ADHESIVELY MOUNTABLE DIE ATTACH FILM

Abstract: A die attach film (11) adapted for adhesive mounting to a dicing frame characterised in that it comprises: (a) a support film (12); (b) a curable die bonding adhesive (13) releasably mounted on the support film; and (c) adhesive means (14) to bond the support film to a dic­ ing frame is disclosed. Also disclosed is a combination of such a film and a dicing frame. The present invention provides advantages over the prior art.

Description: This invention relates to an adhesively mountable die attach film; more particularly, it relates to a die attach film which is adapted to be adhesively mounted to a dicing frame (also termed a "film frame wafer carrier") for use, for example, as a dicing film in the dicing of semiconductor wafers and subsequent die bonding of individual die during die packaging. The present invention is an improved version of the dicing film product disclosed in EP-A-134, 606 and of the die-attach film described in EP-A-150,882. Currently, in the semiconductor industry, semiconductor wafers are diced into individual die by placing the wafer on a tacky film, followed by the scribing or dicing of the wafer into the die which are then removed from the tacky film, without any adherent die bonding adhesive. The die are then placed in the chip carrier after a suitable curable die bonding adhesive has been separately added to the chip carrier. This procedure is labour intensive and costly since it requires that the dicing operation and the die attach step be performed in two distinct stages. Recently, the above-mentioned references have proposed solutions to this problem wherein a novel tape product is supplied which has the necessary curable die-bonding adhesive releasably supported on its surface. Such a tape product can be used to support the semiconductor wafer during the dicing operation and yet provide the necessary die bonding adhesive component for the later die bonding operation to the chip carrier. After the dicing step has been performed with such a product, the die, with adherent partially cured adhesive, can then be removed from the surface of the support film for later placement in the chip carrier. Alternatively, (as described in EP-A-150,882) the tape can merely carry adhesive to which previously cut die can be mated. After the die and adhesive are brought together, the die, with adherent partially cured adhesive, can be removed for placement in the chip carrier. The present invention is specifically directed to an improved version of the general type of products described in each of the above-mentioned references. The present invention relates to an improved version of the types of products described above which is particularly adapted for adhesive mounting in conventional dicing frames which are commonly used during semiconductor wafer dicing and die packaging. The present products comprise a support film, a curable die bonding adhesive pattern releasably mounted on the support film, and adhesive means to bond the support film to a dicing frame. A means for bonding the die attach film to the dicing frame is to affix the support film of the die attach film to a larger tacky film which, at its periphery, is capable of bonding to the frame. The present invention will be further understood by reference to the accompanying illustrative drawings wherein: Fig. 1 is an exploded view showing the die attach film wherein a larger tacky film is the intended adhesive means for bonding to the dicing frame; Fig. 2 is an exploded view showing the dicing frame and the adhesively mountable die attach film according to the present invention; and Fig. 3 is a side view, in exaggerated perspective, showing the composite of dicing frame and adhesively mountable die attach film. The present invention provides a die attach film (11) provided for adhesive mounting to a dicing frame (15) wherein: the said die attach film comprises a support film (12) and a curable die bonding adhesive (13) provided to support a semiconductor wafer (17) for dicing and releasably mounted on the said support film; and the provision for adhesive mounting to a dicing frame comprises a larger tacky sheet (14) having the said support film (12) bonded thereon, the portion (16) of the said tacky sheet under the die bonding adhesive (13) having been removed. The present invention also provides, in combination, a dicing frame and such a film. The present die attach film 11 comprises a suitable support film 12 which can be formed from a wide variety of materials including paper, foil, or polymer. Preferably, the support film has a release layer or coating to facilitate the release of the curable die bonding adhesive which will be described below. The types of support films and release coatings in EP-A-134,606, for example, can be used in regard to the present invention. It is possible to dispense with the release coating if a support film 12 is chosen which has an adherent release characteristic in regard to the curable die bonding adhesive which is selected. For example, a heating step, as described more fully in EP-A-146,197 can be utilized when polyolefin support films are used. The curable die bonding adhesive 13 can be of the general type that is used by the semiconductor industry for die bonding operations. The various requirements for such adhesives are known in the art and are described, for example, in above-mentioned EP-A-182,079. One preferred adhesive is the polyimide-modified epoxy adhesive composition which is described in EP-A-171,157, which comprises an epoxy resin, a soluble polyimide resin, and a reactive monoepoxy diluent to dissolve the soluble polyimide resin into the epoxy resin. This adhesive is preferred for relatively low temperature die bonding operations. Another adhesive 13 which has utility for relatively higher temperature die bonding operations is described in EP-A-182,079. It comprises a soluble polyimide resin, a solvent for the polyimide resin, an epoxy resin, a hardener, a catalyst to accelerate the curing of the epoxy resin, a cross linking agent reactive with the polyimide solvent, and a catalyst to catalyse the cross linking reaction. The adhesives which can be used as die bonding adhesives for the present purposes are broadly selected from electrically conductive and/or thermally conductive adhesives which are useful for die bonding. The adhesive 13 is preferably partially reacted, to a tacky state prior to affixing the wafer or die to its surface. As the film 11 in accordance with the present invention is applied to a larger, tacky sheet 14, it is possible to use the conventional tacky sheet used to support semiconductor wafers during dicing. This sheet is denoted "NITTO film" in the industry and merely has a sufficient degree of tackiness to hold the present film product and to provide a point of attachment of the composite structure to a conventional dicing frame 15. Using this sheet 14, the tacky portions of the sheet holding the present film 11 must be peripheral to the film itself and any curable die bonding adhesive that it may carry. In regard to use of the composite film for wafer dicing, the area 16 under the section of the support film 12 which will hold the adhesive 13/wafer 17 composite is cut out from the tacky sheet 14. This is designated by reference numeral 16a in accompanying Fig. 1. By doing so, the mating of the support film 12 carrying the die bonding adhesive 13 and the tacky sheet 14 will not lead to undesired air entrapment under the area to be occupied by the adhesive/wafer subcombination. Such air entrapment can undesirably give the adhesive (and adherent wafer) an undulating surface which might exceed the close tolerances required during the dicing step. The exposed curable adhesive 13 may be protected with a suitable release covering. If desired, the release covering can comprise a suitable sheet of release coated paper, for example.

Claims: A die attach film (11) provided for adhesive mounting to a dicing frame (15) wherein: the said die attach film comprises a support film (12) and a curable die bonding adhesive (13) provided to support a semiconductor wafer (17) for dicing and releasably mounted on the said support film; and the provision for adhesive mounting to a dicing frame comprises a larger tacky sheet (14) having the said support film (12) bonded thereon, the portion (16) of the said tacky sheet under the die bonding adhesive (13) having been removed. A film as claimed in claim 1 wherein the die bonding adhesive is provided to support a semi-conductor die after it has been diced. A film as claimed in claim 1 wherein the die bonding adhesive comprises an electrically conductive adhesive. A film as claimed in claim 1 wherein there is also provided a release covering to protect the adhesive (b). In combination, a dicing frame and a film as claimed in any of claims 1 to 4.

Inventors: AURICHIO, JOSEPH ANTHONY, SHEYON, GREGORY MICHAEL
Applicants: NATIONAL STARCH AND CHEMICAL INVESTMENT HOLDING CORPORATION
Application year: 1986
Main classification: H01L21
IPC codes: H01L21, C09J7