碩士 / 國立清華大學 / 工程與系統科學系 / 103 / FinFET devices have higher on current and lower leakage current due to better gate control ability compared to the conventional single gate planar FETs. With the scaling of gate length, threshold voltage tuning by channel doping will be an issue. With the scaling of EOT, flat band voltage roll-off caused by oxygen vacancy needs to be solved. There are three parts in this thesis to dicuss the impacts of high-k/metal gate process on device characteristics, which are plasma nitridation, ALD pulse time and ALD growth temperature modulation.
In the first part, different time of plasma assisted nitridation is implemented on metal gate to adjust work function and achieve multi-Vt FinFET. It has been reported that threshold voltage in PFinFET decreases with a higher nitrogen concentration in metal gate. However, results in this work are contrary to expectation. It supposes that nitrogen concentration of metal gate is already saturated, and effective work function may be decreased with further nitridation treatment. The on current is increased over 5-6% for PFinFET and slightly decreased for NFinFET, which are consistent with the results of EOT. Two possible mechanisms are proposed to explain electrical characteristics of FINFET, which are nitrogen diffusion into high-k layer and interfacial layer regrowth.
In the second part, two different H2O pulse time in ALD are implemented to study the oxygen vacancy effect. The crystallization of high-k is transferred into monoclinic phase with higher oxygen content by a longer H2O pulse time. Less oxygen vacancy can be also obtained, which is verified by the increased and decreased threshold voltage for NFinFET and PFinFET, respectively. Sub-threshold swing, Dit, and leakage current are decreased, and good reliability is obtained by longer H2O pulse time in ALD although EOT is slightly increased.
In the third part, two different deposition temperatures in ALD are implemented to study the oxygen vacancy effect. The crystallization phase of high-k is transferred to more stable monoclinic by a higher deposition temperature in ALD. Smaller standard deviation of threshold voltage can be achieved by a higher deposition temperature in ALD because of the reduced oxygen vacancy. EOT is slightly increased due to the higher oxygen content in high-k, and it doesn’t decrease the on current. Sub-threshold swing, Dit, and leakage current are decreased, and good reliability is obtained as well.
| Identifer | oai:union.ndltd.org:TW/103NTHU5593054 |
| Date | January 2015 |
| Creators | Yu, Szu Chun, 尤思淳 |
| Contributors | Chang-Liao, Kuei Shu, Wang, Tien Ko, 張廖貴術, 王天戈 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 102 |
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