JPH08304204A - Manufacture of diaphragm unit and pressure sensor using the unit - Google Patents

Abstract

PURPOSE: To provide a method for manufacturing a diaphragm unit for obtaining a flat diaphragm film which does not bend nor break and an optical fiber type pressure sensor the pressure sensitive section of which can be increased in size against the size of a sensor head. CONSTITUTION: A diaphragm unit D is formed by forming a through hole through a spacer 1 and joining a substrate 4 composed of a removing layer 4b and joining layer 4a to one surface of the spacer 1 with the joining layer 4a, and then, removing the removing layer 4b and a diaphragm film 3 is formed on the upper surface of the joining layer 4a or, after forming the through hole through the spacer 1, joining the joining layer 4a of a substrate composed of a diaphragm film layer and the joining layer 4a to one surface of the spacer 1. An optical fiber type pressure sensor is constituted by fixing the end face of an optical fiber to a transparent substrate with the spacer 1 of the diaphragm unit D in between.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a diaphragm unit which can be easily miniaturized and a compact optical fiber type pressure sensor.

[0002]

2. Description of the Related Art In recent years, research and development of micromachine technology that can be used for inspection and work inside thin tubes and human bodies has been actively conducted. Among them, the diaphragm unit intentionally bends the membrane to extract force (micropump, etc.), uses displacement (microvalve, etc.), and bends the membrane due to external force (change in force, temperature, etc.) Changes in properties can be used (microsensors).

As a method of manufacturing the diaphragm unit, a method shown in FIG. 3 has been tried.
FIG. 3 shows a conventional method for manufacturing a diaphragm unit.
This is an enlargement of one chip out of a large number produced in a wafer. In detail along with this, a silicon wafer 1 (FIG. 3A) to be a spacer is heated and an oxide film 2 is attached to the surface (FIG. 3B), and a diaphragm film is formed on one surface of the silicon wafer 1. 3 is formed into a film (FIG. 3C), and the surface opposite to this is patterned into a predetermined shape (FIG. 3C).
(D)). Then, the diaphragm film 3 is processed by processing the silicon wafer 1 by anisotropic etching of silicon.
From the surface opposite to the surface toward the surface on the diaphragm membrane 3 side, holes having an inclination are provided so that the size of the hole having a rectangular cross section becomes smaller (FIG. 3E). After that, the oxide film 2 is removed (FIG. 3 (f)) to form an element by dicing to produce a chip-shaped diaphragm unit. Such a manufacturing method is excellent in terms of downsizing and mass production of the diaphragm unit.

When the diaphragm unit is used in an optical fiber type pressure sensor, the spacer is transparent on the surface opposite to the surface on which the diaphragm film of the spacer is formed, for example, before forming the element by dicing in the above-mentioned diaphragm unit manufacturing method. Attach a guide plate for positioning the board and optical fiber,
After that, there is a method in which dicing is performed to form an element, an optical fiber is fixed to the guide plate, and a pressure sensor is manufactured.
In the case of such an optical fiber type pressure sensor, the diaphragm film needs to be a flexible reflective film having flexibility and capable of reflecting light.

The pressure sensor manufactured as described above has the structure shown in FIG. That is, the diaphragm film 13 and the diaphragm film 13 are sequentially arranged from the tip of the sensor.
It is composed of a spacer 11 having a taper-like hole extending from one side to the other, a transparent substrate 15, a guide plate 16, and an optical fiber 17.

In the case of the pressure sensor having the above-mentioned structure, the operation thereof will be briefly described. Light emitted from the optical fiber 17 serving both as light sending and light receiving toward the diaphragm film 13 is reflected by the diaphragm film 13. The return light is received by the optical fiber 17. When the diaphragm film 13 is bent by the pressure, the return light reflected by the diaphragm film 13 is modulated and received by the optical fiber 17. The pressure can be detected by comparing the light modulation at this time with that in the normal state.

[0007]

In the diaphragm unit obtained by the above-mentioned diaphragm unit manufacturing method, since the diaphragm film is formed, anisotropic etching of silicon is performed, so that there is a problem that the diaphragm film is bent or broken. Was there. In addition, before the chips are formed, the diaphragm film may be partially peeled off from the silicon wafer serving as the spacer.

When the diaphragm unit is used as a pressure sensor, in addition to the problems that the sensor characteristics vary among individuals due to the above-mentioned problems and the yield is poor, the pressure formed by a through hole of a spacer is also added. Since the shape of the reference chamber is smaller toward the diaphragm membrane side, the size of the entire sensor head is unnecessarily large compared to the size of the diaphragm membrane exposed in the pressure reference chamber, which is actually the pressure sensitive part. There was a problem that became.

Therefore, the present invention is directed to a method of manufacturing a diaphragm unit for obtaining a flat diaphragm film which is free from bending and tearing, and further, an optical fiber type pressure for increasing the size of the pressure sensitive portion with respect to the size of the sensor head. It is intended to provide a sensor.

[0010]

Means for Solving the Problems The method of manufacturing a diaphragm unit of the present invention is (1) a spacer having a through hole,
Bonding the bonding layer side of a substrate composed of two layers of a removal layer and a bonding layer, removing the removal layer of the substrate, and forming a diaphragm film on the upper surface of the bonding layer; A laminate is formed by forming a diaphragm film layer on the material, and the joining layer side of the laminate is joined to a spacer having a through hole.

In (1) and (2), after the spacer and the bonding layer are bonded, the bending of the diaphragm film is utilized by the bonding layer remaining between the diaphragm film and the spacer. In such a case, if the diaphragm film does not bend or the amount of bending is small and the sensitivity is poor, it is preferable to remove the portion of the bonding layer exposed in the opening of the spacer.

In (1), the reason that the substrate is composed of two layers, that is, the removal layer and the bonding layer, is that in a minute structure, uniform bonding between the diaphragm film and the spacer already provided with the through-hole is required. Since it is difficult, it is necessary to first provide a bonding layer that facilitates bonding with the spacer. Since this bonding layer is used together with the diaphragm film in the final diaphragm unit or the part exposed at the opening of the spacer is removed, it is necessary for the former to have flexibility, The latter needs to be easily removable. In order to satisfy these, it is preferable that the bonding layer is as thin as possible, and it is extremely difficult to use these two layers in combination when the diaphragm film needs to be thin depending on the application.

Therefore, a two-layer structure in which a removal layer is provided in advance is used, and after joining, the removal layer, which is an unnecessary portion, is removed and a diaphragm film is formed on the joining layer, so that both the joining layer and the diaphragm film are thin. Thus, the diaphragm unit can be manufactured even after the through hole is further provided in the spacer.

In (2), the reason that the laminated body is composed of two layers, that is, a diaphragm film layer and a bonding layer, is because in a minute structure, the diaphragm film and the spacers already provided with through holes are uniform. Since bonding is difficult, a laminated body having a two-layer structure of the diaphragm film and the bonding layer is formed in order to facilitate uniform bonding between the diaphragm film and the spacer.

The spacer is not particularly limited as long as it can form a through hole, but when the spacer is silicon, the through hole can be formed by a semiconductor technique such as anisotropic etching. It is also preferable in that the diaphragm unit can be miniaturized and a large number of diaphragm units can be simultaneously formed.

There is no particular limitation on the removal layer of the substrate, but it is desirable that the removal layer can be easily removed without affecting the other components such as the bonding layer and the spacer since it is removed in a later step. Specifically, it is preferable to remove silicon by wet etching because existing semiconductor processes can be used.

Further, it is desirable that the spacer and the bonding layer are bonded by an anodic bonding method in order to manufacture a minute structure. When the anodic bonding method is used, glass containing sodium in the bonding layer, for example, Pyrex glass (trade name of Corning Co.), SD2 (H
It is desirable to use OYA Co., Ltd., etc.).

Further, for the diaphragm membrane layer, the material may be selected according to the application of the diaphragm unit,
For example, when operating a diaphragm membrane such as a micropump, a material (such as a bimetal, bimorph or shape memory alloy that combines materials with different coefficients of thermal expansion) that deforms when heated and a voltage are applied. It is desirable to use a piezoelectric material or the like that is distorted when applied, and a material that can reflect light when used as a micro optical fiber pressure sensor.

Further, regarding the surface of the spacer for bonding the bonding layer, when the through hole of the spacer has a taper, the diaphragm unit is downsized and the diaphragm film is larger than the entire diaphragm unit. Since the movable range of the spacer can be increased (for example, the pressure sensing portion can be increased when the diaphragm unit is used as a pressure sensor), the larger side of the opening of the through hole having the spacer of the spacer can be obtained. It is preferable to bond to the surface.

In the optical fiber pressure sensor using the diaphragm unit, a transparent substrate is further provided on the surface opposite to the surface having the diaphragm film sandwiching the spacer of the diaphragm unit manufactured as described above. The transparent substrate and the end face of the optical fiber are fixed to each other so as to face the diaphragm film with the transparent substrate interposed therebetween.

When a diaphragm film is used for the optical fiber pressure sensor, it must be a flexible reflective film capable of reflecting light, and the flexible reflective film has flexibility. It is sufficient that it can reflect light, but stable materials such as gold, silicon, titanium, platinum, Pd, and various metals with less deterioration of properties are preferable.

[0022]

By using the above means, the diaphragm film is formed after the anisotropic etching of silicon in the manufacture of the diaphragm unit, and a flat diaphragm film can be manufactured without causing bending or tearing. . Further, when the diaphragm unit is used for a pressure sensor, the characteristics of the sensor can be stabilized, the yield is improved, and the surface on which the diaphragm film is formed on the diaphragm unit can be selected after the formation of the holes, so that the same sensor head is used. It is also possible to make the pressure-sensitive portion larger by the size of 1, or make the sensor head smaller by the same size of the pressure-sensitive portion.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of one chip of a diaphragm unit manufactured on a wafer, showing an embodiment of the method for manufacturing a diaphragm unit according to the present invention.

FIG. 1A shows a state in which a silicon wafer 1 used as a spacer is heated and an oxide film 2 is provided on the surface thereof. Then, this one surface is patterned into a predetermined shape (FIG. 1B), the silicon wafer 1 is processed by anisotropic etching of silicon, and then the oxide film 2 is removed to form a through hole in the silicon wafer 1. It is produced (FIG. 1 (c)).

Then, a silicon wafer 4b in which a glass 4a containing sodium serving as a bonding layer is vapor-deposited on a silicon wafer 4b serving as a removal layer and a glass 4 containing sodium
The sodium-containing glass layer 4a side of the substrate 4 consisting of two layers of a and the surface of the silicon wafer 1 on the side where the opening is large are joined by the anodic bonding method (FIG. 1 (d)), and the substrate 4 The silicon wafer 4b is removed by etching, leaving only the glass 4a containing sodium that will serve as a substrate for forming the diaphragm film 3 in a later step (see FIG. 1).
(E)).

Gold is formed as the diaphragm film 3 on the remaining glass 4a containing the substrate 4 (see FIG. 1).
(F)), The diaphragm 4 is formed by removing the glass 4a containing sodium exposed at the opening of the silicon wafer 1 (FIG. 1 (g)).

Incidentally, in FIG. 1 (b), usually, the silicon wafer 1 is patterned so as to have a large number of through holes, so that a large number of diaphragm units are formed on the silicon wafer 1 and then cut by dicing. Then, a method of chipping is adopted.

The diaphragm film formed on the 2-inch silicon wafer before being made into chips was visually extremely flat, and the film was not broken.

Further, when a pressure sensor is obtained by using the diaphragm unit manufactured as described above, as a manufacturing method thereof, for example, a diaphragm film (optical fiber of a spacer of a diaphragm unit of a diaphragm unit in a wafer state before being made into chips) is used. Type pressure sensor must be a diaphragm film) A transparent glass substrate is bonded to the surface opposite to the surface on which the film is formed by anodic bonding, and the silicon of the spacer is formed on the opposite surface of the transparent glass substrate. A guide plate having the same structure as the wafer portion (see the manufacturing method of the diaphragm unit shown in FIG.
(A) to FIG. 1 (c) are joined by anodic bonding, cut by dicing and made into chips, and then an optical fiber is inserted into the guide plate to fix the optical fiber and the transparent glass substrate. .

The optical fiber type pressure sensor thus obtained is shown in FIG. Referring to this figure in detail, a gold film to be the diaphragm film 23 is provided on the larger side of the opening of the spacer 21 by the above-described method of manufacturing the diaphragm unit, and then the glass containing sodium as the bonding layer 24 is provided. Of the diaphragm 21 from which the portion exposed to the opening of the spacer 21 is removed, the transparent glass substrate 25 provided on the surface of the diaphragm unit opposite to the surface having the diaphragm film 23, and the transparent Glass substrate 2
5, a sensor head comprising a guide plate 26 having a through hole having a taper on the side opposite to the diaphragm unit, and the smaller side of the opening of the through hole is joined, and the through hole of the guide plate 26. It is an optical fiber type pressure sensor consisting of the transparent glass substrate 25 and an optical fiber 27 fixed inside.

Next, specific dimension examples of the embodiment of the present invention and the conventional example will be described. [Example] As an example of the dimensions of the above-mentioned example, the outer diameter is 125 μm.
The case of using the optical fiber of is shown. The outer diameter of the entire sensor head is 375 μm in width, 375 μm in depth, and 350 μm in height. The thickness of each sensor head constituent member (the height direction in the dimension of the sensor head) is 1 μm in the diaphragm film 23 and the bonding layer. Glass 24 containing sodium is 0.2 μm, spacer 21 is 100 μm,
Transparent glass substrate 25 150 μm, guide plate 26 100
μm. Furthermore, the shape of the pressure reference chamber is a square of 275 μm × 275 μm on the diaphragm film side, and the transparent glass substrate 2
5 side is a square of 130μm × 130μm, height is 100μ
The through hole of the guide plate 26 is 130 μm × 130 μm on the transparent glass substrate 25 side and 275 μm × 275 μm on the open portion (sensor head end portion) side.

[Comparative Example] In the above-mentioned conventional example, the outer diameter is 1
An example of dimensions when using a 25 μm optical fiber is shown. The outer diameter of the entire sensor head is 375 μm in width, 375 μm in depth, and 350 μm in height. The thickness of each sensor head constituent member (height direction in the dimension of the sensor head) is 1 μm in the diaphragm film 13 and thermal oxide film layer. 12
Is 0.6 μm, the spacer 11 is 100 μm, the transparent glass substrate 15 is 150 μm, and the guide plate 16 is 100 μm. Furthermore, the shape of the pressure reference chamber is 13 on the diaphragm membrane side.
0μm × 130μm square, transparent glass substrate 15 side is 2
It has a square shape of 75 μm × 275 μm and a height of 100 μm. The through hole of the guide plate 16 is 13 on the transparent glass substrate 25 side.
0 μm × 130 μm, and 275 μm × 275 μm on the open side (end of the sensor head).

When the sensor characteristics of these pressure sensors were evaluated by applying a pressure of 0.1 MPa to 50 sensors, a pressure sensor manufactured using the diaphragm unit obtained by the conventional method for manufacturing the diaphragm unit was used. In the characteristics of the sensors, the average received light intensity is about 1.2 μW, and the standard deviation is 0.302, which is a large individual difference, whereas the pressure sensor of the present invention has an average received light intensity of about 1.20. 2 μW with a standard deviation of 0.0
There was little individual difference with 5.

The accuracy of the resolution of the sensor under the above measurement conditions is 0.01MP in the conventional pressure sensor.
In contrast, the pressure sensor of the present invention is 0.00
It was 2 MPa, and the accuracy of the sensor resolution and the like became five times.

Further, the method of manufacturing the diaphragm unit of the present invention can be applied not only to the above-mentioned optical fiber type pressure sensor but also to the above-mentioned micropump, microvalve, etc., and in this case as well, the operation is stable. A diaphragm unit can be supplied. Further, when the diaphragm film is attached to the larger side of the opening of the spacer, the operating range of the diaphragm film can be increased.

[0036]

In the production of the diaphragm unit, by forming the diaphragm film after forming the through holes in the spacer, it is possible to form a flat film without bending or tearing, improving the yield, and improving the yield between chips. Individual differences can be reduced. Further, by making the diaphragm film on the larger side of the opening of the spacer, the movable range of the diaphragm film with respect to the size of the diaphragm unit can be increased.

Further, by using the diaphragm unit thus obtained for the pressure sensor, individual differences in sensor characteristics are eliminated and the yield can be reduced. Further, since the pressure sensing portion (diaphragm membrane) can be increased without increasing the size of the sensor head of the pressure sensor by the method of manufacturing the diaphragm unit of the present invention, the accuracy of resolution and the like can be increased with the same size as the conventional pressure sensor. It is also possible to downsize the pressure sensor with the same accuracy as the conventional one.

[Brief description of drawings]

FIG. 1 is a first method of manufacturing a diaphragm unit of the present invention.
It is sectional drawing which expanded the chip part.

FIG. 2 is a cross-sectional view of an optical fiber type pressure sensor using a diaphragm unit obtained by the method for manufacturing a diaphragm unit of the present invention.

FIG. 3 is an enlarged cross-sectional view of one chip of a conventional method for manufacturing a diaphragm unit.

FIG. 4 is a cross-sectional view of an optical fiber type pressure sensor using a diaphragm unit obtained by a conventional method for manufacturing a diaphragm unit.

[Explanation of symbols]

 1, 11, 21 Spacer 2,12 Thermal oxide film 3,13,23 Diaphragm film 4 Substrate 4a, 24a Bonding layer 4b Removal layer 15,25 Transparent substrate 16,26 Guide plate 17,27 Optical fiber D Diaphragm unit

Claims (7)

[Claims] 1. A spacer having a through hole is bonded to the bonding layer side of a substrate having two layers of a removal layer and a bonding layer, the removal layer of the substrate is removed, and a diaphragm film is formed on the upper surface of the bonding layer. A method for manufacturing a diaphragm unit, which comprises forming a film. 2. A laminate in which a diaphragm film layer is formed on a base material to be a joining layer in advance, and the joining layer side of the laminate is joined to a spacer having a through hole. A method for manufacturing a diaphragm unit, comprising: 3. The diaphragm unit according to claim 1, wherein after the spacer and the bonding layer are bonded together, the part of the bonding layer exposed in the opening of the spacer is removed. Of manufacturing. 4. The through hole has a taper, and the spacer and the bonding layer are bonded to each other on a surface of the through hole having a larger opening. A method for manufacturing the described diaphragm unit. 5. The method of manufacturing a diaphragm according to claim 1, wherein the through hole is formed by anisotropic etching of silicon. 6. The method for producing a diaphragm according to claim 1, wherein the bonding layer is glass containing sodium. 7. A spacer having a hole serving as a pressure reference chamber having a taper, a diaphragm film provided on a surface of the spacer on the side of a large opening, and a diaphragm film of the spacer. A transparent substrate attached to a surface opposite to a certain surface, and an optical fiber in which the transparent substrate and the end face of the optical fiber are fixed so as to face the diaphragm film with the spacer and the transparent substrate interposed therebetween. An optical fiber-type pressure sensor.