KR100395246B1 - Resistance thermometer device for micro thermal sensors and its fabrication method - Google Patents

Abstract

The present invention relates to a RTD type temperature sensor formed using a silicon substrate and a magnesium oxide film as an intermediate layer, and a manufacturing method thereof.

To this end, the silicon substrate is washed before the natural oxide film of the silicon substrate is removed, the natural oxide film of the silicon substrate is removed, the natural oxide film of the silicon substrate is removed, a thermal oxide film is deposited, and a magnesium oxide film is deposited on the thermal oxide film. And depositing a platinum thin film on the deposited magnesium oxide film.

Description

RTD type temperature sensor for micro thermal sensor and its manufacturing method {Resistance thermometer device for micro thermal sensors and its fabrication method}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a temperature resistance resistor type temperature sensor and a method for manufacturing the same, and more particularly, to a platinum thin film type temperature sensor formed using a silicon substrate and a magnesium oxide film as an interlayer.

In general, microelectromechanical systems using silicon micromachining technology is accelerating research and development to enable small size, light weight, low cost, high-speed response, integration and mass production. To date, platinum thin film type resistance thermometers have been manufactured on alumina substrates. However, since the development of micro thermal sensors requires the integration of temperature sensors, the production of RTD type temperature sensors is required on silicon substrates. In particular, micro thermal sensors (including gas sensors, flow / flow sensors, vacuum sensors, and acceleration sensors) play an important role in optimizing the characteristics of the sensor's sensitivity, selectivity, and response time. Therefore, the development of micro thermal sensor temperature sensor with low power consumption, accurate operating temperature control, low thermal capacity, easy sensor array, high resistance temperature coefficient, and easy integration, and excellent linearity of resistance change with temperature It is required.

Currently, a temperature sensor for a micro thermal sensor using a temperature sensor using a pn junction diode and a thin film type RTD temperature sensor using platinum as a sensor material has been studied. In the case of a temperature sensor using a pn junction diode, there is an advantage that it can be manufactured using a process for manufacturing CMOS, but the linearity of the output value due to temperature change is poor. The thin film type RTD temperature sensor is capable of precise temperature control by the excellent thermal and chemical properties of platinum, high resistance temperature coefficient and excellent linearity of resistance change with temperature over wide temperature range. In the case of manufacturing a thin film type RTD temperature sensor on a silicon substrate, since the adhesion property of platinum to the thermal oxide film is poor, research and development are being conducted to manufacture using an intermediate layer such as chromium or aluminum oxide.

However, when the metal is used, the metal material used as the intermediate layer in the high temperature heat treatment process for the crystallization of the platinum thin film reacts with the platinum, thereby lowering the intrinsic properties of the platinum and the adhesion properties. Platinum has a melting point ( 1780 ° C.) is a material that is quite high and requires the heat treatment at a high temperature of 1000 ° C. or more for the platinum thin film to have bulk characteristics. As such, it is more stable to use a dielectric material rather than a metallic material as an intermediate layer in order to improve adhesion characteristics without reaction with platinum at a high temperature. Therefore, by using such a dielectric material, a temperature sensor for improving adhesion characteristics without reaction with platinum at a high temperature is used. Development is required.

Accordingly, an object of the present invention is to avoid reaction with the platinum thin film during high temperature heat treatment on a thermally oxidized silicon substrate that is easy to integrate, and has excellent insulation properties, and can improve adhesion properties of sensing materials. The present invention provides a temperature resistance resistor temperature sensor and a method of manufacturing the same.

Another object of the present invention is a temperature resistance resistor temperature sensor for micro thermal sensors using platinum as a sensing material having high chemical and thermal stability and good response characteristics by using a magnesium oxide thin film which is an ionic oxide having excellent heat resistance as a medium. In providing a method.

It is still another object of the present invention to provide a platinum thin film type temperature resistance temperature sensor for a micro thermal sensor and a method for manufacturing the same, which are lightweight, small size, high-speed response, mass production, and easy sensor array using a thermally oxidized silicon substrate and a magnesium oxide film as intermediate layers. Is in.

Still another object of the present invention is to provide a resistance thermometer for a micro thermal sensor, and a method of manufacturing the same, which can avoid a reaction between a substrate and a sensing material that may affect the characteristics of the sensor at a high temperature.

1 is a cross-sectional view showing the structure of a temperature sensor according to an embodiment of the present invention

Figure 2 is a SEM image of the surface of the intermediate layer magnesium oxide thin film deposited by reactive sputtering on the thermally oxidized silicon substrate of the present invention.

Figure 3 is a SEM image of the surface of the platinum thin film deposited on the thermally oxidized silicon substrate of the present invention as a medium layer of a magnesium oxide film.

Figure 4 is an XRD diffraction pattern of the heat treatment of the platinum thin film deposited on the thermally oxidized silicon substrate of the magnesium oxide film as a media layer.

Figure 5 is a graph of the change in the resistivity value of the platinum thin film deposited on the thermally oxidized silicon substrate of the present invention as a medium layer of a magnesium oxide film.

FIG. 6 is a graph showing resistance temperature coefficient change and resistance change rate according to temperature of a platinum thin film type RTD temperature sensor manufactured on a silicon substrate and an alumina substrate according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: silicon substrate 110: thermal oxide film

120: magnesium oxide film 130: platinum thin film layer

140: shield

The thin film type RTD temperature sensor according to the present invention for achieving the above object is formed by sequentially forming a thermal oxide film and a magnesium oxide film on a silicon substrate, characterized in that the platinum thin film layer is formed using a magnesium oxide film as a mediating layer.

In the method of manufacturing the RTD temperature sensor of the present invention for achieving the above object, a process of removing a natural oxide film of a silicon substrate, a process of depositing a thermal oxide film after removing the natural oxide film of the silicon substrate, and on the thermal oxide film And a process of depositing a magnesium oxide film and depositing a platinum thin film on the deposited magnesium oxide film using a high frequency sputtering method.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

On the platinum thin film layer of the RTD temperature sensor of the present invention, a protective film for insulation from the outside of the sensing material is formed, conductive wires are bonded, and micro-processed silicon substrates by micromachining technology, and are light, small, high-speed response, The RTD temperature sensor for micro thermal sensors can be easily realized in mass production and sensor array.

The thermal oxide film, the magnesium oxide film and the platinum thin film layer are formed by a semiconductor manufacturing process. For example, a thermal oxide film is formed by a thermal oxidation method in a semiconductor manufacturing process, and a magnesium oxide film and a platinum thin film layer are formed by depositing reactive and magnetron high frequency sputtering, respectively, and each of the thermal oxide film, magnesium oxide film, and platinum thin film layer has a thickness of about 1 μm. to be.

In addition, the electrical and physical properties of the intermediate layer magnesium oxide film and the platinum thin film formed by reactive sputtering were analyzed by a four-point probe, a SEM, and an XRD. In addition, after fabricating a thin film type RTD temperature sensor on a silicon substrate and an alumina substrate, the resistance temperature coefficient value and the resistance change rate according to temperature were measured and compared and evaluated.

1 is a cross-sectional view showing the structure of a temperature sensor according to an embodiment of the present invention.

Referring to FIG. 1, a thermal oxide film 110 is deposited on a silicon substrate 100, a magnesium oxide film 120 is deposited on the thermal oxide film 11, and platinum is deposited on the magnesium oxide film 120. A plurality of thin film layers 130 are formed at set intervals. In addition, a conductive wire is bonded on the platinum thin film layer 130, and a protective film 140 for insulating the outside of the sensing material is formed.

In addition, the silicon substrate 100 is finely processed by micromachining technology, and can manufacture a temperature resistance resistor temperature sensor for a micro thermal sensor that is lightweight, small size, high-speed response, mass production and easy to array the sensor, for the micro thermal sensor The RTD temperature sensor includes a gas sensor, a flow / flow sensor, a vacuum sensor, an acceleration sensor, and the like.

The thermal oxide film 110, the magnesium oxide film 120, and the platinum thin film layer 130 are formed by a semiconductor manufacturing process.

For example, the silicon substrate 100 used in the present invention is a N-type or P-type resistivity of about 4 ~ 5Ω · cm, 530㎛ thickness after the basic cleaning process of the semiconductor process and remove the natural oxide film, and then the thermal oxide film ( A silicon substrate on which 110) was grown by 1 mu m was used. In order to improve the adhesion characteristics of the thermal oxide film 110 and the platinum thin film layer 130, the magnesium oxide film 120 was deposited by 1 μm by reactive sputtering using a target of the magnesium oxide 120.

The platinum thin film layer 130, which is a temperature sensor material, was deposited with platinum, which is a sensor material, by 1 μm by high frequency sputtering. The heat treatment characteristics of the magnesium oxide film 120 formed by reactive sputtering and the effect on the platinum thin film layer 130 were analyzed by using a 4-point probe, α-step, SEM, and XRD after a high temperature heat treatment in a nitrogen atmosphere using a quartz tube. And analyzed. Table 1 shows the deposition and heat treatment conditions of the magnesium oxide film 120 and the platinum thin film layer 130.

In the present invention, the temperature sensor is manufactured in the structure shown in FIG. 1 using the silicon substrate 100. In addition, the pattern of the temperature sensor before the heat treatment was formed by a photolithography process and analyzed after the heat treatment. After spin coating SOG (spin-on-glass), 100 ° C (30 minutes), 200 ° C (30 minutes), 350 ° C (30 minutes), and 500 ° C (30 minutes) in air ) Was used as a protective film for insulation from the outside of the sensing material by sequentially baking (), and the platinum wire was bonded using a silver epoxy (silver epoxy).

In addition, the characteristics of the fabricated temperature sensor were analyzed in a closed system that can control the atmospheric gas and the degree of vacuum to minimize the effects of convection.

2 is a SEM image of the surface of the magnesium oxide thin film 120 deposited on the thermally oxidized silicon substrate of the present invention. (a) is the surface SEM photograph which is not heat-treated, and (b) is the surface SEM photograph which was heat-processed at 1000 degreeC.

Prior to heat treatment, the microstructures were easily formed in an amorphous form. When comparing before and after heat treatment (1000 ° C., 2 hours) of FIGS. 2 (a) and 2 (b), the entire thin film showed uniform surface characteristics and no pinholes or cracks were formed due to high temperature heat treatment. Therefore, it can be seen that the platinum thin film can obtain the same characteristics as before the heat treatment even after the heat treatment at 1000 ° C.

3 is a surface SEM photograph according to the heat treatment of the platinum thin film deposited on the magnesium oxide thin film of the present invention. (a) is the surface SEM photograph which is not heat-treated, and (b) is the surface SEM photograph which was heat-processed at 1000 degreeC.

FIG. 3 (a) shows uniform surface properties advantageous for forming a micropattern on the surface of the platinum thin film before heat treatment. However, by performing the heat treatment of the platinum thin film layer 130 at 1000 ° C. for 2 hours as shown in FIG. 3 (b), crystal grains are formed and the boundaries of the particles are remarkably and electrically unstable, and the gaps between structural cracks are in close contact. have. The sheet thickness and resistivity of the platinum thin film layer 130 were 0.246 Ω / □ and 24.6 μΩ · cm, respectively, before the heat treatment, and the sheet resistance and resistivity of the platinum thin film layer were 0.1288 Ω / □ and 12.88 μΩ · cm, respectively. It can be seen that the specific resistance is close to 10.8 μΩcm. Therefore, it can be seen that the platinum thin film is greatly improved by performing high temperature heat treatment.

Figure 4 shows the XRD diffraction pattern analysis results of the heat treatment of the platinum thin film layer 130 deposited on the magnesium oxide thin film 120 of the present invention.

In the diffraction pattern of the platinum thin film layer 130, it can be seen that only the platinum peak is prominent in the vicinity of 2 = 39.6 ° before and after the heat treatment, and the indensity is further increased and the residual peak is significantly reduced by performing the high temperature heat treatment. have. Therefore, it can be seen that even after the heat treatment, the platinum thin film layer 130 does not react with the magnesium oxide thin film 120 and has unique platinum properties.

5 shows a change in specific resistance according to the heat treatment temperature of the platinum thin film deposited on the magnesium oxide thin film 120 of the present invention.

The heat treatment time was fixed at 2 hours, and as the heat treatment temperature was increased, the specific resistance value was closer to bulk platinum. It can be seen that due to the crystal grain formation of platinum at 1000 ° C., various structural defects in the thin film are reduced, thereby improving the resistivity of the thin film. However, when the high temperature heat treatment above 1000 ℃, due to the excessive heat treatment, the formation of the island due to the growth of the grain and the hole is formed in the part without the thin film on the substrate, the characteristics of the thin film was greatly reduced.

6 (a) and 6 (b) show the resistance temperature coefficient and the resistance change rate according to the platinum thin film type RTD temperature sensor according to the embodiment of the present invention, respectively.

The resistance temperature coefficient and resistance change rate of the temperature sensor fabricated on the silicon substrate 100 on the magnesium oxide thin film 120 and on the silicon substrate (alumina substrate) 100 are as follows.

The resistance change rate was measured in a temperature range from room temperature to 400 ° C. in an electric furnace, which is a nitrogen atmosphere. The characteristics of the platinum thin film type RTD temperature sensor fabricated using the magnesium oxide thin film 120 on the silicon substrate 100 as the intermediate layer were similar to those of the thin film type temperature sensor fabricated on the silicon substrate 100. .

In FIG. 6 (a), the resistance temperature coefficient of the sample 1 temperature sensor had an average value of 3927 ppm / ° C. close to bulk platinum. In addition, as a result of analyzing the standard deviation of the temperature coefficient of resistance, very good linearity of 0.7 ppm / ℃ per 1 ℃ was obtained.

6 (b) shows the resistance temperature coefficient of (a) as the resistance change rate. It can be seen that the resistance change rate due to temperature change is almost a straight line and the linearity is good.

While the embodiments of the present invention have been described so far, the present invention is not limited thereto, and various embodiments that can be modified and changed within the true spirit and scope of the principles described and claimed in the present specification are within the protection scope of the present invention. It should be understood that it belongs.

As described above, according to the present invention, the platinum thin film type resistance thermometer for a micro thermal sensor using a thermally oxidized silicon substrate and a magnesium oxide film as a medium layer has a reaction between a substrate and a sensing material that may affect the characteristics of the sensor at a high temperature. The temperature sensor for the micro thermal sensor, which can be avoided and improves the adhesion property of the sensing material, in particular, the silicon substrate which is easy to finely process by micromachining technology, and the chemical and thermal stability and the linear response characteristic is excellent. In addition to the sensor, when developing an integrated micro thermal sensor by micromachining technology, there is an effect that can be usefully used as a temperature sensor and a micro heating element.

In addition, the resistance temperature coefficient of the platinum thin film type RTD type temperature sensor fabricated on the thermally oxidized silicon substrate using a magnesium oxide film as a medium layer in the temperature range of 25 ~ 400 ℃ is 3927ppm / ℃, which is equivalent to bulk platinum and has excellent linearity. There is.

In addition, since the silicon substrate is used, there is an advantage in that light weight, small size, high speed response, mass production, and sensor array are easy due to the ease of fine processing.

Claims (13)

Silicon substrate A thermal oxide film deposited on the silicon substrate; A magnesium oxide film deposited on the thermal oxide film and Comprising a plurality of platinum thin film layer formed at a predetermined interval on the magnesium oxide film A conductive wire is bonded to the platinum thin film layer and forms a protective film for insulation from the outside of the sensing material. The silicon substrate is micro-machined by micromachining technology, light weight, small size, high-speed response, mass production and sensor array to facilitate the thin film platinum thin film type resistance thermometer type temperature sensor. delete delete The method of claim 1, The magnesium oxide film, target: magnesium oxide, substrate temperature: room temperature, gas flow rate: Ar (72 sccm), O ₂ (8 sccm), initial vacuum: 1 × 10 ^-6 Torr or less, working vacuum: 20 mTorr, input Powder: A platinum thin film type resistance thermometer for micro thermal sensors, characterized in that it is formed by reactive sputtering under a condition of 150 W and is subjected to high temperature heat treatment in an N ₂ gas atmosphere. The method of claim 1, The platinum thin film layer, target: platinum, substrate temperature: room temperature, gas flow rate: Ar (80 sccm), initial vacuum: 1 × 10 ^-6 Torr or less, working vacuum: 20 mTorr, input powder: 90 W sputtering And a high temperature heat treatment in an N ₂ gas atmosphere to form a platinum thin film type resistance thermometer for a micro thermal sensor. In the manufacturing method of the platinum thin film type RTD type temperature sensor for micro thermal sensor Cleaning the silicon substrate Removing the natural oxide film of the silicon substrate Removing the native oxide film of the silicon substrate and depositing a thermal oxide film; Depositing a magnesium oxide film on the thermal oxide film; Depositing a platinum thin film on the deposited magnesium oxide film; Bonding a conductive wire on the platinum thin film layer; After bonding the conductive wire, forming a protective film for insulation from the outside of the sensing material, characterized in that the platinum thin film type resistance thermometer type temperature sensor for a thermal sensor. delete The method of claim 6, Depositing the magnesium oxide film is Target: Magnesium oxide, Substrate temperature: Room temperature, Gas flow rate: Ar (72 sccm), O ₂ (8 sccm), Initial vacuum: 1 × 10 ^-6 Torr or less, Working vacuum: 20 mTorr, Input power: 150 W Performing reactive sputtering under conditions After the reactive sputtering, the method of manufacturing a high temperature platinum thin film type resistance temperature sensor for a micro thermal sensor, characterized in that the step of performing a high temperature heat treatment in an N ₂ gas atmosphere. The method of claim 6, Depositing the platinum thin film is Target: Platinum, Substrate temperature: Room temperature, Gas flow rate: Ar (80 sccm), Initial vacuum: 1 × 10 ^-6 Torr or less, Working vacuum: 20 mTorr, Input powder: 90 W After the sputtering, a high temperature heat treatment in a N ₂ gas atmosphere, characterized in that the platinum thin film type resistance thermometer type temperature sensor for a thermal sensor. The method of claim 6, The thermal oxide film, the magnesium oxide film, and the platinum thin film are each deposited to have a thickness of 1 ㎛ platinum thin film type resistance thermometer type temperature sensor for a thermal sensor characterized in that the deposition. delete The method of claim 6, The magnesium oxide film and the platinum thin film is a method of manufacturing a platinum thin film type resistance temperature sensor for a micro thermal sensor, characterized in that the deposition by using a high frequency sputtering method. The method of claim 9, The high temperature heat treatment is a platinum thin film type resistance thermometer type temperature sensor for a micro thermal sensor, characterized in that the heat treatment at 1000 ℃ for 2 hours.