What is Wafer Bonding?

Wafer bonding is commonly used in Front-end of line (FEOL) operational steps as wafer-to-wafer bonding provides strength if the device wafer is to be thinned to ultra-thin dimensions.

Precision bonding of a wafer to a substrate in the TSV and BSI processes and some MEMS processes is done primarily for the purpose of providing strength and wafer safety during follow-on process steps and handling.  Device wafers in the TSV and BSI processes are put through an ultra-thin grinding process, which reduces the device wafer thickness to 50 µm for TSV and even thinner for BSI.  Without a supportive substrate, silicon wafers this thin will not survive follow-on multi-step processing.  As a part of the bonding procedure, it is common for both the device wafer and the “carrier” substrate to pass through one or more CMP steps for planarization and surface smoothness preparation.

Axus Technology offers a variety of wafer bonding process techniques including: temporary wax-on and tape-on bonding, permanent wafer bonding and enhanced temporary bonds where follow-on processing requires stronger bonding of the substrates.

In certain advanced wafer applications such as TSV and BSI, and certain MEMS applications, which can benefit from, or even require the support of a carrier substrate to protect the device wafer in thin wafer processing, customers soon understand that bonding their device wafers to support-substrates can provide the needed protection.  The type of bonding that is chosen is based upon the application and the materials involved.  Superior bonding results are dependent upon upstream processing steps such as superior precision grinding, edge treatments such as profiling and trimming, along with Chemical Mechanical Polishing (CMP), and post-process cleaning.  Relying on one supplier, such as Axus Technology to be responsible for all of these process steps mitigates the customer’s risk and shortens the overall processing time.

For more information and a complete description of the process used at Axus Technology, please see our Wafer Bonding Application Note.

HOW AXUS TECHNOLOGY CAN HELP YOU

FOR PROCESS SERVICES:  Axus Technology’s Process Services Department has the required equipment and expertise available to perform a number of critical process steps including wafer bonding on a contractual basis on your wafer substrates.