JP2010216819A - Non-cooled infrared image sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a manufacturing process from becoming complicated as much as possible. <P>SOLUTION: A plurality of pixel groups are arranged in a matrix shape on a semiconductor substrate, and each of the pixel groups has the same number of pixels arranged in a matrix shape, respectively. Each of the pixels includes: an infrared absorbing film for absorbing incident infrared radiation, and converting the absorbed infrared radiation to heat; and a thermoelectric transducer which is electrically insulated from the infrared absorbing film, and generates an electric signal by detecting the heat from the infrared absorbing film. A non-cooled infrared image sensor includes: the pixel groups; a row selection line group provided between the pixel groups adjacent in a column direction, and having the same number of row selection lines as the number of pixels arranged in the same column direction in each of the pixel groups; and a read signal line group provided between the pixel groups adjacent in a row direction, and having the same number of read signal lines as the number of pixels arranged in the same row direction in each of the pixel groups. The intersection of the row selection line group and the read signal line group is supported by a support of the semiconductor substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an uncooled infrared image sensor.

  In general, an uncooled infrared image sensor is provided with a plurality of row selection lines formed in a row direction and a plurality of readout signal lines formed in a column direction on a silicon substrate. A pixel portion having at least one diode is provided corresponding to a region where the readout signal line and the readout signal line intersect. Further, the uncooled infrared image sensor is provided with an infrared absorption part that absorbs infrared rays and converts the infrared rays into heat, and a change in the heat converted by the infrared absorption part is detected by the diode. In this uncooled infrared image sensor, the cavity is formed in the substrate region below the pixel portion, so that the diode is not affected by the heat from the substrate and the sensitivity is increased. Note that the pixel portion has a configuration in which one end is connected to the substrate and the other end is supported above the cavity portion by a support leg connected to the pixel portion.

  In order to improve the sensitivity, the area occupied by the pixel portion, that is, the diode is increased, and the direction in which the wiring extends in the substrate region on which the row selection line and the readout signal line are placed is substantially orthogonal The width is set to be at least one of making the width as narrow as possible. For this reason, when the cavity is formed, the substrate is anisotropically formed by wet etching using an alkaline solution in order to prevent the substrate region on which the row selection line and the readout signal line are placed further narrowing. (For example, refer patent document 1).

In addition, when wet etching is used, after forming the cavity, the cavity needs to be washed with a chemical solution or the like and dried (see, for example, Patent Document 2). In this drying process, one of the pixel portion and the support leg may stick to the other. In order to avoid this, it is desirable to form the cavity by etching the silicon substrate by isotropic dry etching using XeF ₂ gas or the like. Therefore, in Patent Document 2, in order to prevent the substrate region on which the row selection line and the readout signal line are placed further narrowing, an etching stop layer is formed around the cavity, or an etching hole is formed. It is provided near the center of the cavity.

JP 2001-267542 A Japanese Patent No. 3040356

  As described above, when wet etching is used to form the cavity, it is necessary to avoid that one of the pixel portion and the support leg sticks to the other, and the manufacturing process becomes complicated. Further, when isotropic dry etching is used, it is necessary to form an etching stop layer or etching hole around the cavity, and the manufacturing process becomes complicated.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an uncooled infrared image sensor capable of preventing the manufacturing process from becoming complicated as much as possible.

  An uncooled infrared image sensor according to a first aspect of the present invention includes a semiconductor substrate having a plurality of support portions provided on a surface thereof, and a plurality of pixel groups arranged in a matrix on the semiconductor substrate. Each group has the same number of pixels arranged in a matrix, and each pixel absorbs incident infrared rays and converts the absorbed infrared rays into heat, and the infrared absorption layer electrically A plurality of pixel groups having a thermoelectric conversion element that generates an electrical signal by detecting heat from the infrared absorption film, and is provided between the pixel groups adjacent to each other in the column direction. Are provided between the row selection line group having the same number of row selection lines as the number of pixels arranged in the same column direction and the pixel group adjacent in the row direction, and arranged in the same row direction in each pixel group. A readout signal line group having the same number of readout signal lines as the number of pixels formed, and a pixel provided corresponding to each pixel, one end of which is electrically connected to the corresponding pixel and the other end includes the corresponding pixel A first wiring electrically connected to one row selection line in one of the two row selection line groups adjacent to the group, and a first insulating film covering the first wiring; One supporting leg and one readout signal of two readout signal line groups provided corresponding to each pixel, one end electrically connected to the corresponding pixel and the other end adjacent to the pixel group including the corresponding pixel A second support leg having a second wiring electrically connected to one readout signal line in the line group and a second insulating film covering the second wiring, and corresponding to each pixel group A cavity is formed in the surface portion of the semiconductor substrate below each pixel group, and each pixel corresponds to The first and second support legs are supported above the corresponding cavity, and the intersection of the row selection line group and the read signal line group is supported by the support part of the semiconductor substrate. It is characterized by.

  According to the present invention, it is possible to prevent the manufacturing process from becoming complicated as much as possible.

The top view of the uncooled infrared image sensor by 1st Embodiment. Sectional drawing of the uncooled infrared image sensor of 1st Embodiment. Sectional drawing of the uncooled infrared image sensor of 1st Embodiment. Sectional drawing of the uncooled infrared image sensor of 1st Embodiment. Sectional drawing of the uncooled infrared image sensor of 1st Embodiment. Sectional drawing of the uncooled infrared image sensor of 1st Embodiment. Sectional drawing of the uncooled infrared image sensor of 1st Embodiment. The top view of the pixel group of the uncooled infrared image sensor by 1st Embodiment. The top view of the pixel group of the non-cooling infrared image sensor by a comparative example. Sectional drawing of the manufacturing process of the uncooled infrared image sensor of 1st Embodiment. Sectional drawing of the manufacturing process of the uncooled infrared image sensor of 1st Embodiment. Sectional drawing of the manufacturing process of the uncooled infrared image sensor of 1st Embodiment. Sectional drawing of the manufacturing process of the uncooled infrared image sensor of 1st Embodiment. The top view of the non-cooling infrared image sensor by 2nd Embodiment. The top view of the non-cooling infrared image sensor by 3rd Embodiment. The top view of the non-cooling infrared image sensor by 4th Embodiment. The top view of the non-cooling infrared image sensor by 5th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
A plan view of an uncooled infrared image sensor according to the first embodiment of the present invention is shown in FIG. In FIG. 1, an infrared absorption film described later is not shown. Also, cross sections cut along cutting lines AA ′, BB ′, CC ′, DD ′, and EE ′ in FIG. 1 are shown in FIGS. 2, 3, 4, 5, respectively. And shown in FIG. In FIGS. 2 to 6, the cross section cut along each cutting line is enlarged and displayed. Moreover, the cross section cut | disconnected by the cutting line FF 'in FIG. 2 is shown in FIG.

  The uncooled infrared image sensor of this embodiment has a plurality of pixel groups 4 arranged in a matrix on a substrate (for example, a silicon substrate) 2. Each pixel group 4 has a plurality of pixels 4a, 4b, 4c, and 4d (in this embodiment, a total of four pixels of 2 rows × 2 columns) arranged in a matrix. A row selection line group 6 is provided between adjacent pixel groups 4 in the column direction. Each row selection line group 6 has row selection lines 6a and 6b for selecting pixels adjacent in the column direction among the pixel groups adjacent in the column direction. For example, the row selection line 6a is a row selection line for selecting the pixels 4a and 4b of the pixel group 4 shown in the center of FIG. 1, and the row selection line 6b is adjacent above the pixel group 4 shown in the center of FIG. This is a row selection line for selecting the pixels 4c and 4d of the pixel group 4 to be selected. Row selection lines 6a and 6b included in the same row selection line group are arranged side by side in the row direction.

  A readout signal line group 8 is provided between the pixel groups 4 adjacent in the row direction. Each readout signal line group 8 includes readout signal lines 8a and 8b for reading out signals from pixels adjacent in the row direction in the pixel groups adjacent in the row direction. For example, the readout signal line 8a is a readout signal line for reading out signals from the pixels 4a and 4c of the pixel group 4 shown in the center of FIG. 1, and the readout signal 8b is on the left side of the pixel group 4 shown in the center of FIG. Are read signal lines for reading signals from the pixels 4b and 4d of the adjacent pixel group 4. Read signal lines 8a and 8b included in the same read signal line group are arranged side by side in the column direction.

  Further, a cavity 3 is provided in the surface region of the substrate 2 corresponding to each pixel group 4 (see FIG. 2). Further, as shown in FIG. 1, corresponding to each pixel in each pixel group 4, for example, the pixel 4a, one end is connected to the pixel 4a and the other end is connected to the corresponding row selection line 6a. And a support leg 10b having one end connected to the pixel 4a and the other end connected to the corresponding readout signal line 8a. These support legs 10a and 10b have a planar shape formed in a ninety-nine fold or meander shape. Each pixel in each pixel group 4, for example, the pixel 4a, is configured to be supported by the corresponding support legs 10a and 10b above the corresponding cavity 3.

  As shown in FIG. 2, each pixel has an insulating film 12a, a thermal diode (thermoelectric conversion element) 14 formed on the insulating film 12a, and an infrared absorptivity formed so as to cover the thermal diode 14. A high insulating film 16a and an infrared absorbing film 18 formed on the insulating film 16a and absorbing incident infrared rays at a higher rate and converting them into heat are provided. The infrared absorption film 18 is formed so as to cover not only the corresponding pixels but also the support legs 10a, 10b, the row selection lines, and the readout signal lines provided correspondingly.

  As shown in FIG. 2, the support leg 10a includes an insulating film 12b, a wiring 15a formed on the insulating film 12b, and an insulating film 16b formed so as to cover the wiring 15a. . Similarly, the support leg 10b includes an insulating film 12c, a wiring 15b formed on the insulating film 12c, and an insulating film 16c formed so as to cover the wiring 15b. One end of the wiring 15a of the support leg 10a is connected to one end of the thermal diode of the corresponding pixel, and the other end is electrically connected to the corresponding row selection line. On the other hand, the wiring 15b of the support leg 10b has one end connected to the other end of the thermal diode of the corresponding pixel and the other end electrically connected to the corresponding readout signal line.

  Similarly, the row selection lines 6a and 6b of the row selection line group 6 are provided on the insulating film 12d and covered with the insulating film 16d (see FIG. 4). The read signal lines 8a and 8b of the read signal line group 8 are provided on the insulating film 12e and covered with the insulating film 16e.

In the present embodiment, the row selection line group 6 is provided above the read signal group 8. The row selection line group 6 and the readout signal line group 8 are supported by the support portion 2a of the substrate 2 at least at the intersection between the row selection line group 6 and the readout signal line group 8 (FIG. 2, see FIG. In the present embodiment, the support portion 2a is also provided immediately below the row selection line group 6 (see FIGS. 5, 6, and 7). However, the read signal line group 8 other than the intersecting portion is used. It is not provided immediately below (see FIG. 3). That is, the cavities 3 corresponding to each of the adjacent pixel groups 4 arranged in the column direction are blocked by the support portions 2a also provided immediately below the row selection line group 6, but are not connected, but are arranged in the row direction. The hollow portions 3 corresponding to the adjacent pixel groups 4 are connected to each other. This is because in this embodiment, the row selection line group 6 is wider than the readout signal line group 8 because the row selection line is wider than the readout signal line. As a result, when isotropic etching is performed using a gas (for example, XeF ₂ gas) as an etchant for forming the cavity 3, the substrate region immediately below the read signal line group 8 is directly below the row selection line 6. This is because the etching is performed earlier than the substrate region. Since gaps are provided between the adjacent infrared absorption films 18, between the infrared absorption film 18 and the support legs 10a and 10b, and between the support legs corresponding to the pixels, the etchant passes through these gaps. As a result of the gas flowing on the surface of the substrate being etched, the cavity 3 is formed. As can be seen from this description, when forming the cavity 3, it becomes possible to perform isotropic etching using a gas as an etchant without forming an etching stopper around the cavity 3. It is possible to prevent complications as much as possible.

  When such isotropic etching is performed, a support for supporting the row selection line group 6 and the readout signal line group 8 from the substrate 2 side at least at the intersection of the row selection line group 6 and the readout signal line group 8. In order for the portion 2a to exist, as shown in FIG. 1, the diameter d1 of the inscribed circle 20 in the plane of the intersecting portion is equal to the diameter d2 of the inscribed circle 22 in the plane of each pixel of each pixel group 4. It is necessary to be larger than.

  Next, the operation of the uncooled infrared image sensor of this embodiment will be described. When infrared rays from the outside are irradiated onto the infrared absorption film 18, the infrared rays are converted into heat by the infrared absorption film 18. The converted heat is transmitted to the thermal diode 14 through the insulating film 16a, and is converted into an electric signal by the thermal diode 14. That is, as the resistance of the thermal diode 14 changes in accordance with the temperature change of the thermal diode 14, the current flowing through the thermal diode 14 or the voltage between the terminals of the thermal diode 14 changes, and this change is detected through the readout signal line. .

Further, as shown in FIG. 8, in the uncooled infrared image sensor of this embodiment, the size in the extending direction (row direction) of the row selection line of each pixel of each pixel group 4 is X1, and each pixel is supported. The size in the row direction of the support leg 10a is Y1, the size in the row direction of the support leg 10b is Y2, the size (width) in the row direction of the read signal lines 8a and 8b is a, and one read signal line (for example, a read signal) The size in the row direction between the line 8a) and the end face of the insulating film 16e covering the signal line is b, and the size in the row direction between the two signal lines 8a and 8b in the same read signal line group 6 When (interval) is c, the size in the row direction between adjacent support legs 10a in the same pixel group 4 is e, and the pitch in the row direction of the pixel group 4 is 2P, the following equation (1) 2P = 2a + 2b + c + 2Y1 + 2Y2 + e + 2X1 (1)
Meet.

On the other hand, as a comparative example of this embodiment, as shown in FIG. 9, one row selection line 6a is provided in the row direction between adjacent pixels, and one readout signal line is provided in the column direction between adjacent pixels. Consider an uncooled infrared image sensor provided with 8a. In this comparative example, a set of 4 pixels in 2 rows and 2 columns is considered to correspond to the pixel group of the present embodiment, and the pitch in the row direction of a pixel group consisting of 4 pixels in 2 rows and 2 columns is set. 2P, the size of the row selection line of each pixel in the extending direction (row direction) is X2, the size of the support leg 10a supporting each pixel in the row direction is Y1, and the size of the support leg 10b in the row direction is Y2. The size (width) in the row direction of the signal line 8a is a, the size in the row direction between the read signal line 8a and the end face of the insulating film 16e covering the signal line is b, and the adjacent in the same pixel group. Assuming that the size in the row direction between the supporting legs 10a is e, the following equation (2) 2P = 2a + 4b + 2Y1 + 2Y2 + 2e + 2X1 (2)
Meet.

From the above formulas (1) and (2), 2 (X1-X2) = 2b + ec (3)
Is obtained. As can be seen from this equation (3), the following condition 2b + e−c> 0
That is,
2b + e> c (4)
If you meet
X1> X2
It becomes. This means that in the present embodiment and the comparative example, when the pixel groups have the same pitch, each pixel in the present embodiment is more than the pixel in the comparative example if the condition of the expression (4) is satisfied. That means you can make it bigger. That is, if the condition of the expression (4) is satisfied, the area of the pixel can be increased, so the number of thermal diodes in each pixel can be increased, and the sensitivity of the image sensor can be increased. . This effect is obtained by arranging a plurality of row selection lines in parallel to form one row selection line group, and arranging a plurality of read signal lines in parallel as in this embodiment. It is obtained by setting it as the structure.

  Note that the interval between adjacent pixels in the same pixel group in the column direction, the interval between the pixel and the support leg, the interval between the pixel and the row selection line group, the interval between the support leg and the readout signal line group, and the same row The larger the gap between the row selection lines in the selection line group, the smaller the heat transfer and interference with each other, but the lower the integration density, the lower the sensitivity. On the other hand, if the interval is too small, it is difficult to manufacture. For this reason, the interval is preferably 0.2 μm or more and 2 μm or less.

  In addition, the insulating film covering the row selection line is increased in insulation, stability in the manufacturing stage, and mechanical stability as the width is increased. However, since the integration density is decreased, the sensitivity is decreased. On the other hand, if the width of the insulating film is too small, it is difficult to manufacture. Therefore, the width of the insulating film is desirably 0.3 μm or more and 3 μm or less.

  In this embodiment, each row selection line group 6 is provided with two row selection lines 6a and 6b, and each readout signal line group 8 is provided with two readout signal lines 8a and 8b. However, the number of row selection lines or readout signal lines corresponding to the number of pixels in each pixel group can be used.

  Next, a method for manufacturing the uncooled infrared image sensor according to the present embodiment will be described with reference to FIGS. 10 to 13 are cross sections cut along a cutting line A-A 'in FIG.

  First, as shown in FIG. 10, the insulating film 12 is formed on the silicon substrate 2, and the first insulating film 16 having good thermal conductivity is formed on the insulating film 12. On the first insulating film 16, a thermal diode 14 constituting a pixel is formed, and readout signal lines 8a and 8b are formed. Thereafter, a second insulating film 16 having a good thermal conductivity is formed so as to cover the thermal diode 14 and the read signal lines 8a and 8b, and row selection lines 6a and 6b are formed on the second insulating film 16. . Thereafter, a third insulating film 16 having good thermal conductivity is formed so as to cover these row selection lines 6a and 6b. In order to simplify the description, the first to third insulating films are denoted by reference numeral 16. Subsequently, a plurality of openings reaching the upper surface of the substrate 2 from the upper surface of the insulating film 16 are formed. By forming the opening, the pixel, the support leg, the row selection line group, and the readout signal line group are patterned into respective shapes. Thereafter, a sacrificial layer 17 is formed on the insulating film 16 so as to fill these openings. Then, after patterning the sacrificial layer 17, an infrared absorption film 18 is formed on the region of the insulating film 16 that becomes each pixel.

Next, as shown in FIG. 11, the sacrificial layer 17 is removed by wet etching. As a result, an opening 30 leading to the surface of the substrate 2 exists at the trace where the sacrificial layer 17 is removed. Subsequently, as shown in FIG. 12, isotropic etching using a gas (for example, XeF ₂ gas) as an etchant is performed through the opening 30 to etch from the surface of the substrate 2 exposed at the bottom of the opening 30. The formation of the cavity 3 is started on the surface of the substrate 2. Furthermore, the etching of the substrate 2 proceeds by performing isotropic etching using the above gas. Then, by completing this etching, the cavity 3 is formed in the substrate region immediately below each pixel group 4.

  As described above, according to this embodiment, it is possible to prevent the manufacturing process from becoming complicated as much as possible. In addition, a plurality of row selection lines are arranged in parallel to form one row selection line group, and a plurality of readout signal lines are arranged in parallel to form one readout signal line group. As a result, the number of thermal diodes in each pixel can be increased, and the sensitivity of the image sensor can be increased.

(Second Embodiment)
Next, the top view of the uncooled infrared image sensor by 2nd Embodiment of this invention is shown in FIG. The uncooled infrared image sensor of the present embodiment is a support leg 10a provided corresponding to each pixel in the uncooled infrared image sensor of the first embodiment shown in FIG. 1, and supporting the corresponding pixel on the cavity, The configuration is such that the shape of 10b is changed from a spiral ninety-nine fold or meander shape to a spiral shape around the corresponding pixel.

  In this embodiment, as in the first embodiment, at least the row selection line group is used in order to perform isotropic etching without forming an etching stop layer around the cavity. 6 and the readout signal line group 8 need to have a support portion 2a that supports the row selection line group 6 and the readout signal line group 8 from the substrate 2 side. For this purpose, as in the first embodiment, the diameter of the inscribed circle in the plane of the intersection is required to be larger than the diameter of the inscribed circle in the plane of each pixel of each pixel group. .

  Similarly to the first embodiment, the uncooled infrared image sensor of this embodiment can prevent the manufacturing process from becoming complicated as much as possible. In addition, a plurality of row selection lines are arranged in parallel to form one row selection line group, and a plurality of readout signal lines are arranged in parallel to form one readout signal line group. As a result, the number of thermal diodes in each pixel can be increased, and the sensitivity of the image sensor can be increased.

(Third embodiment)
Next, FIG. 15 shows a plan view of an uncooled infrared image sensor according to the third embodiment of the present invention. The uncooled infrared image sensor of the present embodiment is a support leg 10a provided corresponding to each pixel in the uncooled infrared image sensor of the second embodiment shown in FIG. 14, and supporting the corresponding pixel on the cavity. The shape of 10b is changed to a spiral shape different from that of the second embodiment. In the third embodiment, unlike the second embodiment, out of the pixels 4a, 4b, 4c, and 4d of the same pixel group 4, the pixels 4a and 4b are arranged on the pixel group in FIG. 4 are respectively connected to the row selection lines 6a and 6b of the row selection line group 6 located on the lower side, and the pixels 4c and 4d are selected by the row selection line group 6 located on the upper side of the pixel group 4 in FIG. The wires 6b and 6a are connected to the support legs 10a, respectively. Further, unlike the second embodiment, among the pixels 4a, 4b, 4c, and 4d of the same pixel group 4, the pixels 4a and 4c are positioned on the right side of the pixel group 4 on FIG. 15 by the respective support legs 10b. The pixels 4b and 4d are respectively connected to the readout signal lines 8a and 8b of the readout signal line group 8, and the pixels 4b and 4d are supported by the row selection lines 8b and 8a of the readout signal line group 8 located on the left side of the pixel group 4 in FIG. 10b, respectively. That is, in the present embodiment, each pixel in each pixel group 4 is connected to a different row selection line and is connected to a different readout signal line.

  In this embodiment, as in the first embodiment, at least the row selection line group is used in order to perform isotropic etching without forming an etching stop layer around the cavity. 6 and the readout signal line group 8 need to have a support portion 2a that supports the row selection line group 6 and the readout signal line group 8 from the substrate 2 side. For this purpose, as in the first embodiment, the diameter of the inscribed circle in the plane of the intersection is required to be larger than the diameter of the inscribed circle in the plane of each pixel of each pixel group. .

  Similarly to the second embodiment, the uncooled infrared image sensor of this embodiment can prevent the manufacturing process from becoming complicated as much as possible. In addition, a plurality of row selection lines are arranged in parallel to form one row selection line group, and a plurality of readout signal lines are arranged in parallel to form one readout signal line group. As a result, the number of thermal diodes in each pixel can be increased, and the sensitivity of the image sensor can be increased.

(Fourth embodiment)
Next, the top view of the uncooled infrared image sensor by 4th Embodiment of this invention is shown in FIG. The uncooled infrared image sensor of the present embodiment is the same as the uncooled infrared image sensor of the first embodiment shown in FIG. 1, but each pixel group 4 composed of a total of four pixels of 2 rows × 2 columns is arranged in the column direction. The read signal line group having two read signal lines provided between the pixel groups 4 adjacent to each other in the row direction is replaced with the pixel group 4 including the two pixels 4 a and 4 b in total of 2 rows × 1 column. 6 is replaced with a read signal line group composed of one read signal line. The row selection line group 6 has the same configuration as the row selection line group 6 in the first embodiment.

  In this embodiment, as in the first embodiment, at least the row selection line group is used in order to perform isotropic etching without forming an etching stop layer around the cavity. 6 and the readout signal line group 8 need to have a support portion 2a that supports the row selection line group 6 and the readout signal line group 8 from the substrate 2 side. For this purpose, as in the first embodiment, the diameter of the inscribed circle in the plane of the intersection is required to be larger than the diameter of the inscribed circle in the plane of each pixel of each pixel group. .

  Similarly to the first embodiment, the uncooled infrared image sensor of this embodiment can prevent the manufacturing process from becoming complicated as much as possible. In addition, since a plurality of row selection lines are arranged in parallel to form one row selection line group, the area of the pixel can be increased, and the number of thermal diodes in each pixel is increased. Therefore, the sensitivity of the image sensor can be increased.

  As a modification of the present embodiment, each pixel group is configured to include a total of two pixels of 1 row × 2 columns, each row selection line group is configured from one row selection line, and each readout signal The line group is composed of two readout signal lines, and the two pixels in each pixel group are electrically connected to the same row selection line and are electrically connected to different readout signal lines. It may be.

(Fifth embodiment)
Next, the top view of the uncooled infrared image sensor by 5th Embodiment of this invention is shown in FIG. The uncooled infrared image sensor of this embodiment has a configuration in which the size of the intersection between the row selection line group 6 and the readout signal line group 8 is increased in the uncooled infrared image sensor of the first embodiment shown in FIG. ing. This can be achieved by increasing the width of the insulating film covering the row selection line group 6 at the intersection (the size in the direction substantially perpendicular to the direction in which the row selection lines extend).

  In this embodiment, as in the first embodiment, at least the row selection line group is used in order to perform isotropic etching without forming an etching stop layer around the cavity. 6 and the readout signal line group 8 need to have a support portion 2a that supports the row selection line group 6 and the readout signal line group 8 from the substrate 2 side. For this purpose, as in the first embodiment, the diameter of the inscribed circle in the plane of the intersection is required to be larger than the diameter of the inscribed circle in the plane of each pixel of each pixel group. .

  Similarly to the first embodiment, the uncooled infrared image sensor of this embodiment can prevent the manufacturing process from becoming complicated as much as possible. In addition, a plurality of row selection lines are arranged in parallel to form one row selection line group, and a plurality of readout signal lines are arranged in parallel to form one readout signal line group. As a result, the number of thermal diodes in each pixel can be increased, and the sensitivity of the image sensor can be increased.

  In the first to fifth embodiments, the cavity 3 is formed by isotropic etching using a gas as an etchant. However, it can be formed by anisotropic wet etching.

  In the first to fifth embodiments, each pixel preferably has a plurality of thermal diodes connected in series in order to increase the sensitivity of the uncooled infrared image sensor.

  In addition, due to the mounting of the uncooled infrared image sensor, if the pitch of each pixel is too large, the obtained image tends to be rough. If the pitch is too small, the sensitivity is lowered. Therefore, the pitch of each pixel is desirably any size between 10 μm and 50 μm.

  Further, if the thermal diode constituting the pixel is too thick, the sensitivity is lowered and it is difficult to manufacture a support leg and the like. Also, it becomes difficult to manufacture a thermal diode whose thickness is too thin. Therefore, the thickness of the thermal diode is preferably 0.1 μm or more and 10 μm or less.

  Further, if the thickness of the infrared absorbing film is too thick, it is difficult to manufacture and the sensitivity is lowered. On the other hand, if the thickness is too thin, the infrared absorption efficiency decreases. Accordingly, the material of the infrared absorption film is a silicon oxide film, a silicon nitride film, or a laminated film thereof, and the thickness is desirably 0.1 μm or more and 5 μm or less.

  In the first to fifth embodiments, the width of the row selection line group is larger than the width of the read signal line group. However, the width of the read signal line is made larger than the width of the row selection line. The width of the read signal line group may be made larger than the width of the row selection line group.

2 Substrate (silicon substrate)
2a Support part 3 Cavity part 4 Pixel group 4a, 4b, 4c, 4d Pixel 6 Row selection line group 6a Row selection line 6b Row selection line 8 Read signal line group 8a Read signal line 8b Read signal line 12 Insulating film 12a Insulating film 12b Insulating film 12c Insulating film 12d Insulating film 14 Thermal diode 16 Insulating film 16a Insulating film 16b Insulating film 16c Insulating film 16d Insulating film 16e Insulating film 18 Infrared absorbing film

Claims (9)

A semiconductor substrate having a plurality of support portions on the surface;
A plurality of pixel groups arranged in a matrix on the semiconductor substrate, each pixel group having the same number of pixels arranged in a matrix, each pixel absorbing incident infrared rays An infrared absorption film that converts the absorbed infrared light into heat, and a thermoelectric conversion element that is electrically insulated from the infrared absorption film and generates an electric signal by detecting heat from the infrared absorption film, A group of pixels;
A row selection line group provided between the pixel groups adjacent in the column direction and having the same number of row selection lines as the number of pixels arranged in the same column direction in each pixel group;
A readout signal line group provided between the adjacent pixel groups in the row direction and having the same number of readout signal lines as the number of pixels arranged in the same row direction in each pixel group;
1 in one row selection line group of two row selection line groups provided corresponding to each pixel, having one end electrically connected to the corresponding pixel and the other end adjacent to the pixel group including the corresponding pixel. A first support leg having a first wiring electrically connected to the row selection line and a first insulating film covering the first wiring;
One of the two readout signal line groups of one readout signal line group provided corresponding to each pixel, one end of which is electrically connected to the corresponding pixel and the other end adjacent to the pixel group including the corresponding pixel. A second support leg having a second wiring electrically connected to the read signal line and a second insulating film covering the second wiring;
With
A cavity is formed in the surface portion of the semiconductor substrate below each pixel group corresponding to each pixel group,
Each pixel is supported above the corresponding cavity by corresponding first and second support legs,
An uncooled infrared image sensor, wherein an intersection between the row selection line group and the readout signal line group is supported by a support part of the semiconductor substrate.   Each pixel group has 4 pixels arranged in 2 rows × 2 columns, each row selection line group has 2 row selection lines, and each readout signal line group has 2 readout signal lines. The two pixels arranged in the same row direction in each pixel group are electrically connected to the same row selection line and electrically connected to different readout signal lines. The uncooled infrared image sensor according to 1.   Each pixel group has 4 pixels arranged in 2 rows × 2 columns, each row selection line group has 2 row selection lines, and each readout signal line group has 2 readout signal lines. 2. The pixel according to claim 1, wherein each pixel in each pixel group is electrically connected to a different row selection line and electrically connected to a different readout signal line. Cooling infrared image sensor.   4. The uncooled infrared image sensor according to claim 2, wherein the first and second support legs have a spiral shape.   Each pixel group has two pixels arranged in 2 rows × 1 column, each row selection line group has two row selection lines, and each readout signal line group has one readout signal line. 2. The non-cooling according to claim 1, wherein the two pixels in each pixel group are electrically connected to different row selection lines and electrically connected to the same readout signal line. Infrared image sensor.   Each pixel group has two pixels arranged in one row × 2 columns, each row selection line group has one row selection line, and each readout signal line group has two readout signal lines. 2. The non-cooling according to claim 1, wherein two pixels in each pixel group are electrically connected to the same row selection line and are electrically connected to different readout signal lines. Infrared image sensor.   The uncooled infrared image sensor according to claim 2, wherein the first and second support legs have a meander shape.   Each intersection of the row selection line group and the readout signal line group has a diameter of an inscribed circle of the intersection in a plane larger than a diameter of an inscribed circle of each pixel in the plane. An uncooled infrared image sensor according to any one of claims 1 to 7.   The uncooled infrared image sensor according to claim 1, wherein the thermoelectric conversion element includes a plurality of thermal diodes connected in series.

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