US 20050006786 A1
A semiconductor device is disclosed which has a first substrate with wiring formed thereon, a second substrate mounted above the first substrate with a conductive plug buried in the second substrate to penetrate between upper and lower surfaces thereof, a plurality of semiconductor chips mounted above the second substrate and having a terminal electrode as electrically connected to the first substrate through the conductive plug of the second substrate, and a resin buried in an empty space or gap between adjacent ones of the plurality of semiconductor chips.
7. A method of fabricating a semiconductor device comprising:
mounting above a first substrate with wiring formed thereon a second substrate with a conductive plug buried therein to penetrate between upper and lower surfaces thereof;
mounting above said second substrate a plurality of semiconductor chips having a terminal electrode as electrically connected through said conductive plug to said wiring; and
burying a resin in an empty space between adjacent ones of said plurality of semiconductor chips.
8. The method according to
performing resin sealing between said second substrate and said first substrate; and
performing resin sealing between said semiconductor chips and said second substrate.
9. The method according to
said burying the resin in the empty space between said plurality of semiconductor chips is done as a causing a resin component extruded during resin sealing between said second substrate and said semiconductor chips to fill said empty space.
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-055285, filed on Mar. 1, 2002, the entire content of which is incorporated herein by reference.
1. Field of the Invention
This invention relates to semiconductor devices of the multiple chip mount type with a plurality of semiconductor chips mounted on or above a substrate. The invention also relates to methodology of fabricating the multi-chip type semiconductor devices.
2. Description of Related Art
In recent years, multi-chip semiconductor devices with a plurality of semiconductor chips mounted on a substrate are becoming more and more important. Use of such multi-chip semiconductor devices is aimed at enhancement of performance and reliability of the equipment. Especially, in order to connect together a plurality of multi-pin/ultrafine-pitch semiconductor chips while permitting them to offer high-speed signal transmission capabilities, what is called the silicon interposer (Si-IP) technology attracts the attention of skilled persons, which employs a silicon substrate for use as an intermediate repeater or interexchange substrate that is interposed between an underlying base substrate and an overlying semiconductor chip or chips. A typical silicon interposer substrate is arranged so that more than one conductive through-going plug which penetrates between the upper and lower surfaces is buried to thereby achieve electrical interconnection between the semiconductor chip(s) being mounted thereon and the base or “underlay” substrate.
In accordance with one aspect of this invention, a semiconductor device comprises a first substrate with wiring formed thereon, a second substrate mounted above the first substrate with a conductive plug buried in the second substrate to penetrate between upper and lower surfaces thereof, a plurality of semiconductor chips mounted above the second substrate and having a terminal electrode as electrically connected to the first substrate through the conductive plug of the second substrate, and a resin buried in an empty space between adjacent ones of the plurality of semiconductor chips.
In accordance with another aspect of the invention, a method of fabricating a semiconductor device comprises mounting above a first substrate with wiring formed thereon a second substrate with a conductive plug buried therein to penetrate between upper and lower surfaces thereof, mounting above said second substrate a plurality of semiconductor chips having a terminal electrode as electrically connected through said conductive plug to said wiring, and burying a resin in an empty space between adjacent ones of said plurality of semiconductor chips.
Several illustrative embodiments of this invention will be explained with reference to the accompanying drawings below.
Practically, bumps are used to connect between the dielectric substrate 11 and the silicon interposer 12 and also between the silicon interposer 12 and the semiconductor chips 13. A chosen resin material 14 is sealed between the dielectric substrate 11 and silicon interposer 12; similarly, a resin 15 is between the silicon interposer 12 and semiconductor chips 13. Let a space gap 16 between laterally adjacent ones of the semiconductor chips 13 be as small as possible for high-speed signal transmission applications. For example, the chip gap measures 1 millimeter (mm) or less. And in the case of this embodiment, unlike the prior art, an empty space or gap between neighboring semiconductor chips 13 also is filled with resin material 16. Burying the resin 16 in the gap of semiconductor chips 13 as mounted on the silicon interposer 12 in this way results in that the silicon interposer 12 is enhanced in its resistance to cracking due to thermal stress-say, anti-cracking property. This point will be explained in detail below.
An explanation will first be given of a semiconductor device which is for use as an example for mere comparison purposes, called comparative example. Such a semiconductor chip-mounting structure is depicted in
In the structure of
Although during resin sealing processes a resin-injection technique utilizing capillary action was employed after completion of the bonding process in the prior art, an alternative method has recently been developed which performs the bonding and sealing processes simultaneously in such a way as to perform deposition of a coating film of non-flow underfill material and disposal of a resin sheet prior to the bonding and then perform chip-bonding from above them.
In the silicon interposer (Si-IP), more than one conductive plug is buried in the form of penetration between the upper and lower surfaces of it. A typical approach to burying such interconnect plug is to employ a method having the steps of first defining ultrafine holes by etching in the surface of a Si substrate, burying a metal therein, and thereafter performing polishing to permit the bottom face of each conductive plug to be exposed from the back surface of the Si substrate. Thus, the resulting silicon interposer 2 becomes thinner.
The semiconductor device with multiple semiconductor chips mounted on the silicon interposer in the manner stated above is such that each of the constituent layers must be different in thermal expansion coefficient from the others, resulting in occurrence of thermal stress therein. In particular, the silicon interposer, which is thin and brittle-i.e. hard and easily crackable-among the three layers involved, is high in the risk of cracking upon application of a load such as temperature cycles.
A more practical explanation is as follows. Generally, a laminated or multilayered plate can experience unwanted curving distortion, called the warp, due to the presence of thermal stress. For instance, at low temperatures, a “convex” warp takes place as shown in
The mechanism of crack generation of the silicon interposer used in the structure of the semiconductor device in accordance with the comparative example discussed above with reference to
It would be readily seen from Equation (1) that in order to make the specimem with its fracture toughness value KIC, the load required increases with an increase in a specimem thickness B and also with a decrease in length or distance “a” spanning from the load-applied position of a cutaway portion (notch) up to the tip of a crack. The structures shown in
A brief explanation will be given of the reason why the chip mount pitch becomes 1 mm or less. In the case where signals are transmitted among the semiconductor chips at ultrahigh speeds, it is required to maximally shorten the wiring leads used for interconnection among these semiconductor chips. To do this, the layout interval or pitch between laterally adjacent semiconductor chips must be set as small as possible. The result of this is a semiconductor device of the structure with chip mount pitch (i.e. the width of an empty space between semiconductor chips) being set at 1 mm or less.
An explanation will next be given of a method of fabricating the semiconductor device of this embodiment.
Next, as shown in
Next as shown in
This bonding and resin sealing processes may be arranged so that an underfill resin material is sealed by use of capillarity after completion of the bonding; or alternatively, bonding and sealing are done simultaneously while letting a non-flow underfill material and/or a film-shaped resin be mounted in advance or “pre-mounted” on the substrate. Thereafter, perform after-cure treatment of the resin. This curing may alternatively be done at a later resin cure step in an all-at-once fashion.
Next, as shown in
Lastly as shown in
Although in the above embodiment the resin filling to semiconductor chip bottoms and the resin filling into gaps or voids between adjacent semiconductor chips are done at separate steps, these may also be done at a single step. An embodiment employing such scheme will be explained with reference to
The process up to the step of bonding a silicon interposer 12 onto a dielectric substrate 11 followed by resin sealing is the same as that of the previous embodiment. The step of mounting semiconductor chips 13 onto the silicon interposer 12 is as follows. As shown in
In this way, in case multiple chips to be mounted on the silicon interposer 12 are narrow in layout gap space, it is possible by controlling the amount of chip-sealing resin material to eliminate the step of filling the gap between semiconductor chips with the resin as buried therein.
More specifically, in the embodiment 3, a number of semiconductor chips 13 are mounted on and above a silicon interposer 12. A pair of neighboring semiconductor chips 13 (13 a, 13 b) is arranged so that two semiconductor chips 17 are stacked or laminated above one semiconductor chip 13 a to thereby form a laminate body 19 a while letting two semiconductor chips 17 be stacked above the remaining semiconductor chip 13 b of the chip pair to thereby form a laminate body 19 b. Resin 16 is buried in an empty space or gap between these laminate bodies 19 a, 19 b.
The gap between the laminate bodies 19 a-19 b becomes greater in depth when compared to the case of
It should be noted that although in the embodiment 3 the laminate bodies are made up of mere two units, the inventive concepts as disclosed herein may also be applicable to the case of more than three laminate bodies used. For example, in case two semiconductor chips are stacked above the semiconductor chip 13 (13 c) to form a laminate body, resin is buried into a gap between this body and the laminate body 19 b. Also note that the above-stated semiconductor chips are organized into the three-layer structure, this multilayer structure may alternatively be modified into a two-layer or four-layer structure when a need arises.
Lastly, an embodiment 4 will be explained with reference to
It should be noted that the semiconductor chip (for example, chip 13 a and 13 b) on which another semiconductor chip is located has the (almost) same thickness as that of the silicon interposer 12 in the embodiments 3 and 4.
In the embodiments 1 to 4 stated supra, the second substrate in which more than one conductive plug penetrating between its upper and lower surfaces is buried is employed as the silicon interposer 12. However, in case the second substrate is less in thickness (e.g. 50 μm) and is made of relatively brittle material, these embodiments may be applied thereto while not limiting to silicon. A typical example of such material is glass and ceramic.
It has been stated that according to this invention, in multi-chip semiconductor device structures with a plurality of semiconductor chips mounted, it is possible by filling an empty space between adjacent semiconductor chips with the buried resin material to preclude or at least greatly suppress unwanted creation of cracks due to thermal stress.
While the present invention has been particularly shown and described with reference to the embodiments, it will be understood by those skilled in the art that various changes in form and in detail may be made without departing from the spirit, scope and teachings of the invention.