JP4797771B2 - SENSOR DEVICE HAVING MEMBRANE AND MANUFACTURING METHOD THEREOF - Google Patents

Description

  The present invention relates to a sensor device in which a strain sensor composed of a pressure sensor or an acceleration sensor similarly provided with a membrane is integrally formed with a thermal flow sensor provided with a membrane constituted by a thin film portion, and a method for manufacturing the same. It is about.

  Conventionally, Patent Document 1 discloses a thermal flow sensor using a heating resistor (heater) and a resistance temperature detector. The thermal flow sensor detects the flow rate of the fluid to be measured by installing a heating resistor in the fluid to be measured and detecting the amount of heat released from the heating resistor taken by the fluid to be measured by the temperature measuring resistor. In such a thermal flow sensor, a membrane is provided as a thin film portion that can reduce contact with the substrate and suppress heat transfer to the substrate by forming a recess or a cavity in the substrate. The responsiveness of the thermal flow sensor is enhanced by arranging a heating resistor and a resistance temperature detector on the membrane.

  The thermal flow sensor disclosed in Patent Document 1 is manufactured by a semiconductor micromachining technique and is useful from the viewpoint of low cost and low current consumption. In such a thermal flow sensor, a resistor constituting a heater or a thermometer is formed by doping impurities into single crystal silicon from the point that the change with time of the sensor characteristics is small and the reliability is high.

When the resistor is formed using single crystal silicon as described above, thermal stress is generated in the heater due to a difference in thermal expansion from the membrane. When the thermal stress is generated, a piezoresistive effect in which the resistance value changes due to the stress is generated, and the resistance value change due to temperature occurs, which causes a decrease in sensor accuracy. For this reason, in order to minimize the influence of the piezoresistive effect, the longitudinal direction of the resistor is taken in the crystal direction where the piezoresistive effect is minimized by utilizing the crystal orientation dependency of the piezoresistive effect.
Japanese Patent Laid-Open No. 2001-12985

  There is a desire to form a pressure sensor with the same chip as the thermal fluid sensor described above. In a pressure sensor, a membrane (diaphragm) configured as a thin film portion is formed, and a gauge resistance (strain-sensitive portion) is formed on the membrane configured of single crystal silicon, so that the membrane is adapted according to the pressure applied to the membrane. Pressure detection is performed using the piezoresistive effect in which the resistance value of the gauge resistance changes when is displaced. In such a pressure sensor, in order to actively use the piezoresistance effect, it is preferable to take the longitudinal direction of the resistor in the crystal direction where the piezoresistance effect is maximized.

  For this reason, when it is set as the sensor apparatus which formed integrally the thermal type flow sensor and pressure sensor which were described in patent document 1, the thermal type flow sensor suppressed the influence of the piezoresistance effect, and the pressure sensor had the piezoresistance effect. It will be necessary to realize the mutually contradictory effects of active use.

  On the other hand, the above-described conflicting effects can be obtained by forming the gauge sensor in the longitudinal direction by shifting the longitudinal direction by 45 degrees with respect to the longitudinal direction of the heating resistor and / or the temperature sensitive resistor in the thermal flow sensor. However, by anisotropically etching a silicon substrate, a heat insulating membrane used in a thermal flow sensor and a strain sensitive membrane used in a pressure sensor are formed. There is a problem that it is difficult to obtain a membrane shape suitable for a thermal flow sensor and suitable for a pressure sensor. For this reason, it is difficult to integrate and form these sensors on the same chip.

  Here, the pressure sensor is taken as an example of the strain sensor formed on the same chip as the thermal flow sensor, but the same can be said for the case of forming an acceleration sensor having a weight on the membrane.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a sensor device having a structure capable of suitably forming a strain sensor including a pressure sensor or an acceleration sensor on the same chip as the thermal flow sensor and a method for manufacturing the same. .

  In order to achieve the above object, in the present invention, in the semiconductor layer (14), the conductivity type is inverted between the formation region of the thermal flow sensor (S1) and the formation region of the strain sensor (S2), The longitudinal direction of the heaters (15a, 15b) in the flow rate sensor (S1) and the longitudinal direction of the gauge resistors (18a-18d) in the strain sensor (S2) are the same direction, and the heater in the thermal flow rate sensor (S1) The longitudinal direction of (15a, 15b) is the crystal direction in which the piezoresistance effect in single crystal silicon is minimized, and the longitudinal direction of the gauge resistance (18a to 18d) in the strain sensor (S2) is that the piezoresistance effect in single crystal silicon is maximal. The first characteristic is that the crystal orientation is as follows.

  As described above, in the semiconductor layer (14), the conductivity type is inverted between the formation region of the thermal flow sensor (S1) and the formation region of the strain sensor (S2). In this way, even if the longitudinal direction of the heaters (15a, 15b) in the thermal flow sensor (S1) and the longitudinal direction of the gauge resistors (18a-18d) in the strain sensor (S2) are the same direction, the thermal flow sensor. The longitudinal direction of the heaters (15a, 15b) in (S1) is the crystal direction in which the piezoresistance effect in single crystal silicon is minimized, and the longitudinal direction of the gauge resistance (18a-18d) in the strain sensor (S2) is piezo in single crystal silicon. The crystal direction can maximize the resistance effect. Therefore, a sensor device having a structure in which the strain sensor (S2) can be suitably formed on the same chip as the thermal flow sensor (S1) can be obtained.

  For example, in the semiconductor layer (14), the formation region of the thermal flow sensor (S1) is N-type silicon, the formation region of the strain sensor (S2) is P-type silicon, and the heater (15a in the thermal flow sensor (S1) is formed. 15b) and the longitudinal direction of the gauge resistors (18a to 18d) in the strain sensor (S2) may coincide with the crystal direction of [0-11] or [011].

  The present invention also uses a silicon substrate (10) whose crystal plane orientation in the thickness direction is the (100) plane, and an etching mask (24) is arranged on the back surface (10b) of the silicon substrate (10). When the first and second cavities (11, 12) are formed with an alkaline etching solution, the opening (24a) for forming the first cavities (11) in the etching mask (24) is formed. A second feature is that the first and second cavities (11, 12) are formed in a rectangular shape and the opening (24b) for forming the second cavities (12) has a rhombus or cross shape. .

  In the semiconductor layer (14), when the conductive type is the same in the formation region of the thermal flow sensor (S1) and the formation region of the strain sensor (S2), the heater (15a) in the thermal flow sensor (S1) 15b) and the longitudinal direction of the gauge resistors (18a to 18d) in the strain sensor (S2) may be shifted by 45 degrees. In this case, of the etching mask (24), the opening (24a) for forming the first cavity (11) has a rectangular shape, and the opening (24b) for forming the second cavity (12) has a rhombus. Or if it is set as a cross shape, the 1st, 2nd cavity part (11, 12) can be made into a suitable shape for formation of a heater (15a, 15b) or a gauge resistance (18a-18d).

  The present invention also uses a silicon substrate (10) whose crystal plane orientation in the thickness direction is the (100) plane, and an etching mask (24) is arranged on the back surface (10b) of the silicon substrate (10). An opening for forming the first cavity (11) in the etching mask (24) when forming the first and second cavities (11, 12) with an etching solution in which an organic solvent is added to alkali. The third feature is that the first and second cavities (11, 12) are formed by making the part (24a) rectangular and the opening (24b) for forming the second cavity (12) circular. It is said.

  Thus, the opening (24a) for forming the first cavity (11) in the etching mask (24) has a rectangular shape, and the opening (24b) for forming the second cavity (12). Even if it is circular, the first and second cavities (11, 12) can be made into a shape suitable for forming heaters (15a, 15b) and gauge resistors (18a-18d).

  In the second and third features of the present invention, when the single crystal silicon constituting the semiconductor layer (14) is P-type silicon, the semiconductor layer (14) is formed with respect to the crystal plane orientation of the silicon substrate (10). When the crystal plane orientation of the single crystal silicon to be formed is shifted by 45 degrees, the first and second cavities (11, 12) are shaped to be suitable for forming heaters (15a, 15b) and gauge resistors (18a-18d). be able to.

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

  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)
Fig.1 (a) is a figure which shows schematic plan structure of the sensor apparatus 1 to which 1st Embodiment of this invention is applied, FIG.1 (b) follows the AA line in Fig.1 (a). 2 is a diagram showing a schematic cross-sectional configuration of the sensor device 1. For reference, the crystal direction of each part is shown in FIG.

  The sensor device 1 has a structure in which a thermal flow sensor S1 and a pressure sensor S2 are integrated on the same chip. For example, the sensor device 1 is formed on the basis of a silicon substrate 10 as a semiconductor substrate having a plate thickness of 400 μm or 600 μm. ing.

  The thermal flow sensor S <b> 1 includes a hollow portion 11 in the silicon substrate 10, and thus includes a membrane that is a thin portion above the portion where the hollow portion 11 is formed. In addition, the pressure sensor S2 includes a hollow portion 12 in the silicon substrate 10, and thus includes a membrane (diaphragm) that is a thin portion above the portion where the hollow portion 12 is formed.

  As shown in FIG. 1B, the cavities 11 and 12 are formed so as to penetrate the front surface 10 a and the back surface 10 b of the silicon substrate 10. Specifically, the cavities 11 and 12 are configured as recesses that are recessed from the back surface 10b side of the silicon substrate 10 toward the front surface 10a side with the back surface 10b side of the silicon substrate 10 as openings 10c and 10d. .

  Further, as shown in FIG. 1B, an insulating film 13 made of, for example, a silicon nitride film or a silicon oxide film is formed on the surface 10a of the silicon substrate 10. A semiconductor layer 14 formed by thermally diffusing impurities in the silicon layer is patterned on the surface of the insulating film 13, and the semiconductor layer 14 allows the heater 15a to be formed in the region where the thermal flow sensor S1 is formed. 15b and the thermometers 16a and 16b for measuring the environmental temperature and the resistors constituting the wiring layers 17a to 17f are formed. Regarding the formation region of the pressure sensor S2, the gauge resistors 18a to 18d and the wiring layers 19a to 19b are formed. A resistor constituting 19d is formed.

  The silicon substrate 10, the insulating film 13, and the semiconductor layer 14 configured as described above are formed using an SOI substrate in which the silicon substrate 10 is a supporting substrate, the insulating film 13 is a buried layer (BOX layer), and the semiconductor layer 14 is an SOI layer. It is configured.

  Further, the semiconductor layer 14 is covered with an insulating film 20 made of BPSG or the like, and the formation region of the thermal flow sensor S1 is made of aluminum or the like through a contact hole formed in a predetermined portion of the insulating film 20. The pads 21a to 21f are electrically connected, and the formation region of the pressure sensor S2 is electrically connected to pads 22a to 22d made of aluminum or the like.

  A silicon nitride film 23 is formed on the surface of the insulating film 20 so as to cover almost the entire area of the silicon substrate 10, and the surfaces of the thermal flow sensor S1 and the pressure sensor S2 are protected. In the silicon nitride film 23, openings are formed in portions corresponding to the pads 21a to 21f and the pads 22a to 22d, and wire bonding is performed to the pads 21a to 21f and the pads 22a to 22d through the openings. By this, it is electrically connected to a control circuit provided outside the thermal flow sensor S1 and the pressure sensor S2.

  A silicon nitride film 24 is formed on the back side of the silicon substrate 10. Openings are formed in the silicon nitride film 24 at positions corresponding to the cavities 11 and 12 of the silicon substrate 10, and openings 10 c and 10 d of the silicon substrate 10 are formed through these openings.

  The above is the schematic configuration of the sensor device 1 in which the thermal flow sensor S1 and the pressure sensor S2 are integrated on the same chip. Next, a characteristic structure portion of the sensor device 1 will be described.

  As described above, the heaters 15a and 15b provided in the thermal flow sensor S1 and the gauge resistors 18a to 18d provided in the pressure sensor S2 are both formed by the semiconductor layer 14 constituting the SOI layer. The semiconductor layer 14 is formed by thinning a silicon substrate having a plane orientation of (100). Of the two directions parallel to the surface of the semiconductor layer 14, the left and right direction in FIG. The plane orientation of the silicon substrate is selected so that the crystal direction is [0-11], the crystal direction in the vertical direction of the paper is [011], and the crystal direction in the thickness direction of the semiconductor layer 14 is [100].

  The longitudinal directions of the heaters 15a and 15b and the gauge resistors 18a to 18d are all matched with the crystal direction of [0-11] as shown in FIG. The formation region of the thermal flow sensor S1 including 15b is made of N-type silicon, and the formation region of the pressure sensor S2 including gauge resistors 18a to 18d is made of P-type silicon.

  FIGS. 2A and 2B are correlation diagrams showing the relationship between the piezoresistance coefficient and the crystal direction in N-type silicon and P-type silicon, respectively.

  As shown in FIG. 2A, in the case of N-type silicon, the piezoresistance coefficient is minimized in the crystal directions of [0-11] and [011], and the [100] crystal deviated by 45 degrees therefrom. The piezoresistance coefficient is maximized in the direction. For this reason, when a resistor is formed with [0-11] and [011] having the minimum piezoresistance coefficient in N-type silicon as the longitudinal direction, the piezoresistance effect is minimized and the piezoresistance coefficient is maximized. When the resistor is formed with the crystal direction as the longitudinal direction, the piezoresistance effect is maximized.

  Therefore, as in this embodiment, the region where the thermal flow sensor S1 is formed is N-type silicon, and the longitudinal direction of the heaters 15a and 15b is aligned with the crystal direction of [0-11], thereby minimizing the piezoresistive effect. It becomes possible.

  On the other hand, as shown in FIG. 2B, in the case of P-type silicon, the piezoresistance coefficient is maximized in the crystal directions of [0-11] and [011], and deviated by 45 degrees therefrom [100]. The piezoresistance coefficient is minimized in the crystal direction. Therefore, when a resistor is formed with [0-11] and [011] having the maximum piezoresistance coefficient in the P-type silicon as the longitudinal direction, the piezoresistance effect is maximized and the piezoresistance coefficient is minimized [100]. When the resistor is formed with the crystal direction as the longitudinal direction, the piezoresistive effect is minimized.

  Therefore, as in the present embodiment, the formation region of the pressure sensor S2 is P-type silicon, and the longitudinal direction of the gauge resistors 18a to 18d is matched with the crystal direction of [0-11], thereby maximizing the piezoresistive effect. It becomes possible to do.

  Next, the operation of such a sensor device 1 will be described. First, an example of the operation when the flow rate of air, which is the fluid to be measured, is detected by the thermal flow sensor S1 will be described.

  The heaters 15a and 15b are driven by a control circuit (not shown) and controlled so as to be 200 ° C. higher than the environmental temperature measured by the thermometers 16a and 16b, for example. Specifically, current flows from the control circuit to the heater 15a through the pads 21b and 21c and the wiring layers 17b and 17c, and current flows to the heater 15b through the pads 21d and 21c and the wiring layers 17d and 17e. Thereby, each heater 15a, 15b comprised by the predetermined | prescribed line | wire width is heated, and the temperature of heater 15a, 15b rises in connection with this.

  At this time, the heat of the heaters 15a and 15b is taken away by the air flow. There is a difference in how heat is taken away depending on the air flow rate. The current is adjusted on the control circuit side so that the heaters 15a and 15b always have a constant temperature. The flow rate is calculated using the change in the current value at this time as a signal. Further, depending on the direction of flow, there is a difference in how heat is taken away by the two heaters 15a and 15b. That is, the upstream side is more deprived of heat than the downstream side, and more current is required. From the difference between the two, the flow direction can be detected simultaneously with the flow rate. Each of the thermometers 16a and 16b is used for detecting a reference environmental temperature.

  For example, assume that air flows from the direction of the white arrow in FIG. Here, as described above, the heater 15a of the heaters 15a and 15b is deprived of much heat. Therefore, if the control circuit keeps the temperature (resistance value) of the heater 15a constant, the energization amount to the heater 15a is increased. On the contrary, since the air warmed by the heat generated by the heater 15a passes over the heater 15b, the heat radiation amount is reduced, and the energization amount to the heater 15b is reduced.

  Therefore, the control circuit can detect the air flow rate and the flow direction based on the energization amount to the heater 15a and the heater 15b. With respect to the operation of the thermal flow sensor S1, the heaters 15a and 15b are hardly affected by the piezoresistive effect, so that a suitable flow rate can be detected. The heaters 15a and 15b referred to here are heating resistors whose resistance values change with temperature, and also have the function of a temperature sensitive resistor. That is, the temperature is kept constant by replacing the resistance values of the heaters 15a and 15b. For this reason, if a resistance value change due to stress (piezoresistance effect) occurs, the temperature cannot be maintained correctly, which causes an error.

  Next, the operation of the pressure sensor S2 will be described. Although not shown here, for example, with respect to the pressure sensor S2, a pressure reference chamber is formed by sealing the cavity 12 with a pedestal or the like in a reduced-pressure atmosphere (in a vacuum), for example, and sandwiches the membrane. It operates based on the pressure difference between the pressure reference chamber and the outside.

  For example, the pad 22a is connected to a power source (not shown) and the pad 22c is connected to GND, and current is supplied from the power source (not shown) through the pad 22a and the wiring layer 19a. An intermediate potential of the gauge resistors 18a to 18d connected to form a Wheatstone bridge circuit, that is, a potential between the gauge resistor 18a and the gauge resistor 18d is output through the pad 22d, and the gate resistor 18b and the gauge resistor 18c. Is output through the pad 22b.

  When the membrane is displaced based on the pressure difference between the pressure reference chamber and the outside, the resistance values of the gauge resistors 18a to 18d change with the displacement of the membrane, and the potential output from the pad 22b and the potential output from the pad 22d. A potential difference occurs between the potentials. At this time, the gauge resistors 18a to 18d can sufficiently exhibit the piezoresistive effect and change the resistance value, so that a large potential difference can be generated, and the magnitude of the pressure suitably applied based on the large potential difference. Can be detected.

  As described above, in the sensor device 1 of the present embodiment, the portion of the semiconductor layer 14 for forming the heaters 15a and 15b of the thermal flow sensor S1 is formed of N-type silicon, and the gauge of the pressure sensor S2 A portion for forming the resistors 18a to 18d is made of P-type silicon. For this reason, with respect to the thermal flow sensor S1, the heaters 15a and 15b are hardly affected by the piezoresistive effect, so that it is possible to detect a suitable flow rate. Further, regarding the pressure sensor S2, the gauge resistors 18a to 18d sufficiently exhibit the piezoresistive effect and change the resistance value, so that pressure detection can be suitably performed.

  And since such a structure is implement | achieved by the structure where each longitudinal direction of heater 15a, 15b of thermal type flow sensor S1 and gauge resistance 18a-18d of pressure sensor S2 corresponds, each sensor S1, S2 is equipped. A suitable membrane shape can be easily obtained. That is, in the case of this embodiment, since the side walls of the cavities 11 and 12 for constituting the membranes of the sensors S1 and S2 can be set to the same plane orientation, even if there is crystal plane orientation dependence of etching, A membrane shape suitable for each of the sensors S1 and S2 can be obtained. Therefore, it can be set as the sensor apparatus 1 of the structure which can form the pressure sensor S2 suitably in the same chip | tip as the thermal type flow sensor S1.

  In addition, regarding the manufacturing method of such a sensor apparatus 1, the part for forming the heaters 15a and 15b of the thermal flow sensor S1 in the semiconductor layer 14 is made of N-type silicon, and the gauge resistance of the pressure sensor S2 Except that the portion for forming 18a to 18d is made of P-type silicon, it is the same as the conventional one. Also in this step, the silicon substrate constituting the SOI layer is doped in advance with an N-type impurity in a region where the thermal flow sensor S1 is to be formed, and a P-type impurity is previously doped in the region where the pressure sensor S2 is to be formed. Doping should be done. Of course, before patterning the semiconductor layer 14, an N-type impurity or a P-type impurity may be selectively ion-implanted into a region where each sensor is to be formed.

(Second Embodiment)
A second embodiment of the present invention will be described. Compared to the first embodiment, the sensor device 1 of the present embodiment is a thermal type in that the semiconductor layer 14 is entirely made of N-type silicon and the longitudinal direction of the gauge resistors 18a to 18d of the pressure sensor S2 is the thermal type. The difference is that the flow direction is different from the longitudinal direction of the heaters 15a and 15b of the flow rate sensor S1. Hereinafter, although a different point from 1st Embodiment among this embodiment is demonstrated, since it is the same as that of 1st Embodiment about others, description is abbreviate | omitted.

  Fig.3 (a) is a figure which shows schematic plan structure of the sensor apparatus 1 to which this embodiment is applied, FIG.3 (b) is the sensor apparatus 1 along the BB line in Fig.3 (a). FIG. For reference, the crystal direction of each part is shown in FIG.

  As described above, in the sensor device 1 of the present embodiment, the semiconductor layers 14 constituting the heaters 15a and 15b of the thermal flow sensor S1 and the gauge resistors 18a to 18d of the pressure sensor S2 are all made of N-type silicon. . Then, as shown in FIG. 3A, the longitudinal direction of the heaters 15a and 15b formed in the thermal flow sensor S1 is made to coincide with the crystal direction of [0-11], thereby minimizing the piezoresistance effect, By making the longitudinal direction of the gauge resistors 18a to 18d formed in the sensor S2 coincide with the [100] crystal direction shifted by 45 degrees from [0-11], the piezoresistance effect is maximized.

  Even with the above-described structure, with respect to the thermal flow rate sensor S1, the heaters 15a and 15b are hardly affected by the piezoresistive effect, so that it is possible to detect a suitable flow rate. Further, regarding the pressure sensor S2, the gauge resistors 18a to 18d sufficiently exhibit the piezoresistive effect and change the resistance value, so that pressure detection can be suitably performed.

  With respect to the manufacturing method of such a sensor device 1, the surface orientation in the thickness direction of the silicon substrate 10 is (100), and the cavity of the pressure sensor S 2 in the silicon nitride film 24 formed on the back surface 10 b of the silicon substrate 10. It is necessary that the opening formed at the position of the portion 12 has a shape corresponding to the gauge resistors 18a to 18d of the present embodiment.

  FIGS. 4A and 4B are views showing the layout and cross-sectional shape of the silicon nitride film 24 serving as an etching mask when etching is performed from the back surface 10b of the silicon substrate 10. FIG.

  As shown in FIG. 4A, an opening 24a corresponding to the cavity 11 in the thermal flow sensor S1 and an opening 24b corresponding to the cavity 12 of the pressure sensor S2 are formed in the silicon nitride film 24. ing. The opening 24a has a rectangular shape, and one of two opposing sides is parallel to the crystal direction [0-11] and the other is parallel to the crystal direction [011]. The opening 24b has a rhombus shape, and two pairs of opposite sides are both parallel to the crystal direction of [100].

  When etching is performed using an etching solution of alkali such as potassium hydroxide using such an etching mask, each side of the cavity 12 of the pressure sensor S2 is 45 with respect to each side of the thermal flow sensor S1. The structure is shifted by a degree, that is, a structure having sides that coincide with the crystal direction of [100]. For this reason, the shape of the cavity portion 12, that is, the finished shape of the membrane, is set so that the gauge resistances 18 a to 18 d in the pressure sensor S 2 can be extended to each side of the cavity portion 12 that coincides with the crystal direction of [100]. It can be suitable for forming the sensor S2.

  Here, although the opening of the etching mask used for forming the cavity 12 of the pressure sensor S2 has a rhombus shape, other shapes may be used. For example, as shown in the layout diagram of the silicon nitride film 24 shown in FIG. 5, a cross shape having a [0-11] crystal direction and a side extending in the [011] direction may be used. Even when such an etching mask is used, the shape of the cavity 12, that is, the finished shape of the membrane, can be made suitable for the formation of the pressure sensor S2, as described above.

  Furthermore, it is also possible to utilize the fact that the selection ratio of crystal plane orientation changes when an organic solvent such as isopropyl alcohol (IPA) is added to the etching solution. For example, as shown in the layout diagram of the silicon nitride film 24 shown in FIG. 6A, a circular opening 24b is formed, and etching is performed using an etching solution to which an organic solvent is added. As shown in the layout diagram of the cavities 11 and 12 formed in the silicon substrate 10 shown in FIG. 6B, the shape of the cavities 11 and 12, that is, the finished shape of the membrane is suitable for the formation of the pressure sensor S2. can do.

(Third embodiment)
A third embodiment of the present invention will be described. In this embodiment, compared to the second embodiment, the semiconductor layer 14 is composed of P-type silicon, and the lengths of the heaters 15a and 15b of the thermal flow sensor S1 and the gauge resistors 18a to 18d of the pressure sensor S2. The difference is that the direction is shifted 45 degrees, and the crystal direction of the silicon substrate 10 is shifted 45 degrees with respect to the crystal direction of the semiconductor layer 14. Hereinafter, although a different point from 1st Embodiment among this embodiment is demonstrated, since it is the same as that of 1st Embodiment about others, description is abbreviate | omitted.

  Fig.7 (a) is a figure which shows schematic plan structure of the sensor apparatus 1 to which this embodiment is applied, FIG.7 (b) shows the sensor apparatus 1 along CC line in Fig.7 (a). FIG. For reference, the crystal direction of each part is shown in FIG.

  As described above, in the sensor device 1 of the present embodiment, the semiconductor layers 14 constituting the heaters 15a and 15b of the thermal flow sensor S1 and the gauge resistors 18a to 18d of the pressure sensor S2 are all made of P-type silicon. . Then, as shown in FIG. 7 (a), the longitudinal direction of the heaters 15a and 15b formed in the thermal flow sensor S1 is made to coincide with the crystal direction of [100], thereby minimizing the piezoresistive effect and the pressure sensor S2. The piezoresistive effect is maximized by matching the longitudinal direction of the gauge resistors 18a to 18d formed in [1] with the [0-11] or [011] crystal direction shifted by 45 degrees from [100].

  Even with the above-described structure, with respect to the thermal flow rate sensor S1, the heaters 15a and 15b are hardly affected by the piezoresistive effect, so that it is possible to detect a suitable flow rate. Further, regarding the pressure sensor S2, the gauge resistors 18a to 18d sufficiently exhibit the piezoresistive effect and change the resistance value, so that pressure detection can be suitably performed.

  When the heaters 15a and 15b are formed on such P-type silicon, as can be seen from FIGS. 2 (a) and 2 (b), N-type silicon remains to some extent even if the piezoresistance effect is minimized. Since the piezoresistive effect can be almost completely eliminated, the thermal flow sensor S1 having less influence of the piezoresistive effect can be obtained.

  However, in the case of such a sensor device 1, when the cavity portions 11 and 12 are formed in the silicon substrate 10, if the plane orientation of the silicon substrate 10 is made to coincide with the plane orientation of the semiconductor layer 14, the etching depends on the plane orientation dependency. The cavities 11 and 12 do not have the shape shown in the second embodiment (see FIG. 3). Therefore, as described above, in the present embodiment, the formation of the cavities 11 and 12 is such that the crystal direction of the silicon substrate 10 with respect to the crystal direction of the semiconductor layer 14 is the shape shown in the second embodiment. Is shifted 45 degrees. In this way, the cavities 11 and 12 can be formed in the silicon substrate 10 by the same method as in the second embodiment.

  Thereby, the shape of the cavities 11 and 12, that is, the finished shape of the membrane can be made suitable for the formation of the pressure sensor S2.

(Other embodiments)
In each of the above embodiments, various forms of the sensor device 1 have been shown. However, what is described here is merely an example, and the methods described in each embodiment can be combined. For example, in the first embodiment, the region where the heaters 15a and 15b of the thermal flow sensor S1 are formed in the semiconductor layer 14 is N-type silicon, and the region where the gauge resistors 18a to 18d of the pressure sensor S2 are formed. P-type silicon is used. In contrast to such a configuration, as shown in the third embodiment, the plane orientation of the semiconductor layer 14 and the plane orientation of the silicon substrate 10 may be shifted by 45 degrees. Of course, as shown in the second embodiment, when all the semiconductor layers 14 are made of N-type silicon, the plane orientation of the semiconductor layer 14 and the plane orientation of the silicon substrate 10 are 45 as shown in the third embodiment. You may make it deviate.

  In the above-described embodiment, the heaters 15a and 15b have been described by taking as an example the configuration in which the heating resistor and the resistance temperature detector of Patent Document 1 are combined. However, the heating resistor and the resistance temperature detector are separated. It may be configured as a body.

  Furthermore, in the above embodiment, the pressure sensor S2 has been described as an example of the strain sensor having the gauge resistors 18a to 18d. However, the present invention can also be applied to the acceleration sensor as in the above embodiments.

  Moreover, although the cavity parts 11 and 12 were formed so that it might penetrate from the back surface 10b of the silicon substrate 10 to the surface 10a, the recessed part was previously formed in the surface 10a, and the silicon | silicone for forming an SOI layer (semiconductor layer 14) The pressure reference chamber can be configured by bonding the silicon substrate 10 in which the recesses are formed and the silicon substrate for forming the SOI layer together with the insulating film 13 formed on one surface of the substrate. Therefore, such a structure may be used.

  In addition, when indicating the orientation of a crystal, a bar (-) should be added to a desired number, but there is a limitation in expression based on a personal computer application. A bar shall be placed in front of the number.

(A) is a figure which shows the schematic plane structure of the sensor apparatus 1 to which 1st Embodiment of this invention is applied, (b) is the outline of the sensor apparatus 1 along the AA line in (a). It is a figure which shows a cross-sectional structure. (A), (b) is a correlation diagram showing the relationship between the piezoresistance coefficient and the crystal direction in N-type silicon and P-type silicon, respectively. (A) is a figure which shows schematic plan structure of the sensor apparatus 1 to which this embodiment is applied, (b) shows schematic sectional structure of the sensor apparatus 1 along the BB line in (a). FIG. (A), (b) is the figure which showed the layout and cross-sectional shape of the silicon nitride film 24 used as an etching mask when etching from the back surface 10b of the silicon substrate 10 is performed. 4 is a layout diagram of an etched silicon nitride film 24 when etching is performed from the back surface 10b of the silicon substrate 10. FIG. (A) is a layout diagram of the silicon nitride film 24 when etching from the back surface 10 b of the silicon substrate 10, and (b) is a layout diagram of the cavities 11 and 12 formed in the silicon substrate 10. (A) is a figure which shows schematic planar structure of the sensor apparatus 1 to which this embodiment is applied, (b) shows schematic sectional structure of the sensor apparatus 1 along the CC line in (a). FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sensor apparatus, 10 ... Silicon substrate, 10a ... Front surface, 10b ... Back surface,
10c, 10d ... opening, 11, 12 ... cavity, 13 ... insulating film, 14 ... semiconductor layer,
15a, 15b ... heater, 16a, 16b ... thermometer, 17a-17f ... wiring layer,
18a-18d ... gauge resistance, 19a-19d ... wiring layer, 20 ... insulating film,
21a-21f ... pad, 22a-22d ... pad, 23 ... silicon nitride film,
24 ... Silicon nitride film, 24a, 24b ... Opening, S1 ... Thermal flow sensor,
S2: Pressure sensor.

Claims (7)

The thermal flow sensor (S1) and the strain sensor (S2) are formed on the same chip.
A silicon substrate having a first cavity (11) formed in the formation region of the thermal flow sensor (S1) and a second cavity (12) formed in the formation region of the strain sensor (S2). (10) and
An insulating film (13) formed so as to cover the first and second cavities (11, 12) on the surface (10b) side of the silicon substrate (10);
On the insulating film (13), heaters (15a, 15b) and wiring layers (17a-17f) provided in the formation region of the thermal flow sensor (S1), and the formation region of the strain sensor (S2) A semiconductor layer (14) composed of single crystal silicon with the gauge resistance (18a-18d) provided in
The silicon substrate (10) is formed using an SOI substrate having a supporting substrate, the insulating film (13) as a buried layer, and the semiconductor layer (14) as an SOI layer. A sensor device configured with the insulating film (13) formed in the second cavity (11, 12) as a membrane,
In the semiconductor layer (14), the conductivity type is inverted between the formation region of the thermal flow sensor (S1) and the formation region of the strain sensor (S2), and in the thermal flow sensor (S1) The longitudinal direction of the heaters (15a, 15b) and the longitudinal direction of the gauge resistors (18a to 18d) in the strain sensor (S2) are the same direction, and the heater (15a) in the thermal flow sensor (S1) 15b) is the crystal direction in which the piezoresistance effect in the single crystal silicon is minimized, and the longitudinal direction of the gauge resistances (18a to 18d) in the strain sensor (S2) is the piezoresistance effect in the single crystal silicon. A sensor device characterized by having a maximum crystal orientation. Of the semiconductor layer (14), the formation region of the thermal flow sensor (S1) is N-type silicon, and the formation region of the strain sensor (S2) is P-type silicon, and the thermal flow sensor (S1). ) In the longitudinal direction of the heaters (15a, 15b) and the longitudinal direction of the gauge resistors (18a-18d) in the strain sensor (S2) coincide with the crystal direction of [0-11] or [011]. The sensor device according to claim 1. The sensor according to claim 1, wherein the crystal plane orientation of the single crystal silicon constituting the semiconductor layer (14) is shifted by 45 degrees with respect to the crystal plane orientation of the silicon substrate (10). apparatus. The thermal flow sensor (S1) and the strain sensor (S2) are formed on the same chip.
A silicon substrate having a first cavity (11) formed in the formation region of the thermal flow sensor (S1) and a second cavity (12) formed in the formation region of the strain sensor (S2). (10) and
An insulating film (13) formed so as to cover the first and second cavities (11, 12) on the surface (10b) side of the silicon substrate (10);
On the insulating film (13), heaters (15a, 15b) and wiring layers (17a-17f) provided in the formation region of the thermal flow sensor (S1), and the formation region of the strain sensor (S2) A semiconductor layer (14) composed of single crystal silicon with the gauge resistance (18a-18d) provided in
The silicon substrate (10) is formed using an SOI substrate having a supporting substrate, the insulating film (13) as a buried layer, and the semiconductor layer (14) as an SOI layer. The insulating film (13) formed in the second cavity (11, 12) is configured as a membrane,
In the semiconductor layer (14), the region where the thermal flow sensor (S1) is formed and the region where the strain sensor (S2) is formed have the same conductivity type. In the thermal flow sensor (S1), The longitudinal direction of the heaters (15a, 15b) and the longitudinal direction of the gauge resistors (18a-18d) in the strain sensor (S2) are shifted by 45 degrees, and the heater (15a) in the thermal flow sensor (S1) 15b) is the crystal direction in which the piezoresistance effect in the single crystal silicon is minimized, and the longitudinal direction of the gauge resistances (18a to 18d) in the strain sensor (S2) is the piezoresistance effect in the single crystal silicon. A method of manufacturing a sensor device having a maximum crystal orientation,
As the silicon substrate (10), a substrate whose crystal plane orientation in the thickness direction is the (100) plane, an etching mask (24) is arranged on the back surface (10b) of the silicon substrate (10), and alkali etching is performed. When forming the first and second cavities (11, 12) with a liquid, the opening (24a) for forming the first cavities (11) in the etching mask (24) is rectangular. A sensor device characterized in that the first and second cavities (11, 12) are formed in the shape of an opening (24b) for forming the second cavities (12) with a rhombus or cross shape. Manufacturing method. The thermal flow sensor (S1) and the strain sensor (S2) are formed on the same chip.
A silicon substrate having a first cavity (11) formed in the formation region of the thermal flow sensor (S1) and a second cavity (12) formed in the formation region of the strain sensor (S2). (10) and
An insulating film (13) formed so as to cover the first and second cavities (11, 12) on the surface (10b) side of the silicon substrate (10);
On the insulating film (13), heaters (15a, 15b) and wiring layers (17a-17f) provided in the formation region of the thermal flow sensor (S1), and the formation region of the strain sensor (S2) A semiconductor layer (14) composed of single crystal silicon with the gauge resistance (18a-18d) provided in
The silicon substrate (10) is formed using an SOI substrate having a supporting substrate, the insulating film (13) as a buried layer, and the semiconductor layer (14) as an SOI layer. The insulating film (13) formed in the second cavity (11, 12) is configured as a membrane,
In the semiconductor layer (14), the region where the thermal flow sensor (S1) is formed and the region where the strain sensor (S2) is formed have the same conductivity type. In the thermal flow sensor (S1), The longitudinal direction of the heaters (15a, 15b) and the longitudinal direction of the gauge resistors (18a-18d) in the strain sensor (S2) are shifted by 45 degrees, and the heater (15a) in the thermal flow sensor (S1) 15b) is the crystal direction in which the piezoresistance effect in the single crystal silicon is minimized, and the longitudinal direction of the gauge resistances (18a to 18d) in the strain sensor (S2) is the piezoresistance effect in the single crystal silicon. A method of manufacturing a sensor device having a maximum crystal orientation,
As the silicon substrate (10), a substrate whose crystal plane orientation in the thickness direction is the (100) plane, an etching mask (24) is disposed on the back surface (10b) of the silicon substrate (10), and the organic substrate is alkali-free. An opening for forming the first cavity (11) in the etching mask (24) when the first and second cavities (11, 12) are formed with an etchant added with a solvent. The first and second cavities (11, 12) are formed by making (24a) rectangular and the opening (24b) for forming the second cavity (12) circular. A method for manufacturing a sensor device. The crystal plane orientation of the single crystal silicon constituting the semiconductor layer (14) is shifted by 45 degrees with respect to the crystal plane orientation of the silicon substrate (10). Manufacturing method of the sensor device. Of the semiconductor layer (14), the formation region of the thermal flow sensor (S1) is P-type silicon, and the formation region of the strain sensor (S2) is N-type silicon,
The longitudinal direction of the heaters (15a, 15b) in the thermal flow sensor (S1) and the longitudinal direction of the gauge resistors (18a-18d) in the strain sensor (S2) are equivalent to the crystal direction of [010]. Match,
The sensor according to claim 1, wherein the crystal plane orientation of the single crystal silicon constituting the semiconductor layer (14) is shifted by 45 degrees with respect to the crystal plane orientation of the silicon substrate (10). apparatus.

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