T 0988/93 04-07-1996

I. During oral proceedings held on 13 May before the Examining Division, the proprietor of European patent application No. 88 119 978.0 (publication number 0. 318 954) requested that a European patent be granted on the basis of independent Claim 1 drafted as follows:

"A semiconductor device of a multi-layered interconnection structure comprising:

a semiconductor substrate (21);

at least a first and second patterned interconnection layer (22, 25) subsequently formed over said semiconductor substrate (21);

a first inorganic insulating film (23) formed over said semiconductor substrate (21) and a first interconnection layer (22);

an organic insulating film (24) formed on said first inorganic insulating film (23), said organic insulating film being covered partially by said second interconnection layer (25) and having an eliminated portion (B) spaced apart from an area at which said second interconnection layer (25) is formed; and

a second inorganic insulating film (26) formed on said second interconnection layer (25), said organic insulating film (24) and said first inorganic insulating film, said second inorganic insulating film (26) being in contact with said first inorganic insulating film (23) through said eliminated portion (B) in said organic insulating film (24)."

II. The Examining Division rejected that request setting forth the following reasons:

With respect to a similar semiconductor device described in document

D1: US-A-4 613 888

in relation with Figure 7, the subject-matter of Claim 1 is distinguished in that the organic insulating film (24) is covered partially by the second interconnection layer (25) and has an eliminated portion (B) spaced apart from an area at which said second interconnection layer is formed. This feature does not seem to be disclosed in its generality in the application as filed but, anyway, providing this feature does not require the exercise of inventive ingenuity from a skilled person. Document (D1) copes indeed with the technical problem underlying the present application, namely how to prevent the occurrence of cracks resulting from thermal shocks. Therefore, no inventive step can be perceived in setting this problem. Figure 10 of document (D1) furthermore shows a device in which an organic film (21') is partially covered by the second interconnection layer (16). Providing this feature in a device according to Figure 7 while maintaining a direct contact of the inorganic films (20, 22) would not require the skilled person to display any inventive talent.

III. The Applicant lodged an appeal against the decision of the Examining Division.

With its Statement of Grounds of Appeal, the Appellant filed two sets of claims forming the respective bases of a main and an auxiliary request.

IV. The Board summoned the Appellant to oral proceedings.

V. In response to the summons to attend oral proceedings, the Appellant filed on 4 June 1996 a further set of claims forming the basis of a second auxiliary request.

VI. Oral proceedings were held on 4 July 1996.

During the oral proceedings, the Appellant amended Claim 1 according to the auxiliary request filed with the Statement of Grounds of Appeal and requested that a European patent be granted on the basis of that amended claim.

VII. The claim forming the basis of the Appellant's single request differs from the version of Claim 1 the Examining Division refused in that:

- in the third clause, indefinite article "a" is replaced by definite article "the" before "first interconnection layer (22)", and

- the fourth clause reads "an organic insulating film (24) which is formed on said first inorganic insulating film (23) and on which said second patterned interconnection layer (25) is formed, which has an eliminated position (B) and".

VIII. In support of its request, the Appellant argued in substance as follows:

Document (D1) discloses the most relevant prior art. In the first embodiment described there, the direct contact between the layers (20) and (22) plays a major part. To achieve this contact, the second wiring layer (16) is used as a mask while etching the portions of the silica film (21) it does not cover. The use of the second metal wiring layer as a mask is also an essential feature of the process for manufacturing a semiconductor device according to the second embodiment described in document (D1). It has the obvious advantage that no separate masking step is necessary, so that the manufacturing process is easier to carry out. Therefore, a person skilled in the art has no reason to deviate from the teachings of document (D1). The latter consequently does not suggest to remove the sub-insulating interlayer only in a limited area such that a protruding portion is formed.

The device known from document (D1) already exhibits a high reliability owing to the direct contact between the silicon nitride film (20) and the final passivation layer (22). The object of the present invention is thus to provide a semiconductor device with a multilayered structure achieving a still higher reliability by preventing the occurrence of cracks caused by thermal shocks.

In the achievement of this purpose, the protruding portion of the organic layer (24) not covered by the second interconnection layer (25) is of particular importance. The gist of the invention is indeed to be seen not only in the provision of a direct contact between the inorganic insulating films (23, 26), but also in that the interconnection layer (25) has no contact with the eliminated portion (B), since said portion must be distinct from the bonding pad area. Contrary to what is shown in the Figures 7 and 10 of document (D1), no steep step is thus formed at the eliminated portion of the organic insulating layer, whereby cracks prevention is improved. The surprisingly high efficiency of the proposed measure is evidenced by the diagram annexed to the Statement of Grounds of Appeal and in which the curves A, B and C respectively relate to a conventional semiconductor device according to Figure 2A of the patent application, to the first embodiment disclosed in document (D1) and to a device embodying the invention. The latter device is clearly superior to both known devices.

IX. After deliberation by the Board, the decision was announced that the decision under appeal is set aside and that the case is remitted to the Examining Division with order to grant a European patent with Claim 1 as filed during the oral proceedings and description to be adapted accordingly.