A Circuit And Method For Measuring The Capacitance Of A Nonlinear Device
Publication Date: 2007-Jan-22
The IP.com Prior Art Database
A circuit and method are disclosed for measuring the capacitance of a nonlinear device. The circuit includes a measurement structure which drives the nonlinear device, a reference structure which is substantially identical to the measurement structure, a first adjustable power source which supplies electric charge to both the measurement structure and the reference structure, and a second adjustable power source which draws electric charge from both the measurement structure and the reference structure. The circuit further includes a first control signal source which generates a first control signal and where the first control signal controls processes of charging a test node of the measurement structure and charging a reference node of the reference structure during predetermined periods of the first control signal, and a second control signal source which generates a second control signal and where the second control signal controls processes of discharging the test node and discharging the reference node during predetermined periods of the second control signal.
A CIRCUIT AND METHOD FOR MEASURING THE CAPACITANCE OF
A NONLINEAR DEVICE
FIELD OF THE INVENTION
The present invention relates to the field of measuring characteristics of semiconductor devices within an integrated circuit. In particular, the present invention relates to a circuit and method for measuring the capacitances of nonlinear devices. The present invention also relates to a circuit and method for measuring the capacitance deviation between two circuit components of an integrated circuit.
BACKGROUND OF THE INVENTION
As semiconductor processing technologies continue to improve, the size of a transistor becomes smaller and the operating power becomes lower for each new generation of integrated circuit. As the geometry of circuit components of an integrated circuit continues to shrink, there is a need to accurately measure the capacitance of circuit components, including the capacitance of linear and nonlinear devices in an integrated circuit. An example of the capacitance of a linear device may include the capacitance between metal lines within a same circuit layer or from different circuit layers. An example of the capacitance of a nonlinear device may include the capacitance at a base terminal of a transistor, which usually varies as a function of voltage when the voltage applied at the base terminal of a transistor changes. In addition, as the operating power of an integrated circuit continues to drop, there is a need to accurately measure the capacitance of circuit components with less power applied across the device to be measured.
Figure 1 illustrates a prior art circuit for measuring the capacitance of a linear device. The capacitance of the linear device to be measured is the Metal_1 wire to Metal _2 wire cross-over capacitance. The prior art circuit includes a pair of pseudo inverters, having a first pseudo inverter 100 and a second pseudo inverter 120. The first pseudo inverter 100 includes a PMOS transistor 106 and a NMOS transistor 108 with the drain terminals of the transistors connected to each other.
Also attached to the drain terminals of the first pseudo inverter is a Metal_1 wire 107, which is used
as a reference structure. The source terminal of the PMOS transistor 106 is coupled to a power
supply Vdd (No Cap) 102 through a dc ammeter 104. The source terminal of the NMOS transistor
108 is coupled to a circuit ground 110. The NMOS transistor 108 is controlled by a first voltage
control signal V1, and the PMOS transistor 106 is controlled by a second voltage control signal V2.
Both the first and second voltage control signals are generated by a signal generator 112.
Similarly, the second pseudo inverter 120 also includes a PMOS transistor 126 and a NMOS transistor 128 with the drain terminals of the transistors connected to each other. Also attached...