JP2001110602A - Thin-film resistor forming method and sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To approximate a value of the thin-film temperature coefficient (TCR) of a thin-film resistor to almost zero, without damaging etching property. SOLUTION: When a thin-film resistor is formed by sputtering method, one kind or two or more kinds among Ti, V, Zr, Nb, Mo, Hf, Ta and W are added to combine whose main component is NiCr, and a TCR value of the thin-film resistor is controlled by the kind and the amount of the additives.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a thin film resistor and a sensor.

[0002]

2. Description of the Related Art Heretofore, thin film technology has been used for manufacturing microcircuits. Conventionally known thin film resistors formed using such a thin film technology include Ta,
TaN, a _{Ta-SiO 2, Cr-SiO} 2, NiCr or the like. Among them, NiCr alloys have been widely used because they are relatively stable and easy to manufacture.

Usually, a thin film resistor made of a NiCr alloy is often used in a Ni-rich composition. this is,
This is because, when the amount of Cr is large, the change with time is large and the stability is poor, and the material is also mechanically brittle. Therefore, Ni: 80 wt.
%, Cr: an alloy based on 20 wt% is used.
However, strain sensors and precision resistors for measurement have a temperature coefficient of resistance near zero due to their properties (hereinafter, TCR: Thermal Coef).
ficient of Resistance), whereas a thin film resistor obtained by sputtering using an alloy having such a composition as a target has a TCR of
The value is as large as about 130 ppm / ° C., and it is difficult to obtain a TCR value near zero. On the other hand, conventionally, a NiCr thin film resistor is formed by a vacuum evaporation method, and air or oxygen is introduced into a film forming tank during or after the thin film is formed.
CrO or Cr ₂ by oxidizing a part of Cr in the Cr component
Attempts have been made to generate O ₃ and bring the TCR value closer to zero. However, this method is poor in reproducibility and rarely used in practice.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 58-119601 and Japanese Patent Application Laid-Open No. 58-119603
As disclosed in Japanese Unexamined Patent Publication, NiCrSi and NiCrGe 3 are obtained by adding Si and Ge to a NiCr alloy.
Original alloys have been proposed. Furthermore, a NiCrTaSi quaternary alloy which has reduced TCR value variation and improved stability, particularly, resistance to moisture load life has been disclosed in Japanese Patent Application Laid-Open No. 60-270.
No. 13 discloses this. In addition, JP-A-57-1
73909 also discloses a NiCrSiFe quaternary alloy.

[0005]

SUMMARY OF THE INVENTION Until now, Ni
As a means for adjusting the TCR value of a thin film resistor containing Cr as a main component, addition of Si and Ge to such a thin film resistor has been reported.
Only thin film resistors (NiCrSi, NiCrSiTa, etc.) based on a NiCrSi alloy to which i is added are known.

However, these thin film resistors are made of NiC.
Since it is based on rSi, it is difficult to form a predetermined thin film pattern by a wet etching method. That is, N
When an attempt is made to form a thin film resistor by etching using an iCrSi-based alloy, etching cannot be performed with a normal etching solution.
It is necessary to use a hydrofluoric acid-based etching solution heated to a temperature of not less than ° C. However, since a heated hydrofluoric acid-based etchant has a very strong etching ability, when such an etchant is used, the substrate on which the thin film resistor is formed (especially the NiCrSi film on the back surface of the substrate, etc.) There is a problem that even the non-formed surface is etched. In particular, a glass substrate, an aluminum alloy substrate, and the like are very easily etched, and there is a problem that the application range of the NiCrSi film is restricted in forming devices using these members.

In order to solve such a problem, a new element having a function of adjusting the TCR value of a NiCr alloy to the same extent as NiCrSi has been discovered, and a NiCr alloy formed by adding such an element has been developed. New NiCr with thin film etching performance better than NiCrSi alloy
The realization of a system alloy thin film is desired.

An object of the present invention is to make the TCR value of a thin film resistor close to substantially zero without impairing the etching property.

[0009]

According to the first aspect of the present invention,
In a method of forming a thin film resistor by a sputtering method, Ti, V, Zr, Nb, Mo, Hf, Ta or W is added to an alloy mainly composed of NiCr, alone or in combination of two or more. The temperature coefficient of resistance of the thin film resistor is controlled by the type and amount of the additive.

According to a second aspect of the present invention, there is provided a sensor comprising: a substrate;
Ti, V, Zr, N
a thin film resistor formed on the substrate by adding b, Mo, Hf, Ta or W alone or in combination of two or more,
Is provided.

According to a third aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 23 to 29 wt /.
% Hf.

According to a fourth aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 9 to 12 wt /%.
Of Ti.

According to a fifth aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 18.5 to 22.
Contains 5 wt /% Zr.

According to a sixth aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 14 to 17 wt /.
% Nb.

According to a seventh aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 20 to 24 wt /.
% Ta.

According to an eighth aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 24 to 29 wt /.
% W.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

This embodiment is an example of application to a pressure sensor. First, in the pressure sensor according to the present embodiment, four strain gauges R1 are provided on the surface of the strain-generating portion 2 as a substrate serving as a pressure-sensitive portion of the diaphragm 1 processed using a metal elastic material, for example, an aluminum alloy. , R2, R3, and R4 are formed as a sensor pattern 3 constituting a bridge circuit. As shown in FIG. 2, the cross-sectional structure of the pattern is such that after forming an insulating resin layer 4 on the surface of the strain generating portion 2, a thin film resistor layer 5 as a thin film resistor mainly composed of a NiCr alloy is formed by a sputtering method. It has a formed structure.

Here, the thin-film resistance layer 5 is made of an alloy mainly composed of NiCr, Ti, V, Zr, Nb, Mo, Hf,
Ta or W is added alone or in combination of two or more,
The temperature coefficient of resistance (TCR: Thermal Coefficient of Resistance) of the thin film resistor 5 is controlled so as to be substantially zero depending on the type and amount of the additive. The control of the TCR value of the thin film resistor 5 depending on the type and amount of the additive will be described in detail in the section of “Example”. The thin-film resistance layer 5 is formed to have a thickness of 0.1 μm, and successively forms a 0.2 μm-thick Ti layer and a 1.5 μm-thick Cu layer which become electrode layers. Then, a pressure sensor is completed by forming a sensor pattern as shown in FIG. 1 using a normal thin film pattern forming technique.

In the pressure sensor completed in this manner, the strain gauges R1 and R2 are provided at the portion where the tensile strain of the strain generating portion 2 is generated, and the strain gauges R3 and R4 are provided at the portion where the compressive strain of the strain generating portion 2 is generated. These four gauges
They are connected by a predetermined lead wiring pattern L to form a bridge circuit. Here, in FIG. 1, Vo and Ve indicate an input voltage terminal and an output voltage terminal input to the bridge circuit, respectively.

In such a configuration, the four strain gauges are R1, R2, R3, and R4, and the input voltage and output voltage of the bridge circuit are Ve and Vo, respectively. the output voltage Vo when the applied to be measured pressure is zero becomes _{Vo = Ve · {R 1 /} (R 1 + R 3) -R 4 / (R 2 + R 4)}. Therefore, using this equation, the pressure applied to the pressure sensor can be calculated from the output voltage Vo.

Next, Ti, V, Zr, Nb, Mo, H
The pressure sensor of the present embodiment using the thin-film resistance layer 5 composed of a NiCr alloy to which f, Ta or W is added alone or in combination of two or more types sufficiently satisfies the function as the sensor. In particular, for the zero drift important in the pressure sensor, NiC is used as the material of the thin film resistance layer 5.
It is almost the same as that using rSi. In addition, the finished appearance is NiCrSi as the material of the thin film resistance layer 5.
It was much more beautiful than the one using.
This is because the etching property is improved, so that the periphery of the pressure sensor (except for the sensor surface on which the insulating resin is applied to form the insulating resin layer 4) is not excessively removed by etching. The inventor of the present application has confirmed such zero drift and etching properties by experiments.

As described above, by adding Ti, V, Zr, Nb, Mo, Hf, Ta, and W to an alloy containing NiCr as a main component, the TCR value of the obtained NiCr alloy thin film resistance layer 5 is obtained. Can be made substantially zero, and the etching property can be improved.

Although the present embodiment has been described with respect to an example in which the thin film resistance layer is applied to a pressure sensor, the present invention is also applicable to a load cell for measuring weight and a torque sensor for measuring torque. That is, it can be widely applied to a strain sensor that generically includes a pressure sensor, a load cell, a torque sensor, and the like.
In addition, the present invention can be widely applied to precision resistors and the like used for measurement.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the formation of a thin-film resistor mainly composed of NiCr according to the present embodiment will be described. A thin film resistor is formed on a substrate by using a sputtering method used for forming a general resistor thin film. The target used for sputtering is Ni: 80 having a diameter of 12.7 cm.
wt%, Cr: 20 wt%, and a metal chip (10 mm × 10 mm ×) of various additive elements (Hf, Ti, Zr, Mo, Nb, Ta, W) on such a NiCr alloy target surface. A composite target having a predetermined number of 1 mm (length × width × thickness) was used. The contents (composition) of various additive elements in the NiCr-based alloy thin film obtained using such a composite target were analyzed by an energy dispersive X-ray microanalyzer.

Next, a substrate, for example, a glass substrate is set at a predetermined position of the sputtering apparatus, and the ultimate vacuum degree is 3 × 10 ⁻⁴ Pa or less. Discharge pressure is 0.9 Pa (Ar gas pressure). ℃ Discharge power RF1kW under the condition of about 0.1μ NiCr alloy thin film on the substrate
m, and Ti and Cu as electrodes are continuously formed thereon.
Was formed into a film of 0.2 μm and 1.5 μm, respectively.

The samples formed under the respective sputtering conditions are subjected to predetermined patterning,
A thin-film resistor made of an iCr-based alloy was prepared. afterwards,
After soldering the lead to the electrode of the thin film resistor, a predetermined characteristic evaluation was performed. That is, put in a temperature test tank,
The change in resistance value from 40 degrees to 120 degrees was measured, and the TCR value of the thin film resistor was determined.

FIG. 3 shows a prototype of NiCrH fabricated by the method shown above using Hf, Ti and Zr metal chips.
4 is a graph showing the relationship between the added amount of Hf, Ti, and Zr and the specific resistance of the obtained thin film resistor for the thin film resistors of f, NiCrTi, and NiCrZr. Regarding any of the additional elements, a result was obtained in which the specific resistance increased with an increase in the added amount.

FIG. 4 shows NiCrHf, NiCrTi, N
4 is a graph showing the relationship between the added amount of Hf, Ti, and Zr and the TCR value of a thin film resistor for an iCrZr thin film resistor. Regarding any of the additional elements, the result that the TCR value decreased with an increase in the added amount was obtained. Hf is about 26w
t%, Ti is about 10 wt%, Zr is about 20 wt%, and
The CR value is zero. In addition, since the thin film resistor requires a high specific resistance, when the specific resistance of the thin film resistor having a TCR value near zero in the graphs of FIGS. 3 and 4 is obtained, NiCrHf: 190 μΩcm, NiCrZ
r: 190 μΩcm, NiCrTi: 210 μΩcm. These specific resistance values are set to a specific resistance of 150 μΩcm obtained when the TCR value of the NiCrSi alloy thin film is approximately zero.
This is a preferable value as a higher thin film resistor.

FIG. 5 shows a NiCrM prototype made by the method described above using metal chips of Mo, Nb, Ta, and W.
5 is a graph showing the relationship between the amounts of Mo, Nb, Ta, and W added and the specific resistance of the obtained thin film resistors for thin film resistors of o, NiCrNb, NiCrTa, and NiCrW. In each of the additive elements, the result was obtained that the specific resistance increased with an increase in the added amount.

FIG. 6 shows NiCrNb, NiCrTa, N
4 is a graph showing the relationship between the amount of Nb, Ta, and W added and the TCR value of a thin film resistor for an iCrW thin film resistor. As is clear from the graph of FIG. 6, a result was obtained in which the TCR value decreased with an increase in the addition amount of any of the added elements. Nb is 15 wt%, Ta is 2
At 2 wt% and W at 26 wt%, the TCR value becomes substantially zero.
Further, since the high resistance of the thin film resistor is required, the specific resistance of the thin film resistor having a TCR value near zero in the graphs of FIGS. 5 and 6 is calculated as NiCrNb: 15.
0 μΩcm, NiCrTa: 150 μΩcm, NiCr
W: 140 μΩcm. The value of these specific resistances is N
The TCR value of the iCrSi alloy thin film resistor is substantially the same as the specific resistance of 150 μΩcm obtained near substantially zero.

Here, the TCR value required as a general thin film resistor is ± 50 ppm or less, preferably ± 30 ppm.
ppm or less, more preferably ± 10 ppm or less.
From the experimental results described above, it was found that Ni (80 wt%) Cr (20
wt%), HCR, Ti, Zr, Nb, Ta, and W are added, the resulting alloy thin film resistor has a TCR value of ± 10 p.
A summary of the addition amounts below pm is shown in the table shown in FIG.

Further, the metal element T shown in the above-described embodiment is used.
When i, Zr, Nb, Mo, Hf, Ta, and W are shown in the periodic table, they are as shown in FIG. 8, and therefore, as with other elements, V is a thin film resistor mainly composed of NiCr. Is determined to have a function of adjusting the TCR value of.

The above results show that Ti, Z
This is the case where the elements r, Nb, Mo, Hf, Ta, and W are added alone, but the inventor of the present application discloses that Ti, Ta, Nb
An experiment was also conducted on the addition of two elements such as Ti and Ta, and Ti and Nb. In the experiment, the experiment was performed assuming that the number of chips of the two elements was equal to each other. I will not show details,
With the number of two kinds of metal chips placed on the NiCr target, the specific resistance of the obtained alloy thin film increases,
The value obtained resulted in a decrease. This means that Ti, V, Zr,
Nb, Mo, Hf, Ta, W alone or
It shows that the same phenomenon can be caused by adding more than one kind.

Next, the inventor of the present application examined the etching property of the NiCr alloy thin film to which the various elements described above were added. Here, the etching property is a subjective evaluation obtained by observing with a microscope how much fine pattern can be formed when the thin film is etched into a desired pattern, or whether the pattern contour is smooth. is there. In this experiment, a hydrofluoric acid-based etching solution without heating (normal temperature: 24 ° C.) was used as the etching solution in order to simply compare the difference with the NiCrSi alloy thin film.
As an etching sample, (100 mm × 100 mm ×
T formed on a glass substrate of 1 mm (length x width x thickness)
Ti, Zr, Nb, Mo, whose composition has a CR value of substantially zero
0.1 μm thick NiCr to which Hf, Ta, and W are added
An alloy thin film was used.

FIG. 9 shows the various elements described above, that is, T
Ni added with i, Zr, Nb, Mo, Hf, Ta, W
It is a schematic diagram which shows the table | surface of the evaluation regarding the etching property of a Cr alloy thin film. The evaluation results shown in the table of FIG. 9 show that all the element-added NiCr alloy thin films are better than the etching properties of the NiCrSi alloy thin films. For V, no experiment was conducted to confirm the actual etching properties, but as described above using the periodic table, NiCrSi
It is presumed that the NiCrV alloy thin film has better etching properties than the alloy thin film.

For the NiCr alloy, the positive TCR value gradually decreases as the amount of Cr increases.
It is already known that the concentration becomes approximately zero at approximately 60 wt% and increases in the negative direction by further addition. The elements shown in the present invention are Ni: 80 wt%, Cr: 20 wt% N
When added to the iCr alloy, the TCR value decreased with the added amount of the element. Therefore, it is clear that the base NiCr alloy is effective when the TCR value is in the positive direction. Therefore, it is desirable that the Cr content of the base thin film resistor mainly composed of NiCr be 60 wt% or less.

Further, as a NiCr-based thin film resistor,
In general, it is already known that as the Cr content increases, the change with time increases and the material becomes brittle. NiCrSi
In the alloy thin film, Ni: 80 wt%, Cr: 20 w
Since it is based on t%, in the present invention,
It is desirable to base this composition on.

[0039]

According to the first aspect of the present invention, there is provided a thin film resistor forming method for forming a thin film resistor by a sputtering method, wherein Ti, V, Z is added to an alloy containing NiCr as a main component.
r, Nb, Mo, Hf, Ta or W is added alone or in combination of two or more, and the thin film temperature coefficient of the thin film resistor is controlled by the kind and amount of the additive, so that the etching property is good. , The TCR value of the thin film resistor can be approximated to zero.

According to a second aspect of the present invention, there is provided a sensor comprising: a substrate;
Ti, V, Zr, N
a thin film resistor formed on the substrate by adding b, Mo, Hf, Ta or W alone or in combination of two or more,
So that while maintaining good etching properties,
It is possible to make the TCR value of the thin film resistor close to substantially zero.

According to a third aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 23 to 29 wt /.
%, The control of the TCR value of the thin film resistor is easy, and the TCR value can be easily approximated to zero.

According to a fourth aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 9 to 12 wt /%.
, The control of the TCR value of the thin film resistor is easy, and the TCR value can be easily approximated to zero.

According to a fifth aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 18.5 to 22.
Since Zr is contained at 5 wt /%, the TCR value of the thin film resistor can be easily controlled, and the TCR value can be easily approximated to zero.

According to a sixth aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 14 to 17 wt /.
%, The control of the TCR value of the thin film resistor is easy, and the TCR value can be easily approximated to zero.

According to a seventh aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 20 to 24 wt / wt.
% Of Ta, the control of the TCR value of the thin film resistor is easy, and the TCR value can be easily approximated to zero.

According to an eighth aspect of the present invention, in the sensor according to the second aspect, the thin film resistor is added in an amount of 24 to 29 wt /.
%, The control of the TCR value of the thin film resistor is easy, and the TCR value can be easily approximated to zero.

[Brief description of the drawings]

FIG. 1 is a plan view showing a bridge circuit pattern of a pressure sensor as one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a graph showing the relationship between the added amount of Hf, Ti, and Zr to NiCr and the specific resistance of the obtained thin film resistor.

FIG. 4 is a graph showing the relationship between the amounts of Hf, Ti, and Zr added to NiCr and the TCR value of a thin-film resistor.

FIG. 5 is a graph showing the relationship between the amount of Mo, Nb, Ta, and W added to NiCr and the specific resistance of the obtained thin film resistor.

FIG. 6 is a graph showing the relationship between the amounts of Nb, Ta, and W added to NiCr and the TCR value of a thin-film resistor.

FIG. 7 shows that the TCR value of the obtained alloy thin film resistor is ± 10 p
Hf, Ti, Zr, N for NiCr below pm
It is a schematic diagram which shows the addition amount of b, Ta, and W collectively.

FIG. 8 shows a metal element Ti, Zr,
It is a schematic diagram which shows arrangement | positioning of Nb, Mo, Hf, Ta, and W.

FIG. 9 is a schematic diagram showing an evaluation on the etching property of a NiCr alloy thin film to which Ti, Zr, Nb, Mo, Hf, Ta, and W are added.

[Explanation of symbols]

 2 Substrate (strain-generating part) 5 Thin film resistor (thin film resistance layer)

Claims (8)

[Claims] 1. A thin film resistor forming method for forming a thin film resistor by a sputtering method, wherein Ti, V, Zr, Nb, Mo, Hf,
Ta or W is added alone or in combination of two or more,
A method of forming a thin film resistor, wherein the temperature coefficient of resistance of the thin film resistor is controlled by the type and amount of an additive. 2. A substrate and an alloy containing NiCr as a main component are formed on the substrate by adding Ti, V, Zr, Nb, Mo, Hf, Ta or W alone or in combination of two or more. A thin film resistor. 3. The thin film resistor has an addition amount of 23 to 29 wt /
3. The sensor according to claim 2, comprising% Hf. 4. The thin film resistor has an addition amount of 9 to 12 wt /%.
3. The sensor according to claim 2, comprising Ti. 5. The thin film resistor has an addition amount of 18.5 to 22.
3. The sensor according to claim 2, comprising 5 wt /% Zr. 6. The thin film resistor may be added in an amount of 14 to 17 wt /
3. The sensor according to claim 2, comprising% Nb. 7. The thin film resistor may be added in an amount of 20 to 24 wt /
3. The sensor according to claim 2, comprising% Ta. 8. The thin film resistor may be added in an amount of 24 to 29 wt /
3. The sensor according to claim 2, comprising% W.