JP2016142709A - Thermal flow sensor chip, method for manufacturing thermal flow sensor chip, and flowmeter provided with thermal flow sensor chip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of unevenness on a resist film and, hence, suppress a variation in sensor resistance value in a thermal flow sensor chip film deposition process, and further to improve the yield of a thermal flow sensor chip.SOLUTION: Positions of a silicon wafer (silicon substrate) 40 and a silicon wafer (silicon substrate) 52 are aligned so that a composition plane and a groove 52Gi formed on a reverse side of the silicon wafer (silicon substrate) 40 on which a circuit pattern 40SGi is formed face each other, and then a surface of the silicon wafer (silicon substrate) 52 on which the groove 52Gi is formed and a composition plane formed on the reverse side of the silicon wafer (silicon substrate) 40 are pasted together by low-temperature plasma joint.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal flow sensor chip, a method for manufacturing a thermal flow sensor chip, and a flow meter including the thermal flow sensor chip.

  Thermal flow meters that can measure minute flow rates of fluids are in practical use. A thermal flow sensor chip used in a thermal flow meter (referred to as a flow meter chip in Patent Document 1) passes, for example, a fluid to be measured, as also disclosed in Patent Document 1. A first substrate made of glass having an inlet and an outlet at both ends, and a groove as a channel that is bonded to the first substrate and guides a fluid introduced and measured through the inlet to the outlet The glass-made 2nd board | substrate, the several temperature detection part formed in one surface of a 1st board | substrate, and the heating part which consists of a heater are comprised. The thermal flow sensor chip is connected to a fluid information detection unit that obtains the flow rate of fluid based on detection outputs from a plurality of temperature detection units. A plurality of temperature detection units, a heating unit including a heater, and the like are formed on the surface of the first substrate by vapor deposition, sputtering, or the like.

  A plurality of temperature detection units are formed adjacent to each other at a predetermined interval on both sides of the heating unit provided in the central portion of the first substrate. Accordingly, a plurality of temperature detection units and a heating unit including a heater are arranged at a predetermined interval between the inlet and the outlet of the first substrate.

JP 2009-276264 A

  In Patent Document 1, after the inflow port and the outflow port are formed on the first substrate, when the first substrate and the second substrate are bonded to each other, for example, when a resist film is formed on the first substrate, The already formed inflow port and outflow port may prevent formation of a film around the inflow port and the outflow port, which may cause unevenness in the resist film. If such unevenness occurs, in the process of forming the resistive film pattern, an undesired error occurs in the pattern dimensions, and the obtained thermal flow sensor chip has a sensor resistance value having a large variation. Become. In addition, if the inlet and outlet are formed on the first substrate after the resist film formation on the first substrate, the generated particles may be used for the thermal flow sensor when holes are formed in the inlet and outlet. There is a risk of chip defects.

  In view of the above problems, the present invention is a thermal flow sensor chip, a method for manufacturing a thermal flow sensor chip, and a flow meter including the thermal flow sensor chip, Thermal flow sensor chip and thermal flow sensor chip that do not cause unevenness in the resist film, can suppress variations in sensor resistance values, and can improve the yield of the thermal flow sensor chip An object of the present invention is to provide a manufacturing method and a flow meter including a thermal flow sensor chip.

  In order to achieve the above-mentioned object, a chip for a thermal flow sensor according to the present invention includes a flow path forming substrate including a flow path having open ends at both ends that open into a conduit through which a fluid flows, and a flow path formation A temperature detection element that has a bonding surface bonded to the bonding surface of the substrate and detects the temperature of the fluid, and a heater / temperature detection element substrate that includes a heater for heating the fluid in the surface layer portion. .

  The thermal flow sensor chip manufacturing method according to the present invention includes a temperature detecting element for detecting the temperature of a fluid and a plurality of circuit patterns corresponding to a heater for heating the fluid formed on a surface layer portion. Forming a first substrate material, and forming a second substrate material in which a plurality of grooves aligned with a circuit pattern and holes communicating with both ends of each groove are formed. A step of bonding a bonding surface of the first substrate material facing the surface layer portion and a surface of the second substrate material on which a plurality of grooves are formed to form a composite substrate, and the obtained composite substrate for each circuit pattern And obtaining a chip for a thermal flow sensor.

  Further, a flow meter including the thermal flow sensor chip according to the present invention is arranged in the above-described thermal flow sensor chip and a conduit through which a fluid flows, and the flow path in the conduit and the thermal flow sensor chip A housing having a pair of passages communicating with each other and having a chip accommodating portion for accommodating a thermal flow sensor chip; a flow rate calculating unit for calculating a flow rate based on a detection output from the thermal flow sensor chip; It is configured with.

  According to the thermal flow sensor chip, the thermal flow sensor chip manufacturing method, and the flow meter including the thermal flow sensor chip according to the present invention, the flow path forming substrate is disposed in the conduit through which the fluid flows. Since a flow path having open end portions at both ends is provided, there is no unevenness in the resist film in the heater / temperature detecting element substrate film forming process, and therefore, variations in sensor resistance can be suppressed, and heat The yield of the type flow sensor chip can be improved.

It is sectional drawing which shows an example of the flow meter provided with the chip | tip for thermal type flow sensors which concerns on this invention with a part of pipe line. It is a circuit diagram which shows the temperature control circuit of the heater with which the flow meter shown by FIG. 1 is equipped. It is a circuit diagram which shows the sensor output circuit with which the flow meter shown by FIG. 1 is equipped. (A), (B), (C), and (D) are each used to explain the manufacturing process of the heater / temperature detection element substrate in an example of the manufacturing method of the thermal flow sensor chip according to the present invention. FIG. (A) And (B) is a figure with which it uses for description of the manufacturing process of the heater / temperature detection element board | substrate in an example of the manufacturing method of the chip | tip for thermal type flow sensors based on this invention, respectively. (A) And (B) is a figure with which it uses for description of the manufacturing process of the flow-path formation board | substrate in an example of the manufacturing method of the chip | tip for thermal type flow sensors based on this invention, respectively. (A) And (B) is a figure with which it uses for description of the manufacturing process of the flow-path formation board | substrate in an example of the manufacturing method of the chip | tip for thermal type flow sensors based on this invention, respectively. (A), (B), (C), and (D) are respectively the manufacturing steps of the composite substrate and the thermal flow sensor chip in the example of the thermal flow sensor chip manufacturing method according to the present invention. It is a figure used for description. It is a figure where it uses for description of the manufacturing process of the chip | tip for thermal type flow sensors in an example of the manufacturing method of the chip | tip for thermal type flow sensors which concerns on this invention. It is a top view which shows an example of the chip | tip for thermal type flow sensors which concerns on this invention. It is sectional drawing shown along the XI-XI line in FIG. It is a bottom view in the example shown by FIG. It is sectional drawing shown along the XIII-XIII line | wire in FIG.

  FIG. 1 shows a flow meter including an example of a thermal flow sensor chip according to the present invention together with a part of a pipe line.

  The flow meter 10 is connected to, for example, an intermediate portion of a pipe Du through which a liquid as a fluid to be measured passes in a direction indicated by an arrow. As will be described later, the flow meter 10 is connected to the middle portion of the pipe Du by screwing the male screw portion of the pipe joint of the pipe Du into the female screw holes 12FS formed inside both ends thereof. .

  The flow meter 10 includes a housing 12 having a chip housing portion 12D for housing a thermal flow sensor chip 16ai (hereinafter also referred to as a sensor chip 16ai), which will be described later, and a sensor chip 16ai as main elements. Has been. As will be described later, the flow meter 10 includes a temperature control circuit 20 (see FIG. 2) for controlling the temperature of the heater portion in the sensor chip 16ai, and a sensor output circuit for sending a detection output from the sensor chip 16ai. 26 (see FIG. 3).

  The housing 12 has a through-passage that communicates with a flow path formed by the duct Du. The through passage extends from one end of the housing 12 to the other end along the liquid flow direction. Female threaded portions 12FS are formed at both ends of the through path. A small diameter portion 12C1, a communication path 12C3, and a small diameter portion 12C2 are sequentially formed between the female screw portions 12FS from the upstream side to the downstream side of the through passage. The inner diameter of the communication path 12C3 is appropriately set according to the flow range of the fluid to be measured. Further, the small diameter portion 12C1, the communication path 12C3, and the small diameter portion 12C2 are not limited to such an example, and may be formed to have the same inner diameter, for example, so as not to restrict the fluid.

  In addition, when the flow rate range of the fluid to be measured is a minute flow rate, for example, the communication path 12C3 may be blocked by a plug. As a result, the fluid flows from the upstream female screw portion 12FS to the downstream female screw portion 12FS through the small diameter portion 12C1, a bypass in the sensor chip 16ai described later, and the small diameter portion 12C2. In such a case, the flow path through which the fluid flows is formed by the female screw portion 12FS, the small diameter portion 12C1, the detour in the sensor chip 16ai, and the small diameter portion 12C2.

  The small diameter portions 12C1 and 12C2 are respectively formed with a port 12P1 and a port 12P2 communicating with the chip housing portion 12D. One ends of the port 12P1 and the port 12P2 are opened toward the small diameter portions 12C1 and 12C2, respectively. Thereby, a part of the liquid introduced through the female screw portion 12FS is guided to the port 12P1 along the direction indicated by the arrow, and to a detour in the sensor chip 16ai described later, and then into the small diameter portion 12C2 through the port 12P2. Returned. On the periphery of the other end of the port 12P1 and the port 12P2 at the bottom of the chip accommodating portion 12D, an O-ring 14 for sealing the detour and the port 12P1 and the port 12P2 is provided, respectively.

  Since the O-ring 14 is provided at the peripheral edge of the other end of the port 12P1 and the port 12P2 in this way, for example, as compared with the case where the O-ring is provided at the peripheral edge of the upper surface of the sensor chip 16ai that comes into contact with the pressing plate PL described later. Thus, there is no possibility that the sensor chip 16ai is damaged by the elastic force of the O-ring.

  The sensor chip 16ai inserted into the chip housing portion 12D is held in the chip housing portion 12D by, for example, a pressing plate PL fixed to the housing 12.

  10 to 13, the sensor chip 16ai includes a heater / temperature detection element substrate 16A, a flow path formation substrate 16B, a heater element 16H formed on the heater / temperature detection element substrate 16A, and temperature detection. It includes elements 16TS1, 16TS2, 16TS3, and 16TS4.

  The heater / temperature detection element substrate 16A is made of, for example, silicon having a thickness of about 0.1 mm. A heater element 16H is formed at the center of one surface layer portion of the heater / temperature detection element substrate 16A. At predetermined positions adjacent to both sides of the heater element 16H, a temperature detection element 16TS3 for detecting the ambient temperature upstream of the through passage and a temperature detection element 16TS2 for detecting the ambient temperature downstream of the through passage are formed. Has been. A temperature detection element 16TS4 for detecting the temperature of the liquid in the detour is formed at a position spaced upstream of the through path from the temperature detection element 16TS3. Further, a temperature detection element 16TS1 for detecting the temperature of the liquid in the detour is formed at a position separated from the temperature detection element 16TS2 on the downstream side of the through passage.

  The flow path forming substrate 16B is made of, for example, silicon having a thickness of about 0.9 mm or glass. The flow path forming substrate 16B has a flow path 16PA3 extending along the arrangement direction of the heater element 16H of the heater / temperature detection element substrate 16A and the temperature detection elements 16TS1, 16TS2, 16TS3, and 16TS4. The upstream end portion of the flow path 16PA3 communicates with one end of the flow path 16PA1 extending in the thickness direction of the flow path forming substrate 16B. Further, the downstream end of the flow path 16PA3 communicates with one end of the flow path 16PA2 extending in the thickness direction of the flow path forming substrate 16B. The channel 16PA1 and the channel 16PA2 are formed with a predetermined interval so as to be orthogonal to the channel 16PA3. The lower ends of the flow path 16PA1 and the flow path 16PA2 are opened toward the ports 12P1 and 12P2 of the housing 12, respectively. Thereby, a detour in the sensor chip 16ai is formed by the flow path 16PA1, the flow path 16PA2, and the flow path 16PA3.

  When the flow path forming substrate 16B is made of silicon, the heater / temperature detection element substrate 16A and the flow path forming substrate 16B are bonded and bonded by, for example, low temperature plasma bonding. When the flow path forming substrate 16B is made of glass, the heater / temperature detection element substrate 16A and the flow path forming substrate 16B are bonded and bonded by, for example, anodic bonding.

  The heater temperature control circuit 20 includes, for example, a transistor 24 and an operational amplifier 22 as shown in FIG. The collector of the transistor 24 is connected to a predetermined reference power supply E 1, and the base of the transistor 24 is connected to the output terminal of the operational amplifier 22. The emitter of the transistor 24 is connected to the connection end of the resistor Rr and the resistor Rh connected in parallel. Resistors R2 and R1 are connected in series to the resistor Rr and the resistor Rh, respectively. The connection ends of the resistors R2 and R1 are grounded. The connection end of the resistor Rr and the resistor R2 is connected to the input terminal (−) of the operational amplifier 22. The connection end of the resistor Rh and the resistor R1 is connected to the input terminal (+) of the operational amplifier 22. At that time, as shown in FIG. 1, when the fluid flows in the direction indicated by the arrow, the resistor Rr corresponds to the above-described temperature detection element 16TS4, and the resistor Rh corresponds to the heater element 16H. When the fluid flows in the direction opposite to the direction indicated by the arrow, the resistor Rr corresponds to the above-described temperature detection element 16TS1.

  For example, as shown in FIG. 3, the sensor output circuit 26 includes an operational amplifier 28, a resistor R3, and a resistor R4. A connection end of the resistor R3 and the resistor Ru connected in parallel is connected to a predetermined reference power supply E1. A resistor R4 and a resistor Rd are connected in series to the resistor R3 and the resistor Ru, respectively. The connection end of the resistor R4 and the resistor Rd is grounded. The connection ends of the resistors R3 and R4 are connected to the input terminal (−) of the operational amplifier 28. The connection ends of the resistor Ru and the resistor Rd are connected to the input terminal (+) of the operational amplifier 28. The resistor Ru and the resistor Rd correspond to the temperature detection elements 16TS3 and 16TS2 described above, respectively. As a result, the output voltage is supplied from the output terminal of the operational amplifier 28 according to the input voltage to a flow rate calculation unit (not shown). The flow rate calculation unit calculates the flow rate based on the detection outputs of the temperature detection elements 16TS1, 16TS2, 16TS3, and 16TS4. The flow rate calculation unit converts, for example, the temperature difference measured by the temperature detection element 16TS3 and the temperature detection element 16TS2 into a flow rate by an empirical formula (1) that is an exponential function described below.

y = ae ^-bx (1)
However, y is a flow rate, x is a temperature difference, and a and b are coefficients.

  The temperature detection element 16TS4 and the temperature detection element 16TS1 are respectively used for calculating a reference temperature during temperature correction when the fluid temperature changes and constant temperature difference control of the heater.

  Based on the output voltage from the temperature detection element 16TS1, 16TS2, 16TS3, 16TS4, the temperature indicated by the output voltage from the temperature detection element 16TS4 or the temperature detection element 16TS3 and the temperature indicated by the output voltage from the temperature detection element 16TS2 or the temperature detection element 16TS1. The flow rate is calculated using the fact that the temperature difference between and depends on the flow rate of the liquid. The flow rate calculation unit, for example, calculates a flow rate based on the temperature difference with reference to the map, with a map representing the relationship between the temperature difference and the flow rate stored in advance in the storage unit of the control unit. Is done.

  The sensor chip 16ai described above is manufactured as follows by an example of the method for manufacturing a chip for a thermal flow sensor according to the present invention.

  The heater / temperature detection element substrate 16A is formed by, for example, a lift-off method. First, as shown in FIGS. 4A and 4B, patterning is performed with a photoresist 34 on one surface of a cleaned substantially circular silicon wafer (silicon substrate) 30 (about 0.1 mm thick). Is done. Next, as shown in FIG. 4C, a titanium layer and a platinum layer are formed by sputtering or the like. As a result, a metal film 38 composed of a titanium layer and a platinum layer is deposited and formed on the surface of the photoresist 34 and one surface of the silicon wafer 30. At this time, the platinum layer is deposited so as to be laminated on the titanium layer. Subsequently, as shown in FIG. 4D, only a certain portion of the resist 38 is dissolved. As a result, a plurality of conductor patterns composed of a titanium layer and a platinum layer corresponding to the heater element 16H and the temperature detection elements 16TS1, 16TS2, 16TS3, and 16TS4 in each of the sensor chips described above remain only in the portion without the resist. As a result, as shown in FIGS. 5A and 5B, circuit patterns 40SGi (i = 1 to 9) in each sensor chip are formed, for example, at nine locations. The circuit pattern 40SGi includes a conductor 40H and conductors 40TS1, 40TS2, 40TS3, and 40TS4 corresponding to the heater element 16H and the temperature detection elements 16TS1, 16TS2, 16TS3, and 16TS4, respectively. Thereby, a silicon wafer (silicon substrate) 40 on which the circuit pattern 40SGi is formed is obtained.

  Subsequently, in manufacturing the flow path forming substrate 16B in the sensor chip 16ai, as shown in FIGS. 6A and 6B, a substantially circular silicon wafer having a surface 50A and a surface 50B parallel to each other (silicon After the substrate 50 (thickness of about 0.9 mm) is cleaned, the plurality of grooves 52Gi (i = 1 to 9) corresponding to the flow paths 16PA3 of the sensor chips 16ai are formed into the silicon wafer (silicon substrate) 50. The holes 52Ga corresponding to the flow paths 16PA1 and 16PA2 are formed at both ends of the groove 52Gi by machining or deep RIE, for example. At that time, the position of each groove 52Gi is set to be on a common straight line passing through the center of the conductor 40H, conductors 40TS1, 40TS2, 40TS3, and 40TS4 of each circuit pattern 40SGi in the above-described silicon wafer (silicon substrate) 40. Has been. As a result, as shown in FIGS. 7A and 7B, a silicon wafer (silicon substrate) 52 having grooves 52Gi and holes 52Ga formed on one surface 50A is obtained.

  Subsequently, as shown in FIG. 8A, a silicon wafer (silicon substrate) 40 and a silicon wafer (silicon substrate) 52 are bonded surfaces formed on the back surface of the silicon wafer 40 on which the circuit pattern 40SGi is formed. And the groove 52Gi are aligned so as to face each other, then, as shown in FIG. 8B, the surface of the silicon wafer (silicon substrate) 52 and the back surface of the silicon wafer (silicon substrate) 40 in which the groove 52Gi is formed. Are bonded together by, for example, low-temperature plasma bonding. Thus, a composite substrate 54 in which the silicon wafer (silicon substrate) 52 and the silicon wafer (silicon substrate) 40 are combined is obtained. Since the surface of the silicon wafer 40 on which the circuit pattern 40SGi is thus formed is on the pressing plate PL side, wiring design is facilitated.

  The surface of the silicon wafer (silicon substrate) 52 and the bonding surface formed on the back surface of the silicon wafer (silicon substrate) 40 may be bonded by “direct bonding”. Further, the surface of the silicon wafer 40 on which the circuit pattern 40SGi covered with the protective layer is formed and the surface of the silicon wafer (silicon substrate) 52 on which the grooves 52Gi are formed may be bonded.

  The obtained composite substrate 54 is diced by a predetermined dicing saw.

  As shown in FIGS. 8C and 9, dicing is performed along vertical lines 56R1, 56R2, 56R3, 56R4 and horizontal lines 56L1, 56L2, 56L3, 56L4 formed in a lattice shape. Thereby, as shown in FIG. 8D, the composite substrate 54 is divided so that nine sensor chips 16ai can be obtained at one time. Therefore, the manufacture of the sensor chip 16ai is completed.

  According to an example of the method for manufacturing a thermal flow sensor chip according to the present invention, when a silicon wafer (silicon substrate) 40 on which a circuit pattern 40SGi is formed is manufactured, it is not necessary to provide a fluid passage hole or the like. Resist unevenness does not occur. That is, since the photolithography process can be performed on the uniform resist film, the resistance film of the sensor portion can be formed with high dimensional accuracy. Thereby, the chip | tip for thermal type flow sensors with little dispersion | variation in resistance value can be manufactured. That is, the adjustment time of the sensitivity adjustment process of the thermal flow sensor can be shortened or the adjustment process itself can be omitted.

  When the silicon wafer (silicon substrate) 40 on which the circuit pattern 40SGi is formed is manufactured, the thermal flow sensor can be manufactured in a cleaner environment because no hole processing is performed by drilling, sandblasting, etching, or the like. That is, it is possible to suppress the occurrence of resistance wire defects caused by particles generated by machining. When the silicon wafer (silicon substrate) 40 on which the circuit pattern 40SGi is formed is manufactured, since the hole processing of the thin silicon wafer is eliminated, the occurrence of wafer breakage can be suppressed.

DESCRIPTION OF SYMBOLS 10 Flow meter 12 Housing 12D Chip accommodating part 16ai Sensor chip 16A Heater / temperature detection element substrate 16B Flow path formation substrate 16PA1, 16PA2, 16PA3 Flow path 16TS1, 16TS2, 16TS3, 16TS4 Temperature detection element 16H Heater element

Claims (3)

A flow path forming substrate comprising a flow path having open ends at both ends that open into a conduit through which fluid flows;
A heater / temperature detection element substrate having a bonding surface bonded to the bonding surface of the flow path forming substrate and detecting the temperature of the fluid, and a heater / temperature detection element substrate having a heater for heating the fluid in a surface layer portion;
A chip for a thermal flow sensor comprising: A step of forming a first substrate material in which a plurality of circuit patterns corresponding to a temperature detection element for detecting the temperature of the fluid and a heater for heating the fluid are formed on the surface layer portion;
Forming a plurality of grooves to be aligned with the circuit pattern, and a second substrate material in which holes communicating with both ends of each groove are formed;
Bonding a bonding surface facing the surface layer portion of the obtained first substrate material and a surface of the second substrate material on which the plurality of grooves are formed to form a composite substrate;
Dividing the obtained composite substrate into each circuit pattern to obtain a thermal flow sensor chip; and
A method for manufacturing a chip for a thermal flow sensor comprising: The thermal flow sensor chip according to claim 1,
A housing having a pair of passages which are arranged in a conduit through which fluid flows and communicate with the inside of the conduit and the flow path of the thermal flow sensor chip; When,
A flow rate calculation unit for calculating a flow rate based on the detection output from the thermal flow sensor chip;
A flow meter provided with a chip for a thermal type flow sensor comprising:

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