JP2014139522A - Physical quantity sensor and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress variations in a characteristic of a resistor for detecting a physical quantity in a physical quantity sensor.SOLUTION: A manufacturing method of a physical quantity sensor is configured to execute: a preparing step of preparing a component in which a front surface structure 22 is formed on a front surface 21a of a substrate 21; then a protective film simultaneously-forming step of simultaneously forming a front surface side protective film 23 on the front surface structure 22 and a rear surface side protective film 24 on a rear surface 21b of the substrate 21 (Fig. 4(a)); then a contact forming step of forming pads 25 for electrically connecting a resistor 27 and externals; subsequently an opening forming step of forming an opening 24a which exposes the rear surface 21b of the substrate 21 at a portion of the rear surface side protective film 24 corresponding to a groove part 21c (Fig. 4(c)); and further an etching step of forming the groove part 21c in the substrate 21 by etching the substrate 21 while using as a mask the rear surface side protective film 24 in which the opening 24a is formed (Fig. 4(d)).

Description

  The present invention relates to a physical quantity sensor including a sensing unit and a manufacturing method thereof.

  Conventionally, a semiconductor device having a sensing part formed by sequentially forming a first insulating film, a resistor for detecting a physical quantity, and a second insulating film on one surface side of a diaphragm which is a support substrate, and a method for manufacturing the same However, it is proposed in Patent Document 1, for example. Specifically, a resistor is sandwiched between the insulating films to form a sandwich-shaped thin film portion. In order to improve the sensing sensitivity of the resistor, a structure in which a part of the diaphragm is removed so that a part of the back surface of the thin film portion, that is, the surface on the first insulating film side is exposed is proposed.

  The semiconductor device having the above structure is manufactured as follows. First, a semiconductor wafer to be a diaphragm is prepared, and a first insulating film is formed on one surface of the semiconductor wafer. Next, a conductive thin film serving as a resistor is formed on the first insulating film, and this conductive thin film is etched and patterned to form a resistor. Then, a second insulating film is formed on the resistor. In this way, the sandwich-like thin film portion is formed. Note that formation of a pad or the like for electrically connecting the resistor and the outside is performed after the second insulating film is formed.

  Subsequently, a back polishing process for polishing and thinning the other surface of the semiconductor wafer is performed. A protective film is formed on the other surface of the polished semiconductor wafer. Thereafter, anisotropic etching is performed on the semiconductor wafer through the opening of the protective film to remove a part of the semiconductor wafer and form a diaphragm. Note that after the diaphragm is formed, the protective film on the other surface of the semiconductor wafer becomes unnecessary, and is removed by dry etching or the like. Thus, the above structure is completed.

JP 2001-153708 A

  However, in the above conventional technique, after the second insulating film is formed on one surface side of the semiconductor wafer, the other surface of the semiconductor wafer is polished and thinned, so that the film stress of the second insulating film and the semiconductor wafer The stress difference from the stress increases and warpage occurs in the semiconductor wafer. For this reason, there exists a problem that the characteristic change of the resistor for detecting a physical quantity will occur.

  In view of the above points, it is a first object of the present invention to provide a method of manufacturing a physical quantity sensor having a structure capable of suppressing a change in characteristics of a resistor for detecting a physical quantity. A second object is to provide the physical quantity sensor.

  In order to achieve the above object, in the first aspect of the present invention, first, a substrate (21) having a surface structure (22) formed on the surface (21a) is prepared (preparation step). Moreover, the front surface side protective film (23) on the surface structure (22) and the back surface side protective film (24) on the back surface (21b) of the substrate (21) are simultaneously formed (protective film simultaneous forming step). ).

  Subsequently, an opening (24a) in which the back surface (21b) of the substrate (21) is exposed is formed in a portion corresponding to the groove (21c) in the back surface side protective film (24) (opening forming step). Thereafter, the substrate (21) is etched using the back-side protective film (24) in which the opening (24a) is formed as a mask to form a groove (21c) in the substrate (21) (etching step). Features.

  Thus, since the front surface side protective film (23) on the front surface (21a) side and the back surface side protective film (24) on the back surface (21b) side of the substrate (21) are formed simultaneously, The film stresses of the protective films (23, 24) on the front surface (21a) side and the back surface (21b) side are equal. For this reason, the difference in film stress between the front surface (21a) side and the back surface (21b) side of the substrate (21) can be reduced, and the warpage of the substrate (21) due to the difference in film stress can be suppressed. Therefore, it is possible to manufacture a physical quantity sensor having a structure that can suppress a change in characteristics of the resistor (27) for detecting the physical quantity.

  In the invention according to claim 2, in the protective film simultaneous forming step, a low stress nitride film is formed at a temperature of 750 ° C. or higher and 900 ° C. or lower as the front surface side protective film (23) and the back surface side protective film (24). It is characterized by that. According to this, since the film stress itself of the front surface side protective film (23) and the back surface side protective film (24) is reduced, the warpage of the substrate (21) and the surface structure (22) is further suppressed. Therefore, the characteristic change of the resistor (27) can be suppressed.

  In the invention according to claim 3, the surface structure (22) including the resistor (27) is formed on the surface (21a) of the substrate (21), and the substrate (21) of the resistor (27) is formed on the substrate (21). A physical quantity sensor configured such that a portion corresponding to the formed groove (21c) functions as a sensing unit (22b) that detects a physical quantity, and is characterized by the following points.

  That is, the surface side protective film (23) formed on the surface structure (22) and the back surface (21b) side of the substrate (21) are formed, and an opening is formed in a portion corresponding to the groove (21c). (24a), and further includes a back surface side protective film (24) having a film stress that counteracts the warpage generated by the surface side protective film (23) on the substrate (21) and the surface structure (22). It is characterized by being. Thereby, the same effect as that of claim 1 can be obtained.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a top view of the flow sensor concerning a 1st embodiment of the present invention. It is II-II sectional drawing of FIG. It is the figure which showed the manufacturing process of the flow sensor shown by FIG.1 and FIG.2. It is the figure which showed the manufacturing process following FIG. It is sectional drawing of the sensor chip which concerns on 3rd Embodiment of this invention. It is sectional drawing of the sensor chip which concerns on 4th Embodiment of this invention. It is sectional drawing of the sensor chip which concerns on 5th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the flow sensor according to the present embodiment includes a mold resin 10, a sensor chip 20, a chip adhesive 30, a wire 40, and a protective agent 50.

  The mold resin 10 serves as a base of the flow sensor, and has an upper surface 11 and a recess 12 in which a part of the upper surface 11 is recessed as shown in FIG. The upper surface 11 is a surface provided with a lead frame (not shown). The recess 12 is a portion where the sensor chip 20 is disposed. The mold resin 10 is obtained by molding, for example, PPS (polyphenylene sulfide) or epoxy resin.

  The sensor chip 20 is a plate-like component configured to detect the flow rate of fluid. The sensor chip 20 includes a substrate 21, a surface structure 22, a front surface side protective film 23, a back surface side protective film 24, and a pad 25.

  The substrate 21 has a front surface 21a and a back surface 21b, and serves as a base for the sensor chip 20. The substrate 21 is made of, for example, a silicon substrate and has a thickness of, for example, 500 μm. The substrate 21 has a groove portion 21c through which a predetermined portion of the substrate 21 passes.

  The surface structure 22 is a film structure formed on the surface of the substrate 21 and includes a first oxide film 26, a resistor 27, and a second oxide film 28. Of the first oxide film 26, the resistor 27, and the second oxide film 28, a portion corresponding to the groove 21 c of the substrate 21 is a thin membrane 22 a that floats from the substrate 21.

The first oxide film 26 is an oxide film formed on the surface 21a of the substrate 21 and is, for example, SiO ₂ . The first oxide film 26 serves to insulate the substrate 21 and the resistor 27 from each other. The thickness of the first oxide film 26 is, for example, 0.5 μm.

  The resistor 27 is a resistance or wiring pattern for detecting the flow rate of the fluid. The resistor 27 is formed on the first oxide film 26. Specifically, the resistor 27 includes a heater resistance (not shown), a temperature measuring resistor for measuring the environmental temperature, and wiring. The heater resistance and the temperature measuring resistance are located at a portion corresponding to the groove portion 21c of the substrate 21 described above. The temperature measuring resistor includes a monitor resistor that monitors the heat generation temperature of the heater resistor and a temperature resistor that detects the temperature upstream and downstream of the heater resistor. The heat generation temperature of the heater resistor is controlled to be a constant heat generation temperature by the monitor resistance. Further, a bridge circuit is configured by temperature measuring resistors respectively arranged upstream and downstream of the heater resistance, and the output of the bridge circuit changes due to the temperature difference between the upstream and downstream of the heater resistance, and the flow rate of the fluid flowing above the membrane 22a Is to be detected.

  In the sensor chip 20, a part where the bridge circuit is formed corresponds to the sensing unit 22b. This sensing part 22b is a part corresponding to the groove part 21c formed in the board | substrate 21 among the resistors 27, and this part functions so that the flow volume of the fluid which is a physical quantity may be detected.

  The resistor 27 is patterned so as to pass through the center in the short axis direction of the sensor chip 20 shown in FIG. 1 and be symmetrical with respect to a center line (not shown) along the long axis direction. The resistor 27 is made of a material that can withstand a high temperature of 500 ° C. or higher, such as a semiconductor layer, polysilicon, platinum (Pt), or the like.

  The second oxide film 28 is an oxide film formed on the first oxide film 26 so as to cover the resistor 27. The second oxide film 28 serves to protect the resistor 27. The thickness of the second oxide film 28 is, for example, 0.6 μm.

  The surface-side protective film 23 is a protective film formed on the surface structure 22 in order to protect the surface structure 22. The surface side protective film 23 is a nitride film formed of, for example, silicon nitride (SiN). A tensile stress stronger than that of the first oxide film 26 and the second oxide film 28 is generated in the surface-side protective film 23. The thickness of the surface side protective film 23 is 1 μm, for example.

  The back surface side protective film 24 is a protective film formed on the back surface 21 b of the substrate 21. The back surface side protective film 24 has an opening 24 a in a portion corresponding to the groove portion 21 c in the back surface 21 b of the substrate 21. The back side protective film 24 is a nitride film formed simultaneously with the front side protective film 23. That is, the back surface side protective film 24 plays a role of canceling out the warpage that the front surface side protective film 23 generates on the substrate 21 and the surface structure 22 due to the film stress of the front surface side protective film 23. That is, the back surface side protective film 24 has a film stress that cancels out the warpage. Therefore, the material and thickness of the back surface side protective film 24 are the same as those of the front surface side protective film 23.

  The pad 25 is a connection part for electrically connecting the resistor 27 and the outside. The pad 25 is in contact with the resistor 27 at a location where a part of the second oxide film 28 and the surface side protective film 23 are opened so that a part of the resistor 27 on the opposite side of the groove 21c of the substrate 21 is exposed. It is formed as follows. A plurality of pads 25 are provided according to the pattern of the resistor 27. The material of the pad 25 is, for example, aluminum (Al).

  The chip adhesive 30 is a fixing member for fixing the sensor chip 20 to the bottom surface of the recess 12 of the mold resin 10 so that the pad 25 side of the sensor chip 20 is positioned on the upper surface 11 side of the mold resin 10. The chip adhesive 30 bonds the back surface side protective film 24 and the mold resin 10 together.

  The wire 40 is a wiring member for electrically connecting the pad 25 and a wiring component such as a lead frame provided on the mold resin 10.

  The protective agent 50 is a resin member that protects the wire 40 and the connecting portion of the wire 40. The protective agent 50 is not partly in contact with the membrane 22a of the sensor chip 20, a part of the surface-side protective film 23, a connection portion between the pad 25 and the wire 40, a wire 40, a lead frame of the wire 40 and the mold resin 10, and the like. The connecting part is sealed. As the protective agent 50, for example, an epoxy resin is employed.

  The above is the configuration of the flow sensor according to the present embodiment. The flow rate sensor heats the heater resistance of the sensor chip 20 according to an external command. Then, since the midpoint potential difference of the bridge circuit changes according to the flow rate, the midpoint potential difference is output to the outside. The external device that has acquired the output signal amplifies and corrects the characteristic of the output signal and acquires flow rate data.

Next, a manufacturing method of the flow sensor shown in FIGS. 1 and 2 will be described with reference to FIGS. First, in the step shown in FIG. 3A, a double-sided mirror substrate 21 is prepared. The substrate 21 is a raw stone such as a semiconductor wafer made of silicon and has already been thinned to a thickness of 500 μm. Since the front surface 21a and the back surface 21b of the substrate 21 are double-sided mirrors, the processing on the front surface 21a and the back surface 21b of the substrate 21 can be performed with high accuracy. In the step shown in FIG. 3B, a SiO ₂ first oxide film 26 having a thickness of 0.5 μm is formed on the surface 21a of the substrate 21 by a method such as thermal oxidation.

  On the other hand, unlike FIGS. 3A and 3B, an SOI substrate 60 is prepared in the process shown in FIG. In the SOI substrate 60, a BOX oxide film is formed as a first oxide film 26 on the surface 21a of the substrate 21, and a semiconductor layer 61 such as silicon is formed on the BOX oxide film. The SOI substrate 60 is a so-called SOI wafer. The thickness of the substrate 21 constituting the SOI substrate 60 has already been reduced to a thickness of 500 μm, and the back surface 21b is also polished. 3D, ion implantation of phosphorus (P) or the like is performed from above the semiconductor layer 61. As a result, the semiconductor layer 61 is changed to the conductor layer 62.

  In the step shown in FIG. 3E, the resistor 27 is formed. Specifically, when the steps of FIGS. 3A and 3B are performed, a metal layer is formed on the first oxide film 26 by a method such as sputtering, and is patterned by dry etching or wet etching. . On the other hand, when the processes of FIGS. 3C and 3D are performed, the conductor layer 62 is patterned by dry etching or wet etching. Thus, the resistor 27 having a predetermined pattern is formed.

Thereafter, in the step shown in FIG. 3F, a SiO ₂ second oxide film 28 having a thickness of 0.6 μm is formed on the resistor 27 and the first oxide film 26 by a method such as sputtering. Thus, the surface structure 22 is formed on the surface 21 a of the substrate 21.

  The step shown in FIGS. 3A to 3F, that is, the step of preparing the substrate 21 with the surface structure 22 formed on the surface 21a is the preparation step.

  Subsequently, in the step shown in FIG. 4A, a protective film simultaneous forming step of simultaneously forming the front surface side protective film 23 and the back surface side protective film 24 is performed. Specifically, the surface side protective film 23 is formed on the surface structure 22 on the surface 21a side of the substrate 21 and the back side protective film 24 is simultaneously formed on the back surface 21b of the substrate 21 by sputtering or CVD. To do.

  A silicon nitride film (SiN) is formed as the front surface side protective film 23 and the back surface side protective film 24. Since the protective films 23 and 24 are formed at the same time, not only materials but also films having the same thickness and film stress are formed. For this reason, even if the film stress of the front surface side protective film 23 acts on the front surface 21 a side of the substrate 21 and tries to warp the substrate 21 and the surface structure 22, the film stress of the back surface side protective film 24 is applied to the back surface 21 b of the substrate 21. By acting, the above warpage is canceled out. Since the wafer size is large, warping due to film stress appears remarkably, but the film stress of each of the protective films 23 and 24 on the front and back surfaces of the wafer is simultaneously formed in this step by forming the front surface protective film 23 and the back surface protective film 24 simultaneously. Is offset, so that the warpage of the wafer is suppressed. For this reason, it can suppress that the characteristic of the resistor 27 which functions as the sensing part 22b changes with the curvature of the board | substrate 21. FIG.

Before the surface side protective film 23 is formed, the surface structure 22 is formed on the surface 21a of the substrate 21, but the film side stress of the surface structure 22 made of SiO ₂ or the like is the surface side protective film 23 which is a nitride film. And it is smaller by one digit or more than the film stress of the back side protective film 24. Thus, since the surface structure 22 does not have a film stress enough to warp the substrate 21, the film stress of the surface structure 22 does not matter.

  In the step shown in FIG. 4B, a contact forming step for forming a pad 25 for electrically connecting the resistor 27 and the outside is performed. This is because part of the surface side protective film 23 and the second oxide film 28 are dry-etched or wet-etched in this order to expose a part of the resistor 27. Further, a metal film such as aluminum (Al) is formed on the resistor 27, the second oxide film 28, and the surface-side protective film 23 by a method such as sputtering or vapor deposition. Then, the metal film is patterned into the shape of the pad 25 by wet etching. In this way, the pad 25 is formed.

  Thereafter, in the step shown in FIG. 4C, an opening forming step for forming the opening 24a in the back surface side protective film 24 is performed. In this step, a portion corresponding to the groove 21c in the back surface side protective film 24 is opened by, for example, a photoetching method so that the back surface 21b of the substrate 21 is exposed.

  In the step shown in FIG. 4D, a groove portion is formed in the substrate 21 by wet-etching the back surface 21b side of the substrate 21 with an etching solution such as KOH using the back surface side protective film 24 provided with the opening 24a as a mask. An etching process for forming 21c is performed. As described above, since the back surface 21b of the substrate 21 is a mirror surface, the etching direction of the substrate 21 does not shift. By this etching, the membrane 22a is formed in a portion corresponding to the groove portion 21c in the first oxide film 26, the resistor 27, the second oxide film 28, and the surface side protective film 23. Further, the wafer is diced into individual sensor chips 20. Thus, the sensor chip 20 is completed.

  Thereafter, a mounting step of preparing the mold resin 10 and fixing the sensor chip 20 to the concave portion 12 of the mold resin 10 via the chip adhesive 30 is performed. In addition, a wire bonding process is performed in which the pads 25 of the sensor chip 20 and the lead frames on the upper surface 11 of the mold resin 10 are connected by the wires 40. Finally, the protective agent 50 is formed so as to expose the membrane 22a of the sensor chip 20 and seal the connection portion between the wire 40, the wire 40 and the pad 25, and the connection portion between the wire 40 and the lead frame. In this way, the flow sensor is completed.

  As described above, the present embodiment is characterized in that the surface-side protective film 23 on the surface structure 22 and the back-side protective film 24 on the back surface 21b of the substrate 21 are formed simultaneously. ing. For this reason, since the film stresses of the protective films 23 and 24 on the front surface 21a side and the back surface 21b side of the substrate 21 are equal, the difference in film stress between the front surface 21a side and the back surface 21b side of the substrate 21 can be reduced. it can. That is, since the film stress of each of the protective films 23 and 24 with respect to the substrate 21 is relieved, the warpage of the substrate 21 due to the difference in film stress can be suppressed. Therefore, the characteristic change due to the piezoresistance effect of the resistor 27 due to the warpage of the substrate 21 can be suppressed.

  Moreover, since the curvature of the board | substrate 21 and the surface structure 22 is suppressed, the flatness of the back surface 21b of the sensor chip 20 is securable. For this reason, when the sensor chip 20 is mounted on the mold resin 10, a gap due to the warpage of the substrate 21 does not occur between the bottom surface of the recess 12 of the mold resin 10 and the back surface side protective film 24. Therefore, the mounting strength of the sensor chip 20 can be ensured.

  In particular, as shown in FIG. 1, the sensor chip 20 in which the physical quantity sensor is configured as a flow sensor has a rectangular chip shape due to the characteristics of the flow sensor, so that the influence of warping in the major axis direction becomes significant. . However, as described above, the characteristic variation due to the piezoresistive effect of the resistor 27 can be suppressed, so that the influence of warping based on the shape of the sensor chip 20 can be reduced.

  Further, a thin wafer is used in advance when the sensor chip 20 is manufactured. For this reason, it is possible to omit the back polishing process for polishing the back surface of the wafer and the back side protective film forming process for forming the back side protective film 24 separately from the front side protective film 23. Therefore, process costs can be reduced.

(Second Embodiment)
In the present embodiment, parts different from the first embodiment will be described. In this embodiment, a low stress nitride film is formed at a temperature of 750 ° C. or more and 900 ° C. or less as the front surface side protective film 23 and the back surface side protective film 24 in the protective film simultaneous forming step shown in FIG. The composition ratio of the nitride film is usually the composition ratio of Si ₃ N ₄ , but the composition ratio of the low stress nitride film is slightly different depending on the gas flow rate ratio.

  Thus, by forming a low stress nitride film as the front surface side protective film 23 and the back surface side protective film 24, the film stress itself of the front surface side protective film 23 and the back surface side protective film 24 can be reduced. Accordingly, the warpage of the substrate 21 and the surface structure 22 is further suppressed, so that the characteristic change of the resistor 27 can be suppressed.

(Third embodiment)
In the present embodiment, parts different from the first and second embodiments will be described. As shown in FIG. 5, the sensor chip 20 has a back surface structure 29 between the back surface 21 b of the substrate 21 and the back surface side protective film 24. The back surface structure 29 has an opening at a portion corresponding to the groove 21c and the same structure as the surface structure 22 and the film structure.

  Specifically, the back surface structure 29 is formed on the third oxide film 29a formed on the back surface 21b of the substrate 21, the resistance layer 29b formed on the first oxide film 26, and the resistance layer 29b. And the fourth oxide film 29c. The back surface side protective film 24 is formed on the back surface 21b side of the substrate 21 and is formed on the back surface structure 29, that is, the fourth oxide film 29c.

  The third oxide film 29 a is an oxide film formed simultaneously with the first oxide film 26 formed on the surface 21 a of the substrate 21. The resistance layer 29 b is a layer formed simultaneously with the resistor 27 on the first oxide film 26. Further, the fourth oxide film 29 c is an oxide film formed simultaneously with the second oxide film 28.

  Thus, the configuration of the film formed in order from the front surface 21a of the substrate 21 and the configuration of the film formed in order from the back surface 21b of the substrate 21 are exactly the same. That is, the film configuration is completely symmetric on the front surface 21a side and the back surface 21b side of the substrate 21. Therefore, as a matter of course, the film stress generated by the film configuration on the front surface 21a side of the substrate 21 and the film stress generated by the film configuration on the back surface 21b side of the substrate 21 are completely symmetric.

  As described above, the warpage of the substrate 21 can be suppressed, and as a result, the characteristic change of the resistor 27 can be completely suppressed.

(Fourth embodiment)
In the present embodiment, parts different from the third embodiment will be described. In the present embodiment, as shown in FIG. 6, the second oxide film 28 and the fourth oxide film 29c are not formed in the structure of FIG.

  Thus, the surface structure 22 can be configured not to have the second oxide film 28. Accordingly, the back structure 29 having the same film structure as that of the front surface structure 22 does not have the fourth oxide film 29c. The front surface side protective film 23 is formed so as to cover the first oxide film 26 and the resistor 27, and the back surface side protective film 24 is formed on the resistance layer 29b. As described above, the film structure of the back surface structure 29 can be made the same according to the film structure of the front surface structure 22.

(Fifth embodiment)
In the present embodiment, parts different from the first to fourth embodiments will be described. As shown in FIG. 7, a surface structure 22 is formed on the surface 21 a of the substrate 21, and a surface-side protective film 23 is formed on the surface structure 22. Further, a back surface structure 29 is formed on the back surface 21 b of the substrate 21, and this back surface structure 29 is formed. The film stress of the surface constituent film constituted by the surface structure 22 and the surface side protective film 23 and the film stress of the back face constituent film constituted by the back surface structure 29 and the back surface side protective film 24 are the same. .

  The front surface structure 22 and the back surface structure 29 are each configured by either a single layer or a plurality of layers. Here, the back surface structure 29 and the back surface side protective film 24 may be formed in the same process as the surface structure 22 and the front surface side protective film 23, or the back surface structure 29 in which the film stress is adjusted after the surface structure 22 is formed. It may be formed. As described above, the warpage of the substrate 21 can be suppressed, and consequently the characteristic change of the resistor 27 can be suppressed. In FIG. 7, the pad 25 is omitted.

(Other embodiments)
The configuration of the flow sensor shown in each of the above embodiments is an example, and is not limited to the configuration shown above, and may be another configuration that can realize the present invention. For example, the sensing unit 22b is configured to detect the flow rate of the fluid, but may be configured to detect other physical quantities such as pressure.

  In the configuration according to the first embodiment, the surface structure 22 may be configured by the first oxide film 26 and the resistor 27 as in the present embodiment. In this case, the surface side protective film 23 is formed on the first oxide film 26 and the resistor 27.

  Furthermore, the front surface side protective film 23 and the back surface side protective film 24 are not limited to nitride films, and may be films formed of other materials such as oxide films. The low-stress nitride film shown in the second embodiment may be adopted in each configuration shown in the third to fifth embodiments.

21 Substrate 21a Substrate surface 21b Substrate back surface 21c Groove portion 22 Surface structure 22b Sensing portion 23 Front side protective film 24 Back side protective film 24a Opening portion 27 Resistor

Claims (4)

A surface structure (22) including a resistor (27) is formed on the surface (21a) of the substrate (21), and a groove (21c) formed in the substrate (21) of the resistor (27). Is a method of manufacturing a physical quantity sensor configured so that a part corresponding to 1 functions as a sensing unit (22b) for detecting a physical quantity,
A preparation step of preparing a surface (21a) of the substrate (21) having the surface structure (22) formed thereon;
A protective film simultaneous forming step of simultaneously forming a front surface side protective film (23) on the surface structure (22) and a back surface side protective film (24) on the back surface (21b) of the substrate (21); ,
An opening forming step of forming an opening (24a) in which the back surface (21b) of the substrate (21) is exposed in a portion corresponding to the groove (21c) in the back surface side protective film (24);
An etching step of forming the groove (21c) in the substrate (21) by etching the substrate (21) using the back side protective film (24) in which the opening (24a) is formed as a mask;
The manufacturing method of the physical quantity sensor characterized by including.   In the protective film simultaneous forming step, a low stress nitride film is formed at a temperature of 750 ° C. or more and 900 ° C. or less as the front surface side protective film (23) and the back surface side protective film (24). Item 2. A method for manufacturing a physical quantity sensor according to Item 1. A surface structure (22) including a resistor (27) is formed on the surface (21a) of the substrate (21), and a groove (21c) formed in the substrate (21) of the resistor (27). A physical quantity sensor configured to function as a sensing unit (22b) for detecting a physical quantity in a part corresponding to
A surface-side protective film (23) formed on the surface structure (22);
The substrate (21) is formed on the back surface (21b) side, has an opening (24a) in a portion corresponding to the groove (21c), and the surface-side protective film (23) is the substrate. (21) and a back surface side protective film (24) having a film stress that cancels out the warp generated in the surface structure (22);
A physical quantity sensor comprising: A portion corresponding to the groove (21c) is opened between the back surface (21b) of the substrate (21) and the back surface side protective film (24), and the surface structure (22) and the film configuration are the same. With the same back surface structure (29),
The physical quantity sensor according to claim 3, wherein the back surface side protective film (24) is formed on the back surface structure (29).

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