PECVD films

Silicon. The most widely studied and perhaps the best understood PECVD film is that of amorphous silicon (a-Si). Glow discharge a-Si is an alloy of silicon and hydrogen, with the hydrogen content ranging from 5 to 35 atom percent (atom %), depending upon the deposition conditions (temperature, rf power, rf frequency, etc.) and the resulting film structure. 

In the present chapter, we will review the nature of plasma-enhanced CVD (PECVD) films for a variety of applications. We will look at dielectrics (silicon nitride, silicon dioxide), semiconductors (polysilicon, epi silicon) and metals (refractory metals, refractory metal silicides, aluminum). There are many other important films (i.e., amorphous silicon for solar cells and TiN for tool harden-... 

Up to this point, we have been considering PECVD films that are being used commercially in the manufacture of integrated circuits. We will now consider PECVD of other films that may find practical application in the future. At the present time, they are still considered experimental. 

Figure 6.(a) Composite depth profile plot of a silicon nitride film on Si precoated with Si02. (b) "Hg ratio versus [NH3]/[SiH4] gas ratio for a-SixNyHz PECVD film from ERD, XPS and the deduction based on measured refractive-index. 

Some Concluding Remarks about the Mechanical Stability of Passivation PECVD Films... 

The results on different PECVD films, showed that the failure of the systems was different, depending on the associated materials and on the interfacial behavior when the debonding occurred with buckling, or by interfacial crack deviation, the transverse crack saturation was reached at lower strains. No... 

Thin film dielectrics are usually deposited using chemical vapor deposition (CVD). A variation of CVD utilizing a plasma discharge is called plasma-enhanced CVD (PECVD) and is the standard in IC fabrication for the deposition of dielectric films. Plasma-enhanced CVD involves the formation of a solid film in a substrate surface from volatile precursors (vapor or gas) in a plasma discharge. The precursors are chosen to contain the constituent elements of the final film and chemical reactions in the gas phase are encouraged. They are condensed in a substrate that is heated or cooled. It will be shown later that porosity can be introduced in the PECVD films. Spin coating is another preparation technique and a popular choice... 

Figure 5-12. The oxygen/aluminum ratio as a function of deposition temperature for PECVD films of AEOi using AIMeVNiO (Data from [94 ).

Figure 5-19. Variation of Si/N ratio in PECVD films of SiiN4 as a function of deposition temperature for different SiH4/NHj ratios (Data from [149, 150. ...

Figure 10.148 Anion chromatograms of various BPSG-films. Separator column lonPac AS4A eluent carbonate/bicarbonate mixture flow rate 2 mt/min detection suppressed conductivity samples (a) APCVD-film with good flow properties, (b) PECVD-film with bad flow properties, (c) reference standard with...

Typical anion chromatograms of two different BPSG-films (A, B) and a standard (C) are illustrated in Fig. 9-88. Separation was carried out on lonPac AS4A with a carbonate/bicarbonate eluant mixture. Chromatogram A was obtained after dissolving an APCVD-film (APCVD Atmospheric Pressure Chemical Vapor Deposition) that exhibited good flow properties in 0.2% HF solution. Chromatogram B results from a PECVD-film (PECVD Plasma Enhanced Chemical Vapor... 

Costacurta, S., Malfotti, L., Patelli, A., Amenitsch, H., Marmiroli, B., Falcaro, P., Grenci, G., Piccinini, M., and Innocenzi, P. (2010) Deep X-ray lithography for direct patterning of PECVD films. Plasma Proems. Polym., 7,459-465. 

Dielectric Film Deposition. Dielectric films are found in all VLSI circuits to provide insulation between conducting layers, as diffusion and ion implantation (qv) masks, for diffusion from doped oxides, to cap doped films to prevent outdiffusion, and for passivating devices as a measure of protection against external contamination, moisture, and scratches. Properties that define the nature and function of dielectric films are the dielectric constant, the process temperature, and specific fabrication characteristics such as step coverage, gap-filling capabihties, density stress, contamination, thickness uniformity, deposition rate, and moisture resistance (2). Several processes are used to deposit dielectric films including atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), or plasma-enhanced CVD (PECVD) (see Plasma technology). 

Fig. 1. Multichamber PECVD reaction chamber apparatus for fabrication of i -Si H films, where the /-chamber represents the deposition of the intrinsic...

Dielectric Deposition Systems. The most common techniques used for dielectric deposition include chemical vapor deposition (CVD), sputtering, and spin-on films. In a CVD system thermal or plasma energy is used to decompose source molecules on the semiconductor surface (189). In plasma-enhanced CVD (PECVD), typical source gases include silane, SiH, and nitrous oxide, N2O, for deposition of siUcon nitride. The most common CVD films used are siUcon dioxide, siUcon nitride, and siUcon oxynitrides. 

Many materials have been deposited by PECVD. Typically, the use of a plasma allows equivalent-quaUty films to be deposited at temperatures several hundred degrees centigrade lower than those needed for thermal CVD techniques. Often, the plasma-enhanced techniques give amorphous films and films containing incompletely decomposed precursor species such as amorphous siUcon (i -Si H) and amorphous boron (i -B H). 

At the end of last century, a near frictionless carbon (NFC) coating was reported, which is practically hydrogen contained DLC film grown on steel and sapphire substrates using a plasma enhanced chemical vapor deposition (PECVD) system [50]. By using a ball on a disk tribo-meter, a super low friction coefficient of 0.001-0.003 between the films coated on both the ball and the disk was achieved [50]. A mechanistic model was proposed that carbon atoms on the surface are partially di-hydrogenated, resulting in the chemical inertness of the surface. Consequently, adhesive interaction becomes weak and super low friction is achieved [22],... 

The HWCVD deposition process is more or less the same as for PECVD, and was described in Section 1.7. Important differences between the two is the absence of ions, and the limited number of different species present in the gas phase, in the former. At low pressure atomic Si is the main precursor. This yields void-rich material with a high microstructure factor. Increasing the pressure allows gas phase reactions with Si and H to create more mobile deposition precursors (SiH3), which improves the material quality. A further increase leads to the formation of higher silanes, and consequently to a less dense film. 

Other studies showed the same trends discussed earlier. Films obtained by RF-PECVD, deposited at about the same conditions in other precursor atmospheres [79], showed the same behavior, with the Id/Iq and wq following about the same dependence on nitrogen content as the one shown in Figure 23. 

Chemical vapor deposition (CVD) process, 5 803-813,13 386 16 173, 531 17 209 22 129 23 7, 59 24 743-744 25 373. See also CVD entries Plasma-enhanced chemical vapor deposition (PECVD) Vapor deposition catalyzed, 26 806 ceramics and, 5 663 common precursors and corresponding thin films grown, 5 805t in compound semiconductor processing, 22 188, 189... 

In the Development stage, detailed product design is carried out. This is the key step for the chemical vapor deposition of thin silicon films. As described in the next section, to obtain uniform thin films rapidly, it is desirable to optimize the design of the plasma-enhanced, chemical-vapor-deposition (PECVD) reactor. 

Figure 10.4-6. Schematic of PECVD reactor chamber geometry for deposition of epitaxial films on 30-cm diameter wafers. i = 0.

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