Application of Zr-Si Film as Diffusion Barrier in Cu Metallization

Abstract

The diffusion barrier's performance of Zr-Si film in Cu/Si contacts has been investigated. Cu/Zr-Si/Si contact system was deposited by using radio frequency reactive sputtering technique. Annealing studies for Cu/Zr-Si/Si were then carried out in nitrogen to investigate Cu diffusion and barrier film crystallization. The contact system was characterized by using four-point probe sheet resistance measurements, X-ray diffraction, scanning electron microscope, and Auger electron spectroscopy ͑AES͒, respectively. It is observed that the sheet resistance of Cu/Zr-Si/Si contact system is lower than that of as-deposited specimens even after annealing at 700°C. The Cu/Zr-Si/Si contacts tolerated annealing at 800°C for an hour without structural change of the barrier. AES depth profiles of the annealed Cu/Zr-Si/Si samples are similar to each other and have no intermixing evidence. Zr-Si was found to be a promising diffusion barrier material for Cu metallization.Copper has been intensively investigated to overcome high resistivity and low electromigration resistance of the conventional aluminum and aluminum alloys with the current trends to smaller and smaller device feature sizes. However, Cu reacts with Si or diffuses fast in SiO 2 at relatively low temperature, which can deteriorate device operation. 1,2 Therefore, it is necessary to insert a diffusion barrier between Cu and Si to suppress Cu diffusion and the subsequent reaction with Si. Owing to their high stability and excellent conductivity, refractory metal binary and ternary nitrides are widely recognized as an attractive class of materials that can be used as diffusion barriers in metal-semiconductor contacts. [3][4][5][6][7][8][9][10][11][12] Most of the barrier layers still have the problem of high resistivity, high process temperature, and narrow process window. Among those refractory metal nitrides, zirconium-based nitride thin films such as Zr-N and Zr-Si-N have been studied extensively as suitable diffusion barriers for Cu metallization. [13][14][15][16] It is well known that these thin films generally show excellent barrier properties due to their high crystallization temperatures. Zirconium silicide has a lower resistivity ͑ϳ32 ⍀ cm with thickness of 50 nm͒ 17 than Zr-N film ͑ϳ50 ⍀ cm with thickness of 140 nm͒ 13 and Zr-Si-N film ͑ϳ136 ⍀ cm with thickness of 100 nm͒. 16 In addition, zirconium silicide/silicon interface is a low-resistance ohmic contact. The 0.55 eV barrier height between the silicide and silicon shows that this contact may be useful for both n-and p-type regions. 17 It is true that Zr-Si has not been studied carefully with Cu but with Al it has been tested. 18 In this article, we introduce Zr-Si thin films as Cu diffusion barrier and focus on investigating the diffusion barrier's performance of these films. ExperimentalSubstrates of n-type Si͑100͒ were progressively cleaned in an ultrasonic bath with acetone, methanol, isopropyl alcohol, and diluted HF solution and then rinsed in deionized water before the activation process, in order to r...

1-nm-thick graphene tri-layer as the ultimate copper diffusion barrier

“…The decrease of resistance can be ascribed to grain growth and defect density annihilation of the 65-nmthick Cu film. 40 Grain growth of the Cu film is driven by minimizing the overall surface and interface energies. The Cu/Si sample without a graphene barrier layer shows early dewetting of the Cu film after 30 min annealing at 500 C, whereas the Cu film adhered well onto the graphene/Si substrate after annealing at 500 C, as shown in Figs.…”

Robust ultra-thin RuMo alloy film as a seedless Cu diffusion barrier

“…1 shows the sheet resistance variations of the as-deposited and post-annealed Cu/Ru/Si and Cu/RuMo/Si structures. Both sheet resistances decrease initially with an increasing annealing temperature up to 500 • C. The decrease in resistances could be ascribed to grain growth and decreasing defect density of Cu film [19,20]. For the Cu/5 nm Ru/Si sample, the increase of sheet resistance starts after annealing at 550 • C, and it increases acutely after annealing at 575 • C. The obvious increase of sheet resistance could be considered the signature of Cu 3 Si formation [21].…”

Non-crystalline Zr–Si diffusion barrier for Cu/Si contact system under different sputtering power

“…Cheng and Chen have shown that an amorphous interlayer is observed just after Zr deposition, increasing in thickness by low temperature annealing below 500°C [17]. Our recent work showed that reactively sputtered Zr-Si results in a promising diffusion barrier for copper metallization [18]. The investigation of the relationship between the film microstructure and the deposition condition are very important to further improve the barrier properties of the Zr-Si films.…”