Double-wave infrared detector preparation method and double-wave infrared section detector

Abstract

The invention discloses a preparation method of a double-wave infrared detector and a double-wave infrared section detector. The preparation method comprises the following steps: providing a GaSb substrate; sequentially growing a bottom contact layer, a medium wave absorption layer, a barrier layer, a long wave absorption layer and a top contact layer on the GaSb substrate; performing primary deposition of a passivation layer on the surface of the top contact layer, and performing primary etching from the absorption layer to the top contact layer; performing secondary deposition of a passivation layer in a covering manner, and performing secondary etching from the top contact layer to the bottom contact layer; depositing a passivation layer for the third time in a covering manner; holes are formed in the passivation layer of the table top and the passivation layer of the common electrode area, UBM metal TiPtAu is evaporated at the holes, and a detector chip is manufactured; the plasma exposure time of the surface of the absorption layer is reduced to the greatest extent; the detector chip and the In column of the reading circuit are interconnected to form the detector, and the prepared detector can obtain medium-wave infrared and long-wave infrared image information by using a single detector, and has excellent detection, identification and identification capabilities.

Description

Technical Field

[0001] The invention relates to the technical field of infrared detectors, in particular to a dual-wave infrared detector preparation method and a dual-wave infrared detector. Background Art

[0002] Infrared detectors are the core of the infrared industry chain, and the performance of the detectors directly determines the quality of infrared thermal imaging. Infrared thermal imaging has the advantages of good concealment, strong anti-interference, and strong target recognition ability. It plays an increasingly important role in the fields of special security monitoring such as atmospheric and pollution source emission monitoring, remote sensing of volatile gases such as VOC, online non-stop monitoring of motor vehicle exhaust, and gas leakage.

[0003] Among them, dual-band infrared detectors can obtain more image information than single-band detectors and have excellent detection, recognition and identification capabilities. Dual-band detectors are achieved by sequentially growing each absorption layer and then forming two electrodes to connect each absorption layer. This method can detect two bands at the same time and can increase the frame rate of the detector, but the manufacturing process is complicated and small-pitch focal plane arrays are difficult to achieve. Therefore, a dual-wave infrared detector preparation method and a dual-wave infrared band detector are urgently needed to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a dual-wave infrared detector and a dual-wave infrared detector, which can effectively solve the problems existing in the above-mentioned prior art.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solution: a method for preparing a dual-wave infrared detector, comprising:

[0006] Providing a GaSb substrate;

[0007] A bottom contact layer, a medium-wave absorption layer, a barrier layer, a long-wave absorption layer, and a top contact layer are sequentially grown on a GaSb substrate;

[0008] Depositing a passivation layer once on the surface of the top contact layer and etching once from the absorption layer to the top contact layer;

[0009] A passivation layer is deposited in a blanket manner for a second time, and a second etching is performed from the top contact layer to the bottom contact layer;

[0010] The passivation layer is deposited three times in a blanket manner;

[0011] Holes are made in the passivation layer of the table and the common electrode area, and UBM metal TiPtAu is evaporated at the holes to make a detector chip;

[0012] The detector chip is interconnected with the In column of the readout circuit to form a detector.

[0013] Preferably, the total thickness of the absorption layer is 7 microns.

[0014] Preferably, in one etching, a MESA pattern is formed on the surface of the absorption layer by photolithography, and the MESA is etched by ICP, with a processing temperature of 200°C-250°C, a working pressure of 6.66×10-4KPa, a BCl3 flow rate of 5sccm, an RF power of 30W, and an ICP power of 500W.

[0015] Preferably, after one etching, ICPRIE is used for hydrogen plasma treatment, with a treatment temperature of 200° C.-250° C., a working pressure of 6.66×10-4 kPa, a H2 flow rate of 5 sccm, an RF power of 30 W, and an ICP power of 500 W.

[0016] Preferably, the detector chip and the In column of the readout circuit are interconnected together by a reverse welding machine, and the reverse welding pressure is 16 kg; and

[0017] Use filling glue to interconnect the detector chip and the readout circuit and fill the gap. The curing temperature is 80℃ / 15h;

[0018] The GaSb substrate is thinned to 20-30 microns using chemical mechanical polishing.

[0019] Preferably, the GaSb substrate is removed based on a cro3 solution, and the detector chip is plated with ZnS backside anti-reflection with a thickness of 980 nm.

[0020] The present invention also discloses a dual-wave infrared detector, which includes a GaSb substrate, and a bottom contact layer, a medium-wave absorption layer, a barrier layer, a long-wave absorption layer and a top contact layer which are sequentially arranged on the GaSb substrate, and is prepared by the dual-wave infrared detector preparation method.

[0021] Preferably, the GaSb substrate is a Te-doped GaSb substrate with a thickness of 20 microns; the bottom contact layer is an n-type bottom contact layer, which adopts InAs / GaSb superlattice material, has a cycle period of 10MLInAs / 10MLGaSb, and a thickness of 500nm; the medium-wave absorption layer is an unintentionally doped InAs / GaSb superlattice material, has a cycle period of 10MLInAs / 10MLGaSb, and a thickness of 4 microns; the barrier layer is an unintentionally doped InAs / GaSb superlattice material, has a cycle period of 4MLInAs / 9MLGaSb, and a thickness of 280nm; the long-wave absorption layer is an unintentionally doped InAs / GaSb superlattice material, has a cycle period of 14MLInAs / 17MLGaSb, and a thickness of 3 microns; the top contact layer is an n-type top contact layer, which adopts InAs / GaSb superlattice material, has a cycle period of 14MLInAs / 17MLGaSb.

[0022] Beneficial effects: the dual-wave infrared detector of the present invention can not only obtain more image information, but also has excellent detection, recognition and identification capabilities, and the two absorption layers are separated by a barrier layer, and each band can be detected by a bias bias selection; the prepared dual-band device exhibits dark current and spectral response characteristics of MWIR and LWIR bands under negative bias and positive bias, respectively, and the spectral crosstalk, the main problem of the dual-band detector, is also improved; and the dual-wave infrared detector preparation method of the present invention, on the one hand, can more effectively and accurately perform deeper etching when the absorption layer is thicker, and on the other hand, can minimize the plasma exposure time of the absorption layer surface, thereby improving the quality of the dual-wave infrared detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0024] In the attached picture:

[0025] Figure 1 It is a schematic diagram of the structure of the photoluminescence (PL) graph of the grown epitaxial layer of the present invention;

[0026] Figure 2 It is a schematic diagram of the structure of the initial chip of the present invention;

[0027] Figure 3 It is a schematic diagram of the structure of the chip deposited with a passivation layer after one etching of the present invention;

[0028] Figure 4 This is a schematic diagram of the structure of the chip of the present invention after secondary deposition of a passivation layer and secondary etching;

[0029] Figure 5 It is a schematic diagram of the structure of the chip of the present invention depositing the passivation layer three times;

[0030] Figure 6 It is a schematic diagram of the structure of the opening of the passivation layer of the chip of the present invention;

[0031] Figure 7 It is a schematic diagram of the structure of the evaporated metal of the chip of the present invention;

[0032] Figure 8 It is a schematic diagram of the structure of the chip interconnection In column of the present invention;

[0033] Fig. 9 It is the spectral QE diagram of the dual-band device of the present invention when the thickness of the MWIR and LWIR absorbers are both 2 microns;

[0034] Fig.10 It is the spectral QE diagram of the dual-band device of the present invention when the thickness of the MWIR and LWIR absorbers are both 4 microns;

[0035] Fig.11 is a dark current density diagram of the MWIR and LWIR detectors of the present invention;

[0036] Fig.12 It is a NETD histogram or a Gaussian distribution diagram of the present invention;

[0037] Numbers in the figure: 1. GaSb substrate; 2. bottom contact layer; 3. medium-wave absorption layer; 4. barrier layer; 5. long-wave absorption layer; 6. and top contact layer. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described below in conjunction with the drawings in the embodiments of the present invention. The terms used in the implementation mode of the present invention are only used to explain the specific embodiments of the present invention, and are not intended to limit the present invention. The embodiments of the present application are described below in conjunction with the drawings.

[0039] Embodiment 1: Since the absorption layer is thicker, the dual-band nBn device should be dry-etched deeper than the single-band nBn device to isolate pixels, and the surface of the etched absorption layer may be more unstable due to the longer plasma exposure time. The present invention provides a method for preparing a dual-wave infrared detector, which comprises:

[0040] Initial chip manufacturing: providing a GaSb substrate; sequentially growing a bottom contact layer, a medium-wave absorption layer, a barrier layer, a long-wave absorption layer, and a top contact layer on the GaSb substrate;

[0041] In a specific embodiment, reference Figure 2As shown, an n-type bottom contact layer 2 is sequentially grown on a Te-doped GaSb substrate 1 with a thickness of 20 microns by molecular beam epitaxy (MBE), and the n-type bottom contact layer 2 adopts an InAs / GaSb superlattice material with a cycle period of 10MLInAs / 10MLGaSb and a thickness of 500nm; the medium-wave absorption layer 3 adopts an unintentionally doped InAs / GaSb superlattice material with a cycle period of 10MLInAs / 10MLGaSb and a thickness of 4 microns; the barrier layer 4 (also called the blocking layer) adopts an unintentionally doped InAs / GaSb superlattice material with a cycle period of 4MLInAs / 9MLGaSb and a thickness of 280nm; the long-wave absorption layer 5 adopts an unintentionally doped InAs / GaSb superlattice material with a cycle period of 14MLInAs / 17MLGaSb and a thickness of 3 microns; the n-type top contact layer 6 adopts an InAs / GaSb superlattice material with a cycle period of 14MLInAs / 17MLGaSb and a thickness of 300nm.

[0042] And refer to Figure 1 shows the photoluminescence (PL) images of the grown epitaxial layers; Figure 1 As shown, the material structure shows attenuated total reflection at 77K; the PL peak (indicating bandgap energy) shows that the MWIR (medium wave) and LWIR (long wave) absorption layers are grown according to the original design (the design growth method is: 14MLInAs / 17MLGaSb long wave absorption layer and 10MLInAs / 10MLGaSb medium wave absorption layer)

[0043] Etching treatment: deposit a passivation layer on the surface of the top contact layer once, and etch once from the absorption layer to the top contact layer; deposit a passivation layer twice in a covering manner, and etch twice from the top contact layer to the bottom contact layer; deposit a passivation layer three times in a covering manner; make holes in the passivation layer of the table and the common electrode area, evaporate UBM metal TiPtAu at the openings to make a detector chip; the covering method includes the etching exposure area and the passivation area deposited last time.

[0044] Based on the above, in a specific embodiment:

[0045] First, after the surface of the generated initial chip is organically cleaned with isopropanol, a 100 nm layer of silicon dioxide is first deposited on the surface of the initial chip by CVD. Figure 3 After forming the MESA pattern on the initial chip surface by photolithography, the MESA (table) is etched by ICP at a processing temperature of 200°C to 250°C and a working pressure of 6.66×10 -4 KPa, BCl 3 The flow rate is 5sccm, the RF power is 30W, and the ICP power is 500W;

[0046] ICPRIE was used for hydrogen plasma treatment, with a process temperature of 200°C to 250°C and a working pressure of 6.66×10 -4 kPa, H 2 The flow rate is 5 sccm, the RF power is 30 W, and the ICP power is 500 W. The above operations are used to reduce the potential surface damage of the LWIR absorption layer etched by plasma radicals.

[0047] Finally, the photoresist on the surface of the initial chip was cleaned with acetone to obtain a device with a pixel area of ​​17 square microns manufactured by the first step;

[0048] Second, 200nm SiO was deposited using an inductively coupled plasma chemical vapor deposition (ICPCVD) device. 2 Passivation film to protect the surface of the long-wave infrared absorbing layer, such as Figure 4 ; Isolating the MWIR absorption layer of each pixel by completely etching from the barrier layer to the bottom contact layer under the same conditions as the LWIR absorption layer pixel isolation process, resulting in a device with a pixel area of ​​13 square microns manufactured by the second step process;

[0049] Third, plasma treatment and passivation process are also carried out under the same conditions as the LWIR process; a 100nm layer of silicon dioxide is plated, such as Figure 5 , the passivation layer of the table and the common electrode area are opened, such as Figure 6 ;

[0050] Fourth: By lift-off method, evaporate UBM metal TiPtAu: 50 / 50 / 300nm, such as Figure 7 , at this time, the production of medium-wave / long-wave dual-band detector chips has been completed;

[0051] Based on the above, a detector is made by interconnecting the detector chip with the In column of the readout circuit;

[0052] In a specific embodiment, reference Figure 8 After cleaning the detector chip and the readout circuit die with normal screening performance, the chip and the readout circuit die are interconnected with a flip solder machine, and the flip solder pressure is 16kg; the chip and the readout circuit are interconnected with filling glue and the gap is filled, and the curing temperature is 80℃ / 15h; then the substrate is thinned to a few microns by chemical mechanical polishing (CMP), and then the GaSb substrate is removed using a cro3-based solution because it absorbs the entire IR band; finally, the chip with the substrate completely removed is plated with back-anti-reflection, ZnS back-anti-reflection, with a thickness of 980nm.

[0053] Embodiment 2. The present invention also records a dual-wave infrared detector, which includes a Te-doped GaSb substrate with a thickness of 20 microns; an n-type bottom contact layer, which adopts InAs / GaSb superlattice material with a cycle period of 10MLInAs / 10MLGaSb and a thickness of 500nm; a medium-wave absorption layer, which is an unintentionally doped InAs / GaSb superlattice material with a cycle period of 10MLInAs / 10MLGaSb and a thickness of 4 microns; a barrier layer, which is an unintentionally doped InAs / GaSb superlattice material with a cycle period of 4MLInAs / 9MLGaSb and a thickness of 280nm; a long-wave absorption layer, which is an unintentionally doped InAs / GaSb superlattice material with a cycle period of 14MLInAs / 17MLGaSb and a thickness of 3 microns; a top contact layer, which is an n-type top contact layer, which adopts InAs / GaSb superlattice material with a cycle period of 14MLInAs / 17MLGaSb, and is prepared by the above-mentioned dual-wave infrared detector preparation method.

[0054] The above dual-wave infrared detector was tested and evaluated using imaging test software; the imaging test results are as follows:

[0055] In a 20-micron pitch FPA, the device fabricated by the first-step process had a pixel area of ​​17 square microns, while the long-wave infrared and mid-wave infrared absorbers fabricated by the second-step process had areas of 13 square microns and 17 square microns; the dark current density of the MWIR device all reached the background-limited infrared photodetection (BLIP) condition; and plasma damage on the LWIR surface in the dual-band device that should have deep dry-etched pixels was minimized.

[0056] Fig. 9 The spectral QE of the dual-band device is shown when the thickness of both the MWIR and LWIR absorbers is 2 μm. The average QEs of the MWIR and LWIR devices are 33.7% and 31.2%, respectively. Generally, spectral crosstalk is a key issue in dual-band MWIR / LWIR detectors. In order to improve the average QE of the MWIR device and reduce the spectral crosstalk, the MWIR absorber is grown to a thickness of 4 μm. Fig.10 As shown in Figure 2, the average QE of the MWIR device increases to 53.7% and the spectral crosstalk decreases to 11.1%. Even with a thicker MWIR absorption layer, the dark current density of the MWIR and LWIR detectors reaches the BLIP condition, as shown in Figure 2. Fig.11 shown.

[0057] The FPA installed in the test dewar was measured at an operating temperature of 80K. After capturing image data using the F / 2.0 optical system, the optical characteristics of the black body were analyzed at temperatures of 293K and 308K. Fig.12The NETD histogram or Gaussian distribution is shown, and the average NETD in the mid-wave infrared mode and the long-wave infrared mode are 22.5mK and 25.0mK, respectively.

[0058] Therefore, based on the above, the prepared dual-wave infrared detector exhibits dark current and spectral response characteristics of MWIR and LWIR bands under negative bias and positive bias respectively, and the spectral crosstalk, the main problem of the dual-band detector, is also improved; and through the above, a 640*512 dual-band detector with a spacing of 20 microns was produced, and both MWIR and LWIR images showed an average noise equivalent temperature difference of 30mK or less at 80K.

[0059] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. For ordinary technicians in this technical field, after knowing the contents recorded in the present invention, they can make several equivalent changes and substitutions without departing from the principle of the present invention. These equivalent changes and substitutions should also be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for preparing a dual-wave infrared detector, characterized in that: include: Providing a GaSb substrate; A bottom contact layer, a medium-wave absorption layer, a barrier layer, a long-wave absorption layer, and a top contact layer are sequentially grown on a GaSb substrate; Depositing a passivation layer once on the surface of the top contact layer and etching once from the absorption layer to the top contact layer; A passivation layer is deposited in a blanket manner for a second time, and a second etching is performed from the top contact layer to the bottom contact layer; The passivation layer is deposited three times in a blanket manner; Holes are opened in the passivation layer of the table and the common electrode area, and UBM metal TiPtAu is evaporated at the openings to make a detector chip; The detector chip is interconnected with the In column of the readout circuit to form a detector.

2. The method for preparing a dual-wave infrared detector according to claim 1, characterized in that: The total thickness of the absorbent layer is 7 microns.

3. The method for preparing a dual-wave infrared detector according to claim 1, characterized in that: In one etching, a MESA pattern is formed on the surface of the absorption layer by photolithography, and the MESA is etched by ICP at a processing temperature of 200°C-250°C and a working pressure of 6.66×10 -4 KPa, the flow rate of BCl3 is 5sccm, the RF power is 30W, and the ICP power is 500W.

4. The method for preparing a dual-wave infrared detector according to claim 2, characterized in that: After the first etching, ICPRIE was used for hydrogen plasma treatment at a temperature of 200°C-250°C and a working pressure of 6.66×10 -4 kPa, H 2 The flow rate is 5 sccm, the RF power is 30 W, and the ICP power is 500 W.

5. The method for preparing a dual-wave infrared detector according to claim 1, characterized in that: The detector chip and the In column of the readout circuit are interconnected together using a reverse welding machine with a reverse welding pressure of 16 kg; and Use filling glue to interconnect the detector chip and the readout circuit and fill the gap. The curing temperature is 80℃ / 15h; The GaSb substrate is thinned to 20-30 microns using chemical mechanical polishing.

6. The method for preparing a dual-wave infrared detector according to claim 5, characterized in that: The GaSb substrate is removed by a cro3-based solution, and the detector chip is plated with ZnS backside anti-reflection with a thickness of 980 nm.

7. Dual-wave infrared detector, characterized by: The detector comprises a GaSb substrate, and a bottom contact layer, a medium-wave absorption layer, a barrier layer, a long-wave absorption layer and a top contact layer which are sequentially arranged on the GaSb substrate, and is prepared by the dual-wave infrared detector preparation method according to any one of claims 1 to 6.

8. The dual-wave infrared detector according to claim 7, characterized in that: The GaSb substrate is a Te-doped GaSb substrate with a thickness of 20 microns; the bottom contact layer is an n-type bottom contact layer, which adopts InAs / GaSb superlattice material, has a cycle period of 10MLInAs / 10MLGaSb, and a thickness of 500nm; the medium-wave absorption layer is an unintentionally doped InAs / GaSb superlattice material, has a cycle period of 10MLInAs / 10MLGaSb, and a thickness of 4 microns; the barrier layer is an unintentionally doped InAs / GaSb superlattice material, has a cycle period of 4MLInAs / 9MLGaSb, and a thickness of 280nm; the long-wave absorption layer is an unintentionally doped InAs / GaSb superlattice material, has a cycle period of 14MLInAs / 17MLGaSb, and a thickness of 3 microns; the top contact layer is an n-type top contact layer, which adopts InAs / GaSb superlattice material, and has a cycle period of 14MLInAs / 17MLGaSb.

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