Development of 〈110〉 texture in copper thin films

Abstract

Apart from the scientific interest, texture development in copper thin films is of crucial importance to their applications as interconnects or corrosion resistant coating. We report here a dominant ͗110͘ texture of copper thin films-preferred for oxidation-resistant applications-deposited by direct current magnetron sputtering. Scanning electron microscopy shows that the copper films go through a transition from ͗111͘ columns to ͗110͘ hillocks as the deposition proceeds. Cross-sectional transmission electron microscopy ͑TEM͒ indicates that the ͗110͘ grains nucleate at boundaries of ͗111͘ grains. Further, we have proposed a stress-driven nucleation and growth model of ͗110͘ grains based on the x-ray diffraction characterization and the TEM observations. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1466518͔As the dimension of integrated circuits continues to shrink, it is becoming ever more crucial to control the microstructure-in particular, the texture-of metal thin films as interconnects. Tremendous amounts of effort has been devoted to texture optimization of aluminum interconnects. [1][2][3] With increasing use of copper in place of aluminum as interconnects, development of the ͗111͘ texture in copper has been a focus in recent investigations. 4 -6 On the other hand, development of the ͗110͘ texture is also preferred in oxidation-resistant applications. 7,8 As a result, numerous investigations have focused on these two textures, ͗111͘ and ͗110͘, in copper thin films.These two textures, ͗111͘ and ͗110͘, have been observed in copper films deposited by electroplating, 9,10 cathodic vacuum arcing, 11 and dry etching. 12 The magnetron sputtering deposition-an economic approach in manufacturinghas been found to produce copper films of only weak ͗110͘ texture. 13 For face-center-cubic metals, it has been demonstrated 11,14 that incident energetic particles favor the development of ͗110͘ over the ͗111͘ texture, due to the easier channeling, and thereby less localized radiation damage in the ͗110͘ grains. When the energy of incident particles is in the range of tens of electron volts, channeling effects are absent, and the heat deposition from the kinetic energy favors the thermodynamically preferred ͗111͘ texture.Apart from the damage effects, it is known that stress may be produced in thin films by energetic particles. 11,15 Further, annealing experiments show that stress may favor the ͗110͘ texture in copper films. 16 Under stress and at high temperature, hillocks of ͗110͘ texture grow at the expense of grains of ͗111͘ texture. 17,18 It is scientifically interesting and technologically important to investigate whether the ͗110͘ hillocks are also formed during deposition.In this letter, we report the development of a strong ͗110͘ texture in copper thin films, during direct current ͑dc͒ magnetron sputtering deposition. The experimental conditions are briefly summarized as follows. The sputtering power is variable from 50 to 200 W, and the chamber is filled with 99.999% Ar, flowing into the chamber at a rat...

Growth of Y-Shaped Nanorods through Physical Vapor Deposition

“…The starting point is a series of 〈110〉 Cu nanorods (Figure 1a), which could develop during magnetron sputter deposition. 15 The top of the rods are covered with high-symmetry (and low formation energy) surfaces, {111}, {100}, and {110}. The relative dimensions of these surfaces are close to those from a Wulff construction.…”

“…Below this angle, the columns become mushroom-shaped, as observed in our previous experiments. 15 In addition to demonstrating the proposed mechanism of Y-shaped nanorod formation, the molecular dynamics simulations also reveal the contribution of kinetic barriers between facets. The facets develop on each branch, as shown in Figure 2e.…”

Surface and structural disorder in MBE and sputtering deposited Cu thin films revealed by X-ray measurements

“…Moreover, in order to avoid interdiffusion between different layers of the same device, which in the most common cases is a multilayered structure of different elements, the Cu deposition should be performed at low or at room substrate temperature. This gives rise to textured rather than epitaxial growth confirming that a control of grain dimensions and surface roughness is of fundamental importance when fabricating layered structures [2,3,7,10]. Because the deposition time is one of the decisive parameters in the electronic industry, a study of the surface quality of Cu thin films on Si substrates deposited at different rates can give additional indications about the best growth technique to adopt.…”

“…A renewed interest in Cu thin films deposited with different techniques has been recently observed [1][2][3][4][5][6][7][8][9][10][11] because of the possibility of employing this material for interconnections, cap layers or contacts in the microelectronic industry. Due to the low cost, Cu is replacing Al in the fabrication of electronic devices.…”

“…Cu thin films can be obtained with different methods. Sputtering [1][2][3][4][5], electroplating [6][7][8][9] and thermal evaporation [10,11] are the most commonly used deposition techniques even though the structural and electrical quality of the films strongly depend on the deposition process. In particular, if one is interested in the purity of the final product, thermal evaporation in ultra-high vacuum conditions should be used.…”