Low Temperature Physical-Chemical Vapor Deposition of Ti-Si-N-O Barrier Films

Abstract

Ti-Si-N-O films were grown by radio frequency reactive magnetron sputtering of a titanium target with nitrogen and silane gases introduced at a temperature of 40°C. X-ray diffraction and X-ray photoelectron spectroscopy results show that Ti-N, Si-N, Ti-Si, Ti-O, Si-O, and Si-N-O compounds are formed. High-resolution-transmission-electron-microscopy reveals that the film consists of Ti-N, Si-N, Ti-Si nanocrystals embedded in an amorphous Ti-O, Si-O, and Si-N-O matrix. This type of microstructure gives rise to very high stability against copper diffusion under bias temperature stressing ͑BTS͒ compared to binary barrier materials. The BTS result shows that Ti 24 Si 12 N 35 O 29 film can effectively block copper ion diffusion for up to 200°C at 0.5 MV/cm.It is now well recognized that future improvements in the performance of integrated circuits will depend heavily on improvements in the efficiency with which circuit elements are interconnected. Use of the Cu interconnects in microelectronic devices require development of barrier layers which can effectively prevent Cu diffusion into dielectric layers and Si substrates under the influence of electrical and thermal stresses. Extensive work in the deposition of TiN barrier film by both sputtering 1,2 and chemical vapor deposition 3,4 have 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 down-scaling of devices and more stringent reliability requirements, there is a need for more effective barrier materials. To this end, a class of refractory, ternary nitride materials, such as Ti-Si-N, 5 Ta-Si-N, 6 and W-Si-N 7 have been proposed as candidates for the next generation diffusion barrier in copper/low-k dielectric back-end-of-line device fabrication. 8,9 One of the advantages of these ternary barrier films is attributed to the mixed microstructure which consists of nanocrystalline M-N ͑M = Ti, Ta, W͒ embedded in amorphous matrix ͑Si-N͒.The barrier material that we have investigated is Ti-Si-N-O films which consist of nanocrystals embedded in an amorphous matrix, but the amorphous matrix in this Ti-Si-N-O film is contributed by Ti-O, Si-O, and Si-N-O phases rather than the Si-N phase. It exhibits excellent barrier properties against Cu ion diffusion under biastemperature stress.In this article, we present a process for low-temperature physicalchemical vapor deposition of Ti-Si-N-O barrier films. Film composition, microstructure, and chemical bonding state have been analyzed. The barrier films showed excellent stability against bias temperature stressing ͑BTS͒, which makes them attractive candidates as future generation barrier materials.A 630 nm thick plasma enhanced chemical vapor deposition ͑PECVD͒ SiO 2 layer was first deposited on a p-type silicon substrate using tetraethyl orthosilicate, ͓Si͑OC 2 H 5 ͒ 4 ͔ and oxygen as pre...

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

“…Silicon levels between 12 and 15 atom % was obtained by varying the silane gas ͑SiH 4 ͒ flow rate from 20 to 40 sccm while nitrogen and argon gas flow rate were maintained at 30 and 20 sccm, respectively. The Si/Ti atomic ratio as a function of silane gas flow rate is reported in Table I 29 The barrier performance of these three different compositions of Ti-Si-N-O vs the metal ion diffusion was evaluated through BTS testing.…”

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

“…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.…”

Relationship Between Crystalline Structure and Hardness of Ti-Si-N-O Coatings Fabricated by dc Sputtering

“…Also, Ti-Si-N-O coatings have been fabricated to act as a diffusion barrier ( Ref 11,12) due to their promising properties, which make them strong candidates for the next generation of diffusion barriers in CMOS technology. Smith and Custer (Ref 13), found that resistivity varies from 400 lX cm for TiN to 1 · 10 6 lX cm for Ti-Si-N. Ee et al (Ref 14) obtained resistivity values from 3.63 · 10 3 lX cm to up to 6.45 · 10 6 lX cm for the system Ti-Si-N-O fabricated by rf reactive magnetron sputtering.…”