CN111933748A - Back-incident solar blind ultraviolet detector and manufacturing method thereof - Google Patents

Abstract

The invention is suitable for the technical field of ultraviolet detector preparation, and provides a back-incident solar blind ultraviolet detector and a manufacturing method thereof, wherein the method comprises the following steps: preparing a device layer of the solar blind ultraviolet detector on a sapphire substrate; separating a device layer of the solar blind ultraviolet detector from the sapphire substrate by adopting a laser lift-off technology; bonding the separated device layer of the solar blind ultraviolet detector to the ultraviolet light transmitting substrate. The back of the substrate is used as an ultraviolet photon incidence surface during working, so that the effective incidence area is greatly increased, and meanwhile, the front electrode can be made as large as possible, so that the electric field distribution in the vertical direction is more uniform, and the detection efficiency can be greatly improved. In addition, the sapphire substrate after laser stripping can be recycled, and the development cost of the solar blind ultraviolet detector is greatly reduced.

Description

Back-incidence solar-blind ultraviolet detector and method for making the same

technical field

The invention belongs to the technical field of preparation of ultraviolet light detectors, and in particular relates to a back-incidence solar-blind ultraviolet detector and a preparation method thereof.

Background technique

Ultraviolet light detectors have excellent characteristics such as strong anti-interference ability and suitable for harsh environments (such as high temperature environments), and have important application value in scientific research, military, aerospace, environmental protection, fire protection and many industrial control fields.

Traditional UV light detectors are mainly based on silicon-based UV photocells and photomultiplier tubes. Although they have high sensitivity, they have shortcomings such as the need for additional filters, large size, easy damage, and the need to work under high voltage. Meet the needs of the development of modern electronic technology. In recent years, ultraviolet alarm and tracking technology based on missile ultraviolet radiation detection has developed extremely rapidly, and higher requirements have been put forward for ultraviolet light detection devices. Therefore, new wide-bandgap semiconductor ultraviolet photodetectors with high efficiency, low cost, easy integration and suitable for working in harsh environments have become a hot spot in the field of photodetection internationally.

At present, there are many wide-bandgap semiconductor materials used for ultraviolet photodetectors, mainly including SiC, ZnO, and GaN-based III-V compounds. However, so far, there is no wide-bandgap semiconductor ultraviolet photodetector and imaging device that can become the mainstream products in this field. The main reason is the lack of substrate materials and effective technical means for preparing large-scale integrated devices. In addition, the preparation of UV light detectors with these materials is not only difficult in its own preparation process, but also requires harsh equipment and processing conditions, and the cost is too high, and the upper surface is used to absorb photons, while the top electrode will block some incident photons, making Detection efficiency is reduced.

SUMMARY OF THE INVENTION

In view of this, the embodiments of the present invention provide a back-incidence solar-blind ultraviolet detector and a manufacturing method thereof, aiming to solve the problems of difficult preparation, high cost and low detection efficiency of the ultraviolet detector in the prior art.

To achieve the above object, a first aspect of the embodiments of the present invention provides a method for manufacturing a back-incidence solar-blind ultraviolet detector, including:

The device layer of solar-blind UV detector is prepared on sapphire substrate;

The device layer of the solar-blind UV detector is separated from the sapphire substrate by using laser lift-off technology;

Bonding the separated device layers of the solar-blind UV detector to the UV-transmitting substrate.

As another embodiment of the present application, the use of laser lift-off technology to separate the device layer of the solar-blind UV detector from the sapphire substrate includes:

The sapphire substrate is irradiated with laser light with preset photon energy, so that the laser light passes through the sapphire substrate and is absorbed by the first surface layer in the device layer of the solar-blind ultraviolet detector that is in contact with the sapphire substrate, resulting in Thermal decomposition to generate metal gallium and nitrogen;

The sapphire substrate is heated on a heating plate with a preset temperature to liquefy metal gallium, and the device layer of the solar-blind ultraviolet detector is separated from the sapphire substrate.

As another embodiment of the present application, the preset photon energy is greater than the energy of the first surface layer and less than the bandgap photon energy of the sapphire substrate.

The preset temperature is greater than 40°C.

As another embodiment of the present application, the substrate that transmits ultraviolet light is a substrate with a light transmittance greater than 90% and a thickness of 0.5-1 mm.

As another embodiment of the present application, the substrate that transmits ultraviolet light is a glass substrate with a light transmittance greater than 90% and a thickness of 0.5-1 mm.

As another embodiment of the present application, the device layer of the solar-blind UV detector is a device layer of an AlGaN detector;

The preset photon energy is greater than the energy of the AlGaN surface layer and less than the bandgap photon energy of the sapphire substrate.

As another embodiment of the present application, the process of preparing a device layer of an AlGaN detector on a sapphire substrate includes:

Prepare an N-type AlGaN layer, an intrinsic AlGaN layer and a P-type GaN layer in sequence on a sapphire substrate;

etching the P-type GaN layer and the intrinsic AlGaN layer to form a mesa on the N-type AlGaN layer;

A cathode is prepared on the exposed area of the N-type AlGaN layer, an anode is prepared on the P-type GaN layer of the mesa, and ohmic contact electrodes are formed respectively;

A passivation layer is prepared on the device surface except for the ohmic contact electrode.

A second aspect of the embodiments of the present invention provides a back-incidence solar-blind ultraviolet detector, including:

Ultraviolet light-transmitting substrate;

And the device layer of the solar-blind UV detector bonded on the UV-transmitting substrate.

As another embodiment of the present application, the substrate that transmits ultraviolet light is a substrate with a light transmittance greater than 90% and a thickness of 0.5-1 mm.

As another embodiment of the present application, the device layer of the solar-blind UV detector is a device layer of an AlGaN detector;

The device layer of the AlGaN detector includes:

An N-type AlGaN layer bonded to a UV-transmitting substrate;

an intrinsic AlGaN layer and a P-type GaN layer grown on the N-type AlGaN layer, and the intrinsic AlGaN layer and the P-type GaN layer form a mesa;

an anode disposed on the P-type GaN layer of the mesa and a cathode of the exposed region of the N-type AlGaN layer;

and preparing a passivation layer on the device surface except for the cathode and anode.

The beneficial effects of the embodiments of the present invention compared with the prior art are: compared with the prior art, the present invention first prepares the device layer of the solar-blind ultraviolet detector on a sapphire substrate; The device layer of the blind UV detector is separated from the sapphire substrate; the separated device layer of the solar blind UV detector is bonded to the UV-transmitting substrate. During operation, the back of the substrate is used as the incident surface of ultraviolet photons, which greatly increases the effective incident area. At the same time, the front electrode can be made as large as possible, so that the electric field distribution in the vertical direction is more uniform, and the detection efficiency can be greatly improved. In addition, the sapphire substrate after laser stripping can be reused, which greatly reduces the development cost of solar-blind ultraviolet detectors.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only for the present invention. In some embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

1 is a schematic diagram of a method for fabricating a back-incidence solar-blind ultraviolet detector provided by an embodiment of the present invention;

2 is a schematic diagram of a method for preparing a device layer of an AlGaN detector on a sapphire substrate provided by an embodiment of the present invention;

3 is a schematic diagram of a device layer for preparing an AlGaN detector on a sapphire substrate provided by an embodiment of the present invention;

FIG. 4 is an example diagram of a back-incidence solar-blind ultraviolet detector provided by an embodiment of the present invention.

Detailed ways

In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are set forth in order to provide a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

In order to illustrate the technical solutions of the present invention, the following specific embodiments are used for description.

FIG. 1 is a schematic diagram of an implementation flow of a method for fabricating a back-incidence solar-blind ultraviolet detector according to an embodiment of the present invention, which is described in detail as follows.

In step 101, a device layer of a solar-blind ultraviolet detector is prepared on a sapphire substrate.

The solar-blind ultraviolet wavelength range is 200-285 nm. When passing through the atmosphere, the light in this band is strongly absorbed by the ozone layer, so that there is almost no solar-blind ultraviolet radiation near the surface. Compared with infrared detectors and visible light detectors, solar-blind UV detectors can effectively shield the interference of sunlight and other natural light sources. In this field, solar-blind UV detection technology has received extensive attention.

Optionally, the device layer of the solar-blind UV detector in this step is the device layer of the AlGaN detector. The forbidden band width of AlGaN can be continuously adjusted between 3.4 and 6.2 eV according to the change of Al composition, and the corresponding light absorption wavelength changes in the range of 200 to 365 nm, which is a good choice for the preparation of solar-blind deep ultraviolet detectors.

As shown in FIG. 2 and FIG. 3 , the process of preparing the device layer 11 of the AlGaN detector on the sapphire substrate includes:

In step 201, an N-type AlGaN layer, an intrinsic AlGaN layer and a P-type GaN layer are sequentially prepared on a sapphire substrate.

As shown in FIG. 3 , an N-type AlGaN layer 101 , an intrinsic AlGaN layer 102 and a P-type GaN layer 103 are sequentially prepared on the sapphire substrate 100 . For example, the thickness of the N-type AlGaN layer 101 may be 3 micrometers, the thickness of the intrinsic AlGaN layer 102 may be 0.5 micrometers, and the thickness of the P-type GaN layer 103 may be 50 nanometers.

Step 202 , etching the P-type GaN layer and the intrinsic AlGaN layer to form a mesa on the N-type AlGaN layer.

In this step, firstly, a mask is etched on the P-type GaN layer, and the mask can be an etch-resistant photoresist, such as AZ4620, AZ1500, and the like. Exposure by contact photolithography, and then developing to obtain a mesa pattern, and then use a plasma dry etching method to etch to obtain the mesa. For example, the etching gas can be O ₂ /SF6. As shown in Figure 3, the mesa formed by etching the P-type GaN layer and the intrinsic AlGaN layer. Optionally, the table surface may be a table surface with a certain inclination angle on the side surface, for example, the inclination angle may range from 30° to 90°.

Step 203 , a cathode is prepared on the exposed area of the N-type AlGaN layer, an anode is prepared on the P-type GaN layer of the mesa, and ohmic contact electrodes are respectively formed.

In this step, a single-layer or multi-layer photoresist is firstly coated on the surface of the device, and then the electrode pattern is obtained by photolithography and development, and then the method of electron beam evaporation is used to evaporate the metal stack of a certain thickness in turn. The strong metal can be Ni/Ti/Al/Au, or Ti/Al/Pt/Au or the like. Then, the cathode and anode electrodes are obtained through a stripping process, and finally an ohmic contact is formed by a rapid annealing process. In this embodiment, the annealing temperature may range from 800° C. to 1000° C., and the annealing time may range from 2 minutes to 5 minutes. As shown in FIG. 3 , the ohmic contact electrode is 104 .

Step 204 , a passivation layer is prepared on the surface of the device except for the ohmic contact electrode.

As shown in Figure 3, a passivation medium is generated on the surface of the device to form a passivation layer to achieve surface passivation. The growth method of the passivation medium can be thermal oxidation, low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition and atomic layer deposition, etc. The passivation medium can also be a composite medium grown by different methods, and the passivation medium can include: SiO2, SiN, Al2O3, etc., the thickness of the passivation dielectric layer ranges from 100nm to 500nm. After the dielectric growth is completed, photolithography is performed, and the electrode and photosensitive area are exposed by etching. As shown in Figure 3, 105 is the passivation layer after etching. The passivation layer can reduce the leakage rate and improve the stability of the detector device. .

Since the electrodes in the device layer of the solar-blind UV detector will occupy more area, if the front side is used as the UV photon incident surface, the effective incident area will be small. smaller. However, the effective incident area is still relatively small, so we can use the back incident type, which greatly increases the effective incident area, and at the same time, the front electrode can be made as large as possible to make the electric field distribution in the vertical direction more uniform. When back-incidence irradiation is used, ultraviolet photons incident on the material from different positions on the surface can be fully accelerated by the electric field and then converted into photocurrent to be detected, thereby improving the detection efficiency.

In step 102, the device layer of the solar-blind UV detector is separated from the sapphire substrate by using a laser lift-off technique.

As shown in FIG. 3 , in this step, the use of laser lift-off technology to separate the device layer of the solar-blind UV detector from the sapphire substrate may include: irradiating the sapphire with a laser with preset photon energy substrate, so that the laser light penetrates through the sapphire substrate and is absorbed by the first surface layer in the device layer of the solar-blind ultraviolet detector that is in contact with the sapphire substrate, and thermally decomposes to generate metal gallium and nitrogen; The sapphire substrate is heated on a heating plate with a high temperature to liquefy the metal gallium, and the device layer of the solar-blind ultraviolet detector is separated from the sapphire substrate; the preset photon energy is greater than that of the first surface layer. The energy is less than the bandgap photon energy of the sapphire substrate. The preset temperature is greater than 40°C.

Optionally, when the device layer of the solar-blind ultraviolet detector is the device layer of the AlGaN detector, the preset photon energy is greater than the energy of the AlGaN surface layer and less than the bandgap photon energy of the sapphire substrate. After the laser is absorbed by the AlGaN surface layer, thermal decomposition occurs to generate metal gallium (Ga) and nitrogen gas, and then the wafer is heated on a hot plate above 40°C, so that Ga will liquefy, and the device layer of the AlGaN detector is separated from the sapphire substrate.

The laser-stripped sapphire substrate can be reused, thereby reducing the development cost of solar-blind UV detectors.

Step 103 , bonding the separated device layers of the solar-blind UV detector to the UV-transmitting substrate.

In this step, when the device layer of the solar-blind ultraviolet detector is the device layer of the AlGaN detector, the device layer of the separated AlGaN detector is bonded to the substrate transparent to ultraviolet light. Optionally, the UV-transmitting substrate may be a thin substrate with high light transmittance. For example, a substrate that transmits ultraviolet light is a substrate with a light transmittance greater than 90% and a thickness of 0.5-1 mm. The ultraviolet light-transmitting substrate is a glass substrate with a light transmittance greater than 90% and a thickness of 0.5-1 mm.

When the back-incidence solar-blind UV detector is working, as shown in FIG. 4 , the substrate 106 transparent to UV light serves as the back-incidence surface, and simultaneously plays the role of supporting and protecting the AlGaN UV detector.

The above-mentioned manufacturing method of the solar-blind ultraviolet detector of the back-incidence type is as follows: firstly, the device layer of the solar-blind ultraviolet detector is prepared on a sapphire substrate; Separating; bonding the separated device layer of the solar-blind UV detector to the UV-transmitting substrate. During operation, the back of the substrate is used as the incident surface of ultraviolet photons, which greatly increases the effective incident area. At the same time, the front electrode can be made as large as possible, so that the electric field distribution in the vertical direction is more uniform, and the detection efficiency can be greatly improved. In addition, the sapphire substrate after laser stripping can be reused, which greatly reduces the development cost of solar-blind ultraviolet detectors.

It should be understood that the size of the sequence numbers of the steps in the above embodiments does not mean the sequence of execution, and the execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

Corresponding to the manufacturing method of the back-incidence type solar-blind ultraviolet detector described in the above embodiments, FIG. 4 shows an example diagram of a back-incidence type solar-blind ultraviolet detector provided by an embodiment of the present invention. As shown in Figure 4, the apparatus may include:

UV-transmitting substrate 106;

And the device layer 11 of the solar-blind UV detector bonded on the UV-transmitting substrate.

Optionally, as shown in FIG. 4 , the device layer 11 of the solar-blind ultraviolet detector is a device layer of an AlGaN detector;

The device layer of the AlGaN detector includes:

The N-type AlGaN layer 101 bonded on the UV-transmitting substrate 106;

The intrinsic AlGaN layer 102 and the P-type GaN layer 103 are grown on the N-type AlGaN layer 101, and the intrinsic AlGaN layer 102 and the P-type GaN layer 103 form a mesa; optionally, the side inclination angle of the mesa may be 30°～90°;

The anode is arranged on the P-type GaN layer 103 of the mesa and the cathode of the exposed area of the N-type AlGaN layer 101; optionally, a rapid annealing process can also be used to form an ohmic contact electrode.

And a passivation layer 106 is prepared on the device surface except for the cathode and anode.

Optionally, the UV-transmitting substrate is a substrate with a light transmittance greater than 90% and a thickness of 0.5-1 mm. The ultraviolet light-transmitting substrate is a glass substrate with a light transmittance greater than 90% and a thickness of 0.5-1 mm.

The above-mentioned back-incidence solar-blind ultraviolet detector, a substrate that transmits ultraviolet light; and a device layer of the solar-blind ultraviolet detector bonded on the substrate that transmits ultraviolet light. During operation, the back of the substrate is used as the incident surface of ultraviolet photons, which greatly increases the effective incident area. At the same time, the front electrode can be made as large as possible, so that the electric field distribution in the vertical direction is more uniform, and the detection efficiency can be greatly improved. In addition, the sapphire substrate after laser stripping can be reused, which greatly reduces the development cost of solar-blind ultraviolet detectors.

The above-mentioned embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be used for the foregoing implementations. The technical solutions described in the examples are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the within the protection scope of the present invention.

Claims (10)

1. A method for manufacturing a back-incident solar blind ultraviolet detector is characterized by comprising the following steps:

preparing a device layer of the solar blind ultraviolet detector on a sapphire substrate;

separating a device layer of the solar blind ultraviolet detector from the sapphire substrate by adopting a laser lift-off technology;

bonding the separated device layer of the solar blind ultraviolet detector to the ultraviolet light transmitting substrate.

2. The method for manufacturing the back-incident solar blind ultraviolet detector according to claim 1, wherein the step of separating the device layer of the solar blind ultraviolet detector from the sapphire substrate by using a laser lift-off technology comprises the following steps:

irradiating the sapphire substrate by adopting laser with preset photon energy, enabling the laser to penetrate through the sapphire substrate and be absorbed by a first surface layer, in a device layer of the solar blind ultraviolet detector, in contact with the sapphire substrate, and generating gallium and nitrogen through thermal decomposition;

and heating the sapphire substrate on a heating plate with a preset temperature to liquefy the metal gallium, and separating a device layer of the solar blind ultraviolet detector from the sapphire substrate.

3. The method for manufacturing a back-incident solar-blind ultraviolet detector as claimed in claim 2,

the preset photon energy is larger than the energy of the first surface layer and smaller than the band gap photon energy of the sapphire substrate.

The preset temperature is greater than 40 ℃.

4. The method for manufacturing the back-incident solar blind ultraviolet detector according to any one of claims 1 to 3, wherein the ultraviolet light transmitting substrate is a substrate with light transmittance of more than 90% and thickness of 0.5-1 mm.

5. The method for manufacturing a back-incident solar-blind ultraviolet detector as claimed in claim 4,

the ultraviolet-transmitting substrate is a glass substrate with the light transmittance of more than 90% and the thickness of 0.5-1 mm.

6. The method for manufacturing the back-incident solar-blind ultraviolet detector according to claim 2, wherein the device layer of the solar-blind ultraviolet detector is a device layer of an AlGaN detector;

the preset photon energy is larger than the energy of the AlGaN surface layer and smaller than the band gap photon energy of the sapphire substrate.

7. The method for manufacturing the back-incident solar blind ultraviolet detector as claimed in claim 6, wherein the step of preparing the device layer of the AlGaN detector on the sapphire substrate comprises the following steps:

sequentially preparing an N-type AlGaN layer, an intrinsic AlGaN layer and a P-type GaN layer on a sapphire substrate;

etching the P-type GaN layer and the intrinsic AlGaN layer to form a table top on the N-type AlGaN layer;

preparing a cathode in an exposed area of the N-type AlGaN layer, preparing an anode on the P-type GaN layer of the table top, and respectively forming ohmic contact electrodes;

and preparing a passivation layer on the surface of the device except for the ohmic contact electrode.

8. A back-incident solar blind ultraviolet detector, comprising:

a substrate that is transparent to ultraviolet light;

and a device layer of the solar blind ultraviolet detector bonded on the ultraviolet light transmitting substrate.

9. The back-incident solar blind ultraviolet detector of claim 8, wherein the substrate transmitting ultraviolet light is a substrate having a light transmittance of more than 90% and a thickness of 0.5-1 mm.

10. The back-incident solar-blind ultraviolet detector according to claim 8, wherein the device layer of the solar-blind ultraviolet detector is a device layer of an AlGaN detector;

the device layer of the AlGaN detector comprises:

an N-type AlGaN layer bonded on the ultraviolet light transmitting substrate;

an intrinsic AlGaN layer and a P-type GaN layer which grow on the N-type AlGaN layer, wherein the intrinsic AlGaN layer and the P-type GaN layer form a table board;

an anode arranged on the P-type GaN layer of the table top and a cathode of the exposed region of the N-type AlGaN layer;

and preparing a passivation layer on the surface of the device except for the cathode and the anode.

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