Atomic layer deposited Al2O3 and TiO2 for high-k dielectric and memory applications
Abstract/Contents
- Abstract
- Atomic layer deposited (ALD) metal oxide thin films have promising application in future logic and memory nano-devices. For beyond Si n-channel metal-oxide-semiconductor (MOS) devices, InGaAs and ALD deposited Al2O3 are strong candidates for the high-k dielectric and the channel layer, respectively, due to the high electron mobility of InGaAs, large conduction band off-set between Al2O3 and InGaAs, and a low defect density at the interface. Besides the growth of high-k dielectrics for MOS device scaling, ALD is also widely used to deposit transitional metal oxide, including TiO2 and HfO2, for fabrication of resistive random access memory (RRAM) as a high performance non-volatile memory. The first main section of the dissertation focuses on the ALD Al2O3 as the dielectric layer for InGaAs MOS devices, and the passivation of the interface traps and border traps in the gate stacks as a key issue to improve the device performance. With quantitative analysis by theoretical modelling, we find that by lowering the Al2O3 ALD temperature from 270 °C to 120 °C, combined with large dose TMA pre-exposure prior to ALD and optimized post-metal forming gas anneal (FGA), the border traps can be reduced effectively while interface trap density maintains low. The reduction of border traps is associated with the incorporation of atomic hydrogen that passivates the dangling bonds in the Al2O3 during the FGA. While the FGA treatment effectively reduces both the interface traps and border traps, it also increases the capacitance-voltage hysteresis, indicating a degradation of device stability. This device stability issue is confirmed to be caused by the depassivation of hydrogen from the Al2O3/InGaAs interface under bias stress. In the second section, we report the first use of vertical-field ionic liquid (IL) and aqueous electrolyte gating to study the resistance switching mechanism of ALD TiO2 for RRAM application. A large electric field applied during IL gating induces a conductivity increase in ALD-grown thin TiO2 films caused by the formation and electromigration of oxygen vacancies in the oxide at room temperature. Nevertheless, conductive filaments are not formed during IL gating, presumably because the low programming current minimizes local Joule heating. This hypothesis is supported by experiments in which the ionic liquid is replaced by a conductive salt solution. With significantly increased programming current, electrolyte contact biasing generates a single dominant conductive filament. The reported results indicate the necessity of combined field-driven oxygen ion motion and local kinetic enhancement of oxygen vacancy assembly due to Joule heating to achieve conductive filament formation and dimensionally scalable resistance switching.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2017 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Tang, Kechao |
|---|---|
| Associated with | Stanford University, Department of Materials Science and Engineering. |
| Primary advisor | McIntyre, Paul Cameron |
| Thesis advisor | McIntyre, Paul Cameron |
| Thesis advisor | Chidsey, Christopher E. D. (Christopher Elisha Dunn) |
| Thesis advisor | Salleo, Alberto |
| Advisor | Chidsey, Christopher E. D. (Christopher Elisha Dunn) |
| Advisor | Salleo, Alberto |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Kechao Tang. |
|---|---|
| Note | Submitted to the Department of Materials Science and Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2017. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2017 by Kechao Tang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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