Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Making plural separate devices
Reexamination Certificate
1999-07-01
2001-07-03
Picardat, Kevin M. (Department: 2822)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Making plural separate devices
C438S051000, C438S618000, C438S619000
Reexamination Certificate
active
06255137
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to high-density-interconnect (HDI) structures, and more particularly to improved methods for generating protective air pockets, spaces or gaps over pressure- or adhesive-sensitive structures on semiconductor chips used in HDI circuits.
BACKGROUND OF THE INVENTION
High-density interconnect (HDI) structures have received a great deal of attention, as a result of their advantages in fabrication of complex systems. In general, HDI structures allow the interconnection of relatively large numbers of integrated-circuit chips into complex systems in a cost-effective manner. More particularly, integrated-circuit chips are mounted on heat-conductive or heat-sinking substrates, with their interconnection electrodes or pads lying in a common plane. One or more layers of dielectric film material, patterned with interconnection conductors, are placed over the chips to be interconnected, and connection vias are defined through the dielectric layers to interconnect the chips with the electrically conductive interconnection pattern on the film.
Various aspects of HDI structures and fabrication are defined in U.S. Pat. No. 5,338,975, entitled High Density Interconnect Structure Including A Spacer Structure And A GAP, issued Aug. 16, 1994 in the name of Cole et al., and in U.S. Pat. Nos. 5,561,085 and 5,757,072, entitled Structures for Protecting Air Bridges On Semiconductor Chips From Damage, issued May 26, 1998 in the name of Gorowitz et al. More particularly, these patents describe arrangements for protecting sensitive portions of semiconductor chips from damage due to the presence of interconnection film in HDI structures. Such sensitive portions of semiconductor chips may include airbridge structures, which are liable to be crushed, and transmission-line or resonant structures, the properties of which may be affected by proximity to dielectric materials. These prior techniques for generating protective regions for protecting sensitive regions of the semiconductor chips are effective, but may be too complex for use under some conditions, or too expensive. In particular, some protective techniques required the individual placement of protective caps over sensitive portions of each of the chips before the application of the HDI interconnect layers.
Improved methods for making HDI-connected structures are desired.
SUMMARY OF THE INVENTION
A method for making an HDI circuit with integral air pocket according to an aspect of the invention includes the step of applying an adhesive layer to one side of a dielectric film to form an adhesive-coated film. At locations on the adhesive-coated film selected to register with the locations of pressure or adhesive-sensitive structures or portions of one or more semiconductor chips which is (or are) to be mounted on the film, ablating the adhesive layer on the adhesive-coated film, to define adhesive-free regions. Once the adhesive-free regions are defined, the chip and the film are relatively moved toward each other in an atmosphere, with the pressure- or adhesive-sensitive regions of the chip registered with the adhesive-free regions of the film, to thereby attach the chip to the film. This results in trapping of a bubble of gas of the atmosphere In a region lying over the pressure- or adhesive-sensitive structures of the chip.
In a particular method according to the invention, the step of applying an adhesive layer includes the step of applying a layer of adhesive which is a blend of about 100 parts by weight of Shipley MP9500 photosensitive adhesive with 11 parts by volume Ciba-Geigy CY184 cycloaliphatic epoxy, and the step of ablating is performed with a laser operating at about 248 nanometers. In one method according to the invention, the laser is an excimer laser. One way to perform the ablation step is to pass the laser beam through a mask which defines the adhesive-free portions, and allowing the unmasked portion of the laser beam to fall on the adhesive-coated film. Different masks may be used to define the adhesive-free regions for a particular chip, if the laser beam passing through one mask is not sufficiently large to cover the desired region. Another way to perform the ablation is to scan a narrow laser beam over a mask overlying the region to be ablated. Yet another way to perform the ablation is to scan a laser over a portion of the film which includes regions to be ablated and regions which are not to be ablated, and to controllably turn the beam on and off to ablate the regions to be ablated. It is desirable to flow a gas across the region being ablated to aid in carrying away soot and any other particulates. Helium is a desirable gas for this purpose, because it is inert, and also because it tends to rise, and aids in carrying off the particulate matter. The color of the reflection of light from the region being illuminated by the laser can be used as an indication of the progress of the ablation, since ablation of the preferred adhesive generates a blue reflection, while ablation of Kapton (indicating that the ablation of adhesive has been completed) results in an orange color.
Further steps in the generation of HDI circuits include the step of defining conductive vias through the adhesive-coated film at locations of at least some electrical connection regions of a chip.
REFERENCES:
patent: 5338975 (1994-08-01), Cole, Jr. et al.
patent: 5373627 (1994-12-01), Grebe
patent: 5561085 (1996-10-01), Gorowitz et al.
patent: 5757072 (1998-05-01), Gorowitz et al.
patent: 5798557 (1998-08-01), Salatino et al.
patent: 5824177 (1998-10-01), Yoshihara et al.
patent: 6071427 (2000-06-01), Raulinaitis
Cole Herbert Stanley
Gorczyca Thomas Bert
Lockheed Martin Corp.
Meise W. H.
Picardat Kevin M.
Weinstein S. D.
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