Semiconductor integrated circuit including circuit for driving electrostatic actuator, micro-electro-mechanical systems, and driving method of electrostatic actuator

A semiconductor integrated circuit comprising:

• an electrostatic actuator having a top electrode, a bottom electrode, and an insulating film disposed between the top electrode and the bottom electrode;
• an estimation circuit which monitors a pull-out voltage to separate the top electrode and the bottom electrode from each other;
• and
• a bias circuit which decides, on the basis of the pull-out voltage monitored by the estimation circuit, the direction of an electric field applied to the insulating film by the top electrode and the bottom electrode when the electrostatic actuator is driven.

A semiconductor integrated circuit comprising:

• an electrostatic actuator having a top electrode, a bottom electrode, and an insulating film disposed between the top electrode and the bottom electrode;
• an estimation circuit which estimates whether the amount of a charge accumulated in the insulating film of the electrostatic actuator is within a predetermined range;
• and
• a bias circuit which applies a drive voltage across the top electrode and the bottom electrode to inject or pull out a charge into or from the insulating film so that the charge amount falls within the predetermined range, when it is estimated that the amount of the charge accumulated in the insulating film is not within the predetermined range.

Micro-electro-mechanical systems (MEMS) comprising:

• an electrostatic actuator having a top electrode, a bottom electrode, and a first insulating film disposed between the top electrode and the bottom electrode, the bottom electrode being formed on a substrate, the top electrode being disposed so that a cavity is present between the top electrode and the substrate;
• a first electrode formed on the substrate separately from the bottom electrode;
• a second electrode formed so that an insulating member is interposed between the second electrode and the top electrode, the second electrode being disposed opposite to the first electrode;
• and
• a bias circuit which sets the bottom electrode at a ground voltage while a drive voltage is being applied to the top electrode of the electrostatic actuator and which sets the top electrode at the ground voltage while the drive voltage is being applied to the bottom electrode,
• wherein the drive voltage and the ground voltage are applied to the top electrode and the bottom electrode by the bias circuit, such that the electrostatic actuator varies the distance between the first electrode and the second electrode.

A driving method of an electrostatic actuator which has a top electrode, a bottom electrode, and an insulating film disposed between the top electrode and the bottom electrode, the method comprising:

• detecting one of the power-on and the input of a command;
• estimating whether the amount of a charge accumulated in the insulating film is within a predetermined range, when one of the power-on and the input of the command is detected;
• and
• injecting or pulling out a charge into or from the insulating film so that the amount of the charge accumulated in the insulating film falls within the predetermined range, when it is estimated that the charge amount is not within the predetermined range.