JPH0666552B2 - Method for manufacturing copper polyimide multilayer substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a method for producing a copper-polyimide multilayer substrate having excellent heat resistance and electrical properties.

[Prior Art] In recent years, with the increase in the speed and density of LSI technology, it is required to make the electronic circuit wiring system multi-layered and have high electrical characteristics. In response to these requirements, organic insulation having good heat resistance and dielectric characteristics It is considered to manufacture a multilayer wiring board using polyimide, which is a material.

The method for manufacturing the multilayer wiring board is classified into two methods, that is, a sequential lamination method and a build-up method. Among them, the sequential lamination method is one in which a thin metal film is attached to one surface or both surfaces of an insulating film and a circuit pattern is arranged on the surface by etching as an inner layer board, and two or more of the inner layer boards are semi-cured resin sheets or heat. This is a method of bonding using a curable resin-impregnated base material (prepreg). On the other hand, in the build-up method, insulating layers and conductor layers are alternately stacked. That is, after applying a varnish-like organic insulator on the starting material where the circuit pattern has been formed on the surface, this is cured and an insulating layer is overlaid, and the desired conductive circuit pattern is formed thereon by sputtering or plating. The series of processes of stacking is repeated many times.
The characteristics of polyimide itself can be utilized by adopting a build-up method in which a metal layer and a polyimide layer are sequentially stacked without using an adhesive, rather than by a sequential lamination method in which inner layer boards are bonded and assembled with an adhesive. Therefore, it is considered to be more advantageous in terms of heat resistance and electric characteristics.

When the metal layer and the polyimide layer are laminated by this build-up method, the step of applying the polyimide precursor resin is included in the lamination of the polyimide layer. For the polyimide precursor resin, a type of product with photosensitivity has been developed, and if this type of product is used, the polyimide layer can be patterned / formed by exposure and development. The interlayer connection hole of the layer can be easily processed. This type of resin is generally called a photosensitive polyimide resin, and for example, one in which a crosslinkable group component is added to impart photosensitivity to aromatic polyamic acid that is a precursor of aromatic polyimide is known. Has been.

As a method for producing a multilayer wiring board by a build-up method using a photosensitive polyimide resin other than this, a general polyimide precursor resin having no photosensitivity, for example, a polymer solution prepared by dissolving an aromatic polyamic acid in an organic solvent. Is pre-baked to form a resin layer that has been partially polyimidized, and after printing a mask resist on it, the polyimide is partially chemically dissolved to form an interlayer connection hole, and a mask resist is formed. After removal, there is a method of post-baking to completely imidize and then adding a metal conductor layer. In this case, an etchant having a strong dissolving power is required to dissolve the polyimide, and for example, a mixed solution of hydrazine and ethylenediamine is used.

[Problems to be Solved by the Invention] In order to cope with the speedup of transmission signals in an IC circuit,
It is necessary to control the characteristic impedance including the wiring system. In order to effectively utilize the high speed in the high speed arithmetic element, it is required to suppress the driving power required for the propagation of signals exchanged between the elements to be low. Therefore, it is desirable that the characteristic impedance of the wiring system is high. Further, as the speed increases, the reflection of a signal due to the mismatch of the characteristic impedances on the same substrate causes an increase in noise. Therefore, it is necessary to match the characteristic impedances on the same substrate. For that purpose, it is necessary to consider the dielectric constant of the insulating material, the distance between conductors (that is, the thickness of the insulating layer), the thickness of the conductor, and the width of the conductor. For example, a polyimide resin is used as the insulating layer, In the case of a signal line with a thickness of 20 to 50 μm and a conductor width of 40 to 100 μm, in order to set the characteristic impedance to around 50 ohms, the insulation thickness of the substrate should be 20 to 100 μm. It is required, and it is desired that the thickness of the substrate can be freely set within this range.

When a multi-layer substrate having a polyimide resin as an insulating layer is manufactured by a build-up method, as the thickness of the polyimide layer exceeds 20 μm and further increases, the photosensitive polyimide resin may cause a precise and clear polyimide because of problems in exposure. Obtaining a pattern of layers tends to be difficult. Further, when it is necessary to volatilize the crosslinkable group component added in advance in order to impart photosensitivity after the development, the volumetric shrinkage of that amount deteriorates the positional accuracy of the wiring.

On the other hand, when using a non-photosensitive general polyimide precursor resin to form a multilayer by the build-up method, it is possible to sufficiently form a thick polyimide layer of 20 μm or more, but to form an interlayer connection hole or the like. In order to open the polyimide with advanced imidization by chemical dissolution, chemicals with strong dissolving power,
For example, it is essential to use hydrazine or a mixture of hydrazine and ethylenediamine. Dissolution solutions consisting of these chemicals are used at temperatures of 40 ° C or higher to increase the dissolution rate, but they are difficult to handle because they are flammable, and in order to make the dissolution conditions uniform, Frequent replacement of the dissolution bath is required and the cost of these chemicals adds to the overall production cost.

Also, regardless of the presence or absence of photosensitivity, when manufacturing a multilayer substrate by the build-up method using a polyimide precursor resin, after prebaking the polyimide precursor at 100 ~ 200 ℃, post-baking at 200 ~ 400 ℃. Then, after completely forming the polyimide, a conductor metal layer is additionally added thereon. this is,
If the underlying insulating layer does not have strong heat resistance or chemical resistance like polyimide, when forming a metal conductor layer on it, for example, impact during sputtering or chemicals during pretreatment of electroless plating This is because the insulation layer itself is greatly deteriorated due to the change and the electrical characteristics are deteriorated.

Thus, in the conventional method, before stacking the conductor metal layers,
The underlying insulating layer must be heated to around 300 ° C to imidize each time, and the number of heating steps increases significantly as the number of layers increases, so the overall manufacturing effort is neglected. There is a problem that it can not be done.

An object of the present invention is to provide a method for manufacturing a copper-polyimide multilayer wiring board that does not include the above problems.

[Means for Solving the Problems] The method of the present invention for solving the above problems is to dry a coated polyimide precursor resin at a temperature of 100 ° C. or less to form a resin layer having a solid content of 70% or more, A first step of forming a pattern on the resin layer using a mask resist, selectively dissolving the resin layer in an etching bath to form a polyimide precursor resin layer with an interlayer connection hole, and the resin layer surface A second step of forming a circuit-patterned conductor layer by electroless plating or a combination of electroless plating and electrolytic plating, and the first step and the second step are alternately repeated for lamination. After that, it is heated to 200 to 400 ° C. to make all the polyimide precursor resin layers into polyimide resin layers.

[Operation] In the present invention, copper is used as the material of the conductor layer,
Any metal capable of electroless plating or electrolytic plating can be similarly applied.

The polyimide precursor resin referred to in the present invention, polyamic acid, that is, wholly aromatic polyamic acid, modified polyamic acid, or addition type polyamic acid as an organic solvent, dimethylacetamide, dimethylformamide,
A polymer solution dissolved in N-methyl-2pyrrolidone or diethylene glycol dimethyl ether,
Further, the polyimide referred to in the present invention is a polyimide obtained by removing the solvent from these polymer solutions to cause amide ring closure of the amide bond site of the polyamic acid.

The solid content referred to in the present invention refers to the polymer component in the resin expressed in wt%. When the polymer component is a polyamic acid, when it is heated to a temperature of 200 ° C. or higher, an imidization reaction, which is a dehydration reaction, occurs. Therefore, the solid content undergoes a weight change due to the dehydration reaction in addition to a weight change due to the volatilization of the solvent. However, in the present invention, since the drying is performed at a temperature of 100 ° C. or less, it is not necessary to consider the imidization reaction, and it can be considered that the solid content depends only on the weight change due to the volatilization of the solvent.

By the way, when manufacturing a multilayer wiring board using polyimide as an insulating layer by a build-up method, pre-baking that is repeated each time each polyimide insulating layer is laminated, and if post baking can be omitted, the labor required for manufacturing can be greatly reduced. The object of the present invention can be achieved. In order to achieve this purpose, it is necessary to perform heat treatment after the lamination is completed. In order to do so, after changing the polyimide precursor resin with a solid content of 10 to 30% to be applied on the substrate to a solid layer having a mechanical rigidity to the extent that a conductor layer can be added thereon by a simple process. Therefore, a technique for metallizing the surface of the resin solid layer by a method that does not deteriorate the electrical characteristics of each insulating layer in the final product is required.

Generally as a method of metallizing on the resin surface,
Although there are sputtering and electroless plating methods, in the sputtering method, if the thermal stability of the underlying resin layer is poor, the surface layer deteriorates due to damage from the surface, and the shape tends to wavy, which adversely affects. Further, in the electroless plating method, it is most prominent in the surface hydrophilization that is performed before the catalyst activation in the pretreatment step of electroless plating.

When performing chemical plating on the polyimide precursor resin surface coated on the substrate, it is necessary for lamination because the solid content becomes about 50% due to natural drying after coating and the surface fluidity disappears. The mechanical strength that is said to be sufficiently increased. However, when the surface of the polyimide precursor resin layer in the dry state is treated to be hydrophilic with a basic treatment liquid, the basic treatment liquid easily penetrates into the resin layer,
Secondary chemical damage from the resin surface spreads to the inside in a short time. In order to avoid this, in the present invention, the polyimide precursor resin coated on the substrate is dried at 100 ° C. or lower so that the solid content is 70% or higher. By doing so, it is possible for the first time to prevent the treatment liquid from penetrating into the resin during the hydrophilization treatment, and to stop the secondary chemical changes in the resin within the extremely thin region near the surface. Become.
As a result, it becomes possible to suppress the deterioration of the ability of the polyimide layer as an insulator in the final product to a negligible extent.

Further, in the electroless copper plating on the surface of the polyimide precursor resin layer having a solid content of 70% or more, chemical damage during the pretreatment of plating can be suppressed within the range of only 500 angstroms from the surface, and A good plated surface can be obtained. With such a chemical change in the surface layer, the influence of the chemical change on the dielectric properties of the entire insulator can be neglected.

Also, the insulating property is adversely affected by the ionic impurities adsorbed on the substrate. In the method of the present invention, it is possible that ionic impurities are adsorbed within the range of the chemical damage, but the amount adsorbed in a shallow region of about 500 Å from the surface is considered to have no effect.

The present invention will be described more specifically by using one example below.

1 to 5 are views showing a laminating process of the present invention.

As a first step, a solid content of 10 to 30 is applied on a substrate (FIG. 1) in which a copper circuit pattern 2 is provided on a polyimide film 1.
% Polymide precursor resin is applied and dried at 100 ° C. or lower to form a polymide precursor resin layer 3 having a solid content of 70% or higher. After printing a mask resist on this, it is dipped in a basic etching bath to selectively dissolve the polyimide precursor resin layer to form an opening 4 for interlayer connection, and the mask resist is removed (second Figure).

Then, as a second step, a copper circuit pattern 2 is formed on the surface of the polyimide precursor resin layer by electroless copper plating and additive copper plating utilizing electrolytic copper plating, and at the same time, interlayer connection is achieved (FIG. 3). .

After that, the first step and the second step are repeated a desired number of times to form a desired layer (FIG. 4).

After the lamination of the solidified resin layer and the conductor metal layer is completed by the method described above, the whole resin layer is imidized by heating at 200 to 400 ° C. for about 1 hour (FIG. 5). The mask resist used in the present invention may be a general one, and it is not necessary to use a special and expensive one such as rubber. Further, the conditions for etching the copper or polyimide precursor resin layer may be very general,
It is not specified. The same applies to copper plating.

The method of the present invention can be applied to the production of a copper-polyimide multilayer wiring board including a polyimide insulating layer having a thickness of 20 μm or more.

[Example] Benzophenone tetracarboxylic acid dianhydride was prepared on a substrate having a copper circuit pattern having a thickness of 20 μm provided on a polyimide film having a thickness of 50 μm (product name “Kapton 200H” manufactured by Toray Dupont). The same concentration of diaminobenzophenone was reacted with diethylene glycol dimethyl ether in a polyamic acid solution (Mitsui Toatsu Chemical Co., Inc. product name "Larc TPI Varnish Type") to further adjust the concentration with diethylene glycol dimethyl ether. 80% after applying 20% polymer solution
It was heated at ℃ and dried to obtain a polyimide precursor resin layer having a solid content of 70%. A mask resist was applied on this, exposed, and developed.

Then, it is dipped in a 4N potassium hydroxide aqueous solution for 3 minutes to selectively dissolve the polyimide precursor resin layer to form an opening for interlayer connection, and the mask resist is removed to form a polyimide precursor resin layer surface. On the other hand, a conductor circuit pattern was formed by additive plating using electroless copper plating and electrolytic copper plating, and at the same time, interlayer connection was achieved.

The above operation was repeated in the same manner to further alternately stack polyimide precursor resin layers having a solid content of 70% and conductor circuit patterns, and simultaneously perform interlayer bonding.

Finally, the whole substrate was heated at 300 ° C. for 1 hour for imidization. As a result, the bottom polyimide layer has a thickness of 50 μm, and the other two polyimide layers have the same thickness.
A copper-polyimide multilayer wiring board having a thickness of 40 μm and a total of three layers of conductor circuit patterns of 20 μm was manufactured.

It was found that this copper-polyimide multilayer wiring board exhibited the same or better characteristics as conventional products, and was sufficiently usable.

[Effects of the Invention] According to the method of the present invention, since the heat treatment is performed after the lamination, the manufacturing process when manufacturing the copper-polyimide multilayer wiring board can be greatly simplified.

In addition, instead of a flammable solution such as hydrazine that was indispensable for polyimide etching at the time of opening the interlayer connection hole, it is possible to perform the opening work even with an inexpensive basic aqueous solution, so that the cost can be reduced. Became possible.

Furthermore, since the heat treatment at around 300 ° C for each lamination is not performed unlike the conventional method, no strain is generated in the substrate, and it is possible to cope with the severe processing accuracy accompanying the high density of wiring. The substrate can be manufactured.

[Brief description of drawings]

 1 to 5 are views showing a laminating process of the present invention. 1 ... Polyimide film 2 ... Copper circuit pattern 3 ... Polyimide precursor resin solid layer 4 ... Aperture 5 ... Polyimide layer

Claims (1)

[Claims] 1. The coated polyimide precursor resin is heated to 100 ° C.
A resin layer having a solid content of 70% or more is dried at the following temperature, a pattern is formed on the resin layer using a mask resist, and the resin layer is selectively dissolved in an etching bath to form an interlayer connection hole. And a second step of forming a circuit-patterned conductor layer on the surface of the resin layer by electroless plating or a combination of electroless plating and electrolytic plating. Consisting of the first step and the second step alternately laminated, then heated to 200 ~ 400 ° C., all polyimide precursor resin layer is a polyimide resin layer, characterized in that the copper polyimide multilayer Substrate manufacturing method.