JP6429688B2 - Tunnel field effect transistor and method of using the same - Google Patents

Description

  The present invention relates to a tunnel field effect transistor.

Transistors are indispensable to the world, and low power consumption is an important issue. Various transistor structures with low power consumption have been proposed and developed so far, but tunnel field effect transistors are attracting attention as transistors capable of extremely reducing power consumption.
As described in Non-Patent Document 1, a tunnel field effect transistor is a device that performs a current switching operation by controlling a current tunneling beyond an energy barrier in a semiconductor by a voltage of another electrode.
Tunnel field effect transistors have been developed in various parts of the world, and Patent Document 1 describes a tunnel field effect transistor characterized by having a heterojunction of an elongated single crystal nanostructure silicon and germanium. Document 2 describes a tunnel field effect transistor technique characterized in that a dopant is introduced after the source layer forming region is once amorphized. Patent Document 3 describes a tunnel field-effect transistor including an epitaxial growth layer that is joined to a source region.
Non-Patent Document 2 describes a tunnel field effect transistor having another structure. The tunnel field effect transistor of Non-Patent Document 2 is a proposal to increase the on-state current by about 10 times by adding both aluminum (Al) and nitrogen (N) to the tunnel junction region of the tunnel field effect transistor. is there. Since the tunnel field effect transistor of Non-Patent Document 2 can be formed by a process closer to the normal CMOS transistor process than other tunnel field effect transistors, a circuit combining a CMOS transistor circuit and a tunnel field effect transistor circuit can be configured. This is a highly practical transistor technology. Regarding the transistor proposed in Non-Patent Document 2, Yayama et al. In Non-Patent Document 3 examined the stability and electronic state of the Si structure to which Al and N were added. As a result, it is reported that the case where the Al atom and N atom distributed in the Si single crystal are in the first adjacent arrangement is a stable arrangement having a low energy of 1 eV or more as compared with other arrangements. In this report, when impurity atoms such as Al atom and N atom are separated, Si maintains a covalent bond, but an electron is attracted to an N atom having a large electronegativity in the vicinity of the impurity atom. It has also been reported that N forms localized levels. In this report, Si has an indirect energy gap, but the localized level formed by N relaxes the momentum conservation condition and increases the probability of causing an electron transition without an electron-phonon bond. It also states that the on-current of the tunnel field effect transistor may have increased.

JP2015-19072A JP 2013-69977 A JP 2013-187291 A

International Electron Devices Meeting (IEDM) 2013 Proceedings “High Ion / Ioff and low subthreshold slope planar-type InGaAs Tunnel FETs with Zn-diffused source junctions” T.Mori et al., 2014 Symposium on VLSI Technology Digest of Technical Papers, “Band-to-Band Tunneling Current Enhancement Utilizing Isoelectronic Trap and its Application to TFETs” Yayama, et al. Proceedings of the 62nd JSAP Spring Meeting, 2015 12-366 (2015)

About the tunnel field effect transistor which is proposed in Non-Patent Document 2 and is characterized by adding Al and N in Si, the reason why the on-current is improved by having this feature is unclear, There was a problem that the characteristics could not be further improved.
In Non-Patent Document 3, the cause of the improvement of the on-current is studied to solve this problem, and the condition of momentum conservation is relaxed by the localized level formed by the N atom in the first proximity arrangement with Al. -We came to consider that the on-current of the tunnel field-effect transistor would have increased due to the increased probability of electron transition without phonon coupling.
However, the level has not yet been elucidated, and there remains a problem that further improvement of the on-current in this structure does not progress.

Specifically, the present invention has the following configuration.
(1) According to one aspect of the present invention, a source region that is a high concentration p-type region, a first channel region that is a low concentration p-type region joined to the source region, and a junction surface between the source region Is a high-concentration n-type region that is bonded to a second channel region that is a low-concentration n-type region that is bonded to another surface and a surface that is different from the bonding surface of the second channel region to the first channel region. A drain region; and a gate electrode that is in contact with an energization region composed of the source region, the first channel region, the second channel region, and the drain region through an insulating film, and the first channel region includes: A tunnel field effect transistor is provided in which indium (In) and nitrogen (N) are added as additives to a silicon (Si) single crystal.
(2) Here, the second channel region may be an n-type silicon (Si) single crystal.
(3) Gallium (Ga) may be added instead of indium (In).
(4) According to another aspect of the present invention, in the junction region of the source region and the first channel region, interband between Den gubernaculum of the source region valence band and the first channel region of the There is provided a method of using a tunnel field effect transistor characterized by causing an electron flow from a source region to a drain region by causing a tunneling phenomenon.

  By using the technique of the present invention, the amount of on-current of the tunnel field-effect transistor can be improved.

1 is a cross-sectional view of a tunnel field effect transistor according to an embodiment of the present invention. It is a perspective view which shows the positional relationship of the aluminum atom in a silicon | silicone, and a nitrogen atom. It is a graph which shows the calculation result of the energy regarding the aluminum atom in a silicon | silicone, and a nitrogen atom. It is a conceptual diagram for demonstrating the calculation model and calculation result of an interband tunnel current. It is a graph which shows the calculation result of the transition probability by III-N group element addition.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a cross-sectional view of a tunnel field effect transistor according to an embodiment of the present invention.
A source region 1 that is a high-concentration p-type region is formed in the surface region of the silicon single crystal substrate 100. The source region 1 is in a high-concentration p-type semiconductor state. A first channel region 2 that is a low-concentration p-type region is formed on the left side of the source region 1. The first channel region 2 is formed only near the surface as shown in FIG. The reason is that the band-to-band tunnel current should flow at the junction between the source region 1 and the first channel region 2, and only the surface region to which the external control voltage is most effectively applied as described later. This is because one channel region 2 may be formed.
Indium (In) and nitrogen (N) are added to the first channel region 2. As the addition method, various methods are used such as injecting the same amount of indium and nitrogen by an ion implantation method, and recovering the damage of the silicon crystal due to the implantation by heat treatment.
As for the additive, the same amount of gallium (Ga) and nitrogen (N) may be added instead of indium (In) and nitrogen (N). A second channel region 3 is formed on the right side of the first channel region 2 so as to be joined.
As one embodiment, the first channel region 2 is made of indium (In) and nitrogen (N) or gallium (Ga) and nitrogen (N), and the second channel region 3 is made of a pentium element and nitrogen (N). Both may be added.
As another embodiment, the first channel region 2 may be indium (In) and nitrogen (N) or gallium (Ga) and nitrogen (N), and the second channel region 3 may be added with only a group 5 element. is there. The second channel region 3 is doped with an n-type additive amount. On the right side of the second channel region 3, a drain region 4 which is a high concentration n-type region is formed. By applying a voltage to the source region 1 and the drain region 4 so that the second channel region 3 is at a higher voltage (a deeper potential as the potential) than the first channel region 2, The electron flow to the two-channel region 3 can be made to flow smoothly. A tunnel field effect transistor is formed by a gate electrode 7 which is in contact with an energizing region 5 composed of a source region 1, a first channel region 2, a second channel region 3, and a drain region 4 through which an electron current flows through an insulating film 6. . The voltage applied to the gate electrode 7 can cut off (off) or flow (on) the electron flow flowing in the energized region. A larger on-current can be secured when gallium (Ga) or indium (In) is used than when the additive is aluminum (Al). This is because the localized level of nitrogen (N) generated in the boundary region between the source region and the first channel region is more gallium (Ga) or indium (In) than in the case of aluminum (Al). This is due to the fact that the band-to-band tunneling current is more likely to flow because it is lower.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

FIG. 2 is a perspective view showing the positional relationship between aluminum atoms and nitrogen atoms in silicon. Aluminum (Al) was placed in the lower left corner as Al, and nitrogen (N) atoms were calculated at various positions in the vicinity of the aluminum (Al), and the total energy states in that case were calculated and compared.
FIG. 3 is a graph showing the calculation results of energy regarding aluminum atoms and nitrogen atoms in silicon. As is clear from FIG. 3, when the nitrogen (N) is in the first proximity position closest to aluminum (Al), the energy of this calculation system is about 1 eV lower than that in the position farther than that. In other words, it can be said that it is more stable. From this result, it is predicted that most of the added aluminum (Al) and nitrogen (N) also exist in the first proximity arrangement that is the closest position to each other. This tendency is the same for a combination of indium (In) and nitrogen (N) or a combination of gallium (Ga) and nitrogen (N).

FIG. 4 is a conceptual diagram for explaining a calculation model and a calculation result of the band-to-band tunnel current. In each case of a combination of aluminum (Al) and nitrogen (N), a combination of indium (In) and nitrogen (N), and a combination of gallium (Ga) and nitrogen (N), the high-concentration p-type silicon region and these When the level level generated in the interface region of the region to which the combination is added is calculated, as shown in FIG. 4, indium (In) is the shallowest, gallium (Ga) is the next shallowest, and aluminum (Al) is the deepest. I understood. The shallower the intermediate level, the more efficient band-to-band tunneling occurs.
As a result, the graph of the calculation result of the transition probability by adding the III-N group element shown in FIG. 5 was obtained. It is calculated by adding three group elements and nitrogen that the interband tunneling is improved by about 4 digits as compared with silicon single crystal. Among them, indium (In) and gallium are more than aluminum (Al). (Ga) has a higher transition probability.

  Since tunnel field effect transistors have low power consumption, they are expected to be used in many applications, including ultra-low power circuits for sensor networks that are difficult to supply power to mobile devices where power consumption is a concern.

DESCRIPTION OF SYMBOLS 1 ... Source region, 2 ... 1st channel region, 3 ... 2nd channel region, 4 ... Drain region, 5 ... Current supply region, 6 ... Insulating film, 7 ... Gate electrode, 100 ... silicon single crystal substrate

Claims (4)

A source region that is a high-concentration p-type region; a first channel region that is a low-concentration p-type region joined to the source region;
A second channel region that is a low-concentration n-type region that is bonded to a surface different from a surface that is bonded to the source region;
A drain region which is a high-concentration n-type region joined on a surface different from a joint surface of the second channel region with the first channel region;
A gate electrode that is in contact with an energizing region composed of the source region, the first channel region, the second channel region, and the drain region through an insulating film;
A tunnel field effect transistor, wherein in the first channel region, indium (In) and nitrogen (N) are added as additives to a silicon (Si) single crystal.   The tunnel field effect transistor according to claim 1, wherein the second channel region is an n-type silicon (Si) single crystal.   3. The tunnel field effect transistor according to claim 1, wherein gallium (Ga) is added instead of indium (In). In the junction region between the source region and the first channel region, the drain region from the source region by producing interband tunneling between the heat gubernaculum the valence band and the first channel region of the source region A method of using a tunnel field effect transistor according to any one of claims 1 to 3, wherein an electron flow is applied.