Effect of pH and H[sub 2]O[sub 2] on Ta Chemical Mechanical Planarization

Recently, stainless steel has been widely used as the solar cell substrate. In this paper, chemical mechanical polishing technique was employed to prepare the ultra-smooth 316L stainless steel surface for such application. The effects of solid content, pH, H 2 O 2 and benzotriazole (BTA) on the polishing performance of 316L stainless steel were investigated. The results indicated that, at pH 4.00, with the increase in the H 2 O 2 concentration, the MRR first dramatically increases due to the fact that, with the addition of small amount of H 2 O 2 , a porous outer layer mainly consisting of iron-enriched oxides with relatively low mechanical strength of the bilayer-structure oxide film is rapidly formed on the surface. After reaching the maximum value, the MRR gradually decreases since the outer layer gradually grows compact by the transformation of γ-FeOOH into α-FeOOH and even into α-Fe 2 O 3 . With the addition of BTA, the MRR can be suppressed, which is probably attributed to the formation of BTA passivating film on the top surface. Finally, a two-step polishing method was proposed, by which the ultra-smooth 316L stainless steel surface with the surface roughness R a about 2.0 nm can be achieved within 30 min and it can be subsequently used for thin-film solar cells. Stainless steel plays an important role in the mechanical industry due to the excellent mechanical properties, the high thermostability and the strong corrosion resistance. Recently, various types of stainless steels have been intensively used in precise devices, 1-4 especially been used as the substrate for thin-film solar cells. [5][6][7][8][9][10] In order to achieve satisfactory performance of solar cells, low roughness, low defects as well as excellent flatness of the stainless steel substrate are intensively demanded and even indispensable. It is reported that, by improving the surface roughness of stainless steel substrate from 38 nm to 23 nm, the conversion efficiency of hydrogenated amorphous silicon thin-film solar cells can greatly increase to 5.4%. 10 As is revealed, chemical mechanical polishing (CMP) combines the synergetic effects of chemical corrosion and mechanical abrasion, and can achieve both local and global planarization of the substrate surface. 11-14Hu et al.2 used colloidal silica as the abrasive and investigated the effects of pH and oxidizer on the polishing performance of stainless steel, and it was reported that the combination of oxidizer and strong acidity was the prerequisite for high material removal rate (MRR). However, the microscopic defects of 1-2 μm in size cannot be effectively avoided on the polished surface. Lee et al.10 used electrochemical mechanical polishing technique, which applied an additional anodic potential on the stainless steel substrate besides CMP, to polish the stainless steel surface, and it was reported that the polished surface roughness was reduced from about 38 nm to about 23 nm. However, more detailed polishing performance and the mechanism of chemical reactions during the polishing pr...

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“…immunity, corrosion or passivation. [17][18][19] The effect of pH on the polishing performance of 316L stainless steel is shown in Fig. 2.…”

Section: Resultsmentioning

confidence: 99%

Chemical Mechanical Polishing of Stainless Steel as Solar Cell Substrate

Jiang

Yang

2015

ECS J. Solid State Sci. Technol.

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“…However polishing of Ta with alumina-based slurries over a wide range of pH has been observed. [125][126][127] The variation of Ta polish rate over a wide range of pH has been investigated in the presence of oxidizers 126,128,129 with alumina and silica abrasives. In most acid and alkaline noncomplexing solutions, the Ta surface is well-protected by the formation of tantalum pentoxide, Ta 2 O 5 , which is stable over a wide range of pH.…”

Section: Ta/tan Liner Cmp Processmentioning

confidence: 99%

“…It is also known that Ta ]. 129,131 Under these conditions, in the presence of H 2 O 2 , the thickness of the tantalum oxide is governed by the relative rates of formation and dissolution of the tantalum oxide. For silica slurries, in general, higher Ta polish rates are observed at pH ≈ 2-3 and 11-12.…”

Section: Ta/tan Liner Cmp Processmentioning

confidence: 99%

Chemical Mechanical Planarization: Slurry Chemistry, Materials, and Mechanisms

Krishnan¹,

Nalaskowski²,

Cook³

2009

Chem. Rev.

396

271

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Mahadevaiyer Krishnan received his Ph.D. degree in Physical Chemistry/ Electrochemistry from Georgetown University under the direction of Prof. Robert de Levie. He was a postdoctoral fellow under Prof. A. J. Bard in the University of Texas at Austin. He joined the IBM T. J. Watson Research Center at Yorktown Heights in 1984 as a research scientist. Krishnan's research interests include interfacial electrochemistry, colloid and surface science, and semiconductor process development. He has been leading research and development as well as manufacturing implementation of CMP slurries and processes in IBM since 1994.

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“…Among all factors influencing the removal process, pH and ionic strength value playa crucial role in determining the polishing mechanism. This may be because the variation in the pH and the ionic strength of the slurry will result in changes in the surface electrostatic interaction forces between the particles and the tantalum surface [37][38][39] .…”

Section: Cmp In Ic Fabricationmentioning

confidence: 99%

Progress in material removal mechanisms of surface polishing with ultra precision

Zhang

et al. 2004

Chin. Sci. Bull.

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Chemical mechanical polishing (CMP) process is commonly regarded as the best method for achieving global planarization in the field of surface finishing with ultra-precision. The development of investigation on material removal mechanisms for different materials used in computer hard disk and ultra-large scale integration fabrication are reviewed here. The mechanisms underlying the interaction between the abrasive particles and polished surfaces during CMP are addressed, and some ways to investigate the polishing mechanisms are presented.Keywords: CMP, material removal mechanism, wear, ULSI, computer hard disk. DOl: lO.1360/04we0035According to the International Technology Roadmap for Semiconductors, the chips with a wafer diameter of 450 mm and a feature size of 0.05 flill by the 2011 will serve to decrease manufacturing costS [I]. The corresponding wafer surface quality is expected to meet the unprecedented requirement. For example, surfaces and subsurfaces of wafers must be damage-free after being polished. And in computer hard disk manufacturing, the requirement for surface quality is higher and higher with increasing storage density. For instance, if the hard disk is expected to achieve a storage density larger than 500-1000 Gb/in 2 , the micro-waviness (Wa) and the roughness (Ra) of the hard disk surface must be less than 0.1 and 0.05 urn respectively. These requirements are close to the limits of the present manufacturing technology. The technique of planarization has become the key factor to meet such requirements. Chemical mechanical polishing (CMP) is commonly recognized to be the best method of achieving global planarization in super-precision surface fabrication. It has been a key technology for facilitating the development of high density multilevel interconnected circuit[3-5] and computer magnetic head and hard disk manufacturing [6,7]. With the development of high-performance electrical products, CMF has to be improved to meet even more stringent requirements, and even will face new challenges. The above factors serve as incentives to deepen the basic understanding of material removal mechanisms for super-precision surface finishing [2]. However, to date, the mechanism of material removal from the wafer is still unclear and ambiguous because the difficultly in extracting information about basic mechanisms of CMF can hardly be overcomerS]. CMF's widespread applications have exceeded the growth of the scientific understanding. And therefore, a study of the microscopic material removal mechanism during CMF will help not only to reveal new polishing behaviors and mechanisms followed under the condition of extreme manufacturing but also to explore new principles and methods of extreme manufacturing in microelectronics industries. This paper presents a general review on the material removal mechanisms during CMF in computer magnetic hard disk manufacture and ultra-large scale integration fabrication, such as silicon, dielectric layer and metal layers. The mechanisms underlying the interaction between the...

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Effect of pH and H[sub 2]O[sub 2] on Ta Chemical Mechanical Planarization

Cited by 59 publications

References 18 publications

Chemical Mechanical Polishing of Stainless Steel as Solar Cell Substrate

Chemical Mechanical Polishing of Stainless Steel as Solar Cell Substrate

Chemical Mechanical Planarization: Slurry Chemistry, Materials, and Mechanisms

Progress in material removal mechanisms of surface polishing with ultra precision

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