Study Of Diffusion Barrier In Advanced BEOL

The integrated circuit manufacturing industry has entered the 7nm technology node.RC delay,dynamic power consumption,and crosstalk noise in the interconnect are important factors affecting device performance.The Cu/low-?combination was successfully used to reduce these effects in industry.However,Cu has a high diffusivity in low-?dielectrics,so diffusion barrier is needed to separate them.In this work,the DC sputtering process was used to prepare and study the barrier properties and thermal stability of the Ta?N?ultra-thin metal diffusion barrier.The ALD process was used to prepare and analyze the composition and optical properties of Al-based diffusion barriers that have the potential to become dielectric diffusion barriers.The optical characteristic model of the diffusion barrier materials were established.The main research and achievements of this paper are as follows:1. Ultra-thin Ta?N?diffusion barriers with different thicknesses were prepared on low-?dielectric materials?23%porosity and 0.9 nm pore radius?using DC sputtering process.The effects of thickness on the thermal stability and barrier properties of the Ta?N?diffusion barrier layer were studied.The experimental results show,when the total thickness of the diffusion barrier is not less than 3.5 nm,the single-layer Ta N and multilayer Ta/Ta N have better thermal stability and performance of blocking neutral molecular?N-heptane,water molecules,etc.?diffusion than single-layer Ta.Penetration of Ta?N?into low-?dielectric and formation of Ta O/Ta C type of bonds increase the dielectric function of low-?dielectric.2. Al₂O₃and Al N films were deposited by ALD process,and the optical characteristics and composition of the films were studied.The experimental results show that the optical properties of Al₂O₃deposited on the Si substrate from which Si O₂has been removed are similar to the results of Al₂O₃ deposited directly on the original Si substrate.The Al N film deposited by ALD without a reducing agent precursor has good uniformity.The growth cycle and thickness exhibit a classic self-limiting process.Contents of Al-N bond are about 75%,and Si-O bonds are found in the Al N film.3. Models of metal diffusion barrier and dielectric diffusion barrier were established.The metal diffusion barriers have larger extinction coefficient,it is impossible to measure a thicker film by spectroscopic ellipsometry.And theirs optical characteristic curves deviates greatly from the original low-?dielectric optical characteristic curve.Dielectric barriers have a refractive index and extinction coefficient similar to low-?dielectrics.Theirs optical characteristic curves are closer to that of the original low-? dielectric.