JPH04734A - Inspection of thin film multilayer substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary of the Invention] Regarding a method for inspecting a thin film multilayer substrate, the purpose is to determine whether an impurity in an organic insulating layer is an organic substance or a metal substance. Opposing electrodes are attached to both surfaces, and the capacitance between the opposing electrodes is measured.

[Industrial application field]

The present invention relates to a method for inspecting impurities in an organic insulator used between layers of a thin film multilayer substrate.

BACKGROUND OF THE INVENTION As computer systems have become faster in recent years, there has been a strong desire for small, highly reliable circuits based on high-density thin-film multilayer substrates. The thin film multilayer substrate uses an organic insulating layer made of polyimide resin or the like, and conductive thin film layers are formed on both surfaces of the organic insulating layer. The conductor thin film layers on both surfaces of the organic insulating layer may be provided at opposing positions with the organic insulating layer in between. Opposing conductive thin film layers may be electrically connected via via holes provided in the organic insulating layer, or opposing conductive thin film layers may not be electrically connected to each other and may be connected to conductors at different positions. It may be connected to a thin film layer. If the opposing conductor thin film layers are not electrically connected at all, the organic insulating layer between them must literally act as an insulator to prevent electrical conduction between the opposing conductor thin film layers. However, due to recent high-density packaging, the thickness of the organic insulating layer has been made extremely thin, and has an insulation resistance close to the minimum required amount. On the other hand, if minute metal impurities are mixed into the organic insulating layer, the insulation resistance of the organic insulating layer decreases, causing a short circuit between the conductive thin film layers on both sides of the organic insulating layer. , it was necessary to inspect whether such impurities were mixed into the organic insulating layer.

[Conventional technology]

Conventionally, an optical microscope has been used to inspect the surface of the organic insulating layer where the conductive thin film layer is to be located to check whether impurities have been mixed into the organic insulating layer. When examining the surface of an organic insulating layer using an optical microscope,
If impurities were mixed into the organic insulating layer, the surface of the organic insulating layer would appear partially swollen, and this could be used to determine that impurities were mixed.

[Problem to be solved by the invention]

If it was determined that impurities were mixed into the organic insulating layer in this way, the organic insulating layer (and the conductive thin film layer etc. fixed to it) was considered defective and was discarded. However, even when it is determined that the organic insulating layer is contaminated with impurities by inspection using an optical microscope, it is not always so bad that the organic insulating layer must be discarded. For example, if the impurity is an organic substance, the electrical resistance of the organic insulating layer will not substantially decrease, so even if the organic insulating layer contains organic impurities, there will be short circuits between both sides of the organic insulating layer. There is no need to discard the organic insulating layer.

However, although inspection using a conventional optical microscope can determine whether impurities are mixed into the organic insulating layer, it is not possible to distinguish whether the impurities are organic or metallic substances. There wasn't. Therefore, if it was determined that impurities were mixed in, all were judged to be defective. For this reason, even though the impurity is an organic substance and there is no possibility of short-circuiting, the product becomes defective and causes a decrease in yield. In order to improve the yield, it is preferable to determine whether the impurity is an organic substance or a metal substance, and to discard the organic insulating layer only when the impurity is a metal substance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for inspecting a thin film multilayer substrate by which it can be determined whether impurities in an organic insulating layer are organic substances or metal substances.

[Means to solve the problem]

The method for inspecting a thin film multilayer board of the present invention is a thin film multilayer board in which an organic insulating layer is provided between conductive thin film layers, in order to estimate impurities contained in the organic insulating layer. The method is characterized in that opposing electrodes are attached to the electrodes, and the capacitance between the opposing electrodes is measured.

[For production]

In the above structure, since the organic insulating layer is a dielectric,
The capacitance between both surfaces can be measured. The dielectric constant of the organic insulating layer used is known. Further, if an impurity is mixed into the organic insulating layer and the impurity is an organic substance, the dielectric constant of the impurity is considered to be relatively close to the dielectric constant of the organic insulating layer used. On the other hand, when the impurity is a metallic substance, the dielectric constant is equal to zero.

Therefore, depending on whether the capacitance measured between opposing electrodes is within the capacitance range based on the known dielectric constant of the organic insulating layer used, the impurity is an organic substance or a metal. It can be determined whether it is a substance. If it is determined that the impurity is an organic substance, it is not necessarily necessary to discard the organic insulating layer, and the yield of thin film multilayer substrates can be improved.

〔Example〕

FIG. 2 is a diagram showing an example of a thin film multilayer substrate according to the present invention. This thin film multilayer substrate includes a ceramic substrate 10 and a first conductive thin film layer 1 formed on the surface of the ceramic substrate 10.
2, and a ceramic substrate 10 covering this conductive thin film layer 12.
an organic insulating layer 14 of polyimide resin coated on the
Second conductive thin film layer 1 formed on the surface of the organic insulating layer 14
It consists of 6. The first conductive thin film layer 12 and the second conductive thin film layer 16 are located opposite each other on both sides of the organic insulating layer 14, but are not directly electrically connected. However, the first
Apart from the conductive thin film layer 12 and the second conductive thin film layer 16, there is also a conductive thin film layer (not shown) electrically connected at mutually opposing positions on both sides of the organic insulating layer 14; These conductive thin film layers are connected through via holes provided in the organic insulating layer 16. Additionally, in the embodiment, a via hole 18 is provided in the ceramic substrate 10 for connecting the first conductive thin film layer 12 to another conductive thin film layer (not shown) on the back side of the ceramic substrate 10. used.

FIG. 2 shows an example in which an impurity 20 is mixed into the organic insulating layer 14. If the impurity 20 is a minute metal between the first conductive thin film layer 12 and the second conductive thin film layer 16, the impurity between the first conductive thin film layer 12 and the second conductive thin film layer 16 Before forming the second conductive thin film layer 16 on the surface of the organic insulating layer 14, it is difficult to determine whether such impurities 20 are organic or metallic materials, since this will reduce the insulation resistance and create the possibility of short circuits. It is advisable to carry out tests to make a determination.

FIG. 1 explains that before forming the second conductive thin film layer 16 on the surface of the organic insulating layer 14, an inspection is performed to determine whether the impurity 20 is an organic substance or a metal substance. It is a diagram. The presence or absence of the impurity 20 is accomplished by inspecting the surface of the organic insulating layer 14 using an optical microscope in the previous step shown in FIG. After it is determined that the impurity 20 is present in the first conductive thin film layer 12 and the second conductive thin film layer 16 as a result of optical microscopy, it is determined that the impurity 20 is an organic substance or a metallic substance. Determine whether

In FIG. 1, a capacitance measuring device 30 is prepared.

The capacitance measuring device 30 includes a first electrode 32 and a second electrode 34, as well as current supply means and current measurement means (not shown). The first electrode 32 is brought into contact with a portion of the surface of the organic insulating layer 140 that faces the first conductive thin film layer 12, and the second electrode 34 is inserted into the via hole 18 of the ceramic substrate 10 to remove the first conductive thin film layer. Contact with 12. As a result, the first electrode 32 becomes one of the opposing electrodes, and the second electrode 34 becomes the other opposing electrode together with the first conductive thin film layer 12. Therefore, a current is passed between the first electrode 32 and the second electrode 34 (the first conductive thin film layer 12), and the
The capacitance between the electrode 32 and the second electrode 34 is measured. Capacitance can be measured, for example, from changes in current.

FIG. 3 shows the principle of capacitance measurement according to the present invention.
2) can be compared to a parallel plate capacitor of area S1 and distance β shown in FIG. The capacitance C in this case is expressed by the following formula.

C=εεo [F] Area S of first electrode 32 is φ100-1 second electrode 34
The area S of the first conductive thin film layer 12 which also becomes the counter electrode
is φ100-1 distance n1 (polyimide resin organic insulating layer 1
An example of calculating the capacitance C when the impurity 20 is a metal substance is as follows (thickness of the impurity 20 is 5 M and area φ100 p).

When the impurity 20 is an organic substance, the capacitance C is approximately 13.8×10 −+5 [FI.

When the impurity 20 is a metal substance, the capacitance C is approximately 2
0.7×10-” CVD.

As described above, when the impurity 20 is a metal substance, the capacitance becomes considerably large, and it can be clearly distinguished from when the impurity 20 is an organic substance. Therefore, an allowable range of capacitance is set based on the known dielectric constant of the organic insulating layer 14,
Depending on whether the measured value is within an acceptable range, it can be determined whether the impurity 20 is an organic substance or a metal substance. In the embodiment, the area S of the first conductive thin film layer 12, which serves as a counter electrode together with the second electrode 34, is φ
100-, but the area S of the first conductive thin film layer 12 is often larger than φ100, and in this case, the value of capacitance C will be larger and the measured value will also be larger, so it will be clearer. Be able to make distinctions.

FIG. 4 is a diagram showing another embodiment. In FIG. 4, the thin film multilayer substrate includes a ceramic substrate 10, a first conductive thin film layer 12, an organic insulating layer 14, like the one in FIG.
A second conductive thin film layer (
(not shown, formed after inspection), and
Furthermore, a third conductive thin film layer 22 is formed inside the via hole 18 of the ceramic substrate 10 and on the back surface of the ceramic substrate 10 , and a third conductive thin film layer 22 is coated on the back surface of the ceramic substrate 10 to cover the third conductive thin film layer 22 . The fourth conductive thin film layer 28 is formed inside the via hole 26 of the second organic insulating layer 24 and on the surface of the second organic insulating layer 240. In this case as well, the electrical insulation of the portion of the organic insulating layer 14 where the first conductive thin film layer 12 is located is a problem, and for this reason impurities 20
The second conductive thin film layer 1 is
6 (see Figure 2).

Also in FIG. 4, the capacitance measuring device 30 is connected to the first electrode 32.
and a second electrode 34 , the first electrode 32 is brought into contact with a portion of the surface of the organic insulating layer 140 that faces the first conductive thin film layer 12 , and the second electrode 34 is brought into contact with the back surface side of the ceramic substrate 10 . is brought into contact with the fourth conductive thin film layer 28 of.

Therefore, the second electrode 34 is connected to the first conductive thin film layer 12 via the fourth conductive thin film layer 28 and the third conductive thin film layer 22. Therefore, similar to the previous embodiment, the first electrode 3
The organic Insulating layer 1
4 can be tested for impurities 20.

[Effects of the Invention] As explained above, according to the present invention, opposing electrodes are attached to both surfaces of an organic insulating layer, and by measuring the capacitance between the opposing electrodes, the electrostatic capacitance can be measured during the manufacturing process. It is possible to test whether the impurity contained in the organic insulating layer is an organic substance or a metal substance, and it is possible to improve the yield of products.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing an example of a thin film multilayer substrate according to the present invention, FIG. 3 is a diagram showing the principle of the present invention, and FIG. 4 is a diagram showing the present invention. It is a figure which shows the 2nd Example of invention. DESCRIPTION OF SYMBOLS 10...Ceramic substrate, 12.16...Conductor thin film layer, 14...Organic insulating layer, 18...Piahono 20...Impurity, 22.28...Conductor thin film layer, 30...・Capacity measuring device, 32.34...
electrode.

Claims (1)

[Claims] Organic insulating layer (14) between conductor thin film layers (12, 16)
In the thin film multilayer substrate provided with the organic insulating layer (14)
In order to estimate the impurity (20) contained in the organic insulating layer, opposing electrodes (32, 34) are attached to both surfaces of the organic insulating layer, and the capacitance between the opposing electrodes is measured. Inspection method for thin film multilayer substrates.