Force sensor and method for manufacturing a force sensor

Abstract

To inhibit oxidization of a metal array and a metal layer.SOLUTION: A force sensor includes: a first substrate made of a material which transmits an electromagnetic wave, the first substrate having a metal array arranged in a periodic pattern, on its surface; a second substrate facing the first substrate across a space, the second substrate having a metal layer which reflects an electromagnetic wave having passed through the first substrate, on its surface; a connection member for connecting the first substrate and the second substrate to each other and defining an internal space for containing the metal array and the metal layer; and an inactive material filled in the internal space.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a force sensor and a method for manufacturing the force sensor.

Background Art

[0002] Patent Document 1 discloses a displacement sensor having an air gap structure in which the gap between a metal array and a metal layer can be changed by an external force, and a method for manufacturing the displacement sensor. The gap is an air layer provided between the metal array and the metal layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the displacement sensor of Patent Document 1, the metal array or the metal layer is exposed to the air layer. Therefore, the metal array or the metal layer may be oxidized, and the characteristics of the force sensor may deteriorate. The present disclosure provides a technique for suppressing the oxidation of the metal array and the metal layer.

Means for Solving the Problems

[0005] A force sensor according to one aspect of the present disclosure includes a first substrate, a second substrate, a connecting member, and an inert substance. The first substrate is made of a material that transmits electromagnetic waves and has a metal array arranged in a periodic pattern on the surface. The second substrate is arranged at a distance so as to face the first substrate and has a metal layer on the surface that reflects the electromagnetic waves transmitted through the first substrate. The connecting member connects the first substrate and the second substrate and defines an internal space that houses the metal array and the metal layer. The inert substance is filled in the internal space.

[0006] In this force sensor, an internal space is defined in which a metal array and metal layer are housed. This internal space is filled with an inert material. As a result, this force sensor can avoid exposing the metal array and metal layer to oxygen-containing air. Therefore, this force sensor can suppress oxidation of the metal array and metal layer.

[0007] According to one embodiment, the force sensor may include a sealing member. The connecting member may have an opening that communicates the internal space with the outside. The sealing member may seal the opening. In this case, the force sensor can fill the internal space with an inert substance through the opening, and the sealing member can seal the inert substance in the internal space.

[0008] According to one embodiment, the force sensor may include a spacer member that is positioned in the internal space and regulates the height of the internal space. The height of the internal space is the distance between the first substrate and the second substrate. This force sensor can maintain the positional relationship between the first substrate and the second substrate so that the distance between them remains constant when no load is applied.

[0009] The inert substance may be an inert gas or silicone oil.

[0010] A method for manufacturing a force sensor relating to another aspect of this disclosure comprises the following steps (1) to (3): (1) A step of preparing a first substrate, a second substrate, and a connecting member. The first substrate is made of a material that transmits electromagnetic waves and has a metal array arranged in a periodic pattern on its surface. The second substrate is positioned at a distance from the first substrate and has a metal layer on its surface that reflects electromagnetic waves that have passed through the first substrate. The connecting member connects the first substrate and the second substrate, defines an internal space that houses the metal array, and has an opening that connects the internal space to the outside. (2) A process of reducing the pressure in the internal space through the opening. (3) A step of filling the depressurized internal space with an inert substance through an opening. (4) A step of sealing the opening with a sealing member.

[0011] In this manufacturing method, the inert substance is filled into the internal space through an opening and sealed within the internal space by a sealing member. This prevents the metal array and metal layer from being exposed to oxygen-containing air. Therefore, this manufacturing method can provide a force sensor that can suppress oxidation of the metal array and metal layer. [Effects of the Invention]

[0012] According to this disclosure, oxidation of metal arrays and metal layers can be suppressed. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing an example of a force sensor according to one embodiment. [Figure 2] This is a cross-sectional view along line II-II in Figure 1. [Figure 3] This flowchart shows an example of a manufacturing method according to one embodiment. [Figure 4] This figure illustrates the vacuum step of a manufacturing method according to one embodiment. [Figure 5] This figure illustrates the filling process of a manufacturing method according to one embodiment. [Figure 6] This diagram illustrates the filling process of the manufacturing method related to the modified example. [Figure 7] Figure 2 is a cross-sectional view showing a modified example of the force sensor. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described below with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numeral, and redundant descriptions will not be repeated. The dimensional ratios in the drawings do not necessarily correspond to those described.

[0015] [Force sensor] The force sensor manufactured by the manufacturing method according to this embodiment is a force sensor using electromagnetic waves. The electromagnetic waves are visible light, infrared light, terahertz waves, or microwaves. The force sensor has an air gap structure in which a gap is formed between a metal array and a metal layer. Electromagnetic waves are incident on the air gap structure and reflected waves are measured. A resonance wavelength is obtained based on the incident wave and the reflected wave. The resonance wavelength changes according to the size of the gap. The gap changes due to an external force. That is, the force sensor using electromagnetic waves is a sensor that measures an external force based on a change in the resonance wavelength.

[0016] FIG. 1 is a cross-sectional view showing an example of a force sensor according to an embodiment. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. As shown in FIG. 1, the force sensor 1 includes a lower substrate 10 (an example of a first substrate) and an upper substrate 20 (an example of a second substrate). The lower substrate 10 is made of a material that transmits light (an example of electromagnetic waves). The lower substrate 10 is, for example, a glass substrate. The lower substrate 10 has a metal array 11 arranged in a periodic pattern on its upper surface (an example of a surface). The metal array 11 is, for example, a rod array or a dot array. The metal array 11 may be configured by a pattern in which a substantially square array with a side length of 350 nm is periodically arranged at intervals of 400 nm. The material of the metal array 11 is, for example, Au (gold) or Al (aluminum). The upper substrate 20 does not necessarily need to be made of a material that transmits light, and may be a glass substrate or a silicon substrate, etc. The upper substrate 20 has a metal layer 21 that reflects light on its lower surface (an example of a surface). The material of the metal layer 21 is, for example, Au or Al. The lower substrate 10 and the upper substrate 20 may be formed from alkali-free glass or quartz that does not contain an alkali component.

[0017] The force sensor 1 includes a connecting member 30. As shown in Figures 1 and 2, the lower substrate 10 and the upper substrate 20 are connected by the connecting member 30. The connecting member 30 is provided around the metal array 11 and the metal layer 21, and fixes the lower substrate 10 and the upper substrate 20 with a gap between them. The upper substrate 20 is positioned with a gap between it and the lower substrate 10. As a result, the connecting member 30 defines an internal space V between the lower substrate 10 and the upper substrate 20, which includes the metal array 11 and the metal layer 21. The connecting member 30 is made of a metal that is difficult to oxidize and has a high melting point. The connecting member 30 may also consist of fused metal layers. As an example, the connecting member 30 consists of a metal layer formed by fusing a first metal layer formed on the lower substrate 10 and a second metal layer formed on the second substrate. The first metal layer and the second metal consist of, for example, a three-layer structure of Mo (molybdenum) / Al / Mo. The first metal layer and the second metal may be single layers of Al, Mo, Ag (silver), Ti (titanium), or Cr (chromium).

[0018] The force sensor 1 includes an inert substance 40 that fills the internal space V. The inert substance 40 is a fluid with low chemical activity. The inert substance 40 is, for example, an inert gas. The inert gas is, for example, nitrogen gas, carbon dioxide, or a noble gas. As shown in Figure 2, the connecting member 30 has a sealing member 31 and an opening 30a that connects the internal space V to the outside. The opening 30a is formed by cutting out a portion of the connecting member 30 around the metal array 11 and the metal layer 21. The opening 30a is sealed by the sealing member 31. In other words, the inert substance 40 is sealed in the internal space V by the sealing member 31. The sealing member 31 is, for example, an ultraviolet curing resin.

[0019] A part of the light that passes through the lower substrate 10 and the metal array 11 is reflected by the metal layer 21 and absorbed by resonating between the metal array 11 and the metal layer 21. The wavelength of the absorbed light changes according to the distance between the metal array 11 and the metal layer 21. The force sensor 1 is configured such that the posture of the upper substrate 20 with respect to the lower substrate 10 is changed in response to an external load. Therefore, the load applied to the force sensor 1 is indicated by the change in the wavelength of the light absorbed by the force sensor 1.

[0020] [Manufacturing Method of Force Sensor] FIG. 3 is a flowchart showing an example of a manufacturing method M1 of the force sensor 1 according to the present embodiment. In the manufacturing method M1, first, the lower substrate 10, the upper substrate 20, and the connecting member 30 are prepared (step S10). As described above, the lower substrate 10 is made of a material that transmits electromagnetic waves and has a metal array 11 arranged in a periodic pattern on its surface. The upper substrate 20 is arranged at a distance facing the lower substrate 10 and has a metal layer 21 that reflects electromagnetic waves on its surface. The connecting member 30 connects the lower substrate 10 and the upper substrate 20, defines an internal space V, and has an opening 30a that communicates the internal space V with the outside. Thus, in step S10, the force sensor 1 in which the lower substrate 10 and the upper substrate 20 are connected by the connecting member 30 is prepared.

[0021] Next, the internal space V of the force sensor 1 is depressurized (step S20). FIG. 4 is a diagram for explaining the depressurization process of the manufacturing method according to an embodiment. In FIG. 4, a cross-sectional view of the force sensor 1 along the line IV-IV of FIG. 2 is shown. As shown in FIG. 4, the force sensor 1 is housed inside a container C that can be evacuated. The container C includes a valve B1 to which a vacuum pump (not shown) for evacuating the inside of the container C is connected, and a valve B2 to which a gas source (not shown) for introducing an inert substance 40 (inert gas in this embodiment) into the inside of the container C is connected. By opening the valve B! and operating the vacuum pump, the inside of the container C is depressurized. The force sensor 1 with the internal space V depressurized is deformed such that the lower substrate 10 and the upper substrate 20 approach each other.

[0022] Next, the internal space V of the depressurized force sensor 1 is filled with an inert substance 40 (step S30). Figure 5 is a diagram illustrating the filling process of a manufacturing method according to one embodiment. By closing valve B1 and opening valve B2, the inert substance 40 is introduced into the depressurized container C from valve B2, as shown in Figure 5. The inert substance 40 is filled into the internal space V from opening 30a. As the internal space V is filled with the inert substance 40, the depressurization of the internal space V is eliminated, and the deformation of the lower substrate 10 and the upper substrate 20 is eliminated.

[0023] Finally, the opening 30a of the force sensor 1 is sealed (step S40). A sealing member 31 made of ultraviolet-curing resin is applied to the opening 30a of the force sensor 1. Then, ultraviolet light is irradiated onto the sealing member 31 applied to the opening 30a, and the sealing member 31 hardens, sealing the opening 30a. The force sensor 1 is manufactured through the above steps. Note that the manufacturing method M1 may include a cleaning step of cleaning the metal array 11 before the step S40.

[0024] [Summary of Embodiments] In the force sensor 1, an internal space V is defined in which the metal array 11 and the metal layer 21 are housed. This internal space V is filled with an inert substance 40. As a result, the force sensor 1 can avoid exposing the metal array 11 and the metal layer 21 to air containing oxygen. Therefore, the force sensor 1 can suppress oxidation of the metal array 11 and the metal layer 21.

[0025] Since the connecting member 30 has an opening 30a that connects the internal space V to the outside, the force sensor 1 can fill the internal space V with an inert substance 40 through the opening 30a, and the sealing member 31 can seal the inert substance 40 in the internal space V.

[0026] In the manufacturing method M1 for the force sensor 1, the inert substance 40 is filled into the internal space V through the opening 30a and sealed in the internal space V by the sealing member 31. As a result, the manufacturing method M1 avoids exposing the metal array 11 and the metal layer 21 to oxygen-containing air. Therefore, the manufacturing method M1 can provide a force sensor 1 that suppresses oxidation of the metal array 11 and the metal layer 21.

[0027] Although various exemplary embodiments have been described above, this disclosure is not limited to the embodiments described above, and various omissions, substitutions, and modifications may be made.

[0028] [Differentiation] The inert substance 40 may be silicone oil. In this case, in step S30, the internal space V of the force sensor 1, which has been depressurized, is filled with silicone oil. Figure 6 is a diagram illustrating the filling process of a modified manufacturing method. In Figure 6, the silicone oil is filled into the internal space V through the opening 30a. First, with the internal space V of the container C depressurized, the force sensor 1 is positioned so that the opening 30a is immersed in the silicone oil. Next, with the opening 30a immersed in the silicone oil, the valve B1 is opened. This releases the depressurization of the container C, and the internal space V of the force sensor 1 is filled with silicone oil.

[0029] The inert substance 40 may harden after filling the internal space V. That is, the inert substance 40 may be a solid. For example, the inert substance 40 may be polydimethylsiloxane (PDMS).

[0030] The connecting member 30 does not necessarily have to have an opening 30a. In this case, the connecting member 30 is divided into a first connecting member provided on the lower substrate 10 and a second connecting member provided on the upper substrate 20, and the first connecting member and the second connecting member can be connected by fusion or the like in an inert gas atmosphere.

[0031] Figure 7 is a cross-sectional view showing a modified example of the force sensor shown in Figure 2. When the connecting member 30 is divided into a first connecting member and a second connecting member, and the lower substrate 10 and the upper substrate 20 are connected by fusing the first connecting member provided on the lower substrate 10 with the second connecting member provided on the upper substrate 20, the height of the connecting member 30 may fluctuate due to the fusion, and as a result, the height of the internal space V may deviate from the set value. For this reason, the force sensor 1 may be provided with a spacer member 12. The spacer member 12 is provided on the lower substrate 10 so as to surround the metal array 11, inside the connecting member 30 in the internal space V. The spacer member 12 may be provided on the upper substrate 20, or it may be divided into a first spacer member for the lower substrate 10 and a second spacer member for the upper substrate 20. The spacer member 12 regulates the height of the internal space V when the first connecting member and the second connecting member are fused. The height of the internal space V is the distance between the lower substrate 10 and the upper substrate 20. The spacer member 12 has an opening 12a that communicates with the opening 30a of the connecting member 30. The inert substance 40 is filled into the internal space V through the openings 30a and 12a. The sealing member 31 seals the openings 30a and 12a. The other configurations of the modified force sensor are the same as those of the force sensor 1 shown in Figure 2. By providing the spacer member 12, the force sensor 1 can maintain the positional relationship between the lower substrate 10 and the upper substrate 20 such that the distance between the lower substrate 10 and the upper substrate 20 remains constant when no load is applied.

[0032] The force sensor 1 may include a protective layer covering the surface of the metal array 11. By including a protective layer, the cleaning step described above can be omitted in the manufacturing process of the force sensor 1. The protective layer is formed from, for example, quartz. The protective layer protects the metal array 11 from damage or oxidation.

[0033] The thickness of the spacer member 12 may be 190 nm. The thickness of the metal layer 21 may be 100 nm. The thickness of the metal array 11 may be 30 nm. The thickness of the protective layer may be 35 nm. The gap between the metal layer 21 and the protective layer may be 30 nm. The distance between the metal layer 21 and the metal array 11 may be 65 nm. [Explanation of Symbols]

[0034] 1...force sensor, 10...lower substrate (example of first substrate), 11...metal array, 12...spacer member, 20...upper substrate (example of second substrate), 21...metal layer, 30...connecting member, 30a...opening, 31...sealing member, 40...inert material.

Claims

1. A first substrate having a metal array on its surface, which is made of a material that transmits electromagnetic waves and is arranged in a periodic pattern, A second substrate is positioned at a distance from the first substrate so as to face it, and has a metal layer on its surface that reflects electromagnetic waves that have passed through the first substrate, A connecting member that connects the first substrate and the second substrate and defines an internal space that houses the metal array and the metal layer, The inert substance that fills the internal space, A spacer member is placed in the internal space and restricts the height of the internal space, A force sensor equipped with the following features.

2. Equipped with a sealing member, The force sensor according to claim 1, wherein the connecting member has an opening that communicates the internal space with the outside, and the sealing member seals the opening.

3. The force sensor according to claim 1 or 2, wherein the inert substance is an inert gas or silicone oil.

4. The process involves preparing a first substrate having a metal array on its surface made of a material that transmits electromagnetic waves and arranged in a periodic pattern, a second substrate having a metal layer on its surface that reflects electromagnetic waves that have passed through the first substrate and is positioned at a distance from the first substrate, and connecting a connecting member that connects the first substrate and the second substrate, defines an internal space for housing the metal array, and has an opening that connects the internal space to the outside, and a spacer member that is positioned in the internal space and restricts the height of the internal space. A step of reducing the pressure in the internal space through the opening, A step of filling the depressurized internal space with an inert substance through the opening, A step of sealing the opening with a sealing member, A method for manufacturing a force sensor, comprising the features described above.

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