Abstract
An electrical interconnection. In order to efficiently conduct electrical current in small-scale structures and at high frequencies, the electrical interconnection has a channel portion which includes at least one channel layer made of a weak topological insulator material and having a top surface with a plurality of grooves extending from a first terminal to a second terminal of the electrical interconnection, wherein the top surface and a bottom surface of each groove are insulating, whereas each side surface of each groove includes a conducting zone with a pair of topologically protected one-dimensional electron channels.
Claims
1. An electrical interconnection having a channel portion which comprises a channel layer made of a weak topological insulator material or any other three-dimensional topological insulator material which exhibits topologically protected one-dimensional electron channels and having a top surface with a plurality of grooves extending from a first terminal to a second terminal of the electrical interconnection, wherein the top surface and a bottom surface of each groove are insulating, whereas each side surface of each groove comprises a conducting zone with a pair of topologically protected one-dimensional electron channels.
2. The electrical interconnection according to claim 1, wherein the first terminal comprises a first electrode made of metal and the second terminal comprises a second electrode made of metal, wherein the grooves of the channel layer extend from the first electrode to the second electrode.
3. The electrical interconnection according to claim 1, wherein all grooves of the channel layer are spaced apart.
4. The electrical interconnection according to claim 1, wherein some of the grooves of the channel layer run parallel.
5. The electrical interconnection according to claim 1, wherein the electrical interconnection comprises a plurality of channel layers arranged in a stacked manner.
6. The electrical interconnection according to claim 5, wherein some of the grooves in a plurality of different channel layers among the plurality of channel layers run parallel.
7. The electrical interconnection according to claim 5, wherein two neighboring channel layers among the plurality of channel layers are separated by an insulating layer, which comprises an insulating material different from the topological insulator material.
8. The electrical interconnection according to claim 7, wherein the insulating material has a relative permittivity of less than 10.
9. The electrical interconnection according to claim 7, wherein the insulating material has a relative permittivity of less than 5.
10. The electrical interconnection according to claim 5, wherein the electrical interconnection comprises a first channel layer of the plurality of channel layers having grooves extending from the first terminal to the second terminal and a second channel layer of the plurality of channel layers having grooves extending from a third terminal to a fourth terminal of the electrical interconnection.
11. The electrical interconnection according to claim 10, wherein the third terminal comprises a third electrode made of metal and the fourth terminal comprises a fourth electrode made of metal.
12. The electrical interconnection according to claim 10, wherein each first channel layer is separated from the third and fourth terminal by the insulator material and each second channel layer is separated from the first and second terminal by the insulator material.
13. The electrical interconnection according to claim 10, wherein the first and second channel layers are disposed alternatingly.
14. An integrated circuit, comprising the electrical interconnection according to claim 1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawing, wherein:
(2) FIG. 1 is a schematic top view of a channel layer for an electrical interconnection according to the invention;
(3) FIG. 2 is cross-sectional view according to the line II-II in FIG. 1;
(4) FIG. 3 is a schematic top view similar to FIG. 1 illustrating conducting zones;
(5) FIG. 4 is a cross-sectional view according to the line IV-IV in FIG. 3;
(6) FIG. 5 is a cross-sectional view of a channel layer and an insulating layer;
(7) FIG. 6 is a cross-sectional view of a channel portion comprising a plurality of channel layers and insulating layers;
(8) FIG. 7 is a top view of an electrical interconnection according to a first embodiment of the invention;
(9) FIG. 8 is a cross-sectional view according to the line VIII-VIII in FIG. 7;
(10) FIG. 9 is a cross-sectional view along the line IX-IX in FIG. 7;
(11) FIG. 10 is a top view of an electrical interconnection according to a second embodiment of the invention; and
(12) FIG. 11 is a cross-sectional view according to the line XI-XI in FIG. 10;
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
(13) FIGS. 1 and 2 show a schematic representation of a first channel layer 10 for an electrical interconnection according to the present invention. For ease of reference, a coordinate system with X-, Y- and Z-axis is shown in all figures. The first channel layer 10 has a flat, roughly rectangular shape extending along the X-axis and Y-axis. An upper surface 11 of the first channel layer 10 extends along the X-Y-plane (which can also be referred to as the horizontal plane) and faces in the Z-direction. It should be noted that the dimensions of the embodiment in the figure are not to scale. The total length (along the Y-axis) and width (along the X-axis) of the first channel layer 10 may be e.g. several hundred of nanometers and 15 nm, respectively, and its thickness (along the Z-axis) may be e.g. 3 nm. A plurality of straight grooves 12 running along the Y-direction are disposed within the upper surface 11. Each of these grooves 12 has a rectangular cross-section with side surfaces 12.1 extending along the Y-Z-plane and a bottom surface 12.2 extending along the X-Y-plane. The width of each groove 12 may be e.g. 2 nm while its depth may be 1 nm but at least the distance between two atomic layers. Two neighboring grooves 12 are separated by a ridge 13 having a width that may be equal to the width of each groove 12.
(14) The first channel layer 10 is made of a weak topological insulator material, e.g. Bi.sub.14Rh.sub.3I.sub.9. During the manufacturing process, it may be formed by a deposition processes like electron beam epitaxy while the grooves 12 may be formed afterwards by nano-structuring methods like photolithography, electron-beam lithography or scanning probe microscopy scratching. The use of a weak topological insulator material combined with the structure of the first channel layer 10 leads to a special electrical conduction behavior which is illustrated in FIGS. 3 and 4. While the upper surface 11 as well as the bottom surfaces 12.2 of each groove 12 are electrically insulating, every side surface 12.1 of the grooves 12 comprises an electrically conducting zone 14 with a pair of topologically protected one-dimensional electron channels 15 which are schematically shown in FIG. 3. It is understood that the conducting zones 14 are only illustrated schematically and that their actual size and shape may be different depending on the specific weak topological insulator material. It should however be noted, that a fingerprint of weak topological insulators is that the spatial density of states is very narrow, such that the grooves can be made very narrow as well. Each electron channel 15 allows for a propagation of electrons in the positive or negative Y-direction, respectively. Each electron channel 15 is spin-polarized, i.e. the direction of the spin of an electron correlates with its propagation direction. Due to the properties of the weak topological insulator, each electron channel 15 has a quantized conductance of e.sup.2/h (h being the Planck constant), which does not substantially depend on the length, the depth or the width of the groove 12. Therefore, the length of the first channel layer 10 mentioned above can be largely increased without affecting the conductance at least up to the mean free path length which is of the order of several hundred of nanometers at room temperature. The total conductance of the first channel layer 10 is roughly proportional to the number of grooves 12. Due to the presence of the ridges 13 between the grooves 12 and due to the width of the grooves 12 themselves, there is normally no or only negligible electrical current between two neighboring conducting zones 14, i.e. these conducting zones 14 are electrically insulated.
(15) FIG. 5 shows the first channel layer 10 as in FIGS. 1 to 4 placed on top of an insulating layer 20 made of an electrically insulating material, in this case silicon dioxide. By repeatedly placing the structure shown in FIG. 5 above each other, a channel portion 50 as shown in FIG. 6 can be produced. In such a channel portion 50, a plurality of identical first channel layers 10 are arranged in a stacked manner above each other (i.e. along the Z-axis). One of a plurality of insulating layers 20 is interposed between each two neighboring first channel layers 10. The insulating material also fills the grooves 12, but due to its insulating properties, there is only negligible current flow between neighboring conducting zones 14. It is understood that by stacking a plurality of first channel layers 10, each of which comprises a plurality of grooves 12, the total conductance of the channel portion 50 is considerably increased and the resistance decreased as compared to the single channel layer 10 shown in FIG. 1.
(16) FIGS. 7 to 9 show a first embodiment of an electrical interconnection 1 according to the present invention. It comprises a channel portion 50 that is similar to the one shown in FIG. 6. On two opposite sides of the channel portion 50 along the Y-axis, a first electrode 3 of a first terminal 2 and a second electrode 5 of a second terminal 4 are connected to the channel portion 50. The electrodes 3, 5 may consist of metals known in electronic applications like copper, aluminium, gold or the like and can be grown by additive processes directly on the channel layers 10. All grooves 12 of all first channel layers 10 extend from the first electrode 3 to the second electrode 5. In other words, all grooves 12 are connected in parallel between the first electrode 3 and the second electrode 5. The electrical interconnection 1 can be used, e.g. as part of an integrated circuit, to electrically connect a first electronic component (which is connected to the first terminal 2) with a second electronic component (which is connected to the second terminal 4).
(17) FIGS. 10 and 11 show a second embodiment of an electrical interconnection 1 according to the present invention. It comprises a plurality of first channel layers 10 and a plurality of second channel layers 30. The channel layers 10, 30 are disposed in a stacked manner with insulating layers 20 separating neighboring channel layers 10, 30. The overall structure of the second channel layers 30 is very similar to the first channel layers 10. However, while the grooves 12 of the first channel layers 10 run along the Y-axis, grooves 32 of the second channel layers 30 run along the X-axis. These grooves 32 also comprise conducting zones 34 and are separated by ridges 33. All grooves 12 of the first channel layers 10 extend from the first electrode 3 to the second electrode 5, while all grooves 32 of the second channel layers 30 extend from a third electrode 7 of a third terminal 6 to a fourth electrode 9 of a fourth terminal 8. These electrodes 7, 9 may be manufactured like the first and second electrode 3, 5. As can be seen in FIG. 11, all conducting zones 14, 34 are separated from each other by insulating material. Also, each first channel layer 10 is separated from the third and fourth electrode 7, 9 by insulating material and each second channel layer 30 is separated from the first and second electrode 3, 5 by insulating material.
