InvenSense Inc v. STMicroelectronics Inc

1. Case Identification

• Case #: IPR2013-00241
• Patent #: 6,370,954
• Filed: April 8, 2013
• Petitioner(s): InvenSense, Inc.
• Challenged Claims: 1-19

2. Patent Overview

• Title: Method for Compensating the Position Offset of a Capacitive Inertial Sensor, And Capacitive Inertial Sensor
• Brief Description: The ’954 discloses a semiconductor integrated inertial sensor, such as an angular acceleration sensor or gyroscope. The device includes a stationary stator and a mobile rotor suspended over a substrate, with the rotor containing a mobile mass. The sensor operates using a microactuator and a sensing unit, both of which rely on capacitive coupling between mobile arms on the rotor and fixed arms on the stator to drive and sense the rotor's motion.

3. Grounds for Unpatentability

Ground 1: Anticipation over Juneau - Claims 1-6 and 8-19 are anticipated by Juneau under 35 U.S.C. §102(b).

• Prior Art Relied Upon: Juneau (a December 1997 publication, "Micromachined Dual Input Axis Rate Gyroscope").
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Juneau, a thesis describing a fully functional micromachined gyroscope, disclosed every limitation of the challenged claims. Juneau’s device was described as an inertial sensor integrated on a single silicon substrate with a polysilicon inertial rotor (the claimed "mobile mass"). This rotor was suspended above the substrate (the claimed "stator element") and electrostatically coupled to stationary drive combs, which functioned as the claimed "microactuator means." Petitioner asserted that Juneau’s radially projecting drive combs, integral with the rotor and interdigitated with fixed combs, met the limitations of the actuator arms, electrodes, and their symmetric and equidistant arrangement as recited in various independent and dependent claims.

Ground 2: Obviousness over Hsu in view of Dunn - Claims 5, 8, and 11-19 are obvious over Hsu in view of Dunn under 35 U.S.C. §103.

• Prior Art Relied Upon: Hsu (Patent 5,955,668) and Dunn (Patent 5,377,544).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Hsu disclosed a micro-gyroscope with most of the claimed structural elements, including a ring-shaped rotor with outwardly extending arms and interleaved fingers for actuation. However, Hsu did not explicitly disclose using the same comb drive structures for both driving and sensing the rotor's motion. Dunn disclosed a vibration gyroscope that used its driving plates to also sense differential capacitance, accomplished by periodically sampling the capacitance during the drive cycle to maintain oscillation.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine Dunn's capacitance sampling and sensing method with Hsu's gyroscope structure. Both references addressed the need for efficient operation of micro-mechanical gyroscopes. A POSITA would have been motivated to apply Dunn’s efficient periodic sampling technique to Hsu’s comb drive structure to create a combined drive/sensor system, thereby reducing complexity and improving performance by oscillating the device at its resonant frequency, a desirable goal discussed in both references.
  • Expectation of Success: A POSITA would have a reasonable expectation of success, as the combination involved applying a known sensing technique (Dunn) to a compatible and well-understood mechanical structure (Hsu) to achieve the predictable advantage of efficient, resonant operation.

Ground 3: Obviousness over Admitted Prior Art in view of Juneau - Claims 1-6 and 8-19 are obvious over APA in view of Juneau under 35 U.S.C. §103.

• Prior Art Relied Upon: APA (Patent 6,546,799, referred to as Admitted Prior Art) and Juneau (a December 1997 publication).

• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner contended that APA, a patent issued to two inventors of the ’954 patent, constituted an admission of prior art. The sensor structure described and illustrated in APA was argued to be substantially identical to that in the ’954 patent but without a microactuator. Juneau, as established in Ground 1, disclosed a rotary micromachined sensor with a microactuator and a feedback loop for sensing capacitance.
  • Motivation to Combine: A POSITA would have been motivated to combine Juneau's microactuator with the APA sensor structure. The APA patent itself identified problems in the prior art that a feedback and actuation system could solve. A POSITA, aware of the APA sensor and its limitations, would naturally look to well-known solutions like the microactuator and feedback loop taught by Juneau to create a complete, functional device. This combination would add the missing microactuator to the APA sensor to cure the exact problems the APA identified.
  • Expectation of Success: Success was expected because the integration involved adding a standard, known component (Juneau's actuator) to a compatible sensor design (APA) to achieve the predictable result of an actively controlled inertial sensor.

• Additional Grounds: Petitioner asserted numerous other anticipation and obviousness challenges. These included anticipation grounds based on Touge (Patent 6,134,961), Greiff (Patent 5,817,942), Geen (Patent 6,122,961), Folkmer I (WO 98/15799), Zarabadi (Patent 5,872,313), and Tang (Patent 5,025,346). An additional obviousness ground was based on the combination of Tang and Tang II (a 1990 publication).

4. Key Claim Construction Positions

• "inertial sensor": Petitioner argued this term in the preamble of claim 1 was not a limitation for claims 1-5 and 8-19, as it was not referenced in the body of those claims.
• "angularly equidistant" and "symmetrically": Petitioner proposed these terms should be interpreted broadly. Since the claims failed to specify a point or axis for measurement, any reasonable set of points in the prior art should be considered for determining if the elements meet these limitations. This broad construction was argued to be necessary to prevent the claims from being indefinite.
• "microactuator": This term was construed broadly to include any micromachined actuator used to move the claimed rotor, encompassing the comb drives, electrostatic plates, and other driving mechanisms shown in the prior art.

5. Relief Requested

• Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 1-19 of Patent 6,370,954 as unpatentable.