EP3417483A1 - Electromechanical transducer based on doped gallium nitride - Google Patents
Electromechanical transducer based on doped gallium nitrideInfo
- Publication number
- EP3417483A1 EP3417483A1 EP17705116.6A EP17705116A EP3417483A1 EP 3417483 A1 EP3417483 A1 EP 3417483A1 EP 17705116 A EP17705116 A EP 17705116A EP 3417483 A1 EP3417483 A1 EP 3417483A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- layer
- layers
- electrodes
- stack
- semiconductor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 229910002601 GaN Inorganic materials 0.000 title description 32
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 title description 5
- 239000004065 semiconductor Substances 0.000 claims abstract description 49
- 239000000463 material Substances 0.000 claims abstract description 39
- 239000000758 substrate Substances 0.000 claims abstract description 26
- 239000007789 gas Substances 0.000 claims abstract description 21
- 239000002800 charge carrier Substances 0.000 claims abstract description 13
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 13
- 229910052782 aluminium Inorganic materials 0.000 claims description 12
- 230000005669 field effect Effects 0.000 claims description 11
- 229910045601 alloy Inorganic materials 0.000 claims description 9
- 239000000956 alloy Substances 0.000 claims description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 6
- 229910052796 boron Inorganic materials 0.000 claims description 6
- 229910052733 gallium Inorganic materials 0.000 claims description 6
- 229910052738 indium Inorganic materials 0.000 claims description 6
- 239000002019 doping agent Substances 0.000 claims description 5
- 239000012528 membrane Substances 0.000 claims description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052737 gold Inorganic materials 0.000 claims description 3
- 239000010931 gold Substances 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 239000010410 layer Substances 0.000 description 203
- 101150080264 nit2 gene Proteins 0.000 description 12
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 9
- 239000010703 silicon Substances 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- 150000004767 nitrides Chemical class 0.000 description 8
- 230000008901 benefit Effects 0.000 description 6
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- 238000004519 manufacturing process Methods 0.000 description 6
- 239000000969 carrier Substances 0.000 description 5
- 238000000151 deposition Methods 0.000 description 5
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- 230000010354 integration Effects 0.000 description 5
- 230000004888 barrier function Effects 0.000 description 4
- 239000012159 carrier gas Substances 0.000 description 4
- 230000008021 deposition Effects 0.000 description 4
- 230000033001 locomotion Effects 0.000 description 4
- 230000006911 nucleation Effects 0.000 description 4
- 238000010899 nucleation Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000001451 molecular beam epitaxy Methods 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
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- 239000012535 impurity Substances 0.000 description 2
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- 239000007924 injection Substances 0.000 description 2
- 238000004377 microelectronic Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 230000001154 acute effect Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
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- 239000013078 crystal Substances 0.000 description 1
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- 238000006731 degradation reaction Methods 0.000 description 1
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- 230000008030 elimination Effects 0.000 description 1
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- 238000005530 etching Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000002513 implantation Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
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- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
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- 239000002356 single layer Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 230000002463 transducing effect Effects 0.000 description 1
- 230000026683 transduction Effects 0.000 description 1
- 238000010361 transduction Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 230000005533 two-dimensional electron gas Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/84—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by variation of applied mechanical force, e.g. of pressure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/0657—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape of the body
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/778—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface
- H01L29/7786—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/1051—Piezoelectric or electrostrictive devices based on piezoelectric or electrostrictive films or coatings
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
- H10N30/204—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators using bending displacement, e.g. unimorph, bimorph or multimorph cantilever or membrane benders
- H10N30/2041—Beam type
- H10N30/2042—Cantilevers, i.e. having one fixed end
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
- H10N30/302—Sensors
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N39/00—Integrated devices, or assemblies of multiple devices, comprising at least one piezoelectric, electrostrictive or magnetostrictive element covered by groups H10N30/00 – H10N35/00
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/08—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions with semiconductor regions connected to an electrode carrying current to be rectified, amplified or switched and such electrode being part of a semiconductor device which comprises three or more electrodes
- H01L29/0843—Source or drain regions of field-effect devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/20—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIIBV compounds
- H01L29/2003—Nitride compounds
Definitions
- Electromechanical transducer based on doped gallium nitride.
- the present invention relates to a stack of semiconductor layers, intended for the production of a microelectromechanical device, for example a transducer, comprising at least three semiconductor layers supported by the same substrate, one of these layers consisting of a doped piezoelectric semiconductor III-N material.
- Microelectromechanical transducers make it possible to convert a mechanical quantity into an electrical signal, and vice versa.
- MEMS Microelectromechanical transducers
- These devices have undergone significant development in recent decades. Manufactured using techniques borrowed from microelectronics, these devices typically comprise submillimeter-sized mechanical elements (embedded beams, membranes, etc.), as well as actuators for moving mechanical elements and / or sensors to detect the movement of mechanical elements.
- NEMS for Nano-Electro-Mechanical Systems in English.
- the terms "MEMS” and "micromechanical device” will be used in a broad sense, including nanoelectromechanical devices and systems (NEMS).
- Motion detection at the micromechanical scale still faces significant difficulties, which limit the potential of microelectromechanical systems.
- the difficulties are mainly due to the fact that the output signal of a miniaturized sensor is generally of very low amplitude, and is therefore strongly affected either by the thermal noise, or by the impedance of the cables or the measuring circuit which can be deported. This problem is particularly acute in the case of small sized MEMS which must operate at temperatures above 150 ° C.
- transducers are made on semiconductor substrates.
- silicon-based piezoresistive transducers are among the most widely used devices in the electronics industry. These sensors may comprise doped zones, for example by phosphorus, boron, or arsenic. This doping makes it possible to define ohmic contacts or to achieve the integration of piezoresistive transducers, either by the arrangement of co-integrated transistors.
- WO2012 / 107888 discloses a MEMS comprising a first layer of GaN deposited on a silicon substrate, a second layer of AIGaN deposited on this first layer, and an actuating structure.
- the combination of these different semiconductor and piezoelectric materials forms a heterostructure, and allows to confine a two-dimensional charge carrier gas between the two layers, producing a conduction channel with high electron mobility.
- An intrinsic characteristic of such a conduction channel is defined by the sheet resistance R s , measured in ohms.
- the two-dimensional carrier gases can be exploited for the design of HEMT electronic high-mobility field effect transistors (for High-electron-mobility transistor in English), allowing the realization of high-performance mechanical stress sensors.
- these two-dimensional gases can be present at rest, or obtained by the application of a potential difference across the device.
- the document US2007 / 017621 1 thus discloses micro-beam type MEMS, made in AIGaN / GaN heterostructure, and in which the movements of the micro-beam are detected using a HEMT type transistor integrated into the beam. heterostructure.
- heterostructures such as Al x Ga-i- x N (with x a number between 0.2 and 0.3), make it possible to have a two-dimensional gas of carriers whose sheet resistance is between 300 and 500 ohms for HEMTs.
- high x values are involved, which creates mechanical stresses and / or other difficulties in epitaxial growth.
- the concentration of carriers is also limited in this type of heterostructure by the physical properties of materials such as spontaneous polarization and the thickness of the barrier layer.
- mobility is limited.
- the operation of such devices in the presence of temperatures above 150 ° C remains difficult to implement with these technologies because they are limited by the metallurgies used, which lead to the occurrence of electrical failures.
- the present invention therefore aims to solve the aforementioned drawbacks by modifying the architecture of the microelectromechanical devices known from the state of the art.
- the invention proposes a stack of semiconductor layers comprising: a substrate; a first layer of a semiconductor material deposited on said substrate; a second layer of a semiconductor material deposited on said first layer; a third layer of a semiconductor material deposited on said second layer; and characterized in that at least one of the first, second and third layers is consisting of a piezoelectric semiconductor material doped to produce a very large number of electric charge carriers.
- said stack further comprises at least one suspended element formed by extensions of one or more of said layers extending beyond an edge of said substrate, said suspended element being embedded on part of its perimeter at the level of said edge, and preferably has a shape selected from: a beam; a membrane; a disk ; or a plate.
- the third layer has a thickness of between 0.05 and 20 microns ( ⁇ ), preferably 0.1 to 2 microns ( ⁇ ).
- ⁇ microns
- the first layer and the second layer are combined.
- At least one of said first, second and / or third layer is made of a type III-N material, the group III element being selected from Al, Ga, In, B or any alloy thereof.
- the elements used for doping the material of at least one of the first, second and third layers are chosen from Si, Ge, O and Mg.
- said third layer is made of doped GaN.
- the third layer is characterized by a concentration of doping elements of between 10 18 and 10 21 per cm 3 .
- said third layer is electrically connected to at least one electrical conduction channel, said electrical conduction channel extending in said second layer.
- said second layer comprises a heterostructure confining a two-dimensional charge carrier gas (2DEG), said two-dimensional gas forming electric conduction channel.
- the present invention also relates to a microelectromechanical device comprising such a stack of semiconductor layers, and and further comprising at least two electrodes, at least two of said electrodes being connected to said second layer, and / or to said third layer, and / or a two-dimensional gas of charge carriers.
- at least one of the electrodes is made of doped GaN.
- said electrodes extend at least partially over a surface of said third layer and / or said second layer.
- each of said electrodes comprises at least one extension which extends to the surface of said suspended element, and is electrically connected to the third layer.
- at least one of said electrodes is an ohmic contact, the material constituting said ohmic contact being preferably selected from titanium, nickel, aluminum or gold.
- said electrodes form the contacts of a field effect transistor.
- the doping of element III nitrides constitutes a particularly innovative approach.
- the electrical properties of a stack of semiconductor layers including a gallium nitride GaN layer, in particular, can be modified by appropriate doping, which makes it possible to adjust the electrical resistivity of the device over a wide range of values.
- the MEMS transducers according to the invention are characterized in that at least one of the first, second and third layers is made of a doped piezoelectric semiconductor material.
- the present invention relates to a microelectromechanical device whose operation combines both the realization of a heterostructure of elements III-N and the doping of a semiconductor and piezoelectric material within the same transducer.
- FIG. 2 a sectional view of an exemplary microelectromechanical device according to the state of the art.
- FIG. 5a and 5b respectively, a plan view and a sectional view of a microelectromechanical device according to a second embodiment of the invention.
- FIG. 6 is a plan view of a microelectromechanical device according to a third embodiment of the invention.
- FIG. 7 a plan view of a microelectromechanical device according to a fourth embodiment of the invention.
- FIG. 8 a plan view of a microelectromechanical device according to a fifth embodiment of the invention.
- the design of the MEMS is generally based on the stacking of different piezoelectric semiconductor layers. This stack of layers makes it possible to produce a conduction channel favoring the passage of an electric current, with a determined electrical resistance. This resistance is likely to vary by piezoelectric effect when the device is subjected to mechanical stress.
- a MEMS can convert a mechanical quantity into an electrical signal such that, for example, it can be used as an acceleration sensor.
- a MEMS can serve as an actuator to produce a mechanical displacement when applying an electric current and / or a potential difference.
- FIG. 1 shows a stack of semiconductor and piezoelectric layers according to the state of the art.
- this device comprises a heterostructure for confining a two-dimensional charge carrier gas.
- the stack of layers is made from a substrate Sub, composed of silicon Si for example.
- This substrate is etched chemically, lithographically or by any other means.
- the Sub layer is etched so as to release a nitride layer structure of elements III.
- These layers consist for example of GaN, AlN, InN or any alloy of elements of type III-N. These elements have the property of being both semiconductor and piezoelectric materials.
- a first Naked layer extends on the Sub substrate.
- This layer may be composed of GaN or AlN, produced by chemical vapor deposition (or CVD, for Chemical Vapor Deposition), or by molecular beam epitaxy (or MBE, for Molecular Beam Epitaxy) at high temperature.
- a Nit layer called a "buffer" layer, extends over the Naked layer.
- This Nit layer is composed of a nitride alloy of elements Ga, Al, In and / or B, for example GaN. This layer ensures a smooth transition between several materials with a different crystalline structure.
- the stack may also include one or more additional layers to promote oriented growth of the upper layers by epitaxy.
- a Nit2 layer called "barrier" layer and composed of an alloy containing aluminum such as AlInGaN or AIGaN extends over the Nit layer and has a thickness typically between 15 and 30 nanometers.
- the stack of several layers of semiconductor materials of different nature, for example Si for the substrate, GaN for the nucleation layer and / or the Nit layer, and AIGaN for the Nit2 barrier layer makes it possible to form a heterostructure.
- This heterostructure confines a two-dimensional charge carrier gas, more precisely a two-dimensional electron gas 2DEG (2DEG, for 2-Dimensional Electron Gas in English), in the upper part of the Nit layer.
- This two-dimensional gas is symbolically represented by a region delimited by a dashed line in FIG.
- Charge carriers move in the 2DEG layer, and benefit significantly from electronic mobility greater than that of the other layers of the device.
- Such a two-dimensional carrier gas can be exploited to produce, for example, a field effect transistor of the HEMT type which constitutes an excellent mechanical stress sensor.
- the materials used to constitute the different layers of this device are semiconductors and piezoelectric.
- a deformation occurs in the material composing the layer including the 2DEG layer, for example under the effect of an external mechanical stress, this results in a change in the number of charge carriers.
- This modification results in a modulation of the electrical conductivity of the layer, in proportion to the corresponding stress.
- This so-called piezoresistive effect allows the realization of an electromechanical transducer of the MEMS type.
- FIG. 2 is a sectional view of a microelectromechanical transducer according to the state of the art, in particular a sensor or a piezoelectric actuation structure comprising a field effect transistor.
- the Naked and Nit layers rest on the Sub substrate.
- the Sub layer serves as a mechanical support for the transducer.
- Above the Nit layer extends a Nit2 layer.
- the Nit2 layer is composed of a piezoelectric semiconductor material different from the semiconductor material making up the Nit layer, and is of a lower thickness than the Nit layer.
- the heterostructure formed by the junction of the Nit layer and the Nit2 layer optionally makes it possible to confine a two-dimensional gas of 2DEG carriers, which can form a conduction channel under the upper face of the transducer.
- the transducer shown in FIG. 2 integrates a suspended element P, typically a mobile structure of any shape.
- P is formed by the extension of one or more of the Nue, Nit, and Nit2 layers as previously described, and extends beyond one of the E edges of the Sub substrate. The dimensions of these different layers are determined during the manufacture of the transducer.
- the suspended element P may be formed of a beam embedded in one or both of its ends, a membrane, a disk, plate, or any other type of structure embedded in a part of its perimeter at one of the edges E. This suspended element P can be either rigid or deformable under stress.
- Electrodes can be integrated in this structure. These electrodes can form one or more transistors with the layers Nit and Nit2. The integration of these electrodes can be done by means of different manufacturing steps, including one or more phases of deposition, stoving, cooking, polymerization and / or elimination phases of any sacrificial layers.
- this transistor is for example a field effect transistor.
- the electrodes of this field effect transistor called drain D, source S and gate G, are integrated in the upper layers of the transducer, for example the Nit2 layer and / or 2DEG bidimensional gas.
- the electrodes S and D are arranged to be in contact with the two-dimensional carrier gas confined in the stack of the Nit and Nit2 layers, while the electrode G extends only on the Nit2 layer.
- This variation in conductivity generates a measurable electrical signal at the electrodes of the transistor.
- This device is equivalent to a variable electrical resistance R.
- R variable electrical resistance
- MEMS operating as a sensor
- the injection of an electric current and / or the application of a potential difference at its terminals makes it possible to generate a mechanical movement inside the layer, which in turn allows to cause an actuation of the mobile part of the MEMS, for example a flexion of the beam P.
- the electrical resistivity of the 2DEG two-dimensional gas can be characterized by a sheet resistor R s.
- This resistance is defined in ohms per square because it corresponds to the value of the electrical resistance of the layer measured between two contacts spaced by a distance equal to their width.
- the electron mobility of a doped semiconductor layer is generally less than the electron mobility of a two-dimensional carrier gas.
- the object of the present invention is thus to propose an electromechanical device having improved performances compared to the MEMS known from the state of the art.
- the use of doped piezoelectric materials constitutes an advantageous solution for producing a piezoresistive transducer.
- the use of particular properties of doped gallium nitride GaN makes it possible to fix the density of carriers in the two-dimensional channel.
- the properties of the present invention make it possible to ensure a transducing effect by screening the piezoelectric charge, similarly to the transduction effect that can be generated by a GaN / AIGaN type heterostructure. This use also allows the realization of a device characterized by a low electrical resistance. In addition, the realization of a heterostructure freeing the 2DEG layer for the realization of microelectronic devices more efficient than the current MEMS, is an advantage of the present invention.
- the inventors have found that the deposition of a doped GaN semiconductor layer on an undoped GaN layer makes it possible to perform a MEMS overcoming the aforementioned technical difficulties. Improving the transport of charge carriers within a doped medium makes it possible to overcome several known technical limitations of current MEMS in terms of electronic performance, in particular to reduce the electrical resistivity of the device and to facilitate the manufacture of contacts to electrically connect the transducer to the outside world. This makes it possible to increase the sensitivity of MEMS as a sensor and / or actuator.
- FIG. 3 illustrates a sectional view of a stack of semiconductor layers according to the invention.
- a stack of Naked and Nit layers is formed on a substrate Sub to produce a suspended element P.
- This suspended element is embedded on a part of its perimeter and may be a beam, a membrane, a disk or a plate.
- the Sub layer consisting for example of silicon, serves both as a mechanical support and electrical insulator for the upper layers of the stack.
- the bare layer extends at least partially on the Sub layer and forms a so-called nucleation layer.
- This bare layer may be either a silicon layer, for example the active layer of a SOI substrate (silicon on insulator), or a layer of element nitrides (Ga, Al, In, B), or another material to even to improve crystal growth on the Sub layer (cubic SiC, rare earth oxide, etc.). Naked can be configured to promote nucleation.
- Nue is characterized by a thickness of between 0.01 and 1 microns ( ⁇ ), and preferably between 0.05 and 0.1 microns ( ⁇ ).
- the Nit buffer layer which extends over the Naked layer is composed of an alloy of element nitrides (Ga, Al, In, B). This alloy is preferably composed of undoped GaN.
- the first layer Nue and the second layer Nit can be combined into a single layer, for example a Nit layer.
- An SD layer extends over the Nit layer.
- an SOI substrate can serve as a support for the Nit layer and / or the SD layer.
- the SD layer is a semiconductor layer having the particularity of being doped. The doping of the SD layer may be n-type or p-type, preferably n-type.
- This doping can be obtained by incorporating the dopants (impurities) during the growth of the layer ("in situ" doping), by modifying the growth conditions to incorporate electrically active defects (gaps, complexes) or by implantation.
- the impurities used for the doping may be chosen from the following elements: Si, Ge, O and Mg.
- the SD layer may be partially etched to promote the conduction of electric currents on the suspended structure P.
- the SD layer is a GaN gallium nitride semiconductor layer having the particularity of being doped.
- the dopant concentration of the SD layer is preferably between 10 18 and 10 21 per cm 3.
- the SD layer may be electrically connected to one or more electrical conduction channels, or these channels may extend into the Nit layer. .
- the doping of one or more semiconductor layers, such as the SD layer, or the increase of their thickness, makes it possible to increase the electrical conduction of one or more channels by reducing the sheet resistance R s .
- the ability to design a device with a square resistance that can be selected as less than 400 ohms per square is an important technical advantage of the invention.
- the SD layer here plays an essential role for the operation of the microelectromechanical device as a transducer. When a stress is applied perpendicular to the plane of the layer, this strain produces a variation of electrical conductivity in SD, which can be measured.
- the possibility of modulating the doping concentration and the thickness of the layer makes it possible to fix this electrical conductivity, and therefore the electrical resistance of the device. It will be noted that the realization of this stack does not impose constraints on the relative lengths of the Nue, Nit and SD layers, and that different types of architectures are possible.
- the deposition of a doped layer of GaN is possible on all or part of the stack of layers constituting the suspended element P.
- the mobile part of P can be obtained by etching an insulating layer .
- a plurality of electrodes may be integrated in the layers of the stack to produce a transducer from the stack of semiconductor layers shown in FIG.
- FIG. 4 illustrates a sectional view of an electromechanical device according to a first embodiment of the invention.
- the invention incorporates the presence of an SD doped layer superimposing the stack of Sub, Naked and Nit layers.
- This SD layer is discontinuous and has several disjoint SD layer elements.
- one of these layer elements can be formed in the stack of layers constituting the beam P and another of these layer elements can be formed in the stack of layers superimposing the Sub substrate.
- the arrangement and extent of these SD layer elements may vary according to the architectures of the invention.
- the SD layer consists of doped GaN.
- the SD layer can serve as a contact layer for integrating a plurality of electrodes.
- any part of the SD layer lying on the moving part of the transducer that is to say on extensions of one or more layers extending beyond the edge E, may serve as piezoresistance for said transducer.
- the integration of a field effect transistor can be carried out using source electrodes S, gate G and drain D integrated in the transducer.
- the electrodes S and D are connected to the SD layer in order to make electrical contact with the material making up this layer.
- the electrodes S and D may be separately integrated with two of said disassembled layer elements of the SD layer.
- An electrical conduction channel is present between these disjointed layer elements.
- a 2DEG bidimensional gas may be present in the Nit layer, and may form an electrical conduction channel between said layer elements.
- the gate electrode G possibly consisting of a material different from that constituting the contacts S and D, extends on a surface of the Nit layer and makes it possible to modulate the passage of the current in said conduction channel.
- the electrode G is electrically connected to the Nit layer.
- the field effect transistor consisting of the electrodes S, G and D allows the operation of the device as a microelectromechanical transducer. These electrodes make it possible to inject an electric current into the transducer, to detect and / or to actuate any displacements of the mobile part P. We describe these functions in the context of FIG. 5.
- the contacts S and D of this transistor can be made by depositing a metal such as titanium, aluminum, on the upper surface of the device. This deposit may be followed by an annealing step to allow diffusion of the dopants in the semiconductor material. Preferably, these steps are performed so that the contact or contacts formed are characterized by a very low resistivity. The minimization of the electrical resistivity of these so-called ohmic contacts makes it possible to facilitate the injection and / or the extraction of an electric current in the device.
- the SD layer may have one or more functions: forming an electrical conduction channel on the suspended element P serving as a transducer, and / or constitute a layer forming an electrical contact with the channel of said transistor.
- Figures 5a and 5b respectively show a sectional view and a plan view of a MEMS device according to a second embodiment of the invention.
- the functional part of a transducer according to the invention is integrated in a suspended structure P, for example a semi-recessed beam, obtained by epitaxial semiconductor layers on a silicon Sub substrate.
- the substrate and the suspended structure comprise a stack of Nue, Nit and SD semiconductor layers similar to that described for the first embodiment of the present invention.
- the SD layer may be partially etched and located at least partially on the suspended element P.
- the two layers Nit and SD are, for example, consist of undoped GaN and doped GaN, respectively, and extend over the Sub substrate. These layers extend beyond the edge E delimiting the support of P on S and / or one or more of the layers of the stack, to form the mobile mechanical structure of the device.
- the functional part of the transducer also comprises at least two electrodes C01 and C02. These electrodes extend at least partially on a surface of the SD layer and / or the Nit layer. Typically, C01 and C02 can form expanded metal areas on the surface of the contact layer, and allow to lay a tip or perform a micro-welding.
- the electrodes C01 and C02 may also include extensions PL1 and PL2, for example two metal tracks extending on the surface of the suspended element P.
- the elements C02 and PL2 are not shown.
- the extensions PL1 and PL2 are at least partially electrically connected to the SD layer.
- the electrical contacts are subjected to a potential difference ⁇ V, for example by means of a voltage generator.
- the electrode C01 is connected to a reference of mass.
- the CO 2 electrode can be connected to an electronic circuit, for example a set of bias elements, to fix the operating point of the transducer.
- These biasing elements typically comprise one or more sources of voltage or current, a set of one or more electrical resistors, one or more capacitors and / or one or more inductors.
- an electric current can be injected into one of the two electrical contacts, for example CO 2. Under the effect of a potential difference applied, this current flows through the metal track PL2 towards the beam P. It then flows in the stack towards the lower part of P, and passes through the SD layer perpendicular to the plane of layer. When it reaches the lower part of the SD layer, the electric current then rises towards the upper part of the stack to join the metal track PL1, and flows in the plane to join the contact C01.
- the electrical contacts form the operating electrodes of the device and are preferably ohmic contacts.
- these ohmic contacts are metal-semiconductor contacts promoting the passage of an electric current in the device with a contact resistance as low as possible.
- These ohmic contacts can be obtained by deposition of metal, for example titanium, nickel, aluminum or gold, on the upper surface of the SD layer. After this deposit, the contacts are annealed to facilitate the diffusion of the metal, which reduces the specific contact resistance.
- the electrical connection connected to the transducer can also be adapted according to the required applications.
- the device can be connected to different types of electrical fixtures, such as a measurement system comprising an ammeter, an ohmmeter and / or a voltmeter.
- a voltmeter will be used as a measuring device for measuring the voltage variations produced at the terminals of the transducer when the beam flexes.
- Other electrical assemblies of the MEMS are possible depending on the desired applications, for example as a Wheatstone bridge.
- the architectures allowed for these embodiments make it possible to produce devices in which the surface bulk of the suspended element P is not limited by the dimensions of the Sub substrate.
- the lateral space is often limited because of the small surface available on the upper faces of the moving part.
- the dimensions of the conductive strip must also be small enough to avoid producing an electrical short circuit, which is a well known technical limitation of the transducers made in the current MEMS.
- Figure 6 illustrates a plan view of a third embodiment of the invention.
- the SD layer is etched in a loop pattern, a significant portion of the loop extending over the suspended portion P.
- the loop ends with two larger surface portions in the loop. SD material, positions on which ohmic contacts C01 and C02 are formed.
- FIG. 7 illustrates a plan view of a fourth embodiment of a transducer according to the invention, in which the SD layer is discontinuous and has two disjoint parts which extend on the beam P.
- the 2DEG bidimensional gas of which the outline is shown in dashed lines in FIG. 7, is located in the Nit layer located under the visible plane of the SD layer.
- an electric current injected into the electrode C01 successively passes through the extension PL1, the part of the SD layer on which PL1 extends, and descends in the two-dimensional gas 2DEG.
- the electric current then rises in the portion of the SD layer on which PL2 extends, then passes through PL2 before reaching the CO 2 contact.
- the current flows in these layers according to the geometry of the component and can be extracted by the electrodes C01 or C02.
- FIG. 8 illustrates a microelectromechanical device according to a fifth embodiment of the invention for producing a transducer.
- a Nit layer made for example of undoped GaN, superimposes a stack of layers as described above.
- the integration of a transducer which extends on a movable beam P and the integration of a field effect transistor are made from a single SD-doped semiconductor layer.
- a doped semiconductor layer SD1 extends in part on the beam P.
- Two Bias + and Bias- pads extend on a surface of said layer SD1.
- Said Bias + and Bias-pads form electrodes of said transducer, and are preferably made on the non-released part of the transducer on the beam P. Said electrodes allow the operation of the transducer by means of a potential difference applied thereto .
- SD2 and SD3 layer elements of a doped semiconductor material extend over the surface of the Nit layer.
- a two-dimensional 2DEG gas is located in the Nit layer located under the visible plane of the SD2 and SD3 layers, and between SD2 and SD3.
- a field effect transistor consisting of electrodes S, G and D is thus produced.
- the electrodes do not extend beyond the edge E on the beam P.
- the source S and drain D electrodes extend over the disjoint layer elements SD2 and SD3.
- the gate electrode G of the transistor extends along one or more interconnection extensions IC.
- This interconnection IC is an electrode formed of a metal or the same material as the SD layer, and connects the gate G of the transistor to the Bias-metallic stud of the transducer.
- the doped layers SD1, SD2 and SD3 here allow both the operation of the transducer on the beam P and the formation of an intermediate contact layer between the transistor's electrical conduction channel and the source S and drain D electrodes.
- the embodiments described in the present invention make it possible to design MEMS characterized by electrical resistances of less than 100 ohms per square.
- transistors whose conduction channel has a low electrical resistance, as close as possible to 50 ohms.
- These ranges of resistors are particularly interesting for the development of components capable of providing a high electrical measurement bandwidth, or for the operation of transducers under extreme temperature conditions.
- This technical advantage is also of considerable interest for interfacing transducers with other electronic components, in various architectures and operating configurations.
- the possibility of reducing the electrical resistance of such transducers as a function of the doping level of the GaN layers present, independently of the other parameters, advantageously reduces the thermal noise generated by these devices.
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR1651291A FR3047841B1 (en) | 2016-02-17 | 2016-02-17 | ELECTROMECHANICAL TRANSDUCER BASED ON GALLIUM NITRIDE DOPE. |
PCT/EP2017/053263 WO2017140664A1 (en) | 2016-02-17 | 2017-02-14 | Electromechanical transducer based on doped gallium nitride |
Publications (1)
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EP3417483A1 true EP3417483A1 (en) | 2018-12-26 |
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EP17705116.6A Withdrawn EP3417483A1 (en) | 2016-02-17 | 2017-02-14 | Electromechanical transducer based on doped gallium nitride |
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EP (1) | EP3417483A1 (en) |
FR (1) | FR3047841B1 (en) |
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KR100388011B1 (en) * | 2000-01-17 | 2003-06-18 | 삼성전기주식회사 | SAW Filter by GaN single crystal thin film and A Method for Manufacturing It |
US6647796B2 (en) * | 2000-08-11 | 2003-11-18 | California Institue Of Technology | Semiconductor nitride pressure microsensor and method of making and using the same |
EP1606600A2 (en) | 2003-03-18 | 2005-12-21 | Microgan GmbH | Sensor element with self-supporting bar structures made of group iii nitride based semiconductors |
WO2007131796A2 (en) * | 2006-05-17 | 2007-11-22 | Microgan Gmbh | Micromechanical actuators consisting of semiconductor compounds based on nitrides of main group iii elements |
JP2011077386A (en) * | 2009-09-30 | 2011-04-14 | Sumitomo Electric Ind Ltd | High electron mobility transistor, epitaxial substrate, and method of manufacturing high electron mobility transistor |
FR2971243B1 (en) | 2011-02-09 | 2013-03-08 | Centre Nat Rech Scient | MICROELECTROMECHANICAL DEVICE WITH PIEZOELECTRIC ACTUATION STRUCTURE |
US9147740B2 (en) * | 2012-07-03 | 2015-09-29 | Infineon Technologies Austria Ag | Stress-controlled HEMT |
JP2015177067A (en) * | 2014-03-14 | 2015-10-05 | 株式会社東芝 | semiconductor device |
KR102475233B1 (en) * | 2015-06-26 | 2022-12-09 | 인텔 코포레이션 | Group III-N MEMS Structures on Group IV Substrates |
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2017
- 2017-02-14 WO PCT/EP2017/053263 patent/WO2017140664A1/en active Application Filing
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FR3047841B1 (en) | 2018-05-25 |
WO2017140664A1 (en) | 2017-08-24 |
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