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Vertically stacked RF switches by wafer-scale three-dimensional integration

Published in:
Electron. Lett., Vol. 48, No. 10, 10 May 2012.

Summary

Vertically stacked RF switches implemented by wafer-scale three-dimensional (3D) integration of three completely fabricated silicon-on-insulator wafers are demonstrated. The individual switch performance was maintained through the 3D integration process while the signal path is shortened by vertical interconnects. The footprint of the switch can be shrunk in proportion to the number of tiers it is distributed between, demonstrating the potential of significant size reduction of multiple-throw switches commonly required in many applications.
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Summary

Vertically stacked RF switches implemented by wafer-scale three-dimensional (3D) integration of three completely fabricated silicon-on-insulator wafers are demonstrated. The individual switch performance was maintained through the 3D integration process while the signal path is shortened by vertical interconnects. The footprint of the switch can be shrunk in proportion to the...

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Radiation effects in 3D integrated SOI SRAM circuits

Summary

Radiation effects are presented for the first time for vertically integrated 3 x 64 -kb SOI SRAM circuits fabricated using the 3D process developed at MIT Lincoln Laboratory. Three fully-fabricated 2D circuit wafers are stacked using standard CMOS fabrication techniques including thin-film planarization, layer alignment and oxide bonding. Micron-scale dense 3D vias are fabricated to interconnect circuits between tiers. Ionizing dose and single event effects are discussed for proton irradiation with energies between 4.8 and 500 MeV. Results are compared with 14-MeV neutron irradiation. Single event upset cross section, tier-to-tier and angular effects are discussed. The interaction of 500-MeV protons with tungsten interconnects is investigated usingMonte-Carlo simulations. Results show no tier-to-tier effects and comparable radiation effects on 2D and 3D SRAMs. 3DIC technology should be a good candidate for fabricating circuits for space applications.
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Summary

Radiation effects are presented for the first time for vertically integrated 3 x 64 -kb SOI SRAM circuits fabricated using the 3D process developed at MIT Lincoln Laboratory. Three fully-fabricated 2D circuit wafers are stacked using standard CMOS fabrication techniques including thin-film planarization, layer alignment and oxide bonding. Micron-scale dense...

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SET characterization in logic circuits fabricated in a 3DIC technology

Summary

Single event transients are characterized for the first time in logic gate circuits fabricated in a novel 3DIC technology where SET test circuits are vertically integrated on three tiers in a 20-um-thick layer. This 3D technology is extremely will suited for high-density circuit integration because of the small dimension the tier-to-tier circuit interconnects, which are 1.25-um-wide-through-oxide-vias. Transient pulse width distributions were characterized simultaneously on each tier during exposure to krypton heavy ions. The difference in SET pulse width and cross-section among the three tiers is discussed. Experimental test results are explaine dby considering the electrical characteristics of the FETs on the 2D wafers before 3D integration, and by considering the energy deposited by the Kr ions passing through the various material laters of the 3DIC stack. We also show that the backmetal layer available on the upper tiers can be used to tune independently the nFET and pFET current drive, and change the SET pulse width and cross-section. This 3DIC technology appears to be a good candidate for space applications.
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Summary

Single event transients are characterized for the first time in logic gate circuits fabricated in a novel 3DIC technology where SET test circuits are vertically integrated on three tiers in a 20-um-thick layer. This 3D technology is extremely will suited for high-density circuit integration because of the small dimension the...

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SOI circuits powered by embedded solar cell

Published in:
2011 IEEE SOI Conf., 3-6 October 2011.

Summary

Solar cells embedded in the SOI substrate were successfully used as the sole energy source to power a ring oscillator fabricated using an ultra-low-power fully depleted SOI process on the same wafer. The speed of the ring oscillator increased with increasing light intensity and showed a fastest oscillation with a 4.5 ns stage delay and 0.26 fJ power-delay product. The maximum power generated by the solar cell was 9.6 mW/cm2 with an efficiency of 11.6%.
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Summary

Solar cells embedded in the SOI substrate were successfully used as the sole energy source to power a ring oscillator fabricated using an ultra-low-power fully depleted SOI process on the same wafer. The speed of the ring oscillator increased with increasing light intensity and showed a fastest oscillation with a...

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SOI-enabled three-dimensional integrated-circuit technology

Published in:
2010 IEEE Int. SOI Conf., 11 October 2010.

Summary

We have demonstrated a new 3D device interconnect approach, with direct back side via connection to a transistor in a 3D stack, resulting in a reduced 3D footprint by an estimated ~40% as well as potential for lower series resistance. We have demonstrated high yield 3D through-oxide-via (TOV) with a 40% size reduction to 1.0 ?m and with an associated exclusion zone reduced by a factor of 2, substantially smaller than in bulk-Si 3D through-siliconvia (TSV) approaches. These significant enhancements were demonstrated with our 3D technology based on conventional SOI wafers.
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Summary

We have demonstrated a new 3D device interconnect approach, with direct back side via connection to a transistor in a 3D stack, resulting in a reduced 3D footprint by an estimated ~40% as well as potential for lower series resistance. We have demonstrated high yield 3D through-oxide-via (TOV) with a...

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Improvement of SOI MOSFET RF performance by implant optimization

Published in:
IEEE Microw. Wirel. Compon. Lett., Vol. 20, No. 5, May 2010, pp. 271-273.

Summary

The characteristics of silicon on insulator MOSFETs are modified to enhance the RF performance by varying channel implants. Without adding new masks or fabrication steps to the standard CMOS process, this approach can be easily applied in standard foundry fabrication. The transconductance, output resistance, and breakdown voltage can be increased by eliminating channel and drain extension implants. As a result, the fmax of the modified n-MOSFET with a 150 nm gate length exceeds 120 GHz, showing a 20% improvement over the standard MOSFET for digital circuits on the same wafer.
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Summary

The characteristics of silicon on insulator MOSFETs are modified to enhance the RF performance by varying channel implants. Without adding new masks or fabrication steps to the standard CMOS process, this approach can be easily applied in standard foundry fabrication. The transconductance, output resistance, and breakdown voltage can be increased...

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Three-dimensional integration technology for advanced focal planes

Summary

We have developed a three-dimensional (3D) circuit integration technology that exploits the advantages of silicon-on-insulator (SOI) technology to enable wafer-level stacking and micrometer-scale electrical interconnection of fully fabricated circuit wafers. This paper describes the 3D technology and discusses some of the advanced focal plane arrays that have been built using it.
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Summary

We have developed a three-dimensional (3D) circuit integration technology that exploits the advantages of silicon-on-insulator (SOI) technology to enable wafer-level stacking and micrometer-scale electrical interconnection of fully fabricated circuit wafers. This paper describes the 3D technology and discusses some of the advanced focal plane arrays that have been built using...

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Channel engineering of SOI MOSFETs for RF applications

Summary

Channel engineering of SOI MOSFETs is explored by altering ion implantation without adding any new fabrication steps to the standard CMOS process. The effects of implantation on characteristics important for RF applications, such as transconductance, output resistance, breakdown voltage, are compared. Data show that the best overall RF MOSFET has no body and drain-extension implants.
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Summary

Channel engineering of SOI MOSFETs is explored by altering ion implantation without adding any new fabrication steps to the standard CMOS process. The effects of implantation on characteristics important for RF applications, such as transconductance, output resistance, breakdown voltage, are compared. Data show that the best overall RF MOSFET has...

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Characterization of a three-dimensional SOI integrated-circuit technology

Published in:
2008 IEEE Int. SOI Conf. Proc., 6 October 2008, pp. 109-110.

Summary

At Lincoln Laboratory, we have established a three dimensional (3D) integrated circuit (IC) technology that has been developed and demonstrated over eight designs, bonding two or three active circuit layers or tiers to form monolithically integrated 3D circuits. This technology has been used to successfully demonstrate a large-area 8 x 8 mm2 high-3D-via-count 1024 x 1024 visible image, a 64 x 64 laser radar focal plane based on single-photon-sensitive avalanche photodiodes, and a 10Gb/s/pin low power interconnect for 3DICs. 3DIC technology in our most recently completed 3D multiproject (3DM2) run includes three active fully-depleted-SOI (FDSOI) circuit tiers, eleven interconnect-metal layers, and dense unrestricted 3D vias interconnecting stacked circuit layers, as shown in Figure 1. While we continue our efforts to scale our 3DIC technology and increase 3D via density, we are also working to improve our understanding of 3D integration impact on transistor and process monitor circuits. In this paper, we describe our process and test results after single tier circuit fabrication as well as after three-tier integration, determine impact of 3D vias on ring oscillator performance, and demonstrate functionality of single and multi-tier circuits of varying complexity.
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Summary

At Lincoln Laboratory, we have established a three dimensional (3D) integrated circuit (IC) technology that has been developed and demonstrated over eight designs, bonding two or three active circuit layers or tiers to form monolithically integrated 3D circuits. This technology has been used to successfully demonstrate a large-area 8 x...

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Scaling three-dimensional SOI integrated-circuit technology

Published in:
2007 IEEE Int. SOI Conf. Proc., 1-4 October 2007, pp. 87-88.

Summary

Introduction At Lincoln Laboratory, we have established a three dimensional (3D) integrated circuit (IC) technology that has been developed and demonstrated over seven designs, bonding two or three active circuit layers or tiers to form monolithically integrated 3D circuits. Key features of our 3DIC technology include fully depleted SOI (FDSOI) circuit fabrication, low-temperature wafer-scale oxide-to-oxide bonding, precision wafer-to-wafer alignment, and dense unrestricted 3D vias interconnecting stacked circuit layers, successfully demonstrated in a large area 8 x 8 mm2 high-3D-via-count 1024 x 1024 visible imager. In this paper, we describe details of our bonding protocol for 150-mm diameter wafers, leading to a 50% increase in oxide-oxide bond strength and demonstration of +--0.5 am wafer-to-wafer alignment accuracy. We have established design rules for our 3DIC technology, have quantified process factors limiting our design-rule 3D via pitch, and have demonstrated next generation 3D vias with a 2x size reduction, stacked 3D vias, a backmetal interconnect process to reduce 2D circuit exclusion zones, and buried oxide (BOX) vias to allow both electrical and thermal substrate connections. All of these improvements will allow us to continue to reduce minimum 3D via pitch and reduce 2D layout limitations, making our 3DIC technology more attractive to a broader range of applications.
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Summary

Introduction At Lincoln Laboratory, we have established a three dimensional (3D) integrated circuit (IC) technology that has been developed and demonstrated over seven designs, bonding two or three active circuit layers or tiers to form monolithically integrated 3D circuits. Key features of our 3DIC technology include fully depleted SOI (FDSOI)...

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