CN106653285A - Spiral stacked integrated transformer and inductor - Google Patents

Abstract

A spiral stacked integrated transformer is composed of a first inductor and a second inductor, the spiral stacked integrated transformer comprises: a first helical coil having a first outer coil and a first inner coil, the first inner coil being located within the first outer coil; a second helical coil having an overlap range with the first helical coil, having a second outer coil and a second inner coil, the second inner coil being located within the second outer coil; and a connecting structure for connecting the first helical coil and the second helical coil; the first inductor includes a portion of the first helical coil and a portion of the second helical coil, and the second inductor includes a portion of the first helical coil and a portion of the second helical coil.

Description

Helically stacked integrated transformer and inductor

technical field

The invention relates to a transformer and an inductor, in particular to a spiral stacked integrated transformer and a spiral stacked integrated inductor.

Background technique

Inductors and transformers are important components used in radio frequency integrated circuits to achieve single-ended to differential signal conversion, signal coupling, impedance matching and other functions. With the development of integrated circuits to System on Chip (SoC), integrated inductors (integrated Inductor) and integrated transformer (integrated transformer) have gradually replaced traditional discrete components, and are widely used in radio frequency integrated circuits. However, the inductors and transformers in integrated circuits often occupy a large amount of chip area. Therefore, how to reduce the area of inductors and transformers in integrated circuits while maintaining the characteristics of components, such as electric resistance value, quality factor (quality factor, Q) and coupling coefficient (couplingcoefficient, K), etc., become an important topic.

Contents of the invention

In view of the disadvantages of the prior art, the object of the present invention is to provide a spiral stacked integrated transformer and a spiral stacked integrated inductor, so as to reduce the element area and improve the element efficiency.

The invention discloses a helical stacked integrated transformer, which is composed of a first inductance and a second inductance, including: a first helical coil, a first external coil and a first internal coil, the first an inner coil located within the first outer coil; a second helical coil having an overlapping range with the first helical coil, having a second outer coil and a second inner coil, the second inner coil being located in the Inside the second external coil; and a connection structure for connecting the first helical coil and the second helical coil; wherein the first inductance includes a part of the first helical coil and the second helical coil A part of the second inductor includes a part of the first helical coil and a part of the second helical coil.

The present invention also discloses a helical stacked integrated inductor, which has a first induction unit and a second induction unit, including: a first helical coil, a first outer coil and a first inner coil, the first An inner coil is located within the first outer coil, and the first helical coil includes a first end point and a second end point; a second helical coil has an overlapping range with the first helical coil, and has a a second outer coil and a second inner coil, the second inner coil is located within the second outer coil, and the second helical coil includes a third terminal; and a connecting structure for connecting the first helical coil and the second helical coil; wherein, the first induction unit includes a part of the first helical coil and a part of the second helical coil, and uses the first end point and the third end point as the first The two ends of the induction unit, the second induction unit includes a part of the first helical coil and a part of the second helical coil, and the second end and the third end are used as the two ends of the second induction unit endpoint.

The spiral stacked integrated transformer and the spiral stacked integrated inductor of the present invention have an integrated symmetrical structure, provide two inductors with high symmetry, and are more suitable for use as passive components in integrated circuits.

Regarding the features, practices and effects of the present invention, the embodiments will now be described in detail in conjunction with the accompanying drawings.

Description of drawings

FIG. 1A is a structural diagram of an embodiment of a spiral stacked integrated transformer of the present invention;

Figure 1B is a structural diagram of another embodiment of the spiral stacked integrated transformer of the present invention;

Fig. 1C is a structural diagram of another embodiment of the spiral stacked integrated transformer of the present invention;

FIG. 1D and FIG. 1E are cross-sectional views corresponding to the spiral stacked integrated transformer of the switch module in FIG. 1C under different switching states;

FIG. 2A and FIG. 2B are the simulation results of the inductance value and Q value of the spiral stacked integrated transformer 200 in FIG. 1B;

3A and 3B are structural diagrams of another embodiment of the spiral stacked integrated transformer of the present invention;

4 is a structural diagram of another embodiment of the spiral stacked integrated transformer of the present invention;

FIG. 5 is a structural diagram of an embodiment of the spiral stacked integrated inductor of the present invention; and

6A to 6C are three-dimensional structural views of another embodiment of the spiral stacked integrated transformer of the present invention.

detailed description

The technical terms in the following description refer to the customary terms in this technical field. If some terms are explained or defined in this manual, the explanations or definitions of these terms shall prevail.

FIG. 1A is a structural diagram of an embodiment of the spiral stacked integrated transformer of the present invention. The helical stacked integrated transformer 100 is composed of a helical coil 110 and a helical coil 120. The opening direction of the helical coil 110 is 90 degrees different from the opening direction of the helical coil 120. Most of the metal wire segments of the helical coil 110 are located in the semiconductor The first metal layer in the structure, most of the metal line segments of the helical coil 120 are located in the second metal layer in the semiconductor structure. The helical coil 110 has an end point 117 and an end point 118 and includes a metal wire segment 111 , a metal wire segment 112 , a metal wire segment 113 , and a metal wire segment 114 . The left half of the metal wire segment 111 and the metal wire segment 113 constitute the outer coil of the helical coil 110 , while the right half of the metal wire segment 111 and the metal wire segment 112 constitute the inner coil of the helical coil 110 . Helical coil 120 has end points 127 and 128 and includes wire segments 121 , 122 , 123 , 124 , 125 , 131 , 132 , and 133 . The helical coil 120 also includes an outer coil and an inner coil. Its outer coil includes metal wire segment 121 , metal wire segment 131 , metal wire segment 122 and the lower half of metal wire segment 124 ; its inner coil includes metal wire segment 125 , metal wire segment 133 , the upper part of metal wire segment 124 and metal wire segment 123 .

In the semiconductor structure, the metal line segment 111, the metal line segment 112 and the metal line segment 113 belong to the first metal layer, and the metal line segment 114, the metal line segment 121, the metal line segment 122, the metal line segment 123, the metal line segment 124 and the metal line segment 125 belong to the second metal layer , the metal line segment 131 , the metal line segment 132 and the metal line segment 133 belong to the third metal layer, and the three metal layers are substantially parallel structures. The metal line segment 114 connects the metal line segment 112 and the metal line segment 113 through a penetrating structure (located at the penetrating position shown in the figure) perpendicular to the metal layer, so the metal line segment 114 can be regarded as a part of the helical coil 110 . Similarly, although the metal line segment 131, the metal line segment 132 and the metal line segment 133 are located in the third metal layer, they are actually connected to the metal line segment 121 and the metal line segment 122, the metal line segment 122 and the metal line segment 123 and the metal line segment 123 respectively through a plurality of through structures. The metal wire segment 124 and the metal wire segment 125 , so the metal wire segment 131 , the metal wire segment 132 and the metal wire segment 133 can be regarded as a part of the helical coil 120 . The helical coil 110 and the helical coil 120 are stacked up and down, the outer coils of the two substantially overlap, and the inner coils of the two substantially overlap, that is to say, the helical coil 110 and the helical coil 120 are not in contact with each other, but have an overlapping range in the semiconductor structure.

The helical stacked integrated transformer 100 further includes a connection structure 160 , and the connection structure 160 is located within the overlapping range of the helical coil 110 and the helical coil 120 . The connection structure 160 includes a metal line segment 161 and a metal line segment 162. Please note that in this embodiment, although the metal line segment 161 is connected to the metal line segment 123 and the metal line segment 162 is connected to the metal line segment 125, in order to clearly define the internal coil of the helical coil In order to explain the present invention more easily, the present invention specifically defines the metal wire segment 161 and the metal wire segment 162 as the connection structure 160 to distinguish them from the internal coil. The connection structure 160 is mainly used to connect the inner coil of the helical coil 110 and the inner coil of the helical coil 120 , so it is disposed in the overlapping range of the helical coil 110 and the helical coil 120 . In this embodiment, the connection structure 160 is located on the second metal layer, so the metal line segment 161 is directly connected to the metal line segment 123, the metal line segment 162 is directly connected to the metal line segment 125, and the metal line segment 161 and the metal line segment 162 pass through the position 150-3 The through structure on the through position 150-4 is respectively connected to the metal line segment 112 and the metal line segment 111 on the first metal layer (the through position 150-3 corresponds to the through position 140-3 and the through position 150-4 corresponds to the through position 140 -4), so actually the metal line segment 112 is connected to the metal line segment 161 and the metal line segment 111 is connected to the metal line segment 162 . In different embodiments, the connection structure 160 can be made in different metal layers, and connect metal line segments belonging to different layers through the through structure.

Analyzing the structure of the helical stacked integrated transformer 100, it can be found that the helical stacked integrated transformer 100 actually includes two inductors. The first inductance takes the terminal 117 as one of the endpoints, mainly includes the metal line segment 111, the metal line segment 125, the metal line segment 133 and the metal line segment 124, and takes the terminal point 128 as the other end point. Briefly, the first inductance includes the spiral coil 110 The left half of the outer coil and the right half of the inner coil, and the upper half of the inner coil of the helical coil 120 and the lower half of the outer coil include the metal line segment represented by light gray in FIG. 1A; similarly, The second inductance takes endpoint 118 as one of its endpoints, and mainly includes metal line segment 113, metal line segment 114, metal line segment 112, metal line segment 123, metal line segment 132, metal line segment 122, metal line segment 131 and metal line segment 121, and takes endpoint 127 as The other end, briefly, the second inductance includes the right half of the outer coil and the left half of the inner coil of the helical coil 110, and the lower half of the inner coil and the upper half of the outer coil of the helical coil 120 , which contains the metal line segment shown in dark gray in Figure 1A. The helically stacked integrated transformer 100 realizes the function of a transformer through the interaction of the magnetic fields of the two inductors.

FIG. 1B is a structural diagram of another embodiment of the spiral stacked integrated transformer of the present invention. Basically, the helical stacked integrated transformer 200 is still composed of two helical coils (helical coil 210 and helical coil 220 ). 123 is composed of a metal wire segment 123-1 (second metal layer), a metal wire segment 123-2 (second metal layer) and a metal wire segment 134 (third metal layer) in the helical coil 220, and the helical stacking type is integrated The connection structure 170 of the transformer 200 is also slightly different from the connection structure 160 . The connection structure 170 includes a metal line segment 171, a metal line segment 172, a metal line segment 173 and a metal line segment 174, wherein except the metal line segment 174 is located in the first metal layer, other metal line segments are all located in the second metal layer, that is to say, in this embodiment The connecting structures 170 are distributed on more than one metal layer. The penetration position 140-5 corresponds to the penetration position 150-5 and the penetration position 140-6 corresponds to the penetration position 150-6, so that the metal line segment 112 is connected to the metal line segment 171 through the penetration structure, and the metal line segment 111 is connected to the metal line segment 173 through the penetration structure. connect. Although the connection structures of the helical stacked integrated transformer 100 and the helical stacked integrated transformer 200 are different, the first inductance and the second inductance have substantially the same structure in the helical stacked integrated transformer 100 and the helical stacked integrated transformer 200. configuration.

Fig. 1C is a structural diagram of another embodiment of the spiral stacked integrated transformer of the present invention. In this embodiment, the connection structure 180 of the spiral stacked integrated transformer 300 also includes a switch module 181 in addition to the metal wire segment 161 and the metal wire segment 162 . The switch module 181 can determine the connection mode between the through position 150-3 and the through position 150-4 and the end point of the metal line segment 161 and the end point of the metal line segment 162 through a plurality of internal switch units, for example, switching state (1): through position 150- 3 and the through position 150-4 are connected with the end point of the metal line segment 162 and the end point of the metal line segment 161 respectively; 162 endpoint connections. One embodiment of the switch module 181 includes four switch units to perform the above-mentioned switching, and the switch units may be implemented, for example, by Metal Oxide Semiconductor Field Effect Transistors (MOSEFT). Figure 1D and Figure 1E are cross-sectional views corresponding to the spiral stacked integrated transformer of the switch module in Figure 1C in different switching states, Figure 1D and Figure 1E are drawn according to the AA' cross-section of Figure 1C, in the figure The current directions of the first inductor and the second inductor in the inner coil and the outer coil are also marked (here, the current of the two inductors flows in from the terminal 117 and the terminal 118 respectively as an example). FIG. 1D corresponds to the above switching state (1), and FIG. 1E corresponds to the above switching state (2). It can be found that the switching of the switch module 181 causes the direction of the current in the two inductors to change, so that the self-inductance and mutual inductance of the two inductors change, and the respective inductance values also change accordingly. That is to say, in practice, the inductance values of the two inductors of the spiral stacked integrated transformer 300 can be adjusted through the switch module 181 . In addition, it can be found from the figure that in this embodiment, the first metal layer to which the first helical coil belongs is located above the second metal layer to which the second helical coil belongs, for example, the first metal layer and the second metal layer are respectively It is a redistribution layer (redistribution layer, RDL) and an ultra-thick metal (Ultra-Thick Metal, UTM) layer in the semiconductor structure, and the third metal layer to which the metal line segment 131, the metal line segment 132 and the metal line segment 133 belong uses the UTM layer The underlying metal layer is fabricated.

2A and 2B show the simulation results of the inductance value and Q value of the spiral stacked integrated transformer 200 in FIG. 1B. The line width is 4 μm, the number of turns is 4 turns, the inner diameter is 38 μm, and the line spacing is 2 μm, corresponding to FIG. 2A The structure of Figure 2B does not contain a patterned ground shield (patterned ground shield). In FIG. 2A, the curve 311 represents the inductance value (unit: nH) of the first inductor and the second inductor, and the inductance value curves of the two substantially overlap, and the curve 312 and the curve 313 respectively represent the Q value of the first inductor and the second inductor; Similarly, in Fig. 2B, the curve 314 represents the inductance value (unit: nH) of the first inductance and the second inductance, the inductance value curves of the two substantially overlap, and the curve 315 and the curve 316 represent the first inductance and the second inductance respectively Q value. As expected, the inductance value and Q value have better performance in the case of patterned ground shielding. In addition, it can be seen that under the above-mentioned integrated transformer structure, the first inductance and the second inductance have substantial Equal inductance values and nearly identical Q values. From the above description, it can be found that although the resistance values of the first metal layer and the second metal layer are usually different in the semiconductor structure, and the inner coil and the outer coil of the helical coil may encounter different physical characteristics, but because the first inductance and the second inductance are uniformly distributed in the first metal layer and the second metal layer and the inner coil and outer coil of the helical coil, so the inductance value and Q value of the two are almost identical, and have excellent symmetry.

3A and 3B are structural diagrams of another embodiment of the spiral stacked integrated transformer of the present invention. The helical stacked integrated transformer 400 is composed of a helical coil 410 and a helical coil 420 , and the opening of the helical coil 410 and the opening of the helical coil 420 face the same direction. The metal line segment 411 is applied to the fourth metal layer for connecting the metal line segment 412 and the metal line segment 413 , and the metal line segment 421 is applied to the third metal layer for connecting the metal line segment 424 and the metal line segment 423 . The connection structure 460 of this embodiment is also located in the overlapping range of the helical coil 410 and the helical coil 420 , including the switch module 461 . The switch module 461 is used to connect each end point of the metal line segment 422 and the metal line segment 423 to the penetration position 450-1 and the penetration position 450-2, and the penetration position 450-1 and the penetration position 450-2 correspond to the penetration position 440-1 and the penetration position 450-2 respectively. Run through location 440-2. Similarly, the switch module 461 can determine the connection between the through position 450 - 1 and the through position 450 - 2 and the end points of the metal line segment 422 and the end point of the metal line segment 423 through switching states of multiple internal switch units. 3A shows that the end point of the metal line segment 422 is connected to the penetration position 450-2 and the end point of the metal line segment 423 is connected to the penetration position 450-1, so the first inductance includes the left half of the outer coil of the helical coil 410 and the inner coil The right half of the outer coil of the helical coil 420 and the left half of the inner coil, that is, the corresponding light gray metal line segment, the second inductance includes the right half of the outer coil of the helical coil 410 and the inner The left half of the coil and the left half of the outer coil and the right half of the inner coil of the helical coil 420 correspond to the dark gray metal line segment.

3B shows another switching state of the spiral stacked integrated transformer 400: the end point of the metal line segment 422 is connected to the through position 450-1 and the end point of the metal line segment 423 is connected to the through position 450-2, so the first inductance includes The left half of the outer coil of the helical coil 410 and the right half of the inner coil and the left half of the outer coil of the helical coil 420 and the right half of the inner coil, that is, corresponding to the light gray metal line segment, the second inductance The right half of the outer coil and the left half of the inner coil of the helical coil 410 and the right half of the outer coil and the left half of the inner coil of the helical coil 420 correspond to the dark gray metal line segment. When the configuration of the first inductor and the second inductor is changed, the internal current direction and the self-inductance and mutual inductance of the two inductors all change, so the inductance values of the two inductors can be adjusted.

Fig. 4 is a structural diagram of another embodiment of the spiral stacked integrated transformer of the present invention. The helical stacked integrated transformer 500 is composed of a helical coil 510 and a helical coil 520. The opening of the helical coil 510 and the opening of the helical coil 520 face opposite directions, that is, the opening directions of the two helical coils differ by 180 degrees. Although the metal line segment 511 is located in the second metal layer, it is part of the helical coil 510, so most of the helical coil 510 is located in the first metal layer, and a small part is located in the second metal layer; similarly, although the metal line segment 531 is located in the second metal layer There are three metal layers, but it belongs to a part of the helical coil 520 , so most of the helical coil 520 is located in the second metal layer, and a small part is located in the third metal layer. The through position 540-1 and the through position 540-2 respectively correspond to the through position 550-1 and the through position 550-2. The connection structure 560 is located in the overlapping range of the helical coil 510 and the helical coil 520 , and includes a plurality of metal wire segments and a switch module 561 . By changing the switching state of the switch module 561, the configurations of the first inductor and the second inductor can be changed. The light gray line segment in FIG. 4 constitutes the first inductance, and the dark gray line segment constitutes the second inductance. Please note that although the metal line segment 531 is made on the third metal layer in this embodiment, since there is no metal line segment at the corresponding position (as shown in area 515 ) of the first metal layer, the metal line segment 531 in this case is also It can be fabricated on the first metal layer to reduce the number of metal layers occupied by the spiral stacked integrated transformer 500 .

In addition to the above spiral stacked integrated transformer, the present invention also discloses a spiral stacked integrated inductor. For any of the above helical stacked integrated transformer structures, if the two ends of one of the helical coils are connected, a helical stacked integrated inductor can be obtained. Taking the helical stacked integrated transformer 100 shown in FIG. 1A as an example, after connecting the terminal 127 and the terminal 128 of the helical coil 120 , the structure as shown in FIG. 5 can be obtained. The newly formed terminal 129 can be used as a center tap of the inductor, and the center tap can be connected to a voltage source or ground of a circuit using the helically stacked integrated inductor. In more detail, the integrated inductor contains two sensing units and is symmetrically centered on the central tap. The first sensing unit (light gray metal line segment) has endpoints 117 and 129 as its two endpoints, and the second sensing unit (dark gray metal line segment) has endpoints 118 and 129 as its two endpoints. It can be known from the analysis of the spiral stacked integrated transformer that the first sensing unit and the second sensing unit formed by this structure have good symmetry and are suitable as passive components in integrated circuits. The above method can be applied to the helical stacked integrated transformer 200 , the helical stacked integrated transformer 300 , the helical stacked integrated transformer 400 and the helical stacked integrated transformer 500 to form the helical stacked integrated inductor.

Please note that the helical stacked integrated transformer or the helical stacked integrated inductor of the present invention is not limited to the 2-turn structure of the previous embodiment, in fact any helical coil can be applied with more turns. 6A to 6C are three-dimensional structural views of another embodiment of the spiral stacked integrated transformer of the present invention. FIG. 6A shows the metal line segment made on the first metal layer, and FIG. 6B shows the metal line segment made on the second metal layer and the third metal layer. , and Figure 6C shows two superimposed metal layers. The metal line segment in the third metal layer in the structure is represented by a flat line segment in FIG. 6B , such as the metal line segment 134 . Although the two helical coils in this embodiment are actually 4 turns, they can still be cross-referenced with the helical stacked integrated transformer 200 in FIG. 1B for a better understanding of the present invention, wherein corresponding components have the same reference numerals. It is worth noting that the metal line segment 131 in FIG. 1B is fabricated on the second metal layer in FIG. 6B , and the through structure 601 is used to connect the metal line segment at its corresponding through position, and a via structure or a via structure can be used. Array (via array) to practice. However, if the through structure 601 is connected with a silicon layer between the upper and lower metal layers, the through structure 601 is a through silicon via (TSV). If the through structure is removed, the metal line segment of the first metal layer is not connected to the metal line segment of the second metal layer. The helical stacked integrated transformer or helical stacked integrated inductor of the present invention is not limited to a quadrilateral structure, and the helical coil may have other polygonal structures. Although the metal line segment 602 in FIG. 6B is made on the third metal layer, it can also be made on the second metal layer as shown in FIG. 1A or 1B .

Please note that in the foregoing illustrations, the shapes, sizes, and proportions of elements are only schematic, that is, for those of ordinary skill in the art to understand the present invention, and are not intended to limit the present invention. Although the embodiments of the present invention are as described above, these embodiments are not intended to limit the present invention, and those skilled in the art can make changes to the technical characteristics of the present invention according to the contents of the present invention, expressly or implicitly, and these changes are all may belong to the protection scope of the present invention, in other words, the patent protection scope of the present invention shall be defined according to the patent application scope of this specification.

【Symbol Description】

100, 200, 300, 400, 500 Spiral stacked integrated transformers

110, 120, 210, 220, 410, 420, 510, 520 helical coil

111, 112, 113, 114, 121, 122, 123, 123-1, 123-2, 124, 125, 131, 132, 133, 134, 161, 162, 171, 172, 173, 174, 411, 412, 413, 421, 422, 423, 424, 511, 531, 602 Metal wire segments

117, 118, 127, 128, 129 endpoints

160, 170, 180, 460, 560 connection structure

140-3, 140-4, 140-5, 140-6, 150-3, 150-4, 150-5, 150-6, 440-1, 440-2, 450-1, 450-2, 540- 1, 540-2, 550-1, 550-2 through position

181, 461, 561 switch modules

311, 312, 313, 314, 315, 316 curves

515 area

601 through structure

Claims (10)

1. a kind of helical form stack integrated transformer, is made up of one first inductance and one second inductance, The helical form stack integrated transformer is included：

One first spiral coil, first spiral coil has one first external coil With one first Inside coil, first Inside coil is in first external coil；

One second spiral coil, second spiral coil and first spiral wire Circle has an overlapping range, and second spiral coil has one second external coil and Second Inside coil, second Inside coil is located in second external coil；And

One attachment structure, the attachment structure is used for connecting first spiral coil and institute State the second spiral coil；

Wherein, first inductance includes the part of first spiral coil and described A part for second spiral coil, second inductance includes first spiral coil A part and second spiral coil a part.

2. helical form stack integrated transformer according to claim 1, wherein, the connection Structure is located in the overlapping range.

3. helical form stack integrated transformer according to claim 1, wherein, the connection Structure connects first Inside coil and second Inside coil.

4. helical form stack integrated transformer according to claim 1, wherein, described first Spiral coil is located on a first metal layer of semiconductor structure, second helical form Coil is located in a second metal layer of the semiconductor structure.

5. helical form stack integrated transformer according to claim 4, wherein, the connection Structure include multiple metal wire sections, the plurality of metal wire sections be located at the first metal layer and In one of described second metal layer.

6. helical form stack integrated transformer according to claim 4, wherein, the connection Structure include multiple metal wire sections, the plurality of metal wire sections be located at the first metal layer and In the second metal layer.

7. helical form stack integrated transformer according to claim 1, wherein, the connection Structure includes a switch module, and the switch module has one first switching state and one second Switching state, when the switch module is first switching state, first inductance A Part I comprising second spiral coil, when the switch module is described the During two switching states, first inductance one second comprising second spiral coil Point.

8. helical form stack integrated transformer according to claim 7, wherein, described first Part and the Part II constitute complete second spiral coil.

9. helical form stack integrated transformer according to claim 1, wherein, described first Inductance comprising the part of first external coil, a part for first Inside coil, A part for a part for second external coil and second Inside coil, and A part, first Inside coil of second inductance comprising first external coil A part, the one of a part for second external coil and second Inside coil Part.

10. a kind of helical form stack integrated inductor, the helical form stack integrated inductor has one the One sensing unit and one second sensing unit, the helical form stack integrated inductor is included：

One first spiral coil, first spiral coil has one first external coil With one first Inside coil, first Inside coil be located at first external coil in, And first spiral coil includes a first end point and one second end points；

One second spiral coil, second spiral coil and first spiral wire Circle has an overlapping range, and second spiral coil has one second external coil and Second Inside coil, second Inside coil is located in second external coil, and Second spiral coil includes one the 3rd end points；And

One attachment structure, the attachment structure is used for connecting first spiral coil and institute State the second spiral coil；

Wherein, first sensing unit comprising first spiral coil a part and A part for second spiral coil, and with the first end point and the 3rd end points Used as two end points of first sensing unit, second sensing unit includes described the A part for a part for one spiral coil and second spiral coil, and with described Two end points of second end points and the 3rd end points as second sensing unit.