CN103086320B - A kind of new producing method of flexible wall hot line microsensor - Google Patents

Abstract

The invention discloses a novel manufacturing method of a flexible wall heating wire microsensor, which belongs to the field of microelectromechanical systems (MEMS). The invention uses a flexible metal carrier to realize the fixing of the flexible substrate during processing, realizes the patterning of the devices and wires on the front side of the flexible substrate through a standard photolithography process, and then deposits parylene (Parylene) on the front side as a protective and strengthening layer , and then attach a photosensitive blue film on the back of the flexible metal carrier, use mask exposure and wet etching to realize the patterning of the flexible metal carrier, form a hard mask for flexible substrate etching, and then pass reactive ion etching (RIE ) to realize partial etching of the flexible substrate, and after the etching is completed, the method of high temperature heating is used to realize the separation of the sensor and the flexible metal carrier. The method can effectively protect the sensitive unit of the flexible wall heating wire microsensor, improves the performance of the sensor, and greatly increases the service life.

Description

A new fabrication method of flexible wall hot wire microsensor

Technical field:

The invention relates to a novel manufacturing method of a flexible wall heating wire microsensor, which belongs to the field of micro-electromechanical systems (MEMS).

Background technique:

The hot wire sensor is one of the important measurement devices in the field of flow field information testing. As an efficient and reliable measuring device, it is often used to detect the flow state of the flow field. Due to the advantages of fast dynamic response, high sensitivity and high signal-to-noise ratio, MEMS-based wall hot-wire microsensors have broad application prospects in the measurement of fluid wall shear stress and unsteady flow. The wall hot-wire microsensor using polyimide flexible substrate not only has all the advantages of conventional wall hot-wire microsensors, but also can be applied to the measurement of various complex surfaces such as wings, fuselages, and turbine blades. Aerodynamics provide a reliable means of support.

The typical structure of the flexible wall thermal wire microsensor is to design a cavity structure on the lower surface of the sensitive element, so that the sensitive element is in full contact with the air. The Technical University of Berlin, Germany, began to study the flexible wall thermal wire microsensor of this structure in 2005. The process implementation method is to first form a sensitive element on the surface of a polyimide flexible substrate through a photolithography process, and then deposit a layer of metal film on its surface. , and then pattern the metal thin film layer, use it as a mask for dry etching of polyimide, use the undercut effect (footing effect) to realize the suspending of the sensitive element, and finally pass the mask metal layer through wet etching Erosion removed.

The disadvantage of this manufacturing method is that after forming the cavity structure, wet etching removes the mask metal layer and at the same time it will corrode the already formed sensitive element, which will affect the dimensional parameters and measurement performance of the sensitive element, so that the hot wire sensitive unit cannot reach the design. Requirements, easy to break, reduce its service life, thereby affecting the performance of the sensor.

Invention content:

In order to overcome the disadvantages of corrosion-sensitive units caused by etching the flexible substrate on the front side in the prior art, the invention provides a process method for etching the flexible substrate on the back side of the flexible heating wire microsensor. In order to be compatible with the standard MEMS process, the present invention uses a hard substrate to realize the fixing of the flexible substrate during processing, and realizes the patterning of the front device and wires of the flexible substrate through a standard photolithography process, and then deposits parylene on the front as a protection and strengthening layer, then attach a photosensitive blue film on the back of the hard substrate, use mask exposure and wet etching to realize the patterning of the metal carrier, form a hard mask for flexible substrate etching, and then pass reactive ion etching Realize partial etching of the flexible substrate, and use high-temperature heating to separate the sensor from the hard substrate after the etching is completed.

The technical solution adopted by the present invention to solve the technical problem: a novel manufacturing method of a flexible wall heating wire microsensor, comprising the following steps:

Step 1: Surface polishing and cleaning of the hard substrate;

Step 2: Spin-coat PDMS on the surface of the hard substrate, and the PDMS is used as an adhesive to combine the polyimide film with the hard substrate;

Step 3: Paste the polyimide film on the surface of the hard substrate spin-coated with PDMS, and use a heating and pressing device to realize the lamination. The polyimide film forms a flexible substrate for the flexible wall heating wire microsensor 2 ;

Step 4: sequentially depositing the first metal layer and the second metal layer on the polyimide surface, and forming the sensitive element 1 and the wire 5 after patterning;

Step 5: Deposit parylene 4 on the surface of the formed sensitive element 1 and wire 5;

Step 6: patterning the hard substrate to form a mask layer for the cavity 3;

Step 7: Using the patterned hard substrate as a mask, etch PDMS and polyimide to form a cavity 3;

Step 8: heating the hard substrate to realize the peeling off of the flexible wall hot wire microsensor and the hard substrate.

The beneficial effects of the present invention are:

1) The hard substrate is used as the carrier in the processing process, which is not only compatible with the MEMS process, but also can be used as a mask for polyimide etching;

2) The graphic accuracy of the sensitive element is easy to guarantee during processing, and the sensitive element will not be affected during the backside etching process of the flexible substrate;

3) By depositing a parylene protective film on the upper surface of the sensitive element, the device is protected during processing and use, and the processed flexible hot wire microsensor can be applied even in harsh environments.

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Description of drawings:

Fig. 1 is a structural schematic diagram of a flexible wall heating wire microsensor in an embodiment;

Fig. 2 is A-A sectional view of Fig. 1;

Fig. 3 is the flow chart of the manufacturing process of the flexible wall hot wire microsensor in embodiment 1

In the figure, 1—sensitive element; 2—flexible substrate; 3—cavity; 4—parylene; 5—wire;

Detailed ways:

Embodiment one:

This embodiment proposes a method of etching on the back of the flexible hot wire microsensor, mainly that the patterning process of the sensitive element is a wet etching process, which specifically includes the following steps:

Step 1: Cut the copper foil with a thickness of 100 microns into a disc with a diameter of 80mm, and use a polishing machine to polish the surface, and clean the copper foil after polishing;

Step 2: Spin-coat PDMS with a thickness of 5 microns on the surface of the cleaned copper foil, wherein the ratio of PDMS glue and curing agent is 10:1; the rotation speed is 2500RPM;

Step 3: Lay a polyimide film with a thickness of 125 microns on the surface of copper foil spin-coated with PDMS, and stick it at a temperature of 70°C and a pressure of 130Pa;

Step 4: Put the polyimide with copper foil as the carrier into the sputtering chamber, deposit 0.3 μm nickel and 2 μm copper films respectively, and use a solution with a ratio of ammonium persulfate: hydrogen peroxide: water = 1:1:20 Wet etching realizes the patterning of copper wires, and uses 30% FeCl ₃ solution to realize the patterning of nickel sensitive components;

Step 5: Put the patterned substrate and carrier together in the SCS PDS2010 laboratory dedicated parylene deposition equipment, and deposit 2-3 micron parylene for protection and strengthening.

Step 6: Attach a photosensitive blue film on the back of the copper foil, expose and develop through a mask, and use FeCl ₃ solution to wet-etch the copper foil after development to realize patterning.

Step 7: Turn the entire sheet upside down, put it into the RIE etching equipment, and etch the polyimide through the patterned copper foil.

Step 8: Heat the copper foil to 80°C to separate the polyimide substrate and PDMS.

Embodiment two:

This embodiment proposes a method of etching on the back of the flexible hot wire microsensor, mainly the patterning method of the sensitive element is a stripping process, which specifically includes the following steps:

Step 1: Cut the aluminum foil with a thickness of 100 microns into a disc with a diameter of 80mm, and use a polishing machine to polish the surface, and clean the aluminum foil after polishing;

Step 2: Spin-coat PDMS with a thickness of 5 microns on the surface of the cleaned aluminum foil, wherein the ratio of PDMS glue and curing agent is 10:1; the rotation speed is 2500RPM;

Step 3: Lay a polyimide film with a thickness of 125 microns on the surface of copper foil spin-coated with PDMS, and stick it at a temperature of 70°C and a pressure of 130Pa;

Step 4: Spin-coat the photoresist on polyimide with aluminum foil as the carrier, expose and develop, put the patterned photoresist into the sputtering chamber, deposit 0.3 μm platinum, and deposit the platinum film The carrier undergoes ultrasonic vibration to realize the smooth peeling of the platinum thin film; the same method is used to realize the patterning of the 2 μm gold thin film;

Step 5: Put the patterned substrate and carrier together in the SCS PDS2010 laboratory dedicated parylene deposition equipment, and deposit 2-3 micron parylene for protection and strengthening.

Step 6: Attach a photosensitive blue film on the back of the aluminum foil, expose and develop through a mask, and use an aluminum etching solution to wet-etch the aluminum foil after development to realize patterning.

Step 7: Turn the entire sheet upside down, put it into the RIE etching equipment, and etch the polyimide through the patterned aluminum foil.

Step 8: Heat the aluminum foil to 80°C to separate the polyimide substrate and PDMS.

Claims (1)

1. A novel manufacturing method of a flexible wall heating wire microsensor, comprising the steps of: Step 1: Surface polishing and cleaning of the hard substrate; Step 2: Spin-coat PDMS on the hard substrate; Step 3: Paste the polyimide film on the surface of the hard substrate spin-coated with PDMS, and use a heating and pressing device to achieve lamination. The polyimide film forms the flexible substrate of the flexible wall thermal wire microsensor ( 2); Step 4: sequentially depositing the first metal layer and the second metal layer on the polyimide surface, and forming the sensitive element (1) and the wire (5) after patterning; Step 5: Depositing parylene (4) on the surface of the formed sensitive element (1) and wire (5); Step 6: patterning the hard substrate to form a mask layer of the cavity (3); Step 7: Using the patterned hard substrate as a mask, etch PDMS and polyimide to form a cavity (3); Step 8: heating the hard substrate to realize the peeling off of the flexible wall hot wire microsensor and the hard substrate.