JPH02170401A - thin film thermistor - Google Patents

Abstract

PURPOSE:To expand the range of temperature measurement by the use of one chip with high precision by a method wherein multiple thin film thermistors are formed by the same process. CONSTITUTION:Electrode patterns 13a-13c as well as thermistor thin films 14a-14c are provided on an SiO2 film 12 on the surface of the same chip substrate of an Si water. Thus, the temperature characterisitics of the produced thermistors are made even. Accordingly, when multiple thermistors are used in pairs, required range of temperature measurement can be expanded only by the thermistors provided in the same chip so as to maintain the precision of temperature measurement in case of changing over applications. Furthermore, the specific resistance of the thermistors can be set up at an arbitrary value with high precision by changing the dimensions of electrodes 14a-14c especially those of patterns 13a-13c (interval, length and width of patterns) so that the dimensions may be controlled using photolithography in high reproducibility and with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermistor used as a temperature sensor, and particularly to a thin film thermistor.

[Prior Art] Thermistors are used in a wide range of applications such as consumer products, industrial products, OA equipment, and automobiles. Unlike thermocouples and resistance thermometers, thermistors have nonlinear output characteristics, so they can be measured with high sensitivity in narrow ranges of 1111 m. Measurement is possible using a circuit.

Furthermore, the manufacturing method is suitable for mass production, and the price of the element is low compared to other sensors, so it is used in large quantities.

Conventional thermistors have often been bulk types made from processed sintered bodies or bead types made from sintered powder, but recently thin film thermistors using sputtering technology have also been developed and used. Both types have the same output characteristics as described above.

FIGS. 2(a) and 2(b) are schematic configuration diagrams of one chip of a conventional thin film thermistor, FIG. 2(a) is a plan view thereof, and FIG. 2(b) is a - It is a sectional view along the A line.

In FIGS. 2(a) and 2(b), 1 is a chip substrate, and 2 is an insulating film formed on the chip substrate 1. In FIG. Note that the chip substrate 1 may be an insulator, and in that case, it is not necessary to form an insulator film, but it is generally made of a metal or semiconductor that has good thermal conductivity, that is, a good thermal response during temperature measurement. It is more convenient to use thin film thermistors because they can take advantage of their features.A pair of metal electrodes is formed by forming a pattern of almost the same shape, for example a comb shape, on the insulating film 2 with the comb portions facing each other. Pattern 3a, 3b
A thermistor thin film 5 is uniformly deposited thereon by a PVD method such as sputtering so as to cover each pattern portion (comb-shaped portion) of the electrode patterns 3a and 3b, thereby forming a thin film thermistor. And electrode patterns 3a, 3b
Wiring is performed by connecting electrode leads (not shown) from the exposed portions 4a and 4b, thereby forming the basic portion of the thin film thermistor.

In the above configuration, the pair of electrode patterns 3a.

Utilizing the temperature characteristics of the thermistor resistance between 3b and 3b, it is widely used as a temperature sensor like a normal thermistor. In particular, thin film thermistors have been developed to meet the recently increasing needs of general thermistors for improved responsiveness and surface mountability.

[Problems to be Solved by the Invention] The conventional thin film thermistor as described above has high sensitivity like a normal thermistor, but its characteristics are nonlinear, so it is not suitable for measurement over a wide temperature range.

An example of the narrowest range measuring device is an electronic thermometer. A temperature range of 35 to 42°C is sufficient. When the B constant of the thin film thermistor is 4000, the rate of change is extremely large, about 5%/°C. However, when using this thin film thermistor, for example, when measuring temperatures from 0 to 100 degrees Celsius, the resistance value is 0.
The resistance at 100° C. is about 1/60 of the resistance at 100° C., and at 200° C. it is significantly smaller than 17,800. Therefore,
The temperature range when using a thin film thermistor is said to be limited to about 100°C, although it depends on the circuit.

One way is to devise a circuit system, but it is said to be difficult to implement with an inexpensive circuit because the range of resistance value variation is large. Therefore, the next possible method is to use a pair of thin film thermistors with different resistance values and automatically change the range using an electronic circuit to expand the temperature measurement range.

When adopting such a method, good results cannot be expected if conventional thin film thermistors are used as they are. In other words, with thin film thermistors made separately, there are many problems such as difficulty in matching the characteristics, difficulty in assembling them into a pair of thermistors, difficulty in downsizing even if they are assembled, and difficulty in manufacturing inexpensive thin film thermistors. ing.

This invention was made in order to solve the above-mentioned problems, and it is a composite type that can accurately measure temperature over a wide range with one chip by creating multiple thin film thermistors with different resistance ratios using the same process. The purpose of the present invention is to provide a thin film thermistor.

[Means for Solving the Problems] A thin film thermistor according to the present invention includes an electrode pattern formed on an insulating film on the surface of a chip substrate, and a thermistor thin film deposited to cover the electrode pattern. , a plurality of thermistor film elements having different resistance values are formed on the same chip. These thermistor film elements having different resistance values are formed by changing one or more of the spacing, length, and width between each pair of electrolytic patterns.

[Function] In the present invention, since thin film thermistor elements having different resistance values are formed in the same chip by the same process, the temperature characteristics of the plurality of obtained thermistors can be made uniform. Therefore, by using a combination of these multiple thermistors, the desired temperature measurement range can be expanded using only thermistors formed in the same chip, and the temperature measurement accuracy can be maintained when switching between them. . Further, the resistance ratio of the plurality of thermistors can be accurately set to any value by changing the dimensions of the electrodes, especially the patterns. In particular, by using photolithography technology to control the dimensions of this pattern, both reproducibility and precision can be improved.

[Example] FIGS. 1(a) and 1(b) are structural explanatory diagrams using schematic diagrams of a thin film thermistor showing an example of the present invention.
) is a plan view, and (b) is a BB sectional view shown in (a).

In FIGS. 1(a) and (b), 11 is silicon (
12 is an insulator film of S10° formed by oxidizing the entire upper surface of the chip substrate 11. A common electrode 14a having an electrode pattern 13a on the insulating film 12, an electrode 14b having an electrode pattern 13b, and an electrode 14c having an electrode pattern 13c are formed on the insulating film 12, respectively.
It is formed by sputtering using a patterned photoresist mask (not shown) so that 3a and 13c face each other.

All of these electrodes and electrode patterns are made of the same metal, such as one of Pt, Au, Al, Cr, etc., and the electrode patterns are formed in a comb shape as in the conventional example shown in FIG. However, it is not necessary to limit the shape to a particularly clear comb shape.

A thermistor material is deposited on the regions formed by, for example, the electrode patterns 13a and 13b and 13a and 13c arranged as described above, and the thermistor thin film 15 is deposited, respectively.
a and 15b are formed (the formation method will be described later). That is, in the case of this embodiment, two thin film thermistors having different resistance values constituted by the thermistor thin film 15a and thermistor thin film 15b are connected to the common electrode 14a.
It is formed on the left and right sides of the center.

As described above, in the embodiments shown in FIGS. 1(a) and 1(b), two thin film thermistors are formed on the same chip substrate, but in the thin film thermistor according to the present invention, although N thin film thermistors are configured ( It is formed by arranging N+1) electrodes and N thermistor thin films in series on the same chip.

The embodiment shown in FIG. 1 shows the case of N-2. In this case, (N+1) electrodes (for example, 14a, 14
This device has a feature that the resistances of the N thin film thermistors can be electrically measured individually or by switching the resistances of the N thin film thermistors by pulling out lead wires from the terminals (b, 14c). In addition, for each resistor of the two thin film thermistors, the dimensions between the electrode patterns including the electrodes, that is, the distance between the patterns (one width and the length), are set to predetermined dimensions, and the thermistor thin film is formed to have a constant thickness. This allows the product to be obtained in a container.

The characteristics and operation of this wide range thin film thermistor will be described below with reference to specific numerical examples in the case of the embodiment shown in FIG.

First, when the resistance of the thin film thermistor formed by the thermistor thin film 15a is R1, and the resistance of the thin film thermistor formed by the thermistor thin film 15b is R2, R (25°C)
-50 Ω and R2 (25°C) -1,400 kΩ to obtain a twin thin film thermistor with a resistance ratio of R2 and R1 of 28 times. In this way, the B constant becomes B25~1
oo-4285K.

Table 1 shows the resistance table of thermistors from 825 to 200 K.

Table 1 In the conventional method, only R1 is measured, so even in the range of 0 to 75°C, the resistance value is reduced from 175 to 6.46, which is about 1/30 of Ω. When ΔFJ is determined from 0 to 200℃ using the same circuit,
It is difficult to achieve this because it is necessary to accurately measure the resistance of approximately 1/80 (l).Therefore, measurements at 75 to 200°C are performed using resistor R2.The range of change in the resistance value of R2 is 180 to 8.02Ω.
The resistance change range is designed to be approximately equal to the resistance change range of R1 from 0 to 75°C. By measuring the two resistances while switching between them depending on the temperature range in this way, it is possible to measure a wide range with the same circuit. Although the case where there are two resistors has been described here, it is clear that the temperature range can be further expanded by using three or more resistors. Since it is easy to automatically switch the resistance and set the DI with recent electronic circuit technology, the explanation will be omitted here. In this way, if the wide range thin film thermistor according to the present invention is used,
Processing including temperature conversion can be performed using an IC.

Next, a method for manufacturing a thin film thermistor according to the present invention will be explained based on FIGS. 1(a) and 1(b).

(a) An insulator film 12 of an oxide film 810□ is formed on the chip substrate 11 of a single crystal silicon wafer, a resist (not shown) is applied on the insulator film 12, and electrodes 14a, 14b, 14c are formed by photolithography technology. Electrode patterns 13a, 13b, and 13e are formed. The comb spacing, comb length, number of combs, etc. that constitute the pattern of each electrode are set in consideration of the resistance value and the ratio of the resistance values.

(b) Using the resist pattern as a mask, electrode materials (Pt, ALI, AN,
By removing the resist after forming a film of Cr or one of the like, electrode patterns 13a, 13b, and 13c are formed as comb-shaped electrodes together with electrodes 14a, 14b, and 14c, respectively.

(c) Next, a resist (not shown) is applied again, and a thermistor pattern is formed by photolithography.

(d) Using this resist pattern as a mask, Mn, N1. Thermistor thin films 15a and 15b made of a Co oxide mixed film are formed. As the target material for the thermistor, SIC or other thermistor material may be used, which is a mixture of oxides such as Mn, Ni, and Co. After forming the thermistor thin films 15a and 15b, although not shown, 5IO2 (SIN may also be used) is sputtered as a protective film, and after the film is formed, the resist is peeled off. Due to the thermistor pattern formed on the comb pattern, two thin film thermistors 15a, 1 are placed on the left and right sides of the common electrode 14a.
5b is formed.

(e) The basic structure of this twin-shaped thin film thermistor is fabricated in the above steps, but if the moisture resistance of the thermistor film is a problem, coat a polyimide film etc. in a pattern slightly larger than the thermistor pattern to protect it from moisture. Forming a film is effective.

(f) Desired thermistor chips can be obtained by dicing a silicon wafer along scribe lines and selecting resistance. In the example of two thermistors shown in Table 1, the chip size can be reduced to about 4.5×1.6u+2. The film thicknesses of the thin film thermistors on the same chip are the same, and resistance selection can be made by measuring R or R2.

Since the accuracy of recent photolithography technology is high,
The variation in electrode dimensions is small and can be ignored as a variation in the resistance value of the thermistor.

The above manufacturing method has the following features.

(1) A silicon wafer is used as a substrate. Although there are examples of ceramic substrates such as alumina being used as substrates for thin film thermistors, silicon wafers for ICs are superior in the following points.

・Surface is flat and variation in resistance value is small.

・It has high thermal conductivity and low thermal diffusivity, making it suitable as a substrate for temperature sensors.

It can be mass-produced using IC photolithography equipment. For example, a square alumina substrate does not require IC manufacturing equipment.

(2) Since photolithography technology is used, precision in microfabrication is high. Although it is not impossible to make the wide range thermistor shown in FIG. 1 by screen printing, it is not practical in terms of accuracy, miniaturization, etc.

(3) Because of the fine structure. The ratio of N resistance values is constant. Since the thermistors are close together, the film thickness can be considered constant. In large-scale sputtering equipment, it is a challenge to keep the film thickness distribution constant. Even if there is some thickness distribution within the wafer, as long as the ratio is constant, a decrease in yield can be prevented.

(4) The thermistor film is formed by sputtering, so the film quality is uniform. The thermistor on the chip is formed at the same time, and the manufacturing method does not cause any difference in B constant etc. in principle.

[Effects of the Invention] As described above, according to the present invention, a thin film thermistor for a wide range is constructed by forming a plurality of thermistor elements having different resistance values on the same chip, so that the following effects can be obtained. .

(1) The temperature measurement range of the thermistor can be easily expanded while maintaining high sensitivity and accuracy. Digital thermometers for thermistors are already in widespread use, and with the addition of a sampling circuit to these circuits, the thin film thermistor of the present invention can be used to expand the range to 111 m, making it industrially effective. is extremely large.

(2) Since a plurality of thin film thermistors having different resistance values are formed on the same chip, the structure is simple and the size can be reduced.

It is particularly excellent in surface mounting properties.

(3) Since a plurality of thin film thermistors with different resistance values can be manufactured on the same chip at the same time, it is cheaper than other methods.

(4) Resistance selection is easy. Since the resistance ratio is determined by the electrode dimensions, the resistance can be selected by focusing on a specific thermistor within the chip.

(5) Easy to calibrate. The ratio of resistance is constant and B
Since the constants are the same, the entire measurement range can be adjusted by single-point calibration at a temperature that is easy to calibrate.

In addition to the above, temperature sensors are widely used not only in the industrial range but also in consumer equipment. In particular, thermistors have been used mainly in consumer equipment because they are inexpensive and can perform highly sensitive measurements, but their shortcomings are that they have a narrow temperature measurement range, which limits their use. Since this problem has been solved by this invention, it is expected that the scope of application will be expanded in the fields of both consumer equipment and industrial equipment in the future.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view illustrating the structure of a thin film thermistor showing one embodiment of the present invention, and FIG.
), FIG. 2(a) is a plan view explaining the structure of a conventional thin film thermistor, and FIG. 2(b) is a cross-sectional view of the conventional thin film thermistor.
It is an AA sectional view in figure (a). In FIGS. 1(a) and 1(b), 11 is a chip substrate made of a silicon wafer, 12 is an insulating film of silicon oxide, 13a, 13b, and 13c are electrode patterns;
4a, 14b. 14c is an electrode, and 15a and 15b are thermistor thin films. Agent Patent Attorney Muneharu Sasaki Figure 1 Figure 2 (b) (b)

Claims (2)

[Claims] (1) In a thin film thermistor consisting of an electrode pattern formed on an insulating film on the surface of a chip substrate and a thin film thermistor film element deposited covering at least a portion of the electrode pattern, a plurality of thin film thermistors having different resistance values are used. A thin film thermistor characterized in that the thermistor film elements described above are formed on the same chip. (2) The plurality of thermistor elements having different resistance values form thermistors having different resistance ratios by changing at least one or more of the spacing, width, and length between each pair of the electrode patterns. The thin film thermistor according to claim 1, characterized in that: