CN105185906A - Manufacturing method of high-density inductor - Google Patents

Abstract

The invention relates to a method for manufacturing a high-density inductor, comprising the following steps: forming an etching window on the back surface of the silicon substrate after depositing a mask layer on both sides of the silicon substrate; forming a deep pit in the silicon substrate along the etching window structure; form a first layer of metal pattern on the mask layer on the front side of the silicon substrate; spin-coat a dielectric layer on the structure obtained after step C and pattern it to form a through hole that exposes part of the first metal layer; in step Form the second layer of metal pattern on the structure obtained after D; make part of the second layer of metal pattern contact the first metal layer through the through hole; fill the composite magnetic material of BCB and magnetic powder in the deep pit structure and solidify . The present invention adopts dry-wet mixed etching process to hollow out the silicon substrate below the plane coil inductance, and then fills the deep pit on the back of the inductance and directly above the inductance with a composite magnetic material through a screen printing process to form a sandwich structure (magnetic material-inductor -Magnetic material) to increase the inductance value.

Description

A kind of manufacturing method of high-density inductor

technical field

The invention relates to wafer-level integration of passive devices, in particular to a manufacturing method of high-density inductance.

Background technique

Magnetic devices such as inductive devices and their power transformers, filters, DC/DC converters, amplifiers, oscillators and tuners are essential and important components in electronic circuits. One of the keys of light weight and high performance, especially the miniaturized DC/DC converter composed of magnetic thin film micro-inductance devices will be widely used in various portable electronic products. Therefore, the market has put forward a very urgent demand for the development of high-power miniaturized integrated inductor devices.

Compared with the traditional discrete magnetic core inductors, in order to meet the needs of system integration, micro-inductors with integrated magnetic materials are mainly divided into two categories based on CMOS technology and packaging technology. Compared with the integrated magnetic material inductor in the package, the manufacturing of the inductor on silicon is limited by the compatibility of the silicon process, and the thickness of the inductor coil and the magnetic film is limited. The typical structural cross-section is shown in the figure. The inductance value of the inductor Lower, smaller saturation current, larger DC resistance.

Due to the high cost of traditional packaging, it cannot fully reflect the superiority of embedded passive devices. Wafer-level chip-scale packaging (WLCSP) has been widely used in electronic products due to its low cost and small size. Many companies and research institutions such as Amkor (UltraCSPTM), Fraunhofer, Fujitsu (SuperCSPTM), FormFactor (WowTM, MOSTTM) Each has its own wafer-level packaging technology. Embedding passive devices in wafer-level packaging can well meet the requirements of miniaturization, low cost, and low power consumption. An important indicator of inductance is the inductance density. The higher the inductance density, the smaller the area occupied by the inductance elements with the same inductance value.

How to increase the inductance density is an urgent problem to be solved in this field.

Contents of the invention

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a high-density inductor manufacturing method, which can increase the inductance value with a simple process.

In order to achieve the above purpose and other related purposes, the present invention provides a high-density inductor manufacturing method, the manufacturing method at least including the following steps:

A. Provide a silicon substrate, and form an etching window on the back side of the silicon substrate after depositing a mask layer on both sides of the silicon substrate;

B. Forming a deep pit structure located in the silicon substrate along the etching window; making a thin silicon substrate remain at the bottom of the deep pit structure;

C. forming a first layer of metal patterns on the mask layer on the front side of the silicon substrate;

D. Spin-coat a dielectric layer on the structure obtained after step C and pattern it to form a through hole exposing part of the first metal layer;

E. forming a second-layer metal pattern on the structure obtained after step D; making part of the second-layer metal pattern contact the first metal layer through the through hole;

F. removing the remaining thin silicon substrate at the bottom of the pit structure;

G. Fill the composite magnetic material of BCB and magnetic powder in the pit structure and solidify;

H. Filling and solidifying the composite magnetic material of BCB and magnetic powder on the second layer of metal pattern.

The technical scheme adopted by the present invention is: firstly, on one side of the double-sided polished silicon substrate, a deep pit slightly larger than the metal coil is corroded with an alkaline solution such as KOH or TMAH; the metal layer is completed by photolithography and electroplating; Reactive ion (DRIE) or XeF ₂ isotropic etching gas etches away the remaining silicon at the bottom of the deep pit; finally, the composite magnetic material of BCB and magnetic powder is integrated on both sides of the inductor through a screen printing process.

The invention proposes a method for manufacturing a double-sided integrated magnetic material hollowed-out inductor with a bottom by using a dry-wet mixed etching scheme. The process steps are simple, compatible with other processes, and greatly improve product performance, and have great potential in the field of integrated passive devices. The method adapts to the miniaturization and low-cost development requirements of products.

Description of drawings

Fig. 1 is a schematic plan view of a bottom hollow inductor with magnetic materials integrated on both sides.

2 to 9 are schematic flow charts of the steps for completing the various parts of the inductor.

Among them, FIG. 2 is a schematic diagram of forming a mask layer on both sides of the substrate and patterning the back side.

FIG. 3 is a schematic diagram of a deep pit structure etched on the back of the substrate.

FIG. 4 is a schematic diagram of forming a first layer metal pattern.

Fig. 5 is a schematic diagram of spin-coating and patterning of organic matter in the dielectric layer.

FIG. 6 is a schematic diagram of forming a second layer metal pattern.

Figure 7 is a schematic diagram of etching away the remaining silicon at the bottom of the pit.

Fig. 8 is a schematic diagram of filling deep pits with magnetic materials.

Fig. 9 is a schematic diagram of filling the front side of the inductor with magnetic material.

Component designation description

Silicon substrate 100

mask layer 101

First Layer Metal Graphics 102

Dielectric layer 103

The second layer of metal graphics 104

The first layer of magnetic material 105

The second layer of magnetic material 106

Detailed ways

The implementation of the present invention will be illustrated by specific specific examples below, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

See Figures 1 through 9. It should be noted that the structures, proportions, sizes, etc. shown in the drawings attached to this specification are only used to match the content disclosed in the specification, for those who are familiar with this technology to understand and read, and are not used to limit the implementation of the present invention. Limiting conditions, so there is no technical substantive meaning, any modification of structure, change of proportional relationship or adjustment of size, without affecting the effect and purpose of the present invention, should still fall within the scope of the present invention. The disclosed technical content must be within the scope covered. At the same time, terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit this specification. The practicable scope of the invention and the change or adjustment of its relative relationship shall also be regarded as the practicable scope of the present invention without any substantial change in the technical content.

The invention provides a method for manufacturing high-density inductors, which is an inductor manufacturing method with integrated magnetic materials and a hollow bottom. Its main features include the following points:

A. The inductor structure includes a silicon substrate with a hollow structure, a dielectric layer made of polymers such as Polyimide (PI) or Benzocyclobutene (BCB), and a metal coil on the hollow structure.

B. The hollow structure on the silicon substrate is made by the following method: on one side of the double-sided polished silicon substrate, the projected area on the horizontal plane is slightly larger than the projected area of the metal coil (that is, the first , second-layer metal pattern) deep pit structure, the depth of the deep pit is the thickness of the silicon substrate minus 30-100um, preferably 60um.

C. The manufacturing steps of the inductor on the substrate: a. sputtering seed layer, photoetching the inductor coil pattern, electroplating the metal layer, and then removing the photoresist and metal seed layer; b. spin-coating the first layer of 5-15um polymer (BCB or PI) as a dielectric layer, preferably 10um, and form a through hole by photolithography or etching, and then cure at high temperature; c. Repeat step a to form a second metal layer.

D. The integration method of double-sided magnetic materials: After the bottom hollow inductor is manufactured, the composite magnetic material of BCB and magnetic powder is filled into the deep pit structure at the bottom through the screen printing process, and then solidified. The selected magnetic powder material can be Nickel-zinc or manganese-zinc ferrite powder, the average particle size of the powder is between 10nm and 5um. Then, a second layer of magnetic material is formed on the front of the inductor in the manner described above.

The silicon substrate used in the present invention is used as ordinary silicon, and its cost is relatively low. After the last layer of metal wiring is completed, the remaining silicon at the bottom of the deep pit is etched away using deep reactive ion (DRIE) or XeF ₂ isotropic etching gas. The electroplating metal is copper, and a thin layer of gold can be electroplated on the last layer of copper (the second layer of metal pattern) as a passivation layer. The thickness of the electroplated metal copper is 10-30um, preferably 20um.

The shape of the inductor composed of the first metal layer and the second metal layer is circular spiral, polygonal spiral or zigzag, preferably Archimedes spiral, whose transition is smooth and high-frequency loss is small.

In FIG. 1 , a silicon-based hollow structure 100 and a planar coil inductor structure fabricated thereon are realized. The planar inductor on it is composed of two layers of metal wires 102,104. And the magnetic material 105 is integrated in the deep pit on the back. Since the silicon substrate directly under the coil has been hollowed out and then filled with magnetic materials, the inductance density of the inductance element is increased.

In Fig. 2 to Fig. 9, the process flow of the inductor with hollow structure integrated with magnetic material is introduced.

A <100> oriented silicon substrate 100 with a thickness of 420um is selected for surface pretreatment first, and silicon oxide 101 is deposited as a mask layer, as shown in FIG. 2 . Next, the front and back sides of the silicon substrate 100 are oxidized to form a 2um silicon oxide mask layer 101; finally, an etching window is formed on the back side of the silicon substrate 100 by photolithography, development and dry etching.

Then a pit structure is formed, as shown in FIG. 3 . Specifically, the silicon substrate is put into a KOH anisotropic etching solution, and a deep pit with a depth of about 360 um is etched.

Next, a first-layer metal pattern 102 is formed, as shown in FIG. 4 . Specific steps are as follows:

a) sputtering TiW/Cu seed layer, photolithography and development, electroplating about 20um metal copper 102;

b) Remove the photoresist and remove the TiW/Cu seed layer by dry method.

Then the dielectric layer 103 is spin-coated and patterned, as shown in FIG. 5 . Specific steps are as follows:

a) Spin-coat a photosensitive BCB with a thickness of 12um, and develop through photolithography to form a through hole;

b) Carrying out high-temperature hard curing of BCB;

c) Remove residual organics at the bottom of the vias using deep reactive ion etching (DRIE).

Next, a second layer metal pattern 104 is formed, as shown in FIG. 6 . Specific steps are as follows:

a) Sputter the TiW/Cu seed layer, photolithographically develop, and electroplate a metal copper layer of about 20um. After electroplating the metal copper layer, a thin layer of gold (thickness is preferably 0.5um) can also be electroplated as a passivation layer.

b) remove the photoresist, and remove the TiW/Cu seed layer by dry method, and finally form the second layer of metal (104);

Then complete the release of the inductor structure (hollow structure), as shown in FIG. 7 . The specific steps are as follows: use deep reactive ion (DRIE) or XeF ₂ isotropic etching gas to etch away the remaining silicon at the bottom of the deep pit to form a hollow structure.

Next, the magnetic composite material 105 is filled in the pit structure, as shown in FIG. 8 . Specific steps are as follows:

20-50wt% BCB and 80-50wt% nickel-zinc ferrite magnetic powder, preferably 40wt% BCB and 60wt% nickel-zinc ferrite magnetic powder (average particle size is 50nm) composite by screen printing process The magnetic material is filled into the bottom pit and then cured.

Finally, the magnetic composite material 106 is filled above the inductor coil, as shown in FIG. 9 .

The composite magnetic material of 40wt% BCB and 60wt% nickel-zinc ferrite magnetic powder (average particle size: 50nm) is filled on the inductor through a screen printing process, and then cured.

Since an important indicator of inductance is inductance density, the higher the inductance density, the smaller the area occupied by inductance elements with the same inductance value. Introducing magnetic material into the inductance element can effectively increase the inductance density. The inductor of this application is composed of two layers of metal patterns 102,104. And back 105 and front 106 two layers of magnetic materials. Since the magnetic material is integrated on both sides of the inductor, the magnetic flux leakage is reduced, so the inductance density is significantly increased.

The method mentioned in this patent is suitable for ordinary low-resistance silicon as a substrate, and uses a dry-wet mixed etching process, and the cost is low. By integrating magnetic materials on the back and front of the inductor, a sandwich structure (magnetic material-inductor-magnetic material) is formed, and its inductance density is significantly higher than that of traditional integrated inductors.

To sum up, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

1. a manufacture method for high density inductance, is characterized in that; This manufacture method at least comprises the following steps:

A., one silicon substrate is provided, after described silicon substrate tow sides deposition mask layer, forms corrosion window at this silicon substrate reverse side;

B. the deep pit structure being positioned at this silicon substrate is formed along described corrosion window; Make bottom this deep pit structure, to remain one deck thin silicon substrate;

C. on the mask layer in described silicon substrate front, first layer metal figure is formed;

D. spin-on dielectric layer in the structure obtained after step c is also graphical, forms the through hole of expose portion first metal layer;

E. the structure obtained after step D is formed second layer metal figure; Part second layer metal figure is contacted with the first metal layer by described through hole;

F. remaining one deck thin silicon substrate bottom described deep pit structure is removed;

G. in described deep pit structure, fill the composite magnetic of BCB and magnetic and solidify;

H. on described second layer metal figure, fill the composite magnetic of BCB and magnetic and solidify.

2. the manufacture method of high density inductance according to claim 1, is characterized in that; Specifically comprise the following steps in described steps A: a). select <100> crystal orientation silicon substrate first to carry out surface preparation;

B). oxidation is carried out to the tow sides of this silicon substrate and forms silicon oxide mask layer;

C). the reverse side being dry-etched in silicon substrate by photoetching development forms corrosion window.

3. the manufacture method of high density inductance according to claim 1, is characterized in that; Described step B adopts KOH or TMAH alkaline solution to erode away projected area on horizontal plane slightly larger than first or the deep pit structure of second layer metal figure projected area in the horizontal plane, and the degree of depth of this deep pit structure is that silicon substrate thickness deducts 30 ~ 100um.

4. the manufacture method of high density inductance according to claim 1, is characterized in that; Described step C specifically comprises the following steps: a) sputtered with Ti W/Cu Seed Layer, and photoetching development, electroplates a metal copper layer;

B) remove photoresist, and remove TiW/Cu Seed Layer with dry etching, form first layer metal figure.

5. the manufacture method of high density inductance according to claim 1, is characterized in that; Described step D specifically comprises the following steps: spin coating ground floor 5 ~ 15um polymer as dielectric layer, by photoetching or lithographic method graphically and form the through hole of expose portion first metal layer, then hot setting.

6. the manufacture method of high density inductance according to claim 1, is characterized in that; Described step e specifically comprises the following steps: first sputtered with Ti W/Cu Seed Layer, then electroplates a metal copper layer after photoetching inductance coil figure, then removes photoresist, and removes TiW/Cu Seed Layer formation second layer metal figure with dry etching.

7. the manufacture method of high density inductance according to claim 1, is characterized in that; Described step F specifically comprises the following steps: adopt deep reactive ion or XeF ₂one deck thin silicon base plate carving and corrosion remaining bottom deep pit structure falls by isotropic etching gas.

8. the manufacture method of high density inductance according to claim 1, is characterized in that; Described step G specifically comprises the following steps: be filled in deep pit structure by silk-screen printing technique by the nickel-zinc ferrite magnetic of the BCB of 20 ~ 50Wt% and 80 ~ 50Wt%, be cured subsequently.

9. the manufacture method of the high density inductance according to claim 4 or 6, is characterized in that; Described metal copper layer thickness is 10 ~ 30um, is preferably 20um.

10. the manufacture method of high density inductance according to claim 1, is characterized in that; Described first layer metal figure and second layer metal figure form inductance, and the shape of this inductance is circle spirality, multilateral helical or fold-line-shaped, is preferably Archimedian screw.