Dielectric Specs of Substrates

university wafer substrates

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A PhD candidate requested help with the following.

Could you please send me a quotation giving price and delivery time per Si wafers 150mm x 0.680mm with 4µm of silicon oxide and with 2µm? Could you also give me the dielectric constant for that oxide? And how that oxide is made?

Reference #91282 for specs and pricing.

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Silicon Wafers With Si3N4 As Dielectric

A Postdoc requested a quote for the following.

We are interested in following wafers:

A. Silicon wafer with Si3N4 as dielectric (t~200 nm). Could you send us
quote for it.
Spec for Si wafer:
Diameter: 2" and 4"
Wafer thickness: For 2" = 275- 325 um
                               4" = 500-550 um
Doping:               P/Bo <100>
Resistivity:           0.01-.02 ohm-cm

B. As we use Si/SiO2 substrates for our device fabrication, we found lot of gate leakage current, hence we would like to try Si/Si3N4/SiO2  stack dielectric layer. Do your company supply these type of substrate? What  is the SiO2 growth technique used? Required Spec: Total dielectric thickness~200 nm with Si specs being same as mentioned above.

C. Does your company supply dry Chlorinated thermal oxide and forming gas
anneal (SiO2) substrates Spec being the same for Si and SiO2.

Reference #90555 for specs and pricing.

How Do You Find The Dielectric Spec of a Substrate?

1. Determine the Material Composition

Identify the type of substrate (e.g., silicon, sapphire, quartz, etc.) and any relevant treatments or coatings (e.g., thermal oxide, nitride, etc.).

2. Check Manufacturer’s Datasheets

Most suppliers or manufacturers provide datasheets that include dielectric specifications such as:

  • Dielectric constant (relative permittivity, εr): The ratio of the material’s permittivity to the permittivity of a vacuum.
  • Dielectric strength: The maximum electric field the material can withstand without breakdown.
  • Loss tangent (tan δ): A measure of energy dissipation in the dielectric.

3. Use Reliable Reference Databases

Access material property databases like:

  • MATWEB: Offers dielectric properties for various materials.
  • Refractive index databases: Useful if optical properties relate to the dielectric behavior.
  • CRC Handbook of Chemistry and Physics for standard materials.

4. Experimentally Measure Properties

If datasheets aren't available, measure the properties experimentally:

  • Capacitance Measurement:
    • Use a parallel-plate capacitor setup with a known electrode area and separation.
    • Measure capacitance and calculate the dielectric constant using the formula:
      • εr = (C × d) / (ε0 × A)
Where:
  C = measured capacitance
  d = substrate thickness
  A = electrode area
  ε0 = permittivity of free space (8.854 × 10-12 F/m)
  • Dielectric Strength Measurement:
    • Apply increasing voltage across the substrate until breakdown occurs and calculate dielectric strength:
      • Dielectric Strength = Breakdown Voltage / Thickness

5. Refer to Industry Standards

Use standards from organizations like:

  • IEEE: For electrical and dielectric testing.
  • ASTM: For material-specific dielectric property testing (e.g., ASTM D149 for dielectric strength).

6. Consult with the Supplier

If the dielectric specs aren't in standard documentation, contact the substrate supplier or manufacturer directly.

Are Silicon Wafers Coated With Dry Oxide Good Enough To Be Used As Dielectrics?

Yes – silicon dioxide (SiO₂) layers produced by dry oxidation on silicon wafers are, in fact, among the most widely used dielectric materials in the semiconductor industry. However, whether they are “good enough” for your application depends on several factors. Here are key points to consider:

Quality and Advantages of Dry Oxide:

  • High Purity and Uniformity: Dry oxidation tends to yield a denser, more uniform oxide with fewer defects and impurities compared to wet oxidation. This leads to superior insulating properties and a lower density of interface traps.
  • Electrical Properties: High-quality dry oxide boasts excellent dielectric strength, low leakage current, and good resistance to breakdown. These properties make it ideal for gate dielectrics in MOSFETs, capacitor insulators, and other microelectronic components.
  • Surface Smoothness: Dry oxidation produces a smooth interface between the silicon and the oxide, which is beneficial for device performance and reliability.

Considerations for Use as Dielectrics:

  1. Thickness Requirements:

    • For many integrated circuit applications, silicon wafers use very thin oxide layers (a few nanometers thick) as gate dielectrics. If your dielectric application requires thicker layers (e.g., for high-voltage capacitors), you may need to grow a thicker oxide or use additional deposition steps.
    • The thickness influences the breakdown voltage and capacitance. Ensure the oxide layer meets the voltage and capacitance requirements of your application.

  2. Breakdown Voltage and Reliability:

    • Dry oxides are known for high dielectric strength. However, you should verify that the breakdown voltage of your specific oxide thickness is appropriate for your application.
    • Long-term reliability and stability under electrical stress should also be evaluated, especially if the dielectric will be used in demanding environments.

  3. Application Specifics:

    • While silicon dioxide is a great dielectric for many standard electronic components, some applications might require special dielectric materials (e.g., high-k dielectrics) for enhanced performance, reduced leakage, or other specialized needs.
    • If your application involves non-standard conditions (like high frequencies, extreme temperatures, or unique geometries), further testing or alternative materials may be needed.

Conclusion:

Yes, silicon wafers coated with a dry oxide layer can serve as excellent dielectrics. They are widely trusted in the semiconductor industry due to their high quality, uniformity, and excellent electrical properties. Nonetheless, ensure that the oxide’s thickness, breakdown voltage, and other characteristics align with the requirements of your specific application. It’s always a good idea to perform tests or simulations tailored to your use-case to validate the suitability of the oxide layer as a dielectric in your particular scenario.