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Semicaps PTE Ltd. v. Hamamatsu Corp.

United States District Court, N.D. California

November 6, 2019

SEMICAPS PTE LTD, Plaintiff,
v.
HAMAMATSU CORPORATION, et al., Defendants.

          AMENDED ORDER DENYING DEFENDANT'S MOTION TO DISMISS RE: DKT. NO. 49

          Donna M. Ryu, United States Magistrate Judge

         Plaintiff SEMICAPS Pte Ltd. (“SEMICAPS”) filed this patent case against Defendants Hamamatsu Corporation, Hamamatsu Photonics K.K., and Photonics Management Corp. (collectively, Defendants or “Hamamatsu”), alleging that Hamamatsu infringes the claims of U.S. Patent No. 7, 623, 982 (the “‘982 patent”), which relates to testing of electronic circuits using a laser. Hamamatsu moves to dismiss the complaint, arguing that the asserted claims are invalid because they claim patent-ineligible subject matter. [Docket No. 49.] The court held a hearing on July 11, 2019. For the following reasons, the motion is denied.[1]

         I. BACKGROUND

         A. The ‘982 Patent

         SEMICAPS is the owner by assignment of the ‘982 patent titled, “Method of Testing an Electronic Circuit and Apparatus Thereof.” Compl. ¶ 11, Ex. A (‘982 Patent). The ‘982 patent was issued by the United States Patent and Trademark Office (“USPTO”) on November 24, 2009, and “relates generally to semiconductor processing, and more particularly to a method of testing an electronic circuit, as well as to a respective apparatus, ” ‘982 Patent 1:6-8, in order to “determine the location of defects on the semiconductor circuit.” Opp'n 3.

         SEMICAPS describes the relevant technology as follows: newly-fabricated integrated semiconductor circuits are “typically tested by connecting them to electronic test equipment that applies test signals to each integrated circuit and receives output signals from the circuit as a result.” Id. While this method of testing can reveal defects, it does not identify the location of the defect in the integrated circuit. In order to determine the location of the defect, fabricators use “failure analysis systems . . . to perform fault localization testing, ” which can be done using lasers in scanning microscopes. Id. at 3-4.

         The ‘982 patent's background information describes the problem the patent seeks to solve. It explains that “conventional laser induced techniques generally involve using a scanned laser beam, typically in the infrared frequency range, to stimulate integrated circuit failures which are sensitive to thermal or carrier stimulations.” ‘982 Patent at 1:16-19. These techniques include Optical Beam Induced Resistance Change (“OBIRCH”), Thermal Induced Voltage Alteration (“TIVA”), and Differential Resistance Measurement (“DReM”). Id. at 1:22-27. However, advances in integrated circuit technology, including “the use of more metallization layers and new low k inter-layer dielectric materials with lower thermal conductivity, ” have reduced the laser coupling efficiency, which in turn reduces the detection sensitivity. Id. at 1:28-33. The inventors explain that “conventional approaches” to improve the detection sensitivity of laser induced techniques have not been entirely successful. For example, increasing the power of the laser beam used “in order to compensate for the reduced laser coupling efficiency . . . may not be desirable, ” because “there may be potential laser induced damage on the integrated circuit under test when the power of the laser beam used is too high.” Id. at 1:38-49. Another approach is to use “a pulsed laser in conjunction with a lock-in amplifier, ” which increases detection sensitivity. Id. at 1:50-52. However, lock-in amplifiers are “not used in a real-time integrated circuit testing environment” because “accurate calibration and fine control of the lock-in amplifier parameters is typically difficult to achieve in practice.” Id. at 1:62-67.

         The ‘982 patent attempts to increase detection sensitivity in a laser-based fault detection system without increasing the power of the laser beam or using lock-in amplifiers. ‘982 Patent at 10:19-46. According to the patent, “[t]he method comprises radiating a laser beam onto the electronic circuit, and determining a plurality of samples of a response signal output by the electronic circuit during the period when the laser beam is radiated.” ‘982 Patent, Abstract. A signal processor “process[es] the sample measurements of the response signal of the electronic circuit under test” by “accumulat[ing] the plurality of samples to generate a value, and then generat[ing] a test result based on the value generated.” ‘982 Patent at 3:65-4:2. Based on the generated value, a fault on the electronic circuit may appear as a bright spot, bright line, or bright area at a pixel location corresponding to the location of the fault on the electronic circuit. Id. at 4:16-24, 4:34-38, 5:12-16.

         The ‘982 patent includes 25 claims. SEMICAPS alleges that Hamamatsu infringes at least claims 4-7 and 21-25. Compl. ¶ 13. At the hearing SEMICAPS represented that it also asserts claims 8 and 17. See Mot. 12 n.3; Opp'n 1. Claims 4-8 and claim 17 pertain to a method of testing an electronic circuit, while claims 21-25 describe a related apparatus.

         1. Claims 4-8 and Claim 17

         Claims 4-8 depend from independent Claim 1, which states:

1. A method of testing an electronic circuit, comprising:
radiating a laser beam onto the electronic circuit, determining a plurality of samples of a response signal output by the electronic circuit during the period when the laser beam is radiated,
accumulating the plurality of samples to generate a value, and
generating a test result based on the value.

‘982 Patent at 10:59-67.

Claims 4-8 and claim 17 add the following limitations to Claim 1:
4. The method of claim 1, wherein the laser beam is a pulsed laser beam.
5. The method of claim 4, wherein the frequency of sampling of the response signal is higher than the frequency of the pulsed laser beam.
6. The method of claim 4, wherein the frequency of the pulsed laser beam is in the range from about 50 Hz to about 50 kHz.
7. The method of claim 4, wherein the frequency of sampling of the response signal is in the range from about 100 kHz to about 80 MHz.
8. The method of claim 1, wherein accumulating the plurality of samples is performed after a predetermined time delay from the start of the period when the laser beam is radiated.
17. The method of claim 1, wherein another plurality of samples of another response signal output by the electronic circuit during a period when the laser beam is not radiated is determined, the other plurality of samples is accumulated to generate another value and the test result is generated based on the value and the other value.

‘982 Patent at 11:8-22, 12:4-9.

         2. Claims 21-25

         Claim 21 is an independent claim and describes an apparatus:

21. An apparatus, comprising:
a laser beam source, wherein the laser beam source radiates a laser beam onto the electronic circuit,
a control system operable to direct the laser beam source to dwell on a location on the electronic circuit,
a measuring circuit, wherein the measuring circuit determines a plurality of samples of a response signal output by the electronic circuit during the period when the laser beam is radiated, and
a signal processor, wherein the signal processor accumulates the plurality of samples to generate a value, and generates a test result based on the value.

‘982 Patent at 12:19-31. Claims 22-25 depend from claim 21. They recite:

22. The apparatus of claim 21, wherein the control system is operable to move the laser beam source according to a pattern over a plurality of locations on the electronic circuit.
23. The apparatus of claim 21, wherein the laser beam is a pulsed laser beam.
24. The apparatus of claim 23, wherein the frequency of sampling is higher than the frequency of the ...

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