Microelectronic corrosion microelectronics

Silicon nitride (Si3N4) is an excellent electrical insulator, which is increasingly replacing Si02 because it is a more effective diffusion barrier, especially for sodium and water which are maj or sources of corrosion and instability in microelectronic devices. As a result, it can perform... 

It was also observed that, with the exception of polyacetylene, all important conducting polymers can be electrochemically produced by anodic oxidation moreover, in contrast to chemical methoconducting films are formed directly on the electrode. This stimulated research teams in the field of electrochemistry to study the electrosynthesis of these materials. Most recently, new fields of application, ranging from anti-corrosives through modified electrodes to microelectronic devices, have aroused electrochemists interest in this class of compounds... 

Microelectronic circuits for communications. Controlled permeability films for drug delivery systems. Protein-specific sensors for the monitoring of biochemical processes. Catalysts for the production of fuels and chemicals. Optical coatings for window glass. Electrodes for batteries and fuel cells. Corrosion-resistant coatings for the protection of metals and ceramics. Surface active agents, or surfactants, for use in tertiary oil recovery and the production of polymers, paper, textiles, agricultural chemicals, and cement. 

During recent decades, demands regarding the quality and properties of metal coatings have increased sharply. This is due, on one hand, to advances in microelectronics, and on the other hand, to increasing uses of metal parts in corrosive environments. 

The use of impedance electrochemical techniques to study corrosion mechanisms and to determine corrosion rates is an emerging technology. Electrode impedance measurements have not been widely used, largely because of the sophisticated electrical equipment required to make these measurements. Recent advantages in microelectronics and computers has moved this technique almost overnight from being an academic experimental investigation of the concept... 

All materials will, to some degree, be subject to corrosion and oxidation by their environment, and the critical early stages of attack can often be understood through the use of surface analytical techniques. A similar approach is required to gain an understanding of the fundamental and applied aspects of surface catalysis, which is of great importance in the petrochemical industry. The microelectronics industry has also contributed to the development of modern surface analytical techniques, where there is a necessity to analyse dopant concentration profiles while retaining lateral resolution on the device of better than one micron. 

The method can successfully be used in analyses of impurities in metals and alloys, for estimation of minor elements in monomolecular films of oxide layers of Fe-Cr-Ni alloys, for detection of metal impurities in environmental pollution, for studying the depression of high-grade semiconducting materials and for analysis of the corrosion products of contact junction diodes used in microelectronic circuits. Much sophistication is desirable on the instrumental side so as to incorporate an automatic recording device to make an FR polarograph suitable for wider applications and common use. 

Electroless deposition as we know it today has had many applications, e.g., in corrosion prevention [5-8], and electronics [9]. Although it yields a limited number of metals and alloys compared to electrodeposition, materials with unique properties, such as Ni-P (corrosion resistance) and Co-P (magnetic properties), are readily obtained by electroless deposition. It is in principle easier to obtain coatings of uniform thickness and composition using the electroless process, since one does not have the current density uniformity problem of electrodeposition. However, as we shall see, the practitioner of electroless deposition needs to be aware of the actions of solution additives and dissolved O2 gas on deposition kinetics, which affect deposit thickness and composition uniformity. Nevertheless, electroless deposition is experiencing increased interest in microelectronics, in part due to the need to replace expensive vacuum metallization methods with less expensive and selective deposition methods. The need to find creative deposition methods in the emerging field of nanofabrication is generating much interest in electroless deposition, at the present time more so as a useful process however, than as a subject of serious research. 

The protection of microelectronics from the effects of humidity and corrosive environments presents especially demanding requirements on protective coatings and encapsulants. Silicone polymers, epoxies, and imide resins are among the materials that have been used for the encapsulation of microelectronics. The physiological environment to which implanted medical electronic devices are exposed poses an especially challenging protection problem. In this volume, Troyk et al. outline the demands placed on such systems in medical applications, and discuss the properties of a variety of silicone-based encapsulants. 

Plasma surface treatment of many polymers, including fabrics, plastics, and composites, often occurs. The production of ultra-thin films via plasma deposition is important in microelectronics, biomaterials, corrosion protection, permeation control, and for adhesion control. Plasma coatings are often on the order of 1 100 nm thick. 

The improvement of existing materials as well as the development of new materials is often based on the use of a chemical reaction in which a solid reacts with another solid, a liquid or a gas to form a solid product (an intermetallic, a silicide, an oxide, a salt, etc) at the interface between initial substances. Therefore, kinetics of solid-state formation of chemical compound layers are of interest not only to chemists (researchers and technologists) but also to metal and solid-state physicists, materials scientists, metallurgists, specialists in the field of corrosion, protective coating, welding, soldering and microelectronics. 

Chemical vapor deposition is not restricted to the microelectronics industry. It is the key process in the fabrication of optical fibers where it enables grading of the refractive index as a function of the radial position in the fiber (JO. In the manufacturing industry the technique provides coatings with special properties such as high hardness, low friction, and high corrosion resistance. Examples of CVD reactions and processes are given in Table 1. 

Although it is not yet cmnmon for AW devices, other areas of microelectronics have demonstrated the utility of more exotic metallizations, such as Pt-on-Pd-on-Ti, for demanding, high-temperature applications this combination would also be very corrosion resistant, though the relatively high density and poor conductivity of Pt are less than optimal for AW devices. 

A study on the correlation between electrochemical corrosion and chemical mechanical polishing performance of W and Ti film. Microelectron Eng. Forthcoming. Corrected proof available online 2006 11 Oct. 

In the following, we present two examples related to analysis of the mechanical stability of CVD films on substrates. One case describes systems intended for microelectronic devices (passivation films on a aluminium substrate), and the other describes coatings intended for wear and corrosion protection of steels. 

In the last several years, polymer thin film deposition using chemical vapor deposition (CVD) has become increasingly popular. CVD of polymers offers numerous unique advantages over other polymer synthesis techniques and has been exploited for a multitude of applications in microelectronics, optical devices, biomedical industry, corrosion resistant and protective coatings, and even in the automobile industry. CVD of polymers (also referred to as chemical vapor polymerization, CVP, or sometimes Vapor Deposition Polymerization, VDP) differs from inorganic CVD (such as for metallic or ceramic thin films) and must be developed and optimized... 

Only recently, there has been a tremendous surge of interest in these coatings, particularly in the microelectronic industry, although the deposition of polymers by CVP dates back to 1947. The key to the growing interest can be attributed to both the material properties of the films such as low dielectric constant, low moisture absorption, excellent corrosion resistance as well as the unique capabilities of the CVP process. These polymers and their polymerization mechanisms along with the properties of the films obtained are the focus of this section. The following polymers are discussed in detail separately. 

Although there are relatively only few polymers synthesized using CVD, these polymers have found place in numerous applications in microelectronics, optical devices, biomedical industry, corrosion resistant and protective coatings, and even in the automobile industry. Any attempt to review all of these applications would be over-ambitious. In this section, a few of them are briefly discussed, selected primarily based on the number of reports available in literature. For each application, first, the requirements imposed on the candidate materials are listed. Then the rationale of choice of these polymers and the CVD process, and finally, the performance of the polymers, along with their shortcomings, are discussed. 

Oxides surfaces are finding continuous new applications in advanced technologies like in corrosion protection, coating for thermal applications, in catalysis as inert supports or directly as catalysts, in microelectronics for their dielectric properties films of magnetic oxides are integral components in magnetic recording devices and many microporous materials are based on oxides. For all these reasons there is a considerable effort to better characterize the surface and the interface of oxide materials [1,2]. 

The permeability of the polymer to oxygen should be <1.0 cm -mil 100 in. day atm . Diffusion of oxygen and water through the polymer to the microelectronic circuitry could cause corrosion and is thus undesirable. To establish a value for this physical property constraint, we examined polymers used as barriers. Polymers with a permeability to oxygen of <1.0 cm -mil 100 in. day atm are considered high-barrier materials. 

The properties of alloy and intermetallic compound surfaces play an important role for the development of new materials. Attention has been stimulated from various topics in microelectronics, magnetism, heterogeneous catalysis and corrosion research. The investigation of binary alloys serves also as a first step in the direction to explore multi-component systems and is of particular regard in material science as a consequence of their widespread use in technical applications. The distribution of two elements in the bulk and at the surface probably results in new characteristics of the alloy or compound as compared to a simple superposition of properties known from the pure constituents. Consequently, surfaces of bulk- and surface- alloys have to be investigated like completely new substances by means of appropriate material research techniques and surface science tools. [1-6]. 

Metal oxides are of paramount importance in many areas of chemistry, physics and materials science [1]. They are utilized in microelectronic circuits, sensors, piezoelectric devices, corrosion protection coatings, self-cleaning/antibacterial surfaces. 

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