Preparation and Characterization of High-kPraseodymium and Lanthanoid Oxide Thin Films Prepared by Pulsed Laser Deposition

Abstract

Several lanthanoid oxide thin films such as those of PrO x , Sm 2 O 3 , Tb 4 O 7 , Er 2 O 3 and Yb 2 O 3 have been prepared on Si(100) wafers by the pulsed laser deposition method (PLD). PrO x film shows thin SiO 2 -equivalent oxide thickness (EOT) and low leakage current simultaneously. On the other hand, SmO x thin film does not show good properties. It is revealed by XPS spectra of the PrO x film that the deposition in O 2 ambient of 0.2 Torr produces an interfacial SiO 2 or silicate layer. The sample deposited in a high vacuum at RT has only an ultra-thin interfacial layer, but hysteresis in the C-V characteristic and leakage current are large. Other techniques have been carried out to reduce the energy of ablated particles in order to prevent the growth of an interfacial layer. In the deposition method using a shadow mask, very flat thin films were obtained. However, the deposition rate was very low, and growth of the interfacial layer could not be prevented. By enlarging the distance between substrate and target, the smallest EOT with the PrO x film in our study has been obtained by the reduction of the energy of ablated particles.

Rare-earth oxide thin films for gate dielectrics in microelectronics

“…The thermodynamics of rare-earth oxides predicts their chemical stability on silicon [16], while the permittivity values of rare-earth oxides may be comparable or exceed that of monoclinic HfO 2 (14)(15)(16)(17)(18)(19)(20) or ZrO 2 (18)(19)(20)(21)(22)(23)(24)(25) being, for instance, 24-27 in La 2 O 3 [17,18], 18 in Y 2 O 3 and 12-19 for Lu 2 O 3 [19]. All these oxides have high conduction band offset with silicon [20,21].…”

“…Dating back to 1980's, thermal evaporation of several gate oxides, such as Yb 2 O 3 , Er 2 O 3 , Pr 2 O 3 on II-VI materials as transistor channels was realized [48,54]. Since then, MBE, PLD and other techniques have been developed for silicon and III-V semiconductor based microelectronics [37,38,40,50]. The growth temperature range extends from the room temperature (RT) up to 900 • C (Table 1).…”

“…Kitai et al [50] have studied the homogeneity and insulating properties of several PLD oxides. Among oxides of Pr, Sm, Tb, Er, and Yb, the best performance was demonstrated by Pr 6 O 11 , such as suppressed interfacial layer growth, low EOT, low leakage current density and good flat-band voltage stability.…”

“…Thus the actuality of search for alternative dielectrics, useable after the HfO 2 based oxides, has not ceased. Alternative choices include the rare-earth oxides, which are gaining increasing interest [4,5,[13][14][15]. * Corresponding author.…”

Basic characteristics of metal-ferroelectric-insulator-semiconductor structure using a high-k PrOx insulator layer

“…14 -17 There have been also a few reports that show good retention characteristics of MFIS structure using Sr 2 (Ta,Nb) 2 O 7 , 18,19 high-k insulators of Bi 2 SiO 5 , 20 and LaAlO 3 . 21 It was found from our previous work that PrO x film has simultaneously small EOT and low leakage current, 22 given that the leakage current of the PrO x film is fairly low. 23 We have tried so far to improve the retention characteristics of MFIS structure by suppressing the leakage current through a metal-ferroelectric junction and improving the insulating property of the ferroelectric.…”