MOCVD of Cr[sub 3](C,N)[sub 2] and CrSi[sub x]C[sub y] Films

Abstract

Properties as conducting diffusion barrier against Cu of two types of original Cr-based thin films grown by low-pressure metallorganic chemical vapor deposition ͑MOCVD͒ on Si͑100͒ and SiO 2 /Si patterned substrates were investigated. Amorphous as-deposited CrC x N y and CrSi x C y layers were deposited using Cr͑NEt 2 ͒ 4 and Cr͓CH 2 SiMe 3 ͔ 4 , respectively, as single-source precursor in the low-temperature range 400-420°C and 475-500°C. Then Cu films were grown on top of these barrier by low-pressure MOCVD using Cu͑thd͒ 2 as molecular precursor. These Si/barrier/Cu structures were annealed under various conditions and they were thoroughly characterized in order to analyze the failure mechanism of the barrier. The CrC x N y barrier fails at 650°C due to the crystallization of the ternary compound Cr 3 ͑C 0.8 N 0.2 ͒ 2 . The CrSi x C y barrier is more thermally stable and the failure temperature was found in the range 650-700°C due to Cu diffusion through the barrier and the formation of Cu 3 Si. The behavior of these two barriers is compared and their performances are discussed with literature data.In Cu metallization technology, efficient conducting barriers are required to avoid Cu diffusion in Si, SiO 2 , and low-k dielectrics, which causes the decay of the devices. Stringent requirements for these barrier thin films have been previously discussed, 1 and since this period, extensive works aim at finding the best barriers through the performance evaluation of many materials deposited by various processes. 2,3 Thus, refractory metals and their nitrides, borides, silicides, and carbides have been explored as candidates because of their good thermal and chemical stability, high atomic density, and good conductivity. The binary MN x and ternary MSi x N y nitrides ͑M = Ti,Ta,W͒ are the most studied compounds. 1-3 However, the requirements for an ideal barrier are so stringent and sometimes conflicting that there is still an effort in identifying new diffusion barrier materials, taking into account their deposition process.Moreover, because chemical etching of Cu films appears difficult to make interconnections, 4 selective deposition techniques such as metallorganic chemical vapor deposition ͑MOCVD͒ are considered as metallization processes. 5-8 Thus, a good wettability of Cu on the barrier surface is necessary to obtain robust and continuous metal thin films with the most favorable microstructure and therefore the best electrical properties. For instance, it is known that Cu film orientation is influenced by the texture of the underlayer barrier and that the resistance of Cu electromigration depends on the importance of its preferential growth in the ͗111͘ crystallographic direction. 9,10 Recently, we have proposed MOCVD processes for the lowtemperature deposition of amorphous thin films in the Cr-N-C and Cr-Si-C systems. 11 The potential of Cr-based layers as diffusion barriers is not well known, despite few reports on polycrystalline Cr layers 12,13 and physical vapor deposited ͑PVD͒ CrN films. 13,14 Nevertheles...

MOCVD of Cr[sub 3](C,N)[sub 2] and CrSi[sub x]C[sub y] Films

“…The behavior of these Cr-based thin films as barrier materials is reported in a companion paper. 39 * Electrochemical Society Active Member.…”