|
| 1 | +--- |
| 2 | +# YAML header |
| 3 | +render_macros: true |
| 4 | +--- |
| 5 | + |
| 6 | +# Creating High-k Metal Gate Stack: Si/SiO2/HfO2/TiN |
| 7 | + |
| 8 | +## Introduction |
| 9 | + |
| 10 | +This tutorial demonstrates how to create a high-k metal gate stack heterostructure consisting of four materials: Si (substrate), SiO2 (gate oxide), HfO2 (high-k dielectric), and TiN (metal gate). The process involves: |
| 11 | + |
| 12 | +1. Creating individual slabs for HfO2 and TiN |
| 13 | +2. Building the Si/SiO2 interface using strain matching |
| 14 | +3. Adding the pre-created slabs sequentially using simple interface builder |
| 15 | + |
| 16 | +We use the [Materials Designer](../../../materials-designer/overview.md) to create the high-k metal gate stack as shown in the figure below. |
| 17 | + |
| 18 | + |
| 19 | + |
| 20 | +## 1. Set Up Materials |
| 21 | + |
| 22 | +First, navigate to Materials Designer and import from [Standata](../../../materials-designer/header-menu/input-output/standata-import.md) the following materials: |
| 23 | + |
| 24 | +- Silicon (Si) |
| 25 | +- Silicon dioxide (SiO2) |
| 26 | +- Hafnium dioxide (HfO2) |
| 27 | +- Titanium nitride (TiN) |
| 28 | + |
| 29 | + |
| 30 | + |
| 31 | +## 2. Create HfO2 and TiN Slabs |
| 32 | + |
| 33 | +Before building the stack, we need to create properly terminated slabs for HfO2 and TiN. |
| 34 | + |
| 35 | +### 2.1. Create HfO2 Slab |
| 36 | + |
| 37 | +More detailed instructions on slab creation can be found in the [SrTiO3 Slab](slab-strontium-titanate.md) tutorial. |
| 38 | + |
| 39 | +Open `create_slab_with_termination.ipynb` and set parameters: |
| 40 | + |
| 41 | +```python |
| 42 | +# HfO2 slab parameters |
| 43 | +MILLER_INDICES = (0, 0, 1) |
| 44 | +THICKNESS = 4 # atomic layers |
| 45 | +VACUUM = 0.5 # Angstroms |
| 46 | +XY_SUPERCELL_MATRIX = [[1, 0], [0, 2]] |
| 47 | +USE_ORTHOGONAL_Z = True |
| 48 | +USE_CONVENTIONAL_CELL = True |
| 49 | + |
| 50 | +# Select termination (usually first one is fine) |
| 51 | +TERMINATION_INDEX = 0 |
| 52 | +``` |
| 53 | + |
| 54 | +Run the notebook to create the HfO2 slab and pass it to Materials Designer. |
| 55 | + |
| 56 | + |
| 57 | + |
| 58 | +### 2.2. Create TiN Slab |
| 59 | + |
| 60 | +Open another instance of `create_slab_with_termination.ipynb` for TiN: |
| 61 | + |
| 62 | +```python |
| 63 | +# TiN slab parameters |
| 64 | +MILLER_INDICES = (0, 0, 1) |
| 65 | +THICKNESS = 3 # atomic layers |
| 66 | +VACUUM = 10.0 # Angstroms - more vacuum for final layer |
| 67 | +XY_SUPERCELL_MATRIX = [[1, 0], [0, 1]] |
| 68 | +USE_ORTHOGONAL_Z = True |
| 69 | +USE_CONVENTIONAL_CELL = True |
| 70 | + |
| 71 | +TERMINATION_INDEX = 0 |
| 72 | +``` |
| 73 | + |
| 74 | +Run the notebook to create and pass the TiN slab to Materials Designer. |
| 75 | + |
| 76 | + |
| 77 | + |
| 78 | +## 3. Create Si/SiO2 Interface |
| 79 | + |
| 80 | +### 3.1. Launch ZSL Interface Builder |
| 81 | + |
| 82 | +Open `create_interface_with_min_strain_zsl.ipynb` and configure: |
| 83 | + |
| 84 | +```python |
| 85 | +MAX_AREA = 200 # Maximum area for strain matching |
| 86 | +MAX_AREA_RATIO_TOLERANCE = 0.25 # Maximum area ratio tolerance |
| 87 | +MAX_ANGLE_TOLERANCE = 0.15 # Maximum angle tolerance |
| 88 | +MAX_LENGTH_TOLERANCE = 0.15 # Maximum length tolerance |
| 89 | + |
| 90 | +FILM_INDEX = 1 # SiO2 |
| 91 | +FILM_MILLER_INDICES = (1, 0, 0) |
| 92 | +FILM_THICKNESS = 3 |
| 93 | +FILM_XY_SUPERCELL_MATRIX = [[1, 0], [0, 1]] |
| 94 | +FILM_VACUUM = 0.0 |
| 95 | +FILM_USE_ORTHOGONAL_Z = True |
| 96 | + |
| 97 | +SUBSTRATE_INDEX = 0 # Si |
| 98 | +SUBSTRATE_MILLER_INDICES = (1, 0, 0) |
| 99 | +SUBSTRATE_THICKNESS = 4 |
| 100 | +SUBSTRATE_XY_SUPERCELL_MATRIX = [[1, 0], [0, 1]] |
| 101 | +SUBSTRATE_VACUUM = 5.0 |
| 102 | +SUBSTRATE_USE_ORTHOGONAL_Z = True |
| 103 | + |
| 104 | +INTERFACE_DISTANCE = 2.5 # Angstroms |
| 105 | +INTERFACE_VACUUM = 5.0 # Angstroms |
| 106 | +TERMINATION_PAIR_INDEX = 0 |
| 107 | +``` |
| 108 | + |
| 109 | +We set a higher tolerances to achieve smaller cell with higher strain of the film (SiO2). |
| 110 | + |
| 111 | + |
| 112 | + |
| 113 | +### 3.2. Create Initial Interface |
| 114 | + |
| 115 | +Run the notebook to create the Si/SiO2 interface. This is the most critical interface, so we use strain matching to optimize it. |
| 116 | + |
| 117 | +## 4. Add HfO2 Layer |
| 118 | + |
| 119 | +### 4.1. Configure Simple Interface Builder |
| 120 | + |
| 121 | +Open JupyterLite Session again and select the Si/SiO2 interface and HfO2 slab as input materials. |
| 122 | + |
| 123 | +Open `create_interface_with_no_strain.ipynb` and set: |
| 124 | + |
| 125 | +```python |
| 126 | +# Important: Disable slab creation since we're using pre-created slab |
| 127 | +ENABLE_FILM_SCALING = True |
| 128 | +CREATE_SLABS = False # We already have our HfO2 slab |
| 129 | + |
| 130 | +FILM_INDEX = 1 # Pre-created HfO2 slab |
| 131 | +SUBSTRATE_INDEX = 0 # Si/SiO2 structure |
| 132 | + |
| 133 | +# Interface parameters |
| 134 | +INTERFACE_DISTANCE = 2.5 # Angstroms |
| 135 | +INTERFACE_VACUUM = 0.5 # Angstroms |
| 136 | +``` |
| 137 | + |
| 138 | +Film is the material that will be strained (scaled) to match the substrate. |
| 139 | + |
| 140 | + |
| 141 | + |
| 142 | +### 4.2. Add HfO2 |
| 143 | + |
| 144 | +Run the notebook to add the pre-created HfO2 slab to the Si/SiO2 structure. |
| 145 | + |
| 146 | + |
| 147 | + |
| 148 | +## 5. Add TiN Layer |
| 149 | + |
| 150 | +### 5.1. Configure Final Layer Addition |
| 151 | + |
| 152 | +Similar to steps in Section 4, we add the TiN layer to the Si/SiO2/HfO2 stack. |
| 153 | + |
| 154 | +Use `create_interface_with_no_strain.ipynb` again: |
| 155 | + |
| 156 | +```python |
| 157 | +# Keep slabs disabled |
| 158 | +ENABLE_FILM_SCALING = True |
| 159 | +CREATE_SLABS = False # Using pre-created TiN slab |
| 160 | + |
| 161 | +FILM_INDEX = 1 # Pre-created TiN slab |
| 162 | +SUBSTRATE_INDEX = 0 # Si/SiO2/HfO2 structure |
| 163 | + |
| 164 | +# Final interface parameters |
| 165 | +INTERFACE_DISTANCE = 2.5 # Angstroms |
| 166 | +INTERFACE_VACUUM = 10.0 # Final vacuum spacing |
| 167 | +``` |
| 168 | + |
| 169 | +### 5.2. Complete the Stack |
| 170 | + |
| 171 | +Run the notebook to add the TiN layer and complete the stack. |
| 172 | + |
| 173 | + |
| 174 | + |
| 175 | +The user then can [save or download](../../../materials-designer/header-menu/input-output.md) the material in Material JSON format or POSCAR format. |
| 176 | + |
| 177 | +## Interactive JupyterLite Notebook |
| 178 | + |
| 179 | +The following JupyterLite notebook demonstrates the process of creating target material. Select "Run" > "Run All Cells". |
| 180 | + |
| 181 | +{% with origin_url=config.extra.jupyterlite.origin_url %} |
| 182 | +{% with notebooks_path_root=config.extra.jupyterlite.notebooks_path_root %} |
| 183 | +{% with notebook_name='specific_examples/heterostructure_high_k_metal_gate_stack.ipynb' %} |
| 184 | +{% include 'jupyterlite_embed.html' %} |
| 185 | +{% endwith %} |
| 186 | +{% endwith %} |
| 187 | +{% endwith %} |
| 188 | + |
| 189 | +## References |
| 190 | + |
| 191 | +1. [QuantumATK tutorial](https://docs.quantumatk.com/tutorials/hkmg_builder/hkmg_builder.html) |
| 192 | + |
| 193 | +2. **D. A. Muller et al.** |
| 194 | + "The electronic structure at the atomic scale of ultrathin gate oxides" |
| 195 | + Nature 399, 758–761 (1999) |
| 196 | + [DOI: 10.1038/21602](https://doi.org/10.1038/21602) |
| 197 | + |
| 198 | +3. **J. Robertson** |
| 199 | + "High dielectric constant gate oxides for metal oxide Si transistors" |
| 200 | + Reports on Progress in Physics 69, 327 (2006) |
| 201 | + [DOI: 10.1088/0034-4885/69/2/R02](https://doi.org/10.1088/0034-4885/69/2/R02) |
| 202 | + |
| 203 | +## Tags |
| 204 | + |
| 205 | +`slab-creation`, `interfaces`, `high-k`, `metal-gate`, `semiconductor`, `heterostructure`, `strain-matching`, `Si`, `SiO2`, `HfO2`, `TiN` |
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