JP2830653B2 - Multi-chip module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-chip module, and more particularly to a multi-chip module having excellent high-frequency characteristics such as skin effect and crosstalk.

[0002]

2. Description of the Related Art In a mounted circuit board such as a printed circuit board, noise problems such as signal delay time, signal reflection, and crosstalk have become important as the density and speed have increased. As one of these measures, a multi-chip module (hereinafter abbreviated as MCM), which is a technique for forming one module using a plurality of chips, has become important. In particular, micro-processing using a silicon substrate as a high-performance MCM,
A technique for forming a module has also been developed.For example, as shown in the following document, a technique for forming a microstrip line between a ground electrode and a signal line using a polyimide layer and matching characteristic impedance is used. Have been.

[0003] CT Bartlett et. a
l. "Multi-Chip Packaging D
design for VLSI-Based System
em "IEEE Proc. of 37th EC
C. (1987) pp. 518-525 In the prior art shown in the above-mentioned document, the LSI and the substrate are connected by flip-chip technology using solder bumps, so that noise reduction by lowering the inductance is expected.

[0004]

In the microstrip line used in the MCM using the above-mentioned conventional technology, a signal line using a thin film technology such as a gold wiring is formed on a ground layer via an interlayer film of polyimide or the like. It was the structure that was done. The MCMs using these prior arts have a slightly higher wiring resistance due to the use of a finely processed thin film technology, and have the following major problems particularly when mounting high-speed digital LSIs and analog LSIs. (1) As the signal speed increases, the skin effect becomes a problem. For example, for a thin film wiring having a thickness of 2 μm or less, 2 GHz
For the above signals, almost no current flows at the center of the wiring, and at higher frequencies, current flows only on the surface. For this reason, there is a big problem that the wiring resistance becomes higher at higher frequencies. (2) Crosstalk between wirings is increased, which is 2G
This is a serious problem in the mounting and wiring of an analog LSI of 100 Hz or more and a digital LSI of 100 MHz or more.

An object of the present invention is to provide a multi-chip module having a wiring structure in which the problems of high frequency characteristics such as resistance and crosstalk due to the skin effect are improved.

[0006]

In the MCM of the present invention, a means for providing a convex electrode portion on a signal wiring and arranging the convex electrode portion on a side facing a ground electrode is used.
As one specific example, a method of forming a signal line by forming a plurality of fine wirings and then forming a wide wiring is used.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view in a process order for explaining a structure and a manufacturing method of an embodiment of the present invention.

First, as shown in FIG.
M forms a ground electrode 102, a first polyimide layer 103, a second polyimide layer 104 on a silicon substrate 101, and then forms a first barrier metal layer 105.
Next, after forming a photoresist layer 106, a gold wiring layer 107 is formed by gold plating.

Next, as shown in FIG. 1B, after removing the photoresist layer 106, the MCM is formed by etching and removing the barrier metal layer 105 using the gold wiring layer 107 as a mask.

The surface of the bottom surface of the gold wiring layer 107 formed by the above method can be made about 1.5 times that of the prior art because the convex electrode portion is formed on the bottom surface. It is known that a current flows only within a certain distance from a conductor surface due to a skin effect for a high-frequency signal. For this reason, the first embodiment of the present invention has a great advantage that the bottom area of the signal line can be widened and the resistivity at high frequencies can be reduced.

Further, according to the present invention, the side area of the gold wiring 107 can be reduced as compared with the prior art, so that there is an advantage that crosstalk between wirings can be reduced.

In fact, FIG. 2 shows the frequency dependence of the wiring resistance formed by using the prior art and the technique of the present invention obtained by simulation. It can be seen from FIG. 2 that at 5 GHz or higher, the resistance of the present invention is lower than that of the prior art.

Next, a second embodiment of the present invention will be described. FIG. 3 is a sectional view for explaining the structure and the manufacturing method of the second embodiment of the present invention.

First, as shown in FIG. 3, in this embodiment, a first polyimide layer 203 is formed on a silicon substrate 201, and a first gold wiring layer 207a and a second gold wiring layer 20 are formed.
7b is laminated. Next, an MCM is formed by forming a second polyimide layer 204 and forming a ground electrode 202.

In the second embodiment, similarly to the first embodiment, a second gold wiring 207b is formed as a convex electrode on a first gold wiring 207a which is a signal line facing the ground electrode 202. Since the surface area is thereby increased, there is an advantage that the influence of the skin effect can be reduced and the wiring resistance at high frequencies can be reduced. The second embodiment also has an advantage that the first gold wiring 207a and the second gold wiring 207b can be formed more easily than the first embodiment because they can be formed by plating using a photoresist as a mask.

[0016]

The MCM of the present invention has a great advantage that the surface area can be increased by forming a convex electrode portion on the signal line, and the wiring resistance at high frequencies can be reduced. The present invention also has an advantage that crosstalk can be reduced by reducing the area of the side surface.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure and a manufacturing method of an embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a diagram for explaining an effect of the first embodiment shown in FIG. 1;

FIG. 3 is a cross-sectional view for explaining a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 101 silicon substrate 102 ground electrode 103 first polyimide layer 104 second polyimide layer 105 first barrier metal layer 106 photoresist layer 107 gold wiring layer 201 silicon substrate 202 ground electrode 203 first polyimide film 204 second polyimide Film 207a First metal wiring 207b Second metal wiring

Claims (1)

(57) [Claims] 1. A signal wiring used in a multi-chip module has a plurality of convex electrode portions uniformly formed in a wiring direction of the signal wiring, and the convex electrode portion is provided with an insulating layer interposed therebetween. A multi-chip module characterized by being disposed so as to face a ground electrode.