Edward O. Travis

Thin film properties of low‐pressure chemical vapor deposition TiN barrier for ultra‐large‐scale integration applications

Titanium nitride films deposited by low‐pressure chemical vapor deposition (LPCVD) on Si(100) using TiCl4 and NH3 as reactants, were investigated as a function of deposition temperature between 400 and 700 °C. LPCVD TiN depositions were carried out in a rapid thermal chemical vapor deposition system with a total deposition pressure of 155 mTorr. Stoichiometric TiN films were formed regardless of the deposition temperature and composition was uniform across the entire film. Depending on deposition temperature, varying amounts of chlorine (Cl) and oxygen (O) impurities are found in the TiN films. Films deposited at lower temperatures (400 and 550 °C) contained more than 5 at. % Cl, while the films produced at 700 °C contained as little as 1 at. % Cl. For the films deposited at 650 and 700 °C, the bulk of the TiN films is oxygen‐free. LPCVD TiN deposition rates of 400 A/min with no appreciable incubation time were routinely achieved. The LPCVD TiN deposition process is surface reaction controlled with an act...

Auger electron spectroscopy and Rutherford backscattering characterization of TiNx/TiSiy contact barrier metallization

We have studied both the formation and integrity of TiNx/TiSiy bilayer films formed by reacting sputter deposited Ti films on Si substrates in nitrogen containing ambients. Auger electron spectroscopy and Rutherford backscattering spectrometry have been used to characterize the formation and properties of these bilayer films as a function of the ambient composition, the substrate doping, and the method of heating [furnace or rapid thermal annealing (RTA)]. We have also characterized the B and As substrate dopant redistribution which occurs during the bilayer formation. Barrier integrity was measured by depositing 2 kA of Al–Si(1%)–Cu(1%) on top of the TiNx/TiSiy bilayers and thermally stressing the films at 450 °C for times ranging from 0.5 to 6.0 h. The metallurgical breakdown of the Al/barrier/Si was characterized by Auger depth profiling and the integrity of the barriers was correlated with the various parameters of the barrier formation. It is concluded that the properties of the nitride/silicide bila...

A two-dimensional low pass filter model for die-level topography variation resulting from chemical mechanical polishing of ILD films

This paper presents a new two-dimensional (2-D) low pass filter model for the prediction of post-chemical-mechanical polishing (CMP) die level wafer topography variation caused by the interconnect metal density of a circuit layout. It is demonstrated that the local smoothing and planarization effects of an ILD polishing process can be characterized accurately (in the frequency domain) by a polynomial equation with a small number of fitted parameters. In this method, the design specific metal density patterns with millions of shapes are first captured in the frequency domain using a 2-D Fast Fourier Transform (FFT). A fitted low pass filter CMP model is then applied to filter/remove short range pattern variation. (Die level topography variations are not removed by CMP effectively). Finally, the post-CMP smoothed topography in the spatial domain is computed from inverse FFT. Model predictions and experimental data are compared in three examples (a) a test structure, (b) a die with shallow trench isolation (c) cumulative topography of a die after ILD1, 1LD2 and ILD3 polishing.

Integration Of BPDA-PDA Polyimide With Two Levels Of Al(Cu) Interconnects

As device geometries continue to scale down, a larger portion of the circuit delay is contributed by interconnects, and the majority of this delay is due to capacitive loading. The replacement of plasma-deposited SiO 2 as an intermetal dielectric with an insulator of lower dielectric constant can provide performance improvement through the reduction of capacitance. A commercially available polyimide, BiPhenylene DiAnhydride – Phenylene DiAmine, BPDA-PDA, with an out-of-plane dielectric constant 3.0, is evaluated by integration with AI(Cu) in a double level metal, BiCMOS 4MB SRAM device, with 0.5μm groundrules. Process challenges unique to integration of an organic rather than inorganic insulator are described and experimental features concerning process integration, particularly via etch, Al(Cu) deposition, adhesion and moisture management are presented.

Nucleation and growth of chemical vapor deposition TiN films on Si (100) as studied by total reflection x‐ray fluorescence, atomic force microscopy, and Auger electron spectroscopy

We report for the first time the characteristics of the early growth of chemical vapor deposition (CVD) TiN films on Si (100) in the surface reaction limited regime, using total reflection x‐ray fluorescence (TXRF), atomic force microscopy (AFM), and Auger electron spectroscopy (AES). Small amounts of CVD TiN from TiCl4 and NH3 reactants were deposited on Si (100) at 650 °C using a rapid thermal CVD system, at a total pressure of 155 mTorr. We examined these small amounts of CVD TiN by introducing TXRF as a tool for observing the initial stages of growth, and AFM for characterizing changes in the overall surface morphology. The nucleation and growth of the resulting CVD TiN films as determined by TXRF, AFM, and AES will be discussed.

Ti/borophosphosilicate glass interfacial reactions and their effects on adhesion

The interfacial reaction of sputtered Ti films with borophosphosilicate glass (BPSG) sublayers has been studied using primarily Auger electron spectroscopy depth profiling techniques. Thin interfacial layers formed during rapid thermal annealing in N2 ambients were studied as a function of temperature, time, BPSG composition, and sublayer preclean treatment. A P‐rich (phosphide) layer was found to accumulate at the Ti/BPSG interface during the reactions and in so doing inhibited the Ti/SiO2 reduction reaction. B accumulated only when the consumption of the entire Ti film neared completion. In some cases, adhesion failures could be generated following the deposition of an Al metallization over the reacted Ti/BPSG films. These failures were found to occur between the P‐rich (phosphide) interfacial layer and the BPSG sublayer and could be prevented by backsputtering the BPSG prior to Ti depositon.

0.25-μm logic manufacturability using practical 2D optical proximity correction

Simplified 2-D Optical Proximity Correction (OPC) algorithms have been devised, calibrated and implemented on a state-of- the-art 0.25 micrometer random logic process in order to reduce metal line pullback on critical layers. The techniques used are rules-based, but are characterized by fast and robust data conversion algorithms, calibrations based on actual process data improvements in reticle manufacturability, and inspectability of the resultant OPC corrected reticles. Application to local interconnect and metal patterning has corrected fundamental yield-limiting mechanisms in these levels.

Thin Film Properties of LPCVD TiN Barrier for Silicon Device Technology

Thin film properties of LPCVD TiN barriers deposited on Si(100), using TiCl 4 and NH 3 as reactants, were investigated as a function of deposition temperature between 400 °C and 700 °C. The TiN film chemistry and film composition were studied by AES and RBS techniques, while the microstructural properties (grain size, lattice parameter and texture) were evaluated by XRD. The TiN deposition rates and film resistivities were also determined. Finally the film properties of the TiN barriers as determined by surface analysis were related to the process parameters.