Surface Treatment On Atomic Layer Deposition Of Hfo <sub> 2 </ Sub> Medium High-density Mim Capacitor Performance Improvement Study

High-k HfO₂ dielectrics are deposited using atomic layer deposition(ALD) technique with TEMAH and water as its precursors.Various post-deposition treatments are studied to improve the performance of metal- insulator-metal(MIM) capacitors.The dielectric materials and the MIM capacitors are characterized by physical and electrical analyses.We reported improvements on MIM capacitors using CF_x plasma fluorination for the first time.The treatments cause little damages on the surfaces of HfO₂ films as the surface roughness slightly increases at a low level.According to XPS analyses,Hf-F bonds are observed to passivate oxygen vacancies after the treatments.No significant evidence shows that carbon incorporates inside the dielectrics during the plasma exposure.The capacitance density rises from 9.76 fF/μm² of the control sample to 10.17 fF/μm² of the fluorinated sample.The quadratic voltage coefficient varies a little from 1260 to 1200 ppm/V² with the measurement frequency at 100 kHz.Furthermore,the voltage coefficient of capacitor(VCC) is observed as a linear function of logarithmic frequency and the slope decreases after fluorination.In addition,The leakage current density drops to 1.39×10^-8A/cm²@2V after fluorination,which is nearly one order of magnitude lower than the control sample.The improvements of MIM capacitors by thermal NH₃ nitridation are also investigated.Small amount of nitrogen is introduced into the dielectrics,causing the capacitance density decreases from 8.16 to 7.10 fF/μm².However,the nitridation treatments show distinct improvements on the leakage current and voltage linearity. The leakage current density decreases from 1.18×10^-7 to 3.41×10^-8A/cm² while the quadratic voltage coefficient drops drastically from 1430 to 555 ppm/V² after 20 minutes nitridation.This can be attributed to the defects passivation by nitrogen. Moreover,the effects of different deposition temperature are also investigated and nitrogen residues are observed in the low deposition temperature(280℃) samples. The residues cause higher leakage of the MIM capacitors,indicating that defects such as oxygen vacancies are present during low temperature deposition.Such degradation can be improved by NH₃ annealing at 420℃,but can't be eliminated by N₂ annealing.This reveals that thermal NH₃ nitridation can effectively passivates the defects,while N₂ annealing treatment shows no clear evidence of self-passivation.