CVD apparatus

LPCVD provides excellent uniformity on rough surfaces, excellent purity of the resulting films, and can permit selective deposition under the right conditions. However, it is more complex and expensive, operates at relatively low deposition rates, and often requires higher temperatures. Neither low rates nor high temperatures are a problem if one is trying to produce epitaxial thin films, as both are generally necessary for epitaxy in any case (see Chapter 10). 

---

CVD, the other major deposition process, is used on a large scale. A typical low-E glass is obtained by depositing a thin film of silicon dioxide followed by another thin film of fluorine-doped tin oxide. The Si02 acts as a diffusion barrier and the Sn02 reduces the emissivity. A typical CVD apparatus is shown in Fig. 

Figure 16.6. Diagram of CVD apparatus for the deposition of solar-control coatings on glass.

Figure 16.12. Diagram of plasma-CVD apparatus for optical fiber production.

Silver(I) /3-diketonate derivatives have received significant attention due to the ease with which they can be converted to the elemental metal by thermal decomposition techniques such as metal organic chemical vapor deposition (MOCVD).59 The larger cationic radius of silver(I) with respect to copper(I) has caused problems in achieving both good volatility and adequate stability of silver(I) complexes for the use in CVD apparatus. These problems have been overcome with the new techniques such as super critical fluid transport CVD (SFTCVD), aerosol-assisted CVD (AACVD), and spray pyrolysis, where the requirements for volatile precursors are less stringent. 

Figure 3.15. Schematic representation of a horizontal hot-wall CVD apparatus.

The chemical vapour deposition (CVD) technique can be regarded as an extension of the sublimation method used for the preparation of single crystals discussed before, but adapted to thin him growth implying deposihon on substrates. A schematic diagram of a horizontal hot-wall CVD apparatus is shown in Fig. 3.15. 

To clarify the situation, an on-line study of the decomposition mechanism of 26 was performed by connecting a mass spectrometer to the CVD apparatus. The substrate temperature was increased progressively from 323 to 873 K. Below 353 K, fragments from the amido ligands, similar to those coming from diethylamine were detected. Between 353 K and 873 K, the amount of hydrocarbon fragments rapidly increased (Figure 15.9). This analysis confirmed the important lability of the V-N... 

The preparation method of organosilane SAMs is described below [31, 45], A simple CVD apparatus shown in Fig. 7 was used. Although the precise preparation conditions for substrates is as follows First, the silicon substrate cleaned... 

CVD is a synthesis process in which the chemical constituents react in the vapor phase near or on a heated substrate to form a solid deposit (Pierson 1999). The reactions happened in the CVD system can be divided into homogeneous gas phase reactions and heterogeneous substrate surface reactions. Normally, CVD technique is utilized to make thin films. CVD is also defined as a process whereby a thin solid film is synthesized from the gaseous phase by a chemical reaction (Hitchman and Jensen 1993). The CVD apparatus arrangement is dependant on the particular application. The apparatus is made up with three major components precursors and... 

The deposition experiments were peformed in a CVD apparatus shown in Fig. 1. More details are described in [5]. The precursor was introduced from a thermostated bubbler (1) by adjusting its partial pressure via the temperature and if indicated via the flow rate of the carrier gas (10 seem argon or 10 seem hydrogen with 3 seem argon). 

Fig. 1. Schematic diagram of the OM CVD apparatus used for the deposition study...

Figure 7 is a phase diagram for the V-Ca-O system. Figure 8 shows a schematic diagram of the CVD apparatus. For cleaning a Type 304 SS chamber was heated to 850°C within 1 hr. while purging with 99.999% argon and was then cooled. 

Fig. 6 Schematic view of CVD apparatus used in coating development.

Formation of bismuth-containing thin films by CVD was demonstrated by Sievers and coworkers using the volatile Bi(fod)3 (2) as precursor source. In a hot-waU CVD apparatus (pyrex substrate, pressure 10 -10 Torr, precursor temperature 80-95 °C, Substrate = 400-450 °C, deposition rate 10 nmmin ) fluorine-free uniform layers with 73% bismuth were obtained. The carbon (15%) and oxygen (12%) contaminations may be reduced or eliminated if hydrogen is used as carrier gas. No decomposition mechanism was given. 

Figure 6.4.2 (a) Schematic diagram of CVD apparatus. MFC and RP represent a mass flow controller and a rotary pump, respectively, (b) Schematic structure of the macrocavity reactor consisting of two silicon wafers, each patterned with microcavity trenches. (Reproduced from K. Watanabe and H. Komiyama. Micro/Macrocavity Method Applied to the Study of the Step Coverage Formation Mechanism of Sit),7 Films by LPCVD, J. Electrochem. Soc., 137 (1990) 1222, with pennission of the Electrochemical Society, Inc.)... 

Legend MFC - mass flow controller Figure 3.3. Description of subsystems in a CVD apparatus... 

Figure 2. The schematics drawings for CVD apparatus of silica membrane preparation.

A schematic drawing of the CVD apparatus is shown in Figure 1. Rhenium base powder was reacted with the chlorine gas at 1070 1170 K, resulting in the formation of ReClj gas. This gas decomposed on the substrate, which was thermally heated to 1400 1520 K, and thus rhenium was deposited. The ReClj generation reaction and the thermal decomposition reaction are represented as... 

Figure 3.17 Different apparatus for the chemicai vapor deposition of carbon nanotubes (a) ciassicai CVD-reactor with tube furnace, (b) bias-enhanced CVD reactor, (c) piasma-enhanced CVD-apparatus.

For the direct injection of the catalyst or one of its precursors, the choice of compounds is naturally limited to vaporizable substances. The respective transition metal carbonyls and metallocenes proved their worth here. They decompose upon heating in the CVD apparatus and release the elemental metal in the shape of small, catalytically active clusters. 

The production of hMWNT is possible on different ways. For instance, they are the main product of converting pyridine or toluene in a CVD apparatus in a stream of hydrogen at about 1100°C in the presence of iron pentacarbonyl. But also the reduction of diethyl ether at ca. 700 "C on zinc yields up to 80% of helical nanotubes. 

Figure 6.15 Scheme of an HF-CVD apparatus (hot filament chemical vapor deposition). 

Table 6.1 summarizes some essential parameters of common CVD apparatus. For the time being, however, a final judgment on which of the setups provides the best results cannot be given. Therefore the most suitable method of diamond film deposition must be selected for each individual case depending on the specific requirements (high rate, high quality, good reproducibility, etc.). 

Figure 2-32. Schematic diagram of the Hoechst AG carrier gas-free CVD apparatus (1) furnace, (2) precursor, (3) oxygen pipe, (4) shutter,...

Fig. 7. Schematic diagram of the microwave discharge CVD apparatus. (Reprinted with permission Corn Erickson et al., 1996, Plasma Sources Set. Technol, S, 761, 1996 lOP Publishing, Ltd.)...

YSZ films were prepared a vertical cold-wall type CVD apparatus [II]. Source precursors of Zr(dpm)4 and Y(dpm)3 were vaporized at 483 to 593 and 393 to 473 K, respectively. The source vapors were carried with Ar gas into the CVD reactor. O2 gas was separately introduced by using a double tube nozzle, and mixed with precursor vapors in a mixing chamber placed above a... 

Both, high frequency (HF) [63,64,66,67,100 and direct current (d.c.) [65,1101,102] glow discharge were used for the deposition. The apparatus used for the deposition in an HF discharge has been described [63]. Here we shall briefly describe the plasma CVD apparatus which operates under conditions of an abnormal d.c. glow discharge. 

FIGURE 5.3 Plasma-Enhanced/Thermal CVD Apparatus for CNT Synthesis. 

---