JP6493003B2 - Electronic device and method of manufacturing electronic device - Google Patents

Description

  The present invention relates to an electronic device and a method of manufacturing the electronic device.

A transition metal dichalcogenide (TMDC) has chalcogen atoms X such as sulfur (S) and selenium (Se) bonded vertically to transition metal atoms T such as molybdenum (Mo) and tungsten (W) a layered compound of formula TX _2.

  Techniques etc. which use transition metal dichalcogenide for the field effect transistor (Field Effect Transistor; FET) contained in an electronic device using the mechanical and electrical property which transition metal dichalcogenide has, etc. are known.

Japanese Patent Application Publication No. 2007-506286

  In an electronic device using transition metal dichalcogenide, a metal may be connected to the transition metal dichalcogenide as an electrode for supplying current to the transition metal dichalcogenide or extracting current from the transition metal dichalcogenide. In this case, when the contact resistance between the electrode metal and the transition metal dichalcogenide is large, it may not be possible to obtain an electronic device utilizing the electrical characteristics of the transition metal dichalcogenide.

According to one aspect of the present invention, there is provided a transition metal dichalcogenide having a first surface terminated by a chalcogen atom, wherein at least one transition metal atom is exposed in each of the first portion and the second portion of the first surface. a transition metal dichalcogenides you, the first metal connected to the first portion, an electronic device and a second metal connected to said second portion is provided.

Further, according to an aspect of the present invention, there is provided a transition metal dichalcogenide having a first surface terminated by a chalcogen atom, wherein at least one transition metal atom is formed in each of the first portion and the second portion of the first surface. a step but to form a transition metal dichalcogenides you exposed, said a step of connecting the first metal to the first portion, a method of manufacturing an electronic device including the step of connecting the second metal on the second portion Provided.

  According to the disclosed technology, it is possible to realize an electronic device in which an increase in contact resistance between a transition metal dichalcogenide and a metal connected thereto is suppressed.

It is explanatory drawing of the structure of transition metal dichalcogenide (TMDC). It is a figure which shows the 1st example of the transistor which used TMDC. It is a figure which shows the 2nd example of the transistor which used TMDC. It is a figure which shows an example of the connection part of TMDC and an electrode. It is a figure which shows the 1st example of the connection part of TMDC and an electrode. It is a figure which shows an example of the result of having compared the current value by simulation about a transistor model. It is a figure which shows the 2nd example of the connection part of TMDC and an electrode. It is explanatory drawing (the 1) of an example of the method of exposing the transition metal atom of TMDC. It is explanatory drawing (the 2) of an example of the method of exposing the transition metal atom of TMDC. It is explanatory drawing (the 1) of another example of the method of exposing the transition metal atom of TMDC. It is explanatory drawing (the 2) of another example of the method of exposing the transition metal atom of TMDC. FIG. 18 is a first diagram illustrating a configuration example of a transistor using TMDC having an opening portion. FIG. 18 is a second example of a configuration example of a transistor using TMDC having an opening portion. It is explanatory drawing (the 1) of an example of the transistor formation method. It is explanatory drawing (the 2) of an example of the transistor formation method. It is explanatory drawing (the 3) of an example of the transistor formation method. It is explanatory drawing (the 4) of an example of the transistor formation method. It is explanatory drawing (the 5) of an example of the transistor formation method. It is explanatory drawing (the 6) of an example of the transistor formation method. It is explanatory drawing (the 7) of an example of the transistor formation method. It is explanatory drawing (the 8) of an example of the transistor formation method. It is explanatory drawing (the 1) of another example of the transistor formation method. It is explanatory drawing (the 2) of another example of the transistor formation method. It is a figure which shows the structural example of the conductor part using TMDC.

  FIG. 1 is an explanatory view of the structure of transition metal dichalcogenide (TMDC). FIG. 1A shows a schematic cross-sectional view of a main part of a single layer of TMDC, and FIG. 1B shows a schematic plan view of a main part of a single-layer TMDC. Regions surrounded by dotted lines in FIGS. 1A and 1B are unit cell structures that are periodically repeated.

TMDC is a layered compound having a unit cell structure represented by a chemical formula TX _{2 in} which a chalcogen atom X is bonded to the upper and lower sides of a transition metal atom T. The transition metal atom T is molybdenum, tungsten or the like, and the chalcogen atom X is sulfur, selenium, tellurium (Te) or the like. As shown in FIG. 1A, the single-layer TMDC has a triatomic layer structure in which the layer of chalcogen atoms X sandwiches the top and bottom of the layer of transition metal atoms T in a cross-sectional view. In addition, as illustrated in FIG. 1B, the single layer TMDC has a structure in which atoms are arranged in a honeycomb shape (hexagonal lattice shape) in plan view, like graphene and the like.

  TMDC has a characteristic of being flexible and a characteristic of being transparent. In addition, TMDC has a band gap similar to that of silicon (Si) in a single layer, for example, a direct transition band gap of 1 eV to 2 eV in a single layer, when the transition metal atom T is a group 6 element such as molybdenum or tungsten. It has the characteristic of showing. For example, TMDC having such characteristics is used for semiconductor devices and electronic devices.

As an example, an example in which a single layer of TMDC is used for the material of the channel of the transistor is shown in FIGS. 2 and 3.
FIG. 2 is a diagram showing a first example of a transistor using TMDC. FIG. 2 is a schematic perspective view of the relevant part of the transistor according to the first example.

The transistor 10 illustrated in FIG. 2 includes a substrate 11, an insulating film 12, a TMDC 13, a source electrode 14 a, a drain electrode 14 b, a gate insulating film 15, and a gate electrode 16.
Various substrates can be used as the substrate 11. Various insulating materials can be used for the insulating film 12, and, for example, silicon oxide (SiO ₂ ) is used. A single layer TMDC 13 to be a channel is provided on such an insulating film 12.

For example, molybdenum disulfide (MoS ₂ ) is used for the TMDC 13. In this case, the single-layer TMDC 13 is provided, for example, by transferring the single-layer molybdenum disulfide obtained by a method of peeling from a bulk single crystal of molybdenum disulfide with an adhesive tape onto the insulating film 12.

  In the transistor 10, the source electrode 14a and the end 13b which are both ends (regions inside the end and end respectively) of the TMDC 13 provided on the insulating film 12 in one direction are respectively the source electrode 14a and the end 13b. A drain electrode 14b is provided. For the source electrode 14a and the drain electrode 14b, molybdenum, tungsten, titanium (Ti), cobalt (Co), nickel (Ni), palladium (Pd), aluminum (Al), indium (In), copper (Cu), silver A metal such as (Ag), platinum (Pt) or gold (Au) is used.

The gate electrode 16 is provided on the TMDC 13 between the source electrode 14 a and the drain electrode 14 b as described above via the gate insulating film 15.
The transistor 10 shown in FIG. 2 is a so-called top gate type transistor. In the transistor 10, the potential of the gate electrode 16 is controlled to control the on / off state of the channel using the TMDC 13.

FIG. 3 is a diagram showing a second example of a transistor using TMDC. FIG. 3 is a schematic perspective view of the relevant part of the transistor according to the second example.
A transistor 20 illustrated in FIG. 3 includes a substrate 21, an insulating film 22, TMDC 23, a source electrode 24a, and a drain electrode 24b.

  As the substrate 21, a substrate having conductivity is used, and for example, a semiconductor substrate such as a silicon substrate to which an impurity element of a predetermined conductivity type is added is used. Various insulating materials can be used for the insulating film 22, and, for example, silicon oxide is used. A single-layer TMDC 23 to be a channel, for example, molybdenum disulfide, is provided on such an insulating film 22 using a method such as transfer as described above.

  In the transistor 20, the source electrode 24a and the end 23b, which are both ends (regions inside the end and end, respectively) of TMDC 23 provided on the insulating film 22 in one direction, respectively, the source electrode 24a and the end 23b. A drain electrode 24b is provided. For the source electrode 24a and the drain electrode 24b, metals such as molybdenum, tungsten, titanium, cobalt, nickel, palladium, aluminum, indium, copper, silver, platinum, gold and the like are used.

  The transistor 20 shown in FIG. 3 is a so-called back gate type transistor. In the transistor 20, the conductive substrate 21 functions as a gate electrode, and the potential of the substrate 21 is controlled, whereby the on / off state of the channel using the TMDC 23 is controlled.

For example, a transistor having a configuration as illustrated in FIGS. 2 and 3 described above can be obtained using TMDC.
Note that in the case where TMDC is used for the channel of the transistor, electrodes functioning as a source electrode and a drain electrode are not limited to the upper layer side of TMDC, and can be provided on the lower layer side of TMDC.

Here, the connection between the TMDC and the electrode will be described.
FIG. 4 is a view showing an example of a connection portion between the TMDC and the electrode. FIG. 4 schematically shows an example of a connection portion between a single layer of TMDC and an electrode.

  In FIG. 4, as an example of the connection portion, a portion of a connection portion (lamination portion) 1B between a part 2a (shown by a dotted line frame in FIG. 4) of a single layer TMDC 2 and a metal electrode 3 stacked there The partial cross section schematic diagram is shown.

  Molybdenum disulfide, tungsten diselenide or the like is used for the TMDC 2 of the connection portion 1B. The TMDC 2 has a unit cell structure including a transition metal atom T such as molybdenum or tungsten and a chalcogen atom X such as sulfur or selenium bonded to the upper and lower sides thereof.

For the electrode 3 of the connection part 1B, a metal such as molybdenum, tungsten, titanium, palladium or the like is used. The electrode 3 has a crystal structure in which a large number of metal atoms M are metallurgically bonded to each other.
In a transistor using a single layer of TMDC2 as a channel, metal electrodes 3 are stacked on both ends of TMDC2, and the on / off of the current supplied to them is placed opposite to TMDC2 as a gate electrode (see FIG. No. 4 is controlled by (not shown).

  In the connection (lamination) of single-layer TMDC 2 and metal electrode 3, a Schottky barrier is present as in the case of a normal semiconductor-metal connection interface, and this Schottky barrier increases the contact resistance (Rc). It contributes to In addition, a tunnel barrier 5 (shown by a dashed line in FIG. 4) is formed at the connection interface between the TMDC 2 and the electrode 3 to increase their contact resistance.

  In a transistor using TMDC2 as the channel, if the contact resistance between metal electrode 3 serving as the source electrode and drain electrode and TMDC2 serving as the channel is high, the high contact resistance can limit the transistor characteristics. . When the contact resistance between the metal electrode 3 and the TMDC 2 serving as the channel increases, it is difficult to achieve high speed and low power consumption of the transistor by utilizing the characteristics of the TMDC 2.

On the other hand, depending on the combination of the TMDC 2 and the material of the electrode 3, it may be possible to suppress the increase in the contact resistance thereof.
For example, when molybdenum disulfide is used as TMDC 2 and molybdenum or titanium is used as the electrode 3, an ohmic junction can be realized between the TMDC 2 and the electrode 3. In addition, also in the case where tungsten diselenide (WSe ₂ ) is used as TMDC ₂ and tungsten or palladium is used as the electrode 3, an ohmic junction can be similarly realized between the TMDC 2 and the electrode 3. As described above, the combination of the material of the TMDC 2 and the material of the electrode 3 may realize an ohmic junction and may suppress an increase in the contact resistance thereof.

  However, the combination of materials that can suppress the increase in contact resistance is limited, and the types of materials that can be used for TMDC 2 and the types of materials that can be used for electrode 3 are limited.

  For example, when the connection portion 1B as shown in FIG. 4 is adopted for the transistors 10 and 20 (FIG. 2, FIG. 3), as described above, it is difficult to achieve high speed and low power consumption. I will. In addition, the combination of the materials of the TMDCs 13 and 23 and the source electrodes 14a and 24a and the drain electrodes 14b and 24b is limited.

In view of such a point, here, a method as shown in the following FIG. 5 is adopted.
FIG. 5 is a view showing a first example of the connection portion between the TMDC and the electrode. In FIG. 5, an example of the connection part of TMDC of a single layer and an electrode is shown typically.

  In FIG. 5, as a first example of the connection portion, a connection portion (laminated portion) between a part 2a of a single layer TMDC 2 (shown by a dotted frame in FIG. 5) and a metal electrode 3 stacked there The principal part cross section schematic diagram of 1A is shown.

For the TMDC 2 and the electrode 3 of the connection portion 1A shown in FIG. 5, the same material as the TMDC 2 and the electrode 3 of the connection portion 1B shown in FIG. 4 is used.
Molybdenum disulfide, tungsten diselenide or the like is used for the TMDC 2 of the connection portion 1A. The TMDC 2 has a unit cell structure including a transition metal atom T such as molybdenum or tungsten and a chalcogen atom X such as sulfur or selenium bonded to the upper and lower sides thereof.

  Various metals such as molybdenum, tungsten, titanium, cobalt, nickel, palladium, aluminum, indium, copper, silver, platinum or gold, or a metal containing two or more of these metals are used for the electrode 3 of the connection portion 1A. Used. The electrode 3 has a crystal structure in which a large number of metal atoms M are metallurgically bonded to each other.

  In the connection portion 1A shown in FIG. 5, at least one transition metal atom T is exposed by being partially not bonded to the chalcogen atom X in the portion 2a of the TMDC 2, and the transition metal atom T of the portion 2a is exposed. A metal electrode 3 is stacked on the exposed side. FIG. 5 exemplifies two transition metal atoms T1 as the transition metal atoms T exposed by the partial non-bonding with the chalcogen atom X of TMDC2.

  In the connecting portion 1A shown in FIG. 5, the metal electrode 3 is stacked on the portion 2a of TMDC 2 where the transition metal atom T1 is exposed as described above, and the transition metal atom T1 where TMDC 2 is exposed and the portion 2a are stacked. A metal-metal bond 4 is formed between the metal 3 and the metal atom M of the electrode 3. Thereby, an ohmic junction is realized between the TMDC 2 and the electrode 3, and an increase in their contact resistance is suppressed.

  Thus, at least one transition metal atom T1 is exposed in the portion 2a of the TMDC 2 connected to the electrode 3, and between the transition metal atom T1 and the metal atom M of the electrode 3, metal-metal The bond 4 is formed. By forming the metal-metal bond 4 between the transition metal atom T1 of TMDC 2 and the metal atom M of the electrode 3, the increase in contact resistance between the TMDC 2 and the electrode 3 is suppressed.

  For example, if the connection portion 1A as shown in FIG. 5 is employed for the transistors 10 and 20 (FIG. 2 and FIG. 3), the contact between the TMDCs 13 and 23 and the source electrodes 14a and 24a and the drain electrodes 14b and 24b By suppressing the increase in resistance, high speed and low power consumption can be achieved. In addition, it is possible to suppress the limitation of the combination of the materials of the TMDCs 13 and 23 and the source electrodes 14a and 24a and the drain electrodes 14b and 24b.

  Here, the transistor model A adopting the structure of the connecting portion 1A as shown in FIG. 5 and the transistor model B adopting the structure of the connecting portion 1B as shown in FIG. An example of the comparison result is shown in FIG.

  The transistor model A used in the simulation of FIG. 6 includes the TMDC 2 and the metal electrode 3 connected to both ends where the transition metal atoms T are exposed, such as the connection portion 1A of FIG. The transistor model B includes the TMDC 2 and the metal electrode 3 connected to both ends of the transition metal atom T not exposed (that is, the chalcogen atom X is exposed) such as the connection portion 1B of FIG. including.

The current flowing when a bias is applied between the electrodes 3 on both ends of each of the TMDCs 2 of the transistor model A and the transistor model B is estimated by simulation. In FIG. 6, the horizontal axis represents bias [V], and the vertical axis represents current ratio I _A / I _B [-]. The current ratio I _A / I _B is the ratio of the current value I _A obtained by the transistor model A when a bias is applied to the current value I _B obtained by the transistor model B.

  As shown in FIG. 6, in the transistor model A, a current value about 8 to 20 times that of the transistor model B can be obtained when the applied bias is in the range of 0.1 V or more. That is, in the structure where the metal electrode 3 is connected to the portion where the transition metal atom T of TMDC 2 is exposed (FIG. 5), compared to the structure where the electrode 3 is connected to the portion where the transition metal atom T is not exposed (FIG. 4) The contact resistance is reduced to about 1/8 to 1/20.

  According to the method of forming the metal-metal bond 4 between the transition metal atom T of TMDC 2 and the metal atom M of the electrode 3 as shown in FIG. 5 above, an ohmic junction is realized, and a contact resistance of It is possible to effectively suppress the increase.

  Furthermore, in this method, the material of TMDC 2 and electrode 3 is not limited to a specific combination, in order to form a metal-metal bond 4 to realize an ohmic junction, and various materials can be used for both TMDC 2 and electrode 3. It becomes possible to use.

  By the way, as a method for exposing the transition metal atom of TMDC, for example, at least one chalcogen contained in the chalcogen atom layer on the surface side to which the metal electrode of the chalcogen atom layer sandwiching the transition metal atom layer of TMDC is connected. There is a method to remove atoms. This is the method as shown in FIG. 5 above.

  In addition, as a method of exposing the transition metal atom of TMDC, there is, for example, a method of providing at least one opening in a portion of the TMDC to which a metal electrode is connected. Such a method is described with reference to FIG. 7 below.

FIG. 7 is a view showing a second example of the connection portion between the TMDC and the electrode. FIG. 7 schematically shows an example of a connection portion between a single layer of TMDC and an electrode.
In FIG. 7, as a second example of the connection portion, a connection portion (laminated portion) between a part 2a (shown by a dotted line frame in FIG. 7) of a single layer TMDC 2 and a metal electrode 3 stacked there The principal part cross section schematic diagram of 1C is shown. For the TMDC 2 and the electrode 3 of the connection portion 1C shown in FIG. 7, the same material as the TMDC 2 and the electrode 3 of the connection portion 1A shown in FIG. 5 is used.

  In the example of FIG. 7, the opening 2 b is provided in the part 2 a of the TMDC 2. By providing such an opening 2 b, the transition metal atom T is exposed at the edge of the opening 2 b in the portion 2 a of the TMDC 2. For convenience, in FIG. 7, the exposed transition metal atom T is a transition metal atom T1. An opening 2 b is provided, and a metal electrode 3 is stacked on a part 2 a of TMDC 2 where the transition metal atom T 1 is exposed.

  In the connecting portion 1C shown in FIG. 7, the metal-metal bond 4 is formed between the transition metal atom T1 exposed at the edge of the opening 2b and the metal atom M of the electrode 3. Thereby, an ohmic junction is realized between the TMDC 2 and the electrode 3, and an increase in their contact resistance is suppressed.

A method of providing an opening in TMDC to expose transition metal atoms in this manner will be further described.
FIG. 8 and FIG. 9 are explanatory drawings of an example of the method of exposing the transition metal atom of TMDC. In FIG. 8, the principal part plane schematic diagram of an example of TMDC which has an opening part is shown. FIG. 9 shows an example of the atomic arrangement of TMDC having an opening.

  For example, as shown in FIG. 8, at least one opening 31 is provided in the portion 30 a of the TMDC 30 where the metal electrode is stacked. FIG. 8 shows a form in which a plurality of planar circular openings 31 are periodically arranged in a part 30 a of the TMDC 30. FIG. 9 shows the atomic arrangement in plan view in the vicinity of one opening 31 of a planar circular shape as shown in FIG. 8 of the TMDC 30.

  By providing the opening 31 in the part 30 a of the TMDC 30, the transition metal atom T is exposed at the edge of the opening 31. For example, the number and arrangement of transition metal atoms T exposed to the portion 30 a of the TMDC 30 can be adjusted by the number, size and arrangement of the openings 31.

  A metal electrode is stacked on the portion 30a of the TMDC 30 where the transition metal atom T is exposed, and a metal-metal bond is formed between the transition metal atom T of the TMDC 30 and the metal atom of the metal electrode. Thereby, the connection structure of TMDC30 and a metal electrode which suppressed the increase in contact resistance is obtained.

  10 and 11 are explanatory views of another example of the method of exposing transition metal atoms of TMDC. FIG. 10 shows a schematic plan view of an essential part of an example of TMDC having an opening. FIG. 11 shows an example of the atomic arrangement of TMDC having an opening.

  FIG. 10 shows a form in which a plurality of planar triangular openings 32 are periodically arranged in a part 30 a of the TMDC 30 where metal electrodes are stacked. FIG. 11 shows the atomic arrangement in plan view in the vicinity of one opening 32 of the planar triangular shape as shown in FIG. 10 of the TMDC 30.

  By providing the opening 32 in the portion 30 a of the TMDC 30, the transition metal atom T is exposed at the edge of the opening 32. For example, the number and arrangement of transition metal atoms T exposed to the portion 30 a of the TMDC 30 can be adjusted by the number, size and arrangement of the openings 32.

  A metal electrode is stacked on the portion 30a of the TMDC 30 where the transition metal atom T is exposed, and a metal-metal bond is formed between the transition metal atom T of the TMDC 30 and the metal atom of the metal electrode. Thereby, the connection structure of TMDC30 and a metal electrode which suppressed the increase in contact resistance is obtained.

As an example, a transistor provided with TMDC in which an opening is provided to expose transition metal atoms as described above is shown in FIGS. 12 and 13 below.
12 and 13 are diagrams showing an example of the configuration of a transistor using TMDC having an opening. FIG. 12 is a schematic cross-sectional view of an essential part of an example of a transistor using TMDC having an opening. FIG. 13 is a schematic plan view of an essential part of an example of a transistor using TMDC having an opening, which is a schematic plan view of TMDC and a metal electrode as viewed from the TMDC side (a schematic plan view taken along the arrow LL). It is.

  Similar to the transistor 20 shown in FIG. 3, the transistor 40 shown in FIG. 12 includes the source electrode 44a and the end portion 43b of the TMDC 43 stacked on the insulating film 42 on the substrate 41, respectively. It has a structure in which the drain electrode 44b is connected.

  For the substrate 41, a substrate having conductivity is used, and for example, a semiconductor substrate such as a silicon substrate to which an impurity element of a predetermined conductivity type is added is used. For the insulating film 42, various insulating materials can be used. For example, silicon oxide is used.

  On such an insulating film 42, a single layer of TMDC 43 such as molybdenum disulfide is provided. The TMDC 43 has at least one, and as an example here, a plurality of openings 43c at the end 43a and the end 43b, respectively. The opening 43c of the TMDC 43 may be, for example, a flat circular opening (opening 31) as shown in FIGS. 8 and 9 above, or a flat triangular opening as shown in FIGS. 10 and 11 above. (The opening 32). Further, in the TMDC 43, as the opening 43c, the flat circular opening (opening 31) as shown in FIG. 8 and FIG. 9 and the planar triangular shape as shown in FIG. 10 and FIG. The openings (openings 32) may be mixed. FIG. 12 and FIG. 13 show, as an example, the TMDC 43 provided with a plurality of planar circular openings 43c. An example of a method of forming the TMDC 43 having the opening 43c will be described later.

  For the source electrode 44a and the drain electrode 44b connected to the TMDC 43, various metals such as molybdenum, tungsten, titanium, cobalt, nickel, palladium, aluminum, indium, copper, silver, platinum or gold, or any of them are used. The metal containing 2 or more types is used.

  In the transistor 40, the TMDC 43 is used as a channel, and the source electrode 44a is connected on one end 43a of the TMDC 43 provided with the opening 43c, and the other end 43b provided with the opening 43c. , And the drain electrode 44b are connected. The conductive substrate 41 functions as a gate electrode, and the potential of the substrate 41 is controlled, whereby the on / off state of the channel using the TMDC 43 is controlled.

  By providing the opening 43c at the end 43a and the end 43b of the TMDC 43, a metal is formed between the transition metal atom exposed at the edge of the opening 43c and the metal atom of the source electrode 44a and the drain electrode 44b. A metallic bond is formed. Thereby, the transistor 40 in which the increase in the contact resistance between the one end 43 a of the TMDC 43 and the source electrode 44 a and the other end 43 b of the TMDC 43 and the drain electrode 44 b is suppressed is realized.

Subsequently, an example of a method for forming a transistor having the above configuration is described.
Here, an example of a method for forming the transistor 40 will be described by taking the transistor 40 shown in FIGS. 12 and 13 as an example.

14 to 21 are explanatory diagrams of an example of a method of forming a transistor. Hereinafter, an example of each formation process of a transistor using TMDC will be described in order with reference to FIGS.
FIG. 14 is a schematic sectional view of an essential part of an example of the TMDC transfer step.

First, a single layer of molybdenum disulfide is prepared as TMDC 43 before the opening 43 c is formed, using a method of peeling with a pressure-sensitive adhesive tape from a bulk single crystal of molybdenum disulfide. Then, as shown in FIG. 14, the prepared TMDC 43 is transferred onto the insulating film 42 such as silicon oxide formed on the conductive substrate 41 such as the p ⁺ -type silicon substrate.

FIG. 15 is a schematic sectional view of an essential part of an example of a mask forming process.
After transferring the prepared TMDC 43 onto the insulating film 42 on the substrate 41, as shown in FIG. 15, a silicon oxide film 51, a random copolymer film 52, and a block copolymer are formed on the region including the TMDC 43. The films 53 are formed in order.

The silicon oxide film 51 functions as a protective film of the TMDC 43, and is deposited, for example, to a thickness of 10 nm.
For the random copolymer film 52, styrene-methyl methacrylate random copolymer (poly (styrene-random methyl methacrylate); P (Sr-MMA)) can be used. A toluene solution containing 1 wt% of P (Sr-MMA) is spin-coated on the silicon oxide film 51 and annealed at 170 ° C. for 72 hours to make a random copolymer of P (Sr-MMA). The film 52 is fixed on the silicon oxide film 51. Thereafter, washing is performed using toluene to remove P (Sr-MMA) that is not fixed on the silicon oxide film 51.

  For the block copolymer film 53, a styrene-methyl methacrylate block copolymer (poly (styrene-block methyl methacrylate); P (S-b-MMA)) can be used. A toluene solution containing 1 wt% of P (S-b-MMA) is spin-coated on the random copolymer film 52, and the P (S-b-MMA) is used as the block copolymer film 53 as a random copolymer film 52. Form on. For example, spin coating is performed at 2500 rpm to 4000 rpm to form a block copolymer film 53 with a thickness of 25 nm to 35 nm.

FIG. 16 is a schematic sectional view of an essential part of an example of the annealing process.
After the formation of the silicon oxide film 51, the random copolymer film 52 and the block copolymer film 53, annealing is performed. The annealing is performed, for example, under conditions of 180 ° C. for 12 hours. By performing annealing under predetermined conditions, cylindrical or substantially cylindrical domains (cylinders) oriented in the thickness direction (vertical orientation) in the block copolymer film 53 formed on the random copolymer film 52 ) 53a is formed periodically.

  By forming the block copolymer film 53 on the random copolymer film 52, it is possible to obtain the block copolymer film 53 including the cylinder 53a with good vertical orientation by annealing under predetermined conditions. it can.

  The arrangement (cycle) and size of the cylinder 53a can be adjusted by the molecular weight (molecular chain length) of P (S-b-MMA) used for the block copolymer film 53, the composition ratio of styrene and methyl methacrylate, etc. .

FIG. 17 is a schematic sectional view of an essential part of an example of the mask opening forming step.
After annealing, the block copolymer film 53 including the cylinder 53a is irradiated with ultraviolet light. For example, ultraviolet light with a wavelength of 295 nm is irradiated for 30 minutes. The cylinder 53 a in the block copolymer film 53 is selectively decomposed by irradiating the block copolymer film 53 with ultraviolet light under predetermined conditions.

  Then, the cylinder 53a selectively decomposed by the irradiation of ultraviolet light is removed using a predetermined liquid. As a liquid used for removing the cylinder 53a, for example, acetic acid, preferably glacial acetic acid is used. For example, the structure after ultraviolet irradiation is immersed in such a liquid for 20 minutes, and the cylinder 53a selectively decomposed by the ultraviolet irradiation is removed, and then washed using pure water.

  By performing decomposition and removal of the cylinder 53a by such ultraviolet irradiation, a polystyrene film 53A in which cylindrical opening portions 53Aa are periodically formed as shown in FIG. 17 is obtained.

The polystyrene film 53A having the opening 53Aa is used as a template (mask) in the subsequent etching process (FIG. 18).
FIG. 18 is a schematic sectional view of an essential part of an example of the first etching process.

  After forming the polystyrene film 53A having the opening 53Aa, first, as shown in FIG. 18, a resist film 54 is formed on the polystyrene film 53A so as to cover the region corresponding to the channel formation region of the transistor 40.

Then, the random copolymer film 52 is etched using the resist film 54 as a mask and the polystyrene film 53A having the opening 53Aa as a template. The etching of the random copolymer film 52 can be performed by, for example, reactive ion etching (RIE). The RIE of the random copolymer film 52 supplies oxygen (O ₂ ) gas at a flow rate of 10 sccm (standard cc / min) at a plasma power of 50 W under a pressure of 10 mTorr (1 Torr ≒ 133.322 Pa), for example. While doing.

  By etching the random copolymer film 52 in this manner, as shown in FIG. 18, in the region of the random copolymer film 52 corresponding to the formation regions of the source electrode 44 a and the drain electrode 44 b of the transistor 40. , And the opening 52a. The opening 52a of the random copolymer film 52 is periodically formed in a region under the polystyrene film 53A not covered with the resist film 54 and corresponding to the opening 53Aa.

  When the opening 52a is formed by etching, the size of the opening 52a of the random copolymer film 52 can be made larger than the size of the opening 53Aa of the polystyrene film 53 if overetching is performed. is there.

The random copolymer film 52 having the opening 52a is used as a template (mask) in the subsequent etching step (FIG. 19).
FIG. 19 is a schematic sectional view of an essential part of an example of the second etching process.

After forming the opening 52a in the random copolymer film 52, the resist film 54 and the polystyrene film 53A are removed, and the silicon oxide film 51 is etched using the random copolymer film 52 having the opening 52a as a mask. . The etching of the silicon oxide film 51 can be performed, for example, by RIE. RIE of the silicon oxide film 51 is performed, for example, while supplying trifluoromethane (CHF ₃ ) gas at a flow rate of 45 sccm and oxygen gas at a flow rate of 5 sccm at a plasma power of 300 W under a pressure of 60 mTorr.

  By etching the silicon oxide film 51 in this manner, as shown in FIG. 19, the opening 51 a in the silicon oxide film 51 in the region corresponding to the formation region of the source electrode 44 a and the drain electrode 44 b of the transistor 40. Form The opening 51 a of the silicon oxide film 51 is periodically formed in a region under the random copolymer film 52 corresponding to the opening 52 a.

  When the opening 51a is formed by etching, the size of the opening 51a of the silicon oxide film 51 can be larger than the size of the opening 52a of the random copolymer film 52 by performing over-etching. It is.

The silicon oxide film 51 having the opening 51a is used as a template (mask) in the subsequent etching step (FIG. 20).
FIG. 20 is a schematic sectional view of an essential part of an example of the third etching process.

  After the opening 51a is formed in the silicon oxide film 51, the TMDC 43 is etched using the silicon oxide film 51 as a mask. The etching of TMDC 43 can be performed, for example, by RIE. RIE of TMDC 43 is performed, for example, while supplying oxygen gas at a flow rate of 25 sccm at a plasma power of 90 W under a pressure of 10 mTorr.

  By etching the TMDC 43 in this manner, as shown in FIG. 20, the opening 43 c is formed in the end 43 a and the end 43 b of the TMDC 43 corresponding to the regions where the source electrode 44 a and the drain electrode 44 b of the transistor 40 are formed. Form The opening 43 c of the TMDC 43 is periodically formed in the region under the silicon oxide film 51 corresponding to the opening 51 a.

  In this example, the opening 43 c is not formed in the region of the TMDC 43 corresponding to the formation region of the channel between the source electrode 44 a and the drain electrode 44 b of the transistor 40.

  After forming the opening 43 c in the end 43 a and the end 43 b of the TMDC 43, the silicon oxide film 51 is removed. The silicon oxide film 51 can be removed, for example, using hydrofluoric acid (HF).

The cycle of the openings 43 c of the TMDC 43 can be adjusted, for example, by the molecular weight of P (Sb-MMA) used for the block copolymer film 53. The period of the openings 43c tends to be shorter as the molecular weight of P (S-b-MMA) used becomes smaller. For example, when P (S-b-MMA) having a molecular weight of 47,700 gmol ^-1 is used, the period of the opening 43c is 27 nm, and when P (S-b-MMA) having a molecular weight of 77,000 gmol ^-1 is used. The period of the openings 43c is 39 nm.

  The size of the opening 43c of the TMDC 43 is the size of the opening 51a of the silicon oxide film 51, the size of the opening 52a of the random copolymer film 52, the size of the opening 53Aa of the polystyrene film 53A, the size of the block copolymer film 53 It can be adjusted by the size of the cylinder 53a. The size of each of the openings 51a, 52a, 53Aa can be adjusted by the size of the cylinder 53a or the etching time (over-etching) when forming by etching.

  Furthermore, the size of the opening 43c of the TMDC 43 can also be adjusted by the etching time of the TMDC 43 using the silicon oxide film 51 provided with the opening 51a as a mask. The size of the opening 43c tends to increase as the etching time increases.

FIG. 21 is a schematic sectional view of an essential part of an example of the electrode forming step.
After forming the opening 43c of the TMDC 43, metal is formed at the end 43a and the end 43b of the TMDC 43 in which the opening 43c is formed, whereby the source electrode 44a and the drain electrode 44b as shown in FIG. Form.

  Various metals can be used for the source electrode 44a and the drain electrode 44b. For example, a titanium layer and a gold layer are sequentially deposited on the end 43a and the end 43b of the TMDC 43 where the opening 43c is formed, to form a titanium / gold laminated structure as a source electrode 44a and a drain electrode 44b. Electron beam evaporation can be used to form the source electrode 44a and the drain electrode 44b (deposition of metal), for example.

  A metal-metal bond is formed between the metal atoms of the source electrode 44 a and the drain electrode 44 b to be formed and the transition metal atoms exposed at the edge of the opening 43 c of the TMDC 43. Thereby, an increase in the contact resistance between the source electrode 44a and the drain electrode 44b and the TMDC 43 can be suppressed.

  A back gate type transistor in which the substrate 41 functions as a gate electrode and the portion between the end 43 a and the end 43 b of the TMDC 43 to which the source electrode 44 a and the drain electrode 44 b are respectively connected by the above steps. 40 are formed. That is, the transistor 40 in which the on / off state of the TMDC 43 serving as the channel is controlled by controlling the potential of the substrate 41 is formed.

  Note that, as TMDC 43 used for the channel of the transistor 40, other than single-layer molybdenum disulfide, other single-layer tungsten diselenide or other TMDC may be used. Further, as the TMDC 43 used for the channel of the transistor 40, a multilayer of such a single layer of TMDC such as molybdenum disulfide may be used.

  14 to 21 illustrate the method for forming the transistor 40 using the substrate 41 as a gate electrode. In addition, a gate electrode can be formed on the TMDC 43 to be a channel through a gate insulating film, to obtain a transistor.

22 and 23 are explanatory diagrams of another example of the transistor formation method. Hereinafter, another example of a process for forming a transistor using TMDC will be described with reference to FIGS.
In this method, first, on the insulating film 42A such as silicon oxide formed on a suitable substrate 41A, similarly to the above, prepared using the exfoliation method from bulk single crystal, before forming the opening 43c. Transfer TMDC43.

  Thereafter, each step as shown in FIGS. 15 to 21 is carried out, and as shown in FIG. 22, the source electrode 44a is provided on the end 43a and the end 43b of the TMDC 43 provided with the opening 43c. And the drain electrode 44b is formed. A metal-metal bond is formed between the metal atoms of the source electrode 44a and the drain electrode 44b and the transition metal atoms exposed at the edge of the opening 43c of the TMDC 43, and the source electrode 44a and the drain electrode 44b are in contact with the TMDC 43 The increase in resistance is suppressed.

  Next, as shown in FIG. 23, a gate insulating film 45 is formed on the TMDC 43 between the source electrode 44a and the drain electrode 44b, and on the gate insulating film 45 between the source electrode 44a and the drain electrode 44b. The gate electrode 46 is formed. For the gate insulating film 45, various insulating materials can be used. For example, silicon oxide can be used. For the gate electrode 46, various conductor materials can be used. For example, silicon, polysilicon, metal or the like of a predetermined conductivity type can be used.

  By such a process, a top gate type transistor 40A in which the on / off state of the TMDC 43 serving as a channel is controlled by controlling the potential of the gate electrode 46 is formed.

  Note that, as TMDC 43 used for the channel of the transistor 40A, other TMDC such as single layer tungsten diselenide other than single layer molybdenum disulfide may be used. Further, as the TMDC 43 used for the channel of the transistor 40A, a multilayer of such a single layer of TMDC such as molybdenum disulfide may be used.

  When the metal electrode such as the source electrode 44a and the drain electrode 44b is connected to the TMDC, the metal electrode can be provided not only on the upper side of the TMDC but also on the lower side of the TMDC.

  When a metal electrode is provided on the upper layer side of TMDC, an opening is formed in a predetermined portion of TMDC on a predetermined substrate and the opening is formed, as described in, for example, the method of forming the transistors 40 and 40A. A metal electrode may be formed on the above-mentioned portion.

  When a metal electrode is provided on the lower layer side of TMDC, the predetermined substrate (or layer) on which the metal electrode is formed, or the predetermined substrate (or layer) on which the metal electrode is embedded in the surface layer portion Provide TMDC. Then, an opening may be formed in the portion of the TMDC above the metal electrode in accordance with the example of FIGS.

Moreover, TMDC can be applied not only to a transistor that uses it for a channel, but also to a conductor portion such as a wiring that electrically connects elements or components in an electronic device.
FIG. 24 is a view showing a configuration example of a conductor part using TMDC. FIGS. 24A to 24C schematically show an example of the main configuration of the conductor using TMDC.

  Conductor portion 100A shown in FIG. 24A includes TMDC 110, and conductor layer 120a and conductor layer 120b provided in the lower layer of TMDC 110. A metal is used for the conductor layer 120a and the conductor layer 120b. The conductor layer 120 a and the conductor layer 120 b are wires, vias, and the like. At least one, by way of example here, a plurality of openings 110 a are provided in the portion of the TMDC 110 connected to the conductor layer 120 a and the conductor layer 120 b.

  A metal-metal bond is formed between the metal atoms of the conductor layer 120a and the conductor layer 120b and the transition metal atoms exposed from the opening 110a of the TMDC 110, and the contact resistance between the conductor layer 120a and the conductor layer 120b and the TMDC 110 The increase in

In the conductor portion 100A, the conductor layer 120a and the conductor layer 120b are electrically connected through the TMDC 110 provided on their upper layer.
When forming the conductor portion 100A as shown in FIG. 24A, for example, the conductor layer 120a and the conductor of the layer in which the conductor layer 120a and the conductor layer 120b are formed or the layer in which they are embedded in the surface layer portion The TMDC 110 is provided over the region including the layer 120 b. Then, in the portion of the TMDC 110 above the conductor layer 120a and the conductor layer 120b, the opening 110a is formed in accordance with the example of FIGS. By such a method, a conductor portion 100A as shown in FIG. 24A can be obtained.

  Although FIG. 24A exemplifies the case where the conductor layer 120 a and the conductor layer 120 b are provided in the lower layer of the TMDC 110, the conductor layer 120 a and the conductor layer 120 b are provided in the upper layer of the TMDC 110. It can also be connected to In the case of such a configuration, first, an opening 110a is formed in a portion connecting the conductor layer 120a and the conductor layer 120b of the TMDC 110 provided on a predetermined substrate, and the portion on which the opening 110a is formed is The conductor layer 120a and the conductor layer 120b may be formed.

  Further, conductor portion 100B shown in FIG. 24B includes TMDC 110, and conductor layers 120a and 120b provided on the lower layer and the upper layer of TMDC 110, respectively. The conductor layer 120a and the conductor layer 120b are wires, vias, or the like, and are formed using a metal. At least one, by way of example here, a plurality of openings 110 a are provided in the portion of the TMDC 110 connected to the conductor layer 120 a and the conductor layer 120 b.

  A metal-metal bond is formed between the metal atoms of the conductor layer 120a and the conductor layer 120b and the transition metal atoms exposed from the opening 110a of the TMDC 110, and the contact resistance between the conductor layer 120a and the conductor layer 120b and the TMDC 110 The increase in

In the conductor portion 100B, the conductor layer 120a and the conductor layer 120b are electrically connected through the TMDC 110 provided between the layers.
When forming the conductor portion 100B as shown in FIG. 24B, first, on the region including the conductor layer 120a of the layer in which the conductor layer 120a is formed or the layer in which the conductor layer 120a is embedded in the surface layer portion, TMDC 110 is provided. Next, an opening 110a is formed in the portion of the TMDC 110 above the conductor layer 120a and the portion connecting the other conductor layer 120b. Then, the conductor layer 120 b is formed on the portion where the opening 110 a is formed (the portion to which the conductor layer 120 b is connected) on the layer provided with such a TMDC 110. By such a method, a conductor portion 100B as shown in FIG. 24 (B) can be obtained.

  The conductor portion 100C shown in FIG. 24C includes the conductor layer 120 and the TMDCs 110 provided on the lower layer and the upper layer of the conductor layer 120, respectively. The conductor layer 120 is a wire, a via, or the like, and is formed using a metal. At least one, as an example here, a plurality of openings 110 a are provided in portions of the lower and upper TMDCs 110 connected to the conductor layer 120.

  A metal-metal bond is formed between the metal atoms of the conductor layer 120 and the transition metal atoms exposed from the lower and upper TMDC 110 openings 110a, and the contact resistance between the conductor layer 120 and the lower and upper TMDC 110 is obtained. The increase in

In the conductor portion 100C, the lower and upper TMDCs 110 are electrically connected through the conductor layer 120 provided between the layers.
In forming the conductor portion 100C as shown in FIG. 24C, first, the conductor layer 120 is formed on the portion of the layer including the TMDC 110 in which the opening 110a is formed and in which the opening 110a is formed. . Then, the TMDC 110 is provided on the region including the conductor layer 120 of the layer including the conductor layer 120, and the opening 110a is formed in the portion above the conductor layer 120. By such a method, a conductor portion 100C as shown in FIG. 24 (C) can be obtained.

In addition to the single-layered TMDC, a multi-layered TMDC can also be used as the TMDC 110 used for the conductor portions 100A, 100B, and 100C.
The conductor portions 100A, 100B, and 100C as shown in FIGS. 24A to 24C can be employed as conductor portions of various electronic devices. For example, the conductor portions 100A, 100B, and 100C are semiconductor devices, semiconductor devices including semiconductor devices mounted on a circuit board, pseudo SoC (System On a Chip) in which electronic components such as semiconductor devices are embedded in a resin layer, circuits It can be adopted as a substrate or the like. More specifically, it can be adopted as a conductor provided in a multilayer wiring of a semiconductor element, a conductor provided in a circuit board, a conductor provided in a rewiring layer of a pseudo SoC, or the like.

  By adopting conductor portions 100A, 100B and 100C including TMDC 110 as shown in FIGS. 24A to 24C, an increase in contact resistance between TMDC 110 and conductor layers 120a, 120b and 120 is suppressed. It becomes possible to realize an electronic device. By employing the conductor portions 100A, 100B, and 100C including the TMDC 110, it is possible to realize a high-speed, low-power-consumption electronic device.

  Here, as the TMDC 110 connected to the conductor layers 120a, 120b, 120, one having the opening 110a is taken as an example. Besides, as the TMDC 110 connected to the conductor layers 120a, 120b, 120, at least a part of the chalcogen atom layer on the conductor layers 120a, 120b, 120 is removed to expose at least one transition metal atom. It is also good. Also in the case of using such a TMDC 110, a metal-metal bond is formed between the metal atoms of the conductor layers 120a, 120b, and 120 and the exposed transition metal atoms of the TMDC 110. As a result, as in the above, the increase in the contact resistance between the conductor layers 120a, 120b, 120 and the TMDC 110 can be suppressed, and an electronic device with high speed and low power consumption can be realized.

  The method of connecting a metal to the portion of the TMDC where the transition metal atom is exposed as described above is applicable to a transistor, various electronic devices provided with a transistor, and various electronic devices provided with a conductor portion such as a wiring. .

The following appendices will be further disclosed regarding the embodiment described above.
(Supplementary Note 1) A transition metal dichalcogenide having a first portion to which at least one transition metal atom is exposed,
An electronic device comprising: a first metal connected to the first portion.

  (Supplementary Note 2) The electronic device according to Supplementary note 1, characterized by having a metal-metal bond between a transition metal atom exposed to the first portion of the transition metal dichalcogenide and a metal atom of the first metal. .

  (Supplementary Note 3) The transition metal dichalcogenide has a first opening in the first portion, and at least one transition metal atom is exposed at an edge of the first opening. Electronic device according to claim 1.

(Supplementary Note 4) The transition metal dichalcogenide has a second portion to which at least one transition metal atom is exposed,
The electronic device according to any of the preceding claims, further comprising a second metal connected to the second part.

  (Supplementary Note 5) The electronic device according to Supplementary note 4, including a metal-metal bond between a transition metal atom exposed to the second portion of the transition metal dichalcogenide and a metal atom of the first metal. .

  (Supplementary Note 6) The transition metal dichalcogenide has a second opening in the second portion, and at least one transition metal atom is exposed at an edge of the second opening. Electronic device according to claim 1.

(Supplementary Note 7) The first metal connected to the first portion is a source electrode,
The second metal connected to the second portion is a drain electrode,
An insulating film laminated between the first portion and the second portion of the transition metal dichalcogenide;
The electronic device according to any one of appendices 4 to 6, further comprising: a gate electrode stacked on the side of the insulating film opposite to the transition metal dichalcogenide.

(Supplementary Note 8) The electronic device according to Supplementary note 7, wherein the transition metal dichalcogenide does not have a portion to which a transition metal atom is exposed between the first portion and the second portion.
(Supplementary note 9) forming a transition metal dichalcogenide having a first portion to which at least one transition metal atom is exposed;
Connecting the first metal to the first portion.

  (Supplementary Note 10) The electronic device according to Supplementary note 9, wherein the transition metal dichalcogenide has a first opening in the first portion, and transition metal atoms are exposed at an edge of the first opening. Manufacturing method.

(Supplementary Note 11) In the step of forming the transition metal dichalcogenide, the transition metal dichalcogenide including the first portion and a second portion to which at least one transition metal atom is exposed is formed.
The method of manufacturing the electronic device according to any one of appendices 9 or 10, further comprising the step of connecting a second metal to the second part.

  (Supplementary Note 12) The transition metal dichalcogenide according to Supplementary Note 11, wherein the second portion has a second opening, and at least one transition metal atom is exposed at an edge of the second opening. Of manufacturing electronic devices.

(Supplementary Note 13) The first metal connected to the first portion is a source electrode,
The second metal connected to the second portion is a drain electrode,
Forming an insulating film laminated between the first portion and the second portion of the transition metal dichalcogenide;
The method according to claim 11 or 12, further comprising: forming a gate electrode laminated on the side of the insulating film opposite to the transition metal dichalcogenide.

  (Supplementary Note 14) A method of manufacturing an electronic device, including the step of connecting a metal to a portion of at least one transition metal atom of the transition metal dichalcogenide exposed.

T, T1 Transition metal atom X Chalcogen atom 1A, 1B, 1C Junctions 2, 13, 23, 30, 30, 43, 110 Transition metal dichalcogenide (TMDC)
2a, 30a Part 2b, 31, 32, 43c, 51a, 52a, 53Aa, 110a Opening 3 Electrode 4 Metal-Metal Connection 5 Tunnel Barrier 10, 20, 40, 40A Transistor 11, 21, 41, 41A Substrate 12, 22, 42, 42A Insulating film 13a, 13b, 23a, 23b, 43a, 43b End portion 14a, 24a, 44a Source electrode 14b, 24b, 44b Drain electrode 15, 45 Gate insulating film 16, 46 Gate electrode 51 Silicon oxide film 52 Random copolymer film 53 Block copolymer film 53a Cylinder 53A Polystyrene film 54 Resist film 100A, 100B, 100C Conductor part 120, 120a, 120b Conductor layer

Claims (4)

A transition metal dichalcogenides having a first surface that terminates by a chalcogen atom, a transition metal dichalcogenides you exposed at least one transition metal atom in each of the first and second portions of said first surface,
A first metal connected to the first portion ;
An electronic device comprising: a second metal connected to the second portion . The first metal connected to the first portion as a source electrode;
The second metal connected to the second portion is a drain electrode,
An insulating film stacked on the first surface of the transition metal dichalcogenide between the first portion and the second portion;
The electronic device according to claim 1 , further comprising: a gate electrode stacked on the side of the insulating film opposite to the transition metal dichalcogenide. A transition metal dichalcogenides having a first surface that terminates by chalcogen atoms, forming a transition metal dichalcogenides you exposed at least one transition metal atom in each of the first and second portions of the first surface The process to
Connecting a first metal to the first portion ;
And a step of connecting a second metal to the second portion . The first metal connected to the first portion as a source electrode;
The second metal connected to the second portion is a drain electrode,
Forming an insulating film laminated on the first surface of the transition metal dichalcogenide between the first portion and the second portion;
4. The method of manufacturing an electronic device according to claim 3 , further comprising: forming a gate electrode laminated on the side opposite to the transition metal dichalcogenide of the insulating film.

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