METAL MEMBER WITH INSULATING FILM, PHYSICAL QUANTITY SENSOR, AND PRESSURE SENSOR

A metal member with insulating film includes a metal member, an insulating film, and a reinforcement portion. The metal member includes a film formation surface and a connection surface facing in a different direction from the film formation surface and connecting to the film formation surface. The insulating film covers at least a part of the film formation surface and the connection surface over a connection position between the film formation surface and the connection surface. The reinforcement portion is formed along a periphery of the insulating film at the connection position and covers at least a part of the periphery of the insulating film from an opposite side to the metal member.

BACKGROUND OF THE INVENTION

The present invention relates to a metal member with insulating film and a physical quantity sensor and a pressure sensor including the metal member.

A pressure sensor or a physical quantity sensor may employ an insulating-film-attached metal member in which an insulating film is formed on a metal member. In the insulating-film-attached metal member, the insulating film is formed using excellent characteristics of metal members, such as mechanical characteristics like elasticity and durability at high temperature, and it is thereby possible to add an electrical element of a detection circuit with a strain resistance film to the conductive metal member in an insulated manner.

However, mechanical properties, such as linear expansion coefficient and Young’s modulus, of the insulating film, are significantly different from those of the metal member, and the mechanical strength of the insulating film tends to be inferior to that of the metal member. Thus, there is a problem that the insulating film is easily peeled off or damaged. In addition, the insulating film tends to peel off from the outer edge, and it is thus conceivable that the insulating film is widely formed on the metal member so as to cover a film formation surface for forming a detection circuit or the like and also cover a connection surface such as a side surface connecting to the film formation surface.

BRIEF SUMMARY OF THE INVENTION

However, damage, such as cracking, tends to easily occur at a periphery of the insulating film, where the surface orientation of the insulating film changes along the surface orientation of the metal member. Thus, cracking and peeling may progress from the periphery of the insulating film to the insulating film on the film formation surface, and the insulating film may have a performance degradation in terms of insulation or shielding against liquids and gases.

The present disclosure provides a metal member with insulating film, and the like, capable of preventing generation of cracking and peeling at a periphery of an insulating film.

A metal member with insulating film according to the present disclosure comprises:a metal member including:a film formation surface; anda connection surface facing in a different direction from the film formation surface and connecting to the film formation surface;an insulating film covering at least a part of the film formation surface and the connection surface over a connection position between the film formation surface and the connection surface; anda reinforcement portion formed along a periphery of the insulating film at the connection position and covering at least a part of the periphery of the insulating film from an opposite side to the metal member.

The metal member with insulating film includes the reinforcement portion formed along the periphery of the insulating film and can thus effectively prevent generation of cracking and peeling at the periphery of the insulating film and prevent a performance degradation of the insulating film.

For example, the reinforcement portion may comprise a metal thin film.

The metal thin film has a moderate strength and conformability to the insulating film and favorably functions as the reinforcement portion for the periphery of the insulating film.

For example, the metal thin film may comprise an Au layer containing Au.

The Au layer has a favorable ductility and is less likely to have cracking and thus favorably functions as the reinforcement portion for the periphery of the insulating film. Moreover, the Au layer tends to have a small stress with chemical stability and excellent weather resistance and is less likely to have a peeling due to stress.

For example, the metal thin film may comprise a Pt layer containing Pt.

The Pt layer exhibits an excellent thermal stability and thus favorably functions as the reinforcement portion for the periphery of the insulating film, particularly in a high temperature environment.

For example, the metal thin film comprises an adhesive layer contacted with the insulating layer and at least one other layer, wherein the adhesive layer has an adhesion to the insulating layer being higher than that of the at least one other layer.

The metal thin film including the adhesive layer has a high adhesion to the insulating film. Thus, it is possible to effectively reinforce the periphery of the insulating film and favorably prevent generation of cracking and peeling from the periphery of the insulating film.

A physical quantity sensor according to the first aspect of the present disclosure comprises:the above-mentioned metal member with insulating film;a detection unit detecting a physical quantity of the metal member, the detection unit being formed on an upper side of the film formation surface, the upper side being the opposite side of the insulating layer to a surface thereof facing the film formation surface; andan electrode film formed so as to overlap with a part of the detection unit from above and connected with a wiring unit for ensuring electrical conduction to the outside of the detection unit,wherein the metal thin film of the reinforcement portion comprises a common layer with at least a part of layers of the electrode film.

The physical quantity sensor including the reinforcement portion prevents a performance degradation of the insulating film and has a favorable durability. Moreover, at least a part of the reinforcement portion can be formed simultaneously in the formation process of layers contained in the electrode film, and the physical quantity sensor is thus excellent in productivity

A physical quantity sensor according to the second aspect of the present disclosure comprises:the above-mentioned metal member with insulating film; anda detection unit detecting a physical quantity of the metal member, the detection unit being formed on an upper side of the film formation surface, the upper side being the opposite side of the insulating layer to a surface thereof facing the film formation surface, whereinthe metal member comprises a stem shape including a membrane with the film formation surface and a side wall portion with the connection surface, andthe detection unit detects a deformation amount of the membrane.

The physical quantity sensor including the reinforcement portion favorably prevents damage and performance degradation of the insulating film formed on the metal member having the stem shape and has a favorable durability.

A pressure sensor according to the present disclosure comprises:the above-mentioned metal member with insulating film; anda detection unit detecting a physical quantity of the metal member, the detection unit being formed on an upper side of the film formation surface, the upper side being the opposite side of the insulating layer to a surface thereof facing the film formation surface, whereinthe metal member comprises a stem shape including a membrane with the film formation surface and a side wall portion with the connection surface, andthe detection unit detects a deformation amount of the membrane due to pressure.

The pressure sensor including the reinforcement portion favorably prevents damage and performance degradation of the insulating film formed on the metal member having the stem shape and has a favorable durability. Moreover, the pressure sensor is excellent in durability of the insulating film and can thus particularly favorably be used as a pressure sensor in a high temperature and high pressure environment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is described based on embodiments shown in the figures.

First Embodiment

FIG.1is a schematic cross-sectional view of an insulating-film-attached metal member10according to First Embodiment, andFIG.2AandFIG.2Bare top views of the insulating-film-attached metal member10viewed from its upper surface. In each figure, for the convenience of description of each part included in the insulating-film-attached metal member10, the dimensions of each part are illustrated in different proportions from the actual ones.

As shown inFIG.1, the insulating-film-attached metal member10includes a metal member20, an insulating film50, and a reinforcement portion60. The metal member20shown inFIG.1has a substantially columnar shape, but the shape of the metal member20used for the insulating-film-attached metal member10is not limited to columnar and may be polygonal prism, such as rectangular parallelepiped, cylindrical, polygonal polyhedron, or the like.

The metal member20may be made of any single metal or alloy, such as steel, aluminum alloy, stainless steel, and nickel alloy. Preferably, from the point of enhancement in durability, the material of the metal member20is one material selected from SUS304 and SUS316, which are austenitic stainless steel, and SUS630 and SUS631, which are precipitation austenite.

As shown inFIG.1, the metal member20includes a film formation surface22band a connection surface24a. The film formation surface22bof the metal member20is one of the bottom surfaces of the cylinder, and the connection surface24ais a side surface of the cylinder. However, the shapes of the film formation surface22band the connection surface24aare not limited to those shown inFIG.1, and any surface (film formation surface) and another any surface (connection surface) facing in a different direction from the surface and connecting to the surface can be the film formation surface22band the connection surface24a, respectively.

The film formation surface22bis entirely covered with an insulating film50. The film formation surface22bis directly covered with the insulating film50and is contacted with a lower surface of the insulating film50. However, a part (e.g., 20% or less of the entire area) of the film formation surface22bmay be exposed from the insulating film50. The film formation surface22bshown inFIG.1is flat, but the film formation surface22bmay be curved.

As shown inFIG.1, the film formation surface22bfaces upward, and the connection surface24afaces sideways (horizontal direction) and faces in a different direction from the film formation surface22b. The connection surface24ais connected to the film formation surface22b, and the surface orientation of the metal member20changes at a connection position25between the connection surface24aand the film formation surface22b. The surface orientations of the film formation surface22band the connection surface24aare defined, for example, by a normal direction of each surface. The film formation surface22band the connection surface24aface in directions different from each other by approximately 90 degrees, but the relation between the film formation surface22band the connection surface24ais not limited to the case where they face in directions different from each other by 90 degrees.

At least a part of the connection surface24ais covered with the insulating film50. In particular, since the connection surface24ais a surface connected to the film formation surface22b, the portion of the connection surface24anear the connection position25is directly covered with the insulating film50continuing from the film formation surface22b. As with the film formation surface22b, the connection surface24ais also contacted with the insulating film50.

As with the film formation surface22b, although the connection surface24amay be entirely or mostly covered with the insulating film50, unlike the film formation surface22b, only a part (the vicinity of the connection position 25) may be covered with the insulating film50, and the rest may be exposed from the insulating film50. The boundary between the portion covered with the insulating film50and the portion exposed from the insulating film50on the connection surface24amay be transitional as the film thickness of the insulating film50decreases.

As shown inFIG.1, the insulating film50covers at least a part of the film formation surface22band the connection surface24aover the connection position25between the film formation surface22band the connection surface24a. The insulating film50is composed of, for example, silicon oxide such as SiO2, silicon nitride such as Si3N4, silicon oxynitride such as SiON, or other ceramics such as AlO3, but the material of the insulating film50is not limited as long as it is an insulating film.

The insulating film50is formed on the film formation surface22band the connection surface24aof the metal member20by a thin film formation method, such as CVD, sputtering, and vapor deposition, but the method of forming the insulating film50is not limited. The film thickness of the insulating film50on the film formation surface22bcan be about 0.1 to 10 µm and is preferably 1 to 5 µm

As shown inFIG.1, since the insulating film50is formed over the connection position25between the film formation surface22band the connection surface24a, an insulating-film periphery57is formed in a portion of the insulating film50covering the connection position25. In the insulating-film periphery57of the insulating film50covering the connection position25, the extension direction of the insulating film50changes following the change in the surface orientation of the connection position25of the metal member20, and the insulating film50forms a periphery.

As shown inFIG.2A, the insulating-film periphery57is formed corresponding to the outer edge of the film formation surface22b, that is, the connection position25. The insulating-film periphery57of the insulating-film-attached metal member10has a circular shape. As shown inFIG.1, a portion inside the insulating-film periphery57on the insulating film50covers the film formation surface22bof the metal member20, and this portion is an insulating film first portion54. Preferably, from the point of securing the function of the insulating film50on the film forming surface22b, the insulating film50has a substantially constant film thickness in the insulating film first portion54.

A portion outside the insulating-film periphery57on the insulating film50covers the connection surface24aof the metal member20, and this portion is an insulating film second portion56. The insulating film second portion56may be as thick as the insulating film first portion54or may be thinner than the insulating film first portion54.

As shown inFIG.1, the reinforcement portion60covers at least a part of the insulating-film periphery57from the opposite side to the metal member20. That is, the reinforcement portion60is formed on the insulating-film periphery57and the insulating film50in its vicinity and directly covers the insulating-film periphery57.

As shown inFIG.2A, the reinforcement portion60is formed in a ring shape along the insulating-film periphery57. The reinforcement portion60is formed continuously along the insulating-film periphery57, but does not cover the whole of the insulating-film periphery57and includes a discontinuous portion60afor exposing a part of the insulating-film periphery57.

That is, as shown inFIG.2A, the reinforcement portion60of the insulating-film-attached metal member10has a substantially C-ring shape with the discontinuous portion60a. However, the shape of the reinforcement portion60is not limited to the shape shown inFIG.2A.

FIG.2Bis a top view illustrating an insulating-film-attached metal member110according to First Modification. As shown inFIG.2B, a reinforcement portion160of the insulating-film-attached metal member110has a ring shape continuing along the insulating-film periphery57so as to cover the whole of the insulating-film periphery57. In addition to the shapes shown inFIG.2AandFIG.2B, for example, the reinforcement portion includes a shape intermittently formed along the insulating-film periphery57and having a plurality of discontinuous portions.

The reinforcement portion60shown inFIG.1andFIG.2is made of a film formed on the insulating film50and is preferably made of a metal thin film from the point of the ductility and strength required for the reinforcement portion60. The metals constituting a metal thin film are not limited and include Au, Al, Ru, Rh, Pd, Os, Ir, Pt, Cr, Ti, Ni, Mo, etc. The reinforcement portion60made of a metal thin film may be made of a single layer as shown inFIG.1or may be made of a plurality of layers as shown in Second to Fourth Embodiments mentioned below. A film other than the metal thin film constituting the reinforcement portion60is, for example, an insulating film of a silicon oxide.

The metal thin film constituting the reinforcement portion60is formed on the insulating film50by a thin film formation method, such as sputtering and vapor deposition. The shape of the thin metal film constituting the reinforcement portion60can be formed into any shape along the insulating-film periphery57using photolithography or metal mask.

In particular, when the reinforcement portion60is made of a metal thin film, the reinforcement portion60shown inFIG.1preferably has a thickness of approximately 50 to 500 nm and more preferably has a thickness of 100 to 200 nm. If the thickness of the reinforcement portion60is smaller than a predetermined value, it is difficult for the reinforcement portion60to form a continuous film, and the protection function of the reinforcement portion60for the insulating-film periphery57is lowered. On the other hand, if the thickness of the reinforcement portion60is larger than a predetermined value, there are disadvantages, such as a decrease in throughput due to an increase in film formation time and an increase in raw material costs.

As shown inFIG.2A, the reinforcement portion60may include the discontinuous portion60afor exposing a part of the insulating-film periphery57, but from the point of preventing the damage of the insulating film50generated from the insulating-film periphery57, the reinforcement portion60preferably covers 80% or more of the insulating-film periphery57.

As shown inFIG.2A, the reinforcement portion60is formed in a strip manner along the insulating-film periphery57. As shown inFIG.1, the reinforcement portion60has a predetermined width from the insulating-film periphery57to the insulating film first portion54side and from the insulating-film periphery57to the second insulating film portion56side.

As shown inFIG.1, for example, a first width W1 from the insulating-film periphery57to the end of the reinforcement portion60on the insulating film first portion54side is preferably 50 to 350 µm and is more preferably 100 to 250 µm. When the first width W1 is a predetermined value or more, the insulating-film periphery57can be reliably covered and protected. When the first width W1 is a predetermined value or less, a region exposed from the reinforcement portion60can be formed widely in a central part of the insulating film first portion54. As a result, a region for disposing another structure, such as a detection unit430(seeFIG.6) mentioned below, can be formed on the insulating film first portion54using the metal member20with a limited size.

Preferably, a second width W2 from the insulating-film periphery57to the end of the reinforcement portion60on the insulating film second portion56side is, for example, 50 µm or more. When the second width W2 is a predetermined value or more, the insulating-film periphery57can be reliably covered and protected. The portion of the reinforcement portion60from the insulating-film periphery57to the insulating film second portion56side may have a thickness different from that of the portion of the reinforcement portion60from the insulating-film periphery57to the end on the insulating film first portion54side. For example, the maximum thickness of the portion of the reinforcement portion60from the insulating-film periphery57to the insulating film second portion56side can be 10 to 110%, preferably 70 to 100%, of the portion of the reinforcement portion60from the insulating-film periphery57to the end on the insulating film first portion54side.

In the insulating-film-attached metal member10including the insulating film50and the reinforcement portion60as described above, the insulating film50reliably protects the film formation surface22b, and it is possible to effectively prevent the occurrence of cracking and peeling of the insulating film first portion54on the film formation surface22b. Since the insulating film50continuously covers the metal member20from the film formation surface22bto the connection surface24a, even if cracking or peeling occurs at the outer edge of the insulating film50, it is possible to prevent for the cracking or peeling to travel to the film formation surface22b.

If the metal member20from the film formation surface22bto the connection surface24ais merely covered with an insulating film, cracking or peeling may be likely to occur at the insulating-film periphery57covering the connection position25between the film formation surface22band the connection surface24a. Since the insulating-film-attached metal member10is provided with the reinforcement portion60formed along the insulating-film periphery57covering the connection position25, however, the reinforcement portion60reinforces the insulating-film periphery57, and it is possible to effectively prevent the problem of cracking and peeling occurring at the insulating-film periphery57.

Second Embodiment

FIG.3is a schematic cross-sectional view of an insulating-film-attached metal member210according to Second Embodiment. The insulating-film-attached metal member210is similar to the insulating-film-attached metal member10shown inFIG.1andFIG.2, except that a reinforcement portion260is made of a thin metal film including a plurality of layers. The insulating-film-attached metal member210is mainly described for the differences from the insulating-film-attached metal member10. The common respects with the insulating-film-attached metal member10are provided with common reference numerals and are not described.

As shown inFIG.3, similarly to the reinforcement portion60shown inFIG.1, the reinforcement portion260of the insulating-film-attached metal member210is made of a metal thin film formed along the insulating-film periphery57. The metal thin film constituting the reinforcement portion260includes a plurality of layers containing different elements or having different composition proportions of contained elements.

As shown inFIG.3, the reinforcement portion260includes an Au layer262containing Au and a Pt layer264containing Pt. The Au layer262constitutes an upper layer of the reinforcement portion260, and the Pt layer264constitutes a lower layer of the reinforcement portion260.

The Au layer262containing Au may contain elements other than Au, but has at least the highest ratio of Au based on the weight ratio of elements contained in the Au layer262. The Au layer262is less likely to have cracking due to its high ductility and can effectively prevent the generation of peeling and cracking at the insulating-film periphery57under the reinforcement portion260. Moreover, since the Au layer262has an excellent weather resistance, when the upper layer of the reinforcement portion260is the Au layer262, the aging of the reinforcement portion260is prevented, and this contributes to improvement in the durability of the insulating-film-attached metal member210. Moreover, since the stress of the Au layer262is small, a peeling due to stress is less likely to occur in the film and layer (the Pt layer264in the reinforcement portion260) contacted with the Au layer262.

The Au layer262can be formed on the Pt layer264by, for example, a thin film formation method, such as sputtering and vapor deposition. For example, the Au layer262can have a thickness of 50 to 500 nm and preferably has a thickness of 100 to 250 nm. If the thickness of the Au layer262is smaller than a predetermined value, it is difficult for the Au layer262to form a continuous film, and the function of the Au layer262is deteriorated. On the other hand, if the thickness of the Au layer262is larger than a predetermined value, there are disadvantages, such as a decrease in throughput due to an increase in film formation time and an increase in raw material costs.

The Pt layer264containing Pt may contain elements other than Pt, but has at least the highest ratio of Pt based on the weight ratio of elements contained in the Pt layer264. The Pt layer264is contacted with the insulating film50(lower layer) and the Au layer262(upper layer). The Pt layer264favorably functions as a diffusion prevention layer. That is, the Pt layer264can effectively prevent the elements contained in the layer or film in contact on the lower side from moving (diffusing) to the Au layer262in contact on the upper layer. As a result, the Pt layer264can prevent problems, such as surface deposition of elements in the lower layer due to heat in the Au layer262(upper layer), and maintain the thermal stability of the Au layer262.

The Pt layer264can be formed on the insulating film50by, for example, a thin film formation method, such as sputtering and vapor deposition. For example, the Pt layer264can have a thickness of 1 to 500 nm and preferably has a thickness of 5 to 50 nm. If the thickness of the Pt layer264is smaller than a predetermined value, it is difficult for the Pt layer264to form a continuous film, and the diffusion prevention function of the Pt layer264is deteriorated. On the other hand, if the thickness of the Pt layer264is larger than a predetermined value, there are disadvantages, such as a decrease in throughput due to an increase in film formation time and an increase in possibility of film peeling due to stress.

In the insulating-film-attached metal member210shown inFIG.3, since the reinforcement portion260is made of a metal thin film including the Au layer262and the Pt layer264, the reinforcement portion260can favorably prevent the occurrence of cracking and peeling in the insulating-film periphery57for a longer period of time. As for common respects with the insulating-film-attached metal member10shown inFIG.1andFIG.2, the insulating-film-attached metal member210exhibits effects similar to those of the insulating-film-attached metal member10.

Third Embodiment

FIG.4is a schematic cross-sectional view of an insulating-film-attached metal member310according to Third Embodiment. The insulating-film-attached metal member310is similar to the insulating-film-attached metal member210shown inFIG.3, except that a metal thin film constituting a reinforcement portion360includes an adhesive layer366in addition to the Au layer262and the Pt layer264. The insulating-film-attached metal member310is mainly described for the differences from the insulating-film-attached metal member210. The common respects with the insulating-film-attached metal member210are provided with common reference numerals and are not described.

As shown inFIG.4, the reinforcement portion360of the insulating-film-attached metal member310is made of a metal thin film including a plurality of layers (three layers in the embodiment) of the Au layer262, the Pt layer264, and an adhesive layer366. The reinforcement portion360is formed by stacking the adhesive layer366, the Pt layer264, and the Au layer262in this order from the side closer to the insulating film50, and the adhesive layer366is the lowest layer in the reinforcement portion360.

The adhesive layer366is contacted with the insulating film50and has an adhesion to the insulating film50being higher than that of the Au layer262and the Pt layer264, which are the other layers included in the reinforcement portion360. Examples of metal elements contained in the adhesive layer366include Cr, Ti, Ni, and Mo. Comparing with metal elements such as Au and Pt, since Cr, Ti, Ni, Mo, and the like have a property of being more easily combined with other elements, the adhesive layer366containing these metal elements has a high adhesion to the insulating film50containing Si etc. Moreover, since Ti has a property of being difficult to diffuse into Au and is unlikely to precipitate on the surface of the Au layer262, Ti is preferable as an element constituting the adhesive layer366.

The adhesive layer366can be formed on the insulating film50by, for example, a thin film formation method, such as sputtering and vapor deposition. The adhesive layer366can have a thickness of, for example, 1 to 50 nm and preferably has a thickness of 5 to 20 nm. If the thickness of the adhesive layer366is smaller than a predetermined value, it is difficult for the adhesive layer366to form a continuous film, and the function of increasing adhesion is lowered. On the other hand, if the thickness of the adhesive layer366is larger than a predetermined value, there are disadvantages, such as a decrease in throughput due to an increase in film formation time and an increase in possibility of film peeling due to stress.

In the insulating-film-attached metal member310shown inFIG.4, since the reinforcement portion360includes the adhesive layer366contacted with the insulating film50, the adhesion between the reinforcement portion360and the insulating film50is improved, and it is possible to more effectively prevent the occurrence of cracking and peeling the insulating-film periphery57. As for common respects with the insulating-film-attached metal member210shown inFIG.3, the insulating-film-attached metal member310exhibits effects similar to those of the insulating-film-attached metal member210.

Fourth Embodiment

FIG.5is a schematic cross-sectional view of a pressure sensor400using an insulating-film-attached metal member410according to Fourth Embodiment. Hereinafter, the pressure sensor400and the insulating-film-attached metal member410are described usingFIG.5toFIG.7. The insulating-film-attached metal member410is similar to the insulating-film-attached metal member310according to Third Embodiment, except that a metal member constituting the insulating film50is a metal stem420. The insulating-film-attached metal member410according to Fourth Embodiment is mainly described for the differences from the insulating-film-attached metal member310shown inFIG.4. The common respects with the insulating-film-attached metal member310are provided with common reference numerals and are not described.

As shown inFIG.5, the pressure sensor400includes the insulating-film-attached metal member410with a metal stem420as a metal member, a detection unit430for detecting the amount of deformation due to the pressure of a membrane422in the metal stem420, electrode films436(seeFIG.6) connected with an intermediate wiring472as a wiring unit, and the like.

As shown inFIG.5, the metal member of the pressure sensor400has a stem shape including the membrane422with a film formation surface422band a connection surface424aconnected to the membrane422. That is, the membrane422constitutes an end wall formed at one end of the hollow cylindrical metal stem420, and the outer surface of the membrane422serves as the film formation surface422b. In the metal stem420, an outer surface of a tubular side wall portion424connected to the membrane422constitutes the connection surface424aconnected to the film formation surface422b. The film formation surface422bfaces upward, and the connection surface424afaces sideways. Thus, the surface orientation changes by approximately 90 degrees at a connection position425between the film formation surface422band the connection surface424a. The other end of the metal stem420is an open end of a hollow portion, and the hollow portion of the metal stem420communicates with a flow path412bof the connection member412.

In the pressure sensor400, a fluid introduced into the flow path412bis guided from the hollow portion of the metal stem420to an inner surface422aof the membrane422, and a fluid pressure acts on the membrane422. As with the metal member20shown inFIG.1, the metal stem420is made of a metal, such as stainless steel.

A flange portion421is formed around the open end of the metal stem420so as to protrude outward from the core axis of the metal stem420. The flange portion421is interposed between the connection member412and a holding member414so as to seal the flow path412bleading to the inner surface422aof the membrane422.

The connection member412includes a screw groove412afor fixing the pressure sensor400. The pressure sensor400is fixed via the screw groove412ato a pressure chamber or the like in which a fluid to be measured is enclosed. As a result, the flow path412bformed inside the connection member412and the inner surface422aof the membrane422of the metal stem420are airtightly communicated with a pressure chamber containing a fluid to be measured.

A circuit board416is attached to the upper surface of the holding member414. The circuit board416has a ring shape surrounding the metal stem420, but the shape of the circuit board416is not limited to this. The circuit board416incorporates, for example, a circuit to which a detection signal from the detection unit430is transmitted.

As shown inFIG.5, the detection unit430is provided on the film formation surface422b, which is the outer surface of the membrane422, via the insulating film50. The detection unit430and the circuit board416are connected by an intermediate wiring472or the like by wire bonding or the like, and an electrical conduction of the detection unit430to the outside is ensured by the intermediate wiring472.

FIG.6is a top view of the pressure sensor400shown inFIG.5viewed from above the film formation surface422bof the membrane422.FIG.7is a cross-sectional view of the pressure sensor400shown inFIG.6along the cross-sectional line VII-VII. However,FIG.6andFIG.7do not illustrate the flange portion421of the metal stem420, the circuit board416, the intermediate wiring472, and the like. As shown inFIG.6andFIG.7, the detection unit430is formed in the insulating film first portion54of the insulating-film-attached metal member410.

As shown inFIG.5andFIG.6, the detection unit430is formed on the upper side of the film formation surface422bof the metal stem420and on the opposite side of the insulating film50to a surface thereof facing the film formation surface422b. As shown inFIG.6, the detection unit430includes resistances R1, R2, R3, and R4 connected by an electrical wiring434. The electrical wiring434and the resistances R1 to R4 of the detection unit430are made of a strain resistance film432.

As with the detection unit430, the electrode films436are formed above the insulating film first portion54. The electrode film436is formed so as to overlap with a part (e.g., the strain resistance film432) of the detection unit430from above and is electrically and physically connected to the detection unit430. The intermediate wiring472shown inFIG.1is connected to the electrode films436. A detection signal of the detection unit430is transmitted to the circuit board416via the electrode films436and the intermediate wiring472.

The resistances R1 to R4 of the detection unit430are formed at predetermined positions on the membrane422. A strain occurs according to a deformation of the membrane422, and the resistance values change. The resistances R1 to R4 are connected by the electrical wiring434so as to form a Wheatstone bridge circuit. The detection unit430detects a deformation amount of the membrane422, which is one of physical quantities for the metal stem420, and detects a pressure of the fluid contacted with the inner surface422a(seeFIG.5) of the membrane422.

As shown inFIG.7, the resistances R1 to R4, the electrode film436, and the like constituting the detection unit430are insulated from the metal stem420by the insulating film50formed on the film formation surface422band the connection surface424a. As shown inFIG.6andFIG.7, an insulating protection film474covering the detection unit430from above is formed on the upper side of the insulating film first portion54. However, at least a part of the electrode film436is exposed from the protection film474. The thickness, material, and formation method of the protection film474are not limited, but may be similar to those of the insulating film50, for example.

The strain resistance film432constituting the resistances R1 to R4, the electrical wiring434, and the like can be produced by, for example, patterning a conductive thin film of a predetermined material. The strain resistance film432contains Cr and Al. Preferably, the strain resistance film432contains 50 to 99 at% of Cr and 1 to 50 at% of Al. More preferably, the strain resistance film432contains 70 to 90 at% of Cr and 5 to 30 at% of Al. Since the strain resistance film432contains Cr and Al, temperature coefficient of resistance (TCR) and temperature coefficient of sensitivity (TCS) in a high temperature environment are stabilized, and a pressure detection can be performed accurately. When the amount of Cr and Al is within a predetermined range, it is possible to achieve both a high gauge factor and a favorable temperature stability at a higher level.

The strain resistance film432may contain elements other than Cr and Al. For example, the strain resistance film432may contain O and N. The O and N contained in the strain resistance film432may be those taken thereinto after they are not completely removed from a reaction chamber and remain when forming the strain resistance film432. The O and N contained in the strain resistance film432may be intentionally introduced thereinto by being used as atmosphere gases during film formation or annealing.

As shown inFIG.7, the electrode film436includes a contact layer436aoverlapping with the strain resistance film432, a diffusion prevention layer436boverlapping with the contact layer436a, and a mounting layer436coverlapping with the diffusion prevention layer436b. The electrode film436has a multilayer film structure consisting of a plurality of layers made of different materials. However, the electrode film436is not limited to that with a three-layer structure as shown inFIG.7and may have a multilayer structure of one layer, two layers, or four or more layers.

As shown inFIG.7, the contact layer436a, which is the lowest layer of the electrode film436, is directly contacted with the strain resistance film432. Preferably, the contact layer436aensures an ohmic contact with the strain resistance film432and improves electrical characteristics of the detection unit430. The contact layer436aensures an adhesion strength between the strain resistance film432and the electrode film436and prevents peeling defects of the film and layers.

The contact layer436acan be formed by a thin film formation method, such as sputtering and vapor deposition. The thickness of the contact layer436ais not limited and is, for example, 1 to 50 nm, preferably 5 to 20 nm. Preferably, the contact layer436acontains at least one of Cr, Ti, Ni, and Mo. Since these elements easily form alloys with other metals, the contact layer436acontaining such elements secures adhesion strength with the strain resistance film432and the diffusion prevention layer436band can prevent peeling defects between the film and the layers.

Particularly preferably, the contact layer436acontains Ti. Ti is difficult to diffuse into the mounting layer436ccontaining Au etc. and tends to be less likely to precipitate on the upper surface of the mounting layer436c. Thus, the electrode film436including the contact layer436acontaining Ti exhibits a favorable adhesion to the intermediate wiring472even after the electrode film436is exposed to a high temperature environment.

Moreover, since Ti is also difficult to diffuse into Cr, Ti constituting the contact layer436ahas a property of being difficult to diffuse into the strain resistance film432containing Cr and Al even in a high temperature environment. Thus, since the contact layer436acontains Ti, the detection unit430can prevent the elements in the electrode film436from diffusing into the strain resistance film432even when used in a high temperature environment and can prevent a performance degradation of the strain resistance film432due to composition change.

As shown inFIG.7, the diffusion prevention layer436bis disposed between the contact layer436aand the mounting layer436cin the electrode film436and is vertically interposed by the mounting layer436cand the contact layer436a. The diffusion prevention layer436bprevents the elements contained in the film and layers arranged below the diffusion prevention layer436b, such as the strain resistance film432and the contact layer436a, from diffusing into the mounting layer436cdisposed above the diffusion prevention layer436band from precipitating on the upper surface of the mounting layer436c.

The diffusion prevention layer436bcan be formed by a thin film formation method, such as sputtering and vapor deposition. The thickness of the diffusion prevention layer436bis not limited and is, for example, 1 to 500 nm, preferably 5 to 50 nm. If the thickness of the diffusion prevention layer436bis too small, it is difficult to form a continuous film, and the diffusion prevention function may be weakened. If the thickness of the diffusion prevention layer436bis too large, there may be a problem of film peeling, or there may be a problem of decrease in productivity (throughput) due to increase in film formation time.

More preferably, the diffusion prevention layer436bcontains a platinum group element. Specifically, preferably, the diffusion prevention layer436bcontains one or more elements selected from Ru, Rh, Pd, Os, Ir, and Pt. Since platinum group elements have a low reactivity and are chemically stable, the diffusion prevention layer436bcontaining the platinum group element exhibits a particularly favorable diffusion prevention effect even in a high temperature environment. In particular, among platinum group elements, Pt has a technical track record of being also used in other electrode fields and has more technological accumulation than other platinum group elements.

As shown inFIG.2, the mounting layer436c, which is the uppermost layer of the electrode film436, is exposed on the upper surface of the electrode film436. The intermediate wiring472made of a fine wire of Au, Al, etc. is bonded to the mounting layer436cby wire bonding or the like. The pressure sensor400using the intermediate wiring472made of a fine wire of Au, Al, etc. can be used even in a high temperature environment with the melting point of solder or higher and has a favorable heat resistance. The pressure sensor400using the intermediate wiring472made of a fine wire of Au can improve the heat resistance more than a pressure sensor using the intermediate wiring472made of a fine wire of Al.

The mounting layer436ccan be formed by a thin film formation method, such as sputtering and vapor deposition. The thickness of the mounting layer436cis not limited and is, for example, 10 to 400 nm, preferably 100 to 300 nm. If the thickness of the mounting layer436cis too small, it is difficult to form a continuous film, and the adhesion to the intermediate wiring472may deteriorate. If the thickness of the mounting layer436cis too large, there may be a problem of film peeling, or there may be a problem of decrease in productivity (throughput) due to an increase in film formation time.

Preferably, from the point of heat resistance and bondability with the intermediate wiring472, the mounting layer436ccontains at least any of Au, Al, and Ni. More preferably, from the point of improving heat resistance and further improving compatibility with a high temperature environment, the mounting layer436ccontains Au, which exhibits a low resistance even in a high temperature environment and has a high melting point. When a fine wire of Au is used as the material of the intermediate wiring472, the mounting layer436ccontains Au, and the materials of both of the intermediate wiring472and the mounting layer436care thereby Au. As a result, the adhesion of the connection portion between the intermediate wiring472and the mounting layer436cis improved.

As shown inFIG.6andFIG.7, the insulating-film-attached metal member410of the pressure sensor400includes the reinforcement portion360similar to that of the insulating-film-attached metal member310shown inFIG.4. That is, the reinforcement portion360is formed along the insulating-film periphery57and covers the insulating-film periphery57except for a discontinuous portion360a. The reinforcement portion360of the insulating-film-attached metal member410is made of a metal thin film including the adhesive layer366, the Pt layer264, and the Au layer262.

As shown inFIG.6andFIG.7, the detection unit430and the electrode films436arranged on the insulating film first portion54are arranged with a predetermined interval from the reinforcement portion360. Since the detection unit430and the electrode films436are arranged away from the reinforcement portion360, the insulation between: the detection unit430and the electrode films436; and the reinforcement portion360is ensured.

Preferably, the metal thin film constituting the reinforcement portion360shown inFIG.7includes a common layer with at least a part of the layers of the electrode film436. For example, the Au layer262of the reinforcement portion360and the mounting layer436cof the electrode film436can be a common layer including approximately the same constituent elements containing Au. The Pt layer264of the reinforcement portion360and the diffusion prevention layer436bof the electrode film436can be a common layer including substantially the same constituent elements containing Pt. The adhesive layer366of the reinforcement portion360and the contact layer436aof the electrode film436can be a common layer including substantially the same constituent elements containing Ti, etc.

As shown inFIG.7, when both of the metal thin film constituting the reinforcement portion360and the electrode film436include a plurality of layers and also include a plurality of common layers, the vertical relation of the common layers is preferably matched between the reinforcement portion360and the electrode film436. The reinforcement portion360and the electrode film436have a favorable productivity because their common layers can be formed in the same process.

Moreover, the constituent layers of the reinforcement portion360and the electrode film436may be all common and may have the same vertical relation (lamination order). In such a pressure sensor400, the reinforcement portion360and the electrode film436can be formed in the same process. In this case, the metal thin film constituting the reinforcement portion360is not limited to the three-layer structure of the Au layer262, the Pt layer264, and the adhesive layer366and may be any metal lamination film common with the electrode film436.

As a metal member, the pressure sensor400shown inFIG.7employs the metal stem420with a stem shape including the membrane422. The metal stem420can effectively transmit pressure to the detection unit430and can improve the sensitivity of the pressure sensor400. In the pressure sensor400, the insulating film50is formed on the film formation surface422band the connection surface424a, which are the outer surface of the metal stem420, and the reinforcement portion360is further formed so as to prevent cracking and peeling of the insulating film50. The pressure sensor400can ensure favorable detection accuracy and reliability even in an environment requiring a high durability, such as a high temperature environment and a high pressure environment.

As for the common respects with the insulating-film-attached metal member310shown inFIG.4, the insulating-film-attached metal member410included in the pressure sensor400exhibits effects similar to those of the insulating-film-attached metal member310. Needless to say, the present disclosure includes many other embodiments and modifications in addition to the embodiments and examples described above. For example, Fourth Embodiment is described with an example of the pressure sensor400in which the detection unit430detects a deformation amount of the membrane422due to pressure, but the detection unit430is not limited to one that detects a deformation amount due to pressure. As a physical quantity sensor including the insulating-film-attached metal member410and a detection unit, there is a sensor that detects other physical quantity for a metal member, such as strain, temperature, and vibration, in addition to the pressure sensor400.

Description of the Reference Numerical