Texture in multilayer metallization structures

Abstract

The effects of thin Ti, TiN, or Ti/TiN underlayers on the development of the crystallographic texture and the grain structure are explored. Metal layers ∼0.5 μm in thickness of Al-0.5Cu or of Cu are deposited on these underlayers and on amorphous SiO2 as a reference. A strongly textured underlayer such as Ti〈0002〉 or Ti〈0002〉/TiN〈111〉 induces a similarly strong 〈111〉 texture in the AlCu. In copper with 〈111〉, 〈200〉, and random texture components, an underlayer induces a stronger 〈111〉 component compared to an analogous film deposited on SiO2. A nearly random texture in TiN significantly weakens the texture in subsequent metal films. Grain size distributions in all AlCu films are monomodal reflecting a process of normal grain growth. The grain size distribution for Cu sometimes deviates from lognormal. The bimodal distribution implies that grain growth is abnormal even though the median grain size does not exceed a low multiple of the film thickness.

Texture control of PbTiO3 and Pb(Zr,Ti)O3 thin films with TiO2 seeding

“…The processes have been optimized for obtaining highly textured (111) platinum films, as measured by x-ray θ-2θ diffraction scans, and verified by pole figures. For the platinum film, the Ta and Ti adhesion layers play the role of texture seeding, as is also reported for other systems like Al and Cu on Ti and TiN [13].…”

“…The small line width with half signal tilt ω 50 (see Ref. [13]) of 2° to 3° proves that a very good texture was indeed obtained. Comparison to quantitative analysis performed in Ref.…”

“…It shows that an almost complete (111) orientation of the diffracting grains is obtained. The texture quality was verified by means of pole figures, because the absence of peaks of other orientations in the θ-2θ diffraction scan is only a necessary, yet not sufficient condition for a high degree of texture [13]. Figure 2 shows the (111) peak as a function of the substrate tilt angle.…”

Increasing the mean grain size in copper films and features

“…Despite the fact that two-dimensional normal grain growth can easily be modelled or simulated, and that in (2.4) practice thin films with structures as shown in figure 2.4a are very attractive candidates for testing those models, two-dimensional normal grain growth rarely occurs even in films with quasi-2D structures. In practice, grain structures of films that have undergone grain growth do not have grain size distributions that are well fit by Weibull distribution functions, but are instead well fit by lognormal grain size distributions [58][59][60]. Moreover, when grain growth leads to grain sizes significantly larger than the film thickness, it usually involves the favoured growth of a subpopulation of grains with specific crystallographic textures.…”

X-ray microdiffraction study of Cu interconnects

“…The sample has a 30 min 450°C annealing history. The microstructures of Cu/Ti bilayers have been investigated by several researchers; 21,22 various textures and grain sizes have been reported, ranging from 0.03-0.15 m before to 0.05-0.4 m after annealing, depending on the process. 23 The electromigration test was conducted on the Cu/Ti sample at 250°C and about 7.8ϫ10 6 A/cm 2 .…”