Detection Of Dopants Distribution By Electrostatic Force Microscope

Electrostatic Force Microscope(EFM),a promising non-destructive technique used to detect electrostatic force landscape,now receives exceptional attention of a wide community of scientists in semiconductor.The electrostatic force profile measured by EFM can be utilized to deduce the dopants distribution in the semiconductor material.Traditional dopants-detection method,like Scanning Tunneling Microscopy(STM),can only get the dopants information for several top-most atomic layers.EFM,on the other hand,outperforms STM with a much wider measurement range.Despite EFM has been developed for years,no research has been done to obtain the electrostatic force image of semiconductor device by EFM.The electrostatic force information measured by EFM can be transformed into the distribution of dopants subsequently.Here,EFM results of two semiconductor samples are introduced.EFM images reveal that electrostatic force can be used to detect dopants distribution.When the tip is biased,the sample with different doping concentration patterns induce different electrostatic force towards the tip and thus render a phase shift profile.The difference in electrostatic force between tip and sample causes image fluctuation.In order to produce better EFM image,cryo-temperature EFM system was used.Cryo-temperature can suppress the screening effect created by free-moving electrons,leading to larger electrostatic force fluctuation.Another way to get better image is to passivate the sample.Passivation can eliminate the influence of surface charges or trap charges during EFM measurement.