Linear Technology Corp v. In Depth Test LLC

1. Case Identification

• Case #: IPR2015-01998
• Patent #: 6,792,373
• Filed: September 28, 2015
• Petitioner(s): Linear Technology Corporation
• Patent Owner(s): In-Depth Test LLC
• Challenged Claims: 1-20

2. Patent Overview

• Title: Statistical Outlier Detection in Semiconductor Testing
• Brief Description: The ’373 patent relates to a system for testing semiconductors that uses a computer connected to test equipment. The system is configured to receive test data, identify "outliers" using statistical analysis, and generate a report, allowing for the detection of statistically unusual components that have not necessarily failed traditional pass/fail tests.

3. Grounds for Unpatentability

Ground 1: Claims 1-20 are anticipated by Lane under 35 U.S.C. §102(b).

• Prior Art Relied Upon: Lane (Patent 4,967,381).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Lane discloses a complete system for semiconductor testing and data analysis that meets every limitation of the challenged claims. Lane's system comprises a tester (e.g., a resistivity tester) connected to a computer that receives test data. The computer in Lane is configured to automatically generate Statistical Quality Control (SQC) charts, which identify and plot data points based on their deviation from a statistical mean. Specifically, Lane’s SQC charts divide the space between the centerline (mean) and the upper/lower control limits into zones (Zones A, B, C), each representing one standard deviation. Petitioner contended that data points falling within these zones (e.g., Zone A or B) are identified as straying from statistically similar values but do not exceed the control limits. This directly corresponds to the controlling definition of an "outlier." Finally, Lane’s system generates an output report (the SQC chart itself) that includes the identified outlier, which can be printed or displayed for analysis.
  • Key Aspects: The central thrust of this ground is that Lane’s disclosure of standard SQC charts, which inherently identify data points based on their statistical deviation within control limits, anticipates the claimed invention when viewed under the patent owner’s own proposed claim construction for "outlier."

Ground 2: Claims 1-20 are obvious over Lane in view of Western under 35 U.S.C. §103.

• Prior Art Relied Upon: Lane (Patent 4,967,381), Western (STATISTICAL QUALITY CONTROL HANDBOOK, 1956).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted this ground as an alternative, arguing that if Lane alone is deemed insufficient, the combination with Western renders the claims obvious. Lane teaches the fundamental automated testing system and the use of SQC charts. Western, a foundational handbook on statistical process control, is explicitly incorporated by reference in Lane. Western provides extensive detail on creating and interpreting SQC charts, including the well-known "Western Electric Rules" for identifying unnatural patterns in data. It explicitly teaches dividing control charts into one-sigma zones and applying rules to identify points that, while within control limits, indicate a process may be shifting. This provides a detailed blueprint for the outlier identification claimed in the ’373 patent.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would have been directly motivated to apply the established statistical techniques from Western to the automated semiconductor test data system of Lane. The motivation is explicit, as Lane itself incorporates Western by reference for the purpose of describing its SQC charts. A POSITA would combine them to enhance the analytical capabilities of Lane’s system, a predictable application of a known analysis method to a relevant data set.
  • Expectation of Success: A POSITA would have had a high expectation of success. The combination involves applying well-established, rule-based statistical principles (Western) to electronic measurement data (from Lane), which is a straightforward and predictable implementation that would yield the expected result of identifying statistically significant deviations.

4. Key Claim Construction Positions

• Petitioner, for the purposes of the IPR, adopted the Patent Owner's construction of the term "outlier" from a prior, denied petition (IPR2015-00421).
• "outlier": "a test result whose value strays from a set of test results having statistically similar values, but does not exceed control limits or otherwise fail to be detected."
• This construction was central to Petitioner's arguments, as it framed an "outlier" as a data point that is statistically unusual but not an outright failure. Petitioner argued this specific definition is precisely what Lane's SQC charts, with their sigma-based zones inside the control limits, are designed to identify.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under 35 U.S.C. §325(d) would be inappropriate, despite a previously filed petition (IPR2015-00421) on the same patent being denied institution.
• Petitioner contended that this petition was not based on the same or substantially the same prior art or arguments. The arguments herein were specifically tailored to the narrow construction of "outlier" proffered by the Patent Owner and adopted by the Board in the first proceeding, which necessitated a new prior art search and a fundamentally different invalidity theory.

6. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-20 of Patent 6,792,373 as unpatentable.