellipsometry. The surface was found to be more hydrophobic compared to conventional CVD oxide. The stretching mode of the Si‐O bond peak in the FTIR spectrum shifts to lower wavenumber, which corresponds to lower Si‐O bonding energy, with increase in the methyl concentration inside the film. The CMP removal rate decreases as the methyl concentration in the film increases. An atomically smooth surface with root mean square surface roughness <1 nm over an area 2 × 2 μm was obtained after CMP. Our results suggest that the incorporation of methyl groups results in a reduction in the CMP removal rate. We speculate that the diffusion of water into the film is probably the CMP removal rate‐limiting step. © 2000 The Electrochemical Society. All rights reserved.

Microstructure-related resistivity change after chemical–mechanical polish of Al and W thin films

The correlation between microstructures of Al and W metal thin films and their respective chemical–mechanical polishing (CMP) performance is investigated. It is found that CMP removal rate decreases with increasing grain size. In both cases, the textures of the metal films are altered and their resistivity increased after CMP. The phenomenon is more pronounced for polish under a greater down-force. The table speed, on the other hand, has only minimum effects on microstructure and resistivity. The possible underlying mechanisms leading to this phenomenon are proposed and their potential impact on metallization reliability is discussed.

Effect of Applied Potential on the Chemical Mechanical Polishing of Aluminum in Phosphoric Acid Base Slurry

The electrochemical behavior of Al in phosphoric acid base slurry was investigated under chemical mechanical polishing (CMP) condition. The effect of applied potential on the CMP metal removal rate was also evaluated. The results from potentiodynamic polarization curve measurements indicated that a contact pressure in the range of 3 to 9 psi greatly modified the passivation behavior of Al in 5 vol % citric acid + 5 wt % slurry by a decrease in corrosion potential and an increase in passive current density. The experimental results also showed that CMP removal rate strongly depended on the contact pressure and potential applied. The potential dependence behavior of the removal rate could be divided into three regions depending on the direction of polarization and the magnitude of potential applied. The results of electrochemical impedance spectroscopy and Auger electron spectroscopy examinations showed that passive film formation on Al in the testing slurry was affected by the applied potential, which in term caused a change in the relative contribution of the corrosion and mechanical abrasion to the total removal rate of Al. © 2000 The Electrochemical Society. All rights reserved.

Chemical Mechanical Polishing of Low‐Dielectric‐Constant Polymers: Hydrogen Silsesquioxane and Methyl Silsesquioxane

In the study, the film properties and chemical mechanical polishing (CMP) characteristics of the low‐dielectric‐constant materials hydrogen silsesquioxane (HSQ) and methyl silsesquioxane (MSQ) were presented. The Fourier transform infrared spectra, refractive index, dielectric constant, and atomic force microscopy results showed the successful preparation of the HSQ and MSQ films. The CMP characteristics of both materials were studied by two different slurries, A‐1 and B‐1. Our results showed that the CMP removal rate and nonuniformity increased with increasing the slurry solid content. The removal rate of the polished HSQ film was much larger than that of the polished MSQ film due to the hydrophobic surface of the MSQ film. The removal rate using the A‐1 slurry was larger than the B‐1 slurry for polishing both films. This result can be explained from the consideration of the isoelectric point and the electrostatic force between the abrasive surface and the film surface. The downforce pressure of the CMP process also showed a significant effect on the removal rate and the nonuniformity of the polished HSQ film. © 1999 The Electrochemical Society. All rights reserved.

Chemical‐Mechanical Polishing and Material Characteristics of Plasma‐Enhanced Chemically Vapor Deposited Fluorinated Oxide Thin Films

The chemical‐mechanical polishing (CMP) process has been proven to be the most promising method for accomplishing global planarization. In this paper, results of chemical‐mechanical polishing of fluorinated silicon dioxide (SiOF) thin films are presented. Nanohardness, elastic modulus, and bonding structure of fluorinated silicon dioxides are characterized in order to evaluate their correlations with CMP performance. The results show that under fixed chemistry and mechanical parameters, the CMP removal rate increases significantly with increasing fluorine content in the oxides due to the lower hardness and elastic modulus in the films. Higher CMP removal rate is observed for fluorinated oxides polished with slurry of pH 10 relative to pH 9. Compared with undoped oxides, SiOF films are more sentisitive to chemical and moisture attacks as reflected by the post‐CMP increase in refractive index.

Effects of mechanical characteristics on the chemical-mechanical polishing of dielectric thin films

The effects of as-deposited (intrinsic) stress, externally applied (extrinsic) stresses, hardness, and modulus of various dielectric films on chemical-mechanical polishing (CMP) removal and post-CMP cleaning processes are studied in this article. Intrinsic stresses of the polished dielectrics do not contribute directly to the CMP removal rate. Extrinsic stresses including normal and shear components are calculated using principles of elasticity and fluid mechanics respectively and their roles in the material removal process are discussed. Theoretical evaluation and experimental results both suggest that hardness and modulus are the two most important material characteristics affecting the CMP process. Efficiency of post-CMP particle extraction can be monitored using an adhesion probability which is related to the hardness of wafer and pad. In addition, particle removal rate can be remarkably enhanced by increasing pressure (normal stress) while increasing pad rotation speed (shear stress) contributes little to reduce the particle count.