JP2565362B2 - Method for manufacturing multilayer wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a multilayer wiring board.

(Prior Art) Conventionally, a multilayer wiring board on which a semiconductor integrated circuit element or the like is mounted has a base made of an electrically insulating material such as alumina ceramics, and tungsten (W) and molybdenum (embedded in the surface and inside of the base and baked). Mo) etc. and a conductor layer for electric wiring made of a high melting point metal.

Such a conventional multilayer wiring board usually uses a green sheet made of ceramics such as alumina (Al ₂ O ₃ ) having excellent electric insulation property, and has tungsten (W), molybdenum (Mo), manganese (Mn) on its surface. It is formed by printing a thick film of a conductive paste composed of a high melting point metal such as a screen printing method into a predetermined pattern and laminating a plurality of these, and then firing the laminated ones at a temperature of about 1500 ° C. ing.

However, in recent years, with the rapid progress in high density and high integration of semiconductor integrated circuit devices such as hybrid ICs and LSIs, it is possible to increase the wiring density of a multilayer wiring board on which the LSIs are mounted. In the conventional multilayer wiring board, it is difficult to miniaturize the wiring conductor layer because the conductor layer for electric wiring is formed of a thick film in the conventional multilayer wiring board, and it becomes difficult to form a multilayer because the entire thickness becomes thick. There was a problem that high density could not be achieved.

Therefore, in order to solve the above-mentioned drawbacks of the conventional multilayer wiring board, the conductor layer for electric wiring as the circuit wiring is formed by using a thin film forming technique by a vapor deposition method such as a vapor deposition method or a sputtering method instead of the thick film method. In addition, the insulation of each conductor layer for electrical wiring is performed by applying a polymer material by a spin coating method or the like to form an insulating film, which makes the conductor layer thin and fine and enhances the conductor layer for electrical wiring. A multilayer wiring board having a high density has been proposed.

(Problems to be Solved by the Invention) However, in the above-mentioned multilayer wiring board, a conductor layer is adhered to the side surface of the via hole provided in the insulating film made of a polymer material, and the side surface conductor layer positions the insulating film above and below the insulating film. When connecting a conductor layer for electric wiring, it is difficult to deposit the conductor layer on the side surface of the via hole provided in the insulating film by the vapor phase growth method, and the adherence of the conductor layer is extremely poor. Therefore MIL-STD 883C 101
When an accelerated test such as a thermal shock test based on 0 standard is performed,
The connection resistivity between the conductor layer on the upper surface of the insulating film and the conductor layer deposited on the wall surface of the via hole is 1% or more, the rate of change in total resistance reaches several tens of percent, and as a result, the change in voltage level is large.
The connection reliability on the side surface of the via hole is extremely poor. This is because the thickness of the conductor layer on the wall surface of the via hole is smaller than the layer thickness of the conductor layer on the upper surface of the insulating film, so that the insulating film expands due to heating when attaching the semiconductor integrated circuit element to the multilayer wiring board. It is considered that, when a tensile stress is generated in the thickness direction of the wall surface of the via hole, the conductor layer on the wall surface of the via hole having a small layer thickness is broken.

(Object of the Invention) In view of the above-mentioned drawbacks, the present inventors have conducted various experiments and, as a result of vapor phase epitaxy, deposit a base metal layer on the upper surface of an insulating film and the wall surface of a via hole provided in the insulating film. When a conductive layer is deposited on the metal layer by electrolytic plating and the conductor layer for electric wiring has a two-layer structure of a base metal layer and a conductive layer, for electric wiring provided on the upper surface of the insulating film and the wall surface of the via hole. It has been found that the connection with the conductor layer becomes strong, and thereby the connection reliability at the step portion is extremely excellent even in an accelerated test such as a thermal shock test.

Based on the above findings, the present invention makes the connection of the conductor layer for electrical wiring provided on the upper surface of the insulating film and the wall surface of the via hole provided in the insulating film strong, and makes the connection reliability of both layers extremely high. To provide a wiring board.

(Means for Solving the Problems) A method for manufacturing a multilayer wiring board according to the present invention comprises a polyimide resin having a via hole, a silicone resin, a polybutadiene resin, a polyamideimide resin, and a polytetrafluoroethylene resin on an insulating substrate having a wiring conductor on the upper surface. After forming an insulating film made of any polymer material of fluoroethylene resin, titanium is formed on the upper surface of the insulating film and the wall surface of the via hole by vapor phase epitaxy,
A base metal layer composed of at least one type of molybdenum and a plurality of layers of copper is deposited, and a conductive layer made of copper is deposited on the base metal layer by electrolytic plating to form a two-layer structure of the base metal layer and the conductive layer. And forming a conductor layer for electric wiring having.

(Example) Next, the present invention will be described in detail based on an example shown in the accompanying drawings.

FIG. 1 is an enlarged cross-sectional view of an essential part of a multilayer wiring board for explaining the manufacturing method of the present invention, and 1 is an insulating base made of alumina ceramics or the like.

The insulating substrate 1 is prepared by adding and mixing an appropriate solvent and a solvent to a ceramic raw material powder such as alumina (Al ₂ O ₃ ) or silica (SiO ₂ ) to prepare a slurry, which is prepared by a conventionally known doctor blade method. It is manufactured by forming it into a sheet and baking it at a high temperature.

A wiring conductor 2 is formed on the upper surface of the insulating substrate 1 by a vapor phase growth method such as a well-known ion plating method and a sputtering method. Further, a polymer material is spin-coated on the wiring conductor 2 and heat treatment is performed. The insulating film 3 thus formed is deposited. Polyimide resin, silicone resin, polyptadiene resin, polyamideimide resin, and polytetrafluoroethylene resin are preferably used as the polymer material used for the insulating film 3.

Next, a thin film of silica or titanium is formed on the insulating film 3 by the same vapor phase growth method, and a conductor pattern is formed by photolithography, and the insulating film 3 is formed by reactive ion etching or the like using the pattern as a mask. It is selectively removed to form a via hole 4.

Then, a first base metal layer 5 made of titanium, molybdenum or the like and a second base metal layer 6 made of copper are sequentially deposited on the insulating film having the via holes 4 by the same vapor deposition method as described above. To do.

Finally, a copper conductive layer 7 is deposited on the second base metal layer 6 by electrolytic plating to complete a multilayer wiring board as a product.

That is, in the present invention, the conductor layer for electric wiring as the circuit wiring has a two-layer structure of the underlying metal layers 5 and 6 deposited by vapor deposition and the conductive layer 7 deposited by electrolytic plating. Therefore, the conductor layer located on the wall surface of the via hole of the insulating film has a large layer thickness and is strongly bonded to the wall surface of the via hole, and as a result, the conductive layer of each conductive layer adhered to the upper surface of the insulating film 3 and the wall surface of the via hole is The connection can be made reliable.

When the layer thickness of the conductor layer for electrical wiring is 1/10 or more of the thickness of the insulating film on the wall surface of the via hole, heat is applied when the semiconductor integrated circuit element is mounted, etc., and the insulating film expands to cause the via hole. Even if tensile stress occurs in the conductor layer on the side surface, the conductor layer does not break.

If the thickness of the first base metal layer 5 made of at least one of the insulating film titanium and molybdenum is less than 0.03 μm, when heat is applied when mounting a semiconductor integrated circuit element, the first base metal layer 5 is Interdiffusion occurs between the underlayer metal layer 5 and the second underlayer metal layer 6 made of copper deposited on the underlayer metal layer 5 of
First comprising at least one of titanium and molybdenum
There is a tendency that the underlying metal layer 5 directly contacts the insulating film to cause poor adhesion and the rate of change in connection resistance increases. Further, when the layer thickness exceeds 0.5 μm, the internal stress of the first base metal layer 5 becomes high, and when applied to the insulating film, the internal stress causes cracks in the insulating film, resulting in insulation resistance and adhesion strength. Tend to deteriorate. Therefore, the thickness of the first base metal layer composed of at least one of titanium and molybdenum
It is preferably in the range of 0.03 to 0.50 μm.

On the other hand, the second base metal layer 6 made of copper has a layer thickness of 0.
When the thickness is less than 1 μm, unevenness occurs in the conductive layer when the conductive layer is deposited on the upper surface later by electrolytic plating.
The coverage on the wall surface of the via hole tends to deteriorate. Further, when the layer thickness exceeds 2.0 μm, the internal stress of the second underlayer metal layer 6 becomes high, and the first underlayer metal layer 5 is
Similarly to the above, there is a tendency that cracks are generated in the insulating film. Therefore, the second base metal layer 6 has a layer thickness of 0.1 to 2.0.
It is preferably in the range of μm.

When the thickness of the conductive layer made of copper is less than 1 μm, the connection reliability at the stepped portion such as a via hole is deteriorated. On the contrary, when it exceeds 10 μm, the internal stress of the conductive layer becomes high and cracks occur in the insulating film. Therefore, the conductive layer preferably has a thickness in the range of 1 to 10 μm.

As described above in detail, the present invention is extremely useful as a method for manufacturing a multilayer wiring board in which a conductor layer for electric wiring as circuit wiring is formed on the wall surface of a via hole.

The above-mentioned remarkable advantages of the present invention can be easily recognized by the following experimental examples and comparative examples.

Example 1 A film thickness made of a polyimide resin having a via hole on a ceramic substrate made of alumina ceramics provided with a wiring conductor made of tungsten or molybdenum.
A 25 μm insulating film is formed, and a first base metal layer made of molybdenum is formed on the insulating film by a vapor phase growth method to a thickness of 0.2 μm.
Then, a second base metal layer made of copper and having a layer thickness of 1.0 μm was formed, and a copper conductive layer was further deposited thereon by electrolytic copper plating to prepare a sample having 100 μm in thickness. These MIL
-Based on STD 883C 1010 standard, heat shock of 5 minutes each at -65 ° C and 150 ° C is applied 30 times, and the rate of change of resistance value after the thermal shock test with respect to the resistance value between the upper and lower layers of the via hole before the thermal shock test. The change rate was 1% or less, and there was no breakage of the conductor layer.

Example 2 By the same method as in Example 1, a first base metal layer made of molybdenum and a second base metal layer made of copper were formed on the insulating film made of silicone resin and having a film thickness of 25 μm with a layer thickness of 0.2 μm. Fifty samples, each having a thickness of 1.0 μm and sequentially deposited with a copper conductive layer by electroplating to a layer thickness of 2 μm, were prepared, and the rate of change in resistance was determined by the same method as in Example 1.

As a result, the rate of change in resistance was 1% or less, and the conductive layer was not broken at all.

Example 3 By the same method as in Example 1, a first base metal layer made of molybdenum was formed on an insulating film made of polyamideimide resin having a thickness of 25 μm to a thickness of 0.2 μm, and a second base metal layer made of copper was made. Samples were sequentially deposited to a layer thickness of 1.0 μm, and a copper conductive layer was deposited thereon to a layer thickness of 2 μm by electrolytic plating.
Individual pieces were prepared and the rate of change in resistance was determined by the same method as in Experimental Example 1.

As a result, the rate of change in resistance was 1% or less, and the conductive layer was not broken at all.

Example 4 By the same method as in Example 1, a first base metal layer made of titanium was formed on a 25 μm-thick insulating film made of polybutadiene resin to a thickness of 0.2 μm, and a second base metal layer made of copper was formed. Fifty samples were prepared by sequentially depositing a layer thickness of 1.0 μm and then depositing a copper conductive layer on the layer thickness of 2 μm by electrolytic plating. The rate of change in resistance was determined by the same method as in Example 1. .

As a result, the rate of change in resistance was 1% or less, and the conductive layer was not broken at all.

Example 5 By the same method as in Example 1, a first base metal layer made of titanium was formed on an insulating film made of polytetrafluoroethylene having a thickness of 25 μm to a thickness of 0.2 μm, and a second base made of copper was made. Fifty samples were prepared by sequentially depositing a metal layer to a layer thickness of 1.0 μm and depositing a copper conductive layer on the layer to a layer thickness of 2 μm by electrolytic plating. The rate of change in resistance was determined by the same method as in Example 1. I asked.

As a result, the rate of change in resistance was 1% or less, and the conductive layer was not broken at all.

Comparative example Film thickness made of polyimide resin with via holes on a ceramic substrate made of alumina ceramics with wiring conductors made of dangsten or molybdenum
A 25 μm insulating film is formed, a molybdenum base metal layer of 0.2 μm is deposited on the insulating film by vapor deposition, and a conductive layer of copper is deposited by 3 μm by the same vapor deposition method. 100 adhered samples were prepared. When the rate of change in resistance of these was examined by the same method as in Example 1, the rate of change in resistance was 3% or more, and some conductor layers were ruptured.

(Effects of the Invention) As described in detail above, according to the method for manufacturing a multilayer wiring board of the present invention, the conductor layer for electrical wiring that is adhered to the upper surface of the insulating film and the wall surface of the via hole provided in the insulating film is formed. Since the two-layer structure of the underlying metal layer by the phase growth method and the conductive layer by electroplating is formed, the thickness of the conductor layer on the wall surface of the via hole becomes large, and as a result, the conductor layer is firmly bonded on the wall surface of the via hole, and the connection reliability In addition, it is possible to prevent breakage of the conductor layer for electric wiring.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part of a multilayer wiring board for explaining a method for manufacturing a multilayer wiring board according to the present invention. 1 ... Insulating substrate, 2 ... Wiring conductor, 3 ... Insulating film, 4 ... Via hole, 5 ... First underlying metal layer, 6 ... Second underlying metal layer, 7 ... Conductive layer, 8 ... For electrical wiring Conductor layer

Claims (4)

(57) [Claims] 1. An insulating film having a via hole is formed on an insulating substrate having a wiring conductor on the upper surface, and then a base metal layer is deposited on the upper surface of the insulating film and the wall surface of the via hole by a vapor phase growth method. Along with at least the underlying metal layer on the wall surface of the via hole, a conductive layer having a thickness of 1/10 or more of the thickness of the insulating film is deposited by an electrolytic plating method, and an electrical wiring having a two-layer structure of the underlying metal layer and the conductive layer. A method for manufacturing a multi-layer wiring board, comprising forming a conductor layer for use in wiring. 2. The method of manufacturing a multilayer wiring board according to claim 1, wherein the conductive layer deposited by the electrolytic plating method is made of copper (Cu). 3. The insulating film is made of a polymer material selected from the group consisting of polyimide resin, silicone resin, polybutadiene resin, polyamideimide resin and polytetrafluoroethylene resin. Manufacturing method of multilayer wiring board. 4. The multilayer wiring according to claim 1, wherein the underlying metal layer has a two-layer structure of at least one of titanium (Ti) and molybdenum (Mo) and copper (Cu). Substrate manufacturing method.