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Meander comb test structure at whe r e t he t wo t r a ce s c onve rge.
the stitch line. Figure 12 shows a Additionally, Figure 13a presents
2µm line/space meander comb test the I-V curve of the meander trace,
structure positioned at the stitch line demonstrating good connectivity for
between the two masks in the field. A the stitched Cu traces. The measured
slight taper is visible at the junction i n t r a - l a y e r l e a k a g e c u r r e n t i s

Figure 8: Cu RDL traces located at the stitch line Figure 9: Chiplets assembled on a carrier: a) an array of chiplets assembled on the RDL layers; b) after wafer-
(blue dash line) between the 2 mask fields: a) 2µm level molding to encapsulate the chiplets assembly and RDL layer.
L/S Cu traces stitched; and b) magnified images
showing the section of the stitched traces.
molding, respectively. X-ray inspection
was carried out on the assembled
chiplets, indicating good solder joint
alignment and formation with the RDL
stack layer (Figure 10). Figures 11a-
b depict the fabricated RDL interposer
package after singulation and solder
bump attachment, respectively. Finally,
the RDL interposer was assembled
onto the organic build-up substrate
using a TCB process, as illustrated in
Figure 11c.

Electrical measurements
The following sections discuss
various electrical measurements that Figure 10: X-ray images of solder interconnects: a) a single RDL interposer with the 12 chiplets; b) magnified
were conducted. X-ray images of fine-pitch solder bumps.

Figure 11: An RDL interposer package after solder ball drop and attachment to organic substrate: a) tilted optical image of the solder bump side of the RDL interposer; b)
a magnified image showing the SAC305 solder bumps; and c) after attachment to organic substrate.

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