JPH07202365A - Semiconductor mounting board - Google Patents

Abstract

(57) [Summary] [Purpose] It is extremely easy to put a thin film (multi-layer) substrate with excellent strength into practical use, by skillfully configuring it so that it can use a certain metal that was considered unsuitable for the substrate. Its purpose is to serve. A metal film 2 having a high conductivity and a non-magnetic material is formed on substantially the entire surface of a metal substrate 1, and a strip line (conductor) 3 is formed on the metal film 2. Since it is configured to be used as the ground layer or the power supply layer of No. 3, an electromagnetic field is unlikely to be generated in the metal substrate 1, that is, the influence of the metal substrate 1 on a high frequency can be ignored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor mounting board.

[0002]

2. Description of the Related Art A wiring board using a thin film circuit can have a high wiring density and a polyimide resin having a low relative dielectric constant can be used as a dielectric, so that the packaging density can be improved and the circuit can operate at high speed. Is perfect for However, the thin film circuit board is high in cost and has not come into widespread use. The thin film circuit board is conventionally formed on a ceramic substrate or a silicon substrate, but since the ceramic substrate has pores inevitably on the surface,
This is because surface treatment (formation of a grace layer or the like) and subsequent expensive polishing are indispensable, and on the other hand, a silicon substrate has weak mechanical strength and large manufacturing cost is disadvantageous.

For this reason, it has been considered to use a large-sized substrate made of metal which has good thermal conductivity and can be easily manufactured at a low cost. Here, the characteristics of typical metals are shown in Table 1.

[0004]

[Table 1]

For example, inexpensive metals such as Cu, Al and Ni have a large thermal expansion coefficient, so that their applications are necessarily limited, and refractory metals such as Mo and Ta have no problem in characteristics. It has the disadvantage that the material itself is expensive and not easy to process. In that respect, the so-called 4-2 alloy (F
e58% -Ni42%) and stainless steel (Fe78%-
Cr12%) has a good balance in characteristics, is easy to process (a plate material can be easily obtained by rolling), and is also relatively inexpensive.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Alloys or stainless steels are ferromagnetic materials,
If the conductor is arranged in the vicinity of the conductor, the inductance of the conductor increases, that is, it is not suitable for a high-speed circuit. Therefore, in the present invention, by reasonably overcoming the inherent characteristics of the 4-2 alloy and the stainless steel, which can cause such deterioration of the electrical characteristics, those metals can be practically used as a substrate. The object is to realize an inexpensive thin film substrate (thin film multilayer substrate).

[0007]

FIG. 1 is a principle diagram for explaining the basic principle of the present invention for achieving the above object. A nonmagnetic and electrically conductive metal film 2 is formed on substantially the entire surface of the metal substrate 1, and a strip line (belt-shaped conductor) 3 on which an electric component (semiconductor component) or the like (not shown) can be mounted is formed on the metal film 2. And the metal film 2 is used as a ground layer or a power supply layer of the strip line 3.

The metal substrate 1 may be made of stainless steel containing iron and chromium of 10 to 15% and other elements of about 5% or less. (In particular, it is preferable that the chromium content is 10 to 12% from the viewpoint of thermal expansion. Further, in order to improve the corrosion resistance, Mo, Ni and the like can be added within 5%.) The metal substrate 1 , Alloys containing about 42% iron and nickel and up to about 5% other elements.

The conductor on the metal substrate 1 may be formed on the entire surface of the substrate without pattern formation. Metal substrate 1
Can consist of hard-plating the surface and then polishing.

[0010]

Since the metal film 2 having a high conductivity and a non-magnetic material is formed on substantially the entire surface of the metal substrate 1 and the strip line (conductor) 3 is formed on the metal film 2, the transmission characteristics are improved. Assuming the high frequency region where
When a high frequency voltage is applied between the strip line 3 and the metal film 2, the width (W: several 10 μ) and the thickness (t: several μ) of the strip line are compared with the size of the substrate (several cm). Is small enough, current flows only on the surface of the metal film 2,
No electromagnetic field is generated in the metal substrate 1, that is, the influence of the metal substrate 1 on the high frequency can be ignored.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First, referring to FIG. 2 for explaining the first embodiment, the metal substrate 11 is so-called 4-2 in terms of composition.
Composed of alloy (Fe58% -Ni42%), easily rolled into a plate shape and then polished (mirror finish)
Is applied. Note that stainless steel (for example, stainless steel composed of Fe78% -Cr12%) can be used in place of the 4-2 alloy, but any material of the 4-2 alloy or stainless steel can be used as a semiconductor (silicon). Since it may have a thermal expansion coefficient close to that of the semiconductor (see Table 1), it does not need to exert an excessive thermal force on the semiconductor, which is preferable. Further, any of the above-mentioned materials is very convenient because there are almost no restrictions on the material size and the processing size (substrate size) and they can be obtained at low cost. By the way, the above polishing process is an important step because it is necessary to smooth the substrate surface in order to prevent short-circuiting of the dielectric layer or lower the impedance of the power supply layer when forming fine wiring. is there. When a particularly smooth surface is required, instead of polishing the 4-2 alloy as it is, the surface is first plated (for example, dense and inexpensive electroless Ni plating is suitable) and then polished. It is preferable to carry out.

Next, Cr (0.1 μ) and Cu (5.0 μm) are formed on the metal substrate 11 (on the lower side in the figure).
μ) and Cr (0.1 μ) (hereinafter Cr / Cu
/ Cr film) 13 is formed. This film (layer) 1
3 is used as a ground layer. In this embodiment, it is planned to form a film by using the DC magnetron sputtering method, but a vacuum vapor deposition method or a plating method can also be used.
Cr / Cu / C using known photolithography method
The pattern of the r film can be formed, but in the usual case, the pattern formation is unnecessary.

Next, a photosensitive polyimide precursor varnish is applied on the Cr / Cu / Cr film 13 by spin coating, and then the solvent is dried. Then, a via is formed by irradiating ultraviolet light through the mask and developing this. Next, 350 to 4 in nitrogen
Baking at 50 ° C. gives a polyimide resin. Then Cr
A / Cu / Cr film is formed in the same manner as above. After forming a resist pattern by a normal method, Cr is etched using a mixed solution of potassium ferricyanide and potassium hydroxide, Cu is etched using a mixed solution of sulfuric acid and hydrogen peroxide solution, and Cr of the lower layer is further removed. Etching. The resist is peeled off with an appropriate peeling solution, and the conductor pattern (signal layer 1
5, 17 and the power supply layer 19) are obtained. By repeating the above steps a required number of times, a multilayer wiring pattern can be obtained.

The uppermost pad 21 is made of Ni on the Cu film.
Are formed by plating Au and Au, the semiconductor component, that is, the IC chip 23 is bonded and mounted with a resin, and a bonding connection is made via a gold wire.
In the case of a metal substrate made of a 4-2 alloy, the heat conductivity is relatively poor (see Table 1), so that a radiation fin 25 can be attached to the opposite surface of the substrate, if necessary.

In the following, to describe the embodiment of Table 2,
Please refer to FIG. The metal substrate 31 is made of the 4-2 alloy or stainless steel as in the first embodiment, and on the metal substrate 31 (the lower side in the figure), as in the first embodiment, A Cr / Cu / Cr film 33 is formed.
The film (layer) 33 is used as a ground layer.

Then, on the Cr / Cu / Cr film 33, a silicon dioxide film 35 (thickness:
1 μm or less, preferably about 300 nm) is formed. still,
The Cr / Cu / Cr film (conductor) 33 and the silicon dioxide film (dielectric layer) 35 form a large-capacity capacitor and lower the impedance of the power supply, so that voltage noise caused by the operating current of the IC or the like is reduced. Has been preferred.

Then, vias (not shown) are formed in the silicon dioxide film 35 at the necessary places by the reactive ion etching method. Then another Cr / Cu /
The Cr film 37 is formed thereon. In addition, this film (layer) 3
7 is used as a power supply layer. On the metal substrate 31,
As described above, the conductor 33, the dielectric layer 35, and the conductor 37 are formed in this order, and one conductor (33) is used as a ground layer and the other conductor (37) is used as a power supply layer.
This is to reduce the impedance of.

Subsequent steps of forming the substrate portion (signal layers 39, 41, pads 43, etc.) are the same as those in the first embodiment, and therefore the description thereof is omitted.

[0019]

As described above, according to the present invention, an inexpensive thin film (multilayer) substrate excellent in strength is used because it is constructed so that a predetermined metal, which is considered unsuitable for a substrate, can be used as the substrate. Can be put to practical use very easily.

[Brief description of drawings]

FIG. 1 is a principle diagram illustrating a basic principle of the present invention.

FIG. 2 is a side sectional view of a semiconductor mounting substrate according to a first embodiment of the present invention.

FIG. 3 is a side sectional view of the second embodiment.

[Explanation of symbols]

 11, 31 ... Metal substrate 13, 33, 37 ... Cr / Cu / Cr film 15, 17, 39, 41 ... Signal layer 19 ... Power supply layer 21, 43 ... Pad 23 ... IC chip 35 ... Silicon dioxide film

Claims (5)

[Claims] 1. A metal substrate (1), a metal film (2) of non-magnetic and good electric conductor formed on substantially the entire surface of the metal substrate (1), and a strip formed on the metal film (2). And a line (3), wherein the metal film (2) is used as a ground layer or a power supply layer of the strip line (3). 2. The metal substrate (1) is made of iron and chromium.
The semiconductor mounting board according to claim 1, wherein the semiconductor mounting board is composed of stainless steel containing ˜15% and other elements of about 5% or less. 3. The metal substrate (1) according to claim 1, wherein the metal substrate (1) is composed of an alloy containing about 30 to 50% of iron and nickel and about 5% or less of other elements. Semiconductor mounting board. 4. The semiconductor mounting substrate according to claim 1, wherein the conductor on the metal substrate (1) is formed on the entire surface of the substrate without pattern formation. 5. The semiconductor mounting substrate according to claim 1, wherein the metal substrate (1) is formed by applying hard plating to the surface thereof and then polishing the surface.