We report a systematic study of nickel chrome (NiCr) thin film resistors (TFRs) used as resistors in InP-based monolithic microwave integrated circuits (MMICs). The effects of fabrication process parameters (such as surface treatments or thermal cycles) and substrate materials on the electrical properties of NiCr TFRs are discussed. After completion of MMIC fabrication, the NiCr thin film resistors were found to exhibit lower sheet resistance (R sh ) as compared to the as-deposited films. The origin of this variation has been found to be mainly related to the post-NiCr thermal cycles involved in the IC process technology. In contrast, the R sh values of NiCr TFRs deposited on GaAs or SiN x coated substrates were almost unaffected by thermal annealing. Hence, a thin SiN x passivation layer on the InP substrate has been integrated in the InP-based MMIC process to avoid the NiCr-InP interaction. As a result, NiCr thin film resistors with high sheet resistance uniformity and reproducibility, as well as low temperature coefficient of resistance (TCR) have been achieved. Moreover, the use of a SiN x layer on the InP substrate was also found to improve the inter-device isolation.Although novel material resistors have been developed, nickel chromium (NiCr), and tantalum nitride (TaN) remain the thin film resistors (TFRs) of choice for most applications in the microelectronic industry because of their wide resistivity range, low temperature coefficient of resistance (TCR), good reproducibility and good compatibility with various integrated circuit technologies. In particular, NiCr and related materials have been the subject of numerous investigations, 1-12 covering different aspects of deposition techniques and material properties, as well as potential applications.In monolithic microwave integrated circuit (MMIC) technologies, TFRs are extensively used in feedback circuits, bias circuits, and as terminations. Owing to their properties, they are particularly attractive components for analog and mixed signal circuits, which require precise control of the resistance and thermal stability of the TFR, such as operational amplifiers, and analog to digital converters (ADCs).NiCr resistors are usually deposited as very thin layers (tens of nanometers), directly on the substrate or on dielectric polymer layer, using standard sputtering or e-beam evaporation techniques. As for other thin film resistors, the TCR and resistance of NiCr has, however, been reported to be affected by various process parameters (temperature, composition) and environmental conditions, 2,7,8 which might be at the origin of various performance and reliability problems encountered in integrated circuit.Concerning the properties of NiCr films deposited on III-V substrates, only a few results have, so far, been reported in the literature. Shen et al. 1 compared the characteristics of NiCr, TaN and NiV (nickel vanadium) thin film resistors intended for use in GaAsbased power amplifiers. While TaN and NiV TFRs were directly sputtered on GaAs substrates, NiCr fi...

The structural properties of piezoelectric AlN/Mo/AlN stacks have been investigated for obtaining an improved c-axis oriented, piezoelectric AlN thin film on Mo electrodes to be employed in suspended nano- and micromechanical devices. With increasing thickness of the AlN interlayer up to 80 nm, the texture of the overgrown Mo layer improves significantly, marked by a significant reduction in full-width-at-half-maximum of the rocking curve obtained around 220 Bragg reflections. The improved orientation of Mo crystallites promotes the growth of preferentially c-axis oriented columns in the overgrown AlN film as evidenced by analyzes of crystal orientation determined by scanning nano-beam transmission electron diffraction. Atomic-Force Microscopy revealed only a slight deterioration of the surface roughness of AlN films upon introduction of the interlayer. The whole film stack has a total thickness of less than 1 μm and is, thus, promising for suspended piezoelectric active RF devices.

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