Kyeong-Keun Choi

Chemical vapor deposition of copper film from hexafluoroacetyl-acetonateCu(I)vinylcyclohexane

Abstract An organometallic precursor, (hexafluoroacetyl-acetonate, hfac)Cu(I)(vinylcyclohexane, VCH) was studied for metallorganic chemical vapor deposition of copper thin films. The vapor pressure of (hfac)Cu(I)(VCH) is approximately 0.1 torr at 40°C and no appreciable amount of precipitation was observed while holding at 65°C for 1 month. The resistivity, purity, texture, adhesion, conformality and surface morphology of the film were investigated. The (hfac)Cu(I)(VCH) allowed the deposition at temperatures as low as 75°C. Copper film had a low resistivity of approximately 2.0 μΩ·cm for deposition temperatures ranging from 125 to 175°C. The copper film on physical vapor deposition (PVD) TiN was continuous and smoother than on chemical vapor deposition (CVD) TiN. The concentration level of impurities, including C, F and O at the interface was lower on PVD TiN than on CVD TiN. Films deposited at higher temperature showed better adhesion. It is believed that (hfac)Cu(I)(VCH) is stable with low vapor pressure and suitable as a precursor for seed layer formation with conformal coverage.

Effect of hydrogen remote plasma annealing on the characteristics of copper film

Abstract The effect of hydrogen remote plasma annealing on the characteristics of copper film such as resistivity, chemical composition and morphology was investigated. The hydrogen remote plasma enhanced the reflow of Cu and the preferential growth of Cu (111). With the increase of H2 gas flow rate ratio {[H2]/([H2]+[N2])}, plasma treatment time, and RF power, the resistivity of Cu film decreased due to the removal of impurity inside the film. The surface roughness decreased due to the smoothing of the surface, as the annealing time was increased up to 5 min but above that, the surface roughness increased because of agglomeration. The profile of Cu film in the trench opening became more conformal due to the enhanced reflow.

Effect of the neutral ligand (L) on the characteristics of hexafluoroacetylacetonate (hfac)Cu(I)-L precursor and on the copper deposition process

The effect of the neutral ligand (L) on the characteristics of hexafluoroacetylacetonate (hfac)Cu(I)-L precursor and on the copper deposition process was studied. It was found that the property of the ligand has an influence on the properties of the precursor such as vapor pressure and dissociation temperature and also on the deposition characteristics such as deposition temperature, deposition rate and film properties. Copper films were deposited at substrate temperatures ranging from 70 to 300 °C. When the dissociation temperature of the Cu(I)-L bond of the (hfac)Cu(I)-L was low, low-temperature deposition below 100 °C was possible, and lower resistivity of the copper film was obtained. The thermal stability of the precursor, however, was low in this case. Regardless of the molecular weight of L, the resistivity of the film was almost the same at substrate temperatures ranging from 125 to 175 °C. However, the resistivity increased as the molecular weight of L became higher above 225 °C. The vapor pressure of the (hfac)Cu(I)-L was higher when the molecular weight of L is low. Also the L had a strong influence on the morphology and texture of the copper film.

Effects of H2 plasma and annealing on atomic-layer-deposited Al2O3 films and Al/Al2O3/Si structures

We evaluated the effects of H2 plasma and thermal treatment on current–voltage (I–V) and capacitance–voltage (C–V) characteristics using Al/Al2O3/Si. H2 plasma treatment reduced the concentration of C and enhanced the diffusion of Si and O atoms and the mean breakdown field strength. The breakdown field increased significantly after rapid thermal annealing (RTA) due to crystallization and the formation of an interface layer between Si and Al2O3, which was confirmed by TEM, secondary ion mass spectroscopy (SIMS), and three-dimensional (3D) atom probe tomography. H2 plasma treatment produced a negative fixed charge due to the outgassing of C and H2, and RTA produced a positive fixed charge.

Metalorganic Chemical Vapor Deposition of Copper Using (Hexafluoroacetylacetonate)Cu(I)(3,3-dimethyl-1-butene) with a Liquid Delivery System.

From variable temperature (VT) 1H-nuclear magnetic resonance (NMR) and a heating test, it was found that (hexafluoroacetylacetonate)Cu(I)(3,3-dimethyl-1-butene) [(hfac)Cu(I)(DMB)] was stable up to 65°C. The effects of various process conditions such as substrate temperature, liquid precursor flow rate and hydrogen carrier gas flow rate on the deposition rate, texture, microhardness, surface roughness and uniformity were studied using a direct liquid injection 200 mm metalorganic chemical vapor deposition (MOCVD) reactor with hollow-cathode magnetron (HCM) sputter-deposited Cu substrate on silicon wafer. The MOCVD Cu process with (hfac)Cu(I)(DMB) showed good conformality, continuous film morphology and low resistivity at a substrate temperature of 190°C, vaporizer temperature of 55°C, total pressure of 2.5 Torr and precursor flow rate of 0.5 cm3/min. X-ray diffraction (XRD) analyses demonstrated a strong (111) texture of the copper film. The higher (111) peak intensity and the narrower width at half maximum were obtained when the source feed rate was low. Also the higher (111) peak intensity was observed at higher substrate temperature. At temperature below about 200°C, the microhardness was increased with increasing substrate temperature. In the high temperature regime (>200°C), the hardness was decreased.

Effect of Carrier Gas on Chemical Vapor Deposition of Copper with ( Hexafluoroacetylacetonate ) Cu ( I ) ( 3 , 3 ­ Dimethyl ­ 1 ­ butene )

The effect of carrier gases, such as argon, nitrogen, and hydrogen on the deposition rate, film morphology, resistivity, and chemical composition of copper films deposited with (hfac: hexafluoroacetylacetonate) Cu (1) (DMB: 3,3-dimethyl-1-butene) precursor was investigated at suhstrate temperatures between 100 and 275°C. The deposition rate was the highest and the resistivity was the lowest with the hydrogen carrier gas and the film had the smallest amount of impurities such as carbon, oxygen, and fluorine, It is believed that hydrogen enhances the surface reaction and forms more volatile species with impurity atoms The diffusion of the reactant in hydrogen gas is higher, which also leads to the higher deposition rate. Below the substrate temperature of 150°C, the activation energy of the deposition rate was about 150 kJ mol 1 on thermal oxide and about 84 ∼ 96 kJ mol -1 on TiN with both argon and nitrogen, hut it is about 54 kJ mol 1 with hydrogen carrier gas on both surfaces, The copper film deposited with hydrogen carrier gas has a higher ratio of the Cu(111) peak intensity to the Cu(200) peak intensity than in argon carrier gas.

Limitation of WSix/WN Diffusion Barrier for Tungsten Dual Polymetal Gate Memory Devices

We compared WSix/WN and Ti/WN diffusion barriers for tungsten dual polymetal gate (W-DPG) application, in terms of device performance and gate oxide reliability. WSix/WN diffusion barrier shows degradation of gate oxide, which is found to be due to the B-N dielectric formation and subsequent breakdown of diffusion barrier. Relatively, Ti/WN diffusion barrier shows excellent device performance in terms of R/O delay and gate oxide reliability

Electrical characteristics and step coverage of ZrO2 films deposited by atomic layer deposition for through-silicon via and metal–insulator–metal applications

The electrical characteristics and step coverage of ZrO2 films deposited by atomic layer deposition were investigated for through-silicon via (TSV) and metal–insulator–metal applications at temperatures below 300 °C. ZrO2 films were able to be conformally deposited on the scallops of 50-µm-diameter, 100-µm-deep TSV holes. The mean breakdown field of 30-nm-thick ZrO2 films on 30-nm-thick Ta(N) increased about 41% (from 2.7 to 3.8 MV/cm) upon H2 plasma treatment. With the plasma treatment, the breakdown field of the film increased and the temperature coefficient of capacitance decreased significantly, probably as a result of the decreased carbon concentration in the film.

Oxidation of the TA Diffusion Barrier and Its Effect on the Reliability of CU Interconnects

The oxidation of the Ta diffusion barrier and its effect on the reliability of Cu interconnects were investigated by high temperature storage (HTS) and via-to-line biased temperature stressing (BTS) tests. Cu/FSG, Cu/OSG, and Cu/porous low-k interconnects were investigated in vacuum (~ 1 torr), 0.1 atm air, and air. The exponential increase of resistance over the entire temperature range of the test was commonly found during HTS in via-chain test structures of all interconnects. It was different from typical stress migration behavior as the failure rate did not exhibit a peak at an intermediate temperature but increased exponentially with temperature. No voids were found in the failed samples that had resistance increases up to infinity. Instead, the Ta diffusion barrier was oxidized partially according to transmission electron microscopy/electron energy-loss spectroscopy (TEM/EELS) analysis. The oxidation of the Ta barrier at the via bottom was determined to be the cause of the electrical failure during HTS, which agreed with experimental results. During HTS tests, the Ta diffusion barrier was found to be more oxidized at the via sidewalls than at the M1 or M2 trench sidewalls. This oxidized Ta barrier at the via sidewalls was less protective. In the case of Cu/porous low k interconnects, Cu was found to diffuse out through the oxidized barrier at the via sidewalls, whereas Cu out-diffusion through the M1 or M2 trench sidewall was not noticeable. In via-to-line BTS tests, failure was also found to be caused by Cu out-diffusion/drift through the oxidized Ta diffusion barrier at the via sidewalls. The preferential oxidation of the Ta barrier at the via sidewalls and Cu out-diffusion through it suggests that the Ta barrier was more oxidizable and more permeable at the via sidewalls than at the M1 or M2 trench sidewall. Among the three kinds of interconnects used in this study, Cu/porous low-k was the most susceptible to the Ta diffusion barrier oxidation

Impact of graphene–graphite films on electrical properties of Al2O3 metal–insulator–semiconductor structure

The diffusion barrier property of directly grown graphene–graphite films between Al2O3 films and Si substrates was evaluated using metal–insulator–semiconductor (MIS) structures. The roughness, morphology, sheet resistance, Raman spectrum, chemical composition, and breakdown field strength of the films were investigated after rapid thermal annealing. About 2.5-nm-thick graphene–graphite films effectively blocked the formation of the interfacial layer between Al2O3 films and Si, which was confirmed by the decreased breakdown field strength of graphene–graphite film structures. After annealing at 975 °C for 90 s, the increase in the mean breakdown field strength of the structure with the ~2.5-nm-thick graphene–graphite film was about 91% (from 8.7 to 16.6 MV/cm), while that without the graphene–graphite film was about 187% (from 11.2 to 32.1 MV/cm). Si atom diffusion into Al2O3 films was reduced by applying the carbon-based diffusion barrier.