Transverse ZnO nanowire ultraviolet detector array readout electrode structure and preparation method thereof

Abstract

The invention discloses a transverse ZnO nanowire ultraviolet detector array readout electrode structure and a preparation method, and belongs to the field of semiconductor microelectronics. According to the structure, a longitudinal electrode and a transverse electrode integrally form a grid structure, an adhesion layer and an isolation layer which are stacked are arranged between the stacked lap joint parts of the longitudinal electrode and the transverse electrode, and a ZnO ultraviolet detector is prepared in each grid. The thickness of the longitudinal electrode is d1, the thickness of the ZnO seed layer of the device is d2, the thickness of the Ti / Au electrode layer of the device is d3, and the requirements are as follows: d3 > d1 > d2, 150nm < d1 < 200nm, 100nm < d2 < 150nm, and 200nm < d3 < 250nm. Signal crosstalk between devices can be avoided, stable connection between the devices and electrodes and isolation between hierarchical electrodes are achieved, and a stable readout electrode structure is obtained.

Description

Technical Field

[0001] The invention relates to a readout electrode structure process of a bridged ZnO nanowire ultraviolet detector array and a preparation method thereof, and belongs to the field of semiconductor microelectronics. Background Art

[0002] In recent years, ultraviolet (UV) detectors have been increasingly used in many fields, especially in environmental monitoring, space detection, radiation monitoring, safety detection and medical diagnosis. UV detection technology has become increasingly important. UV detectors have key functions such as detecting UV light sources, monitoring air quality, and measuring UV radiation intensity. Therefore, the development of UV detectors with high sensitivity, fast response and high integration has always been the research focus of scientific researchers and engineering technicians.

[0003] The third-generation semiconductor material zinc oxide (ZnO) has shown great application potential in the field of ultraviolet detection due to its strong optoelectronic properties, wide bandgap, good thermal stability and other advantages. ZnO nanowire devices have wide bandgap, high electron mobility, low carrier scattering rate and high surface area, which can achieve high-sensitivity and high-response speed ultraviolet detection, becoming an important research direction in the field of ultraviolet detectors.

[0004] At present, UV detectors based on zinc oxide nanowires have received extensive attention and research. However, existing ZnO nanowire UV detectors still face several challenges in practical applications, especially in device arraying and integration. Traditional electrode structures often cannot effectively meet the requirements of device arrays for signal reading efficiency and stability. How to avoid signal crosstalk between devices, achieve stable connection between devices and electrodes, and isolate hierarchical electrodes are still the difficulties of current research. Summary of the invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a stable detector array readout electrode structure, by controlling the corrosion time of the isolation layer, the seed layer thickness of the detector, the detector electrode layer thickness and the thickness of the readout electrode and other parameters to obtain a readout electrode structure with high uniformity and high stability.

[0006] The present invention provides a detector array readout electrode structure process based on a ZnO ultraviolet detector array, using a ZnO nanowire ultraviolet detector array as a demonstration. Figure 1 , from the top view of part of the readout electrode structure, the structure includes: longitudinal electrode Ti / Au (101), adhesion layer Ti (102), isolation layer SiO2 (103), transverse electrode Ti / Au (104), device array structure ZnO / Ti / Au (105);

[0007] A plurality of strip-shaped, parallel and independent Ti / Au films are deposited on the substrate as longitudinal electrodes (101), and a block Ti layer is deposited on a part of the longitudinal electrodes as an adhesion layer (102); a SiO2 film is deposited on the surface of the substrate and patterned by wet etching, leaving a SiO2 film on the adhesion layer that is larger than the adhesion layer as an isolation layer (103), that is, the isolation layer (103) and the longitudinal electrodes (101) completely cover the adhesion layer (102), and the isolation layer cross-sectional structure is shown in FIG. Figure 2 The corrosion progress of the isolation layer (103) is required to be not too large, so that over-etching does not occur, so that the horizontal and vertical electrodes are linked together. The cross-sectional structure of the isolation layer with excessive corrosion is as shown in FIG. Figure 3 As shown, the optimal corrosion progress is under-corrosion.

[0008] At this time, a plurality of strip-shaped, parallel and independent Ti / Au films are further deposited on the substrate as transverse electrodes (104). The transverse electrodes are perpendicular to the longitudinal electrodes. The transverse electrodes (104) are stacked on the longitudinal electrodes (101) to form a complete readout electrode structure. The longitudinal electrodes (101) and the transverse electrodes (104) form a grid structure as a whole. The overlapping parts of the longitudinal electrodes (101) and the transverse electrodes (104) are stacked with an adhesion layer (102) and an isolation layer (103).

[0009] Test the readout electrode structure (using 1V voltage test, when the current is 0 during the test, the isolation layer has the best isolation effect, and the isolation effect is judged according to the current size) to test the isolation effect of the isolation layer. If most of the isolation layer has poor effect, it may be due to the long corrosion time of the isolation layer, and over-corrosion has occurred, so it needs to be remade from the substrate. If most of the isolation layer has good effect, only part or even individual isolation layers have poor isolation effect, it may be due to uneven deposition when depositing the SiO2 layer, resulting in holes. The cross-sectional structure of the isolation layer with holes is shown in the figure below. Figure 4 As shown, some impurities (401) are deposited in the hole during the preparation process, and some electrode materials also enter the hole when preparing the lateral electrode, resulting in poor isolation effect. A large voltage is applied to the isolation layer with holes for repair (a voltage of 5-10V is applied to the lateral electrode and the longitudinal electrode of the readout electrode structure for repair), that is, an aging process step is performed to make the impurities reach a state similar to breakdown and burnout, and the isolation effect is restored, such as Figure 5 As shown; it is ensured that each isolation layer (103) between the longitudinal electrode and the transverse electrode has a good isolation effect, so that there will be no crosstalk and other problems between the read-write circuits.

[0010] A ZnO ultraviolet detector array is prepared on the readout electrode structure, that is, a ZnO ultraviolet detector is prepared in each grid formed by the longitudinal electrode (101) and the transverse electrode (104), or ZnO ultraviolet detectors are prepared in different grids as needed; the ZnO ultraviolet detector includes: depositing two parallel, symmetrical and independent ZnO thin film layers as seed layers, one seed layer is parallel to the longitudinal electrode and is in contact with the other seed layer, and the other seed layer is perpendicular to the transverse electrode, and the transverse electrode is provided with a side protrusion or extension connected to the other seed layer; a metal electrode layer is deposited on the ZnO seed layer; ZnO nanowires are grown on the opposite sides of the ZnO seed layer to form a complete bridged ZnO nanowire ultraviolet detector array structure. The cross-sectional structure of the area where the detector array intersects the transverse and longitudinal electrodes is shown in FIG. Figure 6 As shown, taking the intersection with the longitudinal electrode as an example, the intersection with the transverse electrode is the same, and the dotted line in the figure is the location of the cross section.

[0011] Requirements are put forward for the electrode thickness (601), the seed layer (602) thickness and the thickness of the longitudinal electrode (101) below the seed layer of the conventional device array that needs to use a seed layer to grow nanowires, so that an absolutely stable and reliable connection is achieved between the readout electrode structure and the device. This requirement is not only applicable to the bridge ZnO nanowire ultraviolet detector array, but also has universal applicability to other device arrays that need to grow nanowires using a seed layer. The thickness of the longitudinal electrode (101) is the same as that of the transverse electrode.

[0012] The requirements are as follows Figure 7 As shown, the thickness of the longitudinal electrode is d1, the thickness of the ZnO seed layer of the device is d2, and the thickness of the Ti / Au electrode layer of the device is d3. The requirement is d3>d1>d2, and the thickness range is 150nm<d1<200nm, 100nm<d2<150nm, 200nm<d3<250nm, in order to ensure a stable connection from the device array to the read-write electrodes.

[0013] The present invention also provides a method for manufacturing a readout electrode structure process based on a zinc oxide ultraviolet detection device array. The present invention adopts the following technical solution, including the following steps:

[0014] Step 1: After cleaning the glass substrate, the desired pattern is obtained by photolithography;

[0015] Step 2: sputtering Ti / Au by magnetron sputtering to obtain a longitudinal electrode;

[0016] Step 3: removing the photoresist by a stripping process to obtain a longitudinal electrode of a desired shape;

[0017] Step 4: sputtering Ti by magnetron sputtering to obtain an adhesion layer;

[0018] Step 5: Remove the photoresist by a stripping process to obtain an adhesion layer of a desired shape;

[0019] Step 6: Sputter SiO2 using a PECVD method to obtain an isolation layer;

[0020] Step 7: Use a wet etching process to remove excess SiO2 to obtain an isolation layer of a desired shape;

[0021] Step 8: sputtering Ti / Au by magnetron sputtering to obtain a lateral electrode;

[0022] Step 9: removing the photoresist by a stripping process to obtain a lateral electrode of a desired shape, thereby forming a readout electrode structure;

[0023] Step 10: Test the readout electrode structure to ensure that there is no crosstalk between the readout electrodes;

[0024] Step 11: sputtering ZnO thin film and Ti / Au by magnetron sputtering to obtain a device structure;

[0025] Step 12: removing the photoresist by a stripping process to obtain a ZnO seed layer and an electrode of a desired shape to form a device structure;

[0026] Step 13: Place the sample with the pattern facing downward, float it in the prepared culture solution, and grow ZnO nanowires using a hydrothermal method;

[0027] Step 14: Connect the peripheral circuits and use the test equipment to test the performance of the obtained detection device array.

[0028] The advantages of the present invention compared with the prior art are:

[0029] The present invention proposes requirements for the design of a readout electrode structure based on a device array, and proposes specifications for parameters such as the isolation layer corrosion time, the device seed layer thickness, the device electrode layer thickness, and the thickness of the readout electrode. This can avoid signal crosstalk between devices, achieve stable connection between devices and electrodes, and isolation between hierarchical electrodes, and obtain a stable readout electrode structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the readout electrode structure and partial area enlargement of the lateral ZnO nanowire UV detector array of the present invention

[0031] Figure 2 Sectional view of the isolation layer of the present invention

[0032] Figure 3 Cross-sectional view of the over-etched isolation layer of the present invention

[0033] Figure 4Cross-sectional view of the isolation layer with holes of the present invention

[0034] Figure 5 Schematic diagram of repairing an isolation layer with holes according to the present invention

[0035] Figure 6 Schematic diagram of the cross section of the device array and the longitudinal electrode intersection area of ​​the present invention (the dotted line indicates the cross section location)

[0036] Figure 7 A cross-sectional view of the intersection of the device array and the longitudinal electrode of the present invention that meets the requirements

[0037] Figure 8 Preparation flow chart of the ultraviolet detector array of the present invention

[0038] Fig. 9 Light microscopy image of a part of the prepared UV detector array provided in Example 1 of the present invention

[0039] Fig.10 Schematic diagram of the UV detector array provided by Example 1 of the present invention for connecting to peripheral circuits and performing tests

[0040] Fig.11 Device test performance diagram provided by Example 1 of the present invention (light-dark current comparison diagram) DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the following examples, but the present invention is not limited to the following examples. The present invention provides a stable manufacturing process for the detector array readout electrode structure, using the ZnO nanowire ultraviolet detector as an exemplary verification. Figure 8 As shown, it includes: depositing a strip-shaped, parallel and independent Ti / Au film on the substrate as a longitudinal electrode. Depositing a block Ti layer in a partial area on the longitudinal electrode, which is used as an adhesion layer for the isolation layer. Depositing a SiO2 film on the surface of the substrate, patterning it by wet etching, leaving a SiO2 film on the adhesion layer and larger than the adhesion layer as an isolation layer. Requirements are put forward for the corrosion progress of the isolation layer so that it does not have over-etching phenomenon, and under-etching phenomenon is the best. Through testing and applying voltage, it is ensured that each isolation layer between the longitudinal electrode and the transverse electrode has a good isolation effect, so that there will be no crosstalk and other problems between the readout electrode structures.

[0042] The present invention also provides a method for manufacturing a readout electrode structure process based on a zinc oxide ultraviolet detection device array. The present invention adopts the following technical solution, including the following steps:

[0043] Step 1: After cleaning the glass substrate, the desired pattern is obtained by photolithography;

[0044] Step 2: sputtering Ti / Au by magnetron sputtering to obtain a longitudinal electrode;

[0045] Step 3: removing the photoresist by a stripping process to obtain a longitudinal electrode of a desired shape;

[0046] Step 4: sputtering Ti by magnetron sputtering to obtain an adhesion layer;

[0047] Step 5: Remove the photoresist by a stripping process to obtain an adhesion layer of a desired shape;

[0048] Step 6: Sputter SiO2 using a PECVD method to obtain an isolation layer;

[0049] Step 7: Use a wet etching process to remove excess SiO2 to obtain an isolation layer of a desired shape;

[0050] Step 8: sputtering Ti / Au by magnetron sputtering to obtain a lateral electrode;

[0051] Step 9: removing the photoresist by a stripping process to obtain a lateral electrode of a desired shape, thereby forming a readout electrode structure;

[0052] Step 10: Test the readout electrode structure to ensure that there is no crosstalk between the readout electrodes;

[0053] Step 11: sputtering ZnO thin film and Ti / Au by magnetron sputtering to obtain a device structure;

[0054] Step 12: removing the photoresist by a stripping process to obtain a ZnO seed layer and an electrode of a desired shape to form a device structure;

[0055] Step 13: Place the sample with the pattern facing downward, float it in the prepared culture solution, and grow ZnO nanowires using a hydrothermal method;

[0056] Step 14: Connect the peripheral circuits and use the test equipment to test the performance of the obtained detection device array.

[0057] The magnetron sputtering power is preferably 150W to 250W;

[0058] The solution used in the hydrothermal method for growing ZnO nanowires is a culture solution composed of zinc salt and hexamethylenetetramine, and the molar ratio of the corresponding agents is 1:1 to 1:2;

[0059] The preferred concentration of zinc salt in the culture solution is 0.5-1 mmol, and the preferred concentration of hexamethylenetetramine is 0.5-2 mmol;

[0060] The preferred temperature for the hydrothermal reaction is 70 to 90 degrees Celsius and the duration is 7 to 15 hours.

[0061] Example 1

[0062] A glass sheet is used as a substrate, and acetone, ethanol, and deionized water are used to clean the substrate twice, and a pattern of a desired readout electrode structure is photoetched on the substrate using ultraviolet photolithography technology;

[0063] Use radio frequency magnetron sputtering to sputter 15 / 150nm Ti / Au as the longitudinal electrode on the photolithographic pattern. Note that the sputtering target needs to be rotated and tilted 60 degrees. Use acetone immersion and ultrasonic stripping to remove the photoresist on the substrate, leaving only the required longitudinal electrode shape.

[0064] Use RF magnetron sputtering to sputter 15nm of Ti as an adhesion layer on the photolithographic pattern. Note that the sputtering target needs to be rotated and tilted 60 degrees. Use acetone immersion and ultrasonic stripping to remove the photoresist on the substrate, leaving only the desired adhesion layer shape.

[0065] 300 nm of SiO2 is sputtered on the substrate at this time using PECVD, and excess SiO2 is etched away using wet etching, leaving a SiO2 film on the adhesion layer that is larger than the adhesion layer as an isolation layer.

[0066] Use radio frequency magnetron sputtering to sputter 15 / 150nm Ti / Au as lateral electrodes on the photolithographic pattern. Note that the sputtering target needs to be rotated and tilted 60 degrees. Use acetone immersion and ultrasonic stripping to remove the photoresist on the substrate, leaving only the required lateral electrode shape.

[0067] Test the readout electrode structure to ensure the isolation effect of the isolation layer.

[0068] Use RF magnetron sputtering to sputter a 100nm zinc oxide seed layer and a 15 / 200nm electrode on the photolithographic pattern. Note that the sputtering target needs to be rotated and tilted 60 degrees. Use acetone immersion and ultrasonic stripping to remove the photoresist on the substrate, leaving only the required detection device shape.

[0069] The nanowire culture medium was prepared by using zinc nitrate hexahydrate and hexamethylenetetramine in a ratio of 1:1, 1 mmol and 1 mmol respectively were dissolved in 1 L of deionized water, and stirred for 2 hours using a magnetic stirring bar;

[0070] Pour the prepared nanowire culture solution into a container, place the SiO2 substrate with the pattern face down, gently place it into the culture solution, and place it in a constant temperature oven at 80°C for 8 hours to grow nanowires to form a complete detector array structure, such as Fig. 9 As shown;

[0071] Connect the peripheral circuits to test the performance of the detection device array. Use the Keithley 4200 semiconductor parameter tester to connect the Faraday dark box and the probe station, and connect the probe to the readout electrode port of the device array for testing. Fig.10 As shown; the test uses a wavelength of 365nm and 10mw / cm 2 The UV lamp was used with a test voltage of -1.0V to 1.0V. The dark current and photocurrent were tested respectively. The dark current of the device was 2.20E-5 and the photocurrent was 7.07E-3. The test results are as follows: Fig.11 shown.

Claims

1. A lateral ZnO nanowire UV detector array readout electrode structure, characterized in that: The structure includes: a longitudinal electrode Ti / Au (101), an adhesive layer Ti (102), an isolation layer SiO2 (103), a transverse electrode Ti / Au (104), and a device array structure ZnO / Ti / Au (105); Depositing a plurality of strip-shaped, parallel and independent Ti / Au thin films on a substrate as longitudinal electrodes (101), depositing a block Ti layer on a portion of the longitudinal electrodes as an adhesion layer (102); the isolation layer (103) and the longitudinal electrodes (101) completely cover the adhesion layer (102); depositing a plurality of strip-shaped, parallel and independent Ti / Au thin films on the substrate as transverse electrodes (104), the transverse electrodes being perpendicular to the longitudinal electrodes, the transverse electrodes (104) being stacked on the longitudinal electrodes (101) to form a complete readout electrode structure, the longitudinal electrodes (101) and the transverse electrodes (104) forming a grid structure as a whole, and the stacked adhesion layer (102) and the isolation layer (103) being between the stacked portions of the longitudinal electrodes (101) and the transverse electrodes (104); A ZnO ultraviolet detector array is prepared on the readout electrode structure, that is, a ZnO ultraviolet detector is prepared in each grid formed by the longitudinal electrode (101) and the transverse electrode (104), or ZnO ultraviolet detectors are prepared in different grids as required; The ZnO ultraviolet detector includes: depositing two parallel, symmetrical and independent ZnO thin film layers as seed layers, one seed layer is parallel to and in contact with the longitudinal electrode, and the other seed layer is perpendicular to the transverse electrode, and the transverse electrode is provided with a side protrusion or extension to be connected and in contact with the other seed layer; a metal electrode layer is deposited on the ZnO seed layer; ZnO nanowires are grown on two opposite sides of the ZnO seed layer to form a complete bridged ZnO nanowire ultraviolet detector array structure.

2. A lateral ZnO nanowire UV detector array readout electrode structure according to claim 1, characterized in that: The thickness of the longitudinal electrode is d1, the thickness of the ZnO seed layer of the ultraviolet detector is d2, and the thickness of the ultraviolet detector electrode layer is d3. The requirements are d3>d1>d2, and the thickness range is 150nm<d1<200nm, 100nm<d2<150nm, 200nm<d3<250nm, so as to ensure a stable connection from the device array to the read-write electrode; the thickness of the longitudinal electrode (101) and the transverse electrode are the same.

3. A lateral ZnO nanowire UV detector array readout electrode structure according to claim 1, characterized in that: The electrode layer of the UV detector is Ti / Au.

4. The method for preparing a lateral ZnO nanowire ultraviolet detector array readout electrode structure according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: After cleaning the glass substrate, the desired pattern is obtained by photolithography; Step 2: sputtering Ti / Au by magnetron sputtering to obtain a longitudinal electrode; Step 3: removing the photoresist by a stripping process to obtain a longitudinal electrode of a desired shape; Step 4: sputtering Ti by magnetron sputtering to obtain an adhesion layer; Step 5: Remove the photoresist by a stripping process to obtain an adhesion layer of a desired shape; Step 6: Sputter SiO2 using a PECVD method to obtain an isolation layer; Step 7: Use a wet etching process to remove excess SiO2 to obtain an isolation layer of a desired shape; Step 8: sputtering Ti / Au by magnetron sputtering to obtain a lateral electrode; Step 9: removing the photoresist by a stripping process to obtain a lateral electrode of a desired shape, thereby forming a readout electrode structure; Step 10: Test the readout electrode structure to ensure that there is no crosstalk between the readout electrodes; Step 11: sputtering a ZnO seed layer and a UV detector electrode layer by a magnetron sputtering method to obtain a device structure; Step 12: removing the photoresist by a stripping process to obtain a ZnO seed layer and an electrode of a desired shape to form a device structure; Step 13: Place the sample with the pattern side facing downward, float it in the prepared culture solution, and grow ZnO nanowires using a hydrothermal method.

5. The method according to claim 4, characterized in that Step 10 tests the readout electrode structure, including: using 1V voltage test, when the current is 0 during the test, the isolation effect of the isolation layer is the best, judging the isolation effect according to the current size, testing the isolation effect of the isolation layer, if most of the isolation layers have poor effects, it may be due to the isolation layer corrosion time is too long, over-corrosion occurs, and thus it is necessary to start from the substrate to re-make; if most of the isolation layers have good effects, only part or even individual isolation layers have poor isolation effects, it may be that the deposition is uneven when depositing the SiO2 layer, resulting in holes; the holes are deposited in the preparation process. Part of the impurities (401), when preparing the lateral electrode, part of the electrode material also enters the holes, and then the isolation effect is poor; a large voltage is applied to the isolation layer with holes for repair, and a voltage of 5-10V is applied to the lateral electrode and the longitudinal electrode of the readout electrode structure for repair, that is, an aging process step is performed to make the impurities reach a state similar to breakdown and burning, and the isolation effect is restored; it is ensured that each isolation layer between the longitudinal electrode and the lateral electrode has a good isolation effect, so that there will be no crosstalk and other problems between the read-write circuits.

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