CN108807519B - Electronic Fabry-Perot interference device and preparation method thereof - Google Patents
Electronic Fabry-Perot interference device and preparation method thereof Download PDFInfo
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66977—Quantum effect devices, e.g. using quantum reflection, diffraction or interference effects, i.e. Bragg- or Aharonov-Bohm effects
Abstract
The invention provides an electronic Fabry-Perot interference device and a preparation method thereof. The device comprises a measuring unit for detecting interference signals of the edge state and a characterization unit which is independently arranged at a preset area of the sample. The measurement cell includes a sample, a conductive channel, an ohmic contact, and a top gate structure. The first conductive channel is located in a preset area of the sample, has a preset Hall strip shape, is made by etching the sample, is of an integrated structure with the sample, and is used for conducting current. Ohmic contacts are distributed around the conductive channels for use as conductive electrodes. The top gate structure is located at the center of the upper surface of the first conductive channel, and is respectively connected with the ohmic contact for generating periodic interference oscillation to change the characteristics of the sample. The invention also provides a preparation method for preparing the Fabry-Perot interference device. By adopting the device and the preparation method, the structure of the device is optimized, the preparation time is saved, and the preparation cost is reduced.
Description
Technical Field
The invention relates to the field of semiconductors, in particular to a design and preparation method of an electronic Fabry-Perot interference device.
Background
The topological quantum computing stores and controls quantum information by using the topological quantum state in the multi-body system, has internal fault-tolerant capability, brings hope to physical realization of quantum computing, and promotes the exploration of material topological quantum behaviors. In the field of condensed state physics, finding non-abelian quasi-particles that can be used for topological quantum computing has become a very big hotspot problem. Two-dimensional electron gas (2 DEG) refers to a phenomenon in which electrons can move freely in a Two-dimensional plane, but are restricted in a third dimension. It is the basis for the operation of many field effect devices (e.g., MOSFETs, HEMTs). Theoretically, in a two-dimensional electron gas with ultra-high mobility, the excited quasi-particles in the 5/2 fractional state are non-abelian statistical. Quasi-particles of 5/2 state which obey non-Abel statistics can be used for topological quantum computing, and the problem that the core in quantum computing is difficult to decoherence is expected to be solved, so that the research of 5/2 state is paid more attention in the last 10 years.
An important characteristic of the quasi-particle in the 5/2 state is an effective charge of e/4, where e represents the electronic charge. It is theoretically proposed that fabry-perot interferometers can be made to obtain the effective charge of the quasi-particle in the 5/2 state by the AB interference effect of the edge state. Of course, to further confirm that the quasi-particles in the 5/2 state satisfy the non-abelian statistical law, a pigtail operation or the like is required to perform the transition between degenerate ground states, and a complex pigtail operation is also implemented by using a fabry-perot interference device (FPQHI) as a basic module. So the preparation and research of FPQHI is crucial.
However, currently, only a few international experimental groups measure the AB interference pattern of 5/2 states through FPQHI, which is complicated and expensive to manufacture.
Therefore, there is an urgent need to prepare an optimized FPQHI to solve the above problems in the prior art.
Disclosure of Invention
The invention aims to solve the problems of complex process, high preparation cost and the like of a Fabry-Perot interference device in the prior art, and provides an optimized Fabry-Perot interference device.
The invention also aims to provide a preparation method applied to the Fabry-Perot interference device, which reduces the preparation cost and saves the time.
In particular, the present invention provides an electronic fabry-perot interference device comprising a measurement unit for detecting an interference signal of an edge state and a characterization unit independently disposed at a preset region of the sample, the characterization unit being configured to characterize a sample, wherein the measurement unit comprises:
a sample which is a heterojunction material and has a flat upper surface in a preset area, wherein the sample is provided with a conductive layer;
the first conductive channel is formed in the preset area by etching the sample, has a preset Hall strip shape, is of an integrated structure with the sample, is used for conducting current, and is rectangular in pattern;
a plurality of ohmic contacts, which are in contact with the sample, distributed around the first conductive channel, and used as conductive electrodes, wherein the plurality of ohmic contacts are divided into a first group of ohmic contacts and a second group of ohmic contacts, the first group of ohmic contacts includes four ohmic contacts, which are first to fourth ohmic contacts, which are respectively connected to four vertices of the rectangular pattern of the first conductive channel and are in contact with the conductive layer, the second group of ohmic contacts includes six ohmic contacts, which are fifth to tenth ohmic contacts, which are symmetrically distributed on two opposite sides of the rectangular pattern of the first conductive channel and are not connected with the conductive channel; and
and the three pairs of top gate structures are positioned at the center of the upper surface of the first conductive channel and are respectively connected with the fifth ohmic contact, the tenth ohmic contact and the fifth ohmic contact to form a core part of an interference device, and periodic interference oscillation can be generated to change the characteristics of the sample.
Further, the characterization unit includes:
the second conductive channel and the sample are of an integrated structure, are manufactured by etching the sample, are independent from the first conductive channel, and have a preset Hall strip shape;
the third group of ohmic contacts are positioned in the preset area of the sample, are connected with the second conductive channel and are used as conductive electrodes;
preferably, the second conductive channel has a zigzag shape with five pins, and the third group of ohmic contacts includes five ohmic contacts respectively connected to the five pins of the second conductive channel.
Further, the first set of ohmic contacts is for functioning as a source, a drain, and a measurement electrode.
Further, each pair of top gate structures comprises a pair of top gates and internal electrodes correspondingly connected with the top gates, and the internal electrodes of each pair of top gate structures are respectively and correspondingly connected with the second group of ohmic contacts.
Further, the three pairs of top gates are sequentially arranged and respectively comprise a first top gate, a second top gate and a third top gate, wherein the first top gate and the third top gate are Quantum Point Contacts (QPC), the second top gate is a side gate, and the three pairs of top gates form a central region;
preferably, the area of the central region is variable by adjusting the side door.
Further, an alignment mark for positioning and adjusting focus astigmatism for electron beam exposure is also included;
preferably, the number of the alignment marks is four, and the alignment marks are respectively located at four vertexes of the first conductive channel;
preferably, the alignment marks are cross-shaped structures, and are as high as the first conductive vias.
Particularly, the invention also provides a preparation method applied to the Fabry-Perot interference device, which comprises the following steps:
s1, preparing the ohmic contact on the sample by adopting an ultraviolet exposure technology to obtain a first sample;
s2, preparing the first conductive channel on the first sample by adopting an ultraviolet exposure technology to obtain a second sample;
and S3, preparing a top door structure on the upper surface of the first conductive channel by adopting an electron beam exposure technology.
Further, the S1 includes:
step 101, cutting the sample into a preset structure, and cleaning the surface of the sample;
102, spin-coating a photoresist on the surface of the sample;
step 103, exposing an ohmic contact pattern by using an ultraviolet lithography machine;
104, developing and fixing the sample;
105, cleaning residual glue in an exposure area by adopting plasma;
step 106, coating a film by adopting an electron beam coating machine;
step 107, soaking the sample in a degumming solution to remove the degumming;
step 108, cleaning the sample, and annealing the sample to obtain the first sample;
preferably, in step 103, the pattern of ohmic contacts comprises a pattern of a first set of ohmic contacts, a second set of ohmic contacts and a third set of ohmic contacts.
Further, the S2 includes:
step 201, cleaning the first sample, and spin-coating a photoresist on the surface of the first sample;
step 202, exposing the pattern of the first conductive channel by using an ultraviolet lithography machine;
step 203, developing and fixing the first sample;
step 204, etching the first sample to obtain the first conductive channel;
step 205, soaking the first sample in a degumming solution to remove the degumming solution to obtain a second sample;
preferably, in the step 202, the pattern of the first conductive path and the pattern of the second conductive path to be aligned are exposed by an ultraviolet lithography machine.
Further, the S3 includes:
step 301, spin coating a layer of polymethyl methacrylate on the second sample;
step 302, using electron beam exposure to obtain the three pairs of top door structures;
step 303, developing and fixing the second sample;
304, coating by using an electron beam coating machine;
305, removing the photoresist of the second sample bubble in a photoresist removing solution to obtain a Fabry-Perot interference device;
and step 306, cleaning the interference device, and finishing the preparation.
According to the Fabry-Perot interference device, two independent units are designed on the same sample, the measuring unit is used for measuring interference signals, and the characterization unit is used for basic sample characterization, so that the structure of the interference device is optimized, and the preparation cost is reduced.
Furthermore, the preparation method of the electronic Fabry-Perot interference device considers the time and cost consumption of the preparation of the whole device, utilizes the advantages of short ultraviolet exposure time and simple operation, places some large electrodes in the electron beam exposure into the ultraviolet exposure, saves the time of the electron beam exposure and reduces the preparation cost.
The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
Some specific embodiments of the invention will be described in detail hereinafter, by way of illustration and not limitation, with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the drawings:
FIG. 1 is a device diagram of a Fabry-Perot interference device according to one embodiment of the invention under an optical microscope;
FIG. 2 is a mask pattern for ohmic contacts for UV exposure in a Fabry-Perot interference device according to one embodiment of the invention;
FIG. 3 is a reticle pattern of a conductive via for UV exposure in a Fabry-Perot interference device according to one embodiment of the present invention;
FIG. 4 is a schematic block diagram of the longitudinal direction of a sample in a Fabry-Perot interference device according to one embodiment of the invention;
FIG. 5 is a schematic block diagram of the longitudinal direction of a sample after etching to form conductive channels after making ohmic contacts according to one embodiment of the invention;
FIG. 6 is a drawing of a device under an optical microscope that has been etched to form conductive vias after making ohmic contacts according to one embodiment of the present invention;
fig. 7 is a schematic structural view of a top gate structure for electron beam exposure in a fabry-perot interference device according to an embodiment of the present invention;
FIG. 8 is an atomic force microscope image of a central region of a Fabry-Perot interference device according to one embodiment of the invention under an optical microscope;
FIG. 9 is a functional diagram of a central region of a Fabry-Perot interference device according to an embodiment of the present invention;
figure 10 is a schematic flow diagram of a method of fabricating a fabry-perot interference device according to one embodiment of the present invention.
The symbols in the drawings represent the following meanings:
1. the samples were taken from the test piece and,
11. conductive layer, 12, GaAs substrate, 13, AlGaAs spacer layer, 14, AlGaAs layer, 15, GaAs capping layer, 16, doped silicon layer
2. The electrically conductive path is formed by a conductive material,
21. a first conductive path, 22, a second conductive path,
3. the ohmic contact is made with the metal layer,
31. a first set of ohmic contacts, 311, a first ohmic contact, 312, a second ohmic contact, 313, a third ohmic contact, 314, a fourth ohmic contact,
32. a second set of ohmic contacts, 321, a fifth ohmic contact, 322, a sixth ohmic contact, 323, a seventh ohmic contact, 324, an eighth ohmic contact, 325, a ninth ohmic contact, 326, a tenth ohmic contact,
33. a third set of ohmic contacts 331, an eleventh ohmic contact 332, a twelfth ohmic contact 333, a thirteenth ohmic contact 334, a fourteenth ohmic contact 335, a fifteenth ohmic contact,
4. a structure of a top door is provided,
41. a first top gate structure, 411, a first top gate, 412, a first internal electrode,
42. a second opposing top gate structure 421, a second top gate, 422, a second inner electrode,
43. a third pair of top gate structures, 431, a third top gate, 432, a third inner electrode,
5. and aligning the mark.
Detailed Description
Fig. 1 is a device diagram of a fabry-perot interference device according to an embodiment of the present invention under an optical microscope. As shown in fig. 1, an electronic fabry-perot interferometer includes a measuring unit for detecting an interference signal of an edge state and a characterization unit independently disposed at a predetermined region of a sample 1, wherein the characterization unit is used for characterizing characteristics of the sample 1. The measurement cell comprises a sample 1, a conductive channel 2, an ohmic contact 3 and a top gate structure 4. The black material on the ohmic contact 3 was indium applied for the purpose of bonding gold wires when measuring the sample 1. The bright yellow portions are the electron beam exposed pattern, i.e. the top gate structure 4.
Fig. 4 is a schematic structural view of a longitudinal direction of a sample 1 in a fabry-perot interference device according to an embodiment of the present invention. As shown, sample 1 is a heterojunction material having a flat upper surface in a predetermined region, and the heterojunction material has a conductive layer 11. In one embodiment of the present invention, sample 1 has a structure with a very thin doped layer 16 of silicon between the undoped GaAs substrate 12, the conductive layer 11, the AlGaAs spacer layer 13, the AlGaAs layer 14, and the surface GaAs cap layers 15, 13, and 14 from bottom to top. The conductive layer 11 is a two-dimensional electron gas structure having high mobility in which carriers exist for participating in transportation.
Figure 3 is a schematic block diagram of electrically conductive channels in a fabry-perot interference device according to one embodiment of the present invention. As shown in fig. 3, the conductive path 2 (see fig. 1) includes a first conductive path 21. The first conductive channel 21 is located in a preset region of the sample 1 and has a predetermined hall bar shape, is made by etching the sample 1, and is of an integrated structure with the sample 1 for conducting current. The pattern of the first conductive bump 21 may be rectangular, or may have other shapes that can fulfill its function.
Fig. 2 is a schematic block diagram of an ohmic contact in a fabry-perot interference device according to an embodiment of the present invention. As shown in fig. 2, the device includes a plurality of ohmic contacts 3. Each ohmic contact 3 is in contact with the sample 1 and is distributed around a first conductive path 21 (see fig. 3) for acting as a conductive electrode. The ohmic contacts 3 are divided into a first set of ohmic contacts 31 and a second set of ohmic contacts 32. The first group 31 of ohmic contacts includes four ohmic contacts, i.e., first to fourth ohmic contacts 311, 312, 313 and 314, which are respectively connected to four pins of the rectangle and are in contact with the conductive layer 11 (see fig. 4).
The first set of ohmic contacts 31 is used as source, drain and measurement electrodes. The source and drain electrodes are mainly the injection terminal and the ground terminal of the current. The measuring electrodes are mainly used for measuring voltage signals, and the voltage signals are converted into resistance values, so that interference signals are observed on the longitudinal resistors and the Hall resistors. The edge states of the interference occur mainly at the edges of the first conductive path 21 (see fig. 3). If the longitudinal resistance is measured, current enters from the fourth ohmic contact 314, the second ohmic contact 312 is grounded, and the voltage between the first ohmic contact 311 and the third ohmic contact 313 is measured; if the Hall signal is measured, current enters from the fourth ohmic contact 314, the third ohmic contact 313 is grounded, and the voltage between the first ohmic contact 311 and the second ohmic contact 312 is measured. The two measuring terminals of the longitudinal resistor are parallel to the current direction, while the two measuring terminals of the hall resistor or diagonal resistor are perpendicular to the current direction. It will be appreciated that the first set of ohmic contacts 31 is not limited to only four ohmic contacts 3, and that there may be other numbers of ohmic contacts 3.
As shown in fig. 2, the second group of ohmic contacts 32 includes six ohmic contacts 3, which are fifth to tenth ohmic contacts 321, 322, 323, 324, 325, 326 symmetrically disposed on opposite sides of the rectangle and not connected to the conductive via 2 (see fig. 3). The second set of ohmic contacts 32 is used for electron beam exposure of the outer electrodes of the resulting top gate structure 4 (see fig. 7).
Fig. 7 is a schematic structural view of a top gate structure in a fabry-perot interference device according to an embodiment of the present invention. As shown in fig. 7, referring also to fig. 3, the number of the top gate structures 4 is three pairs, and the top gate structures are located at the center of the upper surface of the first conductive via 21 (see fig. 3) and are respectively connected to the fifth to tenth ohmic contacts 321, 322, 323, 324, 325 and 326 (see fig. 2) to form the core portion of the interference device, so as to generate periodic interference oscillation and change the characteristics of the sample 1. Each pair of top door structures 4 includes a pair of top doors and an internal electrode correspondingly connected to the top doors. The internal electrodes are respectively connected to the second group of ohmic contacts 32, wherein the first internal electrode 412 is connected to the fifth and eighth ohmic contacts 321 and 324, the second internal electrode 422 is connected to the sixth and ninth ohmic contacts 322 and 325, and the third internal electrode 432 is connected to the seventh and tenth ohmic contacts 323 and 326, respectively, see fig. 1. In order to facilitate measurement of experiments, the top door structures 4 are mutually independent, and the internal electrodes are asymmetric electrode structures. The asymmetric electrode structure can reduce the number of squares of sample 1 after the gate voltage is applied, and thus can reduce the magnitude of the longitudinal resistance.
Fig. 5 is a schematic structural view of a longitudinal direction of sample 1 after etching to form a conductive path after preparation of ohmic contact according to an embodiment of the present invention. As shown in fig. 5, on sample 1 on which ohmic contacts were successfully prepared, a portion of sample 1 was etched away by an etching process to form conductive paths 2, wherein conductive paths 2 are portions that were not etched. The conductive channel 2 comprises a conductive layer 11, an AlGaAs spacer layer 13, a doped silicon layer 16, an AlGaAs layer 14 and a superficial GaAs cap layer 15. Due to the presence of the conductive layer 11, the conductive channel 2 may become a transport channel. The etched part of sample 1 does not contain the conductive layer 11 and thus cannot constitute a transport channel. Figure 6 is a drawing of a device under an optical microscope etched to form conductive channels after making ohmic contacts according to sample 1 of one embodiment of the present invention. As shown in fig. 6, and also in fig. 2, a first set of ohmic contacts 31 is connected to the first conductive paths 21 and the conductive layer 11 between the second set of ohmic contacts 32 and the first conductive paths 21 is etched away.
Figure 8 is an atomic force microscope image of a central region of a fabry-perot interference device according to one embodiment of the invention under an optical microscope. Figure 9 is a functional diagram of a central region of a fabry-perot interference device according to one embodiment of the present invention. As shown in fig. 9, three pairs of top gates are sequentially arranged, namely a first top gate 411, a second top gate 421 and a third top gate 431, wherein the first top gate 411 and the third top gate 431 are Quantum Point Contacts (QPC), the second top gate 421 is a side gate, and the three pairs of top gates form a central region. The area a of the central area is changed by adjusting the side door. In a preferred embodiment, the spacing between the Quantum Point Contacts (QPC) is 400nm, the spacing between the side gates is 2.2 μm, and the horizontal distance between two Quantum Point Contacts (QPC) is 1.5 μm.
Two-dimensional electron gas can form a non-dissipative and energy gap-free edge state under a higher vertical magnetic field and a lower temperature, and the bulk state is an insulating state with energy gaps. When the interference device is well defined, the two-dimensional system can form quantum hall edge states under high magnetic field, as shown by the black dotted line with arrows in fig. 9. When an edge state comes out from the electrode at the lower left corner and passes through Quantum Point Contact (QPC) at the left side, there is a certain probability that t1 scatters to the opposite edge state, and the edge state passing through continues to be transmitted forward until meeting the QPC at the right side, at which time there is a certain probability that t2 scatters, t2 interferes with t1 after surrounding the central region for one circle, and when the magnetic flux in the central region is changed, periodic interference oscillation is generated, which is called Aharonov-Bohm effect. Since the interference phase changes by 2 pi for each change of one magnetic flux quantum h/e, the effective charge e of the quasi-particle can be obtained by the period of the interference oscillation.
By adopting the Fabry-Perot interference device, periodic interference oscillation is generated by optimizing the top gate structure 4, so that the effective charge e of the quasi-particles is obtained. The interference device also has a characterization unit designed on the same sample for basic sample characterization. The Fabry-Perot interference device is simple in structure and low in preparation cost.
The invention also provides a preparation method for preparing the Fabry-Perot interference device. Figure 10 is a schematic flow diagram of a method of fabricating a fabry-perot interference device according to one embodiment of the present invention. As shown in fig. 10, the device manufacturing process according to the present invention is as follows:
s1, preparing ohmic contact on the sample 1 by using an ultraviolet exposure technique to obtain a first sample 1 (see fig. 1);
s2, preparing a first conductive channel 21 (see fig. 3) on the first sample 1 by using an ultraviolet exposure technique, to obtain a second sample 1;
s3, a top gate structure 4 is prepared on the upper surface of the first conductive via 21 by using an electron beam exposure technique (see fig. 1).
The specific preparation process of the device is as follows:
s1 preparation of ohmic contact 3 (see fig. 1), which in turn comprises the steps of,
1. exposing the ohmic contact 3 region by using ultraviolet photoetching;
2. the exposure area is cleaned by using plasma, so that the residual glue is reduced, and the contact is improved;
3. coating in an electron beam coating machine;
4. annealing was carried out using a rapid annealing furnace which was self-made in the laboratory.
S2, preparing a first conductive channel 21, namely, an overlay Hall bar (Hall bar), wherein the method further comprises the following steps of 1, exposing a Hall bar pattern by ultraviolet photoetching;
2. and carrying out wet etching to etch away the exposed area.
S3 preparing the top door, which further comprises the steps of,
1. after the clean sample 1 surface is thrown with a layer of PMMA glue through the second step, a layer of conductive glue is thrown, and the conductivity of the GaAs material is not good, so that the conductivity of the sample 1 can be increased, and the exposure of a fine structure is facilitated;
2. the exposure as shown in fig. 7 is performed using electron beam lithography;
3. and (4) performing metal deposition by using an electron beam coating machine.
Furthermore, the preparation method of the electronic Fabry-Perot interference device considers the time and cost consumption of the preparation of the whole device, utilizes the advantages of short ultraviolet exposure time and simple operation, places some large electrodes in the electron beam exposure into the ultraviolet exposure, saves the time of the electron beam exposure and reduces the preparation cost.
In another embodiment of the present invention, the fabry-perot interference device further comprises a characterization unit independently disposed at a predetermined region of the sample 1 for characterizing the sample 1. The characterization unit and the measurement unit are two completely separate parts. The two are separated by an etched region, and no current carrier passes through. As shown in fig. 3, the characterization unit includes a second conductive path 22 and a third set of ohmic 33 contacts. The second conductive path 22 is of an integral structure with the sample 1, is made by etching the sample 1, is independent of the first conductive path 21, and has a predetermined hall bar shape. The second conductive path 22 may be a letter-of-earth having five legs. A third set of ohmic 33 contacts is located in a predetermined area of the sample 1 and is connected to the second conductive path 22 for acting as a conductive electrode. The third set of ohmic 33 contacts includes five ohmic contacts 331, 332, 333, 334, 335, which are connected to the five legs of the second conductive path 22, respectively.
It will be understood that the basic parameters characterizing the electrical properties of a material are mainly the concentration n and the mobility μ of the charge carriers, which can be determined by measuring the longitudinal resistance R of the materialxx(RL) And a Hall resistor Rxy(RH) The measurement methods are general hall effect and quantum hall effect, and are not described in detail here. Mobility [ mu ] 1/rho0ne，ρ0The longitudinal resistivity under the zero magnetic field is shown, and the concentration n can be obtained by the slope 1/ne of a relation curve of the Hall resistance and the magnetic field.
In this embodiment, the measuring unit and the characterization unit are located at the same area of 3 × 3mm2The two were independent of each other in sample 1. The sample 1 surface of the measuring unit is provided with the top gate structure 4, which can affect the mobility of the sample 1, so that the actual parameters of the sample 1 can be truly reflected by the measurement of the adjacent characterization unit. This allows comparison to know whether the presence of the top gate structure 4 affects the mobility of the sample 1, and also allows monitoring of the conditions in the bulk sample 1 while measuring the interference signal.
By adopting the Fabry-Perot interference device, two independent units are designed on the same sample 1, the measuring unit is used for measuring interference signals, and the characterization unit is used for basic sample 1 characterization, so that the structure of the interference device is optimized, and the preparation cost is reduced.
In another embodiment of the invention, the fabry-perot interference device further comprises alignment marks 5 for positioning of the electron beam exposure and adjusting the focus astigmatism. The alignment marks 5 are prepared by an ultraviolet exposure technology, and the number of the alignment marks 5 is four, and the four alignment marks are respectively positioned at four vertexes of the first conductive channel 21. The alignment mark 5 is a cross structure and has the same height as the first conductive channel 21. As shown in fig. 3, four alignment marks 5 (enclosed by black dashed circles) are designed at four vertices of the first conductive via 21, and are spaced apart by 0.6mm both vertically and horizontally, which can be used for positioning and adjusting focus astigmatism during electron beam exposure. Since the cross structure is at the same height as the central etched portion and is located close to the central area, focus and astigmatism adjustments can be made on the cross structure, resulting in a finer structure. And the cross structure can be found when the magnification factor is smaller, so that the cross structure can be directly found under the magnification factor of 50 times without influencing the glue characteristic to adjust the exposure parameters. Therefore, the whole process of top gate exposure can be completed only by one-time electron beam exposure, the micro-processing flow is greatly simplified, and the unnecessary exposure range formed on the surface of the two-dimensional electron gas is avoided.
In order to understand the manufacturing process, the following describes in detail the manufacturing process of the device according to the embodiment of the present invention, and the specific process is as follows:
step one, cutting 3 multiplied by 3mm2The GaAs sample 1 is subjected to surface cleaning by a conventional method, and the sample 1 is subjected to ultrasonic treatment when necessary, so that a cleaner surface can be obtained;
step two, throwing 5350 photoresist on the surface of the clean sample 1, and drying for 4min at 100 ℃;
exposing an ohmic contact pattern by using an ultraviolet photoetching machine;
step four, developing the developing solution AR300-26 with DI being 1:7 for 50 s; fixing for 1min by DI;
step five, cleaning the residual glue in the exposure area by using plasma, and cleaning for 2min by 30s under the argon gas of 30 Pa;
step six, sequentially coating Pd/Ge/Au (22/55/150 nm) by using an electron beam coating machine;
removing the photoresist, soaking in acetone for more than three hours, and blowing off the unnecessary metal film by using a dropper;
step eight, cleaning the sample 1, and putting the sample into a fast annealing furnace self-made by a laboratory for annealing at 450 ℃ for 900 s;
step nine, cleaning the annealed sample 1 again, and spin-drying in the same step two;
step ten, exposing a Hall bar pattern to be aligned by using an ultraviolet lithography machine;
step eleven, synchronously developing and fixing;
step twelve, etching liquid (H)2SO4:H2O2DI 1:8:100) at a rate of 7nm/s, the etching time being selected according to the actual growth structure of sample 1;
step thirteen, removing the photoresist;
step fourteen, throwing a layer of PMMA glue on the sample 1 which is subjected to photoetching, and drying for 2min at 180 ℃; then throwing a layer of conductive adhesive (AR-PC 5090) and drying for 2min at 90 ℃;
step fifteen, using electron beam exposure to obtain three pairs of top door structures 4; the exposure parameters of the inner layer electrode are as follows: high voltage 10kV, diaphragm 20 μm, surface exposure dose 100 μ AS/cm2(ii) a The exposure parameters of the outer layer electrode are as follows: high voltage 10kV, aperture 120 μm, surface exposure dose 100 μ AS/cm2；
Sixthly, using a developing solution MIBK with DI being 1: 3 developing for 33s, and carrying out DI fixing for 1 min;
seventhly, sequentially plating Ti/Au of 10/60nm by using an electron beam plating machine;
eighteen, removing the photoresist, soaking for more than five hours by using acetone, and carrying out ultrasonic treatment for 10s to enable the metal film to fall off;
and step nineteen, cleaning the sample 1, and completing the preparation.
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (15)
1. An electronic fabry-perot interferometer, comprising a measurement unit for detecting an interference signal of an edge state and a characterization unit independently disposed at a predetermined region of a sample, the characterization unit being configured to characterize the sample, wherein the measurement unit comprises:
a sample which is a heterojunction material and has a flat upper surface in a preset area, wherein the sample is provided with a conductive layer;
the first conductive channel is formed in the preset area by etching the sample, has a preset Hall strip shape, is of an integrated structure with the sample, is used for conducting current, and is rectangular in pattern;
a plurality of ohmic contacts, which are in contact with the sample, distributed around the first conductive channel, and used as conductive electrodes, the ohmic contacts being divided into a first group of ohmic contacts and a second group of ohmic contacts, the first group of ohmic contacts including four ohmic contacts, which are first to fourth ohmic contacts, which are respectively connected to four vertices of the rectangular pattern of the first conductive channel and are in contact with the conductive layer, the second group of ohmic contacts including six ohmic contacts, which are fifth to tenth ohmic contacts, which are symmetrically distributed on opposite sides of the rectangular pattern of the first conductive channel and are not connected with the conductive channel; and
the three pairs of top gate structures are positioned at the center of the upper surface of the first conductive channel, are respectively connected with the fifth ohmic contact, the tenth ohmic contact and the fifth ohmic contact, and form a core part of an interference device for generating periodic interference oscillation and changing the characteristics of the sample;
the characterization unit includes:
the second conductive channel and the sample are of an integrated structure, are manufactured by etching the sample, are independent from the first conductive channel, and have a preset Hall strip shape;
and the third group of ohmic contacts are positioned in the preset area of the sample, are connected with the second conductive channel and are used as conductive electrodes.
2. The Fabry-Perot interference device according to claim 1,
the second conductive channel is in a shape of a Chinese character 'tu', and is provided with five pins, and the third group of ohmic contacts comprises five ohmic contacts which are respectively connected with the five pins of the second conductive channel.
3. Fabry-Perot interference device according to claim 1 or 2, characterized in that the first set of ohmic contacts is used as source, drain and measurement electrodes.
4. The fabry-perot interference device of claim 3, wherein each pair of top gate structures comprises a pair of top gates and internal electrodes connected to the top gates, the internal electrodes of each pair of top gate structures being connected to the second set of ohmic contacts, respectively.
5. The Fabry-Perot interference device according to claim 4, wherein said three pairs of top gates are arranged in sequence, being a first top gate, a second top gate and a third top gate, wherein said first top gate and said third top gate are quantum point contacts, said second top gate is a side gate, and wherein said three pairs of top gates form a central interference region.
6. The Fabry-Perot interference device according to claim 5,
the area of the central region is changed by adjusting the side door.
7. The fabry-perot interference device of claim 1, further comprising alignment marks for positioning of electron beam exposure and adjusting of focus astigmatism.
8. The Fabry-Perot interference device according to claim 7,
the number of the alignment marks is four, and the alignment marks are respectively positioned at four vertexes of the first conductive channel.
9. The Fabry-Perot interference device according to claim 7,
the alignment mark is a cross structure and has the same height as the first conductive channel.
10. A method for producing a fabry-perot interference device according to any of claims 1 to 9, comprising:
s1, preparing the ohmic contact on the sample by adopting an ultraviolet exposure technology to obtain a first sample;
s2, preparing the first conductive channel on the first sample by adopting an ultraviolet exposure technology to obtain a second sample;
and S3, preparing a top door structure on the upper surface of the first conductive channel by adopting an electron beam exposure technology.
11. The method according to claim 10, wherein said S1 includes:
step 101, cutting the sample into a preset structure, and cleaning the surface of the sample;
102, spin-coating a photoresist on the surface of the sample;
step 103, exposing an ohmic contact pattern by using an ultraviolet lithography machine;
104, developing and fixing the sample;
105, cleaning residual glue in an exposure area by adopting plasma;
step 106, coating a film by adopting an electron beam coating machine;
step 107, soaking the sample in a degumming solution to remove the degumming;
step 108, cleaning the sample, and annealing the sample to obtain the first sample.
12. The production method according to claim 11,
in step 103, the pattern of ohmic contacts includes a pattern of a first set of ohmic contacts, a second set of ohmic contacts, and a third set of ohmic contacts.
13. The method according to claim 11, wherein S2 includes:
step 201, cleaning the first sample, and spin-coating a photoresist on the surface of the first sample;
step 202, exposing the pattern of the first conductive channel by using an ultraviolet lithography machine;
step 203, developing and fixing the first sample;
step 204, etching the first sample to obtain the first conductive channel;
and step 205, soaking the first sample in a degumming solution to carry out degumming to obtain the second sample.
14. The method of claim 13,
in step 202, the pattern of the first conductive path and the pattern of the second conductive path to be aligned are exposed by an ultraviolet lithography machine.
15. The method according to claim 10, wherein said S3 includes:
step 301, spin coating a layer of polymethyl methacrylate on the second sample;
step 302, using electron beam exposure to obtain the three pairs of top door structures;
step 303, developing and fixing the second sample;
304, coating by using an electron beam coating machine;
305, removing the photoresist of the second sample bubble in a photoresist removing solution to obtain a Fabry-Perot interference device;
and step 306, cleaning the interference device, and finishing the preparation.
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Non-Patent Citations (3)
| Title |
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| Distinct signatures for Coulomb blockade and Aharonov-Bohm interference in electronic Fabry-Perot interferometers;Yiming Zhang et al;《PHYSICAL REVIEW B》;20091231;全文 * |
| Fabry-Perot Interferometry with Fractional Charges;D. T. McClure et al;《physical review letters》;20120622;全文 * |
| role of interactions in an electronic Fabry-Perot interferometer operating in the quantum hall effect regime;Nissim Ofek et al;《applied physical science》;20100323;第107卷(第12期);全文 * |
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