Capacitive pressure sensor and method of forming same
There is no limit to creativity, and the instrument is invented. Today we introduce a national invention patent for the invention - a capacitive pressure sensor and its formation method. The patent was filed by SMIC International (Shanghai) Co., Ltd. and was granted an authorization announcement on March 1, 2017.
Description
The present invention relates to the field of microelectromechanics (MEMS), and more particularly to a capacitive pressure sensor and a method of forming the same.
Background of the invention
At present, the types of pressure sensors mainly include piezoresistive, piezoelectric, capacitive, potentiometer, inductive bridge, and strain gauge. Among them, the capacitive pressure sensor has high sensitivity and is not easily affected by the external environment, and has gradually attracted attention in the market.
Due to the limitations of traditional pressure sensors, such as large size, complicated manufacturing process and inconvenient operation. MEMS (Micro-Electro-Mechanical Systems, MEMS) technology is widely used in the manufacture of pressure sensors. The pressure sensor made by MEMS technology has the advantages of miniaturization, mass production, low cost, high precision, etc., and the pressure sensor and the control circuit can be integrated on the same substrate, so that the weak output signal of the sensor can be amplified and processed nearby, thereby avoiding External electromagnetic interference improves the reliability of the transmitted signal.
Summary of the invention
The problem addressed by the present invention is to reduce the surface area of ​​the substrate occupied by the capacitive pressure sensor.
In order to solve the above problems, the present invention provides a method of forming a capacitive pressure sensor, comprising: providing a substrate, forming an etched hole in the substrate; forming a first sacrificial layer on the substrate, the first sacrificial layer a first portion filling the etched hole and a second portion covering the surface of the portion, the first portion being directly under the second portion; forming a diaphragm on the first sacrificial layer and the substrate; forming a second sacrificial layer on the portion of the spacer And the second sacrificial layer is located above the second portion of the first sacrificial layer; opposite first and second electrodes are formed on sidewall surfaces of both sides of the second sacrificial layer, and the first electrode And the second electrode portion is located on the surface of the diaphragm; removing the second sacrificial layer, forming a first cavity between the first electrode and the second electrode; planarizing or etching the back surface of the substrate until the etching hole is exposed a first sacrificial layer at the bottom; removing the first sacrificial layer, forming a second cavity at the bottom of the diaphragm; forming a sealing layer on the back surface of the substrate that seals the bottom opening of the second cavity.
FIG. 3 is a cross-sectional structural diagram showing a forming process of a capacitive pressure sensor according to an embodiment of the present invention.
Optionally, the second sacrificial layer has a width smaller than a width of the second portion of the first sacrificial layer, and the second sacrificial layer has a length equal to or smaller than a length of the second portion of the first sacrificial layer. The second portion of the first sacrificial layer has a thickness of 0.1 to 10 μm, and the second portion of the first sacrificial layer has a width of 0.1 to 10000 μm. The forming process of the first electrode and the second electrode is: forming an electrode material layer on sidewalls and surfaces of the second sacrificial layer and a surface of the separator; forming a mask layer on the electrode material layer, the mask The film layer covers the electrode material layer on the sidewalls of the two sacrificial layers and on the partial separator; the electrode material layer not covered by the mask layer is removed, and the opposite side surfaces are formed on the sidewall surfaces of the second sacrificial layer a first electrode and a second electrode.
The first electrode or the second electrode includes a first portion located on both side wall surfaces of the second sacrificial layer, and a second portion located on a top portion and a sidewall of the second portion of the first sacrificial layer The surface of the membrane and the surface of the membrane on the substrate on either side of the second sacrificial layer. The spacing between the first electrode and the second electrode is from 0.1 to 10,000 microns. The width of the etched hole is smaller than the width of the second portion of the first sacrificial layer, and the etched hole has a depth of more than 50 micrometers and a width of 0.1 to 10,000 micrometers. The first sacrificial layer or second sacrificial layer material has a high etch selectivity ratio relative to the substrate, the separator, the first electrode, and the second electrode material. The material of the first sacrificial layer or the second sacrificial layer is a bottom anti-reflective coating, polycrystalline silicon, amorphous silicon, amorphous carbon, SiN, SiON, SiCN, SiC, BN, SiCOH, BN or SiGe. The method further includes forming a control circuit and an interconnect structure on other regions of the substrate or other substrate, the first electrode and the second electrode being connected to the control circuit through the interconnect structure. The separator has a thickness of 0.1 to 10 μm.
The present invention also provides a capacitive pressure sensor comprising: a substrate, an etching hole in the substrate and penetrating the thickness thereof; a diaphragm covering the substrate and the etching hole, and a portion of the diaphragm above the etching hole is convex upward a third cavity is formed between the upwardly convex diaphragm and the substrate, the third cavity and the etching hole constitute a second cavity; the first electrode and the second electrode are opposite to each other on the opposite ends of the protruding diaphragm, first There is a first cavity between the electrode and the second electrode; a sealing layer on the back side of the substrate, the sealing layer sealing the opening of the lower end of the second cavity.
Compared with the prior art, the technical solution of the present invention has the following advantages: the capacitive pressure sensor of the present invention comprises a convex diaphragm, opposite first and second electrodes on opposite ends of the convex diaphragm, the first electrode There is a first cavity between the second electrode and the second electrode. Compared to the upper and lower electrodes of the prior art capacitive pressure sensor parallel to the semiconductor substrate, the first electrode and the second electrode of the present invention are perpendicular to the surface of the substrate such that the first electrode and the second electrode occupy The surface area of ​​the substrate is reduced, which saves the area occupied by the capacitive pressure sensor, thereby facilitating the integration of the device.
Further, the first electrode or the second electrode includes a first portion located on both side wall surfaces of the second sacrificial layer, and a second portion located on the top and side walls of the second portion of the first sacrificial layer The surface of the diaphragm. The second portion of the first electrode or the second electrode is in contact with the surface of the diaphragm on the top portion and the sidewall of the second portion of the first sacrificial layer, and the contact area is large, which improves the contact adhesion of the first electrode or the second electrode to the diaphragm. Sexual and mechanical strength, effectively preventing the first electrode or the second electrode from falling off or deforming.
The method for forming a capacitive pressure sensor of the present invention has a simple forming process, and the formed capacitive pressure sensor has a high degree of integration. In addition, after the substrate is thinned, the first sacrificial layer is removed from the bottom of the diaphragm. The raised portion of the diaphragm maintains integrity, allowing the diaphragm to maintain strong mechanical strength and withstand greater pressure, improving the performance of the capacitive pressure sensor.
Description
The present invention relates to the field of microelectromechanics (MEMS), and more particularly to a capacitive pressure sensor and a method of forming the same.
Background of the invention
At present, the types of pressure sensors mainly include piezoresistive, piezoelectric, capacitive, potentiometer, inductive bridge, and strain gauge. Among them, the capacitive pressure sensor has high sensitivity and is not easily affected by the external environment, and has gradually attracted attention in the market.
Due to the limitations of traditional pressure sensors, such as large size, complicated manufacturing process and inconvenient operation. MEMS (Micro-Electro-Mechanical Systems, MEMS) technology is widely used in the manufacture of pressure sensors. The pressure sensor made by MEMS technology has the advantages of miniaturization, mass production, low cost, high precision, etc., and the pressure sensor and the control circuit can be integrated on the same substrate, so that the weak output signal of the sensor can be amplified and processed nearby, thereby avoiding External electromagnetic interference improves the reliability of the transmitted signal.
Summary of the invention
The problem addressed by the present invention is to reduce the surface area of ​​the substrate occupied by the capacitive pressure sensor.
In order to solve the above problems, the present invention provides a method of forming a capacitive pressure sensor, comprising: providing a substrate, forming an etched hole in the substrate; forming a first sacrificial layer on the substrate, the first sacrificial layer a first portion filling the etched hole and a second portion covering the surface of the portion, the first portion being directly under the second portion; forming a diaphragm on the first sacrificial layer and the substrate; forming a second sacrificial layer on the portion of the spacer And the second sacrificial layer is located above the second portion of the first sacrificial layer; opposite first and second electrodes are formed on sidewall surfaces of both sides of the second sacrificial layer, and the first electrode And the second electrode portion is located on the surface of the diaphragm; removing the second sacrificial layer, forming a first cavity between the first electrode and the second electrode; planarizing or etching the back surface of the substrate until the etching hole is exposed a first sacrificial layer at the bottom; removing the first sacrificial layer, forming a second cavity at the bottom of the diaphragm; forming a sealing layer on the back surface of the substrate that seals the bottom opening of the second cavity.
FIG. 3 is a cross-sectional structural diagram showing a forming process of a capacitive pressure sensor according to an embodiment of the present invention.
Optionally, the second sacrificial layer has a width smaller than a width of the second portion of the first sacrificial layer, and the second sacrificial layer has a length equal to or smaller than a length of the second portion of the first sacrificial layer. The second portion of the first sacrificial layer has a thickness of 0.1 to 10 μm, and the second portion of the first sacrificial layer has a width of 0.1 to 10000 μm. The forming process of the first electrode and the second electrode is: forming an electrode material layer on sidewalls and surfaces of the second sacrificial layer and a surface of the separator; forming a mask layer on the electrode material layer, the mask The film layer covers the electrode material layer on the sidewalls of the two sacrificial layers and on the partial separator; the electrode material layer not covered by the mask layer is removed, and the opposite side surfaces are formed on the sidewall surfaces of the second sacrificial layer a first electrode and a second electrode.
The first electrode or the second electrode includes a first portion located on both side wall surfaces of the second sacrificial layer, and a second portion located on a top portion and a sidewall of the second portion of the first sacrificial layer The surface of the membrane and the surface of the membrane on the substrate on either side of the second sacrificial layer. The spacing between the first electrode and the second electrode is from 0.1 to 10,000 microns. The width of the etched hole is smaller than the width of the second portion of the first sacrificial layer, and the etched hole has a depth of more than 50 micrometers and a width of 0.1 to 10,000 micrometers. The first sacrificial layer or second sacrificial layer material has a high etch selectivity ratio relative to the substrate, the separator, the first electrode, and the second electrode material. The material of the first sacrificial layer or the second sacrificial layer is a bottom anti-reflective coating, polycrystalline silicon, amorphous silicon, amorphous carbon, SiN, SiON, SiCN, SiC, BN, SiCOH, BN or SiGe. The method further includes forming a control circuit and an interconnect structure on other regions of the substrate or other substrate, the first electrode and the second electrode being connected to the control circuit through the interconnect structure. The separator has a thickness of 0.1 to 10 μm.
The present invention also provides a capacitive pressure sensor comprising: a substrate, an etching hole in the substrate and penetrating the thickness thereof; a diaphragm covering the substrate and the etching hole, and a portion of the diaphragm above the etching hole is convex upward a third cavity is formed between the upwardly convex diaphragm and the substrate, the third cavity and the etching hole constitute a second cavity; the first electrode and the second electrode are opposite to each other on the opposite ends of the protruding diaphragm, first There is a first cavity between the electrode and the second electrode; a sealing layer on the back side of the substrate, the sealing layer sealing the opening of the lower end of the second cavity.
Compared with the prior art, the technical solution of the present invention has the following advantages: the capacitive pressure sensor of the present invention comprises a convex diaphragm, opposite first and second electrodes on opposite ends of the convex diaphragm, the first electrode There is a first cavity between the second electrode and the second electrode. Compared to the upper and lower electrodes of the prior art capacitive pressure sensor parallel to the semiconductor substrate, the first electrode and the second electrode of the present invention are perpendicular to the surface of the substrate such that the first electrode and the second electrode occupy The surface area of ​​the substrate is reduced, which saves the area occupied by the capacitive pressure sensor, thereby facilitating the integration of the device.
Further, the first electrode or the second electrode includes a first portion located on both side wall surfaces of the second sacrificial layer, and a second portion located on the top and side walls of the second portion of the first sacrificial layer The surface of the diaphragm. The second portion of the first electrode or the second electrode is in contact with the surface of the diaphragm on the top portion and the sidewall of the second portion of the first sacrificial layer, and the contact area is large, which improves the contact adhesion of the first electrode or the second electrode to the diaphragm. Sexual and mechanical strength, effectively preventing the first electrode or the second electrode from falling off or deforming.
The method for forming a capacitive pressure sensor of the present invention has a simple forming process, and the formed capacitive pressure sensor has a high degree of integration. In addition, after the substrate is thinned, the first sacrificial layer is removed from the bottom of the diaphragm. The raised portion of the diaphragm maintains integrity, allowing the diaphragm to maintain strong mechanical strength and withstand greater pressure, improving the performance of the capacitive pressure sensor.
Household Electrical Appliances
gree , https://www.greegroups.com