HERMETIC SEAL AND RELIABLE BONDING STRUCTURES FOR 3D APPLICATIONS
A sealed microelectronic structure which provides mechanical stress endurance and includes at least two chips being electrically connected to a semiconductor structure at a plurality of locations. Each chip includes a continuous bonding material along it's perimeter and at least one support column connected to each of the chips positioned within the perimeter of each chip. Each support column extends outwardly such that when the at least two chips are positioned over one another the support columns are in mating relation to each other. A seal between the at least two chips results from the overlapping relation of the chip to one another such that the bonding material and support columns are in mating relation to each other. Thus, the seal is formed when the at least two chips are mated together, and results in a bonded chip structure.
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This invention was made with Government support under Contract No. N66001-00-C-8003 and N66001-04-C-8032 awarded by Defense. Advanced Research Projects Agency (DARPA). The Government has certain rights in this invention.FIELD OF THE INVENTION
The present invention relates to a sealed semiconductor structure using a bonding technique and, more specifically, relates to a bonded sealed semiconductor structure including structural support elements.BACKGROUND OF THE INVENTION
Integrated circuits (ICs) form the basis for many electronic systems. Essentially, an integrated circuit (IC) or chip includes a vast number of transistors and other circuit elements that are formed on a single semiconductor wafer and are interconnected to implement a desired function. The complexity of these integrated circuits (ICs) requires the use of an increasing number of linked transistors and other circuit elements.
Many modern electronic systems are created through the use of a variety of different integrated circuits, where each integrated circuit (IC or chip) performs one or more specific functions. For example, computer systems include at least one microprocessor and a number of memory chips. Conventionally, each of these integrated circuits (ICs) are formed on a separate chip, packaged independently and interconnected on, for example, a printed circuit board (PCB).
In micoelectronics, a wafer is a thin slice of semiconducting material, such as a silicon crystal, upon which microcircuits are constructed for example, by doping, etching, or deposition. Wafers are used in the fabrication of semiconductor devices such as integrated circuits or chips or dies. A single wafer may have a plurality of chips formed on the wafer. The wafer may be used having a plurality of chips formed therein, or the wafer may be cut to provide individual dies or chips. The wafers and chips or dies can form a stack by positioning the wafers and/or chips on top of one another. Copper bonding (Cu bonding) processes can be used to stack dies/chips at a chip-to-chip, chip-to-wafer, or wafer-to-wafer level.
As integrated circuit (IC) technology progresses, a need for a “system on a chip” in which the functionality of all of the IC devices of the system are packaged together without a conventional printed circuit board (PCB). Ideally, a computing system should be fabricated with all the necessary IC devices on a single chip. In practice, however, it is very difficult to implement a truly high-performance “system on a chip” because of vastly different fabrication processes and different manufacturing yields for the logic and memory circuits.
As a compromise, various “system modules” have been introduced that electrically connect and package integrated circuit (IC) devices which are fabricated on the same or on different semiconductor wafers. Initially, system modules have been created by simply stacking two chips, e.g., a logic and memory chip, on top of one another in an arrangement commonly referred to as chip-on-chip structure. Subsequently, multi-chip module (MCM) technology has been utilized to stack a number of chips on a common substrate to reduce the overall size and weight of the package which directly translates into reduced system size.
Existing multi-chip module (MCM) technology provides performance enhancements over single chip or chip-on-chip (COC) packaging approaches. For example, when several semiconductor chips are mounted and interconnected on a common substrate through very high density interconnects, higher silicon packaging density and shorter chip-to-chip interconnections can be achieved. In addition, low dielectric constant materials and higher wiring density can also be obtained which lead to increased system speed and reliability, reduced weight, volume, power consumption, and heat to be dissipated for the same level of performance. However, MCM approaches still suffer from additional problems, such as, bulky packaging, wire length and wire bonding that gives rise to stray inductances which interfere with the operation of the system module.
Typically, optimization of Cu bonding was achieved by utilizing one pattern density with specific bond pad dimensions and/or via dimensions. Vias and electrically connected pads refer to vias/pads with a plated hole that connects conductive tracks from one layer of a chip to another layer(s). Current solutions are not compatible with standard CMOS processes in which a variety of pattern densities and pad/via sizes may be used. Additionally, due to mechanical stability issues most of the bonding fails occur at the edge of the bonded pattern which often, in addition to degraded bonding yield, leads to corrosion issues. Additionally, for 3D applications, a method or device is needed to provide additional protection from mechanical damage (such as crack propagation, chipping, dicing, etc.) caused during the semiconductor fabrication process.
In the current state of the art, electrically active bonded pads and/or vias had to be often placed in the central location of the pattern to provide good reliability for these contacts. One major challenge of three dimensional (3-D) wafer-to-wafer vertical stack integration technology is the metal bonding between wafers and between die in a single chip, and the wafer protection from possible corrosion and contamination caused or generated by process steps after the wafers are bonded from reaching active IC devices on the bonded wafers.
Therefore, a need exists to erect a barrier structure by the edge of bonded wafers and individual die to protect the bonded wafers and die against corrosion and contamination in a three-dimensional (3-D) wafer-to-wafer vertical stack. It would also be desirable to provide an improved metal bonding method having acceptable bonding yield and reliability without being limited to pattern density or pad/via dimensions.SUMMARY OF THE INVENTION
In an aspect of the invention, a sealed microelectronic structure providing mechanical stress endurance is provided which comprises at least two chips including and being electrically connected to a semiconductor structure and comprising outer edges. Each chip includes a continuous length of bonding material on a planar surface area thereof defining a perimeter in spaced adjacency to the outer edge. At least one support column is connected to each of the chips and positioned within the perimeter of each chip. Each support column extends outwardly such that when the at least two chips are positioned in overlapping relation to one another, opposing support columns mate with each other or with an opposing planar surface area on the overlapping chip. A seal between the at least two chips results from the at least two chips being positioned in overlapping relation to one another such that the bonding material on each chip is in mating relation to each other whereby the seal is formed when the at least two chips are mated together resulting in a bonded chip structure.
In a related aspect of the invention, the bonding material on the at least two chips is compressed and the bonding material is heated to form the seal.
In another related aspect of the invention, a plurality of chips are positioned on at least two wafers. The wafers each include a continuous bonding material along a perimeter substantially adjacent to an outer edge of the wafer. The at least two wafers are sealed together when the bonding material on each of the wafers is compressed on each other in mating relation and heated to form the seal.
In another related aspect of the invention, the chips are electrically connected to their respective substrates to form an electrical circuit on the chips and the support columns are non-electrical and thereby are not part of the electrical circuit.
In another related aspect of the invention, the chips are electrically connected to their respective substrates and electrical connected to their respective wafers to form an electrical circuit on the chips and the wafers and the support columns are non-electric and thereby not part of the electrical circuit.
In another related aspect of the invention the chips have multiple layers and the support columns are positioned between the layers and adapted to provide support between the layers.
In an aspect of the present invention, a method for sealing a microelectronic structure and providing mechanical stress endurance comprises providing at least two chips including and being electrically connected to a semiconductor structure at a plurality of locations. A length of continuous bonding material is deposited on each chip on a planar surface thereof defining a perimeter substantially adjacent to the outer edge. At least one support column is connected on each of the chips and within the perimeter of each chip, and each support column extends outwardly. The chips are positioned in overlapping relation such that the bonding material and the support columns are in mating relation to each other. The chips are compressed and thereby the bonding material is also compressed together. The bonding material is heated to form a seal about the perimeter of the chips whereby a bonded chip structure is formed.
In a related aspect of the invention, a plurality of chips are positioned on at least two wafers, and a bonding material is deposited along a perimeter adjacent to an outer edge of the wafer. The bonding material is compressed on each of the wafers together with each other in mating relation. The mated bonding material is heated to form a seal, thereby forming a bonded wafers structure.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings, in which:
Generally, the present invention provides the ability to seal chip/structures/wafers which enables mechanical stability of critical joined components and protects from outside environmental damage. The sealing procedure of the present invention for sealing stacked wafer or chips enables structures to be hermetically sealed at a chip/die level and also allows wafer-level sealing which will enable downstream full-wafer processing. Furthermore, the sealing solution can also be utilized for electrical signal propagation and thermal dissipation or as a thermal conductor (through sealant material itself or using sealant as a thermal structure for dissipation). Materials that can be used to seal together chips or wafers include: metals (for example: Cu—Cu, Au—Au, etc.); alloys (such as: Cu—Sn, AuSn, etc.); solders; dielectrics (oxide-oxide); conductive adhesives (Cu-loaded pastes) and any combination thereof (example indium-oxide).
More specifically, referring to
The chips 104 also include dummy bonding pads (ads, support columns/pillars) 116 (shown in
The chips 200a, 200b also include dummy bonding pads 208a, 208b, respectively (similarly to the chips 104 shown in
Each of the pads 208a on chip 200a have a specified height to contact mating pads 208b on chip 200b when the chips 200a, 200b are placed in overlapping relation and bonded as shown in
It is understood that a chip or wafer may have multiple electrical reference layers connected by vertical vias (not shown). The dummy pads, for example, as described in relation to
Wafers 300a and 300b are combined by positioning one wafer over the other to form bonded wafer 350, shown in
While the present invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that changes in forms and details may be made without departing from the spirit and scope of the present application. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated herein, but falls within the scope of the appended claims.
7. A method for sealing a microelectronic structure and providing mechanical stress endurance, comprising:
- providing and positioning a plurality of chips on at least two wafers being electrically connected to a semiconductor structure at a plurality of locations, the chips comprising outer edges;
- depositing a length of continuous bonding material on each chip on a planar surface thereof defining a perimeter substantially adjacent to the outer edge of each chip;
- connecting at least one support column on each of the chips and within the perimeter of each chip, each support column extending outwardly;
- positioning the chips in overlapping relation such that the bonding material and the support columns are in mating relation to each other, respectively;
- compressing the chips and thereby the bonding material together;
- heating the bonding material to form a seal about the perimeter of the chips whereby a bonded chip structure is formed;
- positioning a plurality of support columns between multiple layers in the chips to provide support between the layers;
- depositing a bonding material along a perimeter adjacent to an outer edge of the wafer;
- compressing the bonding material on each of the wafers together with each other in mating relation; and
- heating the mated bonding material to form a seal and a bonded wafer structure.
Filed: Nov 3, 2006
Publication Date: May 29, 2008
Applicant: INTERNATIONAL BUSINESS MACHINES CORPORATION (Armonk, NY)
Inventors: Kuan-Neng Chen (White Plains, NY), Bruce K. Furman (Pouquag, NY), Edmund J. Sprogis (Underhill, VT), Anna W. Topol (Jefferson Valley, NY), Cornelia K. Tsang (Mohegan Lake, NY), Matthew R. Wordeman (Kula, HI), Albert M. Young (Fishkill, NY)
Application Number: 11/534,366
International Classification: H01L 21/50 (20060101);