JPH01124282A - Wiring structure body and its formation - Google Patents

Abstract

PURPOSE:To enhance contact adhesion performance between an insulating film and a wiring conductor and to enhance reliability of moistureproofness at an interface by a method wherein a mixed layer composed of the insulating film containing a hydropholic group and of a metal material constituting the wiring conductor is provided at a boundary part between the wiring conductor and the insulating film. CONSTITUTION:While the surface of a polyimide film 2 is being irradiated by a plasma of individual gases of helium and oxygen and, in succession, the surface of a polyimide is being irradiated with ions of helium, Al is electron- evaporated; after the evaporation, a photoetching operation is executed and a wiring conductor 4 of Al is formed. In addition, a process identical to this is repeated and an Al wiring part is laminated; an LSI 7 is bonded by using a solder 6; a multilayer wiring structure body is manufactured. A mixed layer formed at an interface between the polyimide and Al or Cu prevents water from penetrating because an ethyl group (-C2H5) as a hydrophobic group exists; in addition, the Al and the polyimide are bonded by laying a carbonyl group as a hydrophile group; a bonding force between both is enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a wiring board, and particularly to a wiring structure formed by laminating a wiring conductor and an insulating film made of a heat-resistant resin. It relates to its formation method.

[Conventional technology]

In order to increase the wiring density and mount LSIs at high density as substrates for electronic computer modules, a wiring structure made of thin multilayers using metal for the wiring conductor and polyimide for the insulating film, that is, a multilayer wiring board, has been developed. It is being applied. Conventionally, in thin-film multilayer wiring using polyimide, the first layer of wiring conductor is formed, then polyimide is coated, heat-cured, and then the second layer of wiring conductor is formed. This is a so-called sequential lamination method in which layers are formed one after the other. Further, as a method for forming a wiring conductor on polyimide, a method such as vapor deposition sputtering is applied. At this time, in order to ensure adhesion between the wiring conductor and the insulating film, the surface of the polyimide film is subjected to 02 plasma ashing, that is, a process in which oxygen plasma generated by high-frequency plasma is applied to the polyimide to vaporize C, or As shown in Japanese Unexamined Patent Publication No. 51-31175, a coating film of AQ/chelate compound is formed on the surface of a semiconductor substrate including a conductor, heat treated at 200"C, and then a polyimide resin is formed on the coating film. An adhesive layer is provided to increase the adhesive strength, and a process such as Ar sputtering that has adhesive properties is performed to modify the surface so as not to roughen it.

Multilayer wiring boards for module boards are required to have high reliability, and moisture resistance reliability of wiring is particularly important, as it accelerates peeling of wiring in high temperature containers and predicts wiring life. exam.

That is, P CT (Pressure Cooker
It is required that the wiring does not peel off, corrode, or break even after long-term accelerated tests such as thermal cycle tests (Te5t) and tests that apply thermal cycles between -50 and 150 degrees Celsius at atmospheric pressure, i.e., thermal cycle tests. Ru.

[Problem that the invention seeks to solve]

However, problems remain regarding the moisture resistance reliability of wiring structures using polyimide as an insulating film. In particular, there is a problem with the reliability of the interface between the wiring conductor and the insulating film.
In particular, the adhesiveness of wiring conductors on polyimide is low, causing corrosion of the wiring conductors. Therefore, in the past, treatments such as 02 plasma ashing and Ar sputtering were applied to the surface of polyimide in an attempt to improve its adhesion to the wiring metal. Deterioration is inevitable under high humidity. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a wiring structure that does not deteriorate the adhesion between a wiring conductor and an insulating film and has high moisture resistance and reliability at the interface, and a method for forming the same.

[Means for solving problems]

An object of the present invention is to provide a wiring structure formed by sequentially laminating a wiring conductor and an insulating film, in which an insulating film containing a hydrophobic group and the wiring conductor are provided at a boundary between the wiring conductor and the insulating film. Provided is a wiring structure characterized by providing a mixed layer made of a metal material, and a method for forming a wiring structure in which a wiring conductor and an insulating film are successively laminated. After irradiating the surface with plasma of an inert gas, oxygen gas, or ethylene-based hydrocarbon gas to form a hydrophobic group on the surface of the insulating film, depositing a conductor metal on the surface of the insulating film having the hydrophobic group, This is achieved by providing a method for forming a wiring structure characterized by performing ion mixing by accelerating and implanting inert gas ions.

[Effect]

The operation of the present invention will be explained with reference to FIGS. 4(a,) to (c).

As shown in FIG. 4(a), polyimide used as an insulating film is composed of a benzene ring as a basic skeleton and an imide carbonyl group (-N-C=O) bonded to the benzene ring. When this polyimide is irradiated with three types of plasma: an inert gas, an ethylene hydrocarbon gas, and an oxygen gas, the inert gas ions roughen the surface of the polyimide and change the benzene ring. That is, as shown in FIG. 4(b), the C=C bond of the benzene ring opens, and ethylene hydrocarbon gas (e.g. ethylene gas) is released.
due to the action of hydrophobic alkyl groups (for example, ethyl groups)
When Cz Ha ) is added, the C-H bond opens under the action of oxygen, a hydrophilic carbonyl group (e.g. AQ) is deposited, and ion mixing is performed by irradiation with inert gas, as shown in Figure 4(c). As shown in FIG. 4(b), the carbonyl group shown in FIG.
Q) binds to oxygen, creating a new bond (e.g. C-0-AQ
) is born. However, the alkyl group exists as it is added to the basic skeleton. In this way, in the interface layer between the polyimide of the insulating film and the conductor metal, the presence of the hydrophobic alkyl group prevents water from entering, and the interposition of the conductor metal and the polyimide through the hydrophilic carbonyl group. bond to increase adhesive strength.

〔Example〕

To summarize this embodiment, the present invention relates to a wiring structure and a method for forming the same, and its feature is a multilayer thin film wiring structure composed of a wiring conductor and an insulating film made of an insulating resin. In the body, the surface of the insulating film is made hydrophobic by plasma treatment to make it difficult for water to penetrate, and a conductive metal is vapor-deposited on the surface of the insulating film, and metal particles are created in the insulating film by the ion mixing effect of inert gas ions. By implanting a mixed layer to form a mixed layer, it also improves the adhesion between the insulating film and the wiring conductor, thereby improving the moisture resistance reliability of the wiring.

When polyimide is used as the insulating film of the wiring structure and its surface is irradiated with plasma of inert gas, oxygen gas, and ethylene hydrocarbon gas, hydrophobic ethyl groups ((, z
It was found that alkyl groups such as Ha) and phenyl groups (CeHs) were formed.

Further, after AQ was deposited on the polyimide surface by electron beam evaporation, or at the same time, ion mixing was performed by irradiating inert gas ions. It has been found that when a wiring conductor is formed on polyimide using the above method, the moisture resistance life of a wiring structure in PCT can be significantly improved compared to conventional oxygen plasma treatment or Ar sputtering treatment.

Details of embodiments of the present invention will be explained with reference to FIGS. 1 to 4.

FIRST EMBODIMENT FIG. 2 is a schematic process diagram showing an example of the order in which a wiring structure according to the present invention is formed. Section A in FIG. 2(a) is an inert gas, as shown in the detailed view of section A.

This is an enlarged cross-sectional view of the surface layer of the insulating film (polyimide film) after the plasma irradiation process using oxygen gas and ethylene-based hydrocarbon gas. FIG. 3 is an enlarged cross-sectional view of the mixed layer after the vapor deposition of the conductor metal (part A) and the ion mixing process using an inert gas. In addition, Figure 3 shows the results of XPS (X-ray photoelectron spectroscopy) analysis of the polyimide surface in the detailed view of part A in Figure 2(a), and Figure 1 shows the details of part B in Figure 2(b). AQ
The results of analysis of and C are shown.

As shown in FIG. 2(a), the surface of the polyimide film 2 is irradiated with plasma of ethylene, helium, and oxygen gases, and the plasma-irradiated polyimide film surface 3 shown in the detailed view of part A is The analysis results of the film structure in polyimide are shown in FIG. 3(a) by XPS analysis. Further, as comparison materials, the analysis results of the surface subjected to conventional oxygen plasma treatment are shown in FIG. 3(b), and the analysis results of the polyimide surface not subjected to any treatment are shown in FIG. 3(c).

As a result, in FIG. 3(c), no processing is performed.

The peak of the benzene ring, which is the basic skeleton of polyimide,
Figure 3 (a) of hydrophilic carbonyl groups other than benzene rings
In addition to the carbonyl group, a hydrophobic ethyl group (-Cz
A peak of Hs) was detected.

Here, the carbonyl groups detected were the carbonyl groups possessed by polyimide and the carbonyl groups formed by irradiation with oxygen gas ions, and the ethyl groups were formed by irradiation with ethylene gas ions.

Subsequently, on the polyimide surface 3 of FIG. 2(a).

AQtl-electronic evaporation is performed while irradiating with helium ions. After the vapor deposition, photo-etching was performed to form the AQ wiring conductor 4 shown in FIG. 2(b). Figure 2 (
The interface between polyimide and AQ in the detailed view of part B in b) was analyzed in the depth direction from the AM side using SIMS, and AQ and C
Figure 1 shows the results of an analysis of the distribution of . AQ
The analysis was performed while etching from the layer side to the polyimide layer.

There was a mixed layer of AQ and C between the AQ layer and the polyimide layer, and in particular, there were regions where AQ and C were present at a certain mixing ratio. Since C is C in polyimide, AQ
It can be seen that a mixed layer containing polyimide is formed at the interface.

Furthermore, as shown in FIG. 2(c), by repeating the same process, AQ wiring is laminated and solder 6 is applied to the LSI 7.
A multilayer wiring structure was fabricated by bonding the two.

For the wiring structure fabricated in this manner, changes in the chemical structure of the mixed layer formed at the boundary between the insulating film and the wiring conductor during the formation process are shown in Figure 4(a). The chemical structure of the mixed layer finally formed is shown in FIG. 4(Q).

That is, Figure 4(a) shows the chemical structure of polyimide, which is an insulating film, and has a structure in which an imide carbonyl group (-N-C=0) is bonded to a benzene ring, which is the basic skeleton of polyimide. .

By irradiating this polyimide with plasma of a mixture of three gases: helium gas, ethylene gas, and oxygen gas, or plasma of each of three gases: helium gas and then ethylene gas or oxygen gas, the polyimide surface is heated by helium ion irradiation. As it becomes coarser, changes occur in the benzene ring. That is, as shown in FIG. 4(b), the C=C bond in the benzene ring opens, a hydrophobic ethyl group (-CzHs) is added under the action of ethylene gas, and C,- is added under the action of oxygen gas. By performing helium ion irradiation after the H bond opens and the carbonyl group of the hydrophilic group, or by performing ion mixing by performing vapor deposition and irradiation simultaneously,
), the carbonyl group (C=O
) opens, and AQ, which has a strong affinity for oxygen, bonds to ○, creating a new bond (C-0-Afi). When Cu is used instead of Afi, Cu is placed in the position of AQ.

The ethyl group exists as it is added to the basic skeleton of the benzene ring.

In this way, in the mixed layer formed at the interface between polyimide and A2 or Cu, the presence of the ethyl group (-C2Hs), which is a type of alkyl group that is a hydrophobic group, prevents water from entering and also makes it hydrophilic. By bonding AIl and polyimide through the carbonyl group of the group, the adhesive strength between the two is increased.

As the alkyl group which is a hydrophobic group, the above-mentioned ethyl group (
Similar effects can be obtained by using a methyl group (-CHa), a propyl group (-C3H7), a butyl group (-C4H9), or an amyl group (-C5H11) in addition to -CzHa).

With such a chemical structure, a wiring structure with high adhesive strength, good moisture resistance, and excellent moisture resistance reliability can be obtained.

Second Example Next, in the process of manufacturing the wiring structure shown in FIG. A sample subjected to oxygen plasma ashing as a treatment (Sample B
), and a sample (Sample C) prepared using plasma processing and ion mixing according to the present invention, were evaluated for high temperature humidity resistance by PCT (121°C e 2atm).
(maintained in an atmosphere with 100% humidity) and the results are shown in Table 1.

As a result, in sample A, which is a comparative material, corrosion occurred on the surface of the wiring conductor after 50 hours of PCT, and corrosion occurred on the entire surface after 100 hours. Also, for sample B, which is a comparative material.

Corrosion occurred after 100 hours, further progressed after 500 hours, and complete corrosion occurred after 1000 hours. On the other hand, in Sample C of the present invention material, no corrosion occurred in the AQ wiring even after 1000 hours of PCT. From the above results, it has become clear that according to the present invention, a wiring structure with higher moisture resistance and reliability than the conventional wiring structure can be provided.

〔Effect of the invention〕

According to the configuration of the present invention, the surface of the insulating film is roughened by plasma irradiation with an inert gas, ethylene hydrocarbon gas, or oxygen gas.

A hydrophobic alkyl group and a hydrophilic carbonyl group are formed on the surface layer of the insulating film, and then by ion mixing by vapor deposition of a conductor metal and ion irradiation with an inert gas, the oxygen of the carbonyl group becomes a conductor. Since the metals are in a bonded state, the presence of hydrophobic alkyl groups at the interface between the insulating film and the conductor metal prevents water from entering.
Since the conductor metal and the insulating film are bonded to each other through the carbonyl group of the parent wood group and the adhesive strength is increased, the adhesion between the insulating film and the wiring conductor is improved, and the moisture resistance reliability of the interface is increased.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the results of SIMS analysis of a mixed layer formed at the interface layer between an insulating film and a conductive metal according to the present invention, and FIG. 2 shows a wiring structure according to the present invention and its formation method. FIG. 3 is an explanatory diagram showing an example of a schematic process, and FIG. 3 shows the xPS of the polyimide film surface after plasma treatment according to the present invention.
FIG. 4 is an explanatory diagram showing the formation process of a mixed layer according to the present invention in molecular structure. 2... Insulating film (polyimide film), 3... Insulating film surface irradiated with plasma, 4... Wiring conductor, 5... Mixed layer.

Claims (8)

[Claims] 1. In a wiring structure formed by sequentially laminating a wiring conductor and an insulating film, an insulating film containing a hydrophobic group and a metal material forming the wiring conductor are formed at the boundary between the wiring conductor and the insulating film. A wiring structure characterized in that a mixed layer is provided. 2. 2. The wiring structure according to claim 1, wherein the material of the insulating film is made of polyimide resin. 3. 3. The wiring structure according to claim 1, wherein the hydrophobic group is an alkyl group or a phenyl group. 4. In a method for forming a wiring structure in which a wiring conductor and an insulating film are sequentially laminated, the surface of the insulating film is irradiated with plasma of an inert gas, oxygen gas, or ethylene-based hydrocarbon gas. 1. A method for forming a wiring structure, comprising: forming a hydrophobic group on the surface of the insulating film, depositing a conductor metal on the surface of an insulating film having the hydrophobic group, and performing ion mixing by accelerating and implanting inert gas ions. 5. 5. The method of forming a wiring structure according to claim 4, wherein the material of the insulating film is poimide. 6. 6. The method for forming a wiring structure according to claim 4, wherein the hydrophobic group is an alkyl group or a phenyl group. 7. Claims 4 to 6 are characterized in that the ion mixing is performed simultaneously with the vapor deposition of the conductor metal.
A method for forming a wiring structure according to any one of Items 1 to 9. 8. 7. The method of forming a wiring structure according to claim 4, wherein the ion mixing is performed after the conductor metal is vapor-deposited.