Electronic device comprising enhancement mode pHEMT devices, depletion mode pHEMT devices, and power pHEMT devices on a single substrate and method of creation

The present invention comprises an integrated circuit fabricated on a single substrate where the integrated circuit comprises a first block comprising an enhancement mode pHEMT transistor on a substrate; a second block comprising a depletion mode pHEMT transistor on the substrate, the second block operatively connected to the first block; and a third block comprising a power pHEMT transistor on the substrate, the third block operatively connected to at least one of the first block and the second block. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope of meaning of the claims.

FIELD OF THE INVENTION

The present invention relates to integrated circuits, especially those capable of operating at high frequencies.

BACKGROUND OF THE INVENTION

Numerous integrated circuits have been proposed and fabricated over the years. As devices gain faster clock speeds, a need has arisen for integrated circuits that possess the ability to function at high clock speeds with appropriate power consumption and power generation.

Some circuits, e.g. analog/digital converters, typically operate at lower frequencies as the typical method of constructing such circuits involves using printed wiring boards which can limit the functional processing speed, lower frequency integrated circuits, or a combination thereof. These circuits typically have additional cost due to the cost of housing the separate components.

Over the years, specialized devices have been developed which lend themselves to a certain class or range of operation. Pseudomorphic high electron mobility transistor (pHEMT) devices are currently used for microwave and millimeter wave integrated circuit devices (MMIC) having extremely high performance. Frequencies typically range from X-band (8 GHz) to W-band (110 GHz) for such MMIC devices.

At least three different pHEMT devices are currently fabricated: enhancement mode pHEMT, depletion mode pHEMT, and power pHEMT.

SUMMARY

The present invention comprises an integrated circuit fabricated on a single substrate where the integrated circuit comprises devices comprising enhancement mode pHEMT, depletion mode pHEMT, and power pHEMT blocks, fabricated in a single process, wherein predetermined portions of the blocks may be interconnected to form a functional, operational electronic device.

The scope of protection is not limited by the summary of an exemplary embodiment set out above, but is only limited by the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now toFIG. 1, electronic device10comprises enhancement mode pHEMT20, depletion mode pHEMT30, and power pHEMT40fabricated onto a single substrate, e.g.50.

Depletion mode pHEMT30may be single or multiple recess pHEMT30. A typical circuit element using depletion mode pHEMT30is shown inFIG. 1a.

Referring now toFIG. 2, an operational integrated circuit may be fabricated which contains a plurality of functional blocks110,200,300,400to form a useful, operational electronic device. Functional blocks, generally referred to by200,300, and400, may comprise enhancement mode pHEMT blocks200comprising enhancement mode pHEMT20(shown in an exemplary layout inFIG. 3), depletion mode pHEMT blocks300comprising depletion mode pHEMT30(shown in an exemplary layout inFIG. 4), power pHEMT blocks400comprising power pHEMT40. Other circuit blocks may be present as well, e.g. blocks100. A plurality of blocks, e.g. integrated circuits, may therefore be present on a single substrate50(FIG. 1), at least one of the plurality of blocks100,200,300,400comprising enhancement mode-pHEMT20, a further one of the plurality of blocks comprising depletion mode pHEMT30, and yet a further one of the plurality of blocks comprising power pHEMT40. Blocks100,200,300,400may be operatively interconnected, e.g. one or more devices and/or circuits in enhancement mode pHEMT block200may be operatively interconnected to one or more devices and/or circuits in depletion mode pHEMT block300and/or one or more devices and/or circuits in power pHEMT block400such as with conductive traces.

Functional blocks200,300,400may themselves comprise higher level functional logic, e.g. may comprise digital gates, serial shift registers, serial to parallel converters, parallel to serial converters, level shift registers, variable gain radio frequency (RF) amplifiers, variable RF phase shifters, variable RF attenuators, resistors, inductors, capacitors, and the like, or combinations thereof.

For example, referring additionally toFIG. 2a, analog inputs52may be fabricated and interconnected with at least one of enhancement mode pHEMT block200, depletion mode pHEMT block300, power pHEMT block400, circuit block110, or a combination thereof. Circuit block110may further comprise clock input56in communication with at least one of enhancement mode pHEMT block200, depletion mode pHEMT block300, power pHEMT block400, or a combination thereof. Digital input54may be further fabricated to be in communication with at least one of enhancement mode pHEMT block200, depletion mode pHEMT block300, power pHEMT block400, or a combination thereof. One or more outputs of the functional circuitry may be fabricated as well, e.g. radio frequency output58.

Referring back toFIG. 2, when fabricated, functional blocks110,200,300,400may then be interconnected to form an active or passive electronic device, e.g. an analog to digital converter or a microwave and millimeter wave integrated circuit (MMIC). Devices fabricated according to the present invention comprise an operational circuit, i.e. active or passive electronic devices, capable of operating at a frequency within the range of from very low frequency up to and including X-band frequencies.

Referring additionally toFIG. 3andFIG. 4, each functional block200,300,400may comprise one or more active devices, e.g. as shown inFIG. 3enhancement mode pHEMT block200may comprise a plurality of enhancement mode pHEMT devices20. As shown inFIG. 4, depletion mode pHEMT block300may comprise a plurality of depletion mode pHEMT devices30. In a preferred embodiment, power mode pHEMT block400may be laid out similarly to depletion mode pHEMT block300.

Additional elements consisting of resistors, capacitors and inductors may be included in all blocks. Referring additionally toFIG. 7, resistor, capacitor and inductor contacts may be formed, at step618. A nitride layer may be formed, step620, to form a capacitor dielectric as well as an inductor spacer. A top contact may be formed, at step622Metal1. Resistors may be formed, e.g. at step616.

FIG. 5aillustrates an exemplary gain stage of an exemplary pHEMT device10.FIG. 5billustrates an exemplary three input AND cell of an exemplary pHEMT device10.

In the operation of an exemplary embodiment, referring now toFIG. 6and.FIG. 2, in a preferred embodiment, electronic device10(FIG. 2) may be created in a single fabrication process to form one or more functional blocks100,200,300,400(FIG. 2) where functional blocks100,200,300,400can be combined to create an operational device, e.g. device10. An operational integrated circuit10may be fabricated according to the present invention in a single fabrication process by creating, at step500, first block200comprising a pHEMT enhancement mode transistor20on substrate50; using the same fabrication processing, creating, at step502, second block300comprising a pHEMT depletion mode transistor30on substrate50, where second block300is operatively connected to first block200; and, using the same fabrication processing, creating, at step504, third block400comprising a power pHEMT transistor30on substrate50, third block400operatively connected to at least one of first block200and second block300. Additional functional blocks100may be fabricated in the same fabrication process. The order in which blocks100,200,300,400are created is not material.

In a currently preferred embodiment, logic circuitry design utilizes a four μm spacing for all interconnects. For depletion mode pHEMT30, a single recess is preferred where Vp=one tenth of a volt (0.1v). For enhancement mode pHEMT20, a single recess is also preferred where Vp=a negative one volt (−1v). For power pHEMT30, a double recess is preferred where Vp=a negative one volt (−1v).

Referring now toFIG. 6andFIG. 1, in a preferred embodiment a triple etch-stop process is employed in fabricating device10(FIG. 1), e.g. to create wide recess, e-mode, and d-mode gates. An ohmic layer may be created,600, on substrate50(FIG. 1) and devices20,30,40(FIG. 1) isolated, at step602. A typical recess is illustrated at40inFIG. 1, and a wide recess,604, illustrated at20inFIG. 1. Thickness of layers, e.g.60,61,62(FIG. 1) may be fine tuned to meet pinch-off voltage specifications.

A first T-gate, as that term is understood by those of ordinary skill in the art, may then be fabricated, step606, typically for all devices to be fabricated according to the present invention. Gate recess and metal may be fabricated,608. Optionally, a second T-gate pass,610, and gate recess and metal,612, may be fabricated.

Additional elements consisting of resistors, capacitors and inductors may be included in all blocks. Additional layers may be fabricated on substrate50, step614, and various additional devices fabricated, e.g. resistors at step616. These additional layers may be created on substrate50to form resistors, capacitors, and inductors, e.g. steps616-622. Referring still toFIG. 6, resistor, capacitor and inductor contacts may be formed, at step618. A nitride layer may be formed, step620, to form a capacitor dielectric as well as an inductor spacer. A top contact may be formed, at step622Metal1. Resistors may be formed, e.g. at step616.

An MIM top metal layer may be created,626followed by an air bridge metal layer,628, and a protective overcoat,630. Various finishing operations may then be accomplished, e.g. steps634-642.

Using the present inventions method of fabrication, one watt power amplifiers, small signal monolithic microwave and millimeter wave integrated circuits (MMICs), and control circuits may be integrated on a single substrate such as substrate50(FIG. 1). One such device10may be an analog to digital converter (A/DC) capable of operating a X-band frequencies, e.g. up to 10 GHz. However, as will be appreciated by those in the art, functional blocks100,200,300,400may be combined in numerous ways to form numerous circuits, e.g. devices10combining digital, radio frequency (RF), and power functional blocks100,200,300,400on common substrate50. Moreover, A/DC devices10could be integrated into an even higher function device10, e.g. one that may be used to replace heterodyne receiver technology and have complete integration of RF to Receiver I and Q data on one chip, e.g. a receiver on a chip.

It will be understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated above in order to explain the nature of this invention may be made by those skilled in the art without departing from the principle and scope of the invention as recited in the following claims.