Veeco Fiji G3 ALD
Status | UP | |
Issue Date and Description |
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Estimated Fix Date and Comments | ||
Responding Staff |
Cambridge Nanotech Fiji ALD - Internal Resources
Cambridge Nanotech Fiji ALD - Staff
iLab Name: C - Veeco Fiji G3 Atomic Layer Deposition Tool
iLab Kiosk: BRK Growth Core
FIC: Zhihong Chen
Owner: Mihailo Bradash & Thi Anh Ho
Location: Cleanroom - G Bay
Maximum Wafer Size: 8"/200 mm
Overview
Type | Films Available | Restricted Materials | Available Gases | Wafer Size |
|---|---|---|---|---|
Thermal / Plasma ALD | Aluminum Oxide Hafnium Oxide Silicon Oxide Zirconium Oxide | Backside must be clean! No outgassing materials in mTorr range No thermally unstable materials | Carrier Gas: Argon Plasma Gases: Argon, Nitrogen, Oxygen, Hydrogen | Small pieces up to full 8 inch wafer. Maximum sample thickness is approximately 6mm. |
gas valve numbers |
|---|
0: H2O - 01/2025 1: N/A 2: Al2O3 - 01/2025 3: SiO2 - 01/2025 4: HfO2 - 01/2025 5: ZrO2 - 01/2025 |
Growth rates (Thermal) | Growth rates (Plasma) |
|---|---|
Al2O3 ~ TBD | Al2O3 ~ TBD |
HfO2 ~ TBD | HfO2 ~ TBD |
ZrO2 ~ TBD | ZrO2 ~ TBD |
SiO2 ~ N/A | SiO2 ~ TBD |
General Description
Atomic Layer Deposition (ALD) is a technique that takes advantage of self limiting surface reactions, the nature of the reactions ensures atomic-level thickness control and excellent conformality. Following the standard example, growth of Al2O3 film from water and trimethylaluminum (TMA) precursors will be used here to discuss the principle of ALD film growth. Recipes for other materials use different precursors, but are similar in principle and procedure.
Principles of Atomic Layer Deposition Film Growth (Aluminum Oxide used for this discussion) | ||
Thermal Atomic Layer Deposition - The required reaction energy comes from elevated temperatures of the sample and chamber surfaces. | ||
Processing Steps | Images | |
|---|---|---|
In air, H2O vapor is adsorbed onto most surfaces forming hydroxyl groups with Silicon. (Si - O - H). This is the typical condition of the substrate when placed into the chamber. | | |
The four steps of the ALD Cycle consists of the steps shown to the right. Repeated ALD cycles build self limiting atomic layers at a rate of approximately one angstrom per cycle. | 1. Next, Trimethylaluminum ((CH3)3Al) is introduced into the chamber. Trimethylaluminum reacts with the hydroxyl groups, creating methane as a gaseous reaction byproduct. Al(CH3)3 + :Si-O-H > :Si-O-Al(CH3)2 + CH4 | |
2. Trimethylaluminum continues to react with the adsorbed hydroxyl groups until the surface is passivated. Trimethylaluminum does not react with itself, once all the available hydroxyl groups have been consumed the reaction stops. This self limiting causes the perfect uniformity and conformity of ALD processing. The excess Trimethylaluminum and CH4 byproducts are pumped away. | | |
3. The second precursor, H2O, is introduced to the chamber. Water vapor reacts with the CH3 groups on the new surface, forming Al-O bridges and hydroxylating the surface. Methane is produced as a byproduct of this reaction. 2 H2O + :Si-O-Al(CH3)2 > Si-O-Al(OH)2 + 2 CH4 | | |
4. H2O continues to react with the CH3 groups until the surface is passivated. Water vapor does not react with OH groups, once all the available OH groups have been consumed the reaction stops. This self limiting causes the perfect uniformity and conformity of ALD processing. The excess water vapor and CH4 byproducts are pumped away. | | |
One complete ALD cycle will produce approximately 1 angstrom (0.1 nm) of film thickness. The ALD cycle can be repeated in this way until the appropriate film thickness is grown. | Two reaction steps in the ALD cycle: Al(CH3)3 + :Si-O-H > :Si-O-Al(CH3)2 + CH4 2 H2O + :Si-O-Al(CH3)2 > Si-O-Al(OH)2 + 2 CH4 | |
Plasma Assisted Atomic Layer Deposition - Plasma is used to crack precursor molecules and/or add energy for surface reactions. | ||
Processing Steps | Images | |
Oxidizing step of the plasma assisted atomic layer deposition cycle. | 3. The plasma assisted ALD cycle proceeds exactly as above until reaching step 3. During this step, O2 plasma or Ozone (O3) is introduced into the chamber. The oxygen radicals react with the CH3 groups on the new surface, forming Al-O bridges and forming a hydroxylated surface. CO, CO2, H2O, and CH4 are produced as byproducts of these reactions. Oxygen Plasma reaction during Al2O3 film growth 4 O(plasma) + :Si-O-Al(CH3)2 > Si-O-Al(OH)2 + CO2 + H20 | |
ALD Temperature Window
The chemical and physical conditions necessary to obtain self-limiting growth differ for each ALD process. Furthermore, each process is deemed to have a specific temperature window in which ALD behavior is obtained. An idealized temperature window is plotted to the right where the growth per cycle is plotted as a function of temperature. The ideal temperature window represents the temperature range over which the growth per cycle shows weak or no temperature dependence. This is indicated by the horizontal in the plot to the right. Outside the temperature window, chemical and physical processes can disrupt the ALD behavior. Condensation - At low temperatures, some precursors and co-reactants can condense on the surface, leading to an increase in growth per cycle. Low reactivity - The reactivity of the molecules with the surface sites can be too low because of limited thermal energy at low temperatures. This prevents saturation of the reaction and leads to a decrease in growth per cycle. Decomposition - At high temperatures the precursors or co-reactants can decompose, leading to a CVD component and an increase in growth per cycle. Desorption - At high temperatures the film itself or the reactive surface groups involved may desorb or etch. This leads to a decrease in growth per cycle. | |
Safety Considerations
Danger! Fire Hazard! Trimethylaluminum (TMA) is a liquid at room temperature and is pyrophoric. This means that it burns upon exposure to air. TMA reacts with water vapor in the air. For this reason, the TMA bottle may only be opened in a glove box with inert atmosphere by experienced professionals.
Temperature of the precursors and heating jackets should not exceed safety or decomposition temperature of the chemical being used.
Maintaining cleanliness and proper function of the system is critical for high quality, low leakage dielectric films. It is the responsibility of all users to follow standard operating procedures and to use the system within the prescribed limitations.
You must gain permission from Professor Zhihong Chen and/or the staff engineer before you can be trained for this tool. You will be asked to describe your intended use and sample stack. If you intend to process other substrates and stacks in the future you must first gain permission from Professor Zhihong Chen and/or the staff engineer.
Processing substrates or stacks without prior approval may result in chamber contamination due to outgassing/melting of the materials. This will result in loss of privilege to the tool and your PI may be held accountable for the cost of restoring the tool to operating condition.
Specifications
Available Chemistry
Precursor | Skeletal Formula | Notes |
H2O (Water) | | Ultrapure Water (UPW) from the Birck UPW system. Chemical Formula: H2O CAS Number: 7732-18-5 |
Aluminum Oxide | | Trimethylaluminum, min. 98% Chemical Formula: (CH₃)₃Al CAS Number: 75-24-1 Strem # 98-4003 |
Zirconium Oxide | | Tetrakis(dimethylamino)zirconium(IV), 98% (99.99%-Zr) TDMAZ Chemical Formula: Zr[N(CH₃)₂]₄ CAS Number: 19756-04-8 Strem # 40-4115 |
Hafnium Oxide | | Tetrakis(dimethylamino)hafnium, 98+% (99.99+%-Hf, <0.2%-Zr) TDMAH Chemical Formula: Hf(N(CH₃)₂)₄ CAS Number: 19782-68-4 Strem # 72-8000 |
Silicon Oxide | | Bis(diethylamino)silane Chemical Formula: SiH₂[N(CH₂CH₃)₂]₂ CAS Number: 27804-64-4 Strem # 98-8810 |
Gas | Max Flow Rate (sccm) | Notes |
|---|---|---|
Argon Carrier | 200 | Flows through the manifold, into the process chamber. This gas is used to carry the precursors from the precursor manifold, into the process chamber. |
Argon Plasma | 1000 | Flows from the plasma generating coil (above the chamber) to the process chamber. If not using plasma, this gas should still be used to prevent precursors from entering the quartz plasma tube. |
Nitrogen | 200 | Can be used alone, or as a fraction of a plasma gas mixture. |
Oxygen | 200 | Can be used alone, or as a fraction of a plasma gas mixture. Mass flow controller cannot be powered at the same time the Hydrogen controller is powered. |
Hydrogen | 200 | Can be used alone, or as a fraction of a plasma gas mixture. Mass flow controller cannot be powered at the same time the Oxygen controller is powered. |
Thermal Limits
Heater ID | Max Temp |
|---|---|
ALD Valves | Remains set to 150 C in all conditions and processes. |
Precursor Delivery | Remains set to 150 C in all conditions and processes. |
Reactor 1 | 250 C |
Reactor 2 | 250C |
Chuck | 500 C |
Cone | 250 C |
Precursor Heating Jacket | 200 C |
RF Plasma Controls
RF Source | Max Power (watts) |
|---|---|
ICP Coil | 300 |
Available Standard Recipes
Sample Requirements and Preparation
Sample Specification Clean, vacuum compatible non-outgassing substrates and film stacks. Backside must be clean and free of any metals or photoresist to prevent contaminating the sample carrier. Check with Professor Zhihong Chen or staff engineer for compatibility of your sample. Maximum sample size: Small pieces up to full 200 mm diameter wafer. Approximately 6mm of vertical clearance when inserting the sample carrier, will accommodate thick non traditional samples. Common Substrates: Si, SiO2, GaAs, Glass, Quartz. Common Films (None allowed on backside): Ti, Au, Ag, ......... Not Allowed: ..... | |
Small Samples Small silicon samples, on the order of 5 x 5 mm and smaller, can be lost in the chamber during pumping. These samples cannot be retrieved. A good solution to this problem is presented in the image to the right. Two glass slides are placed such that they are perpendicular to the loading tool arm. The sample is placed between these two slides to shield the sample from gas flows created by initial pumping and stabilize its position on the chuck. New glass slides are not clean! You must clean them using the standard TAI solvent cleaning process before placing them on the chuck or inside the ALD chamber. | |
Software Interface Reference
The control program allows the operator to control the ALD valves, pumping system, heaters, and to set deposition recipes. Do not close the program while the system is running. | |
| Section 1 - System Control buttons. Heaters
Recipe
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