CN112086436A - Solar blind ultraviolet focal plane imaging detector and manufacturing method thereof - Google Patents

Abstract

The present application discloses a solar-blind ultraviolet focal plane imaging detector and a manufacturing method thereof. The detector includes a detector array, a readout circuit, a passivation layer, a metal layer with a first through hole, and an insulating layer with a second through hole. layer, filler layer, connection post; the metal layer is located on the lower surface of the passivation layer, the first through hole corresponds to the P-type electrode in the detector array, and the size of the first through hole is smaller than that of the P-type electrode, so that the metal The layer corresponds to the mesa array gap in the detector array and the area of the surface of the mesa array that is not covered by the P-type electrode; the insulating layer is located on the lower surface of the metal layer and in the first through hole, the second through hole corresponds to the first through hole, and the third through hole corresponds to the first through hole. The size of the second through hole is smaller than that of the first through hole. The insulating layer in the solar-blind UV focal plane imaging detector avoids short circuit between the metal layer and the readout circuit, and the metal layer prevents visible light from being incident on the read-out circuit through the gap of the array mesa, thereby improving the solar-blind UV focal plane imaging detector. Helioblind/visible inhibition ratio.

Description

A solar-blind ultraviolet focal plane imaging detector and method of making the same

technical field

The present application relates to the technical field of photodetectors, in particular to a solar-blind ultraviolet focal plane imaging detector and a manufacturing method thereof.

Background technique

The schematic diagram of the solar-blind UV focal plane imaging detector structure is shown in Figure 1, including a detector array, a readout circuit, a filler layer, a passivation layer with openings, and a connecting column connecting the detector array and the readout circuit. The device array includes a substrate 1, a nucleation layer 2, a superlattice layer 3, an intrinsic AlGaN layer 4, an N-type AlGaN layer 5, a mesa array formed by an I-type AlGaN layer 6 and a P-type AlGaN layer 7, and a common N-type The electrode 8, the pixel P-type electrode 9, the detector array is used as a photosensitive component to realize the conversion of the photoelectric signal of the solar-blind ultraviolet focal plane imaging detector, and the readout circuit is used for the reading of the photoelectric signal.

The substrate in the detector array can transmit light from visible light to near-infrared wavelengths. Since the readout circuit itself is a good visible light/near-infrared photoelectric imaging detector, it has sensitive spectral response characteristics to light with wavelengths above 350 nm. When the solar-blind UV focal plane imaging detector is working, the ambient light (mainly visible light) is transmitted to the readout circuit through the pixel gap of the detector array (the mesa array gap), so that the readout circuit produces a visible light spectral response, causing solar radiation. Blind UV focal plane imaging detectors have a low solar-blind/visible suppression ratio and cannot take advantage of the solar-blind UV intrinsic cutoff of AlGaN materials.

Therefore, how to solve the above technical problems should be the focus of those skilled in the art.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide a solar-blind UV focal plane imaging detector and a manufacturing method thereof, so as to improve the solar-blind/visible suppression ratio of the solar-blind UV focal-plane imaging detector.

In order to solve the above technical problems, the present application provides a solar-blind ultraviolet focal plane imaging detector, comprising a detector array, a readout circuit, a passivation layer, a metal layer with a first through hole, and an insulating layer with a second through hole , packing layer, connecting column;

The metal layer is located on the lower surface of the passivation layer, the first through hole corresponds to the P-type electrode in the detector array, and the size of the first through hole is smaller than the size of the P-type electrode, so that the metal layer corresponds to the mesa array gap in the detector array and the area of the mesa array surface not covered by the P-type electrode;

The insulating layer is located on the lower surface of the metal layer and in the first through hole, the second through hole corresponds to the first through hole, and the size of the second through hole is smaller than that of the first through hole size of the hole.

Optionally, the metal layer is an aluminum layer or a gold layer.

Optionally, the insulating layer is a silicon dioxide layer or a silicon nitride layer.

Optionally, the readout circuit is a CMOS readout circuit or a CCD readout circuit.

Optionally, the thickness of the metal layer ranges from 200 nm to 300 nm, inclusive.

Optionally, the thickness of the insulating layer ranges from 200 nm to 1 μm, inclusive.

The present application also provides a method for preparing a solar-blind ultraviolet focal plane imaging detector, comprising:

obtain a detector array;

preparing a passivation layer on the upper surface of the detector array;

A photoresist layer is coated on the upper surface of the passivation layer, and exposed and developed, so that the photoresist layer corresponds to the mesa array gap in the detector array and the surface of the mesa array is free from P-type electrodes The covered area forms a hollow area, and the size of the photoresist layer is smaller than the size of the corresponding P-type electrode;

A metal layer is prepared on the upper surface of the photoresist layer, and the photoresist layer and the metal layer stacked on the surface of the photoresist layer are removed, so that the metal layer has a first through hole;

preparing an insulating layer on the upper surface of the metal layer;

etching the insulating layer and the passivation layer in the first through hole to form a second through hole, and the size of the second through hole is smaller than the size of the first through hole, the The second through hole ends at the surface of the P-type electrode to obtain a processed detector array;

The readout circuit and the processed detector array are connected by connecting posts using flip-chip bonding technology, and a filler layer is formed between the readout circuit and the insulating layer.

Optionally, the preparing a metal layer on the upper surface of the photoresist layer includes:

The metal layer is prepared on the upper surface of the photoresist layer by an electron beam evaporation process or a magnetron sputtering process.

Optionally, the preparing an insulating layer on the upper surface of the metal layer includes:

The insulating layer is formed on the upper surface of the metal layer using a plasma enhanced chemical vapor deposition process.

Optionally, the etching of the insulating layer and the passivation layer in the first through hole to form the second through hole includes:

The second through hole is formed by etching the insulating layer and the passivation layer in the first through hole by using photolithography and plasma etching processes.

A solar-blind UV focal plane imaging detector provided in this application includes a detector array, a readout circuit, a passivation layer, a metal layer with a first through hole, an insulating layer with a second through hole, and a filler layer , a connecting column; the metal layer is located on the lower surface of the passivation layer, the first through hole corresponds to the P-type electrode in the detector array, and the size of the first through hole is smaller than the P-type electrode the size of the electrode, so that the metal layer corresponds to the mesa array gap in the detector array and the area of the mesa array surface not covered by the P-type electrode; the insulating layer is located on the lower surface of the metal layer and all the Among the first through holes, the second through holes correspond to the first through holes, and the size of the second through holes is smaller than that of the first through holes.

It can be seen that the solar-blind UV focal plane imaging detector in this application not only includes a detector array, a readout circuit, a passivation layer filling layer, and a connecting column, but also includes a metal layer with a first through hole and a second through hole. The insulating layer avoids short circuit between the metal layer and the readout circuit. The metal layer corresponds to the mesa array gap in the detector array and the area on the surface of the mesa array that is not covered by the P-type electrode, so as to prevent visible light from passing through the array mesa gap. On the readout circuit, the visible light spectral response of the readout circuit is avoided, thereby improving the solar blind/visible suppression ratio of the solar blind UV focal plane imaging detector.

In addition, the present application also provides a method for fabricating a solar-blind ultraviolet focal plane imaging detector with the above advantages.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present application or the prior art 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 some embodiments of the present application, 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 structural diagram of a solar-blind ultraviolet focal plane imaging detector in the prior art;

2 is a schematic structural diagram of a solar-blind ultraviolet focal plane imaging detector provided by an embodiment of the application;

Fig. 3 is the transmission spectrum comparison diagram of the solar-blind ultraviolet focal plane imaging detector of the application and the solar-blind ultraviolet focal plane imaging detector of the prior art;

4 is a flowchart of a method for preparing a solar-blind ultraviolet focal plane imaging detector provided by an embodiment of the application;

In the figure, 1. substrate, 2. nucleation layer, superlattice layer 3., 4. intrinsic AlGaN layer, 5. N-type AlGaN layer, 6. I-type AlGaN layer, 7. P-type AlGaN layer, 8. Common N-type electrode, 9. Pixel P-type electrode, 10. Passivation layer, 11. Connection column, 12. Readout circuit, 13. Filler layer, 14. Pixel upper electrode, 15. Metal layer, 16 .Insulation.

Detailed ways

In order to make those skilled in the art better understand the solution of the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can do so without departing from the connotation of the present invention. Similar promotion, therefore, the present invention is not limited by the specific embodiments disclosed below.

AlGaN is a direct wide-bandgap semiconductor material with physicochemical stability and adjustable band gap. By adjusting the Al composition higher than 45%, the solar-blind UV intrinsic cutoff can be achieved. Ideal material for suppression ratio, radiation-hardened solar-blind UV focal-plane imaging detectors.

As described in the Background Art section, in the existing solar-blind UV focal plane imaging detector, ambient light passes through the mesa array gap of the detector array and is incident on the readout circuit, causing the readout circuit to generate a visible light spectral response, resulting in solar-blind UV light. Focal plane imaging detectors have low solar blindness/visibility suppression ratios.

In view of this, the present application provides a solar-blind ultraviolet focal plane imaging detector, please refer to FIG. 2 , which is a schematic structural diagram of a solar-blind ultraviolet focal plane imaging detector provided by an embodiment of the present application. Blind UV focal plane imaging detectors include:

a detector array, a readout circuit 12, a passivation layer 10, a metal layer 15 with a first through hole, an insulating layer 16 with a second through hole, a filler layer 13, and a connection post 11;

The metal layer 15 is located on the lower surface of the passivation layer 10 , the first through hole corresponds to the P-type electrode in the detector array, and the size of the first through hole is smaller than that of the P-type electrode. size, so that the metal layer 15 corresponds to the mesa array gap in the detector array and the area of the mesa array surface not covered by the P-type electrode;

The insulating layer 16 is located on the lower surface of the metal layer 15 and in the first through hole, the second through hole corresponds to the first through hole, and the size of the second through hole is smaller than that of the first through hole. The size of a through hole.

The detector array includes a substrate 1, a nucleation layer 2, a superlattice layer 3, an intrinsic AlGaN layer 4, an N-type AlGaN layer 5, a mesa array formed by an I-type AlGaN layer 6 and a P-type AlGaN layer 7, a common N Type electrode 8 and pixel P-type electrode 9, specifically, the substrate 1 is a double-sided polished sapphire substrate, the nucleation layer 2 is an AlN layer, and the superlattice layer 3 is an AlGaN/AlN layer.

The readout circuit 12 is provided with a pixel upper electrode 14, the pixel upper electrode 14 is connected with a connection column 11, the pixel P-type electrode and the common N-type electrode are also connected with the connection column 11, and the detector array is connected by the connection of the connection column 11. Mixed integration with readout circuit 12 . The material of the connection post 11 is generally indium, and the material of the filler layer 13 is generally epoxy resin.

It should be noted that the type of the readout circuit 12 is not specifically limited in this application. For example, the readout circuit 12 is a CMOS (Complementary Metal Oxide Semiconductor, complementary metal oxide semiconductor) readout circuit 12 or a CCD (Charge -coupled Device, electrically coupled element) readout circuit 12.

In the present application, the purpose of setting the first through hole corresponding to the P-type electrode and the size of the first through hole is smaller than that of the P-type electrode is to ensure that the metal layer 15 completely covers the mesa array gap in the detector array and the surface of the mesa array is not covered. The area covered by the P-type electrode is used to prevent light from irradiating on the readout circuit 12 . Optionally, the distance between the edge of the first through hole and the edge of the P-type electrode is between 1 μm and 2 μm.

Preferably, the metal layer 15 is an aluminum layer or a gold layer. Since gold and aluminum have high reflectivity to light, they can better block the light in the gap of the mesa array, wherein the cost of the aluminum layer is lower.

Optionally, the thickness of the metal layer 15 ranges from 200 nm to 300 nm, including the endpoint value, to avoid that the thickness of the metal layer 15 is too thin, causing light to pass through the metal layer 15 and irradiate on the readout circuit 12, while avoiding the metal layer 15. If the thickness of the layer 15 is too thick, raw materials are wasted and the cost is increased.

The shape of the first through hole in the metal layer 15 includes, but is not limited to, a circle, a square, and a rectangle.

The material of the insulating layer 16 is not specifically limited in this application, and can be set by yourself. For example, the insulating layer 16 is a silicon dioxide layer or a silicon nitride layer.

It should be pointed out that, in order to reduce the difficulty of the manufacturing process, the material of the passivation layer 10 is generally the same as that of the insulating layer 16 .

Optionally, the thickness of the insulating layer 16 ranges from 200 nm to 1 μm, inclusive, to ensure that the insulating layer 16 has good insulating properties. Preferably, the thickness of the insulating layer 16 is 500 nm.

The shape of the second through hole in the insulating layer 16 includes, but is not limited to, circle, square, and rectangle. The size of the second through hole is smaller than the size of the first through hole, and the difference in size may range from 1 μm to 3 μm.

The solar-blind UV focal plane imaging detector in this application not only includes a detector array, a readout circuit 12, a passivation layer 10, a filler layer 13, and a connection post 11, but also includes a metal layer 15 with a first through hole and a metal layer 15 with a first through hole. The insulating layer 16 of the two through holes, the insulating layer 16 avoids short circuit between the metal layer 15 and the readout circuit 12, the metal layer 15 corresponds to the mesa array gap in the detector array and the area of the mesa array surface that is not covered by the P-type electrode, Thus, visible light is prevented from being incident on the readout circuit 12 through the array mesa gap, and visible light spectral response of the readout circuit 12 is avoided, thereby improving the solar blindness/visibility suppression ratio of the solar blind UV focal plane imaging detector.

Fig. 3 is the transmission spectrum comparison diagram of the solar-blind UV focal plane imaging detector of the present application and the prior art solar-blind UV focal plane imaging detector, the abscissa is the wavelength, the ordinate is the transmittance, and the solid line in Fig. 3 represents The transmittance of the solar-blind ultraviolet focal plane imaging detector of the present application at different wavelengths, the dotted line represents the transmittance of the solar-blind ultraviolet focal plane imaging detector of the prior art at different wavelengths, it can be concluded that the solar-blind ultraviolet focal plane imaging detector of the present application The visible light/near-infrared light transmittance of the focal plane imaging detector is less than 1%, and the visible light/near-infrared light transmittance of the solar-blind ultraviolet focal plane imaging detector in the prior art is higher than 25%. The helioblind/visible suppression ratio of the planar imaging detector is significantly improved.

The present application also provides a method for preparing a solar-blind ultraviolet focal plane imaging detector. Please refer to FIG. 4 . FIG. 4 is a flowchart of a method for preparing a solar-blind ultraviolet focal plane imaging detector provided by an embodiment of the application. The method includes: :

Step S101: Obtain a detector array.

Specifically, a nucleation layer, a superlattice layer, an intrinsic AlGaN layer, an N-type AlGaN layer, an I-type AlGaN layer, and a P-type AlGaN layer are grown on the substrate, and the I-type AlGaN layer and the P-type AlGaN layer are etched A mesa array is formed by etching, and a common N-type electrode and a pixel P-type electrode are fabricated. The specific fabrication process is well known to those skilled in the art and will not be described in detail here.

Step S102 : preparing a passivation layer on the upper surface of the detector array.

The passivation layer is prepared by using a plasma enhanced chemical vapor deposition process. Preferably, the material of the passivation layer is controlled to be the same as the material of the insulating layer, so that when the second through hole is formed by etching, the passivation layer and the passivation layer are formed by using the same etching gas. The insulating layers are etched together to reduce the difficulty of the fabrication process.

Step S103: Coating a photoresist layer on the upper surface of the passivation layer, and performing exposure and development, so that the photoresist layer corresponds to the mesa array gap in the detector array and the surface of the mesa array is not free. The area covered by the P-type electrode forms a hollow area, and the size of the photoresist layer is smaller than the size of the corresponding P-type electrode.

It should be noted that the shape of the photoresist layer is not specifically limited in this application, and it depends on the situation. For example, the shape of the photoresist layer may be circular, rectangular, square, or the like.

Step S104 : preparing a metal layer on the upper surface of the photoresist layer, and removing the photoresist layer and the metal layer stacked on the surface of the photoresist layer, so that the metal layer has a first through hole .

Optionally, the preparing a metal layer on the upper surface of the photoresist layer includes:

The metal layer is prepared on the upper surface of the photoresist layer by an electron beam evaporation process or a magnetron sputtering process.

Preferably, the control metal layer is an aluminum layer or a gold layer. Since gold and aluminum have high reflectivity to light, they can better block light in the gap of the mesa array, wherein the cost of the aluminum layer is lower.

Optionally, the thickness of the generated metal layer is controlled to be in the range of 200nm to 300nm, including the endpoint value, to avoid the thickness of the generated metal layer being too thin, causing light to pass through the metal layer and irradiating the readout circuit, while avoiding the generated metal layer. If the thickness is too thick, raw materials are wasted and the cost increases.

Specifically, the lift-off process is used to remove the photoresist layer and the metal layer stacked on the surface of the photoresist layer. Since the photoresist layer corresponds to the mesa array gap and the area of the mesa array surface that is not covered by the P-type electrode is a hollow area, Therefore, the metal layer formed in the hollow area is in direct contact with the passivation layer, that is, the metal layer in the solar-blind UV focal plane imaging detector obtained. In addition, the size of the photoresist layer is smaller than the size of the corresponding P-type electrode , the metal layer stacked on the photoresist layer is removed together with the photoresist, that is, a first through hole is formed, so the first through hole corresponds to the P-type electrode and the size of the first through hole is smaller than that of the P-type electrode. The shape of the first through hole is the shape of the photoresist layer.

Step S105 : preparing an insulating layer on the upper surface of the metal layer.

It should be pointed out that since the metal layer has the first through hole, there is also an insulating layer in the first through hole.

The insulating layer is prepared on the upper surface of the metal layer by a plasma-enhanced chemical vapor deposition process, and the prepared insulating layer is not specifically limited in this application, and may be a silicon dioxide layer or a silicon nitride layer.

Optionally, the thickness of the generated insulating layer is controlled to be between 200 nm and 1 μm, including the endpoint value, to ensure that the insulating layer has good insulating properties. Preferably, the thickness of the insulating layer is 500 nm.

Step S106 : etching the insulating layer and the passivation layer in the first through hole to form a second through hole, and the size of the second through hole is smaller than the size of the first through hole , the second through hole ends at the surface of the P-type electrode, and the processed detector array is obtained.

Optionally, the etching of the insulating layer and the passivation layer in the first through hole to form the second through hole includes:

The second through hole is formed by etching the insulating layer and the passivation layer in the first through hole by using photolithography and plasma etching processes.

Step S107 : using flip-chip bonding technology to connect the readout circuit and the processed detector array through connecting posts, and form a filler layer between the readout circuit and the insulating layer.

It should be noted that the process of connecting the readout circuit and the detector array by connecting posts and preparing the filler is consistent with the prior art, which is well known to those skilled in the art, and will not be described in detail here.

The solar-blind UV focal-plane imaging detector detector prepared by the solar-blind UV focal-plane imaging detector manufacturing method in the present application includes, in addition to a detector array, a readout circuit, a passivation layer filling layer, and a connecting column, and also includes A metal layer with a first through hole and an insulating layer with a second through hole, the insulating layer avoids short circuit between the metal layer and the readout circuit, the metal layer corresponds to the mesa array gap in the detector array and the surface of the mesa array is not protected by P Therefore, the visible light can be prevented from being incident on the readout circuit through the gap of the array mesa, and the visible light spectral response of the readout circuit can be avoided, thereby improving the solar-blind/visible suppression ratio of the solar-blind UV focal plane imaging detector.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments may be referred to each other. As for the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

The solar-blind ultraviolet focal plane imaging detector and its fabrication method provided by the present application are described in detail above. Specific examples are used herein to illustrate the principles and implementations of the present application, and the descriptions of the above embodiments are only used to help understand the methods and core ideas of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the principles of the present application, several improvements and modifications can also be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims (10)

1. A solar-blind ultraviolet focal plane imaging detector, characterized in that, comprising a detector array, a readout circuit, a passivation layer, a metal layer with a first through hole, an insulating layer with a second through hole, a filler layer, connecting column; The metal layer is located on the lower surface of the passivation layer, the first through hole corresponds to the P-type electrode in the detector array, and the size of the first through hole is smaller than the size of the P-type electrode, so that the metal layer corresponds to the mesa array gap in the detector array and the area of the mesa array surface not covered by the P-type electrode; The insulating layer is located on the lower surface of the metal layer and in the first through hole, the second through hole corresponds to the first through hole, and the size of the second through hole is smaller than that of the first through hole size of the hole. 2 . The solar-blind ultraviolet focal plane imaging detector according to claim 1 , wherein the metal layer is an aluminum layer or a gold layer. 3 . 3. The solar-blind ultraviolet focal plane imaging detector according to claim 1 or 2, wherein the insulating layer is a silicon dioxide layer or a silicon nitride layer. 4. The solar-blind ultraviolet focal plane imaging detector according to claim 3, wherein the readout circuit is a CMOS readout circuit or a CCD readout circuit. 5 . The solar-blind ultraviolet focal plane imaging detector according to claim 4 , wherein the thickness of the metal layer ranges from 200 nm to 300 nm, inclusive. 6 . 6 . The solar-blind ultraviolet focal plane imaging detector according to claim 5 , wherein the thickness of the insulating layer ranges from 200 nm to 1 μm, inclusive. 6 . 7. A method for preparing a solar-blind ultraviolet focal plane imaging detector, comprising: obtain a detector array; preparing a passivation layer on the upper surface of the detector array; A photoresist layer is coated on the upper surface of the passivation layer, and exposed and developed, so that the photoresist layer corresponds to the mesa array gap in the detector array and the surface of the mesa array is free from P-type electrodes The covered area forms a hollow area, and the size of the photoresist layer is smaller than the size of the corresponding P-type electrode; A metal layer is prepared on the upper surface of the photoresist layer, and the photoresist layer and the metal layer stacked on the surface of the photoresist layer are removed, so that the metal layer has a first through hole; preparing an insulating layer on the upper surface of the metal layer; etching the insulating layer and the passivation layer in the first through hole to form a second through hole, and the size of the second through hole is smaller than the size of the first through hole, the The second through hole ends at the surface of the P-type electrode to obtain a processed detector array; The readout circuit and the processed detector array are connected by connecting posts using flip-chip bonding technology, and a filler layer is formed between the readout circuit and the insulating layer. 8. The method for preparing a solar-blind ultraviolet focal plane imaging detector according to claim 7, wherein the preparing a metal layer on the upper surface of the photoresist layer comprises: The metal layer is prepared on the upper surface of the photoresist layer by an electron beam evaporation process or a magnetron sputtering process. 9. The method for preparing a solar-blind ultraviolet focal plane imaging detector according to claim 8, wherein the preparing an insulating layer on the upper surface of the metal layer comprises: The insulating layer is formed on the upper surface of the metal layer using a plasma enhanced chemical vapor deposition process. 10 . The method for preparing a solar-blind ultraviolet focal plane imaging detector according to claim 9 , wherein the insulating layer and the passivation layer located in the first through hole are formed by etching. 11 . The second through hole includes: The second through hole is formed by etching the insulating layer and the passivation layer in the first through hole by using photolithography and plasma etching processes.

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