JP2007071594A - Manufacturing method of dynamic quantity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an initial investment or running cost in manufacture of a dynamic quantity sensor. <P>SOLUTION: An insulating film 20 is formed by a plating technology on the surface of a diaphragm 10 of a pressure receiving tube 2. In addition, a metal thin film 30 is formed by the plating technology on the upper surface of the insulating film 20. Then, the metal thin film 30 is removed partially to thereby process a strain gage 35. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a mechanical quantity sensor used for detecting externally applied force and the like.

Some pressure sensors that use thin film materials have an amorphous Si thin film. In order to manufacture this pressure sensor, highly managed silane utilization facilities and expensive facilities such as plasma CVD or photo CVD are required. In addition, there is a pressure sensor in which a silicon oxide insulating film is formed on a surface of a diaphragm by sputtering, and then a chromium oxide film is further formed, and a strain gauge is formed by using a photolithography technique (for example, Patent Documents) 1).
Japanese Patent No. 2838361

  However, when the pressure sensor is manufactured, expensive equipment such as plasma CVD, photo CVD, or sputtering equipment and expensive target material are required, and the operation of each equipment requires strict management. Therefore, there is a big problem that initial investment and running cost become high. Further, there is a problem that film formation is difficult on a material having a relatively high processing temperature and a low melting point. In addition, since toxic silane gas is used, an exhaust gas treatment facility is required, and strict cautions are required in the work, resulting in a large environmental load. In addition, these methods cannot be processed in a relatively large amount because of the film pressure uniformity of the thin film to be formed.

  Accordingly, an object of the present invention is to provide a method of manufacturing a mechanical quantity sensor capable of reducing initial investment and running cost.

Means for Solving the Problems and Effects of the Invention

  The method of manufacturing a mechanical quantity sensor according to the present invention is a method of manufacturing a mechanical quantity sensor having a diaphragm or a strain generating portion that generates a strain by receiving a force or pressure, and an insulating film is plated on the surface of the diaphragm or the strain generating portion. And an insulating film forming step of forming a metal thin film on the surface of the insulating film by a plating technique.

  The method of manufacturing a mechanical quantity sensor of the present invention is a method of manufacturing a mechanical quantity sensor having a diaphragm or a strain generating portion that generates a strain by receiving force or pressure, and chemically reacts an insulating film on the surface of the diaphragm or the strain generating portion. And an insulating film forming step of forming a metal thin film on the surface of the insulating film by a plating technique.

  In the insulating film forming step of the method of manufacturing a mechanical quantity sensor of the present invention, the insulating film may be formed by dissolving silazane in a solvent and applying it in a thin film and oxidizing it with ozone.

  The manufacturing method of a mechanical quantity sensor of the present invention is a manufacturing method of a mechanical quantity sensor that generates a strain by receiving force or pressure and has a diaphragm or a strain generating portion made of aluminum. An insulating film forming step for forming an insulating film by oxidizing the surface of the strained portion, and a metal thin film forming step for forming a metal thin film on the surface of the insulating film by a plating technique are provided.

  According to this configuration, expensive equipment such as plasma CVD, photo CVD, or sputtering apparatus is not required. Therefore, initial investment (capital investment amount) and running cost can be reduced. As a result, the product cost is reduced.

  The method for manufacturing a mechanical quantity sensor of the present invention may further include a strain gauge processing step of processing a strain gauge from the metal thin film formed in the metal thin film formation step.

  According to this configuration, the strain gauge can be easily manufactured.

  The method for manufacturing a mechanical quantity sensor of the present invention may further include a pressure receiving tube manufacturing step of manufacturing a pressure receiving tube having the diaphragm.

  According to this configuration, it is possible to manufacture a pressure sensor-integrated mechanical quantity sensor.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a pressure sensor manufactured by a manufacturing method according to an embodiment of the present invention. The present invention can be applied to a mechanical quantity sensor that detects pressure, force, moment, acceleration, angular acceleration, and the like by using a strain gauge. In the present embodiment, a pressure sensor will be described as an example.

  A pressure sensor 1 shown in FIG. 1 has a pressure receiving tube 2 made of stainless steel. A diaphragm 10 is formed at one end of the pressure receiving tube 2, and the other end serves as a pressure inlet 4 for introducing a gas or liquid to be measured. An insulating film 20 such as a SiO2 thin film is formed on the surface of the diaphragm 10, and a metal thin film 30 to be a strain gauge 35 is further formed thereon. A conductive thin film 40 is disposed at the end of the strain gauge 35 as a solder land for connecting a lead wire. A non-conductive protective film 50 is formed on a portion other than the conductive thin film 40.

Insulating film 20, in addition to S _i O ₂ film, a silicon nitride film may be formed of such an aluminum oxide film (alumite). The metal thin film 30 serving as the strain gauge 35 is a metal thin film such as a chromium oxide film, a chromium film, a copper / nickel alloy film, a nichrome-based alloy film, a nickel film, or a tungsten film. In addition, an arbitrary strain gauge 35 pattern is formed on the metal thin film 30 by using a photolithography technique. The arbitrary strain gauge 35 is connected by a lead wire to form a bridge circuit. Here, since the configuration of the bridge circuit is a known technique, a detailed description thereof will be omitted.

  Next, the manufacturing method of the pressure sensor 1 is demonstrated with reference to FIG.2 and FIG.3. FIG. 2 is a flowchart showing a manufacturing procedure of the pressure sensor. FIG. 3 is a diagram illustrating a manufacturing procedure of the pressure sensor.

  First, using a suitable material (for example, stainless steel), the pressure receiving tube 2 is manufactured as shown in FIG. 3A (step S101). Then, as shown in FIG. 3B, the surface (the surface on which the thin film is formed) of the diaphragm 10 of the pressure receiving tube 2 is mirror-polished to be flat (step S102), and the other surface is a resist film or masking. By covering with a cover 15 such as a tape, plating is prevented from attaching (step S103).

  Next, as shown in FIG. 3C, an insulating film 20 such as a silicon oxide film is formed on the surface of the diaphragm 10 by using an oxide film manufacturing technique from an aqueous solution (step S104). The insulating film 20 is preferably formed to be as flat as possible. In addition, the generation of pinholes must be suppressed so that the base material diaphragm 10 and the metal thin film 30 to be formed later are not electrically connected. Further, in order to increase the withstand voltage, care must be taken so that moisture does not remain in the insulating film 20 as much as possible.

  Here, although an example of an oxide film manufacturing technique is shown, the liquid composition and conditions may be changed as appropriate.

First method: Method using electrolytic oxide formation technology Liquid composition (NH ₄ ) ₂ SiF ₆ : 0.1 mol / l
Conditions 25 ° C pH 3.3 -1V (Ag / AgCl)

The second method: method liquid composition utilizes a chemical oxide formation _{(NH 4) 2 SiF 6:} 0.5mol / l
DMAB: 0.2 mol / l
Condition 50 ℃

Third method: liquid phase precipitation (LPD)
Liquid composition H ₂ SiF ₆ : 2 mol / l
H ₃ BO ₃
Condition 35 ℃

Fourth method: Anodizing method (when the material of the pressure-receiving tube 1 is aluminum, titanium, or magnesium)
However, the insulating film 20 becomes an oxide of the material. When the material is aluminum, it is generally called alumite treatment. In particular, since hard anodized film can be thickened to about 100 μm, it can be flattened by mirror polishing and can easily and reliably form a strain gauge by photolithography in the subsequent process.

  Fifth method: Silazane is dissolved in a solvent and applied in a thin film, which is oxidized with ozone to form the insulating film 20.

  Next, as shown in FIG. 3D, a metal thin film 30 such as a chromium oxide film, a chromium film, a copper / nickel alloy film, a nichrome-based alloy film, a nickel film, or a tungsten film is plated on the upper surface of the insulating film 20. (Step S105). Plating is preferably electroless plating that is less susceptible to electrolysis and tends to have a uniform film pressure. Since the thickness and specific resistance of the metal thin film 30 affect the gauge resistance value, it is better to strictly control the film thickness. If the film thickness is large, the resistance value of the strain gauge becomes small, and if the film thickness is thin, the resistance value of the strain gauge becomes large.

In electroless plating, it is known that the stability of a bath is improved by adding a small amount of an additive. As an example, conditions for electroless nickel plating are shown.
<Electroless nickel plating bath>
Nickel sulfate 0.04mol / l
Titanium trichloride 0.04mol / l
Titanium tetrachloride 0.04mol / l
Sodium citrate 0.24mol / l
Nitrilotriacetic acid 0.04mol / l
Sulfur-containing compounds 10-100mg / l
Amino acid 100-500mg / l
pH (adjusted with ammonia water) 8-9
Bath temperature 50 ° C

  Next, an excess portion of the metal thin film 30 is removed with an etching solution using photolithography, and the strain gauge 35 is processed as shown in FIG. 3E (step S106). And after forming a strain gauge, as shown in FIG.3 (f), the electroconductive thin film 40 is attached by plating as a solder land for connecting a lead wire to the both ends of the strain gauge 35 (step S107). The material of the conductive thin film 40 may be, for example, a nickel film or a copper film having excellent solder wettability. At this time, if a resist film is attached to a portion other than the conductive thin film 40 using a photolithographic technique, a nickel film is selectively formed to form the conductive thin film 40. be able to. If necessary, a lead wire may be soldered to a solder land formed of the conductive thin film 40 at this stage. Further, as shown in FIG. 3G, a non-conductive protective film 50 is formed by plating on a portion other than the conductive thin film 40 by using a photolithography technique (step S108). As the protective film 50, a silicon oxide film or the like can be used. As described above, when the formation of all thin films using the plating technique is completed and the covering such as the resist film and the masking tape is removed, the pressure sensor 1 is completed as shown in FIG.

  As described above, in the manufacturing method of the pressure sensor 1 of the present embodiment, equipment such as an expensive sputtering device, a plasma CVD device, and a photo CVD device is unnecessary, and an inexpensive plating tank may be used instead. Therefore, the capital investment is small. Further, in the plating technique, the capacity of the plating tank can be used effectively and a relatively large amount of processing can be performed. As a result, the initial capital investment can be suppressed, the running cost can be reduced, and a large amount of the pressure sensor 1 can be manufactured at low cost.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various design changes can be made as long as they are described in the claims. For example, in the above-described embodiment, the case where all the thin films are formed by the plating technique has been described. However, if the insulating film 20 and the metal thin film 30 are formed by the plating technique, the conductive thin film 40 and the protective film 50 are It may be formed by a method other than the plating technique. In addition to the formation of the insulating film 20 and the metal thin film 30, if necessary, a sputtering technique or a CVD film forming technique may be partially used. For example, the surface to be plated with a sputtering apparatus may be cleaned as a pretreatment. In this case, since the process is performed for a short time, the mass productivity is not greatly reduced.

  Further, in the above-described embodiment, when the insulating film 20 and the metal thin film 30 are formed, the portions other than the side opposite to the pressure inlet 4 of the diaphragm 10 are covered with a resist film, a masking tape, or the like so as not to be plated. However, there is a method that does not cover. For example, after the insulating film 20 and the metal thin film 30 are formed on the entire surface, only necessary portions may be covered with a resist film or a masking tape, and unnecessary portions may be removed with an etching solution. Of course, if there is no trouble, the insulating film 20 and the metal thin film 30 may be left on the entire surface of the pressure receiving tube 1.

  In the above-described embodiment, the manufacturing method of the pressure sensor 1 including the diaphragm is described. However, a strain gauge such as a force sensor other than the pressure sensor, an acceleration sensor, an angular velocity sensor, or an angular acceleration sensor is basically used. And can be applied to a method of manufacturing a mechanical quantity sensor using a piezoresistive element. Further, the strain gauge may be formed on the diaphragm, or may be a strain generating portion that generates a strain instead of a shape like a diaphragm. However, since a photolithography technique is used, the portion where the strain gauge is formed is preferably a flat plane.

It is typical sectional drawing of the pressure sensor manufactured by the manufacturing method which concerns on embodiment of this invention. It is a flowchart which shows the manufacture procedure of a pressure sensor. It is a figure which shows the manufacture procedure of a pressure sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure sensor 2 Pressure-receiving pipe 10 Diaphragm 20 Insulating film 30 Metal thin film 35 Strain gauge 40 Conductive thin film 50 Protective film

Claims (6)

In the manufacturing method of a mechanical quantity sensor having a diaphragm or a strain generating portion that generates a strain by receiving force or pressure,
An insulating film forming step of forming an insulating film on a surface of the diaphragm or the strain generating portion by a plating technique;
And a metal thin film forming step of forming a metal thin film on the surface of the insulating film by a plating technique. In the manufacturing method of a mechanical quantity sensor having a diaphragm or a strain generating portion that generates a strain by receiving force or pressure,
An insulating film forming step of forming an insulating film on the surface of the diaphragm or the strain generating portion by a chemical reaction;
And a metal thin film forming step of forming a metal thin film on the surface of the insulating film by a plating technique.   3. The method of manufacturing a mechanical quantity sensor according to claim 2, wherein in the insulating film forming step, the insulating film is formed by dissolving silazane in a solvent and applying it in a thin film and oxidizing the same with ozone. In the manufacturing method of the mechanical quantity sensor having a diaphragm or a strain generating part made of aluminum as a material, generating strain by receiving force or pressure,
An insulating film forming step of forming an insulating film by oxidizing the surface of the diaphragm or the strain-generating portion by an anodic oxidation method;
And a metal thin film forming step of forming a metal thin film on the surface of the insulating film by a plating technique.   5. The method of manufacturing a mechanical quantity sensor according to claim 1, further comprising a strain gauge processing step of processing a strain gauge from the metal thin film formed in the metal thin film formation step.   The method of manufacturing a mechanical quantity sensor according to claim 1, further comprising a pressure-receiving tube manufacturing step of manufacturing a pressure-receiving tube having the diaphragm.

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