Key points
- In this examination appeal, the PCT application was filed in 2001.
- The Board finds the claims to lack inventive step.
- “To summarize the above [findings regarding inventive step], the skilled person, starting from D4 disclosing features a) and b) as well as an AlN nitride layer and being faced with the objective technical problem of how to avoid cracking of thick GaN films grown on Si substrates would have considered to apply solutions found for similar problems when growing GaN on SiC instead of on silicon. They would thereby have consulted D5 and would have been incited by the teaching of D5 relating to figure 8 to replace the AlN buffer layer on the Si substrate of D4 by an AlGaN layer arranged directly on the substrate and thereby adjacent to it, the AlGaN layer being continuously compositionally graded over its entire thickness as required by feature c), starting with an initial composition of AlN (i.e. an Al content of 100 %) at the substrate/buffer interface and ending with a final composition of GaN (i.e. an Al content of 0 %) at the buffer/GaN interface, in line with the requirements of feature d). They would thereby have arrived at a graded ALGaN layer grown in the same manner as the one proposed in the present application. The resulting graded AlGaN layer inevitably would have had a net compressive stress to the same extent as [...] required by feature e). Hence, the subject-matter of independent claim 1 of the main request is not inventive under Article 56 EPC 1973 in view of D4 combined with the teaching of D5 relating to figure 8.”
- The selection of D4 as the closest prior art was not contentious.
- The distinguishing features are identified.
- “the technical effect of the distinguishing features is that the GaN films grown on Si do not exhibit cracking, even if they are relatively thick ”
- The objective technical problem is “how to avoid cracking of thick GaN films grown on Si substrates”
- The Board then first checks the solution proposed in the CPA D4 itself and finds that “the skilled person would, starting from D4, continue to look for (further) solutions of the cracking problem, despite the solution proposed in D4 itself.”
- The next step is showing that the skilled person would have consulted D5 even if D5 is about “growing GaN on SiC instead of on silicon”
- As to D5, it must both teach 'something falling within' the distinguishing features and give a motivation (incentive) to apply that teaching to the CPA to solve the objective technical problem, i.e. teach that the relevant feature of D5 can be used to avoid cracking of thick GaN films.
- As to the motivation to apply the feature: “D5 discloses that the problem of cracking of the GaN layer grown on an SiC substrate can be resolved by using a compositionally graded AlGaN buffer layer (column 18, lines 53 to 56). ”
- Claim 1 at issue specifies as distinguishing feature “the graded layer having a net compressive stress”. The CPA D4 does not have the graded layer, D5 is cited as teaching the graded layer. However, “D5 does not describe compressive stress”. So D5 teaches a graded layer and teaches that such a layer can be used to avoid cracking, but does not teach that the graded layer at issue has ‘net compressive stress’.
- “However, the type of graded AlGaN buffer layer disclosed in D5 - which the skilled person would have selected to replace the AlN buffer disclosed in D4 as set out above - is grown in a continuous manner starting from AlN” .... “The appellant [applicant] submits that uninterrupted growth of this type of graded AlGaN buffer layer on an Si substrate causes compressive stress. If that is the case, such compressive stress will inevitably also be present when the AlN buffer layer of D4 is replaced by an AlGaN buffer layer grown continuously as described in Example V of D5. It must be concluded that a graded layer grown in that manner has a compressive stress to the same extent as required by feature e).”
- So applying the graded layer of D5 to the structure of D4 inherently gives a structure exhibiting a net compressive stress as specified in feature e of claim 1.
- Full marks for the Board if it was a Paper C of the EQE, in my view, though 5 years (appeal pendency 2017-2021 inclusive) is more time than available on the EQE let alone 20 years (since the filing date).
- The present decision may illustrate that the 13-step problem-solution approach as I outlined in epi Information is indeed applied in practice.
T 1094/17 -
https://www.epo.org/law-practice/case-law-appeals/recent/t171094eu1.html
Reasons for the Decision
1. The appeal is admissible.
2. Main request
2.1 D4 as closest prior art
The appellant considers D4 to be the closest prior art (grounds of appeal, page 3, first paragraph under the heading "Inventive step of claim 1 based on D4 combined with D5"). The contested decision also discusses this approach (section II A 2 and the corresponding subsections).
D4 is directed at semiconductors structures including an Si substrate and a nitride layer and addresses the same problem as the application, i.e. the cracking of GaN films grown on Si substrates (see abstract).
The Board thus concurs with the appellant concerning the selection of D4 as the closest prior art.
2.2 Distinguishing features
source http://justpatentlaw.blogspot.com/2021/07/t-109417-example-of-modern-psa.html
