JP2006153511A - Humidity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a humidity sensor constituted so as to lower power consumption without lowering sensitivity as compared with a constitution that a heater is formed to the periphery of a sensitive part on one side of a conventional element forming substrate. <P>SOLUTION: The humidity sensor is equipped with an element forming substrate 1 comprising a single crystal silicon substrate, the sensitive part 2, which comprises a porous silicon layer, formed on one side of the element forming substrate 1, a pair of comb tooth-shaped electrodes 3 and 4 for detecting a change in capacity formed on the side in the thickness direction of the sensitive part 2 and the zigzag heater 7 formed on the other side of the element forming substrate 1. The heater 7 is provided in order to evaporate the moisture adsorbed on the sensitive part 2 and formed on the region overlapped with the sensitive part 2 on the other side in the thickness direction of the sensitive part 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a humidity sensor.

  Conventionally, a humidity sensor that employs a porous material as a material of a sensitive part that is sensitive to moisture is known (for example, see Non-Patent Document 1).

  For example, as shown in FIG. 15, this type of humidity sensor includes a porous silicon layer formed by making a part of one surface side of the element forming substrate 1 made of a single crystal silicon substrate porous. The sensing part 2, a pair of capacitance change detection electrodes 3 and 4 formed on the sensing part 2, and two refreshing electrodes formed around the sensing part 2 on the one surface of the element forming substrate 1 Heaters 7 and 7 are provided. Here, aluminum is adopted as the material of the electrodes 3 and 4.

  In the humidity sensor shown in FIG. 15, the planar shape of each of the pair of electrodes 3, 4 is a comb shape, the comb bone portions 3 a, 4 a of each electrode 3, 4 face each other, and the comb teeth of each electrode 3, 4 By designing the layout of both electrodes 3 and 4 so that 3b and 4b enter the comb grooves 4c and 3c of the other electrode 4 and 3, the chip size (planar size of the element forming substrate 1) can be reduced. There is also an advantage that the capacity between the pair of electrodes 3 and 4 can be made relatively large.

In forming the sensitive portion 2 in the humidity sensor described above, after forming the electrodes 3 and 4 on the one surface of the element forming substrate 1, the electrodes 3 and 4 are sensitive to the one surface side of the element forming substrate 1. After forming a protective film (not shown) made of a silicon nitride film patterned so as to protect the periphery of the portion where the portion 2 is to be formed, a part of the element forming substrate 1 is anodized to make it porous. A sensitive part 2 made of a quality silicon layer is formed. Note that the width dimension (line width) of each of the comb teeth portions 3b and 4b is set to about 10 to 12 μm, and the thickness of the protective film is set to 500 nm.
P. Furjes, et al, “Porous Silicon Based Humidity Sensor with Interdigital Electrodes and Internal Heaters”, The 16th European Conference on Solid-State Transducers, September 15-18,2002, Prague, Czech Republic, Abstract No.6-58

  In the humidity sensor shown in FIG. 15, heaters 7 are formed around the sensitive portion 2 on the one surface side of the element forming substrate 1, but the porous silicon layer constituting the sensitive portion 2 is an element. Since the thermal conductivity and heat capacity are smaller than the single crystal silicon substrate which is the formation substrate 1, the heat generated by the heaters 7 and 7 is difficult to be transmitted to the central portion of the sensitive portion 2 and the power consumption is increased. was there. Moreover, although the said nonpatent literature 1 also discloses the humidity sensor which formed the heater in the space between a pair of electrodes 3 and 4 on the sensitive part 2, in this humidity sensor, the sensitive part 2 is required. In order to secure the exposed area (sensing area) and ensure the relative alignment accuracy between the heater and each comb tooth portion 3b, 4b, the distance between the facing comb tooth portions 3b, 4b becomes large. The capacity between the pair of electrodes 3 and 4 is reduced, and the sensitivity is lowered.

  The present invention has been made in view of the above-mentioned reasons, and its purpose is to reduce the sensitivity as compared with a configuration in which a heater is formed around a sensitive portion on one surface of a conventional element forming substrate. An object of the present invention is to provide a humidity sensor capable of reducing power consumption.

  The invention according to claim 1 is a sensitive part formed of a porous layer formed on one surface side of the element forming substrate, and a pair of comb-shaped electrodes formed on one surface side in the thickness direction of the sensitive part. Each comb tooth portion includes a pair of comb-shaped electrodes that enter the comb groove portion of the other electrode, and a heater for evaporating moisture adsorbed on the sensitive portion, and the heater is provided on the other surface in the thickness direction of the sensitive portion. It is formed in the area | region which overlaps with a sensitive part in the side.

  According to the present invention, the heater is formed in a region overlapping the sensitive portion on the other surface side in the thickness direction of the sensitive portion, so that the heater is not provided between the comb tooth portions of the pair of comb-shaped electrodes. Compared to the conventional structure in which the heater is formed around the sensitive part on the surface of the element forming substrate, the heat of the heater is more easily transmitted to the entire sensitive part, so the sensitivity is lowered compared to the conventional case. The power consumption can be reduced without any problem.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the heater is in contact with the other surface of the sensitive portion.

  According to the present invention, the heat of the heater is transmitted to the sensitive part as compared with the case where a part of the element forming substrate is interposed between the heater and the sensitive part in the thickness direction of the sensitive part. Since heat efficiency is easily increased, power consumption can be further reduced.

  According to a third aspect of the present invention, in the second aspect of the invention, a recess is formed on the other surface of the element forming substrate to expose the other surface of the sensitive portion, and the sensitive portion is an inner bottom surface of the concave portion. The heater is in contact with the other surface.

  According to the present invention, the heat of the heater is more easily transmitted to the sensitive part than in the case where a part of the element forming substrate exists on the other surface side of the sensitive part, and the power consumption can be further reduced. It becomes.

  The invention according to claim 4 is a sensitive part formed of a porous layer formed on one surface side of the element forming substrate, and a pair of comb-shaped electrodes formed on one surface side in the thickness direction of the sensitive part. Each comb tooth part includes a pair of comb-shaped electrodes that enter the comb groove part of the other electrode, and a heater for evaporating water adsorbed on the sensitive part, and the heater is disposed on the one surface side of the element forming substrate. A recess is formed around the sensitive portion, and a recess is formed on the other surface of the element formation substrate to expose the other surface in the thickness direction of the sensitive portion.

  According to this invention, the heater is formed around the sensitive portion on the one surface side of the element forming substrate, and a recess is formed on the other surface of the element forming substrate to expose the other surface in the thickness direction of the sensitive portion. Therefore, compared to the conventional structure where the heater is formed around the sensitive part on the surface of the element forming substrate, the heat of the heater is more easily transmitted to the entire sensitive part, so the sensitivity is lower than the conventional one. It is possible to reduce power consumption without reducing the power consumption.

  According to a fifth aspect of the present invention, a sensitive portion made of a porous layer is formed on one surface side of the element forming substrate, and a recess is formed on the other surface of the element forming substrate to expose one surface in the thickness direction of the sensitive portion. A pair of comb-shaped electrodes, each having a comb-tooth portion of each electrode inserted into a comb groove portion of the other electrode, is formed on the one surface side of the portion, and the other surface in the thickness direction of the sensitive portion The two unit sensor structures formed with heaters for evaporating the moisture adsorbed on the sensitive part are fixed so that the heaters overlap each other.

  According to the present invention, since the pair of electrodes and the heater are in contact with different surfaces with respect to the sensitive portion in each unit sensor structure, the heater is provided between the comb teeth of the pair of comb-shaped electrodes. Compared to a conventional structure in which a heater is formed around the sensitive part on one surface of the element formation substrate, the heat of the heater is more easily transmitted to the entire sensitive part, and the planar size of the element formation substrate The sensing area of the sensitive part can be increased without increasing the value of the sensor, so that the sensitivity can be increased and the power consumption can be reduced as compared with the prior art.

  According to a sixth aspect of the present invention, in the fifth aspect of the invention, a plurality of laminated structures in which the two unit sensor structures are fixed so that the heaters overlap each other are stacked, and the sensitive portion of the two laminated structures laminated. A communication portion that communicates the space formed between the outside and the outside is provided at a key point of the laminated structure.

  According to the present invention, the sensing area can be increased without increasing the planar size of the element formation substrate as compared with the invention of claim 5, and further higher sensitivity can be achieved.

  According to the first and fourth aspects of the invention, it is possible to reduce the power consumption without lowering the sensitivity as compared with the configuration in which the heater is formed around the sensitive portion on the surface of the conventional element forming substrate. There is.

  According to the invention of claim 5, it is possible to achieve higher sensitivity and lower power consumption than in the prior art.

(Embodiment 1)
As shown in FIGS. 1 and 2, the humidity sensor of the present embodiment is formed on an element forming substrate 1 made of a single crystal silicon substrate and on one surface side (upper surface side in FIG. 2) of the element forming substrate 1. A sensitive portion 2 made of a porous silicon layer, a pair of electrodes 3 and 4 for detecting a change in capacitance formed on one surface side of the sensitive portion 2 in the thickness direction (upper surface side in FIG. 2), and other elements forming substrate 1 The heater 7 formed in the surface (lower surface in FIG. 2) is provided. In the present embodiment, the porous silicon layer constitutes the porous layer.

  The planar shape of the element forming substrate 1 is rectangular, and the planar shape of the sensitive portion 2 is also rectangular. Here, the sensitive portion 2 is formed by making a part of the one surface side of the element forming substrate 1 porous by anodizing treatment.

  Each of the pair of electrodes 3 and 4 has a comb shape in plan view, and on the one surface of the sensitive portion 2, the comb bone portions 3 a and 4 a of the electrodes 3 and 4 face each other. , 4 are arranged so that the respective comb teeth 3b, 4b enter the comb grooves 4c, 3c of the other electrodes 4, 3. Here, the electrodes 3 and 4 are electrically connected to the pads 32 and 42 for wire bonding via the wirings 31 and 41 on the one surface of the element forming substrate 1, respectively. In short, the pads 32 and 42 are formed around the sensitive portion 2 on the one surface of the element forming substrate 1. The pads 32 and 42 and the wirings 31 and 41 are made of the same material as the electrodes 3 and 4. The planar shape of each pad 32, 42 is rectangular.

  The heater 7 is provided to evaporate the moisture adsorbed on the sensitive part 2 (for refreshing the sensitive part 2 after humidity measurement), and the planar shape is formed into a folded shape. Both end portions are connected to wire bonding pads 72, 72 formed on the other surface of the element forming substrate 1. Therefore, the heater 7 can generate heat by energizing between the pads 72 and 72. Here, the heater 7 is formed in a region overlapping the sensitive portion 2 on the other surface side in the thickness direction of the sensitive portion 2. The pads 72 and 72 are made of the same material as the heater 7. The planar shape of each pad 72, 72 is rectangular.

  Although the thickness of the sensitive part 2 is set to 6 μm, the thickness of the sensitive part 2 is not particularly limited. Each of the electrodes 3 and 4 is composed of a laminated film of a Cr film having a thickness of 0.03 μm and an Au film having a thickness of 0.4 μm, and the width dimension (line width) of the comb teeth portions 3b and 4b. Is set to about 10 to 12 μm, and the heater 7 is composed of an A-Si film having a thickness of 1 μm and the width dimension (line width) is set to about 10 μm. The numerical value is not particularly limited.

  Hereinafter, the manufacturing method of the humidity sensor of this embodiment is demonstrated, referring FIG.

  First, a Cr film having a first predetermined film thickness (for example, 0.03 μm) and a second predetermined film thickness (for example, 0.4 μm) are formed on the one surface side of the element formation substrate 1 made of a single crystal silicon substrate. After the laminated film with the Au film is formed by sputtering, the laminated film is patterned by using a photolithography technique and an etching technique, whereby the electrodes 3 and 4 and the wirings 31 and 41 and the pads 32 and 42 are formed. By forming, the structure shown in FIG.

Next, a conductive layer (for example, a multilayer film such as an Ag film / Ni film / NiCr film / Cr film) having a third predetermined thickness (for example, 0.4 μm) is formed on the other surface of the element formation substrate 1. After forming the back electrode (not shown) to be formed by the vapor deposition method, the back electrode is connected to the positive side of the constant current source through the wiring, and a portion other than the surface of the portion where the anodizing treatment is performed on the element forming substrate 1 is formed. In addition, a sealant having hydrofluoric acid resistance (for example, a fluororesin such as Teflon (registered trademark)) so as not to touch an electrolytic solution used in anodizing treatment (a mixed solution of HF and ethanol mixed at 1: 1). To be sealed. And the to-be-processed object which makes the element formation board | substrate 1 the main structure is immersed in the electrolyte solution put into the processing tank. Thereafter, a platinum electrode connected to the negative side of the constant current source via a wiring is disposed so as to face the one surface side of the element forming substrate 1 in the electrolytic solution, and subsequently the back electrode is an anode, a platinum electrode Is used as a cathode, and a predetermined constant current (for example, a current having a current density of 5 mA / cm ² ) is passed between the anode and the cathode from a constant current source for a predetermined time (for example, 20 minutes). The sensitive part 2 made of a porous silicon layer having a predetermined thickness (for example, 6 μm) is formed on the one surface side of the element forming substrate 1, and then the sealing material of the object to be processed taken out from the processing tank is peeled off, The wiring shown in FIG. 3B is obtained by removing the back electrode after removing the wiring connected to the power source.

  Further, after a metal film (for example, Al-Si film) having a fourth predetermined film thickness (for example, 1 μm) is formed on the other surface of the element formation substrate 1 by a sputtering method, a photolithography technique and an etching technique are then performed. The heater 7 and the pads 72 and 72 are formed by patterning the metal film using the above, thereby obtaining the structure shown in FIG.

  In the humidity sensor of the present embodiment described above, the heater 7 is formed in a region overlapping the sensitive part 2 on the other surface side in the thickness direction of the sensitive part 2, so that a pair of comb-shaped electrodes 3, 4 is formed. Compared to the structure in which the heaters 7 are formed around the sensitive portion 2 on the one surface of the conventional element forming substrate 1 without providing a heater between the comb teeth portions 3b and 4b, the heat of the heater 7 is increased. Can easily be transmitted uniformly to the entire sensitive portion 2 (the entire other surface of the sensitive portion 2), so that the power consumption can be reduced without lowering the sensitivity as compared with the conventional case.

  By the way, in the above-described example, the planar shape of the heater 7 is a folded shape, but it may be a shape that allows the heat of the heater 7 to be transmitted uniformly to the entire sensitive portion 2, for example, as shown in FIG. Such a ladder-like planar shape may be used.

(Embodiment 2)
The humidity sensor of the present embodiment will be described with reference to FIG. 5, but the same components as those of the humidity sensor of the first embodiment are denoted by the same reference numerals and description thereof will be omitted as appropriate.

  In the humidity sensor of this embodiment, an element forming substrate 1 is constituted by a single crystal silicon substrate 1a and a single crystal silicon layer 1b epitaxially grown on one surface of the silicon substrate 1a, and is sensitive to the silicon layer 1b. Part 2 is formed, and a pair of comb-shaped electrodes 3 and 4 are formed on one surface in the thickness direction of the sensitive portion 2 (upper surface in FIG. 5), while the other surface in the thickness direction of the sensitive portion 2 (lower surface in FIG. 5) ) Is in contact with the heater 7 made of a high impurity concentration diffusion layer. The planar shape of the heater 7 is formed in a folded shape as in the first embodiment, and pads (not shown) connected to both ends of the heater 7 are in contact with, for example, the silicon layer 1b. A hole may be formed and connected to both ends of the heater 7 through the contact hole.

  Hereinafter, the manufacturing method of the humidity sensor according to the present embodiment will be described with reference to FIG. 6, but the description of the steps similar to those of the first embodiment will be appropriately omitted regarding the manufacturing method.

  First, a heater 7 made of a high-concentration impurity diffusion layer is formed on one surface side of the silicon substrate 1a using photolithography technology and impurity diffusion technology, and then the sensitive portion 2 is defined on the one surface of the silicon substrate 1a. A structure shown in FIG. 6A in which a heater 7 is embedded in an element formation substrate 1 composed of a silicon substrate 1a and a silicon layer 1b by epitaxially growing a silicon layer 1b having a thickness (for example, 6 μm) by, for example, MBE. obtain.

  Thereafter, a laminated film of a Cr film and an Au film is formed on one surface side of the element formation substrate 1 (upper surface side in FIG. 6A) by sputtering, and the above-mentioned lamination is performed using a photolithography technique and an etching technique. By patterning the film, the electrodes 3 and 4 and the wirings 31 and 41 (see FIG. 1A) and the pads 32 and 42 (see FIG. 1A) are formed, so that FIG. Get the structure shown.

Next, after forming a back electrode on the other surface (the lower surface in FIG. 6B) of the element formation substrate 1 by vapor deposition, the back electrode is connected to the positive side of the constant current source via a wiring, and the element formation substrate The sealing material having hydrofluoric acid resistance so that the portion other than the surface of the portion to be anodized in 1 does not come into contact with the electrolytic solution used in the anodizing treatment (mixed solution of HF and ethanol mixed 1: 1) After being sealed, the object to be processed mainly comprising the element forming substrate 1 is immersed in an electrolytic solution placed in a processing tank. Thereafter, a platinum electrode connected to the negative side of the constant current source via a wiring is disposed so as to face the one surface side of the element forming substrate 1 in the electrolytic solution, and subsequently the back electrode is an anode, a platinum electrode Is used as a cathode, and a predetermined constant current (for example, a current having a current density of 5 mA / cm ² ) is passed between the anode and the cathode from a constant current source for a predetermined time (for example, 20 minutes). The sensitive part 2 made of a porous silicon layer having the specified thickness (for example, 6 μm) is formed on the one surface side of the element forming substrate 1 (that is, a part of the silicon layer 1b of the element forming substrate 1 is heated from the surface to the heater). 7), and after removing the sealing material of the workpiece taken out from the processing tank, removing the wiring connected to the back surface power supply, and then removing the back surface electrode, 6 (c) Obtain to structure.

  In the humidity sensor of the present embodiment described above, the heater 7 is formed in a region overlapping the sensitive part 2 on the other surface side in the thickness direction of the sensitive part 2, so that a pair of comb-shaped electrodes 3, 4 is formed. Compared to the structure in which the heaters 7 are formed around the sensitive portion 2 on the one surface of the conventional element forming substrate 1 without providing a heater between the comb teeth portions 3b and 4b, the heat of the heater 7 is increased. Can easily be transmitted uniformly to the entire sensitive portion 2 (the entire other surface of the sensitive portion 2), so that the power consumption can be reduced without lowering the sensitivity as compared with the conventional case. Moreover, in the humidity sensor of this embodiment, since the heater 7 is in contact with the other surface in the thickness direction of the sensitive portion 2, the heater 7 and the sensitive portion 2 are arranged in the thickness direction of the sensitive portion 2 as in the first embodiment. Compared with the case where a part of the element formation substrate 1 made of a silicon substrate is interposed, the heat of the heater 7 is easily transmitted to the sensitive part 2 and the thermal efficiency is increased, so that the power consumption can be further reduced.

(Embodiment 3)
The humidity sensor of the present embodiment will be described with reference to FIG. 7, but the same components as those of the conventional example shown in FIG. 15 and the humidity sensor of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate. .

  The humidity sensor of the present embodiment includes two heaters 7 as in the conventional example shown in FIG. 15, and pads (not shown) connected to both ends of the heater 7 are on one surface of the element forming substrate 1 ( The upper surface in FIG. 7 is arranged around the sensitive portion 2, and the heater 7 and pads connected to both ends of the heater 7 (hereinafter referred to as heater pads) are the same as the electrodes 3 and 4. The difference is that it is formed of a material, and that a recess 11 that exposes the other surface (lower surface in FIG. 7) of the sensitive portion 2 is formed on the other surface (lower surface in FIG. 7) of the element formation substrate 1. . The recess 11 on the other surface of the element forming substrate 1 is formed to a depth reaching the sensitive portion 2. Further, each heater 7 is formed in a folded shape like the conventional example shown in FIG.

  Hereinafter, the manufacturing method of the humidity sensor of the present embodiment will be described with reference to FIG. 8, but the description of the same steps as those of the first embodiment will be appropriately omitted regarding the manufacturing method.

  First, a laminated film of a Cr film having a first predetermined film thickness (for example, 0.03 μm) and an Au film having a second predetermined film thickness (for example, 0.4 μm) is formed on the one surface side of the element forming substrate 1. After the film is formed by sputtering, the laminated film is patterned by using a photolithography technique and an etching technique, whereby a pair of comb-shaped electrodes 3 and 4, wirings 31 and 41, pads 32 and 42, and heaters By forming the heater pads 7 and 7, the structure shown in FIG. 8A is obtained.

  Next, after forming a back electrode (not shown) on the other surface of the element forming substrate 1 by vapor deposition, the back electrode is connected to the positive side of the constant current source via wiring, and the anode is formed on the element forming substrate 1. A part other than the surface of the part to be oxidized is sealed with a sealing material having hydrofluoric acid resistance so as not to come into contact with the electrolytic solution used in the anodizing process, and then an object to be processed mainly comprising the element formation substrate 1 is prepared. Immerse in the electrolyte placed in the treatment tank. Thereafter, a platinum electrode connected to the negative side of the constant current source via a wiring is disposed so as to face the one surface side of the element forming substrate 1 in the electrolytic solution, and subsequently the back electrode is an anode, a platinum electrode The sensitive part 2 made of a porous silicon layer on the one surface side of the element forming substrate 1 by performing an anodic oxidation treatment using a constant current source between the anode and the cathode as a cathode for a predetermined time. After that, the sealing material of the object to be processed taken out from the processing tank is peeled off, the wiring connected to the back surface power supply is removed, and then the back surface electrode is removed, whereby the structure shown in FIG. Get.

  Thereafter, the entire element forming substrate 1 is covered with a protective film (for example, a silicon nitride film), and then the recess 11 is formed on the other surface of the element forming substrate 1 using a photolithography technique and an etching technique. The protective film is patterned so that the part is exposed, and the element forming substrate 1 is anisotropically etched from the other surface to a depth reaching the sensitive portion 2 with an alkaline solution (for example, a KOH solution heated to 70 ° C.). Then, the recess 11 is formed, and then the protective film is removed to obtain the structure shown in FIG.

  In the humidity sensor of the present embodiment described above, the heater 7 is formed around the sensitive portion 2 on the one surface side of the element forming substrate 1, and the above-mentioned thickness direction of the sensitive portion 2 is formed on the other surface of the element forming substrate 1. Since the recess 11 exposing the other surface is formed, the heat of the heater 7 is higher than that of the conventional structure in which the heaters 7 are formed around the sensitive portion 2 on one surface of the element forming substrate 1. Since it becomes easy to transmit to the whole of the sensitive part 2, it becomes possible to reduce power consumption without lowering the sensitivity as compared with the prior art.

(Embodiment 4)
The humidity sensor of the present embodiment will be described with reference to FIG. 9, but the same components as those of the humidity sensor of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The basic configuration of the humidity sensor of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 9, the other surface (the lower surface in FIG. 9) of the element forming substrate 1 is arranged in the thickness direction of the sensitive portion 2. A recess 11 that exposes the other surface (the lower surface in FIG. 9) is formed, and the heater 7 is in contact with the other surface of the sensitive portion 2 that is the inner bottom surface of the recess 11.

  Hereinafter, the manufacturing method of the humidity sensor of the present embodiment will be described with reference to FIG. 10, but the description of the same steps as those of the first embodiment will be appropriately omitted regarding the manufacturing method.

  First, a Cr film having a first predetermined film thickness (for example, 0.03 μm) and a second predetermined film thickness (for example, 0.4 μm) are formed on the one surface side (the upper surface side in FIG. 9) of the element formation substrate 1. After the laminated film with the Au film is formed by sputtering, the electrodes 3 and 4, the wirings 31 and 41, and the pads 32 and 42 are formed by patterning the laminated film using a photolithography technique and an etching technique. By forming, the structure shown in FIG.

  Next, after forming a back electrode (not shown) on the other surface of the element forming substrate 1 by vapor deposition, the back electrode is connected to the positive side of the constant current source via wiring, and the anode is formed on the element forming substrate 1. A part other than the surface of the part to be oxidized is sealed with a sealing material having hydrofluoric acid resistance so as not to come into contact with the electrolytic solution used in the anodizing process, and then an object to be processed mainly comprising the element formation substrate 1 is prepared. Immerse in the electrolyte placed in the treatment tank. Thereafter, a platinum electrode connected to the negative side of the constant current source via a wiring is disposed so as to face the one surface side of the element forming substrate 1 in the electrolytic solution, and subsequently the back electrode is an anode, a platinum electrode The sensitive part 2 made of a porous silicon layer on the one surface side of the element forming substrate 1 by performing an anodic oxidation treatment using a constant current source between the anode and the cathode as a cathode for a predetermined time. After that, the sealing material of the object to be processed taken out from the processing tank is peeled off, the wiring connected to the back surface power supply is removed, and then the back surface electrode is removed, whereby the structure shown in FIG. Get.

  Thereafter, the entire element forming substrate 1 is covered with a protective film (for example, a silicon nitride film), and then the recess 11 is formed on the other surface of the element forming substrate 1 using a photolithography technique and an etching technique. The protective film is patterned so that the part is exposed, and the element forming substrate 1 is anisotropically etched from the other surface to a depth reaching the sensitive portion 2 with an alkaline solution (for example, a KOH solution heated to 70 ° C.). Then, the recess 11 is formed, and then the protective film is removed. Thereafter, a metal film (for example, an Al—Si film) having a predetermined film thickness (for example, 1 μm) is formed on the other surface side of the element formation substrate 1 by a sputtering method, and then the above-mentioned film is formed using a lithography technique and an etching technique. By patterning the metal film to form the heater 7 and the pads 72 and 72 (see FIG. 1B), the structure shown in FIG. 10C is obtained.

  Thus, in the humidity sensor of the present embodiment, the recess 11 that exposes the other surface of the sensitive portion 2 is formed on the other surface of the element forming substrate 1, and the sensitive portion 2 that is the inner bottom surface of the concave portion 11 is formed. Since the heater 7 is in contact with the other surface, the heat of the heater 7 is higher than that when the element forming substrate 1 made of a silicon substrate is present on the other surface side of the sensitive portion 2 as in the first embodiment. It becomes easier to be transmitted to the sensitive part 2, and the power consumption can be further reduced.

(Embodiment 5)
Although the humidity sensor of this embodiment is demonstrated referring FIG. 11, the same code | symbol is attached | subjected to the component similar to the humidity sensor of Embodiment 1, and description is abbreviate | omitted suitably.

  In the humidity sensor of the present embodiment, as shown in FIG. 11, a sensitive portion 2 made of a porous silicon layer is formed on one surface side of the element forming substrate 1 made of a silicon substrate (the upper surface side in FIG. 12C). A recess 11 is formed on the other surface of the element forming substrate 1 (the lower surface in FIG. 12C) to expose one surface in the thickness direction of the sensitive portion 2 (the lower surface in FIG. 12C). Two unit sensor structures 10 each having a pair of comb-shaped electrodes 3 and 4 formed on one surface and a heater 7 formed on the other surface in the thickness direction of the sensitive portion 2 (upper surface in FIG. 12C) 7 are fixed in an overlapping manner. Here, the two unit sensor structures 10 may be bonded by a known bonding technique.

  Hereinafter, the manufacturing method of the humidity sensor of the present embodiment will be described with reference to FIG. 12, but the description of the same steps as those of the first embodiment will be appropriately omitted regarding the manufacturing method.

  First, a laminated film of a Cr film having a first predetermined film thickness (for example, 0.03 μm) and an Au film having a second predetermined film thickness (for example, 0.4 μm) is formed on the one surface side of the element forming substrate 1. After the film formation by the sputtering method, the heater 7 and the pads 72 and 72 (see FIG. 1B) are formed by patterning the laminated film using the photolithography technique and the etching technique, thereby forming the structure shown in FIG. The structure shown in (a) is obtained.

  Next, after forming a back electrode (not shown) on the other surface of the element forming substrate 1 by vapor deposition, the back electrode is connected to the positive side of the constant current source via wiring, and the anode is formed on the element forming substrate 1. A part other than the surface of the part to be oxidized is sealed with a sealing material having hydrofluoric acid resistance so as not to come into contact with the electrolytic solution used in the anodizing process, and then an object to be processed mainly comprising the element formation substrate 1 is prepared. Immerse in the electrolyte placed in the treatment tank. Thereafter, a platinum electrode connected to the negative side of the constant current source via a wiring is disposed so as to face the one surface side of the element forming substrate 1 in the electrolytic solution, and subsequently the back electrode is an anode, a platinum electrode The sensitive part 2 made of a porous silicon layer on the one surface side of the element forming substrate 1 by performing an anodic oxidation treatment using a constant current source between the anode and the cathode as a cathode for a predetermined time. After that, the above sealing material of the object to be processed taken out from the processing tank is peeled off, the wiring connected to the back surface power supply is removed, and then the back surface electrode is removed, whereby the structure shown in FIG. Get.

  Thereafter, the entire element forming substrate 1 is covered with a protective film (for example, a silicon nitride film), and then the recess 11 is formed on the other surface of the element forming substrate 1 using a photolithography technique and an etching technique. The protective film is patterned so that the part is exposed, and the element forming substrate 1 is anisotropically etched from the other surface to a depth reaching the sensitive portion 2 with an alkaline solution (for example, a KOH solution heated to 70 ° C.). Then, the recess 11 is formed, and then the protective film is removed. Thereafter, a metal film (for example, an Al—Si film) having a predetermined film thickness (for example, 1 μm) is formed on the other surface side of the element formation substrate 1 by a sputtering method, and then the above-mentioned film is formed using a lithography technique and an etching technique. By patterning the metal film, a pair of comb-shaped electrodes 3 and 4 and wirings 31 and 41 (see FIG. 1A) and pads 32 and 42 (see FIG. 1A) are formed. A unit sensor structure 10 having the structure shown in FIG.

  Subsequently, the two unit sensor structures 10 are bonded together by overlapping the two unit sensor structures 10 so that the heaters 7 overlap each other and joining the surfaces of the unit sensor structures 10 to each other, as shown in FIG. ) Is obtained.

  In the humidity sensor of the present embodiment described above, the pair of comb-shaped electrodes 3 and 4 and the zigzag heater 7 are in contact with different surfaces with respect to the sensitive portion 2 in each unit sensor structure 10. Therefore, the heaters 7 and 7 are formed around the sensitive portion 2 on one surface of the conventional element forming substrate 1 without providing a heater between the comb teeth 3b and 4b of the pair of comb-shaped electrodes 3 and 4. Compared to the configuration, the heat of the heater 7 is easily transmitted uniformly to the entire sensitive portion 2, and the sensing area of the sensitive portion 2 can be increased without increasing the planar size of the element forming substrate 1, Compared with the prior art, the sensitivity can be increased and the power consumption can be reduced.

(Embodiment 6)
The basic configuration of the humidity sensor of the present embodiment is substantially the same as that of the fifth embodiment, and as shown in FIG. 13, a laminated structure in which two unit sensor structures 10 are fixed so that the heaters 7 overlap each other (FIG. 11). And a communication portion (not shown) that communicates the space formed between the sensitive portions 2 and 2 of the two laminated structures stacked with the outside is provided at the main point of the laminated structure. There is a feature in that.

  Hereinafter, the manufacturing method of the humidity sensor according to the present embodiment will be described with reference to FIG. 14, but the description of the steps similar to those of the fifth embodiment will be appropriately omitted regarding the manufacturing method.

  First, similarly to the manufacturing method described in the fifth embodiment, the heater 7 and the pads 72 and 72 (see FIG. 1B) are formed on the one surface side of the element formation substrate 1 to obtain FIG. By obtaining the structure shown in a) and then forming the sensitive part 2 made of a porous silicon layer on the one surface side of the element forming substrate 1 in the same manner as in the manufacturing method described in the fifth embodiment. The structure shown in 14 (b) is obtained. Thereafter, similar to the manufacturing method described in the fifth embodiment, the recess 11 is formed on the other surface of the element forming substrate 1, and then the pair of comb-shaped electrodes 3 and 4 and the wirings 31 and 41 ( The unit sensor structure 10 having the structure shown in FIG. 14C is obtained by forming the pads 32 and 42 (see FIG. 1A) and the pads 32 and 42 (see FIG. 1A). Subsequently, similarly to the manufacturing method described in the fifth embodiment, the two unit sensor structures 10 are overlapped so that the heaters 7 overlap each other, and the surfaces of the unit sensor structures 10 are joined (two unit sensor structures). By fixing the body 10), a laminated structure shown in FIG. 14D is obtained.

  Then, a structure shown in FIG. 14E is obtained by laminating a plurality of (here, three) laminated structures.

  In the humidity sensor of the present embodiment described above, the sensing area can be increased without increasing the planar size of the element formation substrate 1 as compared with the humidity sensor of the fifth embodiment, and further higher sensitivity can be achieved ( In short, the sensing area can be increased without increasing the plane size of the entire sensor, and the sensitivity can be further increased.

  By the way, in each said embodiment, although Si is employ | adopted as a material of the element formation board | substrate 1, the material of the element formation board | substrate 1 is not restricted to Si, For example, anodic oxidation, such as Ge, SiC, GaP, GaAs, InP, etc. Other semiconductor materials that can be made porous by processing may be used. In short, in each of the above embodiments, the porous silicon layer constitutes the porous layer, but the porous layer is not limited to the porous silicon layer. In each of the above embodiments, the element forming substrate 1 employs a single crystal silicon substrate or a single crystal silicon substrate and a substrate epitaxially grown on the silicon substrate. You may employ | adopt what formed the polycrystalline-silicon layer on the single crystal silicon substrate.

Embodiment 1 is shown, (a) is a schematic perspective view, (b) is a schematic bottom view. It is a schematic sectional drawing which shows the same as the above. It is principal process sectional drawing for demonstrating the manufacturing method same as the above. It is a schematic bottom view which shows the other structural example same as the above. FIG. 6 is a schematic cross-sectional view showing a second embodiment. It is principal process sectional drawing for demonstrating the manufacturing method same as the above. FIG. 6 is a schematic cross-sectional view showing a third embodiment. It is principal process sectional drawing for demonstrating the manufacturing method same as the above. FIG. 6 is a schematic cross-sectional view showing a fourth embodiment. It is principal process sectional drawing for demonstrating the manufacturing method same as the above. FIG. 6 is a schematic cross-sectional view showing a fifth embodiment. It is principal process sectional drawing for demonstrating the manufacturing method same as the above. FIG. 9 is a schematic cross-sectional view showing a sixth embodiment. It is principal process sectional drawing for demonstrating the manufacturing method same as the above. A prior art example is shown, (a) is a schematic perspective view, (b) is a schematic sectional view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Element formation board 2 Sensing part 3, 4 Electrode 3a, 4a Comb bone part 3b, 4b Comb tooth part 3c, 4c Comb groove part 7 Heater 31, 41 Wiring 32, 42, 72 Pad

Claims (6)

  A sensitive part formed of a porous layer formed on one surface side of the element forming substrate, and a pair of comb-shaped electrodes formed on one surface side in the thickness direction of the sensitive part, each comb tooth part of each electrode being the other And a heater for evaporating the moisture adsorbed on the sensitive part, the heater overlaps the sensitive part on the other side in the thickness direction of the sensitive part. A humidity sensor formed in a region.   The humidity sensor according to claim 1, wherein the heater is in contact with the other surface of the sensitive portion.   A recess is formed on the other surface of the element forming substrate to expose the other surface of the sensitive portion, and the heater is in contact with the other surface of the sensitive portion which is an inner bottom surface of the concave portion. The humidity sensor according to claim 2.   A sensitive part formed of a porous layer formed on one surface side of the element forming substrate, and a pair of comb-shaped electrodes formed on one surface side in the thickness direction of the sensitive part, each comb tooth part of each electrode being the other And a heater for evaporating the moisture adsorbed on the sensitive part, and the heater is formed around the sensitive part on the one surface side of the element forming substrate. A humidity sensor, wherein a recess for exposing the other surface in the thickness direction of the sensitive portion is formed on the other surface of the element forming substrate.   A sensitive part made of a porous layer is formed on one surface side of the element forming substrate, a recess is formed on the other surface of the element forming substrate to expose one surface in the thickness direction of the sensitive part, and a pair is formed on the one surface side of the sensitive part. A pair of comb-shaped electrodes in which each comb tooth portion of each electrode enters the comb groove portion of the other electrode is formed, and moisture adsorbed by the sensitive portion on the other surface in the thickness direction of the sensitive portion A humidity sensor characterized in that two unit sensor structures each having a heater for evaporating water are fixed so that the heaters overlap each other.   A plurality of laminated structures in which the two unit sensor structures are fixed so that the heaters overlap each other are stacked, and a communication portion that communicates the space formed between the sensitive portions of the two laminated structures stacked with the outside is provided. The humidity sensor according to claim 5, wherein the humidity sensor is provided at an important point of the laminated structure.

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