Metal gate work function extraction using Fowler-Nordheim tunneling techniques

In this work, we demonstrate the advantages of using Fowler-Nordheim tunneling on degenerately doped substrates as an alternative to the capacitance-based VFB-EOT method for determining metal gate work functions. The work functions of PVD and ALD TaN on SiO2 /p-Si are shown to be 4.4 and 4.8 eV respectively, which agrees well with standard internal photoemisson measurements (IPE) done on similar test capacitors. The method also detects barrier height shifts owing to the presence of interfacial ALD HfO2 as well as the effects of anneals at activation temperatures. The importance of proper measurement technique and stack preparation is also discussed.