Compact CMOS in wide bandgap semiconductor

Abstract

CMOS Systems formed in Wide Bandgap Semiconductor and involving use of a material that forms a rectifying junction with either N and P-type Field Induced Semiconductor, in combination with, preferably, Parallel and Adjacent Channels subject to control by a Gate removed from said Channels by insulator.

Claims

1. A CMOS structure comprising a region of material in a wide bandgap substrate which forms rectifying junctions with both field induced N and P-type regions therein, said CMOS structure further comprising at least two channels projecting from electrical contact with said region of material in a said wide bandgap substrate which forms rectifying junctions with both field induced N and P-type regions therein; said CMOS structure further comprising gate structures offset with respect to said channels by insulating material; said CMOS structure further comprising substantially non-rectifying junctions to said material which forms rectifying junctions with both field induced N and P-type wide bandgap semiconductor, at distal ends of said at least two channels; said wide bandgap semiconductor substrate, at least in the regions of said channels being characterized by a selection from the group consisting of: it is substantially or per se. intrinsic; it is substantially or per se. metallurigically compensated; it contains both metallurgical N and P-type dopants in unequal concentrations; it is metallurgically doped to provide at least one area of P-type material and at least one separate area of N-type material in each channel region; such that in use a voltage is applied between the substantially non-rectifying junctions at the distal ends of said at least two channels and a voltage is applied to said gate which, when switched between the voltages applied to the substantially non-rectifying distal ends of said at least two channels, causes a voltage to appear at the substantially non-rectifying junction to said region of material which forms rectifying junctions with both field induced N and P-type wide bandgap semiconductor which is inverted, in that when the higher of said voltages applied to the substantially non-rectifying junctions to said distal ends of said at least two channels is applied to said gate, the voltage at the substantially non-rectifying junction to said region of material which forms rectifying junctions with both field induced N and P-type silicon carbide is low, and vice-versa.

2. A CMOS structure as in claim 1, in which the wide bandgap semiconductor is selected from the group consisting of: silicon carbide (SiC); gallium nitride (GaN) gallium arsenide (GaAs); zinc oxide (ZnO); and diamond (C).

3. A CMOS structure comprising a region of material in a silicon carbide substrate which forms rectifying junctions with both field induced N and P-type silicon carbide, said CMOS structure further comprising at least two channels projecting from electrical contact with said region of material in a silicon carbide substrate which forms rectifying junctions with both field induced N and P-type silicon carbide; said CMOS structure further comprising gate structures offset with respect to said channels by insulating material; said CMOS structure further comprising substantially non-rectifying junctions to said material which forms rectifying junctions with both field induced N and P-type silicon carbide, and to distal ends of said at least two channels; said silicon carbide substrate, at least in the regions of said channels being characterized by a selection from the group consisting of: it is substantially or per se. intrinsic; it is substantially or per se. metallurigically compensated; it contains both metallurgical N and P-type dopants in unequal concentrations; it is metallurgically doped to provide at least one area of P-type material and at least one separate area of N-type material in each channel region; such that in use a voltage is applied between the substantially non-rectifying junctions at the distal ends of said at least two channels and a voltage is applied to said gate which, when switched between the voltages applied to the substantially non-rectifying distal ends of said at least two channels, causes a voltage to appear at the substantially non-rectifying junction to said region of material which forms rectifying junctions with both field induced N and P-type silicon carbide which is inverted, in that when the higher of said voltages applied to the substantially non-rectifying junctions to said distal ends of said at least two channels is applied to said gate, the voltage at the substantially non-rectifying junction to said region of material which forms rectifying junctions with both field induced N and P-type silicon carbide is low, and vice-versa.

4. A CMOS structure as in claim 3, in which the material in said silicon carbide substrate which forms rectifying junctions with both field induced N and P-type silicon carbide, is vanadium doped silicon carbide.

5. A CMOS structure as in claim 3, in which the material comprising substantially non-rectifying junctions to said distal regions of channels comprises nickel.

6. A compact CMOS structure comprising a region of material in a silicon carbide substrate which forms rectifying junctions with both field induced N and P-type silicon carbide, said compact CMOS structure further comprising at least two channels projecting from electrical contact with said region of material in a silicon carbode substrate which forms rectifying junctions with both field induced N and P-type silicon carbide, said channels being substantially parallel and adjacent to one another; said compact CMOS structure further comprising a gate structure offset with respect to said channels by insulating material; said compact CMOS structure further comprising substantially non-rectifying junctions to said material which forms rectifying junctions with both field induced N and P-type silicon carbide, and to distal ends of said at least two channels; said silicon carbide substrate, at least in the regions of said channels being characterized by a selection from the group consisting of: it is substantially or per se. intrinsic; it is substantially or per se. metallurigically compensated; it contains both metallurgical N and P-type dopants in unequal concentrations; it is metallurgically doped to provide at least one area of P-type material and at least one separate area of N-type material in each channel region; such that in use a voltage is applied between the substantially non-rectifying junctions at the distal ends of said at least two channels and a voltage is applied to said gate which, when switched between the voltages applied to the substantially non-rectifying distal ends of said at least two channels, causes a voltage to appear at the substantially non-rectifying junction to said region of material which forms rectifying junctions with both field induced N and P-type silicon carbide which is inverted, in that when the higher of said voltages applied to the substantially non-rectifying junctions to said distal ends of said at least two channels is applied to said gate, the voltage at the substantially non-rectifying junction to said region of material which forms rectifying junctions with both field induced N and P-type silicon carbide is low, and vice-versa.

7. A compact CMOS structure as in claim 6, in which the material in said silicon carbide substrate which forms rectifying junctions with both field induced N and P-type silicon carbide, is vanadium doped silicon carbide.

8. A compact CMOS structure as in claim 6, in which the material comprising substantially non-rectifying junctions to said distal regions of channels comprises nickel.

9. A CMOS structure as in claim 1, in which said channels are present in FINS which project from a surface of said wide bandgap semiconductor substrate.

10. A CMOS structure as in claim 3, in which said channels are present in FINS which project from a surface of said wide bandgap semiconductor substrate.

11. A compact CMOS structure as in claim 6, in which said channels are present in FINS which project from a surface of said wide bandgap semiconductor substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 shows a perspective view of a prior art FINFET.

[0041] FIG. 2 shows a perspective view of a present invention Compact FINFET CMOS system.

[0042] FIG. 3 is shows a front elevational view of the FIG. 2 system, showing the Insulator (I) between the Gate (G) and FIN (F2).

[0043] FIGS. 4 and 5 are adapted from patent to Welch, U.S. Pat. No. 6,624,493 and serve to indicate the Inverting Nature of the present invention.

DETAILED DESCRIPTION

[0044] FIG. 1 shows a perspective view of a prior art early depiction of a FINFET, adapted from U.S. Pat. No. 6,413,802. This Figure is provided as it provides insight as to how inventor Welch herein conceived the present invention. Basically, replacing the Drain (D) with a Material that forms rectifying junctions with both N and P-type material, results in the present invention structure.

[0045] FIG. 2 shows a perspective view of a present invention Compact CMOS system in a planar substrate. Note the presence of a region of material (M) in a semiconductor substrate (SUB) which forms rectifying junctions with both field induced N and P-type semiconductor. The compact CMOS structure further comprises at least two Channels, (eg. indicated as FINS (F1) (F2)) projecting from electrical contact with said region of material in a semiconductor substrate which forms rectifying junctions with both field induced N and P-type semiconductor (M), said FINS (F1) (F2) being substantially parallel and adjacent to one another to make the system as compact as possible. Said compact CMOS structure further comprises a gate (G) structure offset with respect to said FINS (F1) (F2) by insulating material (I) as shown better in FIG. 3. The compact CMOS structure further comprises substantially non-rectifying junctions (C1), (C2) and (MP) to said distal ends of said at least two FINS material (F1) (F2) and to the Material (M), respectively. It is to be understood that a region out from under the Gate that provides indication of FINS (F1) and (F2) FIG. 2 is not meant to imply that any distance must be present in a fabricated system, but is there only to allow indication (F1) and (F2). In a preferred embodiment there is little such gap between the left and right side of the Gate (G) and the substantially non-rectifying junctions (C1) (C2) and (M).

[0046] It is noted that while FIG. 2 in particular shows Gate (G) Material over a relatively large area, it must be present only over Channel Regions (F1) and (F2). To reduce Gate Capacitance a significant area of Gate (G) Material can be removed leaving only Electrical Connected Material over Channel Regions. Is to be interpreted consistent with this.

[0047] FIG. 3 is included to as a front elevational view of the FIG. 2 system, showing the Insulator (I) between the Gate (G) and FIN (F2). Note that the Gate (G) can be a metal or a composite of metal and non-metal components. Further, the Insulator under the Gate (G) can be much thinner than at other locations, and/or the Gate (G) can be of a nature that is present only above a Channel Region (F1) (F2), as FIG. 2 can be interpreted to show, or it can be present on one of both sides and above a FIN Channel region in a semiconductor substrate, as shown in FIG. 1. The later point is not a determining factor as regards patentability. That, it is believed is found in the unique combination teachings regarding application of material in a semiconductor substrate which forms rectifying junctions with both field induced N and P-type semiconductor in the identified patents by Welch, which teaching have not previously been applied to systems comprising parallel adjacent FINS or channels (F1) (F2), and in the many FINFET related patents, such as U.S. Pat. No. 6,413,802 to Hu et al. Inventor Welch has combined elements, each arguably present in various prior art publications, in a novel way he was positioned to appreciate resulting from a chance discovery in his Masters work that Chromium annealed to N-type Silicon formed a very good rectifying junction, in combination with discovery of the previously mentioned Lepselter and Sultanov article which reported Chromium did likewise with P-type Silicon, all in combination with recently developed insight to the FINFET structure which naturally lends itself to providing substantially parallel and adjacent Channel regions (F1) (F2) which can both be conveniently subject to a single Gate (G) voltage in use. MOSFET structures that are formed from sequential N and P-Channel devices in N and P doped regions on a substrate must use a split gate as did the results Welch reported in his previous patents. The present invention, again, does not require space consuming alternating N and P-type regions in a substrate, but rather uses only a substantially Intrinsic or at least partially or substantially completely Compensated substrate, in the region of substantially parallel and adjacent channels, to achieve a Compact CMOS system.

[0048] FIGS. 4 and 5 are adapted from patent to Welch, U.S. Pat. No. 6,624,493, amongst other publications by Welch, and serve to indicate the Inverting Nature of the present invention. Said FIGS. show an exemplary biasing situation wherein a Positive Voltage is applied to (C1), and (C2) is Grounded. The Ground could just as well be a Negative Voltage and therefore FIGS. 4 and 5 are not limiting. Note that when the Gate (G) Voltage is at +V in FIG. 4, the Midpoint (MP) of the present Compact FINFET CMOS system is at Ground (GND). FIG. 5 shows that when the Gate (G) Voltage is at Ground (GND), the Midpoint (MP) of the present Compact FINFET CMOS system is at +V, thus Inversion occurs. As perhaps better described in the previously mentioned unpublished Thesis by Welch, it should be appreciated that the same Gate voltage is applied to Gates (G) in both Channel Regions (F1) and (F2). When the Gate Voltage is High at +V, electrons are attracted into both Cannels (F1) and (F2), which makes the Lower junction D2 Forward Biased, and when Gate Voltage is Low at Ground (or a negative value) Holes are pulled into both Channel Regions (F1) and (F2) the Upper junction (D1) is Forward-biased. In the First Case the voltage appearing at the Midpoint (MP) is Low and in the Second Cases the midpoint (MP) Voltage is high, thus Inversion is accomplished. It is also noted that an Off Side will present barriers to Conduction as a result of at least two sources. First a Channel Pinchoff Voltage (ΔV′), and Second a Channel Resistance (ΔV″) will be present.

[0049] It is noted that in Inventor Welch's earlier Single Device CMOS fabrication work under the previously mentioned DOE Grant, the two device channels (equivalent to the two FINS (F1) and (F2) were sequential, hence the Gate was split and the resulting S-CMOS devices were not very compact, much as is the case with conventional P-N Junction based CMOS systems. In the present Compact FINFET CMOS system however, the substantially parallel and adjacent FINS (Channels) (F1) and (F2) are present adjacent to one another, and operated from a single Gate (G) structure. This is why the present FINFET system is compact. The present Device Configuration is not, to Inventor Welch's knowledge, remotely suggested in any prior art. It was only because of Inventor Welch's prior experience that the Present Invention conceived. Note as well that no N and P-type wells are necessary to fabricate P and N Channel MOSFETS as now Claimed. Inventor Welch did his earlier DOE sponsored fabrication of Single Device CMOS on Intrinsic Silicon, (see his U.S. Pat. Nos. 6,624,493; 5,663,584; 5,760,449; 6,091,128 and 6,286,636) and the previously mentioned Unpublished Thesis, but it is thought that use of Compensated Semiconductor might provide benefit, though there was not time to try that prior work. This lack of the need for space consuming N and P-doped wells is another factor that enables the present system to be compact, and makes the present invention less energy intensive to realize. For emphasis, the major factor enabling the present invention is that some materials (M) form rectifying junctions with either N or P-type filed induced effective doping n a Channel region of a MOSFET. FIGS. 4 and 5 demonstrate the benefit that provides. A further consideration is that P-N junctions involve space-charge regions which limit how small a channel can be without punch-through occurring. This is not a problem where the junctions are hot carrier type as in the present invention. It is believed patentability attaches to the Present Invention as it overcomes many problems associated with previously known CMOS structures, while importantly, providing a very compact system via placement of channels adjacent to one another both of which are influenced by a single Gate (G).

[0050] It is noted that “substantially non-rectifying” and “Substantially ohmic” are to be read as equivalent herein.

[0051] The present invention in FIG. 2 can be viewed as a prior art FIG. 1 system in which the Drain (D) is replaced with a region of material (M) that forms rectifying junctions with both field induced N and P-type semiconductor, and the Gate (G) is expanded to cover more of the FIG. 1 FIN Channels (F's). Nothing in Hu et al. 802 or any other known reference remotely suggests that. Further nothing in Hu et al. 802 remotely suggests that one skilled in the art of FINFET systems should seek out material that forms rectifying junctions with both field induced N and P-type semiconductor. It is only because of Inventor Welch's experience and insight in the area that he conceived the present invention. Further, Inventor Welch has found that his idea of using material that forms rectifying junctions with both field induced N and P-type semiconductor seems not to have been generally appreciated by people involved in solid state device design. A Professor at Illinois University for instance, when asked by the Government to evaluate his work based on his first patent in the area using Silicon as the Semiconductor—thoroughly trashed it. When Inventor Welch phoned that Professor and walked him through it, he commented that he had completely missed the invention—and that Welch had performed Ph.D. level research. No further funding developed, however.

[0052] It is also noted that Terry J. Pirruccello is included as a Co-Inventor for conceiving fabricating the Welch CMOS in Silicon Carbide.

[0053] Having hereby disclosed the subject matter of the present invention, it should be obvious that many modifications, substitutions and variations of the present invention are possible in view of the teachings. It is therefore to be understood that the invention may be practiced other than as specifically described, and should be limited only in its breadth and scope only by the Claims.