1. Field of the Invention
The present invention relates to a method and device for measuring interface trap density in a semiconductor device.
2. Description of the Related Art
As a semiconductor technology develops constantly, the length of gates gradually become shorter and the thickness of gate oxide layers gradually become thinner. Accordingly, characteristics of semiconductor devices are inevitably affected by these smaller dimensions. One of the characteristics affected is the interface trap density between a silicon substrate and a gate oxide layer.
Generally, when a gate oxide layer is grown, a sufficient bonding is not made between a silicon atom and an oxygen atom, so that a dangling bond (where there are insufficient oxygen atoms) is generated at an interface between a silicon substrate and the gate oxide layer.
A dangling bond easily attracts an electron when a transistor operates, thereby increasing the interface trap density of the gate oxide layer. Accordingly, the quality of the gate oxide layer deteriorates or the driving current is reduced, which may degrade some characteristics of a semiconductor device.
Traditionally, a charge pumping test has been used as a method for measuring a surface state located under a gate oxide layer. The interface trap density may be calculated from data obtained using this test. However, when the conventional method is applied to a device having a very thin gate oxide layer, gate tunneling leakage current and/or quantum mechanical effects can result in an incorrect calculation of the interface trap density (generally resulting in a calculated interface trap density that is too high).