CN102522181A - Planar spiral inductor with wide-narrow-alternatingly line width and space - Google Patents

Abstract

The invention discloses a planar spiral inductor with alternating line width and spacing structure that can be applied to radio frequency integrated circuits. An insulating layer of the spiral inductor is grown on a silicon substrate, and a metal film is coated on the insulating layer to etch the bottom metal layer of the inductor. The bottom metal An insulating layer is deposited on the layer, and the insulating layer etches a through hole to connect the underlying metal layer and the spiral inductor layer. The metal layer is coated with a metal film on the insulating layer and the spiral inductor metal layer is etched. The coil of the spiral inductor metal layer is multi-turn, and the coil pattern is made of conductive metal. . The width of the metal wires of the present invention changes alternately from the outer ring to the inner ring, and the distance between the metal wires changes alternately from the outer ring to the inner ring, which reduces the ohmic loss caused by the series equivalent resistance, reduces the proximity effect between the metal wires, and improves The Q value of the quality factor of the spiral inductor is increased, the mutual inductance between the metal coils is increased, and the inductance value of the spiral inductor is improved.

Description

Alternating Line Width and Spacing Structure Type Planar Spiral Inductor

technical field

The invention belongs to the field of electronic technology, and further relates to a planar spiral inductor with alternating line width and spacing structure in the field of microelectronic technology. The metal line width and spacing of the invention adopts a width-narrow alternating structure, which can be used in the fields of microwave integrated circuits, filter nets, radio frequency transceiver circuits, LC oscillators, radio frequency ICs and the like.

Background technique

With the development of the field of radio frequency integrated circuits, the demand for high-performance planar spiral inductors is increasingly urgent. Whether spiral inductors can obtain high quality factor Q value and high inductance value has become a research hotspot in the field of microelectronics technology.

At present, there are two main methods to improve the performance of planar spiral inductors: one is to optimize the structural parameters. By rationally optimizing the layout structure of planar spiral inductors, the ohmic loss and eddy current loss of the spiral inductor can be minimized, and the Q value of the inductor can be improved. For example, adopting a tapered structure or adopting a multi-layer structure inductor can effectively improve the Q value of the inductor. The second method is to reduce the coupling between the substrate and the inductor as much as possible from the perspective of technology, reduce the magnetic loss, and improve the Q value of the inductor. For example, inserting a graphic ground shielding layer between the silicon substrate and the metal layer of the inductor, or hollowing out the silicon substrate with a special process, etc., all reduce the coupling between the substrate and the inductor from the perspective of technology, and improve the Q value of the inductor.

The patent "non-equal planar spiral inductor" (application number 200620042881, publication number 200983296) applied by Shanghai Integrated Circuit R&D Center Co., Ltd. proposes a non-equal planar spiral inductor. At least one turn of the metal coil in the spiral inductor is in a different plane from any other metal coil, so that the influence of the eddy current effect and the proximity effect at high frequencies is reduced, and the quality factor of the inductance is improved. However, the disadvantages of this patent application are: the mutual inductance between the metal coils is reduced, resulting in a low inductance value, and the processing technology is more difficult.

The patent "Spiral Inductor" (Application No. 01136623, Publication No. 1350310) applied by Alps Electric Co., Ltd. proposes a spiral inductor. The pitch of the metal wires of the spiral inductor is fixed, and the width of the metal wires gradually decreases from the outer ring to the inner ring, so the inner diameter of the inductor increases, the influence of the magnetic force line decreases, the inductance value increases, and the Q value improves. However, the shortcomings of this patent application are: the size of the spiral inductor is too large, which does not meet the small size and high integration design requirements of today's radio frequency integrated circuits, the metal line spacing and line width of the spiral inductor have a single change, and the Q value and inductance value are limited .

Shanghai Huahong (Group) Co., Ltd. applied for the patent "Planar Spiral Inductor with Gradual Variation of Metal Line Width and Metal Space" (Application No. 200420114664, Publication No. 20060329), which proposes a planar spiral inductor with gradual change of metal line width and metal spacing. The wire width of the metal wire of the inductor increases sequentially from the inside to the outside, and the distance between the metal wires increases with the increase of the wire width from the inside to the outside, thereby reducing the ohmic loss of the metal wire, and the quality factor Q value is high. However, the disadvantage of this patent application is that the mutual inductance between the spiral inductor coils is reduced, and the inductance value is relatively low.

Li Qinghua, Shao Zhibiao and others published an article (Optimization of double-layer planar inductors in high-frequency monolithic DC/DC converters, Li Qinghua, Shao Zhibiao, Geng Li, School of Electronics and Information Engineering, Xidian Jiaotong University, Journal of Xidian University (Natural Science Edition), Volume 34, Issue 2, April 2007, 321-324]) This paper proposes a circular planar spiral inductor with constant line width and spacing. The disadvantages of this planar spiral inductor are: the quality factor Q value is too low (the maximum Q value is only 5), and the process requirements are very high.

Lu Huang et al published a document (Lu Huang, Wan-Rong Zhang, Hong-Yun Xie, Pei Shen, Jun-Ning Gan, Yi-Wen Huang, Ning Hu. Analysis and Optimum Design of RFSpiral Inductors on Silicon Substrate , 3rd IEEE International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, 2009, Beijing, 990-993) This article proposes a planar spiral inductor with a gradient structure whose line width and spacing gradually decrease from the outer ring to the inner ring , improving the Q value of the inductor. The disadvantage of this planar spiral inductor is that the inductance value has not been significantly improved.

Contents of the invention

In order to overcome the disadvantages of the above-mentioned prior art, the object of the present invention is to provide a planar spiral inductor with alternating metal line width and spacing from the perspective of inductor structure parameters, which is compatible with traditional CMOS technology. The invention can simultaneously improve the Q value and the inductance value.

The idea of the invention is proposed on the basis of the loss mechanism of radio frequency passive devices, and aims to reduce the ohmic loss and eddy current loss of metal conductors and enhance the mutual inductance between inductive metal wires. Ohmic losses are caused by conduction current and eddy current losses are caused by eddy currents. When conduction current flows through a metal conductor, the ohmic loss it produces will be related to the resistance value of the metal conductor, which is proportional to the resistivity and total length of the metal conductor and inversely proportional to the width of the metal wire. It can be concluded from Faraday and Lenz theorem that the eddy current effect will greatly enhance the magnetic induction intensity at the center of the inductor, and make the current density in the metal wire uneven, thereby increasing the series resistance of the metal conductor. In addition, it can be seen from the eddy current effect that when the distance between two adjacent metal conductors is smaller, the magnetic field interaction between them is stronger, and the proximity effect is seriously affected, resulting in more uneven current density in the metal conductors and further increasing the series resistance of the metal conductors. becomes larger, thereby affecting the Q value of the inductor. Moreover, the smaller the distance between the inductor wires, the more severely the metal wires will be affected by the magnetic lines of force, resulting in a decrease in inductance. Based on the above principles, the present invention proposes alternately changing metal wire widths and metal wire spacing, and adopts alternately changing metal wires in width to make the inner ring wire width narrow, increase the inner diameter of the inductor, and reduce eddy current loss; , the use of wide-width metal wires achieves the purpose of reducing the ohmic loss of metal conductors. In addition, the alternate spacing structure is adopted, which reduces the influence of the magnetic field lines between the metal wires, enhances the mutual inductance between the wires, and increases the inductance value. Therefore, the present invention adopts the alternating structure of metal wire spacing from the outer ring to the inner ring, which can enhance mutual inductance, reduce loss, and increase inductance Q value and inductance value.

The invention includes a silicon substrate, an insulating layer, a bottom metal layer of a planar spiral inductor, a through hole, and a metal layer of a planar spiral inductor. The insulating layer of the spiral inductor is grown on the silicon substrate, and the insulating layer is coated with a metal film to etch the bottom metal layer of the inductor. , an insulating layer is deposited on the bottom metal layer, the insulating layer etches a through hole, connects the bottom metal layer and the spiral inductor layer, the metal layer is coated with a metal film on the insulating layer, and the spiral inductor metal layer is etched. The coil of the spiral inductor metal layer is multi-turn, and the coil pattern is composed of Composed of conductive metal; the metal line width of the planar spiral inductor metal layer changes alternately from the outer ring to the inner ring, and the distance between the metal lines changes alternately from the outer ring to the inner ring.

Compared with the prior art, the present invention has the following advantages:

First, the metal line width of the present invention adopts an alternating structure, which reduces the ohmic loss of the inductance metal wire, and overcomes the defect in the prior art that the inductance Q value is too low due to the excessive ohmic loss of the inductance, thus making the present invention in The Q value of the inductor is improved without changing the layout size.

Second, the metal line width of the present invention adopts an alternating structure, the inner diameter of the inductor is reduced, and the eddy current loss is reduced, which overcomes the defect in the prior art that the Q value of the inductance is too low due to excessive eddy current loss, thus making the present invention in On the basis of not changing the size of the layout, the eddy current loss is reduced and the Q value of the inductor is improved.

Third, the pitch of the metal wires in the present invention adopts an alternating structure, which reduces the proximity effect between the wires and overcomes the defect in the prior art that the equivalent series resistance of the inductor increases due to the proximity effect, thereby reducing the inductance of the present invention. The influence of the proximity effect in the inductance coil reduces the equivalent resistance in series and increases the Q value of the inductance.

Fourth, the spacing between the metal wires of the present invention adopts an alternating structure, which enhances the magnetic flux in the metal wires, reduces the influence of the magnetic force lines, and overcomes the defect that the mutual inductance between the inductance coils in the prior art is not strong, thus making the present invention enhance the inductance The mutual inductance between the coils increases the inductance value.

Fifth, the present invention is compatible with traditional CMOS, and overcomes the defect that the special process in the prior art leads to increased process difficulty in inductive processing, thus making the present invention simple to process and easy to implement.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the simulation result comparison figure of the present invention and traditional spiral inductor quality factor Q value;

Fig. 3 is a comparison diagram of the simulation results of the inductance value of the present invention and the traditional spiral inductor.

Detailed ways

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

The planar spiral inductor with alternating line width and spacing structure shown in Figure 1 includes a silicon substrate, an insulating layer, a bottom metal layer of the planar spiral inductor, through holes, and a metal layer of the planar spiral inductor. A layer of 1 μm thick oxide is grown on a 450 μm thick silicon base to form an insulating layer, a layer of 10 nm thick titanium gold film is sputtered on the insulating layer, and a 500 nm thick metal film is plated on the surface of the titanium gold film, etched Metal film, forming the bottom metal layer of the spiral inductor, depositing a 900nm thick oxide on the bottom metal layer of the spiral inductor to form an insulating layer, etching the insulating layer to form a through hole, and plating a 2μm thick metal film on the insulating layer, selectively Etching forms the spiral inductor metal layer.

The metal line width of the metal layer of the planar spiral inductor changes alternately from the outer ring to the inner ring, which means that the width of the metal wires 1, 5, 9, 12, and 13 is the widest among all metal wires; the metal wires 2, 6, and 10 , 14 are narrower than metal wires 1, 5, 9, 12, and 13; metal wires 3, 7, 11, and 15 are wider than metal wires 2, 6, 10, and 14, and narrower than metal wires 1, 1, and 14. 5, 9, 12, 13; the width of the metal conductors 4, 8 is narrowed, and its width is narrower than that of the metal wires 2, 6, 10, 14.

The metal line spacing of the metal layer of the planar spiral inductor changes alternately from the outer ring to the inner ring, which means that the spacing between the metal wires 1, 5, 9, 13 and the metal wires 2, 6, 10, 14 is the largest among the wire spacings. ; The distance between the metal wires 2, 6, 10, 14 and the metal wires 3, 7, 11, 15 is less than the distance between the metal wires 1, 5, 9, 13 and the metal wires 2, 6, 10, 14; The distance between the wires 3, 7 and the metal wires 4, 8 is greater than the distance between the metal wires 2, 6 and the metal conductor lines 3, 7.

The range of the width of the metal wire is 0.03 microns to 20 microns. The distance between the metal wires ranges from 0.04 microns to 10 microns. The outer diameter of the planar spiral inductor ranges from 0.1 microns to 400 microns.

FIG. 2 is a graph showing the comparison of the Q value of the inductance quality factor of the present invention with the simulation results of the Q value of the traditional planar spiral inductor with fixed metal line width and spacing. The solid line represents the variation curve of the quality factor Q value of the spiral inductor of the present invention with frequency, and the dotted line represents the variation curve of the quality factor Q value of the traditional planar spiral inductor with frequency.

As shown in FIG. 2 , the Q value of the inductance quality factor of the present invention reaches the maximum value of 14.86 at 2.70 GHz, and the Q value of the inductance quality factor of the traditional planar spiral inductor reaches the maximum value of 13.37 at 2.55 GHz. The Q value of the invention is 11% higher than that of the traditional spiral inductor.

FIG. 3 is a graph showing the comparison of the inductance value of the present invention and the inductance value simulation results of the traditional planar spiral inductor with fixed metal line width spacing. Wherein the solid line represents the variation curve of the inductance value of the spiral inductor of the present invention with frequency, and the dotted line represents the variation curve of the inductance value of the traditional planar spiral inductor with frequency.

As shown in FIG. 3 , the inductance value of the present invention is 7.31nH at 2GHz, and the inductance value of the traditional planar spiral inductor is 5.52nH at 2GHz. The inductance value of the invention is 36% higher than that of the traditional inductance.

It can be seen from the simulation results that the performance of the spiral inductor can be effectively improved by adopting the planar spiral inductor with alternating line width and spacing structure of the present invention.

Claims (6)

1. A planar spiral inductor with alternating line width and spacing structure, comprising a silicon substrate, an insulating layer, a bottom metal layer of a planar spiral inductor, a through hole, and a metal layer of a planar spiral inductor; spiral inductors are grown on the silicon substrate The insulating layer, metallized film on the insulating layer etches the bottom metal layer of the inductor, deposits the insulating layer on the bottom metal layer, etches the through hole on the insulating layer, connects the bottom metal layer and the spiral inductor layer, and coats the metal film on the insulating layer to etch the spiral The inductance metal layer, the coil of the spiral inductance metal layer has multiple turns, and the coil pattern is made of conductive metal; it is characterized in that the metal line width of the plane spiral inductance metal layer changes alternately from the outer circle to the inner circle, and the distance between the metal lines changes from the outer circle to the inner circle. The width of the circle changes alternately towards the inner circle. 2. the line-width-spacing alternating structure type planar spiral inductor according to claim 1, is characterized in that, the metal line width of described planar spiral inductor metal layer changes alternately from outer ring to inner ring width and narrow and refers to, metal wire ( 1), (5), (9), (12), (13) are the widest among all metal wires; metal wires (2), (6), (10), (14) are wider than metal wires (1), (5), (9), (12), (13) are narrowed; metal wires (3), (7), (11), (15) are wider than metal wires (2), (6) , (10), (14) width becomes wider, and its width is narrower than metal wire (1), (5), (9), (12), (13); Metal conductor (4), (8) width narrows , whose width is narrower than that of the metal wires (2), (6), (10), (14). 3. the line-width-spacing alternating structure type planar spiral inductor according to claim 1, is characterized in that, the metal line spacing of described planar spiral inductor metal layer changes alternately from outer ring to inner ring width and is meant that metal wire ( 1), (5), (9), (13) and the spacing between the metal wires (2), (6), (10), (14) are the largest in the wire spacing; the metal wires (2), ( 6), (10), (14) and the distance between the metal wires (3), (7), (11), (15) are smaller than the metal wires (1), (5), (9), (13) and the spacing between the metal wires (2), (6), (10), (14); the spacing between the metal wires (3), (7) and the metal wires (4), (8) is greater than the metal wire ( 2), (6) and the spacing between metal conductors (3), (7). 4 . The planar spiral inductor with alternating line width and pitch structure according to claim 1 , wherein the width of the metal wires ranges from 0.03 microns to 20 microns. 5 . The planar spiral inductor with alternating line width and spacing structure according to claim 1 , wherein the distance between the metal wires ranges from 0.04 μm to 10 μm. 5 . 6 . The planar spiral inductor with alternating line width and pitch structure according to claim 1 , wherein the outer diameter of the planar spiral inductor ranges from 0.1 μm to 400 μm.

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