JP3061680B2 - Manufacturing method of sensor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a sensor device suitable for manufacturing a sensor having a thin film portion formed on a cavity in order to suppress heat capacity.

[0002]

2. Description of the Related Art Conventionally, a method of manufacturing a flow sensor has been provided, for example, as described in Japanese Patent Publication No. 3-52028. In the manufacturing method described in the publication, a silicon nitride layer is formed on a silicon substrate by sputtering, a permalloy layer is formed on the surface of the silicon nitride layer as the insulating film by sputtering, and a silicon nitride layer is formed on the surface of the permalloy layer by sputtering. Finally, a part of the silicon substrate below each layer is removed by anisotropic etching to form a cavity for thermal insulation, thereby providing a sensor device having a thin film portion for suppressing heat capacity. Manufacture a flow sensor. In this case, when forming the cavity,
Electrode (metal film) for connecting to an external circuit for flow measurement
Is exposed. On the other hand, a silicon nitride layer is formed on the silicon substrate by sputtering, and at this stage, a cavity is formed on the silicon substrate by anisotropic etching to form a thin film portion of the silicon nitride layer, and then a thin film portion of the silicon nitride layer is formed. Each layer such as a permalloy layer as described above is formed, and an electrode (metal film) is formed.
A method for manufacturing a sensor device by forming a sensor is also known.

[0003]

However, the prior art as described above has the following problems. In the former sensor manufacturing method, when forming a cavity in a silicon substrate by anisotropic etching, if the time of immersion in an etching solution (potassium hydroxide solution) or the like becomes longer, the electrode (metal film) is easily peeled. Problem occurs. On the other hand, in the latter sensor manufacturing method, when forming a pattern of an electrode (metal film) after forming a cavity, a thin film sensor portion formed of a silicon nitride layer or the like formed on the cavity is easily damaged, As a result, there is a problem that the sensor is easily damaged.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a method of manufacturing a sensor device which prevents peeling of an electrode (metal film) and damage of a sensor during manufacturing.

[0005]

In order to achieve the above object, the present invention forms a thin film sensor section having a heating means for heating a fluid to be measured on a substrate, and the substrate below the sensor section has the thin film sensor section. A method of manufacturing a sensor device, comprising: forming a space for thermally insulating a sensor unit; and forming an electrode on the substrate for electrically connecting the sensor unit to an external circuit outside the substrate. Forming a thin-film sensor portion having a heating means for heating a fluid to be measured on a substrate, and forming an electrode for electrically connecting the sensor portion to an external circuit outside the substrate; and Forming a protective film for protecting the surfaces of the thin-film sensor portion and the electrode; and forming a protective portion on the substrate below the sensor portion to form a space for thermally insulating the sensor portion. To expose the surface Removing a part of the protective film, etching a predetermined surface of the substrate to form the space portion, and removing a remaining portion of the thin film of the protective film covering the sensor portion and the surface of the electrode. And a step of performing

[0006]

According to the present invention, after a sensor portion of a thin film having a heating means for heating a fluid to be measured is formed on a substrate and an electrode for electrically connecting the sensor portion to an external circuit outside the substrate is formed. A protective film for protecting the surface of the thin film sensor part and the electrode is formed on the substrate, and the substrate below the sensor part is formed on the substrate to form a space for thermally insulating the sensor part. A part of the protective film is removed so as to expose a predetermined surface, and then etching is performed to form a space in the substrate. Finally, the protective film is removed, thereby causing peeling of electrodes and damage to the sensor. And the sensor device can be manufactured in perfect condition.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a sensor device according to an embodiment of the present invention; FIG. 1 is a perspective view of a flow sensor according to the present embodiment. The flow sensor includes a silicon substrate 1, an insulating layer 2, flow detection circuit conductors 3, 4, 5, an insulating layer 6, an insulating layer 7, , And a cavity 8. In this case, the flow rate detection circuit conductors 3, 4, 5 are provided with electrode pads 9 for connection to an external circuit (not shown) for flow rate measurement.

The detailed configuration of the flow sensor will be described.
An insulating layer 2 is formed on the surface of the silicon substrate 1,
On the surface of the insulating layer 2, a flow rate detection circuit conductor 3 as an upstream temperature-sensitive resistor, a flow rate detection circuit conductor 4 as a heater (heating element), and a flow rate detection circuit conductor as a downstream temperature-sensitive resistor 5 are sequentially formed from the upstream side to the downstream side with respect to the fluid flow direction (arrow X direction). An insulating layer 6 is formed on the surface of the flow rate detection circuit conductors 3, 4, and 5, while an insulating layer 7 is formed on the lower surface of the silicon substrate 1. Further, on the back side of the flow rate detection circuit conductors 3, 4, and 5, there is formed a cavity 8 that partially removes the silicon substrate 1 to expose the insulating layer 2 to the back side. That is, the flow rate detection circuit conductors 3, 4, 5 and the insulating layers 2, 6 in the upper portion of the cavity 8 constitute a sensor section. In this case, the insulating layer 7 is formed to form the cavity 8 in the silicon substrate 1 by etching. The present flow rate sensor is mounted such that the back surface of the sensor is located at the inner surface of a pipe forming a flow path and the like, and the fluid flows in the direction of arrow X on the front surface of the sensor.

Next, a description will be given of a process of manufacturing the flow sensor according to the present embodiment configured as described above with reference to FIG.

Step 1: A silicon substrate 1 having a desired thickness is prepared. Step 2: An insulating layer (silicon nitride) on the upper and lower surfaces of the silicon substrate 1 by a sputtering method, a plasma CVD method, or the like.
Is formed, and the insulating layer on the upper surface is defined as the insulating layer 2, while the insulating layer on the lower surface is defined as the insulating layer 7. The insulating layer 7 is provided for forming the cavity 8 in the silicon substrate 1 in a step 8 described later. Step 3: On the surface of the insulating layer 2, a metal film to be a flow detection circuit conductor (upstream temperature sensing resistor) 3, a flow detection circuit conductor (heater) 4, and a flow detection circuit conductor (downstream temperature sensing resistor) 5 And these circuit conductors are formed into a desired shape by photolithography. As the metal film, Ni, Ni-F
e, Pt or the like is used to form a film by a vacuum evaporation method, a sputtering method, or the like. Step 4: The insulating layer 6 is formed on the surfaces of the flow rate detection circuit conductors 3, 4, and 5 by a sputtering method, a plasma CVD method, or the like. Step 5: In order to connect the flow detection circuit conductors 3, 4, 5 to an external circuit (not shown), a part of the insulating layer 6 is removed, and a part of the flow detection circuit conductors 3, 4, 5 (metal The surface of the film is exposed. Further, as a pre-process for forming the cavity 8 in the silicon substrate 1 in a process 8 described later, a part of the insulating layer 7 on the lower surface of the silicon substrate 1 is removed, and a part of the lower surface of the silicon substrate 1 (that is, the flow rate circuit The surface of the silicon substrate 1 corresponding to the lower side of the detection conductors 3, 4, 5 is exposed. Step 6: A metal film as an electrode pad 9 is formed in a desired shape by a lift-off method on the exposed portion where a part of the insulating layer 6 is removed. Au is mainly used as the electrode pad 9, but Au itself has low adhesion as a base, so that Au is used.
A metal film of Cr, Ti, or the like is formed as an intermediate layer underneath. Step 7: A protective film 10 (insulating layer) is formed on the surface of the insulating layer 6 and the electrode pad 9 to protect the insulating layer 6 and the electrode pad 9 when the cavity 8 is formed in the silicon substrate 1 in the step 8 described later. ) Is formed. Step 8: The silicon substrate 1 is partially removed from the exposed portion of the insulating layer 7 formed in Step 5 by anisotropic etching using a potassium hydroxide solution as an etchant, thereby forming the insulating layer 2 described above. Is formed to expose the back side to the back side. Step 9: protective film 10 on surfaces of insulating layer 6 and electrode pad 9
Is removed using buffered hydrofluoric acid to expose the metal film of the electrode pad 9. After that, a lead wire is connected to the electrode pad 9 by wire bonding, and an external circuit (not shown) is connected via the lead wire.

As described above, the flow sensor according to the present embodiment is manufactured by the above steps 1 to 9. That is, according to the sensor manufacturing method of the present embodiment, the insulating layer 2 and the insulating layer 7 are formed on the upper and lower surfaces of the silicon substrate 1, and the flow rate detection circuit conductors 3, 4, and 5 are formed on the surface of the insulating layer 2, Each flow detection circuit conductor 3, 4,
5, an insulating layer 6 is formed on the surface of the silicon substrate 1, an electrode pad 9 is formed on a portion where the insulating layer 6 is partially removed, and a protective film 10 is formed on the surface of the insulating layer 6 and the electrode pad 9. In order to form the cavity 8 and finally remove the protective film 10,
The flow sensor can be manufactured in a complete state without causing peeling of the electrode pad 9 or breakage of the sensor.

In this case, during the anisotropic etching in the step 8, the potassium hydroxide solution completely etches the silicon substrate 1 and hardly etches the insulating layers 2, 6, and 7; If the time of the reactive etching is long, conventionally, the insulating layer 6 under the electrode pad 9 is removed, and the electrode pad (metal film) 9 is peeled off. However, in this embodiment, since the surfaces of the insulating layer 6 and the electrode pad 9 are covered with the protective film 10 before performing the anisotropic etching,
The intrusion of the potassium hydroxide solution into the interface side of the electrode pad 9 can be reliably prevented, whereby the separation of the electrode pad 9 can be prevented. In addition, unlike the conventional manufacturing method of forming a pattern of a metal film after forming a cavity, it is possible to prevent a problem that an insulating layer is easily damaged and a sensor is easily damaged. In the present embodiment, the method of manufacturing a sensor device having a configuration in which the cavity 8 is formed by etching from the lower surface of the substrate 1 has been described as an example, but the flow rate detection circuit conductors 3, 4, 5, etc. of the substrate 1 are formed. Needless to say, the present invention can also be applied to a method of manufacturing a sensor device having a configuration in which a cavity 8 having a concave portion with a bottom is formed in the substrate 1 from the upper surface side of the substrate 1.

[0013]

As described above, according to the present invention, the following effects can be obtained. After covering the insulating layer on the conductor surface of the substrate and the surface of the electrode with a protective film, a cavity is formed in the substrate by anisotropic etching, preventing the anisotropic etching solution from entering the electrode side. Thus, peeling of the electrode can be prevented. In addition, since the protective film is removed with an etching solution for removing the protective film after the cavity is formed in the substrate, patterning becomes unnecessary, and damage to the insulating layer formed on the flow rate detection circuit conductor surface of the substrate can be prevented. Thus, damage to the sensor device can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view of a flow sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view illustrating a manufacturing process of the flow sensor according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Insulating layer 3, 4, 5 Flow rate detection circuit conductor 6, 7 Insulating layer 8 Cavity

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01P 5/10 G01F 1/68

Claims (1)

(57) [Claims] 1. A thin-film sensor portion having a heating means for heating a fluid to be measured is formed on a substrate, and a space portion for thermally insulating the sensor portion is formed on a substrate below the sensor portion. In addition, in the method for manufacturing a sensor device in which an electrode for electrically connecting the sensor unit to an external circuit outside the substrate is formed on the substrate, the method further includes a heating unit configured to heat a fluid to be measured on the substrate. Forming a thin-film sensor portion and forming an electrode for electrically connecting the sensor portion to an external circuit outside the substrate; and a protective film for protecting the thin-film sensor portion and the surface of the electrode. Forming, and removing a part of the protective film so as to expose a predetermined surface of the substrate in order to form a space in the substrate below the sensor unit for thermally insulating the sensor unit. Process and a predetermined process of the substrate Forming a space by etching the surface, and removing the remaining portion of the thin film of the protective film covering the sensor portion and the surface of the electrode. .