Alpha and Omega Semiconductor Limited v. Force MOS Technology Co., Ltd.

CourtDistrict Court, N.D. California
DecidedDecember 13, 2023
Docket5:22-cv-05448
StatusUnknown

This text of Alpha and Omega Semiconductor Limited v. Force MOS Technology Co., Ltd. (Alpha and Omega Semiconductor Limited v. Force MOS Technology Co., Ltd.) is published on Counsel Stack Legal Research, covering District Court, N.D. California primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Alpha and Omega Semiconductor Limited v. Force MOS Technology Co., Ltd., (N.D. Cal. 2023).

Opinion

1 2 3 4 UNITED STATES DISTRICT COURT 5 NORTHERN DISTRICT OF CALIFORNIA 6 7 ALPHA AND OMEGA Case No. 22-cv-05448-PCP SEMICONDUCTOR LIMITED, et al., 8 Plaintiffs, ORDER DENYING MOTION TO 9 STRIKE v. 10 Dkt. No. 59 FORCE MOS TECHNOLOGY CO., LTD., 11 Defendant.

12 13 Defendant Force MOS Technology Co., Ltd. has moved to strike plaintiffs’ patent 14 infringement contentions, filed pursuant to Patent Local Rules 3-1 and 3-2. For the reasons set 15 forth below, the Court upon review concludes that each of the infringement contentions at issue is 16 sufficient to provide reasonable notice to Force MOS. The motion is therefore denied. 17 I. Background 18 This is a patent case involving metal oxide semiconductor field effect transistors, or 19 MOSFETs. The parties have filed several rounds of pleadings. As the case now stands, seven 20 patents are at issue. Force MOS claims that plaintiffs Alpha and Omega Semiconductor Limited 21 and Alpha and Omega Semiconductor Inc. (AOS) have infringed three of its U.S. patents, 22 numbered 7,629,634; 7,847,346; and 7,646,058. AOS, in turn, claims that Force MOS has 23 infringed four of AOS’s patents, numbers 8,067,304; 7,511,361; 7,781,265; and 8,928,079. The 24 parties also variously claim invalidity and seek declaratory judgments of non-infringement. 25 Pursuant to Patent Local Rules 3-1 and 3-2, AOS served its “Disclosure of Asserted Patent 26 Claims and Infringement Contentions” as to its ’304, ’361, and ’265 patents on January 31, 2023, 27 and served supplemental infringement contentions as to its ’079 patent on April 14, 2023. Force 1 to resolve this dispute on their own, Force MOS filed this motion. Force MOS asks the Court to 2 || strike AOS’s infringement contentions as to several of the claims of AOS’s and ’079 patents. 3 MOSFETs are semiconductor chips. The fabrication process begins with a wafer, a thin 4 || disc of semiconductive material that can be used to produce many individual chips. AOS’s □□□□ 5 patent involves a method for forming a layer of metal 3-6 microns thick on the top surface of a 6 || wafer that has built-in “alignment marks.” Alignment marks are indentations at specified locations 7 around the wafer which are used to line up a mask for a later step in the fabrication process. But 8 adding a layer of metal on top of the wafer can degrade the sharpness of the alignment marks, 9 which in turn makes alignment for the masking process less precise—a problem as manufacturers 10 || aim to make chips smaller and smaller. Using “hot” metal (400° C) to create this layer is 11 beneficial in some ways because hot metal has good “step coverage,” or in other words, is better 12 || than “cold” metal (300° + 50° C) at filling in voids in the surface of the wafer. But this same 5 13 property means that using hot metal can degrade the sharpness of the alignment marks. Figure 1D 14 || from the ’304 patent shows a cross section of an alignment mark before the metal layer is added, 3 15 and Figure 2B illustrates how the alignment mark can be degraded when a layer of metal is added: 16

20 21 Fig. 1D Fig. 2B 22 23 || The gist of the ’304 patent is that by adding two metallization layers—a thin hot one followed by a 24 || thicker cold one—instead of a single thick layer (as illustrated in Figure 2B), the beneficial 25 || properties of the hot layer’s contact with the surface of the wafer can be taken advantage of while 26 || better preserving the sharpness of the alignment mark. Figure 3B illustrates the difference: 27 28

5 Fig. 2B Fig. 3B 6 7 There are some inherent tradeoffs between certain characteristics of MOSFETs, and 8 || depending on the intended application manufactures can seek to strike a different balance. One 9 such characteristic is the resistance between the transistor’s “source” and “drain” terminals when it 10 || is “on,” or in other words, when a voltage is applied to the “gate” terminal. This resistance value is 11 referred to as Rpgcon) Or the on-resistance. A MOSFET’s on-resistance is typically proportional to 12 || the length of the channel between the source and drain terminals and inversely proportional to the 13 concentration of individual cells in the chip. The MOSFET’s gate capacitance is proportional to 14 |) both channel length and cell concentration. If the goal is to minimize on-resistance, two options 2 15 are to reduce channel length or increase cell concentration. But cell concentration is limited by the 16 || current state of manufacturing technology, and channel length is limited by what is known as the 2 17 “punch-through” phenomenon. AOS’s ’079 patent outlines a MOSFET manufacturing process that Z 18 aims to address some of these tradeoffs and reduce both the on-resistance and gate capacitance. 19 || II. — Legal Standard 20 Patent Local Rule 3-1 requires a party alleging patent infringement to serve a “Disclosure 21 of Asserted Claims and Infringement Contentions.” The infringement contentions must, for each 22 || claim allegedly infringed, identify “each accused apparatus, product, device, process, method, act, 23 or other instrumentality.” Next, for each accused instrumentality, the claimant must provide a 24 || “chart identifying specifically where and how each limitation of each asserted claim is found.” 25 Rule 3-1 is essentially a discovery shortcut: It “takes the place of a series of interrogatories 26 || that defendants would likely have propounded had the patent local rules not provided for 27 streamlined discovery.” Network Caching Tech. LLC v. Novell, Inc., No. 01-cv-02079-VRW, 28 2002 WL 32126128, at *4 (N.D. Cal. Aug. 13, 2002). “These rules require parties to crystallize

1 their theories of the case early in litigation,” and they “provide structure to discovery” to enable 2 efficient resolution of the dispute. Creagri, Inc. v. Pinnaclife Inc., LLC, No. 11-CV-06635-LHK- 3 PSG, 2012 WL 5389775, at *2 (N.D. Cal. Nov. 2, 2012) (cleaned up). The rules do not “require 4 the disclosure of specific evidence nor do they require a plaintiff to prove its infringement case.” 5 Id. Instead, “to the extent appropriate information is reasonably available,” the rules require the 6 plaintiff “to disclose the elements in each accused instrumentality that it contends practices each 7 and every limitation of each asserted claim” Id. The minimum standard is that “the degree of 8 specificity under Local Rule 3-1 must be sufficient to provide reasonable notice to the defendant 9 why the plaintiff believes it has a reasonable chance of proving infringement,” and the contentions 10 “must map specific elements of Defendants’ alleged infringing products onto the Plaintiff’s claim 11 construction.” Shared Memory Graphics LLC v. Apple, Inc., 812 F. Supp. 2d 1022, 1025 (N.D. 12 Cal. 2010) (cleaned up). 13 “Where appropriate, courts treat a motion to strike as a motion to compel amendment to 14 include additional information.” France Telecom, S.A. v. Marvell Semiconductor, Inc., No. 12- 15 CV-04967-WHA-NC, 2013 WL 1878912, at *2 (N.D. Cal. May 3, 2013). 16 III. Analysis 17 Force MOS argues that several of AOS’s infringement contentions are deficient. The 18 contentions at issue are addressed in turn below. For the reasons set forth, the Court concludes that 19 all of these contentions provide adequate notice and are sufficient under Patent Local Rule 3-1. 20 A. The ’304 Patent 21 1. Claim 4 22 Claim 4 of the ’304 patent states:

23 The power semiconductor device of claim 1 wherein said first metal 24 layer comprising a hot metallization layer in the bottom and a cold metallization layer on the top. 25 26 Dkt. No. 59-2, at 32. AOS provides the following infringement contention for this claim with 27 respect to Force MOS’s MEE7816AS-G device: 1 claim 1 above.

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Alpha and Omega Semiconductor Limited v. Force MOS Technology Co., Ltd., Counsel Stack Legal Research, https://law.counselstack.com/opinion/alpha-and-omega-semiconductor-limited-v-force-mos-technology-co-ltd-cand-2023.