Gate Oxide Integrity Test Using Dual Voltage Leakage Measurement
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Solution Overview
Problem
Conventional methods for testing gate oxide integrity in semiconductor integrated circuits face challenges with smaller feature sizes, particularly in the sub-90 nm era, where leakage current increases, making it difficult to accurately test smaller structures efficiently, and traditional methods are time-consuming.
Innovation Solution
A method and device for testing gate oxide integrity using extrinsic measurements, involving a semiconductor wafer with test patterns, applying operating and secondary voltages, measuring leakage currents, and categorizing devices as failures or good based on predetermined thresholds, allowing for efficient determination of intrinsic characteristics without requiring actual breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional gate oxide integrity testing methods are used, then measurement precision is maintained, but test time increases significantly
Solution Approach 1:
The patent applies partial action by performing only two specific voltage measurements instead of a complete breakdown curve. The first measurement at a low voltage (e.g., 0.7V) detects initial leakage current, and the second measurement at a higher voltage (e.g., 2.0V) detects extrinsic failures. This partial measurement approach achieves sufficient precision for gate oxide integrity assessment while dramatically reducing test time compared to conventional methods that require full breakdown characterization.
Solution Approach 2:
The patent changes the measurement parameters by selecting specific voltage points rather than performing a continuous voltage sweep to breakdown. By measuring leakage current at two predetermined voltage levels (first voltage and second voltage), the method transforms the testing approach from a time-consuming full characterization to a rapid targeted measurement that maintains precision for detecting both intrinsic and extrinsic failures.
2Productivity
If feature size is reduced to increase circuit density, then device complexity and performance improve, but leakage current increases making testing more difficult
Solution Approach 1:
The patent applies preliminary action by performing an initial low-voltage measurement to detect devices with high leakage current before proceeding to higher voltage measurements. This first measurement at a low voltage (e.g., 0.7V) identifies devices that fail the initial threshold, allowing early rejection of defective devices and preventing unnecessary higher voltage stress that could damage already-failed devices or create false breakdown events.
Solution Approach 2:
The patent segments the testing process into two distinct stages: first, a low-voltage measurement to detect intrinsic failures and high leakage current devices; second, a higher-voltage measurement to detect extrinsic failures. This segmentation allows each measurement to be optimized for its specific detection purpose, improving overall measurement difficulty by breaking down the complex task into manageable, targeted steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables faster and more accurate testing of gate oxide integrity, reducing test time and cost while maintaining high device yields, and is compatible with conventional processes without substantial modifications.
Implementation Method 1
a gate dielectric layer, which has a thickness of about 50 Angstroms or less... measuring a first leakage current associated with the operating voltage
Implementation Method 2
applying an operating voltage on a gate of a test pattern device on the semiconductor wafer using one or more probing devices, which are coupled to a probing system... measuring a first leakage current associated with the operating voltage
Data Source
AI summary
A method for testing a semiconductor wafer using an in-line process control, e.g., within one or more manufacturing processes in a wafer fabrication facility and/or test/sort operation. The method includes transferring a semiconductor wafer to a test station. The method includes applying an operating voltage on a gate of a test pattern on a semiconductor wafer using one or more probing devices. The method includes measuring a first leakage current associated with the operating voltage. If the measured first current is higher than a first predetermined amount, the device is an initial failure. If the measured first current is below the first predetermined amount, the device is subjected to a second voltage. The method includes applying the second voltage on the gate of the test pattern on the semiconductor wafer and measuring a second leakage current associated with the second voltage. If the second measured leakage current is higher than a second predetermined amount, the device is an extrinsic failure. If the second measured leakage current is below the second predetermined amount, the device a good device. The method provides a way to monitor gate oxide integrity and/or process stability using extrinsic measurements according to a specific embodiment. The method includes determining a breakdown voltage associated with the second measured leakage value. In a preferred embodiment, the second measured leakage current is characterized as extrinsic information and the breakdown voltage is characterized as intrinsic information.