APCVD

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). 

Fry, H., et al., Applications of APCVD TEOS/O3 Thin Films in ULSIIC Fabrication, Ao/zi/Atote Technology, pp. 31 0 (March... 

Ma, H., et al., Electrical and Optical Properties ofF-doped Sn02 Films Deposited by APCVD, Solar Energy Materials and Solar Ce//5,40(4)371-380 (Aug. 1996)... 

Atmospheric plant discharge, 21 849-850 Atmospheric pollutants, 10 30 Atmospheric pressure, 24 285-287 Atmospheric pressure chemical vapor deposition (APCVD), 5 807, 811, 812 Atmospheric pressure flow pyrolysis, 21 134... 

Although Eq. 27 appears to be the most likely initiation reaction, we cannot rule out a process in which water vapor and DMTC react, based on the ab initio results described in Sect. 4.6. If this does occur, however, it apparently does not lead to homogeneous nucleation of particles, since anecdotal evidence from the glass industry indicates that DMTC and water vapor can be premixed prior APCVD of tin oxide without substantial buildup of solids in delivery lines. Perhaps this is due to significant kinetic barriers to the decomposition of the tin-water complexes that initially form, so that further gas-phase reaction does not occur until the reactants enter the heated boundary layer above the substrate. 

The ISFET transducer, described in a previous paper (2), is an n-Si, p-well type device with the sensitive gate consisting of a thermally deposited SiC>2 (1000 A) and an APCVD deposited AI2O3 (600 A) layers. The gate area is 20 pm x 500 pm and the overall chip dimensions are 0.75 mm x 3 mm x 0.38 mm. 

Curtis TO, Pye JT, Poreda JT. APCVD TEOS 03 advanced trench isolation applications. 9th ed. Semiconductor Fabtech 1999. 

The pressure of the reactor must also be defined, and acronyms APCVD, LPCVD, and SCF-CVD are used to denote ambient, in vacuo, and supercritical pressure conditions within the deposition chamber, respectively. In general, the resultant... 

The preparation of tin phosphides has received attention due to their interesting mechanical, optical, and electrical properties catalyst applications. Atmospheric pressure chemical vapor deposition (APCVD) of tin phosphide thin films was achieved on glass substrates from the reaction of SnCU or SnBr4 with (R = Cy or Ph) at 500-600 °C. The films showed good uniformity and surface... 

Chemical vapor deposition includes various systems, and they are low-pressure CVD (LPCVD), atmospheric pressure CVD (APCVD), plasma enhanced CVD (PECVD), and others. Each type of CVD system has its own advantages and limitations. For instance, in LPCVD, the reactor is usually operated at 1 torr. Under this condition, the diffusivity of the gaseous species increases significantly compared to that under atmospheric pressure. Consequently, this increase in transport of the gaseous species to the reaction sites and the by-products from the reaction sites in LPCVD will not become the rate-limiting steps. This leads to the surface reaction step to be the rate limiting one. 

Atmospheric pressure CVD was first used for CVD in the microelectronics industry. The reactor for APCVD is, in general, relatively simple. However, as compared to LPCVD, APCVD can be mass-transport rate limited. Most of the APCVD used are for low-temperature oxide deposition and epitaxy. 

A wide variety of deposition methods are available, and several systems of each type are produced commercially. A review of typical systems has been published [10]. In regard to the CVD of insulating films, four general reactors are presently used atmospheric pressure CVD (APCVD), low and medium temperature low pressure CVD (LPCVD), and plasma-enhanced CVD (PECVD). 

APCVD systems allow for high throughput and even continuous operation, while LPCVD provides for superior conformal step coverage and better film homogeneity. PECVD has been traditionally used where low temperatures are required, however, film quality is often poor, e.g., silicon nitride grown by PECVD contains significant... 

The most widely used method for Si02 thin film CVD is the oxidation of silane (SiH4), first developed in 1967 for APCVD [13]. Nonetheless, LPCVD systems have since become increasingly employed [14, 15], and exceptionally high growth rates (30000 Amin" ) have been obtained by the use of rapid thermal CVD [16]. 

Figure 5-6. Deposition rate as a function of 02/SiH4 ratio for APCVD growth of Si02 (Data from...

SiH4 N2O N2 APCVD 490-690 200-1200 Si rich at high SiH4 cone. [18]... 

The SiH4/02 and SiH4/N20 routes to Si02 thin films are perhaps the most widely studied photochemical CVD of dielectrics [21], mainly due to their importance in VLSI technology. Photo-CVD of Si02 provides a suitable route to deposition at low substrate temperatures, thereby avoiding potential thermal effects of wafer warpage and deleterious dopant redistribution. In addition, other low temperature methods, such as APCVD and PECVD, often provide poor purity of films. 

Addition of O2 for APCVD growth does not decrease the deposition temperature, however, if ozone (O3) is used as the oxidation source, deposition temperatures as low as 300°C may be obtained for uniform crack-free films [38]. Figure 5-8 shows the dramatic effects of ozone on the LPCVD growth of Si02 compared to deposition with TEOS/oxygen, or TEOS only. It has been postulated that the ozone traps the TEOS molecule on the surface as it reacts with the ethoxysubstituent, providing a lower... 

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