District Court Corrects Patent by Inserting Missing Temperature Range, Finds Claims Indefinite for Insufficient Structure: VTT Technical Research Centre of Finland v. SiTime

Indefiniteness was decided in a claim construction order from the Northern District of California in VTT Technical Research Centre of Finland v. SiTime. The court corrected a claim by inserting a missing element, but also invalidated all the claims for indefiniteness because the means-plus-function element “drive or sense means” lacked sufficient structure. VTT thus won a battle but lost the war.

VTT is a Finnish state-owned nonprofit research company, including for microelectromechanical systems (MEMS). SiTime is a MEMS manufacturer. VTT is suing for infringement of U.S. Patent No. 8,558,643, covering a MEMS device used in semiconductors to reduce deformation as a result of temperature fluctuations. Independent claim 29 states:

29. A method for designing a micromechanical device comprising

a semiconductor element capable of deflecting or resonating and comprising at least two regions having different material properties,

drive or sense means functionally coupled to said semiconductor element,

the method comprising

choosing a basic semiconductor material for the semiconductor element,

choosing at least one n-dopant to be added to the semiconductor material,

designing the inner structure of the semiconductor material,

wherein said designing of the inner structure comprises determining at least two n-dopants, n-dopant concentrations and/or crystal orientations of n-doped material, and their relative volumes in the distinct regions of the semiconductor element so that the overall temperature drift of the generalized stiffness of the semiconductor element is less than 50 ppm.

Independent claim 1 recited a similar final element with an additional prepositional phrase: “the overall temperature drift of the generalized stiffness of the semiconductor element is 50 ppm or less on a temperature range of 100° C.” SiTime contended that, because claim 29 lacked the phrase “on a temperature range of 100° C,” the claim was indefinite. VTT argued that the omission of the temperature range was an obvious error that the court could correct by interpreting claim 29 to include the temperature range.

To count as an obvious error, the error must be apparent from the face of the patent. The court found that to be the case here. In the specification, the term “temperature drift” was defined as “on a temperature range.” Every other example of temperature drift in the patent mentioned a temperature range. SiTime argued that claim 29 was grammatical without the temperature range, but according to the court, “[e]ven if a lay person would find claim 29 coherent without a temperature range, a person of ordinary skill in the art would not.”

For a court to correct an error, it’s not enough that the error be obvious. Additionally, the proper correction cannot be subject to reasonable debate. SiTime argued that any temperature range could be a proper correction, not necessarily 100° C, but the court again sided with VTT. The most important fact was that claim 30 recited “the temperature range of 100° C.” The “the” indicated that the limitation should have an antecedent basis of “a temperature range of 100° C” in claim 29, strongly suggesting that that temperature range was the proper correction. Moreover, every specific example in the specification used a temperature range of 100° C. Although one sentence in the specification stated that the benefits of the invention could cover a temperature range of 300° C, the court did not find that that sentence created a reasonable disagreement over the content of the correction. The dependent claim outweighed that statement, and every experiment described in the specification had a temperature range of 100° C, meaning that “[b]roader ranges are therefore not apparently enabled.” Thus, the court could confidently say that the correction should be a temperature range of 100° C.

But VTT did not fare so well with the term “drive or sense means,” which appeared in both independent claims. The court first found that the term was a means-plus-function term. The use of the word “means” created a presumption that the term was a means-plus-function term, making the question whether the words “drive” and “sense” provided sufficient structure to overcome that presumption. The court did not find any of VTT’s arguments persuasive for “sense means.” The specification listed a transducer as a drive means, but nothing similar was recited as a sense means. The specification also listed “piezoelectric actuator element” and “electrostatic actuator means” as types of “drive or sense means,” but those phrases were functional, not structural. VTT pointed to several dictionary definitions, but those were not persuasive to the court because they were for “driver” and “sensor” instead of “drive” and “sense.” Finally, VTT pointed to prior art that stated “drive or sense circuitry,” but there the word “circuitry” was what provided the structure, not “drive” or “sense.”

To be definite, a means-plus-function term must be supported by structure recited in the specification. Because the specification contained nothing structural to describe “sense means,” the court invalidated the claims as indefinite.

Lessons for Practice

Even though VTT successfully got claim 29 corrected, it wouldn’t have had to litigate the issue at all if claim 29 had explicitly included the temperature range. This shows the importance of proofreading. Claims should be proofread both before filing the application and once the claims are allowed.

The more substantive issue is providing support in the specification for means-plus-function element. First, whether a claim element is means-plus-function should be an explicit decision made when drafting the claims. If a means-plus-function claim is desired, then the word “means” should be used; if not, it should be avoided. Second, once the decision to use a means-plus-function claim has been made, the patent drafter should brainstorm the possible ways to perform the function, and err on the side of overinclusion.