JP2000275078A - Thin-film heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent wiring from being deteriorated due to the concentration of electrodes on the inner wall of a bending part by forming the bending part of the heater wiring with a material with different quality of low resistance so that the bending part has a lower resistance than that of a body part, or by increasing a sectional area. SOLUTION: On the surface of a semiconductor substrate 2 consisting of a silicon substrate, an insulation layer 3 made of silicon oxide is subjected to thin-film formation, and a pattern for etching the semiconductor substrate 2 is formed in the insulation layer 3. Then, on the insulation layer 3, a thin-film heater 11 and upstream- and downstream-side temperature sensing resistors 12 and 13 are formed, and, on them, a protection film made of the silicon oxide is formed. Then, onto the protection film, a contact hole such as wire pads 11a and 11b, and the pattern for etching the semiconductor 2 are formed, and gold is deposited for forming the wire pad 11a and 11b or the like. Finally, the semiconductor substrate 2 is etched, and a void part 4 is formed, thus lowering the amount of generation of heat of the bending part, and suppressing the deterioration of an inner wall when the thin-film heater 11 is allowed to generate heat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-film heater used for a heat-sensitive flow sensor and the like, and more particularly to a thin-film heater which suppresses deterioration at a bent portion of a heater wiring.

[0002]

2. Description of the Related Art Conventionally, a heat-sensitive flow sensor using a thin-film heater has been proposed for measuring the flow rate and flow rate of a fluid such as gas or liquid. This heat-sensitive flow sensor has a configuration in which a thin film heater and two temperature sensors are arranged on both sides of the thin film heater on the surface of a bridge portion having a bridge structure formed on the surface of a semiconductor substrate.

[0003] This thermal flow sensor utilizes the fact that the temperature distribution of heat generated by passing an electric current through a thin film heater changes according to the flow rate and flow velocity of a fluid, and the amount of change is applied to both sides of the thin film heater. This is detected by a provided temperature sensor.

FIG. 9 is a plan view (a) showing an example of such a conventional heat-sensitive flow sensor and a schematic cross-sectional view (b) thereof along the line AA.

In FIG. 1, a thermal flow sensor 1 is
The insulating layer 3 is formed as a thin film on the surface of the semiconductor substrate 2, and the central region of the semiconductor substrate 2 is removed by etching from the surface side to form the void portion 4.
The upper insulating layer 3 has a configuration in which the bridge portion 5 is formed in a cross-linked manner.

On the surface of the bridge portion 5, a thin-film heater 11 is formed by forming a heating element in a concave shape, and a fluid flow direction F (left-right direction in the drawing) is formed adjacent to the thin-film heater 11. An upstream temperature measuring resistor 12 is formed on the upstream side, and a downstream temperature measuring resistor 13 is formed on the downstream side. Wire pads 11 a and 11 b formed on the semiconductor substrate 2 outside the bridge portion 5 are connected to both ends of the heater wiring of the thin film heater 11.

[0007] The upstream resistance temperature detector 12 and the downstream resistance temperature detector 13 are formed, for example, by a platinum thin film resistor in a fluid flow direction F.
Are formed in a zigzag shape, and wire pads 12a, 12b and wire pads 13a, 13a formed on the semiconductor substrate 2 outside the bridge portion 5 are formed at both ends thereof.
b is connected.

In this configuration, the thermal flow sensor 1
Are arranged in a direction in which the longitudinal direction of the thin film heater 11 is orthogonal to the flow direction F of the fluid, and when a current flows between the wire pads 11a and 11b, the thin film heater 11 generates heat.

When there is no fluid flow, the thin film heater 11
Since the temperature distribution of the heat generated from the thin film heater 11 is symmetrical on both sides, the two temperature measuring resistors 1
2 and 13 have the same resistance value.

When the fluid flows, the upstream temperature measuring resistor 12
Is cooled by the flow of the fluid, and the downstream resistance temperature detector 13
Is heated by the heat of the thin film heater 11. Thereby, the resistance value of the upstream-side resistance thermometer 12 and the resistance value of the downstream-side resistance thermometer 1
There is a difference between the resistance value and the resistance value. The difference between the resistance values is the difference between the wire pads 12a and 12b and the wire pads 13a and 13b.
Is recognized as a difference between the voltage values. This difference increases as the flow velocity of the fluid increases, so that the flow velocity of the fluid can be measured.

[0011]

By the way, when the thin film heater 11 is heated by passing an electric current, as shown in FIG.
Electromigration causes electrons to concentrate near the inner wall of the bent portion of the heater wiring, and the current density only temporarily increases inside the bent portion, causing deterioration, and eventually breaking the heater wiring. was there.

The present invention has been made to solve such a conventional problem, and a thin film for suppressing deterioration of the heater wiring due to concentration of electrons on the inner wall of the bent portion of the heater wiring. It is an object to provide a heater.

[0013]

According to a first aspect of the present invention, there is provided a thin film heater comprising a plurality of linear main body portions and a heater wiring comprising a bent portion connecting between the main body portions. The curved portion is processed so as to have a lower resistance value than the main body portion.

According to the present invention, when the thin film heater generates heat, the bent portion is processed to have a lower resistance value than the main body portion, so that the calorific value is lower than that of the main body portion. This has the effect of suppressing deterioration of the inner wall of the device.

According to a second aspect of the present invention, there is provided the thin film heater according to the first aspect, wherein the bent portion of the heater wiring is made of a dissimilar material having a lower resistance value than the heating element constituting the main body. Is what it is.

According to the present invention, when the thin-film heater generates heat, electrons are concentrated near the inner wall of the bent portion of the heater wiring. However, the bent portion is made of a different material having a lower resistance than the main body. It has an effect that the amount of heat generation is low and deterioration on the inner wall of the bent portion of the heater wiring can be suppressed.

According to a third aspect of the present invention, there is provided the thin film heater according to the first aspect, wherein the bent portion of the heater wiring is made of a dissimilar material having a lower resistance value than a heating element constituting the heater wiring on the surface thereof. It is fixed.

According to the present invention, when the thin-film heater generates heat, electrons flow more frequently in the bent portion of the heater wiring toward the dissimilar material having a lower resistance value, so that deterioration of the inner wall of the bent portion of the heater wiring is suppressed. Has the effect of being able to.

According to a fourth aspect of the present invention, in the thin film heater according to the first aspect, the bent portion of the heater wiring is configured to be larger than the cross-sectional area of the main body.

According to the present invention, when the thin-film heater generates heat, the current density decreases due to the large cross-sectional area at the bent portion of the heater wiring, and the electromigration phenomenon hardly occurs. Has the effect of suppressing degradation in

According to a fifth aspect of the present invention, there is provided a thin film heater according to the first aspect, wherein the bent portion of the heater wiring has a resistance value at an outer edge or a center portion lower than a resistance value at an inner edge portion. It is configured.

According to the present invention, when the thin film heater generates heat, electrons easily flow to the outer edge or the center of the bent portion of the heater wiring where the resistance value is low, and the electrons concentrate on the inner edge of the bent portion. Therefore, it is possible to suppress deterioration of the inner wall of the bent portion of the heater wiring.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS. In the following description, the same components as those shown in FIG. 9 are denoted by the same reference numerals.

(Embodiment 1) FIG. 1 is a plan view of a heat-sensitive flow sensor using a thin-film heater according to Embodiment 1 of the present invention. The thermosensitive flow sensor 1 includes an insulating layer 3 formed on a surface of a semiconductor substrate 2 as a thin film, a gap 4 formed by etching a central region of the semiconductor substrate 2 from the front side, and an insulating layer on the gap 4. 3 has a bridge portion 5 formed in a cross-linking shape.

The heat-sensitive flow sensor 1 has a thin film heater 11 according to the present invention on the surface of the bridge portion 5, an upstream temperature measuring resistor 12 on the upstream side in the fluid flow direction F with respect to the thin film heater 11, and a downstream side. And the downstream temperature measuring resistors 13 are arranged respectively. The upstream temperature measuring resistor 12 and the downstream temperature measuring resistor 13 have wire pads 12a,
12b and wire pads 13a and 13b are connected respectively.

As shown in FIG. 2, the thin-film heater 11 has a linear main body 11A of the heater wiring formed by using a heating element M1 such as polysilicon, and a bent part 11B is formed of aluminum having a low resistance value. It is configured using such a dissimilar material M2. Note that wire pads 11 a and 11 b formed on the semiconductor substrate 2 outside the bridge portion 5 are connected to both ends of the thin film heater 11.

The method of manufacturing the thermosensitive flow sensor 1 is as follows.
First, an insulating layer 3 made of, for example, silicon oxide SiO2 is formed as a thin film on a surface of a semiconductor substrate 2 made of a silicon substrate having a high thermal conductivity. Next, a pattern for etching the semiconductor substrate 2 is formed on the insulating layer 3 later.

Next, a thin-film heater 11, an upstream temperature measuring resistor 12, and a downstream temperature measuring resistor 13 are formed on the insulating layer 3. Then, the thin film heater 11, the upstream temperature measuring resistor 12,
For example, silicon oxide SiO2 is placed on the downstream resistance temperature detector 13.
Is formed.

Next, a wire pad 11 is formed on the protective film.
A contact hole such as a and 11b and a pattern for etching the semiconductor substrate 2 are formed, and gold is deposited to form wire pads 11a and 11b. Finally, the semiconductor substrate 2 is etched to form the voids 4.

In this configuration, the wire pads 11a,
When a current is applied between the thin film heater 11 and the thin film heater 11 to generate heat, the bent portion 11B is made of a material having a lower resistance value than the main body portion 11A. Deterioration can be suppressed.

(Embodiment 2) FIG. 3 is a perspective view showing Embodiment 2 of a thin film heater according to the present invention. In the thin film heater 11 according to the present embodiment, the linear main body 11A and the bent portion 11B of the heater wiring are integrally formed of a heating element M1 such as polysilicon, and the heating element M1 is formed on the surface of the bent section 11B. It has a configuration in which a different material M3 such as aluminum having a lower resistance value is deposited and fixed.

In this configuration, the wire pads 11a,
When a current flows between the thin film heaters 11b to cause the thin film heater 11 to generate heat, electrons tend to flow to the dissimilar material M3 having a lower resistance value in the bent portion 11B of the heater wiring. Therefore, it is possible to suppress deterioration of the inner wall of the bent portion 11B of the heater wiring.

(Embodiment 3) FIG. 4 is a perspective view showing Embodiment 3 of a thin film heater according to the present invention. In the thin-film heater 11 according to the present embodiment, the linear main body 11A and the bent part 11B of the heater wiring are integrally formed by a heating element M1 such as polysilicon, and the bent part 11B is further formed by the main body 11A. It is made thicker by making it higher.

In this configuration, the wire pads 11a,
When a current flows between the thin films 11b and the thin film heater 11 generates heat, the electromigration phenomenon is less likely to occur because the current density decreases as the cross-sectional area of the wiring increases.
Therefore, it is possible to suppress deterioration of the inner wall of the bent portion 11B of the heater wiring.

(Embodiment 4) FIG. 5 is a perspective view showing Embodiment 4 of a thin film heater according to the present invention. In the thin film heater 11 according to the present embodiment, the linear main body 11A and the bent portion 11B of the heater wiring are integrally formed of a heating element M1 such as polysilicon, and the outer edge of the bent portion 11B is formed as the main body 11A. It is configured so that it is higher and thicker, and the cross-sectional area of the bent portion becomes larger.

In this configuration, the wire pads 11a,
When a current flows between the thin film heater 11b and the thin film heater 11 generates heat, the resistance value decreases because the outer edge of the bent portion 11B is thick,
Since electrons easily flow to the outer edge portion, the concentration of electrons on the inner wall of the bent portion 11B can be reduced. Therefore, it is possible to suppress deterioration of the inner wall of the bent portion 11B of the heater wiring.

(Embodiment 5) FIG. 6 is a plan view showing Embodiment 5 of a thin film heater according to the present invention. In the thin-film heater 11 according to the present embodiment, the linear main body 11A and the bent part 11B of the heater wiring are integrally formed by a heating element M1 such as polysilicon, and the bent part 11B is further formed by the main body 11A. It is configured to be wider and the cross-sectional area of the bent portion is increased.

In this configuration, the wire pads 11a,
When a current flows between the thin films 11b and the thin film heater 11 generates heat, the electromigration phenomenon is less likely to occur because the current density decreases as the cross-sectional area of the wiring increases.
Therefore, it is possible to suppress deterioration of the inner wall of the bent portion 11B of the heater wiring.

(Embodiment 6) FIG. 7 is a plan view showing a thin film heater according to Embodiment 6 of the present invention. In the thin-film heater 11 according to the present embodiment, the linear main body 11A and the bent portion 11B of the heater wiring are integrally formed by a heating element M1 such as polysilicon, and the outer edge of the bent portion 11B (see FIG. The portion indicated by the arrow B) is configured such that the resistance value is reduced by increasing the doping amount or the like.

In this configuration, the wire pads 11a,
When a current flows between the thin film heater 11b and the thin film heater 11 generates heat, electrons easily flow to the outer edge of the bent portion 11B of the heater wiring having a low resistance value, and the electrons concentrate on the inner edge of the bent portion 11B. Can be alleviated. Therefore, it is possible to suppress deterioration of the inner wall of the bent portion 11B of the heater wiring.

(Embodiment 7) FIG. 8 is a plan view showing Embodiment 7 of a thin film heater according to the present invention. In the thin-film heater 11 according to the present embodiment, the linear body portion 11A and the bent portion 11B of the heater wiring are integrally formed by a heating element M1 such as polysilicon, and furthermore, the central portion of the bent portion 11B (see FIG. The portion indicated by arrow C) is configured so that the resistance value is reduced by increasing the doping amount or the like.

In this configuration, the wire pads 11a,
When a current flows between the thin film heater 11b and the thin film heater 11 generates heat, electrons easily flow to the center of the bent portion 11B of the heater wiring having a low resistance value, and the electrons concentrate on the inner edge of the bent portion 11B. Can be alleviated. Therefore, it is possible to suppress deterioration of the inner wall of the bent portion 11B of the heater wiring.

[0043]

As described above, according to the present invention, the amount of heat generated by the bent portion of the heater wiring is reduced by processing the bent portion of the heater wiring so as to have a lower resistance value than the heating element constituting the main body. Since it can be kept low, an advantageous effect that deterioration of the inner wall of the bent portion can be suppressed can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a heat-sensitive flow sensor using a thin-film heater of the present invention.

FIG. 2 is a plan view of the thin-film heater according to the first embodiment of the present invention.

FIG. 3 is a perspective view of a thin-film heater according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a thin-film heater according to Embodiment 3 of the present invention.

FIG. 5 is a perspective view of a thin film heater according to a fourth embodiment of the present invention.

FIG. 6 is a plan view of a thin-film heater according to a fifth embodiment of the present invention.

FIG. 7 is a plan view of a thin-film heater according to a sixth embodiment of the present invention.

FIG. 8 is a plan view of a thin-film heater according to a seventh embodiment of the present invention.

9A is a plan view of a heat-sensitive flow sensor using a conventional thin-film heater, and FIG. 9B is a schematic cross-sectional view taken along line AA.

FIG. 10 is an explanatory diagram of an electromigration phenomenon.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Thermal flow sensor 2 Semiconductor substrate 3 Insulating layer 4 Void portion 5 Bridge portion 11 Thin film heater 11a, 11b Wire pad 11A Main body portion 11B Bent portion 12 Upstream temperature measuring resistor 12a, 12b Wire pad 13 Downstream temperature measuring resistor Body 13a, 13b Wire pad M1 Heating element M2, M3 Different materials

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Masaaki Sasaki 10F, Hanazono Todocho, Ukyo-ku, Kyoto City, Kyoto Prefecture F-term (reference) 2F035 EA04 EA08

Claims (5)

[Claims] 1. A heater wiring comprising a plurality of linear body portions and a bent portion connecting the main body portions, wherein the bent portion of the heater wire has a lower resistance value than the main body portion. A thin film heater characterized by being processed. 2. The thin film heater according to claim 1, wherein the bent portion of the heater wiring is made of a dissimilar material having a lower resistance value than a heating element constituting the main body. 3. The thin film heater according to claim 1, wherein a dissimilar material having a lower resistance value than a heating element forming the heater wiring is fixed to a surface of the bent portion of the heater wiring. . 4. The thin-film heater according to claim 1, wherein a bent portion of the heater wiring is configured to be larger than a cross-sectional area of the main body. 5. The thin film heater according to claim 1, wherein the bent portion of the heater wiring is configured such that a resistance value at an outer edge or a center portion is lower than a resistance value at an inner edge.