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Variation resistant metal-oxide-semiconductor field effect transistor (MOSFET)
Patent number: 8994123
Abstract: Variation resistant metal-oxide-semiconductor field effect transistors (MOSFETs) are manufactured using a high-K, metal-gate ‘channel-last’ process. A cavity is formed between spacers formed over a well area having separate drain and source areas, and then a recess into the well area is formed. The active region is formed in the recess, comprising an optional narrow highly doped layer, essentially a buried epitaxial layer, over which a second un-doped or lightly doped layer is formed which is a channel epitaxial layer. The high doping beneath the low doped epitaxial layer can be achieved utilizing low-temperature epitaxial growth with single or multiple delta doping, or slab doping. A high-K dielectric stack is formed over the channel epitaxial layer, over which a metal gate is formed within the cavity boundaries. In one embodiment of the invention a cap of polysilicon or amorphous silicon is added on top of the metal gate.
Type: Grant
Filed: March 20, 2012
Date of Patent: March 31, 2015
Assignee: Gold Standard Simulations Ltd.
Inventors: Asen Asenov, Gareth Roy
Variation resistant MOSFETs with superior epitaxial properties
Patent number: 9012276
Abstract: Variation resistant metal-oxide-semiconductor field effect transistors (MOSFET) are manufactured using a high-K, metal-gate ‘channel-last’ process. Between spacers formed over a well area having separate drain and source areas, a recess in the underlying is formed using a crystallographic etch to provide [111] boundaries adjacent the source and drain regions. An ion implant step localized by the cavity results in a localized increase in well-doping directly beneath the recess. Within the recess, an active region is formed using an un-doped or lightly doped epitaxial layer, deposited at a very low temperature. A high-K dielectric stack is formed over the lightly doped epitaxial layer, over which a metal gate is formed within the cavity boundaries.
Type: Grant
Filed: July 3, 2014
Date of Patent: April 21, 2015
Assignee: Gold Standard Simulations Ltd.
Inventors: Ashok K. Kapoor, Asen Asenov
Fluctuation resistant FDSOI transistor with implanted subchannel
Patent number: 9190485
Abstract: The structure, and fabrication method thereof, implements a fully depleted silicon-on-insulator (SOI) transistor using a “Channel Last” procedure in which the active channel is a low-temperature epitaxial layer in an etched recess in the SOI silicon film. A highly localized ion implantation is used to set the threshold voltage of the transistor and to improve the short channel behavior of the final device. Based on high-K metal gate technology, this transistor has reduced threshold uncertainty and superior source and drain conductance.
Type: Grant
Filed: July 25, 2013
Date of Patent: November 17, 2015
Assignee: Gold Standard Simulations Ltd.
Inventor: Asen Asenov
Fluctuation resistant low access resistance fully depleted SOI transistor with improved channel thickness control and reduced access resistance
Patent number: 9263568
Abstract: The structure, and fabrication method thereof, implements a fully depleted silicon-on-insulator (SOI) transistor using a “Channel Last” procedure in which the active channel is a low-temperature epitaxial layer in an etched recess in the SOI silicon film. An optional ?-layer of extremely high doping allows its threshold voltage to be set to a desired value. Based on high-K metal gate last technology, this transistor has reduced threshold uncertainty and superior source and drain conductance. The use of epitaxial layer improves the thickness control of the active channel and reduces the process
induced variations. The utilization of active silicon layer that is two or more times thicker than those used in conventional fully depleted SOI devices, reduces the access resistance and improves the on-current of the SOI transistor.
Type: Grant
Filed: July 25, 2013
Date of Patent: February 16, 2016
Assignee: SemiWise Limited
Inventor: Asen Asenov
Gate recessed FDSOI transistor with sandwich of active and etch control layers
Patent number: 9269804
Abstract: The structure and the fabrication methods herein implement a fully depleted, recessed gate silicon-on-insulator (SOI) transistor with reduced access resistance, reduced on-current variability, and strain-increased performance. This transistor is based on an SOI substrate that has an epitaxially grown sandwich of SiGe and Si layers that are incorporated in the sources and drains of the transistors. Assuming a metal gate last complementary metal-oxide semiconductor (CMOS) technology and using the sidewall spacers as a hard mask, a recess under the sacrificial gate reaching all the way through the SiGe layer is created, and the high-K gate stack and metal gate are formed within that recess. The remaining Si region, having a precisely controlled thickness, is the fully depleted channel.
Type: Grant
Filed: July 25, 2013
Date of Patent: February 23, 2016
Assignee: SemiWise Limited
Inventor: Asen Asenov
Manufacture of a variation resistant metal-oxide-semiconductor field effect transistor (MOSFET)
Patent number: 9312362
Abstract: Variation resistant metal-oxide-semiconductor field effect transistors (MOSFETs) are manufactured using a high-K, metal-gate ‘channel-last’ process. A cavity is formed between spacers formed over a well area having separate drain and source areas, and then a recess into the well area is formed. The active region is formed in the recess, comprising an optional narrow highly doped layer, essentially a buried epitaxial layer, over which a second un-doped or lightly doped layer is formed which is a channel epitaxial layer. The high doping beneath the low doped epitaxial layer can be achieved utilizing low-temperature epitaxial growth with single or multiple delta doping, or slab doping. A high-K dielectric stack is formed over the channel epitaxial layer, over which a metal gate is formed within the cavity boundaries. In one embodiment of the invention a cap of polysilicon or amorphous silicon is added on top of the metal gate.
Type: Grant
Filed: March 20, 2015
Date of Patent: April 12, 2016
Assignee: SemiWise Limited
Inventors: Asen Asenov, Gareth Roy
Method of manufacturing variation resistant metal-oxide-semiconductor field effect transistor (MOSFET)
Patent number: 9373684
Abstract: Variation resistant metal-oxide-semiconductor field effect transistors (MOSFET) are manufactured using a high-K, metal-gate ‘channel-last’ process. Between spacers formed over a well area having separate drain and source areas, a cavity is formed. Thereafter an ion implant step through the cavity results in a localized increase in welldoping directly beneath the cavity. The implant is activated by a microsecond annealing which causes minimum dopant diffusion. Within the cavity a recess into the well area is formed in which an active region is formed using an un-doped or lightly doped epitaxial layer. A high-K dielectric stack is formed over the lightly doped epitaxial layer, over which a metal gate is formed within the cavity boundaries. In one embodiment of the invention a cap of poly-silicon or amorphous silicon is added on top of the metal gate.
Type: Grant
Filed: March 20, 2012
Date of Patent: June 21, 2016
Assignee: SemiWise Limited
Inventors: Asen Asenov, Gareth Roy
Fluctuation resistant FinFET
Patent number: 9847404
Abstract: This improved, fluctuation resistant FinFET, with a doped core and lightly doped epitaxial channel region between that core and the gate structure, is confined to the activegate span because it is based on a channel structure having a limited extent. The improved structure is capable of reducing FinFET random doping fluctuations when doping is used to control threshold voltage, and the channel structure reduces fluctuations attributable to doping-related variations in effective channel length. Further, the transistor design affords better source and drain conductance when compared to prior art FinFETs. Two
representative embodiments of the key structure are described in detail.
Type: Grant
Filed: September 11, 2013
Date of Patent: December 19, 2017
Assignees: SemiWise Limited, Semi Solutions LLC
Inventors: Robert J. Strain, Asen Asenov