TW201908527A - Method for fabricating thin film electrode of normal temperature gas sensor chip by using ultrafast laser performing a more complicated and faster processing procedure in a green production manner to meet the needs of a product - Google Patents

Abstract

This invention provides a method for fabricating a thin film electrode of a normal temperature gas sensor chip by using an ultrafast laser. The method includes the following steps: fabricating a thin film on a substrate, and ablating the thin film by an ultrafast laser process at a normal temperature to form a thin film electrode with an electrode pattern. This invention mainly utilizes a non-contact machining manner of an ultrafast laser scanning process, in combination with a mirror group scanning integration technique, to fabricate a conductive thin film electrode, and integrate a wireless gas sensor chip, produces less pollution and wear in terms of fabrication and can perform a more complicated and faster processing procedure in a green production manner to meet the needs of a product.

Description

 Method for producing film electrode of normal temperature gas detecting wafer by ultra-fast laser  

The present invention relates to a method for fabricating a thin film electrode of a gas detecting wafer, and more particularly to a method for producing a thin film electrode of a gas detecting wafer by ultrafast laser.

In recent years, the technology of gas sensor has developed at a relatively fast speed, and in addition to the continuous breakthrough of the prior art, the application range has been continuously expanded. The operation principle of the gas sensor is to use the surface of the film to adsorb the gas to be tested, to catalyze the gas, to make a change in the resistance of the film, and then to analyze the change signal to obtain the concentration of the gas to be detected.

In general, gas sensors are commonly used to detect alcohol, flammable gases, environmental gases, and volatile organic compounds. They can be used to detect indoor, outdoor, and even human gases for safe maintenance.

At the level of personal health applications, countries such as Europe and the United States have found that the human body has a certain increase in gas concentration when it is sick. At present, research has focused on detecting the carbon dioxide concentration of the human body, so if the gas sensor can be made into Portable and integrated on mobile devices, it can effectively monitor human health, assist in diagnosis, achieve immediate monitoring effects and its motivation for development.

However, there are still areas for improvement in the fabrication and application of conventional gas sensors.

At present, the gas detection film on the market is a fork-shaped electrode made of metal and metal oxide, which is fabricated by an optical lithography process, and the optical lithography process is commonly used in the semiconductor and optoelectronic industries. The technology, however, because it requires multiple processes such as exposure, development, etching, etc., the error of each process will accumulate, affecting the uniformity of the final product, and the gas detection film thus produced is not sensitive. . And because of the material characteristics, it is generally necessary to add a heater to heat the gas to about 300 ° C to detect harmful gases.

When you want to make a gas sensing electrode that can work at room temperature, you need to use other materials, such as graphene, reduced graphene oxide, indium tin oxide, zinc gallium oxide, etc., but such materials are usually not optical lithography. The process generally produces a good thin film electrode. In summary, how to propose a convenient and rapid process to fabricate such a material into a thin film electrode of a gas detecting wafer is obviously an urgent problem to be solved in the art.

In order to solve the problems disclosed above, the object of the present invention is to provide a process with a simple step to provide a thin film electrode for fabricating a gas detecting wafer, to improve the speed of film electrode fabrication, and to improve the uniformity of the film electrode quality, and to apply to non- Material of metal materials.

In order to achieve the above object, the present invention provides a method for fabricating a thin film electrode of a normal temperature gas detecting wafer by an ultra-fast laser, which comprises forming a thin film on a substrate, and at an ordinary temperature, an ultra-fast lightning The film is ablated to attenuate the film to form a film electrode having an electrode pattern.

Wherein the ultra-fast laser process comprises a first ultra-fast laser pulse ablation film having a first scanning speed and a first scanning power; and a second ultra-fast laser having a second scanning speed and a second scanning power Pulse ablation film. Specifically, the first scanning speed is greater than the second scanning speed, and the first scanning power is greater than the second scanning power. Among them, the ultra-fast laser pulse used in the ultra-fast laser process has a pulse duration of 10 ^-12 ~ 10 ^-15 seconds.

In the present invention, the material of the substrate is one of a polymer material, glass or germanium. The material of the film is metal, polymer conductive material, or graphene, reduced graphene oxide, indium tin oxide, zinc gallium oxide.

In the present invention, the electrode pattern has a spiral shape. Specifically, the electrode pattern has a polygonal spiral shape, a circular spiral shape, a cylindrical spiral shape, a spherical spiral shape, or an aspherical spiral shape.

In summary, the method for producing a gas detecting wafer of a wafer by ultra-fast laser has at least the following advantages:

1. Compared with the conventional lithography process, the process of the invention is simple and the final product has better consistency.

2. Using ultra-fast laser process, because ultra-fast laser has very low heat accumulation effect, the surface damage of the wafer is lower than the traditional process, which makes the gas detection wafer produced with higher sensitivity and better which performed.

3. Conventional gas sensor, a heater (Heater) must be installed inside, and the gas can be sensed after heating the gas to a high temperature (about 300 degrees). However, the gas detection wafer produced by the process can be used at normal temperature. Work, so the heater can be omitted, the cost is lower, and the use is more convenient.

S21, S22, S221, S222‧‧ steps

1‧‧‧Ultrafast laser system

11‧‧‧Ultrafast laser source

12‧‧ ‧Shutter

13‧‧‧beam expander

14‧‧‧ Focusing lens group

15‧‧‧Mirror group

16‧‧‧ Piezoelectric Actuator

17‧‧‧F-theta flat field laser focusing lens

18‧‧‧ computer

20‧‧‧ wafer

50‧‧‧Test cavity

61‧‧‧ gas detector

611‧‧‧Substrate

612‧‧‧film electrode

613‧‧‧Power supply

62‧‧‧Wireless sensing module

621‧‧‧Induction coil

622‧‧‧ Computing Module

S‧‧‧ spacing

W‧‧‧Width

L‧‧‧Bian Chang

1 is a schematic view of an ultrafast laser system of the present invention.

2 is a flow chart of a method for producing a thin film electrode of a normal temperature gas detecting wafer by ultra-fast laser in the present invention.

Fig. 3 is a schematic view showing the type of the electrode pattern of the present invention.

4 is a flow chart of a method of the ultrafast laser process of the present invention.

Figure 5 is a schematic diagram of the system of the gas detection system.

Fig. 6 is a rectangular spiral electrode pattern.

Figure 7 is a graph showing the results of a continuous cycle test using 150 ppm of CO.

Figure 8 is a graph showing the results of a continuous cycle test using 50 ppm of CO.

The specific embodiments are described below to illustrate the embodiments of the invention, but are not intended to limit the scope of the invention.

Referring to FIG. 1, the method for fabricating a thin film electrode of a gas detecting wafer by ultra-fast laser is fabricated by using an ultra-fast laser system including an ultrafast laser (Ultrafast laser). The light source 11, a shutter 12, a beam expander 13, a focusing lens, a mirror group 15, a piezoelectric transducer stage (PZT stage, a piezoelectric transducer stage) An F-theta flat field laser focusing lens 17 (F-theta lens) and a computer 18. The computer is used to control the shutter and the piezoelectric actuator to adjust the process parameters.

The ultra-fast laser source produces laser light with a wavelength of 532 nm, which is sequentially projected through the shutter, beam expander, focusing lens group, mirror group, piezoelectric actuator, and F-theta flat field laser focusing lens. The processed wafer 20 is on.

Referring to FIG. 2, the present invention provides a method for fabricating a thin film electrode of a normal temperature gas detecting wafer using the above ultrafast laser system, comprising the following steps:

S21: Making a film on a substrate.

S22: The film is ablated by an ultra-fast laser process at a normal temperature to form a film electrode having an electrode pattern.

The following is a detailed explanation of the above steps.

In step S21, the substrate used may be made of different materials based on different considerations, such as a polymer material (such as PET (Polyethylene), PDMS (Polydimethylsiloxane), glass or germanium.

Similarly, the material of the film can also be based on different considerations, such as metal (such as gold, silver, copper, aluminum, nickel, zinc, etc.) or poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT: PSS). Molecular conductive materials, or related conductive film substrates, such as graphene, reduced graphene oxide, indium tin oxide, zinc oxide gallium and other materials.

The method for producing the film can be produced by a spin coating process. For the production of graphene film, the specific production process is as follows: at room temperature, using graphite as a raw material, liquid phase exfoliation is used to make graphene ink, followed by precise spin coating. A precision spin coater coats the graphene ink uniformly on the surface of the substrate to form a multilayer graphene film on the substrate.

After step S21 is completed, the substrate coated with the film is placed in an ultra-fast laser system, and step S22 is performed.

In step S22, because the gas sensing wafer is in need of sensing, the electrode pattern of the thin film electrode has a spiral shape or other meander shape, so that it has a large inductance. Referring to FIG. 3 in detail, the shape of the spiral electrode pattern may be (a) polygonal spiral, (b) circular spiral or (c) Fermat spiral, and other electrode patterns include (d) Zigzag, (e) Contour-parallel, (f) Hilbert Curve, and the like.

The ultra-fast laser process in step S22 is to use a laser pulse having a pulse length of 10 ^-12 to 10 ^-15 seconds, and the ultra-fast laser process proposed by the present invention is such that the film electrode has a good ablation edge. The film is ablated at two different power and scanning speed laser pulses until the film is ablated to the desired electrode pattern. Wherein, the scanning speed refers to the moving speed of the laser on the plane to be ablated of the substrate.

Referring to FIG. 4, the ultra-fast laser process proposed by the present invention specifically includes the following steps:

S221: The film is ablated by a first ultra-fast laser pulse having a first scanning speed and a first scanning power.

S222: The film is ablated by a second ultrafast laser pulse having a second scanning speed and a second scanning power.

Wherein, the first ultra-fast laser pulse is used to ablate most of the film on the substrate, so that it has a faster scanning speed and a higher scanning power, and the second ultra-fast laser pulse is used for denuding The remaining film on the substrate has a slower scanning speed and lower scanning power.

That is, the first scanning speed is greater than the second scanning speed, and the first scanning power is greater than the second scanning power. For example, the first scanning speed may be 700 mm/s, the first scanning power may be 4.40 J/cm ² , the second scanning speed may be 500 mm/s, and the second scanning power may be 1.90 J/cm ² .

Please refer to Annex 1 and Appendix 2, which are photographs taken by an electron microscope on a graphene film electrode manufactured by using the ultrafast laser process of the present invention, which is a structural edge of the film electrode, and the magnification of the accessory 1 is 300 times. The magnification of Annex 2 is 750 times. As can be seen, the glass substrate is almost undamaged, with few debris, and the film does not have any significant cracks, while the edges of the film have a good, steep slope.

In order to make the advantages of the present invention clearer, an example of a graphene film electrode produced by the method of the present invention will be described below.

Please refer to FIG. 5 , which is a schematic diagram of a system of a gas detection system, including a test cavity 50 , a gas detector 61 , and a wireless sensing module 62 . The gas detector is placed in the test chamber and the wireless sensing module is placed outside the test chamber.

The gas detector comprises a substrate 611 on which a thin film electrode 612 made by the method of the present invention is provided, and both ends of the electrode are connected by wires to a power source 613 (i.e., a battery) to supply an electric current. The wireless sensing module includes an induction coil 621 and an operation module 622. The calculation module calculates a mutual inductance of the induction coil and the membrane electrode to calculate a resistance value of the membrane electrode of the gas detector.

In the present embodiment, a rectangular spiral electrode pattern as shown in Fig. 6 was used, and a type 1 and type 2 graphene film electrode was produced and placed in the gas detecting system shown in Fig. 5 for testing. The sides of the two types of electrode patterns have the same side length (L, Length), the electrode spacing (S, Spacing) is the same, and the electrode width (W, Width) is different from the number of turns (T, Turns), as shown in Table 1. Show.

Please refer to FIG. 7 and FIG. 8 , which are the results of a continuous cycling test in a test chamber using a gas sensor of a type 1 and type 2 graphene film electrode. The test temperature was room temperature, the CO (carbon monoxide) concentration of Fig. 7 was 150 ppm, and the CO concentration of Fig. 8 was 50 ppm.

Among them, the gray part in the figure is the gas valve opening, the test cavity is introduced into the test gas, the part between the gray parts is closed by the gas valve, and the test cavity stops the intake air. This experiment uses the continuous circulation mode to carry out the sensor The sensing test was repeated to test the sensor's ability to be reused. As shown in the figure, this test was performed three times in total.

As can be seen from Fig. 7, the film electrode produced by the method of the present invention has a significant change in resistance at room temperature, indicating that it can effectively detect a concentration of 150 ppm of CO gas. Similarly, as is clear from Fig. 8, the film electrode produced by the method of the present invention has a change in electrical resistance when the CO gas concentration is 50 ppm, indicating that it has a certain sensitivity to CO at this concentration.

Compared with the conventional gas sensor, the fork electrode made of metal and metal oxide is usually made of a metal electrode and a metal oxide, and a heater is generally required. The gas is heated to about 300 ° C to detect harmful gases. The thin film electrode produced by the method of the present invention can have good sensitivity at room temperature without the need of a heater because of the characteristics of the film material.

In another embodiment of the present invention, the gas detecting wafer fabricated by the method of the present invention can be applied to detect gases including carbon monoxide, carbon dioxide, nitrogen monoxide, nitrogen dioxide, methane, ammonia, and the like.

The detailed description of the preferred embodiments of the present invention is intended to be limited to the scope of the invention, and is not intended to limit the scope of the invention. The patent scope of this case.

Claims (10)

 A method for fabricating a thin film electrode of a normal temperature gas detecting wafer by ultra-fast laser comprises: forming a thin film on a substrate; and etching the thin film at an ordinary temperature in an ultrafast laser process to form a thin film having an electrode pattern electrode.    The method for fabricating a thin film electrode of a normal temperature gas detecting wafer by ultra-fast laser according to claim 1, wherein the ultra-fast laser process comprises: a first ultra-fast lightning having a first scanning speed and a first scanning power A pulse erodes the film; and etches the film with a second ultrafast laser pulse having a second scan speed and a second scan power.    The method of claim 1, wherein the first scanning speed is greater than the second scanning speed, and the first scanning power is greater than the second scanning power.   A method for producing a film electrode of a normal temperature gas detecting wafer by ultra-fast laser according to claim 2, wherein the first scanning speed is 700 mm/s, and the first scanning power is 4.40 J/cm ² , the second The scanning speed was 500 mm/s, and the second scanning power was 1.90 J/cm ² . A method for fabricating a thin film electrode of a normal temperature gas detecting wafer by ultra-fast laser according to claim 1, wherein the ultrafast laser pulse used in the ultrafast laser process has a pulse length of 10 ^-12 to 10 ^-15 seconds.  The method of claim 1, wherein the material of the substrate is one of a polymer material, a glass or a crucible.    A method for producing a film electrode of a normal temperature gas detecting film by ultra-fast laser as described in claim 1, wherein the material of the film is a metal or polymer conductive material.    The method for producing a thin film electrode of a normal temperature gas detecting wafer by ultra-fast laser according to claim 1, wherein the material of the thin film comprises: graphene, reduced graphene oxide, indium tin oxide, and zinc gallium oxide.    A method for producing a film electrode of a normal temperature gas detecting wafer by ultra-fast laser as described in claim 1, wherein the electrode pattern is a polygonal spiral shape, a circular spiral shape or a Fermat spiral shape.    A method for producing a film electrode of a normal temperature gas detecting wafer by ultra-fast laser as described in claim 1, wherein the electrode pattern is a zigzag shape, a contour parallel shape or a Hilbert curve.