Photoelectric heterogeneous integrated microwave emission chip and preparation method thereof

Abstract

The invention relates to the field of semiconductor devices, and particularly discloses a photoelectric heterogeneous integrated microwave emission chip and a preparation method thereof, the chip is composed of a GaN HEMT amplifier and an InP UTC type detector on a SiC substrate; the preparation method comprises the following steps: preparing an amplifier on a SiC epitaxial wafer; growing a UTC type detector epitaxial layer on the InP substrate, and preparing a mesa structure; bonding the sapphire slide and the detector wafer; the InP epitaxial wafer substrate is removed; transferring the detector to an amplifier wafer through metal bonding; removing the temporary sapphire slide; and the detector is in electric signal communication with the amplifier. Compared with a method of firstly transferring an InP epitaxial layer and then preparing a detector device, the method has the advantages that the adverse effect of an InP-based detector processing technology on an amplifier is avoided; and secondly, the InP-based detector prepared by the method has the characteristic that the N-type contact metal faces downwards, and the structure is beneficial to reducing the junction region temperature and enhancing the heat dissipation capability of the device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor devices, and specifically discloses a photoelectric heterogeneous integrated microwave emitting chip and its fabrication method. Background Technology

[0002] With the rapid development of the information society, the sixth-generation (6G) mobile communication technology, geared towards the future, has become the focus of global research and competition. Compared with fifth-generation mobile communication, 6G uses higher radio frequency bands. Traditional pure electronics-based microwave transmission schemes have inherent bottlenecks in high-frequency bands, such as high cost and poor frequency purity. Photonics-generated microwave signals have advantages such as low cost, high frequency, and large bandwidth, but their output power is insufficient, limiting practical applications.

[0003] Against this backdrop, optoelectronic heterogeneous integration technology has emerged. The optoelectronic heterogeneous integrated microwave transmitter chip proposed in this invention simplifies the manufacturing process and significantly improves the heat dissipation capacity of the device. It can generate pure high-frequency carrier waves by utilizing the frequency tunability and high stability of photonics technology, and amplify and radiate signals by leveraging the high efficiency and maturity of electronic technology. Thus, it achieves integrated signal generation and amplification functions at the chip level, which has important strategic significance and practical value for seizing the commanding heights of 6G communication technology. Summary of the Invention

[0004] The purpose of this invention is to provide a photoelectric heterogeneous integrated microwave transmitting chip and its fabrication method, which improves the heat dissipation capability of the detector device, enhances the saturated incident light power and radio frequency output power of the microwave transmitting chip, and overcomes the shortcomings of the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A photoelectric heterogeneous integrated microwave emitting chip includes a SiC substrate, a SiC-based GaN HEMT amplifier and an InP-based UTC detector disposed on the SiC substrate; The SiC-based GaN HEMT amplifier consists of, from bottom to top, a GaN buffer layer, a GaN channel, an AlGaN layer, and source, drain, and gate electrodes. The InP-based UTC detector consists of, from bottom to top, N-type contact metal, detector functional layer, and P-type contact metal. The gate electrode of the SiC-based GaN HEMT amplifier is electrically connected to the P-type contact metal of the InP-based UTC detector via an air bridge.

[0006] As a further preferred option, the detector functional layer structure from bottom to top is as follows: n-type InP contact layer, n-type InP depletion layer, n-type InP kurtosis layer, i-type InGaAs absorption layer, p-type InGaAs absorption layer, p-type InP blocking layer, and p-type InGaAs contact layer.

[0007] As a further preferred option, the thickness of the n-type InP contact layer is 50~150 nm.

[0008] A method for fabricating a photoelectric heterogeneous integrated microwave emitting chip includes the following steps: S1: Fabricate a GaN HEMT amplifier on an epitaxial wafer of a SiC substrate (amplifier wafer); S2: Grow a UTC-type photodetector epitaxial layer on an InP substrate (the epitaxial layer and the InP substrate are bonded together to form a detector wafer), forming the functional layer structure of an InP-based UTC-type detector. This structure, from the InP substrate end upwards, consists of: an n-type InP contact layer, an n-type InP depletion layer, an n-type InP kurtosis layer, an i-type InGaAs absorption layer, a p-type InGaAs absorption layer, a p-type InP blocking layer, and a p-type InGaAs contact layer. S3: A mesa structure of the functional layer structure is formed by wet etching process on the functional layer structure, a passivation layer is formed by plasma chemical vapor deposition, and holes are made at the electrodes on the passivation layer (the SiN on the electrodes is etched away), and the P-type contact metal is prepared. S4: Using sapphire as a temporary carrier, a temporary adhesive is used to bond the sapphire to the detector wafer; S5: Remove the InP substrate from the detector wafer (bottom of the functional layer structure) through mechanical polishing and chemical etching; S6: Fabricate the detector N-type contact metal; fabricate the metal on the SiC substrate (amplifier wafer), and bond the detector functional layer structure to the SiC substrate through metal bonding; S7: Remove the sapphire temporary substrate by melting the adhesive 305 at high temperature; S8: The electrical signal connection between the SiC-based GaN HEMT amplifier and the InP-based UTC detector is completed through an air bridge process.

[0009] As a further preferred option, in S4, the bonding temperature is 200°C and the bonding pressure is 6000 mbar.

[0010] As a further preferred option, in S6, the bonding temperature is 200°C and the bonding pressure is 4000 mbar.

[0011] As a further preferred option, in S7, the high-temperature melting temperature is 230°C.

[0012] As a further preferred embodiment, in S8, photoresist is spin-coated to prepare the bridge pier, and then an air bridge is prepared between the gate electrode of the SiC-based GaN HEMT amplifier and the P-type contact metal of the InP-based UTC detector.

[0013] The beneficial effects of this invention are: compared with the integration method of first transferring the InP epitaxial layer and then fabricating the detector device, this method avoids the adverse effects of the detector fabrication process on the amplifier. For example, wet etching and dry etching processes in the detector fabrication process can damage the amplifier, and high-temperature annealing processes can degrade the amplifier performance. However, fabricating the detector mesa first and then integrating it avoids the above problems. Secondly, the InP-based detectors prepared by this method have the characteristic of N-type contact metal facing downwards, that is, the N-type contact metal is in direct contact with the highly thermally conductive SiC substrate. This structure helps to reduce the junction temperature and enhance the heat dissipation capability of the device. Therefore, this microwave transmitting chip can withstand higher incident light power and has a greater RF output power. Finally, the thinner n-type InP contact layer of the detector helps reduce the series resistance of the device, increase the detector bandwidth, and further reduce the junction temperature of the device. Attached Figure Description

[0014] Figure 1 This is a cross-sectional schematic diagram of the optoelectronic heterogeneous integrated microwave transmitting chip in specific embodiment 1 of the present invention; Figure 2 This is a flowchart illustrating the fabrication process of the optoelectronic heterogeneous integrated microwave emitting chip in specific embodiment 2 of the present invention; Figure 3 This is a cross-sectional schematic diagram of the SiC-based GaN HEMT amplifier completed in step S1 of the present invention. Figure 4 This is a schematic diagram of the InP UTC type detector chip bonded to the SiC substrate in step S6 of the present invention. Figure 5 This is a cross-sectional schematic diagram of the GaN HEMT amplifier and InP UTC detector heterogeneous integrated chip after removing the temporary carrier in step S7 of the present invention. Figure 6 These are simulation diagrams of different detector structures and junction temperatures. Among them, (a) is a detector structure with P-type contact metal facing down, (b) is a simulation diagram of the junction temperature of the detector structure with P-type contact metal facing down, (c) is a detector structure with N-type contact metal facing down, and (d) is a simulation diagram of the junction temperature of the detector structure with N-type contact metal facing down. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example 1

[0016] This embodiment provides a microwave transmitting chip with optoelectronic heterogeneous integration, such as... Figure 1 As shown, it consists of a SiC-based GaNHEMT amplifier and an InP-based UTC detector.

[0017] The SiC-based GaN HEMT amplifier consists of a SiC substrate, a GaN buffer layer, a GaN channel, an AlGaN layer, and source, drain, and gate electrodes. The InP-based UTC detector has a layer structure from bottom to top consisting of N-type contact metal, detector functional layer, and P-type contact metal. The detector and amplifier are electrically connected via an air bridge.

[0018] The detector's functional layer structure, from bottom to top, consists of: an n-type InP contact layer, an n-type InP depletion layer, an n-type InP kurtosis layer, an i-type InGaAs absorber layer, a p-type InGaAs absorber layer, a p-type InP blocking layer, and a p-type InGaAs contact layer. The N-type contact metal is located at the bottom of the device and is in direct contact with the amplifier's SiC substrate via gold-to-gold bonding. The thickness of the n-type InP contact layer is 100 nm.

[0019] Figure 6 The junction temperatures of detector structures with N-type contact metal facing down (N-down) and P-type contact metal facing down (P-down) were compared. A P-down structure refers to a structure where, from the substrate end upwards, the layers are a P-type contact metal, a detector functional layer, and an N-type contact metal. The detector functional layers, from the substrate end upwards, consist of: a p-type InGaAs contact layer, a p-type InP blocking layer, a p-type InGaAs absorber layer, an i-type InGaAs absorber layer, an n-type InP kurtosis layer, an n-type InP depletion layer, and an n-type InP contact layer.

[0020] According to the simulation results, for the same device power dissipation, the junction temperature of the N-down device is 13K lower than that of the P-down device, which shows the effect of the N-down device structure in reducing the junction temperature. Example 2

[0021] This embodiment provides a method for fabricating a microwave emitting chip with optoelectronic heterogeneous integration, the flowchart of which is shown below. Figure 2 As shown, the specific steps include: Step S1: Fabricate a GaN-based HEMT amplifier on a SiC epitaxial wafer. The specific method is as follows: Use ICP etching process to etch the AlGaN layer, GaN channel layer and GaN buffer layer with Cl2 / BCl3 gas to form the required mesa structure; etch away part of the AlGaN material, fabricate ohmic contact metal on the GaN buffer layer and perform rapid thermal annealing; use electron beam evaporation process to deposit a stable gate metal layer on the AlGaN layer. Figure 3 This is a schematic cross-sectional view of the completed SiC-based GaN HEMT amplifier.

[0022] Step S2: Grow an epitaxial layer of an InP UTC type photodetector on an InP substrate to form the functional layer structure of the detector. The structure consists of the following layers from the InP substrate end upwards: n-type InP contact layer, n-type InP depletion layer, n-type InP kurtosis layer, i-type InGaAs absorption layer, p-type InGaAs absorption layer, p-type InP blocking layer, and p-type InGaAs contact layer, wherein the thickness of the n-type InP contact layer is 100 nm. Step S3: Fabricate the detector P-type contact metal Ti / Pt / Au, use a wet etching process to etch the functional layer of the epitaxial wafer to form the detector mesa structure, and deposit SiN. x Passivation layer and electrode opening; Step S4: Using sapphire as a temporary carrier, bond the sapphire to the detector wafer using a temporary adhesive (305 adhesive). The bonding temperature is 200℃ and the bonding pressure is 6000mbar. Step S5: Remove the InP substrate of the detector wafer by mechanical polishing and chemical etching. Specifically, remove most of the substrate of the detector epitaxial wafer by mechanical polishing, remove the remaining substrate by wet etching, and finally remove the InGaAsP etching stop layer at the bottom of the functional layer by wet etching. Step S6: Prepare the N-type contact metal Ti / Pt / Au of the detector, prepare the bonding metal Ti / Au on the amplifier wafer, and bond the detector wafer to the SiC-based GaN HEMT amplifier wafer through metal bonding. The bonding temperature is 200℃ and the bonding pressure is 4000mbar. Figure 4 This is a schematic diagram of the structure of an InP UTC type detector wafer bonded to a SiC substrate.

[0023] Step S7: Heat the bonding sheet to 230°C to melt the temporary adhesive 305 and remove the sapphire temporary carrier; Figure 5 This is a cross-sectional schematic diagram of the GaN HEMT amplifier and InP UTC detector heterogeneous integrated chip after the temporary carrier has been removed.

[0024] Step S8: Spin-coat photoresist to prepare the bridge pier, and then prepare an air bridge between the G electrode of the amplifier and the P-type contact metal of the detector, thereby realizing the electrical signal connection between the InP detector chip and the GaN HEMT amplifier. Figure 6 This is a cross-sectional schematic diagram of a microwave transmitter chip that completes optoelectronic heterogeneous integration for electrical signal interconnection.

[0025] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A microwave transmitting chip with optoelectronic heterogeneous integration, characterized in that: Including a SiC substrate, and a SiC-based GaN HEMT amplifier and an InP-based UTC detector placed on the SiC substrate; The SiC-based GaN HEMT amplifier consists of, from bottom to top, a GaN buffer layer, a GaN channel, an AlGaN layer, and source, drain, and gate electrodes. The InP-based UTC detector consists of, from bottom to top, N-type contact metal, detector functional layer, and P-type contact metal. The gate electrode of the SiC-based GaN HEMT amplifier is electrically connected to the P-type contact metal of the InP-based UTC detector via an air bridge.

2. The optoelectronic heterogeneous integrated microwave transmitting chip according to claim 1, characterized in that: The detector's functional layer structure, from bottom to top, consists of: an n-type InP contact layer, an n-type InP depletion layer, an n-type InP kurtosis layer, an i-type InGaAs absorption layer, a p-type InGaAs absorption layer, a p-type InP blocking layer, and a p-type InGaAs contact layer.

3. The optoelectronic heterogeneous integrated microwave transmitting chip according to claim 2, characterized in that: The thickness of the n-type InP contact layer is 50~150 nm.

4. The method for fabricating a photoelectric heterogeneous integrated microwave emitting chip according to claim 3, characterized in that, Includes the following steps: S1: Fabrication of a GaN HEMT amplifier on an epitaxial wafer of a SiC substrate; S2: An epitaxial layer of a UTC photodetector is grown on an InP substrate to form a functional layer structure of an InP-based UTC detector. The structure consists of the following layers from the InP substrate end upwards: n-type InP contact layer, n-type InP depletion layer, n-type InP kurtosis layer, i-type InGaAs absorption layer, p-type InGaAs absorption layer, p-type InP blocking layer, and p-type InGaAs contact layer. S3: A mesa structure of the functional layer structure is formed by wet etching process on the functional layer structure, a passivation layer is formed by plasma chemical vapor deposition, and holes are made at the electrode on the passivation layer to complete the preparation of P-type contact metal. S4: Using sapphire as a temporary carrier, a temporary adhesive is used to bond the sapphire to the detector wafer; S5: Remove the InP substrate from the detector wafer through mechanical grinding and chemical etching; S6: Fabricate the detector N-type contact metal; fabricate the metal on the SiC substrate, and bond the detector functional layer structure to the SiC substrate through metal bonding; S7: Remove the sapphire temporary carrier by melting the adhesive at high temperature; S8: The electrical signal connection between the SiC-based GaN HEMT amplifier and the InP-based UTC detector is completed through an air bridge process.

5. The method for fabricating a photoelectric heterogeneous integrated microwave emitting chip according to claim 4, characterized in that: In S4, the bonding temperature is 200℃ and the bonding pressure is 6000mbar.

6. The method for fabricating a photoelectric heterogeneous integrated microwave emitting chip according to claim 4, characterized in that: In S6, the bonding temperature is 200℃ and the bonding pressure is 4000mbar.

7. The method for fabricating a photoelectric heterogeneous integrated microwave emitting chip according to claim 4, characterized in that: In S7, the high-temperature melting temperature is 230℃.

8. The method for fabricating a photoelectric heterogeneous integrated microwave emitting chip according to claim 4, characterized in that: In S8, photoresist is spin-coated to prepare the bridge pier, and then an air bridge is prepared between the gate electrode of the SiC-based GaN HEMT amplifier and the P-type contact metal of the InP-based UTC detector.

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