KR100884525B1 - Single electron transistor for spin quibit dection and fabrication method thereof - Google Patents

Abstract

A single electron transistor for sensing a spin quantum bit and a manufacturing method thereof are provided to facilitate integration of a quantum gate element by performing a manufacturing process similar to a CMOS step. A source(10), a drain(20), first and second quantum dots, first to third gates(30,31,32), a single electron transistor are formed on an upper silicon layer of SOI(Silicon On Insulator) substrate. A quantum bit of dual quantum dots composed of the first and second quantum dots is sensed by a single electron transistor. The rest silicon layer except for the formed pattern is etched. A doping mask is formed in a conductive channel formed by the third quantum dot of the single electron transistor and the first and second quantum dots. A gate oxidation film is formed in an upper side of a silicon layer. A control gate(61) covering the first to third quantum dots is formed and the rest is etched. A metallization process is performed on the substrate.

Description

Single-electron transistor for spin qubit detection and its manufacturing method {Single Electron Transistor for Spin Quibit Dection and Fabrication Method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-electron transistor for spin qubit sensing and a method of manufacturing the same, and indirectly through double quantum bits through charge distribution (base state and excited state) according to the change in the magnetic field of two electrons in a coupled double quantum dot The present invention relates to a single-electron transistor for spin qubit sensing and a method of manufacturing the same, capable of sensing quantum bit changes that are key to the operation of a quantum computational logic gate.

In general, computers such as computers that are currently used to operate using binary method. That is, from a physical point of view with 1 bit, which is the most basic information unit, conventional logic operations are divided into two logic values, yes and no, true and false, or 0 and 1 to perform logic and operations.

Unlike the conventional irreversible calculation method, such a logical operation has recently introduced a new concept called quantum information technology, that is, a new type of quantum computer based on quantum mechanics theory.

Here, quantum information technology refers to an information processing method that is different from the classical logic gate by using uncertainty, superposition, interference, or entanglement, which are characteristics of the quantum mechanical system.

Such quantum information technology can be classified into quantum communication technology and quantum computing technology. In particular, quantum information transmission technology includes quantum cryptography and quantum teleportation technology, and quantum computing technology includes a quantum bit and a quantum gate, which are the minimum units of quantum information processing. It includes hardware and software called quantum algorithms.

In particular, while the conventional bits can have only 0 and 1, the qubit, which is an information processing unit in quantum computation, may have 0 and 1 and their intermediate values. This is because, in the case of qubits, in the information processing with two electrons, a state in which two electronic states overlap each other may be an intermediate value.

Currently, in quantum physics, the spin state of a particle with a spin of 1/2 and a qubit, a polarization state of photons, are used. In particular, the qubit of the spin state is a transfer of information that is impossible to eavesdropping at all by using the quantum characteristics newly appearing in the clock as the size of the semiconductor device becomes smaller. It has been applied in various fields as a semiconductor device, such as a quantum computer that can solve the multi-factor prime factorization problem that could not be solved.

For example, it takes about 1000 years with a conventional computer to randomly find a 56-bit secret encryption key, but it takes about 4 minutes using a quantum algorithm. In addition, the quantum computer itself is a quantum mechanical system, so it can be used for simulation of the quantum mechanical system which is impossible with the existing computer, which means that the time and money required for the synthesis of new materials or the development of new drugs can be significantly reduced.

In order to obtain effects such as high integration or high speed quantum parallel processing using spin qubits, development of a transistor capable of detecting such spin qubits is required.

The present invention for solving this,

(a) first and second quantum dots connecting a source and a drain and these to an upper layer oxide film of a double oxide film formed on a substrate, at least three first to third gates formed on one side thereof, and opposite sides thereof; Patterning single-electron transistors on the same plane to sense qubits in the double quantum dots formed by the first and second quantum dots;

(b) etching the remaining oxide film except for the pattern;

(c) forming a doping mask in the conductive channel formed by the first and second quantum dots and the third quantum dots of the single-electron transistor and doping the remaining portions;

(d) forming a gate oxide film on the top surface of the silicon layer;

(e) forming a control gate to a size to cover the first to third quantum dots and etching the remaining portions; And

(f) a metallization step for forming a metal thin film of the substrate.

In addition, the second gate may be configured to adjust a coupling constant between the double quantum dots by receiving a negative voltage.

In addition, the single-electron transistor is positioned between the third quantum dot and the source and drain connected in a "V" shape around the third quantum dot disposed between the first and second quantum dots, and positioned between the source and drain It characterized in that it comprises a side gate formed to.

In the patterning step (a), an insulating film (SOI) substrate is used as a substrate, and a pattern is formed by electron beam lithography or focused ion beam (FIB).

In addition, the etching treatment step (b) is characterized in that to remove the oxide film other than the pattern by using a reactive ion etching treatment method.

In addition, the doping step (c) is characterized by using a negative resist as the doping mask.

In addition, the etching step (e) is characterized in that the etching process by patterning by a photolithography method.

In addition, the method for manufacturing a spin qubit sensing single-electron transistor according to the present invention is characterized in that it further comprises a conventional CMOS step (g).

Meanwhile, the single-electron transistor for spin qubit sensing according to the present invention is manufactured by the above-described method.

According to the present invention has the following effects.

1) It is easy to integrate the quantum gate element on a large scale because a spin qubit sense single-electron transistor is manufactured in accordance with the normal CMOS step.

2) The spin qubit, which is one of the representative methods of the quantum gate operation used in the calculation method of the quantum computer, can be easily detected.

3) The flexibility and scalability of the number and placement of multiple side gates makes it easier to compute multiple quantum bits. Therefore, based on this, the expansion of prime factorization by Shaw's algorithm and data retrieval by Guru's method is superior to other conventional computational structures.

4) It is possible to fundamentally solve the security problem that may occur when transmitting various information derived from this and to increase the multi-bit encryption resolution.

Hereinafter, the configuration and operation according to the present invention with reference to the accompanying drawings.

Here, the accompanying drawings are views showing only a part of the substrate on which one qubit is formed as an example for explaining the configuration according to the present invention.

In the method of manufacturing a single-electrode transistor for spin qubit sensing according to the present invention, first, a step (a) of patterning is performed on the substrate 100. Herein, the substrate 100 may use a silicon on insulator (SOI) substrate having an oxide layer formed thereon to not only increase the operating speed but also to lower the operating voltage compared to the same operating speed.

In addition, in the preferred embodiment of the present invention, as a pretreatment step of starting the patterning step (a), a general alignment-key process is performed to form a pattern on the substrate 100.

In the patterning step (a), a pattern is formed on the upper oxide layer of the double oxide layer 110 of the substrate 100. The pattern formed at this time includes a source 10, a drain 20, a plurality of gates 30, 31, 32, and a single electron transistor formed on the same plane as illustrated in FIG. 1.

In more detail, the source 10 and the drain 20 are formed to face each other, wherein the source 10 and the drain 20 are formed at the first and second quantum points QD1 and Qd2. Are electrically connected to each other.

Although the first to third gates 30 to 32 are formed on one side of the source 10 and the drain 20, that is, the lower portion of FIG. 1, the first to third gates 30 to 32 are provided to explain the formation position of the gate. It is also possible to form.

In this case, each gate 30 to 32 is preferably formed so that each end is located at both ends and the center of the conductive channel formed by the two quantum dots (QD1, QD2) respectively. In particular, the second gate 31 formed to be positioned at the center of the conduction channel has an effect of arbitrarily adjusting the coupling constant value between the double quantum dots by the negative voltage applied thereto.

Meanwhile, a single-electron transistor for sensing a qubit through a minute voltage measurement generated in a conduction channel on the upper side of the source 10 and the drain 20 in a position opposite to the position where the gates 30 to 32 are formed. Is formed.

In the single-electron transistor, the source 40 and the drain 41 are electrically connected to each other through the third quantum point QD3. In particular, the source 40 and the drain 41 are formed to be disposed in a “V” shape, and the side gate 42 is formed to be positioned between the source 40 and the drain 41.

In a preferred embodiment of the present invention, the pattern formed in the patterning step (a) is the same at intervals of several to several tens of nanometers through an electron-beam direct writing method or a focused ion beam (FIB) method. It is preferable to form on a plane. Of course, the spacing, width and width of each pattern may be arbitrarily adjusted.

As a next step, after the patterning step (a) is completed, the step (b) of etching the top surface silicon of the double oxide film 110 is performed to form a pattern. At this time, the etching for forming the pattern is preferably to increase the uniformity of the etching by using reactive ion etching (RIE).

As such, when the etching step (b) is completed, the substrate 100 having the pattern shown in FIG. 1 is obtained.

In the doping step (c), the doping mask 50 is formed on the conductive channel except for the conductive channel formed by the three quantum dots QD1 to QD3. In this case, the doping mask 50 may be formed by using a negative resist so that the doping may be performed on portions other than the doping mask 50, that is, the conductive channel portion.

2 shows an example in which a doping mask 50 according to the invention is formed over a conducting channel. When the doping mask 50 is formed as described above, the doping process is performed on the portion of the double oxide layer 110 except for the conductive channel and the portion where the pattern is not formed through the normal doping process.

In the oxide film forming step (d), after the doping step, the gate oxide film 60 having a predetermined thickness with respect to the entire upper cylinder of the double oxide film 110 is performed by a conventional method. 3 is a partial perspective view illustrating a formation state of a gate oxide film according to a method of manufacturing a single-electrode transistor for spin qubit sensing according to the present invention.

The etching step (e) is to form a control gate 61 by etching a portion of the oxide film 60 formed in the above-described oxide film forming step. In this case, the control gate 61 is patterned to a size sufficient to cover all of the above-described three quantum dots QD1 to QD3, that is, a size including all of the single-electron transistors, and then etched with respect to the remaining portions. As shown in the drawing, the control gate 61 is formed.

In addition, the etching step (e) is preferably etched by applying a conventional photolithography method.

Finally, the metallization step (f) completes the manufacture of the single-electron transistor for spin qubit detection according to the present invention. Here, metallization refers to a process of forming a metal thin film which has three functions: contact with an element (Ohmic, Schottky), interconnection between elements, and connection between a chip and an external circuit in an integrated circuit. .

delete

Hereinafter, with reference to the accompanying drawings will be described the operation of the single-electron transistor for spin qubit detection according to the present invention.

First, an initial operating condition for coupling two quantum dots QD1 and QD2 electrically connecting the source 10 and the drain 20 is created.

To this end, an appropriate negative voltage is applied to each of the first to third gates 30 to 32. Subsequently, a positive voltage is supplied to the control gate 61 to induce a two-dimensional electron gas layer to the conduction channel, and then a voltage of the control gate 61 is scanned to locate one electron in each of the two quantum dots QD1 and QD2. Do it. In addition, when a negative voltage is applied to the second gate 31, the coupling constant between the quantum dots may be adjusted according to the strength.

After the initial condition is made, the voltage of the control gate 61 is fixed to the second coulomb containment area, and the two quantum dots QD1 and QD2 are controlled to be limited to one electron each, and then the external magnetic field is changed. Given.

Accordingly, the two electrons constrained and coupled within the quantum dot have a spin part that varies according to a change in the magnetic field. Conventionally, a method of optically measuring a change in the spin portion is known, but this is difficult to detect.

Here, the characteristics of the wave function of the coupled electrons are as follows.

In general, when two electrons are subjected to a magnetic force, the spin state of the system changes to an ellipse or an ellipse having a node in the center as shown in FIG. 5 according to Pauli's anti-symmetric principle. In other words, the double wave function of the coupled electrons exhibits an anti-symmetric characteristic of the spin part and the orbital part.

5 shows a case where the spin state of two coupled electrons is changed from spin singlet to spin triplet or vice versa. That is, in FIG. 5 showing the orbital portion of the wave function, when the spin-entanglement is a single term (S1), the orbit is formed in an ellipse shape so that the charge distribution of electrons is concentrated in the center. In addition, in the case of the spin triplet T1, a node is formed at the center portion, and the electron distribution is separated and distributed around each electron.

In the present invention, the charge distribution according to the characteristics of the wave function of the coupled electrons is changed as described above, and the change of voltage according to the charge distribution at this time is performed by using a single electron transistor including the third quantum point QD3. By detecting the micro-change of, it is possible to indirectly detect the intrinsic state of the two electron spins.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims will cover such modifications and variations as fall within the spirit of the invention.

1 is a partial perspective view showing a pattern formed by the method of manufacturing a single electron transistor for spin qubit detection according to the present invention.

2 is a partial perspective view showing an example in which a doping mask is formed by a method of manufacturing a single-electrode transistor for spin qubit detection according to the present invention.

3 is a partial perspective view showing the formation state of the gate oxide film according to the manufacturing method of the single-electron transistor for spin qubit sensing in accordance with the present invention.

4 is a partial perspective view showing a state in which a control gate is formed in accordance with the manufacturing method of the single-electron transistor for spin qubit detection according to the present invention.

FIG. 5 is a conceptual diagram illustrating a form in which a quantum dot may change depending on a spin state according to a change in an external magnetic field. FIG.

<Description of the symbols for the main parts of the drawings>

10, 40: source

20, 41: drain

30, 31, 32: gate

42: side gate

50: doping mask

60: gate oxide film

61: control gate

100: substrate

110: silicon layer

QD1, QD2, QD3: Quantum Dots

S1: spin singlet

T1: spin triplet

Claims (10)

(a) first and second quantum dots connecting a source and a drain and these to an upper silicon layer on an insulating film (SOI) substrate, and at least three first to third gates formed on one side of the first and second quantum dots; And a single-electron transistor formed on the other side of the first and second quantum points facing the one side where the first to third gates are formed to sense a qubit within the double quantum point formed by the first and second quantum points. Forming a pattern on the same plane; (b) etching the remaining silicon layer except for the pattern formed in the patterning step (a); (c) forming a doping mask in the conductive channel formed by the first and second quantum dots and the third quantum dots of the single-electron transistor and doping the remaining portions; (d) forming a gate oxide film on the top surface of the silicon layer; (e) forming a control gate to a size to cover the first to third quantum dots and etching the remaining portions; And (f) a metallization step for forming a metal thin film of the substrate; manufacturing method of a single electron transistor for spin qubit sensing comprising a. delete The method of claim 1, The single-electron transistor may be positioned between the third quantum dot disposed between the first and second quantum dots, a source and a drain connected in a "V" shape around the third quantum dot, and positioned between the source and the drain. A method of manufacturing a single-electron transistor for spin qubit detection, comprising the formed side gate. delete The method of claim 1, The patterning step (a) is a method of manufacturing a single electron transistor for spin qubit sensing, characterized in that to form a pattern by electron beam lithography or focused ion beam (FIB). delete delete delete delete A single electron transistor for spin qubit sensing, comprising the manufacturing method according to any one of claims 1, 3, and 5.

Images