US20100019362A1

US20100019362A1 - Isolated stacked die semiconductor packages

Info

Publication number: US20100019362A1
Application number: US12/178,023
Authority: US
Inventors: Manolito Galera; Leocadio Morona Alabin
Original assignee: Fairchild Semiconductor Corp
Current assignee: Semiconductor Components Industries LLC
Priority date: 2008-07-23
Filing date: 2008-07-23
Publication date: 2010-01-28
Also published as: US8053883B2; US20110062570A1; US20120015482A1; US8198132B2

Abstract

Semiconductor packages that contain isolated stacked dies and methods for making such devices are described. The semiconductor package contains both a first die with a first integrated circuit and a second die with a second integrated circuit that is stacked onto the first die while also being isolated from the first die. The first and second dies are connected using differing arrays of metal strips that serve as interposers between the first and second dies. This configuration provides a thinner semiconductor package since wire-bonding is not used. As well, since the integrated circuit devices in the first and second dies are isolated from each other, local heating and/or hot spots are diminished or prevented in the semiconductor package. Other embodiments are also described.

Description

FIELD

This application relates generally to semiconductor devices and methods for making such devices. More specifically, this application describes semiconductor packages that contain multiple dies containing integrated circuit devices and methods for making such devices.

BACKGROUND

Semiconductor packages are well known in the art. Often, these packages may include one or more semiconductor devices, such as an integrated circuit (“IC”) die or chip, which may be connected to a die pad that is centrally formed in a lead frame. In some cases, bond wires electrically connect the IC die to a series of terminals that serve as an electrical connection to an external device, such as a printed circuit board (“PCB”). An encapsulating material can be used to cover the bond wires, the IC die, the terminals, and/or other components of the semiconductor device to form the exterior of the semiconductor package. A portion of the terminals and possibly a portion of the die pad may be externally exposed from the encapsulating material. In this manner, the die may be protected from environmental hazards—such as moisture, contaminants, corrosion, and mechanical shock—while being electrically and mechanically connected to an intended device that is external to the semiconductor package.
After it has been formed, the semiconductor package is often used in an ever growing variety of electronic applications, such as disk drives, USB controllers, portable computer devices, cellular phones, and so forth. Depending on the die and the electronic application, the semiconductor package may be highly miniaturized and may need to be as small as possible.
In most instances, each semiconductor package only contains a single die that contains the integrated circuit device, or a discrete device such as a diode or a transistor. Thus, the functionality of each semiconductor package is often limited to that discrete device or integrated circuit on the single die that it contains. To combine the functions of devices in more than a single die, two or more semiconductor packages are needed.

SUMMARY

This application relates to semiconductor packages that contain isolated stacked dies and methods for making such devices. The semiconductor package contains both a first die with a first integrated circuit and a second die with a second integrated circuit that is stacked onto the first die while also being isolated from the first die. The first and second dies are connected using differing arrays of metal strips that serve as interposers between the first and second dies. This configuration provides a thinner semiconductor package since wire-bonding is not used. As well, since the integrated circuit devices in the first and second dies are isolated from each other, local heating and/or hot spots are diminished or prevented in the semiconductor package.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description can be better understood in light of the Figures, in which:

FIGS. 1 and 2 shows some embodiments of a semiconductor package containing multiple dies;

FIGS. 3-4 shows other embodiments of a semiconductor package containing multiple dies;

FIGS. 5-13 depict some embodiments of the methods for manufacturing a semiconductor package containing multiple dies; and

FIGS. 14-15 illustrate some embodiments of an isolated, stacked-die structure of the semiconductor packages before encapsulation.

The Figures illustrate specific aspects of the semiconductor packages that contain multiple dies with discrete devices and methods for making such devices. Together with the following description, the Figures demonstrate and explain the principles of the methods and structures produced through these methods. In the drawings, the thickness of layers and regions are exaggerated for clarity. It will also be understood that when a layer, component, or substrate is referred to as being “on” another layer, component, or substrate, it can be directly on the other layer, component, or substrate, or intervening layers may also be present. The same reference numerals in different drawings represent the same element, and thus their descriptions will not be repeated.

DETAILED DESCRIPTION

The following description supplies specific details in order to provide a thorough understanding. Nevertheless, the skilled artisan would understand that the semiconductor devices and associated methods of using the devices can be implemented and used without employing these specific details. Indeed, the devices and associated methods can be placed into practice by modifying the illustrated devices and associated methods and can be used in conjunction with any other apparatus and techniques conventionally used in the industry. For example, while the description below focuses on methods for making for semiconductor devices in the IC industry, it could be used for and applied to other electronic devices like optoelectronic devices, solar cells, MEMS structures, lighting controls, power supplies, and amplifiers. As well, while the description below describes using two dies in the same semiconductor package, it could be configured to contain more than two, including 3 or even more dies.
Some embodiments of the semiconductor packages that contain multiple dies and methods for making such devices are shown in the Figures. In the embodiments shown in FIG. 1 (top view) and FIG. 2 (bottom view), the semiconductor package 100 contains a substrate 102, a plurality of terminals 106, a first die 112 containing a first IC device, a second die 114 containing a second IC device, land pads 116, connectors 120, and encapsulation 130.
The first IC device and the second IC device may be the same or different and may be any known integrated circuit (including any discrete device) in the art. Some non-limiting examples of these devices may include logic or digital IC, linear regulators, audio power amplifiers, LDO, driver IC, diodes, and/or transistors, including zener diodes, schottky diodes, small signal diodes, bipolar junction transistors (“BJT”), metal-oxide-semiconductor field-effect transistors (“MOSFET”), insulated-gate-bipolar transistors (“IGBT”), and insulated-gate field-effect transistors (“IGFET”). In some embodiments, the first IC device comprises an audio amplifier and the second IC device comprises a low drop-out device (LDO).
The semiconductor package 100 contains a substrate 102 on which the other components of the semiconductor package are located. The substrate can be any low-cost, recycleable material such as steel, stainless steel, or any steel alloy known in the art. The substrate 102 can be configured with any shape and size consistent with its use in the semiconductor package 100. The substrate 102 can have any thickness that provides the needed support for the device. In some embodiments, such as where the substrate 102 comprises stainless steel, it may have a non-limiting thickness ranging from about 0.15 millimeters to about 0.25 millimeters.
In some embodiments, the substrate 102 has the shape illustrated in the Figures since it contains an area to which multiple land pads 116 are attached. In turn, the bottom of the first die 112 is then connected to the land pads 116. Due to the overlap of the surfaces of the die attach pad area and the first die 112, the die attach pad area can act as both a thermal and/or an electrical conductor. Such a configuration also permits the substrate lands 116 to dissipate the heat generated by the IC devices, increasing the efficiency of the heat dissipation from the semiconductor package 100. As described herein, the land pads 116 can also be used to bond or attach the second die 114 to the substrate 102.
In some embodiments, the land pads 116 can also serve as leads for the semiconductor package. In these embodiments, the substrate 102 is removed or peeled-off after molding process but with the land pads 116 retained on the molded body. Thus, the ends of the land pads 116 serve as the terminals 106. Accordingly, the lay-out of the land pads 116 and the terminals 106 are substantially similar. In other embodiments, though, the land pads 116 and the terminals 106 are formed separate from each other and a redistribution layer can be used to change the lay-out from the land pads to the terminals.
In some embodiments, the land pads 116 can comprise any bonds pads known in the semiconductor art. For example, the landing pads could comprise a metal stud and a reflowed solder material or metal deposit like Au, Ni, Ag, or combinations of these materials.
The semiconductor package 100 also contains connectors 120 that are used to connect the landing pads to the second die 114. In some embodiments, the connectors 120 comprise an array of metal strips that can be used as interposers. The metal strips used as connectors can contain any conductive metal or metal alloy that are similar to standard leadframe known in the art, including Cu, Ni—Pd, Ni—Pd—Au, or Ni—Pd—Au/Ag. In some embodiments, the metal strips comprise Cu. The array of metal strips can be configured to substantially match the desired connection points in the second die 114. Thus, for the semiconductor package 100 illustrated in FIGS. 1-2, the array of Cu strips are configured to be substantially in the form of a column. While the connectors 120 are depicted in the Figures as being substantially square, other shapes can be used including substantially rectangular, circular, or any known geometrical shapes.
The first and second dies, the upper surface of the substrate 102, and the connectors 120 can be encapsulated in any molding material 130 known in the art, as shown in FIG. 1. In some embodiments, the molding material can comprise an epoxy molding compound, a thermoset resin, a thermoplastic material, or potting material. In other embodiments, the molding material comprises an epoxy molding compound. In FIGS. 1-2, the molding material 130 is shown in phantom to better illustrate the internal components of semiconductor package 100.
Other embodiments of the semiconductor packages are illustrates in FIGS. 3-4. In these Figures, the semiconductor package 200 contains components substantially similar to those described for semiconductor package 100, including substrate 102, first die 112, landing pads 116, and molding material 130. But in these embodiments, the semiconductor package 200 contains a different configuration of terminals (labeled as 206) on the bottom of the package 200. As well, the number of terminals 206 are fewer than the number of terminals 106 that are contained in the embodiments depicted in FIGS. 1-2.
As well, the semiconductor package 200 also contains a second die 214 that is different than the second die 114. This second die 214 is relatively smaller than the second die 114 depicted in FIG. 1 and so has been labeled 214. In some configurations, the second die 214 can be about the same size as the first die 114, smaller, or even slightly larger. In yet other configurations, the top die can be substantially smaller than the inner distance between the external leads 216.
Because the second die 214 is not significantly larger than the first die, the connectors 120 depicted in FIG. 1 cannot be used for the second die 214. Rather, connectors 220 are used in the semiconductor package 200. As shown in FIG. 3, connectors 220 are configured to contain a first portion that extends away from the landing pads 216. Thus, this first portion is substantially similar in size to the landing pages 216. The connectors 220 also contain a second portion that extends from the first potion towards the area above the first die 112. In the embodiments depicted in FIGS. 3-4, the second portion can be given a finger-like configuration. In some configurations, the design and size of the interposing connectors can be different since they depend on the die size.
To support the second portion, the first portion of the connectors 220 is configured to be longer in width and length than the connectors 120. And to properly support the larger first portion of the connectors 220, the semiconductor package 200 contains landing pads 216 which are correspondingly larger that the landing pads 116 depicted in FIG. 1.
The semiconductor packages 100 and 200 can be made using any known process that provides the structures described above. In some embodiments, the methods described herein can be used. The method begins, as illustrated in FIG. 5, by providing the substrate 102. The substrate can be provided by metal stamping or etching a frame of the desired material (i.e., stainless steel) to contain multiple lands or terminals. The substrates can be peeled-off after the molding process used to form the semiconductor package.
Next, or at the same time, the first and second dies containing their IC devices are manufactured using any known processes. In some embodiments, the first and second IC devices can be manufactured separately in the first and second dies. But in other embodiments, the first and second IC devices are manufactured in their respective dies at the same time.
As shown in FIG. 5, the landing pads 116 are formed on the substrate 102 using any process known in art. In some embodiments, the landing pads can be formed by depositing the material and then etching the undesired portions of that material, thereby forming the landing pads 116 with the desired shape. Of course, for the landing pads 216, less material is etched so that larger landing pads are formed, as illustrated in FIG. 3 and FIG. 7 (which does not show the substrate 102). The terminals (106 or 206) are formed using any known process.
Next, as shown in FIG. 6, the first die 112 containing the first IC device is then attached to the landing pads 116 using any known flip-chip process which does not use wirebonding. One example of these processes includes solder bumping, which may include the use of solder bumps, balls, studs, and combinations thereof along with a solder paste, followed by a cure and reflow process. Another example of these processes includes the use of a conductive adhesive between the the substrate terminals 116 substrate 102 and the first IC device. The conductive adhesive may be, for example, a conductive epoxy, a conductive film, a screen printable solder paste, or a solder material, such as a lead-containing solder or a lead-free solder. In some embodiments, this attachment is performed by a chip-on-lead (COL) with wirebonding process. For the semiconductor package 200, the resulting structure after this attachment process (when solder bumps 122 are used) is shown in FIG. 7.
Next, as shown in FIG. 8, the connectors are attached to those landing pads which remain exposed after the first die 112 has been attached. This process can be performed using any known technique. In the embodiments illustrated in FIG. 8, the connectors 120 are formed by mounting array of connectors using any known conductive adhesives in the art. In the embodiments illustrated in FIG. 9, the connectors 220 are formed by stamping or etching or a combination of both. And in the embodiments illustrated in FIG. 10, the connectors 320 are formed in a similar manner, but with a different configuration so that they can support a smaller second die. This configuration generally has the second portion of the connectors formed closer together than the configuration shown in FIG. 9.
The second (or upper) die is then attached to the connectors. This process can be carried out using any known flip-chip process which does not use wirebonding. One example of these attachment processes include solder bumping, which may include the use of solder bumps, balls, studs, and combinations thereof along with a solder paste, followed by a cure and reflow process. Another example of these processes includes the use of a conductive adhesive between the connector and the second die. The conductive adhesive may be, for example, a conductive epoxy, a conductive film, a screen printable solder paste, or a solder material, such as a lead-containing solder or a lead-free solder. In some embodiments, this attachment is performed by a chip-on-lead (COL) with wirebonding process.
The resulting structure from attaching the second die is shown in FIGS. 11-13. For the embodiments in FIG. 11 (where the second die is larger than the first die), the second die 114 has been attached to the connectors 120. For the embodiments in FIG. 12 (where the second die is substantially the same size as the first die), the second die 214 has been attached to the connectors 220. And for the embodiments in FIG. 13 (where the second die is smaller than the first die), the second die 314 has been attached to the connectors 320. FIG. 14 depicts a side view of the structure illustrated in FIG. 11 with bumps 124 shown to connect the second die 114 to the connectors 120. And FIG. 15 depicts a side view of the structures illustrated in FIGS. 12 and 13 with bumps 122 shown to connect the first die 112 to the landing pads 116 and bumps 224 shown to connect the second die 214 (or 314) to the connectors 220 (or 320).
After the second die has been attached to the respective connectors, the molding material 130 is then formed around the substrate 102, first and second dies, and the connectors by any known encapsulation process, including potting, transfer molding, or injection. In some embodiments, the encapsulation process does not require any underfill. The resulting semiconductor package (such as those illustrated in FIGS. 1-4) is then optionally marked, trimmed, formed, and singulated using processes known in the art.
The semiconductor packages formed from this process contain two dies with IC devices that are isolated from each other because the molding material is contained between them. This configuration serves to separates the dies. In this configuration, since there is no direct contact between the dies, their respective thermal stability is easier to maintain and heat is dissipated quicker.
The above semiconductor packages have a reduced size while at the same time also keeping the stacked dies isolated. In some embodiments, the thickness of the semiconductor packages can be less than about 1 mm. In other embodiments, the thickness of the semiconductor packages can range from about 0.8 mm to about 1 mm.
In some embodiments, the semiconductor packages can be configured to contain more than 2 stacked dies. The additional dies can be incorporated by including additional land pads on which additional connectors (120, 220, or 320 depending on the size of the additional die) can be located. Then, the additional dies can be attached to the additional connectors by using a flip-chip process similar to those described above.
In addition to any previously indicated modification, numerous other variations and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of this description, and appended claims are intended to cover such modifications and arrangements. Thus, while the information has been described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred aspects, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, form, function, manner of operation and use may be made without departing from the principles and concepts set forth herein. Also, as used herein, examples are meant to be illustrative only and should not be construed to be limiting in any manner.

Claims

1. A semiconductor package, comprising:

multiple land pads;

a first die connected to a first portion of the lands pads without wirebonding;

an array of connectors connected to a second portion of the land pads; and

a second die connected to the array of connectors without wirebonding, wherein the second die is isolated from the first die.

2. The semiconductor package of claim 1, wherein the first die contains a first integrated circuit device and the second die contains a second integrated circuit device.

3. The semiconductor package of claim 1, wherein the second die does not contact the first die.

4. The semiconductor package of claim 3, wherein the semiconductor package has a thickness less than about 1 mm.

5. The semiconductor package of claim 4, wherein the semiconductor package has a thickness ranging from about 0.8 mm to about 1 mm.

6. The semiconductor package of claim 1, wherein the first die is smaller than the second die and the connectors are substantially columnar in shape.

7. The semiconductor package of claim 1, wherein the first die is substantially the same size or smaller than the second die and the connectors contain a first portion extending away from the landing pads and a second portion extending towards the second die.

8. The semiconductor package of claim 1, further comprising a molding material encapsulating the connectors and the first and second dies.

9. The semiconductor package of claim 1, wherein the multiple land pads terminate in terminals for the package.

10. A semiconductor package, comprising:

multiple land pads;

a first die containing a first integrated circuit device and connected to a first portion of the lands pads without wirebonding;

an array of connectors connected to a second portion of the land pads; and

a second die containing a second integrated circuit device and connected to the array of connectors without wirebonding, wherein the second die is isolated from the first die and does not contact the first die.

11. The semiconductor package of claim 10, wherein the semiconductor package has a thickness less than about 1 mm.

12. The semiconductor package of claim 11, wherein the semiconductor package has a thickness ranging from about 0.8 mm to about 1 mm.

13. The semiconductor package of claim 10, wherein the first die is smaller than the second die and the connectors are substantially columnar in shape.

14. The semiconductor package of claim 10, wherein the first die is substantially the same size or smaller than the second die and the connectors contain a first portion extending away from the landing pads and a second portion extending towards the second die.

15. The semiconductor package of claim 10, further comprising a molding material encapsulating the connectors and the first and second dies.

16. The semiconductor package of claim 10, wherein the multiple land pads terminate in terminals for the package.

17. A method for making semiconductor package, comprising:

providing multiple land pads;

connecting a first die to a first portion of the lands pads without using wirebonding;

connecting an array of connectors to a second portion of the land pads; and

connecting a second die to the array of connectors without using wirebonding and without contacting the second die to the first die.

18. The method of claim 17, further including providing the semiconductor package with a thickness less than about 1 mm.

19. The method of claim 18, wherein the semiconductor package has a thickness ranging from about 0.8 mm to about 1 mm.

20. The method of claim 17, wherein the first die is smaller than the second die and the connectors are substantially columnar in shape.

21. The method of claim 17, wherein the first die is substantially the same size or smaller than the second die and the connectors contain a first portion extending away from the landing pads and a second portion extending towards the second die.

22. The method of claim 1, further comprising encapsulating a molding material around the connectors and the first and second dies.

23. A method for making semiconductor package having a thickness less than about 1 mm, comprising:

providing a substrate;

forming multiple land pads on the substrate by a deposition and etch procedure;

connecting a first die to an inner portion of the lands pads by using a flip chip procedure without using wirebonding;

connecting an array of connectors to an outer portion of the land pads;

connecting a second die to the array of connectors by using a flip chip procedure without using wirebonding, wherein the second die rests on the connectors without contacting the first die;

encapsulating a molding material around the connectors and the first and second dies without underfilling; and

removing the substrate.

24. The method of claim 23, wherein the first die is smaller than the second die and the connectors are substantially columnar in shape.

25. The method of claim 23, wherein the first die is substantially the same size or smaller than the second die and the connectors contain a first portion extending away from the landing pads and a second portion extending towards the second die.