AbstractâThis work discusses the thermal stability of metal- insulator-semiconductor (MIS) contacts. A case study is performed on a typical low-Schottky barrier ...
> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < TABLE I DEFINITION AND DESCRIPTION OF TI/N-SI AND TI/TIO2/N-SI. TiO2 Nd ID Mechanism a thickness Test structures -3 (cm ) (nm) MS1 2×1014 TE -SBD MIS1 2×1014 TE 0.8 SBD MS2 MIS2
2×1018 2×1018
TFE TFE
-1.4
CTLM CTLM
MS3 3×1020 FE -(MR-)CTLM MIS3 3×1020 FE 0.8 (MR-)CTLM a Depending on Nd, the mechanism of electron conduction through the contact is classified as thermionic emission (TE), thermionic-field emission (TFE), and field emission (FE) [29].
cm-3. For MIS contacts, a ~1 nm TiO2 layer was deposited by Atomic Layer Deposition (ALD). Then for both the MIS and MS contacts, 5 nm Ti was deposited by gentle Physical Vapor Deposition (PVD) and was in-situ capped by 10 nm PVD TiN. The rest of the processing details for SBD, CTLM and MRCTLM structures have been reported in [16] and [17]. Table I gives brief description of the samples studied in this work. It is important to emphasize that all processes after Ti deposition were restricted to operation temperatures below 250°C. This is because, as will be discussed later, any heating easily deforms the Ti/TiO2/n-Si MIS contact. After the fabrication, all MIS wafers, including both SBD and CTLM structures, were
Fig. 1 (a) IV characteristics and (b) qφ b of Ti/TiO2/n-Si SBDs before and after RTP treatment. The information of as deposited Ti/n-Si SBD is also shown as a reference.
2
cleaved into coupons and annealed with 1 min N2 RTP at 250500°C. The current-voltage (IV) characteristics of the SBD, CTLM and MR-CTLM were measured with an HP-4156 parameter analyzer; while the cryogenic capacitance-voltage (CV) measurement of SBD was performed in a homemade liquid N2 based system connected to an Agilent 4156c meter. III. VARIATIONS OF MIS ELECTRICAL PROPERTIES The responses of qφb and ρc of Ti/TiO2/n-Si contacts to 1min N2 RTP are recorded at different RTP temperature. Ti/nSi contacts serve as a control. A. Schottky barrier variation The thermal stability of Ti/TiO2/n-Si contacts is first studied on SBD. Cryogenic CV method was used for accurate determination of those low qφb from the MIS contacts [18], [19]. In Fig. 1, the as formed Ti/TiO2/n-Si MIS contacts show nicely ohmic behavior and low qφb of ~0.12 eV. However, the MIS contacts lose the low qφb after merely a 250-300°C RTP; with increasing RTP temperature, the IV behavior of Ti/TiO2/n-Si becomes gradually rectifying and simultaneously qφb grows up. After a 500°C RTP, in terms of both IV characteristics and qφb, the Ti/TiO2/n-Si MIS contact becomes close to its Ti/n-Si MS counterpart, which has a typical rectifying IV behavior and a qφb of ~0.46 eV.
Fig. 2 ρc of Ti/TiO2/n+-Si contact with Nd of (a) 2×1018 cm-3 and (b) 3×1020 cm-3 before and after RTP treatment. ρc of as deposited Ti/n-Si contact is also shown as a reference. Schematics of ρc test structures, CTLM and MRCTLM, are shown in the insets of (a) and (b), respectively.
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