Pressure sensor and manufacturing method therefor
A pressure sensor (e.g., a condenser microphone) includes a plate having a fixed electrode, a diaphragm having a moving electrode positioned opposite to the fixed electrode, and a support, wherein the diaphragm is subjected to displacement due to pressure variations applied thereto, and the support has a first interior wall forming a first cavity, in which the end portions of the plate are fixed, and a second interior wall, in which a step portion is formed in the thickness direction of the diaphragm in relation to the first interior wall and which forms a second cavity whose cross-sectional area is larger than the cross-sectional area of the first cavity in the plane direction of the diaphragm. The first and second cavities can be redesigned to communicate with each other via a passage, whereby it is possible to improve both of low-frequency characteristics and high-frequency characteristics in the pressure sensor.
1. A manufacturing method of a pressure sensor including a plate having a fixed electrode, a diaphragm that has a moving electrode positioned opposite to the fixed electrode and that is subjected to displacement due to pressure variations applied thereto, and a support having at least one cavity for supporting the plate, said manufacturing method comprising:
depositing a thin film forming the plate and a thin film forming the diaphragm on a first surface of a substrate;
forming a first mask having a first opening on a second surface opposite to the first surface of the substrate;
forming a second mask having a second opening on the second surface of the substrate, wherein the second mask covers the first mask so that a prescribed portion of the substrate just above the thin film forming the plate is exposed in the second opening;
forming a recess by performing anisotropic etching on the substrate exposed in the second opening by use of the second mask;
removing the second mask while allowing the first mask to remain; and
performing anisotropic etching using the remaining first mask on the substrate exposed in the first opening such that a bottom of the recess is removed, thus forming a through-hole forming the cavity in the substrate.
2. A manufacturing method of a pressure sensor including a plate having a fixed electrode, a diaphragm that has a moving electrode positioned opposite to the fixed electrode and that is subjected to displacement due to pressure variations applied thereto, and a support having at least one cavity for supporting the pate, said manufacturing method comprising:
depositing a thin film forming the plate and a thin film forming the diaphragm on a first side of a substrate;
forming one mask having a first opening on a second side opposite to the first side of the substrate;
forming a recess by performing a first anisotropic etching on the substrate exposed in the first opening by using the one mask;
forming another mask having a second opening on the second side of the substrate, wherein an area of the second opening differs from an area of the first opening; and
performing a second anisotropic etching on the substrate exposed in the second opening by using the other mask such that a bottom of the recess is removed so as to form a through-hole forming the cavity.
3. The manufacturing method of the pressure sensor according to claim 2 , wherein the area of the second opening is larger than the area of the first opening and the one mask is constituted of a plurality of layers, the other mask being formed by removing at least one of the layers constituting the one mask.
4. A manufacturing method of a pressure sensor including a plate having a fixed electrode, a diaphragm that has a moving electrode positioned opposite to the fixed electrode and that is subjected to displacement due to pressure variations applied thereto, and a support having at least one cavity for supporting the plate, said manufacturing method comprising:
depositing a thin film forming the plate and a thin film forming the diaphragm on a first side of a substrate;
forming a first mask having a first opening on a second side opposite to the first side of the substrate;
forming a second mask having a second opening on the second side of the substrate, wherein an area of the second opening is smaller than an area of the first opening;
forming a recess by performing a first anisotropic etching on the substrate exposed in the second opening by using the second mask;
removing the second mask; and
performing a second anisotropic etching on the substrate exposed in the first opening by using the first mask such that a bottom of the recess is removed so as to form a through-hole forming the cavity.
5. The manufacturing method of the pressure sensor according to claim 4 , wherein the second mask is formed to cover the first mask.