Surface Roughness Of Cu Films Research Articles

Effect of Novel pH Regulators on Copper film Chemical Mechanical Polishing for Ruthenium-Based Copper Interconnect under Weak Alkalinity Conditions

For Ruthenium (Ru)-based copper (Cu) interconnects Cu film chemical mechanical polishing (CMP), it is crucial to select appropriate pH regulators in the slurry to ensure the chemical reactions and maintain the stability of the polishing chemical environment. In this study, the effects of inorganic pH regulator KOH, organic pH regulator diethanolamine (DEA), and 2-amino-2-methyl-1-propanol (AMP) on CMP and slurry properties of Cu film were compared. It was found when using AMP as a pH regulator, the Cu/Ru removal rate selectivity (RRS) can reach 598:1, the surface roughness of Cu film decreased to 0.76 nm, and the slurry can remain stable for at least 7 d. The performance order of the three pH regulators is AMP＞KOH＞DEA. Meanwhile, through experimental results and test analysis, it has been confirmed that AMP can also play a multifunctional role as a complexing agent, dispersant, and surfactant. Therefore, AMP can replace KOH as a new pH regulator in weak alkaline slurries. This result plays an important role in guiding the selection of organic pH regulators in the optimization of Cu film CMP slurry.

Effects of accelerator in a copper plating bath on interfacial microstructure and mechanical properties of SAC305/Cu solder joints

An accelerator, 3-(2-benzthiazolylthio)-1-propanesulfonsaure (ZPS), was used and formulated with a suppressor (polyethylene glycol, PEG) and chloride ions (Cl−) in electroplated Cu plating solution containing electrolytes (Cu sulfate and sulfuric acid) to prepare the Cu films. The preferred orientation of Cu film transformed from (200) to (220) with the addition of ZPS in plating solution containing (PEG and Cl−). The addition of ZPS in basic plating solution promoted the growth of Cu grains and increased the surface roughness of Cu film. The root mean square roughness of Cu film increased from 206.9 to 230.8 nm with increasing ZPS concentration. The impurity elements of electroplated Cu film were O, C, Cl, and S elements. With the further increase in ZPS, the number of void within Cu3Sn layer obviously reduced, improving the stability of the electroplated Cu solder joints subjected to thermal aging.

Surface roughness analysis of Cu films deposited on Si substrates: A molecular dynamic analysis

Cu is a promising material to replace Al and Au in integrated circuits and microscale devices because of its low electrical resistivity, high electromigration resistance, and low cost. However, surface roughness affects the contact resistance of these devices, especially when the device is on a microscale or nanoscale. This paper focuses on surface roughness analysis of Cu films deposited on Si substrates by molecular dynamic simulation based on the mechanism of physical vapor deposition. The effects of film thickness, deposition temperature, deposition interval, and reflow temperature on the surface roughness of Cu films are studied in detail. The simulation results show that the surface roughness can be improved by appropriate adjustments of these parameters. They also provide a foundation for further work on the deposition of Cu films on Si substrates.

Effect of electroplating parameters on electroplated Cu film and microvoid formation of solder joints

The influences of electroplating parameters on electroplated Cu (EPC) film and void formation at the Sn3.0Ag0.5Cu (SAC305)/Cu interface were investigated. It is found that the size of Cu particles increased with the increase of current density or deposit thickness. The surface roughness of Cu films also increased with increasing current density. And the surface roughness of EPC films demonstrated decrement at first and then increment with the increase of deposit thickness. It is observed that the electrodeposition with higher current density or thicker Cu film tended to inhibit the growth of Cu(111) and favor the growth of Cu(220). After reflowing and thermal aging, the voiding level increased greatly as the current density and deposit thickness increased, and that total microvoid area increased gradually with increasing aging time for all electroplating conditions. Additionally, the variation in the current density and deposit thickness did not influence the intermetallic compound growth rate.

Morphology and microstructure control of sputter-deposited copper films by addition of Cr

Pure Cu and Cu with 1 at.% and 2.6 at.% Cr films were sputtered on (100) single crystal Si wafers in the presence of native suboxide (SiOx). Samples were vacuum-annealed to investigate effects of Cr on the microstructural characteristics of Cu films. Cr refines the columnar structure and decreases the surface roughness of Cu films. Upon annealing, most films undergo the process of crystallite growth and coalescence. Cross-sectional images show that Cr stabilizes the columnar structure and inhibits the agglomeration of annealed Cu(Cr) films at high temperatures. The fine grains of Cu(Cr) films suggest that the extensive Cu crystallite/grain growth at 400 °C is effectively impeded by the presence of Cr. The noticeable grain growth occurs around 450 °C with Cr precipitates in Cu(Cr) films. After annealing, the final resistivity of the annealed Cu(Cr) film is approached to that of the Cu film. Adding Cr to films has obtained significant changes in morphology and microstructure of Cu films before and after annealing.

Characterisation of lead free solderability of immersion Sn finish on PWBs using wetting balance technique

Lead free solderability of pure Sn/Cu finish is investigated in terms of microetch process in printed wiring boards manufacturing. Factors affecting the solderability have been known as whisker, contamination, copper tin intermetallic compound, and the thickness of coating. Lead free solderability, in this paper, is correlated with the surface roughness of Cu film after the microetch process. Solderability is measured by wetting balance technique, and the result shows that the wetting force and the wetting time are negatively correlated with the coefficient of –0˙613. Employing statistical design of experiment, two significant factors, etching time and the mount of Piperidine, affecting the wetting force with respect to the surface roughness of Cu film are successfully identified, and response surface plot for the wetting force is also generated for visual an aid of interaction between the two parameters.

Investigation of Ar incident energy and Ar incident angle effects on surface roughness of Cu metallic thin film in ion assisted deposition

This paper employs molecular dynamics (MD) simulations to investigate the influence of the Ar ion incident energy and incident angle on the surface roughness of Cu films fabricated using the ion assisted deposition (IAD) process. The MD simulations use the tight-binding potential and the Molière potential to simulate the Cu–Cu and Cu–Ar + interactions, respectively. The numerical results indicate that the dependency of the surface roughness on the incident angle of the ions is a function of the ion incident energy. At lower incident energies, a weaker dependency exists, and the surface roughness is improved irrespective of the ion incident angle. However, at intermediate and higher ion incident energies, the dependency of the surface roughness on the incident angle becomes more apparent. Under these conditions, a higher incident angle yields an improved surface roughness. Increasing the ion assisted ratio has a similar effect on the surface roughness as increasing the ion incident energy. The results indicate that an excessive ion assisted ratio leads to the formation of a rougher surface; particularly at higher ion incident energies.

下地層ならびに超高真空中加熱プロセスによるＣｕ薄膜の面内結晶粒径の増大と表面平坦化

The effects of body centered cubic (BCC) solid solution underlayers on the metallurgical size and flatness of Cu thin films, fabricated on them, were investigated. As the underlayer materials, Cr80Al20, Cr90Ni10, Cr80Fe20, Fe75Cr25 and Fe were examined. Lateral grain size of the Cu films fabricated on the Cr-Al, Cr-Ni, Cr-Fe, Fe-Cr under layer was enlarged, comparing to that on the Fe underlayer. The difference between the surface energy (γXS) and the interfacial energy (γX-Cu-SL) of these underlayer is close to the surface energy of Cu at the melting point (γCuS (Tm)). However, the surface roughness of Cu films simultaneously increased with increasing the lateral grain size. In order to suppress the surface roughening of Cu films, post-thermal annealing procedure was applied under the ultra-high vacuum for the films fabricated on the Cr-Ni and Cr-Ni-Fe underlayers. We finally succeeded to enlarge the lateral grain diameter more than 100 nm for 50-nm-thick Cu films, maintaining a flat surface (Ra = 0.32 nm).

Surface Roughness Evolution for Cu Electrodeposition on Microelectrodes

We have used atomic force microscopy (AFM) to measure the surface roughness of Cu films electrodeposited on photolithographically patterned microelectrodes. The data is consistent with anomalous scaling, where both the local and large-scale roughness show a power law dependence on the film thickness. Our results point to the role of diffusion control in determining the scaling behavior. Although the current distribution was nonuniform, and both the film thickness and roughness were greater near the edge than at the center, the scaling exponents were the same wherever measured. Data from both the center and near the edge lie on a single line when saturation roughness is plotted against correlation length © 2003 The Electrochemical Society. All rights reserved.

Combining AFM and EQCM for the in situ investigation of surface roughness effects during electrochemical metal depositions

In this communication we clearly show that the surface roughness of Cu films strongly influences the signal of an EQCM. These effects were studied with a novel combination of AFM and EQCM, which proved to be a powerful tool for the in situ investigation of surface roughness effects during electrochemical metal depositions and dissolutions.

Structural and electrical properties of porous silicon with rf-sputtered Cu films

Thin semi-transparent Cu films were deposited at room temperature, using rf-sputtering on porous silicon (PS). The porous layer with the thickness of about 15–17 μm were obtained on p-type (100) silicon wafers, by applying various current densities viz. 25, 45, 65 and 85 mA cm −2. Various thicknesses of Cu films ranging from 45 to 170 Å were obtained by varying sputtering time. The red shift from 620 to 750 nm was observed in PL peaks for the Cu deposited PS. To analyze the surface morphology of the films scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses of the films were carried out. The surface roughness of Cu films as measured from AFM varies from 0.669 to 1.8575 nm. The refractive index (RI) of the films measured by ellipsometry, varies from 1.38 to 1.95 with increasing Cu film thickness. The I– V characteristics show the shift of the barrier from 0.65 to 0.77 eV with decreasing the etching current density from 85 to 25 mA cm −2.

Controls of Crystallinity and Surface Roughness of Cu Film in Partially Ionized Beam Deposition

AbstractChanges of crystallinity and surface roughness are discussed in terms of the average energy per deposited atom in the partially ionized beam(PIB) deposition. The average energy per deposited atom can be controlled by adjusting the ionization potential, Vi and acceleration potential, Va. The ion beam consists of a Cu ion beam and residual gas ion beam and residual gases as well as Cu particles that were ionized and accelerated to provide the film with energy required for film-growth. The relative contribution of residual gas ions and Cu ions to total average energy per deposited atom was varied with the ionization potential. At fixed ionization potentials of Vi=400 V and Vi=450 V, the average energy per deposited atom was varied in the range of 0 to 120 eV with acceleration potential Va, of 0 to 4 kV. The relative intensity ratio, 1(111)/I(200), of the Cu films increased from 6 to 37 and the root mean square(Rms) surface roughness decreased with an increase in acceleration potential at Vi=400 V. The relative intensity ratio, I(lll)/I(200), of Cu films increased up to Va=2 kV at Vi=2 kV, above which a decrease occurred, and the surface roughness of Cu films increased as a funtion of acceleration potential. The degree of preferred orientation was closely related with the average energy per deposited atom. The change of Rms roughness might be affected by ion flux, particle energy and preferred orientation.