In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2015-02, No. 18 ( 2015-07-07), p. 813-813
Abstract:
The achievement of a good high-k oxide/InGaAs interface quality is a key challenge to obtain high performance MOSFET. Associating Al 2 O 3 and HfO 2 in a bilayer oxide is interesting to benefit from the good interface quality obtained with Al 2 O 3 and the better electrostatic control achievable with HfO 2 . Furthermore, some recent work evidenced the reduction of the interface trap density (D it ) by using a plasma nitridation process [1]. For the first time, we evaluated the passivation properties of a Al 2 O 3 /HfO 2 bilayer and a nitridation treatment on industrial equipment compatible with 300 mm Si wafers. First, we investigated the number of Al 2 O 3 ALD cycles required to obtain a good interface. Second, we evaluated the effect of a nitridation treatment on the Al 2 O 3 /InGaAs interface properties performed on a 300 mm capacitive plasma tool. MOSCAP structures were fabricated on a 27 nm thick In 0.53 Ga 0.47 As layer grown on InP substrates. The samples were cleaned in a NH 4 OH solution (4%) for 1 min at room temperature and rinsed in deionized water. Then, Al 2 O 3 and HfO 2 films were deposited in a ALD chamber at 300°C with trimethylaluminium (TMA), Hafnium tetrachloride (HfCl 4 ) and H 2 O as precursors. The ALD cycle numbers for Al 2 O 3 were 0, 3, 5, 8 and 10 and 32 for HfO 2 . A post-deposition annealing was carried out at 370°C for 30 min in N 2 ambient. For the nitridation study, one InGaAs sample was directly treated with a NH 3 plasma for 120 s at 50W and two samples were treated with a NH 3 plasma or a N 2 plasma for 120 s at 50W after the deposition of Al 2 O 3 (10 ALD cycles) to prevent damages on the III-V layer. After the plasma treatment, Al 2 O 3 was again deposited to reach a 8 nm-thick layer for electrical characterization. Ni/Au gate electrode was deposited through a shadow mask by e-beam evaporation. The sample without Al 2 O 3 (Fig1.a) presents distorted profiles, especially at 10 kHz, sign of a poor InGaAs/HfO 2 interface quality. Depositing three Al 2 O 3 cycles (fig.1.b) allows a limited improvement of the characteristics. The dispersion in accumulation of the 10 and 30 kHz curves is reduced but no clear accumulation plateau can be seen. From 5 to 10 cycles, samples (c-e), the situation is significantly improved with a clear accumulation regime. The interface trap densities (D it ) were estimated using the conductance method [2] and were found equal to ~11, 6.1 and 5.5 ×10 12 cm -2 eV -1 for the 5, 8 and 10 cycles samples respectively. A clear improvement is obtained from 5 to 8 cycles while only a slight improvement is obtained from 8 to 10 cycles. Compare to the Al 2 O 3 /InGaAs capacitor (fig.1.f), the best compromise between low D it and high level capacitance appears to be 8 Al 2 O 3 cycles. Wide frequency dispersion in accumulation can be seen after NH 3 treatment without the Al 2 O 3 protection (fig.2c) due to border traps in the dielectric. The plasma treatment prior to the dielectric deposition induces defects at the beginning of the nucleation. This dispersion is reduced when the treatment is implemented through an Al 2 O 3 layer (fig.2b and d). N 2 plasma reduces the capacitance whereas NH 3 plasma does not deteriorate the C-V characteristics and keeps the same capacitance as the sample without nitridation. According to XPS analysis, N is clearly detected after plasma treatment. The N1s peak can be divided into two components, N1s A at 399.0 eV and N1s B at 397.9 eV. The N1s A component has been attributed to N-O bonds, and N1s B to N-Ga bonds [3]. Residual As oxides are reduced with NH 3 (fig. 3e and f) but no As nitride is evidenced. After plasma treatment, the Ga 3+ peak increases significantly (fig.3c and d), because of N incorporation at the interface. The Ga 3+ component can be attributed to Ga-O and Ga-N bonds resulting in an oxynitride formation [1]. In conclusion, Al 2 O 3 /HfO 2 bilayer was optimized on a 300 mm equipment to achieve low D it and high level capacitance (1.75 µF/cm²). NH3 nitridation process performed on a 300 mm capacitive plasma tool integrates nitrogen at the InGaAs surface without deterioration of the C-V characteristics. Low D it is estimated at 2×10 12 cm -2 eV -1 at room temperature after NH 3 plasma which is close to the value shown in [1] obtained with an ECR plasma. Measurements at lower temperature will further explain the D it energy distribution. [1] T. Hoshii, J. Appl. Phys., vol. 112, no. 7, p. 073702, 2012. [2] R. Engel-Herbert, Appl. Phys. Lett., vol. 97, no. 6, p. 062905, 2010. [3] T. S. Lay, J. Vac. Sci. Technol. B Microelectron. Nanom. Struct., vol. 22, no. 3, p. 1491, 2004. Figure 1
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2015-02/18/813
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2015
detail.hit.zdb_id:
2438749-6
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