Parylene copolymer material and method for improving adhesive force of parylene film

Abstract

The invention relates to a parylene copolymer material and a method for improving the adhesive force of a parylene film. According to the invention, a conventional parylene monomer and a parylene H monomer are subjected to chemical vapor deposition copolymerization to prepare the parylene copolymerization material. The invention further provides a method for improving the adhesive force of the parylene film, and the method comprises the following steps: putting a pre-cleaned base material into a deposition chamber for later use; the method comprises the following steps: mixing a conventional parylene monomer to be plated with a parylene H monomer, and putting the mixture into an evaporation chamber; under the condition that the vacuum degree is-10 Pa to-0.5 Pa, a conventional parylene monomer and a parylene H monomer in the evaporation chamber are evaporated, after pyrolysis is conducted through the cracking furnace, deposition is conducted on a base material in the deposition chamber, and the parylene film is formed. According to the method, the adhesive force of the parylene material is greatly improved, and meanwhile, the uniformity and the surface smoothness of the film are kept.

Description

Technical Field

[0001] The present invention relates to the technical field of parylene materials, and in particular to a parylene copolymer material and a method for improving the adhesion of a parylene film. Background Art

[0002] Parylene C is a polymer thin film material prepared by a chemical vapor deposition (CVD) process, and has excellent formability, a smooth surface, and no holes. Due to its excellent biostability and hydrolysis resistance, this thin film material has become the first parylene derivative recognized as having the highest biocompatibility grade among plastic materials, and is widely used in the field of bio-MEMS (see: Noh H-S, Huang Y, Hesketh P J. Sensors and Actuators B: Chemical, 2004, 102(1): 78-85).

[0003] Although the parylene film exhibits excellent properties, since it is deposited on the surface of a substrate by the CVD process, its molecular structure is special and its surface energy is low, resulting in poor natural adhesion between the parylene film and common substrates (see: Charmet J, Bitterli J, Sereda O, et al. Journal of Microelectromechanical Systems, 2013, 22(4): 855-864). The insufficient adhesion performance greatly limits the service life of the parylene film in some applications with long-term stability and high reliability. The detachment or interfacial failure between the film and the substrate may seriously affect the overall performance of related products or applications (see: Ortigoza-Diaz J, Scholten K, Meng E. Journal of Microelectromechanical Systems, 2018, 27(5): 874-885).

[0004] Currently, the common strategy to improve the adhesion of parylene films is to use adhesives. These adhesives are usually surface-active materials, such as silane coupling agents and plasma polymerization adhesives, etc., which can significantly enhance the adhesion by forming chemical bonds between the parylene film and various substrates (such as silicon-based substrates, etc.). However, this method has certain limitations: Since the chemical properties and physical behaviors of the adhesives may be incompatible with the parylene film, it may have an adverse impact on the properties of the film such as temperature resistance and corrosion resistance (see: Hassler C, Von Metzen R P, Ruther P, Stieglitz T. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2010, 93(1): 266 - 74).

[0005] Therefore, it is urgent to provide a method to improve the adhesion of parylene films to silicon-based substrates, so as to overcome the deficiencies of the existing methods and provide a new technical approach for improving the film properties. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a parylene copolymer material and a method for enhancing the adhesion of parylene films. The present invention aims to overcome the inherent defects of traditional methods in improving the adhesion of parylene films. The present invention prepares films by copolymerizing common parylene monomers with parylene H monomers, which can significantly improve the adhesion of parylene films to silicon-based substrates while maintaining the uniformity and surface flatness characteristics of the films.

[0007] The present invention is achieved through the following technical solutions:

[0008] The first object of the present invention is to provide a parylene copolymer material, and the structure of the parylene copolymer material is as follows:

[0009]

[0010] Among them, R1, R2, R3, and R4 each independently selected from one of a hydrogen atom, a halogen, an amino group, a nitro group, an ester group, an aldehyde group, a methoxy group, an ethoxy group, a cyano group, a trifluoromethyl group, an ethynyl group, a vinyl group, and a saturated alkyl group; where m ≧ 1 and n ≧ 1.

[0011] The second object of the present invention is to provide a preparation method of a parylene copolymer material, including the following steps:

[0012] Prepared by chemical vapor deposition copolymerization of a conventional parylene monomer and a parylene H monomer;

[0013] The conventional parylene monomer is selected from one or more of parylene N monomer, parylene C monomer, parylene D monomer, parylene F monomer and parylene HT monomer.

[0014] In one embodiment of the present invention, the mass ratio of the conventional parylene monomer to the parylene H monomer is 0-3:1-3.

[0015] In one embodiment of the present invention, the parylene H monomer is prepared by the following method:

[0016] (1) mixing a para-xylene cyclodimer and a catalyst in an organic solvent, adding liquid bromine dropwise, heating under reflux for reaction, separating the solid and the liquid after the reaction is completed, and recrystallizing the obtained solid phase to obtain brominated para-xylene;

[0017] (2) fully stirring the obtained bromo-p-xylene and ether, and cooling; adding n-butyl lithium dropwise, heating the mixture to room temperature, stirring, and cooling; adding N,N-dimethylformamide, heating the mixture to room temperature, and stirring to obtain parylene H monomer;

[0018] The catalyst is iron powder; the organic solvent is selected from dichloromethane.

[0019] The third object of the present invention is to provide the use of the parylene copolymer material in the preparation of parylene film.

[0020] A fourth object of the present invention is to provide a method for improving the adhesion of a parylene film, comprising the following steps:

[0021] S1, placing the pre-cleaned substrate into a deposition chamber for standby use;

[0022] S2, mixing the conventional parylene monomer to be plated with the parylene H monomer, and placing them in an evaporation chamber; the conventional parylene monomer is selected from one or more of parylene N monomer, parylene C monomer, parylene D monomer, parylene F monomer and parylene HT monomer;

[0023] S3. Under the condition of a vacuum degree of -10Pa to -0.5Pa, the conventional parylene monomer and the parylene H monomer in the evaporation chamber are evaporated, pyrolyzed in the cracking furnace, and then deposited on the substrate in the deposition chamber to form a parylene film.

[0024] In one embodiment of the present invention, in step S1, the substrate is a silicon substrate; the silicon substrate is selected from one or more of a silicon wafer, a glass wafer and PDMS.

[0025] In one embodiment of the present invention, in step S2, the mass ratio of the conventional parylene monomer to the parylene H monomer is 0-3:1-3.

[0026] In one embodiment of the present invention, in step S3, the temperature of evaporation is 80°C to 200°C.

[0027] In one embodiment of the present invention, in step S3, the temperature of cracking is 600°C to 680°C.

[0028] The present invention discovers through research that parylene H monomer (with a formyl substituent on its benzene ring) has excellent adhesion properties. By copolymerizing parylene H with other common parylene monomers, the adhesion force between the parylene film and silicon-based substrates can be significantly improved, thereby overcoming the deficiencies of existing methods and providing a new technical approach for improving the film properties.

[0029] The above technical solution of the present invention has the following advantages compared with the prior art:

[0030] 1. The present invention significantly improves the adhesion force of the parylene film through copolymerization, and the copolymerized film still maintains the excellent characteristics of parylene-based materials, such as no pinholes, good conformal properties, and uniform integrity.

[0031] 2. The present invention significantly improves the adhesion force of the film through copolymerization, greatly enhancing the adhesion force between parylene and the substrate.

[0032] 3. The method of significantly improving the adhesion force of the film through copolymerization in the present invention is simple to operate and does not require pre-complex treatment of the substrate or coating with a coupling agent.

[0033] 4. The copolymerization ratio and the type of initial parylene in the method of significantly improving the adhesion force of the film through copolymerization in the present invention can be adjusted, and the application range is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to the specific embodiments of the present invention in combination with the drawings, where

[0035] Figure 1 is the adhesion strength diagram of parylene - silicon wafer in the present invention;

[0036] Figure 2 is the electron microscope image of the parylene film in the present invention; where A is the plan view; B is the interface view. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following further illustrates the present invention in combination with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited do not limit the present invention.

[0038] The present invention provides a parylene copolymer material and a method for improving the adhesion of a parylene film. The method for improving the adhesion of the parylene film according to the present invention is prepared by chemical deposition copolymerization based on parylene H monomer raw materials and conventional parylene raw materials. This method significantly improves the adhesion of the parylene material while maintaining the uniformity and flat surface of the film. The adhesion of the film on various silicon-containing substrates is significantly improved. The specific steps are as follows:

[0039] S1. Place the pre-cleaned substrate into the deposition chamber for later use;

[0040] S2. Mix the conventional parylene monomer to be plated with the parylene H monomer and place them into the evaporation chamber; the conventional parylene monomer is selected from one or more of parylene N monomer, parylene C monomer, parylene D monomer, parylene F monomer, and parylene HT monomer.

[0041] S3. Under the condition that the vacuum degree is -10 Pa to -0.5 Pa, evaporate the conventional parylene monomer and the parylene H monomer in the evaporation chamber, pyrolyze them through a cracking furnace, and deposit them on the substrate in the deposition chamber to form a parylene film.

[0042] Preferably, in step S1, the pre-cleaning specifically is: soak the substrate with acetone or ethanol and perform ultrasonic cleaning, then rinse with deionized water, and finally dry for standby.

[0043] Preferably, in step S2, the conventional parylene monomer is selected from one or more of parylene N monomer, parylene C monomer, parylene D monomer, parylene F monomer, and parylene HT monomer; the mass ratio of the conventional parylene monomer to the parylene H monomer is 0 to 3:1 to 3.

[0044] Preferably, in step S3, the evaporation temperature is controlled at 80°C to 200°C. The pyrolysis temperature is controlled at 600°C to 680°C. The temperature of the deposition chamber is controlled at 30°C. The vacuum degree is -10 Pa to -0.5 Pa.

[0045] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels.

[0046] The parylene C monomer and parylene F monomer in the examples of the present invention are both purchased from Suzhou Kerry Nano Technology Co., Ltd.

[0047] Table 1

[0048]

[0049]

[0050] Example 1

[0051] This embodiment provides a method for preparing parylene H monomer, and the specific steps are as follows:

[0052] (1) Synthesis of bromo-p-xylene: Add p-xylene cyclodimer (41.6 g, 20.0 mmol) and iron powder (1.2 g, 21.43 mmol) into a reaction flask, then add 600 mL of dichloromethane solvent. Slowly add 24 mL of liquid bromine dropwise at room temperature. After the addition is complete, heat to reflux and react for 24 h. Quench the reaction with saturated sodium sulfite solution. After the red color of the solution disappears, perform liquid separation, remove the organic layer, filter the organic layer, collect the solid, and recrystallize the crude product with ethanol to obtain white solid bromo-p-xylene (30.66 g, 8.36 mmol, yield 42%).

[0053] Synthesis of parylene H monomer: Take the above-prepared bromo-p-xylene (10.0 g, 2.73 mmol), add 700 mL of ultra-dry ether, stir well and cool to 0 °C. Slowly add n-butyllithium solvent (65.0 ml, 81.20 mmol) dropwise using a syringe. Slowly raise the temperature to room temperature and stir for 6 h. Add (40.0 mL, 516.0 mmol) of ultra-dry N,N-dimethylformamide at 0 °C. Slowly raise the temperature to room temperature and stir for 3 h. Add 30 mL of 6N hydrochloric acid to quench the reaction solution, dilute with 50 mL of distilled water, and then extract with dichloromethane (2×100 mL). The obtained organic layer is washed with saturated sodium bicarbonate solution (2×100 mL) and saturated brine (2×100 mL). After drying with anhydrous magnesium sulfate and evaporating the solvent under reduced pressure, a pale yellow crude product is obtained. After recrystallizing the crude product with toluene, white solid parylene H monomer (6.2 g, 23.50 mmol, yield 86.0%) is obtained.

[0054] Example 2

[0055] This embodiment provides a method for improving the adhesion of parylene film, and the specific steps are as follows:

[0056] Soak the silicon wafer in acetone and perform ultrasonic cleaning, then rinse with deionized water, and finally dry for standby.

[0057] Weigh parylene C monomer and parylene H monomer according to a mass ratio of 3:1. After fully mixing the weighed parylene C monomer and parylene H monomer, put them into the evaporation chamber. Under the condition of a vacuum degree of -4.0 Pa, wait until the cracking furnace is heated to 680 °C, and at the same time heat the evaporation chamber to 160 °C. After the parylene C monomer and parylene H monomer evaporate, a chemical reaction occurs in the cracking furnace. Subsequently, at room temperature, a film is deposited on the surface of the silicon wafer in the deposition chamber to obtain a parylene coating.

[0058] Example 3

[0059] This embodiment provides a method for improving the adhesion of parylene film, and the specific steps are as follows:

[0060] Soak the silicon wafer in acetone and perform ultrasonic cleaning, then rinse it with deionized water, and finally dry it for standby.

[0061] Weigh parylene C monomer and parylene H monomer according to a mass ratio of 1:1. After fully mixing the weighed parylene C monomer and parylene H monomer, put them into the evaporation chamber. Under the condition of a vacuum degree of -4.0 Pa, wait until the cracking furnace is heated to 680 °C, and at the same time heat the evaporation chamber to 160 °C. After the parylene C monomer and parylene H monomer evaporate, the mixture undergoes a chemical reaction in the cracking furnace, and then at room temperature, a film is deposited on the surface of the silicon wafer in the deposition chamber to obtain a parylene coating.

[0062] Example 4

[0063] This embodiment provides a method for improving the adhesion of parylene film, and the specific steps are as follows:

[0064] Soak the silicon wafer in acetone and perform ultrasonic cleaning, then rinse it with deionized water, and finally dry it for standby.

[0065] Weigh parylene C monomer and parylene H monomer according to a mass ratio of 1:3. After fully mixing the weighed parylene C monomer and parylene H monomer, put them into the evaporation chamber. Under the condition of a vacuum degree of -4.0 Pa, wait until the cracking furnace is heated to 680 °C, and at the same time heat the evaporation chamber to 160 °C. After the parylene C monomer and parylene H monomer evaporate, the mixture undergoes a chemical reaction in the cracking furnace, and then at room temperature, a film is deposited on the surface of the silicon wafer in the deposition chamber to obtain a parylene coating.

[0066] Example 5

[0067] This embodiment provides a method for improving the adhesion of parylene film, and the specific steps are as follows:

[0068] Soak the silicon wafer in acetone and perform ultrasonic cleaning, then rinse it with deionized water, and finally dry it for standby.

[0069] Weigh a certain mass of parylene H monomer, and its mass is the same as the total mass of parylene C monomer and parylene H monomer in Example 2; put the parylene H monomer into the evaporation chamber. Under the condition of a vacuum degree of -4.0 Pa, wait until the cracking furnace is heated to 680 °C, and at the same time heat the evaporation chamber to 160 °C. After the parylene H monomer evaporates, the monomer undergoes cracking in the cracking furnace, and then at room temperature, a film is deposited on the surface of the silicon wafer in the deposition chamber to obtain a parylene coating.

[0070] Example 6

[0071] This embodiment provides a method for improving the adhesion of parylene film, and the specific steps are as follows:

[0072] Soak the silicon wafer in acetone and perform ultrasonic cleaning, then rinse it with deionized water, and finally dry it for standby.

[0073] Weigh parylene F monomer and parylene H monomer according to a mass ratio of 1:3. After fully mixing the weighed parylene F monomer and parylene H monomer, put them into the evaporation chamber. Under the condition of a vacuum degree of -4.0 Pa, wait until the cracking furnace is heated to 680 °C, and at the same time heat the evaporation chamber to 160 °C. After the parylene F monomer and parylene H monomer evaporate, the mixture undergoes a chemical reaction in the cracking furnace, and then at room temperature, a film is deposited on the surface of the silicon wafer in the deposition chamber to obtain a parylene coating.

[0074] Example 7

[0075] This embodiment provides a method for improving the adhesion of parylene film, and the specific steps are as follows:

[0076] Soak the glass slide in acetone and perform ultrasonic cleaning, then rinse it with deionized water, and finally dry it for standby.

[0077] Weigh parylene C monomer and parylene H monomer according to a mass ratio of 3:1. After fully mixing the weighed parylene C monomer and parylene H monomer, put them into the evaporation chamber. Under the condition of a vacuum degree of -4.0 Pa, wait until the cracking furnace is heated to 680 °C, and at the same time heat the evaporation chamber to 160 °C. After the parylene C monomer and parylene H monomer evaporate, the mixture undergoes a chemical reaction in the cracking furnace, and then at room temperature, a film is deposited on the surface of the glass slide in the deposition chamber to obtain a parylene coating.

[0078] Comparative Example 1

[0079] This comparative example provides a method for preparing parylene film, and the specific steps are as follows:

[0080] Soak the silicon wafer in acetone and perform ultrasonic cleaning, then rinse it with deionized water, and finally dry it for standby.

[0081] Weigh a certain mass of parylene C monomer, and its mass is the same as the total mass of parylene C monomer and parylene H monomer in Example 2; put the parylene C monomer into the evaporation chamber. Under the condition of a vacuum degree of -4.0 Pa, wait until the cracking furnace is heated to 680 °C, and at the same time heat the evaporation chamber to 160 °C. After the parylene C monomer evaporates, the monomer undergoes cracking in the cracking furnace, and then at room temperature, a film is deposited on the surface of the silicon wafer substrate in the deposition chamber to obtain a parylene coating.

[0082] Comparative Example 2

[0083] This comparative example provides a method for preparing a parylene film, and the specific steps are as follows:

[0084] Soak the silicon wafer in acetone and perform ultrasonic cleaning, then rinse it with deionized water, and finally dry it for standby.

[0085] Weigh a certain mass of parylene F monomer, whose mass is the same as the total mass of parylene C monomer and parylene H monomer in Example 2; put the parylene F monomer into the evaporation chamber. Under the condition of a vacuum degree of -4.0 Pa, wait until the cracking furnace is heated to 680 °C, and at the same time heat the evaporation chamber to 160 °C. After the parylene F monomer evaporates, the monomer cracks in the cracking furnace, and then at room temperature, a film is deposited on the surface of the silicon wafer substrate in the deposition chamber to obtain a parylene coating.

[0086] Performance characterization

[0087] (1) Measure the adhesion strength of parylene - silicon wafer through a scratch test, taking Comparative Example 1 as a reference. As Figure 1 shown, at the inflection point in the depth and scratch distance graph, the film cracked and peeled off. At this time, the corresponding load value (also known as the critical load) is the adhesion force between the film and the substrate, which is 2.03 mN.

[0088] Perform an adhesion force test on the parylene coatings obtained in the above - mentioned examples and comparative examples, and the results are shown in Table 1:

[0089] Table 1

[0090]

[0091]

[0092] It can be seen from Table 1 that compared with the parylene C monomer coating in Comparative Example 1, the multiple of the adhesion force improvement of the parylene coating in the examples of the present invention is 11.7 - 17 times, and it is significantly improved. It can be seen that the present invention has good application prospects in improving the adhesion force of parylene films.

[0093] (2) Figure 2 This is the electron microscope image of the parylene film prepared in Example 3 of the present invention. It can be seen from this figure that the parylene film prepared by the present invention maintains the excellent characteristics of parylene - type materials, such as no pinholes, good conformal property, uniform and complete.

[0094] Obviously, the above - mentioned examples are only examples clearly described and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A parylene copolymer material, characterized in that: The structure of the parylene copolymer material is shown below: Wherein, R1, R2, R3, and R4 are each independently selected from one of hydrogen atom, halogen, amino, nitro, ester group, aldehyde group, methoxy group, ethoxy group, cyano group, trifluoromethyl group, ethynyl group, vinyl group and saturated alkyl group; wherein m≧1, n≧1.

2. The method for preparing the parylene copolymer material according to claim 1, characterized in that: The following steps are involved: The conventional parylene monomer and parylene H monomer are prepared by chemical vapor deposition copolymerization; The conventional parylene monomer is selected from one or more of parylene N monomer, parylene C monomer, parylene D monomer, parylene F monomer and parylene HT monomer.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the conventional parylene monomer to the parylene H monomer is 0-3:1-3.

4. The preparation method according to claim 1, characterized in that: The parylene H monomer is prepared by the following method: (1) mixing a para-xylene cyclodimer and a catalyst in an organic solvent, adding liquid bromine dropwise, heating under reflux for reaction, separating the solid and the liquid after the reaction is completed, and recrystallizing the obtained solid phase to obtain brominated para-xylene; (2) The obtained bromo-p-xylene is fully stirred with diethyl ether and cooled; n-butyl lithium is added dropwise, the temperature is raised to room temperature, stirred, and the temperature is lowered; N,N-dimethylformamide is added, the temperature is raised to room temperature, and stirred to obtain parylene H monomer.

5. Use of the parylene copolymer material according to claim 1 in the preparation of parylene film.

6. A method for improving the adhesion of a parylene film, characterized in that: The following steps are involved: S1, placing the pre-cleaned substrate into a deposition chamber for standby use; S2, mixing the conventional parylene monomer to be plated with the parylene H monomer, and placing them in an evaporation chamber; the conventional parylene monomer is selected from one or more of parylene N monomer, parylene C monomer, parylene D monomer, parylene F monomer and parylene HT monomer; S3. Under the condition of a vacuum degree of -10Pa to -0.5Pa, the conventional parylene monomer and the parylene H monomer in the evaporation chamber are evaporated, pyrolyzed in the cracking furnace, and then deposited on the substrate in the deposition chamber to form a parylene film.

7. The method according to claim 6, characterized in that In step S1, the substrate is a silicon substrate; the silicon substrate is selected from one or more of a silicon wafer, a glass wafer and PDMS.

8. The method according to claim 6, characterized in that In step S2, the mass ratio of the conventional parylene monomer to the parylene H monomer is 0-3:1-3.

9. The method according to claim 6, characterized in that In step S3, the evaporation temperature is 80°C to 200°C.

10. The method according to claim 6, characterized in that In step S3, the cracking temperature is 600°C to 680°C.

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