Query: post-CMP brush cleaning

Candidate papers:

abstract: Tribological attributes of post chemical mechanical planarization ~CMP! brush scrubbing are investigated as a function of tool kinematics, applied pressure, pH, and flow rate of the cleaning solution. Coefficient of friction ~COF! results show that at high pressures, for low and neutral pH, the lubrication mechanism is that of 'partial lubrication, while 'hydrodynamic lubrication' is observed at low pressures. The existence of hydrodynamic lubrication corresponding to lower of COF values continues at high values of pH irrespective of brush pressure. Furthermore, flow rate does not impact the overall tribology of the system. The effect of solution pH on COF is explained by considering the effect of pH on the solubility and gellation characteristics of silica in the silica water system. At pH values below 2.0, silicic acid monomers are believed to collide and aggregate into chains and three dimensional networks representative of gelling, thus resulting in high COF values. The lower COF at pH 7.0 is believed to be due to the presence of network terminated silanol groups and the absence of gels. At pH values above 10.5, surface silanol groups completely dissociate, causing the hydrated silica surface to dissolve as soluble silicates, thus lowering the frictional forces. Widespread use of chemical mechanical planarization ~CMP! has made brush scrubbing a conventional cleaning method in semiconductor manufacturing. In post CMP cleaning, brush scrubbing is based on direct contact between a rotating spongy PVA brush and the wafer surface whereby the exposed part of the particle is first adsorbed on brush asperities. Next, the rotation of the brush in the presence of a cleaning fluid dislodges and carries the particle away from the wafer surface. Thus, the influence of factors such as applied pressure, tool kinematics, brush and cleaning fluid properties, wafer surface conditions, cleaning time, and the magnitude of the frictional forces present at the brush wafer interface are essential for effective particle removal. Various studies have focused on tool kinematics, brush properties as well as general process characterization, and optimization. 1 4 However, few attempts have been made to directly study measurement of the frictional forces at the brushwafer interface. 5 This study focuses on precise quantification of the frictional forces needed in characterizing the system tribology, because a low amount of force does not remove particles embedded on the wafer surface, and excess amounts may lead to scratching and other defects.
author_names: Ara Philipossian

Lateef Mustapha
title: Tribological Attributes of Post CMP Brush Scrubbing
year: 2004

abstract: Due to the emergence of sub 7 nm technologies, next generation CMP slurry formulations have continued to increase in additive (nanoparticle and chemistry) complexity to meet stringent device specifications. Therefore, it is essential to probe the molecular level interactions at the nanoparticle/slurry chemistry/substrate interface and in turn correlate them to key performance metrics such as removal rate, post CMP defects, and planarization efficiency. This work will address key interactions through a series of case studies focusing on the role of supramolecular structure and cleaning method (i.e. contact vs. non contact) during STI post CMP cleaning, probing the impact of supramolecular structure and mode of cleaning relevant to Cu post CMP, and development of a biomimetic matrix with chemical activity to act as a brush in STI post CMP cleaning processes. Results show in both BEOL and FEOL post CMP cleaning there is a strong correlation to the delivery and "soft" nature of the chemistry to allow for effective particle removal at low mechanical force and prevent further defect formation. Furthermore, this work shows a clear correlation between supramolecular structure and particle removal efficiency under both contact and non contact post CMP processes.
author_names: Katherine M Wortman-Otto

Abigail N Linhart

Allie M Mikos

Kiana A Cahue

Jason J Keleher
title: Contact Vs. Non Contact Cleaning: Correlating Interfacial Reaction Mechanisms to Processing Methodologies for Enhanced FEOL/BEOL Post CMP Cleaning
year: 2021

author_names: Ryu Sun Joong
title: Contact Pressure Distribution Measurement of PVA Brush for Post CMP Cleaning
year: 2016

abstract: Chemical mechanical polishing (CMP) is widely used in the surface planarization process of semiconductor fabrication. The planarization process produces a large amount of surface residue that must be removed before the next process is initiated. Typically, a combination of roll and pen type polyvinyl acetal (PVA) brushes is used for removing such contaminants. In the subsequent 450 mm wafer processing step, PVA brush cleaning is a viable candidate for post CMP cleaning. However, given that the mechanisms of nanoscale particle cleaning are still under investigation [1 the designs and operating conditions for brush cleaning are determined by trial and error. In this study, as a first step toward understanding the cleaning mechanisms, the tribological contact condition of the PVA roll brush (i.e. hydrodynamic, mixed, or boundary lubrication) is considered by measuring the frictional coefficients. In particular, the effects of rotation speed, compression distance, brush length, and fluid viscosity on the friction force are investigated.
author_names: Takashi Fujiwara

T Sanada

Akira Fukunaga

Hirokuni Hiyama
title: Frictional Analysis of PVA Brush for Post CMP Cleaning: Effects of Rotation Speed, Compression Distance, and Fluid Viscosity
year: 2012

abstract: Abstract A 3D lubrication model between a soft porous brush and rigid flat surface in the post CMP (chemical mechanical polishing) cleaning process for wafer or hard disc surface is set up in this article. The mesh porous structure of the brush and the kinematic relations between the brush and the surface are taken into account. The flow governing equations for cleaning process are deduced with Newtonian fluids between the brush nodule and the substrate. The distributions of fluid pressure and hydrodynamic removal moment are calculated. The simulation results show that the fluid pressure has negative regions in inlet area. The removal force is depended on system parameter, location, time and particle size. The load and hydrodynamic moment increase with the increase of brush velocity and deflection of brush nodule, which is effective for cleaning. A low wafer rotation speed is recommended to keep the cleaning uniformity. The removal moment is increasing during the cleaning process. The hydrodynamic drag force decreases rapidly with decreasing of particle size. The models are coincident with the actual process and can be used as reference for designing a higher level cleaning process and the analysis of the formation of particle defect.
author_names: Yating Huang

Dan Guo

Xinchun Lu

Jianbin Luo
title: A lubrication model between the soft porous brush and rigid flat substrate for post CMP cleaning
year: 2011

author_names: Hanssen Soondrum
title: Brush Scrubbing Scratches Reduction Methods in Post CMP Cleaning
year: 2012

abstract: Abstract Chemical mechanical polishing (CMP) has become widely accepted for the planarization of device interconnect structures in deep submicron semiconductor manufacturing. However, during CMP process the foreign particles, metal contaminants, and other chemical components are introduced onto the wafer surface, so CMP process is considered as one of the dirtiest process to wafer surface defects which may damage the GLSI patterns and the metallic impurities can induce many crystal defects in wafers during the following furnace processing. Therefore, the post CMP cleaning of wafers has become a key step in successful CMP process and the polyvinyl alcohol (PVA) brush cleaning is the most effective method for post CMP in situ cleaning. In this study, the effect of the chelating agent with different concentrations on defect removal by using PVA brush cleaning was discussed emphatically. It can be seen from the surface images obtained by scanning electron microscopy and KLA digital comparison system analysis confirmed that the chelating agent can effectively act on the defect removal.
author_names: Jiao Hong

Xinhuan Niu

Yu-ling Liu

Yangang He

Baoguo Zhang

Juan Wang

Liying Han

Chenqi Yan

Jin Zhang
title: Effect of a novel chelating agent on defect removal during post CMP cleaning
year: 2016

abstract: This paper presents recent developments in the design and characterization of chemical mechanical planarization (CMP) consumables, with specific emphasis on post CMP (PCMP) cleaning polyvinyl alcohol (PVA) brushes. Special nodule design and modified charge super clean PVA brushes were developed to obtain more effective near wafer edge cleaning and significantly improved overall PCMP cleaning performance in advanced applications. The profiled nodule top, elongated nodule brushes provided optimum cleaning contact area and contact force at the brush wafer interface in the wafer edge region, whereas the negative zeta potential (NZP) modified PVA brushes resulted in significantly improved PCMP cleaning efficiency in smaller node high sensitive copper/low k processes. The effects of extended exposure of one alkaline and four acidic PCMP cleaning chemistries on brush PVA discoloration and properties were investigated. All the tested acidic cleans caused significant discoloration, whereas the alkaline clean caused minimal change. Further, all the tested chemistries did not show much change in PVA physical properties and compressive stress.
author_names: Rakesh Kumar Singh

Chintan V Patel

David Trio

Eric Mcnamara

Christopher Wargo
title: PVA Brush Technology for Next Generation Post CMP Cleaning Applications
year: 2010

abstract: Post CMP defect is a critical process parameter to yield enhancement and device reliability in sub 14nm semiconductor manufacturing as "killing" particle size has shrunk according to device shrinkage. In order to improve defect at post CMP step, CMP has an in situ cleaning module, commonly composed of megasonic cleaning, brush scrubber cleanings, fluid jet cleaning and their combination. Among the module, brush scrubber cleaning is the most effective method in particle removal due to its physical force. Although many studies have been conducted to optimize particle removal efficiency of brush cleaning, its cross contamination effect has not been considered for the optimization of post CMP defects. In this paper, effect of brush scrubber cleaning on the post CMP defect and its optimization process are explored. In addition to cross contamination effect, equipment aspect of optimization is also investigated. Chemical spray bar position to the wafer and mechanical operation are key controlling factors. Brush motor torque analysis suggests how to optimize brush operation. Experimental results in this paper provide insight into post CMP cleaning optimization.
author_names: Hong Jin Kim

Tae Hoon Lee

Venugopal Govindarajulu

Jason Mazzotti
title: Effect of post CMP in situ cleaning and its optimization on the defect improvement: CFM: Contamination free manufacturing
venue: 2016 27th Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC)
year: 2016

abstract: Display Omitted Brush itself caused cross contamination to wafer in post CMP in situ cleaning.Brush rotational speed is the key parameter to control cross contamination.Fluid (DIW) flow rate does not much influence on cross contamination. Scaling of gate lengths has led to significant improvement in semiconductor device performance. However, fabrication complexities have also increased and surface defects control becomes very critical for yield enhancement. In particular, chemical mechanical polishing (CMP) process is considered as one of the dirtiest processes to wafer surface contamination. And brush scrubber is the most effective method for post CMP in situ cleaning. Many literatures have reported brush scrubber mechanism and proposed particle removal efficiency based on remaining particles at post brush scrubber cleaning. However, concerns associated with brush to wafer surface contamination have not been addressed properly although real manufacturing has a lot of issues on that effect. This paper discuss cross contamination at brush scrubber process and emphasize that optimum cleaning should consider brush cross contamination in addition to brush particle removal efficiency.
author_names: Hong Jin Kim

Girish Bohra

Hyucksoo Yang

Si-Gyung Ahn

Liqiao Qin

Dinesh Koli
title: Study of the cross contamination effect on post CMP in situ cleaning process
year: 2015