John Michael Hergenrother

Bio: John Michael Hergenrother is an academic researcher from Alcatel-Lucent. The author has contributed to research in topics: Gate oxide & Layer (electronics). The author has an hindex of 5, co-authored 11 publications receiving 578 citations.

Analytic description of short-channel effects in fully-depleted double-gate and cylindrical, surrounding-gate MOSFETs

Abstract: Short-channel effects in fully-depleted double-gate (DG) and cylindrical, surrounding-gate (Cyl) MOSFETs are governed by the electrostatic potential as confined by the gates, and thus by the device dimensions. The simple but powerful evanescent-mode analysis shows that the length /spl lambda/, over which the source and drain perturb the channel potential, is 1//spl pi/ of the effective device thickness in the double-gate case, and 1/4.810 of the effective diameter in the cylindrical case, in excellent agreement with PADRE device simulations. Thus for equivalent silicon and gate oxide thicknesses, evanescent-mode analysis indicates that Cyl-MOSFETs can be scaled to 35% shorter channel lengths than DG-MOSFETs.

Process for fabricating vertical transistors

Abstract: A process for fabricating a vertical MOSFET device for use in integrated circuits is disclosed. In the process, at least three layers of material are formed sequentially on a semiconductor substrate. The three layers are arranged such that the second layer is interposed between the first and third layers. The second layer is sacrificial, that is, the layer is completely removed during subsequent processing. The thickness of the second layer defines the physical gate length of the vertical MOSFET. In the process the first and third layers have etch rates that are significantly lower than the etch rate of the second layer in an etchant selected to remove the second layer. The top layer, which is either the third or subsequent layer, is a stop layer for a subsequently performed mechanical polishing step that is used to remove materials formed over the at least three layers. After the at least three layers of material are formed on the substrate, a window or trench is formed in the layers. The window terminates at the surface of the silicon substrate in which one of either a source or drain region is formed in the silicon substrate. The window or trench is then filled with a semiconductor material. This semiconductor plug becomes the vertical channel of the transistor. Therefore the crystalline semiconductor plug is doped to form a source extension, a drain extension, and a channel region in the plug. Subsequent processing forms the other of a source or drain on top of the vertical channel and removes the sacrificial second material layer. The removal of the sacrificial second layer exposes a portion of the doped semiconductor plug. The device gate dielectric is then formed on the exposed portion of the doped semiconductor plug. The gate electrode is then deposited. The physical gate length of the resulting device corresponds to the deposited thickness of the second material layer.

CMOS integrated circuit having vertical transistors and a process for fabricating same

Abstract: A process for fabricating a CMOS integrated circuit with vertical MOSFET devices is disclosed. In the process, at least three layers of material are formed sequentially on a semiconductor substrate. The three layers are arranged such that the second layer is interposed between the first and third layers. The second layer is sacrificial, that is, the layer is completely removed during subsequent processing. The thickness of the second layer defines the physical gate length of the vertical MOSFET devices. After the at least three layers of material are formed on the substrate, the resulting structure is selectively doped to form an n-type region and a p-type region in the structure. Windows or trenches are formed in the layers in both the n-type region and the p-type region. The windows terminate at the surface of the silicon substrate in which one of either a source or drain region is formed. The windows or trenches are then filled with a semiconductor material. This semiconductor plug becomes the vertical channel of the transistor. Therefore the crystalline semiconductor plug is doped to form a source extension, a drain extension, and a channel region in the plug. Subsequent processing forms the other of a source or drain on top of the vertical channel and removes the sacrificial second material layer. The removal of the sacrificial second layer exposes a portion of the doped semiconductor plug. The device gate dielectric is then formed on the exposed portion of the doped semiconductor plug. The gate electrode is then deposited. The physical gate length of the resulting device corresponds to the deposited thickness of the second material layer.

50 nm Vertical Replacement-Gate (VRG) pMOSFETs

Abstract: We present the first p-channel Vertical Replacement-Gate (VRG) MOSFETs Like the VRG-nMOSFETs demonstrated last year, these devices show promise as a successor to planar MOSFETs for highly-scaled ULSI Our pMOSFETs retain the key features of the nMOSFETs and add channel doping by ion implantation and raised source/drain extensions (SDEs) We have significantly improved the core VRG process to provide high-performance devices with gate lengths of 100 nm and below Since both sides of the device pillar drive in parallel, the drive current per /spl mu/m of coded width can far exceed that of planar MOSFETs Our 100 nm VRG-pMOSFETs with t/sub ox/=25 /spl Aring/ drive 615 /spl mu/A//spl mu/m at 15 V with I/sub OFF/=8 nA//spl mu/m-80% more drive than specified in the 1999 ITRS Roadmap at the same I/sub OFF/ We demonstrate 50 nm VRG-pMOSFETs with t/sub ox/=25 /spl Aring/ that approach the 10 V roadmap target of I/sub ON/=350 /spl mu/A//spl mu/m at I/sub OFF/=20 nA//spl mu/m without the need for a hyperthin (<20 /spl Aring/) gate oxide

Method for forming vertical transistor cmos integrated circuit

Abstract: PROBLEM TO BE SOLVED: To integrate a vertical transistor by providing a device with a source extending portion and a drain extending portion, where the source extending portion and the drain extending portion in a semiconductor substrate are regulated by the thickness of the doped first and third layers of a material, and by providing the second layer with a place for a gate to be formed later. SOLUTION: The active region of a device is formed by depositing at least three kinds of layers on a substrate. The first and third layers among these layers are three kinds of layers and regulate a source-extending portion which extends in a plug of a semiconductor material or a drain-extending portion. That is, in the case where the source of the device is formed under a semiconductor plug, the first layer regulates the source extending portion and the third layer regulates the drain-extending portion. In the case where the drain of the device is formed under the semiconductor plug, the first layer regulates the drain-extending portion, and the third layer regulates the source extending portion. The thickness of the second layer regulates the length of gate of the device.

Fundamentals of Modern VLSI Devices

Abstract: Learn the basic properties and designs of modern VLSI devices, as well as the factors affecting performance, with this thoroughly updated second edition. The first edition has been widely adopted as a standard textbook in microelectronics in many major US universities and worldwide. The internationally-renowned authors highlight the intricate interdependencies and subtle tradeoffs between various practically important device parameters, and also provide an in-depth discussion of device scaling and scaling limits of CMOS and bipolar devices. Equations and parameters provided are checked continuously against the reality of silicon data, making the book equally useful in practical transistor design and in the classroom. Every chapter has been updated to include the latest developments, such as MOSFET scale length theory, high-field transport model, and SiGe-base bipolar devices.

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Device scaling limits of Si MOSFETs and their application dependencies

Abstract: This paper presents the current state of understanding of the factors that limit the continued scaling of Si complementary metal-oxide-semiconductor (CMOS) technology and provides an analysis of the ways in which application-related considerations enter into the determination of these limits. The physical origins of these limits are primarily in the tunneling currents, which leak through the various barriers in a MOS field-effect transistor (MOSFET) when it becomes very small, and in the thermally generated subthreshold currents. The dependence of these leakages on MOSFET geometry and structure is discussed along with design criteria for minimizing short-channel effects and other issues related to scaling. Scaling limits due to these leakage currents arise from application constraints related to power consumption and circuit functionality. We describe how these constraints work out for some of the most important application classes: dynamic random access memory (DRAM), static random access memory (SRAM), low-power portable devices, and moderate and high-performance CMOS logic. As a summary, we provide a table of our estimates of the scaling limits for various applications and device types. The end result is that there is no single end point for scaling, but that instead there are many end points, each optimally adapted to its particular applications.

Low-Voltage Tunnel Transistors for Beyond CMOS Logic

Abstract: Steep subthreshold swing transistors based on interband tunneling are examined toward extending the performance of electronics systems. In particular, this review introduces and summarizes progress in the development of the tunnel field-effect transistors (TFETs) including its origin, current experimental and theoretical performance relative to the metal-oxide-semiconductor field-effect transistor (MOSFET), basic current-transport theory, design tradeoffs, and fundamental challenges. The promise of the TFET is in its ability to provide higher drive current than the MOSFET as supply voltages approach 0.1 V.

Vertically-stacked, field-programmable, nonvolatile memory and method of fabrication

Abstract: A very high density field programmable memory is disclosed. An array is formed vertically above a substrate using several layers, each layer of which includes vertically fabricated memory cells. The cell in an N level array may be formed with N+1 masking steps plus masking steps needed for contacts. Maximum use of self alignment techniques minimizes photolithographic limitations. In one embodiment the peripheral circuits are formed in a silicon substrate and an N level array is fabricated above the substrate.