JP2010139339A - Thermal type flow sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal type flow sensor capable of simplifying a constitution, while suppressing fluctuation of a sensor characteristic. <P>SOLUTION: In this thermal type flow sensor including a sensor chip having a semiconductor substrate whose partial domain having a prescribed depth from one surface is a void domain, an insulating film formed on one surface of the semiconductor substrate so as to bridge the void domain, and a sensing part including a heater arranged on a portion on the void domain as a resister arranged on the insulating film, an upstream side end face in the flow direction of fluid at a normal time between end faces of the semiconductor substrate includes a first inclined plane connected to one surface, and approaching a rear surface in the thickness direction of the semiconductor substrate in proportion to the degree of separation from the heater in the flow direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermal flow sensor including a sensor chip on which a heater is formed.

  Conventionally, for example, as shown in Patent Document 1, a thermal flow sensor including a sensor chip on which a heater is formed is known.

  In the thermal type flow sensor shown in Patent Document 1, the rectifying unit (side surface covering unit) and the sealing resin arranged adjacent to the sensor chip are integrally formed by molding by injecting molten resin into the mold. Has been. Moreover, the rectification | straightening part is in contact with the side surface of a sensor chip, and becomes a structure without a clearance gap between a sensor chip and a rectification | straightening part. The rectifying unit is disposed adjacent to the sensor chip on the upstream side and the downstream side in the normal flow direction of the fluid, and has a part of the surface that is flush with the surface of the sensor chip.

In the thermal flow sensor disclosed in Patent Document 2, a flow rate detection element (sensor chip) is provided from the second induction surface side to a support member having a first induction surface and a second induction surface on both sides for inducing a fluid. It is buried and the second guide surface is a smooth flat surface with no protrusion. That is, the support member also serves as the rectifying unit described above.
JP 2008-175780 A Japanese Patent No. 3416526

  By the way, when this inventor further examined about the thermal type flow sensor, as shown in patent documents 1 and 2, in a configuration without a gap between the sensor chip and the rectifying unit (configuration in contact with each other), It became clear that the sensor characteristics fluctuate due to temperature changes in the external atmosphere. This is because stress occurs due to the difference in linear expansion coefficient between the material constituting the rectifying unit and the sensor chip, and the resistance value of a resistor such as a heater constituting the sensing unit varies due to the piezoresistance effect. it is conceivable that. It is also conceivable that the resistance value varies due to creep (relaxation of stress over time).

  On the other hand, it is also conceivable to provide a gap between the sensor chip and the rectifying unit so that the rectifying unit does not adhere to the end face of the sensor chip in the fluid flow direction. However, in order to take advantage of the turbulent flow suppressing function (rectifying function) by the rectifying unit, it is preferable that the width of the gap in the fluid flow direction is narrow (for example, 100 μm or less). The fluid collides with the end face of the sensor chip and turbulence is generated. In the configurations shown in Patent Documents 1 and 2, in order to suppress the turbulent flow caused by the fluid colliding with the end face of the sensor chip, a rectifying unit that is a separate member from the sensor chip is necessary in the first place. Therefore, the rectifying unit, which is a separate member, must be accurately positioned with respect to the sensor chip in the thickness direction of the chip and the fluid flow direction.

  In addition, when forming a rectification | straightening part by mold shaping | molding as shown in patent document 1, since a clearance gap is narrow as mentioned above, it mentioned above by making a metal mold | die contact the sensor chip end surface (side surface) at the time of mold shaping | molding. It is difficult to provide such a narrow gap.

  On the other hand, a rigid frame separate from the mold is fixed on a support base (for example, an island of a lead frame) on which the sensor chip is mounted so as to surround the side surface of the sensor chip with a gap. It is also conceivable that the sealing part is formed by molding while ensuring a gap in the frame by bringing the mold into contact with the frame. In this case, the frame body constitutes at least a part of the rectification unit. However, since the molten resin is supplied onto the pad portion of the sensor chip in order to form the sealing portion, in order to prevent the molten resin from flowing into the gap between the side surface of the sensor chip and the frame body, A dam that closes the end on the sealing portion side is required as a separate member from the frame. Also, it is conceivable that the rectifying part is constituted by a member different from the sealing part, and the sealing part is formed by molding so as to cover the vicinity of the end of the rectifying part on the sealing part side. In order to prevent the molten resin from flowing into the gap between the side surface of the sensor chip and the rectifying unit, a separate dam is required. Furthermore, it is conceivable to form a sealing portion by potting and solidifying (curing or gelling) a liquid insulating material such as a resin. In this case as well, the side surface of the sensor chip and the rectifying portion may be formed. In order to prevent the liquid insulating material from flowing into the gaps between them, a separate dam is required. That is, in both molding and potting, since the liquid insulating material is solidified to form the sealing portion, the liquid insulating material is prevented from flowing into the gap between the side surface of the sensor chip and the rectifying portion. A dam is required separately from the rectification unit. Therefore, the number of parts of the thermal flow sensor increases and the manufacturing process becomes complicated.

  In view of the above problems, an object of the present invention is to provide a thermal flow sensor capable of simplifying the configuration while suppressing fluctuations in sensor characteristics.

  In order to achieve the above object, the invention according to claim 1 is configured to bridge a low thermal conductivity region with a semiconductor substrate in which a part of a predetermined depth from one surface is a region having a lower thermal conductivity than other regions. A thermal type comprising a sensor chip having an insulating film formed on one surface of a semiconductor substrate, and a sensing unit including a heater disposed in a region on a low heat conduction region as a resistor disposed on the insulating film A flow sensor, which is connected to one surface as an upstream end surface in a normal flow direction (forward flow) of a semiconductor substrate, and is separated from a heater in the flow direction. The first inclined portion that approaches the back surface in the thickness direction of the semiconductor substrate is included.

  In the present invention, the upstream end surface of the semiconductor substrate constituting the sensor chip is connected to one surface, and includes a first inclined portion that approaches the back surface in the thickness direction of the semiconductor substrate as the distance from the heater in the flow direction increases. Yes. That is, by forming at least a part of the upstream end surface of the semiconductor substrate into a tapered shape, the rectifying function (in other words, the turbulent flow suppressing function) that has been conventionally performed by the rectifying unit, which is another member, can be applied to the sensor chip itself. I'm giving it back. As a result, the fluid flowing in the forward direction is guided to one surface along the first inclined portion on the upstream end surface, and passes over the sensing unit such as a heater while being rectified. Therefore, it is possible to detect the flow rate of the fluid with high accuracy even though the rectifying unit is not provided as a separate member.

  Further, as described above, since the rectification function is provided to the semiconductor substrate (sensor chip) itself, a rectification unit or a dam as a separate member is unnecessary, and the rectification unit as a separate member is thicker than the sensor chip. It is not necessary to position with high accuracy in the direction and the flow direction. Therefore, the configuration of the thermal flow sensor can be simplified. That is, the number of parts of the thermal type flow sensor can be reduced and the manufacturing process can be simplified as compared with the conventional case.

  Furthermore, since the rectifying function is provided to the semiconductor substrate (sensor chip) itself and a separate rectifying unit is not required, the difference in linear expansion coefficient between the material constituting the rectifying unit and the sensor chip (semiconductor substrate) in the first place. There will be no stress caused by. Therefore, fluctuations in sensor characteristics can be suppressed.

  As described above, according to the thermal flow sensor of the present invention, it is possible to detect the flow rate with high accuracy by suppressing the turbulence, but the configuration is simplified as compared with the conventional one and the fluctuation of the sensor characteristics is also suppressed. be able to. Since the semiconductor substrate (sensor chip) itself is provided with a rectifying function and the positional accuracy of the rectifying portion (the first inclined portion in the present invention) with respect to the sensor chip is higher than before, the flow rate can be detected with higher accuracy. Can do.

  According to a second aspect of the present invention, the first inclined surface includes a second inclined portion that is connected to the back surface as the upstream end surface and approaches the one surface in the thickness direction of the semiconductor substrate as the distance from the heater in the flow direction increases. The part and the second inclined part may be connected to each other.

  According to this, the fluid flowing on the back surface side of the semiconductor substrate can also be rectified by the second inclined portion. Therefore, turbulent flow is generated in the fluid flowing on the back surface side, and it is possible to suppress the turbulent flow from adversely affecting the fluid flowing on the one surface side.

  According to a third aspect of the present invention, in the semiconductor substrate, the corner portion including the upstream end face may have a rounded shape. According to this, since the fluid flow becomes smoother, the detection accuracy of the flow rate can be improved. In addition, the corner | angular part containing an upstream end surface includes the connection part of a 1st inclination part and one surface at least. In addition, when it has a 2nd inclination part, the connection part of a 1st inclination part and a 2nd inclination part and the connection part of a 2nd inclination part and a back surface are also included. In addition, when the upstream end surface has only the first inclined portion, a connecting portion between the first inclined portion and the back surface is also included.

  According to a fourth aspect of the present invention, the downstream end surface in the flow direction may be connected to one surface, and may include a third inclined portion that approaches the back surface in the thickness direction as the distance from the heater increases in the flow direction.

  According to this, the fluid flowing in the direction opposite to the forward direction is guided to one surface along the third inclined portion on the downstream end surface, and passes over the sensing unit such as the heater while being rectified. It will be. Therefore, the flow rate in the reverse direction can be detected with high accuracy by the rectification function using the third inclined portion, although the rectification unit as a separate member is not provided.

  Further, as described in claim 5, as a downstream side end surface in the flow direction, it is connected to the one surface and the back surface, and as it approaches the one surface in the thickness direction, it includes a fourth inclined portion that is farther from the heater in the flow direction. Also good.

  If the vehicle is decelerated while forward fluid is flowing transiently without backflow, the backflow caused by Karman vortices generated on the downstream end face side extends over the entire surface of the sensor chip. It is known that a larger swirling vortex is generated by the flow of the flow and a reverse flow is locally generated on one surface. On the other hand, in the present invention, the Karman vortex is collapsed at the fourth inclined portion, and the swirling vortex is generated on one surface of the sensor chip by the fluid flowing into the pressure drop portion generated at the fourth inclined portion. Can be suppressed. That is, the flow rate of the fluid can be detected with high accuracy by the rectifying function by the fourth inclined portion.

  According to a sixth aspect of the present invention, in the semiconductor substrate, the corner portion including the downstream end face may have a rounded shape. According to this, since the fluid flow becomes smoother, the detection accuracy of the flow rate can be improved. In addition, when the corner | angular part containing a downstream end surface contains a 3rd inclination part, the connection part of a 3rd inclination part and one surface is included at least. Moreover, when the 4th inclination part is included, the connection part of a 4th inclination part and one surface and the connection part of a 4th inclination part and a back surface are included.

  According to a seventh aspect of the present invention, the semiconductor substrate is made of single crystal silicon, the one surface and the back surface are (100) surfaces, and the end surface of the semiconductor substrate is a surface excluding the upstream end surface and the downstream end surface. As the distance from the heater is increased, the fifth inclined portion that is closer to the back surface in the thickness direction of the semiconductor substrate and the sixth surface that is connected to the back surface and is closer to the first surface in the thickness direction of the semiconductor substrate are separated from the heater. In addition, at least one of the inclined portions may be included, and each inclined portion may be formed by etching the semiconductor substrate.

  According to this, a semiconductor substrate made of single crystal silicon is etched to form an inclined portion around the entire end face, and is separated (chiped) into the size of the sensor chip. Therefore, the semiconductor substrate can be formed into a chip only by etching (processing for forming the inclined portion) while having the inclined portion exhibiting the rectifying function on the upstream end face and the downstream end face. That is, dicing can be eliminated.

  Next, according to an eighth aspect of the present invention, there is provided a semiconductor substrate in which a partial region having a predetermined depth from one surface is a region having a lower thermal conductivity than other regions, and a surface of the semiconductor substrate so as to bridge the low thermal conductivity region. A thermal flow sensor comprising a sensor chip having an insulating film formed thereon, and a sensing unit including a heater disposed in a region on a low heat conduction region as a resistor disposed on the insulating film. In addition, a groove portion is formed on one surface of the semiconductor substrate so as to be separated from the low heat conduction region, and one end is an upstream end surface in the normal flow direction of the fluid among the end surfaces connecting the one surface and the back surface thereof. And an upstream groove extending toward the heater along the flow direction. And the concave part corresponding to the groove part is formed in the surface of the one surface side in a sensor chip, It is characterized by the above-mentioned.

  In the present invention, a groove is formed on one surface of the semiconductor substrate constituting the sensor chip. As the groove, an upstream groove having an end opened on the upstream end surface and extending toward the heater along the flow direction is provided. include. Further, an insulating film or the like deposited on one surface of the semiconductor substrate imitates the shape of the groove, so that a recess is formed on the surface of the sensor chip corresponding to the groove including the upstream groove. Thereby, the fluid flowing in the forward direction is guided through the flow path in the recess on the surface of the sensor chip corresponding to the upstream groove portion, and passes over the sensing portion such as a heater while being rectified. Therefore, it is possible to detect the flow rate of the fluid with high accuracy even though the rectifying unit is not provided as a separate member.

  In addition, as described above, since the rectifying function is provided to the sensor chip itself, a rectifying unit or a dam as a separate member is unnecessary, and the rectifying unit as a separate member is disposed in the thickness direction and the flow direction with respect to the sensor chip. It is not necessary to position with high accuracy. Therefore, the configuration of the thermal flow sensor can be simplified. That is, the number of parts of the thermal type flow sensor can be reduced and the manufacturing process can be simplified as compared with the conventional case.

  Furthermore, since the rectifying function is provided to the sensor chip itself and a separate rectifying unit is not required, stress caused by the difference in linear expansion coefficient between the material constituting the rectifying unit and the sensor chip (semiconductor substrate) in the first place. Will not occur. Therefore, fluctuations in sensor characteristics can be suppressed.

  As described above, according to the thermal flow sensor of the present invention, it is possible to detect the flow rate with high accuracy by suppressing the turbulence, but the configuration is simplified as compared with the conventional one and the fluctuation of the sensor characteristics is also suppressed. be able to.

  According to a ninth aspect of the present invention, the upstream groove may be configured such that the size of the opening area perpendicular to the flow direction is increased as the distance from the heater increases in the flow direction. According to this, the recessed part corresponding to an upstream groove part exhibits not only the above-mentioned rectification function but the function which raises the flow velocity. Therefore, the detection sensitivity in the sensing unit can be improved.

  According to a tenth aspect of the present invention, as the groove portion, one end includes a downstream groove portion that opens to the downstream end surface in the normal flow direction of the fluid in the end surface and extends toward the heater along the flow direction. A configuration is preferable.

  In the present invention, the groove portion includes a downstream groove portion whose one end opens on the downstream end surface and extends toward the heater along the flow direction. Then, an insulating film or the like deposited on one surface of the semiconductor substrate imitates the shape of the groove, so that a recess is formed on the surface of the sensor chip corresponding to the downstream groove. Thereby, the fluid of the flow of a reverse direction is induced | guided | derived through the flow path in the recessed part of the sensor chip surface corresponding to a downstream groove part, and passes over on sensing parts, such as a heater, with the rectified state. Therefore, the flow rate in the reverse direction can be detected with high accuracy even though the rectifying unit is not provided as a separate member.

  In the case where the groove portion is provided, as described in claim 11, the semiconductor substrate is such that, as the wall surface of the end portion on the heater side among the wall surfaces of the groove portion connected to the one surface, the semiconductor substrate is separated from the heater in the flow direction. It is preferable to include a seventh inclined portion that approaches the back surface in the thickness direction.

  According to this, the fluid guided through the flow path in the recess is smoothly guided to the heater via the seventh inclined portion. In other words, the turbulent flow generated at the end on the heater side can be suppressed in the recesses corresponding to the upstream groove portion and the downstream groove portion, and the flow rate detection accuracy can be further improved.

  According to a twelfth aspect of the present invention, the low heat conduction region is suitable for a configuration including a void region that opens on at least one surface of the semiconductor substrate. The heater as the resistor is configured in the insulating film disposed on the semiconductor substrate at a position on the gap area of the semiconductor substrate, that is, the heater is thermally separated from other parts of the sensor chip by the gap area. In this configuration, the heater is located in a thin part (membrane) made of an insulating film on the gap region, and this is caused by a difference in linear expansion coefficient between the sensor chip and another member (for example, an island of the lead frame) that contacts the sensor chip. The heater is particularly susceptible to the effects of stress. However, according to the above-described invention, the stress transmitted to the heater can be effectively reduced. As the low thermal conductivity region, a porous silicon region formed on the substrate can be employed in addition to the void region.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a plan view showing a schematic configuration of the thermal flow sensor according to the first embodiment. 2 is a cross-sectional view taken along line II-II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a plan view showing a schematic configuration of the sensor chip. FIG. 5 is a cross-sectional view taken along line VV in FIG. The white arrows shown in FIGS. 1, 3, and 4 indicate the flow direction of the fluid in a normal state. In FIG. 4, for convenience, the heater, the temperature sensing element, the insulating film on the connecting wiring, and the sealing member are omitted.

  In the following, the fluid flow direction (both normal forward direction and reverse direction during reverse flow) is simply the flow direction, the thickness direction of the semiconductor substrate is simply the thickness direction, and the direction perpendicular to the thickness direction is It shall be simply indicated as the vertical direction.

  As shown in FIGS. 1 to 5, the thermal flow sensor 1 has a sensor chip 10 in which a sensing part including a heater 13 described later is formed as a main part. In this embodiment, the island 50 and the lead 51 that are configured as a part of the lead frame, and the sealing resin portion 52 that covers the electrical connection portions such as the pad portion 19 and the wire 54 of the sensor chip 10 are further provided. is doing. Such a thermal flow sensor 1 is disposed, for example, in an intake pipe of a vehicle internal combustion engine.

  The sensor chip 10 is formed on the one surface 11a of the semiconductor substrate 11 so as to bridge the low thermal conductivity region with the semiconductor substrate 11 in which a partial region of a predetermined depth from one surface is a lower thermal conductivity region than the other regions. And a sensing unit including a heater 13 disposed in a region on the low heat conduction region as a resistor disposed on the insulating film 12.

  In the present embodiment, as shown in FIGS. 4 and 5, the semiconductor substrate 11 having a substantially rectangular plane made of single crystal silicon is provided, and the surface (one surface 11a and the back surface 11b) of the semiconductor substrate 11 is (100). It is a surface. The semiconductor substrate 11 is arranged so that both end surfaces on the long side of the end surface (side surface) connecting the one surface 11a and the back surface 11b face the fluid flow (substantially perpendicular). Of the longitudinal end faces, the upstream end face 14 located upstream and the downstream end face 15 located downstream of the normal fluid flow direction (forward direction) have inclined portions, respectively. It is configured.

  The upstream end surface 14 of the semiconductor substrate 11 is connected to the one surface 11a, and a first inclined surface 14a is configured as a first inclined portion that approaches the back surface 11b in the thickness direction as the distance from the heater 13 increases in the flow direction. Has been. The first inclined surface 14a is formed by etching the semiconductor substrate 11 made of single crystal silicon with an alkaline solution such as KOH from the one surface 11a side, and the (111) surface of silicon is the first inclined surface 14a. It has become.

  Further, the upstream end surface 14 is also connected to the back surface 11b, and a second inclined surface 14b is configured as a second inclined portion that approaches the one surface 11a in the thickness direction as the distance from the heater 13 in the flow direction increases. Yes. The second inclined surface 14b is formed by etching the semiconductor substrate 11 with an alkaline solution such as KOH from the back surface 11b side. Like the first inclined surface 14a, the (111) plane of silicon is the second inclined surface. It becomes the surface 14b. The first inclined surface 14a and the second inclined surface 14b are connected to each other in the vicinity of the center of the semiconductor substrate 11 in the thickness direction, and this connecting portion is connected to the apex position on the upstream side in the flow direction in the semiconductor substrate 11. It has become. That is, the upstream end surface 14 is configured by the first inclined surface 14a and the second inclined surface 14b.

  On the other hand, the downstream end surface 15 of the semiconductor substrate 11 is connected to the one surface 11a, and the third inclined surface 15a as a third inclined portion that approaches the back surface 11b in the thickness direction as the distance from the heater 13 in the flow direction increases. Is configured. Similarly to the first inclined surface 14a, the third inclined surface 15a is formed by etching the semiconductor substrate 11 made of single crystal silicon from the one surface 11a side with an alkaline solution such as KOH. The surface is the third inclined surface 15a.

  The downstream end surface 15 is also connected to the back surface 11b, and a fourth inclined surface 15b is formed as an inclined portion that approaches the one surface 11a in the thickness direction as the distance from the heater 13 in the flow direction increases. Similar to the second inclined surface 14b, the fourth inclined surface 15b is formed by etching the semiconductor substrate 11 with an alkaline solution such as KOH from the back surface 11b side, and the (111) surface of silicon is the fourth inclined surface. It is a surface 15b. Then, the third inclined surface 15a and the fourth inclined surface 15b are connected to each other in the vicinity of the center of the semiconductor substrate 11 in the thickness direction, and this connecting portion is connected to the apex position on the downstream side in the flow direction in the semiconductor substrate 11. It has become. That is, the downstream side end surface 15 is configured by the third inclined surface 15a and the fourth inclined surface 15b.

  As described above, the upstream end surface 14 and the downstream end surface 15 are each tapered and are symmetrical to each other.

  The semiconductor substrate 11 is formed with a void region 16 that opens to at least one surface side of the semiconductor substrate 11 as a portion corresponding to the low heat conduction region. In this embodiment, as an example, by using a silicon oxide film as the insulating film 12 as an etching stopper and etching with an alkaline solution such as KOH from the back surface 11b side, a void region 16 having a (111) plane as a wall surface is formed. Has been. The void region 16 is a through hole penetrating the semiconductor substrate 11 in the thickness direction, and the opening area is smaller toward the one surface 11a side of the semiconductor substrate 11 and the opening area is larger toward the back surface 11b side. In addition, the code | symbol 16a shown with a rectangular broken line in FIG. 4 has shown the back surface side opening end of the space | gap area | region 16, and the code | symbol 16b has shown the 1st surface side opening end of the space | gap area | region 16. FIG. Although not shown, an insulating film as an etching mask is also disposed on the back surface 11 b of the semiconductor substrate 11.

  A heater 13 is formed in a portion of the insulating film 12 that bridges the void region 16. As described above, the portion of the insulating film 12 that crosslinks the void region 16 is a thin portion (so-called membrane) in the sensor chip 10, thereby suppressing the heat capacity to be low, and the heater 13 and the heater of the sensor chip 10. Thermal insulation from the surrounding part (the peripheral part of the void region 16) is ensured.

  In the present embodiment, the pair of heaters 13a and 13b are sandwiched between the portions of the insulating film 12 on the region excluding the void region 16 of the semiconductor substrate 11, and the pair of temperature sensitive bodies 17a and 17b as the resistors are located upstream. Each is formed on the downstream side. Specifically, the heaters 13a and 13b and the temperature sensitive bodies 17a and 17b are arranged on a straight line, in the direction of flow. The heaters 13a and 13b and the temperature sensitive bodies 17a and 17b constitute a sensing unit. The heaters 13a and 13b and the temperature sensing elements 17a and 17b are electrically connected to the pad portion 19 as an external connection terminal (electrode) through a connecting wire 18 formed integrally using the same material as the heater 13, for example. It is connected. A protective film 20 such as a silicon nitride film is laminated so as to cover the heaters 13a and 13b, the temperature sensing elements 17a and 17b, and the connecting wiring 18. In the present embodiment, single crystal silicon into which impurities such as phosphorus and boron are introduced is used as a wiring material for the heater 13 and the like.

  In the sensing unit configured as described above, the heaters 13a and 13b have a function of sensing its own temperature based on a change in its own resistance value in addition to a function of generating heat by supplying current. Then, the flow rate of the fluid is detected based on the heat deprived by the fluid among the heat generated in the upstream and downstream heaters 13a and 13b. Further, the flow direction of the fluid is detected based on the difference in the amount of heat taken away by the fluid among the heat generated in each of the upstream heater 13a and the downstream heater 13b. Furthermore, the current supplied to the heaters 13a and 13b based on the temperature difference between the upstream heater 13a and the upstream temperature sensor 17a and the temperature difference between the downstream heater 13b and the downstream temperature sensor 17b. The amount is also controlled. The configuration of such a sensing unit is basically the same as that described in, for example, Japanese Patent Application Laid-Open No. 2008-180739 by the applicant of the present application, and reference should be made for details.

  As shown in FIG. 2, the sensor chip 10 has a back surface 10 b of a heater forming side surface 10 a (hereinafter simply referred to as a front surface 10 a) on the side where the heater 13 is formed as a mounting surface, and an adhesive member 53. , And is fixed on one surface of the island 50 as a support member. Further, only a part of the back surface 10 b is a contact area with the adhesive member 53. In the present embodiment, as shown in FIG. 2, on the back surface 10 b of the sensor chip 10, a partial range from one end on the pad portion 19 side to the heater 13 side in the longitudinal direction is an adhesion site. Specifically, the adhesion portion includes a portion corresponding to the formation region of the pad portion 19 on the back surface 11b of the semiconductor substrate 11, and is separated from the void region 16 as the low heat conduction region.

  In addition, the code | symbol 21 shown with a dashed-two dotted line in FIG. 4 has shown the boundary line of the site | part exposed to the to-be-measured fluid in the sensor chip 10, and the site | part which is not exposed. In the measurement environment, the part closer to the heater 13 than the boundary line 21 is exposed to the fluid to be measured, and the part closer to the pad part 19 than the boundary line 21 is sealed by the sealing resin part 52. Yes. Further, reference numeral 22 shown in FIGS. 2, 3, and 5 denotes the one surface 11 a of the semiconductor substrate 11 including the insulating film 12, the wiring layer such as the heater 13, and the protective film 20 positioned on the one surface 11 a of the semiconductor substrate 11. The upper structure located above is shown.

  The island 50 is a support member that supports the sensor chip 10, and is configured using a material different from that of the semiconductor substrate 11 that configures the sensor chip 10. In the present embodiment, the lead 51 is configured as a part of the same lead frame. Thus, if it comprises with the same material as the lead 51, the structure of the thermal type flow sensor 1 can be simplified. Further, the planar rectangular island 50 faces only a part of the back surface 10 b of the sensor chip 10, and an adhesive member 53 is disposed on the one surface, and the sensor chip 10 is interposed via the adhesive member 53. It is fixed to the island 50. That is, the sensor chip 10 is cantilevered on the island 50 via the adhesive member 53. The adhesive member 53 is a so-called die bond material, and the constituent material is not particularly limited as long as the sensor chip 10 can be bonded and fixed to the island 50. Only an organic component may be used, or an organic component mixed with an inorganic component or a metal component (for example, an Ag paste) may be used. In this embodiment, a general epoxy resin having a Young's modulus after curing of 1 GPa or more is employed.

  The lead 51 fulfills an electrical relay function between the sensing unit of the sensor chip 10 and an external device. In the present embodiment, as described above, it is formed by processing the same metal member as the island 50. For example, a wire 54 made of Al or Au is connected to the lead 51 and the sensor by a bonding method using ultrasonic waves. The lead 51 and the sensor chip 10 (sensing part) are electrically connected to the pad part 19 of the chip 10 respectively.

  The sealing resin portion 52 is made of an electrically insulating material, and seals the formation region of the pad portion 19 while exposing the formation region of the sensing portion to the external atmosphere in the surface 10a of the sensor chip 10. In the present embodiment, the sealing resin portion 52 is formed by solidifying (curing or gelling) the liquid insulating material, specifically by curing the molten resin (for example, epoxy resin) by a transfer molding method. In addition, the sensor chip 10 is bonded and fixed on the island 50, and the wire 54, the wire 54, and the sensor chip 10 (pad portion 19) are connected with the pad portion 19 of the sensor chip 10 and the lead 51 connected via the wire 54. ) And the connection portion between the wire 54 and the lead 51 are integrally covered.

  Next, a method for manufacturing the above-described thermal flow sensor 1 will be described. FIGS. 6A and 6B are cross-sectional views for explaining a method for manufacturing a thermal flow sensor, and FIGS. 6A to 6C show steps of forming a tapered upstream end surface and a downstream end surface.

  First, the sensor chip 10 having the above-described configuration is prepared. In the present embodiment, as an example, a so-called SOI (Silicon On Insulator) substrate having a configuration in which a semiconductor layer made of silicon is stacked on an insulating layer on a support substrate made of silicon is employed. In this SOI substrate, the support substrate corresponds to the semiconductor substrate 11 described above, and the insulating layer corresponds to the insulating film 12. Then, after implanting impurities such as boron into the semiconductor layer, the semiconductor layer is patterned by reactive ion etching or the like to form the heaters 13a and 13b, the temperature sensing elements 17a and 17b, and the connecting wiring 18. By this patterning, the semiconductor layer at a portion that will later form the upstream end face 14 and the downstream end face 15 is also removed. Further, after patterning the semiconductor layer, a silicon nitride film as the protective film 20 is formed by, for example, a low pressure CVD method so as to cover the insulating film 12, and a pad portion 19 is formed at a predetermined position. Such a manufacturing method of the sensor chip 10 is described in, for example, Japanese Patent Application Laid-Open No. 2008-180739 by the applicant of the present application, and thus a detailed description thereof is omitted.

  Next, as shown in FIG. 6A, an insulating film (not shown) (for example, a silicon nitride film) is formed on the back surface 11b of the semiconductor substrate 11 by a plasma CVD method or the like, and the void region 16 and the upper surface side end surface 14 ( The insulating film is etched by reactive ion etching or the like so as to form a planar rectangular opening corresponding to the second inclined surface 14b) and the downstream end surface 15 (fourth inclined surface 15b). Then, using the insulating film as a mask, the semiconductor substrate 11 is etched from the back surface 11b side with an alkaline solution such as KOH. In this etching, since the back surface 11b of the semiconductor substrate 11 is the (100) plane as described above, the etching can be performed along the (111) plane.

  At this time, the opening of the mask is larger in the part corresponding to the gap region 16 than in the part corresponding to the upper surface side end surface 14 and the downstream side end surface 15. Therefore, using the insulating film 12 of the upper structure 22 as an etching stopper, a void region 16 penetrating the semiconductor substrate 11 is formed, and a V-shaped groove 14c having a depth from the back surface 11b to about half of the semiconductor substrate 11 is formed. 15c can be formed. In addition, the groove | channel 14c is a groove | channel corresponding to the upper surface side end surface 14, and the wall surface of the groove | channel 14c becomes the 2nd inclined surface 14b later. Further, the groove 15c is a groove corresponding to the downstream end face 15, and the wall surface of the groove 15c later becomes the fourth inclined face 15b.

  After the etching on the back surface 11b side, as shown in FIG. 6 (b), a planar rectangular opening corresponding to the upper surface side end surface 14 (first inclined surface 14a) and the downstream side end surface 15 (third inclined surface 15a). The upper structure 22 (the protective film 20 and the insulating film 12) is etched by reactive ion etching or the like. Then, using the upper structure 22 (protective film 20) as a mask, the semiconductor substrate 11 is etched from the one surface 11a side with an alkaline solution such as KOH. Also in this etching, since the one surface 11a of the semiconductor substrate 11 is the (100) surface as described above, the etching can be performed along the (111) surface.

  In this etching, V-shaped grooves 14d and 15d having a depth from one surface 11a to about half of the semiconductor substrate 11 are formed, and the etching ends when the grooves are connected to the previously formed grooves 14c and 15c. The groove 14d is a groove corresponding to the upper surface side end face 14, and the wall surface of the groove 14d becomes the first inclined surface 14a. Further, the groove 15d is a groove corresponding to the downstream end face 15, and the wall surface of the groove 15d becomes the third inclined surface 15a. As described above, as shown in FIG. 6C, the tapered upstream end surface 14 having the first inclined surface 14a and the second inclined surface 14b, and the tapered shape having the third inclined surface 15a and the fourth inclined surface 15b. The sensor chip 10 having the downstream end face 15 can be prepared.

  After that, various known manufacturing methods can be applied. In the present embodiment, in parallel with the preparation of the sensor chip 10, the metal plate is subjected to press processing, etching, or the like, and a lead frame including the island 50 and the lead 51 as a partial position is prepared. Then, in a state where the adhesive member 53 is disposed on the island 50, the sensor chip 10 is mounted on the bonding surface of the island 50 using the back surface 10b as a mounting surface. As a result, a part of the back surface 10 b of the sensor chip 10 is in contact with the adhesive member 53. And the hardening process (in this embodiment, heat processing) of the adhesive member 53 is implemented in this positioning state. Thereby, the adhesive member 53 is cured, and the sensor chip 10 is bonded and fixed to the island 50.

  After the sensor chip 10 is fixed, the pad portion 19 of the sensor chip 10 and the lead 51 are electrically connected by wire bonding. In this embodiment, the wire 54 made of Au is connected to the lead 51 and the pad portion 19 of the sensor chip 10 using a bonding method using ultrasonic waves. In particular, in the present embodiment, the bonding part is located immediately below the formation position of the pad portion 19 and wire bonding is performed in the vicinity of the bonding part, so that a good bonding state is formed even by a bonding method using ultrasonic waves. can do.

  After wire bonding, the sensing portion including the heater 13 is exposed by a transfer molding method, and the connection portion between the wire 54, the wire 54 and the sensor chip 10 (pad portion 19), and the connection portion between the wire 54 and the lead 51 are integrated. The sealing resin portion 52 to be covered is formed. At this time, if the resin material constituting the sealing resin portion 52 may flow into the sensing portion side, a dam made of a resin film or rubber is formed on the surface 10a of the sensor chip 10, and the resin It is better to keep the material dammed up. And the thermal type flow sensor 1 shown in FIGS. 1-3 can be obtained by removing the unnecessary part of a lead frame.

  Next, the characteristic part of the thermal type flow sensor 1 which concerns on this embodiment is demonstrated. First, in the present embodiment, the first inclined surface that approaches the back surface 11b in the thickness direction as the upstream end surface 14 of the semiconductor substrate 11 constituting the sensor chip 10 is connected to the one surface 11a and is separated from the heater 13 in the flow direction. 14a. Accordingly, as shown in FIG. 7, the fluid 100 flowing in the forward direction is guided and rectified on the one surface 11a (the surface 10a of the sensor chip 10) along the first inclined surface 14a in the upstream end surface 14. As it is, it passes over a sensing unit such as the heater 13. As described above, the upstream end face 14 of the semiconductor substrate 11 is tapered, so that the rectifying function (in other words, the turbulent flow suppressing function) that has been conventionally performed by the rectifying unit, which is another member, is applied to the sensor chip 10 itself. Therefore, the flow rate of the fluid can be detected with higher accuracy than the configuration in which the upstream end surface 14 is substantially perpendicular to the one surface 11a and the back surface 11b, although the rectifying unit is not provided as a separate member. it can. FIG. 7 is a cross-sectional view showing the rectifying effect and corresponds to FIG.

  Further, as described above, since the rectifying function is provided to the semiconductor substrate 11 (sensor chip 10) itself, a rectifying unit or a dam as a separate member is unnecessary, and a rectifying unit that is a separate member with respect to the sensor chip 10. Is not required to be positioned with high accuracy in the thickness direction and the flow direction. Therefore, the configuration of the thermal flow sensor 1 can be simplified. That is, the number of components of the thermal flow sensor 1 can be reduced and the manufacturing process can be simplified as compared with the conventional case.

  Furthermore, since the rectifying function is provided to the semiconductor substrate 11 (sensor chip 10) itself and a rectifying unit which is a separate member is not required, the material constituting the rectifying unit and the sensor chip 10 (semiconductor substrate 11) are originally provided. No stress is caused by the difference in linear expansion coefficient. Therefore, fluctuations in sensor characteristics due to the stress can be suppressed. As described above, since fluctuations in sensor characteristics can be suppressed, as shown in the present embodiment, the heater 13 is disposed at a portion of the insulating film 12 that bridges the void region 16 as the low thermal conduction region, and the heater 13 is linearly expanded. It is suitable for a configuration that is particularly susceptible to the influence of stress due to the coefficient difference.

  As described above, according to the thermal flow sensor 1 according to the present embodiment, the structure can be detected with high accuracy by suppressing turbulence, but the structure is simplified as compared with the conventional one, and the fluctuation of the sensor characteristics is also increased. Can be suppressed. In addition, since the rectification | straightening part (1st inclined surface 14a) is made to rest on the semiconductor substrate 11 (sensor chip 10) itself, and the positional accuracy of the rectification | straightening part with respect to the sensor chip 10 is higher than before, it detects a flow volume more accurately. Can do.

  In the present embodiment, the upstream end surface 14 is also connected to the back surface 11b, and has a second inclined surface 14b that approaches the one surface 11a in the thickness direction as the distance from the heater 13 in the flow direction increases. Therefore, as shown in FIG. 7, the fluid 100 flowing in the forward direction and flowing on the back surface 10b side (the back surface 11b side of the semiconductor substrate 11) of the sensor chip 10 can also be rectified. Therefore, turbulent flow is generated in the fluid flowing on the back surface 10b side, and the turbulent flow can be suppressed from adversely affecting the fluid flowing on the front surface 10a side.

  Further, in the present embodiment, the downstream end surface 15 is connected to the one surface 11a, and the farther away from the heater 13 in the flow direction, the third inclined surface 15a that approaches the back surface 11b in the thickness direction, and the back surface 11b. It has the 4th inclined surface 15b which approaches one surface 11a in the thickness direction, so that it leaves | separates from the heater 13 in the flow direction. Therefore, when the fluid flows in the direction opposite to the forward direction, the fluid is guided on the surface 10a along the third inclined surface 15a in the downstream end surface 15 and remains in a rectified state such as the heater 13. It will pass over the sensing part. Therefore, the flow rate in the reverse direction can be detected with high accuracy even though the rectifying unit is not provided as a separate member. Further, the fourth inclined surface 15b can suppress the turbulent flow caused by the fluid in the reverse direction flowing on the back surface 10b side, and the turbulent flow adversely affecting the fluid flowing on the front surface 10a side.

  In the present embodiment, an example in which the upstream end surface 14 includes the first inclined surface 14a and the second inclined surface 14b has been described. However, as shown in FIG. 8, it is good also as a structure which has only the 1st inclined surface 14a. In this case, in the manufacturing process described above, the groove 14d penetrating the semiconductor substrate 11 may be formed by etching from the one surface 11a side without forming the groove 14c by etching on the back surface 11b side. FIG. 8 is a cross-sectional view showing a modification, and corresponds to FIG. Moreover, as shown in FIG. 8, it is good also as a structure in which the downstream end surface 15 has only the 3rd inclined surface 15a. Also in this case, in the manufacturing process described above, the groove 15d penetrating the semiconductor substrate 11 may be formed by etching from the one surface 11a side without forming the groove 15c by etching on the back surface 11b side.

  Further, as shown in FIG. 9, in the semiconductor substrate 11 constituting the sensor chip 10, the tapered upstream end face 14 and the corner 23 of the downstream end face 15 are preferably rounded. Thus, if the corner part 23 which is a connection part with an inclined surface is made into the rounded shape, since the fluid flow becomes smoother, the detection accuracy of the flow rate can be improved. In the example shown in FIG. 9, as the corner portion 23 including the upstream end surface 14, the corner portion 23, which is a connection portion between the first inclined surface 14 a and the one surface 11 a, the first inclined surface 14 a and the second inclined surface 14 b. The corner part 23 which is a connection part and the corner part 23 which is a connection part between the second inclined surface 14b and the back surface 11b are rounded. Moreover, the corner | angular part 23 which is a connection part of the 3rd inclined surface 15a and the one surface 11a as the corner | angular part 23 containing the downstream end surface 15 and the angle | corner which is a connection part of the 3rd inclined surface 15a and the 4th inclined surface 15b. The corner 23, which is a connecting portion between the portion 23, the fourth inclined surface 15b and the back surface 11b, has a rounded shape. Such rounded corners 23 can be formed by performing isotropic etching after the upstream end face 14 and the downstream end face 15 are formed by etching. FIG. 9 is a cross-sectional view showing a modification, and corresponds to FIG.

  In the present embodiment, an SOI substrate is employed, and after the upper structure 22 is formed on the one surface 11a of the semiconductor substrate 11, etching is performed to form the upstream end surface 14 and the downstream end surface 15. Indicated. However, as shown in FIG. 10A, for example, grooves 14d and 15d are formed by etching through a mask (not shown) from the one surface 11a side of the semiconductor substrate 11, and then the insulating film 12 is deposited and the conductive material (multiple The formation of a wiring layer such as a heater 13 by deposition of crystal silicon or a metal material) and patterning, and the deposition of the protective film 20 are sequentially performed, and as shown in FIG. 10B, the surface 11a and the walls of the grooves 14d and 15d are formed. The upper structure 22 is integrally formed thereon. Then, as shown in FIG. 10C, the gap region 16 and the grooves 14c and 15c are formed by etching through the mask (not shown) from the back surface 11b side of the semiconductor substrate 11, and the tapered upstream end face 14 and the downstream side are formed. The sensor chip 10 having the side end face 15 may be obtained. 10A to 10C are cross-sectional views showing a modification of the manufacturing method.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 11 is a cross-sectional view illustrating a schematic configuration of a sensor chip in the thermal flow sensor according to the second embodiment. FIG. 11 corresponds to FIG. 7 shown in the first embodiment.

  Since the thermal flow sensor according to the second embodiment is common in common with the thermal flow sensor shown in the first embodiment, the detailed description of the common parts will be omitted below, and different parts will be mainly described. . In addition, the same code | symbol shall be provided to the element same as the element shown in 1st Embodiment.

  In 1st Embodiment, the downstream end surface 15 showed the example which has the 3rd inclined surface 15a at least. However, as shown in FIG. 11, the downstream end surface 15 is connected to the one surface 11 a and the back surface 11 b of the semiconductor substrate 11, and the fourth inclined portion that is farther from the heater 13 in the flow direction as it approaches the one surface 11 a in the thickness direction. It is good also as a structure which has only the 5th inclined surface 15e. In the example shown in FIG. 11, the upstream end surface 14 has a first inclined surface 14a and a second inclined surface 14b, as in the first embodiment.

  When the vehicle is decelerated while the forward fluid is transiently flowing without backflow, the backflow due to Karman vortex generated on the downstream end face 15 side reaches the surface 10a of the sensor chip 10 and this backflow. It is known that a larger swirling vortex is generated by the forward flow and the forward flow, and a local reverse flow is generated on the surface 10a.

  On the other hand, according to the configuration shown in FIG. 11, even if the vehicle is decelerated, for example, when the forward fluid 100 is transiently flowing, the fifth inclined surface 15e causes the Karman vortex to collapse and The generation of a rotating vortex on the surface 10a of the sensor chip 10 can be suppressed by the flow of the fluid into the pressure drop portion generated on the five inclined surfaces 15e. That is, the flow rate of the fluid can be accurately detected by the rectifying function by the fifth inclined surface 15e.

  Note that such a fifth inclined surface 15e can also be formed by etching using an alkaline solution such as KOH, as shown in the first embodiment. In the case of the example shown in FIG. 11, for example, by etching from the back surface 11 b side, the upper structure 22 (insulating film 12) is used as an etching stopper to form the void region 16. What is necessary is just to form the groove | channel 15c which penetrates. Further, by forming a hole in the upper structure 22 during the etching from the one surface 11a side, the downstream end surface 15 having the fifth inclined surface 15e can be obtained.

(Third embodiment)
Next, 2nd Embodiment of this invention is described based on FIGS. FIG. 12 is a plan view showing a schematic configuration of a thermal flow sensor according to the third embodiment. FIG. 12 corresponds to FIG. 1 shown in the first embodiment. 13 is a cross-sectional view taken along line XIII-XIII in FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG.

  Since the thermal type flow sensor according to the third embodiment is in common with the thermal type flow sensor shown in each of the above-described embodiments, a detailed description of the common part will be omitted below, and different parts will be described mainly. To do. In addition, the same code | symbol shall be provided to the element same as the element shown to said each embodiment.

  In the said embodiment, the upstream end surface 14 and the downstream end surface 15 were made into the taper shape, and the example which gives a rectification | straightening function to these end surfaces 14 and 15 was shown. On the other hand, in the present embodiment, as illustrated in FIG. 12, the upstream concave portion that opens toward the upstream end surface 14 on the surface 10 a of the sensor chip 10 and extends toward the heater 13 along the flow direction. The first feature is that 24 is formed. The second feature is that the surface 10a is formed with a downstream recess 25 that opens toward the downstream end face 15 and extends toward the heater 13 along the flow direction. In this embodiment, in addition to the upstream-side recess 24 and the downstream-side recess 25, the recess extends through the flow direction in which one end opens on the upstream end surface 14 side and the other end opens on the downstream end surface 15 side. The recess 26 is also formed on the surface 10a. In addition, the upstream recessed part 24 and the downstream recessed part 25 are equivalent to the recessed part as described in a claim.

  The upstream recess 24 is configured by forming an upstream groove 27 on the one surface 11 a of the semiconductor substrate 11. As shown in FIGS. 12 to 14, the upstream groove 27 corresponds to the upstream recess 24, and one end thereof opens to the upstream end surface 14 of the semiconductor substrate 11 and extends toward the heater 13 along the flow direction. In addition, the groove is long in the flow direction. Further, it is separated from the void region 16 as a low heat conduction region.

  In this embodiment, the position of the end of the upstream groove 27 on the heater 13 side is on the gap area 16 in the flow direction, although it is separated from the gap area 16. In detail, although it does not open to the space | gap area | region 16 side, the position of the edge part by the side of the heater 13 of the upstream groove part 27 becomes a position nearer to the heater 13 than the opening end 16a (refer FIG. 4) in the back surface 11b side. Yes. Further, among the wall surfaces of the upstream groove portion 27, as the wall surface of the end portion on the heater 13 side, an inclined surface 27a as a seventh inclined portion that approaches the back surface 11b in the thickness direction as the distance from the heater 13 in the flow direction increases. Have. Also in this embodiment, the one surface 11a and the back surface 11b of the semiconductor substrate 11 made of single crystal silicon are the (100) surface, and the inclined surface 27a is the (111) surface of silicon. Further, the width of the upstream groove 27 in the longitudinal direction of the planar rectangular semiconductor substrate 11 is shorter than the length of the heater 13 in the longitudinal direction, and the width of the upstream groove 27 is substantially uniform in the flow direction. ing.

  The upper structure 22 including the insulating film 12, the wiring layer such as the heater 13, the protective film 20, and the like shown in the above embodiment is integrally formed on the upstream groove 27 and the one surface 11 a of the semiconductor substrate 11. An upstream recess 24 is formed following the upstream groove 27. Therefore, the wall surface of the end portion on the heater 13 side in the upstream recess 24 is also an inclined surface 24a that approaches the back surface 11b in the thickness direction as the distance from the heater 13 increases in the flow direction, corresponding to the inclined surface 27a. . In the present embodiment, two such upstream concave portions 24 and two upstream groove portions 27 are formed.

  On the other hand, the downstream recess 25 is configured by forming a downstream groove 28 in the one surface 11 a of the semiconductor substrate 11. As shown in FIGS. 12 to 14, the downstream groove portion 28 has one end opened to the downstream end surface 15 of the semiconductor substrate 11 and extends toward the heater 13 along the flow direction, corresponding to the downstream recess 25. In addition, the groove is long in the flow direction. Further, it is separated from the void region 16 as a low heat conduction region.

  In the present embodiment, the position of the end of the downstream groove 28 on the heater 13 side is on the gap area 16 in the flow direction, although it is separated from the gap area 16. In detail, although it does not open to the space | gap area | region 16 side, the position of the edge part by the side of the heater 13 of the downstream groove part 28 becomes a position nearer to the heater 13 than the opening end 16a (refer FIG. 4) in the back surface 11b side. Yes. Further, among the wall surfaces of the downstream groove portion 28, as the wall surface of the end portion on the heater 13 side, an inclined surface 28a as a seventh inclined portion that approaches the back surface 11b in the thickness direction as the distance from the heater 13 in the flow direction increases. Have. The inclined surface 28a is also a (111) surface of silicon. Furthermore, the width of the downstream groove 28 in the longitudinal direction of the planar rectangular semiconductor substrate 11 is shorter than the length of the heater 13 in the longitudinal direction, and the width of the downstream groove 28 is substantially uniform in the flow direction. ing.

  An upper structure 22 is formed on the downstream groove 28 and the one surface 11 a of the semiconductor substrate 11, and a downstream recess 25 is formed following the downstream groove 28. Therefore, the wall surface of the end portion on the heater 13 side in the downstream concave portion 25 is also an inclined surface 25a that approaches the back surface 11b in the thickness direction as the distance from the heater 13 increases in the flow direction, corresponding to the inclined surface 28a. . In the present embodiment, two such downstream recesses 25 and downstream grooves 28 are formed, and the upstream recess 24 and the downstream recess 25 (upstream groove 27 and The downstream grooves 28) are symmetrically arranged. In other words, the upstream concave portion 24 and the downstream concave portion 25 (the upstream groove portion 27 and the downstream groove portion 28) are arranged on the same straight line along the flow direction.

  The through recess 26 is configured by forming a through groove 29 in the one surface 11 a of the semiconductor substrate 11. As shown in FIGS. 12 and 14, the through groove portion 29 has one end opened in the upstream end face 14 of the semiconductor substrate 11 and the other end opened in the downstream end face 15 of the semiconductor substrate 11, corresponding to the through recess 26. The groove extends in the flow direction and is long in the flow direction. Further, it is separated from the void region 16 as a low heat conduction region.

  In the present embodiment, the through-groove portions are formed on both sides of the gap region 16 in the direction perpendicular to the flow direction (longitudinal direction of the planar rectangular semiconductor substrate 11) so as to sandwich the gap region 16 (heater 13). 29 are formed. Specifically, two through groove portions 29 are formed on the pad portion 19 side of the heater 13, and one through groove portion 29 is formed on the opposite side.

  An upper structure 22 is formed on the through groove 29 and the one surface 11 a of the semiconductor substrate 11, and a through recess 26 is formed following the through groove 29. In the present embodiment, in the longitudinal direction of the semiconductor substrate 11, the upstream recess 24, the downstream recess 25, and the through recess 26 have the same width in the longitudinal direction and are formed at equal intervals.

  In the thermal flow sensor 1 configured as described above, as described above, the upstream groove 27 is formed on the one surface 11a of the semiconductor substrate 11, and the upper structure 22 deposited on the upstream groove 27 is formed in the upstream groove. An upstream concave portion 24 is formed on the surface 10 a of the sensor chip 10 by imitating the shape of the portion 27. As described above, one end of the upstream recess 24 opens toward the upstream end face 14 and extends toward the heater 13 along the flow direction. That is, the upstream recess 24 forms a fluid passage (flow path). Therefore, the fluid flowing in the forward direction is guided through the flow path in the upstream recess 24 and passes over the sensing unit such as the heater 13 while being rectified. Therefore, it is possible to detect the flow rate of the fluid with high accuracy even though the rectifying unit is not provided as a separate member.

  Further, as described above, since the rectification function is provided to the sensor chip 10 itself, a rectification unit or a dam as a separate member is unnecessary, and the rectification unit as a separate member is provided in the thickness direction and the sensor chip 10. It is not necessary to position with high accuracy in the flow direction. Therefore, the configuration of the thermal flow sensor 1 can be simplified. That is, the number of components of the thermal flow sensor 1 can be reduced and the manufacturing process can be simplified as compared with the conventional case.

  Furthermore, since the rectifying function is provided to the sensor chip 10 itself and a separate rectifying unit is not required, the difference between the linear expansion coefficients of the material constituting the rectifying unit and the sensor chip 10 (semiconductor substrate 11) is essentially the same. The resulting stress does not occur. Therefore, fluctuations in sensor characteristics can be suppressed.

  As described above, according to the thermal flow sensor 1 according to the present embodiment, the structure can be detected more accurately by suppressing the turbulent flow, and the structure can be simplified as compared with the conventional one, and the fluctuation of the sensor characteristics can be achieved. Can also be suppressed.

  In the present embodiment, as described above, the downstream groove 28 is formed on the one surface 11 a of the semiconductor substrate 11, and the upper structure 22 deposited on the downstream groove 28 imitates the shape of the downstream groove 28. In addition, a downstream recess 25 is formed on the surface 10 a of the sensor chip 10. As described above, one end of the downstream recess 25 opens toward the downstream end face 15 and extends toward the heater 13 along the flow direction. That is, the downstream recess 25 forms a fluid passage (flow path). Therefore, the fluid flowing in the reverse direction is guided through the flow path in the downstream recess 25 and passes over the sensing unit such as the heater 13 while being rectified. Therefore, it is possible to accurately detect the flow rate of the fluid flowing in the reverse direction, even though the rectifying unit is not provided as a separate member.

  In the present embodiment, in the upstream recess 24 and the downstream recess 25, the inclined surfaces 24a and 25a that approach the back surface 11b in the thickness direction as the end wall surface on the heater 13 side is separated from the heater 13 in the flow direction. It has become. Therefore, the fluid guided in the upstream recess 24 or the downstream recess 25 is smoothly guided to the heater 13 via the inclined surfaces 24a and 25a. Therefore, the flow rate detection accuracy can be further improved.

  In the present embodiment, the upstream recess 24 and the downstream recess 25 are located on the same straight line with the heater 13 interposed therebetween. Therefore, when the fluid flows in the forward direction, the fluid is guided in the flow path of the upstream recessed portion 24 and reaches the heater 13, and then is guided in the flow path in the downstream recessed portion 25 to be the downstream end face 15. Exit to the side. Further, when the fluid flows in the opposite direction, the fluid is guided in the flow path of the downstream concave portion 25 and reaches the heater 13, and then is guided in the flow channel in the upstream concave portion 24 to be the upstream end face 14. Exit to the side. Therefore, in any case, the flow of the fluid is smooth, so that the flow rate detection accuracy can be further improved.

  Further, in the present embodiment, the through recess 26 is provided, and the recesses 24 to 26 on the surface 10 a are formed in a predetermined range larger than the void region 16 including the entire void region 16 in the longitudinal direction of the semiconductor substrate 11. ing. Therefore, the flow of fluid around the void region 16 can be rectified by the through recess 26 as a flow path.

  The above-described thermal flow sensor 1 (sensor chip 10) can be formed by, for example, the following manufacturing method. FIG. 15 is a cross-sectional view for explaining a method of manufacturing a sensor chip in the thermal flow sensor of FIG. 12, and (a) to (c) show a recess forming step. This manufacturing method is almost the same as the modification of the first embodiment (see FIG. 10).

  First, as shown in FIG. 15A, for example, V-shaped grooves 27 to 29 (in FIG. 15, by etching) from one surface 11 a side of the semiconductor substrate 11 made of single crystal silicon through a mask (not shown). Only the upstream groove 27 and the through groove 29 are shown). At this time, since the one surface 11a is the (100) surface, it can be etched along the (111) surface with an alkaline solution such as KOH. That is, the wall surfaces of the grooves 27 to 29 are (111) planes. Thereby, the upstream groove 27 and the downstream groove 28 have inclined surfaces 27a and 28a as end wall surfaces on the heater 13 side. In addition, the shape of each groove part 27-29 is not limited to V shape, For example, it is good also as U shape. Moreover, the depth of each groove part 27-29 is taken as the depth which the recessed parts 24-26 are comprised in the state which formed the upper structure 22. As shown in FIG.

  Next, a wiring layer such as a heater 13 formed by depositing an insulating film 12, depositing a conductive material (for example, polycrystalline silicon or metal material) and patterning on one surface 11a of the semiconductor substrate 11 so as to cover the formed grooves 27 to 29. And the deposition of the protective film 20 are sequentially performed to form the upper structure 22 as shown in FIG. At this time, since the upper structure 22 is formed following the grooves 27 to 29, the recesses 24 to 26 are also formed in a state where the upper structure 22 is formed.

  And as shown in FIG.15 (c), the above-mentioned sensor chip 10 can be obtained by forming the space | gap area | region 16 by etching through the mask which is not shown in figure from the back surface 11b side of the semiconductor substrate 11. FIG.

  In the present embodiment, an example is shown in which the width of the upstream groove portion 27 and hence the upstream recess portion 24 is uniform in the flow direction. In other words, the upstream side groove portion 27 has shown an example in which the size of the opening area perpendicular to the flow direction is uniform in the flow direction. However, the width of the upstream recess 24 (upstream groove 27) is not limited to the above example. For example, as illustrated in FIGS. 16 to 18, the upstream recess 24 (upstream groove 27) may have a configuration in which the size of the opening area perpendicular to the flow direction is increased as the distance from the heater 13 increases in the flow direction. In other words, the width of the upstream groove 27, and hence the upstream recess 24, may be configured so as to be wider from the heater 13 in the flow direction. Such an upstream groove 27 and by extension the upstream recess 24 can also be formed by enlarging the mask opening in the above-described manufacturing method. The upstream groove 27 is a U-shaped groove. FIG. 16 is a plan view showing a modification of the thermal flow sensor, and corresponds to FIG. FIG. 17 is a cross-sectional view taken along line XVII-XVII in FIG. 18 is a cross-sectional view taken along line XVIII-XVIII in FIG.

  With such a configuration, the upstream recess 24 corresponding to the upstream groove 27 exhibits not only the above-described rectifying function but also a function of increasing the flow velocity. Therefore, the detection sensitivity in the heater (sensing unit) can also be improved.

  In the example shown in FIG. 18, the width of the downstream groove 28 and the downstream recess 25 is wider as the distance from the heater 13 increases in the flow direction. This effect is the same as that of the upstream recess 24 described above. As described above, the widths of the downstream groove 28 and the downstream recess 25 are not uniformly limited in the flow direction.

  Further, in the present embodiment, the end wall surface on the heater 13 side in the upstream groove 27 is the inclined surface 27a, and the wall surface on the heater 13 side in the upstream recess 24 is also an inclined surface corresponding to the inclined surface 27a. An example of 24a is shown. However, the end wall surface of the upstream groove 27 on the heater 13 side may be a surface perpendicular to the one surface 11a and the back surface 11b. Similarly, the end wall surface of the downstream groove 28 on the heater 13 side may be a surface perpendicular to the one surface 11a and the back surface 11b instead of the inclined surface 28a. When the upper structure 22 such as the insulating film 12 is formed, it is deposited on the wall surface of the end portion on the heater 13 side with a slight inclination, so that it is inclined to the corresponding portion in the upstream recess 24 or the downstream recess 25. Can be given. In this case, anisotropic dry etching can be employed. However, as shown in the present embodiment, when the inclined surfaces 27a and 28a are provided, the end wall surfaces on the heater 13 side in the upstream concave portion 24 and the downstream concave portion 25 also become the inclined surfaces 24a and 25a. Therefore, the fluid can be smoothly guided to the heater 13 through the inclined surfaces 24a and 25a, and the flow rate detection accuracy can be further improved.

  Moreover, it is good also as a structure which combined the structure shown in this embodiment, and the structure shown in 1st Embodiment or 2nd Embodiment.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In each of the above embodiments, the example of the void region 16 formed by etching the semiconductor substrate 11 from the back surface side and penetrating the semiconductor substrate 11 is shown as the low heat conduction region. That is, the example of the back surface processing type thermal flow sensor 1 was shown. However, the low heat conduction region is not limited to the above example. For example, the void region 16 formed by etching from the back surface side may be a non-through hole that does not open on one surface. Further, a non-penetrating void region 16 that is etched from one surface side of the semiconductor substrate 11 through an etching hole (not shown) formed in the protective film 20 and the insulating film 12 may be employed. That is, a surface-processed thermal flow sensor 1 may be used. Furthermore, in addition to the void region 16, a porous region such as porous silicon or porous silicon oxide formed on the semiconductor substrate 11 can also be employed.

  In the above-described embodiment, an example in which the upstream end face 14 is tapered and the downstream end face 15 is also tapered in the semiconductor substrate 11 of the sensor chip 10 has been described. However, only the upstream end face 14 may be tapered, that is, the downstream end face 15 may be configured to have no end face substantially perpendicular to the one face 11a and the back face 11b, that is, a tapered face.

  In each of the above embodiments, the example in which the sensor chip 10 and the lead 51 are electrically connected via the wire 54 has been described. However, the thermal flow sensor 1 may further include a circuit chip, and the sensor chip 10 may be electrically connected to the lead 51 via the circuit chip. In the thermal flow sensor 1, a wiring board can be used instead of the lead 51.

  In each said embodiment, the example of the sealing resin part 52 formed by the transfer mold method was shown. However, the sealing resin portion 52 is not limited to the above example. For example, the sealing resin portion 52 formed by potting can be employed. In this case, the sealing resin portion 52 can be formed by potting and then solidifying (curing or gelling) the liquid insulating material. In addition, the sealing resin portion 52 may be formed by curing a resin film that has been formed into a sheet shape in advance by heat treatment. In this case, a dam can be eliminated.

  In each of the above embodiments, the example in which the island 50 and the lead 51 are configured as a part of the lead frame has been described. However, it is not limited to the lead frame. For example, both the island 50 and the lead 51 may be printed boards. The island 50 and the lead 51 may be made of different members.

  In each of the embodiments described above, an example in which the pad portion 19 of the sensor chip 10 and the lead 51 are electrically connected via the wire 54 has been described. However, the connection between the sensor chip 10 and the lead 51 is not limited to wire bonding. For example, it is good also as a structure connected by the bump etc.

  In each of the above-described embodiments, an example in which the thermal flow sensor 1 (sensor chip 10) includes a pair of heaters 13a and 13b and temperature sensitive bodies 17a and 17b as a sensing unit has been described. However, the configuration of the thermal flow sensor 1 (sensor chip 10) is not limited to the above example. The thin film portion of the insulating film 12 on the low heat conduction region (for example, the void region 16) has at least one heater 13, and the heat generated by the heater 13 is taken away by the fluid. Any configuration may be used as long as the flow rate of fluid is detected from changes in voltage (eg, voltage, current, resistance value).

  In the first and second embodiments described above, only the upstream end face 14 and the downstream end face 15 that are both end faces on the long side among the end faces of the substantially rectangular planar semiconductor substrate 11 made of single crystal silicon are inclined portions. An example in which is formed is shown. That is, an example is shown in which the inclined portion is not formed on the end surface on the short side, and the surface is substantially perpendicular to the one surface 11 a and the back surface 11 b of the semiconductor substrate 11. In such a configuration, when the semiconductor substrate 11 is made into chips, the end faces on the long side (the upstream end face 14 and the downstream end face 15) can be separated into chips by etching that forms an inclined portion. The end face on the side must be separated into chips by dicing. That is, when the semiconductor substrate 11 is chipped, a dicing process and an etching process are performed.

  On the other hand, in the thermal flow sensor 1 shown in FIGS. 19 and 20, the upstream side of the end surface of the substantially rectangular semiconductor substrate 11 made of single crystal silicon and having the one surface 11 a and the back surface 11 b as a (100) plane is upstream. The first inclined surface 14a and the second inclined surface 14b (not shown) are formed on the side end surface 14, and the third inclined surface 15a and the fourth inclined surface 15b (not shown) are formed on the downstream end surface 15. . In addition, the short-side end surface is connected to the one surface 11a, and as the distance from the heater 13 increases, the inclined surface 30a as a fifth inclined portion that approaches the back surface 11b in the thickness direction is connected to the back surface 11b and the inclined surface 30a. As the distance from the heater 13 increases, an inclined surface 30b is formed as a sixth inclined portion that approaches the one surface 11a in the thickness direction. These inclined surfaces 30a and 30b are formed by etching the semiconductor substrate 11 with an alkaline solution such as KOH, and the (111) plane of silicon is the inclined surfaces 30a and 30b. The inclined surface 30a and the inclined surface 30b are connected to each other near the center of the semiconductor substrate 11 in the thickness direction. In addition, the inclined surface 30a is connected to the first inclined surface 14a and the third inclined surface 15a, and the inclined surface 30b is connected to the second inclined surface 14b and the fourth inclined surface 15b.

  As described above, in the thermal flow sensor 1 shown in FIGS. 19 and 20, the entire periphery of the end surface of the sensor chip 10 (semiconductor substrate 11) is an inclined surface having the (111) plane of silicon as the wall surface. Therefore, as shown in FIG. 21, the inclined surfaces 14a, 14b, 15a, 15b, and 15b are formed by etching the semiconductor substrate 11w in the wafer state from the one surface 11a and the back surface 11b (see the first embodiment). 30a and 30b can be formed, and the semiconductor substrate 11w in the wafer state can be divided into chip sizes. Accordingly, the semiconductor substrate 11w can be formed into a chip only by etching for forming the inclined surface, although the upstream end surface 14 and the downstream end surface 15 have the inclined surfaces 14a, 14b, 15a, and 15b that exhibit the rectifying function. Can do. That is, dicing can be eliminated.

  FIG. 19 is a plan view showing another modification. 20 is a cross-sectional view taken along line XX-XX in FIG. 21A and 21B are schematic diagrams for explaining chip formation, in which FIG. 21A is a plan view, FIG. 21B is a side view seen from the end face on the long side, and FIG. 21C is a view seen from the end face on the short side. FIG. FIG. 21 shows an example in which the shape of the semiconductor substrate 11w in the wafer state is a plane rectangular shape for convenience, and the semiconductor substrate 11w is divided into four sensor chips 10. However, the shape of the semiconductor substrate 11w in the wafer state and the number of divisions into the sensor chip 10 are not limited to the above example. In addition, in the example shown in FIGS. 19 to 21, an inclined surface (14a, 15a, 30a) that is connected to the one surface 11a over the entire end surface and approaches the back surface 11b in the thickness direction as the distance from the heater 13 increases. An example is shown in which inclined surfaces (14b, 15b, 30b) are formed which are connected to the inclined surface and the back surface 11b and approach the one surface 11a in the thickness direction as they are separated from the heater 13. However, if the inclined surface is formed in the thickness direction over the entire circumference of the end surface of the semiconductor substrate 11, the semiconductor substrate 11w can be divided into the sensor chips 10 only by etching. For example, the upstream end surface 14 has a first inclined surface 14a that connects the one surface 11a and the back surface 11b, the downstream inclined surface 15 has a third inclined surface 15a that connects the one surface 11a and the back surface 11b, and the upstream end surface. 14 and the end surface portion (short-side end surface) excluding the downstream end surface 15 may have an inclined surface 30a connecting the one surface 11a and the back surface 11b. Further, the upstream side end surface 14 has a first inclined surface 14a connecting the one surface 11a and the back surface 11b, the downstream side inclined surface 15 has a fourth inclined surface 15b connecting the one surface 11a and the back surface 11b, and the upstream side end surface. 14 and the end surface portion (short-side end surface) excluding the downstream end surface 15 may have an inclined surface 30a connecting the one surface 11a and the back surface 11b.

  In the first and second embodiments described above, the example in which the inclined portions are respectively formed on the entire length of the upstream end surface 14 and the downstream end surface 15 has been described. However, a configuration may be adopted in which inclined portions are respectively formed only on part of the length of the upstream end surface 14 and the downstream end surface 15. Since each inclined part is a part for exhibiting a rectifying function, the inclined part may be formed at least in a part corresponding to the formation region of the sensing unit in the longitudinal direction. For example, it is good also as a structure by which the inclination site | part was formed only in the site | part exposed from the sealing resin part 52 (exposed to the fluid) among the upstream end surface 14 and the downstream end surface 15.

It is a top view which shows schematic structure of the thermal type flow sensor which concerns on 1st Embodiment. It is sectional drawing which follows the II-II line. It is sectional drawing which follows an III-III line. It is a top view which shows schematic structure of a sensor chip. It is sectional drawing which follows the VV line. It is sectional drawing for demonstrating the manufacturing method of a thermal type flow sensor, (a)-(c) has shown the process of forming a taper-shaped upstream end surface and downstream end surface. It is sectional drawing which shows a rectification effect. It is sectional drawing which shows a modification. It is sectional drawing which shows a modification. (A)-(c) is sectional drawing which shows the modification of a manufacturing method. It is sectional drawing which shows schematic structure of a sensor chip among the thermal type flow sensors which concern on 2nd Embodiment. It is a top view which shows schematic structure of the thermal type flow sensor which concerns on 3rd Embodiment. It is sectional drawing which follows a XIII-XIII line. It is sectional drawing which follows a XIV-XIV line. It is sectional drawing for demonstrating the manufacturing method of the sensor chip in a thermal type flow sensor, (a)-(c) has shown the recessed part formation process. It is a top view which shows the modification of a thermal type flow sensor. It is sectional drawing which follows a XVII-XVII line. It is sectional drawing which follows a XVIII-XVIII line. It is a top view which shows another modification. It is sectional drawing which follows the XX-XX line. It is the typical figure for explaining chip formation, (a) is a top view, (b) is a side view seen from the end face on the long side, (c) is a side view seen from the end face on the short side is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Thermal type flow sensor 10 ... Sensor chip 11 ... Semiconductor substrate 13, 13a, 13b ... Heater 14 ... Upstream end surface 14a ... 1st inclined surface (1st inclined part) )
14b ... 2nd inclined surface (2nd inclined part)
15 ... downstream end face 15a ... third inclined surface (third inclined portion)
15b ... 4th inclined surface 15e ... 5th inclined surface (4th inclined part)
16 ... void area (low heat conduction area)
24: Upstream concave portion 25: Downstream concave portion 27: Upstream groove portion 28: Downstream groove portions 27a, 28a: Inclined surface (seventh inclined portion)

Claims (12)

A semiconductor substrate in which one region of a predetermined depth from one surface is a region having a lower thermal conductivity than the other region, an insulating film formed on one surface of the semiconductor substrate so as to bridge the low thermal conductivity region, and As a resistor disposed on an insulating film, a thermal flow sensor comprising a sensor chip having a sensing unit including a heater disposed at a site on the low thermal conduction region,
Of the end surfaces connecting the one surface and the back surface of the semiconductor substrate, the upstream end surface in the normal flow direction of the fluid is connected to the one surface, and as the distance from the heater in the flow direction increases, A thermal flow sensor comprising a first inclined portion that approaches the back surface in the thickness direction. As the upstream side end surface, including the second inclined portion that is connected to the back surface and approaches the one surface in the thickness direction of the semiconductor substrate as it is separated from the heater in the flow direction,
The thermal flow sensor according to claim 1, wherein the first inclined portion and the second inclined portion are connected to each other.   2. The thermal flow sensor according to claim 1, wherein a corner portion including the upstream end surface of the semiconductor substrate has a rounded shape.   The downstream side end surface in the flow direction includes a third inclined portion that is connected to the one surface and approaches the back surface in the thickness direction as the distance from the heater in the flow direction increases. The thermal flow sensor according to any one of? 3.   The downstream end surface in the flow direction is connected to the one surface and the back surface, and includes a fourth inclined portion that is farther from the heater in the flow direction as it approaches the one surface in the thickness direction. Item 4. The thermal flow sensor according to any one of Items 1 to 3.   6. The thermal flow sensor according to claim 4, wherein a corner portion including the downstream side end surface of the semiconductor substrate has a rounded shape. The semiconductor substrate is made of single crystal silicon, and the one surface and the back surface are (100) surfaces,
Of the end face of the semiconductor substrate, as a portion excluding the upstream end face and the downstream end face, the fifth end is connected to the one face and is closer to the back face in the thickness direction of the semiconductor substrate as it is separated from the heater. Including at least one of an inclined portion and a sixth inclined portion that is connected to the back surface and approaches the one surface in the thickness direction of the semiconductor substrate as it is separated from the heater;
The thermal flow sensor according to claim 4, wherein each of the inclined portions is formed by etching the semiconductor substrate. A semiconductor substrate in which one region of a predetermined depth from one surface is a region having a lower thermal conductivity than the other region, an insulating film formed on one surface of the semiconductor substrate so as to bridge the low thermal conductivity region, and As a resistor disposed on an insulating film, a thermal flow sensor comprising a sensor chip having a sensing unit including a heater disposed at a site on the low thermal conduction region,
On one surface of the semiconductor substrate, a groove is formed apart from the low thermal conductivity region,
As the groove portion, one end has an upstream groove portion that opens toward the upstream end surface in the normal flow direction of the fluid among the end surfaces connecting the one surface and the back surface thereof, and extends toward the heater along the flow direction. Including
The thermal flow sensor according to claim 1, wherein a recess is formed on the surface of the sensor chip corresponding to the groove.   9. The thermal flow sensor according to claim 8, wherein the upstream groove portion has a size of an opening area perpendicular to the flow direction that increases with distance from the heater in the flow direction.   One end of the groove portion includes a downstream groove portion that opens to a downstream end surface of the end surface in the normal flow direction of the fluid and extends toward the heater along the flow direction. The thermal type flow sensor of Claim 8 or Claim 9.   The semiconductor substrate, as the wall surface of the end portion on the heater side, of the wall surface of the groove portion connected to the one surface, the farther away from the heater in the flow direction, the closer to the back surface in the thickness direction of the semiconductor substrate. The thermal flow sensor according to any one of claims 8 to 10, including a seventh inclined portion that approaches.   The thermal flow sensor according to any one of claims 1 to 11, wherein the low thermal conduction region is a void region that opens on at least one surface of the semiconductor substrate.

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