JPH07335779A - Multi-chip module - Google Patents

Abstract

PURPOSE:To provide a multi-chip module board provided with a prescribed electrostatic capacity between a power source layer and a grounding layer. CONSTITUTION:On an insulating substrate 2, a grounding layer 3, a first insulating layer, a power source,layer 5, a second insulating layer 6, a first signal layer 7 and a third insulating layer 8 are successively laminated, and a microwave circuit is formed. A multi-chip module is provided by mounting a semiconductor integrated circuit chip on the third insulating layer 8, which is the topmost layer. The first insulating layer between the grounding layer 3 and the power source layer 5 is formed of the composite dielectric layer 13, which is composed of the two layers, which are a dielectric with a high dielectric constant and an organic or inorganic dielectric with excellent electric characteristics.

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 (abbreviated as MCM) having improved characteristics.

Since it is necessary to process a large amount of information quickly, the semiconductor device that constitutes the main body of an information processing device has a large capacity due to the miniaturization of unit elements, and LSI and VLSI have been put into practical use. Although it is being put to practical use, the mounting method is also advancing along with this, and multiple flip-chip type semiconductor elements are mounted on a multilayer circuit board formed on a silicon (Si) substrate, and this is used as a replacement unit. M
Commercialization is in full swing.

[0003]

2. Description of the Related Art Various types of MCM substrates have been proposed to date, but each has its advantages and disadvantages, and there is no definitive one yet.

FIG. 2 shows the structure of a typical MCM substrate, in which a ground layer 3, a silicon (Si) substrate 2 covered with a silicon dioxide (SiO ₂ ) layer 1 and electrically insulated. The first insulating layer 4, the power supply layer 5, the second insulating layer 6, the first signal layer 7, and the third insulating layer 8 are sequentially stacked, and when the circuit is complicated, the second insulating layer is further formed on the second insulating layer. An MCM substrate is formed by sequentially stacking a signal layer and an insulating layer, and a plurality of semiconductor integrated circuits (abbreviated as ICs) 9 are arranged and mounted in a matrix on the MCM substrate.

The IC 9, the signal layer 7, the power supply layer 5, and the ground layer 3 are circuit-connected by vias (not shown). Note that FIG. 2 shows the simplest configuration with only one signal layer for easy understanding.

As described above, the MCM has the ground layer 3 / power source layer 5
/ The signal layer 7 and the conductive layer are formed by laminating via an insulating layer. However, when a large number of ICs 9 simultaneously switch during operation, a large amount of current flows at a time, resulting in a drop in the power supply voltage. However, there is a problem that power supply noise is generated. As a method of removing this power supply noise, a capacitor is interposed between the power supply layer 5 and the ground layer 3.

That is, as a method therefor, there is adopted a method in which a ceramic chip capacitor is mounted on the third insulating layer 8 on which the IC 9 is mounted and the power supply layer 5 and the ground layer 3 are circuit-connected by vias. However, this is not suitable because the line inductance increases.

A resin such as polyimide is generally used as a constituent material of the first insulating layer 4. Instead of this, the ground layer 3 is formed of aluminum (Al) and anodized to form it. It has been proposed to use the above mentioned aluminum oxide as a dielectric.

However, aluminum oxide produced by anodic oxidation has a different crystal structure from alumina (Al ₂ O ₃ ) which has excellent dielectric properties, has pinholes due to the presence of impurity elements, and has a thickness Since it can be made as thin as 1 μm or less, a short circuit easily occurs.

Therefore, there is a demand for a structure in which a capacitor is formed between the power supply layer 5 and the ground layer 3 by another method to remove power supply noise generated in the power supply layer 5.

[0011]

The MCM is formed on the Si substrate in a multilayer structure of a ground layer / power source layer / signal layer. When the ICs arranged in a matrix form simultaneous switching, etc. Since power supply noise is generated in, we want to remove this noise by capacitive connection. Therefore, it is a problem to form a necessary capacitance between the power supply layer and the ground layer.

[0012]

[Means for Solving the Problems] The above problems are three-dimensionally formed by sequentially laminating a ground layer, a first insulating layer, a power source layer, a second insulating layer, a signal layer, and a third insulating layer on an insulating substrate. In a multi-chip module in which a circuit is formed and a chip-shaped semiconductor integrated circuit is mounted on the uppermost third insulating layer,
The problem can be solved by forming the first insulating layer between the ground layer and the power supply layer with a composite dielectric layer composed of two layers of a high dielectric constant dielectric and an organic or inorganic dielectric having excellent electrical characteristics. it can.

[0013]

As a method of forming a capacitor between the power supply layer and the ground layer of the MCM substrate, it is conceivable to form the insulating layer existing between them with a high dielectric constant dielectric. That is, strontium titanate (SrTiO ₃ ), barium titanate (Ba
TiO ₃ ), lead zirconate titanate (abbreviated as PZT) and other ceramics having a perovskite structure are formed on the ground layer constituting the MCM substrate by a sputtering method or the like, and a required wiring area is formed on the ground layer. The required capacitance should be able to be formed by patterning the provided power supply layer.

However, since the high dielectric constant dielectric film thus formed cannot be fired at a high temperature, a stable structure cannot be obtained, and therefore, there are problems that the insulation resistance value is low and the leakage current is large. Yes, and for that reason it is not used in MCM substrates.

However, the inventor has paid attention to the fact that the ceramic having such a perovskite structure has a large dielectric constant. Then, by laminating such a high-dielectric-constant dielectric layer with a dielectric layer having excellent electrical characteristics, the insulation resistance is increased and the dielectric layer can be used as an insulating layer.

When the two dielectric layers are laminated to form a composite dielectric as described above, the electrical characteristics are improved. However, the composite dielectric constant is dominated by the low dielectric constant material. An excellent low dielectric constant material needs to be formed as thin as possible.

The inventor cannot expect a large capacitance value when such a configuration is adopted. The signal frequency of the MCM is as high as several hundreds MHz, and the required capacitance is several to several tens. From the size of nF, it was found that the required capacitance can be obtained with such a structure.

As the high dielectric constant dielectric material having the perovskite structure, SrTiO ₃ , BaTiO ₃ , PZT, (Sr _1-x
Ba _x ) TiO _{3 and the} like. On the other hand, examples of dielectrics having excellent electric characteristics include silicon dioxide (SiO ₂ ), spin-on-glass (abbreviated as SOG) and other silicon oxide compounds, and resins such as polyimide.

Here, the composite permittivity when SrTiO ₃ is used as a high-permittivity dielectric having a perovskite structure and is combined with SiO ₂ , SOG and polyimide is as follows.

[0020]

[Table 1] In order to carry out the present invention, a combination and a thickness of a high dielectric constant dielectric material forming a first insulating layer between a power supply layer and a ground layer and a dielectric material having excellent characteristics are formed prior to formation of an MCM substrate. The composite permittivity is determined in advance and the line forming the power supply layer is pattern-designed to obtain the required capacitance.

[0021]

【Example】

Example 1: (Refer to FIG. 1) Chromium (Cr) / copper (Cu) was formed on a Si substrate 2 which was subjected to an insulation treatment by providing a SiO ₂ layer 1 on the surface by heat treatment by a sputtering method.
A ground layer 3 having a three-layer structure of / Cr was formed.

Here, Cr is for improving the adhesion to the substrate, the thickness is about 1000Å, and the thickness of Cu is 2 μm.
Is. Then, it sets again a sputtering apparatus, the Si substrate 2, while keeping the substrate temperature at 400 ° C. by sputtering until the SrTiO ₃ in a thickness of 0.8 [mu] m, to form a SrTiO ₃ layer 11.

Next, a polyamic acid whose viscosity was adjusted with N-methylpyrrolidone was applied so that the thickness after curing would be 0.2 μm, dried, and then heated at 350 ° C. for 3 hours to be cured to obtain a polyimide. Layer 12 was formed.

The composite dielectric constant of the composite dielectric layer 13 composed of the SrTiO ₃ layer 11 and the polyimide layer 12 thus formed is about 16
From 1 μm thick composite dielectric layer 13 to 14.1 nF / c
Capacitance of m ² can be obtained.

Next, the power source layer 5 having a three-layer structure of Cr / Cu / Cr is formed on the composite dielectric layer 13 by the sputtering method as described above, and the photolithography technique (photolithography) is applied. It was selectively etched to form a power supply wiring having a required capacitance.

Then, a polyamic acid, the viscosity of which was adjusted with N-methylpyrrolidone in the same manner as above, was applied thereon so that the thickness after curing would be 5 μm, and after drying, it was dried at 350 ° C. for 3 hours.
The second insulating layer 6 made of polyimide was formed by heating for curing for a time.

Next, a Cr / Cu / Cr film is formed on this layer in the same manner as in the prior art, and then selective etching is performed to form the first signal layer 7.
Made of polyimide, and the thickness is 5μ.
An MCM substrate was completed by forming m 3rd insulating layer 8.

[0028]

By implementing the present invention, a required capacitance can be interposed between the power supply layer and the ground layer which form the MCM substrate, and thereby the power supply noise can be removed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an MCM substrate embodying the present invention.

FIG. 2 is a cross-sectional view showing the structure of an MCM.

[Explanation of symbols]

1 SiO ₂ Layer 2 Si Substrate 3 Ground Layer 4 First Insulating Layer 5 Power Supply Layer 6 Second Insulating Layer 7 First Signal Layer 8 Third Insulating Layer 13 Composite Dielectric Layer

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Claims (2)

[Claims] 1. A ground layer (3), a first layer on an insulating substrate (2).
Insulation layer (4), power supply layer (5), second insulation layer (6),
The first signal layer (7) and the third insulating layer (8) are sequentially laminated to form a three-dimensional circuit, and the third insulating layer (8), which is the uppermost layer, has a chip-shaped semiconductor integrated circuit ( 9) In a multi-chip module equipped with the same, the first insulating layer (4) is formed of a composite dielectric layer (13) composed of two layers of a high dielectric constant dielectric and an organic or inorganic dielectric. Multi-chip module characterized by the following. 2. The multi-chip module according to claim 1, wherein the high dielectric constant dielectric is a perovskite oxide, and the organic or inorganic dielectric is a polyimide or a silicon oxide compound.