JP2005236064A - Signal transmission pair wiring and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in a conventional signal transmission line using a single line, characteristics depending on the shape of a line are not good, and especially when vias intervene in a longitudinal direction, a high frequency characteristic deteriorates depending on a frequency. <P>SOLUTION: In signal transmission pair wiring wherein its multilayers are connected with vias and a plurality of patternized metal layers and a dielectric layer are laminated, the signal transmission wiring with a good transmission characteristic which does not contain a characteristics error till tens of GHz high frequency region is obtained by controlling the diameter and the gap of the via which connect a plurality of wiring where the metal layers are patternized, and by using the signal transmission pair wiring characterized by arranging so that characteristic impedance may serve as a fixed value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a signal transmission wiring structure of a high-density mounting substrate for mounting an ultrahigh frequency signal processing IC of several tens of GHz band.

  FIG. 8 shows an example of a wiring structure in a conventional multilayer substrate. The wiring is formed of a metal film wiring formed on the surface, a metal film wiring sandwiched between dielectrics, a vertical via that connects both wirings, and a via pad portion that connects the metal film wiring and the via. . Conventional wiring is single-ended transmission in which the signal level is determined with respect to the ground. The metal film wiring is configured such that the characteristic impedance of both the wiring formed on the surface and the wiring sandwiched between the dielectrics has a certain value (usually 50Ω). Since there is no impedance control method, the vertical via structure is usually formed based on the rules of the manufacturing process. Further, the via pad portion needs to be formed to be about twice as large as the diameter of the vertical via in order to guarantee the connectivity.

  However, in the conventional signal transmission line using a single line, the characteristic depending on the shape of the line is not good, and particularly when a vertical via is interposed, there is a problem that the high frequency characteristic deteriorates depending on the frequency. there were.

  In order to solve this problem, in the present invention, as a means according to claim 1, the signal transmission line has a pair wiring structure in which two wires are paired, and each characteristic in the pair wiring transmission line and the vertical via The via diameter and via interval were controlled so that the impedance was a constant value.

  The means according to claim 2 is characterized in that, in addition to the means of claim 1, the via pad is formed to have the same size as the cross-sectional area of the via or a size of 125% or less of the cross-sectional area.

  The means according to claim 3 is characterized in that, in addition to the means of claim 1, the distance between the pair wirings of the metal layer and the distance between the pair wirings of the via are formed to be equal.

  The means according to claim 4 is characterized in that, in addition to the means of claim 1, the means according to claims 2 and 3 are used simultaneously to form a signal transmission pair wiring.

  As means according to claim 5, as means for realizing 1, 2, 3 and 4, grooves and / or holes are formed in the substrate, and a metal film is formed on the substrate surface including the grooves and / or holes. Then, the manufacturing method of forming a wiring pattern and / or a via by flattening the surface by mechanical polishing is used in part.

  A pair wiring structure with the same characteristic impedance for each of the transmission line on the substrate and the vertical via enables the formation of a transmission line that does not deteriorate in frequency-dependent characteristics even at high frequencies of several tens of GHz. Become.

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

(Embodiment 1)
FIG. 1 shows a top view and a cross-sectional view of a signal transmission pair wiring according to claim 1. The pair structure of the metal thin film wiring on the surface is controlled so that the characteristic impedance becomes Z0 (for example, 100Ω) by controlling the width and interval of the lines. The pair structure of metal thin film wirings sandwiched between dielectrics controls the characteristic impedance to be Z0 by controlling the width and interval of the lines. The vertical via wiring is controlled so that the characteristic impedance becomes Z0 by controlling the via diameter and interval.

  FIG. 2 shows a simulation result for determining the relationship between the ratio of the via diameter and the via interval and the impedance of the line. For example, it is possible to control the impedance to 100Ω by forming vias at intervals of 200 μm in a via diameter of 100 μm.

(Embodiment 2)
FIG. 3 shows a top view and a cross-sectional view of a signal transmission pair wiring according to claim 2. In addition to the structure shown in FIG. 1, the via pad part connecting the wiring and the via is formed with the size equal to or smaller than 125% of the size of the vertical via wiring, thereby eliminating noise caused by reflection from the via pad part in the middle of the via. Thus, a transmission line with better signal transmission characteristics can be formed.

(Embodiment 3)
FIG. 4 shows a top view and a cross-sectional view of the signal transmission pair wiring according to claim 3. In addition to the structure of FIG. 1, this is realized by making the interval between the pair wiring formed with the metal layer and the pair wiring formed with the via constant.

(Embodiment 4)
FIG. 5 shows a top view and a cross-sectional view of a signal transmission pair wiring according to claim 4. In addition to the structure shown in FIG. 1, a via pad portion for connecting a wiring and a via is formed in a size equal to or smaller than 125% of the size of a vertical via wiring, and the metal having a vertical via diameter sandwiched between dielectrics. This is achieved by designing to the same thickness as the width of the membrane wiring.

(Embodiment 5)
FIG. 6 is a diagram comparing the signal transmission characteristic when the signal transmission pair wiring according to claim 5 is used and the signal transmission characteristic of the conventional structure by simulation. The transmission characteristics of a pair wiring including a via structure when a 9-layer multilayer substrate is used is shown. Reference numeral 601 denotes transmission characteristics according to the present invention, and reference numeral 602 denotes transmission characteristics according to the prior art. By using the structure of claim 5 of the present invention, it was possible to expand the transmittable frequency band from 35 GHz to 90 GHz when the allowable attenuation was −0.1 dB / mm.

(Embodiment 6)
FIG. 7 is an example of a method for forming a wiring structure according to claim 5. A damascene process used to realize a multilayer wiring structure in a semiconductor process is used. The damascene process in claim 5 is one of metal wiring forming methods, in which a groove is first formed on a substrate, a metal is deposited thereon, and then the surface is flattened by mechanical polishing to form a pattern. . First, a pattern is formed on the core circuit of (1) as shown in (2). Dielectrics are stacked as in (3), and vias and wiring patterns are simultaneously formed on the dielectric as in (4). Next, wiring metal is deposited by plating or the like as in (5), and unnecessary metal wiring 706 is removed as in (6) using physical polishing or the like to form wiring. Next, a multilayer wiring board is formed by repeating the steps (7), (8), and (9) again. By simultaneously forming the via and the wiring pattern on the dielectric, it is possible to create the structure shown in claims 1, 2, 3, and 4.

  As described above, according to the present invention, it is possible to provide a signal transmission wiring having a good transmission characteristic with no characteristic error up to a high frequency region of several tens of GHz.

Top view and sectional view of signal transmission pair wiring according to claim 1 of the present invention Simulation results showing the relationship between the via diameter and via spacing ratio and the characteristic impedance of the vertical via wiring Top view and sectional view of signal transmission pair wiring according to claim 2 of the present invention Top view and sectional view of signal transmission pair wiring according to claim 3 of the present invention Top view and sectional view of signal transmission pair wiring according to claim 4 of the present invention Comparison diagram of transmission characteristics when using the conventional wiring structure and the structure of claim 4 according to the present invention Explanatory drawing of the pair wiring structure preparation process which concerns on Claim 5 A top view and a cross-sectional view of a conventional typical signal transmission wiring in the background art

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Metal layer wiring of surface layer 102 Metal layer wiring pinched | interposed between dielectrics 103 Via pad part which connects wiring and a via 104 Longitudinal via wiring 105 Dielectric layer 601 Graph of transmission characteristic by this invention 602 Wiring using conventional technology Transmission characteristic graph 701 Metal wiring layer 702 Dielectric layer 703 Wiring groove 704 Via hole 705 Via wiring 706 Unnecessary metal layer

Claims (5)

In a signal transmission pair wiring of a multilayer substrate in which a plurality of patterned metal layers and dielectric layers are stacked and the layers are connected by vias,
A signal transmission pair wiring characterized by controlling the diameter of vias and the interval between vias interconnecting a plurality of wirings patterned on a metal layer so that the characteristic impedance becomes a constant value. 2. The signal transmission pair wiring according to claim 1, wherein a contact area at a connection portion between the wiring pattern and the via is formed to be equal to or smaller than 125% of the via cross-sectional area. 2. The signal transmission pair wiring according to claim 1, wherein the pair of wirings in the planar direction patterned on the metal layer and the pair wiring by the vertical via are formed so as to have a constant interval. 4. The signal transmission pair wiring according to claim 1, which has the characteristics of claim 2 and claim 3 at the same time. Grooves and / or holes are formed in the substrate, a metal film is formed on the substrate surface including the grooves and / or holes, and then the surface is flattened by mechanical polishing to form wiring patterns and / or vias. The method for manufacturing a signal transmission pair wiring according to claim 1, further comprising a manufacturing process.

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