This chapter provides an introduction to silicon nanostructures, which are often called black silicon (b-Si) due to their dark appearance to the naked eye.The discussion covers both nanoporous structures and more solid needle-shaped b-Si.It reviews the most common b-Si fabrication techniques, including reactive ion etching, electrochemical etching and laser treatment, which all produce nanostructures with different morphologies and properties.Additionally, the chapter introduces the special properties of b-Si, such as negligible reflectance, superhydrophobicity and widened band gap, which significantly differ from those of larger surface structures.Finally, various applications are discussed, where b-Si can be used to enhance device performance, including biological and chemical sensors, photovoltaic devices, photodiodes and batteries.

Due to the functional limitations of SiO2 for SOI applications, alternative dielectric materials have been investigated. Alternative SOI materials in this work include, AlN and AlGaN. The dielectrics were deposited using MOCVD, and with the aid of PECVD deposited SiO2, and the SiO2 was directly bonded to a handle Si wafer. Tensile tests were performed on the samples to examine the fracture behavior and maximum tensile stresses, with results being comparable to a traditional SOI. Characterization was undertaken using TEM to understand the microstructural and interfacial properties of alternative SOI. High crystal quality Al(Ga)N was achieved on a Si(111) substrate that generally contained well defined chemical interfaces. Finally, synchrotron X-ray diffraction topography was used to understand the topographical strain profile of the device and handle wafers. Topography results showed different strain network properties between the device and handle wafer. This work has demonstrated preliminary feasibility of using alternative dielectrics for SOI applications.

Atomic-layer-deposited Al2O3 films can be used for passivation, protective, and functional purposes in electronic devices. However, as-deposited, amorphous alumina is susceptible to chemical attack and corrosion during manufacturing and field-use. On the contrary, crystalline Al2O3 is resistant against aggressive chemical treatments and corrosion. Here, high-temperature treatments in N-2, H-2, and vacuum were used to crystallize alumina which exhibited different crystalline phases. The annealing process was monitored continuously in situ by measuring the film temperature and surface reflectance to understand the crystallization kinetics. Ex-situ x-ray diffraction, electron microscopy, and composition analysis were used to probe the structure of the crystallized films and explain the formation of different alumina phases. This study provides a set of boundary conditions, in terms of temperature and atmosphere, for crystallizing chemically stable atomic-layer-deposited alumina for applications requiring a film thickness in the range of tens of nanometers without defects such as cracks.

Atomic-layer-deposited alumina (ALD Al2O3) can be utilized for passivation, structural, and functional purposes in electronics. In all cases, the deposited film is usually expected to maintain chemical stability over the lifetime of the device or during processing. However, as-deposited ALD Al2O3 is typically amorphous with poor resistance to chemical attack by aggressive solutions employed in electronics manufacturing. Therefore, such films may not be suitable for further processing as solvent treatments could weaken the protective barrier properties of the film or dissolved material could contaminate the solvent baths, which can cause crosscontamination of a production line used to manufacture different products. On the contrary, heat-treated, crystalline ALD Al2O3 has shown resistance to deterioration in solutions, such as standard clean (SC) 1 and 2. In this study, ALD Al2O3 was deposited from four different precursor combinations and subsequently annealed either at 600, 800, or 1000 °C for 1 h. Crystalline Al2O3 was achieved after the 800 and 1000 °C heat treatments. The crystalline films showed apparent stability in SC-1 and HF solutions. However, ellipsometry and electron microscopy showed that a prolonged exposure (60 min) to SC-1 and HF had induced a decrease in the refractive index and nanocracks in the films annealed at 800 °C. The degradation mechanism of the unstable crystalline film and the microstructure of the film, fully stable in SC-1 and with minor reaction with HF, were studied with transmission electron microscopy. Although both crystallized films had the same alumina transition phase, the film annealed at 800 °C in N2, with a less developed microstructure such as embedded amorphous regions and an uneven interfacial reaction layer, deteriorates at the amorphous regions and at the substrate−film interface. On the contrary, the stable film annealed at 1000 °C in N2 had considerably less embedded amorphous regions and a uniform Al−O−Si interfacial layer.

Atomic-layer-deposited alumina (ALD Al2O3) can be utilized for passivation, structural, and functional purposes in electronics. In all cases, the deposited film is usually expected to maintain chemical stability over the lifetime of the device or during processing. However, as-deposited ALD Al2O3 is typically amorphous with poor resistance to chemical attack by aggressive solutions employed in electronics manufacturing. Therefore, such films may not be suitable for further processing as solvent treatments could weaken the protective barrier properties of the film or dissolved material could contaminate the solvent baths, which can cause crosscontamination of a production line used to manufacture different products. On the contrary, heat-treated, crystalline ALD Al2O3 has shown resistance to deterioration in solutions, such as standard clean (SC) 1 and 2. In this study, ALD Al2O3 was deposited from four different precursor combinations and subsequently annealed either at 600, 800, or 1000 °C for 1 h. Crystalline Al2O3 was achieved after the 800 and 1000 °C heat treatments. The crystalline films showed apparent stability in SC-1 and HF solutions. However, ellipsometry and electron microscopy showed that a prolonged exposure (60 min) to SC-1 and HF had induced a decrease in the refractive index and nanocracks in the films annealed at 800 °C. The degradation mechanism of the unstable crystalline film and the microstructure of the film, fully stable in SC-1 and with minor reaction with HF, were studied with transmission electron microscopy. Although both crystallized films had the same alumina transition phase, the film annealed at 800 °C in N2, with a less developed microstructure such as embedded amorphous regions and an uneven interfacial reaction layer, deteriorates at the amorphous regions and at the substrate−film interface. On the contrary, the stable film annealed at 1000 °C in N2 had considerably less embedded amorphous regions and a uniform Al−O−Si interfacial layer.

Atomic-layer-deposited alumina (ALD Al2O3) can be utilized for passivation, structural, and functional purposes in electronics. In all cases, the deposited film is usually expected to maintain chemical stability over the lifetime of the device or during processing. However, as-deposited ALD Al2O3 is typically amorphous with poor resistance to chemical attack by aggressive solutions employed in electronics manufacturing. Therefore, such films may not be suitable for further processing as solvent treatments could weaken the protective barrier properties of the film or dissolved material could contaminate the solvent baths, which can cause cross-contamination of a production line used to manufacture different products. On the contrary, heat-treated, crystalline ALD Al2O3 has shown resistance to deterioration in solutions, such as standard clean (SC) 1 and 2. In this study, ALD Al2O3 was deposited from four different precursor combinations and subsequently annealed either at 600, 800, or 1000 °C for 1 h. Crystalline Al2O3 was achieved after the 800 and 1000 °C heat treatments. The crystalline films showed apparent stability in SC-1 and HF solutions. However, ellipsometry and electron microscopy showed that a prolonged exposure (60 min) to SC-1 and HF had induced a decrease in the refractive index and nanocracks in the films annealed at 800 °C. The degradation mechanism of the unstable crystalline film and the microstructure of the film, fully stable in SC-1 and with minor reaction with HF, were studied with transmission electron microscopy. Although both crystallized films had the same alumina transition phase, the film annealed at 800 °C in N2, with a less developed microstructure such as embedded amorphous regions and an uneven interfacial reaction layer, deteriorates at the amorphous regions and at the substrate-film interface. On the contrary, the stable film annealed at 1000 °C in N2 had considerably less embedded amorphous regions and a uniform Al-O-Si interfacial layer.

Large-area back-reflection and transmission X-ray diffraction topographs of bonded silicon-on-insulator (SOI) wafers made with synchrotron radiation allowed direct and simultaneous imaging of bonding-induced strain patterns of both the 7μm thick (011) top layers and the (001) Si substrates of the SOI structures. The bonding-induced strain pattern consists of cells having a diameter of about 40μm. Section topographs show a lattice misorientation of the adjacent cells of about 0.001° and the maximum observed strain-induced lattice plane rotation ten times larger, i.e. about 0.01°. Topographs made after etching away the insulator layer show no indication of residual strain or defects either in the silicon-on-insulator layer or in the substrate. This is in agreement with the experimentally determined maximum bonding stress of 30MPa, which is much smaller than the estimated stress needed to nucleate dislocations.

This chapter discusses the preparation and properties of silicon wafers in detail. MEMS manufacturing sets special requirements for silicon wafers. MEMS processes are traditionally divided into surface micromachining and bulk micromachining. Wafers are cut from the ingot, shaped, polished, and cleaned to be ready for further processing or for device manufacturing. Silicon crystals or ingots grown with either CZ or FZ technique are typically up to 2 m in length. Manufacturing includes ingot cutting and shaping, wafering where ingot is sliced to wafers, ID cutting is done with a thin diamond blade, wire cutting allows simultaneous cutting of hundreds of wafers routinely. Wafer marking is done with a laser, according to SEMI standard. Edge grinding, wafers after cutting have sharp edges, these are shaped to remove sharp edges. Lapping/grinding, this is an operation where wafers where material removal is done with abrasive slurry. Chemical etching, after lapping or grinding wafer edges have residual damage this damage is removed. Wafer is cleaned from impurities coming from mechanical operations in the etching step. Donor killing is done after etching and cleaning by heating the wafer. Polishing, wafers for MEMS applications are commonly doubleside polished. Clean room operation, typically silicon wafers are cleaned by RCA-type cleaning sequence. Resistivity of the wafer is measured with a contact method according. Wafer measurements for thickness, thickness variation and shape are done with a noncontact capacitive method. SEMI are used as a reference and guideline in specifications.

The modification of material characteristics by introducing dopant atoms into a crystal lattice is a fundamental basis for modern micro- and nanosystems technology. In this work, the uneven distribution of dopants is shown to have a remarkable effect on the residual stress and the consequent deformation of released, mechanical silicon structures. In particular, the focus is on segregation of initial dopants inside the bulk silicon which takes place in such fabrication processes as thermal oxidation. A theoretical model based on perceiving the dopant-induced change in Si crystal lattice parameter is developed. We experimentally investigate a series of silicon-on-insulator wafers, including samples with dopant types B, P, and Sb, and concentrations in the range from 1015 to 5 × 1019 atoms cm−3. Released cantilevers are fabricated as test structures and the residual stress is determined by measuring their final curvature. Experimental results are compared with the modelled values obtained utilizing the dopant profiles determined by secondary ion mass spectrometry and concentration distribution simulations. The use of lightly doped substrates or the selection of processes not modifying the underlying Si surface (e.g., plasma enhanced chemical vapour deposition PECVD or metal deposition) is shown to be an effective solution for minimizing the dopant redistribution-induced stress. Besides the scientific impact, knowledge of the stress generated by dopants is of great significance for industrial manufacturing of a wide range of micro- and nanomechanical systems.

This is a comprehensive guide to MEMS materials, technologies and manufacturing, examining the state of the art with a particular emphasis on current and future applications. The key topics covered include: silicon as MEMS material; Material properties and measurement techniques; Analytical methods used in materials characterization; modeling in MEMS; measuring MEMS; micromachining technologies in MEMS; encapsulation of MEMS components; and, emerging process technologies, including ALD and porous silicon. Written by 73 world class MEMS contributors from around the globe, this volume covers materials selection as well as the most important process steps in bulk micromachining, fulfilling the needs of device design engineers and process or development engineers working in manufacturing processes. It also provides a comprehensive reference for the industrial R&D and academic communities. Veikko Lindroos is Professor of Physical Metallurgy and Materials Science at Helsinki University of Technology, Finland. Markku Tilli is Senior Vice President of Research at Okmetic, Vantaa, Finland. Ari Lehto is Professor of Silicon Technology at Helsinki University of Technology, Finland. Teruaki Motooka is Professor at the Department of Materials Science and Engineering, Kyushu University, Japan. This book provides vital packaging technologies and process knowledge for silicon direct bonding, anodic bonding, glass frit bonding, and related techniques. It shows how to protect devices from the environment and decrease package size for dramatic reduction of packaging costs. It discusses properties, preparation, and growth of silicon crystals and wafers. It explains the many properties (mechanical, electrostatic, optical, etc), manufacturing, processing, measuring (incl. focused beam techniques), and multiscale modeling methods of MEMS structures.

In this chapter, properties of silicon are explained in detail. Silicon is an abundant element found in the Earth's crust in various compounds. Semiconductor and microelectromechanical systems (MEMS) applications use annually about 70,000 t of high-purity silicon. Quartz or silicon dioxide is the most common starting raw material for purified silicon for semiconductor and sensor applications, and the Siemens process is the most commonly used in semiconductor-grade silicon production. Silicon crystallizes into a diamond cubic crystal structure in which the atoms are covalently bonded. Silicon is a hard, brittle material, and at room temperature under stress silicon single crystal elongates elastically until fracture stress appears without significant plastic deformation. Silicon is a group IV element in the periodic table and is a semiconductor with a bandgap of 1.12 eV, which means that pure silicon at room temperature is almost an insulator. By doping with group III or group V elements the resistivity of silicon can be varied over a wide range. In this chapter, mechanical and electrical properties of silicon are explained in detailed. Schematic diagrams help to better understand the reaction of silicon and its various properties.

This chapter discusses the preparation and properties of silicon wafers in detail. Microelectromechanical systems (MEMS) manufacturing sets special requirements for silicon wafers. MEMS processes are traditionally divided into surface micromachining and bulk micromachining. Wafers are cut from the ingot, shaped, polished, and cleaned to be ready for further processing or for device manufacturing. Silicon crystals or ingots grown with either Czochralski or float zone technique are typically up to 2 m in length. Manufacturing includes ingot cutting and shaping; wafering where ingot is sliced to wafers; ID cutting is done with a thin diamond blade; wire cutting allows simultaneous cutting of hundreds of wafers routinely. Wafer marking is done with a laser, according to Semiconductor Equipment and Materials International (SEMI) standards. Wafers after cutting have sharp edges; edge grinding is carried out to remove sharp edges. Lapping/grinding is an operation where material is removed from wafers with abrasive slurry. After lapping or grinding, wafer edges have residual damage that is removed by chemical etching. Impurities from mechanical operations in the etching step are then cleaned. Donor killing is done after etching and cleaning by heating the wafer. Wafers for MEMS applications are commonly double-side polished. Silicon wafers are cleaned by RCA-type cleaning sequence in a clean room operation. Wafer measurements for resistivity, thickness, thickness variation, and shape are done with a noncontact capacitive method. SEMI standards are used as a reference and guideline in specifications.

In order to succeed in consumer markets microsystems have to achieve a very low cost level. This forces device manufacturers to minimize device sizes and make design cycles shorter. The same trend also can be seen in automotive products although high reliability needs and harsh environments set some extra limitations. A silicon wafer manufacturer can help in this by developing more intelligent substrates for customer needs. Possibilities for adding new cost-saving features into silicon wafers designed for microsystem fabrication have been developed. SOI wafers with sealed cavities and gettering of metal impurities in SOI wafers, are given as examples.

We have designed and fabricated micromechanical magnetometers intended for a 3D electronic compass which could be embedded in portable devices. The sensors are based on the Lorentz force acting on a current-carrying coil, processed on a single crystal silicon resonator, and they are operated in vacuum to reach high enough Q values. Sensors for all cartesian components of the magnetic field vector can be processed on the same chip. The vibration amplitude is detected capacitively and the resonance is tracked by a phase-locked-loop circuit. The fabrication process is based on aligned direct bonding of a double side polished silicon wafer and a SOI wafer. Magnetometers measuring the field component along the chip surface have a flux density resolution of about 10 nT/√Hz at a coil current of 100 μA. Magnetometers measuring the field component perpendicular to the chip surface are currently less sensitive with a flux density resolution of about 70 nT/√Hz. The standard deviation of the signal was less than 1% over a period of a few days.

Rapidly developing silicon-based sensor technology also necessitates new material solutions in the field of silicon wafers. Combined with the constantly accelerating product cycles, this means that new sensors need to be launched cost-effectively and quickly. Collaboration between the material supplier and the customer must be seamless and continuous in order to be able to avoid unnecessary business risks. Traditional sensor technologies are now joined by high aspect ratio (HAR) structures that enable the products' cost-effectiveness to be improved even further, as the method makes allowances for small sensors and large wafer sizes, and is mostly compatible with the technology used in the manufacture of semiconductors. HAR technology also enables full advantage to be taken of the possibilities presented by SOI: in the manufacture of SOI wafers, it is possible to introduce tailored buried structures in the wafer. This opens up new vistas in terms of manufacturing high-performance sensors that integrate multiple functions. This presentation focuses on SOI technology that enables HAR structures with DRIE processing.

Objective: Prove the benefits of the use of ML in the diagnosis of endometriosis for patients in their adolescence and adulthood within fertile age with CPP ovarian cysts and 2nd look after previous treatments.Design: Since 1996 we have bee using microlaparoscopy (ML) in the certainty diagnosis of many diseases: Chronic pelvic pain (CPP), endometriosis cysts with an ecographic or resonance diagnosis, 2nd look in those cases that have been previously treated or that have undergone surgery and finally in patients who have been treated in other fertility centers. We also include ML in the study of every couple that starts a fertility study.Materials/Methods: Out of 296 ML, we separated only those who had consulted for: 1—Chronic Pelvic Pain: In adolescents to whom we gave the certainty diagnosis of endometriosis, thus preventing their fertility future. In women within fertile age we found different degrees of endometriosis and we were able to practice biopsies, coagulation, releasing of adherence or surgical treatment within the same surgery. 2—Ovarian tumors: We had a 70% of agreement with the ecographic diagnosis, these patients were treated with translaparoscopic surgery (TLS). 3—2nd look ML: This was practiced on 40 patients to observe their current stage and evaluate the previous treatment.Results: 1—Chronic Pelvic Pain: Out of 49 adolescents: 11 endometriosis; 54 adult women: 41 endometriosis. We used coagulation and section of utero-sacral ligaments in those cases with severe CPP without endometriosis or with a minimal endometriosis (7 cases). 2—Endometriomas that had ecographic or resonance diagnosis. We drew a concordance of 70%. In all cases we practiced the TLS. 3—2nd look: Out of 40 cases, 100% allowed the evaluation of the previous treatment and the procedures to be followed.Conclusions: ML is still the selected technique in the diagnosis of endometriosis for those cases of CPP, ovarian cysts and 2nd look after treatment. It provides the appropriate treatment to be followed with the minor physical and physical trauma.Supported By: U.B.A., French Hospital, Buenos Aires, Argentina. Objective: Prove the benefits of the use of ML in the diagnosis of endometriosis for patients in their adolescence and adulthood within fertile age with CPP ovarian cysts and 2nd look after previous treatments. Design: Since 1996 we have bee using microlaparoscopy (ML) in the certainty diagnosis of many diseases: Chronic pelvic pain (CPP), endometriosis cysts with an ecographic or resonance diagnosis, 2nd look in those cases that have been previously treated or that have undergone surgery and finally in patients who have been treated in other fertility centers. We also include ML in the study of every couple that starts a fertility study. Materials/Methods: Out of 296 ML, we separated only those who had consulted for: 1—Chronic Pelvic Pain: In adolescents to whom we gave the certainty diagnosis of endometriosis, thus preventing their fertility future. In women within fertile age we found different degrees of endometriosis and we were able to practice biopsies, coagulation, releasing of adherence or surgical treatment within the same surgery. 2—Ovarian tumors: We had a 70% of agreement with the ecographic diagnosis, these patients were treated with translaparoscopic surgery (TLS). 3—2nd look ML: This was practiced on 40 patients to observe their current stage and evaluate the previous treatment. Results: 1—Chronic Pelvic Pain: Out of 49 adolescents: 11 endometriosis; 54 adult women: 41 endometriosis. We used coagulation and section of utero-sacral ligaments in those cases with severe CPP without endometriosis or with a minimal endometriosis (7 cases). 2—Endometriomas that had ecographic or resonance diagnosis. We drew a concordance of 70%. In all cases we practiced the TLS. 3—2nd look: Out of 40 cases, 100% allowed the evaluation of the previous treatment and the procedures to be followed. Conclusions: ML is still the selected technique in the diagnosis of endometriosis for those cases of CPP, ovarian cysts and 2nd look after treatment. It provides the appropriate treatment to be followed with the minor physical and physical trauma. Supported By: U.B.A., French Hospital, Buenos Aires, Argentina.