Terahertz chip, terahertz component and preparation method thereof

Abstract

The invention provides a terahertz chip, an assembly and a preparation method thereof, and belongs to the technical field of terahertz chip assembly. The GSG electrode comprises a first signal electrode, a second signal electrode, a first grounding electrode and a second grounding electrode. The first grounding electrode, the first signal electrode and the second grounding electrode which are sequentially arranged at the edge of the substrate at equal intervals are used for GSG probe testing, the size of the electrodes used for probe testing can be consistent with the size of the structure before improvement, and the consistency and accuracy of probe testing are kept. And extending the first signal electrode towards the edge of the substrate to form a second signal electrode, wherein the second signal electrode is used for bonding. Since the probe test position in the GSG electrode is separated from the bonding position, the size of the second signal electrode is not limited by the distance between the probes, and the size of the second signal electrode can be increased to match multi-wire bonding. The multiple bonding wires are connected in parallel, parasitic inductance is reduced after parallel connection, limitation on the length and height of the bonding wires is reduced, and the bonding process difficulty is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz chip assembly, and in particular to a terahertz chip, a component and a preparation method thereof. Background Art

[0002] With the widespread application of terahertz technology in wireless communications, radar, imaging systems and other fields, terahertz chips, such as terahertz monolithic integrated circuit chips, have achieved rapid development. Terahertz chips are planar integrated circuits, and the interface generally uses GSG electrodes in the form of coplanar waveguides for on-wafer probe testing and gold wire bonding assembly. For example, the GSG electrode includes two ground electrodes and one signal electrode; the GSG electrode is first used for on-wafer probe testing, and then packaged after passing the test, and gold wire bonding assembly is performed on the GSG electrode.

[0003] The operating frequency of the terahertz chip is relatively high, for example, usually between 0.3THz and 10THz. In order to ensure the accuracy of the probe test, the size and spacing of the high-frequency microwave probe are relatively small. To adapt to the high-frequency microwave probe, the electrode size and electrode spacing of the terahertz chip are relatively small. For example, to adapt to the high-frequency microwave probe with a spacing of 50 microns, the width of the signal electrode is set to 40 microns, the width of the ground electrode is set to 80 microns, and the spacing between the two electrodes is set to 20 microns. The small spacing between the test probes limits the electrode size, which in turn limits the bonding process. For example, a 40-micron-wide signal electrode can only bond a single bonding wire with a diameter of 25 microns. In the single-wire bonding method, if the bonded gold wire is too long, the parasitic inductance introduced will be relatively large, and the input return loss and insertion loss will be significantly deteriorated. Therefore, in order to improve the transmission performance, the single-wire bonding method in the terahertz frequency band requires the arc length of the gold wire to be as short as possible, the arc height to be as low as possible, and the bonding difficulty is relatively high. Therefore, this single-wire bonding is particularly dependent on the ability of refined bonding processes, the process is difficult, and has limitations. Summary of the invention

[0004] The present invention provides a terahertz chip, a component and a preparation method thereof, so as to solve the problems of large parasitic inductance and high process difficulty in the single-wire bonding method of the existing terahertz chip.

[0005] In a first aspect, the present invention provides a terahertz chip, comprising: a main substrate, a GSG electrode and a signal line; the GSG electrode is arranged at the edge of the front side of the main substrate; the GSG electrode comprises a first signal electrode, a second signal electrode, a first ground electrode and a second ground electrode; the first ground electrode, the first signal electrode and the second ground electrode are arranged in sequence and at equal intervals at the edge of the main substrate for GSG probe testing, and the distance from the edge of the main substrate is greater than the length of the second signal electrode; one end of the first signal electrode is connected to the signal line, and the line width is the same as that of the signal line; the second signal electrode is arranged between the first signal electrode and the edge of the main substrate, and is connected to the other end of the first signal electrode for multi-wire bonding; the width of the second signal electrode is greater than the width of the first signal electrode, and greater than the sum of the diameters of each bonding wire; the length of the second signal electrode is greater than the diameter of any bonding wire.

[0006] In a possible implementation, the multi-wire bonding is double-wire bonding.

[0007] In a possible implementation manner, the length of the second signal electrode is greater than the sum of diameters of each bonding wire.

[0008] In a possible implementation, a third signal electrode is further provided between the first signal electrode and the second signal electrode; the third signal electrode is a trapezoid, wherein the length of the upper base of the trapezoid is equal to the width of the first signal electrode, and the length of the lower base of the trapezoid is equal to the width of the second signal electrode.

[0009] In a possible implementation, a metal ground hole is further provided below the first ground electrode and the second ground electrode; a back ground layer is further provided on the back side of the main substrate; and the metal ground hole is used to connect the ground electrode and the back ground layer.

[0010] In a possible implementation, a third ground electrode is further disposed on the front side of the main body substrate; the third ground electrode is connected to the first ground electrode and the second ground electrode; a portion of the third ground electrode is disposed between the second signal electrode and the edge of the main body substrate.

[0011] In a possible implementation manner, the second signal electrode is in a square shape.

[0012] In a possible implementation manner, the first signal electrode and the signal line are in a bar shape; and the first ground electrode and the second ground electrode are in a rectangular shape.

[0013] In a second aspect, the present invention provides a terahertz component, including a microstrip transmission line, and a terahertz chip provided in any possible implementation as described above.

[0014] In a third aspect, the present invention provides a method for preparing a terahertz component, which is used to prepare the above-mentioned terahertz component, and the method includes: preparing the terahertz chip; inserting a GSG probe on a first ground electrode, a first signal electrode, and a second ground electrode of the terahertz chip to test the terahertz chip; after the test, bonding a plurality of bonding wires on the second signal electrode of the terahertz chip to connect an external microstrip transmission line to prepare the terahertz component.

[0015] The present invention provides a terahertz chip, a component and a preparation method thereof. The GSG electrode of the present invention comprises a first signal electrode, a second signal electrode, a first ground electrode and a second ground electrode. The first ground electrode, the first signal electrode and the second ground electrode arranged in sequence and at equal intervals on the edge of the substrate are used for GSG probe testing, and the size of the electrode used for the probe test can be consistent with the size of the structure before the improvement, so as to maintain the consistency and accuracy of the probe test. The second signal electrode is extended toward the edge of the substrate to set the first signal electrode, and the second signal electrode is used for bonding. Because the probe test position and the bonding position in the GSG electrode are separated, the size of the second signal electrode is not limited by the probe spacing, and the size of the second signal electrode can be increased to match the multi-wire bonding. Multiple bonding wires are connected in parallel with each other, and the parasitic inductance is reduced after parallel connection, and the restrictions on the length and height of the bonding wires are reduced, and the difficulty of the bonding process is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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 in the following description 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.

[0017] Figure 1 is a schematic diagram of the existing GSG electrode structure provided by an embodiment of the present invention;

[0018] Figure 2 is a schematic structural diagram of an existing GSG probe test provided by an embodiment of the present invention;

[0019] Figure 3 is a schematic structural diagram of an existing single-filament bonding provided by an embodiment of the present invention;

[0020] Figure 4 is a schematic diagram of an improved GSG electrode structure provided by an embodiment of the present invention;

[0021] Figure 5 is a schematic diagram of the structure of the GSG electrode probe test provided by an embodiment of the present invention;

[0022] Figure 6is a schematic diagram of the structure of double-wire bonding provided by an embodiment of the present invention;

[0023] Figure 7 is a schematic diagram of a single-wire bonding equivalent circuit model provided by an embodiment of the present invention;

[0024] Figure 8 is a schematic diagram of a double-wire bonding equivalent circuit model provided by an embodiment of the present invention;

[0025] Fig. 9 is a schematic diagram for comparing insertion loss simulation curves provided by an embodiment of the present invention;

[0026] Fig.10 is a schematic diagram for comparing return loss simulation curves provided by an embodiment of the present invention;

[0027] Fig.11 It is a schematic diagram of another improved GSG electrode structure 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 is a schematic diagram of the existing GSG electrode structure provided by an embodiment of the present invention; Figure 1 , GSG electrode, also known as GSG pressure point. GSG electrode includes two ground electrodes and one signal electrode. For example, in the commonly used terahertz chip GSG electrode, the width of the middle signal electrode used for signal transmission is 40 microns, the width of the RF ground electrodes on both sides is 80 microns, and the distance between the RF ground electrode and the signal electrode is 20 microns. Such GSG size can adapt to the high-frequency microwave probe with a needle spacing of 50 microns on the market to ensure the accuracy of the test.

[0032] Figure 2is a schematic diagram of the structure of the existing GSG probe test provided by an embodiment of the present invention; Figure 2 A high-frequency microwave probe with a needle spacing of 50 microns was inserted into the GSG electrode of the existing structure for testing.

[0033] Figure 3 is a schematic diagram of the structure of the existing single-filament bonding provided by an embodiment of the present invention; Figure 3 The signal electrode of the chip is connected to the external microstrip line through a single bonding wire. This single-wire bonding method introduces a large parasitic inductance, which will cause a significant deterioration in both input return loss and insertion loss, and has high requirements for the bonding process.

[0034] The embodiment of the present invention extends the first signal electrode toward the edge of the substrate to arrange the second signal electrode, so as to solve the problem of large parasitic inductance and high process difficulty of the single-wire bonding method of the existing terahertz chip.

[0035] Figure 4 Schematic diagram of an improved GSG electrode structure provided by an embodiment of the present invention. Figure 4 An embodiment of the present invention provides a terahertz chip, which includes: a main body substrate, a GSG electrode and a signal line; the GSG electrode is arranged at the edge of the front side of the main body substrate; the GSG electrode includes a first signal electrode, a second signal electrode, a first grounding electrode and a second grounding electrode; the first grounding electrode, the first signal electrode and the second grounding electrode are arranged in sequence at equal intervals at the edge of the main body substrate for GSG probe testing, and the distance from the edge of the main body substrate is greater than the length of the second signal electrode; one end of the first signal electrode is connected to the signal line, and the line width is the same as that of the signal line; the second signal electrode is arranged between the first signal electrode and the edge of the main body substrate, and is connected to the other end of the first signal electrode for multi-wire bonding; the width of the second signal electrode is greater than the width of the first signal electrode, and greater than the sum of the diameters of each bonding wire; the length of the second signal electrode is greater than the diameter of any bonding wire.

[0036] In some embodiments, the chip includes: a body substrate, a GSG electrode, and a signal line.

[0037] Exemplarily, the main body substrate generally includes a substrate and a chip structure prepared on the substrate. The specific chip structure on the main body substrate is not limited here.

[0038] For example, a GSG electrode is generally composed of two ground electrodes (G) and one signal electrode (S). The GSG electrode is a capacitive coupling structure that can ensure good electrical connection performance and reduce interference between the signal line and the surrounding environment.

[0039] Exemplarily, the signal line is used to connect the chip structure part on the body substrate with the GSG electrode. For example, the signal line is used to connect the signal electrode of the GSG electrode.

[0040] In some embodiments, as an interface between the chip and the outside, the GSG electrode is usually disposed at the edge of the front surface of the main substrate. The specific structure of the GSG electrode is described below.

[0041] In some embodiments, the GSG electrode includes a first signal electrode, a second signal electrode, a first ground electrode, and a second ground electrode.

[0042] Exemplarily, the first signal electrode and the signal line are in the shape of bars.

[0043] Exemplarily, the first ground electrode and the second ground electrode are in a rectangular shape.

[0044] Exemplarily, the shape of the second signal electrode is a square. In another exemplary embodiment, the shape of the second signal electrode can also be a rectangle. For ease of description, the following embodiments are described in terms of a square.

[0045] In some embodiments, the first ground electrode, the first signal electrode and the second ground electrode are sequentially arranged at equal intervals on the edge of the body substrate for GSG probe testing.

[0046] Exemplarily, the first ground electrode, the first signal electrode, and the second ground electrode are at the same distance from the edge of the body substrate.

[0047] It should be noted that the equal spacing arrangement is for the convenience of GSG probe testing. The GSG probe includes two G probes and one S probe, that is, two ground probes and one signal probe, and the spacing between adjacent probes is the same. During the test, the GSG probe is inserted into the GSG electrode. Exemplarily, the probe spacing of the GSG probe is 50 microns, that is, the spacing between adjacent probes is 50 microns.

[0048] In some embodiments, one end of the first signal electrode is connected to the signal line, and the line width is the same as the signal line. Since the GSG electrode is arranged at the edge of the chip, usually the end of the first signal electrode away from the edge of the chip is connected to the signal line. The line width of the first signal electrode is the same as the line width of the signal line, thus, the first signal electrode can also be regarded as an extension of the signal line.

[0049] In some embodiments, the distance between the first signal electrode and the edge of the body substrate is greater than the length of the second signal electrode. In another embodiment, the distance between the first ground electrode, the first signal electrode and the second ground electrode and the edge of the body substrate is greater than the length of the second signal electrode.

[0050] It should be noted that in the plane of the front side of the substrate, the dimension perpendicular to the chip edge direction is the length, and the dimension parallel to the chip edge direction is the width. The edge distance and length are defined here to reserve enough space for setting the second signal electrode. The second signal electrode is described in detail below.

[0051] In some embodiments, the second signal electrode is disposed between the first signal electrode and an edge of the body substrate and connected to the other end of the first signal electrode for multi-wire bonding.

[0052] Exemplarily, the multi-wire bonding is a double-wire bonding.

[0053] Exemplarily, the second signal electrode is connected to an end of the first signal electrode that faces an edge of the chip.

[0054] It should be noted that the second signal electrode is used for multi-wire bonding, that is, multiple bonding wires need to be bonded to the second signal electrode later. The width of the first signal electrode is the same as the signal line, which is usually narrower. For example, the width of the first signal electrode is 40 microns, and the diameter of the bonding wire is 25 microns, so only a single bonding wire can be bonded. On the one hand, the second signal electrode is set between the probe test position and the edge of the chip, and the size of the second signal electrode is no longer limited by the probe spacing, and the size can be increased.

[0055] Furthermore, in some embodiments, the width of the second signal electrode is greater than the width of the first signal electrode and greater than the sum of the diameters of the bonding wires, and the length of the second signal electrode is greater than the diameter of any bonding wire. Thus, the width of the second signal electrode is sufficient to bond multiple bonding wires, and the length is sufficient to bond a single row of bonding wires, so multiple bonding wires can be bonded to the second signal electrode.

[0056] Furthermore, the second signal electrode is in a square shape and the length of the second signal electrode is also greater than the sum of the diameters of the bonding wires.

[0057] Figure 5 is a schematic diagram of the structure of the GSG electrode probe test provided by an embodiment of the present invention; Figure 5 , the GSG probe is inserted into the first ground electrode, the first signal electrode and the second ground electrode to perform terahertz chip testing.

[0058] Figure 6 is a schematic diagram of the structure of the double wire bonding provided by the embodiment of the present invention; Figure 6 The terahertz core can be connected to the microstrip line of the RF board. One end of the bonding wire is connected to the second signal electrode, and the other end is connected to the microstrip line. The second signal electrode can be double-wire bonded.

[0059] The GSG electrode of the embodiment of the present invention includes a first signal electrode, a second signal electrode, a first ground electrode and a second ground electrode. The first ground electrode, the first signal electrode and the second ground electrode arranged at equal intervals on the edge of the substrate are used for GSG probe testing. The electrode size used for probe testing can be consistent with the size of the structure before improvement to maintain the consistency and accuracy of probe testing. The second signal electrode is extended toward the edge of the substrate to set the first signal electrode, and the second signal electrode is used for bonding. Thus, in the GSG electrode, the first signal electrode used for GSG probe testing and the second signal electrode used for bonding are located at different positions. Because the probe test position and the bonding position in the GSG electrode are separated, and the second signal electrode is not set between the two ground electrodes, the size of the second signal electrode is not limited by the probe spacing, and the size of the second signal electrode can be increased to match the multi-wire bonding. Multiple bonding wires are connected in parallel with each other, and the parasitic inductance is reduced after parallel connection, and the restrictions on the length and height of the bonding wires are reduced, and the difficulty of the bonding process is reduced. Regarding the reduction of parasitic inductance of multiple bonding wires, the following is a detailed description.

[0060] Figure 7 is a schematic diagram of a single-wire bonding equivalent circuit model provided by an embodiment of the present invention; Figure 8 is a schematic diagram of a double-wire bonding equivalent circuit model provided by an embodiment of the present invention; Figure 7 , 8 , the ideal equivalent circuit models of single-wire bonding and double-wire bonding with a length of 100 μm and a diameter of 25 μm are given.

[0061] The bonding wire length of terahertz frequency chips is generally no more than 100 microns, and the corresponding equivalent inductance value is about 0.1nH. If double-wire bonding can be achieved while meeting the requirements of on-wafer probe testing, the series parasitic inductance can be reduced by half, which will effectively improve the input return loss and insertion loss.

[0062] Fig. 9 is a schematic diagram for comparing insertion loss simulation curves provided by an embodiment of the present invention; Fig.10 is a schematic diagram of comparison of return loss simulation curves provided by an embodiment of the present invention; Fig. 9 , 10 , the input return loss and insertion loss simulation curves under the above equivalent circuit are given. It can be found that in the terahertz frequency band (above 100GHz), the transition method of two 100-micron bonding wires is compared with the transition method of one 100-micron bonding wire: the input return loss is improved by 3dB, and the insertion loss is improved by 1-2dB.

[0063] Fig.11 is another improved GSG electrode structure schematic diagram provided by an embodiment of the present invention; Fig.11In a possible implementation, a third signal electrode is further provided between the first signal electrode and the second signal electrode; the third signal electrode is a trapezoid, wherein the length of the upper base of the trapezoid is equal to the width of the first signal electrode, and the length of the lower base of the trapezoid is equal to the width of the second signal electrode.

[0064] Exemplarily, the distance between the first signal electrode and the edge of the body substrate is greater than the sum of the length of the second signal electrode and the height of the trapezoid.

[0065] Exemplarily, the following improvements are made on the basis of conventional pressure points: a larger pressure point is extended outward from the middle signal pressure point of the commonly used pressure points. The pressure point is a special-shaped pad with six sides and a maximum width of 80 microns near the edge of the chip. It extends inward by 40 microns and then passes through a gradient area with a length of 40 microns to be cascaded with the conventional signal pressure point with a width of 40 microns.

[0066] The following embodiments illustrate the grounding method of the lower ground electrode.

[0067] In a possible implementation, a metal ground hole is further provided below the first ground electrode and the second ground electrode; a back ground layer is further provided on the back side of the main substrate; and the metal ground hole is used to connect the ground electrode and the back ground layer.

[0068] It should be noted that the first grounding electrode and the second grounding electrode can also be grounded by gold wire bonding. The specific grounding method is not limited. The following provides another improvement of the grounding electrode.

[0069] In a possible implementation, a third ground electrode is further disposed on the front side of the main body substrate; the third ground electrode is connected to the first ground electrode and the second ground electrode; a portion of the third ground electrode is disposed between the second signal electrode and the edge of the main body substrate.

[0070] For example, the following improvements are made on the basis of conventional pressure points: the upper surface metal of the ground pads on both sides of the chip is connected through the outer end, providing an additional common ground channel. And during assembly bonding, the gold wire can directly cross the connection on the upper surface of the ground pad. In addition, this 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.

[0071] The present invention provides a terahertz component, including a microstrip transmission line and a terahertz chip provided in any possible implementation manner as described above.

[0072] The present invention provides a method for preparing a terahertz component, which is applied to preparing the above-mentioned terahertz component, and the method comprises: preparing a terahertz chip; inserting a GSG probe into a first ground electrode, a first signal electrode and a second ground electrode of the terahertz chip to test the terahertz chip; bonding a plurality of bonding wires to the second signal electrode of the tested terahertz chip to connect an external microstrip transmission line to prepare the terahertz component.

[0073] Exemplarily, the probe spacing of the GSG probe is 50 microns.

[0074] 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, characterized in that: The chip comprises: a main body substrate, a GSG electrode and a signal line; the GSG electrode is arranged at the edge of the front side of the main body substrate; The GSG electrode includes a first signal electrode, a second signal electrode, a first ground electrode, and a second ground electrode; The first ground electrode, the first signal electrode and the second ground electrode are arranged at equal intervals on the edge of the main substrate for GSG probe testing, and the distance from the edge of the main substrate is greater than the length of the second signal electrode; One end of the first signal electrode is connected to a signal line, and the line width is the same as that of the signal line; The second signal electrode is arranged between the first signal electrode and the edge of the main substrate, and is connected to the other end of the first signal electrode for multi-wire bonding; the width of the second signal electrode is greater than the width of the first signal electrode, and greater than the sum of the diameters of each bonding wire; the length of the second signal electrode is greater than the diameter of any bonding wire.

2. The terahertz chip according to claim 1, characterized in that: The multi-wire bonding is double-wire bonding.

3. The terahertz chip according to claim 1, characterized in that: The length of the second signal electrode is greater than the sum of the diameters of the bonding wires.

4. The terahertz chip according to claim 1, characterized in that: A third signal electrode is further provided between the first signal electrode and the second signal electrode; The third signal electrode is in the shape of a trapezoid, wherein the length of the upper base of the trapezoid is equal to the width of the first signal electrode, and the length of the lower base of the trapezoid is equal to the width of the second signal electrode.

5. The terahertz chip according to claim 1, characterized in that: A metal ground hole is also provided below the first ground electrode and the second ground electrode; A back grounding layer is also provided on the back side of the main body substrate; The metal ground hole is used to connect the ground electrode and the back ground layer.

6. The terahertz chip according to claim 1, characterized in that: A third grounding electrode is also provided on the front side of the main body substrate; The third grounding electrode is connected to the first grounding electrode and the second grounding electrode; A portion of the third ground electrode is disposed between the second signal electrode and an edge of the body substrate.

7. The terahertz chip according to claim 1, characterized in that: The second signal electrode is in a square shape.

8. The terahertz chip according to claim 1, characterized in that: The first signal electrode and the signal line are in the shape of bars; The first ground electrode and the second ground electrode are rectangular in shape.

9. A terahertz component, characterized in that: It comprises a microstrip transmission line and the terahertz chip according to any one of claims 1 to 8.

10. A method for preparing a terahertz component, characterized in that: Applied to preparing the terahertz component as claimed in claim 9, the method comprises: Preparing the terahertz chip; Inserting a GSG probe on a first ground electrode, a first signal electrode, and a second ground electrode of the terahertz chip to test the terahertz chip; After the test, a plurality of bonding wires are bonded to the second signal electrode of the terahertz chip to connect an external microstrip transmission line, thereby preparing a terahertz component.

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