Millimeter wave band glass-based radio frequency microsystem and preparation method thereof

Abstract

The invention discloses a millimeter wave band glass-based radio frequency microsystem and a preparation method thereof, and relates to the technical field of radio frequency communication systems, the glass-based radio frequency microsystem comprises a radio frequency module, the radio frequency module comprises a first glass substrate having a first surface and a second surface opposite to each other; the millimeter wave communication chip is fixed in the first glass substrate; the millimeter wave communication chip is electrically connected with the interconnection circuit on the surface of the first glass substrate; the antenna module comprises a second glass substrate which is provided with a third surface and a fourth surface which are opposite to each other, and the third surface and the second surface are relatively fixed; and the radiation unit is arranged on the fourth surface and is electrically connected with the interconnection circuit. According to the invention, system loss can be reduced and bandwidth can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of radio frequency communication systems, and more specifically, to a millimeter wave band glass-based radio frequency microsystem and a preparation method thereof. Background Art

[0002] In the field of wireless communications, in order to achieve ultra-bandwidth, low latency, and ultra-large capacity transmission requirements, one way to achieve this is to migrate the frequency band to the millimeter wave band, using the wide bandwidth and high directivity of the millimeter wave band to meet the above transmission requirements. This method can integrate multiple antennas in combination with MIMO (multiple input multiple output) technology to enhance gain and combat the spatial loss of the millimeter wave band. Each antenna requires an RF module to cooperate with power amplifiers and filters.

[0003] At present, in order to cope with the challenges of system volume, loss and complexity, the antenna and RF module can be integrated to shorten the transmission loss and reduce the system volume. Among the existing integrated solutions, such as the conventional AoC (antenna on chip) solution using silicon substrate, the system loss is still large and the bandwidth is narrow. Summary of the invention

[0004] In view of this, the present application provides a millimeter wave band glass-based radio frequency microsystem and a preparation method thereof, the scheme is as follows:

[0005] The first aspect of the present application provides a millimeter wave band glass-based radio frequency microsystem, comprising:

[0006] The radio frequency module comprises: a first glass substrate having a first surface and a second surface opposite to each other; a millimeter wave communication chip fixed in the first glass substrate; the millimeter wave communication chip is electrically connected to an interconnection circuit on the surface of the first glass substrate;

[0007] The antenna module comprises: a second glass substrate having a third surface and a fourth surface opposite to each other, the third surface being fixed relative to the second surface; a radiation unit, the radiation unit being arranged on the fourth surface and being electrically connected to an interconnection circuit; wherein the thickness of the second glass substrate is greater than 800 μm.

[0008] Preferably, in the above-mentioned glass-based radio frequency microsystem, the bottom surface of the millimeter wave communication chip facing away from the antenna module has a chip active area;

[0009] The interconnection circuit includes: a first circuit located on the first surface and a second circuit located on the second surface; the first circuit is electrically connected to the second circuit; the second circuit is electrically connected to the radiation unit; and the first circuit is electrically connected to the active area.

[0010] Preferably, in the above-mentioned glass-based radio frequency microsystem, the bottom surface of the millimeter wave communication chip facing away from the antenna module has a chip active area;

[0011] A side of the radio frequency module facing away from the antenna module has a heat dissipation opening, and the heat dissipation opening exposes at least a portion of the surface of the millimeter wave communication chip.

[0012] Preferably, in the above-mentioned glass-based radio frequency microsystem, a receiving cavity is provided in the first surface, and the millimeter wave communication chip is fixed in the receiving cavity;

[0013] The glass-based RF microsystem also includes a grounding metal layer; the grounding metal layer includes a first part and a second part that are integrally formed; the first part covers the top surface of the millimeter wave communication chip facing the antenna module and is electrically contacted with the top surface of the millimeter wave communication chip; the second part is arranged on the side wall of the accommodating cavity and surrounds the side wall of the millimeter wave communication chip.

[0014] Preferably, in the above-mentioned glass-based radio frequency microsystem, the interconnection circuit comprises a first conductive hole penetrating the first glass substrate;

[0015] The grounding metal layer and the filling metal in the first conductive hole are prepared based on the same electroplating process.

[0016] Preferably, in the above-mentioned glass-based RF microsystem, the antenna module and the RF module are fixedly connected based on gold-gold low-temperature bonding.

[0017] Preferably, in the above-mentioned glass-based radio frequency microsystem, the thickness of the first glass substrate is smaller than the thickness of the second glass substrate.

[0018] The second aspect of the present application provides a preparation method for preparing the above-mentioned glass-based radio frequency microsystem, the preparation method comprising:

[0019] Prepare radio frequency modules and antenna modules;

[0020] The RF module and the antenna module are stacked and fixed;

[0021] The radio frequency module includes: a first glass substrate having a first surface and a second surface opposite to each other; a millimeter wave communication chip fixed in the first glass substrate; the millimeter wave communication chip is electrically connected to the interconnection circuit on the surface of the first glass substrate;

[0022] The antenna module includes: a second glass substrate having a third surface and a fourth surface opposite to each other, the third surface being fixed relative to the second surface; a radiation unit, the radiation unit being arranged on the fourth surface and electrically connected to the interconnection circuit; wherein the thickness of the second glass substrate is greater than 800 μm.

[0023] Preferably, in the above preparation method, the method for preparing the radio frequency module comprises:

[0024] A blind hole and a receiving cavity are formed on the first surface; the depth of the blind hole is not less than the depth of the receiving cavity;

[0025] Based on the electroplating process, metal is filled in the blind hole to form a first conductive hole, and a grounding metal layer is formed on the surface of the accommodating cavity;

[0026] After the millimeter wave communication chip is fixed in the accommodating cavity, a first line of the interconnection circuit is formed on the first surface, and the first line is electrically connected to the millimeter wave communication chip;

[0027] After the second surface is thinned, a second line of the interconnection circuit is formed on the second surface, and the second line is electrically connected to the first line through the first conductive hole.

[0028] Preferably, in the above-mentioned preparation method, the method for preparing the antenna module comprises:

[0029] forming a second conductive hole penetrating through the second glass substrate;

[0030] forming a radiation unit on the fourth surface;

[0031] A bonding layer for bonding and fixing with the radio frequency module is formed on the third surface.

[0032] From the above description, it can be seen that in the millimeter wave band glass-based RF microsystem and its preparation method provided by the technical solution of this application, the antenna module and the RF module of the glass-based RF microsystem are respectively prepared based on a glass substrate. Compared with the conventional AoC solution using a silicon substrate, the technical solution of this application has at least the following advantages:

[0033] Glass substrates do not have the physical field coupling problem of silicon-based materials, which can avoid the loss caused by the physical field coupling effect and effectively improve the system bandwidth;

[0034] Compared with silicon substrate, glass substrate has smaller dielectric constant and lower loss tangent. The thickness of glass substrate is easy to adjust, which can better realize the performance of millimeter wave band antenna module.

[0035] The glass substrate has good rigidity and can effectively prevent warping problems;

[0036] Glass substrates can meet wafer-level processes and form smaller line widths and line spacings, which can reach 10μm or even 5μm, making the line widths and line spacings meet the signal transmission requirements of RF systems.

[0037] In addition, the second glass substrate needs to be provided with a conductive hole (such as the second conductive hole described below) so that the radiation unit can be electrically connected to the interconnection circuit on the first glass plate below through the conductive hole that penetrates the second glass substrate. In the embodiment of the present application, the antenna module is prepared with a second glass substrate made of glass material, and the thickness of the second glass substrate is greater than 800μm. A glass plate substrate with a thicker thickness can be used, and the radiation unit is set through the second glass substrate with a larger thickness to facilitate isolation from the interconnection circuit below. In addition, based on the glass material, the second glass substrate is convenient for forming a conductive hole with a larger depth, and the thickness of the second glass substrate has little effect on the preparation of the conductive hole. However, when using a conventional silicon substrate or an organic substrate, it is more difficult to form a penetrating conductive hole when the substrate thickness is greater than 800μ. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, 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 embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0039] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.

[0040] Figure 1 A cross-sectional view of a millimeter-wave-band glass-based radio frequency microsystem provided in an embodiment of the present application;

[0041] Figure 2 A cross-sectional view of another millimeter-wave-band glass-based radio frequency microsystem provided in an embodiment of the present application;

[0042] Figure 3 A schematic flow chart of a method for preparing a glass-based radio frequency microsystem provided in an embodiment of the present application;

[0043] Figure 4-Figure 10 A product structure diagram of a method for preparing a radio frequency module in different process steps provided in an embodiment of the present application;

[0044] Figure 11-13 A product structure diagram of different process steps of a method for preparing an antenna module provided in an embodiment of the present application;

[0045] Fig.14This is a schematic diagram of the structure after the RF module and antenna module are bonded and fixed.

[0046] Reference numerals:

[0047] 100-RF module; 101-first glass substrate; 102-millimeter wave communication chip; 103-interconnection circuit; 1031-first line; 1032-second line; 104-chip active area; 105-heat dissipation opening; 106-ground metal layer; 1061-first part; 1062-second part; 107-insulating dielectric material; 108-conductive glue; 109-tin ball; 110-blind hole; 111-accommodating cavity; 112-temporary bonding layer; 200-antenna module; 201-second glass substrate; 202-radiating unit; S1-first surface; S2-second surface; S3-third surface; S4-fourth surface; Via1-first conductive hole; Via2-second conductive hole. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0049] AiP (antenna in package) solution is another integrated solution that can effectively shorten the interconnection distance and reduce transmission loss. It can also flexibly select high-frequency substrate materials with low dielectric constant and low dielectric loss as antenna substrates to improve antenna performance. Therefore, compared with AoC solution, AiP solution can improve the performance of millimeter wave communication to a certain extent.

[0050] Among them, the AiP solution mainly includes packaging technologies such as LTCC (low-temperature co-fired ceramics), FOWLP (fan-out wafer-level packaging), organic substrate lamination and silicon-based processes.

[0051] The LTCC packaging technology in the AiP solution has excellent high-frequency, high-speed transmission and heat dissipation performance, but due to the expansion and contraction during the sintering process, it is difficult to meet the requirements of the millimeter-wave antenna for the minimum line width and line spacing and inter-layer alignment accuracy. In addition, the high temperature during the sintering process also makes it difficult for RF devices to be integrated only through micro-assembly. It is difficult to shorten the interconnection distance through embedding and other methods. The parasitic effect is relatively obvious, which is not suitable for high-frequency applications.

[0052] The FOWLP packaging technology in the AiP solution eliminates the parasitic effects caused by solder bumps and additional substrate thickness, and has the advantages of low parasitic inductance, low insertion loss, good signal integrity, and high I / O (input / output) density. However, due to warping problems, stacking is limited, and RDL (rewiring layer) multi-layer preparation is difficult. Therefore, it cannot meet the micron-level accuracy and tolerance required for the millimeter wave band. The use of epoxy molding compounds with high loss tangent values ​​also leads to poor antenna performance. When used as an antenna substrate material, TMV (true micro via) is highly limited, which imposes certain restrictions on antenna design.

[0053] Although the organic substrate stacking packaging technology in the AiP solution can take into account the advantages of processing accuracy and low cost, the dimensional stability of the organic substrate is poor and requires a larger pad, making it difficult to achieve high I / O fine pitch interconnection. Limited by the substrate process, there are also certain problems with the stacking thickness and the accuracy of the hole position.

[0054] The silicon-based packaged antenna in the AiP solution has the same problems as AoC because it also uses a silicon substrate.

[0055] From the above description, we can see that different packaging technologies in conventional AiP solutions still have their own limitations. Therefore, in the field of millimeter wave communications, how to ensure the bandwidth, gain, and radiation efficiency of the antenna while taking into account the electrical performance and integration of the package is an urgent problem to be solved.

[0056] In view of this, the embodiment of the present application provides a glass-based radio frequency microsystem in the millimeter wave band, and the antenna module and radio frequency module of the glass-based radio frequency microsystem are prepared based on glass substrates. Compared with the conventional AoC solution using a silicon substrate, in the embodiment of the present application, the glass substrate does not have the physical field coupling problem of silicon-based materials, can avoid the loss caused by the physical field coupling effect, and can effectively improve the system bandwidth; the glass substrate has a smaller dielectric constant than the silicon substrate, has a lower loss tangent, and the thickness of the glass substrate is easy to adjust, which can better achieve the performance of the antenna module in the millimeter wave band; the glass substrate has good rigidity and can effectively prevent warping problems; the glass substrate can meet the wafer-level process, and can form a smaller line width and line spacing, so that the line width and line spacing can well meet the signal transmission requirements of the radio frequency system.

[0057] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0058] refer to Figure 1 , Figure 1 A cross-sectional view of a millimeter-wave-band glass-based radio frequency microsystem provided in an embodiment of the present application, wherein the glass-based radio frequency microsystem includes:

[0059] The radio frequency module 100 includes: a first glass substrate 101, the first glass substrate 101 having a first surface S1 and a second surface S2 relative to each other; a millimeter wave communication chip 102, the millimeter wave communication chip 102 is fixed in the first glass substrate 101; the millimeter wave communication chip 102 is electrically connected to an interconnection circuit 103 on the surface of the first glass substrate 101;

[0060] The antenna module 200 includes: a second glass substrate 201, the second glass substrate 201 has a third surface S3 and a fourth surface S4 relative to each other, and the third surface S3 is relatively fixed to the second surface S2; a radiation unit 202, the radiation unit 202 is arranged on the fourth surface S4 and is electrically connected to the interconnection circuit 103; wherein the thickness of the second glass substrate 201 is greater than 800 μm.

[0061] Optionally, the thickness of the second glass substrate 201 can be set as required, such as 900 μm or 1000 μm. The second glass substrate 201 needs to be provided with a conductive hole (such as the second conductive hole Via2 described below) so that the radiation unit 202 is electrically connected to the interconnection circuit 103 on the first glass plate 101 below through the conductive hole penetrating the second glass substrate 201.

[0062] In the embodiment of the present application, the antenna module 200 is prepared with a second glass substrate 201 made of glass. A glass plate substrate 201 with a relatively large thickness can be used. The radiation unit 202 is arranged through the second glass substrate 201 with a relatively large thickness, so as to facilitate isolation from the interconnection circuit 103 below. In addition, based on the glass material, the second glass substrate 201 is convenient for forming a conductive hole with a relatively large depth, and the thickness of the second glass substrate 201 has little effect on the preparation of the conductive hole. However, when using a conventional silicon substrate or an organic substrate, it is difficult to form a penetrating conductive hole when the substrate thickness is greater than 800μ.

[0063] In addition, the thickness of the first glass substrate 101 is less than 800 μm, and the thickness of the first glass substrate 101 can be reduced to 100 μm. Based on the glass material, the first glass substrate 101 can be greatly thinned, and at this time, the first glass substrate 101 is an ultra-thin glass with a very thin thickness. Compared with the solution using a conventional silicon substrate or an organic substrate, ultra-wave glass has good mechanical strength, lower flexibility and lower weight, which can reduce the thickness and weight of the RF module 100 while ensuring its mechanical strength. In addition, the use of conventional silicon substrates or organic substrates cannot ensure sufficient mechanical strength at a thinner thickness and is not convenient for forming conductive holes at a thinner thickness. In the embodiment of the present application, the first glass substrate 101 can prepare conductive holes (such as the first conductive hole Via1 described below) at a thinner thickness.

[0064] In addition, based on the first glass substrate 101 and the second glass substrate 201, the RF module 100 and the antenna module 200 can be integrated by gold-gold low-temperature bonding based on the glass material.

[0065] In the embodiment of the present application, the antenna module 200 and the radio frequency module 100 are respectively prepared based on glass substrates. Compared with the conventional AoC solution using a silicon substrate, in the embodiment of the present application, the glass substrate does not have the physical field coupling problem of silicon-based materials, can avoid the loss caused by the physical field coupling effect, and can effectively improve the system bandwidth; the glass substrate has a smaller dielectric constant than the silicon substrate, has a lower loss tangent, and the thickness of the glass substrate is easy to adjust, which can better achieve the antenna module performance in the millimeter wave band; the glass substrate has good rigidity and can effectively prevent warping problems; the glass substrate can meet the wafer-level process, can form a smaller line width and line spacing, so that the line width and line spacing can well meet the signal transmission requirements of the radio frequency system.

[0066] In one implementation of the present application, the Figure 1 As shown, the millimeter wave communication chip 102 has a chip active area 104 on the bottom surface facing away from the antenna module 200; the interconnection circuit 103 includes: a first line 1031 located on the first surface S1 and a second line 1032 located on the second surface S2; the first line 1031 is electrically connected to the second line 1032; the second line 1032 is electrically connected to the radiation unit 202; the first line 1031 is electrically connected to the chip active area 104.

[0067] The chip active area 104 of the millimeter wave communication chip 102 is located on the surface of a side away from the antenna module 200. When the thickness of the two glass substrates is constant, a larger distance can be created between the chip active area 104 and the radiation unit 202, thereby reducing coupling interference between the radiation unit 202 and the chip active area 104.

[0068] In addition, the chip active area 104 of the millimeter wave communication chip 102 is located on the side surface away from the antenna module 200, which is also convenient for dividing the interconnection circuit 103 into two parts, which are respectively arranged on the first surface S1 and the second surface S2, respectively serving as the first line 1031 and the second line 1032, so as to facilitate the layout of the interconnection circuit 103; the interconnection circuit 103 can have a larger layout space, which is convenient for the impedance matching design of the interconnection circuit 103, and can optimize the millimeter wave communication performance.

[0069] Optionally, the first circuit 1031 and the second circuit 1032 may be electrically connected through a first conductive via Via1 penetrating the first glass substrate 101 .

[0070] Optionally, the antenna module 200 includes a second conductive via Via2 penetrating the second glass substrate 201 , and the radiation unit 202 is electrically connected to the interconnection circuit 103 in the radio frequency module 100 through the second conductive via Via2 .

[0071] If the chip active area 104 of the millimeter wave communication chip 102 is located on the side surface away from the antenna module 200, the side of the radio frequency module 100 away from the antenna module 200 has a heat dissipation opening 105, and the heat dissipation opening 105 exposes at least part of the surface of the millimeter wave communication chip 102. In this way, the chip active area 104 is arranged on the side surface of the millimeter wave communication chip 102 away from the antenna module 200, so that the chip active area 104 can be closer to the outside of the glass-based radio frequency microsystem, and the heat dissipation opening 105 facilitates the heat dissipation of the millimeter wave communication chip 102, which can improve the heat dissipation effect and the working performance of the millimeter wave communication chip 102.

[0072] In other implementations, the chip active area 104 may also be arranged to be located on the top surface of the millimeter wave communication chip 102 facing the antenna module 200 .

[0073] In the embodiment of the present application, the first surface S1 has a receiving cavity, and the millimeter wave communication chip 102 is fixed in the receiving cavity. Figure 1 The through hole shown in the figure passes through the first glass substrate 101 . In other embodiments, the accommodating cavity may also be a groove disposed in the first surface S1 , and the depth of the groove is less than the thickness of the first glass substrate 101 .

[0074] Optionally, an insulating dielectric material 107 is provided in the accommodating cavity, and the insulating dielectric material 107 is used to fill the gap between the side walls of the millimeter wave communication chip 102 .

[0075] The glass-based RF microsystem further includes solder balls 109 disposed on the first surface S1 . The solder balls 109 are electrically connected to the interconnection circuit 103 to achieve electrical connection between the glass-based RF microsystem and an external circuit.

[0076] refer to Figure 2 , Figure 2 A cross-sectional view of another millimeter-wave glass-based radio frequency microsystem provided in an embodiment of the present application, based on any of the above implementations, Figure 2The glass-based radio frequency microsystem shown also includes a grounding metal layer 106; the grounding metal layer 106 includes an integrally formed first part 1061 and a second part 1062; the first part 1061 covers the top surface of the millimeter wave communication chip 102 facing the antenna module 200, and is in electrical contact with the top surface of the millimeter wave communication chip 102; the second part 1062 is arranged on the side wall of the accommodating cavity, surrounding the side wall of the millimeter wave communication chip 102. In this way, by arranging the grounding metal layer 106 surrounding the millimeter wave communication chip 102 on the surface of the accommodating cavity, the top surface of the millimeter wave communication chip 102 can be grounded, and the grounding metal layer 106 surrounding the millimeter wave communication chip 102 can also realize electromagnetic protection of the millimeter wave communication chip 102, and avoid the interference of the external electromagnetic signal of the millimeter wave communication chip 102 on the millimeter wave communication chip 102.

[0077] The top surface of the millimeter wave communication chip 102 may be bonded and fixed to the first part 1061 by means of a conductive adhesive 108 .

[0078] Alternatively, if Figure 2 As shown, the interconnection circuit 103 includes a first conductive hole Via1 penetrating the first glass substrate 101; wherein the grounding metal layer 106 and the filling metal in the first conductive hole Via1 are prepared based on the same electroplating process. In this way, the first conductive hole Via1 and the grounding metal layer 106 are prepared based on the metal of the same electroplating process, and there is no need to prepare the grounding metal layer 106 by a separate metal process, and the manufacturing process is simple.

[0079] In the embodiment of the present application, the antenna module 200 and the RF module 100 are fixedly connected based on gold-gold (Au-Au) low-temperature bonding, which can not only achieve a reliable and stable electrical connection effect between the antenna module 200 and the RF module 100, but also avoid the adverse effects of high-temperature processes on the components in the RF module 100.

[0080] Optionally, the thickness of the first glass substrate 101 and the second glass substrate 201 is not less than 100 μm. The thickness of the first glass substrate 101 can also be set to be less than the thickness of the second glass substrate 201. Since the thickness of the first glass substrate 101 and the second glass substrate 201 is not less than 100 μm, not only can the mechanical strength of the two be guaranteed, but also the coupling problem between different surfaces of the glass substrates can be effectively prevented. Compared with the first glass substrate 101, the second glass substrate 201 has a larger thickness, which facilitates the antenna module 200 to achieve a larger bandwidth. In one embodiment, the thickness of the second glass substrate 201 can be set to 900 μm.

[0081] From the above description, it can be seen that in the glass-based RF microsystem provided in the embodiment of the present application, the antenna module 200 and the RF module 100 both use a glass substrate as a substrate. From the perspective of package performance, in terms of electrical performance, since the glass substrate has a lower dielectric constant than the silicon substrate, the glass substrate has a smaller response in the electric field, which helps to reduce crosstalk and noise in the circuit.

[0082] Compared with silicon-based packaged antennas and FOWLP packaging technology, glass substrates have lower high-frequency dielectric losses. The loss tangent value of the glass substrate at 50GHz is 0.00036, which helps to reduce the energy loss of signals during transmission and improve the efficiency of signal transmission.

[0083] Compared with silicon substrates, when processing glass substrates, it is not necessary to deposit an insulating layer on the substrate surface and the inner wall of TGV (through glass via), and the preparation process of the conductive hole is simple. In addition, the antenna module 200 can be prepared directly based on ultra-wave glass as the second glass substrate 201, without the need for secondary thinning, and the manufacturing process of the antenna module 200 is simple.

[0084] In terms of integration, the glass substrate process has wafer-level process accuracy. Circuits with smaller line widths and line spacings can be prepared on the glass substrate, such as line widths and line spacings of 2μm~5μm. It can be combined with glass substrate stacking to achieve high wiring density, reduce the amount of metal required, reduce unnecessary parasitics and the system thickness of the AiP solution, and have high dimensional stability. It is also possible to achieve vertical interconnection through conductive holes that penetrate the glass substrate, reduce the connection distance between lines on different surfaces, and thus reduce connection impedance and parasitic problems caused by the connection.

[0085] In terms of reliability, the glass substrate has good weather resistance to temperature and humidity, and is not easily affected by humidity and temperature and warped. Even when the thickness of the glass substrate is less than 100μm, the warping is still very small and the impact on the system can be ignored.

[0086] From the perspective of antenna performance, the thickness of the glass substrate can be designed according to usage requirements. The lower high-frequency loss of the glass material also helps to improve the radiation efficiency of the antenna. TGV can also be used to reduce the surface wave effect and increase the gain.

[0087] In terms of the integration of antennas and RF devices, the CTE (coefficient of thermal expansion) of the glass substrate is adjustable. The CTE of the glass substrate can be adjusted by adjusting the proportion of glass material components, which facilitates the CTE matching of the glass substrate and electronic devices, thereby preventing warping and fragmentation problems caused by stress mismatch between the glass substrate and electronic devices.

[0088] Furthermore, the glass substrate can be grooved / cavified using high-precision manufacturing technology to realize an embedded structure of the millimeter wave communication chip 102 in the RF module 100, thereby facilitating system integration.

[0089] It can be seen from the above description that the RF module 100 and the antenna module 200 in the glass-based RF microsystem provided in the embodiment of the present application can be prepared separately, and then the RF module 100 and the antenna module 200 can be integrated by Au-Au low-temperature bonding. The technical solution of the embodiment of the present application effectively utilizes the advantages of the adjustable thickness and low high-frequency loss of the glass substrate, improves the communication performance of the antenna in the millimeter wave band, and utilizes the advantages of the low dielectric constant, wafer-level process accuracy and small warpage of the glass substrate to improve the system integration and electrical performance.

[0090] In the technical solution of the embodiment of the present application, the glass-based RF microsystem adopts a layered bonding solution of double glass substrates, which effectively avoids the impact of the single-layer integration solution on the antenna performance and the grounding limitations. Moreover, the RF module 100 uses a cavity integration solution to embed and fix the millimeter wave communication chip 102, and combines Au-Au low-temperature bonding to fix the RF module 100 and the antenna module 200, which can reduce the problem of signal leakage during transmission, and can realize a millimeter wave communication AiP system with large bandwidth, high integration and low loss. In addition, based on the stacked fixed structure of two glass substrates, it is convenient to achieve a better integration of the antenna module 200 and the RF module 100.

[0091] Optionally, in the embodiment of the present application, one or more millimeter wave communication chips 102 may be embedded in the first glass substrate 101, and a plurality of array-arranged radiation units 202 may be provided on the fourth surface S4 of the second glass substrate 201 to realize a matrix communication structure in the millimeter wave band. This method does not require a coplanar splicing structure of multiple substrates, and can realize a matrix distribution of multiple radiation units 202 based on an integrated large-size glass substrate, thereby facilitating the realization of multi-antenna matrix communication.

[0092] Based on the glass-based radio frequency microsystem provided in the above embodiments, another embodiment of the present application further provides a preparation method for preparing the glass-based radio frequency microsystem provided in any one of the above embodiments. The preparation method can be as follows: Figure 3 shown.

[0093] refer to Figure 3 , Figure 3 A schematic diagram of a process for preparing a glass-based radio frequency microsystem provided in an embodiment of the present application, combined with the accompanying drawings and Figure 3 As shown, the preparation method comprises:

[0094] Step S11: preparing the RF module 100 and the antenna module 200 .

[0095] Step S12: stack and fix the RF module 100 and the antenna module 200.

[0096] The RF module 100 includes: a first glass substrate 101, the first glass substrate 101 has a first surface S1 and a second surface S2 relative to each other; a millimeter wave communication chip 102, the millimeter wave communication chip 102 is fixed in the first glass substrate 101; the millimeter wave communication chip 102 is electrically connected to the interconnection circuit 103 on the surface of the first glass substrate 101.

[0097] Optionally, the millimeter wave communication chip 102 may be a GaAs-based chip or a Si-based chip. The embodiment of the present application does not limit the type of the millimeter wave communication chip 102.

[0098] The antenna module 200 includes: a second glass substrate 201, the second glass substrate 201 has a third surface S3 and a fourth surface S4 relative to each other, and the third surface S3 is relatively fixed to the second surface S2; a radiation unit 202, the radiation unit 202 is arranged on the fourth surface S4 and is electrically connected to the interconnection circuit 103; wherein the thickness of the second glass substrate 201 is greater than 800 μm.

[0099] The preparation method provided in the embodiment of the present application prepares the antenna module 200 and the RF module 100 respectively based on two glass substrates. Compared with the antenna packaging technology using a silicon substrate, it can effectively reduce the loss, increase the bandwidth, and greatly improve the communication performance in the millimeter wave band.

[0100] refer to Figure 4-Figure 10 , Figure 4-Figure 10 The product structure diagram of a method for preparing a radio frequency module in different process steps provided in an embodiment of the present application, the method for preparing the radio frequency module 100 includes:

[0101] Step S21: Figure 4 As shown, a blind hole 110 and a receiving cavity 111 are formed on the first surface S1 ; the depth of the blind hole 110 is not less than the depth of the receiving cavity 111 .

[0102] Optionally, the blind hole 110 and the receiving cavity 111 may be prepared by a laser induced etching process.

[0103] Step S22: Figure 5 As shown, based on the electroplating process, metal is filled in the blind hole 110 to form a first conductive via Via1 , and a grounding metal layer 106 is formed on the surface of the accommodating cavity 111 .

[0104] The grounding metal layer 106 includes an integrally formed first portion 1061 and a second portion 1062 . The first portion 1061 covers the bottom surface of the accommodation cavity 111 , and the second portion 1062 covers the side wall of the accommodation cavity 111 .

[0105] Step S23: Figure 6 As shown, after the millimeter wave communication chip 102 is fixed in the accommodating cavity 111 , a first line 1031 of the interconnection circuit 103 is formed on the first surface S1 , and the first line 1031 is electrically connected to the millimeter wave communication chip 102 .

[0106] In step S23, the millimeter wave communication chip 102 may be fixed in electrical contact with the first portion 1061 by means of the conductive adhesive 108. The gap between the sidewall of the millimeter wave communication chip 102 and the second portion 1062 is filled with an insulating dielectric material 107.

[0107] In the first glass substrate 101, the surfaces of the first circuit 1031 and the second circuit 1032 can be covered with an insulating dielectric material 107, and the first circuit 1031 and the second circuit 1032 can be electrically connected to the bonding pads on the surfaces through conductive holes. In step S23, after the millimeter wave communication chip 102 is embedded and fixed, the first circuit 1031 is formed on the first surface S1. The surface of the first circuit 1031 has a pad for ball planting and a heat dissipation opening 105 that exposes a portion of the surface of the millimeter wave communication chip 102.

[0108] Step S24: Figure 7-Figure 9 As shown, after the second surface S2 is thinned, a second line 1032 of the interconnection circuit 103 is formed on the second surface S2, and the second line 1032 is electrically connected to the first line 1031 through the first conductive via Via1.

[0109] First, Figure 7 As shown, a temporary bonding layer 112 is formed on the first surface S1 to protect the first circuit 1031 and the heat dissipation opening 105 .

[0110] Then as Figure 8 As shown, after the second surface S2 is thinned, the first conductive hole Via1 is exposed, and then the second surface S2 is metallized, and a patterned metal circuit layer is formed by a photolithography process to form a second circuit 1032. The metal circuit layer includes Ti-Ni-Au stacked in sequence, wherein Ti is an adhesion layer, Ni is a seed layer, and Au is a bonding layer.

[0111] Finally Fig. 9 As shown, debonding is performed to remove the temporary bonding layer 112 on the first surface.

[0112] exist Figure 4-Figure 9 In the manner shown, the depth of the blind hole 110 is equal to the depth of the accommodating cavity 111. Figure 2 The radio frequency module 100 is shown in the illustrated manner.

[0113] In other embodiments, the depth of the blind hole 110 can be set to be greater than the depth of the accommodating cavity 111. After the second surface S2 is thinned, a portion of the thickness of the first glass substrate 101 is reserved at the position corresponding to the accommodating cavity 111. In this case, the structure of the RF module 100 can be as follows: Fig.10 shown.

[0114] refer to Fig.10 , Fig.10 A cross-sectional view of a radio frequency module provided in an embodiment of the present application, in which the depth of the accommodating cavity 111 in the radio frequency module 100 is less than the depth of the first conductive hole Via1. A portion of the first glass substrate 101 is retained between the second surface S2 and the accommodating cavity 111. In this manner, the flatness of the second surface S2 can be better ensured, and the second circuit 1032 and the insulating dielectric material 107 covering the second circuit 1032 can be formed on the second surface. The flatness on one side of the second surface S2 can be better ensured, and a bonding pad can be formed above the second circuit 1032, so as to facilitate bonding and fixing the antenna module 200.

[0115] Optionally, the method for preparing the antenna module 200 includes: forming a second conductive hole Via2 penetrating the second glass substrate 201; forming a radiation unit 202 on the fourth surface S4; and forming a bonding layer for bonding and fixing with the radio frequency module on the third surface S3, wherein the bonding layer includes a bonding pad. The method can be implemented as follows: Figure 11-13 shown.

[0116] refer to Figure 11-13 , Figure 11-13 The product structure diagram of a method for preparing an antenna module in different process steps provided in an embodiment of the present application, the method for preparing the antenna module 200 includes:

[0117] Step S31: Fig.11 As shown, after forming a through hole in the second glass substrate 201, as shown in Fig.12 As shown, electroplating is performed based on the through hole to form a second conductive hole Via2.

[0118] Step S32: Fig.13 As shown, the third surface S3 and the fourth surface S4 are metallized respectively to form a radiation unit 202 on the fourth surface S4, and the radiation unit 202 is electrically connected to the second conductive via 2. A bonding pad for bonding and fixing with the RF module 100 is formed on the third surface S3 by Au.

[0119] After the preparation of the RF module 100 and the antenna module 200 is completed, Fig.14 As shown, the two are bonded and fixed.

[0120] refer to Fig.14 , Fig.14 It is a schematic diagram of the structure after the RF module and the antenna module are bonded and fixed. The RF module 100 and the antenna module 200 are fixed by low-temperature Au-Au interlayer planar bonding to achieve single-chip-level planar bonding of the two glass-based modules.

[0121] After the RF module 100 and the antenna module 200 are stacked and fixed, a ball planting process is performed to form solder balls 109 electrically connected to the interconnection circuit 103 on the first surface S1.

[0122] In the embodiment of the present application, the Au surface is subjected to plasma activation treatment to optimize the process conditions and reduce the Au-Au bonding process temperature to about 200°C. The characteristics of low-temperature process and high-temperature service are utilized to achieve a temperature gradient design suitable for 3D integration process.

[0123] In the specification of this application, each embodiment is described in a progressive, parallel, or progressive and parallel manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. The implementation methods provided in the embodiments of this application can be combined with each other if there is no contradiction.

[0124] It should be noted that in the description of the present application, it should be understood that the description of the drawings and embodiments is illustrative rather than restrictive. The same reference numerals throughout the embodiments of the specification identify the same structure. In addition, for the sake of understanding and ease of description, the drawings may exaggerate the thickness of some layers, films, panels, regions, etc. It is also understood that when an element such as a layer, film, region, or substrate is referred to as "on" another element, the element may be directly on the other element or there may be an intermediate element. In addition, "on" refers to positioning an element on or below another element, but does not essentially refer to positioning on the upper side of another element according to the direction of gravity.

[0125] The terms "upper", "lower", "top", "bottom", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.

[0126] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the above elements.

[0127] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A millimeter-wave glass-based radio frequency microsystem, characterized in that: include: A radio frequency module, the radio frequency module comprising: a first glass substrate having a first surface and a second surface opposite to each other; a millimeter wave communication chip fixed in the first glass substrate; the millimeter wave communication chip is electrically connected to an interconnection circuit on a surface of the first glass substrate; An antenna module, comprising: a second glass substrate having a third surface and a fourth surface opposite to each other, the third surface being fixed relative to the second surface; a radiation unit, the radiation unit being arranged on the fourth surface and electrically connected to the interconnection circuit; wherein the thickness of the second glass substrate is greater than 800 μm.

2. The glass-based radio frequency microsystem according to claim 1, characterized in that: The bottom surface of the millimeter wave communication chip facing away from the antenna module has a chip active area; The interconnection circuit includes: a first circuit located on the first surface and a second circuit located on the second surface; the first circuit is electrically connected to the second circuit; the second circuit is electrically connected to the radiation unit; and the first circuit is electrically connected to the active area.

3. The glass-based radio frequency microsystem according to claim 1, characterized in that: The bottom surface of the millimeter wave communication chip facing away from the antenna module has a chip active area; A side of the radio frequency module facing away from the antenna module has a heat dissipation opening, and the heat dissipation opening exposes at least a portion of the surface of the millimeter wave communication chip.

4. The glass-based radio frequency microsystem according to claim 1, characterized in that: The first surface has a receiving cavity, and the millimeter wave communication chip is fixed in the receiving cavity; The glass-based radio frequency microsystem further includes a grounding metal layer; the grounding metal layer includes a first part and a second part that are integrally formed; the first part covers the top surface of the millimeter wave communication chip facing the antenna module and is in electrical contact with the top surface of the millimeter wave communication chip; The second part is arranged on the side wall of the accommodating cavity and surrounds the side wall of the millimeter wave communication chip.

5. The glass-based radio frequency microsystem according to claim 4, characterized in that: The interconnection circuit includes a first conductive via penetrating the first glass substrate; The grounding metal layer and the filling metal in the first conductive hole are prepared based on the same electroplating process.

6. The glass-based radio frequency microsystem according to claim 1, characterized in that: The antenna module and the radio frequency module are fixedly connected based on gold-gold low-temperature bonding.

7. The glass-based radio frequency microsystem according to any one of claims 1 to 6, characterized in that: The thickness of the first glass substrate is smaller than the thickness of the second glass substrate.

8. A preparation method, characterized in that: For preparing the glass-based radio frequency microsystem according to any one of claims 1 to 7, the preparation method comprising: Prepare radio frequency modules and antenna modules; The radio frequency module and the antenna module are stacked and fixed; The radio frequency module includes: a first glass substrate having a first surface and a second surface opposite to each other; a millimeter wave communication chip fixed in the first glass substrate; the millimeter wave communication chip is electrically connected to the interconnection circuit on the surface of the first glass substrate; The antenna module includes: a second glass substrate having a third surface and a fourth surface opposite to each other, the third surface being fixed relative to the second surface; a radiation unit, the radiation unit being arranged on the fourth surface and electrically connected to the interconnection circuit; wherein the thickness of the second glass substrate is greater than 800 μm.

9. The preparation method according to claim 8, characterized in that: The method for preparing the radio frequency module comprises: A blind hole and a receiving cavity are formed on the first surface; the depth of the blind hole is not less than the depth of the receiving cavity; Based on the electroplating process, metal is filled in the blind hole to form a first conductive hole, and a grounding metal layer is formed on the surface of the accommodating cavity; After the millimeter wave communication chip is fixed in the accommodation cavity, a first line of the interconnection circuit is formed on the first surface, wherein the first line is electrically connected to the millimeter wave communication chip; After the second surface is thinned, a second line of the interconnection circuit is formed on the second surface, and the second line is electrically connected to the first line through the first conductive hole.

10. The preparation method according to claim 8, characterized in that: The method for preparing the antenna module comprises: forming a second conductive hole penetrating through the second glass substrate; forming the radiation unit on the fourth surface; A bonding layer for bonding and fixing with the radio frequency module is formed on the third surface.

Images