Reduction of plasma-induced fluorine damage to P-HEMTs using x-ray emission

Abstract

Investigation of the surface state of plasma-induced fluorine damage in pseudomorphic high electron mobility transistors (P-HEMTs) using x-ray photoemission spectroscopy (XPS) revealed that the 1s core-level spectrum of fluorine faded out after lengthy x-ray exposure. The x-ray emission apparently caused fluorine desorption from the plasma-damaged P-HEMTs. We thus investigated whether x-ray emission enables P-HEMTs to recover from plasma-induced fluorine damage. The carrier density and electron mobility of P-HEMTs without thermal annealing improved by 63 and 34% with x-ray exposure, while P-HEMTs with thermal annealing improved by 18 and 17%. A secondary ion mass spectrometry (SIMS) profile of fluorine in P-HEMTs with x-ray exposure without thermal annealing showed a reduction in the amount of fluorine in the δ-doped layer and the channel layer, while the profile in P-HEMTs with thermal annealing showed fluorine reduction only below 40nm. Thus, x-ray photoemission is effective in enabling non-thermally annealed P-HEMTs to recover from plasma-induced fluorine damage but not for thermally annealed P-HEMTs.