Introduction of BF33 glass wafer

The BF33 glass wafer—widely known as BOROFLOAT 33 or BF 33—is a premium borosilicate float glass wafer manufactured by SCHOTT, noted for its exceptional thermal, optical, chemical, and mechanical properties. The “33” in its name refers to its coefficient of thermal expansion (CTE) of approximately 3.3 ppm/°C, a characteristic that closely matches silicon, making it a preferred choice for semiconductor and microelectronic applications.

BOROFLOAT 33 is created using SCHOTT’s pioneering microfloat process, which yields a homogenous material with mirror-like surface quality, high flatness, minimal microroughness, and overall outstanding optical clarity .

Material Composition & Structural Integrity of BF33 glass wafer

The glass composition of BF33 is approximately:

•  SiO₂

•  B₂O₃

•  Na₂O/K₂O

•  Al₂O₃ 

This formulation yields key benefits:

• Low density, lighter than typical soda-lime glass, enabling lightweight laminated structures (e.g., bulletproof glass) .

• Low alkali content, which reduces leaching in analytical or biomedical devices, minimizing interference during measurements.

Thermal & Mechanical Properties of BF33 glass wafer

Thermal Performance

• Coefficient of Thermal Expansion (CTE): ≈ 3.25 ppm/°C—closely matching silicon—ensures minimal stress during temperature changes and is essential for processes like anodic bonding.

• Temperature resistance: Up to 450 °C for long-term use, and 500 °C for short-term (<10 h) operations .

• Thermal Shock Resistance: Its low CTE and structural integrity offer excellent resistance to rapid temperature fluctuations, preventing cracking or warping .

Mechanical Strength

• Hardness: High Knoop hardness (≈ 480 HK) and robust abrasion resistance, significantly outperforming ordinary soda-lime glass .

• Elastic Modulus: Approximately 64 kN/mm² with Poisson’s ratio around 0.2.

• These characteristics make BF33 highly resistant to penetration, scratching, and mechanical wear .

Optical & Chemical Properties of BF33 glass wafer

Optical Characteristics

• High transparency across UV, visible, and near-IR wavelengths, with very low autofluorescence—ideal for high-precision optical and analytical systems .

• UV Transmission: At 0.5 mm thickness, transmittance > 90% at 308 nm, and still > 35% at 248 nm—significantly outperforming other thin glass materials .

Chemical Durability

• Excellent resistance to water, strong acids, alkalis, and organic solvents—making BF33 especially suited for harsh chemical environments such as wet etching, CMP, or analytical instruments .

• Hydrolytic and corrosive resistance is rated class 1 according to ISO/DIN standards .

Surface Quality & Fabrication of BF33 glass wafer

Many suppliers offer double-side polished (DSP) BF33 wafers, often with sub-nanometer surface roughness (< 1 nm Ra), tight TTV (<10 µm), and low-defect finishes (e.g., scratch/dig 60/40), suitable for demanding microfabrication requirements .

Such specifications ensure superb flatness and bonding compatibility, particularly for anodic bonding, laser debonding, and optical assembly where surface quality is critical .

Typical Applications of BF33 glass wafer

BF33’s exceptional properties make it a go-to material across diverse domains:

• Semiconductor & Microelectronics: Carrier wafers, anodic bonding with silicon, wafer thinning, microfluidics, MEMS, optical sensors, and lab-on-chip devices .

• Optics & Photonics: Laser optics, filters, mirrors, microscope slides, and optics in demanding thermal environments .

• Analytical & Biomedical: Biochips, titration plates, microfluidic systems, diagnostic tools—thanks to low autofluorescence and chemical purity .

• Industrial Applications: High-temperature optics, kiln windows, floodlight covers, sight glasses for chemical reactors .

• Energy & Environmental Tech: Substrates for photovoltaic systems, environmental sensors, and microfluidic environmental monitoring devices .

• Aerospace & Defense: Durable, thermally stable components like instrumentation panels, sensor windows, and space optics .

Summary & Advantages of BF33 glass wafer

In summary, the BF33 / BOROFLOAT 33 glass wafer offers an unmatched combination of properties:

These attributes make it a versatile and high-performance substrate for applications where reliability, precision, and durability are indispensable.

Conclusion of BF33 glass wafer

The BF33/BOROFLOAT 33 glass wafer stands out as a top-tier borosilicate glass substrate, engineered via SCHOTT’s microfloat process. Its synergy of low thermal expansion, thermal shock resistance, high optical quality, chemical inertness, mechanical robustness, and surface excellence makes it indispensable across scales—from advanced semiconductor packaging to cutting-edge optical systems, biomedical instrumentation, and aerospace technologies.

Frequently Asked Questions (FAQ) of BF33 glass wafer

What is BF33 glass?

BF33, also known as BOROFLOAT 33, is a high-quality borosilicate float glass manufactured using SCHOTT’s proprietary microfloat process. It features low thermal expansion (~3.3 × 10⁻⁶ K⁻¹), high thermal shock resistance, excellent chemical durability, and outstanding optical clarity. It is often supplied in wafer form for semiconductor, microfluidic, and optical applications.

What is the difference between BF33 and ordinary glass?

Unlike soda-lime glass, BF33 contains more than 80% silica and significant boron oxide, which:

• Reduces thermal expansion, preventing cracking during temperature cycling.

• Increases chemical resistance against acids, bases, and solvents.

• Improves UV and infrared transmission.

• Enhances mechanical strength and scratch resistance.

Why is BF33 glass widely used in semiconductor and MEMS fabrication?

Its thermal expansion matches that of silicon, enabling stress-free anodic bonding. Additionally, its chemical durability allows it to withstand wet etching, CMP, and other cleanroom processes without degradation.

Can BF33 glass wafers be polished?

Yes. BF33 wafers are often supplied as DSP (Double-Side Polished) or SSP(Single-Side Polished) with surface roughness < 1 nm Ra and low total thickness variation (TTV), which is critical for photolithography and wafer bonding.