JP2008294288A - Thin film thermistor element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the adhesion strength of an electrode and a thermistor thin film, to attain a sufficient resistance value as the electrode and to suppress resistance value increase in a heat resistance test as well in a thin film thermistor element, and its manufacturing method. <P>SOLUTION: The thin film thermistor element comprises an Si substrate 2, a first thermistor thin film 5A and a second thermistor thin film 5B formed on the Si substrate 2 and a comb-shaped electrode 3 formed on the first thermistor thin film 5A and the second thermistor thin film 5B. For the combe-shaped electrode 3, at least a part to be in contact with the first thermistor thin film 5A and the second thermistor thin film 5B is an electrode layer composed of platinum or its alloy film-formed in an amorphous state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thin film thermistor element used for sensors such as a temperature sensor and a flow rate sensor, and a method for manufacturing the same.

  For example, thin film thermistor elements, which are sintered oxide semiconductors with a large negative temperature coefficient, are used as temperature sensors and flow sensors for information equipment, communication equipment, medical equipment, housing equipment, automotive transmission equipment, etc. It has been. In order to manufacture such a thin film thermistor element, a thermistor thin film is formed after first forming an electrode on the substrate and heat-treated at a temperature of 1400 ° C. or lower, and a thermistor thin film is formed on the substrate and heat-treated. In some cases, the electrode is formed later.

For example, in Patent Document 1, a base layer such as Cr (chromium) or Ti (titanium) is formed on an insulating substrate as an adhesive layer, and a Pt (platinum) layer is formed thereon at a substrate temperature of 650 ° C. to 750 ° C. Filmed thin film thermistors have been proposed.
Patent Document 2 proposes a thin film thermistor element in which a Pt thin film is formed after a thermistor thin film is first formed on an alumina substrate.
Furthermore, Patent Document 3 proposes a thin film thermistor in which a thermosensitive film of thermistor material is provided on a ceramic substrate, a metal underlayer having high adhesion such as Cr or Ti is formed thereon, and an electrode film is further formed thereon. Has been.

Japanese Patent Publication No. 3-54841 JP 2000-348906 A JP-A-6-61012

The following problems remain in the conventional technology.
That is, when the electrode is formed first before the thermistor thin film is formed, there is a problem that the structure is limited. In addition, when an electrode layer made of platinum or an alloy thereof is formed after forming Cr, Ti, or the like as the adhesive layer, there is a disadvantage that the resistance value increases after the heat resistance test due to oxidation of the adhesive layer. Furthermore, in the case where an electrode layer made of platinum or an alloy thereof is formed by raising the substrate temperature by heating film formation, a special film forming apparatus is required and a special gas that uses corrosive gas is also used for patterning. This necessitates a simple etching apparatus and increases the equipment cost. In this case, the adhesion strength of the electrode layer is slightly weaker than that in the case where an adhesive layer such as Cr or Ti is provided, which may cause electrode peeling.

  The present invention has been made in view of the above-described problems, and improves the adhesion strength between an electrode and a thermistor thin film, has a resistance value sufficient as an electrode, and suppresses an increase in resistance value in a heat resistance test, and a thin film thermistor element It aims at providing the manufacturing method.

The present invention employs the following means in order to solve the above problems.
A thin film thermistor element according to the present invention is a thin film thermistor element comprising a base, a thermistor thin film formed on the base, and a pair of electrodes formed on the thermistor thin film, wherein the pair of electrodes However, at least a portion in contact with the thermistor thin film is an electrode layer made of platinum or an alloy thereof formed in an amorphous state.

  The method of manufacturing a thin film thermistor element according to the present invention is a method of manufacturing a thin film thermistor element in which a pair of electrodes is formed on a film of a thermistor thin film formed on a substrate. The step of performing has a step of forming an electrode layer made of platinum or an alloy thereof in which at least a portion in contact with the thermistor thin film is in an amorphous state.

  In these thin film thermistor elements and the manufacturing method thereof, the pair of electrodes is an electrode layer made of platinum or an alloy thereof formed in an amorphous state at least at a portion in contact with the thermistor thin film. The electrode layer formed in (1) has sufficient adhesion strength with the thermistor thin film while maintaining sufficient conductivity, and electrode peeling does not occur even in the heat resistance test, thereby suppressing an increase in resistance value.

The thin film thermistor element according to the present invention is characterized in that the pair of electrodes are formed to include at least one of oxygen and nitrogen.
In the method of manufacturing a thin film thermistor element according to the present invention, the step of forming the electrode layer forms the electrode layer by adding at least one of oxygen and nitrogen.

  In these thin film thermistor elements and the manufacturing method thereof, the electrode layer can be preferably made amorphous by including at least one of oxygen and nitrogen at the time of forming the electrode layer.

Furthermore, in the thin film thermistor element according to the present invention, the content of at least one of oxygen and nitrogen in the pair of electrodes is 5 wt% or more and 15 wt% or less.
Further, in the method for manufacturing a thin film thermistor element according to the present invention, the step of forming the electrode layer may include a content of at least one of oxygen and nitrogen in the electrode layer of 5 wt% or more and 15 wt% or less. It is characterized by doing.

  In these thin film thermistor elements and the manufacturing method thereof, the electrode layer can be sufficiently amorphized by setting the content of at least one of oxygen and nitrogen to 5 wt% or more and 15 wt% or less. In addition, a significant increase in the resistance value of the electrode layer can be suppressed.

The present invention has the following effects.
That is, according to the thin film thermistor element and the method of manufacturing the same of the present invention, the pair of electrodes is an electrode layer made of platinum or an alloy thereof formed in an amorphous state at least at a portion in contact with the thermistor thin film. In addition, it is possible to realize sufficient adhesion strength and suppression of increase in resistance value in a heat resistance test while maintaining sufficient conductivity. An electrode layer made of platinum or an alloy thereof formed in an amorphous state is hardly affected by the surface shape of the thermistor thin film, and can be formed without generating a gap at the thermistor-electrode layer interface. Therefore, it is possible to obtain a highly reliable thin film thermistor element having a stable resistance value with little fluctuation even when a heat resistance test of 150 ° C. or the like is performed and maintaining suitable electrical characteristics.

  An embodiment of a thin film thermistor element and a method for manufacturing the same according to the present invention will be described with reference to FIGS. In each drawing used for the following description, the scale of each member is appropriately changed in order to make each member a recognizable size.

A thin film thermistor element 1 according to the present embodiment is, for example, an infrared detection sensor, and as shown in FIGS. 1 and 2, a Si substrate (base body) 2 having a SiO ₂ layer 2A formed on its surface as an underlayer, and the first thermistor thin film (thermistor thin film) which is formed on the SiO ₂ layer 2A 5A and a second thermistor thin film (thermistor thin film) 5B, the first thermistor thin film 5A and the second thermistor thin film 5B and the SiO ₂ layer 2A on And a pair of comb-shaped electrodes (electrodes) 3 patterned on each other, and a passivation film 6 covering the SiO ₂ layer 2A, the comb-shaped electrode 3, the first thermistor thin film 5A, and the second thermistor thin film 5B.

The first thermistor thin film 5A and the second thermistor thin film 5B are made of Mn—Co based composite metal oxide (for example, Mn ₃ O ₄ —Co ₃ O ₄ based composite metal oxide) or Mn—Co based composite metal oxide. A composite metal oxide film comprising a composite metal oxide containing at least one of Ni, Fe, and Cu (for example, Mn ₃ O ₄ —Co ₃ O ₄ —Fe ₂ O ₃ composite metal oxide), It has a spinel crystal structure and a columnar crystal structure extending in the film thickness direction.
The first thermistor thin film 5A and the second thermistor thin film 5B are each formed in a rectangular shape, and one is used for measurement and the other is used for monitoring.

The comb-shaped electrode 3 is a metal electrode for measuring electrical resistance, and at least a portion in contact with the first thermistor thin film 5A and the second thermistor thin film 5B is platinum (Pt) or an alloy thereof. An electrode layer (conductive layer) made of
Each of these comb-shaped electrodes 3 is formed in a comb-teeth shape, and is arranged in an opposing state with a predetermined interval therebetween. Each comb-shaped electrode 3 has an electrode terminal portion 7 extending to the outside of the first thermistor thin film 5A and the second thermistor thin film 5B.

The electrode layer of the comb-shaped electrode 3 is made amorphous by including at least one of oxygen (O ₂ ) and nitrogen (N ₂ ) at the time of lamination by a method described later. At this time, the content of at least one of oxygen and nitrogen is 5% by weight or more and 15% by weight or less. In addition, in content of at least one of the said oxygen and nitrogen, when both oxygen and nitrogen are included, the total content of both is said.

The passivation film 6 is made of a SiO ₂ film. Note that an insulating film made of glass, ceramics, heat-resistant resin, or the like may be used instead of the SiO ₂ film as long as it has an insulating property and can block the external atmosphere.

Next, a method for manufacturing the thin film thermistor element 1 according to this embodiment will be described.
In the method of manufacturing the thin film thermistor element 1 according to the present embodiment, as shown in FIG. 3, the first thermistor thin film 5A and the second thermistor thin film 5B are formed on the SiO ₂ layer 2A of the Si substrate 2 (S01). A step of patterning the first thermistor thin film 5A and the second thermistor thin film 5B (S02), a step of heat treating (annealing) the first thermistor thin film 5A and the second thermistor thin film 5B (S03), and the comb electrode 3 Forming the electrode layer (S04), patterning the electrode layer to form the comb electrode 3 (S05), the SiO ₂ layer 2A, the comb electrode 3, the first thermistor thin film 5A, and the second thermistor thin film A step (S06) of forming a passivation film 6 on 5B and a step (S07) of patterning the passivation film 6;

First, a SiO ₂ / Si substrate 2 having a SiO ₂ layer 2A formed on the upper surface of the Si substrate 2 by thermal oxidation to a thickness of 0.5 μm, for example, is prepared.
On the SiO ₂ / Si substrate 2, a composite metal oxide film to be the first thermistor thin film 5A and the second thermistor thin film 5B is formed by sputtering with a film thickness of 0.5 μm, for example (S01). Note that the composite metal oxide film is preferably set to a film thickness of 0.3 μm or more in which the film resistivity dependency of the volume resistivity is reduced.

At this time, the sputtering film forming conditions are set to, for example, an atmospheric pressure of 400 mPa to 1330 mPa, an argon (Ar) gas flow rate of 10 sccm to 50 sccm, and high frequency power of 150 W to 1000 W. A method of performing sputtering while heating the SiO ₂ / Si substrate 2 on which the first thermistor thin film 5A and the second thermistor thin film 5B are formed may be used. The substrate temperature at this time is preferably set within a range of 200 to 600 ° C. In this case, it is possible to suppress a change in resistance value during the heat treatment described later.

After sputtering, the first thermistor thin film 5A and the second thermistor thin film 5B are patterned into a predetermined shape (S02), and a predetermined heat treatment is performed to anneal the first thermistor thin film 5A and the second thermistor thin film 5B (S03). This heat treatment is performed in the atmosphere at a temperature of 400 ° C. to 1000 ° C. for 1 to 24 hours.
The heat treatment is performed in an atmosphere of an inert gas such as argon gas or nitrogen gas, and O ₂ may be added to these gases, for example, in an amount of 0.1% by volume to 5% by volume.

Next, the comb-shaped electrode 3 is patterned on the SiO ₂ layer 2A, the first thermistor thin film 5A, and the second thermistor thin film 5B using a high-frequency sputtering device or the like (S04, S05). That is, an electrode layer is formed as an amorphous conductive layer made of platinum (Pt) or an alloy thereof on the SiO ₂ layer 2A, the first thermistor thin film 5A, and the second thermistor thin film 5B (S04).
At this time, in addition to the application of an atmospheric pressure of 400 mPa to 1330 mPa, an argon gas flow rate of 10 sccm to 50 sccm, and a high frequency power of 150 W to 1000 W using an RF sputtering apparatus or the like, an atmospheric gas to which at least one of oxygen gas and nitrogen gas is added is used. To form a film.

At this time, the gas concentration is set so that the content of at least one of oxygen and nitrogen after film formation is 5 wt% or more and 15 wt% or less. Note that the method may be used as long as it can be made amorphous without adding oxygen gas or nitrogen gas.
The electrode layer may have a two-layer structure including a first electrode layer in an amorphous state and a second electrode layer in a crystalline state. In this case, the first electrode layer in an amorphous state is first formed under the sputtering conditions in which at least one of oxygen gas and nitrogen gas is added to the argon gas, and then the second electrode in the crystalline state is formed only with the argon gas. An electrode layer is formed.
After the film formation, the electrode layer is patterned by general-purpose photolithography and etching to obtain the comb-shaped electrode 3 (S05).

Finally, the process proceeds to the step of forming the passivation film 6 (S06), and the SiO ₂ passivation film 6 is laminated on the first thermistor thin film 5A and the second thermistor thin film 5B as a protective film, an infrared absorption film or the like. Further, the passivation film 6 is patterned into a predetermined shape except for the upper portion of the electrode terminal portion 7 (S07).
Thus, the thin film thermistor element 1 as an infrared detection sensor is produced.

  According to the thin film thermistor element 1 and the manufacturing method thereof, platinum or an alloy thereof in which the pair of comb-shaped electrodes 3 is formed in an amorphous state at least at a portion in contact with the first thermistor thin film 5A and the second thermistor thin film 5B. The electrode layer formed in an amorphous state while maintaining sufficient conductivity has sufficient adhesion strength with the first thermistor thin film 5A and the second thermistor thin film 5B, In the heat resistance test, electrode peeling does not occur, and an increase in resistance value can be suppressed.

  In addition, by including at least one of oxygen and nitrogen when forming the electrode layer to be the comb-shaped electrode 3, the electrode layer can be suitably amorphized. In particular, since the content of at least one of oxygen and nitrogen in the electrode layer is 5 wt% or more and 15 wt% or less, the electrode layer can be sufficiently amorphized, and the resistance of the electrode layer A significant increase in value can be suppressed.

  When the oxygen or nitrogen element is less than 5% by weight, there are few amorphous portions of the electrode layer made of Pt or its alloy, and it is difficult to obtain a sufficient effect of improving the adhesion strength. Moreover, when there is more oxygen or nitrogen element than 15 weight%, the resistance value as an electrode material will raise significantly. Therefore, if the content is within the set range, for example, even if a heat resistance test at 150 ° C. is performed, sufficient adhesion strength between the first and second thermistor thin films 5A and 5B and the comb electrode 3 is maintained. In addition, the electrical characteristics can be suitably maintained.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, an alumina (Al ₂ O ₃ ) substrate or the like may be used instead of the SiO ₂ / Si substrate 2, and a silicon nitride film or the like may be used instead of the SiO ₂ layer 2 A that is the underlayer.

  Next, the results of actually producing and evaluating the thin film thermistor element according to the present invention by the manufacturing method of the above embodiment will be specifically described.

  The electrode layer to be the comb-shaped electrode 3 was manufactured by changing a plurality of high-frequency outputs, film thicknesses, types and pressures of contained gases, annealing conditions (temperatures), and annealing times. Further, for the first thermistor thin film 5A and the second thermistor thin film 5B, the high frequency output, the film thickness, the gas type and pressure, the presence / absence of substrate heating, the presence / absence of application of the substrate bias voltage are changed, and the annealing temperature and time are further changed. It was made by changing a plurality of. That is, the thin film thermistor element of this example was manufactured based on a combination of these plural conditions.

  About these Examples, the heat resistance test of 1000 hours was implemented, heating at 150 degreeC, respectively, and the electrical resistance value of the comb-shaped electrode 3 was measured. In addition, as a comparative method, a conventional method was used in which a comb-shaped electrode was formed using an electrode layer made of platinum in a crystalline state only. These film forming conditions and heat test results are shown in Table 1 below.

  As can be seen from the above evaluation results, in the thin film thermistor element of this example, the rate of change in the electrical resistance value could be significantly lower than that of the conventional one even after the heat resistance test.

It is a top view which shows the thin film thermistor element of one Embodiment which concerns on this invention. It is AA arrow sectional drawing of FIG. It is a flowchart which shows the manufacturing method of the thin film thermistor element in this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Thin film thermistor element, 2 ... Si substrate (base | substrate), 3 ... Comb-shaped electrode (electrode), 5A ... 1st thermistor thin film (thermistor thin film), 5B ... 2nd thermistor thin film (thermistor thin film), 6 ... Passivation film

Claims (6)

A substrate;
A thermistor thin film formed on the substrate;
A thin film thermistor element comprising a pair of electrodes formed on the thermistor thin film,
The thin film thermistor element, wherein the pair of electrodes is an electrode layer made of platinum or an alloy thereof formed in an amorphous state at least at a portion in contact with the thermistor thin film. The thin film thermistor element according to claim 1,
The thin film thermistor element, wherein the pair of electrodes are formed to contain at least one of oxygen and nitrogen. The thin film thermistor element according to claim 2,
The thin film thermistor element, wherein the content of at least one of oxygen and nitrogen in the pair of electrodes is 5% by weight or more and 15% by weight or less. A method for manufacturing a thin film thermistor element, wherein a pair of electrodes is patterned on a film of a thermistor thin film formed on a substrate,
The step of patterning the pair of electrodes includes the step of forming an electrode layer made of platinum or an alloy thereof in which at least a portion in contact with the thermistor thin film is in an amorphous state. Manufacturing method. In the manufacturing method of the thin film thermistor element of Claim 4,
The method of manufacturing a thin film thermistor element, wherein the step of forming the electrode layer forms the electrode layer by adding at least one of oxygen and nitrogen. In the manufacturing method of the thin film thermistor element according to claim 5,
The method for producing a thin film thermistor element, wherein the step of forming the electrode layer comprises setting the content of at least one of oxygen and nitrogen in the electrode layer to 5 wt% or more and 15 wt% or less.

Images