JP4865686B2 - Acceleration sensor manufacturing method and acceleration sensor - Google Patents

Description

  The present invention relates to a method for manufacturing a capacitive acceleration sensor that measures acceleration by detecting a change due to acceleration of a distance between opposed electrodes as a change in capacitance of a capacitor formed by these electrodes.

A capacitive acceleration sensor measures acceleration by detecting the capacitance of a capacitor due to a gap formed between a fixed electrode and a movable electrode. The movable electrode that constitutes such an acceleration sensor is held by a structure and a beam on which the fixed electrode is formed, and the deflection due to the acceleration of the beam causes the movement of the movable electrode, and the gap between the fixed electrode and the fixed electrode is generated. A change in the capacitance of the capacitor is generated. The gap between the fixed electrode and the movable electrode is about several μm to several tens of μm, and the thickness of the beam holding the movable electrode is also several μm to several tens of μm. In order to increase the deflection of the beam, the movable electrode has a structure with a weight. For such a capacitive acceleration sensor, a MEMS method using silicon is often employed because of its dimensional accuracy and the like (see, for example, Patent Document 1).
JP-A-8-320343

  However, in the MEMS method using silicon, a silicon body is used as a weight, a weight or a movable electrode is held, and a beam for moving the movable electrode is formed using a silicon nitride film or an oxide film. In this case, it is necessary to pass through a step of etching silicon with a high aspect ratio and a step of etching the silicon compound. At this time, a special gas with high risk is used by using an expensive dry etching apparatus, and a dangerous chemical such as hydrofluoric acid is frequently used in wet etching because a silicon compound is used. . For this reason, the manufacturing equipment becomes expensive and expensive, and at the same time, there is a problem in terms of safety in manufacturing.

  The present invention has been made in view of the above circumstances, and provides an acceleration sensor manufacturing method and an acceleration sensor that can suppress the burden on manufacturing equipment as much as possible and can use chemicals with high safety. With the goal.

  The present invention employs the following means in order to solve the above problems.

  A method of manufacturing an acceleration sensor according to the present invention includes a fixed electrode and a movable electrode that are opposed to each other with a gap therebetween, and detects a change in electrostatic capacitance due to a change in the distance between the electrode gaps caused by the movement of the movable electrode due to acceleration. A method of manufacturing a capacitive acceleration sensor for measuring acceleration by forming a fixed electrode and a wiring for connecting to the outside on a substrate having at least one surface having electrical insulation, and the fixing Forming a first photoresist layer having a predetermined opening on the surface of the substrate on which the electrode and the wiring are formed; and forming a first photoresist layer on the surface of the substrate on which the first photoresist layer is formed. Forming a first metal layer, forming a second photoresist layer having a predetermined opening on the surface of the first metal layer, and opening the second photoresist layer. Forming a second metal layer on the surface by wet plating, and forming a third photoresist layer having a predetermined opening on the surface of the second photoresist layer and the second metal layer A step of forming a third metal layer in the opening of the third photoresist layer by a wet plating method, a step of removing the third and second photoresist layers, and the first And a step of etching the metal layer using the second and third metal layers as a mask, and a step of removing the first photoresist layer.

  According to the present invention, a first photoresist layer having an opening at a predetermined portion connected to a movable electrode and a predetermined thickness is formed on a substrate on which a fixed electrode and a wiring connected to the movable electrode are formed. Thus, by forming the first metal layer over the entire surface, conductivity is imparted to the entire substrate surface. A second metal layer serving as a beam is formed on the second photoresist layer having a beam-shaped opening for holding a movable electrode that also serves as a weight of the acceleration sensor by a wet plating method such as electroplating or electroless plating. At the same time, the beam and the electrode formed on the substrate can be connected. A third metal layer serving as a movable electrode that also serves as a weight can be formed in the opening of the third photoresist layer having the movable electrode-shaped opening by a wet plating method such as electroplating or electroless plating. The third photoresist and the second photoresist are peeled off, and the first metal layer is formed using the second metal layer having the beam shape and the third metal layer having the movable electrode shape as a mask. The first photoresist layer appears by etching. All of the first photoresist is removed including under the beam and under the movable electrode. As a result, the beam and the movable electrode form a gap with the substrate to provide an acceleration sensor. The gap distance can be determined by the thickness of the first photoresist layer.

  A method of manufacturing an acceleration sensor according to the present invention includes a fixed electrode and a movable electrode that are opposed to each other with a gap interposed therebetween, and detects a change in capacitance accompanying a change in the distance between the electrode gaps caused by the movement of the movable electrode due to acceleration. A method of manufacturing a capacitive acceleration sensor for measuring acceleration by forming a fixed electrode and a wiring for connecting to the outside on a substrate having at least one surface having electrical insulation, and the fixing Forming a first photoresist layer having a predetermined opening on the surface of the substrate on which electrodes and wiring are formed; and a first surface on the surface of the substrate on which the first photoresist layer is formed. Forming a second metal layer, forming a second photoresist layer having a predetermined opening on the surface of the first metal layer, and opening the second photoresist layer A step of forming a second metal layer by a wet plating method, and a step of forming a third photoresist layer having a predetermined opening on the surface of the second photoresist layer and the second metal layer. A step of forming a third metal layer in the opening of the third photoresist layer by a wet plating method, a step of removing the third and second photoresist layers, and the first metal Etching the layer using the second and third metal layers as a mask, removing the first photoresist layer, removing the first photoresist layer, and then removing the first metal Etching the remaining exposed surface portion of the layer, and forming a fourth metal layer by electroless plating on the exposed surfaces of the second and third metal layers and the cross-sectional exposed portion of the first metal layer And equipped with The features.

  According to the present invention, a first photoresist layer having an opening at a predetermined portion connected to a movable electrode and a predetermined thickness is formed on a substrate on which a fixed electrode and a wiring connected to the movable electrode are formed. Thus, by forming the first metal layer over the entire surface, conductivity is imparted to the entire substrate surface. A second metal layer serving as a beam is formed on the second photoresist layer having a beam-shaped opening for holding a movable electrode that also serves as a weight of the acceleration sensor by a wet plating method such as electroplating or electroless plating. At the same time, the beam and the electrode formed on the substrate can be connected. A third metal layer serving as a movable electrode that also serves as a weight can be formed in the opening of the third photoresist layer having the movable electrode-shaped opening by a wet plating method such as electroplating or electroless plating. The third photoresist and the second photoresist are peeled off, and the first metal layer is formed using the second metal layer having the beam shape and the third metal layer having the movable electrode shape as a mask. The first photoresist layer appears by etching. All of the first photoresist is removed including under the beam and under the movable electrode. After removing the first photoresist layer, etching the remaining exposed portion of the first metal layer that has not been etched by the first photoresist; the second and third metal layers; By forming the fourth metal layer by electroless plating on the exposed surface and the cross-section exposed portion of the first metal layer, the metal layer inferior in chemical resistance can be removed, and the chemical resistance that appears unavoidably The inferior metal layer portion can be completely covered with the fourth metal excellent in corrosion resistance and durability, and an acceleration sensor excellent in durability can be provided. As a result, the beam and the movable electrode form a gap with the substrate to provide an acceleration sensor. The gap distance can be determined by the thickness of the first photoresist layer.

  The acceleration sensor manufacturing method according to the present invention is characterized in that the first metal layer is a metal layer composed of at least two layers of chromium and copper.

  In the present invention, the adhesion between the electrode part connected to the movable electrode formed on the substrate and the first metal layer is enhanced by chromium, and at the same time, the surface is cleaned by a wet method through the opening of the first photoresist layer. The adhesion with the second metal layer is enhanced through copper constituting the first metal layer. Further, when etching the first metal layer, an alkaline etching solution can be used, so that the metal layer constituting the other parts and the metal wiring such as the substrate and the fixed electrode are damaged by corrosion, etching, and the like. Not give.

  The acceleration sensor manufacturing method according to the present invention is characterized in that the second metal layer is a metal layer made of nickel or a nickel alloy.

  In the present invention, since the second metal layer to be the beam is nickel or a nickel alloy, it can be formed by wet plating such as electroplating or electroless plating which is easy to manufacture and has high cost merit. In addition, since it is nickel or nickel alloy, it has high corrosion resistance against alkaline chemicals. Therefore, it is not damaged at all by etching the first metal layer, and it is also reliable as an acceleration sensor. Get higher.

  The acceleration sensor manufacturing method according to the present invention is characterized in that the second metal layer is a metal layer composed of two or more layers of at least nickel or a nickel alloy and gold, copper, and an alloy containing these. To do.

  In the present invention, since the second metal layer to be the beam is a metal layer composed of two or more layers of nickel or a nickel alloy and gold, copper, and an alloy containing these, the opening of the third photoresist layer When the beam and the movable electrode main body are connected via the portion, the connection can be made with good adhesion by a wet plating method such as electroplating or electroless plating.

  In the acceleration sensor manufacturing method according to the present invention, the third metal layer contains at least nickel or a nickel alloy.

  The present invention provides a wet plating method such as electroplating or electroless plating by forming the third metal layer into nickel or a nickel alloy when forming the third metal layer in the opening of the third photoresist layer. Can be easily formed. Furthermore, a substance having a higher specific gravity can be formed by eutectizing a substance having a higher specific gravity, such as tungsten, with nickel plating.

  The acceleration sensor manufacturing method according to the present invention is characterized in that the fourth metal layer is composed of a layer including at least a metal layer selected from gold, nickel, or an alloy containing these.

  In this invention, the surface of the movable electrode, the beam, and the beam holding portion constituting the acceleration sensor is covered with a metal layer selected from gold, nickel, or an alloy containing these, so that the corrosion resistance is improved and the reliability is improved. To do.

  According to the present invention, a capacitive acceleration sensor having a weight and a beam made of metal can be formed.

  Embodiments according to the present invention will be described with reference to FIGS.

  As shown in FIG. 1 shown from above and in a cross-sectional direction of the acceleration sensor according to the present invention, the acceleration sensor includes a substrate 1 having at least one electrically insulating surface, and a fixed electrode 2a provided on the surface of the substrate 1. 2b, 2c and 2d, a wiring 3 for connecting a movable electrode, which will be described later, and the outside, a support portion 4 provided on the surface of the substrate 1 and fixing a beam, which will be described later, and a beam fixed to the support portion 4 5a, 5b, 5c, and 5d, and movable electrodes serving as weights, which are supported by the beams 5a to 5d so as to face the fixed electrodes 2a to 2d with a gap in the direction perpendicular to the surface of the substrate, respectively. It consists of electrodes 6a, 6b, 6c and 6d. The support portion 4, the beams 5a to 5d, and the movable electrodes 6a to 6d are each made of metal.

  As shown in FIG. 2, the manufacturing process of the acceleration sensor having such a configuration includes the steps of forming the fixed electrodes 2a to 2d and the wiring 3 on the substrate 1, forming the electrodes on the substrate (S10), and the fixed electrode. A step (S11) of forming a first photoresist layer for creating gaps between 2a to 2d and a part of the support portion 4 and the movable electrodes 6a to 6d; and beams 5a to 5d and movable electrodes 6a to 6d. Forming a first metal layer 13 for forming 6d by wet plating, forming a first metal layer (S12), and a second photoresist layer for providing the shapes of the beams 5a to 5d Forming the second metal layer to be the beams 5a to 5d (S14), and forming a third photoresist layer for giving the shapes of the movable electrodes 6a to 6d Step (S15) and movable electrodes 6a-6 Forming a third metal layer (S16), removing the third and second photoresist layers (S17), etching the first metal layer (S18), A step (S19) of removing the photoresist layer, a step (S20) of etching the first metal surface path exposed portion for removing the remaining surface exposed portion of the first metal layer 13, a second and Forming a fourth metal layer by electroless plating on the exposed surface of the third metal layer and the cross-section exposed portion of the first metal layer (S21).

  Hereinafter, each step will be described.

  In the step of forming electrodes on the substrate (S10), as shown in FIG. 3A, a thermal oxide film is formed on the surface, and a silicon substrate is formed on the electrically insulating silicon substrate 7 by sputtering. From the 7th side, a metal layer 8 composed of 50 nm of chromium, 200 nm of nickel, and 100 nm of gold is sequentially formed. Next, as shown in FIG. 3B, a photoresist layer 9 having a desired electrode pattern is formed. Thereafter, gold, nickel, and chromium are sequentially etched (FIG. 3C), and the photoresist layer 9 is peeled and removed, thereby producing a substrate 10 with wiring.

  In the step of forming the first photoresist layer (S11), as shown in FIG. 4A, the positive photoresist 11 is applied on the substrate 10 on which the wiring has been applied, and the solvent is removed by heating. Evaporate. At this time, the thickness of the positive photoresist 11 is set to be a gap distance between the stationary electrodes 2a to 2d and the movable electrodes 6a to 6d when stationary. Next, the first photoresist layer 12 is formed by exposing and developing the positive photoresist 11.

  In the step of forming the first metal layer (S12), as shown in FIG. 5, the first metal layer 13 made of a chromium film of 50 nm and a copper film of 200 nm is formed by sputtering on the treated surface of the substrate 10 on which wiring is applied. Form on the entire surface.

  In the step of forming the second photoresist layer (S13), as shown in FIG. 6, on the surface of the first metal layer surface 13, a dry film photo that is an acrylic negative photoresist having excellent thickness accuracy. A resist 14 is pasted. Next, the second photoresist layer 15 is formed by exposure and development.

  In the step of forming the second metal layer (S14), as shown in FIG. 7, the nickel plating layer 16 is formed by electroplating up to the desired thickness in the opening of the second photoresist layer 15, A copper plating layer 17 is further formed thereon by electroplating to form a plating layer 18. Next, the thickness of the second metal layer 18 is adjusted by polishing as necessary. At this time, in the second metal layer 18, the copper plating layer 17 was formed on the nickel plating layer 16 because when the nickel plating layer 16 appeared on the surface, an oxide layer that was difficult to remove on the surface was formed. Since it is easy to cause a problem in adhesion in forming the layer in the subsequent process, the polishing is covered with the copper plating layer 17 which is easy to process, and the nickel plating layer 16 alone is a problem for the subsequent process. If it does not occur, it is not always necessary to form the copper plating layer 17. In addition, when the film thickness distribution and flatness of the second metal layer 18 are good, it is not necessary to perform this polishing step.

  In the step of forming the third photoresist layer (S15), as shown in FIG. 8, a dry film photoresist 19, which is an acrylic negative photoresist with excellent thickness accuracy, is applied to the surface. Next, the third photoresist layer 20 is formed by exposure and development.

  In the step of forming the third metal layer (S16), as shown in FIG. 9, the nickel plating layer is formed by electroplating up to a desired thickness in the opening of the third photoresist layer 20. 3 metal layers 21 are formed. Next, the thickness and surface state of the second metal layer 21 are stabilized by performing polishing as necessary.

  In the step of removing the third and second photoresist layers (S17), as shown in FIG. 10, the third and second photoresist layers made of dry film photoresist are removed with an organic solvent or an alkaline stripping solution. To do. By using an organic solvent or an alkaline stripping solution, the dry film photoresist can be removed without damaging the members constituting the acceleration sensor.

  In the step of etching the first metal layer (S18), as shown in FIG. 11, the copper film and the chromium film, which are metals constituting the first metal layer 13, are sequentially etched. By using an etching solution in which ammonia is added to an aqueous ammonium persulfate solution, the copper film can be etched without damaging nickel, chromium, and gold constituting other portions. A part of the surface of the copper plating layer 17 in the second metal layer 18 is exposed, but if the copper plating layer 17 is formed sufficiently thick with respect to the film thickness of 200 nm of the copper film constituting the first metal layer 13. The etching amount does not pose any problem, and when it is thin, the second metal layer 18 and the third metal layer 21 are removed even if the exposed portion of the copper plating layer 17 is exposed. Since the connection is only exposed in the cross-sectional direction, the etching hardly progresses and does not cause a problem. The chromium film can be etched without affecting other metal parts by using an alkaline aqueous solution of potassium ferricyanide as an etchant.

  In the step of removing the first photoresist layer (S19), as shown in FIG. 12, the positive photoresist constituting the first photoresist 12 is removed by using an alkaline aqueous solution as a stripping solution.

  As described above, the acceleration sensor can be manufactured through the steps S10 to S19. In the acceleration sensor according to this manufacturing method, a part of the first metal layer 13 and the second metal layer 18 form the beams 5a to 5d. Copper and chromium are exposed in a part of these layers. If there is a need for higher reliability, the following process is performed.

  In the step of etching the exposed first metal layer surface (S20), as shown in FIG. 13, among the first metal layers 13 remaining in the step of etching the first metal layer (S18), the first The chromium film and the copper film constituting the first metal layer 13 attached to the lower part of the second metal layer 18 are etched by the step (S19) of removing the photoresist layer. For etching the chromium film, an alkaline aqueous solution of potassium ferricyanide is used as the etching solution, and for etching the copper film, an etching solution in which ammonia is added to the ammonium persulfate aqueous solution is used, so that the other parts are not affected. The first metal layer 13 exposed to can be etched.

  In the step of forming the fourth metal layer (S21), as shown in FIG. 14, the fourth metal layer 22 is formed on part or all of the exposed metal part surface by electroless plating. For electroless plating, nickel, gold and their alloy plating are used. When nickel or nickel alloy plating is used as the electroless plating, since nickel is used for the second and third metal layers, the electroless plating is deposited by the self-catalytic action of nickel and appears on a part of the surface. Although it also deposits on the copper surface at the same time, if the precipitation is insufficient, a substitutional palladium catalyst may be attached to the surfaces of nickel and copper, and then electroless nickel plating may be applied. In order to further improve the reliability, electroless gold plating may be applied directly or after electroless nickel plating. In this case, since all the metal parts of the acceleration sensor are covered with gold, the electrical characteristics are extremely excellent. In addition, the manufactured acceleration sensor is entirely made of metal except for the substrate 1, and is excellent in each stage in terms of strength and reliability.

  In this way, by applying the method for manufacturing an acceleration sensor according to the present invention, an acceleration sensor can be provided with a high-strength metal material without using a brittle material such as silicon or a silicon compound. Further, since the method for manufacturing the acceleration sensor does not use expensive equipment, dangerous gas, chemicals, etc., it can be provided in a relatively safe manner and at a low cost.

It is the figure shown from the upper direction and the cross-sectional direction of the acceleration sensor which concerns on this invention. It is a flowchart which shows the manufacturing method for producing the acceleration sensor which concerns on embodiment of this invention. It is explanatory drawing which shows the process of forming an electrode on a board | substrate among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of forming a 1st photoresist layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of forming the process of forming a 1st metal layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of forming a 2nd photoresist layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of forming a 2nd metal layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of forming a 3rd photoresist layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of forming a 3rd metal layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of removing the 3rd and 2nd photoresist layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of etching a 1st metal layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of removing the 1st photoresist layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of etching the 1st metal layer surface exposure remainder among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention. It is a figure which shows the process of forming a 4th metal layer among the manufacturing methods for producing the acceleration sensor which concerns on embodiment of this invention.

Explanation of symbols

1 Substrate 2a, 2b, 2c, 2d Fixed electrode 3a, 3b, 3c, 3d Wiring 4 Support portion 5a, 5b, 5c, 5d Beam 6a, 6b, 6c, 6d Movable electrode 7 Silicon substrate 8 Metal layer 9 Photoresist layer 10 Wiring substrate 11 Positive photoresist 12 First photoresist layer 13 First metal layer 14, 19 Dry film photoresist 15 Second photoresist layer 16 Nickel plating layer 17 Copper plating layer 18 Second Metal layer 20 Third photoresist layer 21 Third metal layer 22 Fourth metal layer

Claims (8)

A capacitive acceleration sensor that includes a fixed electrode and a movable electrode that face each other with a gap therebetween, and that measures acceleration by detecting changes in capacitance that accompany changes in the distance between these electrode gaps caused by movement of the movable electrode due to acceleration. A manufacturing method comprising:
Forming a fixed electrode and a wiring for connection to the outside on a substrate having at least one surface having electrical insulation;
Forming a first photoresist layer having a predetermined opening on the surface of the substrate on which the fixed electrode and wiring are formed;
Forming a first metal layer on a surface of the substrate on which the first photoresist layer is formed;
Forming a second photoresist layer having a predetermined opening on the surface of the first metal layer; and forming a second metal layer by wet plating on the opening of the second photoresist layer And a process of
Forming a third photoresist layer having a predetermined opening on the surfaces of the second photoresist layer and the second metal layer;
Forming a third metal layer in the opening of the third photoresist layer by a wet plating method;
Removing the third and second photoresist layers;
An acceleration sensor manufacturing method comprising: etching the first metal layer using the second and third metal layers as a mask; and removing the first photoresist layer. Method. Etching the remaining exposed surface of the first metal layer after removing the first photoresist layer;
Forming a fourth metal layer by electroless plating on the exposed surfaces of the second and third metal layers and the cross-section exposed portion of the first metal layer. A method for manufacturing the acceleration sensor according to claim 1.   3. The method of manufacturing an acceleration sensor according to claim 1, wherein the first metal layer is a metal layer composed of at least two layers of chromium and copper.   The acceleration sensor manufacturing method according to any one of claims 1 to 3, wherein the second metal layer is a metal layer made of nickel or a nickel alloy.   The said 2nd metal layer is a metal layer which consists of two or more layers of at least nickel or a nickel alloy and gold | metal | money, copper, and an alloy containing these, In any one of Claim 1 to 4 characterized by the above-mentioned. The manufacturing method of the acceleration sensor of description.   The acceleration sensor manufacturing method according to claim 1, wherein the third metal layer contains at least nickel or a nickel alloy.   The method for manufacturing an acceleration sensor according to claim 2, wherein the fourth metal layer is a layer including at least a metal layer selected from gold, nickel, or an alloy containing these.   An acceleration sensor manufactured by the method for manufacturing an acceleration sensor according to claim 1.

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