Failure Mechanism of Amorphous and Crystalline Ta-N Films in the Cu/Ta-N/Ta/SiO[sub 2] Structure

Abstract

The diffusion barrier properties of as-deposited amorphous TaN x (x Ϸ 0.5) and crystalline TaN between Cu and SiO 2 have been investigated in Cu/Ta-N/Ta/SiO 2 structures. The thermal reactions of Cu/TaN x /Ta/SiO 2 and Cu/TaN/Ta/SiO 2 after annealing in vacuum at 500 to 900°C were investigated by using sheet resistance measurements, glancing incident angle X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, and Rutherford backscattering spectrometry. No significant reaction and change of sheet resistance were detected for both systems after annealing up to 800°C. As compared to TaN, TaN x exhibited better electrical properties and capability for preventing Cu diffusing through it. However, the sheet resistance of both systems increased abruptly after annealing at 900°C, especially the TaN x system. The severe increase in sheet resistance corresponds to the deterioration of Cu surfaces. Broken holes were seen in the TaN x layer, which were the initial sites for the structural failure. The cause of failure in Cu/Ta-N/Ta/SiO 2 stacks is discussed on the basis of the characteristics of Ta-N films upon heat-treatment.With demands for an increase in the packing density and improvement in device performance, the linewidths of integrated circuits have reduced continuously to deep submicrometer dimensions. In ultralarge-scale integrated ͑ULSI͒ circuits, resistance-capacitance ͑RC͒ time delay and electromigration become the important issues. Consequently, aluminum-based metallurgy is no larger adequate for deep submicrometer metallization. In order to solve these problems, copper has been adopted as the interconnection metal because of its lower resistivity ͑1.67 ⍀ cm͒ as compared with aluminum ͑2.7 ⍀ cm͒. Meanwhile, the resistance to electromigration of copper is higher, also. 1-3 However, copper diffuses easily into Si and SiO 2 to form Cu-Si compounds at quite low temperatures. 4,5 This causes device performance to degrade seriously. To avoid copper diffusion, a barrier between copper and its underlying dielectric layer is essential. For copper metallization, diffusion barriers of refractory metals and their nitrides have been studied extensively owing to their superior thermal stability and high conductivity, including Ti-N, 6,7 Ta-N, 8-12 and W-N. 13-16 Among them, tantalum and its nitride draw lots of attention because they possess better thermal stability and chemical inertness than the other transition metal nitrides when coming into contact with copper.However, tantalum nitride may be in the form of TaN or Ta 2 N, and it can be crystalline or amorphous. Due to the different deposition conditions, the properties of tantalum nitride barriers can vary widely. 11,[17][18][19] In the literature, most studies related with barrier performance concern only one tantalum nitride film of one specific composition and structure. In the present study, we deposited tantalum nitride film by reactive sputtering. Amorphous tantalum nitride films (TaN x , x Ϸ 0.5) and polycrystalline tantalum nitri...

Effect of Under-Layer Treatment of Ta/TaN Barrier Film on Corrosion Between Cu Seed and Ta in Chemical-Mechanical-Polishing Slurry

“…Current density (mA/cm 2 ) Time (s) (1) TaN/Ta (2) TaN re-sputterred 10A/ Ta (3) TaN re-sputterred 20A/Ta (4) TaN re-sputterred 40A/Ta (5) TaN re-sputterred 80A/Ta Figure 7(b). As the ratio of Ta(002)/Ta(110) decreased, the potential difference between the Cu seeds and the upper Ta films decreased.…”

“…[1][2][3][4][5][6][7][8] In general, a bi-layer film made of Ta and tantalum nitride (TaN x is used as a Cu diffusion barrier and as an adhesion promoter between Cu metals and the dielectric layers because the adhesion of Cu on the dielectric films is not good enough to prevent film peeling during the CMP process. 3 9-10 The Ta layer contributes to the adhesion between TaN x and Cu while the TaN x film is used as an adhesion layer between Ta and dielectric films.…”

Study on microstructural, chemical and electrical properties of tantalum nitride thin films deposited by reactive direct current magnetron sputtering

“…high temperatures and/or aggressive media). Typically, they are used for resistors because of their excellent long term stability (Abdin and Val 1979;Lovejoy et al 1996) and as diffusion barriers in copper based conductor lines for microelectronic applications (Chang et al 2004;Wieser et al 2002;Chen et al 1999). For the synthetization of TaN x films reactive sputter deposition is a standard, but the successful application of other techniques like chemical vapour deposition (CVD) (Hieber 1974), atomic layer deposition (ALD) (Wu et al 2004) and ion beam assisted deposition (IBAD) (Wei and Shieh 2006;Baba and Hatada 1996) is also reported in literature.…”

Under-layer behavior study of low resistance Ta/TaNx barrier film

“…[1][2][3][4][5][6][7][8][9][10] The Ta layer contributes to the adhesion ability between TaN x and Cu metals while the TaN x film is used as an adhesion layer between Ta and dielectric films. Previous studies have pointed out that a TaN x film with an amorphous structure had better barrier property than a Ta metal to keep Cu from diffusion into dielectric films.…”

“…Previous studies have pointed out that a TaN x film with an amorphous structure had better barrier property than a Ta metal to keep Cu from diffusion into dielectric films. [1][2][3][4] However, the high-resistivity TaN x film will dominate and increase overall contact resistance (Rc), as its thickness on the feature bottom is too thick. Ionized metal plasma (IMP) is the promising method for the deposition of thin barrier and seed layers in high-aspect-ratio damascene structures.…”