Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
1999-01-14
2001-07-31
Grimley, Arthur T. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C324S551000
Reexamination Certificate
active
06269315
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reliability testing method of a dielectric thin film. More particularly, the present invention relates to a method for testing the reliability of a dielectric thin film layer by using an exponential current ramp test (ECR).
2. Description of the Related Art
Reliability of thin dielectric films such as silicon dioxide has been a major concern throughout the history of MOS integrated circuit production. The quality of a gate oxide layer is of great importance, which is particularly true when more stringent customer requirements are demanded. It is essential to monitor oxide performance in production to provide early warning of reliability excursions and provide measures toward continuous process improvement.
It is widely accepted that highly accelerated measurement of gate oxide charge-to-breakdown (Q
BD
) is employed as a process monitor/control parameter. Traditionally, Q
BD
is determined by using a constant current stress test (CCS). In a CCS test, a stress current density is held constant, and time-to-breakdown (t
BD
) is measured and multiplied by a current density to obtain a Q
BD
. Although the determination of Q
BD
through CCS is simple and straightforward, the measurement is time consuming. Thus, the application of quick monitoring and improvement of gate oxide layer quality and integrity is limited.
On the other hand, an exponential current ramp test (ECR) provides a fast way to determine the Q
BD
. In an ECR test, a current is injected into the oxide in exponential steps until a breakdown occurs.
The ECR test provides a way of monitoring Q
BD
in a very short measurement time with reasonable resolution of early failures. Thus, for production monitors, the ECR test has a significant speed advantage over the CCS test. Accordingly, the ECR test should replace the traditional CCS test in industry for fast wafer level reliability (fWLR) of Q
BD
evaluation as long as it can well correlate with the CCS test.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a method for testing the reliability of a dielectric thin film with a reduced testing time. The method provides a conversion mechanism between an exponential current ramp test and a constant current stress test.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method for testing the reliability of a dielectric thin film. An exponential current ramp test is performed with a delay time on a dielectric thin film. An exponential current ramp charge-to-breakdown distribution, which is represented by cumulative distribution failure percentage, is obtained. An exponential current ramp charge-to-breakdown at a cumulative distribution failure percentage is calculated. An exponential current ramp constant and a constant current stress constant at the cumulative distribution failure percentage are calculated. A constant current stress charge-to-breakdown at the cumulative distribution failure percentage is calculated by using a specified current density and the constant current stress constant at the cumulative distribution failure percentage. The constant current stress charge-to-breakdown at the cumulative distribution failure percentage is compared to a specified constant current stress charge-to-breakdown to determine the reliability of the gate oxide layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5420513 (1995-05-01), Kimura
patent: 5594349 (1997-01-01), Kimura
patent: 5793212 (1998-08-01), Om
patent: 6047243 (2000-04-01), Bang et al.
Cheng Donald
Fu Kuan-Yu
Liu Chuan H.
Wang Mu-Chun
Yang Sheng-Hsing
Grimley Arthur T.
Le John
Thomas Kayden Horstemeyer & Risley LLP
United Microelectronics Corp.
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