Chip with beamforming network based on photonic crystal resonant cavity tree structure and fabrication method thereof

Abstract

The application relates to radars, and provides a chip with a beamforming network based on a photonic crystal resonant cavity tree structure and a fabrication method thereof. The chip includes a beamforming network layer, including an incidence coupling grating, first to Nth photonic crystal resonant cavity combinations, first to (N+1)th optical waveguides and an emergence coupling grating which are successively connected; branches of each photonic crystal resonant cavity combination is an integral multiple of that of the previous photonic crystal resonant cavity combination, and two photonic crystal resonant cavity combinations are connected by an optical waveguide.

Claims

1. A chip with beamforming network based on a photonic crystal resonant cavity tree structure, comprising: a beamforming network layer, wherein the beamforming network layer comprises an incidence coupling grating, a first photonic crystal resonant cavity combination, a second photonic crystal resonant cavity combination, an Nth photonic crystal resonant cavity combination, a first optical waveguide, a second waveguide, an Nth optical waveguide, an (N+1)th optical waveguide, and an emergence coupling grating; the second photonic crystal resonant cavity combination comprises B.sub.1 branches, and the Nth photonic crystal resonant cavity combination comprises B.sub.N1 branches; the incidence coupling grating is connected to the first photonic crystal resonant cavity combination via the first optical waveguide, and the first photonic crystal resonant cavity combination is connected to the second optical waveguide having B.sub.1 branches at an end away from the first photonic crystal resonant cavity combination, and the branches of the second optical waveguide is connected with the respective branches of the second photonic crystal resonant cavity combination in a one-to-one fashion, each branch of the (N1)th photonic crystal resonant cavity combination is connected with an Nth optical waveguide having B.sub.N1 branches at an end away from the (N1)th photonic crystal resonant cavity combination, and the branches of the Nth optical waveguide is connected with the respective branches of the Nth photonic crystal resonant cavity combinationwhich is connected to the emergence coupling grating through the (N+1)th optical waveguide in a one-to-one fashion; wherein N is a positive integer that is equal to or greater than 2; B.sub.1B.sub.N1 are positive integers, and B.sub.N1=2.sup.N1; the first photonic crystal resonant cavity combination and each branch of the second to Nth photonic crystal resonant cavity combinations comprise a photonic crystal waveguide and an even number of photonic crystal resonant cavities symmetrically distributed on both sides of the photonic crystal waveguide; and the first optical waveguide is connected with the photonic crystal waveguide of the first photonic crystal resonant cavity combination, and both ends of the second to Nth optical waveguides are connected with the photonic crystal waveguide of the corresponding photonic crystal resonant cavity combinations.

2. The chip of claim 1, wherein the photonic crystal resonant cavities of the second to Nth photonic crystal resonant cavity combinations have the same branch structure.

3. The chip of claim 1, wherein B.sub.N1 is a positive even number.

4. The chip of claim 1, wherein the chip further comprises an electrode layer, comprising a heating chrome electrode surrounded the photonic crystal resonant cavity, and an anode and a cathode which are covered with a gold film are connected to the heating chrome electrode via a lead.

5. A method for fabricating the chip of claim 1, comprising: 1) fabricating the optical waveguide, the photonic crystal resonant cavities,the incidence coupling grating and the emergence coupling grating on an SOI substrate by photolithography; 2) fabricating the heating chrome electrode on the SOI substrate obtained in step 1 by thermal evaporation and lift-off; and 3) depositing a gold film on surfaces of an anode and a cathode of the heating chrome electrode obtained in step 2 by thermal evaporation and lift-off; wherein the SOI substrate comprises a top silicon layer and a bottom silicon substrate, and a silicon dioxide buried layer therebetween.

6. The method of claim 5, wherein step 2 comprises: 2.1) applying a photoresist film with a thickness of 100 nm onto the SOI substrate obtained in step 1 as a main structure of the chip with beamforming network based on the photonic crystal resonant cavity tree structure; 2.2) soft baking the photoresist film; 2.3) exposing the photoresist film; 2.4) transferring a pattern of a mask onto the photoresist film by developing and hardening; 2.5) depositing a chrome film with a thickness of 100 nm by thermal evaporation; and 2.6) lifting off the chrome film on a region without electrode pattern to obtain a chrome electrode.

7. The method of claim 6, wherein step 3 comprises: 3.1) applying a photoresist film with a thickness of 200 nm onto the chrome electrode fabricated in step 2.6; 3.2) soft baking the photoresist film; 3.3) exposing the photoresist film; 3.4) transferring a pattern of a mask onto the photoresist film by developing and hardening; and 3.5) depositing a gold film with a thickness of 200 nm on the anode and cathode by thermal evaporation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to further illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained according to these drawings by those skilled in the art without any creative work.

(2) FIG. 1 is a schematic diagram of a beamforming network layer of a chip with beamforming network based on a photonic crystal resonant cavity tree structure according to the present invention;

(3) FIG. 2 is a perspective view of the chip with beamforming network based on the photonic crystal resonant cavity tree structure according to an embodiment of the present invention;

(4) FIG. 3 is a top view of FIG. 2;

(5) FIG. 4 is a top view of an electrode layer of the chip with the chip with beamforming networking based on the photonic crystal resonant cavity tree structure according to the present invention;

(6) FIG. 5 is a side view of FIG. 2;

(7) FIGS. 6A-F are schematic diagrams showing a flow chart of an SOI substrate processed by steps 1.1, 1.2, 1.4, 1.5, 1.6 and 1.7;

(8) FIGS. 7A-E are schematic diagrams showing a flow chart of the SOI substrate processed by steps 2.1, 2.3, 2.4, 2.5 and 2.6;

(9) FIG. 8 is a schematic diagram showing an electrode covered with a gold film.

REFERENCE NUMERALS

(10) 1, silicon substrate layer; 2, silicon dioxide buried layer; 3, beamforming network layer; 4, electrode layer; 5, incidence coupling grating; 6, first photonic crystal resonant cavity combination; 7, second photonic crystal resonant cavity combination; 8, Nth photonic crystal resonant cavity combination; 9, first optical waveguide; 10, second optical waveguide; 11, Nth optical waveguide; 12, (N+1)th optical waveguide; 13, emergence coupling grating; 14, photonic crystal waveguide; 15, anode; 16, cathode; 17, photonic crystal resonant cavity; 18, heating chrome electrode.

DETAILED DESCRIPTION OF EMBODIMENTS

(11) The technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings, from which the objects, technical solutions and advantages of the present invention will be clearer. The described embodiments are only a part of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

EXAMPLE 1

(12) As shown in FIGS. 1-5, when N is 3, the first photonic crystal resonant cavity combination comprises two photonic crystal resonant cavities 17; the second photonic crystal resonant cavity combination 7 comprises two branches, and each branch comprises 4 photonic crystal resonant cavities 17; and the third photonic crystal resonant cavity combination 8 comprises 4 branches, and each branch comprises two photonic crystal resonant cavities 17. It should be noted that all the photonic crystal resonant cavities 17 correspond to the same electrode layer 4, which are not fully shown in FIGS. 1-3 and 5. Based on the deficiencies of the prior art, the present embodiment provides a chip with beamforming network based on a photonic crystal resonant cavity tree structure, comprising a beamforming network layer 3 that comprises an incidence coupling grating 5, a first photonic crystal resonant cavity combination 6, a second photonic crystal resonant cavity combination 7, . . . , the Nth photonic crystal resonant cavity combination 8, a first optical waveguide 9, a second optical waveguide 10, . . . , the Nth optical waveguide 11, the (N+1)th optical waveguide 12 and an emergence coupling grating 13.

(13) The second photonic crystal resonant cavity combination 7 comprises B.sub.1 branches, . . . , and the Nth photonic crystal resonant cavity combination 8 comprises B.sub.N1 branches.

(14) The incidence coupling grating 5 is connected to the first photonic crystal resonant cavity combination 6 via the first optical waveguide 9, and the first photonic crystal resonant cavity combination 6 is connected to the second optical waveguide 10 having B.sub.1 branches on an end away from the first photonic crystal resonant cavity combination 6, and the branches of the second optical waveguide 10 is connected with the respective branches of the second photonic crystal resonant cavity combination 7 in a one-to-one fashion, . . . , each branch of the (N1)th photonic crystal resonant cavity combination is connected with an Nth optical waveguide 11 having B.sub.N1 branches at an end away from the (N1)th photonic crystal resonant cavity combination 8, and the branches of the Nth optical waveguide is connected with the branches of the Nth photonic crystal resonant cavity combination 8 which is connected to the emergence coupling grating 13 via the (N+1)th optical waveguide 12 in a one-to-one fashion.

(15) It should be noted that N is a positive integer that is equal to or greater than 2; and B.sub.1-B.sub.N1 are positive integers, and B.sub.N1=2.sup.N1.

(16) In the above embodiment, the second photonic crystal resonant cavity combination 7 comprises B.sub.1 branches connected to the second to Nth photonic crystal resonant cavity combination, and from the third photonic crystal resonant cavity combination, the branch number of each photonic crystal resonant cavity combination is the multiple of that of the previous photonic crystal resonant cavity combination, so with the same amount of scanning interfaces (i.e., the emergence coupling grating 13), the sharing of photonic crystal resonant cavity combinations before the Nth photonic crystal resonator combination 8 is realized, such that a large number of the photonic crystal resonant cavities 17 are spared and the difficulty of adjusting the photonic crystal resonant cavity device is reduced. As shown in FIGS. 2-3, 32 photonic crystal resonant cavities 17 are needed in the prior art to adjust 4 scanning interfaces (i.e. 4 emergence coupling gratings) and 8 photonic crystal resonant cavities 17 at the same time, whereas only 18 photonic crystal resonant cavities 17 are needed in the present invention, which saves 14 photonic crystal resonant cavities.

(17) In an embodiment, the first photonic crystal resonant cavity combination 6 and each branch of the second to Nth photonic crystal resonant cavity combinations each comprise a photonic crystal waveguides 14 and an even number of the photonic crystal resonant cavities 17 symmetrically distributed on both sides of the crystal waveguide; the first optical waveguide 9 is connected with the photonic crystal waveguide 14 of the first photonic crystal resonant cavity combination 6, and both ends of the second to Nth optical waveguides are connected with the photonic crystal waveguide 14 of the corresponding photonic crystal resonant cavity combinations.

(18) It should be noted that N is a positive integer that is equal to or greater than 2.

(19) In the embodiment, the photonic crystal resonant cavities 17 of each photonic crystal resonant cavity combination are symmetrically distributed on both sides of the photonic crystal waveguide 14 to ensure the continuous regulation of the optical delay.

(20) The photonic crystal resonant cavities of the second to Nth photonic crystal resonant cavity combinations have the same branch structure; where N is a positive integer that is equal to or greater than 2.

(21) The embodiment ensures each light beam exited from the emergence coupling grating 13 is regulated by the same amount of the photonic crystal resonant cavity combinations after entering the incidence coupling grating 5 and passing through the first to Nth photonic crystal resonant cavity combinations and the first to Nth optical waveguides. The retardation of each light beam exited from the emergence coupling grating 13 is regulated by adjusting the photonic crystal resonant cavities 17 of each branch of the Nth photonic crystal resonant cavity combination 8 when the retardation of each branch of the second to (N1)th photonic crystal resonant cavity combinations are the same, such that the retardation of each light exited from the emergence coupling grating 13 could be increased or decreased successively along the direction perpendicular to the (N+1)th optical waveguide 12, thereby enabling the radar to perform bidirectional scanning.

(22) The B.sub.N1 is a positive integer, since the emergence coupling grating 13 of radar should be an even number, the branch number of the Nth photonic crystal resonant cavity combination 8 is limited to M times that of the Nth photonic crystal resonant cavity combination, where M is an even number, so that the use of extra photonic crystal resonant cavity combinations (i.e. photonic crystal resonant cavities) is spared.

(23) In this embodiment, the chip further comprises an electrode layer 4 comprising the heating chrome electrode 18 surrounded the photonic crystal resonant cavity 17, and the anode 15 and the cathode 16 which are connected to the heating chrome electrode 18 are covered with a gold film on the surface thereof.

(24) In the embodiment, the retardation of the light is regulated by heating the photonic crystal resonant cavity 17 with the heating chrome electrode 18; and the gold film can effectively increase the conductivity of the anode 15 and the cathode 16.

(25) In some embodiments, a silicon substrate layer 1 and a silicon dioxide buried layer 2 are further provided, where the silicon substrate layer 1, the silicon dioxide buried layer 2 and the beamforming network layer 3 are made of an SOI material; and the SOI substrate comprises a top silicon layer 103 and a bottom silicon substrate 101, and a silicon dioxide buried layer 102 therebetween.

EXAMPLE 2

(26) As shown in the FIGS. 6-8, in this embodiment, illustrated is a method for fabricating the chip with beamforming network based on a photonic crystal resonant cavity tree structure, which comprises:

(27) 1) the optical waveguide, photonic crystal resonant cavity , the incidence coupling grating and the emergence coupling grating are fabricated on the SOI substrate by photolithography;

(28) 2) the heating chrome electrode is fabricated on the SOI substrate in the step 1 by thermal evaporation and lift-off; and

(29) 3) the gold film is deposited on the surface of an anode and a cathode of the heating chrome electrode in step 2 by thermal evaporation and lift-off.

(30) Step 1 comprises the following steps:

(31) 1.1) the SOI substrate comprising a top silicon layer 103 with a thickness of 220 nm, a silicon dioxide buried layer 102 with a thickness of 3 m and a thick bottom silicon substrate 101 with a thickness of 600 m is cleaned;

(32) 1.2) a photoresist film 104 with a thickness of 2-3 nm is applied onto the SOI substrate;

(33) 1.3) the SOI substrate covered with the photoresist film is put into an oven to soft bake;

(34) 1.4) the photoresist film 104 is exposed under a deep ultraviolet;

(35) 1.5) a pattern of a mask is transferred onto the exposed photoresist film 104 by developing and hardening;

(36) 1.6) a photonic crystal resonant cavity and a main structure of the chip with beamforming network based on a photonic crystal resonant cavity tree structure is fabricated on a surface of the SOI substrate by plasma etching, where the etching depth is 220 nm;

(37) 1.7) the photoresist film on the surface of the plasma-etched SOI substrate is removed, so that the main structure of the chip with beamforming network based on the photonic crystal resonant cavity tree structure is obtained, that is, the silicon substrate 101, the silicon dioxide buried layer 102 and an optical waveguide structure layer 103 which are distributed from up to down;

(38) The SOI substrate comprises a top silicon layer 103 and a bottom silicon substrate 101, and a silicon dioxide buried layer 102 therebetween.

(39) Step 2 further comprises the following steps:

(40) 2.1) a photoresist film 201 with a thickness of 100 nm is applied onto the SOI substrate obtained in step 1.7 as the main structure of the chip with beamforming network based on the photonic crystal resonant cavity tree structure;

(41) 2.2) the photoresist film is soft baked;

(42) 2.3) the photoresist film 201 is exposed;

(43) 2.4) a pattern of a mask is transferred onto the photoresist film by developing and hardening;

(44) 2.5) a thin film of chrome film with a thickness of 100 nm is deposited by the thermal evaporation;

(45) 2.6) the chrome electrode 202 is obtained by lifting off the chrome film on a region without electrode pattern;

(46) The SOI substrate comprises a top silicon layer 103 and a bottom silicon substrate 101, and a silicon dioxide buried layer 102 therebetween.

(47) Step 3 further comprises the following steps:

(48) 3.1) a photoresist film with a thickness of 200 nm is applied onto the chrome electrode obtained in step 2.6;

(49) 3.2) the photoresist film is soft baked;

(50) 3.3) the photoresist film is exposed;

(51) 3.4) the pattern of the mask is transferred onto the photoresist film by developing and hardening;

(52) 3.5) a gold film 301 with a thickness of 200 nm is deposited on the anode and the cathode by the thermal evaporation.

Conclusion

(53) 1. The second photonic crystal resonant cavity combination comprises B.sub.1 branches connected with the second to Nth photonic crystal resonant cavity combinations, and from the third photonic crystal resonant cavity combination, the branch number of each photonic crystal resonant cavity combination is the multiple of that of the previous photonic crystal resonant cavity combination, so with the same amount of scanning interfaces (i.e., the emergence coupling grating 13), the sharing of photonic crystal resonant cavity combinations before the Nth photonic crystal resonator combination is realized, such that a large number of the photonic crystal resonant cavities 17 are spared and the difficulty of adjusting the photonic crystal resonant cavity device is reduced. The N and B.sub.1 are positive integers that are equal to or greater than 2.

(54) 2. The number of the emergence coupling grating 13 of radar should be even, so the branch number of the Nth photonic crystal resonant cavity combination 8 is limited to M times the branch number of the Nth photonic crystal resonant cavity combination, where M is an even number, so that the use of extra photonic crystal resonant cavity combinations (i.e. photonic crystal resonant cavities) are spared. N is a positive integer that is equal to or greater than 2.

(55) 3. Each light beam exited from the emergence coupling grating 13 is ensured to be regulated by the same amount of the photonic crystal resonant cavity combinations after entering the incidence coupling grating 5 and passing the first to Nth photonic crystal resonant cavity combinations and the first to Nth optical waveguides; the retardation of each light beam exited from the emergence coupling grating 13 is regulated by adjusting the photonic crystal resonant cavities 17 of each branch of the Nth photonic crystal resonant cavity combination 8 when the retardation of each branch of the second to (N1)th photonic crystal resonant cavity combinations are the same, such that the retardation of each light exited from the emergence coupling grating 13 could be increased or decreased successively along the direction perpendicular to the (N+1)th optical waveguide 12, thereby enabling the radar to perform bidirectional scanning. N is a positive integer that is equal to or greater than 2.

(56) It should be noted that relational terms in the present invention such as first and second are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between such entities or operations. Furthermore, the term comprise or any other variations thereof is intended to encompass a non-exclusive inclusion, such that a process, method, article, or device that comprises a plurality of elements comprises not only those elements but also other elements that are not explicitly listed, or elements that are inherent to such a process, method, article, or device. An element defined by the phrase comprising a . . . without further limitation does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

(57) The embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood that modifications, equivalent replacements of the technical solutions can be made by those of ordinary skill in the art without departing from the spirit and scope of the present invention.