Texture and stress of Ag films in Ag/Ti, Ag/Cr bilayers, and self-encapsulated structures

Abstract

The texture of evaporated Ag films prepared on Ti or Cr underlayers before and after encapsulation process has been studied by x-ray diffraction. In addition, the stress state in self-encapsulated Ag/Ti structures has also been investigated using a “sin2 ψ” technique. Silver films deposited on Ti layers exhibit a strong 〈111〉 texture, which is in contrast to the nearly random orientation of Ag films on Cr underlayers. The minimization of interfacial energy with respect to lattice match can account for this underlayer dependence. After an encapsulation process involving Ti reactions in an ammonia ambient, the texture of Ag films in Ag/Ti bilayers is further enhanced. Highly textured Ag films may provide the basis for electromigration-resistant Ag metallization in integrated circuit devices. For the Ag/Ti bilayer structures, a low tensile stress of approximately 61 MPa arising from the nonequilibrium growth during the film deposition is present in the Ag films. This results in a lattice tension state in the film plane and a lattice compression state along the film normal. Thermal mismatch stress is produced by the encapsulation process at 600 °C. Most of this stress relaxes during the cooling stage and a residual tensile stress of ∼320 MPa in the film plane was determined.

Characterization of silver selenide thin films grown on Cr‐covered Si substrates

“…The binding energies were corrected with reference to the C 1s line at 284.6 eV. RBS experiments were performed using normally incident 4 He + beam having energy of 2 MeV and with a beam current in the order of 5 nA. The scattered particles were collected through a surface barrier detector positioned at an angle of 160…”

“…For instance, Ti underlayer greatly improves the thermal stability of Ag films on oxide substrates and simultaneously aids the textured (111) growth of Ag. [4] Buffer layers can also help improve certain physical and chemical properties of overlayer films. For example, a Cu underlayer has been shown to reduce the ordering temperature as well as to enhance the formation of L 10 -CoPt phase, [5] whereas a Ta adhesion layer is found to improve the ferroelectric properties of SrBi 2 Ta 2 O 9 thin films considerably.…”

Texture Evolution and Stress in Silver Thin Films on Different Substrates Using X-ray Diffraction

“…where the ' c s are the stiffness coefficients of Ag in the film coordinate system and can be determined by using the transformation equations (i.e., 11 ' c = 154.8 GPa, 12 ' c = 83.1 GPa, 13 ' c = 72.9 GPa, 33 ' c = 165.1 GPa) [8].…”

“…The strain in the silver thin films was obtained by the sin 2 ψ technique [8]. Silver layers of the same thickness (200 nm) were deposited to remove the thickness effect.…”

“…Assuming that the stress is biaxial, the stress tensor components are determined by the following[8]: Assuming that the stress is biaxial, the stress tensor components are determined by the following[8]:…”