Semiconductor device with conductive die attach material

A semiconductor device includes a carrier such as a lead frame, a semiconductor die and an attachment member affixing the semiconductor die to the carrier. The attachment device includes an electrically conductive organic material.

BACKGROUND

Semiconductor devices, such as integrated circuit (IC) packages, typically include a one or more semiconductor devices arranged on a lead frame or carrier. A die attach material affixes a semiconductor die to the lead frame. Bond wires are attached to bond pads on the semiconductor devices and to lead fingers on the carrier. In other instances, one die is mounted on a lower die and affixed thereto in the same manner. The device is then encapsulated to provide protection and form a housing from which the leads extend.

Known die attach materials have been unsatisfactory in many situations. For instance, reliable electrical and thermal binding of the die to the carrier or lower chip (chip on chip) is often problematic.

Adhesives commonly used for die attach films and pastes have limited electrical conductivity due to the limited quantity of electrically conductive particles—typically silver particles are used but the quantity of the silver particles must be limited to limit brittleness. Additionally, such adhesives are prone to separation between the polymer matrix and the electrically conductive filler particles. Known adhesive films also typically include silver particles to provide electrical conductivity, and thus, exhibit similar disadvantages.

SUMMARY

In accordance with aspects of the present disclosure, a semiconductor device includes a carrier such as a lead frame, a semiconductor die and an attachment member affixing the semiconductor die to the carrier. The attachment device includes an electrically conductive organic material.

DETAILED DESCRIPTION

FIG. 1is a side view conceptually illustrating an exemplary semiconductor device100that includes a semiconductor die110mounted on a lead frame or carrier112. In other embodiments, the semiconductor die110is mounted on another die (chip-on-chip). An attachment member200, such as an adhesive film or paste, is used to affix the die110to the carrier112. Typically, the finished device100is encapsulated in a mold compound102.

In accordance with aspects of the present invention, the attachment member200includes an electrically conductive organic material. By using intrinsically electrically conductive polymers in the formulations of the adhesive of the attachment member200, additional electrically conductive fillers can be reduced or eliminated. Further, such intrinsically conductive polymers can be used in conjunction with conductive metal particles in order to produce an optimal combination of conductive volumes, heat conductivity and connecting polymer matrix or adhesive. Such a formulation thus functions as adhesive matrix, electrical guidance medium and adhesion mediator between additional conductive fillers in one.

Further advantages include eliminating or at least reducing separation of the conductive adhesive formulation. The resulting formulation is very stable, resulting in little or no segregation of particles, and manufacturing processes are relatively simple using these materials. Moreover, the back side of the die is better protected from damages caused by hard metallic fillers, since they can be reduced or eliminated from the adhesive and the electrically conductive polymer is significantly more flexible than commonly used formulations using silver or carbon-based fillers. Mechanical reliability is improved due to increased flexibility of the polymer matrix resulting from fewer hard filler required to realize the desired electrical conductivity. Temperature stability is improved, and electrically conductive polymers generally have a low tendency for hydrolyzing. Extremely thin (<1 μm) conductive adhesive layers are possible with low resistance.

Thus, the use of such electrically conductive polymers in electrically conductive adhesive pastes and/or adhesive films accomplishes electrical and thermal binding of the chip on a metallic system support, such as a lead frame or metal-coated substrate. Suitable conductive polymers include Polythiophene, Polypyrrole, Polysulfone, Polyaniline and Polyindophenine.

Such polymers provide a high thermal stability as well as a high specific conductivity with sufficient doping. A suitable conductive polymer is Poly-(3,4-ethylenedioxythiophene), available under the trade name Baytron M. Another alternative is the substance class of the Polyindophenine, which are hydrolysis and temperature stable and are intrinsically electrically conductive without dopants.

FIG. 2conceptually illustrates portions of an embodiment of the semiconductor device100in accordance with aspects of the present invention. In the embodiment ofFIG. 2, the attachment member200is an adhesive film or paste, wherein the polymer matrix of the adhesive includes an electrically conductive polymer212. Arrows202illustrate current flow through the attachment member200from the semiconductor die110to the chip carrier112. Such a configuration is suitable in devices requiring a relatively small electrical conductivity.

FIG. 3illustrates another exemplary embodiment in which the polymer matrix of the attachment member200includes electrically conductive filler particles210and electrically conductive polymer particles212. Metals, such as sliver, are suitable for the electrically conductive filler particles210. In exemplary implementations of such an embodiment, the electrically conductive polymer particles212are mixed into the adhesive polymer matrix200filled with the conductive particles210, resulting in increased electrical conductivity. Moreover, thermal-mechanical stress is reduced due to increased elasticity of the adhesive, resulting in improved reliability overall.

InFIG. 4, an embodiment is illustrated in which the attachment member200includes a polymer adhesive matrix with electrically conductive filler particles210coated with an electrically conductive polymer212. This provides a greater electrical conductivity, with the conductive polymer212coating serving simultaneously as an electrical guidance medium and adhesion mediator between the conductive particles and the adhesive matrix.

FIG. 5illustrates yet another embodiment, where the attachment member200includes electrically insulating filler particles220in an electrically conductive polymer matrix212. In certain embodiments, the electrically insulating filler particles220are thermally conductive. This arrangement is good for applications requiring small electrical and high thermal conductivity. Carbon based materials such as diamond, aluminum nitride, beryllium oxide, boron nitride, etc. are suitable thermally conductive, electrically insulating materials.