CN104682910A - Mutual inductance coupling filter - Google Patents

Abstract

The invention discloses a mutual inductance coupling filter, the mutual inductance structural unit has two or more mutually overlapping but not short-circuited inductances. The filter of the present invention is based on IPD technology, and realizes a mutual inductance coupling filter with high integration and good performance through reasonable simulation calculation. The invention uses high-resistance silicon as the base material, which has better high-frequency characteristics; uses semiconductor technology to complete all the processes, can precisely control the size of each layer of metal and medium, and ensures the quality and reliability of the product; realizes two Or a structure in which multiple inductors overlap each other and are not short-circuited to obtain a large overlapping coupling. The layout of the inductors in a partially overlapping manner can easily obtain a large mutual inductance value, thereby realizing a filter with less loss and reducing Small filter size; moreover, multiple adjustable transmission zeros can be introduced in the filter based on the mutual inductance structure.

Description

A Mutual Inductance Coupling Filter

technical field

The present invention relates to the technical field of filters, in particular to a mutual inductance coupling filter.

Background technique

With the rapid development of wireless communication technology in recent years, more and more mobile devices have wireless communication functions such as Bluetooth and Wi-Fi. Due to the small size, light weight and low power consumption of mobile devices, it is of great practical significance to design a miniaturized, high-performance bandpass filter suitable for mobile devices. At present, most wireless communication systems such as Bluetooth and Wi-Fi work in the industrial, scientific and medical (ISM) frequency band. In this frequency band, traditional lumped parameter filters have been difficult to meet the performance requirements, and it is also quite difficult to design surface acoustic wave (SAW) filters and ceramic filters in this frequency band. With the development of technology, the low temperature co-fired ceramic (Low Temperature Co-fired Ceramic, LTCC) technology that appeared at the end of the last century can better solve this problem. LTCC technology introduces a layered structure based on the original planar circuit design, and the components in the circuit can be arranged on different layers. By utilizing the coupling relationship of circuit elements on different layers, the circuit size can be reduced to a certain extent. In industrial production, LTCC technology is to embed prefabricated metal strips into the medium, sinter them at low temperature (700°C-800°C), and then obtain finished products through a series of treatments. At present, many passive modules such as microwave filters and baluns based on LTCC technology have been applied in production. However, due to the limitation of process parameters, the passive module based on LTCC has a large line width and thickness, which makes the volume of the whole module relatively large, and it is difficult to meet the requirements of miniaturization and high integration. Moreover, high-temperature ceramic sintering is used. high cost.

With the development of system packaging, the new technology of passive integration on silicon-based or glass-based surfaces using semiconductor technology has received widespread attention, that is, passive modules such as inductors, capacitors, and LC filters are realized on silicon wafers or glass original chips. Especially on silicon wafers, wafer-level semiconductor processes can be used to realize the interconnection of fine lines, and at the same time, it is easy to integrate with the entire system. Therefore, there is an increasing demand for using silicon-based materials to make passive filters. However, due to the semiconductor characteristics of the silicon base and the limitation of the metal stack on the surface, the Q value of the spiral inductor fabricated on the silicon by the traditional method is limited. Even if the high-resistance silicon substrate is used, the coil metal thickness exceeds 10 μm, and the Q value is also low. It's hard to get above 50. At present, the method of implementing a filter on a silicon base is mainly as follows: select a suitable LC filter transfer function, such as a Chebyshev filter or a Butterworth filter; then select an appropriate order according to the suppression requirement; then according to The technical parameters such as filter center frequency and bandwidth determine the specific parameters of various components in the filter; then the required passive inductors and capacitors are rationally designed, laid out and electrically connected on the surface of the silicon substrate, and finally film deposition, metal sputtering The structure is fabricated by a series of semiconductor processes such as radiation, electroplating, photolithography, and etching.

Passive modules made using silicon-based IPD (Integrated Passive Device) technology have high reliability, compact structure, and low cost. They have great cost and performance advantages and can be better applied to wireless radio frequency communication systems. It can replace the traditional LTCC technology to make filters. However, in the realization of some high-performance filters, silicon-based filters still have shortcomings. Such as adopting the filter of the inductively coupled structure so as to obtain a suitable transmission zero point, it is easy to realize on the LTCC. But on a silicon base, even two very close transmission lines or inductors cannot achieve a large enough magnetic field coupling.

Contents of the invention

Based on the above technical problems, the main purpose of the present invention is to provide a mutual inductance coupling filter to realize a mutual inductance coupling filter with high integration and good performance based on IPD technology through reasonable simulation calculations.

In order to achieve the above object, the present invention provides a mutual inductance coupling filter, which is characterized in that the mutual inductance structural unit of the mutual inductance coupling filter has two or more mutually overlapping but not short-circuited inductors.

Wherein, the mutual inductance coupling filter is fabricated on silicon, glass or ceramic substrate materials.

Wherein, the inductor is composed of two or more layers of metal.

Wherein, the metal layers of the inductor are electrically connected through metal vias or direct contact.

Wherein, the mutual inductance coupling filter further includes capacitors, and the capacitors include but not limited to rectangular, circular, polygonal capacitors, and capacitors with unconventional longitudinal structures.

Wherein, the inductive coupling part of the mutual inductance structural unit exists between two or more resonant circuits.

Wherein, the inductance changes the coupling coefficient between the inductances by changing the size of the overlapping portion.

Wherein, the two or more inductors are arranged alternately and overlapped, thereby reducing the size of the mutual inductance coupling filter.

Wherein, an adjustable transmission zero point is introduced into the mutual inductance coupling filter, so as to increase the suppression of the filter in a specific frequency band.

Wherein, the mutual inductance coupling filter is manufactured by silicon-based IPD technology.

Based on the above technical solution, it can be seen that the mutual inductance coupling filter of the present invention uses high-resistance silicon as the base material, and has good high-frequency characteristics; the use of semiconductor technology to complete all the process can precisely control the size of each layer of metal and medium, ensuring The quality and reliability of the product; the structure of two or more inductors overlapping each other without short circuit is realized, and a larger overlapping coupling is obtained. The layout of the inductors in a partially overlapping manner can simply obtain a larger mutual inductance value. Therefore, a filter with less loss can be realized, and the size of the filter can be reduced at the same time; in addition, multiple adjustable transmission zeros can be introduced into the filter based on the mutual inductance structure.

Description of drawings

Fig. 1 is the lumped circuit structure schematic diagram of the mutual inductance coupling filter of the present invention;

Fig. 2 is the sectional structure schematic diagram of the realization mode of resistance, capacitance and inductance on the silicon substrate;

Fig. 3 is a schematic cross-sectional structure diagram of overlapping coupled inductor traces of the present invention;

The left and right figures of Figure 4 are the top views of the coupled inductor traces with no overlap and partial overlap respectively;

Fig. 5 is the top view of the specific structure of mutual inductance coupling filter of the present invention;

The left and right graphs in Figure 6 show the insertion loss of filters using a coupled structure and an uncoupled structure, respectively, where the abscissa is the frequency (GHz), and the ordinate is the attenuation loss (dB).

Explanation of reference signs:

101-high resistance silicon material substrate; 102-silicon dioxide layer; 103-PI layer 1; 104-PI layer 2; 105-resistive material, TaSi; 106-silicon nitride; Lower plate; 109-capacitor structure upper plate; 110-capacitor dielectric layer; 111-TaSi layer on the lower plate of the capacitor; 112-capacitor lead-out layer; 113-first inductance metal layer; 115-second inductor metal layer; 201-input port of one inductor; 202-output port of one inductor; 203-input port of another inductor; 204-output port of another inductor; 301-overlapping coupled inductor structure; 302 - Capacitive structure.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The invention discloses a method for designing and realizing a high-performance mutual inductance coupling filter on a substrate material. Firstly, the corresponding lumped circuit is determined according to the design index, and these parameter indexes include center frequency, bandwidth, in-band insertion loss and out-of-band attenuation etc. According to the determined lumped circuit, using semiconductor technology, realize the corresponding resistance, capacitance, inductance and mutual inductance structural unit, in which the mutual inductance structural unit realizes the structure of two or more inductors overlapping each other but not short circuit, and obtains a larger Overlap coupling, which introduces controllable transmission zeros. Then each device is built into a corresponding filter circuit, and the overall field simulation is carried out on the designed filter structure, so as to analyze and optimize the performance of the filter.

Wherein, the interposer material includes but not limited to substrate materials such as silicon, glass, and ceramics.

Wherein, the passive components include but are not limited to passive components such as passive resistors, capacitors, inductors, and mutual inductance structures.

Wherein, the inductive structure is composed of two or more layers of metal, and the formed inductive coupling structure can be composed of two or more superimposed couplings.

Wherein, the capacitor structure includes but not limited to capacitors in shapes such as rectangles, circles, and polygons, and capacitors with unconventional longitudinal structures.

Wherein, the filter can be a filter of two or more orders, and the inductive coupling part can exist between two resonant or multiple resonant circuits.

Taking the substrate of high-resistance silicon material as an example, a two-order mutual inductance coupling filter is designed and formed on it, and its typical optimal implementation is as follows:

Determine the corresponding lumped circuit according to the design index. Take a certain design index as an example: the range of the passband includes 2400-2500MHz. A typical lumped circuit is shown in Figure 1, which consists of two sets of LC circuits connected in parallel, L1 and C3 form an LC circuit, and L2 and C4 form an LC circuit.

On silicon material substrates, capacitors, resistors, and inductors are manufactured using thin-film technology. A typical implementation process of resistors, capacitors and inductors is shown in Figure 2. From left to right in the figure are layered structure diagrams of resistors, capacitors and inductors, where the resistors provide a specified resistance between the resistor lead-out electrodes 107 by setting the material, length and cross-sectional area of the resistor material layer 105. value, the capacitor provides a specified capacitance between the capacitor lead-out layers 112 by setting the materials, relative areas and distances of the capacitor structure lower plate 108, the capacitor structure upper plate 109, and the capacitor dielectric layer 110, while the inductance is Using the usual planar spiral inductor, as the invention point of the present invention, the inductor of the present invention is composed of the first inductive metal layer 113 and the second inductive metal layer 115 which are located in different layers and have the nature of wires, and the inductive metal vias are passed between them. layer 114, in addition, the two inductive metal layers can also be electrically connected through direct contact.

On the high-resistance silicon-based substrate 101 , inductive coupling is realized by partially overlapping planar spiral inductors. The structure of overlapping coupled inductors is shown in Figure 3. Wherein, the inductance structure has at least two layers of metal (113, 115), one layer of inductance metal via layer 114, at the position where the sides of the two inductances overlap, one edge goes through the upper layer of metal, and the other side goes through the lower layer of metal, thereby preventing Short circuit between inductive structures. By changing the size d2 of the overlapping portion, the coupling coefficient between inductors can be changed. Compared with the non-overlapped coupled inductor structure, the coupling coefficient of the overlapped coupled inductor structure is much larger, so that the size of the coupled inductor required in the schematic diagram of Figure 1 can be achieved, and the area of the entire structure is also greatly reduced . As shown in FIG. 4 , in order to ensure a positive coupling coefficient, the input ports of the two inductors are respectively (201, 203), and the output ports are respectively (202, 204). The left picture shows the situation without overlap, and the two inductors are completely separated; the right picture shows the situation with partial overlap, in which the two inductors are staggered. It can be seen from the figure that the area of the overlapping part indicating the coupling strength is much larger than that of In the case of no overlap, the coupling inductance value is much larger than that of the case of no overlap after actual detection.

According to the lumped circuit, the filter is built with passive components on the silicon material substrate, and the overall field simulation of the filter structure is carried out. The specific structure of the filter is shown in Figure 5, and the insertion loss of the field simulation is shown in Figure 6. In Fig. 6, the insertion loss of the third-order Chebyshev filter without the coupling structure is also compared. By comparative analysis, using the inductive coupling structure and introducing a suitable transmission zero point, the required attenuation can be obtained in the sensitive frequency band. Moreover, lower order filters can be used to meet the attenuation requirements, thereby reducing the loss in the passband. The inductive coupling structure filter can make the structure more compact because of the overlapping coupling structure.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. a Mutual Inductance Coupling filter, is characterized in that, the mutual inductance structure unit of described Mutual Inductance Coupling filter has two or more mutually overlapping but inductance of not short circuit.

2. Mutual Inductance Coupling filter as claimed in claim 1, wherein said Mutual Inductance Coupling filter is produced on silicon, glass or ceramic substrate material.

3. Mutual Inductance Coupling filter as claimed in claim 1, wherein said inductance is made up of two-layer or multiple layer metal.

4. Mutual Inductance Coupling filter as claimed in claim 3, is electrically connected by the mode of metallic vias or directly contact between each metal level of wherein said inductance.

5. Mutual Inductance Coupling filter as claimed in claim 1, also comprise electric capacity in wherein said Mutual Inductance Coupling filter, described electric capacity includes but not limited to the electric capacity of rectangle, circle, polygonal shape, and the electric capacity of unconventional vertical structure.

6. Mutual Inductance Coupling filter as claimed in claim 1, the inductance coupling high part of wherein said mutual inductance structure unit is present between two or more resonant tank.

7. Mutual Inductance Coupling filter as claimed in claim 1, wherein said inductance changes the coupling coefficient between inductance by the size changing overlapping part.

8. Mutual Inductance Coupling filter as claimed in claim 1, wherein said two or more inductance interlocks folded array, thus reduces the size of described Mutual Inductance Coupling filter.

9. Mutual Inductance Coupling filter as claimed in claim 1, introduces adjustable transmission zero in wherein said Mutual Inductance Coupling filter, thus increases the suppression of filter in characteristic frequency section.

10. Mutual Inductance Coupling filter as claimed in claim 1, wherein said Mutual Inductance Coupling filter is by silica-based IPD fabrication techniques.