Microstructure and electrical resistivity of Cu and Cu3Ge thin films on Si1−xGex alloy layers

Abstract

We have studied the reaction between Cu and ε1-Cu3Ge thin films and Si1−xGex (x=0.5) alloy layers epitaxially grown on Si(100) in the temperature range of 250–400 °C. In this temperature range, Cu reacts with the alloy to form a Cu3Si1−xGex ternary phase with an ordered body-centered-cubic crystal structure, and no Ge segregation occurs during the reaction. Unlike ε1-Cu3Ge, the Cu3Si1−xGex films exhibit a high-room-temperature resistivity of ∼150 μΩ cm. However, the Cu3Si1−xGex phase is not observed when Ge is added to Cu to form ε1-Cu3Ge. In contrast to the results reported for films of ε1-Cu3Ge formed on Si(100) substrates, the outdiffusion of Si into the ε1-Cu3Ge films is found to be suppressed when the films are formed on Si0.5Ge0.5 layers at temperatures up to 500 °C, and their resistivity remains low (typically less than 10 μΩ cm at room temperature), indicating the increased stability of ε1-Cu3Ge on Si1−xGex alloys. Furthermore, the ε1-Cu3Ge films form a sharp interface with the Si0.5Ge0.5 layers. These results indicate that ε1-Cu3Ge is an attractive candidate for contacts to SiGe-based devices.

Epitaxial Cu3Ge Thin Film: Fabrication, Structure, and Property

“…Furthermore, the service life of Cu 3 Ge is considerably longer than Cu because the out-diffusion of Cu [4] is reduced. Not only different substrates have been used for growth of polycrystalline Cu 3 Ge films (including GaAs [5][6][7], Si [4,[8][9][10], Ge [10,11], YBa 2 Cu 3 O 7-x [12], Si x Ge 1-x [8,9,13], Ta/TaN [14] and GaN [15]), but also various deposition methods have been used for Cu 3 Ge thin film fabrication. For example, multiple physical vapor deposition methods, such as electron beam deposition, sputtering [1,2,4,11,12,16] and thermal evaporation [17], or chemical approaches such as vapor-solid reaction [14], have been exploited.…”

“…For example, multiple physical vapor deposition methods, such as electron beam deposition, sputtering [1,2,4,11,12,16] and thermal evaporation [17], or chemical approaches such as vapor-solid reaction [14], have been exploited. Despite the achievements in this field, the Cu 3 Ge films reported up to now were mostly polycrystalline with impurity phase [1,2,[4][5][6][7][8][9][10][11][12][13]. Consequently, Cu 3 Ge films with better crystallinity are highly desired, in order to minimize diffusion paths (grain boundaries) and lower electrical resistivity.…”

“…(a) An HRTEM image showing the atomic structure at the interface region between the Cu 3 Ge island and csapphire substrate. The viewing direction is [1 1 0] zone of c-sapphire ([11][12][13][14][15][16][17][18][19][20] zone in Miller-Bravais Indices system),…”

Growth evolution and characterization of ultra-thin CoGe2 films synthesized via a catalytic solid–vapour reaction technique

“…Thin lms of metal germanides are of considerable interest to be integrated into very large scale integration (VLSI) circuits as interconnects or ohmic contacts not only for Si and Ge based electronic devices but also for other alternative compound semiconductors. [1][2][3][4][5][6][7][8][9][10][11][12] This is primarily due to their low resistivity, good thermal stability and resistance to oxidation. Among the transition metal germanides, CoGe 2 has been well studied by many researchers for Ge based technology and scarcely for other semiconductor substrates.…”