A unique range of exceptional properties make MEMpax® a go-to product for a broad range of applications. Durability in processing, suitability for high-temperature bonding, a wide array of sizes, and its availability in unrivalled low thickness ranges make MEMpax® truly stand out.

High durability in extremely low thicknesses

Outstanding chemical resistance

As with SCHOTT’s groundbreaking BOROFLOAT®, MEMpax® offers the highest chemical durability, enabling it to withstand the most aggressive conditions during processing and application. Due to its glass composition, MEMpax® is also a high-quality electrical insulator.

Built for bonding

MEMpax® has a coefficient of thermal expansion (CTE) that matches a silicon wafer, enabling very low stresses in the anodic bonding of glass to silicon wafers. Extremely low roughness of its surface (typically Ra ≤ 0.5 nm) further facilitates this process.

Wavelengths you can work with

Similar to BOROFLOAT®, MEMpax® exhibits high transmission in the visible wavelength range, including deep into the UV-range. This makes the material highly suitable for UV debonding in semiconductor processes.

Shapes, sizes and thicknesses to suit

SCHOTT prides itself on working with customers to meet their needs as specifically as possible, and our glass wafers are no exception. Available in custom shapes, as well as standard round varieties, the spectrum of sizes ranges from 2-12", with thicknesses from 0.07-0.55 mm.

Material properties


1. Optical properties

Optical Properties Value
Refractive index* ng 1.4803
Refractive index* nF' 1.4768
Refractive index* nF 1.4765
Refractive index* ne 1.4732
Refractive index* nd 1.4715
Refractive index* nD 1.4714
Refractive index* nC' 1.4696
Refractive index* nC 1.4693
Abbe value νe 65.4
Photoelastic constant in (nm/cm)/Mpa 39.8

* Refractive indices: Pretreatment of samples.
Condition as supplied ["as drawn"] 


2. Thermal properties

General thermal properties Unit Value
CTE (Coefficient of thermal expansion) α  10-6·K-1  (20 °C; 300 °C)  3.26 
Mean specific heat capacity cp in J/(g·K)(20 °C; 100 °C) 0.82
Transformation temperature Tg in °C 532


Viscosities Viscosity lg ŋ in dPas Temperature in °C
Strain point 14.5 528
Annealing point 13.0 570
Softening point 7.6 831


3. Mechanical properties

Mechanical Properties
Unit Value
Density ρ in g/cm³ 2.22
Young's modulus E in kN/mm² 62.7
Poisson's ratio µ 0.196
Torsion modulus G in kN/mm² 26.2
Knoop hardness HK 0.1/20 430
Vickers hardness HV 0.2/25 510


Chemical toughening (for thickness = 0.2 mm)

Temperature ϑ in °C 430
Time t in h 4
Compressive stress (CS) in MPa 120
Depth of layer (DoL) in µm 8


4. Chemical properties

Hydrolytic resistance (acc. to DIN ISO 719) Value
Class HGB 1
Equivalent of alkali per gram glass grains in µg/g < 31


Acid resistance (acc. to DIN 12116) Value
Class S 1
Half surface weight loss after 6 hours in mg/dm² 0.16


Alkali resistance (acc. to DIN ISO 695) Value
Class A 2
Surface weight loss after 3 hours in mg/dm² 132


5. Electrical properties

Dielectric constant εr (at ϑ = 25 °C) Value
at 1 MHz 4.8
at 1 GHz 4.4
at 2 GHz 4.5
at 5 GHz 4.4
at 24 GHz 4.4
at 77 GHz  4.4 


Dissipation factor tan δ (at ϑ = 25 °C)
at 1 MHz 38 · 10-4
at 1 GHz 58 · 10-4
at 2 GHz 62 · 10-4
at 5 GHz 73 · 10-4
at 24 GHz 100 · 10-4
at 77 GHz  150 · 10-4 


Electric volume resistivity ρD in Ω·cm direct current
1.18 ·108 ( ϑ = 250 °C)
4.24 ·106 (ϑ = 350 °C)


6. Transmittance values

Spectral transmittance (250 - 3150 nm)

Chart showing the spectral transmittance of MEMPax® borosilicate glass (250-3150 nm)


Spectral transmittance (250 - 500 nm)

Chart showing the spectral transmittance of MEMPax® borosilicate glass (250-500 nm)


Wavelength in nm at thickness 0.2 mm: τ (λ) in %
254 28
380 92.4
632.8 92.8
1064 92.7


Edge wavelength λc (τ = 0.46) at thickness in mm Wavelength in nm
0.2 269 
0.3  279 
0.5  283 
0.7  288 


Luminous transmittance at thickness in mm τvD65in %
0.2 92.8
0.5  92.8 


MEMpax® products

SCHOTT MEMpax® is available as:

  • Unpolished substrates and wafers

To find out more, please see the related products on the overview page.

Want to know more? Let’s talk

Whether you need more information, samples, a quote, or advice for a project, we would be delighted to talk to you.

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