Method for testing infrared focal plane array pixel thermal conductance

Abstract

This invention discloses a method for testing the thermal conductivity of pixels in an infrared focal plane array, comprising: performing resistance-temperature correlation tests and current-voltage correlation tests on the pixel thermal conductivity test structure; interpolating the resistance data obtained from the current-voltage correlation test with the test data from the resistance-temperature correlation test to obtain a preliminary thermal conductivity value; fitting the preliminary thermal conductivity value to obtain the activation energy of the thermistor; calculating the temperature data corresponding to the resistance data based on the activation energy and the resistance data obtained from the current-voltage correlation test, and recalculating an intermediate thermal conductivity value; repeatedly iterating the calculation of the activation energy, temperature data, and intermediate thermal conductivity value until the difference between the last two calculated intermediate thermal conductivity values ​​is less than a preset threshold, and taking the last calculated intermediate thermal conductivity value as the final thermal conductivity value. This method can improve the measurement accuracy of the final thermal conductivity value.

Description

Technical Field

[0001] This invention relates to the field of infrared imaging technology, and in particular to a method for testing the thermal conductivity of pixels in an infrared focal plane array. Background Technology

[0002] Currently, in some existing methods for testing the thermal conductivity of infrared focal plane array pixels, the use of additional thermistors to measure the temperature of the structure under test has two main drawbacks. First, it increases the complexity of the process, and the thermistors still require external temperature control equipment to calibrate the relationship between resistance and temperature. In actual use, the pixel temperature is measured by looking up tables or interpolating based on the calibration relationship, which results in a complex testing process and difficulty in guaranteeing accuracy. Second, it requires energizing the thermistor in the floating layer of the pixel thermal conductivity testing structure to measure resistance. This energizing channel inevitably affects the thermal conductivity of the bridge legs of the pixel thermal conductivity testing structure, resulting in the measured value not being the thermal conductivity value of the pixel's bridge legs, thus affecting the accuracy of the thermal conductivity measurement. Summary of the Invention

[0003] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a method for testing the thermal conductivity of pixels in an infrared focal plane array, which can improve the accuracy of the final thermal conductivity value measurement.

[0004] In a first aspect, embodiments of the present invention provide a pixel thermal conductivity testing method for an infrared focal plane array, applied to a pixel thermal conductivity testing structure. The infrared focal plane array includes a rectangular array composed of pixels arranged in X rows and Y columns. The pixel thermal conductivity testing structure is disposed on the periphery of a wafer containing the rectangular array. The rectangular array is cut out of the wafer to form a die, and the die is vacuum-encapsulated within a package. The pixel thermal conductivity testing structure is electrically connected to the electrode pins of the package. The pixel thermal conductivity testing structure includes a thermistor material, and the pixel thermal conductivity testing method includes: The resistance-temperature relationship and the current-voltage relationship were tested on the pixel thermal conductivity test structure. Based on the resistance data obtained from the current-voltage correlation test, the test data from the resistance-temperature correlation test are interpolated to obtain the preliminary thermal conductivity value of the pixel thermal conductivity test structure. The activation energy of the thermosensitive material is obtained by fitting the preliminary thermal conductivity value. Based on the activation energy and the resistance data obtained from the current-voltage correspondence test, the temperature data corresponding to the resistance data is calculated, and the intermediate thermal conductivity value is recalculated based on the power data obtained from the current-voltage correspondence test and the temperature data. The activation energy, the temperature data, and the intermediate thermal conductivity value are repeatedly iterated until the difference between the last two calculated intermediate thermal conductivity values ​​is less than a preset threshold, and the intermediate thermal conductivity value obtained in the last calculation is taken as the final thermal conductivity value.

[0005] The pixel thermal conductivity testing method for an infrared focal plane array provided by the present invention has at least the following beneficial effects: by setting a pixel thermal conductivity testing structure on the periphery of the die containing the rectangular array, electrically connecting the pixel thermal conductivity testing structure to the electrode pins of the package, and performing resistance-temperature correspondence tests and current-voltage correspondence tests, the preliminary thermal conductivity value of the pixel thermal conductivity testing structure is further calculated, and the activation energy of the thermosensitive material is obtained by fitting, and then the intermediate thermal conductivity value is calculated. The calculation is repeated iteratively until the difference between the last two intermediate thermal conductivity values ​​is less than a preset threshold, thereby obtaining a more accurate final thermal conductivity value than the preliminary thermal conductivity value, which can improve the measurement accuracy of the final thermal conductivity value.

[0006] According to some embodiments of the present invention, a pixel thermal conductivity testing method for an infrared focal plane array is provided, wherein multiple pixel thermal conductivity testing structures are provided, and the multiple pixel thermal conductivity testing structures are respectively used to test the thermal conductivity value of pixels at different positions within the die.

[0007] According to some embodiments of the present invention, the pixel thermal conductivity testing structure of the infrared focal plane array is the same as or different from that of the pixels in the rectangular array.

[0008] According to some embodiments of the present invention, the pixel thermal conductivity testing structure for an infrared focal plane array is prepared by the following method: The ROIC wafer is cleaned and dried to remove surface impurities and moisture; A PI-1 layer is fabricated on the ROIC wafer, and PI-1 holes are formed by photolithography etching. A first dielectric layer is prepared on the ROIC wafer, and a first hole structure for the pixel structure electrically connected to the ROIC electrode is formed by photolithography etching. A first dielectric layer, a thermistor layer, and a second dielectric layer are fabricated on the ROIC wafer, and photolithography is performed on the second dielectric layer and the thermistor layer. A third dielectric layer is prepared on the thermistor layer and an aperture is made therein. Then, an electrically conductive layer is prepared. One end of the electrically conductive layer is connected to the thermistor layer through the aperture, and the other end of the electrically conductive layer is connected to the ROIC electrode on the ROIC wafer. A fourth dielectric protective layer is prepared on the electrically conductive layer to form an insulating protection; the first dielectric layer, the thermistor layer, the second dielectric layer, the third dielectric layer, the electrically conductive layer, and the fourth dielectric protective layer together constitute a pixel bridge surface layer; A PI-2 layer is prepared on the pixel bridge surface layer, and a thermal contact hole communicating with the pixel bridge surface layer is formed by photolithography etching. An infrared absorption umbrella layer was prepared on the PI-2 layer, and the PI-1 and PI-2 materials were released in a vacuum chamber using a plasma release process to form a test pixel structure with two suspension layers. A detector containing the pixel thermal conductivity test structure is obtained by vacuum encapsulating a die with the test pixel structure.

[0009] According to some embodiments of the present invention, the pixel thermal conductivity testing method of an infrared focal plane array includes Si3N4 or SiO2 as the material of the first dielectric layer, the second dielectric layer, the third dielectric layer, and the fourth dielectric protective layer; the material of the conductive layer includes Ti, Al, Cu, W, Cr, Ni, TiN, or polycrystalline silicon; and the material of the thermistor layer is vanadium oxide.

[0010] According to some embodiments of the present invention, the pixel thermal conductivity testing method for an infrared focal plane array is provided in which the bridge layer in the pixel thermal conductivity testing structure is suspended on the substrate wafer to form a thermally insulating structure, and the bridge layer is electrically connected to the ROIC electrode on the ROIC wafer through bridge legs.

[0011] According to some embodiments of the present invention, the method for testing the thermal conductivity of an infrared focal plane array is provided in which the detector is placed on a temperature regulating device with temperature regulation capability. The temperature regulating device conducts heat through the test package of the detector and the substrate wafer to transfer heat to the pixel thermal conductivity test structure.

[0012] According to some embodiments of the present invention, the pixel thermal conductivity testing method for an infrared focal plane array includes the following: Multiple different temperature points are set on the temperature adjustment device, and the resistance value of the pixel thermal conductivity test structure is detected at each temperature point to obtain the test data of the resistance-temperature correspondence test.

[0013] According to some embodiments of the present invention, the pixel thermal conductivity testing method for an infrared focal plane array includes the following: The temperature adjustment device is set to a fixed temperature, and multiple different current points are applied to the pixel thermal conductivity test structure. The voltage, resistance, and power values ​​of the pixel thermal conductivity test structure at each current point are measured.

[0014] Secondly, embodiments of the present invention provide a method for preparing a pixel thermal conductivity testing structure, comprising: The ROIC wafer is cleaned and dried to remove surface impurities and moisture; A PI-1 layer is fabricated on the ROIC wafer, and PI-1 holes are formed by photolithography etching. A first dielectric layer is prepared on the ROIC wafer, and a first hole structure for the pixel structure electrically connected to the ROIC electrode is formed by photolithography etching. A first dielectric layer, a thermistor layer, and a second dielectric layer are fabricated on the ROIC wafer, and photolithography is performed on the second dielectric layer and the thermistor layer. A third dielectric layer is prepared on the thermistor layer and an aperture is made therein. Then, an electrically conductive layer is prepared. One end of the electrically conductive layer is connected to the thermistor layer through the aperture, and the other end of the electrically conductive layer is connected to the ROIC electrode on the ROIC wafer. A fourth dielectric protective layer is prepared on the electrically conductive layer to form an insulating protection; the first dielectric layer, the thermistor layer, the second dielectric layer, the third dielectric layer, the electrically conductive layer, and the fourth dielectric protective layer together constitute a pixel bridge surface layer; A PI-2 layer is prepared on the pixel bridge surface layer, and a thermal contact hole communicating with the pixel bridge surface layer is formed by photolithography etching. An infrared absorption umbrella layer was prepared on the PI-2 layer, and the PI-1 and PI-2 materials were released in a vacuum chamber using a plasma release process to form a test pixel structure with two suspension layers. A detector containing the pixel thermal conductivity test structure is obtained by vacuum encapsulating a die with the test pixel structure.

[0015] According to some embodiments of the present invention, the method for preparing a pixel thermal conductivity test structure includes the following materials: the first dielectric layer, the second dielectric layer, the third dielectric layer, and the fourth dielectric protective layer are Si3N4 or SiO2; the conductive layer is made of Ti, Al, Cu, W, Cr, Ni, TiN, or polycrystalline silicon; and the thermistor layer is made of vanadium oxide.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0017] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a flowchart of a pixel thermal conductivity testing method for an infrared focal plane array provided in an embodiment of the present invention; Figure 2 This is a flowchart of a method for preparing a pixel thermal conductivity testing structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a pixel thermal conductivity testing structure provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of another pixel thermal conductivity testing structure provided in an embodiment of the present invention. Detailed Implementation

[0019] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0020] In the description of the embodiments of the present invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the number itself, while "above," "below," "within," etc. are understood to include the number itself. "At least one" refers to one or more, and "at least one of the following" and similar expressions refer to any combination of these items, including any combination of single or multiple items. If "first," "second," etc., are used in the description, they are only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features.

[0021] It should be noted that the terms "setting," "installing," and "connecting" in the embodiments of this invention should be interpreted broadly. Those skilled in the art can reasonably determine the specific meaning of the above terms in the embodiments of this invention in conjunction with the specific content of the technical solution. For example, the term "connection" can be a mechanical connection, an electrical connection, or a connection that allows for mutual communication; it can be a direct connection or an indirect connection through an intermediate medium.

[0022] It should be noted that the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Currently, in existing methods for testing the thermal conductivity of pixels in infrared focal plane arrays, using an additional thermistor to measure the temperature of the structure under test has two main drawbacks. First, it increases the complexity of the process, and the thermistor still requires external temperature control equipment to calibrate the relationship between resistance and temperature. In actual use, the pixel temperature is measured by looking up a table or interpolating based on the calibration relationship, which results in a complex testing process and difficulty in guaranteeing accuracy. Second, it requires energizing the thermistor in the floating layer of the pixel thermal conductivity testing structure to measure resistance. This energizing channel inevitably affects the thermal conductivity of the bridge legs of the pixel thermal conductivity testing structure, resulting in the measured value not being the thermal conductivity value of the pixel's bridge legs, thus affecting the accuracy of the thermal conductivity measurement.

[0024] Based on this, embodiments of the present invention provide a method for testing the thermal conductivity of pixels in an infrared focal plane array and a method for preparing a pixel thermal conductivity testing structure, which can improve the accuracy of the final thermal conductivity value measurement.

[0025] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0026] A first aspect of the present invention provides a pixel thermal conductivity testing method for an infrared focal plane array. Specifically, the infrared focal plane array can be a MEMS uncooled infrared focal plane array. The pixel thermal conductivity testing method is applied to a pixel thermal conductivity testing structure. The infrared focal plane array includes a rectangular array composed of X rows and Y columns of pixels. The pixel thermal conductivity testing structure is disposed on the periphery of the rectangular array. The rectangular array is cut out on a wafer to form a die, which is vacuum-encapsulated within a package. The pixel thermal conductivity testing structure is electrically connected to the electrode pins of the package. The pixel thermal conductivity testing structure includes a thermistor material. Exemplarily, the pixel thermal conductivity testing structure refers to... Figure 3 As shown, Figure 3 The heat-sensitive layer in the middle is a heat-sensitive material; refer to Figure 1 The pixel thermal conductivity testing method includes, but is not limited to, steps S110 to S150, specifically: Step S110: Perform resistance-temperature correlation test and current-voltage correlation test on the pixel thermal conductivity test structure; Step S120: Based on the resistance data obtained from the current-voltage correspondence test, interpolate the test data from the resistance-temperature correspondence test to obtain the preliminary thermal conductivity value of the pixel thermal conductivity test structure; Step S130: Obtain the activation energy of the thermosensitive material by fitting the preliminary thermal conductivity value; Step S140: Calculate the temperature data corresponding to the resistance data based on the resistance data obtained from the activation energy and current-voltage correspondence test, and recalculate the intermediate thermal conductivity value based on the power data and temperature data obtained from the current-voltage correspondence test. Step S150: Repeatedly iterate the calculation of activation energy, temperature data, and intermediate thermal conductivity value until the difference between the last two calculated intermediate thermal conductivity values ​​is less than a preset threshold, and take the intermediate thermal conductivity value obtained in the last calculation as the final thermal conductivity value.

[0027] The pixel thermal conductivity testing method for an infrared focal plane array provided by the present invention involves setting a pixel thermal conductivity testing structure around a rectangular array. The pixel thermal conductivity testing structure is electrically connected to the electrode pins of the package. Resistance-temperature correspondence test and current-voltage correspondence test are performed. The preliminary thermal conductivity value of the pixel thermal conductivity testing structure is further calculated, and the activation energy of the thermosensitive material is obtained by fitting. The intermediate thermal conductivity value is then calculated, and the calculation is repeated iteratively until the difference between the last two intermediate thermal conductivity values ​​is less than a preset threshold. This allows for a more accurate final thermal conductivity value than the preliminary thermal conductivity value, thereby improving the measurement accuracy of the final thermal conductivity value.

[0028] According to some embodiments of the present invention, the pixel thermal conductivity testing method for an infrared focal plane array is provided, wherein multiple pixel thermal conductivity testing structures are provided, and the multiple pixel thermal conductivity testing structures are respectively used to test the thermal conductivity value of pixels at different positions within the die.

[0029] According to some embodiments of the present invention, the pixel thermal conductivity testing structure of the infrared focal plane array is the same as or different from that of the pixels in the rectangular array.

[0030] According to some embodiments of the present invention, the pixel thermal conductivity testing structure for an infrared focal plane array is prepared by the following method: The ROIC wafer is cleaned and dried to remove surface impurities and moisture; A PI-1 layer is fabricated on a ROIC wafer, and PI-1 holes are formed by photolithography etching. A first dielectric layer is fabricated on a ROIC wafer, and a first hole structure for the pixel structure electrically connected to the ROIC electrode is formed by photolithography etching; wherein the first hole structure is... Figure 3 The PI-1 hole structure shown; A first dielectric layer, a thermistor layer, and a second dielectric layer are fabricated on a ROIC wafer, and the second dielectric layer and the thermistor layer are etched by photolithography. A third dielectric layer is prepared on the thermistor layer and an opening is made. Then, an electrically conductive layer is prepared. One end of the electrically conductive layer is connected to the thermistor layer through the opening, and the other end of the electrically conductive layer is connected to the ROIC electrode on the ROIC wafer. A fourth dielectric protective layer is fabricated on the electrically conductive layer to form an insulating protection layer; the first dielectric layer, the thermistor layer, the second dielectric layer, the third dielectric layer, the electrically conductive layer, and the fourth dielectric protective layer together constitute the pixel bridge layer; wherein, the part with a slender structure between the bridge layer and the ROIC electrode, which serves to support the pixel bridge layer and conduct electricity, is the bridge leg, and its material includes an electrically conductive material and a dielectric layer; preferably, the material of each dielectric layer includes Si3N4 or SiO2, the material of the electrically conductive layer includes Ti, Al, Cu, W, Cr, Ni, TiN or polycrystalline silicon, and the material of the thermistor layer is vanadium oxide; A PI-2 layer is fabricated on the pixel bridge surface layer, and thermal contact holes are formed through photolithography etching to penetrate the pixel bridge surface layer. These thermal contact holes are... Figure 3 The PI-2 orifice is shown. An infrared absorption umbrella layer is prepared on the PI-2 layer, and the materials of the PI-1 and PI-2 layers are released in a vacuum chamber using a plasma release process to form a test pixel structure with two suspension layers; the infrared absorption umbrella layer is generally composed of a dielectric and a conductive layer with a certain resistance. A detector containing a pixel thermal conductivity test structure is obtained by vacuum encapsulating a die with a test pixel structure.

[0031] According to some embodiments of the present invention, the pixel thermal conductivity testing method for an infrared focal plane array is provided in which the bridge layer in the pixel thermal conductivity testing structure is suspended on the substrate wafer to form a thermally insulating structure, and the bridge layer is electrically connected to the ROIC electrode on the ROIC wafer through bridge legs.

[0032] It should be noted that the heat transfer process of the pixel thermal conductivity test structure involves Joule heating generated in the thermistor layer and the conductive layer after applying a certain electrical bias. Part of this heat is transferred to the ROIC electrode via thermal conduction through the bridge legs, another part is radiated to the surrounding area via gray body radiation, and a third part is transferred through heat exchange via collisions of residual gas molecules in the vacuum. Since the test bias power is relatively small, the resulting radiation effect is also small and can be ignored. The vacuum level of vacuum-sealed detectors is generally on the order of E⁻² Pa, and the distance between the detector package and the pixel is less than 5 mm. Under these two constraints, the gas inside the detector package is in a free molecular flow state, meaning the mean free path of the molecules is much greater than the distance between the detector package and the pixel. In this state, the gas molecules only transfer heat through collisions between the inner wall of the package and the pixel, which is very low compared to the solid thermal conductivity of the pixel and can also be ignored.

[0033] According to some embodiments of the present invention, the method for testing the thermal conductivity of an infrared focal plane array is provided in which the detector is placed on a temperature regulating device with temperature regulation capability. The temperature regulating device conducts heat through the test package of the detector and the substrate wafer to transfer heat to the pixel thermal conductivity test structure.

[0034] According to some embodiments of the present invention, a method for testing the thermal conductivity of pixels in an infrared focal plane array is provided, including resistance-temperature correlation testing, i.e., R... RT -T RT Tests, including: Multiple different temperature points are set on the temperature control device, and the resistance value of the pixel thermal conductivity test structure is detected at each temperature point to obtain test data of the resistance-temperature relationship test.

[0035] Specifically, in step S110, R RT -T RT During the test, n pixel thermal conductivity test structures were connected in series between the two electrodes of the detector, and simultaneously, the thermal conductivity test structures of the n pixels were connected in series with R. RT -T RT To avoid random errors in testing due to individual process variations, a series of temperature values ​​T are set. RT , by T RT1 Gradually rise to T RTm At each temperature, a small current is used to test the resistance value R of the pixel thermal conductivity test structure within the detector. RT A series of R values ​​were obtained. RT -T RTCorrespondence. At this point, it is assumed that the temperature of the pixel structure bridge surface is equal to the set temperature of the equipment. However, due to the heat loss caused by heat transfer through the detector package, wafer substrate, and pixel structure bridge legs, there is a certain error between the set temperature and the pixel structure bridge surface temperature. This error needs to be corrected in subsequent processes.

[0036] The pixel thermal conductivity testing method for infrared focal plane arrays provided in some embodiments of the present invention includes current-voltage correspondence testing, i.e., IV testing, comprising: The temperature control device was set to a fixed temperature, and multiple different current points were applied to the pixel thermal conductivity test structure. The voltage, resistance, and power values ​​of the pixel thermal conductivity test structure at each current point were measured.

[0037] Specifically, in the IV test in step S110, the device temperature is set to the initial temperature T. IV0 First, a small current I0 is applied across the two ends of n thermal conductivity test structures to measure R. IV0 Then the current applied to the pixel thermal conductivity test structure is increased from I1 (I1 is much greater than I0) to I... n Ampere, to obtain a series of power P i With resistance R IVi , where P i =I i ^2×R IVi .

[0038] In step S120, for R RT -T RT The test data uses R in the IV test. IVi Interpolation, calculating R IVi The corresponding temperature T IVi .

[0039] The initial thermal conductivity value G is calculated according to the following formula, thus obtaining the initial thermal conductivity value G corresponding to a series of IV tests. i : G i =[P i+1 - P i ] / [ T IVi+1 - T IVi ]; (1) In step S130, the resistance of the thermistor layer material conforms to the semiconductor material resistance calculation formula, and the resistance R measured by IV is... IV =r×exp[E a / (k B ×T IV E a k is the activation energy of the thermosensitive material. B E is the Boltzmann constant.a It can be obtained by fitting the calculated preliminary thermal conductivity value G, where the fitting formula is shown in the following equation: ; (2) in: ; (3) Substitute the test data into the above fitting formula to perform a straight line fit, where the slope k B / E a This is the term to be fitted. Substitute the known value k into the slope. B That is, the activation energy E is obtained. a In the IV test, a small current I0 is applied across both ends of the thermal conductivity test structure to measure R. IV0 Since the temperature rise of the bridge deck was not significant, the bridge deck temperature was approximately equal to the equipment's set temperature T. IV0 Then E a Substituting into equation (3) yields the value of r. Based on r and E... a A series of R values ​​and IV tests IV The value can be calculated using equation (3) to obtain a new series of T values. IVn Value. At this time, T IVn It is assumed to be the temperature of the bridge surface, rather than the temperature after heat loss through the detector's package, wafer substrate, and pixel structure bridge legs, based on the equipment's set temperature. This process corrects the error of using the equipment's set temperature instead of the bridge surface temperature.

[0040] In step S140, the bridge deck temperature T obtained through the above process is used IVn The intermediate thermal conductivity value Gi of the pixel thermal conductivity test structure is recalculated using Equation (1).

[0041] In step S150, the above steps S130 to S140 are iterated to calculate the intermediate thermal conductivity value Gi until the difference between the two calculated intermediate thermal conductivity values ​​Gi is less than a set threshold, at which point the iteration ends and a relatively accurate final thermal conductivity value Gin is obtained.

[0042] The detailed iterative calculation process is shown below.

[0043] Table 1: Basic Parameters Boltzmann constant kB 8.62E-05 eV / K Serial pixels n 2 Initial equipment temperature <![CDATA[T IV0 ]]> 298.15 K Small current <![CDATA[I0]]> 5.00E-08 A Loading current range <![CDATA[I1~I8]]> 1E-6~8E-6 A (1) R RT -T RT test.

[0044] Table 2: R RT -T RT Raw test data (25~60℃) 25 2.98E02 400 35 3.08E02 350 45 3.18E02 300 55 3.28E02 260 60 3.33E02 240 (2) IV test.

[0045] Table 3: Raw data from the IV test 0 5.00E-08 400 1 1.00E-06 380 2 2.00E-06 360 3 3.00E-06 340 4 4.00E-06 320 5 5.00E-06 300 6 6.00E-06 285 7 7.00E-06 270 8 8.00E-06 260 (3) Initial calculation of thermal conductivity Table 4: Iteration 0: Calculation of initial thermal conductivity (without temperature error correction) 1 3.8E-07 300.15 2 1.44E-06 305.13 2.13E-07 3 3.06E-06 310.22 3.18E-07 4 5.12E-06 314.63 4.67E-07 5 7.5E-06 318.65 5.92E-07 6 1.026E-05 321.97 8.31E-07 7 1.323E-05 325.2 9.20E-07 8 1.664E-05 328.1 1.18E-06 average <![CDATA[G0=6.45E-07]]> (4) Iterate once, correct the bridge surface temperature, and update the thermal conductivity.

[0046] Table 5: Bridge deck temperature and updated thermal conductivity after one iteration.

[0047] 1 301.5 - - 2 307.8 1.68E-07 20.95% 3 311.5 4.38E-07 37.57% 4 315.8 4.79E-07 2.56% 5 320.8 4.76E-07 19.60% 6 323.6 9.86E-07 18.57% 7 326.6 9.90E-07 7.67% 8 328.2 2.13E-06 81.25% average 8.10E-07 (5) Iterate twice, correct the bridge deck temperature, and update the thermal conductivity.

[0048] Table 6: Bridge deck temperature and updated thermal conductivity after two iterations.

[0049] 1 301.5 - 2 307.7 1.71E-07 1.61% 3 311.3 4.50E-07 2.78% 4 316 4.38E-07 8.51% 5 320.6 5.17E-07 8.70% 6 323.8 8.63E-07 12.50% 7 326.5 1.10E-06 11.11% 8 327.9 2.44E-06 14.29% average 8.54E-07 5.41% (6) After 3 iterations, the circuit finally converges.

[0050] 1 301.5 - 2 307.8 1.68E-07 1.59% 3 311.2 4.76E-07 5.88% 4 315.8 4.48E-07 2.17% 5 320.5 5.06E-07 2.13% 6 323.6 8.90E-07 3.23% 7 326.5 1.02E-06 6.90% 8 328 2.27E-06 6.67% average 8.27E-07 3.15%, convergence <5% Reference Figure 2 A second aspect of the present invention provides a method for preparing a pixel thermal conductivity testing structure, including but not limited to steps S210 to S280, specifically: Step S210: Clean the ROIC wafer and dry it to remove impurities and moisture from the surface; Step S220: Prepare a PI-1 layer on the ROIC wafer and form PI-1 holes by photolithography etching; Step S230: Prepare a first dielectric layer, a thermistor layer, and a second dielectric layer on the ROIC wafer, and perform photolithography etching on the second dielectric layer and the thermistor layer; preferably, the material of the thermistor layer is vanadium oxide; Step S240: Prepare a third dielectric layer and make an opening on the thermistor layer, and then prepare an electrically conductive layer. One end of the electrically conductive layer is connected to the thermistor layer through the opening, and the other end of the electrically conductive layer is connected to the ROIC electrode on the ROIC wafer. Step S250: A fourth dielectric protective layer is prepared on the electrically conductive layer to form an insulating protection; the first dielectric layer, the thermistor layer, the second dielectric layer, the third dielectric layer, the electrically conductive layer, and the fourth dielectric protective layer together constitute the pixel bridge layer; wherein, the part with a slender structure between the bridge layer and the ROIC electrode that supports the pixel bridge layer and conducts electricity is the bridge leg, and its material includes an electrically conductive material and a dielectric layer; preferably, the material of each dielectric layer includes Si3N4 or SiO2, and the material of the electrically conductive layer includes Ti, Al, Cu, W, Cr, Ni, TiN, or polycrystalline silicon; Step S260: A PI-2 layer is fabricated on the pixel bridge surface layer, and a thermal contact hole is formed through the pixel bridge surface layer by photolithography etching. The thermal contact hole is... Figure 3 The PI-2 orifice is shown. Step S270: An infrared absorption umbrella layer is prepared on the PI-2 layer, and the materials of the PI-1 and PI-2 layers are released in a vacuum chamber using a plasma release process to form a test pixel structure with two suspension layers; wherein, the infrared absorption umbrella layer is generally composed of a dielectric and a conductive layer with a certain resistance. Step S280: Vacuum encapsulate the die with the test pixel structure to obtain a detector containing the pixel thermal conductivity test structure.

[0051] According to some embodiments of the present invention, the materials of the first dielectric layer, the second dielectric layer, the third dielectric layer, and the fourth dielectric protective layer include Si3N4 or SiO2; the materials of the electrically conductive layer include Ti, Al, Cu, W, Cr, Ni, TiN, or polycrystalline silicon.

[0052] According to the method for preparing a pixel thermal conductivity test structure provided in some embodiments of the present invention, the process of the above embodiments is similar. First, a test pixel structure with two suspension layers is prepared. Then, an umbrella-less, unreleased pixel structure is set at a position adjacent to the test pixel structure. The umbrella layer is set as the release protective shell of the bridge layer. The umbrella-less, unreleased pixel structure with the release protective shell is called a reference structure, for example, a reference. Figure 4 As shown.

[0053] The reference structure is configured with a matrix of multiple unreleased unumbrellad pixel structures. Due to the multidirectional nature of plasma etching, when the PI-2 layer is released, the PI-1 layer of one or more unreleased unumbrellad pixels in the center of the matrix is ​​not released, while the PI-1 layer of several unreleased unumbrellad pixels in the periphery is released. The unreleased unumbrellad pixels that have not been released are selected and electrically connected to the pin electrodes of the vacuum package for subsequent power-on testing.

[0054] The process of releasing the protective shell is as follows: In the step of processing PI-2 holes, smaller PI-2 holes are set around the unreleased pixel matrix without umbrella. A thin film with umbrella layer is deposited in the smaller PI-2 holes, but there is no umbrella layer structure, forming a release protective shell support structure. During the PI release process, the release protective shell support structure supports a larger piece of umbrella layer film to form a release protective shell, protecting the unreleased pixel structure PI-1 without umbrella from being released.

[0055] The testing process in this embodiment is as follows: [The above...] Figure 1 In the corresponding embodiment test, step S110, R RT -T RTThe test was changed to test the unreleased, umbrella-less pixels. Because PI-1 was filled between the bridge deck layer and the ROIC in the unreleased, umbrella-less pixels, thermal conductivity was increased. This structure reduces the temperature difference between the temperature regulation device's set temperature and the bridge deck temperature. The remaining test procedures are the same as in Example 1. Because the unreleased, umbrella-less pixel structure was used to test R... RT -T RT The beneficial effect is that it makes the initially calculated thermal conductivity value G closer to the value G calculated in subsequent iterations. i This reduces the number of iterations and improves testing efficiency.

[0056] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for testing a thermal conductance of a pixel of an infrared focal plane array, applied to a pixel thermal conductance test structure, the method comprising: The infrared focal plane array includes a rectangular array of pixels arranged in X rows and Y columns. The pixel thermal conductivity test structure is disposed on the periphery of the rectangular array. The rectangular array is cut out on the wafer to form a die. The die is vacuum-encapsulated in a package. The pixel thermal conductivity test structure is electrically connected to the electrode pins of the package. The pixel thermal conductivity testing structure includes a thermosensitive material, and the pixel thermal conductivity testing method includes: The resistance-temperature relationship and the current-voltage relationship were tested on the pixel thermal conductivity test structure. Based on the resistance data obtained from the current-voltage correlation test, the test data from the resistance-temperature correlation test are interpolated to obtain the preliminary thermal conductivity value of the pixel thermal conductivity test structure. The activation energy of the thermosensitive material is obtained by fitting the preliminary thermal conductivity value. Based on the activation energy and the resistance data obtained from the current-voltage correspondence test, the temperature data corresponding to the resistance data is calculated, and the intermediate thermal conductivity value is recalculated based on the power data obtained from the current-voltage correspondence test and the temperature data. The activation energy, the temperature data, and the intermediate thermal conductivity value are repeatedly iterated until the difference between the last two calculated intermediate thermal conductivity values ​​is less than a preset threshold, and the intermediate thermal conductivity value obtained in the last calculation is taken as the final thermal conductivity value.

2. The pixel thermal conductivity testing method for an infrared focal plane array according to claim 1, characterized in that, Multiple pixel thermal conductivity test structures are provided, and each of the multiple pixel thermal conductivity test structures is used to test the thermal conductivity value of pixels at different locations within the die.

3. The pixel thermal conductivity testing method for an infrared focal plane array according to claim 1, characterized in that, The pixel thermal conductivity test structure may be the same as or different from the pixels in the rectangular array.

4. The pixel thermal conductivity testing method for an infrared focal plane array according to claim 1, characterized in that, The pixel thermal conductivity test structure was prepared using the following method: The ROIC wafer is cleaned and dried to remove surface impurities and moisture; A PI-1 layer is fabricated on the ROIC wafer, and PI-1 holes are formed by photolithography etching. A first dielectric layer is prepared on the ROIC wafer, and a first hole structure for the pixel structure electrically connected to the ROIC electrode is formed by photolithography etching. A thermistor layer and a second dielectric layer are fabricated on the ROIC wafer, and photolithography is performed on the second dielectric layer and the thermistor layer. A third dielectric layer is prepared on the thermistor layer and an aperture is made therein. Then, an electrically conductive layer is prepared. One end of the electrically conductive layer is connected to the thermistor layer through the aperture, and the other end of the electrically conductive layer is connected to the ROIC electrode on the ROIC wafer. A fourth dielectric protective layer is prepared on the electrically conductive layer to form an insulating protection layer; The first dielectric layer, the thermal layer, the second dielectric layer, the third dielectric layer, the electrically conductive layer, and the fourth dielectric protective layer together constitute the pixel bridge layer; A PI-2 layer is prepared on the pixel bridge surface layer, and a thermal contact hole communicating with the pixel bridge surface layer is formed by photolithography etching. An infrared absorption umbrella layer was prepared on the PI-2 layer, and the PI-1 and PI-2 materials were released in a vacuum chamber using a plasma release process to form a test pixel structure with two suspension layers. A detector containing the pixel thermal conductivity test structure is obtained by vacuum encapsulating a die with the test pixel structure.

5. The method for preparing the pixel thermal conductivity testing structure according to claim 4, characterized in that, The materials of the first dielectric layer, the second dielectric layer, the third dielectric layer, and the fourth dielectric protective layer include Si3N4 or SiO2; the material of the electrically conductive layer includes Ti, Al, Cu, W, Cr, Ni, TiN, or polycrystalline silicon; and the material of the thermistor layer is vanadium oxide.

6. The pixel thermal conductivity testing method for an infrared focal plane array according to claim 4, characterized in that, The pixel bridge layer in the pixel thermal conductivity test structure is suspended on the substrate wafer to form a thermally insulating structure, and the pixel bridge layer is electrically connected to the ROIC electrode on the ROIC wafer through bridge legs.

7. The pixel thermal conductivity testing method for an infrared focal plane array according to claim 6, characterized in that, The detector is placed on a temperature regulating device with temperature regulation capability. The temperature regulating device conducts heat through the detector's test package and the substrate wafer to transfer heat to the pixel thermal conductivity test structure.

8. The pixel thermal conductivity testing method for an infrared focal plane array according to claim 7, characterized in that, The resistance-temperature correlation test includes: Multiple different temperature points are set on the temperature adjustment device, and the resistance value of the pixel thermal conductivity test structure is detected at each temperature point to obtain the test data of the resistance-temperature correspondence test.

9. The pixel thermal conductivity testing method for an infrared focal plane array according to claim 7, characterized in that, The current-voltage correspondence test includes: setting the temperature adjustment device to a fixed temperature, applying multiple different current points to the pixel thermal conductivity test structure, and measuring the voltage, resistance, and power values ​​of the pixel thermal conductivity test structure at each current point.

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