Impact of Deposition and Annealing Temperature on Material and Electrical Characteristics of ALD HfO[sub 2]

Abstract

Hafnium oxide (HfO 2 ) is one of the most promising high-k materials to replace SiO 2 as a gate dielectric. Here we report material and electrical characterization of atomic layer deposition ͑ALD͒ hafnium oxide and the correlations between the results. The HfO 2 films were deposited at 200, 300, or 370°C and annealed in a nitrogen ambient at 550, 800, and 900°C. Results indicate that deposition temperature controls both the material and the electrical properties. Materials and electrical properties of films deposited at 200°C are most affected by annealing conditions compared to films deposited at higher temperatures. These films are amorphous as deposited and become polycrystalline after 800°C anneals. Voids are observed after a 900°C anneal for the 200°C deposited films. The 200°C deposited films have charge trapping and high leakage current following anneals at 900°C. The 300°C deposited films have lower chlorine content and remain void-free following high-temperature anneals. These films show a thickness-dependent crystal structure. Annealing the films reduces leakage current by four orders of magnitude. Finally, films deposited at 370°C have the highest density, contain the least amount of impurities, and contain more of the monoclinic phase of HfO 2 than those deposited at 300 and 200°C. The best electrical performance was obtained for films deposited at 370°C.

A HfO2‐Based Complementary Switching Crossbar Adder

“…The HfO 2 -layer is sputtered reactively by using a Hf target as metal source and the shows that the Hf-4f peak is split into a doublet due to a spin-orbital interaction. A higher energetic peak ( [ 31,32 ] Additionally, the spectral analysis gives a ratio of Hf:O about 1:1.9, i.e., the oxide is reduced slightly.…”

First-principles calculations of structural and electronic properties of monoclinic hafnia surfaces

“…1 and 2 we only report the atomic displacements of the ͑001͒ and ͑111͒ surfaces with respect to slab thickness as these faces were most prominent during the growth of HfO 2 . [14][15][16][17] In Figs. 1͑a͒ and 1͑b͒ we show the unrelaxed and relaxed ͑001͒ surfaces of a four layered slab.…”

“…These faces are also the ones corresponding to the most intense peaks in the XRD of various ALD films grown by various groups. 14,15,18 However, some groups observed the peak corresponding to the ͑111͒ surface as the most intense peak along with that of the ͑001͒ face. 4,16 This can be explained if the ͑111͒ and ͑111͒ surfaces are ascribed as the thermodynamically favored surfaces while the ͑001͒ face could correspond to the kinetically favored surface, We predict a surface stability order for the surfaces we consider very similar to that predicted for the ZrO 2 surface.…”

“…For instance, various experimental studies found that HfO 2 films deposited by ALD at 300°C using HfCl 4 and H 2 O as precursors are polycrystalline, and mainly consist of the monoclinic phase with the ͑111͒ surface exhibited as the main growth face. 14,15 Upon annealing the intensities of the monoclinic peaks increase in the x-ray diffraction ͑XRD͒ spectra with the ͑111͒ and ͑111͒ monoclinic surfaces primarily populated. 14 On the other hand, Aarik et al reported that reflections from the ͑002͒, ͑200͒, and ͑111͒ monoclinic surfaces at 300°C displayed the highest intensities rather than the ͑111͒ surface and that ͑111͒ reflections were weak or absent in the plane in which the XRD pattern was recorded, including at elevated temperatures.…”

Work Function and Effective Oxide Thickness Engineering via Alloying of Metal Gate Electrodes

“…The gate dielectric for the metal oxide semiconductor (MOS) transistors characterized in this work were fabricated with atomic layer deposited HfO 2 (3) or Hf x Zr 1-x O 2 (4,5). The Al 2 O 3 capping layers were deposited via atomic layer deposition and the MgO capping layers were deposited by cycling thin layers of sputtered Mg with low pressure, room temperature oxidation.…”