KR101794764B1 - Mems pressure sensor and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a MEMS pressure sensor that minimizes temperature sensitivity and a method of manufacturing the same, and a MEMS pressure sensor according to an embodiment of the present invention includes a glass substrate on which a via hole is formed; A silicon substrate formed on the glass substrate; A piezoresistor filled in a groove formed in the silicon substrate; An insulating layer formed on the exposed surface of the silicon substrate and the piezoresistor; A temperature compensation resistor formed on the insulating film, the resistance value of which decreases as the temperature increases; And a fine metal wiring connecting the temperature compensation resistor and the piezoresistor.

Description

[0001] MEMS PRESSURE SENSOR AND MANUFACTURING METHOD THEREOF [0002]

The present invention relates to a MEMS (Micro Electro Mechanical System) pressure sensor and a manufacturing method thereof.

In general, MEMS pressure sensors are made by a combination of insulating film deposition technology, metal deposition and wiring technology, ion implantation technology, fine patterning technology, silicon etching technology, glass etching technology and substrate bonding technology. The pressure of the pressure sensor is sensed by a piezo resistance, and the piezoresistance is injected or diffused into a silicon wafer substrate to form a plurality of resistance terminals. However, the piezoresistance is affected by the temperature even if there is no change in the pressure. As the temperature increases, the resistance value increases. When the temperature decreases, the resistance value decreases. Also, in order to form a Wheatstone bridge circuit by connecting a plurality of these piezoresistors, a metal thin film deposition and fine pattern formation technique is required, and an insulating film deposition technique is also applied for metal wiring insulation.

It is an object of the present invention to provide a MEMS pressure sensor that minimizes temperature sensitivity and a method of manufacturing the same.

A MEMS pressure sensor according to an embodiment of the present invention is a MEMS pressure sensor having a piezoresistor, comprising: a glass substrate on which a via hole is formed; A silicon substrate formed on the glass substrate; A piezoresistor filled in a groove formed in the silicon substrate; An insulating layer formed on the exposed surface of the silicon substrate and the piezoresistor; A temperature compensation resistor formed on the insulating film, the resistance value of which decreases as the temperature increases; And a fine metal wiring connecting the temperature compensation resistor and the piezoresistor.

In an embodiment of the present invention, a portion of the silicon substrate located between the lower portion of the piezoresistor and the via hole may be a thin film.

In an embodiment of the present invention, the piezoresistors may be one or more.

In an embodiment of the present invention, the temperature compensation resistors may be one or more.

In an embodiment of the present invention, the temperature compensation resistor may be a thin film.

In an embodiment of the present invention, the temperature compensation resistor may be a resistor having a negative temperature coefficient (NTC) characteristic.

In an embodiment of the present invention, the temperature compensating resistor may be a thin film of transition metal oxide.

In an embodiment of the present invention, the temperature compensating resistor is formed on an insulating film formed on the exposed surface of the silicon substrate, and the insulating film formed with the temperature compensating resistor is formed to have a thickness larger than the height of the insulating film formed on the piezo- It can be projected high.

A method of manufacturing a MEMS pressure sensor according to an embodiment of the present invention includes the steps of: forming a piezoresistor in a groove formed in a silicon substrate; Forming an insulation layer on the exposed surface of the silicon substrate and the piezoresistor; Forming a temperature compensation resistor in which a resistance value decreases as a temperature increases on an insulating film formed on an exposed surface of the silicon substrate; Forming a metal wiring connecting the temperature compensation resistor and the piezoresistor; And bonding the silicon substrate to a glass substrate having a pressure hole formed thereon.

The present invention can reduce the temperature sensitivity by disposing one or more temperature compensation resistors opposite in temperature characteristics to a plurality of pressure resistive sensing resistors in the MEMS structure to offset the temperature characteristic of the piezoelectric resistors.

The present invention can minimize the size of the pressure sensor while reducing the influence on the temperature change of the MEMS pressure sensor.

1 is a block diagram showing a configuration of a MEMS pressure sensor according to an embodiment of the present invention.
2 is a top view of a MEMS pressure sensor (MEMS structure) according to the present invention.
3 is a cross-sectional view illustrating a method of manufacturing a MEMS pressure sensor (MEMS structure) according to the present invention.
4 is a cross-sectional view showing another embodiment according to the present invention.
5 is a circuit diagram of a piezoresistor and an NTC resistor according to an embodiment of the present invention.
6 is an output characteristic diagram of an evaluation test result of a pressure sensor according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals are used to designate identical or similar elements, and redundant description thereof will be omitted. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role. In the following description of the embodiments of the present invention, a detailed description of related arts will be omitted when it is determined that the gist of the embodiments disclosed herein may be blurred. In addition, it should be noted that the attached drawings are only for easy understanding of the embodiments disclosed in the present specification, and should not be construed as limiting the technical idea disclosed in the present specification by the attached drawings.

In general, MEMS pressure sensors are made by a combination of insulating film deposition technology, metal deposition and wiring technology, ion implantation technology, fine patterning technology, silicon etching technology, glass etching technology and substrate bonding technology. The pressure of the pressure sensor is sensed by a piezo resistance, and the piezoresistance is injected or diffused into a silicon wafer substrate to form a plurality of resistance terminals. However, the piezoresistance is affected by the temperature even if there is no change in the pressure. As the temperature increases, the resistance value increases. When the temperature decreases, the resistance value decreases. Also, in order to form a Wheatstone bridge circuit by connecting a plurality of these piezoresistors, a metal thin film deposition and fine pattern formation technique is required, and an insulating film deposition technique is also applied for metal wiring insulation.

In general, the resistance of most objects increases with increasing temperature. The piezoresistance formed through ion implantation increases as the temperature increases. This increase in resistance affects the intrinsic function of the pressure sensor, in which the resistance and output must change only by pressure. Therefore, a conventional precision pressure sensor uses a method of forming and compensating a compensation circuit by forming a piezoresistance in the MEMS structure to reduce the influence on the temperature, or attaching a temperature compensation circuit to the outside. These methods require additional temperature sensors, compensation circuits, etc. in addition to the MEMS pressure sensor structure, and the post-processing of the sensor output is costly and time consuming and increases in size.

In the present invention, not only the MEMS technology but also a metal oxide deposition technique is applied to manufacture a compensation resistor. Among these metal oxides, there are transition metal oxides formed by mixing Mn, Co, Ni, Cr, Fe, etc., and the resistance thereof decreases with increasing temperature. The resistance of this characteristic is called NTC (Negative Temperature Coefficient) resistance.

That is, in the present invention, a piezoresistance is formed inside a silicon substrate by applying a micro electro mechanical system (MEMS) technology, and a compensation resistor formed by a thin film deposition technique is connected to a fine metal wiring. The applied MEMS technology minimizes the size of the pressure sensor and makes it insensitive to temperature.

In manufacturing a MEMS pressure sensor, in order to minimize the influence of the piezoresistance sensing pressure on the characteristics of the piezoresistive sensor, The temperature characteristic of the resistor can be compensated. These NTC resistors may be deposited as a thin film by depositing a transition metal oxide or may be subjected to individual NTC resistors. When the NTC resistance is fabricated or placed on the MEMS structure together with the piezoresistance, the temperature compensation effect can be obtained by attenuating the increase in the piezoresistance value as the temperature rises.

In addition, the present invention minimizes the size of the MEMS pressure sensor structure by preventing the size of the MEMS pressure sensor structure from increasing by forming or arranging the piezoresistance and NTC resistor in the same manner, and minimizing the use of a complicated compensation circuit or temperature sensor The production cost can also be reduced.

Hereinafter, a MEMS pressure sensor according to an embodiment of the present invention and a method of manufacturing the same will be described with reference to the drawings.

1 is a block diagram showing a configuration of a MEMS pressure sensor according to an embodiment of the present invention.

1, a MEMS pressure sensor 100 according to an embodiment of the present invention includes:

A glass substrate 160 on which a via hole (pressure hole) 161 is formed;

A silicon substrate 150 formed on a glass substrate 160;

A piezoresistor (piezoresistive thin film) 110 filled in a groove formed in the silicon substrate 150;

An insulation layer 120 formed on the exposed surface of the silicon substrate 150 and the piezoresistor (piezoresistive thin film) 110;

And a fine metal wiring 130 formed on the insulating film 120 and connecting the piezoresistor 110 with a temperature compensation resistor (NTC resistor) 140 whose resistance value decreases as the temperature increases. A temperature compensation resistor (NTC resistor) 140 may be formed on the insulating film 120. A portion of the silicon substrate 150 located between the lower portion of the piezoresistor 110 and the via hole (pressure hole) 161 is formed in the form of a thin film 151.

The MEMS pressure sensor 100 according to the embodiment of the present invention may have one or more piezoresistors 110 formed thereon. One or more temperature compensation resistors (NTC resistors) 140 may be formed on the MEMS pressure sensor 100 according to an embodiment of the present invention. The temperature compensation resistor (NTC resistor) 140 may be formed as a thin film.

2 is a plan view of a MEMS pressure sensor (MEMS structure) according to the present invention,

3 is a cross-sectional view illustrating a method of manufacturing a MEMS pressure sensor (MEMS structure) according to the present invention. Such a MEMS structure is fabricated by a process in the order of (a) to (e) in FIG.

As shown in FIGS. 2 and 3, a plurality of resist patterns are formed on the silicon substrate 150, and the resistors 110 are formed by ion implantation or diffusion according to the pattern.

The lower silicon substrate 150 of the formed piezoresistor 110 is etched to form a thin film 151.

The piezoresistor 110 is protected by an insulating film 120 and the insulating film 120 is formed not only on the piezoresistor 110 but also on the exposed surface (support) of the silicon substrate 150.

One or more temperature compensating resistors 140 having a temperature characteristic opposite to that of the piezoresistor 110 are formed on the insulating layer 120. The temperature compensating resistor 140 is formed on the exposed surface of the silicon substrate 150, (Not shown).

Since the piezoresistor 110 increases in resistance as the temperature increases, the temperature compensation resistor 140 forms an NTC resistor whose resistance decreases as the temperature increases. The NTC resistor has a cubic spinel crystal structure of a transition metal oxide composed of some combination of Mn, Co, Ni, Cr, and Fe, and the material is not limited in the present invention. Such a transition metal oxide can be deposited as a thin film by vapor deposition at room temperature, sputtering or the like, and the deposition method is not limited in the present invention.

A fine metal wiring 130 is formed to connect the electrical signals of the piezoresistor 110 and the NTC resistor 140. The silicon substrate 150 having the piezoresistor 110 and the NTC resistor 140 thus fabricated is bonded to the glass substrate 160. When a pressure hole (via hole) 161 is formed in the lower part of the glass substrate 160, the differential pressure sensor MEMS structures 100 and 101 measure the difference between the lower pressure and the upper pressure. At the lower part of the glass substrate 160, (Not shown) to measure the atmospheric pressure.

In addition, the NTC resistors can be individually joined to the pressure sensor MEMS structure, and this other embodiment is shown in Fig.

4 is a cross-sectional view showing another embodiment according to the present invention.

4, in order to connect one or more NTC resistors 141 to the piezoresistor 110, steps (C) and (d) of FIG. 3 may be performed. In order to electrically connect the individual NTC resistor 141 to the piezoresistor 110 by the metal wire 130, a conductive bonding agent may be applied to the metal wire 130. However, in the present invention, It does not.

The temperature compensating resistor 141 is formed on the insulating layer 120 formed on the exposed surface of the silicon substrate 150 and the insulating film on which the temperature compensating resistor 141 is formed is separated from the piezo- Is higher than the height of the insulating film formed on the substrate 110.

An embodiment in which a plurality of the piezoresistors 110 and one NTC resistor 150 are connected to each other is shown in Fig.

5 is a circuit diagram of the piezoresistors 201 to 204 and the NTC resistor 205 according to the embodiment of the present invention.

As shown in FIG. 5, it is expressed that the resistances of the plurality of piezoresistors 202, 203, 204, and 205 increase as the temperature increases, and the resistance of the NTC resistor 205 decreases as the temperature increases . 5, the input signal and the output signal of the pressure sensor can be known.

Next, an NTC resistor 140 for temperature compensation is applied to evaluate whether or not the effect of temperature on the target pressure sensor can be reduced.

6 is an output characteristic diagram of an evaluation test result of a pressure sensor according to another embodiment of the present invention. As shown in FIG. 4, in another embodiment of the present invention, from -40 ° C to 85 ° C, application of an individual NTC resistor 141 The results are as follows. The axis of abscissas is an axis with respect to temperature, and the axis of ordinates is an axis showing a change in output characteristic of the pressure sensor according to temperature. At this time, no pressure was applied to eliminate the influence on the pressure. 4, the pressure sensor output characteristic with the NTC resistor 141 removed is shown by the dotted line 301, and the pressure sensor output characteristic of the embodiment using the NTC resistor 141 is shown by the solid line 302. It can be seen that the solid line 302 to which the individual NTC resistor 141 is applied has a small slope with respect to the temperature increase as compared with the dotted line 301 showing a large change as the temperature increases. It can be seen that the pressure sensor according to the present invention has a compensation effect in which the characteristics of the NTC resistor cancel the temperature characteristic of the piezoresistor.

The foregoing detailed description should not be construed in all aspects as limiting and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

Claims (6)

In a MEMS pressure sensor having a piezoresistor,
A glass substrate on which a via hole is formed;
A silicon substrate formed on the glass substrate;
A piezoresistor filled in a groove formed in the silicon substrate;
An insulating layer formed on the exposed surface of the silicon substrate and the piezoresistor;
A temperature compensation resistor formed on the insulating film so as not to be affected by the pressure, the resistance value of which decreases as the temperature increases;
And a fine metal wiring connecting the temperature compensation resistor and the piezoresistor,
Wherein the temperature compensating resistor cancels the temperature characteristic of the piezoresistor. The MEMS pressure sensor according to claim 1, wherein the temperature compensation resistors are one or more. The MEMS pressure sensor according to claim 1, wherein the temperature compensation resistor is a resistor having a negative temperature coefficient (NTC) characteristic. The MEMS pressure sensor of claim 1, wherein the temperature compensating resistor is a thin film of transition metal oxide. The temperature compensation device according to claim 1,
Wherein the insulating layer formed on the exposed surface of the silicon substrate is protruded higher than the insulating layer formed on the piezoresistors so as to be spaced apart from the piezoresistors. A method of manufacturing a MEMS pressure sensor having a piezoresistor,
Forming a piezoresistor in a groove formed in the silicon substrate;
Forming an insulation layer on the exposed surface of the silicon substrate and the piezoresistor;
Forming a temperature compensation resistor whose resistance value decreases as the temperature increases on the insulating film formed on the exposed surface of the silicon substrate so as not to be affected by the pressure;
Forming a metal wiring connecting the temperature compensation resistor and the piezoresistor;
And bonding the silicon substrate and the glass substrate on which the pressure hole is formed,
Wherein the temperature compensating resistor cancels the temperature characteristic of the piezoresistor.

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