Graphitic polycrystalline carbon (polycarbon) is a candidate material for gate and local interconnect applications in MOS technology. High conductivity polycrystalline carbon films have been grown using Plasma Enhanced Chemical Vapor Deposition. Methane is used as the carbon source gas, and boron trichloride provides the boron doping. In this work, the electrical properties of polycarbon films are studied as a function of deposition temperature, gas-phase boron-to-carbon ratio, and plasma power. A more uniform grain alignment is obtained for samples deposited at low plasma power (˜ 3 W) and high growth temperatures (˜880°C). In these highly oriented samples, the C-axis tends to be aligned parallel to the growth direction. In-plane film resistivities were obtained by Hall measurements, and it was found that the highly-oriented samples exhibit the lowest resistivity (˜300 μΩ-cm). This result is consistent with the higher in-plane mobility in single crystalline graphite. Although the presence of boron trichloride appears to be important for the growth of polycarbon at low temperatures, the boron concentration in the film does not affect the resistivity as strongly as the grain alignment.

TiN has been recognized as an excellent barrier material for W as well as Al planarization gap filling of contacts and vias. The need for conformality over extreme topography necessitates the use of CVD rather than sputtering for the deposition of TiN. In this paper we will first review the various deposition techniques of CVD TiN. Then, we will present a recently developed approach: thermal decomposition of TDMAT followed by nitrogen-based rf plasma treatments for resistivity reduction. This approach utilizes the advantages of thermal decomposition: excellent step coverage, good barrier properties, and low particle content. The resistivity reduction of the post deposition plasma treatment is followed by excellent stability upon long term air exposure. Vias and salicide contacts utilizing this unique process exhibit resistance values equivalent to those obtained when sputtered TiN is used. Conformal films as thin as 200Å can be utilized as excellent barriers for deep sub-0.5μm devices with large aspect ratios, where sputtered TiN can not be used any more.

Encapsulated Ag(Ti) films on oxidized silicon were obtained by nitridation of Ag(19 at.% Ti) alloys in NH3 at temperatures between 400-700°C for various times. Upon annealing Ti segregates to the surface and alloy/SiO2 interface to form a TiN(O) surface layer and a TiO/Ti5Si3 interfacial bilayer structure. Resistivity values of 2.5 μΩ-cm were measured in the encapsulated Ag alloys. The results suggest that resistivity is controlled by the residual Ti concentration.

Structurally disordered refractory ternary films such as titanium silicon nitride (Ti-Si-N) have potential as advanced diffusion barriers in future ULSI metallization schemes. Here we present results on purely thermal metalorganic chemical vapor deposition (CVD) of Ti-Si-N. At temperatures between 300 and 450°C, tetrakis(diethylamido)titanium (TDEAT), silane, and ammonia react to grow Ti-Si-N films with Si contents of 0-20 at.%. Typical impurity contents are 5-10 at.%H and 0.5 to 1.5 at.% C, with no O or other impurities detected in the bulk of the film. Although the film resistivity increases with increasing Si content, it remains below 1000 μΩ-cm for films with less than 5 at.% Si. These films are promising candidates for advanced diffusion barriers.

TaCN films were deposited at low temperature (≤400 °C) by metallorganic chemical vapor deposition (MOCVD) using pentakis(diethylamido)tantalum (PDEAT) as a precursor. The activation energy of the surface reaction is about 0.79 eV and the maximum deposition rate is about 100 Å/min at 350 °C. The resistivity of the as-deposited film decreases as the deposition temperature increases and the minimum value of resistivity obtained is 6000 μΩ-cm for the sample deposited at 400 °C. Major chemical elements in the films were detected as Ta, C, and N with some amounts of O by Auger electron spectroscopy (AES). By x-ray photoelectron spectroscopy (XPS), it is identified that the most of carbon in the films was bonded to Ta. The microstructural investigation using high resolution transmission electron microscopy reveals a nanocrystalline phase with an average grain size of about 30 Å. Preliminary investigation of the diffusion barrier property for copper showed that the 300 Å of TaCN diffusion barrier was failed after annealing at 500°C for 1 hr.

Ag/Ti bilayer films deposited on silicon dioxide substrates were annealed in ammonia ambient in the temperature range of 400 - 600 °C. Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES) have shown that Ti segregates to both the surface to form a TiN(O) layer and to the Ti/SiO2 interface to form a Ti-oxide/Ti-silicide bilayer. The annealed bilayer structure had minimal Ti accumulations in Ag. Resistivity values of ˜2 μΩ-cm were obtained in encapsulated Ag bilayer films, which are comparable to that of the as-deposited. X-ray analysis confirmed the absence of intermetallic phase transformation.

We have measured by the four-point probe or Van der Pauw technique the resistivity in vacuum from 77 K to 873 K or 1073 K of Ti34Si23N43 and Ti53N47. These films were reactively sputter-deposited on oxidized silicon wafers, with thickness ranging from 200 nm to 500 nm. The resistivity of the Ti34 Si23N43 films decreases with temperature from 680. μΩcm at 80 K to about 570 μΩcm at 873 K. In contrast, resistivity of our Ti53N47 films rises with temperature, reaching a stable value of 62 μΩcm at above 673 K.

The influence of rapid thermal annealing (RTA) of Ti/TiN on the stress in the subsequently deposited tungsten (W) films and on the impurity contents at the TiN-W interface was investigated for two types of Ti/TiN bilayers sputter-deposited at 300 °C and 550 °C. A post treatment of the Ti/TiN bilayers resulted in a substantially decreased stress in the W films. It also led to a considerable reduction of the fluorine contents at the TiN-W interface. Both effects were more pronounced for the W deposited on the low-temperature Ti/TiN bilayers and/or annealed in the NH3 atmosphere, than on the high-temperature Ti/TiN bilayers and/or annealed in the N2 atmosphere. Annealed in N2, the interfacial oxygen at the TiN-W interface increased slightly, which can be attributed to the presence of trace amounts of O2 in the N2 atmosphere. A slight increase in the W film resistivity was thus found for the W films deposited on the N2 annealed Ti/TiN bilayers, while the resistivity decreased somewhat for the W films deposited on the NH3 annealed Ti/TiN bilayers. After the post treatment, a large amount of nitrogen was found incorporated in the Ti layer forming TiNx (× < 0.3). However, the post treatment led to a considerable increase in the tensile stress in the Ti/TiN bilayers, and then an increase in the total stress of the whole Ti/TiN/W system. This stress increase could be controlled by using moderate anneal temperatures (e.g. < 550 °C) for the post treatment.

TiN films have been deposited by chemical vapor deposition (CVD) from a new TiN precursor, tetrakis(ethylmethylamino)titanium (TEMAT), and compared with those from tetrakis(diethylamino)titanium (TDEAT) and tetrakis(dimethylamino)titanium (TDMAT) in terms of film quality and conformality. The TDEAT process at 350°C provides films with low resistivity of ˜2500μΩ-cm and 30% carbon. In addition, films deposited from TDEAT contain no oxygen and show good stability in resistivity with time. Furthermore, this process provides bottom-coverage ranging from 65% at 275°C to 30% at 350°C. In contrast, excellent bottom-coverage of ˜90% over 0.5μΩ contact holes is obtained by the TDMAT process. However, films deposited from TDMAT are air-reactive upon air-exposure, resulting in a large increase in resistivity when exposed to air. The use of TEMAT, possessing physical properties between those of TDMAT and TDEAT, allows less air-reactive and better crystalline films, compared with TiN films from TDMAT. It is also observed that the carbon level is ˜2x lower than that in TiN films from TDEAT. Futhermore, this process provides good step-coverage in 0.35μΩ contacts with an aspect ratio of 2.9. Consequently, the TEMAT process can be an attractive choice for sub-0.5 μΩ application.

Thermal stability and failure mechanisms of Au/TiW(N)/Si and Au/TiW(N)/SiO2/Si systems have been studied by both conventional and high-resolution transmission electron microscopy, X- ray diffraction and Auger electron spectroscopy. For films deposited in Ar gas containing 20% N2, a single face-centered-cubic phase was the only crystalline phase detected to form. The samples were found to remain stable after annealing at 700 °C for 30 min. The stability temperature for Au/TiW(N)(Ar:N2=80:20)/SiO2/Si samples was found to be higher than those of Au/TiW(N) (Ar:N2=90:10)/SiO2/Si and Au/TiW/SiO2/Si samples.

A novel plasma enhanced CVD TiN process was integrated with high density plasma sputter etch preclean (PCII) and 1:1.5 collimated PVD Ti (c-PVD Ti) process to deposit a Ti/TiN liner for tungsten contact and via plugs. The integrated liner process was optimized for a 0.35 μm nonsalicide CMOS device application. RF power and sputter depth used for contact preclean were the major process variants affecting the contact resistance, junction leakage and transistor threshold voltage. Low contact resistance was obtained for a c-PVD Ti thickness of ∼375 Å. Via resistance was significantly lower with c-PVD Ti/CVD TiN liner as compared to only a TiN liner. Contact resistance for c-PVD Ti/c-PVD TiN and c-PVD Ti/CVD TiN liners were comparable while contacts with conventional PVD Ti/TiN liner showed significantly higher values due to poor step coverage. Low junction leakage current was obtained for integrated c- PVD Ti/CVD TiN stack.

We have used chemical vapor deposition to grow ternary tungsten based diffusion barriers to determine if they exhibit properties similar to those of sputter deposited ternaries. A range of different W-Si-N compositions were produced. The deposition temperature was low, 350°C, and the precursors used are accepted by the industry. Deposition rates are acceptable for a diffusion barrier application. Resistivities range from 350 to 20000 μΩ-cm, depending on composition. Step coverage of films with compositions expected to be of interest for diffusion barrier applications is 100%.

Contact implants can increase the etch rate of BPSG during HF precleans used prior to metallization. As a result, troughs form in the implanted BPSG that can trap metal and cause leakage between interconnects. It is shown that the increase in HF etch rate is especially pronounced for BF2, implants, due to the presence of F. The topography, and hence the leakage, can be reduced by capping the BPSG with an undoped oxide prior to implantation.

Selective tungsten chemical vapor deposition (W-CVD) is one of the most attractive technique for filling deep submicron contact hole and via hole for the ULSI application. In this work, we firstly find out the anomalous selective W growth for the contact hole. The tungsten only nucleates from the side ring of the contact hole bottom. Several predeposition treatments prior to W growth can improve this anomalous feature and excellently selective W growth can be achieved. Auger electron spectroscopy (AES) is utilized to investigate the interface of Si/W. A model has been proposed to explain this anomalous selective tungsten growth.

In our 0.8μm BICMOS process flow, TiW fusible links are defined by concentrated H2O2 wet etching. Our investigation to improve uniformity, reproducibility and reliability of TiW wet etching showed that in our etch system, the flow characteristics were the most critical. There is a tradeoff between TiW residues between metal lines and the amount of undercut of the TiW fuses: longer etch times to remove residues result in more undercut. With improved flow dynamics and optimum etch time, we achieved less residue and lower undercut. Results of the pre-etch treatment which reduces lot-to-lot induction time variation were encouraging. When the AlCu/TiW/PtSi metal stack resided on a P+/N junction, we observed an enhanced etching of the TiW due to a photovoltaic effect.

In high performance integrated circuits, low dielectric constant (low-ε) materials are required as inter-level dielectric (ILD) for on-chip interconnect to provide advantages in high speed, low dynamic power dissipation and low cross-talk noise. A variety of low dielectric constant materials, which include fluorinated silicon-oxide, porous silica and porous organic materials, chemical vapor deposited and spin-on deposited (SOD) organic materials, have been developed or are under development to fulfill this need. In this paper, we first review the need and integration architecture of low-ε materials for on-chip interconnect. Then, we discuss the consequence of using low-ε materials as ILD in advanced interconnect with emphasis on the ILD electrical characteristics and the interconnect reliability. Although the focus is on several new promising SOD low-ε materials, the developed evaluation methodology is applicable to other type low-ε materials as well.

Low dielectric constant fluorine doped silicon oxide films were deposited by using ECR plasma CVD with SiF4 and O2 as source gases diluted in Ar gas. Characterization of films was carried out in terms of various gas flow ratios (SiF4/O2 = 0.2 ∼ 1.6). The microwave power and substrate temperature during deposition were fixed at 700W and 300°C, respectively. The chemical bonding structure of the films was evaluated by Fourier transform infrared spectroscopy (FTIR), fluorine concentration by X-ray photoelectron spectroscopy (XPS) and refractive index by ellipsometry. Dielectric constant was determined from C-V measurements at 1MHz. FTIR spectra shows that as the fluorine concentration increases, peak intensities of Si-F bonding and shoulder peak at around 1160cm−1 of Si-O stretching mode increased. Moreover, with increasing the fluorine concentration in the SiOF film, the peak position of Si-O stretching mode shifts to the higher wavenumber side. The Si-F2 bond peak is observed to rise when the SiF4/O2 gas flow ratio is larger than 1.0. Refractive index and film density decreased with increasing the SiF4/O2 gas flow ratio. The SiOF film deposited at SiF4/O2 gas flow ratio of 1.0 exhibited fluorine content of 11.8 at.% and dielectric constant of 3.14.

In this work, we study the thermal stability and interaction between SiOF and Cu. Blanket SiOF films with various F concentration were deposited by PE-CVD. A dielectric constant as low as 3.2 was obtained. Copper were deposited on these SiOF and a series of post-deposition anneal were performed. Dielectric constant of SiOF was measured after deposition and again after anneal. AES and SIMS depth profile are utilized to determine the interdiffusion between Cu and SiOF under different annealing conditions. Breakdown voltage and dielectric constant were determined form C-V and I-V measurement using a MIS ( Cu/ SiOF/ p-Si) diode. This results of leakage current measurement and flat band shift measurement suggest that the fluorine in the SiOF film will retard the cu diffusion.

Nanohardness, modulus, and bonding structure of fluorinated silicon dioxides are characterized in order to evaluate their correlations with chemical-mechanical polishing (CM[P) performance. Alkaline-based slurry with adjusted pH is used for polishing in an attempt to delineate the chemical erosion from mechanical abrasion effects during CMIP of fluorinated oxides. The increase in CMIP removal rate and the reduction in refractive index with increasing fluorine content in the fluorinated oxides are related to the change in bonding configuration. The enhanced moisture absorption is due to the presence of fluorine in the oxide network.

Parylene-n (pa-n) and benzocyclobutene (BCB) are novel candidate materials for interlevel dielectrics in future multilevel interconnects, due to their dielectric constant being much lower than that of silicon dioxide. We describe the fine line patterning of these materials by reactive ion etching in O2/CF4 plasmas. Examples of high aspect ratio trenches and dual damascene structures are presented involving processes with single and double hardmasks.