導電性カンチレバーを用いた原子間力顕微鏡によるゲート絶縁膜の局所特性計測

摘要

以上，C－AFMを超高真空環境で利用することにより，一つ一つのリークパスが出現，あるいは消滅する様子を再現性よく観察したり，リークパス個々の電気特性を測定することができることを示した．今後さらに，解像度を上げるなどの性能向上により，デバイスの微細化に必要な基礎的な知見が得られるだけでなく，インライン計測への利用が期待される．%A conducting atomic force microscopy (C-AFM) in ultrahigh vacuum is used to directly observe the evolution of leakage path in HfO_2 gate dielectrics. Thanks to the UHV environment, reproducible results for both positive and negative tip biases are obtained without material formation on the surface, which has been a problem for atmospheric C-AFM. It is found that the density of leakage spots increases exponentially as a function of tip bias and that it is a large factor for leakage current increase. It is also found that these local leakage paths in HfO_2 films annihilate after applying a reverse tip bias. This process seems to be related to the initial stage of the forming process of resistive switching materials. The fact that these paths annihilate by a very small reverse bias suggests that this behavior is caused by local reduction and oxidation in the HfO_2 layer.