Back to results
US 12,288,017 B2Granted
Simulation method for characteristics of transistor, simulation method for characteristics of electronic circuit including transistor, and nontransitory recording medium that stores simulation program for characteristics of transistor
AssigneeWuhan Tianma Micro-Electronics Co., Ltd.
InventorGenshiro Kawachi
Life of this patent
Estimating the term…
Abstract
A simulation method includes a process of calculating a transient charge density qT of trapped charges after applying a voltage between a gate electrode and a semiconductor layer of a transistor, the charge density qT being calculated with a time variance of the charge density qT being expressed by a function obtained by superimposing multiple exponential functions having mutually different time constants.
Claims7
A design method for characteristics of a pixel circuit of a display device through simulation,
- the pixel circuit including at least a light emitting element and a transistor that controls a current flowing in the light emitting element,
- the transistor including a semiconductor layer that includes a source and a drain that are separated from each other and a channel positioned between the source and the drain, and a gate electrode facing the channel of the semiconductor layer,
- wherein a model parameter predetermined at least based on a measured result of the transistor is set by an input device,
- wherein, the input device is caused to set a mathematical model equation including
- a process (a) of calculating a thermal equilibrium trap charge density Q′T, based on the Poisson's equation expressing a relationship between an electrostatic potential inside the channel and charges including free carrier charges and trapped charges trapped in trapping states in the channel, and on the law of charge neutrality applied to charges accumulated on the gate electrode and the channel;
- a process (b) of calculating a transient trap charge density qT after applying a voltage between the gate electrode and the semiconductor layer, in which assuming that a time variance of the transient trap charge density qT is expressed by a function obtained by superimposing multiple exponential functions having mutually different time constants;
- a process (c) of calculating a free carrier charge density qI, based on the transient trap charge density qT;
- and
- a process (d) of calculating a drain current Id flowing between the source and the drain, based on the free carrier charge density qI, and
- wherein the subprocesses below are set to the process (b) of the mathematical model equation:
- a subprocess (b1) of determining n delay time constants τNQS1 to τNQSn corresponding to the time constants included in the exponential functions, and charge densities QT1 to QTn of partial charges constituting the trapped charges having the delay time constants τNQS1 to τNQSn, respectively, where n is an integer of 2 or greater, based on a probability distribution of the partial charges constituting the trapped charges, the probability variable of which is delay time constant corresponding time required for the partial charges constituting the trapped charge to be trapped in the trapping states, and
- a subprocess (b2) of calculating the transient trap charge density qT based on the delay time constants τNQS1 to τNQSn of the trapped charges and the charge densities QT1 to QTn of the trapped charges, and
- wherein the design method includes
- simulating, by an analog electronic circuit simulator, a transient response characteristic of the current flowing in the transistor in the pixel circuit based on the mathematical model equation, and
- displaying, by an output device, a result of the simulation of the analog electronic circuit simulator.
12 more elements
A non-transitory recording medium that stores a program for designing characteristics of a pixel circuit of a display device through simulation, the program including at least an analog electronic circuit simulator,
- the pixel circuit including at least a light emitting element and a transistor that controls a current flowing in the light emitting element,
- the transistor including a semiconductor layer that includes a source and a drain that are separated from each other and a channel positioned between the source and the drain, and a gate electrode facing the channel of the semiconductor layer,
- wherein a model parameter predetermined at least based on a measured result of the transistor is set by an input device,
- the program causing a computer to execute:
- causing the input device to set a mathematical model equation including
- a step (a) of calculating a thermal equilibrium trap charge density Q′T, based on the Poisson's equation expressing a relationship between an electrostatic potential inside the channel and charges including free carrier charges and trapped charges trapped in trapping states in the channel, and on the law of charge neutrality applied to charges accumulated on the gate electrode and the channel;
- a step (b) of calculating a transient trap charge density qT after applying a voltage between the gate electrode and the semiconductor layer, in which assuming that a time variance of the transient trap charge density qT is expressed by a function obtained by superimposing multiple exponential functions having mutually different time constants;
- a step (c) of calculating a free carrier charge density qI, based on the transient trap charge density qT;
- and
- a step (d) of calculating a drain current Id flowing between the source and the drain, based on the free carrier charge density qI,
- wherein the subprocesses below are set to the step (b) of the mathematical model equation:
- a substep (b1) of determining n delay time constants τNQS1 to τNQSn corresponding to the time constants included in the exponential functions, and charge densities QT1 to QTn of partial charges constituting the trapped charges having the delay time constants τNQS1 to τNQSn, respectively, where n is an integer of 2 or greater, based on a probability distribution of the partial charges constituting the trapped charges, the probability variable of which is delay time constant corresponding time required for the partial charges constituting the trapped charge to be trapped in the trapping states, and
- a substep (b2) of calculating the transient trap charge density qT based on the delay time constants τNQS1 to τNQSn of the trapped charges and the charge densities QT1 to QTn of the trapped charges,
- wherein the program further causing the computer to execute
- a simulation of a transient response characteristic of the current flowing in the transistor in the pixel circuit based on the mathematical model equation, and
- displaying, by an output device, a result of the simulation.
13 more elements
Dependencies are inferred from the claim text.