WO2018176549A1

WO2018176549A1 - Method for manufacturing gas-sensitive resistor, and gas sensor manufactured by using method

Info

Publication number: WO2018176549A1
Application number: PCT/CN2017/082347
Authority: WO
Inventors: 赖建文
Original assignee: 上海申矽凌微电子科技有限公司
Priority date: 2017-04-01
Filing date: 2017-04-28
Publication date: 2018-10-04
Also published as: CN107192744A

Abstract

A method for manufacturing a gas-sensitive resistor, and a gas sensor manufactured by using the method. The method comprises the following steps: step 1, manufacturing a hollow silicon cavity (8) on the back side of a silicon wafer (1) by means of a two-stage etching process; step 2, simultaneously manufacturing a heating resistor (16) and gas-sensitive resistor measurement electrodes (11, 12, 13) on the front side of the silicon wafer (1) by using the same metal layer (6); and step 3, manufacturing electrodes of the gas-sensitive resistor and the heating resistor (16) on the front side of the silicon wafer (1). According to the method for manufacturing a gas-sensitive resistor, a dry and wet two-step etching process is used, and thus the etching efficiency and quality are significantly improved. By means of the technological process, one layer of metal wiring can be used for achieving both the heating function and the resistance testing function of the gas-sensitive resistor, and the process is simplified. A four-end Kevin structure is used to measure a gas-sensitive material, and the electric resistivity change of the material can be precisely measured. A Lift-off process is used to manufacture the gas-sensitive resistor and an aluminum wire, and multiple sensor units made of a gas-sensitive material can be independently manufactured. Moreover, the method is compatible with a low-cost aluminum-copper metal wiring process.

Description

Method for manufacturing gas sensitive resistor and gas sensor manufactured by using same

Technical field

The present invention relates to a method of manufacturing a sensor, and more particularly to a method of manufacturing a gas sensitive resistor and a gas sensor manufactured using the same.

Background technique

Sensors for detecting gases with gas-sensitive metal oxides have been studied for a long time, and related patents have also been applied for and granted. Because the gas sensing properties of metal oxides can only be manifested at higher temperatures, typical gas sensors require heating and thermal insulation. Therefore, the structure of the gas sensor is relatively complicated. The general structure has the following parts: a silicon back cavity structure; a metal heating layer, a wiring metal layer, and a gas sensing material layer. The conventional gas sensor of the prior art has the following disadvantages: (1) the selectivity difference of the silicon cavity prepared by dry etching makes the structure uneven and unstable; (2) the electrode connection of the heating resistor and the gas sensitive resistor is different. The metal layer makes the structure complicated and the consistency is poor; (3) It can only be used as a gas-sensitive material, and it is difficult to make a variety of gas sensors; (4) It is difficult to be compatible with the aluminum-copper metal wiring process with low cost and reliable process.

The quality of the environment is closely related to people's lives and work comfort and health. In recent years, as people's requirements for the environment have become higher and higher, people hope to have simple, reliable and inexpensive methods and products to detect the quality of ambient air, such as carbon monoxide, flammable gases, ethanol, NO2, etc. The amount of gas in the air. The use of gas sensing properties of metal oxides to measure gas content is a relatively common method. However, such sensors have a long manufacturing process, a complicated structure, and low consistency and reliability.

Summary of the invention

In view of the deficiencies in the prior art, the object of the present invention is to provide a gas varistor which is simplified in process, high in structural stability, and capable of fabricating a plurality of gas sensing units on the same structure to realize multi-gas detecting function. Method and gas sensor manufactured using the method.

To solve the above technical problem, the present invention provides a method of manufacturing a gas sensitive resistor, comprising the following steps:

Step 1: forming an empty silicon cavity on the back side of the silicon wafer;

Step 2, fabricating a heating resistor and a gas resistance measuring electrode on the front side of the silicon wafer;

In step 3, a heating resistor electrode is formed on the front side of the silicon wafer.

Preferably, step 1 comprises:

Step 1, in the back side of the silicon wafer, a two-step etching method is used to fabricate an empty silicon cavity;

Step 2: simultaneously fabricating a measuring electrode of a heating resistor and a gas resistance resistor on the front surface of the silicon wafer with the same metal layer;

In step 3, a gas sensing resistor and an electrode for heating the resistor are fabricated on the front side of the silicon wafer.

Preferably, step 1 comprises:

Step 1.1, simultaneously growing a first dielectric layer on the front and back sides of the silicon wafer;

Step 1.2, performing photoreceptor sensing on the back side of the silicon wafer;

Step 1.3, dry etching the silicon wafer substrate on the back surface to form a first-order silicon cavity;

In step 1.4, the silicon substrate on the back side is wet-etched until the first dielectric layer forms a second-order silicon cavity; the first-order silicon cavity and the second-order silicon cavity are combined into an empty silicon cavity.

Preferably, step 2 comprises:

Step 2.1, depositing a metal thin film layer by physical vapor deposition on the first dielectric layer;

Step 2.2, performing photolithography and dry etching on the metal thin film layer to form four gas resistance measuring electrodes and heating resistors;

Step 2.3, depositing a second dielectric layer on the metal thin film layer by plasma enhanced chemical vapor deposition;

Step 2.4, performing photolithography and dry etching on the second dielectric layer, forming a first contact hole penetrating the second dielectric layer on the second dielectric layer;

Step 2.5, coating a photoresist on the second dielectric layer;

Step 2.6, performing photoreceptor sensitization and development on the photoresist to obtain a metal oxide gas varistor pattern, and the photoresist in the gas varistor pattern is removed by the developer after development, and the photoresist outside the pattern is retained;

Step 2.7, depositing a metal oxide film on the photoresist and the second dielectric layer by physical vapor deposition, the metal oxide film covering the second dielectric layer and the four gas resistance measuring electrodes and heating in the gas resistance pattern a metal oxide film covering the photoresist outside the gas resistance pattern;

Step 2.8, removing the photoresist, removing the metal oxide film covering the photoresist from the gas resistance pattern, leaving a metal oxide film in the gas resistance pattern;

In step 2.9, the metal oxide film is baked to form a gas sensitive resistor.

Preferably, step 3 comprises:

Step 3.1, performing photolithography and etching on the second dielectric layer covered by the non-metal oxide film, forming a second contact hole penetrating through the second dielectric layer on the second dielectric layer, and simultaneously retaining the photoresist;

Step 3.2, depositing an alloy thin film on the photoresist and the second contact hole by physical vapor deposition;

In step 3.3, the photoresist is removed, and the alloy film is formed into a Pad pattern. The Pad alloy film is connected to the underlying metal film layer of the heating resistor or the metal film layer of the measuring electrode of the gas sensor through the second contact hole.

Preferably, the thickness of the first dielectric layer is 0.5 micrometer to 2 micrometers, the material of the first dielectric layer is silicon oxide or silicon nitride; the thickness of the second dielectric layer is 100 nanometers to 1000 nanometers, and the material of the second dielectric layer is Silicon oxide or silicon nitride.

Preferably, in step 1.3, the silicon wafer substrate on the back side is dry etched, and the remaining silicon wafer substrate has a thickness of 10 micrometers to 100 micrometers to form a first-order silicon cavity.

Preferably, the metal thin film layer has a thickness of 100 nm to 2 μm, and the metal thin film layer is made of a refractory metal, preferably a metal tungsten or a tungsten titanium alloy.

Preferably, the metal oxide film has a thickness of 100 nm to 800 nm, and the metal oxide film is made of a gas sensing material, preferably SnO ₂ , ZnO, TiO ₂ or SnO ₂ doped with Fe, Zn, Pt or Pd. , ZnO or TiO ₂ ;

The alloy film has a thickness of 0.5 μm to 3 μm, and the alloy film is made of an aluminum-copper alloy or an aluminum-copper-silicon alloy.

Preferably, in step 2.9, the metal oxide film is baked in a vacuum or nitrogen atmosphere at a temperature of 300 ° C to 900 ° C for a period of 10 minutes to 8 hours.

A gas sensor manufactured by a method of manufacturing a gas sensitive resistor.

Compared with the prior art, the beneficial effects of the present invention are as follows: the dry-wet two-step process can significantly improve the efficiency and quality of etching. The process can use a layer of metal wiring to simultaneously achieve the heating function and resistance test function of the gas sensor, simplifying the process. Gas-sensitive materials are measured using a four-terminal Kevin structure that accurately measures the resistivity of a material at the same time. The invention adopts the Liftoff process to manufacture a gas-sensitive resistor and an aluminum metal wire, and can independently manufacture a sensing unit of a plurality of gas-sensitive materials. The process flow of the invention can be compatible with the mature low-cost aluminum-copper metal wiring process at the same time, which is beneficial to mass production of the product.

DRAWINGS

Other features and advantages of the present invention will become more apparent from the detailed description of the appended claims.

1 is a schematic view showing a manufacturing method of a gas-sensitive resistor of the present invention;

2 is a schematic view showing the manufacturing method of the gas-sensitive resistor of the present invention

3 is a schematic view 3 of a method for manufacturing a gas sensitive resistor of the present invention;

4 is a schematic view showing the manufacturing method of the gas sensitive resistor of the present invention.

FIG. 5 is a schematic view showing the manufacturing method of the gas sensitive resistor of the present invention.

6 is a schematic view showing a manufacturing method of a gas-sensitive resistor of the present invention.

Figure 7 is a schematic view showing the manufacturing method of the gas sensitive resistor of the present invention.

Figure 8 is a schematic view showing the manufacturing method of the gas-sensitive resistor of the present invention

Fig. 9 is a schematic view 9 showing a method of manufacturing a gas-sensitive resistor of the present invention.

detailed description

The invention will now be described in detail in connection with specific embodiments. The following examples are intended to further understand the invention, but are not intended to limit the invention in any way. It should be noted that a number of changes and modifications may be made by those skilled in the art without departing from the inventive concept. These are all within the scope of protection of the present invention.

As shown in FIG. 1 to FIG. 9, the manufacturing method of the gas-sensitive resistor of the present invention comprises: Step 1: growing a first dielectric layer of silicon oxide or silicon nitride on the front and back surfaces of a 100-crystal N-type or P-type silicon wafer 1. 2, the thickness is between 0.5 microns and 2 microns;

Step 2: Make the first mask 3 (photosensitive) on the back of the silicon wafer;

Step 3: first dry etching the back silicon substrate, the remaining silicon thickness is between about 10 microns and 100 microns, forming a first-order silicon cavity 4;

Step 4: further wet etching the back silicon wafer 1 to stop on the first dielectric layer 2 on the surface to form a second-order silicon cavity 5, a first-order silicon cavity 4 and a second-order silicon cavity 5 to synthesize an empty silicon cavity Body 8; Since the wet silicon etching has good selectivity to the dielectric layer, the etching is automatically stopped on the dielectric layer, the process is stable, and the structure is reliable.

Step 5: depositing a metal thin film layer 6 with a thickness of between 100 nanometers and 2 micrometers, and the material may be metal tungsten, or a tungsten-titanium alloy, or other refractory metal. The metal thin film layer 6 simultaneously serves two important functions: one as a heating resistor and the other as an electrode for measuring a gas-sensitive metal oxide.

Step 6: Perform a second front side photolithography and dry etching on the metal thin film layer 6 to form a measuring electrode of a heating resistor and a gas resistance resistor.

Step 7: depositing a second dielectric layer 7 of silicon oxide or silicon nitride on the metal thin film layer 6 by a PECVD process to a thickness of between 100 nm and 1000 nm.

Step 8: performing a third front side photolithography and a second dielectric layer etching on the silicon oxide or silicon nitride second dielectric layer 7, to obtain a first contact hole 9. The first contact hole 9 is exposed by the first gas-sensitive resistance measuring electrode 11, the second gas-sensitive resistance measuring electrode 12, the third gas-sensitive resistance measuring electrode 13, and the fourth gas-sensitive resistance measuring electrode 14, which is measuring gas sensitivity. The four electrodes of the Keven structure of the resistor.

Step 9: doing the fourth photomask sensitization, obtaining a metal oxide gas varistor pattern, leaving the photoresist 17;

Step 10: depositing a metal oxide film 10 on the photoresist 17 by a PVD method, the thickness of which is between 100 nm and 800 nm, and the material may be a gas sensitive substance such as SnO ₂ , ZnO or TiO ₂ , or through Fe, Such a gas-sensitive substance doped with an element such as Zn, Pt or Pd.

Step 11: removing the photoresist using a solvent, and leaving the gas-sensitive metal oxide film covering the first gas-resistance measuring electrode 11, the second gas-resistance measuring electrode 12, the third gas-resistance measuring electrode 13 and the first The first gas sensing resistor measures the first contact hole 9 of the electrode 14 and is connected to the outer test pad, respectively. At the same time, the metal oxide film 10 is covered under the heating resistor 16 formed of the first metal layer 6, but is electrically isolated from the second dielectric layer 7 by silicon oxide or silicon nitride.

Step 12: Baking in a vacuum or nitrogen atmosphere at a certain temperature to crystallize the metal oxide to form a gas-sensitive resistor of a desired stable property. The baking temperature is between 300 ° C and 700 ° C and the time is between 10 minutes and 8 hours.

Step 13: If two or more gas sensitive materials are required, the above process steps 9 to 12 can be repeated.

Step 14: performing a fifth photolithography on the silicon oxide or silicon nitride second dielectric layer 7, etching the silicon oxide or silicon nitride second dielectric layer 7, forming a second contact hole, and leaving the photoresist.

Step 15: PVD deposits an aluminum or aluminum-copper alloy film 15 having a thickness between 0.5 microns and 3 microns. After removing the photoresist with a solvent, the aluminum or aluminum-copper alloy film 15 is formed on the electrode of the heating resistor 16 formed in the second contact hole and the first metal layer 6, and the first gas-resistance measuring electrode 11, and the second gas-sensitive resistance measurement The electrode 12, the third gas-sensitive resistance measuring electrode 13 and the fourth gas-sensitive resistance measuring electrode 14 are connected as an external pad.

Step 16: Plan view of the entire structure, including the heating resistor 16 and its electrodes, the first gas-sensitive resistance measuring electrode 11, the second gas-sensitive resistance measuring electrode 12, and the third gas-sensitive resistor of the Kevin structure for measuring the characteristics of the gas-sensing resistance The measuring electrode 13 and the fourth gas-sensitive resistance measuring electrode 14 are used.

Step 17: At this point, the new gas sensor MEMS structure completes the process.

Figure 9 is an equivalent circuit diagram including the both ends of the heating resistor 16Rheater, the first gas-sensitive resistance measuring electrode 11, the second gas-sensitive resistance measuring electrode 12, the third gas-sensitive resistance measuring electrode 13 and the first of the gas-sensitive resistor Rgas The four gas resistance measuring electrode 14 is used.

The present invention also provides a gas sensor manufactured using the above-described manufacturing method of a gas-sensitive resistor.

The specific embodiments of the present invention have been described above. It is to be understood that the invention is not limited to the specific embodiments described above, and various changes or modifications may be made by those skilled in the art without departing from the scope of the invention. The features of the embodiments and the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims

A method of manufacturing a gas sensitive resistor, comprising the steps of:

Step 1, in the back side of the silicon wafer, a two-step etching method is used to fabricate an empty silicon cavity;

Step 2: simultaneously fabricating a measuring electrode of a heating resistor and a gas resistance resistor on the front surface of the silicon wafer with the same metal layer;

In step 3, a gas sensing resistor and an electrode for heating the resistor are fabricated on the front side of the silicon wafer.
The method of manufacturing a gas resistance resistor according to claim 1, wherein the step 1 comprises:

Step 1.1, simultaneously growing a first dielectric layer on the front and back sides of the silicon wafer;

Step 1.2, performing photoreceptor sensing on the back side of the silicon wafer;

Step 1.3, dry etching the silicon wafer substrate on the back surface to form a first-order silicon cavity;

In step 1.4, the silicon substrate on the back side is wet-etched until the first dielectric layer forms a second-order silicon cavity; the first-order silicon cavity and the second-order silicon cavity are combined into an empty silicon cavity.
The method of manufacturing a gas resistance resistor according to claim 2, wherein the step 2 comprises:

Step 2.1, depositing a metal thin film layer by physical vapor deposition on the first dielectric layer;

Step 2.2, performing photolithography and dry etching on the metal thin film layer to form four gas resistance measuring electrodes and heating resistors;

Step 2.3, depositing a second dielectric layer on the metal thin film layer by plasma enhanced chemical vapor deposition;

Step 2.4, performing photolithography and dry etching on the second dielectric layer, forming a first contact hole penetrating the second dielectric layer on the second dielectric layer;

Step 2.5, coating a photoresist on the second dielectric layer;

Step 2.6, performing photoreceptor sensitization and development on the photoresist to obtain a metal oxide gas varistor pattern, and the photoresist in the gas varistor pattern is removed by the developer after development, and the photoresist outside the pattern is retained;

Step 2.7, depositing a metal oxide film on the photoresist and the second dielectric layer by physical vapor deposition, the metal oxide film covering the second dielectric layer and the four gas resistance measuring electrodes and heating in the gas resistance pattern a metal oxide film covering the photoresist outside the gas resistance pattern;

Step 2.8, removing the photoresist, removing the metal oxide film covering the photoresist from the gas resistance pattern, leaving a metal oxide film in the gas resistance pattern;

In step 2.9, the metal oxide film is baked to form a gas sensitive resistor.
The method of manufacturing a gas resistance resistor according to claim 3, wherein the step 3 comprises:

Step 3.1, performing photolithography and etching on the second dielectric layer covered by the non-metal oxide film, in the second dielectric layer Forming a second contact hole penetrating through the second dielectric layer in the upper Pad region while retaining the photoresist;

Step 3.2, depositing an alloy thin film on the photoresist and the second contact hole by physical vapor deposition;

In step 3.3, the photoresist is removed, and the alloy film is formed into a Pad pattern. The Pad alloy film is connected to the underlying metal film layer of the heating resistor or the metal film layer of the measuring electrode of the gas sensor through the second contact hole.
The method of manufacturing a gas-sensitive resistor according to claim 4, wherein the first dielectric layer has a thickness of 0.5 μm to 2 μm, the first dielectric layer is made of silicon oxide or silicon nitride, and the second dielectric layer is The thickness is from 100 nm to 1000 nm, and the material of the second dielectric layer is silicon oxide or silicon nitride.
The method of manufacturing a gas-sensitive resistor according to claim 4, wherein in step 1.3, the silicon wafer substrate on the back surface is dry-etched, and the remaining silicon wafer substrate has a thickness of 10 μm to 100 μm. First-order silicon cavity.
The method of manufacturing a gas-sensitive resistor according to claim 4, wherein the metal thin film layer has a thickness of 100 nm to 2 μm, and the metal thin film layer is made of a refractory metal, preferably a metal tungsten or a tungsten-titanium alloy.
The method of manufacturing a gas-sensitive resistor according to claim 4, wherein the metal oxide film has a thickness of from 100 nm to 800 nm, and the metal oxide film is made of a gas sensing material, preferably SnO 2 , ZnO or TiO. 2 or SnO 2 , ZnO or TiO 2 doped with Fe, Zn, Pt or Pd;

The alloy film has a thickness of 0.5 μm to 3 μm, and the alloy film is made of an aluminum-copper alloy or an aluminum-copper-silicon alloy.
The method of manufacturing a gas-sensitive resistor according to claim 4, wherein in step 2.9, the metal oxide film is baked in a vacuum or a nitrogen atmosphere at a temperature of 300 ° C to 900 ° C for a period of time. It is 10 minutes to 8 hours.
A gas sensor manufactured by the method for producing a gas resistance resistor according to any one of claims 1 to 9.