Browse Prior Art Database

Backside Silicon Integrated Circuit Infrared Immersion Lens Heat Sink

IP.com Disclosure Number: IPCOM000110686D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 4 page(s) / 248K

Publishing Venue

IBM

Related People

Heinrich, HK: AUTHOR [+4]

Abstract

Disclosed is the concept of using a combination lens/ heat-sink for submicron imaging through the backside of operational silicon integrated circuits. This lens/ heat-sink design solves the problem of simultaneously achieving submicron backside imaging while cooling high-power integrated circuits (ICs).

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Backside Silicon Integrated Circuit Infrared Immersion Lens Heat Sink

       Disclosed is the concept of using a combination lens/
heat-sink for submicron imaging through the backside of operational
silicon integrated circuits.  This lens/ heat-sink design solves the
problem of simultaneously achieving submicron backside imaging while
cooling high-power integrated circuits (ICs).

      Fig. 1 shows a diagram of the backside silicon integrated
circuit infrared immersion lens/heat-sink (ILHS).  The ILHS consists
of 4 substructures: 1) a custom near-infrared (1.0 - 1.3 mm)
immersion microscope objective that corrects for the aberrations
generated by focusing through the thick substrate of the silicon IC;
2) a coolant distribution jacket surrounding the objective; 3) a
silicon manifold (Fig. 2); and 4) a silicon cold-plate (Fig. 2).  The
final lens of the objective is mounted in a hole in the center of the
manifold and cold-plate.  This lens and cold-plate rest on a thin
layer of immersion oil, which improves the thermal and optical
interface between the ILHS and the silicon IC.

      The optical elements for the custom microscope objective are
mounted in an internal sleeve inside the coolant distribution jacket.
Light enters from the left of the objective, traveling in the Z
direction (ILHS coordinate system in Fig. 1), and passes through the
various lenses.  These are antireflection coated for the
near-infrared (1.0 - 1.3 mm), and they also compensate for the severe
spherical aberration generated by focusing through the thick
substrate of the silicon IC.  Between the final lens and the silicon
IC is a thin (1 - 5 mm) layer of immersion oil (Fig. 2).  This
has a large optical refractive index, which allows us to achieve a
high numerical aperture and submicron resolution in spite of the
relatively long wavelength.  The objective lens focuses the light
through the substrate of the silicon IC and onto devices on the
opposite (right-hand) side.  The light is reflected from the devices
in the circuit, passes back through the silicon substrate, and back
through the lens, where the optical aberrations from imaging through
the substrate are once again corrected.

      Heat generated in the silicon IC is conducted through the
substrate of the chip through the fluid coupling layer, and into the
cold-plate of the heat-sink (Fig. 2).  The cold-plate consists of a
flat silicon wafer with grooves etched in the top surface, and a hole
in the center for the final lens of the objective (Fig. 3).  Coolant
flowing between the fins of the cold-plate convects away the heat.
This design differs from previous silicon heat-sink designs in
providing for a lens hole through the center of the heat-sink and by
matching the cylindrical geometry...