CN107359135A - Transfer bonding structure of integrated device and preparation method thereof in Terahertz antenna sheet - Google Patents

Abstract

The preparation method of the transfer bonding structure of integrated device in a kind of Terahertz antenna sheet, including step：(1) cushion, barrier layer, n-type GaAs layers and GaAs cryospheres are made successively on a SI-substrate；(2) the GaAs cryospheres are bonded with a polymer substrate；(3) SI-substrate and cushion are peeled off；(4) barrier layer is peeled off.Integrated device on transfer bonding structure prepared by the above method and the piece comprising the structure is also provided.Integrated device containing said structure can reduce THz wave loss, improve utilization ratio, realize that it is detected to micro-example and liquid sample.

Description

Transfer bonding structure and preparation method of terahertz antenna chip integrated device

technical field

The invention belongs to the technical field of semiconductor materials and devices, and further relates to a transfer bonding structure of a terahertz antenna chip integrated device, a preparation method thereof, and a terahertz antenna chip integrated device including the transfer bonding structure.

Background technique

Terahertz (THz) radiation refers to electromagnetic waves with a frequency between 0.1 and 10 THz (wavelength between 30 and 3000 μm). In the high frequency band, it crosses with infrared rays. The special position of the terahertz wave determines that it exhibits a series of special properties different from electromagnetic waves in other frequency bands, which makes it have great scientific value and broad application prospects in many aspects, such as radar imaging, material analysis, environmental Monitoring and high-capacity communication, etc. The unique properties of terahertz waves mainly include the following aspects: transient, easy to conduct time-resolved research on various materials, and effectively suppress the interference of background radiation noise; broadband, which is conducive to analyzing the spectral properties of substances in a wide range ; Terahertz waves have a strong interaction with polar molecules, and can be used for environmental monitoring and gas analysis, to detect internal defects and hidden objects in materials that cannot be detected by X-rays, visible light and infrared rays; the photon energy of terahertz waves is low, and can Non-destructive safety testing; with "fingerprint" characteristics, studying the spectrum of materials in the terahertz frequency band is of great significance for revealing the structure and properties of substances. In view of the above characteristics of terahertz, it is determined that it has very important scientific value and broad application prospects in basic research fields such as physics, chemistry, information science, astronomy and biology, as well as in technical fields such as communication, security and material processing. .

An important application of THz is the Terahertz-Time-Domain-Spectroscopy system (Terahertz-Time-Domain-Spectroscopy, THz-TDS) of free space radiation, which uses femtosecond laser to excite photoconductive materials or electro-optic After the Hertz pulse is focused, it is irradiated on the sample, the terahertz pulse is modulated by the sample, and the terahertz pulse carrying the sample information is focused on the detector again. Coherent measurement of pulses in the time domain. Then Fourier transform is performed on the drawn terahertz time-domain spectrum, and finally the frequency-domain information of the sample is obtained. It plays an important role in the research of semiconductors, pharmaceuticals, biomolecules, spectroscopy, etc. However, the existing free-space THz-TDS system has many defects, such as the required sample size is too large, the spectral resolution is low, the system size is large, and the absorption of water in the air weakens the THz wave. The on-chip integration of terahertz antennas can effectively make up for the shortcomings of existing free-space THz-TDS.

The terahertz antenna chip integrated device integrates the terahertz generation and receiving ends on the same substrate, and connects the pumping area and the detection area with a metal waveguide. When a femtosecond laser pulse of a certain wavelength is focused on the low-temperature GaAs in the pumping area When the photoconductive switch is on, a terahertz pulse is excited, and the pulse is transmitted to the detection area through the waveguide, thereby completing the coherent detection of the terahertz pulse. The sample is placed above the waveguide transmission line, and the spectrum measurement is completed through the interaction between the sample to be tested and the evanescent field of the waveguide transmission line. Because the device length is far below the diffraction limit, the sample volume is minimal. Since the pumping and receiving are on the same chip, not only does it not need to collimate the terahertz optical path, but it can also greatly reduce the size and weight of the overall instrument, which facilitates the realization of smaller portable devices.

Contents of the invention

In view of this, the object of the present invention is to propose a transfer bonding structure and a manufacturing process of a terahertz antenna on-chip integrated device.

In order to achieve the above object, according to one aspect of the present invention, a method for preparing a transfer bonding structure of a terahertz antenna on-chip integrated device is provided, including steps:

(1) Fabricate a buffer layer, a barrier layer, an n-type GaAs layer and a GaAs low-temperature layer sequentially on half of the insulating substrate;

(2) bonding the GaAs low temperature layer to a polymer substrate;

(3) peeling off the semi-insulating substrate and buffer layer;

(4) Peel off the barrier layer.

According to a specific embodiment of the present invention, the material of the semi-insulating substrate and the buffer layer is GaAs.

According to a specific embodiment of the present invention, the barrier layer is made of Al _0.9 Ga _0.1 As.

According to a specific embodiment of the present invention, each layer in step (1) is fabricated by molecular beam epitaxy.

According to a specific embodiment of the present invention, the GaAs low temperature layer is fabricated at a temperature of 200-500°C.

According to a specific embodiment of the present invention, the bonding in step (2) is thermocompression bonding.

According to a specific embodiment of the present invention, step (3) is specifically: first use the corrosion solution containing _HNO3 to quickly peel off the semi-insulating substrate and the buffer layer, and then use the corrosion solution containing _NH3 to remove the semi-insulating substrate and the buffer layer. The layer continues to be peeled off, and finally the corrosion solution containing C ₃ H ₈ O ₇ is used for slow peeling.

According to a specific embodiment of the present invention, step (4) specifically includes: stripping the barrier layer with a solution containing HCl.

According to one aspect of the present invention, there is provided a transfer bonding structure of an integrated device on a terahertz antenna chip, including:

polymer substrate;

a GaAs low temperature layer bonded to said polymer substrate;

The N-type GaAs layer is arranged on the GaAs low-temperature layer.

According to an aspect of the present invention, a terahertz antenna chip integrated device is provided, including the transfer bonding structure described above.

Through the above technical scheme, the beneficial effects of the present invention are:

(1) Expand the application field of terahertz spectroscopy through on-chip integrated devices of terahertz antennas, and lay the foundation for the chip-based terahertz time-domain spectroscopy system, which has broad application prospects;

(2) By effectively transferring the epitaxially grown low-temperature GaAs material used as a photoconductive switch to the substrate, the loss of terahertz waves is reduced, the utilization efficiency is improved, and the subsequent process is guaranteed;

(3) The realization of the inventive process technology is beneficial to the realization of the preparation of the terahertz antenna on-chip integrated device, and realizes the detection of trace samples and liquid samples.

Description of drawings

Fig. 1 is a schematic diagram of the epitaxial material structure of a specific embodiment of the present invention;

Fig. 2 is a schematic diagram of epitaxial material bonding in a specific embodiment of the present invention;

Fig. 3 is a flow chart of a stripping process according to a specific embodiment of the present invention.

FIG. 4 is a schematic diagram of a transfer bonding structure of a specific embodiment of the present invention.

detailed description

In the present invention, the position terms such as "upper" and "lower" only indicate the relative relationship between layers and/or substrates, which can be reversed or rotated as a whole, and the above terms are not used to limit the present invention.

According to the general concept of the invention, a method for preparing a transfer bonding structure of an integrated device on a terahertz antenna chip is provided, which is characterized in that it includes the steps:

(1) Fabricate a buffer layer, a barrier layer, an n-type GaAs layer and a GaAs low-temperature layer sequentially on half of the insulating substrate;

(2) bonding the GaAs low temperature layer to a polymer substrate;

(3) peeling off the semi-insulating substrate and buffer layer;

(4) Peel off the barrier layer.

For the photoconductive switch structure of the integrated device, the photoconductive switch in the pumping region is preferred. When a femtosecond laser pulse of a certain wavelength is focused on the switch structure, a terahertz pulse is excited, and the pulse is transmitted to the detection region through the waveguide. In order to complete the coherent detection of terahertz pulses.

The specific process and setting method in the step (1) are as follows:

For the selection of the semi-insulating substrate, it can be the semi-insulating substrate material commonly used in the prior art for preparing the GaAs low-temperature layer, and the preferred material is GaAs material. The preferred substrate thickness is 200-500 μm, more preferably 300-400 μm.

For the buffer layer, which is used for depositing on the semi-insulating substrate to make its surface flat to facilitate the subsequent deposition process, the preferred material is similar to or the same as that of the semi-insulating substrate, and gallium arsenide is more preferably used. As for the deposition method of the buffer layer, the deposition process can be chemical vapor deposition, more preferably molecular beam epitaxy, and the deposition temperature is controlled at 550-700°C. A preferred deposition thickness of the buffer layer is 30-300 nm, and a further preferred deposition thickness is 50-200 nm.

For the barrier layer, its function is to prevent the chemical stripping corrosion solution from corroding the internal materials and protect the low temperature layer and n-type GaAs layer in the subsequent process when the semi-insulating substrate and buffer layer are stripped. The preferred material is aluminum gallium arsenic material, more preferably Al _0.9 Ga _0.1 As. For the deposition method of the barrier layer, its deposition process can be a chemical vapor deposition method, preferably the same as the deposition method of the buffer layer, and more preferably deposited by molecular beam epitaxy, and its deposition temperature is controlled at 550-700 ° C . A preferred deposition thickness of the barrier layer is 60nm-6μm, and a further preferred deposition thickness is between 80nm-5μm.

For the n-type GaAs layer, its function is to facilitate the growth of subsequent materials. For the deposition method of the n-type GaAs layer, its deposition process can be a physical vapor deposition method, and it is also preferably the same as the deposition method of the buffer layer. More preferably, it is deposited by molecular beam epitaxy, and its deposition temperature is controlled at 550- 700°C. A preferred deposition thickness of the n-type GaAs layer is 0.5-5 μm, and a further preferred deposition thickness is 1-3 μm.

For the GaAs low-temperature layer, its deposition temperature is lower than the substrate temperature of other layers, and it is deposited at a low temperature by molecular beam epitaxy. The carrier life is short, the electron-hole recombination speed is fast, and the corresponding oscillating current change frequency is at the terahertz level. , so that terahertz waves can be radiated outward.

Concrete process and setting mode in the step (2) are as follows:

For the polymer substrate, it is preferred to use a material with a lower dielectric constant to reduce the loss of terahertz waves. For example, cycloolefin polymer or polyimide can be selected, and the preferred substrate size is 1-2cm ² , and the heat-resistant temperature is 60-180 ° C, indicating that it is clean, smooth, and free of scratches, so as to ensure the realization of thermocompression bonding.

As for the bonding method, it is preferable to use intermolecular force to thermally bond the low-temperature layer on the polymer substrate, so as to realize the effective transmission of terahertz waves in the on-chip waveguide structure.

Concrete process and setting mode in the step (3) are as follows:

Firstly, the semi-insulating substrate and buffer layer are quickly stripped with an etchant containing HNO ₃ , and then the semi-insulating substrate and buffer layer are continuously stripped with an etchant containing NH ₃ , and finally, the etchant containing C ₃ H ₈ O ₇ is used Perform a slow peel.

For example, fast stripping uses HNO ₃ , H ₂ O ₂ , H ₂ O (preferred ratio 1:2:1) etchant to quickly etch the semi-insulating substrate and buffer layer, and the corrosion rate is preferably about 5 at about 20°C. -9 μm/min. Continue stripping and use NH ₃ ·H ₂ O, H ₂ O ₂ etchant to etch the semi-insulating substrate and the buffer layer. The corrosion rate is preferably about 4-7 μm/min at around 20°C. Slow peeling Use C ₃ H ₈ O ₇ ·H ₂ O, H ₂ O ₂ (preferred ratio 3:1) etchant to slowly etch the semi-insulating substrate 10 and buffer layer 20, the corrosion rate is about 20°C It is about 30-80nm/min, so that the semi-insulating substrate 10 and the buffer layer 20 are etched completely.

Concrete process and setting mode in the step (4) are as follows:

Preferably, the barrier layer is etched using an etchant containing HCl, and the preferred etching rate is about 80-150 nm/min at around 20°C.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention, but should not be construed as a limitation of the present invention.

Please refer to FIG. 1, this embodiment firstly provides an epitaxial material structure of an integrated device on a terahertz antenna chip, including:

half of the insulating substrate 10, the thickness of the semi-insulating substrate 10 is 300-400 μm;

A buffer layer 20, which is made on the semi-insulating substrate 10, the thickness of the buffer layer 20 is between 50-200nm, growing this layer can make the substrate surface smooth;

An Al _0.9 Ga _0.1 As barrier layer 30 is fabricated on the 20 with a thickness of 80nm-5μm. This barrier layer effectively prevents the etching solution from corroding the n-type GaAs layer 40 and the low temperature layer 50 mentioned below;

An n-type GaAs layer 40, which is fabricated on the layer 30, with a thickness of 100-150nm;

A low-temperature layer 50 is fabricated on 40 with a thickness of 1-3 μm and is grown at a temperature range of 200-500° C. The material of this layer serves as a photoconductive switch. The low-temperature layer 50 has a short lifetime of carriers and a fast electron-hole recombination rate, and the corresponding frequency of the oscillating current is at the terahertz level, so that terahertz waves can be radiated outward.

The materials of the semi-insulating substrate 10 , the buffer layer 20 and the low temperature layer 50 mentioned above are all GaAs. Except for the low-temperature layer 50, the growth temperature of the other layers is 550-700°C. Among them, the Al _0.9 Ga _0.1 As barrier layer 30 , the n-type GaAs layer 40 , and the low temperature layer 50 together constitute the epitaxial material 60 . The method for growing the epitaxial material 60 is molecular beam epitaxy (MBE) method.

Please refer to Fig. 2, this embodiment then provides a kind of epitaxial material bonding of an integrated device on a terahertz antenna chip, the method used for bonding is thermocompression bonding, including:

A polymer substrate 70, the substrate material is a material with a low dielectric constant such as cyclo-olefin polymer (Cyclo-olefin polymer, COP), polyimide, the size is 1-2cm ² , to reduce the terahertz wave loss. And the heat-resistant temperature is 60-180°C, which shows that it is clean, smooth and free of scratches, so as to ensure the realization of thermocompression bonding;

An epitaxial material 60 with a size of 6-8mm ² . Place the semi-insulating substrate 10 in the epitaxial material 60 facing up under the conditions of 50-200kPa, 50-200°C. The low-temperature layer 50 is in close contact with the polymer substrate 70, and is thermally bonded to the polymer substrate 70 by utilizing intermolecular forces, so as to realize effective transmission of terahertz waves in the on-chip waveguide structure.

Referring to FIG. 3 , this embodiment provides an epitaxial material stripping process for an integrated device on a terahertz antenna chip. After obtaining a structure in which the epitaxial material 60 is well bonded to the polymer substrate 70 , a lift-off process is performed to transfer the epitaxial material 60 . This process is divided into four steps, using HNO ₃ -NH ₃ ·H ₂ OC ₃ H ₈ O ₇ ·H ₂ OH ₂ O ₂ -HCl corrosion system, including:

In the first step, use HNO ₃ : H ₂ O ₂ : H ₂ O = 1: 2: 1 etchant to rapidly etch the semi-insulating substrate 10 and the buffer layer 20, and the corrosion rate is about 5-9 μm at about 20°C /min. The etchant has almost no selectivity for etching the semi-insulating substrate 10, the buffer layer 20 and the Al _0.9 Ga _0.1 As barrier layer 30.

In the second step, the semi-insulating substrate 10 and the buffer layer 20 are continuously etched using an etchant of NH ₃ ·H ₂ O:H ₂ O ₂ , and the etching rate is about 4-7 μm/min at about 20° C. The corrosion selectivity of the etching solution to the semi-insulating substrate 10, the buffer layer 20 and the Al _0.9 Ga _0.1 As barrier layer 30 is poor.

In the third step, the semi-insulating substrate 10 and the buffer layer 20 are etched slowly with an etching solution of C ₃ H ₈ O ₇ ·H ₂ O:H ₂ O ₂ =3:1, and the etching rate is about 30-80nm/min, so that the semi-insulating substrate 10 and the buffer layer 20 are etched completely. Among them, C ₃ H ₈ O ₇ ·H ₂ O is prepared by fully dissolving C ₃ H ₈ O ₇ ·H ₂ O crystals and H ₂ O in equal amounts. The etching selectivity ratio of the etching solution to the semi-insulating substrate 10, the buffer layer 20 and the Al _0.9 Ga _0.1 As barrier layer 30 is about 60-80. The semi-insulating substrate 10 and the buffer layer 20 can be effectively etched away, leaving the Al _0.9 Ga _0.1 As barrier layer 30 .

In the fourth step, the Al _0.9 Ga _0.1 As barrier layer 30 is etched with an etching solution of HCI:H ₂ O=2:1, and the etching rate is about 80-150 nm/min at about 20° C. This etchant has good selectivity to the Al _0.9 Ga _0.1 As barrier layer 30 and to the n-type GaAs layer 40 and the low-temperature layer 50, and can effectively etch the Al _0.9 Ga _0.1 As barrier layer 30 completely, leaving the n-type GaAs layer 40, Low temperature layer 50.

The above four-step corrosion needs to be uniformly corroded in a constant temperature environment of about 20 °C. After the above four steps of etching are completed, the epitaxial material stripping process integrated on the terahertz antenna chip is completed, and the n-type GaAs layer 40 and the low-temperature layer 50 are bonded on the polymer substrate 70 to obtain a smooth and clean structure (see FIG. 4 shown) for subsequent processing.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. A method for preparing a transfer bonding structure of an integrated device on a terahertz antenna chip, characterized in that it comprises steps: (1) Fabricate a buffer layer, a barrier layer, an n-type GaAs layer and a GaAs low-temperature layer sequentially on half of the insulating substrate; (2) bonding the GaAs low temperature layer to a polymer substrate; (3) peeling off the semi-insulating substrate and buffer layer; (4) Peel off the barrier layer. 2. The preparation method according to claim 1, characterized in that the semi-insulating substrate and the buffer layer are made of GaAs. 3. The preparation method according to claim 1, characterized in that, the material of the barrier layer is Al _0.9 Ga _0.1 As. 4. The preparation method according to claim 1, characterized in that each layer in step (1) is produced by molecular beam epitaxy. 5. The preparation method according to claim 4, characterized in that, the GaAs low temperature layer is fabricated at a temperature of 200-500°C. 6. The preparation method according to claim 1, characterized in that the bonding in step (2) is thermocompression bonding. 7. preparation method according to claim 1, is characterized in that, step (3) is specially: at first use containing HNO ₃ corrosive liquid is carried out rapid stripping to semi-insulating substrate and buffer layer, then use containing NH ₃ corrosive liquid Continue to peel off the semi-insulating substrate and buffer layer, and finally use an etchant containing C ₃ H ₈ O ₇ for slow peeling. 8 . The preparation method according to claim 1 , wherein step (4) specifically comprises: peeling off the barrier layer with a solution containing HCl. 8 . 9. A transfer bonding structure of an integrated device on a terahertz antenna chip, characterized in that it comprises: polymer substrate; a GaAs low temperature layer bonded to said polymer substrate; The N-type GaAs layer is arranged on the GaAs low-temperature layer. 10. An on-chip integrated device for a terahertz antenna, characterized by comprising the transfer bonding structure according to claim 9.