Molybdenum silicides

Compared to the detailed studies of WSi2, relatively less has been reported on LPCVD of the other refractory metals. One study in which MoSi2 has been deposited from MoCIS( SiH4 and H2 has been described recently.9 In this work, a hot tube furnace was used with a M0CI5 sublimator using an H2 carrier gas attached to it. The sublimator was operated at 160°C and all lines leading to the furnace were heat traced to prevent M0CI5 condensation. 

The as-deposited films had resistivities of 1000 /u 2-cm. After annealing at 1000°C for 20 minutes, this reduced to 120 /ifi-cm, which compared to the WSi2 described earlier is more than twice the value. One advantage of this film is that some small amount of chlorine remains after deposition, and this chlorine can act as a getter for any mobile impurities such as Na. 

Another recent study has examined the MoSi2 deposition using MoF6 and Si H4 rather than the chloride.10 These experiments were carried out in a quartz cold-wall system. Best results were found at a deposition temperature of 150°C, which is much lower than needed by the chloride process. Typical deposition conditions were 250 mTorr pressure, 2 to 6 seem of MoF6 and 100 seem of SiH4. All films were annealed at 1100°C for 30 seconds. They were found to be very stable and adherent on both silicon and silicon dioxide. A minimum resistivity of 100 fifl-cm was found for deposition temperatures below 150°C. Compared to the chloride process, the major advantage is the low temperature at which these films can be deposited. 

---

Gaczi, P. J., and Reynolds, G. J., Identification of Reaction Products in the Low-Pressure Chemical Vapor Deposition of Molybdenum Silicide, J. Electrochem. Soc., 136(9) 2661-2666 (Sept. 1989)... 

The results of two studies of silicide films are presented in Tables IV and V. For the results shown in Table IV, molybdenum silicides were deposited on vitreous carbon disks. One set was stripped with base (2 N NaOH), and the other set was stripped with acid (HF-HN03-H20, 1 1 10). The study of chromium silicides (Table V) gave similar results. 

Klemm H, Tangermann K, Reich T, Herrmann M, Schubert C, Hermel W (1995) High-Temperature Properties of Silicon Nitride Molybdenum Silicide Composites. In Bellosi A (ed) Fourth Europ Ceramics, Vol 4, Grupp Editoriale faenca Editrice, Faenza, p 233... 

Depth profiles are usually presented as atomic concentrations versus sputter time, assuming we know the rate at which the sample sputters. A typical depth profile is shown in Figure 25. It is interesting to see that at the surface there is carbon, silicon dioxide and some molybdenum. As soon as the surface layer is sputtered off (300 A), the oxygen and carbon impurities drop to constant and small values. For this CVD film, the molybdenum silicide came out to be very silicon rich. We can also see that the stoichiometry of the silicide changed with position (depth) in the film. 

Figure 24 Auger spectrograph of molybdenum silicide film both (a) before and (b) after sputter cleaning.

Figure 25 Auger depth profile of molybdenum silicide film.

Mcdifler, in glass structure, 59, 62 Modulus of elasticity, see elasticity modulus Molar volume, 82—83 Molybdenum silicide, 345, 346, 416 Monolithic lining, 391 Monticell ite, 240 Monfmorillonite, 33 Mullife, 38-42, 232, 372 in porcelain, 304—306 refractories, 373 Multi-chamber kiln, 298—299... 

Some of the compounds mentioned, especially 10 and 11, possibly have the potential to be used in MOCVD processes for the generation of thin molybdenum silicide films (Eq. 5). Deposition experiments are planned. 

In a related study, the deposition of molybdenum silicide from a composite target was compared to that cosputtered from elemental targets (42). SIMS depth profiles showed that the concentration of carbon and argon was lower and the level of oxygen was higher In the cosputtered film. Sheet resistance and C-V measurements for both types of films were also compared and were found to be not grossly different. 

Molybdenum silicide (MoSij) MoSij 12136-78-6 162.11 gray tetr cry -1900 6.2 H,0 sHE... 

Furthermore, because chromium has proven difficult to dry etch, there have been considerable efforts expended in finding alternative mask opaque absorber materials. Molybdenum silicide (MoSi) appears to be gaining traction in certain applications, particularly in attenuated phase-shifting mask (att-PSM) and EUV mask applications (see Section 14.3), and even for binary masks. ... 

---