Query: Effect of polishing pad material properties on chemical mechanical polishing (CMP) processes

Candidate papers:

abstract: Chemical mechanical polishing (CMP) technology has successfully met the stringent requirements of ultraplanarized surfaces in semiconductor manufacture. Commonly, polyurethane based pads have been used to achieve this level of planarization. Recent studies have shown that the material properties of polishing pads used in the CMP process strongly influence the ability to reduce topography. In addition, past work has shown that in the absence of pad regeneration, polishing rate drops dramatically with polishing time. This decrease in material removal rate is believed to coincide with deterioration of the pad surface due to "cold flow" and/or "caking" of the pad material. This study attempts to correlate the intrinsic polymer properties and cellular structure of the pad material to CMP process indices like polishing rate and planarity. For example, the drop off in removal rate as a function of time can be attributed to the mechanical response of polyurethanes under conditions of critical shear. Moreover, planarity achieved is a function of pad stiffness which itself is dependant upon intrinsic polymer stiffness and cell density.
author_names: Rajeev Bajaj

Mukesh Desai

Rahul Jairath

Matt Stell

Robert D Tolles
title: Effect of Polishing Pad Material Properties on Chemical Mechanical Polishing (Cmp) Processes
year: 1994

abstract: Abstract As circuits become increasingly complex and device sizes shrink, the demands placed on manufacturing processes increases. For successful manufacture of such circuits, high levels of wafer planarity are required. Chemical mechanical polishing (CMP) is a manufacturing process used to achieve global planarity. Studies have shown that the degree of planarity achieved is influenced by the pad properties. During polishing, the properties of the pad can deteriorate causing reduced polish rates and reduced planarity. It has been shown that this is caused by plastic deformation of the pad material, leading to glazed areas on the surface. Conditioning is used to regenerate the pad surface by breaking up these areas, but in doing so induces pad wear. As some areas of the pad will experience a higher degree of glazing, varying conditioning densities are necessary to counter this effect. The conditioning profile dictates the travel of the conditioning arm over the pad and hence the conditioning density experienced at each point. The aim of such a profile is to aid planarity by creating a uniform and constant removal rate over the whole wafer. The variations in pad properties between new and worn out pads and the effect of conditioning in changing the pad properties will be examined. By examining correlations between conditioning densities experienced and pad properties over the radius of the pad, it is hoped to further understand the effect of conditioning on the process. Such understanding is vital in improving process reliability and yields in semiconductor manufacture.
author_names: Bonnie J Hooper

Gerry Byrne

Siobhan Catherine Galligan
title: Pad conditioning in chemical mechanical polishing
year: 2002

abstract: Abstract A novel semi empirical model was developed for predicting the material removal rate (MRR) during chemical mechanical polishing (CMP) based on the following assumptions: plastic contact at the wafer particle interface, elastic contact at the pad particle interface, a particle size distribution, and a randomly distributed surface roughness of the polishing pad. The proposed model incorporates the effects of particle size, concentration, and distribution, as well as the slurry flow rate, pad surface topography, material properties, and chemical reactions during the silicon dioxide (SiO 2 CMP. To obtain the unknown parameters and ensure the validity of the model, a SiO 2 CMP experiment was conducted by using various sized CMP slurries. The spatial distribution of the MRRs is expressed with respect to the normal contact stress distribution and the relative velocity distribution. The proposed MRR model can be used for the development of a CMP simulator, the optimization of CMP process parameters, and the design of next generation CMP machines.
author_names: H S Lee

Hae-do Jeong

David A Dornfeld
title: Semi empirical material removal rate distribution model for SiO2 chemical mechanical polishing (CMP) processes
year: 2013

abstract: Abstract As the most basic interconnection metallic material, copper (Cu) has been widely used in giant large scale integrated circuits (GLSI) Corrosion inhibitors always play a crucial role in the Cu chemical mechanical polishing (CMP) process. The passivation of hydrogen peroxide (H2O2) alone is too weak to adequately protect against chemical corrosion on the surface of Cu film, thus, it is necessary to add corrosion inhibitors to the slurry. As a representative corrosion inhibitor, 1, 2, 4 triazole was compared with a novel corrosion inhibitor known as TT LYK (ethanol, 2, 2' (methyl 1H benzotriazol 1 yl) methyl] imino] bis and their mixed inhibitor was studied in this paper. Different analytical methods such as the potentiodynamic polarization test, physical appearance phenomenon analysis, contact angle measurement and dynamic polishing experiment were used to compare their inhibition properties, and the fitting of different adsorption isotherms and static erosion tests were used to clarify the adsorption types and passivation processes respectively. The results indicated that both TT LYK and 1, 2, 4 triazole achieved the goal of inhibiting Cu surface corrosion, but the inhibition effect of TT LYK was slightly weaker at the same mass fraction. The corrosion protection of the two inhibitors is mainly attributable to the presence of organic inhibitor molecules on the surface of Cu by chemisorption and physisorption simultaneously. The passivation processes of both can be divided into two steps. First, the direct growth of the Cu inhibitor passivation film occurs, followed by the redeposition of the Cu inhibitor complex. From the results of electrochemical experiments, it can be concluded that the structure of the thin passivation film growing on the Cu surface varies with the inhibitor, and the composition of the passivation film was investigated by XPS and Raman spectrum analysis. At the same time, the surface roughness after polishing was found to decrease with the increase in inhibition effect of the inhibitors. According to the inhibition characteristics of these two inhibitors, a mixed corrosion inhibitor (TT LYK and 1, 2, 4 triazole) was proposed in this study. Under the synergistic inhibition action, better inhibition effect and surface quality for Cu CMP were obtained. This outcome may be ascribed to the variation in the structure and density of the passivation film.
author_names: Jiakai Zhou

Xinhuan Niu

Yaqi Cui

Zhi Feng Wang

Jianchao Wang

Ru Wang
title: Study on the film forming mechanism, corrosion inhibition effect and synergistic action of two different inhibitors on copper surface chemical mechanical polishing for GLSI
year: 2020

abstract: Chemical mechanical polishing (CMP) of optical glasses is widespread and forms the basis for many high precision polishing processes. The pads, slurries and glass materials used in polishing have many different properties. The effects of these properties on the process results are often unknown. The right choice and combination is therefore often a challenge. By means of a plan processing of N BK7 and SF56 samples by a plan polishing process, the influence on the process results, material removal rate (MRR) micro roughness and cleanliness caused by slurry and polishing pad is shown. It turns out that the type of polish pad has the biggest impact on the results. The easy to process material N BK7 shows only little influence by the type of slurry used. The more challenging SF56, however, shows significant effects, especially in the area of the resulting micro roughness and the appearance of surface damages like orange peel. Especially the use of Auerpol(r) PZ500 shows clear advantages here. For a selection of three out of nine polishing pads, the effect of density variation of the slurry was also investigated. Lower particle concentrations lead to lower material removal rates. This applies to both materials. The more sensitive SF56 shows a reduction in micro roughness by the use of a less dense slurry. The correct selection of the polishing pad has a positive effect on the material removal rate and/or the micro roughness in all tested materials. An adaptation of the type and concentration of the slurry is especially important for more sensitive materials and in combination with the right polishing pad. In view of the development towards special materials and small lot sizes, the targeted and correct selection of polishing slurries and pads becomes more and more important. The information required for this purpose on the behavior of the pads and slurries available on the market must therefore first be determined in a targeted manner and clearly presented.
author_names: Christian J Trum

Sebastian Sitzberger

Rolf Rascher
title: Improved performance of CMP processes through targeted adjustment of polishing slurry and polish pad
venue: Optical Engineering Applications
year: 2018

abstract: Abstract As technology nodes continue to decrease, traditional Copper (Cu) interconnects in the back end of the line (BEOL) will encounter more and more problems. Ruthenium (Ru) is expected to be a barrier layer or even as a novel type of interconnection material because of its good electrical properties. However, because of its high chemical inertness, Ru is challenging to achieve a higher removal rate in the chemical mechanical polishing (CMP) process. In this study, the synergist effect of potassium periodate (KIO4) and potassium persulfate (K2S2O8) on the removal rate of Ru during CMP was investigated. The theory of advanced oxidation process (AOPs) is used to explain the reaction process of Ru with KIO4 and K2S2O8. X ray photoelectron spectroscopy (XPS) combined with electrochemical are applied to explore the removal machanism and chemical reaction mechanism of Ru under the synergistic effect of KIO4 and K2S2O8. The CMP tests shows that the Ru removal rate (1123 A/min) in the presence of KIO4 and K2S2O8 composite could be increased by more than 221% compared to the removal rate (507 A/min) of KIO4 alone. In addition, Ru oxidation process is more affected by diffusion controlled. Excessive oxidant concentration will reduce the removal rate of Ru. The mechanism analysis shows that the RuO3 activated persulfate generates sulfate radical (SO4 which can further generate more oxides on the Ru surface, and Ru oxide is easily removed under the CMP process. Therefore, the Ru removal rate will be significantly improved. Simultaneously, the surface roughness Sq can be reduced to 0.667 nm after polishing.
author_names: Jianwei Zhou

Chenwei Wang
title: Synergist effect of potassium periodate and potassium persulfate on improving removal rate of Ruthenium during chemical mechanical polishing
venue: Materials Science and Engineering: B
year: 2020

abstract: Chemical mechanical polishing (CMP) is the most important process for global planarization. The micro material removal and planarization of the optical surface is a complicated process, and the surface shape of optics is effected by kinematics, pressure, and chemical conditions. Moreover, it is a remarkable fact that the distribution characterization of polishing particles also has an important effect on material removal uniformity, especially for leather pad and Tin polishing lap. Large optics were always polished to a convex shape for the low density of valid abrasives in optic center. The porosity and grooves distribution of pad plays a major role in slurry delivering. The novel model of contact and material removal is presented in which pad characterization, and polishing particles delivery and distribution effects are included. With the modified pad asperity and optimized grooves, the particles have been inclined towards well distributed, and experiments validated that the optic figure is significantly promoted.
author_names: Shijie Zhao

Ruiqing Xie

Defeng Liao

Xian-hua Chen

Qinghua Zhang

Jinyan Wang

Qiao Xu
title: Particle distribution characterization on material removal uniformity in chemical mechanical polishing
venue: Optifab
year: 2019

abstract: Abstract In a typical chemical mechanical polishing (CMP) process, the type, morphology, structure, mechanical, and surface characteristics of abrasive particles play an important role in influencing the material removal process. The novel abrasive particles with special mechanical and/or tribochemical properties have been introduced into CMP processes for the improvement of surface quality and finishing efficiency. In this work, the composite particles containing solid silica s SiO 2 cores and mesoporous silica m SiO 2 shells were prepared via a developed Stober method using cetyltrimethylammonium bromide as a structure templating surfactant. The as synthesized core/shell structured s SiO 2 m SiO 2 composite particles were characterized by powder X ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen sorption desorption measurements. The effect of the s SiO 2 core size of the composite particles on oxide CMP performance was evaluated in terms of surface roughness and material removal rate MRR The root mean square surface roughness (0.15 0.31 nm) of the polished substrates slightly increased with increasing of the s SiO 2 core size (168 353 nm) of the composites with a comparable m SiO 2 shell thickness (16 18 nm) The s SiO 2 m SiO 2 composite particles with a relatively smaller or larger core presented a relatively high MRR for silicon oxide films. These oxide CMP results could be rationalized according to the contact area mechanism and indentation based mechanism, incorporating the total contact area and chemical reactivity between particles and wafers, and the indentation depth of an abrasive particle onto the substrate surface.
author_names: Yang Chen

Changzhi Zuo

Ailian Chen
title: Core/shell structured sSiO2/mSiO2 composite particles: The effect of the core size on oxide chemical mechanical polishing
year: 2018

abstract: During the Chemical mechanical planarization (CMP) the pad conditioning process can affect the pad surface characteristics. Among many CMP process parameters, the improper applied load on the conditioner arm may have adverse effects on the polyurethane pad. In this work, we evaluated the pad surface properties under the various conditioner arm applied during pad conditioning process. The conditioning pads were evaluated for surface topography, surface roughness parameters such as Rt and Rvk and Material removal rate (MRR) and within wafer non uniformity after wafer polishing. We observed that, the pad asperities were collapsed in the direction of conditioner rotation and blocks the pad pores applied conditioner load. The Rvk value and MRR were founded to be in relation with 4 1 7 kgF conditioner load. Hence, this study shows that, 4 kgF applied load by conditioner is most suitable for the pad conditioning during CMP.
author_names: Cheolmin Shin

Hongyi Qin

Seokjun Hong

Sanghyuk Jeon

Atul Kulkarni

Taesung Kim
title: Effect of conditioner load on the polishing pad surface during chemical mechanical planarization process
year: 2016

abstract: Chemical mechanical polishing (CMP) of SiO2 is a key issue in IC and optical components manufacturing. Therefore, the mechanism of material removal during CMP has attracted substantial interests. To study the effects of mechanical and chemical actions on material removal process, a polyoxymethylene (Pom) ball was used to mimic a single pad asperity and polish a SiO2 film surface, fused silica surface and BK7 surface. The material removal results show differences for composition and structure of materials. The material removal depth (MRD) per cycle reaches its limit with load increasing, indicating the chemical control of removal for different physicochemical properties at different surface layer depths. Moreover, with load increasing, the bottom morphology of trench deteriorates. Chemical mechanical synergy (CMS) is the basis for MRR prediction, and the CMS mechanism can provide a basis for removal stability analysis and control.
author_names: Shuo Yang

Lin Wang

Ping Zhou

Ying Yan

Zhuji Jin
title: Chemical Mechanical Material Removal of Silicon Dioxide by a Single Pad Asperity
venue: 2019 China Semiconductor Technology International Conference (CSTIC)
year: 2019