JP2010272625A - Spiral inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spiral inductor having a low self-resonant frequency and a high Q value. <P>SOLUTION: A spiral inductor 1 has a planar insulating substrate, and a conductor wire 11a having a spiral shape arranged on a main surface of the insulating substrate. A function of a line width of the conductor wire 11a, in which winding numbers Tu1-Tu9 of the conductor wire 11a serve as variables, is a V-shape function or a U-shape function. When the interval of the conductor wires 11a is constant and when outer diameters of the conductor wires 11a are equivalent to each other, a static capacitance between the conductor wire 11a in the winding numbers Tu2-Tu8 except for the innermost periphery and the outermost periphery of the conductor wire 11a and the leading line 10 becomes dominant concerning a parasitic capacitance of the spiral inductor 1. Since the spiral inductor 1 of the U-shape function or the V-shape function has a wide line width of the innermost periphery Tu1 and the outermost periphery Tu9, even when the total sum of the line width is equivalent, the line width of the conductor wire 11a crossing over the leading line 10 is decreased as a result to reduce the parasitic capacitance of the spiral inductor 1. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a spiral inductor in which conductor line widths differ according to the number of turns.

  With advances in technology for manufacturing semiconductor elements by finely processing semiconductors, etc., circuit elements such as various types of transistors, diodes, resistors, and capacitors have been reduced in size. Many challenges remain.

  For example, a spiral inductor made of a spiral metal wiring formed on a metal wiring layer above a semiconductor substrate is conventionally known. However, since the resistance of the spiral metal wiring is high, the Q value of the spiral inductor decreases. End up.

  Therefore, in order to increase the inductance and improve the Q value, a spiral shape in which the line width of the metal wiring located on the inner side is narrower than the line width of the metal wiring located on the outer side in the state where the intervals of the metal wirings are made equal. Inductors have been proposed (see Patent Document 1).

  In order to suppress the decrease in self-resonance frequency and improve the Q value, a spiral inductor has been proposed in which the spacing between the metal wirings located inside the spiral is narrower than the spacing between the metal wirings located outside the spiral. (See Patent Document 2).

JP 2002-134319 A JP 2005-32976 A

  In Patent Document 1, the line width of the spiral metal wiring is narrower on the inner side and wider toward the outer side. That is, the function of the width of the metal wiring with the number of turns of the metal wiring as a variable is a function that monotonously increases from the inner periphery to the outer periphery of the metal wiring. The inventor of the present invention has found a function of the line width of the metal wiring such that the Q value is higher than the monotonically increasing function disclosed in Patent Document 1.

  An object of the present invention is to provide a spiral inductor having a high Q value.

  A feature of the present invention is a spiral inductor having a flat insulating substrate and a conductor wire having a spiral shape disposed on the main surface of the insulating substrate, the conductor wire having a variable number of turns of the conductor wire. The width function is a V-shaped function or a U-shaped function.

  When the spacing between conductor wires (gap between wires) is constant and the outer diameters of the conductor wires are the same, the parasitic capacitance of the spiral inductor is the conductor wire and lead-out at the number of turns excluding the innermost and outermost circumferences of the conductor wire. The capacitance between the lines becomes dominant. When comparing a U-shaped function or V-shaped function spiral inductor with a spiral inductor having a constant line width, the U-shaped function or V-shaped function spiral inductor has a wider line width at the innermost circumference and outermost circumference. Even if the sum of the line widths is the same for both, as a result, the line width of the conductor line crossed by the lead line decreases. Therefore, when the ratio of the innermost circumference and the outermost circumference in the total line width is large, the parasitic capacitance decreases. If the parasitic capacitance is reduced, the self-resonant frequency is lowered and the Q value of the spiral inductor is improved.

  In the characteristics of the present invention, the function of the line width of the conductor wire may be a function that takes a minimum value in the number of turns excluding the outermost circumference and the innermost circumference of the conductor line. The function of the line width of the conductor wire is a V-shaped function when the number of turns having a minimum value is one, and a U-shaped function when the number of turns having a minimum value is two or more. The minimum value of the function may be the minimum value of the function at the same time.

  In the feature of the present invention, the line width function of the conductor wire may be a function that takes a minimum value in the number of turns near the center. Here, “the number of windings near the center” is, for example, in the range of 4 to 6 windings when the total number of windings is 9.

  According to the spiral inductor of the present invention, the self-resonant frequency can be lowered and the Q value can be improved.

It is a top view which shows the planar shape of the spiral inductor 1 concerning embodiment of this invention. It is a top view which shows the planar shape of the spiral inductor 2 in connection with a 1st comparative example. It is a top view which shows the planar shape of the spiral inductor 3 in connection with the 2nd comparative example. It is a graph which shows the function of the line | wire width of the conductor wire 11a which makes the number of turns Tu1-Tu9 of the conductor wire 11a of FIGS. 1-3 a variable. It is a graph which shows the simulation result (inductance L) of spiral inductors 1-3. 5 is a graph showing a ratio of a Q value of a spiral inductor 1 to a spiral inductor 2 and a ratio of a Q value of the spiral inductor 3 to the spiral inductor 2; It is a graph which shows the function of the line | wire width of the conductor wire 11a which makes the winding number Tu1-Tu9 of the conductor wire 11a a variable about the spiral inductors H1-H6 and H9 concerning the 2nd calculation example. It is a graph which shows the simulation result (Q value) of spiral inductors H1, H2, H4-H6, and H9 performed about the line | wire width shown in FIG. It is a table | surface which shows the internal diameter Din, inductance Ltot, Q value, and the outer diameter Dout of the spiral inductors 1-3.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same parts are denoted by the same reference numerals.

  First, the planar shape of the spiral inductor 1 according to the embodiment of the present invention will be described with reference to FIG. The spiral inductor 1 according to the embodiment of the present invention includes a flat insulating substrate, a conductor wire 11a having a spiral shape disposed on the main surface of the insulating substrate, and the potential at the inner end of the conductor wire 11a outward. The lead wire 10 is led out, and a pad portion 11b connected to the lead wire 10 outside the conductor wire 11a.

  The total number of turns of the conductor wire 11a is 9, and when the number of turns is counted from the inside to the outside of the conductor wire 11a, the number of turns Tu1, Tu2, Tu3,... Tu7, Tu18, Tu9. The line width of the conductor wire 11a differs depending on the number of turns Tu1 to Tu9 of the conductor wire 11a. Specifically, the line width function of the conductor wire 11a with the number of turns Tu1 to Tu9 of the conductor wire 11a as a variable takes a minimum value or a minimum value in the number of turns Tu4 to Tu6 near the center. A function of the line width of the conductor line 11a with the number of turns Tu1 to Tu9 of the conductor line 11a as a variable will be described later with reference to FIG.

  The conductor wire 11a further has a shape approximating a square. Specifically, the “shape approximating a square” has a shape in which the outermost periphery of the conductor wire 11a has a shape in which line-segment elements P1, P2, and P3 having substantially the same length are connected in series, and the outermost periphery. A shape in which line-shaped elements are connected in series sequentially along the elements P1, P2, and P3 is shown. Line-shaped elements are connected at right angles.

The conductor wire 11a and the pad portion 11b are disposed on the main surface of the flat insulating substrate. The insulating substrate includes, for example, a semiconductor substrate made of single crystal silicon and an insulating film made of a silicon oxide film (SiO ₂ ) or a silicon nitride film (Si ₃ O ₄ ) disposed on the semiconductor substrate. The conductor line 11a and the pad portion 11b are disposed on the insulating film. A protective film made of a laminated film such as a silicon oxide film or a silicon nitride film is further disposed on the conductor wire 11a and the pad portion 11b. The conductor line 11a and the pad portion 11b are made of a conductor including a semiconductor to which a metal such as aluminum or copper or a high-concentration impurity is added, for example.

  The insulating film includes a first insulating layer disposed on the semiconductor substrate and a second insulating layer disposed on the first layer, and includes a first insulating layer and a second insulating layer. A lead wire 10 is disposed between them. In FIG. 1, one end of the lead wire 10 is overlapped with the inner end of the conductor wire 11a. A contact plug 14b penetrating the second insulating layer is disposed in the overlapped portion, and the contact plug 14b electrically connects one end of the lead wire 10 and the inner end portion of the conductor wire 11a. .

  The pad portion 11b is disposed adjacent to the outer end portion of the conductor wire 11a. In FIG. 1, the other end of the lead wire 10 is overlapped with the pad portion 11b. A contact plug 14a penetrating the second insulating layer is disposed in the overlapped portion, and the contact plug 14a electrically connects the other end of the lead wire 10 and the pad portion 11b. In FIG. 1, the lead wire 10 intersects the conductor wire 11a substantially perpendicularly in all the winding numbers Tu1 to Tu9 of the conductor wire 11a.

  The spiral inductor 1 shown in FIG. 1 can be manufactured using a known semiconductor manufacturing technique. For example, semiconductors described in JN Burghartz, M. Soyuer, and KA Jenkins, “Integrated RF and Microwave Components in BiCMOS Technology,” IEEE Trans. Electron Devices, vol. 43, no. 9, pp. 1559-1570. It can be manufactured using manufacturing techniques. A specific example of the manufacturing method of the spiral inductor is shown below.

  First, a semiconductor substrate such as a silicon substrate is prepared, and a first insulating layer made of a silicon oxide film is stacked on the semiconductor substrate by a chemical vapor deposition method (CVD method). A metal film of an alloy of aluminum and copper (AlCu) is deposited on the first insulating layer by sputtering. A resist pattern corresponding to the planar shape of the lead line 10 is formed by photolithography, and the metal film is selectively etched using an anisotropic etching method such as reactive ion etching (RIE) using the resist pattern as a mask. Thus, the lead line 10 is formed. Then, a second insulating layer is formed on the lead line 10 using the CVD method.

  An opening is formed in the second insulating layer at a position corresponding to the contact plugs 14a and 14b by using a photolithography method, an anisotropic etching method such as RIE, and the like, and a conductive material such as AlCu is formed in the opening. The body is embedded to form contact plugs 14a and 14b.

  Then, an AlCu metal film is deposited on the second insulating layer and the contact plugs 14a and 14b by sputtering. A resist pattern corresponding to the planar shape of the conductor line 11a and the pad portion 11b is formed by photolithography, and the metal film is selectively etched by anisotropic etching such as RIE using the resist pattern as a mask. A line 11a and a pad portion 11b are formed. Then, a protective film is formed on the conductor wire 11a and the pad portion 11b by using the CVD method. Through the above semiconductor manufacturing process, the spiral inductor 1 shown in FIG. 1 is completed.

  With reference to FIG. 2, the planar shape of the spiral inductor 2 according to the first comparative example will be described. Unlike the spiral inductor 1, the spiral inductor 2 has a constant line width regardless of the number of turns Tu1 to Tu9. The other configuration of the spiral inductor 2 is the same as that of the spiral inductor 1, and a description thereof will be omitted.

  With reference to FIG. 3, the planar shape of the spiral inductor 3 according to the second comparative example will be described. Similar to the spiral inductor 1, the spiral inductor 3 differs in the line width of the conductor wire 11a depending on the number of turns Tu1 to Tu9. However, in the spiral inductor 3, the function of the line width of the conductor wire 11a with the number of turns Tu1 to Tu9 of the conductor wire 11a as a variable is from the inner periphery to the outer periphery of the conductor wire 11a, that is, from the turn number Tu1. The function increases monotonously toward Tu9. That is, the spiral inductor 3 corresponds to the spiral inductor disclosed in Patent Document 1. The other configuration of the spiral inductor 3 is the same as that of the spiral inductor 1, and a description thereof will be omitted.

  With reference to FIG. 4, a function of the line width of the conductor wire 11a with the number of turns Tu1 to Tu9 of the conductor wire 11a as variables is described for the spiral inductors 1 to 3 of FIGS. The vertical axis represents the line width of the conductor wire 11a, and the horizontal axis represents the number of turns Tu1 to Tu9. The function of the line width of the conductor wire 11a in the spiral inductor 1 takes a minimum value (9 μm) in the number of turns near the center. Here, the “number of turns near the center” is, for example, in the range of the number of turns Tu4 to the number of turns Tu6 when the total number of turns is nine. The number of minimum values is two or more (three in FIG. 4). In this case, the function of the line width of the conductor wire 11a is a “U-shaped function”. The “minimum value” is also the minimum value of the function at the same time, and the line width at the number of turns Tu1 to Tu3 and Tu7 to Tu9 is wider than the line width at the number of turns Tu4 to Tu6. The line width decreases monotonously at the number of turns Tu1 to Tu4, and the line width increases monotonically at the number of turns Tu6 to Tu9.

  Note that the number of local minimum values may be only one. In this case, the function of the line width of the conductor wire 11a is a “V-shaped function”. Moreover, although the case where the function of the line width of the conductor wire 11a in the spiral inductor 1 has a minimum value in the number of turns Tu4 to Tu6 near the center is shown, it is not limited to this. The function of the line width of the conductor wire 11a in the spiral inductor 1 is a “U-shaped function” or “V-shaped function” that takes a minimum value in the number of turns Tu2 to Tu8 excluding the outermost circumference Tu9 and the innermost circumference Tu1. I just need it. Furthermore, the “minimum value” may not be the minimum value.

  On the other hand, the function of the line width of the conductor line 11a in the spiral inductor 2 is a function in which the line width of the conductor line 11a takes a constant value (10 μm) regardless of the number of turns Tu1 to Tu9. Moreover, the function of the line width of the conductor wire 11a in the spiral inductor 3 is a function that monotonously increases from the number of turns Tu1 toward the number of turns Tu9.

  The spiral inductors 1 to 3 shown in FIGS. 1 to 3 are designed so that the outer diameter Dout (284 μm) and the inductance L (18.5 nH) at a specific frequency (429 MHz) are equal.

Specifically, the inner diameters Din of the spiral inductors 1 to 3 shown in FIGS. 1 to 3 are 93 μm, 97 μm, and 101 μm, respectively. The spiral inductors 1 to 3 shown in FIGS. 1 to 3 commonly have an outer diameter Dout of 284 μm, a gap between the conductor wires 11a of 1 μm, and a thickness of the conductor wire 11a of 0.57 μm. The first insulating layer, the second insulating layer, and the protective film are all made of a silicon oxide film, and the thickness of each of the first insulating layer, the second insulating layer, and the protective film is 5. It is 35 micrometers, 1.42 micrometers, and 2.84 micrometers.
(First calculation example)

  The result of the simulation performed on the spiral inductors 1 to 3 will be described. FIG. 5 is a graph showing a simulation result (inductance L) of the spiral inductors 1 to 3. The vertical axis is inductance (nL), and the horizontal axis is frequency (GHz). In the frequency band up to ˜1.5 GHz, the inductances L of the spiral inductors 1 to 3 are almost equal.

  FIG. 6 is a graph showing the ratio of the Q value of the spiral inductor 1 to the spiral inductor 2 and the ratio of the Q value of the spiral inductor 3 to the spiral inductor 2. The vertical axis is the Q value ratio, and the horizontal axis is the frequency (GHz). Since FIG. 1 / FIG. 2 is larger than FIG. 3 / FIG. 2 in the low frequency band, it can be seen that the Q value of the spiral inductor 1 is larger than that of the spiral inductor 3. 1 and 2 is larger than 1.00 in the low frequency band, it can be seen that the Q value of the spiral inductor 1 is larger than that of the spiral inductor 2.

  Further, the total line width of the conductor line 11a overlapping the lead wire 10 was 70 μm for the spiral inductor 2 of FIG. 2 and 69 μm for the spiral inductor 1 of FIG.

The inner diameter Din, inductance Ltot, Q value, and outer diameter Dout of the spiral inductors 1 to 3 are summarized in the table of FIG. It can be seen that the Q value of the spiral inductor 1 is the largest.
(Second calculation example)

  A simulation result of spiral inductors H1 to H6 and H9 performed for the line width shown in FIG. 7 instead of the line width shown in FIG. 4 will be described. The configuration of the spiral inductors H1 to H6 and H9 is the same as that of the spiral inductor 1 shown in FIG. 1 except for the function of the line width of the conductor wire 11a with the number of turns Tu1 to Tu9 as a variable, and illustration and description thereof are omitted. To do.

  FIG. 7 is a graph showing a function of the line width of the conductor wire 11a with the number of turns Tu1 to Tu9 of the conductor wire 11a as variables for the spiral inductors H1 to H6 and H9. The function of the line width of the spiral inductor H6 is a V-shaped function that takes a minimum value (6 μm) at the number of turns Tu5 that is the number of turns at the center. The function of the line width of the spiral inductor H1 is a V-shaped function that takes a minimum value (8 μm) at the number of turns Tu5 that is the number of turns at the center. The function of the line width of the spiral inductor H3 is a U-shaped function that takes a minimum value (9 μm) in a plurality of turns Tu4 to Tu6 that are the number of turns near the center. The function of the line width of the spiral inductor H5 is a V-shaped function that takes the minimum value (9 μm) at the number of turns Tu5 that is the number of turns at the center. The function of the line width of the spiral inductor H4 is a function that monotonously increases from the number of turns Tu1 to the number of turns Tu9. The function of the line width of the spiral inductor H2 is a function that takes a constant value (10 μm) regardless of the number of turns Tu1 to Tu9. The function of the line width of the spiral inductor H9 is an “inverse V-shaped function” that takes a maximum value (12 μm) at the number of turns Tu5 that is the number of turns at the center.

  FIG. 8 is a graph showing simulation results (Q values) of the spiral inductors H1, H2, H4 to H6, and H9 performed for the line width shown in FIG. The horizontal axis indicates the outer diameter Dout of the conductor wire 11a, and the vertical axis indicates the Q value. The Q values of the spiral inductors H1, H5, and H6 whose line width functions are U-shaped functions or V-shaped functions are larger than those of the spiral inductors H2, H4, and H9 whose line width functions are not U-shaped functions or V-shaped functions. became.

  As described above, according to the embodiment of the present invention, the following effects can be obtained.

When the distance between the conductor wires 11a (the gap between the wires) is constant and the outer diameter Dout of the conductor wire 11a is equal, the parasitic capacitance Cp of the spiral inductor is the innermost circumference (the number of turns Tu1) and the outermost circumference (the number of turns). The electrostatic capacitance between the conductor wire 11a and the lead wire 10 becomes dominant at the number of turns Tu2 to Tu8 excluding Tu9). When the spiral inductor 1 having a U-shaped function and the spiral inductor 2 having a constant line width are compared, the spiral inductor 1 has a wider line width at the innermost circumference and the outermost circumference. However, as a result, the line width of the conductor line 11a crossed by the lead wire 10 is reduced. Therefore, when the ratio of the innermost circumference and the outermost circumference in the total line width is large, the parasitic capacitance Cp decreases. If the parasitic capacitance Cp is reduced, the self-resonant frequency is lowered and the Q value of the spiral inductor is improved. Therefore, according to the embodiment of the present invention, a spiral inductor having a low self-resonant frequency and a high Q value can be provided.
(Other embodiments)

  As mentioned above, although this invention was described by one embodiment and its modification, it should not be understood that the statement and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  Although the case where the conductor wire 11a has a shape that approximates a square has been described, the conductor wire 11a has a shape that approximates another polygon, for example, a quadrilateral other than a square, or three or more polygons. It doesn't matter.

  Although not shown in FIG. 1, the bend part which notched the corner | angular part of the outer side of the conductor wire 11a may be formed in the connection location of line-segment-shaped elements, respectively. Thereby, the reflection which generate | occur | produces in the corner | angular part outside the conductor wire 11a in the field | area of a high frequency can be suppressed, transmission efficiency can be improved and the resistance value of the conductor wire 11a can be lowered | hung. Therefore, the Q value of the spiral inductor can be improved.

  Although the case where the line width of the conductor line 11a is changed stepwise for each round is shown, the line width of the conductor line 11a may be changed for each of the elements P1 to P4 or continuously changed. May be.

  As an example of “a flat insulating substrate”, a configuration including a semiconductor substrate and an insulating film laminated thereon is shown. However, a flat insulating substrate has other configurations, for example, the entire substrate is made of glass or the like. It may be a glass substrate or a printed wiring board.

  The spiral inductor has been described as having one conductor wire 11a, but the number of conductor wires may be two or more. In this case, the spiral inductor includes a plurality of conductor lines having substantially the same spiral shape formed in each of the plurality of wiring layers, an insulating film disposed between the plurality of conductor lines, and penetrating the insulating film. And a plurality of vias connecting in parallel between two conductor lines adjacent in the stacking direction. As a result, the resistance of the conductor wire can be reduced and the Q value can be improved without increasing the area occupied by the spiral inductor.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters according to the scope of claims reasonable from this disclosure.

1-3, H1-H6, H9 Spiral inductor 10 Lead wire 11a Conductor wire 11b Pad portion 14a, 14b Contact plug Cp Parasitic capacitance Din Inner diameter Dout Outer diameter L Inductance P1-P3 Line segment element Tu1-Tu9 Number of turns Tu1 Maximum Inner circumference Tu9 outermost circumference

Claims (3)

  A spiral inductor having a flat insulating substrate and a conductor wire having a spiral shape disposed on the main surface of the insulating substrate, the function of the line width of the conductor wire having the number of turns of the conductor wire as a variable Is a spiral inductor characterized by being a V-shaped function or a U-shaped function.   2. The spiral inductor according to claim 1, wherein the function of the line width of the conductor wire takes a minimum value in the number of turns excluding the outermost circumference and the innermost circumference of the conductor line.   The spiral inductor according to claim 2, wherein the function of the line width takes a minimum value in the number of turns near the center.

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