Substrate for semiconductor apparatus.

0001This invention relates to a substrate for loading a semiconductor chip used in integrated circuit apparatus or the like. An object of the invention is to provide a superior substrate for loading the semiconductor chip, which is capable of efficiently radiating heat developed from the loaded semiconductor chip and has the inherent characteristic of having a thermal expansion coefficient similar to those of semiconductor chip and material of other apparatus surrounding the same.

0002The material of substrate for loading the semiconductor chip has conventionally employed Ni alloy consisting of Kovar (29 % Ni - 17 % Co - Fe), 42 alloy; etc. or ceramics, such as alumina, forsterite, etc. in serious consideration that the substrate has hitherto had the thermal expansion coefficient similar to that of semiconductor chip, especially for the demand of high heat radiation, various Cu alloys have been used.

0003However, recent remarkable progress of semiconductor industry has promoted greater size of semiconductor chip or the increased amount of heat generation and the demand for substrate material to meet both the characteristics of thermal expansion coefficient and heat radiation has been on the increase.

0004Under such conditions, tungsten, molybdenum, beryllia, etc., have been proposed as materials to meet both the above characteristics.

0005Beryllia, however, in fact is not usable from the problem of environmental pollution. Although the thermal expansion coefficient of tungsten or beryllia is well coincident with that of semiconductor chip, but has a large difference from that of alumina often used as the enclosure material and also from that of GaAs recently having increased in the amount used, and furthermore the tungsten and molybdenum are inferior to beryllia in the aspect of heat radiation so as to be largely restricted in the packaging design.

0006The inventors, after research of elimination of the above defects of material of conventional substrate loading semiconductor chip to thereby control the thermal expansion coefficient and obtain the substrate material of good heat conductivity, have been designed the present invention.

0007In other words, the semiconductor chip loading substrate has the thermal expansion coefficient similar to those of semiconductor chip and enclosure material, and is superior in heat conductivity and comprises a sintered compact containing copper of 2 to 30 % in tungsten and/or molybdenum.

0008Such substrate, when the electrical-insulated property is required, is subjected at the surface to thin-layer coating of ceramic or organic insulator, thereby being usable instead of conventional ceramic.

0009In this invention, a Cu content of 2 to 30 wt. % in W and/or Mo aims at that the thermal expansion coefficient of substrate is made as similar as possible to those of Si and GaAs or sintered alumina for other enclosure material, thereby reducing as much as possible the influence of stress caused by the mismatch between the thermal expansion coefficients of the substrate and semiconductor chip and enclosure material.

0010Hence, a proper amount of Cu need only be selected in the above range corresponding to the formation and size of package.

0011This invention is defined to get the substrate by containing Cu in W and/or Mo by the powder metallurgy, because the manufacture of the same by melting method is difficult due to the melting point and specific gravity difference of Cu, W and Mo. Among the powder metallurgy methods, the sintering and the infiltration are preferable.

0012Also, it is possible for making W and/or Mo skeleton to add thereto the iron group element of 20 wt. % or less.

0013A preferable amount of iron group element to be added is below 5 wt. % enough, but even above that, when up to 20 wt. %, will demonstrate the effect to form the skeleton.

0014The addition of an amount over 20 wt. %, however, is not preferable because the sintered compact produced is defective in the thermal characteristic not to attain the object of the invention.

0015The amount of iron group element, even when added to both W and Mo, is equal enough to be added to W or Mo independently.

0016As seen from the above, the use of substrate of the invention can meet the demand steadily on the increase hereafter for the semiconductor chip large-sized and of high density and be applicable to the substrate for GaAs chip which is promoted to be put into practical use together with Si chip.

0017Next, embodiments of the invention will be detailed as follows.

Example 1

0018Tungsten and a powder mixture of the same and iron group element were compacted in the size of 100 x 100 x 5 mm respectively, and sintered under the H₂ gas atmosphere at a temperature of 1000 to 1400°C, thereby obtaining an intermediate sintered compact with porosity of 1 to 5 %. Cu was infiltrated into the sintered compact under the H₂ gas atmosphere at a temperature of 1200°C to produce Cu - W alloy of Cu content of 1 to 40 Wt. %.

0019The Cu - W alloy thus produced was measured of the thermal expansion coefficient and thermal conductivity to obtain the results in Table 1.

0020In addition, the thermal expansion coefficients of Al₂O₃. Si, and GaAs were entered therein.

0021The marks ^* in Table 1 represent comparison examples out of the scope of claims of the invention.

0022<tables id="tabl0001" num="0001"><img file="EP0100232A2_D0001.tif" /></tables>

0023In the above table 1,IC package using Cu - W alloy sintered compact (No. 3) of Cu content of 10 wt.% as the substrate material for loading Si chip produced no heat distortion due to a small difference between the thermal expansion coefficients of Si chip and other enclosure base material of Al₂0₃ during the mounting process and an extremely good heat radiation as the device could produce IC longer in the life span and of high reliability.

Example 2

0024Molybdenum and a powder mixture of the same and iron group element were compacted in the size of 100 x 100 x 5 mm respectively, and then sintered under the H₂ gas atmosphere at a temperature of 1000 to 1400°C, thereby obtaining an intermediate sintered compact with porosity of 1 to 50 %.

0025Copper was infiltrated into the intermediate sintered compact under the H₂ gas atmosphere at a temperature of 1200°C, thereby producing Cu - Mo alloy of copper content of 1 to 50 wt.%.

0026The Cu - Mo alloy thus produced was measured of the thermal expansion coefficient and heat conductivity, thereby having obtained the results in Table 2.

0027In addition, the marks ^* show comparison examples out of the scope of claim of the invention. <tables id="tabl0002" num="0002"><img file="EP0100232A2_D0002.tif" /></tables>

0028In the above table 2, IC package using Cu - Mo alloy sintered compact (No. 4 ) as the substrate base material for loading Si chip produced no heat distortion at all due to a small difference between the thermal expansion coefficients of Si chip and other enclosure base material of Alz03 during the mounting process and an extremely good heat radiation as the device could obtain IC longer in the life span and of high reliability.

Example 3

0029Tungsten, 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 in the size of 30 x 30 x 5 mm under pressure of 1 t/cm , and then sintered under the H₂ gas atmosphere at a temperature of 1450 °C for one hour.

0030The alloy thus produced was measured of the thermal expansion coefficient and heat conductivity, thereby having obtained the results in Table 3. In addition, in Table 3, the marks ^* show the comparison examples out of the scope of claims of the invention. <tables id="tabl0003" num="0003"><img file="EP0100232A2_D0003.tif" /></tables>