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carrier. These structures are laminated into dielectric to embed the © 2017 Brewer Science, Inc.
circuits, and then built up with an mSAP or SAP type process.
Figure 1 describes the process for the fabrication of a
panel-level substrate over 6 steps by using a combination of
ETS and mSAP processes. ETS technology involves using a
photolithographic process to create pattern-plated metallization
structures onto a conductive carrier after photo imaging as seen Creating Safe
in steps 1 and 2. The fine-line traces created are then laminated
onto the dielectric to embed the circuits, forming the M1 layer,
in step 3. The conductive carrier is removed in step 6 after the Environments
substrate is processed with the M2 layer and M3 layers using
mSAP technology. The mSAP process starts in step 3 with a thin
copper foil of approximately 1 to 5µm in thickness on the organic
substrate, which allows for good adhesion. This foil, along with Laser Release System
electroless copper, are plated with electrolytic plating processes to
create the M2 or M3 layer, which can contain both fine-line RDL In the laser release system, the device wafer
and vias, as seen in steps 4 and 5. This is the previously mentioned
2-in-1 plating step. The copper carrier that covers the embedded is bonded to a transparent glass carrier using
trace is removed in step 6. a bonding material and a release material.
Once processing is completed, the pair is
Factors influencing copper plating quality
Typical acid copper electrolytes contain copper sulfate, sulfuric separated by exposing the release material
acid, chloride ions, and organic additives. These additives play a with an excimer laser or solid-state laser. Low-
crucial role in controlling the deposit distribution as well as the
physical properties of the copper deposit. To meet the specific stress separation coupled with high throughput
objectives of the plating process these additives must be monitored make the laser release system suitable for all
and controlled properly. The additives work in combination
when they are controlled within a given range to improve plating production environments.
uniformity. Namely, these additives are the wetter, brightener
and leveler. The wetter works in the presence of chloride ion to
adsorb onto the cathode and increase the effective thickness of
the diffusion layer. As a result, the plating current increases at
the cathode and the deposit becomes more uniform, so a densely- Transparent Laser
packed copper deposit can be obtained without burning. This Carrier Thin Device Wafer
modified diffusion layer improves the distribution of the deposit
in fine-line plating. The brightener reduces suppression and acts Release Layer Bonding Material
as a grain refiner to deposit copper with a fine grain structure in
random orientation. Because of its strong effects on overall grain
structure, the brightener has the greatest influence on physical
properties of the deposit, such as tensile strength and elongation.
The leveler is a mild suppressor that adsorbs onto specific
locations such as corners and peaks of base materials, aiding
in evening out the thickness of copper deposit. Within the Laser Release System Benefits:
microprofile at the surface of the panel, the diffusion layer tends
to be thin at the peaks and thick at the valleys. Without a leveler, •Highest-throughput system available with a
the copper plating will exaggerate the microprofile resulting in release time of less than 30 seconds
higher peaks. On the other hand, the plating on the peaks will be
•Ultraviolet laser does not heat or penetrate
the bulk bonded structure

•Low-stress processing through use of CTE-
matched carrier and room temperature
separation

Compatible with: 308 nm 343 nm 355 nm

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Table 1: ETS electrolyte and plating parameters.

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