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When is a salami sandwich inventive?

At the European Patent Office (EPO), the gold standard for assessing inventive step is called the ‘problem-and-solution’ approach, and it is applied almost without exception. The Boards of Appeal of the EPO frequently cite Rule 42(1)(c) EPC as the basis for this approach, with the first application of this approach dating back to the first case heard by the Boards, T 0001/80 (Carbonless copying paper).

The ‘problem-and-solution’ approach, as comprehensively detailed in the EPO Guidelines for Examination, includes three main stages:

(i) determining the ‘closest prior art’,

(ii) establishing the ‘objective technical problem’ to be solved, starting from that ‘closest prior art’ and

(iii) considering whether or not the claimed invention, starting from the closest prior art and the objective technical problem, would have been obvious to the skilled person.

Considering the first step of determining the closest prior art, the Boards have repeatedly pointed out that the closest prior art for assessing inventive step is normally a prior art document disclosing subject-matter conceived for the same purpose or aiming at the same objective as the claimed invention and having the most relevant technical features in common.

The recently published decision T 1841/11 appears to take a different approach. This decision has been included in the recent summary of EPO Boards of Appeal Case Law for 2015 and 2016, indicating that it should be considered as a key decision. In this case, prior art relating to the same purpose as the claimed invention (a method for manufacturing a semiconductor substrate comprising a silicon/germanium film) was available for selection as closest prior art. Instead, the Board of Appeal considered it appropriate to select a different piece of prior art having a similar – but not same – purpose (a method for manufacturing a semiconductor substrate comprising a germanium film). In other words, the prior art used as a starting point for the assessment of inventive step was not the closest prior art according to established practice. This in itself is perhaps not surprising. The Boards generally take the approach that if one or more pieces of prior art are equally appropriate as a starting point for assessment of inventive step, then the ‘problem and solution’ analysis should be carried out starting from each one.

However, in this case, the next step of the Board was unconventional. Particularly, the Board indicated that the increased difference in subject matter between the claimed invention and the chosen closest prior art, arising because the chosen closest prior art had been selected, could not be argued as supporting inventive step. In this case, the Board had construed the purpose used to assess what should be chosen as closest prior art narrowly, because the application did not identify a particular purpose or problem solved for what became the granted claim. Hence, the Board justified requiring prior art that almost provided the claimed method, rather than requiring prior art that addressed a similar technical problem to the subject matter claimed.

As noted by the Board, even if prior art relating to the same purpose is available, it is not excluded that a document relating to a similar purpose might be considered to represent a better – or at least an equally plausible – choice of closest prior art, provided that it would be immediately apparent to the skilled person that what is disclosed in the document could be adapted to the purpose of the claimed invention in a straightforward manner, using no more than common general knowledge.

However, the Board indicated that the difference, arising because close – but not the closest – prior art was selected, is not one which can legitimately be invoked in support of inventive step. The problem-solution approach presupposes that the skilled person has a purpose in mind from the very beginning of the inventive process.

The opinion of the Board is best expressed in their own words:

4.2 In the present case, the purpose of the invention is to provide a method for manufacturing a semiconductor substrate comprising a SiGe film, such substrates and manufacturing methods therefor being known per se, and hence the material of the film being SiGe is something which is assumed to be in the mind of the skilled person from the outset. An argument that it would not be obvious to select SiGe could be no more persuasive than an argument that where it is intended to make a salami sandwich, it would be inventive to choose salami as the filling.

Generally, in decisions of the Boards, the skilled person is considered as being tied to their chosen starting point. In T 570/91, the Board emphasised that although a person skilled in the art was completely free in choosing a starting point, he or she would of course be bound afterwards by that choice (specifically, starting with prior art relating to a compressor piston design could only lead to a result that was also a compressor piston). However, in this decision T 1841/11, the Board has decided that skilled person was not bound to a method for manufacturing a semiconductor substrate comprising a Ge film, as specified in the closest prior art, but was able to replace the Si film with a Si/Ge film in an obvious step.

It will be interesting to see how other Boards interpret and apply this decision. For applicants and patentees, overcoming inventive step objections may become more challenging as a result of this decision, as it seems to widen the options for selection of closest prior art. For opponents, new routes for attack may have been opened. This decision serves as a reminder of the benefits of identifying, in a patent application, the problem solved by the claimed invention and of emphasising, in the application, the technical benefits provided by the claimed invention.

Significant decisions of the Boards of Appeal are distilled in the recently-published EPO Case Law 2015 and 2016 (Supplementary publication 4 – Official Journal EPO 2017). These selected decisions are typically included the next edition of the Case Law of the Boards of Appeal. Subsequently, such decisions often provide basis for amendments to the Guidelines for Examination in the European Patent Office. Hence, these decisions may provide an informed insight into future practice at the EPO.

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