JP6905188B2 - Semiconductor devices and their manufacturing methods - Google Patents

Description

The present invention relates to a semiconductor device and a method for manufacturing the same.

Graphene, which is a two-dimensional material having extremely high charge mobility, is attracting attention as a material for overcoming the limit of miniaturization of LSI. ^{Graphene has a high mobility of about 100,000 cm 2} / Vs even at room temperature, and since there is no difference in electron and hole mobilities, graphene is expected as a channel material in future electronic devices. However, since there is no band gap, the on / off ratio is small as it is, and it is difficult to use it as a switching element. Various methods for forming a bandgap have been proposed, and as one of them, a method for forming a bandgap by converting graphene into nanoribbons and producing graphene nanoribbons (GNR) has been proposed. Since the GNR can modulate the electronic state with a modifying group that terminates its edge, a heterojunction can be realized by combining GNRs having different termination modifying groups.

However, the diffusion potential of the heterojunction due to the combination of GNRs having different terminal modifying groups is small, and sufficient characteristics cannot be obtained.

Japanese Unexamined Patent Publication No. 2016-090510 Japanese Unexamined Patent Publication No. 2015-1975 Japanese Unexamined Patent Publication No. 2016-194424 Japanese Patent Application Laid-Open No. 2014-505580

J. Cai et al., Nature 466 (2010) 470

An object of the present invention is to provide a semiconductor device capable of obtaining a large diffusion potential and a method for manufacturing the same.

One aspect of the semiconductor device includes graphene nanoribbons and gas molecules that modify the surface of the graphene nanoribbons. The graphene nanoribbon has a first region whose end is terminated by a first modifying group and a second modifying group that is heterojunction to the first region and is different from the first modifying group. A second region, which is terminated, is included.

In one aspect of the method for manufacturing a semiconductor device, a first region whose end is terminated by a first modifying group and a second region that is heterobonded to the first region and is different from the first modifying group. A graphene nanoribbon having a second region whose end is terminated by a modifying group is formed, and the surface of the graphene nanoribbon is modified with a gas molecule.

In one aspect of the gas sensor, a first region whose ends are terminated by a first modifying group and a second modifying group that is heterojunction to the first region and is different from the first modifying group. Included is a graphene nanoribbon with a second region that is terminated at the ends. The first region and the second region are exposed.

According to the above-mentioned semiconductor device or the like, an appropriate graphene nanoribbon is included, and the surface of the graphene nanoribbon is modified with gas molecules, so that a large diffusion potential can be obtained.

It is a figure which shows the example of the graphene nanoribbon (GNR) whose end is a modifying group R. It is a figure which shows the relationship between the type of a modifying group R, and the energy of the bottom of the conduction band of GNR and the top of a valence band. It is a figure which shows the composite GNR which contains the 1st region which the end part is a modification group R ₁ and the 2nd region which end is a modification group R _2. It is a figure which shows the structure which modified the surface of the composite GNR of FIG. 3 with a gas molecule X. It is a figure which shows the band structure at the time of adsorbing a gas molecule to GNR of H terminal. It is a figure which shows the band structure at the time of adsorbing a gas molecule to GNR of F terminal. It is a figure which shows the electronic state when the surface of the composite GNR of FIG. 3 is modified with a gas molecule X. It is a figure which shows the change of the current-voltage characteristic of a pn junction diode with change of a diffusion potential. It is a figure which shows the semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the manufacturing method of the semiconductor device which concerns on 1st Embodiment in process order. Following FIG. 10A, it is a cross-sectional view showing the manufacturing method of the semiconductor device in the order of processes. It is a figure which shows the semiconductor device which concerns on 2nd Embodiment. It is sectional drawing which shows the manufacturing method of the semiconductor device which concerns on 2nd Embodiment in process order. Following FIG. 12A, it is a cross-sectional view which shows the manufacturing method of a semiconductor device in process order. It is a figure which shows the semiconductor device which concerns on 3rd Embodiment. It is sectional drawing which shows the manufacturing method of the semiconductor device which concerns on 3rd Embodiment in process order. It is sectional drawing which shows the gas sensor which concerns on 4th Embodiment. It is sectional drawing which shows the manufacturing method of the gas sensor which concerns on 4th Embodiment in process order. It is a figure which shows the modification of 1st Embodiment. It is a figure which shows the modification of the 2nd Embodiment. It is a figure which shows the modification of the 3rd Embodiment. It is sectional drawing which shows the transistor of the n ⁺ p ⁻ p ^{+ structure.} It is sectional drawing which shows the transistor of another n ⁺ p ^- p ^{+ structure.} It is sectional drawing which shows the transistor of the p ⁺ n ⁻ n ^{+ structure.}

(Characteristics of graphene nanoribbon (GNR))
First, the properties of graphene will be described. FIG. 1 shows an example of GNR having a modifying group R at the end. FIG. 2 shows the relationship between the type of modifying group R and the energy at the bottom of the conduction band and the top of the valence band of GNR. In FIG. 2, the vacuum levels of each GNR are aligned. As the structure of the GNR, an armchair GNR having seven dimer lines was assumed as shown in FIG.

Figure 3 shows a composite GNR comprising a second region the first region and the end edge portion is a modifying group R ₁ is a modifying group R _2. FIG. 3A shows a structural formula, and FIG. 3B shows _{an electronic state when the modifying group R 1} is H (H-terminated) and the modifying group R ₂ is F (F-terminated). The diffusion potential V _D0 is the energy difference between the bottom of the conduction band at the H end and the bottom of the conduction band at the F end. Since the Fermi level of the GNR at the H end is shallower than the Fermi level of the GNR at the F end, the first region at the H end is doped with a p-type and the second region at the F end is doped with an n-type. Is equivalent to. Therefore, a pn junction is formed. That is, in this composite GNR, the first region and the second region are heterojunction to each other. Even if, for example, a Cl-terminated GNR is used instead of the F-terminated GNR, since the Fermi levels of the two are close to each other, substantially the same pn junction is formed. Strictly speaking, all GNRs having different modifying groups shown in FIG. 2 have different Fermi levels. Therefore, any combination of GNRs shown in FIG. 2 forms a pn junction. However, the degree of doping differs depending on the difference in Fermi level and the difference in band gap. Generally, the larger the difference in the original Fermi level, the stronger the doping to p-type or n-type. In the example shown in FIG. 2, the combination of the F-terminal or Cl-terminal GNR and the NH _2- terminal GNR forms a pn junction having a particularly large degree of doping.

FIG. 4 shows a structure in which the surface of the composite GNR of FIG. 3 is modified with a gas molecule X. FIG. 4A shows the structure of the composite GNR seen from the thickness direction, and FIG. 4B shows the structure seen from the direction perpendicular to the thickness direction. The gas molecule X is adsorbed in the direction perpendicular to the plane of GNR.

FIG. 5 shows a band structure when gas molecules are adsorbed on the H-terminal GNR, and FIG. 6 shows a band structure when gas molecules are adsorbed on the F-terminal GNR. These band structures are obtained by first-principles calculation. 5 (a) and 6 (a) show a band structure when the gas molecule X is not adsorbed as a reference. 5 (b) and 6 (b) _{show the band structure when the gas molecule X is a nitrogen molecule (N 2} ), and FIGS. 5 (c) and 6 (c) show the gas molecule X. Is an ammonia molecule (NH ₃ ), and FIG. 5 (d) and FIG. 6 (d) show a band structure when the gas molecule X is a nitrogen dioxide molecule (NO ₂ ). As shown in FIG. 5, in the H-terminated GNR, when the gas molecule X is N ₂ or NO ₂ , the energy positions at the bottom of the conduction band and the top of the valence band hardly change, but the gas molecule X is NH. _{If it is 3} , the bottom of the conduction band and the top of the valence band shift upward by about 0.4 eV. As shown in FIG. 6, in the F-terminated GNR, when the gas molecule X is N ₂ or NH ₃ , the energy positions at the bottom of the conduction band and the top of the valence band hardly change, but the gas molecule X is NO. _{If it is 2} , the bottom of the conduction band shifts downward by about 0.3 eV.

FIG. 7 shows the electronic state when the surface of the composite GNR of FIG. 3 is modified with the gas molecule X. FIG. 7A shows an electronic state when the gas molecule X is NH ₃ , and FIG. 7B shows an electronic state when the gas molecule X is NO ₂ . When the gas molecule X is NH ₃ , as shown in FIG. 7 (a), the bottom of the conduction band and the top of the valence band shift upward by _{ΔV 1 in the first region of the H termination, but F} In the second region of the termination, the energy positions at the bottom of the conduction band and at the top of the valence band do not change. Therefore, the diffusion potential V _D1 is larger by _{ΔV 1} than the diffusion potential V _D0. When the gas molecule X is NO ₂ , as shown in FIG. 7 (b), the energy positions of the bottom of the conduction band and the top of the valence band do not change in the first region of the H termination, but the first region of the F termination. In region 2, the bottom of the conduction band shifts downward in energy _{by ΔV 2.} Therefore, the diffusion potential V _{D 2} is larger than the diffusion potential V _{D 0 by ΔV 2.} By modifying the surface of the composite GNR of FIG. 3 with NH ₃ or NO ₂ , a diffusion potential V _D1 or V _D2 larger than the diffusion potential V _D0 can be obtained.

FIG. 8 shows the change in the current-voltage characteristics of the pn junction diode with the change in the diffusion potential. The broken line in FIG. 8 shows the characteristics of the composite GNR not modified with gas molecules (diffusion potential is V _D0 ), and the solid line shows the characteristics of the composite GNR modified with _{NH 3 (diffusion potential is V D1} ). .. As shown in FIG. 8, _{in the composite GNR modified with NH 3} , the yield voltage when the reverse bias is applied increases. This means that the withstand voltage performance is improved and the leakage current is reduced.

In this way, a large diffusion potential can be obtained by providing a region in the GNR where the modifying groups at the ends are different and heterojunction with each other and modifying the surface of the GNR with a predetermined gas molecule, and a semiconductor device (electronic device). Performance can be improved.

Hereinafter, embodiments will be specifically described with reference to the accompanying drawings.

(First Embodiment)
Next, the first embodiment will be described. The first embodiment relates to a transistor having a pnp structure. FIG. 9 is a diagram showing a semiconductor device according to the first embodiment. 9 (a) is a top view, and FIG. 9 (b) is a cross-sectional view taken along the line I-I in FIG. 9 (a).

As shown in FIG. 9, the semiconductor device 100 according to the first embodiment includes a substrate 101 having a groove 102 formed on its upper surface, and a GNR 110 is provided on the substrate 101 so as to close the groove 102. There is. The substrate 101 is, for example, a silicon substrate having an insulating film such as a silicon oxide film formed on its surface. The GNR 110 includes an H-terminal GNR111a, an F-terminal GNR112, and an H-terminal GNR111b, and the F-terminal GNR112 is sandwiched between the H-terminal GNR111a and the H-terminal GNR111b. A pn junction is formed between the H-terminal GNR111a and the F-terminal GNR112, and a pn junction is formed between the H-terminal GNR111b and the F-terminal GNR112. A part of GNR110 is above the groove 102, and the surface of GNR110 on the groove 102 side is modified with _{NH 3} or NO _{2 gas molecules.} That is, the modification layer 109 is provided on the surface of the GNR 110 on the groove 102 side. The H-terminal GNR111a is an example of the first region, the F-terminal GNR112 is an example of the second region, and the H-terminal GNR111b is an example of the third region.

A gate insulating film 105 and a gate electrode 106 are provided on the F-terminal GNR 112, and a source electrode 107 connected to the H-terminal GNR 111a and a drain electrode 108 connected to the H-terminal GNR 111b are provided on the substrate 101. For example, the gate electrode 106, the source electrode 107, and the drain electrode 108 each include a Ti film and an Au film on the Ti film, and the gate insulating film 105 contains an HfO ₂ film.

In the semiconductor device 100 according to the first embodiment, the H-terminal GNR111a and 111b function as p-type semiconductors, and the F-terminal GNR112 functions as an n-type semiconductor. Therefore, the semiconductor device 100 functions as a transistor having a pnp structure. Since the surface of GNR110 _{is modified with NH 3} or NO ₂ gas molecules, a large diffusion potential can be obtained and excellent performance can be obtained.

The size of the GNR 110 is not limited, but the width in the lateral direction, that is, the channel width is preferably 10 nm or less. This is to obtain the properties of the semiconductor more reliably.

Next, a method of manufacturing the semiconductor device 100 according to the first embodiment will be described. 10A to 10B are cross-sectional views showing the manufacturing method of the semiconductor device 100 according to the first embodiment in the order of processes.

First, as shown in FIG. 10A (a), a groove 102 is formed in the substrate 101. For example, the groove 102 can be formed by irradiating or etching a laser beam. The groove 102 is preferably formed so that the length in the source / drain direction is smaller than the length in the longitudinal direction of the GNR 110, and the length (width) in the direction perpendicular to the direction is smaller than the channel width. That is, it is preferable that the groove 102 is formed so that the size in the longitudinal direction is smaller than the size in the longitudinal direction of the GNR 110 and the size in the lateral direction is smaller than the size in the lateral direction of the GNR 110. Further, for example, the depth of the groove 102 is preferably 1 nm or more.

The H-terminal GNR111 is prepared separately, and as shown in FIG. 10A (b), the H-terminal GNR111 is provided on the substrate 101 so as to close the groove 102. Here, an example of a method of forming the H-terminated GNR111 will be described. In this method, first, an anthracene dimer precursor whose end is terminated with H is deposited on an Au (111) substrate or an Ag (111) substrate heated to, for example, about 180 ° C. to about 250 ° C. At this time, the anthracene dimer precursors are linearly linked by radical polymerization. Next, the temperature of the substrate is raised to, for example, about 350 ° C. to about 450 ° C., and the temperature is maintained for about 10 minutes to about 20 minutes. As a result, an anthracene GNR having a uniform width of about 0.7 nm and having an armchair-shaped end of the armchair-shaped edge structure along the longitudinal direction is formed by the ring-condensation reaction. In this way, the H-terminated GNR111 can be formed. This method is described, for example, in Non-Patent Document 1. Instead of the anthracene dimer, a pentacene dimer, a nonacene dimer, or the like may be used.

The atmosphere when the H-terminated GNR 111 is provided on the substrate 101 is, for example, an NH ₃ gas atmosphere. By setting the atmosphere to the NH ₃ gas atmosphere, the NH ₃ molecules in the groove 102 are adsorbed on the H-terminated GNR 111, and the modified layer 109 is formed. When the atmosphere is a NO ₂ gas atmosphere, a NO ₂ modified layer 109 is formed. When the depth of the groove 102 is 1 nm or more, the modified layer 109 can be easily formed.

After the H-terminal GNR111 is provided on the substrate 101, as shown in FIG. 10A (c), the other H-terminal GNR111 is provided with an opening 122 that exposes the area where the F-terminal GNR112 of the H-terminal GNR111 is to be formed. A resist mask 121 covering the region is formed. When forming the resist mask 121, a resist is applied onto the substrate 101 so as to cover the H-terminated GNR 111, and the resist is patterned by lithography. In this way, the resist mask 121 having the opening 122 is formed.

Next, by heating the H-terminal GNR111 together with the substrate 101 in a fluorine atmosphere, the central portion of the H-terminal GNR111 exposed from the opening 122 is fluorinated. As a result, as shown in FIG. 10B (d), the F-terminal GNR112 is formed in the central portion of the H-terminal GNR111, the H-terminal GNR111a is obtained on one side thereof, and the H-terminal GNR111b is obtained on the other side. In this way, the H-terminal GNR111a, the F-terminal GNR112, and the H-terminal GNR111b are arranged in this order to form a heterojunction GNR110.

Then, as shown in FIG. 10B (e), the resist mask 121 is removed. The resist mask 121 can be removed by, for example, an ashing treatment or a wet treatment. Subsequently, the gate insulating film 105 and the gate electrode 106 are formed on the F-terminal GNR 112. The gate insulating film 105 and the gate electrode 106 can be formed by, for example, a lift-off method. For example, a resist is applied onto the substrate 101 so as to cover the GNR 110, and the resist is patterned by lithography in a shape that exposes the F-terminal GNR 112. Next, Al is thinly deposited on the entire surface by a sputtering method or the like to about 1 nm, and an insulator, for example, HfO _2, is deposited by an atomic layer deposition (ALD) method using this Al as a seed layer. Then, metals such as Ti and Au are deposited on an insulating material such as _{HfO 2 by a vapor deposition method or a sputtering method.} Then, the resist mask and the insulators and metals deposited on the resist mask are removed. In this way, the gate insulating film 105 of the insulator and the metal gate electrode 106 are formed.

Next, as shown in FIG. 10B (f), the source electrode 107 connected to the H-terminal GNR111a and the drain electrode 108 connected to the H-terminal GNR111b are formed on the substrate 101. The source electrode 107 and the drain electrode 108 can be formed by, for example, a lift-off method. For example, a resist is applied onto the substrate 101 so as to cover the GNR 110, and the resist is patterned by lithography in a shape that exposes the regions where the source electrode 107 and the drain electrode 108 are to be formed. Then, a metal such as Ti and Au is deposited on the entire surface by a vapor deposition method or a sputtering method. Then, the resist mask and the metal deposited on the resist mask are removed. In this way, the metal source electrode 107 and drain electrode 108 are formed.

In this way, the semiconductor device 100 can be manufactured. After that, wiring, a passivation film, and the like may be formed.

Although the semiconductor device 100 according to the first embodiment has a pnp structure, it may have an npn structure. In order to obtain an npn structure, for example, the central portion of the GNR may be an H-terminal GNR, both end portions of the GNR may be an F-terminal GNR, and these may be heterojunctioned.

(Second embodiment)
Next, the second embodiment will be described. The second embodiment relates to a transistor having ^{a p +} in ^{+ structure.} FIG. 11 is a diagram showing a semiconductor device according to the second embodiment. 11 (a) is a top view, and FIG. 11 (b) is a cross-sectional view taken along the line I-I in FIG. 11 (a).

As shown in FIG. 11, the semiconductor device 200 according to the second embodiment includes a substrate 101 having a groove 102 formed on the upper surface thereof, and a GNR 210 is provided on the substrate 101 so as to close the groove 102. There is. The substrate 101 is, for example, a silicon substrate having an insulating film such as a silicon oxide film formed on its surface. The GNR 210 includes an NH ₂ terminal GNR211 and an H terminal GNR213 and an F terminal GNR212, and the H terminal GNR213 is _{sandwiched between the NH 2} terminal GNR211 and the F terminal GNR212. A _{heterojunction is formed between the NH 2} terminal GNR211 and the H terminal GNR213, and a heterojunction is formed between the H terminal GNR213 and the F terminal GNR212. A part of GNR210 is above the groove 102, and the surface of GNR210 on the groove 102 side is modified with _{NH 3} or NO _{2 gas molecules.} That is, the modification layer 209 is provided on the surface of the GNR 210 on the groove 102 side. The NH ₂ terminal GNR211 is an example of the first region, the H terminal GNR213 is an example of the second region, and the F terminal GNR212 is an example of the third region.

A gate insulating film 105 and a gate electrode 106 are provided on the H-terminal GNR _{213, and a source electrode 107 connected to the NH 2-} terminal GNR 211 and a drain electrode 108 connected to the F-terminal GNR 212 are provided on the substrate 101. .. For example, the gate electrode 106, the source electrode 107, and the drain electrode 108 each include a Ti film and an Au film on the Ti film, and the gate insulating film 105 contains an HfO ₂ film.

In the semiconductor device 200 according to the second embodiment, the NH _2- terminal GNR211 functions as a p-type semiconductor, the H-terminal GNR213 functions as an i-type semiconductor, and the F-terminal GNR212 functions as an n-type semiconductor. Therefore, the semiconductor device 200 functions as a transistor having ^{a p +} in ^{+ structure.} Since the surface of GNR210 _{is modified with NH 3} or NO ₂ gas molecules, a large diffusion potential can be obtained and excellent performance can be obtained.

The size of the GNR 210 is not limited, but the width in the lateral direction, that is, the channel width is preferably 10 nm or less. This is to obtain the properties of the semiconductor more reliably.

Next, a method of manufacturing the semiconductor device 200 according to the second embodiment will be described. 12A to 12B are cross-sectional views showing the manufacturing method of the semiconductor device 200 according to the second embodiment in the order of processes.

First, as shown in FIG. 12A (a), a groove 102 is formed in the substrate 101 as in the first embodiment. The groove 102 is preferably formed so that the size in the longitudinal direction is smaller than the size in the longitudinal direction of the GNR 210 and the size in the lateral direction is smaller than the size in the lateral direction of the GNR 210. Further, for example, the depth of the groove 102 is preferably 1 nm or more. The NH ₂ terminal GNR211 is prepared separately, and as shown in FIG. 12A (a), the NH ₂ terminal GNR211 is provided on the substrate 101 so as to close the groove 102. Here, an example of a method of forming the _{NH 2 terminal GNR211 will be described.} In this method, instead of the anthracene dimer precursor whose end is terminated with H, an anthracene dimer precursor whose end is _{terminated with NH 2} is used, and the same heat treatment as in the first embodiment is performed. As a result, the condensed reaction, has a uniform width of about 0.7 nm, the edge structure along the longitudinal direction end portions of the armchair is terminated anthracene GNR with NH ₂ is formed. In this way, the NH ₂ terminal GNR211 can be formed. Instead of the anthracene dimer, a pentacene dimer, a nonacene dimer, or the like may be used.

Atmosphere for providing the NH ₂ end GNR211 on the substrate 101 is, for example, NH ₃ gas atmosphere. By setting the atmosphere to the NH ₃ gas atmosphere, the NH ₃ molecules _{in the groove 102 are adsorbed on the NH 2} terminal GNR211 to form the modified layer 209. When the atmosphere is a NO ₂ gas atmosphere, a NO ₂ modified layer 209 is formed. When the depth of the groove 102 is 1 nm or more, the modified layer 209 can be easily formed.

_{After the NH 2} terminal GNR 211 is provided on the substrate 101, as shown in FIG. 12A (b), the NH ₂ terminal GNR 211 is provided with an opening 222 that exposes the area where the F terminal GNR 212 of _{the NH 2 terminal GNR 211 is to be formed, and the NH 2} terminal GNR 211 is provided. A resist mask 221 is formed to cover other regions. When forming the resist mask 221, a resist is applied onto the substrate 101 so as to cover the _{NH 2 terminal GNR 211, and the resist is patterned by lithography.} In this way, the resist mask 221 having the opening 222 is formed.

_{Next, by heating the NH 2} terminal GNR 211 together with the substrate 101 in a fluorine atmosphere, a part of the _{NH 2} terminal GNR 211 exposed from the opening 222 is fluorinated. As a result, as shown in FIG. 12A (c), an F-terminal GNR212 is formed in a part of the _{NH 2-terminal GNR211.}

Then, as shown in FIG. 12A (d), the resist mask 221 is removed. The resist mask 221 can be removed by, for example, an ashing treatment or a wet treatment. Subsequently, a resist mask 223 is provided with an opening 224 that exposes the region where the H-terminal GNR 213 of _{the NH 2-} terminal GNR 211 is to be formed, and covers the other region of _{the NH 2-terminal GNR 211.} The F-terminal GNR212 may be exposed from the resist mask 223 or may be covered with the resist mask 223. When forming the resist mask 223 _{, a resist is applied onto the substrate 101 so as to cover the NH 2} terminal GNR211 and the F terminal GNR212, and the resist is patterned by lithography. In this way, a resist mask 223 with an opening 224 is formed.

_{Next, by heating the NH 2} terminal GNR 211 together with the substrate 101 in a hydrogen atmosphere, _{NH 2 at} a part of the end of the NH ₂ terminal GNR 211 exposed from the opening 224 is replaced with H. As a result, as shown in FIG. 12B (e), an H-terminal GNR 213 is formed in a part of the _{NH 2-terminal GNR 211.} Since the F-terminal GNR212 is _{more heat-stable than the NH 2-} terminal GNR211, the structure of the F-terminal GNR212 hardly changes. In this way, a _{GNR 210 in which the NH 2-} terminal GNR211, the H-terminal GNR213, and the F-terminal GNR212 are arranged in this order and heterojunction is formed is formed.

Then, as shown in FIG. 12B (f), the resist mask 223 is removed. The resist mask 223 can be removed by, for example, an ashing treatment or a wet treatment. Subsequently, the gate insulating film 105 and the gate electrode 106 are formed on the H-terminal GNR 213. The gate insulating film 105 and the gate electrode 106 can be formed by the lift-off method as in the first embodiment.

Next, as shown in FIG. 12B (g), a _{source electrode 107 connected to the NH 2} terminal GNR 211 and a drain electrode 108 connected to the F terminal GNR 212 are formed on the substrate 101. The source electrode 107 and the drain electrode 108 can be formed by the lift-off method as in the first embodiment.

In this way, the semiconductor device 200 can be manufactured. After that, wiring, a passivation film, and the like may be formed.

(Third Embodiment)
Next, a third embodiment will be described. A third embodiment relates to a pn junction diode. FIG. 13 is a diagram showing a semiconductor device according to the third embodiment. 13 (a) is a top view, and FIG. 13 (b) is a cross-sectional view taken along the line I-I in FIG. 13 (a).

As shown in FIG. 13, the semiconductor device 300 according to the third embodiment includes a substrate 101 having a groove 102 formed on the upper surface thereof, and a GNR 310 is provided on the substrate 101 so as to close the groove 102. There is. The substrate 101 is, for example, a silicon substrate having an insulating film such as a silicon oxide film formed on its surface. The GNR 310 includes an H-terminal GNR311 and an F-terminal GNR312, and a pn junction is formed between the H-terminal GNR311 and the F-terminal GNR312. A part of GNR310 is above the groove 102, and the surface of GNR310 on the groove 102 side is modified with _{NH 3} or NO _{2 gas molecules.} That is, the modification layer 309 is provided on the surface of the GNR 310 on the groove 102 side. The H-terminal GNR311 is an example of the first region, and the F-terminal GNR312 is an example of the second region.

An anode electrode 307 connected to the H-terminal GNR311 and a cathode electrode 308 connected to the F-terminal GNR312 are provided on the substrate 101. For example, the anode electrode 307 and the cathode electrode 308 each include a Ti film and an Au film on it.

In the semiconductor device 300 according to the third embodiment, the H-terminal GNR311 functions as a p-type semiconductor, and the F-terminal GNR312 functions as an n-type semiconductor. Therefore, the semiconductor device 300 functions as a pn junction diode. Since the surface of GNR310 _{is modified with NH 3} or NO ₂ gas molecules, a large diffusion potential can be obtained and excellent performance can be obtained.

The size of the GNR 310 is not limited, but the width in the lateral direction is preferably 10 nm or less. This is to obtain the properties of the semiconductor more reliably.

Next, a method of manufacturing the semiconductor device 300 according to the third embodiment will be described. FIG. 14 is a cross-sectional view showing the manufacturing method of the semiconductor device 300 according to the third embodiment in the order of processes.

First, as shown in FIG. 14A, a groove 102 is formed in the substrate 101 as in the first embodiment. The groove 102 is preferably formed so that the size in the longitudinal direction is smaller than the size in the longitudinal direction of the GNR 310 and the size in the lateral direction is smaller than the size in the lateral direction of the GNR 310. Further, for example, the depth of the groove 102 is preferably 1 nm or more. The H-terminal GNR311 is prepared separately, and as shown in FIG. 14A, the H-terminal GNR311 is provided on the substrate 101 so as to close the groove 102. The H-terminal GNR311 can be formed in the same manner as the H-terminal GNR111.

The atmosphere when the H-terminated GNR311 is provided on the substrate 101 is, for example, an NH ₃ gas atmosphere. By setting the atmosphere to the NH ₃ gas atmosphere, the NH ₃ molecules in the groove 102 are adsorbed on the H-terminated GNR311 to form the modified layer 309. When the atmosphere is a NO ₂ gas atmosphere, a NO ₂ modified layer 309 is formed. When the depth of the groove 102 is 1 nm or more, the modified layer 309 can be easily formed.

After the H-terminated GNR311 is provided on the substrate 101, as shown in FIG. 14B, it is provided with an opening 322 that exposes the area where the F-terminated GNR312 of the H-terminated GNR311 is to be formed, and the other H-terminated GNR311. A resist mask 321 that covers the region is formed. When forming the resist mask 321, a resist is applied onto the substrate 101 so as to cover the H-terminated GNR311 and the resist is patterned by lithography. In this way, the resist mask 321 having the opening 322 is formed.

Next, by heating the H-terminal GNR311 together with the substrate 101 in a fluorine atmosphere, a part of the H-terminal GNR311 exposed from the opening 322 is fluorinated. As a result, as shown in FIG. 14C, the F-terminal GNR312 is formed in a part of the H-terminal GNR311. In this way, a GNR 310 is formed in which the H-terminal GNR311 and the F-terminal GNR312 are joined to each other.

Then, as shown in FIG. 14 (d), the resist mask 321 is removed. The resist mask 321 can be removed by, for example, an ashing treatment or a wet treatment. Subsequently, the anode electrode 307 connected to the H-terminal GNR311 and the cathode electrode 308 connected to the F-terminal GNR312 are formed on the substrate 101. The anode electrode 307 and the cathode electrode 308 can be formed by the lift-off method in the same manner as the source electrode 107 and the drain electrode 108.

In this way, the semiconductor device 300 can be manufactured. After that, wiring, a passivation film, and the like may be formed.

(Fourth Embodiment)
Next, a fourth embodiment will be described. A fourth embodiment relates to a gas sensor having an npn structure. FIG. 15 is a cross-sectional view showing a gas sensor according to a fourth embodiment.

As shown in FIG. 15A, the gas sensor 400 according to the fourth embodiment includes a GNR 410 provided on the substrate 401. The substrate 401 is, for example, a silicon substrate having an insulating film such as a silicon oxide film formed on its surface. The GNR 410 includes an F-terminal GNR412a, an H-terminal GNR411, and an F-terminal GNR412b, and the H-terminal GNR411 is sandwiched between the F-terminal GNR412a and the F-terminal GNR412b. A pn junction is formed between the H-terminal GNR411 and the F-terminal GNR412a, and a pn junction is formed between the H-terminal GNR411 and the F-terminal GNR412b.

An electrode 407 connected to the F-terminal GNR412a and an electrode 408 connected to the F-terminal GNR412b are provided on the substrate 401. For example, the electrodes 407 and 408 include a Ti film and an Au film on it, respectively.

In the gas sensor 400 according to the fourth embodiment, the F-terminal GNR412a and 412b function as n-type semiconductors, and the H-terminal GNR411 functions as p-type semiconductors. Further, since GNR410 is exposed, gas molecules can be adsorbed on GNR410. Then, as shown in FIG. 15B, when the gas molecule is adsorbed on the GNR 410, a modified layer 409 of the gas molecule is formed, and if the gas molecule is NH ₃ or NO ₂ , the diffusion potential changes before and after the adsorption. do. Therefore, gas adsorption can be detected through a change in the threshold value of the current-voltage characteristic.

The size of GNR410 is not limited, but the width in the lateral direction is preferably 10 nm or less. This is to obtain the properties of the semiconductor more reliably.

Next, a method of manufacturing the gas sensor 400 according to the fourth embodiment will be described. FIG. 16 is a cross-sectional view showing the manufacturing method of the gas sensor 400 according to the fourth embodiment in the order of processes.

First, the H-terminal GNR411 is prepared, and as shown in FIG. 16A, the H-terminal GNR411 is provided on the substrate 401. The H-terminal GNR411 can be formed in the same manner as the H-terminal GNR111.

Next, as shown in FIG. 16B, an opening 422a that exposes the region where the F-terminal GNR412a of the H-terminal GNR411 is to be formed and an opening 422b that exposes the region where the F-terminal GNR412b is to be formed are provided. A resist mask 421 that covers the other region (central portion) of the H-terminated GNR411 is formed. When forming the resist mask 421, a resist is applied onto the substrate 401 so as to cover the H-terminated GNR411, and the resist is patterned by lithography. In this way, a resist mask 421 having openings 422a and 422b is formed.

Next, by heating the H-terminal GNR411 together with the substrate 401 in a fluorine atmosphere, a part of the H-terminal GNR411 exposed from the openings 422a and 422b is fluorinated. As a result, as shown in FIG. 16C, the F-terminal GNR412a is formed in a part of the H-terminal GNR411, and the F-terminal GNR412b is formed in the other part. In this way, the F-terminal GNR412a, the H-terminal GNR411, and the F-terminal GNR412b are arranged in this order to form a heterojunction GNR410.

Then, as shown in FIG. 16D, the resist mask 421 is removed. The resist mask 421 can be removed by, for example, an ashing treatment or a wet treatment. Subsequently, an electrode 407 connected to the F-terminal GNR412a and an electrode 408 connected to the F-terminal GNR412b are formed on the substrate 401. The electrodes 407 and 408 can be formed by the lift-off method in the same manner as the source electrode 107 and the drain electrode 108.

In this way, the gas sensor 400 can be manufactured. After that, wiring, a passivation film, and the like may be formed.

The gas sensor 400 according to the fourth embodiment has an npn structure, but may have a pnp structure. In order to obtain a pnp structure, for example, the central portion of the GNR may be an F-terminal GNR, both end portions of the GNR may be H-terminal GNRs, and these may be heterojunctioned.

Instead of the resist mask 421, a sacrificial layer having a high heat resistant temperature may be used. Examples of the material of the sacrificial layer include metal.

As shown in FIG. 17, in the first embodiment, the groove 102 may be formed so as to protrude from the GNR 110 and the GNR 110 may be formed so as to bridge above the groove 102 in a plan view. In this case, it is preferable to cover the groove 102 with an insulating protective film 115 such as _{HfO 2.} This is to facilitate holding the gas molecules contained in the modified layer 109 on the surface of the GNR 110. The protective film 115 can be formed by, for example, the ALD method. The protective film 115 also serves as a gate insulating film. As shown in FIG. 18, in the second embodiment, the groove 102 may be formed so as to protrude from the GNR 210 and the GNR 210 may be formed so as to bridge above the groove 102 in a plan view. Also in this case, it is preferable to cover the groove 102 with an insulating protective film 115 such as _{an HfO 2 film.} As shown in FIG. 19, in the third embodiment, the groove 102 may be formed so as to protrude from the GNR 310 and the GNR 310 may be formed so as to bridge above the groove 102 in a plan view. Also in this case, it is preferable to cover the groove 102 with an insulating protective film 115 such as _{an HfO 2 film.}

As shown in FIG. 20, ^{GNR510 having an n +} p ^- p ⁺ structure may be used. In this semiconductor device 500, the F-terminal GNR511, the CH _3- terminal GNR512, and the NH _2- terminal GNR513 are arranged in this order and heterojunction is performed. The F-terminal GNR 511 is connected to the source electrode 107, the NH _2- terminal GNR 513 is connected to the drain electrode 108, and the gate insulating film 105 and the gate electrode 106 are formed on _{the CH 3-terminal GNR 512.} The surface of GNR510 on the groove 102 side is modified with _{NH 3} or NO _{2 gas molecules.} That is, the modification layer 509 is provided on the surface of the GNR 510 on the groove 102 side.

In this semiconductor device 500, _{the p-type doping of the CH 3-} terminal GNR 512 is weaker than the p-type doping of the NH _2- terminal GNR 513. Therefore, the semiconductor device 500 functions as a transistor having ^{an n +} p ⁻ p ^{+ structure.}

As shown in FIG. 21, ^{GNR610 having an n +} p ^- p ⁺ structure may be used. In this semiconductor device 600, the F-terminal GNR611 and the H-terminal GNR612 are heterojunctioned to each other. The F-terminal GNR611 is connected to the source electrode 107, the end of the H-terminal GNR612 is connected to the drain electrode 108, and the gate insulating film 105 and the gate electrode 106 are formed on the portion of the H-terminal GNR612 that joins with the F-terminal GNR611. .. Polyethyleneimine on F termination GNR611 between the gate electrode 106 and the source electrode 107 (polyethylenimine: PEI) 616 is provided, F ₄ -TCNQ on H-terminated GNR612 between the gate electrode 106 and the drain electrode 108 (2 , 3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) 617 is provided. The surface of GNR610 on the groove 102 side is modified with _{NH 3} or NO _{2 gas molecules.} That is, the modification layer 609 is provided on the surface of the GNR 610 on the groove 102 side.

In the semiconductor device 600, PEI616 functions as an n-type dopant, F ₄ -TCNQ617 functions as a p-type dopant. Therefore, the semiconductor device 600 functions as a transistor having ^{an n +} p ^- p ^{+ structure.}

As shown in FIG. 22, ^{GNR710 having a p +} n ⁻ n ⁺ structure may be used. In this semiconductor device 700, the NH _2- terminal GNR711 and the H-terminal GNR712 are heterojunctioned with each other. The NH ₂ terminal GNR 711 is connected to the source electrode 707, the end of the H terminal GNR 712 is connected to the drain electrode 708, and the gate insulating film 105 and the gate electrode 106 are formed on the portion of _{the H terminal GNR 712 that joins with the NH 2 terminal GNR 711.} Will be done. The source electrode 707 and the drain electrode 708 include a Sc film and an Au film on the Sc film. The work function of Sc is close to the Fermi level (about 3.3 eV) of GNR710. A PEI 716 is provided on the H-terminated GNR 712 between the gate electrode 106 and the drain electrode 108. The surface of GNR710 on the groove 102 side is modified with _{NH 3} or NO _{2 gas molecules.} That is, the modification layer 709 is provided on the surface of the GNR 710 on the groove 102 side.

In this semiconductor device 700, PEI 616 functions as an n-type dopant. Therefore, the semiconductor device 700 functions as a transistor having ^{a p +} n ⁻ n ^{+ structure.}

The surface of GNR may be modified with both _{NH 3} and NO _2. The modifying group of GNR is, for example, H, F, Cl, OH, NH ₂ or CH ₃ . The edges of one region may be modified with two or more of these.

Hereinafter, various aspects of the present invention will be collectively described as appendices.

(Appendix 1)
Graphene nanoribbon and
Gas molecules that modify the surface of the graphene nanoribbon and
Have,
The graphene nanoribbon is
A first region whose ends are terminated with a first modifying group,
A second region that is heterozygous to the first region and whose ends are terminated with a second modifying group that is different from the first modifying group.
A semiconductor device characterized by having.

(Appendix 2)
The semiconductor device according to Appendix 1, wherein the first modifying group and the second modifying group are H, F, Cl, OH, NH ₂ or CH _{3, or any combination thereof.}

(Appendix 3)
The semiconductor device according to Appendix 1 or 2, wherein the gas molecule is NH ₃ or NO _{2 or both.}

(Appendix 4)
The semiconductor device according to any one of Supplementary note 1 to 3, wherein one of the first region and the second region is doped in a p-type and the other is doped in an n-type.

(Appendix 5)
The graphene nanoribbon has a third region that is heterozygous to the second region and whose ends are terminated with a third modifying group that is different from the second modifying group.
The semiconductor device according to any one of Supplementary note 1 to 3, wherein the graphene nanoribbon has a pnp structure or an npn structure.

(Appendix 6)
The graphene nanoribbon has a third region that is heterozygous to the second region and whose ends are terminated with a third modifying group that is different from the second modifying group.
The semiconductor device according to any one of Supplementary note 1 to 3, wherein the graphene nanoribbon has a p ⁺ in ⁺ structure, a p ⁺ n ⁻ n ⁺ structure, or a p ⁺ p ⁻ n ^{+ structure.}

(Appendix 7)
The graphene nanoribbon is provided on a grooved substrate so as to close the groove.
The semiconductor device according to any one of Supplementary note 1 to 6, wherein the gas molecule is confined in the groove.

(Appendix 8)
The semiconductor device according to any one of Supplementary note 1 to 7, wherein the graphene has a width of 10 nm or less.

(Appendix 9)
A first region whose ends are terminated by a first modifying group and a second region that is heterojunctioned to the first region and whose ends are terminated by a second modifying group different from the first modifying group. A step of forming a graphene nanoribbon having two regions,
The step of modifying the surface of the graphene nanoribbon with gas molecules and
A method for manufacturing a semiconductor device.

(Appendix 10)
The manufacture of the semiconductor device according to Appendix 9, wherein the first modifying group and the second modifying group are H, F, Cl, OH, NH ₂ or CH _{3, or any combination thereof.} Method.

(Appendix 11)
The method for manufacturing a semiconductor device according to Appendix 9 or 10, wherein the gas molecule is NH ₃ or NO _{2 or both.}

(Appendix 12)
A first region whose ends are terminated by a first modifying group and a second region that is heterojunctioned to the first region and whose ends are terminated by a second modifying group different from the first modifying group. Has a graphene nanoribbon with 2 regions and
A gas sensor characterized in that the first region and the second region are exposed.

(Appendix 13)
The gas sensor according to Appendix 12, wherein the first modifying group and the second modifying group are H, F, Cl, OH, NH ₂ or CH _{3 or any combination thereof.}

100, 200, 300, 500, 600, 700: Semiconductor devices 110, 210, 310, 410, 510, 610, 710: GNR
109, 209, 309, 409, 509, 609, 709: Modified layer 400: Gas sensor

Claims (9)

Graphene nanoribbon and
Gas molecules that modify the surface of the graphene nanoribbon and
Have,
The graphene nanoribbon is
A first region whose ends are terminated with a first modifying group,
A second region that is heterozygous to the first region and whose ends are terminated with a second modifying group that is different from the first modifying group.
A semiconductor device characterized by having. The semiconductor device according to claim 1, wherein the first modifying group and the second modifying group are H, F, Cl, OH, NH ₂ or CH _3, or any combination thereof. The semiconductor device according to claim 1 or 2, wherein the gas molecule is NH ₃ or NO _{2 or both.} The semiconductor device according to any one of claims 1 to 3, wherein one of the first region and the second region is doped in a p-type and the other is doped in an n-type. The graphene nanoribbon has a third region that is heterozygous to the second region and whose ends are terminated with a third modifying group that is different from the second modifying group.
The semiconductor device according to any one of claims 1 to 3, wherein the graphene nanoribbon has a pnp structure or an npn structure. The graphene nanoribbon has a third region that is heterozygous to the second region and whose ends are terminated with a third modifying group that is different from the second modifying group.
The semiconductor device according to any one of claims 1 to 3, wherein the graphene nanoribbon has a p ⁺ in ⁺ structure, a p ⁺ n ⁻ n ⁺ structure, or a p ⁺ p ⁻ n ^{+ structure.} The graphene nanoribbon is provided on a grooved substrate so as to close the groove.
The semiconductor device according to any one of claims 1 to 6, wherein the gas molecule is confined in the groove. A first region whose ends are terminated by a first modifying group and a second region that is heterojunctioned to the first region and whose ends are terminated by a second modifying group different from the first modifying group. A step of forming a graphene nanoribbon having two regions,
The step of modifying the surface of the graphene nanoribbon with gas molecules and
A method for manufacturing a semiconductor device. A first region whose ends are terminated by a first modifying group and a second region that is heterojunctioned to the first region and whose ends are terminated by a second modifying group different from the first modifying group. Has a graphene nanoribbon with 2 regions and
A gas sensor characterized in that the first region and the second region are exposed.

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