JP2010032538A - Capacitance type acceleration sensor and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance type acceleration sensor that can prevent a mass body from being stuck to a rear side glass substrate and a front side glass substrate by an electrostatic force and prevent a mass body from being damaged when it receives an excessive impact, and to provide a method for manufacturing a capacitance type acceleration sensor capable of using an inexpensive material easy to process as a sticking prevention film and an impact absorption film to be formed on the rear side glass substrate and the front side glass substrate at respective recessed portions. <P>SOLUTION: Layers 8A, 8B made of Al (Ni or Ti can be used) are respectively provided on the rear side and front side glass substrates 6, 7 at the respective recessed portions 6a, 7b so as to form sticking prevention films and impact absorption films. In the manufacturing process, a protection cover of a silicon nitride film is formed on the layer 8B so as to prevent the layer 8B from being damaged when etching a substrate 1. After that, the protection cover is removed. In addition, a corner portion of the mass body 41 is chamfered. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a capacitive acceleration sensor including a pair of fixed electrodes and a mass body that is a movable electrode disposed between them and is displaced by acceleration, and a method for manufacturing the same.

  FIG. 16 is a top view showing an example of the structure of a conventional capacitive acceleration sensor. This capacitive acceleration sensor includes fixed electrodes 2 and 3, a mass body 4 that is a movable electrode, and an outer frame portion 5. A gap G is provided between the fixed electrodes 2, 3 and the mass body 4, and they are arranged facing each other so as not to contact each other. Further, gaps are also provided between the fixed electrodes 2 and 3 and the mass body 4 and the outer frame portion 5, and the three members are arranged so as not to contact each other.

  The mass body 4 is displaced when subjected to acceleration. Therefore, a change occurs in the distance of each gap G between the mass body 4 and the fixed electrodes 2 and 3. By detecting this change as a change in capacitance, the capacitive acceleration sensor converts the acceleration into an electrical signal.

  In addition, perspective views of the capacitive acceleration sensor viewed from the back side and the front side are shown in FIGS. 17 and 18, respectively. FIG. 19 is a cross-sectional view taken along the cutting line AA in FIGS.

  The fixed electrodes 2 and 3, the mass body 4, and the outer frame portion 5 are all formed from a single substrate 1 such as a silicon substrate by using a photolithography technique or an etching technique. The fixed electrodes 2, 3, the mass body 4, and the outer frame portion 5 are sandwiched between the rear surface side glass substrate 6 and the front surface side glass substrate 7 on the front surface side and the rear surface side thereof. In FIGS. 17 and 18, in order to clearly show the internal structure of the capacitive acceleration sensor, the back glass substrate 6 and the front glass substrate 7 are shown separately from the capacitive acceleration sensor.

  As shown in FIGS. 17 to 19, the mass body 4 has a rectangular parallelepiped shape having an H-shaped protrusion 4 b on one surface. And the beam-like part 4a is extended from each of a pair of opposite sides in a rectangular parallelepiped, and the beam-like part 4a is connected to the support part 4g.

  The support part 4g is joined to the back side glass substrate 6 and the front side glass substrate 7, and the mass body 4 is maintained in a displaceable floating state by these and the beam-like part 4a. The fixed electrodes 2 and 3 and the outer frame portion 5 are also bonded to the back side glass substrate 6 and the front side glass substrate 7. That is, the fixed electrodes 2 and 3 and the mass body 4 are hermetically protected by the outer frame portion 5, the back side glass substrate 6, and the front side glass substrate 7.

  In addition, the back surface side glass substrate 6 and the front surface side glass substrate 7 are the surfaces of the mass body 4 so that the back surface side glass substrate 6 and the front surface side glass substrate 7 do not contact the mass body 4 through the gaps X and Y, respectively. Recessed portions 6a and 7b are provided in portions facing 4f and 4c. The recessed portions 6a and 7b are provided with an aluminum layer 8A and a gold / chrome layer 8C in which gold and chromium are laminated.

  In any of these films, when the substrate 1, the back glass substrate 6 and the front glass substrate 7 are bonded by an anodic bonding method or when used after commercialization, the mass body 4 is recessed by electrostatic force. 6a, 7b is a conductive film that prevents sticking to the back side glass substrate 6 or the front side glass substrate 7. At the same time, it also functions as an impact buffering film that prevents the mass body 4 from colliding with the back-side glass substrate 6 and the front-side glass substrate 7 when subjected to an excessive impact such as dropping after commercialization.

  The front glass substrate 7 is provided with contact holes 7a and 7c for connection to the fixed electrodes 2 and 3, and a contact hole 7d for connection to the support portion 4g of the mass body 4, respectively. Further, terminal portions 2a, 3a, 4h serving as contact terminals to the outside are provided in the portions exposed to the contact holes of the fixed electrodes 2, 3 and the support portion 4g, respectively. Then, the potential of each electrode is detected from the contact holes 7a, 7c, 7d, and the change in capacitance between the electrodes is detected.

  Further, a mask 10C such as a silicon oxide film formed at the time of manufacture is left between the surface side glass substrate 7 and the fixed electrodes 2 and 3, the mass body 4 and the outer frame portion 5.

JP 2000-187041 A

  When manufacturing the capacitive acceleration sensor having the above structure, first, contact holes 7a, 7c, 7d, and the like are formed on the substrate 1 on which the fixed electrodes 2 and 3, the mass body 4 and the outer frame portion 5 are formed halfway. The surface side glass substrate 7 on which the recessed portion 7b and the gold / chrome layer 8C have been formed is bonded by an anodic bonding method or the like. Then, the substrate 1 to which the surface side glass substrate 7 is bonded is etched to form the fixed electrodes 2 and 3, the mass body 4 and the outer frame part 5, respectively, and then the recessed part 6a and the aluminum layer 8A are formed. The back glass substrate 6 is bonded to the substrate 1 by anodic bonding or the like.

  Now, the gold / chrome layer 8C formed in the recessed portion 7b is expensive and has poor workability. Therefore, it is desirable to use other materials as a film for preventing sticking due to electrostatic force and an impact buffering film.

  For example, it is conceivable to form an aluminum layer on the front side glass substrate 7 in place of the gold / chromium layer 8C, similarly to the aluminum layer 8A provided in the recessed portion 6a of the back side glass substrate 6. This is because an aluminum layer is cheaper and easier to process than a gold / chrome layer.

  Note that the concept of forming an aluminum layer in both of the recessed portions 6a and 7b of the capacitive acceleration sensor is disclosed in paragraph [0060] of Patent Document 1, for example.

  However, when the aluminum layer is formed in the recessed portion 7 b and the front side glass substrate 7 is bonded to the substrate 1 and the substrate 1 is etched, the aluminum is formed when the fixed electrodes 2 and 3, the mass body 4 and the outer frame portion 5 are formed. There is a problem that the layer is exposed to the etching solution, and the aluminum layer is damaged under the influence. In particular, when a silicon substrate is employed as the substrate 1 to form a fixed electrode or a mass body by wet etching, an alkaline etching solution such as an aqueous potassium hydroxide solution is used as the etching solution. It is easy to damage the etching solution. If the aluminum layer is not sufficiently formed, sticking due to electrostatic force and shock buffering cannot be performed sufficiently.

  Therefore, in the conventional capacitive acceleration sensor, the anti-sticking film and the impact buffering film formed in the recessed portion 7b are resistant to an etching solution for the substrate 1, but are expensive and inferior in workability. 8C had to be used.

  Therefore, an object of the present invention is to prevent the mass body from sticking to the back side glass substrate and the front side glass substrate by electrostatic force, and to prevent the mass body from being damaged even when subjected to an excessive impact. Capacitive type capable of adopting a low-priced and easy-to-process film as a possible capacitive acceleration sensor and an anti-sticking film and an impact buffering film formed on the back glass substrate and the recessed portion of the front glass substrate It is providing the manufacturing method of an acceleration sensor.

  The invention according to claim 1 includes a fixed electrode, a mass body that has a corner portion and is a movable electrode facing the fixed electrode through a gap, and the fixed electrode and the mass body are sandwiched between the fixed electrode and the fixed electrode. Is a capacitive acceleration sensor including first and second insulating substrates that support the mass body while keeping the mass body in a floating state, and the corner portions of the mass body are chamfered.

  The invention according to claim 2 includes a step (a) of bonding a non-insulating substrate selectively etched on one main surface to the surface of the first insulating substrate, and the step facing the one main surface. Selectively etching the other main surface of the non-insulating substrate, from the non-insulating substrate, having a fixed electrode, a corner portion, and facing the fixed electrode through a gap; and A step (b) of forming a mass body that is a movable electrode that is opposed to the first insulating substrate through a gap and is supported in a floating state on the first insulating substrate; (C) chamfering the corner portion by etching, and bonding the second insulating substrate to the non-insulating substrate so that the mass body faces the second insulating substrate through a gap. A step (d) of manufacturing a capacitive acceleration sensor.

  Invention of Claim 3 is a manufacturing method of the capacitive acceleration sensor of Claim 2, Comprising: The said non-insulating board | substrate is a silicon substrate, The said etching in the said process (c) is alkaline etching liquid It is the manufacturing method of the capacitive acceleration sensor performed by the wet etching which used this.

  According to the invention described in claim 1, since the corners of the mass body are chamfered, the mass body is displaced by impact and collides with the first or second insulating substrate or the fixed electrode. Even so, the mass body is less likely to be damaged.

  According to the invention described in claim 2, since the corner portion is chamfered by etching the mass body in the step (c), the capacitive acceleration sensor according to claim 5 can be manufactured.

  According to the third aspect of the present invention, the non-insulating substrate is a silicon substrate, and the etching in the step (c) is performed by wet etching using an alkaline etching solution. Easy to do.

1 is a cross-sectional view showing a capacitive acceleration sensor according to a first embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. FIG. 10 is a diagram showing a one-step method of manufacturing a capacitive acceleration sensor according to a second embodiment. FIG. 10 is a diagram illustrating a step of a method for manufacturing the capacitive acceleration sensor according to the second embodiment. 6 is a cross-sectional view showing a capacitive acceleration sensor according to Embodiment 3. FIG. FIG. 10 is a cross-sectional view showing one step in a method for manufacturing a capacitive acceleration sensor according to Embodiment 4. FIG. 10 is a cross-sectional view showing one step in a method for manufacturing a capacitive acceleration sensor according to Embodiment 4. FIG. 10 is a cross-sectional view showing one step in a method for manufacturing a capacitive acceleration sensor according to Embodiment 4. It is a top view which shows the conventional capacitive acceleration sensor. It is a perspective view which shows the conventional capacitive acceleration sensor. It is a perspective view which shows the conventional capacitive acceleration sensor. It is sectional drawing which shows the conventional capacitive acceleration sensor.

<Embodiment 1>
The present embodiment is a capacitive acceleration sensor manufactured by the manufacturing method according to the second embodiment to be described later, and has an anti-adhesion film on any recessed portion of the back side glass substrate and the front side glass substrate. This is a capacitive acceleration sensor provided with an aluminum layer as an impact buffering film.

  FIG. 1 is a cross-sectional view showing the structure of a capacitive acceleration sensor according to the present embodiment. As shown in FIG. 1, the structure of the capacitive acceleration sensor according to the present embodiment is the same as that of the conventional capacitive acceleration sensor shown in FIGS. 16 to 19 except that the gold / chrome layer 8C is replaced with an aluminum layer 8B. It has the same structure as the sensor.

  That is, the capacitive acceleration sensor according to the present embodiment includes fixed electrodes 2 and 3, a mass body 4 that is a movable electrode, and an outer frame portion 5. The thicknesses of the fixed electrodes 2 and 3, the mass body 4 and the outer frame portion 5 are all about 140 μm, for example. A gap G is provided between the fixed electrodes 2 and 3 and the mass body 4, and the fixed electrodes 2 and 3 are arranged to face each other on the side surfaces 4 d and 4 e of the mass body 4 so as not to contact each other. In addition, the length of the side surfaces 4d and 4e in the direction perpendicular to the paper surface in FIG. 1 is, for example, about 3000 μm. Further, the distance between the fixed electrodes 2 and 3 and the mass body 4 in the gap G is, for example, about 5 μm. Further, gaps are also provided between the fixed electrodes 2 and 3 and the mass body 4 and the outer frame portion 5, and the three members are arranged so as not to contact each other.

  The fixed electrodes 2 and 3, the mass body 4, and the outer frame portion 5 are all formed from a single substrate 1 such as a silicon substrate by using a photolithography technique or an etching technique. The fixed electrodes 2, 3, the mass body 4, and the outer frame portion 5 are sandwiched between the rear surface side glass substrate 6 and the front surface side glass substrate 7 on the front surface side and the rear surface side thereof. The back-side glass substrate 6 and the front-side glass substrate 7 function as protective covers for the fixed electrodes 2, 3 and the mass body 4, and have a silicic acid-based heat resistance whose thermal expansion coefficient is set close to the thermal expansion coefficient of the substrate 1. It is a glass substrate. The thickness is about 400 μm, for example.

  The mass body 4 has a rectangular parallelepiped shape having an H-shaped protrusion 4b on one surface, and a beam-like portion (corresponding to reference numeral 4a in FIG. 16) from each of a pair of opposite sides in the rectangular parallelepiped. The beam-like portion extends and is connected to a support portion (corresponding to 4g in FIG. 16). Note that the thickness of the portion of the mass body 4 where the protrusions 4b do not exist is, for example, about 50 μm.

  Here, the protrusion 4b is provided on the mass body 4 in order to reduce the weight of the mass body 4 in order to increase the sensitivity to acceleration, and the distance between the surface side glass substrate 7 and the mass body 4 This is because the displacement of the mass body 4 toward the back surface side glass substrate 6 is restricted without excessively increasing the distance between the back surface side glass substrate 6 and the mass body 4.

  For example, when a capacitive acceleration sensor is dropped and receives a large impact, if the projection 4b is not provided, the mass body 4 can be greatly displaced toward the rear glass substrate 6 and the beam-like portion can be damaged. There is sex. However, if there is a protrusion 4b that regulates the displacement, it functions as a stopper for the back surface side glass substrate 6 of the mass body 4, so that the possibility of damage to the beam-like portion can be reduced.

  And the support part of the mass body 4 is joined to the back surface side glass substrate 6 and the front surface side glass substrate 7, and the mass body 4 is maintained in the displaceable floating state by these and the beam-shaped part. The fixed electrodes 2 and 3 and the outer frame portion 5 are also bonded to the back side glass substrate 6 and the front side glass substrate 7. That is, the fixed electrodes 2 and 3 and the mass body 4 are hermetically protected by the outer frame portion 5, the back side glass substrate 6, and the front side glass substrate 7.

  The back glass substrate 6 and the front glass substrate 7 are opposed to the mass body 4 so that the back glass substrate 6 and the front glass substrate 7 do not contact the mass body 4 through the gaps X and Y, respectively. For example, recessed portions 6a and 7b having a depth of about 15 μm are provided in the portion. The recessed portions 6a and 7b are provided with aluminum layers 8A and 8B that function as a sticking prevention film and an impact buffer film, respectively. The aluminum layers 8A and 8B have a thickness of about 5 μm, for example. The distance between the mass body 4 and the aluminum layers 8A and 8B in the gaps X and Y is, for example, about 10 μm.

  The front side glass substrate 7 has contact holes 7a and 7c for connection to the fixed electrodes 2 and 3, and a contact hole for connection to the support portion of the mass body 4 (corresponding to 7d in FIG. 18). ) Is provided. Further, the portions exposed to the contact holes of the support portions of the fixed electrodes 2 and 3 and the mass body 4 are respectively provided with terminal portions 2a and 3a serving as contact terminals to the outside and those corresponding to reference numeral 4h in FIG. ing.

  The potential of each electrode is detected from these contact holes. Then, a change in capacitance between the electrodes is detected. Even if there is only one fixed electrode, the same operation can be performed. In that case, it is only necessary to provide one of the contact holes 7a or 7c and the contact hole connected to the support portion of the mass body 4 in the surface side glass substrate 7.

  Further, a mask 10C such as a silicon oxide film formed at the time of manufacture is left between the surface side glass substrate 7 and the fixed electrodes 2 and 3, the mass body 4 and the outer frame portion 5.

  In addition to aluminum, nickel and titanium are examples of materials that are cheaper and easier to process than gold / chromium layers and are easily damaged by an alkaline etching solution. Therefore, here, the aluminum layers 8A and 8B are mentioned as the anti-sticking films and the impact buffer films formed in the recessed portions 6a and 7b, but instead, a nickel layer or a titanium layer is formed in the recessed portions 6a and 7b. It may be.

  Also in this case, as in the case of the aluminum layers 8A and 8B, the mass body 4 is prevented from adhering to the back side glass substrate 6 and the front side glass substrate 7 by electrostatic force, and the mass 4 is also subjected to excessive impact. A capacitive acceleration sensor capable of preventing the body 4 from being damaged can be obtained.

<Embodiment 2>
The present embodiment is a manufacturing method for manufacturing the capacitive acceleration sensor according to the first embodiment.

  2-11 is sectional drawing which shows the manufacturing method of the capacitive acceleration sensor based on this Embodiment.

  First, as shown in FIG. 2, a back glass substrate 6 on which an aluminum layer 8A is formed is prepared. For example, a glass substrate having a thickness of about 400 μm is prepared for forming the back side glass substrate 6, and the recessed portion 6 a is formed by selectively sandblasting on one main surface. Then, an aluminum film is deposited on the entire surface, and an aluminum layer 8A is formed using the photolithography technique and the etching technique, leaving the aluminum film only in the recessed portion 6a.

  Next, the surface side glass substrate 7 on which the aluminum layer 8B is formed is prepared. As an example in forming the surface side glass substrate 7, first, as shown in FIG. 3, for example, a glass substrate having a thickness of about 400 μm is prepared, and a mask 10A such as a resist film is provided on one main surface thereof, and this is patterned. Then, sand blasting is performed to form the recessed portion 7b. Then, the mask 10A is removed and an aluminum film is deposited on the entire surface, and an aluminum layer 8B is formed using the photolithography technique and the etching technique, leaving the aluminum film only in the recessed portion 7b as shown in FIG.

  Then, for example, a silicon nitride film 11 serving as a protective film for the aluminum layer 8B in the subsequent etching process of the substrate 1 is formed on the entire main surface of the surface-side glass substrate 7 so as to cover the aluminum layer 8B. Then, as shown in FIG. 5, the silicon nitride film 11 is left only in the recessed portion 7b by using the photolithography technique and the etching technique. Specifically, for example, a resist may be formed only on the upper portion of the recessed portion 7b, and a portion of the silicon nitride film not covered with the resist may be removed by dry etching.

  Next, as shown in FIG. 6, a mask 10B such as a resist is formed on the main surface of the surface side glass substrate 7 opposite to the surface where the recessed portion 7b is formed, and the fixed electrodes 2 and 3 and the mass body are formed. Patterning for forming a contact hole on the support portion 4 is performed. At this time, a contact hole for applying a ground potential to the outer frame portion 5 may be further provided. Then, sandblasting is performed from the mask 10B side to form contact holes such as 7a and 7c as shown in FIG. 7, and the formation of the surface side glass substrate 7 is completed. The reason why sandblasting is used here is that when wet etching is adopted, the amount of side etching is large and the opening width of the contact hole is widened, so that downsizing of the capacitive acceleration sensor is prevented. This is because the etching rate is smaller than that of sand blasting and much time is required for production.

  Subsequently, a silicon wafer having a thickness of about 250 μm with one side mirror-polished is prepared as a material for the substrate 1, and a mask 10 C made of, for example, a silicon oxide film is formed on the mirror-polished surface of the substrate 1. Patterning is performed by isotropic etching. Then, by performing etching using the mask 10C, the narrow groove 1a having a narrow groove width and the groove 1b having a wider groove width than the narrow groove 1a are selectively formed on the substrate 1.

  When a silicon wafer is used as the material for the substrate 1A, a wafer having a main surface crystal orientation of <110> (that is, a (110) wafer) is preferably used. In forming the narrow grooves 1a and 1b, wet etching using an alkaline etching solution such as an aqueous potassium hydroxide solution having a concentration of about 20% by weight may be performed. In addition, as an alkaline etching liquid, you may employ | adopt tetramethylammonium hydroxide aqueous solution other than potassium hydroxide aqueous solution.

  In the case of a (110) wafer, anisotropic etching is easily performed along the crystal plane {111} perpendicular to the crystal plane (110), and the narrow groove 1a and the groove 1b are compared with the depth d. The groove width w can be made extremely small. For example, it is possible to obtain a high aspect ratio such that w / d <0.05.

  Further, since anisotropic etching is easily performed along the crystal plane {111}, the etching depth can be changed depending on the difference in opening width. Therefore, the opening width of the mask 10C can be set as appropriate to make the narrow groove 1a shallow and the groove 1b deep. Here, the depth of the narrow groove 1a may be set to about 50 μm, for example.

  The reason why the silicon wafer having a thickness of about 250 μm is exemplified as the material of the substrate 1 is that it is easy to handle.

  And as shown in FIG. 9, the surface in which the recessed part 7a of the surface side glass substrate 7 was formed, and the surface in which the fine groove 1a and the groove 1b of the substrate 1 were formed are brought into close contact, and these are subjected to anodic bonding. Join.

  When a silicon oxide film is used as the mask 10C, if the thickness is about 1 μm, the surface side glass substrate 7 and the substrate 1 can be bonded by the anodic bonding method even when the silicon oxide film is sandwiched therebetween. Since it is possible, joining may be performed with the mask 10C remaining.

  Then, wrap-off (grinding) is performed from the surface opposite to the bonding surface of the substrate 1 on which the bonding has been performed, and the thickness is finished to be, for example, about 140 μm.

  Next, as shown in FIG. 10, for example, a silicon nitride film that can be deposited at a relatively low temperature is formed as a mask 10 </ b> D on the lap-off surface. Then, patterning is performed on the mask 10D, and etching is performed using the mask 10D, thereby forming the fixed electrodes 2 and 3, the mass body 4, and the outer frame portion 5.

  That is, the groove 1b completely divides the fixed electrodes 2 and 3 and the outer frame portion 5 to form the gap Z, and the narrow groove 1a communicates with the recessed portion 1c that is an etching pattern to connect the mass body 4 and the protrusion. Etching is performed to form the portion 4b. In this etching, wet etching using an alkaline etching solution such as a potassium hydroxide aqueous solution having a concentration of about 32% by weight may be performed.

  Since the silicon nitride film 11 is resistant to an alkaline etching solution, the aluminum layer 8B is not damaged during this etching. The same applies to materials that are not resistant to alkaline etching solutions such as titanium and nickel. Therefore, even a material that is cheaper and easier to process than a gold / chromium film but does not have resistance to etching can be used as an impact buffer film. If a silicon nitride film is used as a protective film for the impact buffer film, it can be formed at a low cost and can be easily removed.

  The reason why the substrate 1 is thinned by wrapping off in the step shown in FIG. 9 is to make the etching depth of the recessed portion 1c as small as possible when the mass body 4 having a thickness of about 50 μm is formed.

  Next, the portion of the mask 10C that is not the bonding surface, the mask 10D, and the silicon nitride film 11 are removed by wet etching using, for example, hydrofluoric acid. Then, the surface of the rear glass substrate 6 on which the aluminum layer 8A is formed is bonded to the substrate 1 by an anodic bonding method or a bonding method utilizing a eutectic phenomenon as shown in FIG.

  Then, aluminum thin films 2a and 3a having a thickness of about 3 μm, for example, are deposited in the contact holes such as 7a and 7c, and the capacitive acceleration sensor shown in FIG. 1 is completed.

<Embodiment 3>
The present embodiment is a modification of the capacitive acceleration sensor according to the first embodiment. In the present embodiment, the corners of the mass body are chamfered.

  FIG. 12 is a cross-sectional view showing the capacitive acceleration sensor according to the present embodiment. In FIG. 12, elements having the same functions as those of the capacitive acceleration sensor according to the first embodiment are denoted by the same reference numerals.

  As shown in FIG. 12, in the capacitive acceleration sensor according to the present embodiment, instead of the mass body 4 in FIG. 1, a mass body 41 including chamfered portions 41 a to 41 d whose corner portions are chamfered is provided. Instead of the fixed electrodes 2 and 3 in FIG. 1, a fixed electrode 21 having chamfered portions 21a and 21b and a fixed electrode 31 having chamfered portions 31a and 31b are provided.

  If the corners of the mass body are chamfered in this way, the mass body 41 is displaced by an impact and collides with either the back-side glass substrate 6, the front-side glass substrate 7, or the fixed electrodes 21 and 31. Even if it does, the mass body 41 is hard to be damaged.

  The chamfered portions 21a, 21b, 31a, and 31b of the fixed electrodes 21 and 31 are formed as the chamfered portions 41a to 41d are formed on the mass body 41, and the formation thereof is not necessarily required. Absent.

<Embodiment 4>
The present embodiment is a method for manufacturing the capacitive acceleration sensor according to the third embodiment. Since the second embodiment is a method for manufacturing a capacitive acceleration sensor according to the first embodiment, this embodiment is also a modification of the second embodiment. Therefore, in the present embodiment, only differences from the second embodiment will be described.

  13 to 15 are diagrams showing steps added in the present embodiment. First, similarly to the second embodiment, the steps shown in FIGS. 2 to 10 are performed to form the fixed electrodes 2 and 3, the mass body 4 and the outer frame portion 5 from the substrate 1.

  Next, as shown in FIG. 13, for example, by wet etching using hydrofluoric acid whose concentration is adjusted, the mask 10D and the silicon nitride film 11 are left and the portions exposed to the surface of the mass body 4 and the contact holes 7a and 7c are left. The mask 10C (silicon oxide film) is removed.

  Subsequently, as shown in FIG. 14, the mass body 4 is further etched to chamfer the corners to obtain the mass body 41. Also in this etching, wet etching using an alkaline etching solution such as a potassium hydroxide aqueous solution having a concentration of about 32% by weight may be performed for an appropriate time. When a silicon substrate is used as the substrate 1, the corner portions of the mass body 41 can be easily chamfered by performing wet etching using an alkaline etching solution.

  At this time, the corner portions of the fixed electrodes 2 and 3 are also etched to form the fixed electrode 21 having the chamfered portions 21a and 21b and the fixed electrode 31 having the chamfered portions 31a31b.

  In this etching, portions of the substrate 1 covered with the masks 10C and 10D are difficult to be etched, but other portions are further etched, and particularly corner portions are easily etched. Therefore, the corner portion can be chamfered. Further, this etching makes the thickness t of the mass body 41 (shown in the enlarged view of FIG. 12) slightly smaller than that of the mass body 4 of the first embodiment, for example. It can be suppressed to the extent that there is no problem.

  Finally, as shown in FIG. 15, the mask 10D and the silicon nitride film 11 are removed by wet etching using, for example, hydrofluoric acid.

  Then, after the additional step, the back glass substrate 6 is joined, and the aluminum thin films 2a and 3a are deposited in the contact holes such as 7a and 7c, thereby completing the capacitive acceleration sensor shown in FIG. .

  The present invention is applicable to a capacitive acceleration sensor and a method for manufacturing the same.

  DESCRIPTION OF SYMBOLS 1 Board | substrate, 2,21,3,31 Fixed electrode, 4,41 Mass body, 5 Outer frame part, 6 Back surface side glass substrate, 7 Front surface side glass substrate, 8A, 8B Aluminum layer, 11 Silicon nitride film, 41a-41d Chamfered part.

Claims (3)

A fixed electrode;
A mass body having a corner portion and being a movable electrode facing the fixed electrode via a gap;
The fixed electrode and the mass body are sandwiched, and the fixed electrode is joined, and includes first and second insulating substrates that support the mass body while keeping it in a floating state.
A capacitive acceleration sensor in which the corner portion of the mass body is chamfered. A step (a) of bonding a non-insulating substrate selectively etched on one main surface to the surface of the first insulating substrate;
The other main surface of the non-insulating substrate opposite to the one main surface is selectively etched to have a fixed electrode, a corner portion from the non-insulating substrate, and a gap in the fixed electrode. And a mass body that is a movable electrode that is opposed to the first insulating substrate via a gap and is supported in a floating state on the first insulating substrate ( b) and
Etching the mass body to chamfer the corner portion (c);
A step (d) of joining a second insulating substrate to the non-insulating substrate so that the mass body faces the second insulating substrate through a gap. It is a manufacturing method of the capacity type accelerometer according to claim 2,
The non-insulating substrate is a silicon substrate;
The method of manufacturing a capacitive acceleration sensor, wherein the etching in the step (c) is performed by wet etching using an alkaline etching solution.

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