Niwano and Hirose are world authorities in ALD research. In particular, Hirose has conducted detailed research on the adsorption and oxidation mechanisms of raw materials for high-k, as well as the decomposition and stacking processes of raw materials, and has achieved numerous research results. [40]~[58]
AB-doped Si (100) substrate with a resistivity of approximately 10 Ωcm was used the sample. The same sample was introduced a stainless steel vacuum chamber for ALD with facilities for infrared absorption spectroscopy (IRAS) with a multiple internal reflection (MIR) geometry as a directed in situ, as shown in Figure 46.
We started with basic research on high-k raw materials such as TDMAS, TEMAH (Figure 47), and TEMAZ, and eventually established mass production technology using 500-5000L reaction vessels. We also developed a 50 kg scale feeder system to supply feedstock to ALD production machines, and delivered it to a semiconductor manufacturer. Figure 48 compares the Vg-leakage characteristics of an ultra-pure TEMAH (P-TEMAH) synthesized using my original purification method with those of a HfO2 capacitor made with average commercial s-TEMAH.
High-purity TEMAH was synthesized by a chemical refinement and distilling method using ethylmethylaminolithium and hafnium tetrachloride. It is possible to reduce impurities in HfO2 film by reducing the impurities in the hafnium raw material. And, the reduction efficiency in the HfO2 film is proportional to the reduction number in the raw material. Electrical evaluation using high-purity TEMAH showed a low leakage current and low CFT value before annealing.