KR20100121942A - Spin transistor - Google Patents

Abstract

PURPOSE: A spin transistor is provided to uniformly the spin at a channel by making the length of channel between a source and a drain short. CONSTITUTION: A channel(120) formed with magnetic materials selectively passes a spin-polarized electrons in a certain direction. A source(130) is formed with the magnetic materials. A gate electrode(110) controls the magnetization state of the channel to pass the electrons which is flowed into the channel from a drain and a source. The source, channel, and drain which are perpendicularly formed to the substrate.

Description

Spin transistor

It relates to a spin transistor stacked vertically on a substrate.

When manufacturing semiconductor devices on a nano scale, the increase in carrier mobility does not follow the growth rate of the devices, and the power requirement may not decrease despite the size reduction of the devices. In order to solve this problem, a technique using an electron spin has been proposed.

The spin transistor is a device that is turned on by the movement of spin-polarized electrons. The spin transistor may have a small amount of power required for the movement of electrons and may be turned on quickly.

On the other hand, if the channel length of the spin transistor is longer, the probability that the electron spin direction is changed can be increased. Therefore, it is important to shorten the channel length of the spin transistor.

In addition, in the case of forming the source and the drain on the channel of the spin transistor, the layers for the gate, the channel, the source and the drain are subsequently deposited in order to ensure the flatness of the interface compatibility of the device, and then the gate is exposed through the patterning process. Ion milling is performed to Ion milling is difficult to control the etching thickness, and if the thickness of the etch stop layer is thin, device defects may occur.

An embodiment of the present invention provides a spin transistor having a short channel length and minimizing a problem that may occur during etching.

Spin transistor according to an embodiment of the present invention is:

A channel formed of a magnetic material for selectively passing electrons spin-polarized in a specific direction;

A source formed of magnetic material;

drain; And

And a gate electrode for controlling the magnetization state of the channel to selectively pass electrons injected from the source into the channel.

The source, channel, and drain are sequentially formed perpendicular to the substrate, and the gate electrode is formed to surround the channel.

The channel is controlled by an electric field generated by the voltage applied to the gate electrode to control the passage of spin polarized electrons injected from the source.

In an embodiment, a spin transistor includes: a source electrode pad formed between the source and the substrate; And

A drain electrode pad formed on the drain may be further provided.

In addition, a first tunnel barrier between the channel and the source; And

And a second tunnel barrier between the channel and the drain.

The source includes a ferromagnetic layer on the first tunnel barrier; And

A metal layer on the ferromagnetic layer; may be further provided.

The source may further include an antiferromagnetic layer formed between the ferromagnetic layer and the metal layer.

The drain may include a magnetic layer on the second tunnel barrier; And a metal layer on the magnetic layer.

The magnetic layer of the drain may be a ferromagnetic layer.

The drain may further include an antiferromagnetic layer between the ferromagnetic layer and the metal layer.

The tunnel barrier may be formed of magnesium oxide or aluminum oxide.

The channel may be formed of a ferromagnetic material.

The ferromagnetic material may be CrAs, MnAs, CrSe having half metal or half metal properties.

In addition, the channel may be formed of any one material of CoFe, CoFeB, Fe, Co, Mn, permoloy.

The channel may be formed of a diluted magnetic semiconductor material that is doped with a transition metal to the semiconductor to make it magnetic.

The channel may be formed of a general semiconductor or an insulator.

According to the spin transistor according to the embodiment of the present invention, the distance of the channel between the source and the drain can be formed short, so that the spin state in the channel can be kept constant.

In addition, by forming the source, the channel and the drain perpendicular to the substrate to form a thick source electrode pad under the source to use as an etch blocking layer of the ion milling, it is possible to prevent damage to the device during the etching process and selective etching The process can be simplified by eliminating the need for

Hereinafter, a spin transistor according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this process, the thicknesses of layers or regions illustrated in the drawings are exaggerated for clarity.

1 and 2 are schematic cross-sectional and perspective views of a spin transistor 100 according to an embodiment of the present invention. 2 is a view of a part of the insulating layer of FIG. 1 is omitted.

1 and 2, an insulating layer 104 and a source electrode pad 139 are formed on a substrate 102. The substrate 102 may be a conventional silicon substrate, and the insulating layer 104 may be formed of silicon oxide. The source electrode pad 139 may be formed of a conductive material, and may be formed of a material having good ion milling, such as titanium nitride (TiN).

The source 130, the channel 120, and the drain 140 are sequentially stacked on the source electrode pad 139. The drain electrode pad 149 is formed on the drain 140. The gate 110 is surrounded by the gate oxide layer 112 around the channel 120. The gate electrode pad 119 is formed on one side of the gate 110. An insulating layer 150 is formed between the gate 110, the drain electrode pad 149, and the gate electrode pad 119. The insulating layer 150 may be formed of the same material as the gate oxide layer 112, for example, silicon oxide.

A first tunnel barrier 132 may be formed between the channel 120 and the source 130, and a second tunnel barrier 142 may be formed between the channel 120 and the drain 140. have. The first tunnel barrier 132 and the second tunnel barrier 142 may be formed of a material disposed between both magnetization layers in a tunneling magneto resistivity (TMR) device. For example MgO, aluminum oxide (AlOx), such as Al ₂ O ₃ , can be used, in particular high MR ratios can be obtained when using MgO as a tunnel barrier.

Source 130 may be formed of a magnetic material, for example a ferromagnetic material. The source 130 may include a ferromagnetic layer 134 on the first tunnel barrier 132 and a metal layer 138 on the ferromagnetic layer 134. In addition, the source 130 may further include an antiferromagnetic layer 136 between the ferromagnetic layer 134 and the metal layer 138.

The ferromagnetic layer 134 facilitates injection of spin polarized electrons into the source 130.

The antiferromagnetic layer 136 fixes the spin direction of the spin polarized electrons of the ferromagnetic layer 134.

The drain 140 may be formed of a general metal. In addition, the drain 140 may be formed of a magnetic material, for example, a ferromagnetic material. The drain 140 may be formed of only the metal layer 148. The drain 140 may include a ferromagnetic layer 144 between the second tunnel barrier 142 and the metal layer 148. In addition, the drain 140 may further include an antiferromagnetic layer 146 between the ferromagnetic layer 144 and the metal layer 148.

The channel 120 may be formed to be several nm to several tens of nm in height, thus reducing the operational error of the transistor due to the change in the direction of the spin.

Channel 120 is a passage of spin polarized electrons between source 130 and drain 140. Channel 120 acts as a filter to selectively pass spin polarized electrons in a particular direction, such as an upspin or downspin direction, injected from source 130. The filter role of the channel 120 may depend on the voltage applied to the gate electrode 110.

At this time, the first tunnel barrier 132 filters electrons having an undesired spin direction entering the channel 120, and the second tunnel barrier 142 moves from the channel 120 to the drain 140. It filters out passage of electrons with unwanted spin direction.

In this case, the spin transistor 100 according to the embodiment of the present invention becomes a transistor using the field effect.

Channel 120 may be formed of a ferromagnetic material, such as half metal. The half metal is formed of a semiconductor having a magnetic oxide, a magnetic double perovskite structure material, a magnetic Heusler alloy, a magnetic half Heaulser alloy and a half metal property. Can be.

The magnetic oxide may be CrO ₂ , Fe ₃ O ₄ , NiO, TiO ₂ .

The magnetic double perovskite structure material, the chemical composition is represented by A ₂ BB'O ₆ A is at least one selected from Ca, Sr, Ba, B is a 3d orbital transition metal, such as Fe or Co, B 'corresponds to a 4d orbital transition metal such as Mo or Re. For example, Sr ₂ FeMoO ₆ , Sr ₂ FeReO _6, and the like.

The magnetic hoistler alloy is made of at least one selected from the composition consisting of X ₂ YZ, X ₂ YZ ', X ₂ Y'Z, X ₂ Y'Z', and X is at least one selected from Co, Fe, and Ru. Y is one of Cr, Mn, and Z is one of Si, Ge, Sn, Al, Ga, Sb, Pb. For example, Co ₂ CrAl, Co ₂ MnSi can be used.

The magnetic anti-Hoissler alloy may be made of NiMnSb, PdMnSb, PtMnSb, CoMnSb, IrMnSb, NiCrSb, FeMnSb, CoCrSb, NiVSb, CoVSb, CoTiSb, NiMnSe, NiMnTe, CoFeSb, or NiFeSb group.

The semiconductor exhibiting the half metal property may be one of CrAs, MnAs, and CrSe.

The channel 120 is CoFe, CoFeB, Fe, Co, Mn It may be formed of a ferromagnetic metal of any one of the permoloy. The channel 120 may be formed of a dilute magnetic semiconductor material which is doped with a transition metal to the semiconductor to show magnetism. The diluted magnetic semiconductor is (In, Mn) As, (Ga, Mn) As, (Zn, Co) O, (Zn, V) O, (Ga, Mn) N, (Ga, Cr) N, (Cd , Mn) GeP ₂ , (Zn, Mn) GeP ₂ , (Ti, Cr) O ₂ , (Zn, Cr) Se. Here, the former in parentheses is the parent, and the latter is the doping substance (or substitution substance). In addition, transition metal doped semiconductors such as Manganite series such as NiMnSb, La _{(1 ?? x)} A _x MnO ₃ (A = Ca, Ba, Sr, 0.2 <x <0.3) and Cu doped GaN Doped semiconductor) also has the characteristics of half metal.

Half metals have down spin electrons and up spin electrons, and a gap is formed around the Fermi level in one spin electron and has semiconductor properties, and the other spin metal has metal properties.

 When the source 130 and the drain 140 include the ferromagnetic layers 134 and 144, the ferromagnetic layers 134 and 144 are manufactured so that the spin directions are predominantly formed in the same direction, respectively. As the ferromagnetic metal, NiFe alloys, CoFe alloys, CoFeB alloys, Fe, Co, Mn, permolloy and the like can be used. The ferromagnetic layers 134 and 144 may have higher density of states (DOS) in one direction, for example, up spin electrons than down spin electrons. In contrast, the general metal may have almost the same density of states (DOS) of the up and down spin electrons, and the drain 140 may be formed of the normal metal.

The antiferromagnetic layers 136 and 146 may be formed of FeMn, PtMn, PtCrMn, or the like.

When the channel 120 is formed of half metal, and the source 130 and the drain 140 are formed of a ferromagnetic material, the channel 120 is a semiconductor in the predominant electron spin direction of the source 130 and the drain 140. It can be formed to have properties. A driving method of the spin transistor 100 of FIGS. 1 and 2 will be described with reference to FIGS. 3 and 4. 3 and 4 are energy band diagrams of the source 130, the drain 140, and the first tunnel barrier 132 and the second tunnel barrier 142. The same reference numerals are used for the same components as those in FIG. 1 and detailed descriptions thereof will be omitted.

Referring to FIG. 3, the source 130 and the drain 140 are formed of ferromagnetic metal, and the channel 120 is formed of half metal. The upstream of the source 130 and the drain 140 are predominantly formed, respectively, and the channel 120 has a semiconductor property in the upspin direction. A 1 V bias voltage is applied to the drain 140 and a ground voltage is applied to the source 130 to move the electron spin from the source 130 to the drain 140.

The amount of down spin electrons, which are minor carriers in the source 130, is small, and the tunnel barriers (MgO layers) 132 and 142 selectively tunnel only upspin electrons, which are major carriers. The channel 120 blocks the flow of upspin electrons to prevent the upspin electrons from moving to the drain 140, so that no current flows in the channel 120. In other words, the transistor 100 is turned off. The turn-off state of the transistor 100 may be determined based on the current (drain current) measured at the drain 140. Referring to FIG. 3, when a 0.5 V gate voltage is applied to the gate electrode 110, the conduction band of the upspin electrons of the channel 120 aligns with the Fermi level of the source 130, and thus the source 130. Upspin electrons in the N-S are moved to the channel 120 through the first tunnel barrier 132, and up-spin electrons in the channel 120 are moved to the drain 140 through the second tunnel barrier 142. . Accordingly, current flows in the channel 120, and thus the transistor 100 is turned on.

As such, electrons spin-polarized to the gate voltage may selectively pass through the channel 120, and thus the spin transistor 100 is turned on. In the spin transistor 100 according to the exemplary embodiment of the present invention, the mobility is increased as compared with the conventional semiconductor device, and the power required for the movement of the spin electrons is smaller than the power required for the electron movement. Can be reduced. Therefore, it is possible to manufacture a miniaturized transistor by scaling down.

The channel 120 according to the embodiment of the present invention may also be formed of a general semiconductor such as silicon. Spin electrons injected from the source 130 enter the channel 120 and flow through the conduction band to the drain 140.

The channel 120 according to another embodiment of the present invention may also be formed of an insulator such as alumina or silicon oxide. In this case, the channel 120 is formed vertically, and the distance between the source 130 and the drain 140 may be formed by the deposition thickness of the channel material, so that the channel 120 may be formed to have a thickness of several nm. In principle it may pass through channel 120.

5 to 8 illustrate a method of manufacturing a spin transistor according to an exemplary embodiment of the present invention. The same reference numerals are used for components substantially the same as those in FIG. 1, and detailed description thereof will be omitted.

A method of manufacturing a spin transistor will be described with reference to FIGS. 5 to 8.

Referring to FIG. 5, the silicon oxide layer 104 is formed on the silicon substrate 102. Subsequently, the source electrode pad layer 139, the source layer 130, the channel layer 120, and the drain layer 140 are sequentially deposited on the silicon oxide layer 104.

Referring to FIG. 6, the pillars 150 may be formed by sequentially patterning the layers 140, 120, and 130 on the source electrode pad 139. Even when the filler 150 is formed, ion milling can be stopped in the source electrode pad layer 139 having a relatively high thickness, so that damage to the device due to etching can be prevented.

A first tunnel barrier layer (132 of FIG. 1) may be further formed between the source 130 and the channel 120, and a second tunnel barrier layer (142 of FIG. 1) may be formed between the drain 140 and the channel 120. ) May be further formed, and the first tunnel barrier layer 132 and the second tunnel barrier layer 142 are omitted in FIGS. 5 and 6 for convenience.

In addition, the source 130 and the drain 140 are formed of three layers of antiferromagnetic layers (134 and 144 in FIG. 1), ferromagnetic layers 136 and 146 and metal layers 138 and 148 on the channel 120, respectively. 5 and 6 are shown as one layer for convenience.

Referring to FIG. 7, the gate oxide 112 and the gate 110 are sequentially deposited on the filler 150. The gate oxide 112 may be silicon oxide, and the gate 110 may be formed of polysilicon. Subsequently, the gate 110 and the gate oxide 112 are patterned sequentially.

Referring to FIG. 8, an interlayer insulating layer 160 is formed on the source electrode pad layer 139 to cover the gate 110. Subsequently, the interlayer insulating layer 160, the gate 110, and the gate oxide 112 are exposed to the drain 140 by a chemical mechanical planarization (CMP) process.

Subsequently, after further forming a second insulating layer (not shown) on the resultant of FIG. 8, the drain electrode pad 149 of FIG. 1 and the gate electrode pad 119 are formed. Since the method for manufacturing the electrode pads 149 and 119 is well known in the semiconductor process, detailed description thereof will be omitted.

Although the present invention has been described with reference to the embodiments with reference to the drawings, this is merely exemplary, it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined only by the appended claims.

1 and 2 are schematic cross-sectional and perspective views of a spin transistor 100 according to an embodiment of the present invention.

3 and 4 are schematic energy band diagrams of the spin transistor of FIG. 1.

5 to 8 illustrate a method of manufacturing a spin transistor according to an exemplary embodiment of the present invention.

Claims (16)

A channel formed of a magnetic material for selectively passing electrons spin-polarized in a specific direction; A source formed of magnetic material; drain; And And a gate electrode for controlling the magnetization state of the channel to selectively pass electrons injected from the source into the channel. The source, channel, and drain are sequentially formed perpendicular to the substrate, and the gate electrode is formed to surround the channel. The method of claim 1 And controlling the channel with the electric field generated by the voltage applied to the gate electrode to control the passage of spin polarized electrons injected from the source. The method of claim 1 A source electrode pad formed between the source and the substrate; And And a drain electrode pad formed on the drain. The method of claim 1 A first tunnel barrier between the channel and the source; And And a second tunnel barrier between the channel and the drain. The method of claim 4 The source includes a ferromagnetic layer on the first tunnel barrier; And And a metal layer on the ferromagnetic layer. The method of claim 5 And the source further comprising an antiferromagnetic layer formed between the ferromagnetic layer and the metal layer. The method of claim 4 The drain may include a magnetic layer on the second tunnel barrier; And a metal layer on the magnetic layer. The method of claim 7, The magnetic layer of the drain is a ferromagnetic layer. The method of claim 8 The drain further comprises an antiferromagnetic layer between the ferromagnetic layer and the metal layer. The method of claim 4, wherein The tunnel barrier is a spin transistor formed of magnesium oxide or aluminum oxide. The method of claim 1 And the channel is a ferromagnetic material. The method of claim 11 The ferromagnetic material is a spin metal having a half metal or half metal properties CrAs, MnAs, CrSe. 13. The method of claim 12, The channel is a spin transistor formed of any one of CoFe, CoFeB, Fe, Co, Mn, Permolloy. The method of claim 11 And the channel is formed of a diluted magnetic semiconductor material made of a semiconductor by doping a semiconductor with a transition metal. The method of claim 11 The channel is a spin transistor formed of a general semiconductor. The method of claim 11 And the channel is formed of a non-conductor.

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