CN220963708U - Silicon-based GaN wide-stopband high-selectivity millimeter wave on-chip filter - Google Patents
Silicon-based GaN wide-stopband high-selectivity millimeter wave on-chip filter Download PDFInfo
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Abstract
The utility model discloses a silicon-based GaN wide stop band high-selectivity millimeter wave on-chip filter. The filter includes an improved coupling feed structure, a stepped impedance resonator, a dual-ended ground transmission line, and a ground plane. According to the utility model, the double-end grounding transmission lines are added between every two step impedance resonators, so that the coupling between the resonators and the grounding surface is effectively enhanced, the frequency selectivity is effectively improved, and the length of the resonators is effectively reduced by the improved feed structure, and the area is saved. The high-selectivity wide-stop-band improved interdigital bandpass filter provided by the utility model has the advantages that the layout area is saved, the frequency selectivity of the device is improved, and the device is easy to interconnect and integrate with other radio frequency devices.
Description
Technical Field
The utility model relates to the technical field of radio frequency microwaves, in particular to a silicon-based GaN wide-stop-band high-selectivity millimeter wave on-chip filter.
Background
GaN belongs to III nitride, has the advantages of excellent breakdown capability, higher electron density and speed, high temperature resistance, radiation resistance and the like, and electronic devices based on GaN have great advantages in microwave radar, satellite communication and 5G communication. Passive functional blocks are an integral part of the front-end of the radio frequency transceiver and they typically occupy a considerable chip/module area. Chip interconnects are a common cause of unwanted parasitic losses in lumped element devices, which can degrade overall RF performance. Thus, in an increasing industry trend, there is a need to increase the level of integration and there is an increasing demand for integrating passive devices and active devices simultaneously on silicon-based GaN, as integrated passive devices have advantages over standard discrete passive devices with higher bandwidth, more compact size and higher reliability. Due to GaN active device processes such as: HEMTs are still under development and are therefore unsuitable for complex processes to fabricate passive devices. By embedding the single planar coplanar waveguide filter into a single monolithic microwave integrated circuit, no via process is required, significantly reducing interconnection loss, and providing smaller footprint and lower energy consumption for electronic devices. As one of the most suitable technologies for implementing passive devices in a system on chip, in recent years, a coplanar waveguide structure has received attention from more and more students, and it has become more widespread to design a microwave filter using the structure.
With development of microwave technology, the design of a microwave filter is mature, and in-band flatness, return loss and out-of-band rejection are paid more attention to when the insertion loss performance requirement of the filter is met nowadays.
The integration of coplanar waveguide systems on a chip is a hot spot of current research, and the utility model is optimized for the silicon-based gallium nitride system on a chip. Because of the small lattice coefficient difference between Si and GaN, it is necessary to grow an AlN, alGaN layer on Si first to buffer the stress. But the AlN/Si interface forms a parasitic channel, which leads to electric leakage of the device and presents a small challenge for a monolithic integrated system. The utility model is optimized for the purpose of the consumption medium of electric leakage, and the required narrow bandwidth is realized by enhancing the coupling between the resonators and the reference ground instead of the traditional weakening of the coupling between the resonators. Meanwhile, the feed structure is further optimized and adjusted, the length of the resonator is reduced, the resonator is affected by less substrate electric leakage, smaller insertion loss is realized, and meanwhile, the area of the whole layout is reduced.
The prior patent (publication number: CN 107634292A) is composed of an interdigital filter embedded with a plurality of open-circuit branches. The transmission line resonator is directly fed and input, and a transmission line resonator close to the input end and the output end is embedded with a plurality of open branches, and only one transmission pole is arranged in the passband of the transmission line resonator. The principle of the prior patent (publication number: CN 107634292A) is to suppress the higher harmonic (parasitic) passband of an interdigital filter, which is represented by a wide stopband in the range of 3-28GHz, and although the suppression is obviously reduced at 29-30GHz, no result is given which is larger than 30 GHz.
Disclosure of utility model
The utility model aims to provide a silicon-based GaN wide-stop-band high-selectivity millimeter wave on-chip filter, which solves the problem that the silicon-based GaN wide-stop-band high-selectivity millimeter wave on-chip filter can be manufactured under various technical conditions of an active region in the existing monolithic integrated system, and the silicon-based GaN wide-stop-band high-selectivity millimeter wave on-chip filter is fragile due to the fact that through holes are needed for interconnection. And low frequency selectivity, poor adjacent channel rejection; the harmonic response is obvious, and the out-of-band suppression is insufficient.
The object of the utility model is achieved by at least one of the following technical solutions.
A silicon-based GaN wide-stop-band high-selectivity millimeter wave on-chip filter comprises a single-plane coplanar waveguide metal part and a nonmetal part nested on the single-plane coplanar waveguide metal part, and the metal parts are all arranged in the metal plane of the same layer;
The single-plane coplanar waveguide metal part comprises a grounding surface, two coupling feed structures, two feed taps, three single-end grounding transmission line resonators, two double-end grounding transmission lines, a signal input port and a signal output port;
the single-end grounded transmission line resonator includes: an open low impedance section and a short high impedance section; one end of the short-circuit high-impedance section is connected with the grounding surface and is called a short-circuit end, and the other end of the short-circuit high-impedance section is connected with one end of the open-circuit low-impedance section; the other end of the open-circuit low-impedance section is not connected with the ground plane and is called an open-circuit end;
The three single-end grounding transmission line resonators are arranged in parallel, and the connecting direction of the middle single-end grounding transmission line resonator and the grounding surface is opposite to that of the single-end grounding transmission line resonators on two sides;
The two double-end grounding transmission lines are respectively arranged between the middle single-end grounding transmission line resonator and the single-end grounding transmission line resonators at the two sides, and the two ends of the double-end grounding transmission lines are connected with the grounding surface;
The two coupling feed structures are respectively arranged at two sides of the three single-end grounding transmission line resonators; the two feed taps are respectively arranged at one side of the two coupling feed structures, which is far away from the single-end grounding transmission line resonator;
the signal input port and the signal output port are respectively connected with a coupling feed structure through a feed tap;
One end of the feed tap is connected with the grounding end of the coupling feed structure, and the other end of the feed tap is connected with the signal input port or the signal output port;
The signal input port and the signal output port are perpendicular to the feed taps and are respectively arranged at one side of the two feed taps far away from the coupling feed structure;
one end of the coupling feed structure is connected with the ground plane, and the other end of the coupling feed structure is open;
The nonmetallic portion includes: the slot that sets up between feed tap and the ground plane, the gap that sets up between coupling feed structure and the feed tap, the gap that sets up between coupling feed structure and the single-end ground connection transmission line resonator, the gap that sets up between single-end ground connection transmission line resonator and the double-end ground connection transmission line to and the inside fluting gap of short circuit high impedance section.
Further, only three single-end grounding transmission line resonators after horizontal translation can be overlapped, after horizontal translation, the single-end grounding transmission line resonators at two sides are completely overlapped, the open ends of the single-end grounding transmission line resonators at two sides are overlapped with the open ends of the single-end grounding transmission line resonators at the middle, and the open ends of the single-end grounding transmission line resonators at two sides are overlapped with the open ends of the single-end grounding transmission line resonators at the middle; the single-ended grounded transmission line resonators on both sides are symmetrical with respect to the single-ended grounded transmission line resonator in the middle.
Further, the feed tap is shorter than the coupling feed structure;
In order to realize the characteristic of wide stop band, the feed tap is arranged in parallel with the coupling feed structure, and after horizontally shifting the feed tap, the feed tap coincides with the connecting end of the signal input port or the signal output port and the open end of the coupling feed structure; only horizontally translating the feed tap or the coupling feed structure, both of which can coincide with one end of the connecting ground plane of the single-ended grounded transmission line resonator on both sides;
the two feed taps are symmetrical about the middle single-ended grounded transmission line resonator;
the two coupling feed structures are symmetrical about the middle single-ended grounded transmission line resonator;
the signal input port and the signal output port are symmetrical about the intermediate single-ended grounded transmission line resonator.
Further, the slotted gap is rectangular, and one short side edge of the slotted gap coincides with the short side of the grounding end of the single-end grounding transmission line resonator; the single-end grounding transmission line resonators before and after slotting are in symmetrical patterns, namely the slotting slot and the symmetrical axis of the single-end grounding transmission line resonator are the same.
Further, the single-plane coplanar waveguide metal part and the nonmetal part nested on the single-plane coplanar waveguide metal part are both arranged on the silicon-based gallium nitride;
The silicon-based gallium nitride comprises a silicon substrate and an etched AlGaN/GaN heterojunction epitaxial layer positioned on the silicon substrate;
The etched AlGaN/GaN heterojunction epitaxial layer comprises: an AlN layer, an AlGaN layer, a GaN barrier layer, a GaN channel layer, an AlN layer, an AlGaN layer and a GaN cap layer.
Further, the complete AlGaN/GaN heterojunction epitaxial layer comprises an AlN layer, an AlGaN layer, a GaN barrier layer, a GaN channel layer, an AlN layer, an AlGaN layer and a GaN cap layer which are sequentially laminated from bottom to top;
Completely etching one side of the GaN channel layer, the AlN layer, the AlGaN layer and the GaN cap layer, reserving the other side, and etching a part of the top of the GaN barrier layer to obtain an etched AlGaN/GaN heterojunction epitaxial layer in order to ensure complete etching of the GaN channel layer;
In the etched AlGaN/GaN heterojunction epitaxial layer, one side of the reserved GaN channel layer, alN layer, alGaN layer and GaN cap layer is called an active area, and one side of the etched GaN channel layer, alN layer, alGaN layer, gaN cap layer and part of GaN barrier layer is called a passive area;
Growing an insulating medium layer which is the same as the gate medium of the active region on the GaN barrier layer at the bottom part of the passive region which is left after the active region is etched immediately, and then sputtering a top metal on the insulating medium layer;
The single-plane coplanar waveguide metal portion and the non-metal portion nested on the single-plane coplanar waveguide metal portion are both disposed in the top-level metal.
Further, for the top metal, stripping the nonmetal part of the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter in the top metal, and reserving the metal part to form the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter.
The silicon-based GaN wide-stopband high-selectivity millimeter wave on-chip filter can be prepared by the following steps:
S1, growth of GaN: sequentially growing an AlN layer, an AlGaN layer, a GaN barrier layer, a GaN channel layer, an AlN layer, an AlGaN layer and a GaN cap layer on a silicon substrate from bottom to top to obtain a complete AlGaN/GaN heterojunction epitaxial layer;
S2, isolation of active areas and passive areas and isolation of devices: defining the position of an active region on the upper surface of the complete AlGaN/GaN heterojunction epitaxial layer by using photoresist, covering the position of the active region, and carrying out plasma bombardment etching on the upper surface of the AlGaN/GaN heterojunction epitaxial layer of the non-active region until part of the GaN barrier layer is etched to obtain an etched AlGaN/GaN heterojunction epitaxial layer;
S3, preparing a medium: depositing a dielectric layer on the whole surface of the etched passive region of the AlGaN/GaN heterojunction epitaxial layer; defining a position where an insulating dielectric layer needs to be deposited by using photoresist, and etching and removing the dielectric layer which is not covered by the photoresist by using a dry etching process; after etching is finished, removing the photoresist by using organic solvent through ultrasonic;
S4, sputtering a top metal and stripping the nonmetallic part: defining the position and pattern of the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter by using photoresist, enabling the position of the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter to be on a passive area, covering a non-metal part in the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter by using photoresist, and forming a metal part positioned on a top metal layer by using an electron beam evaporation or magnetron sputtering method and a stripping process; and removing the photoresist and the nonmetal parts through ultrasonic stripping of an organic solvent to obtain the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter.
Further, the dielectric layer deposition mode is any one of plasma enhanced chemical vapor deposition, atomic layer deposition and physical vapor deposition.
Further, the dry etching process is any one of an inductively coupled plasma etching process, a reactive ion etching process or other ion etching processes.
Compared with the prior art, the utility model has the advantages that:
According to the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter provided by the utility model, the coupling between the resonators and the ground plane is effectively enhanced by adding the double-end grounding transmission line between every two step impedance resonators, the frequency selectivity is effectively improved, and the contradiction between the performance and the area in the current filter design is solved. Compared with the conventional method of directly feeding, the method is realized by adopting the coupling feeding input, so that more transmission poles are more flat in passband, and compared with the triangular window frequency response of a filter with single transmission poles, the frequency response of the multi-transmission poles is more approximate to a rectangular window, namely better rectangular coefficient and better frequency selectivity. The utility model also improves the tap structure of the coupling feed, allowing the same resonant frequency to be achieved with a shorter resonator length while maintaining wide stop band rejection. The smaller resonator length also results in a smaller final area, which satisfies the filtering performance while also reducing the area. And the characteristics of the silicon-based gallium nitride parasitic channel are fully utilized, and even though the harmonic response is shown at about four times of the fundamental frequency, the S21 is still strictly lower than-15 dB, and the wide stop band characteristic is shown. Compared with the conventional method for adjusting the coupling distance between resonators to adjust the bandwidth, the method provided by the utility model has the advantages that the characteristic of silicon-based gallium nitride leakage is optimized in a targeted manner, the reference ground plane is extended between every two resonators, the coupling to ground is enhanced, and the out-of-band suppression is enhanced. The method is realized in a smaller area, the influence of substrate leakage is reduced, and lower insertion loss is realized.
The improved on-chip interdigital bandpass filter provided by the utility model is characterized in that a coplanar waveguide single-end grounding lambda g/4 type coupling transmission line resonator and a double-end grounding lambda g/4 type transmission line structure are nested to obtain a narrow passband bandpass filter with high frequency selectivity. And the feeding extension line is added by adjusting the tap position of the feeding line and the feeding line structure. A narrow passband bandpass filter with high frequency selectivity is achieved by attenuating the coupling between resonators or cascading notch filters as compared to conventional ones. The utility model enhances the coupling between the resonator and the ground plane and enhances the frequency selectivity. By improving the tap structure, the same resonant frequency can be realized by a shorter resonator length while the good characteristic of wide stop band suppression is maintained, a miniaturized wide stop band filter is realized, and the contradiction between the performance and the area in the current filter design is solved.
Drawings
FIG. 1 is an equivalent circuit diagram of a high selectivity wide stop band improved interdigital bandpass filter in an embodiment of the utility model;
FIG. 2 is a schematic cross-sectional view of a passive device structure in an embodiment of the utility model;
FIG. 3 is a metal distribution diagram of a modified interdigital bandpass filter according to an embodiment of the present utility model;
FIG. 4 is a graph of the dielectric profile of a modified interdigital bandpass filter in an embodiment of the utility model;
FIG. 5 is a schematic diagram of a step impedance resonator in an embodiment of the utility model;
FIG. 6 is a dimensioning illustration of an embodiment of an improved interdigital bandpass filter in an embodiment of the utility model;
FIG. 7 is a schematic diagram of a test and simulation S11 curve of a high selectivity wide stop band modified interdigital bandpass filter of a passive process flow provided in an embodiment of the present utility model;
Fig. 8 is a schematic diagram of a test and simulation S21 curve of a high selectivity wide stop band modified interdigital bandpass filter of a passive process flow provided in an embodiment of the present utility model.
Detailed Description
The silicon-based GaN wide-stop band high-selectivity millimeter wave on-chip filter is obtained mainly through structure optimization; such a structure can be produced by this embodiment.
The following describes the embodiments of the present utility model further with reference to specific examples and drawings, but the embodiments of the present utility model are not limited thereto.
Examples
The silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter comprises a single-plane coplanar waveguide metal part and a nonmetal part nested on the single-plane coplanar waveguide metal part; and are all arranged in the metal layer 10 in fig. 2, because only a single metal plane is used, unlike a biplane structure such as a grounded coplanar waveguide structure, a two-layer metal plane is used, so that it is called a monoplane coplanar waveguide structure;
As shown in fig. 3, the single-plane coplanar waveguide metal part includes a ground plane 101, two coupling feed structures 102 and two feed taps 105, three single-end grounded transmission line resonators 103, two double-end grounded transmission lines 104, and a signal input port 001 and a signal output port 002;
as shown in fig. 5, the single-end grounded transmission line resonator 103 includes: an open low impedance section 113 and a short high impedance section 123; wherein one end of the short-circuit high-impedance section 123 is connected to the ground plane 101, called a short-circuit end, and the other end is connected to one end of the open-circuit low-impedance section 113; the other end of the open low impedance section 113, which is not connected to the ground plane 101, is called an open end;
Three single-end grounded transmission line resonators 103 are placed in parallel, and the direction in which the middle single-end grounded transmission line resonator 103 is connected to the ground plane 101 is opposite to the single-end grounded transmission line resonators 103 on both sides;
the two double-end grounding transmission lines 104 are respectively arranged between the single-end grounding transmission line resonator 103 in the middle and the single-end grounding transmission line resonators 103 at the two sides, and the two ends of the double-end grounding transmission lines 104 are connected with the grounding surface 101;
The double-ended grounded transmission line 104 enhances the coupling of the single-ended grounded transmission line resonator 103 to the ground plane 101, resulting in a narrower passband over a relatively compact device area.
The two coupling feed structures 102 are respectively arranged at two sides of the three single-end grounding transmission line resonators 103; the two feed taps 105 are respectively arranged at one side of the two coupling feed structures 102 away from the single-end grounding transmission line resonator 103;
The signal input port 001 and the signal output port 002 are each connected to a coupling feed structure 102 through a feed tap 105;
One end of the feed tap 105 is connected with the grounding end of the coupling feed structure 102, and the other end is connected with the signal input port 001 or the signal output port 002;
The signal input port 001 and the signal output port 002 are perpendicular to the feed taps 105 and are respectively arranged at one side of the two feed taps 105 away from the coupling feed structure 102;
One end of the coupling feed structure 102 is connected with the ground plane 101, and the other end is open-circuited;
As shown in fig. 4, the nonmetallic portion includes: a gap 201 provided between the feed tap 105 and the ground plane 101, a gap 205 provided between the coupling feed structure 102 and the feed tap 105, a gap 202 provided between the coupling feed structure 102 and the single-ended ground transmission line resonator 103, a gap 204 provided between the single-ended ground transmission line resonator 103 and the double-ended ground transmission line 104, and a slotted gap 203 inside the short-circuited high-impedance section 123.
In one embodiment, only three single-end grounded transmission line resonators 103 after horizontal translation can be overlapped, after horizontal translation, the single-end grounded transmission line resonators 103 on two sides are completely overlapped, the open-circuited ends of the single-end grounded transmission line resonators 103 on two sides are overlapped with the open-circuited ends of the single-end grounded transmission line resonators 103 in the middle, and the open-circuited ends of the single-end grounded transmission line resonators 103 on two sides are overlapped with the open-circuited ends of the single-end grounded transmission line resonators 103 in the middle; the single-ended grounded transmission line resonators 103 on both sides are symmetrical with respect to the single-ended grounded transmission line resonator 103 in the middle.
In one embodiment, the feed tap 105 is shorter than the coupling feed structure 102;
In order to realize the wide stopband characteristic, the feed tap 105 is placed in parallel with the coupling feed structure 102, and after horizontally translating the feed tap 105, the feed tap 105 coincides with the connection end of the signal input port 001 or the signal output port 002, and the open end of the coupling feed structure 102; only the horizontal translational feed tap 105 or the coupling feed structure 102, both of which can coincide with one end of the connecting ground plane 101 of the single-ended grounded transmission line resonator 103 on both sides;
The two feed taps 105 are symmetrical about the middle single-ended grounded transmission line resonator 103;
The two coupling feed structures 102 are symmetrical about the middle single-ended grounded transmission line resonator 103;
The signal input port 001 and the signal output port 002 are symmetrical about the intermediate single-ended grounded transmission line resonator 103.
In one embodiment, the slotted slot 203 is rectangular, and one short side edge thereof coincides with the short side of the ground terminal of the single-end grounded transmission line resonator 103; the slotted front and rear single-end grounding transmission line resonators 103 are both in a symmetrical pattern, i.e., the slotted slot 203 is identical to the symmetry axis of the single-end grounding transmission line resonators 103.
Further, the single-plane coplanar waveguide metal part and the nonmetal part nested on the single-plane coplanar waveguide metal part are both arranged on the silicon-based gallium nitride;
As shown in fig. 2, in one embodiment, the silicon-based gallium nitride includes a 1000 μm thick silicon substrate 8 and an etched AlGaN/GaN heterojunction epitaxial layer on the silicon substrate 8;
In one embodiment, the etched AlGaN/GaN heterojunction epitaxial layer comprises: 100nm thick AlN layer 7, 300nm thick AlGaN layer 6, 1000nm thick GaN barrier layer 5, 200nm thick GaN channel layer 4, 0.8nm thick AlN layer 3, 19nm thick AlGaN layer 2, and 3nm thick GaN cap layer 1.
Further, the complete AlGaN/GaN heterojunction epitaxial layer comprises an AlN layer 7, an AlGaN layer 6, a GaN barrier layer 5, a GaN channel layer 4, an AlN layer 3, an AlGaN layer 2 and a GaN cap layer 1 which are sequentially laminated from bottom to top;
Completely etching one side of the GaN channel layer 4, the AlN layer 3, the AlGaN layer 2 and the GaN cap layer 1, reserving the other side, and etching a part of the top of the GaN barrier layer 5 to obtain an etched AlGaN/GaN heterojunction epitaxial layer in order to ensure complete etching of the GaN channel layer 4;
In the etched AlGaN/GaN heterojunction epitaxial layer, one side of the reserved GaN channel layer 4, the AlN layer 3, the AlGaN layer 2 and the GaN cap layer 1 is called an active region 9, and one side of the etched GaN channel layer 4, the AlN layer 3, the AlGaN layer 2, the GaN cap layer 1 and part of the GaN barrier layer 5 is called a passive region;
Growing an insulating medium layer 11 which is the same as the gate medium of the active area on the GaN barrier layer 5 at the bottom part left after the immediate etching of the passive area, and then sputtering a top metal 10 on the insulating medium layer 11;
the monoplane coplanar waveguide metal portion and the non-metal portion nested on the monoplane coplanar waveguide metal portion are both disposed in the top layer metal 10.
Further, for the top metal 10, stripping the non-metal part of the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter in the top metal 10, and reserving the metal part to form the silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter.
In one embodiment, a silicon-based gallium nitride wide-stop-band high-selectivity on-chip band-pass filter device is provided, and the filter is based on a step impedance resonant coupling, has high frequency selectivity of rapid attenuation of stop band, good harmonic suppression and wide stop band characteristics, is embedded with a double-ended grounding lambda g/4 type transmission line structure, has compact size of harmonic suppression and GaN on silicon, has size 0.662mm x 0.814mm (0.148 lambda g x 0.182 lambda g, lambda g= 4.473 mm), is easy to design and is easy to integrate. The single metal layer CPW is easy to realize the series connection and parallel connection of circuits, the grounding does not need through hole punching, the characteristic impedance range is wider, and the testing on the wafer is easy to realize.
Due to different application scene requirements, the thicknesses of GaN barrier layers of different wafers are different, and the dielectric constant of the equivalent medium is stabilized by growing the medium. In this example, the GaN and silicon substrates were equivalent to 1mm thick uniform media, the relative dielectric constant was 12.5, the tangent loss angle was 0.01, and the electrical conductivity was 0.07S/m.
As can be read from the test S 21 (fig. 8), the minimum insertion loss in the passband is about 3.63dB, the second harmonic suppression is higher than 13.9dB. The stop band inhibition is higher than 15dB in the range of 35.1-110GHz, and the ultra-wide stop band is realized. The 3dB bandwidth of the filter is 16.3% and the 12dB bandwidth is only 36.7%, i.e. the 12dB-3dB rectangular factor is only 2.25. Far less than similar papers and patents, has high selectivity of rapid attenuation of stop band. The proposed filter covers 24.75-27.5GHz, the center frequency is 26.1GHz, the bandwidth is 10.5%, the minimum insertion loss of the passband is 3.63dB, and the passband ripple is 1.47dB.
The BPF size including the pads was 0.662 x 0.814mm 2. The specific dimensions of the filter produced are as follows, as shown in fig. 6:
The feed tap line length L t3 =725 μm, the feed line length L l2 =807 μm, the feed tap line width and feed line width W t =32 μm, the test pad width W pad =50 μm, the resonator line width W l =112 μm, the resonator slot width W m =52 μm, the resonator slot length L m =265 μm, the double-ended ground transmission line width W g2 =13 μm, the feed line-to-resonator spacing S 2 =28 μm, the resonator-to-double-ended ground transmission line spacing G l =25 μm, the feed line-to-feed tap spacing S t =20 μm, and the tap feed line-to-ground plane spacing G t =25 μm.
The equivalent LC circuit diagram of the present utility model is shown in fig. 1, and although only reactive elements are considered, it is very convenient for theoretical analysis.
C1＝0.0365pF,C2＝0.11pF,C3＝0.0365pF,L1＝0.11nH,L2＝0.055nH,L3＝
0.12nH,L4＝0.19nH,L5＝0.028nH,L6＝0.042nH。
Passive device processes were developed for integration and high performance in microwave applications. The process will begin with GaN cleaning on a silicon wafer and then etch 300nm GaN cap layer, alGaN, alN and GaN channels for MESA. Thereafter, top interconnect metallization (M2) is achieved using a Ni/Ag metal layer with a thickness of 50nm/1000 nm. A schematic cross-sectional view of a passive device technology is shown.
In one embodiment, a method for preparing a silicon-based gallium nitride wide stop band high selectivity on-chip band pass filter is provided, as shown in fig. 2, comprising the steps of:
step 1, growth of GaN: growing a 100nm thick AlN layer 7, a 300nm thick AlGaN layer 6, a 1000nm thick GaN barrier layer 5, a 200nm thick GaN channel layer 4, a 0.8nm thick AlN layer 3, a 19nm thick AlGaN layer 2 and a 3nm thick GaN cap layer 1 on a 1000 μm thick silicon substrate 8 in sequence from bottom to top to obtain a complete AlGaN/GaN heterojunction epitaxial layer;
Step 2, isolation of active area and passive area and isolation of devices: defining the position of an active region on the upper surface of the complete AlGaN/GaN heterojunction epitaxial layer by using photoresist, covering the position, and carrying out plasma bombardment etching on the upper surface of the AlGaN/GaN heterojunction epitaxial layer in a non-active region to enable the etching depth to be 300nm9, and etching to a part of GaN barrier layer 5 to obtain an etched AlGaN/GaN heterojunction epitaxial layer;
Step 3, preparing a medium: depositing a dielectric layer such as SiO2 on the whole surface of the etched passive region of the AlGaN/GaN heterojunction epitaxial layer, wherein the thickness of the dielectric layer is different from 20 nm to 1000nm according to specific requirements; defining the position where the insulating dielectric layer 11 needs to be deposited by using photoresist, and etching and removing the dielectric layer which is not covered by the photoresist by using a dry etching process; after etching is finished, removing the photoresist by using organic solvent through ultrasonic;
Step 4, stripping the nonmetallic part: defining the position and pattern of the filter by using photoresist, so that the position of the filter is on the passive area, the non-metal area is covered by the photoresist, and forming Ni with the metal part 10 of 50nm and Ag with the thickness of 1000nm on the top layer M2 by using an electron beam evaporation stripping process; and removing the photoresist and the nonmetal parts through ultrasonic stripping of an organic solvent.
The prior patent (publication number: CN 107634292A) is composed of an interdigital filter embedded with a plurality of open-circuit branches. The transmission line resonator is directly fed and input, and a transmission line resonator close to the input end and the output end is embedded with a plurality of open branches, and only one transmission pole is arranged in the passband of the transmission line resonator. The utility model is a coupling feed, and the passband is flatter with three transmission poles (in the embodiment, two transmission poles are heavy, namely, two transmission poles are represented, but one resonance depth is obviously higher). And the feed structure is improved, so that the length of the resonator is reduced while the wide stop band characteristic is maintained (S21 is smaller than 15dB in 35.1-110 GHz), and the layout area is fully utilized. The principle of the prior patent (publication number: CN 107634292A) is to suppress the higher harmonic (parasitic) passband of an interdigital filter, which is represented by a wide stopband in the range of 3-28GHz, and although the suppression is obviously reduced at 29-30GHz, no result is given which is larger than 30 GHz. The principle of the utility model is an improved interdigital filter, besides the wide band rejection is realized by restraining harmonic components, the 'electric leakage' attribute of a parasitic channel existing in silicon-based gallium nitride is fully utilized, and even though a parasitic passband of higher harmonic is displayed near 100GHz, the S21 is strictly less than-15 dB, namely, all the harmonic has enough insertion loss. Compared with the prior coplanar waveguide wide stop band filter, the utility model has more compact size.
The above-described embodiments are only preferred examples of the present utility model and do not constitute any limitation of the present utility model, and it will be apparent to those skilled in the art that various modifications and changes in form and details can be made according to the method of the present utility model without departing from the principle and scope of the utility model, but these modifications and changes based on the present utility model are still claimed in the present utility model.
Claims (10)
1. The silicon-based GaN wide-stop-band high-selectivity millimeter wave on-chip filter is characterized by comprising a single-plane coplanar waveguide metal part and a nonmetal part nested on the single-plane coplanar waveguide metal part, wherein the metal parts are all arranged in the metal plane of the same layer;
The single-plane coplanar waveguide metal part comprises a grounding surface (101), two coupling feed structures (102) and two feed taps (105), three single-end grounding transmission line resonators (103), two double-end grounding transmission lines (104), a signal input port (001) and a signal output port (002);
The single-end grounded transmission line resonator (103) includes: an open low impedance section (113) and a short high impedance section (123); wherein one end of the short-circuit high-impedance section (123) is connected with the ground plane (101), called a short-circuit end, and the other end is connected with one end of the open-circuit low-impedance section (113); the other end of the open low impedance section (113) is not connected with the ground plane (101) and is called an open end;
The three single-end grounding transmission line resonators (103) are arranged in parallel, and the connecting direction of the middle single-end grounding transmission line resonator (103) and the grounding surface (101) is opposite to that of the single-end grounding transmission line resonators (103) at two sides;
The two double-end grounding transmission lines (104) are respectively arranged between the middle single-end grounding transmission line resonator (103) and the single-end grounding transmission line resonators (103) at the two sides, and the two ends of the double-end grounding transmission lines (104) are connected with the grounding surface (101);
The two coupling feed structures (102) are respectively arranged at two sides of the three single-end grounding transmission line resonators (103); the two feed taps (105) are respectively arranged at one side of the two coupling feed structures (102) far away from the single-end grounding transmission line resonator (103);
One end of the feed tap (105) is connected with the grounding end of the coupling feed structure (102), and the other end is connected with the signal input port (001) or the signal output port (002);
The nonmetallic portion includes: a gap (201) arranged between the feed tap (105) and the ground plane (101), a gap (205) arranged between the coupling feed structure (102) and the feed tap (105), a gap (202) arranged between the coupling feed structure (102) and the single-end grounding transmission line resonator (103), a gap (204) arranged between the single-end grounding transmission line resonator (103) and the double-end grounding transmission line (104), and a slotted gap (203) inside the short-circuit high-impedance section (123).
2. The silicon-based GaN wide stop band high-selectivity millimeter wave on-chip filter according to claim 1, wherein the signal input port (001) and the signal output port (002) are perpendicular to the feed taps (105) and are respectively disposed on one side of the two feed taps (105) away from the coupling feed structure (102).
3. The silicon-based GaN wide stop band high-selectivity millimeter wave on-chip filter according to claim 2, wherein the signal input port (001) and the signal output port (002) are perpendicular to the feed taps (105) and are respectively disposed on one side of the two feed taps (105) away from the coupling feed structure (102).
4. The silicon-based GaN wide stop band high-selectivity millimeter wave on-chip filter according to claim 2, wherein the coupling feed structure (102) has one end connected to the ground plane (101) and the other end open.
5. The silicon-based GaN wide stop band high-selectivity millimeter wave on-chip filter according to claim 1, wherein after horizontal translation, three single-end grounded transmission line resonators (103) can be overlapped, after horizontal translation, the single-end grounded transmission line resonators (103) on two sides are completely overlapped, the open ends of the single-end grounded transmission line resonators (103) on two sides are overlapped with the open ends of the single-end grounded transmission line resonators (103) in the middle, and the open ends of the single-end grounded transmission line resonators (103) on two sides are overlapped with the open ends of the single-end grounded transmission line resonators (103) in the middle; the single-ended grounded transmission line resonators (103) on both sides are symmetrical with respect to the single-ended grounded transmission line resonator (103) in the middle.
6. A silicon-based GaN wide stop band high selectivity millimeter wave on-chip filter according to claim 1, characterized in that the feed tap (105) is shorter than the coupling feed structure (102);
In order to realize the characteristic of wide stop band, the feed tap (105) is placed in parallel with the coupling feed structure (102), and after horizontally translating the feed tap (105), the feed tap (105) coincides with the connecting end of the signal input port (001) or the signal output port (002) and the open end of the coupling feed structure (102); only horizontally translating the feed tap (105) or the coupling feed structure (102), both of which can coincide with one end of the connecting ground plane (101) of the single-ended grounded transmission line resonator (103) on both sides;
The two feed taps (105) are symmetrical about the middle single-ended grounded transmission line resonator (103);
The two coupling feed structures (102) are symmetrical with respect to the middle single-ended grounded transmission line resonator (103);
the signal input port (001) and the signal output port (002) are symmetrical about the intermediate single-ended grounded transmission line resonator (103).
7. The silicon-based GaN wide stop band high-selectivity millimeter wave on-chip filter according to claim 1, wherein the slotted slot (203) is rectangular, and one short side coincides with the short side of the grounding end of the single-end grounding transmission line resonator (103); the front end and the rear end of the slotting are both symmetrical patterns, namely the slotting gap (203) and the symmetry axis of the single-end grounding transmission line resonator (103) are the same.
8. The silicon-based GaN wide stop band high-selectivity millimeter wave on-chip filter according to claim 1, wherein the single-plane coplanar waveguide metal part and the nonmetal part nested on the single-plane coplanar waveguide metal part are both arranged on silicon-based gallium nitride;
The silicon-based gallium nitride comprises a silicon substrate (8) and an etched AlGaN/GaN heterojunction epitaxial layer positioned on the silicon substrate (8);
The etched AlGaN/GaN heterojunction epitaxial layer comprises: an AlN layer (7), an AlGaN layer (6), a GaN barrier layer (5), a GaN channel layer (4), an AlN layer (3), a 19 nm-thick AlGaN layer (2), and a GaN cap layer (1).
9. The silicon-based GaN wide stop band high-selectivity millimeter wave on-chip filter according to claim 8, wherein the complete AlGaN/GaN heterojunction epitaxial layer comprises an AlN layer (7), an AlGaN layer (6), a GaN barrier layer (5), a GaN channel layer (4), an AlN layer (3), an AlGaN layer (2) and a GaN cap layer (1) which are sequentially laminated from bottom to top;
Completely etching one side of the GaN channel layer (4), the AlN layer (3), the AlGaN layer (2) and the GaN cap layer (1), reserving the other side, and etching a part of the top of the GaN barrier layer (5) to obtain an etched AlGaN/GaN heterojunction epitaxial layer in order to ensure that the GaN channel layer (4) is completely etched;
In the etched AlGaN/GaN heterojunction epitaxial layer, one side of the reserved GaN channel layer (4), the AlN layer (3), the AlGaN layer (2) and the GaN cap layer (1) is called an active region (9), and one side of the etched GaN channel layer (4), the AlN layer (3), the AlGaN layer (2), the GaN cap layer (1) and part of the GaN barrier layer (5) is called a passive region;
Growing an insulating medium layer (11) which is the same as the gate medium of the active area on the GaN barrier layer (5) at the bottom part after the passive area is etched immediately, and then sputtering a top metal (10) on the insulating medium layer (11);
the single plane coplanar waveguide metal portion and the non-metal portion nested on the single plane coplanar waveguide metal portion are both disposed in a top layer metal (10).
10. The silicon-based GaN wide stop band high selectivity millimeter wave on-chip filter of claim 8, wherein for the top metal (10), the non-metal portion of the silicon-based GaN wide stop band high selectivity on-chip band pass filter in the top metal (10) is stripped, and the metal portion is reserved, so as to form the silicon-based GaN wide stop band high selectivity on-chip band pass filter.
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