Al2O3 formation on Si by catalytic chemical vapor deposition

The mechanism of alumina formation from TMA and molecular oxygen using Catalytic-CVD with a tungsten catalyzer

“…It should be noted that alumina can be deposited in a wide range of substrate temperatures, as low as room temperature. The increase seen at 800 -C can be explained due to the reaction on Si substrate surface, because, when the catalyzer was switched off, the film was deposited [9]. Abrupt decrease above 800 -C is considered to be due to prevention of the adsorption of O 2 , since the film altered to white colored grains in exposure to the air after the deposition, which was the same as that observed for the films deposited without O 2 .…”

“…Despite the excellent properties of Cat-CVD, it has never been studied in the production of oxide films except for SiO 2 [7,8]. Thus, we have developed Cat-CVD with a tungsten (W) catalyzer to deposit alumina thin films, resulting from tri-methyl aluminum (TMA) and O 2 , onto Si wafers in order to produce MIS (metal insulator semiconductor) diodes with high-k oxide gates [9]. These MIS diodes exhibited good capacitance -voltage characteristics [9,10].…”

“…Thus, we have developed Cat-CVD with a tungsten (W) catalyzer to deposit alumina thin films, resulting from tri-methyl aluminum (TMA) and O 2 , onto Si wafers in order to produce MIS (metal insulator semiconductor) diodes with high-k oxide gates [9]. These MIS diodes exhibited good capacitance -voltage characteristics [9,10]. However, the understanding of the mechanism of alumina formation is not well understood.…”

Catalytic CVD processes of oxidizing species and the prevention of oxidization of heated tungsten filaments by H2

“…This is because tungsten, one of the most widely used catalyzer materials, is easily oxidized and the vapor pressure of tungsten oxide is much higher than that of tungsten metal. According to Ogita and his coworkers, the typical lifetime of tungsten catalyzers used in the presence of trimethyl aluminum and O 2 to deposit Al 2 O 3 is as short as 25 min [1,2]. This problem can be avoided by using Ir instead of W [3,4].…”

The mechanism of alumina formation from TMA and molecular oxygen using catalytic-CVD with an iridium catalyzer

“…The formation of SiO 2 films using a Cat-CVD with W filaments has been attempted by Izumi et al [7]. We have also tried to produce alumina using W filaments [9]. Unfortunately, the short lifetime of the W filaments, which is caused by oxidation, poses a serious problem with this method.…”