Epitaxy deposition process

The vibrating ring/disk structure as well as the drive mechanism consists of 1 l- rm-thick poly-Si, which has been structured by deep RIE and released from the sacrificial oxide layer underneath by HE vapor phase etching. For the deposition of the thick poly-Si, a modified epitaxy deposition process (EPI poly) has been used [24]. However, as can be seen in Fig. 14.6, the deposition process leads to a rough poly-Si surface with Ra 100nm. For the removal of underlying topography, the surface has to be planarized by CMP in order to... 

Chemical vapor deposition may be defined as the deposition of a solid on a heated surface from a chemical reaction in the vapor phase. It belongs to the class of vapor-transfer processes which is atomistic in nature, that is the deposition species are atoms or molecules or a combination ofthese. Beside CVD, they include various physical-vapor-deposition processes (PVD) such as evaporation, sputtering, molecular-beam epitaxy, and ion plating. 

LED materials include gallium arsenic phosphide, gallium aluminum arsenide, gallium phosphide, gallium indium phosphide, and gallium aluminum phosphide. The preferred deposition process is MOCVD, which permits very exacting control of the epitaxial growth and purity. Typical applications of LED s are watches, clocks, scales, calculators, computers, optical transmission devices, and many others. 

The mechanisms of the deposition process will be of crucial importance in determining the quality of the grown layers and when growth is optimal, with epitaxial layers grown, the process... 

The primary difference in the operating conditions for growth of crystalline as compared with amorphous material is the deposition temperature. In the current design, 500 K is assumed for amorphous film deposition, while higher temperatures in the range 700-950 K are required for epitaxial growth. The low-temperature amorphous film deposition first is used to optimize the process, while the high-temperature epitaxial deposition subsequently is used as the basis for a detailed economic analysis. 

When reading the literature, in many (probably most) cases it is not clear whether the deposition proceeds by an ion-by-ion process. The reason is that, unless another mechanism is specifically discussed, it is often assumed that the deposition proceeds via the ion-by-ion mechanism. If the exact deposition parameters are known, which mechanism is operative can, in most cases, be calculated. Two criteria have often been cited in the literature as proof of deposition via the ion-by-ion mechanism. One is epitaxial deposition of the CD film. (Epitaxy refers to growth of one material on another in such a way as to result in coherence between the lattice of the substrate and the deposit. Often—although not necessarily—the lattice of the deposit is aligned in the same direction as that of the substrate.) This is based on the expectation that a cluster mechanism will not result in an epitaxial film for this to occur, clusters of maybe thousands of atoms would need to be able to rearrange themselves on the substrate. Some examples of epitaxial growth are given in Sections 3.4.2 and 4.I.5.2. 

Growth of various semiconductors onto certain single-crystal substrates has resulted in epitaxial growth in a number of cases. This epitaxy has been well studied for CdS deposition by Lincot et al. [59-63]. Although the epitaxy requires a certain degree of lattice matching between semiconductor and substrate, chemical interactions between the constituents of the deposition solution and the substrate are important as well (discussed in more detail in Chap. 4). It is a reasonable assumption that epitaxial deposition occurs via an ion-by-ion process. Indeed, it has... 

Silicon Epitaxy. A critical step in IC fabrication is the epitaxial deposition of silicon on an integrated circuit. Epitaxy is defined as a process whereby a thin crystalline film is grown on a crystalline substrate. Silicon epitaxy is used in bipolar ICs to create a high resistivity layer on a low resistivity substrate. Most epitaxial depositions are done either by chemical vapor deposition (CVD) or by molecular beam epitaxy (MBE) (see Thin FILMS). CVD is the mainstream process. 

In molecular beam epitaxy (MBE) [317], molecular beams are used to deposit epitaxial layers onto the surface of a heated crystalline substrate (typically at 500-600° C). Epitaxial means that the crystal structure of the grown layer matches the crystal structure of the substrate. This is possible only if the two materials are the same (homoepitaxy) or if the crystalline structure of the two materials is very similar (heteroepitaxy). In MBE, a high purity of the substrates and the ion beams must be ensured. Effusion cells are used as beam sources and fast shutters allow one to quickly disrupt the deposition process and create layers with very sharply defined interfaces. Molecular beam epitaxy is of high technical importance in the production of III-V semiconductor compounds for sophisticated electronic and optoelectronic devices. Overviews are Refs. [318,319],... 

Epitaxial Layers. Epitaxial deposition produces a single crystal layer on a substrate for device fabrication or a layer for multilevel conductive interconnects which may be of much higher quality than the substrate. The epitaxial layer may have a different dopant concentration as a result of introducing the dopant during the epitaxial growth process or may have a different composition than the substrate as in silicon on sapphire. Methods used for epitaxial growth include chemical vapor deposition (CVD), vapor phase epitaxy (VPE), liquid phase epitaxy (LPE), molecular beam epitaxy (MBE) and solid phase epitaxy (SPE). 

A silicon dioxide layer 3 is formed on an insulating CdTe substrate 1. A photo-resist coating 5 is formed over the silicon dioxide layer. The photo-resist layer is patterned and the silicon layer is partly etched away. The photo-resist layer is removed and a film of HgCdTe 9 of a first mercury to cadmium ratio is deposited by liquid phase epitaxial deposition over the entire surface of the substrate. The HgCdTe film is only formed at regions where the CdTe substrate is exposed and does not adhere to the silicon dioxide. Next, the silicon dioxide layer is removed. In order to increase the window of frequency response of the detectors, the process is repeated using a second mercury to cadmium ratio different from the first ratio. 

The potential benefits of CVD over other film deposition techniques are that CVD-derived films can be deposited under conditions that give conformal coverage, they can be deposited at low temperatures, there can be a high level of compositional control, thin layers can be deposited, the technique can be scaled to coat large areas uniformly, and there is also the possibility for area-selective deposition13 as a result of the chemical nature of this process. The details of CVD and related chemical deposition processes such as atomic layer epitaxy (ALE), organometallic vapor-phase epitaxy (OMVPE), and others have been described elsewhere.6... 

Atomic layer deposition (also termed atomic layer epitaxy) a process in which alternate pulses of two volatile precursors are passed over the substrate to promote layer-by-layer film growth... 

Chemical beam epitaxy a process in which one or more beams of volatile metal-organic precursors is directed to the substrate surface to effect film growth Chemical vapor deposition (CVD also termed vapor-phase epitaxy) the deposition of a thin film of an element or compound using some form of excitation for the decomposition of a volatile precursor... 

The liquid solution CCVD process does not deposit droplets (these evaporate in the flame environment) or powders as in traditional thermal spray processes. The CCVD technology is drastically different from spray pyrolysis In spray pyrolysis, a liquid mixture is sprayed onto a heated substrate, while CCVD atomizes a precursor solution into sub-micron droplets followed by vaporization of said droplets. The resulting coating capabilities and properties described hereafter qualifies CCVD as a true vapor deposition process. For example, depositions are not line-of-sight limited and achieve epitaxy, 10 nm dielectric coatings onto silicon wafers in a Class 100 clean room resulted... 

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