Ultrasonic sensor and manufacturing method for the same

A manufacturing method for an ultrasonic sensor, the ultrasonic sensor including:

• a substrate disposed on an XY plane, the XY plane being a plane formed by an X axis and a Y axis, the X axis and the Y axis being two orthogonal axes;
• a plurality of spaces formed in the substrate in at least one of an X-axis direction along the X axis and a Y-axis direction along the Y axis;
• a vibrating plate that is provided on the substrate and that has a first surface and a second surface opposite to each other, the first surface being directly on the substrate, the vibrating plate spanning entirely across at least two of the plurality of spaces so that the two of the plurality of spaces are closed by the vibrating plate;
• a plurality of piezoelectric elements that are provided at discrete positions on the second surface of the vibrating plate, the discrete positions corresponding to the plurality of spaces, each of the plurality of piezoelectric elements being configured to transmit/receive an ultrasonic wave;
• and
• a plurality of dummy piezoelectric elements that are provided at second discrete positions on the second surface of the vibrating plate,
• the manufacturing method comprising:
• preparing the substrate;
• forming the vibrating plate on one surface of the substrate;
• forming the plurality of piezoelectric elements and the plurality of dummy piezoelectric elements on the vibrating plate;
• forming an etching mask on the other surface, which is opposite to one surface, of the substrate, the etching mask being laterally shifted from the discrete positions on the XY plane;
• and
• etching the substrate from the other surface of the substrate so that the plurality of spaces are formed,
• wherein at least some of the plurality of spaces are arranged in a zigzag pattern relative to one another,
• wherein the substrate has a plurality of partitions, and the plurality of spaces and the plurality of partitions are alternatively arranged in at least one of the X-axis direction and the Y-axis direction,
• the second discrete positions correspond to the plurality of partitions, and
• one of the plurality of dummy piezoelectric elements is sandwiched by two adjacent elements of the plurality of piezoelectric elements in at least one of the X-axis direction and the Y-axis direction.