CN115201283A - High-temperature-resistant high-humidity-resistant humidity sensor and preparation method thereof - Google Patents

High-temperature-resistant high-humidity-resistant humidity sensor and preparation method thereof Download PDF

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CN115201283A
CN115201283A CN202210585553.2A CN202210585553A CN115201283A CN 115201283 A CN115201283 A CN 115201283A CN 202210585553 A CN202210585553 A CN 202210585553A CN 115201283 A CN115201283 A CN 115201283A
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humidity
temperature
photosensitive
silicon substrate
film
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张宾
李婷
陈新准
赵罗恒
谢傲臻
朱瑞
邱国财
陈善任
傅凯强
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Guangzhou Aosong Electronics Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
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    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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    • G01N27/227—Sensors changing capacitance upon adsorption or absorption of fluid components, e.g. electrolyte-insulator-semiconductor sensors, MOS capacitors
    • G—PHYSICS
    • G01—MEASURING; TESTING
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    • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity
    • G01N27/225—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity by using hygroscopic materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/226—Construction of measuring vessels; Electrodes therefor

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Abstract

The application discloses a high temperature and high humidity resistant humidity sensor, which comprises a silicon wafer and a humidity sensitive film; the silicon wafer comprises a silicon substrate and a metal electrode formed on the silicon substrate; the humidity sensitive film is formed on the surface of the metal electrode; the moisture-sensitive film is a cross-linking type polyamic acid film obtained by introducing photosensitive groups and polyfunctional amines into a reaction system. The application also discloses a preparation method of the high temperature and high humidity resistant sensor. The high-temperature-resistant high-humidity sensor adopts the fluorine-containing cross-linked polyimide film as the humidity sensitive film, so that the moisture absorption rate and the dielectric constant of the humidity sensitive film are reduced, and the humidity sensitive film is endowed with the performances of heat resistance, stability, hydrolysis resistance and the like; the humidity deviation of the humidity sensor is reduced, and the high measurement accuracy is improved.

Description

High-temperature-resistant high-humidity-resistant humidity sensor and preparation method thereof
Technical Field
The invention relates to the technical field of sensors, in particular to a high-temperature high-humidity resistant sensor and a preparation method thereof.
Background
The humidity generally refers to the amount of water vapor contained in an environment to be detected, reflects the degree of dryness and humidity of the environment, the humidity sensor is not only indispensable in the traditional industry, agriculture, medical treatment and meteorology, but also plays an important role in the advanced scientific and technological fields of military, aviation, aerospace, microelectronic devices and the like, however, compared with parameters such as temperature and the like, the humidity detection difficulty is much higher, mainly because the content of the water vapor in the air is less, impurities in the air and the water vapor form a chemical reaction to generate substances such as acid and alkali and the like, irreversible damage is generated on sensitive materials of the humidity sensor, and the corrosion and the aging of the humidity sensor are accelerated; the moisture sensitive material of the humidity sensor must be in direct contact with the environment to be measured to change, which reduces the lifetime of the humidity sensor.
Dew point tester and wet and dry bulb thermometer etc. are more traditional humidity tools, and their principle, structure are all simpler, but have bulky, need regularly add water, need often rectify defects such as so, so gradually replaced by modern novel measurement mode's humidity transducer. Modern micro-humidity sensors are usually based on MEMS technology, and combine with semiconductor technology to manufacture intelligent devices with resistor or capacitor output, wherein capacitive sensors manufactured based on MEMS (micro electro mechanical system) technology have the advantages of low price, small volume, wide test range, good linearity, high sensitivity, small hysteresis, fast response speed, and good stability, which are very popular with users.
The conventional materials for humidity detectors mainly include ceramics, high molecular polymers and porous silicon, and in recent years, with the rapid development of a method for combining the high molecular polymers with a semiconductor process, the materials have the advantages of high sensitivity, low cost, simple manufacture and the like, so that the high molecular humidity sensor is widely and rapidly developed. Common high polymer humidity sensing materials include polymethyl methacrylate, polyimide, polyacetylene benzene, polysulfone, cellulose acetate, silicone resin and the like, and the humidity sensing mechanism of the high polymer materials is as follows: the dielectric constant epsilon = 2-7 of the high polymer material with the humidity sensing characteristic, the dielectric constant epsilon of water molecules is approximately equal to 80, when the ambient humidity changes, the high polymer humidity sensing material adsorbs or releases the water molecules with corresponding proportion, the dipole moment of the humidity sensing film changes, macroscopically, the change is shown as the change of the dielectric constant, after the high polymer humidity sensing material with the characteristic is manufactured into a capacitance sensor, the capacitance response of the humidity sensor is measured, and the relative humidity of the environment can be obtained. As a humidity detection tool with wide application, a humidity sensor with the advantages of high range, high precision, high stability, high response speed, low wet retardation effect, moisture resistance, pollution resistance, low manufacturing cost and the like is a constantly pursued target.
Polyimide (PI) is an organic polymer material containing aromatic heterocyclic structures, and is one of the most temperature-resistant materials with humidity-sensing performance in current high-molecular polymers. The humidity sensor made of the polyimide material has the advantages of excellent performance, high mechanical strength, high elastic modulus, stability and difficult decomposition at high temperature, good corrosion resistance, safety, no toxicity and good linearity, and in addition, because the polyimide is compatible with a mature CMOS (complementary metal oxide semiconductor) process, the mass production can be realized by utilizing the mature process of an integrated circuit, the consistency of products is greatly improved, and the cost of the products is reduced.
Polyimide is easy to undergo self ring-opening hydrolysis at high temperature, particularly in the presence of oxygen and moisture, so that the capacitive polyimide humidity sensor generally has some defects in practical application, such as wet retardation, temperature drift, long-term stability and the like, and the commercialization and application range of the capacitive polyimide humidity sensor are limited.
Disclosure of Invention
In order to overcome the defects in the prior art, the purpose of the application is to provide a high temperature and high humidity resistant humidity sensor, a fluorine-containing cross-linked polyimide film is used as a humidity sensitive film, the moisture absorption rate and the dielectric constant of the humidity sensitive film are reduced, the humidity sensitive film is endowed with heat resistance, stability, hydrolysis resistance and other performances, the humidity deviation of the humidity sensor is reduced, and the measurement accuracy is improved.
In order to solve the above problems, the technical solution adopted by the present application is as follows:
a high temperature and high humidity resistant humidity sensor comprises
A silicon wafer and a humidity sensitive film; the silicon wafer comprises a silicon substrate, a passivation layer formed on the silicon substrate and a metal electrode formed on the passivation layer; the humidity sensitive film is formed on the surface of the metal electrode;
the moisture-sensitive film adopts a cross-linking type polyamic acid film obtained by introducing photosensitive groups and polyfunctional amines into a reaction system.
The photosensitive group is derived from a photosensitive compound containing a double bond.
As a further scheme, the double bond-containing photosensitive compound is one or two of hydroxypropyl methacrylate, beta-hydroxyethyl acrylate and pentaerythritol triacrylate.
As a further scheme, the crosslinking type polyamic acid film described herein is a fluorine-containing crosslinking type polyamic acid film into which a fluorine-containing group is introduced.
As a further proposal, the thickness of the cross-linked polyimide film is 2-4 μm.
The other purpose of the present application is to provide a preparation method of the high temperature and high humidity resistant humidity sensor, wherein a dianhydride and a diamine precursor are adopted, and a polyfunctional amine precursor and a photosensitive group are introduced to obtain the capacitive humidity sensor with the cross-linked polyimide film humidity sensitive film.
The preparation method of the high temperature and high humidity resistant humidity sensor comprises the following steps
Dianhydride and diamine are used as precursors, wherein at least one precursor has a fluorine-containing functional group, a polyfunctional amine precursor is introduced into a reaction system to prepare a carboxyl-terminated polyamic acid solution, and a photosensitive compound is added into the carboxyl-terminated polyamic acid to obtain a precursor solution of photosensitive polyimide;
adding a photoinitiator into the prepolymer solution, uniformly stirring, coating the mixture on a silicon substrate with a prepared metal electrode, and then transferring the silicon substrate to an electric heating plate for baking to imidize the prepolymer coated on the silicon substrate and form a photosensitive cross-linked polyimide film on the silicon substrate;
exposing the silicon substrate with the photosensitive cross-linked polyimide film, immersing the silicon substrate into a developing solution, and treating the silicon substrate with the developing solution to obtain a patterned photosensitive cross-linked polyimide film;
transferring the patterned photosensitive cross-linked polyimide film and the silicon substrate into a nitrogen oven to be baked in a segmented manner to realize complete imidization, thereby obtaining a fully imidized photosensitive cross-linked polyimide film silicon wafer;
and processing the fully imidized photosensitive cross-linked polyimide film silicon wafer into a high temperature and high humidity resistant sensor.
As a further scheme, in the present application, the method for obtaining the prepolymer solution is as follows:
the method comprises the following steps: putting a diamine precursor, a polyfunctional amine precursor and a solvent into a reaction device, stirring and dissolving, and introducing nitrogen;
step two: adding a dianhydride precursor and a solvent into the reaction device, adjusting the solid content of the solution to be 20-25%, reacting at room temperature, adding a capping reagent, and continuously reacting to obtain a carboxyl-capped polyamic acid solution;
step three: adding a catalyst, a dehydrating agent and a photosensitive compound into the polyamic acid solution, and obtaining the photosensitive polyamic acid solution after the reaction is finished.
As a further scheme, the diamine precursor is one or two of 2, 2-bis [4- (4-aminophenoxy benzene) ] hexafluoropropane, 2 '-bis (trifluoromethyl) diaminobiphenyl, 2' -bis (trifluoromethyl) -4,4 '-diaminophenyl ether and 4,4' -diaminodiphenyl ether, and the multifunctional amine precursor is one or more of tris (4-aminophenyl) amine and tetra- (4-aminobenzene) ethylene; the dianhydride is one or more than two of 4,4' - (hexafluoroisopropylidene) diphthalic anhydride, 4,4' - (2- (3 ' -trifluoromethyl-phenyl) -1, 4-phenoxy) -phthalic anhydride, 3', 4' -benzophenonetetracarboxylic dianhydride and 3,3', 4' -biphenyltetracarboxylic dianhydride.
As a further alternative, the ratio of total moles of amine to anhydride described herein amine: anhydride = (1.02 to 1.08) 1.
As a further embodiment, the organic solvent described herein is N, N' -dimethylformamide; the end capping agent is one or more than two of 2, 3-anthracene dicarboxylic anhydride, phthalic anhydride, glutaric anhydride and maleic anhydride; the photosensitization compound is one or more than two of hydroxypropyl methacrylate (HPMA), acrylic acid-beta-Hydroxyethyl Ester (HEA) and pentaerythritol triacrylate (PETA).
As a further scheme, the application adopts a spin coating method to coat the prepolymer solution, the baking temperature is 60-110 ℃, and the baking time is 3-5min.
As a further scheme, the developing solution is one or a mixture of 0.01-0.1% of sodium hydroxide and 2-3% of tetramethyl ammonium hydroxide.
As a further scheme, the temperature raising procedure of the sectional baking described in the present application is as follows:
in the first stage, the temperature is increased from room temperature to 80 ℃, and the baking is carried out for 1h;
in the second stage, the temperature is increased from 80 ℃ to 150 ℃, and the baking is carried out for 1h;
in the third stage, the temperature is increased from 150 ℃ to 250 ℃, and the baking is carried out for 1h;
in the third stage, the temperature is increased from 250 ℃ to 300 ℃, and the baking is carried out for 1h;
in the fifth stage, the temperature is raised to 350 ℃ at 300 ℃, and the baking is carried out for 0.5h;
the heating rate of each stage is 0.5-3 deg.C/min.
Compared with the prior art, the invention has the beneficial effects that:
1. humidity transducer adopt fluorine-containing cross-linked type polyimide film as the quick membrane of humidity, because the existence of fluorine atom in this quick membrane of humidity, reduce humidity transducer's damp stagnation, reduce the purpose of humidity deviation, improved humidity transducer's stability and measurement accuracy nature.
2. According to the preparation method of the high temperature and high humidity resistant humidity sensor, the fluorine-containing dianhydride and the diamine monomer are adopted, the fluorine-containing group is introduced to the polyimide film, the moisture absorption rate and the dielectric constant of the humidity sensor are effectively reduced, the polyfunctional amine precursor is added to a reaction system, so that cross-linking occurs in the polycondensation reaction to obtain cross-linking type polyimide acid, the photosensitive group is introduced to the polyamic acid, secondary cross-linking is performed after photo-curing under the action of the photoinitiator, the heat resistance, the stability and the hydrolysis resistance of the obtained fluorine-containing cross-linking type polyimide film are greatly improved, and the heat resistance and the humidity resistance of the humidity sensor are improved.
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a capacitive humidity sensor according to one embodiment of the present application;
FIG. 2 is a flow chart of a process for manufacturing the capacitive humidity sensor according to embodiment 1 of the present application;
FIG. 3 is a graph showing the humidity deviation of the capacitive humidity sensor according to examples 1 to 3 after high temperature reflow (260 ℃);
fig. 4 is a graph of humidity deviation of the capacitive humidity sensor of embodiments 1-3 after a double 85 pass.
Wherein the reference symbols are: 1. a silicon substrate; 2. a passivation layer; 3. a metal electrode; 4. a moisture sensitive membrane.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In this application, where the specification and claims refer to the term "comprising" and other equivalents, this is intended to cover non-exclusive inclusions, including those explicitly described in the specification and claims, or including those steps or elements not expressly described in the specification and claims but inherent to the product, method, or structure.
The application provides a high temperature resistant high humidity sensor adopts fluorine-containing cross-linked polyimide film as the quick membrane of humidity to solve humidity transducer's damp stagnation, reduce the problem of humidity deviation, improved humidity transducer's stability and measurement accuracy nature.
The high temperature and high humidity resistant humidity sensor comprises
A silicon wafer and a humidity sensitive film; the silicon wafer comprises a silicon substrate and a metal electrode formed on the silicon substrate; the humidity sensitive film is formed on the surface of the metal electrode;
the moisture-sensitive film adopts a cross-linking type polyamic acid film obtained by introducing photosensitive groups and polyfunctional amine into a reaction system, and the glass transition temperature of the fluorine-containing cross-linking type polyamic acid film is not less than 350 ℃ but not more than 430 ℃.
[ Cross-Linked Polyamic acid film ]
In the present application, a cross-linking type polyamic acid film is used. In the embodiment of the present application, polyfunctional amine is introduced into the reaction system for preparing the cross-linked polyamic acid film during the reaction processThe proportion of rigid structures in the polyimide film can be improved by the occurrence of cross-linking reaction, so that the glass transition temperature Tg of the polyimide film is more than or equal to 350 ℃, and the thermal decomposition temperature T is 5％ More than or equal to 530 ℃; meanwhile, the hydrolysis resistance and the stability of the polyimide film are improved.
Furthermore, the high temperature and high humidity resistant sensor preferably adopts a fluorine-containing cross-linked polyamic acid film with introduced fluorine-containing groups, fluorine atoms are introduced into the structure of the polyimide film, the fluorine atoms have high electronegativity, and in the structure of the polyimide polymer, on one hand, the fluorine-containing polyimide film has high thermal and thermo-oxidative stability due to the high bond energy of C-F parts, and C-F parts have high thermal and thermo-oxidative stability 3 The volume of the group is large, so that the low stacking density of macromolecules is caused, and the fluorine-containing polyimide film has high air permeability and low dielectric constant; on the other hand, because the electronic polarization degree of fluorine element is low, the fluorine element has lower cohesive energy and surface free energy, so that the material has low water absorption, and is hydrophobic and oleophobic. Therefore, in the embodiment of the application, fluorine is introduced into the polyimide humidity sensitive membrane, so that the purposes of reducing the humidity hysteresis of the humidity sensor and reducing the humidity deviation can be achieved, and the stability and the measurement accuracy of the humidity sensor are improved. Compared with the conventional polyimide film, the moisture absorption rate and the moisture absorption expansion coefficient of the cross-linked polyimide film introduced with the fluorine-containing group are obviously reduced.
The fluorine-containing cross-linked polyamic acid film can effectively improve the stability, the measurement accuracy and the heat resistance of the humidity sensor, but in the research process, the thickness of the fluorine-containing cross-linked polyamic acid film can also influence the performance of the humidity sensor, specifically, when the thickness of the fluorine-containing cross-linked polyamic acid film is too thin, two problems of small capacitance variation, reduced precision of the humidity sensor and poor consistency can occur, and when the thickness of polyimide is too thick, water in the film is difficult to remove, so that the increase of wet retardation is caused. Therefore, in the examples of the present application, the thickness of the fluorine-containing cross-linked polyimide film is set to 2 to 4 μm, which can further ensure the measurement accuracy and consistency of the humidity sensor and reduce the hysteresis. Preferably, the thickness may be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm.
[ PHOTOSENSITIVE GROUPS ]
In the reaction, unsaturated photosensitive groups are introduced through photosensitive compounds, so that not only can addition polymerization reaction be carried out, but also polycondensation reaction can be carried out, and during photocuring, the curing speed is high, and the polymerization reaction can be easily carried out only by the presence of a small amount of initiator. In the present application, in order to enable rapid crosslinking polymerization by photocuring, a photosensitive compound having a double bond derived from a photosensitive group is used. Specifically, the double bond-containing photosensitive compound is one or two of hydroxypropyl methacrylate, beta-hydroxyethyl acrylate and pentaerythritol triacrylate.
The other purpose of the application is to provide a preparation method of the high temperature and high humidity resistant humidity sensor, which adopts fluorine-containing dianhydride and fluorine-containing diamine precursors, and introduces multifunctional amine precursors and photosensitive groups to obtain the capacitive humidity sensor with the fluorine-containing cross-linked polyimide film humidity sensitive film.
The preparation method of the high temperature and high humidity resistant humidity sensor comprises the following steps
Dianhydride and diamine are used as precursors, wherein at least one precursor has a fluorine-containing functional group, a polyfunctional amine precursor is introduced into a reaction system to prepare a carboxyl-terminated polyamic acid solution, and a photosensitive compound is added into the carboxyl-terminated polyamic acid to obtain a precursor solution of photosensitive fluorine-containing polyimide;
adding a photoinitiator into the prepolymer solution, uniformly stirring, coating the mixture on a silicon substrate with a prepared metal electrode, transferring the silicon substrate to an electric heating plate for baking, imidizing the prepolymer coated on the silicon substrate, and forming a photosensitive fluorine-containing cross-linked polyimide film on the silicon substrate;
exposing the silicon substrate with the photosensitive cross-linked polyimide film, and treating the silicon substrate with a developing solution to obtain a patterned photosensitive cross-linked polyimide film;
transferring the patterned photosensitive cross-linked polyimide film and the silicon substrate into a nitrogen oven to be baked in a segmented manner to realize complete imidization, thereby obtaining a fully imidized photosensitive cross-linked polyimide film silicon wafer;
and processing the fully imidized photosensitive cross-linked polyimide film silicon wafer into a high temperature and high humidity resistant sensor.
[ DIAMINES AND DIACHLORIDE ]
In order to obtain a fluorine-containing polyimide film, at least one of dianhydride and diamine precursors having a fluorine-containing group is used in the present application. Specifically, the diamine precursor used in the present application is selected from one or more of, but not limited to, 2-bis [4- (4-aminophenoxyphenyl) ] hexafluoropropane, 2 '-bis (trifluoromethyl) diaminobiphenyl, 2' -bis (trifluoromethyl) -4,4 '-diaminophenyl ether, and 4,4' -diaminodiphenyl ether. The dianhydride is one or more than two of 4,4' - (hexafluoroisopropylidene) diphthalic anhydride, 4,4' - (2- (3 ' -trifluoromethyl-phenyl) -1, 4-phenoxy) -phthalic anhydride, 3', 4' -benzophenonetetracarboxylic dianhydride and 3,3', 4' -biphenyltetracarboxylic dianhydride.
[ polyfunctional amines ]
The multifunctional amine precursor is introduced into the reaction system, and the multifunctional amine introduced into the crosslinking structure can improve the proportion of rigid structures in the polyimide film and endow the polyimide film with high glass transition temperature (Tg is more than or equal to 350 ℃) and thermal decomposition temperature (T is more than or equal to 350 ℃) 5％ 530 ℃ or more) and the like, thereby improving the stability of the humidity sensor, and reducing the hydrolysis degree of the humidity sensor after the humidity sensor is subjected to double 85 (85 ℃,85 percent RH) condition treatment; after half a year of standing under high humidity conditions (90% RH), the humidity deviation measured was still less than or equal to 2%. Preferably, the multifunctional amine precursor in the embodiments of the present application is selected from, but not limited to, one or more of tris (4-aminophenyl) amine and tetrakis- (4-aminostyrene).
[ ratio of amine to anhydride ]
In order to ensure the complete reaction of diamine and dianhydride, the ratio of the total moles of amine and anhydride described herein is amine: anhydride = (1.02 to 1.08) 1.
[ other Agents ]
Preferably, the dehydrating agent used in the examples of the present application is N, N' -Dicyclohexylcarbodiimide (DCC) and the catalyst used is 4-Diaminopyridine (DMAP).
Examples of organic solvents useful in the present application are, but are not limited to, N' -Dimethylformamide (DMF); the capping agent used in the embodiments of the present application is selected from one or more of, but not limited to, 2, 3-anthracene anhydride, phthalic anhydride, glutaric anhydride, and maleic anhydride; the photosensitive compound used in the examples of the present application is selected from one or more of hydroxypropyl methacrylate (HPMA), beta-hydroxyethyl acrylate (HEA), pentaerythritol triacrylate (PETA), but is not limited thereto.
[ PREPARATION TECHNOLOGY ]
In the examples of the present application, the method for obtaining the prepolymer solution is as follows:
the method comprises the following steps: total moles of amine: anhydride = 1.02-1.08 (anhydride is calculated as 100, amine precursor is slightly excessive), adding fluorine-containing diamine precursor, polyfunctional amine precursor and solvent N, N' -Dimethylformamide (DMF) into a reaction bottle, stirring at room temperature to dissolve, and introducing nitrogen for 30min;
step two: adding a fluorine-containing dianhydride precursor, adding a proper amount of N, N' -Dimethylformamide (DMF) to enable the solid content of the solution to be 20-25%, reacting for 5 hours at room temperature, then adding 1-5 parts of anhydride end capping agent, and reacting for 3 hours at room temperature to obtain carboxyl end capped polyamide acid (PAA) solution;
step three: adding 5-10 parts of N, N' -dicyclohexylcarbodiimide, 0.5-1 part of 4-dimethylamino pyridine and 5-10 parts of a photosensitive group-containing compound into the fluorine-containing polyamic acid solution, and reacting at room temperature for 8 hours to obtain a photosensitive polyimide (PSPI) prepolymer solution.
In the embodiment of the application, 1-2 parts by weight of photosensitive polyimide (PSPI) prepolymer solution mixed with initiator is coated by a spin coating method, the baking temperature is 60-110 ℃, and the baking time is 3-5min. Preferably, the baking temperature is 80-100 deg.C, and the baking temperature can be 60-65 deg.C, 65-70 deg.C, 70-75 deg.C, 75-80 deg.C, 80-85 deg.C, 85-90 deg.C, 90-95 deg.C, 95-100 deg.C, 100-105 deg.C, and 105-110 deg.C.
In the embodiment of the application, the developing solution is one or a mixture of 0.01-0.1% of sodium hydroxide and 2-3% of tetramethyl ammonium hydroxide.
Because polyamic acid and polar aprotic solvent are easy to form certain complexes, the solvent removal is more difficult, and the adoption of the step-by-step imidization process creates sufficient conditions for the completion of imidization and the removal of residual solvent. Therefore, in the embodiment of the present application, the step of baking the patterned polyimide film employs a step baking, specifically, the temperature rise procedure of the step baking is as follows:
in the first stage, the temperature is increased from room temperature to 80 ℃, and the baking is carried out for 1h;
in the second stage, the temperature is increased from 80 ℃ to 150 ℃, and the baking is carried out for 1h;
in the third stage, the temperature is increased from 150 ℃ to 250 ℃, and the baking is carried out for 1h;
in the third stage, the temperature is increased from 250 ℃ to 300 ℃, and the baking is carried out for 1h;
the fifth stage is that the temperature is raised to 350 ℃ at 300 ℃ and the baking is carried out for 0.5h.
In the segmented baking process, the quality and the performance of the polyimide film are influenced by the heating rate, the heating rate is too high, pores are easy to appear on the surface of the film, and the solvent residual rate is high; slow heating rate, long time consumption and power consumption. And the too fast or too slow heating rate is not favorable for the formation of the regular crystalline structure of the film. Therefore, in order to improve the quality of the polyimide film and meet the performance requirement as a humidity-sensitive film, the temperature rise rate of each stage of the above-mentioned stage baking is 0.5 to 3 ℃/min in the present application.
Example 1:
as shown in FIG. 1, the humidity sensor with high temperature and humidity resistance of the present embodiment comprises
A silicon wafer and a humidity sensitive film; the silicon wafer comprises a silicon substrate 1, a passivation layer 2 formed on the silicon substrate 1 and a metal electrode 3 formed on the passivation layer 2; the humidity sensitive film 4 is formed on the surface of the metal electrode 3;
the moisture-sensitive film is a fluorine-containing crosslinking type polyamic acid film with a photosensitive group introduced, and the glass transition temperature of the crosslinking type polyamic acid film is 371.5 ℃.
The preparation method of the high temperature and high humidity resistant sensor comprises the following steps:
raw materials: the diamine is 2, 2-bis [4- (4-aminophenoxy benzene) ] hexafluoropropane; the polyfunctional amine is tetra- (4-aminostyrene); the dianhydride is 4,4' - (hexafluoroisopropylidene) diphthalic anhydride, 3,3',4,4' -biphenyltetracarboxylic dianhydride; the photosensitive compound is hydroxypropyl methacrylate; the photoinitiator is sold under the trade name photoinitiator 184; the developer solution was 0.02% NaOH.
The method comprises the following steps: weighing 28.51g of 2, 2-bis [4- (4-aminophenoxy benzene) ] hexafluoropropane and 1.51g of tetra- (4-aminostyrene) ethylene, dissolving in 180g of N, N-dimethylformamide, and fully stirring to completely dissolve the amine monomer; weighing 8.88g of 4,4' - (hexafluoroisopropenylidene) diphthalic anhydride and 11.69g of 3,3', 4' -biphenyltetracarboxylic dianhydride, adding the mixture into the amine solution for three times at intervals of 20min, adding 20g of DMF into the amine solution to ensure that the solid content of the solution is 20%, reacting the solution for 5 hours at room temperature, then continuously adding 0.88g of phthalic anhydride, and reacting the solution for 3 hours at room temperature to obtain polyamide acid PAA solution. Adding 1.23g of N, N' -dicyclohexylcarbodiimide, 0.07g of 4-dimethylaminopyridine and 1g of hydroxypropyl methacrylate into the PAA solution, reacting for 8 hours at 50 ℃ to obtain a polyimide (PSPI) prepolymer solution containing photosensitive groups, adding 0.1g of photoinitiator 184 into the polyimide (PSPI) prepolymer solution, stirring for 30 minutes at room temperature to uniformly mix the photoinitiator 184, coating the mixture on a silicon substrate material with an interdigital gold electrode by using a spin coating method, and baking for 5 minutes at 60 ℃. And (3) exposing the baked polyimide film for 3-4min by an ultraviolet lamp, immersing the polyimide film into 0.02 percent NaOH developing solution for 30-40s, taking out the polyimide film, washing the residual NaOH developing solution by deionized water, and treating the polyimide film at 80-100 ℃ for 10-20min to remove residual solvent in the film to obtain the patterned polyimide film. Placing patterned polyimide in a nitrogen oven, and performing imidization treatment according to the placement of a program temperature, wherein the heating mode is as follows: room temperature is 80 ℃ and 1h; at 150 ℃, for 1h; at 250 ℃ for 1h;300 ℃ for 1h; cutting the polyimide film silicon substrate material which is completely imidized, routing, packaging and then calibrating at room temperature at 350 ℃ for 0.5h with the heating rate of 1 ℃/min.
Example 2:
in this embodiment, the raw materials for preparing the humidity sensor include: the precursor diamine is 4,4' -diaminodiphenyl ether; the polyfunctional polyamine is tetra- (4-aminostyrene); the dianhydride is 3,3', 4' -biphenyl tetracarboxylic dianhydride; the photosensitive compound is hydroxypropyl methacrylate; the photoinitiator is sold under the trade name photoinitiator 184; the developing solution was 0.02% by weight of NaOH solution. The glass transition temperature of the resulting crosslinked polyamic acid film was 392.4 ℃.
In this example, the total molar ratio of amines to anhydrides is 1.05:1; the procedure was as in example 1.
Example 3:
in this embodiment, the raw material for preparing the sensor includes 4,4' -diaminodiphenyl ether; the dianhydride is 3,3', 4' -biphenyl tetracarboxylic dianhydride; the photosensitive compound is hydroxypropyl methacrylate; the photoinitiator is sold under the trade name photoinitiator 184; the developing solution was 0.02% NaOH solution. The glass transition temperature of the obtained crosslinked polyamic acid film was 301.9 ℃.
In this example, no polyfunctional amine was added, and the total molar ratio of amine to anhydride was 1.08:1; the reaction procedure was the same as in example 1.
[ Performance test and results ]
1. Performance of fluorine-containing cross-linked polyimide film
The properties of the fluorine-containing crosslinked polyimide films obtained in examples 1 to 3 were measured, and the results are shown in Table 1.
TABLE 1 EXAMPLES 1-3 Properties of fluorine-containing crosslinked polyimide film
Figure BDA0003665799180000131
Figure BDA0003665799180000141
From the results of Table 1, it can be seen that the dielectric constant is significantly decreased and the glass transition temperature is significantly increased relative to the conventional polyimide, indicating the presence of a crosslinked structure. Besides, other properties are also obviously improved. On the other hand, comparing examples 1 to 3, it can be seen that the mechanical strength of the fluorine-containing cross-linked polyimide film obtained in example 3 in which the polyfunctional amine was not added to the raw material was significantly lower than that of examples 1 and 2 in which the polyfunctional amine was added, the dielectric constant thereof was also significantly higher than that of examples 1 and 2, the glass transition temperature thereof was lower than that of examples 1 and 2, and it was demonstrated that the mechanical strength of the fluorine-containing cross-linked polyimide film having a cross-linking degree lower than that of examples 1 and 2 was significantly lower than that of examples 1 and 2 in which the polyfunctional amine was added.
2. Capacitance value of humidity sensor
The humidity sensors obtained in examples 1 to 3 were tested for capacitance values at different humidities, and the test results are shown in table 2.
Table 2: capacitance values of humidity sensors of examples 1-3 under different humidity conditions
Example numbering 30％ 40％ 50％ 60％ 70％ 80％ 90％
Example 1 67.96 68.44 68.98 69.49 70.05 70.57 71.12
Example 2 68.35 69.05 69.75 70.45 71.15 71.85 72.55
Example 3 69.87 70.84 71.81 72.78 73.75 74.72 75.69
3. Humidity deviation after high temperature reflow soldering (260 deg.C)
The humidity deviation of the humidity sensor obtained in examples 1 to 3 was shown in Table 3 and FIG. 3 after the high temperature reflow (260 ℃ C.) process.
The results show that: the humidity deviation of the humidity sensors of the embodiments 1-2 after high temperature reflow (260 ℃) treatment is less than or equal to 2 percent, and relatively speaking, the humidity deviation of the embodiment 3 is larger than that of the embodiments 1 and 2.
4. Humidity deviation before and after 10 days of double 85 treatment
The humidity sensors obtained in examples 1 to 3 were subjected to a double 85 (85 ℃ C., 85% humidity) treatment for 10 days, and the humidity deviations of the humidity sensors before and after the treatment were shown in Table 3 and FIG. 4.
The results show that: the humidity deviation of the humidity sensors of the embodiments 1-2 after two 85 days treatment is less than or equal to 4%, and relatively speaking, the humidity deviation of the embodiment 3 is greater than that of the embodiments 1 and 2.
TABLE 3 measurement bias of humidity sensor for various examples after different treatments
Figure BDA0003665799180000151
The above embodiments are only preferred embodiments of the present invention, and the scope of the present invention should not be limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are intended to be covered by the claims.

Claims (12)

1. A high temperature and high humidity resistant humidity sensor comprises
A silicon wafer and a humidity sensitive film; the silicon wafer comprises a silicon substrate, a passivation layer formed on the silicon substrate and a metal electrode formed on the passivation layer; the humidity sensitive film is formed on the surface of the metal electrode;
the humidity-sensitive film is characterized in that a crosslinking type polyamic acid film obtained by introducing photosensitive groups and polyfunctional amines into a reaction system is adopted.
2. The high temperature and humidity resistant sensor according to claim 1, wherein the photosensitive group is derived from a photosensitive compound containing a double bond.
3. The high temperature, high humidity and humidity resistant sensor according to claim 1, wherein the cross-linked polyamic acid film is a fluorine-containing cross-linked polyamic acid film with a fluorine-containing group introduced.
4. The high temperature and high humidity resistant sensor according to claim 1 or 3, wherein the thickness of the cross-linked polyimide film is 2 to 4 μm.
5. The preparation method of the high temperature and high humidity resistant humidity sensor is characterized by comprising the following steps
Dianhydride and diamine are used as precursors, a polyfunctional amine precursor is introduced into a reaction system to prepare a carboxyl-terminated polyamic acid solution, and a photosensitive compound is added into the carboxyl-terminated polyamic acid to obtain a precursor solution of photosensitive polyimide;
adding a photoinitiator into the prepolymer solution, uniformly stirring, coating the mixture on a silicon substrate with a prepared metal electrode, and then transferring the silicon substrate to an electric heating plate for baking to imidize the prepolymer coated on the silicon substrate and form a photosensitive cross-linked polyimide film on the silicon substrate;
exposing the silicon substrate with the photosensitive cross-linked polyimide film, immersing the silicon substrate into a developing solution, and treating the silicon substrate with the developing solution to obtain a patterned photosensitive cross-linked polyimide film;
transferring the patterned photosensitive cross-linked polyimide film and the silicon substrate into a nitrogen oven to be baked in a segmented mode to achieve complete imidization, and obtaining a fully imidized cross-linked polyimide film silicon wafer;
and processing the fully imidized photosensitive cross-linked polyimide film silicon wafer into a high temperature and high humidity resistant sensor.
6. The method according to claim 5, wherein the prepolymer solution is obtained by the following method:
the method comprises the following steps: putting a diamine precursor, a polyfunctional amine precursor and a solvent into a reaction device, stirring and dissolving, and introducing nitrogen;
step two: adding a dianhydride precursor and a solvent into the reaction device, adjusting the solid content of the solution to be 20-25%, reacting at room temperature, adding a capping agent, and continuously reacting to obtain a carboxyl-capped polyamic acid solution;
step three: adding a catalyst, a dehydrating agent and a photosensitive compound into the fluorine-containing polyamic acid solution, and obtaining the photosensitive polyamic acid solution after the reaction is finished.
7. The method according to claim 5, wherein the diamine is one or two selected from 2, 2-bis [4- (4-aminophenoxyphenyl) ] hexafluoropropane, 2 '-bis (trifluoromethyl) diaminobiphenyl, 2' -bis (trifluoromethyl) -4,4 '-diaminophenyl ether and 4,4' -diaminodiphenyl ether, and the polyfunctional amine precursor is one or more selected from tris (4-aminophenyl) amine and tetrakis- (4-aminostyrene); the dianhydride is one or more than two of 4,4' - (hexafluoroisopropylidene) diphthalic anhydride, 4,4' - (2- (3 ' -trifluoromethyl-phenyl) -1, 4-phenoxy) -phthalic anhydride, 3', 4' -benzophenonetetracarboxylic dianhydride and 3,3', 4' -biphenyltetracarboxylic dianhydride.
8. The production method according to claim 5, wherein the ratio of the total moles of amine to the total moles of anhydride of amine: anhydride = (1.02 to 1.08) 1.
9. The method according to claim 8, wherein the organic solvent is N, N' -dimethylformamide; the end capping agent is one or more than two of 2, 3-anthracene dicarboxylic anhydride, phthalic anhydride, glutaric anhydride and maleic anhydride; the photosensitization compound is one or more than two of hydroxypropyl methacrylate (HPMA), acrylic acid-beta-Hydroxyethyl Ester (HEA) and pentaerythritol triacrylate (PETA).
10. The preparation method according to claim 5, wherein the coating of the prepolymer solution is carried out by a spin coating method, the baking temperature is 60-110 ℃, and the baking time is 3-5min.
11. The method according to claim 5, wherein the developing solution is one or a mixture of 0.01-0.1% of sodium hydroxide and 2-3% of tetramethylammonium hydroxide.
12. The method according to claim 5, wherein the temperature raising procedure of the staged baking is as follows:
in the first stage, the temperature is increased from room temperature to 80 ℃, and the baking is carried out for 1h;
in the second stage, the temperature is increased from 80 ℃ to 150 ℃, and the baking is carried out for 1h;
in the third stage, the temperature is increased from 150 ℃ to 250 ℃, and the baking is carried out for 1h;
in the third stage, the temperature is increased from 250 ℃ to 300 ℃, and the baking is carried out for 1h;
the fifth stage is that the temperature is increased to 350 ℃ at 300 ℃ and the baking is carried out for 0.5h;
the heating rate of each stage is 0.5-5 deg.C/min.
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* Cited by examiner, † Cited by third party
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CN117402351A (en) * 2023-12-14 2024-01-16 山东广垠新材料有限公司 Photo-induced cross-linking/de-cross-linking nylon material, and preparation method and application thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117402351A (en) * 2023-12-14 2024-01-16 山东广垠新材料有限公司 Photo-induced cross-linking/de-cross-linking nylon material, and preparation method and application thereof
CN117402351B (en) * 2023-12-14 2024-02-13 山东广垠新材料有限公司 Photo-induced cross-linking/de-cross-linking nylon material, and preparation method and application thereof

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