Electrical properties of 0.5 nm thick Hf-silicate top-layer∕HfO2 gate dielectrics by atomic layer deposition

Abstract

The electrical properties have been studied for hafnium (Hf)-based gate stack structures, fabricated using atomic layer deposition (ALD) technology. The very thin ALD Hf-silicate layers on the top of HfO2 gate structures were very important in obtaining good electrical properties, because these surface films prevented a reaction between the polysilicon electrodes and HfO2 films during high temperature activation annealing. From subthreshold characteristic measurements, Ioff values were less than about 10pA∕μm and Ion values at ∣Vg∣=1.1V were greater than 350 and 120μA∕μm for n- and p- metal oxide semiconductor field effect transistors, respectively. The effective mobility curves for the Hf-based gate stack structures were at the same level as those of 1.6 nm SiON reference films at 0.8MV∕cm. Furthermore, the interfacial trap densities were less than 5*1010cm−2 for the Hf-based gate stack structures, achieving the same level as in the 1.6 nm SiON reference films.

Comparison between SiO2 films deposited by atomic layer deposition with SiH2[N(CH3)2]2 and SiH[N(CH3)2]3 precursors

“…Currently, sputtering and or metal organic chemical vapor deposition methods are used for the high-k film formation [3][4][5][6][7][8][9]. Furthermore, the very thin Hf-silicate layers on the top of HfO 2 gate structures are very important in obtaining good electrical properties, because these surface films prevent a reaction between the poly-silicon electrodes and HfO 2 films during high temperature activation annealing [10].…”

“…Hafnium-tetrachloride (HfCl 4 ) and water (H 2 O) have been widely used for depositing HfO 2 using ALD [11][12][13][14]. Recently, there have been reports of using Hf amide type precursors such as Hf(N(CH 3 )(C 2 H 5 )) 4 for HfO 2 or Hf-aluminate to overcome problems such as the excessive particles or residual chlorine obtained when using HfCl 4 precursors [10,14,15,20]. Furthermore, ALD HfO 2 films have been deposited at low temperatures (around 300°C), using a Hf(N(CH 3 )(C 2 H 5 )) 4 precursor and O 3 instead of H 2 O as the oxidant.…”

“…Of the deposition techniques used for high-k films [10][11][12][13][14][15][16][17][18][19][20], atomic layer deposition (ALD) technology is desirable for precise control of the composition, film thickness, conformality and uniformity. Hafnium-tetrachloride (HfCl 4 ) and water (H 2 O) have been widely used for depositing HfO 2 using ALD [11][12][13][14].…”

Suppression of phase separation in Hf-silicate films using NH3 annealing treatment

“…4 However, it has been reported that Hf and Zr silicate systems can decompose into SiO 2 and metal oxide at temperature annealing above ϳ800°C due to the positive enthalpy of mixing of SiO 2 and metal oxides. 5 These phase separations lead to the degradation of thermal stability, dielectric and electrical properties.…”

Electrical Properties of Poly-Si∕ALD Hf-Silicate Gate Stacks with Various Controlled Hf∕(Hf+Si) Composition Ratios Fabricated Using Hf[N(CH[sub 3])(C[sub 2]H[sub 5])][sub 4] and SiH[N(CH[sub 3])[sub 2]][sub 3] Precursors

“…[3][4][5][6][7][8] Another possible deposition technique is atomic layer deposition ͑ALD͒, which has some desirable features in that it allows precise control of composition, film thickness, conformality, and uniformity. [9][10][11][12][13][14][15] Hafnium tetrachloride ͑HfCl 4 ͒ and water ͑H 2 O͒ have been widely used to deposit HfO 2 using the ALD technique. 9,10 There have been reports of groups using Hf-amide-type precursors such as Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 for growing HfO 2 or Hf-aluminate films in order to solve the problem of particles that occurs when using HfCl 4 precursors.…”