JP2002008906A - Resistor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a resistor provided with a resistive laminate, composed of a plurality of resistors laminated on the surface of an insulating board to be improved in long-term stability, by reducing its temperature coefficient of resistance TCR to zero over a wide range of temperature. SOLUTION: When the rote of change of a resistance with temperature [Δt] for eaching resistor layer of the resistive laminate is approximated by the quadratic formula, [αΔt+β(Δt)2], or the formula of higher order, at least the signs of the linear temperature coefficient α and quadratic temperature coefficient β of a certain resistor layer are set opposite to those of the other resistor layer. A resistor layer of superior long-term reliability, how ever, is used as the uppermost layer of the resistive laminate. At least, α and β may be both set positive for one of the resistor layers, and α and β be both set negative for the other of the resistor layers. At least, one of the resistor layers may be formed of Ni-Cr alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film resistor in which a thin film resistor is formed on the surface of an insulating substrate by vapor deposition or sputtering, or to a metal foil resistor using a metal foil resistor. The present invention also relates to a method for manufacturing the resistor.

[0002]

2. Description of the Related Art A thin film resistor is formed by depositing or sputtering a thin film resistor material on an insulating substrate such as glass or alumina, and a thin film is formed by forming a pattern on the thin film resistor by photoetching or laser processing. Resistors are known. Further, a metal foil resistor in which a metal foil is bonded to a substrate and a pattern is formed by photoetching, laser processing, or the like is also known.

In this type of resistor, it is necessary that the resistance is stable over a temperature range as wide as possible, and that the change in the resistance over time is small and the characteristics are stable for a long period of time.

The temperature coefficient of resistance (Temperature Coefficient of Resistance) indicates the stability of the resistance value with respect to temperature.
tance (hereinafter referred to as TCR). TCR here
Is defined by the following equation, for example, when 25 ° C. is a reference temperature, the resistance value at this temperature is R (25), and the resistance value at the temperature t is R (t). TCR (ppm / ° C.) = {R (t) −R (25)} / R
(25) × [1 / (t−25)] × 10 ⁶

When a resistance thin film or a metal foil is formed, it is generally desired to make the temperature coefficient of resistance TCR zero. Therefore, it is common to change the conditions for vapor deposition and sputtering, and to change the thickness and the type of the substrate. At present, a thin film resistor using Ta (tantalum) is known as one of the most stable resistors. Also N
Conventionally, the TCR approaches zero by adding Al (aluminum) or Si (silicon) to an i-Cr (nickel-chrome) alloy.

It is also known to connect a resistor having a positive TCR and a resistor having a negative TCR in series or in series to make the TCR close to zero. For example, Japanese Patent Publication No. 8-2148
No. 2 discloses a technique for reducing the non-linearity of the temperature change of the resistance value (described as the temperature dependence of TCR) by laminating a CrSiN thin film and a NiCrAl thin film.

In order to reduce the change in the resistance value of the resistor over time, it is necessary to cover the resistor thin film formed on the substrate with an antioxidant film or to hermetically seal the entire resistor. It was known.

[0008]

When it is desired to further reduce the TCR in a wide temperature range, for example, -55 ° C. to +125
If it is desired to keep the TCR within ± 5 ppm / ° C. in the temperature range of ° C., it is conceivable to control the non-linear component of the temperature change of the resistance value. That is, in this case, the resistance value change rate 値 R
(T) −R (25)｝ / R (25) is approximated by the following quadratic equation, and first, a primary temperature coefficient α (ppm / ° C.) and a secondary temperature coefficient β (ppm / ° C. ² ) are obtained. [R (t) -R (25)] / R (25) = α (Δt) +
β (Δt) ² where Δt = t−25

The secondary temperature coefficient β representing the non-linearity of the temperature change of the resistance value was conventionally considered to be uncontrollable.
In the -Cr alloy system, it is possible to control both the primary temperature coefficient α and the secondary temperature coefficient β.
Applicants have found that a TCR within ± 5 ppm / ° C. can be achieved in a temperature range of 25 ° C. Applicant is Japanese Patent Application No. Hei 1
0-351496 shows this method and the composition of the Ni-Cr alloy-based resistor.

However, it has been difficult for conventional resistors to simultaneously achieve a very small TCR and long-term stability. For example, N
In an i-Cr-based alloy resistor, it is difficult to reduce the TCR over a wide temperature range if the composition can achieve long-term stability. In some cases, protection from oxidation was not possible. Even if resistors other than the Ni-Cr alloy can achieve long-term stability, it is impossible to control the non-linearity of the temperature change of the resistance value, so that the TCR cannot be reduced over a wide temperature range.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a resistor which can make the temperature coefficient of resistance TCR close to zero in a wide temperature range and has excellent long-term stability. As a first object. A second object is to provide a method for manufacturing this resistor.

[0012]

According to the present invention, a first object is to provide a resistor having a resistor laminated body in which a plurality of resistors are laminated on a surface of an insulating substrate, wherein each layer of the resistor laminated body is formed of a respective resistor. When the rate of change of the resistance value due to temperature is approximated by a quadratic expression [αΔt + β (Δt) ² ] of the temperature change [Δt] or a higher-order expression, at least one of the primary temperature coefficient α and the secondary temperature coefficient β The sign is set opposite to the signs of the primary temperature coefficient α and the secondary temperature coefficient β of the other layers, while the uppermost layer is formed of a resistor having excellent long-term stability. You.

At least one layer of the resistor can have both α and β positive, and both α and β of the other layers can be negative. At least one of the layers can be a Ni-Cr based alloy resistor, which is convenient because α and β can be adjusted over a fairly wide range by additives and processing methods. Therefore, α, β
By appropriately laminating at least two kinds of Ni—Cr-based alloy resistors each having a desired TCR, a resistor having a desired TCR can be produced.

At least one of the stacked resistance laminates
The layer is made of a Ni— layer containing one or more elements of at least one of a group of Al, Si, Be, Mg, Ti, and Mn and a group of Mn, Fe, Co, Ti, and V.
It can be a Cr-based alloy.

[0015] Further, in the laminated resistor laminate, at least one layer can be constituted by a thin film resistor or a metal foil resistor. Alternatively, a thin film resistor and a metal foil resistor may be combined and laminated.

The resistor having excellent long-term stability, which is the uppermost layer of the resistor laminate, may be a Ni-Cr-Al alloy. This is because aluminum oxide film is formed by self-oxidation of Al contained in this alloy, and long-term stability can be obtained by this aluminum oxide film.

A second object of the present invention is to provide a method of manufacturing a resistor having a resistor laminated body formed by laminating resistors having different compositions on the surface of an insulating substrate. It is approximated by a quadratic expression [αΔt + β (Δt) ² ] of the temperature change [Δt] or a higher-order expression so that the rate of change in the resistance value of the resistance laminate due to the temperature calculated from this expression falls within a predetermined range. This is achieved by a method of manufacturing a resistor, characterized in that values of a primary temperature coefficient α and a secondary temperature coefficient β of a resistor in each layer are determined and a thickness of each layer is determined.

[0018]

FIG. 1 is a cross-sectional view showing the structure of a resistor according to an embodiment of the present invention. FIG. 2 is a diagram showing a comparison between a calculation result and a measurement result of a change in a rate of change in resistance with temperature. FIG. 3 is a view showing a measurement result of long-term stability of a resistance value change rate. FIG.
In the figure, reference numeral 10 denotes an insulating substrate, 12 denotes a lower layer formed on the substrate 10, and 14 denotes an upper layer formed on the lower layer 12. Here, the insulating substrate 10 is made of alumina.

The lower layer 12 is made of a high frequency (RF, Radio Freque
ncy) formed by sputtering, Ni-
Thin film resistor with Mn added to Cr alloy (hereinafter NiCrMn)
Thin film resistor). The upper layer 14 is formed on the lower layer 12 by high frequency sputtering.
Thin film resistor with l (hereinafter referred to as NiCrAl thin film resistor)
It is.

The atmosphere at this time was an Ar (argon) gas pressure of 0.5 Pa, an insulating substrate of alumina, an RF power of 300 W, and a thin film thickness of both resistors of 0.3 μm.
m. Further, the composition ratio of the Ni—Cr alloy, Ni / Cr (at
%) Is 77/23, the addition amount of Al is 12 at%,
The amount of n added is 10 at%. The heat treatment is performed at a temperature of 300 ° C. or higher, preferably about 5
By leaving at 00 ° C. for about 3 hours.

For each of the two types of thin film resistors,
The rate of change of resistance value with temperature was analyzed. That is, the rate of change in resistance value (R (t) -R (25)) / R (25) is approximated by the following quadratic equation, and the primary temperature coefficient α (ppm / ° C.) and the secondary temperature coefficient β (ppm / ° C.) ² ) Asked. [R (t) -R (25)] / R (25) = α (Δt) +
β (Δt) ² where Δt = t−25

As a result, the upper layer 14 made of a NiCrAl thin film resistor has α = −59.5 ppm / ° C. and β = −0.
035 ppm / ° C. ² , and the lower layer 12 made of a NiCrMn thin film resistor has α = 44.8 ppm / ° C. and β = 0.
It was 055 ppm / ° C ² .

The fact that the above-mentioned NiCrAl thin film resistor has very high long-term stability is disclosed in, for example, Japanese Patent Application No. 10-351.
As shown in FIG. 497, in this resistor, the value of the primary temperature coefficient tends to be negatively large, and the value of the secondary temperature coefficient β also tends to be negatively large. Therefore, it is difficult to make TCR close to zero in a wide temperature range. on the other hand,
In the NiCrMn thin-film resistor, the primary temperature coefficient α has a positive value, and the secondary temperature coefficient β also has a positive value. Therefore, by laminating these two thin film resistors, T
It becomes possible to make CR close to zero.

Here, the rate of change in resistance value with temperature when two layers of resistors were stacked was calculated. If the resistance in the upper layer 14 and the resistance in the lower layer 12 are regarded as parallel resistance, the rate of change in resistance value of the resistor in which two layers are laminated [(R (Δt) −R
(25)) / R (25)] is represented by the following equation.

[0025]

[Equation 1] [[(1 + α_U(Δt) + β_U(Δt)^Two) (1 + α_L(Δt) + β
_L(Δt)^Two) {ρ_U(1−h) + ρ_Lh}] / {ρ _U(1−h) (1 + α_U(Δt) +
β_U(Δt)^Two) + ρ_Lh (1 + α_L(Δt) + β_L(Δt)^Two)}]-1

Here, ρ _U is the resistivity of the upper resistor, ρ _L is the resistivity of the lower resistor, α _U and β _U are the primary and secondary temperature coefficients of the upper resistor, and α _L and β _L are the lower layer resistors. The temperature coefficient h of the resistor is the thickness of the upper resistor when the thickness of the laminated resistor is 1.

In this embodiment, since both the upper layer and the lower layer are made of a Ni--Cr alloy, the resistivity is substantially equal.
In this case, by setting ρ _U = ρ _L , the above equation is simplified as follows.

[0028]

## EQU2 ## [(1 + α _U (Δt) + β _U (Δt) ² ) (1 + α _L (Δt) + β _L
(Δt) ² ) / {(1 + α _U (Δt) + β _U (Δt) ² ) (1-h) + (1 + α _L (Δ
t) + β _L (Δt) ² ) h}]-1

In the above equation, NiCrAl thin film and NiCrM
By substituting α and β of the n thin film, the resistance value change rate with temperature at several thicknesses h was calculated. Curve A shown in FIG.
B and C show the calculation results when h = 0.3, 0.4, and 0.5, respectively. According to FIG. 3, it was found that when h = 0.4, the rate of change in resistance value due to temperature can be minimized.

On the basis of the above results, a laminated resistor composed of a NiCrAl thin film and a NiCrMn thin film was manufactured so that h = 0.4. That is, Ni is used as a lower layer on an alumina substrate.
A 0.24 μm CrMn thin film was formed, and a 0.16 μm NiCrAl thin film was formed thereon as an upper layer. Thereafter, heat treatment was performed.

As described above, the heat treatment is performed by leaving the film at about 500 ° C. for about 3 hours in a vacuum. By this heat treatment, Al contained in the upper layer 16 precipitates on the surface. The deposited Al is self-oxidized by a trace amount of oxygen remaining in the vacuum vessel to form an aluminum oxide film 16.

The points indicated by the squares in FIG. 2 show the measurement results of the rate of change of the resistance value of the laminated resistor according to the temperature. From FIG. 2, the actual rate of change in resistance with temperature substantially matches the calculated value at the time of h = 0.4 calculated above, and is −55 ° C. to +1.
TCR of ± 5 ppm / ° C over a wide temperature range of 25 ° C
It can be seen that the value is as small as within.

FIG. 3 is a graph showing the result of leaving the resistor with the resistor laminate at a high temperature. In the graph of FIG. 3, “a” is for six resistors of the conventional example, and “b” is for sixteen resistors according to the present invention.
It shows the rate of change in resistance when left unloaded for a period of time. According to the measurement results, it can be seen that the resistor according to the present invention has a significantly smaller change in the resistance value than the conventional product.

In the above embodiment, the heat treatment is performed after the resistance thin films are laminated. However, if the lower resistor is made of a material that does not affect the temperature characteristics even after a plurality of heat treatments, the heat treatment may be performed each time each layer is formed.

[0035]

FIG. 4 is a sectional view showing the structure of a resistor according to another embodiment. In the embodiment shown in FIG. 1, since the upper layer is directly laminated on the lower layer 12, diffusion of elements between the layers may occur after the heat treatment or immediately after the film formation. For this reason, it is considered that it is difficult to obtain a TCR as calculated.

In the embodiment shown in FIG. 4, an intermediate layer 18 made of a very thin insulating film such as oxide or nitride having a thickness of several nm is formed between the layers to suppress the diffusion between the layers. The intermediate layer 18 is formed by introducing nitrogen, oxygen or air into a vacuum chamber before forming the upper layer 14 which is easily diffused.
By adsorbing gas molecules on the surface of the thin film to form a very thin nitride or oxide, diffusion between layers can be suppressed. In addition, another resistor that hardly causes diffusion in both the upper layer 14 and the lower layer 12 is selected, and this resistor is used as the intermediate layer 18 as the lower layer 12 and the upper layer 14.
May be added in between.

[0037]

Other Embodiments In the above embodiments, the resistor laminate is formed by a thin film resistor. However, the present invention includes a laminate of a plurality of metal foil resistors and a laminate of a thin film resistor and a metal foil resistor. The heat treatment may be performed after all the layers are stacked, or may be performed each time one layer is formed. In the case of a metal foil resistor, heat treatment is performed before fixing the metal foil to the substrate.

In the above-described embodiment, the rate of change in resistance value due to temperature is approximated by a quadratic equation [αΔt + β (Δt) ² ], but a higher-order equation, for example, [αΔt + β (Δt) ^2]
+ Γ (Δt) ³ ]. In this case, considering not only α and β but also γ, the TCRs of the respective layers may be offset each other and the entire TCR may be set within a desired range.

[0039]

As described above, according to the first aspect of the present invention, when a plurality of resistors are stacked, the TCR of each layer is approximated by a quadratic equation, and the primary temperature coefficient α and the secondary temperature coefficient of at least one layer are obtained. Since the sign of the coefficient β is set opposite to the signs of α and β of the other layers, the non-linearity of the entire TCR is improved as a resistance laminate by offsetting the TCR of each layer with each other,
The TCR can approach zero over a wide temperature range.

Further, since the resistor in the uppermost layer can have excellent long-term stability, the long-term stability of the resistor laminate can be improved. That is, if a material having good long-term stability is used as the uppermost resistor, the T
The nonlinearity of the CR may increase or the TCR may increase. However, by combining the CR with a lower resistor, it is possible to satisfy the TCR of the entire resistor stack. In other words, the uppermost resistor exposed to the outside can be arbitrarily selected to have excellent long-term stability, and the resistance change rate due to temperature can be corrected by the second and subsequent resistors.

If α and β of at least one layer are both positive and α and β of the other layer are both negative, the T
This is convenient for canceling CR (claim 2). Ni-
In a Cr-based alloy, α and β can be controlled in a considerably wide range by the type of element to be added and the heat treatment, so that each layer or at least one layer has this Ni-Cr
Use of a system alloy is convenient for controlling α and β of the entire laminate.

The resistive thin film of the Ni—Cr alloy is formed by adding a certain element and performing a heat treatment to form a dense oxide film on the surface of the resistive thin film, thereby protecting the inside of the resistive thin film from oxidation. Good (claims 3 and 4). For example, an aluminum oxide film can be formed on the surface of the uppermost layer by self-oxidizing Al by using a Ni-Cr-Al alloy as the uppermost layer, thereby improving long-term stability (claim 8).

Since the method of controlling the primary temperature coefficient α and the secondary temperature coefficient β of the Ni—Cr alloy resistor has been clarified (see Japanese Patent Application No. 10-351496), the temperature characteristics of the uppermost layer are not limited. Can be corrected even if it has the above, and it is possible to make the TCR of the stacked resistors close to zero in a wide temperature range. Ni-C used here
r-based alloy thin-film resistors include Al, Si, Be, Mg, T
It is desirable that the Ni-Cr alloy contains at least one element of at least one of a group of i and Mn and a group of Mn, Fe, Co, Ti and V (claim 5).

NiCrAl with excellent long-term stability as the uppermost layer
When a resistor is used, since the primary temperature coefficient α and the secondary temperature coefficient β are both negative, the primary temperature coefficient α
It is preferable to use a NiCrMn resistor having both positive and secondary temperature coefficients β.

At least one or all of the layers may be a thin film resistor formed by vapor deposition or sputtering (Claim 6) or a metal foil resistor (Claim 7). Further, a thin film resistor and a metal foil resistor may be combined.

According to the ninth aspect, it is possible to obtain the optimum α, β and thickness of each layer when the resistor is laminated.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a comparison between a calculation result and a measurement result of a resistance value change rate depending on temperature.

FIG. 3 is a diagram showing actual measurement results of a change with time in a resistance value change rate;

FIG. 4 is a cross-sectional view showing another embodiment.

[Explanation of symbols]

 Reference Signs List 10 alumina substrate (insulating substrate) 12 NiCrMn resistor (lower layer) 14 NiCrAl resistor (upper layer) 16 aluminum oxide film 18 intermediate layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoki Honda 4-21, Sanda-Yoro, Niiyacho, Akita City, Akita Prefecture Inside the Advanced Technology Research Institute, Akita (72) Inventor Kiyoshi Yamakawa, Naoya-cho, Shinyacho, Akita City, Akita Prefecture 4-21 Inside Akita Prefectural Advanced Technology Research Institute (72) Inventor Makio Sato 238-1, Itaizawa, Nakatadai, Ouchi-cho, Yuri-gun, Akita Prefecture Alpha Electronics Co., Ltd. Akita Plant (72) Inventor Akira Oishi Akita Alpha Electronics Co., Ltd., 238-1, Itaizawa, Nakatadai, Ouchi-cho, Yuri-gun Inside the Akita Factory (72) Inventor Hiroshi Sasaki 238-1, Itaizawa, Nakatadai, Ouchi-cho, Yuri-gun, Akita Alpha Electronics Co., Ltd. F-term in Akita factory (reference) 5E032 BA12 BB01 BB20 CC18 5E033 AA00 AA02 BA03 BB02 BC01 BD12

Claims (9)

[Claims] 1. A resistor having a resistor laminated body in which a plurality of resistors are laminated on the surface of an insulating substrate, wherein each layer of the resistor laminated body has a resistance value change rate depending on the temperature of each resistor, and a temperature change [Δt [ΑΔt + β (Δt) ² ] or a higher-order equation, the sign of the primary temperature coefficient α and the secondary temperature coefficient β of at least one layer is changed to the primary temperature coefficient α and A resistor characterized in that the sign is opposite to that of the secondary temperature coefficient β, and the uppermost layer is formed of a resistor having excellent long-term stability. 2. At least one layer of the stacked resistors has a positive primary temperature coefficient α and a secondary temperature coefficient β, and the other layers have a primary temperature coefficient α and a secondary temperature coefficient β. 2. The resistor of claim 1 which is negative. 3. The resistor according to claim 1, wherein at least one of the stacked resistors is a Ni—Cr alloy resistor. 4. At least two kinds of Ni having different components.
3. The resistor according to claim 1, wherein a resistor laminated body is formed by stacking a plurality of Cr-based alloy resistors. 5. The Ni—Cr alloy used for the resistor is:
Al, Si, Be, Mg, Ti, Mn group, and M
The resistor according to any one of claims 1 to 4, wherein the resistor contains one or more elements of at least one group of n, Fe, Co, Ti, and V groups. 6. The resistor according to claim 1, wherein at least one of the plurality of resistors is a thin film resistor formed by vapor deposition or sputtering. 7. The resistor according to claim 1, wherein at least one of the plurality of resistors is a metal foil resistor. 8. The method according to claim 1, wherein the uppermost layer of the resistance laminate is Ni-Cr-Al.
8. The resistor according to claim 1, wherein an aluminum oxide film is formed on the surface of the uppermost layer by self-oxidizing Al contained in the alloy. 9. A method of manufacturing a resistor having a resistor laminated body formed by laminating resistors having different compositions on the surface of an insulating substrate, comprising: Δt] is approximated by a quadratic equation [αΔt + β (Δt) ² ] or a higher-order equation, and the resistance of each layer is adjusted so that the rate of change in the resistance value of the resistance laminate according to the temperature calculated within the equation falls within a predetermined range. A method for manufacturing a resistor, comprising determining values of a primary temperature coefficient α and a secondary temperature coefficient β of a body and determining a thickness of each layer.