JPH0955303A - Chip type thin film thermistor element and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate production of a temperature compensaticn circuit by decreasing the number of components to be mounted. SOLUTION: The chip type thin film thermistor element comprises a base material 1 having an element forming surface, a first electrode layer 2 provided on the element forming surface, a thermistor thin film 3 provided on the first electrode layer, and second and third electrode layers 4, 5 facing the first electrode layer through the thermistor thin film. At the time of producing an element, the thermistor thin film is not required to be patterned separately for each element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a chip type thin film thermistor element, which is preferably used as a thermistor having a negative temperature coefficient used for compensating a low temperature part of a crystal oscillator.

[0002]

2. Description of the Related Art A small-sized communication device such as a mobile phone used outdoors is a temperature-compensated type including an AT-cut crystal oscillator, an amplifier and a temperature compensating circuit so that the change of the oscillation frequency due to the operating temperature is slight. Although the crystal oscillator of
As this temperature compensation circuit, the one shown in FIG. 4 is conventionally known.

This temperature compensation circuit, as shown in FIG.
A low temperature compensation circuit L and a high temperature compensation circuit H connected in series to the crystal unit are provided. The low temperature compensation circuit L has a capacitor C _L and a thermistor Th _L connected in parallel with each other, and the high temperature compensation circuit H has a capacitor C _H and a thermistor Th _H connected in parallel with each other. Both of the thermistors Th _L and Th _H have negative temperature characteristics. The amount of change in the ratio of the capacitances of the capacitors C _L and C _H to the equivalent series capacitance of the temperature compensation circuit as a whole with respect to temperature changes is small in the low temperature compensation circuit L at room temperature (25 ° C.) or higher, but at low temperatures. The capacitors C _L and C _H and the thermistors Th _L and Th _H are set so as to become large in the high temperature part and in the high temperature part compensating circuit H so as to become small in the high temperature part although it is small at room temperature and below. .

In order to adjust the compensation sensitivity of the temperature compensating circuit, a resistor R _L is inserted in parallel with the thermistor Th _L in the low temperature compensating circuit L, and a resistor R is connected in series with the thermistor Th _H in the high temperature compensating circuit 2. Inserting _H. Therefore, the chip type elements used in the low temperature part compensation circuit L and the high temperature part compensation circuit H require three types of thermistors, capacitors and adjusting resistors.

[0005]

However, with the recent demand for miniaturization of crystal oscillators, there is a demand for a smaller number of mounted components and easier manufacture.

Therefore, the present invention provides a chip-type thin film thermistor element useful as a thermistor for compensating a low temperature portion of a temperature compensation circuit of a crystal oscillator and a method of manufacturing the same, in which the number of mounting components is reduced and the production of the compensation circuit is further improved. The purpose is to facilitate.

[0007]

In order to achieve this object, the chip type thin film thermistor element of the present invention comprises a base material (1) having an element forming surface, and a first element provided on the element forming surface. An electrode layer (2), a thermistor thin film (3) provided on the first electrode layer, and second and third electrodes facing the first electrode layer via the thermistor thin film.
It is characterized by comprising the electrode layers (4, 5).

In this structure, the second electrode layer and the first electrode layer
The electrode layers act as a first thermistor element, and the third electrode layer and the first electrode layer act as a second thermistor element. Therefore, the first and second thermistor elements are connected in series. The desired characteristics can be obtained by controlling the temperature characteristics of the thermistor thin film, the dielectric constant, the film thickness, the crossing area between the electrodes, and the like.

In a specific embodiment, the thermistor element has a negative temperature coefficient of resistance, 25 ° C., 5 to 25M.
The capacitance value between the second and third electrode layers at 1 Hz is 1
The resistance value is 5 pF or more and the resistance value is 100 Ω or less. When the capacitance value is less than 15 pF, the oscillation of the crystal oscillator becomes unstable, and when the resistance value exceeds 100Ω, the loss resistance becomes large, which is not desirable.
By controlling such characteristics, the thermistor element has the functions of the capacitor C _L of the low temperature compensation circuit and the adjusting resistor R _L in the conventional example of FIG. 4, and as shown in FIG. It is also possible to form the thermistor element Th _L only.

In manufacturing such a chip type thin film thermistor element of the present invention, a thin film pattern in which the first electrode layers for a plurality of chips are arranged in a matrix is formed on the substrate (31) as the base material. Next, a layer to be the thermistor thin film is formed as one thin film layer over the area of the plurality of chips, and then a thin film pattern of the second and third electrode layers corresponding to the first electrode layer is formed. This can be performed by forming a film, forming the thin film patterns of the second and third electrode layers, and then cutting each chip (34). According to this, it is possible to form the thermistor thin film as one continuous thin film over all chips, and it is not necessary to form an isolated pattern for each chip, so that the productivity is improved. At the same time, the characteristics of the thermistor thin film or element can be improved.

In a more specific aspect, the first
The protective layer (6) covers the element portion where the electrode layer and the second and third electrode layers face each other with the thermistor thin film interposed therebetween.
Further, on both end faces of the element perpendicular to the X direction, end face electrode layers (7) connected to the second electrode layer and the third electrode layer are provided for connection to the outside. In addition, for connection to the outside, not only the end face electrode but other means such as wire bonding may be used.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a plan view showing a chip type thin film thermistor element according to an embodiment of the present invention, and FIG.
Is a sectional view taken along the line AA. As shown in the figure, this element has a substantially rectangular parallelepiped shape in which each surface is orthogonal to the XYZ directions, and is provided on the substrate 1 and the element forming surface having one surface perpendicular to the Z direction as the element forming surface. Provided first electrode layer 2, a thermistor thin film 3 which covers the first electrode layer 2 and is provided from one end in the X direction of the element formation surface to the other end, and the first electrode layer through the thermistor thin film 3 2nd and 3rd facing 2
Of the electrode layers 4 and 5. The element layer where the first electrode layer 2 and the second and third electrode layers 4 and 5 face each other via the thermistor thin film 3 is covered with a protective layer 6. In addition, from both end surfaces perpendicular to the X direction of the element to the second and third electrode layers 4 and 5 are connected to the second electrode layer and the third electrode layer 4 and 5 for connection with the outside, respectively. The end face electrode layer 7 is provided.

The substrate 1 is made of barium borosilicate glass or the like. The first to third electrode layers 2, 4, 5 are thin films of nickel, chromium, aluminum, titanium, copper or the like. The thermistor thin film 3 is a manganese-cobalt complex oxide, which is a complex oxide containing at least one of nickel, copper, and calcium.

The thermistor thin film 3 has a thickness of 0.5 to 20 μm.
When the thickness is less than 0.5 μm, it is difficult to control the capacitance value (Cp) and the resistance value (Rp) of the device, and when the thickness exceeds 20 μm, a thick film region is formed, resulting in high cost. The area (electrode area) of the overlapping portion of the first electrode layer 2 and the second and third electrode layers 4 and 5 has a length of 1
The width is 100 to 600 μm. If the electrode area is smaller than this, the later-described requirement that the capacitance value (Cp) at 25 ° C. and 15 MHz is 15 pF or more cannot be satisfied, and since it is limited by the chip size, it cannot be made larger than this.

The protective layer 6 is provided so that the X-direction end portions of the second and third electrode layers 4 and 5 are exposed.
Examples of the material of the protective layer 6 include insulating heat resistant resins such as silicone resin, epoxy resin, and polyimide resin.
Further, a silicon oxide thin film is formed on the second and third electrode layers 4 and 5, and an insulating heat-resistant resin is provided thereon, and the protective layer 6 is constituted by these layers to improve heat resistance. You may

The end face electrode layer 7 is composed of an adhesive layer, an electrode layer, and a solder layer in this order from the bottom, and the adhesive layer of each end face electrode layer 7 is connected to the second and third electrode layers 4 and 5, respectively. are doing. The adhesion layer of the end face electrode layer 7 is made of a titanium or chromium thin film, and the electrode layer is made of a nickel thin film or a polymer or cermet thick film containing copper, nickel, or silver as a main component. The surface layer is composed of a solder underlayer such as a tin thin film or a layer of Pb / Sn, Ag / Sn or the like on the solder underlayer. Each of the end face electrode layers 7 is formed so as to cover the exposed portion of the second and third electrode layers 4 and 5 in the X direction. As the adhesive layer of the end face electrode layer 7, a resin-curable paste containing silver powder as a main component applied to both end faces and cured may be used.

This thermistor element has a negative temperature coefficient of resistance, and by utilizing the electric conduction characteristic and the dielectric characteristic of the thermistor, a low temperature compensation circuit is realized in one chip Th _{L as shown} in FIG. It is a thing. That is,
By thinning the complex oxide forming the thermistor and adding dielectric characteristics, the capacitor C _L and the resistor R _L shown in FIG. 4 which are conventionally required for compensating for the low temperature portion are not required. For that purpose, 25 ° C, 5-25 MH
It is necessary that the capacitance value (Cp) at z is 15 pF or more and the resistance value (Rp) is 100Ω or less. Capacity value (C
When p) is less than 15 pF, the oscillation of the crystal oscillator becomes unstable, and when the resistance value (Rp) exceeds 100Ω, loss resistance becomes large, which is not desirable.

Next, a method of manufacturing the thermistor element will be described. The manufacturing is performed by the following procedures (1) to (10).

(1) Substrate treatment: 100 m in length, which is the substrate 1.
A barium borosilicate glass substrate having a size of m, a width of 100 mm and a thickness of 0.5 mm was prepared, degreased in an ultrasonic cleaning tank filled with a neutral detergent, and then washed with ultrapure water, and a clean room Dry in a room temperature at room temperature.

(2) Lower electrode film formation: Using a drum type sputtering apparatus as shown in FIG.
First electrode 2 patterns for a plurality of chips arranged in a matrix in the XY directions are formed. That is, first, a portion other than the portion where the first electrode 2 pattern is formed on the substrate is covered with a resist, and the substrate is mounted on the rotary drum 11. Next, titanium and nickel are sequentially sputtered onto the sputtering target 13.
The rotary drum 11 is rotated, and sputtering is performed while supplying the argon gas flow 12. After the sputtering is completed, the resist is peeled off. This allows
The first electrode 2 made of a nickel thin film having a thickness of 0.3 μm, which uses a titanium layer having a thickness of 0.1 μm as an adhesion layer to the substrate.
Pattern is formed. The adhesion layer of titanium is
This is in consideration of the adhesion to the barium borosilicate glass that constitutes the base material 1 and the influence on the thermistor thin film 3 (manganese-cobalt-nickel composite oxide thin film). The film forming conditions are as follows.

[Film forming conditions] Sputtering pressure: 5 mm Tor
r, Ar gas flow rate: 120 cc / min. , DC power: 3 KW, titanium film formation time: 20 minutes, nickel film formation time: 30 minutes, drum rotation: 10 rpm.

(3) Thermistor film formation: Using the drum type sputtering apparatus of FIG. 2, the substrate on which the pattern of the first electrode 2 is formed is mounted on the rotary drum 11. Next, the manganese-cobalt-nickel composite oxide is used as the sputtering target 13, the rotary drum 11 is rotated, and sputtering is performed while supplying the mixed gas flow 12 of argon and oxygen. As a result, a thermistor thin film (manganese / cobalt / nickel composite oxide thin film) having a thickness of 0.6 μm is formed on the substrate and the lower electrode 2. The film forming conditions are as follows.

[Film forming conditions] Sputtering pressure: 2 mm Tor
Flow rate of mixed gas of r, Ar and O ₂ : 20 cc / mi
n. (Ar: 18 cc / min., O ₂ : ₂ cc / mi
n. ), DC power: 1 kW, film formation time: 4 hours, drum rotation: 10 rpm.

(4) Upper electrode film formation: The pattern of the second and third electrodes 4 and 5 is formed by the lift-off method using the drum type sputtering apparatus shown in FIG. That is, first,
The second on the substrate on which the pattern of the thermistor thin film 3 is formed
Then, the substrate other than the portions where the pattern of the third electrodes 4 and 5 is formed is covered with a resist, and this substrate is mounted on the rotary drum 11. Next, using nickel as the sputtering target 13, the rotary drum 11 is rotated and sputtering is performed while supplying the argon gas flow 12. Then, after the sputtering is completed, the resist is peeled off. As a result, a pattern (nickel thin film) of the second and third electrodes 4 and 5 having a thickness of 0.3 μm is formed. The film forming conditions are as follows.

[Film forming conditions] Sputtering pressure: 5 mm Tor
r, Ar gas flow rate: 120 cc / min. , DC power: 3 kW, film formation time: 30 minutes, drum rotation: 10 rp
m.

(5) Protective film formation: Using the drum type sputtering apparatus of FIG. 2, a silicon oxide thin film forming the protective layer 6 is formed on the second and third electrodes 4 and 5 pattern by the lift-off method. That is, first, the portion of the protective layer 6 other than the portion where the pattern is formed is covered with a resist. At this time, the protective layer 6 is formed so that the end face portions of the second and third electrodes 4 and 5 are exposed, and the pattern of the protective layer 6 is continuous between adjacent elements in the Y direction. The resist is arranged so as to be formed as a stripe shape.
Next, using SiO ₂ as the target 13, the rotary drum 11
Is rotated, and sputtering is performed while supplying the argon gas flow 12. Then, after the sputtering is completed, the resist is peeled off. As a result, a 0.4 μm thick silicon oxide thin film forming the protective layer 5 is formed. The film forming conditions are as follows.

[Deposition conditions] Sputtering pressure: 2 mm Tor
r, Ar gas flow rate: 20 cc / min. , DC power:
1 kW, film formation time: 4 hours, drum rotation: 10 rpm.

(6) Annealing: 3 by air oven
Annealing is carried out at 00 ° C. for 4 hours, and then naturally cooled in air. By this annealing and the mixing of O ₂ gas with Ar gas in the thermistor film forming step (3), the thermistor thin film 3 has improved thermal stability and reduced change over time.

(7) Printing of protective resin: Using a patterned metal mask having a thickness of 0.1 mm, epoxy thermosetting resin was screen-printed by a screen printing machine, and this was printed in an exhaust type oven at 200 ° C. for 30 minutes. By heat-curing for a minute, an insulating heat-resistant resin layer having a thickness of 50 μm is formed on the silicon oxide thin film. Thereby, the pattern of the protective layer 6 including the silicon oxide thin film and the insulating heat resistant resin layer is formed.

(8) Sticking: In the following description of the steps, FIG. 3 is mainly referred to. The substrate 31 on which the thin film pattern up to the protective layer 6 is formed is placed on the adhesive tape, and this is placed in a dicing device, and the substrate 31 on the adhesive tape is placed by the diamond blade rotating at a high speed.
Are cut into sticks one after another. The cutting direction is parallel to the YZ direction according to the XYZ directions of FIGS. 1 and 3 with the thermistor element as a reference, and the cutting interval matches the width W _x of the substrate 1 in the X direction. Next, the base material 1 cut in this way
From the adhesive tape. This gives a length of 10
A large number of stick-shaped objects 32, each having a width of 0 mm, a width of 1.6 mm and a thickness of 0.5 mm, are obtained by cutting the stick-shaped material 32.

(9) Film formation of end face electrode: stick-like material 32
A plurality of sticks are aligned in the direction of each stick, and the stick-like objects 32 are stacked in the Z direction.

Next, the product 33 is mounted on the rotary drum 11 of the sputtering apparatus of FIG. 2 so that the sputtering is performed from the positive X direction. And titanium,
Nickel and silver are sequentially used as the sputtering target 13 in this order, and the rotary drum 11 is rotated, and the stack is sputtered in the positive X direction (direction A). Also from the opposite direction, ie X
Similarly, sputtering is performed from the negative direction (direction B). As a result, an end face electrode including an adhesion layer (titanium thin film) having a thickness of 0.05 μm, an electrode layer (nickel thin film) having a thickness of 0.5 μm, and a surface layer (silver thin film) having a thickness of 0.2 μm is obtained. It is formed. FIG. 1B shows an enlarged view of a part of the pavement 33 after completion of the sputtering, as viewed from the Y direction. Since the pattern of the protective layer is formed as a continuous stripe pattern between the elements adjacent to each other in the Y direction, as shown in FIG. The thin film patterns 23 are formed separately from each other. The film forming conditions are as follows.

[Film forming conditions] Sputtering pressure: 5 mm Tor
r, Ar gas flow rate: 120 cc / min. , DC power: 3 kW, titanium film formation time: 10 minutes, nickel film formation time: 30 minutes, silver film formation time: 10 minutes, drum rotation: 10r
pm.

(10) Chip formation: The above-mentioned stacked mats were separated by 0.8 mm intervals (W) in parallel with the XZ plane by the dicing device.
Cut with _y ). As a result, the length (dimension in X direction) of one chip is 1.6 mm, and the width (dimension in Y direction) is approximately 0.8 m.
A plurality of thermistor elements 34 having a thickness of m and a thickness (dimension in the Z direction) of 0.5 mm are obtained.

The AC value of the thermistor element thus obtained was evaluated by the following method, and the result was evaluated for a thermistor (manganese-cobalt complex oxide sintered body) and a capacitor conventionally used for compensating for a low temperature part. Table 1 with values
Shown in

[AC value] After the element was set on a measuring jig installed in a circulating-type constant temperature bath at 25 ° C and 0 ° C, the resistance value (Rp) and capacitance (Cp) of the element at 15 MHz were measured by an impedance analyzer. ) Is measured.

[0037]

[Table 1] The results of evaluating the temperature compensation characteristics of this thermistor element by the following method are also shown. First, FIG. 6 shows the temperature compensation characteristics of the temperature compensation circuit of the crystal oscillator shown in FIG. 4, which has a thermistor, a capacitor and a resistor in the conventional low temperature compensation circuit. FIG. 7 shows the temperature compensation characteristics of the temperature compensation circuit of the crystal oscillator using the above, and the temperature compensation characteristics of the temperature compensation circuit of the crystal oscillator shown in FIG. 5 using only the thermistor element of the present invention as the low temperature compensation circuit. Each is shown in FIG.

[Temperature Compensation Characteristic] A crystal oscillator in which a desired element is connected to a low temperature compensating circuit is installed in an air-circulation type constant temperature bath capable of adjusting from −30 ° C. to + 80 ° C. A DC power source (5V) and a frequency counter are connected to the crystal oscillator, and the oscillation frequency is measured while changing the temperature.
When the oscillation frequency at 25 ° C. is f25, the frequency deviation value at T ° C. is expressed by the following equation. Δf / f = (fT−f25) / f25 As is clear from the comparison of FIGS. 6 to 8, the temperature compensation characteristic shown in FIG. 8 is almost the same as that in FIG. 6, and the temperature compensation characteristic shown in FIG. You can see that it has improved.

The thermistor (manganese-cobalt composite oxide sintered body) and capacitor conventionally used for compensating low temperature parts and the capacitance (Cp) and resistance (Rp) at 5 to 25 MHz were measured as follows. The measurement was performed under the conditions, and the results are shown in FIG. 9, and the capacitance value (Cp) and the resistance value (Rp) at 5 to 25 MHz of the thermistor element of the present example were similarly measured, and the results are shown in FIG.

[Measurement conditions] The capacitance value (Cp) and the resistance value (Rp) are measured by an impedance analyzer installed in a room whose temperature is adjusted to 25 ° C.

[0041]

As described above, according to the present invention,
Since the thermistor element has the function of the capacitor of the low temperature part compensation circuit and the function of the adjusting resistor, the low temperature part compensation circuit can be configured only by the thermistor element of the present invention. Therefore, the number of mounted components can be reduced, and the manufacturing of the compensation circuit can be facilitated. Further, according to the manufacturing method of the present invention, since the pattern of the thermistor thin film is formed as a stripe pattern corresponding to the first electrode layer in each column in the X direction, productivity can be improved and at the same time. The characteristics of the thermistor thin film or element can be improved.

[Brief description of drawings]

FIG. 1 is a plan view showing a chip type thin film thermistor element according to an embodiment of the present invention and a sectional view taken along line AA thereof.

FIG. 2 is a side view and a top view showing a drum type sputtering apparatus used for manufacturing the device of FIG.

FIG. 3 is a diagram conceptually showing steps from sticking to chipping in manufacturing the device of FIG.

FIG. 4 is a circuit diagram showing a temperature compensation circuit according to a conventional example.

FIG. 5 is a circuit diagram showing a temperature compensation circuit using a thermistor element manufactured by the manufacturing method of the present invention.

FIG. 6 is a graph showing temperature compensation characteristics of a temperature compensation circuit used in a conventional crystal oscillator.

FIG. 7 is a graph showing a temperature compensation characteristic when a low temperature part compensation circuit of a temperature compensation circuit used for a crystal oscillator is removed.

8 is a graph showing a temperature compensation characteristic of a temperature compensation circuit using the thermistor element of FIG. 1 as a thermistor for compensating a low temperature portion of a temperature compensation circuit in a crystal oscillator.

[Fig. 9] 5 to 5 of thermistors (manganese-cobalt composite oxide sintered bodies) that have been conventionally used for compensating for low temperature parts
It is a graph which shows the capacitance value (Cp) and resistance value (Rp) in 25 MHz.

10 is a graph showing the capacitance value (Cp) and the resistance value (Rp) of the thermistor element of FIG. 1 at 5 to 25 MHz.

[Explanation of symbols]

1: base material, 2: first electrode layer, 3: thermistor thin film, 4:
Second electrode layer, 5: third electrode layer, 6: protective film, 7: end face electrode layer, 11: rotating drum, 12: gas flow, 13: target.

Claims (3)

[Claims] 1. A base material (1) having an element forming surface, a first electrode layer (2) provided on the element forming surface, and a first electrode layer (2).
It is characterized by comprising a thermistor thin film (3) provided on the electrode layer, and second and third electrode layers (4, 5) opposed to the first electrode layer via the thermistor thin film. Chip type thin film thermistor element. 2. The thermistor element has a negative temperature coefficient of resistance, the capacitance value between the second and third electrode layers at 25 ° C. and 5 to 25 MHz is 15 pF or more, and the resistance value is 10 ps.
The chip type thermistor element according to claim 1, which has a resistance of 0 Ω or less. 3. A base material (1) having an element formation surface, a first electrode layer (2) provided on the element formation surface, and a first electrode layer (2).
Chip type thin film thermistor element comprising a thermistor thin film (3) provided on an electrode layer, and second and third electrode layers (4,5) facing the first electrode layer through the thermistor thin film. A method of manufacturing a substrate, which comprises: forming a thin film pattern in which the first electrode layers for a plurality of chips are arranged in a matrix on the substrate (31) serving as the base material; and a pattern of the first electrode layer. And forming a layer to be the thermistor thin film as one thin film layer over the region of the plurality of chips, and forming a layer of the thermistor thin film on the first electrode layer corresponding to the first electrode layer. The method further comprises the steps of forming a thin film pattern of the second and third electrode layers, and cutting the chip (34) after forming the thin film patterns of the second and third electrode layers. To say Method for manufacturing a p-type thin film thermistor element.