Strain gauge, strain gauge manufacturing method and strain sensor

Abstract

A strain gauge 10 according to one embodiment of the present invention is provided with a pattern of a multilayer body 11 which comprises a strain resistance layer 12 and a protective layer 13 that is provided so as to have a portion that is in contact with the strain resistance layer 12. The specific resistance of the protective layer 13 may be higher than the specific resistance of the strain resistance layer 12. Since the protective layer 13 is electrochemically more noble than the strain resistance layer 12, the protective layer 13 becomes unlikely to be etched in the vicinity of the strain resistance layer 12 when wet etching is carried out for the purpose of forming the pattern of the multilayer body 11, thereby suppressing separation of a resist pattern and reducing variation in the amount of side etching. Consequently, variation in the resistance of the strain gauge 10 is reduced.

Description

[Technical Field]

[0001] The present invention relates to a strain gauge, a method for manufacturing a strain gauge, and a strain sensor. [Background technology]

[0002] Strain gauges are known that are attached to a measurement object (a strain-generating body) to detect the strain of the measurement object. Strain gauges are made of, for example, strain resistors whose resistance changes as their volume changes when subjected to an external force, specifically metallic materials containing Ni, Cr, Cu, etc. The strain resistors are formed, for example, in the form of a film on a substrate, and then formed into a desired pattern, such as a meander pattern, using photolithography and etching techniques (see, for example, Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-74934 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-161286 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] As described in Patent Document 2, when forming a pattern of a strain resistor, the resistance value of the strain gauge inevitably varies due to variations that occur in the photolithography process and variations that occur in the etching process. For this reason, in the technology disclosed in Patent Document 2, a resistance wiring pattern for adjusting the resistance is provided on the strain gauge.

[0005] However, providing such a resistive wiring pattern makes it difficult to miniaturize the strain gauge. When the measurement object (flexural element) is miniaturized, accurate measurement becomes difficult unless the area where the strain gauge is attached is reduced. Therefore, with the technology disclosed in Patent Document 2, it is difficult to accurately measure the strain of a small flexural element.

[0006] In light of the above circumstances, the present invention aims to provide a strain gauge with little resistance variation and a method for manufacturing the same, and also to provide a strain sensor using the strain gauge that can measure strain with high accuracy even when the strain generating element is small. [Means for solving the problem]

[0007] In order to solve the above problem, one aspect of the present invention provides a strain gauge having a laminate pattern including a strain resistance layer and a protective layer having a portion in contact with the strain resistance layer, wherein the protective layer is electrochemically more noble than the strain resistance layer.

[0008] As described above, since the protective layer is electrochemically more noble than the strain-resistant layer, when wet etching is performed to form a pattern of the laminate, the protective layer is less likely to be etched in the vicinity of the strain-resistant layer, and peeling of the resist pattern is suppressed, thereby reducing variation in the amount of side etching.

[0009] In the above strain gauge, the resistivity of the protective layer is preferably higher than that of the strain resistance layer, which makes it difficult for current to flow through the protective layer, thereby increasing the strain detection sensitivity of the strain sensor.

[0010] In the above strain gauge, the protective layer is preferably etchable with an etching solution for etching the strain-resistant layer. In this specification, "etchable" means that the protective layer has an etching rate that is industrially applicable to wet etching. Specifically, the etching rate is preferably 1 nm / min or more, and more preferably 3 nm / min or more. There is no upper limit to the etching rate of the protective layer, but it is preferable that the etching rate be lower than that of the strain-resistant layer when measured independently (i.e., when the protective layer and the strain-resistant layer are not electrically connected).

[0011] In the above strain gauge, the strain-resistant layer may contain one or more first elements selected from the group consisting of Ni, Cr, and Cu, and the protective layer may contain one or more second elements selected from the group consisting of Ni and Cr, and a third element having a first ionization energy higher than that of the first element having the largest content (unit: atomic %) in the strain-resistant layer, which makes it easier to realize that the protective layer is electrochemically more noble than the strain-resistant layer.

[0012] In the above-mentioned protective layer, it may be preferable that the content of the third element is 50 atomic % or less from the viewpoint of the protective layer having suitable etching processability.

[0013] In the above-mentioned protective layer, it is preferable that the content of the third element is 10 atomic % or more from the viewpoint of stably realizing a reduction in the variation in the amount of side etching.

[0014] The third element may include a semi-metal element or a typical element, which makes it easier to achieve a higher resistivity for the protective layer than for the strain-resistant layer.

[0015] The third element may include one or more elements selected from the group consisting of B, C, Si, P, and Ge. When the third element includes these elements, the resistivity of the protective layer may be more stably increased compared to the strain-resistant layer.

[0016] The Pauling's electronegativity of the third element may be 2.6 or less, which may be preferable in terms of the protective layer having suitable etching processability.

[0017] The first element may include Cr, and the strain-resistant layer may further include a typical element.

[0018] It may be preferable that the resistivity of the strain-resistant layer is 100 μΩcm or less and lower than the resistivity of the protective layer.

[0019] In another aspect, the present invention provides a strain sensor including the above strain gauge and an electrode for applying current to the strain gauge.

[0020] In another aspect, the present invention provides a method for manufacturing a strain gauge having a laminate pattern including a strain-resistant layer and a protective layer disposed on at least a portion of the strain-resistant layer and being electrochemically more noble than the strain-resistant layer, the method including forming the laminate pattern by forming a protective layer on the strain-resistant layer disposed on a substrate, forming a resist pattern on the protective layer, and removing by wet etching the protective layer and the strain-resistant layer located below the protective layer that are not covered by the resist pattern.

[0021] In the above manufacturing method, it may be preferable that the etching rate of the strain-resistant layer in the etching solution used for wet etching is 50 nm / min or more.

[0022] In the above manufacturing method, it may be preferable that the etching rate of the protective layer in the etching solution used for wet etching is 5 nm / min or more. [Effects of the Invention]

[0023] According to the present invention, a strain gauge with little resistance variation and a method for manufacturing the same, as well as a strain sensor capable of measuring strain with high accuracy even when the strain generating element is small, are provided. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram illustrating an example of a strain sensor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a conceptual diagram showing a cross section taken along line AA in FIG. [Figure 3A] 4 is an explanatory diagram of a method for manufacturing a strain gauge according to one embodiment of the present invention (in a state where a strain resistance layer and a protective layer are laminated); FIG. [Figure 3B] 4 is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (in a state where a resist film has been formed). FIG. [Figure 3C] 4 is an explanatory diagram of a method for manufacturing a strain gauge according to one embodiment of the present invention (in a state where a resist pattern has been formed). FIG. [Figure 3D] 4 is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (a state in which etching of a protective layer is being performed); FIG. [Figure 3E] 1 is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (in a state where the protective layer has been etched and the strain resistance layer is exposed); [Figure 3F] 4 is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (a state in which etching of a strain resistance layer is being performed); FIG. [Figure 3G] 4 is an explanatory diagram of a method for manufacturing a strain gauge according to one embodiment of the present invention (a state in which etching of a strain resistance layer is completed); FIG. [Figure 3H] 4 is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (in a state where the resist pattern has been removed); FIG. [Figure 4A] FIG. 1 is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (in a state where strain resistance layers are stacked); [Figure 4B] FIG. 10 is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (in a state where a resist film is formed). [Figure 4C] FIG. 10 is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (in a state where a resist pattern has been formed). [Figure 4D]FIG. 1 is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (a state in which etching of a strain resistance layer is being performed); [Figure 4E] FIG. 10 is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (after etching of the strain resistance layer is completed); [Figure 4F] FIG. 10 is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (in a state where the resist pattern has been removed); [Figure 5] 1 is a graph showing the average value and 3σ of the side etch amount of the strain-resistant layer produced in Example 1. [Figure 6] 1 is a graph showing 3σ of the side etching amount of the strain-resistant layer manufactured in Example 1. [Figure 7] 1 is a graph showing the average value of inter-electrode resistance of the strain gauges manufactured in Example 1. [Figure 8] 1 is a graph showing the variation index of inter-electrode resistance of the strain gauge manufactured in Example 1. [Figure 9] 10 is a graph showing the average value and 3σ of the side etch amount of the strain-resistant layer produced in Example 2. [Figure 10] 10 is a graph showing 3σ of the side etching amount of the strain-resistant layer manufactured in Example 2. BEST MODE FOR CARRYING OUT THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals, and the description of components that have already been described will be omitted as appropriate.

[0026] FIG. 1 is a diagram illustrating an example of a strain sensor according to an embodiment of the present invention. As shown in FIG. 1, the strain sensor 100 according to this embodiment includes a strain gauge 10 having a meandering pattern and an electrode 20 for passing current through the strain gauge 10. Both the strain gauge 10 and the electrode 20 are formed on a substrate 30. Non-limiting examples of materials for the electrode 20 include Cu, Au, and alloys containing these. The electrode 20 includes a first electrode 201 connected to one end of the strain gauge 10 and a second electrode 202 connected to the other end. Each of the first electrode 201 and the second electrode 202 is provided with a plating layer 21 for the purpose of increasing solder adhesion strength.

[0027] Fig. 2 is a conceptual diagram showing a cross section taken along line AA in Fig. 1. As shown in Fig. 2, the strain gauge 10 includes a laminate 11 including a strain resistance layer 12 and a protective layer 13 provided with a portion in contact with the strain resistance layer 12, and the laminate 11 forms a meander pattern.

[0028] The resistance of the strain-resistant layer 12 changes when it receives an external force and its length changes in the direction of current flow. This property can be quantitatively evaluated by the gauge factor Gf shown in the following equation (1). Gf=(ΔR / R) / (ΔL / L) (1)

[0029] Here, L is the length in the direction of current flow (length in the current direction) of the strain gauge 10 when no external force is applied (unloaded), ΔL is the change in the length of the strain gauge 10 in the current direction when an external force is applied to the strain gauge 10 (loaded) compared to when it is unloaded, R is the resistance value of the strain gauge 10 when it is unloaded, and ΔR is the change in the resistance value of the strain gauge 10 when it is loaded compared to when it is unloaded.

[0030] The strain-resistant layer 12 is made of a metal material containing, for example, Ni, Cr, Cu, or the like as a main component. A typical example of such a material is NiCr. 20 (Nichrome, resistivity: 104μΩcm), CuNi 45(Constantan, resistivity: 48 μΩcm) The resistivity of the strain-resistant layer 12 is preferably low, and a non-limiting example is preferably 100 μΩcm or less.

[0031] From the viewpoint of improving the balance between the gauge factor Gf and the temperature coefficient of resistance (TCR), it may be preferable that the strain-resistant layer 12 contains, for example, Cr as a main component and a non-metallic element, specifically, a typical element (for example, N).

[0032] The strain gauge 10 according to this embodiment includes a laminate 11 in which a protective layer 13 is laminated on a strain resistance layer 12. The protective layer 13 is electrochemically more noble than the strain resistance layer 12. Such a property of the protective layer 13 reduces variations in the amount of side etching when the strain resistance layer 12 is wet-etched. This will be described in detail when explaining the manufacturing method of the strain gauge 10.

[0033] The material for the protective layer 13 is not particularly limited as long as it is electrochemically more noble than the strain-resistant layer 12. However, it is preferable that the resistivity (unit: Ωcm) of the protective layer 13 is higher than that of the strain-resistant layer 12 so that when a current is applied to the laminate 11 having the strain-resistant layer 12 and the protective layer 13, the current flows preferentially through the strain-resistant layer 12. For example, the above-mentioned NiCr 20 (Nichrome) and CuNi 45 Considering the resistivity of (constantan), the protective layer 13 preferably has a resistivity of at least 50 μΩcm or more, more preferably 120 μΩcm or more, and particularly preferably 150 μΩcm or more.

[0034] Furthermore, as will be explained later in the manufacturing method of the strain gauge 10, when the laminate 11 is patterned by wet etching, the protective layer 13 should be etchable with the etching solution used to etch the strain-resistant layer 12.

[0035] The strain-resistant layer 12 of the strain gauge 10 may contain one or more first elements selected from the group consisting of Ni, Cr, and Cu. In this case, the protective layer 13 preferably contains one or more second elements selected from the group consisting of Ni and Cr, and a third element having a first ionization energy higher than that of the first element with the highest content (unit: atomic %) in the strain-resistant layer 12. This makes it easier to make the protective layer 13 electrochemically more noble than the strain-resistant layer 12.

[0036] The first ionization energies of Ni are 737.1 kJ / mol, Cr are 652.9 kJ / mol, and Cu are 745.5 kJ / mol. Therefore, elements with a first ionization energy of 750 kJ / mol or higher are suitable as the third element. Such elements are often found among metalloid elements and typical elements. Therefore, it may be preferable to include a metalloid element or typical element as the third element. Non-limiting preferred examples of the third element include B (800.6 kJ / mol), C (1086.5 kJ / mol), Si (786.5 kJ / mol), P (1011.8 kJ / mol), and Ge (762 kJ / mol) (first ionization energies are shown in parentheses). Therefore, it is preferable that the third element include one or more elements selected from the group consisting of these elements.

[0037] When the protective layer 13 contains the second and third elements as described above, it is preferable that the content of the third element be 50 atomic % or less in order to easily ensure etching processability. Furthermore, it is preferable that the content of the third element be 10 atomic % or more in order to stably reduce the variation in the amount of side etching. As will be shown in the examples described later, if the content of the third element is about 25 atomic %, even if the content of the third element is increased beyond that, the effect on the variation in the amount of side etching may be reduced.

[0038] The Pauling electronegativity of the third element may be 2.6 or less. When the electronegativity is 2.6 or less, the material constituting the protective layer 13 is less likely to exhibit high ionic bonding, which may result in the protective layer 13 having suitable etching processability more reliably. Furthermore, because elements with high electronegativity tend to have multiple valences, there is a concern that the composition and structure of the protective layer 13 may vary locally. Such variations may result in electrochemical variations, which may affect the functionality of the protective layer 13 (i.e., suppression of variations in the amount of side etching of the strain-resistant layer 12).

[0039] Here, when the constituent material of the strain-resistant layer 12 and the constituent material of the electrode 20 both contain Cu, for example, the strain-resistant layer 12 may be CuNi 45 In the case where the electrode 20 is made of Cu, by appropriately selecting the material of the protective layer 13, the protective layer 13 can prevent Cu contained in the electrode 20 from diffusing into the strain-resistant layer 12. If Cu diffuses from the electrode 20 into the strain-resistant layer 12, the composition of the strain-resistant layer 12 may change, possibly reducing the gauge factor Gf of the strain gauge 10. A protective layer 13 having a Cu barrier function is easily obtained when the protective layer 13 contains the second and third elements described above, and is particularly easily obtained by selecting a semimetallic element or a typical element as the third element.

[0040] A method for manufacturing the strain gauge 10, specifically, a method for forming the pattern of the laminate 11 included in the strain gauge 10, will be described below.

[0041] 3A to 3H are explanatory diagrams of a method for manufacturing a strain gauge according to one embodiment of the present invention, and show the following states, respectively. FIG. 3A: The strain-resistant layer 12 and the protective layer 13 are laminated. FIG. 3B: The state in which the resist film 40 is formed FIG. 3C: The state in which the resist pattern 41 is formed FIG. 3D: The state in which the protective layer 13 is being etched FIG. 3E: The state in which the protective layer 13 is etched and the strain-resistant layer 12 is exposed. FIG. 3F: The strain-resistant layer 12 is being etched. FIG. 3G: The state after etching of the strain-resistant layer 12 is completed FIG. 3H: The state after the resist pattern 41 is removed

[0042] In the manufacturing method according to this embodiment, first, a protective layer 13 is formed on a strain-resistant layer 12 provided on a substrate 30 ( FIG. 3A ). This forms a laminated film in which the protective layer 13 is laminated on the strain-resistant layer 12 on the substrate 30. The manufacturing method of the strain-resistant layer 12 and the protective layer 13 is not limited. They may be formed by a dry process such as vapor deposition, sputtering, or reactive sputtering, or by a wet process such as electroplating or electroless plating. When the strain-resistant layer 12 or the protective layer 13 contains a typical element, it may be preferable to employ reactive sputtering, electroless plating, or the like.

[0043] After the laminated film is thus formed on the substrate 30, a resist film 40 is formed on the protective layer 13 of the laminated film (FIG. 3B). The resist film 40 may be formed by laminating a dry film resist, or may be formed by, for example, spin coating a liquid resist.

[0044] Next, the resist film 40 is subjected to a photolithography process (exposure and development) to form a resist pattern 41. This results in a state in which the resist pattern 41 is provided on the protective layer 13 (FIG. 3C).

[0045] Next, the protective layer 13 that is not covered by the resist pattern 41 is etched. This etching is generally wet etching using an etching solution. The etching solution is appropriately selected based on the materials constituting the strain-resistant layer 12, the protective layer 13, and the resist pattern 41. Specifically, the etching solution has the ability to dissolve the strain-resistant layer 12. The etching rate of the strain-resistant layer 12 is appropriately selected depending on the processing process. For example, the etching rate when the strain-resistant layer 12 is etched alone may preferably be 50 nm / min or more, more preferably 80 nm / min or more, and particularly preferably 100 nm / min or more.

[0046] The etching solution has the ability to dissolve the protective layer 13 as well, but does not require an etching rate as high as that for the strain-resistant layer 12. The etching rate for the protective layer 13 is appropriately set depending on the processing process, but for example, a rate of 5 nm / min or more may be preferable when the protective layer 13 is etched alone. As will be described later, in the manufacturing method according to this embodiment, the protective layer 13 is in contact with the strain-resistant layer 12, and therefore the etching rate is slower than when the protective layer 13 is etched alone.

[0047] It is preferable that the etching solution does not easily attack the resist pattern 41. A specific example of such an etching solution is cerium ammonium nitrate.

[0048] In wet etching, etching generally progresses isotropically, so that when the etchant etches the protective layer 13, the protective layer 13 is etched in the stacking direction and also side-etched, as shown in Fig. 3D. When etching of the protective layer 13 in the stacking direction progresses, the strain-resistant layer 12 is exposed in the region not covered by the resist pattern 41, and the unetched protective layer 13 is separated between the resist pattern 41 and the strain-resistant layer 12 to form a protective layer pattern 131, as shown in Fig. 3E.

[0049] When both the protective layer pattern 131 and the strain-resistant layer 12 are exposed to the etching solution as shown in FIG. 3E, the protective layer 13 (protective layer pattern 131) is electrochemically more noble than the strain-resistant layer 12. This results in the formation of a local cell between them, resulting in a decrease in the etching rate of the protective layer pattern 131. Therefore, the strain-resistant layer 12 is preferentially etched, and side etching occurring below the resist pattern 41 also preferentially progresses in the strain-resistant layer 12. As a result, as shown in FIG. 3F, the protective layer pattern 131 remains between the side-etched portion of the strain-resistant layer 12 and the resist pattern 41. This protective layer pattern 131 protects the resist pattern 41 from physical phenomena (such as the generation of bubbles and localized and irregular fluctuations in the flow of the etching solution) caused by the side etching of the strain-resistant layer 12. In other words, the protective layer pattern 131 functions as a protective member for the resist pattern 41. This makes the resist pattern 41 less susceptible to damage during wet etching. Specific examples of damage include local peeling, deformation, and loss of the resist pattern 41, and such damage causes variations in the amount of side etching of the strain resistance layer 12.

[0050] In the manufacturing method according to this embodiment, a protective layer 13 (protective layer pattern 131) is provided to protect the resist pattern 41. Therefore, as shown in FIG. 3G, when etching of the strain-resistive layer 12 in the stacking direction is completed and the strain-resistive layer pattern 121 is properly formed, the wet etching amount of the strain-resistive layer 12 (strain-resistive layer pattern 121) is less likely to vary.

[0051] Note that the electrochemical protection of the protective layer pattern 131 weakens as it moves away from the contact portion with the strain-resistant layer 12. Therefore, the etching rate of the protective layer pattern 131 increases toward the tip, and the protective layer pattern 131 is moderately etched during etching of the strain-resistant layer 12. Therefore, when the resist pattern 41 is removed and the pattern of the laminate 11 is formed on the substrate 30, the protective layer pattern 131 is unlikely to protrude horizontally from the strain-resistant layer pattern 121 ( FIG. 3H ).

[0052] FIG. 4A is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (with a strain resistance layer laminated). FIG. 4B is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (with a resist film formed). FIG. 4C is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (with a resist pattern formed). FIG. 4D is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (with the strain resistance layer being etched). FIG. 4E is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (with the strain resistance layer etching completed). FIG. 4F is an explanatory diagram of a method for manufacturing a strain gauge according to the prior art (with the resist pattern removed).

[0053] In the conventional manufacturing method, the protective layer 13 provided in the manufacturing method according to the present embodiment is not formed on the strain-resistant layer 12 on the substrate 30, but a resist film 40 is formed thereon (FIGS. 4A and 4B). Therefore, a resist pattern 41 formed by photolithography is disposed so as to contact the strain-resistant layer 12 (FIG. 4C).

[0054] When wet etching is performed using an etching solution in this state, side etching of the strain-resistant layer 12 occurs directly below the resist pattern 41 (FIG. 4D). The dissolution reaction of the strain-resistant layer 12 that causes side etching is accompanied by the generation of gas, which causes localized and irregular fluctuations in the flow of the etching solution near the contact interface between the resist pattern 41 and the strain-resistant layer 12. In the conventional manufacturing method, this uncontrollable physical phenomenon results in large variations in the amount of side etching of the strain-resistant layer 12, as conceptually shown in FIG. 4E (FIG. 4E). The two-dot chain line in FIG. 4E conceptually shows the result of side etching when the variations are small.

[0055] For the reasons described above, in the manufacturing method according to the prior art, the shape of the strain resistance layer pattern 121 formed on the substrate 30 varies greatly, and the sensitivity variation of the strain gauge becomes so large that a resistive wiring pattern for resistance adjustment is required in Patent Document 1.

[0056] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0057] The present invention will be specifically described below using examples. [Example]

[0058] Example 1 The strain gauge 10 was manufactured based on the manufacturing method shown in Fig. 3. Details of the components such as the strain resistance layer 12 and the protective layer 13 and the manufacturing method were as follows. Substrate 30: Polyimide film Strain-resistant layer 12: Both were formed by sputtering. NiCr 20 , thickness 140nm CuNi 45 , thickness 70nm Cr, thickness 35 nm Protective layer 13: Both were formed by sputtering and had a thickness of 10 nm. CrB 15 CrC 15 CrSi 15 CrGe 15 Cr CrTi 15 Ta Resist film 40: Obtained by spin coating a liquid resist. Etching solution: cerium ammonium nitrate

[0059] Table 1 shows the etching rate (unit: μm / min) and the resistivity (unit: μmΩcm) of each layer when each layer is etched independently with the above etching solution.

[0060] The protective layer 13 made of Ta could not be etched with the above etching solution, and was etched by a dry process (reactive ion etching).

[0061] [Table 1]

[0062] The side etch depth (unit: μm) of the strain-resistant layer 12 of the resulting laminate 11 (80 pieces measured in each example) was measured, and the average value and 3σ (three times the standard deviation) were calculated. The inter-electrode resistance (unit: kΩ) of the strain gauges 10 (80 pieces measured in each example) was also measured, and the average value, 3σ, and 3σ / average value (unit: %, referred to herein as the "variation index") were calculated. Furthermore, the gauge factor Gf of the strain gauges 10 was measured. The measurement results are shown in Table 2 and Figures 5 to 8.

[0063] [Table 2]

[0064] As shown in Table 2 and other data, when the protective layer 13 is electrochemically more noble than the strain-resistant layer 12 (Examples 1-2 to 1-6, 1-11, and 1-13), the side-etch amount variation (3σ) is smaller than when the protective layer 13 is not present (Examples 1-1, 1-10, and 1-12) or when the protective layer 13 is not electrochemically more noble than the strain-resistant layer 12 (Examples 1-7 and 1-8). It was also confirmed that when the protective layer 13 is present, the variation (variation index) of the resistance value of the strain gauge 10 is also smaller. Note that when the protective layer 13 is made of Ta (Examples 1-9 and 1-14), processing using the etching solution used in these examples was not possible, and therefore these examples are considered reference examples.

[0065] Example 2 The same manufacturing method as in Example 1 was used, and the material of the strain-resistant layer 12 was NiCr. 20 The material of the protective layer 13 is CrBX (X is 0 to 60) to fabricate strain gauges 10. The side etching depth (unit: μm) was measured for the strain resistance layers 12 of the laminates 11 of the resulting strain gauges 10 (80 pieces measured in each example), and the average value and 3σ (three times the standard deviation) were calculated. The results are shown in Table 3 and Figs. 9 and 10.

[0066] [Table 3]

[0067] As shown in Table 3, the CrB X When X was 5 atomic % (Example 2-2), the variation (3σ) in the amount of side etching was significantly reduced compared to when the protective layer 13 did not contain B (Example 2-1). X By increasing the amount of B added, the variation (3σ) in the amount of side etch was further reduced, but the degree of reduction was less than in Examples 2-1 and 2-2. It was confirmed that the inversion of the electrochemical noble-potential relationship between the strain-resistant layer 12 and the protective layer 13 by adding B to the protective layer 13 had the greatest effect on reducing the variation (3σ) in the amount of side etch. From the viewpoint of suppressing the variation (3σ) in the amount of side etch, a B addition amount of 20 atomic % to the protective layer 13 is sufficient, and even when considering the manufacturing variation when forming the protective layer 13, it was shown by this example that a B addition amount of 25 atomic % is sufficient. Note that CrB X When X was 60 atomic %, the metallic properties of the protective layer 13 were excessively reduced and etching processing was not possible with the etching solution used in this example, and therefore this was used as a reference example. [Explanation of symbols]

[0068] 100: Strain sensor 10: Strain gauge 11: Laminate 12: Strain resistance layer 121: Strain resistance layer pattern 13:Protective layer 131: Protective layer pattern 20: Electrode 201: 1st electrode 202:Second electrode 21: Plating layer 30: Substrate 40: Resist film 41: Resist pattern

Claims

1. A strain gauge comprising a laminated pattern including a strain resistance layer and a protective layer provided with a portion in contact with the strain resistance layer, the protective layer is electrochemically more noble than the strain-resistant layer; The resistivity of the protective layer is higher than the resistivity of the strain-resistant layer. A strain gauge characterized by:

2. 2. The strain gauge according to claim 1, wherein the protective layer can be etched with an etching solution used to etch the strain resistance layer.

3. the strain-resistant layer contains one or more first elements selected from the group consisting of Ni, Cr, and Cu; 2. The strain gauge according to claim 1, wherein the protective layer contains one or more second elements selected from the group consisting of Ni and Cr, and a third element having a first ionization energy higher than that of an element having the largest content (unit: atomic %) of the first elements in the strain resistance layer.

4. 4. The strain gauge according to claim 3, wherein the content of the third element in the protective layer is 50 atomic % or less.

5. 4. The strain gauge according to claim 3, wherein the content of the third element in the protective layer is 10 atomic % or more.

6. The strain gauge according to claim 3 , wherein the third element includes a semi-metallic element or a typical element.

7. 4. The strain gauge according to claim 3, wherein the third element includes one or more elements selected from the group consisting of B, C, Si, P, and Ge.

8. 4. The strain gauge of claim 3, wherein the Pauling electronegativity of the third element is 2.6 or less.

9. The strain gauge according to claim 3 , wherein the first element includes Cr, and the strain resistance layer further includes a typical element.

10. 10. The strain gauge according to claim 9, wherein the resistivity of the strain resistance layer is 100 μΩcm or less, which is lower than the resistivity of the protective layer.

11. A strain gauge having a laminate pattern including a strain-resistant layer and a protective layer provided with a portion in contact with the strain-resistant layer, the protective layer is electrochemically more noble than the strain-resistant layer; the strain-resistant layer contains one or more first elements selected from the group consisting of Ni, Cr, and Cu; the protective layer contains one or more second elements selected from the group consisting of Ni and Cr, and a third element having a first ionization energy higher than that of an element having the largest content (unit: atomic %) of the first elements in the strain-resistant layer; The resistivity of the strain-resistant layer is 100 μΩcm or less, which is lower than the resistivity of the protective layer. A strain gauge characterized by:

12. A strain sensor comprising: the strain gauge according to any one of claims 1 to 11; and an electrode for applying current to the strain gauge.

13. 1. A method for manufacturing a strain gauge having a laminate pattern including a strain-resistant layer and a protective layer provided on at least a portion of the strain-resistant layer and electrochemically more noble than the strain-resistant layer, comprising: the resistivity of the protective layer is higher than the resistivity of the strain-resistant layer; The pattern of the laminate is forming the protective layer on the strain-resistant layer provided on a substrate; forming a resist pattern on the protective layer; and removing, by wet etching, the protective layer that is not covered with the resist pattern and the strain resistance layer that is located below the protective layer.

14. 14. The method for manufacturing a strain gauge according to claim 13, wherein an etching rate of the strain resistance layer in an etching solution used for the wet etching is 50 nm / min or more.

15. 14. The method for manufacturing a strain gauge according to claim 13, wherein an etching rate of the protective layer in an etching solution used for the wet etching is 5 nm / min or more.

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