Structure and method for improving the frequency characteristics of lithium niobate modulator chip on quartz substrate

Abstract

The present invention provides a structure and method for improving the frequency characteristics of a lithium niobate modulator chip on a quartz substrate. The structure includes: a carrier chip; a coplanar waveguide structure with ground arranged on the upper surface of the carrier chip and a coplanar waveguide structure without ground arranged on the upper surface of the modulator chip; a core group interconnection structure respectively arranged at both ends of the coplanar waveguide structure with ground; a metal grounding layer arranged on the lower surface of the carrier chip; a plurality of metal grounding holes respectively arranged on the first grounding area; a plurality of grounding micro-bumps respectively arranged on the first grounding area and / or the second grounding area; input electrodes and output electrodes arranged at both ends of a traveling wave transmission line; input micro-bumps arranged on the input electrode and / or the input end of a broadband transmission line; output micro-bumps arranged on the output electrode and / or the output end of a broadband transmission line; the upper surface of the modulator chip is arranged on the upper surface of the carrier chip. The present invention can improve the grounding continuity, thereby improving the chip operating frequency.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor chips, and in particular to a structure and method for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip. Background Art

[0002] Lithium niobate is one of the commonly used materials for preparing electro-optic modulator chips. Compared with InP and silicon-based materials, lithium niobate has the advantages of extremely low light absorption loss and highly linear electro-optical effect, so it can be used to prepare electro-optic modulator chips. The quartz substrate lithium niobate modulator prepared from lithium niobate has the advantages of high integration, small half-wave voltage, and high modulation coefficient.

[0003] The traveling wave electrode of the quartz substrate lithium niobate modulator chip adopts a groundless coplanar waveguide structure, which has problems such as poor grounding and significant resonance, which directly affects the frequency characteristics of the electro-optic modulator chip. Therefore, improving the grounding continuity of the electro-optic modulator chip becomes the key to improving the performance indicators of the thin-film lithium niobate modulator chip.

[0004] Referring to Figure 1(a) and Figure 1(b), the traditional method to improve the ground continuity of the lithium niobate modulator chip on a quartz substrate is to add port bonding wires on both sides of the coplanar waveguide so that the coplanar waveguide ground plane is connected to the external unit plane. However, the traveling wave electrode of the lithium niobate modulator chip on a quartz substrate adopts a groundless coplanar waveguide structure and a surface mounting method, which easily triggers the resonant mode of the transmission line and causes the resonance of the transmission signal. At the same time, the interconnection circuit is long and the high-frequency signal ground is discontinuous, which further restricts basic indicators such as the operating frequency. Summary of the invention

[0005] The embodiment of the present invention provides a structure and method for improving the frequency characteristics of a lithium niobate modulator chip on a quartz substrate, so as to solve the problem that the operating frequency of the existing electro-optic modulator chip is restricted.

[0006] In a first aspect, an embodiment of the present invention provides a structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip, comprising:

[0007] Carrier chip;

[0008] A grounded coplanar waveguide structure disposed on the upper surface of the carrier chip and a groundless coplanar waveguide structure disposed on the upper surface of the modulator chip, wherein the grounded coplanar waveguide structure comprises a broadband transmission line and first grounding regions on both sides of the broadband transmission line, and the groundless coplanar waveguide structure comprises a traveling wave transmission line, second grounding regions on both sides of the traveling wave transmission line, and a traveling wave electrode between the traveling wave transmission line and the second grounding region;

[0009] Core group interconnect structures are respectively arranged at two ends of the grounded coplanar waveguide structure, each core group interconnect structure is respectively connected to the input end and the output end of the broadband transmission line;

[0010] A metal grounding layer disposed on the lower surface of the carrier chip;

[0011] A plurality of metal grounding holes respectively arranged on the first grounding area, the plurality of metal grounding holes penetrating the upper surface of the corresponding first grounding area and the lower surface of the corresponding metal grounding layer; a plurality of grounding micro-bumps respectively arranged on the first grounding area and / or the second grounding area;

[0012] Input electrodes and output electrodes are arranged at both ends of the traveling wave transmission line of the modulator chip, and input micro-bumps are arranged on the input electrodes and / or on the input end of the broadband transmission line, and output micro-bumps are arranged on the output electrodes and / or on the output end of the broadband transmission line;

[0013] The upper surface of the modulator chip is arranged on the upper surface of the carrier chip, and the traveling wave transmission line corresponds to the broadband transmission line, the input micro-bump contacts the input end and / or the input electrode of the broadband transmission line, the output micro-bump contacts the output end and / or the output electrode of the broadband transmission line, and the multiple grounding micro-bumps contact the second grounding area and / or the first grounding area, so that the multiple grounding micro-bumps connect the ground signal in the metal grounding hole to the modulator chip.

[0014] In a possible implementation, the radii of the input micro-bumps, the output micro-bumps, and the ground micro-bumps are any value between 40 microns and 50 microns;

[0015] The plurality of grounding micro-bumps include: a plurality of first-class grounding micro-bumps;

[0016] The plurality of first-class ground micro-bumps are arranged on the first ground area and / or the second ground area, and are close to the edge of the broadband transmission line and / or the traveling wave transmission line, and the interval between adjacent first-class ground micro-bumps is smaller than the signal wavelength.

[0017] In a possible implementation, the plurality of first-class grounding micro-bumps are evenly arranged on the first grounding area and / or the second grounding area;

[0018] The plurality of first-class grounding micro-bumps on each first grounding region and / or each second grounding region are arranged in a straight line parallel to the broadband transmission line and / or the traveling wave transmission line.

[0019] In a possible implementation, the plurality of grounding micro-bumps further include: a plurality of second-type grounding micro-bumps;

[0020] The plurality of second-class grounding micro-bumps are arranged on a side of the straight line where the plurality of first-class grounding micro-bumps are located, away from the broadband transmission line or the traveling wave transmission line, and the interval between adjacent second-class grounding micro-bumps is smaller than the signal wavelength.

[0021] In a possible implementation, the plurality of second-type grounding micro-bumps are evenly arranged on a side of a straight line where the plurality of first-type grounding micro-bumps are located that is away from the broadband transmission line or the traveling wave transmission line;

[0022] The plurality of second-type grounding micro-bumps on each first grounding region and / or each second grounding region are arranged in a straight line parallel to the broadband transmission line or the traveling wave transmission line.

[0023] In a possible implementation, the plurality of second-type grounding micro-bumps and the plurality of first-type grounding micro-bumps are arranged alternately.

[0024] In a possible implementation, the plurality of metal grounding holes include: a plurality of first-class metal grounding holes;

[0025] The plurality of first-class metal grounding holes are all arranged on the first grounding area close to the edge of the broadband transmission line, and the interval between adjacent first-class metal grounding holes is smaller than the signal wavelength.

[0026] In a possible implementation, the plurality of metal grounding holes further include: a plurality of second-class metal grounding holes;

[0027] The plurality of second-class metal grounding holes are all arranged on a side of the straight line where the plurality of first-class metal grounding holes are located, away from the broadband transmission line, and the interval between adjacent second-class metal grounding holes is smaller than the signal wavelength;

[0028] The plurality of metal grounding holes do not overlap with the plurality of grounding micro-bumps.

[0029] In a second aspect, an embodiment of the present invention provides a method for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip, comprising:

[0030] A coplanar waveguide structure with ground is prepared on the upper surface of the carrier chip, and a coplanar waveguide structure without ground is prepared on the upper surface of the modulator chip, wherein the coplanar waveguide structure with ground includes a broadband transmission line and first grounding areas on both sides of the broadband transmission line, and the coplanar waveguide structure without ground includes a traveling wave transmission line, second grounding areas on both sides of the traveling wave transmission line, and a traveling wave electrode between the traveling wave transmission line and the second grounding area;

[0031] Preparing core group interconnection structures at both ends of the grounded coplanar waveguide structure, and connecting each core group interconnection structure to the input end and the output end of the broadband transmission line respectively;

[0032] Preparing a metal grounding layer on the lower surface of the carrier chip;

[0033] A plurality of metal grounding holes are respectively prepared on the first grounding area, and the plurality of metal grounding holes penetrate the upper surface of the corresponding first grounding area and the lower surface of the corresponding metal grounding layer; a plurality of grounding micro-bumps are respectively prepared on the first grounding area and / or the second grounding area;

[0034] An input electrode and an output electrode are respectively prepared at both ends of the traveling wave transmission line of the modulator chip, and an input micro-bump is prepared on the input electrode and / or the input end of the broadband transmission line, and an output micro-bump is prepared on the output electrode and / or the output end of the broadband transmission line;

[0035] The upper surface of the modulator chip is flipped on the upper surface of the carrier chip, and the traveling wave transmission line corresponds to the broadband transmission line, the input micro-bump contacts the input end and / or the input electrode of the broadband transmission line, the output micro-bump contacts the output end and / or the output electrode of the broadband transmission line, and the multiple grounding micro-bumps contact the second grounding area and / or the first grounding area.

[0036] In a possible implementation, the step of preparing a plurality of grounding micro-bumps on the first grounding area and / or the second grounding area respectively includes:

[0037] A plurality of grounding micro-bumps with corresponding positions are prepared on the first grounding area and the second grounding area respectively.

[0038] The embodiment of the present invention provides a structure and method for improving the frequency characteristics of a lithium niobate modulator chip on a quartz substrate. The structure includes: a carrier chip; a grounded coplanar waveguide structure arranged on the upper surface of the carrier chip and a groundless coplanar waveguide structure arranged on the upper surface of the modulator chip; a core group interconnection structure respectively arranged at both ends of the grounded coplanar waveguide structure; a metal grounding layer arranged on the lower surface of the carrier chip; a plurality of metal grounding holes respectively arranged on a first grounding area; a plurality of grounding micro-bumps respectively arranged on the first grounding area and / or on the second grounding area; input electrodes and output electrodes arranged at both ends of a traveling wave transmission line of the modulator chip, as well as input micro-bumps arranged on the input electrodes and / or on the input ends of the broadband transmission lines, and output micro-bumps arranged on the output electrodes and / or on the output ends of the broadband transmission lines; the upper surface of the modulator chip is arranged on the upper surface of the carrier chip, so that a plurality of grounding micro-bumps are used to connect the ground signal in the metal grounding hole to the modulator chip, which can effectively improve the grounding continuity, thereby improving the chip operating frequency, optimizing the high-frequency performance, and at the same time, having a good electromagnetic shielding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] FIG. 1( a ) is a schematic front view of a conventional lithium niobate modulator chip structure on a quartz substrate;

[0041] FIG1( b ) is a top view schematic diagram of a conventional quartz substrate lithium niobate modulator chip structure;

[0042] FIG. 2( a ) is a front view schematic diagram of a structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip provided by an embodiment of the present invention;

[0043] FIG2( b ) is a schematic top view of a structure for improving the frequency characteristics of a lithium niobate modulator chip on a quartz substrate provided by an embodiment of the present invention;

[0044] FIG2(c) is a schematic top view of a carrier chip in a structure for improving the frequency characteristics of a lithium niobate modulator chip on a quartz substrate provided by an embodiment of the present invention;

[0045] FIG2(d) is a schematic top view of a modulator chip in a structure for electrically improving the frequency characteristics of a lithium niobate modulator chip on a quartz substrate provided by an embodiment of the present invention;

[0046] Figure 3 It is a schematic diagram of the arrangement of a preferred type of grounding micro-bumps provided by an embodiment of the present invention;

[0047] Figure 4 It is a schematic diagram of the arrangement of a preferred second type of grounding micro-bumps provided by an embodiment of the present invention;

[0048] Figure 5 It is a schematic diagram of setting a preferred type of metal grounding hole provided by an embodiment of the present invention;

[0049] Figure 6 It is a schematic diagram of a preferred arrangement of a second type of metal grounding hole provided by an embodiment of the present invention;

[0050] Figure 7 The present invention is a flowchart of a method for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to enable people in the technical field to better understand the present solution, the technical solution in the embodiment of the present solution will be clearly described below in conjunction with the drawings in the embodiment of the present solution. Obviously, the described embodiment is an embodiment of a part of the present solution, not all of the embodiments. Based on the embodiments in the present solution, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present solution.

[0052] The term "including" and any other variations in the specification and claims of this solution and the above drawings mean "including but not limited to", and is intended to cover non-exclusive inclusions and is not limited to the examples listed in the text. In addition, the terms "first" and "second" are used to distinguish different objects, not to describe a specific order.

[0053] In the field of electro-optic modulators, thin-film quartz substrate lithium niobate modulators made of lithium niobate have the advantages of high integration, small half-wave voltage, and high modulation coefficient. Therefore, quartz substrate thin-film lithium niobate modulator chips are the most widely used. However, quartz substrate thin-film lithium niobate modulator chips have problems with poor grounding and significant resonance, which directly affects the frequency characteristics of the modulator chip. Therefore, improving the grounding continuity of the modulator chip has become the key to improving the performance indicators of quartz substrate lithium niobate modulator chips.

[0054] Laser drilling to prepare metalized vias is a common way to improve grounding continuity. However, quartz substrate lithium niobate modulator chips often use silicon and quartz materials as chip substrates. Silicon and quartz materials themselves have poor laser absorption efficiency due to their high permeability, so it is necessary to prepare an absorption layer with a higher laser absorption efficiency than the melting point of quartz, such as ZrO2, which greatly increases the complexity of electro-optic modulator chip preparation. In addition, due to the insufficient adhesion of quartz to metals such as copper and gold, quartz substrate lithium niobate modulator chips cannot achieve stacked grounding through metalized vias.

[0055] Referring to Figure 1(a) and Figure 1(b), the traditional method to improve the ground continuity of the lithium niobate modulator chip on a quartz substrate is to add port bonding wires A2 on both sides of the coplanar waveguide structure A1 on the upper surface of the modulator chip A0, so that the coplanar waveguide ground plane is connected to the external unit A3 plane. However, the traveling wave electrode of the electro-optic modulator chip adopts a groundless coplanar waveguide structure and adopts a surface assembly method, which is easy to trigger the resonant mode of the transmission line and cause the resonance of the transmission signal. At the same time, the interconnection circuit is long and the high-frequency signal is discontinuous, which further restricts basic indicators such as the operating frequency.

[0056] In view of this, an embodiment of the present invention provides a structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip, as shown in FIG. 2(a), FIG. 2(b), FIG. 2(c) and FIG. 2(d). The structure includes:

[0057] Carrier chip 1;

[0058] A grounded coplanar waveguide structure 11 is arranged on the upper surface of the carrier chip 1, and a groundless coplanar waveguide structure 21 is arranged on the upper surface of the modulator chip 2, wherein the grounded coplanar waveguide structure 11 comprises a broadband transmission line 111 and first grounding regions 112 on both sides of the broadband transmission line 111, and the groundless coplanar waveguide structure 21 comprises a traveling wave transmission line 211, second grounding regions 212 on both sides of the traveling wave transmission line 211, and a traveling wave electrode 213 between the traveling wave transmission line 211 and the second grounding region 212;

[0059] The core group interconnection structures 12 are respectively arranged at both ends of the ground coplanar waveguide structure 11, and each core group interconnection structure 12 is respectively connected to the input end and the output end of the broadband transmission line 111;

[0060] A metal grounding layer 14 disposed on the lower surface of the carrier chip;

[0061] A plurality of metal grounding holes 13 are respectively arranged on the first grounding area 112, and the plurality of metal grounding holes 13 penetrate the upper surface of the corresponding first grounding area 112 and the lower surface of the corresponding metal grounding layer 14; a plurality of grounding micro-bumps 33 are respectively arranged on the first grounding area 112 and / or the second grounding area 212;

[0062] An input electrode 22 and an output electrode 23 are arranged at both ends of the traveling wave transmission line 211 of the modulator chip 2, and an input micro-bump 31 is arranged on the input electrode 22 and / or on the input end of the broadband transmission line 111, and an output micro-bump 32 is arranged on the output electrode 23 and / or on the output end of the broadband transmission line 111;

[0063] The upper surface of the modulator chip 2 is arranged on the upper surface of the carrier chip 1, and the traveling wave transmission line 211 corresponds to the broadband transmission line 111, the input micro-bump 31 contacts the input electrode 22 of the modulator chip 2 and / or the input end of the broadband transmission line 111, and the output micro-bump 32 contacts the output electrode 23 of the modulator chip 2 and / or the output end of the broadband transmission line 111, so that multiple grounding micro-bumps 33 connect the ground signal in the metal grounding hole 13 to the modulator chip 2.

[0064] In one possible implementation, the radius of the input micro-bumps, the output micro-bumps, and the ground micro-bumps is any value between 40 microns and 50 microns; for example: 40 microns, 45 microns, or 50 microns.

[0065] The modulator chip 2 is flip-chip stacked on the carrier chip 1, and the ground signal in the carrier chip is introduced into the modulator chip 2 through the grounding micro-bump 33. At the same time, the microwave signal transmitted along the traveling wave transmission line in the modulator chip 2 can be connected to the core group interconnection structure 12 through the input micro-bump 31 and the output micro-bump 32, so as to transmit the microwave signal to other core groups. The vertical interconnection of microwave signals can be realized between the carrier chip 1 and the modulator chip 2 through the input micro-bump 31, the output micro-bump 32 and the grounding micro-bump 33. Since the radius of the input micro-bump 31, the output micro-bump 32 and the grounding micro-bump 33 are all in the micron level (depending on the process accuracy, the radius value has a slight deviation, usually between 40 microns and 50 microns), that is, the interconnection distance between the chip electrodes is extremely small, resulting in the high-frequency parasitic characteristics of the interconnection structure being very weak, which can greatly improve the frequency characteristics of the quartz substrate lithium niobate modulator chip.

[0066] In a possible implementation, the plurality of grounding micro-bumps 33 include: a plurality of first-class grounding micro-bumps 331;

[0067] A plurality of first-class ground micro-bumps 331 are disposed on the first grounding region 112 and / or the second grounding region 212 and are close to the edge of the broadband transmission line 111 and / or the traveling wave transmission line 211, and the interval between adjacent first-class ground micro-bumps 331 is smaller than the signal wavelength.

[0068] In practical applications, multiple first-class grounding micro-bumps 331 can be set on the first grounding area 112 and / or the second grounding area 212, and both can achieve the technical effect of continuously introducing the ground signal into the modulator chip 2.

[0069] However, it should be noted that, in order to improve the electromagnetic shielding properties of the quartz substrate lithium niobate modulator chip, a type of grounding micro-bumps 331 need to be arranged near the edge of the broadband transmission line 111 and / or the traveling wave transmission line 211, that is, a type of grounding micro-bumps 331 need to be arranged on the first grounding area 112 and / or the second grounding area 212, and need to be as close as possible to the broadband transmission line 111 and / or the traveling wave transmission line 211. At the same time, in order to avoid high-frequency signal leakage, the interval between adjacent types of grounding micro-bumps 331 is less than the signal wavelength (i.e., λ).

[0070] In essence, as long as the manufacturing process accuracy is met, the grounding micro-bumps do not stick to each other causing height changes, and the grounding micro-bumps do not short-circuit with broadband transmission lines and traveling wave transmission lines, the spacing between adjacent types of grounding micro-bumps 331 can be any spacing that is smaller than the signal wavelength.

[0071] As a preferred implementation method, multiple first-class grounding micro-bumps 331 are arranged on the first grounding area 112 and the second grounding area 212, and the positions of the multiple first-class grounding micro-bumps 331 located on the first grounding area 112 correspond one-to-one to the positions of the multiple first-class grounding micro-bumps 331 located on the second grounding area 212.

[0072] Accordingly, the input micro-bumps 31 are respectively arranged on the input electrode 22 and the input end of the broadband transmission line 111, and when the upper surface of the modulator chip 2 is flip-chip mounted on the upper surface of the carrier chip 1, the two input micro-bumps 31 are in contact with each other. The output micro-bumps 32 are respectively arranged on the output electrode 23 and the output end of the broadband transmission line 111, and when the upper surface of the modulator chip 2 is flip-chip mounted on the upper surface of the carrier chip 1, the two output micro-bumps 32 are in contact with each other.

[0073] See Figure 3 In a possible implementation, a plurality of first-class grounding micro-bumps 331 are evenly arranged on the first grounding region 112 and / or the second grounding region 212;

[0074] The plurality of first-class ground micro-bumps 331 on each first ground region 112 and / or each second ground region 212 are arranged in a straight line parallel to the broadband transmission line 111 and / or the traveling wave transmission line 211 .

[0075] As a preferred implementation, adjacent ground micro-bumps 331 of the first type are evenly arranged on the first ground area 112 and the second ground area 212 at intervals of one quarter of the signal wavelength (i.e., λ / 4), and the multiple ground micro-bumps 331 of the first type on each first ground area 112 are arranged in a straight line parallel to the broadband transmission line 111, and the multiple ground micro-bumps 331 of the first type on each second ground area 212 are arranged in a straight line parallel to the traveling wave transmission line 211. At the same time, the positions of the multiple ground micro-bumps 331 of the first type on the first ground area 112 and the multiple ground micro-bumps 331 of the second ground area 212 correspond one to one.

[0076] Along the direction of the traveling wave transmission line, a type of grounding micro-bumps 331 are arranged at a λ / 4 interval to introduce the modulator chip 2 into the ground, which can effectively improve the grounding continuity of the modulator chip.

[0077] In a possible implementation, the plurality of grounding micro-bumps 33 further include: a plurality of second-type grounding micro-bumps 332;

[0078] The plurality of second-class grounding micro-bumps 332 are arranged on a side of the straight line where the plurality of first-class grounding micro-bumps 331 are located, away from the broadband transmission line 111 or the traveling wave transmission line 211, and the interval between adjacent second-class grounding micro-bumps 332 is smaller than the signal wavelength.

[0079] On the basis of the first type of grounding micro-bumps 331 , in order to further improve the grounding continuity and electromagnetic shielding effect, a second type of grounding micro-bumps 332 may be further arranged outside the first type of grounding micro-bumps 331 .

[0080] In a possible implementation, the plurality of second-class grounding micro-bumps 332 are evenly arranged on a side of the straight line where the plurality of first-class grounding micro-bumps 331 are located, away from the broadband transmission line 111 or the traveling wave transmission line 211;

[0081] The plurality of second-type grounding micro-bumps 332 on each first grounding region 112 and / or each second grounding region 212 are arranged in a straight line parallel to the broadband transmission line 111 or the traveling wave transmission line 211 .

[0082] As a preferred implementation, based on the first type of grounding micro-bumps, adjacent second type of grounding micro-bumps 332 are evenly arranged at a quarter of the signal wavelength (i.e., λ / 4) on the side of the straight line where the first type of grounding micro-bumps 331 are located, away from the broadband transmission line and the traveling wave transmission line;

[0083] The plurality of second-class grounding micro-bumps 332 on each first grounding region 112 are arranged in a straight line parallel to the broadband transmission line, and the plurality of second-class grounding micro-bumps 332 on each second grounding region 212 are arranged in a straight line parallel to the traveling wave transmission line. At the same time, the positions of the plurality of second-class grounding micro-bumps 332 on the first grounding region 112 and the plurality of second-class grounding micro-bumps 332 on the second grounding region 212 correspond one to one.

[0084] See also Figure 4 As a preferred implementation method, multiple second-class grounding micro-bumps 332 and multiple first-class grounding micro-bumps 331 are arranged alternately.

[0085] The second type of grounding micro-bumps 332 and the first type of grounding micro-bumps 331 are alternately arranged to further enhance the electromagnetic shielding properties.

[0086] Figure 3 and Figure 4 Only the schematic diagram of the first type of grounding micro-bumps 331 and the second type of grounding micro-bumps 332 on the carrier chip 1 is shown. The first type of grounding micro-bumps 331 and the second type of grounding micro-bumps 332 on the modulator chip 2 are arranged in the same way and are not further illustrated.

[0087] In a possible implementation, the plurality of metal grounding holes 13 include: a plurality of first-class metal grounding holes 131;

[0088] A plurality of first-class metal grounding holes 131 are disposed on the first grounding region 112 close to the edge of the broadband transmission line 111 , and the interval between adjacent first-class metal grounding holes 131 is smaller than the signal wavelength.

[0089] As a preferred implementation, see Figure 5 Adjacent first-class metal grounding holes are evenly arranged on the first grounding area at intervals of one quarter of the signal wavelength (ie, λ / 4), and multiple first-class metal grounding holes on each first grounding area are arranged in a straight line parallel to the broadband transmission line.

[0090] It should be noted that the multiple metal grounding holes do not overlap with the multiple grounding micro-bumps.

[0091] Although the first type of metal grounding hole 131 is also arranged on the first grounding area 112 near the edge of the broadband transmission line 111, it should be noted that the straight line where the first type of metal grounding hole 131 is located and the straight line where the first type of grounding micro-bump 331 is located can be parallel or overlapped, and no specific limitation is made here.

[0092] As a preferred implementation, a plurality of first-class metal grounding holes 131 and a plurality of first-class grounding micro-bumps 331 are arranged alternately.

[0093] In a possible implementation, the plurality of metal grounding holes 13 further include: a plurality of type II metal grounding holes 132;

[0094] The plurality of Class II metal grounding holes 132 are all arranged on a side of the straight line where the plurality of Class I metal grounding holes 131 are located, away from the broadband transmission line, and the interval between adjacent Class II metal grounding holes 132 is smaller than the signal wavelength;

[0095] It should be noted that the multiple metal grounding holes do not overlap with the multiple grounding micro-bumps.

[0096] The same as the setting rules of the grounding micro-bumps, accordingly, as a preferred implementation method, see Figure 6 On the basis of the first type of metal grounding holes 131, adjacent second type of metal grounding holes 132 are evenly arranged at a quarter signal wavelength (i.e., λ / 4) interval on the side of the straight line where the first type of metal grounding holes 131 are located away from the broadband transmission line 111;

[0097] The multiple type II metal grounding holes 132 on each first grounding region 112 are arranged in a straight line parallel to the broadband transmission line 111. The multiple type II metal grounding holes and the multiple type I metal grounding holes are arranged alternately.

[0098] The beneficial effects of the structure for improving the frequency characteristics of the quartz substrate lithium niobate modulator chip provided by the embodiment of the present invention are:

[0099] 1. Good grounding performance. Since the modulator chip is grounded at a fixed spacing (λ / 4 is optimal) along the traveling wave transmission direction, the ground continuity will be significantly better than the traditional coplanar waveguide input / output port bonding method;

[0100] 2. High-frequency performance optimization. Compared with the traditional gold wire bonding process, the standing wave deteriorates due to the size difference in the six degrees of freedom of vertical and horizontal, the use of grounded micro-bump flip-chip can greatly reduce the degrees of freedom, so the high-frequency vertical interconnection performance is better;

[0101] 3. Protect the modulator chip to a certain extent. Due to the flip-chip process, the coplanar waveguide structure on the upper surface of the modulator chip is in the micrometer-level gap formed by the modulator chip and the carrier chip (the gap is about 100 micrometers), thus avoiding the contamination of the modulator chip surface by foreign matter to a certain extent, and extending the service life of the modulator chip;

[0102] 4. Good electromagnetic shielding effect. The grounding micro-bumps are prepared with a fixed spacing (λ / 4 is optimal) and good grounding is achieved through metallized grounding holes, so it has a good signal electromagnetic shielding effect.

[0103] On the other hand, see Figure 7The embodiment of the present invention also provides a method for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip, comprising:

[0104] Step 701, preparing a grounded coplanar waveguide structure on the upper surface of the carrier chip and a groundless coplanar waveguide structure on the upper surface of the modulator chip, wherein the grounded coplanar waveguide structure comprises a broadband transmission line and first grounding regions on both sides of the broadband transmission line, and the groundless coplanar waveguide structure comprises a traveling wave transmission line, second grounding regions on both sides of the traveling wave transmission line, and a traveling wave electrode between the traveling wave transmission line and the second grounding region;

[0105] Step 702, preparing core group interconnection structures at both ends of the grounded coplanar waveguide structure, and connecting each core group interconnection structure to the input end and the output end of the broadband transmission line respectively;

[0106] Step 703, preparing a metal grounding layer on the lower surface of the carrier chip;

[0107] Step 704, preparing a plurality of metal grounding holes on the first grounding regions respectively, wherein the plurality of metal grounding holes penetrate the corresponding upper surface of the first grounding regions and the lower surface of the carrier chip;

[0108] Step 705, preparing a plurality of grounding micro bumps on the first grounding area and / or the second grounding area respectively;

[0109] Step 706, respectively preparing input electrodes and output electrodes at both ends of the traveling wave transmission line of the modulator chip, preparing input micro-bumps on the input electrodes and / or the input end of the broadband transmission line, and preparing output micro-bumps on the output electrodes and / or the output end of the broadband transmission line;

[0110] Step 707, flip-chip the upper surface of the modulator chip onto the upper surface of the carrier chip, and the traveling wave transmission line corresponds to the broadband transmission line, the input micro-bump contacts the input end and / or the input electrode of the broadband transmission line, the output micro-bump contacts the output end and / or the output electrode of the broadband transmission line, and the multiple grounding micro-bumps contact the second grounding area and / or the first grounding area.

[0111] The carrier chip may include: Si chip, GaAs chip and SiC chip.

[0112] In a possible implementation, a plurality of grounding micro-bumps are prepared on the first grounding area and / or the second grounding area, respectively, including:

[0113] A plurality of grounding micro-bumps with corresponding positions are prepared on the first grounding area and the second grounding area respectively.

[0114] It should be noted that when preparing input micro-bumps, output micro-bumps and ground micro-bumps, the heights of different micro-bumps need to be kept consistent to avoid the problem of subsequent inability to align and flip-chip due to height differences between the micro-bumps.

[0115] The method for preparing an electro-optic modulator chip structure provided by an embodiment of the present invention comprises the following steps: preparing a coplanar waveguide structure with a ground on the upper surface of a carrier chip and preparing a coplanar waveguide structure without a ground on the upper surface of a modulator chip; preparing core group interconnection structures at both ends of the coplanar waveguide structure with a ground; preparing a plurality of metal grounding holes on a first grounding area; preparing a plurality of grounding micro-bumps on the first grounding area and / or on a second grounding area; preparing input micro-bumps on an input electrode and / or on an input end of a broadband transmission line, and preparing output micro-bumps on an output electrode and / or on an output end of the broadband transmission line; and flipping the upper surface of the modulator chip onto the upper surface of the carrier chip, with the traveling wave transmission line corresponding to the broadband transmission line, the input micro-bumps contacting the input end and / or the input electrode of the broadband transmission line, the output micro-bumps contacting the output end and / or the output electrode of the broadband transmission line, and the plurality of grounding micro-bumps contacting the second grounding area and / or the first grounding area, thereby obtaining a complete electro-optic modulator chip. Implementing multiple grounding micro-bumps to connect the ground signal in the metal grounding hole to the modulator chip can effectively improve the grounding continuity, thereby increasing the chip operating frequency and optimizing high-frequency performance. At the same time, it also has a good electromagnetic shielding effect.

[0116] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip, characterized in that: include: Carrier chip; A grounded coplanar waveguide structure disposed on the upper surface of the carrier chip and a groundless coplanar waveguide structure disposed on the upper surface of the modulator chip, wherein the grounded coplanar waveguide structure comprises a broadband transmission line and first grounding regions on both sides of the broadband transmission line, and the groundless coplanar waveguide structure comprises a traveling wave transmission line, second grounding regions on both sides of the traveling wave transmission line, and a traveling wave electrode between the traveling wave transmission line and the second grounding region; Core group interconnect structures are respectively arranged at two ends of the grounded coplanar waveguide structure, each core group interconnect structure is respectively connected to the input end and the output end of the broadband transmission line; A metal grounding layer disposed on the lower surface of the carrier chip; A plurality of metal grounding holes are respectively arranged on the first grounding area, and the plurality of metal grounding holes penetrate the upper surface of the corresponding first grounding area and the lower surface of the corresponding metal grounding layer; A plurality of grounding micro-bumps respectively arranged on the first grounding area and / or the second grounding area; Input electrodes and output electrodes are arranged at both ends of the traveling wave transmission line of the modulator chip, and input micro-bumps are arranged on the input electrodes and / or on the input end of the broadband transmission line, and output micro-bumps are arranged on the output electrodes and / or on the output end of the broadband transmission line; The upper surface of the modulator chip is arranged on the upper surface of the carrier chip, and the traveling wave transmission line corresponds to the broadband transmission line, the input micro-bump contacts the input end and / or the input electrode of the broadband transmission line, the output micro-bump contacts the output end and / or the output electrode of the broadband transmission line, and the multiple grounding micro-bumps contact the second grounding area and / or the first grounding area, so that the multiple grounding micro-bumps connect the ground signal in the metal grounding hole to the modulator chip.

2. The structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip as claimed in claim 1, characterized in that: The radius of the input micro-bump, the output micro-bump and the ground micro-bump is any value between 40 microns and 50 microns; The plurality of grounding micro-bumps include: a plurality of first-class grounding micro-bumps; The plurality of first-class ground micro-bumps are arranged on the first ground area and / or the second ground area, and are close to the edge of the broadband transmission line and / or the traveling wave transmission line, and the interval between adjacent first-class ground micro-bumps is smaller than the signal wavelength.

3. The structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip as claimed in claim 2, characterized in that: The plurality of first-class grounding micro-bumps are uniformly arranged on the first grounding area and / or the second grounding area; The plurality of first-class grounding micro-bumps on each first grounding region and / or each second grounding region are arranged in a straight line parallel to the broadband transmission line and / or the traveling wave transmission line.

4. The structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip as claimed in claim 3, characterized in that: The plurality of grounding micro-bumps further include: a plurality of second-class grounding micro-bumps; The plurality of second-class grounding micro-bumps are arranged on a side of the straight line where the plurality of first-class grounding micro-bumps are located, away from the broadband transmission line or the traveling wave transmission line, and the interval between adjacent second-class grounding micro-bumps is smaller than the signal wavelength.

5. The structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip as claimed in claim 4, characterized in that: The plurality of second-class grounding micro-bumps are evenly arranged on a side of the straight line where the plurality of first-class grounding micro-bumps are located, away from the broadband transmission line or the traveling wave transmission line; The plurality of second-type grounding micro-bumps on each first grounding region and / or each second grounding region are arranged in a straight line parallel to the broadband transmission line or the traveling wave transmission line.

6. The structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip as claimed in claim 5, characterized in that: The plurality of second-type grounding micro-bumps and the plurality of first-type grounding micro-bumps are arranged alternately.

7. The structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip as claimed in claim 1, characterized in that: The plurality of metal grounding holes include: a plurality of first-class metal grounding holes; The plurality of first-class metal grounding holes are all arranged on the first grounding area close to the edge of the broadband transmission line, and the interval between adjacent first-class metal grounding holes is smaller than the signal wavelength.

8. The structure for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip as claimed in claim 7, characterized in that: The plurality of metal grounding holes further include: a plurality of type II metal grounding holes; The plurality of second-class metal grounding holes are all arranged on a side of the straight line where the plurality of first-class metal grounding holes are located, away from the broadband transmission line, and the interval between adjacent second-class metal grounding holes is smaller than the signal wavelength; The plurality of metal grounding holes do not overlap with the plurality of grounding micro-bumps.

9. A method for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip, characterized in that: include: A coplanar waveguide structure with ground is prepared on the upper surface of the carrier chip, and a coplanar waveguide structure without ground is prepared on the upper surface of the modulator chip, wherein the coplanar waveguide structure with ground includes a broadband transmission line and first grounding areas on both sides of the broadband transmission line, and the coplanar waveguide structure without ground includes a traveling wave transmission line, second grounding areas on both sides of the traveling wave transmission line, and a traveling wave electrode between the traveling wave transmission line and the second grounding area; Preparing core group interconnection structures at both ends of the grounded coplanar waveguide structure, and connecting each core group interconnection structure to the input end and the output end of the broadband transmission line respectively; Preparing a metal grounding layer on the lower surface of the carrier chip; Prepare a plurality of metal grounding holes on the first grounding regions respectively, wherein the plurality of metal grounding holes penetrate the corresponding upper surface of the first grounding region and the corresponding lower surface of the metal grounding layer; Prepare a plurality of grounding micro-bumps on the first grounding area and / or the second grounding area respectively; An input electrode and an output electrode are respectively prepared at both ends of the traveling wave transmission line of the modulator chip, and an input micro-bump is prepared on the input electrode and / or the input end of the broadband transmission line, and an output micro-bump is prepared on the output electrode and / or the output end of the broadband transmission line; The upper surface of the modulator chip is flipped on the upper surface of the carrier chip, and the traveling wave transmission line corresponds to the broadband transmission line, the input micro-bump contacts the input end and / or the input electrode of the broadband transmission line, the output micro-bump contacts the output end and / or the output electrode of the broadband transmission line, and the multiple grounding micro-bumps contact the second grounding area and / or the first grounding area.

10. The method for improving the frequency characteristics of a quartz substrate lithium niobate modulator chip as claimed in claim 9, characterized in that: The step of preparing a plurality of grounding micro-bumps on the first grounding area and / or the second grounding area comprises: A plurality of grounding micro-bumps with corresponding positions are prepared on the first grounding area and the second grounding area respectively.

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