Substrate for semiconductor apparatus

Abstract

This invention relates to a substrate for semiconductor apparatus loading a semiconductor chip in integrated circuit apparatus and is characterized in that a sintered compact containing copper of 2 to 30 wt. % in tungsten and/or molybdenum is used as the substrate having the heat radiation capable of efficiently radiating heat developed from the loaded semiconductor chip and thermal expansion coefficient similar to those of semiconductor chip and other enclosure material except for the substrate.

Description

This invention relates to a substrate for mounting a semiconductor chip an in integrated circuit or the like. An object of the invention is to provide a superior substrate for mounting the semiconductor chip, which substrate is capable of efficiently radiating heat developed from the mounted semiconductor chip and said substrate having a thermal expansion coefficient similar to those of semiconductor chip and other materials surrounding the same.

Substrates for loading semiconductor chips have conventionally been made of a Ni alloy conisting of Kovar (29% Ni--17% Co--Fe), 42 alloy; etc, or ceramics, such as alumina, forsterite, etc.

The conventional substrates have thermal expansion coefficients similar to that of the semiconductor chip, and when high heat radiation is also required, various Cu alloys have been used.

However, recent remarkable progress in the semiconductor industry has promoted greater size of semiconductor chips or increased amounts of heat generation and the demand for a substrate material to meet both the characteristics of thermal expansion coefficient and heat radiation has been on the increase.

Under such conditions, tungsten, molybdenum, beryllia, etc., have been proposed as materials to meet both of the above characteristics.

Beryllia, however, in fact, is not usable from the standpoint of environmental pollution. Although the thermal expansion coefficient of tungsten or beryllia is corresponds well to that of the semiconductor chip, it has a large difference from that of alumina often used as the enclosure material and also from that of GaAs which has been used in increasing amounts for semiconductor chips. Furthermore tungsten and molybdenum are inferior to beryllia in respect of heat radiation so as to be largely restricted in packaging design.

The inventors, after conducting research on elimination of the above defects in materials for conventional substrates for mounting semiconductor chips to thereby control a thermal expansion coefficient and obtain a substrate material of good heat conductivity, have arrived at the present invention.

In other words, the semiconductor chip bearing substrate of the present invention has the thermal expansion coefficient similar to those of semiconductor chips and enclosure materials, is superior in heat conductivity. It comprises a sintered compact containing copper at 2 to 30% and tungsten and/or molybdenum.

When electrical-insulation is required, the substrate is given a thin-layer surface coating of a ceramic or organic insulator, instead of conventional ceramic.

In this invention, there is employed Cu in the amount of 2 to 30 wt. % and W and/or Mo to obtain a thermal expansion coefficient of the substrate as similar as possible to those of Si and GaAs or sintered alumina or other enclosure materials, thereby reducing, to the extent possible, the influence of stress caused by the mismatch between the thermal expansion coefficients of the substrate and semiconductor chip and enclosure material. Hence, a proper amount of Cu need only be selected in the above range corresponding to the formation and size of the package.

The inventive substrate containing Cu and W and/or Mo is produced powder metallurgy, because the manufacture of the same by the melting method is difficult due to the melting point and specific gravity difference between Cu, W and Mo. Among the powder metallurgy methods, sintering and infiltration are preferable.

Also, it is possible to make the W and/or Mo skeleton by adding thereto an iron group element at 20 wt. % or less.

A preferred amount of iron group element to be added is below 5 wt. %, but even above that, when up to 20 wt. %, will form the skeleton.

The addition of an amount over 20 wt. %, however, is not preferred because the sintered compact produced is defective in thermal characteristics and thus will not attain the objects of the invention.

The amount of iron group element, even when added to both W and Mo, can be added to W or Mo independently.

As seen from the above, the substrate of the invention can meet the increasing demand for large and high density semiconductor chip and be applicable as a substrate for the GaAs chip which is being put into practical use together with an Si chip.

Next, embodiments of the invention will be detailed as follows.

EXAMPLE 1

Tungsten and a powder mixture of the same and an iron group element were compacted in the size of 100.times.100.times.5 mm respectively, and sintered under an H.sub.2 gas atmosphere at a temperature of 1000.degree. to 1400.degree. C., thereby obtaining an intermediate sintered compact with porosity of 1 to 5%. Cu was infiltrated into the sintered compact under the H.sub.2 gas atmosphere at a temperature of 1200.degree. C. to produce Cu-W alloy of Cu content of 1 to 40 wt. %.

The Cu-W alloy thus produced was measured for thermal expansion coefficient and thermal conductivity to obtain the results in Table 1.

In addition, the thermal expansion coefficients of Al.sub.2 O.sub.3, Si, and GaAs were entered therein.

The marks * in Table 1 represent comparative examples outside the scope of the invention.

TABLE 1______________________________________ Thermal Expan- Thermal sion Coefficient ConductivityNo. Alloy Composition (.times.10.sup.-6 /.degree.C.) (cal/cm.sec..degree.C.)______________________________________ 1* 1Cu--99W 4.7 0.402 5Cu--95W 5.2 0.453 10Cu--90W 7.0 0.504 15Cu--85W 7.9 0.545 20Cu--80W 8.3 0.586 25Cu--75W 9.0 0.627 30Cu--70W 9.7 0.65 8* 35Cu--65W 11.0 0.69 9* 40Cu--60W 11.8 0.7310 10Cu--89W--1Ni 7.0 0.4811 20Cu--79.5W--0.5Ni 8.2 0.5712 5Cu--80W--15Fe 7.9 0.4213 10Cu--79W--11Co 8.1 0.4614* Al.sub.2 O.sub.3 7.215* Si 4.016* GaAs 6.7______________________________________

In the above table, or IC package using a Cu-W alloy sintered compact (No. 3) Cu content of 10 wt. % as the substrate material for mounting an Si chip produced no heat distortion due to small difference between the thermal expansion coefficients of the Si chip and other enclosure base material made of Al.sub.2 O.sub.3 during the mounting process and an extremely good heat radiation as the device could produce an IC longer in life span and of high reliability.

EXAMPLE 2

Molybdenum and a powder mixture of the same and iron group element were compacted to the size of 100.times.100.times.5 mm respectively, and then were sintered under an H.sub.2 gas atmosphere at a temperature of 1000.degree. to 1400.degree. C., thereby obtaining an intermediate sintered compact with a porosity of 1 to 50%.

Copper was infiltrated into the intermediate sintered compact under an H.sub.2 gas atmosphere at a temperature of 1200.degree. C., thereby producing a Cu-Mo alloy of copper content of 1 to 50 wt. %.

The Cu-Mo alloy thus produced was measured for the thermal expansion coefficient and heat conductivity, thereby having obtained the results in Table 2.

In addition, the marks * represent comparative examples outside the scope of the invention.

TABLE 2______________________________________ Thermal Expan- Thermal sion Coefficient ConductivityNo. Alloy Composition (.times.10.sup.-6 /.degree.C.) (cal/cm.sec..degree.C.)______________________________________ 1* 1Cu--99Mo 5.3 0.352 5Cu--95Mo 5.9 0.383 10Cu--90Mo 6.5 0.414 15Cu--85Mo 7.1 0.445 20Cu--80Mo 7.9 0.486 25Cu--75Mo 8.4 0.507 30Cu--70MO 9.1 0.54 8* 35Cu--65Mo 9.7 0.57 9* 40Cu--60Mo 10.3 0.6010* 50Cu--50Mo 11.5 0.6611 10Cu--89.5Mo--0.5Ni 6.5 0.3912 15Cu--82.0Mo--3.0Ni 7.2 0.4113 5Cu--78Mo--17Fe 8.2 0.3614 10Cu--82Mo--8Co 7.8 0.40______________________________________

In the above Table 2, an IC package using a Cu-Mo alloy sintered compact (No. 4) as the substrate base material for mounting the Si chip produced no heat distortion at all due to a small difference between the thermal expansion coefficients of the Si chip and other enclosure base materials made of Al.sub.2 O.sub.3 during the mounting process and extremely good heat radiation, and the device can obtain an IC longer in life span and of high reliability.

EXAMPLE 3

Tungsten, molybdenum powder or tungsten-molybdenum alloy powder and the required amounts of copper powder and iron group powder were mixed as shown in Table 3, and the powder was mixed by an attrition mixer uniformly for three hours, compacted to the size of 30.times.30.times.5 mm under pressure of 1 t/cm.sup.2, and then sintered under the H.sub.2 gas atmosphere at a temperature of 1450.degree. C. for one hour.

The alloy thus produced was measured for thermal expansion coefficient and heat conductivity, with the results being set forth in Table 3. In addition, in Table 3, the marks * represent comparative examples outside the scope of the invention.

TABLE 3______________________________________ Thermal Expan- Thermal sion Coefficient ConductivityNo. Alloy Composition (.times.10.sup.-6 /.degree.C.) (cal/cm.sec..degree.C.)______________________________________1 15Cu--85W 8.2 0.502 20Cu--79W--1Ni 8.5 0.483 20Cu--75W--5Co 8.7 0.474 30Cu--68W--2Fe 9.9 0.505 20Cu--70W--10Mo 8.5 0.54 6* 35Cu--65W 11.5 0.61______________________________________

Claims

1. An IC package for housing a semiconductor comprising a substrate and an enclosure base material made of Al.sub.2 O.sub.3, said substrate consisting essentially of a material containing copper and at least one of tungsten and molybdenum, said material being produced by pressing and sintering at least one of tungsten and molybdenum powders to form a sintered compact, said sintered compact being infiltrated with molten copper at 10-30 weight percent, the thermal expansion coefficient of said substrate being in the range of 5.2 to 9.7.times.10.sup.-6 /.degree.C. and the thermal conductivity being at least 0.35 cal/cm. sec. .degree.C.

2. The IC package according to claim 1 wherein said sintering and infiltration are performed in a hydrogen atmosphere.

3. An IC package for housing a semiconductor comprising a substrate and an enclosure base material made of Al.sub.2 O.sub.3, said substrate consisting essentially of a material containing copper and at least one of tungsten and molybdenum, said material being produced by pressing and sintering a uniform mixture of at least one of tungsten and molybdenum powders with not more than 20 weight percent of iron group metal powders to form a sintered compact, said sintered compact being infiltrated with molten copper at 10-30 weight percent, the thermal expansion coefficient of said substrate being in the range of 5.2 to 9.7.times.10.sup.-6 /.degree.C. and thermal conductivity being at least 0.35 cal/cm. sec. .degree.C.

4. The IC package according to claim 3 wherein said sintering and infiltration are performed in a hydrogen atmosphere.