JPH11233303A - Heat generating type thin-film element sensor and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat generating type thin-film element sensor having high durability and detection accuracy. SOLUTION: This sensor is provided with a cavity part 14, which is open in the lower side of a substrate 10 and a conductive film 13 which is formed on the surfacial side of the substrate 10 via an insulation layer 12. A heat generating part 20 is provided in the cavity part 14, under the conductive film 13 with the insulation layer 12 in between. The substrate 10 is formed of a wafer of semiconductor single crystal type, and the heat generating part 20 is formed of diffused part in which specified impurities are diffused in a semiconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-generating thin-film element sensor having a heat-generating thin-film element for detecting relative humidity, relative flow rate, gas, etc. from a change in resistance of a thin-film element in a heat-generating state, and a method of manufacturing the same. About.

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional sensor provided with a heating type thin film element of this type has a lower insulating film 2 formed on an upper surface of a semiconductor substrate 1 made of, for example, silicon single crystal. In some cases, a conductive film 3 made of a thin film including a heat-generating portion, a current-carrying portion, and an electrode portion was provided. The conductive film 3 is provided on the semiconductor substrate 1.
A cavity 4 is formed to open downward on the opposite side to the lower insulating film 2. The cavity 4 was formed by anisotropic etching, and the heat-generating thin-film element 5 was constituted by the lower insulating film 2 in the cavity 4 and the conductive film 3 including the heat-generating portion. Further, on the lower insulating film 2, an upper insulating film 6 was provided so as to cover the heat generating portion of the conductive film 3.

[0003] Production of a sensor having the heat generating thin film element 5 forms a lower insulating film 2 by SiO ₂ or Ta ₂ O ₅ or the like by sputtering on the upper surface of the semiconductor substrate 1 of silicon single crystal or the like, on which Then, a conductive film 3 such as Pt is formed, and is formed into a predetermined shape by etching or the like. On the surface of the lower insulating film 2, an upper insulating film 6 of SiO ₂ or Ta ₂ O ₅ is formed by sputtering or the like so as to cover the conductive film 3 if necessary. Next, anisotropic etching is performed from below the semiconductor substrate 1 to the lower insulating film 2 to form the cavity 4.

[0004]

A sensor provided with such a conventional heat-generating thin-film element is disclosed in US Pat.
In order to detect the humidity and the flow rate from the change in the resistance value of the conductive film 3 by changing the lower insulating film 2 into a beam shape, a current is applied to the conductive film 3 to increase the sensitivity, and the conductive film 3 is heated. The data to be detected was detected. Further, in order to remove dust and impurities on the surface of the conductor film 3, the surface can be removed by heating the surface to about 700 ° C., but the heating greatly reduces the durability of the conductor film 3. There was a problem.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and has as its object to provide a heat-generating thin-film element sensor having high durability and high detection accuracy, and a method of manufacturing the same.

[0006]

According to the present invention, there is provided a heat-generating thin-film element sensor comprising: a hollow portion opened below a substrate; a conductive film formed on a surface side of the substrate via an insulating layer; And a heat generating portion formed in the cavity on the opposite side via the insulating layer. The substrate is a semiconductor single crystal wafer, and the heat generating portion is a diffusion portion in which a predetermined impurity is diffused into the semiconductor. The conductive film and the electrode of the heat generating portion are separately provided on the surface side of the substrate.

In this heat-generating thin-film element sensor, a conductive film serving as a detecting portion and a heat-generating portion for heating the conductive film are separately formed via an insulating layer. At the time of detection, a current is applied to the heat generating portion to heat the conductive film to a predetermined temperature to perform a predetermined detection. If dust or the like adheres to the surface,
The conductive portion is heated to a high temperature by the heat generating portion to remove dust.

According to the method of manufacturing a heat-generating thin-film element sensor of the present invention, a heat-generating portion having a predetermined pattern is formed on a substrate, an insulating layer is formed on the surface side of the heat-generating portion, and a conductive film is formed on the surface of the insulating layer. Forming, etching from the back side of the substrate toward the heat generating portion to form a cavity on the back surface of the substrate and leave the heat generating portion in the cavity by a method of manufacturing a heat generating type thin film element sensor. is there.

In particular, according to the method of manufacturing a heat-generating thin-film element sensor of the present invention, an impurity diffusion portion serving as a heat-generating portion having a predetermined pattern is formed on a semiconductor substrate. Then, an insulating layer is formed on the surface of the substrate on which the impurity diffusion portions are formed, and a conductor film is formed on the surface of the insulating layer. Further, an insulating layer that covers and protects the conductive film is formed. Thereafter, anisotropic etching is performed from the rear surface side of the substrate toward the impurity diffusion portion to form a cavity in the rear surface of the substrate. At this time,
The anisotropic etching is performed so that the impurity diffusion portion is selectively left without being etched.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the heat-generating thin-film element sensor according to the present invention will be described below with reference to the drawings. The heat-generating thin-film element sensor of this embodiment has a semiconductor substrate 10 made of silicon (Si) single crystal, and a cavity 14 opened downward is formed in the semiconductor substrate 10. , SiO ₂ and a thin insulating layer 12 of about 1 μm.

On the surface of the substrate 10, a conductive film 13 having a thickness of about 4000 to 5000 ° is formed in a U shape on the surface of the insulating layer 12. The conductive film 13 is made of platinum (Pt)
And a metal thin film having a large temperature coefficient, such as titanium or titanium (Ti). At both ends of the conductive film 13, as shown in FIG.
An electrode 18 is formed on the side of the surface of the substrate 10. Further, on the surface of the conductor layer 13, a protective film 1
An insulating layer 16 of SiO ₂ as thin as about μm is laminated.

On the back side of the insulating layer 12 in the cavity 14,
The heating portion 20 is formed in a U-shape along the conductor film 13. The heat generating portion 20 is made of P ⁺ Si in which boron (B), which is an impurity, is diffused in silicon at a high concentration. The boron concentration of the heat generating part 20 as the impurity diffusion part is, for example, about 10 ²⁰ cm ⁻³ .

Diffusion portions 26 extending from both ends of the U-shaped heat generating portion 20 extend to the side of the substrate 10 along the back surface of the insulating layer 12 and are formed on the surface of the substrate 10 as shown in FIG. It is connected to the electrode 28. Surface electrode 28 and diffusion part 2
The connection with the end of 6 is such that a window is formed in the insulating layer 12 at the position of the electrode 28, and the electrode 28 and the diffusion portion 26 are connected by forming the electrode 28.

Next, a method of manufacturing the heat-generating thin-film element sensor according to this embodiment will be described with reference to FIG. In this manufacturing method, first, as shown in FIG.
An oxide film 22 is formed on the surface of the i-single-crystal substrate 10, and a window 24 is opened in a pattern forming the shape of the heat generating portion 20.
Then, a P-type dopant such as boron is diffused into the Si substrate 10 at a high concentration. Thereby, impurity diffusion portion 26 is formed in a predetermined shape.

After that, the oxide film 22 is removed, and FIG.
As shown in FIG. 1, an insulating film 12 is formed on the surface of the substrate 10 by sputtering or the like. Furthermore, the conductor film 1 of a metal thin film
3 is formed on the surface of the insulating film 12. As a method of forming into a predetermined shape, a metal thin film is formed on the entire surface by vapor deposition or sputtering and then etched, as shown in FIG.
The conductor film 13 is formed in a predetermined shape.

Next, anisotropic etching is performed from the back side of the substrate 10 so that the impurity diffusion portions 26 forming the heat generating portions 20 are selectively left as shown in FIG. The impurity diffusion portion 26 is made of KOH (potassium hydroxide), TMAH
When Si is anisotropically etched with an alkali etchant such as (tetramethylammonium hydroxide), it remains without being selectively etched.

The heat-generating thin-film element sensor according to this embodiment comprises:
A conductive film 13 serving as a detection portion and a heat generating portion 20 are separately provided via the insulating layer 12. Even when the conductive film 13 becomes dirty, the heat generating portion 20 is heated to, for example, about 700 ° C. Should be heated, heating is performed uniformly and appropriately,
Heat is not concentrated on a part of the conductor, and there is no disconnection. Therefore, the durability of the sensor is extended and the reliability is high. Further, also in heating at the time of detection, the conductor 13 is indirectly heated to, for example, 200 to 300 ° C. by the heat generating unit 20, so that it is not necessary to constantly supply a current necessary for heat generation to the conductor 13, which is necessary for detection. It is only necessary to pass an appropriate current, and the durability of the conductor portion 13 is further increased. Further, since the electrodes 18 and 28 are separately provided on the front side of the substrate 10, connection to the detection circuit and the heat generation circuit is also easy.

The heating type thin film element sensor and the method of manufacturing the same according to the present invention are not limited to the above-described embodiment.
Other semiconductors and insulators may be used other than the i single crystal.
Further, for the insulating layer, SiO ₂ , Ta ₂ O ₅ or the like can be appropriately selected. The heat generating portion may be formed by diffusing boron or by diffusing other impurities.In addition to selectively etching by diffusion, the heat generating portion may be formed in a predetermined shape on the substrate surface by vapor deposition or the like to form an insulating layer. Another substrate may be etched to form a heat generating portion in a predetermined shape on the back surface of the insulating layer.

[0019]

According to the heat generating type thin film element sensor of the present invention, it is not necessary to apply a large current directly to the conductive film to be detected to generate heat, and the conductive film is indirectly heated by the heat generating portion. In this case, unevenness in heating does not occur and the temperature is not locally increased, and the durability of the sensor is improved. In addition, the detection portion can be easily cleaned by setting the temperature of the heating portion to a high temperature.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of one embodiment of a heat-generating thin-film element sensor according to the present invention.

FIG. 2 is a longitudinal sectional view of the heat-generating thin-film element sensor according to the embodiment.

FIG. 3 is a longitudinal sectional view showing a manufacturing process of the heat-generating thin-film element sensor of this embodiment.

FIG. 4 is a partially cutaway plan view of the heat-generating thin-film element sensor of this embodiment.

FIG. 5 is a longitudinal sectional view of a heat-generating thin-film element sensor according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 12 Insulating layer 13, 16 Conductive film 14 Cavity 20 Heating part

Claims (5)

[Claims] 1. A hollow portion opened below a substrate, a conductive film formed on a surface side of the substrate via an insulating layer, and a hollow portion opposite to the conductive film and the insulating layer via the insulating layer. A heat-generating thin-film element sensor having a formed heat-generating portion. 2. The heat-generating thin-film element sensor according to claim 1, wherein the substrate is a semiconductor single crystal, and the heat-generating portion is a diffusion portion in which a predetermined impurity is diffused in the semiconductor. 3. The heat-generating thin-film element sensor according to claim 1, wherein the conductive film and the electrode of the heat-generating portion are separately provided on the surface side of the substrate. 4. A heat generating portion having a predetermined pattern is formed on a substrate, an insulating layer is formed on a front surface side of the heat generating portion, a conductor film is formed on a surface of the insulating layer, and the heat generating portion is formed from a back surface of the substrate. And forming a cavity in the back surface of the substrate and leaving the heating section in the cavity. 5. An impurity diffusion portion serving as a heating portion having a predetermined pattern is formed on a semiconductor substrate, an insulating layer is formed on the surface of the substrate on which the impurity diffusion portion is formed, and a conductive film is formed on the surface of the insulating layer. Forming a cavity on the back surface of the substrate and selectively leaving the impurity diffusion portion as the heating portion to form a heating portion. Manufacturing method of sensor.