VTT Technical Research Centre of Finland Ltd. v. SiTime Corporation

Background

VTT brought a patent-infringement action against SiTime concerning U.S. Patent No. 8,558,643, which addresses temperature compensation in resonators and other micromechanical devices. The patent describes semiconductor structures with regions having different material properties, including regions with n-type dopants. By configuring the regions’ dopants, concentrations, crystal orientations, and relative volumes, the invention seeks to reduce temperature-related changes in stiffness and resonant frequency.

The order addressed the parties’ disputes over the meaning of patent-claim language. Claim construction is the court’s determination of what patent claims mean and how broad they are. The opinion addressed four terms or issues: “at least two regions having different material properties”; “being configured so that the temperature sensitivities of the generalized stiffness are opposite in sign at least at one temperature for the regions”; “the overall temperature drift of the generalized stiffness of the semiconductor element is less than 50 ppm”; and “drive or sense means.”

Claim constructions

For “at least two regions having different material properties,” the court adopted: “at least two regions within the semiconductor element that have different material properties.” The court rejected SiTime’s proposed requirement that the regions be either distinct or a continuous gradient. It also rejected SiTime’s attempt to include the requirement that the regions be designed so their temperature coefficients cancel each other to the claimed level, reasoning that other limitations in claim 1 captured that effect.

For the temperature-sensitivity term in claim 1, the court adopted a construction requiring that, at least at one temperature, the generalized stiffness of one region increase as temperature increases while the generalized stiffness of a second region decreases as temperature increases, with the reverse relationship when temperature decreases. The court declined to require that the regions’ temperature coefficients be exactly equal and opposite.

For claim 29’s requirement that overall temperature drift be less than 50 parts per million, the court found that the patent’s omission of a temperature range was an obvious error. It corrected claim 29 by adding the words “over a temperature range of the semiconductor element that extends at least 100 ℃.” The court concluded that claim 29 was not indefinite for lacking a temperature range. The court relied on the language of dependent claim 30, the patent specification, and prosecution history indicating that the omitted range was 100 degrees Celsius.

“Drive or sense means” and indefiniteness

The court ruled that 35 U.S.C. § 112 paragraph 6, the provision governing “means-plus-function” claim language, applied to “drive or sense means.” Under that framework, a claim may describe a function generically, but the patent must disclose corresponding structure for performing the function.

The court construed the claimed functions as driving the semiconductor element, sensing the semiconductor element, or driving and sensing it. It found that the specification disclosed a transducer corresponding to the driving function but did not disclose corresponding structure for the sensing function. Because the specification lacked adequate structure linked to sensing, the court found all asserted claims containing the “drive or sense means” limitation indefinite. An indefinite claim is not sufficiently clear in its scope to be enforced.

Disposition

The court adopted the stated claim constructions, corrected claim 29 to include a temperature range of at least 100 degrees Celsius, found claim 29 not indefinite for lack of a temperature range, and found all asserted claims containing “drive or sense means” indefinite. The order was a claim-construction ruling; it did not determine whether SiTime infringed the patent.