Harris Corp. v. IXYS Corp.

114 F.3d 1149, 1997 WL 307769
CourtCourt of Appeals for the Federal Circuit
DecidedJune 10, 1997
DocketNo. 96-1526
StatusPublished
Cited by21 cases

This text of 114 F.3d 1149 (Harris Corp. v. IXYS Corp.) is published on Counsel Stack Legal Research, covering Court of Appeals for the Federal Circuit primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Harris Corp. v. IXYS Corp., 114 F.3d 1149, 1997 WL 307769 (Fed. Cir. 1997).

Opinion

BRYSON, Circuit Judge.

IXYS Corporation appeals from a district court’s ruling on summary judgment that IXYS infringed U.S. Patent No. 4,364,073 (the ’073 patent), owned by Harris Corporation, and that the patent is not invalid. A summary judgment may be upheld only if there are no material issues of fact in dispute and the judgment is not premised on any error of law. Because the district court erred in construing the claims of the ’073 patent and in concluding that the patent satisfies the enablement requirement of 35 U.S.C. § 112, we reverse the grant of summary judgment on infringement and enablement, vacate the summary judgment on the other issues of patent validity, and remand the case to the district court.

I

A

Harris and IXYS manufacture semiconductor devices called IGBTs (insulated-gate bipolar transistors). An IGBT is used to control the flow of electric power. It contains four regions of semiconductor material of alternate conductivity type, and it has three external terminals. The device controls the flow of power in response to a signal applied [1151]*1151to one of its terminals, called the gate. The presence of an appropriate gate signal turns the device on and allows electric current to flow through it; removing the gate signal turns the device off, blocking the flow of current.

A thyristor is a semiconductor device similar to an IGBT. Like an IGBT, a thyristor contains four regions of semiconductor material of alternate conductivity type and has three external terminals, one of which is the gate. As in the IGBT, applying an appropriate gate signal turns the thyristor on, allowing the flow of electric current through it. Unlike an IGBT, however, removing the gate signal from a thyristor does not shut off the flow of electric current through the device. Once a thyristor turns on in response to the application of a gate signal, it cannot be turned off simply by removing the gate signal. The thyristor thus exhibits “latching” behavior: In response to the application of an appropriate gate signal, the device turns on and remains on even if the gate control signal is removed. Turning a thyristor off typically requires reduction of the current flowing through the device below a threshold level.

The latching property of the thyristor arises from the structure of the device. The four alternating semiconductor regions in a thyristor inherently incorporate two three-layer combinations, each of which has a forward current gain, denoted as al and a2, respectively. It is well known that a thyristor will not latch if the sum of al and a2 is less than one, as is recited in a 1967 prior art reference of record in this ease. See F.E. Gentry, Four Layer Semiconductor Switch with the Third Layer Defining a Continuous, Uninterrupted Internal Junction, U.S. Pat. No. 3,324,359 (issued June 6, 1967) at col. 3,11. 62-67 (Gentry).

A MOSFET (metal-oxide-semiconductor field-effect transistor) is also a three-terminal device that is used to control the flow of electric power. Unlike IGBTs and thyristors, however, MOSFETs have only three semiconductor regions. A MOSFET controls the flow of power through the device in response to an appropriate control signal applied to its gate terminal. MOSFETs are similar to IGBTs in that they can be used to control the flow of electric power by selectively applying and removing an appropriate gate signal. MOSFETs do not exhibit the “latching” behavior of thyristors, but thyristors can typically carry larger amounts of electric power.

IGBTs combine the controllability of a MOSFET with the high-power-earrying capabilities of a thyristor. Because they incorporate a four-layer structure similar to a thyristor, however, IGBTs incorporate two three-layer combinations of regions of alternate conductivity and therefore exhibit latching if subjected to certain electrical conditions, such as high voltages.

B

The ’073 patent has 17 claims. Claim 1, the only independent claim, recites an IGBTlike structure. It provides (emphasis added):

A vertical MOSFET device, comprising:
a semiconductor substrate, including in series, adjacent source, body, drain and anode regions of alternate conductivity type;
the body region being adjacent to a surface of the substrate;
the source and drain regions being spaced so as to define a channel portion in the body region at said surface;
the source, body and drain regions having a first forward current gain a 1 and the anode, drain and body regions having a second forward current gain a 2, such that the sum al + a2 is less than unity, and no thyristor action occurs under any device operating conditions.

The dispute in this case centers on the emphasized portion of the claim.

In addition to Gentry, the prior art of record includes a U.S. patent issued in 1980 to Plummer. See James D. Plummer, Monolithic Semiconductor Switching Device, U.S. Pat. No. 4,199,774 (issued Apr. 22, 1980) (Plummer). Plummer discloses a four-layer semiconductor device with a structure identical to that of the device recited in claim 1 of the ’073 patent. Plummer’s device operates as a transistor at lower voltages and currents [1152]*1152(i.e., it exhibits no latching behavior), but beyond a certain threshold of voltage or current it acts as a thyristor (i.e., it latches).

C

In 1994, Harris brought this action against IXYS, alleging infringement of the ’073 patent. IXYS moved for summary judgment of non-infringement and patent invalidity. Harris cross-moved for summary judgment, arguing that the IXYS devices literally infringe claim 1 of the ’073 patent, and that the patent is not invalid.

The district court denied IXYS’s motion for summary judgment and, adopting Harris’s claim construction, granted Harris’s motion. The court ruled as a matter of law that IXYS’s IGBTs infringe the ’073 patent, and that the ’073 patent is not invalid because of indefiniteness, obviousness, anticipation, or non-enablement.

II

On appeal, the parties debate the proper construction of claim 1 of the ’073 patent. Specifically, they disagree as to the meaning of the last clause of the claim, which recites “such that the sum al + a2 is less than unity, and no thyristor action occurs under any device operating conditions.” IXYS construes that clause as covering only four-layer devices that, because of their structure, never act as thyristors (i.e., devices in which the sum al + a2 is less than one under all circumstances). Harris, on the other hand, construes the disputed clause as covering four-layer devices that have a transistor (or non-latching) mode of operation in addition to a threshold point beyond which the devices act like thyristors, as long as the devices were intended to be operated below the thyristor threshold. We agree with IXYS.

With respect to the first part of the disputed clause, the phrase “such that the sum al + a2 is less than unity” merely restates a basic characteristic of four-layer semiconductor devices that is well known to any electrical engineering student and is recited in the 1967 Gentry reference.

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Cite This Page — Counsel Stack

Bluebook (online)
114 F.3d 1149, 1997 WL 307769, Counsel Stack Legal Research, https://law.counselstack.com/opinion/harris-corp-v-ixys-corp-cafc-1997.