CN108303567B

CN108303567B - Preparation method of three-mass MEMS capacitance differential type triaxial accelerometer integrated by single chip

Info

Publication number: CN108303567B
Application number: CN201810108278.9A
Authority: CN
Inventors: 郭小伟; 李绍荣; 张孔欣; 王毅
Original assignee: Yangzhou J & V Semiconductor Co ltd
Current assignee: Yangzhou J & V Semiconductor Co ltd
Priority date: 2018-02-02
Filing date: 2018-02-02
Publication date: 2020-04-24
Anticipated expiration: 2038-02-02
Also published as: CN108303567A

Abstract

A method for manufacturing a three-mass MEMS capacitance differential triaxial accelerometer integrated by a single chip. The invention relates to the field of sensors, in particular to a method for manufacturing a three-mass MEMS capacitance differential triaxial accelerometer integrated by a single chip. The three axes of the triaxial accelerometer have respective mass blocks, X, Y, Z triaxial accelerometers are integrated on a single substrate, X, Y axis accelerometers are arranged on two sides of the Z axis accelerometer, and each axis adopts a flat plate differential capacitor. The accelerometer adopts three mass blocks, the cross interference among three axes is minimum, and the stability is good; x, Y, Z, the three directions are all detected by adopting a flat plate differential capacitor, and the detection accuracy is high; the SOI silicon chip process is adopted, the three-axis accelerometers are formed simultaneously, the process is simple, the batch production is easy, and the repeatability is high. The single-chip integrated three-axis accelerometer has the advantages of small size, no need of manual calibration and the like.

Description

Preparation method of three-mass MEMS capacitance differential type triaxial accelerometer integrated by single chip

Technical Field

The invention relates to the field of sensors, in particular to a method for manufacturing a three-mass MEMS capacitance differential type triaxial accelerometer integrated by a single chip.

Background

The capacitive accelerometer is a typical microsensor developed by applying an MEMS technology, has very wide application range, is not only used for general aviation, vehicle control, high-speed railway, robots, industrial automation, prospecting, toys, mobile phones and the like, but also has application in aspects of missile guidance, aircraft navigation and the like, and along with the development of science and technology and further demands of the market, the development of a three-axis accelerometer becomes a trend in order to more comprehensively know motion information of an object. At present, three modes of the three-axis accelerometer are realized, namely a hybrid integrated mode, an in-chip integrated mode, an out-chip integrated mode and a single-chip integrated mode.

The hybrid integrated accelerometer is formed by separately manufacturing 3 single-axis accelerometers and then assembling the accelerometers together to form a three-axis accelerometer. However, in practical application, the defects of overlarge exposed volume, manual calibration and the like cannot meet the market demand, and the method cannot be applied to the field of consumer electronics;

the on-chip and off-chip integrated type accelerometers adopt an integrated type on a horizontal plane, the accelerometers in the vertical direction need a bolt locking device to be connected with the horizontal plane, and the accelerometers also need calibration as the mixed integrated type accelerometers, so that mass production cannot be realized;

the monolithic integration type uses MEMS bulk silicon processing technology or surface micro-machining technology, three axial directions are made on the same substrate, a single mass block or multi-mass block structure is generally adopted, and compared with the former two methods, the monolithic integration type MEMS bulk silicon processing technology or surface micro-machining technology has the characteristics of small volume, no need of manual calibration, easiness in batch production, high repeatability and the like.

However, the single mass block, namely X, Y, Z directions share one mass block, such as an off-set structure based accelerometer, the structure is simple in manufacturing process, acceleration detection in each direction has serious interference, differential detection cannot be realized in the Z direction, and the detection accuracy is not high. Two mass blocks are adopted, usually one mass block is used in the direction of a plane X, Y, a torsion bar type differential comb structure such as a seesaw type accelerometer is adopted in the vertical Z axis, and the Z direction is also interfered by signals detected in the X, Y direction, so that the detection accuracy is influenced; more than three qualities are adopted, a nested structure is usually adopted, the preparation is complex, and the mutual signal interference problem also exists.

Disclosure of Invention

The invention provides a method for preparing a monolithic integrated three-mass differential capacitive accelerometer, wherein three shafts of the three-shaft accelerometer are provided with respective mass blocks, X, Y, Z three-shaft accelerometers are integrated on a single substrate, X, Y-shaft accelerometers are respectively arranged on two sides of a Z-shaft accelerometer, and each axial direction adopts a flat plate differential capacitor.

The technical scheme of the invention is that the method comprises the following steps:

1) slotting on the glass substrate;

2) depositing metal and etching the pattern;

3) etching the device layer of the partial SOI silicon chip;

4) further etching the device layer;

5) connecting the SOI silicon chip and the glass substrate together;

6) thinning the SOI silicon chip operation layer;

7) depositing metal on the operation layer of the SOI silicon chip, and then etching a pattern;

8) etching the SOI silicon chip operation layer by using the mask;

9) etching to remove the oxygen buried layer in the partial region of the SOI silicon chip;

10) and manufacturing the triaxial accelerometer.

In the step 1) of the method provided by the invention, a groove is formed by a wet etching method under the action of a mask and is used for the horizontal axial accelerometer.

In step 2) of the method provided by the invention, the metal deposited on the glass substrate is used as a metal contact of the horizontal and vertical accelerometers;

in the step 3) of the method, part of the SOI device layer is etched, so that a capacitance gap exists between the bottom electrode of the vertical accelerometer and the detection mass;

in the step 4) of the method, the device layer is continuously etched to form the detection quality of the vertical accelerometer and the detection quality of the horizontal accelerometer;

in step 5) of the method provided by the invention, the glass substrate and the SOI silicon wafer are connected;

in the step 6) of the method provided by the invention, the thickness of the operating layer of the SOI silicon chip is reduced;

in the method step 7), the metal deposited on the SOI silicon wafer operation layer is used for electrode contact of the vertical axis accelerometer;

in the method step 8), the mask is used for etching the SOI silicon chip operation layer to obtain a perforated top electrode of the vertical axis accelerometer;

in the step 9), the buried oxide layer in the partial region of the SOI silicon wafer is removed by etching.

The horizontal accelerometer and the horizontal axial accelerometer in the triaxial accelerometer are positioned at two sides of the vertical accelerometer and are arranged in a straight line.

The accelerometer adopts three mass blocks, the cross interference among three axes is minimum, and the stability is good; x, Y, Z, the three directions are all detected by adopting a flat plate differential capacitor, and the detection accuracy is high; the SOI silicon chip process is adopted, the three-axis accelerometers are formed simultaneously, the process is simple, the batch production is easy, and the repeatability is high. The single-chip integrated three-axis accelerometer has the advantages of small size, no need of manual calibration and the like.

Drawings

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a schematic diagram of step 1);

FIG. 3 is a schematic diagram of step 2);

FIG. 4 is a schematic view of step 3);

FIG. 5 is a schematic view of step 4);

FIG. 6 is a schematic view of step 5);

FIG. 7 is a schematic view of step 6);

FIG. 8 is a schematic view of step 7);

FIG. 9 is a schematic view of step 8);

FIG. 10 is a schematic view of step 9);

FIG. 11 is a schematic diagram of the structure of a three-axis accelerometer of the present invention;

figure 12 is a partial block diagram of a tri-axial accelerometer of the present invention.

Detailed Description

The following describes in detail a specific implementation of a method for designing and manufacturing a single-piece single-three-mass differential capacitive accelerometer according to an embodiment of the present invention with reference to the accompanying drawings.

The thickness, shape and size of the layers in the drawings are not to be construed as actual proportions, but are merely illustrative of the invention.

The embodiment of the invention provides a design and preparation method of a single-chip three-mass differential capacitive accelerometer, the method integrates a three-axis accelerometer into a single chip, and the preparation process is simple. As shown in fig. 1, the method specifically comprises the following steps:

110 slotting on the glass substrate;

120 depositing metal and etching the pattern;

130 etching part of the device layer of the SOI silicon wafer;

140 further etching the SOI silicon device layer;

150 connecting the SOI silicon chip and the glass substrate together;

160 thinning an SOI silicon chip operation layer;

170 depositing metal on the operation layer of the SOI silicon chip and etching a pattern;

etching the operation layer by 180 masks;

190 etching the oxygen buried layer in the partial area of the SOI silicon chip;

and (5) manufacturing the triaxial accelerometer.

Since the manufacturing methods in the x and y directions are the same, but the orientations are different, the following explanation of the manufacturing method only presents the manufacturing method of the accelerometer in the x or y direction and the z direction.

Wherein, as shown in fig. 2, a groove is formed on the glass substrate, and the glass substrate is wet-etched by using 49% HF solution, so as to achieve the effect shown in fig. 2, wherein 1 in the figure represents the glass substrate, and 2 represents the groove formed by wet etching;

metal deposited on the glass substrate as shown in fig. 3, wherein 3 represents Cr/Au;

etching the SOI device layer as shown in FIG. 4 so that there is a 3um capacitance gap between the bottom electrode of the vertical accelerometer and the proof mass, where 4 represents the 300um thick operating layer of the SOI wafer, 5 represents the 2um thick buried oxide layer of the SOI wafer, and 6 represents the partially etched 35um thick device layer;

as shown in fig. 5, the device layer is etched continuously, wherein 7 represents the detection quality in the horizontal direction, and 8 represents the detection quality in the vertical direction;

as shown in fig. 6, the silicon wafer and the glass substrate are connected by using an anodic bonding mode, the temperature of the anodic bonding mode is low, no intermediate material is required to be added, and the deformation of the workpiece is small;

as shown in fig. 7, the operation layer of the SOI silicon wafer is thinned to 50um by polishing, and 9 in the figure shows the thinned operation layer of the SOI silicon wafer;

as shown in fig. 8, metal is deposited on the SOI operating layer as the top electrode of the vertical axis accelerometer, and 10 is deposited metal Cr/Au;

as shown in fig. 9, the operation layer of the SOI silicon wafer is etched to form a plate capacitor, where 11 denotes the plate capacitor of the accelerometer in the vertical direction, and multiple plates are detected by a difference method to eliminate the interference of ambient temperature, humidity, and other factors to the signal, and 12 denotes the plate capacitor in the horizontal direction;

as shown in fig. 10, BHF etches the buried oxide layer of the SOI silicon wafer to form a plate capacitor in the vertical and horizontal directions;

As shown in fig. 11, a top view of the single-element single-mass capacitance differential accelerometer is shown, in which 13 is a top view of the accelerometer in the Y-axis direction, 14 is a top view of the accelerometer in the Z-axis direction, and 15 is an X-axis one. The X-axis accelerometer and the Y-axis accelerometer are positioned on two sides of the Z-axis accelerometer and are arranged in a straight line, so that the space is fully utilized, and the arrangement is reasonable.

As shown in fig. 12, a partial detail view of a monolithic three-mass capacitance differential accelerometer, in which 16, 18 represent two electrodes in the X direction, 23, 25 represent two electrodes in the Y direction, 17, 24 represent masses in the X and Y directions, respectively, and 19, 20, and 21 represent top, mass, and bottom electrodes in the Z direction, respectively.

In the invention, X, Y, Z accelerometers in three directions are integrated on a single substrate; x, Y, Z the accelerometers in three directions have respective mass blocks, and the directions are detected independently without mutual interference; each axial accelerometer adopts flat plate differential capacitance detection;

the X-axis accelerometer and the Y-axis accelerometer are positioned at two sides of the Z-axis accelerometer and are arranged in a straight line; and (3) adopting an SOI (silicon on insulator) process, and simultaneously molding the three-axis accelerometers.

Claims

1. A method for preparing a three-mass MEMS capacitance differential triaxial accelerometer integrated by a single chip is characterized by comprising the following steps:

1) slotting the top surface of the glass substrate and being used for the horizontal axial accelerometer;

2) depositing metal on the top surface of the glass substrate for metal contact of the horizontal and vertical accelerometers;

3) the SOI silicon chip comprises a device layer, an oxygen burying layer and an operation layer from top to bottom in sequence, and the device layer of the SOI silicon chip is etched;

4) further etching the device layer to form the detection quality of the vertical accelerometer and the horizontal accelerometer;

5) bonding and connecting the SOI silicon chip and the glass substrate;

6) thinning the thickness of the SOI silicon chip operation layer;

7) depositing metal on an operation layer of the SOI silicon wafer for electrode contact of the vertical axis accelerometer;

8) etching the operation layer of the SOI silicon chip by using the mask to form a perforated top electrode of the vertical axis accelerometer;

9) etching to remove the oxygen buried layer in the SOI silicon chip;

10) obtaining a three-axis accelerometer;

and 5) connecting the device layer of the SOI silicon chip with the metal on the glass substrate in an anodic bonding mode.

2. The method for manufacturing a monolithically integrated three-mass MEMS capacitive differential triaxial accelerometer according to claim 1, wherein in step 1), the glass substrate is wet etched with an HF solution.

3. The method for manufacturing a monolithically integrated three-mass MEMS capacitive differential triaxial accelerometer according to claim 1, wherein in step 9), the partially buried oxide layer of the SOI silicon wafer is etched by BHF to form the plate capacitors in vertical and horizontal directions.

4. The method of claim 1, wherein horizontal accelerometers and horizontal axial accelerometers of the three-axis accelerometer are positioned on two sides of a vertical accelerometer and are arranged in a straight line.