Large Leakage-Current Reduction of Ultrathin Industrial SiON Wafers Induced by Phonon-Energy-Coupling Enhancement

Ong, Pang-Leen; Chen, Zhi; Haggag, A.; Luo, Tien-Ying

doi:10.1149/1.2969029

Cited by 2 publications

(9 citation statements)

References 6 publications

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“…Using this approach, 8,9 the reproducibility of the processes is very poor. To understand the phenomenon more clearly, we did a series of experiments on IPA rinse because the organic residues might come from IPA.…”

Section: Improvement Of the Bilayer Resist Fabricationmentioning

confidence: 99%

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Reliable Observation of Large Leakage-Current Reduction of Thin SiO[sub 2] Induced by Phonon-Energy-Coupling Enhancement: Problems and Solution

Chen

Ong

Wang

2010

J. Electrochem. Soc.

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The problems encountered in the observation of large leakage-current reduction of thin SiO 2 due to enhanced phonon-energy coupling were thoroughly analyzed. A lithographic method based on bilayer resists ͑SU-8 and Shipley S1813͒ and an organic developer ͑SU-8 developer͒ was developed to fabricate Ni-gate metal-oxide-semiconductor ͑MOS͒ capacitors. After development, an undercut profile of the bilayer resists was clearly demonstrated. A key step, thorough deionized water rinse after a quick isopropyl alcohol rinse during resist patterning, is critical to obtain well-defined Ni electrodes reproducibly. Experimental currentvoltage and capacitance-voltage ͑C-V͒ curves of the Ni-gate MOS capacitors, together with the C-V curves simulated using the Berkeley Quantum simulator, demonstrate that a large leakage-current reduction ͑ ϳ 100ϫ ͒ can be reliably and reproducibly achieved on thin SiO 2 ͑ ϳ 23 Å͒ after proper rapid thermal processing.Complimentary metal oxide semiconductor ͑CMOS͒ technology needs thin gate silicon oxide dielectrics for metal-oxidesemiconductor ͑MOS͒ transistors ͑ Ͻ 15 Å͒. However, the gate leakage current increases exponentially as the gate dielectrics are further scaled down due to direct quantum tunneling. Currently, the industry uses alternative high permittivity ͑high-k͒ gate dielectrics such as HfO 2 and HfSiON to solve the gate leakage problem. However, an interfacial SiO 2 layer ͑4-6 Å͒ between the high-k dielectric and Si is necessary to maintain a good interface. Therefore, any improvement of leakage current of SiO 2 is very helpful to MOS transistors.Recently, phonon-energy-coupling enhancement ͑PECE͒ was discovered. 1-5 Surprisingly, this leads to a reduction of quantum tunneling current of SiO 2 by 2-5 orders of magnitude. 1-5 Because of the nature of the phonon coupling, any attack of the SiO 2 structure by chemicals and plasmas may result in a partial loss of the PECE effect. 3 Alkaline-based chemicals and plasmas must be avoided, including regular photoresist ͑PR͒ developer and sputtering deposition. In the past, we patterned Al gate metal by the evaporation of Al through shadow masks. 1-4 This may produce unreliable results because the area of MOS capacitors varies during evaporation through shadow masks at different angles across a large substrate. It was strongly suggested by researchers in industry that only both currentvoltage ͑I-V͒ and capacitance-voltage ͑C-V͒ curves from the same device fabricated using a lithographic method are required to validate the observed effect. 6 For aggressively scaled CMOS logic devices, the industry uses a high-k gate oxide stack, which consists of a chemical oxide ͑SiO 2 ͒ interfacial layer of ϳ0.7 nm and an atomic layer deposited HfO 2 film of 1.8-2.0 nm ͓equivalent oxide thickness ͑EOT͒ = ϳ 0.3 nm͔. 7 The scaling is achieved by thinning the chemical oxide while the thickness of HfO 2 remains the same at 1.8-2.0 nm. If the PECE effect can be applied to the high-k gate stack, both the chemical oxide and HfO 2 can be scaled down while the leakag...

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Section: Improvement Of the Bilayer Resist Fabricationmentioning

confidence: 99%

“…8,9 However, later we found that using our previous reported procedure, 8,9 we encountered another problem. After patterning the resist we must load the samples into the vacuum chamber within 15 min; otherwise, the Ni electrodes peel off.…”

mentioning

confidence: 92%

Reliable Observation of Large Leakage-Current Reduction of Thin SiO[sub 2] Induced by Phonon-Energy-Coupling Enhancement: Problems and Solution

Chen

Ong

Wang

2010

J. Electrochem. Soc.

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“…From our experiments, there was no flatband voltage shift for C-V curves on p-type Si after LHP. 6 Therefore, the valence band is not changed after LHP. This is illustrated schematically in Figure 4.…”

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confidence: 99%

“…3,4 However, we could only reproduce leakage current reduction of 2-3 orders of magnitude for SiO 2 and silicon oxynitride. [5][6][7] It was very difficult to reproduce the best results (4-5 orders). In addition, how could phonon-energy coupling enhancement cause the tunneling current reduction?…”

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confidence: 99%

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Lateral heating of SiO2/Si: Interfacial Si structure change causing tunneling current reduction

Chen

Ong

Wang

et al. 2012

Applied Physics Letters

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Lateral heating processing of SiO2/Si samples can reduce the tunneling current of SiO2 by 5 orders of magnitude with very good reproducibility. There is a strong correlation between the flatband voltage shift of metal-oxide-semiconductor capacitors and the tunneling current reduction. Analysis of the flatband voltage shift suggests that origin of the tunneling current reduction after lateral heating is caused by the structure change of Si, most likely tensor strained Si, near the SiO2/Si interface.

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Large Leakage-Current Reduction of Ultrathin Industrial SiON Wafers Induced by Phonon-Energy-Coupling Enhancement

Cited by 2 publications

References 6 publications

Reliable Observation of Large Leakage-Current Reduction of Thin SiO[sub 2] Induced by Phonon-Energy-Coupling Enhancement: Problems and Solution

Reliable Observation of Large Leakage-Current Reduction of Thin SiO[sub 2] Induced by Phonon-Energy-Coupling Enhancement: Problems and Solution

Lateral heating of SiO2/Si: Interfacial Si structure change causing tunneling current reduction

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