Hybrid structure for generating and receiving ultra wide band terahertz for semiconductor device

Abstract

An ultra-wideband hybrid structure (100) for transmitting high-frequency electrical signals, the structure comprising a substrate (110), a high-speed semiconductor substrate (105) connected to the substrate (110) of the ultra-wideband structure (100), an electrically conductive interface (115) established between the substrate (110) and the high-speed semiconductor substrate (105), an ultra-high-speed device, a structure (DRW) and a structure (TSA) connected to the substrate (110), the electrically conductive interface (115) being connected to the substrate (110) of the ultra-wideband structure (100). The ultra-high-speed device defines a first access port (P1) and is established on a high-speed semiconductor substrate (105), a dielectric waveguide structure (DRW) defining a second access is established on the substrate (110) and the high-speed semiconductor substrate (105), the structure (DRW) comprising a tapered end connectable to the first access port (P1) of the ultra-high-speed device, a metal waveguide structure (TSA) providing a low-pass characteristic interconnect, a metal waveguide structure (TSA) is established on a substrate (110) and a high speed semiconductor substrate (105), where the metal waveguide structure (TSA) comprises a metal waveguide pattern defining a tapered coupler connected to an access port (P1) of a high speed circuit or component.

Description

Technical Field

[0001] The present invention relates to a novel structure that can generate and detect ultra-wideband radio frequency signals using semiconductor devices with two significant features: first, the structure of semiconductor material is shaped to form a radio frequency (RF) waveguide, and second, the structure is produced by hybrid integration of a small tube core (die) of III-V semiconductor material and a silicon material with a larger size, the small tube core is used to generate the RF active device and a part of the transmitting antenna, and the silicon material is used to generate the rest of the antenna and other passive RF components. Background Art

[0002] Terahertz systems operate in a spectral range covering a frequency band between 0.1 THz and 10 THz, which lies between the microwave and optical bands. Different technologies for generating and detecting terahertz signals require the integration of components into a die (unpackaged bare chip), which can be electronic or photonic. Photonic-based systems require photoelectric converters, where the active components of the system are most commonly ultrafast photodiodes (mainly pin photodiodes PIN-PD (pi-nphotodiode) and single-carrier photodiodes UTC-PD (uni-traveling-carrierphotodiode)) and low-temperature-grown photoconductive antennas (LTG-PCA) opto-mixers, which are made using III-V semiconductor compound alloys. There is also a wide range of electronic-based components, typically Gunn diodes, IMPATT diodes, Resonant-Tunneling Diodes (RTDs), and varactor Schottky diode multipliers, which generate high frequencies in the form of higher harmonics from a microwave reference source.

[0003] The semiconductor material substrate most commonly used to make photonic and electronic devices is indium phosphide (InP), a III-V semiconductor compound in which the highest operating frequencies have been achieved and is the preferred substrate for terahertz systems. However, the main drawbacks of this material are its extreme brittleness and its high cost.

[0004] These characteristics have a strong impact on the size of the die, especially for terahertz generation and reception devices, where in addition to components (with micrometer size range), it is desirable to integrate RF antennas with larger footprints (with millimeter size range). The substrate size cannot fall below a minimum size (>0.5x0.2 mm 2 ) so that the device can be handled during assembly, nor is it recommended to be larger than a maximum size (<12mm x 6mm) because of the brittleness of the material. Chips with sizes outside these limits are of course possible, at the expense of considerably higher assembly costs and lower yields. These limitations also lead to the fact that for systems operating in the lower bands of the spectrum (i.e., the microwave range from 3 GHz to 30 GHz, or the millimeter wave range from 30 GHz to 300 GHz), the die chip area is insufficient for monolithic integration of the antenna on the substrate used for the component.

[0005] Figure 1 A current method of assembling a chip die and an antenna is shown, showing a 3D model of an assembly (50) comprising an optical fiber aligned with an optical input end of an ultrafast photodiode (PD (photodiode) chip), wherein the electrical contact pads of the ultrafast photodiode excite a planar tapered slot antenna (Tapered-Slot Antenna, TSA) through a microwave access port (excitation port 1). Specifically, Figure 1 It is shown that in InP (ε r =12.4) and connected to a high-speed photodiode device on a 110RT / Duroid 5880 low-k substrate (ε r =2.2). The size of the antenna prevents its integration on an InP substrate and then implementation in a suitable RF substrate, which makes the electrical interconnection between the ultrafast photodiode and the antenna extremely critical, especially when the desired operating frequency range extends to higher frequency bands.

[0006] Among the different interconnect technologies currently available, the most common in the electronics industry is gold wire bonding. Figure 2 A photograph of an InP integrated ultrafast photodiode chip (200) is shown, wherein its electrical contact pads are connected to the access port of the antenna by gold wire bonds. However, the gold wire series parasitic inductance (partially mitigated by using two bond wires in each connection) represents a limit to the maximum operating frequency.

[0007] Another difficulty with interconnections between the component die and the antenna RF substrate is the difference in dielectric constant between the substrates. The higher refractive index die generates reflections at this interface, which is particularly harmful for high-frequency signals. These reflections mean that part of the signal returns to the transmitting device, reducing the efficiency of the transmitter module.

[0008] The present invention overcomes the above-mentioned limitations and disadvantages. Summary of the invention

[0009] The present invention provides a solution to exploit the full bandwidth of ultra-wideband antennas driven by ultra-high-speed semiconductor devices, capable of combining different substrates, overcoming the current limitations of available electrical interconnects that limit the bandwidth of terahertz and sub-terahertz systems.

[0010] Thus, the present invention represents a new structure for ultra-high-speed devices based on hybrid dielectric-conductor waveguides that operate from direct-current (DC) to at least 300 GHz. The present invention proposes an ultra-wideband hybrid structure optimized for high-frequency electrical signals that can operate up to 340 GHz and can be designed to achieve higher frequencies by changing the thickness and / or dielectric constant of the substrate. The ultra-wideband structure allows coupling of high-frequency signals from high-speed circuits or components processed on high-speed semiconductor substrates (such as indium phosphide) that may be limited in size (that is, there are restrictions on their size that prevent the integration of large-size components, i.e., broadband waveguides or antennas, such as tapered two-wire metal waveguides) due to technology, processing or handling reasons. The ultra-wideband structure solves this problem and achieves high-performance radiation of high-frequency signals. Thus, as FIG. 4A to FIG. 4D As shown, the ultra-wideband structure according to the present invention allows most signals to be coupled to the single mode at all frequencies within the operating bandwidth.

[0011] The main aspects of the hybrid structure according to the invention are:

[0012] A dielectric waveguide excited in a single-mode manner performs coupling of signals from / to the component die chip in a high-frequency band. This dielectric waveguide structure includes a high-pass filter characteristic so that frequencies above a low cutoff frequency (f CL ) signals can be electrically interconnected. The dielectric waveguide comprises a tapered end facing an access port (P1) of an ultra-high-speed semiconductor device (electronic or optoelectronic) fabricated on a high dielectric constant substrate (e.g., indium phosphide) cut into a die chip. For example, the dielectric waveguide structure can be designed to operate in the following range: from a low cutoff frequency (f1) in the microwave range (i.e., between 3 GHz and 30 GHz) or in the millimeter wave range (i.e., between 30 GHz and 300 GHz) CL ) (e.g., operating frequency is 60 GHz), covering a wide frequency range extending to the terahertz wave range (i.e., between 300 GHz and 3000 GHz) and beyond. The dielectric waveguide structure can be built on a substrate (110) and a high-speed semiconductor substrate, wherein the structure includes a tapered end facing a first access port of the ultra-high-speed device.

[0013] The hybrid structure according to the invention also comprises a metal waveguide structure with low-pass filter characteristics, which enables the establishment of a metal electrical contact with the access port of an ultra-high-speed device, which allows the interconnection operation frequency range to start at low frequencies (i.e. preferably starting at DC, 0 Hz). This enables the realization of high cut-off frequencies (f CH ). For example, the metallic waveguide structure can be designed to operate in a range starting from 0 Hz and extending upward to the millimeter wave range (i.e., between 30 GHz and 300 GHz, for example, at an operating frequency of 100 GHz). In a preferred embodiment of broadband operation, such a metallic waveguide structure operates starting at a low frequency (i.e., starting from DC at 0 Hz) and extending above the low cut-off frequency (f CH >f CL , for example, a frequency range above 60 GHz in the previous example).

[0014] A metal waveguide structure, which can be built on a substrate and a high-speed semiconductor substrate, wherein the metal waveguide structure includes a metal waveguide pattern, which defines a tapered coupler, preferably a tapered slot antenna (Tapered Slot Antenna) "TSA", which surrounds the tapered end of the dielectric waveguide structure and is connected to the first access port (P1) of the ultra-high-speed device.

[0015] The hybrid structure according to the invention also comprises an electrical connection at low frequencies which can be made by different techniques (e.g. by bonding or conductive epoxy), which allows less restrictive requirements both in terms of space and electrical precision. The hybrid structure allows ultra-wideband interconnection of electrical signals between substrates of the same or different dielectric constants at high frequencies, wherein the change of the substrate is critical due to the introduction of discontinuities. By bridging the discontinuities, high frequency signal reflections are reduced, for example with conductive epoxy allowing coupling of the signal to the dielectric waveguide structure.

[0016] The hybrid structure according to the invention may also include an ultra-high speed device for which the semiconductor material of the chip die is structured to shape it into an RF waveguide which mitigates surface modes and maximizes RF power transfer between the ultra-high speed device and the metal waveguide structure at its contact pads. The semiconductor structure is made during its processing by an additional chemical etching (wet etching) process on the substrate of the ultra-high speed device in a single additional lithography step.

[0017] BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a better understanding of the above explanations and for the sole purpose of providing examples, some non-limiting drawings are included which schematically depict practical embodiments.

[0019] Figure 1 and Figure 2 An embodiment of the prior art is shown.

[0020] FIG. 3A to FIG. 3D Four different embodiments of the hybrid structure according to the invention are shown.

[0021] FIG. 4A to FIG. 4D The simulated electric field amplitude distributions at 10 GHz (a), 60 GHz (b), 140 GHz (c) and 300 GHz (d) are shown respectively.

[0022] Figure 5A and Figure 5B Shown are the S parameters obtained from the simulations performed.

[0023] Fig. 6A and Figure 6B The interconnection of an ultra-high speed device made on a high dielectric constant substrate with another substrate having the same or different dielectric constant, the other substrate having a rectangular shape or having a shape matching the metal pattern is shown. DETAILED DESCRIPTION

[0024] Figure 3A An example of an electrical interconnection according to the present invention is shown, and in particular, the figure shows an ultra-wideband hybrid structure (100) for high-frequency electrical signals. The structure (100) includes ultra-high-speed devices on a high-speed semiconductor substrate (105) (such as but not limited to indium phosphide "InP") and a substrate (110), and an electrical interconnection (115) established in a split point between the substrate (110) and the high-speed semiconductor substrate (105). The split point can be selected at a location where the frequency does not cause the hybrid structure (100) to degrade signal transmission in the electrical interconnection.

[0025] The high-speed semiconductor substrate (105) contains an ultra-high-speed device for generating or detecting high-frequency signals (i.e., in the millimeter wave and terahertz wave range). The electrical contact pads of the ultra-high-speed device define an access port (P1) at which the antenna is monolithically defined by its corresponding metallization features. Due to the size limitations of the high-speed semiconductor substrate (105) (e.g., indium phosphide), these metallizations do not have the dimensions required for the antenna to cover the entire frequency range and are limited to operating above the cut-off frequency. However, as the antenna is monolithically integrated on the high-speed semiconductor substrate (105), the interface between the ultra-high-speed device and the antenna is optimized to operate at the highest frequency. As an example, Figure 3AAn edge-illuminated optical hybrid device (ie, a waveguide-accessed photodiode) illuminated by an optical fiber (130) is shown as an ultra-high speed device.

[0026] Furthermore, when the optical fiber (130) provides edge optical illumination, the ultra-wideband hybrid structure (100) includes an optical waveguide (125) between the optical fiber (130) and the waveguide access photodiode.

[0027] The substrate (110) is a substrate (e.g., RF substrates such as quartz, laminates, and ceramics) or silicon that allows for larger sizes, on which larger metallization features corresponding to the TSA antenna or the two-wire metal waveguide can be built. The larger features of the antenna enable operation over a frequency range starting from the cutoff frequency of the antenna of the ultra-high-speed device in the high-speed semiconductor substrate (105) and extending to lower frequencies.

[0028] The substrate (110) is located next to the high-speed semiconductor substrate (105), matching the metallization corresponding to the TSA antenna on each substrate, and they are interconnected by electrical interconnects (115) (such as bonding or conductive epoxy resin, etc.). The electrical interconnects (115) avoid affecting the performance of the structure (100) at high frequencies, and an effective connection with low insertion loss is obtained. Therefore, both reflection and excitation of surface waves are mitigated.

[0029] The structure (100) further comprises a dielectric waveguide structure (DRW) comprising a second access port (P2) providing a high-pass characteristic interconnection operating in a high frequency range starting from a low cut-off frequency fCL in the microwave range or the millimeter wave range. The structure (DRW) is built on a substrate (110) and a high-speed semiconductor substrate (105), and the structure (DRW) comprises a tapered end facing or connected to the access port (P1) of the ultra-high-speed device.

[0030] The structure (100) further comprises a two-wire metal waveguide structure (TSA), the TSA providing a low-pass characteristic interconnection, operating in a low frequency range from DC to a high cut-off frequency fCH in the millimeter wave range, the structure (TSA) being built on a substrate (110) and a high-speed semiconductor substrate (105). The two-wire metal waveguide structure (TSA) is a tapered structure, i.e. it comprises a metal waveguide pattern defining a tapered coupler, preferably a tapered slot antenna "TSA" surrounding the tapered end of the dielectric waveguide structure (DRW) and located in the near field of the access port (P1) of the ultra-high-speed device.

[0031] A tapered double-wire metal waveguide structure (TSA) is built between a high-speed semiconductor substrate (105) and a substrate (110), wherein the larger features of the tapered double-wire metal waveguide are fabricated. By separating the tapered double-wire metal waveguide structure (TSA) between the substrate (110) and the high-speed semiconductor substrate (105), high frequencies are coupled to a dielectric waveguide (DRW) before reaching the electrical interconnection via an electrical interconnection (115) (e.g., conductive epoxy between the substrate (110) and the high-speed semiconductor substrate (105)), thereby avoiding reflections.

[0032] By appropriately selecting the split point between the substrate (110) and the high speed semiconductor substrate (105), each substrate containing complementary portions of the tapered twin-wire metal waveguide structure (TSA), the electrical interconnection between the respective metallizations of the tapered twin-wire metal waveguide structure (TSA) on each substrate (105, 110) will not interfere with the high frequencies already coupled to the dielectric waveguide structure (DRW).

[0033] The structure (100) also includes a second dielectric structure (120), preferably a cone structure etched on the high-speed semiconductor substrate (105). In some examples, the cone structure is a horn structure that can be built on one or both substrates (105, 110) and that mitigates surface waves.

[0034] therefore, FIG. 3A to FIG. 3D The invention discloses an interconnection of an ultra-high speed device (electronic or optoelectronic) fabricated on a high speed semiconductor substrate (105) to another substrate (110) which may include the same or different dielectric constant, with an electrical interconnect (115) (e.g. epoxy) established between the two substrates (105, 110). Various embodiments of the structure (100) include utilizing horizontal (edge) ( Figure 3A and Figure 3C ) and vertical ( Figure 3B and Figure 3D )illumination.

[0035] In order to mitigate the surface mode on the ultra-high speed device substrate, a second dielectric structure (120), preferably a pyramidal structure ( Figure 3C and Figure 3D ). This increases the amount of signal coupled in the fundamental mode of the dielectric waveguide (DRW), which makes it possible to bridge the discontinuity created by the substrate bonding with very few reflections.

[0036] FIG. 4A to FIG. 4D shows a horizontally illuminated photodiode ( Figure 4A , Figure 4C and Figure 4E) Figure 4A 10GHz, Figure 4B 60GHz in b, Figure 4C 140GHz and Figure 4D Figure 3. Simulated electric field amplitude distribution at 300 GHz in a photodiode made of substrate InP attached to an alumina substrate (Al2O3, εr=9.8) (logarithmic amplitude scale). In the simulation, it is shown how, at each frequency, most of the signal is transmitted in a single mode between access ports (P1) and (P2). It can be seen that at higher frequencies (B, C and D), the signal is coupled from the antenna (TSA) (acting as a near-field coupler) to the silicon (DRW) tapered end. This coupling occurs close to the photodiode, away from discontinuities in the substrate (105, 110), thus reducing signal reflections.

[0037] Figure 5A and Figure 5B Shows from FIG. 4A to FIG. 4D The S parameters obtained in the simulation are shown. Due to the discontinuity created by the transition between the substrates (105, 110), reflections may occur, such as Figure 5A As shown, although the transmission of the signal may reach at least 340GHz (assuming the level in S12 and S21 is -3dB). To mitigate these reflections, the edge of the high-speed semiconductor substrate (105) to which the ultra-high-speed device is connected can be wrapped with (TSA) (Figure 6b). As can be seen from the S parameters shown in Figure 5b, the reflections are suppressed, which reduces the ripple level in the S parameters.

[0038] Fig. 6A Another example of an ultra-wideband hybrid structure (100) for high-frequency electrical signals is shown, which includes interconnections for ultra-high-speed devices for generating or detecting high-frequency signals on a high-speed semiconductor substrate (105) and a substrate (110), and electrical interconnections (115) therebetween, the high-speed semiconductor substrate (105) including a high dielectric constant (such as but not limited to indium phosphide "InP").

[0039] In this particular example, the substrate (110) comprises a rectangular shape that is easier to cut. The substrate (110) is a substrate (i.e., an RF substrate such as quartz, laminate, and ceramic, etc.) or silicon that allows for larger sizes, on which larger metallization features corresponding to TSA antennas or two-wire metal waveguides can be built.

[0040] also, Fig. 6A Also shown is an ultra-high speed device comprising an edge-illuminated optical hybrid device (ie, waveguide-connected photodiode) illuminated by an optical fiber (130).

[0041] Due to the discontinuity caused by the transition between the substrates (105, 110), the following may occur: Figure 5ATo mitigate these reflections, the edges of the substrate (110) can be wrapped with (TSA). In this regard, Figure 6B The invention shows the interconnection between an ultra-high speed device processed or built on a high dielectric constant substrate and another substrate (110) having a shape matching with a metal pattern (TSA) or gradually narrowing toward the metal pattern (TSA). Figure 6B Also shown is an ultra-high speed device comprising an edge-illuminated optical hybrid device (ie, a waveguide-accessed photodiode) illuminated by an optical fiber (130) and a second dielectric structure (120), preferably a pyramidal structure etched on a high speed semiconductor substrate (105).

Claims

1. An ultra-wideband hybrid structure (100) for transmitting or receiving high-frequency electrical signals, the structure (100) comprising: substrate(110); a high-speed semiconductor substrate (105) connected to the substrate (110); an electrical interconnect (115) established between the substrate (110) and the high-speed semiconductor substrate (105); An ultra-high-speed device for generating or detecting a high-frequency signal, the ultra-high-speed device comprising a first access port (P1) and being built on the high-speed semiconductor substrate (105); The dielectric waveguide structure DRW comprises a second access port (P2) which provides a low cut-off frequency f from the microwave range or the millimeter wave range. CL The high-pass characteristic interconnection operating in the high-frequency range of the ultra-high speed device is provided, wherein the dielectric waveguide structure DRW is built on the substrate (110) and the high-speed semiconductor substrate (105), wherein the dielectric waveguide structure DRW includes a tapered end facing the first access port (P1) of the ultra-high speed device; Metal waveguide structure TSA, providing high cutoff frequency f in the range from DC to mmWave CH The invention relates to a low-pass interconnection having low-pass characteristics operating in a low frequency range of the ultra-high speed device, wherein the metal waveguide structure TSA is built on the substrate (110) and the high-speed semiconductor substrate (105), wherein the metal waveguide structure TSA includes a metal waveguide pattern, and the metal waveguide pattern is used to define a tapered coupler, and the tapered coupler is a tapered slot antenna "TSA" which surrounds the tapered end of the dielectric waveguide structure DRW and is connected to the first access port (P1) of the ultra-high speed device.

2. The ultra-wideband hybrid structure (100) according to claim 1, wherein: The substrate (110) has a rectangular shape.

3. The ultra-wideband hybrid structure (100) according to claim 1, wherein: The substrate (110) has a shape that gradually narrows toward the metal waveguide structure TSA.

4. The ultra-wideband hybrid structure (100) for high-frequency electrical signals according to any one of the preceding claims, further comprising a tapered structure (120), wherein the tapered structure (120) is etched on the high-speed semiconductor substrate (105) and / or the substrate (110).

5. The ultra-wideband hybrid structure (100) for high-frequency electrical signals according to claim 4, wherein: The conical structure (120) is a horn structure.

6. The ultra-wideband hybrid structure (100) for high-frequency electrical signals according to claims 1 to 5, wherein: The ultra-high-speed device is an optoelectronic device.

7. The ultra-wideband hybrid structure (100) for high-frequency electrical signals according to claim 6, further comprising: An optical fiber (130) provides edge optical illumination or vertical optical illumination to a high-speed photodiode.

8. The ultra-wideband hybrid structure (100) for high-frequency electrical signals according to claim 6 or 7, wherein: The optoelectronic device is a high-speed photodiode or a photoconductive antenna.

9. The ultra-wideband hybrid structure (100) for high-frequency electrical signals according to claim 8, further comprising: An optical waveguide (125) is located between the optical fiber (130) and the high-speed photodiode or the photoconductive antenna when the optical fiber (130) provides edge optical illumination.

10. The ultra-wideband hybrid structure (100) for high-frequency electrical signals according to claims 1 to 5, wherein: The ultra-high-speed device is an electronic device.

11. An ultra-wideband hybrid structure (100) for high frequency electrical signals according to any one of the preceding claims, wherein: The high-speed semiconductor substrate (105) includes III-V compound semiconductors, such as indium phosphide, gallium nitride, gallium arsenide, InAlAs / InGaAs or AlGaN / GaN.

12. An ultra-wideband hybrid structure (100) for high frequency electrical signals according to any one of the preceding claims, wherein: The electrical interconnect (115) includes wire bonding, ribbon bonding, flip chip bonding or epoxy resin.

13. An ultra-wideband hybrid structure (100) for high frequency electrical signals according to any one of the preceding claims, wherein: The substrate (110) includes a radio frequency substrate such as quartz, laminate, ceramic or silicon.

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