The performance requirements for glass wafers used for anodic bonding or as carrier wafers in wafer thinning processes are mainly determined by their ability to perfectly match those of the silicon wafer to which they shall be permanently or temporarily bonded. Well-adapted thermal expansion behaviour is as important as excellent flatness and process robustness. BOROFLOAT® glass wafers provide such outstanding material properties along with exceptionally high UV transmission – a special requirement for high speed laser de-bonding processes.
BOROFLOAT® - The sum of its properties is what makes it unique for glass wafers!
Glass wafers made of BOROFLOAT® glass offer outstanding thermal resistance
The glass composition of BOROFLOAT® is tailored to perfectly match the thermal expansion coefficient of silicon which is essential for good bonding behavior.
Wafers are often exposed to thermally changing environments during processing. The low coefficient of linear thermal expansion (C.T.E.) allows BOROFLOAT® glass wafers to easily handle elevated temperatures and – often even more importantly - sudden thermal changes without breaking or warping.
Carrier wafers with unmatched light transmission allow for exceptional UV bonding
Laser de-bonding through glass carrier wafers offers the fastest de-bonding time as well as a good price / performance ratio. Deep UV light transmission at the relevant laser wavelength range is crucial for the principal feasibility and efficiency of this type of wafer de-bonding. The laseractivated release will be achieved through irradiation using a 248 nm or 308 nm excimer laser. Extra-low iron BOROFLOAT® glass of desirable 0.5 mm carrier thickness shows over 90 % transmission at 308 nm and still over 35 % for 248 nm, thus significantly outperforming other thin flat glasses.
Acids, alkalis and organic substances have virtually no negative impact on BOROFLOAT® glass wafers
Glass wafers made of BOROFLOAT® stand out for their reliable process robustness
Many wafers require microstructures which are often created via ultrasonic drilling, powder blasting or a combination of photolithography and dry etching. Mechanical strength and stability during a process where thousands of accurate features have to be machined are essential in order to produce high precision textured wafers with a consistently perfect surface pattern and accurate size. As shown in the graph below, BOROFLOAT® glass has an exceptional abrasion resistance compared to other alternative substrates.
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