Thermal Oxide on Silicon
PAM-XIAMEN provide thermal oxide wafer with/without Ti layer/Pt layer in diameter from 2″ to 12″,now we give examples as follows:
1) 4 inch,silicon prime/test wafer,deposited with 5000 Angstroms of silicon oxide
2) Pt layer+Ti layer+thermal oxide layer deposit on silicon wafer:
4 inch Prime grade silicon,1-20 ohm cm,500 um thick ,Single side polished
+ 3000 Angstroms of thermal oxide
+ 500 Angstroms of Ti
+1500 Angstroms of Pt
1. How to Obtain Thermal Oxide on Silicon?
Thermal Oxide is normally grown in a diffusion furnace (either vertical or horizontal) or it can also be grown in a Rapid Thermal Processor. RTP systems are normally used for thin dry Thermal Oxides or Implant annealing on devices where tight thermal budgets are an issue. Large Horizontal or Vertical diffusion furnaces are usually the tool of choice when growing most Thermal Oxides.
Growth methods: Thermal oxide is grown at high temperatures from 800°C – 1100°C using either a “Wet” or “Dry” growth method.
1) for dry oxidation: Si (solid) + O2 (vapor) –> SiO2 (solid); and
2) for wet oxidation: Si (solid) + 2H2O (vapor) –> SiO2 (solid) + 2H2 (vapor).
Today’s Wet Oxides are grown pyrogenically using Hydrogen and Oxygen gases in a internal or external torch. Most large IC manufactures use external torch technology, this is where H2 & O2 gases are combined in a quartz torch unit outside of the quartz furnace tube. This torch unit is housed in it’s own small high temperature furnace element (separate from the main furnace) that is heated to a temperature >800°C. At this temperature the gases will ignite and burn on their own without an outside ignition source. The flame produced is blue in color and usually contained in a secondary quartz vessel called a steam chamber, the result of this blue flame is pure steam.
2. Physical Properties of SiO2 Thin Film
The physical properties of SiO2 thin films are shown in the table below. The physical properties of SiO2 thin films obtained by different preparation processes vary slightly, such as density, refractive index, resistivity, dielectric constant, dielectric strength, etc.
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Physical Properties of SiO2 Thin Film |
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| Oxidation Method | Density (g/cm3) | Refractive Index (λ=546nm) | Resistivity (ohm.cm) | Dielectric Constant | Dielectric Strength (106V/cm) |
| Dry Oxidize | 2.24~2.27 | 1.460~1.466 | 3E5~2E6 | 3.4(10KHz) | 9 |
| Wet Oxidize | 2.18~2.21 | 1.435~1.458 | / | 3.82(1MHz) | / |
| Water Vapor | 2.00~2.21 | 1.452~1.462 | 1E15~1E17 | 3.2(10KHz) | 6.8~9 |
| Thermal Decomposition Deposition | 2.09~2.15 | 1.430~1.450 | 1E7~1E8 | / | / |
| Epitaxial Deposition | 2.3 | 1.460~1.470 | 7E14~8E14 | 3.54(1MHz) | 5~6 |
3. Role of Thermal Oxide on Silicon Substrate
The oxidation of silicon is an important process in ultra large scale integrated circuits. The typical functions of SiO2 are:
1) Insulation function
Silicon oxide is composed of Si-O covalent bonds, with no free electrons inside and a wide bandgap (8-9eV). It is an insulator with high resistivity, low dielectric constant, and high breakdown field strength. As an isolation layer, it helps to reduce crosstalk between different parts; As a gate oxide layer, it can effectively control the gate voltage to regulate the charge carriers in the channel, thereby controlling the current flowing through the transistor; As a dielectric layer, it is used to isolate metal layers between different layers, which can prevent current leakage and short circuits.
2) Surface passivation
The SiO2 layer has high chemical stability and is the most stable compound of silicon. It is insoluble in water and can only react with hydrofluoric acid to form hexafluorosilicic acid H2 [SiF6]. As a passivation layer to improve the chemical and electrical properties of semiconductor surfaces. It can effectively prevent the activity of surface atoms, reduce surface defects, and thus improve the electrical performance of the device.
3) Used as mask
Silicon oxide can prevent various impurities in the surrounding environment, such as metal ions, organic compounds, etc., from coming into contact with the silicon surface, in order to avoid changing the electrical properties of silicon and causing a decrease in device performance. In addition, by blocking with silicon dioxide, impurity atoms can diffuse in specific regions and depths according to predetermined process requirements, thereby controlling the impurity concentration distribution in the source and drain regions of the transistor. The thicker and denser the silica, the more difficult it is for impurity atoms to pass through and the slower the diffusion rate. This is because impurity atoms experience more scattering and obstruction when passing through silicon dioxide.
4) Improve interface features
The crystal structure and physical properties of silicon dioxide match those of silicon and silicon nitride, and it can act as a buffer between the two, reducing stress caused by lattice mismatch and differences in thermal expansion coefficients.
Whether you need thermal oxide wafers for research or for industrial applications, please contact us email at [email protected] and [email protected].