Terahertz chip pressure point, chip and connection method

Abstract

The invention provides a terahertz chip pressure point, a chip and a connection method. The terahertz chip pressure point comprises a signal bonding pad and two grounding bonding pads arranged on the two sides of the signal bonding pad. The two grounding pads are respectively grounded, and the surfaces of the two grounding pads are connected. Under the condition that the two grounding bonding pads are grounded respectively, the surfaces of the two grounding bonding pads are additionally connected, it is guaranteed that the two grounding bonding pads are equal in potential, the better common-ground effect is achieved, pressure point parasitic inductance is reduced, high-frequency resonance is restrained, dielectric loss and radiation loss are reduced, and the signal transmission performance of coplanar waveguide pressure points can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz chip design, and in particular to a terahertz chip pressure point, a chip and a connection method. Background Art

[0002] With the widespread application of terahertz technology in wireless communications, imaging systems and other fields, terahertz monolithic integrated circuit chips have achieved rapid development. Terahertz chips are planar integrated circuits, and the interface generally uses coplanar waveguide (GSG) pressure points. The middle pad of the pressure point is the signal pad, and the pads on both sides are ground pads, which are used to adapt to the GSG high-frequency microwave probe.

[0003] When electromagnetic wave signals are transmitted, the energy is mainly concentrated in the gap between the signal pad and the ground pad, and between the signal pad and the common ground on the back. In order to meet the equipotential, the ground pads on both sides are generally connected to the common ground on the back of the chip through independent vias. However, the applicant found that when the chip operating frequency reaches the terahertz frequency band, the parasitic inductance effect of the via will become more and more obvious, and there will be a potential difference between the ground pads on both sides. When the signal passes through the chip pressure point, it is easy to generate high-frequency resonance in the band, affecting signal transmission. Summary of the invention

[0004] The embodiments of the present invention provide a terahertz chip pressure point, a chip and a connection method to solve the problem of poor signal transmission performance of coplanar waveguide pressure points.

[0005] In a first aspect, an embodiment of the present invention provides a terahertz chip pressure point, including a signal pad and two ground pads arranged on both sides of the signal pad;

[0006] The two ground pads are grounded respectively, and surfaces of the two ground pads are connected.

[0007] In a possible implementation, surfaces of two ground pads are connected by a bonding gold wire.

[0008] In a possible implementation, the bonding gold wire is U-shaped.

[0009] In a possible implementation, the plane where the bonding gold wire is located is parallel to the surfaces of the two ground pads.

[0010] In a possible implementation, the gold bonding wire is connected to one side of the surface of the two ground pads close to the edge of the chip.

[0011] In a possible implementation, the bonding wire includes two short sides and one long side, and the signal pad is flush with the outer edges of the two ground pads; wherein the outer edge is a side of the pad surface close to the chip edge;

[0012] The length of the two short sides is half the distance between the outer edge of the signal pad and the edge of the chip.

[0013] In a possible implementation, the two ground pads are grounded through vias respectively.

[0014] In a second aspect, an embodiment of the present invention provides a terahertz chip having a terahertz chip pressure point according to the first aspect or any possible implementation manner of the first aspect.

[0015] In a third aspect, an embodiment of the present invention provides a method for connecting a terahertz chip pressure point, which is applied to the terahertz chip pressure point of the first aspect or any possible implementation of the first aspect, and the method includes:

[0016] The signal pads of the terahertz chip pressure points are connected to the external microstrip through bonding gold wires.

[0017] The embodiment of the present invention provides a terahertz chip pressure point, a chip and a connection method. When two grounding pads are grounded respectively, the surfaces of the two grounding pads are additionally connected to ensure that the two grounding pads have equal potential, achieve a better common ground effect, reduce the parasitic inductance of the pressure point, suppress high-frequency resonance, reduce dielectric loss and radiation loss, and improve the signal transmission performance of the coplanar waveguide pressure point. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 It is a structural diagram of the GSG pressure point;

[0020] Figure 2 It is a schematic diagram of the structure of the connection between the GSG pressure point and the external microstrip line;

[0021] Figure 3 It is a structural diagram of the ground pad common ground equivalent circuit of the GSG pressure point;

[0022] Figure 4 This is a schematic diagram of the radiation loss of the signal pad at the GSG pressure point;

[0023] Figure 5 It is a schematic diagram of the electric field distribution on the GSG pressure point bonding path;

[0024] Figure 6 It is a schematic structural diagram of the terahertz chip pressure point bonding transition provided by an embodiment of the present invention;

[0025] Figure 7 is a structural schematic diagram of a common ground equivalent circuit of a ground pad of a terahertz chip pressure point provided by an embodiment of the present invention;

[0026] Figure 8 is a structural schematic diagram of a common ground equivalent circuit of a ground pad of a terahertz chip pressure point provided by an embodiment of the present invention;

[0027] Fig. 9 It is a schematic diagram of the electric field distribution of the terahertz chip bonding path provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to enable people in the technical field to better understand the present solution, the technical solution in the embodiment of the present solution will be clearly described below in conjunction with the drawings in the embodiment of the present solution. Obviously, the described embodiment is an embodiment of a part of the present solution, not all of the embodiments. Based on the embodiments in the present solution, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present solution.

[0029] The term "including" and any other variations in the specification and claims of this solution and the above drawings mean "including but not limited to", and is intended to cover non-exclusive inclusions and is not limited to the examples listed in the text. In addition, the terms "first" and "second" are used to distinguish different objects, not to describe a specific order.

[0030] The following is a detailed description of the implementation of the present invention in conjunction with the specific drawings:

[0031] Figure 1 The structure of a conventional GSG pressure point is shown. In order to meet the common ground and equipotential requirements, the ground pads G1 and G2 on both sides are generally connected to the common ground on the back of the chip through independent vias. The signal pad is connected to the external microstrip line through a bonding wire, such as Figure 2 As shown. The ground via can generally be equivalent to a ground inductor. The equivalent circuit of the common ground path of the ground pads on both sides of the chip pressure point can be simulated by two ground inductors L1 and L2, as shown in Figure 3 .

[0032] When the chip operating frequency reaches the terahertz frequency band, the parasitic inductance effect of the via will become more and more obvious. There will be a significant potential difference between the ground pads on both sides, resulting in an unbalanced electric field distribution. When the signal passes through the chip pressure point, it is easy to generate high-frequency resonance within the band, affecting signal transmission.

[0033] In addition, when the terahertz chip is used for microstrip bonding with other high-frequency boards, on the one hand, the edge of the signal pad close to the outside will have an open-circuit capacitor effect, radiating part of the high-frequency signal to the outside, resulting in increased transmission loss, such as Figure 4 On the other hand, the chip pressure point is generally 40um away from the chip edge, which will cause the signal to be transmitted to the chip pressure point through the bonding wire. The electric field is distributed in the air and the substrate, the discontinuity of the field distribution increases, and the dielectric loss also increases. The electric field distribution is as follows: Figure 5 .

[0034] Based on this, the patent of the present invention improves the design of a terahertz chip pressure point structure with a common ground on the surface of the ground pad based on the conventional terahertz pressure point. This structure has a better common ground effect, can reduce the parasitic inductance of the pressure point, suppress high-frequency resonance, reduce dielectric loss and radiation loss, and can meet the testing and assembly needs of terahertz chips.

[0035] Figure 6 A schematic diagram of a terahertz chip pressure point structure provided by an embodiment of the present invention. Figure 6 The terahertz chip pressure point includes a signal pad S and two ground pads G1 and G2 arranged on both sides of the signal pad;

[0036] The two ground pads G1 and G2 are grounded respectively, and the surfaces of the two ground pads G1 and G2 are connected.

[0037] In this embodiment, the three-dimensional structure after the surfaces of the two ground pads G1 and G2 are connected is as follows: Figure 7 As shown in FIG. 1 , the common ground equivalent circuit of a new type of pressure point is formed by connecting the surfaces of the two ground pads G1 and G2. Figure 8 As shown, the additional common ground line equivalent inductance L3 forms a parallel relationship with the via equivalent inductances L1 and L2, which reduces the parasitic inductance between the ground pads G1 and G2 paths on both sides and suppresses high-frequency resonance.

[0038] In the embodiment of the present invention, when the two ground pads are grounded respectively, the surfaces of the two ground pads are additionally connected to ensure that the two ground pads have equal potential, achieve a better common ground effect, reduce the parasitic inductance of the pressure point, suppress high-frequency resonance, reduce dielectric loss and radiation loss, and improve the signal transmission performance of the coplanar waveguide pressure point.

[0039] In a possible implementation, surfaces of two ground pads are connected by a bonding gold wire.

[0040] In this embodiment, the bonding gold wire has the advantages of high reliability, easy implementation, and strong adaptability. It is used to connect the surfaces of two ground pads to ensure long-term reliable electrical connection. The operation is simple and efficient, and the bonding gold wire can be changed to adapt to different scene requirements.

[0041] In the terahertz chip pressure point provided in this embodiment, the width of the middle signal pad is 70μm, the width of the ground pads on both sides is 100μm, the gap between the signal pad and the ground pad is 40μm, and a bonding gold wire with a width of 15μm can be used to connect the two ground pads. This pressure point is generally bonded to the external microstrip line through a single gold wire with a diameter of 25μm, and there is a certain radiation loss and dielectric loss.

[0042] In a possible implementation, the bonding gold wire is U-shaped.

[0043] In this embodiment, since the signal pad and the two ground pads are in a straight line, a U-shaped gold bonding wire is used to connect the two ground pads to avoid contact between the gold bonding wire and the signal pad. Figure 6 The position shown in FIG. 1 is connected to two ground pads on the left side, and can also be connected to two ground pads from above across the signal pad, or connected to two ground pads on the right side.

[0044] In a possible implementation, the plane where the bonding gold wire is located is parallel to the surfaces of the two ground pads.

[0045] In this embodiment, the terahertz chip assembly generally requires the bonding wire length to be as short as possible and the curvature to be as low as possible to reduce the mismatch effect of parasitic inductance. When the plane where the U-shaped bonding wire is located is parallel to the surfaces of the two ground pads, the bonding wires interconnecting the terahertz chip with other microstrip lines can achieve a lower height and curvature without contacting the U-shaped bonding wire.

[0046] In a possible implementation, the gold bonding wire is connected to one side of the surface of the two ground pads close to the edge of the chip.

[0047] In this embodiment, the connection relationship between the bonding wire and the two ground pads is as follows: Figure 6 As shown, the stereo connection effect is as follows Figure 7 As shown in the figure, the pressure point and the microstrip line on the high-frequency board are bonded through a single gold wire with a diameter of 25um, and connected to the signal pad across the U-shaped bonding wire. After the connection, the electric field of the bonding wire between the pressure point and the microstrip line on the high-frequency board is as follows Fig. 9 shown.

[0048] In this way, on the one hand, the electric field near the chip signal pad can be wrapped and bound between the ground pad and the signal pad, reducing radiation loss; and the ground line close to the edge of the chip provides a reference ground for the electric field of the signal transmitted on the bonding wire path, allowing the energy to be concentrated in the air as much as possible, reducing dielectric loss.

[0049] In a possible implementation, the bonding wire includes two short sides and one long side, and the signal pad is flush with the outer edges of the two ground pads; wherein the outer edge is a side of the pad surface close to the chip edge;

[0050] The length of the two short sides is half the distance between the outer edge of the signal pad and the edge of the chip.

[0051] In this embodiment, the terahertz chip assembly generally requires the bonding wire length to be as short as possible and the curvature to be as low as possible to reduce the mismatch effect of parasitic inductance. The bonding length of the bonding operation table equipment close to the process limit can generally be controlled at about 100um and the height at about 30um.

[0052] In addition, the installation gap between the chip and the microstrip line of the RF board needs to be as small as possible to ensure that the bonding wire is short enough. Taking into account the errors in installation and machining, the gap is generally around 30um.

[0053] Under the above two constraints, it is necessary to optimize the width of the U-shaped bonding wire and the distance from the U-shaped bonding wire to the signal pad to achieve the best matching state.

[0054] When the width of the signal pad in the middle is 70μm, the width of the ground pads on both sides is 100μm, the gap between the signal pad and the ground pad is 40μm, the distance between the chip pressure point and the chip edge is 40μm, the width of the U-shaped bonding wire is 15μm, and the distance between the long side and the chip edge and the signal pad is 20μm to achieve the best matching state.

[0055] In a possible implementation, the two ground pads are grounded through vias respectively.

[0056] In this embodiment, in order to achieve the best effect, the number, location and size of ground vias are usually optimized according to specific application requirements. Ground vias allow designers to flexibly route on multi-layer circuit boards, especially when space is limited. Reasonable layout of ground vias can simplify design and improve performance.

[0057] An embodiment of the present invention further provides a terahertz chip having a terahertz chip pressure point according to the first aspect or any possible implementation manner of the first aspect.

[0058] An embodiment of the present invention further provides a method for connecting terahertz chip pressure points, which is applied to the terahertz chip pressure points of the first aspect or any possible implementation of the first aspect, and the method includes:

[0059] The signal pads of the terahertz chip pressure points are connected to the external microstrip through bonding gold wires.

[0060] In a possible implementation, the gold bonding wire between the signal pad and the external microstrip line is higher than the gold bonding wire between the two ground pads.

[0061] In this embodiment, the commonly used terahertz chip RF pressure point adopts a GSG structure, the width of the middle pressure point for signal transmission is 40um, the width of the RF ground pressure points on both sides is 80um, and the distance between the RF ground pressure point and the signal pressure point is 40um. Such pressure point size can adapt to the high-frequency microwave probe with a needle spacing of 100um on the market to ensure the accuracy of the test. However, when the chip pressure point is interconnected with other microstrip transmission lines, it is generally transitioned through a single gold wire bonding with a diameter of 25um. This single-wire bonding method has a large parasitic inductance, and the discontinuity of signal transmission is very obvious, resulting in deterioration of RF transmission performance. In addition, when the chip is interconnected with other microstrip lines, a gap of tens of microns will be reserved in the middle. At this time, the bonding wire and the reference ground directly below it are generally tens to one hundred microns away. This gap will also cause the matching of signal transmission to deteriorate in the terahertz frequency band, and in severe cases, the signal cannot even be transmitted.

[0062] This embodiment makes the following improvements on the basis of conventional pressure points: the metal on the upper surface of the ground pads on both sides of the chip is connected through the outer end, providing an additional common ground channel. In addition, during assembly bonding, the bonding gold wire between the signal pad and the external microstrip line can directly cross the connection on the upper surface of the ground pad, which can also reduce the distance between the gold wire and the reference ground, reduce the discontinuity introduced by the assembly gap, and improve the terahertz signal transmission performance. This structure has a better grounding effect, can suppress high-frequency resonance, and can meet the testing and assembly requirements of terahertz chips.

[0063] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A terahertz chip pressure point, characterized in that: It includes a signal pad and two ground pads arranged on both sides of the signal pad; The two ground pads are grounded respectively, and surfaces of the two ground pads are connected.

2. The terahertz chip pressure point according to claim 1, characterized in that: The surfaces of the two ground pads are connected by a bonding gold wire.

3. The terahertz chip pressure point according to claim 2, characterized in that: The bonding gold wire is U-shaped.

4. The terahertz chip pressure point according to claim 3, characterized in that: The plane where the bonding gold wire is located is parallel to the surfaces of the two ground pads.

5. The terahertz chip pressure point according to claim 4, characterized in that: The bonding gold wire is connected to one side of the surface of the two ground pads close to the edge of the chip.

6. The terahertz chip pressure point according to claim 5, characterized in that: The bonding wire includes two short sides and one long side, and the signal pad is flush with the outer edges of the two ground pads; wherein the outer edge is a side on the pad surface close to the chip edge; The lengths of the two short sides are half of the distance between the outer edge of the signal pad and the edge of the chip.

7. The terahertz chip pressure point according to claim 1, characterized in that: The two ground pads are grounded through via holes respectively.

8. A terahertz chip, characterized in that: A terahertz chip pressure point as claimed in any one of claims 1 to 7.

9. A method for connecting pressure points of a terahertz chip, characterized in that: Applied to the terahertz chip pressure point according to any one of claims 1 to 7, the method comprising: The signal pads of the terahertz chip pressure points are connected to the external microstrip through bonding gold wires.

10. The method for connecting the terahertz chip pressure points according to claim 9, characterized in that: The bonding gold wire between the signal pad and the external microstrip line is higher than the bonding gold wire between the two ground pads.

Images