Inversion channel mobility in high-κ high performance MOSFETs

Analysis of electron mobility in HfO2/TiN gate metal-oxide-semiconductor field effect transistors: The influence of HfO2 thickness, temperature, and oxide charge

“…7 Since we are working at a relatively high electric field region, the contributions of the silicon phonon and surface roughness scattering mechanisms to the overall electron mobility cannot be neglected. Following the approach used in a range of recent studies of mobility in high-k gate MOSFETs, [2][3][4][5][6][7][8][9][10] we use the Matthiessen's rule to provide an empirical model for the various contributions to the channel mobility by including soft optical phonon scattering in the high-k layer ͑ Ph-Hk ͒, phonon scattering from the silicon channel region ͑ Ph-Si ͒, Coulomb scattering from bulk high-k and interface charge ͑ C ͒, and surface roughness scattering ͑ SR ͒.…”

“…An additional scattering mechanism due to soft optical phonons in the high-k layer has been theoretically predicted by Fischetti et al, 10 and experimental evidence of the soft optical phonons influence on carriers mobility was found through temperature dependence studies. [2][3][4][5][6][7][8][9][10] The beneficial effect of metal gate electrode screening on the high-k phonon-electron interaction has been reported by Datta et al 2 and Chau et al 3 to result in a higher mobility value than measured in the corresponding high-k/polysilicon gate stacks. However, a more recent work by Maitra et al 8 did not observe a difference between polysilicon or metal gate electrodes for HfO 2 gate MOSFETs.…”

“…[2][3][4][5][6][7][8][9] In this paper, we report a detailed study of electron mobility at high inversion charge density ͑ϳ8 ϫ 10 12 cm −2 ͒ in TiN/ HfO 2 / SiO x / Si n-channel MOSFETs. The devices examined have HfO 2 film thickness values of 1.6, 2, 2.4, and 3 nm and a fixed interface SiO͑N͒ layer of ϳ1.0 nm with identical device processing in all respects, allowing us to examine the influence of HfO 2 thickness on mobility degradation.…”

“…[1][2][3][4][5][6][7][8][9][10][11] This degradation has been attributed to the contributions of oxide charge in the high-k layer ͑columbic scattering͒, high-k phonon scattering, silicon phonon scattering, and surface roughness scattering. It has recently been demonstrated that interface defect densities in the range of ͑3-4͒ ϫ 10 10 cm −2 and fixed positive oxide charge densities Ͻ2 ϫ 10 12 cm −2 do not yield significant mobility degradation.…”

“…Hafnium-based high-k dielectrics and metal gate electrodes have been extensively investigated as alternative gate materials, [1][2][3][4][5][6][7][8][9][10][11] and the successful incorporation of hafnium based high-k materials into the gate stack of MOSFETs with minimum feature sizes of 45 nm has recently been announced. 12 However, there are still many issues associated with the implementation of these materials.…”