JP5772307B2 - Electronic device and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electronic device using a graphene sheet.

Graphene for example an atomic layer made of carbon atoms of sp ² bonds constituting the hexagonal lattice of carbon in the graphite crystal, if suppressing the effect of scattering beyond the 200000cm ² V ^-1 cm ^-1 at room temperature very Since high electron mobility can be achieved, research on fabricating ultrafast electronic devices using graphene sheets has been conducted.

  However, as with graphite crystals, graphene sheets are also semimetals, and since the valence band and conduction band overlap and there is no band gap, it cannot be used for current switching as it is.

  For this reason, a technique has been proposed in which a ribbon-like structure having a width of 10 nm or less is formed by a graphene sheet as in Patent Document 1 and a band gap is generated by a quantum confinement effect.

  In addition, a technique has been proposed in which holes having a radius of around 10 nm are formed in a graphene sheet in a mesh shape and a band gap is generated by the effect of periodic arrangement of the formed holes (Non-Patent Documents 1 to 3).

JP 2009-94190 A

J. Bai et al., Nature Nanotech. 5, 190 (2010) M. Kim et al., Nano. Lett. 10, 1125 (2010) X. Liang et al., Nano Lett. 10, 2454 (2010) K. S. Noveselov, et al., Science 306, 666 (2004) C. Berger, et al., J. Phys. Chem. B 108, 19912 (2004) A. Reina et.al., Nano. Lett. 9, 30 (2009)

  FIG. 1 is a plan view showing an example of the graphene sheet 1.

Referring to FIG. 1, the graphene sheet 1 is an atomic layer composed of hexagonal lattices of carbon atoms having sp ² bonds as described above. The hexagonal lattices constituting the graphene sheet 1 are mutually connected. A first edge 1A including CC bonds 1a and CC bonds 1b arranged in parallel and staggered and extending in the direction of the CC bonds 1a and 1b as a whole, and a CC repeating in a zigzag manner It includes (carbon-carbon) bonds 1c and 1d, and is entirely defined by a second edge 1B extending in a direction orthogonal to the edge 1A.

In the first edge 1A, the C—C bond 1a continues to the next C—C bond 1b with an oblique CC bond 1e, and the C—C bond 1b becomes the next C—C bond 1a. It is continuous by an oblique CC bond 1f and forms an edge shape called an armchair end. On the other hand, the second edge 1B has a shape called a zigzag end because the CC bond 1c and CC bond 1d are repeated. Referring to FIG. 1, for example, a zigzag end 1B in which a CC bond 1c and a CC bond 1d are repeated as 1d-1c-1d-1c... Includes 5 or more carbon atoms, of which It is clear that two or more carbon atoms have bonds not bonded to other carbon atoms.

  The edge 1A forming the armchair end or the edge 1B forming the zigzag end causes an electron quantum confinement effect. Therefore, in Patent Document 1, the band structure of the graphene sheet is formed by the armchair end or zigzag end. A band gap was generated in the inside, enabling the on / off operation of the electronic device.

  However, in the method described in Patent Document 1, since the channel is effectively formed corresponding to the armchair end or the zigzag end, the channel width is narrowed to 10 nm or less. Alternatively, it is necessary to produce a large number of ribbon-like structures having zigzag edges with a graphene sheet, and to arrange these ribbon-like structures in parallel and at high density between the source region and the drain region. For this reason, in such a prior art, the problem which the manufacturing process of an electronic device becomes complicated arises.

  In the methods described in Non-Patent Documents 1 to 3, since the band gap is generated by the two-dimensional periodic arrangement of holes, it is necessary to two-dimensionally arrange holes having a radius of about 10 nm in the graphene sheet. It cannot be used for a miniaturized electronic device having a channel length of about several tens of nanometers. Furthermore, the band gap formed by such periodicity of the order of 10 nm is as small as about 0.1 eV, and it is not easy to reliably perform the on / off operation with an operating voltage used in a normal electronic device.

  In addition, a technique for generating a band gap by applying an electric field perpendicular to the surface of the two-layer graphene sheet has also been proposed, but the band gap obtained with such a configuration is at most about 0.3 eV. Of course, application to electronic devices is difficult.

  According to one aspect, an electronic device includes a substrate, a graphene sheet formed on the substrate via a gate insulating film, a source electrode formed at one end of the graphene sheet, and the other end of the graphene sheet. A drain electrode formed; a gate electrode for applying a gate voltage between the source region and the drain region to the graphene sheet; and the source electrode and the drain electrode between the source electrode and the drain electrode on the graphene sheet. A row of openings formed across a plurality of openings, each opening being defined by at least one zigzag end, wherein the at least one zigzag end is Both of them form an angle of 30 ° with respect to the direction connecting the source electrode and the drain electrode.

  According to another aspect, an electronic device includes a substrate, a graphene sheet formed on the substrate, a source electrode formed on one end of the graphene sheet, and a drain electrode formed on the other end of the graphene sheet. A gate insulating film that covers the graphene sheet between the source electrode and the drain electrode, and is formed on the graphene sheet between the source electrode and the drain electrode via the gate insulating film. A gate electrode for applying a gate voltage between the source region and the drain region, and a plurality of openings formed between the source electrode and the drain electrode across the direction connecting the source electrode and the drain electrode to the graphene sheet Each of the openings is at least one zigzag end. Riga has made is in said at least one zig-zag end, with respect to the direction which connects the source electrode and the drain electrode, both at an angle of 30 °.

  According to another aspect, an electronic device manufacturing method includes a step of forming a graphene sheet on a substrate, a step of forming an insulating film on the graphene sheet, and a step of forming a mask opening in the insulating film Patterning the graphene sheet using the insulating film as a mask, forming an opening corresponding to the mask opening in the graphene sheet, heat-treating the graphene sheet in a non-oxidizing atmosphere, A step of changing the shape of the opening in the graphene sheet to a stable shape, a step of forming a source electrode on one side and a drain electrode on the other side across the opening on the graphene sheet; And the step of forming the mask opening is such that the mask opening is in a clockwise direction with respect to a straight line connecting the source electrode and the drain electrode. It is formed as defined by one or more edges forming an angle of 30 ° in the counterclockwise direction.

  According to the present invention, a zigzag end that forms an angle of 30 ° with respect to the moving direction of the carrier can be formed in the graphene sheet. Due to the effect of the zigzag end, a large conduction gap is formed in the band structure of the graphene sheet. It becomes possible to form.

It is a top view which shows the hexagonal lattice of graphene. It is a top view which shows the electronic device by 1st Embodiment. FIG. 3 is a sectional view taken along line AA ′ in FIG. 2. 3 is a graph showing a band gap generated in a graphene sheet in the electronic device of FIG. 2. It is a top view which shows the example of the other opening part formed in a graphene sheet. It is a top view which shows the example of the other opening part formed in a graphene sheet. 3 is a graph showing a relationship between electron transmittance and energy generated in the electronic device of FIG. 2. It is a graph which shows the switching characteristic which arises in the electronic device of FIG. 2 compared with the thing of a comparative example. It is a top view which shows the electronic device by 2nd Embodiment. It is a graph which shows the band gap which arises in a graphene sheet in the electronic device of FIG. 10 is a graph showing a relationship between electron transmittance and energy generated in the electronic device of FIG. 9. 10 is a graph showing switching characteristics generated in the electronic device of FIG. 9 in comparison with the comparative example and those of the electronic device of FIG. 2. 10 is a flowchart illustrating a method for manufacturing the electronic device of FIGS. 2 and 9. FIG. 10 is a process cross-sectional view (part 1) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9; FIG. 10 is a process cross-sectional view (part 2) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9. FIG. 10 is a process cross-sectional view (part 3) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9. FIG. 10 is a process cross-sectional view (part 4) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9. FIG. 10 is a process cross-sectional view (part 5) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9; FIG. 10 is a process cross-sectional view (part 6) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9; FIG. 10 is a process cross-sectional view (part 7) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9. FIG. 10 is a process cross-sectional view (No. 8) for explaining the method of manufacturing the electronic device of FIGS. 2 and 9; FIG. 10 is a process cross-sectional view (part 9) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9. FIG. 10 is a process cross-sectional view (No. 10) illustrating the method for manufacturing the electronic device of FIGS. 2 and 9. It is a top view which shows the example of the mask used for patterning of the opening part to a graphene sheet. It is a top view which shows the graphene sheet by the modification of 2nd Embodiment. It is sectional drawing which shows the electronic device by 3rd Embodiment. It is a flowchart explaining the manufacturing method of the electronic device of FIG. FIG. 18 is a process cross-sectional view (No. 1) illustrating the method for manufacturing the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (part 2) illustrating the manufacturing method of the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (part 3) illustrating the manufacturing method of the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (part 4) illustrating the method for manufacturing the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (part 5) illustrating the method for manufacturing the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (part 6) illustrating the method for manufacturing the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (part 7) illustrating the method for manufacturing the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (No. 8) for explaining the manufacturing method of the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (part 9) illustrating the manufacturing method of the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (part 10) illustrating the manufacturing method of the electronic device of FIG. 17; FIG. 18 is a process cross-sectional view (No. 11) illustrating the method for manufacturing the electronic device of FIG. 17.

[First Embodiment]
FIG. 2 is a plan view of the electronic device 20 according to the first embodiment, and FIG. 3 is a cross-sectional view taken along line AA ′ in FIG.

  First, referring to the cross-sectional view of FIG. 3, for example, a silicon oxide film 22 serving as a gate insulating film is formed on a silicon substrate 21 that is doped p + type and also serves as a gate electrode. A graphene sheet 23 similar to the graphene sheet 1 of FIG. 1 is formed on the top.

  Further, on the silicon substrate 21, a source electrode 23S is formed at one end of the graphene sheet 23, and a drain electrode 23D is formed at the other end.

In the graphene sheet 23, as shown in the plan view of FIG. 2, a plurality of openings 23A cross the direction connecting the source electrode 23S and the drain electrode 23D (hereinafter referred to as “channel direction”), It is formed in the form of an opening row 23N extending in the channel width direction orthogonal to the channel direction. Each of the openings 23A in the illustrated embodiment is without a heptagon distorted defined by edges _23a 1 _{~23a 7,} wherein the edge portion 23a ₁ is zigzag edge and said edge portions _23a 2 _{~23a 7} has an armchair end. Here, the “channel direction” is also a direction in which electrons emitted from the source electrode 23S to the graphene sheet 23 travel in the graphene sheet 23 toward the drain electrode 23D, and are straight lines AA ′ in FIG. Is parallel to the direction.

  In the configuration of FIG. 2, the source electrode 23S and the drain electrode 23D face each other in parallel, and the straight line AA ′ is orthogonal to the source electrode 23S and the drain electrode 23D.

In the electronic device 20 having the configuration of FIG. 2, the pair of sides facing each other in parallel among hexagonal lattices of carbon atoms constituting the graphene sheet 23 on the silicon substrate 21 are arranged in the channel direction. They are arranged in a direction such as to be parallel, as a result, the zigzag edge 23a are at an angle inclined 30 ° in the counterclockwise direction with respect to the channel direction.

FIG. 4 shows the size of the band gap Eg generated in the graphene sheet 23 in the electronic device 20 having such a configuration, as shown in FIG. 5 (a) instead of the opening 23A formed in the graphene sheet 23. When an opening 23B having a regular hexagonal shape and defined only by an armchair end is formed, and (b) a distorted heptagon as shown in FIG. 6, one zigzag end 23c ₁ and six is a graph comparing with the case of forming the openings 23C with armchairs end _23c 2 _{~23c 7.} The data indicated by (c) in FIG. 4 is for the electronic device 20 in FIGS. 2 and 3. The calculation in FIG. 4 is performed by a tightly bound approximation calculation based on one pz orbital per carbon atom and considering only the interaction between the nearest atoms.

In the calculation of FIG. 4, the orientation of the graphene sheet 23 in FIGS. 5 and 6 is the same as the orientation of the graphene sheet 23 in FIG. 2, and as a result, in the configuration of FIG. six armchair edge 23b ₁ ~23b ₆ defining the can an angle of 60 ° to 60 ° or clockwise counterclockwise direction with respect to the channel direction, or at an angle of 0 °. In the configuration of FIG. 6, the zigzag end 23c ₁ that defines the opening 23C is orthogonal to the channel direction, that is, has an orientation in the channel width direction, while the armchair ends 23c _{2 to} 23c ₇ are An angle of 60 ° or 0 ° is formed counterclockwise or clockwise with respect to the channel direction.

  In FIG. 4, the vertical axis indicates the half value (Eg / 2) of the band gap Eg thus obtained in units of electron volts, and the horizontal axis indicates the opening row 23N arranged so as to cross the carrier flow. The repetition period of the opening 23A (or openings 23B and 23C) in the inside is expressed in units of the size of one carbon six-membered ring forming the hexagonal lattice. In FIG. 4, the data (c) is for the electronic device 20 of the present embodiment shown in FIGS.

  In the configuration of FIG. 2 in which the opening row 23N is formed by the opening 23A in the graphene sheet 23, the size of one opening 23A in the channel width direction is the size of 15 carbon atom six-membered rings. Therefore, when the period is “17” in FIG. 4, the two openings 23A are adjacent to each other in the channel width direction with a distance of 1 to 2 carbon atom rings. As a result, the value of the period is a practically minimum value. Here, the “channel width direction” means a direction orthogonal to the “channel direction” in the plane of the graphene sheet 23.

  Referring to FIG. 4, in the case of the electronic device 20 shown in FIG. 2 and FIG. 3 shown in FIG. 4C, the band gap Eg is in the range where the repetition period of the opening 23A in the opening row 23N is 17-19. Whereas the value is 1.2 eV or more and close to 1.6 eV (half-value Eg / 2 and 0.6 eV or more and close to 0.8 eV), the electronic device 20 shown in FIGS. It can be seen that a high band gap can be obtained only with a specific repetition period when the graphene sheet having the opening 23B having the shape is used.

  However, the result of FIG. 4 is that the graphene sheet 23 is formed with the opening 23B that forms the armchair end of FIG. 5, or the opening having the zigzag end in the direction orthogonal to the moving direction of the carrier of FIG. Even when 23C is formed, it is shown that a band gap greatly exceeding the conventional value of about 0.3 eV can be realized by optimizing the repetition period of the openings in the opening row.

FIG. 7 shows the relationship between electron transmittance and energy in the graphene sheet 23 of FIG. 2 when the openings 23A are repeatedly arranged with 17 carbon six-membered rings as one period to form the opening row 23N. It is a graph. Figure in E _F represents the Fermi level.

  Referring to FIG. 7, it can be seen that a band gap energy Eg of about 1.5 eV appears in the graphene sheet 23 of the present embodiment, whereas a normal graphene sheet has no band gap.

  In FIG. 8, a curve A indicates that the opening 23A in the graphene sheet 23 of FIG. 2 is repeatedly arranged with 17 carbon six-membered rings as one cycle to form an opening row 23N, and the opening row 5 is a graph in which the relationship between the bias voltage applied to the graphene sheet 23 and the current density when a current is passed in the direction perpendicular to is estimated from the result of the tight binding approximation calculation. In FIG. 8, the horizontal axis represents the bias voltage, and the vertical axis represents the current density. In FIG. 8, the bias voltage on the horizontal axis is applied to the graphene sheet 23 by the p + type silicon substrate 21 acting as a gate electrode through the silicon oxide film 22 acting as a gate insulating film. This is the density of current flowing from the source electrode 23S to the drain electrode 23D.

  Referring to FIG. 8, in the electronic device 20, when the current density serving as a conduction / non-conduction threshold is 0.2 μA / nm, a bias voltage of 1.5 V is used to make the graphene sheet 23 conductive. It is necessary for the threshold voltage (conduction gap), and it can be seen that clear threshold characteristics are obtained. In FIG. 8, a curve “REF” indicates a case where graphene having no opening is used instead of the graphene sheet 23.

  In FIG. 8, curve B shows the characteristics when the opening 23B of FIG. 5 is formed instead of the opening 23A, and curve C shows the characteristics when the opening 23C of FIG. 6 is formed. Even in such a case, if the repetition period in the opening row 23N is optimized, for example, to 18 pieces or 21 pieces in the diameter of the carbon six-membered ring (1.7 nm), the openings shown in FIG. It can be seen that a band gap Eg equivalent to that in the case of forming 23A can be generated.

  In addition, the thermodynamically stable shape when a general opening including the openings 23A, 23B, and 23C is formed in the graphene sheet is hexagonal as shown in FIG. 2, FIG. 5, or FIG. When a pair of mutually parallel edges of the lattice are arranged in a direction perpendicular to the channel direction, the opening is 0 ° relative to the channel direction, or 30 ° counterclockwise or clockwise, or counterclockwise. Or it is limited to the shape defined by the edge part which makes an angle of either 60 degrees or 90 degrees in the clockwise direction, and makes an angle of 60 degrees in the 0 degree direction and the counterclockwise or clockwise direction. The edge becomes the armchair end, and the edge forming an angle of 30 ° counterclockwise or clockwise and the edge forming the angle of 90 ° become the zigzag end.

  The manufacturing process of the electronic device 20 will be described in relation to the following embodiment.

[Second Embodiment]
FIG. 9 is a plan view showing the configuration of the electronic device 40 according to the second embodiment. In the figure, the parts described above are denoted by corresponding reference numerals, and the description thereof is omitted. The sectional view 9 is the same as that described above with reference to FIG.

Referring to FIG. 9, in the electronic device 40, an octagonal opening 23E is formed in the graphene sheet 23 in the illustrated example instead of the opening 23A in FIG. 2, and the opening 23E extends in the channel width direction. It forms the opening sequence 23N by causing periodic sequence, each opening 23E, the first zigzag edge 23e ₁ inclined 30 ° counterclockwise with respect to the channel direction, clockwise The second zigzag end 23e ₂ tilted by 30 ° and an edge portion including armchair ends 23e _{3 to} 23e ₈ are defined. At that time, the the said armchair end 23e ₃ and 23e ₆ in the opening 23F extends in the channel direction, the armchair edge 23e ₇ and 23e _8, counterclockwise each direction with respect to the channel direction Tilted 60 ° clockwise and clockwise. The armchair ends 23e ₄ and 23e ₅ are inclined 60 ° and 60 ° counterclockwise and clockwise, respectively, with respect to the channel direction.

  FIG. 10 shows the result of obtaining the size of the band gap Eg generated in the graphene sheet 23 in the electronic device 40 of FIG. 9 as a function of the repetition period in the channel width direction of the opening 23E in addition to the result of FIG. It is a graph which shows. As in the case of FIG. 4, the calculation of the band gap Eg is performed by a tightly bound approximation calculation based on one pz orbital per carbon atom and considering only the interaction between the nearest atoms.

  Referring to FIG. 10, the curves (a) and (c) correspond to the curves (a) and (c) in FIG. 4, respectively, and the graphene sheet 23 has the opening 23 </ b> B in FIG. 5 or the opening in FIG. 2. The relationship between the band gap Eg and the repetition period of the opening when the opening row 23N is formed by forming the portion 23A is shown. On the other hand, the curve (d) corresponds to the embodiment of FIG. 9 and shows the relationship between the band gap Eg and the repetition period when the opening row 23N is formed in the graphene sheet 23 by the opening 23E. Show.

Referring to FIG. 10, above the opening 23E in addition to the zigzag edge 23e ₁ which is inclined in the counterclockwise direction with respect to the channel direction, the zigzag edge 23e ₂ are formed in addition to the clockwise direction Correspondingly, the band structure of the graphene sheet 23 has a band gap Eg that is almost twice as large as that of the curve (d), and even if the repetition period of the opening 23E is increased from 17, which is the minimum value, the band It can be seen that the decrease in the value of the gap Eg is more gradual than in the case of the curve (a) or (c).

  FIG. 11 shows a graphene sheet 23 in the electronic device 40 corresponding to FIG. 7 in which the opening 23E is repeatedly arranged with 17 carbon six-membered rings as one cycle to form an opening row 23N. It is a graph which shows the relationship between an electron transmittance and energy. In the figure, for comparison, the relationship between the electron transmittance and energy in the electronic device 20 shown in FIG. 7 is shown.

  Referring to FIG. 11, it can be seen that the electronic device 40 has a large band gap reaching 2.7 eV corresponding to the relationship of FIG.

  FIG. 12 is a graph corresponding to FIG. 8, in which the relationship between the bias voltage applied to the graphene sheet 23 and the current density is estimated from the result of the tight binding approximation calculation. In FIG. 12, a curve A corresponds to the electronic device 20 according to the previous embodiment, and a characteristic of the electronic device 40 according to the present embodiment is indicated by a curve B. As in FIG. 8, for comparison, the characteristic when the opening is not formed in the graphene sheet 23 is indicated by a curve “Ref”.

  Referring to FIG. 12, it can be seen that the electronic device 40 can achieve a higher threshold voltage of about 2.7 V as a result of the increased band gap Eg.

In each of the above embodiments, the “graphene sheet” does not necessarily have to be a strictly single atomic layer made of carbon atoms having sp ² bonds constituting a hexagonal lattice of carbon. Multiple may be included.

  Next, the manufacturing process of the electronic device 40 of FIG. 9 will be described with reference to the flowchart of FIG. 13 and the process cross-sectional views of FIGS. 14A to 14L. The electronic device 20 according to the first embodiment described with reference to FIGS. 2 and 3 can also be manufactured by the same manufacturing process.

  Referring to the flowchart of FIG. 13, in step 1, as shown in FIG. 14A, a silicon oxide film 22 having a thickness of, eg, 300 nm serving as a gate insulating film is formed on a silicon substrate 21 doped, for example, p + type. Thus, the graphene sheet 23 is formed. Here, the silicon oxide film 22 can be formed by thermal oxidation of the silicon substrate 21 or the like. In addition to the p + type doped silicon substrate, other conductive substrates such as an n + type doped silicon substrate and a metal substrate can be used as the substrate 21. In this case, the silicon oxide film 22 can be formed by sputtering, for example.

  Next, in step 2 of FIG. 13, a graphene sheet 23 is formed on the silicon oxide film 22 as shown in FIG. 14B. The graphene sheet 23 is made of, for example, a scotch tape (registered trademark) or a cello tape (registered trademark) such as a highly oriented pyrolytic graphite (HOPG), a natural graphite, or a bulk graphite crystal surface such as quiche graphite. By a process of mechanically peeling or cleaving with an adhesive medium such as an adhesive tape or an adhesive sheet and further cleaving with another adhesive tape as described in Non-Patent Document 4, etc. Can be obtained. The graphene sheet 23 obtained in this way is further rubbed and transferred to the surface of the silicon oxide film 22 together with the adhesive medium to obtain the structure of FIG. 14B.

  Alternatively, as described in Non-Patent Document 5 or the like, a hexagonal 6H—SiC substrate is prepared and heated to 1200 ° C. or higher in a vacuum or in a non-oxidizing atmosphere such as Ar to form Si from the substrate surface. It is also possible to obtain a graphene sheet epitaxially depending on the hexagonal atomic arrangement of SiC on the SiC substrate surface by desorbing atoms. Also in this case, the structure of FIG. 14B can be obtained by transferring the obtained graphene sheet to an adhesive medium or the like and transferring it to the surface of the silicon oxide film 22.

  In addition, as described in Non-Patent Document 6 and the like, a graphene sheet can be formed by a CVD method. In this case, a metal catalyst such as Fe, Ni, or Cu is deposited on the silicon oxide film surface on the silicon substrate, and a thermal CVD process using acetylene as a raw material is performed at a temperature of about 650 to 1000 ° C. Graphene can be synthesized on a metal catalyst. Also in this case, the structure of FIG. 14B can be obtained by transferring the obtained graphene to the adhesive medium and further transferring it to the surface of the silicon oxide film 22.

  Next, in step 3, as shown in FIG. 14C, a silicon oxide film HM1 serving as a hard mask is formed by covering the graphene sheet 23 by, for example, CVD or sputtering, and in step 4, the resist pattern R1 is formed. After aligning the mask orientation, the silicon oxide film HM1 is patterned using the resist pattern R1 as a mask, as shown in FIG. 14D, and the source region 23s of the graphene sheet 23 where the source electrode 23S is formed. A line connecting the source region 23s and the drain region 23d and the drain region 23d where the drain electrode 23D is formed extend in parallel with each other in the hexagonal lattice of carbon constituting the graphene sheet 23. It is exposed so as to be orthogonal to the existing two sides.

Moreover source electrode pattern 23S on the structure of Figure 14D in step 5, the metal film 23M serving as the drain electrode pattern 23D, as is to cover the resist pattern R ₁ on the silicon oxide film HM1 as shown in FIG. 14E e.g. is deposited by a sputtering method or an electron beam deposition method, further in step 7 using the resist pattern R ₁ as shown in FIG. 14F, metal film 23M together liftoff deposited thereon. As a result, the source electrode pattern 23S is formed in the source region 23s of the graphene sheet 23, and the drain electrode pattern 23D is formed in the drain region 23d. The metal film 23M may have a structure in which, for example, a Ti adhesion film (not shown) having a thickness of 5 nm and an Au film (not shown) having a thickness of 30 nm, for example, are sequentially stacked.

Then the resist film R ₂ is formed on the silicon oxide film HM ₁ in step 8, the in the resist film R ₂ using the mask pattern M of Fig. 15 is a resist opening R2A as shown in FIG. 14G, the It is formed corresponding to the mask opening 23M in the mask pattern M. The mask opening 23M has a shape corresponding to the opening sequence 23E formed in the graphene sheet 23, a zigzag edge 23e ₁ and 23e ₂ are edges of the mask opening 23M each of the openings 23E 23m ₁ and 23m ₂ , and the armchair ends 23e _{3 to} 23e _{8 of the} opening 23E correspond to the edges 23m _{3 to} 23m ₈ , respectively.

In step 8, the orientation of the mask opening 23M is set with respect to the graphene sheet 23 so that the orientation of the mask opening 23M matches the orientation of the opening 23A desired to be formed in the graphene sheet 23. As a result of such mask orientation alignment, the edge 23m ₁ is inclined 30 ° counterclockwise from the channel direction, while the edge 23m ₂ is inclined 30 ° clockwise from the channel direction.

In the step 8, further this way the silicon oxide film HM ₁ by the formed resist opening R2A and is patterned as shown in FIG. 14H, corresponding to the mask opening 23M in the silicon oxide film HM ₁ The mask opening HMA thus formed is formed.

Next to the graphene sheet 23 in the process of the step 9, and supplied to mask the silicon oxide film HM ₁ as shown in FIG. 14I, for example, under a pressure of 10 mTorr, an oxygen gas at a flow rate of 25sccm with plasma power of 90W Reactive ion etching (RIE) is performed while opening the opening 23A corresponding to the mask opening HMA in the graphene sheet 23 so as to have a predetermined relationship with the orientation of the graphene sheet 23, that is, opening The zigzag ends 23e ₁ and 23e _{2 of the} portion 23A are formed so as to be inclined 30 ° counterclockwise and clockwise with respect to the channel direction, respectively. In the mask M, the mask openings 23M are periodically formed in the direction of the openings as shown in FIG. 15, whereby the opening rows 23N are formed in the graphene sheet 23 by the openings 23A. It is formed in the width direction.

The silicon oxide film HM ₁ as shown in FIG. 14J In still step 10, it is selectively removed by wet etching using HF, then, in a reducing atmosphere such as hydrogen atmosphere, a heat treatment at a temperature of, for example 1000 ° This stabilizes the arrangement of the carbon atoms at the end of the opening 23A. As a result of such stabilization, even if the orientation of the mask M is slightly shifted in the step of FIG. 14H, the carbon atoms are rearranged at the edge of the opening 23A and counterclockwise or clockwise in the channel direction. A zigzag end having an angle of 30 ° in the rotation direction can be stably obtained.

  The above manufacturing method can also be applied to the electronic device 20 of the first embodiment.

In the present embodiment, instead of the opening 23E of FIG. 9, as shown in FIG. 16, they face each other in the channel width direction and are inclined by 30 ° counterclockwise and clockwise with respect to the channel direction, respectively. a zigzag edge 23f ₁ and 23f _2, facing each other in the channel width direction, image at the edges including a zigzag edge 23f ₃ and 23f ₄ inclined 30 ° in the clockwise and counterclockwise directions, respectively to the channel direction It is also possible to form the formed opening 23F. In the configuration of FIG. 16, the number of zigzag edges inclined by 30 ° with respect to the channel direction increases, so that the band gap Eg can be further increased.

  In the configuration of FIG. 16, the opening 23F is repeatedly formed in the channel width direction.

[Third Embodiment]
FIG. 17 is a cross-sectional view illustrating a configuration of an electronic device 60 according to the third embodiment. In the figure, portions corresponding to the portions described above are denoted by the same reference numerals, and description thereof is omitted.

  Referring to FIG. 17, the electronic device 60 is formed on the (0001) plane of the 6H—SiC substrate 61 and is formed directly on the (0001) plane, and the above-described FIG. 2, FIG. 9, or FIG. Of the graphene sheet 23 in which the opening portion row 23N is formed by the opening portions 23A, 23E or 23F shown in the plan view, and the hexagonal lattice of carbon atoms constituting the graphene sheet 23 on the graphene sheet 23, A source electrode 23S and a drain electrode 23D are formed so as to face each other in a direction orthogonal to two parallel sides.

Further, the graphene sheet 23 is covered with the gate insulating film 62 made of hafnium oxide (HfO ₂ ) having a thickness of 10 nm, for example, for each of the opening rows 23N. A gate electrode 63 having a structure in which a 5 nm titanium (Ti) film and a gold (Au) film having a thickness of, for example, 30 nm are sequentially stacked is formed.

  In the configuration shown in the drawing, the source electrode 23S and the drain electrode 23D are also covered with the hafnium oxide film 62, and via holes (not shown) are formed in the hafnium oxide film 62 corresponding to the source electrodes 23S and 23D.

  Also in the electronic device having such a configuration, the straight line connecting the source electrode 23S and the drain electrode 23D and the source electrode 23S and the drain electrode 23D is opposed to each other in the hexagonal lattice of carbon constituting the graphene sheet 23S. Since it is formed so as to be orthogonal to the two sides, the graphene sheet 23 has a clockwise rotation with respect to the channel direction as in the embodiment of FIG. 2, FIG. 9 or FIG. As shown in FIG. 4 or FIG. 10, the graphene sheet 23 has a large value of 1.6 eV or more, or 2.8 eV or more. The band gap Eg is shown. Therefore, also in the electronic device 17 of FIG. 17, the flow of electrons from the source electrode 23S to the drain electrode 62D can be reliably controlled by the gate voltage applied to the gate electrode 63.

  Hereinafter, a method of manufacturing the electronic device 60 of FIG. 17 will be described with reference to the flowchart of FIG. 18 and the process cross-sectional views of FIGS. 19A to 19K. In the figure, portions corresponding to the portions described above are denoted by the same reference numerals, and description thereof is omitted.

  Referring to FIG. 18, in step 21, as shown in FIG. 19A, a 6H—SiC substrate 61 having a (0001) plane as a main surface is prepared. In step 22, the 6H—SiC substrate is vacuumed or 1200 ° or more. Then, heat treatment is performed in a non-oxidizing atmosphere such as argon (Ar), and the Si element is desorbed from the (0001) plane defining the main surface of the substrate 21. As a result, on the main surface of the 6H—SiC substrate 21 made of the (0001) plane, a carbon atom layer made of carbon atoms arranged in a hexagonal system as shown in FIG. 19B remains, and the desired graphene sheet 23 is epitaxially formed. It is formed.

  Next, in step 23 of FIG. 18, as shown in FIG. 19C, a hard mask film HM1 made of a silicon oxide film is formed by, eg, sputtering or CVD, and in step 24, the hard mask film HM1 is masked with the resist pattern R1. As shown in FIG. 19D, the source region 23s and the drain region 23d of the graphene sheet 23 are exposed.

  Further, in step 25 of FIG. 18, a titanium film having a thickness of 5 nm and a gold film having a thickness of 30 nm are sequentially deposited on the structure of FIG. 19D by electron beam evaporation or sputtering, and the metal shown in FIG. A film 23M is formed, and in step 26 of FIG. 18, the resist pattern R1 is lifted off together with the metal film 23M thereon as shown in FIG. 19F, a source electrode 23S is formed in the source region 23s of the graphene sheet 23, and the drain A drain electrode 23D is formed in each region 23d.

  Further, in step 27 of FIG. 18, the hard mask film HM1 is patterned using, for example, the mask M described in FIG. 15 to form an opening HMA that exposes the graphene sheet 23 as shown in FIG. 19G. In FIG. 28, the graphene sheet 23 is patterned using the hard mask film HM1 as a mask, and as shown in FIG. 19H, an opening row 23N made of, for example, openings 23A is formed in the graphene sheet 23. In step 28, an opening 23E or 23F may be formed instead of the opening 23A.

Further, in step 29 of FIG. 18, the graphene sheet 23 is heat-treated in a reducing atmosphere such as a hydrogen atmosphere at a temperature of 1000 °, for example, to stabilize the arrangement of carbon atoms at the edge such as the opening 23A previously formed. . Further, in step 30, as shown in FIG. 19I, the hard mask film HM1 is removed by wet processing using HF, for example, and in step 31, a gate insulating film 62 is formed on the graphene sheet 23 as shown in FIG. 19J. In the illustrated example, a hafnium oxide (HfO ₂ ) film is used as the gate insulating film 62, but a zirconium oxide (ZrO ₂ ) film, a hafnium silicate (HfSiO ₄ ) film, a hafnium zirconate (ZrSiO ₄ ) film, or the like is used. It can also be used.

  Further, in step 32, a gate electrode 63 having a laminated structure of a Ti film and a gold film, which is the same as the source electrode pattern 23S or the drain electrode pattern 23D, is formed on the gate insulating film 62 as shown in FIG. 19K. An electronic device having a gate structure can be obtained.

  As mentioned above, although this invention was described about preferable embodiment, this invention is not limited to this specific embodiment, A various deformation | transformation and change are possible within the summary described in the claim.

1,23 graphene sheet 1A armchair end 1B zigzag ends 1a, 1b, 1c, 1d, 1e C-C bonds 20, 40, 60 electronic device 21 silicon substrate 23A, 23B, 23C, 23E, 23F openings 23a ₁ ~23a _{7, 23b 1 ~23b 6, 23c} 1 ~23c 7, 23e 1 ~23e 8, 23f 1 ~23f 4 edge 23N opening column 23M mask opening 23m1~23m8 edge 23S source electrode pattern 23D drain electrode pattern 61 SiC substrate 62 Gate insulating film 63 Gate electrode

Claims (8)

A substrate,
A graphene sheet formed on the substrate via a gate insulating film;
A source electrode formed at one end of the graphene sheet;
A drain electrode formed on the other end of the graphene sheet;
A gate electrode for applying a gate voltage between the source electrode and the drain electrode to the graphene sheet;
An opening row formed of a plurality of openings formed between the source electrode and the drain electrode on the graphene sheet and across a direction connecting the source electrode and the drain electrode;
With
Each of the openings is defined by at least one zigzag end, and each of the at least one zigzag end forms an angle of 30 ° with respect to a direction connecting the source electrode and the drain electrode. An electronic device. A substrate,
A graphene sheet formed on the substrate;
A source electrode formed at one end of the graphene sheet;
A drain electrode formed on the other end of the graphene sheet;
A gate insulating film covering the graphene sheet between the source electrode and the drain electrode;
A gate electrode formed between the source electrode and the drain electrode on the graphene sheet via the gate insulating film, and applying a gate voltage between the source electrode and the drain electrode on the graphene sheet;
Between the source electrode and the drain electrode, an opening row composed of a plurality of openings formed across the direction connecting the source electrode and the drain electrode to the graphene sheet,
With
Each of the openings is defined by at least one zigzag end, and each of the at least one zigzag end forms an angle of 30 ° with respect to a direction connecting the source electrode and the drain electrode. An electronic device.   One of the at least one zigzag edges forms an angle of 30 ° clockwise with respect to a direction connecting the source electrode and the drain electrode when viewed from a direction perpendicular to the surface of the graphene sheet. The electronic device according to claim 1, wherein:   One of the at least one zigzag edges forms an angle of 30 ° counterclockwise with respect to the direction connecting the source electrode and the drain electrode when viewed from a direction perpendicular to the surface of the graphene sheet. The electronic device according to claim 1, wherein the electronic device is an electronic device.   The at least one zigzag end increases a mutual distance from the source electrode toward the drain electrode, and a third zigzag end decreases the mutual distance from the source electrode toward the drain electrode. And a fourth zigzag end, and the first and third zigzag ends form an angle of 30 ° counterclockwise and clockwise with respect to a direction connecting the source electrode and the drain electrode, respectively. 3. The second and fourth zigzag ends form an angle of 30 degrees clockwise and counterclockwise, respectively, with respect to a direction connecting the source electrode and the drain electrode. Electronic equipment. The Jiguza grayed end, of the preceding claims, characterized in that it is constituted of carbon atoms having a bond that is not bonded to another carbon atom of five or more carbon atoms, including two or more, The electronic device as described in any one. Forming a graphene sheet on the substrate;
Forming an insulating film on the graphene sheet;
Forming a mask opening in the insulating film;
Patterning the graphene sheet using the insulating film as a mask, and forming an opening corresponding to the mask opening in the graphene sheet;
Heat-treating the graphene sheet in a non-oxidizing atmosphere, and changing the shape of the opening in the graphene sheet to a stable shape;
On the graphene sheet, forming a source electrode on one side and a drain electrode on the other side across the opening; and
Including
The step of forming the mask opening includes at least one edge that forms an angle of 30 ° clockwise or counterclockwise with respect to a straight line connecting the source electrode and the drain electrode. It is performed as defined by section, an opening formed to correspond to the mask opening in the graphene sheet by the patterning, to a straight line connecting the source electrode and the drain electrode, both clockwise A method of manufacturing an electronic device, characterized by being defined by one or more zigzag edges that form an angle of 30 ° in a direction or counterclockwise direction . Process line that runs on the source electrode and the drain electrode, opposing flat row to so that two sides of the hexagonal grid of the carbon atoms constituting the graphene sheet forming the said source and drain electrodes The method for manufacturing an electronic device according to claim 7 , further comprising a step of aligning.