JPH0438157B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for forming multilayer wiring.

(Conventional technology) With the increasing density and integration of electronic devices,
There is a growing demand for multilayer wiring boards. FIGS. 2A to 2E are process diagrams for explaining an example of a conventional method for forming a multilayer wiring board (Electronic Technology, 24 (4),
p.26-30).

Prior to explaining the present invention, this conventional example will be briefly explained.

First, as shown in FIG. 2A, a plurality of conductive layers 12 of a lower wiring pattern are formed on a ceramic substrate as a base layer 10.

Next, as shown in FIG. 2B, an insulating layer 14 made of an insulating photosensitive resin, such as polyimide, is
The exposed surface 10a of the substrate 10 and the conductive layer 1 are coated using a means such as a spin coater or a roll coater.
2 on the exposed surface 12a.

Subsequently, this insulating layer 14 is patterned by exposure and development to form through holes 16 at a plurality of locations on the conductive layer 12 to obtain a structure as shown in FIG. 2C.

Next, as shown in FIG. 2D, conductive paste 18 is embedded in these through holes 16 and
8a is exposed at the surface 14a of the insulating layer 14.

Thereafter, the conductive layer 20 of the upper layer wiring pattern is formed on the surface of the insulating layer 14 through processes such as vapor deposition and photolithography, and these conductive pastes 18 are selectively bonded. A multilayer wiring structure as shown in Figure E is obtained.

(Problems to be Solved by the Invention) However, in this conventional method, the base layer 1
There was a drawback that the unevenness of the lower layer wiring 12 formed on the insulating layer 14 affected the surface condition, and the surface of the insulating layer 14 had unevenness, resulting in poor flatness.

In addition, in order to reduce the unevenness of the surface, the lower layer wiring 12 must be formed thinly, or if the insulating layer 14 is to be formed thickly, the through holes 16 may not be formed if the thickness exceeds a certain level. The drawback was that it was difficult.

Furthermore, the conventional method has had the disadvantage of high manufacturing costs because it requires the use of expensive insulating materials such as photosensitive polyimide.

An object of the present invention is to provide a method for forming multilayer interconnections that eliminates the drawbacks of the conventional methods.

(Means for Solving the Problems) In order to achieve this object, the multilayer interconnection forming method of the present invention includes the steps of forming a plurality of first conductive layers as lower interconnections on a base layer; a step of forming second conductive layers as contact posts at predetermined locations on the first conductive layer at a distance from each other; a step of applying an epoxy resin; a step of curing the resin while pressing the surface of the resin to expose the surface of the second conductive layer; and exposing the second conductive layer on the surface of the resin. The method is characterized in that it includes a step of forming a plurality of third conductive layers as upper layer wirings selectively coupled to the surface.

(Function) If multilayer wiring is formed in this way, it is possible to press the epoxy resin to flatten the surface and eliminate unevenness, so it is possible to achieve a desired thickness and no unevenness regardless of the thickness of the underlying wiring. An insulating layer can be formed. Therefore, no surface smoothness is required when applying the resin, making it simple and easy to form multilayer wiring over a large area.

Furthermore, since the second conductive layer acts as a contact post with the same function as a conventional through hole, when forming an upper layer wiring, it is easy to obtain selective electrical coupling with the desired lower layer wiring according to the design. I can do it.

Further, in this invention, since a relatively inexpensive epoxy resin is used as the insulating resin, manufacturing costs can be reduced.

(Example) Examples of the present invention will be described below.

FIG. 1 is a process diagram for explaining one embodiment of the multilayer interconnection forming method of the present invention, and each figure is a sectional view schematically showing the main part of the structure obtained at the main process steps. Note that this figure is only shown schematically to the extent that this invention can be understood, so the dimensions and
The shape and arrangement relationship are not limited to the illustrated example, and can be set according to the design.

First, as shown in FIG. 1A, a first conductive layer 12 is formed in a lower wiring pattern on a ceramic substrate as an underlayer 10. This first conductive layer 12 is
For example, copper is deposited by electroless plating or electrolytic plating at a pitch of 3 pieces per 1 mm and a thickness of 15 μm. This deposition provides a copper wiring pattern as the lower layer wiring.

Next, a photoresist pattern 22 is formed on the exposed surface 10a of the base layer 10 and the surface 12a of the first conductive layer 12 using a conventional photolithography technique to obtain a structure as shown in FIG. 1B.

Next, on the exposed surface 12a of the first conductive layer 12 exposed through the holes 23 of the photoresist 22, electrolytic plating is performed using the same or different material as the first conductive layer to form a plurality of second conductive layers 24. be coated with. This example uses copper. Thereafter, this photoresist 22 is peeled off to obtain a structure as shown in FIG. 1C. Surface 1 of base layer 10 of this second conductive layer 24
As an example, the dimension in the plane parallel to 0a is 0.167μm
×0.167μm, and the height is approximately 20μm. This second conductive layer 24 acts as a contact post (protruding electrode).

Next, the surface 12a of the first conductive layer 12 on which the second conductive layer 24 is formed and the exposed surface 1 of the base layer 10
An epoxy resin 26, which is an insulating resin with a low rate of change in volume before and after curing, is applied to the entire surface of 0a to obtain a structure as shown in FIG. 1D. An example of such a resin is Ecobond (trade name manufactured by Emerson & Cuming), but it is not limited to this.When cured, the volume shrinks and the surface becomes uneven, which impairs the required flatness. It is also possible to use other resins other than epoxy that do not cause the formation of epoxy.

Subsequently, the resin layer (insulating layer) 26 is cured while being pressed from the surface toward the base layer 10 at a pressure of, for example, about 15 kg/cm ² and a temperature of 80° C. for one hour. Obtain the structure shown in .
As a result, the surface 26a of the insulating layer 26 is completely flattened, and the contact post 24 made of the second conductive layer is formed in the insulating layer 26, and the surface 24a is exposed to the surface 26a of the insulating layer 26. The structure is as follows.

The steps in this embodiment for exposing the surface of the contact post simply by pressing the epoxy resin layer will be briefly described.

During pressing, a release film (generally a Teflon sheet is used) is spread on the surface of the substrate, and the substrate is pressed with a surface plate. The resin on the contact post is removed by pressing, and the contact post is exposed on the surface.
The purpose of pressing using a release film is to prevent the resin from adhering to the surface plate. This process completely exposes the contact posts. However, assuming that an extremely thin resin layer remains, it is desirable to soft-etch the resin. By this etching, resin residue on the post can be removed and the connection with the third conductor layer can be completed. In this example, since epoxy is used as the resin, chromium sulfate (CrO ₃ :100g/1 and
It is appropriate to immerse it in a H ₂ SO ₄ :100ml/1) solution.

Next, the exposed surface 2 of the contact post 24 is placed at a predetermined location on the surface 26a of the insulating layer 26.
A third conductive layer 28 for electrically selectively coupling 4a is provided by vapor deposition, and this is used as an upper layer wiring. This third conductive layer 28 can be made of a metal layer consisting of two layers of Ni--Cu and Au, for example. The structure thus obtained is shown in FIG. 1F.

The invention is not limited only to the embodiments described above, but can be subjected to many modifications and changes. For example, the materials used for each component other than the epoxy resin for forming the insulating layer are merely examples, and other suitable materials can be used depending on the design.

For example, the first, second, and third conductive layers may all be made of the same material, or may be made of different materials.

(Effects of the Invention) As is clear from the above description, the greatest feature of the present invention is that flattening and exposing the connecting conductor (contact post) can be done simultaneously by pressing using a resin with low curing shrinkage. It's about doing.
Therefore, according to the method for forming multilayer wiring according to the present invention, the surface of the resin formed in a single resin pouring process is pressed, thereby removing and exposing the resin on the contact posts and flattening the surface. conduct.
As a result, regardless of the thickness of the multilayer wiring, it is possible to obtain a multilayer wiring that has no irregularities, has good surface flatness, and has contact posts formed in the insulating layer. Therefore, as a matter of course, it is possible to reduce the manufacturing cost, and there is no need for any surface polishing process.

Further, according to the present invention, since surface smoothness is not required when applying the resin to form the insulating layer, the formation of multilayer wiring becomes simple and easy.

Further, since an inexpensive epoxy resin can be used as the resin for the insulating layer, manufacturing costs can be reduced.

The method of this invention can be applied not only to two-layer wiring but also to multilayer wiring of three or more layers.

[Brief explanation of drawings]

1A to 1F are process diagrams for explaining the method for forming multilayer wiring according to the present invention, and FIGS. 2A to 2E are process diagrams for explaining the conventional method for forming multilayer wiring. DESCRIPTION OF SYMBOLS 10... Base layer, 10a... Exposed surface of base layer, 12... First conductive layer (or lower wiring), 12
a... Surface of first conductive layer, 22... Photoresist, 23... Hole in photoresist, 24... Second conductive layer (or contact post), 24a... Surface of second conductive layer, 26... Insulating layer (epoxy resin layer), 26a... surface of insulating layer, 28... third conductive layer (or upper layer wiring).

Claims (1)

[Claims] 1. A step of forming a plurality of first conductive layers as lower layer interconnects on a base layer, and forming second conductive layers as contact posts at a plurality of predetermined locations on the first conductive layer spaced apart from each other. a step of forming a layer; a step of depositing an epoxy resin on the exposed surfaces of each of the base layer, the first conductive layer, and the second conductive layer; and applying the epoxy resin while pressing the surface of the epoxy resin. curing to expose the surface of the second conductive layer; and forming a plurality of third conductive layers as upper layer wirings on the surface of the epoxy resin to selectively bond to the exposed surface of the second conductive layer. A method for forming multilayer wiring, comprising the steps of: