JP2016171170A - Signal propagation structure in integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow for propagation of a high frequency AC signal between a transmission line and a circuit element in an integrated circuit through an interlayer via, while compensating for the inductance of the interlayer via.SOLUTION: A plurality of dielectric layers 4 are laminated between a first metal layer 1 and a second metal layer 2. A land 5 is provided between one dielectric layer 4 and another dielectric layer. Furthermore, an interlayer via 6 penetrating the dielectric layer 4 and being connected with the land 5 is provided. In a signal propagation structure 10 within an integrated circuit, the interlayer via 6 does not exist in at least one dielectric layer 4. In the drawing, the interlayer via 6 does not exist in the lowermost dielectric layer 4 of the signal propagation structure 10 within an integrated circuit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique capable of propagating a high-frequency AC signal through an interlayer via between a transmission line and a circuit element in an integrated circuit and compensating for the inductance of the interlayer via.

  In general, in an integrated circuit process using a high-frequency signal, a metal thick film suitable for a high-frequency signal with low loss exists in the uppermost layer of the integrated circuit, and a circuit element such as a transistor (active element) exists in the lowermost layer of the integrated circuit. To do.

  FIG. 10 shows an equivalent circuit of a portion connecting the uppermost layer and the lowermost layer of the integrated circuit.

  The thick metal film constituting the transmission line of the circuit 100 shown in FIG. 10 exists in the uppermost layer of the integrated circuit, and the transistor 200 exists in the lowermost layer.

  In order to transmit a high-frequency signal from the transmission line of the circuit 100 existing in the uppermost layer to the lowermost transistor 200 or vice versa, the transmission line and the transistor 200 are electrically connected by a plurality of interlayer vias (non- Patent Document 2). FIG. 10 shows an inductance L as an equivalent circuit of the interlayer via.

  FIG. 11A is a partial cross-sectional view of the signal propagation structure configured in the conventional integrated circuit as described above, and FIG. 11B is a top view of the signal propagation structure shown in FIG. It is.

  The first metal layer 1 constitutes a transmission line in the circuit 100 shown in FIG. 10, and the second metal layer 2 is connected to the circuit element 3 in the integrated circuit such as the transistor 200 shown in FIG.

  A plurality of dielectric layers 4 are stacked between the first metal layer 1 and the second metal layer 2. In the figure, the dielectric layer 4 has four layers.

  A land 5 is provided between one dielectric layer 4 and another dielectric layer. In addition, an interlayer via 6 penetrating the dielectric layer 4 and connected to the land 5 is provided.

  The interlayer via 6 is a lumped constant type element whose electrical length is negligible, and the frequency response is assumed to be flat up to an infinite frequency.

  Generally, in the microwave band, the mutual inductance of the interlayer via 6 is ignored. Therefore, the interlayer via 6 did not affect the circuit performance and was not considered in the design.

  However, in the high frequency band, for example, the millimeter wave band, the mutual inductance of the interlayer via 6 starts to affect the circuit.

  That is, when the frequency is increased and the millimeter wave or terahertz wave region is entered, the effective wavelength of the high-frequency signal in the integrated circuit becomes approximately the same as the physical length of the interlayer via 6, and the above assumption does not hold.

  For example, the inductance of the interlayer via 6 causes an impedance mismatch and a large reflection loss occurs. Also, such reflection loss due to impedance mismatch results in a decrease in overall performance such as gain and frequency stability.

  Therefore, the inductance of the interlayer via 6 cannot be ignored, and design considerations are indispensable (Non-Patent Document 2).

C.K.Liang et al., JSSC vol 44, no. 2, 2009 C. H. Doan et al., JSSC vol. 40, no. 1, 2005

  The present invention has been made in view of the above problems, and provides a technique capable of propagating a high-frequency AC signal via an interlayer via between a transmission line and a circuit element in an integrated circuit and compensating for the inductance of the interlayer via. For the purpose.

  In order to solve the above-described problems, the signal propagation structure in an integrated circuit according to the present invention includes a first metal layer constituting a transmission line in the integrated circuit and a second metal layer connected to a circuit element in the integrated circuit. A plurality of dielectric layers stacked in between, a land provided between one dielectric layer and another dielectric layer, and an interlayer via penetrating the dielectric layer and connected to the land A signal propagation structure in an integrated circuit that propagates an AC signal between the first metal layer and the second metal layer via the interlayer via and the land, wherein the interlayer via is provided in at least one of the dielectric layers. It does not exist.

  For example, the interlayer via does not exist in the dielectric layer stacked on one side of one or more dielectric layers where the interlayer via exists, and is stacked on the other side of the one or more dielectric layers. The interlayer via does not exist in the dielectric layer.

  For example, a land connected to one side of the dielectric layer where the interlayer via does not exist, or a via connected to the first metal layer or the second metal layer disposed on the one side The first metal layer or the second metal layer disposed on the other side or the land between the dielectric layer connected to the via and the dielectric layer laminated on the other side of the dielectric layer where the interlayer via does not exist On the other hand, a land that is opposed to a part of the dielectric layer in which the interlayer via does not exist is provided.

  For example, the part of the dielectric layer where the interlayer via does not exist is formed of a material different from the other part of the dielectric layer.

  According to the signal propagation structure in an integrated circuit of the present invention, since there is no interlayer via in at least one dielectric layer, a capacitance is formed in a place where the interlayer via does not exist, and between the transmission line and the circuit element in the integrated circuit. A high-frequency AC signal can be propagated through the interlayer via, and the inductance of the interlayer via can be compensated by the capacitance.

FIG. 1 is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to the present embodiment. 2A is a partial cross-sectional view of another signal propagation structure in an integrated circuit in which the interlayer via 6 is not present in the lowermost dielectric layer 4, and FIG. 2B is a cross-sectional view of FIG. It is a top view of the signal propagation | transmission structure in an integrated circuit shown. FIG. 3A is a partial cross-sectional view of another integrated circuit signal propagation structure in which the interlayer via 6 does not exist in the lowermost dielectric layer 4, and FIG. 3B is a cross-sectional view of FIG. FIG. 3C is a diagram showing a relationship between the frequency and the return loss value for the circuit shown in FIG. 3B and the comparative example. FIG. 4 is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a first modification. FIG. 5A is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a second modification, and FIG. 5B is an integration shown in FIG. It is a top view of the in-circuit signal propagation structure. FIG. 6 is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a third modification. FIG. 7A is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a fourth modification, and FIG. 7B is an integration shown in FIG. It is a top view of the in-circuit signal propagation structure. FIG. 8 is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a fifth modification. FIG. 9A is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a sixth modification, and FIG. 9B is an integration shown in FIG. It is a top view of the in-circuit signal propagation structure. The equivalent circuit of the part which connects the uppermost layer and lowermost layer of an integrated circuit is shown. 1 shows a signal propagation structure configured in a conventional integrated circuit.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to the present embodiment.

  The first metal layer 1 constitutes a transmission line in the integrated circuit, and the second metal layer 2 is connected to the circuit element 3 in the integrated circuit. The circuit element 3 is, for example, a heterojunction bipolar transistor (HBT). For example, the circuit element 3 is configured on a substrate 30 and includes a thin film transistor 31.

  A plurality of dielectric layers 4 are stacked between the first metal layer 1 and the second metal layer 2. In the figure, the dielectric layer 4 has four layers.

  A land 5 is provided between one dielectric layer 4 and another dielectric layer. In addition, an interlayer via 6 penetrating the dielectric layer 4 and connected to the land 5 is provided.

  That is, between the first metal layer 1 and the second metal layer 2, a signal propagation structure 10 in an integrated circuit that propagates an AC signal through the interlayer via 6 and the land 5 is provided.

  In the integrated circuit signal propagation structure 10, the interlayer via 6 does not exist in at least one dielectric layer 4. In the figure, the interlayer via 6 does not exist in the lowermost dielectric layer 4 of the signal propagation structure 10 in the integrated circuit.

  2A is a partial cross-sectional view of another signal propagation structure in an integrated circuit in which the interlayer via 6 does not exist in the lowermost dielectric layer 4 like the signal propagation structure 10 in the integrated circuit of FIG. FIG. 2B is a top view of the signal propagation structure in the integrated circuit shown in FIG.

  The capacitance of the portion 8 where the interlayer via 6 does not exist depends on the area of the region where the lowest land 5 and the second metal layer 2 overlap (shaded portion in FIG. 2B).

  Here, a simple example of a calculation method for determining the area will be shown.

  Assume that the distance h between the lowest land 5 and the second metal layer 2 is 6 μm, and the diameter of the interlayer via 5 is 1 μm.

  In this case, the total inductance due to the interlayer via 5 is about 80 pH, and at 300 GHz, the reactance is about 150Ω. In order to compensate for this inductance, the area A is calculated by the following equation (1).

A = h / {(2πf) ² Lε} (1)
Here, f, L, ε, and h are the operating frequency, the total inductance due to the interlayer via 5, the dielectric constant of the dielectric layer 4 in the overlapping region, and the distance between the lowest land 5 and the second metal layer 2, respectively. It is.

Substituting ε = 4 and h = 1 μm, equation (1) becomes about 100 μm ^2. For example, the hatched portion may be a square of 10 μm × 10 μm.

  FIG. 3A is a partial cross-sectional view of another integrated circuit signal propagation structure in which the interlayer via 6 does not exist in the lowermost dielectric layer 4, and FIG. 3B is a cross-sectional view of FIG. FIG. 3C is a diagram showing a relationship between the frequency and the return loss value for the circuit shown in FIG. 3B and the comparative example.

The equivalent circuit of the signal propagation structure in the integrated circuit shown in FIG. 3A has a resistance of the first metal layer 1 between the first metal layer 1 and the second metal layer 2 as shown in FIG. The component R ₁ , the inductance L due to the interlayer via 6 and the land 5, the capacitance C of the portion 8 where the interlayer via 6 does not exist, and the resistance component R ₂ of the second metal layer ₂ are directly connected.

Symbol S _{0 in} FIG. 3C indicates the relationship between the frequency and the return loss value when an interlayer via is provided in a location where the interlayer via 6 does not exist, and symbol S ₁ indicates the circuit shown in FIG. The relationship between the frequency and the return loss value is shown.

  Since the reactance at a high frequency of the inductance L due to the interlayer via 6 and the land 5 is compensated by the capacitance C of the portion 8 where the interlayer via 6 does not exist, the return loss value is improved at the target frequency of 300 GHz. .

  FIG. 4 is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a first modification.

  In the signal propagation structure in the integrated circuit of FIG. 2, the interlayer via 6 is not present in the lowermost dielectric layer 4, but the position of the dielectric layer 4 where the interlayer via 6 is not present is arbitrary, and is the second from the bottom. There may be no interlayer via 6 in the dielectric layer 4.

  FIG. 5A is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a second modification, and FIG. 5B is an integration shown in FIG. It is a top view of the in-circuit signal propagation structure.

  In the signal propagation structure in the integrated circuit of FIG. 2, the interlayer vias 6 of each dielectric layer 4 are arranged in a straight line, but may be arranged in a staircase pattern as shown in FIG. 5.

  FIG. 6 is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a third modification.

  In the above description, the capacitance C where the interlayer via 6 does not exist depends on the area of the expression (1). However, when the area cannot be adjusted, for example, two dielectric layers 4 without the interlayer via 6 exist. You may provide above.

  For example, the dielectric layer 4 laminated on one side of the dielectric layer 4 where the interlayer via 6 exists does not have an interlayer via, and the dielectric is laminated on the other side of the dielectric layer 4 where the interlayer via 6 exists. There are no interlayer vias in layer 4. A structure in which a plurality of dielectric layers 4 (dielectric layers 4 with interlayer vias 6) are sandwiched between dielectric layers 4 without interlayer vias 6 may be adopted.

  As a result, the capacitance C is connected in series, and the value of the capacitance C can be reduced. That is, the degree of freedom in compensating for the inductance of the interlayer via 6 and the land 5 can be increased.

  FIG. 7A is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a fourth modification, and FIG. 7B is an integration shown in FIG. It is a top view of the in-circuit signal propagation structure.

  In FIG. 2, the land 5 where the interlayer via 6 does not exist and the portion where the second metal layer 2 overlaps (the hatched portion in FIG. 2B) is slightly larger than the interlayer via 6. However, by enlarging the land 5 of the portion 8 where the interlayer via 6 does not exist, as shown by the shaded portion in FIG. 7B, the shaded portion can be enlarged and the capacitance value can be increased.

  Therefore, the degree of freedom in compensating the inductance of the interlayer via 6 and the land 5 can be increased.

  FIG. 8 is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a fifth modification.

  As shown in the drawing, a via 6A is connected to a land 5 between a dielectric layer 4 (lowermost layer) where no interlayer via 6 exists and a dielectric layer 4 laminated on one side (upper side) thereof. The via 6A does not penetrate the dielectric layer 4 and is referred to as an interlayer via.

  Further, the dielectric layer 4 (lowermost layer) which is connected to the via 6A and has no interlayer vias with respect to the second metal layer 2 disposed on the other side of the dielectric layer 4 (lowermost layer) where the interlayer via 6 does not exist. Land 5A opposes through a part (reference numeral 4A). The portion 4A is formed of a material different from other portions of the dielectric layer 4 (lowermost layer) where the interlayer via 6 is not present.

  Since the value of the capacitance C depends on this material, it can be different from the values in the other examples. Therefore, the degree of freedom in compensating the inductance of the interlayer via 6 and the land 5 can be increased.

  The via 6A may be provided on the second metal layer 2 side, and the portion 4A may be provided on the upper dielectric layer 4 side. That is, the via 6A and the reference numeral 4A may be reversely arranged.

  The dielectric layer 4 having such a structure (dielectric layer 4 in which the interlayer via 6 does not exist and the via 6A and the portion 4A exist) may be another dielectric layer 4 other than the lowermost layer. .

  Further, the portion 4A may be formed of the same material as the other dielectric layer portions. Even if it is made of the same material as other parts, the distance corresponding to h1 in FIG. 2 is different, so that the value of the capacitance C can be made different, and the freedom in compensating the inductance of the interlayer via 6 and the land 5 can be made. The degree can be increased.

  FIG. 9A is a partial cross-sectional view showing an example of an integrated circuit having a signal propagation structure in an integrated circuit according to a sixth modification, and FIG. 9B is an integration shown in FIG. It is a top view of the in-circuit signal propagation structure.

  In FIG. 9, the land denoted by reference numeral 5 (51) is integrated with the transmission line extending to the right in the figure, and the land denoted by reference numeral 5 (52) is integral with the transmission line extending above the figure. Thus, the land does not have to be a so-called island shape.

  As described above, according to the signal propagation structure in the integrated circuit of the present embodiment, since there is no interlayer via in at least one dielectric layer, the inductance due to the interlayer via is compensated by the capacitance at the location where the interlayer via does not exist. It is possible to reduce reflection loss due to impedance mismatch and improve overall performance such as gain and frequency stability.

DESCRIPTION OF SYMBOLS 1 1st metal layer 2 2nd metal layer 3 Circuit element 4 Dielectric layer 5 Land 6 Interlayer via 6A Via 10 Signal propagation structure in integrated circuit

Claims (4)

A plurality of dielectric layers stacked between a first metal layer constituting a transmission line in the integrated circuit and a second metal layer connected to a circuit element in the integrated circuit;
A land provided between one of the dielectric layers and another of the dielectric layers;
An interlayer via that penetrates the dielectric layer and is connected to the land,
In the signal propagation structure in an integrated circuit that propagates an AC signal between the first metal layer and the second metal layer through the interlayer via and the land,
The signal propagation structure in an integrated circuit, wherein the interlayer via does not exist in at least one of the dielectric layers. The interlayer via does not exist in the dielectric layer stacked on one side of one or more dielectric layers in which the interlayer via exists,
2. The signal propagation structure in an integrated circuit according to claim 1, wherein the interlayer via does not exist in the dielectric layer laminated on the other side of the one or more dielectric layers. A land between the dielectric layer laminated on one side of the dielectric layer where the interlayer via does not exist or a via connected to the first metal layer or the second metal layer disposed on the one side;
To the land between the dielectric layer connected to the via and the dielectric layer laminated on the other side of the dielectric layer where the interlayer via does not exist or to the first metal layer or the second metal layer disposed on the other side 3. The signal propagation structure in an integrated circuit according to claim 1, further comprising: a land facing through a part of the dielectric layer in which the interlayer via does not exist. The signal propagation structure in an integrated circuit according to claim 3, wherein the part of the dielectric layer where the interlayer via does not exist is formed of a material different from that of the other part of the dielectric layer.

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