Bias-Temperature Stability of Ti–Si–N–O Films

Abstract

Copper shows a tendency to drift into contiguous dielectric material under bias and temperature stressing. The stability of different compositions ͑by changing silane gas flow rate͒ of Ti-Si-N-O films has been investigated using metal-oxide-semiconductor ͑MOS͒ capacitors. MOS samples preannealed at 250°C and subjected to bias temperature stressing ͑BTS͒ at 150°C, 200°C under an electrical field of 0.5 or 1 MV/cm show stable capacitance-voltage behavior with no flatband voltage shift from as-annealed to 90 min of BTS for Ti-Si-N-O film with Si/Ti ratio of 0.48. The lack of flatband voltage shift indicates that Ti-Si-N-O film is able to prevent Cu ion penetration. It is found that the electrical stability of Ti-Si-N-O film is reduced with higher Si/Ti ratio. For Ti-Si-N-O film with Si/Ti ratio of 0.91, flatband voltage shifts 0.75 V after 90 min of BTS at 150°C and 0.5 MV/cm, and this shift is attributed to the interface states at the Ti-Si-N-O/oxide interface that were generated during the plasma process and could not be fully healed after 250°C annealing. Thus, it is suggested that with low silane gas flow rate, an electrically stable Ti-Si-N-O film can be achieved with fewer interface states.The implementation of copper in back-end-of-line metallization yields advantages such as low electrical resistivity, superior resistance to electromigration, and faster signal speed. However, copper in comparison to aluminum has a higher tendency to drift into interlevel dielectric as well as into the silicon substrate in the presence of an electrical field even at low temperature, 1-4 resulting in a degradation of the electrical properties. Thus, a barrier layer is required between Cu/dielectric for reliable integration.Various refractory metals and their nitrides have been heavily examined as barrier materials. For example, TaN has been recognized as one of the most promising diffusion barriers for copper due to its high thermal stability, chemical inactivity with Cu, 5,6 and no intermetallic formation at elevated temperatures. 5 Besides TaN, extensive work in the deposition of TiN by both sputtering 7,8 and chemical vapor deposition 9,10 has been reported. A common denominator underlying many of the above references is the columnar structure of TiN, typically with a ͑111͒ or ͑200͒ preferred orientation. Such a structure can lead to short-circuit diffusion paths via grain boundaries and result in the failure of the devices. With the downscaling of devices and more stringent reliability requirements, there is a need for more effective barrier materials. To this end, a class of refractory ternary nitrides, such as Ti-Si-N, Ta-Si-N, and W-Si-N, has been proposed as candidates for the next-generation diffusion barrier in copper/low-k dielectric back-end-of-line device fabrication. 11,12 Various research groups have explored the formation of ternary nitride films by physical vapor deposition ͑PVD͒, metallorganic chemical vapor deposition, and metallorganic atomic layer deposition techniques, documenting their resulting electric...

Influencia del Flujo de Nitrógeno en la Estructura, Dureza y Resistividad de Recubrimientos de TiSiNO

“…Las muestras presentan fases cristalinas con una orientación preferencial (220), excepto la muestra M2 que presenta una orientación preferencial (200). La orientación cristalina (220), es más eficiente que la (111) y (200), ideal para poder utilizarse en recubrimientos como barreras para los circuitos integrados (Ee et al, 2006a(Ee et al, , 2006b, garantizando así el éxito de los dispositivos electrónicos. No obstante, esta orientación cristalina preferencial no es tan fácil de obtener, ya que la estructura columnar del TiN, presenta la orientación cristalina preferencial (111) ó (200).…”

“…Recientemente se han fabricado películas de TiSiNO para que actúen como barreras contra la difusión (Ee et al, 2006b(Ee et al, , 2006c(Ee et al, , 2006dShalaeva et al, 1999), debido a sus prometedoras propiedades, que los hacen fuertes candidatos para la siguiente generación de barreras de difusión en la tecnología CMOS. Estudios realizados sobre este sistema cuaternario, revelan que estos recubrimientos están formados de nanocristales embebidos generalmente en fases amorfas de Ti-O, Si-O, Si-N y Si-N-O (Shalaeva et al, 1999).…”

“…Shalaeva desarrollo un estudio muy completo acerca de la composición de fases (diagrama metaestable) de estas películas de Ti-Si-N-O (Shalaeva et al, 1999), el cual es formado a partir del diagrama de equilibrio de los sistemas Ti-Si-N y Ti-Si-O. Otros autores se han enfocado a estudiar la resistividad de dicho sistema cuaternario en función del efecto que producen los parámetros de fabricación sobre su microestructura, morfología superficial, rugosidad y tipos de enlace químico (Ee et al, 2006b(Ee et al, , 2006c(Ee et al, , 2006d. Sin embargo, un estudio referente a su dureza, aun no ha sido reportado y mucho menos comparado con su resistividad.…”

Formation and characterization of Ti–Si–N–O barrier films

“…Detailed analysis carried out elsewhere [10] has indicated that this small flatband voltage shift is due to the interface states and/or hot holes injection from the Si substrate into the oxide layer. The reason for such a shift with high Si content could be explained by the interface defects generated during deposition process.…”

Plasma assisted deposition of Ti-Si-N and Ti-Si-N-O diffusion barrier films

“…(1) Thermodynamical stablility when in contact with materials: A viable barrier material must not react with copper or underlying substrate under the thermal, mechanical and electrical stress conditions encountered in subsequent processing steps or normal operating conditions (2) High density so as to eliminate diffusion across voids, defects or loosely packed grain boundaries (3) Microstructure which minimizes grain boundaries as diffusion paths (4) Low contact resistance and a reasonable thermal conductivity (5) Excellent adhesion to all materials used in the metallization scheme (6) Electrochemical potential close to that of surrounding materials in order to avoid the formation of galvanic corrosion cells with the metallization layers (7) Low film stresses [Baluffi, 1975] and enhanced resistance to thermal and mechanical stresses (8) thickness requirements for copper are anticipated to be less than 5.6 nm [ITRS 2005] as shown in Table 1-1.…”