• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1241-1246
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• 2010

Ternary Cu/ZnO/$Al_2O_3$ catalysts were prepared by a co-precipitation method. The precursor structures were monitored during the aging. The first precipitate structure was amorphous georgeite, which transformed into the unknown crystalline structure. The transition crystalline structure was assigned to the crystalline georgeite, which was suggested with elemental analysis, IR and XRD. The final structure of precursors was malachite. The Cu surface area of the resulting Cu/ZnO/$Al_2O_3$ was maximized to be 30.6 $m^2$/g at the aging time of 36 h. The further aging rapidly decreased Cu surface areas of Cu/ZnO/$Al_2O_3$. ZnO characteristic peaks in oxide samples almost disappeared after 24 h aging, indicating that ZnO was dispersed in around bulk CuO. TOF of the prepared catalysts of the Cu surface area ranges from 13.0 to 30.6 $m^2/g_{cat}$ was to be 2.67 ${\pm}$ 0.27 mmol/$m^2$.h in methanol synthesis at the condition of $250^{\circ}C$, 50 atm and 12,000 mL/$g_{cat}$. h irrespective of the XRD and TPR patterns of CuO and ZnO structure in CuO/ZnO/$Al_2O_3$. The pH of the precipitate solution during the aging time can be maintained at 7 by $CO_2$ bubbling into the precipitate solution. Then, the decrease of Cu surface area by a long aging time can be prevented and minimize the aging time to get the highest Cu surface area.

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.459-464
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• 2012

We investigated cleaning effects using $NH_4OH$ solution on the surface of Cu film. A 20 nm Cu film was deposited on Ti / p-Si (100) by sputter deposition and was exposed to air for growth of the native Cu oxide. In order to remove the Cu native oxide, an $NH_4OH$ cleaning process with and without TS-40A pre-treatment was carried out. After the $NH_4OH$ cleaning without TS-40A pretreatment, the sheet resistance Rs of the Cu film and the surface morphology changed slightly(${\Delta}Rs:{\sim}10m{\Omega}/sq.$). On the other hand, after $NH_4OH$ cleaning with TS-40A pretreatment, the Rs of the Cu film changed abruptly (${\Delta}Rs:till{\sim}700m{\Omega}/sq.$); in addition, cracks showed on the surface of the Cu film. According to XPS results, Si ingredient was detected on the surface of all Cu films pretreated with TS-40A. This Si ingredient(a kind of silicate) may result from the TS-40A solution, because sodium metasilicate is included in TS-40A as an alkaline degreasing agent. Finally, we found that the $NH_4OH$ cleaning process without pretreatment using an alkaline cleanser containing a silicate ingredient is more useful at removing Cu oxides on Cu film. In addition, we found that in the $NH_4OH$ cleaning process, an alkaline cleanser like Metex TS-40A, containing sodium metasilicate, can cause cracks on the surface of Cu film.

• Journal of the Korean institute of surface engineering
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• v.47 no.2
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• pp.68-74
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• 2014

The seed step-coverage enhancement process (SSEP) using Pd/Cu/PVP colloids was investigated for the filling of through silicon via (TSV) without void. TEM analysis showed that the Pd/Cu nano-particles were well dispersed in aqueous solution with the average diameter of 6.18 nm. This Pd/Cu nano-particles were uniformly deposited on the substrate of Si/$SiO_2$/Ti wafer using electrophoresis with the high frequency Alternating Current (AC). After electroless Cu deposition on the substrate treated with Pd/Cu/PVP colloids, the adhesive property between deposited Cu layer and substrate was evaluated. The Cu deposit obtained by SSEP with Pd/Cu/PVP colloids showed superior adhesion property to that on Pd ion catalyst-treated substrate. Finally, by implementing the SSEP using Pd/Cu/PVP colloids, we achieved 700% improvement of step coverage of Cu seed layer compared to PVD process, resulting in void-free filling in high aspect ratio TSV.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.570-576
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• 1996

Cu films for future ULSI metallization were prepared by partially ionized beam (PIB) deposition and characterized in terms of preferred orientation, grain size, roughness and resistivity. PIB-Cu films were prepared on Si (100) at pressure of $8 \times 10^{-7}$~$1 \times 10^{-6}$ Torr. Effects of acceleration voltage and ionization potential on the properties of PIB-Cu films have been investigated. As the acceleration voltage increased at constant ionization potential of 400 V, the degree of preferred orientation and surface smoothness of the Cu film increased. At the ionization potential of 450 V, the degree of preferred orientation at the acceleration voltage higher than 2 kV decreased and surface roughness increased with acceleration voltage. Grain size of Cu films increased to 1100 $\AA$ initially up to applied acceleration voltage of 1 kV, above which a little increase occurred with the acceleration voltage. There was no indication of impurities such as C, O in all sample. Resistivity of Cu film had the same trends as the surface roughness with acceleration voltage and ionization potential. The increase of electrical resistivity of PIB-Cu films was explained in terms of grain size and surface roughness

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.175.1-175.1
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• 2015

CuSn thin films were deposited by rf magnetron co-sputtering method with pure Cu and Sn metal targets with a variety of rf powers. CuSn thin films were studied with a surface profiler (alpha step), X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), X-ray diffraction (XRD), and contact angle measurement. The thickness of CuSn thin films was fixed at $200{\pm}10nm$ and deposition rate was calculated by the measured with a surface profiler. From the survey XPS spectra, the characteristic peaks of Cu and Sn were observed. Therefore, CuSn thin films were successfully synthesized on the Si (100) substrate. The oxidation state and chemical environment of Cu and Sn were investigated with the binding energy regions of Cu 2p XPS spectra, Sn 3d XPS spectra, and Cu LMM Auger spectra. Change of the crystallinity of the films was observed with XRD spectra. Using contact angle measurement, surface free energy (SFE) and wettability of the CuSn thin films were studied with distilled water (DW) and ethylene glycol (EG).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.113-113
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• 2008

Cu CMP (Chemical Mechanical Planarization) has been used to remove copper film and obtain a planar surface which is essential for the semiconductor devices. Generally, it is known that chemical reaction is a dominant factor in Cu CMP comparing to Silicon dioxide CMP. Therefore, Cu CMP slurry has been regarded as an important factor in the entire process. This investigation focused on understanding the effect of corrosion inhibitor on copper surface and CMP results. Benzotriazole (BTA) was used as a corrosion inhibitor in this experiment. For the surface analysis, electrochemical characteristics of Cu was measured by a potentiostat and surface modification was investigated by X-ray photoelectron spectroscopy (XPS). As a result, corrosion potential (Ecorr) increased and nitrogen concentration ratio on the copper surface also increased with BTA concentration. These results indicate that BTA prevents Cu surface from corrosion and forms Cu-BTA layer on Cu surface. CMP results are also well matched with these results. Material removal rate (MRR) decreased with BTA concentration and static etch rate also showed same trend. Consequently, adjustment of BTA concentration can give us control of step height variation and furthermore, this can be applicable for Cu pattern CMP.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2002.05a
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• pp.48-48
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• 2002

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.45-46
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• 1999

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.246-246
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• 2010

As the trench width in the interconnect technology decreases down to nano-scale below 50 nm, superconformal gap-filling process of Cu becomes very critical for Cu interconnect. Obtaining superconfomral gap-filling of Cu in the nano-scale trench or via hole using MOCVD is essential to control nucleation and growth of Cu. Therefore, nucleation of Cu must be suppressed near the entrance surface of the trench while Cu layer nucleates and grows at the bottom of the trench. In this study, suppression of Cu nucleation was achieved by treating the Ru barrier metal surface with capacitively coupled hydrogen plasma. Effect of hydrogen plasma pretreatment on Cu nucleation was investigated during MOCVD on atomic-layer deposited (ALD)-Ru barrier surface. It was found that the nucleation and growth of Cu was affected by hydrogen plasma treatment condition. In particular, as the plasma pretreatment time and electrode power increased, Cu nucleation was inhibited. Experimental data suggests that hydrogen atoms from the plasma was implanted onto the Ru surface, which resulted in suppression of Cu nucleation owing to prevention of adsorption of Cu precursor molecules. Due to the hydrogen plasma treatment of the trench on Ru barrier surface, the suppression of Cu nucleation near the entrance of the trenches was achieved and then led to the superconformal gap filling of the nano-scale trenches. In the case for without hydrogen plasma treatments, however, over-grown Cu covered the whole entrance of nano-scale trenches. Detailed mechanism of nucleation suppression and resulting in nano-scale superconformal gap-filling of Cu will be discussed in detail.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.6-11
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• 2012

In order to understand a process of contaminants removal on surface of Cu seed layer (Cu seed/Ti/Si) by sputter deposition, we investigated the changed morphology and states of Cu seed surface after pretreatment in alkali degreasing Metex TS-40A solution according to dipping time. After TS-40A pretreatment, the surface morphology with clearer grains was observed by Field emission scanning electron microscope and the changed surface chemical states and impurities on surface of samples were checked by X-ray photoelectron spectroscopy. Dipping time in TS-40A solution had very little effect on surface of Cu seed layer. After pretreatment, much carbons and little oxygens on surface of Cu seed were eliminated and the decrease of peaks corresponded to O=C and $Cu(OH)_2$ was estimated. However, Si content (=silicate) was detected on sample surface. We think that the silicate impurity forms on Cu seed by chemical reaction of TS-40A solution included silicate component. By pretreatment of alkali degreasing Metex TS-40A solution, it showed an excellent effect in removal of O=C and $Cu(OH)_2$ on Cu seed layer, but the silicate was formed on surface of Cu seed. Therefore, another cleaning process such as acid cleaning is required for removal of this silicate in use of this alkali degreasing.