Microelectronic corrosion

To apply CVD grown TIN successfully to microelectronics, corrosion on aluminum has to be studied, since it appears that chlorine contents of 8-14 at. % are destructive... 

The research of modem surface science has attracted considerable attention because of its links to important technological advances in microelectronics, corrosion smdies and heterogeneous catalysis. This chapter addresses the latter field in the form of catalysis at the gas-solid interface, and more specifically touches on the role that lasers play in the study of surface reactions. We start with a short resume of metal surface properties before the main features of molecule-surface interaction and, subsequently, the basic mechanisms of surface chemical reactions are covered. 

The body of this chapter is divided into three main sections. Initially, to enable a better understanding of the application of corrosion science to this subject, a very brief description of the hardware technologies and physical structures of these devices is presented. In the subsequent section on microelectronic corrosion, important environmental factors... 

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. 

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