Deposition and etching

Maurice H. Francombe and John L. Vossen, Physics of Thin Films, Advances in Research and Development, Plasma Sources for Thin Film Deposition and Etching,yo ivat 18, 1994. 

Reactions involving solids are very important in many technologies such as microelectronics processing, ceramics, ore refining, electrochemical deposition and etching, chemical vapor deposition and etching, and food processing. We will consider some of these applications in problems, but we first note several important examples. 

In recent years the surface science approach has led to a dramatic increase in our knowledge of the surface chemistry and kinetics. Processes that have been studied using the surface science approach include the deposition and etching of semiconductors (e.g., Si, Ge,... 

At present, reproducibility and control are the primary limitations to the implementation of plasma processes clearly, the large number of interacting parameters accounts for such problems. In addition, deposition and etching processes are inordinately sensitive to small (part-per-billion) concentrations of impurities. These difficulties can be overcome only by careful investigation of the complex chemistry and physics of glow discharges. 

Theoretically, electrical patterning is one the simplest method to structure materials since they can be patterned directly on the surface of an electrode. Creating conducting microelectrodes is, nowadays, fast and simple using micro and nanotechnology tools. Deposition and etching, or deposition followed by lift-off, are the conventional methods [35], Other solutions based on electrodeposition of metals... 

Smith, G.C., CVD tungsten contact plugs by in-situ deposition and etch-... 

No literature has been published in this area but, as a rule of thumb, metals which dissolve to give complexes that have linear or tetrahedral geometries, e.g. Cu, Ag, Zn, Sn, Pb, can be reversibly deposited and etched. Those with octahedral geometries, e.g. Fe, Ni, Co and Cr, are less reversible. The exceptions to this are the very electronegative metals, most notably A1 which is difficult to electrodeposit from some ionic liquids. The reversibility is also dependent upon the type of ionic liquid and the metal being deposited. Endres has shown that the adhesion of aluminum to mild steel is greatly enhanced by an anodic pulse prior to deposition. It has been shown that this alloy was formed between the steel substrate and the aluminum coating [1],... 

It is the opinion of the author that future research on reactor modeling should focus on developing models for reactors and processes which are as yet poorly understood. Examples of such systems include fluidized-bed reactors, membrane reactors, reactors used for the synthesis of ceramics, and low-pressure reactors used for the deposition and etching of thin films. 

An integrated circuit is a multilayer, three-dimensional structure of electrically interconnected solid-state circuit elements isolated with patterned dielectric films. The dielectric, conductor, and semiconductor films are deposited or formed by sophisticated chemical reactions. The successful growth and manipulation of these films depend heavily on the proper design of chemical reactors used in deposition and etching, the choice of appropriate chemical reagents, separation and ultrapurification, and operation of sophisticated control systems. 

Plasma deposition and etch rates are affected by a large number of process parameters and physicochemical processes, illustrated schematically in Fig. 2, making the development and operation of plasma processes difficult. Moreover, given a particular process chemistry, it is not obvious how readily accessible parameters (e.g., feed rate, pressure, power, and frequency) should be manipulated to obtain the desired film uniformity and material properties. Glow discharge physics is complex, and the chemical mechanisms are not well known, in particular those underlying the plasma-surface interactions. Consequently, there is considerable incentive for gaining... 

Klavs Jensen I want to address some of the control issues that are involved because they re very different from what we traditionally have done with continuous processes. In most of these processes, materials are deposited and etched in batch processes. In the next generation of production equipment, the wafer will travel in vacuum channels from one piece of equip-... 

In addition, NF3 prepares no deposited layers on the substrate. Formation of such deposited layers cannot be avoided in case of CF4. To remove the deposited film, atomic fluorine is required. NF3 gives no deposit and etching proceeds well without any contamination on the silicon surface. NF3 thus has an advantage of being free from contamination by carbon atom. 

Several contending technologies are presently being used to achieve local and global planarizations that include spin on deposition (SOD), reflow of boron phosphorous silicate glass (BPSG), spin etch planarization (SEP), reactive ion etching and etch back (RIE EB), spin on deposition and etch back... 

A second method of surface smoothing is to deposit a thick layer of SiOj and then a thin the layer by RIE or sputter etching. Because the sputter yield of the SiOj is greatest at an angle of 45°, the corners in the SiOj film etch quicker than the rest of the film and are therefore rounded by the etch process. With some deposition systems, for example, biased electron cyclotron resonance (ECR) plasma deposition, it is possible to deposit and etch concurrently, yielding a one-step process with a reduced deposition rate. ... 

Deposition and etching of Si can be accomplished at line widths <0.4 Jim (204). Practical applications of this laser microchemical processing include ohmic contact formation on p-InP (p-type indium phosphide) and hard-surface-mask repair (205). Further details on recent applications of this process can be found (204-206). 

Another solution to reduce the loading effect was investigated by van Laarhoven et. al.61, (see figure 2.19). In their approach there was a 0.3 urn PECVD silicon nitride layer deposited atop the oxide prior to the contact opening. The normal procedure of adhesion layer (TiW), tungsten deposition and etch back was followed. Since the nitride etches with about the same rate as the tungsten (selectivity W SiN=0.8) both the loading is... 

A planar substrate, such as silicon wafer, could be micromachined by a sequence of deposition and etching processes. This results in three-dimensional microstructures which can be implemented in cavities, grooves, holes, diaphragms, cantilever beams etc. The process referred to as silicon micromachining often employs anisotropic etchants such as potassium hydroxide and ethylene diamine pyrocatechol. The crystallographic orientation is important as the above-mentioned etchants show an etch-rate anisotropy. The ratio for the (100)-, (110)- and (111)- planes is typically 100 16 1. The technique of electrochemical etch stop could be applied for control of the microstructural dimensions. An alternative... 

There are a variety of chemical processes used in the manufacturing of MEMS and ICs. These include deposition and etching processes. Some of the more common examples of these processes are described briefly in the sections that follow. 

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