Query: post CMP megasonic cleaning

Candidate papers:

abstract: Non contact cleaning or wet cleaning processes, were the megasonic play a key role in the separation of the particles from the wafer is a commonly used technique in semiconductor manufacturing. CMP process can be very damaging to the production yield if not followed by an effective post clean process. McQueen identified the effect of the acoustic boundary layer and its role in the removal of small particles at high frequency. Busnaina et alt studied ultrasonic and megasonic particle removal and the effect of acoustic streaming. They showed that the cleaning efficiency increased with power until a certain range and then decrease slightly. Busnaina et al result indicted that SCI removes more particles than DI water particularly at lower megasonic powers specially in the case were the slurry particles are deposited onto the wafer surface by dipping experiments. But they also demonstrated that it was possible to achieve 100 removal in DI water when using the optimum conditions. This paper presents the latest results of the post CMP megasonic cleaning process, this study is focused on the cleaning of thermal oxide silicone wafer polished using silica based slurry and cleaned using diluted SC1 (H 2 0/H 2 0 2 /NH 4 OH: 40/2/1)
author_names: Ahmed Busnaina

N Moumen

J Piboontum

M Guarrera
title: Post CMP Megasonic Cleaning Using Dilute SCI Solution
year: 1999

abstract: In this study, the development of post chemical mechanical polishing (CMP) protocols for cleaning abrasive nanoparticles from In0.53Ga0.47As surfaces was systematically analyzed. Abrasive silica nanoparticles (130 and 289 nm) were intentionally deposited onto InGaAs surfaces. Various concentration ratios of chemical etchants such as HCl and H2O2 were used to control material loss and surface oxides of InGaAs. The optimal concentration ratio of the HCl/H2O2 cleaning solution exhibited 40% particle removal efficiency (PRE) Application of megasonic (MS) cleaning improved the PRE to 80% To prevent particle re contamination, ammonium dodecyl sulfate (ADS) was used as an anionic surfactant to modify surface charge in the InGaAs substrate. Addition of surfactant further improved the PRE to over 96% Optimal cleaning of InGaAs surfaces was achieved with a combination of HCl/H2O2, surfactant, and MS.
author_names: In-Chan Choi

Hyun-Tae Kim

Nagendra Prasad Yerriboina

Jung-Hwan Lee

Lieve Teugels

Tae-Gon Kim

Jin-Goo Park
title: Post CMP Cleaning of InGaAs Surface for the Removal of Nanoparticle Contaminants for Sub 10nm Device Applications
year: 2019

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: Scaling of gate length below 14nm has a lot of advantages such as high speed with low power consumption in device aspects. However, process requirement also becomes much tighter and defect control becomes the key to the yield enhancement. Every single surface particle can be potential killer defect depending on the particle location and process step. To remove large slurry particle to help following wet cleaning efficiency, in situ cleaning modules such as brush scrubber cleaning and megasonic tank are implemented in most CMP equipment. However, due to device complexity, limitation of post CMP clean chemical and insufficient wet cleaning at post CMP step, fabrication process strongly relies on CMP in situ cleaning for the clean surface. This study focuses on the brush cleaning performance and its optimization for sub 14nm device manufacturing. The experimental results show how brush scrubber cleaning optimization is achieved, and address effective process sequence to minimize cross contamination and to maximize particle removal efficiency. Challenges and requirements of brush manufacturing are also presented.
author_names: Hong Jin Kim

Tae Hoon Lee

Liqiao Qin

Sumeet Kashyap
title: Challenges in Post CMP in situ cleaning for sub 14nm device yield enhancement
venue: 2015 International Conference on Planarization/CMP Technology (ICPT)
year: 2015

abstract: Abstract Chemical mechanical planarization (CMP) has emerged as a critical step in integrated circuit fabrication for achieving global surface planarization of various thin films in the front and back end processing. This has led to the development of novel and advanced post CMP cleaning techniques that can effectively remove different types of contaminants (e.g. particulate, organic, metallic, etc. from surfaces. There is an increasing effort toward improving the fundamental understanding of the interfacial phenomena and the underlying physical and mechanical mechanisms that drive the post CMP cleaning process. In this chapter, a review of batch and single wafer brush and megasonic cleaning processes with emphasis on the effect of different process variables on particle removal is provided. The first few sections briefly describe the forces that drive particle adhesion and removal in a post CMP cleaning process. The last part of the chapter focuses on the typical chemical formulations and the role of additives in post CMP cleaning of silicon dioxide, tungsten, and copper films.
author_names: Manish Keswani

Zhenxing Han
title: Post CMP Cleaning
year: 2015

abstract: CMP is extensively used in silica based semiconductor manufacturing, and the post CMP cleaning is therefore a critical process after the wafers being polished by CMP slurries [1] Often with the UPW rinse as the last step, particles in the effluent from the UPW rinse can be characterized for their size and corresponding concentration as an essential parameter to evaluate the effectiveness and outcome of the overall cleaning process. This paper presents an application of using the Liquid Nanoparticle Sizer (LNS) system as an inline monitor to measure the size distribution of particles in the rinse effluent. 1. BACKGROUND Post CMP (pCMP) cleaning is one of the most important steps in the CMP process flow. A typical process flow will involve multiple polish steps, followed by several pCMP clean steps involving megasonic tanks, brush stations, and different chemical treatments. The last step in the pCMP sequence is typically an Ultrapure Water (UPW) rinse followed by a Marangoni dry step. The final UPW step is intended to remove any last particles from the wafer before sending the wafer to the drying step. The effluent from UPW the rinse may be monitored for particles to determine the cleanliness of the wafer and check for any excursions or unexpected behavior. In despite of the increasing demand of accuracy and sensitivity in monitoring the cleaning performance, to take out this measurement of sizing low concentration nanoparticles in UPW has been a challenge due to the limitation in currently available optical particle counting technologies [2, 3] far less to apply it as an evaluation parameter. 2. SYSTEM INTRODUCTION The Liquid Nanoparticle Sizer (LNS) System can be used to fill this gap [4] The LNS measures particles at above 80% counting efficiency across the 6 360 nm size range with a sizing resolution of 64 channels per decade, and it provides actual (not relative) number concentration for each corresponding particle size independent of particle shape or composition, and scans through the entire size range in less than 5 minutes. In addition to the scan mode which measures concentration and size spectra of the entire size range, the LNS can also be used in a single size mode that monitors the concentration change of a certain size as fast as one count per second. This fast response capability allows for the rinse process to be continuously monitored and endpointed to ensure that only clean wafers are passed on to the drying step. 3. EXPERIMENT AND RESULTS The experiment was setup in a way to mimic the UPW rinse situation, as shown in Figure 1. A silicon wafer was deposited with 500 mL CMP slurry, such as might be left behind in the pCMP clean process, a UPW flow is introduced at a constant flowrate towards the deposited surface as the rinse liquid, and the effluent is collected in a prewashed Nalgene container which is continuously sampled by the LNS System. Figure 1. Experimental Setup Experimental results are plotted in Figure 2. The size distribution of particles in the effluent was continuously measured from before and throughout the rinse process with results plotted in a sequence of time points, as shown in Figure 2(a) Each line represents the concentration spectrum measured from one LNS scan, with the ending time of that scan marked to the right. Lines are color coded to reflect the total concentration level, with red showing the post CMP Kanomax LNS System Model 9310
author_names: Siqin He

Derek R Oberreit

S L Kosier
title: Post CMP Clean Effluent Endpointing and Monitoring with the LNS System
year: 2019

abstract: Scrub, ultrasonic and megasonic are widely used in industry as post CMP cleaning procedure. In this paper, experiments are taken to analyze the particle contaminations after each process. A scatter spot method has been exploited to exam the particles' location and features. SEM with EDX is used to observe and analyze the particles' shape and size as well as the elements. The results indicate that brush scrub is not sufficient for submicron abrasive particle removal. Megasonic is a better method of cleaning but contaminations like metallic particles and bacteria fiom the equipment may pollute the clean disk. The abrasive particles embedded in the plating pits are hard to remove by mechanical force. Pollution in the dryer is also discussed.
author_names: Yating Huang

Xinchun Lu

Guoshun Pan

Bill Lee

Jianbin Luo
title: Particles Detection and Analysis of Hard Disk Substrate after Post CMP Cleaning
year: 2009

abstract: Optimization of post Cu CMP cleaning performance can be accomplished through dilution ratio tuning and pad rinse of clean chemicals. Excessive chemical etching as well as megasonic power can induce high Cu roughness. Generation of hollow metal and Cu dendrite defects depends not only on the clean chemistry but also the queue time between plating and anneal and between CMP and cap. AFM and XPS provide insights into the cleaning mechanism. EM and TDDB tests are the ultimate tests for the effectiveness of post Cu CMP cleaning.
author_names: Wei-tsu Tseng

Donald F Canaperi

Adam Ticknor

Vamsi Krishna Devarapalli

Leo Tai

Laertis Economikos

J MacDougal

Christine Bunke

Matthew Angyal

Jennifer Muncy

Xiaomeng Chen

Jack Zhang

Qiang Fang

Jianping Zheng
title: Post Cu CMP cleaning process evaluation for 32nm and 22nm technology nodes
venue: 2012 SEMI Advanced Semiconductor Manufacturing Conference
year: 2012

abstract: The invention provides a post chemical mechanical polishing (CMP) cleaning method for polysilicon and a CMP method. The post CMP cleaning method provided by the invention comprises the steps that firstly, in a megasonic cleaning step, an H2O2 rich SC1 solution in which the mass percentage of NH4OH is 2.8 plus/minus 0.2 percent and the mass percentage of H2O2 is 3.0 plus/minus 0.2 percent is utilized to conduct megasonic cleaning; and afterwards, in a subsequent polyvinyl alcohol (PVA) brush cleaning step, NH4OH (ammonia water) and deionized water (DIW) are utilized to clean a wafer and brush the surface of the wafer. According to the post CMP cleaning method, the high concentration SC1 solution (in which the NH4OH serves as an etching agent) is utilized to improve the etching efficiency of a natural oxide layer, so that a better cleaning effect can be achieved; meanwhile, the H2O2 with higher concentration in the SC1 solution is utilized to oxidize the polysilicon to form the oxide layer, so that the natural oxide layer of a certain thickness can be generated on the surface of the polysilicon while the better effect is achieved, an organic pollutant layer cannot be formed on the polysilicon in the subsequent brush cleaning process, and the growth of the natural oxide layer of the polysilicon in the air cannot be influenced by pollutants on the polysilicon.
title: Post chemical mechanical polishing (CMP) cleaning method and CMP method
year: 2012

abstract: Abstract Post CMP wafer cleaning commonly uses a combination of double sided brush scrubbing, megasonic cleaning, and spin rinse drying to remove polishing residues from wafer surfaces. This paper investigates double sided brush scrubbing and spin rinse drying by evaluating IPEC Planar's Avanti 9000 post CMP cleaner for the removal of diluted slurry solutions from previously polished and cleaned W sheet wafers. Diluted SC 1 (H 2 O/NH 4 OH/H 2 O 2 20:1:1) and DI water were used as the cleaning solutions in the brush and spin rinse drying units, respectively. Results show that the number of brush cycles, the brush pressure, and the brush rotating speed are key parameters in the removal of particles with diameters greater than 0.21 mm from the wafer. Two factor interactions between: (1) the number of brush cycles and the brush pressure, and (2) the number of brush cycles and the brush rotating speed are also important to the process performance. In addition, operating the spin rinse drying unit at the typical rotating speed (1000 rev./min) is not adequate for submicron particle removal from the wafer. A theoretical analysis of the hydrodynamics of the brush cleaning suggests that particles are removed from wafers due to direct particle brush contact, but that particle redeposition onto the wafers may occur.
author_names: G Zhang

Garry M Burdick

F Dai

Thomas Frederick Allen Bibby

Stephen P Beaudoin
title: Assessment of post CMP cleaning mechanisms using statistically designed experiments
year: 1998