Marvin Liao

Resistivity reduction and chemical stabilization of organometallic chemical vapor deposited titanium nitride by nitrogen rf plasma

In situ, nitrogen rf plasma treatment of organometallic chemical vapor deposited (OMCVD) TiN, synthesized by thermal decomposition of tetrakis(dimethylamido) titanium, yielded films with low resistivity and enhanced chemical stability. A sequential OMCVD‐plasma treatment process allowed deposition of films with bulk resistivity as low as 400 μΩ cm. The nitridation resulted in reduction of the carbon concentration in the films, and crystallization of TiN. The composition and electrical properties of the nitridized films were found to be stable upon air exposure. The films possess excellent step coverage (≳70% in 0.35 μm device structures with aspect ratio ∼3) and low defect density (∼0.06 cm−2 for defect size ≥0.2 μm).

Enhanced Metalorganic Chemical Vapor Deposition Titanium Nitride Film Fabricated Using Tetrakis-Dimethylamino-Titanium for Barrier Metal Application in Sub-Half-Micron Technology

Enhanced metalorganic chemical vapor deposition (MOCVD) titanium nitride (TiN:C) film with low resistivity (<700 µ Ω cm) has been fabricated by thermal decomposition of tetrakis-dimethylamino-titanium (TDMAT; Ti[N(CH3)2]4). Enhancement is carried out by in-situ N2 plasma treatment of as-deposited TiN:C film and the enhanced TiN:C film has good stability: less than 4% increase in film resistivity after exposure to air for 24 days. The amount of oxygen absorbed in this enhanced TiN:C film after air exposure, determined by Auger electron spectroscopy (AES) was significantly reduced. This enhanced MOCVD TiN:C film has been successfully applied to sub-half-micron devices. A void-tree tungsten plug (W plug) for sub-half-micron holes can be achieved. Good barrier performance and low contact/via resistance have also been demonstrated.

Application of spectroscopic ellipsometer technology to titanium nitride process monitoring

Titanium nitride (TiN) is increasingly used in multilevel metallization processing for a variety of applications: as an antireflective coating, an aluminum diffusion barrier layer and a tungsten interconnect and plug adhesion layer. Typical process control techniques are optical measurement of reflectivity of film thickness, or four-point probe measurements of sheet resistance monitor wafers. Reflectivity measurements of titanium nitride antireflective coatings at the stepper exposure wavelength are straightforward, but direct optical thickness measurements of TiN layers have been difficult to make. Spectroreflectometers rely on accurate values of refractive index dispersion (the change in RI as a function of wavelength) to calculate thickness. Single wavelength ellipsometers do not collect sufficient data to calculate thickness as well as the real and imaginary portions of the refractive index. Spectroscopic ellipsometry offers the ability to determine thickness and refractive index dispersion. This paper investigates possible correlation between the refractive index of TiN and its composition. Refractive index and thickness of TiN are determined by spectroscopic ellipsometry, and composition is determined by Rutherford backscatter spectrometry and Auger electron spectroscopy. If a correlation can be identified, the possibility exists for nondestructive process monitoring of TiN composition. A standard coherent sputtered TiN and two different CVD TiN processes will be examined.