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 laminate (11) including a strain resistance layer (12) and a protective layer (13) provided so as to have a portion in contact with the strain resistance layer (12), the resistivity of the protective layer (13) being higher than the resistivity of the strain resistance layer (12), and the protective layer (13) being electrochemically more expensive than the strain resistance layer (12). Thus, when wet etching is performed in order to form a pattern of the laminate (11), the protective layer (13) in the vicinity of the strain resistance layer (12) is less likely to be etched, peeling of a resist pattern and the like can be suppressed, unevenness in the amount of side etching is reduced, and unevenness in resistance as a strain gauge (10) is reduced.

Description

Technical Field

[0001] The invention relates to a strain gauge, a manufacturing method of the strain gauge and a strain sensor. Background Art

[0002] Strain gauges are known that are attached to a measurement object (strain-generating body) to detect the strain of the measurement object. As constituent materials of the strain gauge, strain resistors that change resistance as a result of volume change due to external force are exemplified, and specifically, metal materials containing Ni, Cr, Cu, etc. are used. The strain resistor is formed, for example, in a film form on a substrate, and is formed into a desired pattern such as a meander pattern by photolithography and etching techniques (for example, Patent Documents 1 and 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-74934

[0006] Patent Document 2: Japanese Patent Application Publication No. 2017-161286 Summary of the invention

[0007] Problems to be solved by the invention

[0008] 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 in the photolithography process or the etching process. Therefore, in the technology disclosed in Patent Document 2, a resistance wiring pattern for adjusting resistance is provided in the strain gauge.

[0009] However, if such a resistor wiring pattern is provided, it is difficult to miniaturize the strain gauge. If the object to be measured (strain-generating body) is miniaturized, accurate measurement becomes difficult unless the attachment area of ​​the strain gauge is reduced. Therefore, in the technology disclosed in Patent Document 2, it is difficult to accurately measure the strain of a small strain-generating body.

[0010] The present invention is based on the above situation and aims to provide a strain gauge with less resistance variation and a method for manufacturing the same. Another object is to provide a strain sensor that can measure strain with high accuracy even if the strain-generating body is small by using the strain gauge.

[0011] Means for solving problems

[0012] A strain gauge according to one aspect of the present invention for solving the above-mentioned problems includes a pattern of a laminate including a strain resistor layer and a protective layer having a portion in contact with the strain resistor layer, wherein the protective layer is electrochemically more expensive than the strain resistor layer.

[0013] As described above, since the protective layer is electrochemically more expensive than the strain resistor layer, the protective layer is less likely to be etched near the strain resistor layer when wet etching is performed to form a pattern of the laminate, peeling of the resist pattern can be suppressed, and the variation in the side etching amount can be reduced.

[0014] In the strain gauge described above, the resistivity of the protective layer is preferably higher than the resistivity of the strain resistance layer. This makes it difficult for current to flow through the protective layer, and the strain detection sensitivity of the strain sensor can be improved.

[0015] In the above-mentioned strain gauge, the protective layer is preferably capable of being etched by an etching solution used to etch the strain resistor layer. The so-called "capable of being etched" in this specification refers to an etching rate in wet etching that is industrially acceptable. Specifically, it is preferably 1 nm / minute or more, and more preferably 3 nm / minute or more. There is no upper limit on the etching rate of the protective layer, but when measured alone (i.e., when the protective layer and the strain resistor layer are not electrically connected), it is preferably lower than the etching rate of the strain resistor layer.

[0016] In the above-mentioned strain gauge, the strain resistance 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 the element having the largest content (unit: atomic %) of the first element in the strain resistance layer. Thus, it is easy to realize that the protective layer becomes electrochemically more expensive than the strain resistance layer.

[0017] In the protective layer described above, it is sometimes preferred that the content of the third element is 50 atomic % or less from the viewpoint of obtaining suitable etching processability of the protective layer.

[0018] The protective layer preferably has a content of the third element of 10 atomic % or more from the viewpoint of stably achieving reduction in unevenness of the side etching amount.

[0019] The third element may include a semi-metal element or a typical element. In this case, it is easy to realize that the resistivity of the protective layer is higher than that of the strain resistance layer.

[0020] 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, it may be possible to more stably achieve a higher resistivity of the protective layer than that of the strain resistance layer.

[0021] The Pauling electronegativity of the third element may be 2.6 or less. An electronegativity of 2.6 or less is sometimes preferred from the viewpoint of having suitable etching processability of the protective layer.

[0022] The first element may include Cr, and the strain resistance layer may further include a typical element.

[0023] In some cases, the resistivity of the strain resistance layer is preferably 100 μΩcm or less and lower than the resistivity of the protective layer.

[0024] As another aspect, the present invention provides a strain sensor including the above-mentioned strain gauge and an electrode for conducting electricity to the strain gauge.

[0025] As another embodiment, the present invention provides a method for manufacturing a strain gauge, the strain gauge having a pattern of a laminated body, the laminated body including a strain resistor layer and a protective layer disposed on at least a portion of the strain resistor layer and electrochemically more expensive than the strain resistor layer. In the manufacturing method, the pattern of the laminated body is formed by the following steps: forming a protective layer on a strain resistor layer disposed on a substrate; forming an anti-etching pattern on the protective layer; and removing the protective layer not covered by the anti-etching pattern and the strain resistor layer located under the protective layer by wet etching.

[0026] In the above-mentioned production method, the etching rate of the strain resistance layer in the etching solution used for wet etching is preferably 50 nm / minute or more in some cases.

[0027] In the above-mentioned production method, the etching rate of the protective layer in the etching solution used for wet etching is preferably 5 nm / minute or more in some cases.

[0028] Effects of the Invention

[0029] According to the present invention, it is possible to provide a strain gauge with less electrical resistance variation and a method for manufacturing the same, and a strain sensor capable of measuring strain with high accuracy even if the strain generating body is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. 1 is a diagram showing an example of a strain sensor according to an embodiment of the present invention.

[0031] Figure 2 It means Figure 1 Conceptual diagram of the cross section along line AA.

[0032] Figure 3A It is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (a state in which a strain resistance layer and a protective layer are stacked).

[0033] Figure 3B It is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (a state where a resist film is formed).

[0034] Figure 3C It is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (a state where a resist pattern is formed).

[0035] Figure 3D It 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 processing of a protective layer is performed).

[0036] Figure 3E It is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (a state in which the protective layer is etched and the strain resistance layer is exposed).

[0037] Figure 3F It is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (a state where the strain resistance layer is etched).

[0038] Figure 3G It 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 completed).

[0039] Figure 3H It is an explanatory diagram of a method for manufacturing a strain gauge according to an embodiment of the present invention (a state where the resist pattern is removed).

[0040] Figure 4A This is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where strain resistance layers are stacked).

[0041] Figure 4B It is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where a resist film is formed).

[0042] Figure 4C It is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where a resist pattern is formed).

[0043] Figure 4D It is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where the strain resistance layer is etched).

[0044] Figure 4E This is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where etching of the strain resistance layer is completed).

[0045] Figure 4F It is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where the resist pattern is removed).

[0046] Figure 5 This is a graph showing the average value and 3σ of the side etching amount of the strain resistance layer manufactured in Example 1.

[0047] Figure 6 This is a graph showing 3σ of the side etching amount of the strain resistance layer manufactured in Example 1.

[0048] Figure 7 This is a graph showing the average value of the inter-electrode resistance of the strain gauge manufactured in Example 1.

[0049] Figure 8 This is a graph showing the variation index of the inter-electrode resistance of the strain gauge manufactured in Example 1.

[0050] Fig. 9 This is a graph showing the average value and 3σ of the side etching amount of the strain resistance layer manufactured in Example 2.

[0051] Fig.10 This is a graph showing 3σ of the side etching amount of the strain resistance layer manufactured in Example 2. DETAILED DESCRIPTION

[0052] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same components are denoted by the same reference numerals, and description of components once described will be appropriately omitted.

[0053] Figure 1 FIG. 1 is a diagram showing an example of a strain sensor according to an embodiment of the present invention. Figure 1 As shown in , the strain sensor 100 of the present embodiment includes a strain gauge 10 having a meander-shaped pattern and an electrode 20 for conducting electricity to the strain gauge 10. The strain gauge 10 and the electrode 20 are both formed on a substrate 30. As non-limiting examples of the constituent material of the electrode 20, Cu, Au, and alloys containing them can be cited. 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, and a plating layer 21 is provided on each of the first electrode 201 and the second electrode 202 for the purpose of improving the solder bonding strength.

[0054] Figure 2 It means Figure 1 Conceptual diagram of the cross section of line AA. Figure 2 As shown in FIG. 1 , the strain gauge 10 includes a laminate 11 including a strain resistor layer 12 and a protective layer 13 having a portion in contact with the strain resistor layer 12 , and the laminate 11 has a meander pattern formed therein.

[0055] The strain resistance layer 12 has a property of changing resistance value when its length changes in the direction of current flow due to external force. This property can be quantitatively evaluated by the strain coefficient Gf shown in the following formula (1).

[0056] Gf=(ΔR / R) / (ΔL / L) (1)

[0057] Here, L is the length of the direction of current flow in the strain gauge 10 when no external force is applied (under no load) (current direction length), ΔL is the change in the current direction length of the strain gauge 10 when an external force is applied to the strain gauge 10 (under load) relative to the state when there is no load, R is the resistance value of the strain gauge 10 when there is no load, and ΔR is the change in the resistance value of the strain gauge 10 when there is load relative to the state when there is no load.

[0058] The strain resistor layer 12 is formed of a metal material having Ni, Cr, Cu, etc. as a main component, and typical examples of the material include NiCr. 20 (Ni-Cr alloy, resistivity: 104μΩcm), CuNi 45 (Constantan, resistivity: 48 μΩcm), etc. The resistivity of the strain resistor layer 12 is preferably low, and is preferably 100 μΩcm or less, if not specifically limited.

[0059] From the viewpoint of improving the balance between the gauge factor Gf and the temperature coefficient of resistance (TCR), the strain resistor layer 12 may preferably contain Cr as a main component and a non-metallic element, specifically a typical element (eg, N).

[0060] The strain gauge 10 of the present 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 expensive than the strain resistance layer 12. The protective layer 13 has the above-mentioned characteristics, and the unevenness of the side etching amount when the strain resistance layer 12 is wet-etched can be suppressed. This point will be described in detail when describing the manufacturing method of the strain gauge 10.

[0061] The material constituting the protective layer 13 is not particularly limited as long as it is electrochemically expensive compared to the strain resistor layer 12. However, when the laminate 11 having the strain resistor layer 12 and the protective layer 13 is energized, the resistivity (unit: Ωcm) of the protective layer 13 is preferably higher than that of the strain resistor layer 12 so that the current flows preferentially in the strain resistor layer 12. For example, if the NiCr 20 (Ni-Cr alloy) or CuNi 45 If the resistivity of the protective layer 13 is 50 μΩcm or more, it is more preferably 120 μΩcm or more, and particularly preferably 150 μΩcm or more.

[0062] Furthermore, as described in the method for manufacturing the strain gauge 10 described later, when the laminate 11 is patterned by wet etching, the protective layer 13 should be capable of being etched by the etching solution used to etch the strain resistor layer 12 .

[0063] The strain gauge 10 may include one or more first elements selected from the group consisting of Ni, Cr, and Cu. In this case, the protective layer 13 preferably includes 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 the first element having the largest content (unit: atomic %) in the strain gauge 10. Thus, it is easy to make the protective layer 13 electrochemically more expensive than the strain gauge 12.

[0064] It should be noted that, about the first ionization energy, Ni is 737.1kJ / mol, Cr is 652.9kJ / mol, and Cu is 745.5kJ / mol. Therefore, the first ionization energy is that the element above 750kJ / mol is suitable as the third element. Such elements are often regarded as semi-metallic elements and typical elements. Therefore, it is sometimes preferred to include the third element semi-metallic elements or typical elements. As preferred specific examples of the third element that is not limited, B (800.6kJ / mol), C (1086.5kJ / mol), Si (786.5kJ / mol), P (1011.8kJ / mol) and Ge (762kJ / mol) (the first ionization energy in brackets) can be listed. Therefore, the third element preferably includes one or more elements selected from the group consisting of these elements.

[0065] When the protective layer 13 contains the second element and the third element as described above, the content of the third element is preferably 50 atomic % or less from the viewpoint of easily ensuring the etching processability. In addition, the content of the third element is preferably 10 atomic % or more from the viewpoint of stably reducing the unevenness of the side etching amount. As shown in the embodiment described later, if the content of the third element is about 25 atomic %, even if the content of the third element is increased above this, the influence on the unevenness of the side etching amount is sometimes reduced.

[0066] It should be noted that the Pauling electronegativity of the third element can also be less than 2.6. When the electronegativity is less than 2.6, the material constituting the protective layer 13 is not easy to improve due to ionic bonding, so it is sometimes more stable to achieve that the protective layer 13 has suitable etching processability. In addition, since elements with high electronegativity are easy to obtain multiple valences, it is worried that the composition / organization of the protective layer 13 is locally uneven. Such unevenness sometimes causes electrochemical unevenness, which can affect the realization of the function of the protective layer 13 (suppressing the unevenness of the side etching amount of the strain resistor layer 12).

[0067] Here, when both the constituent material of the strain resistor layer 12 and the constituent material of the electrode 20 contain Cu, as a specific example, when the strain resistor layer 12 is made of CuNi 45In the case where the electrode 20 is composed of Cu (constantan), by appropriately selecting the constituent material of the protective layer 13, the diffusion of Cu contained in the electrode 20 into the strain resistor layer 12 can be suppressed by the protective layer 13. If Cu diffuses from the electrode 20 into the strain resistor layer 12, there is a concern that the composition of the strain resistor layer 12 changes, and the gauge factor Gf of the strain gauge 10 decreases. The protective layer 13 having a Cu barrier function is easily obtained when it contains the above-mentioned second element and third element, and is particularly easy to obtain by selecting a semi-metallic element or a typical element as the third element.

[0068] Hereinafter, a method for manufacturing the strain gauge 10 , specifically, a method for forming a pattern of the laminated body 11 included in the strain gauge 10 will be described.

[0069] Figure 3A to Figure 3H The following diagrams are explanatory diagrams of a method for manufacturing a strain gauge according to an embodiment of the present invention, and each shows the following states.

[0070] Figure 3A : The state where the strain resistance layer 12 and the protective layer 13 are stacked

[0071] Figure 3B : State where the resist film 40 is formed

[0072] Figure 3C : State where the resist pattern 41 is formed

[0073] Figure 3D : State where the protective layer 13 has been etched

[0074] Figure 3E : The protective layer 13 is etched and the strain resistance layer 12 is exposed

[0075] Figure 3F : The state where the strain resistance layer 12 is etched

[0076] Figure 3G : The etching process of the strain resistor layer 12 is completed

[0077] Figure 3H : State where the resist pattern 41 is removed

[0078] In the manufacturing method of this embodiment, first, a protective layer 13 ( Figure 3A). Thus, a laminated film is formed by laminating the protective layer 13 on the strain resistor layer 12 on the substrate 30. The manufacturing method of the strain resistor layer 12 and the protective layer 13 is not limited. They can be formed by dry processes such as evaporation, sputtering, and reactive sputtering, or by wet processes such as electroplating and electroless plating. When the strain resistor layer 12 and the protective layer 13 contain typical elements, it is sometimes preferred to use reactive sputtering, electroless plating, etc.

[0079] When the laminated film is formed on the substrate 30 in this manner, the anti-etching film 40 ( Figure 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.

[0080] Next, the resist film 40 is subjected to a photolithography process (exposure and development) to form a resist pattern 41. Thus, the resist pattern 41 is provided on the protective layer 13 ( Figure 3C ).

[0081] Next, the protective layer 13 not covered by the anti-etching pattern 41 is etched. The etching process is generally wet etching using an etching solution. The etching solution is appropriately set based on the materials constituting the strain resistor layer 12, the protective layer 13, and the anti-etching pattern 41. Specifically, the etching solution has the ability to dissolve the strain resistor layer 12. The etching rate of the strain resistor layer 12 is appropriately set according to the processing technology. For example, as the rate when the strain resistor layer 12 is etched alone, it is sometimes preferably 50 nm / minute or more, sometimes more preferably 80 nm / minute or more, and sometimes particularly preferably 100 nm / minute or more.

[0082] The etching liquid has the ability to dissolve the protective layer 13, but it is not necessary to set the etching rate to the same as that of the strain resistor layer 12. The etching rate of the protective layer 13 is appropriately set according to the processing technology, for example, as the rate when the protective layer 13 is etched alone, it is sometimes preferably 5nm / minute or more. As described below, in the manufacturing method of this embodiment, since the protective layer 13 is in contact with the strain resistor layer 12, its etching rate is slower than that of the case of etching alone.

[0083] It should be noted that the etching liquid is preferably not likely to corrode the resist pattern 41. A specific example of such an etching liquid is ammonium cerium nitrate.

[0084] In wet etching, since etching generally proceeds isotropically, Figure 3D As shown in FIG. 1 , if the etching solution etches the protective layer 13, the protective layer 13 is etched along the stacking direction, and the side etching of the protective layer 13 is also generated. If the etching of the protective layer 13 in the stacking direction is carried out, as shown in FIG. Figure 3E As shown in FIG. 1 , the strain resistor layer 12 is exposed in the region not covered by the resist pattern 41 , and the protection layer 13 that has not been etched is separated between the resist pattern 41 and the strain resistor layer 12 to form a protection layer pattern 131 .

[0085] If Figure 3E In this way, both the protective layer pattern 131 and the strain resistor layer 12 are exposed in the etching solution. Since the protective layer 13 (protective layer pattern 131) is electrochemically more expensive than the strain resistor layer 12, a local battery is formed between them, and the etching rate of the protective layer pattern 131 is reduced. Therefore, the strain resistor layer 12 is etched first, and the side etching generated under the anti-etching pattern 41 also proceeds first in the strain resistor layer 12. As a result, Figure 3F As shown in , a protective layer pattern 131 remains between the portion of the strain resistor layer 12 where side etching occurs and the resist pattern 41. The protective layer pattern 131 protects the resist pattern 41 from physical phenomena (the generation of bubbles, local and irregular changes in the flow of the etching solution) caused by the side etching of the strain resistor layer 12. That is, the protective layer pattern 131 functions as a protective member of the resist pattern 41. As a result, the resist pattern 41 becomes less susceptible to damage during the wet etching process. As specific examples of damage, local peeling, deformation, and defects of the resist pattern 41 can be listed, and such damage can cause uneven side etching of the strain resistor layer 12.

[0086] In the manufacturing method of this embodiment, since the protective layer 13 (protective layer pattern 131) is provided to protect the resist pattern 41, Figure 3G As shown in , when the etching of the strain resistor layer 12 in the stacking direction is completed and the strain resistor layer pattern 121 is appropriately formed, the wet etching amount of the strain resistor layer 12 (strain resistor layer pattern 121) is unlikely to become uneven.

[0087] It should be noted that if the protective layer pattern 131 is separated from the contact portion with the strain resistor layer 12, the electrochemical protection is weakened. Therefore, the etching rate of the protective layer pattern 131 increases as it is closer to the front end, and the strain resistor layer 12 is moderately etched during the etching. Therefore, when the resist pattern 41 is removed and the pattern of the laminate 11 is formed on the substrate 30, it is not easy to produce the protective layer pattern 131 protruding from the strain resistor layer pattern 121 in the horizontal direction ( Figure 3H ).

[0088] Figure 4A This is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where strain resistance layers are stacked). Figure 4B It is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where a resist film is formed). Figure 4CIt is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where a resist pattern is formed). Figure 4D It is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where the strain resistance layer is etched). Figure 4E This is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where etching of the strain resistance layer is completed). Figure 4F It is an explanatory diagram of a conventional method of manufacturing a strain gauge (a state where the resist pattern is removed).

[0089] In the manufacturing method of the prior art, the protective layer 13 provided in the manufacturing method of the present embodiment is not formed in the strain resistance layer 12 on the substrate 30, and the anti-etching film 40 ( Figure 4A , Figure 4B Therefore, the resist pattern 41 formed by photolithography is arranged in contact with the strain resistor layer 12 ( Figure 4C ).

[0090] If wet etching is performed using an etching solution in this state, side etching of the strain resistor layer 12 occurs directly below the resist pattern 41 ( Figure 4D ). The dissolution reaction of the strain resistor layer 12 that causes the side etching is accompanied by the generation of gas, etc., thereby causing local and irregular changes in the flow of the etching solution near the contact interface between the resist pattern 41 and the strain resistor layer 12. In the manufacturing method of the prior art, due to this uncontrollable physical phenomenon, such as Figure 4E As conceptually shown in FIG. , the variation in the amount of side etching of the strain resistor layer 12 becomes larger ( Figure 4E ). Figure 4E The two-dot chain line in FIG. 1 conceptually shows the result of side etching when the unevenness is small.

[0091] For the above reasons, in the conventional manufacturing method, the shape of the strain resistor layer pattern 121 formed on the substrate 30 varies greatly, and as in Patent Document 1, a resistor wiring pattern for resistance adjustment is required, which increases the sensitivity variation of the strain gauge.

[0092] The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, the elements disclosed in the above embodiments are intended to include all design changes and equivalents that fall within the technical scope of the present invention.

[0093] Hereinafter, the present invention will be specifically described using examples.

[0094] Example

[0095] (Example 1)

[0096] The strain gauge 10 is 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 are as follows.

[0097] ·Substrate 30: Polyimide film

[0098] ·Strain resistor layer 12: All layers are formed by sputtering.

[0099] NiCr 20 、Thickness 140nm

[0100] CuNi 45 、Thickness 70nm

[0101] Cr, thickness 35nm

[0102] Protective layer 13: formed by sputtering and having a thickness of 10 nm.

[0103] CrB 15

[0104] C 15

[0105] CrSi 15

[0106] CrGe 15

[0107] Cr

[0108] CrTi 15

[0109] Ta

[0110] Resist film 40: obtained by spin coating a liquid resist.

[0111] Etching solution: ammonium cerium nitrate

[0112] Table 1 shows the etching rate (unit: μm / min) and the resistivity (unit: μmΩcm) of each layer when each layer is etched using the above-mentioned etching solution alone.

[0113] It should be noted that the protective layer 13 formed of Ta cannot be etched by the above-mentioned etching solution, and is etched by a dry process (reactive ion etching).

[0114] [Table 1]

[0115]

[0116] For the strain resistance layer 12 of the obtained laminate 11 (the number of measurements in each case was 80), the side etching amount (unit: μm) was measured, and the average value and 3σ (3 times the standard deviation) were calculated. In addition, the inter-electrode resistance (unit: kΩ) of the strain gauge 10 (the number of measurements in each case was 80) was measured, and the average value and 3σ, as well as 3σ / average value (unit: %, referred to as "unevenness index" in this specification) were calculated. Furthermore, the strain coefficient Gf of the strain gauge 10 was measured. The measurement results are shown in Tables 2 and Figures 5 to 8 middle.

[0117] [Table 2]

[0118]

[0119] As shown in Table 2, etc., it is confirmed that in the case of having a protective layer 13 that is electrochemically expensive compared to the strain resistor layer 12 (Examples 1-2 to 1-6, Example 1-11, Example 1-13), the unevenness (3σ) of the side etching amount is smaller than that in the case of no protective layer 13 (Example 1-1, Example 1-10, Example 1-12) and the case of the protective layer 13 not being electrochemically expensive compared to the strain resistor layer 12 (Example 1-7, Example 1-8). In addition, it is confirmed that in the case of having a protective layer 13, the unevenness (unevenness index) of the resistance value of the strain gauge 10 is also reduced. It should be noted that in the case where the protective layer 13 is formed of Ta (Example 1-9, Example 1-14), since it cannot be processed by the etching solution used in this example, it is positioned as a reference example.

[0120] (Example 2)

[0121] The material of the strain resistor layer 12 is set to NiCr by the same manufacturing method as in Example 1. 20 , the material of the protective layer 13 is set to CrB X (X is 0 to 60) to produce a strain gauge 10. The side etching amount (unit: μm) was measured for the strain resistance layer 12 of the laminated body 11 of the obtained strain gauge 10 (the number of measurements in each case was 80), and the average value and 3σ (3 times the standard deviation) were calculated. The results are shown in Table 3 and Fig. 9 and Fig.10 middle.

[0122] [Table 3]

[0123]

[0124] As shown in Table 3, etc., in the CrB of the protective layer 13 XWhen X is 5 atomic % (Example 2-2), the unevenness (3σ) of the side etching amount is significantly reduced compared to the case where the protective layer 13 does not contain B (Example 2-1). X The unevenness (3σ) of the side etching amount is further reduced by increasing the amount of B added, but the degree of reduction is slower than that in Example 2-1 and Example 2-2. It is confirmed that the inclusion of B in the protective layer 13 and the reversal of the electrochemical noble relationship between the strain resistor layer 12 and the protective layer 13 have the greatest impact on reducing the unevenness (3σ) of the side etching amount. This embodiment shows that from the viewpoint of suppressing the unevenness (3σ) of the side etching amount, an amount of B added to the protective layer 13 of 20 atomic % is sufficient. Considering the manufacturing unevenness when forming the protective layer 13, an amount of B added of 25 atomic % is sufficient. It should be noted that in CrB X When X is 60 atomic %, the metallic property of the protective layer 13 is excessively reduced, and etching cannot be performed with this etching solution, so this is used as a reference example.

[0125] Explanation of symbols

[0126] 100: Strain sensor

[0127] 10: Strain gauge

[0128] 11: Laminated body

[0129] 12: Strain resistor layer

[0130] 121: Strain resistor layer pattern

[0131] 13: Protective layer

[0132] 131: Protective layer pattern

[0133] 20: Electrode

[0134] 201: 1st electrode

[0135] 202: Second electrode

[0136] 21: Plating

[0137] 30: Substrate

[0138] 40: Anti-corrosion film

[0139] 41: Resist pattern

Claims

1. A strain gauge, characterized in that: The present invention is a strain gauge having a pattern of a laminated body, wherein the laminated body includes a strain resistor layer and a protective layer having a portion in contact with the strain resistor layer. The protective layer is electrochemically noble compared to the strain resistance layer.

2. The strain gauge according to claim 1, wherein: The resistivity of the protection layer is higher than that of the strain resistance layer.

3. The strain gauge according to claim 1, wherein: The protective layer can be etched by an etching solution used to etch the strain resistor layer.

4. The strain gauge according to claim 1, wherein: The strain resistance layer includes 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 an element having the highest content in the strain resistance layer among the first elements, wherein the unit of the content is atomic %.

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

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

7. The strain gauge according to claim 4, wherein: The third element includes a semi-metal element or a typical element.

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

9. The strain gauge according to claim 4, wherein: The Pauling electronegativity of the third element is 2.6 or less.

10. The strain gauge according to claim 4, wherein: The first element includes Cr, and the strain resistance layer further includes a typical element.

11. The strain gauge according to claim 10, wherein: The resistivity of the strain resistance layer is 100 μΩcm or less, which is lower than the resistivity of the protection layer. 12 . A strain sensor comprising the strain gauge according to claim 1 and an electrode for conducting electricity to the strain gauge.

13. A method for manufacturing a strain gauge, the method comprising manufacturing a strain gauge having a pattern of a laminate, the laminate comprising a strain resistor layer and a protective layer provided on at least a portion of the strain resistor layer and being electrochemically more expensive than the strain resistor layer, The pattern of the stacked body is formed by the following steps: forming the protective layer on the strain resistor layer disposed on the substrate; forming a resist pattern on the protective layer; and The protective layer not covered by the resist pattern and the strain resistance layer under the protective layer are removed by wet etching.

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

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

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