JP3049122B2 - Flow sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow sensor, and more particularly, to a flow sensor suitable for detecting a flow rate of an extremely small gas.

[0002]

2. Description of the Related Art FIG. 33 is a view showing the structure of a main part for explaining an example of a conventional flow sensor.
(B) is a sectional view taken along the line BB of (a), wherein 1 is a substrate, 2 is a through hole or a cavity formed in the substrate 1,
A film-like heater section and a detection section are attached to the upper portion of the through hole or the cavity 2 in a doubly supported or cantilevered manner. In FIG. 32, a heater unit 4 is mounted at the center, and detection units 3 and 5 are mounted on both front and rear sides.

As is well known, when the heater section 4 is energized and heated, when the gas to be measured flows in the direction of arrow F, the temperature of the detecting section 5 rises due to heat conduction in accordance with the flow rate of the gas to be measured. If 5 is a resistor having a positive temperature coefficient, the flow rate can be detected as an increase in the resistance value. In this case, the detecting unit 3 functions as a resistor for correcting the influence of the ambient temperature or as a detector when the gas flows in a direction opposite to the F direction. Here, in order to efficiently heat the detection unit 5 by the heater unit 4, it is necessary to make the heater unit 4 and the detection unit 5 as close as possible by using a fine processing technique. The interval L of 5 is at most 2-
3 μm was the limit. Further, even if the distance L can be further reduced, the right end of the detection unit 5 is separated from the heater unit 4, so that this structure has a limit in improving the thermal efficiency.

In the relationship between the heater unit 4 and the detection unit 5, various improvements have been studied to improve the detection capability. For example, the output voltage is increased by increasing the resistance values of the heat generating and heat receiving resistors. The output voltage difference at a minute flow rate, the influence of an error, and the difficulty of signal processing in a discrimination circuit can be canceled. In the illustrated example, the resistance value can be increased by reducing the film thickness of the resistor, reducing the pattern width, or increasing the pattern length. However, when the film is thin, the film has many defects, and has difficulty in durability and change with time. When the thickness is 0.3 μm or less, there are many defects. The width is limited to 1 μm in terms of the precision of fine processing, and if the width is less than 1 μm, the variation, the yield, and the change with time increase with difficulty. As for the length, since the area becomes large depending on the pattern arrangement, the heat capacity increases, causing an increase in power consumption and a delay in response time, which is a disadvantage. In addition, when the area becomes large, the distance between the end of the heating element and the end of the heat receiving body increases, and in such places, the mutual conduction of heat is completely out of the range. It gets feverish.

[0005] Figure 34 is a diagram for explaining the relationship between the detection unit 5 and the heater unit 4, if the heat resistance of H ₂ heater 4 is conducted to the resistance L ₁ of the detection unit 5, the distance Is small, the heat transfer efficiency is good, but when the heat of H ₁ is transmitted to L ₂ , the distance becomes long and the efficiency is small. Further, since the gas flow, towards the H ₂ parts than H ₁ parts in the heater unit 4 is upstream temperature, cause localized heating, may cause melt breakage.

FIG. 35 is a diagram showing the temperature of each part in FIG. 34. Curve A shows a state in which the flow of gas is stopped, and B shows a state in which a constant flow is generated. L ₂ is not climbed the temperature for you are away from the heater,
Therefore, the detection sensitivity is poor, and H ₂ and L ₁ may cause a local temperature rise when the fluid to be measured is flowing, resulting in melting and disconnection. In summary, in the above-mentioned prior art, there is necessarily a bias in the heat distribution along the flow direction F.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and particularly, in a flow sensor having a high-speed response performance of a heat conduction detection method manufactured by using a microfabrication method of an integrated circuit, a heater unit and An object of the present invention is to provide a flow sensor that reduces the spatial distance between the detection units, and that aims at high speed response, high accuracy, minute flow rate, and high efficiency.

[0008]

To achieve the above object, the present invention provides (1)
In a flow sensor having a substrate having a through hole or a cavity, and a membrane heater section and a membrane detection section bridged on the through hole or the cavity in a cantilever or cantilever manner, the heater section and the detection section are It is characterized by being laminated in two layers or two or more layers along the flow direction of the fluid to be measured, and having a space between each layer.
(2) In the above (1), the heater section and the detection section are constituted only by a resistive film. (3) In the above (1) or (2), both the heater section and the detection section, or
(4) In the above (3), the position of the pores of the heater unit and the position of the pores of the detection unit are shifted from each other, and (5) in the above (1). )
(3) In any one of (1) to (5), the heater unit and / or the detection unit may be disposed so as to be shifted from each other. (7) In any one of the above (1) to (6), the heater section is an intermediate layer, and a detection section is provided above and below (or left and right) of the intermediate layer. In any one of the above (1) to (7),
On the side of the through-hole opposite to the side having the heater section and the detection section, characterized by having a rectifier or dust filter film having a large number of small holes, or
(9) A substrate having a through-hole and a heater portion provided on one side of the substrate by bridging the through-hole in a doubly supported or cantilevered manner, and the through-hole on the other surface. And (10) a first substrate having a through-hole, and a first substrate having a through-hole, and A heater portion bridged on a cantilever or cantilever type, a second substrate having a through hole, and a cantilever or cantilever type on the through hole of the second substrate; Wherein the first substrate and the second substrate are integrally joined with the through hole concentrically. Hereinafter, a description will be given based on an example of the present invention.

FIG. 1 is a sectional view of a main part for explaining an embodiment of a flow sensor according to the present invention.
Is a substrate, 11 is a through hole or cavity provided in the substrate 10, and 12 and 13 are a heater unit and a detection unit provided on the through hole or cavity 11 in a cantilever type or a cantilever type. In the present invention, the heater section (heat generating body) 12 and the detecting section (heat receiving body) 13 are formed in layers in the flow direction F of the fluid to be measured. In FIG.
The flow direction F of the fluid to be measured is shown as a vertical direction, and the heater unit 12 and the detection unit 13 are formed in a vertical direction along the flow direction. Thus, in the present invention, the gap G between the heating element portion 12 and the heat receiving member portion 13 is provided.
Can be adjusted with high precision by the film thickness.
In particular, it is possible to provide a close arrangement capable of coping with a very small flow rate, and furthermore, since the heat distribution of the heating element portion 12 is uniform and the heat receiving portion 13 can receive the heat uniformly, To be more efficient.

FIGS. 2 and 3 are schematic views for explaining the structure of the flow sensor according to the present invention. FIG. 2 shows an upper heater unit, and FIG. 3 shows a lower detector unit. FIG. 3B is a plan view, FIG. 3B is a cross-sectional view taken along line BB of FIG. 3A, and FIG. 3C is a cross-sectional view taken along line CC of FIG. 2 and 3, reference numeral 10 denotes a substrate, and 11 denotes a through-hole provided in the substrate 10. An upper heating unit 12 and a lower detection unit 13 are provided on the through-hole 11 in a cantilever type or a cantilever type. It is formed in layers and is bridged. As a creation method, after forming the detection unit 13 as shown in FIG.
Al, Ni, Mo, Si
Any of materials such as O ₂ , Ti, W, polyimide, etc. is patterned, and the upper heater section 12 is formed thereon as shown in FIG. 2, and thereafter, the Al, Ni,... To provide a space G. The through-hole 11
May be formed in advance as described above, or may be formed after the space G is formed.

Next, the method of manufacturing the flow sensor will be described in detail with reference to FIGS. 4 to 8, in which (a) is a plan view and (b) is a view of (a). If there is a sectional view taken along the line BB and (c), the figure (c) is C-
It is a C line sectional view. 4 to 8, reference numeral 10 denotes S
i, glass, alumina, heat-resistant resin (epoxy, polyimide) or Ni, Cr, NiCr, Mo, W, Al,
A substrate made of any of Cu, stainless steel, copearl material, and the like. On this substrate 10, MgO, SiO ₂ , Si ₃ N ₄ ,
One or a combination of two or more of Al ₂ O ₃ and Ta ₂ O _{5 is} used, and the heat-resistant insulating material layer 22 is formed with a thickness of 0.2 to 3.0 μm by a method such as CVP, vapor deposition, or sputtering. Film 2 similar to heat-resistant insulating material layer 22 on the back surface
Form one. The substrate 10 will be described later.
In the case of forming the substrate 1, a laminated substrate of a different material, for example, Ni
A laminated substrate made of / Al / Ni, Cu / polyimide / Cu or the like may be used. Reference numeral 23 denotes a resistor layer, which is formed of NiCr, TaN, Pt, SiC, W,
A material serving as a heater material such as a Kanthal material is formed to a thickness of 0.1 to 3.0 μm by a method such as vapor deposition or sputtering, and then an electrode extraction portion, a lead portion, and a heater portion are formed by a method such as pattern etching. Finally, the upper layer 24 is formed in the same manner as the heat-resistant insulating material layer 22 to complete the lower detecting section shown in FIG.

FIG. 5 shows a state in which the lower detection unit shown in FIG.
A material 25 for forming the space G, for example, Ni,
5 shows a diagram in which one of Cu, Mo, Ti, Al, W, NiCr, and Cr is patterned and etched to a thickness of 0.2 to 10 μm by vapor deposition and sputtering. Instead of material 25 in FIG. As shown in FIG. 6, SiO ₂ , Ni, C
The material 26 of any one of u, Mo, Ti, Al, W, NiCr, and Cr may be formed to have a thickness of 0.2 to 10 μm as described above. However, in the case of FIG. 6, as in the case of FIG.
It is not necessary to perform pattern etching. 5 and 6
FIG. 4 is a diagram for explaining a process for forming the intermediate space layer G between a lower detection layer and an upper heater layer;
In the subsequent step, it is necessary to selectively remove all the material 25 in the case of FIG. 5 and a part of the material 26 in the case of FIG. 6 by side etching so as not to etch other layers. Therefore, there is a condition in combination of these materials and the etching solution.

FIG. 7 shows the space forming material layer 25 shown in FIG.
FIG. 5 is a view for explaining a step of forming an upper heater section layer above the space, and as shown in FIG.
Is formed, an MgO layer 27 is formed on the entire surface, and
The Pt layer 28 is patterned, and further, an MgO layer 29 is formed on the entire surface. When the formation conditions of the layer 27 and the layer 22 are made the same, the formation condition of the layer 28 and the formation condition of the layer 23 are made the same, and the formation condition of the 29 is made the same as the formation condition of the 24, the upper layer and the lower The thermal conditions of the layers are matched, the detection capability is stable and very convenient.

FIG. 8 is a diagram for explaining a process of opening front and back windows for forming through-holes 11 and extraction electrodes a, b, c, and d for connecting bonding wires.
The gO layer is pattern-etched by dry etching with CF ₄ or CF ₄ + O ₂ plasma or ion etching with Ar +. Next, the single-crystal Si substrate 10 was treated with an ethylenediamine + catechol or NaOH aqueous solution,
The through hole 11 is formed by anisotropic etching using either a KOH aqueous solution or ammonia water. In FIG. 8, the heater section is arranged at an angle of 5-85 ° with respect to the (111) plane so that the etch stop can be performed at the (111) plane using a Si (100) substrate (about 45 in FIG. 8). ), The etching is advanced from the front and back positions facing the substrate to form the through holes 11. Next, the space G
Is formed, the Ni layer 25 is etched.
Since the side of the Ni layer 25 is exposed by the etching of MgO, the Ni layer 25 is side-etched with an etching solution such as an HNo ₃ aqueous solution or a phosphoric acid solution to form a space G. Incidentally, 31 functions as a rectifier for the flow F of the gas to be measured.

[0015] Figure 9 is a take-out electrode a flow sensor formed by as described above, b, c, and connect the d form a bridge circuit, the resistor the resistance R ₁ of the upper heater layer, R ₂
Is the resistance of the lower detection layer, and these resistances R ₁ , R ₂
When the fluid to be measured flows in the direction F through the output circuit, an output voltage Vout corresponding to the flow rate of the gas flows between the output terminals of the bridge circuit.
Can be obtained.

FIG. 10 is a view showing a modified embodiment of FIG.
As is clear from FIG. 9, since the electrodes b and c are short-circuited, FIG. 10 shows the connection of the electrodes b and c in the arrangement of the lead pattern of the flow sensor pattern. In order to connect the lower Pt film 23 and the upper Pt film 28 at the stage of FIG. 7, the connection portion 32 is formed by etching away a part of the MgO layer 24 and a part of the MgO layer 27. As a result, one extraction electrode and one wiring are not required, and waste can be reduced.

FIGS. 11 to 13 are views for explaining the subsequent steps of the modified embodiment shown in FIG.
As shown in FIG. 1, an MgO layer 33 is formed on the SiO ₂ layer 26,
The Pt layer 34 and the MgO 35 are formed, and then, as shown in FIG. 12, a bonding wire extraction electrode and a window for forming a through hole are formed by plasma etching the MgO layers 33 and 35 to form the exposed SiO ₂ layer 26. The part is removed with hydrofluoric acid. The exposed MgO layer is again plasma-etched, and the Si layer is etched from the front and back to form through holes.
Since the side wall of the intermediate SiO ₂ layer 26 is exposed, a space G is formed by side etching.
Is completed.

FIG. 14 shows an example in which the upper heater layer and the lower detection layer are constituted only by the resistance film Pt. In the embodiment shown in FIGS. 4 to 13, the Pt film around the through hole 11 is wrapped in an insulating material such as MgO. Therefore, in the embodiment shown in FIG. 14, this insulating material MgO is not used. Therefore, on the upper heating side, there is no insulating material that does not directly participate in the heating, so that the heat capacity for extra heating is not required, the heating time is shortened, the electric power applied to the heater is further reduced, and the life is extended. Further, on the lower heat receiving side, the temperature rises further faster, and the sensitivity becomes higher.

FIG. 15 is a view showing a modification of the embodiment shown in FIGS. 4 to 13 on the side where the pores 36 are provided only in the upper layer and the lower layer or the upper layer. The plan view and the figure (b) show B when pores are provided in the upper layer and the lower layer.
FIG. 3C is a cross-sectional configuration diagram taken along a line B, and FIG.
FIG. 15 shows a state of the pores 36 around the through hole 11. In the example shown in FIG. 2B, the heating section (upper layer) 12 and a part of the heat receiving section (lower layer) 13 are provided with the pores 36 to make the gas flow even and improve the efficiency. (C) shows pores 3 only on the heating side of upper layer 12.
6 and no pores are provided on the heat receiving side of the lower layer 13, and the gas flowing into the space G from the pores 36 of the upper layer is:
It flows through the interlayer clearance between these upper and lower layers. Note that in FIG.
Although an example in which a plurality of holes are provided is shown, it can be easily understood that a series of holes may be provided or a plurality of holes may be provided.

FIG. 16 is a cross-sectional view showing an example in which the positions of the pores 36 of the upper layer 12 and the lower layer 13 are shifted from each other. ,
Since the heat reaches the heat receiving layer, heat exchange is efficiently performed, and the sensitivity is further increased. Further, if heat is applied as uniformly as possible to the heat receiving layer, high sensitivity (high S / N) to the flow rate is obtained. And if the temperature distribution of the heat generating layer becomes uniform, it is possible to prevent deterioration due to disconnection deterioration that causes local heat generation. If the heat exchange is uniform as in this example, these can be expected sufficiently.

FIG. 17 is a cross-sectional view showing an example in which the positions of the heat generation and heat reception patterns of the upper layer 12 and the lower layer 13 are shifted from each other. According to this example, this example is different from the example shown in FIG. As a result, the pores 36 are subdivided, and the flow of gas spreads throughout.

FIG. 18 is a view showing a structure in the case where the upper layer 12 and the lower layer 13 are alternately arranged, and the upper layer 12 and the lower layer 13 are formed by the same process. FIG. The plan view and the figure (b) are sectional views taken along the line BB of the figure (a). As shown in the figure, a step is provided for the upper heat generating layers 12 ₁ and 12 ₂ , and the lower heat receiving layers 13 ₁ , 13 ₂ , by forming the 13 _3, it can be a film of the same process. As a result, the process is simplified, and since the film is of the same quality as the upper and lower portions, the characteristics (sheet resistance value, aging characteristics) are uniform, and there is little variation.
There are advantages such as good yield and high reliability.

Next, with reference to FIG. 19, a description will be given of a method of manufacturing the sensor when the upper layer and the lower layer are formed in the same step. On a Si substrate 10, Ni, Cu, T
After a film 51 of i, Mo, W, Cr, Al or SiO _{2 is} deposited or sputtered (within a range of 0.5 to 10 μm), it is photo-etched, and as shown in FIG.
Make into a strip shape. In order to dispose a heat generating layer on the upper part of the strip-shaped film 51, the rise angle θ of the peripheral edge of the strip-shaped film 51 is shown in FIG. As shown in the figure, it is preferable to adopt a structure in which the maximum angle is not more than about 45 °. This is possible by using side etching at the time of photoetching. (C) is a view showing another embodiment different from the embodiment shown in FIG. (B). In this embodiment, a strip-shaped pattern is formed on a Si substrate 10 by isotropic etching or Si substrate. If the material has a (100) plane orientation, it is removed by anisotropic etching so that the (111) plane can be arranged by the pattern film 51 ′ at a depth of 1 μm (0.5 to 10 μm).
A groove pattern 52 similar to the pattern 51 is formed. The subsequent steps of this embodiment will be described with reference to FIG.

FIG. 20 is a continuation of the process of the embodiment shown in FIG. 19B, in which the substrate 10 and Ni, Co, Ti, Mo,
An MgO layer 53 and a Pt layer 54 are pattern-formed on a strip pattern 51 such as a W, Cr, Al, SiO ₂ film or the like, and then an MgO film 55 is formed. At this time, the upper heating layer 54 ₂
There the top of pattern 51, the lower heat layer 54 _1, 54 ₃ are arranged to come to the side of the pattern 51. Also, substrate 1
The MgO layer 56 is also provided on the entire back surface of the substrate 0, but may be provided at the stage shown in FIG. Next,
As shown in FIG. 21, 55 and 53 MgO were taken out by photoetching or plasma etching.
The electrodes, heat generation, heat receiving layer pattern, and windows for Si etching are removed. Next, the Al layer of the layer 51 (when the layer 51 is Al) is completely removed by side etching with an acid.
Thereafter, the Si substrate 10 is anisotropically etched from the front and back to form through holes, and the example shown in FIG. 18 is completed.

FIG. 22 is a continuation step of the embodiment shown in FIG. 19B, in which 61 and 62 are MgO layers, 63 is a Pt pattern, and 64 is an MgO layer. As shown in FIG. 23, the MgO layer is pattern-etched, and then, as shown in FIG.

Next, with reference to FIG. 25, a description will be given of an example in which the heat transfer efficiency is improved by hybridizing a rectifier. In FIG. 25, 65 is an upper heating element, 66 is a lower heat receiving element, and 67 is a rectifying element. In this embodiment, a gas rectifying element 67 is provided in order to efficiently transfer the heat of the heating element 65 to the heat receiving element 66. Is controlled. what if,
If a heat receiver is set at the position of the rectifier 67, the heat received from the heat generator 65 will be greater than the heat receivers at both ends, and the temperature will inevitably be higher. However, if the temperature distribution is the same as that of the heat receivers at both ends, complicated output characteristics are unlikely to be exhibited with respect to the flow rate, so that circuit processing of the output signal is easy. Further, when a heat receiving body is provided at the position of the rectifying body 67 with respect to the dimension between the 65 heating elements, the density is increased, high accuracy is required, and it is relatively difficult to manufacture. On the other hand, if gas does not pass through this portion in a straight line, heat is not applied to the heat receiving members 66 at both ends, so that the efficiency is low. Therefore, in this embodiment, a rectifier 67 is provided to make the flow approach the heat receivers 66 at both ends.

FIG. 26 is a view for explaining an example of a multi-stage flow sensor comprising an upper detection layer, an intermediate heater layer, and a lower detection layer. In the above, the two-stage flow sensor composed of the upper heater layer and the lower detection layer has been described. However, as shown in the drawing, the flow sensor has a three-stage structure of an upper detection layer 71, an intermediate heater layer 72, and a lower detection layer 73. Is also possible,
In this way, the detection layer 7
Since 1, 73 are disposed on both the upper and lower sides, it is possible to detect even when the flow direction of the gas is reversed. In addition,
In the figure, there are six extraction electrodes, but it is possible to use four electrodes in common. Further, it is also possible to provide pores as indicated by 36 in FIG. (C) is a diagram for explaining an example of use of the flow sensor having a three-section configuration as described above, in which 80 is a flow meter unit, 81 is a flow pipe, 82 is a valve, and 70 is a diagram (a). In the flow sensor shown in FIG. 3B and FIG. 3C, assuming that the gas flow is from IN to OUT in FIG. 4C, the detection unit 73 receives the heat of the heater heating unit 72 and the resistance value. And the flow rate can be known. However, when valve 82 is closed, the flow stops and there is no heat conversion. Where I
If there is a leak in the pipe on the N side, the direction of the flow from the OUT side to the IN side temporarily occurs (due to the IN side pressure reduction). In this case, the flow rate at this time is determined by using the detection unit 71 as a detector. Can be detected. Accordingly, the flow sensor 70 can perform maintenance inspection such as a search for leakage on the IN side, safety confirmation, and the like. In this case, ie, IN
When the pressure is reduced on the side, when the inner volume between the flow sensor 70 and the valve 82 is large, the flow to the IN side is large, so that leakage can be detected reliably. Therefore, the position where the flow sensor 70 is mounted in the flow meter unit 80 is IN
It is better to install it at a position as close to the side as possible. In addition,
When the direction of the flow is as shown in the figure, not only can the flow rate be detected by heat exchange from 72 to 73, but also the original temperature of the gas is detected by the detector 71 and the temperature is compensated for the heater 72 and the detector 73. Available.

FIG. 27 is a view for explaining an embodiment in which a heat-generating layer and a heat-receiving layer on the front and back of one substrate are provided.
(A) is a plan view, (b) is a sectional view taken along the line BB of (a), wherein 10 is a substrate, 11 is a through hole, 12 is an upper heating element, 13 is a lower heat receiving element, 85 Is a passivation film (for protection), a is an extraction electrode on the surface, and as shown in FIG.
Since the same combination material is disposed on the front and back surfaces of the substrates 10, it is not necessary to consider the adhesion strength between the films at the time of film formation in the case of the multilayer structure as in the above-described embodiment.

FIG. 28 shows a structure in which a heating element 12 and a heat receiving element 13 are arranged on _two substrates 10 ₁ and 10 ₂ , respectively, and are adhered to each other with an adhesive 86 as shown in FIG. FIG. 27 is a cross-sectional configuration diagram when a similar effect is obtained, and its plan view is the same as FIG. However, the extraction electrodes a and b are staggered so as not to overlap. In addition, as the adhesive 86, an acrylic-epokine-based material, frit glass, solder, brazing material, or the like is used.

FIG. 29 shows the structure of the through hole 11 formed in the substrate 10.
FIG. 8 is a view for explaining an embodiment in which a rectifier and a dust filter are provided by using the etching window of FIG. 8, which shows an example in which the present invention is applied to the flow sensor shown in FIG. As described above, a large number of small holes 87 are provided in the etching window of the film 21 provided on the back surface of the substrate 10. FIG. 30 shows this when viewed from the F side in the gas flow direction. Now, as the substrate 10, Si (100)
When a substrate is used, a square hole 87 is formed in the Si (11) as shown in FIG. 30 so that the Si (111) plane is not left in the through hole 11 due to the fact that the through hole 11 is formed by etching.
It is installed at an angle showing a diamond shape with respect to 1). In the case of a round hole, the angle does not matter. Due to the restrictive condition that the small holes 87 must be selectively etched with respect to the substrate 10 and other layer materials, the material 21 is, in the case of SiO ₂ , photo-etched with a known etching solution containing hydrofluoric acid as a main component. Pattern etching can be performed using the resist as a mask. S
In addition to iO ₂ , Ta ₂ O ₅ , MgO, Si ₃ N ₄ , Al ₂ O ₃
However, depending on the combination of the limiting conditions, Ni, A
1, NiCr, Kovar, stainless steel, Mo, Cr, or other metal materials, or epoxy, polyimide, or photoresist itself. Note that these small holes 87 are intended to serve as a rectifier or a dust filter, and are designed to be suitable for a series of fine processing processes.

FIG. 31 is a view for explaining an example in which a flow sensor of the type in which gas passes through the through hole as described above is attached to the flow meter main body. In FIG. Is a flow sensor, and as shown, the flow sensor 91 is installed at right angles to the flow in the flow path. In addition, it is also possible to attach the flow sensor according to the present invention to a full-dick flow meter or a Karman vortex flow meter to form a composite flow meter.

An example of a double-supported beam sensor has been described above. FIG. 32 shows an outline of a case where the above-described flow sensor is configured as a cantilever-type sensor. 32, (a) is a plan view, (b) is a sectional view taken along the line BB of (a), in which 10 is a substrate, 11 is a through hole, 12 is an upper heating element layer, and 13 is a lower part. A heat receiving layer is shown, and the upper heat generating layer 12 and the lower heat receiving layer 13 are layered in a cantilever manner above the through hole 11 with a gap G therebetween.
Here, a is an electrode for the upper heating element, b and c are common electrodes for the upper heating element layer and the lower heat receiving layer, and d is an electrode for the lower heating element.

[0033]

As is apparent from the above description, according to the present invention, since the heat generating portion and the heat receiving portion have a layered structure, the heat generating portion and the heat receiving portion can be brought close to each other, and a flow sensor with high thermal efficiency can be provided. Can be. Since the layer between the heat-generating part and the heat-receiving part can be formed with high precision in film thickness, the layer spacing is 0.3 to 10 μ
It is possible to provide a flow sensor having a minute interval of about m. Since the heat distribution from the heat generating portion can be made uniform and can be received uniformly in the heat receiving portion, an efficient flow sensor can be provided. Further, since the gas flowing into the heating element and the heat receiving element is supplied through a layer having a large number of small holes serving as a laminar flow forming member and a dust filter, a flow sensor having no trouble and a long life is provided. be able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main part of a flow sensor according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a structure of a heater unit of the flow sensor according to the present invention.

FIG. 3 is a schematic diagram for explaining a structure of a detection unit of the flow sensor according to the present invention.

FIG. 4 is a diagram illustrating details of a method for manufacturing a flow sensor.

FIG. 5 is a diagram illustrating a part of a process for forming an intermediate space layer G between a lower detection layer and an upper heater layer.

FIG. 6 is a view for explaining a part of another process for forming an intermediate space layer G between a lower detection layer and an upper heater layer.

FIG. 7 is a view for explaining a step of forming a heater section layer above the space forming material layer.

FIG. 8 is a view for explaining an extraction electrode for connecting a bonding wire and a window opening step for forming a through hole.

FIG. 9 is a diagram illustrating a bridge circuit formed by connecting extraction electrodes of a flow sensor.

FIG. 10 is a diagram showing a modified example of FIG. 8;

FIG. 11 is a view for explaining a subsequent step for the modified example shown in FIG. 6;

FIG. 12 is a view illustrating a step following the step of FIG. 11 to form a window for forming a bonding wire extraction electrode and a through hole.

FIG. 13 is a view illustrating a step subsequent to the step shown in FIG. 11;

FIG. 14 is a diagram illustrating an example in which an upper heater layer and a lower detection layer are configured only with resistive films.

FIG. 15 is a diagram showing a side where pores are provided only in the upper layer and the lower layer or the upper layer.

FIG. 16 is a cross-sectional configuration diagram showing an example in which the positions of pores in the upper layer and the lower layer are shifted from each other.

FIG. 17 is a cross-sectional configuration diagram showing an example in which the positions of an upper heat generating layer and a lower heat receiving layer are shifted from each other.

FIG. 18 is a diagram showing a structure in a case where upper layers and lower layers are alternately arranged, and where upper layers and lower layers are formed by the same process.

FIG. 19 is a diagram for explaining a method of manufacturing a sensor when the upper layer and the lower layer are formed in the same step.

FIG. 20 is a view illustrating a continuation of the steps of the example illustrated in FIG. 19 (b).

FIG. 21 is a diagram for removing an electrode, heat generation, a heat receiving layer pattern, and a window for Si etching.

FIG. 22 is a view showing a step subsequent to the example shown in FIG. 21 (c).

FIG. 23 is a view for pattern-etching the MgO layer of FIG. 22;

FIG. 24 is a view for completing a through hole by performing anisotropic etching from the back side of FIG. 23;

FIG. 25 is a diagram for describing an example in which a heat exchanger is mixed to improve heat transfer efficiency.

FIG. 26 is a diagram illustrating an example of a three-stage flow sensor including an upper detection layer, an intermediate heater layer, and a lower detection layer.

FIG. 27 is a diagram for explaining an example in which a heat generating layer and a heat receiving layer on the front and back of one substrate are provided.

FIG. 28 is a cross-sectional configuration diagram in a case where a heating element and a heat receiving element are respectively arranged on two substrates, and these are bonded with an adhesive.

FIG. 29 is a view for explaining an example in which a rectifier and a dust filter are provided using an etching window of a through hole formed in a substrate.

FIG. 30 is a view for installing a square hole of the rectifier of FIG. 29 at an angle indicating a rhombus with respect to Si (111).

FIG. 31 is a view for explaining an example in which a flow sensor of a type in which a gas passes through a through hole is attached to a flow meter main body.

FIG. 32 is a diagram showing an outline when a flow sensor according to the present invention is configured in a cantilever type.

FIG. 33 is a diagram illustrating an example of a conventional flow sensor.

FIG. 34 is a diagram for explaining a relationship between a heater unit and a detection unit of a conventional flow sensor.

FIG. 35 is a diagram showing the temperature of each part of the flow sensor shown in FIG.

[Explanation of symbols]

Reference numeral 10: substrate, 11: through hole, 12: upper heating element, 13:
Lower heat receiving body, 31 ... Rectifier, 36 ... pore, 70 ... Flow sensor, 80 ... Flow meter unit, 81 ... Flow pipe, 82 ...
Valve, 86 ... adhesive.

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01F 1/68 G01P 5/10 H01L 21/306

Claims (10)

(57) [Claims] 1. A flow sensor comprising: a substrate having a through hole or a cavity; and a membrane heater section and a membrane detecting section bridged on the through hole or the cavity in a cantilever or cantilever manner. A flow sensor, wherein two layers or three or more layers are laminated along the flow direction of the fluid to be measured, and a space is provided between each layer. 2. The flow sensor according to claim 1, wherein the heater section and the detection section are constituted only by a resistive film. 3. The flow sensor according to claim 1, wherein a pore is provided in both the heater section and the detection section, or only in the heater section. 4. The heater according to claim 3, wherein the positions of the pores of the heater are shifted from the positions of the pores of the detector.
The flow sensor according to 1. 5. The apparatus according to claim 1, wherein the heater and the detector are disposed at different positions.
The flow sensor according to 1. 6. The flow sensor according to claim 1, wherein a rectifier is mixed in the heater and / or the detector. 7. The flow sensor according to claim 1, wherein the heater section is an intermediate layer, and a detection section is provided above and below (or left and right) of the intermediate layer. 8. A rectifier having a large number of small holes or a dust filter film on a side of the through-hole opposite to a side having the heater section and the detection section. 2. The flow sensor according to 1. 9. A substrate having a through-hole and a heater portion provided on one side of the substrate by bridging the through-hole in a doubly supported or cantilevered manner, and A flow sensor comprising a through-hole and a detection unit which is arranged so as to be bridged in a cantilever type or a cantilever type. 10. A first substrate having a through hole, a heater section bridged over the through hole of the first substrate in a cantilever or cantilever manner, and a second substrate having a through hole. And a detection unit bridged over the through hole of the second substrate in a doubly supported or cantilever manner, wherein the first substrate and the second substrate are connected to each other through the through hole. A flow sensor characterized by being concentrically joined together.