JPH0767003B2 - Copper / organic insulation film wiring board manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a copper / organic insulating film wiring board.

<Prior Art> With the increase in the speed and integration of LSIs, the wiring boards on which they are mounted are also required to support it. As a high-density mounting board for LSIs, copper with low electrical resistance and low dielectric constant are used. In addition, a wiring board using polyimide capable of forming a thick film is attracting attention because it can perform high-speed signal processing.

By the way, as a manufacturing method of this kind of wiring board, alumina,
Applying polyimide varnish to a desired thickness by spin coating etc. on a ceramic substrate such as mullite or AlN,
It is general that the copper film is formed into a desired thickness by a vacuum evaporation method after being subjected to a basing treatment to be solidified, and a circuit is formed by using the copper film. Also,
If necessary, the formation of the polyimide film and the copper film can be alternately repeated by such a method to manufacture a multilayer wiring board.

<Problems to be Solved by the Invention> In the production of the copper-polyimide wiring board, when a wiring circuit is formed by a photoetching method, the adhesion between the copper film and the polyimide film is poor, and the copper film sometimes peels off. is there. Further, if the wiring circuit width to be formed is small even before peeling, the lead width may be locally changed or chipped due to local variation in adhesive strength.

As a result of a detailed material investigation, it was found that the local change in the lead width and the occurrence of chipping are deeply related to not only the variation in the adhesive strength but also the corrosion resistance of the deposited copper film.
That is, when the corrosion resistance of the copper film is poor, some crystal grains of the copper film are likely to be lost during etching. For this reason, when the lead width becomes extremely fine, there is a risk that the loss of crystal grains may lead to disconnection of the lead.

The present invention eliminates the above-mentioned drawbacks of the prior art, an organic insulating film,
For example, it is an object of the present invention to provide a copper / organic insulating film wiring board having a copper film having high adhesion strength to a polyimide film, good corrosion resistance, and excellent patterning property (wiring circuit formability).

<Means for Solving the Problems> In order to achieve the above object, according to the present invention, an organic insulating film is formed on a ceramic substrate, and a purity of 99.999% or more is then formed on the organic insulating film by a vacuum deposition method. The method for producing a copper / organic insulating film wiring board is characterized in that the copper film is formed and then patterned by a photoetching method.

According to the present invention, an organic insulating film is formed on a ceramic substrate, and then the surface of the organic insulating film is subjected to ion bombardment treatment in an atmosphere of an inert gas or a weak oxidizing gas. 99.999% purity by vacuum deposition method
There is provided a method for manufacturing a copper / organic insulating film wiring board, which comprises forming the above copper film and then performing patterning by a photoetching method.

The organic insulating film is preferably a polyimide film.

The present invention will be described in more detail below.

Examples of the ceramic substrate used in the present invention include an alumina plate, a mullite plate, an AlN plate, and a SiC plate.

As the organic insulating film used in the present invention, in addition to the polyimide film, various polymer films such as maleimide and Teflon, which have a small dielectric constant and excellent heat resistance, can be mentioned.In particular, the polyimide film is compared with other organic insulating films. It is preferable because it has good adhesion to metal and is economically inexpensive.

Further, the purity of the copper film formed in the present invention is preferably 99.999% or more. If the purity is less than 99.999%, a part of the crystal is likely to be lost during the etching in the subsequent step due to segregation of contained trace impurities or variation in crystal grain size due to the segregation. In particular, when the purity is 99.9996% or more, crystal loss is remarkably reduced, which is desirable.

First, a raw material for the organic insulating film, such as varnish, is applied on the ceramic substrate by a conventional method, and baked to solidify and form a film.

Next, the copper film is formed on the surface of the organic insulating film by a vacuum deposition method. Prior to forming this copper film, the surface of the organic insulating film is preliminarily subjected to an inert gas or a weak acidifying gas such as Ar, N ₂ , (Ar + N ₂ ), O ₂ , (N ₂ + O ₂ ), (Ar + O ₂ ). It is preferable to perform the ion bombardment treatment in an atmosphere such as (4) because the adhesion between the organic insulating film and the copper film is improved. As the ion bombardment treatment, a high frequency excitation type, a DC electric field type or the like can be used.

The thickness of the copper film can be appropriately selected according to need, but is generally about 0.3 to 10 μm. If it is less than 0.3 μm, the electric resistance is too large, and if it exceeds 10 μm, it takes a long time to form a film, resulting in high cost.

Subsequent to the formation of the copper film, patterning is carried out by a photoetching method in a usual manner to obtain a copper polyamide wiring board.

The formation of the organic insulating film and the copper film can be repeated as necessary to manufacture a multilayer wiring board.

Further, the case where copper is directly vapor-deposited on the organic insulating film has been described, but different kinds of gold layers such as Ti and C are previously formed on the organic insulating film.
It is also possible to deposit a thin layer of r, Ni, Zn, etc., and then deposit copper on it.

<Examples> The present invention will be specifically described below based on Examples.

(Example 1) A polyimide varnish having a thickness of 5 μm was applied on an alumina plate having a thickness of 1 mm, baking was performed at 350 ° C., and solidification was repeated 4 times to obtain a polyimide film having a thickness of about 20 μm. , 99.997% pure copper with electron beam heating and vacuum degree of 4 × without any special treatment on its surface
Samples vacuum-deposited with a thickness of 5 μm under the conditions of 10 ⁻⁵ torr, substrate temperature of 200 ° C., and film formation rate of 30 Å / sce, and the polyimide film surface was subjected to ion bombardment treatment in advance under the conditions described below before vapor deposition. A vacuum evaporated sample was prepared.

When the adhesion of the deposited film of the sample thus prepared was measured, the density strength of the sample subjected to ion bombardment of the polyimide surface before deposition was 1.31 gf / cm in peeling strength, It was about 1.2 times of (1.11 gf / cm).

The ion bombardment process is 1.
High-frequency power was set to 200 W under Ar gas pressure of 4 × 10 ⁻⁴ torr for about 5 minutes.

Example 2 A polyimide varnish having a thickness of 5 μm was applied to a mullite plate having a thickness of 1 mm, baking was performed at 350 ° C., and solidification was repeated 4 times to obtain a polyimide film having a thickness of about 20 μm. Ion bombardment treatment was performed under the same conditions as in Example 1, and 99.997% pure copper and 99.997% copper were vacuum-deposited on the surface thereof under the same conditions as in Example 1 to a thickness of about 5 μm.

The deposited film thus obtained was patterned by a photoetching method using a copper chloride solution with a line width of 40 μm and a pitch between lines of 40 μm. As a result, a copper film of 99.997% purity was formed on the side surface of the lead 1 shown in FIG. The loss of crystal grains in 1a is large as shown by the black dots in Fig. 2a, whereas the one with 99.9997% purity is second.
As shown in Fig. b, the crystal grains were scarcely missing.
In addition, 2 in FIG. 1 is an organic insulating film (polyimide film), 3 is a ceramic substrate, and 4 in FIGS. 2a and 3b are crystal grains.

<Effects of the Invention> Since the present invention is configured as described above, by forming a high-purity copper film by a vacuum deposition method, the adhesion between the copper film and the organic insulating film is excellent, and the product reliability is high. And the residual stress is small, so that the etching proceeds uniformly.

In addition, a copper film having less crystal grains during etching and good patterning properties can be obtained. In addition, there is an effect that fine wiring becomes possible as compared with the conventional method.

If the surface of the organic insulating film is subjected to the ion bombardment treatment before the formation of the copper film, the adhesiveness of the copper film is significantly improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a side surface of a lead at the time of patterning. Figures 2a and 2b show 99.997% and 99.9% purity, respectively.
It is a partial enlarged view of the side surface of the lead in the copper film of 997%. Explanation of symbols 1 ... Lead, 1a ... Side surface, 2 ... Organic insulating film (polyimide film), 3 ... Ceramic plate, 4 ... Crystal grain

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Mamoru Mita, 3-1-1 Sukegawa-cho, Hitachi City, Ibaraki Prefecture, Hitachi Cable Electric Wire Co., Ltd. (56) Reference JP-A-53-135840 (JP, A) KOSHO 55-41275 (JP, B2)

Claims (3)

[Claims] 1. An organic insulating film is formed on a ceramic substrate,
Next, a method of manufacturing a copper / organic insulating film wiring board, which comprises forming a copper film having a purity of 99.999% or more on the organic insulating film by a vacuum deposition method and then performing patterning by a photoetching method. 2. An organic insulating film is formed on a ceramic substrate,
Next, the surface of each organic insulating film is subjected to an ion bombardment treatment in an atmosphere of an inert gas or a weak oxidizing gas, and then a copper film having a purity of 99.999% or more is formed on this organic insulating film by a vacuum deposition method, and then a photo film is formed. A method for manufacturing a copper / organic insulating film wiring board, which comprises patterning by an etching method. 3. The method for producing a copper / organic insulating film wiring board according to claim 1, wherein the organic insulating film is a polyimide film.