Electromagnetic wave sensor

Abstract

To provide an electromagnetic sensor with which it is possible to grasp the state of a decrease in the sealing performance of the electromagnetic sensor.SOLUTION: An electromagnetic sensor (infrared sensor) 1 comprises: a first substrate; a second substrate that faces the first substrate and allows an infrared ray to pass through in at least a portion; a first circumferential wall 4a that is located between the first and the second substrates and forms a first space 8a together with the first and second substrates; a plurality of bolometer structures 7 that are provided in the first space 8a; a first element 9a for measurement that is provided in the first space 8a and is used for measuring a first measurement value associated with the pressure P1 of the first space 8a; and a monitoring unit. The monitoring unit acquires the first measurement value having been measured using the first element 9a for measurement, and outputs a prescribed signal that indicates abnormality, on the basis of at least the first measurement value.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an electromagnetic wave sensor and a method for manufacturing the same, and particularly relates to a configuration of an infrared sensor provided with a bolometer structure.

Background Art

[0002] Infrared sensors that are provided with a bolometer structure and detect the temperature distribution of a target object in the infrared wavelength region are known. In such an infrared sensor, infrared rays incident on the bolometer structure from the outside and absorbed by the bolometer structure cause a temperature change in the bolometer structure, and the temperature change of the bolometer structure is extracted as a resistance change. There is a correlation (Stefan-Boltzmann's law) between the temperature of a target object and the emissivity (radiant energy) radiated from the target object. Therefore, the temperature distribution of the target object can be measured by detecting the temperature change of the bolometer structure caused by the radiant heat radiated from the target object. In order to detect radiant heat with high accuracy, the bolometer structure is housed in a sealed vacuum container. Patent Document 1 discloses an electromagnetic wave sensor provided with a vacuum container formed by two substrates and a peripheral wall.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] Since a vacuum container that houses a bolometer structure is generally produced by joining a plurality of members, the sealing performance may deteriorate due to aged deterioration of the joined portion or the like. Deterioration in sealing performance leads to a decrease in the degree of vacuum or loss of the vacuum state of the vacuum container, and causes performance degradation or loss of function of the electromagnetic wave sensor. An object of the present invention is to provide an electromagnetic wave sensor capable of grasping the state of deterioration in sealing performance. [Means for solving the problem]

[0005] According to one aspect of the present invention, the electromagnetic wave sensor comprises a first substrate, a second substrate facing the first substrate and transmitting infrared rays in at least a portion thereof, and a first peripheral wall located between the first substrate and the second substrate and forming a first space together with the first and second substrates, A second peripheral wall is located between the first substrate and the second substrate, surrounding the first peripheral wall, and together with the first and second substrates and the first peripheral wall, forming a second space. A plurality of bolometer structures provided in a first space, and a first measuring element provided in the first space and used for measuring a first measurement value related to the pressure P1 of the first space, A second measuring element provided in the second space and used to measure a second measurement value related to the pressure P2 of the second space, It has a monitoring unit. The monitoring unit measures a first measurement value measured using a first measuring element. And, the second measurement value obtained using the second measuring element, Obtain at least the first measurement and the second measurement Based on this, a predetermined signal indicating an abnormality is output. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an electromagnetic wave sensor that can determine the degree of deterioration in sealing performance. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of an infrared sensor relating to one embodiment of the present invention. [Figure 2] Figure 1 is a partial cross-sectional view of the infrared sensor shown. [Figure 3] Figure 1 is a schematic diagram showing the pressure range and arrangement of measuring elements of the infrared sensor. [Figure 4] This diagram shows the normal mode and several abnormal modes of an infrared sensor. [Figure 5] This is a schematic diagram showing the manufacturing process of infrared sensors. [Modes for carrying out the invention]

[0009] Embodiments of the electromagnetic wave sensor of the present invention will be described below with reference to the drawings. In the following description and drawings, the first direction X and the second direction Y are parallel to the main surfaces of the first substrate 2 and the second substrate 3, respectively, with the first direction X corresponding to the rows of the bolometer structure array and the second direction Y corresponding to the columns of the bolometer structure array. The first direction X and the second direction Y are orthogonal. The third direction Z is orthogonal to the first direction X and the second direction Y, and is perpendicular to the main surfaces of the first substrate 2 and the second substrate 3.

[0010] The following embodiments focus on infrared sensors in which multiple bolometer structures are arranged as a two-dimensional array. Such infrared sensors are mainly used as image sensors in infrared cameras. Infrared cameras can be used as night vision scopes and goggles in dark places, as well as for measuring the temperature of people and objects. In recent years, infrared cameras have also been used as part of the sensor systems of automobiles. Furthermore, infrared sensors in which multiple bolometer structures are arranged in a one-dimensional manner can be used as sensors for measuring various temperatures or temperature distributions. Although not explained in detail, infrared sensors in which multiple bolometer structures are arranged in a one-dimensional manner are also included in the scope of the present invention. Moreover, the electromagnetic waves to be detected are not limited to infrared, and the electromagnetic wave sensor of the present invention may, for example, detect terahertz waves with wavelengths of 100 μm to 1 mm.

[0011] (Overall structure) Figure 1(a) is a schematic plan view of an infrared sensor 1 according to one embodiment of the present invention, Figure 1(b) is an enlarged view of part A in Figure 1(a), Figure 1(c) is a cross-sectional view along the line 1B-1B in Figure 1(b), and Figure 2 is an enlarged view of part B in Figure 1(c). The infrared sensor 1 has a first substrate 2, a second substrate 3 facing the first substrate 2, and a first peripheral wall 4a and a second peripheral wall 4b located between the first substrate 2 and the second substrate 3. The first peripheral wall 4a and the second peripheral wall 4b are made of a metal such as permalloy or nickel. The first peripheral wall 4a, together with the first and second substrates 2 and 3, forms a first space 8a where a plurality of bolometer structures 7 are provided. The second peripheral wall 4b surrounds the first peripheral wall 4a on the outside of it, and together with the first and second substrates 2, 3 and the first peripheral wall 4a, forms the second space 8b. The first space 8a and the second space 8b are sealed spaces under negative pressure or vacuum under normal conditions. This prevents or suppresses gas convection in the first space 8a, thereby reducing the thermal influence on the bolometer structure 7. The pressure (first pressure P1) or vacuum level of the first space 8a and the pressure (second pressure P2) of the second space 8b are substantially the same. Also, under normal conditions, the first pressure P1 and the second pressure P2 are less than the pressure outside the second space 8b (third pressure P3).

[0012] The first substrate 2 has a silicon substrate and an insulating film (neither shown), and a readout IC (ROIC) consisting of a regulator, A / D converter, multiplexer, etc., as well as various elements and wiring (not shown) are formed on the surface of the silicon substrate or inside the insulating film. The second substrate 3 has an insulating layer 31 covering the leads 10 (described later), an anti-reflective film 32 adjacent to the insulating layer 31, a silicon substrate 33 adjacent to the anti-reflective film 32, and an anti-reflective film 34 adjacent to the silicon substrate 33. The insulating layer 31 is formed from aluminum nitride, silicon nitride, aluminum oxide, silicon oxide, magnesium oxide, etc. The silicon substrate 33 and the anti-reflective films 32 and 34 transmit long-wavelength infrared light. In addition, the insulating layer 31 transmits less long-wavelength infrared light than the silicon substrate 33 and the anti-reflective films 32 and 34, and has through holes 13 facing the bolometer structure 7 in the third direction Z. The through holes 13 function as light incident parts that inject long-wavelength infrared light into the first space 8a. Therefore, the second substrate 3 transmits long-wavelength infrared light in at least a portion of its surface. The wavelength of long-wavelength infrared light is approximately 8 to 14 μm.

[0013] The first space 8a is provided with a plurality of roughly square-shaped bolometer structures 7. The plurality of bolometer structures 7 form a two-dimensional grid array consisting of a plurality of rows R arranged at regular intervals in the first direction X and a plurality of columns C arranged at regular intervals in the second direction Y. Each bolometer structure 7 constitutes one cell or pixel in this array. The number of rows and columns of the array is, for example, 640 rows × 480 columns or 1024 rows × 768 columns, but is not limited to these. In this embodiment, the bolometer structure 7 has a thermistor film that outputs temperature changes as resistance changes, a substrate on which the thermistor film is formed and which absorbs infrared radiation heat to be detected, and an electrode film that electrically connects the thermistor film to the wiring of the first substrate 2 via a second electrical connection member 6, etc., which will be described later. The thermistor film is composed of, for example, a film of a metal such as vanadium oxide (VOx), amorphous silicon (a-Si), nitride, or platinum. Radiation absorbers are composed of materials such as silicon oxide (SiO2), silicon nitride (SiN), aluminum oxide (Al2O3), or combinations thereof.

[0014] The first space 8a is provided with a first electrical connection member 5 that connects the first substrate 2 to the second substrate 3. The first electrical connection member 5 is a conductor with a pillar-like shape and a circular cross-section, which can be made, for example, by plating. The first electrical connection member 5 has a larger (higher) dimension in the Z direction than the second electrical connection member 6, which will be described later, and therefore has a larger cross-sectional area than the second electrical connection member 6 for ease of manufacture. The first electrical connection member 5 includes a first row electrical connection member 5a connected to the row lead 10a, which will be described later, on the second substrate 3, and a first row electrical connection member 5b connected to the row lead 10b, which will be described later, on the second substrate 3.

[0015] Each bolometer structure 7 is supported on the second substrate 3 via a pair of second electrical connection members 6. The second electrical connection members 6 are also conductors with a pillar-like shape and a circular cross-section, and can be made, for example, by plating. The pair of second electrical connection members 6 consists of a second row electrical connection member 6a connected to the row lead 10a and a second column electrical connection member 6b connected to the column lead 10b. The second row electrical connection member 6a and the second column electrical connection member 6b extend downward in the Z direction from the row lead 10a and the column lead 10b toward the first substrate 2, respectively, and terminate between the first substrate 2 and the second substrate 3. Thus, the bolometer structure 7 is suspended in the first space 8a at a distance in the Z direction from the first substrate 2 and the second substrate 3. This reduces the thermal influence from elements provided on the first substrate 2 to the bolometer structure 7. The second electrical connection members 6 support the bolometer structure 7 and supply sense current to the bolometer structure 7.

[0016] The second substrate 3 has leads 10 formed on it that connect the first electrical connection member 5 to the bolometer structure 7 and supply sense current to the bolometer structure 7. The leads 10 are made of a conductor such as copper. The leads 10 are formed in a grid pattern for each row R and each column C of the bolometer structure 7. That is, the leads 10 consist of row leads 10a extending in the row direction (first direction X) and column leads 10b extending in the column direction (second direction Y). The row leads 10a connect the first row electrical connection member 5a to the second row electrical connection member 6a, and the column leads 10b connect the first column electrical connection member 5b to the second column electrical connection member 6b. The row leads 10a sequentially connect the bolometer structures 7 included in the corresponding row R, and the column leads 10b sequentially connect the bolometer structures 7 included in the corresponding column C. In Figure 2, for convenience, the row lead 10a is shown to be interrupted at a position opposite the bolometer structure 7, but the row lead 10a extends continuously. The same applies to the column lead 10b. The leads 10 extend between adjacent bolometer structures 7. This avoids interference between the leads 10 and the bolometer structures 7, and also suppresses the effect on the bolometer structures 7 caused by the leads 10 being heated by infrared radiation. The row leads 10a and the column leads 10b extend at different positions in the Z direction, with an insulating film (not shown) in between, so that they intersect without conducting electricity to each other.

[0017] Multiple first row electrical connection members 5a are alternately arranged on one end and the other end of row R of multiple row leads 10a. In other words, one first row electrical connection member 5a is placed every other on one end and the other end of row R of multiple row leads 10a. Similarly, multiple first column electrical connection members 5b are alternately arranged on one end and the other end of column C of multiple column leads 10b. In other words, one first column electrical connection member 5b is placed every other on one end and the other end of column C of multiple column leads 10b. This makes it possible to ensure a sufficient cross-sectional area of ​​the first electrical connection members 5 while suppressing an increase in the size of the infrared sensor 1.

[0018] Infrared light incident on the infrared sensor 1 from the second substrate 3 is incident on the array of bolometer structures 7. A sense current sequentially flows through the first row electrical connection member 5a, the row lead 10a, the second row electrical connection member 6a, the selected bolometer structure 7, the second column electrical connection member 6b, the column lead 10b, and the first column electrical connection member 5b. A resistance change of the thermistor film included in the bolometer structure 7 is extracted as a voltage change, and an electric signal (voltage signal) is supplied to the ROIC of the first substrate 2. The ROIC converts this voltage signal into a luminance temperature. A plurality of selection transistors (not shown) for selecting one bolometer structure 7 from the plurality of bolometer structures 7 are formed on the second substrate 3. The bolometer structures 7 are sequentially selected in time series by the selection transistors, and resistance changes extracted from the selected bolometer structures 7 are sequentially converted into luminance temperatures. In this way, all the bolometer structures 7 are scanned, and imaging data for one screen is obtained.

[0019] (Measurement Element) The infrared sensor 1 includes a first measurement element 9a provided in the first space 8a, a second measurement element 9b provided in the second space 8b, and a third measurement element 9c provided outside the second space 8b. The first measurement element 9a is an element used for measuring a first measurement value related to the first pressure P1, the second measurement element 9b is an element used for measuring a second measurement value related to the second pressure P2, and the third measurement element 9c is an element used for measuring a third measurement value related to the third pressure P3. The infrared sensor 1 has a monitoring unit 11 that acquires the first measurement value measured using the first measurement element 9a, the second measurement value measured using the second pressure measurement element 9b, and the third measurement value (or a reference measurement value to be described later) measured using the third measurement element 9c. For convenience, the monitoring unit 11 is illustrated outside the infrared sensor 1 in FIG. 1, but may be provided inside the infrared sensor 1. The function of the monitoring unit 11 will be described later. The monitoring unit 11 is composed of, for example, an arithmetic unit and a memory, and the arithmetic unit includes, for example, a resistance measurement circuit and a microprocessor, or a resistance measurement circuit and an operational amplifier.

[0020] The first measurement element 9a can be at least any one of the plurality of bolometer structures 7. That is, the first measurement element 9a is shared with at least any one of the plurality of bolometer structures 7. The first measurement element 9a may be shared with some of the plurality of bolometer structures 7. In the infrared sensor 1, the first measurement element 9a is used to measure a first measurement value related to pressure based on the same principle as a Pirani gauge or Pirani vacuum gauge. In a Pirani gauge, a heated metal wire is suspended in the measurement target space, and the electrical resistance of the metal wire is measured. When gas molecules exist in the measurement target space, the gas molecules collide with the metal wire, and the temperature of the metal wire decreases. The amount of decrease in the temperature of the metal wire depends on the amount of gas molecules, that is, the pressure of the measurement target space. Since the electrical resistance of a metal decreases as the temperature lowers, the pressure of the measurement target space can be measured indirectly by measuring the electrical resistance.

[0021] When an electric current is passed through the bolometer structure 7 used as the first measuring element 9a to supply power, the thermistor film inside the bolometer structure 7 generates heat according to the power value, causing the temperature of the bolometer structure 7 to rise compared to before power supply. When a predetermined value of power is supplied to the bolometer structure 7 for a predetermined time, the relationship between the number of gas molecules present in the space surrounding the bolometer structure 7 and the amount of temperature rise of the bolometer structure 7 is as follows: If the number of gas molecules present in the space surrounding the bolometer structure 7 is large, the amount of temperature rise of the bolometer structure 7 will be small. If the number of gas molecules present in the space surrounding the bolometer structure 7 is small, the amount of temperature rise of the bolometer structure 7 will be large. This is because when there are many gas molecules present in the space surrounding the bolometer structure 7, more of the energy of the power supplied to the bolometer structure 7 is distributed to the gas molecules. Thus, the amount of temperature change of the bolometer structure 7 used as the first measuring element 9a before and after supplying a predetermined value of power for a predetermined time depends on the ambient pressure around the bolometer structure 7. The temperature change of the bolometer structure 7 is detected as a change in the output of the bolometer structure 7. Therefore, the change in output ΔV1 of the bolometer structure 7 used as the first measuring element 9a, before and after applying a predetermined value of power for a predetermined time, depends on the ambient pressure (pressure P1) surrounding the bolometer structure 7.

[0022] Thus, as a first method, the infrared sensor 1 acquires the change in output value ΔV1 of the bolometer structure 7, which is used as the first measuring element 9a, before and after applying a predetermined amount of power for a predetermined time, as a first measured value. Furthermore, the infrared sensor 1 can estimate the first pressure P1 based on the change in output ΔV1 (first measured value) and the value of the power applied, and can indirectly measure the first pressure P1. For example, by keeping the value of the power applied to the bolometer structure 7, which is used as the first measuring element 9a, and the power application time always the same during measurement, the first pressure P1 can be estimated based on the change in output ΔV1 (first measured value) of the first measuring element 9a (bolometer structure 7), and the first pressure P1 can be indirectly measured. The time for which power is supplied to the bolometer structure 7 used as the first measuring element 9a during measurement may be a predetermined time sufficient for the temperature rise of the bolometer structure 7 to saturate, or it may be a predetermined time before the temperature rise of the bolometer structure 7 saturates.

[0023] Only one bolometer structure 7 is needed to be used as the first measuring element 9a, and its installation position is not particularly limited (the position of the first measuring element 9a shown in Figure 1(b) is merely an example). Thus, in the infrared sensor 1 using the bolometer structure 7, there is no need to provide a separate first measuring element 9a.

[0024] As a second method for estimating the first pressure P1, a third measuring element 9c, which is installed outside the first space 8a under a reference pressure (e.g., atmospheric pressure), may be used as a reference measuring element. The third measuring element 9c can also be configured using a bolometer structure 7, similar to the first measuring element 9c. The third measuring element 9c is also installed on the second substrate 3, but it may also be installed on the first substrate 2 or the second peripheral wall 4b. Since the third measuring element 9c is installed in the atmosphere, it may be covered with a cover as needed, provided that a large pressure difference with atmospheric pressure is not generated.

[0025] Current is passed through the bolometer structure 7 used as the first measuring element 9a and the bolometer structure 7 used as the reference measuring element (third measuring element 9c) to supply power. The thermistor film in these bolometer structures 7 generates heat according to the power value, and the temperature of the bolometer structure 7 rises compared to before power supply. After a predetermined value of power has been supplied to these bolometer structures 7 for a predetermined time, the relationship between the first pressure P1 and the temperatures of the first measuring element 9a and the reference measuring element (third measuring element 9c) is as follows: If the first pressure P1 is lower than the reference pressure (atmospheric pressure in this example), the temperature of the first measuring element 9a will be higher than the temperature of the reference measuring element (third measuring element 9c) according to the difference between the first pressure P1 and the reference pressure. If the first pressure P1 is higher than the reference pressure, the temperature of the first measuring element 9a will be lower than the temperature of the reference measuring element (third measuring element 9c) according to the difference between the first pressure P1 and the reference pressure. The temperature of the bolometer structure 7 is detected as the output value of the bolometer structure 7. Therefore, the difference V1-V3 or ratio V1 / V3 between the output value V1 of the first measuring element 9a and the output value V3 of the reference measuring element (third measuring element 9c) after the predetermined power has been applied for a predetermined time depends on the first pressure P1.

[0026] Thus, as a second method, the infrared sensor 1 applies predetermined power to the bolometer structure 7 used as the first measuring element 9a and the bolometer structure 7 used as the reference measuring element for a predetermined time, then acquires the output value V1 of the first measuring element 9a as the first measured value and the output value V3 of the reference measuring element as the reference measured value. Furthermore, the infrared sensor 1 can estimate the first pressure P1 based on the output value V1 (first measured value), the output value V3 (reference measured value), and the value of the applied power, and can indirectly measure the first pressure P1. For example, during measurement, the value of the power applied to the bolometer structure 7 used as the first measuring element 9a and the bolometer structure 7 used as the reference measuring element, and the power application time, can always be kept the same. This allows the first pressure P1 to be estimated based on the output value V1 (first measured value) and output value V3 (reference measured value) of the first measuring element 9a, and the first pressure P1 to be indirectly measured. The time for which power is supplied to the bolometer structure 7 used as the first measuring element 9a during measurement may be a predetermined time sufficient for the temperature rise of the bolometer structure 7 to saturate, or it may be a predetermined time before the temperature rise of the bolometer structure 7 saturates.

[0027] The second measuring element 9b can also use a configuration that utilizes the bolometer structure 7. The second measuring element 9b is provided on the second substrate 3. Since the bolometer structure 7 is formed in the wafer process, the bolometer structure 7 used as the second measuring element 9b can be formed simultaneously with the other bolometer structures 7. However, the installation position of the second measuring element 9b is not particularly limited and may be provided on the first substrate 2, the first peripheral wall 4a, or the second peripheral wall 4b, or it may be suspended within the second space 8b. Similar to the case of the first pressure P1 described above (similar to the first or second method), a second measurement value measured using the second measuring element 9b can be obtained, and the second pressure P2 can be estimated based on at least the second measurement value.

[0028] The second measuring element 9b also functions as a blind cell 12. In addition to the grid-like arrangement of bolometer structures 7 (active cells) described above, the infrared sensor 1 has a blind cell 12 for temperature correction of the output of the bolometer structures 7. The blind cell 12 has the same configuration as the active cell. The blind cell 12 receives radiation from surrounding structures, such as the first substrate 2 and the second substrate 3, similar to the active cell, but does not receive infrared radiation from the outside. For this reason, the blind cell 12 is used as a calibration cell to remove background noise generated by factors other than infrared radiation from the outside. Therefore, it is necessary that the blind cell 12 be configured so as not to receive infrared radiation from the outside. The portion of the second substrate 3 that forms the second space 8b does not have a light incident portion, so there is no need to provide a portion to shield from infrared radiation from the outside. Moreover, since the second measuring element 9b is shared with the blind cell 12, there is no need to provide a separate second measuring element 9b.

[0029] The second measuring element 9b can be mounted without thermal separation from the second substrate 3 (or the first substrate 2 if it is mounted on the first substrate 2). That is, the bolometer structure 7 constituting the blind cell 12 is mounted in contact with the surface of the second substrate 3. When the bolometer structure 7 constituting the blind cell 12 as the second measuring element 9b is mounted on the first substrate 2, the bolometer structure 7 constituting the blind cell 12 is mounted in contact with the surface of the first substrate 2. This is because, since there are no heat-generating elements such as the first electrical connection member 5 in the second space 8b, the bolometer structure in the second space 8b is less susceptible to thermal influence than the bolometer structure 7 in the first space 8a, and therefore does not need to be suspended in the second space 8b. However, considering the manufacturing process, it is also possible to configure it to be thermally separated from the second substrate 3, similar to the other bolometer structures 7.

[0030] The third pressure P3 can be estimated by obtaining a third measurement value using the third measuring element 9c, similar to the first method described above for the first pressure P1, and based on at least the third measurement value.

[0031] (Pressure monitoring method) Next, a method for monitoring the internal pressure of the infrared sensor 1 using the first to third measuring elements 9a to 9c and the monitoring unit 11 will be described. As mentioned above, the infrared sensor 1 is sometimes used as part of a vehicle's sensor system. Sensor systems related to vehicle safety functions must comply with ISO 26262, and in vision systems, ASIL (Automotive Safety Integrity Level) grade B is often required. ASIL grade B requires a self-diagnostic function, that is, the system to recognize that it has failed after it has failed. As the required reliability of the system increases, a failure prediction function may also be required. The infrared sensor 1 of this embodiment can meet the above requirements by the method described below.

[0032] Figure 3 conceptually shows the spatial divisions and arrangement of measuring elements of the infrared sensor 1. Figure 4(a) shows the relationship between time and the first to third pressures P1 to P3 when the infrared sensor 1 is functioning normally, and Figures 4(b) to 4(d) show the relationship between time and the first to third pressures P1 to P3 when the infrared sensor 1 is functioning abnormally. The term "abnormal" is a concept that includes both a state in which the infrared sensor 1 has lost its function (a state subject to the self-diagnosis function) and a state in which the possibility of loss of function has increased or signs of loss of function are observed (a state subject to the failure prediction function).

[0033] In the following description, the third pressure P3 is assumed to be atmospheric pressure. However, the third pressure P3 does not have to be atmospheric pressure as long as it is greater than the first pressure P1 and the second pressure P2 and does not fluctuate significantly. For example, depending on the environment in which the infrared sensor 1 is installed, the third pressure P3 may be a pressure different from atmospheric pressure. The monitoring unit 11 continuously or intermittently acquires (receives) first to third measurement values ​​related to the first to third pressures P1 to P3 from the first to third measuring elements 9a to 9c. The monitoring unit 11 outputs a predetermined signal indicating an abnormality based on at least the first measurement value. The predetermined signal indicating an abnormality is, for example, a signal indicating an abnormality related to at least one of the first pressure P1 and the pressure of the space outside the first space 8a. When the first to third measurement values ​​are acquired intermittently, the monitoring unit 11, for example, periodically energizes the first to third measuring elements 9a to 9c to acquire the first to third measurement values ​​and stores them. The monitoring unit 11 examines the trends of the first and second measurement values, and based on this trend, when it determines that the degree of increase of at least one of the first pressure P1 and the second pressure P2 exceeds a preset degree of increase, it outputs a predetermined signal indicating an abnormality. This will be explained in detail below.

[0034] Referring to Figure 4(a), when the infrared sensor 1 is operating normally, the first pressure P1 and the second pressure P2 are substantially equal and less than the third pressure P3. Since the third pressure P3 is atmospheric pressure, there is some fluctuation, but this fluctuation does not affect the pressure monitoring method of this embodiment. The monitoring unit 11 acquires the first to third measurement values ​​from the first to third measuring elements 9a to 9c, but since it determines that the first to third pressures P1 to P3 are within the normal range based on the first to third measurement values, it does not output any signals such as alarms.

[0035] Referring to Figure 4(b), the second pressure P2 increases while the first pressure P1 remains at a normal value (abnormal mode 1). This phenomenon indicates the possibility of a leak in the second peripheral wall 4b. The infrared sensor 1 can operate normally, but a leak in the first peripheral wall 4a may cause the infrared sensor 1 to lose its function. When the monitoring unit 11 determines, based on at least the first and second measured values, that the second pressure P2 has become substantially larger than the first pressure P1, it outputs a predetermined alarm signal indicating an abnormality in the second peripheral wall 4b. The alarm signal is sent, for example, to the control unit of the device into which the infrared sensor 1 is incorporated, and the user is notified by an appropriate method such as display on the device's display or by sound. Alternatively, the alarm signal can be stored as log information in the control unit of the device without notifying the user.

[0036] The fact that the second pressure P2 has substantially become greater than the first pressure P1 can be determined, for example, when using the first method described above, by using the difference ΔV1-ΔV2 or the ratio ΔV1 / ΔV2, where the first measured value is ΔV1 (the absolute value of the change in output of the first measuring element 9b) and the second measured value is ΔV2 (the absolute value of the change in output of the second measuring element 9b). It is preferable to output an alarm signal when the difference ΔV1-ΔV2 exceeds a predetermined value, or when the ratio ΔV1 / ΔV2 exceeds a predetermined value greater than 1 (e.g., 1.05, 1.1, etc.), taking into account the measurement errors of the first and second measured values ​​ΔV1 and ΔV2. Furthermore, for example, when using the second method described above, it can be determined that the second pressure P2 has substantially increased compared to the first pressure P1 by using the difference V1-V2 or the ratio V1 / V2, where V1 is the output value of the first measuring element 9a and V2 is the output value of the second measuring element 9b. If the outputs of the first measuring element 9a and the second measuring element 9b increase with increasing temperature, it is preferable to output an alarm signal when the difference V1-V2 exceeds a predetermined value, or when the ratio V1 / V2 exceeds a predetermined value greater than 1 (e.g., 1.05, 1.1, etc.). If the outputs of the first measuring element 9a and the second measuring element 9b decrease with increasing temperature, it is preferable to output an alarm signal when the difference V1-V2 falls below a predetermined value, or when the ratio ΔV1 / ΔV2 falls below a predetermined value less than 1 (e.g., 0.95, 0.9, etc.). The timing of outputting the alarm signal is not limited to just once; multiple alarm signals may be output depending on when it is determined that the difference P2-P1 or the ratio P2 / P1 has increased.

[0037] Alternatively, the monitoring unit 11 may output a predetermined alarm signal indicating an abnormality in the second peripheral wall 4b when it determines, based on at least the second and third measured values, that the second pressure P2 is approaching the third pressure P3. In this case, the monitoring unit 11 determines that the first pressure P1 is within the normal range based on the first measured value ΔV1 (in the case of the first method) or the first measured value V1 and the third measured value V3 (reference measured value V3) (in the case of the second method). The fact that the second pressure P2 is approaching the third pressure P3 can be determined, for example, when using the first method described above, by the behavior of the absolute value of the difference ΔV3-ΔV2 decreasing, or by the behavior of the ratio ΔV3 / ΔV2 approaching 1, where the second measured value is ΔV2 (absolute value of the output change amount of the second measuring element 9b) and the third measured value is ΔV3 (absolute value of the output change amount of the third measuring element 9c). Furthermore, for example, when using the second method described above, it can be determined that the second pressure P2 is approaching the third pressure P3 by observing that the absolute value of the difference V3-V2 decreases, or that the ratio V3 / V2 approaches 1, where V2 is the output value of the second measuring element 9b and V3 is the output value of the third measuring element 9c.

[0038] Furthermore, the monitoring unit 11 may output a predetermined alarm signal indicating an abnormality in the second peripheral wall 4b when it determines, based on at least the second and third measured values, that the second pressure P2 has become substantially equal to the third pressure P3. The fact that the second pressure P2 has become substantially equal to the third pressure P3 can be determined, for example, when using the first method described above, by the absolute value of the difference ΔV3-ΔV2 falling below a predetermined value, or by the absolute value of the difference between the ratio ΔV3 / ΔV2 and 1 falling below a predetermined value. Alternatively, for example, when using the second method described above, the fact that the second pressure P2 has become substantially equal to the third pressure P3 can be determined by the absolute value of the difference V3-V2 falling below a predetermined value, or by the absolute value of the difference between the ratio V3 / V2 and 1 falling below a predetermined value.

[0039] Referring to Figure 4(c), both the first pressure P1 and the second pressure P2 are increasing (abnormal mode 2). This phenomenon indicates the possibility of leakage in the first and second peripheral walls 4a and 4b. Because the first pressure P1 is increasing, it is highly likely that the infrared sensor 1 cannot operate normally. The monitoring unit 11 outputs a predetermined alarm signal indicating an abnormality when it determines, based on at least the first measured value, that the pressure P1 has become equal to or exceeded a predetermined value. Whether the pressure P1 has become equal to or exceeded a predetermined value can be determined, for example, from the first measured value ΔV1 (the change in output of the first measuring element 9a) when using the first method described above. Alternatively, for example, when using the second method described above, whether the pressure P1 has become equal to or exceeded a predetermined value can be determined from the difference V1-V3 or ratio V1 / V3 between the first measured value V1 (the output value of the first measuring element 9a) and the reference measured value V3 (the output value of the reference measuring element (third measuring element 9c)). In abnormal mode 2, both the first pressure P1 and the second pressure P2 increase. Therefore, the monitoring unit 11 may output a predetermined alarm signal indicating an abnormality in the first and second peripheral walls 4a and 4b when it determines, based on at least the first and second measured values, that both the first pressure P1 and the second pressure P2 have increased. The fact that both the first pressure P1 and the second pressure P2 have increased can be determined, for example, from the time variation of the first measured value ΔV1 and the time variation of the second measured value ΔV2 when using the first method described above. Furthermore, for example, when using the second method described above, an increase in both the first pressure P1 and the second pressure P2 can be determined from the difference V1-V3 or ratio V1 / V3 between the first measured value V1 (output value of the first measuring element 9a) and the reference measured value V3 (output value of the reference measuring element (third measuring element 9c)), and from the difference V2-V3 or ratio V2 / V3 between the second measured value V2 (output value of the second measuring element 9b) and the reference measured value V3.

[0040] Furthermore, the monitoring unit 11 may output a predetermined alarm signal indicating an abnormality in the first and second peripheral walls 4a, 4b when it determines, based on at least the first, second, and third measured values, that the first pressure P1 and the second pressure P2 have become substantially equal to the third pressure P3. The fact that the first to third pressures P1 to P3 have become substantially equal can be determined, for example, when using the first method described above, by the absolute value of the difference ΔV1-ΔV3 or the absolute value of the difference between the ratio ΔV1 / ΔV3 and 1 for the first measured value ΔV1, the second measured value ΔV2, and the third measured value ΔV3 falling below a predetermined value, and by the absolute value of the difference ΔV2-ΔV3 or the absolute value of the difference between the ratio ΔV2 / ΔV3 and 1 falling below a predetermined value. Furthermore, for example, when using the second method described above, it can be determined that the first to third pressures P1 to P3 have become substantially equal by the absolute value of the difference V1-V3 or the absolute value of the difference between the ratio V1 / V3 and 1 falling below a predetermined value, and by the absolute value of the difference V2-V3 or the absolute value of the difference between the ratio V2 / V3 and 1 falling below a predetermined value.

[0041] Referring to Figure 4(d), the first pressure P1 increases while the second pressure P2 remains at a normal value (abnormal mode 3). This phenomenon indicates the possibility of an abnormality in the first space 8a. While it is unlikely that a leak has occurred in the first or second peripheral walls 4a,4b, it would affect the operation of the infrared sensor 1. The first space 8a may be provided with a getter film or the like to adsorb residual gas and suppress the decrease in the vacuum level of the first space 8a. If gas molecules are released from such a film, the first pressure P1 may increase. The monitoring unit 11 outputs a predetermined alarm signal indicating an abnormality in the first space 8a when it determines, based on at least the first and second measured values, that the first pressure P1 has become substantially greater than the second pressure P2. The method for determining that the first pressure P1 has become substantially greater than the second pressure P2 is the same as the method for determining abnormal mode 1, except that the first and second measured values ​​are swapped. Furthermore, similar to abnormal mode 2, the monitoring unit 11 may output a predetermined alarm signal indicating an abnormality when it determines, based on at least the first measured value, that the pressure P1 has become equal to or exceeded a predetermined value.

[0042] (Manufacturing method) Next, an example of a method for manufacturing the infrared sensor 1 of the present invention will be described. Since the infrared sensor 1 is manufactured by a wafer process, in the following description, the first substrate 2 and the second substrate 3 refer to wafers. Figure 5 shows a schematic flow of the method for manufacturing the infrared sensor 1. The infrared sensor 1 of the present invention is manufactured by step 1, in which elements such as ROIC are formed on the first substrate 2; step 2, in which a bolometer structure 7 and the like are formed on the second substrate 3; and step 3, in which the first substrate 2 and the second substrate 3 are bonded together. Since step 3 is carried out in a vacuum atmosphere, the first pressure P1 and the second pressure P2 are approximately the same. The first electrical connection member 5 and the first and second peripheral walls 4a and 4b are formed on the second substrate 3 in step 2, and these members 5, 4a and 4b are bonded to the first substrate 2 in step 3.

[0043] In step 2, the first electrical connection member 5 and the first and second peripheral walls 4a and 4b are formed simultaneously by plating. Specifically, a cylindrical hole is made in the resist for forming the first electrical connection member 5, and an annular-shaped hole is made in the resist for forming the first and second peripheral walls 4a and 4b, and these members 5, 4a and 4b are formed simultaneously in these holes by plating. If the thicknesses t1 to t3 (see Figure 1(c)) of the first electrical connection member 5 and the first and second peripheral walls 4a and 4b are made to be approximately the same, the heights (Z-direction dimension) of the first electrical connection member 5 and the first and second peripheral walls 4a and 4b after plating are more likely to be aligned.

[0044] Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, the third measuring element 9c can be omitted. Since the third pressure P3 is atmospheric pressure, the pressure or voltage equivalent to, for example, standard atmospheric pressure (approximately 101.3 kPa) may be compared with the first pressure P1 or the second pressure P2. Also, the number of peripheral walls 4a and 4b is not limited to two, and three or more peripheral walls can be provided concentrically. In this case, the second measuring element 9b can be placed in the space between any pair of adjacent peripheral walls. Providing three or more peripheral walls is preferable because it increases the redundancy of the peripheral walls and also ensures the bonding strength between the first substrate 2 and the third substrate 2. [Explanation of symbols]

[0045] 1. Infrared sensor (electromagnetic wave sensor) 2. First substrate 3. Second substrate 4a,4b First and second surrounding walls 5. First electrical connection member 7. Bolometer Structure 8a,8b First and second spaces 9a~9c First to third measuring elements 11 Monitoring Department 12 Blind Cells

Claims

1. The first substrate and A second substrate facing the first substrate and transmitting infrared light in at least a portion thereof, A first peripheral wall located between the first substrate and the second substrate, which together with the first and second substrates form a first space, A second peripheral wall is located between the first substrate and the second substrate, surrounding the first peripheral wall, and together with the first and second substrates and the first peripheral wall, forming a second space. A plurality of bolometer structures provided in the first space, A first measuring element provided in the first space and used for measuring a first measurement value related to the pressure P1 of the first space, A second measuring element provided in the second space and used to measure a second measurement value related to the pressure P2 of the second space, The monitoring department, It has, The monitoring unit acquires a first measurement value measured using the first measuring element and a second measurement value measured using the second measuring element, and outputs a predetermined signal indicating an abnormality based on at least the first measurement value and the second measurement value, as an electromagnetic wave sensor.

2. The electromagnetic wave sensor according to claim 1, wherein the first measurement value is the amount of change in the output value of the first measuring element before and after applying a predetermined power to the first measuring element for a predetermined time.

3. It has a reference measuring element provided under a reference pressure outside the first space, The monitoring unit acquires the output value of the reference measuring element as the reference measurement value after applying a predetermined power to the reference measuring element for a predetermined time. The first measurement value is the output value of the first measuring element after a predetermined power has been applied to the first measuring element for a predetermined time. The electromagnetic wave sensor according to claim 1, wherein the monitoring unit outputs a predetermined signal based on at least the first measurement value and the reference measurement value.

4. The electromagnetic wave sensor according to claim 1, wherein the first measuring element is at least one of the plurality of bolometer structures.

5. The electromagnetic wave sensor according to claim 1, wherein the monitoring unit outputs a predetermined signal when it determines, based on at least the first measured value, that the pressure P1 has become equal to or exceeded a predetermined value.

6. The monitoring unit periodically energizes the first measuring element to periodically acquire the first measurement value. The first measurement value is retained, and the trend of the first measurement value is examined. The electromagnetic wave sensor according to claim 1, which outputs a predetermined signal when it is determined that the degree of increase of the pressure P1 exceeds a predetermined degree of increase based on the aforementioned trend.

7. The electromagnetic wave sensor according to claim 1, wherein the second measuring element also serves as a blind cell.

8. The electromagnetic wave sensor according to claim 7, wherein the second measuring element is mounted without thermal separation from the first substrate or the second substrate.

9. The electromagnetic wave sensor according to claim 1, wherein the monitoring unit outputs the predetermined signal when it determines, based on at least the first measurement and the second measurement, that the pressure P2 has become substantially greater than the pressure P1.

10. The electromagnetic wave sensor according to claim 1, wherein the monitoring unit outputs the predetermined signal when it determines, based on at least the first measurement and the second measurement, that the pressure P1 has become substantially greater than the pressure P2.

11. The electromagnetic wave sensor according to claim 1, wherein the monitoring unit outputs a predetermined signal when it determines that both pressure P1 and pressure P2 have increased based on at least the first and second measured values.

12. It has a third measuring element provided outside the second space and used to measure a third measurement value related to the pressure P3 outside the second space, The electromagnetic wave sensor according to claim 1, wherein the monitoring unit acquires the third measurement value measured using the third measuring element and outputs the predetermined signal based on at least the first measurement value, the second measurement value and the third measurement value.

13. The electromagnetic wave sensor according to claim 12, wherein the monitoring unit outputs the predetermined signal when it determines, based on at least the second measurement value and the third measurement value, that the pressure P2 is approaching the pressure P3.

14. The electromagnetic wave sensor according to claim 12, wherein the monitoring unit outputs the predetermined signal when it determines, based on at least the second measurement and the third measurement, that the pressure P2 has become substantially equal to the pressure P3.

15. The electromagnetic wave sensor according to claim 12, wherein the monitoring unit outputs the predetermined signal when it determines that the pressures P1 and P2 have become substantially equal to the pressure P3 based on at least the first measurement, the second measurement, and the third measurement.

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