Temporary Bonding: Enabling the Next Generation of Ultrathin Wafers

What’s necessary to enable continued scaling and 3D integration.

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Innovative materials are critical for maintaining integrity during advanced semiconductor manufacturing processes. Temporary bonding is being enabled by these new materials and is making a name for itself in the next generation of ultrathin wafer manufacturing.

Semiconductor wafers are being forced to become thinner as the push to shrink feature sizes and introduce full-scale 3D integration continues to grow.

While grinding wafers to less than 100 micrometers in thickness is a readily available process, moving to even thinner wafers (<50 µm) makes them exceedingly fragile. The stress of these extreme thinning processes and subsequent downstream metallization can cause additional stress on ultrathin wafers, contributing to warp or breakage.

The thin wafer handling process consists of temporarily mounting a device wafer to a carrier wafer with a polymeric bonding material system. This process is used to stabilize a wafer through harsh back-end processes while supporting the ultrathin device substrate. Two of the fastest growing release methods for debonding the wafer pairs are the laser and mechanical methods.

Laser Release
The laser method employs a special release layer that is deposited on the carrier and used in conjunction with a temporary adhesive that ablates when exposed to either an excimer or solid-state laser. There is a lot of interest surrounding this technology for several reasons.

Thermal Stability
Newer laser debonding materials can offer temperature survivability up to 400°C, making this release method ideal for high-stress and high-temperature processing.

Throughput
A high-quality release material can also enable the laser method in high-volume production, allowing manufacturers to process up to 50 wafers per hour.

Very Low Stress
The laser release method does not impart any stress on the wafer, making it a flawless fit for even the thinnest semiconductors.

Mechanical Release
Mechanical release may be the simplest method of debonding. It makes it possible to separate wafers with minimal force. One essential attribute of mechanical release materials is their ability to enable room-temperature debonding. Typically, the material is used to treat a reusable carrier, allowing it to adhere to the device wafer during processing, while separating away at the end of the process. The latest bonding and debonding materials for mechanical release have a high temperature survivability of up to 300°C.

The Right Process
The mechanical and laser release methods are emerging as key enablers for the next generation of ultrathin semiconductor wafers. Each has its own strengths and both methods are making great advances, enabling the latest innovations in advanced packaging applications. As temporary bonding continues to build a name for itself in the next generation of ultrathin wafer manufacturing, these methods will only continue to see more use in the semiconductor industry.



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