JPH0648714B2 - Trimmable tip low drag - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a trimable chip resistor that adjusts a resistance value by trimming a resistor mounted on a substrate.

[Prior Art] In recent years, electronic components have been used to stabilize the quality of products using them.
With the demand for improved productivity and reduction in size and weight, the usefulness of chip components is increasing.

The semi-fixed resistor used for adjustment in the hybrid IC circuit is unsatisfactory in terms of its shape size and long-term stability for high-density mounting of components and high reliability. Is replaced by a chip resistor, a hybrid IC is assembled, and the chip resistance is laser-trimmed under actual operating conditions to adjust the circuit characteristics.

[Problems to be Solved by the Invention] There are thick film and thin film chip resistors used in the above method. However, thick film chip resistors have a large change in resistance value after trimming and require high accuracy. There is a problem in the application to the applied circuit. On the other hand, the thin film chip resistor has high precision by trimming, and the change in resistance value after trimming is small, and high-precision functional trimming is possible. Therefore, it is necessary to use silicon nitride on the substrate and the resistor beforehand. The resistance value of the resistor is adjusted by forming a thin protective film, irradiating the resistor with laser through the protective film, and oxidizing a part of the resistor.

However, when an unpolished ceramic or the like having a rough surface is used for the substrate, airtightness cannot be ensured unless the protective film is made thick. Therefore, if a thick protective film is formed, it will spontaneously occur without laser trimming. Defects such as cracks occurred in the protective film of silicon nitride, and the resistor could not be protected from the environment (particularly moisture).

[Means for Solving the Problems] As a result of earnest research for solving the above problems, YAG / laser light was applied to a protective film which must be formed thickly on a metal thin film resistor formed on an alumina substrate having a rough surface. When forming a silicon oxide film that transmits well, laser trimming the metal thin film resistor from above this protective film,
By making the protective film a thickness corresponding to the film thickness of the metal thin film resistor and irradiating the YAG / laser light whose output is adjusted, the metal thin film resistor can be trimmed to a desired resistance value without damaging the protective film. There was found.

As described above, in recent years, so-called functional trimming, in which a small number of elements are trimmed while monitoring the function of a circuit including the elements, has been put into practical use.

Generally, metal thin film resistors have good stability in laser trimming, and the trimming accuracy reaches the precision of the measuring instrument relatively easily, and high precision trimming is possible, but after trimming, the characteristics of the resistance element depend on the operating environment. A protective film is indispensable to suppress the change.

As in the present invention, directly on an alumina substrate, a structure in which a metal thin film resistor and a silicon oxide-based protective film are combined, and if the film thickness of the protective film is increased according to the film thickness of the metal thin film resistor, Not only is it possible to perform accurate trimming using the YAG / laser beam, but since the protective film is not damaged during trimming, it is not necessary to take any protective measures after trimming.

Regarding the mechanism of trimming the metal thin film resistor of the resistor configured as described above by the laser beam, the metal thin film resistor that has become high temperature by absorbing the laser beam is oxidized by oxygen contained in the substrate or the silicon oxide film. It is presumed that it will change to an insulator.

From such a trimming mechanism, selection of the film thickness of the protective film according to the film thickness of the metal thin film resistor used in the resistor of the present invention is important in the configuration of the present invention.

That is, to trim the metal thin film resistor without damaging the protective film, the film thickness of the metal thin film resistor should be 200Å to 30.
In the case of about 0Å, the thickness of the protective film may be about 3 to 5 μm, but when the film thickness of the metal thin film resistor is as thick as about 1000Å, the thickness of the protective film may be set to 25 to 30 μm. is necessary.

The reason is that when the laser light is irradiated from above the protective film, the protective film does not absorb the laser beam, so after passing through the protective film and reaching the metal thin film resistor, it is absorbed and generates heat. Is larger as the film thickness of the metal thin film resistor is larger, and the generated heat is transferred to the substrate and the protective film, and as a result, the temperature of the protective film rises and the protective film is melted and destroyed.

The reason why the thickness of the protective film is made thicker according to the film thickness of the metal thin film resistor is to prevent the protective film from becoming higher than its melting temperature in response to the above heat generation. It is safe to use a protective film that is thick enough for the film thickness.
However, from the viewpoint of manufacturing economy, it is desirable that the thickness of the protective film be kept to the minimum necessary depending on the thickness of the metal thin film resistor.

The material of the protective film is not particularly limited as long as it can transmit a laser beam used for trimming and has a function as a protective film. For example, in addition to silicon oxide, silicon oxide film containing phosphorus oxide and boron oxide, germanium
A silicon mixed oxide film or the like can also be used. Although these films are stoichiometrically saturated with oxygen for the purpose of the present invention, for example, in the case of silicon oxide, the protective film having a large proportion of silicon is usually slightly colored and absorbs YAG / laser rays. Therefore, even if the laser output is adjusted, the protective film will be damaged and the protective performance after trimming will be incomplete.

Another structure of the present invention is that an organic protective film is further laminated on an inorganic protective film such as silicon oxide.

That is, a YAG / laser light transmissive photoresist is used as the organic film, and by stacking this on the silicon oxide film, the temperature rise of the silicon oxide protective film at the time of laser trimming can be prevented by melting and evaporating the organic film. There is an effect that it can be reduced by the endothermic action due to, etc. Furthermore, since the protective film of the resistor is essentially two layers, it is possible to complement the film defects due to pinholes that may exist individually in both films. Therefore, the effect of improving the reliability of the resistance element can be provided.

Furthermore, since the above-mentioned organic film can be used as a resist for etching a silicon oxide film in manufacturing the trimable chip resistor of the present invention, after the silicon oxide film is etched, a resist removing step for the organic film is performed. Instead, it can be directly solder-plated for electrodes into a product, which is advantageous in simplifying the manufacturing process.

As a resist that can be used for such a purpose, for example, there is a negative type photoresist which becomes insoluble in a developing solution by exposure and whose film strength is further increased by heating after development. As another method, YA
An organic polymer film that transmits G / laser light may be formed by a method such as printing.

The substrate material used in the present invention may be glass, forsterite, or the like, in addition to alumina, but is not particularly limited as long as it is a material that transmits a laser beam well and can be stably used as a substrate.

A metal thin film resistor is formed on an alumina substrate by sputtering or ordinary vacuum deposition, and then a protective film can be deposited at a relatively low temperature (a temperature that does not adversely affect the metal thin film resistor or the electrode) by the plasma CVD method. Can be formed by.

[Examples] The present invention will be described below based on Examples.

Embodiment 1 FIG. 1 shows Embodiment 1 of the present invention.

Nichrome alloy is sputter-deposited on the alumina substrate 1 as the metal thin film resistor 2 to a thickness of about 200Å, and then the electrode 4 is formed.
As a result, a copper thin film was laminated on the metal thin film resistor 2. Then, in order to form the electrode 4 for the metal thin film resistor 2, the electrode 4 on the metal thin film resistor 2 was removed by etching leaving a predetermined portion at both ends to expose the surface of the metal thin film resistor 2. Next, a silicon oxide film having a thickness of about 3 μm was deposited on the entire surfaces of the metal thin film resistor 2 and the electrode 4 by the plasma CVD method to form a protective film 3 for the metal thin film resistor 2. Then, a positive type photoresist was applied to a thickness of 3 μm, exposed and developed, and then the protective film 3 on the electrode 4 was removed by etching with a buffered hydrofluoric acid solution.

After dissolving and removing the photoresist with acetone, finally,
Solder 5 is coated on the exposed surface of the electrode 4 to implement the laser trimming resistor (the first embodiment of the present invention).
Figure).

The trimming resistor is set on a YAG laser trimmer (laser beam diameter: 50 μm) and the laser output is adjusted in the range of 0.05 W to 0.3 W to perform trimming. However, the thin metal film resistor 2 remained thin in the trimmed portion, but no damage was observed in the protective film 3. On the other hand, at 0.3 W, the metal thin film resistor 2 in the trimming portion and the protective film 3 thereon were also melted and damaged in some cases.

In the range of 0.15W to 0.25W, no damage was observed in the protective film 3 and only the metal thin film resistor 2 changed to light transmissive by laser irradiation, and light was transmitted from under the ceramic substrate under an optical microscope. I was able to confirm the trimming pattern.

As a result of splitting the trimming pattern portion with an electron beam microanalyzer, the metal thin film resistor 2 having almost the same level as the portion not irradiated with YAG / laser is obtained.
The components of nickel and chromium were detected. From this, it was confirmed that the metal thin film resistor 2 was present as an insulator between the alumina substrate 1 and the silicon oxide protective film 3.

Further, the trimming accuracy is 0.
It was less than 05%.

The protective film 3 having a YAG / laser output range of 0.15 to 0.25 W capable of trimming the metal thin film resistor 2 without damaging the protective film 3 which is a feature of the present invention.
As a result of testing the moisture-proof effect of No. 1, no change such as corrosion of the metal thin film resistor 2 due to the invasion of moisture was observed. Further, no change in DC resistance value or other characteristics of the metal thin film resistor 2 was observed.

Embodiment 2 FIG. 2 shows Embodiment 2 of the present invention.

A metal thin film resistor 2 is sputter-deposited on the alumina substrate 1 to a thickness of 1000 Å of a nichrome alloy, and then a copper thin film is laminated as an electrode 4 on the metal thin film resistor 2 leaving the electrode 4 at a predetermined portion. The electrode 4 was removed by etching to expose the surface of the metal thin film resistor 2.

Next, a silicon oxide film having a thickness of about 5 μm is formed on the entire surfaces of the metal thin film resistor 2 and the electrode 4 by the plasma CVD method.
m and 25 μm deposited on two levels, and a metal thin film resistor 2
Was used as the protective film 3.

Next, a negative type photoresist (OMR-83: Tokyo Ohka Co., Ltd.) is applied as the organic film 6 to a thickness of 3 μm, exposed and developed, and then the protective film 3 on the electrode 4 is etched with a buffered hydrofluoric acid solution. Removed. Finally, the organic film 6 is sufficiently washed with water, and then the solder 5 is placed on the exposed electrode 4.
Was coated to obtain a resistor for implementing laser trimming (FIG. 2) in the present invention.

When a trimming test was conducted in the same manner as in Example 1, it was observed that the organic film 6 on the surface of the trimmed sample resistor was melted and evaporated around the trimmed portion to become thin. No carbonization phenomenon was observed.

In the present embodiment, as described above, the metal thin film resistor 2 is 100
0Å sputter vapor deposition was performed, and the film thickness of the protective film 3 thereon was set to two levels (5 μm, 25 μm), and the degree of damage to the protective film 3 in the trimming portion was compared.

As a result, as shown in Table 1, the thickness of the protective film 3 is 25
In the case of μm, compared with the case of 5 μm, the laser output range where the protective film 3 is not damaged was expanded, and the effect of increasing the film thickness was recognized. Further, as a result of testing the moisture-proof effect of the protective film 3 on the sample in which the protective film 3 is not damaged, no corrosion or change in characteristics of the metal thin film resistor 2 due to invasion of moisture was observed.

Example 3 A nichrome alloy was sputter-deposited to a thickness of 500 Å as a metal thin film resistor 2 on an alumina substrate 1, and then a copper thin film was laminated thereon as an electrode 4 and then a predetermined portion of the electrode 4 was left to leave a metal thin film. The electrode 4 on the resistor 2 was removed by etching to expose the surface of the metal thin film resistor 2. Next, a silicon oxide film having a thickness of about 5 μm was deposited on the entire surface of the metal thin film resistor 2 and the electrode 4 by plasma CVD to form a protective film 3 for the metal thin film resistor 2.

Then, a negative type photoresist (OMR-83: Tokyo Ohka Co., Ltd.) is applied as the organic film 6 to a thickness of 3 μm, and after exposure and phenomenon, the protective film 3 on the electrode 4 is etched with a buffered hydrofluoric acid solution. Removed. The organic film 6 is dissolved and removed by a resist removing solution to expose the protective film 3, and then the electrode 4 is coated with solder 5 (only the protective film 3 is coated).
Layer structure) and the organic film 6 are sufficiently washed with water,
Two kinds of resistors, one having solder 5 coated on the exposed electrode 4 (two-layer structure of protective film 3 + organic film 6), were used as the resistors for carrying out laser trimming in the present invention (FIGS. 1 and 2). .

As a result of performing the trimming test in the same manner as in Example 1, the second
As shown in the table, when the organic film 6 is overlaid on the protective film 3, the range of the laser output without damage of the protective film 3 is expanded as compared with the case where only the protective film 3 is provided. The effect of overlapping 3 was recognized. Further, as a result of testing the moisture-proof effect of the protective film 3 on the sample in which the protective film 3 is not damaged, no corrosion or change in characteristics of the metal thin film resistor 2 due to invasion of moisture was observed.

[Effects of the Invention] As described above, the present invention uses silicon oxide that transmits laser light well as a protective film that must be formed thickly on a thin film resistor formed on a substrate having a rough surface.
The thin-film resistor can be trimmed with high accuracy without damaging the protective film during laser trimming via the protective film. Further, if an organic film is further formed on the protective film, the laser output range in which the protective film is not damaged is expanded, so that trimming to the metal thin film resistor becomes easy.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of the trimming resistor of the present invention, and FIG. 2 is a sectional view showing another configuration of the trimming resistor of the present invention. 1 ... Alumina substrate, 2 ... Metal thin film resistor, 3 ... Protective film, 4 ... Electrode, 5 ... Solder, 6 ... Organic film.

Claims (3)

[Claims] 1. A thin film resistor formed on a non-polished ceramic substrate is provided with a silicon oxide protective film having a thickness of 3 μm to 30 μm, and the thin film resistor is oxidized by laser irradiation through the protective film. A trimable chip resistor characterized by adjusting the resistance value by doing. 2. A resistance value is adjusted by further providing an organic film on a protective film of silicon oxide, and irradiating a laser through the protective film and the organic film to oxidize the thin film resistor.
Trimmable chip resistor described. 3. The trimable chip resistor according to claim 1, wherein the protective film of silicon oxide is formed by a plasma CVD method.