Atomic Layer Deposition of Hafnium Silicate Gate Dielectric Films 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

Abstract

Hf-silicate gate dielectrics were formed by atomic layer deposition ͑ALD͒ technology using the liquid Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 and SiH͓N͑CH 3 ͒ 2 ͔ 3 precursors. The advantages of these precursors as good materials is because their melting points and vapor pressures are in a comfortable working range. In SiO 2 ALD film formation, the growth rate per cycle was dependent on reactor pressures between 0.5 and 5.0 Torr chamber pressure. In order to obtain a good uniformity of less than 5%, the pressures of the reactor chamber were kept at 0.5 and 5.0 Torr for ALD of HfO 2 and ALD of SiO 2 films, respectively. The SiH͓N͑CH 3 ͒ 2 ͔ 3 precursor made it possible to deposit the SiO 2 layers not only on SiO 2 films but also on HfO 2 films. Hf-silicate films were deposited at 275°C using alternating HfO 2 and SiO 2 ALD cycles. The thickness and the Hf/͑Hf + Si͒ compositions of Hf-silicate films could be easily controlled by the number of the deposition cycles.Conventional thermal silicon dioxide ͑SiO 2 ͒ films have been used as a gate dielectric for standard complementary metal oxide semiconductor ͑CMOS͒ devices because of their superior properties such as large energy bandgap ͑8.9 eV͒, low leakage current, low interface state density, and low impurities in the SiO 2 films. For the gate oxide thickness of less than 3.5 nm, direct tunneling current increases 100 times for every 0.4-0.5 nm decrease of thickness. 1,2 This high gate leakage current would increase standby power consumption. In order to reduce the leakage current by direct tunneling, the high dielectric constant ͑high-k͒ materials allow for an increase in the physical thickness to maintain a low equivalent oxide thickness. Among many high-k materials, Hf-based and its nitride films are good for low leakage current and high carrier mobility. Therefore, sputter and or metal organic chemical vapor deposition ͑MOCVD͒ methods are currently used for the high-k film formation. [3][4][5][6][7][8][9][10][11] Atomic layer deposition ͑ALD͒ technology is desirable for precise control of composition, film thickness, conformality, and uniformity among many high-k film deposition techniques. [12][13][14][15][16][17][18][19] Hafnium-tetrachloride ͑HfCl 4 ͒ and water ͑H 2 O͒ were widely used for ALD HfO 2 film formations. [12][13][14][15] Recently, there were reports using Hf amide-type precursors such as Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 for ALD of HfO 2 or Hf-aluminate films to solve the problem of particle formation or residual chlorine with HfCl 4 precursors. 15,16,19 Furthermore, ALD HfO 2 films were deposited at low temperature ͑around 300°C͒ using Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 precursor and O 3 as the oxidant during ALD instead of H 2 O, those films contained a much smaller amount of residual impurities such as carbon or nitrogen from previous precursors. 16 However, there are few papers about Hf-silicate gate dielectric fabrication by the ALD method because of the lack of the applicable Si precursor. 19 We described a newly developed ALD Hf-silicate film formation that could fabricate t...

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

“…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].…”

“…And, ALD process temperature about 275°C have been suitable for the fabrication of ultrathin HfO 2 gate dielectrics to improve the leakage current characteristics due to formation of low residual impurity concentrations such as carbon [18]. However, there have been few papers on the subject of Hfsilicate gate dielectrics using the ALD method because of the lack of a suitable Si precursor [19,20]. In this study, we investigated SiO 2 layers using Bis-dimethylamino-silane (BDMAS: SiH 2 (N(CH 3 ) 2 ) 2 ) and Tris-dimethylamino-silane (TDMAS: SiH(N(CH 3 ) 2 ) 3 ) precursors.…”

Impact of O[sub 3] Concentration on Ultrathin HfO[sub 2] Films Deposited on HF-Cleaned Silicon Using Atomic Layer Deposition with Hf[N(CH[sub 3])(C[sub 2]H[sub 5])][sub 4]

“…[3][4][5][6][7] Atomic layer deposition ͑ALD͒ is desirable for precise control of composition, film thickness, conformity, and uniformity among many high-k film deposition techniques. [8][9][10][11][12][13] Hafnium-tetrachloride ͑HfCl 4 ͒ and water ͑H 2 O͒ were widely used for ALD HfO 2 film formations. 8,9 Recently, there were reports using Hf-amide-type precursors such as Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 for ALD of HfO 2 or Hf-aluminate films to solve the problem of particle formation with HfCl 4 precursors.…”

“…11 A tetrakis͑ethylmethylamino͒hafnium ͕Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 ͖ precursor is a good material because the melting point is very low ͑less than −70°C͒ to maintain the middle vapor pressure ͑4.8 Torr at 120°C͒. 12 The ALD process temperature of 275°C was very important for the fabrication of high-quality HfO 2 gate dielectrics to improve the leakage current characteristics using Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 and O 3 . 13 Metal-gate and high-k dielectric transistors can be fabricated by using the damascene gate process 14 and the replacement gate process.…”

Comparison of the Electrical Properties of Poly-Si/Hf-Silicate Gate Stacks Fabricated by ALD Employing BDMAS and TDMAS Precursors

“…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. [11][12][13][14][15][16] Furthermore, SiH͓N͑CH 3 ͒ 2 ͔ 3 and SiH 2 ͓N͑CH 3 ͒ 2 ͔ 2 precursors are interesting materials because their melting points are very low ͑less than −90°C͒ and they exhibit high vapor pressures ͑92 and 512 Torr at 80°C, respectively͒. 15,16 It has been reported that the thickness and Hf/͑Hf + Si͒ composition ratios of ALD Hf-silicate films could be easily controlled by regulating the number of deposition cycles using Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 and TDMAS ͑SiH͓N͑CH 3 ͒ 2 ͔ 3 ͒, or Hf͓N͑CH 3 ͒͑C 2 H 5 ͔͒ 4 and BDMAS ͑SiH 2 ͓N͑CH 3 ͒ 2 ͔ 2 ͒ precursors.…”