Youn-Jin Oh

Planarization of Copper Layer for Damascene Interconnection by Electrochemical Polishing in Alkali-Based Solution

Recently, electrochemical-mechanical polishing (ECMP) has been suggested as an alternative to the conventional chemical-mechanical polishing process, in order to overcome the difficulties encountered in the latter. In the ECMP process, Cu ions are electrochemically dissolved by applying an anodic potential to the Cu surface in an electrolyte. The dishing effect, however, still exists for wide-width lines even in the case of the ECMP method. In this study, we focus on minimizing the dishing effect and enhancing the uniformity of the within-wafer profile by applying not only electrochemical dissolution to the wafer, but also mechanical force. First, we studied the alkali-based ECMP process. We reduced the dissolution rate of the Cu ions by using KOH-based electrolyte instead of an acidic-based one, and we fundamentally studied the chemical state of the Cu surface according to the concentration of the electrolyte and the anodic potential using X-ray photoelectron spectroscopy analysis. In this way, we monitored the oxidation of the Cu surface by the anodic potential in KOH electrolyte and found that the oxidation rate was increased by adding H 2 O 2 . Also, the uniformity of the within-wafer profile was enhanced bv using benzotriazole.

Thermodynamic Stability of RuO2 Bottom Electrodes and Their Effect on the Ba-Sr-Ti Oxide Film Quality

We have performed calculations to evaluate the thermodynamic stability of RuO 2 film and its effect on (Ba, Sr)TiO 3 (BST) film quality when it is deposited on RuO 2 thin film by metallorganic chemical vapor deposition. RuO 2 is rather stable when it is annealed in oxygen ambient. However, it was etched by gaseous oxygen when too much oxygen was fed at high temperatures, The degradation of RuO 2 occurs in two different reaction pathways depending on process conditions. One is the thermal decomposition of RuO 2 that mainly happens when no excess O 2 is present in the feed at low pressures. The other is the etching of RuO 2 film by excess O 2 , which produces gaseous RuO 3 and RuO 4 species. The calculation results on the Ba-Sr-Ti-Ru-C-H-O system also present optimal feed composition and process conditions that result in high-quality (Ba, Sr)TiO 3 lilm.

An In Situ ATR-FTIR Study on Palladium Displacement Reaction on Hydrogen-Terminated Silicon Surface

We have studied the mechanism of Pd autocatalytic displacement reaction on a silicon surface in both PdCl 2 -HCl-HF-NH 4 OH and PdCl 2 -HCl-HF baths. Using in situ and ex situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) experiments, it has been shown that Pd(NH 3 ) 2 Cl 2 in the electrolyte is reduced to metallic Pd particles by a displacement reaction and an (NH 4 ) 2 SiF 6 compound is generated during the Pd activation in PdCl 2 -HCl-HF-NH 4 OH electrolyte. From our results, we have concluded that different mechanisms of displacement reactions in each electrolyte result in the different characteristics of Pd growth. Hydrofluoric acid, which is generated in the Si etching reaction, is directly dissolved to SiF 2 - 6 during the Pd displacement reaction. The SiF 2 - 6 in the PdCl 2 -HCl-HF electrolyte plays a role as the Si etchant, whereas SiF 2 - 6 bonds with NH + 4 ion in the PdCl 2 -HCl-HF-NH 4 OH electrolyte. These different mechanisms result in the different of Pd growth speeds and characteristics.

An in-situ FTIR Study on Palladium Displacement Reaction for Autocatalytic Electroless Copper Deposition

We have investigated on the mechanism of palladium autocatalytic displacement reaction on the Si substrate in PdCl 2 -HCl-HF-NH 4 OH bath, which occurs in the Pd activation step in electroless Cu deposition process. It has been monitored that Pd(NH 3 ) 4 Cl 2 in the electrolyte is reduced to Pd particles by displacement reaction with substrate silicon and NH 4 + complex are generated during the Pd activation. In the in-situ FTIR analysis, N-H vibration peaks in Pd(NH 3 ) 4 Cl 2 of electrolyte are shifted to N-H peaks in NH 4 + complex. The IR peaks of SiF 6 2- and N-H bonds of NH 4 + are also evident during the Pd activation on the Si surface. It reveals that palladium in Pd(NH 3 ) 4 Cl 2 has been reduced to metallic Pd particles on Si substrate and (NH 4 ) 2 SiF 6 compound has been produced.