Analysis of condition for ALD deposition of ferroelectric HZO

Sammanfattning

Deposition of ferroelectric hafnium zirconium oxide (HZO) on semiconductor samples with Atomic Layer Deposition (ALD) has proven to be a viable method of production. But while the physical processes of ALD deposition is relatively well know, there exists some gaps in knowledge about different parameters for the ALD and the resulting depositions. This work is about analysing mainly how the purge time and chamber temperature of a thermal ALD affects the deposited HZO films thickness, defect density and general ferroelectric switching capabili- ties. This involved depositing ferroelectric HZO using the different recipes, mea- suring the thickness of the samples with an ellipsometer and testing the electric characteristics with high frequency IV measurements. The results seemed to align fairly well with known theory. Higher temperatures generally result in faster re- actions but also increases the evaporation of the deposited. To counteract this, shorter purge times should be used at higher temperatures, giving a ”sweet spot” of temperature and purge time. Even though the results seemed to agree with the theory to an extent, extrapolating clear linear trends were nearly impossible with the measurements. But more importantly, all the samples showed ferroelectric properties which was earlier hard to achieve with certain ALD depositions within Lunds University. This speaks to the stability of the current method of deposition. Another important result was that samples deposited with the same parameters showed very similar thickness and electric properties, once again showing how stable and reliable the ALD process seems to be. Since there isn’t enough results to draw clear conclusions, further testing and analysis is encouraged. This would mean testing other temperatures and purge times, and perhaps also measuring other electric properties, like endurance.