Date: 21 October 2021

【Volume 62】

On October 13, 2021, the Supreme Court dismissed Phoenix Silicon International Corporation’s appeal, and the ruling has become binding. We have previously covered the decision of the first instance. In the second instance, the Taiwan Intellectual Property Court (IP Court) clarified that though patentees usually strengthen their argument by focusing on the differences between the patent and the prior art, and thereby distinguish the technical means from each other when claiming a patent is non-obvious, if the description of the specification itself cannot support, or even conflicts with, the claim, it may put the patentees at a disadvantage.

Case Facts

Phoenix Silicon International Corporation (patentee and appellant, “Psi”) is the patentee of Taiwan Invention Patent No. I588880 “MANUFACTURING PROCESS OF WAFER THINNING” (“’880 patent”), believing that Integrated Service Technology (accused infringer and appellee, “iST”) infringed its patent right. iST advocated that amended claims 1 and 2 of ‘880 patent are obvious. Psi lost at the first instance as the IP Court found the claims obvious ^[1]. Psi then filed an appeal, and adopted different defense strategies regarding the issue of patent validity in the second instance. The IP Court dismissed the appeal on May 20, 2021 in its 2020 Minzhuanshangzi No. 36 Civil Judgment , upholding that claims 1 and 2 of the ‘880 patent are obvious.

Technical Features of the ‘880 Patent and Disclosure of Evidence

The ‘880 patent relates to a manufacturing process of wafer thinning which performs a TAIKO grinding manufacturing process on a wafer and then performs an etching manufacturing process on the ground central portion of the wafer.

The following is a summary of the main steps of the manufacturing process of wafer thinning disclosed by claim 1 of ‘880 patent:

Among them, TAIKO grinding manufacturing process steps of claim 1 have been disclosed by prior art references, in particular the wafer etching steps.

The following is a summary of disclosure of the main evidence:

The rest of the technical features of the ‘880 patent (e.g., steps B-4 to B-9) are disclosed by other evidence respectively. Based on the evidence, iST claimed that the combination of evidence 14+24, evidence 14+26, evidence 1+24+23, and evidence 1+26+27 can prove that claim 1 of the ‘880 patent is obvious.

The Appellant’s (Psi) Arguments

Psi claimed that prior art did not teach to “use etching steps to further reduce the thickness of wafer after TAIKO grinding steps”. The reasons include:

1. The ‘880 patent is wafer thinning using etching technology to make the wafer to have a predetermined thickness. However, all of the above evidence use etching to remove damage layer left by grinding process to achieve stress relief.

    

2. The term “predetermined” in claim 1 of ‘880 patent means to regulate or appoint in advance. The terms “first predetermined thickness” and “second predetermined thickness” in amended claim 1 have reflected a two-staged thinning manufacturing process with purpose.

    

3. Evidence 1 has taught that the thickness of damage layer generated by the specific thinning process of wafer by TAIKO grinding is very small. Therefore, if the purpose of performing etching steps after TAIKO grinding manufacturing process is to remove the damage layer, the thickness of wafer would not be further reduced in essence.

    

The Opinion of the Taiwan Intellectual Property Court at the Second Instance

IP court dismissed the appeal filed by Psi at the second instance for the following reasons:

(1) Specification of the ‘880 patent does not specifically define the substantial reduction in thickness that etching steps intend to achieve. It is hard to say that the main purpose of the ‘880 patent is to use etching steps to further reduce the thickness of wafer:

Both the amended claim 1 and the specification do not define the specific range of the first predetermined thickness and the second predetermined thickness. The specification only defines that “the second predetermined thickness is between 700 to 10 µm”, which is a very wide range, and does not define the so-called substantial influential thickness. Therefore, it is difficult to infer that the main purpose of wet etching in the ‘880 patent is to reduce the thickness of the wafer.

Additionally, referring to the fourth to fifth lines in page 1 “…and an etching process upon the wafer orderly so as to effectively reduce the internal stress of the wafer during the wafer-thinning process…”, the fifth to sixth lines in page 2 and the fifth to sixth lines in page 4 “…according to the present invention, a single grinding and etching process upon the wafer is applied. Thereupon, the internal stress of the wafer during the wafer-thinning process can be effectively reduced…” of the specification, the specification has disclosed that the internal stress caused by wafer grinding leads to wafer-cracking; thus, etching manufacturing process is utilized to release internal stress. It does not specifically define the etching manufacturing process reduces thickness with purpose.

(2) It is known from the evidence that TAIKO grinding also causes damage layer with certain thickness. Therefore, the adopted technical means based on teaching of prior art can also substantially reduce the thickness of wafer:

From the above paragraph of evidence 1, it is only known that T2 is about 200 µm to the total thickness of the semiconductor wafer 10, T3 is less than about 150 µm, and T3< T4< T2. It is not yet possible to infer that removing the damage layer by releasing stress does not have an impact on the thickness of the central portion of the wafer. In addition, evidence 14 has disclosed reducing some thickness by etching. From evidence 3, 24, and 17, it is known that grinding damage layer is at least 8 to 20 µm. The mechanical damage removed by etching in evidence 14 is at least 8 to 20 µm. It cannot be said for sure that this degree of thickness reduction does not substantially influence the thickness of the wafer.