Thin-film thermistors and electronic devices

Abstract

The present invention provides a thin-film thermistor and electronic device that can further reduce the peeling of the protective film. [Solution] The thin-film thermistor (1) comprises an insulating substrate, a temperature sensing section located on the first surface of the insulating substrate, and a protective layer covering the temperature sensing section. The temperature sensing section has a temperature sensing layer (31), and a first electrode (321) and a second electrode (322) spaced apart from each other and connected to the temperature sensing layer (31). The first electrode (321) and the second electrode (322) each include a current collecting section (812, 822) and a first conductor section (811) and a second conductor section (821) extending from the current collecting sections (812, 822). The current collecting sections (812, 822) have recesses (83, 84) in the contact portion with the protective layer on the second surface (32a) opposite to the surface in contact with the temperature sensing layer (31).

Description

Technical Field

[0001] The present disclosure relates to thin film thermistors and electronic devices.

Background Art

[0002] A thin film thermistor having a temperature-sensitive layer and a set of electrodes spaced apart on the temperature-sensitive layer is suitably used as a small element for measuring temperature. The electrodes are each connected to a lead-out electrode via a current collector. The electrode patterns on these temperature-sensitive layers are covered and protected by a protective film. Patent Document 1 discloses a technique for reducing peeling of a connection pad by fixing lead-out electrode lines to both the connection pad and the ceramic substrate. Further, Patent Document 1 discloses a technique for increasing the bonding strength of the protective film by having a portion where a part of the temperature-sensitive layer, the electrode, and the connection pad are directly joined to the protective film on the ceramic substrate, and reducing peeling of the protective film and the electrode film that are easily peeled off simultaneously with the connection pad.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, on the current collector, since the current collector and the protective film are continuously joined, the protective film is relatively likely to peel off. Therefore, a thin film thermistor and an electronic device capable of further reducing peeling of the protective film are provided.

Means for Solving the Problems

[0005] One aspect of the present disclosure is [1] an insulating substrate, A temperature sensing unit located on the first surface of the insulating substrate, having a temperature-sensing layer and a plurality of electrodes spaced apart from each other and connected to the temperature-sensing layer, A protective layer covering the temperature measuring section, Equipped with, Each of the aforementioned plurality of electrodes includes a current collector and a conductor extending from the current collector. The current collector has a recess in the portion of the second surface opposite to the surface in contact with the temperature-sensing layer that is in contact with the protective layer. Thin-film thermistor. [2] The thin-film thermistor according to [1], wherein the protective layer has a recess on a third surface opposite to the surface in contact with the second surface in a plan view that overlaps with the current collector, corresponding to the recess of the current collector. [3] Each of the plurality of electrodes includes a connection pad that is in contact with a portion of the second surface and is exposed from the portion without the protective layer and connectable to the outside, The recess extends from a position that does not overlap with the connecting pad in a plan view to a position that overlaps with the connecting pad in a plan view. A thin-film thermistor as described in [1] or [2]. [4] The depth of the recess is 10 nm or more, a thin-film thermistor according to any one of [1] to [3]. [5] The depth of the recess is 7.5% or more of the thickness of the current collector, the thin-film thermistor according to any one of [1] to [3]. [6] The current collector is a thin-film thermistor according to any one of [1] to [5], having a plurality of recesses. [7] The electrode is a thin-film thermistor according to any one of [1] to [6], wherein the conductive portion has a plurality of linear members, and the linear members are comb-shaped electrodes that extend from the current collector along the temperature-sensing layer. [8] The temperature-sensing layer comprises a metal oxide containing manganese, cobalt, zinc, and oxygen, as described in any one of [1] to [7]. [9] The plurality of electrodes are connected to the current collector and include connection pads that are exposed from the portion without the protective layer and can be connected to the outside, The thin-film thermistor according to any one of [1] to [8], wherein the conductor portion and the current collector portion have a titanium layer on the second surface side, and the titanium layer does not contact the lower surface of the connection pad. An electronic device comprising a thin-film thermistor as described in any one of

[10] [1] to [9]. [Effects of the Invention]

[0006] According to this disclosure, peeling of the protective film in a thin-film thermistor can be further reduced. [Brief explanation of the drawing]

[0007] [Figure 1] This is an overall perspective view of the thin-film thermistor of this embodiment. [Figure 2] This is a schematic cross-sectional view showing an example of an electronic device equipped with a thin-film thermistor. [Figure 3] This is a plan view of a thin-film thermistor. [Figure 4] This is a cross-sectional view of a thin-film thermistor. [Figure 5] This is a plan view showing another example of a recess. [Figure 6] This is a cross-sectional view showing another example of a recess. [Modes for carrying out the invention]

[0008] The embodiments will be described below with reference to the drawings. Figure 1 is an overall perspective view of the thin-film thermistor 1 of this embodiment. The thin-film thermistor 1 comprises an insulating substrate 2, a temperature sensing section 3, and a protective layer 4.

[0009] The insulating substrate 2 may, for example, have a silicon substrate 21 and an insulating film 22 overlapping (see Figure 4(c)). The insulating film 22 only needs to have a thickness appropriate for maintaining insulation, for example, 0.1 μm or more. The silicon substrate 21 may be a crystalline substrate or an amorphous substrate. The thickness of the silicon substrate 21 may be, for example, about 50 μm. Alternatively, the insulating substrate 2 may be a quartz glass substrate or an alumina substrate.

[0010] The temperature sensing unit 3 outputs an electrical signal corresponding to the temperature. The temperature sensing unit 3 is located on the first surface 2a (see Figure 4(c)), which is the +z side surface of the insulating substrate 2, and has a temperature sensing layer 31 and an electrode 32. Hereafter, the +z direction will be considered the upper side of the thin film thermistor 1, and the -z direction will be considered the lower side of the thin film thermistor 1. The temperature sensing layer 31 is a thin film of a resistance thermometer whose resistivity changes according to temperature. The thickness of the temperature sensing layer is, for example, several hundred nm or less, and may be one hundred nm or less. On the other hand, the thickness of the temperature sensing layer 12 may be 20 nm or more. The temperature sensing layer 31 may contain, for example, a metal oxide containing manganese (Mn), cobalt (Co), zinc (Zn), and oxygen (O). That is, the atomic composition of the temperature sensing layer 31 is Mn x Co y Zn z O (1-w-x-y-z)It may also be expressible as such. The atomic composition percentage w represents the amount of incorporation of other transition metals, rare earth elements, etc. described above. The temperature-sensitive layer 31 may contain other 3d transition metals such as iron Fe and other 4d transition metals such as yttrium Y as other transition metals. Further, the temperature-sensitive layer 31 may contain lanthanum La as a rare earth element. The temperature-sensitive layer 31 may have a cubic spinel crystal structure. By including zinc Zn in the temperature-sensitive layer 31, a high B constant can be easily obtained. For example, the B constant may be 3500K to 7000K. On the other hand, by making the atomic composition percentage z of zinc smaller than x and y, the resistivity of the film can be reduced. Also, it leads to the compatibility of the stable structure of the thin-film thermistor 1 and the increase in sensitivity. By forming such a temperature-sensitive layer 31 in the range of 300°C to 680°C, the film strain is reduced compared to the temperature-sensitive layer obtained by performing heat treatment after film formation at room temperature. Further, the temperature-sensitive layer 31 may contain some or all of other components that may be incorporated during manufacturing, such as carbon C, nitrogen N, hydrogen H, and argon Ar. Alternatively, the temperature-sensitive layer 31 may have any configuration having the property that the resistivity changes according to temperature.

[0011] In order to reduce the peeling between the temperature-sensitive layer 31 and the electrode 32, the magnitude of the surface irregularities of the temperature-sensitive layer 31 may be within an appropriate range. The irregularities of the temperature-sensitive layer 31 are measured in an arbitrary cross-section along the ±z direction of the thin-film thermistor 1. For example, the irregularities of the temperature-sensitive layer 31 may be measured at a magnification of, for example, 500,000 times of the field of view where the interface between the temperature-sensitive layer 31 and the electrode 32 enters by a scanning transmission electron microscope (STEM). In this measurement, the magnitude of the irregularities may be represented by the value [%] obtained by dividing the difference in the z component between the position of the interface on the most +z side and the position of the interface on the most -z side by the thickness of the temperature-sensitive layer 31. The thickness of the temperature-sensitive layer 31 may be determined by X-ray reflectivity measurement (XRR). The magnitude of the irregularities of the temperature-sensitive layer 31 may be, for example, 5% or more, 8% or more, or 15% or more. On the other hand, the magnitude of the irregularities of the temperature-sensitive layer 31 may be, for example, 50% or less, 30% or less, or 20% or less.

[0012] The electrodes 32 are located at intervals from each other in the y direction and each are in contact with the temperature-sensitive layer 31. Here, they include the first electrode 321 and the second electrode 322. In the present disclosure, the y direction is perpendicular to the z direction and is the direction along the longitudinal direction of the thin-film thermistor 1. The x direction is the direction perpendicular to the y direction and the z direction. The resistance value between the electrodes 32 changes according to the temperature of the temperature-sensitive layer 31. Therefore, the above temperature can be obtained by measuring the electrical signal between the electrodes 32. The structure of the electrodes 32 will be described later.

[0013] In order to reduce the peeling between the electrode 32 and the protective layer 4, the unevenness of the electrode 32 may be affected by the unevenness of the temperature-sensitive layer 31. The unevenness of the electrode 32 is measured in an arbitrary cross-section along the ±z direction of the thin-film thermistor 1. For example, the unevenness of the electrode 32 may be measured at a magnification of the field of view where the surface on the side of the protective layer 4 in the electrode 32 enters, for example, 500,000 times, by a scanning transmission electron microscope (STEM). In this measurement, the size of the unevenness may be represented by the value [%] obtained by dividing the difference in the z component between the position of the surface on the most +z side and the position of the surface on the most -z side by the thickness of the electrode 32. The thickness of the electrode 32 may be measured as the average thickness of the thickest part and the thinnest part in a STEM cross-section with a magnification of the field of view where the entire thickness of the electrode 32 enters, for example, 500,000 times. Also, when the electrode 32 is substantially trapezoidal, the part corresponding to the hypotenuse may be excluded from the measurement area. The size of the unevenness of the electrode 32 may be, for example, such that the ratio obtained by dividing the size of the unevenness by the average electrode thickness measured by measuring the thickest part and the thinnest part on the STEM cross-section is 14% or more, may be 18% or more, may be 19% or more. On the other hand, the size of the unevenness of the electrode 32 may be, for example, such that the above ratio is 50% or less, may be 40% or less, may be 30% or less.

[0014] The protective layer 4 may cover the first surface 2a of the insulating substrate 2 and the upper surface of the temperature sensing section 3. However, the protective layer 4 does not cover the upper and side surfaces of the connection pads 813 and 823 (see Figure 3), which will be described later. The upper surface of the temperature sensing section 3 includes the second surface 32a. The protective layer 4 is an insulating film and may be silicon dioxide, silicon nitride, or the like. The protective layer 4 may be light-transmitting, allowing the covered temperature sensing section 3 to be visible from the outside. The thickness of the protective layer 4 may be 10 nm or more and 500 nm or less. The protective layer 4 can reduce thermal warping of the insulating substrate 11. The protective layer 4 may be, for example, 30 nm or more in thickness, taking into consideration reliable insulation of the temperature sensing section 3. The upper surface of the protective layer 4 that is in contact with the outside is the third surface 4a. Furthermore, when mounting the thin-film thermistor 1 in a package, even if conductive adhesive or the like protrudes from the electrode pad and spreads onto a part of the electrode 32, the protective layer 4 can reduce the risk of short circuits.

[0015] The +z-side irregularities of the protective layer 4 may be affected by the irregularities of the temperature-sensing layer 31 and the electrodes 32. The irregularities of the protective layer 4 are measured in any cross-section along the ±z direction of the thin-film thermistor 1. For example, the thickness of the protective layer 4 may be measured by a scanning transmission electron microscope (STEM) at a magnification of the field of view that includes the surface of the protective layer 4, for example, 500,000 times. In this measurement, the magnitude of the irregularities may be expressed as a value [%] obtained by dividing the difference in the z component between the position of the surface of the protective layer 4 on the +z side and the position of the surface of the protective layer 4 on the -z side by the thickness of the protective layer 4. The ratio of the magnitude of the irregularities of the protective layer 4 to the average electrode thickness measured between the thickest and thinnest points on the STEM cross-section may be, for example, 5% or more, 10% or more, or 15% or more. On the other hand, the magnitude of the irregularities of the protective layer 4 may be 50% or less, 30% or less, or 20% or less.

[0016] Figure 2 is a schematic cross-sectional view showing an example of an electronic device 100 equipped with a thin-film thermistor 1. This schematic cross-sectional view schematically shows the cross-section of the thin-film thermistor 1 in the plane containing cross-sectional line ii in Figure 1 when the thin-film thermistor 1 is mounted on the electronic device 100. The electronic device 100 comprises a package 503, a piezoelectric vibration element 502, a thin-film thermistor 1, and a cover 504.

[0017] Package 503 has a recess 503a. The recess 503a may have a step inside. An electrode pad 533 is located on the upper step of the step. The piezoelectric vibration element 502 may be bonded to the electrode pad 533 via a bonding member 512. Electrode pads 531 and 532 are located on the lower step of the recess 503a. The thin film thermistor 1 may be bonded to the electrode pads 531 and 532 via a bonding member 511. The electrode 32 of the thin film thermistor 1 may be electrically connected to the electrode pads 531 and 532 via a wiring conductor 33 running along the side, as shown in Figure 2(a). Alternatively, the electrode 32 of the thin film thermistor 1 may be electrically connected to the electrode pads 531 and 532 by a bonding wire 514, as shown in Figure 2(b). Furthermore, as shown in Figure 2(c), the connection surface of the thin-film thermistor 1 may face the electrode pads 531 and 532 of the package 503 and be electrically connected directly by a wiring conductor such as a conductive paste. The opening surface of the recess 503a is sealed by the lid 504. The sealed recess 503a may be filled with a specific gas or may be vacuum sealed.

[0018] Package 503 is a housing made of, for example, a ceramic material, a semiconductor material, or a glass material, or a combination thereof. The package 503 also has conductive signal lines on its interior and surface. These signal lines include those for power supply and grounding. The signal lines are made of, for example, molybdenum, copper, silver, or tungsten. Some or all of the signal lines may have nickel plating and gold plating laminated on their surfaces.

[0019] The piezoelectric vibrating element 502 may be, for example, a quartz crystal oscillator. The piezoelectric vibrating element 502 may have a connecting electrode at one end in the longitudinal direction in a plan view, and this connecting electrode may be joined to the electrode pad 533.

[0020] The bonding members 511 and 512 may be heat-cured conductive adhesives. The conductive adhesive may be, for example, a silver paste containing silver particles. Bonding members 511 and 512 may be different from each other. The conductive adhesive may be applied to the electrode pads 531 to 533 in a substantially elliptical area. Bonding members 511 and 512 can be bonded by spreading to an appropriate area depending on the wettability of the electrode pads 531 to 532. Note that if the bonding wire 514 directly connects the electrode 32 and the electrode pads 531 and 532, the bonding member 511 is necessary for fixing to the package 503, but it does not need to be conductive.

[0021] The lid 504 is a flat plate of metal conductor, and may be a metal containing, for example, iron, copper, nickel, cobalt, molybdenum, or tungsten, or an alloy thereof, such as Kovar. The bonding material used for sealing with the lid 504 may be bondable by heating within a temperature range that does not adversely affect the properties of the thin-film thermistor 1 sealed inside. For example, the lid 504 may be bonded with a brazing material. A frame-shaped metallized layer may be located between the upper end of the package 503 and the lid 504. The metallized layer may be a plated layer or a coated and fired conductive layer.

[0022] Figure 3 is a plan view of the thin-film thermistor 1, viewed from the +z side. The first electrode 321 includes a first conductor portion 811, a current collector portion 812, and a connecting pad 813, etc. The first conductor portion 811 has a plurality of linear members. One end of each linear member of the first conductor portion 811 is connected to the current collector portion 812. Each linear member extends from the current collector portion 812 along the temperature-sensitive layer 31 in the -y direction. The length of the linear member is greater than the width of the linear member. As a result, the first conductor portion 811 and the current collector portion 812 form a comb-tooth electrode. The first conductor portion 811 and the current collector portion 812 may be made of the same material, have an integral shape and the same thickness. The thickness may be, for example, 20 nm or more and 200 nm or less, or 130 nm or more. The first conductor portion 811 and the current collector portion 812 may be made of the same conductive material, for example, they may contain some or all of platinum Pt, palladium Pd, gold Au, or titanium Ti. When the second conductor portion 821 and the current collector portion 822 contain multiple materials, layers of each material may be laminated, or layers of alloys of the multiple materials may be included. From the viewpoint of reducing delamination, it is preferable that the first electrode 321 be made of a material with a coefficient of linear expansion similar to that of the temperature-sensing layer 31. For example, if the coefficient of linear expansion of the temperature-sensing layer 31 is between the value of platinum Pt and the value of gold Au, and is closer to the value of gold Au, then in the first conductor portion 811 and the current collector portion 812, the stress generated during heating is reduced if the proportion of gold Au is higher than the sum of the proportions of platinum Pt and titanium Ti. For example, the ratio of the sum of the thickness of the platinum Pt layer and the titanium Ti layer to the thickness of the gold Au layer may be 1% or more and 60% or less. Such a ratio reduces delamination of the first conductor portion 811 and the current collector portion 812 from the temperature-sensing layer 31. The current collector portion 812 is electrically connected to a connecting pad 813 located on the opposite side from the first conductor portion 811 in the xy plane. The connection pad 813 is connected to external terminals and wiring, and outputs electrical signals.

[0023] The second electrode 322 includes a second conductor portion 821, a current collector portion 822, and a connecting pad 823, etc. The second conductor portion 821 has the same number of linear members as the first conductor portion 811, or the same number ±1. In addition, in order to obtain a desired resistance value in accordance with the resistivity of the temperature-sensing layer 31, the length of each tooth of the outermost comb teeth in the +x direction and / or -x direction may be shorter than the length of each tooth of the comb teeth located further inward. One end of each linear member of the second conductor portion 821 is connected to the current collector portion 822. Each linear member extends from the current collector portion 822 along the temperature-sensing layer 31 in the +y direction. Thus, the second conductor portion 821 and the current collector portion 822 form a comb-tooth electrode. The second conductor portion 821 and the current collector portion 822 may be made of the same material, structure, and thickness as the first conductor portion 811 and the current collector portion 812. For example, the second conductor portion 821 and the current collector portion 822 may contain some or all of platinum Pt, palladium Pd, gold Au, and titanium Ti. From the viewpoint of reducing peeling, it is preferable that the second electrode 322 be made of a material with a coefficient of thermal expansion similar to that of the temperature-sensing layer 31. For example, if the coefficient of thermal expansion of the temperature-sensing layer 31 is between the value of platinum Pt and the value of gold Au, and is closer to the value of gold Au, then in the second conductor portion 821 and the current collector portion 822, the stress generated during heating is reduced if the proportion of gold Au is higher than the sum of the proportions of platinum Pt and titanium Ti. For example, the ratio of the sum of the thickness of the platinum Pt layer and the titanium Ti layer to the thickness of the gold Au layer may be 1% or more and 60% or less. Such a ratio reduces peeling of the second conductor portion 821 and the current collector portion 822 from the temperature-sensing layer 31.

[0024] The current collector 822 is electrically connected to a connecting pad 823 located on the opposite side of the second conductor 821 in the xy plane. If the distance between the tip of the first conductive part 811 and the current collector 822, and the distance between the tip of the second conductive part 821 and the current collector 812 are both d2, then the distance d2 may be d2 > d1 with respect to the distance d1 between adjacent first conductive parts 811 and second conductive parts 821 in the x direction. Alternatively, d2 = d1. When d2 = d1, the cross-sectional area of ​​the current path in the temperature-sensitive layer 31 flowing through the first conductive part 811 and second conductive part 821 at the above distance d1 = d2 increases compared to the total length of the first conductive part 811 and second conductive part 821. In other words, as the current path of the temperature-sensitive layer 31 increases, the effective total length of the first conductive part 811 and the second conductive part 821 increases by (N-2) units, which is the sum of the width d3 and twice the distance d1 of each linear member in the x-direction, minus the two linear members at both ends, and by two units, i.e., (d3+d1×2)×(N-2)+(d3+d1)×2. In the case of a comb-tooth configuration with a large number of first conductive parts 811 and second conductive parts 821, the cross-sectional area of ​​the current path equivalent to the current path between the linear members of the first conductive part 811 and the linear members of the second conductive part 821 increases particularly effectively. Therefore, the overall length of the first conductive part 811 and the second conductive part 821 in the y-direction can be uniformly shortened. Furthermore, the number of actual first conductive parts 811 and second conductive parts 821 required for the resistance value of the thin-film thermistor 1 can be reduced. Therefore, even if a film with higher resistivity is used for the temperature-sensing layer 31, the comb-tooth region of the thin-film thermistor 1 can be designed to be more compact than in conventional designs.

[0025] The cross-sectional shape of the current collectors 812 and 822 parallel to the yz and xz planes may be approximately rectangular. Alternatively, the shape of the current collectors 812 and 822 may be approximately trapezoidal. With these shapes, the contact area between the current collectors 812 and 822 and the protective layer 4 is increased, thereby reducing the possibility of the protective layer 4 peeling off.

[0026] The upper surface of the current collectors 812 and 822 is the second surface 32a. The current collectors 812 and 822 may, for example, have a maximum width of about 250 μm in the x-direction when viewed from above, and the length of the portion of the second surface 32a of the current collectors 812 and 822 that is visible from above may be about 35 μm in the y-direction.

[0027] The first conductor section 811 and the second conductor section 821 correspond to the conductor sections of this embodiment. The linear members of the first conductor section 811 and the linear members of the second conductor section 821 are arranged alternately in the x-direction. The -y side end of the first conductor section 811 is separated from the current collector section 822. The +y side end of the second conductor section 821 is separated from the current collector section 812. The number of linear members of the first conductor section 811 and the second conductor section 821 can be arbitrarily determined according to the required set resistance value. The overall width of the first conductor section 811 and the second conductor section 821 in the x-direction may be greater than 250 μm if the total number of linear members is large. In this case, the maximum width of the current collector sections 812 and 822 may also be a width corresponding to the width of the linear members in the x-direction, and this width may be greater than or less than the width of the connecting pads 813 and 823. Even with a small maximum width, the wide width of the current collectors 812 and 822 improves thermal conductivity, which has the effect of increasing the temperature tracking ability of the thin-film thermistor 1 to the external temperature.

[0028] The current collector portion 812 has a recess 83 in the contact area with the protective layer 4, which is recessed from the second surface 32a, the side opposite to the side in contact with the first surface of the insulating substrate 2. The current collector portion 822 has a recess 84. The recesses 83 and 84 may extend, for example, in the y direction. The recess 83 does not interfere with the electrical connection between the first conductor portion 811 and the connecting pad 813. The recess 84 does not interfere with the electrical connection between the second conductor portion 821 and the connecting pad 823. The recesses 83 and 84 may be holes that penetrate the current collector portions 812 and 822 to the lower surface side that is in contact with the temperature-sensing layer 31, respectively. Alternatively, the recesses 83 and 84 may be grooves that do not penetrate the current collector portions 812 and 822. The depth of the grooves may be greater than the manufacturing tolerance and clearly distinguishable from the non-groove portions, for example, 10 nm or more. Alternatively, the depth of the groove may be, for example, 7.5% or more of the thickness of the current collectors 812 and 822. In one embodiment, there may be multiple recesses 83 and 84. The width of the recesses 83 and 84 in the x-direction may be, for example, 500 nm to 10 μm, that is, 0.2 to 4% of the total width of the current collectors 812 and 822, which is 250 μm. The distance between the first conductors 811, or the length of the recesses 83 and 84 in the y-direction, may be, for example, 3.5 to 35 μm, that is, the length of the recesses 83 and 84 may be about 10 to 100% of the visible length of the second surface 32a in the y-direction, which is 35 μm.

[0029] The first conductor section 811, the second conductor section 821, and the current collector sections 812, 822 are all covered with a protective layer 4. The upper layer located on the +z side of the first conductor section 811, the second conductor section 821, and the current collector sections 812, 822 may be titanium Ti. Having titanium Ti as the upper layer of the first conductor section 811, the second conductor section 821, and the current collector sections 812, 822 improves the adhesion between the first conductor section 811, the second conductor section 821, and the current collector sections 812, 822 and the protective layer 4. When the protective layer 4 is silicon dioxide, the titanium Ti near the interface with the protective layer 4 tends to combine with the oxygen of the silicon dioxide to form titanium oxide. Therefore, the bond between titanium oxide and silicon dioxide is strengthened, reducing the possibility of the protective layer 4 peeling off from the first conductor section 811, the second conductor section 821, and the current collector sections 812, 822 due to heat.

[0030] The connecting pads 813 and 823 may, for example, have a layer of gold (Au) on their uppermost surface. In addition, the connecting pads 813 and 823 may, for example, have layers of chromium (Cr) and nickel (Ni) as underlayers. The connecting pads 813 and 823 are exposed from the portion without the protective layer 4 and can be connected to external wiring, electrodes, etc.

[0031] Figure 4 shows the cross-sectional views along the cross-sectional lines iva, ivb, and ivc in Figure 3, respectively. The cross-sectional view along the cross-sectional line iva shown in Figure 4(a) shows a cross-section extending parallel to the xz plane through the current collector 812 of the thin-film thermistor 1. In this cross-section, the temperature-sensing layer 31 extends in contact with the upper surface of the insulating substrate 2. The current collector 812, which has a recess 83, is located on the temperature-sensing layer 31. The shape of the cross-section parallel to this cross-section, passing through the current collector 822, is symmetrical to that of Figure 4(a). Therefore, a detailed explanation is omitted here.

[0032] The protective layer 4 is embedded in the recess 83. That is, the protective layer 4 has an uneven shape that is embedded inside the recess 83 of the current collectors 812 and 822 at the joint surface with the current collectors 812 and 822. As a result, delamination of the protective layer 4 from the current collectors 812 and 822 is reduced. The bonding strength between the insulating film component of the protective layer 4, such as silicon dioxide, and the conductive component of the current collectors 812 and 822 is difficult to increase, and stress is generated due to differences in thermal expansion coefficients, making delamination likely. The uneven shape of the joint surface distributes the stress, reducing delamination.

[0033] The protective layer 4 may have a recess 41 on its upper surface, the third surface 4a, corresponding to the plan view position of the recess 83. Similarly, the protective layer 4 may have a recess on its third surface 4a corresponding to the plan view position of the recess 84. The depth of the recess 41 may be approximately the same as the depth of the recess 83, or it may be less than the depth of the recess 83. Furthermore, the depth of the recess 41 may be greater than or less than the thickness of the protective layer 4 on the first conductor portion 811 and the second conductor portion 821.

[0034] The cross-sectional view along the cross-sectional line ivb shown in Figure 4(b) shows a cross-section extending parallel to the xz plane through the connection pad 813 of the thin-film thermistor 1. Note that the shape of the cross-section parallel to this cross-section passing through the connection pad 823 is symmetrical to the shape shown in Figure 4(b), so its explanation is omitted.

[0035] The current collector 812 may extend between the temperature-sensing layer 31 and the connecting pad 813. That is, the connecting pad 813 may be in contact with a portion of the second surface 32a of the current collector 812. The portion of the second surface 32a in contact with the connecting pad 813 is not visible in plan view. In this case, the recess 83 of the current collector 812 may be continuous with a recess 85 extending below the connecting pad 813. A protective layer 45 may be located within the recess 85, i.e., in the gap between the current collector 812 and the connecting pad 813. In this case, the protective layer 45 does not have to completely fill the gap. The connecting pad 813 may have a protrusion that enters into the recess 85 at the joint surface with the current collector 812. The adhesion between this protrusion and the protective layer 45 located in the gap can improve the adhesion at the joint surface with the current collector 812. The upper surface of the connecting pad 813 may have a recess 813a at a position that overlaps with the recess 85 in plan view.

[0036] The upper surface of the connection pad 813 is exposed from the protective layer 4. This allows the connection pad 813 to be connected to external wiring and connecting members.

[0037] The cross-sectional view along the cross-sectional line ivc shown in Figure 4(c) shows a cross-section extending parallel to the yz plane through one of the linear members of the first conductor portion 811 in the first electrode 321 of the thin-film thermistor 1. The insulating substrate 2 has a silicon substrate 21 and an insulating film 22 located on the upper surface of the silicon substrate 21, i.e., the side in contact with the temperature-sensing layer 31. The upper surface of the insulating film 22 is the first surface 2a. As described above, the insulating film 22 may be an amorphous silicon dioxide film. The first conductor portion 811, current collector portions 812 and 822 are made up of a platinum Pt underlayer 8123, a gold Au layer 8122, and a titanium Ti layer 8121. For example, the thickness of the underlayer 8123 is 20 nm. This is a sufficient thickness for the underlayer 8123 to cover the temperature-sensing layer 31 which has irregularities. The irregularities of the temperature-sensing layer 31 can conventionally be about 10 nm. The thickness of the gold (Au) layer 8122 may be 100 nm, and the thickness of the titanium (Ti) layer 8121 may be 10 nm. The presence of the titanium (Ti) layer 8121 between the gold (Au) layer 8122 and the protective layer 4 can further reduce the peeling of the protective layer 4. The connecting pads 813 and 823 may have nickel (Ni) layers 8133 and 8233 and chromium (Cr) layers 8132 and 8232 positioned as underlays for the gold (Au) layers 8131 and 8231. The nickel (Ni) layers 8133 and 8233 may be sufficiently thinner than the gold (Au) layers 8131 and 8231, and may be about the same thickness as or less than the thickness of the underlayment layer 8123, for example, about 10 nm. The chromium (Cr) layers 8132 and 8232 may be about the same thickness as the gold (Au) layers 8131 and 8231, for example, about 1000 nm. Furthermore, in the areas where the current collectors 812 and 822 overlap with the connecting pads 813 and 823, the current collectors 812 and 822 do not need to have the titanium Ti layers 8121 and 8221. In other words, the titanium Ti layers do not need to be in contact with the lower surfaces of the connecting pads 813 and 823. Titanium Ti has a higher ionization tendency compared to other metals used as electrode layers, such as nickel Ni and chromium Cr. By omitting the titanium Ti layers 8121 and 8122 at the junctions with the connecting pads 813 and 823, which are not covered by the protective layer 4, the occurrence of changes over time due to oxidation of the titanium Ti electrode material in the thin-film thermistor 1 can be reduced. Therefore, the thin-film thermistor 1 is more likely to operate stably over a longer period of time.

[0038] Figure 5 is a plan view showing another example of recesses 83 and 84. For example, the recess 83a may include bends and / or branches. Also, for example, the recess 83b may have a semicircular shape at one end. Also, for example, the recesses 83c and 84c may have a shape that does not touch the edges of the current collectors 812 and 822, such as a circle or a square with rounded corners. Also, for example, the extension direction of the recess 84c does not have to be along the y-direction, which is the extension direction of the first conductor portion 811 and the second conductor portion 821. Also, the recess 84a may have an uneven shape with non-uniform width. Also, the recess 84b may have a tapered shape with a width that changes at a constant rate.

[0039] Figure 6 is a cross-sectional view showing another example of the recess 83. The cross-section is identical to the cross-sectional line iva in Figure 3 and includes the current collector 812. For example, the recess 83d may be a groove that does not penetrate the current collector 812, and its bottom surface may not be flat. The recess 83d may have a tapered shape that gradually narrows from the top surface to the bottom. Conversely, the recess 83e may have an inverse tapered shape that gradually widens from the top surface to the bottom surface. Such shapes allow for a stronger and more stable bond between the current collector 812 and the protective layer 4. However, if the recess 83e is formed simultaneously with the first conductor portion 811 and the second conductor portion 821, the bonding area between the first conductor portion 811 and the second conductor portion 821 and the temperature-sensing layer 31 tends to be smaller. Therefore, the degree of taper of the recess 83e may be determined considering the stability of the first conductor portion 811 and the second conductor portion 821.

[0040] These recesses 83-83e of various shapes may be of multiple types mixed together in the thin-film thermistor 1. In this case, the shapes and / or depths of the multiple recesses 41 located on the third surface 4a of the protective layer 4 may differ from each other. Alternatively, the recesses 83-83e may be unified into one type in the thin-film thermistor 1.

[0041] As described above, the thin-film thermistor 1 of this embodiment comprises an insulating substrate 2, a temperature sensing section 3, and a protective layer 4. The temperature sensing section 3 has a temperature-sensing layer 31 located on the first surface 2a, which is the upper surface of the insulating substrate 2, and a plurality of electrodes 32 spaced apart from each other and connected to the temperature-sensing layer 31. The protective layer 4 covers the temperature sensing section 3. The electrodes 32 include a first electrode 321 which includes a current collector 812 and a first conductor 811 extending from the current collector 812. The second electrode 322 which includes a current collector 822 and a second conductor 821 extending from the current collector 822. The current collectors 812 and 822 have recesses 83 and 84 in the contact portions with the protective layer 4 on the second surface 32a opposite to the surface in contact with the temperature-sensing layer 31. Such a thin-film thermistor 1 has high flatness, and it can reduce the decrease in bonding strength and the tendency for peeling to occur when bonding the current collectors 812 and 822, which are made of a different material from the protective layer 4, to the protective layer 4. Therefore, this thin-film thermistor 1 can increase the yield during manufacturing and extend the period of stable use.

[0042] Furthermore, the protective layer 4 may have recesses 41 corresponding to the recesses 83 and 84 of the current collectors 812 and 822 on the third surface 4a opposite to the surface in contact with the second surface 32a of the current collectors 812 and 822, in a plan view. In other words, the material of the protective layer 4 is not increased by the amount that has entered the recesses 83 and 84, and recesses 41 corresponding to the amount that has entered may be created. As long as this does not lead to a decrease in the function of the protective layer 4, the manufacturing process does not become complicated and the bonding strength of the protective layer 4 can be easily improved.

[0043] Furthermore, the electrode 32 may include connection pads 813, 823 that are in contact with a portion of the second surface 32a of the current collectors 812, 822 and are exposed from the portion without the protective layer 4, allowing for external connection. The recesses 83, 84 may extend from portions that do not overlap with the connection pads 813, 823 in a plan view to portions that do overlap with the connection pads 813, 823 in a plan view. Since the current collectors 812, 822 and the connection pads 813, 823 are made of the same or similar material, the connection pads 813, 823 are not as prone to peeling off as the protective layer 4. However, by having recesses 85 on the bonding surface of the current collectors 812, 822 and the connection pads 813, 823, the bonding strength between the current collectors 812, 822 and the connection pads 813, 823 is improved. Furthermore, because recesses 813a and the like are formed in the connection pads 813 and 823 in accordance with the recess 85, when the connection pads 813 and 823 are connected to the electrode pads 531 and 532 of the package 503 using conductive adhesive, the conductive adhesive can enter the recesses 813a and the like, thereby reducing the possibility of the connection pads 813 and 823 peeling off from the electrode pads 531 and 532.

[0044] Furthermore, the depth of the recesses 83 and 84 may be 10 nm or more. By having a depth appropriate for increasing the bonding strength between the protective layer 4 and the current collectors 812 and 822, the thin-film thermistor 1 can reduce the peeling of the protective layer 4 from the current collectors 812 and 822.

[0045] Alternatively, the depth of the recesses 83 and 84 may be 7.5% or more of the thickness of the current collectors 812 and 822. Similarly, by having a depth of at least an appropriate depth relative to the thickness of the current collectors 812 and 822, the thin-film thermistor 1 can reduce the peeling of the protective layer 4 from the current collectors 812 and 822.

[0046] Furthermore, the current collectors 812 and 822 may have multiple recesses 83 and 84. The more complex and numerous the irregularities on the upper surface of the current collectors 812 and 822, the easier it is to increase the bonding strength between the current collectors 812 and 822 and the protective layer 4.

[0047] Furthermore, the electrode 32 may have multiple linear members in each of its first conductor portion 811 and second conductor portion 821. The electrode 32 may also have a comb-tooth electrode where the linear members extend from the current collector portions 812 and 822 along the temperature-sensitive layer 31. Such a comb-tooth electrode allows for accurate measurement of the change in resistance value in response to temperature changes. In such a case, the current collector portions 812 and 822 to which the multiple linear members are connected tend to be flat over a wide area. Therefore, by having recesses 83 and 84 on the bonding surface between the current collector portions 812 and 822 and the protective layer 4, the thin-film thermistor 1 can effectively reduce the peeling of the protective layer 4 from the current collector portions 812 and 822.

[0048] Furthermore, the temperature-sensing layer 31 may contain a metal oxide containing manganese, cobalt, zinc, and oxygen. The inclusion of zinc in the temperature-sensing layer 31 allows the thin-film thermistor 1 to achieve a high B constant, for example, a sensitivity of 4000 or higher. Therefore, the thin-film thermistor 1 achieves both structural stability and sensitivity.

[0049] Furthermore, the first conductor portion 811, the second conductor portion 821, and the current collector portions 812, 822 may have titanium Ti layers 8121, 8221 on the side of the second surface 32a. On the other hand, the titanium Ti layers 8121, 8221 do not need to be in contact with the lower surfaces of the connecting pads 813, 823. Titanium Ti contributes to the surface stability of the first conductor portion 811, the second conductor portion 821, and the current collector portions 812, 822. However, titanium Ti is more susceptible to oxidation than other metal conductors used in electrical wiring. Therefore, if an oxide layer forms between the current collector portions 812, 822 and the connecting pads 813, 823, the electrical conductivity tends to decrease over time. Therefore, by selectively omitting the titanium Ti layer between the current collector portions 812, 822 and the connecting pads 813, 823, the thin-film thermistor 1 operates more stably and accurately.

[0050] Furthermore, the electronic device 100 of this embodiment includes the thin-film thermistor 1 described above. This enables the electronic device 100 to obtain temperature data more stably.

[0051] The above embodiments are illustrative examples, and various modifications are possible. For example, the connecting pads 813 and 823 do not have to be in contact with a part of the second surface 32a. The current collectors 812 and 822 and the connecting pads 813 and 823 may be in contact with each other side by side.

[0052] Furthermore, although the above description described the case where there are recesses 41 on the upper surface of the protective layer 4 corresponding to recesses 83 and 84, it is not limited to this case. Recesses 41 do not have to exist. That is, the protective layer 4 may be embedded and flattened in the portions corresponding to recesses 83 and 84.

[0053] Furthermore, if there are multiple recesses 83 and 84, the area, shape, and depth of each recess 83 and 84 may be different from or the same as those of the other.

[0054] Furthermore, there may be only one recess 83 and one recess 84. In this case, each recess 83 and 84 may have a complex shape to obtain the joint strength of multiple recesses. Also, the plan view shape and / or cross-sectional shape of the recesses 83 and 84 are not limited to the shapes exemplified above. For example, the plan view shape may be a regular polygon or an ellipse. The plan view shape may also be a combination of the shapes exemplified above. Furthermore, the cross-sectional shape may include curved portions, the slope may change midway in the depth direction, or it may be the shape of a staircase with two or more steps.

[0055] Furthermore, the electrode 32 does not necessarily have to have a comb-tooth electrode shape. It may have any electrode shape that allows for the measurement of resistance values ​​according to temperature.

[0056] Furthermore, the first conductor portion 811, the second conductor portion 821, and the current collector portions 812 and 822 do not necessarily have a titanium Ti layer, and the titanium Ti layer of the current collector portions 812 and 822 may be in contact with the lower surface of the connecting pads 813 and 823.

[0057] Furthermore, the electronic device 100 in which the thin-film thermistor 1 is used does not necessarily have to include a piezoelectric vibration element 502. The thin-film thermistor 1 may be combined with other elements. The positional relationship between the thin-film thermistor 1 and other elements in the electronic device 100 may be determined arbitrarily. Also, the electronic device 100 does not necessarily have to have a cover 504. The thin-film thermistor 1 does not have to be used as part of the electronic device 100. It may be incorporated into various other devices or components. Furthermore, the specific details such as structure, configuration, materials, and size shown in the above embodiments may be modified as appropriate without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention as described in the claims and its equivalents. [Explanation of Symbols]

[0058] 1. Thin-film thermistor 2. Insulating substrate 2a 1st page 21 Silicon substrate 22 Insulating film 3. Temperature screening area 31 Temperature sensitive layer 32 electrodes 32a 2nd side 321 1st electrode 322 2nd electrode 33 Wiring conductors 4 protective layer 4a 3rd page 41 Recess 45 Protective layer 83~83e, 84~84c, 85 recess 100 Electronic Devices 502 Piezoelectric Vibration Element 503 Package 503a recess 504 Lid 511, 512 Joining members 514 Bonding Wire 531-533 Electrode Pads 811 First Conductor Section 821 Second Conductor Section 812, 822 Current collector 813, 823 Connection Pads 813a, 823a recess

Claims

1. An insulating substrate and A temperature sensing unit having a temperature-sensing layer and a plurality of electrodes spaced apart from each other and connected to the temperature-sensing layer, located on the first surface of the insulating substrate, A protective layer covering the temperature measuring section, Equipped with, Each of the aforementioned plurality of electrodes includes a current collector and a conductor extending from the current collector. The current collector has a recess in the portion of the second surface opposite to the surface in contact with the temperature-sensing layer that contacts the protective layer. Thin-film thermistor.

2. The thin-film thermistor according to claim 1, wherein the protective layer has a recess corresponding to the recess of the current collector on a third surface opposite to the surface in contact with the second surface in a plan view that overlaps with the current collector.

3. Each of the plurality of electrodes includes a connection pad that is in contact with a portion of the second surface, is exposed from the portion without the protective layer, and can be connected to the outside. The recess extends from a position that does not overlap with the connecting pad in a plan view to a position that overlaps with the connecting pad in a plan view. The thin-film thermistor according to claim 1.

4. The thin-film thermistor according to claim 1, wherein the depth of the recess is 10 nm or more.

5. The thin-film thermistor according to claim 1, wherein the depth of the recess is 7.5% or more of the thickness of the current collector.

6. The thin-film thermistor according to claim 1, wherein the current collecting portion has a plurality of recesses.

7. The thin-film thermistor according to claim 1, wherein the electrode has a comb-tooth electrode in which the conductive portion has a plurality of linear members, and the linear members extend from the current collector along the temperature-sensing layer.

8. The thin-film thermistor according to claim 1, wherein the temperature-sensing layer comprises a metal oxide containing manganese, cobalt, zinc, and oxygen.

9. The plurality of electrodes are connected to the current collector and include connection pads that are exposed from the portion without the protective layer and can be connected to the outside, The thin-film thermistor according to claim 1, wherein the conductor portion and the current collector portion have a titanium layer on the second surface side, and the titanium layer does not contact the lower surface of the connection pad.

10. An electronic device comprising a thin-film thermistor according to any one of claims 1 to 9.

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