JP2010078451A - Infrared sensor and infrared sensor module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an infrared sensor and an infrared sensor module which enable prevention of warping of a thin-film structure part, while making an infrared absorption part be a thin film. <P>SOLUTION: Compensative polysilicon layers 39a and 39b which protect the infrared absorption part 33 and suppress warping of an infrared absorption part 33c on the occasion of forming a p-type polysilicon layer 35 and an n-type polysilicon layer 34 are formed on the infrared incidence surface side of the infrared absorption part 33. Therefore, thinning of the infrared absorption part 33 due to etching can be suppressed in overetching on the occasion of etching a non-doped polysilicon layer to be the base of the p-type polysilicon layer 35 and the n-type polysilicon layer 34, and also the uniformity in a stress balance of the thin-film structure part 3a can be enhanced. Thus, it is possible to prevent warping of the thin-film structure part 3a, while making the infrared absorption part 33 be a thin film, and the sensitivity can be improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an infrared sensor and an infrared sensor module.

  Conventionally, for example, as an infrared sensor capable of detecting infrared rays emitted from the human body (infrared rays having a wavelength of about 8 to 12 μm), infrared absorption that is formed using micromachining technology and absorbs infrared rays and converts them into heat. An infrared sensor including a temperature sensor and a temperature sensing unit that detects a temperature change of the infrared absorption unit has been proposed (see, for example, Patent Documents 1 and 2).

  Here, as shown in FIG. 13, the infrared sensor disclosed in Patent Document 1 includes a silicon substrate 1a ′ and a silicon nitride film 1b ′ formed on one surface of the silicon substrate 1a ′. A base substrate 1 ′, and a diaphragm-like infrared absorbing portion 33 ′ formed by providing a cavity 11 ′ on the one surface of the silicon substrate 1a ′ in the base substrate 1 ′ and comprising a part of the silicon nitride film 1b ′; A thermocouple type temperature sensing unit 30 ′ for detecting a temperature change of the infrared absorption unit 33 ′ and the exposed portion of the temperature sensing unit 30 ′ and the infrared absorption unit 33 ′ on the one surface side of the base substrate 1 ′. And a passivation film (protective film) 60 ′ made of a silicon nitride film, and a temperature-sensitive portion 30 ′ formed across the base substrate 1 ′ and the infrared absorbing portion 33 ′. The con layer 35 and the n-type polysilicon layer 34 are electrically connected to the p-type polysilicon layer 35 and the n-type polysilicon layer 34 on the infrared incident surface side (upper surface side in FIG. 13B) of the infrared absorbing portion 33 ′. The thermopile includes a plurality of thermocouples connected in series and connected in series. Here, the thermopile constituting the temperature sensing part 30 ′ is a p-type that forms a pair with one end of the p-type polysilicon layer 35 and one end of the n-type polysilicon layer 34 disposed on the infrared absorption part 33 ′. A p-type polysilicon layer 35 of thermocouples which are arranged on the base substrate 1 ′ and are different from each other constitute a hot junction with the connection portion 36 where the one end portions of the polysilicon layer 35 and the n-type polysilicon layer 34 are joined. The other end of each other, the other end of the n-type polysilicon layer 34, and a connecting portion 37 joining these other ends constitute a cold junction.

  Note that the infrared sensor disclosed in the above-mentioned Patent Document 1 outputs the outputs of the thin-film structure portion having a laminated structure of the infrared absorption portion 33 ′, a part of the temperature sensing portion 30 ′, and the passivation film 60 ′ and the temperature sensing portion 30 ′. Pixels having MOS transistors for reading are arranged in a two-dimensional array.

Further, as shown in FIG. 14, the infrared sensor disclosed in Patent Document 2 is a base substrate composed of a silicon substrate 1a ″ and an insulating film 1b ″ formed on one surface of the silicon substrate 1a ″. 1 ″, a temperature sensing portion 30 ″ arranged away from the one surface of the base substrate 1 ″, and a heat insulation portion 90 ″ for thermally insulating the temperature sensing portion 30 ″ and the base substrate 1 ″. The warm portion 30 ″ is formed on the polysilicon layer 301 having an impurity concentration of 10 ¹⁷ to 10 ¹⁸ cm ⁻³ , and on both sides in the thickness direction of the polysilicon layer 301 and has a high impurity concentration of 10 ¹⁸ to 10 ²⁰ cm ⁻³ . Bolometer-type infrared detection having concentration polysilicon layers 302 and 303 and electrodes 304 and 305 formed on the opposite sides of the polysilicon layers 301 in the respective high concentration polysilicon layers 302 and 303. It is comprised by the element. Here, the heat insulating portion 90 ″ is disposed so as to be separated from the one surface of the base substrate 1 ″, and a support portion 90a ″ in which the temperature sensitive portion 30 ″ is laminated on the opposite side to the base substrate 1 ″ side, and a support portion It is composed of two legs 90b "and 90b" extended from the side edges of 90a ", and a gap 100" is formed between the support 90a "and the one surface of the base substrate 1". Metal wirings 314 and 315 connected to the electrodes 304 and 305 of the warm portion 30 ″ are formed along the respective leg portions 90b ″ and 90b ″.

In the infrared sensor having the configuration shown in FIG. 14, since the impurity concentration of the high-concentration polysilicon layers 302 and 303 is appropriately set in the range of 10 ¹⁸ to 10 ²⁰ cm ⁻³ , the infrared absorption rate of the detection target is increased. In addition, infrared reflection can be suppressed.

  Further, in the infrared sensor having the configuration shown in FIG. 14, the support portion 90 a ″ of the heat insulating portion 90 ″ is formed of an insulating material having a high infrared absorptivity, and also serves as an infrared absorbing portion that absorbs infrared rays. The sensitivity can be improved.

Note that the infrared sensor disclosed in Patent Document 2 includes a pixel having a temperature sensing unit 30 ″, a heat insulation unit 90 ″, and a MOS transistor for reading the output of the temperature sensing unit 30 ″ arranged in a two-dimensional array. ing.
Japanese Patent No. 2576259 Japanese Patent No. 3287173

  By the way, in the infrared sensor having the configuration shown in FIG. 14, the overall length of each leg 90b ″, 90b ″ in the heat insulating part 90 ″ is lengthened, and the thermal conductance of each leg 90b ″, 90b ″ is reduced (the thermal resistance is reduced). In order to increase the response speed, it is conceivable to reduce the thickness dimension of each leg 90b ″, 90b ″, and in order to increase the response speed, it is conceivable to reduce the thickness dimension of the support 90a ″. In other words, warping occurs in the support portion 90a "which also serves as an infrared absorption portion, resulting in a decrease in structural stability and a decrease in sensitivity.

  Further, in the infrared sensor having the configuration shown in FIG. 14, since the temperature sensing unit 30 ″ is configured by a bolometer-type infrared detection element, it is necessary to pass a current when detecting a change in resistance value, and power consumption is reduced. There is a concern that self-heating is generated and the heat insulating portion 90 ″ is warped due to thermal stress as the size increases. Also, since the temperature coefficient of resistance changes due to temperature changes due to self-heating and ambient temperature changes, it is difficult to achieve high accuracy unless temperature compensation means are provided. If temperature compensation means are provided, the entire sensor becomes large and expensive. turn into.

  On the other hand, in the infrared sensor having the configuration shown in FIG. 13 described above, the temperature sensing unit 30 ′ is composed of a thermopile, and it is not necessary to pass a current through the temperature sensing unit 30 ′, and self-heating does not occur. There are advantages such as no warpage caused by self-heating, low power consumption, and constant sensitivity regardless of temperature and high accuracy.

  However, in the infrared sensor having the configuration shown in FIG. 13, if the thickness dimension of the infrared absorbing portion 33 ′ is increased, the heat capacity of the infrared absorbing portion 33 ′ increases and the response speed decreases, so the infrared absorbing portion 33. It is conceivable to reduce the thickness dimension of ', but when the p-type polysilicon layer 35 and the n-type polysilicon layer 34 are patterned, the infrared absorbing portion 33' is etched to form an infrared absorbing portion 33 'and a temperature sensitive portion. Warpage occurs in a thin film structure portion having a laminated structure of a part of 30 'and a passivation film 60', resulting in a decrease in structural stability and a decrease in sensitivity.

  In using the infrared sensor having the configuration shown in FIG. 13, for example, the infrared sensor, a signal processing IC chip that performs signal processing on the output signal of the infrared sensor, and a package in which the infrared sensor and the signal processing IC chip are mounted. It is conceivable to use an infrared sensor module including

  The present invention has been made in view of the above-mentioned reasons, and an object thereof is to provide an infrared sensor and an infrared sensor module capable of preventing the thin film structure portion from warping while reducing the thickness of the infrared absorption portion. There is.

  According to a first aspect of the present invention, there is provided a base substrate, a thin film structure portion having an infrared absorption portion that is spatially separated from the base substrate and absorbs infrared rays on one surface side of the base substrate, an infrared absorption portion, and the base substrate. The p-type polysilicon layer, the n-type polysilicon layer, and the connection part in which the p-type polysilicon layer and the n-type polysilicon layer are electrically joined on the infrared incident surface side of the infrared absorption part. A thermocouple-type temperature sensing part that detects a temperature difference between the infrared absorption part and the base substrate, and has a p-type polysilicon layer and an n-type polycrystal on the infrared incident surface side of the infrared absorption part. A compensation polysilicon layer is formed which protects the infrared absorbing portion and suppresses the warp of the infrared absorbing portion when the silicon layer is formed.

  According to the present invention, the temperature sensitive part is a p-type polysilicon layer formed over the infrared absorption part and the base substrate, the n-type polysilicon layer, and the p-type polysilicon on the infrared incident surface side of the infrared absorption part. Because it is a thermocouple type temperature sensing part that has a thermocouple composed of a connection part in which an n-type polysilicon layer and an n-type polysilicon layer are electrically joined, and detects the temperature difference between the infrared absorption part and the base substrate, The thin film structure does not warp, and the infrared absorbing part is protected and the warp of the infrared absorbing part is suppressed when the p-type polysilicon layer and the n-type polysilicon layer are formed on the infrared incident surface side of the infrared absorbing part. Since the compensating polysilicon layer is formed, it is possible to prevent the infrared absorbing portion from being etched and thinned when forming the p-type polysilicon layer and the n-type polysilicon layer, and the thin film structure portion. It can enhance the uniformity of the force balance, while achieving thinning of the infrared absorbing section it is possible to prevent warping of the thin film structure, thereby improving the sensitivity.

  According to a second aspect of the present invention, in the first aspect of the invention, the thin film structure portion includes a bridge portion that connects the base substrate and the infrared absorption portion, and the bridge portion is one piece from the base substrate. It is characterized by being connected at points.

  According to this invention, even if the base substrate is deformed by external stress or thermal stress, it is possible to suppress the deformation of the thin film structure and suppress a change in sensitivity. Improve accuracy.

  According to a third aspect of the invention, in the first or second aspect of the invention, the p-type polysilicon layer, the n-type polysilicon layer, and the compensation polysilicon layer are set to have the same thickness. Features.

  According to this invention, the uniformity of the stress balance of the thin film structure part can be improved, and the warp of the infrared absorption part can be suppressed.

  According to a fourth aspect of the present invention, in the first to third aspects of the invention, in the thin film structure portion, the p-type polysilicon layer, the n-type polysilicon layer, and the compensation polysilicon layer are formed on the same plane. It is characterized by being made.

  According to this invention, the uniformity of the stress balance of the thin film structure part can be improved, and the warp of the infrared absorption part can be suppressed.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, an infrared absorption film is formed on the side of the compensation polysilicon layer opposite to the base substrate side, and the refractive index of the infrared absorption film is n. When the center wavelength of the infrared rays to be absorbed is λ, the thickness of the infrared absorbing film is set to λ / 4n.

  According to this invention, it is possible to increase the absorption efficiency of infrared light having a wavelength to be absorbed by the infrared absorption film, and to achieve high sensitivity.

According to a sixth aspect of the invention, in the first to fifth aspects of the invention, the impurity concentration of the compensation polysilicon layer is 10 ¹⁸ to 10 ²⁰ cm ⁻³ , and the p-type polysilicon layer is used as the compensation polysilicon layer. A p-type compensation polysilicon layer formed integrally with the n-type polysilicon layer and an n-type compensation polysilicon layer formed integrally with the n-type polysilicon layer.

  According to this invention, the resistance value of the thermocouple can be reduced, and the S / N ratio can be improved.

According to a seventh aspect of the present invention, in the first to sixth aspects of the invention, the impurity concentration of the compensation polysilicon layer is 10 ¹⁸ to 10 ²⁰ cm ⁻³ , the refractive index of the compensation polysilicon layer is n, and absorption is performed. The thickness of each of the p-type polysilicon layer, the n-type polysilicon layer, and the compensation polysilicon layer is λ / 4n, where λ is the center wavelength of the target infrared ray.

  According to the present invention, the absorption efficiency of infrared rays having a wavelength to be absorbed by the compensation polysilicon layer can be increased, and high sensitivity can be achieved.

According to an eighth aspect of the present invention, in the first to seventh aspects of the invention, the impurity concentration of the compensation polysilicon layer is 10 ¹⁸ to 10 ²⁰ cm ⁻³ , and the p-type polysilicon layer and the n-type polysilicon are provided. At least one of the layers includes the same impurity as the compensation polysilicon layer at the same concentration.

According to the present invention, since the impurity concentration of at least one of the p-type polysilicon layer and the n-type polysilicon layer is 10 ¹⁸ to 10 ²⁰ cm ⁻³ , the S / N ratio of the output of the temperature sensitive part In addition, since the compensation polysilicon layer can be formed in the same process as at least one of the p-type polysilicon layer and the n-type polysilicon layer, the cost can be reduced.

  According to a ninth aspect of the present invention, in the first to eighth aspects of the present invention, the pixels having the thin film structure portion are arranged in an array on the one surface side of the base substrate.

  According to the present invention, an infrared image sensor can be realized.

  The invention of claim 10 is characterized in that, in the invention of claim 9, a MOS transistor for reading out the output of the temperature sensing section is provided for each of the pixels.

  According to the present invention, the number of output pads can be reduced, and the size and cost can be reduced.

  According to an eleventh aspect of the invention, in the tenth aspect of the invention, the thickness of the polysilicon layer constituting the gate electrode of the MOS transistor is set to the same thickness as the compensation polysilicon layer. .

  According to the present invention, the gate electrode of the MOS transistor and the compensation polysilicon layer can be formed simultaneously, and the cost can be reduced by reducing the number of manufacturing steps.

  According to a twelfth aspect of the present invention, there is provided the infrared sensor according to any one of the first to eleventh aspects, a signal processing IC chip that performs signal processing on an output signal of the infrared sensor, an infrared sensor, and a signal processing IC chip. The base board of the infrared sensor has a rectangular outer peripheral shape, and all output pads for taking out output signals output from the temperature sensing unit are arranged along one side of the outer peripheral edge. The signal processing IC chip has a rectangular outer peripheral shape, and all the input pads that are electrically connected to the output pads of the infrared sensor are arranged in parallel along one side of the outer peripheral edge. The infrared sensor and the signal processing IC chip are arranged so that the one side with the signal processing IC chip is closer than the other sides.

  According to this invention, by providing the infrared sensor according to any one of claims 1 to 11, the thin film structure portion is prevented from warping while the infrared absorption portion of the infrared sensor is reduced in thickness. In addition, the base plate of the infrared sensor has a rectangular outer peripheral shape, and all output pads for taking out output signals output from the temperature sensing part are along one side of the outer peripheral edge. The signal processing IC chips have a rectangular outer peripheral shape, and all input pads electrically connected to the output pads of the infrared sensor are arranged in parallel along one side of the outer peripheral edge. Since the infrared sensor and the signal processing IC chip are arranged so that the one side of the base substrate and the signal processing IC chip is closer than the other sides, the output pad of the infrared sensor and the signal The wiring connecting the input pads of the processing IC chip can be shortened, because it is possible to reduce the influence of external noise, noise resistance is improved.

  The invention of claim 1 can prevent the thin film structure from warping while reducing the thickness of the infrared absorbing portion, and has an effect of improving the sensitivity.

  According to the invention of claim 12, it is possible to prevent the thin film structure from warping while reducing the thickness of the infrared absorbing portion in the infrared sensor, and to improve the sensitivity. Also, the infrared sensor output pad and the signal processing The wiring connecting the input pads of the IC chip can be shortened, and the noise resistance is improved.

(Embodiment 1)
The infrared sensor A of the present embodiment is an infrared image sensor. As shown in FIGS. 1 and 2, a pixel 2 having a thermal infrared detector 3 and a MOS transistor 4 serving as a pixel selection switching element is a base substrate 1. Are arranged in an array (here, a two-dimensional array) on one surface side. Here, the base substrate 1 is formed using a silicon substrate 1a. In the present embodiment, m × n (4 × 4 in the illustrated example) pixels 2 are formed on the one surface side of one base substrate 1, but the number and arrangement of the pixels 2 are particularly limited. It is not limited. In FIG. 2B, an equivalent circuit of the thermocouple type temperature sensing unit 30 in the thermal type infrared detection unit 3 is represented by a voltage source Vs corresponding to the thermoelectromotive force of the thermocouple type temperature sensing unit 30. It is.

In addition, the infrared sensor A of the present embodiment has a plurality of vertical readouts in which one end of the temperature sensing unit 30 of each of the plurality of thermal infrared detectors 3 in each column is commonly connected to each column via the MOS transistor 4 described above. A plurality of horizontal signal lines 6 in which the line 7 and the gate electrode 46 of the MOS transistor 4 corresponding to the temperature sensing unit 30 of the thermal infrared detector 3 in each row are connected in common to each row, and the MOS transistors 4 in each column A plurality of ground lines 8 in which p ^{+ -type} well regions 41 are commonly connected for each column, a common ground line 9 in which each ground line 8 is commonly connected, and a plurality of thermal infrared detectors 3 in each column. The other end of the temperature sensing unit 30 is provided with a plurality of reference bias lines 5 commonly connected to each column, and the outputs of the temperature sensing units 30 of all the thermal infrared detection units 3 are read in time series. Can be done. In short, the infrared sensor A of the present embodiment is arranged in parallel with the thermal infrared detector 3 and the thermal infrared detector 3 on the one surface side of the base substrate 1 to read the output of the thermal infrared detector 3. A plurality of pixels 2 having the MOS transistors 4 are formed. Here, in the MOS transistor 4, the gate electrode 46 is connected to the horizontal signal line 6, the source electrode 48 is connected to the reference bias line 5 via the temperature sensing unit 30, and each reference bias line 5 is connected to the common reference bias line 5a. Are connected in common, the drain electrode 47 is connected to the vertical readout line 7, each horizontal signal line 6 is electrically connected to each pixel selection pad Vsel, and each vertical readout line 7 is individually connected to each other. Are electrically connected to the output pad Vout, the common ground line 9 is electrically connected to the ground pad Gnd, the common reference bias line 5a is electrically connected to the reference bias pad Vref, and the silicon substrate 1a is electrically connected. It is electrically connected to the substrate pad Vdd.

  Thus, the output voltage of each pixel 2 can be read sequentially by controlling the potential of each pixel selection pad Vsel so that the MOS transistors 4 are sequentially turned on. For example, if the potential of the reference bias pad Vref is 1.65, the potential of the ground pad Gnd is 0 V, the potential of the substrate pad Vdd is 5 V, and the potential of the pixel selection pad Vsel is 5 V, the MOS transistor 4 Is turned on, the output voltage of the pixel 2 (1.65 V + the output voltage of the temperature sensing unit 30) is read from the output pad Vout, and the MOS transistor 4 is turned off when the potential of the pixel selection pad Vsel is set to 0V. The output voltage of the pixel 2 is not read from the output pad Vout. Therefore, as shown in FIG. 3, an infrared sensor A, a signal processing IC chip B that performs signal processing of an output voltage that is an output signal of the infrared sensor A, and a package in which the infrared sensor A and the signal processing IC chip B are mounted. 4, the signal processing IC chip B includes a plurality of output pads Vout (four in the illustrated example) of the infrared sensor A, as shown in FIG. A plurality of (four in the illustrated example) input pads Vin, an amplifier circuit AMP that amplifies the output voltage of the input pads Vin, and a plurality of input pads Vin. An infrared image can be obtained by providing a multiplexer MUX or the like that selectively inputs the output voltage of the output to the amplifier circuit AMP. The above-mentioned package C is formed in a rectangular box shape that is open on one side, and an infrared sensor A and a signal processing IC chip B are mounted on the inner bottom surface. A package lid (not shown) provided with a lens for converging infrared rays to the absorber 33 is covered.

  By the way, in the above-described infrared sensor module, the base substrate 1 of the infrared sensor A has a rectangular outer peripheral shape, and all output pads Vout for taking out output signals output from the temperature sensing unit 30 are outside the base substrate 1. The signal processing IC chip B is arranged in parallel along one side of the periphery, and the outer peripheral shape of the signal processing IC chip B is rectangular, and all the input pads Vin electrically connected to the output pads Vout of the infrared sensor A are signal processing ICs. The infrared sensor A and the signal processing IC chip are arranged side by side along one side of the outer periphery of the chip B so that the one side of the base substrate 1 and the signal processing IC chip B is closer to each other than the other sides. Since B is arranged, the wiring 80 connecting the output pad Vout of the infrared sensor A and the input pad Vin of the signal processing IC chip B can be shortened, and the influence of external noise can be reduced. Therefore, noise resistance is improved.

  Hereinafter, the structures of the thermal infrared detector 3 and the MOS transistor 4 will be described. In the present embodiment, as the silicon substrate 1a, a single crystal silicon substrate having an n-type conductivity and the (100) plane of the one surface is used.

  The thermal infrared detector 3 is formed in the formation area A1 of the thermal infrared detector 3 in each pixel 2 on the one surface side of the silicon substrate 1a, and the MOS transistor 4 is connected to the one of the silicon substrate 1a. It is formed in the formation region A2 of the MOS transistor 4 in each pixel 2 on the surface side.

  The thermal infrared detecting section 3 is a thin film structure section 3a having an infrared absorbing section 33 which is formed spatially separated from the base substrate 1 on the one surface side of the base substrate 1 based on the silicon substrate 1a and absorbs infrared rays. And the p-type polysilicon layer 35, the n-type polysilicon layer 34, and the infrared incident surface side of the infrared absorbing portion 33 (the upper surface side of FIG. 1B) formed across the infrared absorbing portion 33 and the base substrate 1. ) To detect a temperature difference between the infrared absorbing portion 33 and the base substrate 1, which has a thermocouple including a connection portion 36 in which the p-type polysilicon layer 35 and the n-type polysilicon layer 34 are electrically joined. A pair of temperature sensitive parts 30, and the infrared absorbing part 33 is protected when the p-type polysilicon layer 35 and the n-type polysilicon layer 34 are formed on the infrared incident surface side of the infrared absorbing part 33. Suppress warping Compensation polysilicon layer 39a, 39b are formed to be.

Here, the compensation polysilicon layer 39a on the right side in FIG. 1A has the same concentration (for example, 10 ¹⁸ to 10 ²⁰ cm ⁻³ ) of the same p-type impurity (for example, boron) as the p-type polysilicon layer 35. And is formed integrally with the p-type polysilicon layer 35 continuously. In addition, the left side compensation polysilicon layer 39b in FIG. 1A has the same n-type impurity (for example, phosphorus) as the n-type polysilicon layer 34 at the same concentration (for example, 10 ¹⁸ to 10 ²⁰ cm ⁻³ ). The n-type polysilicon layer 34 is continuously and integrally formed. Hereinafter, the p-type compensation polysilicon layer 39a having the conductivity type may be referred to as a p-type compensation polysilicon layer, and the n-type compensation polysilicon layer 39b having the conductivity type may be referred to as an n-type compensation polysilicon layer. In this embodiment, each of the compensation polysilicon layers 39a and 39b has an impurity concentration of 10 ¹⁸ to 10 ²⁰ cm ⁻³ , and a p-type compensation polysilicon layer 39a formed integrally with the p-type polysilicon layer 35, Since it has the n-type compensating polysilicon layer 39b formed integrally with the n-type polysilicon layer 34, the resistance value of the thermocouple can be reduced and the S / N ratio can be improved.

  By the way, in this embodiment, the refractive index of the p-type polysilicon layer 35, the n-type polysilicon layer 34, and the compensation polysilicon layers 39a and 39b is n, and the absorption targets of these polysilicon layers 35, 34, 39a, and 39b. When the center wavelength of infrared rays of (infrared sensor A detection target) is λ, the thickness t1 of each of the p-type polysilicon layer 35, the n-type polysilicon layer 34, and each of the compensation polysilicon layers 39a and 39b is λ / 4n. Therefore, it is possible to increase the absorption efficiency of infrared light having a wavelength to be detected (for example, 8 to 12 μm), and to achieve high sensitivity. For example, when n = 3.6 and λ = 10 μm, t1≈0.69 μm may be set.

Further, in the present embodiment, the impurity concentration of each of the compensation polysilicon layers 39a and 39b is 10 ¹⁸ to 10 ²⁰ cm ⁻³ , and the p-type polysilicon layer 35 and the n-type polysilicon layer 34 are respectively made of p-type compensation poly. The silicon layer 39a and the n-type compensation polysilicon layer 39b contain the same impurities at the same concentration, and the impurity concentrations of the p-type polysilicon layer 35 and the n-type polysilicon layer 34 are 10 ¹⁸ to 10 ²⁰ cm ⁻³ , respectively. Therefore, as described in the above-mentioned Patent Document 2, it is possible to suppress the reflection of infrared rays while increasing the infrared absorption rate, and to increase the S / N ratio of the output of the temperature sensing unit 30, Further, the p-type compensating polysilicon layer 39a can be formed in the same process as the p-type polysilicon layer 35, and the n-type compensating polysilicon layer 39b is formed in the same process as the n-type polysilicon layer 34. Therefore, the cost can be reduced. If the impurity concentration of at least one of the p-type polysilicon layer 35 and the n-type polysilicon layer 34 is set to 10 ¹⁸ to 10 ²⁰ cm ⁻³ , the S / N ratio of the output of the temperature sensing unit 30 can be increased. If both impurity concentrations are 10 ¹⁸ to 10 ²⁰ cm ⁻³ , the S / N ratio of the output of the temperature sensing unit 30 can be further increased. Further, at least the impurity and impurity concentration of the p-type compensation polysilicon layer 39a and the p-type polysilicon layer 35 are made the same, or the impurity and impurity concentration of the n-type compensation polysilicon layer 39b and the n-type polysilicon layer 34 are set. If the same is set, the cost can be reduced.

The thin film structure portion 3a described above has a bridge portion 3b that connects the base substrate 1 and the infrared absorption portion 33. The bridge portion 3b is connected to the infrared absorption portion 33 at two locations, while the base portion 1b. It is connected to the substrate 1 at one place. Thus, in the present embodiment, since the bridge portion 3b is connected to the base substrate 1 at a single location, even if the base substrate 1 is deformed by external stress or thermal stress, the thin film structure Since the deformation of the portion 3a can be suppressed and the change in sensitivity can be suppressed, high accuracy can be achieved. Here, the bridge portion 3b is U-shaped in a plan view, and the front end portions of both leg pieces are connected to the infrared absorbing portion 33, and the first connecting piece 3b ₁ is disposed along the outer peripheral edge of the infrared absorbing portion 33. The first connecting piece 3b ₁ has a _second connecting piece 3b ₂ which is extended from the center of the central piece of the first connecting piece 3b _{1 to} the side opposite to the infrared absorbing portion 33 side and connected to the base substrate 1. Further, the portion of the base substrate 1 surrounding the thin film structure portion 3a in plan view has a rectangular frame shape. Note that the bridge portion 3 b is spatially separated from the infrared absorbing portion 33 and the base substrate 1 by two slits 13 except for the connecting portion between the infrared absorbing portion 33 and the base substrate 1. Here, the width of each slit 13 may be appropriately set within a range of about 0.2 μm to 5 μm, for example. In addition, in the infrared sensor A of the present embodiment, a thermal insulation cavity 11 is formed for each part corresponding to each thermal infrared detector 3 in the silicon substrate 1a.

  The thin film structure 3a is formed on the silicon oxide film 1b formed on the one surface side of the silicon substrate 1a, the silicon nitride film 32 formed on the silicon oxide film 1b, and the silicon nitride film 32. The thermocouple-type temperature sensing part 30 formed, the interlayer insulating film 50 made of a BPSG film formed so as to cover the temperature sensing part 30 on the surface side of the silicon nitride film 32, and the interlayer insulating film 50 are formed. It is formed by patterning a laminated structure part of a passivation film 60 made of a laminated film of a PSG film and an NSG film formed on the PSG film. In the present embodiment, the portion of the silicon nitride film 32 other than the bridge portion 3b of the thin film structure portion 3a constitutes the infrared absorbing portion 33 described above, and the silicon substrate 1a, the silicon oxide film 1b, the silicon nitride film 32, and the interlayer The insulating film 50 and the passivation film 60 constitute the base substrate 1. In the present embodiment, the laminated film of the interlayer insulating film 50 and the passivation film 60 is formed across the formation area A1 of the thermal infrared detector 3 and the formation area A2 of the MOS transistor 4. The portion formed in the formation region A1 of the thermal infrared detector 3 also serves as the infrared absorption film 70. Here, when the refractive index of the infrared absorbing film 70 is n and the center wavelength of infrared rays of the absorption target of the infrared absorbing film 70 (detection target of the infrared sensor A) is λ, the thickness t2 of the infrared absorbing film 70 is λ / Since it is set to 4n, the absorption efficiency of infrared rays with a wavelength to be detected (for example, 8 to 12 μm) can be increased, and high sensitivity can be achieved. For example, when n = 1.4 and λ = 10 μm, t2≈1.8 μm may be set. In the present embodiment, the thickness of the interlayer insulating film 50 is 0.8 μm (8000 mm), the thickness of the passivation film 60 is 1 μm (PSG film thickness is 5000 mm, and NSG film thickness is 5000 mm).

  The thermocouple-type temperature sensing unit 30 has an n-type polysilicon layer 34 and a p-type polysilicon layer 35 formed on the silicon nitride film 32 described above. Here, the n-type polysilicon layer 34 and the p-type polysilicon layer 35 are formed across the infrared absorption portion 33, the bridge portion 3 b, and the base substrate 1. In addition, the temperature sensing unit 30 is a metal material (for example, an electrical connection between one end of the n-type polysilicon layer 34 and one end of the p-type polysilicon layer 35 on the surface side of the central portion of the infrared absorption unit 33) The n-type polysilicon layer 34, the p-type polysilicon layer 35, and the connection part 36 constitute a thermocouple. Further, in the temperature sensing unit 30, electrodes 38a and 38b are formed on the other end portions of the n-type polysilicon layer 34 and the p-type polysilicon layer 35, respectively.

Here, the connection part 36 of the temperature sensing part 30 and the two electrodes 38 a and 38 b are insulated and separated by the interlayer insulating film 50 on the one surface side of the base substrate 1. That is, the connecting portion 36 is electrically connected to the one end portions of the polysilicon layers 34 and 35 through contact holes 50a ₁ and 50a ₂ formed in the interlayer insulating film 50, and one electrode 38a is connected to the interlayer insulating film. The other end of the n-type polysilicon layer 34 is electrically connected through the contact hole 50b formed in the contact hole 50b, and the other electrode 38b is connected to the p-type polysilicon layer through the contact hole 50c formed in the interlayer insulating film 50. 35 is electrically connected to the other end portion.

Further, as described above, the MOS transistor 4 is formed in the formation region A2 of the MOS transistor 4 in each of the pixels 2 on the one surface side of the silicon substrate 1a. Here, in the MOS transistor 4, a p ^{+ -type} well region 41 is formed on the one surface side of the silicon substrate 1 a, and an n ⁺ -type drain region 43 and an n ^{+ -type} source region 44 are formed in the p ^{+ -type} well region 41. Are formed apart from each other. Further, the ^{p +} -type well region 41, ^{p ++} type channel stopper region 42 which surrounds the ^{n +} -type drain region 43 and ^{the n +} -type source region 44 is formed. Further, on the site located between the n ⁺ -type drain region 43 and the n ⁺ -type source region 44 in the p ⁺ -type well region 41, a gate insulating film 45 made of silicon oxide film (thermal oxide film) A gate electrode 46 made of an n-type polysilicon layer is formed. A drain electrode 47 made of a metal material (for example, Al—Si) is formed on the n ⁺ -type drain region 43, and a metal material (for example, Al—Si) is formed on the n ^{+ -type} source region 44. A source electrode 48 is formed. Here, the gate electrode 46, the drain electrode 47, and the source electrode 48 are insulated and separated by the interlayer insulating film 50 described above. That is, the drain electrode 47 is electrically connected to the n ⁺ -type drain region 43 through the contact hole 50 d formed in the interlayer insulating film 50, and the source electrode 48 is connected to the n ^{+ -type} through the contact hole 50 e formed in the interlayer insulating film 50. It is electrically connected to the source region 44.

By the way, in each pixel 2 of the infrared sensor A of the present embodiment, the source electrode 48 of the MOS transistor 4 and the other electrode 38b of the temperature sensing unit 30 are electrically connected, and the one electrode of the temperature sensing unit 30 is provided. Reference numeral 38 a is electrically connected to the reference bias line 5 via a metal wiring (for example, Al—Si wiring) 59 formed integrally with the reference bias line 5. Further, in each pixel 2 of the infrared sensor A of the present embodiment, the drain electrode 47 of the MOS transistor 4 is electrically connected to the vertical readout line 7, and the gate electrode 46 is formed continuously and integrally with the gate electrode 46. It is electrically connected to a horizontal signal line 6 made of a poly-silicon wiring. In each pixel 2, a ground electrode 49 made of a metal material (for example, Al—Si) is formed on the p ⁺⁺ -type channel stopper region 42 of the MOS transistor 4. The p ^{++ -type} channel stopper region 42 is electrically connected to the common ground line 8 for element isolation by biasing it to a lower potential than the n ⁺ -type drain region 43 and the n ^{+ -type} source region 44. The ground electrode 49 is electrically connected to the p ^{++ type} channel stopper region 42 through a contact hole 50f formed in the interlayer insulating film 50.

  Hereinafter, the manufacturing method of the infrared sensor A of the present embodiment will be briefly described with reference to FIGS.

  First, a first silicon oxide film 31 having a first predetermined film thickness (for example, 3000 mm) and a silicon nitride film 32 having a second predetermined film thickness (for example, 900 mm) are stacked on the one surface side of the silicon substrate 1a. An insulating layer forming step of forming an insulating layer made of a film is performed, and then a part of the insulating layer corresponding to the formation region A1 of the thermal infrared detector 3 is utilized by using a photolithography technique and an etching technique. The structure shown in FIG. 5A is obtained by performing an insulating layer patterning process in which a portion corresponding to the formation region A2 of the MOS transistor 4 is removed by etching. Here, the silicon oxide film 31 is formed by thermally oxidizing the silicon substrate 1a at a predetermined temperature (for example, 1100 ° C.), and the silicon nitride film 32 is formed by LPCVD.

After the above-described insulating layer patterning step, a well region forming step for forming a p ^{+ -type} well region 41 on the one surface side of the silicon substrate 1a is performed, and subsequently, a p ^{+ -type} well on the one surface side of the silicon substrate 1 is performed. A channel stopper region forming step for forming a p ^{++ -type} channel stopper region 42 in the region 41 is performed, and then the n ⁺ -type drain region 43 and the n ^{+ -type} source region 44 in the p ^{+ -type} well region 41 are respectively formed in the planned formation regions. n-type impurities (e.g., phosphorus, etc.) by performing the source and drain formation step of forming a n ⁺ -type drain region 43 and the n ⁺ -type source region 44 by performing the drive from performing ion implantation, FIG. 5 ( The structure shown in b) is obtained. Here, in the well region forming step, the second silicon oxide film (thermal oxide film) 51 is selectively formed by thermally oxidizing the exposed portion on the one surface side of the silicon substrate 1 at a predetermined temperature. The silicon oxide film 51 is patterned using a photolithographic technique and an etching technique using a mask for forming the p ^{+ -type} well region 41, and then ion implantation of a p-type impurity (for example, boron) is performed. Then, drive-in is performed to form the p ^{+ -type} well region 41. Further, in the channel stopper region forming step, a third silicon oxide film (thermal oxide film) 52 is selectively formed by thermally oxidizing the one surface side of the silicon substrate 1a at a predetermined temperature, and thereafter, p ^{++ type} The silicon oxide film 52 is patterned by using a photolithography technique and an etching technique using a mask for forming the channel stopper region 42, and then ion implantation of a p-type impurity (for example, boron) is performed. The p ^{++ type} channel stopper region 42 is formed by performing drive-in. The first silicon oxide film 31, the second silicon oxide film 51, and the third silicon oxide film 52 constitute the silicon oxide film 1b on the one surface side of the silicon substrate 1a.

  After the above-described source / drain formation step, gate insulation for forming a gate insulating film 45 made of a silicon oxide film (thermal oxide film) having a predetermined film thickness (for example, 600 mm) on the one surface side of the silicon substrate 1a by thermal oxidation. A film forming step is performed, and then, the gate electrode 46, the horizontal signal line 6 (see FIG. 1A), the n-type polysilicon layer 34, and the p-type polysilicon layer 35 are formed on the entire surface of the silicon substrate 1a on the one surface side. And a polysilicon layer forming step of forming a non-doped polysilicon layer having a predetermined film thickness (for example, 0.69 μm) serving as a basis of the compensation polysilicon layers 39a and 39b by LPCVD, and thereafter performing a photolithography technique and an etching technique. Among the non-doped polysilicon layers, the gate electrode 46, the horizontal signal line 6, the n-type polysilicon layer 34, the p-type polysilicon are used. Then, a polysilicon layer patterning process is performed so that portions corresponding to the layer 35 and the respective compensation polysilicon layers 39a and 39b remain, and then the p-type polysilicon layer 35 and the p-type compensation layer of the non-doped polysilicon layer are performed. A p-type polysilicon layer is formed by implanting p-type impurities (for example, boron) into a portion corresponding to the polysilicon layer 39a and then driving the p-type polysilicon layer 35 and the p-type compensating polysilicon layer 39a. A silicon layer forming step is performed, and then, n-type impurities (for example, n-type polysilicon layer 34, n-type compensating polysilicon layer 39b, gate electrode 46 and horizontal signal line 6 in the non-doped polysilicon layer are formed in the portion corresponding to the n-type polysilicon layer 34, N-type polysilicon by driving after ion implantation of phosphorus) The structure shown in FIG. 5C is obtained by performing an n-type polysilicon layer forming step for forming the layer 34, the n-type compensating polysilicon layer 39b, the gate electrode 46 and the horizontal signal line 6. The order of the p-type polysilicon layer forming step and the n-type polysilicon layer forming step may be reversed.

After the p-type polysilicon layer forming step and the n-type polysilicon layer forming step are completed, an interlayer insulating film forming step for forming an interlayer insulating film 50 on the one surface side of the silicon substrate 1a is performed, A contact hole forming step for forming the contact holes 50a ₁ , 50a ₂ , 50b, 50c, 50d, 50e, and 50f (see FIG. 1A) in the interlayer insulating film 50 is performed using the lithography technique and the etching technique. As a result, the structure shown in FIG. Here, in the interlayer insulating film forming step, a BPSG film having a predetermined film thickness (for example, 8000 mm) is deposited on the one surface side of the silicon substrate 1a by the CVD method, and then reflowed at a predetermined temperature (for example, 800 ° C.). Thereby, the planarized interlayer insulating film 50 is formed.

  After the contact hole forming step, the connection portion 36, electrodes 38a and 38b, drain electrode 47, source electrode 48, reference bias line 5, metal wiring 59, vertical read line 7 are formed on the entire surface of the silicon substrate 1a. Further, a metal film (for example, Al-Si film) having a predetermined film thickness (for example, 2 μm) serving as a basis for the ground line 8, the common ground line 9, and the pads Vout, Vsel, Vref, Vdd, and Gnd is formed by sputtering or the like. A metal film forming step, and then patterning the metal film using a photolithography technique and an etching technique to connect the connection portion 36, the electrodes 38a and 38b, the drain electrode 47, the source electrode 48, the reference bias line 5, Metal forming the vertical readout line 7, the ground line 8, the common ground line 9, and the pads Vout, Vsel, Vref, Vdd, and Gnd By performing the film patterning step, the structure shown in FIG. 6A is obtained. Etching in the metal film patterning step is performed by RIE.

  After the metal film patterning step, a PSG film having a predetermined thickness (for example, 5000 mm) and a predetermined film thickness (for example, 5000 mm) are formed on the one surface side of the silicon substrate 1a (that is, the surface side of the interlayer insulating film 50). By performing a passivation film forming step of forming a passivation film 60 made of a laminated film with an NSG film by a CVD method, the structure shown in FIG. 6B is obtained. Note that the passivation film 60 is not limited to a stacked film of a PSG film and an NSG film, and may be a silicon nitride film, for example.

  After the above-described passivation film forming step, a thermal insulating layer composed of a laminated film of the silicon oxide film 31 and the silicon nitride film 32, a temperature sensitive portion 30 formed on the thermal insulating layer, and a surface side of the thermal insulating layer The above-mentioned thin film structure portion 3a is formed by patterning the laminated structure portion of the interlayer insulating film 50 formed so as to cover the temperature sensitive portion 30 and the passivation film 60 formed on the interlayer insulating film 50. The structure shown in FIG. 6C is obtained by performing the structure patterning step. In the laminated structure portion patterning step, a plurality (two in this embodiment) of slits 13 (see FIG. 1A) that penetrate in the thickness direction of the laminated structure portion and separate the infrared absorbing portion 33 and the base substrate 1 are used. ) Is formed to form the thin film structure portion 3a.

After the above-described laminated structure patterning step, an opening forming step for forming openings (not shown) for exposing the pads Vout, Vsel, Vref, Vdd, and Gnd is performed using a photolithography technique and an etching technique. Subsequently, by performing the cavity forming step of forming the cavity 11 in the silicon substrate 1a by introducing the etching solution using the slits 13 as the etching solution introduction holes and anisotropically etching the silicon substrate 1a, the process shown in FIG. An infrared sensor in which the pixels 2 having the structure shown in 6 (d) are arranged in a two-dimensional array is obtained. Here, the etching in the opening forming step is performed by RIE. In the cavity forming step, a TMAH solution heated to a predetermined temperature (for example, 85 ° C.) is used as an etching solution. However, the etching solution is not limited to the TMAH solution, and other alkaline solutions (for example, a KOH solution). May be used. Since all processes until the cavity forming process is completed are performed at the wafer level, after the cavity forming process is completed, a separation process for separating into individual infrared sensors may be performed. Further, as can be seen from the above description, as for the manufacturing method of the MOS transistor 4, a well-known general MOS transistor manufacturing method is adopted, and a thermal oxide film is formed by thermal oxidation, a photolithography technique and etching. patterning the thermal oxide film by techniques, ion implantation of an impurity, by repeating the basic steps of the drive-in (diffusion of impurities), and p ⁺ -type well region 41, p ⁺⁺ type channel stopper region 42, n ⁺ form drain regions 43 An n ^{+ -type} source region 44 is formed.

  According to the infrared sensor A of the present embodiment described above, the temperature sensing unit 30 includes the p-type polysilicon layer 35, the n-type polysilicon layer 34, and the n-type polysilicon layer 34, which are formed across the infrared absorption unit 33 and the base substrate 1. The infrared absorption part 33 and the base substrate 1 have a thermocouple including a connection part 36 in which the p-type polysilicon layer 35 and the n-type polysilicon layer 34 are electrically joined to each other on the infrared incident surface side of the infrared absorption part 33. Therefore, the thin film structure 3a is not warped due to self-heating, and the p-type polysilicon layer 35 is formed on the infrared incident surface side of the infrared absorbing portion 33. Since the compensation polysilicon layers 39a and 39b that protect the infrared absorbing portion 33 and suppress the warpage of the infrared absorbing portion 33c are formed when the n-type polysilicon layer 34 is formed, the p-type polysilicon layer 35 In addition, the infrared absorbing portion 33 is prevented from being etched and thinned when the n-type polysilicon layer 34 is formed (here, the p-type polysilicon layer 35 and the n-type polysilicon layer 34 are not formed in the above-described polysilicon layer patterning step). The infrared absorbing portion 33 can be prevented from being etched and thinned during overetching when etching the underlying non-doped polysilicon layer) and the uniformity of the stress balance of the thin film structure portion 3a can be improved. While reducing the thickness of the infrared absorbing portion 33, it is possible to prevent the thin film structure portion 3a from warping, and the sensitivity can be improved. Here, it is preferable that the compensation polysilicon layers 39a and 39b are formed so that the compensation polysilicon layers 39a and 39b and the temperature sensing part 30 cover substantially the entire surface of the infrared absorption part 33. However, the p-type compensation polysilicon layer 39a and the n-type compensation polysilicon layer 39b must be electrically insulated and separated so as not to be in direct contact with each other, and an etching solution (for example, a TMAH solution used in the above-described cavity forming step). In order to prevent etching, it is necessary to design the shape in plan view so as not to be exposed on the inner surface of the slit 13 (in order to prevent the outer peripheral portion of the infrared absorbing portion 33 from being covered in plan view). is there).

  In the infrared sensor A of the present embodiment, the p-type polysilicon layer 35, the n-type polysilicon layer 34, and the compensation polysilicon layers 39a and 39b are set to have the same thickness. The uniformity of the stress balance is improved, and the warp of the infrared absorbing portion 33 can be suppressed. In the infrared sensor A of the present embodiment, the p-type polysilicon layer 35, the n-type polysilicon layer 34, and the compensation polysilicon layers 39a and 39b are formed on the same plane in the thin film structure portion 3a. The uniformity of the stress balance of the structure part 3a is improved, and the warp of the infrared absorption part 33 can be suppressed.

  In addition, since the infrared sensor A of the present embodiment includes the MOS transistor 4 for reading the output of the temperature sensing unit 30 for each pixel 2, the number of output pads Vout can be reduced, and the size and the size of the sensor can be reduced. Cost can be reduced. In the infrared sensor A of the present embodiment, the thickness of the n-type polysilicon layer that is the polysilicon layer constituting the gate electrode 36 of the MOS transistor 4 is set to the same thickness as that of the n-type compensation polysilicon layer 39b. Therefore, the gate electrode 36 of the MOS transistor 4 and the n-type compensation polysilicon layer 39b can be formed simultaneously, and the cost can be reduced by reducing the number of manufacturing steps.

(Embodiment 2)
The basic configuration of the infrared sensor A of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 7, the thermocouple type temperature sensing unit 30 includes an n-type polysilicon layer 34 and a p-type polysilicon layer. The difference is that it is constituted by a thermopile in which four thermocouples constituted by 35 and a connection part 36 are connected in series, and each pixel 2 is not provided with the MOS transistor 4 described in the first embodiment. . In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  The temperature sensing unit 30 is composed of a metal material (for example, Al) with the other end of the p-type polysilicon layer 34 and the other end of the n-type polysilicon layer 35 of the thermocouple adjacent to each other on the one surface side of the base substrate 1. -Si and the like) are joined and electrically connected.

  Here, the thermopile constituting the temperature sensing unit 30 constitutes a thermal contact on the infrared absorption unit 33 side by the one end of the n-type polysilicon layer 34, the one end of the p-type polysilicon layer 35 and the connection part 36. The other end of the p-type polysilicon layer 34, the other end of the n-type polysilicon layer 35, and the connecting portion 37 constitute a cold junction on the base substrate 1 side.

  Further, the manufacturing method of the infrared sensor of the present embodiment is substantially the same as that of the first embodiment, and is formed on the thermal insulation layer composed of the laminated film of the silicon oxide film 31 and the silicon nitride film 32, and the thermal insulation layer. The laminated structure portion of the temperature sensitive portion 30, the interlayer insulating film 50 formed so as to cover the temperature sensitive portion 30 on the surface side of the thermal insulating layer, and the passivation film 60 formed on the interlayer insulating film 50 is patterned. Thus, in the laminated structure portion patterning step for forming the thin film structure portion 3a, four rectangular slits penetrating in the thickness direction of the laminated structure portion are formed at the four corners of the projected region of the region where the cavity 11 is to be formed in the silicon substrate 1a. By forming the thin film structure portion 3a, the four slits 14 are used as etching solution introduction holes in the cavity forming step. Note that the infrared sensor A of the present embodiment does not include the MOS transistor 4 as described above, and the silicon oxide film 1b is configured only by the first silicon oxide film 31 described in the first embodiment.

  In addition, as shown in FIGS. 7 and 8, the infrared sensor A of the present embodiment includes a plurality (four in the illustrated example) of output pads Vout each having one end of each temperature sensing unit 30 connected thereto. , Each reference line includes a plurality of (two in the illustrated example) thermal type infrared detectors 3 and one reference bias pad Vref to which the other ends of the temperature sensing units 30 are commonly connected. The output of the mold infrared detector 3 can be read in time series. Note that the thermosensitive portion 30 made of a thermopile is connected to the common reference bias line 5a whose one end is electrically connected to the output pad Vout via the vertical readout line 7 and the other end is connected to the reference bias pad Vref. It is electrically connected via the bias line 5.

  For example, if the potential of the reference bias pad Vref is set to 1.65 V, the output voltage of the pixel 2 (1.65 V + the output voltage of the temperature sensing unit 30) is read from the output pad Vout. Therefore, as shown in FIG. 9, an infrared sensor A, a signal processing IC chip B that performs signal processing on an output voltage that is an output signal of the infrared sensor A, and a package in which the infrared sensor A and the signal processing IC chip B are mounted. 10, the signal processing IC chip B includes a plurality of (four in the illustrated example) output pads Vout of the infrared sensor A, as shown in FIG. A plurality of (four in the illustrated example) input pads Vin that are electrically connected to each other via a wiring 80 comprising: a pad Vref ′ for applying a reference voltage to the reference bias pad Vref of the infrared sensor A, An amplifier circuit AMP that amplifies the output voltage of the input pad Vin, and a multiplexer that alternatively inputs the output voltages of the plurality of input pads Vin to the amplifier circuit AMP. Be provided such as grasses MUX, it is possible to obtain an infrared image.

(Embodiment 3)
The basic configuration of the infrared sensor of the present embodiment is substantially the same as that of the second embodiment. As shown in FIG. 11, the thermocouple type temperature sensing unit 30 includes an n-type polysilicon layer 34 and a p-type polysilicon layer 35. And a thermopile in which two thermocouples constituted by the connection portion 36 are connected in series, and the thin film structure portion 3a is connected to the base substrate 1 by two bridge portions 3b. Since other configurations are the same as those of the second embodiment, description thereof is omitted.

(Embodiment 4)
The basic configuration of the infrared sensor of the present embodiment is substantially the same as that of the second embodiment. As shown in FIG. 12, the thin film structure 3a is formed by forming the cavity 11 so as to penetrate in the thickness direction of the silicon substrate 1a. The difference is that it is formed in a diaphragm shape. Since other configurations are the same as those of the second embodiment, description thereof is omitted.

  In each of the first to fourth embodiments, an infrared image sensor in which the pixels 2 are arranged in a two-dimensional array is illustrated as the infrared sensor A. However, the infrared sensor A includes only one thermal infrared detector 3. May be good.

1 shows an infrared sensor according to Embodiment 1, wherein (a) is a plan layout diagram of a pixel, (b) is a schematic cross-sectional view corresponding to the AA ′ cross section of (a), and (c) is a BB line of (a). It is a schematic sectional view corresponding to the section. FIG. 4A is a plan layout diagram, and FIG. 4B is an equivalent circuit diagram. It is a principal part schematic plan view of the infrared module provided with the infrared sensor same as the above. It is principal part explanatory drawing of an infrared module provided with the infrared sensor same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of an infrared sensor same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of an infrared sensor same as the above. FIG. 4 shows an infrared sensor according to Embodiment 2, wherein (a) is a plan layout view, (b) is a plan view layout diagram of a pixel, and (c) is a schematic cross-sectional view corresponding to the A-A ′ section of (b). It is an equivalent circuit diagram same as the above. It is a principal part schematic plan view of the infrared module provided with the infrared sensor same as the above. It is principal part explanatory drawing of an infrared module provided with the infrared sensor same as the above. FIG. 5 shows an infrared sensor according to Embodiment 3, wherein (a) is a plan layout view of a pixel, and (b) is a schematic sectional view corresponding to the A-A ′ section of (a). FIG. 6 shows an infrared sensor according to Embodiment 4, wherein (a) is a plan layout view of a pixel, and (b) is a schematic sectional view corresponding to the A-A ′ section of (a). A prior art example is shown, (a) is a principal part schematic plan view, (b) is a principal part schematic sectional drawing. Another example is shown, (a) is a principal part schematic plan view, (b) is a principal part schematic sectional drawing.

Explanation of symbols

A Infrared sensor B Signal processing IC chip C Package Vout Output pad Vin Input pad 1 Base substrate 2 Pixel 3a Thin film structure part 3b Bridge part 4 MOS transistor 30 Temperature sensing part 33 Infrared absorption part 34 n-type polysilicon layer 35 p-type Polysilicon layer 39a Compensation polysilicon layer (p-type compensation polysilicon layer)
39b Compensation polysilicon layer (n-type compensation polysilicon layer)
46 Gate electrode 70 Infrared absorbing film

Claims (12)

  A base substrate, a thin film structure portion having an infrared absorption portion that is formed spatially separated from the base substrate on one surface side of the base substrate and absorbs infrared rays, and a p formed across the infrared absorption portion and the base substrate And a thermocouple including a connection portion in which a p-type polysilicon layer and an n-type polysilicon layer are electrically joined to each other on the infrared incident surface side of the infrared absorption portion. It has a thermocouple type temperature sensing part that detects the temperature difference between the infrared absorption part and the base substrate, and absorbs infrared rays when forming the p-type polysilicon layer and the n-type polysilicon layer on the infrared incident surface side of the infrared absorption part. An infrared sensor characterized in that a compensation polysilicon layer is formed to protect the portion and suppress warping of the infrared absorption portion.   2. The thin film structure portion includes a bridge portion that connects the base substrate and the infrared absorption portion, and the bridge portion is connected to the base substrate at one location. The described infrared sensor.   3. The infrared sensor according to claim 1, wherein the p-type polysilicon layer, the n-type polysilicon layer, and the compensation polysilicon layer are set to have the same thickness.   4. The thin film structure portion according to claim 1, wherein the p-type polysilicon layer, the n-type polysilicon layer, and the compensation polysilicon layer are formed on the same plane. The infrared sensor according to item 1.   An infrared absorption film is formed on the side of the compensation polysilicon layer opposite to the base substrate side, where n is the refractive index of the infrared absorption film and λ is the center wavelength of the infrared ray to be absorbed. The infrared sensor according to any one of claims 1 to 4, wherein the thickness is set to λ / 4n. The compensation polysilicon layer has an impurity concentration of 10 ¹⁸ to 10 ²⁰ cm ⁻³ , and a p-type compensation polysilicon layer continuously formed integrally with the p-type polysilicon layer as the compensation polysilicon layer, and the n-type 6. The infrared sensor according to claim 1, further comprising an n-type compensating polysilicon layer formed integrally with the polysilicon layer. When the impurity concentration of the compensation polysilicon layer is 10 ¹⁸ to 10 ²⁰ cm ⁻³ , the refractive index of the compensation polysilicon layer is n, and the center wavelength of infrared light to be absorbed is λ, the p-type polysilicon layer The infrared sensor according to claim 1, wherein each of the n-type polysilicon layer and the compensation polysilicon layer has a thickness of λ / 4n. Said compensating impurity concentration of the polysilicon layer is 10 ¹⁸ ~10 ²⁰ cm ^-3, at least one of the same concentration of the same impurity as the compensation polysilicon layer and said n-type polysilicon layer and the p-type polysilicon layer The infrared sensor according to claim 1, wherein the infrared sensor is included.   The infrared sensor according to any one of claims 1 to 8, wherein pixels having the thin film structure portion are arranged in an array on the one surface side of the base substrate.   The infrared sensor according to claim 9, further comprising a MOS transistor for reading out the output of the temperature sensing unit for each pixel.   11. The infrared sensor according to claim 10, wherein the thickness of the polysilicon layer constituting the gate electrode of the MOS transistor is set to the same thickness as that of the compensation polysilicon layer.   An infrared sensor according to any one of claims 1 to 11, a signal processing IC chip that performs signal processing on an output signal of the infrared sensor, and a package on which the infrared sensor and the signal processing IC chip are mounted. The base plate of the infrared sensor has a rectangular outer peripheral shape, and all output pads for taking out an output signal output from the temperature sensing unit are arranged along one side of the outer peripheral edge, and the signal processing IC chip is The outer peripheral shape is rectangular, and all the input pads that are electrically connected to the output pads of the infrared sensor are juxtaposed along one side of the outer peripheral edge, and the base substrate and the signal processing IC chip are An infrared sensor module, wherein an infrared sensor and a signal processing IC chip are arranged so that one side is closer than another side.

Images