Terahertz waveguide probe

Abstract

The invention provides a terahertz waveguide probe, which comprises a probe bracket, a waveguide cavity, a microstrip piece and a signal transmission line, and is characterized in that a filtering structure, an isolation structure, a fan-shaped microstrip line, a suspended microstrip line and a coplanar waveguide structure are sequentially arranged in the microstrip piece along the transmission direction of an electric signal; the filtering structure is a novel CMRC filtering structure and is used for improving port isolation; the isolation structure is connected with the filtering structure and the conversion structure and is used for inhibiting leakage of the radio-frequency signal to the direct-current port; the conversion structure is a fan-shaped microstrip line, and the fan-shaped microstrip line is arranged in the waveguide cavity and converts a TE10 mode transmitted in the waveguide cavity into a quasi-TEM mode; the suspended microstrip line transmits a quasi TEM mode signal; the front end of the coplanar waveguide structure is provided with a needle tip, and the coplanar waveguide structure converts a quasi TEM mode into a coplanar waveguide TEM mode. The filter structure and the isolation structure are arranged in the microstrip piece, so that the port isolation degree is remarkably improved, broadband matching and efficient transmission are achieved through the guide probe, and the insertion loss and return loss of the terahertz waveguide probe are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chip testing, and in particular to a terahertz waveguide probe. Background Art

[0002] The terahertz probe is a key core component of the terahertz chip testing system. It can realize the interconnection between the chip to be tested and the testing instrument to avoid the influence of peripheral packaging on chip performance and maximize the performance of the chip to be tested.

[0003] Terahertz probes are mainly divided into two categories: coaxial probes and waveguide probes. Among them, coaxial probes use coaxial lines as input interfaces, and have the characteristics of wide working frequency bands, which can cover the frequency band from DC to terahertz. However, this type of probe requires an external bias device when testing the die, and the test system is complex; in addition, due to the limitations of the processing and manufacturing process, the current maximum frequency of coaxial probe products is only 220GHz, and it is very difficult to expand to higher frequency bands, which is difficult to meet the testing needs of terahertz chips in higher frequency bands. Waveguide probes use rectangular waveguides as input interfaces, and the operating frequency can cover a standard waveguide frequency band. At present, the highest frequency of related products has reached 1100GHz, and the bias device is embedded, which is convenient for die testing. However, due to the influence of processing technology and assembly accuracy, the insertion loss, service life and other performance of existing terahertz waveguide probe products are mutually restricted, which makes it difficult to meet the high-performance and long-life testing needs of terahertz chips. Taking the Infinity series and T-wave series probes of Formfactor Company in the United States as an example, the Infinity series probes in the 330GHz-500GHz frequency band have a long life, and the needle puncture life of the aluminum pad reaches 250,000 times, but the maximum insertion loss is as high as 8.0dB, and the minimum return loss is only 10dB; the T-wave series probes in the 330GHz-500GHz frequency band have an insertion loss better than 4.5dB, and a return loss better than 15dB; but the life of this series of probes is short, and the needle puncture life is less than 1,000 times. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a terahertz waveguide probe, comprising a probe holder, in which a waveguide cavity for transmitting a waveguide signal, a microstrip piece arranged perpendicularly to the waveguide cavity, and a signal transmission line for transmitting an electrical signal connecting a DC port and one end of the microstrip piece, wherein a filtering structure, an isolation structure, a fan-shaped microstrip line, a suspended microstrip line, and a coplanar waveguide structure are sequentially arranged in the microstrip piece along the transmission direction of the electrical signal;

[0005] The filtering structure is a new CMRC filtering structure, which is used to improve port isolation;

[0006] The isolation structure connects the filtering structure and the conversion structure, and is used to suppress the leakage of the radio frequency signal to the DC port;

[0007] The conversion structure is a fan-shaped microstrip line, which is arranged in a waveguide cavity to convert the TE transmitted in the waveguide cavity into 10 mode conversion to quasi-TEM mode;

[0008] The suspended microstrip line transmits a quasi-TEM mode signal;

[0009] A needle tip is arranged at the front end of the coplanar waveguide structure, and the coplanar waveguide structure converts the quasi-TEM mode into a coplanar waveguide TEM mode.

[0010] Specifically, the isolation of the filtering structure is better than -25dB within the operating frequency range of the waveguide probe.

[0011] Specifically, the filtering structure is a fan-shaped branch CMRC filtering structure, each group of CMRC filtering units includes a thin narrow microstrip line arranged along the signal transmission direction and four fan-shaped branches of the same shape, the width of the narrow microstrip line is Y1, the center of the fan-shaped branch is located in the narrow microstrip line, and is symmetrically arranged with the narrow microstrip line as the symmetry axis, one side of the fan-shaped branch is perpendicular to the narrow microstrip line, which is the widest part of the group of branches, with a width of Y2, and the other side faces the adjacent fan-shaped branch on the same side, the angle between the two sides is θ, there is a gap with a width of X1 between the adjacent fan-shaped branches on the same side, and there is a gap with a width of X2 between each group of CMRC filtering units.

[0012] Specifically, the filtering structure is a C-shaped CMRC filtering structure, each group of CMRC filtering structures includes a transverse narrow microstrip line, a longitudinal narrow microstrip line perpendicular to the transverse narrow microstrip line, and two C-shaped branches connected to the longitudinal narrow microstrip line, the opening of the C-shaped branch is arranged toward the transverse narrow microstrip line, and there is a gap between the two ends of the C-shaped branch and the transverse narrow microstrip line.

[0013] Specifically, the isolation structure includes a matching structure and a high impedance line arranged in sequence, the matching structure is a sheet-shaped rectangular structure, and the high impedance line is arranged along the same side edge of the matching structure and the fan-shaped microstrip line, and is respectively connected to a corner of the matching structure and the fan-shaped microstrip line.

[0014] Specifically, the microstrip sheet uses ultra-thin high-resistance silicon as a substrate, and the filtering structure, isolation structure, conversion structure, suspended microstrip line and coplanar waveguide structure are made of a gold-plated layer.

[0015] Specifically, a hard metal protective layer is plated on the surface of the gold-plated layer at the contact portion between the tip of the needle tip and the chip.

[0016] Specifically, the thickness of the ultra-thin high-resistance silicon is 10µm-30µm.

[0017] Specifically, the probe holder includes an upper probe holder and a lower probe holder, the waveguide cavity includes a first waveguide section arranged in the upper probe holder and a second waveguide section arranged in the lower probe holder, and a short-circuit surface is arranged at a terminal of the second waveguide section.

[0018] Specifically, the rear end of the microstrip piece is arranged on the lower probe bracket, and a clamping structure is arranged on both sides of the microstrip line suspended at the front end of the microstrip piece, an arc-shaped transition structure is arranged in the clamping structure, and a clamping groove is arranged in the lower probe bracket. The clamping structure is arranged in the clamping groove, so that the microstrip piece is clamped between the upper probe bracket and the lower probe bracket.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention sets a filtering structure and an isolation structure in the microstrip sheet to significantly improve the port isolation, and optimizes the conversion structure between three different types of transmission lines, namely waveguide, suspended microstrip line, and coplanar waveguide, so that the waveguide probe can achieve broadband matching and efficient transmission, greatly improving the insertion loss and return loss of the terahertz waveguide probe.

[0021] 2. The microstrip sheet of the present invention uses ultra-thin high-resistance silicon as the substrate of the probe microstrip sheet, optimizes the external structure of the high-resistance silicon, and provides a clamping structure with an arc-shaped transition structure, which effectively improves the mechanical properties of the microstrip sheet. A gold-plated layer is provided on the substrate, and a hard metal protective layer is provided on the surface of the gold-plated layer at the needle tip without deteriorating the electrical properties of the terahertz waveguide probe, which effectively prolongs the service life of the waveguide probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure assembly of the waveguide probe of the present invention;

[0023] Figure 2 is a cross-sectional view of a waveguide probe of the present invention;

[0024] Figure 3 This is an enlarged view of part A of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of the probe microstrip sheet of the present invention in the first direction;

[0026] Figure 5 This is a schematic diagram of the structure of the probe microstrip sheet of the present invention in the second direction;

[0027] Figure 6 It is a schematic diagram of a first embodiment of a novel CMRC filter structure of the present invention;

[0028] Figure 7 The equivalent circuit of the first embodiment of the novel CMRC filter structure of the present invention;

[0029] Figure 8 It is a schematic diagram of a second embodiment of the novel CMRC filter structure of the present invention;

[0030] Fig. 9 The equivalent circuit of the second embodiment of the novel CMRC filter structure of the present invention;

[0031] Fig.10 It is a partial cross-sectional view of the needle tip of the present invention.

[0032] Figure numerals: 1. probe holder; 11. upper probe holder; 111. first upper probe holder; 112. second upper probe holder; 12. lower probe holder; 2. microstrip sheet; 21. novel CMRC filtering structure; 22. matching structure; 23. high impedance line; 24. fan-shaped microstrip line; 25. suspended microstrip line; 26. coplanar waveguide structure; 261. needle tip; 262. signal guide strip; 263. ground electrode; 264. clamping structure; 27. substrate; 28. gold-plated layer; 29. ​​hard metal protective layer; 3. waveguide cavity; 31. first waveguide section; 32. second waveguide section. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The specific implementation of the present invention is described in detail below in combination with specific embodiments.

[0034] like Figure 1-Figure 10 As shown, the present invention provides a terahertz waveguide probe, including a probe holder 1, in which a waveguide cavity 3 and a microstrip plate 2 vertically arranged to the waveguide cavity 3 are arranged. The probe can work in the terahertz frequency band, and the port isolation is significantly improved by designing a filtering structure and an isolation structure. In combination with a conversion structure with efficient conversion of signal transmission modes, the waveguide probe can achieve broadband matching and efficient transmission, thereby improving the insertion loss and return loss of the terahertz waveguide probe.

[0035] In the waveguide probe, there is provided a waveguide signal transmission path which is input through the waveguide cavity 3, output to the needle tip 261 through the microstrip piece 2 and interconnected with the chip to be tested for on-chip testing, and an electrical signal transmission path which is input through the SSMP adapter, output to the needle tip 261 through the signal transmission line and the microstrip piece 2 and interconnected with the chip to be tested for die parameter testing.

[0036] like Figure 1-Figure 3As shown, the probe holder 1 includes an upper probe holder 11 and a lower probe holder 12, the upper probe holder 11 includes a first upper probe holder 111 and a second upper probe holder 112, a waveguide cavity 3 is arranged in the probe holder 1, and the waveguide cavity 3 includes a first waveguide section 31 arranged in the upper probe holder 11 and a second waveguide section 32 arranged in the lower probe holder 12. The microstrip sheet 2 is arranged vertically to the waveguide cavity 3, one end of the microstrip sheet 2 is connected to the lower probe holder 12, and the other end is suspended and extends from the front end of the probe holder 1. TE 10 The mode is transmitted in the waveguide cavity 3, and the terminal of the second waveguide section 32 is provided with a short-circuit surface so that the TE 10 The mode forms a standing wave in the waveguide cavity 3. The microstrip patch 2 is located at the antinode of the standing wave, facing the short-circuit surface of the waveguide, and is about a quarter wavelength away from the short-circuit surface. The superposition of the reflected wave and the incident wave makes the field intensity at the microstrip patch 2 maximum, so that the microstrip patch 2 obtains the highest coupling efficiency and reduces the transmission loss, ensuring that the probe can couple the electric field energy in the waveguide to the suspended microstrip patch 2 to the greatest extent.

[0037] like Figure 4 and Figure 5 As shown, the microstrip sheet 2 uses ultra-thin high-resistance silicon as a substrate 27, and a filter structure, an isolation structure, a conversion structure, a suspended microstrip line 25, and a coplanar waveguide structure 26 made of a gold-plated layer 28 are arranged on the surface of the ultra-thin high-resistance silicon along the electrical signal transmission path. The filter structure is connected to the signal transmission line, and a needle tip 261 is arranged at the front end of the coplanar waveguide structure 26. The waveguide signal is transmitted to the needle tip 261 via the conversion structure, the suspended microstrip line 25, and the coplanar waveguide structure 26, and the electrical signal is transmitted to the needle tip 261 via the filter structure, the isolation structure, the conversion structure, the suspended microstrip line 25, and the coplanar waveguide structure 26.

[0038] Silicon has a high elastic modulus. After being thinned, the microstrip strip 2 can produce sufficient deformation when pierced with a needle. The thickness of ultra-thin high-resistance silicon is 10µm-30µm, which can reduce the contact resistance and maintain sufficient rigidity without breaking. It can also return to its original state after being pierced with a needle and has good mechanical properties. The gold-plated layer 28 minimizes the impact of microwave signals due to the superior conductivity of gold, and is not easily oxidized by air, ensuring that the microstrip strip 2 can maintain good conductivity and stability during long-term use. However, since the gold layer is soft and easy to wear, in order to further increase the service life of the microstrip strip 2, such as Fig.10 As shown, at the contact portion between the needle tip of the signal conductor 262 and the ground electrode 263 and the chip, a hard metal protective layer 29 is plated on the surface of the gold-plated layer 28. The hard metal protective layer 29 is in direct contact with the chip. The hard metal protective layer 29 can be made of nickel, rhodium, tungsten, chromium, etc. Although the conductivity of the hard metal protective layer 29 is not as good as that of gold and its ductility is not good, a small area of ​​hard metal protective layer 29 is plated at the needle tip 261, which can improve the wear resistance of the needle tip while avoiding the deterioration of electrical performance.

[0039] The rear end of the microstrip sheet 2 is arranged on the lower probe bracket 12, and a clamping structure 264 is arranged on both sides of the microstrip line 25 suspended at the front end of the microstrip sheet 2, and an arc-shaped transition structure is arranged in the clamping structure 264, and a clamping groove is arranged in the lower probe bracket. The clamping structure 264 is arranged in the clamping groove and clamped between the upper probe bracket 11 and the lower probe bracket 12. The arc-shaped transition structure is designed in the clamping structure 264, so that the stress is gradually distributed along the arc, avoiding the stress concentration in a certain point or a small area, and effectively improving the service life of the microstrip sheet 2.

[0040] The filter structure adopts a new CMRC (Compact Microstrip Resonating Cell) filter structure, and the isolation of the filter structure in the stopband range is better than -25dB at least within the working range of the probe. Further, as a preferred embodiment of the present invention, taking a probe with an operating frequency of 330GHz-500GHz as an example, the isolation of the filter structure is better than -60dB within 330-500GHz. At least one group of CMRC filter units is provided in the new CMRC filter structure 21 to improve the port isolation.

[0041] As a first embodiment of the novel CMRC filter structure 21, Figure 6 As shown, a three-stage fan-shaped branch CMRC filter structure 21 is adopted, each group of CMRC filter units includes a thin narrow microstrip line arranged along the signal transmission direction and four fan-shaped branches of the same shape, the width of the narrow microstrip line is Y1, the center of the fan-shaped branch is located in the narrow microstrip line, and it is symmetrically arranged with the narrow microstrip line as the symmetry axis, one side of the fan-shaped branch is perpendicular to the narrow microstrip line, which is the widest part of the group of branches, with a width of Y2, equivalent to capacitor C2, and the other side faces the adjacent fan-shaped branch on the same side, the angle between the two sides is θ, and there is a gap with a width of X1 between the adjacent fan-shaped branches on the same side, each group of CMRC filter units is connected by a narrow microstrip line with a width of X2, which is equivalent to inductor L1, the adjacent fan-shaped branches are equivalent to capacitor C1, and the narrow microstrip line is equivalent to inductor L2. The equivalent circuit of each group is as follows Figure 7 As shown, by optimizing the dimensions of X1, X2, Y1, Y2, and θ in the figure, the stopband frequency range of the operation is improved, so that it has a wider stopband range and port isolation. The fan-shaped branch CMRC filter structure 21 has better broadband characteristics than the traditional CMRC structure and can effectively improve the intermediate frequency isolation.

[0042] As a second embodiment of the novel CMRC filter structure 21, Figure 8As shown, a three-stage C-shaped branch CMRC filter structure 21 is adopted. Each group of CMRC filter structures 21 includes a transverse narrow microstrip line, a longitudinal narrow microstrip line perpendicular to the transverse narrow microstrip line, and two C-shaped branches connected to the longitudinal narrow microstrip line. The longitudinal narrow microstrip is connected to the center of the C-shaped branch. The opening of the C-shaped branch is set toward the transverse narrow microstrip line. There is a narrow gap between the two ends of the C-shaped branch and the transverse narrow microstrip line. The gap between the two ends of the C-shaped branch and the transverse narrow microstrip line is equivalent to the capacitor C3, the transverse narrow microstrip line is equivalent to the inductor L3, and the longitudinal narrow microstrip line is equivalent to the inductor L4. The equivalent circuit diagram of each group is as shown in FIG. Fig. 9 shown.

[0043] The use of the two new compact CMRC filter structures can effectively reduce the area of ​​the microstrip sheet.

[0044] The isolation structure includes a matching structure 22 and a high impedance line 23 arranged in sequence, which suppresses the leakage of the RF signal to the DC port. The matching structure 22 is a sheet-shaped rectangular structure. The matching structure 22 and the filtering structure 23 are connected by an inductive fine strip line. The matching structure 22 adopts a capacitive rectangular structure matching, which has a good filtering effect and realizes accurate impedance matching. The high impedance line 23 connects the matching structure 22 and the fan-shaped microstrip line 24. The high impedance line 23 is arranged along the same side edge of the matching structure 22 and the fan-shaped microstrip line 24, and is respectively connected to a corner of the matching structure 22 and the fan-shaped microstrip line 24. The high impedance line 23 adopts this connection method to prevent the signal from leaking to the intermediate frequency port.

[0045] Waveguide signals usually have high power and frequency. If the waveguide signals leak to the DC port during chip testing, the accuracy of the test results will be affected. Waveguide signals usually have high power and frequency, and may also damage the DC port and equipment. The present invention adopts a novel CMRC filter structure 21 and an isolation structure to achieve broadband matching and suppress the leakage of RF signals to the DC port, significantly improving the isolation of the port.

[0046] The conversion structure uses a fan-shaped microstrip line 24, which is arranged in the waveguide cavity 3 and is perpendicular to the electric field direction in the waveguide cavity 3. 10 The conversion structure adopts a fan-shaped design. The fan-shaped microstrip input impedance usually changes slowly with frequency, which is more conducive to the design of circuit matching.

[0047] The suspended microstrip line 25 connects the fan-shaped microstrip line 24 and the coplanar waveguide structure 26, and transmits the quasi-TEM mode to the coplanar waveguide structure 26. The quasi-TEM mode is converted into the coplanar waveguide TEM mode in the coplanar waveguide structure 26. At least one signal guide strip 262 (S) and at least two ground electrodes 263 (G) are provided in the coplanar waveguide structure 26. A needle tip 261 is provided at the ends of the signal guide strip 262 and the ground electrode 263. The number of the signal guide strip 262 and the ground electrode 263 can be adjusted according to the test requirements, such as GSG, GSSG, GSGSG, etc. Taking the GSG structure as an example, the ground electrodes 263 are symmetrically provided on both sides of the signal guide strip 262. The ground electrodes 263 provide a low-impedance loop path for the high-frequency signal and form a shielding layer, which helps to reduce the interference of the external electromagnetic field on the transmission signal, and at the same time reduce the radiation of the signal to the external environment, maintain the impedance matching of the transmission line, and reduce the signal reflection and loss, so as to ensure the stability and accuracy of the microwave signal during the transmission process.

[0048] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A terahertz waveguide probe, comprising a probe holder, in which a waveguide cavity for transmitting a waveguide signal, a microstrip sheet arranged perpendicular to the waveguide cavity, and a signal transmission line connecting a DC port and one end of the microstrip sheet for transmitting an electrical signal are arranged, characterized in that: A filtering structure, an isolation structure, a fan-shaped microstrip line, a suspended microstrip line and a coplanar waveguide structure are sequentially arranged in the microstrip sheet along the transmission direction of the electrical signal; The filtering structure is a new CMRC filtering structure, which is used to improve port isolation; The isolation structure connects the filtering structure and the conversion structure, and is used to suppress the leakage of the radio frequency signal to the DC port; The conversion structure is a fan-shaped microstrip line, which is arranged in a waveguide cavity to convert the TE transmitted in the waveguide cavity into 10 mode conversion to quasi-TEM mode; The suspended microstrip line transmits a quasi-TEM mode signal; A needle tip is arranged at the front end of the coplanar waveguide structure, and the coplanar waveguide structure converts the quasi-TEM mode into a coplanar waveguide TEM mode.

2. The terahertz waveguide probe according to claim 1, characterized in that: The isolation of the filtering structure is better than -25dB within the operating frequency range of the waveguide probe.

3. The terahertz waveguide probe according to claim 2, characterized in that: The filtering structure is a fan-shaped branch CMRC filtering structure, each group of CMRC filtering units includes a thin narrow microstrip line arranged along the signal transmission direction and four fan-shaped branches of the same shape, the width of the narrow microstrip line is Y1, the center of the fan-shaped branch is located in the narrow microstrip line, and the fan-shaped branch is symmetrically arranged with the narrow microstrip line as the symmetry axis, one side of the fan-shaped branch is perpendicular to the narrow microstrip line, which is the widest part of the group of branches, with a width of Y2, and the other side faces the adjacent fan-shaped branch on the same side, the angle between the two sides is θ, there is a gap with a width of X1 between the adjacent fan-shaped branches on the same side, and there is a gap with a width of X2 between each group of CMRC filtering units.

4. The terahertz waveguide probe according to claim 2, characterized in that: The filter structure is a C-shaped CMRC filter structure, each group of CMRC filter structures includes a transverse narrow microstrip line, a longitudinal narrow microstrip line perpendicular to the transverse narrow microstrip line, and two C-shaped branches connected to the longitudinal narrow microstrip line, the opening of the C-shaped branch is arranged toward the transverse narrow microstrip line, and there is a gap between the two ends of the C-shaped branch and the transverse narrow microstrip line.

5. The terahertz waveguide probe according to claim 1, characterized in that: The isolation structure includes a matching structure and a high impedance line arranged in sequence. The matching structure is a sheet-shaped rectangular structure. The high impedance line is arranged along the same side edge of the matching structure and the fan-shaped microstrip line and is respectively connected to a corner of the matching structure and the fan-shaped microstrip line.

6. The terahertz waveguide probe according to claim 1, characterized in that: The microstrip sheet uses ultra-thin high-resistance silicon as a substrate, and the filtering structure, isolation structure, conversion structure, suspended microstrip line and coplanar waveguide structure are made of a gold-plated layer.

7. The terahertz waveguide probe according to claim 6, characterized in that: A hard metal protective layer is plated on the surface of the gold-plated layer at the contact point between the tip of the needle and the chip.

8. The terahertz waveguide probe according to claim 6, characterized in that: The thickness of the ultra-thin high-resistance silicon is 10µm-30µm.

9. The terahertz waveguide probe according to claim 1, characterized in that: The probe holder comprises an upper probe holder and a lower probe holder, the waveguide cavity comprises a first waveguide section arranged in the upper probe holder and a second waveguide section arranged in the lower probe holder, and a terminal of the second waveguide section is provided with a short-circuit surface.

10. The terahertz waveguide probe according to claim 9, characterized in that: The rear end of the microstrip piece is arranged on the lower probe bracket, and clamping structures are arranged on both sides of the microstrip line suspended at the front end of the microstrip piece, an arc-shaped transition structure is arranged in the clamping structure, and a clamping groove is arranged in the lower probe bracket. The clamping structure is arranged in the clamping groove, so that the microstrip piece is clamped between the upper probe bracket and the lower probe bracket.

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