Biosensors

Hi I am working on to find alternate substrates to replace Prime grade silicon as substrate in biosensor manufacturing facility.

Currently we are using 6" silicon @ 3300 wafers/week. I would appreciate if you could provide me some estimated costs and avilability matrix.

Material:       Si
Material:       SOI
Material:       Ge
Material:       SiC
Material:       GaAs

An Adjunct Professor requested a quote for the following:

I am interested in carbon thin films deposited atop any convenient substrate (Si, glass, etc.). We will use these in thin film electrochemical cells with an o-ring seal to the Teflon cell. The carbon film must be durable enough to avoid cracking when a mild force is used to seal the o-ring. Is this something that you can do? What form of carbon (glassy carbon, graphite, diamond, etc.) would you sputtered films most closely approximate?

Question:

My lab also uses Au/Ti/glass slides for biosensor experiments, but we don't need any right now. We had some trouble with the purity level we obtained from another company.

We also have some interest in other sputtered thin films, such as Ti or TiO2.

I am using my start-up package to accumulate interesting thin film materials in my lab, but am of course not at all rich.

Answer:

We do not know the structure of our C films.  However, my educated guess is that it is between amorphous and polycrystalline.

Our lot charge for in-situ sputter etch followed by sputter deposition of 1,000Å C

Reference #198203 for specs and pricing.

To whom it may concern, I am interested in purchasing a set of SOI wafers for my biosensor start-up. We have a few critical parameters: Diameter: 150 mm Top layer thickness: 70 - 100 nm Oxide thickness: >300 nm Resistivity: 20 Ohm-cm Do you have anything similar in stock? If not, would you be able to provide custom wafers with such specifications? If so, can you send a quote, including minimum order number and any lead time?

We are interested in your 100 nm thick SOI wafers, ID# 2377 (SOITEC part # G6P-105-02). Could we get an official quote from you for 10 wafers?

We are making plasmonic (surface plasmon resonance) biosensors so the options we need are.

1. High optical purity in the visible and some of the UV range. So starting around 300 nm on up.
2. Clean dry etching - reactive ion etching with fluorine based gases. In the past soda-lime glass etchs slower and dirty than the quartz.
3. Our lab is set up for 8" (200 mm) wafers so I would like to stick with that size, but 4" I will also consider.

Do you offer the single crystal quartz in 8" wafers? i don't see on website? I am guessing those are expensive? How much are these in the 4" size?

Our CVD is a production tool that will only accomodate 8" wafers so for some of the wafers i have to have 8" size. For most of my processes however i can work with a 4" or 6" wafer size. I see the borofloat 33 is in a 8" size but most of your glass isn't. What do you recommend? How can i see the prices for the different types of glasses in 4" and 8" sizes?

Right now i am leaning towards the borofloat 33 for the 8" and the fused quartz for the 4" size can you send me a quote?

Question:

What are the differences between Silicon (Si) and Silicon-on-Insulator (SOI) Wafers for Biosensor fabrication?

Answer:

For developing biosensors using nanoscale CMOS technology, both silicon (Si) and silicon-on-insulator (SOI) have specific advantages. Below is a matrix comparing the two substrates for biosensor fabrication, considering critical factors:

Key Recommendations:

• Silicon (Si) is a good choice if you are focusing on cost-effectiveness, simpler processes, or bulk biosensors where extreme miniaturization is not critical.
• Silicon-on-Insulator (SOI) is preferable for advanced, highly sensitive biosensors, particularly for nanoscale CMOS applications, where low power, high sensitivity, and minimal noise are crucial.

Here’s a detailed analysis comparing Silicon (Si) and Silicon-on-Insulator (SOI) for nanoscale CMOS-based biosensors, considering fabrication, operational parameters, and specific advantages for biosensing applications.

1. Fabrication and Processing

2. Device Performance

3. Biosensor-Specific Factors

4. Use Cases and Application Scenarios

• Silicon (Si):

  • Suitable for simpler, larger-scale biosensors where ultra-high sensitivity is not critical.
  • Lower-cost solutions for wearable or disposable biosensors.
  • Applications involving robust heat dissipation or requiring bulk properties.

• Silicon-on-Insulator (SOI):

  • Ideal for precision biosensors (e.g., DNA, protein detection) requiring high sensitivity.
  • Best for integration with photonic sensors or low-power devices.
  • Nanoscale biosensors needing scalability and minimal parasitic effects.

5. Detailed Advantages of SOI for Biosensors

• Buried Oxide (BOX) Layer:
  • Acts as an insulator, drastically reducing noise and parasitic effects.
  • Provides a stable electrical environment for highly sensitive measurements.
• Active Layer Precision:
  • Thin silicon active layers allow for precise control over sensor characteristics.
  • Enhances signal-to-noise ratio in field-effect transistor (FET) biosensors.
• Thermal Isolation:
  • BOX minimizes thermal cross-talk, critical for temperature-sensitive biomolecules.

Recommendations for Your Research:

• If sensitivity, noise performance, and device miniaturization are critical, SOI is the superior choice despite its higher cost and processing complexity.
• For cost-conscious applications or where bulk properties are beneficial, Silicon (Si) is a practical alternative.

UniversityWafer, Inc. specializes in assisting university researchers in sourcing appropriate substrates for biosensor projects. They offer a wide range of semiconductor materials, including silicon and silicon-on-insulator (SOI) wafers, tailored to meet the specific needs of academic research. Their services include providing substrates with various coatings and treatments, such as thermal oxide and nitride layers, which are essential for biosensor fabrication. UniversityWafer, Inc. has a history of supporting research initiatives by supplying high-quality materials and offering technical guidance to ensure researchers obtain substrates that align with their experimental requirements.

Reference #104382 for specs and pricing.

We are a London based research group from Materials Department. We are working on dual biosensors for cancer cell detection; surface acoustic waves to detect mass and Graphene field effect transistor to detect electric charge. For this research project we want to try quartz substrate. Kindly give a quotation for a following order: ST-cut 90˚, Y-axis (Guided Love Wave using Polymer on Quartz) 2 inches diameter and 500µm thick. 50 to 100 samples. 

Question:

I am working in the Agricultural Research Organization, the Volcani center, Israel. I am using thermal oxide [0.5 (ID:2069) and 1 u (ID:1385)] wafers for biosensor application. But I am not able to functionalize the surface using silane coupling agent (3-Aminopropyl)triethoxysilane (APTES). I treated the surface with piranha solution and oxygen plasma before functionalization. Please suggest me if any other methods to improve the surface binding or suggest me the proper thermal oxide wafer's for amine functionalization. It would be a great helpful.

Answer:

To improve your success with surface functionalization for biosensors, including using silane coupling agents like (3-Aminopropyl)triethoxysilane (APTES), it is critical to ensure that your silicon wafer with thermal oxide has optimal characteristics and that your functionalization protocol is effective. Here's a step-by-step guide to address your challenges:

1. Thermal Oxide Spec Recommendations

For biosensor applications, the following thermal oxide specifications are ideal:

• Oxide Thickness: 50–300 nm
  • Thin enough to maintain good electrical and optical properties.
  • Thick enough to ensure a robust and stable silane layer.
• Oxide Quality:
  • High-quality dry or wet thermal oxide (wet oxide can improve adhesion but may have higher roughness).
  • Ultra-clean and uniform oxide layer.
• Surface Roughness:
  • RMS roughness < 1 nm for uniform silanization.
• Doping Type: Not directly relevant for silanization but ensure the wafer is compatible with the biosensor's intended application.

2. Improving Surface Binding

If piranha solution and oxygen plasma treatments are not sufficient for proper surface preparation, consider the following modifications:

A. Extended Surface Cleaning

1. HF Treatment (Optional):
   • Use diluted HF to remove native oxide and expose fresh oxide. However, this might reduce hydroxyl groups essential for APTES binding, so balance the exposure time carefully.
2. Steam Annealing:
   • Post-cleaning, steam annealing can create more silanol groups (-Si-OH), improving APTES binding.

B. Functionalization Method Optimization

1. Pre-silanization Environment:
   • Ensure the wafer is completely free of organic residues. Use solvents like ethanol or acetone and dry in a dust-free environment.
   • Maintain high humidity (40–60%) during APTES vapor deposition to promote condensation reactions.
2. APTES Concentration:
   • Use a diluted APTES solution in ethanol (1–2%) to prevent multilayer formation.
3. Curing:
   • After applying APTES, bake the wafer at 100–120°C for 10–15 minutes to stabilize the silane layer.

3. Alternative Surface Treatments

If APTES continues to fail, explore other coupling agents or methods:

• Alternative Silane Coupling Agents:

  • (3-Glycidoxypropyl)trimethoxysilane (GPTMS) for epoxide groups.
  • (3-Mercaptopropyl)trimethoxysilane (MPTMS) for thiol groups.
  • Aminopropyl diethoxy(dimethylsilane) for better hydrolytic stability.

• Direct Functionalization with Plasma:

  • Nitrogen plasma treatment can introduce amine groups directly on the surface.

• Polymer Coatings:

  • Apply a thin polymeric layer (e.g., polyethyleneimine, PEI) before silanization.

4. Wafer Supplier Recommendations

If you suspect the wafer quality might be a factor, use wafers with specifications tailored for surface functionalization. Suppliers like University Wafer, Nova Electronic Materials, or Addison Engineering provide high-quality thermal oxide wafers for biosensors.

5. Characterization Post-Functionalization

To confirm success after surface functionalization, use:

• Contact Angle Measurement:
  • A hydrophilic surface (<40° contact angle) after silanization indicates good functionalization.
• Fourier Transform Infrared Spectroscopy (FTIR):
  • Detect amine groups post-functionalization.
• Ellipsometry:
  • Measure the thickness of the APTES layer (~1–2 nm for a monolayer).