The present invention relates generally to the packaging of integrated circuits. More particularly, the invention relates to dice having integrated pedestals.
There are a number of conventional processes for packaging integrated circuits. In many situations it is desirable to incorporate multiple integrated circuit dice into the same package in what is commonly referred to as a multi-chip package. Some multi-chip packages are arranged to stack two or more dice on top of each other. These stacked die packages have several potential advantages including the possibility of a reduced die or package footprint and certain performance advantages. For example, reducing the path length of electrical connections between integrated circuits potentially increases speed and reduces inductance of inter-chip communications.
One existing stacked die configuration is generally illustrated in FIG. 1. In this configuration a first die 104 is mounted on a carrier such as a lead frame 106 or a planar substrate. A second die 105 is then adhesively secured to the top surface of the first die 104 thereby creating a stacked die configuration. Bonding wires 108 are used to electrically connect both of the dice 104, 105 to the carrier (lead frame 106) using conventional wire bonding. An encapsulant material 115 is molded over the stacked dice to create a stacked die package 120. This stacked die approach allows the top die 105 to be electrically connected to both the underlying base die 104 and to a substrate or lead frame 106. This arrangement also generally requires that the top die 105 must be smaller than the base die 104 so that the top die 105 does not cover any of the bond pads on the base die 104.
Another stacked die approach is generally illustrated in FIG. 2. In this approach, a spacer 130 is adhesively secured to (or dispensed onto) the top surface of the bottom die 104. The top die 105 is then adhesively adhered to the spacer 130. The spacer 130 is sized so that it extends higher than the loop height of the bonding wires 108 used to electrically connect the base die, thereby providing clearance for the bonding wires. The spacer 130 can be formed from virtually any material that is compatible with the dice. By way of example, the spacer may be formed from a variety of materials such as silicon, various ceramics, etc. Alternatively, the spacer may be formed in situ by dispensing an adhesive material having ball like spherical support structures therein on the top surface of the lower die 104 in a region that is interior to the bond pads. The spacer 130 effectively forms a plateau on the bottom die that provides structural support for the top die. With this arrangement, the top die 105 can be virtually any size including the same size or even larger than the base die.
Although the foregoing techniques work well in many applications, in the semiconductor industry, there are continuing efforts to provide more efficient packaging approaches. The packaging arrangements described below are particularly useful in forming stacked multi-chip packages.