JP2000348902A - Manufacture of thermistor thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the high-speed formation of a thermistor thin film by a method wherein the respective vapors of compounds, which respectively contain Mn, Co or Ni, and reaction gas are decomposed and are reacted with each other in a reduced pressure plasma and an Mn-Co-Ni composite oxide thin film is formed on a heated base substrate. SOLUTION: Acetylacetonatomanganese, acetylacetonatocobalt and acetylacetonatonickel are put respectively in vaporizers 8, 9 and 10 and the acetylacetonatos are respectively kept hot. Valves 11 to 16 are opened, argon carriers and the vapors of the acetylacetonatos of Mn, Co and Ni are introduced in a reaction chamber 1 decompressed by an exhaust system 7 along with oxygen, which is reaction gas, a plasma is generated in the chamber, the reaction of the vapors with the reaction gas is executed under the reduced pressure and an Mn-Co-Ni oxide thin film is formed on a heated alumina substrate 6. The obtained Mn-Co-Ni oxide thin film is heat-treated and formed into a thermistor thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film thermistor element used for a temperature sensor of information equipment, communication equipment, housing equipment, automobile equipment and the like.

[0002]

2. Description of the Related Art Among elements used for temperature detection, a thermistor using an oxide semiconductor material has a large resistance temperature change and a large temperature resolution as compared with a thermocouple or a platinum resistance thermometer. It can be used in large quantities because of its features such as the ability to measure at high speed, the material is stable and less susceptible to the influence of the outside world, so there is little change in events and high reliability, and mass production is possible and inexpensive. Have been.

Conventional thermistor elements include Mn, Co, N
A structure in which an electrode such as Ag is formed by coating and baking on the end face of an oxide sintered body chip mainly containing a transition metal such as i has been used. Along with the recent miniaturization, weight reduction and high performance of electronic equipment, thermistor elements have been miniaturized (for example, 1 mm x 0.5 mm size or less), and the resistance value and B constant at the measurement temperature have become more accurate. (For example, a variation within 3%). However, in the thermistor having the above-described configuration using a sintered body, it is difficult to miniaturize the thermistor due to a problem of processing accuracy. Further, there is a drawback that the variation in the resistance value or the B constant at the operating temperature of the thermistor element becomes large due to the miniaturization. To solve this problem, thin-film thermistor elements using thin-film technology for forming thermistor materials and electrodes have been actively developed.

[0004] The thin film thermistor element is made of Mn, Ni, Co.
Film formation by a sputtering method using a sintered body of a composite oxide composed of, for example, a target, crystallization into a spinel-type structure by subsequent heat treatment in air (200 to 800 ° C.), and further, electrode pattern on a thermistor thin film (JP-A-3-54842, and Yoichiro Masuda et al .: Bulletin of Hachinohe Institute of Technology, No. 8)
Vol., P25-34).

[0005]

When a composite oxide thin film composed of Mn, Co, Ni or the like used for a thermistor element is formed by a sputtering method, the sputtering rate of a target material is low, so that the film forming speed is extremely low. (About 1
If the target thermistor element requires a thickness of several μm for the thermistor element, it takes several hours to form the film, resulting in a problem in manufacturing.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a manufacturing method capable of forming a thermistor thin film used for a microminiature thin film thermistor element at a high speed.

[0007]

In order to solve the above problems, a thin film thermistor element according to the present invention comprises a vapor of a compound containing Mn, a vapor of a compound containing Co, a vapor of a compound containing Ni, and a reaction gas. Are decomposed and reacted in a reduced-pressure plasma, and Mn, Co, N
i to form a composite oxide thin film.

Further, by supplying a vapor of a compound containing Mn, a vapor of a compound containing Co, a vapor of a compound containing Ni, and a reaction gas to a pre-heated base substrate, the heat of the base substrate is increased. Decomposition and chemical reaction are performed to form a composite oxide thin film of Mn, Co, and Ni on the base substrate.

The reaction gas is desirably oxygen, N ₂ O or H ₂ O.

[0010]

Next, a method for manufacturing a thermistor thin film according to the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic view of a plasma CVD apparatus for producing a thermistor thin film according to the present invention.

In FIG. 1, inside a reaction chamber 1,
An electrode 3 built in the substrate heater 2 and a high-frequency power source (1
An electrode 5 connected to 3.56 MHz) 4 is provided to face the electrode 3, the electrode 3 is installed on the ground, and a base substrate 6 made of alumina or the like is installed below the electrode 3. Further, an exhaust system 7 for keeping the reaction chamber 1 at a low pressure is provided on the lower side surface of the reaction chamber 1.

On the other hand, a vaporizer (1) 8 containing raw materials, a vaporizer
(2) 9, the vaporizer (3) 10 is connected via a valve 11, 12, 13 to a pipe opening between the electrode 5 and the alumina substrate 6 disposed on the electrode 3, and the vaporizer 8, 9 , 10 are fitted with valves 14, 15, 1
6 is connected to an argon cylinder 17 for a carrier gas, and the introduction of the source gas and the carrier gas into the reaction chamber 1 is controlled by opening and closing the valves 11, 12, and 13. Further, the oxygen cylinder 18 is connected to a pipe opened between the alumina substrate 6 and the electrode 5.

Here, the thermistor according to the embodiment is thin.
A method for manufacturing a film will be described. Β-dike as starting material
Mn acetylacetonate [Mn (C_Five
H₇O _Two)_Two], Co acetylacetonate [Co (C_FiveH₇
O_Two)_Two], Ni acetylacetonate [Ni (C_FiveH₇O_Two)
_Two] Was used.

Vaporizer in the plasma CVD apparatus of FIG.
(1) 8, Mn acetylacetonate, Co acetylacetonate, Ni were added to the vaporizer (2) 9 and the vaporizer (3) 10, respectively.
Add acetylacetonate, 205 ° C, 12
Heat to 0 ° C. and 155 ° C. and hold. Valves 11-1
Open 6, open the argon carrier [vaporizer (1) 8, vaporizer (2)
9, 10, 8, 12 (SCC) for the vaporizer (3) 10 respectively.
M)] and the vapors of Mn and Co and Ni acetylacetonate were converted to oxygen (flow rate 100 (SCC)) as a reaction gas.
M)) and introduced into the reaction chamber 1 depressurized by the exhaust system 7 to generate plasma (100 W), 3
The reaction was performed under reduced pressure (0.1 Torr) for 0 minutes,
A Mn-Co-Ni oxide thin film was formed on an alumina substrate heated to ℃. Then, the obtained Mn-Co-Ni oxide thin film was subjected to a heat treatment at 800 ° C. for 10 hours in the air to form a thermistor thin film. The film thickness is 2.6 μm and the deposition rate is 8
66 ° / min.

In the same manner as above, a thermistor thin film was formed on a quartz substrate by a plasma CVD method, and the crystal structure was analyzed by X-ray diffraction and the composition was analyzed by an X-ray microanalyzer. As a result, the thermistor thin film had a spinel type crystal structure. The film composition is Mn:
Co: Ni = 55: 28: 17.

Next, a Pt upper electrode pair was formed on the thermistor thin film formed on the alumina substrate by a sputtering method, and the NTC thermistor characteristics in a temperature range from room temperature to 300 ° C. were examined. NTC thermistor characteristics. Specific resistance is 340 (Ωcm), B
The constant was 3420 (K).

Further, a high temperature durability test was performed. As a result, the change after standing at 250 ° C. in the air for 1000 hours was a specific resistance of 1.4% and a B constant of 0.3%.

The above results are shown in the first embodiment (Table 1) and (Table 2).

[0020]

[Table 1]

[0021]

[Table 2]

(Embodiment 2) A thermistor thin film was manufactured by partially changing the manufacturing conditions in Embodiment 1. That is, the vaporization temperatures of Mn acetylacetonate, Co acetylacetonate, and Ni acetylacetonate are 215 ° C., 140 ° C., and 170 ° C., respectively, and the carrier gas flow rates are 20 (SCCM), 5 (SCCM),
(SCCM), the plasma power was 150 W, the substrate temperature was 450 ° C., the degree of vacuum during film formation was 0.07 Torr, and the film formation time was 45 minutes. The reaction gas was N2O (flow rate 75
(SCCM)). The heat treatment was not performed on the obtained Mn-Co-Ni oxide thin film. The film thickness is 3.8 μm
(A deposition rate of 844 ° / min). The thermistor thin film had a spinel type crystal structure. The film composition is Mn: C
o: Ni = 77: 15: 8.

A Pt upper electrode pair was formed by sputtering, and the NTC thermistor characteristics in a temperature range from room temperature to 300 ° C. were examined. As a result, the obtained film had good NTC thermistor characteristics. Specific resistance is 871 (Ωcm), B
The constant was 3620 (K).

Further, a high temperature durability test was performed. As a result, the change after standing at 250 ° C. in the air for 1000 hours was a specific resistance of 1.1% and a B constant of 0.2%.

The above results are shown in Embodiment 2 of (Table 1) and (Table 2).

(Embodiment 3) A thermistor thin film was manufactured by partially changing the manufacturing conditions in Embodiment 2. That is, the vaporization temperatures of Mn acetylacetonate, Co acetylacetonate, and Ni acetylacetonate are 195 ° C., 120 ° C., and 160 ° C., respectively, and the carrier gas flow rates are 10 (SCCM), 6 (SCCM), and 10 (SCCM), respectively.
(SCCM), plasma power 90 W, substrate temperature 5
50 ° C., the degree of vacuum during film formation is 0.6 Torr, and the film formation time is 90
Minutes. H ₂ O (25 ° C., bubbling at Ar, flow rate 12 (SCCM)) was used as a reaction gas. Then, the obtained Mn—Co—Ni oxide thin film was subjected to a heat treatment at 700 ° C. for 5 hours in the air.

The film thickness is 4.7 μm (deposition rate 671 ° /
Min), and the film composition is Mn: Co: Ni = 40: 13: 47.
Met. The thermistor thin film had a spinel type crystal structure.

A Pt upper electrode pair was formed by sputtering, and the NTC thermistor characteristics in a temperature range from room temperature to 300 ° C. were examined. As a result, the obtained film had good NTC thermistor characteristics. Specific resistance is 640 (Ωcm), B
The constant was 3820 (K).

Further, a high-temperature durability test was performed. As a result, the change after standing at 250 ° C. in the air for 1000 hours was 1.8% in specific resistance and 0.5% in B constant.

The above results are shown in Embodiment 3 of (Table 1) and (Table 2).

(Embodiment 4) A thermistor thin film was manufactured by partially changing the manufacturing conditions in Embodiment 4. That is, the vaporization temperatures of Mn acetylacetonate, Co acetylacetonate, and Ni acetylacetonate are 225 ° C., 140 ° C., 159 ° C., respectively, and the carrier gas flow rates are 120 (SCCM), 38 (SCCM),
45 (SCCM), the substrate temperature was 800 ° C., the degree of vacuum during film formation was 10 Torr, and the film formation time was 60 minutes. O ₂ (flow rate 2000 (SCCM)) was used as a reaction gas. The film was formed only by the thermal decomposition reaction without applying the plasma. The obtained Mn-Co-Ni oxide thin film was not heat-treated.

The film thickness is 3.4 μm (deposition speed 566 ° /
Min), and the film composition is Mn: Co: Ni = 55: 26: 19
Met. The thermistor thin film had a spinel type crystal structure.

The Pt upper electrode pair was formed by a sputtering method, and the NTC thermistor characteristics in a temperature range from room temperature to 300 ° C. were examined. As a result, the obtained film had good NTC thermistor characteristics. Specific resistance is 355 (Ωcm), B
The constant was 3487 (K).

A high-temperature durability test was also performed. As a result, the change after standing at 250 ° C. in the air for 1000 hours was a specific resistance of 1.1% and a B constant of 0.4%.

The above results are shown in (Table 3) and (Table 4) in Embodiment 4.

[0036]

[Table 3]

[0037]

[Table 4]

(Embodiment 5) A thermistor thin film was manufactured by partially changing the manufacturing conditions in Embodiment 1. That is, the vaporization temperatures of Mn acetylacetonate, Co acetylacetonate, and Ni acetylacetonate are 224 ° C., 130 ° C., 170 ° C., respectively, and the carrier gas flow rates are 250 (SCCM), 50 (SCCM), respectively.
30 (SCCM), the substrate temperature was 520 ° C., the degree of vacuum during film formation was 5 Torr, and the film formation time was 115 minutes. N ₂ O (flow rate 1500 (SCCM)) was used as a reaction gas. In addition,
A film was formed only by a thermal decomposition reaction without applying plasma.
And the obtained Mn-Co-Ni oxide thin film is in air 7
Heat treatment was performed at 00 ° C. for 10 hours.

The film thickness is 3.1 μm (deposition speed 270 ° /
), And the film composition is Mn: Co: Ni = 73: 14: 11.
Met. The thermistor thin film had a spinel type crystal structure.

A Pt upper electrode pair was formed by a sputtering method, and the NTC thermistor characteristics in a temperature range from room temperature to 300 ° C. were examined. As a result, the obtained film had good NTC thermistor characteristics. Specific resistance is 826 (Ωcm), B
The constant was 3607 (K).

Further, a high-temperature durability test was performed. As a result, the change after standing at 250 ° C. in the air for 1000 hours was a specific resistance of 1.3% and a B constant of 0.2%.

The above results are shown in (Table 3) and (Table 4) in Embodiment 5.

(Embodiment 6) A thermistor thin film was manufactured by changing some of the manufacturing conditions in Embodiment 1. That is, the vaporization temperatures of Mn acetylacetonate, Co acetylacetonate, and Ni acetylacetonate are respectively 207 ° C., 133 ° C., and 180 ° C., and the carrier gas flow rates are 160 (SCCM), 60 (SCCM), respectively.
40 (SCCM), the substrate temperature was 610 ° C., the degree of vacuum during film formation was 760 Torr, and the film formation time was 45 minutes. The reaction gas is H ₂ O (bubbling with Ar at 25 ° C., flow rate 110 (S
CCM)) was used. The film was formed only by the thermal decomposition reaction without applying plasma. And the obtained Mn-Co-
The Ni oxide thin film was heat-treated at 900 ° C. in the air for 5 hours.

The film thickness is 4.1 μm (deposition speed 911 ° /
), And the film composition is Mn: Co: Ni = 41: 14: 45.
Met. The thermistor thin film had a spinel type crystal structure.

The Pt upper electrode pair was formed by a sputtering method, and the NTC thermistor characteristics in a temperature range from room temperature to 300 ° C. were examined. As a result, the obtained film had good NTC thermistor characteristics. Specific resistance is 691 (Ωcm), B
The constant was 3833 (K).

Further, a high-temperature durability test was performed. As a result, the change after standing at 250 ° C. in the air for 1000 hours was a specific resistance of 1.7% and a B constant of 0.4%.

The above results are shown in Embodiment 6 in (Table 3) and (Table 4).

According to the results of the first to sixth embodiments, the use of the CVD method for the production of the thermistor thin film makes it possible to form the thermistor thin film at a higher speed than the conventional sputtering method. It was revealed.

In the embodiment of the present invention, the thermistor thin film is made of a Mn-Co-Ni oxide, but is not limited to this. Co, Ni, Fe, Al, C
Similarly, excellent results were obtained when the composition was composed of Mn and at least one of u and Cr.

In the embodiment of the present invention, the obtained thermistor thin film has a spinel type crystal structure.
However, the present invention is not limited to this.
Excellent results were similarly obtained with aCl-type crystal structures, bixbite-type crystal structures, or mixed crystals of these crystal structures and spinel-type crystal structures.

In the embodiment of the present invention, alumina was used for the base substrate. However, excellent results were obtained when other ceramics substrates or glass substrates were used.

In the embodiment of the present invention, M
An acetylacetonate complex of a β-diketone metal complex was used as a starting material for n, Co, and Ni, but is not limited to this. For example, in a β-diketone metal complex, a dipivaloylmethane compound [ M (C ₁₁ H ₁₉ O ₂ ) ₂ ,
M = Mn, Co, Ni], a hexafluoroacetylacetonate compound [M (C ₅ F ₆ HO ₂ ) ₂ , M = Mn, Co,
Ni] and other cyclopentadienyl compounds [M
((C ₅ H ₅ ) ₂ , M = Mn, Co, Ni], or a carbonyl compound [M ((CO) ₅ , M = Mn, Co, Ni]) also gives excellent results. Was.

In the embodiment of the present invention, rf
Although plasma (13.56 MHz) was used, it is not limited to this, and microwave plasma (2.45 GHz) was used.
Similarly, excellent results were obtained when z) or ECR (electron cyclotron resonance) plasma was used.

[0054]

As described above, the present invention has a configuration using a plasma CVD method or a thermal CVD method for the production of a thermistor thin film. Thus, it is possible to form a thermistor thin film at a high speed.

[Brief description of the drawings]

FIG. 1 is a view showing a plasma CVD apparatus for producing a thermistor thin film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction chamber 2 Substrate heater 3,5 Electrode 4 High frequency power supply 6 Alumina substrate 7 Exhaust system 8-10 Vaporizer (1) (2) (3) 11-13 Source gas supply valve 14-16 Carrier gas supply cylinder 17 Argon Cylinder 18 oxygen cylinder

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Tomozawa 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 5E034 BA09 BB08 BC02 BC17 DA02 DE16

Claims (3)

[Claims] 1. A vapor of a compound containing Mn, a vapor of a compound containing Co, a vapor of a compound containing Ni, and a reaction gas are decomposed and reacted in a reduced-pressure plasma, and Mn is deposited on a pre-heated base substrate. A method for producing a thermistor thin film, comprising forming a composite oxide thin film of Al, Co and Ni. 2. Supplying a vapor of a compound containing Mn, a vapor of a compound containing Co, a vapor of a compound containing Ni, and a reaction gas onto a pre-heated base substrate, heat is applied to the base substrate. A method for producing a thermistor thin film, comprising forming a composite oxide thin film of Mn, Co, and Ni on the base substrate by decomposition and chemical reaction. 3. The reaction gas is oxygen, N ₂ O or H ₂
3. The method for producing a thermistor thin film according to claim 1, wherein said O is O.