Patent Application
20060270104
The invention relates to method and arrangement for assembling and packaging single and multiple semiconductor dice with an intermediate arranged interposer.
For assembling a package of dice, at least one die is mounted on a package substrate by arranging an adhesive material intermediate the package and the die. Increasingly, a second die is positioned onto the top of the first die. In the same way, further dice can be mounted on the second die.
In a standard process, the bond pads on a die are connected to contact pads on the substrate by wires bonded on the bond pads and the contact pads. In contrast thereto flip-chip technology connects the bond pads with the contact pads by solder bumps conductive adhesive. Therefore, the die is turned around so that its active surface is opposite to the upper surface of the substrate. Furthermore, the bond pads are opposite to the contact pads respectively. Solder balls are arranged either on the contact pads of the substrate or on the bond pads of the die. By applying a solder reflow process the die is connected with the substrate.
For increasing the functionality of semiconductor devices a second die is attached on the upper surface of the first die. Also, the second die is connected with the substrate by wires bonded in the same manner. The bond pads are arranged on the active surface of a die. In this way a third die can be mounted on the second die and so on.
In the case the bottom die of two adjacent dice, i.e., the die with the closest distance to the substrate, are connected with wires and both dice have the same size, a space for the wires has to been excited by the usage of an interposer or a spacer between the two dice in order to protect the bond wires of the bottom die.
After attaching all dice and connecting with wires the package is enclosed with a mold compound. Thereby the mold compound also flows between the substrate and the die or between the dice if there is a space.
The interposer is normally made of a piece of silicon with adhesive on both sides for attaching at the surface of the bottom die on the backside of the upper die or a spacer is made of a polymer material.
Usually interposers or spacers are attached at die level of the process, i.e., during the stack assembly process. In U.S. Patent Application Publication No. 2004/0201088 A1, an attachment of spacers is disclosed wherein spacers made of polymer material are attached on the upper surface, which is also the active surface in the process die level after adhering the bottom chip onto the substrate. Arranging the interposers or the spacers in the die level reduces the productivity.
The productivity can be increased by arranging the interposers or spacers in the wafer level of the process.
A wafer has an active surface including a redistribution layer and a back surface. Furthermore, the wafer includes a plurality of unsingulated semiconductor dice.
Usually the wafer is provided with a dicing tape onto the back surface. Thereafter the wafer is diced from the active surface into singulated dice. Thereafter the whole composite of singulated dice is provided with a grinding tape on the active surface and removing the dicing tape and thereafter the composite of dice is grinded on the backside reducing the thickness of the dice.
In U.S. Patent Publication Application No. 2004/0197955 A1 an attachment of an interposer at the wafer level of the process is disclosed. Therein an interposer is attached to the wafer onto the active side before dicing. Thereafter the wafer together with the interposer is diced from the backside. In addition, this interposer is not suitable for attaching dice to a die package because it is configured as a package substrate interconnecting to the exterior of the package. The dicing of the wafer in the disclosed manner could cause damaging on the active surface.
In one aspect, the invention increases the productivity of die packaging by attaching the interposer in the wafer level process without endangering any functionality of the dice.
Embodiments of the invention relate to methods and arrangements for assembling and packaging single and multiple semiconductor dice (or dies) with an intermediate arranged interposer. In one exemplary embodiment, the invention provides a method for attaching an interposer at dice in wafer level with the following steps:
providing a wafer having an active surface including a redistribution layer, having a back surface and including a plurality of unsingulated semiconductor dice;
providing the wafer with a dicing tape onto the back surface;
dicing the wafer from the active surface into singulated dice;
providing the composite of singulated dice with a grinding tape onto the active surface and removing the dicing tape;
grinding the composite of dice on the backside;
providing each die with an interposer on the grinded surface, the interposer having a mounting surface a distance from the grinded surface according to the high of the interposer;
picking a die from the composite of dice; and
adhering the die with the mounting surface of the interposer onto a surface of an underlying substrate.
With this method all dice are processed at the same time and under the same conditions. The dice are diced from the active side avoiding damaging the structure of the dice. Furthermore, no additional spacer-attach process at die level is necessary and the second die (daughter die or top die) can be attached immediately after the wire bonding process of the bottom die (mother die). Generally the die-attach process stability is improved.
A die with an interposer as mentioned above can be mounted as a daughter die on a mother die as well as such a die can be mounted also on a package substrate.
In a preferred embodiment the interposer is applied by a stencil printing process. Thereby a standard stencil printing process can be used.
Depending on the stencil design there is more effective area for adhesion between mold compound and dice in package.
Embodiments of the invention save silicon spacer and glue material. Furthermore, it is another advantage that a larger throughput due to a simplified die-attach process can be achieved.
In another embodiment, the invention provides an arrangement of dice in a package. The arrangement includes:
a packaging substrate having an upper side with first bonding pads on the upper side;
a first die with an active surface with second bonding pads on the active surface and a backside, the first die is mounted on the packaging substrate with its backside lying opposite to the upper surface wherein the first bonding pads are electrically connected to the bonding pads;
a second die with an active surface with third bonding pads on their active surface and a backside, the second die is mounted onto the active surface of the first die with the backside of the second die opposite to the active surface of the first die with an interposer intermediate arranged between the active surface of the first die and the backside of the second die printed on the backside and glued to the die active side of the first die.
With this arrangement, advantages mentioned above can be achieved.
The invention will be explained in more detail below using exemplary embodiments. In the associated drawings:
a-1e (collectively
a-2f (collectively
a-6f (collectively
a-10c (collectively
The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.
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These dice 7 are remaining in the wafer composite 8 because they are still held by the grinding tape 5.
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After grinding the grinding tape 5 is removed and a dicing tape 4 is added to the backside 6 of the wafer 1. Thereafter the wafer 1 is diced into multiple dice 7. These steps are shown in
To arrange the interposer 9 on the backside as described in the following, the grinding before dicing process is performed and then the wafer composite 8 is turned. Therefore a fixing tape 5a is used. The fixing tape is applied to the active surface of the dice 7 and the dicing tape 4 is removed as shown in
When the interposer 9 as described below is arranged at the active surface 2, it is not necessary to use the fixing tape 5a because the active surface is uncovered in this state.
When the dice 7 are held either by grinding tape 5 by applying the dicing before grinding process or by the fixing tape 5a by applying the grinding before dicing process the following described steps can be applied for arranging interposers 9 on the backside 6.
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