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Self-alignment of silicon chips on wafers: A capillary approach
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View: Figures


Image of FIG. 1.
FIG. 1.

Principle of die self-alignment: (a) sketch of the droplet and the die; (b) sketch of the die before and after evaporation; and (c) view of aligned dies on a wafer (Ref. 9).

Image of FIG. 2.
FIG. 2.

View of the boundary between the hydrophilic and hydrophobic regions; the bonding zone has been functionalized by oxygen plasma.

Image of FIG. 3.
FIG. 3.

Dicing marks (left) permit control of the alignment: a good angular alignment is reached, but a slight shift may occur.

Image of FIG. 4.
FIG. 4.

The four different modes (and possible reasons for misalignment): lift, twist, shift, and tilt.

Image of FIG. 5.
FIG. 5.

(a) After a horizontal displacement, the die is restored to alignment by capillary forces; (b) EVOLVER calculation of the pullback.

Image of FIG. 6.
FIG. 6.

Restoring force vs shift for different values of the droplet volume.

Image of FIG. 7.
FIG. 7.

Comparison between approximate analytical model (plain line) and EVOLVER (dots). Left: surface energy; right: restoring force.

Image of FIG. 8.
FIG. 8.

Die realigns after an initial twist.

Image of FIG. 9.
FIG. 9.

Energy (left) and torque (right) as functions of the twist angle, for three values of the gap. Dotted lines are SURFACE EVOLVER results and plain lines correspond to the analytical model.

Image of FIG. 10.
FIG. 10.

The die regains its stable position after a lift. Top: after an initial lift; bottom: after an initial compression.

Image of FIG. 11.
FIG. 11.

Surface energy as a function of the vertical gap: The continuous line corresponds to the analytical model and the dotted line to EVOLVER results.

Image of FIG. 12.
FIG. 12.

Restoring force vs vertical gap. Continuous line: analytical model; dotted line: EVOLVER results.

Image of FIG. 13.
FIG. 13.

Two morphologies of the liquid having the same surface energy.

Image of FIG. 14.
FIG. 14.

Die tilts to form a dihedral: (a) and (b) large liquid volume; (c) and (d) small liquid volume.

Image of FIG. 15.
FIG. 15.

Comparison between EVOLVER numerical program and analytical model: in case of tilt, the interfacial energy varies extremely slowly.

Image of FIG. 16.
FIG. 16.

Tilt torque vs tilt angle: continuous line indicates a zero torque and the EVOLVER results (dotted line) show a small tilting torque.

Image of FIG. 17.
FIG. 17.

Bulging out/in shape of the surface in the two cases: left, parallel plates; right, dihedral.

Image of FIG. 18.
FIG. 18.

The chip slides after a tilt in the case of a large volume of liquid and/or a heavy chip weight.

Image of FIG. 19.
FIG. 19.

Left: corners are never totally wetted. Right: picture of the chip after a tilt with the dewetted corners.

Image of FIG. 20.
FIG. 20.

Coupled modes: (a): tilt and roll; (b) tilt and twist; (c) shift and twist. The only unstable coupling must include a tilt and/or roll; the other modes are automatically corrected by the capillary forces.

Image of FIG. 21.
FIG. 21.

Misalignment due to water spreading on the wafer outside the hydrophilic pad. The die makes a 10° twist, plus a shift with the pad.

Image of FIG. 22.
FIG. 22.

Canthotaxis limits for planar wafer and wafer with relief.

Image of FIG. 23.
FIG. 23.

Sketch of the shift: left, at alignment; right, after a shift.

Image of FIG. 24.
FIG. 24.

Sketch of the twist. The point M is describing AB while is describing . Note that .

Image of FIG. 25.
FIG. 25.

Three-dimensional view of the twisted surface (only one twisted surface is shown in the figure).

Image of FIG. 26.
FIG. 26.

Sketch of the surface.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Self-alignment of silicon chips on wafers: A capillary approach