CN103043599B - A kind of preparation method of the spiral inductance based on flexible polymer substrate - Google Patents

Abstract

A fabrication method of a spiral inductor based on a flexible polymer substrate. It includes the following steps: (A) growing a flexible film on a substrate; optional (A1) sputtering a seed layer on the film, electroplating a magnetic material, and growing a flexible film; optional (A2) sputtering a seed layer; (B) Plating the coil; (C) plating the magnetic core; optional step (C1) removing photoresist and removing the seed layer; (D) growing a flexible thin film; optional (D1) sputtering the seed layer on the thin film, electroplating the magnetic material , to grow flexible thin films; (E) Peel off the inductor to obtain a sandwich-structured helical inductor on a flexible polymer substrate. The micro-sandwich structure spiral inductor obtained by electroplating copper coils and iron-nickel magnetic cores on a flexible substrate has high L value and Q value, small area, foldable, good biocompatibility, simple process and low cost. The prepared inductor can be widely used in various biological and non-biological microsystems, especially for implantable wireless energy transmission systems.

Description

A preparation method of a spiral inductor based on a flexible polymer substrate

technical field

The invention relates to the field of micro-nano processing, in particular to a method for preparing a spiral inductor based on a flexible polymer substrate.

Background technique

Parylene is a thermoplastic crystalline polymer. Compared with other polymers, Parylene film has the characteristics of good shape retention, strong chemical inertness, insoluble at room temperature, excellent biocompatibility, small film thickness, transparency, low cost, non-toxic, non-polluting, etc., so in MEMS Fields, especially in microfluidic and biological MEMS applications can play an important role.

Flexibility is one of the inherent properties of Parylene. Devices using Parylene as a flexible substrate play an important role in biomedical and other fields, and have become a research hotspot in the field of micro-nano processing in recent years. There are more than 20 known structures of Parylene, but there are only three that can be used in micromachining, namely Parylene N, Parylene C and Parylene D, among which Parylene C is a commonly used structure.

In addition to Parylene, flexible polymers such as polyimide (PI) and polydimethylsiloxane (PDMS) also have similar properties to Parylene, so they can also be used in the preparation of the inductor described in the present invention.

Adding inductance components to integrated circuits or microsystems has always been regarded as a challenge, because existing inductors generally need to occupy a large area to ensure high L value and high Q value, which not only brings a lot of loss, but also makes the The goal of trying to achieve small integrated circuit chips has become difficult to achieve. The method of electroplating copper can effectively reduce the impedance of the coil, thereby improving the performance of the inductor. Adding a magnetic core made of soft magnetic materials (such as iron-nickel alloy, cobalt-nickel-manganese-phosphorus alloy, cobalt-iron alloy, etc.) in the center of the inductor coil can effectively improve the performance of the inductor. According to previous studies, such as Design and Fabrication of Flexible Parylene-based Inductors with Electroplated NiFe Magnetic Core for Wireless PowerTransmission System (IEEE-NEMS 2012, p.238-242) published by Xuming Sun, Yang Zheng et al. in 2012 (Chinese title: Design and preparation of inductors with flexible Parylene substrates with iron-nickel cores for wireless energy transmission systems), compared with inductors without cores, the performance of inductors with cores in the center is superior. Therefore, soft magnetic materials can improve the performance of inductors. However, due to reasons such as simple structure and limited magnetic core area, the performance of existing MEMS inductors still needs to be further improved.

In addition, in the field of biomedicine, many devices implanted in the human body need to ensure their biocompatibility and flexibility. Because the environment of implantable devices is harsh, on the one hand, it is necessary to ensure that the device will not react with the substances in the human body to cause contamination of the human body or damage to the device, so the device must have good biocompatibility; on the other hand, when the human body is active Implantable devices may deform or even bend and fold, so the device must also ensure good flexibility. Parylene, as a highly inert high molecular polymer material, has excellent biocompatibility and is flexible, so it is an excellent material for the covering layer of implantable devices.

From the above introduction, it can be seen that soft magnetic materials can improve the performance of inductors, and flexible polymers can provide flexibility and good biocompatibility. Therefore, higher performance inductors based on these materials are urgently needed to be researched and realized.

Contents of the invention

The purpose of this application is to propose a method for preparing a spiral inductor based on a flexible substrate (such as Parylene), using electroplating to grow a metal coil on the surface of Parylene, and electroplating a magnetic core at the center, bottom and top of the coil to improve the Q value of the inductor. So as to realize the high-performance MEMS inductor.

The application discloses a method for preparing a spiral inductor based on a flexible polymer substrate, which includes the following steps in sequence:

(A) Growth of a flexible thin film on a substrate;

Optional (A1) sputtering seed layer on thin film, electroplating magnetic material, growing flexible thin film;

Optional (A2) sputtering seed layer;

(B) Plated coils;

(C) Electroplated magnetic core;

optional step (C1) removing the photoresist and removing the seed layer;

(D) growing flexible films;

Optional (D1) sputtering seed layer on thin film, electroplating magnetic material, growing flexible thin film;

(E) The inductor was peeled off to obtain a sandwich-structured helical inductor with a flexible polymer substrate.

further:

Step (A) the substrate is a silicon substrate, and the flexible film is a parylene, polyimide or polydimethylsiloxane film;

Step (B) Coil electroplating includes photolithography of thick glue, the coil pattern is determined, and copper coil is electroplated; the photoresist is AZ9260, AZ4620, and the thickness of the glue is 10-15um;

Step (C) electroplating the magnetic core includes thick glue photolithography, determining the position of the magnetic core, and electroplating the magnetic core;

The flexible film deposited in step (D) is a parylene, polyimide or polydimethylsiloxane film;

Step (E) peeling is directly peeling by hand.

further:

Step (A) The thickness of the flexible material film is 8-15um;

The seed layer described in step (A1) is Ti/Cu, the thickness of Ti is 10-30nm, and the thickness of Cu is 100-300nm. Ti is deposited first, and then Cu is deposited; the electroplating magnetic material is iron-nickel alloy and cobalt-iron alloy ;The plating time is 90-120 minutes, the plating density is 2-4ASD; the thickness of the flexible film is 8-15um;

Step (A2) The seed layer is Ti/Cu, the thickness of Ti is 10-30nm, and the thickness of Cu is 100-300nm, first depositing Ti and then depositing Cu;

The electroplating time described in step (B) is 50-70 minutes, and the current density during electroplating is 1ASD;

The magnetic core described in the step (C) is an iron-nickel alloy, a cobalt-iron alloy, a cobalt-nickel-manganese-phosphorus alloy, and when the iron-nickel alloy is used, the ratio of iron to nickel in the electroplating solution is 20:80, 30:70 or 40:60; electroplating The time is 90-120 minutes, and the current density during electroplating is 2-4ASD;

Step (C1) is wet etching to remove the photoresist and remove the seed layer. The process is completed by putting the sample in an organic solvent. The process of removing the seed layer adopts a wet etching method; if the seed layer is Ti and Cu, The method is to put the sample into the copper corrosion solution first, and then put the sample into the titanium corrosion solution after the copper is completely corroded, take it out after the titanium is corroded clean, and rinse it with deionized water;

Step (D) the thickness of the flexible material film is 8-15um;

Step (D1) The seed layer is Ti/Cu, the thickness of Ti is 10-30nm, and the thickness of Cu is 100-300nm. First deposit Ti and then deposit Cu; the electroplating magnetic material is iron-nickel alloy and cobalt-iron alloy; electroplating time 90-120 minutes, plating density 2-4ASD; flexible film thickness 8-15um.

further:

In step (A), the thickness of the film is 10um, and the film is a parylene film;

The thickness of Ti in step (A1) is 15nm, and the thickness of Cu is 150nm;

The photoresist thickness in step (B) is 10um;

Step (C) Electroplating the iron-nickel magnetic core, the main components of the plating solution used are nickel sulfate, nickel chloride, and ferrous sulfate, the electroplating pulse is 4ASD, and the electroplating time is 100min;

In step (C1), acetone is used for degumming, the main components of the copper corrosion solution are glacial acetic acid and hydrogen peroxide, the corrosion time of Cu is 60s-70s, and the titanium corrosion solution is hydrofluoric acid, and the time is 40s-60s;

Step (D) grows a 10um thick parylene film.

The application also discloses a spiral inductor based on a flexible polymer substrate, which is prepared by the above method.

Further is an inductor optionally with a top magnetic film and/or optionally with a bottom magnetic film.

A spiral inductor with a sandwich structure is preferred.

The use of the above-mentioned spiral inductor is characterized in that it is used in various biological and non-biological microsystems, preferably in an implanted wireless energy transmission system.

The method for preparing a sandwich structure MEMS spiral inductor based on a flexible substrate provided by the present invention provides a feasible high-performance inductance structure, and the upper, lower, and center of the copper coil are all coated with magnetic materials, which significantly improves the inductance. performance. The flexible inductance with small area and high Q value can be obtained by the invention, which effectively solves the problems of excessive inductance area, poor performance, poor biocompatibility and difficulty in bending in traditional microsystems. The new method proposed by the invention simultaneously meets the requirements of the implanted microsystem on the flexibility and electrical performance of the inductance. The inductance prepared by the method has been tested and has high L value and Q value, is bendable and foldable, and has a small device size.

Description of drawings

Fig. 1 is the model of the spiral inductor based on flexible substrate of the present invention (in order to see figure conveniently and have omitted the topmost magnetic thin film, therefore also can be regarded as the spiral inductor of above-mentioned simple structure without top magnetic core at the same time Model);

Fig. 2 is the process flow chart of the spiral inductor preparation method based on flexible substrate of the present invention;

Fig. 3 is the process flow chart of the simple structure spiral inductance preparation method based on the flexible substrate of the present invention that does not contain the upper and lower two layers of soft magnetic films;

Fig. 4 is the process flow diagram of the spiral inductor preparation method based on the flexible substrate of the present invention that only contains the bottom soft magnetic film;

Fig. 5 is the electron micrograph after the electroplating copper of step 7 in the preparation method of the present invention;

Fig. 6 is the electron micrograph after the electroplating magnetic core of step 9 in the preparation method of the present invention;

Fig. 7 is the electron micrograph after the wet etching of step 10 in the preparation method of the present invention removes seed layer;

Fig. 8 is the photo of the inductance without the upper and lower magnetic films processed by the preparation method of the present invention (that is, the inductance obtained by the method described in Example 1 below) after peeling off from the silicon substrate. It can be seen that Inductors are flexible.

Fig. 9 is a photo of the inductor with a bottom magnetic film processed by the preparation method of the present invention (that is, the inductor obtained by the method described in Example 2 below) after it is peeled off from the silicon substrate. It can be seen that the inductor is flexible. of.

Fig. 10 is the performance test result of the sandwich structure inductor processed by the preparation method of the present invention, and its inductance value (L value) and quality factor (Q value) are relatively ideal.

Detailed ways

In order to make the above objects, features and advantages of the present invention more obvious and understandable, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

The steps of the manufacturing method of the sandwich spiral inductor with a magnetic core based on a flexible substrate provided by the present invention will be described below with reference to FIGS. 1 to 10 .

Embodiment one:

Embodiment 1 is the preparation process of an inductor without two magnetic films on the top and bottom. Therefore, steps 2-4 and steps 12-14 can be omitted. In this embodiment, Parylene is selected as the substrate material, and iron-nickel alloy is used as the material of the magnetic thin film and the magnetic core.

Step 1: grow a Parylene film of about 10um on the silicon wafer;

Step 5: sputtering a Ti/Cu seed layer on the Parylene film, wherein the thickness of Ti is 15nm, and the thickness of Cu is 150nm;

Step 6: Thick photolithography (AZ9260 photoresist), determine the coil pattern;

Step 7: Electroplating the copper coil, the current density during electroplating is 1ASD, and the electroplating time is 50 minutes;

Step 8: The second photolithography (AZ9260 photoresist), determine the position of the magnetic core;

Step 9: Electroplating the iron-nickel magnetic core, the current density during electroplating is 4ASD, the electroplating time is 120 minutes, and the ratio of iron-nickel in the electroplating solution is 20:80;

Step 10: Acetone degumming, wet etching to remove the seed layer (the copper corrosion solution is a mixed solution of glacial acetic acid and hydrogen peroxide, and the titanium corrosion solution is an aqueous solution of hydrofluoric acid);

Step 11: Cover the coil with a layer of Parylene film;

Step 15: Peel off the Parylene inductor from the silicon substrate.

Referring to FIG. 3 , FIG. 3 is a process flow diagram of a method for manufacturing a spiral inductor with a simple structure based on a flexible substrate of the present invention. The processes described in the above steps are the steps of the preparation method of the present invention, through two photolithography and two electroplating, the high-Q inductor on the flexible substrate is realized.

Referring to FIG. 5 , FIG. 5 is an electron micrograph of the inductor according to the present invention after electroplating in step 5.

Referring to FIG. 6 , FIG. 6 is an electron micrograph of the inductor according to the present invention after electroplating in step 7.

Referring to FIG. 7 , FIG. 7 is an electron micrograph of the inductor according to the present invention after electroplating in step 8. Referring to FIG.

Referring to FIG. 8 , FIG. 8 is a finished product view of the spiral inductor with a simple structure based on the Parylene substrate of the present invention. It can be seen that the Parylene substrate is transparent, and the inductor is small in size and bendable.

Embodiment two:

Embodiment 2 is the preparation process of an inductor without a top magnetic film. Therefore steps 12-14 can be omitted. In this embodiment, PDMS is selected as the substrate material, and cobalt-iron alloy is used as the material of the magnetic thin film and the magnetic core.

Step 1: grow a PDMS film of about 15um on the silicon wafer;

Step 2: sputtering a Ti/Cu seed layer on the PDMS film, wherein the thickness of Ti is 20nm, and the thickness of Cu is 200nm;

Step 3: electroplating a cobalt-ferromagnetic thin film, the current density during electroplating is 2ASD, the electroplating time is 180 minutes, and the ratio of cobalt and iron in the electroplating solution is 70:30;

Step 4: grow a PDMS film of about 15um on the magnetic film;

Step 5: sputtering a Ti/Cu seed layer on the PDMS film, wherein the thickness of Ti is 20nm, and the thickness of Cu is 200nm.

Step 6: Thick photolithography (AZ4620 photoresist), determine the coil pattern;

Step 7: Electroplating the copper coil, the current density during electroplating is 1ASD, and the electroplating time is 70 minutes;

Step 8: Photolithography (AZ4620 photoresist) again to determine the position of the magnetic core;

Step 9: Electroplating the cobalt-iron magnetic core, the current density during electroplating is 2ASD, the electroplating time is 180 minutes, and the ratio of cobalt-iron in the electroplating solution is 70:30;

Step 10: Acetone degumming, wet etching to remove the seed layer (the copper corrosion solution uses a mixed solution of glacial acetic acid and hydrogen peroxide, and the titanium corrosion solution uses an aqueous solution of hydrogen peroxide);

Step 11: grow a PDMS film of about 10um;

Step 15: Peel off the PDMS inductor from the silicon substrate.

Referring to FIG. 1, FIG. 1 is a model of a spiral inductor with a bottom magnetic film based on a flexible substrate of the present invention.

Referring to FIG. 4 , FIG. 4 is a process flow diagram of a method for manufacturing a spiral inductor with a bottom iron-nickel thin film based on a flexible substrate of the present invention. The processes described in the above steps are the steps of the preparation method of the present invention, through two photolithography and two electroplating, the high-Q inductor on the flexible substrate is realized.

Referring to FIG. 9 , FIG. 9 is a finished view of the spiral inductor with bottom magnetic thin film based on PDMS substrate of the present invention.

Embodiment three:

The third embodiment is the preparation process of the sandwich structure spiral inductor based on the flexible substrate. In this embodiment, Parylene is selected as the substrate material, and iron-nickel alloy is used as the material of the magnetic thin film and the magnetic core.

Step 1: grow a Parylene film of about 10um on the silicon wafer;

Step 2: sputtering a Ti/Cu seed layer on the Parylene film, wherein the thickness of Ti is 10nm, and the thickness of Cu is 100nm;

Step 3: Electroplating an iron-nickel magnetic thin film, the current density during electroplating is 4ASD, the electroplating time is 100 minutes, and the ratio of iron and nickel in the electroplating solution is 7:93;

Step 4: grow a Parylene film of about 10um on the magnetic film;

Step 5: sputtering a Ti/Cu seed layer on the Parylene film, wherein the thickness of Ti is 10nm, and the thickness of Cu is 100nm;

Step 6: Thick photolithography (AZ9260 photoresist), determine the coil pattern;

Step 7: Electroplating the copper coil, the current density during electroplating is 1ASD, and the electroplating time is 60 minutes;

Step 8: Photolithography (AZ9260 photoresist) again to determine the position of the magnetic core;

Step 9: Electroplating the iron-nickel magnetic core, the current density during electroplating is 4ASD, the electroplating time is 100 minutes, and the ratio of iron-nickel in the electroplating solution is 7:93;

Step 10: Acetone degumming, wet etching to remove the seed layer (the copper corrosion solution is a mixed solution of glacial acetic acid and hydrogen peroxide, and the titanium corrosion solution is an aqueous solution of hydrofluoric acid);

Step 11: grow a Parylene film of about 10um;

Step 12: sputtering a Ti/Cu seed layer on the Parylene film, wherein the thickness of Ti is 10nm, and the thickness of Cu is 100nm;

Step 13: Electroplating an iron-nickel magnetic thin film, the current density during electroplating is 4ASD, the electroplating time is 100 minutes, and the ratio of iron-nickel in the electroplating solution is 7:93;

Step 14: Cover another layer of Parylene film of about 10um on it;

Step 15: Peel off the Parylene inductor from the silicon substrate.

Referring to FIG. 1 , FIG. 1 is a model (due to) of a sandwich structure spiral inductor based on a flexible substrate of the present invention. The width of the coil is 200um, the pitch is 50um, the thickness is 10um, and the number of turns is 4. The radius of the magnetic core is 1000um.

Referring to FIG. 2 , FIG. 2 is a process flow diagram of a manufacturing method of a sandwich structure spiral inductor based on a flexible substrate of the present invention. The processing process described in the above steps 1-15 and the steps of the preparation method of the present invention realize the high-Q inductor on the flexible substrate through the process shown in FIG. 2 .

Since the top and bottom of the finished picture of the sandwich structure spiral inductor are wrapped with magnetic films, the coil and magnetic core in the middle cannot be directly seen, so the schematic diagram of the finished product is omitted.

The method for preparing a sandwich structure spiral inductor based on a flexible substrate has been introduced in detail above. In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above examples is only for Help to understand the method and core idea of the present invention. At the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation and application scope. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (2)

1., based on a preparation method for the spiral inductance of flexible polymer substrate, comprise the steps: in order

(A) Grown fexible film;

(A1) sputtering seed layer on film, plating magnetic material, growth fexible film;

(A2) sputtering seed layer;

(B) coil is electroplated;

(C) magnetic core is electroplated;

Step (C1) is removed photoresist and is removed Seed Layer;

(D) fexible film is grown;

(D1) sputtering seed layer on film, plating magnetic material, growth fexible film;

(E) peel off inductance, obtain the sandwich structure spiral inductance of flexible polymer substrate;

Step (A) substrate is silicon substrate, and fexible film is Parylene, polyimides or polydimethylsiloxanefilm film;

Step (B) is electroplated coil and is comprised thick resist lithography, makes coil pattern, electro-coppering coil; Photoresist is AZ9260, AZ4620, and the thickness of whirl coating is 10-15um;

Step (C) is electroplated magnetic core and is comprised thick resist lithography, makes magnetic core position, plating magnetic core;

In step (D), the fexible film of deposition is Parylene, polyimides or polydimethylsiloxanefilm film;

Step (E) is peeled off as directly to peel off by hand;

Step (A) flexible material film thickness is 8-15um;

The thickness of to be the thickness of Ti/Cu, Ti be 10-30nm, the Cu of the Seed Layer described in step (A1) is 100-300nm, first deposit Ti, then deposit Cu; Plating magnetic material is iron-nickel alloy, ferro-cobalt; Electroplating time is 90-120 minute, plating density 2-4ASD; Fexible film thickness is 8-15um;

The thickness of step (A2) Seed Layer to be the thickness of Ti/Cu, Ti be 10-30nm, Cu is 100-300nm, first deposit Ti, then deposit Cu;

Electroplating time described in step (B) is 50-70 minute, and current density during plating is 1ASD;

Magnetic core described in step (C) is iron-nickel alloy, ferro-cobalt, cobalt nickel manganese phosphorus alloy, and during employing iron-nickel alloy, in electroplate liquid, the ratio of iron and nickel is 20:80,30:70 or 40:60; Electroplating time is 90-120 minute, and current density during plating is 2-4ASD;

Step (C1) is removed photoresist for wet etching and is removed Seed Layer, and sample is put into organic solvent and completed by process, goes the process of Seed Layer to have employed the method for wet etching; If Seed Layer is Ti and Cu, then method first sample is put into copper corrosion liquid, sample put into titanium corrosive liquid again and take out after clean for titanium corrosion after copper corrosion is clean, and clean with deionized water rinsing;

Step (D) flexible material film thickness is 8-15um;

The thickness of step (D1) Seed Layer to be the thickness of Ti/Cu, Ti be 10-30nm, Cu is 100-300nm, first deposit Ti, then deposit Cu; Plating magnetic material is iron-nickel alloy, ferro-cobalt; Electroplating time is 90-120 minute, plating density 2-4ASD; Fexible film thickness is 8-15um;

In step (A), film thickness is 10um, and film is parylene film;

In step (A1), the thickness of Ti is the thickness of 15nm, Cu is 150nm;

In step (B), photoresist thickness is 10um;

Step (C) electroplating iron-nickel magnetic core, the solution composition of use mainly contains nickelous sulfate, nickel chloride, ferrous sulfate, and plating pulse is 4ASD, and electroplating time is 100min;

In step (C1), acetone removes photoresist, and copper corrosion liquid main component is glacial acetic acid and hydrogen peroxide, and the corrosion Cu time is 60s-70s, and titanium corrosive liquid is hydrofluoric acid, and the time is 40s-60s;

Step (D) grows the thick parylene film of 10um.

2. based on a spiral inductance for flexible polymer substrate, it is characterized in that: the method preparation adopting claim 1; Possess top magnetic film and the inductance possessing bottom magnetic film; The spiral inductance of sandwich structure.