On-Die Parametric Test Modules for Context-Dependent Effects Monitoring
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Solution Overview
Problem
As technology advances to 28 nm and smaller, layout-induced parametric shifts and variations in MOS transistors increase, making it difficult to isolate and monitor context-dependent effects using conventional scribe line test modules without significantly increasing the scribe line area, which would result in fewer die per wafer and higher costs.
Innovation Solution
On-die parametric test modules with a small number of different layout structures are configured to fit on a small area of the IC die, allowing for in-line production monitoring and quantification of significant context-dependent effects, including active reference and variant MOS transistors with specific spacing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional scribe line test modules are used to monitor context-dependent effects, then measurement capability is provided, but the scribe line area increases significantly, reducing die per wafer and increasing costs
Solution Approach 1:
The patent uses on-die test modules that replicate the layout and spacing characteristics of the actual production IC die within the die boundary itself. These test modules are copies of the production device structure, allowing measurement of context-dependent effects without requiring extensive scribe line area. The test modules are positioned within the die and share the same layout context as the production devices, enabling accurate monitoring while minimizing area consumption.
Solution Approach 2:
The patent transitions from using scribe line test modules (external to the die) to on-die test modules (internal to the die). This dimensional change allows the test structures to be positioned within the die boundary, utilizing the die area more efficiently. By placing test modules inside the die rather than outside in the scribe line, the solution reduces the dedicated test area while maintaining measurement capability.
2Measurement precision
If more layout structures are added to monitor all context-dependent effects, then measurement completeness improves, but device complexity and area requirements increase
Solution Approach 1:
The patent implements different layout structures for different test modules within the same on-die test module. Each test module is configured with specific local layout characteristics that correspond to the context-dependent effects being measured. This allows targeted measurement of specific effects (e.g., active area proximity, well proximity, stress liner effects) without requiring all possible layout variations throughout the entire test structure, thereby reducing overall complexity while maintaining measurement completeness.
Solution Approach 2:
The patent divides the monitoring of context-dependent effects into separate test modules, each designed to measure specific effects. Rather than creating a single complex structure to measure all effects simultaneously, the test module is segmented into multiple simpler test structures, each targeting particular context-dependent parameters. This segmentation reduces the complexity of individual test structures while achieving comprehensive monitoring through multiple specialized modules.
3Measurement precision
If scribe line measurements are used, then electrical properties can be assessed, but the measurements may not accurately reflect actual IC die compliance due to surrounding device effects
Solution Approach 1:
The patent creates test modules that are identical copies of the production IC die layout and structure, positioned within the die boundary. These test modules replicate the exact context-dependent effects present in the production devices, ensuring that measurements taken from the test modules accurately reflect the electrical properties and compliance status of the actual IC die. This copying approach eliminates the measurement discrepancies that occur with scribe line test modules due to different surrounding device effects.
Solution Approach 2:
The on-die test modules serve as intermediaries between the production IC die and the measurement system. By placing test modules within the die boundary that share the same layout context as the production devices, these intermediaries provide a more accurate representation of the electrical properties. The test modules act as mediators that translate the context-dependent effects of the production die into measurable electrical characteristics, ensuring reliable compliance indication.
Data Source
AI summary
An integrated circuit (IC) die has an on-die parametric test module. A semiconductor substrate has die area, and a functional IC formed on an IC portion of the die area including a plurality of circuit elements configured for performing a circuit function. The on-die parametric test module is formed on the semiconductor substrate in a portion of the die area different from the IC portion. The on-die parametric test module includes a reference layout that provides at least one active reference MOS transistor, wherein the active reference MOS transistor has a reference spacing value for each of a plurality of context dependent effect parameters. A plurality of different variant layouts are included on the on-die parametric test module. Each variant layout provides at least one active variant MOS transistor that provides a variation with respect to the reference spacing value for at least one of the context dependent effect parameters.