Nano Plating - Microstructure Formation Theory of Plated Films and a Database of Plated Films. Microstructure Control Theory of Plated Film and Data Base of Plated Film Microstructure PDF
Preview Nano Plating - Microstructure Formation Theory of Plated Films and a Database of Plated Films. Microstructure Control Theory of Plated Film and Data Base of Plated Film Microstructure
Preface Purpose of Publication and Background Plating technology has existed for more than 2,000 years and has been practiced steadily over the last two millennia. Modem plating technology is highly advanced, and has developed to cover a wide range of applications, e.g. in addition to the traditional use for surface finishing, plating technology can now offer novel processes to fabricate high- performance films or fine microstructural bodies in the microelectronics industry. This rapid progress reflects the potential for the electroplating method to become one of today's leading-edge technologies. The development of plating technology, however, has been slow due to the lack of a sound theoretical foundation and has often relied on a method of trial and error to obtain films with desirable properties. Despite numerous attempts, a unified theory has yet to be established that can provide this control in a consistent manner. This book is a compilation of vast amounts of experimental results that we have obtained in collaboration with our students over the last 34 years. We will introduce the concept of our new ''Microstructure Control Theory'' for plated films, which is entirely different from previous theories. We will then describe various experimental results that prove the validity of our theory. Finally, a large collection of experimental data on plated metal/alloy systems will be presented with a special emphasis on their microstructure. In the early days of research, we started modestly with fundamental studies on the microstructure of electroless films and on epitaxial phenomenon occurring between a plated film and a substrate. We presented these results as an occasional scientific paper in technical society meetings. During the course of these studies, we became increasingly aware of the possibility of producing amorphous films by plating methods. In 1988, motivated by this curiosity, we proposed a theory that explains why plated films can form an amorphous phase (cf. /. Surface Finish Soc. Japan 40, 375 (1989)). This theory was found to be also applicable to crystalline materials, giving us an opportunity to develop a theory explaining how the microstructure of plated pure metal/alloy films evolves. From this theoretical exercise, it has become apparent that the microstructure of plated films is closely connected to their equilibrium phase diagram. This concept finally led to the establishing of a theory of microstructure control for plated films. In 1999, we found that the microstructure of plated films can be categorized into 7 types. Each microstructural type is unique, and thus could be controlled independently (The 2"*^ Thin Film Basic Seminar, "Plating Methods", Japan Surface Science Society (1999) p. 115; Materia 40, 871 (2001)). Based on this microstructure classification, we are now able to focus on each individual microstructure type and develop its control theory independently. We believe that our efforts are finally paying dividends, as if tangled threads are being separated. vi Preface It is clear that in recent years much progress on theoretical work dealing with the microstructural control of plated films has been made. After leading plating technology discussion groups for the last 10 years, we sensed an urgent need for a specialized book on the microstmcture control theory among researchers/engineers in the plating industry. For this reason, we take the liberty to introduce this book although topics described within are still far from completion. At the same time, we hope that the accomplishments made in plating technology during the 20^^ century can be conveyed through this book into the 21^^ century. To describe an effective manner of conducting plating research, we explain research and experimental methods of plating. We list the microstructures of 53 types of plated pure metals and alloys, which should serve as a useful database for plated films. The unique feature of this database is that most of the plating baths are chosen to be simple and contain no additives. In addition, amorphous materials are used as substrates to avoid the effect of the substrate structure, and single-crystal substrates are chosen to study the epitaxial growth phenomenon. As mentioned above, the coverage in this book is still incomplete. Therefore, our mission is to continue collecting experimental data to fill the many gaps left in this book. At an opportune time, therefore, we will update the book accordingly. We believe that the materials contained within this book represent a crystallization of our students' efforts in conducting plating experiments over the last 34 years. We wish to express our sincere thanks to all the students and collaborators involved and list their names below. Thanks are also due to many companies, which funded, totally or partially, our research activities over the years. Finally my sincere personal thanks go to Dr. Shohei Nakahara for his invaluable assistance in the translation of this book from Japanese into English. Faculty Professor Emeritus Yoshimi Tanabe, Tokyo Metropolitan University. Professor Emeritus Nobuyoshi Baba, Tokyo Metropolitan University. Professor Shohei Nakahara, University of Limerick Professor Emeritus Ryouichi Urao, Ibaragi University. Professor Takeshi Nakata, Shibaura Institute of Technology. Secretary Yoshinari Misaki. Laboratory Faculty and Senior Associates Professor Kazuhisa Ishibashi, Tokai University. Shigeo Urai, Toyama National College of Technology. Shouzo Asano, Senju Metal Co., Ltd. Visiting Professors and Scientists Wei-Ping Yu (China), Dr. Goran Holmbom (Sweden), Dr. Torben Tang (Denmark), Preface vii Dr. Xin-Tan Hu (China), Su-Wei Yao (China), Dr. Imre Bakonyi (Hungary) and M.Sc. Anett Alsted Rasmussen (Denmark). Research Students (Domestic) Shinji Katou, Kazuo Shimizu, Suguru Abe, Yasutaka Mogi, Dr. Susumu Arai, Hiroko Furusawa, Katsuhiko Tashiro, Hiroshi Tsukamoto, and Hirokazu Takagi. Trainee (Foreign) Yin-Qi Zhang. Company Doctor Course Graduates Motonobu Onoda (Nippon Piston Ring Co., Ltd) and Kiyoshi Itoh. Doctor Course Graduates Tokyo Metropolitan University Seiji Kamasaki, Yasuo Shimizu, Masayuki Kakegawa, Hisakazu Ito, Hisashi Fumy a, and Naoki Fukumuro, and Feng Wang. Shibaura Institute of Technology Koichiro Inoue. Master Course Graduates Tokyo Metropolitan University Ken Tone, Hiroshi Matsubayashi, Toshihisa Sudo, Hiroki Shimizu, Hiroshi Ikebuchi, Hiroyasu Kojima, Hideo Suda, Hiroshi Imai, Yukio Numakura, Yoshiaki Ikeda, Naoya Hasegawa, Akira Narita, Hiroyuki Yamaguchi, Norimoto Usuzaka, Satoru Katsumata, Kazuyoshi Arai, Kenji Takahashi, Akira Suzaki, Hai-Ying Liang, lo Mizushima, Toshie Murai, Naoyuki Igarashi, Isao Satou, Kei Imafuji, and Takayuki Ikeda. Yuuichiro Miura and Shouji Matsuda. Shibaura Institute of Technology Takanobu Kanayama, Kenji Ikejima, Ichiro Wada, and Hideki Kotsuji. Tomoya Teshigawara, Takako Terakado, Yuki Makino, and Nobuto Sasaki. Undergraduates Tokyo Metropolitan University Toshiaki Ogura, Toshiie Kurihara, Minoru Kanda, Hiroshi Nakajima, Isao Kawaida, Mitsuru Kasahara, Kouhei Kitukawa, Akiyuki Kuniyoshi, Masao Soranishi, Kenzou Matsui, Yukio Matsumoto, Isao Ikegaya, Minoru Uehara, Hiroshi Takashio, Fumiaki Komatsu, Takakazu Fukuchi, Fujio Kawashima, Zenzaburo Naito, Kazuo Hoso- kawa, Hideo Tomita, Mamoru Arai, Nobuyuki Kataigi, Takashi Inoue, Kazuo Fukuda, Satomi Inoue, Takashi Eguro, Yoshio Kubota, Kazuyoshi Nishizawa, viii Preface Minom Odaka, Masaya Naoi, Satoru Shinohara, Nobuo Tomizawa, Susumu Morohashi, Shinji Tobita, Yukihisa Hiroyama, Takayuki Anma, Jun Tanaka, Takuya Naoe, Keiichi Nozawa, Tetsuo Sakamoto, Wakana Wasa, Takeshi Hirose, Hiroyuki Hoshina, Toshiko Kitagawa, Naoyuki Kanami, Yoshiaki Fukuda, Tomokazu Takasaka, Shusuke Minami, Shinichi Miyazaki, Saeko Yoshioka, Hroo Sawanobori, Mari Tomita, Megumi Osada and Yuji Hanaie. Shibaura Institute of Technology Atushi Mituo, Jun Kubo, Sadanori Tanemura, Junko Hirose, Kenji Asada, and Kazuyuki Koide. Akihiro Inami. Current Students (2004) Doctor Course Tokyo Metropolitan University Takashi Sugizaki (Meltex Inc.), Naoki Okamoto. Master Course Tokyo Metropolitan University Jin-Song Qiu, Sayaka Doi, Kaori Hosoiri, Atushi Kondo and Mituhisa Funatu. Shibaura Institute of Technology Takuya Yoshihara Takahiro Makino and Miki Yachidate. Undergraduate (Senior) Tokyo Metropolitan University Keigo Hoshina and Satoko Shoda. Shibaura Institute of Technology Kyohei Komori, Shinya Okahara, and Kazuya Kitazawa. Companies that Provided Research Funds Alps Electric Co., Ltd. Nippon Piston Ring Co., Ltd. Nihon Steel Corp. Sumitomo Metal Industries, Ltd. Hitachi Ltd. Sumitomo Heavy Industries, Ltd. Ebara-Udylite Co., Ltd. Asahi Glass Co., Ltd. Mitsui Mining & Smelting Co., Ltd. N. E. Chemcat Corp. Mitsubishi Aluminum, Ltd. Mitsubishi Materials Co., Ltd. Preface ix Kyocera Corp. Electroplating Engineering of Japan Ltd. Hitachi Cable Ltd. Limited Liability Company Taw Konika Technology Center Corporation Toppan Prating Co., Ltd. Fuji Electric Co., Ltd This book was originally published in Japanese in February 2003. The title was "FINE PLATING: Microstructure Control and Analysis Methods for Plated Films" published by Technical Information Association, Co., Ltd. This book is an English version. Dr. Tohru Watanabe Department of Applied Chemistry Graduate School of Engineering Tokyo Metropolitan University Minami-ohsawa, Hachioji-shi, Tokyo, 129-0397 Japan Chapter 1 Microstructure Control Theory of Plated Film 1.1. Introduction 3 1.2. Research process of plating technology 4 1.3. Review of previous TMC and practical plated films 7 1.4. Theory of microstructure control for plated films 10 1.4.1 Metallurgical structure (crystalline, solid-solution, intermetallic compound, meta-stable phase, amorphous phase, mixed phases) 10 1.4.2 Surface morphology (leveling, brightness, surface irregularities/ form, dendrite, etc.) 14 1.4.2.1 Surface morphology change with increasing film thickness 14 1.4.2.2 Surface morphology change with current density (overpotential) 24 1.4.2.3 Surface morphology change with the type of anions 29 1.4.2.4 Surface morphology change with solution temperature 32 1.4.2.5 Surface morphology change with solution agitation 32 1.4.2.6 Surface morphology of alloy films 32 1.4.2.7 Summary of the formation principles of surface irregularities 36 1.4.2.8 Formation of dendrites 37 1.4.2.9 Effect of brighteners 38 1.4.3 Grain size (grain size, granular, spherical, columnar, needle-like, etc.) 39 1.4.3.1 Grain size of pure metal deposits 39 1.4.3.2 Grain size of alloy deposits 41 1.4.4 Preferred orientation (texture) (film normal/film plane direction and assembled structure) 46 1.4.4.1 Experimental methods for determining the texture of plated films 50 1.4.4.2 Relationship between the texture of various plated films and plating conditions 50 1.4.4.3 Effect of plating conditions on the film texture 57 1.4.4.4 Texture of electroless films 66 1.4.4.5 Summary 68 1.4.5 Bonding with substrate and crystallographic matching (epitaxy) 68 Nano-Plating .4.6 Residual stress (compressive, tensile stresses, cracks) 74 .4.7 Anomalous morphology 79 1.4.7.1 Nodules 79 1.4.7.2 Pits 82 1.4.7.3 Cracks 82 1.4.7.4 Formation of layer structure 83 1.4.7.5 Initial layer 88 1.4.7.6 Whisker 91 References 91 Chapter 1 Microstructure Control Theory of Plated Film 1.1 INTRODUCTION The ultimate goal of conducting research in the electroplating technology field is to investigate how to produce plated films with desirable mechanical, physical, and chemical properties that meet particular application requirements. In the past, a vast number of papers have been published in the field of electroplating technologies, and their primary emphasis has been placed on electrochemical studies. At the same time, various attempts have been made to establish a unified theory that allows one to control both the microstructure and properties. Attempts to establish such a theory have been unsuccessful due to the complexities in achieving controlled experimental conditions. It is often the case that while fixing one parameter, others change uncontrollably, i.e. all the experimental parameters cannot be fixed at the same time. Furthermore, not all the chemical reactions occurring during electrodeposition processes are well understood. Because of these experimental difficulties and uncertainties, a reliable theoretical work that attempts to find a link to electroplating technologies has been largely hindered. From our extensive electrodeposition research in the past, we have come to the conclusion that all the physical properties of electroplated films must originate from their microstructure. For example, in deriving the microstructure-alloy composition relationship in electro plated alloy films, we found that the microstructural details provided more relevant infor mation than the knowledge of the chemical reactions occurring during electrodeposition. If we realize that "electroplated films are metallurgical materials and thus their properties are closely related to their equilibrium phase diagram", "we can explain the microstructure logically using a metallurgical concept". Understanding of the microstructure led to the development of a theory that suggests a way of controlling the microstructure of plated films. This theory will be called a theory of microstructure control (TMC). Other physical properties, such as the surface morphology, grain size and texture, can also be controlled independently in a similar manner. Based on our previous studies as well as reports from the literature, we constructed seven categories of microstructures in plated films, as depicted in Figure 1.1. Once the TMC is fully developed for each microstructural category, we will be able to control the physical properties of all categories of films. In this book, we will attempt to explain the TMC concept and discuss the validity of the theory using microstructural data for various plated films. Nano-Plating 1) Metallurgical structure crystal, amorphous, (Crystal, Amorphous, Solid solution, intermetalic compound, etc. Metastable, Mixture) \^yWy/y Substrate yCyy/A W///////////////////A 2) Surface morphology (smooth, rough, dendlight, glossness) 3) Crystal size, Crystal shape (Size, round shape, Columnar, needle, etc.) 4) Crystalographic orientation (parallel, perpendicular, texture) 5) Contact with substrate epltaxai (adhesive, epitaxial, coherent, misfit dislocation. Misfit twin) ///// ' SSuubbssttrraattee :Y ////A y////////////////////A p.^^.^.^-^^—^^ tension 6) Remaining stress (tensile stress, compression, crack) 77I 7c7o7m77p7re7s7s7i7o7n; ^ | y//7 Substrate ^^////A y//yyyyyyyyyy////////yA 7) Unusual shape (pit, nodule, whiskers, etc.) 77777777777777 y/yy Substrate y/////A v//yyy/yyy/yyyy/////yA Figure 1.1. Seven microstructure types observed in plated films. 1.2 RESEARCH PROCESS OF PLATING TECHNOLOGY A process diagram describing electrodeposition research is summarized in Figure 1.2. In the past, most of research has been conducted by varying plating conditions by a trial and error method based on an empirical rule stemming from a large number of experimental Microstructure Control Theory of Plated Film Physical properties Physical properties (electrical properties, magnetic properties, etc.) Chemical properties (anti-corrosion, catalytic properties, etc.) Mechanical properties (hardness, plastisity, tensile strength, etc.) Crystal Crystallographic structure (phase, crystal size, orientation, stress, etc.) Amorphous (uniformity, emblio, etc.) Composition Pure metal Alloy Impurity Reaction on electrode Electronic double layer A Diffusion layer Adhesion Discharge etc. Ion, Aqua-ion, Reaction in solution Complex ion. Dissociation, Diffusion, Reaction velocity, etc Plating conditions Bath composition (kinds of metal salt, concentration) pH, Kinds of anion, Addition, Reduction, Orver voltage, Current density. Pulse Agitation,Temperature, Electrode etc. Figure 1.2. A process diagram for conducting electrodeposition research. results. The properties of the resulting film were then matched with the properties of interest, applicable to a specific research objective. The problem with this approach is that the numbers of plating conditions are extremely large, as described below. The possible variables to be considered prior to plating include: (a) Substrate material (metal, non-metal (ceramics, plastic)). (b) Pre-treatment of substrate materials (deoxidation, degreasing, washing, drying). (c) Type of metals (pure metal, alloy). (d) Solution concentration (concentration, alloy composition). (e) Type of metallic salts (effect of anion type).
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