Mems inertial sensor with high resistance to stiction

A device, comprising:

• a substrate;
• a fixed constraint coupled to the substrate;
• a first mass over the substrate, the first mass having a first outer wall and a first opening;
• a first spring coupled between the fixed constraint and the first mass, the fixed constraint arranged outside the first mass and coupled to the first outer wall of the first mass by the first spring;
• a second mass over the substrate, the first mass being between the second mass and the fixed constraint;
• a second spring coupled between the first mass and the second mass;
• a third mass and a fourth mass suspended over the substrate, the fourth mass having a second outer wall and a second opening, the fixed constraint arranged outside the fourth mass and coupled to the second outer wall;
• a first stopper structure coupled between the first mass and the second mass;
• a second stopper structure coupled between the third mass and the fourth mass;
• a first electrode fixed to the substrate, the first electrode being in the first opening;
• and
• a second electrode fixed to the substrate, the second electrode being in the first opening.

A device, comprising:

• a substrate;
• a rigid constraint coupled to the substrate;
• a first spring;
• a first mass having a first opening, the first spring coupled between the rigid constraint and a first side of the first mass, the first mass having a second side opposite to the first side;
• a second mass extending from the second side of the first mass;
• a second spring coupled between the second side of the first mass and the second mass;
• a third mass extending from the second side of the first mass, the third mass being substantially parallel to the second mass;
• a third spring coupled between the second side of the first mass and the third mass, the second and third springs being spaced from the first spring by the first mass;
• a first stopper fixed to the substrate, the first stopper overlapping a first corner of the second side of the first mass;
• a second stopper fixed to the substrate, the first and second stoppers are physically separate from the first mass, the second mass, and the third mass, the second stopper overlapping a second corner of the second side of the first mass, the first stopper is spaced from the second stopper by a first dimension in a first direction, an outer edge of the second mass is spaced from an outer edge of the third mass by a second dimension in the first direction in a resting state, the second dimension being less than the first dimension.