CN104760919A - Method for manufacturing thermal sensitive thin film and thermal sensitive thin film lead - Google Patents

Abstract

The invention discloses a heat-sensitive thin film and a method for making the same. The method includes: selecting PI tape as a flexible base material, attaching the PI tape to a glass substrate, cleaning and drying the surface of the PI tape; swirling photoresist, exposing and developing to form a thin film thermistor light Resist pattern; sputter the film and heat-treat the film in the same sputtering chamber; peel off to form a thin film thermistor; spin photoresist, expose and develop to form the photoresist pattern of the connecting wire of the film; electroplate the film The connecting wires; the PI tape was released from the glass substrate. The technical scheme provided by the invention can obtain a heat-sensitive film with better performance and a connecting wire thereof.

Description

A heat-sensitive thin film and a method for making the same

technical field

The invention relates to the field of micro-electromechanical systems (MEMS), in particular to a heat-sensitive thin film based on a flexible substrate and a method for manufacturing the wire.

Background technique

MEMS (Micro-Electro-Mechanical System) devices made on flexible substrates can be attached to the surface of objects of any shape and size, and can detect shear force, pressure, temperature and humidity on the surface of non-planar objects, etc. Real-time distribution of physical parameters. Therefore, flexible substrates with good properties are very important for the performance of sensing devices.

Polyimide (PI, PolyimideFilm) film is a high temperature resistant organic polymer film, which is yellow and transparent. It is currently the best thin film insulating material in the world, with excellent mechanical properties, electrical properties, chemical stability, high radiation resistance, high temperature resistance and low temperature resistance (-269°C to +400°C). PI materials have good conditions as a flexible substrate. Generally, the required sensitive elements (such as heat-sensitive films)) and their accessories (such as connecting wires) are formed on PI. Therefore, it is very important that the sensitive elements and their accessories are firmly attached and not fall off.

There are generally two types of PI materials, one is liquid polyimide prepolymer, and the other is solid polyimide film. Because the flexible substrate needs to be attached to the hard substrate for subsequent processing, when liquid polyimide forms a PI flexible substrate, a sacrificial layer must be coated on the rigid substrate first, and then cured by multiple coatings and temperature rises. A PI flexible substrate is formed, and then a heat-sensitive film and its connecting wires are formed on the PI flexible substrate. However, this method is time-consuming and labor-intensive, and bubbles and uneven failure phenomena may occur, thereby affecting the adhesion of the heat-sensitive film and its connecting wire obtained in subsequent processing. If the solid polyimide film is directly pasted on the hard substrate to form a PI flexible substrate, although the cumbersome operation of curing can be omitted compared with the former method, it is easy to be damaged due to the unevenness of the PI film itself when pasting. Bubbles are generated between PI and the glue, which also affects the adhesion of the heat-sensitive film and its connecting wires obtained in subsequent processing.

Therefore, the two processing methods of the existing methods have their own defects, which affect the performance of the heat-sensitive film and its connecting wires. the

Contents of the invention

The technical problem to be solved by the present invention is to provide a heat-sensitive thin film and its wire manufacturing method, which can obtain a heat-sensitive thin film and its connecting wire with better performance.

In order to solve the problems of the technologies described above, the technical solutions provided by the invention are as follows:

The invention provides a heat-sensitive film and a method for making a wire thereof, comprising: selecting a polyimide PI tape as a flexible base material, attaching the PI tape to a glass substrate, cleaning and drying the surface of the PI tape Dry; spin photoresist, exposure and development to form a thin film thermistor photoresist pattern; sputter the film and heat treat the film in the same sputtering chamber; peel off to form a thin film thermistor; spin photoresist, exposure and development Forming the photoresist pattern of the connection wire of the film; electroplating the connection wire of the film; releasing the PI adhesive tape from the glass substrate.

Preferably, before the thermal treatment of the thin film thermistor photoresist pattern includes: sputtering a layer of chromium connection layer.

Preferably, the sputtering of the chromium connection layer, the sputtering of the heat-sensitive thin film and the heat treatment of the heat-sensitive thin film are carried out in the same chamber.

Preferably, said spin-coating photoresist, exposure and development before forming the connecting wire photoresist pattern of said film comprises: sputtering a layer of titanium/copper seed layer; said electroplating said connecting wire of said film comprises: removing The titanium/copper seed layer.

Preferably, after the described PI adhesive tape is released from the glass substrate, it also includes: depositing a Parylene protective layer on the surface.

Preferably, the PI tape is polyimide film with organic pressure-sensitive silicone.

Preferably, releasing the PI tape from the glass substrate specifically includes: using toluene to release the PI tape from the glass substrate.

Preferably, the removing the titanium/copper seed layer is specifically: removing the titanium/copper seed layer by using sulfuric acid or sulfuric acid plus hydrogen peroxide solution.

As can be seen from the above technical scheme, the present invention has the following technical effects: the present invention uses PI adhesive tape to replace the polyimide prepolymer used in the traditional method to solidify to form a PI film or a PI cured film (solid polyimide film) ). Compared with the polyimide prepolymer curing to form a PI film, the method of using PI tape is more convenient, and the overall thickness uniformity of the PI film is better, and the most important thing is that the glue and PI are originally integrated, so there will be no impact The air bubbles in the subsequent processing, the heat-sensitive film obtained in this way and its connecting wires and flexible substrates have stronger adhesion. Compared with the PI cured film, the bonding between the PI tape and the substrate is firmer and smoother, and there will be no air bubbles, which ensures the effectiveness and yield of the subsequent process, that is, it can effectively improve the flexibility of the heat-sensitive film and its connecting wires. Adhesion to the substrate.

Further, in the solution of the present invention, a layer of chromium connection layer is sputtered before heat treatment. Since the sputtering process uses three-target magnetron sputtering deposition equipment, it is only necessary to place the chromium and nickel targets in the sputtering chamber at the same time. , so the increase of the connection layer does not make the process engineering complicated, but it greatly increases the connection strength between nickel and PI.

Further, heat treatment is extremely important for the performance of the heat-sensitive film as a sensitive element. In the scheme of the present invention, heat treatment is carried out simultaneously in the sputtering chamber to avoid the oxidation of the nickel film exposed to the air and increase the resistance of the heat-sensitive film and the TCR (temperature coefficient of resistance, temperature coefficient of resistance) decreases. Moreover, the present invention utilizes the same equipment and conditions, and the processing efficiency is higher.

Furthermore, in the solution of the present invention, the titanium/copper seed layer is sputtered before electroplating, so that the electroplated copper is more smooth and dense, and the connection with the substrate is more tightly and firmly.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the first schematic flow sheet of the inventive method;

Fig. 2 is the second schematic flow chart of the method of the present invention;

Fig. 3 is a schematic diagram of the processing flow of the heat-sensitive film based on the flexible substrate and the connecting wire thereof according to the present invention;

Fig. 4 is an electron microscope schematic diagram of a thin film thermistor with a width of 4.92 μm in the present invention.

Among them, in Figure 3: 1-PI tape 2-glass substrate 3-reverse photoresist 4-chromium-nickel film 5-titanium copper film 6-positive photoresist 7-electroplated copper.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The invention provides a heat-sensitive thin film and its wire manufacturing method, which can obtain a heat-sensitive thin film with better performance and its connecting wire.

The content of the technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic flow chart of the first method of the present invention. Include steps:

101. Select PI tape as the flexible base material, attach the PI tape to the glass substrate, and clean and dry the surface of the PI tape;

102. Spin coating photoresist, expose and develop to form photoresist pattern of thin film thermistor;

103. Sputtering the thin film and performing heat treatment on the thin film in the same sputtering chamber;

104. Stripping to form a thin film thermistor;

105. Spin coating the photoresist, exposing and developing to form the connecting wire photoresist pattern of the film;

106. Electroplating the connecting wires of the film;

107. Release the PI tape from the glass substrate.

Fig. 2 is a second schematic flow chart of the method of the present invention. Figure 2 describes the method processing process in more detail relative to Figure 1, including steps:

201. Select PI tape as the flexible base material, attach the PI tape to the glass substrate, and clean and dry the surface of the PI tape;

202. Spin coating the photoresist, exposing and developing to form a thin film thermistor photoresist pattern;

203. Sputtering a layer of chromium connection layer, sputtering the heat-sensitive film and heat-treating the heat-sensitive film;

204, peeling off to form a thin film thermistor;

205, sputtering a layer of titanium/copper seed layer;

206. Spin coating the photoresist, exposing and developing to form the photoresist pattern of the connecting wire of the film;

207. Electroplating the connecting wires of the film;

208. Remove the titanium/copper seed layer;

209. Release the PI adhesive tape from the glass substrate by soaking in toluene;

210. Depositing a Parylene protective layer on the surface.

Fig. 3 is a manufacturing method of a thermosensitive film based on a flexible substrate and its connecting wires proposed in this embodiment of the present invention, and describes the solution of the present invention in more detail. In Figure 3: 1-PI tape 2-glass substrate 3-reverse photoresist 4-chromium nickel film 5-titanium copper film 6-positive photoresist 7-electroplated copper. Fig. 4 is a schematic diagram of an electron microscope of a thin film thermistor with a width of 4.92 μm in the present invention.

The processing shown in Figure 3 includes steps:

Step 1. Attach PI tape 1 to a clean glass substrate (glass substrate 2), and use acetone and alcohol to ultrasonically clean the surface of the PI tape and then dry it.

Among them, the drying temperature can be selected at 150°C, and the drying time can be selected in the range of 10-30 minutes due to seasonal humidity changes. As shown in Figure 3(a).

One of the most important characteristics of PI tape (polyimide tape) is high temperature resistance. Specifically, the PI adhesive tape of the present invention is polyimide film with organic pressure-sensitive silicone.

Step 2: Spin coating the reverse photoresist 3, perform reverse baking and flood exposure after soft baking and exposure, and develop to form a nickel thin film thermistor photoresist pattern. Figure 3(b)(c).

The reverse photoresist 3 in the figure can specifically be the reverse photoresist AZ5214.

Step 3: After sputtering a thin layer of chromium, sputtering a nickel metal film layer 4 with a thickness of 300 nanometers; and annealing the sputtered metal film in the same chamber and under the same environment. As shown in Figure 3(d).

It is very important to form the required sensitive components and their accessories on the PI and firmly attach them without falling off. The present invention finds that the adhesion of metal nickel and copper on PI is actually not so ideal, but the adhesion of chromium and titanium is obviously better, so the present invention sputters a layer of chromium or titanium as the connection before sputtering nickel-copper layer, which greatly increases the adhesion of sensitive components and accessories, making the sensor device more durable, and there is no problem with any turning of the flexible substrate. This step is exemplified by sputtering a thin layer of chromium as a bonding layer.

In the scheme of the present invention, a layer of chromium connection layer is sputtered before heat treatment. Since the sputtering process adopts three-target magnetron sputtering deposition equipment, it is only necessary to place chromium and nickel targets in the sputtering chamber at the same time, so the connection layer The increase of Ni does not complicate the process engineering, but it greatly increases the connection strength between Ni and PI.

Because heat treatment is extremely important for the heat-sensitive thin film performance as sensitive element, in the scheme of the present invention, heat treatment is carried out simultaneously in the sputtering chamber and has just avoided that nickel thin film is exposed to oxidation in the air and makes heat-sensitive thin film resistance increase and TCR (temperature coefficient of resistance, temperature coefficient of resistance) decreases. Moreover, the present invention utilizes the same equipment and conditions, and the processing efficiency is higher.

Step 4, soak in acetone to remove the photoresist and the metal on the glue, and peel off to form a nickel thin film thermistor with a width of 5 microns. Figure 3(e).

Step five, sputtering a titanium/copper seed layer. Figure 3(f). 5 in the figure is a titanium-copper thin film.

In the solution of the present invention, the titanium/copper seed layer is sputtered before electroplating, so that the electroplated copper is smoother and denser, and the connection with the substrate is tighter and firmer.

Step 6. Spin coat positive photoresist AZ4620, expose and develop to form photoresist patterns for connecting wires, and the width of copper wires is 500 μm, as shown in Figure 3 (g), (h). 6 in the figure is a positive photoresist.

Step 7, electroplating copper connecting wires with a thickness of 50 μm. Figure 3(i). Figure 7 is electroplated copper.

Step 8, using sulfuric acid or sulfuric acid plus hydrogen peroxide solution to remove the copper and titanium seed layers, and the overall pattern is completed. As shown in Figure 3(j).

Step 9. Release the PI tape from the glass substrate by soaking in toluene. As shown in Figure 3(k).

Step 10. Deposit a Parylene protective layer on the surface.

It can be found that the method of the present invention is to stick the PI tape on the glass substrate; spin photoresist on the PI tape, expose and develop the metal heat-sensitive film pattern; sputter chromium/nickel and carry out heat treatment in the same sputtering chamber; After peeling off, a heat-sensitive film is formed; sputtering the seed layer of titanium/copper; spin-coating photoresist, exposing and developing to expose the connecting wire pattern; electroplating copper wire; removing the seed layer; removing the glue to release PI from the glass. The process of the invention is simple and efficient, the metal heat-sensitive film is firmly attached to the PI substrate, the performance of the heat-treated metal film as a sensor sensitive element is more superior, and the interference of the connecting wire to the resistance measurement of the heat-sensitive film is minimal.

Specifically, in the solution of the present invention, PI adhesive tape is used instead of the polyimide prepolymer used in the traditional method to be cured to form a PI film or a PI cured film (solid polyimide film). Compared with the polyimide prepolymer curing to form a PI film, the method of using PI tape is more convenient, and the overall thickness uniformity of the PI film is better, and the most important thing is that the glue and PI are originally integrated, so there will be no impact The air bubbles in the subsequent processing, the heat-sensitive film obtained in this way and its connecting wires and flexible substrates have stronger adhesion. Compared with the PI cured film, the bonding between the PI tape and the substrate is firmer and smoother, and there will be no air bubbles, which ensures the effectiveness and yield of the subsequent process, that is, it can effectively improve the flexibility of the heat-sensitive film and its connecting wires. Adhesion to the substrate.

Further, in the solution of the present invention, a layer of chromium connection layer is sputtered before heat treatment. Since the sputtering process uses three-target magnetron sputtering deposition equipment, it is only necessary to place the chromium and nickel targets in the sputtering chamber at the same time. , so the increase of the connection layer does not make the process engineering complicated, but it greatly increases the connection strength between nickel and PI.

Further, heat treatment is extremely important for the performance of the heat-sensitive film as a sensitive element. In the scheme of the present invention, heat treatment is carried out simultaneously in the sputtering chamber to avoid the oxidation of the nickel film exposed to the air and increase the resistance of the heat-sensitive film and the TCR (temperature coefficient of resistance, temperature coefficient of resistance) decreases. Moreover, the present invention utilizes the same equipment and conditions, and the processing efficiency is higher.

Furthermore, in the solution of the present invention, the titanium/copper seed layer is sputtered before electroplating, so that the electroplated copper is more smooth and dense, and the connection with the substrate is more tightly and firmly.

The technical solutions provided by the embodiments of the present invention have been described in detail above. The principles and implementation methods of the present invention have been explained by using specific examples in this paper. The descriptions of the above embodiments are only used to help understand the methods and methods of the present invention. core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and scope of application. In summary, the content of this specification should not be construed as limiting the present invention .

Claims (8)

1. A heat-sensitive thin film and a method for making a wire thereof, characterized in that, comprising: Select polyimide PI adhesive tape as flexible base material, described PI adhesive tape is attached on glass substrate, the surface of described PI adhesive tape is cleaned and dried; Spin coating photoresist, exposure and development to form thin film thermistor photoresist pattern; Sputtering thin films and heat-treating thin films in the same sputtering chamber; Peel off to form a thin film thermistor; Spin coating photoresist, exposure and development to form the connecting wire photoresist pattern of the film; electroplating the connecting wires of the film; The PI tape was released from the glass substrate. 2 . The heat-sensitive thin film and its wire manufacturing method according to claim 1 , wherein, before the heat-sensitive thin film is sputtered and heat-treated, it comprises: sputtering a layer of chromium connecting layer. 3 . 3. The heat-sensitive thin film and its wire manufacturing method according to claim 2, characterized in that the sputtering of the chromium connection layer, the sputtering of the heat-sensitive thin film and the heat treatment of the heat-sensitive thin film are carried out in the same cavity. 4. heat-sensitive thin film according to claim 1 and lead wire manufacturing method thereof, it is characterized in that, described spin coats photoresist, before exposure development forms the connecting wire photoresist pattern of described film, comprises: sputtering one layer Titanium/copper seed layer; After the electroplating of the connecting wire of the thin film includes: removing the titanium/copper seed layer. 5. heat-sensitive thin film according to claim 1 and wire manufacturing method thereof, is characterized in that, described PI adhesive tape also comprises after described PI adhesive tape is released from glass substrate: depositing Parylene protective layer on surface. 6. The heat-sensitive film and its wire manufacturing method according to any one of claims 1 to 5, characterized in that, the PI adhesive tape is a polyimide film with organic pressure-sensitive silica gel. 7. according to any one of claims 1 to 5, the heat-sensitive film and its wire manufacturing method are characterized in that, releasing the PI adhesive tape from the glass substrate is specifically: utilizing toluene to release the PI adhesive tape from the glass substrate On-chip release. 8. The heat-sensitive thin film and its wire manufacturing method according to any one of claims 4 to 5, characterized in that removing the titanium/copper seed layer is specifically: removing the titanium/copper seed layer by using sulfuric acid and sulfuric acid plus hydrogen peroxide solution copper seed layer.