CN116215081A - Microfluidic device, manufacturing method and application thereof - Google Patents

Abstract

The invention provides a microfluidic device, a manufacturing method and application thereof. The manufacturing method of the microfluidic device comprises the following steps: forming a heat insulation layer on a wafer substrate, forming a metal wire and a preset slot structure on the heat insulation layer, forming a thin film resistor on the preset slot structure, forming a passivation layer on a thin film resistor area and the metal wire layer, forming a fluid containing cavity aiming at the preset slot structure area, manufacturing a hydrophilic film on the inner wall of the cavity, manufacturing a nozzle by adopting a process method of a photosensitive dry film, and forming an integrated device with the resistor, the cavity and the nozzle manufactured on the same chip. The invention improves the chip integration level of the microfluidic device, simplifies the process flow, reduces the manufacturing cost, and improves the consistency, stability and reliability of the printing head chip.

Description

Microfluidic device and its manufacturing method and application

technical field

The invention relates to the technical field of microfluidic electronic components, in particular to a microfluidic device and its manufacturing method and application.

Background technique

The core of an inkjet printer is a large number of high-precision micro inkjet nozzles. Several different precision microfabrication techniques for inkjet nozzles are used in commercial production, including electroforming, laser ablation, anisotropic etching, and photolithography. For each color of ink, all nozzles on the carriage are usually formed in a single manufacturing step to precisely control their relative positions, which is important for uniform printing without streaks. In some cases, all nozzles for each color ink are formed together in one step. The inkjet nozzles are all mounted on a moving carriage assembly that moves back and forth at high speed (typically >1 m/s). The nozzles are installed about 1 mm away from the paper, and the ink ejection speed is in the range of 5-10 meters per second. Ink is ejected from the nozzle by applying a pressure pulse to the fluid ink in the supply tube upstream of the nozzle.

The ink ejected from the nozzle mainly depends on the pressure pulse, and there are two ways to generate the pressure pulse: thermal bubble method and piezoelectric method. Among them, in the thermal bubble technology, a thin-film resistive metal layer with a thickness of less than 1 micron is used to form a small heater in the ink channel wall leading to each nozzle. Low-resistance metal conductors are connected to both sides of the heating resistor, and a pulse of current flows through the heating resistor with a duration of approximately 1 microsecond. The magnitude of this current is designed to heat the resistor enough to boil the ink. The thin layer of ink closest to the resistor boils explosively, forming a vapor bubble that expands about a thousand times in volume. This volume expansion creates a pressure pulse in the fluid, causing ink in the nozzle (downstream of the heater) to be ejected towards the paper. After a few microseconds, the vapor bubble cools and bursts. The surface tension of the ink meniscus in the nozzle then draws more ink from the reservoir, refilling the nozzle and preparing it for the next drop.

In an existing conventional inkjet print head chip, resistors and cavities are fabricated on a wafer substrate, and nozzles are fabricated on a separate nozzle plate (NozzlePlate). After the two are manufactured separately, the wafer and the nozzle plate are combined by bonding. This method has disadvantages such as complex process, low integration level, and high manufacturing cost. At the same time, during the bonding process of the wafer and the nozzle, there is an error in the alignment of the nozzle and the resistor, resulting in poor consistency and stability of the device and affecting the printing quality.

Contents of the invention

Based on this, the present invention proposes a new method for manufacturing microfluidic devices, which integrates components such as resistors, cavities, and nozzles in the microfluidic device on the same chip, which improves the integration of the device, simplifies the process, and reduces cost, and improve device consistency and stability.

The present invention adopts following technical scheme:

The invention provides a microfluidic device, comprising: a thin film resistor integrated on a wafer substrate, a fluid containing cavity and a nozzle; the fluid containing cavity has a hydrophilic film layer, and the fluid containing cavity The wall of the device is provided with a thin-film resistor for heating the fluid; the nozzle is made of photosensitive dry film, and the nozzle is connected to the fluid containing cavity.

The present invention also provides a method for manufacturing the above-mentioned microfluidic device, including the following steps: forming a heat-insulating insulating layer on the wafer substrate, forming metal wires and a preset slot structure on the heat-insulating insulating layer; forming a thin film resistor; forming a passivation layer on the thin film resistor area and the metal wire layer; forming a fluid containing cavity for the preset slot structure area; forming a hydrophilic film on the inner wall of the fluid containing cavity; corresponding to the The fluid containing cavity is used to make the photosensitive dry film cap layer and the nozzle for ejecting the fluid; the resistor, the cavity and the nozzle are sequentially fabricated on the wafer to form an integrated chip.

In some of the embodiments, the material of the thermal insulation layer is preferably selected from at least one of silicon oxide, silicon nitride and silicon carbide.

In some of these embodiments, the materials for making thin film resistors include Ni-Co series, Ta series, Si series, cermet series resistance films and resistance films such as Au-Cr and Ni-P, preferably from TaAl, TaN, NiCr, TaSiO At least one of ₂ .

In some of the embodiments, the passivation layer is made of at least one material selected from silicon oxide, silicon nitride, and silicon carbide.

In some of the embodiments, the fluid containing cavity is mainly surrounded by a photoresist layer and a thin film resistor.

In some of these embodiments, the hydrophilic film is preferably made of chromium, aluminum, zinc, oxides of chromium, oxides of aluminum, oxides of zinc, hydroxides of chromium, hydroxides of aluminum, zinc at least one of the hydroxides.

In some of the embodiments, the cap nozzle is a V-shaped opening structure composed of multiple layers of photosensitive dry film. The photosensitive dry film is selected from at least one of photopolymerizable photosensitive dry film and photodecomposable photosensitive dry film. The multi-layer photosensitive dry film includes photopolymerization type and photodecomposition type, and can be two-layer, three-layer or multi-layer, so as to meet the requirements of the device on the mechanical properties of the cavity, the resolution of the nozzle, the shape of the nozzle, and the like.

The present invention can also provide an inkjet nozzle for a printer, which is manufactured by using the method for manufacturing the above-mentioned microfluidic device.

Compared with prior art, the beneficial effect of the present invention is:

The invention proposes a new manufacturing method, which integrates components such as resistors, cavities, and nozzles in the microfluidic device on the same chip, which improves the chip integration of the microfluidic device, simplifies the process flow, and reduces the manufacturing cost. Cost, improve the consistency, stability and reliability of the print head chip.

Description of drawings

Fig. 1 is a schematic diagram of the structural layout relationship between the substrate and the heat insulating layer.

Fig. 2 is a schematic diagram of the manufacturing process of the metal wire.

Fig. 3 is a schematic diagram of the manufacturing process of the thin film resistor.

FIG. 4 is a schematic diagram of the structural layout of the passivation layer.

Fig. 5 is a schematic diagram of the manufacturing process of the cavity.

Fig. 6 is a schematic diagram of the structural layout of the hydrophilic film.

Fig. 7 is a schematic diagram of the production process of the cap and the nozzle.

Fig. 8 is a structural schematic diagram of a cap and a nozzle formed by a multi-layer photosensitive dry film.

FIG. 9 is a schematic diagram of the structure of a wafer.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments, so that those skilled in the art can understand the present invention more clearly.

The following examples are only used to illustrate the present invention, but not to limit the scope of the present invention. Based on the specific embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; in the embodiments of the present invention, if not specifically specified, the technical means used are all well-known conventional means.

The technical idea of the present invention is to provide a method for manufacturing a microfluidic device, which includes the following steps:

S1, providing a substrate.

In this step, the substrate is preferably a substrate containing silicon, such as silicon, sapphire, glass, and the like. The size can be 3-12 inches (or 75-300 mm), and the thickness is between 500-1000 μm.

S2, forming a thermal insulation layer on the substrate.

As shown in FIG. 1, a thermal insulation layer is formed on a substrate. In this step, the material of the thermal insulation layer is preferably at least one of silicon oxide, silicon nitride, and silicon carbide, and the thickness is between 1 μm and 5 μm.

Among them, the methods for preparing _SiO2 thin films mainly include chemical vapor deposition, thermal oxidation, magnetron sputtering, ion beam sputtering and other methods. SiO ₂ thin film has good insulation performance, good stability, strong film layer, long-term use temperature can reach above 1000 ℃.

The silicon nitride thin film can be prepared by physical vapor deposition (PVD), chemical vapor deposition (CVD), thermal reaction, and the like.

Silicon carbide (SiC) has excellent properties such as high hardness, good thermal stability, stable structure, and high thermal conductivity, and silicon carbide thin films can be prepared by physical vapor deposition and chemical vapor deposition.

S3, forming metal wires on the heat insulating layer.

As shown in Fig. 2, in this step, firstly, a metal layer is formed on the heat insulating layer by evaporation or sputtering. The metal material is preferably Al, Cu, AlCu, etc., and the thickness is preferably 0.1-2um. Then a photoresist layer is formed on the metal layer, and it is made by photolithography processes including glue coating, alignment, exposure, development and the like. Further steps such as metal etching, glue removal, and cleaning are performed to form the metal layer with a preset slot structure.

Optionally, the fabrication of metal wires can also be completed by a process called "Metal Lift-off".

S4, forming thin film resistors on the preset slot structure.

As shown in Figure 3, first, the sputtering method is used to form a resistive material layer on the metal layer and the preset slot structure, and then a photolithography process and an etching process are used to form a thin film resistor area for the preset slot structure. It is used to eject the fluid by using the principle of hot air bubbles.

In this step, the material for making the thin film resistor is preferably TaAl, TaN, NiCr, TaSiO ₂ , etc., and the thickness of the thin film resistor is preferably 10-1000 nm.

S5, forming a passivation layer on the thin film resistor region and the metal wire layer.

As shown in FIG. 4, a passivation layer is formed on the thin film resistor area and the metal wiring layer.

In this step, the material for making the passivation layer is preferably silicon oxide, silicon nitride, silicon carbide, etc., and the thickness is preferably 100-1000 nm.

S6, forming a fluid containing chamber for the predetermined slot structure area.

In this step, select a photoresist for fabricating the device structure, such as SU-8 series photoresist. The invention adopts the epoxy resin-based photoresist, which is used in the fabrication of micro-electro-mechanical systems (MEMS) and other microelectronic devices. Its viscosity range allows one-step coating film thickness between 4 ~ 120μm. Glue coating speed is 200-5000rpm, time is 5-30sec, depending on the type and thickness of photoresist.

As shown in FIG. 5 , the process steps include: cleaning the surface of the passivation layer, applying glue, and forming a photoresist layer. Alignment, exposure, exposure dose and time are determined by photoresist type, thickness and exposure equipment. The specific parameters are optimized by exposure matrix experiments to optimize the exposure dose and time. Negative-tone photoresists The exposed portions of the photoresist that become insoluble in the photoresist developer remain, while the unexposed portions of the photoresist are dissolved by the photoresist developer. Developing, stripping, curing and reflow, the developing time is determined by parameters such as the type of photoresist, the type of developer, and the thickness of the glue.

After the above process is completed, the inner wall of the cavity is formed, which is composed of a passivation layer and a photoresist inner wall.

S6, making a hydrophilic film on the inner wall of the cavity.

As shown in Figure 6, in this step, in order to ensure smooth flow channels, continuous liquid supply, liquid injection frequency control, etc., a hydrophilic film layer needs to be added to the inner wall of the cavity, that is, the material of the wall surface is a substance with high surface energy. , so that the interaction force between water molecules and material molecules is greater than the cohesive force between water molecules, resulting in the material surface being fully wetted by water. The hydrophilic material may be metals such as chromium (Cr), aluminum (Al), zinc (Zn) and their oxides or hydroxides. The hydrophilic material can also be other materials, such as glass, aluminum alloy, plastic, and the like.

In order to make the cavity hydrophilic, a layer of hydrophilic material film can be made on the inner wall of the cavity. Taking the metal material Al as an example, it can be produced by evaporation (Evaporation) and sputtering (Sputtering) methods, with a thickness of 100-1000 nm. The metal layers in other parts are removed through process steps such as photolithography and etching.

S7, caps and nozzles for making photosensitive dry film materials:

Make a photosensitive dry film as a cavity capping layer, and make a nozzle. The preparation process specifically includes film attachment, mask calibration, exposure, development, cleaning, etc.

(a) in FIG. 7 shows the film sticking step, that is, laying a layer of photosensitive dry film on the surface of the front photoresist. Specifically, the following process parameters are optimized during the film-attaching process: preheating temperature and time, pressing temperature, pressure roller temperature, film-attaching pressure, film-attaching speed, pressing time, etc.

(b) in FIG. 7 shows the steps of mask alignment (Alignment) and exposure (Exposure). Specifically, after the film is pasted, the mask is aligned, and after the alignment, exposure is performed. The purpose of alignment is to align the alignment mark on the photomask with the mark on the wafer substrate, so as to ensure that the position of the nozzle is consistent with the position of the heater.

If the temperature of the photosensitive dry film is different from room temperature before exposure, it is necessary to let the dry film stand for about 15-30 minutes to cool down to room temperature. The specific exposure process parameters are adjusted and optimized according to the different types of dry film materials selected.

(c) in FIG. 7 shows a developing and cleaning step, that is, developing and cleaning the dry film to remove the unexposed dry film. The photosensitive dry film is a negative photoresist. After being illuminated, the photocuring reaction can quickly occur in the exposed area and become an insoluble substance. The part that has not been exposed can be removed by developing.

It needs to stand for a period of time before developing, about 15-30 minutes. The solvent and development parameters for development, such as temperature, pressure, concentration, time, etc., are adjusted according to the type of dry film.

After cleaning, the remaining photosensitive dry film forms a cavity capping layer, together with the thin film resistor at the bottom, hydrophilic film, and side photoresist to form a cavity, and the photosensitive dry film above the cavity forms a nozzle.

Depending on the application, the size of the nozzle can be between 5 and 100 μm. Because the photosensitive dry film is a negative photoresist, by controlling and optimizing the exposure process, a trumpet-shaped nozzle as shown in (c) in FIG. 7 can be formed.

According to the different applications of the device, the difference in the size of the cavity and the nozzle, the corresponding photosensitive dry film should be selected. For example, in applications where the volume of the cavity is required to be large, the thickness of the photosensitive dry film should be increased accordingly to ensure the mechanical performance requirements of the cavity. The increase in the thickness of the photosensitive dry film will lead to a decrease in resolution and affect the minimum size and precision of the device. Therefore, according to the specific application and design of the device, the corresponding photosensitive dry film should be selected and the process should be optimized to achieve the required device design indicators.

Photosensitive dry film is usually composed of three parts: polyethylene film, photoresist film and polyester film: photosensitive layer, carrier layer and protective layer. Among them, the photosensitive layer, also called photoresist film, is the most important component of the photosensitive dry film, and its main component is the photosensitive material for photolithography. When the composition of the photosensitive layer is a polymer binder (alkali-soluble resin), the main components are acrylic resin, methacrylic acid, butyl acrylate, ethyl acrylate and the like. The main components of the photosensitive layer are glycerin propoxylate triacrylate, ethoxylated bisphenol A dimethacrylate, ethoxylated nonylphenol acrylate, etc.; the thickness of the photosensitive layer is generally between 10 μm and 100 μm. The carrier layer is the carrier of the photosensitive layer, which is a polyester film, which is used to coat the mixed photosensitive material into a film, and the thickness is generally between 10-30 μm; the protective layer of the photosensitive dry film is a polyethylene film, and its main function is to isolate oxygen and separate Layer and avoid mechanical damage, the thickness is generally between 10-40μm. The main technical indicators of photosensitive dry film include resolution, etch resistance, chemical stability, adhesion, mechanical properties, etc., which determine the core performance of photosensitive dry film in the device manufacturing process.

Resolution affects the minimum size and accuracy of the device. Resistance to etch lines and chemical stability affect the quality reliability of the device. Adhesion and mechanical properties affect the strength of the device. In addition, the photosensitivity, development and development resistance of photosensitive dry film will affect the manufacturing process, efficiency and yield.

There are two types of photosensitive dry film: photopolymerization type and photodecomposition type. The photopolymerization type dry film will harden under the light of a specific spectrum, changing from water-soluble to water-insoluble. The photodecomposition type is just the opposite. Specific products and specifications vary widely. Different materials and thicknesses of photosensitive dry film have a great influence on the intensity and resolution.

For different applications, choose the corresponding photosensitive dry film. In order to improve the mechanical properties of the cavity and the resolution of the nozzle, a two-layer or multi-layer structure can also be used.

As an example, Figure 8 shows the structure of two photosensitive dry films. The specific process flow is shown in (a)-(c) in FIG. 7 .

Generally speaking, the resolution is inversely proportional to the thickness of the film, the larger the film thickness, the worse the resolution. To obtain a smaller nozzle size, a thinner dry film thickness should be used.

Photosensitive dry film-1 and photosensitive dry film-2 can be the same or different, including film material type and material thickness. If Photosensitive Dry Film-1 and Photosensitive Dry Film-2 are the same material, the thickness of Photosensitive Dry Film-2 should be smaller than that of Photosensitive Dry Film-1 to make smaller nozzle size.

The final nozzle size is the upper opening size of the photosensitive dry film-2. The size of the lower opening of the photosensitive dry film-2 is equal to or greater than the size of the upper opening of the photosensitive dry film-2, so as to reduce the resistance when the liquid is ejected.

According to the different requirements of the application, three or more layers of photosensitive dry film can also be used to meet the requirements of the shape and size of the nozzle. For multi-layer photosensitive dry film, the material type and thickness can be the same or different. If the photosensitive dry film of each layer is the same material, in general, the thickness of the upper layer should be smaller than that of the previous layer to make a smaller nozzle size.

In the device manufactured by the above method, the heater, the fluid containing body and the nozzle are integrated and manufactured on the same chip, which improves the integration degree of the device, simplifies the manufacturing process, and improves the stability and reliability of the device.

This method can be used to make various microfluidic devices and devices. It can also be used to make inkjet printing chips. Figures 6-8 show a part of the inkjet printing chip, including resistors, fluid containing chambers, and nozzles. All components are fabricated on the same chip. The shape, size, and layout of each component of the device shown in the figure are just an example, not any limitation to the device.

Furthermore, in the fabrication of the inkjet print head chip, the inkjet printing device, including resistors, cavities, flow channels, nozzles, etc., and the CMOS control circuit for power control are integrated on the same chip to form a complete The integrated print head chip further improves the integration of the chip, simplifies the process flow, reduces manufacturing costs, and improves the consistency, stability and reliability of the print head chip.

The integrated print head chip shown is fabricated on a wafer, and the substrate size of the wafer may be 4-12 inches (100-300 mm). The finished wafer is shown in FIG. 9 . Each grid is a chip, and the chip can be square or rectangular. The number of devices on each chip ranges from tens to hundreds, or even thousands. Using semiconductor technology to manufacture MEMS devices and print head chips can improve the integration, reliability, consistency, and uniformity of the chips, simplify the manufacturing process, reduce costs, and facilitate mass production and application.

It must be pointed out here that the above examples are only limited to further elaboration and description of the technical solution of the present invention, and are not further limitations on the technical solution of the present invention. The method of the present invention is only a preferred implementation, not a Used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A microfluidic device, characterized in that it comprises: a resistor, a fluid containing chamber and a nozzle integrated on a wafer substrate; The fluid containing cavity has a hydrophilic film layer, and the wall of the fluid containing cavity is provided with a thin film resistor for heating the fluid; The nozzle is made of photosensitive dry film, and the nozzle is connected to the fluid containing cavity. 2. A method for manufacturing a microfluidic device according to claim 1, comprising the steps of: Forming a thermal insulation layer on the wafer substrate; Forming metal wires and preset slot structures on the heat insulating layer; forming thin film resistors on the preset slot structure; Forming a passivation layer on the thin film resistor area and the metal wiring layer; forming a fluid containing cavity for the predetermined slot structure area; forming a hydrophilic film on the inner wall of the fluid containing cavity; Corresponding to the fluid containing cavity, making a photosensitive dry film cap layer and a nozzle for ejecting fluid; form an integrated chip. 3. The manufacturing method of the microfluidic device according to claim 2, characterized in that, the material of the thermal insulation layer is selected from at least one of silicon oxide, silicon nitride, and silicon carbide. 4. The manufacturing method of the microfluidic device according to claim 2, characterized in that, the material for making the thin film resistor is selected from at least one of TaAl, TaN, NiCr, and TaSiO ₂ . 5. The manufacturing method of the microfluidic device according to claim 2, characterized in that, the material for making the passivation layer is selected from at least one of silicon oxide, silicon nitride, and silicon carbide. 6 . The method for manufacturing a microfluidic device according to claim 2 , wherein the fluid containing cavity is mainly surrounded by a photoresist layer and a thin film resistor. 7. the manufacture method of microfluidic device according to claim 2 is characterized in that, the making material of hydrophilic thin film is selected from the oxide of chromium, aluminum, zinc, chromium, the oxide of aluminum, the oxide of zinc , at least one of chromium hydroxide, aluminum hydroxide, and zinc hydroxide. 8 . The method for manufacturing a microfluidic device according to claim 2 , wherein the nozzle is a V-shaped opening structure composed of multiple layers of photosensitive dry film. 9 . The manufacturing method of the microfluidic device according to claim 8 , wherein the photosensitive dry film is selected from at least one of photopolymerization type photosensitive dry film and photodecomposition type photosensitive dry film. 10. An inkjet nozzle for a printer, characterized in that, the inkjet nozzle for a printer is manufactured by the method for manufacturing a microfluidic device according to any one of claims 2 to 9.

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