JP6492708B2 - Pressure sensor device - Google Patents

Description

  The present invention relates to a pressure sensor device having a sensor chip in which a bottom portion side of a concave portion is a diaphragm by forming a concave portion, and the diaphragm receives pressure from the concave portion side.

  Conventionally, this type of pressure sensor device is a plate-shaped chip made of a semiconductor, and by forming a recess on one surface, the bottom of the recess is a diaphragm as a thin wall portion having a pressure detection function. A device including a sensor chip has been proposed (see, for example, Patent Document 1). And in this thing, pressure detection is performed by exposing a diaphragm to pressure media, such as air and oil, in the recessed part side.

JP2012-154801A

  By the way, since the pressure medium such as air and oil described above contains foreign matters such as water and oil, or impurities such as soot, dust, and precipitates, these foreign matters may adhere to the diaphragm from the concave side. If foreign matter adheres to the bottom of the diaphragm, that is, the bottom of the concave portion, it affects the distortion characteristics due to the pressure received by the diaphragm and causes the sensing function to deteriorate.

  In order to suppress this problem, the present inventor has studied to cover the surface of the concave portion that contacts the pressure medium in the diaphragm with a liquid repellent or lyophilic protective member for the purpose of suppressing adhesion of foreign matter.

  In this case, specifically, the bottom portion corresponding to the diaphragm in the concave portion and the side wall portion positioned around the bottom portion in the concave portion are larger in liquid repellency than the surface of the concave portion (for example, a semiconductor) or lyophilic. Cover with a large protective member.

  The liquid repellency of the protective member is a property that easily repels liquid such as water or oil, and the lyophilic property is a property that the liquid is easily wetted. About the wettability of such a protection member, what is necessary is just to determine according to the flow method and type of the pressure medium which contacts a recessed part.

  For example, when the pressure medium itself is a liquid or when the recess is in an environment where the recess is easily exposed to the liquid, it is conceivable to wash away the foreign matter attached to the protective member in the recess using the liquid. However, when the protective member is liquid repellent, the liquid is repelled, so that the cleaning with the liquid becomes insufficient. In such a case, the protective member may be made lyophilic.

  However, as described above by the inventors, even if the surface of the concave portion of the diaphragm is covered with the protective member, the protective member itself is a harsh environment that is directly exposed to the pressure medium. There is a risk of peeling.

  The present invention has been made in view of the above problems, and has a configuration in which the surface of a concave portion forming a diaphragm is covered with a liquid-repellent or lyophilic protective member in order to suppress foreign matter adhesion in a pressure medium. An object of the present invention is to suppress the peeling of the protective member as much as possible.

In order to achieve the above object, according to the first aspect of the present invention, the bottom portion (21c) of the concave portion has a pressure detecting function by forming the concave portion (21b) on one surface (2a). It has a sensor chip (2) which is a diaphragm (21a) as a thin-walled portion, and pressure detection is performed by exposing the diaphragm to a pressure medium on the concave side,
The bottom part corresponding to the diaphragm in the concave part and the side wall part (21d) located around the bottom part in the concave part are covered with a protective member (8) having a higher liquid repellency or a more lyophilic property than the surface of the concave part. In the bottom part and the side wall part, only the surface of the side wall part is subjected to uneven treatment, and the side wall part is provided with a protective member on the surface subjected to the uneven treatment (21e) ,
The protective member covers the bottom and has a liquid-repellent protective member (81) having a higher liquid repellency than the surface of the recess, and the lyophilic protective member that covers the side wall and has a higher lyophilic property than the surface of the recess. (82) .

  According to this, since the surface of the side wall portion of the surface of the concave portion that forms the diaphragm is an uneven surface, and the protective member is formed on this surface, the anchor effect due to the unevenness is exhibited, and the protective member Improved adhesion. Further, since the surface of the bottom corresponding to the diaphragm is not subjected to the uneven process, no adverse effect on the characteristics of the diaphragm occurs.

  Therefore, according to the present invention, in order to suppress the adhesion of foreign matter in the pressure medium, in the configuration in which the surface of the concave portion forming the diaphragm is covered with a liquid repellent or lyophilic protective member, the protective member is appropriately peeled off. Can be suppressed.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a schematic sectional drawing which shows the pressure sensor apparatus concerning 1st Embodiment of this invention. It is a figure which expands and shows the A section in FIG. It is a schematic plan view which shows the principal part of the pressure sensor apparatus concerning 2nd Embodiment of this invention. It is a schematic plan view which shows the principal part of the pressure sensor apparatus concerning 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings in order to simplify the description. 3 and 4, the surfaces of these films are hatched for the sake of convenience in order to facilitate the distinction between the liquid repellent protective film 81 and the lyophilic protective film 82.

(First embodiment)
A pressure sensor device 1 according to a first embodiment of the present invention will be described with reference to FIGS. The pressure sensor device 1 detects, for example, the pressure of intake air taken into the engine, the detection of exhaust gas pressure such as an EGR (Exhaust Gas Recirculation) system, and the oil that lubricates each part of the engine. Applied to pressure detection.

  The pressure sensor device 1 mainly includes a sensor chip 2, a circuit chip 3, a bonding wire 4, a lead frame 5, and a mold resin 6. As shown in FIGS. 1 and 2, the sensor chip 2 is a plate-shaped chip made of a semiconductor and is formed by a normal semiconductor process.

  Here, the sensor chip 2 is formed into a flat plate shape by bonding two substrates formed in a flat plate shape, that is, the first substrate 21 and the second substrate 22 by direct bonding or the like, thereby forming a sensor element or the like. IC chip. Here, the first substrate 21 is made of a semiconductor such as silicon, and the second substrate 22 is made of a semiconductor, glass, or the like.

  The sensor chip 2 typically has a rectangular plate shape whose longitudinal direction is the left-right direction in FIG. The sensor chip 2 has one surface 2a and another surface 2b opposite to the one surface 2a, and has one end 2c and the other end 2d as both ends in the longitudinal direction. Here, as shown in FIG. 1, the first substrate 21 has one surface 2 a and the second substrate 22 has the other surface 2 b.

  A diaphragm 21a serving as a thin portion which is a sensing portion having a pressure detection function is provided on one end 2c side of the one surface 2a of the sensor chip 2. The diaphragm 21a is provided with a resistor (not shown). The diaphragm 21a has a thickness of about 10 μm, for example.

  The diaphragm 21 a is configured by forming a concave portion 21 b on one surface 2 a of the sensor chip 2 and forming a thin portion on the first substrate 21. The recess 21b is formed on the first substrate 21 by etching or the like, and the inner surface thereof includes a bottom portion 21c and a side wall portion 21d positioned around the bottom portion 21c.

  The diaphragm 21a is configured to correspond to the bottom 21c of the recess 21b in the first substrate 21. The recess 21b has a depth of about 250 μm, for example.

  Then, as shown by the white arrow in FIG. 1, a pressure medium such as air or oil is applied to the diaphragm 21 a from the one surface 2 a side of the sensor chip 2, that is, from the concave portion 21 b side of the first substrate 21. It comes to contact. That is, the bottom 21c of the recess 21b is a pressure receiving surface that receives pressure from the pressure medium in the diaphragm 21a.

  When the pressure is applied by the pressure medium, the diaphragm 21a outputs an electrical signal corresponding to the pressure by utilizing the change in the internal resistance of the resistance due to, for example, a piezoresistance effect. Yes. The electrical signal output from the diaphragm 21a is sequentially transmitted to the circuit chip 3 and a lead portion 52 of the lead frame 5 described later, and finally transmitted to the outside of the pressure sensor device 1.

  Further, as shown in FIG. 1, a recess is formed in a region facing the diaphragm 21a on the surface 22a opposite to the surface 2b of the sensor chip 2 of the second substrate 22. Accordingly, a pressure reference chamber 7 is provided. The pressure reference chamber 7 applies a reference pressure for pressure detection to the diaphragm 21a, and is a constant pressure such as a vacuum pressure or an atmospheric pressure.

  Also, a pad 23 as an electrical connection portion is provided on the other end 2d side of the other surface 2b of the sensor chip 2. The pad 23 is made of aluminum or the like formed by vapor deposition or sputtering.

  Thus, in the sensor chip 2, by forming the concave portion 21b on the one surface 2a, the bottom portion 21c of the concave portion 21b serves as a diaphragm 21a as a thin portion having a pressure detection function. Further, in the present embodiment, the recess 21b has the following unique configuration.

  That is, as shown in FIGS. 1 and 2, the bottom 21c corresponding to the diaphragm 21a in the recess 21b and the side wall 21d located around the bottom 21c in the recess 21b are covered with the protective film 8 as a protective member. Has been.

  Here, the protective film 8 is a film having a higher liquid repellency than the surface of the recess 21b, or a film having a higher lyophilic property than the surface of the recess 21b. Specifically, the liquid-repellent film is a film having higher liquid repellency than the semiconductor constituting the sensor chip 2, here the semiconductor constituting the first substrate 21, and the lyophilic film is The film is more lyophilic than the semiconductor.

  Furthermore, the liquid-repellent film and the lyophilic film in this embodiment are defined by the contact angle as described below. Here, the contact angle measurement is performed with a liquid to be lyophobic in an environment where the pressure sensor device is used. Specifically, when the liquid repellent target is water, it is defined by the contact angle with water. When the liquid repellent target is oil (that is, in the case of oil repellent treatment), the contact angle with oil is determined. Defined by The same applies to cases other than water and oil.

  In this case, the liquid repellent coating has a contact angle of 90 ° or more, and the larger the angle is, the better the liquid repellency. On the other hand, the lyophilic film has a contact angle of less than 90 °, and the smaller the angle is, the better the lyophilic property. The difference in contact angle between the liquid repellent film and the lyophilic film is preferably 50 ° or more.

  As shown in FIGS. 1 and 2, in the present embodiment, the protective film 8 is the same coating that covers the entire surface of the bottom 21c and the side wall 21d, that is, the recess 21b. This film is formed on the semiconductor so as to cover the semiconductor constituting the first substrate 21 in the sensor chip 2.

  Here, the liquid-repellent film as the protective film 8 is a film made of, for example, an organic fluorine compound, and the lyophilic film is a coating film made of, for example, a silica-based coating film or an organic hydrophilizing agent, or the like. It consists of a coating film such as DLC (Diamond Like Carbon). These films are formed by, for example, a method by coating and drying, coating by plasma treatment, sputtering, vapor deposition, or the like.

  Further, the above-mentioned material of the protective film 8 having liquid repellency or lyophilicity is a material that does not obstruct the distortion characteristics of the diaphragm 21a, such as a low elastic modulus, excellent heat resistance, and chemical resistance. It is selected from the point that it is a material having the following characteristics.

  Further, as shown in FIG. 2, in the present embodiment, the surface of the recess 21 b that is the base of the protective film 8 is subjected to uneven processing only on the surface of the side wall 21 d among the bottom 21 c and the side wall 21 d.

  In other words, in the present embodiment, the concave / convex treatment is performed only on the surface of the side wall 21d out of the surfaces of the bottom 21c and the side wall 21d made of a semiconductor, and the concave / convex treatment is not performed on the surface of the bottom 21c. The surface of the side wall 21d is an uneven surface 21e that is an uneven surface, and a protective film 8 is formed on the uneven surface 21e so as to cover the uneven surface 21e.

  Here, the concave portion 21 b is formed by performing plasma etching, wet etching, or the like on the first substrate 21. And the uneven | corrugated processed surface 21e in the side wall part 21d is formed by processing the surface of the side wall part 21d selectively by plasma etching, laser irradiation, sandblasting, etc. FIG.

  Here, the selective processing can be realized by using a mask, for example. In addition, although not limited, the uneven | corrugated process surface 21e is a surface whose Ra (arithmetic mean roughness specified by JIS (Japanese Industrial Standards)) is 50 nm or more and 10,000 nm or less, for example. In FIG. 2, the size of the unevenness is deformed for easy understanding.

  In the pressure sensor device 1 of the present embodiment shown in FIG. 1, the circuit chip 3 is an IC chip that is formed in a flat plate shape using a silicon semiconductor or the like to form a semiconductor integrated circuit. The circuit chip 3 is electrically connected to the sensor chip 2 and controls pressure detection by the sensor chip 2, for example.

  As shown in FIG. 1, the circuit chip 3 is disposed so as to face the other end 2 d of the sensor chip 2. The pads 23 of the sensor chip 2 and the circuit chip 3 are connected and electrically connected via bonding wires 4 made of Au, Al or the like.

  As shown in FIG. 1, the lead frame 5 includes an island portion 51 for supporting the sensor chip 2 and the circuit chip 3, and a lead portion 52 electrically connected to the circuit chip 3 through the bonding wires 4. And made of Cu, 42 alloy, or the like. The circuit chip 3 is fixed to the island portion 51 via a die mount material 3a such as solder or conductive adhesive.

  The mold resin 6 is a member that seals a part of the sensor chip 2 on the other end 2 d side, the circuit chip 3, the bonding wire 4, the island part 51, and a part of the lead part 52. The mold resin 6 is made of a general epoxy resin or the like, and is molded by a transfer mold method using a mold or the like.

  The above is the overall configuration of the pressure sensor device 1 according to the present embodiment. With the pressure sensor device 1 having such a configuration, when the pressure medium is introduced into the recess 21b and pressure is applied to the diaphragm 21a, the pressure of the pressure medium can be measured by the diaphragm 21a.

  By the way, as described above, a pressure medium such as air or oil is introduced into the diaphragm 21a from the recess 21b side and received by the diaphragm 21a, as indicated by the white arrow in FIG. At this time, in the pressure medium, impurities such as water and oil or soot contained in the water and oil are mixed as foreign matters.

  In the present embodiment, the surface of the diaphragm 21a on the side of the recess 21b that contacts the pressure medium, that is, the bottom 21c and the side wall 21d are covered with the liquid-repellent or lyophilic protective film 8; Foreign matter adhesion is suppressed.

  Specifically, when the pressure medium is a gas such as air, the protective film 8 is made liquid repellent so that water or oil in the pressure medium or foreign matters such as impurities adhere to the protective film 8. It becomes difficult to do. On the other hand, when the pressure medium is a liquid such as oil or when the concave portion 21b is in an environment where it is easily exposed to the liquid, the protective film 8 is made lyophilic. By doing so, the foreign substance adhering to the protective film 8 can be washed away using the liquid, and the adhesion of the foreign substance to the protective film 8 can be suppressed.

  As described above, according to the present embodiment, it is possible to prevent foreign matter from adhering to the diaphragm 21a by selecting the liquid repellency and lyophilicity of the protective film 8 in accordance with the flow method and type of the pressure medium. .

  Further, according to the present embodiment, the surface of the side wall portion 21d of the surface of the recess 21b forming the diaphragm 21a is the uneven surface 21e, and the protective film 8 is formed on the surface 21e. The anchor effect is exhibited and the adhesion of the protective film 8 is improved.

  Further, since the surface of the bottom portion 21c corresponding to the diaphragm 21a is not subjected to the uneven treatment, no adverse effect on the characteristics of the diaphragm 21a occurs. Therefore, according to this embodiment, peeling of the protective film 8 can be appropriately suppressed while ensuring the sensing characteristics.

  Further, the protective film 8 is desirably a film thinner than the diaphragm 21a, and is, for example, as thin as several nm. This is because, when these films are formed on the bottom 21c of the recess 21b, which is the diaphragm 21a, it is possible to suppress the influence on the distortion characteristics of the diaphragm 21a by reducing the film thickness as much as possible. .

(Second Embodiment)
The pressure sensor device according to the second embodiment of the present invention will be described with reference to FIG. 3, focusing on the differences from the first embodiment. In the first embodiment, the protective film 8 is the same film that covers the bottom portion 21c and the side wall portion 21d. It may be configured as a film having different properties.

  As shown in FIG. 3, in the present embodiment, the protective film 8 as a protective member covers the bottom 21c and has a liquid repellent protective film 81 having a higher liquid repellency than the surface of the recess 21b, and a side wall 21d. And a lyophilic protective film 82 having a higher lyophilic property than the surface of the recess 21b.

  In the present embodiment as well, it is needless to say that only the surface of the side wall 21d among the surfaces of the recesses 21b is used as the concavo-convex treatment surface 21e. In this embodiment, a lyophilic protective film 82 is formed on the uneven surface 21e.

  Here, the liquid repellent protective film 81 as the protective film 8 is a film made of, for example, an organic fluorine compound, and the lyophilic protective film 82 is a coating film made of, for example, a silica-based coating film or an organic hydrophilic agent. Or a coating film such as DLC.

  In the present embodiment, the foreign matter 100 is preferentially attached to the side wall portion 21d that is not the pressure receiving surface of the diaphragm 21a in the recess 21b, thereby preventing the foreign matter 100 from adhering to the bottom portion 21c that is the pressure receiving surface. It is the composition suitable for.

  Specifically, when the pressure medium is a gas such as air, the foreign matter 100 such as water or oil in the pressure medium or the impurities described above is formed on the bottom 21c made liquid repellent by the liquid repellent protective film 81. Without adhering, it adheres preferentially to the side wall part 21d made lyophilic by the lyophilic protective film 82. In addition, when the pressure medium is a liquid such as oil, the foreign matter 100 such as the impurities in the pressure medium does not adhere to the bottom part 21c that is lyophobic and takes precedence over the side wall part 21d that is lyophilic. Adheres.

  As described above, according to the present embodiment, the foreign material 100 can be preferentially attached to the side wall portion 21d rather than the bottom portion 21c according to the flow method and type of the pressure medium. Adhesion to the bottom 21c is preferable because it easily affects the characteristics of the diaphragm 21a as compared to the side wall 21d.

(Third embodiment)
The third embodiment of the present invention is a modification of the second embodiment, and the pressure sensor device according to the present embodiment will be described with reference to FIG. 4 focusing on the differences from the second embodiment. I will do it.

  In the second embodiment, the surface of the bottom 21c of the recess 21b is covered with the liquid-repellent protective film 81, and the surface of the side wall 21d that is the uneven surface 21e is covered with the lyophilic protective film 82. Met. On the other hand, as shown in FIG. 4, in the present embodiment, contrary to the second embodiment, the bottom 21c is covered with a lyophilic protective film 82, and the uneven side wall 21d is repelled. The structure is covered with a liquid protective film 81.

  That is, in the present embodiment, the protective film 8 as the protective member covers the bottom portion 21c, covers the lyophilic protective film 82 having higher lyophilicity than the surface of the concave portion 21b, and the side wall portion 21d, and forms the concave portion 21b. And a liquid repellent protective film 81 having a liquid repellency greater than that of the surface.

  Also here, only the surface of the side wall 21d is used as the uneven surface 21e, and in this embodiment, the liquid repellent protective film 81 is formed on the uneven surface 21e. The pressure sensor device of this embodiment having such a configuration is preferably applied when a liquid such as oil or water is used as a pressure medium.

  Specifically, the liquid as the pressure medium flows so as to wash away the lyophilic protective film 82 of the lyophilic bottom portion 21c without being repelled. , It becomes difficult to adhere to the bottom 21c. Therefore, according to the present embodiment, foreign matter can be preferentially attached to the side wall 21d rather than the bottom 21c of the recess 21b, as in the second embodiment.

(Other embodiments)
In addition, as a protective member shown in each said embodiment, the thing of a lump shape, for example, a gel etc., may be sufficient besides the protective films 8, 81, and 82 which are films. For example, as a water-repellent gel, fluorine gel and the like can be mentioned, and these are formed by coating or the like, as in a normal gel.

  The sensor chip 2 is a plate-shaped chip, and the recess 21b is formed on the one surface 2a so that the bottom 21c of the recess 21b is a diaphragm 21a. It is not limited to things.

  For example, in the example of FIG. 1 described above, the sensor chip 2 has a stacked configuration of the first substrate 21 and the second substrate 22, but the second substrate 22 is omitted and the recess 21b and the diaphragm 21a are formed. It may be composed only of the first substrate 21 having the same.

  In this case, for example, a structure in which the surface of the diaphragm 21a opposite to the concave portion 21b is covered with a gel or the like may be employed. In any case, any sensor chip 2 may be used as long as the surface on the recess 21b side of the diaphragm 21a is exposed to a pressure medium to receive pressure.

  Further, in the example of FIG. 1, the recess 21 b and the diaphragm 21 a are provided on the one end 2 c side of the sensor chip 2, and the other end 2 d side opposite to the one end 2 c of the sensor chip 2 is sealed with the mold resin 6. It has been stopped. However, the pressure sensor device may have a configuration in which the mold resin 6 is omitted.

  In other words, the entire sensor chip 2 may be exposed. Even in this case, for example, the pressure medium introduction path may be configured such that the pressure medium is introduced only into the concave portion 21b side of the diaphragm 21a.

  Further, the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope described in the claims. The above embodiments are not irrelevant to each other, and can be combined as appropriate unless the combination is clearly impossible, and the above embodiments are not limited to the illustrated examples. Absent.

DESCRIPTION OF SYMBOLS 1 Pressure sensor apparatus 2 Sensor chip 2a One surface of a sensor chip 21a Diaphragm 21b Recessed part 21c Recessed part bottom part 21d Recessed side wall part 21e Irregularity-treated surface as a roughened surface 8

Claims (5)

A sensor chip, which is a plate-shaped chip, wherein a recess (21b) is formed on one surface (2a) so that the bottom (21c) of the recess is a diaphragm (21a) as a thin wall portion having a pressure detection function. (2)
Pressure detection is performed by exposing the diaphragm to a pressure medium on the concave side,
The bottom portion corresponding to the diaphragm in the concave portion and the side wall portion (21d) positioned around the bottom portion in the concave portion have a liquid repellency greater than the surface of the concave portion or a protective member having a large lyophilic property. Covered by (8),
Concavity and convexity treatment is performed only on the surface of the sidewall portion among the bottom portion and the sidewall portion, and the protective member is formed on the surface (21e) subjected to the unevenness treatment in the sidewall portion ,
The protective member covers the bottom portion and has a liquid repellent protective member (81) having a higher liquid repellency than the surface of the recess, and the side wall portion, and is more lyophilic than the surface of the recess. A pressure sensor device comprising a lyophilic protective member (82) . A sensor chip, which is a plate-shaped chip, wherein a recess (21b) is formed on one surface (2a) so that the bottom (21c) of the recess is a diaphragm (21a) as a thin wall portion having a pressure detection function. (2)
Pressure detection is performed by exposing the diaphragm to a pressure medium on the concave side,
The bottom portion corresponding to the diaphragm in the concave portion and the side wall portion (21d) positioned around the bottom portion in the concave portion have a liquid repellency greater than the surface of the concave portion or a protective member having a large lyophilic property. Covered by (8),
Concavity and convexity treatment is performed only on the surface of the sidewall portion among the bottom portion and the sidewall portion, and the protective member is formed on the surface (21e) subjected to the unevenness treatment in the sidewall portion ,
The protective member covers the bottom and has a lyophilic protective member (82) that is more lyophilic than the surface of the recess, and the side wall and has a liquid repellency that is greater than the surface of the recess. A pressure sensor device comprising a liquid repellent protective member (81) . The protective member is a pressure sensor device according to claim 1 or 2, characterized in that a thin film than the diaphragm. The recess and the diaphragm are provided on one end (2c) side of the sensor chip, and the other end (2d) side of the sensor chip is sealed with a mold resin (6). The pressure sensor device according to any one of 1 to 3 . The sensor chip is a pressure sensor device according to any one of claims 1 to 4, characterized in that composed of semiconductor.

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