Performance of deep-submicrometer very large scale integrated (VLSI) circuits is being increasingly dominated by the interconnects due to decreasing wire pitch and increasing die size. Additionally, heterogeneous integration of different technologies in one single chip is becoming increasingly desirable, for which planar (two-dimensional) ICs may not be suitable. This paper analyzes the limitations of the existing interconnect technologies and design methodologies and presents a novel three-dimensional (3-D) chip design strategy that exploits the vertical dimension to alleviate the interconnect related problems and to facilitate heterogeneous integration of technologies to realize a system-on-a-chip (SoC) design. A comprehensive analytical treatment of these 3-D ICs has been presented and it has been shown that by simply dividing a planar chip into separate blocks, each occurring a separate physical level interconnected by short and vertical interlayer interconnects (VILICs), significant improvement in performance and reduction in wire-limited chip area can be achieved, without the aid of any other circuit or design innovations. A scheme to optimize the interconnect distribution among different interconnect tiers is presented and the effect of transferring the repeaters to upper Si layers has been quantified in this analysis for a two-layer 3-D chip. Furthermore, one of the major concerns in 3-D ICs arising due to power dissipation problems has been analyzed and an analytical model has been presented to estimate the temperatures of the different active layers. It is demonstrated that advancement in heat sinking technology will be necessary in order to extract maximum performance from these chips. Implications of 3-D device architecture on several design issues have also been discussed with special attention to SoC design strategies. Finally some of the promising technologies for manufacturing 3-D ICs have been outlined.

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3-D ICs: a novel chip design for improving deep-submicrometer interconnect performance and systems-on-chip integration

Three-dimensional (3D) integrated circuits (ICs), which contain multiple layers of active devices, have the potential to dramatically enhance chip performance, functionality, and device packing density. They also provide for microchip architecture and may facilitate the integration of heterogeneous materials, devices, and signals. However, before these advantages can be realized, key technology challenges of 3D ICs must be addressed. More specifically, the processes required to build circuits with multiple layers of active devices must be compatible with current state-of-the-art silicon processing technology. These processes must also show manufacturability, i.e., reliability, good yield, maturity, and reasonable cost. To meet these requirements, IBM has introduced a scheme for building 3D ICs based on the layer transfer of functional circuits, and many process and design innovations have been implemented. This paper reviews the process steps and design aspects that were developed at IBM to enable the formation of stacked device layers. Details regarding an optimized layer transfer process are presented, including the descriptions of 1) a glass substrate process to enable through-wafer alignment; 2) oxide fusion bonding and wafer bow compensation methods for improved alignment tolerance during bonding; 3) and a single-damascene patterning and metallization method for the creation of high-aspect-ratio (6:1 108 vias/cm2), and extremely aggressive wafer-to-wafer alignment (submicron) capability.

Three-dimensional integrated circuits

Recently, the development of three-dimensional large-scale integration (3D-LSI) has been accelerated. Its stage has changed from the research level or limited production level to the investigation level with a view to mass production. The 3D-LSI using through-silicon via (TSV) has the simplest structure and is expected to realize a high-performance, high-functionality, and high-density LSI cube. This paper describes the current and future 3D-LSI technologies with TSV.

Through-Silicon Via (TSV)

A system includes a semiconductor device. The semiconductor device includes a first single crystal silicon layer comprising first transistors, first alignment marks, and at least one metal layer overlying the first single crystal silicon layer, wherein the at least one metal layer comprises copper or aluminum more than other materials; and a second single crystal silicon layer overlying the at least one metal layer. The second single crystal silicon layer comprises a plurality of second transistors arranged in substantially parallel bands. Each of a plurality of the bands comprises a portion of the second transistors along an axis in a repeating pattern.

System comprising a semiconductor device and structure

A device comprising semiconductor memories, the device comprising: a first layer and a second layer of layer-transferred mono-crystallized silicon, wherein the first layer comprises a first plurality of horizontally-oriented transistors; wherein the second layer comprises a second plurality of horizontally-oriented transistors; and wherein the second plurality of horizontally-oriented transistors overlays the first plurality of horizontally-oriented transistors.

Semiconductor device and structure

A three-dimensional (3-D) integration technology has been developed for the fabrication of a new 3-D shared-memory test chip. This 3-D technology is based on the wafer bonding and thinning method. Five key technologies for 3-D integration were developed, namely, the formation of vertical buried interconnections, metal microbump formations, stacked wafer thinning, wafer alignment, and wafer bonding. Deep trenches having a diameter of 2 mum and a depth of approximately 50 mum were formed in the silicon substrate using inductively coupled plasma etching to form vertical buried interconnections. These trenches were oxidized and filled with n+ polycrystalline silicon or tungsten. The 3-D devices and 3-D shared-memory test chips with three-stacked layers were fabricated by bonding the wafers with vertical buried interconnections after thinning. No characteristic degradation was observed in the fabricated 3-D devices. It was confirmed that fundamental memory operation and broadcast operation between the three memory layers could be successfully performed in the fabricated 3-D shared-memory test chip

Three-Dimensional Integration Technology Based on Wafer Bonding With Vertical Buried Interconnections

We proposed a new three-dimensional (3D) shared memory for a high performance parallel processor system. In order to realize such new 3D shared memory, we have developed a new 3D integration technology based on the wafer stacking method. We fabricated the 3D shared memory test chip with three memory layers using our 3D integration technology. It was demonstrated that the basic memory operation and the broadcast operation of 3D shared memory are successfully performed.

Three-dimensional shared memory fabricated using wafer stacking technology

To achieve ultimate super chip integration, we have developed a three-dimensional integration technology called super-smart-stack technology using a self-assembly technique The chip alignment accuracy of within 1mum is obtained by the self-assembly technique We demonstrated for the first time that 3D SRAM test chip with ten memory layers was successfully fabricated using the super-smart-stack (SSS) technology

New three-dimensional integration technology using self-assembly technique

We have proposed a new three-dimensional (3D) integration technology based on reconfigured wafer-on-wafer bonding technique to solve several problems in 3D integration technology using the conventional wafer-on-wafer bonding technique. 3D LSIs are fabricated by bonding the reconfigured wafers onto the supporting Si wafer. The reconfigured wafer consists of many known good dies (KGDs) which are arrayed and glued on a holding Si wafer with Si steps by chip self-assembly technique. Therefore, the yield of the reconfigured wafer can be 100%. As a result, we can obtain a high production yield even after bonding many wafers. In addition, it is not necessary in the reconfigured wafer that the chip size has to be identical within the wafer. Therefore, we can stack various kinds of chips with different chip sizes, different materials and different devices in our new 3D integration technology based on the configured-wafer-on-wafer bonding technique (Reconfig. W-on-W 3D technology). We have developed key technologies to form W through-Si-Via (TSV) in the reconfigured wafer to fabricated 3D LSI test chips. We obtained excellent electrical characteristics of W-TSV using the daisy chain in 3D LSI test chip.

New Three-Dimensional Integration Technology Based on Reconfigured Wafer-on-Wafer Bonding Technique

A new three-dimensional (3D) integration technology using the chip-to-wafer bonding technique provides the ultimate super-chip integration in which various kinds of chip of different sizes can be vertically stacked and electrically connected through a number of vertical interconnections. We have investigated several key technologies of vertical interconnection formation, chip alignment, chip-to-wafer bonding, adhesive injection, and chip thinning to vertically stack known good dies (KGDs) into 3D LSI chips. By using these key technologies, successful fabrication of 3D LSI test chips with vertical interconnections consisting of In–Au microbumps and buried interconnections filled with polycrystalline silicon (poly-Si) was demonstrated. The test chips was composed of three kinds of very thin chip of 5, 6, and 7 mm2 and ranging in thickness from 30 to 90 µm. Each chip is tightly bonded using a low-viscosity epoxy adhesive as a dielectric material.

https://iopscience.iop.org/article/10.1143/JJAP.45.3030/pdf

Yusuke Yamada

Papers

Three-Dimensional Integration Technology Based on Wafer Bonding With Vertical Buried Interconnections

Three-dimensional shared memory fabricated using wafer stacking technology

New three-dimensional integration technology using self-assembly technique

New Three-Dimensional Integration Technology Based on Reconfigured Wafer-on-Wafer Bonding Technique

New Three-Dimensional Integration Technology Using Chip-to-Wafer Bonding to Achieve Ultimate Super-Chip Integration