Effectiveness of Ti, TiN, Ta, TaN, and W2N as barriers for the integrationof low-k dielectric hydrogen silsesquioxane

The interactions between low-k (dielectric constant) material hydrogen sils esquioxane (HSQ) and barrier layers, Ti, Ta, physical-vapor deposited (PVD) , and chemical-vapor deposited (CVD) TiN, PVD TaN, and CVD W2N, have been i nvestigated by using sheet-resistance measurement, x-ray diffraction, trans mission electron microscopy, Rutherford backscattering spectrometry, elasti c resonance scattering, and forward recoil spectrometry. The conventionally used dielectric PETEOS [plasma-enhanced chemical vapor deposition tetraeth ylorthosilicate (TEOS)] was also studied as a control. The results show tha t none of these barriers except Ti can react with HSQ and PETEOS at elevate d temperatures. However, significant outdiffusion of hydrogen due to the de gradation of the HSQ films upon annealing exists for all barrier/HSQ struct ures, and exhibits a strong barrier dependence. Metal barriers Ti and Ta, a nd CVD TiN can retard the H outdiffusion, whereas PVD TaN and PVD TiN induc e the H outdiffusion from the HSQ films. The microstructural and structural considerations and a proposed "nitride effect" mechanism can give some rea sonable interpretations to these observations. Upon annealing, the structur al and/or compositional changes of these barrier films give rise to corresp onding sheet resistance variations. The phase transformation of the Ta film on HSQ is completely inhibited because of the possible role of diffusing H atoms, as compared to the phase transformation occurring in the Ta film on PETEOS. (C) 2000 American Vacuum Society. [S0734-211X(00)03101-2].