A Study on the Properties of Different IMP Ta, Ta(N) and Multi-Layer Ta/Ta(N) as Diffusion Barriers for Cu Metallization
- PDF / 230,253 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 35 Downloads / 173 Views
A Study on the Properties of Different IMP Ta, Ta(N) and Multi-layer Ta/Ta(N) as Diffusion Barriers for Cu Metallization L. He1, 2; C.Y. Li2; Z.Q. Zeng3, J.J. Wu2; Y. Qian2; Y. Zhang1, 2; H.D. Liu4; Joseph Xie1, 2 1 Advanced Materials Program, Singapore-MIT Alliance, Singapore; 2 Dept of Deep Submicron Integrated Circuit, Institute of Microelectronics, Singapore, 3 School of Materials Engineering,Nanyang Technological University, Singapore, 4 Rudolph Technologies, Inc., Flanders, NJ. ABSTRACT We report a study on the properties of Ionized Metal Plasma (IMP) Ta, Ta(N) and multi-layer Ta/Ta(N) based on a comparative evaluation of their performance as diffusion barriers in Cu based metallization schemes. The film structures used in this study are: IMP Cu(2000Å)/IMP Ta(250Å)/Si; IMP Cu(2000Å)/IMP Ta(N)(250Å)/Si; and IMP Cu(2000Å)/IMP multi-layer Ta/Ta(N)(250Å)/Si. The samples were annealed in N2 ambient at 500 oC, 550 oC, 600 oC and 650 oC, respectively, for 30 minutes. The failure behavior and film properties of different barriers were investigated using MetaPULSE, Film stress measurement (FSM), Four-point probe (FPP), X-ray diffractometry (XRD), Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). It has been observed clearly from the sheet resistance measurements that failures of Ta(N) and Ta barriers occurred at 550oC and 600oC respectively, whereas the multi-layer Ta/Ta(N) could still survive from the annealing up to 650oC. Evidence showing the formation of Cu3Si in the failed film stacks was found from XRD spectra. Based on our studies, it can be concluded that microstructures of the barriers has the major effects on preventing Cu from diffusing through them to react with Si and this makes the multi-layer Ta/Ta(N), in overall, superior to the other two Ta and Ta(N) barriers. INTRODUCTION Tantalum (Ta) is currently one of the most widely used diffusion barrier materials in Cu metallization because it shows not only relatively high melting temperature but also is known to be thermodynamically stable with respect to Cu [1]. Ta’s crystalline microstructure could enhance the lattice continuity between barrier layer and Cu layer, thus stronger texture can be obtained [2]. However, previous studies revealed that Ta film prepared by Chemical Vapor Deposition (CVD) failed to prevent Cu from diffusing through its grain boundaries at 500oC, as detected by leakage current measurements [3]. To prevent grain boundary diffusion, nitrogen was added to Ta to reinforce the diffusion barrier against the Cu diffusion. It was reported that increasing the amount of intentional N contamination in TaxN1-x barriers brought a positive effect on the barrier property [4]. However, the problem of lattice mismatch raised in TaxN1-x barriers may lead to weak Cu texture [5]. In this study, a multi-layer Ta/Ta(N) barrier layer with stacked structure is considered to combine the advantages of these two components. The multi-layer was developed by ionized metal plasma (IMP) sputtering, and its properties s
Data Loading...
