Enhanced Wafer Test Line Structure for Trench Measurement

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Solution Overview

Problem

The increasing complexity and density of integrated circuit devices pose challenges in effectively testing parameters such as sheet resistance, critical dimension, and thickness of Cu trench structures using existing test line structures and methodologies.

Innovation Solution

The enhanced test line structure includes a dummy pad in the scribe area of a semiconductor wafer, filled with a metal layer, which allows for accurate measurement of trench parameters by aligning the trench pattern above the dummy pad, enabling precise probing and measurement during the BEOL process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional test line structures are used in the scribe area, then the manufacturing process is simple, but the measurement precision of trench parameters (sheet resistance, critical dimension, thickness) is insufficient

Engineering Contradiction:

Improvemeasurement precision of trench parametersVSAvoidcomplexity of test line structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The dummy pad structure is formed in advance during the metal layer fabrication process, before the actual trench measurement takes place. This preliminary structure provides a stable reference platform that enables precise measurement of subsequent trench parameters without requiring additional measurement-specific processing steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The dummy pad acts as an intermediary structure between the substrate and the trench features. It provides a stable, well-defined reference platform that mediates the measurement process, allowing for accurate determination of trench parameters such as sheet resistance, critical dimension, and thickness by providing consistent electrical and physical reference points.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If the test line structure is enhanced with dummy pads and aligned trench patterns, then the measurement accuracy improves, but the manufacturing process complexity increases

Engineering Contradiction:

Improveprecision of trench dimensionsVSAvoidease of manufacturing test line structure

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The test line structure merges the dummy pad formation with the existing metal layer fabrication process. The same photolithography and deposition steps used for creating functional metal layers are also used to create the dummy pads and trench patterns, combining testing structure manufacturing with product structure manufacturing without requiring entirely separate process sequences.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The enhanced measurement precision is achieved locally in the scribe area where test line structures are formed, while the rest of the wafer continues to be processed according to standard manufacturing procedures. This localized approach allows for high-precision measurement structures without requiring the entire manufacturing process to be redesigned for enhanced precision.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If existing test methodologies are used, then the test process is straightforward, but the ability to test advanced parameters (sheet resistance, CD, thickness of Cu trenches) is limited

Engineering Contradiction:

Improveversatility in testing parametersVSAvoidcomplexity of test line structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The test line structure with dummy pads and aligned trench patterns serves multiple measurement functions simultaneously. It can measure sheet resistance, critical dimension, and thickness of Cu trench structures using the same physical structure, making the test line universally applicable for testing various parameters that are critical for advanced IC manufacturing processes.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8476629B2Enhanced wafer test line structure

Publication Date: 2013.07.02 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor wafer has a die area and a scribe area. A first dummy pad is formed in a first test line area of the scribe area and filled with a first material as part of a first metal layer. A first interlayer dielectric is formed over the first metal layer. A first interconnect pattern is formed in the die area and above the first interlayer dielectric, and a first trench pattern is formed in the first test line area of the scribe area and above the interlayer dielectric. The first interconnect pattern and the first trench pattern are filled with a second metal layer, and the first trench pattern is aligned above the first dummy pad. An enhanced test line structure including the first trench pattern and the first dummy pad is formed and probed in a back end of line (BEOL) process.