JPH04130757A - Ceramic package for semiconductor element - Google Patents

Abstract

PURPOSE:To enable the propagation delay time and the propagation loss of the signal at very high frequencies to be cut down by a method wherein the title ceramic package for semiconductor element is provided with a composite structure equipped with a multiple layer structure comprising copper conductors and a glass ceramic layer of low permittivity on an aluminum nitride substrate. CONSTITUTION:A glass ceramic layer 17 of low permittivity is formed on a part of one side surface of an AlN substrate 10 while a copper conductors 18 are formed on the glass ceramic layer 17 and the loading part of a semiconductor element 8 of the AlN substrate 10. The semiconductor element 8 loaded on a package is connected to the copper conductor 18 by a bonding wire 9. Since the copper wiring 18 is formed on the glass ceramic layer 17 of low permittivity, the delay time can be cut down comparing with that of the conventional package wherein the W conductor plated with nickel and Au is formed on an alumina substrate of 10 in permittivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a ceramic package for semiconductor devices having high-density wiring.

[Prior Art] As semiconductor devices such as LSIs become faster and more highly integrated, there is a demand for packages for semiconductor devices that have fine, densely wired conductors and many external output metal pins.

In particular, a ceramic package called a PGA (Pin Grid^rray) package, in which several hundred metal pins are arranged in a grid pattern on the package surface, is used because of its heat dissipation properties and high reliability.

FIG. 5 is a sectional view of a conventional ceramic PGA package, and FIG. 6 is a sectional view showing it in detail.

Conventional ceramic PGA packages are made by printing a paste mainly composed of W powder on a green sheet with peer holes formed by tape casting.
Alumina ceramic substrate 1 made by laminating and firing
and tungsten (W>conductor 2). After applying nickel plating 5 to the external metal surface, external output metal pin 4 is vertically joined to a predetermined position with ACICU brazing material 6, and finally Gold plating 7 is applied. After the semiconductor element 8 is mounted on the package, it is connected by wire bonding 9.

However, in recent years, with technological trends increasing the density of internal wiring and the number of external output pins, copper conductors with low electrical resistance suitable for high R-wave circuits and high speed applications have been overlooked.

Copper conductor has an electrical resistance of 17 to 115 compared to conventional W conductor.
Because of its small size, it has many advantages such as low wiring resistance, excellent solder heat resistance, good solder wettability, low signal transmission loss in ultra-high frequency bands, and less electromigration. .

On the other hand, glass ceramics, which have a lower dielectric constant than alumina, which is a conventional ceramic material, and organic polyimide are expected to increase speed. In particular, the development of multilayer wiring boards that co-fire copper paste and glass ceramics is expected and is being actively studied (Published by Nikkei McGraw-Hill, Inc. [Nikkei New Materials J, August 3, 1987).
issue, pp93103). In addition, there have been many reports of polyimide being used to form a multilayer structure of only signal conductor lines such as Cu or Au on a ceramic substrate (Nikkei Microdevices, published by Nikkei McGraw-Hill, June 1989).
Month, pp50-61).

Furthermore, since improving heat dissipation is one of the important properties for semiconductor device packages, aluminum nitride < A
IN> is attracting attention as a packaging material. For example, recently, a ceramic PGA package with a new structure combining AIN ceramics and thin film conductors as shown in Figures 7 and 8 has been developed (Proceed
ings of the 6th International
nal )licrOelectrOnics Con
ference.

1990, 1) 217). This package has a structure in which a multilayer polyimide insulating layer and a multilayer signal wiring 12 are formed by a thin film process on the surface of an AlN ceramic substrate 10 in which W conductors 3 and 11 as power wiring are formed by a co-firing method. There is. In the figure, 13 is a fin, 14 is an AffiN cap, 15 is an adhesive layer, and 16 is a printed circuit board. Since polyimide has a low dielectric constant, it is said to be effective in shortening delay time in high-speed device packaging.

However, such multilayer structures using polyimide and thin film processes have cost and productivity problems such as high polyimide material and equipment costs and long production times. The problem remained.

[Problems to be solved by the invention] Conventional general alumina packages have a dielectric constant of 9 to 1.
0 and 2 to 2 from the values of glass ceramics and polyimide materials.
Since it is three times larger, it is insufficient for speeding up, and Cu
It was not possible to form conductors inside. On the other hand, multilayer wiring boards made of glass ceramics and copper conductors have problems with heat dissipation because the thermal conductivity of the glass ceramic material is about an order of magnitude lower than that of conventional alumina. Furthermore, although AIN has thermal conductivity 5 to 10 times higher than that of alumina, its dielectric constant is about the same as that of alumina, so it is not effective for increasing speed.

Therefore, A with excellent heat dissipation! In addition to combining an N substrate and a copper conductor with excellent electrical properties, the inventors have diligently studied a structure that will further exhibit the characteristics of increased speed.
The composite structure ceramic package of the present invention has been invented.

[Means for Solving the Problems] The present invention provides a semiconductor device having a composite structure equipped with a multilayer structure consisting of a copper conductor and a low dielectric constant glass ceramic layer on an aluminum nitride substrate. It is a ceramic package.

Here, it is desirable that the dielectric constant of the glass ceramic is smaller than that of aluminum nitride.

The present invention will be explained in more detail below.

FIG. 1 shows a cross-sectional structure of an example of a package for a semiconductor device according to the present invention. A glass ceramic layer 17 having a low dielectric constant is formed on one side of a highly thermally conductive AβN substrate 10, and a copper conductor wiring portion 18 is formed roughly thereon. The AbuN substrate contains alkaline earth metals (Ca, Ba, etc.) associated with sintering aids.

It may contain compounds of Sr, etc.) or rare earth metals (Y, La, Gd, etc.) as impurities.

The material for the low dielectric constant glass ceramic layer is a material whose dielectric constant at room temperature is less than the value of aluminum nitride.
- Compositions known for boat fishing are available. For example, specifically, a composite material of borosilicate glass and alumina, a composite material of borosilicate glass and silica, a composite material of borosilicate glass and cordierite, ZnO-MgO-N1203
-5i02 cordierite materials, other single or composite materials selected from borosilicate glass, silica, cordierite, mullite, holsterite, etc., with a value of 3.5 to 8 at a frequency of 1 MHz are effective. It is.

The process for forming a low dielectric constant glass ceramic layer on an AlN substrate is as follows:
In addition to the in-phase method of heat treatment at ~1000'C, methods such as the sputtering method and vapor deposition method, which are gas phase methods, and the sol-gel method, which is a liquid phase method, can also be applied.

Copper wiring as a conductor can be formed by processes such as thick-film printing, which involves printing copper paste and then heat-treating it, physical methods such as vapor deposition and Yasbatta method, and chemical methods such as electroless plating. .

[Function] In the present invention, the heat generated from the semiconductor element is transferred to A!, which has high thermal conductivity. Dissipated by the N substrate.

Zarani Af! The copper conductor in contact with the low-permittivity glass-ceramic on the N-substrate makes it possible to reduce propagation delay time and signal propagation loss at very high frequencies. Therefore, the ceramic package for semiconductor devices of the present invention is excellent thermally and electrically and is suitable for mounting high-speed LSI devices.

[Example] Next, an example of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a sectional view showing an embodiment of the present invention, and A! A glass ceramic layer 17 with a low dielectric constant is formed on a part of one side of the N substrate 10, and a copper conductor 18 is formed on the glass ceramic layer and on the AlN substrate on the mounting portion of the semiconductor element. After the semiconductor element 8 is mounted on the package,
They are connected by wire bonding 9.

In this example, since the copper wiring is formed on a glass ceramic layer having a low dielectric constant, the wiring is made of a W conductor plated with nickel and gold on an alumina substrate with a dielectric constant of 10, as shown in FIG. This is effective in reducing delay time compared to conventional packages in which For example, by providing a 20 JU layer of [-gelite glass ceramics] with a dielectric constant of 5.0 as a glass ceramic material between a 10-thick copper conductor and an AIN substrate, it is possible to reduce This results in a 20% reduction in delay time, which is effective for mounting high-speed LSI devices.

Furthermore, by using a copper conductor that has a lower electrical resistance than W or nickel, it also has the characteristic of less transmission loss of digital signals in the high frequency range. Furthermore, by forming the mounting part of the LSI element with a copper conductor, the thermal conductivity is superior to that of the conventional W layer and Ni layer, so the heat from the LSI element is efficiently transferred to the highly thermally conductive AIN board, and heat dissipation is improved. It is also effective in On the other hand, in the copper conductor forming process of the present invention, there is no shrinkage of the W conductor within the ceramic surface during the simultaneous firing process as in the conventional technology, so the position and dimensions of the conductor can be formed with high precision. It is also effective for fine pitch and high density.

In Figure 1, the copper conductor is Aj! Although it is formed on the glass ceramic layer on the N substrate, Aj! It is also possible to form a copper conductor directly on the N substrate and form a glass ceramic layer thereon. Furthermore, in Figure 1, the low dielectric constant glass ceramic layer is only on the AlN substrate, but as shown in Figure 2, it is also possible to form a multilayer structure in which low dielectric constant glass ceramic layers and copper conductors are alternately laminated. be.

In the case of Figure 2, the multilayer wiring copper conductor on the Al1N substrate is
Aj with simultaneous firing method! It is connected to a metal pin 4 for external output on the opposite side of the element mounting surface by a W internal conductor 3 formed inside the N substrate. The method for joining the metal pin 4 is as follows:
A technique can be used to form the W outer conductor portion plated with Ni using a brazing filler metal 6 made of AgCu or AuSn.

Moreover, the metal pin for external output can also be formed perpendicularly to the element mounting surface side as shown in FIG.

In this case, there is no need to form a W internal conductor inside the AIN substrate. As an external output bin, it is also possible to use a lid 19 formed in the horizontal direction of the substrate, as shown in FIG. 4, instead of vertically standing on the AlN substrate.

[Effects of the Invention] As explained above, the ceramic package for semiconductor elements of the present invention can provide the following excellent effects.

■By being able to mount a semiconductor element on a highly thermally conductive AIN substrate, it improves heat dissipation and is effective in lowering the thermal resistance of the semiconductor element. In particular, when a copper conductor is formed as the metal for the mounting part of a semiconductor element, conventional W conductors and Ni and A
This is even more effective than the combination of u plating.

(2) Since the conductor wiring is formed in contact with a glass ceramic layer having a low dielectric constant, it is effective in reducing propagation delay time and is suitable for mounting high-speed LSIs.

■Using copper, which has low electrical resistance, as a conductor reduces wiring resistance and signal propagation loss in ultra-high frequency bands. In addition to this, copper conductors have many other advantages such as excellent solder heat resistance, good solder wettability, and resistance to electromigration.

■Since the conductor does not shrink on the surface of the ceramic substrate during the co-firing process unlike the conventional technology, the position and dimensions of the conductor can be formed with high precision, and it is also effective in achieving fine pitch and high density.

[Brief explanation of the drawing]

1 to 4 are sectional views of essential parts of an embodiment of the present invention, FIG. 5 is a sectional view of an example of a conventional ceramic package for semiconductor elements, FIG. 6 is an enlarged sectional view thereof, and FIG. FIG. 8 is a cross-sectional view of another example of a conventional ceramic package for semiconductor devices, and FIG. 8 is a partial cross-sectional view thereof. 1... Alumina ceramics substrate 2... W outer conductor 3... W inner conductor 4...
・Metal pin 5...Nickel plating 6...
AgCu brazing material 7... Gold plating 8... Semiconductor element 9... Wire bonding 10... AIN ceramics substrate 11... Power supply conductor layer 12... Polyimide thin film multilayer wiring 13... Fin 14. ... AlN cap 15 ... adhesive layer 16 ... printed circuit board 17 ... glass ceramic layer

Claims (2)

[Claims] (1) A ceramic package for a semiconductor device characterized by having a composite structure equipped with a multilayer structure consisting of a copper conductor and a low dielectric constant glass ceramic layer on an aluminum nitride substrate. (2) The ceramic package for a semiconductor device according to claim 1, wherein the dielectric constant of the glass ceramic is smaller than that of aluminum nitride.