Testing method for buried strap and deep trench leakage current
AssigneeWinbond Electronics Corporation (Taiwan)
InventorsShih-Hsien Yang, Chuan-Jane Chao
Life of this patent
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Abstract
A method for measuring both buried strap and deep trench leakage currents in DRAM cell capacitors. By keeping the voltages on both plates of the capacitor equal, the buried strap leakage current (IBS) may be isolated and measured. A range of voltages is applied to a terminal of an associated transistor to obtain a corresponding range of buried strap leakage currents. An unequal voltage is next applied across the capacitor, and a total leakage current is measured. By applying a known potential to a substrate of the transistor during this total leakage current measurement, the associated IBS may be determined. Next, the IBS is subtracted from the measured total leakage current to obtain the deep trench leakage current (IDT).
Claims21
A method for measuring buried strap leakage current in a DRAM cell having a deep trench storage capacitor and a transistor, where the buried strap is a conductor between one plate of the capacitor and a terminal of the transistor, the transistor further having a gate and a substrate, and the capacitor further having a buried plate, the method comprising:
- applying a biasing voltage to the substrate of the transistor;
- applying a sweep voltage to the terminal of the transistor and to the buried plate of the capacitor;
- and
- measuring the buried strap leakage current at the terminal of the transistor.
A method for measuring deep trench leakage current in a DRAM cell having a deep trench storage capacitor and a transistor, where a buried strap conducts between one plate of the capacitor and a terminal of the transistor, the transistor further having a gate and a substrate, and the capacitor further having a buried plate, the method comprising:
- obtaining a buried strap leakage current value for the capacitor corresponding to a diode voltage between the terminal of the transistor and the substrate;
- applying a biasing voltage to the buried plate of the capacitor;
- applying a first sweep voltage to the substrate of the transistor;
- applying a second sweep voltage to the terminal of the transistor equal to a sun of the first sweep voltage and the diode voltage;
- measuring a current at the terminal of the transistor;
- and
- subtracting the buried strap leakage current value from the measured current to obtain the deep trench leakage current.
A method for measuring deep trench leakage current in a DRAM cell as having a deep trench storage capacitor and a transistor, where a buried strap conducts between one plate of the capacitor and a terminal of the transistor, the transistor further having a gate and a substrate, and the capacitor further having a buried plate, the method comprising:
- obtaining a buried strap leakage current for the capacitor;
- applying a biasing voltage to the buried plate of the capacitor;
- applying a diode voltage to the substrate of the transistor;
- applying a sweep voltage to the terminal of the transistor;
- measuring a current at the terminal of the transistor;
- and
- subtracting the buried strap leakage current from the measured current to obtain the deep trench leakage current.
A method for measuring leakage current in a deep trench DRAM cell having a capacitor electrically connected to a terminal of a transistor, the transistor further having a substrate terminal, and the capacitor further having a buried plate, the method comprising:
- measuring a buried strap leakage current by:
- applying a biasing voltage to the substrate of the transistor,
- applying a sweep voltage to the terminal of the transistor and to the buried plate of the capacitor, and
- measuring a current at the terminal of the transistor;
- and
- measuring deep trench leakage current by:
- applying another biasing voltage to the buried plate of the capacitor,
- applying a predetermined voltage to the substrate of the transistor,
- applying another sweep voltage to the terminal of the transistor,
- measuring a total current at the terminal of the transistor, and
- subtracting the buried strap leakage current from the measured total current to obtain the deep trench leakage current.
Dependencies are inferred from the claim text.