CN106744651A - A kind of condenser type microelectronics baroceptor and preparation method thereof - Google Patents

Abstract

The invention discloses a capacitive microelectronic air pressure sensor based on single crystal silicon epitaxial cavity sealing technology and a preparation method thereof, specifically a capacitive air pressure sensor based on MEMS micromachining technology. Due to mature epitaxial single crystal silicon technology, its The formed silicon microstructure has good mechanical properties, especially the cavity structure formed by epitaxial single crystal silicon has excellent sealing performance. The capacitance value of the capacitive air pressure sensor thus formed is mainly determined by the thickness of the film body, and is also affected by the ambient temperature and pressure. Based on the principle of dielectric stretching effect, the dielectric constant value of capacitor dielectric material changes with the change of pressure, and presents obvious monotonicity. This characteristic can realize data detection such as pressure or air pressure. Combined with MEMS micromachining technology, the capacitive air pressure sensor is small in size, low in power consumption and short in response time.

Description

A capacitive microelectronic air pressure sensor and its preparation method

technical field

The invention relates to a capacitive microelectronic air pressure sensor and a preparation method thereof, in particular to a capacitive microelectronic air pressure sensor based on MEMS micromachining technology and a preparation method thereof, belonging to the technical field of microelectromechanical systems.

Background technique

The sensitive principles of conventional air pressure sensors mainly include two types: resistance sensing and capacitive sensing. The principle of resistance sensing is that when the pressure of the measured gas changes, the deformation of the film drives the thimble, resulting in a change in the resistance value of the resistance on the film. The principle of capacitive sensing is that when the pressure of the gas to be measured changes, the movable electrode of the capacitor produces a certain displacement, and the spacing of the capacitor changes, resulting in a change in the value of the capacitor. The main defects of these two kinds of air pressure sensors are: (1) For resistive air pressure sensors, firstly, ensure that the resistance value, shape and placement of the resistors meet the requirements, and secondly, ensure that the four resistors forming the Wheatstone bridge The resistance values are completely equal, so there are extremely high requirements for the manufacturing process of this type of air pressure sensor; (2) For conventional capacitive air pressure sensors, due to the existence of a movable electrode, it is difficult to lead out the electrode, and the later packaging of the sensor is also relatively difficult. Difficulty, high sealing process requirements, resulting in relatively poor reliability of this type of air pressure sensor.

Contents of the invention

Objective: To solve the shortcomings of the existing technology, provide a capacitive microelectronic air pressure sensor and its preparation method. The device has simple processing technology, stable structure, low cost, etc., and has good compatibility with CMOS IC technology. Basic method: Using MEMS micromachining technology, a cavity is formed in the silicon wafer through the single crystal silicon epitaxial sealed cavity process, and a cavity sensitive capacitor is formed on the sealed cavity to realize the function of the air pressure sensor.

Technical solution: In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is:

A capacitive microelectronic air pressure sensor, characterized in that it includes a single crystal silicon sealed cavity and a capacitive air pressure sensor based on the distance variation between the upper and lower electrodes;

Using single crystal silicon as the substrate, a sealed cavity structure is formed through single crystal silicon epitaxial cavity sealing process; through sputtering, photolithography, and corrosion processes, the lower electrode, sacrificial layer, and upper electrode of the capacitor are sequentially grown on the upper surface of the sealed cavity; Finally, while protecting the upper electrode and the lower electrode of the capacitor, the sacrificial layer is isotropically etched to remove the sacrificial layer; metal pads and leads are provided on the single crystal silicon substrate to lead out the upper and lower electrodes of the capacitor respectively. electrode, lower electrode.

As a preferred solution, silicon oxide and silicon nitride are sequentially grown on the upper surface of the single crystal silicon substrate, and contact holes are formed by photolithography and etching.

As a preferred solution, the materials of the capacitor's lower electrode, upper electrode, lead wire and welding pad are all metal.

As a preferred solution, the materials of the lower electrode, the upper electrode, the lead wire and the welding pad of the capacitor are all Al.

As a preferred solution, the material of the sacrificial layer is phosphosilicate glass.

As a preferred solution, the capacitive microelectronic air pressure sensor is characterized in that: the height of the sealed cavity in the single crystal silicon substrate is 4-6 μm.

The present invention also provides the preparation method of the capacitive microelectronic air pressure sensor, which is characterized in that: comprising the following steps:

Step 1), using N-type single crystal silicon as the substrate, etching shallow grooves on the single crystal silicon substrate through an anisotropic reactive ion etching process;

Step 2), while protecting the sidewall of the shallow groove of the single crystal silicon substrate, the single crystal silicon substrate is isotropically etched to prepare for the subsequent epitaxial single crystal silicon cavity sealing process;

Step 3), growing monocrystalline silicon epitaxially, forming a sealed cavity inside the monocrystalline silicon substrate;

Step 4), growing silicon oxide and silicon nitride sequentially on the upper surface of the single crystal silicon substrate, and forming contact holes by photolithography and etching;

Step 5), sputtering the first layer of metal on the surface of silicon nitride, photoetching and etching to form pads, electrical interconnection lines and lower electrodes of capacitors;

Step 6), sputtering sacrificial layer material on silicon nitride and the first layer of metal, photolithography and etching to form a sacrificial layer;

Step 7), sputtering the second layer of metal on the silicon nitride and the sacrificial layer, forming pads, electrical interconnection lines, and the upper electrode of the capacitor by photolithography and etching, and opening a plurality of square via holes on the upper electrode of the capacitor , as a window for corroding the sacrificial layer between the upper and lower electrodes of the capacitor;

Step 8) While protecting the capacitor upper electrode and the capacitor lower electrode, perform isotropic corrosion on the sacrificial layer to expose the leads and pads of the capacitor lower plate.

Beneficial effects: the capacitive microelectronic air pressure sensor provided by the present invention is based on the sealed cavity structure of single crystal silicon, the device structure is simple, and the sealed cavity structure is formed by the epitaxial growth process of single crystal silicon. Compared with the sealed cavity structure formed by bonding or surface sacrificial layer process, the air pressure sensor structure based on the monocrystalline silicon epitaxial sealed cavity process has the characteristics of simple manufacturing process, high structural stability, and good mechanical properties of the device. Moreover, the processing of the capacitive air pressure sensor device can be completed by utilizing the front sputtering and etching processes, and the processing process and steps are simple and reliable. The entire processing process will not affect the existing CMOS circuits on the front of the silicon wafer. For example, the temperature sensor can be processed by CMOS processing technology, so as to further realize the single-chip intelligence of the chip, reduce the size of the chip, and reduce the cost of the chip. .

Description of drawings

Fig. 1 is the schematic flow chart that the present invention makes;

Fig. 2 is the front view of structure of the present invention;

Fig. 3 is the top view of structure of the present invention;

In the figure: substrate 1, silicon oxide 2, silicon nitride 3, capacitor lower electrode 4, sacrificial layer 5, capacitor upper electrode 6, sealed cavity 7, pad 8.

detailed description

Below in conjunction with example the present invention is described in detail:

Example 1:

As shown in Figures 1 to 3, the capacitive microelectronic air pressure sensor provided by the present invention is prepared through the following steps:

(a) N-type (100) single crystal silicon is used as the substrate 1, and shallow grooves of 1-10 μm are etched on the single crystal silicon substrate 1 by an anisotropic reactive ion etching RIE process;

(b) While protecting the sidewall of the shallow groove of the single crystal silicon substrate 1, perform isotropic etching on the single crystal silicon substrate to prepare for the encapsulation process of the next epitaxial single crystal silicon cavity;

(c) epitaxial growth of single crystal silicon, a sealed cavity 7 is formed inside the single crystal silicon substrate, and the height of the cavity is about 5 μm;

(d) sequentially growing silicon oxide 2 and silicon nitride 3 on the upper surface of the single crystal silicon substrate 1, and forming contact holes by photolithography and etching;

(e) Sputtering the first layer of metal Al on the surface of the silicon nitride 3, photolithography and etching to form the pad 8, the electrical interconnection line and the lower electrode 4 of the capacitor;

(f) sputtering a sacrificial layer material (such as phosphosilicate glass) on the silicon nitride 3 and the first layer of metal, and forming a sacrificial layer 5 by photolithography and etching;

(g) Sputter the second layer of metal Al on the silicon nitride 3 and the sacrificial layer 5, and form pads 8, electrical interconnection lines, and the upper electrode 6 of the capacitor by photolithography and etching, and open multiple layers on the upper electrode 6 of the capacitor. A square through hole, which serves as a window for corroding the sacrificial layer between the upper and lower electrodes of the capacitor;

(h) While protecting the capacitor upper electrode 6 and the capacitor lower electrode 4 , perform isotropic corrosion on the sacrificial layer 5 to expose the leads and pads 8 of the capacitor lower plate 4 .

The above has disclosed the present invention with preferred embodiments, but it is not intended to limit the present invention, and all technical solutions obtained by adopting equivalent replacement or equivalent transformation methods fall within the protection scope of the present invention.

Claims (7)

1. A capacitive microelectronic air pressure sensor, characterized in that: comprise a monocrystalline silicon sealed chamber and a capacitive air pressure sensor based on the distance variation between the upper and lower electrodes; Using single crystal silicon as the substrate, a sealed cavity structure is formed through single crystal silicon epitaxial cavity sealing process; through sputtering, photolithography, and corrosion processes, the lower electrode, sacrificial layer, and upper electrode of the capacitor are sequentially grown on the upper surface of the sealed cavity; Finally, while protecting the upper electrode and the lower electrode of the capacitor, the sacrificial layer is isotropically etched to remove the sacrificial layer; metal pads and leads are provided on the single crystal silicon substrate to lead out the upper and lower electrodes of the capacitor respectively. electrode, lower electrode. 2. The capacitive microelectronic air pressure sensor according to claim 1, characterized in that silicon oxide and silicon nitride are grown sequentially on the upper surface of the single crystal silicon substrate, and contact holes are formed by photolithography and etching. 3. The capacitive microelectronic air pressure sensor according to claim 1, characterized in that: the materials of the lower electrode, the upper electrode, the lead wire and the welding pad of the capacitor are all metal. 4. The capacitive microelectronic air pressure sensor according to claim 1, characterized in that: the lower electrode, the upper electrode, the lead wire and the welding pad of the capacitor are made of Al. 5. The capacitive microelectronic air pressure sensor according to claim 1, characterized in that: the material of the sacrificial layer is phosphosilicate glass. 6. The capacitive microelectronic air pressure sensor according to claim 1, characterized in that: the height of the sealed cavity in the single crystal silicon substrate is 4-6 μm. 7. according to the preparation method of the capacitive microelectronic air pressure sensor described in any one of claim 1-6, it is characterized in that: comprise the following steps: Step 1), using N-type single crystal silicon as the substrate, etching shallow grooves on the single crystal silicon substrate through an anisotropic reactive ion etching process; Step 2), while protecting the sidewall of the shallow groove of the single crystal silicon substrate, the single crystal silicon substrate is isotropically etched to prepare for the subsequent epitaxial single crystal silicon cavity sealing process; Step 3), growing monocrystalline silicon epitaxially, forming a sealed cavity inside the monocrystalline silicon substrate; Step 4), growing silicon oxide and silicon nitride sequentially on the upper surface of the single crystal silicon substrate, and forming contact holes by photolithography and etching; Step 5), sputtering the first layer of metal on the surface of silicon nitride, photoetching and etching to form pads, electrical interconnection lines and lower electrodes of capacitors; Step 6), sputtering sacrificial layer material on silicon nitride and the first layer of metal, photolithography and etching to form a sacrificial layer; Step 7), sputtering the second layer of metal on the silicon nitride and the sacrificial layer, forming pads, electrical interconnection lines and the upper electrode of the capacitor by photolithography and etching, and opening a plurality of through holes on the upper electrode of the capacitor as Corrosion of the window of the sacrificial layer between the upper and lower electrodes of the capacitor; Step 8) While protecting the capacitor upper electrode and the capacitor lower electrode, perform isotropic corrosion on the sacrificial layer to expose the leads and pads of the capacitor lower plate.