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37

Chip Scale Review January • February • 2019

[ChipScaleReview.com

]

nlike mechanical debonding, which generates

significant peel stress on a device’s surface, air-jetting

debonding (AirDebond

®

) injects air streams between

the carrier and the device, pushing the carrier up from underneath

while compressing the device down. As a result, this jetting

technology allows a higher strength bonding adhesive at an elevated

temperature, which is typically associated with excessive warpage

control. Furthermore, the airflow produces the most uniform stress

distribution, and the debonding is instant at room temperature—

characteristics that are best suited for large-area debonding.

Air jetting debonding

This article describes the advancements in air jetting debonding

and the material developments for high-temperature temporary

support of thin-wafer fabrication, fan-out wafer-level packaging

(FOWLP), and integrated circuit (IC) package assembly with a large

thin substrate.

The fabrication of a thin IC wafer requires a temporary support for

grinding, polishing, dry reactive ion etching, dielectric development,

metal deposition, chemical etching, photoresist development and/

or solvent soaking, plasma ashing, and wafer cleaning. Panel-level

packaging also requires temporary support for redistribution layer

(RDL) build-up, flip-chip bonding, fluxing cleaning, molding, and

even the solder reflow process. After fabrication, the thin-wafer/panel

requires debonding from its carrier. The bonding adhesive needs to be

completely removed without any trace of residue contamination.

While a carrier and a device typically bond together under pressure

in vacuum, debonding mechanisms to separate the carrier from the

device vary with the adhesive. It is desirable to have the debonding

done with the shortest cycle time, the minimum tensile stress exerted

on the device surface, the elimination of heat damage on the device’s

structure, and easy cleaning with an environmentally friendly cleaner.

The concept of injecting air for carrier debonding was first

introduced in 2016 for thin-wafer processing [1]. Unlike mechanical

peeling, air jetting debonding introduces air streams to push the carrier

up from underneath while compressing the device down (

Figure 1

).

The structure and pattern of the device are being protected from the

airflow. Furthermore, AirDebond

®

allows the carrier made by materials,

such as silicon, ceramic and metal (as well as glass) to best match the

coefficient of thermal expansion (CTE) of the device wafer for better

warpage control at a high temperature.

Table 1

summarizes the application and materials with the air

jetting technology.

Temporary bonding for a wafer process >400°C

The thermal stability of an adhesive often refers to its ability to resist decomposition and outgassing during high thermal processing.

Z-coat 451 (Z451) is a single-layer bonding adhesive for up to a 400°C processing application.

Figure 2

illustrates a typical process flow

with Z451.

Figure 3

shows the thermogravimetric (TGA) curve of Z451 under a constant heating rate of 10°C/min to 700°C. We can see

that the weight loss of the Z451 is highly stable up to 450°C. The decomposition temperature is around 500°C.

U

Air jetting debonding for thin-wafer/panel and fan-out

wafer-level package processing

By Hao Tang, My Nguyen, Joshua Huffaker, Anastasia Banner

[Micro Materials Inc.]

Figure 1:

Illustration of the air jetting process.

Table 1:

Summary of the application and materials with AirDebond

®

technology.

Figure 2:

Typical process flow with Z451.