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IXYS CORPORATION v. ADVANCED POWER TECHNOLOGY

March 18, 2004.

IXYS CORPORATION, Plaintiff,
v.
ADVANCED POWER TECHNOLOGY, INC., Defendant AND RELATED COUNTERCLAIMS



The opinion of the court was delivered by: MARILYN PATEL, Chief Judge, District

MEMORANDUM AND ORDER RE: DEFENDANT'S MOTION FOR SUMMARY JUDGMENT OF INVALIDITY
Plaintiff IXYS Corporation ("IXYS") filed this action against defendant Advanced Power Technology, Inc. ("APT"), alleging infringement of two U.S. patents, numbered 5,486,715 (the `"715 patent") and 5,801,419 (the `"419 patent"), that it holds on an improved design for power MOSFET devices. APT has counterclaimed for infringement of its patents, numbered 5,283,202 (the `"202 patent") and 5,262,336 (the `"336 patent"), which teach a design for diodes with lifetime control. The parties now come before the court upon APT's motion seeking summary adjudication that IXYS's `715 and `419 patents are invalid for anticipation. After having considered the parties' arguments and submissions, and for the reasons set forth below, the court rules as follows.

BACKGROUND*fn1

  I. Technical Summary

  Although the technology involved in this case will likely be reasonably familiar to frequent students or observers of patent law (particularly in this judicial District), to say nothing of engineers or technicians in Page 2 the field, a brief summary of the basic scientific background information necessary to understand the patents at issue seems appropriate. These patents involve the use of semiconductors, materials which are neither good conductors of electricity (such as metal) nor good electrical insulators (non-conductors, such as glass or wood), but instead will conduct electricity reasonably well only under certain conditions. The typical semiconductor, and the type employed here, involves a wafer of silicon (in which the atoms are arrayed in a crystalline lattice structure) that has been infused or "doped" with trace amounts of other elements in order to either add extra electrons to the lattice or to create "holes" (the absence of electrons) within the lattice where electrons can be placed. The regions of the semiconductor that have been doped to add electrons are called "N" regions, since these extra electrons represent negative charges; the regions that have been doped to add "holes" are referred to as "P" regions, since these holes represent positive charges. Where pure silicon (which is essentially glass or sand) would function as an insulator, these dopants allow the silicon wafers in which they have been implanted to operate as partial conductors of electricity.

  A transistor is a device that functions as an electronic — rather than a mechanical — switch. Every transistor contains three operative regions: a source, a drain, and a gate. An electrical signal flows into a transistor via the source, and is either allowed or prevented from flowing out through the drain by the "gate," which acts like its namesake; when the gate is "closed," charge cannot flow to the drain, and when the gate is "open," charge is able to flow. Transistors are built by placing three oppositely doped regions adjacent to one another (such as in a "PNP" configuration), with the middle region functioning as the "gate." There are several different mechanisms that can be employed to "switch" the gate, reversing its polarity and allowing charge to flow, including directly applying a voltage to the gate itself. The transistors described in IXYS's `715 and `419 patents employ a different, well-known method to control the gate: they utilize a strip of polysilicon and a strip of metal to create an electric field over the gate and switch the gate on or off by modulating this field. This type of transistor is known generally as a "field effect transistor," or "FET;" the particular materials at use here classify this device as a "metal oxide semiconductor FET," or "MOSFET."

  The word "transistor" usually conjures up an image of the millions of microscopic devices, used in every square inch of computer chips, through which flow only minute amounts of current. However, there Page 3 is a subclass of MOSFETs known as "power MOSFETs" that are used to switch and control large amounts current in order to power and operate large mechanical devices, such as motors, computers, or medical devices. At issue in this case are "high-frequency power MOSFETs," which, as their name would indicate, are intended to manage large currents at high frequencies. The improvement over prior art that IXYS claims forms the crux of its patents is the addition of overlapping metallic layers, the first of which is deposited on top of the gate polysilicon and strengthens the field used to operate the gate, and the second of which forms two "buses" through which current can flow to the source and to the gate polysilicon.

  Transistor fabrication involves the repeated deposition of one layer of material (a semiconductor, insulator, or metallic conductor) upon another according to a pre-selected pattern. There are several methods that are commonly utilized to define the locations in which a particular layer will be applied. Transistor manufacturers may rely upon the natural geometry (the high and low points) of the transistor layers that already exist, depositing subsequent layers only in locations that are exposed in some particular manner. An alternative method is "mask photo-lithography," a process that involves first depositing a layer of material, followed by a layer of a photo-sensitive compound, and then removing unwanted sections by exposing them to light while shielding desired areas with a "mask" that has been patterned according to the design specifications.

  II. Procedural History

  Plaintiff IXYS Corporation and defendant Advanced Power Technology, Inc. are both semiconductor manufacturing firms that do business in Santa Clara, California. IXYS filed suit against APT on August 15, 2002, alleging that APT was infringing two related patents detailing an improved design for "high-frequency power MOSFETs" held by IXYS. On October 1, 2002, APT counterclaimed against IXYS for infringement of a patent it held that described an improved design for producing "lifetime control" in semiconductor devices. On January 22, 2004, this court entered an order construing disputed terms in those three patents. That same day, the court also authorized APT to amend its counterclaims to add a claim that IXYS had infringed APT's `336 patent. APT has now filed for summary judgment of invalidity with respect to IXYS's two patents. Page 4

  III. Factual Background

  APT's motion for summary judgment turns on the various generations of APT power MOSFET products, their dates of invention and sale, and their relation to one another and to IXYS's patents. IXYS's infringement allegations are directed at a panoply of APT products, viz., "(a) any and all Power MOS 7(r) products or Power MOS V(r) (Generation 5) products with dual-layer metallization manufactured, used, sold, or offered for sale by APT on or after August 15, 1996, and (b) any and all products manufactured, used, sold, or offered for sale by APT on or after August 15, 1996 that are designed in substantially the same way, or function in substantially the same way, as APT 5018BLL [a Power MOS 7™ MOSFET]." Feeman Dec. Exh. 4, at 2 (P1. Disclosure of Asserted Claims and Preliminary Infringement Contentions) (emphasis added).

  The predecessor to APT's MOS V and MOS VII devices is, unsurprisingly, APT's MOS IV line of products, which includes the APT 208 and APT 526 devices. According to APT, all APT MOS IV products, including the APT 208 and 526, are power MOSFETs that employ a "first metal/polysilicon gate" and a layer of "second metal" through which current flows to the first metal gate and to the MOSFET source. Tsang Dec. ¶ 54. APT marketed the APT 208 as early as January 1991, and a second incarnation of the product (known internally as the "APT 208x") was sold from late 1991 until late 2001. Id. at ¶ 13.*fn2 At that point, APT removed the 208x from the market and replaced it with MOS V generation devices. Id. Meanwhile, APT tested and characterized the 526 during the summer and fall of 1993, and "data sheets were released to marketing on October 8, 1993, for dissemination to the public." Id. at ¶ 14. The APT 526 was first sold on December 27, 1993, and APT currently still markets that product.

  During APT's production of the MOS IV line, IXYS's contemporaneous development of the technology that would lead to the `715 and `419 patents was continuing apace. Dr. Nathan Zommer, the inventor of those patents, states that by December 1992 he had created a power MOSFET that operated at high speed. Zommer Dec. ¶ 10. Dr. Zommer sent a memorandum outlining that technology to a potential customer on or about December 23, 1992, and produced an "Invention Disclosure Form" describing the technology in detail on March 17, 1993. Id. ¶¶ 10-12 & Exh. B. Dr. Zommer later sent a Page 5 copy of this form to the law firm IXYS had retained to prosecute the forthcoming ...


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